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Sample records for comparative simulation study

  1. A simulation study comparing aberration detection algorithms for syndromic surveillance

    Directory of Open Access Journals (Sweden)

    Painter Ian

    2007-03-01

    Full Text Available Abstract Background The usefulness of syndromic surveillance for early outbreak detection depends in part on effective statistical aberration detection. However, few published studies have compared different detection algorithms on identical data. In the largest simulation study conducted to date, we compared the performance of six aberration detection algorithms on simulated outbreaks superimposed on authentic syndromic surveillance data. Methods We compared three control-chart-based statistics, two exponential weighted moving averages, and a generalized linear model. We simulated 310 unique outbreak signals, and added these to actual daily counts of four syndromes monitored by Public Health – Seattle and King County's syndromic surveillance system. We compared the sensitivity of the six algorithms at detecting these simulated outbreaks at a fixed alert rate of 0.01. Results Stratified by baseline or by outbreak distribution, duration, or size, the generalized linear model was more sensitive than the other algorithms and detected 54% (95% CI = 52%–56% of the simulated epidemics when run at an alert rate of 0.01. However, all of the algorithms had poor sensitivity, particularly for outbreaks that did not begin with a surge of cases. Conclusion When tested on county-level data aggregated across age groups, these algorithms often did not perform well in detecting signals other than large, rapid increases in case counts relative to baseline levels.

  2. Comparative Simulation Study on Synchronous Generators Sudden Short Circuits

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    Lucian Lupşa-Tătaru

    2009-01-01

    Full Text Available Although of a great extent in time, the research works directed at studying transients in synchronous generators have not yet provided fully sufficient comparative studies in respect to sudden short circuits of the machine. The present paper puts forward novel and comprehensive process models for dynamic simulation of short circuit faults of initially unloaded synchronous generators, using the generalized d-q-0 mathematical model as starting point in derivation. Distinct from the time-domain analysis, the technique proposed here allows an effective comparative overview by employing a specialized procedure to perform repeated time-domain simulations accompanied by peak values recording for the various circumstances. The time consuming matrix numerical inversion at each step of integration, usually performed when selecting currents as state variables, is eliminated by advancing the process models in a convenient split matrix form that allows the symbolic processing. Also, the computational efficiency is being increased by introducing a set of auxiliary variables common to different state equations. The models derivation is carried out without altering the structural equations of the generalized d-q-0 mathematical model of synchronous generators whilst the simulation results are both compared and discussed in detail.

  3. COMPARATIVE STUDY OF TERTIARY WASTEWATER TREATMENT BY COMPUTER SIMULATION

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    Stefania Iordache

    2010-01-01

    Full Text Available The aim of this work is to asses conditions for implementation of a Biological Nutrient Removal (BNR process in theWastewater Treatment Plant (WWTP of Moreni city (Romania. In order to meet the more increased environmentalregulations, the wastewater treatment plant that was studied, must update the actual treatment process and have tomodernize it. A comparative study was undertaken of the quality of effluents that could be obtained by implementationof biological nutrient removal process like A2/O (Anaerobic/Anoxic/Oxic and VIP (Virginia Plant Initiative aswastewater tertiary treatments. In order to asses the efficiency of the proposed treatment schemata based on the datamonitored at the studied WWTP, it were realized computer models of biological nutrient removal configurations basedon A2/O and VIP process. Computer simulation was realized using a well-known simulator, BioWin by EnviroSimAssociates Ltd. The simulation process allowed to obtain some data that can be used in design of a tertiary treatmentstage at Moreni WWTP, in order to increase the efficiency in operation.

  4. Does interprofessional simulation increase self-efficacy: a comparative study

    OpenAIRE

    Watters, Colm; Reedy, Gabriel; Ross, Alastair; Morgan, Nicola J; Handslip, Rhodri; Jaye, Peter

    2015-01-01

    Objectives In this work, we have compared uniprofessional and interprofessional versions of a simulation education intervention, in an attempt to understand more about whether it improves trainees’ self-efficacy. \\ud \\ud \\ud Background Interprofessionalism has been climbing the healthcare agenda for over 50 years. Simulation education attempts to create an environment for healthcare professionals to learn, without potential safety risks for patients. Integrating simulation and interprofession...

  5. Wavelet Estimators in Nonparametric Regression: A Comparative Simulation Study

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    Anestis Antoniadis

    2001-06-01

    Full Text Available Wavelet analysis has been found to be a powerful tool for the nonparametric estimation of spatially-variable objects. We discuss in detail wavelet methods in nonparametric regression, where the data are modelled as observations of a signal contaminated with additive Gaussian noise, and provide an extensive review of the vast literature of wavelet shrinkage and wavelet thresholding estimators developed to denoise such data. These estimators arise from a wide range of classical and empirical Bayes methods treating either individual or blocks of wavelet coefficients. We compare various estimators in an extensive simulation study on a variety of sample sizes, test functions, signal-to-noise ratios and wavelet filters. Because there is no single criterion that can adequately summarise the behaviour of an estimator, we use various criteria to measure performance in finite sample situations. Insight into the performance of these estimators is obtained from graphical outputs and numerical tables. In order to provide some hints of how these estimators should be used to analyse real data sets, a detailed practical step-by-step illustration of a wavelet denoising analysis on electrical consumption is provided. Matlab codes are provided so that all figures and tables in this paper can be reproduced.

  6. Right-Censored Nonparametric Regression: A Comparative Simulation Study

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    Dursun Aydın

    2016-11-01

    Full Text Available This paper introduces the operating of the selection criteria for right-censored nonparametric regression using smoothing spline. In order to transform the response variable into a variable that contains the right-censorship, we used the KaplanMeier weights proposed by [1], and [2]. The major problem in smoothing spline method is to determine a smoothing parameter to obtain nonparametric estimates of the regression function. In this study, the mentioned parameter is chosen based on censored data by means of the criteria such as improved Akaike information criterion (AICc, Bayesian (or Schwarz information criterion (BIC and generalized crossvalidation (GCV. For this purpose, a Monte-Carlo simulation study is carried out to illustrate which selection criterion gives the best estimation for censored data.

  7. Networked Control System Simulation Methods:A Comparative Study

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    Naser Pariz

    2008-03-01

    Full Text Available In this paper, we examine several frameworks for NCS simulation: a MATLAB-based package called True Time, the Agent/Plant addition to the ns-2 network simulator, and other MATLAB -based frameworks. We analyze the accuracy, speed, and ease of use of two different methods of simulating system dynamics using the Agent/Plant extension to ns-2. We also introduce a hybrid system model, which we simulate in MATLAB, to verify the simulation of system dynamics in ns-2. We then proceed to use the ns-2 framework and Agent/Plant, using an Euler approximation for the continuous system dynamics, to simulate both the inverted pendulum and pitch control systems on the network topology described in Chapter 2. We examine the performance of these systems as the traffic on the network increases, due to both additional NCSs and non-NCS cross-traffic. We also examine the effects of non-random vs. random sample scheduling, and observe the periodicity of packet loss under both scheduling policies.

  8. Comparative Study of the Effectiveness of Three Learning Environments: Hyper-Realistic Virtual Simulations, Traditional Schematic Simulations and Traditional Laboratory

    Science.gov (United States)

    Martinez, Guadalupe; Naranjo, Francisco L.; Perez, Angel L.; Suero, Maria Isabel; Pardo, Pedro J.

    2011-01-01

    This study compared the educational effects of computer simulations developed in a hyper-realistic virtual environment with the educational effects of either traditional schematic simulations or a traditional optics laboratory. The virtual environment was constructed on the basis of Java applets complemented with a photorealistic visual output.…

  9. Simulation and identification of the fractional Brownian motion: a bibliographical and comparative study

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    Jean-Francois Coeurjolly

    2000-09-01

    Full Text Available We present a non exhaustive bibliographical and comparative study of the problem of simulation and identification of the fractional Brownian motion. The discussed implementation is realized within the software S-plus 3.4. A few simulations illustrate this work. Furthermore, we propose a test based on the asymptotic behavior of a self-similarity parameter's estimator to explore the quality of different generators. This procedure, easily computable, allows us to extract an efficient method of simulation. In the Appendix are described the S-plus scripts related to simulation and identification methods of the fBm.

  10. Comparative study of the effectiveness of three learning environments: Hyper-realistic virtual simulations, traditional schematic simulations and traditional laboratory

    Directory of Open Access Journals (Sweden)

    Maria Isabel Suero

    2011-10-01

    Full Text Available This study compared the educational effects of computer simulations developed in a hyper-realistic virtual environment with the educational effects of either traditional schematic simulations or a traditional optics laboratory. The virtual environment was constructed on the basis of Java applets complemented with a photorealistic visual output. This new virtual environment concept, which we call hyper-realistic, transcends basic schematic simulation; it provides the user with a more realistic perception of a physical phenomenon being simulated. We compared the learning achievements of three equivalent, homogeneous groups of undergraduates—an experimental group who used only the hyper-realistic virtual laboratory, a first control group who used a schematic simulation, and a second control group who used the traditional laboratory. The three groups received the same theoretical preparation and carried out equivalent practicals in their respective learning environments. The topic chosen for the experiment was optical aberrations. An analysis of variance applied to the data of the study demonstrated a statistically significant difference (p value <0.05 between the three groups. The learning achievements attained by the group using the hyper-realistic virtual environment were 6.1 percentage points higher than those for the group using the traditional schematic simulations and 9.5 percentage points higher than those for the group using the traditional laboratory.

  11. Simulation and Comparative Study of CO2 Capture in Underwater LSS Using HYSYS

    Institute of Scientific and Technical Information of China (English)

    HUANG Zhi-guang; WANG Rong-shun; GU An-zhong

    2007-01-01

    Long-duration manned submersible missions require advanced life support systems (LSS) that can regenerate air, water and food. This study presented two CO2-capture methods used in LSS, CO2 removal with diethanolamine (DEA) and cryo-freezing with liquid oxygen. Both processes were modeled and simulated with HYSYS simulator. The performance of the two types of module was compared, and the results showed that the latter could be advantageous over the former in specific power, facility scale, operation reliability and safety. Economic evaluation suggested the latter cost only half of the former. Cryo-capture module could be an alternative for underwater LSS because of its efficiency and compactness.

  12. Thermal expansion coefficient of graphene using molecular dynamics simulation: A comparative study on potential functions

    Science.gov (United States)

    Ghasemi, Hamid; Rajabpour, Ali

    2017-01-01

    In this paper, we studied the thermal expansion coefficient (TEC) of pristine graphene sheets (GSs) using molecular dynamics (MD) simulation. We validated our model with previous studies employing AIREBO potential function and repeated the same simulation with the optimized Tersoff potential function. We also discussed the differences of the results and the corresponding reasons: evaluating the negative TEC of graphene by measuring the C-C bond length and out-of-plane vibrations of the GS. We finally showed that the ripples and wrinkles are more represented over the GS during the simulation with the AIREBO potential function rather than the optimized Tersoff. Comparing the results of both potential functions; it is seen that the results obtained by AIREBO potential function are in better agreement with those reported by previous scholars.

  13. Comparative Design Studies for the BESSY FEL Program using the MEDUSA and GENESIS Simulation Codes

    CERN Document Server

    Freund, H

    2005-01-01

    The BESSY FEL is based on a seeded cascade of High Gain Harmonic Generation (HGHG) sections followed by an amplifier to produce coherent and stable short wavelength output. Here, we report on comparative design studies carried out using the MEDUSA [1], and GENESIS [2] simulation codes. These two codes have each been used to successfully predict a variety of FEL designs and have agreed well with a number of important experiments. In addition, they were included in a comparative study of FEL simulation [3] that reported substantial agreement between the codes for the specific configurations studied. However, these codes are based on different assumptions. GENESIS treats the particle dynamics using a wiggler-averaged orbit approximation, the transverse electromagnetic field is treated using a field solver, and harmonics are not included. MEDUSA does not use the wiggler-averaged orbit approximation to treat particle dynamics, the transverse fields are treated using a Gaussian modal superposition, and harmonics ar...

  14. Five-Phase Modular External Rotor PM Machines with Different Rotor Poles: A Comparative Simulation Study

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    A. S. Abdel-Khalik

    2012-01-01

    Full Text Available The performance of fault-tolerant modular permanent magnet machines depends on the proper selection of the pole and slot numbers which result in negligible coupling between phases. The preferred slot and pole number combinations eliminate the effect of low-order harmonics in the stator magnetomotive force and thereby the vibration and stray loss are reduced. In this paper, three external rotor machines with identical machine dimensions are designed with different slots per phase per pole ratios. A simulation study is carried out using finite element analysis to compare the performance of the three machines in terms of machine torque density, ripple torque, core loss, and machine efficiency. A mathematical model based on the conventional-phase-model approach is also used for the comparative study. The simulation study is extended to depict machine performance under fault conditions.

  15. A comparative study of MONTEBURNS and MCNPX 2.6.0 codes in ADS simulations

    Energy Technology Data Exchange (ETDEWEB)

    Barros, Graiciany P.; Pereira, Claubia; Veloso, Maria A.F.; Velasquez, Carlos E.; Costa, Antonella L., E-mail: gbarros@ufmg.br, E-mail: claubia@nuclear.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Nuclear

    2013-07-01

    The possible use of the MONTEBURNS and MCNPX 2.6.0 codes in Accelerator-driven systems (ADSs) simulations for fuel evolution description is discussed. ADSs are investigated for fuel breeding and long-lived fission product transmutation so simulations of fuel evolution have a great relevance. The burnup/depletion capability is present in both studied codes. MONTEBURNS code links Monte Carlo N-Particle Transport Code (MCNP) to the radioactive decay burnup code ORIGEN2, whereas MCNPX depletion/ burnup capability is a linked process involving steady-state flux calculations by MCNPX and nuclide depletion calculations by CINDER90. A lead-cooled accelerator-driven system fueled with thorium was simulated and the results obtained using MONTEBURNS code and the results from MCNPX 2.6.0 code were compared. The system criticality and the variation of the actinide inventory during the burnup were evaluated and the results indicate a similar behavior between the results of each code. (author)

  16. Comparing Simulation Results with Traditional PRA Model on a Boiling Water Reactor Station Blackout Case Study

    Energy Technology Data Exchange (ETDEWEB)

    Zhegang Ma; Diego Mandelli; Curtis Smith

    2011-07-01

    A previous study used RELAP and RAVEN to conduct a boiling water reactor station black-out (SBO) case study in a simulation based environment to show the capabilities of the risk-informed safety margin characterization methodology. This report compares the RELAP/RAVEN simulation results with traditional PRA model results. The RELAP/RAVEN simulation run results were reviewed for their input parameters and output results. The input parameters for each simulation run include various timing information such as diesel generator or offsite power recovery time, Safety Relief Valve stuck open time, High Pressure Core Injection or Reactor Core Isolation Cooling fail to run time, extended core cooling operation time, depressurization delay time, and firewater injection time. The output results include the maximum fuel clad temperature, the outcome, and the simulation end time. A traditional SBO PRA model in this report contains four event trees that are linked together with the transferring feature in SAPHIRE software. Unlike the usual Level 1 PRA quantification process in which only core damage sequences are quantified, this report quantifies all SBO sequences, whether they are core damage sequences or success (i.e., non core damage) sequences, in order to provide a full comparison with the simulation results. Three different approaches were used to solve event tree top events and quantify the SBO sequences: “W” process flag, default process flag without proper adjustment, and default process flag with adjustment to account for the success branch probabilities. Without post-processing, the first two approaches yield incorrect results with a total conditional probability greater than 1.0. The last approach accounts for the success branch probabilities and provides correct conditional sequence probabilities that are to be used for comparison. To better compare the results from the PRA model and the simulation runs, a simplified SBO event tree was developed with only four

  17. A comparative study of divergence cleaning methods of magnetic field in the solar coronal numerical simulation

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    Xueshang eFeng

    2016-03-01

    Full Text Available This paper presents a comparative study of divergence cleaning methods of magnetic field in the solar coronal three-dimensional numerical simulation. For such purpose, the diffusive method, projection method, generalized Lagrange multiplier method and constrained-transport method are used. All these methods are combined with a finite-volume scheme based on a six-component grid system in spherical coordinates. In order to see the performance between the four divergence cleaning methods, solar coronal numerical simulation for Carrington rotation 2056 has been studied. Numerical results show that the average relative divergence error is around $10^{-4.5}$ for the constrained-transport method, while about $10^{-3.1}- 10^{-3.6}$ for the other three methods. Although there exist some differences in the average relative divergence errors for the four employed methods, our tests show they can all produce basic structured solar wind.

  18. Coronal Mass Ejections and Dimmings: A Comparative Study using MHD Simulations and SDO Observations

    Science.gov (United States)

    Jin, Meng; Cheung, Mark; DeRosa, Marc L.; Nitta, Nariaki; Schrijver, Karel

    2017-08-01

    Solar coronal dimmings have been observed extensively in the past two decades. Due to their close association with coronal mass ejections (CMEs), there is a critical need to improve our understanding of the physical processes that cause dimmings and determine their relationship with CMEs. In this study, we investigate coronal dimmings by combining simulation and observational efforts. By utilizing a data-driven global magnetohydrodynamics model (AWSoM: Alfven-wave Solar Model), we simulate coronal dimmings resulting from different CME energetics and flux rope configurations. We synthesize the emissions of different EUV spectral bands/lines and compare with SDO/AIA and EVE observations. A detailed analysis of simulation and observation data suggests that the “core” dimming is mainly caused by the mass loss from the CME, while the “remote” dimming could have a different origin (e.g., plasma heating). Moreover, the interaction between the erupting flux rope with different orientations and the global solar corona could significantly influence the coronal dimming patterns. Using metrics such as dimming depth, dimming slope, and recovery time, we investigate the relationship between dimmings and CME properties (e.g., CME mass, CME speed) in the simulation. Our result suggests that coronal dimmings encode important information about CMEs. We also discuss how our knowledge about solar coronal dimmings could be extended to the study of stellar CMEs.

  19. Comparative Study of Biofuel and Biodiesel Blend with Mineral Diesel Using One-Dimensional Simulation

    Science.gov (United States)

    Rahim, Rafidah; Mamat, Rizalman; Yusof Taib, Mohd

    2012-09-01

    This study is intended to perform one-dimensional simulation for four cylinders diesel engine by using various type of fuels and blend. The testing of biofuels properties conducted according to ASTM standards. The physical properties of the fuel are investigated in chemical laboratory which comprises of flash point, kinematic viscosity, density, cloud & pour point, acid value and moisture content. There are three types of fuels used throughout the study, which are straight vegetable oil (SVO), biodiesel 20% blend (B20) and biodiesel 5% blend (B5). Then, the properties data from the experiment will be used in the simulation GT Power software. Simulation tests have been run with the aim of obtaining comparative measures of torque, power, specific fuel consumption and volumetric efficiency. The results is use to evaluate and analyze the performance of diesel engine running with the mentioned fuels above. The comparison performances for each fuel have been discussed. There is no significant difference in the engine performance when fueled with B5 and diesel. There is only about one percent lower of B5 and four percent higher of B20 and SVO compare to diesel fuel.

  20. Comparative Study of Different SPH Schemes on Simulating Violent Water Wave Impact Flows

    Institute of Scientific and Technical Information of China (English)

    郑兴; 马庆位; 段文洋

    2014-01-01

    Free surface flows are of significant interest in Computational Fluid Dynamics (CFD). However, violent water wave impact simulation especially when free surface breaks or impacts on solid wall can be a big challenge for many CFD techniques. Smoothed Particle Hydrodynamics (SPH) has been reported as a robust and reliable method for simulating violent free surface flows. Weakly compressible SPH (WCSPH) uses an equation of state with a large sound speed, and the results of the WCSPH can induce a noisy pressure field and spurious oscillation of pressure in time history for wave impact problem simulation. As a remedy, the truly incompressible SPH (ISPH) technique was introduced, which uses a pressure Poisson equation to calculate the pressure. Although the pressure distribution in the whole field obtained by ISPH is smooth, the stability of the techniques is still an open discussion. In this paper, a new free surface identification scheme and solid boundary handling method are introduced to improve the accuracy of ISPH. This modified ISPH is used to study dam breaking flow and violent tank sloshing flows. On the comparative study of WCSPH and ISPH, the accuracy and efficiency are assessed and the results are compared with the experimental data.

  1. Comparative study of different SPH schemes on simulating violent water wave impact flows

    Science.gov (United States)

    Zheng, Xing; Ma, Qing-wei; Duan, Wen-yang

    2014-12-01

    Free surface flows are of significant interest in Computational Fluid Dynamics (CFD). However, violent water wave impact simulation especially when free surface breaks or impacts on solid wall can be a big challenge for many CFD techniques. Smoothed Particle Hydrodynamics (SPH) has been reported as a robust and reliable method for simulating violent free surface flows. Weakly compressible SPH (WCSPH) uses an equation of state with a large sound speed, and the results of the WCSPH can induce a noisy pressure field and spurious oscillation of pressure in time history for wave impact problem simulation. As a remedy, the truly incompressible SPH (ISPH) technique was introduced, which uses a pressure Poisson equation to calculate the pressure. Although the pressure distribution in the whole field obtained by ISPH is smooth, the stability of the techniques is still an open discussion. In this paper, a new free surface identification scheme and solid boundary handling method are introduced to improve the accuracy of ISPH. This modified ISPH is used to study dam breaking flow and violent tank sloshing flows. On the comparative study of WCSPH and ISPH, the accuracy and efficiency are assessed and the results are compared with the experimental data.

  2. Exporting simulation technology to the Philippines: a comparative study of traditional versus simulation methods for teaching intravenous cannulation.

    Science.gov (United States)

    Sotto, Juan Alejandro R; Ayuste, Eduardo C; Bowyer, Mark W; Almonte, Josefina R; Dofitas, Rodney B; Lapitan, Marie C M; Pimentel, Elisabeth A; Ritter, E Matthew; Wherry, David C

    2009-01-01

    This study examines effectiveness of a donated Laerdal Virtual I.V. simulator when compared with traditional methods of teaching intravenous (IV) cannulation to third year medical students in the Philippines. Forty novice Filipino medical students viewed an instructional video on how to start intravenous lines and were then randomly divided into two groups of twenty. The "Traditional" group observed an IV insertion on an actual patient performed by an experienced practitioner, and then subsequently performed an IV on an actual patient which was videotaped. The "Simulation" group practiced the Virtual I.V. simulator until they successfully completed level three using the "doctor" setting. These students then performed an IV on an actual patient which was videotaped. The videotapes for both groups were reviewed by two pre-trained (Inter-rater reliability of > or =0.84) observers who were blinded to the group using a previously validated checklist for IV insertion. Students trained on the Virtual I.V. showed significantly greater success in successfully starting an IV on an actual patient (40% VS. 15%, p<0.05), decreased constrictive band time (p<.05), increased raw score on the check list (p<.03), and decreased overall time to start an IV (p<.05). The technology was well received but wider application in the non western world is limited by lack of in country company support and the relative expense.

  3. Comparative Study of Reverse Algorithms via Artificial Neural Networks Based on Simulated Indentation Tests

    Institute of Scientific and Technical Information of China (English)

    Somsak Swaddiwudhipong; Edy Harsono; Liu Zishun

    2008-01-01

    The advances in the instrumented indentation equipments and the need to assess the properties of materials of small volume such as those constitute the micro-electro-mechanical devices, micro-electronic packages, and thin films have propelled the interest in material characterization via indentation tests. The load-displacement curves and their charactedstics, namely, the curvature of the loading path, C, and the ra-tio of the remaining and total work done, WR/WT, can be conveniently obtained from finite element simula-tions for various elasto-plastic material properties. The paper reports the comparative study on two reverse neural networks algorithms involving several combinations of databases established from the results ob-tained from simulated indentation tests. The performance of each set of results is analyzed and the most appropriate algodthm identified and reported. The approach with the selected neural networks model has great potential in practical applications on the characterization of a small volume of materials.

  4. Comparative study of the biodegradability of porous silicon films in simulated body fluid.

    Science.gov (United States)

    Peckham, J; Andrews, G T

    2015-01-01

    The biodegradability of oxidized microporous, mesoporous and macroporous silicon films in a simulated body fluid with ion concentrations similar to those found in human blood plasma were studied using gravimetry. Film dissolution rates were determined by periodically weighing the samples after removal from the fluid. The dissolution rates for microporous silicon were found to be higher than those for mesoporous silicon of comparable porosity. The dissolution rate of macroporous silicon was much lower than that for either microporous or mesoporous silicon. This is attributed to the fact that its specific surface area is much lower than that of microporous and mesoporous silicon. Using an equation adapted from [Surf. Sci. Lett. 306 (1994), L550-L554], the dissolution rate of porous silicon in simulated body fluid can be estimated if the film thickness and specific surface area are known.

  5. Parametric analyses of summative scores may lead to conflicting inferences when comparing groups: A simulation study.

    Science.gov (United States)

    Khan, Asaduzzaman; Chien, Chi-Wen; Bagraith, Karl S

    2015-04-01

    To investigate whether using a parametric statistic in comparing groups leads to different conclusions when using summative scores from rating scales compared with using their corresponding Rasch-based measures. A Monte Carlo simulation study was designed to examine between-group differences in the change scores derived from summative scores from rating scales, and those derived from their corresponding Rasch-based measures, using 1-way analysis of variance. The degree of inconsistency between the 2 scoring approaches (i.e. summative and Rasch-based) was examined, using varying sample sizes, scale difficulties and person ability conditions. This simulation study revealed scaling artefacts that could arise from using summative scores rather than Rasch-based measures for determining the changes between groups. The group differences in the change scores were statistically significant for summative scores under all test conditions and sample size scenarios. However, none of the group differences in the change scores were significant when using the corresponding Rasch-based measures. This study raises questions about the validity of the inference on group differences of summative score changes in parametric analyses. Moreover, it provides a rationale for the use of Rasch-based measures, which can allow valid parametric analyses of rating scale data.

  6. A Comparative study of hyperon equations of state in supernova simulations

    CERN Document Server

    Char, Prasanta; Bandyopadhyay, Debades

    2015-01-01

    A comparative study of the $\\Lambda$ hyperon equations of state of Banik, Hempel and Banyopadhyay (BHB) \\citep{bhb} and \\citet{shen11} (denoted as HShen $\\Lambda$) for core collapse supernova (CCSN) simulations is carried out in this work. The dynamical evolution of a protoneutron star (PNS) into a black hole is investigated in core collapse supernova simulations in the general relativistic one dimensional code using the BHB$\\Lambda \\phi$ and HShen $\\Lambda$ equation of state (EoS) tables and different progenitor models from Woosley and Heger \\citep{Woos}. Radial profiles of the mass fractions of baryons, the density as well as the temperature in the PNS at different moments in time, are compared for both EoS tables. The behaviour of the central density of the PNS with time is demonstrated for those two $\\Lambda$ hyperon EoS tables and compared with their corresponding nuclear EoS tables. It is observed that the black hole formation time is higher in the BHB$\\Lambda \\phi$ case than in the HShen $\\Lambda$ EoS ...

  7. Comparing the Cost-Effectiveness of Simulation Modalities: A Case Study of Peripheral Intravenous Catheterization Training

    Science.gov (United States)

    Isaranuwatchai, Wanrudee; Brydges, Ryan; Carnahan, Heather; Backstein, David; Dubrowski, Adam

    2014-01-01

    While the ultimate goal of simulation training is to enhance learning, cost-effectiveness is a critical factor. Research that compares simulation training in terms of educational- and cost-effectiveness will lead to better-informed curricular decisions. Using previously published data we conducted a cost-effectiveness analysis of three…

  8. Do Professional Practices among Malaysian Private Healthcare Providers Differ? A Comparative Study using Simulated Patients.

    Science.gov (United States)

    Alabid, Alamin Hassan M A; Ibrahim, Mohamed Izham Mohamed; Hassali, Mohamed Azmi

    2013-12-01

    Malaysia, a South East Asian country, legally permits general medical practitioners in private clinics to dispense medicines. This possibly can dilute the pharmacist role in the provision of healthcare and pharmaceutical care and deprive patients to benefit from these services. This study explored, assessed and compared the current status of medicines labeling, patient's counseling, and symptomatic diagnosis by general practitioners and community pharmacists. This study used trained Simulated Patients (SP), who participated in a scenario of common cold symptoms at private clinics and community pharmacies. SPs explored medication labeling, patients counseling and symptomatic diagnosis undertaken by general practitioners and community pharmacists. Later, study authors assessed and compared these practices. The study was conducted during June 2011 in Penang, Malaysia. The study used descriptive statistics and Fisher-exact test to analyze data. Regarding patients counseling standard, among 100 visits by simulated patients, 64 (64%) from community pharmacists provided information about the medicine name, its indication, dosage and route of administration versus 17 (42.5%) general practitioners during 40 visits (p=0.024). Concerning adherence to labeling standard, for instance, only in one pharmacy visit, (1%) the pharmacist wrote the name of the patient on the medication label versus in 32 (80%) of doctors' visits, the doctors adhered to this labeling standard (p<0.001). In all doctors' visits (n=40, 100%), SPs were asked about symptoms, whereas in 87 (87%) CPs' visits, pharmacists fulfilled this counseling standard (p=0.02). Although pharmacists showed less compliance to medicine labeling and symptomatic diagnosis compared to doctors, their counseling of patients was better. Separation will definitely contribute to more concentration of each provider on his/her roles and improve and direct the experiences and skills towards being more patient oriented.

  9. A comparative study of interatomic potentials for copper and aluminum gas phase sputter atom transport simulations

    CERN Document Server

    Kuwata, K T; Doyle, J R

    2003-01-01

    A comparative study of interatomic potential models for use in gas phase sputter atom transport simulations is presented. Quantum chemical interatomic potentials for argon-copper and argon-aluminum are calculated using Kohn-Sham density functional theory utilizing the PW91 functional. These potentials (PW91) are compared to the commonly used Born-Mayer potentials calculated by Abrahamson [Phys. Rev. 178 (1969) 76] using the Thomas-Fermi-Dirac model (TFD) and the screened Coulomb potentials derived from the 'universal' form calculated by Ziegler, Biersack and Littmark (ZBL). Monte Carlo simulations of gas phase sputter atom transport were performed to determine the average energy of atoms arriving at the substrate versus pressure for the three potential models. Overall, the ZBL potential gave results in much better agreement with the PW91 potential than the TFD potential. A characteristic thermalization pressure-distance product of approx 0.11 mTorr cm was found for both copper and aluminum using the PW91 pote...

  10. Comparing the cost-effectiveness of simulation modalities: a case study of peripheral intravenous catheterization training.

    Science.gov (United States)

    Isaranuwatchai, Wanrudee; Brydges, Ryan; Carnahan, Heather; Backstein, David; Dubrowski, Adam

    2014-05-01

    While the ultimate goal of simulation training is to enhance learning, cost-effectiveness is a critical factor. Research that compares simulation training in terms of educational- and cost-effectiveness will lead to better-informed curricular decisions. Using previously published data we conducted a cost-effectiveness analysis of three simulation-based programs. Medical students (n = 15 per group) practiced in one of three 2-h intravenous catheterization skills training programs: low-fidelity (virtual reality), high-fidelity (mannequin), or progressive (consisting of virtual reality, task trainer, and mannequin simulator). One week later, all performed a transfer test on a hybrid simulation (standardized patient with a task trainer). We used a net benefit regression model to identify the most cost-effective training program via paired comparisons. We also created a cost-effectiveness acceptability curve to visually represent the probability that one program is more cost-effective when compared to its comparator at various 'willingness-to-pay' values. We conducted separate analyses for implementation and total costs. The results showed that the progressive program had the highest total cost (p willingness-to-pay value, the progressive training program was generally most educationally- and cost-effective. Our analyses suggest that a progressive program that strategically combines simulation modalities provides a cost-effective solution. More generally, we have introduced how a cost-effectiveness analysis may be applied to simulation training; a method that medical educators may use to investment decisions (e.g., purchasing cost-effective and educationally sound simulators).

  11. Comparative Study of Reynolds Averaged and Embedded Large Eddy Simulations of a High Pressure Turbine Stage

    Science.gov (United States)

    Jones, Sam; Jemcov, Aleksandar; Corke, Thomas

    2016-11-01

    An Embedded Large Eddy Simulation (ELES) approach is used to simulate the flow path through a high pressure turbine stage that includes the entry duct, stationary inlet and exit guide vanes, and a rotor. The flowfield around the rotor is simulated using LES. A Reynolds Averaged Simulation (RAS) is used for the rest of the flow domain. The interface between RAS and LES domains uses the RAS turbulence quantities as a means of obtaining length scales that are used in computing the vorticity required to trigger a proper energy cascade within the LES part of the flow field. The objective is to resolve the unsteady vortical motions that eminate from the gap between the rotor tip and duct walls that are presumably under-resolved in a RAS approach. A comparative analysis between RAS and ELES approaches for this turbomachinery problem is then presented. APS Fellow.

  12. Comparing Simulations of AGN Feedback

    CERN Document Server

    Richardson, Mark L A; Devriendt, Julien; Slyz, Adrianne; Thacker, Robert J; Dubois, Yohan; Wurster, James; Silk, Joseph

    2016-01-01

    We perform adaptive mesh refinement (AMR) and smoothed particle hydrodynamics (SPH) cosmological zoom simulations of a region around a forming galaxy cluster, comparing the ability of the methods to handle successively more complex baryonic physics. In the simplest, non-radiative case, the two methods are in good agreement with each other, but the SPH simulations generate central cores with slightly lower entropies and virial shocks at slightly larger radii, consistent with what has been seen in previous studies. The inclusion of radiative cooling, star formation, and stellar feedback leads to much larger differences between the two methods. Most dramatically, at z=5, rapid cooling in the AMR case moves the accretion shock well within the virial radius, while this shock remains near the virial radius in the SPH case, due to excess heating, coupled with poorer capturing of the shock width. On the other hand, the addition of feedback from active galactic nuclei (AGN) to the simulations results in much better ag...

  13. Empirically simulated study to compare and validate sampling methods used in aerial surveys of wildlife populations

    NARCIS (Netherlands)

    Khaemba, W.M.; Stein, A.; Rasch, D.; Leeuw, de J.; Georgiadis, N.

    2001-01-01

    This paper compares the distribution, sampling and estimation of abundance for two animal species in an African ecosystem by means of an intensive simulation of the sampling process under a geographical information system (GIS) environment. It focuses on systematic and random sampling designs, commo

  14. Empirically simulated study to compare and validate sampling methods used in aerial surveys of wildlife populations

    NARCIS (Netherlands)

    Khaemba, W.M.; Stein, A.; Rasch, D.; Leeuw, de J.; Georgiadis, N.

    2001-01-01

    This paper compares the distribution, sampling and estimation of abundance for two animal species in an African ecosystem by means of an intensive simulation of the sampling process under a geographical information system (GIS) environment. It focuses on systematic and random sampling designs,

  15. Comparative Study of Different Stochastic Weather Generators for Long-Term Climate Data Simulation

    Directory of Open Access Journals (Sweden)

    Sushant Mehan

    2017-03-01

    Full Text Available Climate is one of the single most important factors affecting watershed ecosystems and water resources. The effect of climate variability and change has been studied extensively in some places; in many places, however, assessments are hampered by limited availability of long-term continuous climate data. Weather generators provide a means of synthesizing long-term climate data that can then be used in natural resource assessments. Given their potential, there is the need to evaluate the performance of the generators; in this study, three commonly used weather generators—CLImate GENerator (CLIGEN, Long Ashton Research Station Weather Generator (LARS-WG, and Weather Generators (WeaGETS were compared with regard to their ability to capture the essential statistical characteristics of observed data (distribution, occurrence of wet and dry spells, number of snow days, growing season temperatures, and growing degree days. The study was based on observed 1966–2015 weather station data from the Western Lake Erie Basin (WLEB, from which 50 different realizations were generated, each spanning 50 years. Both CLIGEN and LARS-WG performed fairly well with respect to representing the statistical characteristics of observed precipitation and minimum and maximum temperatures, although CLIGEN tended to overestimate values at the extremes. This generator also overestimated dry sequences by 18%–30% and snow-day counts by 12%–19% when considered over the entire WLEB. It (CLIGEN was, however, well able to simulate parameters specific to crop growth such as growing degree days and had an added advantage over the other generators in that it simulates a larger number of weather variables. LARS-WG overestimated wet sequence counts across the basin by 15%–38%. In addition, the optimal growth period simulated by LARS-WG also exceeded that obtained from observed data by 16%–29% basin-wide. Preliminary results with WeaGETS indicated that additional evaluation is

  16. Simulation study comparing high-purity germanium and cadmium zinc telluride detectors for breast imaging

    Science.gov (United States)

    Campbell, D. L.; Peterson, T. E.

    2014-11-01

    We conducted simulations to compare the potential imaging performance for breast cancer detection with High-Purity Germanium (HPGe) and Cadmium Zinc Telluride (CZT) systems with 1% and 3.8% energy resolution at 140 keV, respectively. Using the Monte Carlo N-Particle (MCNP5) simulation package, we modelled both 5 mm-thick CZT and 10 mm-thick HPGe detectors with the same parallel-hole collimator for the imaging of a breast/torso phantom. Simulated energy spectra were generated, and planar images were created for various energy windows around the 140 keV photopeak. Relative sensitivity and scatter and the torso fractions were calculated along with tumour contrast and signal-to-noise ratios (SNR). Simulations showed that utilizing a ±1.25% energy window with an HPGe system better suppressed torso background and small-angle scattered photons than a comparable CZT system using a -5%/+10% energy window. Both systems provided statistically similar contrast and SNR, with HPGe providing higher relative sensitivity. Lowering the counts of HPGe images to match CZT count density still yielded equivalent contrast between HPGe and CZT. Thus, an HPGe system may provide equivalent breast imaging capability at lower injected radioactivity levels when acquiring for equal imaging time.

  17. Comparative approaches from empirical to mechanistic simulation modelling in Land Evaluation studies

    Science.gov (United States)

    Manna, P.; Basile, A.; Bonfante, A.; Terribile, F.

    2009-04-01

    The Land Evaluation (LE) comprise the evaluation procedures to asses the attitudes of the land to a generic or specific use (e.g. biomass production). From local to regional and national scale the approach to the land use planning should requires a deep knowledge of the processes that drive the functioning of the soil-plant-atmosphere system. According to the classical approaches the assessment of attitudes is the result of a qualitative comparison between the land/soil physical properties and the land use requirements. These approaches have a quick and inexpensive applicability; however, they are based on empirical and qualitative models with a basic knowledge structure specifically built for a specific landscape and for the specific object of the evaluation (e.g. crop). The outcome from this situation is the huge difficulties in the spatial extrapolation of the LE results and the rigidity of the system. Modern techniques instead, rely on the application of mechanistic and quantitative simulation modelling that allow a dynamic characterisation of the interrelated physical and chemical processes taking place in the soil landscape. Moreover, the insertion of physical based rules in the LE procedure may make it less difficult in terms of both extending spatially the results and changing the object (e.g. crop species, nitrate dynamics, etc.) of the evaluation. On the other side these modern approaches require high quality and quantity of input data that cause a significant increase in costs. In this scenario nowadays the LE expert is asked to choose the best LE methodology considering costs, complexity of the procedure and benefits in handling a specific land evaluation. In this work we performed a forage maize land suitability study by comparing 9 different methods having increasing complexity and costs. The study area, of about 2000 ha, is located in North Italy in the Lodi plain (Po valley). The range of the 9 employed methods ranged from standard LE approaches to

  18. A COMPARATIVE STUDY OF SIMULATION AND TIME SERIES MODEL IN QUANTIFYING BULLWHIP EFFECT IN SUPPLY CHAIN

    Directory of Open Access Journals (Sweden)

    T. V. O. Fabson

    2011-11-01

    Full Text Available Bullwhip (or whiplash effect is an observed phenomenon in forecast driven distribution channeland careful management of these effects is of great importance to managers of supply chain.Bullwhip effect refers to situations where orders to the suppliers tend to have larger variance thansales to the buyer (demand distortion and the distortion increases as we move up the supply chain.Due to the fact that demand of customer for product is unstable, business managers must forecast inorder to properly position inventory and other resources. Forecasts are statistically based and in mostcases, are not very accurate. The existence of forecast errors made it necessary for organizations tooften carry an inventory buffer called “safety stock”. Moving up the supply chain from the end userscustomers to raw materials supplier there is a lot of variation in demand that can be observed, whichcall for greater need for safety stock.This study compares the efficacy of simulation and Time Series model in quantifying the bullwhipeffects in supply chain management.

  19. Diphenylhexatriene membrane probes DPH and TMA-DPH: A comparative molecular dynamics simulation study.

    Science.gov (United States)

    do Canto, António M T M; Robalo, João R; Santos, Patrícia D; Carvalho, Alfredo J Palace; Ramalho, J P Prates; Loura, Luís M S

    2016-11-01

    Fluorescence spectroscopy and microscopy have been utilized as tools in membrane biophysics for decades now. Because phospholipids are non-fluorescent, the use of extrinsic membrane probes in this context is commonplace. Among the latter, 1,6-diphenylhexatriene (DPH) and its trimethylammonium derivative (TMA-DPH) have been extensively used. It is widely believed that, owing to its additional charged group, TMA-DPH is anchored at the lipid/water interface and reports on a bilayer region that is distinct from that of the hydrophobic DPH. In this study, we employ atomistic MD simulations to characterize the behavior of DPH and TMA-DPH in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and POPC/cholesterol (4:1) bilayers. We show that although the dynamics of TMA-DPH in these membranes is noticeably more hindered than that of DPH, the location of the average fluorophore of TMA-DPH is only ~3-4Å more shallow than that of DPH. The hindrance observed in the translational and rotational motions of TMA-DPH compared to DPH is mainly not due to significant differences in depth, but to the favorable electrostatic interactions of the former with electronegative lipid atoms instead. By revealing detailed insights on the behavior of these two probes, our results are useful both in the interpretation of past work and in the planning of future experiments using them as membrane reporters. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Comparative study of the performance of quantum annealing and simulated annealing.

    Science.gov (United States)

    Nishimori, Hidetoshi; Tsuda, Junichi; Knysh, Sergey

    2015-01-01

    Relations of simulated annealing and quantum annealing are studied by a mapping from the transition matrix of classical Markovian dynamics of the Ising model to a quantum Hamiltonian and vice versa. It is shown that these two operators, the transition matrix and the Hamiltonian, share the eigenvalue spectrum. Thus, if simulated annealing with slow temperature change does not encounter a difficulty caused by an exponentially long relaxation time at a first-order phase transition, the same is true for the corresponding process of quantum annealing in the adiabatic limit. One of the important differences between the classical-to-quantum mapping and the converse quantum-to-classical mapping is that the Markovian dynamics of a short-range Ising model is mapped to a short-range quantum system, but the converse mapping from a short-range quantum system to a classical one results in long-range interactions. This leads to a difference in efficiencies that simulated annealing can be efficiently simulated by quantum annealing but the converse is not necessarily true. We conclude that quantum annealing is easier to implement and is more flexible than simulated annealing. We also point out that the present mapping can be extended to accommodate explicit time dependence of temperature, which is used to justify the quantum-mechanical analysis of simulated annealing by Somma, Batista, and Ortiz. Additionally, an alternative method to solve the nonequilibrium dynamics of the one-dimensional Ising model is provided through the classical-to-quantum mapping.

  1. A comparative study of interface reconstruction methods for multi-material ALE simulations

    Energy Technology Data Exchange (ETDEWEB)

    Kucharik, Milan [Los Alamos National Laboratory; Garimalla, Rao [Los Alamos National Laboratory; Schofield, Samuel [Los Alamos National Laboratory; Shashkov, Mikhail [Los Alamos National Laboratory

    2009-01-01

    In this paper we compare the performance of different methods for reconstructing interfaces in multi-material compressible flow simulations. The methods compared are a material-order-dependent Volume-of-Fluid (VOF) method, a material-order-independent VOF method based on power diagram partitioning of cells and the Moment-of-Fluid method (MOF). We demonstrate that the MOF method provides the most accurate tracking of interfaces, followed by the VOF method with the right material ordering. The material-order-independent VOF method performs some-what worse than the above two while the solutions with VOF using the wrong material order are considerably worse.

  2. A comparative study of psychophysiological reactions during simulator and real flight

    NARCIS (Netherlands)

    Veltman, J.A.

    2002-01-01

    During selection tests in a flight simulator and a real aircraft, physiological workload measures were evaluated. The selection context guaranteed high motivation in the participant to exert additional effort during difficult flight tasks. The aim of the study was to obtain information about the sen

  3. A comparative study of psychophysiological reactions during simulator and real flight

    NARCIS (Netherlands)

    Veltman, J.A.

    2002-01-01

    During selection tests in a flight simulator and a real aircraft, physiological workload measures were evaluated. The selection context guaranteed high motivation in the participant to exert additional effort during difficult flight tasks. The aim of the study was to obtain information about the sen

  4. Comparative Study on Two Melting Simulation Methods: Melting Curve of Gold

    Science.gov (United States)

    Liu, Zhong-Li; Sun, Jun-Sheng; Li, Rui; Zhang, Xiu-Lu; Cai, Ling-Cang

    2016-05-01

    Melting simulation methods are of crucial importance to determining melting temperature of materials efficiently. A high-efficiency melting simulation method saves much simulation time and computational resources. To compare the efficiency of our newly developed shock melting (SM) method with that of the well-established two-phase (TP) method, we calculate the high-pressure melting curve of Au using the two methods based on the optimally selected interatomic potentials. Although we only use 640 atoms to determine the melting temperature of Au in the SM method, the resulting melting curve accords very well with the results from the TP method using much more atoms. Thus, this shows that a much smaller system size in SM method can still achieve a fully converged melting curve compared with the TP method, implying the robustness and efficiency of the SM method. Supported by the National Natural Science Foundation of China under Grant No. 41574076 and the NSAF of China under Grant No. U1230201/A06, and the Young Core Teacher Scheme of Henan Province under Grant No. 2014GGJS-108

  5. Noninvasive activity-based control of an implantable rotary blood pump: comparative software simulation study.

    Science.gov (United States)

    Karantonis, Dean M; Lim, Einly; Mason, David G; Salamonsen, Robert F; Ayre, Peter J; Lovell, Nigel H

    2010-02-01

    A control algorithm for an implantable centrifugal rotary blood pump (RBP) based on a noninvasive indicator of the implant recipient's activity level has been proposed and evaluated in a software simulation environment. An activity level index (ALI)-derived from a noninvasive estimate of heart rate and the output of a triaxial accelerometer-forms the noninvasive indicator of metabolic energy expenditure. Pump speed is then varied linearly according to the ALI within a defined range. This ALI-based control module operates within a hierarchical multiobjective framework, which imposes several constraints on the operating region, such as minimum flow and minimum speed amplitude thresholds. Three class IV heart failure (HF) cases of varying severity were simulated under rest and exercise conditions, and a comparison with other popular RBP control strategies was performed. Pump flow increases of 2.54, 1.94, and 1.15 L/min were achieved for the three HF cases, from rest to exercise. Compared with constant speed control, this represents a relative flow change of 30.3, 19.8, and -15.4%, respectively. Simulations of the proposed control algorithm exhibited the effective intervention of each constraint, resulting in an improved flow response and the maintenance of a safe operating condition, compared with other control modes.

  6. Comparing Simulations of AGN Feedback

    Science.gov (United States)

    Richardson, Mark L. A.; Scannapieco, Evan; Devriendt, Julien; Slyz, Adrianne; Thacker, Robert J.; Dubois, Yohan; Wurster, James; Silk, Joseph

    2016-07-01

    We perform adaptive mesh refinement (AMR) and smoothed particle hydrodynamics (SPH) cosmological zoom simulations of a region around a forming galaxy cluster, comparing the ability of the methods to handle successively more complex baryonic physics. In the simplest, non-radiative case, the two methods are in good agreement with each other, but the SPH simulations generate central cores with slightly lower entropies and virial shocks at slightly larger radii, consistent with what has been seen in previous studies. The inclusion of radiative cooling, star formation, and stellar feedback leads to much larger differences between the two methods. Most dramatically, at z=5, rapid cooling in the AMR case moves the accretion shock to well within the virial radius, while this shock remains near the virial radius in the SPH case, due to excess heating, coupled with poorer capturing of the shock width. On the other hand, the addition of feedback from active galactic nuclei (AGNs) to the simulations results in much better agreement between the methods. For our AGN model, both simulations display halo gas entropies of 100 keV cm2, similar decrements in the star formation rate, and a drop in the halo baryon content of roughly 30%. This is consistent with the AGN growth being self-regulated, regardless of the numerical method. However, the simulations with AGN feedback continue to differ in aspects that are not self-regulated, such that in SPH a larger volume of gas is impacted by feedback, and the cluster still has a lower entropy central core.

  7. Traditional Instruction versus Virtual Reality Simulation: A Comparative Study of Phlebotomy Training among Nursing Students in Kuwait

    Science.gov (United States)

    William, Abeer; Vidal, Victoria L.; John, Pamela

    2016-01-01

    This quasi-experimental study compared differences in phlebotomy performance on a live client, between a control group taught through the traditional method and an experimental group using virtual reality simulation. The study showed both groups had performed successfully, using the following metrics: number of reinsertions, pain factor, hematoma…

  8. 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.

  9. Nanoindentation of hcp metals: a comparative simulation study of the evolution of dislocation networks

    Science.gov (United States)

    Alabd Alhafez, Iyad; Ruestes, Carlos J.; Gao, Yu; Urbassek, Herbert M.

    2016-01-01

    Using molecular dynamics simulation, we study the nanoindentation of three hcp metals: Mg, Ti, and Zr. Both the basal and two prismatic surface planes are considered. We focus on the characterization of the plasticity generated in the crystal. The similarities to, and the differences from, the behavior of the more commonly investigated fcc and bcc metals are highlighted. We find that hcp metals show a larger variety than the fcc and bcc metals studied up until now. The prolific emission of prismatic loops can lead to extended plastic zones. The size of the plastic zone is quantified by the ratio f of the plastic zone radius to the radius of the contact area. We find values of between 1.6 (an almost collapsed zone) and >5 in the latter case, complex dislocation networks build up which are extended in the direction of easy glide.

  10. Comparative Studies of Different Mesoscale Convection Parameterization Schemes in the Simulation of Mei-Yu Front Heavy Rain

    Institute of Scientific and Technical Information of China (English)

    PING Fan; LUO Zhe-Xian

    2010-01-01

    The mei-yu front heavy rainstorms occurred over Nanjing on 3-5 and 8-9 July 2003 and were simu-lated in this paper using the Weather Research and Fore-casting Model (WRFv3.1) with various mesoscale con-vection parameterization schemes (MCPSs). The simula-tions show that the temporal and spatial evolution and distribution of rainstorms can be modeled; however, there was incongruity between the comparative simulations of four different MCPSs and the observed data. These dis-parities were exhibited in the simulations of both the 24-hour surface rainfall total and the hourly precipitation rate. Further analysis revealed that the discrepancies of vertical velocity and the convective vorticity vector (CVV) between the four simulations were attributed to the devia-tion of rainfall values. In addition, the simulations show that the mid-scale convection, particularly the mesoscale convection system (MCS) formation, can be well simu-lated with the proper mesoscale convection parameteriza-tion schemes and may be a crucial factor of the mei-yu front heavy rainstorm. These results suggest that, in an effort to enhance simulation'and prediction of heavy rain-fall and rainstorms, subsequent studies should focus on the development and improvement of MCPS.

  11. Photospheric Magnetic Flux Emergence: A comparative study between Hinode/SOT Observations and MHD simulations

    Science.gov (United States)

    Cheung, M. C.; Schüssler, M.; Moreno-Insertis, F.; Tarbell, T. D.

