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Sample records for md simulation technique

  1. Accelerating all-atom MD simulations of lipids using a modified virtual-sites technique

    DEFF Research Database (Denmark)

    Loubet, Bastien; Kopec, Wojciech; Khandelia, Himanshu

    2014-01-01

    We present two new implementations of the virtual sites technique which completely suppresses the degrees of freedom of the hydrogen atoms in a lipid bilayer allowing for an increased time step of 5 fs in all-atom simulations of the CHARMM36 force field. One of our approaches uses the derivation...... of the virtual sites used in GROMACS while the other uses a new definition of the virtual sites of the CH2 groups. Our methods is tested on a DPPC (no unsaturated chain), a POPC (one unsaturated chain), and a DOPC (two unsaturated chains) lipid bilayers. We calculate various physical properties of the membrane...... of our simulations with and without virtual sites and explain the differences and similarity observed. The best agreements are obtained for the GROMACS original virtual sites on the DOPC bilayer where we get an area per lipid of 67.3 ± 0.3 A˚2 without virtual sites and 67.6 ± 0.3 A˚2 with virtual sites...

  2. Harvesting graphics power for MD simulations

    NARCIS (Netherlands)

    van Meel, J.A.; Arnold, A.; Frenkel, D.; Portegies Zwart, S.F.; Belleman, R.G.

    2008-01-01

    We discuss an implementation of molecular dynamics (MD) simulations on a graphic processing unit (GPU) in the NVIDIA CUDA language. We tested our code on a modern GPU, the NVIDIA GeForce 8800 GTX. Results for two MD algorithms suitable for short-ranged and long-ranged interactions, and a

  3. Harvesting graphics power for MD simulations

    NARCIS (Netherlands)

    Meel, J.A. van; Arnold, A.; Frenkel, D.; Portegies Zwart, S.F.; Belleman, R.G.

    We discuss an implementation of molecular dynamics (MD) simulations on a graphic processing unit (GPU) in the NVIDIA CUDA language. We tested our code on a modern GPU, the NVIDIA GeForce 8800 GTX. Results for two MD algorithms suitable for short-ranged and long-ranged interactions, and a

  4. MD simulation of cluster formation during sputtering

    International Nuclear Information System (INIS)

    Muramoto, T.; Okai, M.; Yamashita, Y.; Yorizane, K.; Yamamura, Y.

    2001-01-01

    The cluster ejection due to cluster impact on a solid surface is studied through molecular dynamics (MD) simulations. Simulations are performed for Cu cluster impacts on the Cu(1 1 1) surface for cluster energy 100 eV/atom, and for clusters of 6, 13, 28 and 55 atoms. Interatomic interactions are described by the AMLJ-EAM potential. The vibration energy spectrum is independent of the incident cluster size and energy. This comes from the fact that sputtered clusters become stable through the successive fragmentation of nascent large sputtered clusters. The vibration energy spectra for large sputtered clusters have a peak, whose energy corresponds to the melting temperature of Cu. The exponent of the power-law fit of the abundance distribution and the total sputtering yield for the cluster impacts are higher than that for the monatomic ion impacts with the same total energy, where the exponent δ is given by Y n ∝n δ and Y n is the yield of sputtered n-atom cluster. The exponent δ follows a unified function of the total sputtering yield, which is a monotonic increase function, and it is nearly equal to δ ∼ -3 for larger yield

  5. StandsSIM-MD: a Management Driven forest SIMulator

    Energy Technology Data Exchange (ETDEWEB)

    Barreiro, S.; Rua, J.; Tomé, M.

    2016-07-01

    Aim of the study. The existing stand level forest simulators available in Portugal were not developed with the aim of including up-to-date model versions and were limited in terms of accounting for forest management. The simulators’ platform, sIMfLOR was recently created to implement different growth models with a common philosophy. The objective was developing one easily-updatable, user-friendly, forest management and climate change sensitive simulator capable of projecting growth for the main tree species in Portugal. Area of the study: Portugal. Material and methods: The new simulator was programmed in a modular form consisting of several modules. The growth module integrates different forest growth and yield models (empirical and process-based) for the main wood production tree species in Portugal (eucalypt, umbrella and maritime pines); whereas the management module drives the growth projections along the planning horizon according to a range of forest management approaches and climate (at present only available for eucalypt). Main results: The main result is the StandsSIM-MD Management Driven simulator that overcomes the limitations of the existing stand level simulators. It is a step forward when compared to the models currently available in the sIMfLOR platform covering more tree species, stand structures and stand compositions. It is focused on end-users and it is based on similar concepts regarding the generation of required inputs and generated outputs. Research highlights: Forest Management Driven simulations approach. Multiple Prescriptions-Per-Stand functionality. StandsSIM-MD can be used to support landowners decisions on stand forest management. StandsSIM-MD simulations at regional level can be combined with optimization routines. (Author)

  6. PuReMD-GPU: A reactive molecular dynamics simulation package for GPUs

    International Nuclear Information System (INIS)

    Kylasa, S.B.; Aktulga, H.M.; Grama, A.Y.

    2014-01-01

    We present an efficient and highly accurate GP-GPU implementation of our community code, PuReMD, for reactive molecular dynamics simulations using the ReaxFF force field. PuReMD and its incorporation into LAMMPS (Reax/C) is used by a large number of research groups worldwide for simulating diverse systems ranging from biomembranes to explosives (RDX) at atomistic level of detail. The sub-femtosecond time-steps associated with ReaxFF strongly motivate significant improvements to per-timestep simulation time through effective use of GPUs. This paper presents, in detail, the design and implementation of PuReMD-GPU, which enables ReaxFF simulations on GPUs, as well as various performance optimization techniques we developed to obtain high performance on state-of-the-art hardware. Comprehensive experiments on model systems (bulk water and amorphous silica) are presented to quantify the performance improvements achieved by PuReMD-GPU and to verify its accuracy. In particular, our experiments show up to 16× improvement in runtime compared to our highly optimized CPU-only single-core ReaxFF implementation. PuReMD-GPU is a unique production code, and is currently available on request from the authors

  7. PuReMD-GPU: A reactive molecular dynamics simulation package for GPUs

    Energy Technology Data Exchange (ETDEWEB)

    Kylasa, S.B., E-mail: skylasa@purdue.edu [Department of Elec. and Comp. Eng., Purdue University, West Lafayette, IN 47907 (United States); Aktulga, H.M., E-mail: hmaktulga@lbl.gov [Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, MS 50F-1650, Berkeley, CA 94720 (United States); Grama, A.Y., E-mail: ayg@cs.purdue.edu [Department of Computer Science, Purdue University, West Lafayette, IN 47907 (United States)

    2014-09-01

    We present an efficient and highly accurate GP-GPU implementation of our community code, PuReMD, for reactive molecular dynamics simulations using the ReaxFF force field. PuReMD and its incorporation into LAMMPS (Reax/C) is used by a large number of research groups worldwide for simulating diverse systems ranging from biomembranes to explosives (RDX) at atomistic level of detail. The sub-femtosecond time-steps associated with ReaxFF strongly motivate significant improvements to per-timestep simulation time through effective use of GPUs. This paper presents, in detail, the design and implementation of PuReMD-GPU, which enables ReaxFF simulations on GPUs, as well as various performance optimization techniques we developed to obtain high performance on state-of-the-art hardware. Comprehensive experiments on model systems (bulk water and amorphous silica) are presented to quantify the performance improvements achieved by PuReMD-GPU and to verify its accuracy. In particular, our experiments show up to 16× improvement in runtime compared to our highly optimized CPU-only single-core ReaxFF implementation. PuReMD-GPU is a unique production code, and is currently available on request from the authors.

  8. A molecular dynamics (MD simulation on tire-aggregate friction

    Directory of Open Access Journals (Sweden)

    Fengyan Sun

    2017-07-01

    Full Text Available The friction between tire and road surface is fundamentally depending on the molecular forces. In this paper, the nanoscale 3D contact model is employed to investigate the tire-aggregate friction mechanism. The tire and aggregate micro-structure are both constructed to evaluate the microscopic performance of tire-aggregate friction influence. Simulation results show for a high velocity, the energy dissipation of sliding on crystal structure is small, which results in a small friction coefficient; temperature will have influences on the friction coefficient, and with the increasing of velocity, the effect will gradually reduce. Keywords: Tire, Aggregate, Friction coefficient, Microscopic mechanism, MD simulation

  9. StandsSIM-MD: a Management Driven forest SIMulator

    Directory of Open Access Journals (Sweden)

    Susana Barreiro

    2016-07-01

    Full Text Available Aim of the study: The existing stand level forest simulators available in Portugal were not developed with the aim of including up-to-date model versions and were limited in terms of accounting for forest management. The simulators’ platform, sIMfLOR was recently created to implement different growth models with a common philosophy. The objective was developing one easily-updatable, user-friendly, forest management and climate change sensitive simulator capable of projecting growth for the main tree species in Portugal. Area of the study: Portugal. Material and methods: The new simulator was programmed in a modular form consisting of several modules. The growth module integrates different forest growth and yield models (empirical and process-based for the main wood production tree species in Portugal (eucalypt, umbrella and maritime pines; whereas the management module drives the growth projections along the planning horizon according to a range of forest management approaches and climate (at present only available for eucalypt. Main results: The main result is the StandsSIM-MD Management Driven simulator that overcomes the limitations of the existing stand level simulators. It is a step forward when compared to the models currently available in the sIMfLOR platform covering more tree species, stand structures and stand compositions. It is focused on end-users and it is based on similar concepts regarding the generation of required inputs and generated outputs. Research highlights: -          Forest Management Driven simulations approach -          Multiple Prescriptions-Per-Stand functionality -          StandsSIM-MD can be used to support landowners decisions on stand forest management -          StandsSIM-MD simulations at regional level can be combined with optimization routines Keywords: Forest simulator, Forest Management Approaches; StandsSIM-MD; forest management.

  10. Analysis of MD5 authentication in various routing protocols using simulation tools

    Science.gov (United States)

    Dinakaran, M.; Darshan, K. N.; Patel, Harsh

    2017-11-01

    Authentication being an important paradigm of security and Computer Networks require secure paths to make the flow of the data even more secure through some security protocols. So MD-5(Message Digest 5) helps in providing data integrity to the data being sent through it and authentication to the network devices. This paper gives a brief introduction to the MD-5, simulation of the networks by including MD-5 authentication using various routing protocols like OSPF, EIGRP and RIPv2. GNS3 is being used to simulate the scenarios. Analysis of the MD-5 authentication is done in the later sections of the paper.

  11. Dynamics of biopolymers on nanomaterials studied by quasielastic neutron scattering and MD simulations

    Science.gov (United States)

    Dhindsa, Gurpreet K.

    Neutron scattering has been proved to be a powerful tool to study the dynamics of biological systems under various conditions. This thesis intends to utilize neutron scattering techniques, combining with MD simulations, to develop fundamental understanding of several biologically interesting systems. Our systems include a drug delivery system containing Nanodiamonds with nucleic acid (RNA), and two specific model proteins, beta-Casein and Inorganic Pyrophosphatase (IPPase). RNA and nanodiamond (ND) both are suitable for drug-delivery applications in nano-biotechnology. The architecturally flexible RNA with catalytic functionality forms nanocomposites that can treat life-threatening diseases. The non-toxic ND has excellent mechanical and optical properties and functionalizable high surface area, and thus actively considered for biomedical applications. In this thesis, we utilized two tools, quasielastic neutron scattering (QENS) and Molecular Dynamics Simulations to probe the effect of ND on RNA dynamics. Our work provides fundamental understanding of how hydrated RNA motions are affected in the RNA-ND nanocomposites. From the experimental and Molecular Dynamics Simulation (MD), we found that hydrated RNA motion is faster on ND surface than a freestanding one. MD Simulation results showed that the failure of Stokes Einstein relation results the presence of dynamic heterogeneities in the biomacromolecules. Radial pair distribution function from MD Simulation confirmed that the hydrophilic nature of ND attracts more water than RNA results the de-confinement of RNA on ND. Therefore, RNA exhibits faster motion in the presence of ND than freestanding RNA. In the second project, we studied the dynamics of a natively disordered protein beta-Casein which lacks secondary structures. In this study, the temperature and hydration effects on the dynamics of beta-Casein are explored by Quasielastic Neutron Scattering (QENS). We investigated the mean square displacement (MSD) of

  12. Application of MD Simulations to Predict Membrane Properties of MOFs

    Directory of Open Access Journals (Sweden)

    Elda Adatoz

    2015-01-01

    Full Text Available Metal organic frameworks (MOFs are a new group of nanomaterials that have been widely examined for various chemical applications. Gas separation using MOF membranes has become an increasingly important research field in the last years. Several experimental studies have shown that thin-film MOF membranes can outperform well known polymer and zeolite membranes due to their higher gas permeances and selectivities. Given the very large number of available MOF materials, it is impractical to fabricate and test the performance of every single MOF membrane using purely experimental techniques. In this study, we used molecular simulations, Monte Carlo and Molecular Dynamics, to estimate both single-gas and mixture permeances of MOF membranes. Predictions of molecular simulations were compared with the experimental gas permeance data of MOF membranes in order to validate the accuracy of our computational approach. Results show that computational methodology that we described in this work can be used to accurately estimate membrane properties of MOFs prior to extensive experimental efforts.

  13. Water at silica/liquid water interfaces investigated by DFT-MD simulations

    Science.gov (United States)

    Gaigeot, Marie-Pierre

    This talk is dedicated to probing the microscopic structural organization of water at silica/liquid water interfaces including electrolytes by first principles DFT-based molecular dynamics simulations (DFT-MD). We will present our very recent DFT-MD simulations of electrolytic (KCl, NaCl, NaI) silica/liquid water interfaces in order to unravel the intertwined structural properties of water and electrolytes at the crystalline quartz/liquid water and amorphous silica/liquid water interfaces. DFT-MD simulations provide direct knowledge of the structural organization of water and the H-Bond network formed between the water molecules within the different water layers above the silica surface. One can furthermore extract vibrational signatures of the water molecules within the interfacial layers from the DFT-MD simulations, especially non-linear SFG (Sum Frequency generation) signatures that are active at solid/liquid interfaces. The strength of the simulated spectra is that a detailed analysis of the signatures in terms of the water/water H-Bond networks formed within the interfacial water layers and in terms of the water/silica or water/electrolytes H-Bond networks can be given. Comparisons of SFG spectra between quartz/water/electrolytes and amorphous silica/water/electrolytes interfaces allow us to definitely conclude on how the structural arrangements of liquid water at these electrolytic interfaces modulate the final spectroscopic signatures. Invited speaker.

  14. MD and BCA simulations of He and H bombardment of fuzz in bcc elements

    Science.gov (United States)

    Klaver, T. P. C.; Zhang, S.; Nordlund, K.

    2017-08-01

    We present results of MD simulations of low energy He ion bombardment of low density fuzz in bcc elements. He ions can penetrate several micrometers into sparse fuzz, which allows for a sufficient He flux through it to grow the fuzz further. He kinetic energy falls off exponentially with penetration depth. A BCA code was used to carry out the same ion bombardment on the same fuzz structures as in MD simulations, but with simpler, 10 million times faster calculations. Despite the poor theoretical basis of the BCA at low ion energies, and the use of somewhat different potentials in MD and BCA calculations, the ion penetration depths predicted by BCA are only ∼12% less than those predicted by MD. The MD-BCA differences are highly systematic and trends in the results of the two methods are very similar. We have carried out more than 200 BCA calculation runs of ion bombardment of fuzz, in which parameters in the ion bombardment process were varied. For most parameters, the results show that the ion bombardment process is quite generic. The ion species (He or H), ion mass, fuzz element (W, Ta, Mo, Fe) and fuzz element lattice parameter turned out to have a modest influence on ion penetration depths at most. An off-normal angle of incidence strongly reduces the ion penetration depth. Increasing the ion energy increases the ion penetration, but the rate by which ion energy drops off at high ion energies follows the same exponential pattern as at lower energies.

  15. Investigation on single carbon atom transporting through the single-walled carbon nanotube by MD simulation

    International Nuclear Information System (INIS)

    Ding Yinfeng; Zhang Zhibin; Ke Xuezhi; Zhu Zhiyuan; Zhu Dezhang; Wang Zhenxia; Xu Hongjie

    2005-01-01

    The single carbon atom transporting through the single-walled carbon nanotube has been studied by molecular-dynamics (MD) simulation. We got different trajectories of the carbon atom by changing the input parameters. The simulation results indicate that the single carbon atom with low energy can transport through the carbon nanotube under some input conditions and result in different trajectories being straight line or 'rosette' or circular. (authors)

  16. Parallel Object Oriented MD Simulation Program for Long Time Simulations of Metallic Glasses and Undercooled Liquids

    Science.gov (United States)

    Böddeker, B.; Teichler, H.

    The MD simulation program TABB is motivated by the need of long time simulations for the investigation of slow processes near the glass transition of glass forming alloys. TABB is written in C++ with a high degree of flexibility: TABB allows the use of any short ranged pair potentials or EAM potentials, by generating and using a spline representation of all functions and their derivatives. TABB supports several numerical integration algorithms like the Runge-Kotta or the modified Gear-predictor-corrector algorithm of order five. The boundary conditions can be chosen to resemble the geometry of bulk materials or films. The simulation box length or the pressure can be fixed for each dimension separately. TABB may be used in isokinetic, isoenergeric or canonic (with random forces) mode. TABB contains a simple instruction interpreter to easily control the parameters and options during the simulation. The same source code can be compiled either for workstations or for parallel computers. The main optimization goal of TABB is to allow long time simulations of medium or small sized systems. To make this possible, much attention is spent on the optimized communication between the nodes. TABB uses a domain decomposition procedure. To use many nodes with a small system, the domain size has to be small compared to the range of particle interactions. In the limit of many nodes for only few atoms, the bottle neck of communication is the latency time. TABB minimizes the number of pairs of domains containing atoms that interact between these domains. This procedure minimizes the need of communication calls between pairs of nodes. TABB decides automatically, to how many, and to which directions the decomposition shall be applied. E.g., in the case of one dimensional domain decomposition, the simulation box is only split into "slabs" along a selected direction. The three dimensional domain decomposition is best with respect to the number of interacting domains only for simulations

  17. Novel 3D/VR interactive environment for MD simulations, visualization and analysis.

    Science.gov (United States)

    Doblack, Benjamin N; Allis, Tim; Dávila, Lilian P

    2014-12-18

    The increasing development of computing (hardware and software) in the last decades has impacted scientific research in many fields including materials science, biology, chemistry and physics among many others. A new computational system for the accurate and fast simulation and 3D/VR visualization of nanostructures is presented here, using the open-source molecular dynamics (MD) computer program LAMMPS. This alternative computational method uses modern graphics processors, NVIDIA CUDA technology and specialized scientific codes to overcome processing speed barriers common to traditional computing methods. In conjunction with a virtual reality system used to model materials, this enhancement allows the addition of accelerated MD simulation capability. The motivation is to provide a novel research environment which simultaneously allows visualization, simulation, modeling and analysis. The research goal is to investigate the structure and properties of inorganic nanostructures (e.g., silica glass nanosprings) under different conditions using this innovative computational system. The work presented outlines a description of the 3D/VR Visualization System and basic components, an overview of important considerations such as the physical environment, details on the setup and use of the novel system, a general procedure for the accelerated MD enhancement, technical information, and relevant remarks. The impact of this work is the creation of a unique computational system combining nanoscale materials simulation, visualization and interactivity in a virtual environment, which is both a research and teaching instrument at UC Merced.

  18. PyContact: Rapid, Customizable, and Visual Analysis of Noncovalent Interactions in MD Simulations.

    Science.gov (United States)

    Scheurer, Maximilian; Rodenkirch, Peter; Siggel, Marc; Bernardi, Rafael C; Schulten, Klaus; Tajkhorshid, Emad; Rudack, Till

    2018-02-06

    Molecular dynamics (MD) simulations have become ubiquitous in all areas of life sciences. The size and model complexity of MD simulations are rapidly growing along with increasing computing power and improved algorithms. This growth has led to the production of a large amount of simulation data that need to be filtered for relevant information to address specific biomedical and biochemical questions. One of the most relevant molecular properties that can be investigated by all-atom MD simulations is the time-dependent evolution of the complex noncovalent interaction networks governing such fundamental aspects as molecular recognition, binding strength, and mechanical and structural stability. Extracting, evaluating, and visualizing noncovalent interactions is a key task in the daily work of structural biologists. We have developed PyContact, an easy-to-use, highly flexible, and intuitive graphical user interface-based application, designed to provide a toolkit to investigate biomolecular interactions in MD trajectories. PyContact is designed to facilitate this task by enabling identification of relevant noncovalent interactions in a comprehensible manner. The implementation of PyContact as a standalone application enables rapid analysis and data visualization without any additional programming requirements, and also preserves full in-program customization and extension capabilities for advanced users. The statistical analysis representation is interactively combined with full mapping of the results on the molecular system through the synergistic connection between PyContact and VMD. We showcase the capabilities and scientific significance of PyContact by analyzing and visualizing in great detail the noncovalent interactions underlying the ion permeation pathway of the human P2X 3 receptor. As a second application, we examine the protein-protein interaction network of the mechanically ultrastable cohesin-dockering complex. Copyright © 2017 Biophysical Society

  19. Microsecond MD Simulations of Nano-patterned Polymer Brushes on Self-Assembled Monolayers

    Science.gov (United States)

    Buie, Creighton; Qiu, Liming; Cheng, Kwan; Park, Soyeun

    2010-03-01

    Nano-patterned polymer brushes end-grafted onto self-assembled monolayers have gained increasing research interests due to their unique thermodynamic properties and their chemical and biomedical applications in colloids, biosensing and tissue engineering. So far, the interactions between the polymer brushes with the surrounding environments such as the floor and solvent at the nanometer length scale and microsecond time scale are still difficult to obtained experimentally and computationally. Using a Coarse-Grained MD approach, polymer brushes of different monomeric lengths, grafting density and hydrophobicity of the monomers grafted on self-assembled monolayers and in explicit solvent were studied. Molecular level information, such as lateral diffusion, transverse height and volume contour of the brushes, were calculated from our microsecond-MD simulations. Our results demonstrated the significance of the hydration of the polymer in controlling the conformational arrangement of the polymer brushes.

  20. MD simulation: determination of the physical properties and surface vaporization analysis of beryllium armours

    International Nuclear Information System (INIS)

    Prinzio, M. Di; Aquaro, D.

    2006-01-01

    The erosion of the divertor and of the first wall determined on the base of the anticipated operating conditions, is a critical issue that could affect the performance and the operating schedule of the nuclear fusion reactor ITER. This paper deals with the analysis of beryllium thermal properties by means of MD simulations, in order to better predict thermal behaviour of beryllium armoured PFCs in fusion devices. The importance of this analysis is clearly connected to thermal response evaluation of PFCs to high heat flux exposure, during off-normal events and Edge Localized Modes. The ensuing strong over-heating, in fact, produces material ablation through vaporization of surface material layers and possible loss of melting material. The overall PFCs erosion has bearings on plasma contamination, due to eroded material transport, and components lifetime, due to armour thickness reduction. An important feature of beryllium is its high vapour pressure. During thermal transients the strong vaporization keeps surface temperature relatively low but eroded thickness results high as well. Small changes in beryllium vapour pressure produce not negligible differences in thermal analyses results. On the basis of available force fields, classical Molecular Dynamics simulations have been carried out in order to better understand surface vaporization in tokamak conditions and to evaluate the effect of beryllium oxides formation. This effect has been successfully modelled by MD simulation, carried out with Moldy code. Morse stretching and bending potential for Be-O bond simulation have been used, and partial charges method, accounting for molecular polarity, has been employed. Since during short thermal transients, such as ELMs, only a few microns of Be armour will be overheated and reach melting threshold, the effective thermal conductivity is very important in determining the temperature evolution of surface layers and the ensuing erosion. Thermal conductivity can be evaluated

  1. Prediction of Osmotic Pressure of Ionic Liquids Inside a Nanoslit by MD Simulation and Continuum Approach

    Science.gov (United States)

    Moon, Gi Jong; Yang, Yu Dong; Oh, Jung Min; Kang, In Seok

    2017-11-01

    Osmotic pressure plays an important role in the processes of charging and discharging of lithium batteries. In this work, osmotic pressure of the ionic liquids confined inside a nanoslit is calculated by using both MD simulation and continuum approach. In the case of MD simulation, an ionic liquid is modeled as singly charged spheres with a short-ranged repulsive Lennard-Jones potential. The radii of the spheres are 0.5nm, reflecting the symmetry of ion sizes for simplicity. The simulation box size is 11nm×11nm×7.5nm with 1050 ion pairs. The concentration of ionic liquid is about 1.922mol/L, and the total charge on an individual wall varies from +/-60e(7.944 μm/cm2) to +/-600e(79.44 μm/cm2) . In the case of continuum approach, we classify the problems according to the correlation length and steric factor, and considered the four separate cases: 1) zero correlation length and zero steric factor, 2) zero correlation length and non-zero steric factor, 3) non-zero correlation length and zero steric factor, and 4) non-zero correlation and non-zero steric factor. Better understanding of the osmotic pressure of ionic liquids confined inside a nanoslit can be achieved by comparing the results of MD simulation and continuum approach. This research was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MSIP: Ministry of Science, ICT & Future Planning) (No. 2017R1D1A1B05035211).

  2. Characterization of Bitumen Micro-Mechanical Behaviors Using AFM, Phase Dynamics Theory and MD Simulation

    Directory of Open Access Journals (Sweden)

    Yue Hou

    2017-02-01

    Full Text Available Fundamental understanding of micro-mechanical behaviors in bitumen, including phase separation, micro-friction, micro-abrasion, etc., can help the pavement engineers better understand the bitumen mechanical performances at macroscale. Recent researches show that the microstructure evolution in bitumen will directly affect its surface structure and micro-mechanical performance. In this study, the bitumen microstructure and micro-mechanical behaviors are studied using Atomic Force Microscopy (AFM experiments, Phase Dynamics Theory and Molecular Dynamics (MD Simulation. The AFM experiment results show that different phase-structure will occur at the surface of the bitumen samples under certain thermodynamic conditions at microscale. The phenomenon can be explained using the phase dynamics theory, where the effects of stability parameter and temperature on bitumen microstructure and micro-mechanical behavior are studied combined with MD Simulation. Simulation results show that the saturates phase, in contrast to the naphthene aromatics phase, plays a major role in bitumen micro-mechanical behavior. A high stress zone occurs at the interface between the saturates phase and the naphthene aromatics phase, which may form discontinuities that further affect the bitumen frictional performance.

  3. Characterization of Bitumen Micro-Mechanical Behaviors Using AFM, Phase Dynamics Theory and MD Simulation.

    Science.gov (United States)

    Hou, Yue; Wang, Linbing; Wang, Dawei; Guo, Meng; Liu, Pengfei; Yu, Jianxin

    2017-02-21

    Fundamental understanding of micro-mechanical behaviors in bitumen, including phase separation, micro-friction, micro-abrasion, etc., can help the pavement engineers better understand the bitumen mechanical performances at macroscale. Recent researches show that the microstructure evolution in bitumen will directly affect its surface structure and micro-mechanical performance. In this study, the bitumen microstructure and micro-mechanical behaviors are studied using Atomic Force Microscopy (AFM) experiments, Phase Dynamics Theory and Molecular Dynamics (MD) Simulation. The AFM experiment results show that different phase-structure will occur at the surface of the bitumen samples under certain thermodynamic conditions at microscale. The phenomenon can be explained using the phase dynamics theory, where the effects of stability parameter and temperature on bitumen microstructure and micro-mechanical behavior are studied combined with MD Simulation. Simulation results show that the saturates phase, in contrast to the naphthene aromatics phase, plays a major role in bitumen micro-mechanical behavior. A high stress zone occurs at the interface between the saturates phase and the naphthene aromatics phase, which may form discontinuities that further affect the bitumen frictional performance.

  4. Applicability of effective fragment potential version 2 - Molecular dynamics (EFP2-MD) simulations for predicting excess properties of mixed solvents

    Science.gov (United States)

    Kuroki, Nahoko; Mori, Hirotoshi

    2018-02-01

    Effective fragment potential version 2 - molecular dynamics (EFP2-MD) simulations, where the EFP2 is a polarizable force field based on ab initio electronic structure calculations were applied to water-methanol binary mixture. Comparing EFP2s defined with (aug-)cc-pVXZ (X = D,T) basis sets, it was found that large sets are necessary to generate sufficiently accurate EFP2 for predicting mixture properties. It was shown that EFP2-MD could predict the excess molar volume. Since the computational cost of EFP2-MD are far less than ab initio MD, the results presented herein demonstrate that EFP2-MD is promising for predicting physicochemical properties of novel mixed solvents.

  5. Airflow Simulation Techniques

    DEFF Research Database (Denmark)

    Nielsen, Peter V.

    The paper describes the development in airflow simulations in rooms . The research is, as other areas of flow research, influenced by the decreasing cost of computation which seems to indicate an increased use of airflow simulation in the coming years.......The paper describes the development in airflow simulations in rooms . The research is, as other areas of flow research, influenced by the decreasing cost of computation which seems to indicate an increased use of airflow simulation in the coming years....

  6. Prediction of drug-packaging interactions via molecular dynamics (MD) simulations.

    Science.gov (United States)

    Feenstra, Peter; Brunsteiner, Michael; Khinast, Johannes

    2012-07-15

    The interaction between packaging materials and drug products is an important issue for the pharmaceutical industry, since during manufacturing, processing and storage a drug product is continuously exposed to various packaging materials. The experimental investigation of a great variety of different packaging material-drug product combinations in terms of efficacy and safety can be a costly and time-consuming task. In our work we used molecular dynamics (MD) simulations in order to evaluate the applicability of such methods to pre-screening of the packaging material-solute compatibility. The solvation free energy and the free energy of adsorption of diverse solute/solvent/solid systems were estimated. The results of our simulations agree with experimental values previously published in the literature, which indicates that the methods in question can be used to semi-quantitatively reproduce the solid-liquid interactions of the investigated systems. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. Structural and dynamical aspects of Streptococcus gordonii FabH through molecular docking and MD simulations.

    Science.gov (United States)

    Shamim, Amen; Abbasi, Sumra Wajid; Azam, Syed Sikander

    2015-07-01

    β-Ketoacyl-ACP-synthase III (FabH or KAS III) has become an attractive target for the development of new antibacterial agents which can overcome the multidrug resistance. Unraveling the fatty acid biosynthesis (FAB) metabolic pathway and understanding structural coordinates of FabH will provide valuable insights to target Streptococcus gordonii for curing oral infection. In this study, we designed inhibitors against therapeutic target FabH, in order to block the FAB pathway. As compared to other targets, FabH has more interactions with other proteins, located on the leading strand with higher codon adaptation index value and associated with lipid metabolism category of COG. Current study aims to gain in silico insights into the structural and dynamical aspect of S. gordonii FabH via molecular docking and molecular dynamics (MD) simulations. The FabH protein is catalytically active in dimerization while it can lock in monomeric state. Current study highlights two residues Pro88 and Leu315 that are close to each other by dimerization. The active site of FabH is composed of the catalytic triad formed by residues Cys112, His249, and Asn279 in which Cys112 is involved in acetyl transfer, while His249 and Asn279 play an active role in decarboxylation. Docking analysis revealed that among the studied compounds, methyl-CoA disulfide has highest GOLD score (82.75), binding affinity (-11 kcal/mol) and exhibited consistently better interactions. During MD simulations, the FabH structure remained stable with the average RMSD value of 1.7 Å and 1.6 Å for undocked protein and docked complex, respectively. Further, crucial hydrogen bonding of the conserved catalytic triad for exhibiting high affinity between the FabH protein and ligand is observed by RDF analysis. The MD simulation results clearly demonstrated that binding of the inhibitor with S. gordonii FabH enhanced the structure and stabilized the dimeric FabH protein. Therefore, the inhibitor has the potential to become

  8. Simulation Techniques That Work.

    Science.gov (United States)

    Beland, Robert M.

    1983-01-01

    At the University of Florida, simulated experiences with disabled clients help bridge the gap between coursework and internships for recreation therapy students. Actors from the university's drama department act out the roles of handicapped persons, who are interviewed by therapy students. (PP)

  9. Equilibrium Molecular Dynamics (MD Simulation Study of Thermal Conductivity of Graphene Nanoribbon: A Comparative Study on MD Potentials

    Directory of Open Access Journals (Sweden)

    Asir Intisar Khan

    2015-12-01

    Full Text Available The thermal conductivity of graphene nanoribbons (GNRs has been investigated using equilibrium molecular dynamics (EMD simulation based on Green-Kubo (GK method to compare two interatomic potentials namely optimized Tersoff and 2nd generation Reactive Empirical Bond Order (REBO. Our comparative study includes the estimation of thermal conductivity as a function of temperature, length and width of GNR for both the potentials. The thermal conductivity of graphene nanoribbon decreases with the increase of temperature. Quantum correction has been introduced for thermal conductivity as a function of temperature to include quantum effect below Debye temperature. Our results show that for temperatures up to Debye temperature, thermal conductivity increases, attains its peak and then falls off monotonically. Thermal conductivity is found to decrease with the increasing length for optimized Tersoff potential. However, thermal conductivity has been reported to increase with length using 2nd generation REBO potential for the GNRs of same size. Thermal conductivity, for the specified range of width, demonstrates an increasing trend with the increase of width for both the concerned potentials. In comparison with 2nd generation REBO potential, optimized Tersoff potential demonstrates a better modeling of thermal conductivity as well as provides a more appropriate description of phonon thermal transport in graphene nanoribbon. Such comparative study would provide a good insight for the optimization of the thermal conductivity of graphene nanoribbons under diverse conditions.

  10. Estimation of Hydrogen-Exchange Protection Factors from MD Simulation Based on Amide Hydrogen Bonding Analysis

    Science.gov (United States)

    Park, In-Hee; Venable, John D.; Steckler, Caitlin; Cellitti, Susan E.; Lesley, Scott A.; Spraggon, Glen; Brock, Ansgar

    2015-01-01

    Hydrogen exchange (HX) studies have provided critical insight into our understanding of protein folding, structure and dynamics. More recently, Hydrogen Exchange Mass Spectrometry (HX-MS) has become a widely applicable tool for HX studies. The interpretation of the wealth of data generated by HX-MS experiments as well as other HX methods would greatly benefit from the availability of exchange predictions derived from structures or models for comparison with experiment. Most reported computational HX modeling studies have employed solvent-accessible-surface-area based metrics in attempts to interpret HX data on the basis of structures or models. In this study, a computational HX-MS prediction method based on classification of the amide hydrogen bonding modes mimicking the local unfolding model is demonstrated. Analysis of the NH bonding configurations from Molecular Dynamics (MD) simulation snapshots is used to determine partitioning over bonded and non-bonded NH states and is directly mapped into a protection factor (PF) using a logistics growth function. Predicted PFs are then used for calculating deuteration values of peptides and compared with experimental data. Hydrogen exchange MS data for Fatty acid synthase thioesterase (FAS-TE) collected for a range of pHs and temperatures was used for detailed evaluation of the approach. High correlation between prediction and experiment for observable fragment peptides is observed in the FAS-TE and additional benchmarking systems that included various apo/holo proteins for which literature data were available. In addition, it is shown that HX modeling can improve experimental resolution through decomposition of in-exchange curves into rate classes, which correlate with prediction from MD. Successful rate class decompositions provide further evidence that the presented approach captures the underlying physical processes correctly at the single residue level. This assessment is further strengthened in a comparison of

  11. Interaction and dynamics of homologous pairing protein 2 (HOP2) and DNA studied by MD simulation

    Science.gov (United States)

    Moktan, Hem; Pezza, Roberto; Zhou, Donghua

    2015-03-01

    The homologous pairing protein 2 (Hop2) plays an important role in meiosis and DNA repair. Together with protein Mnd1, Hop2 enhances the strand invasion activity of recombinase Dmc1 by over 30 times, facilitating proper synapsis of homologous chromosomes. We recently determined the NMR structure of the N-terminal domain of Hop2 and proposed a model of Protein-DNA complex based on NMR chemical shift perturbations and mutagenesis studies (Moktan, J Biol Chem 2014 10.1074/jbc.M114.548180). However structure and dynamics of the complex have not been studied at the atomic level yet. Here, we used classical MD simulations to study the interactions between the N-terminal HOP2 and DNA. The simulated results indicate that helix3 (H3) interacts with DNA in major groove and wing1 (W1) interacts mostly in minor groove mainly via direct hydrogen bonds. Also it is found that binding leads to reduced fluctuations in both protein and DNA. Several water bridge interactions have been identified. The residue-wise contributions to the interaction energy were evaluated. Also the functional motion of the protein is analyzed using principal component analysis. The results confirmed the importance of H3 and W1 for the stability of the complex, which is consistent with our previous experimental studies.

  12. Low-mass molecular dynamics simulation: A simple and generic technique to enhance configurational sampling

    Energy Technology Data Exchange (ETDEWEB)

    Pang, Yuan-Ping, E-mail: pang@mayo.edu

    2014-09-26

    Highlights: • Reducing atomic masses by 10-fold vastly improves sampling in MD simulations. • CLN025 folded in 4 of 10 × 0.5-μs MD simulations when masses were reduced by 10-fold. • CLN025 folded as early as 96.2 ns in 1 of the 4 simulations that captured folding. • CLN025 did not fold in 10 × 0.5-μs MD simulations when standard masses were used. • Low-mass MD simulation is a simple and generic sampling enhancement technique. - Abstract: CLN025 is one of the smallest fast-folding proteins. Until now it has not been reported that CLN025 can autonomously fold to its native conformation in a classical, all-atom, and isothermal–isobaric molecular dynamics (MD) simulation. This article reports the autonomous and repeated folding of CLN025 from a fully extended backbone conformation to its native conformation in explicit solvent in multiple 500-ns MD simulations at 277 K and 1 atm with the first folding event occurring as early as 66.1 ns. These simulations were accomplished by using AMBER forcefield derivatives with atomic masses reduced by 10-fold on Apple Mac Pros. By contrast, no folding event was observed when the simulations were repeated using the original AMBER forcefields of FF12SB and FF14SB. The results demonstrate that low-mass MD simulation is a simple and generic technique to enhance configurational sampling. This technique may propel autonomous folding of a wide range of miniature proteins in classical, all-atom, and isothermal–isobaric MD simulations performed on commodity computers—an important step forward in quantitative biology.

  13. Atomic level insights into realistic molecular models of dendrimer-drug complexes through MD simulations

    Science.gov (United States)

    Jain, Vaibhav; Maiti, Prabal K.; Bharatam, Prasad V.

    2016-09-01

    Computational studies performed on dendrimer-drug complexes usually consider 1:1 stoichiometry, which is far from reality, since in experiments more number of drug molecules get encapsulated inside a dendrimer. In the present study, molecular dynamic (MD) simulations were implemented to characterize the more realistic molecular models of dendrimer-drug complexes (1:n stoichiometry) in order to understand the effect of high drug loading on the structural properties and also to unveil the atomistic level details. For this purpose, possible inclusion complexes of model drug Nateglinide (Ntg) (antidiabetic, belongs to Biopharmaceutics Classification System class II) with amine- and acetyl-terminated G4 poly(amidoamine) (G4 PAMAM(NH2) and G4 PAMAM(Ac)) dendrimers at neutral and low pH conditions are explored in this work. MD simulation analysis on dendrimer-drug complexes revealed that the drug encapsulation efficiency of G4 PAMAM(NH2) and G4 PAMAM(Ac) dendrimers at neutral pH was 6 and 5, respectively, while at low pH it was 12 and 13, respectively. Center-of-mass distance analysis showed that most of the drug molecules are located in the interior hydrophobic pockets of G4 PAMAM(NH2) at both the pH; while in the case of G4 PAMAM(Ac), most of them are distributed near to the surface at neutral pH and in the interior hydrophobic pockets at low pH. Structural properties such as radius of gyration, shape, radial density distribution, and solvent accessible surface area of dendrimer-drug complexes were also assessed and compared with that of the drug unloaded dendrimers. Further, binding energy calculations using molecular mechanics Poisson-Boltzmann surface area approach revealed that the location of drug molecules in the dendrimer is not the decisive factor for the higher and lower binding affinity of the complex, but the charged state of dendrimer and drug, intermolecular interactions, pH-induced conformational changes, and surface groups of dendrimer do play an

  14. Alamethicin in lipid bilayers: combined use of X-ray scattering and MD simulations.

    Science.gov (United States)

    Pan, Jianjun; Tieleman, D Peter; Nagle, John F; Kucerka, Norbert; Tristram-Nagle, Stephanie

    2009-06-01

    We study fully hydrated bilayers of two di-monounsaturated phospholipids diC18:1PC (DOPC) and diC22:1PC with varying amounts of alamethicin (Alm). We combine the use of X-ray diffuse scattering and molecular dynamics simulations to determine the orientation of alamethicin in model lipids. Comparison of the experimental and simulated form factors shows that Alm helices are inserted transmembrane at high humidity and high concentrations, in agreement with earlier results. The X-ray scattering data and the MD simulations agree that membrane thickness changes very little up to 1/10 Alm/DOPC. In contrast, the X-ray data indicate that the thicker diC22:1PC membrane thins with added Alm, a total decrease in thickness of 4 A at 1/10 Alm/diC22:1PC. The different effect of Alm on the thickness changes of the two bilayers is consistent with Alm having a hydrophobic thickness close to the hydrophobic thickness of 27 A for DOPC; Alm is then mismatched with the 7 A thicker diC22:1PC bilayer. The X-ray data indicate that Alm decreases the bending modulus (K(C)) by a factor of approximately 2 in DOPC and a factor of approximately 10 in diC22:1PC membranes (P/L approximately 1/10). The van der Waals and fluctuational interactions between bilayers are also evaluated through determination of the anisotropic B compressibility modulus.

  15. Single molecule force spectroscopy data and BD- and MD simulations on the blood protein von Willebrand factor

    Directory of Open Access Journals (Sweden)

    Sandra Posch

    2016-09-01

    Full Text Available We here give information for a deeper understanding of single molecule force spectroscopy (SMFS data through the example of the blood protein von Willebrand factor (VWF. It is also shown, how fitting of rupture forces versus loading rate profiles in the molecular dynamics (MD loading-rate range can be used to demonstrate the qualitative agreement between SMFS and MD simulations. The recently developed model by Bullerjahn, Sturm, and Kroy (BSK was used for this demonstration. Further, Brownian dynamics (BD simulations, which can be utilized to estimate the lifetimes of intramolecular VWF interactions under physiological shear, are described. For interpretation and discussion of the methods and data presented here, we would like to directly point the reader to the related research paper, “Mutual A domain interactions in the force sensing protein von Willebrand Factor” (Posch et al., 2016 [1]. Keywords: Atomic force microscopy, Single molecule force spectroscopy, Molecular dynamics simulation, Brownian dynamics simulation, von Willebrand factor

  16. Coarse grained MD simulations of a fracture of filler-filled polymer nanocomposites under uniaxial elongation

    Science.gov (United States)

    Hagita, Katsumi; Morita, Hiroshi; Takano, Hiroshi

    We performed coarse grained molecular dynamics (MD) simulations based on Kremer-Grest model in order to investigate a fracture of polymer nanocomposites filled with spherical nanoparticles (NPs) under uniaxial elongation with a Poisson ratio of 0.4. In our model, the NP consists of 320 surface beads and one center bead. In order to make the NP spherical, a harmonic potential is applied to the surface particles from the center of the NP. Here, the initial volume fraction of the NPs is about 20%. The dependences of the fracture on the interactions between the NPs and polymers were examined. In order to observe the creation of nanovoids, the interaction among the polymers was set to be attractive. When the NP-polymer interaction is attractive, nanovoids appear in the bulk of polymers. On the other hand, for repulsive NP-polymer interaction, nanovoids are created at the surface between the polymers and NPs. At the same time, segregation of NPs is observed. We found that these behaviors depend on crosslink densities.

  17. MD simulations of onset of tungsten fuzz formation under helium irradiation

    International Nuclear Information System (INIS)

    Lasa, A.; Henriksson, K.O.E.; Nordlund, K.

    2013-01-01

    When helium (He) escapes a fusion reactor plasma, a tungsten (W)-based divertor may, under some conditions, form a fuzz-like nano-morphology. This is a highly undesired phenomenon for the divertor, and is not well understood. We performed molecular dynamics simulations of high fluence He and also C-seeded He (He+C) irradiation on W, focusing on the effect of the high fluence, the temperature and the impurities on the onset of the structure formation. We concluded that MD reproduces the experimentally found square root of time dependence of the surface growth. The He atomic density decreases when increasing the number of He atoms in the cell. A higher temperature causes a larger bubble growth and desorption activity, specially for the pure He irradiation cases. It also it leads to W recrystallization for the He+C irradiation cases. Carbon acts as a local He trap for small clusters or single atoms and causes a larger loss of crystallinity of the W surface

  18. Design Techniques and Reservoir Simulation

    Directory of Open Access Journals (Sweden)

    Ahad Fereidooni

    2012-11-01

    Full Text Available Enhanced oil recovery using nitrogen injection is a commonly applied method for pressure maintenance in conventional reservoirs. Numerical simulations can be practiced for the prediction of a reservoir performance in the course of injection process; however, a detailed simulation might take up enormous computer processing time. In such cases, a simple statistical model may be a good approach to the preliminary prediction of the process without any application of numerical simulation. In the current work, seven rock/fluid reservoir properties are considered as screening parameters and those parameters having the most considerable effect on the process are determined using the combination of experimental design techniques and reservoir simulations. Therefore, the statistical significance of the main effects and interactions of screening parameters are analyzed utilizing statistical inference approaches. Finally, the influential parameters are employed to create a simple statistical model which allows the preliminary prediction of nitrogen injection in terms of a recovery factor without resorting to numerical simulations.

  19. Theoretical investigation on the inclusion of TCDD with β-cyclodextrin by performing QM calculations and MD simulations

    International Nuclear Information System (INIS)

    Pan, Wenxiao; Zhang, Dongju; Zhan, Jinhua

    2011-01-01

    Highlights: → We study the inclusion mechanism of TCDD with β-CD by theoretical methods. → Clearly, the formation of inclusion complex is an energetically driven process. → The inclusion complex can be detected by IR and Raman techniques. → The results imply that β-CD may be used as a host molecule to enrich TCDD molecules. - Abstract: The rapid enrichment and detection of trace polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are currently challenging issues in the field of environmental science. In this paper, by performing quantum chemistry (QM) calculations and molecular dynamics (MD) simulations, we studied the inclusion complexation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a representative PCDD molecule, with β-cyclodextrin (β-CD), one of the widely used compounds in supramolecular chemistry. The calculated results reveal that the stable inclusion complex can be formed in both the gas phase and solvent, which proposes that β-CD may serve as a potential substrate enriching TCDD. The calculated vibrational spectra indicate that the infrared (IR) and Raman spectroscopy may be suitable for the detection of β-CD-modified TCDD. The present theoretical results may be informative to environmental scientists who are devoting themselves to developing effective methods for detection and treatment of POPs.

  20. Pyrite: A blender plugin for visualizing molecular dynamics simulations using industry-standard rendering techniques.

    Science.gov (United States)

    Rajendiran, Nivedita; Durrant, Jacob D

    2018-05-05

    Molecular dynamics (MD) simulations provide critical insights into many biological mechanisms. Programs such as VMD, Chimera, and PyMOL can produce impressive simulation visualizations, but they lack many advanced rendering algorithms common in the film and video-game industries. In contrast, the modeling program Blender includes such algorithms but cannot import MD-simulation data. MD trajectories often require many gigabytes of memory/disk space, complicating Blender import. We present Pyrite, a Blender plugin that overcomes these limitations. Pyrite allows researchers to visualize MD simulations within Blender, with full access to Blender's cutting-edge rendering techniques. We expect Pyrite-generated images to appeal to students and non-specialists alike. A copy of the plugin is available at http://durrantlab.com/pyrite/, released under the terms of the GNU General Public License Version 3. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  1. Physical simulations using centrifuge techniques

    International Nuclear Information System (INIS)

    Sutherland, H.J.

    1981-01-01

    Centrifuge techniques offer a technique for doing physical simulations of the long-term mechanical response of deep ocean sediment to the emplacement of waste canisters and to the temperature gradients generated by them. Preliminary investigations of the scaling laws for pertinent phenomena indicate that the time scaling will be consistent among them and equal to the scaling factor squared. This result implies that this technique will permit accelerated-life-testing of proposed configurations; i.e, long-term studies may be done in relatively short times. Presently, existing centrifuges are being modified to permit scale model testing. This testing will start next year

  2. Multilevel techniques for Reservoir Simulation

    DEFF Research Database (Denmark)

    Christensen, Max la Cour

    The subject of this thesis is the development, application and study of novel multilevel methods for the acceleration and improvement of reservoir simulation techniques. The motivation for addressing this topic is a need for more accurate predictions of porous media flow and the ability to carry...... Full Approximation Scheme) • Variational (Galerkin) upscaling • Linear solvers and preconditioners First, a nonlinear multigrid scheme in the form of the Full Approximation Scheme (FAS) is implemented and studied for a 3D three-phase compressible rock/fluids immiscible reservoir simulator...... is extended to include a hybrid strategy, where FAS is combined with Newton’s method to construct a multilevel nonlinear preconditioner. This method demonstrates high efficiency and robustness. Second, an improved IMPES formulated reservoir simulator is implemented using a novel variational upscaling approach...

  3. Role of active site rigidity in activity: MD simulation and fluorescence study on a lipase mutant.

    Directory of Open Access Journals (Sweden)

    Md Zahid Kamal

    Full Text Available Relationship between stability and activity of enzymes is maintained by underlying conformational flexibility. In thermophilic enzymes, a decrease in flexibility causes low enzyme activity while in less stable proteins such as mesophiles and psychrophiles, an increase in flexibility is associated with enhanced enzyme activity. Recently, we identified a mutant of a lipase whose stability and activity were enhanced simultaneously. In this work, we probed the conformational dynamics of the mutant and the wild type lipase, particularly flexibility of their active site using molecular dynamic simulations and time-resolved fluorescence techniques. In contrast to the earlier observations, our data show that active site of the mutant is more rigid than wild type enzyme. Further investigation suggests that this lipase needs minimal reorganization/flexibility of active site residues during its catalytic cycle. Molecular dynamic simulations suggest that catalytically competent active site geometry of the mutant is relatively more preserved than wild type lipase, which might have led to its higher enzyme activity. Our study implies that widely accepted positive correlation between conformation flexibility and enzyme activity need not be stringent and draws attention to the possibility that high enzyme activity can still be accomplished in a rigid active site and stable protein structures. This finding has a significant implication towards better understanding of involvement of dynamic motions in enzyme catalysis and enzyme engineering through mutations in active site.

  4. New technique of identifying the hierarchy of dynamic domains in proteins using a method of molecular dynamics simulations

    Directory of Open Access Journals (Sweden)

    Yesylevskyy S. O.

    2010-04-01

    Full Text Available Aim. Despite a large number of existing domain identification techniques there is no universally accepted method, which identifies the hierarchy of dynamic domains using the data of molecular dynamics (MD simulations. The goal of this work is to develop such technique. Methods. The dynamic domains are identified by eliminating systematic motions from MD trajectories recursively in a model-free manner. Results. The technique called the Hierarchical Domain-Wise Alignment (HDWA to identify hierarchically organized dynamic domains in proteins using the MD trajectories has been developed. Conclusion. A new method of domain identification in proteins is proposed

  5. Testing philosophy and simulation techniques

    International Nuclear Information System (INIS)

    Holtbecker, H.

    1977-01-01

    This paper reviews past and present testing philosophies and simulation techniques in the field of structure loading and response studies. The main objective of experimental programmes in the past was to simulate a hypothetical energy release with explosives and to deduce the potential damage to a reactor from the measured damage to the model. This approach was continuously refined by improving the instrumentation of the models, by reproducing the structures as faithful as possible and by developing new explosive charges. This paper presents an analysis of the factors which are expected to have an influence on the validity of the results e.g. strain rate effects and the use of water instead of sodium. More recently the discussion of a whole series of accidents in the probabilistic accident analysis and the intention to compare different reactor designs has revealed the need to develop and validate computer codes. Consequently experimental programmes have been started in which the primary aim is not to test a specific reactor but to validate codes. This paper shows the principal aspects of this approach and discusses first results. (Auth.)

  6. Md Naimuddin

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics. Md Naimuddin. Articles written in Pramana – Journal of Physics. Volume 79 Issue 5 November 2012 pp 1255-1258 Poster Presentations. Model unspecific search for new physics in collision at s = 7 TeV · Shivali Malhotra Md Naimuddin Thomas Hebbeker Arnd Meyer ...

  7. Exploring the conserved water site and hydration of a coiled-coil trimerisation motif: a MD simulation study.

    Science.gov (United States)

    Dolenc, Jozica; Baron, Riccardo; Missimer, John H; Steinmetz, Michel O; van Gunsteren, Wilfred F

    2008-07-21

    The solvent structure and dynamics around ccbeta-p, a 17-residue peptide that forms a parallel three-stranded alpha-helical coiled coil in solution, was analysed through 10 ns explicit solvent molecular dynamics (MD) simulations at 278 and 330 K. Comparison with two corresponding simulations of the monomeric form of ccbeta-p was used to investigate the changes of hydration upon coiled-coil formation. Pronounced peaks in the solvent density distribution between residues Arg8 and Glu13 of neighbouring helices show the presence of water bridges between the helices of the ccbeta-p trimer; this is in agreement with the water sites observed in X-ray crystallography experiments. Interestingly, this water site is structurally conserved in many three-stranded coiled coils and, together with the Arg and Glu residues, forms part of a motif that determines three-stranded coiled-coil formation. Our findings show that little direct correlation exists between the solvent density distribution and the temporal ordering of water around the trimeric coiled coil. The MD-calculated effective residence times of up to 40 ps show rapid exchange of surface water molecules with the bulk phase, and indicate that the solvent distribution around biomolecules requires interpretation in terms of continuous density distributions rather than in terms of discrete molecules of water. Together, our study contributes to understanding the principles of three-stranded coiled-coil formation.

  8. Nanotribological behavior analysis of graphene/metal nanocomposites via MD simulations: New concepts and underlying mechanisms

    Science.gov (United States)

    Montazeri, A.; Mobarghei, A.

    2018-04-01

    In this article, we report a series of MD-based nanoindentation tests aimed to examine the nanotribological characteristics of metal-based nanocomposites in the presence of graphene sheets. To evaluate the effects of graphene/matrix interactions on the results, nickel and copper are selected as metals having strong and weak interactions with graphene, respectively. Consequently, the influence of graphene layers sliding and their distance from the sample surface on the nanoindentation outputs is thoroughly examined. Additionally, the temperature dependence of the results is deeply investigated with emphasis on the underlying mechanisms. To verify the accuracy of nanoindentation outputs, results of this method are compared with the data obtained via the tensile test. It is concluded that the nanoindentation results are closer to the values obtained by means of experimental setups. Employing these numerical-based experiments enables us to perform parametric studies to find out the dominant factors affecting the nanotribological behavior of these nanocomposites at the atomic-scale.

  9. Simulation of multi-atomic interactions in H-O-W system with the MD code CADAC

    International Nuclear Information System (INIS)

    Landman, I.S.

    2005-01-01

    For future tokamak reactors, chemical erosion of tungsten armour surfaces under impact of hot deuterium-tritium plasma that contains impurities, for instance oxygen, is an important issue. Oxygen can form volatile molecular complexes O x W y at the surface, and the retained H-atoms form the volatile complexes H x O y , which mitigates the erosion (H states for hydrogen isotopes). The plasma impact can substantially destroy the complexes. To describe this H-O-W system, the molecular dynamics (MD) code CADAC was earlier developed using only pair-atomic interactions. Now CADAC is extended for multi-body forces to simulate molecular organization of atoms near the tungsten surface. The approach uses the Abell's model of empirical bond-order potentials in addition combined, for the first time, with a valence concept. CADAC simulates chemical features using atomic valences and the Morse potentials. The new model is introduced and model parameters are estimated

  10. Visual air quality simulation techniques

    Science.gov (United States)

    Molenar, John V.; Malm, William C.; Johnson, Christopher E.

    Visual air quality is primarily a human perceptual phenomenon beginning with the transfer of image-forming information through an illuminated, scattering and absorbing atmosphere. Visibility, especially the visual appearance of industrial emissions or the degradation of a scenic view, is the principal atmospheric characteristic through which humans perceive air pollution, and is more sensitive to changing pollution levels than any other air pollution effect. Every attempt to quantify economic costs and benefits of air pollution has indicated that good visibility is a highly valued and desired environmental condition. Measurement programs can at best approximate the state of the ambient atmosphere at a few points in a scenic vista viewed by an observer. To fully understand the visual effect of various changes in the concentration and distribution of optically important atmospheric pollutants requires the use of aerosol and radiative transfer models. Communication of the output of these models to scientists, decision makers and the public is best done by applying modern image-processing systems to generate synthetic images representing the modeled air quality conditions. This combination of modeling techniques has been under development for the past 15 yr. Initially, visual air quality simulations were limited by a lack of computational power to simplified models depicting Gaussian plumes or uniform haze conditions. Recent explosive growth in low cost, high powered computer technology has allowed the development of sophisticated aerosol and radiative transfer models that incorporate realistic terrain, multiple scattering, non-uniform illumination, varying spatial distribution, concentration and optical properties of atmospheric constituents, and relative humidity effects on aerosol scattering properties. This paper discusses these improved models and image-processing techniques in detail. Results addressing uniform and non-uniform layered haze conditions in both

  11. MD simulations to evaluate effects of applied tensile strain on irradiation-induced defect production at various PKA energies

    International Nuclear Information System (INIS)

    Miyashiro, S.; Fujita, S.; Okita, T.; Okuda, H.

    2012-01-01

    Highlights: ► Strain effects on defect formation were evaluated at various PKA energies by MD. ► Radiation-induced defects were increased numerically by external strain. ► Enhanced formation of larger clusters causes the numerical increase of defects. ► Strain influence on the number of defects was greatest at about 20 keV PKA. ► Cluster size, which is mostly affected by strain, was greater with higher PKA energy. - Abstract: Molecular Dynamics (MD) simulations were conducted to investigate the influence of applied tensile strain on defect production during cascade damages at various Primary Knock-on Atom (PKA) energies of 1–30 keV. When 1% strain was applied, the number of surviving defects increased at PKA energies higher than 5 keV, although they did not increase at 1 keV. The rate of increase by strain application was higher with higher PKA energy, and attained the maximum at 20 keV PKA energy with a subsequent gradual decrease at 30 keV PKA energy The cluster size, mostly affected by strain, was larger with higher PKA energy, although clusters with fewer than seven interstitials did not increase in number at any PKA energy.

  12. Synchronization Techniques in Parallel Discrete Event Simulation

    OpenAIRE

    Lindén, Jonatan

    2018-01-01

    Discrete event simulation is an important tool for evaluating system models in many fields of science and engineering. To improve the performance of large-scale discrete event simulations, several techniques to parallelize discrete event simulation have been developed. In parallel discrete event simulation, the work of a single discrete event simulation is distributed over multiple processing elements. A key challenge in parallel discrete event simulation is to ensure that causally dependent ...

  13. Designing of phenol-based β-carbonic anhydrase1 inhibitors through QSAR, molecular docking, and MD simulation approach.

    Science.gov (United States)

    Ahamad, Shahzaib; Hassan, Md Imtaiyaz; Dwivedi, Neeraja

    2018-05-01

    Tuberculosis (Tb) is an airborne infectious disease caused by Mycobacterium tuberculosis. Beta-carbonic anhydrase 1 ( β-CA1 ) has emerged as one of the potential targets for new antitubercular drug development. In this work, three-dimensional quantitative structure-activity relationships (3D-QSAR), molecular docking, and molecular dynamics (MD) simulation approaches were performed on a series of natural and synthetic phenol-based β-CA1 inhibitors. The developed 3D-QSAR model ( r 2  = 0.94, q 2  = 0.86, and pred_r 2  = 0.74) indicated that the steric and electrostatic factors are important parameters to modulate the bioactivity of phenolic compounds. Based on this indication, we designed 72 new phenolic inhibitors, out of which two compounds (D25 and D50) effectively stabilized β-CA1 receptor and, thus, are potential candidates for new generation antitubercular drug discovery program.

  14. Solid state NMR investigations and MD simulations of triblock copolymers in lipid bilayers

    Czech Academy of Sciences Publication Activity Database

    Baerenwald, R.; Ferreira, T. M.; Ollila, Samuli; Saalwaechter, K.

    2017-01-01

    Roč. 46, Suppl 1 (2017), S117 ISSN 0175-7571. [IUPAB congress /19./ and EBSA congress /11./. 16.07.2017-20.07.2017, Edinburgh] Institutional support: RVO:61388963 Keywords : solid state NMR * molecular dynamic simulations Subject RIV: BO - Biophysics

  15. Urban Road Traffic Simulation Techniques

    Directory of Open Access Journals (Sweden)

    Ana Maria Nicoleta Mocofan

    2011-09-01

    Full Text Available For achieving a reliable traffic control system it is necessary to first establish a network parameter evaluation system and also a simulation system for the traffic lights plan. In 40 years of history, the computer aided traffic simulation has developed from a small research group to a large scale technology for traffic systems planning and development. In the following thesis, a presentation of the main modeling and simulation road traffic applications will be provided, along with their utility, as well as the practical application of one of the models in a case study.

  16. MD simulation of atomic displacement cascades near chromium-rich clusters in FeCr alloy

    International Nuclear Information System (INIS)

    Tikhonchev, M.; Svetukhin, V.; Gaganidze, E.

    2013-01-01

    The paper reports simulation of cascades in Fe–9 at.%Cr binary alloy containing chromium-rich clusters. The simulation is performed by the molecular dynamics method at the initial temperature of 300 K and primary knock-on atom energy of 15 and 20 keV. Spherical clusters containing 95 at.% of Cr with diameter of 1–5 nm have been considered. The properties of cascade evolution in the presence of chromium-rich cluster are studied. It is shown that these clusters tend to dissolve in collision cascades. However, clusters with diameter of ⩾3 nm exhibit only slight modifications and can be considered stable. Parameters of small (1–2 nm) clusters can change significantly and, in some cases, a 1 nm cluster can be totally dissolved

  17. MD simulation of atomic displacement cascades near chromium-rich clusters in FeCr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Tikhonchev, M., E-mail: tikhonchev@sv.ulsu.ru [Ulyanovsk State University, Research Institute of Technology, 42 Leo Tolstoy St., 432970 Ulyanovsk (Russian Federation); Svetukhin, V. [Ulyanovsk State University, Research Institute of Technology, 42 Leo Tolstoy St., 432970 Ulyanovsk (Russian Federation); Gaganidze, E. [Karlsruhe Institute of Technology, Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Karlsruhe (Germany)

    2013-11-15

    The paper reports simulation of cascades in Fe–9 at.%Cr binary alloy containing chromium-rich clusters. The simulation is performed by the molecular dynamics method at the initial temperature of 300 K and primary knock-on atom energy of 15 and 20 keV. Spherical clusters containing 95 at.% of Cr with diameter of 1–5 nm have been considered. The properties of cascade evolution in the presence of chromium-rich cluster are studied. It is shown that these clusters tend to dissolve in collision cascades. However, clusters with diameter of ⩾3 nm exhibit only slight modifications and can be considered stable. Parameters of small (1–2 nm) clusters can change significantly and, in some cases, a 1 nm cluster can be totally dissolved.

  18. X-ray structure, thermodynamics, elastic properties and MD simulations of cardiolipin/dimyristoylphosphatidylcholine mixed membranes

    DEFF Research Database (Denmark)

    Boscia, Alexander L.; Treece, Bradley W.; Mohammadyani, Dariush

    2014-01-01

    TMCL. Coarse grain molecular dynamics simulations confirm the experimental thickening of 2 Å for 20 mol% TMCL and locate the TMCL headgroups near the glycerol-carbonyl region of DMPC; i.e., they are sequestered below the DMPC phosphocholine headgroup. Our results suggest that TMCL plays a role similar...... to cholesterol in that it thickens and stiffens DMPC membranes, orders chains, and is positioned under the umbrella of the PC headgroup. CL may be necessary for hydrophobic matching to inner mitochondrial membrane proteins. Differential scanning calorimetry, S Xray and CGMD simulations all suggest that TMCL does......Cardiolipins (CLs) are important biologically for their unique role in biomembranes that couple phosphorylation and electron transport like bacterial plasma membranes, chromatophores, chloroplasts and mitochondria. CLs are often tightly coupled to proteins involved in oxidative phosphorylation...

  19. Low-energy oxygen bombardment of silicon by MD simulations making use of a reactive force field

    International Nuclear Information System (INIS)

    Philipp, P.; Briquet, L.; Wirtz, T.; Kieffer, J.

    2011-01-01

    In the field of Secondary Ion Mass Spectrometry (SIMS), ion-matter interactions have been largely investigated by numerical simulations. For MD simulations related to inorganic samples, mostly classical force fields assuming stable bonding structure have been used. In materials science, level-three force fields capable of simulating the breaking and formation of chemical bonds have recently been conceived. One such force field has been developed by John Kieffer . This potential includes directional covalent bonds, Coulomb and dipolar interaction terms, dispersion terms, etc. Important features of this force field for simulating systems that undergo significant structural reorganization are (i) the ability to account for the redistribution of electron density upon ionization, formation, or breaking of bonds, through a charge transfer term, and (ii) the fact that the angular constraints dynamically adjust when a change in the coordination number of an atom occurs. In this paper, the modification of the force field to allow for an exact description of the sputtering process, the influence of this modification on previous results obtained for phase transitions in glasses as well as properties of particles sputtered at 250-1000 eV from a mono-crystalline silicon sample will be presented. The simulation results agree qualitatively with predictions from experiments or models. Most atoms are sputtered from the first monolayer: for an impact energy of 250 eV up to 86% of the atoms are sputtered from the first monolayer and for 750 eV, this percentage drops to 61%, with 89% of the atoms being sputtered from the first two monolayers. For sputtering yields, 250 and 500 eV results agree with experimental data, but for 750 eV sub-channelling in the pristine sample becomes more important than in experiments where samples turn amorphous under ion bombardment.

  20. Evaluation of GEOS-5 sulfur dioxide simulations during the Frostburg, MD 2010 field campaign

    Directory of Open Access Journals (Sweden)

    V. Buchard

    2014-02-01

    Full Text Available Sulfur dioxide (SO2 is a major atmospheric pollutant with a strong anthropogenic component mostly produced by the combustion of fossil fuel and other industrial activities. As a precursor of sulfate aerosols that affect climate, air quality, and human health, this gas needs to be monitored on a global scale. Global climate and chemistry models including aerosol processes along with their radiative effects are important tools for climate and air quality research. Validation of these models against in-situ and satellite measurements is essential to ascertain the credibility of these models and to guide model improvements. In this study, the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART module running on-line inside the Goddard Earth Observing System version 5 (GEOS-5 model is used to simulate aerosol and SO2 concentrations. Data taken in November 2010 over Frostburg, Maryland during an SO2 field campaign involving ground instrumentation and aircraft are used to evaluate GEOS-5 simulated SO2 concentrations. Preliminary data analysis indicated the model overestimated surface SO2 concentration, which motivated the examination of the specification of SO2 anthropogenic emission rates. As a result of this analysis, a revision of anthropogenic emission inventories in GEOS-5 was implemented, and the vertical placement of SO2 sources was updated. Results show that these revisions improve the model agreement with observations locally and in regions outside the area of this field campaign. In particular, we use the ground-based measurements collected by the United States Environmental Protection Agency (US EPA for the year 2010 to evaluate the revised model simulations over North America.

  1. Electroreduction Property and MD Simulation of Nitrobenzene in Ionic Liquid [BMim][Tf2N]/[BMim][BF4

    International Nuclear Information System (INIS)

    Zeng, Jianping; Zhang, Yinxu; Sun, Ruyao; Chen, Song

    2014-01-01

    Highlights: • The two different common accessible ionic liquids are mixed in a simple and economic way. • In some compound ratios, the dynamic performance of nitrobenzene is superior to either of ionic liquids. • Modification and functionalization of ionic liquids in electrochemical field is feasible. • The mass transfer of diffusion of nitrobenzene in ionic liquids can be simulated with molecular dynamics. • Molecular dynamics explains the improvement of nitrobenzene in composite ionic liquids. - Abstract: The two different common accessible ionic liquids [BMim][BF 4 ] and [BMim][Tf 2 N] were mixed each other in a simple and economic way. In some compound ratios, the dynamic performance of nitrobenzene in electric reduction was superior to that of any single kind of ionic liquid has been appeared. The interaction and mass transfer of diffusion of nitrobenzene in composite ionic liquids with different volume ratios were studied with molecular dynamics (MD) simulation. The improvement of the electroreduction performance of nitrobenzene in composite ionic liquids was verified and was tried to explain. This provides a new idea for the modification and functionalization of ionic liquids in electrochemical field. The experimental results showed that kinematic viscosity and electroconductibility of different ionic liquid systems display a regular change. And the change law has been basically unchanged after adding water. The two different functional ionic liquids were complemented each other in a simple and economic way, which has compensated for the disadvantage of mono-component ionic liquids. At 25 °C, electroreduction property of V [BMim][BF4] :V [BMim][Tf2N] = 1:1 is the best in cyclic voltammetry experiments of nitrobenzene in different composite ionic liquids. Its electrochemical behavior is significantly affected by scan rate, temperature, concentration of nitrobenzene and concentration of water. The MD simulation results showed most of interaction

  2. Simulation of multi-atomic interactions in H-O-W system with the MD code CADAC

    Energy Technology Data Exchange (ETDEWEB)

    Landman, I.S. [Forschungszentrum Karlsruhe, Institute for Pulsed Power and Microwave Technology, P.O. Box 3640, 76021 Karlsruhe (Germany)]. E-mail: igor.landman@ihm.fzk.de

    2005-11-15

    For future tokamak reactors, chemical erosion of tungsten armour surfaces under impact of hot deuterium-tritium plasma that contains impurities, for instance oxygen, is an important issue. Oxygen can form volatile molecular complexes O {sub x}W {sub y} at the surface, and the retained H-atoms form the volatile complexes H {sub x}O {sub y}, which mitigates the erosion (H states for hydrogen isotopes). The plasma impact can substantially destroy the complexes. To describe this H-O-W system, the molecular dynamics (MD) code CADAC was earlier developed using only pair-atomic interactions. Now CADAC is extended for multi-body forces to simulate molecular organization of atoms near the tungsten surface. The approach uses the Abell's model of empirical bond-order potentials in addition combined, for the first time, with a valence concept. CADAC simulates chemical features using atomic valences and the Morse potentials. The new model is introduced and model parameters are estimated.