    2007-12-01

    With high angular resolution, high temporal cadence and a stable point spread function, the Solar Optical Telescope (SOT) onboard the Hinode satellite is the ideal instrument for the study of magnetic flux emergence and its manifestations on the solar surface. In this presentation, we focus on the development of ephemeral regions and small active regions. In many instances, SOT has been able to capture the entire emergence process from beginning to end: i.e. from the initial stages of flux appearance in granule interiors, through the intermediate stages of G-band bright point formation, and finally to the coalescence of small vertical flux elements to form pores. To investigate the physics of the flux emergence process, we performed 3D numerical MHD simulations with the MURaM code. The models are able to reproduce, and help us explain, various observational signatures of magnetic flux emergence.

  12. A comparative study of leachate quality and biogas generation in simulated anaerobic and hybrid bioreactors.

    Science.gov (United States)

    Xu, Qiyong; Tian, Ying; Wang, Shen; Ko, Jae Hac

    2015-07-01

    Research has been conducted to compare leachate characterization and biogas generation in simulated anaerobic and hybrid bioreactor landfills with typical Chinese municipal solid waste (MSW). Three laboratory-scale reactors, an anaerobic (A1) and two hybrid bioreactors (C1 and C2), were constructed and operated for about 10months. The hybrid bioreactors were operated in an aerobic-anaerobic mode with different aeration frequencies by providing air into the upper layer of waste. Results showed that the temporary aeration into the upper layer aided methane generation by shortening the initial acidogenic phase because of volatile fatty acids (VFAs) reduction and pH increase. Chemical oxygen demand (COD) decreased faster in the hybrid bioreactors, but the concentrations of ammonia-nitrogen in the hybrid bioreactors were greater than those in the anaerobic control. Methanogenic conditions were established within 75d and 60d in C1 and C2, respectively. However, high aeration frequency led to the consumption of organic matters by aerobic degradation and resulted in reducing accumulative methane volume. The temporary aeration enhanced waste settlement and the settlement increased with increasing the frequency of aeration. Methane production was inhibited in the anaerobic control; however, the total methane generations from hybrid bioreactors were 133.4L/kgvs and 113.2L/kgvs. As for MSW with high content of food waste, leachate recirculation right after aeration stopped was not recommended due to VFA inhibition for methanogens.

  13. Key challenges in simulated patient programs: An international comparative case study

    Directory of Open Access Journals (Sweden)

    McNaughton Nancy

    2011-09-01

    Full Text Available Abstract Background The literature on simulated or standardized patient (SP methodology is expanding. However, at the level of the program, there are several gaps in the literature. We seek to fill this gap through documenting experiences from four programs in Australia, Canada, Switzerland and the United Kingdom. We focused on challenges in SP methodology, faculty, organisational structure and quality assurance. Methods We used a multiple case study method with cross-case synthesis. Over eighteen months during a series of informal and formal interactions (focused meetings and conference presentations we documented key characteristics of programs and drew on secondary document sources. Results Although programs shared challenges in SP methodology they also experienced differences. Key challenges common to programs included systematic quality assurance and the opportunity for research. There were differences in the terminology used to describe SPs, in their recruitment and training. Other differences reflected local conditions and demands in organisational structure, funding relationships with the host institution and national trends, especially in assessments. Conclusion This international case study reveals similarities and differences in SP methodology. Programs were highly contextualised and have emerged in response to local, institutional, profession/discipline and national conditions. Broader trends in healthcare education have also influenced development. Each of the programs experienced challenges in the same themes but the nature of the challenges often varied widely.

  14. Unconventional Thin-Film Thermoelectric Converters: Structure, Simulation, and Comparative Study

    Science.gov (United States)

    Haras, Maciej; Lacatena, Valeria; Monfray, Stéphane; Robillard, Jean-François; Skotnicki, Thomas; Dubois, Emmanuel

    2014-06-01

    Bi2Te3 or Sb2Te3 are the materials most widely used in thermoelectric generators (TEG) operating near room temperature. These materials are, however, environmentally harmful, expensive, and incompatible with complementary metal-oxide semiconductor technology, in contrast to silicon (Si), germanium (Ge), or silicon-germanium (SiGe). Although the thermopower ( S) and electrical conductivity ( σ) of Si and Ge are high, use in thermoelectricity is severely hindered by their high thermal conductivity ( κ). By altering the phonon band structure of this Si films by use of an artificial phononic pattern, spectacular reduction of κ by two orders of magnitude has been demonstrated. To take full advantage of phonon band modification and scattering in thin films, converter structure based on thin-film membranes is proposed for κ reduction. To consolidate the position of Si-based materials, coupled charge and heat-transport simulations have been conducted to demonstrate the potential of the materials for thermoelectric conversion compared with such widespread materials as Bi2Te3. The effect of contact resistance on generator performance has been carefully taken into consideration to reflect integration constraints at the TEG level. For a temperature difference Δ T = 30 K, the maximum electrical power density reaches approximately 6 W/cm2 for Si and Ge, and approximately 3 W/cm2 for Si0.7Ge0.3, values which are similar to those for Bi2Te3. Finally, it is emphasized that the proposed approach is compatible with conventional Si technology and naturally provides augmented mechanical flexibility that substantially widens the field of application of thermal harvesting.

  15. A comparative study of leachate quality and biogas generation in simulated anaerobic and hybrid bioreactors

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Qiyong; Tian, Ying; Wang, Shen; Ko, Jae Hac, E-mail: jaehacko@pkusz.edu.cn

    2015-07-15

    Highlights: • Temporary aeration shortened the initial acid inhibition phase for methanogens. • COD decreased faster in the hybrid bioreactor than that in the anaerobic control. • Methane generations from hybrid bioreactors were 133.4 L/kg{sub vs} and 113.2 L/kg{sub vs}. • MSW settlement increased with increasing the frequency of intermittent aeration. - Abstract: Research has been conducted to compare leachate characterization and biogas generation in simulated anaerobic and hybrid bioreactor landfills with typical Chinese municipal solid waste (MSW). Three laboratory-scale reactors, an anaerobic (A1) and two hybrid bioreactors (C1 and C2), were constructed and operated for about 10 months. The hybrid bioreactors were operated in an aerobic–anaerobic mode with different aeration frequencies by providing air into the upper layer of waste. Results showed that the temporary aeration into the upper layer aided methane generation by shortening the initial acidogenic phase because of volatile fatty acids (VFAs) reduction and pH increase. Chemical oxygen demand (COD) decreased faster in the hybrid bioreactors, but the concentrations of ammonia–nitrogen in the hybrid bioreactors were greater than those in the anaerobic control. Methanogenic conditions were established within 75 d and 60 d in C1 and C2, respectively. However, high aeration frequency led to the consumption of organic matters by aerobic degradation and resulted in reducing accumulative methane volume. The temporary aeration enhanced waste settlement and the settlement increased with increasing the frequency of aeration. Methane production was inhibited in the anaerobic control; however, the total methane generations from hybrid bioreactors were 133.4 L/kg{sub vs} and 113.2 L/kg{sub vs}. As for MSW with high content of food waste, leachate recirculation right after aeration stopped was not recommended due to VFA inhibition for methanogens.

  16. Comparative Simulation Studies of Multipacting in Higher-Order-Mode Couplers of Superconducting RF Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y. M. [Peking University, Beijing (China); Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Liu, Kexin [Peking University, Beijing (China); Geng, Rongli [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

    2014-02-01

    Multipacting (MP) in higher-order-mode (HOM) couplers of the International Linear Collider (ILC) baseline cavity and the Continuous Electron Beam Accelerator Facility (CEBAF) 12 GeV upgrade cavity is studied by using the ACE3P suites, developed by the Advanced Computations Department at SLAC. For the ILC cavity HOM coupler, the simulation results show that resonant trajectories exist in three zones, corresponding to an accelerating gradient range of 0.6-1.6 MV/m, 21-34 MV/m, 32-35 MV/m, and > 40MV/m, respectively. For the CEBAF 12 GeV upgrade cavity HOM coupler, resonant trajectories exist in one zone, corresponding to an accelerating gradient range of 6-13 MV/m. Potential implications of these MP barriers are discussed in the context of future high energy pulsed as well as medium energy continuous wave (CW) accelerators based on superconducting radio frequency cavities. Frequency scaling of MP's predicted in HOM couplers of the ILC, CBEAF upgrade, SNS and FLASH third harmonic cavity is given and found to be in good agreement with the analytical result based on the parallel plate model.

  17. Comparative Study of Vehicular Ad-hoc Network Mobility Models and Simulators

    Science.gov (United States)

    K. Patel, Mitul

    2012-06-01

    In this paper we have discussed about the number of automobiles that has been increased on the road in the past few years. Due to high density of vehicles, the potential threats and road accident is increasing. Wireless technology is aiming to equip technology in vehicles to reduce these factors by sending messages to each other. The vehicular safety application should be thoroughly tested before it is deployed in a real world to use. Simulator tool has been preferred over out door experiment because it simple, easy and cheap. VANET requires that a traffic and network simulator should be used together to perform this test. Many tools exist for this purpose but most of them have the problem with the proper interaction. Simulating vehicular networks with external stimulus to analyze its effect on wireless communication but to do this job a good simulator is also needed.

  18. The neural correlates of movement intentions: A pilot study comparing hypnotic and simulated paralysis.

    Science.gov (United States)

    Ludwig, Vera U; Seitz, Jochen; Schönfeldt-Lecuona, Carlos; Höse, Annett; Abler, Birgit; Hole, Günter; Goebel, Rainer; Walter, Henrik

    2015-09-01

    The distinct feeling of wanting to act and thereby causing our own actions is crucial to our self-perception as free human agents. Disturbances of the link between intention and action occur in several disorders. Little is known, however, about the neural correlates of wanting or intending to act. To investigate these for simple voluntary movements, we used a paradigm involving hypnotic paralysis and functional magnetic resonance imaging. Eight healthy women were instructed to sequentially perform left and right hand movements during a normal condition, as well as during simulated weakness, simulated paralysis and hypnotic paralysis of the right hand. Right frontopolar cortex was selectively hypoactivated for attempted right hand movement during simulated paralysis while it was active in all other conditions. Since simulated paralysis was the only condition lacking an intention to move, the activation in frontopolar cortex might be related to the intention or volition to move.

  19. Comparative Simulation Study of Production Scheduling in the Hybrid and the Parallel Flow

    Directory of Open Access Journals (Sweden)

    Varela Maria L.R.

    2017-06-01

    Full Text Available Scheduling is one of the most important decisions in production control. An approach is proposed for supporting users to solve scheduling problems, by choosing the combination of physical manufacturing system configuration and the material handling system settings. The approach considers two alternative manufacturing scheduling configurations in a two stage product oriented manufacturing system, exploring the hybrid flow shop (HFS and the parallel flow shop (PFS environments. For illustrating the application of the proposed approach an industrial case from the automotive components industry is studied. The main aim of this research to compare results of study of production scheduling in the hybrid and the parallel flow, taking into account the makespan minimization criterion. Thus the HFS and the PFS performance is compared and analyzed, mainly in terms of the makespan, as the transportation times vary. The study shows that the performance HFS is clearly better when the work stations’ processing times are unbalanced, either in nature or as a consequence of the addition of transport times just to one of the work station processing time but loses advantage, becoming worse than the performance of the PFS configuration when the work stations’ processing times are balanced, either in nature or as a consequence of the addition of transport times added on the work stations’ processing times. This means that physical layout configurations along with the way transport time are including the work stations’ processing times should be carefully taken into consideration due to its influence on the performance reached by both HFS and PFS configurations.

  20. A comparative simulation study on three lattice systems for the phase separation of polymer-dispersed liquid crystals

    Indian Academy of Sciences (India)

    Y J Jeon; M Jamil; Hyo-Dong Lee; J T Rhee

    2008-09-01

    This article reports a comparative study of the phase separation process in a polymer-dispersed liquid crystal, based on a Metropolis Monte Carlo simulation study of three lattice systems. We propose a model for the different processes occurring in the formation of polymer-dispersed liquid crystals (PDLCs). The mechanism of PDLC is studied as a function of quench temperature, concentration and degree of polymerization of liquid crystals and polymers. The obtained resultant phase diagrams of the three systems are approximated and compared with the Flory–Huggins theory, and show a good agreement. It has been observed in the simulation results that among all the three systems, the 40 × 40 × 40 lattice showed the most accurate, reliable and stable results.

  1. Comparative study by simulation of photovoltaic pumping systems with stationary and polar tracking arrays

    Energy Technology Data Exchange (ETDEWEB)

    Illanes, R.; De Francisco, A. [Universidad Politecnica de Madrid, E.T.S.I. de Montes, Madrid (Spain); Torres, J.L.; De Blas, M. [Universidad Publica de Navarra, Dept. Proyectos e Ingenieria Rural, Navarra (Spain); Appelbaum, J. [Tel Aviv Univ., Faculty of Engineering, Tel Aviv (Israel)

    2003-07-01

    Using mathematical models for the different components of the photovoltaic pumping system: generator, inverter (if applicable), motors, pumps and piping, we have developed a computer program that, for given irradiance and temperature data, calculates the flow of water pumped at any given time. The program has been applied to study the hourly and yearly water flow pumped by a photovoltaic pumping system located in Madrid, employing centrifugal pumps powered by AC motors. The photovoltaic generator consists of, in one case, a stationary array and in the second case a polar tracking array. The hourly radiation data were estimated from the distribution of the atmospheric clearness coefficients and the monthly average daily radiation on a horizontal surface. The results of this study show that the use of a polar tracking array increases the average yearly water flow compared with the stationary array more than the corresponding increase of the incident radiation on the arrays. (Author)

  2. Pore-Network Modeling vs. Direct Numerical Simulation: a Comparative Study

    Science.gov (United States)

    Mehmani, Y.; Tchelepi, H.

    2016-12-01

    Pore-scale models of flow and transport fall into one of two broad categories: (a) direct numerical simulators (DNS) and (b) pore-network models (PNM). The former is more fundamental as it solves the governing equations on the "actual" pore space geometry obtained through some kind of imaging technology (e.g., µCT). Its drawback is that it is computationally very expensive. PNM, however, reduces the complex pore-space geometry into a "ball-and-stick" network representation, which makes it highly efficient. But geometric simplifications are accompanied by secondary simplifications in the flow and transport physics, which result in a loss of predictive accuracy. We perform one-to-one comparisons between PNM and DNS simulations (i.e., on the same porous media) to assess the impact of such simplifications on macroscopic single-phase transport dynamics. DNS simulations are performed using the popular OpenFOAM software, while our PNM utilizes a particle-tracking approach. The influence of order and disorder in the pore space morphology on the accuracy of PNM predictions is discussed.

  3. Comparative study of forward and backward test-kinetic simulation approaches

    CERN Document Server

    Voitcu, Gabriel; Marchand, Richard

    2016-01-01

    In this paper we perform a comparative study of the forward and backward Liouville mapping applied to the modeling of ring-shaped and non-gyrotropic velocity distribution functions of particles injected in a sheared electromagnetic field. The test-kinetic method is used to compute the velocity distribution function in various areas of a proton cloud moving in the vicinity of a region with a sharp transition of the magnetic field and a non-uniform electric field. In the forward approach the velocity distribution function is computed for a two-dimensional spatial bin, while in the backward approach the distribution function is averaged over a spatial bin with the same size as for the forward method and using a two-dimensional trapezoidal integration scheme. It is shown that the two approaches lead to similar results for spatial bins where the velocity distribution function varies smoothly. On the other hand, with bins covering regions of configuration space characterized by sharp spatial gradients of the veloci...

  4. COMPASS – COMparative Particle formation in the Atmosphere using Simulation chamber Study techniques

    Directory of Open Access Journals (Sweden)

    B. Bonn

    2013-06-01

    Full Text Available The anthropogenic influence on climate and environment has increased strongly since industrialization about 150 yr ago. The consequences for the atmosphere became more and more apparent and nowadays affect our life quality on Earth progressively. Because of that it is very important to understand the atmospheric processes, on which these effects are based on, in detail. In this study we report the set-up of a novel twin chamber technique that uses the comparative method and establishes an appropriate connection of atmospheric and laboratory methods to broaden the tools for investigations. It is designed to study the impact of certain parameters and gases on ambient processes such as particle formation online and can be applied in a large variety of conditions. The characterisation of both chambers proved that both chambers operate identically with a residence time (xT (COMPASS 1 = 26.5 ± 0.3 min and xT (COMPASS 2 = 26.6 ± 0.4 min at a typical flow rate of 15 L min−1 and a deposition rate (1.6 ± 0.8 × 10−5 s−1. Comparison measurement showed no significant differences. Therefore operation under atmospheric conditions is trustworthy. To indicate the applicability and the benefit of the system a set of experiments was conducted at different conditions, i.e. urban and remote, enhancing ozone and terpenes as well as reducing sunlight. In the ozone enhanced ambient particle number and volume increased substantially at urban and remote conditions in a different strength. Solar radiation displayed a clear positive effect on particle number as well as terpene addition did at remote conditions. Therefore the system is a useful tool to investigate local precursors, the details of ambient particle formation at surface locations as well as future feedback processes.

  5. A comparative study of ibuprofen and ketoprofen glass-forming liquids by molecular dynamics simulations

    Science.gov (United States)

    Ottou Abe, M. T.; Correia, N. T.; Ndjaka, J. M. B.; Affouard, F.

    2015-10-01

    In this paper, structural and dynamical properties of ibuprofen and ketoprofen glass-forming liquids have been investigated by means of molecular dynamics simulations. Molecular mobility of both materials is analyzed with respect to the different inter-molecular linear/cyclic hydrogen bonding associations. For ibuprofen, the dominant organization is found to be composed of small hydrogen bonding aggregates corresponding to cyclic dimers through the carboxyl group. For ketoprofen, the propensity of cyclic dimers is significantly reduced by the formation of hydrogen bonds with the ketone oxygen of the molecule altering the hydrogen bond (HB) associating structures that can be formed and thus molecular dynamics. The issue of the presence/absence of the peculiar low frequency Debye-type process in dielectric relaxation spectroscopy (DRS) data in these materials is addressed. Results obtained from simulations confirm that the Debye process originates from the internal cis-trans conversion of the —COOH carboxyl group. It is shown that the specific intermolecular HB structures associated to a given profen control the main dynamical features of this conversion, in particular its separation from the α-process, which make it detectable or not from DRS. For ibuprofen, the possible role of the —CCCO torsion motion, more "local" than the —COOH motion since it is less influenced by the intermolecular HBs, is suggested in the microscopic origin of the quite intense secondary γ-relaxation process detected from DRS.

  6. Ultrafast laser processing of copper: A comparative study of experimental and simulated transient optical properties

    Science.gov (United States)

    Winter, Jan; Rapp, Stephan; Schmidt, Michael; Huber, Heinz P.

    2017-09-01

    In this paper, we present ultrafast measurements of the complex refractive index for copper up to a time delay of 20 ps with an accuracy laser fluences in the vicinity of the ablation threshold. The measured refractive index n and extinction coefficient k are supported by a simulation including the two-temperature model with an accurate description of thermal and optical properties and a thermomechanical model. Comparison of the measured time resolved optical properties with results of the simulation reveals underlying physical mechanisms in three distinct time delay regimes. It is found that in the early stage (-5 ps to 0 ps) the thermally excited d-band electrons make a major contribution to the laser pulse absorption and create a steep increase in transient optical properties n and k. In the second time regime (0-10 ps) the material expansion influences the plasma frequency, which is also reflected in the transient extinction coefficient. In contrast, the refractive index n follows the total collision frequency. Additionally, the electron-ion thermalization time can be attributed to a minimum of the extinction coefficient at ∼10 ps. In the third time regime (10-20 ps) the transient extinction coefficient k indicates the surface cooling-down process.

  7. Dynamic Value at Risk: A Comparative Study Between Heteroscedastic Models and Monte Carlo Simulation

    Directory of Open Access Journals (Sweden)

    José Lamartine Távora Junior

    2006-12-01

    Full Text Available The objective of this paper was to analyze the risk management of a portfolio composed by Petrobras PN, Telemar PN and Vale do Rio Doce PNA stocks. It was verified if the modeling of Value-at-Risk (VaR through the place Monte Carlo simulation with volatility of GARCH family is supported by hypothesis of efficient market. The results have shown that the statistic evaluation in inferior to dynamics, evidencing that the dynamic analysis supplies support to the hypothesis of efficient market of the Brazilian share holding market, in opposition of some empirical evidences. Also, it was verified that the GARCH models of volatility is enough to accommodate the variations of the shareholding Brazilian market, since the model is capable to accommodate the great dynamic of the Brazilian market.

  8. Laboratory simulation and modeling of size, shape distributed interstellar graphite dust analogues: A comparative study

    Science.gov (United States)

    Boruah, Manash J.; Gogoi, Ankur; Ahmed, Gazi A.

    2016-06-01

    The computation of the light scattering properties of size and shape distributed interstellar graphite dust analogues using discrete dipole approximation (DDA) is presented. The light scattering properties of dust particles of arbitrary shapes having sizes ranging from 0.5 to 5.0 μm were computed using DDSCAT 7.3.0 software package and an indigenously developed post-processing tool for size and shape averaging. In order to model realistic samples of graphite dust and compute their light scattering properties using DDA, different target geometries were generated to represent the graphite particle composition in terms of surface smoothness, surface roughness and aggregation or their combination, for using as the target for DDSCAT calculations. A comparison of the theoretical volume scattering function at 543.5 nm and 632.8 nm incident wavelengths with laboratory simulation is also presented in this paper.

  9. A comparative study on 3-D solar wind structure observed by Ulysses and MHD simulation

    Institute of Scientific and Technical Information of China (English)

    FENG Xueshang; XIANG Changqing; ZHONG Dingkun; FAN Quanlin

    2005-01-01

    During Ulysses' first rapid pole-to-pole transit from September 1994 to June 1995, its observations showed that middle- or high-speed solar winds covered all latitudes except those between -20° and +20° near the ecliptic plane,where the velocity was 300-450 km/s. At poleward 40°,however, only fast solar winds at the speed of 700-870 km/s were observed. In addition, the transitions from low-speed wind to high-speed wind or vice versa were abrupt. In this paper, the large-scale structure of solar wind observed by Ulysses near solar minimum is simulated by using the three-dimensional numerical MHD model. The model combines TVD Lax-Friedrich scheme and MacCormack Ⅱ scheme and decomposes the calculation region into two regions: one from 1 to 22 Rs and the other from 18 Rs to 1 AU.Based on the observations of the solar photospheric magnetic field and an addition of the volumetric heating to MHD equations, the large-scale solar wind structure mentioned above is reproduced by using the three-dimensional MHD model and the numerical results are roughly consistent with Ulysses' observations. Our simulation shows that the initial magnetic field topology and the addition of volume heating may govern the bimodal structure of solar wind observed by Ulysses and also demonstrates that the three-dimensional MHD numerical model used here is efficient in modeling the large-scale solar wind structure.

  10. A comparative study on simulation performances of rigid and bendable SAW for gas sensor

    Science.gov (United States)

    Sidek, Fatini; Arsat, Rashidah; Ibrahim, Rafidah; Idris, Aizzat Ayuni Mohad; Johari, Zaharah; Ling, Leow Pei

    2017-03-01

    Flexible Surface Acoustic Wave (SAW) devices are very promising technology for various applications that offers excellent flexibility, low in cost and light weight. In this paper, a SAW gas sensor is designed and simulated using COMSOL Multiphysics to investigate the degree of bending effect on the frequency and displacement. The investigations were conducted onto SAW gas sensor as rigid and two different bends direction; bend-in (concave) and bend-out (convex). The operating frequency of the SAW sensor were found to be at the range of 80-200 MHz. The frequency shift of the sensor were obtained after exposing the polyisobutylene (PIB) to the dichloromethane DCM gas which will change the density of sensing layer. From the simulation, it is shown that resonance frequency range of 189MHz for the rigid substrate with displacement of 0.706 nm. Notably, the bending degree of h range from 0.2 µm to 1.25 µm exhibits reduction for displacement and frequency. The higher frequency of bend-out (convex) design achieve is 1.8945 MHz with displacement of 0.68 nm at curve of h= 0.2 µm, Improvement have been observed for the frequency shift of 14 Hz and sensitivity of 1324.24. It shows that the sensor is more sensitive to detect the gas. The evaluation of device bending effect on the eigenfrequency, displacement and frequency shift provide ways to enhance the sensitivity of the gas sensor and expand its possibility of realizing their benefit particularly for sensing device enhancement.

  11. Assessing the Goodness of Fit of Phylogenetic Comparative Methods: A Meta-Analysis and Simulation Study.

    Science.gov (United States)

    Jhwueng, Dwueng-Chwuan

    2013-01-01

    Phylogenetic comparative methods (PCMs) have been applied widely in analyzing data from related species but their fit to data is rarely assessed. Can one determine whether any particular comparative method is typically more appropriate than others by examining comparative data sets? I conducted a meta-analysis of 122 phylogenetic data sets found by searching all papers in JEB, Blackwell Synergy and JSTOR published in 2002-2005 for the purpose of assessing the fit of PCMs. The number of species in these data sets ranged from 9 to 117. I used the Akaike information criterion to compare PCMs, and then fit PCMs to bivariate data sets through REML analysis. Correlation estimates between two traits and bootstrapped confidence intervals of correlations from each model were also compared. For phylogenies of less than one hundred taxa, the Independent Contrast method and the independent, non-phylogenetic models provide the best fit.For bivariate analysis, correlations from different PCMs are qualitatively similar so that actual correlations from real data seem to be robust to the PCM chosen for the analysis. Therefore, researchers might apply the PCM they believe best describes the evolutionary mechanisms underlying their data.

  12. Assessing the Goodness of Fit of Phylogenetic Comparative Methods: A Meta-Analysis and Simulation Study.

    Directory of Open Access Journals (Sweden)

    Dwueng-Chwuan Jhwueng

    Full Text Available Phylogenetic comparative methods (PCMs have been applied widely in analyzing data from related species but their fit to data is rarely assessed.Can one determine whether any particular comparative method is typically more appropriate than others by examining comparative data sets?I conducted a meta-analysis of 122 phylogenetic data sets found by searching all papers in JEB, Blackwell Synergy and JSTOR published in 2002-2005 for the purpose of assessing the fit of PCMs. The number of species in these data sets ranged from 9 to 117.I used the Akaike information criterion to compare PCMs, and then fit PCMs to bivariate data sets through REML analysis. Correlation estimates between two traits and bootstrapped confidence intervals of correlations from each model were also compared.For phylogenies of less than one hundred taxa, the Independent Contrast method and the independent, non-phylogenetic models provide the best fit.For bivariate analysis, correlations from different PCMs are qualitatively similar so that actual correlations from real data seem to be robust to the PCM chosen for the analysis. Therefore, researchers might apply the PCM they believe best describes the evolutionary mechanisms underlying their data.

  13. Simulated carbon irradiation of carbon nanotubes – A comparative study of interatomic potentials

    Energy Technology Data Exchange (ETDEWEB)

    Heredia-Avalos, Santiago, E-mail: sheredia@ua.es [Departament de Física, Enginyeria de Sistemes i Teoria de la Senyal, Universitat d’Alacant, Apartat 99, E-03080 Alacant (Spain); Moreno-Marín, Juan Carlos [Departament de Física, Enginyeria de Sistemes i Teoria de la Senyal, Universitat d’Alacant, Apartat 99, E-03080 Alacant (Spain); Denton, Cristian D. [Departament de Física Aplicada, Universitat d’Alacant, Apartat 99, E-03080 Alacant (Spain)

    2014-05-01

    We simulate the irradiation of carbon nanotubes (CNT) with carbon ions using a molecular dynamics code. In order to describe the interaction between carbon ions we use the Tersoff or Brenner potential, both joined smoothly to the Universal ZBL potential at short distances. We have analyzed the defects produced after irradiation, the subsequent modification of the CNT structure, and their dependence on the used interatomic potential, the projectile energy (from 10 eV to 5 keV) and the dose. For single projectile irradiation, we have obtained that the coordination defect number increases with the projectile energy, although a saturation value is achieved at high projectile energies (∼3 keV). For continuous projectile irradiation, we have observed that for low energies (∼10 eV) the accumulation of adatoms produces a bump in the irradiated region. However, at intermediate energies (∼100 eV) the irradiation produces vacancies which are healed through non-hexagonal rings. This gives rise to a shrinking of the CNT diameter in the irradiated region. Finally, if the projectile energy is high enough (∼1 keV) the continuous irradiation produces the breaking of the CNT.

  14. A comparative study of graph-based, eikonal, and monodomain simulations for the estimation of cardiac activation times.

    Science.gov (United States)

    Wallman, Mikael; Smith, Nicolas P; Rodriguez, Blanca

    2012-06-01

    The bidomain and monodomain equations are well established as the standard set of equations for the simulation of cardiac electrophysiological behavior. However, the computational cost of detailed bidomain/monodomain simulations limits their applicability in scenarios where a large number of simulations needs to be performed (e.g., parameter estimation). In this study, we present a graph-based method, which relies on point-to-point path finding to estimate activation times for single points in cardiac tissue with minimal computational costs. To validate our approach, activation times are compared to monodomain simulation results for an anatomically based rabbit ventricular model, incorporating realistic fiber orientation and conduction heterogeneities. Differences in activation times between the graph-based method and monodomain results are less than 10% of the total activation time, and computational performance is orders of magnitude faster with the proposed method when calculating activation times at single points. These results suggest that the graph-based method is well suited for estimating activation times when the need for fast performance justifies a limited loss of accuracy.

  15. In-car usage-based insurance feedback strategies. A comparative driving simulator study.

    Science.gov (United States)

    Dijksterhuis, Chris; Lewis-Evans, Ben; Jelijs, Bart; Tucha, Oliver; de Waard, Dick; Brookhuis, Karel

    2016-09-01

    Usage-Based Insurances (UBI) enable policyholders to actively reduce the impact of vehicle insurance costs by adopting a safer and more eco-friendly driving style. UBI is especially relevant for younger drivers, who are a high-risk population. The effectiveness of UBI should be enhanced by providing in-car feedback optimised for individual drivers. Thirty young novice drivers were therefore invited to complete six experimental drives with an in-car interface that provided real-time information on rewards gained, their driving behaviour and the speed limit. Reward size was either displayed directly in euro, indirectly as a relatively large amount of credits, or as a percentage of the maximum available bonus. Also, interfaces were investigated that provided partial information to reduce the potential for driver distraction. Compared to a control no-UBI condition, behaviour improved similarly across interfaces, suggesting that interface personalisation after an initial familiarisation period could be feasible without compromising feedback effectiveness. Practitioner Summary: User experiences and effects on driving behaviour of six in-car interfaces were compared. The interface provided information on driving behaviour and rewards in a UBI setting. Results suggest that some personalisation of interfaces may be an option after an initial familiarisation period as driving behaviour improved similarly across interfaces.

  16. A comparative study on the performance of Kesterite based thin film solar cells using SCAPS simulation program

    Science.gov (United States)

    Simya, O. K.; Mahaboobbatcha, A.; Balachander, K.

    2015-06-01

    A comparative study of thin film solar cells based on CZTS, CZTSe, and CZTSSe (Copper Zinc Tin Sulphur Selenium) absorbers layers were simulated with Cadmium Sulphide (CdS) as buffer layer and Zinc Oxide (ZnO) as window layer using a solar cell capacitance simulator (SCAPS). The influences of series resistance, band to band recombination, defects and interfaces, thickness of (CZTS|CZTSe|CZTSSe) absorber layer, (CdS) buffer layer and transparent conductive oxide layer (ZnO) on the photovoltaic cell parameters were studied in detail. Improvements in efficiency were achieved by changing the back contact metal work function (BMWF) and choosing the flat band option in SCAPS software. Based on the best possible optimisation, an efficiency (η) of 12.03%, 13.16% and 15.77% were obtained for CZTS, CZTSe, and CZTSSe respectively. The performance of thin film photovoltaic devices (TFPV), for Mo back contact before optimisation and the SCAPS simulated values (flat band) after optimisation were described in detail to have in-depth understanding for better design of experiments (DOE) to obtain high efficiency solar cells.

  17. A comparative study of cold- and warm-adapted Endonucleases A using sequence analyses and molecular dynamics simulations

    Science.gov (United States)

    Michetti, Davide; Brandsdal, Bjørn Olav; Bon, Davide; Isaksen, Geir Villy; Tiberti, Matteo; Papaleo, Elena

    2017-01-01

    The psychrophilic and mesophilic endonucleases A (EndA) from Aliivibrio salmonicida (VsEndA) and Vibrio cholera (VcEndA) have been studied experimentally in terms of the biophysical properties related to thermal adaptation. The analyses of their static X-ray structures was no sufficient to rationalize the determinants of their adaptive traits at the molecular level. Thus, we used Molecular Dynamics (MD) simulations to compare the two proteins and unveil their structural and dynamical differences. Our simulations did not show a substantial increase in flexibility in the cold-adapted variant on the nanosecond time scale. The only exception is a more rigid C-terminal region in VcEndA, which is ascribable to a cluster of electrostatic interactions and hydrogen bonds, as also supported by MD simulations of the VsEndA mutant variant where the cluster of interactions was introduced. Moreover, we identified three additional amino acidic substitutions through multiple sequence alignment and the analyses of MD-based protein structure networks. In particular, T120V occurs in the proximity of the catalytic residue H80 and alters the interaction with the residue Y43, which belongs to the second coordination sphere of the Mg2+ ion. This makes T120V an amenable candidate for future experimental mutagenesis. PMID:28192428

  18. Comparative simulation study of gas-phase propylene polymerization in fluidized bed reactors using aspen polymers and two phase models

    Directory of Open Access Journals (Sweden)

    Shamiria Ahmad

    2013-01-01

    Full Text Available A comparative study describing gas-phase propylene polymerization in fluidized-bed reactors using Ziegler-Natta catalyst is presented. The reactor behavior was explained using a two-phase model (which is based on principles of fluidization as well as simulation using the Aspen Polymers process simulator. The two-phase reactor model accounts for the emulsion and bubble phases which contain different portions of catalysts with the polymerization occurring in both phases. Both models predict production rate, molecular weight, polydispersity index (PDI and melt flow index (MFI of the polymer. We used both models to investigate the effect of important polymerization parameters, namely catalyst feed rate and hydrogen concentration, on the product polypropylene properties, such as production rate, molecular weight, PDI and MFI. Both the two-phase model and Aspen Polymers simulator showed good agreement in terms of production rate. However, the models differed in their predictions for weight-average molecular weight, PDI and MFI. Based on these results, we propose incorporating the missing hydrodynamic effects into Aspen Polymers to provide a more realistic understanding of the phenomena encountered in fluidized bed reactors for polyolefin production.

  19. A comparative analysis of preprocessing techniques of cardiac event series for the study of heart rhythm variability using simulated signals

    Directory of Open Access Journals (Sweden)

    Guimarães H.N.

    1998-01-01

    Full Text Available In the present study, using noise-free simulated signals, we performed a comparative examination of several preprocessing techniques that are used to transform the cardiac event series in a regularly sampled time series, appropriate for spectral analysis of heart rhythm variability (HRV. First, a group of noise-free simulated point event series, which represents a time series of heartbeats, was generated by an integral pulse frequency modulation model. In order to evaluate the performance of the preprocessing methods, the differences between the spectra of the preprocessed simulated signals and the true spectrum (spectrum of the model input modulating signals were surveyed by visual analysis and by contrasting merit indices. It is desired that estimated spectra match the true spectrum as close as possible, showing a minimum of harmonic components and other artifacts. The merit indices proposed to quantify these mismatches were the leakage rate, defined as a measure of leakage components (located outside some narrow windows centered at frequencies of model input modulating signals with respect to the whole spectral components, and the numbers of leakage components with amplitudes greater than 1%, 5% and 10% of the total spectral components. Our data, obtained from a noise-free simulation, indicate that the utilization of heart rate values instead of heart period values in the derivation of signals representative of heart rhythm results in more accurate spectra. Furthermore, our data support the efficiency of the widely used preprocessing technique based on the convolution of inverse interval function values with a rectangular window, and suggest the preprocessing technique based on a cubic polynomial interpolation of inverse interval function values and succeeding spectral analysis as another efficient and fast method for the analysis of HRV signals

  20. Wetting Boundary Conditions in Phase-Field-Based Simulation of Binary Fluids: Some Comparative Studies and New Development

    CERN Document Server

    Huang, Jun-Jie; Wang, Xinzhu

    2013-01-01

    We studied several wetting boundary conditions (WBCs) in the simulation of binary fluids based on phase-field theory. Five WBCs, three belonging to the surface energy (SE) formulation using the linear, cubic and sine functions (denoted as LinSE, CubSE and SinSE), the fourth using a geometric formulation (Geom), and the fifth using a characteristic interpolation (CI), were compared with each other through the study of several problems: (1) the static contact angle of a drop; (2) a Poiseuille flow-driven liquid column; (3) a wettability gradient (WG)-driven liquid column; (4) drop dewetting. It was found that while all WBCs can predict the static contact angle fairly accurately, they may affect the simulation outcomes of dynamic problems differently, depending on the driving mechanism. For the flow-driven problem, to use different WBCs had almost no effect on the flow characteristics over a large scale. But for other capillarity-driven problems, the WBC had some noticeable effects. For the WG-driven liquid colu...

  1. Disaster Response Team FAST Skills Training with a Portable Ultrasound Simulator Compared to Traditional Training: Pilot Study

    Directory of Open Access Journals (Sweden)

    Paddock, Michael T.

    2015-03-01

    Full Text Available Introduction: Pre-hospital focused assessment with sonography in trauma (FAST has been effectively used to improve patient care in multiple mass casualty events throughout the world. Although requisite FAST knowledge may now be learned remotely by disaster response team members, traditional live instructor and model hands-on FAST skills training remains logistically challenging. The objective of this pilot study was to compare the effectiveness of a novel portable ultrasound (US simulator with traditional FAST skills training for a deployed mixed provider disaster response team. Methods: We randomized participants into one of three training groups stratified by provider role: Group A. Traditional Skills Training, Group B. US Simulator Skills Training, and Group C. Traditional Skills Training Plus US Simulator Skills Training. After skills training, we measured participants’ FAST image acquisition and interpretation skills using a standardized direct observation tool (SDOT with healthy models and review of FAST patient images. Pre- and post-course US and FAST knowledge were also assessed using a previously validated multiple-choice evaluation. We used the ANOVA procedure to determine the statistical significance of differences between the means of each group’s skills scores. Paired sample t-tests were used to determine the statistical significance of pre- and post-course mean knowledge scores within groups. Results: We enrolled 36 participants, 12 randomized to each training group. Randomization resulted in similar distribution of participants between training groups with respect to provider role, age, sex, and prior US training. For the FAST SDOT image acquisition and interpretation mean skills scores, there was no statistically significant difference between training groups. For US and FAST mean knowledge scores, there was a statistically significant improvement between pre- and post-course scores within each group, but again there was not

  2. Simulation study comparing the helmet-chin PET with a cylindrical PET of the same number of detectors

    Science.gov (United States)

    Ahmed, Abdella M.; Tashima, Hideaki; Yoshida, Eiji; Nishikido, Fumihiko; Yamaya, Taiga

    2017-06-01

    There is a growing interest in developing brain PET scanners with high sensitivity and high spatial resolution for early diagnosis of neurodegenerative diseases and studies of brain functions. Sensitivity of the PET scanner can be improved by increasing the solid angle. However, conventional PET scanners are designed based on a cylindrical geometry, which may not be the most efficient design for brain imaging in terms of the balance between sensitivity and cost. We proposed a dedicated brain PET scanner based on a hemispheric shape detector and a chin detector (referred to as the helmet-chin PET), which is designed to maximize the solid angle by increasing the number of lines-of-response in the hemisphere. The parallax error, which PET scanners with a large solid angle tend to have, can be suppressed by the use of depth-of-interaction detectors. In this study, we carry out a realistic evaluation of the helmet-chin PET using Monte Carlo simulation based on the 4-layer GSO detector which consists of a 16  ×  16  ×  4 array of crystals with dimensions of 2.8  ×  2.8  ×  7.5 mm3. The purpose of this simulation is to show the gain in imaging performance of the helmet-chin PET compared with the cylindrical PET using the same number of detectors in each configuration. The sensitivity of the helmet-chin PET evaluated with a cylindrical phantom has a significant increase, especially at the top of the (field-of-view) FOV. The peak-NECR of the helmet-chin PET is 1.4 times higher compared to the cylindrical PET. The helmet-chin PET provides relatively low noise images throughout the FOV compared to the cylindrical PET which exhibits enhanced noise at the peripheral regions. The results show the helmet-chin PET can significantly improve the sensitivity and reduce the noise in the reconstructed images.

  3. A comparative study for different shielding material composition and beam geometry applied to PET facilities: simulated transmission curves

    Energy Technology Data Exchange (ETDEWEB)

    Hoff, Gabriela [Pontificia Univ. Catolica do Rio Grande do Sul (PUCRS), Porto Alegre, RS (Brazil). Grupo de Experimentacao e Simulacao Computacional em Fisica Medica; Costa, Paulo Roberto, E-mail: pcosta@if.usp.br [Universidade de Sao Paulo (IF/USP), SP (Brazil). Dept. de Fisica Nuclear. Lab. de Dosimetria das Radiacoes e Fisica Medica

    2013-03-15

    The aim of this work is to simulate transmission data for different beam geometry and material composition in order to evaluate the effect of these parameters on transmission curves. The simulations are focused on outgoing spectra for shielding barriers used in PET facilities. The behavior of the transmission was evaluated as a function of the shielding material composition and thickness using Geant4 Monte Carlo code, version 9.2 p 03.The application was benchmarked for barited mortar and compared to The American Association of Physicists in Medicine (AAPM) data for lead. Their influence on the transmission curves as well the study of the influence of the shielding material composition and beam geometry on the outgoing spectra were performed. Characteristics of transmitted spectra, such as shape, average energy and Half-Value Layer (HVL), were also evaluated. The Geant4 toolkit benchmark for the energy resulting from the positron annihilation phenomena and its application in transmission curves description shown good agreement between data published by American Association on Physicists in Medicine task group 108 and experimental data published by Brazil. The transmission properties for different material compositions were also studied and have shown low dependency with the considered thicknesses. The broad and narrow beams configuration presented significant differences on the result. The fitting parameter for determining the transmission curves equations, according to Archer model is presented for different material. As conclusion were defined that beam geometry has significant influence and the composition has low influence on transmission curves for shielding design for the range of energy applied to PET. (author)

  4. Hemispheric Coupling: Comparing Dynamo Simulations and Observations

    CERN Document Server

    Norton, Aimee A; Passos, Dario

    2014-01-01

    Numerical simulations that reproduce solar-like magnetic cycles can be used to generate long-term statistics. The variations in N-S hemispheric cycle synchronicity and amplitude produced in simulations has not been widely compared to observations. The observed limits on asymmetry show that hemispheric sunspot area production is no more than 20% asymmetric for cycles 12-23 and phase lags do not exceed 20% (2 yrs) of the total cycle period. Independent studies have found a long-term trend in phase values as one hemisphere leads the other for ~four cycles. Such persistence in phase is not indicative of a stochastic phenomenon. We compare the findings to results from a numerical simulation of solar convection recently produced with the EULAG-MHD model. This simulation spans 1600 yrs and generated 40 regular, sunspot-like cycles. While the simulated cycle length is too long and the toroidal bands remain at too high of latitudes, some solar-like aspects of hemispheric asymmetry are reproduced. The model reproduces ...

  5. Simulative Study into the Development of a Hybrid HVDC System Through a Comparative Research with HVAC: a Futuristic Approach

    Directory of Open Access Journals (Sweden)

    R. S. Narayan

    2017-06-01

    Full Text Available High Voltage Direct Current Transmission (HVDC is considered a better solution for bulk long distance transmissions. The increased use of HVDC is a result of its advantages over the HVAC systems and especially of its fault stability nature. A better solution is proposed by using a Voltage Source Controlled–HVDC as one of the infeed for the Multi-Infeed HVDC (MIDC or MI-HVDC systems. The main advantage with the VSC converter is its flexible power control which enhances the stability of the MIDC systems. In this paper, the behavior of an HVDC system is compared with that of an HVAC during faults. A Hybrid HVDC system that includes a LCC as a rectifier unit and a VSC converter as the inverter is being proposed. It is considered suitable for MIDC systems and particularly for supplying a weak AC system. The performance of the system during steady state and transient conditions for all the proposed topologies including HVDC, HVAC and Hybrid HVDC are studied in MATLAB/SIMULINK. All of the proposed control strategies are evaluated via a series of simulation case studies.

  6. A comparative numerical study of turbulence models for the simulation of fire incidents: Application in ventilated tunnel fires

    Directory of Open Access Journals (Sweden)

    Konstantinos G. Stokos

    2015-12-01

    Full Text Available The objective of this paper is to compare the overall performance of two turbulence models used for the simulation of fire scenarios in ventilated tunnels. Two Reynolds Averaged Navier–Stokes turbulence models were used; the low-Re k–ω SST and the standard k–ε model with wall functions treatment. Comparison was conducted on two different fire scenarios. The varied parameters were the heat release rate and the ventilation rate. Results predicted by the two turbulence models were also compared to the results produced from the commercial package Ansys Fluent. Quite faster simulations were performed using the k–ε turbulence model with wall functions and our findings, as to the basic characteristics of smoke movement, were in good agreement with Ansys Fluent ones.

  7. A comparative study of reinitialization approaches of the level set method for simulating free-surface flows

    Energy Technology Data Exchange (ETDEWEB)

    Sufyan, Muhammad; Ngo, Long Cu; Choi, Hyoung Gwon [Seoul National University, Seoul (Korea, Republic of)

    2016-04-15

    Unstructured grids were used to compare the performance of a direct reinitialization scheme with those of two reinitialization approaches based on the solution of a hyperbolic Partial differential equation (PDE). The problems of moving interface were solved in the context of a finite element method. A least-square weighted residual method was used to discretize the advection equation of the level set method. The benchmark problems of rotating Zalesak's disk, time-reversed single vortex, and two-dimensional sloshing were examined. Numerical results showed that the direct reinitialization scheme performed better than the PDE-based reinitialization approaches in terms of mass conservation, dissipation and dispersion error, and computational time. In the case of sloshing, numerical results were found to be in good agreement with existing experimental data. The direct reinitialization approach consumed considerably less CPU time than the PDE-based simulations for 20 time periods of sloshing. This approach was stable, accurate, and efficient for all the problems considered in this study.

  8. Comparative Study for Improving the Thermal and Fluid Flow Performance of Micro Channel Fin Geometries Using Numerical Simulation

    Directory of Open Access Journals (Sweden)

    S.Subramanian

    2015-07-01

    Full Text Available There is a continuous quest for improving the performance of micro channels for handling the increased dissipation of heat from electronics circuits. The Oblique fin micro channels are attractive as they perform better than plate fin & pin fin configurations. There are scopes for further improvements in oblique fin micro channels. Hence this work is about the investigation for the performance enhancement by modifying the oblique fin geometry. Seven variants of micro channel geometries have been explored using three dimensional numerical simulations. The variants are plate fin, in-line pin fin, staggered pin fin, oblique fin, oblique fin with two slit angles, oblique with nozzle type slit and improved oblique fin. The simulation results are validated using the published data. To ensure a common reference for comparison, hydraulic diameter, inlet flow conditions, heat loads and the boundary conditions are kept identical across all the geometries. The results of simulation are compared for the thermal & fluid flow performances. Heat transfer correlations have been developed using the simulation data. The proposed modification is found to enhance the performance significantly

  9. A comparative study of methods to compute the free energy of an ordered assembly by molecular simulation.

    Science.gov (United States)

    Moustafa, Sabry G; Schultz, Andrew J; Kofke, David A

    2013-08-28

    We present a comparative study of methods to compute the absolute free energy of a crystalline assembly of hard particles by molecular simulation. We consider all combinations of three choices defining the methodology: (1) the reference system: Einstein crystal (EC), interacting harmonic (IH), or r(-12) soft spheres (SS); (2) the integration path: Frenkel-Ladd (FL) or penetrable ramp (PR); and (3) the free-energy method: overlap-sampling free-energy perturbation (OS) or thermodynamic integration (TI). We apply the methods to FCC hard spheres at the melting state. The study shows that, in the best cases, OS and TI are roughly equivalent in efficiency, with a slight advantage to TI. We also examine the multistate Bennett acceptance ratio method, and find that it offers no advantage for this particular application. The PR path shows advantage in general over FL, providing results of the same precision with 2-9 times less computation, depending on the choice of a common reference. The best combination for the FL path is TI+EC, which is how the FL method is usually implemented. For the PR path, the SS system (with either TI or OS) proves to be most effective; it gives equivalent precision to TI+FL+EC with about 6 times less computation (or 12 times less, if discounting the computational effort required to establish the SS reference free energy). Both the SS and IH references show great advantage in capturing finite-size effects, providing a variation in free-energy difference with system size that is about 10 times less than EC. This result further confirms previous work for soft-particle crystals, and suggests that free-energy calculations for a structured assembly be performed using a hybrid method, in which the finite-system free-energy difference is added to the extrapolated (1/N→0) absolute free energy of the reference system, to obtain a result that is nearly independent of system size.

  10. Atomistic comparative study of VUV photodeposited silicon nitride on InP(100) by simulation and atomic force microscopy

    Science.gov (United States)

    Flicstein, J.; Guillonneau, E.; Marquez, J.; How Kee Chun, L. S.; Maisonneuve, D.; David, C.; Wang, Zh.; Palmier, J. F.; Courant, J. L.

    2000-02-01

    We report on an accurate validation of a new Monte Carlo three-dimensional model. Simulations up to 1200 Å layer thickness have been carried out for amorphous thin film layers of SiN:H deposited at low temperature (400-650 K) on (100) InP, by vacuum ultraviolet (VUV, ˜185 nm)-induced chemical vapor deposition (CVD). The computer simulations in the mesoscopic-submicronic range are compared with atomic force microscopy and index of refraction measurements. The reconstituted surface roughness and the voids discrete representations of the bulk are found to be in good agreement with these measurements. Simultaneously at around 450 K (at ˜175°C), thermal characteristic evolution of the both surface roughness and bulk porosity showed a transition from rough to smooth deposition and from low to high density.

  11. A Simulation Study Comparing Epidemic Dynamics on Exponential Random Graph and Edge-Triangle Configuration Type Contact Network Models.

    Directory of Open Access Journals (Sweden)

    David A Rolls

    Full Text Available We compare two broad types of empirically grounded random network models in terms of their abilities to capture both network features and simulated Susceptible-Infected-Recovered (SIR epidemic dynamics. The types of network models are exponential random graph models (ERGMs and extensions of the configuration model. We use three kinds of empirical contact networks, chosen to provide both variety and realistic patterns of human contact: a highly clustered network, a bipartite network and a snowball sampled network of a "hidden population". In the case of the snowball sampled network we present a novel method for fitting an edge-triangle model. In our results, ERGMs consistently capture clustering as well or better than configuration-type models, but the latter models better capture the node degree distribution. Despite the additional computational requirements to fit ERGMs to empirical networks, the use of ERGMs provides only a slight improvement in the ability of the models to recreate epidemic features of the empirical network in simulated SIR epidemics. Generally, SIR epidemic results from using configuration-type models fall between those from a random network model (i.e., an Erdős-Rényi model and an ERGM. The addition of subgraphs of size four to edge-triangle type models does improve agreement with the empirical network for smaller densities in clustered networks. Additional subgraphs do not make a noticeable difference in our example, although we would expect the ability to model cliques to be helpful for contact networks exhibiting household structure.

  12. A comparative study of three simulation optimization algorithms for solving high dimensional multi-objective optimization problems in water resources

    Science.gov (United States)

    Schütze, Niels; Wöhling, Thomas; de Play, Michael

    2010-05-01

    Some real-world optimization problems in water resources have a high-dimensional space of decision variables and more than one objective function. In this work, we compare three general-purpose, multi-objective simulation optimization algorithms, namely NSGA-II, AMALGAM, and CMA-ES-MO when solving three real case Multi-objective Optimization Problems (MOPs): (i) a high-dimensional soil hydraulic parameter estimation problem; (ii) a multipurpose multi-reservoir operation problem; and (iii) a scheduling problem in deficit irrigation. We analyze the behaviour of the three algorithms on these test problems considering their formulations ranging from 40 up to 120 decision variables and 2 to 4 objectives. The computational effort required by each algorithm in order to reach the true Pareto front is also analyzed.

  13. A comparative simulation study of coupled THM processes and their effect on fractured rock permeability around nuclear waste repositories

    Energy Technology Data Exchange (ETDEWEB)

    Rutqvist, Jonny; Barr, Deborah; Birkholzer, Jens T.; Fujisaki, Kiyoshi; Kolditz, Olf; Liu, Quan-Shen; Fujita, tomoo; Wang, Wenqing; Zhang, Cheng-Yuan

    2008-10-23

    This paper presents an international, multiple-code, simulation study of coupled thermal, hydrological, and mechanical (THM) processes and their effect on permeability and fluid flow in fractured rock around heated underground nuclear waste emplacement drifts. Simulations were conducted considering two types of repository settings: (a) open emplacement drifts in relatively shallow unsaturated volcanic rock, and (b) backfilled emplacement drifts in deeper saturated crystalline rock. The results showed that for the two assumed repository settings, the dominant mechanism of changes in rock permeability was thermal-mechanically-induced closure (reduced aperture) of vertical fractures, caused by thermal stress resulting from repository-wide heating of the rock mass. The magnitude of thermal-mechanically-induced changes in permeability was more substantial in the case of an emplacement drift located in a relatively shallow, low-stress environment where the rock is more compliant, allowing more substantial fracture closure during thermal stressing. However, in both of the assumed repository settings in this study, the thermal-mechanically-induced changes in permeability caused relatively small changes in the flow field, with most changes occurring in the vicinity of the emplacement drifts.

  14. Nanofibrous Chitosan-Polyethylene Oxide Engineered Scaffolds: A Comparative Study between Simulated Structural Characteristics and Cells Viability

    Directory of Open Access Journals (Sweden)

    Mohammad Kazemi Pilehrood

    2014-01-01

    Full Text Available 3D nanofibrous chitosan-polyethylene oxide (PEO scaffolds were fabricated by electrospinning at different processing parameters. The structural characteristics, such as pore size, overall porosity, pore interconnectivity, and scaffold percolative efficiency (SPE, were simulated by a robust image analysis. Mouse fibroblast cells (L929 were cultured in RPMI for 2 days in the presence of various samples of nanofibrous chitosan/PEO scaffolds. Cell attachments and corresponding mean viability were enhanced from 50% to 110% compared to that belonging to a control even at packed morphologies of scaffolds constituted from pores with nanoscale diameter. To elucidate the correlation between structural characteristics within the depth of the scaffolds’ profile and cell viability, a comparative analysis was proposed. This analysis revealed that larger fiber diameters and pore sizes can enhance cell viability. On the contrary, increasing the other structural elements such as overall porosity and interconnectivity due to a simultaneous reduction in fiber diameter and pore size through the electrospinning process can reduce the viability of cells. In addition, it was found that manipulation of the processing parameters in electrospinning can compensate for the effects of packed morphologies of nanofibrous scaffolds and can thus potentially improve the infiltration and viability of cells.

  15. Antibiotics dispensing for URTIs by community pharmacists and general medical practitioners in Penang, Malaysia: A comparative study using simulated patients

    OpenAIRE

    Alabid, Alamin Hassan M. A.; Ibrahim, Mohamed Izham Mohamed; Hassali,Mohamed Azmi

    2014-01-01

    Background: In Malaysia, doctors in private clinics (often called dispensing doctors) are permitted to dispense medicines. This potentially may compromise rational dispensing of medicines in general and antibiotics in particular. Aim: This study explored, assessed and compared dispensing of antibiotics between Community Pharmacist (CP) and General Practitioners (GPs) regarding symptomatic diagnosis, antibiotic categories, adherence to therapeutic doses and promotion of generic antibiotics...

  16. Effective use of modeling and simulation in designing bioequivalence and comparability studies of large-molecule compounds: the case of erythropoietin.

    Science.gov (United States)

    Nakai, Kiyohiko; Miyata, Kumiko; Iida, Satofumi; Kawanishi, Takehiko

    2015-06-01

    Bioequivalence and comparability studies are necessary for changing formulations of large-molecule drugs, such as antibody drugs and protein products, and in the development of their biosimilars. This study is the first application of modeling and simulation (M&S) in the design of bioequivalence and comparability studies of erythropoietin as an example of a large-molecule drug. A novel population pharmacokinetic and pharmacodynamic (PPK/PD) model was developed for erythropoietin. Based on this PPK/PD model, the probabilities of success of bioequivalence and comparability studies were simulated with various numbers of subjects and samples. The simulation indicated that the minimum numbers of subjects and samples required to satisfy the criteria for bioequivalence and comparability studies were as follows: fewest for the area under the serum concentration-time curve, more for the area under the efficacy-time curve, and most for the maximum serum concentration of erythropoietin. These results suggested that M&S could be successfully applied in the design of bioequivalence and comparability studies of large-molecule drugs.

  17. Comparative simulation study of effects of eddy-topography interaction in the East/Japan Sea deep circulation

    Institute of Scientific and Technical Information of China (English)

    CHOI Youngjin

    2015-01-01

    In this study the structure and seasonal variations of deep mean circulation in the East/Japan Sea (EJS) were numerically simulated using a mid-resolution ocean general circulation model with two different parameterizations for the eddy-topography interaction (ETI). The strong deep mean circulations observed in the EJS are well reproduced when using the ETI parameterizations. The seasonal variability in the EJS deep layer is shown by using ETI parameterization based on the potential vorticity approach, while it is not shown in the statistical dynamical parameterization. The driving mechanism of the strong deep mean currents in the EJS are discussed by investigating the effects of model grids and parameterizations. The deep mean circulation is more closely related to the baroclinic process and potential vorticity than it is to the wind driven circulation.

  18. Molecular Dynamics Simulations of Ligand-Induced Flap Conformational Changes in Cathepsin-D-A Comparative Study.

    Science.gov (United States)

    Arodola, Olayide A; Soliman, Mahmoud E S

    2016-11-01

    The flap region in aspartic proteases is a unique structural feature to this class of enzymes, and found to have a profound impact on protein overall structure, function, and dynamics. Understanding the structure and dynamic behavior of the flap regions is crucial in the design of selective inhibitors against aspartic proteases. Cathepsin-D, an aspartic protease enzyme, has been implicated in a long list of degenerative diseases as well as breast cancer progression. Presented herein, for the first time, is a comprehensive description of the conformational flap dynamics of cathepsin-D using a comparative 50 ns "multiple" molecular dynamics simulations. Diverse collective metrics were proposed to accurately define flap dynamics. These are distance d1 between the flap tips residues (Gly79 and Met301); dihedral angle ϕ; in addition to TriCα angles Gly79-Asp33-Asp223, θ1 , and Gly79-Asp223-Met301, θ2 . The maximum distance attained throughout the simulation was 17.42 and 11.47 Å for apo and bound cathepsin-D, respectively, while the minimum distance observed was 8.75 and 6.32 Å for apo and bound cathepsin-D, respectively. The movement of the flap as well as the twist of the active pocket can properly be explained by measuring the angle, θ1 , between Gly79-Asp33-Met301 and correlating it with the distance Cα of the flap tip residues. The asymmetrical opening of the binding cavity was best described by the large shift of -6.26° to +20.94° in the dihedral angle, ϕ, corresponding to the full opening of the flap at a range of 31-33 ns. A wide-range of post-dynamic analyses was also applied in this report to supplement our findings. We believe that this report would augment current efforts in designing potent structure-based inhibitors against cathepsin-D in the treatment of breast cancer and other degenerative diseases. J. Cell. Biochem. 117: 2643-2657, 2016. © 2016 Wiley Periodicals, Inc.

  19. Development and application of an UHPLC-MS method for comparative pharmacokinetic study of phenolic components from dragon's blood in rats under simulated microgravity environment.

    Science.gov (United States)

    Li, Yujuan; Li, George Q; Li, Yongzhi; Deng, Yulin; Deng, Li

    2016-03-20

    Dragon's blood is a commonly used Chinese herbal medicine shown to have protective effects in simulated microgravity in rats and mice. The current study aimed to develop an ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS) method for simultaneous determination of four phenolic components from the herb: loureirin A, loureirin C, 7,4'-dihydroxyflavone and pterostilbene in rats, and use the method for comparative study on the pharmacokinetics (PK) and excretion of these components in rats after oral dosage of dragon's blood under simulated microgravity environments. The results showed the developed UHPLC-MS method was sensitive and rapid. The comparative pharmacokinetic study in rats showed loureirin A, loureirin C and 7,4-dihydroxyflavone had decreased Cmax and AUC and increased Vd and CL in simulated microgravity environment; but pterostilbene had the opposite changes. The four phenolic components also showed increased or decreased excretions in simulated microgravity rats. These results indicate the chemical structure and physicochemical property, as well as physiological conditions may have an impact on the absorption and excretion of phenolic components in simulated microgravity environment. It also implies that different drug may behave differently in the same spaceflight condition leading to an increase or a reduction in pharmacodynamic outcomes.

  20. A Comparative CFD Study on Simulating Flameless Oxy-Fuel Combustion in a Pilot-Scale Furnace

    Directory of Open Access Journals (Sweden)

    Mersedeh Ghadamgahi

    2016-01-01

    Full Text Available The current study presents a method to model the flameless oxy-fuel system, with a comparative approach, as well as validation of the predictions. The validation has been done by comparing the predicted results with previously published experimental results from a 200 kW pilot furnace. A suction pyrometer has been used to measure the local temperature and concentrations of CO, CO2, and O2 at 24 different locations. A three-dimensional CFD model was developed and the validity of using different submodels describing turbulence and chemical reactions was evaluated. The standard k-ε model was compared with the realizable k-ε model for turbulence, while Probability Density Function (PDF with either chemical equilibrium or the Steady Laminar Flamelet Model (SLFM was evaluated for combustion. Radiation was described using a Discrete Ordinates Model (DOM with weighted-sum-of-grey-gases model (WSGGM. The smallest deviation between predictions and experiments for temperature (1.2% was found using the realizable k-ε model and the SLFM. This improvement affects the prediction of gaseous species as well since the deviation between predictions and experiments for CO2 volume percentages decreased from 6% to 1.5%. This provides a recommendation for model selections in further studies on flameless oxy-fuel combustion.

  1. Comparative Validation of Building Simulation Software

    DEFF Research Database (Denmark)

    Kalyanova, Olena; Heiselberg, Per

    _2 and DSF200_4, the third empirical test case is also specified as DSF400_3, but it's completion is under consideration. The comparative test cases can not be directly used for the validation of the software due to often disagreement of the results, however the result of the exercises...... is that the comparative validation can be regarded as the main argument to continue the validation of the building simulation software for the buildings with the double skin façade with the empirical validation test cases.......The scope of this subtask is to perform a comparative validation of the building simulation software for the buildings with the double skin façade. The outline of the results in the comparative validation identifies the areas where is no correspondence achieved, i.e. calculation of the air flow...

  2. A Comparative Study of Fluid Flow and Mass Transfer in a Trumpet-Shaped Ladle Shroud Using Large Eddy Simulation

    Science.gov (United States)

    Zhang, Jiangshan; Li, Jingshe; Yan, Yi; Chen, Zhixin; Yang, Shufeng; Zhao, Jingwei; Jiang, Zhengyi

    2016-02-01

    The advantages of trumpet-shaped ladle shrouds (TLS) have been frequently demonstrated over conventional straight-bore ladle shrouds (CLS) with respect to production efficiency and molten steel quality in continuous casting practices. The present study is to shed some lights on why the TLS are better than the CLS design by examining the fluid dynamics and mass transfer using large eddy simulation. The obtained numerical results were validated with particle imaging velocimetry experiments. Flow velocity, deformation, turbulent energy dissipation, and mixing kinetics of tracer were discussed. The results showed that the entering jet of the CLS flowed straight down into the tundish with a relatively high speed (average at 0.710 to 0.815 m/s) and turbulent kinetic energy. However, the trumpet section of a TLS intensified velocity differences, strain rates, and vortices, and promoted an increase on turbulence dissipation rate in the interior of the ladle shroud. The average speed of the entering jet to the tundish was decreased to 0.270 to 0.410 m/s from the 0.708 m/s of the inlet speed. The entering jet from the TLS swung, twisted and well mixed with surrounding fluid in the tundish, and dissipated its kinetic energy. Consequently, the turbulence of the whole flow field as well as the mean skin friction coefficient of tundish wall and the velocity of free liquid surface were reduced. A tracer experiment was carried out to study mass transfer and flow mixing behavior, and the results demonstrated that the use of the TLS increased the plug volume and decreased the dead zone, thereby enhancing inclusion flotation.

  3. Mathematical Modelling, Simulation and Comparative Study of Seven Gases for a Single Pass, Single Duct PVT System

    Directory of Open Access Journals (Sweden)

    Bhaskar B. Gardas

    2012-06-01

    Full Text Available Solar cell produces electricity when it receives solar energy. With the increase in module temperature panel electrical efficiency decreases. This undesirable effect can be partially avoided by applying a cooling unit with fluid circulation around the PV module. Such unit is called photovoltaic/thermal collector (PV/T or hybrid (PV/T. The objective of the present work is to design a heat extracting system for the solar cell in order to increase its power output, electrical efficiency and decrease its specific power output. also to extract the heat energy. A hybrid solar system which generates both electricity and heat energy simultaneously is studied. This hybrid system consists of PV cells attached to an absorber plate with fins attached at the other side of the absorber surface. Simulation model for single pass, single duct solar collector with fins is prepared and performance curves are obtained. Performance with seven different gases analyzed for maximum heat transfer, minimum specific power, minimum mass flow rate & minimum number of fins and maximum electrical efficiency. Hydrogen is found to be the most suitable option with the present. For hydrogen, the system requires a mass flow rate of 0.00275 kg/s, which is the least amongst all, Theoretical number of fins required in this case is found out to be 3.46. Electrical efficiency 32.54 % which is maximum of all other gases, specific power output 3.073x10-3 m2/W, which is the least amongst all for n = 4.

  4. Simulating the germination response to diurnally alternating temperatures under climate change scenarios: comparative studies on Carex diandra seeds.

    Science.gov (United States)

    Fernández-Pascual, Eduardo; Seal, Charlotte E; Pritchard, Hugh W

    2015-02-01

    Environmental temperature regulates plant regeneration via seed in several superimposed ways, and this complex regulation will be disrupted by climate change. The role of diurnally alternating temperatures (ΔT) in terminating dormancy will be a major factor in this disruption, as its effects on seed germination are immediate. The effect of ΔT on seed germination was modelled using two populations of the wetland sedge Carex diandra, one from a montane site and one from a subalpine site. A cardinal-temperature model was fitted to germination results obtained from a thermal gradient plate, and the model was used to simulate changes in germination under two possible future climate scenarios (RCP2·6 and RCP8·5, for representative concentration pathways) as defined by the Intergovernmental Panel on Climate Change. Scenario RCP2·6 projected moderate increases in average temperatures and ΔT, whereas RCP8·5 projected greater warming and higher ΔT. Increasing ΔT decreased the base temperature for seed germination and the thermal time required for germination. The effect of higher ΔT together with the higher temperatures increased germination under both climate scenarios. Carex diandra germination is highly responsive to potential changes in ΔT, and thus this study highlights the role of ΔT in seed responses to climate change. Comprehensive cardinal-temperature models, encompassing the different effects of temperature on seed germination, are needed to understand how climate change will affect plant regeneration. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  5. A comparative study via Monte Carlo simulation of new inorganic scintillator Cs2HfCl6 for applications in nuclear medicine, security and defense, and astrophysics

    Science.gov (United States)

    Chen, Henry; Raby, Paul

    2016-09-01

    Cs2HfCl6 (CHC) is one of the most promising recently discovered new inorganic single crystal scintillator that has high light output, non-hygroscopic, no self-activity, having energy resolution significantly better than NaI(Tl), even approaching that of LaBr3 yet can also potentially be at a much lower cost than LaBr3. This study attempts to use Monte Carlo simulation to examine the great potential offered by this new scintillator. CHC's detector performance is compared via simulation with that of 4 typical existing scintillators of the same size and same PMT readout. Two halide-scintillators: NaI(Tl) and LaBr3 and two oxide-scintillators: GSO and LSO were used in this simulation to compare their 122 keV and 511 keV gamma responses with that of CHC with both spectroscopy application and imaging applications in mind. Initial simulation results are very promising and consistent with reported experimental measurements. Beside detector energy resolution, image-quality measurement parameters commonly used to characterize imaging detectors as in nuclear medicine such as Light Response Function (LRF) which goes in parallel with spatial resolution and simulated position spectra will also be presented and discussed.

  6. A comparative study of a stochastic and deterministic simulation of strong ground motion applied to the Kozani-Grevena (NW Greece 1995 sequence

    Directory of Open Access Journals (Sweden)

    C. Papaioannou

    2000-06-01

    Full Text Available We present the results of a comparative study of two intrinsically different methodologies, a stochastic one and a deterministic one, performed to simulate strong ground motion in the Kozani area (NW Greece. Source parameters were calculated from empirical relations in order to check their reliability, in combination with the applied methodologies, to simulate future events. Strong ground motion from the Kozani mainshock (13 May, 1995, M w = 6.5 was synthesized by using both the stochastic method for finite-fault cases and the empirical Green’s function method. The latter method was also applied to simulate a Mw = 5.1 aftershock (19 May, 1995. The results of the two simulations computed for the mainshock are quite satisfactory for both methodologies at the frequencies of engineering interest (> ~ 2 Hz. This strengthens the idea of incorporating proper empirical relations for the estimation of source parameters in a priori simulations of strong ground motion from future earthquakes. Nevertheless, the results of the simulation of the smaller earthquake point out the need for further investigation of regional or local, if possible, relations for estimating source parameters at smaller magnitude ranges

  7. An OHD-RIKES and simulation study comparing a benzylmethylimidazolium ionic liquid with an equimolar mixture of dimethylimidazolium and benzene.

    Science.gov (United States)

    Xue, Lianjie; Tamas, George; Matthews, Richard P; Stone, Anthony J; Hunt, Patricia A; Quitevis, Edward L; Lynden-Bell, Ruth M

    2015-04-21

    The principal difference between 1-benzyl-3-methyl-imidazolium triflimide [BzC1im][NTf2] and an equimolar mixture of benzene and dimethylimidazolium triflimide [C1C1im][NTf2] is that in the former the benzene moieties are tied to the imidazolium ring, while in the latter they move independently. We use femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES) and molecular simulations to explore some properties of these two systems. The Kerr spectra show small differences in the spectral densities; the simulations also show very similar environments for both the imidazolium rings and the phenyl or benzene parts of the molecules. The low frequency vibrational densities of states are also similar in the model systems. In order to perform the simulations we developed a model for the [BzC1im](+) cation and found that the barriers to rotation of the two parts of the molecule are low.

  8. A Comparative Study of Cognitive Retention Using Simulation-Gaming as Opposed to Lecture-Discussion Techniques.

    Science.gov (United States)

    Lucas, Lawrence A.; And Others

    Research investigated the effect that the uses of simulation-gaming techniques have upon the acquisition and cognitive retention of facts, concepts, and principles. Two hundred and ninety-five students in public secondary schools in Indiana participated in the project; these were divided into experimental and control groups which received…

  9. Comparative waste forms study

    Energy Technology Data Exchange (ETDEWEB)

    Wald, J.W.; Lokken, R.O.; Shade, J.W.; Rusin, J.M.

    1980-12-01

    A number of alternative process and waste form options exist for the immobilization of nuclear wastes. Although data exists on the characterization of these alternative waste forms, a straightforward comparison of product properties is difficult, due to the lack of standardized testing procedures. The characterization study described in this report involved the application of the same volatility, mechanical strength and leach tests to ten alternative waste forms, to assess product durability. Bulk property, phase analysis and microstructural examination of the simulated products, whose waste loading varied from 5% to 100% was also conducted. The specific waste forms investigated were as follows: Cold Pressed and Sintered PW-9 Calcine; Hot Pressed PW-9 Calcine; Hot Isostatic Pressed PW-9 Calcine; Cold Pressed and Sintered SPC-5B Supercalcine; Hot Isostatic pressed SPC-5B Supercalcine; Sintered PW-9 and 50% Glass Frit; Glass 76-68; Celsian Glass Ceramic; Type II Portland Cement and 10% PW-9 Calcine; and Type II Portland Cement and 10% SPC-5B Supercalcine. Bulk property data were used to calculate and compare the relative quantities of waste form volume produced at a spent fuel processing rate of 5 metric ton uranium/day. This quantity ranged from 3173 L/day (5280 Kg/day) for 10% SPC-5B supercalcine in cement to 83 L/day (294 Kg/day) for 100% calcine. Mechanical strength, volatility, and leach resistance tests provide data related to waste form durability. Glass, glass-ceramic and supercalcine ranked high in waste form durability where as the 100% PW-9 calcine ranked low. All other materials ranked between these two groupings.

  10. Simulation and comparative study of tunneling field effect transistors with dopant-segregated Schottky source/drain

    Science.gov (United States)

    Zhang, Yi Bo; Sun, Lei; Xu, Hao; Han, Jing Wen

    2016-04-01

    Dopant-segregated Schottky source/drain tunneling field effect transistors (STFET) are investigated in this paper. The working mechanisms of STFET and the influence of device parameters are studied with Synopsys Sentaurus. Schottky source/drain MOSFETs possess several advantages over conventional MOSFETs, and dopant segregation can be feasibly achieved within current silicidation process. With dopant segregation, highly doped regions can be obtained after silicidation, which is necessary for band-to-band tunneling. With proper parameter setting, STFET can achieve comparable performance as TFET. High segregation doping for STFET is required to increase band-to-band tunneling probability and suppress bipolar behaviors. Increasing the electron barrier height at source side helps to provide larger drive current and higher on/off ratio. It is also found that STFET’s on-state performance is irrelevant to the segregation length when the segregation length is larger than a certain value. Furthermore, STFET is also insensitive to the Schottky barrier at drain side when the Schottky barrier at source side is fixed, which would relax the requirement for source/drain fabrication.

  11. Product Costing in FMT: Comparing Deterministic and Stochastic Models Using Computer-Based Simulation for an Actual Case Study

    DEFF Research Database (Denmark)

    Nielsen, Steen

    2000-01-01

    This paper expands the traditional product costing technique be including a stochastic form in a complex production process for product costing. The stochastic phenomenon in flesbile manufacturing technologies is seen as an important phenomenon that companies try to decreas og eliminate. DFM has...... been used for evaluating the appropriateness of the firm's production capability. In this paper a simulation model is developed to analyze the relevant cost behaviour with respect to DFM and to develop a more streamlined process in the layout of the manufacturing process....

  12. Comparative study of large scale simulation of underground explosions inalluvium and in fractured granite using stochastic characterization

    Science.gov (United States)

    Vorobiev, O.; Ezzedine, S. M.; Antoun, T.; Glenn, L.

    2014-12-01

    This work describes a methodology used for large scale modeling of wave propagation fromunderground explosions conducted at the Nevada Test Site (NTS) in two different geological settings:fractured granitic rock mass and in alluvium deposition. We show that the discrete nature of rockmasses as well as the spatial variability of the fabric of alluvium is very important to understand groundmotions induced by underground explosions. In order to build a credible conceptual model of thesubsurface we integrated the geological, geomechanical and geophysical characterizations conductedduring recent test at the NTS as well as historical data from the characterization during the undergroundnuclear test conducted at the NTS. Because detailed site characterization is limited, expensive and, insome instances, impossible we have numerically investigated the effects of the characterization gaps onthe overall response of the system. We performed several computational studies to identify the keyimportant geologic features specific to fractured media mainly the joints; and those specific foralluvium porous media mainly the spatial variability of geological alluvium facies characterized bytheir variances and their integral scales. We have also explored common key features to both geologicalenvironments such as saturation and topography and assess which characteristics affect the most theground motion in the near-field and in the far-field. Stochastic representation of these features based onthe field characterizations have been implemented in Geodyn and GeodynL hydrocodes. Both codeswere used to guide site characterization efforts in order to provide the essential data to the modelingcommunity. We validate our computational results by comparing the measured and computed groundmotion at various ranges. This work performed under the auspices of the U.S. Department of Energy by Lawrence LivermoreNational Laboratory under Contract DE-AC52-07NA27344.

  13. Comparative Packaging Study

    Science.gov (United States)

    Perchonok, Michele; Antonini, David

    2008-01-01

    This viewgraph presentation describes a comparative packaging study for use on long duration space missions. The topics include: 1) Purpose; 2) Deliverables; 3) Food Sample Selection; 4) Experimental Design Matrix; 5) Permeation Rate Comparison; and 6) Packaging Material Information.

  14. Comparative study of apatite formation on CaSiO3 ceramics in simulated body fluids with different carbonate concentrations.

    Science.gov (United States)

    Iimori, Yusuke; Kameshima, Yoshikazu; Okada, Kiyoshi; Hayashi, Shigeo

    2005-01-01

    Apatite formation on CaSiO3 ceramics was investigated using two different simulated body fluids (SBF) proposed by Kokubo (1990) and Tas (2000) and three sample/SBF (S/S) ratios (1.0, 2.5 and 8.3 mg/ml) at 36.5 degrees C for 1-25 days. The CaSiO3 ceramic was prepared by firing coprecipitated gel with Ca/Si = 0.91 at 1400 degrees C. The bulk density was 2.14 g/cm3 and the relative density about 76%. The two SBF solutions contain different concentrations of HCO3- and Cl- ions, the concentrations of which are closer to human blood plasma in the Tas SBF formulation than in the Kokubo formulation. The pH values in the former solution are also more realistic. The CaSiO3 ceramics show apatite formation in SBF (Kokubo) after soaking for only 1 day at all S/S ratios whereas different phases were formed at each S/S ratio in SBF (Tas). The crystalline phases formed were mainly apatite at S/S = 1.0 mg/ml, carbonate-type apatite at 2.5 mg/ml and calcite at 8.3 mg/ml. At higher S/S ratios the increase in the Ca concentration became higher while the P concentration became lower in the reacted SBF. These changes in SBF concentrations and increasing pH occurred at higher S/S ratios, producing more favorable conditions in the SBF for the formation of carbonate bearing phases, finally leading to the formation of calcite instead of apatite in the higher HCO3- ion concentration SBF (Tas). Apatite is, however, formed in the lower HCO3- ion concentration SBF (Kokubo) even though the Ca and P concentrations change in a similar manner to SBF (Tas).

  15. Comparative visual analysis of 3D urban wind simulations

    Science.gov (United States)

    Röber, Niklas; Salim, Mohamed; Grawe, David; Leitl, Bernd; Böttinger, Michael; Schlünzen, Heinke

    2016-04-01

    Climate simulations are conducted in large quantity for a variety of different applications. Many of these simulations focus on global developments and study the Earth's climate system using a coupled atmosphere ocean model. Other simulations are performed on much smaller regional scales, to study very small fine grained climatic effects. These microscale climate simulations pose similar, yet also different, challenges for the visualization and the analysis of the simulation data. Modern interactive visualization and data analysis techniques are very powerful tools to assist the researcher in answering and communicating complex research questions. This presentation discusses comparative visualization for several different wind simulations, which were created using the microscale climate model MITRAS. The simulations differ in wind direction and speed, but are all centered on the same simulation domain: An area of Hamburg-Wilhelmsburg that hosted the IGA/IBA exhibition in 2013. The experiments contain a scenario case to analyze the effects of single buildings, as well as examine the impact of the Coriolis force within the simulation. The scenario case is additionally compared with real measurements from a wind tunnel experiment to ascertain the accuracy of the simulation and the model itself. We also compare different approaches for tree modeling and evaluate the stability of the model. In this presentation, we describe not only our workflow to efficiently and effectively visualize microscale climate simulation data using common 3D visualization and data analysis techniques, but also discuss how to compare variations of a simulation and how to highlight the subtle differences in between them. For the visualizations we use a range of different 3D tools that feature techniques for statistical data analysis, data selection, as well as linking and brushing.

  16. A Comparative Study On The Action Potential Simulation (APS Therapy And The Routine Physiotherapy Protocol In Knee Osteoarthritisin Elderly People

    Directory of Open Access Journals (Sweden)

    Abbas Rahimi

    2012-04-01

    Full Text Available Background and Aim: Knee osteoarthritis is the most common cause for which the elderly people refere to physiotherapy outpatient clinics. This study aimed to investigate the effects of the Action Potential Stimulation (APS Therapy and the routine physiotherapy (PT protocol on relieving pain and swelling as well as the duration of the relief period in patients with knee osteoarthritis. Materials and Methods: 69 patients (62 females & 7 males with knee osteoarthritis were recruited in this study. The subjects were divided into two groups including APS Therapy (n=37, mean age: 55±13 years old and the routine PT protocol (n=32, mean age: 61±14 years old groups. A 10-session treatment period was carried out for each group; and their pain and swelling were measured at the first, fifth and tenth sessions and also one-month after the last session (follow up. The swelling was measured using measuring the circumference of the knee on the patella, 5 Cm above and 5 Cm below the patella. The routine PT protocol consisted of hot pack, ultrasound, TENS and exercise; and the APS therapy protocol included hot pack, APS Therapy and the same exercise. During the follow up, 50 out of 61 subjects were called on the phone and any pain changes were recorded.Results: In terms of swelling, the results showed significant reduction just on the patella only in the APS Therapy group (P<0.05. Visual Analogue Pain Scale (VAPS indicated a significant pain reduction in both groups. However, the APS Therapy group showed significantly pain reduction at the end of sessions five, ten and the follow up session (P<0.05. It was also revealed that while routine PT subjects showed no significant pain changes between the tenth and the follow up session, a gradual pain reduction was seen in the APS therapy group during this period (P<0.05. A gradual dosage reduction was recorded only in the APS therapy group, indicating a slight correlation with pain reduction (r=0.4.Conclusion: The

  17. Low-Fidelity Haptic Simulation Versus Mental Imagery Training for Epidural Anesthesia Technical Achievement in Novice Anesthesiology Residents: A Randomized Comparative Study.

    Science.gov (United States)

    Lim, Grace; Krohner, Robert G; Metro, David G; Rosario, Bedda L; Jeong, Jong-Hyeon; Sakai, Tetsuro

    2016-05-01

    There are many teaching methods for epidural anesthesia skill acquisition. Previous work suggests that there is no difference in skill acquisition whether novice learners engage in low-fidelity (LF) versus high-fidelity haptic simulation for epidural anesthesia. No study, however, has compared the effect of LF haptic simulation for epidural anesthesia versus mental imagery (MI) training in which no physical practice is attempted. We tested the hypothesis that MI training is superior to LF haptic simulation training for epidural anesthesia skill acquisition. Twenty Post-Graduate Year 2 (PGY-2) anesthesiology residents were tested at the beginning of the training year. After a didactic lecture on epidural anesthesia, they were randomized into 2 groups. Group LF had LF simulation training for epidural anesthesia using a previously described banana simulation technique. Group MI had guided, scripted MI training in which they initially were oriented to the epidural kit components and epidural anesthesia was described stepwise in detail, followed by individual mental rehearsal; no physical practice was undertaken. Each resident then individually performed epidural anesthesia on a partial-human task trainer on 3 consecutive occasions under the direct observation of skilled evaluators who were blinded to group assignment. Technical achievement was assessed with the use of a modified validated skills checklist. Scores (0-21) and duration to task completion (minutes) were recorded. A linear mixed-effects model analysis was performed to determine the differences in scores and duration between groups and over time. There was no statistical difference between the 2 groups for scores and duration to task completion. Both groups showed similarly significant increases (P = 0.0015) in scores over time (estimated mean score [SE]: group MI, 15.9 [0.55] to 17.4 [0.55] to 18.6 [0.55]; group LF, 16.2 [0.55] to 17.7 [0.55] to 18.9 [0.55]). Time to complete the procedure decreased

  18. Comparative evaluation of a novel smart-seal obturating system and its homogeneity of using cone beam computed tomography: In vitro simulated lateral canal study

    Directory of Open Access Journals (Sweden)

    Shashank Arora

    2014-01-01

    Full Text Available Aim: The aim was to evaluate and compare a novel polyamide polymer based obturating system and Gutta-percha and sealer in filling simulated lateral canals and their homogeneity when used for obturating the root canals. Materials and Methods: A total of 60 freshly extracted human single rooted teeth with fully formed apices were selected for this study. Teeth were de-coronated, and roots were standardized to a working length of 15 mm. Root canal preparation was carried out with rotary Protaper file system in all groups. The specimens were then randomly divided into three groups A, B, and C (n = 20. Ten samples from each group were decalcified and simulated lateral canals were made at 2, 4, and 6 mm from the root apex. Remaining ten samples from each group were maintained calcified. Group A was obturated with SmartSeal system (Prosmart-DRFP Ltd., Stamford, UK. Group B was obturated with sectional backfill method. Group C was obutrated with cold lateral compaction method (control. Decalcified samples from the respective groups were analyzed with digital radiography and photography and the measurement of the linear extension and area of lateral canal filling was done using UTHSCSA (UTHSCSA Image Tool for Windows version 3.0, San Antonio, TX, USA software. Calcified samples were subjected to cone beam computed tomography image analysis sectioned axially. Results: Group A 92.46 ± 19.45 showed greatest extent of filling in lateral canals and denser homogeneity of oburation, followed by Group B 78.43 ± 26.45 and Group C 52.12 ± 36.67. Conclusions: Polyamide polymer obturation proved to have greater efficiency when compared with Gutta-percha system, when used for obturation with regards to adaptation of the sealer and penetration into the simulated lateral canals.

  19. Operations dashboard: comparative study

    Science.gov (United States)

    Ramly, Noor Nashriq; Ismail, Ahmad Zuhairi; Aziz, Mohd Haris; Ahmad, Nurul Haszeli

    2011-10-01

    In this present days and age, there are increasing needs for companies to monitor application and infrastructure health. Apart from having proactive measures to secure their application and infrastructure, many see monitoring dashboards as crucial investment in disaster preparedness. As companies struggle to find the best solution to cater for their needs and interest for monitoring their application and infrastructure's health, this paper summarizes the studies made on several known off-the-shelf operations dashboard and in-house developed dashboard. A few criteria of good dashboard are collected from previous studies carried out by several researchers and rank them according to importance and business needs. The finalized criteria that will be discussed in later sections are data visualization, performance indicator, dashboard personalization, audit capability and alert/ notification. Comparative studies between several popular dashboards were then carried out to determine whether they met these criteria that we derived from the first exercise. The findings hopefully can be used to educate and provide an overview of selecting the best IT application and infrastructure operations dashboard that suit business needs, thus become the main contribution of this paper.

  20. Comparing MMS Observations with Theory and Simulation

    Science.gov (United States)

    Moore, Thomas Earle; Burch, James L.; Torbert, Roy B.

    2016-04-01

    MMS completes its first year in orbit on 13 March 2016, and its science data set will by then be open to use by the entire research community, including theorists and simulators. We will briefly summarize observational highlights from the first year of MMS operations to illustrate the unprecedented accuracy and resolution of phenomena that have until now been inaccessible to observation, especially at electron scales. The goal of such observations has always been to test and refine our understanding of reconnection, as embodied in our theoretical and simulation models, with the goal of better predicting the morphology and dynamic evolution of reconnection as a driver of space weather. Toward that end, we summarize the MMS data products and suggest ways for the theory and modeling community to make contact with MMS observations and use them to test their models.

  1. Simulating the implementation of the administrative justice act with ThinkLets and GroupSystems: a comparative analysis from three field studies

    CSIR Research Space (South Africa)

    Phahlamohlaka, J

    2006-09-01

    Full Text Available Presented in this paper are the results of three simulation exercises performed as part of a series of field studies whose object is the implementation of the Promotion of Administrative Justice Act. The unit of analysis of the study is the process...

  2. Comparative study of sea ice dynamics simulations with a Maxwell elasto-brittle rheology and the elastic-viscous-plastic rheology in NEMO-LIM3

    Science.gov (United States)

    Raulier, Jonathan; Dansereau, Véronique; Fichefet, Thierry; Legat, Vincent; Weiss, Jérôme

    2017-04-01

    Sea ice is a highly dynamical environment characterized by a dense mesh of fractures or leads, constantly opening and closing over short time scales. This characteristic geomorphology is linked to the existence of linear kinematic features, which consist of quasi-linear patterns emerging from the observed strain rate field of sea ice. Standard rheologies used in most state-of-the-art sea ice models, like the well-known elastic-viscous-plastic rheology, are thought to misrepresent those linear kinematic features and the observed statistical distribution of deformation rates. Dedicated rheologies built to catch the processes known to be at the origin of the formation of leads are developed but still need evaluations on the global scale. One of them, based on a Maxwell elasto-brittle formulation, is being integrated in the NEMO-LIM3 global ocean-sea ice model (www.nemo-ocean.eu; www.elic.ucl.ac.be/lim). In the present study, we compare the results of the sea ice model LIM3 obtained with two different rheologies: the elastic-viscous-plastic rheology commonly used in LIM3 and a Maxwell elasto-brittle rheology. This comparison is focused on the statistical characteristics of the simulated deformation rate and on the ability of the model to reproduce the existence of leads within the ice pack. The impact of the lead representation on fluxes between ice, atmosphere and ocean is also assessed.

  3. A CT-Based Simulation Study to Compare the Risk of Facet Joint Violation by the Cervical Pedicle Screw Between Degenerative and Nondegenerative Cervical Spines.

    Science.gov (United States)

    Lee, Dong-Ho; Noh, Hyounmin; Hwang, Chang Ju; Lee, Choon Sung; Abumi, Kuniyoshi; Cho, Jae Hwan

    2017-02-01

    A retrospective case-control study. This study aimed (A) to compare entry points and trajectories of the cervical pedicle screw (CPS) between degenerative and nondegenerative spines, and (B) to evaluate the risk of facet joint violation by the CPS according to the degree of facet degeneration. Entry point, trajectories, and risk of misplacement of the CPS have been widely researched; however, its application to degenerative cervical spine has to be elucidated. Sixty patients who underwent cervical surgeries at our institution were classified into two groups according to cervical facet joint degeneration. A simulation program with 0.7-mm thickness axial computed tomographic images was used to evaluate facet joint violation by the CPS from C3 to C6. Horizontal and vertical offsets of entry points were measured from two different anatomical landmarks on lateral mass, namely the lateral notch and the center of the superior ridge. The transverse and sagittal angles of the screws were also measured. Facet joint violation was evaluated and classified into either "minor" (cervical spine group at all levels (P = 0.001-0.026). In addition, facet joint violation was more frequently found in severely degenerated facet joints than in mild to moderately degenerated facet joints (P = 0.011). The entry point of CPS was moved more superiorly in the degenerative cervical spine in this study, which increased the risk of facet joint violation in our patients. Thus, surgeons need to modify the insertion technique of the CPS or to insert lateral mass screw instead of the CPS when it is considered to insert screws at the uppermost vertebra in the degenerative cervical spine. 4.

  4. A Comparative Study of Teaching Comparative Education

    OpenAIRE

    2007-01-01

    The purpose of this paper is to characterize the comparative education subjects offered in different programs in different foreign universities. As a subject, comparative education has not been firmly institutionalized in education programs in Japanese universities. There was a movement which aimed at making comparative education as one of the mandatory subjects in the teacher training program, however it was not successful. To date, comparative education subject has been offered in various p...

  5. Comparative Visualization of Climate Simulation Data

    Science.gov (United States)

    Röber, Niklas; Meier-Fleischer, Karin; Böttinger, Michael

    2014-05-01

    Visualization is the process of transforming abstract (scientific) data into a graphical representation, to aid in the understanding of the information contained within the data. Climate data sets are typically quite large, time varying, and consist of many different variables that are sampled on an underlying grid. A variety of different climate models - and sub models - are developed to simulate the climate system and its components, such as the physics of the atmosphere and the ocean, marine biogeochemical processes and the land biosphere. Visualization software is used to assist in the process of visualization and data analysis by transforming the abstract numerical information into a graphical illustration. Different approaches exist in the design of visualization software and for the process of visualization itself, depending on the type and nature of the data as well as on the visualization goal. In addition to a large high performance compute cluster that is exclusively used for climate simulations, the German Climate Computing Centre (DKRZ) also hosts a dedicated visualization cluster for post-processing, data analysis and visualization. On this visualization server, a variety of software is installed to assist the user in the data visualization task. Amongst others, the software stack includes Avizo Green, CDO, NCL, Paraview and SimVis. Each tool has its own strengths and weaknesses, and is selected by the user with regard to the visualization goal. While Avizo Green is great for visualizing the data out of the box, SimVis and Paraview are better suited for an interactive and explorative data analysis. This PICO presentation uses several different visualization solutions - among them Avizo Green, NCL, Paraview and SimVis - to analyze and visualize the same climate data set. We will thereby explicitly focus on each software's strengths, and not highlight its weaknesses. This PICO interactively shows that - depending on the visualization tool used - not

  6. Learning Oceanography from a Computer Simulation Compared with Direct Experience at Sea

    Science.gov (United States)

    Winn, William; Stahr, Frederick; Sarason, Christian; Fruland, Ruth; Oppenheimer, Peter; Lee, Yen-Ling

    2006-01-01

    Considerable research has compared how students learn science from computer simulations with how they learn from "traditional" classes. Little research has compared how students learn science from computer simulations with how they learn from direct experience in the real environment on which the simulations are based. This study compared two…

  7. Bioaccessibility studies of ferro-chromium alloy particles for a simulated inhalation scenario: a comparative study with the pure metals and stainless steel.

    Science.gov (United States)

    Midander, Klara; de Frutos, Alfredo; Hedberg, Yolanda; Darrie, Grant; Wallinder, Inger Odnevall

    2010-07-01

    The European product safety legislation, REACH, requires that companies that manufacture, import, or use chemicals demonstrate safe use and high level of protection of their products placed on the market from a human health and environmental perspective. This process involves detailed assessment of potential hazards for various toxicity endpoints induced by the use of chemicals with a minimum use of animal testing. Such an assessment requires thorough understanding of relevant exposure scenarios including material characteristics and intrinsic properties and how, for instance, physical and chemical properties change from the manufacturing phase, throughout use, to final disposal. Temporary or permanent adverse health effects induced by particles depend either on their shape or physical characteristics, and/or on chemical interactions with the particle surface upon human exposure. Potential adverse effects caused by the exposure of metal particles through the gastrointestinal system, the pulmonary system, or the skin, and their subsequent potential for particle dissolution and metal release in contact with biological media, show significant gaps of knowledge. In vitro bioaccessibility testing at conditions of relevance for different exposure scenarios, combined with the generation of a detailed understanding of intrinsic material properties and surface characteristics, are in this context a useful approach to address aspects of relevance for accurate risk and hazard assessment of chemicals, including metals and alloys and to avoid the use of in vivo testing. Alloys are essential engineering materials in all kinds of applications in society, but their potential adverse effects on human health and the environment are very seldom assessed. Alloys are treated in REACH as mixtures of their constituent elements, an approach highly inappropriate because intrinsic properties of alloys generally are totally different compared with their pure metal components. A large

  8. Comparative CFD simulations of a hydrogen fire scenario

    Science.gov (United States)

    Nobili, M.; Caruso, G.

    2017-01-01

    Hydrogen leakage and fire ignition and propagation are safety concerns in several industrial plants. In a nuclear fusion power plants the separation of hydrogen and tritium takes place in different steps, among which one or more electrolyzers are foreseen. A fire scenario could take place in case of leakage of hydrogen. In such cases, it is important to prevent the spreading of the fire to adjacent rooms and, at the same time, to withstand the pressure load on walls, to avoid radioactivity release in the surrounding environment. A preliminary study has been carried out with the aim of comparing CFD tools for fire scenario simulations involving hydrogen release. Results have been obtained comparing two codes: ANSYS Fluent© and FDS. The two codes have been compared both for hydrogen dispersion and hydrogen fire in a confined environment. The first scenario is aimed to obtaining of volume fraction 3D maps for the evaluation of the different diffusion/transport models. In the second scenario, characterized by a double-ended guillotine break, the fire is supposed to be ignited at the same time of the impact. Simulations have been carried out for the first 60 seconds. Hydrogen concentration, temperature and pressure fields are compared and discussed.

  9. A Process for Comparing Dynamics of Distributed Space Systems Simulations

    Science.gov (United States)

    Cures, Edwin Z.; Jackson, Albert A.; Morris, Jeffery C.

    2009-01-01

    The paper describes a process that was developed for comparing the primary orbital dynamics behavior between space systems distributed simulations. This process is used to characterize and understand the fundamental fidelities and compatibilities of the modeling of orbital dynamics between spacecraft simulations. This is required for high-latency distributed simulations such as NASA s Integrated Mission Simulation and must be understood when reporting results from simulation executions. This paper presents 10 principal comparison tests along with their rationale and examples of the results. The Integrated Mission Simulation (IMSim) (formerly know as the Distributed Space Exploration Simulation (DSES)) is a NASA research and development project focusing on the technologies and processes that are related to the collaborative simulation of complex space systems involved in the exploration of our solar system. Currently, the NASA centers that are actively participating in the IMSim project are the Ames Research Center, the Jet Propulsion Laboratory (JPL), the Johnson Space Center (JSC), the Kennedy Space Center, the Langley Research Center and the Marshall Space Flight Center. In concept, each center participating in IMSim has its own set of simulation models and environment(s). These simulation tools are used to build the various simulation products that are used for scientific investigation, engineering analysis, system design, training, planning, operations and more. Working individually, these production simulations provide important data to various NASA projects.

  10. Comparing Productivity Simulated with Inventory Data Using Different Modelling Technologies

    Science.gov (United States)

    Klopf, M.; Pietsch, S. A.; Hasenauer, H.

    2009-04-01

    The Lime Stone National Park in Austria was established in 1997 to protect sensible lime stone soils from degradation due to heavy forest management. Since 1997 the management activities were successively reduced and standing volume and coarse woody debris (CWD) increased and degraded soils began to recover. One option to study the rehabilitation process towards natural virgin forest state is the use of modelling technology. In this study we will test two different modelling approaches for their applicability to Lime Stone National Park. We will compare standing tree volume simulated resulting from (i) the individual tree growth model MOSES, and (ii) the species and management sensitive adaptation of the biogeochemical-mechanistic model Biome-BGC. The results from the two models are compared with filed observations form repeated permanent forest inventory plots of the Lime Stone National Park in Austria. The simulated CWD predictions of the BGC-model were compared with dead wood measurements (standing and lying dead wood) recorded at the permanent inventory plots. The inventory was established between 1994 and 1996 and remeasured from 2004 to 2005. For this analysis 40 plots of this inventory were selected which comprise the required dead wood components and are dominated by a single tree species. First we used the distance dependant individual tree growth model MOSES to derive the standing timber and the amount of mortality per hectare. MOSES is initialized with the inventory data at plot establishment and each sampling plot is treated as forest stand. The Biome-BGC is a process based biogeochemical model with extensions for Austrian tree species, a self initialization and a forest management tool. The initialization for the actual simulations with the BGC model was done as follows: We first used spin up runs to derive a balanced forest vegetation, similar to an undisturbed forest. Next we considered the management history of the past centuries (heavy clear cuts

  11. A comparative study on generating simulated Landsat NDVI images using data fusion and regression method-the case of the Korean Peninsula.

    Science.gov (United States)

    Lee, Mi Hee; Lee, Soo Bong; Eo, Yang Dam; Kim, Sun Woong; Woo, Jung-Hun; Han, Soo Hee

    2017-07-01

    Landsat optical images have enough spatial and spectral resolution to analyze vegetation growth characteristics. But, the clouds and water vapor degrade the image quality quite often, which limits the availability of usable images for the time series vegetation vitality measurement. To overcome this shortcoming, simulated images are used as an alternative. In this study, weighted average method, spatial and temporal adaptive reflectance fusion model (STARFM) method, and multilinear regression analysis method have been tested to produce simulated Landsat normalized difference vegetation index (NDVI) images of the Korean Peninsula. The test results showed that the weighted average method produced the images most similar to the actual images, provided that the images were available within 1 month before and after the target date. The STARFM method gives good results when the input image date is close to the target date. Careful regional and seasonal consideration is required in selecting input images. During summer season, due to clouds, it is very difficult to get the images close enough to the target date. Multilinear regression analysis gives meaningful results even when the input image date is not so close to the target date. Average R (2) values for weighted average method, STARFM, and multilinear regression analysis were 0.741, 0.70, and 0.61, respectively.

  12. Comparative evaluation of photovoltaic MPP trackers: A simulated approach

    Directory of Open Access Journals (Sweden)

    Barnam Jyoti Saharia

    2016-12-01

    Full Text Available This paper makes a comparative assessment of three popular maximum power point tracking (MPPT algorithms used in photovoltaic power generation. A 120 Wp PV module is taken as reference for the study that is connected to a suitable resistive load by a boost converter. Two profiles of variation of solar insolation at fixed temperature and varying temperature at fixed solar insolation are taken to test the tracking efficiency of three MPPT algorithms based on the perturb and observe (P&O, Fuzzy logic, and Neural Network techniques. MATLAB/SIMULINK simulation software is used for assessment, and the results indicate that the fuzzy logic-based tracker presents better tracking effectiveness to variations in both solar insolation and temperature profiles when compared to P&O technique and Neural Network-based technique.

  13. Monte Carlo simulation of the electron transport through thin slabs: A comparative study of PENELOPE, GEANT3, GEANT4, EGSnrc and MCNPX

    Energy Technology Data Exchange (ETDEWEB)

    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)]. E-mail: mvilches@ugr.es; 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; Guerrero, R. [Servicio de Radiofisica, Hospital Universitario ' San Cecilio' , Avda. Dr. Oloriz, 16, E-18012 Granada (Spain)]. E-mail: rafael.guerrero.alcalde.sspa@juntadeandalucia.es; Anguiano, M. [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada (Spain)]. E-mail: mangui@ugr.es; Lallena, A.M. [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada (Spain)]. E-mail: lallena@ugr.es

    2007-01-15

    The Monte Carlo simulation of the electron transport through thin slabs is studied with five general purpose codes: PENELOPE, GEANT3, GEANT4, EGSnrc and MCNPX. The different material foils analyzed in the old experiments of Kulchitsky and Latyshev [L.A. Kulchitsky, G.D. Latyshev, Phys. Rev. 61 (1942) 254] and Hanson et al. [A.O. Hanson, L.H. Lanzl, E.M. Lyman, M.B. Scott, Phys. Rev. 84 (1951) 634] are used to perform the comparison between the Monte Carlo codes. Non-negligible differences are observed in the angular distributions of the transmitted electrons obtained with the some of the codes. The experimental data are reasonably well described by EGSnrc, PENELOPE (v.2005) and GEANT4. A general good agreement is found for EGSnrc and PENELOPE (v.2005) in all the cases analyzed.