  3. An MD simulation of interactions between self-interstitial atoms and edge dislocation in bcc transition metals

    Energy Technology Data Exchange (ETDEWEB)

    Kamiyama, H. (Aomori Public College, 153-4 Yamazaki, Goushi-zawa, Aomori 030-01 (Japan)); Rafii-Tabar, H. (Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980 (Japan)); Kawazoe, Y. (Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980 (Japan)); Matsui, H. (Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980 (Japan))

    1994-09-01

    According to our model on the mechanism of dislocation bias reduction based on the interaction of dumbbell self-interstitial atoms (SIAs) with dislocation, the bias is significantly different depending on the dumbbell configuration in the dislocation strain field. A large-scale molecular dynamics (MD) simulation is performed to reveal the stability and the mechanism of diffusion of dumbbell SIAs near the edge dislocation core in bcc iron. Most SIAs take the crowdion configuration parallel to the Burgers vector in the expansion side of the dislocation. Such crowdions are stable in the temperature range of this simulation, i.e. between 373 and 473 K, making one-dimensional random to-and-fro motion parallel to the dislocation Burgers vector staying at several atomic layers below'' the dislocation core. This means that the SIA does not approach the dislocation core. These results suggest that the stable configuration of SIAs is seriously affected by the dislocation resulting in a reduction of bias factor. ((orig.))

  4. An MD simulation of interactions between self-interstitial atoms and edge dislocation in bcc transition metals

    International Nuclear Information System (INIS)

    Kamiyama, H.; Rafii-Tabar, H.; Kawazoe, Y.; Matsui, H.

    1994-01-01

    According to our model on the mechanism of dislocation bias reduction based on the interaction of dumbbell self-interstitial atoms (SIAs) with dislocation, the bias is significantly different depending on the dumbbell configuration in the dislocation strain field. A large-scale molecular dynamics (MD) simulation is performed to reveal the stability and the mechanism of diffusion of dumbbell SIAs near the edge dislocation core in bcc iron. Most SIAs take the crowdion configuration parallel to the Burgers vector in the expansion side of the dislocation. Such crowdions are stable in the temperature range of this simulation, i.e. between 373 and 473 K, making one-dimensional random to-and-fro motion parallel to the dislocation Burgers vector staying at several atomic layers ''below'' the dislocation core. This means that the SIA does not approach the dislocation core. These results suggest that the stable configuration of SIAs is seriously affected by the dislocation resulting in a reduction of bias factor. ((orig.))

  5. MD simulation of plastic deformation nucleation in stressed crystallites under irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Korchuganov, A. V., E-mail: avkor@ispms.tsc.ru; Zolnikov, K. P., E-mail: kost@ispms.tsc.ru; Kryzhevich, D. S., E-mail: kryzhev@ispms.tsc.ru [Russian Academy of Sciences, Institute of Strength Physics and Materials Science, Siberian Branch (Russian Federation); Chernov, V. M., E-mail: VMChernov@bochvar.ru [National Research Tomsk State University (Russian Federation); Psakhie, S. G., E-mail: sp@ispms.tsc.ru [Russian Academy of Sciences, Institute of Strength Physics and Materials Science, Siberian Branch (Russian Federation)

    2016-12-15

    The investigation of plastic deformation nucleation in metals and alloys under irradiation and mechanical loading is one of the topical issues of materials science. Specific features of nucleation and evolution of the defect system in stressed and irradiated iron, vanadium, and copper crystallites were studied by molecular dynamics simulation. Mechanical loading was performed in such a way that the modeled crystallite volume remained unchanged. The energy of the primary knock-on atom initiating a cascade of atomic displacements in a stressed crystallite was varied from 0.05 to 50 keV. It was found that atomic displacement cascades might cause global structural transformations in a region far larger than the radiation-damaged area. These changes are similar to the ones occurring in the process of mechanical loading of samples. They are implemented by twinning (in iron and vanadium) or through the formation of partial dislocation loops (in copper).

  6. Bicelles and Other Membrane Mimics: Comparison of Structure, Properties, and Dynamics from MD Simulations

    DEFF Research Database (Denmark)

    Vestergaard, Mikkel; Kraft, Johan Frederik; Vosegaard, Thomas

    2015-01-01

    present molecular dynamics simulations to elucidate structural and dynamic properties of small bicelles and compare them to a large alignable bicelle, a small nanodisc, and a lipid bilayer. Properties such as lipid packing and properties related to embedding both an α-helical peptide and a transmembrane...... protein are investigated. The small bicelles are found to be very dynamic and mainly assume a prolate shape substantiating that small bicelles cannot be regarded as well-defined disclike structures. However, addition of a peptide results in an increased tendency to form disc-shaped bicelles. The small......The increased interest in studying membrane proteins has led to the development of new membrane mimics such as bicelles and nanodiscs. However, only limited knowledge is available of how these membrane mimics are affected by embedded proteins and how well they mimic a lipid bilayer. Herein, we...

  7. MD simulation of atomic displacement cascades in Fe-10 at.%Cr binary alloy

    International Nuclear Information System (INIS)

    Tikhonchev, M.; Svetukhin, V.; Kadochkin, A.; Gaganidze, E.

    2009-01-01

    Molecular dynamics simulation of atomic displacement cascades up to 20 keV has been performed in Fe-10 at.%Cr binary alloy at a temperature of 600 K. The N-body interatomic potentials of Finnis-Sinclair type were used. According to the obtained results the dependence of 'surviving' defects amount is well approximated by power function that coincides with other researchers' results. Obtained cascade efficiency for damage energy in the range from 10 to 20 keV is ∼0.2 NRT that is slightly higher than for pure α-Fe. In post-cascade area Cr fraction in interstitials is in range 2-5% that is essentially lower than Cr content in the base alloy. The results on size and amount of vacancy and interstitial clusters generated in displacement cascades are obtained. For energies of 2 keV and higher the defect cluster average size increases and it is well approximated by a linear dependence on cascade energy both for interstitials and vacancies.

  8. MD simulation of atomic displacement cascades in Fe-10 at.%Cr binary alloy

    Energy Technology Data Exchange (ETDEWEB)

    Tikhonchev, M., E-mail: tikhonchev@sv.ulsu.r [Ulyanovsk State University, Leo Tolstoy Str., 42, Ulyanovsk 432970 (Russian Federation); Joint Stock Company, ' State Scientific Center Research Institute of Atomic Reactors' , 433510 Dimitrovgrad-10 (Russian Federation); Svetukhin, V.; Kadochkin, A. [Ulyanovsk State University, Leo Tolstoy Str., 42, Ulyanovsk 432970 (Russian Federation); Gaganidze, E. [Forschungszentrum Karlsruhe, IMF II, 3640, D-76021 Karlsruhe (Germany)

    2009-12-15

    Molecular dynamics simulation of atomic displacement cascades up to 20 keV has been performed in Fe-10 at.%Cr binary alloy at a temperature of 600 K. The N-body interatomic potentials of Finnis-Sinclair type were used. According to the obtained results the dependence of 'surviving' defects amount is well approximated by power function that coincides with other researchers' results. Obtained cascade efficiency for damage energy in the range from 10 to 20 keV is approx0.2 NRT that is slightly higher than for pure alpha-Fe. In post-cascade area Cr fraction in interstitials is in range 2-5% that is essentially lower than Cr content in the base alloy. The results on size and amount of vacancy and interstitial clusters generated in displacement cascades are obtained. For energies of 2 keV and higher the defect cluster average size increases and it is well approximated by a linear dependence on cascade energy both for interstitials and vacancies.

  9. Spectroscopic and MD simulation studies on unfolding processes of mitochondrial carbonic anhydrase VA induced by urea.

    Science.gov (United States)

    Idrees, Danish; Prakash, Amresh; Haque, Md Anzarul; Islam, Asimul; Ahmad, Faizan; Hassan, Md Imtaiyaz

    2016-09-01

    Carbonic anhydrase VA (CAVA) is primarily expressed in the mitochondria and involved in numerous physiological processes including lipogenesis, insulin secretion from pancreatic cells, ureagenesis, gluconeogenesis and neuronal transmission. To understand the biophysical properties of CAVA, we carried out a reversible urea-induced isothermal denaturation at pH 7.0 and 25°C. Spectroscopic probes, [θ]222 (mean residue ellipticity at 222 nm), F344 (Trp-fluorescence emission intensity at 344 nm) and Δε280 (difference absorption at 280 nm) were used to monitor the effect of urea on the structure and stability of CAVA. The urea-induced reversible denaturation curves were used to estimate [Formula: see text], Gibbs free energy in the absence of urea; Cm, the mid-point of the denaturation curve, i.e. molar urea concentration ([urea]) at which ΔGD = 0; and m, the slope (=∂ΔGD/∂[urea]). Coincidence of normalized transition curves of all optical properties suggests that unfolding/refolding of CAVA is a two-state process. We further performed 40 ns molecular dynamics simulation of CAVA to see the dynamics at different urea concentrations. An excellent agreement was observed between in silico and in vitro studies.

  10. The Unfolding MD Simulations of Cyclophilin: Analyzed by Surface Contact Networks and Their Associated Metrics

    Science.gov (United States)

    Roy, Sourav; Basu, Sankar; Dasgupta, Dipak; Bhattacharyya, Dhananjay; Banerjee, Rahul

    2015-01-01

    Currently, considerable interest exists with regard to the dissociation of close packed aminoacids within proteins, in the course of unfolding, which could result in either wet or dry moltenglobules. The progressive disjuncture of residues constituting the hydrophobic core ofcyclophilin from L. donovani (LdCyp) has been studied during the thermal unfolding of the molecule, by molecular dynamics simulations. LdCyp has been represented as a surface contactnetwork (SCN) based on the surface complementarity (Sm) of interacting residues within themolecular interior. The application of Sm to side chain packing within proteins make it a very sensitive indicator of subtle perturbations in packing, in the thermal unfolding of the protein. Network based metrics have been defined to track the sequential changes in the disintegration ofthe SCN spanning the hydrophobic core of LdCyp and these metrics prove to be highly sensitive compared to traditional metrics in indicating the increased conformational (and dynamical) flexibility in the network. These metrics have been applied to suggest criteria distinguishing DMG, WMG and transition state ensembles and to identify key residues involved in crucial conformational/topological events during the unfolding process. PMID:26545107

  11. A green process for recovery of 1-propanol/2-propanol from their aqueous solutions: Experimental and MD simulation studies

    International Nuclear Information System (INIS)

    Gupta, Bhupender S.; Taha, Mohamed; Lee, Ming-Jer

    2017-01-01

    Highlights: • A green conceptual design for separating propanols from their aqueous solutions is proposed. • TRIS is biocompatible and non-volatile and can be used as an auxiliary agent for the separation. • Isobaric VLE data for 1-propanol/2-propanol + water + TRIS were measured at 101.3 kPa. • The azeotropic compositions are significantly shifted in the presence of TRIS. • Intermolecular interactions were studied with fluorescence, COSMO-RS, and MD simulation. - Abstract: In the present study, we have found that a common and relatively inexpensive biological buffer tris(hydroxymethyl)aminomethane (TRIS) is potentially applicable to shift the azeotrope compositions of aqueous solutions of 1-propanol and 2-propanol. By taking the advantage of our findings, we are proposing a green process for the recovery of these organics from their respective aqueous solutions. In order to confirm the effect of TRIS buffer on vapor–liquid equilibrium behavior of the aqueous propanol systems, we measured the isobaric vapor–liquid equilibrium (VLE) data at 101.3 kPa for the 1-proponol + water + TRIS and 2-propanol + water + TRIS systems over the azeotropic range with various concentrations of TRIS (0.02, 0.04, 0.08, and 0.12 in mole fraction). The binary interaction parameters were obtained for TRIS with water, TRIS with 1-propanol, and TRIS with 2-propanol by correlating the new VLE data with the NRTL model. The isobaric VLE properties for the investigated propanol + water mixtures in the presence of various concentrations of TRIS were also predicted with the conductor-like screening model COSMO-RS. Based on the predicted excess molar enthalpies (H E m ) from the COSMO-RS, the interactions between all constituent pairs of molecules were estimated. To explore the mechanism of TRIS-based separation of 1-propanol/2-propanol from their aqueous solutions, the interactions between different pairs of molecules were also investigated by using fluorescence analysis and

  12. MD simulation of atomic displacements in metals and metallic bilayers under low energy ion bombardment at 300 K

    International Nuclear Information System (INIS)

    Kornich, G.V.; Betz, G.; Bazhin, A.I.

    1999-01-01

    MD simulations of 100 eV Ar ion bombardment of (1 0 0) Ni and Al as well as Al/Ni bilayer crystals at 300 K have been performed and compared to previous calculations at 0 K. The Al/Ni bilayer crystal consisted of one Al layer on a (1 0 0) Ni substrate. Sputtering yields for Ni and Al/Ni show no temperature dependence, while for Al a pronounced increase with temperature was observed. The contributions of different mechanisms to the production of surface and bulk defects are discussed. The mean square displacement (MSD) of atoms is in all cases larger at 300 K as compared to 0 K. The larger MSD at 300 K is mainly due to an increase in lateral (perpendicular to the ion beam) motion of displaced atoms. Similar the number of atomic jumps, in which an atom leaves its original Wigner-Seitz cell, increases in all cases with temperature. For the pure elements the production of bulk vacancies and interstitials decreases with temperature, but the number of surface vacancies and ad-atoms increases with temperature. For the bilayer system practically no temperature dependence for defects was observed

  13. Assessment of hydrogen bonding effect on ionization of water from ambient to supercritical region–MD simulation approach

    International Nuclear Information System (INIS)

    Swiatla-Wojcik, D.; Mozumder, A.

    2014-01-01

    We present a novel, molecular dynamics (MD) simulation based, strategy to analyze how the degree of hydrogen bonding may influence the ionization and dissociation of water upon heating from ambient to supercritical temperatures. Calculations show a negligible change in the ionization energy up to 200 °C. At higher temperatures the ionization energy increases due to the decreasing degree of hydrogen bonding. The influence of density (pressure) is pronounced in the supercritical region. The ionization is more energy consuming in the less dense fluid. We also show that high temperature and low density may promote dissociation of the electronically excited water molecules. Implications on the initial radiation chemical yields of the hydrated electron, hydrogen atom and hydroxyl radical are discussed. - Highlights: • Up to 200 °C changes in the vertical and adiabatic ionization potentials are negligible. • At higher temperatures ionization is more energy consuming. • Ionization potential increases with decreasing density of supercritical water. • High temperature and low density promote dissociation of the excited molecules

  14. Detailed regulatory mechanism of the interaction between ZO-1 PDZ2 and connexin43 revealed by MD simulations.

    Directory of Open Access Journals (Sweden)

    Fei Xiao

    Full Text Available The gap junction protein connexin43 (Cx43 binds to the second PDZ domain of Zonula occludens-1 (ZO-1 through its C-terminal tail, mediating the regulation of gap junction plaque size and dynamics. Biochemical study demonstrated that the very C-terminal 12 residues of Cx43 are necessary and sufficient for ZO-1 PDZ2 binding and phosphorylation at residues Ser (-9 and Ser (-10 of the peptide can disrupt the association. However, only a crystal structure of ZO-1 PDZ2 in complex with a shorter 9 aa peptide of connexin43 was solved experimentally. Here, the interactions between ZO-1 PDZ2 and the short, long and phosphorylated Cx43 peptides were studied using molecular dynamics (MD simulations and free energy calculation. The short peptide bound to PDZ2 exhibits large structural variations, while the extension of three upstream residues stabilizes the peptide conformation and enhanced the interaction. Phosphorylation at Ser(-9 significantly weakens the binding and results in conformational flexibility of the peptide. Glu210 of ZO-1 PDZ2 was found to be a key regulatory point in Cx43 binding and phosphorylation induced dissociation.

  15. Supramolecular architecture of 5-bromo-7-methoxy-1-methyl-1H-benzoimidazole.3H2O: Synthesis, spectroscopic investigations, DFT computation, MD simulations and docking studies

    Science.gov (United States)

    Murthy, P. Krishna; Smitha, M.; Sheena Mary, Y.; Armaković, Stevan; Armaković, Sanja J.; Rao, R. Sreenivasa; Suchetan, P. A.; Giri, L.; Pavithran, Rani; Van Alsenoy, C.

    2017-12-01

    Crystal and molecular structure of newly synthesized compound 5-bromo-7-methoxy-1-methyl-1H-benzoimidazole (BMMBI) has been authenticated by single crystal X-ray diffraction, FT-IR, FT-Raman, 1H NMR, 13C NMR and UV-Visible spectroscopic techniques; compile both experimental and theoretical results which are performed by DFT/B3LYP/6-311++G(d,p) method at ground state in gas phase. Visualize nature and type of intermolecular interactions and crucial role of these interactions in supra-molecular architecture has been investigated by use of a set of graphical tools 3D-Hirshfeld surfaces and 2D-fingerprint plots analysis. The title compound stabilized by strong intermolecular hydrogen bonds N⋯Hsbnd O and O⋯Hsbnd O, which are envisaged by dark red spots on dnorm mapped surfaces and weak Br⋯Br contacts envisaged by red spot on dnorm mapped surface. The detailed fundamental vibrational assignments of wavenumbers were aid by with help of Potential Energy distribution (PED) analysis by using GAR2PED program and shows good agreement with experimental values. Besides frontier orbitals analysis, global reactivity descriptors, natural bond orbitals and Mullikan charges analysis were performed by same basic set at ground state in gas phase. Potential reactive sites of the title compound have been identified by ALIE, Fukui functions and MEP, which are mapped to the electron density surfaces. Stability of BMMBI have been investigated from autoxidation process and pronounced interaction with water (hydrolysis) by using bond dissociation energies (BDE) and radial distribution functions (RDF), respectively after MD simulations. In order to identify molecule's most important reactive spots we have used a combination of DFT calculations and MD simulations. Reactivity study encompassed calculations of a set of quantities such as: HOMO-LUMO gap, MEP and ALIE surfaces, Fukui functions, bond dissociation energies and radial distribution functions. To confirm the potential

  16. Conformational Ensemble of the Poliovirus 3CD Precursor Observed by MD Simulations and Confirmed by SAXS: A Strategy to Expand the Viral Proteome?

    Science.gov (United States)

    Moustafa, Ibrahim M; Gohara, David W; Uchida, Akira; Yennawar, Neela; Cameron, Craig E

    2015-11-23

    The genomes of RNA viruses are relatively small. To overcome the small-size limitation, RNA viruses assign distinct functions to the processed viral proteins and their precursors. This is exemplified by poliovirus 3CD protein. 3C protein is a protease and RNA-binding protein. 3D protein is an RNA-dependent RNA polymerase (RdRp). 3CD exhibits unique protease and RNA-binding activities relative to 3C and is devoid of RdRp activity. The origin of these differences is unclear, since crystal structure of 3CD revealed "beads-on-a-string" structure with no significant structural differences compared to the fully processed proteins. We performed molecular dynamics (MD) simulations on 3CD to investigate its conformational dynamics. A compact conformation of 3CD was observed that was substantially different from that shown crystallographically. This new conformation explained the unique properties of 3CD relative to the individual proteins. Interestingly, simulations of mutant 3CD showed altered interface. Additionally, accelerated MD simulations uncovered a conformational ensemble of 3CD. When we elucidated the 3CD conformations in solution using small-angle X-ray scattering (SAXS) experiments a range of conformations from extended to compact was revealed, validating the MD simulations. The existence of conformational ensemble of 3CD could be viewed as a way to expand the poliovirus proteome, an observation that may extend to other viruses.

  17. Prediction and analysis of the structure of hydrated Mn2+, V2+, Ti3 and Cr3 ions by means of the MD simulation methods

    International Nuclear Information System (INIS)

    Iglesias, Y.J.

    2002-01-01

    Classical Molecular dynamics (MD) and hybrid Quantum/Molecular Mechanics-Molecular Dynamics (QM/MM-MD) simulations have been performed to investigate structural properties of Mn(II), V(II), Cr(III) and Ti(III) cations in aqueous solution. The first hydration sphere in QM/MM-MD simulations is treated quantum mechanically, while the rest of the system is described by classical analytical two- and three-body potentials. The results obtained for the first hydration shell from this method are in agreement with experimental data, showing 100 % of 6 fold coordination around the ion in all cases. The results prove that non/additive contributions are mandatory for an accurate description of ion hydration. Within the QM/MM method, the inclusion of a perturbation field describing the remaining system was shown to be an accurate tool for evaluating the first shell structure, and thus to be a good alternative for systems, where the construction of a three-body correction function is difficult or too time-consuming. (author)

  18. Developing the MD Explorer

    Science.gov (United States)

    Howie, Philip V.

    1993-04-01

    The MD Explorer is an eight-seat twin-turbine engine helicopter which is being developed using integrated product definition (IPD) team methodology. New techniques include NOTAR antitorque system for directional control, a composite fuselage, an all-composite bearingless main rotor, and digital cockpit displays. Three-dimensional CAD models are the basis of the entire Explorer design. Solid models provide vendor with design clarification, removing much of the normal drawing interpretation errors.

  19. Fast simulation techniques for switching converters

    Science.gov (United States)

    King, Roger J.

    1987-01-01

    Techniques for simulating a switching converter are examined. The state equations for the equivalent circuits, which represent the switching converter, are presented and explained. The uses of the Newton-Raphson iteration, low ripple approximation, half-cycle symmetry, and discrete time equations to compute the interval durations are described. An example is presented in which these methods are illustrated by applying them to a parallel-loaded resonant inverter with three equivalent circuits for its continuous mode of operation.

  20. Visualization needs and techniques for astrophysical simulations

    International Nuclear Information System (INIS)

    Kapferer, W; Riser, T

    2008-01-01

    Numerical simulations have evolved continuously towards being an important field in astrophysics, equivalent to theory and observation. Due to the enormous developments in computer sciences, both hardware- and software-architecture, state-of-the-art simulations produce huge amounts of raw data with increasing complexity. In this paper some aspects of problems in the field of visualization in numerical astrophysics in combination with possible solutions are given. Commonly used visualization packages along with a newly developed approach to real-time visualization, incorporating shader programming to uncover the computational power of modern graphics cards, are presented. With these techniques at hand, real-time visualizations help scientists to understand the coherences in the results of their numerical simulations. Furthermore a fundamental problem in data analysis, i.e. coverage of metadata on how a visualization was created, is highlighted.

  1. Tree Simulation Techniques for Integrated Safety Assessment

    International Nuclear Information System (INIS)

    Melendez Asensio, E.; Izquierdo Rocha, J.M.; Sanchez Perez, M.; Hortal Reymundo, J.; Perez Mulas, A.

    1999-01-01

    techniques are: (a) An unifying theory that should (i) establish the relationship among different approaches and, in particular, be able to demonstrate the standard safety assessment approach as a particular case, (ii) identify implicit assumptions in present practice and (iii) establish a sound scientific reference for an ideal treatment in order to judge the relative importance of implicit and explicit assumptions. In addition, the theoretical developments help to identify the type of applications where the new developments will be a necessary requirement. (b) The capability for simulation of trees. By this we mean the techniques required to be able to efficiently simulate all branches. Historically algorithms able to do this were already implemented in earlier pioneering work for discrete number of branches while stochastic branching requires Montecarlo techniques. (c) The capability to incorporate new types of branching, particularly operator actions. This paper shortly reviews these aspects and justifies in that frame our particular development, denoted here as Integrated Safety Assessment methodology. In this method, the dynamics of the event is followed by transient simulation in tree form, building a Setpoint or Deterministic Dynamic Event Tree (DDET). When a setpoint that should trigger the actuation of a protection is crossed, the tree is opened in branches corresponding to different functioning states of the protection device and each branch followed by the engineering simulator. One of these states is the nominal state, which, in the PSAs, is Associated to the success criterion of the system

  2. Thermal evolution of nanocrystalline co-sputtered Ni–Zr alloy films: Structural, magnetic and MD simulation studies

    International Nuclear Information System (INIS)

    Bhattacharya, Debarati; Rao, T.V. Chandrasekhar; Bhushan, K.G.; Ali, Kawsar; Debnath, A.; Singh, S.; Arya, A.; Bhattacharya, S.; Basu, S.

    2015-01-01

    Monophasic and homogeneous Ni 10 Zr 7 nanocrystalline alloy films were successfully grown at room temperature by co-sputtering in an indigenously developed three-gun DC/RF magnetron sputtering unit. The films could be produced with long-range crystallographic and chemical order in the alloy, thus overcoming the widely acknowledged inherent proclivity of the glass forming Ni–Zr couple towards amorphization. Crystallinity of these alloys is a desirable feature with regard to improved efficacy in applications such as hydrogen storage, catalytic activity and nuclear reactor engineering, to name a few. Thermal stability of this crystalline phase, being vital for transition to viable applications, was investigated through systematic annealing of the alloy films at 473 K, 673 K and 923 K for various durations. While the films were stable at 473 K, the effect of annealing at 673 K was to create segregation into nanocrystalline Ni (superparamagnetic) and amorphous Ni + Zr (non-magnetic) phases. Detailed analyses of the physical and magnetic structures before and after annealing were performed through several techniques effectual in analyzing stratified configurations and the findings were all consistent with each other. Polarized neutron and X-ray reflectometry, grazing incidence x-ray diffraction, time-of-flight secondary ion mass spectroscopy and X-ray photoelectron spectroscopy were used to gauge phase separation at nanometer length scales. SQUID based magnetometry was used to investigate macroscopic magnetic properties. Simulated annealing performed on this system using molecular dynamic calculations corroborated well with the experimental results. This study provides a thorough understanding of the creation and thermal evolution of a crystalline Ni–Zr alloy. - Highlights: • Nanocrystalline Ni 10 Zr 7 alloy thin films deposited successfully by co-sputtering. • Creation of a crystalline alloy in a binary system with a tendency to amorphize. • Quantitative

  3. MD simulation of the Tat/Cyclin T1/CDK9 complex revealing the hidden catalytic cavity within the CDK9 molecule upon Tat binding.

    Directory of Open Access Journals (Sweden)

    Kaori Asamitsu

    Full Text Available In this study, we applied molecular dynamics (MD simulation to analyze the dynamic behavior of the Tat/CycT1/CDK9 tri-molecular complex and revealed the structural changes of P-TEFb upon Tat binding. We found that Tat could deliberately change the local flexibility of CycT1. Although the structural coordinates of the H1 and H2 helices did not substantially change, H1', H2', and H3' exhibited significant changes en masse. Consequently, the CycT1 residues involved in Tat binding, namely Tat-recognition residues (TRRs, lost their flexibility with the addition of Tat to P-TEFb. In addition, we clarified the structural variation of CDK9 in complex with CycT1 in the presence or absence of Tat. Interestingly, Tat addition significantly reduced the structural variability of the T-loop, thus consolidating the structural integrity of P-TEFb. Finally, we deciphered the formation of the hidden catalytic cavity of CDK9 upon Tat binding. MD simulation revealed that the PITALRE signature sequence of CDK9 flips the inactive kinase cavity of CDK9 into the active form by connecting with Thr186, which is crucial for its activity, thus presumably recruiting the substrate peptide such as the C-terminal domain of RNA pol II. These findings provide vital information for the development of effective novel anti-HIV drugs with CDK9 catalytic activity as the target.

  4. Distinct solvent- and temperature-dependent packing arrangements of anti-parallel β-sheet polyalanines studied with solid-state 13C NMR and MD simulation.

    Science.gov (United States)

    Kametani, Shunsuke; Tasei, Yugo; Nishimura, Akio; Asakura, Tetsuo

    2017-08-09

    Polyalanine (polyA) sequences are well known as the simplest sequence that naturally forms anti-parallel β-sheets and constitute a key element in the structure of spider and wild silkworm silk fibers. We have carried out a systematic analysis of the packing of anti-parallel β-sheets for (Ala) n , n = 5, 6, 7 and 12, using primarily 13 C solid-state NMR and MD simulation. HFIP and TFA are frequently used as the dope solvents for recombinant silks, and polyA was solidified from both HFIP and TFA solutions by drying. An analysis of Ala Cβ peaks in the 13 C CP/MAS NMR spectra indicated that polyA from HFIP was mainly rectangular but polyA from TFA was mainly staggered. The transition from the rectangular to the staggered arrangement in (Ala) 6 was observed for the first time from the change in the Ala Cβ peak through heat treatment at 200 °C for 4 h. The removal of the bound water was confirmed by thermal analysis. This transition could be reproduced by MD simulation of (Ala) 6 molecules at 200 °C after removal of the bound water molecules. In this way, the origin of the stability of the different packing arrangements of polyA was clarified.

  5. Thermal evolution of nanocrystalline co-sputtered Ni–Zr alloy films: Structural, magnetic and MD simulation studies

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, Debarati, E-mail: debarati@barc.gov.in [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Rao, T.V. Chandrasekhar; Bhushan, K.G. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Ali, Kawsar [Material Science Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Debnath, A. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Singh, S. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Arya, A. [Material Science Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Bhattacharya, S. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Basu, S. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2015-11-15

    Monophasic and homogeneous Ni{sub 10}Zr{sub 7} nanocrystalline alloy films were successfully grown at room temperature by co-sputtering in an indigenously developed three-gun DC/RF magnetron sputtering unit. The films could be produced with long-range crystallographic and chemical order in the alloy, thus overcoming the widely acknowledged inherent proclivity of the glass forming Ni–Zr couple towards amorphization. Crystallinity of these alloys is a desirable feature with regard to improved efficacy in applications such as hydrogen storage, catalytic activity and nuclear reactor engineering, to name a few. Thermal stability of this crystalline phase, being vital for transition to viable applications, was investigated through systematic annealing of the alloy films at 473 K, 673 K and 923 K for various durations. While the films were stable at 473 K, the effect of annealing at 673 K was to create segregation into nanocrystalline Ni (superparamagnetic) and amorphous Ni + Zr (non-magnetic) phases. Detailed analyses of the physical and magnetic structures before and after annealing were performed through several techniques effectual in analyzing stratified configurations and the findings were all consistent with each other. Polarized neutron and X-ray reflectometry, grazing incidence x-ray diffraction, time-of-flight secondary ion mass spectroscopy and X-ray photoelectron spectroscopy were used to gauge phase separation at nanometer length scales. SQUID based magnetometry was used to investigate macroscopic magnetic properties. Simulated annealing performed on this system using molecular dynamic calculations corroborated well with the experimental results. This study provides a thorough understanding of the creation and thermal evolution of a crystalline Ni–Zr alloy. - Highlights: • Nanocrystalline Ni{sub 10}Zr{sub 7} alloy thin films deposited successfully by co-sputtering. • Creation of a crystalline alloy in a binary system with a tendency to amorphize.

  6. Visualization techniques in plasma numerical simulations

    International Nuclear Information System (INIS)

    Kulhanek, P.; Smetana, M.

    2004-01-01

    Numerical simulations of plasma processes usually yield a huge amount of raw numerical data. Information about electric and magnetic fields and particle positions and velocities can be typically obtained. There are two major ways of elaborating these data. First of them is called plasma diagnostics. We can calculate average values, variances, correlations of variables, etc. These results may be directly comparable with experiments and serve as the typical quantitative output of plasma simulations. The second possibility is the plasma visualization. The results are qualitative only, but serve as vivid display of phenomena in the plasma followed-up. An experience with visualizing electric and magnetic fields via Line Integral Convolution method is described in the first part of the paper. The LIC method serves for visualization of vector fields in two dimensional section of the three dimensional plasma. The field values can be known only in grid points of three-dimensional grid. The second part of the paper is devoted to the visualization techniques of the charged particle motion. The colour tint can be used for particle temperature representation. The motion can be visualized by a trace fading away with the distance from the particle. In this manner the impressive animations of the particle motion can be achieved. (author)

  7. Calibrating and Validating a Simulation Model to Identify Drivers of Urban Land Cover Change in the Baltimore, MD Metropolitan Region

    Directory of Open Access Journals (Sweden)

    Claire Jantz

    2014-09-01

    Full Text Available We build upon much of the accumulated knowledge of the widely used SLEUTH urban land change model and offer advances. First, we use SLEUTH’s exclusion/attraction layer to identify and test different urban land cover change drivers; second, we leverage SLEUTH’s self-modification capability to incorporate a demographic model; and third, we develop a validation procedure to quantify the influence of land cover change drivers and assess uncertainty. We found that, contrary to our a priori expectations, new development is not attracted to areas serviced by existing or planned water and sewer infrastructure. However, information about where population and employment growth is likely to occur did improve model performance. These findings point to the dominant role of centrifugal forces in post-industrial cities like Baltimore, MD. We successfully developed a demographic model that allowed us to constrain the SLEUTH model forecasts and address uncertainty related to the dynamic relationship between changes in population and employment and urban land use. Finally, we emphasize the importance of model validation. In this work the validation procedure played a key role in rigorously assessing the impacts of different exclusion/attraction layers and in assessing uncertainty related to population and employment forecasts.

  8. Unique structure and dynamics of the EphA5 ligand binding domain mediate its binding specificity as revealed by X-ray crystallography, NMR and MD simulations.

    Directory of Open Access Journals (Sweden)

    Xuelu Huan

    Full Text Available The 16 EphA and EphB receptors represent the largest family of receptor tyrosine kinases, and their interactions with 9 ephrin-A and ephrin-B ligands initiate bidirectional signals controlling many physiological and pathological processes. Most interactions occur between receptor and ephrins of the same class, and only EphA4 can bind all A and B ephrins. To understand the structural and dynamic principles that enable Eph receptors to utilize the same jellyroll β-sandwich fold to bind ephrins, the VAPB-MSP domain, peptides and small molecules, we have used crystallography, NMR and molecular dynamics (MD simulations to determine the first structure and dynamics of the EphA5 ligand-binding domain (LBD, which only binds ephrin-A ligands. Unexpectedly, despite being unbound, the high affinity ephrin-binding pocket of EphA5 resembles that of other Eph receptors bound to ephrins, with a helical conformation over the J-K loop and an open pocket. The openness of the pocket is further supported by NMR hydrogen/deuterium exchange data and MD simulations. Additionally, the EphA5 LBD undergoes significant picosecond-nanosecond conformational exchanges over the loops, as revealed by NMR and MD simulations, but lacks global conformational exchanges on the microsecond-millisecond time scale. This is markedly different from the EphA4 LBD, which shares 74% sequence identity and 87% homology. Consequently, the unbound EphA5 LBD appears to comprise an ensemble of open conformations that have only small variations over the loops and appear ready to bind ephrin-A ligands. These findings show how two proteins with high sequence homology and structural similarity are still able to achieve distinctive binding specificities through different dynamics, which may represent a general mechanism whereby the same protein fold can serve for different functions. Our findings also suggest that a promising strategy to design agonists/antagonists with high affinity and selectivity

  9. Do SiO 2 and carbon-doped SiO 2 nanoparticles melt? Insights from QM/MD simulations and ramifications regarding carbon nanotube growth

    Science.gov (United States)

    Page, Alister J.; Chandrakumar, K. R. S.; Irle, Stephan; Morokuma, Keiji

    2011-05-01

    Quantum chemical molecular dynamics (QM/MD) simulations of pristine and carbon-doped SiO 2 nanoparticles have been performed between 1000 and 3000 K. At temperatures above 1600 K, pristine nanoparticle SiO 2 decomposes rapidly, primarily forming SiO. Similarly, carbon-doped nanoparticle SiO 2 decomposes at temperatures above 2000 K, primarily forming SiO and CO. Analysis of the physical states of these pristine and carbon-doped SiO 2 nanoparticles indicate that they remain in the solid phase throughout decomposition. This process is therefore one of sublimation, as the liquid phase is never entered. Ramifications of these observations with respect to presently debated mechanisms of carbon nanotube growth on SiO 2 nanoparticles will be discussed.

  10. Conformational analysis of the Sda determinant-containing tetrasaccharide and two mimics in aqueous solution by using 1H NMR ROESY spectroscopy in combination with MD simulations

    International Nuclear Information System (INIS)

    Blanco, Jose L. Jimenez; Rooijen, Johannes J.M. van; Erbel, Paul J.A.; Leeflang, Bas R.; Kamerling, Johannis P.; Vliegenthart, Johannes F.G.

    2000-01-01

    The conformational behaviour of the spacer-linked synthetic Sd a tetrasaccharide β-d-GalpNAc-(1 → 4)-[α-Neu5Ac-(2 → 3)]-β-d-Galp-(1 → 4)-β-d-GlcpNAc-(1 → O) (CH 2 ) 5 NH 2 (1) and the two mimics β-d-Galp-(1 → 4)-[α-Neu5Ac-(2 → 3)]-β-d-Galp-(1 → 4)-β-d-GlcpNAc-(1 → O)(CH 2 ) 5 NH 2 (2) and β-d-GlcpNAc-(1 → 4)-[α-Neu5Ac-(2 → 3)]-β-d-Galp-(1 → 4)-β-d-GlcpNAc-(1 → O) (CH 2 ) 5 NH 2 (3) were investigated by 1 H NMR spectroscopy in combination with molecular dynamics (MD) simulations in water. Experimental 2D 1 H ROESY cross-peak intensities (ROEs) of the tetrasaccharides were compared with calculated ROEs derived from MD trajectories using the CROSREL program. Analysis of these data indicated that the oligosaccharidic skeletons of the compounds 1-3 are rather rigid, especially the β-d-Hex(NAc)-(1 → 4)-[α-Neu5Ac-(2 → 3)]-β-d-Galp fragments. The α- Neu5-Ac-(2 → 3)-β-d-Galp linkage occurred in two different energy minima in the three-dimensional structure of the compounds 1-3 in aqueous solution. Experimental data and dynamics simulations supported the finding that the higher energy rotamer (CHEAT forcefield) was abundant in compounds 1 and 3 due to the existence of a hydrogen bond between the carboxyl group of the sialic acid and the acetamido group of the terminal monosaccharide (GalNAc or GlcNAc) unit. The conformational similarity between 1 and 3 leads to the suggestion that also their activities will be alike.

  11. Cryptanalysis of MD2

    DEFF Research Database (Denmark)

    Knudsen, Lars Ramkilde; Mathiassen, John Erik; Muller, Frédéric

    2010-01-01

    This paper considers the hash function MD2 which was developed by Ron Rivest in 1989. Despite its age, MD2 has withstood cryptanalytic attacks until recently. This paper contains the state-of-the-art cryptanalytic results on MD2, in particular collision and preimage attacks on the full hash...

  12. Quasielastic neutron scattering measurements and ab initio MD-simulations on single ion motions in molten NaF

    Energy Technology Data Exchange (ETDEWEB)

    Demmel, F. [ISIS Facility, Rutherford Appleton Laboratory, Didcot OX11 0QX (United Kingdom); Mukhopadhyay, S. [ISIS Facility, Rutherford Appleton Laboratory, Didcot OX11 0QX (United Kingdom); Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom)

    2016-01-07

    The ionic stochastic motions in the molten alkali halide NaF are investigated by quasielastic neutron scattering and first principles molecular dynamics simulation. Quasielastic neutron scattering was employed to extract the diffusion behavior of the sodium ions in the melt. An extensive first principles based simulation on a box of up to 512 particles has been performed to complement the experimental data. From that large box, a smaller 64-particle box has then been simulated over a runtime of 60 ps. A good agreement between calculated and neutron data on the level of spectral shape has been obtained. The obtained sodium diffusion coefficients agree very well. The simulation predicts a fluorine diffusion coefficient similar to the sodium one. Applying the Nernst-Einstein equation, a remarkable large cross correlation between both ions can be deduced. The velocity cross correlations demonstrate a positive correlation between the ions over a period of 0.1 ps. That strong correlation is evidence that the unlike ions do not move completely statistically independent and have a strong association over a short period of time.

  13. Fusion Simulation Project. Workshop Sponsored by the U.S. Department of Energy, Rockville, MD, May 16-18, 2007

    Energy Technology Data Exchange (ETDEWEB)

    Kritz, A.; Keyes, D.

    2007-05-18

    The mission of the Fusion Simulation Project is to develop a predictive capability for the integrated modeling of magnetically confined plasmas. This FSP report adds to the previous activities that defined an approach to integrated modeling in magnetic fusion. These previous activities included a Fusion Energy Sciences Advisory Committee panel that was charged to study integrated simulation in 2002. The report of that panel [Journal of Fusion Energy 20, 135 (2001)] recommended the prompt initiation of a Fusion Simulation Project. In 2003, the Office of Fusion Energy Sciences formed a steering committee that developed a project vision, roadmap, and governance concepts [Journal of Fusion Energy 23, 1 (2004)]. The current FSP planning effort involved forty-six physicists, applied mathematicians and computer scientists, from twenty-one institutions, formed into four panels and a coordinating committee. These panels were constituted to consider: Status of Physics Components, Required Computational and Applied Mathematics Tools, Integration and Management of Code Components, and Project Structure and Management. The ideas, reported here, are the products of these panels, working together over several months and culminating in a three-day workshop in May 2007.

  14. Fusion Simulation Project. Workshop sponsored by the U.S. Department of Energy Rockville, MD, May 16-18, 2007

    Energy Technology Data Exchange (ETDEWEB)

    None

    2007-05-16

    The mission of the Fusion Simulation Project is to develop a predictive capability for the integrated modeling of magnetically confined plasmas. This FSP report adds to the previous activities that defined an approach to integrated modeling in magnetic fusion. These previous activities included a Fusion Energy Sciences Advisory Committee panel that was charged to study integrated simulation in 2002. The report of that panel [Journal of Fusion Energy 20, 135 (2001)] recommended the prompt initiation of a Fusion Simulation Project. In 2003, the Office of Fusion Energy Sciences formed a steering committee that developed a project vision, roadmap, and governance concepts [Journal of Fusion Energy 23, 1 (2004)]. The current FSP planning effort involved forty-six physicists, applied mathematicians and computer scientists, from twenty-one institutions, formed into four panels and a coordinating committee. These panels were constituted to consider: Status of Physics Components, Required Computational and Applied Mathematics Tools, Integration and Management of Code Components, and Project Structure and Management. The ideas, reported here, are the products of these panels, working together over several months and culminating in a three-day workshop in May 2007.

  15. Fusion Simulation Project. Workshop sponsored by the U.S. Department of Energy Rockville, MD, May 16-18, 2007

    International Nuclear Information System (INIS)

    2007-01-01

    The mission of the Fusion Simulation Project is to develop a predictive capability for the integrated modeling of magnetically confined plasmas. This FSP report adds to the previous activities that defined an approach to integrated modeling in magnetic fusion. These previous activities included a Fusion Energy Sciences Advisory Committee panel that was charged to study integrated simulation in 2002. The report of that panel (Journal of Fusion Energy 20, 135 (2001)) recommended the prompt initiation of a Fusion Simulation Project. In 2003, the Office of Fusion Energy Sciences formed a steering committee that developed a project vision, roadmap, and governance concepts (Journal of Fusion Energy 23, 1 (2004)). The current FSP planning effort involved forty-six physicists, applied mathematicians and computer scientists, from twenty-one institutions, formed into four panels and a coordinating committee. These panels were constituted to consider: Status of Physics Components, Required Computational and Applied Mathematics Tools, Integration and Management of Code Components, and Project Structure and Management. The ideas, reported here, are the products of these panels, working together over several months and culminating in a three-day workshop in May 2007.

  16. Fusion Simulation Project. Workshop Sponsored by the U.S. Department of Energy, Rockville, MD, May 16-18, 2007

    International Nuclear Information System (INIS)

    Kritz, A.; Keyes, D.

    2007-01-01

    The mission of the Fusion Simulation Project is to develop a predictive capability for the integrated modeling of magnetically confined plasmas. This FSP report adds to the previous activities that defined an approach to integrated modeling in magnetic fusion. These previous activities included a Fusion Energy Sciences Advisory Committee panel that was charged to study integrated simulation in 2002. The report of that panel [Journal of Fusion Energy 20, 135 (2001)] recommended the prompt initiation of a Fusion Simulation Project. In 2003, the Office of Fusion Energy Sciences formed a steering committee that developed a project vision, roadmap, and governance concepts [Journal of Fusion Energy 23, 1 (2004)]. The current FSP planning effort involved forty-six physicists, applied mathematicians and computer scientists, from twenty-one institutions, formed into four panels and a coordinating committee. These panels were constituted to consider: Status of Physics Components, Required Computational and Applied Mathematics Tools, Integration and Management of Code Components, and Project Structure and Management. The ideas, reported here, are the products of these panels, working together over several months and culminating in a three-day workshop in May 2007

  17. Fast, Accurate Memory Architecture Simulation Technique Using Memory Access Characteristics

    OpenAIRE

    小野, 貴継; 井上, 弘士; 村上, 和彰

    2007-01-01

    This paper proposes a fast and accurate memory architecture simulation technique. To design memory architecture, the first steps commonly involve using trace-driven simulation. However, expanding the design space makes the evaluation time increase. A fast simulation is achieved by a trace size reduction, but it reduces the simulation accuracy. Our approach can reduce the simulation time while maintaining the accuracy of the simulation results. In order to evaluate validity of proposed techniq...

  18. QM/MM MD and Free Energy Simulation Study of Methyl Transfer Processes Catalyzed by PKMTs and PRMTs.

    Science.gov (United States)

    Chu, Yuzhuo; Guo, Hong

    2015-09-01

    Methyl transfer processes catalyzed by protein lysine methyltransferases (PKMTs) and protein arginine methyltransferases (PRMTs) control important biological events including transcriptional regulation and cell signaling. One important property of these enzymes is that different PKMTs and PRMTs catalyze the formation of different methylated product (product specificity). These different methylation states lead to different biological outcomes. Here, we review the results of quantum mechanics/molecular mechanics molecular dynamics and free energy simulations that have been performed to study the reaction mechanism of PKMTs and PRMTs and the mechanism underlying the product specificity of the methyl transfer processes.

  19. Modeling the Self-assembly and Stability of DHPC Micelles using Atomic Resolution and Coarse Grained MD Simulations

    DEFF Research Database (Denmark)

    Kraft, Johan Frederik; Vestergaard, Mikkel; Schiøtt, Birgit

    2012-01-01

    Membrane mimics such as micelles and bicelles are widely used in experiments involving membrane proteins. With the aim of being able to carry out molecular dynamics simulations in environments comparable to experimental conditions, we set out to test the ability of both coarse grained and atomistic...... resolution force fields to model the experimentally observed behavior of the lipid 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC), which is a widely used lipid for biophysical characterization of membrane proteins. It becomes clear from our results that a satisfactory modeling of DHPC aggregates...

  20. Enhanced Dynamics of Hydrated tRNA on Nanodiamond Surfaces: A Combined Neutron Scattering and MD Simulation Study.

    Science.gov (United States)

    Dhindsa, Gurpreet K; Bhowmik, Debsindhu; Goswami, Monojoy; O'Neill, Hugh; Mamontov, Eugene; Sumpter, Bobby G; Hong, Liang; Ganesh, Panchapakesan; Chu, Xiang-Qiang

    2016-09-14

    Nontoxic, biocompatible nanodiamonds (ND) have recently been implemented in rational, systematic design of optimal therapeutic use in nanomedicines. However, hydrophilicity of the ND surface strongly influences structure and dynamics of biomolecules that restrict in situ applications of ND. Therefore, fundamental understanding of the impact of hydrophilic ND surface on biomolecules at the molecular level is essential. For tRNA, we observe an enhancement of dynamical behavior in the presence of ND contrary to generally observed slow motion at strongly interacting interfaces. We took advantage of neutron scattering experiments and computer simulations to demonstrate this atypical faster dynamics of tRNA on ND surface. The strong attractive interactions between ND, tRNA, and water give rise to unlike dynamical behavior and structural changes of tRNA in front of ND compared to without ND. Our new findings may provide new design principles for safer, improved drug delivery platforms.

  1. MD Simulation on Collision Behavior Between Nano-Scale TiO₂ Particles During Vacuum Cold Spraying.

    Science.gov (United States)

    Yao, Hai-Long; Yang, Guan-Jun; Li, Chang-Jiu

    2018-04-01

    Particle collision behavior influences significantly inter-nano particle bonding formation during the nano-ceramic coating deposition by vacuum cold spraying (or aerosol deposition method). In order to illuminate the collision behavior between nano-scale ceramic particles, molecular dynamic simulation was applied to explore impact process between nano-scale TiO2 particles through controlling impact velocities. Results show that the recoil efficiency of the nano-scale TiO2 particle is decreased with the increase of the impact velocity. Nano-scale TiO2 particle exhibits localized plastic deformation during collision at low velocities, while it is intensively deformed by collision at high velocities. This intensive deformation promotes the nano-particle adhesion rather than rebounding off. A relationship between the adhesion energy and the rebound energy is established for the bonding formation of the nano-scale TiO2 particle. The adhesion energy required to the bonding formation between nano-scale ceramic particles can be produced by high velocity collision.

  2. Comparative MD Simulations Indicate a Dual Role for Arg1323.50 in Dopamine-Dependent D2R Activation.

    Directory of Open Access Journals (Sweden)

    Ralf C Kling

    Full Text Available Residue Arg3.50 belongs to the highly conserved DRY-motif of class A GPCRs, which is located at the bottom of TM3. On the one hand, Arg3.50 has been reported to help stabilize the inactive state of GPCRs, but on the other hand has also been shown to be crucial for stabilizing active receptor conformations and mediating receptor-G protein coupling. The combined results of these studies suggest that the exact function of Arg3.50 is likely to be receptor-dependent and must be characterized independently for every GPCR. Consequently, we now present comparative molecular-dynamics simulations that use our recently described inactive-state and Gα-bound active-state homology models of the dopamine D2 receptor (D2R, which are either bound to dopamine or ligand-free, performed to identify the function of Arg1323.50 in D2R. Our results are consistent with a dynamic model of D2R activation in which Arg1323.50 adopts a dual role, both by stabilizing the inactive-state receptor conformation and enhancing dopamine-dependent D2R-G protein coupling.

  3. MD simulation of organics adsorption from aqueous solution in carbon slit-like pores. Foundations of the pore blocking effect

    International Nuclear Information System (INIS)

    Gauden, Piotr A; Terzyk, Artur P; Furmaniak, Sylwester; Zieliński, Wojciech; Włoch, Jerzy; Kowalczyk, Piotr

    2014-01-01

    The results of systematic studies of organics adsorption from aqueous solutions (at the neutral pH level) in a system of slit-like carbon pores having different sizes and oxygen groups located at the pore mouth are reported. Using molecular dynamics simulations (GROMACS package) the properties of adsorbent–adsorbate (benzene, phenol or paracetamol) as well as adsorbent–water systems are discussed. After the introduction of surface oxygen functionalities, adsorption of organic compounds decreases (in accordance with experimental data) and this is caused by the accumulation of water molecules at pore entrances. The pore blocking effect decreases with the diameter of slits and practically vanishes for widths larger than approx. 0.68 nm. We observed the increase in phenol adsorption with the rise in temperature. Moreover, adsorbed molecules occupy the external surface of the slit pores (the entrances) in the case of oxidized adsorbents. Among the studied molecules benzene, phenol and paracetamol prefer an almost flat orientation and with the rise in the pore width the number of molecules oriented in parallel decreases. The decrease or increase in temperature (with respect to 298 K) leads to insignificant changes of angular orientation of adsorbed molecules. (paper)

  4. Injector MD Days 2017

    CERN Document Server

    Rumolo, G

    2017-01-01

    The Injector Machine Development (MD) days 2017 were held on 23-24 March, 2017, at CERN with thefollowing main goals:Give a chance to the MD users to present their results and show the relevant progress made in 2016 onseveral fronts.Provide the MD users and the Operation (OP) crews with a general overview on the outcome and theimpact of all ongoing MD activities.Identify the open questions and consequently define - with priorities - a list of machine studies in theinjectors for 2017 (covering the operational beams, LHC Injectors Upgrade, High Luminosity LHC,Physics Beyond Colliders, other projects).Create the opportunity to collect and document the highlights of the 2016 MDs and define the perspectivesfor 2017.Discuss how to make best use of the MD time, in particular let the main MD user express their wishesand see whether/how OP teams can contribute to their fulfilment.

  5. optimal assembly line balancing using simulation techniques

    African Journals Online (AJOL)

    user

    Department of Mechanical Engineering ... perspective on how the business operates, and ... Process simulation allows management ... improvement and change since it would be a costly ... The work content performed on an assembly line.

  6. Real time simulation techniques in Taiwan - Maanshan compact simulator

    International Nuclear Information System (INIS)

    Liang, K.-S.; Chuang, Y.-M.; Ko, H.-T.

    2004-01-01

    Recognizing the demand and potential market of simulators in various industries, a special project for real time simulation technology transfer was initiated in Taiwan in 1991. In this technology transfer program, the most advanced real-time dynamic modules for nuclear power simulation were introduced. Those modules can be divided into two categories; one is modeling related to catch dynamic response of each system, and the other is computer related to provide special real time computing environment and man-machine interface. The modeling related modules consist of the thermodynamic module, the three-dimensional core neutronics module and the advanced balance of plant module. As planned in the project, the technology transfer team should build a compact simulator for the Maanshan power plant before the end of the project to demonstrate the success of the technology transfer program. The compact simulator was designed to support the training from the regular full scope simulator which was already equipped in the Maanshan plant. The feature of this compact simulator focused on providing know-why training by the enhanced graphic display. The potential users were identified as senior operators, instructors and nuclear engineers. Total about 13 important systems were covered in the scope of the compact simulator, and multi-graphic displays from three color monitors mounted on the 10 feet compact panel were facilitated to help the user visualize detailed phenomena under scenarios of interest. (author)

  7. A general software reliability process simulation technique

    Science.gov (United States)

    Tausworthe, Robert C.

    1991-01-01

    The structure and rationale of the generalized software reliability process, together with the design and implementation of a computer program that simulates this process are described. Given assumed parameters of a particular project, the users of this program are able to generate simulated status timelines of work products, numbers of injected anomalies, and the progress of testing, fault isolation, repair, validation, and retest. Such timelines are useful in comparison with actual timeline data, for validating the project input parameters, and for providing data for researchers in reliability prediction modeling.

  8. Enhancement Corrosion Resistance of (γ-Glycidyloxypropyl-Silsesquioxane-Titanium Dioxide Films and Its Validation by Gas Molecule Diffusion Coefficients Using Molecular Dynamics (MD Simulation

    Directory of Open Access Journals (Sweden)

    Haiyan Wang

    2014-01-01

    Full Text Available Based on silsesquioxanes (SSO derived from the hydrolytic condensation of (γ-glycidyloxypropyltrimethoxysilane (GPMS and titanium tetrabutoxide (TTB, hybrid films on aluminum alloy (AA, film-GPMS-SSO (f-GS and f-GS-TTBi% (f-GSTT5%–25%, i = 5, 10, 15, 20 and 25 wt%, were prepared and tested by electrochemical measurements with typical potentiodynamic polarization curves. The Icorr values of the samples were significantly lower, comparing with the Icorr values of the f-GS, AA and f-GS modified tetraethoxysilane (TEOS in the previous study, which implies that the TTB5%–25% (TiO2 additions in the coatings indeed enhance the electrochemical corrosion resistance. Correlations between the film structures and anticorrosion properties were discussed. To validate the corresponding anticorrosion experiment results, different 3D-amorphous cubic unit cells were employed as models to investigate the self-diffusion coefficient (SDC for SO2, NO2 and H2O molecules by molecular dynamics (MD simulation. All of the SDCs calculated for SO2, NO2 and H2O diffusing in f-GSTT5%–25% cells were less than the SDCs in f-GS. These results validated the corresponding anticorrosion experiment results.

  9. Multiscale Free Energy Simulations: An Efficient Method for Connecting Classical MD Simulations to QM or QM/MM Free Energies Using Non-Boltzmann Bennett Reweighting Schemes

    Science.gov (United States)

    2015-01-01

    The reliability of free energy simulations (FES) is limited by two factors: (a) the need for correct sampling and (b) the accuracy of the computational method employed. Classical methods (e.g., force fields) are typically used for FES and present a myriad of challenges, with parametrization being a principle one. On the other hand, parameter-free quantum mechanical (QM) methods tend to be too computationally expensive for adequate sampling. One widely used approach is a combination of methods, where the free energy difference between the two end states is computed by, e.g., molecular mechanics (MM), and the end states are corrected by more accurate methods, such as QM or hybrid QM/MM techniques. Here we report two new approaches that significantly improve the aforementioned scheme; with a focus on how to compute corrections between, e.g., the MM and the more accurate QM calculations. First, a molecular dynamics trajectory that properly samples relevant conformational degrees of freedom is generated. Next, potential energies of each trajectory frame are generated with a QM or QM/MM Hamiltonian. Free energy differences are then calculated based on the QM or QM/MM energies using either a non-Boltzmann Bennett approach (QM-NBB) or non-Boltzmann free energy perturbation (NB-FEP). Both approaches are applied to calculate relative and absolute solvation free energies in explicit and implicit solvent environments. Solvation free energy differences (relative and absolute) between ethane and methanol in explicit solvent are used as the initial test case for QM-NBB. Next, implicit solvent methods are employed in conjunction with both QM-NBB and NB-FEP to compute absolute solvation free energies for 21 compounds. These compounds range from small molecules such as ethane and methanol to fairly large, flexible solutes, such as triacetyl glycerol. Several technical aspects were investigated. Ultimately some best practices are suggested for improving methods that seek to connect

  10. Comparison of radiographic technique by computer simulation

    International Nuclear Information System (INIS)

    Brochi, M.A.C.; Ghilardi Neto, T.

    1989-01-01

    A computational algorithm to compare radiographic techniques (KVp, mAs and filters) is developed based in the fixation of parameters that defines the images, such as optical density and constrast. Before the experience, the results were used in a radiography of thorax. (author) [pt

  11. Simulation of aluminium STIR casting technique

    International Nuclear Information System (INIS)

    Hafizal Yazid; Mohd Harun; Hanani Yazid; Abd Aziz Mohamed; Muhammad Rawi Muhammad Zain; Zaiton Selamat; Mohd Shariff Sattar; Muhamad Jalil; Ismail Mustapha; Razali Kasim

    2006-01-01

    In this paper, the objective is to determine the optimum impeller speed correlated with holding time to achieve homogeneous reinforcement distribution for a particular set of experimental condition. Attempts are made to simulate the flow behaviourof the liquid aluminium using FLUENT software. Stepwise impeller speed ranging from 50 to 300 rpm.with 2 impeller angle blades of 45 and 90 degree with respect to the rotational plane were used

  12. Identification of 253Md

    International Nuclear Information System (INIS)

    Kadkhodayan, B.; Czerwinski, K.R.; Kreek, S.A.; Hannink, N.J.; Gregorich, K.E.; Lee, D.M.; Nurmia, M.J.; Hoffman, D.C.; Hall, H.L.

    1992-01-01

    We have measured the half-life and production cross section of the new isotope 253 Md, produced via the 243 Am( 13 C,3n) reaction. Isolation of Md from other activities was accomplished using elution with ammonium α-hydroxyisobutyrate from a cation exchange resin column. Experiments were performed with different irradiation time intervals, but the chemical separation always began and ended at exactly the same length of time after the end of irradiation. All separations with the same irradation lengths were combined and analyzed for growth and decay of the 3.0-d 253 Fm daughter and 20.47-d 253 Es, granddaugther of 253 Md. The amount of 253 Es in each fraction depends on the length of each irradiation and the 253 Md half-life. An increase in the length of irradiation will cause a corresponding increase in the amount of the new isotope 253 Md and hence, in the amount of 253 Es produced, provided the length of irradiations are not very long compared to the half-life of 253 Md. In this way, the Md half-life was estimated to be about 6 minutes with a production cross section of the order of 50 nb. (orig.)

  13. A QM-MD simulation approach to the analysis of FRET processes in (bio)molecular systems. A case study: complexes of E. coli purine nucleoside phosphorylase and its mutants with formycin A.

    Science.gov (United States)

    Sobieraj, M; Krzyśko, K A; Jarmuła, A; Kalinowski, M W; Lesyng, B; Prokopowicz, M; Cieśla, J; Gojdź, A; Kierdaszuk, B

    2015-04-01

    Predicting FRET pathways in proteins using computer simulation techniques is very important for reliable interpretation of experimental data. A novel and relatively simple methodology has been developed and applied to purine nucleoside phosphorylase (PNP) complexed with a fluorescent ligand - formycin A (FA). FRET occurs between an excited Tyr residue (D*) and FA (A). This study aims to interpret experimental data that, among others, suggests the absence of FRET for the PNPF159A mutant in complex with FA, based on novel theoretical methodology. MD simulations for the protein molecule containing D*, and complexed with A, are carried out. Interactions of D* with its molecular environment are accounted by including changes of the ESP charges in S1, compared to S0, and computed at the SCF-CI level. FRET probability W F depends on the inverse six-power of the D*-A distance, R da . The orientational factor 0 < k(2) < 4 between D* and A is computed and included in the analysis. Finally W F is time-averaged over the MD trajectories resulting in its mean value. The red-shift of the tyrosinate anion emission and thus lack of spectral overlap integral and thermal energy dissipation are the reasons for the FRET absence in the studied mutants at pH 7 and above. The presence of the tyrosinate anion results in a competitive energy dissipation channel and red-shifted emission, thus in consequence in the absence of FRET. These studies also indicate an important role of the phenyl ring of Phe159 for FRET in the wild-type PNP, which does not exist in the Ala159 mutant, and for the effective association of PNP with FA. In a more general context, our observations point out very interesting and biologically important properties of the tyrosine residue in its excited state, which may undergo spontaneous deprotonation in the biomolecular systems, resulting further in unexpected physical and/or biological phenomena. Until now, this observation has not been widely discussed in the

  14. Toward a Rational Design of Bioactive Glasses with Optimal Structural Features: Composition–Structure Correlations Unveiled by Solid-State NMR and MD Simulations

    Science.gov (United States)

    2013-01-01

    The physiological responses of silicate-based bioactive glasses (BGs) are known to depend critically on both the P content (nP) of the glass and its silicate network connectivity (N̅BOSi). However, while the bioactivity generally displays a nonmonotonic dependence on nP itself, recent work suggest that it is merely the net orthophosphate content that directly links to the bioactivity. We exploit molecular dynamics (MD) simulations combined with 31P and 29Si solid-state nuclear magnetic resonance (NMR) spectroscopy to explore the quantitative relationships between N̅BOSi, nP, and the silicate and phosphate speciations in a series of Na2O–CaO–SiO2–P2O5 glasses spanning 2.1 ≤ N̅BOSi ≤ 2.9 and variable P2O5 contents up to 6.0 mol %. The fractional population of the orthophosphate groups remains independent of nP at a fixed N̅BOSi-value, but is reduced slightly as N̅BOSi increases. Nevertheless, P remains predominantly as readily released orthophosphate ions, whose content may be altered essentially independently of the network connectivity, thereby offering a route to optimize the glass bioactivity. We discuss the observed composition-structure links in relation to known composition-bioactivity correlations, and define how Na2O–CaO–SiO2–P2O5 compositions exhibiting an optimal bioactivity can be designed by simultaneously altering three key parameters: the silicate network connectivity, the (ortho)phosphate content, and the nNa/nCa molar ratio. PMID:24364818

  15. Characterization of the immersion properties of the peripheral membrane anchor of the FATC domain of the kinase "target of rapamycin" by NMR, oriented CD spectroscopy, and MD simulations.

    Science.gov (United States)

    Sommer, Lisa A M; Janke, J Joel; Bennett, W F Drew; Bürck, Jochen; Ulrich, Anne S; Tieleman, D Peter; Dames, Sonja A

    2014-05-08

    The multidomain ser/thr kinase "target of rapamycin" (TOR) centrally controls eukaryotic growth and metabolism. The C-terminal FATC domain is important for TOR regulation and was suggested to directly mediate TOR-membrane interactions. Here, we present a detailed characterization of the membrane immersion properties of the oxidized and reduced yeast TOR1 FATC domain (2438-2470 = y1fatc). The immersion depth was characterized by NMR-monitored interaction studies with DPC micelles containing paramagnetically tagged 5- or 16-doxyl stearic acid (5-/16-SASL) and by analyzing the paramagnetic relaxation enhancement (PRE) from Mn(2+) in the solvent. Complementary MD-simulations of micellar systems in the absence and presence of protein showed that 5-/16-SASL can move in the micelle and that 16-SASL can bend such that the doxyl group is close to the headgroup region and not deep in the interior as commonly assumed. Based on oriented CD (OCD) data, the single α-helix of oxidized/reduced y1fatc has an angle to the membrane normal of ∼30-60°/∼35-65° in neutral and ∼5-35°/∼0-30° in negatively charged bilayers. The presented experimentally well-founded models help to better understand how this redox-sensitive peripheral membrane anchor may be part of a network of protein-protein and protein-membrane interactions regulating TOR localization at different cellular membranes. Moreover, the presented work provides a good methodological reference for the structural characterization of other peripherally membrane associating proteins.

  16. Muscular Dystrophy (MD)

    Science.gov (United States)

    ... patients may need assisted ventilation to treat respiratory muscle weakness and a pacemaker for cardiac abnormalities. View Full Treatment Information Definition The muscular dystrophies (MD) are a group of more than 30 ...

  17. Acceleration techniques for dependability simulation. M.S. Thesis

    Science.gov (United States)

    Barnette, James David

    1995-01-01

    As computer systems increase in complexity, the need to project system performance from the earliest design and development stages increases. We have to employ simulation for detailed dependability studies of large systems. However, as the complexity of the simulation model increases, the time required to obtain statistically significant results also increases. This paper discusses an approach that is application independent and can be readily applied to any process-based simulation model. Topics include background on classical discrete event simulation and techniques for random variate generation and statistics gathering to support simulation.

  18. ProtoMD: A prototyping toolkit for multiscale molecular dynamics

    Science.gov (United States)

    Somogyi, Endre; Mansour, Andrew Abi; Ortoleva, Peter J.

    2016-05-01

    ProtoMD is a toolkit that facilitates the development of algorithms for multiscale molecular dynamics (MD) simulations. It is designed for multiscale methods which capture the dynamic transfer of information across multiple spatial scales, such as the atomic to the mesoscopic scale, via coevolving microscopic and coarse-grained (CG) variables. ProtoMD can be also be used to calibrate parameters needed in traditional CG-MD methods. The toolkit integrates 'GROMACS wrapper' to initiate MD simulations, and 'MDAnalysis' to analyze and manipulate trajectory files. It facilitates experimentation with a spectrum of coarse-grained variables, prototyping rare events (such as chemical reactions), or simulating nanocharacterization experiments such as terahertz spectroscopy, AFM, nanopore, and time-of-flight mass spectroscopy. ProtoMD is written in python and is freely available under the GNU General Public License from github.com/CTCNano/proto_md.

  19. Simulation-based optimization parametric optimization techniques and reinforcement learning

    CERN Document Server

    Gosavi, Abhijit

    2003-01-01

    Simulation-Based Optimization: Parametric Optimization Techniques and Reinforcement Learning introduces the evolving area of simulation-based optimization. The book's objective is two-fold: (1) It examines the mathematical governing principles of simulation-based optimization, thereby providing the reader with the ability to model relevant real-life problems using these techniques. (2) It outlines the computational technology underlying these methods. Taken together these two aspects demonstrate that the mathematical and computational methods discussed in this book do work. Broadly speaking, the book has two parts: (1) parametric (static) optimization and (2) control (dynamic) optimization. Some of the book's special features are: *An accessible introduction to reinforcement learning and parametric-optimization techniques. *A step-by-step description of several algorithms of simulation-based optimization. *A clear and simple introduction to the methodology of neural networks. *A gentle introduction to converg...

  20. Recent developments in numerical simulation techniques of thermal recovery processes

    Energy Technology Data Exchange (ETDEWEB)

    Tamim, M. [Bangladesh University of Engineering and Technology, Bangladesh (Bangladesh); Abou-Kassem, J.H. [Chemical and Petroleum Engineering Department, UAE University, Al-Ain 17555 (United Arab Emirates); Farouq Ali, S.M. [University of Alberta, Alberta (Canada)

    2000-05-01

    Numerical simulation of thermal processes (steam flooding, steam stimulation, SAGD, in-situ combustion, electrical heating, etc.) is an integral part of a thermal project design. The general tendency in the last 10 years has been to use commercial simulators. During the last decade, only a few new models have been reported in the literature. More work has been done to modify and refine solutions to existing problems to improve the efficiency of simulators. The paper discusses some of the recent developments in simulation techniques of thermal processes such as grid refinement, grid orientation, effect of temperature on relative permeability, mathematical models, and solution methods. The various aspects of simulation discussed here promote better understanding of the problems encountered in the simulation of thermal processes and will be of value to both simulator users and developers.