  14. The effects of breathing motion on DCE-MRI images: Phantom studies simulating respiratory motion to compare CAIPARINHA-VIBE, radial VIBE, and conventional VIBE

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chang Kyung; Seo, Nieun; Kim, Bohyun; Huh, Jimi; Kim, Jeong Kon; Lee, Seung Soo; KIm, Kyung Won [Dept. of Radiology, and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul (Korea, Republic of); Kim, In Seong [Siemens Healthcare Korea, Seoul (Korea, Republic of); Nickel, Dominik [MR Application Predevelopment, Siemens Healthcare, Erlangen (Germany)

    2017-04-15

    To compare the breathing effects on dynamic contrast-enhanced (DCE)-MRI between controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA)-volumetric interpolated breath-hold examination (VIBE), radial VIBE with k-space-weighted image contrast view-sharing (radial-VIBE), and conventional VIBE (c-VIBE) sequences using a dedicated phantom experiment. We developed a moving platform to simulate breathing motion. We conducted dynamic scanning on a 3T machine (MAGNETOM Skyra, Siemens Healthcare) using CAIPIRINHA-VIBE, radial-VIBE, and c-VIBE for six minutes per sequence. We acquired MRI images of the phantom in both static and moving modes, and we also obtained motion-corrected images for the motion mode. We compared the signal stability and signal-to-noise ratio (SNR) of each sequence according to motion state and used the coefficients of variation (CoV) to determine the degree of signal stability. With motion, CAIPIRINHA-VIBE showed the best image quality, and the motion correction aligned the images very well. The CoV (%) of CAIPIRINHA-VIBE in the moving mode (18.65) decreased significantly after the motion correction (2.56) (p < 0.001). In contrast, c-VIBE showed severe breathing motion artifacts that did not improve after motion correction. For radial-VIBE, the position of the phantom in the images did not change during motion, but streak artifacts significantly degraded image quality, also after motion correction. In addition, SNR increased in both CAIPIRINHA-VIBE (from 3.37 to 9.41, p < 0.001) and radial-VIBE (from 4.3 to 4.96, p < 0.001) after motion correction. CAIPIRINHA-VIBE performed best for free-breathing DCE-MRI after motion correction, with excellent image quality.

  15. Comparing the Nutritional Impact of Dietary Strategies to Reduce Discretionary Choice Intake in the Australian Adult Population: A Simulation Modelling Study.

    Science.gov (United States)

    Grieger, Jessica A; Johnson, Brittany J; Wycherley, Thomas P; Golley, Rebecca K

    2017-05-03

    Dietary strategies to reduce discretionary choice intake are commonly utilized in practice, but evidence on their relative efficacy is lacking. The aim was to compare the potential impact on nutritional intake of three strategies to reducing discretionary choices intake in the Australian adult (19-90 years) population. Dietary simulation modelling using data from the National Nutrition and Physical Activity Survey 2011-2012 was conducted (n = 9341; one 24 h dietary recall). Strategies modelled were: moderation (reduce discretionary choices by 50%, with 0%, 25% or 75% energy compensation); substitution (replace 50% of discretionary choices with core choices); reformulation (replace 50% SFA with unsaturated fats, reduce added sugars by 25%, and reduce sodium by 20%). Compared to the base case (observed) intake, modelled intakes in the moderation scenario showed: -17.3% lower energy (sensitivity analyses, 25% energy compensation -14.2%; 75% energy compensation -8.0%), -20.9% lower SFA (-17.4%; -10.5%), -43.3% lower added sugars (-41.1%; -36.7%) and 17.7% lower sodium (-14.3%; -7.5%). Substitution with a range of core items, or with fruits, vegetables and core beverages only, resulted in similar changes in energy intake (-13.5% and -15.4%), SFA (-17.7% and -20.1%), added sugars (-42.6% and -43%) and sodium (-13.7% and -16.5%), respectively. Reformulating discretionary choices had minimal impact on reducing energy intake but reduced SFA (-10.3% to -30.9%), added sugars (-9.3% to -52.9%), and alcohol (-25.0% to -49.9%) and sodium (-3.3% to -13.2%). The substitution and reformulation scenarios minimized negative changes in fiber, protein and micronutrient intakes. While each strategy has strengths and limitations, substitution of discretionary choices with core foods and beverages may optimize the nutritional impact.

  16. Comparative study of grain-boundary migration and grain-boundary self-diffusion of [0 0 1] twist-grain boundaries in copper by atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Schoenfelder, B. [Institut fuer Metallkunde und Metallphysik, RWTH Aachen University, Kopernikusstrasse 14, D-52056 Aachen (Germany); Gottstein, G. [Institut fuer Metallkunde und Metallphysik, RWTH Aachen University, Kopernikusstrasse 14, D-52056 Aachen (Germany)]. E-mail: gottstein@imm.rwth-aachen.de; Shvindlerman, L.S. [Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow 142432 (Russian Federation)

    2005-04-15

    Molecular-dynamics simulations were used to study grain-boundary migration as well as grain-boundary self-diffusion of low-angle and high-angle [0 0 1] planar twist grain boundaries (GBs) in copper. Elastic strain was imposed to drive the planar [0 0 1] twist GBs. The temperature dependence of the GB mobility was determined over a wide misorientation range. Additionally grain-boundary self-diffusion was studied for all investigated [0 0 1] planar twist GBs. A comparison of the activation energies determined shows that grain-boundary migration and self-diffusion are distinctly different processes. The behavior of atoms during grain-boundary migration was analyzed for all studied GBs. The analysis reveals that usually in absolute pure materials high-angle planar [0 0 1] twist GBs move by a collective shuffle mechanism while low-angle GBs move by a dislocation based mechanism. The obtained activation parameters were analyzed with respect to the compensation effect.

  17. High-resolution MRI velocimetry compared with numerical simulations

    Science.gov (United States)

    Edelhoff, Daniel; Walczak, Lars; Henning, Stefan; Weichert, Frank; Suter, Dieter

    2013-10-01

    Alterations of the blood flow are associated with various cardiovascular diseases. Precise knowledge of the velocity distribution is therefore important for understanding these diseases and predicting the effect of different medical intervention schemes. The goal of this work is to estimate the precision with which the velocity field can be measured and predicted by studying two simple model geometries with NMR micro imaging and computational fluid dynamics. For these initial experiments, we use water as an ideal test medium. The phantoms consist of tubes simulating a straight blood vessel and a step between two tubes of different diameters, which can be seen as a minimal model of the situation behind a stenosis. For both models, we compare the experimental data with the numerical prediction, using the experimental boundary conditions. For the simpler model, we also compare the data to the analytical solution. As an additional validation, we determine the divergence of the velocity field and verify that it vanishes within the experimental uncertainties. We discuss the resulting precision of the simulation and the outlook for extending this approach to the analysis of specific cases of arteriovascular problems.

  18. COMPARATIVE NUMERICAL SIMULATION OF THE TOHOKU 2011 TSUNAMI

    Directory of Open Access Journals (Sweden)

    Baranova N.A.

    2015-10-01

    Full Text Available The comparative numerical simulation of generation and propagation of tsunami waves generated by the source of the catastrophic 2011 Tohoku earthquake in Japan was performed based on the Okada model and the dynamic keyboard block model. The initial model is connected with the choice of orientation of longitudinal and transverse ruptures within the source region and the values of displacements along the main fault. A subsequent model is based on the premise that the initial stress distribution along the fault zone affects essentially the character of movements around the earthquake source and takes into account the stress-strain state of keyboard blocks. In the first case of the present study, the earthquake source was designated and constructed based on the parameters of the ten largest aftershocks within a finite time interval, while in the second case the source used included all aftershocks on the first day following the main event. Based on such comparative source simulations and far-field tsunami wave measurements, the results with both models were determined to have close similarities. However, in the near-field zone, the agreement with observable data was not as good. That can be attributed to inaccuracies in the placement of virtual tide gauges relative to real ones, as well as to features of bottom relief near the coast.

  19. Comparative evaluation of pressure generated on a simulated maxillary oral analog by impression materials in custom trays of different spacer designs: An in vitro study

    OpenAIRE

    Sakshi Chopra; Narendra Kumar Gupta; Amrit Tandan; Ravi Dwivedi; Swati Gupta; Garima Agarwal

    2016-01-01

    Introduction: Literature reveals that masticatory load on denture bearing tissues through complete dentures should be maximum on primary stress bearing areas and least on relief area in accordance with the histology of underlying tissues. A study to validate the existing beliefs was planned to compare the pressure on mucosa using selective pressure technique and minimal pressure technique, with the incorporation of two different impression materials utilizing the pressure sensors during secon...

  20. Comparative study of preparation of hazardous drugs with different closed-system drug transfer devices by means of simulation with fluorescein

    Directory of Open Access Journals (Sweden)

    Eva González-Haba Peña

    2016-12-01

    Full Text Available Objectives: The level of environmental contamination generated during preparation and administration of hazardous drugs using different valve closed-systems and their combinations was compared. The actual impact on the overall time of preparation of cytostatics and the economic cost of the different modalities were also compared. Methods: Comparative study of the preparation of fluorescein mixtures with different modalities of valve closed-system combinations. Environmental contamination was detected in critical points of connection, and in splashes produced at any other points. The main variable was qualitative detection of contamination by splashes through ultraviolet light when modalities with or without a connector were compared. A final number of 160 mixtures were prepared to detect differences of at least 5%. Results: Splashes were produced in 7 preparations without a connector (p = 0.015. No significant differences (p = 0.445 were detected either in the use of a supporting vial spike vs an anchoring spike, or in the ChemoCLAVE® system vs valve systems with Fleboflex® solutions. Contamination at any critical point was produced in all preparations. The use of a supporting vial spike, syringe connector and bag solution with Luer connection was the most efficient modality. Conclusions: A syringe connector is needed to guarantee a closed system. Anchoring spikes do not show higher advantages as compared with supporting vial spikes. Fleboflex® solutions with Luer bags are more efficient than ChemoCLAVE® and show similar safety. However, connections of these closed systems are not leak-tight, and it is therefore important to continue studies of contamination of the different closed system transfer devices

  1. Experimental comparative study and fracture resistance simulation with irrigation solution of 0.2% chitosan, 2.5% NaOCl and 17% EDTA

    Directory of Open Access Journals (Sweden)

    Ernani Ernani

    2015-09-01

    Full Text Available Background: Preparation in endodontic need irrigation materials as root canal debridement and disinfectant. However, irrigation materials is one of the factors that influence the tendency of fracture. Purpose: This study was aimed to see the resistance and fracture distribution if teeth irrigated with high molecular horseshoe crab chitosan at 0.2% concentration, 2.5% NaOCl solution and 17% EDTA solution in endodontic treatment with finite element method (FEM simulation study and experimental studies. Method: Endodontic treatment performed on 28 maxillary premolars with group A: irrigation solution of 17% EDTA and 2.5% NaOCl solution; group B: 2.5% NaOCl irrigation solution; group C: 2.5% NaOCl irrigation solution and 0.2% chitosan solution; group D: 0.2% chitosan solution irrigation. Final restoration was done using prefabricated glass fiber post. Cementation of post using resin cement then restored with direct composite resin restorations. Pressure test was performed with a Universal Testing Machine with a speed of 0.5 mm/min until fracture occurred. A three dimensional finite element analysis was performed for total deformation, equivalent (von-mises stress, and equivalent elastic strains. Result: Anova test showed significant differences in fracture resistance (p0.05. Statistical analysis showed no significant difference (p>0.05 between the results of experiment and FEM analysis results using the t-test. Conclusion: The results of this study demonstrated that there was effect of the use of high molecular 0.2% chitosan as a combined irrigation with NaOCl, but did not affect the fracture pattern distribution of endodontically treated teeth both experimentally and FEM analysis test.

  2. A comparative study of the role of the Saharan air layer in the evolution of two disparate Atlantic tropical cyclones using WRF model simulations and energetics calculations

    Science.gov (United States)

    Ross, Robert S.; Krishnamurti, T. N.; Chaney, Kirsten M.

    2016-02-01

    The Weather Research and Forecasting (WRF) Model 5-day simulations of Major Hurricane Julia (2010) and Tropical Storm Florence (2012), both of which developed from African easterly waves, are used to conduct a complete energetics study to explain why one storm became a major hurricane while the other weakened to a wave. The disparate intensity outcomes are caused by significant differences in the energetics of the two systems that emerge in their storm stages due to differences in the impact of the Saharan air layer (SAL). In their wave stages both waves exhibit a convectively driven energy production cycle, in which the regions of positive barotropic and baroclinic energy conversion and of diabatic heating and rainfall are all superimposed. Convection induces barotropic instability which then enhances the baroclinic overturning through a resonance of the two instabilities, which together produce the eddy kinetic energy. Diabatic heating in the convection generates eddy available potential energy which, along with the eddy kinetic energy, defines the total eddy energy of the system. Florence loses the convectively driven energy production cycle in the storm stage and begins to weaken, while Julia maintains this cycle and becomes a major hurricane. The disruption of the convection in Florence is due to the drying, stabilizing, and vertical shearing effects of an expansive SAL to the north of the storm, effects not present in the Julia case. Consideration is given to the different effects of the SAL on 6-10 day waves (Florence wave) versus 3-5 day waves (Julia wave).

  3. Comparing Simulated Emission from Molecular Clouds Using Experimental Design

    CERN Document Server

    Yeremi, Miayan; Offner, Stella; Loeppky, Jason; Rosolowsky, Erik

    2014-01-01

    We propose a new approach to comparing simulated observations that enables us to determine the significance of the underlying physical effects. We utilize the methodology of experimental design, a subfield of statistical analysis, to establish a framework for comparing simulated position-position-velocity data cubes to each other. We propose three similarity metrics based on methods described in the literature: principal component analysis, the spectral correlation function, and the Cramer multi-variate two sample similarity statistic. Using these metrics, we intercompare a suite of mock observational data of molecular clouds generated from magnetohydrodynamic simulations with varying physical conditions. Using this framework, we show that all three metrics are sensitive to changing Mach number and temperature in the simulation sets, but cannot detect changes in magnetic field strength and initial velocity spectrum. We highlight the shortcomings of one-factor-at-a-time designs commonly used in astrophysics an...

  4. Comparative simulations of Fresnel holography methods for atomic waveguides

    CERN Document Server

    Henderson, Victoria A; Riis, Erling; Arnold, Aidan S

    2016-01-01

    We have simulated the optical properties of micro-fabricated Fresnel zone plates (FZPs) as an alternative to spatial light modulators (SLMs) for producing non-trivial light potentials to trap atoms within a lensless Fresnel arrangement. We show that binary (1-bit) FZPs with wavelength (1 \\mu m) spatial resolution consistently outperform kinoforms of spatial and phase resolution comparable to commercial SLMs in root mean square error comparisons, with FZP kinoforms demonstrating increasing improvement for complex target intensity distributions. Moreover, as sub-wavelength resolution microfabrication is possible, FZPs provide an exciting possibility for the creation of static cold-atom trapping potentials useful to atomtronics, interferometry, and the study of fundamental physics.

  5. Comparing models of star formation simulating observed interacting galaxies

    Science.gov (United States)

    Quiroga, L. F.; Muñoz-Cuartas, J. C.; Rodrigues, I.

    2017-07-01

    In this work, we make a comparison between different models of star formation to reproduce observed interacting galaxies. We use observational data to model the evolution of a pair of galaxies undergoing a minor merger. Minor mergers represent situations weakly deviated from the equilibrium configuration but significant changes in star fomation (SF) efficiency can take place, then, minor mergers provide an unique scene to study SF in galaxies in a realistic but yet simple way. Reproducing observed systems also give us the opportunity to compare the results of the simulations with observations, which at the end can be used as probes to characterize the models of SF implemented in the comparison. In this work we compare two different star formation recipes implemented in Gadget3 and GIZMO codes. Both codes share the same numerical background, and differences arise mainly in the star formation recipe they use. We use observations from Pico dos Días and GEMINI telescopes and show how we use observational data of the interacting pair in AM2229-735 to characterize the interacting pair. Later we use this information to simulate the evolution of the system to finally reproduce the observations: Mass distribution, morphology and main features of the merger-induced star formation burst. We show that both methods manage to reproduce roughly the star formation activity. We show, through a careful study, that resolution plays a major role in the reproducibility of the system. In that sense, star formation recipe implemented in GIZMO code has shown a more robust performance. Acknowledgements: This work is supported by Colciencias, Doctorado Nacional - 617 program.

  6. Comparing Intravenous Insertion Instructional Methods with Haptic Simulators.

    Science.gov (United States)

    McWilliams, Lenora A; Malecha, Ann

    2017-01-01

    Objective. The objective of this review was to compare traditional intravenous (IV) insertion instructional methods with the use of haptic IV simulators. Design. An integrative research design was used to analyze the current literature. Data Sources. A search was conducted using key words intravenous (IV) insertion or cannulation or venipuncture and simulation from 2000 to 2015 in the English language. The databases included Academic Search Complete, CINAHL Complete, Education Resource Information Center, and Medline. Review Methods. Whittemore and Knafl's (2005) strategies were used to critique the articles for themes and similarities. Results. Comparisons of outcomes between traditional IV instructional methods and the use of haptic IV simulators continue to show various results. Positive results indicate that the use of the haptic IV simulator decreases both band constriction and total procedure time. While students are satisfied with practicing on the haptic simulators, they still desire faculty involvement. Conclusion. Combining the haptic IV simulator with practical experience on the IV arm may be the best practice for learning IV insertion. Research employing active learning strategies while using a haptic IV simulator during the learning process may reduce cost and faculty time.

  7. Comparing Intravenous Insertion Instructional Methods with Haptic Simulators

    Science.gov (United States)

    Malecha, Ann

    2017-01-01

    Objective. The objective of this review was to compare traditional intravenous (IV) insertion instructional methods with the use of haptic IV simulators. Design. An integrative research design was used to analyze the current literature. Data Sources. A search was conducted using key words intravenous (IV) insertion or cannulation or venipuncture and simulation from 2000 to 2015 in the English language. The databases included Academic Search Complete, CINAHL Complete, Education Resource Information Center, and Medline. Review Methods. Whittemore and Knafl's (2005) strategies were used to critique the articles for themes and similarities. Results. Comparisons of outcomes between traditional IV instructional methods and the use of haptic IV simulators continue to show various results. Positive results indicate that the use of the haptic IV simulator decreases both band constriction and total procedure time. While students are satisfied with practicing on the haptic simulators, they still desire faculty involvement. Conclusion. Combining the haptic IV simulator with practical experience on the IV arm may be the best practice for learning IV insertion. Research employing active learning strategies while using a haptic IV simulator during the learning process may reduce cost and faculty time.

  8. Comparative evaluation of pressure generated on a simulated maxillary oral analog by impression materials in custom trays of different spacer designs: An in vitro study.

    Science.gov (United States)

    Chopra, Sakshi; Gupta, Narendra Kumar; Tandan, Amrit; Dwivedi, Ravi; Gupta, Swati; Agarwal, Garima

    2016-01-01

    Literature reveals that masticatory load on denture bearing tissues through complete dentures should be maximum on primary stress bearing areas and least on relief area in accordance with the histology of underlying tissues. A study to validate the existing beliefs was planned to compare the pressure on mucosa using selective pressure technique and minimal pressure technique, with the incorporation of two different impression materials utilizing the pressure sensors during secondary impression procedure. The study was performed using a maxillary analog. Three pressure sensors were imbedded in the oral analog, one in the mid palatine area and the other two in the right and left ridge crest. Custom trays of two different configurations were fabricated. The two impression materials tested were light body and zinc oxide eugenol. A total of 40 impressions were made. A constant weight of 1 kg was placed, and the pressure was recorded as initial and end pressures. A significant difference in the pressure produced using different impression materials was found (P materials. The presence of relief did affect the magnitude of pressure at various locations. All impression materials produced pressure during maxillary edentulous impression making. Tray modification is an important factor in changing the amount of pressure produced. The impression materials used also had a significant role to play on the pressures acting on the tissues during impression procedure. Light body VPS impression material may be recommended to achieve minimal pressure on the denture bearing tissues in both selective as well as minimal pressure techniques.

  9. A new framework for quantifying uncertainties in modelling studies for future climates - how more certain are CMIP5 precipitation and temperature simulations compared to CMIP3?

    Science.gov (United States)

    Sharma, A.; Woldemeskel, F. M.; Sivakumar, B.; Mehrotra, R.

    2014-12-01

    We outline a new framework for assessing uncertainties in model simulations, be they hydro-ecological simulations for known scenarios, or climate simulations for assumed scenarios representing the future. This framework is illustrated here using GCM projections for future climates for hydrologically relevant variables (precipitation and temperature), with the uncertainty segregated into three dominant components - model uncertainty, scenario uncertainty (representing greenhouse gas emission scenarios), and ensemble uncertainty (representing uncertain initial conditions and states). A novel uncertainty metric, the Square Root Error Variance (SREV), is used to quantify the uncertainties involved. The SREV requires: (1) Interpolating raw and corrected GCM outputs to a common grid; (2) Converting these to percentiles; (3) Estimating SREV for model, scenario, initial condition and total uncertainty at each percentile; and (4) Transforming SREV to a time series. The outcome is a spatially varying series of SREVs associated with each model that can be used to assess how uncertain the system is at each simulated point or time. This framework, while illustrated in a climate change context, is completely applicable for assessment of uncertainties any modelling framework may be subject to. The proposed method is applied to monthly precipitation and temperature from 6 CMIP3 and 13 CMIP5 GCMs across the world. For CMIP3, B1, A1B and A2 scenarios whereas for CMIP5, RCP2.6, RCP4.5 and RCP8.5 representing low, medium and high emissions are considered. For both CMIP3 and CMIP5, model structure is the largest source of uncertainty, which reduces significantly after correcting for biases. Scenario uncertainly increases, especially for temperature, in future due to divergence of the three emission scenarios analysed. While CMIP5 precipitation simulations exhibit a small reduction in total uncertainty over CMIP3, there is almost no reduction observed for temperature projections

  10. Structural insights into the interactions of phorbol ester and bryostatin complexed with protein kinase C: a comparative molecular dynamics simulation study.

    Science.gov (United States)

    Thangsunan, Patcharapong; Tateing, Suriya; Hannongbua, Supa; Suree, Nuttee

    2016-07-01

    Protein kinase C (PKC) isozymes are important regulatory enzymes that have been implicated in many diseases, including cancer, Alzheimer's disease, and in the eradication of HIV/AIDS. Given their potential clinical ramifications, PKC modulators, e.g. phorbol esters and bryostatin, are also of great interest in the drug development. However, structural details on the binding between PKC and its modulators, especially bryostatin - the highly potent and non-tumor promoting activator for PKCs, are still lacking. Here, we report the first comparative molecular dynamics study aimed at gaining structural insight into the mechanisms by which the PKC delta cys2 activator domain is used in its binding to phorbol ester and bryostatin-1. As anticipated in the phorbol ester binding, hydrogen bonds are formed through the backbone atoms of Thr242, Leu251, and Gly253 of PKC. However, the opposition of H-bond formation between Thr242 and Gly253 may cause the phorbol ester complex to become less stable when compared with the bryostatin binding. For the PKC delta-bryostatin complex, hydrogen bonds are formed between the Gly253 backbone carbonyl and the C30 carbomethoxy substituent of the ligand. Additionally, the indole Nε1 of the highly homologous Trp252 also forms an H-bond to the C20 ester group on bryostatin. Backbone fluctuations also suggest that this latter H-bond formation may abrogate the transient interaction between Trp252 and His269, thus dampening the fluctuations observed on the nearby Zn(2+)-coordinating residues. This new dynamic fluctuation dampening model can potentially benefit future design of new PKC modulators.

  11. Postcoital Sperm Assessment Comparative Study.

    Science.gov (United States)

    Pelekanos, Michael J

    2015-11-01

    This postcoital sperm assessment study was performed over a 10 month time period (November 2014-August 2015). Fifteen couples enrolled in the study. The study was a non-blinded, non-randomized, single-center comparison study comparing The Stork® OTC (Rinovum Women's Health, Monroeville, PA) to natural intercourse (NI), using the subjects as their own control/baseline. This was an efficacy study designed to compare the number of sperm in the cervical mucus following the use of The Stork OTC conception aid with the number of sperm in the cervical mucus following natural intercourse. Subjects used both The Stork OTC conception system and the natural intercourse method to evaluate concentrations of sperm in the cervical mucus. Post-coital test (PCT) data was collected demonstrating higher concentrations of sperm within the cervical mucus with The Stork OTC conception system versus natural intercourse for 85% of test subjects in this study. Of the 15 couples enrolled in the study, 2 were lost to follow-up. Mean age for male subjects was 31.7 +/ 5.4 years of age and mean age for female subjects was 29.7+/- 5.4. The average sperm score value of the 85% of test subjects with higher sperm concentrations from The Stork OTC was 3.23 times the score value of sperm concentration compared to natural intercourse. The remaining 15% of test subjects showed no change in sperm score value between The Stork OTC and natural intercourse.

  12. Comparative Analysis of Dayside Reconnection Models in Global Magnetosphere Simulations

    CERN Document Server

    Komar, C M; Cassak, P A

    2015-01-01

    We test and compare a number of existing models predicting the location of magnetic reconnection at Earth's dayside magnetopause for various solar wind conditions. We employ robust image processing techniques to determine the locations where each model predicts reconnection to occur. The predictions are then compared to the magnetic separators, the magnetic field lines separating different magnetic topologies. The predictions are tested in distinct high-resolution simulations with interplanetary magnetic field (IMF) clock angles ranging from 30 to 165 degrees in global magnetohydrodynamic simulations using the three-dimensional Block-Adaptive Tree Solarwind Roe-type Upwind Scheme (BATS-R-US) code with a uniform resistivity, although the described techniques can be generally applied to any self-consistent magnetosphere code. Additional simulations are carried out to test location model dependence on IMF strength and dipole tilt. We find that most of the models match large portions of the magnetic separators wh...

  13. Bayes or bootstrap? A simulation study comparing the performance of Bayesian Markov chain Monte Carlo sampling and bootstrapping in assessing phylogenetic confidence.

    Science.gov (United States)

    Alfaro, Michael E; Zoller, Stefan; Lutzoni, François

    2003-02-01

    Bayesian Markov chain Monte Carlo sampling has become increasingly popular in phylogenetics as a method for both estimating the maximum likelihood topology and for assessing nodal confidence. Despite the growing use of posterior probabilities, the relationship between the Bayesian measure of confidence and the most commonly used confidence measure in phylogenetics, the nonparametric bootstrap proportion, is poorly understood. We used computer simulation to investigate the behavior of three phylogenetic confidence methods: Bayesian posterior probabilities calculated via Markov chain Monte Carlo sampling (BMCMC-PP), maximum likelihood bootstrap proportion (ML-BP), and maximum parsimony bootstrap proportion (MP-BP). We simulated the evolution of DNA sequence on 17-taxon topologies under 18 evolutionary scenarios and examined the performance of these methods in assigning confidence to correct monophyletic and incorrect monophyletic groups, and we examined the effects of increasing character number on support value. BMCMC-PP and ML-BP were often strongly correlated with one another but could provide substantially different estimates of support on short internodes. In contrast, BMCMC-PP correlated poorly with MP-BP across most of the simulation conditions that we examined. For a given threshold value, more correct monophyletic groups were supported by BMCMC-PP than by either ML-BP or MP-BP. When threshold values were chosen that fixed the rate of accepting incorrect monophyletic relationship as true at 5%, all three methods recovered most of the correct relationships on the simulated topologies, although BMCMC-PP and ML-BP performed better than MP-BP. BMCMC-PP was usually a less biased predictor of phylogenetic accuracy than either bootstrapping method. BMCMC-PP provided high support values for correct topological bipartitions with fewer characters than was needed for nonparametric bootstrap.

  14. A simulation study to compare the phase-shift angle radiofrequency ablation mode with bipolar and unipolar modes in creating linear lesions for atrial fibrillation ablation.

    Science.gov (United States)

    Yan, Shengjie; Wu, Xiaomei; Wang, Weiqi

    2016-05-01

    Purpose In pulmonary veins (PVs) isolation (PVI), radiofrequency (RF) energy is often used to create a linear lesion for blocking the accessory conduction pathways around PVs. By using transient finite element analysis, this study compared the effectiveness of phase-shift mode (PsM) ablation with bipolar mode (BiM) and unipolar mode (UiM) in creating a continuous lesion and lesion depth in a 5-mm thick atrial wall. Materials and methods Computer models were developed to study the temperature distributions and lesion dimensions in atrial walls created through PsM, BiM, and UiM. Four phase-shift angles - 45°, 90°, 135°, and 180° - were considered in PsM ablation (hereafter, PsM-45°, PsM-90°, PsM-135°, and PsM-180°, respectively). Results At 60 s/30 V peak value of RF voltage, UiM and PsM-45° did not create an effective lesion, whereas BiM created a lesion of maximum depth and width approximately 1.01 and 1.62 mm, respectively. PsM-135° and PsM-180° not only created transmural lesions in 5-mm thick atrial walls but also created continuous lesions between electrodes spaced 4 mm apart; similarly, PsM-90° created a continuous lesion with a maximum depth and width of nearly 4.09 and 6.12 mm. Conclusions Compared with UiM and BiM, PsM-90°, PsM-135° and PsM-180° created continuous and larger lesions in a single ablation procedure and at 60 s/30 V peak value of RF voltage. Therefore, the proposed PsM ablation method is suitable for PVI and linear isolation at the left atrial roof for treating atrial fibrillation.

  15. Reader variability in QT measurement due to measurement error and variability in leads selection: a simulation study comparing 2-way vs. 3-way interaction ANOVA model.

    Science.gov (United States)

    Natekar, Mili; Karnad, Dilip R; Salvi, Vaibhav; Ramasamy, Arumugam; Kerkar, Vaibhav; Panicker, Gopi Krishna; Kothari, Snehal

    2014-01-01

    Reader variability (RV) results from measurement differences or variability in lead used for QT measurements; the latter is not reflected in conventional methods for estimating RV. Mean and SD of QT intervals in 12 leads of 100 ECGs measured twice were used to simulate data sets with inter-RV of 5, 10, 15, 20, and 25 ms and intra-RV of 3, 6, 9, 12, and 15 ms. Six hundred twenty-five data sets were simulated such that different leads were used in Read1 and Read2 in 0, 10%, 20%, 30%, 40% of ECGs by 25 readers. RV was estimated using ANOVA interaction models: three-way model using Reader, ECG and lead as factors, and 2-way model using reader and ECG as factors. Estimates from three-way model accurately matched inter- and intra-RV that were introduced during simulation regardless of percent of ECGs with lead selection variability. The two-way model provides identical estimates when both reads are in same leads, but higher, more realistically estimates when measurements are made in different leads. © 2013.

  16. A comparative study of chlorophyll-a concentration during different tropical cyclones in the Bay of Bengal based on measurements and model simulations

    Science.gov (United States)

    Pandey, Suchita; Bhagawati, Chirantan; Patel, Ramkrushnbhai; Chakraborty, Arun; Jayanarayanan, Kuttippurath

    2016-04-01

    Chlorophyll-a (chl-a) pigments derived from ocean color can be used as a tool for estimating phytoplankton distribution in the observed oceanic region. This study aims at providing new insights on the variability of chl-a concentration during the occurrences of different cyclones in the Bay of Bengal (BoB). We consider two tropical cyclones of different intensities observed in the BOB; MALA and NILAM. MALA was a cyclonic storm and was formed on 24 April 2006 and dissipated by 30 April 2006. The wind speed and lowest pressure during the MALA have been recorded as 185‒220 Km/h and 950 hp, respectively. Multi-satellite observations are used for chl-a (SeaWiFS, MODIS, OCM-2), winds (QuickSCAT) and sea surface height (SSH) (TOPEX/POSEIDON) analyses in this study. Argo data taken from CORIOLIS (along the cyclone track) are used for temperature and salinity, from which Mixed Layer Depth (MLD), Isothermal Layer Depth (ILD), Barrier Layer Thickness (BLT) is calculated. A case study for MALA cyclone using daily forcing of winds and surface net heat flux in 'Regional Ocean Modeling System' (ROMS) with NPCHLZD (Nitrate, Phytoplankton, Chlorophyll, Zooplankton and Detritus), five components ecosystem model is used for study the chl-a variability during the cyclone. The results show high chl-a concentration along the track as well as in the right side of the track of the cyclone. The daily variations of MLD, BLT, SSH and wind stress curl (WSC) are compared with the daily time series of chl-a for pre-cyclone, during cyclone and post cyclone period. During and after the passage of cyclone average chl-a values increased from 0.2 mg/l to 0.4 mg/l and greater. It shows good agreement with MLD (30‒40 m), negligible BLT and strong WSC (4*10-6n/m3). It implies the strong winds has initiated upwelling, which subsequently triggered phytoplankton bloom during and after the cyclonic storm. The cyclone NILAM was formed on 28 October 2012 and dissipated by 1 November 2012, which had a

  17. An in vitro comparative study of intracanal fluid motion and wall shear stress induced by ultrasonic and polymer rotary finishing files in a simulated root canal model.

    Science.gov (United States)

    Koch, Jon; Borg, John; Mattson, Abby; Olsen, Kris; Bahcall, James

    2012-01-01

    Objective. This in vitro study compared the flow pattern and shear stress of an irrigant induced by ultrasonic and polymer rotary finishing file activation in an acrylic root canal model. Flow visualization analysis was performed using an acrylic canal filled with a mixture of distilled water and rheoscopic fluid. The ultrasonic and polymer rotary finishing file were separately tested in the canal and activated in a static position and in a cyclical axial motion (up and down). Particle movement in the fluid was captured using a high-speed digital camera and DaVis 7.1 software. The fluid shear stress analysis was performed using hot film anemometry. A hot-wire was placed in an acrylic root canal and the canal was filled with distilled water. The ultrasonic and polymer rotary finishing files were separately tested in a static position and in a cyclical axial motion. Positive needle irrigation was also tested separately for fluid shear stress. The induced wall shear stress was measured using LabVIEW 8.0 software.

  18. Comparative evaluation of pressure generated on a simulated maxillary oral analog by impression materials in custom trays of different spacer designs: An in vitro study

    Directory of Open Access Journals (Sweden)

    Sakshi Chopra

    2016-01-01

    Full Text Available Introduction: Literature reveals that masticatory load on denture bearing tissues through complete dentures should be maximum on primary stress bearing areas and least on relief area in accordance with the histology of underlying tissues. A study to validate the existing beliefs was planned to compare the pressure on mucosa using selective pressure technique and minimal pressure technique, with the incorporation of two different impression materials utilizing the pressure sensors during secondary impression procedure. Materials and Methods: The study was performed using a maxillary analog. Three pressure sensors were imbedded in the oral analog, one in the mid palatine area and the other two in the right and left ridge crest. Custom trays of two different configurations were fabricated. The two impression materials tested were light body and zinc oxide eugenol. A total of 40 impressions were made. A constant weight of 1 kg was placed, and the pressure was recorded as initial and end pressures. Results: A significant difference in the pressure produced using different impression materials was found (P < 0.001. Light body vinyl polysiloxane produced significantly lesser pressure than zinc oxide eugenol impression materials. The presence of relief did affect the magnitude of pressure at various locations. Conclusion: All impression materials produced pressure during maxillary edentulous impression making. Tray modification is an important factor in changing the amount of pressure produced. The impression materials used also had a significant role to play on the pressures acting on the tissues during impression procedure. Clinical Implication: Light body VPS impression material may be recommended to achieve minimal pressure on the denture bearing tissues in both selective as well as minimal pressure techniques.

  19. Simulation of multi-stage nonlinear bone remodeling induced by fixed partial dentures of different configurations: a comparative clinical and numerical study.

    Science.gov (United States)

    Liao, Zhipeng; Yoda, Nobuhiro; Chen, Junning; Zheng, Keke; Sasaki, Keiichi; Swain, Michael V; Li, Qing

    2017-04-01

    This paper aimed to develop a clinically validated bone remodeling algorithm by integrating bone's dynamic properties in a multi-stage fashion based on a four-year clinical follow-up of implant treatment. The configurational effects of fixed partial dentures (FPDs) were explored using a multi-stage remodeling rule. Three-dimensional real-time occlusal loads during maximum voluntary clenching were measured with a piezoelectric force transducer and were incorporated into a computerized tomography-based finite element mandibular model. Virtual X-ray images were generated based on simulation and statistically correlated with clinical data using linear regressions. The strain energy density-driven remodeling parameters were regulated over the time frame considered. A linear single-stage bone remodeling algorithm, with a single set of constant remodeling parameters, was found to poorly fit with clinical data through linear regression (low [Formula: see text] and R), whereas a time-dependent multi-stage algorithm better simulated the remodeling process (high [Formula: see text] and R) against the clinical results. The three-implant-supported and distally cantilevered FPDs presented noticeable and continuous bone apposition, mainly adjacent to the cervical and apical regions. The bridged and mesially cantilevered FPDs showed bone resorption or no visible bone formation in some areas. Time-dependent variation of bone remodeling parameters is recommended to better correlate remodeling simulation with clinical follow-up. The position of FPD pontics plays a critical role in mechanobiological functionality and bone remodeling. Caution should be exercised when selecting the cantilever FPD due to the risk of overloading bone resorption.

  20. Conducting Simulation Studies in Psychometrics

    Science.gov (United States)

    Feinberg, Richard A.; Rubright, Jonathan D.

    2016-01-01

    Simulation studies are fundamental to psychometric discourse and play a crucial role in operational and academic research. Yet, resources for psychometricians interested in conducting simulations are scarce. This Instructional Topics in Educational Measurement Series (ITEMS) module is meant to address this deficiency by providing a comprehensive…

  1. Simulation and comparative study on the oxidation kinetics of atrazine by UV/H₂O₂, UV/HSO₅⁻ and UV/S₂O₈²⁻.

    Science.gov (United States)

    Luo, Congwei; Ma, Jun; Jiang, Jin; Liu, Yongze; Song, Yang; Yang, Yi; Guan, Yinghong; Wu, Daoji

    2015-09-01

    This study comparatively investigated atrazine (ATZ) degradation by irradiation at the wavelength of 254 nm in the presence of peroxides including hydrogen peroxide (H2O2), peroxymonosulfate (HSO5(-)), and persulfate (S2O8(2-)) at various initial ATZ concentrations and oxidant dosages. The effects of water matrix, such as carbonate/bicarbonate (HCO3(-)/CO3(2-)), chloride ions (Cl(-)), and natural organic matter (NOM), were evaluated on these three advanced oxidation processes. A simple steady-state kinetic model was developed based on the initial rates of ATZ destruction, which could well describe the apparent pseudo-first-order rate constants (k(app), s(-1)) of ATZ degradation in these three processes. The specific roles of reactive species (i.e., HO·, SO4(-·), CO3(-·), and Cl2(-·)) under various experimental conditions were quantitatively evaluated based on their steady-state concentrations obtained from this model. Modeling results showed that the steady-state concentrations of HO· and SO4(-·) decreased with the increase of CO3(2-)/HCO3(-) concentration, and the relative contribution of HO· to ATZ degradation significantly decreased in UV/H2O2 and UV/HSO5(-) systems. On the other hand, the scavenging effect of HCO3(-)/CO3(2-) on the relative contribution of SO4(-·) to ATZ degradation was lower than that on HO·. The presence of Cl(-) (0.5-10 mM) significantly scavenged SO4(-·) but had slightly scavenging effect on HO· at the present experimental pH, resulting in greater decrease of k(app) in the UV/S2O8(2-) than UV/H2O2 and UV/HSO5(-) systems. Higher levels of Cl2(-·) were generated in the UV/S2O8(2-) than those in the UV/H2O2 and UV/HSO5(-) systems at the same Cl(-) concentrations. NOM significantly decreased k(app) due to its effects of competitive UV absorption and radical scavenging with the latter one being dominant. These results improve the understanding of the effects of water constituents for ATZ degradation in the UV-based oxidation

  2. Comparing three methods for participatory simulation of hospital work systems

    DEFF Research Database (Denmark)

    Broberg, Ole

    addressed different elements of a hospital work system. Problem statement: Different methods for simulating the future work system for healthcare professionals have been applied in a number of green field and renovation design projects of hospitals in Denmark. The methods differed in the type of simulation...... objects representing the work system. Hence, this was an opportunity to study if these differences influenced which elements of a work system were in focus when healthcare professionals simulated and evaluated future work. Preliminary observations indicated this was the case but it was not understood how...... on how to organize the work in different spatial layouts. In addition to the object attributes other factors may play a role in what work system elements are being addressed. An important one seems to be at which point in the hospital design process the simulation is carried out. Conclusions: Different...

  3. Simulation in International Studies

    Science.gov (United States)

    Boyer, Mark A.

    2011-01-01

    Social scientists have long worked to replicate real-world phenomena in their research and teaching environments. Unlike our biophysical science colleagues, we are faced with an area of study that is not governed by the laws of physics and other more predictable relationships. As a result, social scientists, and international studies scholars more…

  4. Comparing simulated emission from molecular clouds using experimental design

    Energy Technology Data Exchange (ETDEWEB)

    Yeremi, Miayan; Flynn, Mallory; Loeppky, Jason; Rosolowsky, Erik [University of British Columbia, Okanagan Campus, Departments of Physics and Statistics, 3333 University Way, Kelowna BC V1V 1V7 (Canada); Offner, Stella [Yale University Astronomy Department, 260 Whitney Avenue, New Haven, CT 06511 (United States)

    2014-03-10

    We propose a new approach to comparing simulated observations that enables us to determine the significance of the underlying physical effects. We utilize the methodology of experimental design, a subfield of statistical analysis, to establish a framework for comparing simulated position-position-velocity data cubes to each other. We propose three similarity metrics based on methods described in the literature: principal component analysis, the spectral correlation function, and the Cramer multi-variate two-sample similarity statistic. Using these metrics, we intercompare a suite of mock observational data of molecular clouds generated from magnetohydrodynamic simulations with varying physical conditions. Using this framework, we show that all three metrics are sensitive to changing Mach number and temperature in the simulation sets, but cannot detect changes in magnetic field strength and initial velocity spectrum. We highlight the shortcomings of one-factor-at-a-time designs commonly used in astrophysics and propose fractional factorial designs as a means to rigorously examine the effects of changing physical properties while minimizing the investment of computational resources.

  5. Comparative evaluation of the impact of WRF/NMM and WRF/ARW meteorology on CMAQ simulations for PM2.5 and its related precursors during the 2006 TexAQS/GoMACCS study

    OpenAIRE

    Yu, S.; R. Mathur; J. Pleim; G. Pouliot; Wong, D; Eder, B.; Schere, K.; R. Gilliam; S. T. Rao

    2012-01-01

    This study presents a comparative evaluation of the impact of WRF-NMM and WRF-ARW meteorology on CMAQ simulations of PM2.5, its composition and related precursors over the eastern United States with the intensive observations obtained by aircraft (NOAA WP-3), ship and surface monitoring networks (AIRNow, IMPROVE, CASTNet and STN) during the 2006 TexAQS/GoMACCS study. The results at the AIRNow surface sites show that both ARW-CMAQ and NMM-CMAQ reproduced day-to-day variations...

  6. [Comparative studies of face recognition].

    Science.gov (United States)

    Kawai, Nobuyuki

    2012-07-01

    Every human being is proficient in face recognition. However, the reason for and the manner in which humans have attained such an ability remain unknown. These questions can be best answered-through comparative studies of face recognition in non-human animals. Studies in both primates and non-primates show that not only primates, but also non-primates possess the ability to extract information from their conspecifics and from human experimenters. Neural specialization for face recognition is shared with mammals in distant taxa, suggesting that face recognition evolved earlier than the emergence of mammals. A recent study indicated that a social insect, the golden paper wasp, can distinguish their conspecific faces, whereas a closely related species, which has a less complex social lifestyle with just one queen ruling a nest of underlings, did not show strong face recognition for their conspecifics. Social complexity and the need to differentiate between one another likely led humans to evolve their face recognition abilities.

  7. Effect of the electron transport through thin slabs on the simulation of linear electron accelerators of use in therapy: A comparative study of various Monte Carlo codes

    Energy Technology Data Exchange (ETDEWEB)

    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)], E-mail: mvilches@ugr.es; Garcia-Pareja, S. [Servicio de Radiofisica Hospitalaria, Hospital Regional Universitario ' Carlos Haya' , Avda. Carlos Haya, s/n, E-29010 Malaga (Spain); Guerrero, R. [Servicio de Radiofisica, Hospital Universitario ' San Cecilio' , Avda. Dr. Oloriz, 16, E-18012 Granada (Spain); Anguiano, M.; Lallena, A.M. [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada (Spain)

    2007-09-21

    When a therapeutic electron linear accelerator is simulated using a Monte Carlo (MC) code, the tuning of the initial spectra and the renormalization of dose (e.g., to maximum axial dose) constitute a common practice. As a result, very similar depth dose curves are obtained for different MC codes. However, if renormalization is turned off, the results obtained with the various codes disagree noticeably. The aim of this work is to investigate in detail the reasons of this disagreement. We have found that the observed differences are due to non-negligible differences in the angular scattering of the electron beam in very thin slabs of dense material (primary foil) and thick slabs of very low density material (air). To gain insight, the effects of the angular scattering models considered in various MC codes on the dose distribution in a water phantom are discussed using very simple geometrical configurations for the LINAC. The MC codes PENELOPE 2003, PENELOPE 2005, GEANT4, GEANT3, EGSnrc and MCNPX have been used.

  8. Comparative study on CO2 corrosion behavior of N80,P110,X52 and 13Cr pipe lines in simulated stratum water

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    To better understand the carbon dioxide (CO2) corrosion behavior of carbon steel and its influence on petroleum development (including drilling,production and transportation) in the Daqing Oilfield,CO2 corrosion behaviors of N80,P110,X52 and 13Cr pipe lines in simulated solution at high temperature and high pressure condition are investigated by dynamic corrosion experiments,scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses.Results show that the corrosion rate of all pipe lines increases quickly when CO2 partial pressure increases from 0.5 to 1.5 MPa,but it slows down when CO2 partial pressure further increases from 1.5 to 4.5 MPa,during which localized corrosion is prevailing.When the experimental temperature ranges from 60 to 120°C,localized corrosion prevails.The corrosion rate of all pipe lines decreases sharply when the temperature changes from 60 to 100°C,and it becomes stable after the temperature is higher than 100°C.When the flow rate is in the range of 0–1.5 m/s,the corrosion rate of sample X52 remains unchanged,but localized corrosion gradually becomes very serious when the flow rate further increases.By analyzing the corrosion product scales of sample 13Cr,some remarkable phenomena are observed.At the temperature range of 60–100°C,the corrosion product scales are loose and thick,but become very compact when the temperature increases above 100°C.In the later case,localized corrosion is prevailing.The main components of the corrosion product scales are FeCO3 and Cr2O3.

  9. Assessing the bioavailability of polyphenols and antioxidant properties of extra virgin argan oil by simulated digestion and Caco-2 cell assays. Comparative study with extra virgin olive oil.

    Science.gov (United States)

    Seiquer, Isabel; Rueda, Ascensión; Olalla, Manuel; Cabrera-Vique, Carmen

    2015-12-01

    Argan oil is becoming increasingly popular in the edible-oil market as a luxury food with healthy properties. This paper analyzes (i) the bioavailability of the polyphenol content and antioxidant properties of extra virgin argan oil (EVA) by the combination of in vitro digestion and absorption across Caco-2 cells and (ii) the protective role of the oil bioaccessible fraction (BF) against induced oxidative stress. Results were compared with those obtained with extra virgin olive oil (EVO). Higher values of polyphenols and antioxidant activity were observed in the BF obtained after the in vitro digestion of oils compared with the initial chemical extracts; the increase was higher for EVA but absolute BF values were lower than EVO. Bioaccessible polyphenols from EVA were absorbed by Caco-2 cells in higher proportions than from EVO, and minor differences were observed for antioxidant activity. Preincubation of cell cultures with BF from both oils significantly protected against oxidation, limiting cell damage and reducing reactive oxygen species generation.

  10. Linear response properties required to simulate vibrational spectra of biomolecules in various media: (R)-phenyloxirane (A comparative theoretical and spectroscopic vibrational study)

    DEFF Research Database (Denmark)

    Jalkanen, Karl J.; Jürgensen, Vibeke Würtz; Degtyarenko, I.M.

    2005-01-01

    in understanding the photo induced chemical reactivity observed in many systems. This work is a continuation of our goal to interpret the results of experimental studies on the basis of theoretical results, which can help to understand the structure and function of proteins, other biomolecules and ligands...... in their native environments. As the physical tools used to observe and study biological processes have evolved, so have the theoretical methods and models to interpret, understand and completely utilize the results of these new measurements. The work on developing methods for modeling amino acids, peptides...

  11. Exploring PHD fingers and H3K4me0 interactions with molecular dynamics simulations and binding free energy calculations: AIRE-PHD1, a comparative study.

    Directory of Open Access Journals (Sweden)

    Dimitrios Spiliotopoulos

    Full Text Available PHD fingers represent one of the largest families of epigenetic readers capable of decoding post-translationally modified or unmodified histone H3 tails. Because of their direct involvement in human pathologies they are increasingly considered as a potential therapeutic target. Several PHD/histone-peptide structures have been determined, however relatively little information is available on their dynamics. Studies aiming to characterize the dynamic and energetic determinants driving histone peptide recognition by epigenetic readers would strongly benefit from computational studies. Herein we focus on the dynamic and energetic characterization of the PHD finger subclass specialized in the recognition of histone H3 peptides unmodified in position K4 (H3K4me0. As a case study we focused on the first PHD finger of autoimmune regulator protein (AIRE-PHD1 in complex with H3K4me0. PCA analysis of the covariance matrix of free AIRE-PHD1 highlights the presence of a "flapping" movement, which is blocked in an open conformation upon binding to H3K4me0. Moreover, binding free energy calculations obtained through Molecular Mechanics/Poisson-Boltzmann Surface Area (MM/PBSA methodology are in good qualitative agreement with experiments and allow dissection of the energetic terms associated with native and alanine mutants of AIRE-PHD1/H3K4me0 complexes. MM/PBSA calculations have also been applied to the energetic analysis of other PHD fingers recognizing H3K4me0. In this case we observe excellent correlation between computed and experimental binding free energies. Overall calculations show that H3K4me0 recognition by PHD fingers relies on compensation of the electrostatic and polar solvation energy terms and is stabilized by non-polar interactions.

  12. Simulating auditory and visual sensorineural prostheses: a comparative review

    Science.gov (United States)

    Hallum, L. E.; Dagnelie, G.; Suaning, G. J.; Lovell, N. H.

    2007-03-01

    Microelectronic vision prosthesis proposes to render luminous spots (so-called phosphenes) in the visual field of the otherwise blind subject by way of an implanted array of stimulating electrodes, and in doing so restore some spatial vision. There are now many research teams worldwide working towards a therapeutic device, analogous to the cochlear implant, for the profoundly blind. Despite the similarities between the cochlear implant and vision prostheses, there are few instances in the literature where the two approaches are compared and contrasted with a mind to informing the science and engineering of the latter. This is the focus of the present review; specifically, our interest is psychophysics and signal processing. Firstly, we examine the cochlear implant, and review a handful of psychophysical work: the acoustic simulation of cochlear implants and the method used. We focus on the use of normally hearing subjects (played coloured noise bands or sine waves) as a means of investigating cochlear-implant efficacy and speech processing algorithms. These results provide guidance to vision researchers, for they address the interpretation of simulation data, and flag key areas, such as 'artificial' perception in the presence of noise, that require experimental work in coming years. Secondly, we provide an up-to-date review of the body of analogous psychophysical work: the visual simulation, involving normal observers, of microelectronic vision prosthesis. These simulations allow predictions as to the likely clinical efficacy of the prosthesis; indeed, results to date suggest that a number on the order of 100 implanted electrodes will afford subjects mobility and recognition of faces (and other complex stimuli), while even fewer electrodes facilitate reading printed text and very simple visuomanual tasks. Further, the simulations allow investigations of image and signal processing strategies, plus they provide researchers in the field, and other interested persons

  13. Comparative Study of Micro-simulation Performances for Urban Road Network between Vissim and Corsim%Vissim和Corsim在城市道路微观仿真中的对比研究

    Institute of Scientific and Technical Information of China (English)

    吴亦政; 孙健; 彭春露; 徐猛

    2012-01-01

    This study conducted a comparative analysis of two popular simulation models Vissim and Corsim, based on their simulation performances on an urban traffic network. The road network and field traffic data from North Bund, Hongkou District of Shanghai were collected and used as the simulation background and input. Three key indices, including software usability, average control delay and cross-sectional traffic volume, were selected for comparison, and a sensitivity analysis was conducted to compare the performances of both models on each index. Performance differences and particular advantages of each simulator were identified based on comparison analyses of simulations results with different levels of congestion and different scales of intersections. The main reason for performance differences was found to be the configuration of model parameters including driver behavior settings, traffic environment settings, vehicle types and others. Consequently, it is recommended that the appropriate tool should be chosen based on the intersection type and the saturation level of the simulation case.%对2种最为常见的微观仿真模型Vissim和Corsim在城市路网交通仿真中的性能进行对比评价.以上海市虹口区北外滩路网作为仿真对象,对路网和交通数据进行了收集,基于现实数据进行了仿真模拟,并选取编译简易度、平均控制延误以及断面交通量作为关键指标,运用敏感度分析的方法对2种模型的仿真性能进行对比.针对不同程度的拥挤度设置以及不同规模的交叉口,识别了2种仿真模型表现出的不同特点及其交通运行指标输出的差异性.该差异主要由模型的默认参数设置引起,包括驾驶行为,交通环境以及车辆类型的设置等.因此,研究人员应根据交叉口类型以及饱和程度等,来选择适当的仿真工具.

  14. Stigmergy in Comparative Settlement Choice and Palaeoenvironment Simulation

    CERN Document Server

    Ch'ng, Eugene; Hakvoort, Gido

    2015-01-01

    Decisions on settlement location in the face of climate change and coastal inundation may have resulted in success, survival or even catastrophic failure for early settlers in many parts of the world. In this study we investigate various questions related to how individuals respond to a palaeoenvironmental simulation, on an interactive tabletop device where participants have the opportunity to build a settlement on a coastal landscape, balancing safety and access to resources, including sea and terrestrial foodstuffs, whilst taking into consideration the threat of rising sea levels. The results of the study were analysed to consider whether decisions on settlement were predicated to be near to locations where previous structures were located, stigmergically, and whether later settler choice would fare better, and score higher, as time progressed. The proximity of settlements was investigated and the reasons for clustering were considered. The interactive simulation was exhibited to thousands of visitors at th...

  15. A Monte Carlo simulation study comparing linear regression, beta regression, variable-dispersion beta regression and fractional logit regression at recovering average difference measures in a two sample design.

    Science.gov (United States)

    Meaney, Christopher; Moineddin, Rahim

    2014-01-24

    In biomedical research, response variables are often encountered which have bounded support on the open unit interval--(0,1). Traditionally, researchers have attempted to estimate covariate effects on these types of response data using linear regression. Alternative modelling strategies may include: beta regression, variable-dispersion beta regression, and fractional logit regression models. This study employs a Monte Carlo simulation design to compare the statistical properties of the linear regression model to that of the more novel beta regression, variable-dispersion beta regression, and fractional logit regression models. In the Monte Carlo experiment we assume a simple two sample design. We assume observations are realizations of independent draws from their respective probability models. The randomly simulated draws from the various probability models are chosen to emulate average proportion/percentage/rate differences of pre-specified magnitudes. Following simulation of the experimental data we estimate average proportion/percentage/rate differences. We compare the estimators in terms of bias, variance, type-1 error and power. Estimates of Monte Carlo error associated with these quantities are provided. If response data are beta distributed with constant dispersion parameters across the two samples, then all models are unbiased and have reasonable type-1 error rates and power profiles. If the response data in the two samples have different dispersion parameters, then the simple beta regression model is biased. When the sample size is small (N0 = N1 = 25) linear regression has superior type-1 error rates compared to the other models. Small sample type-1 error rates can be improved in beta regression models using bias correction/reduction methods. In the power experiments, variable-dispersion beta regression and fractional logit regression models have slightly elevated power compared to linear regression models. Similar results were observed if the

  16. Biofuel: a comparative case study

    OpenAIRE

    Siddiqui, Aamir; Kading, Christopher; Carter, Kasey

    2013-01-01

    Approved for public release; distribution is unlimited This project analyzes the governments role in the commercialization of biofuel by comparing biofuel commercialization efforts to those of nuclear power and nanotechnology commercialization. The PESTEL framework is applied to nuclear power and nanotechnology to identify key factors relevant to successful commercialization. These success factors are compared to current government biofuel policies to infer the likelihood of successful bio...

  17. A comparative study of high-temperature erosion wear of plasma-sprayed NiCrBSiFe and WC-NiCrBSiFe coatings under simulated coal-fired boiler conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hidalgo, V.H.; Varela, F.J.B.; Menendez, A.C.; Martinez, S.P. [University of Oviedo, Gijon (Spain). Dept of Energy

    2001-03-01

    A comparative study was carried out of the behaviour of plasma sprayed NiCrBSiFe and WC-NiCrBSiFe alloys subjected to conditions which simulate a post-combustion gas atmosphere from a coal-fired boiler combustor. The study first evaluates the effects of thermal exposure at high temperatures on the microstructure of the coatings and on the adherence between substrate (austenitic stainless steel) and coatings. The oxidation rates of these coatings in atmospheres with 3-3.5% of free oxygen at 773 and 1073 K were then evaluated. The effect of WC on the low-velocity corrosion-erosion behaviour produced by the impact of fly ashes in the gas stream at high temperatures (773 and 1073 K) was assessed under impact angles of 30 and 90{degree}C. Finally, the eroded surfaces were analysed using scanning electron microscopy in order to characterize the ash embedment phenomena and the operating erosive micromechanisms.

  18. Comparing Simulations and Observations of Reionization-Epoch Galaxies

    Science.gov (United States)

    Dave, Romeel; Finlator, Kristian

    2006-05-01

    We propose to test and constrain models of early galaxy formation through comparisons with observations of reionization-epoch (z>6) galaxies observed using Spitzer. The goals are to (1) Make predictions for z>6 objects using state-of-the-art cosmological hydrodynamic simulations of galaxy formation tailored to study the reionization epoch; (2) Develop a publicly-available tool called SPOC designed to obtain detailed constraints on physical properties of observed galaxies through comparisons with simulated galaxy catalogs; and (3) Use SPOC to test and constrain models of galaxy formation through comparisons with rapidly- advancing observations in the new frontier of early universe studies. The results of this study will yield deeper insights into the galaxy formation process at these mostly unexplored epochs, with implications for understanding the formation of massive galaxies, studying the topology and evolution of IGM reionization, and designing future surveys to detect first objects. The SPOC tool will facilitate a closer connection between observations and theory by enabling the community to interpret data within the framework of current hierarchical structure formation models, in turn providing detailed tests of these models that is essential for driving the field forward.

  19. Lattice Boltzmann modeling of directional wetting: Comparing simulations to experiments

    NARCIS (Netherlands)

    Jansen, H.P.; Sotthewes, K.; Swigchem, van J.; Zandvliet, H.J.W.; Kooij, E.S.

    2013-01-01

    Lattice Boltzmann Modeling (LBM) simulations were performed on the dynamic behavior of liquid droplets on chemically striped patterned surfaces, ultimately with the aim to develop a predictive tool enabling reliable design of future experiments. The simulations accurately mimic experimental results,

  20. EFQPSK Versus CERN: A Comparative Study

    Science.gov (United States)

    Borah, Deva K.; Horan, Stephen

    2001-01-01

    This report presents a comparative study on Enhanced Feher's Quadrature Phase Shift Keying (EFQPSK) and Constrained Envelope Root Nyquist (CERN) techniques. These two techniques have been developed in recent times to provide high spectral and power efficiencies under nonlinear amplifier environment. The purpose of this study is to gain insights into these techniques and to help system planners and designers with an appropriate set of guidelines for using these techniques. The comparative study presented in this report relies on effective simulation models and procedures. Therefore, a significant part of this report is devoted to understanding the mathematical and simulation models of the techniques and their set-up procedures. In particular, mathematical models of EFQPSK and CERN, effects of the sampling rate in discrete time signal representation, and modeling of nonlinear amplifiers and predistorters have been considered in detail. The results of this study show that both EFQPSK and CERN signals provide spectrally efficient communications compared to filtered conventional linear modulation techniques when a nonlinear power amplifier is used. However, there are important differences. The spectral efficiency of CERN signals, with a small amount of input backoff, is significantly better than that of EFQPSK signals if the nonlinear amplifier is an ideal clipper. However, to achieve such spectral efficiencies with a practical nonlinear amplifier, CERN processing requires a predistorter which effectively translates the amplifier's characteristics close to those of an ideal clipper. Thus, the spectral performance of CERN signals strongly depends on the predistorter. EFQPSK signals, on the other hand, do not need such predistorters since their spectra are almost unaffected by the nonlinear amplifier, Ibis report discusses several receiver structures for EFQPSK signals. It is observed that optimal receiver structures can be realized for both coded and uncoded EFQPSK

  1. Benchmarked Library Websites Comparative Study

    KAUST Repository

    Ramli, Rindra M.

    2015-01-01

    This presentation provides an analysis of services provided by the benchmarked library websites. The exploratory study includes comparison of these websites against a list of criterion and presents a list of services that are most commonly deployed by the selected websites. In addition to that, the investigators proposed a list of services that could be provided via the KAUST library website.

  2. Accuracy of Monte Carlo simulations compared to in-vivo MDCT dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Bostani, Maryam, E-mail: mbostani@mednet.ucla.edu; McMillan, Kyle; Cagnon, Chris H.; McNitt-Gray, Michael F. [Departments of Biomedical Physics and Radiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90024 (United States); Mueller, Jonathon W. [United States Air Force, Keesler Air Force Base, Biloxi, Mississippi 39534 (United States); Cody, Dianna D. [University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 (United States); DeMarco, John J. [Departments of Biomedical Physics and Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90024 (United States)

    2015-02-15

    Purpose: The purpose of this study was to assess the accuracy of a Monte Carlo simulation-based method for estimating radiation dose from multidetector computed tomography (MDCT) by comparing simulated doses in ten patients to in-vivo dose measurements. Methods: MD Anderson Cancer Center Institutional Review Board approved the acquisition of in-vivo rectal dose measurements in a pilot study of ten patients undergoing virtual colonoscopy. The dose measurements were obtained by affixing TLD capsules to the inner lumen of rectal catheters. Voxelized patient models were generated from the MDCT images of the ten patients, and the dose to the TLD for all exposures was estimated using Monte Carlo based simulations. The Monte Carlo simulation results were compared to the in-vivo dose measurements to determine accuracy. Results: The calculated mean percent difference between TLD measurements and Monte Carlo simulations was −4.9% with standard deviation of 8.7% and a range of −22.7% to 5.7%. Conclusions: The results of this study demonstrate very good agreement between simulated and measured doses in-vivo. Taken together with previous validation efforts, this work demonstrates that the Monte Carlo simulation methods can provide accurate estimates of radiation dose in patients undergoing CT examinations.

  3. Comparative study of experimental signals for multipactor and breakdown.

    CERN Document Server

    Dehler, Micha; Wuensch, Walter; Faus-Golfe, Angeles; Gimeno Martinez, Benito; Kovermann, Jan; Boria, Vicente; Raboso, David

    2012-01-01

    Performance limiting high-power rf phenomenon occur in both transmitter systems in satellites and high-gradient accelerating structures in particle accelerators. In satellites the predominant effect is multipactor while in accelerators it is breakdown. Both communities have studied their respective phenomena extensively and developed particular simulation tools and experimental techniques. A series of experiments to directly compare measurements made under multipactor and breakdown conditions has been initiated with the objective to crosscheck and compare the physics, simulation tools and measurement techniques.

  4. Comparative study among simulations of an internal monitoring system using different Monte Carlo codes; Estudo comparativo entre simulacoes de um sistema de monitoracao ocupacional interna utilizando diferentes codigos de Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Fonseca, T.C.F.; Bastos, F.M.; Figueiredo, M.T.T.; Souza, L.S.; Guimaraes, M.C.; Silva, C.R.E.; Mello, O.A.; Castelo e Silva, L.A.; Paixao, L., E-mail: tcff01@gmail.com [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Benavente, J.A.; Paiva, F.G. [Universidade Federal de Minas Gerais (PCTN/UFMG), Belo Horizonte, MG (Brazil). Curso de Pos-Graduacao em Ciencias e Tecnicas Nucleares

    2015-07-01

    Computational Monte Carlo (MC) codes have been used for simulation of nuclear installations mainly for internal monitoring of workers, the well known as Whole Body Counters (WBC). The main goal of this project was the modeling and simulation of the counting efficiency (CE) of a WBC system using three different MC codes: MCNPX, EGSnrc and VMC in-vivo. The simulations were performed for three different groups of analysts. The results shown differences between the three codes, as well as in the results obtained by the same code and modeled by different analysts. Moreover, all the results were also compared to the experimental results obtained in laboratory for meaning of validation and final comparison. In conclusion, it was possible to detect the influence on the results when the system is modeled by different analysts using the same MC code and in which MC code the results were best suited, when comparing to the experimental data result. (author)

  5. GESDB: a platform of simulation resources for genetic epidemiology studies.

    Science.gov (United States)

    Yao, Po-Ju; Chung, Ren-Hua

    2016-01-01

    Computer simulations are routinely conducted to evaluate new statistical methods, to compare the properties among different methods, and to mimic the observed data in genetic epidemiology studies. Conducting simulation studies can become a complicated task as several challenges can occur, such as the selection of an appropriate simulation tool and the specification of parameters in the simulation model. Although abundant simulated data have been generated for human genetic research, currently there is no public database designed specifically as a repository for these simulated data. With the lack of such a database, for similar studies, similar simulations may have been repeated, which resulted in redundant work. Thus, we created an online platform, the Genetic Epidemiology Simulation Database (GESDB), for simulation data sharing and discussion of simulation techniques for genetic epidemiology studies. GESDB consists of a database for storing simulation scripts, simulated data and documentation from published articles as well as a discussion forum, which provides a platform for discussion of the simulated data and exchanging simulation ideas. Moreover, summary statistics such as the simulation tools that are most commonly used and datasets that are most frequently downloaded are provided. The statistics will be informative for researchers to choose an appropriate simulation tool or select a common dataset for method comparisons. GESDB can be accessed at http://gesdb.nhri.org.twDatabase URL: http://gesdb.nhri.org.tw.

  6. A comparative analysis of simulated and observed photosynthetic CO2 uptake in two coniferous forest canopies

    DEFF Research Database (Denmark)

    Ibrom, A.; Jarvis, P.G.; Clement, R.

    2006-01-01

    Gross canopy photosynthesis (Pg) can be simulated with canopy models or retrieved from turbulent carbon dioxide (CO2) flux measurements above the forest canopy. We compare the two estimates and illustrate our findings with two case studies. We used the three-dimensional canopy model MAESTRA to si...

  7. Comparing ballistic wounds with experiments on body simulator.

    Science.gov (United States)

    Bresson, F; Franck, O

    2010-05-20

    This paper demonstrates how ballistic experiments on body simulator can bring a key information in the forensic science field. In the investigated case, a hunter was shot by accident in the back. Two hunters were suspected of having inadvertently shot towards the victim. The deadly bullet left the body and cannot be found on the scene neither in the body. The only way to discriminate the two options was to perform ballistic tests in body simulators. Even though the knowledge about body simulators is not enough advanced yet to expect accurate quantitative results, it was supposed to fully discriminate the two investigated cases as its respective impact energy are highly different (respectively 1200J and 2400J). For each investigated possibility, bullet's expansion state and body wounds were simulated. Bullet impact characteristics were determined by measuring the muzzle velocity, compute the impact velocity in the considered range (the position of each hunter is accurately known). Reloading cartridges allowed to reproduce accuretaly the corresponding velocity. The body was simulated by 3 different means in order to explore the accuracy of the simulation process. We demonstrated that the reported case is situated in a velocity/energy range in which body simulators do not need to be particularly accurate to reproduce the bullet expansion/non-expansion state. It furthermore demonstrated that only one case is compatible with the ballistic wounds of the victim. In the other case, the bullet's expansion would lead to a completely different wound shape.

  8. Lattice Boltzmann modeling of directional wetting: Comparing simulations to experiments

    Science.gov (United States)

    Jansen, H. Patrick; Sotthewes, Kai; van Swigchem, Jeroen; Zandvliet, Harold J. W.; Kooij, E. Stefan

    2013-07-01

    Lattice Boltzmann Modeling (LBM) simulations were performed on the dynamic behavior of liquid droplets on chemically striped patterned surfaces, ultimately with the aim to develop a predictive tool enabling reliable design of future experiments. The simulations accurately mimic experimental results, which have shown that water droplets on such surfaces adopt an elongated shape due to anisotropic preferential spreading. Details of the contact line motion such as advancing of the contact line in the direction perpendicular to the stripes exhibit pronounced similarities in experiments and simulations. The opposite of spreading, i.e., evaporation of water droplets, leads to a characteristic receding motion first in the direction parallel to the stripes, while the contact line remains pinned perpendicular to the stripes. Only when the aspect ratio is close to unity, the contact line also starts to recede in the perpendicular direction. Very similar behavior was observed in the LBM simulations. Finally, droplet movement can be induced by a gradient in surface wettability. LBM simulations show good semiquantitative agreement with experimental results of decanol droplets on a well-defined striped gradient, which move from high- to low-contact angle surfaces. Similarities and differences for all systems are described and discussed in terms of the predictive capabilities of LBM simulations to model direction wetting.

  9. A SOFTWARE TOOL TO COMPARE MEASURED AND SIMULATED BUILDING ENERGY PERFORMANCE DATA

    Energy Technology Data Exchange (ETDEWEB)

    Maile, Tobias; Bazjanac, Vladimir; O' Donnell, James; Garr, Matthew

    2011-11-01

    Building energy performance is often inadequate when compared to design goals. To link design goals to actual operation one can compare measured with simulated energy performance data. Our previously developed comparison approach is the Energy Performance Comparison Methodology (EPCM), which enables the identification of performance problems based on a comparison of measured and simulated performance data. In context of this method, we developed a software tool that provides graphing and data processing capabilities of the two performance data sets. The software tool called SEE IT (Stanford Energy Efficiency Information Tool) eliminates the need for manual generation of data plots and data reformatting. SEE IT makes the generation of time series, scatter and carpet plots independent of the source of data (measured or simulated) and provides a valuable tool for comparing measurements with simulation results. SEE IT also allows assigning data points on a predefined building object hierarchy and supports different versions of simulated performance data. This paper briefly introduces the EPCM, describes the SEE IT tool and illustrates its use in the context of a building case study.

  10. Comparing measured with simulated vertical soil stress under vehicle load

    DEFF Research Database (Denmark)

    Keller, Thomas; Lamandé, Mathieu; Arvidsson, Johan;

    in the soil profile at 0.3, 0.5 and 0.7 m depth was measured during wheeling at field capacity on five soils (13-66% clay). Stress propagation was then simulated with the semi-analytical model, using vertical stress at 0.1 m depth estimated from tyre characteristics as upper boundary condition, and v...

  11. Comparing measured with simulated vertical soil stress under vehicle load

    DEFF Research Database (Denmark)

    Keller, Thomas; Lamandé, Mathieu; Arvidsson, Johan

    in the soil profile at 0.3, 0.5 and 0.7 m depth was measured during wheeling at field capacity on five soils (13-66% clay). Stress propagation was then simulated with the semi-analytical model, using vertical stress at 0.1 m depth estimated from tyre characteristics as upper boundary condition, and v...

  12. SLUDGE BATCH 5 SIMULANT FLOWSHEET STUDIES

    Energy Technology Data Exchange (ETDEWEB)

    Lambert, D; Michael Stone, M; Bradley Pickenheim, B; David Best, D; David Koopman, D

    2008-10-03

    The Defense Waste Processing Facility (DWPF) will transition from Sludge Batch 4 (SB4) processing to Sludge Batch 5 (SB5) processing in early fiscal year 2009. Tests were conducted using non-radioactive simulants of the expected SB5 composition to determine the impact of varying the acid stoichiometry during the Sludge Receipt and Adjustment Tank (SRAT) and Slurry Mix Evaporator (SME) processes. The work was conducted to meet the Technical Task Request (TTR) HLW/DWPF/TTR-2007-0007, Rev. 1 and followed the guidelines of a Task Technical and Quality Assurance Plan (TT&QAP). The flowsheet studies are performed to evaluate the potential chemical processing issues, hydrogen generation rates, and process slurry rheological properties as a function of acid stoichiometry. Initial SB5 flowsheet studies were conducted to guide decisions during the sludge batch preparation process. These studies were conducted with the estimated SB5 composition at the time of the study. The composition has changed slightly since these studies were completed due to changes in the washing plan to prepare SB5 and the estimated SB4 heel mass. Nine DWPF process simulations were completed in 4-L laboratory-scale equipment using both a batch simulant (Tank 51 simulant after washing is complete) and a blend simulant (Tank 40 simulant after Tank 51 transfer is complete). Each simulant had a set of four SRAT and SME simulations at varying acid stoichiometry levels (115%, 130%, 145% and 160%). One additional run was made using blend simulant at 130% acid that included additions of the Actinide Removal Process (ARP) waste prior to acid addition and the Modular Caustic Side Solvent Extraction (CSSX) Unit (MCU) waste following SRAT dewatering. There are several parameters that are noteworthy concerning SB5 sludge: (1) This is the first batch DWPF will be processing that contains sludge that has had a significant fraction of aluminum removed through aluminum dissolution. (2) The sludge is high in mercury

  13. Physics studies in Europe; a comparative study

    NARCIS (Netherlands)

    Steenstrup, S; dalle Rose, LFD; Jones, WG; Tugulea, L; van Steenwijk, FJ

    What are the differences and similarities between physics studies at different universities across Europe (here the definition of Europe is broad)? How much does a student have to work to obtain a degree in physics? Questions like those prompted EUPEN (European Physics Education Network) to make a

  14. Comparative Evaluation of Supply Chain Management Strategies: A Simulation Approach

    OpenAIRE

    Chan, FTS

    2002-01-01

    Supply chain management has become one of the most important sources of competitive advantage in different industries. For years, researchers have investigated the various processes within supply chain. There has been an increasing attention placed on performance, design and analysis of supply chain. However, the supply chain is a complex model so it is difficult to analyze the performance of a supply chain philosophically. To evaluate the control mechanism for a supply chain, simulation is o...

  15. A Comparative Study of VaR Model and Its Demonstration Based on Monte Carlo Simulation%基于蒙特卡洛模拟的VaR模型及其模拟实证对比研究

    Institute of Scientific and Technical Information of China (English)

    喻为民

    2014-01-01

    在对VaR模型基本思想介绍基础上,构建基于蒙特卡洛模拟的VaR计算模型,并结合Matlab2012a计算软件,分别计算基于随机模拟和历史模拟的金融市场VaR数值,并在同类型模拟方法下进行横向对比分析。研究结果表明:t分布模型在高置信水平条件下较标准正态分布模型具有更高的精度要求和优势,且对于金融收益率数据的表征更为合理科学;2013年我国股指期货市场结构较2012年发生较大程度变化,且系统风险有进一步扩大趋势。%Based on the introduction of VaR Model, this paper builds a VaR calculation model with Monte Carlo Simulation, calculates the VaR values in financial market by random simulation and historical simulation combining with Matlab 2012a calculation software and makes a lateral comparative analysis through the same type simulation. The result shows that, compared to the standardized normal distribution model, t distribution model has high precision requirement and advantage in the condition of the high confidence level and the characterization of financial returns is more reasonable. The structure of stock index futures market in 2013 has changed a lot and the system risk has the trend of being enlarged.

  16. The Influence Studies in Comparative Literature

    Institute of Scientific and Technical Information of China (English)

    张宏莹

    2010-01-01

    Comparative literature arose in the 19th century,the approach adopted for its influence study has been developed and diversified in different eras,in this article,the influence study in comparative literature through a reading culture is discussed in order to reveal in what aspects the reading culture may cut across the regional border of influence study.

  17. Comparing simulated carbon budget of a Lei bamboo forest with flux tower data

    Science.gov (United States)

    Li, Xuehe; Jiang, Hong; Liu, Jinxun; Sun, Cheng; Wang, Ying; Jin, Jiaxin

    2014-01-01

    Bamboo forest ecosystem is the part of the forest ecosystem. The distribution area of bamboo forest is limited, but in somewhere, like south China, it has been cultivate for a long time with human management. As the climate change has been take great effect on forest carbon budget, many researchers pay attention to the carbon budget in bamboo forest. Moreover cultivative management had a significant impact on the bamboo forest carbon budget. In this study, we modified a terrestrial ecosystem model named Integrated Biosphere Simulator (IBIS) according the management of Lei bamboo forest. Some management, like fertilization, shoots harvesting and organic mulching in winter, had been incorporated into model. Then we had compared model results with the observation data from a Lei bamboo flux tower. The simulated and observed results had achieved good consistency. Our simulated Lei bamboo forest yearly net ecosystem productivity (NEP) was 0.41 kgC a-1 of carbon, which is very close to the observation data 0.45 kgC a-1 of carbon. And the monthly simulated results can take the change of carbon budget in each month, similar to the data we got from flux tower. It reflects that the modified IBIS model can characterize the growth of bamboo forest and perform the simulation well. And then two groups of simulations were set to evaluate effects of cultivative managements on Lei bamboo forests carbon budget. And results showed that both fertilization and organic mulching had taken positive effects on Lei bamboo forests carbon sequestration.

  18. Identifying tools for comparing simulations and observations of spectral-line data cubes

    Science.gov (United States)

    Koch, Eric W.; Ward, Caleb G.; Offner, Stella; Loeppky, Jason L.; Rosolowsky, Erik W.

    2017-10-01

    We present a statistical framework to compare spectral-line data cubes of molecular clouds and use the framework to perform an analysis of various statistical tools developed from methods proposed in the literature. We test whether our methods are sensitive to changes in the underlying physical properties of the clouds or whether their behaviour is governed by random fluctuations. We perform a set of 32 self-gravitating magnetohydrodynamic simulations that test all combinations of five physical parameters - Mach number, plasma parameter, virial parameter, driving scales and solenoidal driving fraction - each of which can be set to a low or high value. We create mock observational data sets of 13CO(1-0) emission from each simulation. We compare these mock data to those generated from a set of baseline simulations using pseudo-distance metrics based on 18 different statistical techniques that have previously been used to study molecular clouds. We analyse these results using methods from the statistical field of experimental design and find that several of the statistics can reliably track changes in the underlying physics. Our analysis shows that the interactions between parameters are often among the most significant effects. A small fraction of statistics are also sensitive to changes in magnetic field properties. We use this framework to compare the set of simulations to observations of three nearby star-forming regions: NGC 1333, Oph A and IC 348. We find that no one simulation agrees significantly better with the observations, although there is evidence that the high Mach number simulations are more consistent with the observations.

  19. Comparing wall modeled LES and prescribed boundary layer approach in infinite wind farm simulations

    DEFF Research Database (Denmark)

    Sarlak, Hamid; Mikkelsen, Robert; Sørensen, Jens Nørkær

    2015-01-01

    This paper aims at presenting a simple and computationally fast method for simulation of the Atmospheric Boundary Layer (ABL) and comparing the results with the commonly used wall-modelled Large Eddy Simulation (WMLES). The simple method, called Prescribed Mean Shear and Turbulence (PMST) hereafter......, is based on imposing body forces over the whole domain to maintain a desired unsteady ow, where the ground is modeled as a slip-free boundary which in return hampers the need for grid refinement and/or wall modeling close to the solid walls. Another strength of this method besides being computationally...... inexpensive, is high flexibility meaning that the imposed boundary layer can be read from another CFD simulation, or from site measurements. For fundamental studies focusing on the wake structures rather than ABL for example, the grid can be refined in the rotor region and any desired shear layer can...

  20. Simulation study of disruption characteristics in KSTAR

    Science.gov (United States)

    Lee, Jongkyu; Kim, J. Y.; Kessel, C. E.; Poli, F.

    2012-10-01

    A detailed simulation study of disruption in KSTAR had been performed using the Tokamak Simulation Code(TSC) [1] during the initial design phase of KSTAR [2]. Recently, however, a partial modification in the structure of passive plate was made in relation to reduce eddy current and increase the efficiency of control of vertical position. A substantial change can then occur in disruption characteristics and plasma behavior during disruption due to changes in passive plate structure. Because of this, growth rate of vertical instability is expected to be increased and eddy current and its associated electomagnetic force are expected to be reduced. To check this in more detail, a new simulation study is here given with modified passive plate structure of KSTAR. In particular, modeling of vertical disruption that is vertical displacement event (VDE) was carried out. We calculated vertical growth rate for a drift phase of plasma and electromagnetic force acting on PFC structures and compared the results between in a new model and an old model. [4pt] [1] S.C. Jardin, N. Pomphrey and J. Delucia, J. Comp. Phys. 66, 481 (1986).[0pt] [2] J.Y. Kim, S.Y. Cho and KSTAR Team, Disruption load analysis on KSTAR PFC structures, J. Accel. Plasma Res. 5, 149 (2000).

  1. Comparative testing of DNA segmentation algorithms using benchmark simulations.

    Science.gov (United States)

    Elhaik, Eran; Graur, Dan; Josic, Kresimir

    2010-05-01

    Numerous segmentation methods for the detection of compositionally homogeneous domains within genomic sequences have been proposed. Unfortunately, these methods yield inconsistent results. Here, we present a benchmark consisting of two sets of simulated genomic sequences for testing the performances of segmentation algorithms. Sequences in the first set are composed of fixed-sized homogeneous domains, distinct in their between-domain guanine and cytosine (GC) content variability. The sequences in the second set are composed of a mosaic of many short domains and a few long ones, distinguished by sharp GC content boundaries between neighboring domains. We use these sets to test the performance of seven segmentation algorithms in the literature. Our results show that recursive segmentation algorithms based on the Jensen-Shannon divergence outperform all other algorithms. However, even these algorithms perform poorly in certain instances because of the arbitrary choice of a segmentation-stopping criterion.

  2. A COMPARATIVE STUDY UNDER PROGRESSIVELY FIRST FAILURE CENSORED RAYLEIGH DATA

    Directory of Open Access Journals (Sweden)

    Gyan Prakash

    2015-06-01

    Full Text Available A comparative study presented in this article for two different asymmetric loss functions is based on simulation. Two-parameter Rayleigh model is considered here as the underline model for evaluating the properties of Bayes estimators under progressive first failure censored data. Known and unknown both cases of location parameter are considered here for Bayes estimation of scale parameter.

  3. Comparative evaluation of the impact of WRF/NMM and WRF/ARW meteorology on CMAQ simulations for PM2.5 and its related precursors during the 2006 TexAQS/GoMACCS study

    Directory of Open Access Journals (Sweden)

    S. T. Rao

    2012-05-01

    Full Text Available This study presents a comparative evaluation of the impact of WRF-NMM and WRF-ARW meteorology on CMAQ simulations of PM2.5, its composition and related precursors over the eastern United States with the intensive observations obtained by aircraft (NOAA WP-3, ship and surface monitoring networks (AIRNow, IMPROVE, CASTNet and STN during the 2006 TexAQS/GoMACCS study. The results at the AIRNow surface sites show that both ARW-CMAQ and NMM-CMAQ reproduced day-to-day variations of observed PM2.5 and captured the majority of observed PM2.5 within a factor of 2 with a NMB value of −0.4% for ARW-CMAQ and −18% for NMM-CMAQ. Both models performed much better at the urban sites than at the rural sites, with greater underpredictions at the rural sites. Both models consistently underestimated the observed PM2.5 at the rural IMPROVE sites by −1% for the ARW-CMAQ and −19% for the NMM-CMAQ. The greater underestimations of SO42−, OC and EC by the NMM-CMAQ contributed to increased underestimation of PM2.5 at the IMPROVE sites. The NMB values for PM2.5 at the STN urban sites are 15% and −16% for the ARW-CMAQ and NMM-CMAQ, respectively. The underestimation of PM2.5 at the STN sites by the NMM-CMAQ mainly results from the underestimations of the SO42−, NH4+ and TCM components, whereas the overestimation of PM2.5 at the STN sites by the ARW-CMAQ results from the overestimations of SO42−, NO3−, and NH4+. The Comparison with WP-3 aircraft measurements reveals that both ARW-CMAQ and NMM-CMAQ have very similar model performance for vertical profiles for PM2.5 chemical components (SO42−, NH4+ and related gaseous species (HNO3, SO2, NH3, isoprene, toluene, terpenes as both models used the same chemical mechanisms and emissions. The results of ship along the coast of southeastern Texas over the Gulf of Mexico show that both models captured the temporal variations and broad synoptic change seen in the observed HCHO and acetaldehyde with the means NMB 2.

  4. Comparative evaluation of the impact of WRF/NMM and WRF/ARW meteorology on CMAQ simulations for PM2.5 and its related precursors during the 2006 TexAQS/GoMACCS study

    Directory of Open Access Journals (Sweden)

    S. T. Rao

    2011-12-01

    Full Text Available This study presents a comparative evaluation of the impact of WRF-NMM and WRF-ARW meteorology on CMAQ simulations of PM2.5, its composition and related precursors over the eastern United States with the intensive observations obtained by aircraft (NOAA P-3, ship and surface monitoring networks (AIRNow, IMPROVE, CASTNet and STN during the 2006 TexAQS/GoMACCS study. The results at the AIRNow surface sites show that both ARW-CMAQ and NMM-CMAQ reproduced day-to-day variations of observed PM2.5 and captured the majority of observed PM2.5 within a factor of 2 with a NMB value of −0.4% for ARW-CMAQ and −18% for NMM-CMAQ. Both models performed much better at the urban sites than at the rural sites, with greater underpredictions at the rural sites. Both models consistently underestimated the observed PM2.5 at the rural IMPROVE sites by −1% for the ARW-CMAQ and −19% for the NMM-CMAQ. The greater underestimations of SO42−, OC and EC by the NMM-CMAQ contributed to increased underestimation of PM2.5 at the IMPROVE sites. The NMB values for PM2.5 at the STN urban sites are 15% and −16% for the ARW-CMAQ and NMM-CMAQ, respectively. The underestimation of PM2.5 at the STN sites by the NMM-CMAQ mainly results from the underestimations of the SO42−, NH4+ and TCM components, whereas the overestimation of PM2.5 at the STN sites by the ARW-CMAQ results from the overestimations of SO42−, NO3−, and NH4+. The comparison with P-3 aircraft measurements reveals that both ARW-CMAQ and NMM-CMAQ have very similar model performance for vertical profiles for PM2.5 chemical components (SO42−, NH4+ and related gaseous species (HNO3, SO2, NH3, isoprene, toluene, terpenes as both models used the same chemical mechanisms and emissions. The results of ship along the coast of southeastern Texas over the Gulf of Mexico show that both models captured the temporal variations and broad synoptic change seen in the observed HCHO and acetaldehyde with the means NMB 2.

  5. A comparative study of discrete fracture network and equivalent continuum models for simulating flow and transport in the far field of a hypothetical nuclear waste repository in crystalline host rock

    Science.gov (United States)

    Hadgu, Teklu; Karra, Satish; Kalinina, Elena; Makedonska, Nataliia; Hyman, Jeffrey D.; Klise, Katherine; Viswanathan, Hari S.; Wang, Yifeng

    2017-10-01

    One of the major challenges of simulating flow and transport in the far field of a geologic repository in crystalline host rock is related to reproducing the properties of the fracture network over the large volume of rock with sparse fracture characterization data. Various approaches have been developed to simulate flow and transport through the fractured rock. The approaches can be broadly divided into Discrete Fracture Network (DFN) and Equivalent Continuum Model (ECM). The DFN explicitly represents individual fractures, while the ECM uses fracture properties to determine equivalent continuum parameters. We compare DFN and ECM in terms of upscaled observed transport properties through generic fracture networks. The major effort was directed on making the DFN and ECM approaches similar in their conceptual representations. This allows for separating differences related to the interpretation of the test conditions and parameters from the differences between the DFN and ECM approaches. The two models are compared using a benchmark test problem that is constructed to represent the far field (1 × 1 × 1 km3) of a hypothetical repository in fractured crystalline rock. The test problem setting uses generic fracture properties that can be expected in crystalline rocks. The models are compared in terms of the: 1) effective permeability of the domain, and 2) nonreactive solute breakthrough curves through the domain. The principal differences between the models are mesh size, network connectivity, matrix diffusion and anisotropy. We demonstrate how these differences affect the flow and transport. We identify the factors that should be taken in consideration when selecting an approach most suitable for the site-specific conditions.

  6. Comparative modeling of vertical and planar organic phototransistors with 2D drift-diffusion simulations

    Science.gov (United States)

    Bezzeccheri, E.; Colasanti, S.; Falco, A.; Liguori, R.; Rubino, A.; Lugli, P.

    2016-05-01

    Vertical Organic Transistors and Phototransistors have been proven to be promising technologies due to the advantages of reduced channel length and larger sensitive area with respect to planar devices. Nevertheless, a real improvement of their performance is subordinate to the quantitative description of their operation mechanisms. In this work, we present a comparative study on the modeling of vertical and planar Organic Phototransistor (OPT) structures. Computer-based simulations of the devices have been carried out with Synopsys Sentaurus TCAD in a 2D Drift-Diffusion framework. The photoactive semiconductor material has been modeled using the virtual semiconductor approach as the archetypal P3HT:PC61BM bulk heterojunction. It has been found that both simulated devices have comparable electrical and optical characteristics, accordingly to recent experimental reports on the subject.

  7. Simulation study of silicon and gaseous tracking detectors

    CERN Document Server

    Beaumont, W; De Lentdecker, G; Devroede, O; Doninck, W V; Dyck, C V; Udo, Fred; Van Velde, C; Vanlaer, P; Verbeure, F; Zhukov, V

    2002-01-01

    The performance of microstrip gaseous counters (MSGC, MSGC + GEM) and silicon microstrip sensors has been studied in view of their use in high luminosity tracking applications. Simulations of signal development in the detectors and subsequent signal treatment in the readout electronics were performed. The simulation results are compared with experimental data obtained in test beams.

  8. A Comparative Study of Whitman and Frost

    Institute of Scientific and Technical Information of China (English)

    田寨耕

    2014-01-01

    Walt Whitman and Robert Frost are both famous poets in American literary history. They share a great deal in common. This paper attempts to make a study of the two poets by means of comparing their similarities and differences.

  9. CURRICULAR OFFER INFLUENCING STUDENTS’ SATISFACTION: COMPARATIVE STUDY

    OpenAIRE

    Oana DUMITRASCU; Constantin Manuel HILA

    2014-01-01

    The main objective of the study is the determination of students’ satisfaction regarding curricular activities. The study has been accomplished using the qualitative and quantitative research, using the bibliographic study, various secondary sources and different primary sources. The study is developed with a marketing research and accomplished using the survey method. 699 students from four universities have been questioned. Due to a comparative study the University of Applied Sciences Worms...

  10. A Comparative Study on Error Analysis

    DEFF Research Database (Denmark)

    Wu, Xiaoli; Zhang, Chun

    2015-01-01

    Title: A Comparative Study on Error Analysis Subtitle: - Belgian (L1) and Danish (L1) learners’ use of Chinese (L2) comparative sentences in written production Xiaoli Wu, Chun Zhang Abstract: Making errors is an inevitable and necessary part of learning. The collection, classification and analysis...... the occurrence of errors either in linguistic or pedagogical terms. The purpose of the current study is to demonstrate the theoretical and practical relevance of error analysis approach in CFL by investigating two cases - (1) Belgian (L1) learners’ use of Chinese (L2) comparative sentences in written production....... Finally, pedagogical implication of CFL is discussed and future research is suggested. Keywords: error analysis, comparative sentences, comparative structure ‘‘bǐ - 比’, Chinese as a foreign language (CFL), written production...

  11. LES versus DNS: A comparative study

    Science.gov (United States)

    Shtilman, L.; Chasnov, J. R.

    1992-01-01

    We have performed Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES) of forced isotropic turbulence at moderate Reynolds numbers. The subgrid scale model used in the LES is based on an eddy viscosity which adjusts instantaneously the energy spectrum of the LES to that of the DNS. The statistics of the large scales of the DNS (filtered DNS field or fDNS) are compared to that of the LES. We present results for the transfer spectra, the skewness and flatness factors of the velocity components, the PDF's of the angle between the vorticity and the eigenvectors of the rate of strain, and that between the vorticity and the vorticity stretching tensor. The above LES statistics are found to be in good agreement with those measured in the fDNS field. We further observe that in all the numerical measurements, the trend was for the LES field to be more gaussian than the fDNS field. Future research on this point is planned.

  12. Nonlinear analysis of RED - a comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Kai; Wang Xiaofan E-mail: xfwang@sjtu.edu.cn; Xi Yugeng

    2004-09-01

    Random Early Detection (RED) is an active queue management (AQM) mechanism for routers on the Internet. In this paper, performance of RED and Adaptive RED are compared from the viewpoint of nonlinear dynamics. In particular, we reveal the relationship between the performance of the network and its nonlinear dynamical behavior. We measure the maximal Lyapunov exponent and Hurst parameter of the average queue length of RED and Adaptive RED, as well as the throughput and packet loss rate of the aggregate traffic on the bottleneck link. Our simulation scenarios include FTP flows and Web flows, one-way and two-way traffic. In most situations, Adaptive RED has smaller maximal Lyapunov exponents, lower Hurst parameters, higher throughput and lower packet loss rate than that of RED. This confirms that Adaptive RED has better performance than RED.

  13. Comparing of the Deterministic Simulated Annealing Methods for Quadratic Assignment Problem

    Directory of Open Access Journals (Sweden)

    Mehmet Güray ÜNSAL

    2013-08-01

    Full Text Available In this study, Threshold accepting and Record to record travel methods belonging to Simulated Annealing that is meta-heuristic method by applying Quadratic Assignment Problem are statistically analyzed whether they have a significant difference with regard to the values of these two methods target functions and CPU time. Between the two algorithms, no significant differences are found in terms of CPU time and the values of these two methods target functions. Consequently, on the base of Quadratic Assignment Problem, the two algorithms are compared in the study have the same performance in respect to CPU time and the target functions values

  14. Comparative Study of Bio-implantable Acoustic Generator Architectures

    Science.gov (United States)

    Christensen, D.; Roundy, S.

    2013-12-01

    This paper is a comparative study of the design spaces of two bio-implantable acoustically excited generator architectures: the thickness-stretch-mode circular piezoelectric plate and the bending-mode unimorph piezoelectric diaphragm. The generators are part of an acoustic power transfer system for implanted sensors and medical devices such as glucose monitors, metabolic monitors, drug delivery systems, etc. Our studies indicate that at small sizes the diaphragm architecture outperforms the plate architecture. This paper will present the results of simulation studies and initial experiments that explore the characteristics of the two architectures and compare their performance.

  15. Mathematics education and comparative historical studies

    Directory of Open Access Journals (Sweden)

    Wagner RODRIGUES VALENTE

    2013-11-01

    Full Text Available This paper has as its aims: to characterize the area of research «history of mathematics education» and to defend the idea that mathematics education has constituted a privileged research theme within the field of comparative historical studies. To achieve these aims, the text includes references to a review of the literature concerning comparative studies, the analysis of two fundamental moments focused on attempts to internationalize the mathematics curriculum, both of which occurred during the 20th century, and, to end, a case study emanating from an international cooperation between researchers in Brazil and Portugal.

  16. Magnetotactic bacteria and microjets: A comparative study

    NARCIS (Netherlands)

    Khalil, I.S.M.; Magdanz, Veronika; Sanchez, Samuel; Schmidt, Oliver G.; Misra, Sarthak

    2013-01-01

    We provide a comparative study between two self-propelled microrobots, i.e., magnetotactic bacteria and microjets. This study includes characterization of their fluidic properties (linear and rotational drag coefficients) based on their morphologies and characterization of their magnetic properties

  17. A COMPARATIVE STUDY OF BYG SEARCH ENGINES

    Directory of Open Access Journals (Sweden)

    Kailash Kumar

    2013-01-01

    Full Text Available This paper compares the retrieval effectiveness of the Bing, Yahoo and Google (BYG Search Engines. The precision and relative recall of each search engine was considered for evaluating the effectiveness of the search engines. General Queries were tested. Results of the study showed that the precision of Google was high as compared to other two search engines and Yahoo has better precision than Bing

  18. Comparative simulation of wind park design and siting in Algeria

    Energy Technology Data Exchange (ETDEWEB)

    Youcef Ettoumi, Fatiha; Adane, Abd El Hamid; Benzaoui, Mohamed Lassaad; Bouzergui, Nabila [Faculty of Electronics and Computer Science, Telecommunication Department, Laboratory of Image Processing and Radiation, University of Science and Technology of Algiers (U.S.T.H.B.), P.O. Box 32, El Alia, Bab Ezzouar 16111, Algiers DZ (Algeria)

    2008-10-15

    In this paper, five typical regions of Algeria where wind is strong enough are selected. These regions usually intended for traditional agriculture are, centred around the towns of Guelma, El Oued, Tindouf, Touggourt and Tamanrasset. To make wind energy conversion available as an alternative energy source for the populations living in such countries, nine types of small and medium wind turbines constructed by American and European manufacturers are studied for their suitability. To account for the wind variations with height, four possible heights of the pylon holding the turbines are considered: 10, 20, 40 and 60 m. In each of the five locations and at each pylon height, wind energy converted by the turbines, is cumulated over the year and computed. Depending on the site and their size, most of these turbines are found to produce about 1000-10,000 MWh of electricity per year at 60 m of altitude and can easily satisfy the electricity need in irrigation and its household applications in rustic and arid regions. A quick glance of the results of the above computation shows that the choice of pylons of 20 m height yields a trade-off between the production of electrical energy and the requirements of economy. Owing to the sporadic wind variations, wind energy conversion systems can only be used as an auxiliary source. In particular, these systems can advantageously be coupled to stand-alone photovoltaic conversion systems in remote locations or connected to the electric mains in urban zones. (author)

  19. 两种物理吸收法在沼气脱碳中的模拟对比研究%Comparative study of two physical absorption method in the simulation of biogas decarbonization

    Institute of Scientific and Technical Information of China (English)

    李超伟; 仵浩; 范良忠

    2012-01-01

    Simulation comparative study of water scrubbing and propylene carbonate in biogas de-carbonization was dicussed by the software PRO/II,the composition of biogas was that, GH4 was 57%,CO2 was 40%, N2 was 2.8% and O2 was 0.2% when under 2.7,13,0.7 MPa.The results showed that both methods for CH4recovery rate could > 98%,the operating pressure affect the system energy consumption greatly,it should be determined based on terminal biogas application and CO2 recycle value. CH4>93%,CO2

  20. Comparative Analysis and Pedestrian Simulation Evaluation on Emergency Evacuation Test Methods for Urban Rail Transit Stations

    Directory of Open Access Journals (Sweden)

    Zijia Wang

    2012-11-01

    Full Text Available The emergency evacuation test method of rail transit station not only affects the operation safety of the station, but it also has significant influence on the scale and cost of the station. A reasonable test method should guarantee both the safety of evacuation and that the investment is neither excessive nor too conservative. The paper compares and analyzes the differences of the existing emergency evacuation test methods of rail stations in China and other regions on the evacuation load, evacuation time calculation and the capacity of egress components, etc. Based on the field survey analysis, the desired velocity distribution of pedestrians in various station facilities and the capacity of egress components have been obtained, and then the parameters of pedestrian simulation tool were calibrated. By selecting a station for the case study, an evacuation simulation model has been established, where five evacuation scenarios have been set according to different specifications and the simulation results have been carefully analyzed. Through analyzing the simulation results, some modification proposals of the current emergency evacuation test method in the design manual have been considered, including taking into account the section passenger volume, walking time on escalators and stairs of the platform, and the condition in which the escalator most critical to evacuation should be considered as out of service.

  1. Simulação humana digital na concepção de postos de trabalho: estudo comparativo de casos Digital human simulation for ergonomic workplace design: comparative study of cases

    Directory of Open Access Journals (Sweden)

    Daniel Braatz

    2012-01-01

    Full Text Available Este artigo apresenta como a ferramenta computacional de Modelagem e Simulação Humana contextualizada pela Análise Ergonômica do Trabalho (AET e pela análise da Atividade Futura Possível pode auxiliar nos processos de projeto de postos de trabalho. São analisados dois estudos de caso nos quais a Simulação Humana foi empregada com auxílio do software Jack. O primeiro estudo aborda a concepção de um balcão de atendimento em uma empresa pública de serviços postais. O segundo apresenta o desenvolvimento de uma estação de trabalho de abastecimento de agulhas cirúrgicas em uma empresa de manufatura de produtos relacionados às áreas de saúde e higiene. A partir dos resultados dos estudos de caso, são explicitadas as contribuições e desafios da utilização dessa tecnologia em projetos visando equacionar as questões de saúde e produtividade. O uso da simulação integrada ao processo de intervenção da AET permitiu melhorar a antecipação das futuras atividades prováveis das novas situações de trabalho e auxiliou a integração e comunicação dos atores envolvidos nesses processos sociais.This paper investigates a computational tool for Human Modeling and Simulation contextualized by Ergonomic Analysis of Work (EAW and future work activity forecasting that can assist in the design processes of workplaces. Two case studies using Human Simulation was employed and the software Jack were analyzed. The first study presents the design of a counter in a public post office. The second shows the development of a workstation for the supply of surgical needles in a company that manufactures hygiene and healthcare products. The results of the case studies show the contributions and challenges of using this design technology aiming to solve problems related to health and productivity. The use of simulation combined with EAW helped to improve future work activity forecasting of new work situations and helped the integration and

  2. Comparative analysis of turbulence models for flow simulation around a vertical axis wind turbine

    Energy Technology Data Exchange (ETDEWEB)

    Roy, S.; Saha, U.K. [Indian Institute of Technology Guwahati, Dept. of Mechanical Engineering, Guwahati (India)

    2012-07-01

    An unsteady computational investigation of the static torque characteristics of a drag based vertical axis wind turbine (VAWT) has been carried out using the finite volume based computational fluid dynamics (CFD) software package Fluent 6.3. A comparative study among the various turbulence models was conducted in order to predict the flow over the turbine at static condition and the results are validated with the available experimental results. CFD simulations were carried out at different turbine angular positions between 0 deg.-360 deg. in steps of 15 deg.. Results have shown that due to high static pressure on the returning blade of the turbine, the net static torque is negative at angular positions of 105 deg.-150 deg.. The realizable k-{epsilon} turbulent model has shown a better simulation capability over the other turbulent models for the analysis of static torque characteristics of the drag based VAWT. (Author)

  3. COMPARATIVE EVALUATION OF TWO SKIING SIMULATORS AS FUNCTIONAL TRAINING DEVICES FOR RECREATIONAL SKIERS

    Directory of Open Access Journals (Sweden)

    Fausto A. Panizzolo

    2013-03-01

    Full Text Available The aims of this study were to examine two ski simulators, Skimagic and Skier's Edge, and to evaluate their efficacy as functional training devices for skiers. Vertical ground reaction forces, knee flexion angle kinematics and muscles activity were recorded on these devices and compared with those measured in similar condition while skiing on snow. Five ski instructors performed three randomized testing sessions (snow, Skimagic and Skier's Edge. During the testing sessions, vertical ground reaction forces were recorded by means of pressure insoles in synchronisation with a portable data logger that collected values of knee flexion-extension and EMG activation of rectus femoris and vastus medialis. EMG activations and ground reaction forces measured while skiing on simulators were lower than on snow. Although less overall EMG activation was present on the simulators, the pattern of EMG activity was closer to real snow on Skimagic than on Skiers' Edge. Results of the present study suggested that the two devices are not effectively applicable for strength training. However, based on the recorded EMG patterns, the Skimagic treadmill is potentially suitable to act as a functional training device for recreational skiers provided that an increase of speed and slope on Skimagic could induce a closer matching of the studied biomechanical parameters with the snow skiing conditions.