  1. An analog simulation technique for distributed flow systems

    DEFF Research Database (Denmark)

    Jørgensen, Sten Bay; Kümmel, Mogens

    1973-01-01

    earlier[3]. This is an important extension since flow systems are frequently controlled through manipulation of the flow rate. Previously the tech­nique has been applied with constant flows [4, 5]. Results demonstrating the new hardware are presented from simula­tion of a transportation lag and a double......Simulation of distributed flow systems in chemical engine­ering has been applied more and more during the last decade as computer techniques have developed [l]. The applications have served the purpose of identification of process dynamics and parameter estimation as well as improving process...... and process control design. Although the conventional analog computer has been expanded with hybrid techniques and digital simulation languages have appeared, none of these has demonstrated superiority in simulating distributed flow systems in general [l]. Conventional analog techniques are expensive...

  2. mdFoam+: Advanced molecular dynamics in OpenFOAM

    Science.gov (United States)

    Longshaw, S. M.; Borg, M. K.; Ramisetti, S. B.; Zhang, J.; Lockerby, D. A.; Emerson, D. R.; Reese, J. M.

    2018-03-01

    This paper introduces mdFoam+, which is an MPI parallelised molecular dynamics (MD) solver implemented entirely within the OpenFOAM software framework. It is open-source and released under the same GNU General Public License (GPL) as OpenFOAM. The source code is released as a publicly open software repository that includes detailed documentation and tutorial cases. Since mdFoam+ is designed entirely within the OpenFOAM C++ object-oriented framework, it inherits a number of key features. The code is designed for extensibility and flexibility, so it is aimed first and foremost as an MD research tool, in which new models and test cases can be developed and tested rapidly. Implementing mdFoam+ in OpenFOAM also enables easier development of hybrid methods that couple MD with continuum-based solvers. Setting up MD cases follows the standard OpenFOAM format, as mdFoam+ also relies upon the OpenFOAM dictionary-based directory structure. This ensures that useful pre- and post-processing capabilities provided by OpenFOAM remain available even though the fully Lagrangian nature of an MD simulation is not typical of most OpenFOAM applications. Results show that mdFoam+ compares well to another well-known MD code (e.g. LAMMPS) in terms of benchmark problems, although it also has additional functionality that does not exist in other open-source MD codes.

  3. Simulation of wind turbine wakes using the actuator line technique

    DEFF Research Database (Denmark)

    Sørensen, Jens Nørkær; Mikkelsen, Robert Flemming; Henningson, Dan S.

    2015-01-01

    The actuator line technique was introduced as a numerical tool to be employed in combination with large eddy simulations to enable the study of wakes and wake interaction in wind farms. The technique is today largely used for studying basic features of wakes as well as for making performance...... predictions of wind farms. In this paper, we give a short introduction to the wake problem and the actuator line methodology and present a study in which the technique is employed to determine the near-wake properties of wind turbines. The presented results include a comparison of experimental results...

  4. A computer code to simulate X-ray imaging techniques

    International Nuclear Information System (INIS)

    Duvauchelle, Philippe; Freud, Nicolas; Kaftandjian, Valerie; Babot, Daniel

    2000-01-01

    A computer code was developed to simulate the operation of radiographic, radioscopic or tomographic devices. The simulation is based on ray-tracing techniques and on the X-ray attenuation law. The use of computer-aided drawing (CAD) models enables simulations to be carried out with complex three-dimensional (3D) objects and the geometry of every component of the imaging chain, from the source to the detector, can be defined. Geometric unsharpness, for example, can be easily taken into account, even in complex configurations. Automatic translations or rotations of the object can be performed to simulate radioscopic or tomographic image acquisition. Simulations can be carried out with monochromatic or polychromatic beam spectra. This feature enables, for example, the beam hardening phenomenon to be dealt with or dual energy imaging techniques to be studied. The simulation principle is completely deterministic and consequently the computed images present no photon noise. Nevertheless, the variance of the signal associated with each pixel of the detector can be determined, which enables contrast-to-noise ratio (CNR) maps to be computed, in order to predict quantitatively the detectability of defects in the inspected object. The CNR is a relevant indicator for optimizing the experimental parameters. This paper provides several examples of simulated images that illustrate some of the rich possibilities offered by our software. Depending on the simulation type, the computation time order of magnitude can vary from 0.1 s (simple radiographic projection) up to several hours (3D tomography) on a PC, with a 400 MHz microprocessor. Our simulation tool proves to be useful in developing new specific applications, in choosing the most suitable components when designing a new testing chain, and in saving time by reducing the number of experimental tests

  5. A computer code to simulate X-ray imaging techniques

    Energy Technology Data Exchange (ETDEWEB)

    Duvauchelle, Philippe E-mail: philippe.duvauchelle@insa-lyon.fr; Freud, Nicolas; Kaftandjian, Valerie; Babot, Daniel

    2000-09-01

    A computer code was developed to simulate the operation of radiographic, radioscopic or tomographic devices. The simulation is based on ray-tracing techniques and on the X-ray attenuation law. The use of computer-aided drawing (CAD) models enables simulations to be carried out with complex three-dimensional (3D) objects and the geometry of every component of the imaging chain, from the source to the detector, can be defined. Geometric unsharpness, for example, can be easily taken into account, even in complex configurations. Automatic translations or rotations of the object can be performed to simulate radioscopic or tomographic image acquisition. Simulations can be carried out with monochromatic or polychromatic beam spectra. This feature enables, for example, the beam hardening phenomenon to be dealt with or dual energy imaging techniques to be studied. The simulation principle is completely deterministic and consequently the computed images present no photon noise. Nevertheless, the variance of the signal associated with each pixel of the detector can be determined, which enables contrast-to-noise ratio (CNR) maps to be computed, in order to predict quantitatively the detectability of defects in the inspected object. The CNR is a relevant indicator for optimizing the experimental parameters. This paper provides several examples of simulated images that illustrate some of the rich possibilities offered by our software. Depending on the simulation type, the computation time order of magnitude can vary from 0.1 s (simple radiographic projection) up to several hours (3D tomography) on a PC, with a 400 MHz microprocessor. Our simulation tool proves to be useful in developing new specific applications, in choosing the most suitable components when designing a new testing chain, and in saving time by reducing the number of experimental tests.

  6. Growth of CdTe on Si(100) surface by ionized cluster beam technique: Experimental and molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Araghi, Houshang, E-mail: araghi@aut.ac.ir [Department of Physics, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Zabihi, Zabiholah [Department of Physics, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Nayebi, Payman [Department of Physics, College of Technical and Engineering, Saveh Branch, Islamic Azad University, Saveh (Iran, Islamic Republic of); Ehsani, Mohammad Mahdi [Department of Physics, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of)

    2016-10-15

    II–VI semiconductor CdTe was grown on the Si(100) substrate surface by the ionized cluster beam (ICB) technique. In the ICB method, when vapors of solid materials such as CdTe were ejected through a nozzle of a heated crucible into a vacuum region, nanoclusters were created by an adiabatic expansion phenomenon. The clusters thus obtained were partially ionized by electron bombardment and then accelerated onto the silicon substrate at 473 K by high potentials. The cluster size was determined using a retarding field energy analyzer. The results of X-ray diffraction measurements indicate the cubic zinc blende (ZB) crystalline structure of the CdTe thin film on the silicon substrate. The CdTe thin film prepared by the ICB method had high crystalline quality. The microscopic processes involved in the ICB deposition technique, such as impact and coalescence processes, have been studied in detail by molecular dynamics (MD) simulation.

  7. Path integral molecular dynamics within the grand canonical-like adaptive resolution technique: Simulation of liquid water

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Animesh, E-mail: animesh@zedat.fu-berlin.de; Delle Site, Luigi, E-mail: dellesite@fu-berlin.de [Institute for Mathematics, Freie Universität Berlin, Berlin (Germany)

    2015-09-07

    Quantum effects due to the spatial delocalization of light atoms are treated in molecular simulation via the path integral technique. Among several methods, Path Integral (PI) Molecular Dynamics (MD) is nowadays a powerful tool to investigate properties induced by spatial delocalization of atoms; however, computationally this technique is very demanding. The above mentioned limitation implies the restriction of PIMD applications to relatively small systems and short time scales. One of the possible solutions to overcome size and time limitation is to introduce PIMD algorithms into the Adaptive Resolution Simulation Scheme (AdResS). AdResS requires a relatively small region treated at path integral level and embeds it into a large molecular reservoir consisting of generic spherical coarse grained molecules. It was previously shown that the realization of the idea above, at a simple level, produced reasonable results for toy systems or simple/test systems like liquid parahydrogen. Encouraged by previous results, in this paper, we show the simulation of liquid water at room conditions where AdResS, in its latest and more accurate Grand-Canonical-like version (GC-AdResS), is merged with two of the most relevant PIMD techniques available in the literature. The comparison of our results with those reported in the literature and/or with those obtained from full PIMD simulations shows a highly satisfactory agreement.

  8. Eutectic-based wafer-level-packaging technique for piezoresistive MEMS accelerometers and bond characterization using molecular dynamics simulations

    Science.gov (United States)

    Aono, T.; Kazama, A.; Okada, R.; Iwasaki, T.; Isono, Y.

    2018-03-01

    We developed a eutectic-based wafer-level-packaging (WLP) technique for piezoresistive micro-electromechanical systems (MEMS) accelerometers on the basis of molecular dynamics analyses and shear tests of WLP accelerometers. The bonding conditions were experimentally and analytically determined to realize a high shear strength without solder material atoms diffusing to adhesion layers. Molecular dynamics (MD) simulations and energy dispersive x-ray (EDX) spectrometry done after the shear tests clarified the eutectic reaction of the solder materials used in this research. Energy relaxation calculations in MD showed that the diffusion of solder material atoms into the adhesive layer was promoted at a higher temperature. Tensile creep MD simulations also suggested that the local potential energy in a solder material model determined the fracture points of the model. These numerical results were supported by the shear tests and EDX analyses for WLP accelerometers. Consequently, a bonding load of 9.8 kN and temperature of 300 °C were found to be rational conditions because the shear strength was sufficient to endure the polishing process after the WLP process and there was little diffusion of solder material atoms to the adhesion layer. Also, eutectic-bonding-based WLP was effective for controlling the attenuation of the accelerometers by determining the thickness of electroplated solder materials that played the role of a cavity between the accelerometers and lids. If the gap distance between the two was less than 6.2 µm, the signal gains for x- and z-axis acceleration were less than 20 dB even at the resonance frequency due to air-damping.

  9. Application of the PRBS/FFT technique to digital simulations

    International Nuclear Information System (INIS)

    Hinds, H.W.

    1977-01-01

    This paper describes a method for obtaining a small-signal frequency response from a digital dynamic simulation. It employs a modified form of the PRBS/FFT technique, whereby a system is perturbed by a pseudo-random binary sequence and its response is analyzed using a fast Fourier transform-based program. Two applications of the technique are described; one involves a set of two coupled, second-order, ordinary differential equations; the other is a set of non-linear partial differential equations describing the thermohydraulic behaviour of water boiling in a fuel channel. (author)

  10. Application of simulation techniques in the probabilistic fracture mechanics

    International Nuclear Information System (INIS)

    De Ruyter van Steveninck, J.L.

    1995-03-01

    The Monte Carlo simulation is applied on a model of the fracture mechanics in order to assess the applicability of this simulation technique in the probabilistic fracture mechanics. By means of the fracture mechanics model the brittle fracture of a steel container or pipe with defects can be predicted. By means of the Monte Carlo simulation also the uncertainty regarding failures can be determined. Based on the variations in the toughness of the fracture and the defect dimensions the distribution of the chance of failure is determined. Also attention is paid to the impact of dependency between uncertain variables. Furthermore, the influence of the applied distributions of the uncertain variables and non-destructive survey on the chance of failure is analyzed. The Monte Carlo simulation results agree quite well with the results of other methods from the probabilistic fracture mechanics. If an analytic expression can be found for the chance of failure, it is possible to determine the variation of the chance of failure, next to an estimation of the chance of failure. It also appears that the dependency between the uncertain variables has a large impact on the chance of failure. It is also concluded from the simulation that the chance of failure strongly depends on the crack depth, and therefore of the distribution of the crack depth. 15 figs., 7 tabs., 12 refs

  11. A close examination of the structure and dynamics of HC(NH2)2PbI3by MD simulations and group theory

    KAUST Repository

    Carignano, M. A.; Saeed, Y.; Aravindh, S. Assa; Roqan, Iman S.; Even, J.; Katan, C.

    2016-01-01

    The formamidinium lead iodide hybrid perovskite is studied using first principles molecular dynamics simulations and further analyzed using group theory. The simulations are performed on large supercells containing 768 atoms under isothermal

  12. Nuclear fuel cycle cost analysis using a probabilistic simulation technique

    International Nuclear Information System (INIS)

    Won, Il Ko; Jong, Won Choi; Chul, Hyung Kang; Jae, Sol Lee; Kun, Jai Lee

    1998-01-01

    A simple approach was described to incorporate the Monte Carlo simulation technique into a fuel cycle cost estimate. As a case study, the once-through and recycle fuel cycle options were tested with some alternatives (ie. the change of distribution type for input parameters), and the simulation results were compared with the values calculated by a deterministic method. A three-estimate approach was used for converting cost inputs into the statistical parameters of assumed probabilistic distributions. It was indicated that the Monte Carlo simulation by a Latin Hypercube Sampling technique and subsequent sensitivity analyses were useful for examining uncertainty propagation of fuel cycle costs, and could more efficiently provide information to decisions makers than a deterministic method. It was shown from the change of distribution types of input parameters that the values calculated by the deterministic method were set around a 40 th ∼ 50 th percentile of the output distribution function calculated by probabilistic simulation. Assuming lognormal distribution of inputs, however, the values calculated by the deterministic method were set around an 85 th percentile of the output distribution function calculated by probabilistic simulation. It was also indicated from the results of the sensitivity analysis that the front-end components were generally more sensitive than the back-end components, of which the uranium purchase cost was the most important factor of all. It showed, also, that the discount rate made many contributions to the fuel cycle cost, showing the rank of third or fifth of all components. The results of this study could be useful in applications to another options, such as the Dcp (Direct Use of PWR spent fuel In Candu reactors) cycle with high cost uncertainty

  13. Application perspectives of simulation techniques CFD in nuclear power plants

    International Nuclear Information System (INIS)

    Galindo G, I. F.

    2013-10-01

    The scenarios simulation in nuclear power plants is usually carried out with system codes that are based on concentrated parameters networks. However situations exist in some components where the flow is predominantly 3-D, as they are the natural circulation, mixed and stratification phenomena. The simulation techniques of computational fluid dynamics (CFD) have the potential to simulate these flows numerically. The use of CFD simulations embraces many branches of the engineering and continues growing, however, in relation to its application with respect to the problems related with the safety in nuclear power plants, has a smaller development, although is accelerating quickly and is expected that in the future they play a more emphasized paper in the analyses. A main obstacle to be able to achieve a general acceptance of the CFD is that the simulations should have very complete validation studies, sometimes not available. In this article a general panorama of the state of the methods application CFD in nuclear power plants is presented and the problem associated to its routine application and acceptance, including the view point of the regulatory authorities. Application examples are revised in those that the CFD offers real benefits and are also presented two illustrative study cases of the application of CFD techniques. The case of a water recipient with a heat source in its interior, similar to spent fuel pool of a nuclear power plant is presented firstly; and later the case of the Boron dilution of a water volume that enters to a nuclear reactor is presented. We can conclude that the CFD technology represents a very important opportunity to improve the phenomena understanding with a strong component 3-D and to contribute in the uncertainty reduction. (Author)

  14. D Digital Simulation of Minnan Temple Architecture CAISSON'S Craft Techniques

    Science.gov (United States)

    Lin, Y. C.; Wu, T. C.; Hsu, M. F.

    2013-07-01

    Caisson is one of the important representations of the Minnan (southern Fujian) temple architecture craft techniques and decorative aesthetics. The special component design and group building method present the architectural thinking and personal characteristics of great carpenters of Minnan temple architecture. In late Qing Dynasty, the appearance and style of caissons of famous temples in Taiwan apparently presented the building techniques of the great carpenters. However, as the years went by, the caisson design and craft techniques were not fully inherited, which has been a great loss of cultural assets. Accordingly, with the caisson of Fulong temple, a work by the well-known great carpenter in Tainan as an example, this study obtained the thinking principles of the original design and the design method at initial period of construction through interview records and the step of redrawing the "Tng-Ko" (traditional design, stakeout and construction tool). We obtained the 3D point cloud model of the caisson of Fulong temple using 3D laser scanning technology, and established the 3D digital model of each component of the caisson. Based on the caisson component procedure obtained from interview records, this study conducted the digital simulation of the caisson component to completely recode and present the caisson design, construction and completion procedure. This model of preserving the craft techniques for Minnan temple caisson by using digital technology makes specific contribution to the heritage of the craft techniques while providing an important reference for the digital preservation of human cultural assets.

  15. Technique for in situ leach simulation of uranium ores

    International Nuclear Information System (INIS)

    Grant, D.C.; Seidel, D.C.; Nichols, I.L.

    1985-01-01

    In situ uranium mining offers the advantages of minimal environmental disturbance, low capital and operating costs, and reduced mining development time. It is becoming an increasingly attractive mining method for the recovery of uranium from secondary ore deposits. In order to better understand the process, a laboratory technique was developed and used to study and simulate both the chemical and physical phenomena occurring in ore bodies during in situ leaching. The laboratory simulation technique has been used to determine effects of leaching variables on permeability, uranium recovery, and post-leach aquifer restoration. This report describes the simulation system and testing procedure in sufficient detail to allow the construction of the system, and to perform the desired leaching tests. With construction of such a system, in situ leaching of a given ore using various leach conditions can be evaluated relatively rapidly in the laboratory. Not only could optimum leach conditions be selected for existing ore bodies, but also exploitation of new ore bodies could be accelerated. 8 references, 8 figures, 2 tables

  16. A New Multiscale Technique for Time-Accurate Geophysics Simulations

    Science.gov (United States)

    Omelchenko, Y. A.; Karimabadi, H.

    2006-12-01

    Large-scale geophysics systems are frequently described by multiscale reactive flow models (e.g., wildfire and climate models, multiphase flows in porous rocks, etc.). Accurate and robust simulations of such systems by traditional time-stepping techniques face a formidable computational challenge. Explicit time integration suffers from global (CFL and accuracy) timestep restrictions due to inhomogeneous convective and diffusion processes, as well as closely coupled physical and chemical reactions. Application of adaptive mesh refinement (AMR) to such systems may not be always sufficient since its success critically depends on a careful choice of domain refinement strategy. On the other hand, implicit and timestep-splitting integrations may result in a considerable loss of accuracy when fast transients in the solution become important. To address this issue, we developed an alternative explicit approach to time-accurate integration of such systems: Discrete-Event Simulation (DES). DES enables asynchronous computation by automatically adjusting the CPU resources in accordance with local timescales. This is done by encapsulating flux- conservative updates of numerical variables in the form of events, whose execution and synchronization is explicitly controlled by imposing accuracy and causality constraints. As a result, at each time step DES self- adaptively updates only a fraction of the global system state, which eliminates unnecessary computation of inactive elements. DES can be naturally combined with various mesh generation techniques. The event-driven paradigm results in robust and fast simulation codes, which can be efficiently parallelized via a new preemptive event processing (PEP) technique. We discuss applications of this novel technology to time-dependent diffusion-advection-reaction and CFD models representative of various geophysics applications.

  17. Validation techniques of agent based modelling for geospatial simulations

    Directory of Open Access Journals (Sweden)

    M. Darvishi

    2014-10-01

    Full Text Available One of the most interesting aspects of modelling and simulation study is to describe the real world phenomena that have specific properties; especially those that are in large scales and have dynamic and complex behaviours. Studying these phenomena in the laboratory is costly and in most cases it is impossible. Therefore, Miniaturization of world phenomena in the framework of a model in order to simulate the real phenomena is a reasonable and scientific approach to understand the world. Agent-based modelling and simulation (ABMS is a new modelling method comprising of multiple interacting agent. They have been used in the different areas; for instance, geographic information system (GIS, biology, economics, social science and computer science. The emergence of ABM toolkits in GIS software libraries (e.g. ESRI’s ArcGIS, OpenMap, GeoTools, etc for geospatial modelling is an indication of the growing interest of users to use of special capabilities of ABMS. Since ABMS is inherently similar to human cognition, therefore it could be built easily and applicable to wide range applications than a traditional simulation. But a key challenge about ABMS is difficulty in their validation and verification. Because of frequent emergence patterns, strong dynamics in the system and the complex nature of ABMS, it is hard to validate and verify ABMS by conventional validation methods. Therefore, attempt to find appropriate validation techniques for ABM seems to be necessary. In this paper, after reviewing on Principles and Concepts of ABM for and its applications, the validation techniques and challenges of ABM validation are discussed.

  18. [Preparation of simulate craniocerebral models via three dimensional printing technique].

    Science.gov (United States)

    Lan, Q; Chen, A L; Zhang, T; Zhu, Q; Xu, T

    2016-08-09

    Three dimensional (3D) printing technique was used to prepare the simulate craniocerebral models, which were applied to preoperative planning and surgical simulation. The image data was collected from PACS system. Image data of skull bone, brain tissue and tumors, cerebral arteries and aneurysms, and functional regions and relative neural tracts of the brain were extracted from thin slice scan (slice thickness 0.5 mm) of computed tomography (CT), magnetic resonance imaging (MRI, slice thickness 1mm), computed tomography angiography (CTA), and functional magnetic resonance imaging (fMRI) data, respectively. MIMICS software was applied to reconstruct colored virtual models by identifying and differentiating tissues according to their gray scales. Then the colored virtual models were submitted to 3D printer which produced life-sized craniocerebral models for surgical planning and surgical simulation. 3D printing craniocerebral models allowed neurosurgeons to perform complex procedures in specific clinical cases though detailed surgical planning. It offered great convenience for evaluating the size of spatial fissure of sellar region before surgery, which helped to optimize surgical approach planning. These 3D models also provided detailed information about the location of aneurysms and their parent arteries, which helped surgeons to choose appropriate aneurismal clips, as well as perform surgical simulation. The models further gave clear indications of depth and extent of tumors and their relationship to eloquent cortical areas and adjacent neural tracts, which were able to avoid surgical damaging of important neural structures. As a novel and promising technique, the application of 3D printing craniocerebral models could improve the surgical planning by converting virtual visualization into real life-sized models.It also contributes to functional anatomy study.

  19. Validation techniques of agent based modelling for geospatial simulations

    Science.gov (United States)

    Darvishi, M.; Ahmadi, G.

    2014-10-01

    One of the most interesting aspects of modelling and simulation study is to describe the real world phenomena that have specific properties; especially those that are in large scales and have dynamic and complex behaviours. Studying these phenomena in the laboratory is costly and in most cases it is impossible. Therefore, Miniaturization of world phenomena in the framework of a model in order to simulate the real phenomena is a reasonable and scientific approach to understand the world. Agent-based modelling and simulation (ABMS) is a new modelling method comprising of multiple interacting agent. They have been used in the different areas; for instance, geographic information system (GIS), biology, economics, social science and computer science. The emergence of ABM toolkits in GIS software libraries (e.g. ESRI's ArcGIS, OpenMap, GeoTools, etc) for geospatial modelling is an indication of the growing interest of users to use of special capabilities of ABMS. Since ABMS is inherently similar to human cognition, therefore it could be built easily and applicable to wide range applications than a traditional simulation. But a key challenge about ABMS is difficulty in their validation and verification. Because of frequent emergence patterns, strong dynamics in the system and the complex nature of ABMS, it is hard to validate and verify ABMS by conventional validation methods. Therefore, attempt to find appropriate validation techniques for ABM seems to be necessary. In this paper, after reviewing on Principles and Concepts of ABM for and its applications, the validation techniques and challenges of ABM validation are discussed.

  20. Radiotracer technique for leakage detection under simulated conditions

    International Nuclear Information System (INIS)

    Yelgaonkar, V.N.; Sharma, V.K.; Tapase, A.S.

    2001-01-01

    Radiotracer techniques are often used to locate leaks in underground pipelines. An attempt was made to standardize radiotracer pulse migration in terms of minimum detectable limit. For this purpose a 6 inch diameter 1200 long steel pipe was used. Two leak rates viz. 10 litres per minute and 1 litre per minute with an accuracy of ± 10% were simulated. The experiments on this pipeline showed that this method could be used to locate a leak of the order of 1 litre per minute in a 6 inch diameter isolated underground pipeline. (author)

  1. Strategies in edge plasma simulation using adaptive dynamic nodalization techniques

    International Nuclear Information System (INIS)

    Kainz, A.; Weimann, G.; Kamelander, G.

    2003-01-01

    A wide span of steady-state and transient edge plasma processes simulation problems require accurate discretization techniques and can then be treated with Finite Element (FE) and Finite Volume (FV) methods. The software used here to meet these meshing requirements is a 2D finite element grid generator. It allows to produce adaptive unstructured grids taking into consideration the flux surface characteristics. To comply with the common mesh handling features of FE/FV packages, some options have been added to the basic generation tool. These enhancements include quadrilateral meshes without non-regular transition elements obtained by substituting them by transition constructions consisting of regular quadrilateral elements. Furthermore triangular grids can be created with one edge parallel to the magnetic field and modified by the basic adaptation/realignment techniques. Enhanced code operation properties and processing capabilities are expected. (author)

  2. Parallel pic plasma simulation through particle decomposition techniques

    International Nuclear Information System (INIS)

    Briguglio, S.; Vlad, G.; Di Martino, B.; Naples, Univ. 'Federico II'

    1998-02-01

    Particle-in-cell (PIC) codes are among the major candidates to yield a satisfactory description of the detail of kinetic effects, such as the resonant wave-particle interaction, relevant in determining the transport mechanism in magnetically confined plasmas. A significant improvement of the simulation performance of such codes con be expected from parallelization, e.g., by distributing the particle population among several parallel processors. Parallelization of a hybrid magnetohydrodynamic-gyrokinetic code has been accomplished within the High Performance Fortran (HPF) framework, and tested on the IBM SP2 parallel system, using a 'particle decomposition' technique. The adopted technique requires a moderate effort in porting the code in parallel form and results in intrinsic load balancing and modest inter processor communication. The performance tests obtained confirm the hypothesis of high effectiveness of the strategy, if targeted towards moderately parallel architectures. Optimal use of resources is also discussed with reference to a specific physics problem [it

  3. CT simulation technique for craniospinal irradiation in supine position

    International Nuclear Information System (INIS)

    Lee, Suk; Kim, Yong Bae; Chu, Sung Sil; Suh, Chang Ok; Kwon, Soo Il

    2002-01-01

    In order to perform craniospinal irradiation (CSI) in the supine position on patients who are unable to lie in the prone position, a new simulation technique using a CT simulator was developed and its availability was evaluated. A CT simulator and a 3-D conformal treatment planning system were used to develop CSI in the supine position. The head and neck were immobilized with a thermoplastic mask in the supine position and the entire body was immobilized with a Vac-Loc. A volumetric image was then obtained using the CT simulator. In order to improve the reproducibility of the patients' setup, datum lines and points were marked on the head and the body. Virtual fluoroscopy was performed with the removal of visual obstacles such as the treatment table or the immobilization devices. After the virtual simulation, the treatment isocenters of each field were marked on the body and the immobilization devices at the conventional simulation room. Each treatment field was confirmed by comparing the fluoroscopy images with the digitally reconstructed radiography (DRR)/digitally composite radiography (DCR) images from the virtual simulation. The port verification films from the first treatment were also compared with the DRR/DCR images for a geometrical verification. CSI in the supine position was successfully performed in 9 patients. It required less than 20 minutes to construct the immobilization device and to obtain the whole body volumetric images. This made it possible to not only reduce the patients' inconvenience, but also to eliminate the position change variables during the long conventional simulation process. In addition, by obtaining the CT volumetric image, critical organs, such as the eyeballs and spinal cord, were better defined, and the accuracy of the port designs and shielding was improved. The difference between the DRRs and the portal films were less than 3 mm in the vertebral contour. CSI in the supine position is feasible in patients who cannot lie on

  4. CT simulation technique for craniospinal irradiation in supine position

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Suk; Kim, Yong Bae; Chu, Sung Sil; Suh, Chang Ok [Yonsei Cancer Center, College of Medicine, Yonsei University, Seoul (Korea, Republic of); Kwon, Soo Il [Kyonggi University, Seoul (Korea, Republic of)

    2002-06-15

    In order to perform craniospinal irradiation (CSI) in the supine position on patients who are unable to lie in the prone position, a new simulation technique using a CT simulator was developed and its availability was evaluated. A CT simulator and a 3-D conformal treatment planning system were used to develop CSI in the supine position. The head and neck were immobilized with a thermoplastic mask in the supine position and the entire body was immobilized with a Vac-Loc. A volumetric image was then obtained using the CT simulator. In order to improve the reproducibility of the patients' setup, datum lines and points were marked on the head and the body. Virtual fluoroscopy was performed with the removal of visual obstacles such as the treatment table or the immobilization devices. After the virtual simulation, the treatment isocenters of each field were marked on the body and the immobilization devices at the conventional simulation room. Each treatment field was confirmed by comparing the fluoroscopy images with the digitally reconstructed radiography (DRR)/digitally composite radiography (DCR) images from the virtual simulation. The port verification films from the first treatment were also compared with the DRR/DCR images for a geometrical verification. CSI in the supine position was successfully performed in 9 patients. It required less than 20 minutes to construct the immobilization device and to obtain the whole body volumetric images. This made it possible to not only reduce the patients' inconvenience, but also to eliminate the position change variables during the long conventional simulation process. In addition, by obtaining the CT volumetric image, critical organs, such as the eyeballs and spinal cord, were better defined, and the accuracy of the port designs and shielding was improved. The difference between the DRRs and the portal films were less than 3 mm in the vertebral contour. CSI in the supine position is feasible in patients who cannot

  5. ADVANCED TECHNIQUES FOR RESERVOIR SIMULATION AND MODELING OF NONCONVENTIONAL WELLS

    Energy Technology Data Exchange (ETDEWEB)

    Louis J. Durlofsky; Khalid Aziz

    2004-08-20

    Nonconventional wells, which include horizontal, deviated, multilateral and ''smart'' wells, offer great potential for the efficient management of oil and gas reservoirs. These wells are able to contact larger regions of the reservoir than conventional wells and can also be used to target isolated hydrocarbon accumulations. The use of nonconventional wells instrumented with downhole inflow control devices allows for even greater flexibility in production. Because nonconventional wells can be very expensive to drill, complete and instrument, it is important to be able to optimize their deployment, which requires the accurate prediction of their performance. However, predictions of nonconventional well performance are often inaccurate. This is likely due to inadequacies in some of the reservoir engineering and reservoir simulation tools used to model and optimize nonconventional well performance. A number of new issues arise in the modeling and optimization of nonconventional wells. For example, the optimal use of downhole inflow control devices has not been addressed for practical problems. In addition, the impact of geological and engineering uncertainty (e.g., valve reliability) has not been previously considered. In order to model and optimize nonconventional wells in different settings, it is essential that the tools be implemented into a general reservoir simulator. This simulator must be sufficiently general and robust and must in addition be linked to a sophisticated well model. Our research under this five year project addressed all of the key areas indicated above. The overall project was divided into three main categories: (1) advanced reservoir simulation techniques for modeling nonconventional wells; (2) improved techniques for computing well productivity (for use in reservoir engineering calculations) and for coupling the well to the simulator (which includes the accurate calculation of well index and the modeling of multiphase flow

  6. A New Simulation Technique for Study of Collisionless Shocks: Self-Adaptive Simulations

    International Nuclear Information System (INIS)

    Karimabadi, H.; Omelchenko, Y.; Driscoll, J.; Krauss-Varban, D.; Fujimoto, R.; Perumalla, K.

    2005-01-01

    The traditional technique for simulating physical systems modeled by partial differential equations is by means of time-stepping methodology where the state of the system is updated at regular discrete time intervals. This method has inherent inefficiencies. In contrast to this methodology, we have developed a new asynchronous type of simulation based on a discrete-event-driven (as opposed to time-driven) approach, where the simulation state is updated on a 'need-to-be-done-only' basis. Here we report on this new technique, show an example of particle acceleration in a fast magnetosonic shockwave, and briefly discuss additional issues that we are addressing concerning algorithm development and parallel execution

  7. Using simulation-optimization techniques to improve multiphase aquifer remediation

    Energy Technology Data Exchange (ETDEWEB)

    Finsterle, S.; Pruess, K. [Lawrence Berkeley Laboratory, Berkeley, CA (United States)

    1995-03-01

    The T2VOC computer model for simulating the transport of organic chemical contaminants in non-isothermal multiphase systems has been coupled to the ITOUGH2 code which solves parameter optimization problems. This allows one to use linear programming and simulated annealing techniques to solve groundwater management problems, i.e. the optimization of operations for multiphase aquifer remediation. A cost function has to be defined, containing the actual and hypothetical expenses of a cleanup operation which depend - directly or indirectly - on the state variables calculated by T2VOC. Subsequently, the code iteratively determines a remediation strategy (e.g. pumping schedule) which minimizes, for instance, pumping and energy costs, the time for cleanup, and residual contamination. We discuss an illustrative sample problem to discuss potential applications of the code. The study shows that the techniques developed for estimating model parameters can be successfully applied to the solution of remediation management problems. The resulting optimum pumping scheme depends, however, on the formulation of the remediation goals and the relative weighting between individual terms of the cost function.

  8. Simulation error propagation for a dynamic rod worth measurement technique

    International Nuclear Information System (INIS)

    Kastanya, D.F.; Turinsky, P.J.

    1996-01-01

    KRSKO nuclear station, subsequently adapted by Westinghouse, introduced the dynamic rod worth measurement (DRWM) technique for measuring pressurized water reactor rod worths. This technique has the potential for reduced test time and primary loop waste water versus alternatives. The measurement is performed starting from a slightly supercritical state with all rods out (ARO), driving a bank in at the maximum stepping rate, and recording the ex-core detectors responses and bank position as a function of time. The static bank worth is obtained by (1) using the ex-core detectors' responses to obtain the core average flux (2) using the core average flux in the inverse point-kinetics equations to obtain the dynamic bank worth (3) converting the dynamic bank worth to the static bank worth. In this data interpretation process, various calculated quantities obtained from a core simulator are utilized. This paper presents an analysis of the sensitivity to the impact of core simulator errors on the deduced static bank worth

  9. Numerical techniques for large cosmological N-body simulations

    International Nuclear Information System (INIS)

    Efstathiou, G.; Davis, M.; Frenk, C.S.; White, S.D.M.

    1985-01-01

    We describe and compare techniques for carrying out large N-body simulations of the gravitational evolution of clustering in the fundamental cube of an infinite periodic universe. In particular, we consider both particle mesh (PM) codes and P 3 M codes in which a higher resolution force is obtained by direct summation of contributions from neighboring particles. We discuss the mesh-induced anisotropies in the forces calculated by these schemes, and the extent to which they can model the desired 1/r 2 particle-particle interaction. We also consider how transformation of the time variable can improve the efficiency with which the equations of motion are integrated. We present tests of the accuracy with which the resulting schemes conserve energy and are able to follow individual particle trajectories. We have implemented an algorithm which allows initial conditions to be set up to model any desired spectrum of linear growing mode density fluctuations. A number of tests demonstrate the power of this algorithm and delineate the conditions under which it is effective. We carry out several test simulations using a variety of techniques in order to show how the results are affected by dynamic range limitations in the force calculations, by boundary effects, by residual artificialities in the initial conditions, and by the number of particles employed. For most purposes cosmological simulations are limited by the resolution of their force calculation rather than by the number of particles they can employ. For this reason, while PM codes are quite adequate to study the evolution of structure on large scale, P 3 M methods are to be preferred, in spite of their greater cost and complexity, whenever the evolution of small-scale structure is important

  10. Simulation of wind turbine wakes using the actuator line technique.

    Science.gov (United States)

    Sørensen, Jens N; Mikkelsen, Robert F; Henningson, Dan S; Ivanell, Stefan; Sarmast, Sasan; Andersen, Søren J

    2015-02-28

    The actuator line technique was introduced as a numerical tool to be employed in combination with large eddy simulations to enable the study of wakes and wake interaction in wind farms. The technique is today largely used for studying basic features of wakes as well as for making performance predictions of wind farms. In this paper, we give a short introduction to the wake problem and the actuator line methodology and present a study in which the technique is employed to determine the near-wake properties of wind turbines. The presented results include a comparison of experimental results of the wake characteristics of the flow around a three-bladed model wind turbine, the development of a simple analytical formula for determining the near-wake length behind a wind turbine and a detailed investigation of wake structures based on proper orthogonal decomposition analysis of numerically generated snapshots of the wake. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  11. Verina Morton Jones, MD.

    Science.gov (United States)

    Rishworth, Susan K

    2012-01-01

    The purpose of this historical article is to demonstrate, as the biography of Verina Morton Jones, MD, is uncovered, the difficulties inherent in researching original source material on the lives of 19th- and early 20th-century African American physicians as well as the great benefits derived from doing this research. The procedures used include basic archival research and close examination of published materials about her in the past, in conjunction with oral history. Original correspondence from Dr Morton Jones to her niece and nephew is used to illustrate events in her life and the thoughts and attitudes she expressed. Some of these thoughts and attitudes reflect those current situations in which African Americans found themselves, and others are quite unique, no doubt owing to her privileged position in the African American community. The principle conclusions reached include the great benefits derived from doing this kind of research, as difficult and time-consuming as that may be, with the enhanced knowledge and appreciation of the heritage of African American physicians, and insights into American social history during this period.

  12. Harold E. Varmus, MD.

    Science.gov (United States)

    Varmus, H E

    1995-06-01

    On November 19, 1993, the Senate approved the nomination of Harold E. Varmus, MD, as Director of the National Institutes of Health (NIH). Varmus, who received the 1989 Nobel Prize in Medicine, brought unquestioned credentials as a scientist to the NIH. Despite his limited background as an administrator, Varmus has received high marks from most observers for improving the morale of NIH staffers and implementing streamlined procedures in the grant review process. His tenure has not been free of controversy, however. Many clinical researchers have long felt there is a bias in NIH study sections against patient-oriented research. A recent study sponsored by the Division of Research Grants confirmed the lower success rate of patient-oriented research proposals, but the outcome of these findings remains unclear. Faced with mounting political pressure for a balanced budget, and the resultant reduction of funding to many branches of government, Varmus has been a strong voice for non-targeted investigator initiated research. Interviewed in his office in Building One on the NIH campus in Bethesda, Maryland, Varmus discussed the state of patient oriented research, the evolving role of the NIH in supporting science, and just where the money to pay for it should be found.

  13. ADT fast losses MD

    CERN Document Server

    Priebe, A; Dehning, B; Redaelli, S; Salvachua Ferrando, BM; Sapinski, M; Solfaroli Camillocci, M; Valuch, D

    2013-01-01

    The fast beam losses in the order of 1 ms are expected to be a potential major luminosity limitation for higher beam energies after the LHC long shutdown (LS1). Therefore a Quench Test is planned in the winter 2013 to estimate the quench limit in this timescale and revise the current models. This experiment was devoted to determination the LHC Transverse Damper (ADT) as a system for fast losses induction. A non-standard operation of the ADT was used to develop the beam oscillation instead of suppressing them. The sign flip method had allowed us to create the fast losses within several LHC turns at 450 GeV during the previous test (26th March 2012). Thus, the ADT could be potentially used for the studies of the UFO ("Unidentied Falling Object") impact on the cold magnets. Verification of the system capability and investigations of the disturbed beam properties were the main objectives of this MD. During the experiment, the pilot bunches of proton beam were excited independently in the horizontal and vertical ...

  14. Parallel Reservoir Simulations with Sparse Grid Techniques and Applications to Wormhole Propagation

    KAUST Repository

    Wu, Yuanqing

    2015-01-01

    the traditional simulation technique relying on the Darcy framework, we propose a new framework called Darcy-Brinkman-Forchheimer framework to simulate wormhole propagation. Furthermore, to process the large quantity of cells in the simulation grid and shorten

  15. Synergy between NMR measurements and MD simulations of protein/RNA complexes: application to the RRMs, the most common RNA recognition motifs

    Czech Academy of Sciences Publication Activity Database

    Krepl, Miroslav; Clery, A.; Blatter, M.; Allain, F.H.T.; Šponer, Jiří

    2016-01-01

    Roč. 44, č. 13 (2016), s. 6452-6470 ISSN 0305-1048 Institutional support: RVO:68081707 Keywords : molecular- dynamics simulations * particle mesh ewald * pre-ribosomal-rna Subject RIV: BO - Biophysics Impact factor: 10.162, year: 2016

  16. A Monte Carlo simulation technique to determine the optimal portfolio

    Directory of Open Access Journals (Sweden)

    Hassan Ghodrati

    2014-03-01

    Full Text Available During the past few years, there have been several studies for portfolio management. One of the primary concerns on any stock market is to detect the risk associated with various assets. One of the recognized methods in order to measure, to forecast, and to manage the existing risk is associated with Value at Risk (VaR, which draws much attention by financial institutions in recent years. VaR is a method for recognizing and evaluating of risk, which uses the standard statistical techniques and the method has been used in other fields, increasingly. The present study has measured the value at risk of 26 companies from chemical industry in Tehran Stock Exchange over the period 2009-2011 using the simulation technique of Monte Carlo with 95% confidence level. The used variability in the present study has been the daily return resulted from the stock daily price change. Moreover, the weight of optimal investment has been determined using a hybrid model called Markowitz and Winker model in each determined stocks. The results showed that the maximum loss would not exceed from 1259432 Rials at 95% confidence level in future day.

  17. The molecular mechanism of bisphenol A (BPA as an endocrine disruptor by interacting with nuclear receptors: insights from molecular dynamics (MD simulations.

    Directory of Open Access Journals (Sweden)

    Lanlan Li

    Full Text Available Bisphenol A (BPA can interact with nuclear receptors and affect the normal function of nuclear receptors in very low doses, which causes BPA to be one of the most controversial endocrine disruptors. However, the detailed molecular mechanism about how BPA interferes the normal function of nuclear receptors is still undiscovered. Herein, molecular dynamics simulations were performed to explore the detailed interaction mechanism between BPA with three typical nuclear receptors, including hERα, hERRγ and hPPARγ. The simulation results and calculated binding free energies indicate that BPA can bind to these three nuclear receptors. The binding affinities of BPA were slightly lower than that of E2 to these three receptors. The simulation results proved that the binding process was mainly driven by direct hydrogen bond and hydrophobic interactions. In addition, structural analysis suggested that BPA could interact with these nuclear receptors by mimicking the action of natural hormone and keeping the nuclear receptors in active conformations. The present work provided the structural evidence to recognize BPA as an endocrine disruptor and would be important guidance for seeking safer substitutions of BPA.

  18. Virtual synthesis of crystals using ab initio MD: Case study on LiFePO4

    Science.gov (United States)

    Mishra, S. B.; Nanda, B. R. K.

    2017-05-01

    Molecular dynamics simulation technique is fairly successful in studying the structural aspects and dynamics of fluids. Here we study the ability of ab initio molecular dynamics (ab initio MD) to carry out virtual experiments to synthesize new crystalline materials and to predict their structures. For this purpose the olivine phosphate LiFePO4 (LFPO) is used as an example. As transition metal oxides in general are stabilized with layered geometry, we carried out ab initio MD simulations over a hypothetical layered configuration consisting of alternate LiPO2 and FeO2 layers. With intermittent steps of electron minimization, the resulted equilibrium lattice consist of PO4 tetrahedra and distorted Fe-O complexes similar to the one observed in the experimental lattice.

  19. Data supporting beta-amyloid dimer structural transitions and protein–lipid interactions on asymmetric lipid bilayer surfaces using MD simulations on experimentally derived NMR protein structures

    Directory of Open Access Journals (Sweden)

    Sara Y. Cheng

    2016-06-01

    Full Text Available This data article supports the research article entitled “Maximally Asymmetric Transbilayer Distribution of Anionic Lipids Alters the Structure and interaction with Lipids of an Amyloidogenic Protein Dimer Bound to the Membrane Surface” [1]. We describe supporting data on the binding kinetics, time evolution of secondary structure, and residue-contact maps of a surface-absorbed beta-amyloid dimer protein on different membrane surfaces. We further demonstrate the sorting of annular and non-annular regions of the protein/lipid bilayer simulation systems, and the correlation of lipid-number mismatch and surface area per lipid mismatch of asymmetric lipid membranes.

  20. Potential of mean force for ion pairs in non-aqueous solvents. Comparison of polarizable and non-polarizable MD simulations

    Science.gov (United States)

    Odinokov, A. V.; Leontyev, I. V.; Basilevsky, M. V.; Petrov, N. Ch.

    2011-01-01

    Potentials of mean force (PMF) are calculated for two model ion pairs in two non-aqueous solvents. Standard non-polarizable molecular dynamics simulation (NPMD) and approximate polarizable simulation (PMD) are implemented and compared as tools for monitoring PMF profiles. For the polar solvent (dimethylsulfoxide, DMSO) the PMF generated in terms of the NPMD reproduces fairly well the refined PMD-PMF profile. For the non-polar solvent (benzene) the conventional NPMD computation proves to be deficient. The validity of the correction found in terms of the approximate PMD approach is verified by its comparison with the result of the explicit PMD computation in benzene. The shapes of the PMF profiles in DMSO and in benzene are quite different. In DMSO, owing to dielectric screening, the PMF presents a flat plot with a shallow minimum positioned in the vicinity of the van der Waals contact of the ion pair. For the benzene case, the observed minimum proves to be unexpectedly deep, which manifests the formation of a tightly-binded contact ion pair. This remarkable effect arises owing to the strong electrostatic interaction that is incompletely screened by a non-polar medium. The PMFs for the binary benzene/DMSO mixtures display intermediate behaviour depending on the DMSO content.

  1. A close examination of the structure and dynamics of HC(NH2)2PbI3by MD simulations and group theory

    KAUST Repository

    Carignano, M. A.

    2016-06-22

    The formamidinium lead iodide hybrid perovskite is studied using first principles molecular dynamics simulations and further analyzed using group theory. The simulations are performed on large supercells containing 768 atoms under isothermal and fully anisotropic isobaric conditions. Two trajectories, one at 300 K and another at 450 K, were extended for over 50 ps in order to perform a detailed assessment of the rotational dynamics of organic cations. The characteristic rotations of the cation are analyzed by defining two rotation axes. It is found that the formamidinium molecules rotate preferentially around the direction parallel to the line connecting the two nitrogen atoms. The rotational dynamics shows some characteristics already observed in methylammonium lead iodide, like the heterogeneous dynamics at room temperature that disappears at 450 K. The orientational probability of the molecules is explored in terms of an expansion in cubic harmonics up to the 12th order. It reveals a strong directionality at room temperature that relaxes when increasing the temperature. These findings are further rationalized using Landau and group theories suggesting a mixed displacive/order-disorder structural instability at lower temperatures.

  2. Supply chain simulation tools and techniques: a survey

    NARCIS (Netherlands)

    Kleijnen, J.P.C.

    2005-01-01

    The main contribution of this paper is twofold: it surveys different types of simulation for supply chain management; it discusses several methodological issues. These different types of simulation are spreadsheet simulation, system dynamics, discrete-event simulation and business games. Which

  3. MD SIMULATION STUDIES TO INVESTIGATE ISO-ENERGETIC CONFORMATIONAL BEHAVIOUR OF MODIFIED NUCLEOSIDES M2G AND M22G PRESENT IN tRNA

    Directory of Open Access Journals (Sweden)

    Rohit S Bavi

    2013-02-01

    Full Text Available Modified nucleic acid bases are most commonly found in tRNA. These may contain modifications from simple methylation to addition of bulky groups. Methylation of the four canonical nucleotide bases at a wide variety of positions is particularly prominent among the known modification. Methylation of N2 group of guanine is a relatively common modification in tRNA and rRNA. N2-methylguanosine (m2G is the second most often encountered nucleoside in E. coli tRNAs. N2, N2-dimethylguanosine (m22G is found in the majority of eukaryotic tRNAs and involved in forming base pair interactions with adjacent bases. Hence, in order to understand the structural significance of these methylated nucleic acid bases we have carried out molecular dynamics simulation to see the salvation effect. The results obtained shows iso-energetic conformational behaviors for m2G and m22G. The simulation trajectory of m2G shows regular periodical fluctuations suggesting that m2G is equally stable as either s-cis or s-trans rotamers. The two rotamers of m2G may interact canonically or non-canonically with opposite base as s-trans m2G26:C/A/U44 and s-cis m2G26:A/U44. The free rotations around the C-N bond could be the possible reason for these iso-energetic conformations. Dimethylation of G has almost no influence on base pairing with either A or U. Thus, these results reveal that modified nucleosides m2G and m22G may play an important role to prevent tRNA from adopting the unusual mitochondrial like conformation.

  4. Preflight screening techniques for centrifuge-simulated suborbital spaceflight.

    Science.gov (United States)

    Pattarini, James M; Blue, Rebecca S; Castleberry, Tarah L; Vanderploeg, James M

    2014-12-01

    Historically, space has been the venue of the healthy individual. With the advent of commercial spaceflight, we face the novel prospect of routinely exposing spaceflight participants (SPFs) with multiple comorbidities to the space environment. Preflight screening procedures must be developed to identify those individuals at increased risk during flight. We examined the responses of volunteers to centrifuge accelerations mimicking commercial suborbital spaceflight profiles to evaluate how potential SFPs might tolerate such forces. We evaluated our screening process for medical approval of subjects for centrifuge participation for applicability to commercial spaceflight operations. All registered subjects completed a medical questionnaire, physical examination, and electrocardiogram. Subjects with identified concerns including cardiopulmonary disease, hypertension, and diabetes were required to provide documentation of their conditions. There were 335 subjects who registered for the study, 124 who completed all prescreening, and 86 subjects who participated in centrifuge trials. Due to prior medical history, five subjects were disqualified, most commonly for psychiatric reasons or uncontrolled medical conditions. Of the subjects approved, four individuals experienced abnormal physiological responses to centrifuge profiles, including one back strain and three with anxiety reactions. The screening methods used were judged to be sufficient to identify individuals physically capable of tolerating simulated suborbital flight. Improved methods will be needed to identify susceptibility to anxiety reactions. While severe or uncontrolled disease was excluded, many subjects successfully participated in centrifuge trials despite medical histories of disease that are disqualifying under historical spaceflight screening regimes. Such screening techniques are applicable for use in future commercial spaceflight operations.

  5. Development of joining techniques for fabrication of fuel rod simulators

    International Nuclear Information System (INIS)

    Moorhead, A.J.; McCulloch, R.W.; Reed, R.W.; Woodhouse, J.J.

    1980-10-01

    Much of the safety-related thermal-hydraulic tests on nuclear reactors are conducted not in the reactor itself, but in mockup segments of a core that uses resistance-heated fuel rod simulators (FRS) in place of the radioactive fuel rods. Laser welding and furnace brazing techniques are described for joining subassemblies for FRS that have survived up to 1000 h steady-state operation at 700 to 1100 0 C cladding temperatures and over 5000 thermal transients, ranging from 10 to 100 0 C/s. A pulsed-laser welding procedure that includes use of small-diameter filler wire is used to join one end of a resistance heating element of Pt-8 W, Fe-22 Cr-5.5 Al-0.5 Co, or 80 Ni-20 Cr (wt %) to a tubular conductor of an appropriate intermediate material. The other end of the heating element is laser welded to an end plug, which in turn is welded to a central conductor rod

  6. Structural, stability, dynamic and binding properties of the ALS-causing T46I mutant of the hVAPB MSP domain as revealed by NMR and MD simulations.

    Directory of Open Access Journals (Sweden)

    Shixiong Lua

    Full Text Available T46I is the second mutation on the hVAPB MSP domain which was recently identified from non-Brazilian kindred to cause a familial amyotrophic lateral sclerosis (ALS. Here using CD, NMR and molecular dynamics (MD simulations, we characterized the structure, stability, dynamics and binding capacity of the T46I-MSP domain. The results reveal: 1 unlike P56S which we previously showed to completely eliminate the native MSP structure, T46I leads to no significant disruption of the native secondary and tertiary structures, as evidenced from its far-UV CD spectrum, as well as Cα and Cβ NMR chemical shifts. 2 Nevertheless, T46I does result in a reduced thermodynamic stability and loss of the cooperative urea-unfolding transition. As such, the T46I-MSP domain is more prone to aggregation than WT at high protein concentrations and temperatures in vitro, which may become more severe in the crowded cellular environments. 3 T46I only causes a 3-fold affinity reduction to the Nir2 peptide, but a significant elimination of its binding to EphA4. 4 EphA4 and Nir2 peptide appear to have overlapped binding interfaces on the MSP domain, which strongly implies that two signaling networks may have a functional interplay in vivo. 5 As explored by both H/D exchange and MD simulations, the MSP domain is very dynamic, with most loop residues and many residues on secondary structures highly fluctuated or/and exposed to bulk solvent. Although T46I does not alter overall dynamics, it does trigger increased dynamics of several local regions of the MSP domain which are implicated in binding to EphA4 and Nir2 peptide. Our study provides the structural and dynamic understanding of the T46I-causing ALS; and strongly highlights the possibility that the interplay of two signaling networks mediated by the FFAT-containing proteins and Eph receptors may play a key role in ALS pathogenesis.

  7. Oil-soluble and water-soluble BTPhens and their europium complexes in octanol/water solutions: interface crossing studied by MD and PMF simulations.

    Science.gov (United States)

    Benay, G; Wipff, G

    2013-01-31

    Bistriazinyl-phenantroline "BTPhen" ligands L display the remarkable feature to complex trivalent lanthanide and actinide ions, with a marked selectivity for the latter. We report on molecular dynamics studies of tetrasubstituted X(4)BTPhens: L(4+) (X = (+)Et(3)NCH(2)-), L(4-) (X = (-)SO(3)Ph-), and L(0) (X = CyMe(4)) and their complexes with Eu(III) in binary octanol/water solutions. Changes in free energies upon interface crossing are also calculated for typical solutes by potential of mean force PMF simulations. The ligands and their complexes partition, as expected, to either the aqueous or the oil phase, depending on the "solubilizing" group X. Furthermore, most of them are found to be surface active. The water-soluble L(4+) and L(4-) ligands and their (L)Eu(NO(3))(3) complexes adsorb at the aqueous side of the interface, more with L(4-) than with L(4+). The oil soluble ligand L(0) is not surface active in its endo-endo form but adsorbs on the oil side of the interface in its most polar endo-exo form, as well as in its protonated L(0)H(+) and complexed (L(0))Eu(NO(3))(3) states. Furthermore, comparing PMFs of the Eu(III) complexes with and without nitric acid shows that acidifying the aqueous phase has different effects, depending on the ligand charge. In particular, acid promotes the Eu(III) extraction by L(0) via the (L(0))(2)Eu(NO(3))(2+) complex, as observed experimentally. Overall, the results point to the importance of interfacial adsorption for the liquid-liquid extraction of trivalent lanthanide and actinide cations by BTPhens and analogues.

  8. The FADE mass-stat: A technique for inserting or deleting particles in molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Borg, Matthew K., E-mail: matthew.borg@strath.ac.uk [Department of Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow G1 1XJ (United Kingdom); Lockerby, Duncan A., E-mail: duncan.lockerby@warwick.ac.uk [School of Engineering, University of Warwick, Coventry CV4 7AL (United Kingdom); Reese, Jason M., E-mail: jason.reese@ed.ac.uk [School of Engineering, University of Edinburgh, Edinburgh EH9 3JL (United Kingdom)

    2014-02-21

    The emergence of new applications of molecular dynamics (MD) simulation calls for the development of mass-statting procedures that insert or delete particles on-the-fly. In this paper we present a new mass-stat which we term FADE, because it gradually “fades-in” (inserts) or “fades-out” (deletes) molecules over a short relaxation period within a MD simulation. FADE applies a time-weighted relaxation to the intermolecular pair forces between the inserting/deleting molecule and any neighbouring molecules. The weighting function we propose in this paper is a piece-wise polynomial that can be described entirely by two parameters: the relaxation time scale and the order of the polynomial. FADE inherently conserves overall system momentum independent of the form of the weighting function. We demonstrate various simulations of insertions of atomic argon, polyatomic TIP4P water, polymer strands, and C{sub 60} Buckminsterfullerene molecules. We propose FADE parameters and a maximum density variation per insertion-instance that restricts spurious potential energy changes entering the system within desired tolerances. We also demonstrate in this paper that FADE compares very well to an existing insertion algorithm called USHER, in terms of accuracy, insertion rate (in dense fluids), and computational efficiency. The USHER algorithm is applicable to monatomic and water molecules only, but we demonstrate that FADE can be generally applied to various forms and sizes of molecules, such as polymeric molecules of long aspect ratio, and spherical carbon fullerenes with hollow interiors.

  9. The FADE mass-stat: A technique for inserting or deleting particles in molecular dynamics simulations

    International Nuclear Information System (INIS)

    Borg, Matthew K.; Lockerby, Duncan A.; Reese, Jason M.

    2014-01-01

    The emergence of new applications of molecular dynamics (MD) simulation calls for the development of mass-statting procedures that insert or delete particles on-the-fly. In this paper we present a new mass-stat which we term FADE, because it gradually “fades-in” (inserts) or “fades-out” (deletes) molecules over a short relaxation period within a MD simulation. FADE applies a time-weighted relaxation to the intermolecular pair forces between the inserting/deleting molecule and any neighbouring molecules. The weighting function we propose in this paper is a piece-wise polynomial that can be described entirely by two parameters: the relaxation time scale and the order of the polynomial. FADE inherently conserves overall system momentum independent of the form of the weighting function. We demonstrate various simulations of insertions of atomic argon, polyatomic TIP4P water, polymer strands, and C 60 Buckminsterfullerene molecules. We propose FADE parameters and a maximum density variation per insertion-instance that restricts spurious potential energy changes entering the system within desired tolerances. We also demonstrate in this paper that FADE compares very well to an existing insertion algorithm called USHER, in terms of accuracy, insertion rate (in dense fluids), and computational efficiency. The USHER algorithm is applicable to monatomic and water molecules only, but we demonstrate that FADE can be generally applied to various forms and sizes of molecules, such as polymeric molecules of long aspect ratio, and spherical carbon fullerenes with hollow interiors

  10. Spontaneous fission of 259Md

    International Nuclear Information System (INIS)

    Hulet, E.K.; Wild, J.F.; Lougheed, R.W.; Baisden, P.A.; Landrum, J.H.; Dougan, R.J.; Mustafa, M.; Ghiorso, A.; Nitschke, J.M.

    1979-01-01

    The mass and kinetic energy distributions of fission fragments from the spontaneous fission of th newly discovered nuclide 259 Md were obtained. 259 Md was identified as the E. C. daughter of 259 No, and was found to decay entirely (> 95%) by spontaneous fission with a 95-min half-life. From the kinetic energies measured for 397 pairs of coincident fragments, a mass distribution was derived that is symmetric with sigma = 13 amu. 259 Md, together with 258 Fm and 259 Fm, form a select group of three nuclides whose mass division in spontaneous fission is highly symmetric. Unlike the total-kinetic-energy (TKE) distributions of 258 Fm and 259 Fm, which peak at approx. = to 240 MeV, this distribution for 259 Md is broad and is 50 MeV lower in energy. Analysis of the mass and energy distributions shows that events near mass symmetry also exhibit a broad TKE distribution, with one-third of the symmetric events having TKEs less than 200 MeV. The associated of low TKEs with symmetric mass division in the fission of very heavy actinides is anomalous and inconsistent with theories based upon the emergence of fragment shells near the scission point. Either three-body fragmentation or peculiar fragment shapes are assumed as the cause for the large consumption of Coulomb energy observed for a significant fraction of symmetric fissions in 259 Md. 6 figures

  11. Combining Rosetta with molecular dynamics (MD): A benchmark of the MD-based ensemble protein design.

    Science.gov (United States)

    Ludwiczak, Jan; Jarmula, Adam; Dunin-Horkawicz, Stanislaw

    2018-07-01

    Computational protein design is a set of procedures for computing amino acid sequences that will fold into a specified structure. Rosetta Design, a commonly used software for protein design, allows for the effective identification of sequences compatible with a given backbone structure, while molecular dynamics (MD) simulations can thoroughly sample near-native conformations. We benchmarked a procedure in which Rosetta design is started on MD-derived structural ensembles and showed that such a combined approach generates 20-30% more diverse sequences than currently available methods with only a slight increase in computation time. Importantly, the increase in diversity is achieved without a loss in the quality of the designed sequences assessed by their resemblance to natural sequences. We demonstrate that the MD-based procedure is also applicable to de novo design tasks started from backbone structures without any sequence information. In addition, we implemented a protocol that can be used to assess the stability of designed models and to select the best candidates for experimental validation. In sum our results demonstrate that the MD ensemble-based flexible backbone design can be a viable method for protein design, especially for tasks that require a large pool of diverse sequences. Copyright © 2018 Elsevier Inc. All rights reserved.

  12. Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration

    Science.gov (United States)

    Hofer, Thomas S.; Hünenberger, Philippe H.

    2018-06-01

    The absolute intrinsic hydration free energy GH+,w a t ◦ of the proton, the surface electric potential jump χwa t ◦ upon entering bulk water, and the absolute redox potential VH+,w a t ◦ of the reference hydrogen electrode are cornerstone quantities for formulating single-ion thermodynamics on absolute scales. They can be easily calculated from each other but remain fundamentally elusive, i.e., they cannot be determined experimentally without invoking some extra-thermodynamic assumption (ETA). The Born model provides a natural framework to formulate such an assumption (Born ETA), as it automatically factors out the contribution of crossing the water surface from the hydration free energy. However, this model describes the short-range solvation inaccurately and relies on the choice of arbitrary ion-size parameters. In the present study, both shortcomings are alleviated by performing first-principle calculations of the hydration free energies of the sodium (Na+) and potassium (K+) ions. The calculations rely on thermodynamic integration based on quantum-mechanical molecular-mechanical (QM/MM) molecular dynamics (MD) simulations involving the ion and 2000 water molecules. The ion and its first hydration shell are described using a correlated ab initio method, namely resolution-of-identity second-order Møller-Plesset perturbation (RIMP2). The next hydration shells are described using the extended simple point charge water model (SPC/E). The hydration free energy is first calculated at the MM level and subsequently increased by a quantization term accounting for the transformation to a QM/MM description. It is also corrected for finite-size, approximate-electrostatics, and potential-summation errors, as well as standard-state definition. These computationally intensive simulations provide accurate first-principle estimates for GH+,w a t ◦, χwa t ◦, and VH+,w a t ◦, reported with statistical errors based on a confidence interval of 99%. The values obtained

  13. Teaching Behavioral Modeling and Simulation Techniques for Power Electronics Courses

    Science.gov (United States)

    Abramovitz, A.

    2011-01-01

    This paper suggests a pedagogical approach to teaching the subject of behavioral modeling of switch-mode power electronics systems through simulation by general-purpose electronic circuit simulators. The methodology is oriented toward electrical engineering (EE) students at the undergraduate level, enrolled in courses such as "Power…

  14. Determine the feasibility of techniques for simulating coal dust explosions

    CSIR Research Space (South Africa)

    Kirsten, JT

    1994-07-01

    Full Text Available The primary objective of this work is to assess the feasibility of reliably simulating the coal dust explosion process taking place in the Kloppersbos tunnel with a computer model. Secondary objectives are to investigate the viability of simulating...

  15. Large-scale computing techniques for complex system simulations

    CERN Document Server

    Dubitzky, Werner; Schott, Bernard

    2012-01-01

    Complex systems modeling and simulation approaches are being adopted in a growing number of sectors, including finance, economics, biology, astronomy, and many more. Technologies ranging from distributed computing to specialized hardware are explored and developed to address the computational requirements arising in complex systems simulations. The aim of this book is to present a representative overview of contemporary large-scale computing technologies in the context of complex systems simulations applications. The intention is to identify new research directions in this field and

  16. A Simulation of AI Programming Techniques in BASIC.

    Science.gov (United States)

    Mandell, Alan

    1986-01-01

    Explains the functions of and the techniques employed in expert systems. Offers the program "The Periodic Table Expert," as a model for using artificial intelligence techniques in BASIC. Includes the program listing and directions for its use on: Tandy 1000, 1200, and 2000; IBM PC; PC Jr; TRS-80; and Apple computers. (ML)

  17. 360-degree videos: a new visualization technique for astrophysical simulations

    Science.gov (United States)

    Russell, Christopher M. P.

    2017-11-01

    360-degree videos are a new type of movie that renders over all 4π steradian. Video sharing sites such as YouTube now allow this unique content to be shared via virtual reality (VR) goggles, hand-held smartphones/tablets, and computers. Creating 360° videos from astrophysical simulations is not only a new way to view these simulations as you are immersed in them, but is also a way to create engaging content for outreach to the public. We present what we believe is the first 360° video of an astrophysical simulation: a hydrodynamics calculation of the central parsec of the Galactic centre. We also describe how to create such movies, and briefly comment on what new science can be extracted from astrophysical simulations using 360° videos.

  18. Monte Carlo simulation of tomography techniques using the platform Gate

    International Nuclear Information System (INIS)

    Barbouchi, Asma

    2007-01-01

    Simulations play a key role in functional imaging, with applications ranging from scanner design, scatter correction, protocol optimisation. GATE (Geant4 for Application Tomography Emission) is a platform for Monte Carlo Simulation. It is based on Geant4 to generate and track particles, to model geometry and physics process. Explicit modelling of time includes detector motion, time of flight, tracer kinetics. Interfaces to voxellised models and image reconstruction packages improve the integration of GATE in the global modelling cycle. In this work Monte Carlo simulations are used to understand and optimise the gamma camera's performances. We study the effect of the distance between source and collimator, the diameter of the holes and the thick of the collimator on the spatial resolution, energy resolution and efficiency of the gamma camera. We also study the reduction of simulation's time and implement a model of left ventricle in GATE. (Author). 7 refs

  19. Validation techniques of agent based modelling for geospatial simulations

    OpenAIRE

    Darvishi, M.; Ahmadi, G.

    2014-01-01

    One of the most interesting aspects of modelling and simulation study is to describe the real world phenomena that have specific properties; especially those that are in large scales and have dynamic and complex behaviours. Studying these phenomena in the laboratory is costly and in most cases it is impossible. Therefore, Miniaturization of world phenomena in the framework of a model in order to simulate the real phenomena is a reasonable and scientific approach to understand the world. Agent...

  20. Enamel dose calculation by electron paramagnetic resonance spectral simulation technique

    International Nuclear Information System (INIS)

    Dong Guofu; Cong Jianbo; Guo Linchao; Ning Jing; Xian Hong; Wang Changzhen; Wu Ke

    2011-01-01

    Objective: To optimize the enamel electron paramagnetic resonance (EPR) spectral processing by using the EPR spectral simulation method to improve the accuracy of enamel EPR dosimetry and reduce artificial error. Methods: The multi-component superimposed EPR powder spectral simulation software was developed to simulate EPR spectrum models of the background signal (BS) and the radiation- induced signal (RS) of irradiated enamel respectively. RS was extracted from the multi-component superimposed spectrum of irradiated enamel and its amplitude was calculated. The dose-response curve was then established for calculating the doses of a group of enamel samples. The result of estimated dose was compared with that calculated by traditional method. Results: BS was simulated as a powder spectrum of gaussian line shape with the following spectrum parameters: g=2.00 35 and Hpp=0.65-1.1 mT, RS signal was also simulated as a powder spectrum but with axi-symmetric spectrum characteristics. The spectrum parameters of RS were: g ⊥ =2.0018, g ‖ =1.9965, Hpp=0.335-0.4 mT. The amplitude of RS had a linear response to radiation dose with the regression equation as y=240.74x + 76 724 (R 2 =0.9947). The expectation of relative error of dose estimation was 0.13. Conclusions: EPR simulation method has improved somehow the accuracy and reliability of enamel EPR dose estimation. (authors)

  1. Advanced Techniques for Reservoir Simulation and Modeling of Non-Conventional Wells

    Energy Technology Data Exchange (ETDEWEB)

    Durlofsky, Louis J.

    2000-08-28

    This project targets the development of (1) advanced reservoir simulation techniques for modeling non-conventional wells; (2) improved techniques for computing well productivity (for use in reservoir engineering calculations) and well index (for use in simulation models), including the effects of wellbore flow; and (3) accurate approaches to account for heterogeneity in the near-well region.

  2. MD 2179: Scraping of off-momentum halo after injection

    CERN Document Server

    Garcia Morales, Hector; Patecki, Marcin; Wretborn, Sven Joel; CERN. Geneva. ATS Department

    2018-01-01

    In this MD, a beam scraping was performed using the momentum primary collimator in IR3 where dispersion is high. A second scraping was performed using a TCSG in IR7 where dispersion is almost negligible. In such a way, we aim to disentangle the contribution of off-momentum particles to halo population. These scrapings will provide useful information to better understand the usual off-momentum losses we see at the start of the ramp. The MD results would also be used to benchmark simulations of off-momentum beam losses in order to gain confidence in simulation models.

  3. Advancing botnet modeling techniques for military and security simulations

    Science.gov (United States)

    Banks, Sheila B.; Stytz, Martin R.