  4. Species comparative studies and cognitive development.

    Science.gov (United States)

    Gómez, Juan-Carlos

    2005-03-01

    The comparative study of infant development and animal cognition brings to cognitive science the promise of insights into the nature and origins of cognitive skills. In this article, I review a recent wave of comparative studies conducted with similar methodologies and similar theoretical frameworks on how two core components of human cognition--object permanence and gaze following--develop in different species. These comparative findings call for an integration of current competing accounts of developmental change. They further suggest that evolution has produced developmental devices capable at the same time of preserving core adaptive components, and opening themselves up to further adaptive change, not only in interaction with the external environment, but also in interaction with other co-developing cognitive systems.

  5. Comparative study of quantum anharmonic potentials

    Energy Technology Data Exchange (ETDEWEB)

    Amore, Paolo [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima (Mexico)]. E-mail: paolo@ucol.mx; Aranda, Alfredo [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima (Mexico); De Pace, Arturo [Istituto Nazionale di Fisica Nucleare, Sezione di Torino, via P. Giuria 1, I-10125 Torino (Italy); Lopez, Jorge A. [Physics Department, University of Texas at El Paso, El Paso, TX (United States)

    2004-09-06

    We perform a study of various anharmonic potentials using a recently developed method. We calculate both the wave functions and the energy eigenvalues for the ground and first excited states of the quartic, sextic and octic potentials with high precision, comparing the results with other techniques available in the literature.

  6. A Comparative Study of Sparse Associative Memories

    Science.gov (United States)

    Gripon, Vincent; Heusel, Judith; Löwe, Matthias; Vermet, Franck

    2016-07-01

    We study various models of associative memories with sparse information, i.e. a pattern to be stored is a random string of 0s and 1s with about log N 1s, only. We compare different synaptic weights, architectures and retrieval mechanisms to shed light on the influence of the various parameters on the storage capacity.

  7. A Comparative Study of Probabilistic Roadmap Planners

    NARCIS (Netherlands)

    Geraerts, R.J.; Overmars, M.H.

    2004-01-01

    The probabilistic roadmap approach is one of the leading motion planning techniques. Over the past eight years the technique has been studied by many different researchers. This has led to a large number of variants of the approach, each with its own merits. It is difficult to compare the different

  8. A comparative study of map use

    DEFF Research Database (Denmark)

    Bouvin, Niels Olof; Brodersen, Ann Christina; Bødker, Susanne

    2006-01-01

    We present a study comparing the handling of three kinds of maps, each on a physical device: a paper map, a tablet-PC based map, and a cellular phone based one. Six groups of users were asked to locate eight landmarks, looking out a window, and using a particular map. We have begun analyzing video...

  9. Techniques for preparing of guide planes: in vitro comparative study

    OpenAIRE

    Uemura, Eduardo Shigueyuki; Assistant Professor of the Dental Materials and Prosthesis Department of the São José dos Campos School of Dentistry of the São Paulo State University.; Silva, João Maurício; Faculdade de Odontologia de São José dos Campos - UNESP; Borges, Alexandre Luiz Souto; Assistant Professor of the Dental Materials and Prosthesis Department of the São José dos Campos School of Dentistry of the São Paulo State University.; Yamamoto, Eron Toshio Colauto; Clinical Professor of the Dental Materials and Prosthesis Department of the School of Dentistry of the 9th of July University.

    2014-01-01

    The correct parallelism of guiding planes when constructing a Removable Partial Denture not only defines the axis of insertion and removal of the prosthesis, but also limits the possible axes of movement during functioning. Therefore, the purpose of the study was to compare some techniques and the use of an intra-oral device for those preparations. Dummies were performed in a direct manner, simulating the absence of teeth 15, 45, 12 and 42. The four preparation techniques chosen were: Group 1...

  10. Comparative analysis of cogeneration power plants optimization based on stochastic method using superstructure and process simulator

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Leonardo Rodrigues de [Instituto Federal do Espirito Santo, Vitoria, ES (Brazil)], E-mail: leoaraujo@ifes.edu.br; Donatelli, Joao Luiz Marcon [Universidade Federal do Espirito Santo (UFES), Vitoria, ES (Brazil)], E-mail: joaoluiz@npd.ufes.br; Silva, Edmar Alino da Cruz [Instituto Tecnologico de Aeronautica (ITA/CTA), Sao Jose dos Campos, SP (Brazil); Azevedo, Joao Luiz F. [Instituto de Aeronautica e Espaco (CTA/IAE/ALA), Sao Jose dos Campos, SP (Brazil)

    2010-07-01

    Thermal systems are essential in facilities such as thermoelectric plants, cogeneration plants, refrigeration systems and air conditioning, among others, in which much of the energy consumed by humanity is processed. In a world with finite natural sources of fuels and growing energy demand, issues related with thermal system design, such as cost estimative, design complexity, environmental protection and optimization are becoming increasingly important. Therefore the need to understand the mechanisms that degrade energy, improve energy sources use, reduce environmental impacts and also reduce project, operation and maintenance costs. In recent years, a consistent development of procedures and techniques for computational design of thermal systems has occurred. In this context, the fundamental objective of this study is a performance comparative analysis of structural and parametric optimization of a cogeneration system using stochastic methods: genetic algorithm and simulated annealing. This research work uses a superstructure, modelled in a process simulator, IPSEpro of SimTech, in which the appropriate design case studied options are included. Accordingly, the cogeneration system optimal configuration is determined as a consequence of the optimization process, restricted within the configuration options included in the superstructure. The optimization routines are written in MsExcel Visual Basic, in order to work perfectly coupled to the simulator process. At the end of the optimization process, the system optimal configuration, given the characteristics of each specific problem, should be defined. (author)

  11. Comparative simulations of the 2011 Tohoku tsunami with MOST and Cliffs

    CERN Document Server

    Tolkova, Elena

    2014-01-01

    Wet-dry interface which appreciably increases accuracy of tsunami simulations with the MOST model (Method of Splitting Tsunamis, adapted by the NOAA for tsunami forecasting operations) is highlighted here with a few comparative simulations. The new solution, termed Cliffs, exceeds all MOST versions in accuracy of computing later waves. This is demonstrated with simulation of the Tohoku-2011 tsunami to Monterey Bay, CA, and into fiords, bays, and inlets of southeastern Alaska, followed by comparison with tide gage records.

  12. Osmosis : a molecular dynamics computer simulation study

    Science.gov (United States)

    Lion, Thomas

    Osmosis is a phenomenon of critical importance in a variety of processes ranging from the transport of ions across cell membranes and the regulation of blood salt levels by the kidneys to the desalination of water and the production of clean energy using potential osmotic power plants. However, despite its importance and over one hundred years of study, there is an ongoing confusion concerning the nature of the microscopic dynamics of the solvent particles in their transfer across the membrane. In this thesis the microscopic dynamical processes underlying osmotic pressure and concentration gradients are investigated using molecular dynamics (MD) simulations. I first present a new derivation for the local pressure that can be used for determining osmotic pressure gradients. Using this result, the steady-state osmotic pressure is studied in a minimal model for an osmotic system and the steady-state density gradients are explained using a simple mechanistic hopping model for the solvent particles. The simulation setup is then modified, allowing us to explore the timescales involved in the relaxation dynamics of the system in the period preceding the steady state. Further consideration is also given to the relative roles of diffusive and non-diffusive solvent transport in this period. Finally, in a novel modification to the classic osmosis experiment, the solute particles are driven out-of-equilibrium by the input of energy. The effect of this modification on the osmotic pressure and the osmotic ow is studied and we find that active solute particles can cause reverse osmosis to occur. The possibility of defining a new "osmotic effective temperature" is also considered and compared to the results of diffusive and kinetic temperatures..

  13. Simulation Studies in Data Replication Strategies

    Institute of Scientific and Technical Information of China (English)

    HarveyB.Newman; IosifC.Legrand

    2001-01-01

    The aim of this work is to present the simulation studies in evaluating different data replication strategies between Regional Centers.The simulation Framework developed within the "Models of Networked Analysis at Rgional Centers”(MONARC) project,as a design and optimization tool for large scale distributed systems,has been used for these modeling studies.Remote client-serer access to database servers as well as ftp-like data transfers have been ralistically simulated and the performance and limitations are presented as a function of the characteristics of the protocol used and the network parameters.

  14. Crop micrometeorology : a simulation study

    NARCIS (Netherlands)

    Goudriaan, J.

    1977-01-01

    This monograph presents the results of a detailed study in micrometeorology; one of the sciences that play an important role in production ecology. The purpose is to explain the microweather as a function of the properties of plant and soil, and of the weather conditions prevalent at some

  15. Crop micrometeorology: a simulation study

    NARCIS (Netherlands)

    Goudriaan, J.

    1977-01-01

    This monograph presents the results of a detailed study in micrometeorology; one of the sciences that play an important role in production ecology. The purpose is to explain the microweather as a function of the properties of plant and soil, and of the weather conditions prevalent at some height abo

  16. Comparative measurements with seven rainfall simulators on uniform bare fallow land

    NARCIS (Netherlands)

    Iserloh, T.; Ries, J.B.; Cerda, A.; Echeverria, M.T.; Fister, W.; Geissler, C.; Kuhn, N.J.; Leon, F.J.; Peters, P.; Schindewolf, M.; Schmidt, J.; Scholten, T.; Seeger, K.M.

    2013-01-01

    To assess the influence of rainfall simulator type and plot dimensions on runoff and erosion, seven small portable rainfall simulators from Freiberg, Tubingen, Trier (all Germany), Valencia, Zaragoza (both Spain), Basel (Switzerland) and Wageningen (the Netherlands) were compared on a prepared bare

  17. Using the Beopt Automated Residential Simulation Test Suite to Enable Comparative Analysis Between Energy Simulation Engines: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Tabares-Velasco, Paulo Cesar [National Renewable Energy Lab. (NREL), Golden, CO (United States); Maguire, Jeff [National Renewable Energy Lab. (NREL), Golden, CO (United States); Horowitz, Scott [National Renewable Energy Lab. (NREL), Golden, CO (United States); Christensen, Craig [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2014-09-01

    Verification and validation are crucial software quality control procedures to follow when developing and implementing models. This is particularly important because a variety of stakeholders rely on accurate predictions from building simulation programs. This study uses the BEopt Automated Residential Simulation Test Suite (BARTS) to facilitate comparison of two energy simulation engines across various building components and includes building models that isolate the impacts of specific components on annual energy consumption. As a case study, BARTS has been used to identify important discrepancies between the engines for several components of the building models. These discrepancies are caused by differences in the algorithms used by the engines or coding errors.

  18. Using the BEopt Automated Residential Simulation Test Suite to Enable Comparative Analysis Between Energy Simulation Engines: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Tabares-Velasco, P. C.; Maguire, J.; Horowitz, S.; Christensen, C.

    2014-09-01

    Verification and validation are crucial software quality control procedures when developing and implementing models. This is particularly important as a variety of stakeholders rely on accurate predictions from building simulation programs. This study uses the BEopt Automated Residential Simulation Test Suite (BARTS) to facilitate comparison of two energy simulation engines across various building components and includes models that isolate the impacts of specific building components on annual energy consumption. As a case study, BARTS has been used to identify important discrepancies between the engines for several components of the building models; these discrepancies are caused by differences in the models used by the engines or coding errors.

  19. Using the Beopt Automated Residential Simulation Test Suite to Enable Comparative Analysis Between Energy Simulation Engines: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Tabares-Velasco, Paulo Cesar [National Renewable Energy Lab. (NREL), Golden, CO (United States); Maguire, Jeff [National Renewable Energy Lab. (NREL), Golden, CO (United States); Horowitz, Scott [National Renewable Energy Lab. (NREL), Golden, CO (United States); Christensen, Craig [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2014-09-01

    Verification and validation are crucial software quality control procedures to follow when developing and implementing models. This is particularly important because a variety of stakeholders rely on accurate predictions from building simulation programs. This study uses the BEopt Automated Residential Simulation Test Suite (BARTS) to facilitate comparison of two energy simulation engines across various building components and includes building models that isolate the impacts of specific components on annual energy consumption. As a case study, BARTS has been used to identify important discrepancies between the engines for several components of the building models. These discrepancies are caused by differences in the algorithms used by the engines or coding errors.

  20. Using the BEopt Automated Residential Simulation Test Suite to Enable Comparative Analysis Between Energy Simulation Engines: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Tabares-Velasco, P. C.; Maguire, J.; Horowitz, S.; Christensen, C.

    2014-09-01

    Verification and validation are crucial software quality control procedures when developing and implementing models. This is particularly important as a variety of stakeholders rely on accurate predictions from building simulation programs. This study uses the BEopt Automated Residential Simulation Test Suite (BARTS) to facilitate comparison of two energy simulation engines across various building components and includes models that isolate the impacts of specific building components on annual energy consumption. As a case study, BARTS has been used to identify important discrepancies between the engines for several components of the building models; these discrepancies are caused by differences in the models used by the engines or coding errors.

  1. A Comparative Study on Author's Unreliability

    Institute of Scientific and Technical Information of China (English)

    林映凡

    2016-01-01

    Literature appreciation usually follows a"writer-text-reader" process. The author is an inseparable part in literary discussion. Most literary schools have debate on the author's status, which is mainly sorted into two kinds: reliable author or unreliable author. This paper makes a comparative study on the author's status, which is mainly from the perspectives of New Criticism and Deconstruction. Both of them go for unreliability of the author. They share similarities but also bear differences.

  2. Comparative Study on Richard Ⅲ and Macbeth

    Institute of Scientific and Technical Information of China (English)

    冯丽霞; 闫继苗; 徐婷婷

    2013-01-01

    Shakespeare is one of the most prominent drama writers all over the world. His masterpiece displays vivid, delicate and profound humanity. Richard Ⅲ and Macbeth as the main heroes in his two tragedies of the same theme, share quite a lot of simi⁃larities and differences, yet resulting in sharply different readers’response to their fates. The comparative study on these two char⁃acters is aimed at helping readers better understand the two tragedies.

  3. Friendship in Latin American Social Comparative Studies

    Directory of Open Access Journals (Sweden)

    Agnaldo Garcia

    2016-06-01

    Full Text Available Friendship has been traditionally investigated in the field of interpersonal relationships using different theoretical frameworks and approaches. This paper discusses the possibility of investigating friendship from a comparative Latin American perspective, based on a wide literature review on the subject. Based on the theoretical proposals of Hinde (1997 for the investigation of interpersonal relationships, the paper considers that friendship involves several levels of complexity and affects and is affected by distinct dimensions of Latin American society. The paper recognizes that comparative studies have placed the importance of friends and friendship in areas such as economy, health, education, and migration, among others. As expected, Latin American comparative studies are more frequent in some disciplines, mainly those based on censuses data, and theoretically related to social-economic and demographic concepts, including social networks and social capital. The possibility of developing a Latin American perspective for the study of friendship requires not only the need of empirical but also theoretical advances, as well as scientific cooperation and innovation. Friendship is seen as relevant for the constitution of the social tissue of Latin American society, being affected and affecting different areas and levels. In the social economic dimension, friends are relevant, specifically in Latin America, to themes such as poverty and social vulnerability. Some future possibilities for investigation are discussed.

  4. Biases and systematics in the observational derivation of galaxy properties: comparing different techniques on synthetic observations of simulated galaxies

    CERN Document Server

    Guidi, Giovanni; Walcher, C Jakob

    2015-01-01

    We study the sources of biases and systematics in the derivation of galaxy properties of observational studies, focusing on stellar masses, star formation rates, gas/stellar metallicities, stellar ages and magnitudes/colors. We use hydrodynamical cosmological simulations of galaxy formation, for which the real quantities are known, and apply observational techniques to derive the observables. We also make an analysis of biases that are relevant for a proper comparison between simulations and observations. For our study, we post-process the simulation outputs to calculate the galaxies' spectral energy distributions (SEDs) using Stellar Population Synthesis models and also generating the fully-consistent far UV-submillimeter wavelength SEDs with the radiative transfer code SUNRISE. We compared the direct results of simulations with the observationally-derived quantities obtained in various ways, and found that systematic differences in all studied galaxy properties appear, which are caused by: (1) purely observ...

  5. Comparative study of INPIStron and spark gap

    Science.gov (United States)

    Han, Kwang S.; Lee, Ja H.

    1993-01-01

    An inverse pinch plasma switch, INPIStron, was studied in comparison to a conventional spark gap. The INPIStron is under development for high power switching applications. The INPIStron has an inverse pinch dynamics, opposed to Z-pinch dynamics in the spark gap. The electrical, plasma dynamics and radiative properties of the closing plasmas have been studied. Recently the high-voltage pulse transfer capabilities or both the INPIStron and the spark gap were also compared. The INPIStron with a low impedance Z = 9 ohms transfers 87 percent of an input pulse with a halfwidth of 2 mu s. For the same input pulse the spark gap of Z = 100 ohms transfers 68 percent. Fast framing and streak photography, taken with an TRW image converter camera, was used to observe the discharge uniformity and closing plasma speed in both switches. In order to assess the effects of closing plasmas on erosion of electrode material, emission spectra of two switches were studied with a spectrometer-optical multi channel analyzer (OMA) system. The typical emission spectra of the closing plasmas in the INPIStron and the spark gap showed that there were comparatively weak carbon line emission in 658.7 nm and copper (electrode material) line emissions in the INPIStron, indicating low erosion of materials in the INPIStron.

  6. A Simulation Study of Missing Data with Multiple Missing X's

    Science.gov (United States)

    Rubright, Jonathan D.; Nandakumar, Ratna; Glutting, Joseph J.

    2014-01-01

    When exploring missing data techniques in a realistic scenario, the current literature is limited: most studies only consider consequences with data missing on a single variable. This simulation study compares the relative bias of two commonly used missing data techniques when data are missing on more than one variable. Factors varied include type…

  7. Comparative study of hydrogenated and lithiated superhalogens

    Science.gov (United States)

    Xu, Li-Na; Li, Ying; Liu, Jia-Yuan; Wu, Di; Sun, Yan-Bo; Li, Zhi-Ru

    2016-09-01

    The structural features, properties and stability of two kinds of representative superhalogen compounds, namely hydrogenated superhalogens and lithiated superhalogens, are theoretically studied in detail, providing further insight into the behavior of superhalogens. According to topological analysis of the electron localization function, most of superhalogen clusters as a whole combine with Li atom through ionic bond(s). In contrast, the H atom tends to bind with superhalogen by covalent bond although a portion of superhalogens are broken upon hydrogenation. In addition, the electric properties of these superhalogen compounds are also obtained and compared with those of traditional acid and salt molecules.

  8. Simulación Dinámica y Estudio Comparativo de diferentes Configuraciones de Sistemas de Enfriamiento Evaporativo para Mexicali, México Dynamic Simulation and Comparative Study of Several Systems of Evaporative Cooling for Mexicali, México

    Directory of Open Access Journals (Sweden)

    Ricardo O Gallegos

    2010-01-01

    Full Text Available Se ha realizado el dimensionamiento y evaluación de diferentes configuraciones de sistemas de enfriamiento evaporativo para acondicionamiento de espacios en vivienda de tipo económico para Mexicali, México, mediante simulación con TRNSYS 16. Se analizan configuraciones que incluyen intercambiadores de calor, enfriadores evaporativos indirectos y unidades de desecante sólido. Los principales criterios para clasificar las distintas configuraciones fueron el confort térmico, el número de componentes y la eficiencia. Los resultados muestran que la configuración que incluye un intercambiador que pre-enfría el aire con el proveniente de la vivienda, es capaz de proporcionar condiciones de confort con el menor número de componentes, aunque en una pequeña fracción del tiempo durante el día no se satisfacen totalmente. Si se requiere satisfacer totalmente el confort, los sistemas con desecante sólido son la opción más adecuada.The design and evaluation of several configurations of evaporative cooling systems for air conditioning of a dwelling for low-income sectors in Mexicali, Mexico using simulation with TRNSYS 16.A is presented in this paper. The configurations studied include direct as well as indirect evaporative cooling with heat exchange and also systems with solid desiccant. The main rating parameters to classify the different configurations are the internal comfort conditions, the efficiency and the number of required equipments. The results show that the best configuration is one that includes a heat exchanger that pre-cools the air inlet stream with a cooling stream delivered by air coming from the dwell, but there is a small fraction of the time during the day that comfort is not met. If thermal comfort is to be met during the whole day, solid desiccant systems are the best choice.

  9. CURRICULAR OFFER INFLUENCING STUDENTS’ SATISFACTION: COMPARATIVE STUDY

    Directory of Open Access Journals (Sweden)

    Oana DUMITRASCU

    2014-11-01

    Full Text Available The main objective of the study is the determination of students’ satisfaction regarding curricular activities. The study has been accomplished using the qualitative and quantitative research, using the bibliographic study, various secondary sources and different primary sources. The study is developed with a marketing research and accomplished using the survey method. 699 students from four universities have been questioned. Due to a comparative study the University of Applied Sciences Worms, University of Applied Sciences Wiesbaden Rüsselsheim, University of Applied Sciences Frankfurt am Main and Nürtingen-Geislingen University have been analysed and their similarities and differences have been identified. The collected data, based on the established sample, is evaluated through univariate and bivariate analysis. In accordance with the evaluated sample, specific gaps from each region are identified regarding the curricular offer of the analysed universities. As a result to the conducted study, recommendations for the University of Applied Sciences Worms regarding the student’s satisfaction concerning the curricular offer are presented.

  10. CURRICULAR OFFER INFLUENCING STUDENTS’ SATISFACTION: COMPARATIVE STUDY

    Directory of Open Access Journals (Sweden)

    Oana DUMITRASCU

    2014-11-01

    Full Text Available The main objective of the study is the determination of students’ satisfaction regarding curricular activities. The study has been accomplished using the qualitative and quantitative research, using the bibliographic study, various secondary sources and different primary sources. The study is developed with a marketing research and accomplished using the survey method. 699 students from four universities have been questioned. Due to a comparative study the University of Applied Sciences Worms, University of Applied Sciences Wiesbaden Rüsselsheim, University of Applied Sciences Frankfurt am Main and Nürtingen-Geislingen University have been analysed and their similarities and differences have been identified. The collected data, based on the established sample, is evaluated through univariate and bivariate analysis. In accordance with the evaluated sample, specific gaps from each region are identified regarding the curricular offer of the analysed universities. As a result to the conducted study, recommendations for the University of Applied Sciences Worms regarding the student’s satisfaction concerning the curricular offer are presented.

  11. Comparing Simulation Output Accuracy of Discrete Event and Agent Based Models: A Quantitive Approach

    CERN Document Server

    Majid, Mazlina Abdul; Siebers, Peer-Olaf

    2010-01-01

    In our research we investigate the output accuracy of discrete event simulation models and agent based simulation models when studying human centric complex systems. In this paper we focus on human reactive behaviour as it is possible in both modelling approaches to implement human reactive behaviour in the model by using standard methods. As a case study we have chosen the retail sector, and here in particular the operations of the fitting room in the women wear department of a large UK department store. In our case study we looked at ways of determining the efficiency of implementing new management policies for the fitting room operation through modelling the reactive behaviour of staff and customers of the department. First, we have carried out a validation experiment in which we compared the results from our models to the performance of the real system. This experiment also allowed us to establish differences in output accuracy between the two modelling methids. In a second step a multi-scenario experimen...

  12. Virtually simulated social pressure influences early visual processing more in low compared to high autonomous participants.

    Science.gov (United States)

    Trautmann-Lengsfeld, Sina Alexa; Herrmann, Christoph Siegfried

    2014-02-01

    In a previous study, we showed that virtually simulated social group pressure could influence early stages of perception after only 100  ms. In the present EEG study, we investigated the influence of social pressure on visual perception in participants with high (HA) and low (LA) levels of autonomy. Ten HA and ten LA individuals were asked to accomplish a visual discrimination task in an adapted paradigm of Solomon Asch. Results indicate that LA participants adapted to the incorrect group opinion more often than HA participants (42% vs. 30% of the trials, respectively). LA participants showed a larger posterior P1 component contralateral to targets presented in the right visual field when conforming to the correct compared to conforming to the incorrect group decision. In conclusion, our ERP data suggest that the group context can have early effects on our perception rather than on conscious decision processes in LA, but not HA participants.

  13. Comparative bioequivalence study of meloxicam drugs

    Directory of Open Access Journals (Sweden)

    Ekut Karieva

    2011-03-01

    Full Text Available The governments of many countries strongly support the production and clinical use of generic medicinal products which are “copies” of patented drugs and can be marked at lower cost. At present time bioequivalence testing is regarded as a useful methodology to perform comparisons among different products containing the same active ingredient. This report presents the results of comparative bioequivalence study of three meloxicam formulations: brand-drug “Melbek” with tablets and capsules of meloxicam developed at the Tashkent Pharmaceutical Institute. The results obtained confirm the bioequivalence of the studied drugs, which indicate about scientifically based approach to the selection of excipients and technological process in the development of the above generic drugs.

  14. Comparative analysis of RISAT-1 and simulated RADARSAT-2 hybrid polarimetric SAR data for different land features

    OpenAIRE

    Kumar, V; S Rao, Y.

    2014-01-01

    The purpose of this study is to compare the performance of first hybrid polarimetric spaceborne satellite RISAT-1 data and simulated hybrid polarimetric data from quad-pol RADARSAT-2 data for different land use land cover (LULC) classes. The present study compares Stokes (g0, g1, g2 and g3) and its decomposed parameters (m, chi, delta and CPR) for satellite data acquired from RISAT- 1 and RADARSAT-2 over Vijayawada, Andhra Pradesh, India. Further, backscattering coefficients are also...

  15. Comparing coronary stent material performance on a common geometric platform through simulated bench testing.

    Science.gov (United States)

    Grogan, J A; Leen, S B; McHugh, P E

    2012-08-01

    Absorbable metallic stents (AMSs) are a newly emerging cardiovascular technology which has the potential to eliminate long-term patient health risks associated with conventional permanent stents. AMSs developed to date have consisted of magnesium alloys or iron, materials with inferior mechanical properties to those used in permanent stents, such as stainless steel and cobalt-chromium alloys. However, for AMSs to be feasible for widespread clinical use it is important that their performance is comparable to modern permanent stents. To date, the performances of magnesium, iron, and permanent stent materials have not been compared on a common stent platform for a range of stent performance metrics, such as flexibility, radial strength, and recoil. In this study, this comparison is made through simulated bench testing, based on finite-element modelling. The significance of this study is that it allows potential limitations in current AMS performance to be identified, which will aid in focusing future AMS design. This study also allows the identification of limitations in current AMS materials, thereby informing the on-going development of candidate biodegradable alloys. The results indicate that the AMSs studied here can match the recoil characteristics and radial strength of modern permanent stents; however, to achieve this, larger strut dimensions are required. It is also predicted that the AMSs studied are inferior to permanent stents in terms of maximum absolute curvature and longitudinal stiffness.

  16. Evaluating Frontal Precipitation with a Spectral Microphysics Mesoscale Model and a Satellite Simulator as Compared to Radar and Radiometer Observations

    Science.gov (United States)

    Han, M.; Braun, S. A.; Matsui, T.; Iguchi, T.; Williams, C. R.

    2013-12-01

    The Advanced Microwave Scanning Radiometer for EOS (AMSR-E) onboard NASA Aqua satellite and a ground-based precipitation profiling radar sampled a frontal precipitation event in the US west coast on 30 to 31 December 2005. Simulations with bulk microphysics schemes in the Weather Research and Forecast (WRF) model have been evaluated with those remote sensing data. In the current study, we continue similar work to evaluate a spectral bin microphysics (SBM) scheme, HUCM, in the WRF model. The Goddard-Satellite Data Simulation Unit (G-SDSU) is used to simulate quantities observed by the radar and radiometer. With advanced representation of cloud and precipitation microphysics processes, the HUCM scheme predicts distributions of 7 hydrometeor species as storms evolve. In this study, the simulation with HUCM well captured the structure of the precipitation and its microphysics characteristics. In addition, it improved total precipitation ice mass simulation and corrected, to a certain extent, the large low bias of ice scattering signature in the bulk scheme simulations. However, the radar reflectivity simulations with the HUCM scheme were not improved as compared to the bulk schemes. We conducted investigations to understand how microphysical processes and properties, such as snow break up parameter and particle fall velocities would influence precipitation size distribution and spectrum of water paths, and further modify radar and/or radiometer simulations. Influence by ice nuclei is going to be examined as well.

  17. Virtual Reality Compared with Bench-Top Simulation in the Acquisition of Arthroscopic Skill: A Randomized Controlled Trial.

    Science.gov (United States)

    Banaszek, Daniel; You, Daniel; Chang, Justues; Pickell, Michael; Hesse, Daniel; Hopman, Wilma M; Borschneck, Daniel; Bardana, Davide

    2017-04-05

    Work-hour restrictions as set forth by the Accreditation Council for Graduate Medical Education (ACGME) and other governing bodies have forced training programs to seek out new learning tools to accelerate acquisition of both medical skills and knowledge. As a result, competency-based training has become an important part of residency training. The purpose of this study was to directly compare arthroscopic skill acquisition in both high-fidelity and low-fidelity simulator models and to assess skill transfer from either modality to a cadaveric specimen, simulating intraoperative conditions. Forty surgical novices (pre-clerkship-level medical students) voluntarily participated in this trial. Baseline demographic data, as well as data on arthroscopic knowledge and skill, were collected prior to training. Subjects were randomized to 5-week independent training sessions on a high-fidelity virtual reality arthroscopic simulator or on a bench-top arthroscopic setup, or to an untrained control group. Post-training, subjects were asked to perform a diagnostic arthroscopy on both simulators and in a simulated intraoperative environment on a cadaveric knee. A more difficult surprise task was also incorporated to evaluate skill transfer. Subjects were evaluated using the Global Rating Scale (GRS), the 14-point arthroscopic checklist, and a timer to determine procedural efficiency (time per task). Secondary outcomes focused on objective measures of virtual reality simulator motion analysis. Trainees on both simulators demonstrated a significant improvement (p virtual reality simulation group consistently outperformed the bench-top model group in the diagnostic arthroscopy crossover tests and in the simulated cadaveric setup. Furthermore, the virtual reality group demonstrated superior skill transfer in the surprise skill transfer task. Both high-fidelity and low-fidelity simulation trainings were effective in arthroscopic skill acquisition. High-fidelity virtual reality

  18. Evaluation concepts to compare observed and simulated deposition areas of mass movements

    Science.gov (United States)

    Heiser, Micha; Scheidl, Christian; Kaitna, Roland

    2017-04-01

    A delineation of potentially endangered areas by geophysical mass flows, like debris flows, rock and snow avalanches, is an important for regional and urban planning. For this numerical simulation programs have become an important tool in engineering hazard assessment. However, when being confronted with the evaluation of model performance and sensitivity there are no standard, objective approaches. In this contribution we present a new approach to quantitatively compare 2D simulations of observed and simulated deposition patterns - a concept derived from a literature review of 75 peer reviewed articles which inverse modelled real events of different types of mass flows. It seems that existing evaluation concepts with respect to the deposition distribution does only account for one or a combination of two possible evaluation errors based on overestimation, underestimation and/or overlap of the simulation outcome with the observed reference. The proposed evaluation concept integrates all three possible errors and yields a single metric between -1 (no fit) and 1 (perfect fit). Combined with a ternary plot we further show that the proposed evaluation concept might act as a simple decision support tool to i) identify weaknesses and strengths of the simulation model, ii) to find the best simulation setup and iii) to test whether higher complexity of simulation models are balanced by higher accuracies. This method shall help developers and end-users of simulation models to better understand model behavior and provide a possibility for comparison of model results, independent of simulation platform and type of mass flow.

  19. Computer Simulation Study of Bipolaron Formation

    NARCIS (Netherlands)

    Raedt, H. De; Lagendijk, A.

    1986-01-01

    Monte Carlo computer simulation techniques are used to study the formation of bipolarons on a lattice. The transition between the three possible states, extended, two-polaron, and bipolaron is studied. The phase diagram as a function of the strengths of the electron-phonon coupling and repulsive int

  20. Digital Simulation Games for Social Studies Classrooms

    Science.gov (United States)

    Devlin-Scherer, Roberta; Sardone, Nancy B.

    2010-01-01

    Data from ten teacher candidates studying teaching methods were analyzed to determine perceptions toward digital simulation games in the area of social studies. This research can be used as a conceptual model of how current teacher candidates react to new methods of instruction and determine how education programs might change existing curricula…

  1. A comparative study of teenage pregnancy.

    Science.gov (United States)

    Mahavarkar, S H; Madhu, C K; Mule, V D

    2008-08-01

    Teenage pregnancy is a global problem and is considered a high-risk group, in spite of conflicting evidence. Our objective was to compare obstetric outcomes of pregnancy in teenagers and older women. This was a retrospective study of case records of pregnancies from August 2000 to July 2001. Girls aged pregnancy outcomes in older women (19-35 years) in the same hospital. The study took place in the Government General Hospital, Sangli, India, a teaching hospital in rural India, with an annual delivery rate of over 3,500. A total of 386 teenage pregnancies were compared with pregnancies in 3,326 older women. Socioeconomic data, age, number of pregnancies, antenatal care and complications, mode of delivery, and neonatal outcomes were considered. The incidence of teenage pregnancy in the study was 10%. A significant proportion of teenage pregnant mothers were in their first pregnancies. The teenage mothers were nearly three times more at risk of developing anaemia (OR = 2.83, 95% CI = 2.2-3.7, p Teenage mothers were twice as likely to develop hypertensive problems in pregnancy (OR = 2.2, 95% CI = 1.5-3.2, p teenage pregnancies are still a common occurrence in rural India in spite of various legislations and government programmes and teenage pregnancy is a risk factor for poor obstetric outcome in rural India. Cultural practices, poor socioeconomic conditions, low literacy rate and lack of awareness of the risks are some of the main contributory factors. Early booking, good care during pregnancy and delivery and proper utilisation of contraceptive services can prevent the incidence and complications in this high-risk group.

  2. Comparative analysis of realistic CT-scan and simplified human airway models in airflow simulation.

    Science.gov (United States)

    Johari, Nasrul Hadi; Osman, Kahar; Helmi, Nor Harris N; Abdul Kadir, Mohammed A Rafiq

    2015-01-01

    Efforts to model the human upper respiratory system have undergone many phases. Geometrical proximity to the realistic shape has been the subject of many research projects. In this study, three different geometries of the trachea and main bronchus were modelled, which were reconstructed from computed tomography (CT) scan images. The geometrical variations were named realistic, simplified and oversimplified. Realistic refers to the lifelike image taken from digital imaging and communications in medicine format CT scan images, simplified refers to the reconstructed image based on natural images without realistic details pertaining to the rough surfaces, and oversimplified describes the straight wall geometry of the airway. The characteristics of steady state flows with different flow rates were investigated, simulating three varied physical activities and passing through each model. The results agree with previous studies where simplified models are sufficient for providing comparable results for airflow in human airways. This work further suggests that, under most exercise conditions, the idealised oversimplified model is not favourable for simulating either airflow regimes or airflow with particle depositions. However, in terms of immediate analysis for the prediction of abnormalities of various dimensions of human airways, the oversimplified techniques may be used.

  3. Simulation studies of GST phase change alloys

    Science.gov (United States)

    Martyna, Glenn

    2008-03-01

    In order to help drive post-Moore's Law technology development, switching processes involving novel materials, in particular, GeSbTe (GST) alloys are being investigated for use in memory and eFuse applications. An anneal/quench thermal process crystallizes/amorphosizes a GST alloy which then has a low/high resistance and thereby forms a readable/writeable bit; for example, a ``one'' might be the low resistance, conducting crystalline state and a ``zero'' might be the high resistance, glassy state. There are many open questions about the precise nature of the structural transitions and the coupling to electronic structure changes. Computational and experimental studies of the effect of pressure on the GST materials were initiated in order to probe the physics behind the thermal switching process. A new pathway to reversible phase change involving pressure-induced structural metal insulator transitions was discovered. In a binary GS system, a room-temperature, direct, pressure-induced transformation from the high resistance amorphous phase to the low resistance crystalline phase was observed experimentally while the reverse process under tensile load was demonstrated via ab initio MD simulations performed on IBM's Blue Gene/L enabled by massively parallel software. Pressure induced transformations of the ternary material GST-225 (Ge2Sb2Te5) were, also, examined In the talk, the behavior of the two systems will be compared and insight into the nature of the phase change given.

  4. Comparing stochastic differential equations and agent-based modelling and simulation for early-stage cancer.

    Science.gov (United States)

    Figueredo, Grazziela P; Siebers, Peer-Olaf; Owen, Markus R; Reps, Jenna; Aickelin, Uwe

    2014-01-01

    There is great potential to be explored regarding the use of agent-based modelling and simulation as an alternative paradigm to investigate early-stage cancer interactions with the immune system. It does not suffer from some limitations of ordinary differential equation models, such as the lack of stochasticity, representation of individual behaviours rather than aggregates and individual memory. In this paper we investigate the potential contribution of agent-based modelling and simulation when contrasted with stochastic versions of ODE models using early-stage cancer examples. We seek answers to the following questions: (1) Does this new stochastic formulation produce similar results to the agent-based version? (2) Can these methods be used interchangeably? (3) Do agent-based models outcomes reveal any benefit when compared to the Gillespie results? To answer these research questions we investigate three well-established mathematical models describing interactions between tumour cells and immune elements. These case studies were re-conceptualised under an agent-based perspective and also converted to the Gillespie algorithm formulation. Our interest in this work, therefore, is to establish a methodological discussion regarding the usability of different simulation approaches, rather than provide further biological insights into the investigated case studies. Our results show that it is possible to obtain equivalent models that implement the same mechanisms; however, the incapacity of the Gillespie algorithm to retain individual memory of past events affects the similarity of some results. Furthermore, the emergent behaviour of ABMS produces extra patters of behaviour in the system, which was not obtained by the Gillespie algorithm.

  5. Comparing stochastic differential equations and agent-based modelling and simulation for early-stage cancer.

    Directory of Open Access Journals (Sweden)

    Grazziela P Figueredo

    Full Text Available There is great potential to be explored regarding the use of agent-based modelling and simulation as an alternative paradigm to investigate early-stage cancer interactions with the immune system. It does not suffer from some limitations of ordinary differential equation models, such as the lack of stochasticity, representation of individual behaviours rather than aggregates and individual memory. In this paper we investigate the potential contribution of agent-based modelling and simulation when contrasted with stochastic versions of ODE models using early-stage cancer examples. We seek answers to the following questions: (1 Does this new stochastic formulation produce similar results to the agent-based version? (2 Can these methods be used interchangeably? (3 Do agent-based models outcomes reveal any benefit when compared to the Gillespie results? To answer these research questions we investigate three well-established mathematical models describing interactions between tumour cells and immune elements. These case studies were re-conceptualised under an agent-based perspective and also converted to the Gillespie algorithm formulation. Our interest in this work, therefore, is to establish a methodological discussion regarding the usability of different simulation approaches, rather than provide further biological insights into the investigated case studies. Our results show that it is possible to obtain equivalent models that implement the same mechanisms; however, the incapacity of the Gillespie algorithm to retain individual memory of past events affects the similarity of some results. Furthermore, the emergent behaviour of ABMS produces extra patters of behaviour in the system, which was not obtained by the Gillespie algorithm.

  6. The energy budget of stellar magnetic fields: comparing non-potential simulations and observations

    CERN Document Server

    Lehmann, L T; Vidotto, A A; Mackay, D H; See, V; Donati, J -F; Folsom, C P; Jeffers, S V; Marsden, S C; Morin, J; Petit, P

    2016-01-01

    The magnetic geometry of the surface magnetic fields of more than 55 cool stars have now been mapped using spectropolarimetry. In order to better understand these observations, we compare the magnetic field topology at different surface scale sizes of observed and simulated cool stars. For ease of comparison between the high-resolution non-potential magnetofrictional simulations and the relatively low-resolution observations, we filter out the small-scale field in the simulations using a spherical harmonics decomposition. We show that the large-scale field topologies of the solar-based simulations produce values of poloidal/toroidal fields and fractions of energy in axisymmetric modes that are similar to the observations. These global non-potential evolution model simulations capture key magnetic features of the observed solar-like stars through the processes of surface flux transport and magnetic flux emergence. They do not, however, reproduce the magnetic field of M-dwarfs or stars with dominantly toroidal ...

  7. Comparative microscopy study of Vibrio cholerae flagella

    Science.gov (United States)

    Konnov, Nikolai P.; Baiburin, Vil B.; Zadnova, Svetlana P.; Volkov, Uryi P.

    1999-06-01

    A fine structure of bacteria flagella is an important problem of molecular cell biology. Bacteria flagella are the self-assembled structures that allow to use the flagellum protein in a number of biotechnological applications. However, at present, there is a little information about high resolution scanning probe microscopy study of flagellum structure, in particular, about investigation of Vibrio cholerae flagella. In our lab have been carried out the high resolution comparative investigation of V. cholerae flagella by means of various microscopes: tunneling (STM), scanning force (SFM) and electron transmission. As a scanning probe microscope is used designed in our lab versatile SPM with replaceable measuring heads. Bacteria were grown, fixed and treated according to the conventional techniques. For STM investigations samples were covered with Pt/Ir thin films by rotated vacuum evaporation, in SFM investigations were used uncovered samples. Electron microscopy of the negatively stained bacteria was used as a test procedure.

  8. Comparative studies on ecotoxicology of synthetic detergents.

    Science.gov (United States)

    Lal, H; Misra, V; Viswanathan, P N; Krishna Murti, C R

    1983-12-01

    To predict the comparative toxicological response of synthetic detergents on aquatic ecosystems, the effects of various concentrations of neutralized alkyl benzene sulfonate were studied. The median tolerance limit at 48 hr, 95% confidence limit, slope function, presumable harmless concentration, and rate of survival of different species of aquatic fauna such as water fleas (Daphnia magna), mosquito larvae (Culex pipiens), slug worms (Tubifex rivulorum), snails (Lymnaea vulgaris), tadpoles (Rana cyanophlyctis), and fish fingerlings (Cirrhina mrigala) were followed at 0, 24, 48, 72, and 96 hr. Any effect on quality of the water was also tested after the addition of various concentrations of detergents. The results showed that water fleas are more susceptible to detergent toxicity than fish fingerlings, tadpoles, slug worms, snails, and mosquito larvae. Behavioral changes were also observed as an index for detergent toxicity. The relative toxicity of the detergents to various species is discussed in relation to selective ecotoxicological response.

  9. A COMPARATIVE STUDY IN WIRELESS SENSOR NETWORKS

    Directory of Open Access Journals (Sweden)

    Hasan Al-Refai

    2014-02-01

    Full Text Available Sensor networks consist of a large number of small, low-powered wireless nodes with limited computation, communication, and sensing abilities, in a battery-powered sensor network, energy and communication bandwidth are a precious resources. Thus, there is a need to adapt the networking process to match the application in order to minimize the resources consumed and extend the life of the network. In this paper, we introduce a comparative study in different routing algorithms that propose vital solutions to the most important issues that should be taken into account when designing wireless network which are reliability, lifetime, communication bandwidth, transmission rand, and finally the limited energy issue, so we will introduce their algorithms and discuss how did they propose to solve such of these challenges and finally we will do some evaluation to each approach.

  10. COSMOS - a study comparing peripheral intravenous systems.

    Science.gov (United States)

    López, Juan Luis González; Del Palacio, Encarnación Ferenández; Marti, Carmen Benedicto; Corral, Javier Olivares; Portal, Pilar Herrera; Vilela, Ana Arribi

    In many areas of the world, safety peripheral intravenous systems have come into widespread use. The Madrid region was the first in Spain to adopt such an approach. These systems, though initially introduced to protect users from sharps injuries, have now evolved to include patient protection features as well. Patient protection, simply stated, means closing the system to pathogen entry. The authors' purpose was to investigate, in a prospective and randomized study, the clinical performance of a closed safe intravenous system versus an open system (COSMOS - Compact Closed System versus Mounted Open System). COSMOS is designed to provide definitive answers, from a nursing perspective, to many topics related to peripheral venous catheterization, which have important implications in intravenous therapy and which have not been validated scientifically. Furthermore, it forms pioneering research in that it is the first clinical trial on medical devices in a legislated environment carried out entirely by nurses and whose promoter and principal investigator is a nurse. The objectives of COSMOS are to compare the effectiveness (as defined by time of survival without complications) and rates of catheter-related complications, such as phlebitis, pain, extravasation, blockage and catheter-related infections. It also looks at rates of catheter colonization, the ease of handling of both systems and overall costs. This article outlines the authors' approach, both in preparing hospital units for such an evaluation as well as in the choice of parameters and their method of study. Further articles will detail the results and findings of the study.

  11. Are two heads better than one? Comparing dyad and self-regulated learning in simulation training.

    Science.gov (United States)

    Shanks, David; Brydges, Ryan; den Brok, Wendie; Nair, Parvathy; Hatala, Rose

    2013-12-01

    The optimal learner to simulator ratio for procedural skills training is not known. Research in motor learning suggests observational training in pairs, termed 'dyad training', may be as effective as directed self-regulated learning (DSRL). This study was conducted to compare the relative effectiveness and efficiency of dyad versus DSRL training of simulation-based lumbar puncture (LP). We conducted a two-group randomised equivalence trial. First-year internal medicine residents (n = 50) were randomly assigned to learn LP either in dyads or as individual learners on a simulator, using a directed self-regulated approach (i.e. the learning sequence was defined for them, but they defined the pace of learning). Participants were videotaped performing a simulated LP on a pre-test, an immediate post-test, and a 6-week delayed retention test. In duplicate, blinded raters independently evaluated all trainee performances using a previously validated 5-point global rating scale (GRS) and 35-item checklist. Our analyses showed no significant differences (p = 0.69) on pre-test, post-test or retention test GRS scores between the dyad (mean ± standard deviation [SD] scores by test: 2.39 ± 0.57, 3.48 ± 0.62, 3.12 ± 0.85, respectively) and DSRL (mean ± SD scores by test: 2.67 ± 0.50, 3.34 ± 0.77, 3.21 ± 0.79, respectively) groups. Both groups improved significantly from pre-test to post-test (p groups (20.94 minutes for individuals and 24.20 minutes for dyads; p = 0.175). Our results indicate that learning in pairs is as effective as independent DSRL. Dyad training permits the more efficient use of simulators as two learners use the same resources as an individual. © 2013 John Wiley & Sons Ltd.

  12. A Comparative Study of Actuator Configurations for Satellite Attitude Control

    Directory of Open Access Journals (Sweden)

    Raymond Kristiansen

    2005-10-01

    Full Text Available In this paper a controllability study of different actuator configurations consisting of magnetic torquers, reaction wheels and a gravity boom is presented. The theoretical analysis is performed with use of controllability gramians, and simulation results with the different configurations are presented and compared regarding settling time and power consumption to substantiate the theoretical analysis. A reference model is also introduced to show how the power consumption can he lowered to the same magnitude as when magnetic torquers are used, without degrading the satellite response significantly.

  13. Intentional burns in Nepal: a comparative study.

    Science.gov (United States)

    Lama, Bir Bahadur; Duke, Janine M; Sharma, Narayan Prasad; Thapa, Buland; Dahal, Peeyush; Bariya, Nara Devi; Marston, Wendy; Wallace, Hilary J

    2015-09-01

    Intentional burns injuries are associated with high mortality rates, and for survivors, high levels of physical and psychological morbidity. This study provides a comprehensive assessment of intentional burn admissions to the adult Burns Unit at Bir Hospital, Kathmandu, Nepal, during the period 2002-2013. A secondary data analysis of de-identified data of patients hospitalized at Bir Hospital, Kathmandu, with a burn during the period of 1 January 2002 to 31 August 2013. Socio-demographic, injury and psychosocial factors of patients with intentional and unintentional burns are described and compared. Chi-square tests, Fisher's exact test and Wilcoxon rank sum tests were used to determine statistical significance. There were a total of 1148 burn admissions of which 329 (29%) were for intentional burn, 293 (26%) were self-inflicted and 36 (3%) were due to assault. Mortality rates for intentional burns were approximately three times those for unintentional burns (60 vs. 22%). When compared to unintentional burns, patients with intentional burns were more likely to be female (79 vs. 48%), married (84 vs. 67%), younger (25 vs. 30 years), have more extensive burns (total body surface area, %: 55 vs. 25) and higher mortality (60 vs. 22%). Intentional burns were more likely to occur at home (95 vs. 67%), be caused by fire (96 vs. 77%), and kerosene was the most common accelerant (91 vs. 31%). A primary psychosocial risk factor was identified in the majority of intentional burn cases, with 60% experiencing adjustment problems/interpersonal conflict and 32% with evidence of a pre-existing psychological condition. A record of alcohol/substance abuse related to the patient or other was associated with a greater proportion of intentional burns when compared with unintentional burns (17 vs. 4%). The majority of intentional burn patients were female. Almost all intentional burns occurred in the home and were caused by fire, with kerosene the most common accelerant used. Underlying

  14. Bias-correction in vector autoregressive models: A simulation study

    DEFF Research Database (Denmark)

    Engsted, Tom; Pedersen, Thomas Quistgaard

    We analyze and compare the properties of various methods for bias-correcting parameter estimates in vector autoregressions. First, we show that two analytical bias formulas from the existing literature are in fact identical. Next, based on a detailed simulation study, we show that this simple and...

  15. Comparing simulations and test data of a radiation damaged CCD for the Euclid mission

    Science.gov (United States)

    Skottfelt, Jesper; Hall, David; Gow, Jason; Murray, Neil; Holland, Andrew; Prod'homme, Thibaut

    2016-07-01

    The radiation damage effects from the harsh radiative environment outside the Earth's atmosphere can be a cause for concern for most space missions. With the science goals becoming ever more demanding, the requirements on the precision of the instruments on board these missions also increases, and it is therefore important to investigate how the radiation induced damage affects the Charge-Coupled Devices (CCDs) that most of these instruments rely on. The primary goal of the Euclid mission is to study the nature of dark matter and dark energy using weak lensing and baryonic acoustic oscillation techniques. The weak lensing technique depends on very precise shape measurements of distant galaxies obtained by a large CCD array. It is anticipated that over the 6 year nominal lifetime of mission, the CCDs will be degraded to an extent that these measurements will not be possible unless the radiation damage effects are corrected. We have therefore created a Monte Carlo model that simulates the physical processes taking place when transferring signal through a radiation damaged CCD. The software is based on Shockley-Read-Hall theory, and is made to mimic the physical properties in the CCD as close as possible. The code runs on a single electrode level and takes charge cloud size and density, three dimensional trap position, and multi-level clocking into account. A key element of the model is that it takes device specific simulations of electron density as a direct input, thereby avoiding to make any analytical assumptions about the size and density of the charge cloud. This paper illustrates how test data and simulated data can be compared in order to further our understanding of the positions and properties of the individual radiation-induced traps.

  16. The BEST study - a prospective study to compare business class ...

    African Journals Online (AJOL)

    ... a prospective study to compare business class versus economy class air travel as a cause of thrombosis. ... Patients/methods. ... Logistical regression analysis was used to determine the risk factors related to abnormally high D-dimer levels.

  17. Study of Cardiac Defibrillation Through Numerical Simulations

    Science.gov (United States)

    Bragard, J.; Marin, S.; Cherry, E. M.; Fenton, F. H.