    2011-06-01

    Simulation environments serve many purposes, but they are only as good as their content. One of the most challenging and pressing areas that call for improved content is the simulation of bot armies (botnets) and their effects upon networks and computer systems. Botnets are a new type of malware, a type that is more powerful and potentially dangerous than any other type of malware. A botnet's power derives from several capabilities including the following: 1) the botnet's capability to be controlled and directed throughout all phases of its activity, 2) a command and control structure that grows increasingly sophisticated, and 3) the ability of a bot's software to be updated at any time by the owner of the bot (a person commonly called a bot master or bot herder.) Not only is a bot army powerful and agile in its technical capabilities, a bot army can be extremely large, can be comprised of tens of thousands, if not millions, of compromised computers or it can be as small as a few thousand targeted systems. In all botnets, their members can surreptitiously communicate with each other and their command and control centers. In sum, these capabilities allow a bot army to execute attacks that are technically sophisticated, difficult to trace, tactically agile, massive, and coordinated. To improve our understanding of their operation and potential, we believe that it is necessary to develop computer security simulations that accurately portray bot army activities, with the goal of including bot army simulations within military simulation environments. In this paper, we investigate issues that arise when simulating bot armies and propose a combination of the biologically inspired MSEIR infection spread model coupled with the jump-diffusion infection spread model to portray botnet propagation.

  4. Simulation techniques for determining reliability and availability of technical systems

    International Nuclear Information System (INIS)

    Lindauer, E.

    1975-01-01

    The system is described in the form of a fault tree with components representing part functions of the system and connections which reproduce the logical structure of the system. Both have the states intact or failed, they are defined here as in the programme FESIVAR of the IRS. For the simulation of components corresponding to the given probabilities, pseudo-random numbers are applied; these are numbers whose sequence is determined by the producing algorithm, but which for the given purpose sufficiently exhibit the behaviour of randomly successive numbers. This method of simulation is compared with deterministic methods. (HP/LH) [de

  5. Development of a technique for inflight jet noise simulation. I, II

    Science.gov (United States)

    Clapper, W. S.; Stringas, E. J.; Mani, R.; Banerian, G.

    1976-01-01

    Several possible noise simulation techniques were evaluated, including closed circuit wind tunnels, free jets, rocket sleds and high speed trains. The free jet technique was selected for demonstration and verification. The first paper describes the selection and development of the technique and presents results for simulation and in-flight tests of the Learjet, F106, and Bertin Aerotrain. The second presents a theoretical study relating the two sets of noise signatures. It is concluded that the free jet simulation technique provides a satisfactory assessment of in-flight noise.

  6. Atomic Force Microscopy and MD Simulations Reveal Pore-Like Structures of All-D-Enantiomer of Alzheimer’s β-Amyloid Peptide: Relevance to the Ion Channel Mechanism of AD Pathology

    Science.gov (United States)

    Connelly, Laura; Arce, Fernando Teran; Jang, Hyunbum; Capone, Ricardo; Kotler, Samuel A.; Ramachandran, Srinivasan; Kagan, Bruce L.; Nussinov, Ruth; Lal, Ratnesh

    2012-01-01

    Alzheimer’s disease (AD) is a protein misfolding disease characterized by a build-up of β-amyloid (Aβ) peptide as senile plaques, uncontrolled neurodegeneration, and memory loss. AD pathology is linked to the destabilization of cellular ionic homeostasis and involves Aβ peptide-plasma membrane interactions. In principle, there are two possible ways through which disturbance of the ionic homeostasis can take place: directly, where the Aβ peptide either inserts into the membrane and creates ion-conductive pores or destabilizes the membrane organization; or, indirectly, where the Aβ peptide interacts with existing cell membrane receptors. To distinguish between these two possible types of Aβ-membrane interactions, we took advantage of the biochemical tenet that ligand-receptor interactions are stereospecific; L-amino acid peptides, but not their D-counterparts, bind to cell membrane receptors. However, with respect to the ion channel-mediated mechanism, like L-amino acids, D-amino acid peptides will also form ion channel-like structures. Using atomic force microscopy (AFM) we imaged the structures of both D- and L-enantiomers of the full length Aβ1-42 when reconstituted in lipid bilayers. AFM imaging shows that both L- and D-Aβ isomers form similar channel-like structures. Molecular dynamics (MD) simulations support the AFM imaged 3D structures. Earlier we have shown that D-Aβ1-42 channels conduct ions similarly to their L-counter parts. Taken together, our results support the direct mechanism of Aβ ion channel-mediated destabilization of ionic homeostasis rather than the indirect mechanism through Aβ interaction with membrane receptors. PMID:22217000

  7. Two dimensional numerical simulation of gas discharges: comparison between particle-in-cell and FCT techniques

    Energy Technology Data Exchange (ETDEWEB)

    Soria-Hoyo, C; Castellanos, A [Departamento de Electronica y Electromagnetismo, Facultad de Fisica, Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012 Sevilla (Spain); Pontiga, F [Departamento de Fisica Aplicada II, EUAT, Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012 Sevilla (Spain)], E-mail: cshoyo@us.es

    2008-10-21

    Two different numerical techniques have been applied to the numerical integration of equations modelling gas discharges: a finite-difference flux corrected transport (FD-FCT) technique and a particle-in-cell (PIC) technique. The PIC technique here implemented has been specifically designed for the simulation of 2D electrical discharges using cylindrical coordinates. The development and propagation of a streamer between two parallel electrodes has been used as a convenient test to compare the performance of both techniques. In particular, the phase velocity of the cathode directed streamer has been used to check the internal consistency of the numerical simulations. The results obtained from the two techniques are in reasonable agreement with each other, and both techniques have proved their ability to follow the high gradients of charge density and electric field present in this type of problems. Moreover, the streamer velocities predicted by the simulation are in accordance with the typical experimental values.

  8. Two dimensional numerical simulation of gas discharges: comparison between particle-in-cell and FCT techniques

    International Nuclear Information System (INIS)

    Soria-Hoyo, C; Castellanos, A; Pontiga, F

    2008-01-01

    Two different numerical techniques have been applied to the numerical integration of equations modelling gas discharges: a finite-difference flux corrected transport (FD-FCT) technique and a particle-in-cell (PIC) technique. The PIC technique here implemented has been specifically designed for the simulation of 2D electrical discharges using cylindrical coordinates. The development and propagation of a streamer between two parallel electrodes has been used as a convenient test to compare the performance of both techniques. In particular, the phase velocity of the cathode directed streamer has been used to check the internal consistency of the numerical simulations. The results obtained from the two techniques are in reasonable agreement with each other, and both techniques have proved their ability to follow the high gradients of charge density and electric field present in this type of problems. Moreover, the streamer velocities predicted by the simulation are in accordance with the typical experimental values.

  9. Simulation tools for industrial applications of phased array inspection techniques

    International Nuclear Information System (INIS)

    Mahaut, St.; Roy, O.; Chatillon, S.; Calmon, P.

    2001-01-01

    Ultrasonic phased arrays techniques have been developed at the French Atomic Energy Commission in order to improve defects characterization and adaptability to various inspection configuration (complex geometry specimen). Such transducers allow 'standard' techniques - adjustable beam-steering and focusing -, or more 'advanced' techniques - self-focusing on defects for instance -. To estimate the performances of those techniques, models have been developed, which allows to compute the ultrasonic field radiated by an arbitrary phased array transducer through any complex specimen, and to predict the ultrasonic response of various defects inspected with a known beam. Both modeling applications are gathered in the Civa software, dedicated to NDT expertise. The use of those complementary models allows to evaluate the ability of a phased array to steer and focus the ultrasonic beam, and therefore its relevancy to detect and characterize defects. These models are specifically developed to give accurate solutions to realistic inspection applications. This paper briefly describes the CIVA models, and presents some applications dedicated to the inspection of complex specimen containing various defects with a phased array used to steer and focus the beam. Defect detection and characterization performances are discussed for the various configurations. Some experimental validation of both models are also presented. (authors)

  10. Estimation of fracture aperture using simulation technique; Simulation wo mochiita fracture kaiko haba no suitei

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, T [Geological Survey of Japan, Tsukuba (Japan); Abe, M [Tohoku University, Sendai (Japan). Faculty of Engineering

    1996-10-01

    Characteristics of amplitude variation around fractures have been investigated using simulation technique in the case changing the fracture aperture. Four models were used. The model-1 was a fracture model having a horizontal fracture at Z=0. For the model-2, the fracture was replaced by a group of small fractures. The model-3 had an extended borehole diameter at Z=0 in a shape of wedge. The model-4 had a low velocity layer at Z=0. The maximum amplitude was compared each other for each depth and for each model. For the model-1, the amplitude became larger at the depth of the fracture, and became smaller above the fracture. For the model-2, when the cross width D increased to 4 cm, the amplitude approached to that of the model-1. For the model-3 having extended borehole diameter, when the extension of borehole diameter ranged between 1 cm and 2 cm, the change of amplitude was hardly observed above and below the fracture. However, when the extension of borehole diameter was 4 cm, the amplitude became smaller above the extension part of borehole. 3 refs., 4 figs., 1 tab.

  11. Modeling and Simulation Techniques for Large-Scale Communications Modeling

    National Research Council Canada - National Science Library

    Webb, Steve

    1997-01-01

    .... Tests of random number generators were also developed and applied to CECOM models. It was found that synchronization of random number strings in simulations is easy to implement and can provide significant savings for making comparative studies. If synchronization is in place, then statistical experiment design can be used to provide information on the sensitivity of the output to input parameters. The report concludes with recommendations and an implementation plan.

  12. Assessing suturing techniques using a virtual reality surgical simulator.

    Science.gov (United States)

    Kazemi, Hamed; Rappel, James K; Poston, Timothy; Hai Lim, Beng; Burdet, Etienne; Leong Teo, Chee

    2010-09-01

    Advantages of virtual-reality simulators surgical skill assessment and training include more training time, no risk to patient, repeatable difficulty level, reliable feedback, without the resource demands, and ethical issues of animal-based training. We tested this for a key subtask and showed a strong link between skill in the simulator and in reality. Suturing performance was assessed for four groups of participants, including experienced surgeons and naive subjects, on a custom-made virtual-reality simulator. Each subject tried the experiment 30 times using five different types of needles to perform a standardized suture placement task. Traditional metrics of performance as well as new metrics enabled by our system were proposed, and the data indicate difference between trained and untrained performance. In all traditional parameters such as time, number of attempts, and motion quantity, the medical surgeons outperformed the other three groups, though differences were not significant. However, motion smoothness, penetration and exit angles, tear size areas, and orientation change were statistically significant in the trained group when compared with untrained group. This suggests that these parameters can be used in virtual microsurgery training.

  13. Measurement and Simulation Techniques For Piezoresistive Microcantilever Biosensor Applications

    Directory of Open Access Journals (Sweden)

    Aan Febriansyah

    2012-12-01

    Full Text Available Applications of microcantilevers as biosensors have been explored by many researchers for the applications in medicine, biological, chemistry, and environmental monitoring. This research discusses a design of measurement method and simuations for piezoresistive microcantilever as a biosensor, which consist of designing Wheatstone bridge circuit as object detector, simulation of resonance frequency shift based on Euler Bernoulli Beam equation, and microcantilever vibration simulation using COMSOL Multiphysics 3.5. The piezoresistive microcantilever used here is Seiko Instrument Technology (Japan product with length of 110 ?m, width of 50 ?m, and thickness of 1 ?m. Microcantilever mass is 12.815 ng, including the mass receptor. The sample object in this research is bacteria EColi. One bacteria mass is assumed to 0.3 pg. Simulation results show that the mass of one bacterium will cause the deflection of 0,03053 nm and resonance frequency value of 118,90 kHz. Moreover, four bacterium will cause the deflection of 0,03054 nm and resonance frequency value of 118,68 kHz. These datas indicate that the increasing of the bacteria mass increases the deflection value and reduces the value of resonance frequency.

  14. Filament winding technique, experiment and simulation analysis on tubular structure

    Science.gov (United States)

    Quanjin, Ma; Rejab, M. R. M.; Kaige, Jiang; Idris, M. S.; Harith, M. N.

    2018-04-01

    Filament winding process has emerged as one of the potential composite fabrication processes with lower costs. Filament wound products involve classic axisymmetric parts (pipes, rings, driveshafts, high-pressure vessels and storage tanks), non-axisymmetric parts (prismatic nonround sections and pipe fittings). Based on the 3-axis filament winding machine has been designed with the inexpensive control system, it is completely necessary to make a relative comparison between experiment and simulation on tubular structure. In this technical paper, the aim of this paper is to perform a dry winding experiment using the 3-axis filament winding machine and simulate winding process on the tubular structure using CADWIND software with 30°, 45°, 60° winding angle. The main result indicates that the 3-axis filament winding machine can produce tubular structure with high winding pattern performance with different winding angle. This developed 3-axis winding machine still has weakness compared to CAWIND software simulation results with high axes winding machine about winding pattern, turnaround impact, process error, thickness, friction impact etc. In conclusion, the 3-axis filament winding machine improvements and recommendations come up with its comparison results, which can intuitively understand its limitations and characteristics.

  15. Reliability assessment of restructured power systems using reliability network equivalent and pseudo-sequential simulation techniques

    International Nuclear Information System (INIS)

    Ding, Yi; Wang, Peng; Goel, Lalit; Billinton, Roy; Karki, Rajesh

    2007-01-01

    This paper presents a technique to evaluate reliability of a restructured power system with a bilateral market. The proposed technique is based on the combination of the reliability network equivalent and pseudo-sequential simulation approaches. The reliability network equivalent techniques have been implemented in the Monte Carlo simulation procedure to reduce the computational burden of the analysis. Pseudo-sequential simulation has been used to increase the computational efficiency of the non-sequential simulation method and to model the chronological aspects of market trading and system operation. Multi-state Markov models for generation and transmission systems are proposed and implemented in the simulation. A new load shedding scheme is proposed during generation inadequacy and network congestion to minimize the load curtailment. The IEEE reliability test system (RTS) is used to illustrate the technique. (author)

  16. Improved importance sampling technique for efficient simulation of digital communication systems

    Science.gov (United States)

    Lu, Dingqing; Yao, Kung

    1988-01-01

    A new, improved importance sampling (IIS) approach to simulation is considered. Some basic concepts of IS are introduced, and detailed evolutions of simulation estimation variances for Monte Carlo (MC) and IS simulations are given. The general results obtained from these evolutions are applied to the specific previously known conventional importance sampling (CIS) technique and the new IIS technique. The derivation for a linear system with no signal random memory is considered in some detail. For the CIS technique, the optimum input scaling parameter is found, while for the IIS technique, the optimum translation parameter is found. The results are generalized to a linear system with memory and signals. Specific numerical and simulation results are given which show the advantages of CIS over MC and IIS over CIS for simulations of digital communications systems.

  17. FEM Techniques for High Stress Detection in Accelerated Fatigue Simulation

    Science.gov (United States)

    Veltri, M.

    2016-09-01

    This work presents the theory and a numerical validation study in support to a novel method for a priori identification of fatigue critical regions, with the aim to accelerate durability design in large FEM problems. The investigation is placed in the context of modern full-body structural durability analysis, where a computationally intensive dynamic solution could be required to identify areas with potential for fatigue damage initiation. The early detection of fatigue critical areas can drive a simplification of the problem size, leading to sensible improvement in solution time and model handling while allowing processing of the critical areas in higher detail. The proposed technique is applied to a real life industrial case in a comparative assessment with established practices. Synthetic damage prediction quantification and visualization techniques allow for a quick and efficient comparison between methods, outlining potential application benefits and boundaries.

  18. Simulation of land mine detection processes using nuclear techniques

    International Nuclear Information System (INIS)

    Aziz, M.

    2005-01-01

    A computer models were designed to study the processes of land mine detection using nuclear technique. Parameters that affect the detection were analyzed . Mines of different masses at different depths in the soil are considered using two types of sources , 252 C f and 14 MeV neutron source. The capability to differentiate between mines and other objects such as concrete , iron , wood , Aluminum ,water and polyethylene were analyzed and studied

  19. Dielectric properties of proteins from simulations: tools and techniques

    Science.gov (United States)

    Simonson, Thomas; Perahia, David

    1995-09-01

    Tools and techniques to analyze the dielectric properties of proteins are described. Microscopic dielectric properties are determined by a susceptibility tensor of order 3 n, where n is the number of protein atoms. For perturbing charges not too close to the protein, the dielectric relaxation free energy is directly related to the dipole-dipole correlation matrix of the unperturbed protein, or equivalently to the covariance matrix of its atomic displacements. These are straightforward to obtain from existing molecular dynamics packages such as CHARMM or X- PLOR. Macroscopic dielectric properties can be derived from the dipolar fluctuations of the protein, by idealizing the protein as one or more spherical media. The dipolar fluctuations are again directly related to the covariance matrix of the atomic displacements. An interesting consequence is that the quasiharmonic approximation, which by definition exactly reproduces this covariance matrix, gives the protein dielectric constant exactly. Finally a technique is reviewed to obtain normal or quasinormal modes of vibration of symmetric protein assemblies. Using elementary group theory, and eliminating the high-frequency modes of vibration of each monomer, the limiting step in terms of memory and computation is finding the normal modes of a single monomer, with the other monomers held fixed. This technique was used to study the dielectric properties of the Tobacco Mosaic Virus protein disk.

  20. Purpose compliant visual simulation: towards effective and selective methods and techniques of visualisation and simulation

    NARCIS (Netherlands)

    Daru, R.; Venemans, P.

    1998-01-01

    Visualisation, simulation and communication were always intimately interconnected. Visualisations and simulations impersonate existing or virtual realities. Without those tools it is arduous to communicate mental depictions about virtual objects and events. A communication model is presented to

  1. Variance reduction techniques in the simulation of Markov processes

    International Nuclear Information System (INIS)

    Lessi, O.

    1987-01-01

    We study a functional r of the stationary distribution of a homogeneous Markov chain. It is often difficult or impossible to perform the analytical calculation of r and so it is reasonable to estimate r by a simulation process. A consistent estimator r(n) of r is obtained with respect to a chain with a countable state space. Suitably modifying the estimator r(n) of r one obtains a new consistent estimator which has a smaller variance than r(n). The same is obtained in the case of finite state space

  2. Simulation of California's Major Reservoirs Outflow Using Data Mining Technique

    Science.gov (United States)

    Yang, T.; Gao, X.; Sorooshian, S.

    2014-12-01

    The reservoir's outflow is controlled by reservoir operators, which is different from the upstream inflow. The outflow is more important than the reservoir's inflow for the downstream water users. In order to simulate the complicated reservoir operation and extract the outflow decision making patterns for California's 12 major reservoirs, we build a data-driven, computer-based ("artificial intelligent") reservoir decision making tool, using decision regression and classification tree approach. This is a well-developed statistical and graphical modeling methodology in the field of data mining. A shuffled cross validation approach is also employed to extract the outflow decision making patterns and rules based on the selected decision variables (inflow amount, precipitation, timing, water type year etc.). To show the accuracy of the model, a verification study is carried out comparing the model-generated outflow decisions ("artificial intelligent" decisions) with that made by reservoir operators (human decisions). The simulation results show that the machine-generated outflow decisions are very similar to the real reservoir operators' decisions. This conclusion is based on statistical evaluations using the Nash-Sutcliffe test. The proposed model is able to detect the most influential variables and their weights when the reservoir operators make an outflow decision. While the proposed approach was firstly applied and tested on California's 12 major reservoirs, the method is universally adaptable to other reservoir systems.

  3. Developing improved MD codes for understanding processive cellulases

    International Nuclear Information System (INIS)

    Crowley, M F; Nimlos, M R; Himmel, M E; Uberbacher, E C; Iii, C L Brooks; Walker, R C

    2008-01-01

    The mechanism of action of cellulose-degrading enzymes is illuminated through a multidisciplinary collaboration that uses molecular dynamics (MD) simulations and expands the capabilities of MD codes to allow simulations of enzymes and substrates on petascale computational facilities. There is a class of glycoside hydrolase enzymes called cellulases that are thought to decrystallize and processively depolymerize cellulose using biochemical processes that are largely not understood. Understanding the mechanisms involved and improving the efficiency of this hydrolysis process through computational models and protein engineering presents a compelling grand challenge. A detailed understanding of cellulose structure, dynamics and enzyme function at the molecular level is required to direct protein engineers to the right modifications or to understand if natural thermodynamic or kinetic limits are in play. Much can be learned about processivity by conducting carefully designed molecular dynamics (MD) simulations of the binding and catalytic domains of cellulases with various substrate configurations, solvation models and thermodynamic protocols. Most of these numerical experiments, however, will require significant modification of existing code and algorithms in order to efficiently use current (terascale) and future (petascale) hardware to the degree of parallelism necessary to simulate a system of the size proposed here. This work will develop MD codes that can efficiently use terascale and petascale systems, not just for simple classical MD simulations, but also for more advanced methods, including umbrella sampling with complex restraints and reaction coordinates, transition path sampling, steered molecular dynamics, and quantum mechanical/molecular mechanical simulations of systems the size of cellulose degrading enzymes acting on cellulose

  4. Hybrid simulation techniques applied to the earth's bow shock

    Science.gov (United States)

    Winske, D.; Leroy, M. M.

    1985-01-01

    The application of a hybrid simulation model, in which the ions are treated as discrete particles and the electrons as a massless charge-neutralizing fluid, to the study of the earth's bow shock is discussed. The essentials of the numerical methods are described in detail; movement of the ions, solution of the electromagnetic fields and electron fluid equations, and imposition of appropriate boundary and initial conditions. Examples of results of calculations for perpendicular shocks are presented which demonstrate the need for a kinetic treatment of the ions to reproduce the correct ion dynamics and the corresponding shock structure. Results for oblique shocks are also presented to show how the magnetic field and ion motion differ from the perpendicular case.

  5. Drift simulation of MH370 debris using superensemble techniques

    Science.gov (United States)

    Jansen, Eric; Coppini, Giovanni; Pinardi, Nadia

    2016-07-01

    On 7 March 2014 (UTC), Malaysia Airlines flight 370 vanished without a trace. The aircraft is believed to have crashed in the southern Indian Ocean, but despite extensive search operations the location of the wreckage is still unknown. The first tangible evidence of the accident was discovered almost 17 months after the disappearance. On 29 July 2015, a small piece of the right wing of the aircraft was found washed up on the island of Réunion, approximately 4000 km from the assumed crash site. Since then a number of other parts have been found in Mozambique, South Africa and on Rodrigues Island. This paper presents a numerical simulation using high-resolution oceanographic and meteorological data to predict the movement of floating debris from the accident. Multiple model realisations are used with different starting locations and wind drag parameters. The model realisations are combined into a superensemble, adjusting the model weights to best represent the discovered debris. The superensemble is then used to predict the distribution of marine debris at various moments in time. This approach can be easily generalised to other drift simulations where observations are available to constrain unknown input parameters. The distribution at the time of the accident shows that the discovered debris most likely originated from the wide search area between 28 and 35° S. This partially overlaps with the current underwater search area, but extends further towards the north. Results at later times show that the most probable locations to discover washed-up debris are along the African east coast, especially in the area around Madagascar. The debris remaining at sea in 2016 is spread out over a wide area and its distribution changes only slowly.

  6. Limits of validity of photon-in-cell simulation techniques

    International Nuclear Information System (INIS)

    Reitsma, A. J. W.; Jaroszynski, D. A.

    2008-01-01

    A comparison is made between two reduced models for studying laser propagation in underdense plasma; namely, photon kinetic theory and the slowly varying envelope approximation. Photon kinetic theory is a wave-kinetic description of the electromagnetic field where the motion of quasiparticles in photon coordinate-wave number phase space is described by the ray-tracing equations. Numerically, the photon kinetic theory is implemented with standard particle-in-cell techniques, which results in a so-called photon-in-cell code. For all the examples presented in this paper, the slowly varying envelope approximation is accurate and therefore discrepancies indicate the failure of photon kinetic approximation for these cases. Possible remedies for this failure are discussed at the end of the paper

  7. Visualization and simulation techniques for surgical simulators using actual patient's data.

    Science.gov (United States)

    Radetzky, Arne; Nürnberger, Andreas

    2002-11-01

    Because of the increasing complexity of surgical interventions research in surgical simulation became more and more important over the last years. However, the simulation of tissue deformation is still a challenging problem, mainly due to the short response times that are required for real-time interaction. The demands to hard and software are even larger if not only the modeled human anatomy is used but the anatomy of actual patients. This is required if the surgical simulator should be used as training medium for expert surgeons rather than students. In this article, suitable visualization and simulation methods for surgical simulation utilizing actual patient's datasets are described. Therefore, the advantages and disadvantages of direct and indirect volume rendering for the visualization are discussed and a neuro-fuzzy system is described, which can be used for the simulation of interactive tissue deformations. The neuro-fuzzy system makes it possible to define the deformation behavior based on a linguistic description of the tissue characteristics or to learn the dynamics by using measured data of real tissue. Furthermore, a simulator for minimally-invasive neurosurgical interventions is presented that utilizes the described visualization and simulation methods. The structure of the simulator is described in detail and the results of a system evaluation by an experienced neurosurgeon--a quantitative comparison between different methods of virtual endoscopy as well as a comparison between real brain images and virtual endoscopies--are given. The evaluation proved that the simulator provides a higher realism of the visualization and simulation then other currently available simulators. Copyright 2002 Elsevier Science B.V.

  8. Monte Carlo simulation techniques for predicting annual power production

    International Nuclear Information System (INIS)

    Cross, J.P.; Bulandr, P.J.

    1991-01-01

    As the owner and operator of a number of small to mid-sized hydroelectric sites, STS HydroPower has been faced with the need to accurately predict anticipated hydroelectric revenues over a period of years. The typical approach to this problem has been to look at each site from a mathematical deterministic perspective and evaluate the annual production from historic streamflows. Average annual production is simply taken to be the area under the flow duration curve defined by the operating and design characteristics of the selected turbines. Minimum annual production is taken to be a historic dry year scenario and maximum production is viewed as power generated under the most ideal of conditions. Such an approach creates two problems. First, in viewing the characteristics of a single site, it does not take into account the probability of such an event occurring. Second, in viewing all sites in a single organization's portfolio together, it does not reflect the varying flow conditions at the different sites. This paper attempts to address the first of these two concerns, that being the creation of a simulation model utilizing the Monte Carlo method at a single site. The result of the analysis is a picture of the production at the site that is both a better representation of anticipated conditions and defined probabilistically

  9. Simulated Annealing Technique for Routing in a Rectangular Mesh Network

    Directory of Open Access Journals (Sweden)

    Noraziah Adzhar

    2014-01-01

    Full Text Available In the process of automatic design for printed circuit boards (PCBs, the phase following cell placement is routing. On the other hand, routing process is a notoriously difficult problem, and even the simplest routing problem which consists of a set of two-pin nets is known to be NP-complete. In this research, our routing region is first tessellated into a uniform Nx×Ny array of square cells. The ultimate goal for a routing problem is to achieve complete automatic routing with minimal need for any manual intervention. Therefore, shortest path for all connections needs to be established. While classical Dijkstra’s algorithm guarantees to find shortest path for a single net, each routed net will form obstacles for later paths. This will add complexities to route later nets and make its routing longer than the optimal path or sometimes impossible to complete. Today’s sequential routing often applies heuristic method to further refine the solution. Through this process, all nets will be rerouted in different order to improve the quality of routing. Because of this, we are motivated to apply simulated annealing, one of the metaheuristic methods to our routing model to produce better candidates of sequence.

  10. Review of the fundamental theories behind small angle X-ray scattering, molecular dynamics simulations, and relevant integrated application

    Directory of Open Access Journals (Sweden)

    Lauren Boldon

    2015-02-01

    Full Text Available In this paper, the fundamental concepts and equations necessary for performing small angle X-ray scattering (SAXS experiments, molecular dynamics (MD simulations, and MD-SAXS analyses were reviewed. Furthermore, several key biological and non-biological applications for SAXS, MD, and MD-SAXS are presented in this review; however, this article does not cover all possible applications. SAXS is an experimental technique used for the analysis of a wide variety of biological and non-biological structures. SAXS utilizes spherical averaging to produce one- or two-dimensional intensity profiles, from which structural data may be extracted. MD simulation is a computer simulation technique that is used to model complex biological and non-biological systems at the atomic level. MD simulations apply classical Newtonian mechanics’ equations of motion to perform force calculations and to predict the theoretical physical properties of the system. This review presents several applications that highlight the ability of both SAXS and MD to study protein folding and function in addition to non-biological applications, such as the study of mechanical, electrical, and structural properties of non-biological nanoparticles. Lastly, the potential benefits of combining SAXS and MD simulations for the study of both biological and non-biological systems are demonstrated through the presentation of several examples that combine the two techniques.

  11. Review of the fundamental theories behind small angle X-ray scattering, molecular dynamics simulations, and relevant integrated application.

    Science.gov (United States)

    Boldon, Lauren; Laliberte, Fallon; Liu, Li

    2015-01-01

    In this paper, the fundamental concepts and equations necessary for performing small angle X-ray scattering (SAXS) experiments, molecular dynamics (MD) simulations, and MD-SAXS analyses were reviewed. Furthermore, several key biological and non-biological applications for SAXS, MD, and MD-SAXS are presented in this review; however, this article does not cover all possible applications. SAXS is an experimental technique used for the analysis of a wide variety of biological and non-biological structures. SAXS utilizes spherical averaging to produce one- or two-dimensional intensity profiles, from which structural data may be extracted. MD simulation is a computer simulation technique that is used to model complex biological and non-biological systems at the atomic level. MD simulations apply classical Newtonian mechanics' equations of motion to perform force calculations and to predict the theoretical physical properties of the system. This review presents several applications that highlight the ability of both SAXS and MD to study protein folding and function in addition to non-biological applications, such as the study of mechanical, electrical, and structural properties of non-biological nanoparticles. Lastly, the potential benefits of combining SAXS and MD simulations for the study of both biological and non-biological systems are demonstrated through the presentation of several examples that combine the two techniques.

  12. Shower library technique for fast simulation of showers in calorimeters of the H1 experiment

    International Nuclear Information System (INIS)

    Raičević, N.; Glazov, A.; Zhokin, A.

    2013-01-01

    Fast simulation of showers in calorimeters is very important for particle physics analysis since shower simulation typically takes significant amount of the simulation time. At the same time, a simulation must reproduce experimental data in the best possible way. In this paper, a fast simulation of showers in two calorimeters of the H1 experiment is presented. High speed and good quality of shower simulation is achieved by using a shower library technique in which the detector response is simulated using a collection of stored showers for different particle types and topologies. The library is created using the GEANT programme. The fast simulation based on shower library is compared to the data collected by the H1 experiment

  13. Simulation techniques for spatially evolving instabilities in compressible flow over a flat plate

    NARCIS (Netherlands)

    Wasistho, B.; Geurts, Bernardus J.; Kuerten, Johannes G.M.

    1997-01-01

    In this paper we present numerical techniques suitable for a direct numerical simulation in the spatial setting. We demonstrate the application to the simulation of compressible flat plate flow instabilities. We compare second and fourth order accurate spatial discretization schemes in combination

  14. Progress in the development of a video-based wind farm simulation technique

    OpenAIRE

    Robotham, AJ

    1992-01-01

    The progress in the development of a video-based wind farm simulation technique is reviewed. While improvements have been achieved in the quality of the composite picture created by combining computer generated animation sequences of wind turbines with background scenes of the wind farm site, extending the technique to include camera movements has proved troublesome.

  15. Parallel Reservoir Simulations with Sparse Grid Techniques and Applications to Wormhole Propagation

    KAUST Repository

    Wu, Yuanqing

    2015-09-08

    In this work, two topics of reservoir simulations are discussed. The first topic is the two-phase compositional flow simulation in hydrocarbon reservoir. The major obstacle that impedes the applicability of the simulation code is the long run time of the simulation procedure, and thus speeding up the simulation code is necessary. Two means are demonstrated to address the problem: parallelism in physical space and the application of sparse grids in parameter space. The parallel code can gain satisfactory scalability, and the sparse grids can remove the bottleneck of flash calculations. Instead of carrying out the flash calculation in each time step of the simulation, a sparse grid approximation of all possible results of the flash calculation is generated before the simulation. Then the constructed surrogate model is evaluated to approximate the flash calculation results during the simulation. The second topic is the wormhole propagation simulation in carbonate reservoir. In this work, different from the traditional simulation technique relying on the Darcy framework, we propose a new framework called Darcy-Brinkman-Forchheimer framework to simulate wormhole propagation. Furthermore, to process the large quantity of cells in the simulation grid and shorten the long simulation time of the traditional serial code, standard domain-based parallelism is employed, using the Hypre multigrid library. In addition to that, a new technique called “experimenting field approach” to set coefficients in the model equations is introduced. In the 2D dissolution experiments, different configurations of wormholes and a series of properties simulated by both frameworks are compared. We conclude that the numerical results of the DBF framework are more like wormholes and more stable than the Darcy framework, which is a demonstration of the advantages of the DBF framework. The scalability of the parallel code is also evaluated, and good scalability can be achieved. Finally, a mixed

  16. Simulation of sustainability aspects within the industrial environment and their implication on the simulation technique

    OpenAIRE

    Rabe, M.; Jäkel, F.-W.; Weinaug, H.

    2010-01-01

    Simulation is a broadly excepted analytic instrument and planning tool. Today, industrial simulation is mainly applied for engineering and physical purposes and covers a short time horizon compared to intergenerational justice. In parallel, sustainability is gaining more importance for the industrial planning because themes like global warming, child labour, and compliance with social and environmental standards have to be taken into account. Sustainability is characterized by comprehensively...

  17. Cavity Voltage Phase Modulation MD

    CERN Document Server

    Mastoridis, Themistoklis; Molendijk, John; Timko, Helga; CERN. Geneva. ATS Department

    2016-01-01

    The LHC RF/LLRF system is currently configured for extremely stable RF voltage to minimize transient beam loading effects. The present scheme cannot be extended beyond nominal beam current since the demanded power would exceed the peak klystron power and lead to saturation. A new scheme has therefore been proposed: for beam currents above nominal (and possibly earlier), the cavity phase modulation by the beam will not be corrected (transient beam loading), but the strong RF feedback and One-Turn Delay feedback will still be active for loop and beam stability in physics. To achieve this, the voltage set point will be adapted for each bunch. The goal of this MD was to test a new algorithm that would adjust the voltage set point to achieve the cavity phase modulation that would minimize klystron forward power.

  18. Quality comparison between DEF-10 digital image from simulation technique and Computed Tomography (CR) technique in industrial radiography

    International Nuclear Information System (INIS)

    Siti Nur Syatirah Ismail

    2012-01-01

    The study was conducted to make comparison of digital image quality of DEF-10 from the techniques of simulation and computed radiography (CR). The sample used is steel DEF-10 with thickness of 15.28 mm. In this study, the sample is exposed to radiation from X-ray machine (ISOVOLT Titan E) with certain parameters. The parameters used in this study such as current, volt, exposure time and distance are specified. The current and distance of 3 mA and 700 mm respectively are specified while the applied voltage varies at 140, 160, 180 and 200 kV. The exposure time is reduced at a rate of 0, 20, 40, 60 and 80 % for each sample exposure. Digital image of simulation produced from aRTist software whereas digital image of computed radiography produced from imaging plate. Therefore, both images were compared qualitatively (sensitivity) and quantitatively (Signal to-Noise Ratio; SNR, Basic Spatial Resolution; SRb and LOP size) using Isee software. Radiographic sensitivity is indicated by Image Quality Indicator (IQI) which is the ability of the CR system and aRTist software to identify IQI of wire type when the time exposure is reduced up to 80% according to exposure chart ( D7; ISOVOLT Titan E). The image of the thinnest wire diameter achieved by radiograph from simulation and CR are the wire numbered 7 rather than the wire numbered 8 required by the standard. In quantitative comparison, this study shows that the SNR values decreases with reducing exposure time. SRb values increases for simulation and decreases for CR when the exposure time decreases and the good image quality can be achieved at 80% reduced exposure time. The high SNR and SRb values produced good image quality in CR and simulation techniques respectively. (author)

  19. Simulation into Reality: Some Effects of Simulation Techniques on Organizational Communication Students.

    Science.gov (United States)

    Allen, Richard K.

    In an attempt to discover improved classroom teaching methods, a class was turned into a business organization as a way of bringing life to the previously covered lectures and textual materials. The simulated games were an attempt to get people to work toward a common goal with all of the power plays, secret meetings, brainstorming, anger, and…

  20. Simulation of the fissureless technique for thoracoscopic segmentectomy using rapid prototyping.

    Science.gov (United States)

    Akiba, Tadashi; Nakada, Takeo; Inagaki, Takuya

    2015-01-01

    The fissureless lobectomy or anterior fissureless technique is a novel surgical technique, which avoids dissection of the lung parenchyma over the pulmonary artery during lobectomy by open thoracotomy approach or direct vision thoracoscopic surgery. This technique is indicated for fused lobes. We present two cases where thoracoscopic pulmonary segmentectomy was performed using the fissureless technique simulated by three-dimensional (3D) pulmonary models. The 3D model and rapid prototyping provided an accurate anatomical understanding of the operative field in both cases. We believe that the construction of these models is useful for thoracoscopic and other complicated surgeries of the chest.

  1. Simulation of the Fissureless Technique for Thoracoscopic Segmentectomy Using Rapid Prototyping

    Science.gov (United States)

    Nakada, Takeo; Inagaki, Takuya

    2014-01-01

    The fissureless lobectomy or anterior fissureless technique is a novel surgical technique, which avoids dissection of the lung parenchyma over the pulmonary artery during lobectomy by open thoracotomy approach or direct vision thoracoscopic surgery. This technique is indicated for fused lobes. We present two cases where thoracoscopic pulmonary segmentectomy was performed using the fissureless technique simulated by three-dimensional (3D) pulmonary models. The 3D model and rapid prototyping provided an accurate anatomical understanding of the operative field in both cases. We believe that the construction of these models is useful for thoracoscopic and other complicated surgeries of the chest. PMID:24633132

  2. A 3D technique for simulation of irregular electron treatment fields using a digital camera

    International Nuclear Information System (INIS)

    Bassalow, Roustem; Sidhu, Narinder P.

    2003-01-01

    Cerrobend inserts, which define electron field apertures, are manufactured at our institution using perspex templates. Contours are reproduced manually on these templates at the simulator from the field outlines drawn on the skin or mask of a patient. A previously reported technique for simulation of electron treatment fields uses a digital camera to eliminate the need for such templates. However, avoidance of the image distortions introduced by non-flat surfaces on which the electron field outlines were drawn could only be achieved by limiting the application of this technique to surfaces which were flat or near flat. We present a technique that employs a digital camera and allows simulation of electron treatment fields contoured on an anatomical surface of an arbitrary three-dimensional (3D) shape, such as that of the neck, extremities, face, or breast. The procedure is fast, accurate, and easy to perform

  3. An overview of uncertainty quantification techniques with application to oceanic and oil-spill simulations

    KAUST Repository

    Iskandarani, Mohamed; Wang, Shitao; Srinivasan, Ashwanth; Carlisle Thacker, W.; Winokur, Justin; Knio, Omar

    2016-01-01

    We give an overview of four different ensemble-based techniques for uncertainty quantification and illustrate their application in the context of oil plume simulations. These techniques share the common paradigm of constructing a model proxy that efficiently captures the functional dependence of the model output on uncertain model inputs. This proxy is then used to explore the space of uncertain inputs using a large number of samples, so that reliable estimates of the model's output statistics can be calculated. Three of these techniques use polynomial chaos (PC) expansions to construct the model proxy, but they differ in their approach to determining the expansions' coefficients; the fourth technique uses Gaussian Process Regression (GPR). An integral plume model for simulating the Deepwater Horizon oil-gas blowout provides examples for illustrating the different techniques. A Monte Carlo ensemble of 50,000 model simulations is used for gauging the performance of the different proxies. The examples illustrate how regression-based techniques can outperform projection-based techniques when the model output is noisy. They also demonstrate that robust uncertainty analysis can be performed at a fraction of the cost of the Monte Carlo calculation.

  4. An overview of uncertainty quantification techniques with application to oceanic and oil-spill simulations

    KAUST Repository

    Iskandarani, Mohamed

    2016-04-22

    We give an overview of four different ensemble-based techniques for uncertainty quantification and illustrate their application in the context of oil plume simulations. These techniques share the common paradigm of constructing a model proxy that efficiently captures the functional dependence of the model output on uncertain model inputs. This proxy is then used to explore the space of uncertain inputs using a large number of samples, so that reliable estimates of the model\\'s output statistics can be calculated. Three of these techniques use polynomial chaos (PC) expansions to construct the model proxy, but they differ in their approach to determining the expansions\\' coefficients; the fourth technique uses Gaussian Process Regression (GPR). An integral plume model for simulating the Deepwater Horizon oil-gas blowout provides examples for illustrating the different techniques. A Monte Carlo ensemble of 50,000 model simulations is used for gauging the performance of the different proxies. The examples illustrate how regression-based techniques can outperform projection-based techniques when the model output is noisy. They also demonstrate that robust uncertainty analysis can be performed at a fraction of the cost of the Monte Carlo calculation.

  5. An analytical simulation technique for cone-beam CT and pinhole SPECT

    International Nuclear Information System (INIS)

    Zhang Xuezhu; Qi Yujin

    2011-01-01

    This study was aimed at developing an efficient simulation technique with an ordinary PC. The work involved derivation of mathematical operators, analytic phantom generations, and effective analytical projectors developing for cone-beam CT and pinhole SPECT imaging. The computer simulations based on the analytical projectors were developed by ray-tracing method for cone-beam CT and voxel-driven method for pinhole SPECT of degrading blurring. The 3D Shepp-Logan, Jaszczak and Defrise phantoms were used for simulation evaluations and image reconstructions. The reconstructed phantom images were of good accuracy with the phantoms. The results showed that the analytical simulation technique is an efficient tool for studying cone-beam CT and pinhole SPECT imaging. (authors)

  6. Analytical vs. Simulation Solution Techniques for Pulse Problems in Non-linear Stochastic Dynamics

    DEFF Research Database (Denmark)

    Iwankiewicz, R.; Nielsen, Søren R. K.

    Advantages and disadvantages of available analytical and simulation techniques for pulse problems in non-linear stochastic dynamics are discussed. First, random pulse problems, both those which do and do not lead to Markov theory, are presented. Next, the analytical and analytically-numerical tec......Advantages and disadvantages of available analytical and simulation techniques for pulse problems in non-linear stochastic dynamics are discussed. First, random pulse problems, both those which do and do not lead to Markov theory, are presented. Next, the analytical and analytically...

  7. Research on integrated simulation of fluid-structure system by computation science techniques

    International Nuclear Information System (INIS)

    Yamaguchi, Akira

    1996-01-01

    In Power Reactor and Nuclear Fuel Development Corporation, the research on the integrated simulation of fluid-structure system by computation science techniques has been carried out, and by its achievement, the verification of plant systems which has depended on large scale experiments is substituted by computation science techniques, in this way, it has been aimed at to reduce development costs and to attain the optimization of FBR systems. For the purpose, it is necessary to establish the technology for integrally and accurately analyzing complicated phenomena (simulation technology), the technology for applying it to large scale problems (speed increasing technology), and the technology for assuring the reliability of the results of analysis when simulation technology is utilized for the permission and approval of FBRs (verifying technology). The simulation of fluid-structure interaction, the heat flow simulation in the space with complicated form and the related technologies are explained. As the utilization of computation science techniques, the elucidation of phenomena by numerical experiment and the numerical simulation as the substitute for tests are discussed. (K.I.)

  8. Development of a Car Racing Simulator Game Using Artificial Intelligence Techniques

    Directory of Open Access Journals (Sweden)

    Marvin T. Chan

    2015-01-01

    Full Text Available This paper presents a car racing simulator game called Racer, in which the human player races a car against three game-controlled cars in a three-dimensional environment. The objective of the game is not to defeat the human player, but to provide the player with a challenging and enjoyable experience. To ensure that this objective can be accomplished, the game incorporates artificial intelligence (AI techniques, which enable the cars to be controlled in a manner that mimics natural driving. The paper provides a brief history of AI techniques in games, presents the use of AI techniques in contemporary video games, and discusses the AI techniques that were implemented in the development of Racer. A comparison of the AI techniques implemented in the Unity platform with traditional AI search techniques is also included in the discussion.

  9. The discovery of 260Md and the decay properties of 258Fm, 258m,gMd and 259Md

    International Nuclear Information System (INIS)

    Lougheed, R.W.; Hulet, E.K.; Dougan, R.J.; Wild, J.F.; Dupzyk, R.J.; Henderson, C.M.; Moody, K.J.; Hahn, R.L.; Suemmerer, K.; Bethune, G.

    1986-01-01

    We have discovered a new neutron-rich isotope, 260 Md, from 18 O and 22 Ne bombardments of 254 Es. We observed a spontaneous-fission (SF) activity with a half-life of 32 days in electromagnetically separated fractions with mass number 260 from these bombardments and we measured the mass and kinetic energy distributions of this SF activity. The mass distribution was symmetric with the principal energy peak at a total kinetic energy (TKE) of 234 MeV, similar to previous observations for heavy fermium isotopes. Surprisingly, we also observed a smaller symmetric component with a TKE of 195 MeV. We interpret these two peaks in the TKE distribution as arising from two types of fission in the same nucleus, or bimodal fission. The observed fission activity may be either from the SF decay of 260 Md or from 260 Fm which would arise from electron-capture (EC) decay of 260 Md. We have eliminated the possible β - decay of 260 Md by measuring β - -SF time correlations for the decay of 260 Md and we plan to determine whether 260 Md decays by EC by measuring time correlations between fermium X-rays and SF events. We also measured various properties of the heavy fermium and mendelevium isotopes and obtained 1. more accurate cross-sections for the neutron-rich mendelevium isotopes which we use to predict the production rates of yet undiscovered nuclides, 2. improved half-life measurements for 258m,g Md and 259 Md, 3. confirmation of the EC decay of 258m Md by measurement of the fermium X-rays preceding the SF decay of 258 Fm and 4. very substantially improved mass and TKE distributions for the SF decay of 258 Fm and 259 Md. (orig.)

  10. pMD-Membrane: A Method for Ligand Binding Site Identification in Membrane-Bound Proteins.

    Directory of Open Access Journals (Sweden)

    Priyanka Prakash

    2015-10-01

    Full Text Available Probe-based or mixed solvent molecular dynamics simulation is a useful approach for the identification and characterization of druggable sites in drug targets. However, thus far the method has been applied only to soluble proteins. A major reason for this is the potential effect of the probe molecules on membrane structure. We have developed a technique to overcome this limitation that entails modification of force field parameters to reduce a few pairwise non-bonded interactions between selected atoms of the probe molecules and bilayer lipids. We used the resulting technique, termed pMD-membrane, to identify allosteric ligand binding sites on the G12D and G13D oncogenic mutants of the K-Ras protein bound to a negatively charged lipid bilayer. In addition, we show that differences in probe occupancy can be used to quantify changes in the accessibility of druggable sites due to conformational changes induced by membrane binding or mutation.

  11. Modeling and numerical techniques for high-speed digital simulation of nuclear power plants

    International Nuclear Information System (INIS)

    Wulff, W.; Cheng, H.S.; Mallen, A.N.

    1987-01-01

    Conventional computing methods are contrasted with newly developed high-speed and low-cost computing techniques for simulating normal and accidental transients in nuclear power plants. Six principles are formulated for cost-effective high-fidelity simulation with emphasis on modeling of transient two-phase flow coolant dynamics in nuclear reactors. Available computing architectures are characterized. It is shown that the combination of the newly developed modeling and computing principles with the use of existing special-purpose peripheral processors is capable of achieving low-cost and high-speed simulation with high-fidelity and outstanding user convenience, suitable for detailed reactor plant response analyses

  12. Virtual X-ray imaging techniques in an immersive casting simulation environment

    International Nuclear Information System (INIS)

    Li, Ning; Kim, Sung-Hee; Suh, Ji-Hyun; Cho, Sang-Hyun; Choi, Jung-Gil; Kim, Myoung-Hee

    2007-01-01

    A computer code was developed to simulate radiograph of complex casting products in a CAVE TM -like environment. The simulation is based on the deterministic algorithms and ray tracing techniques. The aim of this study is to examine CAD/CAE/CAM models at the design stage, to optimize the design and inspect predicted defective regions with fast speed, good accuracy and small numerical expense. The present work discusses the algorithms for the radiography simulation of CAD/CAM model and proposes algorithmic solutions adapted from ray-box intersection algorithm and octree data structure specifically for radiographic simulation of CAE model. The stereoscopic visualization of full-size of product in the immersive casting simulation environment as well as the virtual X-ray images of castings provides an effective tool for design and evaluation of foundry processes by engineers and metallurgists

  13. First thoughts on MD priorities for 2012

    CERN Document Server

    Zimmermann, F; Assmann, R

    2012-01-01

    In 2012, 22 days of beam time will be allocated for LHC MDs. In this paper, after recalling the 2011 LHC MD experience, the MD rrequests for 2012 are reviewed. Three primary MD themes for 2012 can be identified: 1)pushing performance in 2012, 2)preparing for 2014/15, and 3)towards maximum luminosity. Example topics include emittance growth in collision or enhanced satellites for theme 1), 25 ns operation for 2), and ATS optics for 3). Structures lists of MD requests and topics for each theme as well as some initial thoughts on the MD priorities are presented. For certain topics, "start-of-fill MDs" are proposed in order to most efficiently use of the available beam time.

  14. Multilevel techniques lead to accurate numerical upscaling and scalable robust solvers for reservoir simulation

    DEFF Research Database (Denmark)

    Christensen, Max la Cour; Villa, Umberto; Vassilevski, Panayot

    2015-01-01

    approach is well suited for the solution of large problems coming from finite element discretizations of systems of partial differential equations. The AMGe technique from 10,9 allows for the construction of operator-dependent coarse (upscaled) models and guarantees approximation properties of the coarse...... implementation of the reservoir simulator is demonstrated....

  15. The Generalized Multipole Technique for the Simulation of Low-Loss Electron Energy Loss Spectroscopy

    DEFF Research Database (Denmark)

    Kiewidt, Lars; Karamehmedovic, Mirza

    2018-01-01

    In this study, we demonstrate the use of a Generalized Multipole Technique (GMT) to simulate low-loss Electron Energy Loss Spectroscopy (EELS) spectra of isolated spheriodal nanoparticles. The GMT provides certain properties, such as semi-analytical description of the electromagnetic fields...

  16. An Improved Simulated Annealing Technique for Enhanced Mobility in Smart Cities.

    Science.gov (United States)

    Amer, Hayder; Salman, Naveed; Hawes, Matthew; Chaqfeh, Moumena; Mihaylova, Lyudmila; Mayfield, Martin

    2016-06-30

    Vehicular traffic congestion is a significant problem that arises in many cities. This is due to the increasing number of vehicles that are driving on city roads of limited capacity. The vehicular congestion significantly impacts travel distance, travel time, fuel consumption and air pollution. Avoidance of traffic congestion and providing drivers with optimal paths are not trivial tasks. The key contribution of this work consists of the developed approach for dynamic calculation of optimal traffic routes. Two attributes (the average travel speed of the traffic and the roads' length) are utilized by the proposed method to find the optimal paths. The average travel speed values can be obtained from the sensors deployed in smart cities and communicated to vehicles via the Internet of Vehicles and roadside communication units. The performance of the proposed algorithm is compared to three other algorithms: the simulated annealing weighted sum, the simulated annealing technique for order preference by similarity to the ideal solution and the Dijkstra algorithm. The weighted sum and technique for order preference by similarity to the ideal solution methods are used to formulate different attributes in the simulated annealing cost function. According to the Sheffield scenario, simulation results show that the improved simulated annealing technique for order preference by similarity to the ideal solution method improves the traffic performance in the presence of congestion by an overall average of 19.22% in terms of travel time, fuel consumption and CO₂ emissions as compared to other algorithms; also, similar performance patterns were achieved for the Birmingham test scenario.

  17. Optimizing Availability of a Framework in Series Configuration Utilizing Markov Model and Monte Carlo Simulation Techniques

    Directory of Open Access Journals (Sweden)

    Mansoor Ahmed Siddiqui

    2017-06-01

    Full Text Available This research work is aimed at optimizing the availability of a framework comprising of two units linked together in series configuration utilizing Markov Model and Monte Carlo (MC Simulation techniques. In this article, effort has been made to develop a maintenance model that incorporates three distinct states for each unit, while taking into account their different levels of deterioration. Calculations are carried out using the proposed model for two distinct cases of corrective repair, namely perfect and imperfect repairs, with as well as without opportunistic maintenance. Initially, results are accomplished using an analytical technique i.e., Markov Model. Validation of the results achieved is later carried out with the help of MC Simulation. In addition, MC Simulation based codes also work well for the frameworks that follow non-exponential failure and repair rates, and thus overcome the limitations offered by the Markov Model.

  18. Advanced particle-in-cell simulation techniques for modeling the Lockheed Martin Compact Fusion Reactor

    Science.gov (United States)

    Welch, Dale; Font, Gabriel; Mitchell, Robert; Rose, David

    2017-10-01

    We report on particle-in-cell developments of the study of the Compact Fusion Reactor. Millisecond, two and three-dimensional simulations (cubic meter volume) of confinement and neutral beam heating of the magnetic confinement device requires accurate representation of the complex orbits, near perfect energy conservation, and significant computational power. In order to determine initial plasma fill and neutral beam heating, these simulations include ionization, elastic and charge exchange hydrogen reactions. To this end, we are pursuing fast electromagnetic kinetic modeling algorithms including a two implicit techniques and a hybrid quasi-neutral algorithm with kinetic ions. The kinetic modeling includes use of the Poisson-corrected direct implicit, magnetic implicit, as well as second-order cloud-in-cell techniques. The hybrid algorithm, ignoring electron inertial effects, is two orders of magnitude faster than kinetic but not as accurate with respect to confinement. The advantages and disadvantages of these techniques will be presented. Funded by Lockheed Martin.

  19. Wind Turbine Rotor Simulation via CFD Based Actuator Disc Technique Compared to Detailed Measurement

    Directory of Open Access Journals (Sweden)

    Esmail Mahmoodi

    2015-10-01

    Full Text Available In this paper, a generalized Actuator Disc (AD is used to model the wind turbine rotor of the MEXICO experiment, a collaborative European wind turbine project. The AD model as a combination of CFD technique and User Defined Functions codes (UDF, so-called UDF/AD model is used to simulate loads and performance of the rotor in three different wind speed tests. Distributed force on the blade, thrust and power production of the rotor as important designing parameters of wind turbine rotors are focused to model. A developed Blade Element Momentum (BEM theory as a code based numerical technique as well as a full rotor simulation both from the literature are included into the results to compare and discuss. The output of all techniques is compared to detailed measurements for validation, which led us to final conclusions.

  20. Student perception of two different simulation techniques in oral and maxillofacial surgery undergraduate training.

    Science.gov (United States)

    Lund, Bodil; Fors, Uno; Sejersen, Ronny; Sallnäs, Eva-Lotta; Rosén, Annika

    2011-10-12

    Yearly surveys among the undergraduate students in oral and maxillofacial surgery at Karolinska Institutet have conveyed a wish for increased clinical training, and in particular, in surgical removal of mandibular third molars. Due to lack of resources, this kind of clinical supervision has so far not been possible to implement. One possible solution to this problem might be to introduce simulation into the curriculum. The purpose of this study was to investigate undergraduate students' perception of two different simulation methods for practicing clinical reasoning skills and technical skills in oral and maxillofacial surgery. Forty-seven students participating in the oral and maxillofacial surgery course at Karolinska Institutet during their final year were included. Three different oral surgery patient cases were created in a Virtual Patient (VP) Simulation system (Web-SP) and used for training clinical reasoning. A mandibular third molar surgery simulator with tactile feedback, providing hands on training in the bone removal and tooth sectioning in third molar surgery, was also tested. A seminar was performed using the combination of these two simulators where students' perception of the two different simulation methods was assessed by means of a questionnaire. The response rate was 91.5% (43/47). The students were positive to the VP cases, although they rated their possible improvement of clinical reasoning skills as moderate. The students' perception of improved technical skills after training in the mandibular third molar surgery simulator was rated high. The majority of the students agreed that both simulation techniques should be included in the curriculum and strongly agreed that it was a good idea to use the two simulators in concert. The importance of feedback from the senior experts during simulator training was emphasised. The two tested simulation methods were well accepted and most students agreed that the future curriculum would benefit from

  1. Validation of a low dose simulation technique for computed tomography images.

    Directory of Open Access Journals (Sweden)

    Daniela Muenzel

    Full Text Available PURPOSE: Evaluation of a new software tool for generation of simulated low-dose computed tomography (CT images from an original higher dose scan. MATERIALS AND METHODS: Original CT scan data (100 mAs, 80 mAs, 60 mAs, 40 mAs, 20 mAs, 10 mAs; 100 kV of a swine were acquired (approved by the regional governmental commission for animal protection. Simulations of CT acquisition with a lower dose (simulated 10-80 mAs were calculated using a low-dose simulation algorithm. The simulations were compared to the originals of the same dose level with regard to density values and image noise. Four radiologists assessed the realistic visual appearance of the simulated images. RESULTS: Image characteristics of simulated low dose scans were similar to the originals. Mean overall discrepancy of image noise and CT values was -1.2% (range -9% to 3.2% and -0.2% (range -8.2% to 3.2%, respectively, p>0.05. Confidence intervals of discrepancies ranged between 0.9-10.2 HU (noise and 1.9-13.4 HU (CT values, without significant differences (p>0.05. Subjective observer evaluation of image appearance showed no visually detectable difference. CONCLUSION: Simulated low dose images showed excellent agreement with the originals concerning image noise, CT density values, and subjective assessment of the visual appearance of the simulated images. An authentic low-dose simulation opens up opportunity with regard to staff education, protocol optimization and introduction of new techniques.

  2. Simulation of white light generation and near light bullets using a novel numerical technique

    Science.gov (United States)

    Zia, Haider

    2018-01-01

    An accurate and efficient simulation has been devised, employing a new numerical technique to simulate the derivative generalised non-linear Schrödinger equation in all three spatial dimensions and time. The simulation models all pertinent effects such as self-steepening and plasma for the non-linear propagation of ultrafast optical radiation in bulk material. Simulation results are compared to published experimental spectral data of an example ytterbium aluminum garnet system at 3.1 μm radiation and fits to within a factor of 5. The simulation shows that there is a stability point near the end of the 2 mm crystal where a quasi-light bullet (spatial temporal soliton) is present. Within this region, the pulse is collimated at a reduced diameter (factor of ∼2) and there exists a near temporal soliton at the spatial center. The temporal intensity within this stable region is compressed by a factor of ∼4 compared to the input. This study shows that the simulation highlights new physical phenomena based on the interplay of various linear, non-linear and plasma effects that go beyond the experiment and is thus integral to achieving accurate designs of white light generation systems for optical applications. An adaptive error reduction algorithm tailor made for this simulation will also be presented in appendix.

  3. MD2036: UFO Dynamics Studies and UFO Fast Detection

    CERN Document Server

    Belanger, Philippe; Valette, Matthieu; Lindstrom, Bjorn Hans Filip; Grob, Laura Katharina; Schmidt, Rudiger; Wollmann, Daniel

    2017-01-01

    UFOs are one of the remaining unknown related to LHC operation. Therefore, improving the understanding of UFO dynamics and validating the developed models against direct beam measurements is of fundamental importance in view of LHC operation at 7 TeV and with HL-LHC beam intensities. If not understood, UFOs could also be a showstopper for future machines such as FCC. This MD demonstrates new methods to study the dynamic behaviour of a calibrated UFO, simulated by the interaction of wire scanners with the beam. The events created during the MD were monitored using diamond BLMs in IR7, providing bunch-by-bunch resolution measurements. The analysis presented herein shows that blown-up bunches can be used to identify the plane of movement of UFOs, that bunch profiles and bunch sizes can be measured with dBLMs with good precision, that simulation of expected losses are in good agreement with measurements for oscillating bunches and that the space resolution of the acquisition system used during the MD is about 10 ...

  4. Crack growth simulation for plural crack using hexahedral mesh generation technique

    International Nuclear Information System (INIS)

    Orita, Y; Wada, Y; Kikuchi, M

    2010-01-01

    This paper describes a surface crack growth simulation using a new mesh generation technique. The generated mesh is constituted of all hexahedral elements. Hexahedral elements are suitable for an analysis of fracture mechanics parameters, i.e. stress intensity factor. The advantage of a hexahedral mesh is good accuracy of an analysis and less number of degrees of freedoms than a tetrahedral mesh. In this study, a plural crack growth simulation is computed using the hexahedral mesh and its distribution of stress intensity factor is investigated.

  5. Selecting the Most Economic Project under Uncertainty Using Bootstrap Technique and Fuzzy Simulation

    Directory of Open Access Journals (Sweden)

    Kamran Shahanaghi

    2012-01-01

    Full Text Available This article, by leaving pre-determined membership function of a fuzzy set which is a basic assumption for such subject, will try to propose a hybrid technique to select the most economic project among alternative projects in fuzziness interest rates condition. In this way, net present worth (NPW would be the economic indicator. This article tries to challenge the assumption of large sample sizes availability for membership function determination and shows that some other techniques may have less accuracy. To give a robust solution, bootstrapping and fuzzy simulation is suggested and a numerical example is given and analyzed.

  6. Timesaving techniques for decision of electron-molecule collisions in Monte Carlo simulation of electrical discharges

    International Nuclear Information System (INIS)

    Sugawara, Hirotake; Mori, Naoki; Sakai, Yosuke; Suda, Yoshiyuki

    2007-01-01

    Techniques to reduce the computational load for determination of electron-molecule collisions in Monte Carlo simulations of electrical discharges have been presented. By enhancing the detection efficiency of the no-collision case in the decision scheme of the collisional events, we can decrease the frequency of access to time-consuming subroutines to calculate the electron collision cross sections of the gas molecules for obtaining the collision probability. A benchmark test and an estimation to evaluate the present techniques have shown a practical timesaving efficiency

  7. Application of data assimilation technique for flow field simulation for Kaiga site using TAPM model

    International Nuclear Information System (INIS)

    Shrivastava, R.; Oza, R.B.; Puranik, V.D.; Hegde, M.N.; Kushwaha, H.S.

    2008-01-01

    The data assimilation techniques are becoming popular nowadays to get realistic flow field simulation for the site under consideration. The present paper describes data assimilation technique for flow field simulation for Kaiga site using the air pollution model (TAPM) developed by CSIRO, Australia. In this, the TAPM model was run for Kaiga site for a period of one month (Nov. 2004) using the analysed meteorological data supplied with the model for Central Asian (CAS) region and the model solutions were nudged with the observed wind speed and wind direction data available for the site. The model was run with 4 nested grids with grid spacing varying from 30km, 10km, 3km and 1km respectively. The models generated results with and without nudging are statistically compared with the observations. (author)

  8. Optimisation of 12 MeV electron beam simulation using variance reduction technique

    International Nuclear Information System (INIS)

    Jayamani, J; Aziz, M Z Abdul; Termizi, N A S Mohd; Kamarulzaman, F N Mohd

    2017-01-01

    Monte Carlo (MC) simulation for electron beam radiotherapy consumes a long computation time. An algorithm called variance reduction technique (VRT) in MC was implemented to speed up this duration. This work focused on optimisation of VRT parameter which refers to electron range rejection and particle history. EGSnrc MC source code was used to simulate (BEAMnrc code) and validate (DOSXYZnrc code) the Siemens Primus linear accelerator model with the non-VRT parameter. The validated MC model simulation was repeated by applying VRT parameter (electron range rejection) that controlled by global electron cut-off energy 1,2 and 5 MeV using 20 × 10 7 particle history. 5 MeV range rejection generated the fastest MC simulation with 50% reduction in computation time compared to non-VRT simulation. Thus, 5 MeV electron range rejection utilized in particle history analysis ranged from 7.5 × 10 7 to 20 × 10 7 . In this study, 5 MeV electron cut-off with 10 × 10 7 particle history, the simulation was four times faster than non-VRT calculation with 1% deviation. Proper understanding and use of VRT can significantly reduce MC electron beam calculation duration at the same time preserving its accuracy. (paper)

  9. Assessment of Robotic Patient Simulators for Training in Manual Physical Therapy Examination Techniques

    Science.gov (United States)

    Ishikawa, Shun; Okamoto, Shogo; Isogai, Kaoru; Akiyama, Yasuhiro; Yanagihara, Naomi; Yamada, Yoji

    2015-01-01

    Robots that simulate patients suffering from joint resistance caused by biomechanical and neural impairments are used to aid the training of physical therapists in manual examination techniques. However, there are few methods for assessing such robots. This article proposes two types of assessment measures based on typical judgments of clinicians. One of the measures involves the evaluation of how well the simulator presents different severities of a specified disease. Experienced clinicians were requested to rate the simulated symptoms in terms of severity, and the consistency of their ratings was used as a performance measure. The other measure involves the evaluation of how well the simulator presents different types of symptoms. In this case, the clinicians were requested to classify the simulated resistances in terms of symptom type, and the average ratios of their answers were used as performance measures. For both types of assessment measures, a higher index implied higher agreement among the experienced clinicians that subjectively assessed the symptoms based on typical symptom features. We applied these two assessment methods to a patient knee robot and achieved positive appraisals. The assessment measures have potential for use in comparing several patient simulators for training physical therapists, rather than as absolute indices for developing a standard. PMID:25923719

  10. Assessment of robotic patient simulators for training in manual physical therapy examination techniques.

    Directory of Open Access Journals (Sweden)

    Shun Ishikawa

    Full Text Available Robots that simulate patients suffering from joint resistance caused by biomechanical and neural impairments are used to aid the training of physical therapists in manual examination techniques. However, there are few methods for assessing such robots. This article proposes two types of assessment measures based on typical judgments of clinicians. One of the measures involves the evaluation of how well the simulator presents different severities of a specified disease. Experienced clinicians were requested to rate the simulated symptoms in terms of severity, and the consistency of their ratings was used as a performance measure. The other measure involves the evaluation of how well the simulator presents different types of symptoms. In this case, the clinicians were requested to classify the simulated resistances in terms of symptom type, and the average ratios of their answers were used as performance measures. For both types of assessment measures, a higher index implied higher agreement among the experienced clinicians that subjectively assessed the symptoms based on typical symptom features. We applied these two assessment methods to a patient knee robot and achieved positive appraisals. The assessment measures have potential for use in comparing several patient simulators for training physical therapists, rather than as absolute indices for developing a standard.

  11. Assessment of robotic patient simulators for training in manual physical therapy examination techniques.

    Science.gov (United States)

    Ishikawa, Shun; Okamoto, Shogo; Isogai, Kaoru; Akiyama, Yasuhiro; Yanagihara, Naomi; Yamada, Yoji

    2015-01-01

    Robots that simulate patients suffering from joint resistance caused by biomechanical and neural impairments are used to aid the training of physical therapists in manual examination techniques. However, there are few methods for assessing such robots. This article proposes two types of assessment measures based on typical judgments of clinicians. One of the measures involves the evaluation of how well the simulator presents different severities of a specified disease. Experienced clinicians were requested to rate the simulated symptoms in terms of severity, and the consistency of their ratings was used as a performance measure. The other measure involves the evaluation of how well the simulator presents different types of symptoms. In this case, the clinicians were requested to classify the simulated resistances in terms of symptom type, and the average ratios of their answers were used as performance measures. For both types of assessment measures, a higher index implied higher agreement among the experienced clinicians that subjectively assessed the symptoms based on typical symptom features. We applied these two assessment methods to a patient knee robot and achieved positive appraisals. The assessment measures have potential for use in comparing several patient simulators for training physical therapists, rather than as absolute indices for developing a standard.

  12. A Dynamic Operation Permission Technique Based on an MFM Model and Numerical Simulation

    International Nuclear Information System (INIS)

    Akio, Gofuku; Masahiro, Yonemura

    2011-01-01

    It is important to support operator activities to an abnormal plant situation where many counter actions are taken in relatively short time. The authors proposed a technique called dynamic operation permission to decrease human errors without eliminating creative idea of operators to cope with an abnormal plant situation by checking if the counter action taken is consistent with emergency operation procedure. If the counter action is inconsistent, a dynamic operation permission system warns it to operators. It also explains how and why the counter action is inconsistent and what influence will appear on the future plant behavior by a qualitative influence inference technique based on a model by the Mf (Multilevel Flow Modeling). However, the previous dynamic operation permission is not able to explain quantitative effects on plant future behavior. Moreover, many possible influence paths are derived because a qualitative reasoning does not give a solution when positive and negative influences are propagated to the same node. This study extends the dynamic operation permission by combining the qualitative reasoning and the numerical simulation technique. The qualitative reasoning based on an Mf model of plant derives all possible influence propagation paths. Then, a numerical simulation gives a prediction of plant future behavior in the case of taking a counter action. The influence propagation that does not coincide with the simulation results is excluded from possible influence paths. The extended technique is implemented in a dynamic operation permission system for an oil refinery plant. An MFM model and a static numerical simulator are developed. The results of dynamic operation permission for some abnormal plant situations show the improvement of the accuracy of dynamic operation permission and the quality of explanation for the effects of the counter action taken

  13. Advanced Hydroinformatic Techniques for the Simulation and Analysis of Water Supply and Distribution Systems

    OpenAIRE

    Herrera, Manuel; Meniconi, Silvia; Alvisi, Stefano; Izquierdo, Joaquin

    2018-01-01

    This document is intended to be a presentation of the Special Issue “Advanced Hydroinformatic Techniques for the Simulation and Analysis of Water Supply and Distribution Systems”. The final aim of this Special Issue is to propose a suitable framework supporting insightful hydraulic mechanisms to aid the decision-making processes of water utility managers and practitioners. Its 18 peer-reviewed articles present as varied topics as: water distribution system design, optimization of network perf...

  14. New techniques and results for worldline simulations of lattice field theories

    Science.gov (United States)

    Giuliani, Mario; Orasch, Oliver; Gattringer, Christof

    2018-03-01

    We use the complex ø4 field at finite density as a model system for developing further techniques based on worldline formulations of lattice field theories. More specifically we: 1) Discuss new variants of the worm algorithm for updating the ø4 theory and related systems with site weights. 2) Explore the possibility of canonical simulations in the worldline formulation. 3) Study the connection of 2-particle condensation at low temperature to scattering parameters of the theory.

  15. An Improved Simulated Annealing Technique for Enhanced Mobility in Smart Cities

    Directory of Open Access Journals (Sweden)

    Hayder Amer

    2016-06-01

    Full Text Available Vehicular traffic congestion is a significant problem that arises in many cities. This is due to the increasing number of vehicles that are driving on city roads of limited capacity. The vehicular congestion significantly impacts travel distance, travel time, fuel consumption and air pollution. Avoidance of traffic congestion and providing drivers with optimal paths are not trivial tasks. The key contribution of this work consists of the developed approach for dynamic calculation of optimal traffic routes. Two attributes (the average travel speed of the traffic and the roads’ length are utilized by the proposed method to find the optimal paths. The average travel speed values can be obtained from the sensors deployed in smart cities and communicated to vehicles via the Internet of Vehicles and roadside communication units. The performance of the proposed algorithm is compared to three other algorithms: the simulated annealing weighted sum, the simulated annealing technique for order preference by similarity to the ideal solution and the Dijkstra algorithm. The weighted sum and technique for order preference by similarity to the ideal solution methods are used to formulate different attributes in the simulated annealing cost function. According to the Sheffield scenario, simulation results show that the improved simulated annealing technique for order preference by similarity to the ideal solution method improves the traffic performance in the presence of congestion by an overall average of 19.22% in terms of travel time, fuel consumption and CO2 emissions as compared to other algorithms; also, similar performance patterns were achieved for the Birmingham test scenario.

  16. Space Geodetic Technique Co-location in Space: Simulation Results for the GRASP Mission

    Science.gov (United States)

    Kuzmicz-Cieslak, M.; Pavlis, E. C.

    2011-12-01

    The Global Geodetic Observing System-GGOS, places very stringent requirements in the accuracy and stability of future realizations of the International Terrestrial Reference Frame (ITRF): an origin definition at 1 mm or better at epoch and a temporal stability on the order of 0.1 mm/y, with similar numbers for the scale (0.1 ppb) and orientation components. These goals were derived from the requirements of Earth science problems that are currently the international community's highest priority. None of the geodetic positioning techniques can achieve this goal alone. This is due in part to the non-observability of certain attributes from a single technique. Another limitation is imposed from the extent and uniformity of the tracking network and the schedule of observational availability and number of suitable targets. The final limitation derives from the difficulty to "tie" the reference points of each technique at the same site, to an accuracy that will support the GGOS goals. The future GGOS network will address decisively the ground segment and to certain extent the space segment requirements. The JPL-proposed multi-technique mission GRASP (Geodetic Reference Antenna in Space) attempts to resolve the accurate tie between techniques, using their co-location in space, onboard a well-designed spacecraft equipped with GNSS receivers, a SLR retroreflector array, a VLBI beacon and a DORIS system. Using the anticipated system performance for all four techniques at the time the GGOS network is completed (ca 2020), we generated a number of simulated data sets for the development of a TRF. Our simulation studies examine the degree to which GRASP can improve the inter-technique "tie" issue compared to the classical approach, and the likely modus operandi for such a mission. The success of the examined scenarios is judged by the quality of the origin and scale definition of the resulting TRF.

  17. MD210 Note: Creation of Hollow Bunches in the PSB

    CERN Document Server

    Oeftiger, Adrian; Findlay, Alan James; Hancock, Steven; Rumolo, Giovanni; CERN. Geneva. ATS Department

    2016-01-01

    MD210 aims for the creation of longitudinally hollow bunches in the CERN PS Booster. The first three sessions have been carried out using the radial loop feedback system in order to drive the beam on a dipolar parametric resonance (instead of the phase loop). It has been found that the damping by the phase loop inhibits the excitation of the resonance to a major extent. The hollow distributions generated under these circumstances fail to reach a satisfying bunching factor. Nonetheless, proving the principally successful application of this technique to the PS Booster promises good results once the phase loop system supports trim functions. The approach, actions and detailed results of the first three MD sessions are presented in this paper.

  18. Loading pattern optimization by multi-objective simulated annealing with screening technique

    International Nuclear Information System (INIS)

    Tong, K. P.; Hyun, C. L.; Hyung, K. J.; Chang, H. K.

    2006-01-01

    This paper presents a new multi-objective function which is made up of the main objective term as well as penalty terms related to the constraints. All the terms are represented in the same functional form and the coefficient of each term is normalized so that each term has equal weighting in the subsequent simulated annealing optimization calculations. The screening technique introduced in the previous work is also adopted in order to save computer time in 3-D neutronics evaluation of trial loading patterns. For numerical test of the new multi-objective function in the loading pattern optimization, the optimum loading patterns for the initial and the cycle 7 reload PWR core of Yonggwang Unit 4 are calculated by the simulated annealing algorithm with screening technique. A total of 10 optimum loading patterns are obtained for the initial core through 10 independent simulated annealing optimization runs. For the cycle 7 reload core one optimum loading pattern has been obtained from a single simulated annealing optimization run. More SA optimization runs will be conducted to optimum loading patterns for the cycle 7 reload core and results will be presented in the further work. (authors)

  19. Automatic domain updating technique for improving computational efficiency of 2-D flood-inundation simulation

    Science.gov (United States)

    Tanaka, T.; Tachikawa, Y.; Ichikawa, Y.; Yorozu, K.

    2017-12-01

    Flood is one of the most hazardous disasters and causes serious damage to people and property around the world. To prevent/mitigate flood damage through early warning system and/or river management planning, numerical modelling of flood-inundation processes is essential. In a literature, flood-inundation models have been extensively developed and improved to achieve flood flow simulation with complex topography at high resolution. With increasing demands on flood-inundation modelling, its computational burden is now one of the key issues. Improvements of computational efficiency of full shallow water equations are made from various perspectives such as approximations of the momentum equations, parallelization technique, and coarsening approaches. To support these techniques and more improve the computational efficiency of flood-inundation simulations, this study proposes an Automatic Domain Updating (ADU) method of 2-D flood-inundation simulation. The ADU method traces the wet and dry interface and automatically updates the simulation domain in response to the progress and recession of flood propagation. The updating algorithm is as follow: first, to register the simulation cells potentially flooded at initial stage (such as floodplains nearby river channels), and then if a registered cell is flooded, to register its surrounding cells. The time for this additional process is saved by checking only cells at wet and dry interface. The computation time is reduced by skipping the processing time of non-flooded area. This algorithm is easily applied to any types of 2-D flood inundation models. The proposed ADU method is implemented to 2-D local inertial equations for the Yodo River basin, Japan. Case studies for two flood events show that the simulation is finished within two to 10 times smaller time showing the same result as that without the ADU method.

  20. Effect of Simulation Techniques and Lecture Method on Students' Academic Performance in Mafoni Day Secondary School Maiduguri, Borno State, Nigeria

    Science.gov (United States)

    Bello, Sulaiman; Ibi, Mustapha Baba; Bukar, Ibrahim Bulama

    2016-01-01

    The study examined the effect of simulation technique and lecture method on students' academic performance in Mafoni Day Secondary School, Maiduguri. The study used both simulation technique and lecture methods of teaching at the basic level of education in the teaching/learning environment. The study aimed at determining the best predictor among…

  1. Recent advances in 3D computed tomography techniques for simulation and navigation in hepatobiliary pancreatic surgery.

    Science.gov (United States)

    Uchida, Masafumi

    2014-04-01

    A few years ago it could take several hours to complete a 3D image using a 3D workstation. Thanks to advances in computer science, obtaining results of interest now requires only a few minutes. Many recent 3D workstations or multimedia computers are equipped with onboard 3D virtual patient modeling software, which enables patient-specific preoperative assessment and virtual planning, navigation, and tool positioning. Although medical 3D imaging can now be conducted using various modalities, including computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), and ultrasonography (US) among others, the highest quality images are obtained using CT data, and CT images are now the most commonly used source of data for 3D simulation and navigation image. If the 2D source image is bad, no amount of 3D image manipulation in software will provide a quality 3D image. In this exhibition, the recent advances in CT imaging technique and 3D visualization of the hepatobiliary and pancreatic abnormalities are featured, including scan and image reconstruction technique, contrast-enhanced techniques, new application of advanced CT scan techniques, and new virtual reality simulation and navigation imaging. © 2014 Japanese Society of Hepato-Biliary-Pancreatic Surgery.

  2. Atmospheric Pre-Corrected Differential Absorption Techniques to Retrieve Columnar Water Vapor: Theory and Simulations

    Science.gov (United States)

    Borel, Christoph C.; Schlaepfer, Daniel

    1996-01-01

    Two different approaches exist to retrieve columnar water vapor from imaging spectrometer data: (1) Differential absorption techniques based on: (a) Narrow-Wide (N/W) ratio between overlapping spectrally wide and narrow channels; (b) Continuum Interpolated Band Ratio (CIBR) between a measurement channel and the weighted sum of two reference channels. (2) Non-linear fitting techniques which are based on spectral radiative transfer calculations. The advantage of the first approach is computational speed and of the second, improved retrieval accuracy. Our goal was to improve the accuracy of the first technique using physics based on radiative transfer. Using a modified version of the Duntley equation, we derived an "Atmospheric Pre-corrected Differential Absorption" (APDA) technique and described an iterative scheme to retrieve water vapor on a pixel-by-pixel basis. Next we compared both, the CIBR and the APDA using the Duntley equation for MODTRAN3 computed irradiances, transmissions and path radiance (using the DISORT option). This simulation showed that the CIBR is very sensitive to reflectance effects and that the APDA performs much better. An extensive data set was created with the radiative transfer code 6S over 379 different ground reflectance spectra. The calculated relative water vapor error was reduced significantly for the APDA. The APDA technique had about 8% (vs. over 35% for the CIBR) of the 379 spectra with a relative water vapor error of greater than +5%. The APDA has been applied to 1991 and 1995 AVIRIS scenes which visually demonstrate the improvement over the CIBR technique.

  3. A research on applications of qualitative reasoning techniques in Human Acts Simulation Program

    International Nuclear Information System (INIS)

    Far, B.H.

    1992-04-01

    Human Acts Simulation Program (HASP) is a ten-year research project of the Computing and Information Systems Center of JAERI. In HASP the goal is developing programs for an advanced intelligent robot to accomplish multiple instructions (for instance, related to surveillance, inspection and maintenance) in nuclear power plants. Some recent artificial intelligence techniques can contribute to this project. This report introduces some original contributions concerning application of Qualitative Reasoning (QR) techniques in HASP. The focus is on the knowledge-intensive tasks, including model-based reasoning, analytic learning, fault diagnosis and functional reasoning. The multi-level extended qualitative modeling for the Skill-Rule-Knowledge (S-R-K) based reasoning, that included the coordination and timing of events, Qualitative Sensitivity analysis (Q S A), Subjective Qualitative Fault Diagnosis (S Q F D) and Qualitative Function Formation (Q F F ) techniques are introduced. (author) 123 refs

  4. Dynamic Simulation of a Trigeneration Scheme for Domestic Purposes Based on Hybrid Techniques

    Directory of Open Access Journals (Sweden)

    Luis Acevedo

    2016-11-01

    Full Text Available In this paper, the design of a system providing electricity by coupling photovoltaic/thermal (PVT collectors and a wind turbine (WT, sanitary hot water (SHW coming from the PVT and evacuated tube collectors (ETCs and fresh water (FW produced in two seawater desalting facilities (membrane distillation, MD, and reverse osmosis, RO, has been carefully analyzed by means of a dynamic model developed in TRNSYS®. This analysis is compulsory to operate a lab-scale pilot plant that is being erected at Zaragoza, Spain. A new model-type has been included in TRNSYS® in order to include the MD unit in the scheme. A sensitivity analysis of some free-design variables, such that the ETC surface, PVT and ETC tilt, water storage tank, batteries capacities, and mass flow rates delivered to the SHW service and/or feeding the MD unit has been performed in order to propose the definite design of the scheme. The proposed base case was able to produce up to 15,311 L per year in the MD system and cover an electric energy demand of 1890 kWh. Coverage of SHW, water (including RO and MD and power is respectively 99.3%, 100% and 70%. However, daily and yearly assessment of FW, SHW and power produced with the optimized design gave a better coverage of water and energy demands for a typical single family home. The improved and definite design was able to increase its MD production in 35% and the electric energy in 7% compared with base case.

  5. A review on computational fluid dynamic simulation techniques for Darrieus vertical axis wind turbines

    International Nuclear Information System (INIS)

    Ghasemian, Masoud; Ashrafi, Z. Najafian; Sedaghat, Ahmad

    2017-01-01

    Highlights: • A review on CFD simulation technique for Darrieus wind turbines is provided. • Recommendations and guidelines toward reliable and accurate simulations are presented. • Different progresses in CFD simulation of Darrieus wind turbines are addressed. - Abstract: The global warming threats, the presence of policies on support of renewable energies, and the desire for clean smart cities are the major drives for most recent researches on developing small wind turbines in urban environments. VAWTs (vertical axis wind turbines) are most appealing for energy harvesting in the urban environment. This is attributed due to structural simplicity, wind direction independency, no yaw mechanism required, withstand high turbulence winds, cost effectiveness, easier maintenance, and lower noise emission of VAWTs. This paper reviews recent published works on CFD (computational fluid dynamic) simulations of Darrieus VAWTs. Recommendations and guidelines are presented for turbulence modeling, spatial and temporal discretization, numerical schemes and algorithms, and computational domain size. The operating and geometrical parameters such as tip speed ratio, wind speed, solidity, blade number and blade shapes are fully investigated. The purpose is to address different progresses in simulations areas such as blade profile modification and optimization, wind turbine performance augmentation using guide vanes, wind turbine wake interaction in wind farms, wind turbine aerodynamic noise reduction, dynamic stall control, self-starting characteristics, and effects of unsteady and skewed wind conditions.

  6. Simulating the x-ray image contrast to setup techniques with desired flaw detectability

    Science.gov (United States)

    Koshti, Ajay M.

    2015-04-01

    The paper provides simulation data of previous work by the author in developing a model for estimating detectability of crack-like flaws in radiography. The methodology is developed to help in implementation of NASA Special x-ray radiography qualification, but is generically applicable to radiography. The paper describes a method for characterizing the detector resolution. Applicability of ASTM E 2737 resolution requirements to the model are also discussed. The paper describes a model for simulating the detector resolution. A computer calculator application, discussed here, also performs predicted contrast and signal-to-noise ratio calculations. Results of various simulation runs in calculating x-ray flaw size parameter and image contrast for varying input parameters such as crack depth, crack width, part thickness, x-ray angle, part-to-detector distance, part-to-source distance, source sizes, and detector sensitivity and resolution are given as 3D surfaces. These results demonstrate effect of the input parameters on the flaw size parameter and the simulated image contrast of the crack. These simulations demonstrate utility of the flaw size parameter model in setting up x-ray techniques that provide desired flaw detectability in radiography. The method is applicable to film radiography, computed radiography, and digital radiography.

  7. 3D DIGITAL SIMULATION OF MINNAN TEMPLE ARCHITECTURE CAISSON'S CRAFT TECHNIQUES

    Directory of Open Access Journals (Sweden)

    Y. C. Lin

    2013-07-01

    Full Text Available Caisson is one of the important representations of the Minnan (southern Fujian temple architecture craft techniques and decorative aesthetics. The special component design and group building method present the architectural thinking and personal characteristics of great carpenters of Minnan temple architecture. In late Qing Dynasty, the appearance and style of caissons of famous temples in Taiwan apparently presented the building techniques of the great carpenters. However, as the years went by, the caisson design and craft techniques were not fully inherited, which has been a great loss of cultural assets. Accordingly, with the caisson of Fulong temple, a work by the well-known great carpenter in Tainan as an example, this study obtained the thinking principles of the original design and the design method at initial period of construction through interview records and the step of redrawing the "Tng-Ko" (traditional design, stakeout and construction tool. We obtained the 3D point cloud model of the caisson of Fulong temple using 3D laser scanning technology, and established the 3D digital model of each component of the caisson. Based on the caisson component procedure obtained from interview records, this study conducted the digital simulation of the caisson component to completely recode and present the caisson design, construction and completion procedure. This model of preserving the craft techniques for Minnan temple caisson by using digital technology makes specific contribution to the heritage of the craft techniques while providing an important reference for the digital preservation of human cultural assets.

  8. Statistical learning techniques applied to epidemiology: a simulated case-control comparison study with logistic regression

    Directory of Open Access Journals (Sweden)

    Land Walker H

    2011-01-01

    Full Text Available Abstract Background When investigating covariate interactions and group associations with standard regression analyses, the relationship between the response variable and exposure may be difficult to characterize. When the relationship is nonlinear, linear modeling techniques do not capture the nonlinear information content. Statistical learning (SL techniques with kernels are capable of addressing nonlinear problems without making parametric assumptions. However, these techniques do not produce findings relevant for epidemiologic interpretations. A simulated case-control study was used to contrast the information embedding characteristics and separation boundaries produced by a specific SL technique with logistic regression (LR modeling representing a parametric approach. The SL technique was comprised of a kernel mapping in combination with a perceptron neural network. Because the LR model has an important epidemiologic interpretation, the SL method was modified to produce the analogous interpretation and generate odds ratios for comparison. Results The SL approach is capable of generating odds ratios for main effects and risk factor interactions that better capture nonlinear relationships between exposure variables and outcome in comparison with LR. Conclusions The integration of SL methods in epidemiology may improve both the understanding and interpretation of complex exposure/disease relationships.

  9. Numerical simulation of 3D unsteady flow in a rotating pump by dynamic mesh technique

    International Nuclear Information System (INIS)

    Huang, S; Guo, J; Yang, F X

    2013-01-01

    In this paper, the numerical simulation of unsteady flow for three kinds of typical rotating pumps, roots blower, roto-jet pump and centrifugal pump, were performed using the three-dimensional Dynamic Mesh technique. In the unsteady simulation, all the computational domains, as stationary, were set in one inertial reference frame. The motions of the solid boundaries were defined by the Profile file in FLUENT commercial code, in which the rotational orientation and speed of the rotors were specified. Three methods (Spring-based Smoothing, Dynamic Layering and Local Re-meshing) were used to achieve mesh deformation and re-meshing. The unsteady solutions of flow field and pressure distribution were solved. After a start-up stage, the flow parameters exhibit time-periodic behaviour corresponding to blade passing frequency of rotor. This work shows that Dynamic Mesh technique could achieve numerical simulation of three-dimensional unsteady flow field in various kinds of rotating pumps and have a strong versatility and broad application prospects

  10. Simulating GPS radio signal to synchronize network--a new technique for redundant timing.

    Science.gov (United States)

    Shan, Qingxiao; Jun, Yang; Le Floch, Jean-Michel; Fan, Yaohui; Ivanov, Eugene N; Tobar, Michael E

    2014-07-01

    Currently, many distributed systems such as 3G mobile communications and power systems are time synchronized with a Global Positioning System (GPS) signal. If there is a GPS failure, it is difficult to realize redundant timing, and thus time-synchronized devices may fail. In this work, we develop time transfer by simulating GPS signals, which promises no extra modification to original GPS-synchronized devices. This is achieved by applying a simplified GPS simulator for synchronization purposes only. Navigation data are calculated based on a pre-assigned time at a fixed position. Pseudo-range data which describes the distance change between the space vehicle (SV) and users are calculated. Because real-time simulation requires heavy-duty computations, we use self-developed software optimized on a PC to generate data, and save the data onto memory disks while the simulator is operating. The radio signal generation is similar to the SV at an initial position, and the frequency synthesis of the simulator is locked to a pre-assigned time. A filtering group technique is used to simulate the signal transmission delay corresponding to the SV displacement. Each SV generates a digital baseband signal, where a unique identifying code is added to the signal and up-converted to generate the output radio signal at the centered frequency of 1575.42 MHz (L1 band). A prototype with a field-programmable gate array (FPGA) has been built and experiments have been conducted to prove that we can realize time transfer. The prototype has been applied to the CDMA network for a three-month long experiment. Its precision has been verified and can meet the requirements of most telecommunication systems.

  11. Application of parallel computing techniques to a large-scale reservoir simulation

    International Nuclear Information System (INIS)

    Zhang, Keni; Wu, Yu-Shu; Ding, Chris; Pruess, Karsten

    2001-01-01

    Even with the continual advances made in both computational algorithms and computer hardware used in reservoir modeling studies, large-scale simulation of fluid and heat flow in heterogeneous reservoirs remains a challenge. The problem commonly arises from intensive computational requirement for detailed modeling investigations of real-world reservoirs. This paper presents the application of a massive parallel-computing version of the TOUGH2 code developed for performing large-scale field simulations. As an application example, the parallelized TOUGH2 code is applied to develop a three-dimensional unsaturated-zone numerical model simulating flow of moisture, gas, and heat in the unsaturated zone of Yucca Mountain, Nevada, a potential repository for high-level radioactive waste. The modeling approach employs refined spatial discretization to represent the heterogeneous fractured tuffs of the system, using more than a million 3-D gridblocks. The problem of two-phase flow and heat transfer within the model domain leads to a total of 3,226,566 linear equations to be solved per Newton iteration. The simulation is conducted on a Cray T3E-900, a distributed-memory massively parallel computer. Simulation results indicate that the parallel computing technique, as implemented in the TOUGH2 code, is very efficient. The reliability and accuracy of the model results have been demonstrated by comparing them to those of small-scale (coarse-grid) models. These comparisons show that simulation results obtained with the refined grid provide more detailed predictions of the future flow conditions at the site, aiding in the assessment of proposed repository performance

  12. Application of simulation techniques for accident management training in nuclear power plants

    International Nuclear Information System (INIS)

    2003-05-01

    core. These capabilities include the optimized use of design margins as well as complementary measures for the prevention of accident progression, its monitoring, and the mitigation of severe accidents. Finally, level 5 includes off-site emergency response measures, the objective of which is to mitigate the radiological consequences of significant releases of radioactive material. Accident management is defined in the IAEA Safety Report on Development and Implementation of Accident Management Programmes in Nuclear Power Plants. The IAEA definitions are in line with the definitions of severe accident management in OECD/NEA documents as given, for example. This report describes simulation techniques used in the training of personnel involved in accident management of NPPs. This concerns both the plant personnel and the persons involved in the management of off-site releases. The report pertains to light water reactors (LWRs) and pressurized heavy water reactors (PHWRs), but it can equally be applied to power reactors of other types. The report is intended for use by experts responsible for planning, developing, executing or supervising the training of personnel involved in the implementation of AMPs in NPPs. It concentrates on existing techniques, but future prospects are also discussed. Various simulation techniques are considered, from incorporating graphical interfaces into existing severe accident codes to full-scope replica simulators. Both preventive and mitigative accident management measures, different training levels and different target personnel groups are taken into account. Based on the available information compiled worldwide, present views on the applicability of simulation techniques for the training of personnel involved in accident management are provided in this report. Apart from the introduction, this report consists of four sections and three appendices. In Section 2, specific aspects of accident management are summarized. Basic approaches in the

  13. eLearning techniques supporting problem based learning in clinical simulation.

    Science.gov (United States)

    Docherty, Charles; Hoy, Derek; Topp, Helena; Trinder, Kathryn

    2005-08-01

    This paper details the results of the first phase of a project using eLearning to support students' learning within a simulated environment. The locus was a purpose built clinical simulation laboratory (CSL) where the School's philosophy of problem based learning (PBL) was challenged through lecturers using traditional teaching methods. a student-centred, problem based approach to the acquisition of clinical skills that used high quality learning objects embedded within web pages, substituting for lecturers providing instruction and demonstration. This encouraged student nurses to explore, analyse and make decisions within the safety of a clinical simulation. Learning was facilitated through network communications and reflection on video performances of self and others. Evaluations were positive, students demonstrating increased satisfaction with PBL, improved performance in exams, and increased self-efficacy in the performance of nursing activities. These results indicate that eLearning techniques can help students acquire clinical skills in the safety of a simulated environment within the context of a problem based learning curriculum.

  14. A NEW TECHNIQUE FOR THE PHOTOSPHERIC DRIVING OF NON-POTENTIAL SOLAR CORONAL MAGNETIC FIELD SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Weinzierl, Marion; Yeates, Anthony R. [Department of Mathematical Sciences, Durham University, South Road, Durham DH1 3LE (United Kingdom); Mackay, Duncan H. [School of Mathematics and Statistics, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS (United Kingdom); Henney, Carl J.; Arge, C. Nick, E-mail: marion.weinzierl@durham.ac.uk [Air Force Research Lab/Space Vehicles Directorate, 3550 Aberdeen Avenue SE, Kirtland AFB, NM (United States)

    2016-05-20

    In this paper, we develop a new technique for driving global non-potential simulations of the Sun’s coronal magnetic field solely from sequences of radial magnetic maps of the solar photosphere. A primary challenge to driving such global simulations is that the required horizontal electric field cannot be uniquely determined from such maps. We show that an “inductive” electric field solution similar to that used by previous authors successfully reproduces specific features of the coronal field evolution in both single and multiple bipole simulations. For these cases, the true solution is known because the electric field was generated from a surface flux-transport model. The match for these cases is further improved by including the non-inductive electric field contribution from surface differential rotation. Then, using this reconstruction method for the electric field, we show that a coronal non-potential simulation can be successfully driven from a sequence of ADAPT maps of the photospheric radial field, without including additional physical observations which are not routinely available.

  15. Simulation technique for slurries interacting with moving parts and deformable solids with applications

    Science.gov (United States)

    Mutabaruka, Patrick; Kamrin, Ken

    2018-04-01

    A numerical method for particle-laden fluids interacting with a deformable solid domain and mobile rigid parts is proposed and implemented in a full engineering system. The fluid domain is modeled with a lattice Boltzmann representation, the particles and rigid parts are modeled with a discrete element representation, and the deformable solid domain is modeled using a Lagrangian mesh. The main issue of this work, since separately each of these methods is a mature tool, is to develop coupling and model-reduction approaches in order to efficiently simulate coupled problems of this nature, as in various geological and engineering applications. The lattice Boltzmann method incorporates a large eddy simulation technique using the Smagorinsky turbulence model. The discrete element method incorporates spherical and polyhedral particles for stiff contact interactions. A neo-Hookean hyperelastic model is used for the deformable solid. We provide a detailed description of how to couple the three solvers within a unified algorithm. The technique we propose for rubber modeling/coupling exploits a simplification that prevents having to solve a finite-element problem at each time step. We also developed a technique to reduce the domain size of the full system by replacing certain zones with quasi-analytic solutions, which act as effective boundary conditions for the lattice Boltzmann method. The major ingredients of the routine are separately validated. To demonstrate the coupled method in full, we simulate slurry flows in two kinds of piston valve geometries. The dynamics of the valve and slurry are studied and reported over a large range of input parameters.

  16. Lattice Boltzmann flow simulations with applications of reduced order modeling techniques

    KAUST Repository

    Brown, Donald

    2014-01-01

    With the recent interest in shale gas, an understanding of the flow mechanisms at the pore scale and beyond is necessary, which has attracted a lot of interest from both industry and academia. One of the suggested algorithms to help understand flow in such reservoirs is the Lattice Boltzmann Method (LBM). The primary advantage of LBM is its ability to approximate complicated geometries with simple algorithmic modificatoins. In this work, we use LBM to simulate the flow in a porous medium. More specifically, we use LBM to simulate a Brinkman type flow. The Brinkman law allows us to integrate fast free-flow and slow-flow porous regions. However, due to the many scales involved and complex heterogeneities of the rock microstructure, the simulation times can be long, even with the speed advantage of using an explicit time stepping method. The problem is two-fold, the computational grid must be able to resolve all scales and the calculation requires a steady state solution implying a large number of timesteps. To help reduce the computational complexity and total simulation times, we use model reduction techniques to reduce the dimension of the system. In this approach, we are able to describe the dynamics of the flow by using a lower dimensional subspace. In this work, we utilize the Proper Orthogonal Decomposition (POD) technique, to compute the dominant modes of the flow and project the solution onto them (a lower dimensional subspace) to arrive at an approximation of the full system at a lowered computational cost. We present a few proof-of-concept examples of the flow field and the corresponding reduced model flow field.

  17. Why use case studies rather than simulation-gaming techniques or library research?

    Science.gov (United States)

    Mcdonald, S. W.

    1981-01-01

    Method which present a student with a more challenging and true to life situation of needing to conduct research in a problem solving context--and not thinking about organization of format until research and thinking are complete are investigated. Simulation-gaming techniques which attempt to teach initiative and creativity that library research are used for this purpose. However, it is shown case studies provide the greatest opportunities to engage the students in problem solving situations in which they develop skills as researchers and writers.

  18. Structural investigation and simulation of acoustic properties of some tellurite glasses using artificial intelligence technique

    International Nuclear Information System (INIS)

    Gaafar, M.S.; Abdeen, Mostafa A.M.; Marzouk, S.Y.

    2011-01-01

    Research highlights: → Simulation the acoustic properties of some tellurite glasses using one of the artificial intelligence techniques (artificial neural network). → The glass network is strengthened by enhancing the linkage of Te-O chains. The tellurite network will also come to homogenization, because of uniform distribution of Nb 5+ ions among the Te-O chains, though some of the tellurium-oxide polyhedra still link each other in edge sharing. → Excellent agreements between the measured values and the predicted values were obtained for over 50 different tellurite glass compositions. → The model we designed gives a better agreement as compared with Makishima and Machenzie model. - Abstract: The developments in the field of industry raise the need for simulating the acoustic properties of glass materials before melting raw material oxides. In this paper, we are trying to simulate the acoustic properties of some tellurite glasses using one of the artificial intelligence techniques (artificial neural network). The artificial neural network (ANN) technique is introduced in the current study to simulate and predict important parameters such as density, longitudinal and shear ultrasonic velocities and elastic moduli (longitudinal and shear moduli). The ANN results were found to be in successful good agreement with those experimentally measured parameters. Then the presented ANN model is used to predict the acoustic properties of some new tellurite glasses. For this purpose, four glass systems xNb 2 O 5 -(1 - x)TeO 2 , 0.1PbO-xNb 2 O 5 -(0.9 - x)TeO 2 , 0.2PbO-xNb 2 O 5 -(0.8 - x)TeO 2 and 0.05Bi 2 O 3 -xNb 2 O 5 -(0.95 - x)TeO 2 were prepared using melt quenching technique. The results of ultrasonic velocities and elastic moduli showed that the addition of Nb 2 O 5 as a network modifier provides oxygen ions to change [TeO 4 ] tbps into [TeO 3 ] tps.

  19. Structural investigation and simulation of acoustic properties of some tellurite glasses using artificial intelligence technique

    Energy Technology Data Exchange (ETDEWEB)

    Gaafar, M.S., E-mail: mohamed_s_gaafar@hotmail.com [Ultrasonic Department, National Institute for Standards, Giza (Egypt); Physics Department, Faculty of Science, Majmaah University, Zulfi (Saudi Arabia); Abdeen, Mostafa A.M., E-mail: mostafa_a_m_abdeen@hotmail.com [Dept. of Eng. Math. and Physics, Faculty of Eng., Cairo University, Giza (Egypt); Marzouk, S.Y., E-mail: samir_marzouk2001@yahoo.com [Arab Academy of Science and Technology, Al-Horria, Heliopolis, Cairo (Egypt)

    2011-02-24

    Research highlights: > Simulation the acoustic properties of some tellurite glasses using one of the artificial intelligence techniques (artificial neural network). > The glass network is strengthened by enhancing the linkage of Te-O chains. The tellurite network will also come to homogenization, because of uniform distribution of Nb{sup 5+} ions among the Te-O chains, though some of the tellurium-oxide polyhedra still link each other in edge sharing. > Excellent agreements between the measured values and the predicted values were obtained for over 50 different tellurite glass compositions. > The model we designed gives a better agreement as compared with Makishima and Machenzie model. - Abstract: The developments in the field of industry raise the need for simulating the acoustic properties of glass materials before melting raw material oxides. In this paper, we are trying to simulate the acoustic properties of some tellurite glasses using one of the artificial intelligence techniques (artificial neural network). The artificial neural network (ANN) technique is introduced in the current study to simulate and predict important parameters such as density, longitudinal and shear ultrasonic velocities and elastic moduli (longitudinal and shear moduli). The ANN results were found to be in successful good agreement with those experimentally measured parameters. Then the presented ANN model is used to predict the acoustic properties of some new tellurite glasses. For this purpose, four glass systems xNb{sub 2}O{sub 5}-(1 - x)TeO{sub 2}, 0.1PbO-xNb{sub 2}O{sub 5}-(0.9 - x)TeO{sub 2}, 0.2PbO-xNb{sub 2}O{sub 5}-(0.8 - x)TeO{sub 2} and 0.05Bi{sub 2}O{sub 3}-xNb{sub 2}O{sub 5}-(0.95 - x)TeO{sub 2} were prepared using melt quenching technique. The results of ultrasonic velocities and elastic moduli showed that the addition of Nb{sub 2}O{sub 5} as a network modifier provides oxygen ions to change [TeO{sub 4}] tbps into [TeO{sub 3}] tps.

  20. Evaluation of convergence behavior of metamodeling techniques for bridging scales in multi-scale multimaterial simulation

    International Nuclear Information System (INIS)

    Sen, Oishik; Davis, Sean; Jacobs, Gustaaf; Udaykumar, H.S.

    2015-01-01

    The effectiveness of several metamodeling techniques, viz. the Polynomial Stochastic Collocation method, Adaptive Stochastic Collocation method, a Radial Basis Function Neural Network, a Kriging Method and a Dynamic Kriging Method is evaluated. This is done with the express purpose of using metamodels to bridge scales between micro- and macro-scale models in a multi-scale multimaterial simulation. The rate of convergence of the error when used to reconstruct hypersurfaces of known functions is studied. For sufficiently large number of training points, Stochastic Collocation methods generally converge faster than the other metamodeling techniques, while the DKG method converges faster when the number of input points is less than 100 in a two-dimensional parameter space. Because the input points correspond to computationally expensive micro/meso-scale computations, the DKG is favored for bridging scales in a multi-scale solver

  1. A molecular dynamics simulation code ISIS

    International Nuclear Information System (INIS)

    Kambayashi, Shaw

    1992-06-01

    Computer simulation based on the molecular dynamics (MD) method has become an important tool complementary to experiments and theoretical calculations in a wide range of scientific fields such as physics, chemistry, biology, and so on. In the MD method, the Newtonian equations-of-motion of classical particles are integrated numerically to reproduce a phase-space trajectory of the system. In the 1980's, several new techniques have been developed for simulation at constant-temperature and/or constant-pressure in convenient to compare result of computer simulation with experimental results. We first summarize the MD method for both microcanonical and canonical simulations. Then, we present and overview of a newly developed ISIS (Isokinetic Simulation of Soft-spheres) code and its performance on various computers including vector processors. The ISIS code has a capability to make a MD simulation under constant-temperature condition by using the isokinetic constraint method. The equations-of-motion is integrated by a very accurate fifth-order finite differential algorithm. The bookkeeping method is also utilized to reduce the computational time. Furthermore, the ISIS code is well adopted for vector processing: Speedup ratio ranged from 16 to 24 times is obtained on a VP2600/10 vector processor. (author)

  2. Microsecond-Scale MD Simulations of HIV-1 DIS Kissing-Loop Complexes Predict Bulged-In Conformation of the Bulged Bases and Reveal Interesting Differences between Available Variants of the AMBER RNA Force Fields

    Czech Academy of Sciences Publication Activity Database

    Havrila, Marek; Zgarbová, M.; Jurečka, P.; Banáš, P.; Krepl, Miroslav; Otyepka, M.; Šponer, Jiří

    2015-01-01

    Roč. 119, č. 49 (2015), s. 15176-15190 ISSN 1520-6106 R&D Projects: GA ČR(CZ) GBP305/12/G034 Institutional support: RVO:68081707 Keywords : MOLECULAR-DYNAMICS SIMULATIONS * DIMERIZATION INITIATION SITE * QUANTUM-CHEMICAL COMPUTATIONS Subject RIV: BO - Biophysics Impact factor: 3.187, year: 2015

  3. Atmospheric pre-corrected differential absorption techniques to retrieve columnar water vapor: Theory and simulations

    Energy Technology Data Exchange (ETDEWEB)

    Borel, C.C.; Schlaepfer, D.

    1996-03-01

    Two different approaches exist to retrieve columnar water vapor from imaging spectrometer data: (1) Differential absorption techniques based on: (a) Narrow-Wide (N/W) ratio between overlapping spectrally wide and narrow channels (b) Continuum Interpolated Band Ratio (CIBR) between a measurement channel and the weighted sum of two reference channels; and (2) Non-linear fitting techniques which are based on spectral radiative transfer calculations. The advantage of the first approach is computational speed and of the second, improved retrieval accuracy. Our goal was to improve the accuracy of the first technique using physics based on radiative transfer. Using a modified version of the Duntley equation, we derived an {open_quote}Atmospheric Pre-corrected Differential Absorption{close_quote} (APDA) technique and described an iterative scheme to retrieve water vapor on a pixel-by-pixel basis. Next we compared both, the CIBR and the APDA using the Duntley equation for MODTRAN3 computed irradiances, transmissions and path radiance (using the DISORT option). This simulation showed that the CIBR is very sensitive to reflectance effects and that the APDA performs much better. An extensive data set was created with the radiative transfer code 6S over 379 different ground reflectance spectra. The calculated relative water vapor error was reduced significantly for the APDA. The APDA technique had about 8% (vs. over 35% for the CIBR) of the 379 spectra with a relative water vapor error of greater than {+-}5%. The APDA has been applied to 1991 and 1995 AVIRIS scenes which visually demonstrate the improvement over the CIBR technique.

  4. 75 FR 47203 - Airworthiness Directives; McDonnell Douglas Corporation Model MD-11 and MD-11F Airplanes Equipped...

    Science.gov (United States)

    2010-08-05

    ... Airworthiness Directives; McDonnell Douglas Corporation Model MD- 11 and MD-11F Airplanes Equipped With General... Sec. 39.13 by adding the following new AD: 2010-16-03 McDonnell Douglas Corporation: Amendment 39... applies to McDonnell Douglas Corporation Model MD-11 and MD-11F airplanes, certified in any category...

  5. Physical simulation technique on the behaviour of oil spills in grease ice under wave actions

    International Nuclear Information System (INIS)

    Li, Z.; Hollebone, B.; Fingas, M.; Fieldhouse, B.

    2008-01-01

    Light or medium oil spilled on ice tends to rise and remain the surface in unconsolidated frazil or grease ice. This study looked for a new system for studying the oil emulsion in grease ice under experimental conditions. A physical simulation technique was designed to test the effect of wave energy on the spilled oil grease ice emulsion. The newly developed test system has the ability to perform simulation tests in wave, wave-ice, wave-oil and wave-ice-oil. This paper presented the design concept of the developed test system and introduced the experimental certifications of its capability in terms of temperature control, wave-making and grease ice-making. The key feature of the technique is a mini wave flume which derives its wave making power from an oscillator in a chemical laboratory. Video cameras record the wave action in the flume in order to obtain wave parameters. The wave making capability tests in this study were used to determine the relation of wave height, length and frequency with oscillator power transfer, oscillator frequency and the depth of the water flume. 16 refs., 10 figs

  6. MD2190: Q" Stabilization during injection

    CERN Document Server

    Schenk, Michael; Li, Kevin Shing Bruce; Malina, Lukas; Metral, Elias; Tomas Garcia, Rogelio; CERN. Geneva. ATS Department

    2018-01-01

    This MD is a follow-up study of MD1831, where single bunches were stabilized against impedance-driven instabilities at 6.5 TeV in the LHC with Q''. The goals are (i) to explore whether an amplitude detuning free Q'' knob can be implemented at injection energy, and (ii) whether Q'' can provide beam stability at injection, where the beams suffer mostly from electron cloud effects. Ideally, this would relax the use of the Landau octupoles and may help in preserving the beam quality by reducing dynamic aperture limitations originating from the octupoles. The MD has been split into two parts: First, optics corrections were put in place to minimize beta-beating and linear coupling introduced by the knobs. The corrections were achieved by means of orbit bumps and skew quadrupole knobs. Machine safety was then validated with loss maps. While the betatron loss maps were approved, the off-momentum maps showed a priori unexpected losses in several arcs and the MD was stopped at this point for reasons of machine protecti...

  7. MD2725: 16L2 aperture measurement

    CERN Document Server

    Mirarchi, Daniele; Rossi, Roberto; CERN. Geneva. ATS Department

    2018-01-01

    Dumps induced by sudden increase of losses in the half-cell 16L2 have been a serious machine limitation during the 2017 run. The aim of this MD was to perform local aperture measurements in order to assess differences after the beam screen regeneration, compared to first measurements in 2017.

  8. The simulation of Typhoon-induced coastal inundation in Busan, South Korea applying the downscaling technique

    Science.gov (United States)

    Jang, Dongmin; Park, Junghyun; Yuk, Jin-Hee; Joh, MinSu

    2017-04-01

    Due to typhoons, the south coastal cities including Busan in South Korea coastal are very vulnerable to a surge, wave and corresponding coastal inundation, and are affected every year. In 2016, South Korea suffered tremendous damage by typhoon 'Chaba', which was developed near east-north of Guam on Sep. 28 and had maximum 10-minute sustained wind speed of about 50 m/s, 1-minute sustained wind speed of 75 m/s and a minimum central pressure of 905 hpa. As 'Chaba', which is the strongest since typhoon 'Maemi' in 2003, hit South Korea on Oct. 5, it caused a massive economic and casualty damage to Ulsan, Gyeongju and Busan in South Korea. In particular, the damage of typhoon-induced coastal inundation in Busan, where many high-rise buildings and residential areas are concentrated near coast, was serious. The coastal inundation could be more affected by strong wind-induced wave than surge. In fact, it was observed that the surge height was about 1 m averagely and a significant wave height was about 8 m at coastal sea nearby Busan on Oct. 5 due to 'Chaba'. Even though the typhoon-induced surge elevated the sea level, the typhoon-induced long period wave with wave period of more than 15s could play more important role in the inundation. The present work simulated the coastal inundation induced by 'Chaba' in Busan, South Korea considering the effects of typhoon-induced surge and wave. For 'Chaba' hindcast, high resolution Weather Research and Forecasting model (WRF) was applied using a reanalysis data produced by NCEP (FNL 0.25 degree) on the boundary and initial conditions, and was validated by the observation of wind speed, direction and pressure. The typhoon-induced coastal inundation was simulated by an unstructured gird model, Finite Volume Community Ocean Model (FVCOM), which is fully current-wave coupled model. To simulate the wave-induced inundation, 1-way downscaling technique of multi domain was applied. Firstly, a mother's domain including Korean peninsula was

  9. Behavior of solvent-exposed hydrophobic groove in the anti-apoptotic Bcl-XL protein: clues for its ability to bind diverse BH3 ligands from MD simulations.

    Directory of Open Access Journals (Sweden)

    Dilraj Lama

    Full Text Available Bcl-XL is a member of Bcl-2 family of proteins involved in the regulation of intrinsic pathway of apoptosis. Its overexpression in many human cancers makes it an important target for anti-cancer drugs. Bcl-XL interacts with the BH3 domain of several pro-apoptotic Bcl-2 partners. This helical bundle protein has a pronounced hydrophobic groove which acts as a binding region for the BH3 domains. Eight independent molecular dynamics simulations of the apo/holo forms of Bcl-XL were carried out to investigate the behavior of solvent-exposed hydrophobic groove. The simulations used either a twin-range cut-off or particle mesh Ewald (PME scheme to treat long-range interactions. Destabilization of the BH3 domain-containing helix H2 was observed in all four twin-range cut-off simulations. Most of the other major helices remained stable. The unwinding of H2 can be related to the ability of Bcl-XL to bind diverse BH3 ligands. The loss of helical character can also be linked to the formation of homo- or hetero-dimers in Bcl-2 proteins. Several experimental studies have suggested that exposure of BH3 domain is a crucial event before they form dimers. Thus unwinding of H2 seems to be functionally very important. The four PME simulations, however, revealed a stable helix H2. It is possible that the H2 unfolding might occur in PME simulations at longer time scales. Hydrophobic residues in the hydrophobic groove are involved in stable interactions among themselves. The solvent accessible surface areas of bulky hydrophobic residues in the groove are significantly buried by the loop LB connecting the helix H2 and subsequent helix. These observations help to understand how the hydrophobic patch in Bcl-XL remains stable in the solvent-exposed state. We suggest that both the destabilization of helix H2 and the conformational heterogeneity of loop LB are important factors for binding of diverse ligands in the hydrophobic groove of Bcl-XL.

  10. Taxi Time Prediction at Charlotte Airport Using Fast-Time Simulation and Machine Learning Techniques

    Science.gov (United States)

    Lee, Hanbong

    2016-01-01

    Accurate taxi time prediction is required for enabling efficient runway scheduling that can increase runway throughput and reduce taxi times and fuel consumptions on the airport surface. Currently NASA and American Airlines are jointly developing a decision-support tool called Spot and Runway Departure Advisor (SARDA) that assists airport ramp controllers to make gate pushback decisions and improve the overall efficiency of airport surface traffic. In this presentation, we propose to use Linear Optimized Sequencing (LINOS), a discrete-event fast-time simulation tool, to predict taxi times and provide the estimates to the runway scheduler in real-time airport operations. To assess its prediction accuracy, we also introduce a data-driven analytical method using machine learning techniques. These two taxi time prediction methods are evaluated with actual taxi time data obtained from the SARDA human-in-the-loop (HITL) simulation for Charlotte Douglas International Airport (CLT) using various performance measurement metrics. Based on the taxi time prediction results, we also discuss how the prediction accuracy can be affected by the operational complexity at this airport and how we can improve the fast time simulation model before implementing it with an airport scheduling algorithm in a real-time environment.

  11. Mining MaNGA for Merging Galaxies: A New Imaging and Kinematic Technique from Hydrodynamical Simulations

    Science.gov (United States)

    Nevin, Becky; Comerford, Julia M.; Blecha, Laura

    2018-06-01

    Merging galaxies play a key role in galaxy evolution, and progress in our understanding of galaxy evolution is slowed by the difficulty of making accurate galaxy merger identifications. Mergers are typically identified using imaging alone, which has its limitations and biases. With the growing popularity of integral field spectroscopy (IFS), it is now possible to use kinematic signatures to improve galaxy merger identifications. I use GADGET-3 hydrodynamical simulations of merging galaxies with the radiative transfer code SUNRISE, the later of which enables me to apply the same analysis to simulations and observations. From the simulated galaxies, I have developed the first merging galaxy classification scheme that is based on kinematics and imaging. Utilizing a Linear Discriminant Analysis tool, I have determined which kinematic and imaging predictors are most useful for identifying mergers of various merger parameters (such as orientation, mass ratio, gas fraction, and merger stage). I will discuss the strengths and limitations of the classification technique and then my initial results for applying the classification to the >10,000 observed galaxies in the MaNGA (Mapping Nearby Galaxies at Apache Point) IFS survey. Through accurate identification of merging galaxies in the MaNGA survey, I will advance our understanding of supermassive black hole growth in galaxy mergers and other open questions related to galaxy evolution.

  12. MD-11 PCA - Research flight team photo

    Science.gov (United States)

    1995-01-01

    On Aug. 30, 1995, a the McDonnell Douglas MD-11 transport aircraft landed equipped with a computer-assisted engine control system that has the potential to increase flight safety. In landings at NASA Dryden Flight Research Center, Edwards, California, on August 29 and 30, the aircraft demonstrated software used in the aircraft's flight control computer that essentially landed the MD-11 without a need for the pilot to manipulate the flight controls significantly. In partnership with McDonnell Douglas Aerospace (MDA), with Pratt & Whitney and Honeywell helping to design the software, NASA developed this propulsion-controlled aircraft (PCA) system following a series of incidents in which hydraulic failures resulted in the loss of flight controls. This new system enables a pilot to operate and land the aircraft safely when its normal, hydraulically-activated control surfaces are disabled. This August 29, 1995, photo shows the MD-11 team. Back row, left to right: Tim Dingen, MDA pilot; John Miller, MD-11 Chief pilot (MDA); Wayne Anselmo, MD-11 Flight Test Engineer (MDA); Gordon Fullerton, PCA Project pilot; Bill Burcham, PCA Chief Engineer; Rudey Duran, PCA Controls Engineer (MDA); John Feather, PCA Controls Engineer (MDA); Daryl Townsend, Crew Chief; Henry Hernandez, aircraft mechanic; Bob Baron, PCA Project Manager; Don Hermann, aircraft mechanic; Jerry Cousins, aircraft mechanic; Eric Petersen, PCA Manager (Honeywell); Trindel Maine, PCA Data Engineer; Jeff Kahler, PCA Software Engineer (Honeywell); Steve Goldthorpe, PCA Controls Engineer (MDA). Front row, left to right: Teresa Hass, Senior Project Management Analyst; Hollie Allingham (Aguilera), Senior Project Management Analyst; Taher Zeglum, PCA Data Engineer (MDA); Drew Pappas, PCA Project Manager (MDA); John Burken, PCA Control Engineer.

  13. The relationship of superficial cerebral veins with meningiomas by simulation craniotomy technique

    International Nuclear Information System (INIS)

    Zhao Hongwei; Gong Xiangyang

    2012-01-01

    Objective: To assess the value of simulation craniotomy (SC) technique in evaluation of superficial cerebral veins (SCVs) and its relationship with convexity, parasagittal and falcine meningiomas. Methods: Forty-nine consecutive patients with convexity,parasagittal, and falcine meningiomas performed SC technique and three-dimensional contrast enhanced MR venography (3D CE MRV) in a prospective study. The number of SCVs (diameter > 1 mm) within 2 cm around the margin of tumors detected by two techniques were compared with the paired t test. Furthermore, 49 cases were divided into groups according to the tumor largest diameter, position, and dural enhancement. The image quality of SC technique in different groups were analyzed by Wilcoxon test in order to find influence factors. Results: The number of SCVs within 2 cm around the margin of tumor in SC was 4.4 ± 1.9, which was significantly less than that on 3D CE MRV (5.1 ± 2.7) (t=3.131, P<0.05). The relationship between meningiomas and the SCVs was demonstrated well on SC in majority of cases with the score of image quality was 2.5 ±0.7. The score of image quality of 12 patients with obvious dural enhancement was 1.5 ± 0.5, which was significantly lower than that of 37 patients without dural enhancement (2.8 ± 0.3) (Z=-3.093, P<0.05). The score of image quality of 18 patients with tumor larger than 4 cm in diameter (2.2 ± 0.9)was significantly lowed than that of 31 patients with small tumors (2.7 ± 0.5) (Z=-2.057, P<0.05). The score of image quality of convexity group (n=10) and parasagittal and falcine group (n=39) was 2.2 ± 0.9 and 2.6 ± 0.6,and there was no significant difference between different location group (Z=-0.604, P>0.05). Conclusions: Simulation craniotomy can exactly display SCVs avoiding the influence of deep cerebral veins and skull veins. This simple technique can provide useful information about the SCVs and their relationships with cortical structures and tumors for preoperative surgical

  14. Simulation and prediction for energy dissipaters and stilling basins design using artificial intelligence technique

    Directory of Open Access Journals (Sweden)

    Mostafa Ahmed Moawad Abdeen

    2015-12-01

    Full Text Available Water with large velocities can cause considerable damage to channels whose beds are composed of natural earth materials. Several stilling basins and energy dissipating devices have been designed in conjunction with spillways and outlet works to avoid damages in canals’ structures. In addition, lots of experimental and traditional mathematical numerical works have been performed to profoundly investigate the accurate design of these stilling basins and energy dissipaters. The current study is aimed toward introducing the artificial intelligence technique as new modeling tool in the prediction of the accurate design of stilling basins. Specifically, artificial neural networks (ANNs are utilized in the current study in conjunction with experimental data to predict the length of the hydraulic jumps occurred in spillways and consequently the stilling basin dimensions can be designed for adequate energy dissipation. The current study showed, in a detailed fashion, the development process of different ANN models to accurately predict the hydraulic jump lengths acquired from different experimental studies. The results obtained from implementing these models showed that ANN technique was very successful in simulating the hydraulic jump characteristics occurred in stilling basins. Therefore, it can be safely utilized in the design of these basins as ANN involves minimum computational and financial efforts and requirements compared with experimental work and traditional numerical techniques such as finite difference or finite elements.

  15. Simulation Tools and Techniques for Analyzing the Impacts of Photovoltaic System Integration

    Science.gov (United States)

    Hariri, Ali

    utility simulation software. On the other hand, EMT simulation tools provide high accuracy and visibility over a wide bandwidth of frequencies at the expense of larger processing and memory requirements, limited network size, and long simulation time. Therefore, there is a gap in simulation tools and techniques that can efficiently and effectively identify potential PV impact. New planning simulation tools are needed in order to accommodate for the simulation requirements of new integrated technologies in the electric grid. The dissertation at hand starts by identifying some of the potential impacts that are caused by high PV penetration. A phasor-based quasi-static time series (QSTS) analysis tool is developed in order to study the slow dynamics that are caused by the variations in the PV generation that lead to voltage fluctuations. Moreover, some EMT simulations are performed in order to study the impacts of PV systems on the electric network harmonic levels. These studies provide insights into the type and duration of certain impacts, as well as the conditions that may lead to adverse phenomena. In addition these studies present an idea about the type of simulation tools that are sufficient for each type of study. After identifying some of the potential impacts, certain planning tools and techniques are proposed. The potential PV impacts may cause certain utilities to refrain from integrating PV systems into their networks. However, each electric network has a certain limit beyond which the impacts become substantial and may adversely interfere with the system operation and the equipment along the feeder; this limit is referred to as the hosting limit (or hosting capacity). Therefore, it is important for utilities to identify the PV hosting limit on a specific electric network in order to safely and confidently integrate the maximum possible PV systems. In the following dissertation, two approaches have been proposed for identifying the hosing limit: 1. Analytical

  16. Full scope simulator of a nuclear power plant control room using 3D stereo virtual reality techniques for operators training

    International Nuclear Information System (INIS)

    Aghina, Mauricio A.C.; Mol, Antonio Carlos A.; Almeida, Adino Americo A.; Pereira, Claudio M.N.A.; Varela, Thiago F.B.

    2007-01-01

    Practical training of nuclear power plants operators are partially performed by means of simulators. Usually these simulators are physical copies of the original control roam, needing a large space on a facility being also very expensive. In this way, the proposal of this paper is to implement the use of Virtual Reality techniques to design a full scope control room simulator, in a manner to reduce costs and physical space usage. (author)

  17. Exploring intentions of physician-scientist trainees: factors influencing MD and MD/PhD interest in research careers.

    Science.gov (United States)

    Kwan, Jennifer M; Daye, Dania; Schmidt, Mary Lou; Conlon, Claudia Morrissey; Kim, Hajwa; Gaonkar, Bilwaj; Payne, Aimee S; Riddle, Megan; Madera, Sharline; Adami, Alexander J; Winter, Kate Quinn

    2017-07-11

    Prior studies have described the career paths of physician-scientist candidates after graduation, but the factors that influence career choices at the candidate stage remain unclear. Additionally, previous work has focused on MD/PhDs, despite many physician-scientists being MDs. This study sought to identify career sector intentions, important factors in career selection, and experienced and predicted obstacles to career success that influence the career choices of MD candidates, MD candidates with research-intense career intentions (MD-RI), and MD/PhD candidates. A 70-question survey was administered to students at 5 academic medical centers with Medical Scientist Training Programs (MSTPs) and Clinical and Translational Science Awards (CTSA) from the NIH. Data were analyzed using bivariate or multivariate analyses. More MD/PhD and MD-RI candidates anticipated or had experienced obstacles related to balancing academic and family responsibilities and to balancing clinical, research, and education responsibilities, whereas more MD candidates indicated experienced and predicted obstacles related to loan repayment. MD/PhD candidates expressed higher interest in basic and translational research compared to MD-RI candidates, who indicated more interest in clinical research. Overall, MD-RI candidates displayed a profile distinct from both MD/PhD and MD candidates. MD/PhD and MD-RI candidates experience obstacles that influence their intentions to pursue academic medical careers from the earliest training stage, obstacles which differ from those of their MD peers. The differences between the aspirations of and challenges facing MD, MD-RI and MD/PhD candidates present opportunities for training programs to target curricula and support services to ensure the career development of successful physician-scientists.

  18. A simulation technique for 3D MR-guided acoustic radiation force imaging

    International Nuclear Information System (INIS)

    Payne, Allison; Bever, Josh de; Farrer, Alexis; Coats, Brittany; Parker, Dennis L.; Christensen, Douglas A.

    2015-01-01

    Purpose: In magnetic resonance-guided focused ultrasound (MRgFUS) therapies, the in situ characterization of the focal spot location and quality is critical. MR acoustic radiation force imaging (MR-ARFI) is a technique that measures the tissue displacement caused by the radiation force exerted by the ultrasound beam. This work presents a new technique to model the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model. Methods: When a steady-state point-source force acts internally in an infinite homogeneous medium, the displacement of the material in all directions is given by the Somigliana elastostatic tensor. The radiation force field, which is caused by absorption and reflection of the incident ultrasound intensity pattern, will be spatially distributed, and the tensor formulation takes the form of a convolution of a 3D Green’s function with the force field. The dynamic accumulation of MR phase during the ultrasound pulse can be theoretically accounted for through a time-of-arrival weighting of the Green’s function. This theoretical model was evaluated experimentally in gelatin phantoms of varied stiffness (125-, 175-, and 250-bloom). The acoustic and mechanical properties of the phantoms used as parameters of the model were measured using independent techniques. Displacements at focal depths of 30- and 45-mm in the phantoms were measured by a 3D spin echo MR-ARFI segmented-EPI sequence. Results: The simulated displacements agreed with the MR-ARFI measured displacements for all bloom values and focal depths with a normalized RMS difference of 0.055 (range 0.028–0.12). The displacement magnitude decreased and the displacement pattern broadened with increased bloom value for both focal depths, as predicted by the theory. Conclusions: A new technique that models the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model theory has been rigorously validated through comparison

  19. Real-time surgical simulation for deformable soft-tissue objects with a tumour using Boundary Element techniques

    Science.gov (United States)

    Wang, P.; Becker, A. A.; Jones, I. A.; Glover, A. T.; Benford, S. D.; Vloeberghs, M.

    2009-08-01

    A virtual-reality real-time simulation of surgical operations that incorporates the inclusion of a hard tumour is presented. The software is based on Boundary Element (BE) technique. A review of the BE formulation for real-time analysis of two-domain deformable objects, using the pre-solution technique, is presented. The two-domain BE software is incorporated into a surgical simulation system called VIRS to simulate the initiation of a cut on the surface of the soft tissue and extending the cut deeper until the tumour is reached.

  20. Real-time surgical simulation for deformable soft-tissue objects with a tumour using Boundary Element techniques

    International Nuclear Information System (INIS)

    Wang, P; Becker, A A; Jones, I A; Glover, A T; Benford, S D; Vloeberghs, M

    2009-01-01

    A virtual-reality real-time simulation of surgical operations that incorporates the inclusion of a hard tumour is presented. The software is based on Boundary Element (BE) technique. A review of the BE formulation for real-time analysis of two-domain deformable objects, using the pre-solution technique, is presented. The two-domain BE software is incorporated into a surgical simulation system called VIRS to simulate the initiation of a cut on the surface of the soft tissue and extending the cut deeper until the tumour is reached.

  1. Experience with the Large Eddy Simulation (LES) Technique for the Modelling of Premixed and Non-premixed Combustion

    OpenAIRE

    Malalasekera, W; Ibrahim, SS; Masri, AR; Gubba, SR; Sadasivuni, SK

    2013-01-01

    Compared to RANS based combustion modelling, the Large Eddy Simulation (LES) technique has recently emerged as a more accurate and very adaptable technique in terms of handling complex turbulent interactions in combustion modelling problems. In this paper application of LES based combustion modelling technique and the validation of models in non-premixed and premixed situations are considered. Two well defined experimental configurations where high quality data are available for validation is...

  2. Managerial Techniques in Educational Administration.

    Science.gov (United States)

    Lane, John J.

    1983-01-01

    Management techniques developed during the past 20 years assume the rational bureaucratic model. School administration requires contingent techniques. Quality Circle, Theory Z, and the McKenzie 7-Framework are discussed as techniques to increase school productivity. (MD)

  3. Apple fruit acidity is genetically diversified by natural variations in three hierarchical epistatic genes MdSAUR37, MdPP2CH and MdALMTII.

    Science.gov (United States)

    Jia, Dongjie; Shen, Fei; Wang, Yi; Wu, Ting; Xu, Xuefeng; Zhang, Xinzhong; Han, Zhenhai

    2018-05-11

    Many efforts have been made to map quantitative trait loci (QTLs) to facilitate practical marker-assisted selection (MAS) in plants. In the present study, we identified four genome-wide major QTLs responsible for apple fruit acidity by MapQTL and BSA-seq analyses using two independent pedigree-based populations. Candidate genes were screened in major QTL regions, and three functional gene markers, including a non-synonymous A/G single nucleotide polymorphism (SNP) in the coding region of MdPP2CH, a 36-bp insertion in the promoter of MdSAUR37, and a previously reported SNP in MdALMTII, were validated to influence the malate content of apple fruits. In addition, MdPP2CH inactivated three vacuolar H + -ATPases (MdVHA-A3, MdVHA-B2 and MdVHA-D2) and one aluminium-activated malate transporter (MdALMTII) via dephosphorylation and negatively influenced fruit malate accumulation. The dephosphotase activity of MdPP2CH was suppressed by MdSAUR37, which implied a higher hierarchy of genetic interaction. Therefore, the MdSAUR37/MdPP2CH/MdALMTII chain cascaded hierarchical epistatic genetic effects to precisely determine apple fruit malate content. An A/G SNP (-1010) on MdMYB44 promoter region from a major QTL (qtl08.1) was closely associated with fruit malate content. The predicted phenotype values (PPVs) were estimated using the tentative genotype values of the gene markers, and the PPVs were significantly correlated with the observed phenotype values. Our findings provide an insight into plant genome-based selection in apples and will aid in conducting research to understand the physiological fundamentals of quantitative genetics. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  4. MD on UFOs at MKIs and MKQs

    CERN Document Server

    Baer, T; Bartmann, W; Bracco, C; Carlier, E; Dehning, B; Garrel, N; Goddard, B; Jackson, S; Jimenez, M; Kain, V; Mertens, V; Misiowiec, M; Nordt, A; Papotti, G; Uythoven, J; Wenninger, J; Zerlauth, M; Zamantzas, C; Zimmermann, F

    2012-01-01

    UFOs ("Unidentified Falling Objects") are expected to be one of the major known performance limitation of the LHC. In this MD, the production mechanism and the dynamics of UFOs at the injection kicker magnets (MKIs) and the tune kicker magnets (MKQs) were studied. This was done by pulsing the MKIs and MKQs on a gap in the partly filled machine. During the MD, in total 58 UFO-type beam loss patterns were observed directly after pulsing the MKIs. None were observed after pulsing the MKQs, which provides important input for possible mitigation strategies. The temporal and spatial distribution of the UFO events could be determined by using a dedicated BLM Study Buffer, the implications for the UFO dynamics are discussed.

  5. Verification of time-delay interferometry techniques using the University of Florida LISA interferometry simulator

    Energy Technology Data Exchange (ETDEWEB)

    Mitryk, Shawn J; Wand, Vinzenz; Mueller, Guido, E-mail: smitryk@phys.ufl.ed, E-mail: mueller@phys.ufl.ed [Department of Physics, University of Florida, PO Box 118440, Gainesville, FL 32611-8440 (United States)

    2010-04-21

    Laser Interferometer Space Antenna (LISA) is a cooperative NASA/ESA mission proposed to directly measure gravitational waves (GW) in the frequency range from 30 muHz to 1 Hz with an optimal strain sensitivity of 10{sup -21}/sq root(Hz) at 3 mHz. LISA will utilize a modified Michelson interferometer to measure length changes of 40 pm/sq root(Hz) between drag-free proof masses located on three separate spacecraft (SC) separated by a distance of 5 Gm. The University of Florida has developed a hardware-in-the-loop simulator of the LISA constellation to verify the laser noise cancellation technique known as time-delay interferometry (TDI). We replicate the frequency stabilization of the laser on the local SC and the phase-locking of the lasers on the far SC. The laser photodetector beatnotes are electronically delayed, Doppler shifted and applied with a mock GW signal to simulate the laser link between the SC. The beatnotes are also measured with a LISA-like phasemeter and the data are used to extract the laser phase and residual phase-lock loop noise in post-processing through TDI. This uncovers the GW modulation signal buried under the laser noise. The results are then compared to the requirements defined by the LISA science collaboration.

  6. MATLAB Simulation of UPQC for Power Quality Mitigation Using an Ant Colony Based Fuzzy Control Technique.

    Science.gov (United States)

    Kumarasabapathy, N; Manoharan, P S

    2015-01-01

    This paper proposes a fuzzy logic based new control scheme for the Unified Power Quality Conditioner (UPQC) for minimizing the voltage sag and total harmonic distortion in the distribution system consequently to improve the power quality. UPQC is a recent power electronic module which guarantees better power quality mitigation as it has both series-active and shunt-active power filters (APFs). The fuzzy logic controller has recently attracted a great deal of attention and possesses conceptually the quality of the simplicity by tackling complex systems with vagueness and ambiguity. In this research, the fuzzy logic controller is utilized for the generation of reference signal controlling the UPQC. To enable this, a systematic approach for creating the fuzzy membership functions is carried out by using an ant colony optimization technique for optimal fuzzy logic control. An exhaustive simulation study using the MATLAB/Simulink is carried out to investigate and demonstrate the performance of the proposed fuzzy logic controller and the simulation results are compared with the PI controller in terms of its performance in improving the power quality by minimizing the voltage sag and total harmonic distortion.

  7. Modeling and Simulation of Voids in Composite Tape Winding Process Based on Domain Superposition Technique

    Science.gov (United States)

    Deng, Bo; Shi, Yaoyao

    2017-11-01

    The tape winding technology is an effective way to fabricate rotationally composite materials. Nevertheless, some inevitable defects will seriously influence the performance of winding products. One of the crucial ways to identify the quality of fiber-reinforced composite material products is examining its void content. Significant improvement in products' mechanical properties can be achieved by minimizing the void defect. Two methods were applied in this study, finite element analysis and experimental testing, respectively, to investigate the mechanism of how void forming in composite tape winding processing. Based on the theories of interlayer intimate contact and Domain Superposition Technique (DST), a three-dimensional model of prepreg tape void with SolidWorks has been modeled in this paper. Whereafter, ABAQUS simulation software was used to simulate the void content change with pressure and temperature. Finally, a series of experiments were performed to determine the accuracy of the model-based predictions. The results showed that the model is effective for predicting the void content in the composite tape winding process.

  8. MATLAB Simulation of UPQC for Power Quality Mitigation Using an Ant Colony Based Fuzzy Control Technique

    Directory of Open Access Journals (Sweden)

    N. Kumarasabapathy

    2015-01-01

    Full Text Available This paper proposes a fuzzy logic based new control scheme for the Unified Power Quality Conditioner (UPQC for minimizing the voltage sag and total harmonic distortion in the distribution system consequently to improve the power quality. UPQC is a recent power electronic module which guarantees better power quality mitigation as it has both series-active and shunt-active power filters (APFs. The fuzzy logic controller has recently attracted a great deal of attention and possesses conceptually the quality of the simplicity by tackling complex systems with vagueness and ambiguity. In this research, the fuzzy logic controller is utilized for the generation of reference signal controlling the UPQC. To enable this, a systematic approach for creating the fuzzy membership functions is carried out by using an ant colony optimization technique for optimal fuzzy logic control. An exhaustive simulation study using the MATLAB/Simulink is carried out to investigate and demonstrate the performance of the proposed fuzzy logic controller and the simulation results are compared with the PI controller in terms of its performance in improving the power quality by minimizing the voltage sag and total harmonic distortion.

  9. Bioavailability and distribution and of ceria nanoparticles in simulated aquatic ecosystems, quantification with a radiotracer technique

    International Nuclear Information System (INIS)

    Zhang Zhiyong; Zhang Peng; He Xiao; Ma Yuhui; Lu Kai; Zhao Yuliang

    2014-01-01

    Although the presence of manufactured nanoparticles in the aquatic environment is still largely undocumented, their release could certainly occur in the future, particularly via municipal treatment plant effluents of cities supporting nano-industries. To get an initial estimate of the environmental behavior of nanomaterials, we investigated the distribution and accumulation of ceria nanoparticles in simulated aquatic ecosystems which included aquatic plant, shellfish, fish, water, and sediment using a radiotracer technique. Radioactive ceria ( 141 CeO 2 ) nanoparticles with a diameter of ca. 7 nm were synthesized by a precipitation method and added to the simulated aquatic ecosystems. The results indicate that the concentration of ceria nanoparticles in water decreased to a steady-state value after 3 days; meanwhile, the concentrations of ceria nanoparticles in the aquatic plant and sediment increased to their highest values. The distribution and accumulation characteristics of ceria nanoparticles in various aquatic organisms were different. Ceratophyllum demersum showed a high ability of accumulation of ceria nanoparticles from water. (authors)

  10. Use of sting-response techniques for simulate diagnostics in human esophagus

    International Nuclear Information System (INIS)

    Rodriguez, I.; Gonzalez, Y.; Valdes, L.; Alfonso, J.A.; Estevez, E.