    Three-dimensional numerical simulations of the defibrillation problem are presented. In particular, in this study we use the rabbit ventricular geometry as a realistic model system for evaluating the efficacy of defibrillatory shocks. Statistical data obtained from the simulations were analyzed in term of a dose-response curve. Good quantitative agreement between our numerical results and clinically relevant values is obtained. An electric field strength of about 6.6 V/cm indicates a fifty percent probability of successful defibrillation for a 12-ms monophasic shock. Our validated model will be useful for optimizing defibrillation protocols.

  18. COMPARATIVE STUDY ON ACCOUNTING AND FISCAL AMORTIZATION

    Directory of Open Access Journals (Sweden)

    MARIANA GURAU

    2012-05-01

    Full Text Available Placed in the international trend, Romanian accounting had experienced various changes, especially as regards of progress on disconnection between accounting and fiscality. In the present, fiscal rules should not have any role in accounting decisions, because accounting rules are applied to produce accounting information that is useful in making decisions and to provide a "true and fair view" upon financial reality of the entity. However, the barrier in the habit of accounting to thinking for fiscal point of view all economic transactions remains insurmountable, yet. Starting from this perspective on disconnection between accounting and fiscality would mean that amortization recorded in the accounting, as a result of management policy, to be different from fiscality amortization, to calculate income tax. Although formally accepted, disconnect between accounting and fiscality continues to meet many difficulties. In this sense, it is usual in practice to use the same method of amortization for accounting purposes and for fiscal purposes to prevent complications of double track amortization and prevent wandering in the rules in this field. Accounting rule is deliberately eluded in favor of the fiscal rules. This is the reason we proposed to make in this paper a comparative study between norms and rules on accounting and fiscal amortization, paper in which we intend to show the benefits of applying accounting and fiscal rules separately.

  19. Comparative study of selected parallel tempering methods

    Science.gov (United States)

    Malakis, A.; Papakonstantinou, T.

    2013-07-01

    We review several parallel tempering schemes and examine their main ingredients for accuracy and efficiency. The present study covers two selection methods of temperatures and several choices for the exchange of replicas, including a recent novel all-pair exchange method. We compare the resulting schemes and measure specific heat errors and efficiency using the two-dimensional (2D) Ising model. Our tests suggest that an earlier proposal for using numbers of local moves related to the canonical correlation times is one of the key ingredients for increasing efficiency, and protocols using cluster algorithms are found to be very effective. Some of the protocols are also tested for efficiency and ground state production in 3D spin-glass models where we find that a simple nearest-neighbor approach using a local n-fold-way algorithm is the most effective. Finally, we present evidence that the asymptotic limits of the ground state energy for the isotropic case and for an anisotropic case of the 3D spin-glass model are very close and may even coincide.

  20. Design, simulation and comparative analysis of CNT based cascode operational transconductance amplifiers

    Science.gov (United States)

    Nizamuddin, M.; Loan, Sajad A.; Alamoud, Abdul R.; Abbassi, Shuja A.

    2015-10-01

    In this work, design and calibrated simulation of carbon nanotube field effect transistor (CNTFET)-based cascode operational transconductance amplifiers (COTA) have been performed. Three structures of CNTFET-based COTAs have been designed using HSPICE and have been compared with the conventional CMOS-based COTAs. The proposed COTAs include one using pure CNTFETs and two others that employ CNTFETs, as well as the conventional MOSFETs. The simulation study has revealed that the CNTFET-based COTAs have significantly outperformed the conventional MOSFET-based COTAs. A significant increase in dc gain, output resistance and slew rate of 81.4%, 25% and 13.2%, respectively, have been achieved in the proposed pure CNT-based COTA in comparison to the conventional CMOS-based COTA. The power consumption in the pure CNT-COTA is 324 times less in comparison to the conventional CMOS-COTA. Further, the phase margin (PM), gain margin (GM), common mode and power supply rejection ratios have been significantly increased in the proposed CNT-based COTAs in comparison to the conventional CMOS-based COTAs. Furthermore, to see the advantage of cascoding, the proposed CNT-based cascode OTAs have been compared with the CNT-based OTAs. It has been observed that by incorporating the concept of cascode in the CNTFET-based OTAs, significant increases in gain (12.5%) and output resistance (13.07%) have been achieved. The performance of the proposed COTAs has been further observed by changing the number of CNTs (N), CNT pitch (S) and CNT diameter (DCNT) in the CNTFETs used. It has been observed that the performance of the proposed COTAs can be significantly improved by using optimum values of N, S and DCNT.

  1. When experts are oceans apart: comparing expert performance values for proficiency-based laparoscopic simulator training.

    Science.gov (United States)

    Luursema, Jan-Maarten; Rovers, Maroeska M; Alken, Alexander; Kengen, Bas; van Goor, Harry

    2015-01-01

    Surgical training is moving away from the operating room toward simulation-based skills training facilities. This has led to the development of proficiency-based training courses in which expert performance data are used for feedback and assessment. However, few expert value data sets have been published, and no standard method for generating expert values has been adopted by the field. To investigate the effect of different proficiency value data sets on simulator training courses, we (1) compared 2 published expert performance data sets for the LapSim laparoscopic virtual-reality simulator (by van Dongen et al. and Heinrichs et al.) and (2) assessed the effect of using either set on LapSim training data obtained from 16 local residents in surgery and gynecology. Across all simulator tasks, the experts consulted by van Dongen et al. performed better on motion efficiency, but not on duration or damage control. Applying both proficiency sets to training data collected during a basic skills laparoscopic simulator course, residents would have graduated on an average in 1.5 fewer sessions using the Heinrichs expert values compared with the van Dongen expert values. The selection of proficiency values for proficiency-based simulator training courses affects training length, skills level assessment, and training costs. Standardized, well-controlled methods are necessary to create valid and reliable expert values for use in training and research. Copyright © 2015 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

  2. Empathy Development Through Case Study and Simulation.

    Science.gov (United States)

    Mennenga, Heidi A; Bassett, Susan; Pasquariello, Libby

    2016-01-01

    Because empathy is integral to the nurse-patient relationship, nurse educators are challenged to explore teaching strategies that may aid in the development of empathy among students. The purpose of this study was to determine whether consistent exposure to a single patient through case study and simulation had an impact on empathy levels in senior-level baccalaureate nursing students. Results provide interesting conclusions for faculty members and offer a basis for ongoing discussion.

  3. Study of Nanowires Using Molecular Dynamics Simulations

    OpenAIRE

    Monk, Joshua D

    2007-01-01

    In this dissertation I present computational studies that focus on the unique characteristics of metallic nanowires. We generated virtual nanowires of nanocrystalline nickel (nc-Ni) and single crystalline silver (Ag) in order to investigate particular nanoscale effects. Three-dimensional atomistic molecular dynamics studies were performed for each sample using the super computer System X located at Virginia Tech. Thermal grain growth simulations were performed on 4 nm grain size nc-Ni by o...

  4. Comparative Implementation of High Performance Computing for Power System Dynamic Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Shuangshuang; Huang, Zhenyu; Diao, Ruisheng; Wu, Di; Chen, Yousu

    2017-05-01

    Dynamic simulation for transient stability assessment is one of the most important, but intensive, computations for power system planning and operation. Present commercial software is mainly designed for sequential computation to run a single simulation, which is very time consuming with a single processer. The application of High Performance Computing (HPC) to dynamic simulations is very promising in accelerating the computing process by parallelizing its kernel algorithms while maintaining the same level of computation accuracy. This paper describes the comparative implementation of four parallel dynamic simulation schemes in two state-of-the-art HPC environments: Message Passing Interface (MPI) and Open Multi-Processing (OpenMP). These implementations serve to match the application with dedicated multi-processor computing hardware and maximize the utilization and benefits of HPC during the development process.

  5. Programming PHREEQC calculations with C++ and Python a comparative study

    Science.gov (United States)

    Charlton, Scott R.; Parkhurst, David L.; Muller, Mike

    2011-01-01

    The new IPhreeqc module provides an application programming interface (API) to facilitate coupling of other codes with the U.S. Geological Survey geochemical model PHREEQC. Traditionally, loose coupling of PHREEQC with other applications required methods to create PHREEQC input files, start external PHREEQC processes, and process PHREEQC output files. IPhreeqc eliminates most of this effort by providing direct access to PHREEQC capabilities through a component object model (COM), a library, or a dynamically linked library (DLL). Input and calculations can be specified through internally programmed strings, and all data exchange between an application and the module can occur in computer memory. This study compares simulations programmed in C++ and Python that are tightly coupled with IPhreeqc modules to the traditional simulations that are loosely coupled to PHREEQC. The study compares performance, quantifies effort, and evaluates lines of code and the complexity of the design. The comparisons show that IPhreeqc offers a more powerful and simpler approach for incorporating PHREEQC calculations into transport models and other applications that need to perform PHREEQC calculations. The IPhreeqc module facilitates the design of coupled applications and significantly reduces run times. Even a moderate knowledge of one of the supported programming languages allows more efficient use of PHREEQC than the traditional loosely coupled approach.

  6. A Comparative Study of Principals' Administrative Behaviour.

    Science.gov (United States)

    Chung, Kyung Ae

    1989-01-01

    Compared are the managerial behaviors and beliefs of Korean and American secondary school principals. Generalizations are proposed in the areas of work hours, work pace, communication skills, organizational style, instructional leadership, and other managerial behaviors. (16 references) (SI)

  7. Comparative study of environmental impact assessment methods ...

    African Journals Online (AJOL)

    STORAGESEVER

    2009-07-20

    Jul 20, 2009 ... Then both approaches required be comparing and contrasting. Among these methods .... should include political powers (factors related to the poli- cy test) and .... mental system and predict the component behavior. Using the ...

  8. SKIN STAPLED OR SUTURED: A COMPARATIVE STUDY

    Directory of Open Access Journals (Sweden)

    Veerendra Kumar

    2015-01-01

    Full Text Available BACKGROUND: The choice of wound closure after a surgical procedure has been a surgeon’s dilemma . The concerns have been as to how fast , uneventful , less painful , with minimal complications and comfortable will the patient’s recovery be. A well - known technology is surgical staples which are easier to use , less time consuming and a needle free method o f wound closure. OBJECTIVE: To compare skin staples with non - absorbable skin suture for skin closure in surgical laparotomy procedures for the following character : wound infection , dehiscence , cosmesis and postoperative pain . METHODS: This is a comparative study conducted on 100 patients divided in two groups randomly at Bapuji Hospital for cases undergoing surgical laparotomy procedures. Skin closure was done with 2 - 0 polyamide skin sutures in one group and skin closure was achieved with skin staples in th e other group. The outcome of wound was assessed on 3rd , 5th and 7th postoperative days using ASEPSIS score. Wound cosmesis was assessed on the 7th postoperative day and followed up at 1st month and 3rd month , using modified Hollander cosmesis scale. Postoperative pain was assessed using the visual analogue scale on the 1st , 3rd and 7th postoperative days. RESULTS : The mean wound ASPESIS scores on day 3 for skin staples and sutured group was 0.28 and 0.36 (p=0.7 respectively. The score on day 5 for staples and sutured group was 0.12 and 0.28 (p=0.4 respectively. The results in both the groups were the same , 0.08 on day 7(p=0. Wound cosmesis mean score assessment on day 7 for skin staples suturing group was 5.84 and 5.68 respectively (p=0.3. The mean score for cosmesis assessment at 1 month , and 3 rd month for skin staples and suturing group was 5.92 and 5.68 (p=0.1 and was 6.00 and 5.92 (p=0.36 respectively which was not satistically significant . The visual analogue scale score for postopera tive pain on 1st day , 3 rd and 7 th day for skin staples and suturing group 54

  9. The intensity contrast of solar granulation: comparing Hinode SP results with MHD simulations

    NARCIS (Netherlands)

    Danilovic, S.; Gandorfer, A.; Lagg, A.; SchÜssler, M.; Solanki, S.K.; Vögler, A.; Katsukawa, Y.; Tsuneta, S.

    2008-01-01

    Context. The contrast of granulation is an important quantity characterizing solar surface convection. Aims. We compare the intensity contrast at 630 nm, observed using the Spectro-Polarimeter (SP) aboard the Hinode satellite, with the 3D radiative MHD simulations of Vögler & Schüssler (2007, A&A, 4

  10. Polarization data from SCIAMACHY limb backscatter observations compared to vector radiative transfer model simulations

    Directory of Open Access Journals (Sweden)

    P. Liebing

    2012-03-01

    Full Text Available SCIAMACHY is a passive imaging spectrometer onboard ENVISAT, designed to obtain trace gas abundances from measured radiances and irradiances in the UV to SWIR range in nadir, limb and occultation viewing modes. Its grating spectrometer introduces a substantial sensitivity to the polarization of the incoming light with nonnegligible effects on the radiometric calibration. To be able to correct for the polarization sensitivity, SCIAMACHY utilizes broadband Polarization Measurement Devices (PMDs. While for the nadir viewing mode the measured atmospheric polarization has been validated against POLDER data (Tilstra and Stammes, 2007, 2010, a similar validation study regarding the limb viewing mode has not yet been performed. This paper aims at an assessment of the quality of the SCIAMACHY limb polarization data. Since limb polarization measurements by other air- or spaceborne instruments in the spectral range of SCIAMACHY are not available, a comparison with radiative transfer simulations by SCIATRAN V3.1(Rozanov et al., 2012 using a wide range of atmospheric parameters is performed. SCIATRAN is a vector radiative transfer model (VRTM capable of performing calculations of the multiply scattered radiance in a~spherically symmetric atmosphere.

    The study shows that the limb polarization data exhibit a large systematic bias which is decreasing with wavelength. The most likely reason for this bias is an instrumental phase shift which changes the relative contributions of different Stokes vector components to the PMD signal as compared to on-ground calibration measurements. It is also shown that it is in principle feasible to recalibrate the polarization sensitivity using the in-flight data and the VRTM simulations, enabling also the monitoring of its degradation. Together with an optimization of the algorithm used to calculate the in-flight polarization data an improved polarization correction can increase the radiometric accuracy of SCIAMACHY

  11. The Teaching of Anthropology: A Comparative Study.

    Science.gov (United States)

    Lombard, Jacques

    1984-01-01

    College-level anthropology teaching in various countries, including Belgium, France, Germany, the Netherlands, Portugal, South Africa, the United Kingdom, and Yugoslavia, is compared. Terminology is examined and historical background is provided. Also discussed are educational crises, the organization of teaching, and teaching methods. (RM)

  12. Comparing semi-analytic particle tagging and hydrodynamical simulations of the Milky Way's stellar halo

    CERN Document Server

    Cooper, Andrew P; Frenk, Carlos S; Bret, Theo Le; Pontzen, Andrew

    2016-01-01

    Particle tagging is an efficient, but approximate, technique for using cosmological N-body simulations to model the phase space evolution of the stellar populations predicted, for example, by a semi-analytic model of galaxy formation. We test the technique developed by Cooper et al. (which we call STINGS here) by comparing particle tags with stars in a smooth particle hydrodynamic (SPH) simulation. We focus on the spherically averaged density profile of stars accreted from satellite galaxies in a Milky Way-like system. The stellar profile in the SPH simulation can be recovered accurately by tagging dark matter particles in the same simulation according to a prescription based on the rank order of particle binding energy. Applying the same prescription to an N-body version of this simulation produces very similar results. This confirms that particle tagging can provide a faithful and robust approximation to a self-consistent hydrodynamical simulation in this regime (in contradiction to previous claims in the l...

  13. Study of numerical errors in direct numerical simulation and large eddy simulation

    Institute of Scientific and Technical Information of China (English)

    YANG Xiao-long; FU Song

    2008-01-01

    By comparing the energy spectrum and total kinetic energy, the effects of numerical errors (which arise from aliasing and discretization errors), subgrid-scale (SGS) models, and their interactions on direct numerical simulation (DNS) and large eddy simulation (LES) are investigated. The decaying isotropic turbulence is chosen as the test case. To simulate complex geometries, both the spectral method and Pade compact difference schemes are studied. The truncated Navier-Stokes (TNS) equation model with Pade discrete filter is adopted as the SGS model. It is found that the discretization error plays a key role in DNS. Low order difference schemes may be unsuitable. However, for LES, it is found that the SGS model can represent the effect of small scales to large scales and dump the numerical errors. Therefore, reasonable results can also be obtained with a low order discretization scheme.

  14. Impact comparative study of phone carcasses behavior by FEM

    Science.gov (United States)

    Constantin, Cărăuşu; Plăvănescu, Simona; Dumitru, Nedelcu

    2015-07-01

    A constant concern of scientific research is based on plastics replace with biodegradable materials that reduce the adverse impact of waste on the environment. A biodegradable material that arouses interest lately is Arboform which is made of lignin, a component of wood and woody plants. Replacing plastic with Arboform in carrying components of products requires technical and economic studies on the implications of such replacement. Numerical simulation methods are a fast and economical way of analyzing the behavior of a product in various mechanical, thermal, electromagnetic and so on. The paper presents comparative results of numerical simulation using the software package SolidWorks impact behavior through the “Drop Test” of half shells made of High Density Polyethylene (HDPE) and of the Arboform LV3 Nature. Simulation watched the half-carcass behavior in three cases of accidental impact, “head”, “corner” and the “back side”. We analyzed the size and location of the maximum voltage and maximum deformation resulting from impact. Simulations have shown for all three cases a maximum voltage increase when using Arboform to use PEDH 93% for impact “forward” and “corner” and only 48.77% “back side” impact. If the maximum displacement, it increasing from carcasses of Arboform 4% for impact “head” and 6% for impact “corner”, but fell by 2.7% for the “back side” impact. The significant increase of stress can be attributed to the higher density of Arboform to PEDH, which led to different weights of the two half-carcasses.

  15. A simulator-based curriculum to promote comparative and reflective analysis in an internal medicine clerkship.

    Science.gov (United States)

    McMahon, Graham T; Monaghan, Colleen; Falchuk, Kenneth; Gordon, James A; Alexander, Erik K

    2005-01-01

    To develop and evaluate a novel curricular framework using high-fidelity patient simulation in an internal medicine clerkship. Two 90-minute simulator-based modules of ischemic heart failure and hypoxemic respiratory failure were developed from adult and experiential learning principles. Three short simulated cases focused on each pathophysiologic concept were intermixed with two short teaching sessions and a period of comparative analysis. In 2002-03, the program was piloted among 90 third-year medical students at Harvard Medical School assigned to complete their core internal medicine clerk-ship. An entry and two follow-up questionnaires were used to assess the process. The instructors conducted quantitative and qualitative data analysis and directly observed students' performances. Instructors consistently noted students' ability to appropriately extract a history, perform a basic examination, and order appropriate tests. However, students demonstrated repeated errors in the application of knowledge to the clinical circumstance. A final comparative discussion was essential to new learning and students recognized this integrative analysis as the most critical component of the exercise. Every student reported the experience as useful. Ninety-four percent (n = 85) felt the simulator should become a routine part of the clerkship and 68% (n = 71) desired three or more sessions during their internal medicine clerkship. Simulator-based curricular modules are feasible in an internal medicine clerkship and can successfully complement existing curricula. By comparing similar cases in a compressed time frame, students may achieve enhanced efficiencies in reflective and meta-cognitive learning. As medical simulation is increasingly available, such a curriculum may represent valuable additions to the internal medicine educational environment.

  16. Comparing semi-analytic particle tagging and hydrodynamical simulations of the Milky Way's stellar halo

    Science.gov (United States)

    Cooper, Andrew P.; Cole, Shaun; Frenk, Carlos S.; Le Bret, Theo; Pontzen, Andrew

    2017-08-01

    Particle tagging is an efficient, but approximate, technique for using cosmological N-body simulations to model the phase-space evolution of the stellar populations predicted, for example, by a semi-analytic model of galaxy formation. We test the technique developed by Cooper et al. (which we call stings here) by comparing particle tags with stars in a smooth particle hydrodynamic (SPH) simulation. We focus on the spherically averaged density profile of stars accreted from satellite galaxies in a Milky Way (MW)-like system. The stellar profile in the SPH simulation can be recovered accurately by tagging dark matter (DM) particles in the same simulation according to a prescription based on the rank order of particle binding energy. Applying the same prescription to an N-body version of this simulation produces a density profile differing from that of the SPH simulation by ≲10 per cent on average between 1 and 200 kpc. This confirms that particle tagging can provide a faithful and robust approximation to a self-consistent hydrodynamical simulation in this regime (in contradiction to previous claims in the literature). We find only one systematic effect, likely due to the collisionless approximation, namely that massive satellites in the SPH simulation are disrupted somewhat earlier than their collisionless counterparts. In most cases, this makes remarkably little difference to the spherically averaged distribution of their stellar debris. We conclude that, for galaxy formation models that do not predict strong baryonic effects on the present-day DM distribution of MW-like galaxies or their satellites, differences in stellar halo predictions associated with the treatment of star formation and feedback are much more important than those associated with the dynamical limitations of collisionless particle tagging.

  17. The use of discrete-event simulation modeling to compare handwritten and electronic prescribing systems.

    Science.gov (United States)

    Ghany, Ahmad; Vassanji, Karim; Kuziemsky, Craig; Keshavjee, Karim

    2013-01-01

    Electronic prescribing (e-prescribing) is expected to bring many benefits to Canadian healthcare, such as a reduction in errors and adverse drug reactions. As there currently is no functioning e-prescribing system in Canada that is completely electronic, we are unable to evaluate the performance of a live system. An alternative approach is to use simulation modeling for evaluation. We developed two discrete-event simulation models, one of the current handwritten prescribing system and one of a proposed e-prescribing system, to compare the performance of these two systems. We were able to compare the number of processes in each model, workflow efficiency, and the distribution of patients or prescriptions. Although we were able to compare these models to each other, using discrete-event simulation software was challenging. We were limited in the number of variables we could measure. We discovered non-linear processes and feedback loops in both models that could not be adequately represented using discrete-event simulation software. Finally, interactions between entities in both models could not be modeled using this type of software. We have come to the conclusion that a more appropriate approach to modeling both the handwritten and electronic prescribing systems would be to use a complex adaptive systems approach using agent-based modeling or systems-based modeling.

  18. Indoor Environment and Energy Use in Historic Buildings - Comparing Survey Results with Measurements and Simulations

    DEFF Research Database (Denmark)

    Rohdin, P.; Dalewski, M.; Moshfegh, B.

    2012-01-01

    Increasing demand for energy efficiency places new requirements on energy use in historic buildings. Efficient energy use is essential if a historic building is to be used and preserved, especially buildings with conventional uses such as residential buildings and offices. This paper presents...... results which combine energy auditing with building energy simulation and an indoor environment survey among the occupants of the building. Both when comparing simulations with measurements as well as with survey results good agreement was found. The two efficiency measures that are predicted to increase...... energy and thermal performance the most for this group of buildings were reduced infiltration and increasing heat-exchanger efficiency....

  19. A comparative analysis of 9 multi-model averaging approaches in hydrological continuous streamflow simulation

    Science.gov (United States)

    Arsenault, Richard; Gatien, Philippe; Renaud, Benoit; Brissette, François; Martel, Jean-Luc

    2015-10-01

    This study aims to test whether a weighted combination of several hydrological models can simulate flows more accurately than the models taken individually. In addition, the project attempts to identify the most efficient model averaging method and the optimal number of models to include in the weighting scheme. In order to address the first objective, streamflow was simulated using four lumped hydrological models (HSAMI, HMETS, MOHYSE and GR4J-6), each of which were calibrated with three different objective functions on 429 watersheds. The resulting 12 hydrographs (4 models × 3 metrics) were weighted and combined with the help of 9 averaging methods which are the simple arithmetic mean (SAM), Akaike information criterion (AICA), Bates-Granger (BGA), Bayes information criterion (BICA), Bayesian model averaging (BMA), Granger-Ramanathan average variant A, B and C (GRA, GRB and GRC) and the average by SCE-UA optimization (SCA). The same weights were then applied to the hydrographs in validation mode, and the Nash-Sutcliffe Efficiency metric was measured between the averaged and observed hydrographs. Statistical analyses were performed to compare the accuracy of weighted methods to that of individual models. A Kruskal-Wallis test and a multi-objective optimization algorithm were then used to identify the most efficient weighted method and the optimal number of models to integrate. Results suggest that the GRA, GRB, GRC and SCA weighted methods perform better than the individual members. Model averaging from these four methods were superior to the best of the individual members in 76% of the cases. Optimal combinations on all watersheds included at least one of each of the four hydrological models. None of the optimal combinations included all members of the ensemble of 12 hydrographs. The Granger-Ramanathan average variant C (GRC) is recommended as the best compromise between accuracy, speed of execution, and simplicity.

  20. Catatonic schizophrenia: an international comparative study.

    Science.gov (United States)

    Chandrasena, R

    1986-04-01

    Thirty-five hospitalized catatonic schizophrenic patients from Sri Lanka were compared with 22 patients in the U.K. and 13 in Canada. The phenomenology was established using the Present State Examination. Results suggest that ethnicity, chronicity of illness and reception of neuroleptic treatment may influence the lower prevalence of catatonic symptoms among the U.K. and Canadian schizophrenics. Onset of illness appears to be among young adults and mutism, stupor, mannerisms, stereotypes and negativism were the common catatonic symptoms observed.

  1. Biases and systematics in the observational derivation of galaxy properties: comparing different techniques on synthetic observations of simulated galaxies

    Science.gov (United States)

    Guidi, Giovanni; Scannapieco, Cecilia; Walcher, C. Jakob

    2015-12-01

    We study the sources of biases and systematics in the derivation of galaxy properties from observational studies, focusing on stellar masses, star formation rates, gas and stellar metallicities, stellar ages, magnitudes and colours. We use hydrodynamical cosmological simulations of galaxy formation, for which the real quantities are known, and apply observational techniques to derive the observables. We also analyse biases that are relevant for a proper comparison between simulations and observations. For our study, we post-process the simulation outputs to calculate the galaxies' spectral energy distributions (SEDs) using stellar population synthesis models and also generate the fully consistent far-UV-submillimetre wavelength SEDs with the radiative transfer code SUNRISE. We compared the direct results of simulations with the observationally derived quantities obtained in various ways, and found that systematic differences in all studied galaxy properties appear, which are caused by: (1) purely observational biases, (2) the use of mass-weighted and luminosity-weighted quantities, with preferential sampling of more massive and luminous regions, (3) the different ways of constructing the template of models when a fit to the spectra is performed, and (4) variations due to different calibrations, most notably for gas metallicities and star formation rates. Our results show that large differences can appear depending on the technique used to derive galaxy properties. Understanding these differences is of primary importance both for simulators, to allow a better judgement of similarities and differences with observations, and for observers, to allow a proper interpretation of the data.

  2. Beware the black box: investigating the sensitivity of FEA simulations to modelling factors in comparative biomechanics.

    Science.gov (United States)

    Walmsley, Christopher W; McCurry, Matthew R; Clausen, Phillip D; McHenry, Colin R

    2013-01-01

    Finite element analysis (FEA) is a computational technique of growing popularity in the field of comparative biomechanics, and is an easily accessible platform for form-function analyses of biological structures. However, its rapid evolution in recent years from a novel approach to common practice demands some scrutiny in regards to the validity of results and the appropriateness of assumptions inherent in setting up simulations. Both validation and sensitivity analyses remain unexplored in many comparative analyses, and assumptions considered to be 'reasonable' are often assumed to have little influence on the results and their interpretation. HERE WE REPORT AN EXTENSIVE SENSITIVITY ANALYSIS WHERE HIGH RESOLUTION FINITE ELEMENT (FE) MODELS OF MANDIBLES FROM SEVEN SPECIES OF CROCODILE WERE ANALYSED UNDER LOADS TYPICAL FOR COMPARATIVE ANALYSIS: biting, shaking, and twisting. Simulations explored the effect on both the absolute response and the interspecies pattern of results to variations in commonly used input parameters. Our sensitivity analysis focuses on assumptions relating to the selection of material properties (heterogeneous or homogeneous), scaling (standardising volume, surface area, or length), tooth position (front, mid, or back tooth engagement), and linear load case (type of loading for each feeding type). Our findings show that in a comparative context, FE models are far less sensitive to the selection of material property values and scaling to either volume or surface area than they are to those assumptions relating to the functional aspects of the simulation, such as tooth position and linear load case. Results show a complex interaction between simulation assumptions, depending on the combination of assumptions and the overall shape of each specimen. Keeping assumptions consistent between models in an analysis does not ensure that results can be generalised beyond the specific set of assumptions used. Logically, different comparative datasets would

  3. The coefficient of error of optical fractionator population size estimates: a computer simulation comparing three estimators.

    Science.gov (United States)

    Glaser, E M; Wilson, P D

    1998-11-01

    The optical fractionator is a design-based two-stage systematic sampling method that is used to estimate the number of cells in a specified region of an organ when the population is too large to count exhaustively. The fractionator counts the cells found in optical disectors that have been systematically sampled in serial sections. Heretofore, evaluations of optical fractionator performance have been made by performing tests on actual tissue sections, but it is difficult to evaluate the coefficient of error (CE), i.e. the precision of a population size estimate, by using biological tissue samples because they do not permit a comparison of an estimated CE with the true CE. However, computer simulation does permit making such comparisons while avoiding the observational biases inherent in working with biological tissue. This study is the first instance in which computer simulation has been applied to population size estimation by the optical fractionator. We used computer simulation to evaluate the performance of three CE estimators. The estimated CEs were evaluated in tests of three types of non-random cell population distribution and one random cell population distribution. The non-random population distributions varied by differences in 'intensity', i.e. the expected cell counts per disector, according to both section and disector location within the section. Two distributions were sinusoidal and one was linearly increasing; in all three there was a six-fold difference between the high and low intensities. The sinusoidal distributions produced either a peak or a depression of cell intensity at the centre of the simulated region. The linear cell intensity gradually increased from the beginning to the end of the region that contained the cells. The random population distribution had a constant intensity over the region. A 'test condition' was defined by its population distribution, the period between consecutive sampled sections and the spacing between consecutive

  4. Comparative Transport Studies of '1212' Superconductors

    Directory of Open Access Journals (Sweden)

    Albert Gapud

    1999-12-01

    Full Text Available HgBa2CaCu2O6+δ (Hg -1212 thin films were fabricated by exchanging the T1 cations in TlBa2CaCu2O7-δ (Tl-1212 thin films with Hg cations, causing a 30-K increase in Tc. To determine how this exchange effects such a Tc increase, the irreversibility lines, temperature dependence of critical current density, and temperature dependence of Hall angle ofHg-1212 and TI-1212 thin films were measured and then compared. The results strongly suggest that the Tc shift is caused by a doubling of charge carrier density.

  5. [COMPARATIVE CHARACTERISTIC OF VARIOUS METHODS OF SIMULATION OF BILIARY PERITONITIS IN EXPERIMENT].

    Science.gov (United States)

    Nichitaylo, M Yu; Furmanov, Yu O; Gutsulyak, A I; Savytska, I M; Zagriychuk, M S; Goman, A V

    2016-02-01

    In experiment on rabbits a comparative analysis of various methods of a biliary peritonitis simulation was conducted. In 6 animals a biliary peritonitis was simulated, using perforation of a gallbladder, local serous-fibrinous peritonitis have occurred in 50% of them. In 7 animals biliary peritonitis was simulated, applying intraabdominal injection of medical sterile bile in a 5-40 ml volume. Diffuse peritonitis with exudates and stratification of fibrin was absent. Most effective method have appeared that, when intraabdominal injection of bile was done together with E. coli culture in the rate of 0.33 microbal bodies McF (1.0 x 10(8) CFU/ml) on 1 kg of the animal body mass. Diffuse biliary peritonitis have occurred in all 23 animals, including serous-fibrinous one--in 17 (76%), and purulent-fibrinous--in 6 (24%).

  6. Genetic network models: a comparative study

    Science.gov (United States)

    van Someren, Eugene P.; Wessels, Lodewyk F. A.; Reinders, Marcel J. T.

    2001-06-01

    Currently, the need arises for tools capable of unraveling the functionality of genes based on the analysis of microarray measurements. Modeling genetic interactions by means of genetic network models provides a methodology to infer functional relationships between genes. Although a wide variety of different models have been introduced so far, it remains, in general, unclear what the strengths and weaknesses of each of these approaches are and where these models overlap and differ. This paper compares different genetic modeling approaches that attempt to extract the gene regulation matrix from expression data. A taxonomy of continuous genetic network models is proposed and the following important characteristics are suggested and employed to compare the models: inferential power; predictive power; robustness; consistency; stability and computational cost. Where possible, synthetic time series data are employed to investigate some of these properties. The comparison shows that although genetic network modeling might provide valuable information regarding genetic interactions, current models show disappointing results on simple artificial problems. For now, the simplest models are favored because they generalize better, but more complex models will probably prevail once their bias is more thoroughly understood and their variance is better controlled.

  7. Advertisement Analysis: A Comparative Critical Study

    Science.gov (United States)

    Abdelaal, Noureldin Mohamed; Sase, Amal Saleh

    2014-01-01

    This study aimed at analyzing two advertisements, and investigating how advertisers use discourse and semiotics to make people and customers buy into their ideas, beliefs, or simply their products. The two advertisements analyzed are beauty products which have been selected from internet magazines. The methodology adopted in this study is…

  8. Simulation Study of a Vehicle Production Line for Productivity Improvement

    Directory of Open Access Journals (Sweden)

    M.F.F. Ab Rashid

    2015-06-01

    Full Text Available This paper presents the study of a motorcycle frame production line in a particular company in Malaysia. Due to the high demand, the company needs to increase its production by at least 12% compared with current output. In order to improve productivity, the production-floor data was collected and simulated using the discrete event simulation approach. Later, a number of suggestions for improvement were simulated to identify the effect of the suggestions on productivity. In addition, cost analysis was also undertaken to identify the profit margin for a particular period of time for each suggestion. Simulation results indicate that there are three suggestions that are able to fulfill the 12% volume increment. In the short term, the suggestion to hire an assistant line leader will give instant effect to the profit. Meanwhile, for the medium term, Poka-yoke will give higher profit compared with the others, while in the long term, SOP (standard operating procedure implementation will yield a better profit margin. In future, the simulation of a dynamic demand model for this product is suggested to cope with new trends in the market.

  9. DWPF Simulant CPC Studies For SB8

    Energy Technology Data Exchange (ETDEWEB)

    Newell, J. D.

    2013-09-25

    Prior to processing a Sludge Batch (SB) in the Defense Waste Processing Facility (DWPF), flowsheet studies using simulants are performed. Typically, the flowsheet studies are conducted based on projected composition(s). The results from the flowsheet testing are used to 1) guide decisions during sludge batch preparation, 2) serve as a preliminary evaluation of potential processing issues, and 3) provide a basis to support the Shielded Cells qualification runs performed at the Savannah River National Laboratory (SRNL). SB8 was initially projected to be a combination of the Tank 40 heel (Sludge Batch 7b), Tank 13, Tank 12, and the Tank 51 heel. In order to accelerate preparation of SB8, the decision was made to delay the oxalate-rich material from Tank 12 to a future sludge batch. SB8 simulant studies without Tank 12 were reported in a separate report.1 The data presented in this report will be useful when processing future sludge batches containing Tank 12. The wash endpoint target for SB8 was set at a significantly higher sodium concentration to allow acceptable glass compositions at the targeted waste loading. Four non-coupled tests were conducted using simulant representing Tank 40 at 110-146% of the Koopman Minimum Acid requirement. Hydrogen was generated during high acid stoichiometry (146% acid) SRAT testing up to 31% of the DWPF hydrogen limit. SME hydrogen generation reached 48% of of the DWPF limit for the high acid run. Two non-coupled tests were conducted using simulant representing Tank 51 at 110-146% of the Koopman Minimum Acid requirement. Hydrogen was generated during high acid stoichiometry SRAT testing up to 16% of the DWPF limit. SME hydrogen generation reached 49% of the DWPF limit for hydrogen in the SME for the high acid run. Simulant processing was successful using previously established antifoam addition strategy. Foaming during formic acid addition was not observed in any of the runs. Nitrite was destroyed in all runs and no N2O was detected

  10. COMPARATIVE STUDY OF LIGHT SOURCES FOR HOUSEHOLD

    Directory of Open Access Journals (Sweden)

    Andrzej PAWLAK

    2017-01-01

    Full Text Available The article describes test results that provided the ground to define and evaluate basic photometric, colorimetric and electric parameters of selected, widely available light sources, which are equivalent to a traditional incandescent 60-Watt light bulb. Overall, one halogen light bulb, three compact fluorescent lamps and eleven LED light sources were tested. In general, it was concluded that in most cases (branded products, in particular the measured and calculated parameters differ from the values declared by manufacturers only to a small degree. LED sources prove to be the most beneficial substitute for traditional light bulbs, considering both their operational parameters and their price, which is comparable with the price of compact fluorescent lamps or, in some instances, even lower.

  11. Earthquake Correlations and Networks- A Comparative Study

    CERN Document Server

    G., T R Krishna Mohan P

    2010-01-01

    We quantify the correlation between earthquakes and use the same to distinguish between relevant causally connected earthquakes. Our correlation metric is a variation on the one introduced by Baiesi and Paczuski (2004). A network of earthquakes is constructed, which is time ordered and with links between the more correlated ones. Recurrences to earthquakes are identified employing correlation thresholds to demarcate the most meaningful ones in each cluster. Data pertaining to three different seismic regions, viz. California, Japan and Himalayas, are comparatively analyzed using such a network model. The distribution of recurrence lengths and recurrence times are two of the key features analyzed to draw conclusions about the universal aspects of such a network model. We find that the unimodal feature of recurrence length distribution, which helps to associate typical rupture lengths with different magnitude earthquakes, is robust across the different seismic regions. The out-degree of the networks shows a hub ...

  12. A comparative study of microbiological and physicochemical ...

    African Journals Online (AJOL)

    Ethiopian Journal of Environmental Studies and Management ... Rwandan Water and Sanitation Corporation ltd (WASAC) water branches: Kimisagara WASAC water ... strategy for better water quality especially along the distribution network.

  13. Achieving Closed-Loop Control Simulation of Human-Artefact Interaction: A Comparative Review

    Directory of Open Access Journals (Sweden)

    Wilhelm Frederik van der Vegte

    2011-01-01

    Full Text Available To include user interactions in simulations of product use, the most common approach is to couple human subjects to simulation models, using hardware interfaces to close the simulation-control loop. Testing with virtual human models could offer a low-cost addition to evaluation with human subjects. This paper explores the possibilities for coupling human and artefact models to achieve fully software-based interaction simulations. We have critically reviewed existing partial solutions to simulate or execute control (both human control and product-embedded control and compared solutions from literature with a proof-of-concept we have recently developed. Our concept closes all loops, but it does not rely on validated algorithms to predict human decision making and low-level human motor control. For low-level control, validated solutions are available from other approaches. For human decision making, however, validated algorithms exist only to predict the timing but not the reasoning behind it. To identify decision-making schemes beyond what designers can conjecture, testing with human subjects remains indispensable.

  14. Simulation study supporting wastewater treatment plant upgrading.

    Science.gov (United States)

    Hvala, N; Vrecko, D; Burica, O; Strazar, M; Levstek, M

    2002-01-01

    The paper presents a study where upgrading of an existing wastewater treatment plant was supported by simulation. The aim of the work was to decide between two technologies to improve nitrogen removal: a conventional activated sludge process (ASP) and a moving bed biofilm reactor (MBBR). To perform simulations, the mathematical models of both processes were designed. The models were calibrated based on data from ASP and MBBR pilot plants operating in parallel on the existing plant. Only two kinetic parameters needed to be adjusted to represent the real plant behaviour. Steady-state analyses have shown a similar efficiency of both processes in relation to carbon removal, but improved performance of MBBR in relation to nitrogen removal. Better performance of MBBR can be expected especially at low temperatures. Simulations have not confirmed the expected less volume required for the MBBR process. Finally, the MBBR was chosen for plant upgrading. The developed process model will be further used to evaluate the final plant configuration and to optimise the plant operating parameters.

  15. A simulation study on garment manufacturing process

    Science.gov (United States)

    Liong, Choong-Yeun; Rahim, Nur Azreen Abdul

    2015-02-01

    Garment industry is an important industry and continues to evolve in order to meet the consumers' high demands. Therefore, elements of innovation and improvement are important. In this work, research studies were conducted at a local company in order to model the sewing process of clothes manufacturing by using simulation modeling. Clothes manufacturing at the company involves 14 main processes, which are connecting the pattern, center sewing and side neating, pockets sewing, backside-sewing, attaching the front and back, sleeves preparation, attaching the sleeves and over lock, collar preparation, collar sewing, bottomedge sewing, buttonholing sewing, removing excess thread, marking button, and button cross sewing. Those fourteen processes are operated by six tailors only. The last four sets of processes are done by a single tailor. Data collection was conducted by on site observation and the probability distribution of processing time for each of the processes is determined by using @Risk's Bestfit. Then a simulation model is developed using Arena Software based on the data collected. Animated simulation model is developed in order to facilitate understanding and verifying that the model represents the actual system. With such model, what if analysis and different scenarios of operations can be experimented with virtually. The animation and improvement models will be presented in further work.

  16. Simulation study of China's net primary production

    Institute of Scientific and Technical Information of China (English)

    GAO ZhiQiang; LIU JiYuan

    2008-01-01

    Spatial and temporal distribution of vegetation net primary production (NPP) in China was studied us-ing three light-use efficiency models (CASA, GLOPEM and GEOLUE) and two mechanistic ecological process models (CEVSA, GEOPRO). Based on spatial and temporal analysis (e.g. monthly, seasonally and annually) of simulated results from ecological process mechanism models of CASA, GLOPEM and CEVSA, the following conclusions could be made: (1) during the last 20 years, NPP change in China followed closely the seasonal change of climate affected by monsoon with an overall trend of increas-ing; (2) simulated average seasonal NPP was: 0.571±0.2 GtC in spring, 1.573±0.4 GtC in summer, 0.6±0.2 GtC in autumn, and 0.12±0.1 GtC in winter. Average annual NPP in China was 2.864±1 GtC. All the five models were able to simulate seasonal and spatial features of biomass for different ecological types in China. This paper provides a baseline for China's total biomass production. It also offers a means of estimating the NPP change due to afforestation, reforestation, conservation and other human activities and could aid people in using for-mentioned carbon sinks to fulfill China's commitment of reducing greenhouse gases.

  17. OpenSimulator Interoperability with DRDC Simulation Tools: Compatibility Study

    Science.gov (United States)

    2014-09-01

    conversion. iv These tools include Blender, AutoCAD , 3DS Max and SketchUp. Thus, DRDC use case (1) was demonstrated as feasible. However...supplementary support for the creation of content and resources compatible with OpenSimulator. These include programs such as Blender, GIMP, AutoCAD , 3DS MAX...support the PDS, PDMS, ACIS (.sat), MicroStation (.dgn), and AutoCAD (.dwg) formats, but not COLLADA directly [14]. An important limitation of

  18. Study on corrosion simulation device for marine structural steel

    Indian Academy of Sciences (India)

    Hou Baorong; Xiang Bin

    2003-04-01

    A corrosion simulation device was studied using offshore long scale hanging specimens. An Ni–Cu–P steel specimen was studied by analysing its corrosion products and corrosion types. The appearance of the samples and the surface of the metallic substrate after the removal of the rust layer produced by these two methods were observed and compared after 470 days of exposure. The phase structure of the corrosion products under different marine environments were analysed and compared. It further indicated good correlation between the electrically connected hanging specimen method and the long scale hanging specimen method.

  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. Advertisement Analysis: A Comparative Critical Study

    Directory of Open Access Journals (Sweden)

    Noureldin Mohamed Abdelaal

    2014-12-01

    Full Text Available This study aimed at analyzing two advertisements, and investigating how advertisers use discourse and semiotics to make people and customers buy into their ideas, beliefs, or simply their products. The two advertisements analyzed are beauty products which have been selected from internet magazines. The methodology adopted in this study is qualitative method. The first advertisement is analyzed qualitatively in terms of content; there was no focus on a specific theoretical frame work, while the second advertisement analysis is based on Fairclough’s framework, the critical discourse analysis framework.

  1. Annual Journal citation indices: a comparative study

    CERN Document Server

    Khaleque, Abdul; Sen, Parongama

    2016-01-01

    We study the statistics of citations made to the indexed Science journals in the Journal Citation Reports during the period 2004-2013 using different measures. We consider different measures which quantify the impact of the journals. To our surprise, we find that the apparently uncorrelated measures, even when defined in an arbitrary manner, show strong correlations. This is checked over all the years considered. Impact factor being one of these measures, the present work raises the question whether it is actually a nearly perfect index as claimed often. In addition we study the distributions of the different indices which also behave similarly.

  2. Child Labor in Africa: A Comparative Study

    DEFF Research Database (Denmark)

    Canagarajah, Sudharshan; Nielsen, Helena Skyt

    2001-01-01

    This paper analyzes the determinants of child labor in Africa as inferred from recent empirical studies. The empirical analysis is based upon five country studies undertaken in three different African countries, namely Côte d'Ivoire, Ghana, and Zambia. Some support is found for the popular belief...... of poverty as a determinant of child labor, however other determinants are of similar importance. Among school costs, transportation costs have the greatest effect on child labor and school attendance, whereas the hypothesis of imperfect capital markets and that of household composition generally find some...

  3. Child Labor in Africa: A Comparative Study

    DEFF Research Database (Denmark)

    Nielsen, Helena Skyt; Canagarajah, Sudharshan

    1999-01-01

    This paper analyzes the determinants of child labor in Africa as inferred from recent empirical studies. The empirical analysis is based upon five country studies undertaken in three different African countries, namely Côte d'Ivoire, Ghana, and Zambia. Some support is found for the popular belief...... of poverty as a determinant of child labor, however other determinants are of similar importance. Among school costs, transportation costs have the greatest effect on child labor and school attendance, whereas the hypothesis of imperfect capital markets and that of household composition generally find some...

  4. Annual Journal Citation Indices: A Comparative Study

    Directory of Open Access Journals (Sweden)

    Abdul Khaleque

    2016-06-01

    Full Text Available We study the statistics of citations made to the indexed Science journals in the Journal Citation Reports during the period 2004-2013 using different measures. We consider different measures which quantify the impact of the journals. To our surprise, we find that the apparently uncorrelated measures, even when defined in an arbitrary manner, show strong correlations. This is checked over all the years considered. Impact factor being one of these measures, the present work raises the question whether it is actually a nearly perfect index as claimed often. In addition, we study the distributions of the different indices which also behave similarly.

  5. A Comparative Comment on the Case Studies

    DEFF Research Database (Denmark)

    Kjeldsen, Christian Christrup; Ley, Thomas; Jensen, Niels Rosendal;

    2012-01-01

    Denne konklusion sammenfatter hovedtrækkene af de gennemførte case studies i WorkAble-projektet. Vigtige pointer er, at unge på tværs af de forskellige case studies har vanskeligt ved at blive hørt og taget alvorligt. I stedet spises de af med "realistisk vejledning" eller dårlige uddannelses- og...... arbejdstilbud. Konklusionen foreslår at give unge mere tid til at træffe de alvorlige valg vedr. deres fremtid ved at indføre et refugium, som i tankegang minder om Eriksons ungdomsmoratorium....

  6. Formation factor in Bentheimer and Fontainebleau sandstones: Theory compared with pore-scale numerical simulations

    Science.gov (United States)

    Ghanbarian, Behzad; Berg, Carl F.

    2017-09-01

    Accurate quantification of formation resistivity factor F (also called formation factor) provides useful insight into connectivity and pore space topology in fully saturated porous media. In particular the formation factor has been extensively used to estimate permeability in reservoir rocks. One of the widely applied models to estimate F is Archie's law (F = ϕ- m in which ϕ is total porosity and m is cementation exponent) that is known to be valid in rocks with negligible clay content, such as clean sandstones. In this study we compare formation factors determined by percolation and effective-medium theories as well as Archie's law with numerical simulations of electrical resistivity on digital rock models. These digital models represent Bentheimer and Fontainebleau sandstones and are derived either by reconstruction or directly from micro-tomographic images. Results show that the universal quadratic power law from percolation theory accurately estimates the calculated formation factor values in network models over the entire range of porosity. However, it crosses over to the linear scaling from the effective-medium approximation at the porosity of 0.75 in grid models. We also show that the effect of critical porosity, disregarded in Archie's law, is nontrivial, and the Archie model inaccurately estimates the formation factor in low-porosity homogeneous sandstones.

  7. Comparative Anticonvulsant Study of Epoxycarvone Stereoisomers

    Directory of Open Access Journals (Sweden)

    Paula Regina Rodrigues Salgado

    2015-10-01

    Full Text Available Stereoisomers of the monoterpene epoxycarvone (EC, namely (+-cis-EC, (−-cis-EC, (+-trans-EC, and (−-trans-EC, were comparatively evaluated for anticonvulsant activity in specific methodologies. In the pentylenetetrazole (PTZ-induced anticonvulsant test, all of the stereoisomers (at 300 mg/kg increased the latency to seizure onset, and afforded 100% protection against the death of the animals. In the maximal electroshock-induced seizures (MES test, prevention of tonic seizures was also verified for all of the isomers tested. However, the isomeric forms (+ and (−-trans-EC showed 25% and 12.5% inhibition of convulsions, respectively. In the pilocarpine-induced seizures test, all stereoisomers demonstrated an anticonvulsant profile, yet the stereoisomers (+ and (−-trans-EC (at 300 mg/kg showed a more pronounced effect. A strychnine-induced anticonvulsant test was performed, and none of the stereoisomers significantly increased the latency to onset of convulsions; the stereoisomers probably do not act in this pathway. However, the stereoisomers (+-cis-EC and (+-trans-EC greatly increased the latency to death of the animals, thus presenting some protection. The four EC stereoisomers show promise for anticonvulsant activity, an effect emphasized in the isomers (+-cis-EC, (+-trans-EC, and (−-trans-EC for certain parameters of the tested methodologies. These results serve as support for further research and development of antiepileptic drugs from monoterpenes.

  8. Bilingual Language Proficiency : A comparative study

    NARCIS (Netherlands)

    Duarte, Joana

    2011-01-01

    his book investigates the role native language plays in the process of acquiring a second language within a bilingual educational model. The research presented is based on a 2 year longitudinal study of students in a bilingual school. Particular attention is paid to the development of academic

  9. A comparative study on permissiveness toward euthanasia

    NARCIS (Netherlands)

    Verbakel, C.M.C.; Jaspers, E.

    2010-01-01

    This study explores explanations for the approval of euthanasia by assessing differences among individuals and countries, using four main arguments used by opponents and proponents in the public debate over euthanasia. We performed multilevel analysis on data from thirty-three countries, obtained fr

  10. A comparative study on permissiveness toward euthanasia

    NARCIS (Netherlands)

    Verbakel, C.M.C.; Jaspers, E.

    2010-01-01

    This study explores explanations for the approval of euthanasia by assessing differences among individuals and countries, using four main arguments used by opponents and proponents in the public debate over euthanasia. We performed multilevel analysis on data from thirty-three countries, obtained

  11. Metacognition and Group Differences: A Comparative Study

    Science.gov (United States)

    Al-Hilawani, Yasser A.

    2014-01-01

    In this study, metacognition refers to performing visual analysis and discrimination of real life events and situations in naïve psychology, naïve physics, and naïve biology domains. It is used, along with measuring reaction time, to examine differences in the ability of four groups of students to select appropriate pictures that correspond with…

  12. Children's Friendship Development: A Comparative Study

    Science.gov (United States)

    Yu, SeonYeong; Ostrosky, Michaelene M.; Fowler, Susan A.

    2011-01-01

    Establishing friendships is an important developmental goal of early childhood, but little research has addressed ways in which parents support the friendship development of their young children with disabilities. The purpose of this survey study was to explore the support strategies that parents use to facilitate their children's friendships.…

  13. A Comparative Study between Two Control Strategies for Matrix Converter

    OpenAIRE

    BENDIABDELLAH, A.; BACHIR, G.