    2003-01-01

    In this work a study of simulation of the gamma graphic studies that are carried out in human esophagus in the Dept. of Nuclear Medicine of the 'Celestino Hernandez Robau Hospital of Santa Clara is presented. For the investigation tubular reactors were used and sting-response techniques with radioactive tracer of Technetium 99 metastable to a concentration of 1 mCi and several flows were applied. The distribution curves of residences times were obtained, those that respond to an equation of the type: Y = A + B exp (- exp((x-C)/D)) - ((x-C/D)+1). They were also carried out, optimizations studies of the doses of the radioactive to give to the patients from 1 mCi (that is the one used in studies) up to 0,5 mCi, and the influences on the obtained distributions of residence time were analyzed. It was confirmed the possibility to lower the doses with clear information of the signal. It was also carried out a simulation of the attenuation of the radiations that takes place in the patients by the interposition of tissues among the analyzed organ, and the detection equipment. It was used paraffin for tissue simulation. It was found the almost independence of the intensity of the radiations with the thickness, for the assayed doses. Lastly it was found a complex mathematical model that responds to the diagnostic curves obtained in these studies, being correlated the coefficients of the pattern with the most important physical parameters of the system, giving it a practical and useful value, all time that the error among the values that this it predicts and the experimental ones do not surpass of 5%. (Author)

  11. The influence of wheelchair propulsion technique on upper extremity muscle demand: a simulation study.

    Science.gov (United States)

    Rankin, Jeffery W; Kwarciak, Andrew M; Richter, W Mark; Neptune, Richard R

    2012-11-01

    The majority of manual wheelchair users will experience upper extremity injuries or pain, in part due to the high force requirements, repetitive motion and extreme joint postures associated with wheelchair propulsion. Recent studies have identified cadence, contact angle and peak force as important factors for reducing upper extremity demand during propulsion. However, studies often make comparisons between populations (e.g., able-bodied vs. paraplegic) or do not investigate specific measures of upper extremity demand. The purpose of this study was to use a musculoskeletal model and forward dynamics simulations of wheelchair propulsion to investigate how altering cadence, peak force and contact angle influence individual muscle demand. Forward dynamics simulations of wheelchair propulsion were generated to emulate group-averaged experimental data during four conditions: 1) self-selected propulsion technique, and while 2) minimizing cadence, 3) maximizing contact angle, and 4) minimizing peak force using biofeedback. Simulations were used to determine individual muscle mechanical power and stress as measures of muscle demand. Minimizing peak force and cadence had the lowest muscle power requirements. However, minimizing peak force increased cadence and recovery power, while minimizing cadence increased average muscle stress. Maximizing contact angle increased muscle stress and had the highest muscle power requirements. Minimizing cadence appears to have the most potential for reducing muscle demand and fatigue, which could decrease upper extremity injuries and pain. However, altering any of these variables to extreme values appears to be less effective; instead small to moderate changes may better reduce overall muscle demand. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Study of flow characteristics in a secondary clarifier by numerical simulation and radioisotope tracer technique

    International Nuclear Information System (INIS)

    Kim, H.S.; Shin, M.S.; Jang, D.S.; Jung, S.H.; Jin, J.H.

    2005-01-01

    Numerical simulation in a 2-D rectangular coordinate and experimental study have been performed to figure out the flow characteristics and concentration distribution of a large-scale rectangular final clarifier in wastewater treatment facility located in Busan, S. Korea. The purpose of numerical calculation is to verify the experimentally measured data by radioisotope tracer technique and further to understand the important physical feature occurring in a large-scale clarifier, in many cases which is not sufficient by the aid of limited number of experimental data. To this end, a comprehensive computer program is basically made by SIMPLE algorithm by Patankar with the special emphasis on the parametric evaluation of the various phenomenological models. Calculation results are successfully evaluated against experimental data obtained by the method of radioisotope tracer. Detailed comparison is made on the calculated residence time distribution (RTD) curves with measurement inside the clarifier as well as the exhaust. Further the calculation results predict well the well-known characteristics of clarifier flow such as the waterfall phenomenon at the front end of the clarifier, the bottom density current in the settling zone and the upward flow in the withdrawal zone. Thus it is believed that the flow calculation program and the data incorporation technique of radioisotope measurement employed in this study show the high possibility as a complementary tool of experiment in this area

  13. Determination of true coincidence correction factors using Monte-Carlo simulation techniques

    Directory of Open Access Journals (Sweden)

    Chionis Dionysios A.

    2014-01-01

    Full Text Available Aim of this work is the numerical calculation of the true coincidence correction factors by means of Monte-Carlo simulation techniques. For this purpose, the Monte Carlo computer code PENELOPE was used and the main program PENMAIN was properly modified in order to include the effect of the true coincidence phenomenon. The modified main program that takes into consideration the true coincidence phenomenon was used for the full energy peak efficiency determination of an XtRa Ge detector with relative efficiency 104% and the results obtained for the 1173 keV and 1332 keV photons of 60Co were found consistent with respective experimental ones. The true coincidence correction factors were calculated as the ratio of the full energy peak efficiencies was determined from the original main program PENMAIN and the modified main program PENMAIN. The developed technique was applied for 57Co, 88Y, and 134Cs and for two source-to-detector geometries. The results obtained were compared with true coincidence correction factors calculated from the "TrueCoinc" program and the relative bias was found to be less than 2%, 4%, and 8% for 57Co, 88Y, and 134Cs, respectively.

  14. Comparisons of Particle Tracking Techniques and Galerkin Finite Element Methods in Flow Simulations on Watershed Scales

    Science.gov (United States)

    Shih, D.; Yeh, G.

    2009-12-01

    This paper applies two numerical approximations, the particle tracking technique and Galerkin finite element method, to solve the diffusive wave equation in both one-dimensional and two-dimensional flow simulations. The finite element method is one of most commonly approaches in numerical problems. It can obtain accurate solutions, but calculation times may be rather extensive. The particle tracking technique, using either single-velocity or average-velocity tracks to efficiently perform advective transport, could use larger time-step sizes than the finite element method to significantly save computational time. Comparisons of the alternative approximations are examined in this poster. We adapt the model WASH123D to examine the work. WASH123D is an integrated multimedia, multi-processes, physics-based computational model suitable for various spatial-temporal scales, was first developed by Yeh et al., at 1998. The model has evolved in design capability and flexibility, and has been used for model calibrations and validations over the course of many years. In order to deliver a locally hydrological model in Taiwan, the Taiwan Typhoon and Flood Research Institute (TTFRI) is working with Prof. Yeh to develop next version of WASH123D. So, the work of our preliminary cooperationx is also sketched in this poster.

  15. A Simulation Technique for Three-Dimensional Mechanical Systems Using Universal Software Systems of Analysis

    Directory of Open Access Journals (Sweden)

    V. A. Trudonoshin

    2015-01-01

    Full Text Available The article proposes a technique to develop mathematical models (MM of elements of the three-dimensional (3D mechanical systems for universal simulation software systems that allow us automatically generate the MM of a system based on MM elements and their connections. The technique is based on the MM of 3 D body. Linear and angular velocities are used as the main phase variables (unknown in the MM of the system, linear and angular movements are used as the additional ones, the latter being defined by the normalized quaternions that have computational advantages over turning angles.The paper has considered equations of dynamics, formulas of transition from the global coordinate system to the local one and vice versa. A spherical movable joint is presented as an example of the interaction element between the bodies. The paper shows the MM equivalent circuits of a body and a spherical joint. Such a representation, as the equivalent circuit, automatically enables us to obtain topological equations of the system. Various options to build equations of the joint and advices for their practical use are given.

  16. Applications Of Monte Carlo Radiation Transport Simulation Techniques For Predicting Single Event Effects In Microelectronics

    International Nuclear Information System (INIS)

    Warren, Kevin; Reed, Robert; Weller, Robert; Mendenhall, Marcus; Sierawski, Brian; Schrimpf, Ronald

    2011-01-01

    MRED (Monte Carlo Radiative Energy Deposition) is Vanderbilt University's Geant4 application for simulating radiation events in semiconductors. Geant4 is comprised of the best available computational physics models for the transport of radiation through matter. In addition to basic radiation transport physics contained in the Geant4 core, MRED has the capability to track energy loss in tetrahedral geometric objects, includes a cross section biasing and track weighting technique for variance reduction, and additional features relevant to semiconductor device applications. The crucial element of predicting Single Event Upset (SEU) parameters using radiation transport software is the creation of a dosimetry model that accurately approximates the net collected charge at transistor contacts as a function of deposited energy. The dosimetry technique described here is the multiple sensitive volume (MSV) model. It is shown to be a reasonable approximation of the charge collection process and its parameters can be calibrated to experimental measurements of SEU cross sections. The MSV model, within the framework of MRED, is examined for heavy ion and high-energy proton SEU measurements of a static random access memory.

  17. A new and efficient transient noise analysis technique for simulation of CCD image sensors or particle detectors

    International Nuclear Information System (INIS)

    Bolcato, P.; Jarron, P.; Poujois, R.

    1993-01-01

    CCD image sensors or switched capacitor circuits used for particle detectors have a certain noise level affecting the resolution of the detector. A new noise simulation technique for these devices is presented that has been implemented in the circuit simulator ELDO. The approach is particularly useful for noise simulation in analog sampling circuits. Comparison between simulations and experimental results has been made and is shown for a 1.5 μ CMOS current mode amplifier designed for high-rate particle detectors. (R.P.) 5 refs., 7 figs

  18. Test/score/report: Simulation techniques for automating the test process

    Science.gov (United States)

    Hageman, Barbara H.; Sigman, Clayton B.; Koslosky, John T.

    1994-01-01

    A Test/Score/Report capability is currently being developed for the Transportable Payload Operations Control Center (TPOCC) Advanced Spacecraft Simulator (TASS) system which will automate testing of the Goddard Space Flight Center (GSFC) Payload Operations Control Center (POCC) and Mission Operations Center (MOC) software in three areas: telemetry decommutation, spacecraft command processing, and spacecraft memory load and dump processing. Automated computer control of the acceptance test process is one of the primary goals of a test team. With the proper simulation tools and user interface, the task of acceptance testing, regression testing, and repeatability of specific test procedures of a ground data system can be a simpler task. Ideally, the goal for complete automation would be to plug the operational deliverable into the simulator, press the start button, execute the test procedure, accumulate and analyze the data, score the results, and report the results to the test team along with a go/no recommendation to the test team. In practice, this may not be possible because of inadequate test tools, pressures of schedules, limited resources, etc. Most tests are accomplished using a certain degree of automation and test procedures that are labor intensive. This paper discusses some simulation techniques that can improve the automation of the test process. The TASS system tests the POCC/MOC software and provides a score based on the test results. The TASS system displays statistics on the success of the POCC/MOC system processing in each of the three areas as well as event messages pertaining to the Test/Score/Report processing. The TASS system also provides formatted reports documenting each step performed during the tests and the results of each step. A prototype of the Test/Score/Report capability is available and currently being used to test some POCC/MOC software deliveries. When this capability is fully operational it should greatly reduce the time necessary

  19. Efficient CT simulation of the four-field technique for conformal radiotherapy of prostate carcinoma

    International Nuclear Information System (INIS)

    Valicenti, Richard K.; Waterman, Frank M.; Croce, Raymond J.; Corn, Benjamin; Suntharalingam, Nagalingam; Curran, Walter J.

    1997-01-01

    Purpose: Conformal radiotherapy of prostate carcinoma relies on contouring of individual CT slices for target and normal tissue localization. This process can be very time consuming. In the present report, we describe a method to more efficiently localize pelvic anatomy directly from digital reconstructed radiographs (DRRs). Materials and Methods: Ten patients with prostate carcinoma underwent CT simulation (the spiral mode at 3 mm separation) for conformal four-field 'box' radiotherapy. The bulbous urethra and bladder were opacified with iodinated contrast media. On lateral and anteroposterior DRRs, the volume of interest (VOI) was restricted to 1.0-1.5 cm tissue thickness to optimize digital radiograph reconstruction of the prostate and seminal vesicles. By removing unessential voxel elements, this method provided direct visualization of those structures. For comparison, the targets of each patient were also obtained by contouring CT axial slices. Results: The method was successfully performed if the target structures were readily visualized and geometrically corresponded to those generated by contouring axial images. The targets in 9 of 10 patients were reliable representations of the CT-contoured volumes. One patient had 18 mm variation due to the lack of bladder opacification. Using VOIs to generate thin tissue DRRs, the time required for target and normal tissue localization was on the average less than 5 min. Conclusion: In CT simulation of the four-field irradiation technique for prostate carcinoma, thin-tissue DRRs allowed for efficient and accurate target localization without requiring individual axial image contouring. This method may facilitate positioning of the beam isocenter and provide reliable conformal radiotherapy

  20. Comparative evaluation of a two stroke compressed natural gas mixer design using simulation and experimental techniques

    Energy Technology Data Exchange (ETDEWEB)

    Ramasamy, D.; Bakar, R.A.; Rahim, M.F.; Noor, M.M. [Malaysia Pahang Univ., Pahang (Malaysia). Automotive Focus Group

    2008-07-01

    A study was conducted in which a two-stroke engine was converted for use with bi-fuel, notably compressed natural gas and gasoline. The excessive by-products generated by two-stroke engine combustion can be attributed to the inefficient combustion process. This prototype uniflow-type single-cylinder engine was equipped with a bi-fuel conversion system. A dedicated mixer was also developed to meter the gaseous fuel through the engine intake system. It was designed to meet air and fuel requirement similar to its gasoline counterpart. The mixer was modeled to obtain optimum orifice diameter using three different sizes of 14, 16 and 18 mm respectively. A standard computational fluid dynamics (CFD) software package was used to simulate the flow. A pressure reading was obtained during the prototype test. The drop in pressure across the venturi was shown to be an important parameter as it determined the actual fuel-air ratio in the actual engine. A good agreement of CFD outputs with that of the experimental outputs was recorded. The experimental technique validated the pressure distribution predicted by CFD means on the effects of the three insert rings in the CNG mixer. The simulation exercise can be used to predict the amount of CNG consumed by the engine. It was concluded that the 14 mm throat ring was best suited for the CNG mixer because it provided the best suction. Once the mixer is tested on a real engine, it will clear any doubts as to whether the throat can function at high engine speeds. 5 refs., 3 tabs., 8 figs.

  1. Correlating TEM images of damage in irradiated materials to molecular dynamics simulations

    International Nuclear Information System (INIS)

    Schaeublin, R.; Caturla, M.-J.; Wall, M.; Felter, T.; Fluss, M.; Wirth, B.D.; Diaz de la Rubia, T.; Victoria, M.

    2002-01-01

    TEM image simulations are used to couple the results from molecular dynamics (MD) simulations to experimental TEM images. In particular we apply this methodology to the study of defects produced during irradiation. MD simulations have shown that irradiation of FCC metals results in a population of vacancies and interstitials forming clusters. The limitation of these simulations is the short time scales available, on the order of 100 s of picoseconds. Extrapolation of the results from these short times to the time scales of the laboratory has been difficult. We address this problem by two methods: we perform TEM image simulations of MD simulations of cascades with an improved technique, to relate defects produced at short time scales with those observed experimentally at much longer time scales. On the other hand we perform in situ TEM experiments of Au irradiated at liquid-nitrogen temperatures, and study the evolution of the produced damage as the temperature is increased to room temperature. We find that some of the defects observed in the MD simulations at short time scales using the TEM image simulation technique have features that resemble those observed in laboratory TEM images of irradiated samples. In situ TEM shows that stacking fault tetrahedra are present at the lowest temperatures and are stable during annealing up to room temperature, while other defect clusters migrate one dimensionally above -100 deg. C. Results are presented here

  2. Molecular dynamics simulation of impact test

    International Nuclear Information System (INIS)

    Akahoshi, Y.; Schmauder, S.; Ludwig, M.

    1998-01-01

    This paper describes an impact test by molecular dynamics (MD) simulation to evaluate embrittlement of bcc Fe at different temperatures. A new impact test model is developed for MD simulation. The typical fracture behaviors show transition from brittle to ductile fracture, and a history of the impact loads also demonstrates its transition. We conclude that the impact test by MD could be feasible. (orig.)

  3. Molecular dynamics simulation of impact test

    Energy Technology Data Exchange (ETDEWEB)

    Akahoshi, Y. [Kyushu Inst. of Tech., Kitakyushu, Fukuoka (Japan); Schmauder, S.; Ludwig, M. [Stuttgart Univ. (Germany). Staatliche Materialpruefungsanstalt

    1998-11-01

    This paper describes an impact test by molecular dynamics (MD) simulation to evaluate embrittlement of bcc Fe at different temperatures. A new impact test model is developed for MD simulation. The typical fracture behaviors show transition from brittle to ductile fracture, and a history of the impact loads also demonstrates its transition. We conclude that the impact test by MD could be feasible. (orig.)

  4. Development and validation of predictive simulation model of multi-layer repair welding process by temper bead technique

    International Nuclear Information System (INIS)

    Okano, Shigetaka; Miyasaka, Fumikazu; Mochizuki, Masahito; Tanaka, Manabu

    2015-01-01

    Stress corrosion cracking (SCC) has recently been observed in the nickel base alloy weld metal of dissimilar pipe joint used in pressurized water reactor (PWR) . Temper bead technique has been developed as one of repair procedures against SCC applicable in case that post weld heat treatment (PWHT) is difficult to carry out. In this regard, however it is essential to pass the property and performance qualification test to confirm the effect of tempering on the mechanical properties at repair welds before temper bead technique is actually used in practice. Thus the appropriate welding procedure conditions in temper bead technique are determined on the basis of the property and performance qualification testing. It is necessary for certifying the structural soundness and reliability at repair welds but takes a lot of work and time in the present circumstances. Therefore it is desirable to establish the reasonable alternatives for qualifying the property and performance at repair welds. In this study, mathematical modeling and numerical simulation procedures were developed for predicting weld bead configuration and temperature distribution during multi-layer repair welding process by temper bead technique. In the developed simulation technique, characteristics of heat source in temper bead welding are calculated from weld heat input conditions through the arc plasma simulation and then weld bead configuration and temperature distribution during temper bead welding are calculated from characteristics of heat source obtained through the coupling analysis between bead surface shape and thermal conduction. The simulation results were compared with the experimental results under the same welding heat input conditions. As the results, the bead surface shape and temperature distribution, such as A cl lines, were in good agreement between simulation and experimental results. It was concluded that the developed simulation technique has the potential to become useful for

  5. MD Test of a Ballistic Optics

    CERN Document Server

    Garcia-Tabares Valdivieso, Ana; Salvachua Ferrando, Belen Maria; Skowronski, Piotr Krzysztof; Solfaroli Camillocci, Matteo; Tomas Garcia, Rogelio; Wenninger, Jorg; Coello De Portugal - Martinez Vazquez, Jaime Maria; CERN. Geneva. ATS Department

    2016-01-01

    The ballistic optics is designed to improve the understanding of optical errors and BPM systematic effects in the critical triplet region. The particularity of that optics is that the triplet is switched off, effectively transforming the triplets on both sides of IR1 and IR5 into drift spaces. Advantage can be taken from that fact to localize better errors in the Q4-Q5-triplet region. During this MD this new optics was tested for the first time at injection with beam 2.

  6. Modeling and simulation of PEM fuel cell's flow channels using CFD techniques

    International Nuclear Information System (INIS)

    Cunha, Edgar F.; Andrade, Alexandre B.; Robalinho, Eric; Bejarano, Martha L.M.; Linardi, Marcelo; Cekinski, Efraim

    2007-01-01

    Fuel cells are one of the most important devices to obtain electrical energy from hydrogen. The Proton Exchange Membrane Fuel Cell (PEMFC) consists of two important parts: the Membrane Electrode Assembly (MEA), where the reactions occur, and the flow field plates. The plates have many functions in a fuel cell: distribute reactant gases (hydrogen and air or oxygen), conduct electrical current, remove heat and water from the electrodes and make the cell robust. The cost of the bipolar plates corresponds up to 45% of the total stack costs. The Computational Fluid Dynamic (CFD) is a very useful tool to simulate hydrogen and oxygen gases flow channels, to reduce the costs of bipolar plates production and to optimize mass transport. Two types of flow channels were studied. The first type was a commercial plate by ELECTROCELL and the other was entirely projected at Programa de Celula a Combustivel (IPEN/CNEN-SP) and the experimental data were compared with modelling results. Optimum values for each set of variables were obtained and the models verification was carried out in order to show the feasibility of this technique to improve fuel cell efficiency. (author)

  7. Analysis and simulation of wireless signal propagation applying geostatistical interpolation techniques

    Science.gov (United States)

    Kolyaie, S.; Yaghooti, M.; Majidi, G.

    2011-12-01

    This paper is a part of an ongoing research to examine the capability of geostatistical analysis for mobile networks coverage prediction, simulation and tuning. Mobile network coverage predictions are used to find network coverage gaps and areas with poor serviceability. They are essential data for engineering and management in order to make better decision regarding rollout, planning and optimisation of mobile networks.The objective of this research is to evaluate different interpolation techniques in coverage prediction. In method presented here, raw data collected from drive testing a sample of roads in study area is analysed and various continuous surfaces are created using different interpolation methods. Two general interpolation methods are used in this paper with different variables; first, Inverse Distance Weighting (IDW) with various powers and number of neighbours and second, ordinary kriging with Gaussian, spherical, circular and exponential semivariogram models with different number of neighbours. For the result comparison, we have used check points coming from the same drive test data. Prediction values for check points are extracted from each surface and the differences with actual value are computed. The output of this research helps finding an optimised and accurate model for coverage prediction.

  8. Modeling and simulation of PEM fuel cell's flow channels using CFD techniques

    Energy Technology Data Exchange (ETDEWEB)

    Cunha, Edgar F.; Andrade, Alexandre B.; Robalinho, Eric; Bejarano, Martha L.M.; Linardi, Marcelo [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)]. E-mails: efcunha@ipen.br; abodart@ipen.br; eric@ipen.br; mmora@ipen.br; mlinardi@ipen.br; Cekinski, Efraim [Instituto de Pesquisas Tecnologicas (IPT-SP), Sao Paulo, SP (Brazil)]. E-mail: cekinski@ipt.br

    2007-07-01

    Fuel cells are one of the most important devices to obtain electrical energy from hydrogen. The Proton Exchange Membrane Fuel Cell (PEMFC) consists of two important parts: the Membrane Electrode Assembly (MEA), where the reactions occur, and the flow field plates. The plates have many functions in a fuel cell: distribute reactant gases (hydrogen and air or oxygen), conduct electrical current, remove heat and water from the electrodes and make the cell robust. The cost of the bipolar plates corresponds up to 45% of the total stack costs. The Computational Fluid Dynamic (CFD) is a very useful tool to simulate hydrogen and oxygen gases flow channels, to reduce the costs of bipolar plates production and to optimize mass transport. Two types of flow channels were studied. The first type was a commercial plate by ELECTROCELL and the other was entirely projected at Programa de Celula a Combustivel (IPEN/CNEN-SP) and the experimental data were compared with modelling results. Optimum values for each set of variables were obtained and the models verification was carried out in order to show the feasibility of this technique to improve fuel cell efficiency. (author)

  9. Assessing Uncertainty in Deep Learning Techniques that Identify Atmospheric Rivers in Climate Simulations

    Science.gov (United States)

    Mahesh, A.; Mudigonda, M.; Kim, S. K.; Kashinath, K.; Kahou, S.; Michalski, V.; Williams, D. N.; Liu, Y.; Prabhat, M.; Loring, B.; O'Brien, T. A.; Collins, W. D.

    2017-12-01

    Atmospheric rivers (ARs) can be the difference between CA facing drought or hurricane-level storms. ARs are a form of extreme weather defined as long, narrow columns of moisture which transport water vapor outside the tropics. When they make landfall, they release the vapor as rain or snow. Convolutional neural networks (CNNs), a machine learning technique that uses filters to recognize features, are the leading computer vision mechanism for classifying multichannel images. CNNs have been proven to be effective in identifying extreme weather events in climate simulation output (Liu et. al. 2016, ABDA'16, http://bit.ly/2hlrFNV). Here, we compare three different CNN architectures, tuned with different hyperparameters and training schemes. We compare two-layer, three-layer, four-layer, and sixteen-layer CNNs' ability to recognize ARs in Community Atmospheric Model version 5 output, and we explore the ability of data augmentation and pre-trained models to increase the accuracy of the classifier. Because pre-training the model with regular images (i.e. benches, stoves, and dogs) yielded the highest accuracy rate, this strategy, also known as transfer learning, may be vital in future scientific CNNs, which likely will not have access to a large labelled training dataset. By choosing the most effective CNN architecture, climate scientists can build an accurate historical database of ARs, which can be used to develop a predictive understanding of these phenomena.

  10. Thermoreflectance temperature imaging of integrated circuits: calibration technique and quantitative comparison with integrated sensors and simulations

    International Nuclear Information System (INIS)

    Tessier, G; Polignano, M-L; Pavageau, S; Filloy, C; Fournier, D; Cerutti, F; Mica, I

    2006-01-01

    Camera-based thermoreflectance microscopy is a unique tool for high spatial resolution thermal imaging of working integrated circuits. However, a calibration is necessary to obtain quantitative temperatures on the complex surface of integrated circuits. The spatial and temperature resolutions reached by thermoreflectance are excellent (360 nm and 2.5 x 10 -2 K in 1 min here), but the precision is more difficult to assess, notably due to the lack of comparable thermal techniques at submicron scales. We propose here a Peltier element control of the whole package temperature in order to obtain calibration coefficients simultaneously on several materials visible on the surface of the circuit. Under high magnifications, movements associated with thermal expansion are corrected using a piezo electric displacement and a software image shift. This calibration method has been validated by comparison with temperatures measured using integrated thermistors and diodes and by a finite volume simulation. We show that thermoreflectance measurements agree within a precision of ±2.3% with the on-chip sensors measurements. The diode temperature is found to underestimate the actual temperature of the active area by almost 70% due to the thermal contact of the diode with the substrate, acting as a heat sink

  11. Dynamics of fibres in a turbulent flow field - A particle-level simulation technique

    International Nuclear Information System (INIS)

    Sasic, Srdjan; Almstedt, Alf-Erik

    2010-01-01

    A particle-level simulation technique has been developed for modelling the flow of fibres in a turbulent flow field. A single fibre is conceived here as a chain of segments, thus enabling the model fibre to have all the degrees of freedom (translation, rotation, bending and twisting) needed to realistically reproduce the dynamics of real fibres. Equations of motion are solved for each segment, accounting for the interaction forces with the fluid, the contact forces with other fibres and the forces that maintain integrity of the fibre. The motion of the fluid is resolved as a combination of 3D mean flow velocities obtained from a CFD code and fluctuating turbulent velocities derived from the Langevin equation. A case of homogeneous turbulence is treated in this paper. The results obtained show that fibre flocs in air-fibre flows can be created even when attractive forces are not present. In such a case, contacts between fibres, properties of an individual fibre (such as flexibility and equilibrium shapes) and properties of the flow of the carrying fluid are shown to govern the physics behind formation and breaking up of fibre flocs. Highly irregular fibre shapes and stiff fibres lead to strong flocculation. The modelling framework applied in this work aims at making possible a numerical model applicable for designing processes involving transport of fibres by air at industrial scale.

  12. Monte Carlo simulation and gaussian broaden techniques for full energy peak of characteristic X-ray in EDXRF

    International Nuclear Information System (INIS)

    Li Zhe; Liu Min; Shi Rui; Wu Xuemei; Tuo Xianguo

    2012-01-01

    Background: Non-standard analysis (NSA) technique is one of the most important development directions of energy dispersive X-ray fluorescence (EDXRF). Purpose: This NSA technique is mainly based on Monte Carlo (MC) simulation and full energy peak broadening, which were studied preliminarily in this paper. Methods: A kind of MC model was established for Si-PIN based EDXRF setup, and the flux spectra were obtained for iron ore sample. Finally, the flux spectra were broadened by Gaussian broaden parameters calculated by a new method proposed in this paper, and the broadened spectra were compared with measured energy spectra. Results: MC method can be used to simulate EDXRF measurement, and can correct the matrix effects among elements automatically. Peak intensities can be obtained accurately by using the proposed Gaussian broaden technique. Conclusions: This study provided a key technique for EDXRF to achieve advanced NSA technology. (authors)

  13. A Simple Ensemble Simulation Technique for Assessment of Future Variations in Specific High-Impact Weather Events

    Science.gov (United States)

    Taniguchi, Kenji

    2018-04-01

    To investigate future variations in high-impact weather events, numerous samples are required. For the detailed assessment in a specific region, a high spatial resolution is also required. A simple ensemble simulation technique is proposed in this paper. In the proposed technique, new ensemble members were generated from one basic state vector and two perturbation vectors, which were obtained by lagged average forecasting simulations. Sensitivity experiments with different numbers of ensemble members, different simulation lengths, and different perturbation magnitudes were performed. Experimental application to a global warming study was also implemented for a typhoon event. Ensemble-mean results and ensemble spreads of total precipitation, atmospheric conditions showed similar characteristics across the sensitivity experiments. The frequencies of the maximum total and hourly precipitation also showed similar distributions. These results indicate the robustness of the proposed technique. On the other hand, considerable ensemble spread was found in each ensemble experiment. In addition, the results of the application to a global warming study showed possible variations in the future. These results indicate that the proposed technique is useful for investigating various meteorological phenomena and the impacts of global warming. The results of the ensemble simulations also enable the stochastic evaluation of differences in high-impact weather events. In addition, the impacts of a spectral nudging technique were also examined. The tracks of a typhoon were quite different between cases with and without spectral nudging; however, the ranges of the tracks among ensemble members were comparable. It indicates that spectral nudging does not necessarily suppress ensemble spread.

  14. Determination of two- and three-body correlation functions in ionic solutions by means of MD and EXAFS investigations

    International Nuclear Information System (INIS)

    D'Angelo, P.; Pavel, N.V.

    1999-01-01

    The solvation structure of Sr 2+ ions in acetonitrile has been studied by x-ray absorption spectroscopy (XAS) and molecular dynamics (MD) simulations. The extended x-ray absorption fine structure (EXAFS) above the Sr K-edge has been interpreted in the framework of the multiple scattering (MS) formalism and, for the first time, clear evidence of MS contributions has been found for non-complexing ions in solution. Molecular dynamics has been used to generate the partial pair g(r) and the three-body g(r 1 , r 2 , θ) distribution functions from which a model χ(k) has been constructed. An excellent agreement has been found between the theoretical and experimental data. This result demonstrates the ability of the XAS technique in probing three-body correlation functions in solutions. (au)

  15. Helped positioning by using a simulation tool for qualification of PWR vessel examination technique

    International Nuclear Information System (INIS)

    Lasserre, Frederic; Pasquier, Thierry; Haiat, Guillaume; Calmon, Pierre; Leberre, Stephane; Lutsen, Mickael

    2006-01-01

    INTERCONTROLE have been performing the examination of all PWR vessels in France from the inside, using UT techniques since 1975. The in-service inspection machine (MIS) features several tools equipped with focussed transducers; each tool is dedicated to one specific area of the vessel. In the core region, the very first millimeters from the cladding-base metal interface has to be inspected with accuracy because of the under-cladding cracks type defects (perpendicular to the inner surface) likely to be found. The technique used up to now was qualified according to the RSE-M code in 1998. It is based on a set of 63 angle L-waves transducers specifically designed for the detection of defect tip diffraction echoes in the 25 first millimeters in through-wall thickness. The analysis methods for defect characterization are based on a global integration of various cladding induced phenomena. The technique, the procedure and the analysis methods were qualified for a given limited volume. The new qualification in process in France, requires that INTERCONTROLE find solutions for increasing the accuracy of the analysis, in a larger qualification volume than before, while remaining in close compliance with the RSE-M code. A new computer assisted analysis tool for the characterization, the sizing and the positioning of defects is part of the improvements currently in progress or already completed. This tool is the result of a thesis commissioned to the CEA (Atomic Energy Commission), now implemented in the CIVAMIS software (developed on a CIVA based system). The updated version of CIVAMIS including this characterization tool and the RSE-M qualification of the new analysis method (with validation on mock-ups) is now qualified. Despite of a larger qualification volume, the results obtained (mentioned in the present paper) fulfill the customer's requirements thanks to the amount of data, of information and of knowledge, available today. The ability to simulate the cladding in terms

  16. QM/MM-MD simulations of conjugated polyelectrolytes

    DEFF Research Database (Denmark)

    Sjöqvist, Jonas; Linares, Mathieu; Mikkelsen, Kurt Valentin

    2014-01-01

    A methodological development is reported for the study of luminescence properties of conjugated polyelectrolytes, encompassing systems in which dihedral rotational barriers are easily overcome at room temperature. The components of the model include (i) a molecular mechanics (MM) force field desc...

  17. Solving optimisation problems in metal forming using Finite Element simulation and metamodelling techniques

    NARCIS (Netherlands)

    Bonte, M.H.A.; van den Boogaard, Antonius H.; Huetink, Han

    2005-01-01

    During the last decades, Finite Element (FEM) simulations of metal forming processes have become important tools for designing feasible production processes. In more recent years, several authors recognised the potential of coupling FEM simulations to mathematical optimisation algorithms to design

  18. Application of a Cycle Jump Technique for Acceleration of Fatigue Crack Growth Simulation

    DEFF Research Database (Denmark)

    Moslemian, Ramin; Berggreen, Christian; Karlsson, A.M.

    2010-01-01

    A method for accelerated simulation of fatigue crack growth in a bimaterial interface is proposed. To simulate fatigue crack growth in a bimaterial interface a routine is developed in the commercial finite element code ANSYS and a method to accelerate the simulation is implemented. The proposed m...... of the simulation show that with fair accuracy, using the cycle jump method, more than 70% reduction in computation time can be achieved....

  19. Innovations in surgery simulation: a review of past, current and future techniques

    OpenAIRE

    Badash, Ido; Burtt, Karen; Solorzano, Carlos A.; Carey, Joseph N.

    2016-01-01

    As a result of recent work-hours limitations and concerns for patient safety, innovations in extraclinical surgical simulation have become a desired part of residency education. Current simulation models, including cadaveric, animal, bench-top, virtual reality (VR) and robotic simulators are increasingly used in surgical training programs. Advances in telesurgery, three-dimensional (3D) printing, and the incorporation of patient-specific anatomy are paving the way for simulators to become int...

  20. The simulated early learning of cervical spine manipulation technique utilising mannequins.

    Science.gov (United States)

    Chapman, Peter D; Stomski, Norman J; Losco, Barrett; Walker, Bruce F

    2015-01-01

    Trivial pain or minor soreness commonly follows neck manipulation and has been estimated at one in three treatments. In addition, rare catastrophic events can occur. Some of these incidents have been ascribed to poor technique where the neck is rotated too far. The aims of this study were to design an instrument to measure competency of neck manipulation in beginning students when using a simulation mannequin, and then examine the suitability of using a simulation mannequin to teach the early psychomotor skills for neck chiropractic manipulative therapy. We developed an initial set of questionnaire items and then used an expert panel to assess an instrument for neck manipulation competency among chiropractic students. The study sample comprised all 41 fourth year 2014 chiropractic students at Murdoch University. Students were randomly allocated into either a usual learning or mannequin group. All participants crossed over to undertake the alternative learning method after four weeks. A chi-square test was used to examine differences between groups in the proportion of students achieving an overall pass mark at baseline, four weeks, and eight weeks. This study was conducted between January and March 2014. We successfully developed an instrument of measurement to assess neck manipulation competency in chiropractic students. We then randomised 41 participants to first undertake either "usual learning" (n = 19) or "mannequin learning" (n = 22) for early neck manipulation training. There were no significant differences between groups in the overall pass rate at baseline (χ(2) = 0.10, p = 0.75), four weeks (χ(2) = 0.40, p = 0.53), and eight weeks (χ(2) = 0.07, p = 0.79). This study demonstrates that the use of a mannequin does not affect the manipulation competency grades of early learning students at short term follow up. Our findings have potentially important safety implications as the results indicate that students could initially

  1. Employ Simulation Techniques. Second Edition. Module C-5 of Category C--Instructional Execution. Professional Teacher Education Module Series.

    Science.gov (United States)

    Ohio State Univ., Columbus. National Center for Research in Vocational Education.

    One of a series of performance-based teacher education learning packages focusing upon specific professional competencies of vocational teachers, this learning module deals with employing simulation techniques. It consists of an introduction and four learning experiences. Covered in the first learning experience are various types of simulation…

  2. Computational Dehydration of Crystalline Hydrates Using Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Larsen, Anders Støttrup; Rantanen, Jukka; Johansson, Kristoffer E

    2017-01-01

    Molecular dynamics (MD) simulations have evolved to an increasingly reliable and accessible technique and are today implemented in many areas of biomedical sciences. We present a generally applicable method to study dehydration of hydrates based on MD simulations and apply this approach...... to the dehydration of ampicillin trihydrate. The crystallographic unit cell of the trihydrate is used to construct the simulation cell containing 216 ampicillin and 648 water molecules. This system is dehydrated by removing water molecules during a 2200 ps simulation, and depending on the computational dehydration....... The structural changes could be followed in real time, and in addition, an intermediate amorphous phase was identified. The computationally identified dehydrated structure (anhydrate) was slightly different from the experimentally known anhydrate structure suggesting that the simulated computational structure...

  3. Shallow boron dopant on silicon An MD study

    International Nuclear Information System (INIS)

    Perez-Martin, A. Mari Carmen; Jimenez-Rodriguez, Jose J.; Jimenez-Saez, Jose Carlos

    2004-01-01

    Low energy boron bombardment of silicon has been simulated at room temperature by molecular dynamics (MD). Tersoff potential T3 was used in the simulation smoothly linked up with the universal potential. The boron-silicon (B-Si) interaction was simulated according to Tersoff potential for SiC but modified to account for the B-Si interaction. The algorithm can distinguish a B from a Si neighbour. Si-c, with (2 x 1) surface reconstruction, was bombarded with boron at 200 and 500 eV. These energies were initially chosen as good representative values of the low energy range. Reliable results require of a reasonable good statistic so that 1000-impact points were chosen uniformly distributed over a representative area of a 2 x 1 surface. The distribution of mean projected range for B is given. All kinds of point defect were looked for in a Si damaged target after bombardment. Energetically stable substitutional and interstitial configurations are presented and the relative appearances of the different types of interstitials, for both Si and B, are given. It is also determined the mean length of the distance to the first neighbours of defects

  4. Who is that masked educator? Deconstructing the teaching and learning processes of an innovative humanistic simulation technique.

    Science.gov (United States)

    McAllister, Margaret; Searl, Kerry Reid; Davis, Susan

    2013-12-01

    Simulation learning in nursing has long made use of mannequins, standardized actors and role play to allow students opportunity to practice technical body-care skills and interventions. Even though numerous strategies have been developed to mimic or amplify clinical situations, a common problem that is difficult to overcome in even the most well-executed simulation experiences, is that students may realize the setting is artificial and fail to fully engage, remember or apply the learning. Another problem is that students may learn technical competence but remain uncertain about communicating with the person. Since communication capabilities are imperative in human service work, simulation learning that only achieves technical competence in students is not fully effective for the needs of nursing education. Furthermore, while simulation learning is a burgeoning space for innovative practices, it has been criticized for the absence of a basis in theory. It is within this context that an innovative simulation learning experience named "Mask-Ed (KRS simulation)", has been deconstructed and the active learning components examined. Establishing a theoretical basis for creative teaching and learning practices provides an understanding of how, why and when simulation learning has been effective and it may help to distinguish aspects of the experience that could be improved. Three conceptual theoretical fields help explain the power of this simulation technique: Vygotskian sociocultural learning theory, applied theatre and embodiment. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. Student’s Perceptions on Simulation as Part of Experiential Learning in Approaches, Methods, and Techniques (AMT Course

    Directory of Open Access Journals (Sweden)

    Marselina Karina Purnomo

    2017-03-01

    Full Text Available Simulation is a part of Experiential Learning which represents certain real-life events. In this study, simulation is used as a learning activity in Approaches, Methods, and Techniques (AMT course which is one of the courses in English Language Education Study Program (ELESP of Sanata Dharma University. Since simulation represents the real-life events, it encourages students to apply the approaches, methods, and techniques being studied based on the real-life classroom. Several experts state that students are able to involve their personal experiences through simulation which additionally is believed to create a meaningful learning in the class. This study aimed to discover ELESP students’ perceptions toward simulation as a part of Experiential Learning in AMT course. From the findings, it could be inferred that students agreed that simulation in class was important for students’ learning for it formed a meaningful learning in class.  DOI: https://doi.org/10.24071/llt.2017.200104

  6. MD-11 PCA - First Landing at Edwards

    Science.gov (United States)

    1995-01-01

    This McDonnell Douglas MD-11 approaches the first landing ever of a transport aircraft under engine power only on Aug. 29, 1995, at NASA's Dryden Flight Research Center, Edwards, California. The milestone flight, flown by NASA research pilot and former astronaut Gordon Fullerton, was part of a NASA project to develop a computer-assisted engine control system that enables a pilot to land a plane safely when it normal control surfaces are disabled. The Propulsion-Controlled Aircraft (PCA) system uses standard autopilot controls already present in the cockpit, together with the new programming in the aircraft's flight control computers. The PCA concept is simple--for pitch control, the program increases thrust to climb and reduces thrust to descend. To turn right, the autopilot increases the left engine thrust while decreasing the right engine thrust. The initial Propulsion-Controlled Aircraft studies by NASA were carried out at Dryden with a modified twin-engine F-15 research aircraft.

  7. MD-11 PCA - Research flight team egress

    Science.gov (United States)

    1995-01-01

    This McDonnell Douglas MD-11 has parked on the flightline at NASA's Dryden Flight Research Center, Edwards, California, following its completion of the first and second landings ever performed by a transport aircraft under engine power only (on Aug. 29, 1995). The milestone flight, with NASA research pilot and former astronaut Gordon Fullerton at the controls, was part of a NASA project to develop a computer-assisted engine control system that enables a pilot to land a plane safely when its normal control surfaces are disabled. Coming down the steps from the aircraft are Gordon Fullerton (in front), followed by Bill Burcham, Propulsion Controlled Aircraft (PCA) project engineer at Dryden; NASA Dryden controls engineer John Burken; John Feather of McDonnell Douglas; and Drew Pappas, McDonnell Douglas' project manager for PCA.

  8. Development of techniques for joining fuel rod simulators to test assemblies

    International Nuclear Information System (INIS)

    Moorhead, A.J.; Reed, R.W.

    1980-01-01

    A unique tubular electrode carrier is described for gas tungsten-arc welding small-diameter nuclear fuel rod simulators to the tubesheet of a test assembly. Both the close-packed geometry of the array of simulators and the extension of coaxial electrical conductors from each simulator hindered access to the weld joint. Consequently, a conventional gas tungsten-arc torch could not be used. Two seven-rod assemblies that were mockups of the simulator-to-tubesheet joint area were welded and successfully tested. Modified versions of the electrode carrier for brazing electrical leads to the upper ends of the fuel pin simulators are also described. Satisfactory brazes have been made on both single-rod mockups and an array of 25 simulators by using the modified electrode carrier and a filler metal with a composition of 71.5 Ag-28 Cu-0.5 Ni

  9. Innovations in surgery simulation: a review of past, current and future techniques.

    Science.gov (United States)

    Badash, Ido; Burtt, Karen; Solorzano, Carlos A; Carey, Joseph N

    2016-12-01

    As a result of recent work-hours limitations and concerns for patient safety, innovations in extraclinical surgical simulation have become a desired part of residency education. Current simulation models, including cadaveric, animal, bench-top, virtual reality (VR) and robotic simulators are increasingly used in surgical training programs. Advances in telesurgery, three-dimensional (3D) printing, and the incorporation of patient-specific anatomy are paving the way for simulators to become integral components of medical training in the future. Evidence from the literature highlights the benefits of including simulations in surgical training; skills acquired through simulations translate into improvements in operating room performance. Moreover, simulations are rapidly incorporating new medical technologies and offer increasingly high-fidelity recreations of procedures. As a result, both novice and expert surgeons are able to benefit from their use. As dedicated, structured curricula are developed that incorporate simulations into daily resident training, simulated surgeries will strengthen the surgeon's skill set, decrease hospital costs, and improve patient outcomes.

  10. Pilot study: evaluation of the use of the convergent interview technique in understanding the perception of surgical design and simulation.

    Science.gov (United States)

    Logan, Heather; Wolfaardt, Johan; Boulanger, Pierre; Hodgetts, Bill; Seikaly, Hadi

    2013-06-19

    It is important to understand the perceived value of surgical design and simulation (SDS) amongst surgeons, as this will influence its implementation in clinical settings. The purpose of the present study was to examine the application of the convergent interview technique in the field of surgical design and simulation and evaluate whether the technique would uncover new perceptions of virtual surgical planning (VSP) and medical models not discovered by other qualitative case-based techniques. Five surgeons were asked to participate in the study. Each participant was interviewed following the convergent interview technique. After each interview, the interviewer interpreted the information by seeking agreements and disagreements among the interviewees in order to understand the key concepts in the field of SDS. Fifteen important issues were extracted from the convergent interviews. In general, the convergent interview was an effective technique in collecting information about the perception of clinicians. The study identified three areas where the technique could be improved upon for future studies in the SDS field.

  11. An Efficient Hybrid DSMC/MD Algorithm for Accurate Modeling of Micro Gas Flows

    KAUST Repository

    Liang, Tengfei

    2013-01-01

    Aiming at simulating micro gas flows with accurate boundary conditions, an efficient hybrid algorithmis developed by combining themolecular dynamics (MD) method with the direct simulationMonte Carlo (DSMC)method. The efficiency comes from the fact that theMD method is applied only within the gas-wall interaction layer, characterized by the cut-off distance of the gas-solid interaction potential, to resolve accurately the gas-wall interaction process, while the DSMC method is employed in the remaining portion of the flow field to efficiently simulate rarefied gas transport outside the gas-wall interaction layer. A unique feature about the present scheme is that the coupling between the two methods is realized by matching the molecular velocity distribution function at the DSMC/MD interface, hence there is no need for one-toone mapping between a MD gas molecule and a DSMC simulation particle. Further improvement in efficiency is achieved by taking advantage of gas rarefaction inside the gas-wall interaction layer and by employing the "smart-wall model" proposed by Barisik et al. The developed hybrid algorithm is validated on two classical benchmarks namely 1-D Fourier thermal problem and Couette shear flow problem. Both the accuracy and efficiency of the hybrid algorithm are discussed. As an application, the hybrid algorithm is employed to simulate thermal transpiration coefficient in the free-molecule regime for a system with atomically smooth surface. Result is utilized to validate the coefficients calculated from the pure DSMC simulation with Maxwell and Cercignani-Lampis gas-wall interaction models. ©c 2014 Global-Science Press.

  12. 3D micro-crack propagation simulation at enamel/adhesive interface using FE submodeling and element death techniques.

    Science.gov (United States)

    Liu, Heng-Liang; Lin, Chun-Li; Sun, Ming-Tsung; Chang, Yen-Hsiang

    2010-06-01

    This study investigates micro-crack propagation at the enamel/adhesive interface using finite element (FE) submodeling and element death techniques. A three-dimensional (3D) FE macro-model of the enamel/adhesive/ceramic subjected to shear bond testing was generated and analyzed. A 3D micro-model with interfacial bonding structure was constructed at the upper enamel/adhesive interface where the stress concentration was found from the macro-model results. The morphology of this interfacial bonding structure (i.e., resin tag) was assigned based on resin tag geometry and enamel rod arrangement from a scanning electron microscopy micrograph. The boundary conditions for the micro-model were determined from the macro-model results. A custom iterative code combined with the element death technique was used to calculate the micro-crack propagation. Parallel experiments were performed to validate this FE simulation. The stress concentration within the adhesive occurred mainly at the upper corner near the enamel/adhesive interface and the resin tag base. A simulated fracture path was found at the resin tag base along the enamel/adhesive interface. A morphological observation of the fracture patterns obtained from in vitro testing corresponded with the simulation results. This study shows that the FE submodeling and element death techniques could be used to simulate the 3D micro-stress pattern and the crack propagation noted at the enamel/adhesive interface.

  13. A fast simulation method for the Log-normal sum distribution using a hazard rate twisting technique

    KAUST Repository

    Rached, Nadhir B.

    2015-06-08

    The probability density function of the sum of Log-normally distributed random variables (RVs) is a well-known challenging problem. For instance, an analytical closed-form expression of the Log-normal sum distribution does not exist and is still an open problem. A crude Monte Carlo (MC) simulation is of course an alternative approach. However, this technique is computationally expensive especially when dealing with rare events (i.e. events with very small probabilities). Importance Sampling (IS) is a method that improves the computational efficiency of MC simulations. In this paper, we develop an efficient IS method for the estimation of the Complementary Cumulative Distribution Function (CCDF) of the sum of independent and not identically distributed Log-normal RVs. This technique is based on constructing a sampling distribution via twisting the hazard rate of the original probability measure. Our main result is that the estimation of the CCDF is asymptotically optimal using the proposed IS hazard rate twisting technique. We also offer some selected simulation results illustrating the considerable computational gain of the IS method compared to the naive MC simulation approach.

  14. A fast simulation method for the Log-normal sum distribution using a hazard rate twisting technique

    KAUST Repository

    Rached, Nadhir B.; Benkhelifa, Fatma; Alouini, Mohamed-Slim; Tempone, Raul

    2015-01-01

    The probability density function of the sum of Log-normally distributed random variables (RVs) is a well-known challenging problem. For instance, an analytical closed-form expression of the Log-normal sum distribution does not exist and is still an open problem. A crude Monte Carlo (MC) simulation is of course an alternative approach. However, this technique is computationally expensive especially when dealing with rare events (i.e. events with very small probabilities). Importance Sampling (IS) is a method that improves the computational efficiency of MC simulations. In this paper, we develop an efficient IS method for the estimation of the Complementary Cumulative Distribution Function (CCDF) of the sum of independent and not identically distributed Log-normal RVs. This technique is based on constructing a sampling distribution via twisting the hazard rate of the original probability measure. Our main result is that the estimation of the CCDF is asymptotically optimal using the proposed IS hazard rate twisting technique. We also offer some selected simulation results illustrating the considerable computational gain of the IS method compared to the naive MC simulation approach.

  15. Redirection of Metabolic Hydrogen by Inhibiting Methanogenesis in the Rumen Simulation Technique (RUSITEC)

    Science.gov (United States)

    Guyader, Jessie; Ungerfeld, Emilio M.; Beauchemin, Karen A.

    2017-01-01

    A decrease in methanogenesis is expected to improve ruminant performance by allocating rumen metabolic hydrogen ([2H]) to more energy-rendering fermentation pathways for the animal. However, decreases in methane (CH4) emissions of up to 30% are not always linked with greater performance. Therefore, the aim of this study was to understand the fate of [2H] when CH4 production in the rumen is inhibited by known methanogenesis inhibitors (nitrate, NIT; 3-nitrooxypropanol, NOP; anthraquinone, AQ) in comparison with a control treatment (CON) with the Rumen Simulation Technique (RUSITEC). Measurements started after 1 week adaptation. Substrate disappearance was not modified by methanogenesis inhibitors. Nitrate mostly seemed to decrease [2H] availability by acting as an electron acceptor competing with methanogenesis. As a consequence, NIT decreased CH4 production (−75%), dissolved dihydrogen (H2) concentration (−30%) and the percentages of reduced volatile fatty acids (butyrate, isobutyrate, valerate, isovalerate, caproate and heptanoate) except propionate, but increased acetate molar percentage, ethanol concentration and the efficiency of microbial nitrogen synthesis (+14%) without affecting gaseous H2. Nitrooxypropanol decreased methanogenesis (−75%) while increasing both gaseous and dissolved H2 concentrations (+81% and +24%, respectively). Moreover, NOP decreased acetate and isovalerate molar percentages and increased butyrate, valerate, caproate and heptanoate molar percentages as well as n-propanol and ammonium concentrations. Methanogenesis inhibition with AQ (−26%) was associated with higher gaseous H2 production (+70%) but lower dissolved H2 concentration (−76%), evidencing a lack of relationship between the two H2 forms. Anthraquinone increased ammonium concentration, caproate and heptanoate molar percentages but decreased acetate and isobutyrate molar percentages, total microbial nitrogen production and efficiency of microbial protein synthesis (

  16. Forest Vegetation Simulator translocation techniques with the Bureau of Land Management's Forest Vegetation Information system database

    Science.gov (United States)

    Timothy A. Bottomley

    2008-01-01

    The BLM uses a database, called the Forest Vegetation Information System (FORVIS), to store, retrieve, and analyze forest resource information on a majority of their forested lands. FORVIS also has the capability of easily transferring appropriate data electronically into Forest Vegetation Simulator (FVS) for simulation runs. Only minor additional data inputs or...

  17. Experimental simulation techniques for the evaluation of structural changes in metals and alloys

    International Nuclear Information System (INIS)

    Lucki, Georgi

    1992-01-01

    In this work, high-doses irradiation in nuclear reactor were simulated using a cyclotron in order to study mechanical, electric, magnetic and structural changes in materials. Results of such simulations for portland cement, binary alloys and stainless steels are presented and discussed. 15 refs., 11 figs., 1 tab

  18. Performance of medical residents in sterile techniques during central vein catheterization: randomized trial of efficacy of simulation-based training.

    Science.gov (United States)

    Khouli, Hassan; Jahnes, Katherine; Shapiro, Janet; Rose, Keith; Mathew, Joseph; Gohil, Amit; Han, Qifa; Sotelo, Andre; Jones, James; Aqeel, Adnan; Eden, Edward; Fried, Ethan

    2011-01-01

    Catheter-related bloodstream infection (CRBSI) is a preventable cause of a potentially lethal ICU infection. The optimal method to teach health-care providers correct sterile techniques during central vein catheterization (CVC) remains unclear. We randomly assigned second- and third-year internal medicine residents trained by a traditional apprenticeship model to simulation-based plus video training or video training alone from December 2007 to January 2008, with a follow-up period to examine CRBSI ending in July 2009. During the follow-up period, a simulation-based training program in sterile techniques during CVC was implemented in the medical ICU (MICU). A surgical ICU (SICU) where no residents received study interventions was used for comparison. The primary outcome measures were median residents' scores in sterile techniques and rates of CRBSI per 1,000 catheter-days. Of the 47 enrolled residents, 24 were randomly assigned to the simulation-based plus video training group and 23 to the video training group. Median baseline scores in both groups were equally poor: 12.5 to 13 (52%-54%) out of maximum score of 24 (P = .95; median difference, 0; 95% CI, 0.2-2.0). After training, median score was significantly higher for the simulation-based plus video training group: 22 (92%) vs 18 (75%) for the video training group (P training in sterile techniques during CVC is superior to traditional training or video training alone and is associated with decreased rate of CRBSI. Simulation-based training in CVC should be routinely used to reduce iatrogenic risk. ClinicalTrials.gov; No.: NCT00612131; URL: clinicaltrials.gov.

  19. Nuclear power plant human computer interface design incorporating console simulation, operations personnel, and formal evaluation techniques

    International Nuclear Information System (INIS)

    Chavez, C.; Edwards, R.M.; Goldberg, J.H.

    1993-01-01

    New CRT-based information displays which enhance the human machine interface are playing a very important role and are being increasingly used in control rooms since they present a higher degree of flexibility compared to conventional hardwired instrumentation. To prototype a new console configuration and information display system at the Experimental Breeder Reactor II (EBR-II), an iterative process of console simulation and evaluation involving operations personnel is being pursued. Entire panels including selector switches and information displays are simulated and driven by plant dynamical simulations with realistic responses that reproduce the actual cognitive and physical environment. Careful analysis and formal evaluation of operator interaction while using the simulated console will be conducted to determine underlying principles for effective control console design for this particular group of operation personnel. Additional iterations of design, simulation, and evaluation will then be conducted as necessary

  20. All-atom molecular dynamics simulations of spin labelled double and single-strand DNA for EPR studies.

    Science.gov (United States)

    Prior, C; Danilāne, L; Oganesyan, V S

    2018-05-16

    We report the first application of fully atomistic molecular dynamics (MD) simulations to the prediction of electron paramagnetic resonance (EPR) spectra of spin labelled DNA. Models for two structurally different DNA spin probes with either the rigid or flexible position of the nitroxide group in the base pair, employed in experimental studies previously, have been developed. By the application of the combined MD-EPR simulation methodology we aimed at the following. Firstly, to provide a test bed against a sensitive spectroscopic technique for the recently developed improved version of the parmbsc1 force field for MD modelling of DNA. The predicted EPR spectra show good agreement with the experimental ones available from the literature, thus confirming the accuracy of the currently employed DNA force fields. Secondly, to provide a quantitative interpretation of the motional contributions into the dynamics of spin probes in both duplex and single-strand DNA fragments and to analyse their perturbing effects on the local DNA structure. Finally, a combination of MD and EPR allowed us to test the validity of the application of the Model-Free (M-F) approach coupled with the partial averaging of magnetic tensors to the simulation of EPR spectra of DNA systems by comparing the resultant EPR spectra with those simulated directly from MD trajectories. The advantage of the M-F based EPR simulation approach over the direct propagation techniques is that it requires motional and order parameters that can be calculated from shorter MD trajectories. The reported MD-EPR methodology is transferable to the prediction and interpretation of EPR spectra of higher order DNA structures with novel types of spin labels.

  1. Wind Energy System Time-domain (WEST) analyzers using hybrid simulation techniques

    Science.gov (United States)

    Hoffman, J. A.

    1979-01-01

    Two stand-alone analyzers constructed for real time simulation of the complex dynamic characteristics of horizontal-axis wind energy systems are described. Mathematical models for an aeroelastic rotor, including nonlinear aerodynamic and elastic loads, are implemented with high speed digital and analog circuitry. Models for elastic supports, a power train, a control system, and a rotor gimbal system are also included. Limited correlation efforts show good comparisons between results produced by the analyzers and results produced by a large digital simulation. The digital simulation results correlate well with test data.

  2. Wettability of graphitic-carbon and silicon surfaces: MD modeling and theoretical analysis

    International Nuclear Information System (INIS)

    Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.

    2015-01-01

    The wettability of graphitic carbon and silicon surfaces was numerically and theoretically investigated. A multi-response method has been developed for the analysis of conventional molecular dynamics (MD) simulations of droplets wettability. The contact angle and indicators of the quality of the computations are tracked as a function of the data sets analyzed over time. This method of analysis allows accurate calculations of the contact angle obtained from the MD simulations. Analytical models were also developed for the calculation of the work of adhesion using the mean-field theory, accounting for the interfacial entropy changes. A calibration method is proposed to provide better predictions of the respective contact angles under different solid-liquid interaction potentials. Estimations of the binding energy between a water monomer and graphite match those previously reported. In addition, a breakdown in the relationship between the binding energy and the contact angle was observed. The macroscopic contact angles obtained from the MD simulations were found to match those predicted by the mean-field model for graphite under different wettability conditions, as well as the contact angles of Si(100) and Si(111) surfaces. Finally, an assessment of the effect of the Lennard-Jones cutoff radius was conducted to provide guidelines for future comparisons between numerical simulations and analytical models of wettability

  3. Parameter identification using optimization techniques in the continuous simulation programs FORSIM and MACKSIM

    International Nuclear Information System (INIS)

    Carver, M.B.; Austin, C.F.; Ross, N.E.

    1980-02-01

    This report discusses the mechanics of automated parameter identification in simulation packages, and reviews available integration and optimization algorithms and their interaction within the recently developed optimization options in the FORSIM and MACKSIM simulation packages. In the MACKSIM mass-action chemical kinetics simulation package, the form and structure of the ordinary differential equations involved is known, so the implementation of an optimizing option is relatively straightforward. FORSIM, however, is designed to integrate ordinary and partial differential equations of abritrary definition. As the form of the equations is not known in advance, the design of the optimizing option is more intricate, but the philosophy could be applied to most simulation packages. In either case, however, the invocation of the optimizing interface is simple and user-oriented. Full details for the use of the optimizing mode for each program are given; specific applications are used as examples. (O.T.)

  4. A Novel Technique for Running the NASA Legacy Code LAPIN Synchronously With Simulations Developed Using Simulink

    Science.gov (United States)

    Vrnak, Daniel R.; Stueber, Thomas J.; Le, Dzu K.

    2012-01-01

    This report presents a method for running a dynamic legacy inlet simulation in concert with another dynamic simulation that uses a graphical interface. The legacy code, NASA's LArge Perturbation INlet (LAPIN) model, was coded using the FORTRAN 77 (The Portland Group, Lake Oswego, OR) programming language to run in a command shell similar to other applications that used the Microsoft Disk Operating System (MS-DOS) (Microsoft Corporation, Redmond, WA). Simulink (MathWorks, Natick, MA) is a dynamic simulation that runs on a modern graphical operating system. The product of this work has both simulations, LAPIN and Simulink, running synchronously on the same computer with periodic data exchanges. Implementing the method described in this paper avoided extensive changes to the legacy code and preserved its basic operating procedure. This paper presents a novel method that promotes inter-task data communication between the synchronously running processes.

  5. Metamodeling Techniques to Aid in the Aggregation Process of Large Hierarchical Simulation Models

    National Research Council Canada - National Science Library

    Rodriguez, June F

    2008-01-01

    .... More specifically, investigating how to accurately aggregate hierarchical lower-level (higher resolution) models into the next higher-level in order to reduce the complexity of the overall simulation model...

  6. Site characterization and validation - equipment design and techniques used in single borehole hydraulic testing, simulated drift experiment and crosshole testing

    International Nuclear Information System (INIS)

    Holmes, D.C.; Sehlstedt, M.

    1991-10-01

    This report describes the equipment and techniques used to investigate the variation of hydrogeological parameters within a fractured crystalline rock mass. The testing program was performed during stage 3 of the site characterization and validation programme at the Stripa mine in Sweden. This programme used a multidisciplinary approach, combining geophysical, geological and hydrogeological methods, to determine how groundwater moved through the rock mass. The hydrogeological work package involved three components. Firstly, novel single borehole techniques (focused packer testing) were used to determine the distribution of hydraulic conductivity and head along individual boreholes. Secondly, water was abstracted from boreholes which were drilled to simulate a tunnel (simulated drift experiment). Locations and magnitudes of flows were measured together with pressure responses at various points in the SCV rock mass. Thirdly, small scale crosshole tests, involving detailed interference testing, were used to determine the variability of hydrogeological parameters within previously identified, significant flow zones. (au)

  7. New technique for global solar radiation forecasting by simulated annealing and genetic algorithms using

    International Nuclear Information System (INIS)

    Tolabi, H.B.; Ayob, S.M.

    2014-01-01

    In this paper, a novel approach based on simulated annealing algorithm as a meta-heuristic method is implemented in MATLAB software to estimate the monthly average daily global solar radiation on a horizontal surface for six different climate cities of Iran. A search method based on genetic algorithm is applied to accelerate problem solving. Results show that simulated annealing based on genetic algorithm search is a suitable method to find the global solar radiation. (author)

  8. Computer simulation of stochastic processes through model-sampling (Monte Carlo) techniques.

    Science.gov (United States)

    Sheppard, C W.

    1969-03-01

    A simple Monte Carlo simulation program is outlined which can be used for the investigation of random-walk problems, for example in diffusion, or the movement of tracers in the blood circulation. The results given by the simulation are compared with those predicted by well-established theory, and it is shown how the model can be expanded to deal with drift, and with reflexion from or adsorption at a boundary.

  9. Simulation Techniques and Prosthetic Approach Towards Biologically Efficient Artificial Sense Organs- An Overview

    OpenAIRE

    Neogi, Biswarup; Ghosal, Soumya; Mukherjee, Soumyajit; Das, Achintya; Tibarewala, D. N.

    2011-01-01

    An overview of the applications of control theory to prosthetic sense organs including the senses of vision, taste and odor is being presented in this paper. Simulation aspect nowadays has been the centre of research in the field of prosthesis. There have been various successful applications of prosthetic organs, in case of natural biological organs dis-functioning patients. Simulation aspects and control modeling are indispensible for knowing system performance, and to generate an original a...

  10. Improvement in visibility of simulated lung nodules on computed radiography (CR) chest images by use of temporal subtraction technique

    International Nuclear Information System (INIS)

    Oda, Nobuhiro; Fujimoto, Keiji; Murakami, Seiichi; Katsuragawa, Shigehiko; Doi, Kunio; Nakata, Hajime

    1999-01-01

    A temporal subtraction image obtained by subtraction of a previous image from a current one can enhance interval change on chest images. In this study, we compared the visibility of simulated lung nodules on CR images with and without temporal subtraction. Chest phantom images without and with simulated nodules were obtained as previous and current images, respectively, by a CR system. Then, subtraction images were produced with an iterative image warping technique. Twelve simulated nodules were attached on various locations of the chest phantom. The diameter of nodules having a CT number of 47 ranged from 3 mm to 10 mm. Seven radiologists subjectively evaluated the visibility of simulated nodules on CR images with and without temporal subtraction using a three-point rating scale (0: invisible, +1: questionable, +2:visible). The minimum diameter of simulated nodules visible at a frequency greater than 50% was 4 mm on the CR images with temporal subtraction and 6 mm on those without. Our results indicated that the subtraction images clearly improved the visibility of simulated nodules. (author)

  11. Ant colony method to control variance reduction techniques in the Monte Carlo simulation of clinical electron linear accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Pareja, S. [Servicio de Radiofisica Hospitalaria, Hospital Regional Universitario ' Carlos Haya' , Avda. Carlos Haya, s/n, E-29010 Malaga (Spain)], E-mail: garciapareja@gmail.com; Vilches, M. [Servicio de Fisica y Proteccion Radiologica, Hospital Regional Universitario ' Virgen de las Nieves' , Avda. de las Fuerzas Armadas, 2, E-18014 Granada (Spain); Lallena, A.M. [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada (Spain)

    2007-09-21

    The ant colony method is used to control the application of variance reduction techniques to the simulation of clinical electron linear accelerators of use in cancer therapy. In particular, splitting and Russian roulette, two standard variance reduction methods, are considered. The approach can be applied to any accelerator in a straightforward way and permits, in addition, to investigate the 'hot' regions of the accelerator, an information which is basic to develop a source model for this therapy tool.

  12. Ant colony method to control variance reduction techniques in the Monte Carlo simulation of clinical electron linear accelerators

    International Nuclear Information System (INIS)

    Garcia-Pareja, S.; Vilches, M.; Lallena, A.M.

    2007-01-01

    The ant colony method is used to control the application of variance reduction techniques to the simulation of clinical electron linear accelerators of use in cancer therapy. In particular, splitting and Russian roulette, two standard variance reduction methods, are considered. The approach can be applied to any accelerator in a straightforward way and permits, in addition, to investigate the 'hot' regions of the accelerator, an information which is basic to develop a source model for this therapy tool

  13. Orbit Feedback Operation with RCBX (MD 1209)

    CERN Document Server

    Wenninger, Jorg; Nisbet, David; Ponce, Laurette; Louro Alves, Diogo Miguel; CERN. Geneva. ATS Department

    2017-01-01

    The LHC Orbit Feedback (OFB) is able to drive any orbit corrector circuit (COD) to steer the LHC orbit. But during the first feedback tests in 2010, all attempts to use the common triplet orbit correctors (MCBX) failed because the QPS system installed to protect those magnets triggered power aborts as soon as the OFB steered the beam with those CODs. The reason was most likely the violation of the RCBX circuit acceleration limits. For this reason the MCBX orbit correctors were never driven by the OFB in regular operation. Although the performance of the OFB is generally excellent, the quality of the beam steering around IRs could be improved if the OFB could correct the orbit with the MCBX to counteract locally triplet quadrupole movements. The aim of this MD was to make a new attempt to use the MCBX in the OFB. The test was successful at injection (no circuit trip) and failed during the ramp (QPS power abort). The PC voltages and QPS Ures signals revealed the presence of voltage spikes with a period of 10~s...

  14. Modeling ramp compression experiments using large-scale molecular dynamics simulation.

    Energy Technology Data Exchange (ETDEWEB)

    Mattsson, Thomas Kjell Rene; Desjarlais, Michael Paul; Grest, Gary Stephen; Templeton, Jeremy Alan; Thompson, Aidan Patrick; Jones, Reese E.; Zimmerman, Jonathan A.; Baskes, Michael I. (University of California, San Diego); Winey, J. Michael (Washington State University); Gupta, Yogendra Mohan (Washington State University); Lane, J. Matthew D.; Ditmire, Todd (University of Texas at Austin); Quevedo, Hernan J. (University of Texas at Austin)

    2011-10-01

    Molecular dynamics simulation (MD) is an invaluable tool for studying problems sensitive to atomscale physics such as structural transitions, discontinuous interfaces, non-equilibrium dynamics, and elastic-plastic deformation. In order to apply this method to modeling of ramp-compression experiments, several challenges must be overcome: accuracy of interatomic potentials, length- and time-scales, and extraction of continuum quantities. We have completed a 3 year LDRD project with the goal of developing molecular dynamics simulation capabilities for modeling the response of materials to ramp compression. The techniques we have developed fall in to three categories (i) molecular dynamics methods (ii) interatomic potentials (iii) calculation of continuum variables. Highlights include the development of an accurate interatomic potential describing shock-melting of Beryllium, a scaling technique for modeling slow ramp compression experiments using fast ramp MD simulations, and a technique for extracting plastic strain from MD simulations. All of these methods have been implemented in Sandia's LAMMPS MD code, ensuring their widespread availability to dynamic materials research at Sandia and elsewhere.

  15. Technique for Simulation of Black Sea Circulation with Increased Resolution in the Area of the IO RAS Polygon

    Science.gov (United States)

    Gusev, A. V.; Zalesny, V. B.; Fomin, V. V.

    2017-11-01

    A numerical technique is presented for simulating the hydrophysical fields of the Black Sea on a variable-step grid with refinement in the area of IO RAS polygon. Model primitive equations are written in spherical coordinates with an arbitrary arrangement of poles. In order to increase the horizontal resolution of the coastal zone in the area of the IO RAS polygon in the northeastern part of the sea near Gelendzhik, one of the poles is placed at a land point (38.35° E, 44.75° N). The model horizontal resolution varies from 150 m in the area of the IO RAS polygon to 4.6 km in the southwestern part of the Black Sea. The numerical technique makes it possible to simulate a large-scale structure of Black Sea circulation as well as the meso- and submesoscale dynamics of the coastal zone. In order to compute the atmospheric forcing, the results of the regional climate model WRF with a resolution of about 10 km in space and 1 h in time are used. In order to demonstrate the technique, Black Sea hydrophysical fields for 2011-2012 and a passive tracer transport representing self-cleaning of Gelendzhik Bay in July 2012 are simulated.

  16. NBodyLab: A Testbed for Undergraduates Utilizing a Web Interface to NEMO and MD-GRAPE2 Hardware

    Science.gov (United States)

    Johnson, V. L.; Teuben, P. J.; Penprase, B. E.

    An N-body simulation testbed called NBodyLab was developed at Pomona College as a teaching tool for undergraduates. The testbed runs under Linux and provides a web interface to selected back-end NEMO modeling and analysis tools, and several integration methods which can optionally use an MD-GRAPE2 supercomputer card in the server to accelerate calculation of particle-particle forces. The testbed provides a framework for using and experimenting with the main components of N-body simulations: data models and transformations, numerical integration of the equations of motion, analysis and visualization products, and acceleration techniques (in this case, special purpose hardware). The testbed can be used by students with no knowledge of programming or Unix, freeing such students and their instructor to spend more time on scientific experimentation. The advanced student can extend the testbed software and/or more quickly transition to the use of more advanced Unix-based toolsets such as NEMO, Starlab and model builders such as GalactICS. Cosmology students at Pomona College used the testbed to study collisions of galaxies with different speeds, masses, densities, collision angles, angular momentum, etc., attempting to simulate, for example, the Tadpole Galaxy and the Antenna Galaxies. The testbed framework is available as open-source to assist other researchers and educators. Recommendations are made for testbed enhancements.

  17. High-precision numerical simulation with autoadaptative grid technique in nonlinear thermal diffusion

    International Nuclear Information System (INIS)

    Chambarel, A.; Pumborios, M.

    1992-01-01

    This paper reports that many engineering problems concern the determination of a steady state solution in the case with strong thermal gradients, and results obtained using the finite-element technique are sometimes inaccurate, particularly for nonlinear problems with unadapted meshes. Building on previous results in linear problems, we propose an autoadaptive technique for nonlinear cases that uses quasi-Newtonian iterations to reevaluate an interpolation error estimation. The authors perfected an automatic refinement technique to solve the nonlinear thermal problem of temperature calculus in a cast-iron cylinder head of a diesel engine

  18. Dose point kernel simulation for monoenergetic electrons and radionuclides using Monte Carlo techniques.

    Science.gov (United States)

    Wu, J; Liu, Y L; Chang, S J; Chao, M M; Tsai, S Y; Huang, D E

    2012-11-01

    Monte Carlo (MC) simulation has been commonly used in the dose evaluation of radiation accidents and for medical purposes. The accuracy of simulated results is affected by the particle-tracking algorithm, cross-sectional database, random number generator and statistical error. The differences among MC simulation software packages must be validated. This study simulated the dose point kernel (DPK) and the cellular S-values of monoenergetic electrons ranging from 0.01 to 2 MeV and the radionuclides of (90)Y, (177)Lu and (103 m)Rh, using Fluktuierende Kaskade (FLUKA) and MC N-Particle Transport Code Version 5 (MCNP5). A 6-μm-radius cell model consisting of the cell surface, cytoplasm and cell nucleus was constructed for cellular S-value calculation. The mean absolute percentage errors (MAPEs) of the scaled DPKs, simulated using FLUKA and MCNP5, were 7.92, 9.64, 4.62, 3.71 and 3.84 % for 0.01, 0.1, 0.5, 1 and 2 MeV, respectively. For the three radionuclides, the MAPEs of the scaled DPKs were within 5 %. The maximum deviations of S(N←N), S(N←Cy) and S(N←CS) for the electron energy larger than 10 keV were 6.63, 6.77 and 5.24 %, respectively. The deviations for the self-absorbed S-values and cross-dose S-values of the three radionuclides were within 4 %. On the basis of the results of this study, it was concluded that the simulation results are consistent between FLUKA and MCNP5. However, there is a minor inconsistency for low energy range. The DPK and the cellular S-value should be used as the quality assurance tools before the MC simulation results are adopted as the gold standard.

  19. A Novel Temporal Bone Simulation Model Using 3D Printing Techniques.

    Science.gov (United States)

    Mowry, Sarah E; Jammal, Hachem; Myer, Charles; Solares, Clementino Arturo; Weinberger, Paul

    2015-09-01

    An inexpensive temporal bone model for use in a temporal bone dissection laboratory setting can be made using a commercially available, consumer-grade 3D printer. Several models for a simulated temporal bone have been described but use commercial-grade printers and materials to produce these models. The goal of this project was to produce a plastic simulated temporal bone on an inexpensive 3D printer that recreates the visual and haptic experience associated with drilling a human temporal bone. Images from a high-resolution CT of a normal temporal bone were converted into stereolithography files via commercially available software, with image conversion and print settings adjusted to achieve optimal print quality. The temporal bone model was printed using acrylonitrile butadiene styrene (ABS) plastic filament on a MakerBot 2x 3D printer. Simulated temporal bones were drilled by seven expert temporal bone surgeons, assessing the fidelity of the model as compared with a human cadaveric temporal bone. Using a four-point scale, the simulated bones were assessed for haptic experience and recreation of the temporal bone anatomy. The created model was felt to be an accurate representation of a human temporal bone. All raters felt strongly this would be a good training model for junior residents or to simulate difficult surgical anatomy. Material cost for each model was $1.92. A realistic, inexpensive, and easily reproducible temporal bone model can be created on a consumer-grade desktop 3D printer.

  20. A hybrid method for flood simulation in small catchments combining hydrodynamic and hydrological techniques

    Science.gov (United States)

    Bellos, Vasilis; Tsakiris, George

    2016-09-01

    The study presents a new hybrid method for the simulation of flood events in small catchments. It combines a physically-based two-dimensional hydrodynamic model and the hydrological unit hydrograph theory. Unit hydrographs are derived using the FLOW-R2D model which is based on the full form of two-dimensional Shallow Water Equations, solved by a modified McCormack numerical scheme. The method is tested at a small catchment in a suburb of Athens-Greece for a storm event which occurred in February 2013. The catchment is divided into three friction zones and unit hydrographs of 15 and 30 min are produced. The infiltration process is simulated by the empirical Kostiakov equation and the Green-Ampt model. The results from the implementation of the proposed hybrid method are compared with recorded data at the hydrometric station at the outlet of the catchment and the results derived from the fully hydrodynamic model FLOW-R2D. It is concluded that for the case studied, the proposed hybrid method produces results close to those of the fully hydrodynamic simulation at substantially shorter computational time. This finding, if further verified in a variety of case studies, can be useful in devising effective hybrid tools for the two-dimensional flood simulations, which are lead to accurate and considerably faster results than those achieved by the fully hydrodynamic simulations.

  1. 77 FR 5201 - Drawbridge Operation Regulation; Bear Creek, Dundalk, MD

    Science.gov (United States)

    2012-02-02

    ...-AA09 Drawbridge Operation Regulation; Bear Creek, Dundalk, MD AGENCY: Coast Guard, DHS. ACTION: Notice... operation of the Baltimore County highway bridge at Wise Avenue across Bear Creek, mile 3.4, between Dundalk... Avenue across Bear Creek, mile 3.4 between Dundalk and Sparrows Point, MD. This change would require the...

  2. MD290: Q4 IP6 Quench Level

    CERN Document Server

    Bednarek, Mateusz Jakub; Lechner, Anton; CERN. Geneva. ATS Department

    2016-01-01

    The detailed program proposed for the LHC Machine Development concerning a quench induced by fast losses on the MQY.4L6 quadrupole is presented. The merit of the MD, the necessary modifications of the machine protection systems are presented together with a preliminary analysis of the MD results.

  3. Chosen-Prefix Collisions for MD5 and Applications

    NARCIS (Netherlands)

    M.M.J. Stevens (Marc); A.K. Lenstra (Arjen); B. de Weger (Benne)

    2012-01-01

    textabstractWe present a novel, automated way to find differential paths for MD5. Its main application is in the construction of \\emph{chosen-prefix collisions}. We have shown how, at an approximate expected cost of $2^{39}$ calls to the MD5 compression function, for any two chosen

  4. Waiting time distribution in M/D/1 queueing systems

    DEFF Research Database (Denmark)

    Iversen, Villy Bæk; Staalhagen, Lars

    1999-01-01

    The well-known formula for the waiting time distribution of M/D/1 queueing systems is numerically unsuitable when the load is close to 1.0 and/or the results for a large waiting time are required. An algorithm for any load and waiting time is presented, based on the state probabilities of M/D/1...

  5. Simulation and experimental tests of a real-time DPWM technique ...

    African Journals Online (AJOL)

    This control strategy is a simple and an easy technique generating the same switching ..... Inverter”, Energy Conversion Congress and Exposition (ECCE ), IEEE, ... Minimize the Switching Loss”, Innovative Smart Grid Technologies (ISGT Asia), ...

  6. Advanced Numerical Integration Techniques for HighFidelity SDE Spacecraft Simulation

    Data.gov (United States)

    National Aeronautics and Space Administration — Classic numerical integration techniques, such as the ones at the heart of several NASA GSFC analysis tools, are known to work well for deterministic differential...

  7. An alternative technique for simulating volumetric cylindrical sources in the Morse code utilization

    International Nuclear Information System (INIS)

    Vieira, W.J.; Mendonca, A.G.

    1985-01-01

    In the solution of deep-penetration problems using the Monte Carlo method, calculation techniques and strategies are used in order to increase the particle population in the regions of interest. A common procedure is the coupling of bidimensional calculations, with (r,z) discrete ordinates transformed into source data, and tridimensional Monte Carlo calculations. An alternative technique for this procedure is presented. This alternative proved effective when applied to a sample problem. (F.E.) [pt

  8. 3D DIGITAL SIMULATION OF MINNAN TEMPLE ARCHITECTURE CAISSON'S CRAFT TECHNIQUES

    OpenAIRE

    Y. C. Lin; T. C. Wu; M. F. Hsu

    2013-01-01

    Caisson is one of the important representations of the Minnan (southern Fujian) temple architecture craft techniques and decorative aesthetics. The special component design and group building method present the architectural thinking and personal characteristics of great carpenters of Minnan temple architecture. In late Qing Dynasty, the appearance and style of caissons of famous temples in Taiwan apparently presented the building techniques of the great carpenters. However, as the y...

  9. A graphical simulator for teaching basic and advanced MR imaging techniques

    DEFF Research Database (Denmark)

    Hanson, Lars G

    2007-01-01

    Teaching of magnetic resonance (MR) imaging techniques typically involves considerable handwaving, literally, to explain concepts such as resonance, rotating frames, dephasing, refocusing, sequences, and imaging. A proper understanding of MR contrast and imaging techniques is crucial for radiolog...... be visualized in an intuitive way. The cross-platform software is primarily designed for use in lectures, but is also useful for self studies and student assignments. Movies available at http://radiographics.rsnajnls.org/cgi/content/full/e27/DC1 ....

  10. A Survey on Modeling and Simulation of MEMS Switches and Its Application in Power Gating Techniques

    OpenAIRE

    Pramod Kumar M.P; A.S. Augustine Fletcher

    2014-01-01

    Large numbers of techniques have been developed to reduce the leakage power, including supply voltage scaling, varying threshold voltages, smaller logic banks, etc. Power gating is a technique which is used to reduce the static power when the sleep transistor is in off condition. Micro Electro mechanical System (MEMS) switches have properties that are very close to an ideal switch, with infinite off-resistance due to an air gap and low on-resistance due to the ohmic metal to m...

  11. Computed simulation of radiographies of pipes - validation of techniques for wall thickness measurements

    International Nuclear Information System (INIS)

    Bellon, C.; Tillack, G.R.; Nockemann, C.; Wenzel, L.

    1995-01-01

    A macroscopic model of radiographic NDE methods and applications is given. A computer-aided approach for determination of wall thickness from radiographs is presented, guaranteeing high accuracy and reproducibility of wall thickness determination by means of projection radiography. The algorithm was applied to computed simulations of radiographies. The simulation thus offers an effective means for testing such automated wall thickness determination as a function of imaging conditions, pipe geometries, coatings, and media tracking, and likewise is a tool for validation and optimization of the method. (orig.) [de

  12. Flight test techniques for validating simulated nuclear electromagnetic pulse aircraft responses

    Science.gov (United States)

    Winebarger, R. M.; Neely, W. R., Jr.

    1984-01-01

    An attempt has been made to determine the effects of nuclear EM pulses (NEMPs) on aircraft systems, using a highly instrumented NASA F-106B to document the simulated NEMP environment at the Kirtland Air Force Base's Vertically Polarized Dipole test facility. Several test positions were selected so that aircraft orientation relative to the test facility would be the same in flight as when on the stationary dielectric stand, in order to validate the dielectric stand's use in flight configuration simulations. Attention is given to the flight test portions of the documentation program.

  13. Intermolecular Interactions and Cooperative Effects from Electronic Structure Calculations: An Effective Means for Developing Interaction Potentials for Condensed Phase Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Xantheas, Sotiris S.

    2004-05-01

    The modeling of the macroscopic properties of homogeneous and inhomogeneous systems via atomistic simulations such as molecular dynamics (MD) or Monte Carlo (MC) techniques is based on the accurate description of the relevant solvent-solute and solvent-solvent intermolecular interactions. The total energy (U) of an n-body molecular system can be formally written as [1,2,3

  14. Quasi-monte carlo simulation and variance reduction techniques substantially reduce computational requirements of patient-level simulation models: An application to a discrete event simulation model

    NARCIS (Netherlands)

    Treur, M.; Postma, M.

    2014-01-01

    Objectives: Patient-level simulation models provide increased flexibility to overcome the limitations of cohort-based approaches in health-economic analysis. However, computational requirements of reaching convergence is a notorious barrier. The objective was to assess the impact of using

  15. Quasielastic neutron scattering and molecular dynamics simulation studies of the melting transition in butane and hexane monolayers adsorbed on graphite

    DEFF Research Database (Denmark)

    Hervig, K.W.; Wu, Z.; Dai, P.

    1997-01-01

    Quasielastic neutron scattering experiments and molecular dynamics (MD) simulations have been used to investigate molecular diffusive motion near the melting transition of monolayers of flexible rod-shaped molecules. The experiments were conducted on butane and hexane monolayers adsorbed...... comparison with experiment, quasielastic spectra calculated from the MD simulations were analyzed using the same models and fitting algorithms as for the neutron spectra. This combination of techniques gives a microscopic picture of the melting process in these two monolayers which is consistent with earlier...... neutron diffraction experiments. Butane melts abruptly to a liquid phase where the molecules in the trans conformation translationally diffuse while rotating about their center of mass. In the case of the hexane monolayer, the MD simulations show that the appearance of quasielastic scattering below T...

  16. Temperature dependence of gafchromic MD-55 dosimeter

    International Nuclear Information System (INIS)

    Klassen, Norman V.; Zwan, Len van der; Cygler, Joanna

    1997-01-01

    Objective: Gafchromic MD-55 is a fairly new, thin film dosimeter that develops a blue color (λ max = 676 nm) when irradiated with ionizing radiation. The increase in absorbance is nearly proportional to the absorbed dose. MD-55 can be used for high precision dosimetry if care is taken to assure reproducible film orientation in the spectrophotometer as well as temperature control during both irradiation and reading. In order to achieve the maximum sensitivity of this dosimeter the readings of the optical density should be taken at λ max . It was reported for another type of Gafchromic film (DM-1260), that both λ max and ε max decrease with an increase in the temperature of the spectrophotometer. The purpose of this study was to characterize the reading temperature dependence of the new type of Gafchromic film available on the market and to find optimal conditions for using it for high precision dosimetry. Materials and Methods: Irradiations were carried out using 60 Co gamma rays from an Eldorado irradiator. The dosimeters were sandwiched in a lucite phantom with 4.4 mm build-up and irradiated in the center of a 10 cm x 10 cm field at 1 meter from the source. The temperature during irradiations was 22 deg. C. The dose rate was about 0.68 Gy/min. Measurements of optical density were made using a Cary 210 spectrophotometer. A bandpass of 3.5 nm was used. The temperature of the baseplate of the sample holder was regulated to +/-0.05 deg. C and measured by a probe lying on the baseplate. In all cases, values of OD were only recorded after they had come to a constant value, which was reached within 5 minutes of inserting the dosimeter into the sample chamber of the spectrophotometer. Results: The temperature dependence of the OD at 676 nm was measured in 2 studies using 6 dosimeters that had received 0, 1.0, 3.5, 6.2, 14.5 Gy. Readings were taken at 7 temperatures between 18.8 and 28.1 deg. C. By returning to the initial temperature several hours later, it was found

  17. Monte Carlo particle simulation and finite-element techniques for tandem mirror transport

    International Nuclear Information System (INIS)

    Rognlien, T.D.; Cohen, B.I.; Matsuda, Y.; Stewart, J.J. Jr.

    1987-01-01

    A description is given of numerical methods used in the study of axial transport in tandem mirrors owing to Coulomb collisions and rf diffusion. The methods are Monte Carlo particle simulations and direct solution to the Fokker-Planck equations by finite-element expansion. (author)

  18. 360-degree videos: a new visualization technique for astrophysical simulations, applied to the Galactic Center

    Science.gov (United States)

    Russell, Christopher

    2018-01-01

    360-degree videos are a new type of movie that renders over all 4π steradian. Video sharing sites such as YouTube now allow this unique content to be shared via virtual reality (VR) goggles, hand-held smartphones/tablets, and computers. Creating 360-degree videos from astrophysical simulations not only provide a new way to view these simulations due to their immersive nature, but also yield engaging content for outreach to the public. We present our 360-degree video of an astrophysical simulation of the Galactic center: a hydrodynamics calculation of the colliding and accreting winds of the 30 Wolf-Rayet stars orbiting within the central parsec. Viewing the movie, which renders column density, from the location of the supermassive black hole gives a unique and immersive perspective of the shocked wind material inspiraling and tidally stretching as it plummets toward the black hole. We also describe how to create such movies, discuss what type of content does and does not look appealing in 360-degree format, and briefly comment on what new science can be extracted from astrophysical simulations using 360-degree videos.

  19. Multispectral Terrain Background Simulation Techniques For Use In Airborne Sensor Evaluation

    Science.gov (United States)

    Weinberg, Michael; Wohlers, Ronald; Conant, John; Powers, Edward

    1988-08-01

    A background simulation code developed at Aerodyne Research, Inc., called AERIE is designed to reflect the major sources of clutter that are of concern to staring and scanning sensors of the type being considered for various airborne threat warning (both aircraft and missiles) sensors. The code is a first principles model that could be used to produce a consistent image of the terrain for various spectral bands, i.e., provide the proper scene correlation both spectrally and spatially. The code utilizes both topographic and cultural features to model terrain, typically from DMA data, with a statistical overlay of the critical underlying surface properties (reflectance, emittance, and thermal factors) to simulate the resulting texture in the scene. Strong solar scattering from water surfaces is included with allowance for wind driven surface roughness. Clouds can be superimposed on the scene using physical cloud models and an analytical representation of the reflectivity obtained from scattering off spherical particles. The scene generator is augmented by collateral codes that allow for the generation of images at finer resolution. These codes provide interpolation of the basic DMA databases using fractal procedures that preserve the high frequency power spectral density behavior of the original scene. Scenes are presented illustrating variations in altitude, radiance, resolution, material, thermal factors, and emissivities. The basic models utilized for simulation of the various scene components and various "engineering level" approximations are incorporated to reduce the computational complexity of the simulation.

  20. Refinement of homology-based protein structures by molecular dynamics simulation techniques

    NARCIS (Netherlands)

    Fan, H; Mark, AE

    The use of classical molecular dynamics simulations, performed in explicit water, for the refinement of structural models of proteins generated ab initio or based on homology has been investigated. The study involved a test set of 15 proteins that were previously used by Baker and coworkers to

  1. Monte Carlo particle simulation and finite-element techniques for tandem mirror transport

    International Nuclear Information System (INIS)

    Rognlien, T.D.; Cohen, B.I.; Matsuda, Y.; Stewart, J.J. Jr.

    1985-12-01

    A description is given of numerical methods used in the study of axial transport in tandem mirrors owing to Coulomb collisions and rf diffusion. The methods are Monte Carlo particle simulations and direct solution to the Fokker-Planck equations by finite-element expansion. 11 refs

  2. Synchrotron and Simulations Techniques Applied to Problems in Materials Science: Catalysts and Azul Maya Pigments

    International Nuclear Information System (INIS)

    Chianelli, R.

    2005-01-01

    Development of synchrotron techniques for the determination of the structure of disordered, amorphous and surface materials has exploded over the past twenty years due to the increasing availability of high flux synchrotron radiation and the continuing development of increasingly powerful synchrotron techniques. These techniques are available to materials scientists who are not necessarily synchrotron scientists through interaction with effective user communities that exist at synchrotrons such as the Stanford Synchrotron Radiation Laboratory (SSRL). In this article we review the application of multiple synchrotron characterization techniques to two classes of materials defined as ''surface compounds.'' One class of surface compounds are materials like MoS 2-x C x that are widely used petroleum catalysts used to improve the environmental properties of transportation fuels. These compounds may be viewed as ''sulfide supported carbides'' in their catalytically active states. The second class of ''surface compounds'' is the ''Maya Blue'' pigments that are based on technology created by the ancient Maya. These compounds are organic/inorganic ''surface complexes'' consisting of the dye indigo and palygorskite, a common clay. The identification of both surface compounds relies on the application of synchrotron techniques as described in this report

  3. Integrated Stamping Simulation Using State Of The Art Techniques To Fulfill Quality Assessment Requirements

    International Nuclear Information System (INIS)

    Ling, David; Lambriks, Marc; El Khaldi, Fouad

    2005-01-01

    The last few years have seen the use of stamping simulation evolve to the extent that it is now a mainstream activity; a core part of the press tool engineering process. Now, new requirements for the use of challenging materials like Dual phase / Complex phase steel, VHSS, and aluminum, together with more stringent quality expectations, and shorter development cycles, there is a need to assess the panel quality in a wider context, before committing to tool manufacture.The integrated approach from ESI Group allows early up-front feasibility assessment, geometry and process optimization, and detailed process validation all within one system. Rapid die design and quick forming simulation modules play an essential role in the early stages of the process. A seamless connection between simulation and geometry is a vital characteristic, with the accurate simulation being used to validate and fine tune the process in order to assess final component quality in unprecedented detail, utilizing some of the most accurate material models available today. The combination of the distributed memory processing (DMP) solver together with new cost effective cluster based compute servers provide a practical solution to the problems of 'one million element' model sizes, and more sophisticated modeling methodologies become realistic for the first time.It is no longer sufficient to merely focus on the draw die, forming simulation must now consider the entire die line up. Typically, around half of forming issues arise from the draw die, so the time has now come to address the other half as well! This paper will discuss how the PAM-STAMP 2G TM integrated solution is successfully used to deliver a positive business impact, by providing virtual panel quality assessment, tolerance control, and springback compensation. The paper will also discuss how other forming processes can be accurately modeled using the new modules

  4. MCNP simulations of a new time-resolved Compton scattering imaging technique

    International Nuclear Information System (INIS)

    Ilan, Y.

    2004-01-01

    Medical images of human tissue can be produced using Computed Tomography (CT), Positron Emission Tomography (PET), Ultrasound or Magnetic Resonance Imaging (MRI). In all of the above techniques, in order to get a three-dimensional (3D) image, one has to rotate or move the source, the detectors or the scanned target. This procedure is complicated, time consuming and increases the cost and weight of the scanning equipment. Time resolved optical tomography has been suggested as an alternative to the above conventional methods. This technique implies near infrared light (NIR) and fast time-resolved detectors to obtain a 3D image of the scanned target. However, due to the limited penetration of the NIR light in the tissue, the application of this technique is limited to soft tissue like a female breast or a premature infant brain

  5. Numerical methodologies for investigation of moderate-velocity flow using a hybrid computational fluid dynamics - molecular dynamics simulation approach

    International Nuclear Information System (INIS)

    Ko, Soon Heum; Kim, Na Yong; Nikitopoulos, Dimitris E.; Moldovan, Dorel; Jha, Shantenu

    2014-01-01

    Numerical approaches are presented to minimize the statistical errors inherently present due to finite sampling and the presence of thermal fluctuations in the molecular region of a hybrid computational fluid dynamics (CFD) - molecular dynamics (MD) flow solution. Near the fluid-solid interface the hybrid CFD-MD simulation approach provides a more accurate solution, especially in the presence of significant molecular-level phenomena, than the traditional continuum-based simulation techniques. It also involves less computational cost than the pure particle-based MD. Despite these advantages the hybrid CFD-MD methodology has been applied mostly in flow studies at high velocities, mainly because of the higher statistical errors associated with low velocities. As an alternative to the costly increase of the size of the MD region to decrease statistical errors, we investigate a few numerical approaches that reduce sampling noise of the solution at moderate-velocities. These methods are based on sampling of multiple simulation replicas and linear regression of multiple spatial/temporal samples. We discuss the advantages and disadvantages of each technique in the perspective of solution accuracy and computational cost.

  6. Simulation and experimental tests of a real-time DPWM technique ...

    African Journals Online (AJOL)

    This control strategy is a simple and an easy technique generating the same switching pattern as space vector modulation with less switching losses and reduced total harmonic distortion. The main motivation of the present paper is that the DPWM is not largely and deeply investigated and can present a serious alternative ...

  7. Simulation of limiting dilution technique in determination of immunocompetent cells frequency in irradiated cell cultures

    International Nuclear Information System (INIS)

    Martini Filho, R.J.; Barlette, V.E.; Goes, E.G.; Covas, D.T.; Orellana, M.

    2001-01-01

    Limiting dilution techniques (LDA) dose-response data have been used to detect immunocompetent T-Cells in microcultures. In this work, LDA frequencies estimates was obtained using χ2 minimization for irradiated cells in a range of 500 to 1,500 cGy. (author)

  8. Simulations

    CERN Document Server

    Ngada, Narcisse

    2015-06-15

    The complexity and cost of building and running high-power electrical systems make the use of simulations unavoidable. The simulations available today provide great understanding about how systems really operate. This paper helps the reader to gain an insight into simulation in the field of power converters for particle accelerators. Starting with the definition and basic principles of simulation, two simulation types, as well as their leading tools, are presented: analog and numerical simulations. Some practical applications of each simulation type are also considered. The final conclusion then summarizes the main important items to keep in mind before opting for a simulation tool or before performing a simulation.

  9. Monte Carlo simulation for scanning technique with scattering foil free electron beam: A proof of concept study.

    Directory of Open Access Journals (Sweden)

    Wonmo Sung

    Full Text Available This study investigated the potential of a newly proposed scattering foil free (SFF electron beam scanning technique for the treatment of skin cancer on the irregular patient surfaces using Monte Carlo (MC simulation. After benchmarking of the MC simulations, we removed the scattering foil to generate SFF electron beams. Cylindrical and spherical phantoms with 1 cm boluses were generated and the target volume was defined from the surface to 5 mm depth. The SFF scanning technique with 6 MeV electrons was simulated using those phantoms. For comparison, volumetric modulated arc therapy (VMAT plans were also generated with two full arcs and 6 MV photon beams. When the scanning resolution resulted in a larger separation between beams than the field size, the plan qualities were worsened. In the cylindrical phantom with a radius of 10 cm, the conformity indices, homogeneity indices and body mean doses of the SFF plans (scanning resolution = 1° vs. VMAT plans were 1.04 vs. 1.54, 1.10 vs. 1.12 and 5 Gy vs. 14 Gy, respectively. Those of the spherical phantom were 1.04 vs. 1.83, 1.08 vs. 1.09 and 7 Gy vs. 26 Gy, respectively. The proposed SFF plans showed superior dose distributions compared to the VMAT plans.

  10. Monte Carlo simulation for scanning technique with scattering foil free electron beam: A proof of concept study.

    Science.gov (United States)

    Sung, Wonmo; Park, Jong In; Kim, Jung-In; Carlson, Joel; Ye, Sung-Joon; Park, Jong Min

    2017-01-01

    This study investigated the potential of a newly proposed scattering foil free (SFF) electron beam scanning technique for the treatment of skin cancer on the irregular patient surfaces using Monte Carlo (MC) simulation. After benchmarking of the MC simulations, we removed the scattering foil to generate SFF electron beams. Cylindrical and spherical phantoms with 1 cm boluses were generated and the target volume was defined from the surface to 5 mm depth. The SFF scanning technique with 6 MeV electrons was simulated using those phantoms. For comparison, volumetric modulated arc therapy (VMAT) plans were also generated with two full arcs and 6 MV photon beams. When the scanning resolution resulted in a larger separation between beams than the field size, the plan qualities were worsened. In the cylindrical phantom with a radius of 10 cm, the conformity indices, homogeneity indices and body mean doses of the SFF plans (scanning resolution = 1°) vs. VMAT plans were 1.04 vs. 1.54, 1.10 vs. 1.12 and 5 Gy vs. 14 Gy, respectively. Those of the spherical phantom were 1.04 vs. 1.83, 1.08 vs. 1.09 and 7 Gy vs. 26 Gy, respectively. The proposed SFF plans showed superior dose distributions compared to the VMAT plans.

  11. The corner rounding modeling technique in SPICE simulations for deeply scaled MOSFETs

    International Nuclear Information System (INIS)

    Sun Wei; Yang Dake

    2013-01-01

    This paper presents a novel poly (PC) and active (RX) corner rounding modeling approach to SPICE simulations. A set of specially designed structures was used for measurement data collection. PC and RX corner rounding equations have been derived based on an assumption that the corner rounding area is a fragment of a circle. The equations were modified to reflect the gouging effect of physical silicon wafers. The modified general equations were implemented in the SPICE model to enable the model to describe the corner rounding effect. The good fittings between the SPICE model simulation results and the silicon data demonstrated in this paper proved that the designed corner rounding model is practical and accurate. (semiconductor devices)

  12. Comparison of Different Measurement Techniques and a CFD Simulation in Complex Terrain

    International Nuclear Information System (INIS)

    Schulz, Christoph; Lutz, Thorsten; Hofsäß, Martin; Anger, Jan; Wen Cheng, Po; Rautenberg, Alexander; Bange, Jens

    2016-01-01

    This paper deals with a comparison of data collected by measurements and a simulation for a complex terrain test site in southern Germany. Lidar, met mast, unmanned aerial vehicle (UAV) measurements of wind speed and direction and Computational Fluid Dynamics (CFD) data are compared to each other. The site is characterised regarding its flow features and the suitability for a wind turbine test field. A Delayed-Detached-Eddy- Simulation (DES) was employed using measurement data to generate generic turbulent inflow. A good agreement of the wind profiles between the different approaches was reached. The terrain slope leads to a speed-up, a change of turbulence intensity as well as to flow angle variations. (paper)

  13. Simulation of radionuclide chemistry and sorption characteristics in the geosphere by artificial intelligence technique

    International Nuclear Information System (INIS)

    Liu Shangjyh; National Tsing Hua Univ., Hsinchu; Wang Shigang; Ho Liwei

    1988-01-01

    An expert system operated in a personal computer is employed to simulate chemistry and sorption phenomena of radionuclides in the geosphere. The system handles both qualitative and quantitative analyses primarily for the actinides and fission products. The system also incorporates data bases of several groundwater and rock types with mineral and chemical compositions, the distribution coefficients of nuclides for minerals, etc. The decision rule base facilitates this system to carry out the reasoning procedures to predict the solubility-limiting phase, solute species, oxidation states and possible complex formations of radionuclides, as well as to calculate the distribution coefficients and retardation factors in a geological formation, provided that the essential groundwater and host rock information are available. It is concluded that this device of artificial intelligence provides a vehicle to accumulate developed human knowledge and serves as a tool not only for simulating the complicated radionuclide behaviour in the geosphere, but also for instructional or educational purpose in this field. (orig.)

  14. Dosimetric study of prostate brachytherapy using techniques of Monte-Carlo simulation, experimental measurements and comparison with a treatment plan

    International Nuclear Information System (INIS)

    Teles, Pedro; Barros, Silvia; Vaz, Pedro; Goncalves, Isabel; Facure, Alessandro; Rosa, Luiz da; Santos, Maira; Pereira Junior, Pedro Paulo; Zankl, Maria

    2013-01-01

    Prostate Brachytherapy is a radiotherapy technique, which consists in inserting a number of radioactive seeds (containing, usually, the following radionuclides 125 l, 241 Am or 103 Pd ) surrounding or in the vicinity of, prostate tumor tissue . The main objective of this technique is to maximize the radiation dose to the tumor and minimize it in other tissues and organs healthy, in order to reduce its morbidity. The absorbed dose distribution in the prostate, using this technique is usually non-homogeneous and time dependent. Various parameters such as the type of seed, the attenuation interactions between them, their geometrical arrangement within the prostate, the actual geometry of the seeds,and further swelling of the prostate gland after implantation greatly influence the course of absorbed dose in the prostate and surrounding areas. Quantification of these parameters is therefore extremely important for dose optimization and improvement of their plans conventional treatment, which in many cases not fully take into account. The Monte Carlo techniques allow to study these parameters quickly and effectively. In this work, we use the program MCNPX and generic voxel phantom (GOLEM) where simulated different geometric arrangements of seeds containing 125 I, Amersham Health model of type 6711 in prostates of different sizes, in order to try to quantify some of the parameters. The computational model was validated using a phantom prostate cubic RW3 type , consisting of tissue equivalent, and thermoluminescent dosimeters. Finally, to have a term of comparison with a treatment real plan it was simulate a treatment plan used in a hospital of Rio de Janeiro, with exactly the same parameters, and our computational model. The results obtained in our study seem to indicate that the parameters described above may be a source of uncertainty in the correct evaluation of the dose required for actual treatment plans. The use of Monte Carlo techniques can serve as a complementary

  15. A Computer Program to Model Passive Acoustic Antisubmarine Search Using Monte Carlo Simulation Techniques.

    Science.gov (United States)

    1983-09-01

    duplicate a continuous function on a digital computer, and thus the machine representatic- of the GMA is only a close approximation of the continuous...error process. Thus, the manner in which the GMA process is digitally replicated has an effect on the results of the simulation. The parameterization of...Information Center 2 Cameron Station Alexandria, Virginia 22314 2. Libary , Code 0142 2 Naval Postgraduate School Monterey, California 93943 3. Professor

  16. FABRICATION OF TISSUE-SIMULATIVE PHANTOMS AND CAPILLARIES AND THEIR INVESTIGATION BY OPTICAL COHERENCE TOMOGRAPHY TECHNIQUES

    Directory of Open Access Journals (Sweden)

    A. V. Bykov

    2013-03-01

    Full Text Available Methods of tissue-simulative phantoms and capillaries fabrication from PVC-plastisol and silicone for application as test-objects in optical coherence tomography (OCT and skin and capillary emulation are considered. Comparison characteristics of these materials and recommendations for their application are given. Examples of phantoms visualization by optical coherence tomography method are given. Possibility of information using from B-scans for refractive index evaluation is shown.

  17. Hot air impingement on a flat plate using Large Eddy Simulation (LES) technique

    Science.gov (United States)

    Plengsa-ard, C.; Kaewbumrung, M.

    2018-01-01

    Impinging hot gas jets to a flat plate generate very high heat transfer coefficients in the impingement zone. The magnitude of heat transfer prediction near the stagnation point is important and accurate heat flux distribution are needed. This research studies on heat transfer and flow field resulting from a single hot air impinging wall. The simulation is carried out using computational fluid dynamics (CFD) commercial code FLUENT. Large Eddy Simulation (LES) approach with a subgrid-scale Smagorinsky-Lilly model is present. The classical Werner-Wengle wall model is used to compute the predicted results of velocity and temperature near walls. The Smagorinsky constant in the turbulence model is set to 0.1 and is kept constant throughout the investigation. The hot gas jet impingement on the flat plate with a constant surface temperature is chosen to validate the predicted heat flux results with experimental data. The jet Reynolds number is equal to 20,000 and a fixed jet-to-plate spacing of H/D = 2.0. Nusselt number on the impingement surface is calculated. As predicted by the wall model, the instantaneous computed Nusselt number agree fairly well with experimental data. The largest values of calculated Nusselt number are near the stagnation point and decrease monotonically in the wall jet region. Also, the contour plots of instantaneous values of wall heat flux on a flat plate are captured by LES simulation.

  18. CFD simulation of the pulsed neutron activation technique for water flow measurements

    International Nuclear Information System (INIS)

    Mattsson, H.; Nordlund, A.

    2005-01-01

    A pulse neutron activation (PNA) flowmeter uses a radioactive substance to measure water flow in pipes. The water in the pipe is bombarded with neutron pulses, thus introducing activity into the pipe. The activity is then transported and mixed with the flow. Gamma radiation emitted from the activity is measured with one or two detectors downstream from the activation point. The average velocity of the water is calculated using the time-resolved signal from the detector. The CFD program FLUENT was used to simulate the transport and mixing of the activity induced in the pipe. The turbulence of the flow is described with the k-ε model. Some parameters affecting a PNA measurement have been investigated. From the calculations it was possible to quantify how much the average initial velocity of the activity differs from the average velocity of the water. Results also show that activity initially produced far away from the wall has a substantial effect on the detector signal. To accurately simulate the detector signal it is necessary to include activity produced in a large part of the pipe. The results also indicate that the collimation of the detectors have a significant impact on the data and should be included when evaluating simulated data. Three different response functions were also tested. (authors)

  19. BAYESIAN TECHNIQUES FOR COMPARING TIME-DEPENDENT GRMHD SIMULATIONS TO VARIABLE EVENT HORIZON TELESCOPE OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Junhan; Marrone, Daniel P.; Chan, Chi-Kwan; Medeiros, Lia; Özel, Feryal; Psaltis, Dimitrios, E-mail: junhankim@email.arizona.edu [Department of Astronomy and Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States)

    2016-12-01

    The Event Horizon Telescope (EHT) is a millimeter-wavelength, very-long-baseline interferometry (VLBI) experiment that is capable of observing black holes with horizon-scale resolution. Early observations have revealed variable horizon-scale emission in the Galactic Center black hole, Sagittarius A* (Sgr A*). Comparing such observations to time-dependent general relativistic magnetohydrodynamic (GRMHD) simulations requires statistical tools that explicitly consider the variability in both the data and the models. We develop here a Bayesian method to compare time-resolved simulation images to variable VLBI data, in order to infer model parameters and perform model comparisons. We use mock EHT data based on GRMHD simulations to explore the robustness of this Bayesian method and contrast it to approaches that do not consider the effects of variability. We find that time-independent models lead to offset values of the inferred parameters with artificially reduced uncertainties. Moreover, neglecting the variability in the data and the models often leads to erroneous model selections. We finally apply our method to the early EHT data on Sgr A*.

  20. Using Elearning techniques to support problem based learning within a clinical simulation laboratory.

    Science.gov (United States)

    Docherty, Charles; Hoy, Derek; Topp, Helena; Trinder, Kathryn

    2004-01-01

    This paper details the results of the first phase of a project that used eLearning to support students' learning within a simulated environment. The locus was a purpose built Clinical Simulation Laboratory (CSL) where the School's newly adopted philosophy of Problem Based Learning (PBL) was challenged through lecturers reverting to traditional teaching methods. The solution, a student-centred, problem-based approach to the acquisition of clinical skills was developed using learning objects embedded within web pages that substituted for lecturers providing instruction and demonstration. This allowed lecturers to retain their facilitator role, and encouraged students to explore, analyse and make decisions within the safety of a clinical simulation. Learning was enhanced through network communications and reflection on video performances of self and others. Evaluations were positive, students demonstrating increased satisfaction with PBL, improved performance in exams, and increased self-efficacy in the performance of nursing activities. These results indicate that an elearning approach can support PBL in delivering a student centred learning experience.

  1. Real-Time Simulation Technique of a Microgrid Model for DER Penetration

    Directory of Open Access Journals (Sweden)

    Konstantina Mentesidi

    2014-12-01

    Full Text Available Comprehensive analysis of Distributed Energy Resources (DER integration requires tools that provide computational power and flexibility. In this context, throughout this paper PHIL simulations are performed to emulate the energy management system of a real microgrid including a diesel synchronous machine and inverter-based sources. Moreover, conventional frequency and voltage droops were incorporated into the respective inverters. The results were verified at the real microgrid installation in the Centre for Renewable Energy Sources (CRES premises. This research work is divided into two steps: A Real time in RSCAD/RTDS and Power Hardware-in-the-Loop (PHIL simulations where the diesel generator´s active power droop control is evaluated, the battery inverter´s droop curves are simulated and the load sharing for parallel operation of the system´s generation units is examined. B microgrid experiments during which various tests were executed concerning the diesel generator and the battery inverters in order to examine their dynamic operation within the LV islanded power system.

  2. ANALYSIS OF MONTE CARLO SIMULATION SAMPLING TECHNIQUES ON SMALL SIGNAL STABILITY OF WIND GENERATOR- CONNECTED POWER SYSTEM

    Directory of Open Access Journals (Sweden)

    TEMITOPE RAPHAEL AYODELE

    2016-04-01

    Full Text Available Monte Carlo simulation using Simple Random Sampling (SRS technique is popularly known for its ability to handle complex uncertainty problems. However, to produce a reasonable result, it requires huge sample size. This makes it to be computationally expensive, time consuming and unfit for online power system applications. In this article, the performance of Latin Hypercube Sampling (LHS technique is explored and compared with SRS in term of accuracy, robustness and speed for small signal stability application in a wind generator-connected power system. The analysis is performed using probabilistic techniques via eigenvalue analysis on two standard networks (Single Machine Infinite Bus and IEEE 16–machine 68 bus test system. The accuracy of the two sampling techniques is determined by comparing their different sample sizes with the IDEAL (conventional. The robustness is determined based on a significant variance reduction when the experiment is repeated 100 times with different sample sizes using the two sampling techniques in turn. Some of the results show that sample sizes generated from LHS for small signal stability application produces the same result as that of the IDEAL values starting from 100 sample size. This shows that about 100 sample size of random variable generated using LHS method is good enough to produce reasonable results for practical purpose in small signal stability application. It is also revealed that LHS has the least variance when the experiment is repeated 100 times compared to SRS techniques. This signifies the robustness of LHS over that of SRS techniques. 100 sample size of LHS produces the same result as that of the conventional method consisting of 50000 sample size. The reduced sample size required by LHS gives it computational speed advantage (about six times over the conventional method.

  3. Modeling and simulation of defects detection in conductive multi-layered pieces by the eddy current technique

    International Nuclear Information System (INIS)

    Bennoud, S; Zergoug, M

    2015-01-01

    It has been shown that the eddy current method is one of the most effective techniques for the detection and characterization of surface and near-surface defects in conductive mediums especially in aluminum alloy. It is one of the most applied methods in industries which require a maximum of reliability and security (aerospace, aeronautics, nuclear, Etc). In this study, a code to solve electromagnetic problems by employing the finite element method is developed. The suggested model can simulate the probe response to the presence of a defect hidden in a multi-layered structure or a riveted structure on aluminum alloy. The developed code is based on the discretization in three dimensions of the Maxwell's equations in harmonic mode by the finite element method based on the combined potential formulations. That will enable us to interpret the results, to present them in graphical form and to carry out simulations for various applications

  4. A fitting algorithm based on simulated annealing techniques for efficiency calibration of HPGe detectors using different mathematical functions

    Energy Technology Data Exchange (ETDEWEB)

    Hurtado, S. [Servicio de Radioisotopos, Centro de Investigacion, Tecnologia e Innovacion (CITIUS), Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012 Sevilla (Spain)], E-mail: shurtado@us.es; Garcia-Leon, M. [Departamento de Fisica Atomica, Molecular y Nuclear, Facultad de Fisica, Universidad de Sevilla, Aptd. 1065, 41080 Sevilla (Spain); Garcia-Tenorio, R. [Departamento de Fisica Aplicada II, E.T.S.A. Universidad de Sevilla, Avda, Reina Mercedes 2, 41012 Sevilla (Spain)

    2008-09-11

    In this work several mathematical functions are compared in order to perform the full-energy peak efficiency calibration of HPGe detectors using a 126cm{sup 3} HPGe coaxial detector and gamma-ray energies ranging from 36 to 1460 keV. Statistical tests and Monte Carlo simulations were used to study the performance of the fitting curve equations. Furthermore the fitting procedure of these complex functional forms to experimental data is a non-linear multi-parameter minimization problem. In gamma-ray spectrometry usually non-linear least-squares fitting algorithms (Levenberg-Marquardt method) provide a fast convergence while minimizing {chi}{sub R}{sup 2}, however, sometimes reaching only local minima. In order to overcome that shortcoming a hybrid algorithm based on simulated annealing (HSA) techniques is proposed. Additionally a new function is suggested that models the efficiency curve of germanium detectors in gamma-ray spectrometry.

  5. Improving image quality in Electrical Impedance Tomography (EIT using Projection Error Propagation-based Regularization (PEPR technique: A simulation study

    Directory of Open Access Journals (Sweden)

    Tushar Kanti Bera

    2011-03-01

    Full Text Available A Projection Error Propagation-based Regularization (PEPR method is proposed and the reconstructed image quality is improved in Electrical Impedance Tomography (EIT. A projection error is produced due to the misfit of the calculated and measured data in the reconstruction process. The variation of the projection error is integrated with response matrix in each iterations and the reconstruction is carried out in EIDORS. The PEPR method is studied with the simulated boundary data for different inhomogeneity geometries. Simulated results demonstrate that the PEPR technique improves image reconstruction precision in EIDORS and hence it can be successfully implemented to increase the reconstruction accuracy in EIT.>doi:10.5617/jeb.158 J Electr Bioimp, vol. 2, pp. 2-12, 2011

  6. The Structural Basis for Lipid and Endotoxin Binding in RP105-MD-1, and Consequences for Regulation of Host Lipopolysaccharide Sensitivity.

    Science.gov (United States)

    Ortiz-Suarez, Maite L; Bond, Peter J

    2016-01-05

    MD-1 is a member of the MD-2-related lipid-recognition (ML) family, and associates with RP105, a cell-surface protein that resembles Toll-like receptor 4 (TLR4). The RP105⋅MD-1 complex has been proposed to play a role in fine-tuning the innate immune response to endotoxin such as bacterial lipopolysaccharide (LPS) via TLR4⋅MD-2, but controversy surrounds its mechanism. We have used atomically detailed simulations to reveal the structural basis for ligand binding and consequent functional dynamics of MD-1 and the RP105 complex. We rationalize reports of endogenous phospholipid binding, by showing that they prevent collapse of the malleable MD-1 fold, before refining crystallographic models and uncovering likely binding modes for LPS analogs. Subsequent binding affinity calculations reveal that endotoxin specificity arises from the entropic cost of expanding the MD-1 cavity to accommodate bulky lipid tails, and support the role of MD-1 as a "sink" that sequesters endotoxin from TLR4 and stabilizes RP105/TLR4 interactions. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. A Novel Idea for Optimizing Condition-Based Maintenance Using Genetic Algorithms and Continuous Event Simulation Techniques

    Directory of Open Access Journals (Sweden)

    Mansoor Ahmed Siddiqui

    2017-01-01

    Full Text Available Effective maintenance strategies are of utmost significance for system engineering due to their direct linkage with financial aspects and safety of the plants’ operation. At a point where the state of a system, for instance, level of its deterioration, can be constantly observed, a strategy based on condition-based maintenance (CBM may be affected; wherein upkeep of the system is done progressively on the premise of monitored state of the system. In this article, a multicomponent framework is considered that is continuously kept under observation. In order to decide an optimal deterioration stage for the said system, Genetic Algorithm (GA technique has been utilized that figures out when its preventive maintenance should be carried out. The system is configured into a multiobjective problem that is aimed at optimizing the two desired objectives, namely, profitability and accessibility. For the sake of reality, a prognostic model portraying the advancements of deteriorating system has been employed that will be based on utilization of continuous event simulation techniques. In this regard, Monte Carlo (MC simulation has been shortlisted as it can take into account a wide range of probable options that can help in reducing uncertainty. The inherent benefits proffered by the said simulation technique are fully utilized to display various elements of a deteriorating system working under stressed environment. The proposed synergic model (GA and MC is considered to be more effective due to the employment of “drop-by-drop approach” that permits successful drive of the related search process with regard to the best optimal solutions.

  8. Tsunami Simulators in Physical Modelling Laboratories - From Concept to Proven Technique

    Science.gov (United States)

    Allsop, W.; Chandler, I.; Rossetto, T.; McGovern, D.; Petrone, C.; Robinson, D.

    2016-12-01

    Before 2004, there was little public awareness around Indian Ocean coasts of the potential size and effects of tsunami. Even in 2011, the scale and extent of devastation by the Japan East Coast Tsunami was unexpected. There were very few engineering tools to assess onshore impacts of tsunami, so no agreement on robust methods to predict forces on coastal defences, buildings or related infrastructure. Modelling generally used substantial simplifications of either solitary waves (far too short durations) or dam break (unrealistic and/or uncontrolled wave forms).This presentation will describe research from EPI-centre, HYDRALAB IV, URBANWAVES and CRUST projects over the last 10 years that have developed and refined pneumatic Tsunami Simulators for the hydraulic laboratory. These unique devices have been used to model generic elevated and N-wave tsunamis up to and over simple shorelines, and at example defences. They have reproduced full-duration tsunamis including the Mercator trace from 2004 at 1:50 scale. Engineering scale models subjected to those tsunamis have measured wave run-up on simple slopes, forces on idealised sea defences and pressures / forces on buildings. This presentation will describe how these pneumatic Tsunami Simulators work, demonstrate how they have generated tsunami waves longer than the facility within which they operate, and will highlight research results from the three generations of Tsunami Simulator. Of direct relevance to engineers and modellers will be measurements of wave run-up levels and comparison with theoretical predictions. Recent measurements of forces on individual buildings have been generalized by separate experiments on buildings (up to 4 rows) which show that the greatest forces can act on the landward (not seaward) buildings. Continuing research in the 70m long 4m wide Fast Flow Facility on tsunami defence structures have also measured forces on buildings in the lee of a failed defence wall.

  9. Wideband simulation of earthquake ground motion by a spectrum-matching, multiple-pulse technique

    International Nuclear Information System (INIS)

    Gusev, A.; Pavlov, V.

    2006-04-01

    To simulate earthquake ground motion, we combine a multiple-point stochastic earthquake fault model and a suite of Green functions. Conceptually, our source model generalizes the classic one of Haskell (1966). At any time instant, slip occurs over a narrow strip that sweeps the fault area at a (spatially variable) velocity. This behavior defines seismic signals at lower frequencies (LF), and describes directivity effects. High-frequency (HF) behavior of source signal is defined by local slip history, assumed to be a short segment of pulsed noise. For calculations, this model is discretized as a grid of point subsources. Subsource moment rate time histories, in their LF part, are smooth pulses whose duration equals to the rise time. In their HF part, they are segments of non-Gaussian noise of similar duration. The spectral content of subsource time histories is adjusted so that the summary far-field signal follows certain predetermined spectral scaling law. The results of simulation depend on random seeds, and on particular values of such parameters as: stress drop; average and dispersion parameter for rupture velocity; rupture nucleation point; slip zone width/rise time, wavenumber-spectrum parameter defining final slip function; the degrees of non-Gaussianity for random slip rate in time, and for random final slip in space, and more. To calculate ground motion at a site, Green functions are calculated for each subsource-site pair, then convolved with subsource time functions and at last summed over subsources. The original Green function calculator for layered weakly inelastic medium is of discrete wavenumber kind, with no intrinsic limitations with respect to layer thickness or bandwidth. The simulation package can generate example motions, or used to study uncertainties of the predicted motion. As a test, realistic analogues of recorded motions in the epicentral zone of the 1994 Northridge, California earthquake were synthesized, and related uncertainties were

  10. Bridging the scales in atmospheric composition simulations using a nudging technique

    Science.gov (United States)

    D'Isidoro, Massimo; Maurizi, Alberto; Russo, Felicita; Tampieri, Francesco

    2010-05-01

    Studying the interaction between climate and anthropogenic activities, specifically those concentrated in megacities/hot spots, requires the description of processes in a very wide range of scales from local, where anthropogenic emissions are concentrated to global where we are interested to study the impact of these sources. The description of all the processes at all scales within the same numerical implementation is not feasible because of limited computer resources. Therefore, different phenomena are studied by means of different numerical models that can cover different range of scales. The exchange of information from small to large scale is highly non-trivial though of high interest. In fact uncertainties in large scale simulations are expected to receive large contribution from the most polluted areas where the highly inhomogeneous distribution of sources connected to the intrinsic non-linearity of the processes involved can generate non negligible departures between coarse and fine scale simulations. In this work a new method is proposed and investigated in a case study (August 2009) using the BOLCHEM model. Monthly simulations at coarse (0.5° European domain, run A) and fine (0.1° Central Mediterranean domain, run B) horizontal resolution are performed using the coarse resolution as boundary condition for the fine one. Then another coarse resolution run (run C) is performed, in which the high resolution fields remapped on to the coarse grid are used to nudge the concentrations on the Po Valley area. The nudging is applied to all gas and aerosol species of BOLCHEM. Averaged concentrations and variances over Po Valley and other selected areas for O3 and PM are computed. It is observed that although the variance of run B is markedly larger than that of run A, the variance of run C is smaller because the remapping procedure removes large portion of variance from run B fields. Mean concentrations show some differences depending on species: in general mean

  11. Pricing Survivor Forwards and Swaps in Incomplete Markets Using Simulation Techniques

    DEFF Research Database (Denmark)

    Boyer, M. Martin; Favaro, Amélie; Stentoft, Lars

    2012-01-01

    This article considers how to manage longevity risk using longevity derivatives products. We review the potential counterparties that naturally have exposure to this type of risk and we provide details on two very simple products, the survivor forward and the survivor swap, that can be used...... to trade this type of risk. We then discuss how such products can be priced using a simulation-based approach that has been shown to be successful in pricing financial derivatives. To illustrate the flexibility of the approach we price survivor forwards and swaps using the simple dynamics of the Lee...

  12. Use of the FDA nozzle model to illustrate validation techniques in computational fluid dynamics (CFD) simulations.

    Science.gov (United States)

    Hariharan, Prasanna; D'Souza, Gavin A; Horner, Marc; Morrison, Tina M; Malinauskas, Richard A; Myers, Matthew R

    2017-01-01

    A "credible" computational fluid dynamics (CFD) model has the potential to provide a meaningful evaluation of safety in medical devices. One major challenge in establishing "model credibility" is to determine the required degree of similarity between the model and experimental results for the model to be considered sufficiently validated. This study proposes a "threshold-based" validation approach that provides a well-defined acceptance criteria, which is a function of how close the simulation and experimental results are to the safety threshold, for establishing the model validity. The validation criteria developed following the threshold approach is not only a function of Comparison Error, E (which is the difference between experiments and simulations) but also takes in to account the risk to patient safety because of E. The method is applicable for scenarios in which a safety threshold can be clearly defined (e.g., the viscous shear-stress threshold for hemolysis in blood contacting devices). The applicability of the new validation approach was tested on the FDA nozzle geometry. The context of use (COU) was to evaluate if the instantaneous viscous shear stress in the nozzle geometry at Reynolds numbers (Re) of 3500 and 6500 was below the commonly accepted threshold for hemolysis. The CFD results ("S") of velocity and viscous shear stress were compared with inter-laboratory experimental measurements ("D"). The uncertainties in the CFD and experimental results due to input parameter uncertainties were quantified following the ASME V&V 20 standard. The CFD models for both Re = 3500 and 6500 could not be sufficiently validated by performing a direct comparison between CFD and experimental results using the Student's t-test. However, following the threshold-based approach, a Student's t-test comparing |S-D| and |Threshold-S| showed that relative to the threshold, the CFD and experimental datasets for Re = 3500 were statistically similar and the model could be

  13. Simulation technique on combustion of solid propellant; Kotai suishin`yaku nensho no simyureshon gijutsu

    Energy Technology Data Exchange (ETDEWEB)

    Iida, Akihide.; Bazaki, Hakobu.; Douke, Kiyotaka. [Asahi Chemical Industry Corp., Tokyo (Japan). Oita Plant

    1999-04-30

    The burning area of propellant grain is one of the most important parameter in conducting of design on solid rocket performance. However, it has been difficult to calculate the burning area of propellant grain with precise and speed by geometrical way since most of propellant configuration have been adopted as complicated. In the present study, the simulation system was developed and produced, which was adapted `particle chasing method` to and made ot compute the burning area transition. Moreover, the reliability on computation by the system was check up on. It was found that the discrepancy of calculation between by the geometrical way and by the system was less than 1%. (author)

  14. Decision Simulation Technique (DST) as a scanning tool for exploring and explicating sustainability issues in transport decision making

    DEFF Research Database (Denmark)

    Jeppesen, Sara Lise

    2009-01-01

    This paper places focus on explicit consideration of sustainability issues in transport decision making by presenting and using a developed “Decision Simulation Technique” (DST). This technique can be used by an analyst to ‘scan’ a transport planning problem with regard to what in DST terms...... is called a sustainability strategy. This scanning can serve the purpose of informing a group of decision makers before they actually have to deal with, for example, the choice among a number of alternatives that have all been formulated as being relevant. The main focus of the paper is to illustrate how...

  15. Synergistic Applications of MD and NMR for the Study of Biological Systems

    Directory of Open Access Journals (Sweden)

    Olivier Fisette

    2012-01-01

    same time, theoretical and computational approaches gain in reliability and their field of application widens. In this short paper, we discuss recent advances in the areas of solution nuclear magnetic resonance (NMR spectroscopy and molecular dynamics (MD simulations that were made possible by the combination of both methods, that is, through their synergistic use. We present the main NMR observables and parameters that can be computed from simulations, and how they are used in a variety of complementary applications, including dynamics studies, model-free analysis, force field validation, and structural studies.

  16. Preparing MD-PhD students for clinical rotations: navigating the interface between PhD and MD training.

    Science.gov (United States)

    Goldberg, Charles; Insel, Paul A

    2013-06-01

    Many aspects of MD-PhD training are not optimally designed to prepare students for their future roles as translational clinician-scientists. The transition between PhD research efforts and clinical rotations is one hurdle that must be overcome. MD-PhD students have deficits in clinical skills compared with those of their MD-only colleagues at the time of this transition. Reimmersion programs (RPs) targeted to MD-PhD students have the potential to help them navigate this transition.The authors draw on their experience creating and implementing an RP that incorporates multiple types of activities (clinical exam review, objective structured clinical examination, and supervised practice in patient care settings) designed to enhance the participants' skills and readiness for clinical efforts. On the basis of this experience, they note that MD-PhD students' time away from the clinical environment negatively affects their clinical skills, causing them to feel underprepared for clinical rotations. The authors argue that participation in an RP can help students feel more comfortable speaking with and examining patients and decrease their anxiety regarding clinical encounters. The authors propose that RPs can have positive outcomes for improving the transition from PhD to clinical MD training in dual-degree programs. Identifying and addressing this and other transitions need to be considered to improve the educational experience of MD-PhD students.

  17. Simulating the performance of adaptive optics techniques on FSO communications through the atmosphere

    Science.gov (United States)

    Martínez, Noelia; Rodríguez Ramos, Luis Fernando; Sodnik, Zoran

    2017-08-01

    The Optical Ground Station (OGS), installed in the Teide Observatory since 1995, was built as part of ESA efforts in the research field of satellite optical communications to test laser telecommunication terminals on board of satellites in Low Earth Orbit and Geostationary Orbit. As far as one side of the link is settled on the Earth, the laser beam (either on the uplink or on the downlink) has to bear with the atmospheric turbulence. Within the framework of designing an Adaptive Optics system to improve the performance of the Free-Space Optical Communications at the OGS, turbulence conditions regarding uplink and downlink have been simulated within the OOMAO (Object-Oriented Matlab Adaptive Optics) Toolbox as well as the possible utilization of a Laser Guide Star to measure the wavefront in this context. Simulations have been carried out by reducing available atmospheric profiles regarding both night-time and day-time measurements and by having into account possible seasonal changes. An AO proposal to reduce atmospheric aberrations and, therefore, ameliorate FSO links performance is presented and analysed in this paper

  18. Conventional QT Variability Measurement vs. Template Matching Techniques: Comparison of Performance Using Simulated and Real ECG

    Science.gov (United States)

    Baumert, Mathias; Starc, Vito; Porta, Alberto

    2012-01-01

    Increased beat-to-beat variability in the QT interval (QTV) of ECG has been associated with increased risk for sudden cardiac death, but its measurement is technically challenging and currently not standardized. The aim of this study was to investigate the performance of commonly used beat-to-beat QT interval measurement algorithms. Three different methods (conventional, template stretching and template time shifting) were subjected to simulated data featuring typical ECG recording issues (broadband noise, baseline wander, amplitude modulation) and real short-term ECG of patients before and after infusion of sotalol, a QT interval prolonging drug. Among the three algorithms, the conventional algorithm was most susceptible to noise whereas the template time shifting algorithm showed superior overall performance on simulated and real ECG. None of the algorithms was able to detect increased beat-to-beat QT interval variability after sotalol infusion despite marked prolongation of the average QT interval. The QTV estimates of all three algorithms were inversely correlated with the amplitude of the T wave. In conclusion, template matching algorithms, in particular the time shifting algorithm, are recommended for beat-to-beat variability measurement of QT interval in body surface ECG. Recording noise, T wave amplitude and the beat-rejection strategy are important factors of QTV measurement and require further investigation. PMID:22860030

  19. Conventional QT variability measurement vs. template matching techniques: comparison of performance using simulated and real ECG.

    Directory of Open Access Journals (Sweden)

    Mathias Baumert

    Full Text Available Increased beat-to-beat variability in the QT interval (QTV of ECG has been associated with increased risk for sudden cardiac death, but its measurement is technically challenging and currently not standardized. The aim of this study was to investigate the performance of commonly used beat-to-beat QT interval measurement algorithms. Three different methods (conventional, template stretching and template time shifting were subjected to simulated data featuring typical ECG recording issues (broadband noise, baseline wander, amplitude modulation and real short-term ECG of patients before and after infusion of sotalol, a QT interval prolonging drug. Among the three algorithms, the conventional algorithm was most susceptible to noise whereas the template time shifting algorithm showed superior overall performance on simulated and real ECG. None of the algorithms was able to detect increased beat-to-beat QT interval variability after sotalol infusion despite marked prolongation of the average QT interval. The QTV estimates of all three algorithms were inversely correlated with the amplitude of the T wave. In conclusion, template matching algorithms, in particular the time shifting algorithm, are recommended for beat-to-beat variability measurement of QT interval in body surface ECG. Recording noise, T wave amplitude and the beat-rejection strategy are important factors of QTV measurement and require further investigation.

  20. Numerical Simulation of Molten Flow in Directed Energy Deposition Using an Iterative Geometry Technique

    Science.gov (United States)

    Vincent, Timothy J.; Rumpfkeil, Markus P.; Chaudhary, Anil

    2018-06-01

    The complex, multi-faceted physics of laser-based additive metals processing tends to demand high-fidelity models and costly simulation tools to provide predictions accurate enough to aid in selecting process parameters. Of particular difficulty is the accurate determination of melt pool shape and size, which are useful for predicting lack-of-fusion, as this typically requires an adequate treatment of thermal and fluid flow. In this article we describe a novel numerical simulation tool which aims to achieve a balance between accuracy and cost. This is accomplished by making simplifying assumptions regarding the behavior of the gas-liquid interface for processes with a moderate energy density, such as Laser Engineered Net Shaping (LENS). The details of the implementation, which is based on the solver simpleFoam of the well-known software suite OpenFOAM, are given here and the tool is verified and validated for a LENS process involving Ti-6Al-4V. The results indicate that the new tool predicts width and height of a deposited track to engineering accuracy levels.

  1. Numerical Simulation of Molten Flow in Directed Energy Deposition Using an Iterative Geometry Technique

    Science.gov (United States)

    Vincent, Timothy J.; Rumpfkeil, Markus P.; Chaudhary, Anil

    2018-03-01

    The complex, multi-faceted physics of laser-based additive metals processing tends to demand high-fidelity models and costly simulation tools to provide predictions accurate enough to aid in selecting process parameters. Of particular difficulty is the accurate determination of melt pool shape and size, which are useful for predicting lack-of-fusion, as this typically requires an adequate treatment of thermal and fluid flow. In this article we describe a novel numerical simulation tool which aims to achieve a balance between accuracy and cost. This is accomplished by making simplifying assumptions regarding the behavior of the gas-liquid interface for processes with a moderate energy density, such as Laser Engineered Net Shaping (LENS). The details of the implementation, which is based on the solver simpleFoam of the well-known software suite OpenFOAM, are given here and the tool is verified and validated for a LENS process involving Ti-6Al-4V. The results indicate that the new tool predicts width and height of a deposited track to engineering accuracy levels.

  2. Simulation model of harmonics reduction technique using shunt active filter by cascade multilevel inverter method

    Science.gov (United States)

    Andreh, Angga Muhamad; Subiyanto, Sunardiyo, Said

    2017-01-01

    Development of non-linear loading in the application of industry and distribution system and also harmonic compensation becomes important. Harmonic pollution is an urgent problem in increasing power quality. The main contribution of the study is the modeling approach used to design a shunt active filter and the application of the cascade multilevel inverter topology to improve the power quality of electrical energy. In this study, shunt active filter was aimed to eliminate dominant harmonic component by injecting opposite currents with the harmonic component system. The active filter was designed by shunt configuration with cascaded multilevel inverter method controlled by PID controller and SPWM. With this shunt active filter, the harmonic current can be reduced so that the current wave pattern of the source is approximately sinusoidal. Design and simulation were conducted by using Power Simulator (PSIM) software. Shunt active filter performance experiment was conducted on the IEEE four bus test system. The result of shunt active filter installation on the system (IEEE four bus) could reduce THD current from 28.68% to 3.09%. With this result, the active filter can be applied as an effective method to reduce harmonics.

  3. Evaluation of Automated Model Calibration Techniques for Residential Building Energy Simulation

    Energy Technology Data Exchange (ETDEWEB)

    and Ben Polly, Joseph Robertson [National Renewable Energy Lab. (NREL), Golden, CO (United States); Polly, Ben [National Renewable Energy Lab. (NREL), Golden, CO (United States); Collis, Jon [Colorado School of Mines, Golden, CO (United States)

    2013-09-01

    This simulation study adapts and applies the general framework described in BESTEST-EX (Judkoff et al 2010) for self-testing residential building energy model calibration methods. BEopt/DOE-2.2 is used to evaluate four mathematical calibration methods in the context of monthly, daily, and hourly synthetic utility data for a 1960's-era existing home in a cooling-dominated climate. The home's model inputs are assigned probability distributions representing uncertainty ranges, random selections are made from the uncertainty ranges to define "explicit" input values, and synthetic utility billing data are generated using the explicit input values. The four calibration methods evaluated in this study are: an ASHRAE 1051-RP-based approach (Reddy and Maor 2006), a simplified simulated annealing optimization approach, a regression metamodeling optimization approach, and a simple output ratio calibration approach. The calibration methods are evaluated for monthly, daily, and hourly cases; various retrofit measures are applied to the calibrated models and the methods are evaluated based on the accuracy of predicted savings, computational cost, repeatability, automation, and ease of implementation.

  4. Evaluation of Automated Model Calibration Techniques for Residential Building Energy Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, J.; Polly, B.; Collis, J.

    2013-09-01

    This simulation study adapts and applies the general framework described in BESTEST-EX (Judkoff et al 2010) for self-testing residential building energy model calibration methods. BEopt/DOE-2.2 is used to evaluate four mathematical calibration methods in the context of monthly, daily, and hourly synthetic utility data for a 1960's-era existing home in a cooling-dominated climate. The home's model inputs are assigned probability distributions representing uncertainty ranges, random selections are made from the uncertainty ranges to define 'explicit' input values, and synthetic utility billing data are generated using the explicit input values. The four calibration methods evaluated in this study are: an ASHRAE 1051-RP-based approach (Reddy and Maor 2006), a simplified simulated annealing optimization approach, a regression metamodeling optimization approach, and a simple output ratio calibration approach. The calibration methods are evaluated for monthly, daily, and hourly cases; various retrofit measures are applied to the calibrated models and the methods are evaluated based on the accuracy of predicted savings, computational cost, repeatability, automation, and ease of implementation.

  5. Comparison between fluorimetry and oximetry techniques to measure photosynthesis in the diatom Skeletonema costatum cultivated under simulated seasonal conditions.

    Science.gov (United States)

    Lefebvre, Sébastien; Mouget, Jean-Luc; Loret, Pascale; Rosa, Philippe; Tremblin, Gérard

    2007-02-01

    This study reports comparison of two techniques measuring photosynthesis in the ubiquitous diatom Skeletonema costatum, i.e., the classical oximetry and the recent modulated fluorimetry. Microalgae in semi-continuous cultures were exposed to five different environmental conditions simulating a seasonal effect with co-varying temperature, photoperiod and incident light. Photosynthesis was assessed by gross rate of oxygen evolution (P(B)) and the electron transport rate (ETR) measurements. The two techniques were linearly related within seasonal treatments along the course of the P/E curves. The light saturation intensity parameters (Ek and Ek(ETR)), and the maximum electron transport rate increased significantly with the progression of the season while the maximum light utilization efficiency for ETR (alpha(ETR)) was constant. By contrast, the maximum gross oxygen photosynthetic capacity (Pmax(B)) and the maximum light utilization efficiency for P(B) (alpha(B)) increased from December to May treatment but decreased from May to July treatment. Both techniques showed clear photoacclimation in microalgae with the progression of the season, as illustrated by changes in photosynthetic parameters. The relationship between the two techniques changed when high temperature, photoperiod and incident light were combined, possibly due to an overestimation of the PAR--averaged chlorophyll-specific absorption cross-section. Despite this change, our results illustrate the strong suitability of in vivo chlorophyll fluorimetry to estimate primary production in the field.

  6. Uncertainty estimates of a GRACE inversion modelling technique over Greenland using a simulation

    Science.gov (United States)

    Bonin, Jennifer; Chambers, Don

    2013-07-01

    The low spatial resolution of GRACE causes leakage, where signals in one location spread out into nearby regions. Because of this leakage, using simple techniques such as basin averages may result in an incorrect estimate of the true mass change in a region. A fairly simple least squares inversion technique can be used to more specifically localize mass changes into a pre-determined set of basins of uniform internal mass distribution. However, the accuracy of these higher resolution basin mass amplitudes has not been determined, nor is it known how the distribution of the chosen basins affects the results. We use a simple `truth' model over Greenland as an example case, to estimate the uncertainties of this inversion method and expose those design parameters which may result in an incorrect high-resolution mass distribution. We determine that an appropriate level of smoothing (300-400 km) and process noise (0.30 cm2 of water) gets the best results. The trends of the Greenland internal basins and Iceland can be reasonably estimated with this method, with average systematic errors of 3.5 cm yr-1 per basin. The largest mass losses found from GRACE RL04 occur in the coastal northwest (-19.9 and -33.0 cm yr-1) and southeast (-24.2 and -27.9 cm yr-1), with small mass gains (+1.4 to +7.7 cm yr-1) found across the northern interior. Acceleration of mass change is measurable at the 95 per cent confidence level in four northwestern basins, but not elsewhere in Greenland. Due to an insufficiently detailed distribution of basins across internal Canada, the trend estimates of Baffin and Ellesmere Islands are expected to be incorrect due to systematic errors caused by the inversion technique.

  7. MD and FFM Electron Broadening for Warm and Dense Hydrogen Plasmas

    International Nuclear Information System (INIS)

    Ferri, S.; Calisti, A.; Mosse, C.; Talin, B.; Gonzalez, M. A.; Gigosos, M. A.

    2006-01-01

    Direct integration of the semi-classical evolution equation based on Molecular Dynamics simulations (MD) and the Frequency Fluctuation Model (FFM) have long been used to synthesize spectra accounting for ion dynamics. Cross comparisons of these approaches generally show results in good agreement. Recently, interest in low temperature (Te ∼ 1eV) and high density (Ne ∼ 1018 cm-3) hydrogen plasma spectroscopy has motivated extended applications of FFM. Arising discrepancies were found to originate in electron collision operators suggesting an improper use of impact approximations for warm and dense plasma conditions. In order to clarify this point, new useful cross comparisons between MD and FFM have been carried out for electron broadening

  8. Applications of soft computing in time series forecasting simulation and modeling techniques

    CERN Document Server

    Singh, Pritpal

    2016-01-01

    This book reports on an in-depth study of fuzzy time series (FTS) modeling. It reviews and summarizes previous research work in FTS modeling and also provides a brief introduction to other soft-computing techniques, such as artificial neural networks (ANNs), rough sets (RS) and evolutionary computing (EC), focusing on how these techniques can be integrated into different phases of the FTS modeling approach. In particular, the book describes novel methods resulting from the hybridization of FTS modeling approaches with neural networks and particle swarm optimization. It also demonstrates how a new ANN-based model can be successfully applied in the context of predicting Indian summer monsoon rainfall. Thanks to its easy-to-read style and the clear explanations of the models, the book can be used as a concise yet comprehensive reference guide to fuzzy time series modeling, and will be valuable not only for graduate students, but also for researchers and professionals working for academic, business and governmen...

  9. Simulation on the Effect of Bottle Wall Thickness Distribution using Blow Moulding Technique

    International Nuclear Information System (INIS)

    Suraya, S; Azman, M D; Fatchurrohman, N; Jaafar, A A; Yusoff, A R

    2016-01-01

    The aims of this study are to assess the deformation behavior of a polymeric material during a blow moulding process. Transient computations of two dimensional model of a PP bottle were performed using ANSYS Polyflow computer code to predict the wall thickness distribution at four different parison's diameter; 8mm, 10mm, 18mm, and 20mm. Effects on the final wall thickness diameter and time step are studied. The simulated data shows that the inflation performance degrades with increasing parison diameter. It is concluded that the blow moulding process using 10mm parison successfully meet the product processing requirements. Factors that contribute to the variation in deformation behaviour of the plastic during the manufacturing process are discussed. (paper)

  10. Complex Langevin simulation of QCD at finite density and low temperature using the deformation technique

    Science.gov (United States)

    Nagata, Keitro; Nishimura, Jun; Shimasaki, Shinji

    2018-03-01

    We study QCD at finite density and low temperature by using the complex Langevin method. We employ the gauge cooling to control the unitarity norm and intro-duce a deformation parameter in the Dirac operator to avoid the singular-drift problem. The reliability of the obtained results are judged by the probability distribution of the magnitude of the drift term. By making extrapolations with respect to the deformation parameter using only the reliable results, we obtain results for the original system. We perform simulations on a 43 × 8 lattice and show that our method works well even in the region where the reweighing method fails due to the severe sign problem. As a result we observe a delayed onset of the baryon number density as compared with the phase-quenched model, which is a clear sign of the Silver Blaze phenomenon.

  11. A dynamic mesh refinement technique for Lattice Boltzmann simulations on octree-like grids

    KAUST Repository

    Neumann, Philipp

    2012-04-27

    In this contribution, we present our new adaptive Lattice Boltzmann implementation within the Peano framework, with special focus on nanoscale particle transport problems. With the continuum hypothesis not holding anymore on these small scales, new physical effects - such as Brownian fluctuations - need to be incorporated. We explain the overall layout of the application, including memory layout and access, and shortly review the adaptive algorithm. The scheme is validated by different benchmark computations in two and three dimensions. An extension to dynamically changing grids and a spatially adaptive approach to fluctuating hydrodynamics, allowing for the thermalisation of the fluid in particular regions of interest, is proposed. Both dynamic adaptivity and adaptive fluctuating hydrodynamics are validated separately in simulations of particle transport problems. The application of this scheme to an oscillating particle in a nanopore illustrates the importance of Brownian fluctuations in such setups. © 2012 Springer-Verlag.

  12. 75 FR 80744 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-9-81 (MD-81), DC-9-82 (MD-82...

    Science.gov (United States)

    2010-12-23

    ...-1203; Directorate Identifier 2010-NM-168-AD] RIN 2120-AA64 Airworthiness Directives; McDonnell Douglas... amends Sec. 39.13 by adding the following new airworthiness directive (AD): McDonnell Douglas Corporation... Douglas Corporation Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), DC-9-87 (MD-87) and MD-88...

  13. Md-miR156ab and Md-miR395 Target WRKY Transcription Factors to Influence Apple Resistance to Leaf Spot Disease.

    Science.gov (United States)

    Zhang, Qiulei; Li, Yang; Zhang, Yi; Wu, Chuanbao; Wang, Shengnan; Hao, Li; Wang, Shengyuan; Li, Tianzhong

    2017-01-01

    MicroRNAs (miRNAs) are key regulators of gene expression that post-transcriptionally regulate transcription factors involved in plant physiological activities. Little is known about the effects of miRNAs in disease resistance in apple ( Malus × domestica ). We globally profiled miRNAs in the apple cultivar Golden Delicious (GD) infected or not with the apple leaf spot fungus Alternaria alternaria f. sp. mali (ALT1), and identified 58 miRNAs that exhibited more than a 2-fold upregulation upon ALT1 infection. We identified a pair of miRNAs that target protein-coding genes involved in the defense response against fungal pathogens; Md-miR156ab targets a novel WRKY transcription factor, MdWRKYN1, which harbors a TIR and a WRKY domain. Md-miR395 targets another transcription factor, MdWRKY26, which contains two WRKY domains. Real-time PCR analysis showed that Md-miR156ab and Md-miR395 levels increased, while MdWRKYN1 and MdWRKY26 expression decreased in ALT1-inoculated GD leaves; furthermore, the overexpression of Md-miR156ab and Md-miR395 resulted in a significant reduction in MdWRKYN1 and MdWRKY26 expression. To investigate whether these miRNAs and their targets play a crucial role in plant defense, we overexpressed MdWRKYN1 or knocked down Md-miR156ab activity, which in both cases enhanced the disease resistance of the plants by upregulating the expression of the WRKY-regulated pathogenesis-related (PR) protein-encoding genes MdPR3-1, MdPR3-2, MdPR4, MdPR5, MdPR10-1 , and MdPR10-2 . In a similar analysis, we overexpressed MdWRKY26 or suppressed Md-miR395 activity, and found that many PR protein-encoding genes were also regulated by MdWRKY26 . In GD, ALT-induced Md-miR156ab and Md-miR395 suppress MdWRKYN1 and MdWRKY26 expression, thereby decreasing the expression of some PR genes, and resulting in susceptibility to ALT1.

  14. Validating clustering of molecular dynamics simulations using polymer models

    Directory of Open Access Journals (Sweden)

    Phillips Joshua L

    2011-11-01

    Full Text Available Abstract Background Molecular dynamics (MD simulation is a powerful technique for sampling the meta-stable and transitional conformations of proteins and other biomolecules. Computational data clustering has emerged as a useful, automated technique for extracting conformational states from MD simulation data. Despite extensive application, relatively little work has been done to determine if the clustering algorithms are actually extracting useful information. A primary goal of this paper therefore is to provide such an understanding through a detailed analysis of data clustering applied to a series of increasingly complex biopolymer models. Results We develop a novel series of models using basic polymer theory that have intuitive, clearly-defined dynamics and exhibit the essential properties that we are seeking to identify in MD simulations of real biomolecules. We then apply spectral clustering, an algorithm particularly well-suited for clustering polymer structures, to our models and MD simulations of several intrinsically disordered proteins. Clustering results for the polymer models provide clear evidence that the meta-stable and transitional conformations are detected by the algorithm. The results for the polymer models also help guide the analysis of the disordered protein simulations by comparing and contrasting the statistical properties of the extracted clusters. Conclusions We have developed a framework for validating the performance and utility of clustering algorithms for studying molecular biopolymer simulations that utilizes several analytic and dynamic polymer models which exhibit well-behaved dynamics including: meta-stable states, transition states, helical structures, and stochastic dynamics. We show that spectral clustering is robust to anomalies introduced by structural alignment and that different structural classes of intrinsically disordered proteins can be reliably discriminated from the clustering results. To our

  15. Velocity-Resolved LES (VR-LES) technique for simulating turbulent transport of high Schmidt number passive scalars

    Science.gov (United States)

    Verma, Siddhartha; Blanquart, Guillaume; P. K. Yeung Collaboration

    2011-11-01

    Accurate simulation of high Schmidt number scalar transport in turbulent flows is essential to studying pollutant dispersion, weather, and several oceanic phenomena. Batchelor's theory governs scalar transport in such flows, but requires further validation at high Schmidt and high Reynolds numbers. To this end, we use a new approach with the velocity field fully resolved, but the scalar field only partially resolved. The grid used is fine enough to resolve scales up to the viscous-convective subrange where the decaying slope of the scalar spectrum becomes constant. This places the cutoff wavenumber between the Kolmogorov scale and the Batchelor scale. The subgrid scale terms, which affect transport at the supergrid scales, are modeled under the assumption that velocity fluctuations are negligible beyond this cutoff wavenumber. To ascertain the validity of this technique, we performed a-priori testing on existing DNS data. This Velocity-Resolved LES (VR-LES) technique significantly reduces the computational cost of turbulent simulations of high Schmidt number scalars, and yet provides valuable information of the scalar spectrum in the viscous-convective subrange.

  16. Developing close combat behaviors for simulated soldiers using genetic programming techniques.

    Energy Technology Data Exchange (ETDEWEB)

    Pryor, Richard J.; Schaller, Mark J.

    2003-10-01

    Genetic programming is a powerful methodology for automatically producing solutions to problems in a variety of domains. It has been used successfully to develop behaviors for RoboCup soccer players and simple combat agents. We will attempt to use genetic programming to solve a problem in the domain of strategic combat, keeping in mind the end goal of developing sophisticated behaviors for compound defense and infiltration. The simplified problem at hand is that of two armed agents in a small room, containing obstacles, fighting against each other for survival. The base case and three changes are considered: a memory of positions using stacks, context-dependent genetic programming, and strongly typed genetic programming. Our work demonstrates slight improvements from the first two techniques, and no significant improvement from the last.

  17. Simulative Investigation on Spectral Efficiency of Unipolar Codes based OCDMA System using Importance Sampling Technique

    Science.gov (United States)

    Farhat, A.; Menif, M.; Rezig, H.

    2013-09-01

    This paper analyses the spectral efficiency of Optical Code Division Multiple Access (OCDMA) system using Importance Sampling (IS) technique. We consider three configurations of OCDMA system namely Direct Sequence (DS), Spectral Amplitude Coding (SAC) and Fast Frequency Hopping (FFH) that exploits the Fiber Bragg Gratings (FBG) based encoder/decoder. We evaluate the spectral efficiency of the considered system by taking into consideration the effect of different families of unipolar codes for both coherent and incoherent sources. The results show that the spectral efficiency of OCDMA system with coherent source is higher than the incoherent case. We demonstrate also that DS-OCDMA outperforms both others in terms of spectral efficiency in all conditions.

  18. Annual International Meeting on Medical Simulation (5th); Simulating Change Together, Held at the Radisson Miami Florida, on January 13-16, 2005

    Science.gov (United States)

    2005-02-01

    Challenging Superiors in the Healthcare Environment: The Two-Challenge Center for Medical Simulation Rule IMMS Singh Shashank Trauma and Awareness Pen...Rochester * Dallas Rochester MN Rochester NY Dallas TX SMartin Eason MD JD Marc Horowitz MD - Swati Argarwal, MD ETSU University of NM Stanford...Murphy, MD Simluation-based training allows educators in medicine to finally Swati Argarwal, MD address the needs of the adult learner. This high

  19. Determination of the overall migration from silicone baking moulds into simulants and food using 1H-NMR techniques.

    Science.gov (United States)

    Helling, Ruediger; Mieth, Anja; Altmann, Stefan; Simat, Thomas Joachim

    2009-03-01

    Different silicone baking moulds (37 samples) were characterized with respect to potential migrating substances using 1H-NMR, RP-HPLC-UV/ELSD and GC techniques. In all cases cyclic organosiloxane oligomers with the formula [Si(CH3)2-O]n were identified (n = 6 ... 50). Additionally, linear, partly hydroxyl-terminated organosiloxanes HO-[Si(CH3)2-O]n-H (n = 7 ... 20) were found in 13 samples. No substances other than siloxanes could be detected, meaning the migrants mainly consist of organopolysiloxanes. Based on this knowledge, a 1H-NMR quantification method for siloxanes was established for the analysis of both simulants and foodstuffs. Validation of the 1H-NMR method gave suitable performance characteristics: limit of detection 8.7 mg kg(-1) oil, coefficient of variation 7.8% (at a level of 1.0 mg kg(-1) food). Migration studies were carried out with simulants (olive oil, isooctane, ethanol (95%), Tenax) as well as preparation of different cakes. From the 1st to 10th experiment, siloxane migration into cakes only slightly decreased, with a significant dependence on fat content. Migration never exceeded a level of 21 mg kg(-1) (3 mg dm(-2)) and was, therefore, well below the overall migration limit of 60 mg kg(-1) (10 mg dm(-2)). However, migration behaviour into simulants differed completely from these results.

  20. Computer-assisted preoperative simulation for positioning and fixation of plate in 2-stage procedure combining maxillary advancement by distraction technique and mandibular setback surgery

    Directory of Open Access Journals (Sweden)

    Hideyuki Suenaga

    2016-01-01

    Conclusion: The implementation of the computer-assisted preoperative simulation for the positioning and fixation of plate in 2-stage orthognathic procedure using distraction technique and mandibular setback surgery yielded good results.

  1. Objective mapping of observed sub-surface mesoscale cold core eddy in the Bay of Bengal by stochastic inverse technique with tomographically simulated travel times

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, T.V.R.; Rao, M.M.M.; Sadhuram, Y.; Sridevi, B.; Maneesha, K.; SujithKumar, S.; Prasanna, P.L.; Murthy, K.S.R.

    of Bengal during south-west monsoon season and explore possibility to reconstruct the acoustic profile of the eddy by Stochastic Inverse Technique. A simulation experiment on forward and inverse problems for observed sound velocity perturbation field has...

  2. Electron Irradiation of Conjunctival Lymphoma-Monte Carlo Simulation of the Minute Dose Distribution and Technique Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Brualla, Lorenzo, E-mail: lorenzo.brualla@uni-due.de [NCTeam, Strahlenklinik, Universitaetsklinikum Essen, Essen (Germany); Zaragoza, Francisco J.; Sempau, Josep [Institut de Tecniques Energetiques, Universitat Politecnica de Catalunya, Barcelona (Spain); Wittig, Andrea [Department of Radiation Oncology, University Hospital Giessen and Marburg, Philipps-University Marburg, Marburg (Germany); Sauerwein, Wolfgang [NCTeam, Strahlenklinik, Universitaetsklinikum Essen, Essen (Germany)

    2012-07-15

    Purpose: External beam radiotherapy is the only conservative curative approach for Stage I non-Hodgkin lymphomas of the conjunctiva. The target volume is geometrically complex because it includes the eyeball and lid conjunctiva. Furthermore, the target volume is adjacent to radiosensitive structures, including the lens, lacrimal glands, cornea, retina, and papilla. The radiotherapy planning and optimization requires accurate calculation of the dose in these anatomical structures that are much smaller than the structures traditionally considered in radiotherapy. Neither conventional treatment planning systems nor dosimetric measurements can reliably determine the dose distribution in these small irradiated volumes. Methods and Materials: The Monte Carlo simulations of a Varian Clinac 2100 C/D and human eye were performed using the PENELOPE and PENEASYLINAC codes. Dose distributions and dose volume histograms were calculated for the bulbar conjunctiva, cornea, lens, retina, papilla, lacrimal gland, and anterior and posterior hemispheres. Results: The simulated results allow choosing the most adequate treatment setup configuration, which is an electron beam energy of 6 MeV with additional bolus and collimation by a cerrobend block with a central cylindrical hole of 3.0 cm diameter and central cylindrical rod of 1.0 cm diameter. Conclusions: Monte Carlo simulation is a useful method to calculate the minute dose distribution in ocular tissue and to optimize the electron irradiation technique in highly critical structures. Using a voxelized eye phantom based on patient computed tomography images, the dose distribution can be estimated with a standard statistical uncertainty of less than 2.4% in 3 min using a computing cluster with 30 cores, which makes this planning technique clinically relevant.

  3. Development of an interpretive simulation tool for the proton radiography technique

    Energy Technology Data Exchange (ETDEWEB)

    Levy, M. C., E-mail: levymc@stanford.edu [Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Ryutov, D. D.; Wilks, S. C.; Ross, J. S.; Huntington, C. M.; Fiuza, F.; Martinez, D. A.; Park, H.-S. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Kugland, N. L. [Lam Research Corporation, 4400 Cushing Parkway, Fremont, California 94538 (United States); Baring, M. G. [Department of Physics and Astronomy, Rice University, Houston, Texas 77005 (United States)

    2015-03-15

    Proton radiography is a useful diagnostic of high energy density (HED) plasmas under active theoretical and experimental development. In this paper, we describe a new simulation tool that interacts realistic laser-driven point-like proton sources with three dimensional electromagnetic fields of arbitrary strength and structure and synthesizes the associated high resolution proton radiograph. The present tool’s numerical approach captures all relevant physics effects, including effects related to the formation of caustics. Electromagnetic fields can be imported from particle-in-cell or hydrodynamic codes in a streamlined fashion, and a library of electromagnetic field “primitives” is also provided. This latter capability allows users to add a primitive, modify the field strength, rotate a primitive, and so on, while quickly generating a high resolution radiograph at each step. In this way, our tool enables the user to deconstruct features in a radiograph and interpret them in connection to specific underlying electromagnetic field elements. We show an example application of the tool in connection to experimental observations of the Weibel instability in counterstreaming plasmas, using ∼10{sup 8} particles generated from a realistic laser-driven point-like proton source, imaging fields which cover volumes of ∼10 mm{sup 3}. Insights derived from this application show that the tool can support understanding of HED plasmas.

  4. Comparison of rheological evaluation techniques and turbulent flow prediction of a simulated nuclear waste melter slurry

    International Nuclear Information System (INIS)

    Carleson, T.E.; Hart, R.E.; Drown, D.C.; Peterson, M.E.

    1987-03-01

    An experimental study was performed on a simulated nuclear waste slurry containing the type of waste sludge and glass-forming chemicals that will be converted to a stable glass in a high-temperature furnace. The rheological properties of the slurry must be determined in order to design the transport and mixing systems. The rheological parameters for the slurry were determined by a variety of viscometers including a rotational viscometer, a capillary tube viscometer, and a pipe flow apparatus. Experiments revealed the absence of wall slip and sufficient non-Newtonian behavior to require adjustments of the results. The slurry was characterized as a yield pseudoplastic fluid. Different rheological constants were obtained for all three viscometers. Predictions of the shear stress as a function of shear rate showed good agreement between the constants determined by the rotational viscometer and the pipe loop apparatus. Laminar and turbulent flows in the pipe loop correlated closely with a recent theoretical model. 16 refs., 16 figs., 5 tabs

  5. Development of an interpretive simulation tool for the proton radiography technique

    Science.gov (United States)

    Levy, M. C.; Ryutov, D. D.; Wilks, S. C.; Ross, J. S.; Huntington, C. M.; Fiuza, F.; Martinez, D. A.; Kugland, N. L.; Baring, M. G.; Park, H.-S.

    2015-03-01

    Proton radiography is a useful diagnostic of high energy density (HED) plasmas under active theoretical and experimental development. In this paper, we describe a new simulation tool that interacts realistic laser-driven point-like proton sources with three dimensional electromagnetic fields of arbitrary strength and structure and synthesizes the associated high resolution proton radiograph. The present tool's numerical approach captures all relevant physics effects, including effects related to the formation of caustics. Electromagnetic fields can be imported from particle-in-cell or hydrodynamic codes in a streamlined fashion, and a library of electromagnetic field "primitives" is also provided. This latter capability allows users to add a primitive, modify the field strength, rotate a primitive, and so on, while quickly generating a high resolution radiograph at each step. In this way, our tool enables the user to deconstruct features in a radiograph and interpret them in connection to specific underlying electromagnetic field elements. We show an example application of the tool in connection to experimental observations of the Weibel instability in counterstreaming plasmas, using ˜108 particles generated from a realistic laser-driven point-like proton source, imaging fields which cover volumes of ˜10 mm3. Insights derived from this application show that the tool can support understanding of HED plasmas.

  6. Optimal design of minimum mean-square error noise reduction algorithms using the simulated annealing technique.

    Science.gov (United States)

    Bai, Mingsian R; Hsieh, Ping-Ju; Hur, Kur-Nan

    2009-02-01

    The performance of the minimum mean-square error noise reduction (MMSE-NR) algorithm in conjunction with time-recursive averaging (TRA) for noise estimation is found to be very sensitive to the choice of two recursion parameters. To address this problem in a more systematic manner, this paper proposes an optimization method to efficiently search the optimal parameters of the MMSE-TRA-NR algorithms. The objective function is based on a regression model, whereas the optimization process is carried out with the simulated annealing algorithm that is well suited for problems with many local optima. Another NR algorithm proposed in the paper employs linear prediction coding as a preprocessor for extracting the correlated portion of human speech. Objective and subjective tests were undertaken to compare the optimized MMSE-TRA-NR algorithm with several conventional NR algorithms. The results of subjective tests were processed by using analysis of variance to justify the statistic significance. A post hoc test, Tukey's Honestly Significant Difference, was conducted to further assess the pairwise difference between the NR algorithms.

  7. A data-based technique for monitoring of wound rotor induction machines: A simulation study

    KAUST Repository

    Harrou, Fouzi

    2016-05-09

    Detecting faults induction machines is crucial for a safe operation of these machines. The aim of this paper is to present a statistical fault detection methodology for the detection of faults in three-phase wound rotor induction machines (WRIM). The proposed fault detection approach is based on the use of principal components analysis (PCA). However, conventional PCA-based detection indices, such as the T2T2 and the Q statistics, are not well suited to detect small faults because these indices only use information from the most recent available samples. Detection of small faults is one of the most crucial and challenging tasks in the area of fault detection and diagnosis. In this paper, a new statistical system monitoring strategy is proposed for detecting changes resulting from small shifts in several variables associated with WRIM. The proposed approach combines modeling using PCA modeling with the exponentially weighted moving average (EWMA) control scheme. In the proposed approach, EWMA control scheme is applied on the ignored principal components to detect the presence of faults. The performance of the proposed method is compared with those of the traditional PCA-based fault detection indices. The simulation results clearly show the effectiveness of the proposed method over the conventional ones, especially in the presence of faults with small magnitudes.

  8. Evaluation and simulation of event building techniques for a detector at the LHC

    CERN Document Server

    Spiwoks, R

    1995-01-01

    The main objectives of future experiments at the Large Hadron Collider are the search for the Higgs boson (or bosons), the verification of the Standard Model and the search beyond the Standard Model in a new energy range up to a few TeV. These experiments will have to cope with unprecedented high data rates and will need event building systems which can offer a bandwidth of 1 to 100GB/s and which can assemble events from 100 to 1000 readout memories at rates of 1 to 100kHz. This work investigates the feasibility of parallel event building sys- tems using commercially available high speed interconnects and switches. Studies are performed by building a small-scale prototype and by modelling this proto- type and realistic architectures with discrete-event simulations. The prototype is based on the HiPPI standard and uses commercially available VME-HiPPI interfaces and a HiPPI switch together with modular and scalable software. The setup operates successfully as a parallel event building system of limited size in...

  9. Nano structures for Medical Diagnostics Md

    International Nuclear Information System (INIS)

    Bellah, M.; Iqbal, S.M.; Bellah, M.; Iqbal, S.M.; Christensen, S.M.; Iqbal, S.M.; Iqbal, S.M.

    2012-01-01

    Nano technology is the art of manipulating materials on atomic or molecular scales especially to build nano scale structures and devices. The field is expanding quickly, and a lot of work is ongoing in the design, characterization, synthesis, and application of materials, structures, devices, and systems by controlling shape and size at nanometer scale. In the last few years, much work has been focused on the use of nano structures toward problems of biology and medicine. In this paper, we focus on the application of various nano structures and nano devices in clinical diagnostics and detection of important biological molecules. The discussion starts by introducing some basic techniques of micro-/nano scale fabrication that have enabled reproducible production of nano structures. The prospects, benefits, and limitations of using these novel techniques in the fields of bio detection and medical diagnostics are then discussed. Finally, the challenges of mass production and acceptance of nano technology by the medical community are considered.

  10. Monte Carlo simulation of X-ray imaging and spectroscopy experiments using quadric geometry and variance reduction techniques

    Science.gov (United States)

    Golosio, Bruno; Schoonjans, Tom; Brunetti, Antonio; Oliva, Piernicola; Masala, Giovanni Luca

    2014-03-01

    The simulation of X-ray imaging experiments is often performed using deterministic codes, which can be relatively fast and easy to use. However, such codes are generally not suitable for the simulation of even slightly more complex experimental conditions, involving, for instance, first-order or higher-order scattering, X-ray fluorescence emissions, or more complex geometries, particularly for experiments that combine spatial resolution with spectral information. In such cases, simulations are often performed using codes based on the Monte Carlo method. In a simple Monte Carlo approach, the interaction position of an X-ray photon and the state of the photon after an interaction are obtained simply according to the theoretical probability distributions. This approach may be quite inefficient because the final channels of interest may include only a limited region of space or photons produced by a rare interaction, e.g., fluorescent emission from elements with very low concentrations. In the field of X-ray fluorescence spectroscopy, this problem has been solved by combining the Monte Carlo method with variance reduction techniques, which can reduce the computation time by several orders of magnitude. In this work, we present a C++ code for the general simulation of X-ray imaging and spectroscopy experiments, based on the application of the Monte Carlo method in combination with variance reduction techniques, with a description of sample geometry based on quadric surfaces. We describe the benefits of the object-oriented approach in terms of code maintenance, the flexibility of the program for the simulation of different experimental conditions and the possibility of easily adding new modules. Sample applications in the fields of X-ray imaging and X-ray spectroscopy are discussed. Catalogue identifier: AERO_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AERO_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland

  11. 3D dose imaging for arc therapy techniques by means of Fricke gel dosimetry and dedicated Monte Carlo simulations

    International Nuclear Information System (INIS)

    Valente, Mauro; Castellano, Gustavo; Sosa, Carlos

    2008-01-01

    Full text: Radiotherapy is one of the most effective techniques for tumour treatment and control. During the last years, significant developments were performed regarding both irradiation technology and techniques. However, accurate 3D dosimetric techniques are nowadays not commercially available. Due to their intrinsic characteristics, traditional dosimetric techniques like ionisation chamber, film dosimetry or TLD do not offer proper continuous 3D dose mapping. The possibility of using ferrous sulphate (Fricke) dosimeters suitably fixed to a gel matrix, along with dedicated optical analysis methods, based on light transmission measurements for 3D absorbed dose imaging in tissue-equivalent materials, has become great interest in radiotherapy. Since Gore et al. showed in 1984 that the oxidation of ferrous ions to ferric ions still happen even when fixing the ferrous sulphate solution to a gelatine matrix, important efforts have been dedicated in developing and improving real continuous 3D dosimetric systems based on Fricke solution. The purpose of this work is to investigate the capability and suitability of Fricke gel dosimetry for arc therapy irradiations. The dosimetric system is mainly composed by Fricke gel dosimeters, suitably shaped in form of thin layers and optically analysed by means of visible light transmission measurements, acquiring sample images just before and after irradiation by means of a commercial flatbed-like scanner. Image acquisition, conversion to matrices and further analysis are accomplished by means of dedicated developed software, which includes suitable algorithms for optical density differences calculation and corresponding absorbed dose conversion. Dedicated subroutines allow 3D dose imaging reconstruction from single layer information, by means of computer tomography-like algorithms. Also, dedicated Monte Carlo (PENELOPE) subroutines have been adapted in order to achieve accurate simulation of arc therapy irradiation techniques

  12. Improving Conductivity Image Quality Using Block Matrix-based Multiple Regularization (BMMR Technique in EIT: A Simulation Study

    Directory of Open Access Journals (Sweden)

    Tushar Kanti Bera

    2011-06-01

    Full Text Available A Block Matrix based Multiple Regularization (BMMR technique is proposed for improving conductivity image quality in EIT. The response matrix (JTJ has been partitioned into several sub-block matrices and the highest eigenvalue of each sub-block matrices has been chosen as regularization parameter for the nodes contained by that sub-block. Simulated boundary data are generated for circular domain with circular inhomogeneity and the conductivity images are reconstructed in a Model Based Iterative Image Reconstruction (MoBIIR algorithm. Conductivity images are reconstructed with BMMR technique and the results are compared with the Single-step Tikhonov Regularization (STR and modified Levenberg-Marquardt Regularization (LMR methods. It is observed that the BMMR technique reduces the projection error and solution error and improves the conductivity reconstruction in EIT. Result show that the BMMR method also improves the image contrast and inhomogeneity conductivity profile and hence the reconstructed image quality is enhanced. ;doi:10.5617/jeb.170 J Electr Bioimp, vol. 2, pp. 33-47, 2011

  13. Milestone report on MD potential development for uranium silicide

    International Nuclear Information System (INIS)

    Yu, Jianguo; Zhang, Yongfeng; Hales, Jason Dean

    2016-01-01

    This report summarizes the progress on the interatomic potential development of triuranium-disilicide (U 3 Si 2 ) for molecular dynamics (MD) simulations. The development is based on the Tersoff type potentials for single element U and Si. The Si potential is taken from the literature and a Tersoff type U potential is developed in this project. With the primary focus on the U 3 Si 2 phase, some other U-Si systems such as U 3 Si are also included as a test of the transferability of the potentials for binary U-Si phases. Based on the potentials for unary U and Si, two sets of parameters for the binary U-Si system are developed using the Tersoff mixing rules and the cross-term fitting, respectively. The cross-term potential is found to give better results on the enthalpy of formation, lattice constants and elastic constants than those produced by the Tersoff mixing potential, with the reference data taken from either experiments or density functional theory (DFT) calculations. In particular, the results on the formation enthalpy and lattice constants for the U 3 Si 2 phase and lattice constants for the high temperature U 3 Si (h-U 3 Si) phase generated by the cross-term potential agree well with experimental data. Reasonable agreements are also reached on the elastic constants of U 3 Si 2 , on the formation enthalpy for the low temperature U 3 Si (m-U 3 Si) and h-U 3 Si phases, and on the lattice constants of m-U 3 Si phase. All these phases are predicted to be mechanically stable. The unary U potential is tested for three metallic U phases (α, β, γ). The potential is found capable to predict the cohesive energies well against experimental data for all three phases. It matches reasonably with previous experiments on the lattice constants and elastic constants of αU.

  14. Imposed Work of Breathing for Flow Meters with In-Line versus Flow-Through Technique during Simulated Neonatal Breathing.

    Directory of Open Access Journals (Sweden)

    Snorri Donaldsson

    Full Text Available The ability to determine airflow during nasal CPAP (NCPAP treatment without adding dead space or resistance would be useful when investigating the physiologic effects of different NCPAP systems on breathing. The aim of this study was to investigate the effect on pressure stability of different flow measuring devices at the in-line and flow-through position, using simulated neonatal breathing.Six different flow measure devices were evaluated by recording pressure changes and imposed work of breathing for breaths with 16 and 32 ml tidal volumes. The tests were performed initially with the devices in an in line position and with 5 and 10 L/min using flow through technique, without CPAP. The flow meters were then subsequently tested with an Infant Flow CPAP system at 3, 5 and 8 cm H2O pressure using flow through technique. The quality of the recorded signals was compared graphically.The resistance of the measuring devices generated pressure swings and imposed work of breathing. With bias flow, the resistance also generated CPAP pressure. Three of the devices had low resistance and generated no changes in pressure stability or CPAP pressure. The two devices intended for neonatal use had the highest measured resistance.The importance of pressure stability and increased work of breathing during non-invasive respiratory support are insufficiently studied. Clinical trials using flow-through technique have not focused on pressure stability. Our results indicate that a flow-through technique might be a way forward in obtaining a sufficiently high signal quality without the added effects of rebreathing and increased work of breathing. The results should stimulate further research and the development of equipment for dynamic flow measurements in neonates.

  15. Imposed Work of Breathing for Flow Meters with In-Line versus Flow-Through Technique during Simulated Neonatal Breathing.

    Science.gov (United States)

    Donaldsson, Snorri; Falk, Markus; Jonsson, Baldvin; Drevhammar, Thomas

    2015-01-01

    The ability to determine airflow during nasal CPAP (NCPAP) treatment without adding dead space or resistance would be useful when investigating the physiologic effects of different NCPAP systems on breathing. The aim of this study was to investigate the effect on pressure stability of different flow measuring devices at the in-line and flow-through position, using simulated neonatal breathing. Six different flow measure devices were evaluated by recording pressure changes and imposed work of breathing for breaths with 16 and 32 ml tidal volumes. The tests were performed initially with the devices in an in line position and with 5 and 10 L/min using flow through technique, without CPAP. The flow meters were then subsequently tested with an Infant Flow CPAP system at 3, 5 and 8 cm H2O pressure using flow through technique. The quality of the recorded signals was compared graphically. The resistance of the measuring devices generated pressure swings and imposed work of breathing. With bias flow, the resistance also generated CPAP pressure. Three of the devices had low resistance and generated no changes in pressure stability or CPAP pressure. The two devices intended for neonatal use had the highest measured resistance. The importance of pressure stability and increased work of breathing during non-invasive respiratory support are insufficiently studied. Clinical trials using flow-through technique have not focused on pressure stability. Our results indicate that a flow-through technique might be a way forward in obtaining a sufficiently high signal quality without the added effects of rebreathing and increased work of breathing. The results should stimulate further research and the development of equipment for dynamic flow measurements in neonates.

  16. Application of a local linearization technique for the solution of a system of stiff differential equations associated with the simulation of a magnetic bearing assembly

    Science.gov (United States)

    Kibler, K. S.; Mcdaniel, G. A.

    1981-01-01

    A digital local linearization technique was used to solve a system of stiff differential equations which simulate a magnetic bearing assembly. The results prove the technique to be accurate, stable, and efficient when compared to a general purpose variable order Adams method with a stiff option.

  17. Going beyond clustering in MD trajectory analysis: an application to villin headpiece folding.

    Directory of Open Access Journals (Sweden)

    Aruna Rajan

    2010-04-01

    Full Text Available Recent advances in computing technology have enabled microsecond long all-atom molecular dynamics (MD simulations of biological systems. Methods that can distill the salient features of such large trajectories are now urgently needed. Conventional clustering methods used to analyze MD trajectories suffer from various setbacks, namely (i they are not data driven, (ii they are unstable to noise and changes in cut-off parameters such as cluster radius and cluster number, and (iii they do not reduce the dimensionality of the trajectories, and hence are unsuitable for finding collective coordinates. We advocate the application of principal component analysis (PCA and a non-metric multidimensional scaling (nMDS method to reduce MD trajectories and overcome the drawbacks of clustering. To illustrate the superiority of nMDS over other methods in reducing data and reproducing salient features, we analyze three complete villin headpiece folding trajectories. Our analysis suggests that the folding process of the villin headpiece is structurally heterogeneous.

  18. Numerical models: Detailing and simulation techniques aimed at comparison with experimental data, support to test result interpretation

    International Nuclear Information System (INIS)

    Lin Chiwen

    2001-01-01

    This part of the presentation discusses the modelling details required and the simulation techniques available for analyses, facilitating the comparison with the experimental data and providing support for interpretation of the test results. It is organised to cover the following topics: analysis inputs; basic modelling requirements for reactor coolant system; method applicable for reactor cooling system; consideration of damping values and integration time steps; typical analytic models used for analysis of reactor pressure vessel and internals; hydrodynamic mass and fluid damping for the internal analysis; impact elements for fuel analysis; and PEI theorem and its applications. The intention of these topics is to identify the key parameters associated with models of analysis and analytical methods. This should provide proper basis for useful comparison with the test results

  19. A correction scheme for thermal conductivity measurement using the comparative cut-bar technique based on 3D numerical simulation

    International Nuclear Information System (INIS)

    Xing, Changhu; Folsom, Charles; Jensen, Colby; Ban, Heng; Marshall, Douglas W

    2014-01-01

    As an important factor affecting the accuracy of thermal conductivity measurement, systematic (bias) error in the guarded comparative axial heat flow (cut-bar) method was mostly neglected by previous researches. This bias is primarily due to the thermal conductivity mismatch between sample and meter bars (reference), which is common for a sample of unknown thermal conductivity. A correction scheme, based on finite element simulation of the measurement system, was proposed to reduce the magnitude of the overall measurement uncertainty. This scheme was experimentally validated by applying corrections on four types of sample measurements in which the specimen thermal conductivity is much smaller, slightly smaller, equal and much larger than that of the meter bar. As an alternative to the optimum guarding technique proposed before, the correction scheme can be used to minimize the uncertainty contribution from the measurement system with non-optimal guarding conditions. It is especially necessary for large thermal conductivity mismatches between sample and meter bars. (paper)

  20. Development of an immobilisation technique by cementation for non-radioactive simulated liquid waste, from Mo-99 production process

    International Nuclear Information System (INIS)

    Arva, E A; Marabini, S G; Varani, J L

    2012-01-01

    The Argentine Atomic Energy Commission (CNEA) is the responsible for developing a management nuclear waste disposal programme. This programme contemplates the strictly environmental safe and efficient management of the radioactive waste from different sources. Since 1985, CNEA has been producing commercially Mo-99 for medical use. In this process two types of liquid waste are produced. One of them has high alkaline (NaOH 3,5M) and aluminate contents. Since Mo-99 production started, such liquid waste was stored in specially designed containers during production, and after a decay period in smaller containers in interim storage conditions. As this waste is still a liquid, development of an immobilisation technique is required. Immobilisation of radioactive liquid waste by cementation is a frequently used technique, and will be studied in the present work using Mo-99 non-radioactive simulated liquid waste. In this second stage, a full scale (200 liters drum) cementation test using simulated non radioactive waste was carried out. Such test included: using the BEBA 201 mixing machine - the same that will be used with real waste in the future for 'tuning up' the process, construction of a specially designed temperature sensor for measuring the maximum temperature value (five different positions, four inside the drum and one outside) and the time elapsed after all components mixing. Finally, standard specimens (IRAM 1622) were made for mechanical resistance tests after cement setting at 28 days. The results show values of temperature not above 40 o C with the maximum at 12 hours before component mixing and compression strength of 14 MPa. Such values are compatible for a waste immobilisation process by cementation (author)

  1. Airflow and air quality simulations over the western mountainous region with a four-dimensional data assimilation technique

    Science.gov (United States)

    Yamada, Tetsuji; Kao, Chih-Yue; Bunker, Susan

    We apply a three-dimensional meteorological model with a four-dimensional data assimilation (4-DDA) technique to simulate diurnal variations of wind, temperature, water vapor, and turbulence in a region extending from the west coast to east of the Rockies and from northern Mexico to Wyoming. The wind data taken during the 1985 SCENES ( Subregional Cooperative Electric Utility, Dept. of Defense, National Park Service, and Environmental Protection Agency Study on Visibility) field experiments are successfully assimilated into the model through the 4-DDA technique by 'nudging' the modeled winds toward the observed winds. The modeled winds and turbulence fields are then used in a Lagrangian random-particle statistical model to investigate how pollutants from potential sources are transported and diffused. Finally, we calculate the ground concentrations through a kernel density estimator. Two scenarios in different weather patterns are investigated with simulation periods up to 6 days. One is associated with the evolution of a surface cold front and the other under a high-pressure stagnant condition. In the frontal case, the impact of air-mass movement on the ground concentrations of pollutants released from the Los Angeles area is well depicted by the model. Also, the pollutants produced from Los Angeles can be transported to the Grand Canyon area within 24 h. However, if we use only the data that were obtained from the regular NWS rawinsonde network, whose temporal and spatial resolutions are coarser than those of the special network, the plume goes north-northeast and never reaches the Grand Canyon area. In the stagnant case, the pollutants meander around the source area and can have significant impact on local air quality.

  2. Teaching aseptic technique for central venous access under ultrasound guidance: a randomized trial comparing didactic training alone to didactic plus simulation-based training.

    Science.gov (United States)

    Latif, Rana K; Bautista, Alexander F; Memon, Saima B; Smith, Elizabeth A; Wang, Chenxi; Wadhwa, Anupama; Carter, Mary B; Akca, Ozan

    2012-03-01

    Our goal was to determine whether simulation combined with didactic training improves sterile technique during ultrasound (US)-guided central venous catheter (CVC) insertion compared with didactic training alone among novices. We hypothesized that novices who receive combined didactic and simulation-based training would perform similarly to experienced residents in aseptic technique, knowledge, and perception of comfort during US-guided CVC insertion on a simulator. Seventy-two subjects were enrolled in a randomized, controlled trial of an educational intervention. Fifty-four novices were randomized into either the didactic group or the simulation combined with didactic group. Both groups received didactic training but the simulation combined with didactic group also received simulation-based CVC insertion training. Both groups were tested by demonstrating US-guided CVC insertion on a simulator. Aseptic technique was scored on 8 steps as "yes/no" and also using a 7-point Likert scale with 7 being "excellent technique" by a rater blinded to subject randomization. After initial testing, the didactic group was offered simulation-based training and retesting. Both groups also took a pre- and posttraining test of knowledge and rated their comfort with US and CVC insertion pre- and posttraining on a 5-point Likert scale. Subsequently, 18 experienced residents also took the test of knowledge, rated their comfort level, and were scored while performing aseptic US-guided CVC insertion using a simulator. The simulation combined with didactic group achieved a 167% (95% confidence interval [CI] 133%-167%) incremental increase in yes/no scores and 115% (CI 112%-127%) incremental increase in Likert scale ratings on aseptic technique compared with novices in the didactic group. Compared with experienced residents, simulation combined with didactic trained novices achieved an increase in aseptic scores with a 33.3% (CI 16.7%-50%) increase in yes/no ratings and a 20% (CI 13

  3. Validity of displacement energy evaluation using molecular statics simulation in Li2O

    International Nuclear Information System (INIS)

    Oda, Takuji; Tanaka, Satoru

    2007-01-01

    Understanding on radiation damage processes in Li-containing oxides has been regarded as an important subject in fusion blanket engineering, because radiation defects significantly affect the tritium behavior and the material property. The displacement energy is a key parameter that determines the number of defects created by radiation, and thus should be evaluated. However, its determination by experiments has not been done, probably due to difficulties arising from insulating property and complicated crystalline structures of Li-containing oxides. Molecular simulation is an alternative method to evaluate the displacement energy. Two techniques have been used; one is molecular dynamics simulation (MD) and the other is molecular statics simulation (MS) with the sudden approximation. MD can provide atomic-scale views of radiation events in the dynamics and has been more widely applied. MS seems to provide less reliable results than MD for lack of the dynamics. Nevertheless, its low computational cost could be attractive for application to ternary Li-containing oxides of complicated structures. In the present work, therefore, we aimed to verify how reliable values MS can provide in comparison with MD. Li2O was chosen to be a test material, because Li2O has the simplest structure among Li-containing oxides, which facilitates verification of MS results. We evaluated threshold displacement energies by MS for a few tens of different irradiation direction, and compared with previous MD results. DL-POLY code was used for MD, while GULP code for MS. In MD, lower threshold energies have been observed for Li than O (20 eV for Li and 50 eV for O on average). This tendency was also realized in MS (15 eV for Li and 40 eV for O), although values were often underestimated by a few tens %. As for dependence of displacement energy on irradiation direction, MS basically gave results different from MD, not only in quantity but also in quality. It was considered that MS is useful to

  4. Use of human patient simulation and the situation awareness global assessment technique in practical trauma skills assessment.

    Science.gov (United States)

    Hogan, Michael P; Pace, David E; Hapgood, Joanne; Boone, Darrell C

    2006-11-01

    Situation awareness (SA) is defined as the perception of elements in the environment within a volume of time and space, the comprehension of their meaning, and the projection of their status in the near future. This construct is vital to decision making in intense, dynamic environments. It has been used in aviation as it relates to pilot performance, but has not been applied to medical education. The most widely used objective tool for measuring trainee SA is the Situation Awareness Global Assessment Technique (SAGAT). The purpose of this study was to design and validate SAGAT for assessment of practical trauma skills, and to compare SAGAT results to traditional checklist style scoring. Using the Human Patient Simulator, we designed SAGAT for practical trauma skills assessment based on Advanced Trauma Life Support objectives. Sixteen subjects (four staff surgeons, four senior residents, four junior residents, and four medical students) participated in three scenarios each. They were assessed using SAGAT and traditional checklist assessment. A questionnaire was used to assess possible confounding factors in attaining SA and overall trainee satisfaction. SAGAT was found to show significant difference (analysis of variance; p level of training lending statistical support to construct validity. SAGAT was likewise found to display reliability (Cronbach's alpha 0.767), and significant scoring correlation with traditional checklist performance measures (Pearson's coefficient 0.806). The questionnaire revealed no confounding factors and universal satisfaction with the human patient simulator and SAGAT. SAGAT is a valid, reliable assessment tool for trauma trainees in the dynamic clinical environment created by human patient simulation. Information provided by SAGAT could provide specific feedback, direct individualized teaching, and support curriculum change. Introduction of SAGAT could improve the current assessment model for practical trauma education.

  5. Development of Quality Assessment Techniques for Large Eddy Simulation of Propulsion and Power Systems in Complex Geometries

    Energy Technology Data Exchange (ETDEWEB)

    Lacaze, Guilhem [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Oefelein, Joseph [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-03-01

    Large-eddy-simulation (LES) is quickly becoming a method of choice for studying complex thermo-physics in a wide range of propulsion and power systems. It provides a means to study coupled turbulent combustion and flow processes in parameter spaces that are unattainable using direct-numerical-simulation (DNS), with a degree of fidelity that can be far more accurate than conventional engineering methods such as the Reynolds-averaged Navier-Stokes (RANS) approx- imation. However, development of predictive LES is complicated by the complex interdependence of different type of errors coming from numerical methods, algorithms, models and boundary con- ditions. On the other hand, control of accuracy has become a critical aspect in the development of predictive LES for design. The objective of this project is to create a framework of metrics aimed at quantifying the quality and accuracy of state-of-the-art LES in a manner that addresses the myriad of competing interdependencies. In a typical simulation cycle, only 20% of the computational time is actually usable. The rest is spent in case preparation, assessment, and validation, because of the lack of guidelines. This work increases confidence in the accuracy of a given solution while min- imizing the time obtaining the solution. The approach facilitates control of the tradeoffs between cost, accuracy, and uncertainties as a function of fidelity and methods employed. The analysis is coupled with advanced Uncertainty Quantification techniques employed to estimate confidence in model predictions and calibrate model's parameters. This work has provided positive conse- quences on the accuracy of the results delivered by LES and will soon have a broad impact on research supported both by the DOE and elsewhere.

  6. Shoulder strengthening exercises adapted to specific shoulder pathologies can be selected using new simulation techniques: a pilot study.

    Science.gov (United States)

    Charbonnier, Caecilia; Lädermann, Alexandre; Kevelham, Bart; Chagué, Sylvain; Hoffmeyer, Pierre; Holzer, Nicolas

    2018-02-01

    Shoulder strength training exercises represent a major component of rehabilitation protocols designed for conservative or postsurgical management of shoulder pathologies. Numerous methods are described for exercising each shoulder muscle or muscle group. Limited information is available to assess potential deleterious effects of individual methods with respect to specific shoulder pathologies. Thus, the goal of this pilot study was to use a patient-specific 3D measurement technique coupling medical imaging and optical motion capture for evaluation of a set of shoulder strength training exercises regarding glenohumeral, labral and subacromial compression, as well as elongation of the rotator cuff muscles. One volunteer underwent magnetic resonance imaging (MRI) and motion capture of the shoulder. Motion data from the volunteer were recorded during three passive rehabilitation exercises and twenty-nine strengthening exercises targeting eleven of the most frequently trained shoulder muscles or muscle groups and using four different techniques when available. For each exercise, glenohumeral and labral compression, subacromial space height and rotator cuff muscles elongation were measured on the entire range of motion. Significant differences in glenohumeral, subacromial and labral compressions were observed between sets of exercises targeting individual shoulder muscles. Muscle lengths computed by simulation compared to MRI measurements showed differences of 0-5%. This study represents the first screening of shoulder strengthening exercises to identify potential deleterious effects on the shoulder joint. Motion capture combined with medical imaging allows for reliable assessment of glenohumeral, labral and subacromial compression, as well as muscle-tendon elongation during shoulder strength training exercises.

  7. 3MdB: the Mexican Million Models database

    Science.gov (United States)

    Morisset, C.; Delgado-Inglada, G.

    2014-10-01

    The 3MdB is an original effort to construct a large multipurpose database of photoionization models. This is a more modern version of a previous attempt based on Cloudy3D and IDL tools. It is accessed by MySQL requests. The models are obtained using the well known and widely used Cloudy photoionization code (Ferland et al, 2013). The database is aimed to host grids of models with different references to identify each project and to facilitate the extraction of the desired data. We present here a description of the way the database is managed and some of the projects that use 3MdB. Anybody can ask for a grid to be run and stored in 3MdB, to increase the visibility of the grid and the potential side applications of it.

  8. Methodological issues in lipid bilayer simulations

    NARCIS (Netherlands)

    Anezo, C; de Vries, AH; Holtje, HD; Tieleman, DP; Marrink, SJ

    2003-01-01

    Methodological issues in molecular dynamics (MD) simulations, such as the treatment of long-range electrostatic interactions or the type of pressure coupling, have important consequences for the equilibrium properties observed. We report a series of long (up to 150 ns) MD simulations of

  9. Systematic study of the effects of scaling techniques in numerical simulations with application to enhanced geothermal systems

    Science.gov (United States)

    Heinze, Thomas; Jansen, Gunnar; Galvan, Boris; Miller, Stephen A.

    2016-04-01

    Numerical modeling is a well established tool in rock mechanics studies investigating a wide range of problems. Especially for estimating seismic risk of a geothermal energy plants a realistic rock mechanical model is needed. To simulate a time evolving system, two different approaches need to be separated: Implicit methods for solving linear equations are unconditionally stable, while explicit methods are limited by the time step. However, explicit methods are often preferred because of their limited memory demand, their scalability in parallel computing, and simple implementation of complex boundary conditions. In numerical modeling of explicit elastoplastic dynamics the time step is limited by the rock density. Mass scaling techniques, which increase the rock density artificially by several orders, can be used to overcome this limit and significantly reduce computation time. In the context of geothermal energy this is of great interest because in a coupled hydro-mechanical model the time step of the mechanical part is significantly smaller than for the fluid flow. Mass scaling can also be combined with time scaling, which increases the rate of physical processes, assuming that processes are rate independent. While often used, the effect of mass and time scaling and how it may influence the numerical results is rarely-mentioned in publications, and choosing the right scaling technique is typically performed by trial and error. Also often scaling techniques are used in commercial software packages, hidden from the untrained user. To our knowledge, no systematic studies have addressed how mass scaling might affect the numerical results. In this work, we present results from an extensive and systematic study of the influence of mass and time scaling on the behavior of a variety of rock-mechanical models. We employ a finite difference scheme to model uniaxial and biaxial compression experiments using different mass and time scaling factors, and with physical models

  10. Report from LHC MD 2171: Amplitude dependent closest tune approach from normal and skew octupoles

    CERN Document Server

    Maclean, Ewen Hamish; Persson, Tobias Hakan Bjorn; Carlier, Felix Simon; CERN. Geneva. ATS Department

    2018-01-01

    Simulation-based studies predict significant amplitude-dependent closest tune approach can be generated by skew octupole sources in conjunction with their normal octupolar counterparts. This has the potential to significantly influence Landau damping at small β∗, where skew octupole errors in the experimental IRs, together with b4 introduced by the Landau octupoles, is predicted to cause large distortion of the tune footprint. This MD aimed to perform a first exploration of these predictions with beam, by enhancing skew octupole sources in the IRs at injection and measuring amplitude detuning with free kicks in the plane approaching the coupling resonance.

  11. Swiss national MD-PhD-program: an outcome analysis.

    Science.gov (United States)

    Kuehnle, Katrin; Winkler, David T; Meier-Abt, Peter J

    2009-09-19

    This study aims at a first evaluation of the outcome of the Swiss national MD-PhD program during the last 16 years. One hundred and twenty six former and current students in the Swiss national MD-PhD program were surveyed via a Web-based questionnaire in September 2007. Twenty-four questions assessed information regarding participant demographics, information on the PhD thesis and publication activity, current positions and research activity, as well as participant's opinions, attitudes and career goals. Eighty questionnaires were received from 126 MD-PhD students and graduates (63.5% response rate). The responders consisted of present students (36%), former graduates (56%), and dropouts (8%). The percentage of women in the program was 23%, and the average duration of the program was 4.2 +/- 1.4 years. Research interests were predominantly in the fields of neuroscience, immunology, molecular biology and cancer research. A considerable portion of the MD-PhD graduates had an excellent publication record stemming from their PhD research work, and 89% were planning to continue a research-orientated career. Over 50% of those MD-PhD graduates completing their thesis before 2002 had already reached an assistant or full professor position at the time of the survey. Nearly all participants considered the MD-PhD training helpful to their career and high quality standards were assigned to the acquired practical and intellectual skills. However, criticism was expressed concerning the general mentoring and the career related mentoring. Moreover, general mentoring and career related mentoring were significantly less well perceived in research groups employing more than seven PhD students at the same time. The MD-PhD students and graduates surveyed were satisfied with their education and most of them continued a research-orientated career. Regarding the overall positive evaluation, this study supports the view that MD-PhD graduates are well qualified for a successful career in

  12. BayesMD: flexible biological modeling for motif discovery

    DEFF Research Database (Denmark)

    Tang, Man-Hung Eric; Krogh, Anders; Winther, Ole

    2008-01-01

    We present BayesMD, a Bayesian Motif Discovery model with several new features. Three different types of biological a priori knowledge are built into the framework in a modular fashion. A mixture of Dirichlets is used as prior over nucleotide probabilities in binding sites. It is trained on trans......We present BayesMD, a Bayesian Motif Discovery model with several new features. Three different types of biological a priori knowledge are built into the framework in a modular fashion. A mixture of Dirichlets is used as prior over nucleotide probabilities in binding sites. It is trained...

  13. Molecular dynamics simulation of three plastic additives' diffusion in polyethylene terephthalate.

    Science.gov (United States)

    Li, Bo; Wang, Zhi-Wei; Lin, Qin-Bao; Hu, Chang-Ying

    2017-06-01

    Accurate diffusion coefficient data of additives in a polymer are of paramount importance for estimating the migration of the additives over time. This paper shows how this diffusion coefficient can be estimated for three plastic additives [2-(2'-hydroxy-5'-methylphenyl) (UV-P), 2,6-di-tert-butyl-4-methylphenol (BHT) and di-(2-ethylhexyl) phthalate (DEHP)] in polyethylene terephthalate (PET) using the molecular dynamics (MD) simulation method. MD simulations were performed at temperatures of 293-433 K. The diffusion coefficient was calculated through the Einstein relationship connecting the data of mean-square displacement at different times. Comparison of the diffusion coefficients simulated by the MD simulation technique, predicted by the Piringer model and experiments, showed that, except for a few samples, the MD-simulated values were in agreement with the experimental values within one order of magnitude. Furthermore, the diffusion process for additives is discussed in detail, and four factors - the interaction energy between additive molecules and PET, fractional free volume, molecular shape and size, and self-diffusion of the polymer - are proposed to illustrate the microscopic diffusion mechanism. The movement trajectories of additives in PET cell models suggested that the additive molecules oscillate slowly rather than hopping for a long time. Occasionally, when a sufficiently large hole was created adjacently, the molecule could undergo spatial motion by jumping into the free-volume hole and consequently start a continuous oscillation and hop. The results indicate that MD simulation is a useful approach for predicting the microstructure and diffusion coefficient of plastic additives, and help to estimate the migration level of additives from PET packaging.

  14. Apple MdACS6 Regulates Ethylene Biosynthesis During Fruit Development Involving Ethylene-Responsive Factor.

    Science.gov (United States)

    Li, Tong; Tan, Dongmei; Liu, Zhi; Jiang, Zhongyu; Wei, Yun; Zhang, Lichao; Li, Xinyue; Yuan, Hui; Wang, Aide

    2015-10-01

    Ethylene biosynthesis in plants involves different 1-aminocyclopropane-1-carboxylic acid synthase (ACS) genes. The regulation of each ACS gene during fruit development is unclear. Here, we characterized another apple (Malus×domestica) ACS gene, MdACS6. The transcript of MdACS6 was observed not only in fruits but also in other tissues. During fruit development, MdACS6 was initiated at a much earlier stage, whereas MdACS3a and MdACS1 began to be expressed at 35 d before harvest and immediateley after harvest, respectively. Moreover, the enzyme activity of MdACS6 was significantly lower than that of MdACS3a and MdACS1, accounting for the low ethylene biosynthesis in young fruits. Overexpression of MdACS6 (MdACS6-OE) by transient assay in apple showed enhanced ethylene production, and MdACS3a was induced in MdACS6-OE fruits but not in control fruits. In MdACS6 apple fruits silenced by the virus-induced gene silencing (VIGS) system (MdACS6-AN), neither ethylene production nor MdACS3a transcript was detectable. In order to explore the mechanism through which MdACS3a was induced in MdACS6-OE fruits, we investigated the expression of apple ethylene-responsive factor (ERF) genes. The results showed that the expression of MdERF2 was induced in MdACS6-OE fruits and inhibited in MdACS6-AN fruits. Yeast one-hybrid assay showed that MdERF2 protein could bind to the promoter of MdACS3a. Moreover, down-regulation of MdERF2 in apple flesh callus led to a decrease of MdACS3a expression, demonstrating the regulation of MdERF2 on MdACS3a. The mechanism through which MdACS6 regulates the action of MdACS3a was discussed. © The Author 2015. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  15. Apple (Malus domestica) MdERF2 negatively affects ethylene biosynthesis during fruit ripening by suppressing MdACS1 transcription.

    Science.gov (United States)

    Li, Tong; Jiang, Zhongyu; Zhang, Lichao; Tan, Dongmei; Wei, Yun; Yuan, Hui; Li, Tianlai; Wang, Aide

    2016-12-01

    Ripening in climacteric fruit requires the gaseous phytohormone ethylene. Although ethylene signaling has been well studied, knowledge of the transcriptional regulation of ethylene biosynthesis is still limited. Here we show that an apple (Malus domestica) ethylene response factor, MdERF2, negatively affects ethylene biosynthesis and fruit ripening by suppressing the transcription of MdACS1, a gene that is critical for biosynthesis of ripening-related ethylene. Expression of MdERF2 was suppressed by ethylene during ripening of apple fruit, and we observed that MdERF2 bound to the promoter of MdACS1 and directly suppressed its transcription. Moreover, MdERF2 suppressed the activity of the promoter of MdERF3, a transcription factor that we found to bind to the MdACS1 promoter, thereby increasing MdACS1 transcription. We determined that the MdERF2 and MdERF3 proteins directly interact, and this interaction suppresses the binding of MdERF3 to the MdACS1 promoter. Moreover, apple fruit with transiently downregulated MdERF2 expression showed higher ethylene production and faster ripening. Our results indicate that MdERF2 negatively affects ethylene biosynthesis and fruit ripening in apple by suppressing the transcription of MdACS1 via multiple mechanisms, thereby acting as an antagonist of positive ripening regulators. Our findings offer a deep understanding of the transcriptional regulation of ethylene biosynthesis during climacteric fruit ripening. © 2016 The Authors The Plant Journal © 2016 John Wiley & Sons Ltd.

  16. A Simulation Based Analysis of Motor Unit Number Index (MUNIX) Technique Using Motoneuron Pool and Surface Electromyogram Models

    Science.gov (United States)

    Li, Xiaoyan; Rymer, William Zev; Zhou, Ping

    2013-01-01

    Motor unit number index (MUNIX) measurement has recently achieved increasing attention as a tool to evaluate the progression of motoneuron diseases. In our current study, the sensitivity of the MUNIX technique to changes in motoneuron and muscle properties was explored by a simulation approach utilizing variations on published motoneuron pool and surface electromyogram (EMG) models. Our simulation results indicate that, when keeping motoneuron pool and muscle parameters unchanged and varying the input motor unit numbers to the model, then MUNIX estimates can appropriately characterize changes in motor unit numbers. Such MUNIX estimates are not sensitive to different motor unit recruitment and rate coding strategies used in the model. Furthermore, alterations in motor unit control properties do not have a significant effect on the MUNIX estimates. Neither adjustment of the motor unit recruitment range nor reduction of the motor unit firing rates jeopardizes the MUNIX estimates. The MUNIX estimates closely correlate with the maximum M wave amplitude. However, if we reduce the amplitude of each motor unit action potential rather than simply reduce motor unit number, then MUNIX estimates substantially underestimate the motor unit numbers in the muscle. These findings suggest that the current MUNIX definition is most suitable for motoneuron diseases that demonstrate secondary evidence of muscle fiber reinnervation. In this regard, when MUNIX is applied, it is of much importance to examine a parallel measurement of motor unit size index (MUSIX), defined as the ratio of the maximum M wave amplitude to the MUNIX. However, there are potential limitations in the application of the MUNIX methods in atrophied muscle, where it is unclear whether the atrophy is accompanied by loss of motor units or loss of muscle fiber size. PMID:22514208

  17. A new technique to characterize CT scanner bow-tie filter attenuation and applications in human cadaver dosimetry simulations

    Science.gov (United States)

    Li, Xinhua; Shi, Jim Q.; Zhang, Da; Singh, Sarabjeet; Padole, Atul; Otrakji, Alexi; Kalra, Mannudeep K.; Xu, X. George; Liu, Bob

    2015-01-01

    Purpose: To present a noninvasive technique for directly measuring the CT bow-tie filter attenuation with a linear array x-ray detector. Methods: A scintillator based x-ray detector of 384 pixels, 307 mm active length, and fast data acquisition (model X-Scan 0.8c4-307, Detection Technology, FI-91100 Ii, Finland) was used to simultaneously detect radiation levels across a scan field-of-view. The sampling time was as short as 0.24 ms. To measure the body bow-tie attenuation on a GE Lightspeed Pro 16 CT scanner, the x-ray tube was parked at the 12 o’clock position, and the detector was centered in the scan field at the isocenter height. Two radiation exposures were made with and without the bow-tie in the beam path. Each readout signal was corrected for the detector background offset and signal-level related nonlinear gain, and the ratio of the two exposures gave the bow-tie attenuation. The results were used in the geant4 based simulations of the point doses measured using six thimble chambers placed in a human cadaver with abdomen/pelvis CT scans at 100 or 120 kV, helical pitch at 1.375, constant or variable tube current, and distinct x-ray tube starting angles. Results: Absolute attenuation was measured with the body bow-tie scanned at 80–140 kV. For 24 doses measured in six organs of the cadaver, the median or maximum difference between the simulation results and the measurements on the CT scanner was 8.9% or 25.9%, respectively. Conclusions: The described method allows fast and accurate bow-tie filter characterization. PMID:26520720

  18. Lessons learned from accident simulation exercises and their implications for operation of the IPSN Centre Technique de Crise

    International Nuclear Information System (INIS)

    Manesse, D.; Ney, J.; Crabol, B.; Ginot, P.

    1990-01-01

    The Centre Technique de Crise (CTC) of the Institut de Protection et de Surete Nucleaire (IPSN) has an important role to play in the event of an accident at a nuclear installation of Electricite de France (EdF) concerning diagnosis of the situation and forecasting its evolution. For this purpose the CTS is organized into various groups; only that responsible for the evaluation of the radiological consequences is considered in the present paper. Since the beginning of the eighties numerous simulations of nuclear accidents have been organized both by the public authorities and by the nuclear operators. These exercises, of growing complexity, are distinguished according to the type of installation concerned, the scenario (with and without a simulator), the equipment involved, the participants (local and national officials), the accident phase used (at the time of the accident or post-accident), the use of actual or pre-determined meteorological conditions etc.. Different combinations are imposed as a function of the specific aims of each exercise. Numerous lessons have been drawn progressively from these very varied exercises for the operation of the CTC and, in particular, of the Radiological Consequences Group. The principal Lessons concern: development of calculation and mapping tools, specific liaison with the national meteorological services, modification of the centre's facilities, composition of the team and definition of the role of each of its members, improved liaison with the Site Evaluation Group and the provision of appropriate documentation. The need for continuous training of duty teams in the form of presentations and exercises has also been confirmed

  19. Milestone report on MD potential development for uranium silicide

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Jianguo [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Zhang, Yongfeng [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Hales, Jason Dean [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.

    2016-03-01

    This report summarizes the progress on the interatomic potential development of triuranium-disilicide (U3Si2) for molecular dynamics (MD) simulations. The development is based on the Tersoff type potentials for single element U and Si. The Si potential is taken from the literature and a Tersoff type U potential is developed in this project. With the primary focus on the U3Si2 phase, some other U-Si systems such as U3Si are also included as a test of the transferability of the potentials for binary U-Si phases. Based on the potentials for unary U and Si, two sets of parameters for the binary U-Si system are developed using the Tersoff mixing rules and the cross-term fitting, respectively. The cross-term potential is found to give better results on the enthalpy of formation, lattice constants and elastic constants than those produced by the Tersoff mixing potential, with the reference data taken from either experiments or density functional theory (DFT) calculations. In particular, the results on the formation enthalpy and lattice constants for the U3Si2 phase and lattice constants for the high temperature U3Si (h-U3Si) phase generated by the cross-term potential agree well with experimental data. Reasonable agreements are also reached on the elastic constants of U3Si2, on the formation enthalpy for the low temperature U3Si (m-U3Si) and h-U3Si phases, and on the lattice constants of m-U3Si phase. All these phases are predicted to be mechanically stable. The unary U potential is tested for three metallic U phases (α, β, γ). The potential is found capable to predict the cohesive energies well against experimental data for all three phases. It matches reasonably with previous experiments on the lattice constants and elastic constants of αU.

  20. 76 FR 51887 - Safety Zone; Patuxent River, Patuxent River, MD

    Science.gov (United States)

    2011-08-19

    ...-AA00 Safety Zone; Patuxent River, Patuxent River, MD AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a temporary safety zone during the ``NAS Patuxent River... held over certain waters of the Patuxent River adjacent to Patuxent River, Maryland from September 1...