    2009-01-01

    The authors compare two control strategies for direct AC-AC matrix converters; namely the Venturini method and the scalar strategy control method. The performance comparison of the two strategies is made under unbalanced distorted torque, rotor speed and stator current operation. The simulation of the three-phase matrix converter feeding an induction motor was accomplished by means of the Matlab/Simulink software. This package makes it possible to simulate the dynamic systems in a simple wa...

  14. Comparative Performance of Tabu Search and Simulated Annealing Heuristics for the Quadratic Assignment Problem

    CERN Document Server

    Paul, Gerald

    2010-01-01

    For almost two decades the question of whether tabu search (TS) or simulated annealing (SA) performs better for the quadratic assignment problem has been unresolved. To answer this question satisfactorily, we compare performance at various values of targeted solution quality, running each heuristic at its optimal number of iterations for each target. We find that for a number of varied problem instances, SA performs better for higher quality targets while TS performs better for lower quality targets.

  15. Comparative Study of Turbines for Wave Energy Conversion

    Institute of Scientific and Technical Information of China (English)

    Hideaki Maeda; Toshiaki Setoguchi; Manabu Takao; Keita Sakurada; Tae-Ho Kin; Kenji Kaneko

    2001-01-01

    The objective of this paper is to compare the performances of the turbines, which could be used for wave energy conversion in the near future, under various irregular wave conditions. The turbines included in the paper are as follows: (a) Wells turbine with guide vanes; (b) impulse turbine with self-pitch-controlled guide vanes; (c) impulse turbine with fixed guide vanes. In this study, experimental investigations were carried out to clarify the performances of the turbines under steady flow conditions, and then a numerical simulation was used for predicting the performances under irregular wave conditions with various significant wave heights. As a result, it was found that the running and starting characteristics of the impulse turbines could be superior to those of the Wells turbine.

  16. A Comparative Study of Distribution System Parameter Estimation Methods

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yannan; Williams, Tess L.; Gourisetti, Sri Nikhil Gup

    2016-07-17

    In this paper, we compare two parameter estimation methods for distribution systems: residual sensitivity analysis and state-vector augmentation with a Kalman filter. These two methods were originally proposed for transmission systems, and are still the most commonly used methods for parameter estimation. Distribution systems have much lower measurement redundancy than transmission systems. Therefore, estimating parameters is much more difficult. To increase the robustness of parameter estimation, the two methods are applied with combined measurement snapshots (measurement sets taken at different points in time), so that the redundancy for computing the parameter values is increased. The advantages and disadvantages of both methods are discussed. The results of this paper show that state-vector augmentation is a better approach for parameter estimation in distribution systems. Simulation studies are done on a modified version of IEEE 13-Node Test Feeder with varying levels of measurement noise and non-zero error in the other system model parameters.

  17. A comparative study of two stochastic mode reduction methods

    Energy Technology Data Exchange (ETDEWEB)

    Stinis, Panagiotis

    2005-09-01

    We present a comparative study of two methods for thereduction of the dimensionality of a system of ordinary differentialequations that exhibits time-scale separation. Both methods lead to areduced system of stochastic differential equations. The novel feature ofthese methods is that they allow the use, in the reduced system, ofhigher order terms in the resolved variables. The first method, proposedby Majda, Timofeyev and Vanden-Eijnden, is based on an asymptoticstrategy developed by Kurtz. The second method is a short-memoryapproximation of the Mori-Zwanzig projection formalism of irreversiblestatistical mechanics, as proposed by Chorin, Hald and Kupferman. Wepresent conditions under which the reduced models arising from the twomethods should have similar predictive ability. We apply the two methodsto test cases that satisfy these conditions. The form of the reducedmodels and the numerical simulations show that the two methods havesimilar predictive ability as expected.

  18. Conjunctivitis in the newborn- A comparative study

    Directory of Open Access Journals (Sweden)

    Meenakshi Wadhwani

    2011-01-01

    Full Text Available Background: Conjunctivitis of the newborn is defined as hyperemia and eye discharge in the neonates and is a common infection occurring in the neonates in the first month of life. In the United States, the incidence of neonatal conjunctivitis ranges from 1-2%, in India, the prevalence is 0.5-33% and varies in the world from 0.9-21% depending on the socioeconomic status. Aim: To study the organisms causing conjunctivitis of the newborn and to correlate the etiology with the mode of delivery. Design: Single center, prospective, observational study. Materials and Methods: A total of 300 mothers and their newborns, born over a period of one year, were included in the study. Of these 200 newborns were delivered through vaginal route (Group A and 100 (Group B delivered by lower segment caesarean section (LSCS. At the time of labour, high vaginal swabs were taken from the mothers. Two conjunctival swabs each from both eyes of the newborn were collected at birth and transported to Microbiology department in a candle jar immediately. Results: Eight babies in Group A, developed conjunctivitis at birth. None of the babies in Group B developed conjunctivitis, this difference was statistically highly significant (P<0.000. The organisms found in the conjunctiva of the newborns in Group A were Coagulase negative Staphylococcus, α hemolytic Streptococcus, Escherichia coli and Pseudomonas spps. However, the commonest organism leading to conjunctivitis in the newborn in this study was Coagulase negative Staphylococcus. It was observed that the mothers of 5 out of 8 babies (60% developing conjunctivitis gave history of midwife interference and premature rupture of membranes so the presence of risk factors contribute to the occurrence of conjunctivitis in the newborn. Conclusions: It is inferred that the mode of delivery and the presence of risk factors is responsible for conjunctivitis in the newborn.

  19. Agoraphobia and Panic Disorder: A Comparative Study

    Directory of Open Access Journals (Sweden)

    Ayse Kart

    2016-01-01

    Full Text Available Aim: In this study we aim to get more information about agoraphobia (AG which is an independent diagnosis in Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5 and to evaluate overlaps or differences between agoraphobia and panic disorder (PD upon sociodemographic features and comorbidity with considering relation of these two disorders. Material and Method: Sociodemographic Data Form was given and Structural Clinical Interview for DSM Axis I Disorders (SCID-I was applied to 33 patients diagnosed as AG and 34 patients diagnosed as PD with AG (PDA.Results: AG group consisted of 21 females (63.1%, 12 males (36%, totally 33 patients and PDA group consisted of 23 females (67.6%, 11 males (32.4%, totally 34 patients. Mean age of onset was 32.4±10.2 in PDA group and 31.1±12.1 in AG group. According to sociodemographic features, violence in family and smoking rates were significantly higher in PDA group than AG group. Major Depressive Disorder (MDD as a comorbidity was higher in PDA group. Discussion: In this study, we tried to identify the overlaps and differences of PDA and AG. For a better recognition of AG, further studies are needed.

  20. A comparative study of various decalcification techniques

    Directory of Open Access Journals (Sweden)

    Prathibha Prasad

    2013-01-01

    Full Text Available Background : Study of fibrilar, cellular and sub cellular structures of mineralized tissues is only possible after the removal of the calcium apatite of these tissues by the process of demineralization. Aims: The present study aims to evaluate six commonly used demineralizing agents to identify the best decalcifying agent. Materials and Methods: The present study included six different decalcifying solutions: 10% formal nitric acid, 8% formal nitric acid, 10% formic acid, 8% formic acid, Perenyi′s fluid and Ethylene Di-Amine Tetra Acetic Acid. eight samples of posterior mandible of rat were decalcified in each of the decalcifying solutions and subjected to chemical end-point test. Ehrlich′s Hematoxylin stain was used. Statistical Analysis Used: One way ANOVA was used for multiple group comparisons and Chi-square test was used for analyzing categorical data. P value of 0.05/less was set for statistical significance. Results: Samples treated with EDTA showed the best overall histological impression and the tissue integrity were well preserved. Formal nitric of both the percentages 10 and 8% gave fairly good cellular detail and were rapid in their action. Conclusion: The final impression led to the proposition that EDTA was indeed the best decalcifying agent available. However, with time constraint, the use of formal nitric acid is advocated.

  1. Teaching Business Simulation Games: Comparing Achievements Frontal Teaching vs. eLearning

    Science.gov (United States)

    Bregman, David; Keinan, Gila; Korman, Arik; Raanan, Yossi

    This paper addresses the issue of comparing results achieved by students taught the same course but in two drastically different - a regular, frontal method and an eLearning method. The subject taught required intensive communications among the students, thus making the eLearning students, a priori, less likely to do well in it. The research, comparing the achievements of students in a business simulation game over three semesters, shows that the use of eLearning method did not result in any differences in performance, grades or cooperation, thus strengthening the case for using eLearning in this type of course.

  2. Comparative study of the 2016 DPRK event

    Science.gov (United States)

    Kebede, Fekadu; Jonathan, Ezekiel; Graham, Gerhard

    2016-04-01

    Effective monitoring of any violations of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) depends upon the State Parties' ability to determine the nature of the source of the signals recorded by the IMS stations. Analysis by the IDC of the data gives some of the required information but makes no effort to determine the nature of source as specified by the Treaty. On January 6, 2016 the IMS network of stations recorded unusual seismic event from the DPRK. This was the fourth time that such an event from a man-made event was recorded from this area. Past detections of announced nuclear tests were on 9 October 2006, 25 May 2009, and 12 February 2013. There are a few natural earthquakes that have been recorded in this region. This study presents results of an assessment of waveform data and amplitude spectra obtained from seismic events observed at regional and/or local distance ranges, for both natural and man-made events located in the DPRK. The study reveals that the waveform displays of the four man-made events are practically simple and have nearly the same signature, yet they are significantly different to those of the observed natural earthquakes occurring in the region. The similarities of the waveforms obtained from the man-made events are due to the closeness of the epicentres and hence no difference in path effects for the Stations considered. The computed amplitude spectra of the waveform for the man-made and natural events also show differences in their relative amplitudes between the respective Primary and Secondary seismic phases, indicating that their sources are different. The study clearly shows the importance of studying the signature of the recorded seismic waves to determine the nature of the source of the energy, if it is man-made or natural, particularly for regions where records of natural earthquakes exist. Determination of the nature of source of recorded seismic waves is fundamental to CTBT verification. Thus data observed at regional and

  3. Observer study to evaluate the simulation of mammographic calcification clusters

    Science.gov (United States)

    Sousa, Maria A. Z.; Marcomini, Karem D.; Bakic, Predrag R.; Maidment, Andrew D. A.; Schiabel, Homero

    2016-03-01

    Numerous breast phantoms have been developed to be as realistic as possible to ensure the accuracy of image quality analysis, covering a greater range of applications. In this study, we simulated three different densities of the breast parenchyma using paraffin gel, acrylic plates and PVC films. Hydroxyapatite was used to simulate calcification clusters. From the images acquired with a GE Senographe DR 2000D mammography system, we selected 68 regions of interest (ROIs) with and 68 without a simulated calcification cluster. To validate the phantom simulation, we selected 136 ROIs from the University of South Florida's Digital Database for Screening Mammography (DDSM). Seven trained observers performed two observer experiments by using a high-resolution monitor Barco mod. E-3620. In the first experiment, the observers had to distinguish between real or phantom ROIs (with and without calcification). In the second one, the observers had to indicate the ROI with calcifications between a pair of ROIs. Results from our study show that the hydroxyapatite calcifications had poor contrast in the simulated breast parenchyma, thus observers had more difficulty in identifying the presence of calcification clusters in phantom images. Preliminary analysis of the power spectrum was conducted to investigate the radiographic density and the contrast thresholds for calcification detection. The values obtained for the power spectrum exponent (β) were comparable with those found in the literature.

  4. Detailed characteristics of drop-laden mixing layers: Large eddy simulation predictions compared to direct numerical simulation

    Science.gov (United States)

    Okong'o, Nora; Leboissetier, Anthony; Bellan, Josette

    2008-10-01

    Results are compared from direct numerical simulation (DNS) and large eddy simulation (LES) of a temporal mixing layer laden with evaporating drops to assess the ability of LES to reproduce detailed characteristics of DNS. The LES used computational drops, each of which represented eight physical drops, and a reduced flow field resolution using a grid spacing four times larger than that of the DNS. The LES also used models for the filtered source terms, which express the coupling of the drops with the flow, and for the unresolved subgrid-scale (SGS) fluxes of species mass, momentum, and enthalpy. The LESs were conducted using one of three different SGS-flux models: dynamic-coefficient gradient (GRD), dynamic-coefficient Smagorinsky (SMD), and constant-coefficient scale similarity (SSC). The comparison of the LES with the filtered-and-coarsened (FC) DNS considered detailed aspects of the flow that are of interest in ignition or full combustion. All LESs captured the largest-scale vortex, the global amount of vapor emanating from the drops, and the overall size distribution of the drops. All LESs tended to underpredict the global amount of irreversible entropy production (dissipation). The SMD model was found unable to capture either the global or local vorticity variation and had minimal small-scale activity in dynamic and thermodynamic variables compared to the FC-DNS. The SMD model was also deficient in predicting the spatial distribution of drops and of the dissipation. In contrast, the GRD and SSC models did mimic the small-scale activity of the FC-DNS and the spatial distribution of drops and of the dissipation. Therefore, the GRD and SSC models are recommended, while the SMD model seems inappropriate for combustion or other problems where the local activity must be predicted.

  5. A chemical EOR benchmark study of different reservoir simulators

    Science.gov (United States)

    Goudarzi, Ali; Delshad, Mojdeh; Sepehrnoori, Kamy

    2016-09-01

    chemical design for field-scale studies using commercial simulators. The benchmark tests illustrate the potential of commercial simulators for chemical flooding projects and provide a comprehensive table of strengths and limitations of each simulator for a given chemical EOR process. Mechanistic simulations of chemical EOR processes will provide predictive capability and can aid in optimization of the field injection projects. The objective of this paper is not to compare the computational efficiency and solution algorithms; it only focuses on the process modeling comparison.

  6. A randomized trial comparing didactics, demonstration, and simulation for teaching teamwork to medical residents.

    Science.gov (United States)

    Semler, Matthew W; Keriwala, Raj D; Clune, Jennifer K; Rice, Todd W; Pugh, Meredith E; Wheeler, Arthur P; Miller, Alison N; Banerjee, Arna; Terhune, Kyla; Bastarache, Julie A

    2015-04-01

    Effective teamwork is fundamental to the management of medical emergencies, and yet the best method to teach teamwork skills to trainees remains unknown. In a cohort of incoming internal medicine interns, we tested the hypothesis that expert demonstration of teamwork principles and participation in high-fidelity simulation would each result in objectively assessed teamwork behavior superior to traditional didactics. This was a randomized, controlled, parallel-group trial comparing three teamwork teaching modalities for incoming internal medicine interns. Participants in a single-day orientation at the Vanderbilt University Center for Experiential Learning and Assessment were randomized 1:1:1 to didactic, demonstration-based, or simulation-based instruction and then evaluated in their management of a simulated crisis by five independent, blinded observers using the Teamwork Behavioral Rater score. Clinical performance was assessed using the American Heart Association Advanced Cardiac Life Support algorithm and a novel "Recognize, Respond, Reassess" score. Participants randomized to didactics (n = 18), demonstration (n = 17), and simulation (n = 17) were similar at baseline. The primary outcome of average overall Teamwork Behavioral Rater score for those who received demonstration-based training was similar to simulation participation (4.40 ± 1.15 vs. 4.10 ± 0.95, P = 0.917) and significantly higher than didactic instruction (4.40 ± 1.15 vs. 3.10 ± 0.51, P = 0.045). Clinical performance scores were similar between the three groups and correlated only weakly with teamwork behavior (coefficient of determination [Rs(2)] = 0.267, P teamwork training by expert demonstration resulted in similar teamwork behavior to participation in high-fidelity simulation and was more effective than traditional didactics. Clinical performance was largely independent of teamwork behavior and did not differ between training modalities.

  7. A comparative study on showerhead cooling performance

    Energy Technology Data Exchange (ETDEWEB)

    Falcoz, C.; Ott, P. [Ecole Polytechnique Federale de Lausanne (EPFL), Laboratoire de Thermique Appliquee et de Turbomachines (LTT), 1015 Lausanne (Switzerland); Weigand, B. [Institut fuer Thermodynamik der Luft- und Raumfahrt (ITLR), Stuttgart University, Pfaffenwaldring 31, 70569 Stuttgart (Germany)

    2006-04-15

    In modern gas turbines, the turbine airfoil leading edge is currently protected from the hot gas by specific film cooling schemes, so called showerhead cooling. The present paper shows a numerical study of different showerhead cooling geometries. The 3D finite element program ABAQUS as well as a 2D finite element program have been employed to predict the showerhead cooling performance. In the numerical calculations, the different cooling effects and their contribution to the total showerhead cooling performance have been investigated separately. From the numerical calculations a simple method has been derived which enables the prediction of the performance of a 3D showerhead cooling scheme by simple 2D computations. Experimental investigations on showerhead cooling have been presented in a companion paper [C. Falcoz, B. Weigand, P. Ott, Experimental investigations on showerhead cooling on a blunt body. Int. J. Heat Mass Transfer, in press. r publication]. (author)

  8. Pavement Crack Classifiers: A Comparative Study

    Directory of Open Access Journals (Sweden)

    S. Siddharth

    2012-12-01

    Full Text Available Non Destructive Testing (NDT is an analysis technique used to inspect metal sheets and components without harming the product. NDT do not cause any change after inspection; this technique saves money and time in product evaluation, research and troubleshooting. In this study the objective is to perform NDT using soft computing techniques. Digital images are taken; Gray Level Co-occurrence Matrix (GLCM extracts features from these images. Extracted features are then fed into the classifiers which classifies them into images with and without cracks. Three major classifiers: Neural networks, Support Vector Machine (SVM and Linear classifiers are taken for the classification purpose. Performances of these classifiers are assessed and the best classifier for the given data is chosen.

  9. Internet patent databases: a comparative study.

    Directory of Open Access Journals (Sweden)

    Borja González-Albo Manglano

    2008-02-01

    Full Text Available The patent is an essential document in the evaluation of technological investigation that has been used as approximation of innovation. The patent databases on the Internet are one principal source of information for this kind of analysis. However they are many databases and they are very different; reason why the election of one of them in the accomplishment of bibliometric analysis is a crucial aspect. In this sense, this survey studies some of main free –Esp@cenet, PatentScope, national databases and commercial –Derwent Innovatios Index, Chemical Abstracts Plus, Thomson Delphion Intellectual Property Network– patent databases. The results show that commercial systems provide value-added –data revision, analysis tools, etc.–; althought the free ones are going to become trustworthy resources thanks to the improvements and options that are introduced in them.

  10. Simulation studies for the evaluation of health information technologies

    DEFF Research Database (Denmark)

    Ammenwerth, Elske; Hackl, Werner; Binzer, Kristine

    2012-01-01

    It is essential for new health information technologies (IT) to undergo rigorous evaluations to ensure they are effective and safe for use in real-world situations. However, evaluation of new health IT is challenging, as field studies are often not feasible when the technology being evaluated...... is not sufficiently mature. Laboratory-based evaluations have also been shown to have insufficient external validity. Simulation studies seem to be a way to bridge this gap. The aim of this study was to evaluate, using a simulation methodology, the impact of a new prototype of an electronic medication management...... and lessons learnt while conducting the study. Although the new electronic medication management system showed tendencies to improve medication safety when compared with the standard system, this tendency was not significant. Altogether, five distinct situations were identified where the new medication...

  11. Simulation Studies for the evaluation of health information technologies:

    DEFF Research Database (Denmark)

    Ammenwerth, Elske; Hackl, Werner O; Binzer, Kristine

    2012-01-01

    It is essential for new health information technologies (IT) to undergo rigorous evaluations to ensure they are effective and safe for use in real-world situations. However, evaluation of new health IT is challenging, as field studies are often not feasible when the technology being evaluated...... is not sufficiently mature. Laboratory-based evaluations have also been shown to have insufficient external validity. Simulation studies seem to be a way to bridge this gap. The aim of this study was to evaluate, using a simulation methodology, the impact of a new prototype of an electronic medication management...... and lessons learnt while conducting the study. Although the new electronic medication management system showed tendencies to improve medication safety when compared with the standard system, this tendency was not significant. Altogether, fi ve distinct situations were identifi ed where the new medication...

  12. Comparative study for thermal-hydraulic performance

    Directory of Open Access Journals (Sweden)

    Alok Kumar

    2016-03-01

    Full Text Available Several researchers have worked on the passive approach of heat transfer enhancement in tube heat exchangers. Some of them tried to modify the surface by creating dimple or using wire coil of different cross-section, while some worked on core fluid disturbance by using some insert geometries such as twisted tapes. But the ultimate aim of all was to create some disturbance in the flow in order to obtain enhanced heat transfer. This paper focuses on comparison of some of the most commonly used insert geometries. Insert geometry selected for this comparison is collection of core fluid disturbance, surface modification and combination of both. Different geometries taken in this study include twisted tape, twisted tape with ring, circular band, multiple twisted tape, twisted tape with conical rings, and so on and used air under turbulent flow regime as working fluid. On the basis of comparison made, it is observed that, in case of “single twisted tape insert” the thermal performance factor was maximum and in the event of “twisted tape with circular ring” the overall heat transfer rate is maximum. Future aspect is also proposed, which includes perforation in circular ring, and causes decrease in friction factor value because of less flow blockage.

  13. A comparative assessment of nursing students' cognitive knowledge of blood transfusion using lecture and simulation.

    Science.gov (United States)

    Flood, Lisa S; Higbie, Julie

    2016-01-01

    Professional nurses must have the knowledge and skills to safely administer blood products and monitor for life-threatening complications. Nurse educators should ensure that student nurses also learn how to safely administer blood products; however students rarely have the opportunity to witness and manage adverse transfusion reactions. Despite the low incidence of rare adverse transfusion reactions, nursing students must be able to immediately recognize transfusion reactions, implement appropriate interventions, and communicate effectively with health care providers. To reinforce blood transfusion knowledge, practice technical skills, and promote management of adverse reactions, a human patient simulation experience was created for baccalaureate nursing students to provide application of related classroom content. Using a quasi-experimental design, students who received a related didactic lecture preceding the simulation were compared with students who did not receive the lecture. The lecture group's pre/posttest mean scores (n = 42) were significantly higher than the no lecture group's mean scores (n = 44). This simulation design included proper blood administration procedures, patient monitoring, management of transfusion reactions, and practice with interdisciplinary communication. Participation in a human patient simulation following a related didactic lecture may be useful to strengthen cognitive learning and help bridge the didactic-clinic gap.

  14. Comparing Natural Gas Leakage Detection Technologies Using an Open-Source "Virtual Gas Field" Simulator.

    Science.gov (United States)

    Kemp, Chandler E; Ravikumar, Arvind P; Brandt, Adam R

    2016-04-19

    We present a tool for modeling the performance of methane leak detection and repair programs that can be used to evaluate the effectiveness of detection technologies and proposed mitigation policies. The tool uses a two-state Markov model to simulate the evolution of methane leakage from an artificial natural gas field. Leaks are created stochastically, drawing from the current understanding of the frequency and size distributions at production facilities. Various leak detection and repair programs can be simulated to determine the rate at which each would identify and repair leaks. Integrating the methane leakage over time enables a meaningful comparison between technologies, using both economic and environmental metrics. We simulate four existing or proposed detection technologies: flame ionization detection, manual infrared camera, automated infrared drone, and distributed detectors. Comparing these four technologies, we found that over 80% of simulated leakage could be mitigated with a positive net present value, although the maximum benefit is realized by selectively targeting larger leaks. Our results show that low-cost leak detection programs can rely on high-cost technology, as long as it is applied in a way that allows for rapid detection of large leaks. Any strategy to reduce leakage should require a careful consideration of the differences between low-cost technologies and low-cost programs.

  15. Comparing simulated and theoretical sampling distributions of the U3 person-fit statistic

    NARCIS (Netherlands)

    Emons, W.H.M.; Meijer, R.R.; Sijtsma, K.

    2002-01-01

    The accuracy with which the theoretical sampling distribution of van der Flier's person-.t statistic U3 approaches the empirical U3 sampling distribution is affected by the item discrimination. A simulation study showed that for tests with a moderate or a strong mean item discrimination, the Type I

  16. Comparative analysis as a management tool for broiler breeder farms: simulated individual farm analysis (IFAS)

    NARCIS (Netherlands)

    Yassin, H.; Velthuis, A.G.J.; Giesen, G.W.J.; Oude Lansink, A.G.J.M.

    2012-01-01

    The objective of this study was to develop a management information system to evaluate the tactical management of a breeder flock using individual farm analysis with a deterministic simulation model (IFAS). Individual farm analysis is a method that evaluates the performance of individual farms by

  17. DWPF simulant CPC studies for SB8

    Energy Technology Data Exchange (ETDEWEB)

    Koopman, D. C.; Zamecnik, J. R.

    2013-06-25

    The Savannah River National Laboratory (SRNL) accepted a technical task request (TTR) from Waste Solidification Engineering to perform simulant tests to support the qualification of Sludge Batch 8 (SB8) and to develop the flowsheet for SB8 in the Defense Waste Processing Facility (DWPF). These efforts pertained to the DWPF Chemical Process Cell (CPC). Separate studies were conducted for frit development and glass properties (including REDOX). The SRNL CPC effort had two primary phases divided by the decision to drop Tank 12 from the SB8 constituents. This report focuses on the second phase with SB8 compositions that do not contain the Tank 12 piece. A separate report will document the initial phase of SB8 testing that included Tank 12. The second phase of SB8 studies consisted of two sets of CPC studies. The first study involved CPC testing of an SB8 simulant for Tank 51 to support the CPC demonstration of the washed Tank 51 qualification sample in the SRNL Shielded Cells facility. SB8-Tank 51 was a high iron-low aluminum waste with fairly high mercury and moderate noble metal concentrations. Tank 51 was ultimately washed to about 1.5 M sodium which is the highest wash endpoint since SB3-Tank 51. This study included three simulations of the DWPF Sludge Receipt and Adjustment Tank (SRAT) cycle and Slurry Mix Evaporator (SME) cycle with the sludge-only flowsheet at nominal DWPF processing conditions and three different acid stoichiometries. These runs produced a set of recommendations that were used to guide the successful SRNL qualification SRAT/SME demonstration with actual Tank 51 washed waste. The second study involved five SRAT/SME runs with SB8-Tank 40 simulant. Four of the runs were designed to define the acid requirements for sludge-only processing in DWPF with respect to nitrite destruction and hydrogen generation. The fifth run was an intermediate acid stoichiometry demonstration of the coupled flowsheet for SB8. These runs produced a set of processing

  18. Bayesian Techniques for Comparing Time-dependent GRMHD Simulations to Variable Event Horizon Telescope Observations

    Science.gov (United States)

    Kim, Junhan; Marrone, Daniel P.; Chan, Chi-Kwan; Medeiros, Lia; Özel, Feryal; Psaltis, Dimitrios

    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*.

  19. Hospital occupancy and discharge strategies: a simulation-based study.

    Science.gov (United States)

    Qin, Shaowen; Thompson, Campbell; Bogomolov, Tim; Ward, Dale; Hakendorf, Paul

    2017-08-01

    Increasing demand for hospital services has resulted in more arrivals to emergency department (ED), increased admissions, and, quite often, access block and ED congestion, along with patients' dissatisfaction. Cost constraints limit an increase in the number of hospital beds, so alternative solutions need to be explored. To propose and test different discharge strategies, which, potentially, could reduce occupancy rates in the hospital, thereby improving patient flow and minimising frequency and duration of congestion episodes. We used a simulation approach using HESMAD (Hospital Event Simulation Model: Arrivals to Discharge) - a sophisticated simulation model capturing patient flow through a large Australian hospital from arrival at ED to discharge. A set of simulation experiments with a range of proposed discharge strategies was carried out. The results were tabulated, analysed and compared using common hospital occupancy indicators. Simulation results demonstrated that it is possible to reduce significantly the number of days when a hospital runs above its base bed capacity. In our case study, this reduction was from 281.5 to 22.8 days in the best scenario, and reductions within the above range under other scenarios considered. Some relatively simple strategies, such as 24-h discharge or discharge/relocation of long-staying patients, can significantly reduce overcrowding and improve hospital occupancy rates. Shortening administrative and/or some treatment processes have a smaller effect, although the latter could be easier to implement. © 2017 Royal Australasian College of Physicians.

  20. Comparative evaluation of photon cross section libraries for materials of interest in PET Monte Carlo simulations

    CERN Document Server

    Zaidi, H

    1999-01-01

    the many applications of Monte Carlo modelling in nuclear medicine imaging make it desirable to increase the accuracy and computational speed of Monte Carlo codes. The accuracy of Monte Carlo simulations strongly depends on the accuracy in the probability functions and thus on the cross section libraries used for photon transport calculations. A comparison between different photon cross section libraries and parametrizations implemented in Monte Carlo simulation packages developed for positron emission tomography and the most recent Evaluated Photon Data Library (EPDL97) developed by the Lawrence Livermore National Laboratory was performed for several human tissues and common detector materials for energies from 1 keV to 1 MeV. Different photon cross section libraries and parametrizations show quite large variations as compared to the EPDL97 coefficients. This latter library is more accurate and was carefully designed in the form of look-up tables providing efficient data storage, access, and management. Toge...

  1. Comparing two methods of simulating mirco-scale viscous flows in a porous channel

    Science.gov (United States)

    Gao, Hui; Han, Jie; Jin, Yan; Wang, Lian-Ping

    2007-11-01

    Water flows in natural soil porous media are important to colloid-facilitated transport of contaminants and other phenomena with groundwater as the carrier. The 3D micro-scale flow is complicated due to the complex geometry. The transport and deposition of colloids in such flows are affected by several physical and chemical forces involved. In this talk, we first compare two methods of simulating viscous flows in both 2D and 3D channels filled with glass-bead particles. The first method is Physalis developed by Prosperetti's group, at Johns Hopkins, based on solving the Navier-Stokes equation using a combination of numerical solution and local analytical Stokes flow representation. The second method is a meso-scale approach by solving a lattice Boltzmann equation. Specific implementation issues will be discussed. The two methods yield almost identical flows. Preliminary simulation results as well as parallel experimental results on colloid deposition in the porous channel will also be presented.

  2. Comparing Shape and Texture Features for Pattern Recognition in Simulation Data

    Energy Technology Data Exchange (ETDEWEB)

    Newsam, S; Kamath, C

    2004-12-10

    Shape and texture features have been used for some time for pattern recognition in datasets such as remote sensed imagery, medical imagery, photographs, etc. In this paper, we investigate shape and texture features for pattern recognition in simulation data. In particular, we explore which features are suitable for characterizing regions of interest in images resulting from fluid mixing simulations. Three texture features--gray level co-occurrence matrices, wavelets, and Gabor filters--and two shape features--geometric moments and the angular radial transform--are compared. The features are evaluated using a similarity retrieval framework. Our preliminary results indicate that Gabor filters perform the best among the texture features and the angular radial transform performs the best among the shape features. The feature which performs the best overall is dependent on how the groundtruth dataset is created.

  3. Simulation study of plane motion of air cushion vehicle

    Institute of Scientific and Technical Information of China (English)

    ZHAO Shu-qin; SHI Xiao-cheng; SHI Yi-long; BIAN Xin-qian

    2003-01-01

    This research is on horizontal plane motion equations of Air Cushion Vehicle (ACV) and its simulation. To investigate this, a lot of simulation study including ACV's voyage and turning performance has been done. It was found that the voyage simulation results were accorded with ACV own characteristic and turning simulation results were accorded with USA ACV's movement characteristic basically.

  4. Simulation study of plane motion of air cushion vehicle

    Science.gov (United States)

    Zhao, Shu-Qin; Shi, Xiao-Cheng; Shi, Yi-Long; Bian, Xin-Qian

    2003-12-01

    This research is on horizontal plane motion equations of Air Cushion Vehicle (ACV) and its simulation. To investigate this, a lot of simulation study including ACV’s voyage and turning performance has been done. It was found that the voyage simulation results were accorded with ACV own characteristic and turning simulation results were accorded with USA ACV’s movement characteristic basically.

  5. North Pacific Mesoscale Coupled Air-Ocean Simulations Compared with Observations

    Energy Technology Data Exchange (ETDEWEB)

    Koracin, Darko; Cerovecki, Ivana; Vellore, Ramesh; Mejia, John; Hatchett, Benjamin; McCord, Travis; McLean, Julie; Dorman, Clive

    2013-04-11

    Executive summary The main objective of the study was to investigate atmospheric and ocean interaction processes in the western Pacific and, in particular, effects of significant ocean heat loss in the Kuroshio and Kuroshio Extension regions on the lower and upper atmosphere. It is yet to be determined how significant are these processes are on climate scales. The understanding of these processes led us also to development of the methodology of coupling the Weather and Research Forecasting model with the Parallel Ocean Program model for western Pacific regional weather and climate simulations. We tested NCAR-developed research software Coupler 7 for coupling of the WRF and POP models and assessed its usability for regional-scale applications. We completed test simulations using the Coupler 7 framework, but implemented a standard WRF model code with options for both one- and two-way mode coupling. This type of coupling will allow us to seamlessly incorporate new WRF updates and versions in the future. We also performed a long-term WRF simulation (15 years) covering the entire North Pacific as well as high-resolution simulations of a case study which included extreme ocean heat losses in the Kuroshio and Kuroshio Extension regions. Since the extreme ocean heat loss occurs during winter cold air outbreaks (CAO), we simulated and analyzed a case study of a severe CAO event in January 2000 in detail. We found that the ocean heat loss induced by CAOs is amplified by additional advection from mesocyclones forming on the southern part of the Japan Sea. Large scale synoptic patterns with anomalously strong anticyclone over Siberia and Mongolia, deep Aleutian Low, and the Pacific subtropical ridge are a crucial setup for the CAO. It was found that the onset of the CAO is related to the breaking of atmospheric Rossby waves and vertical transport of vorticity that facilitates meridional advection. The study also indicates that intrinsic parameterization of the surface fluxes

  6. Theoretical studies of lipid bilayer electroporation using molecular dynamics simulations

    Science.gov (United States)

    Levine, Zachary Alan

    system where lipids can become damaged or severely impacted from interacting with reactive oxygen species, and these events become more frequent with age. The results are then compared to experiments where we show agreement between our simulations, theoretical models, and experiments with peroxidized cells in our lab. In Chapter 3 I outline a set of unique metrics which can be used to quantitatively measure the life cycle of a discrete electropore for the first time, across multiple lipid species, and I compare these results to analytical models where we find good agreement with theory. In Chapter 4 I use the life cycle of an electropore as a tool to measure the effects of electrolyte and lipid headgroup charge on electroporation compared to electrolyte-free and zwitterionic systems, in addition to presenting ion binding isotherms to determine the validity of our simulated electrolyte models. Chapters 5 and 6 focus on the roles of water and lipid respectively on electroporation using simplified water:vacuum systems, osmotic swelling simulations, systems at varying temperature, and systems where we successfully modulated the electropore radius using customized time-dependent electric fields. I conclude this dissertation with a brief summary of these studies followed by a short outlook on the future of electroporation simulations as a whole.

  7. Comparative evaluation of two sediment tracers in a rainfall simulation experiment

    Science.gov (United States)

    Strauss, Peter; Guzman, Gema; Mentler, Axel

    2015-04-01

    The use of sediment tracers tries to contribute to solving problems of traditional soil erosion measurements such as allocation of erosional and depositional areas. A number of different tracing approaches have already been established however, as none of available techniques are able to fully satisfy all the requirements for being an ideal tracer the search for alternative methods continues. Clays tagged with quaternary ammonium compounds are widely used in industry and are easy to incorporate into soils for sediment tracing experiments. To explore the potential of these clays a laboratory experiment was carried out in order to characterize their behaviour as compared to the well-established sediment tracer magnetic iron oxide. The experiment consisted of a simulated rainfall event of 60 mm/h in a box laboratory flume divided in two ridge-furrow subplots (200 x 57 cm). In order to evaluate transport and redistribution of soil from the ridges to the furrow and to measure the dynamic behaviour of the tracers during the rainfall a dense grid of soil samples was taken before and after the experiment (140 samples in total). Runoff and sediment were collected and all samples were analysed for both tracers. Results indicate the general suitability of organophilic clays to monitor soil redistribution by water erosion. The average relative contributions from shoulders and furrow to total sediment export determined by both tracers were similar and indicated a higher contribution from ridges. A key advantage of using organophilic clays is that the detection limit of organophilic clays is extremely low and the background concentration is zero. Despite the inherent differences between both tracers such as way of bounding, sediment enrichment or analytical technique, this experimental comparison of an established and more novel tracer method underscores the potential suitability of the latter for soil erosion studies.

  8. Kinematics Comparative Study of Two Overconstrained Parallel Manipulators

    Directory of Open Access Journals (Sweden)

    Qiang Yan

    2016-01-01

    Full Text Available A comparison study of kinematics characteristics of two overconstrained 2-RPU&SPR parallel manipulators (PMs is introduced in this paper. The two 2-RPU&SPR PMs have the same kinematics properties in terms of one translational degree of freedom (DOF and two rotational DOFs kinematics outputs. But there are some differences between the two PMs as far as joints distribution is concerned, leading to the differences in respect of workspace and dexterity of the two PMs. Firstly, based on screw theory, the structural characteristics and DOFs of the two PMs are analyzed. Secondly, the inverse and forward displacements problems for the two PMs are formulated by analytic formulae. Some numerical examples are simulated by software. Thirdly, based on algorithm for the direct displacement solution, the workspace characteristics of the two PMs are analyzed and compared. Then, the Jacobian matrices of the mechanisms are formulated. Based on the Jacobian matrices, the dexterities of the two PMs are established and compared. Finally, according to the comparisons of the properties between the two PMs, some useful conclusions are provided.

  9. Comparing Subspace Methods for Closed Loop Subspace System Identification by Monte Carlo Simulations

    Directory of Open Access Journals (Sweden)

    David Di Ruscio

    2009-10-01

    Full Text Available A novel promising bootstrap subspace system identification algorithm for both open and closed loop systems is presented. An outline of the SSARX algorithm by Jansson (2003 is given and a modified SSARX algorithm is presented. Some methods which are consistent for closed loop subspace system identification presented in the literature are discussed and compared to a recently published subspace algorithm which works for both open as well as for closed loop data, i.e., the DSR_e algorithm as well as the bootstrap method. Experimental comparisons are performed by Monte Carlo simulations.

  10. Comparing Two Numerical Models in Simulating Hydrodynamics and Sediment Transport at a Dual Inlet System, West-Central Florida

    Science.gov (United States)

    2015-05-15

    1 COMPARING TWO NUMERICAL MODELS IN SIMULATING HYDRODYNAMICS AND SEDIMENT TRANSPORT AT A DUAL INLET SYSTEM, WEST-CENTRAL FLORIDA PING WANG1...numerical modeling systems, CMS and DELFT3D, in simulating the hydrodynamic and sediment transport processes. The model results are compared with...Introduction Simulating complex fields of wave, current, sediment transport , and morphology change in the vicinity of tidal inlets is a

  11. Experimental study and numerical simulation of evacuation from a dormitory

    Science.gov (United States)

    Lei, Wenjun; Li, Angui; Gao, Ran; Zhou, Ning; Mei, Sen; Tian, Zhenguo

    2012-11-01

    The evacuation process of students from a dormitory is investigated by both experiment and modeling. We investigate the video record of pedestrian movement in a dormitory, and find some typical characteristics of evacuation, including continuous pedestrian flow, mass behavior and so on. Based on the experimental observation, we found that simulation results considering pre-movement time are closer to the experimental results. With the model considering pre-movement time, we simulate the evacuation process and compare the simulation results with the experimental results, and find that they agree with each other closely. The crowd massing phenomenon is conducted in this paper. It is found that different crowd massing phenomena will emerge due to different desired velocities. The crowd massing phenomenon could be more serious with the increase of the desired velocity. In this study, we also found the faster-is-slower effect. When the positive effect produced by increasing the desired velocity is not sufficient for making up for its negative effect, the phenomenon of the greater the desired velocity the longer the time required for evacuation will emerge. From the video record, it can be observed that the mass behavior is obvious during the evacuation process. And the mass phenomenon could also be found in simulation. The results obtained from our study are also suitable to all these buildings in which both living and resting areas occupy the majority space, such as dormitories, residential buildings, hotels (restaurants) and so on.

  12. Comparing the model-simulated global warming signal to observations using empirical estimates of unforced noise.

    Science.gov (United States)

    Brown, Patrick T; Li, Wenhong; Cordero, Eugene C; Mauget, Steven A

    2015-04-21

    The comparison of observed global mean surface air temperature (GMT) change to the mean change simulated by climate models has received much public and scientific attention. For a given global warming signal produced by a climate model ensemble, there exists an envelope of GMT values representing the range of possible unforced states of the climate system (the Envelope of Unforced Noise; EUN). Typically, the EUN is derived from climate models themselves, but climate models might not accurately simulate the correct characteristics of unforced GMT variability. Here, we simulate a new, empirical, EUN that is based on instrumental and reconstructed surface temperature records. We compare the forced GMT signal produced by climate models to observations while noting the range of GMT values provided by the empirical EUN. We find that the empirical EUN is wide enough so that the interdecadal variability in the rate of global warming over the 20(th) century does not necessarily require corresponding variability in the rate-of-increase of the forced signal. The empirical EUN also indicates that the reduced GMT warming over the past decade or so is still consistent with a middle emission scenario's forced signal, but is likely inconsistent with the steepest emission scenario's forced signal.

  13. Nonlinear Simulation Studies of Tokamaks and STs

    Energy Technology Data Exchange (ETDEWEB)

    W. Park; J. Breslau; J. Chen; G.Y. Fu; S.C. Jardin; S. Klasky; J. Menard; A. Pletzer; B.C. Stratton; D. Stutman; H.R. Strauss; L.E. Sugiyama

    2003-07-07

    The multilevel physics, massively parallel plasma simulation code, M3D, has been used to study spherical tori (STs) and tokamaks. The magnitude of outboard shift of density profiles relative to electron temperature profiles seen in NSTX [National Spherical Torus Experiment] under strong toroidal flow is explained. Internal reconnection events in ST discharges can be classified depending on the crash mechanism, just as in tokamak discharges; a sawtooth crash, disruption due to stochasticity, or high-beta disruption. Toroidal shear flow can reduce linear growth of internal kink. It has a strong stabilizing effect nonlinearly and causes mode saturation if its profile is maintained, e.g., through a fast momentum source. Normally, however, the flow profile itself flattens during the reconnection process, allowing a complete reconnection to occur. In some cases, the maximum density and pressure spontaneously occur inside the island and cause mode saturation. Gyrokinetic hot particle/MHD hybrid studies of NSTX show the effects of fluid compression on a fast-ion-driven n = 1 mode. MHD studies of recent tokamak experiments with a central current hole indicate that the current clamping is due to sawtooth-like crashes, but with n = 0.

  14. A Comparative Numerical Study on GEM, MHSP and MSGC

    CERN Document Server

    Bhattacharya, Purba; Majumdar, Nayana; Bhattacharya, Sudeb

    2012-01-01

    In this work we have concentrated on the detailed understanding of the physical processes occurring in those variants of Micro Pattern Gas Detectors that share micro hole and micro strip geometry. Here, we will present numerical results obtained using the simulation framework, recently developed especially for MPGDs that combines packages such as GARFIELD, neBEM, MAGBOLTZ and HEED. Using this framework, we have estimated quantitatively and qualitatively, some of the important and fundamental characteristics of these MPGDs such as detector gain, transparency, efficiency and their operational dependence on different detector parameters. The estimates have been compared with available experimental and simulation data and an encouraging agreement has been observed.

  15. A Comparative Study between Two Control Strategies for Matrix Converter

    Directory of Open Access Journals (Sweden)

    BENDIABDELLAH, A.

    2009-06-01

    Full Text Available The authors compare two control strategies for direct AC-AC matrix converters; namely the Venturini method and the scalar strategy control method. The performance comparison of the two strategies is made under unbalanced distorted torque, rotor speed and stator current operation. The simulation of the three-phase matrix converter feeding an induction motor was accomplished by means of the Matlab/Simulink software. This package makes it possible to simulate the dynamic systems in a simple way and in graphic environment.

  16. A comparative study of RNA-seq analysis strategies.

    Science.gov (United States)

    Jänes, Jürgen; Hu, Fengyuan; Lewin, Alexandra; Turro, Ernest

    2015-11-01

    Three principal approaches have been proposed for inferring the set of transcripts expressed in RNA samples using RNA-seq. The simplest approach uses curated annotations, which assumes the transcripts in a sample are a subset of the transcripts listed in a curated database. A more ambitious method involves aligning reads to a reference genome and using the alignments to infer the transcript structures, possibly with the aid of a curated transcript database. The most challenging approach is to assemble reads into putative transcripts de novo without the aid of reference data. We have systematically assessed the properties of these three approaches through a simulation study. We have found that the sensitivity of computational transcript set estimation is severely limited. Computational approaches (both genome-guided and de novo assembly) produce a large number of artefacts, which are assigned large expression estimates and absorb a substantial proportion of the signal when performing expression analysis. The approach using curated annotations shows good expression correlation even when the annotations are incomplete. Furthermore, any incorrect transcripts present in a curated set do not absorb much signal, so it is preferable to have a curation set with high sensitivity than high precision. Software to simulate transcript sets, expression values and sequence reads under a wider range of parameter values and to compare sensitivity, precision and signal-to-noise ratios of different methods is freely available online (https://github.com/boboppie/RSSS) and can be expanded by interested parties to include methods other than the exemplars presented in this article. © The Author 2015. Published by Oxford University Press.

  17. Comparing a simple methodology to evaluate hydrodynamic parameters with rainfall simulation experiments

    Science.gov (United States)

    Di Prima, Simone; Bagarello, Vincenzo; Bautista, Inmaculada; Burguet, Maria; Cerdà, Artemi; Iovino, Massimo; Prosdocimi, Massimo

    2016-04-01

    Studying soil hydraulic properties is necessary for interpreting and simulating many hydrological processes having environmental and economic importance, such as rainfall partition into infiltration and runoff. The saturated hydraulic conductivity, Ks, exerts a dominating influence on the partitioning of rainfall in vertical and lateral flow paths. Therefore, estimates of Ks are essential for describing and modeling hydrological processes (Zimmermann et al., 2013). According to several investigations, Ks data collected by ponded infiltration tests could be expected to be unusable for interpreting field hydrological processes, and particularly infiltration. In fact, infiltration measured by ponding give us information about the soil maximum or potential infiltration rate (Cerdà, 1996). Moreover, especially for the hydrodynamic parameters, many replicated measurements have to be carried out to characterize an area of interest since they are known to vary widely both in space and time (Logsdon and Jaynes, 1996; Prieksat et al., 1994). Therefore, the technique to be applied at the near point scale should be simple and rapid. Bagarello et al. (2014) and Alagna et al. (2015) suggested that the Ks values determined by an infiltration experiment carried applying water at a relatively large distance from the soil surface could be more appropriate than those obtained with a low height of water pouring to explain surface runoff generation phenomena during intense rainfall events. These authors used the Beerkan Estimation of Soil Transfer parameters (BEST) procedure for complete soil hydraulic characterization (Lassabatère et al., 2006) to analyze the field infiltration experiment. This methodology, combining low and high height of water pouring, seems appropriate to test the effect of intense and prolonged rainfall events on the hydraulic characteristics of the surface soil layer. In fact, an intense and prolonged rainfall event has a perturbing effect on the soil surface

  18. SIMULATION STUDY ON AIRBORNE SAR ECHO SIGNAL

    Institute of Scientific and Technical Information of China (English)

    Bao Houbing; Liu Zhao

    2004-01-01

    Through analyzing the influence on echo signal by factors of kinematical parameters of airborne SAR platform and radar antenna direction, this letter, on the basis of classical SAR echo signal analogue algorithm, puts forward certain airborne SAR echo signal analogue algorithm of distance directional frequency domain pulse coherent accumulation, and goes through simulation. The simulation results have proved the effectiveness of this algorithm.

  19. Simulation Higher Order Language Requirements Study.

    Science.gov (United States)

    Goodenough, John B.; Braun, Christine L.

    The definitions provided for high order language (HOL) requirements for programming flight training simulators are based on the analysis of programs written for a variety of simulators. Examples drawn from these programs are used to justify the need for certain HOL capabilities. A description of the general structure and organization of the…

  20. Quench Simulation Studies: Program documentation of SPQR

    CERN Document Server

    Sonnemann, F

    2001-01-01

    Quench experiments are being performed on prototypes of the superconducting magnets and busbars to determine the adequate design and protection. Many tests can only be understood correctly with the help of quench simulations that model the thermo-hydraulic and electrodynamic processes during a quench. In some cases simulations are the only method to scale the experimental results of prototype measurements to match the situation of quenching superconducting elements in the LHC. This note introduces the theoretical quench model and the use of the simulation program SPQR (Simulation Program for Quench Research), which has been developed to compute the quench process in superconducting magnets and busbars. The model approximates the heat balance equation with the finite difference method including the temperature dependence of the material parameters. SPQR allows the simulation of longitudinal quench propagation along a superconducting cable, the transverse propagation between adjacent conductors, heat transfer i...

  1. Simulation study of pixel detector charge digitization

    Science.gov (United States)

    Wang, Fuyue; Nachman, Benjamin; Sciveres, Maurice; Lawrence Berkeley National Laboratory Team

    2017-01-01

    Reconstruction of tracks from nearly overlapping particles, called Tracking in Dense Environments (TIDE), is an increasingly important component of many physics analyses at the Large Hadron Collider as signatures involving highly boosted jets are investigated. TIDE makes use of the charge distribution inside a pixel cluster to resolve tracks that share one of more of their pixel detector hits. In practice, the pixel charge is discretized using the Time-over-Threshold (ToT) technique. More charge information is better for discrimination, but more challenging for designing and operating the detector. A model of the silicon pixels has been developed in order to study the impact of the precision of the digitized charge distribution on distinguishing multi-particle clusters. The output of the GEANT4-based simulation is used to train neutral networks that predict the multiplicity and location of particles depositing energy inside one cluster of pixels. By studying the multi-particle cluster identification efficiency and position resolution, we quantify the trade-off between the number of ToT bits and low-level tracking inputs. As both ATLAS and CMS are designing upgraded detectors, this work provides guidance for the pixel module designs to meet TIDE needs. Work funded by the China Scholarship Council and the Office of High Energy Physics of the U.S. Department of Energy under contract DE-AC02-05CH11231.

  2. Magnetic Nozzle Simulation Studies for Electric Propulsion

    Science.gov (United States)

    Tarditi, Alfonso

    2010-11-01

    Electric Propulsion has recently re-gained interest as one of the key technologies to enable NASA's long-range space missions. Options are being considered also in the field of aneutronic fusion propulsion for high-power electric thrusters. To support these goals the study of the exhaust jet in a plasma thruster acquires a critical importance because the need of high-efficiency generation of thrust. A model of the plasma exhaust has been developed with the 3D magneto-fluid NIMROD code [1] to study the physics of the plasma detachment in correlation with experimentally relevant configurations. The simulations show the role of the plasma diamagnetism and of the magnetic reconnection process in the formation of a detached plasma. Furthermore, in direct fusion-propulsion concepts high-energy (MeV range) fusion products have to be efficiently converted into a slower and denser plasma jet (with specific impulse down to few 1000's seconds, for realistic missions in the Solar System). For this purpose, a two-stage conversion process is being modeled where high-energy ions are non-adiabatically injected and confined into a magnetic duct leading to the magnetic nozzle, transferring most of their energy into their gyro-motion and drifting at slower speed along with the plasma propellant. The propellant acquires then thermal energy that gets converted into the direction of thrust by the magnetic nozzle. [1] C. R. Sovinec et al., J. Comput. Phys. 195, 355 (2004).

  3. Educational Objectives Of Different Laboratory Types: A Comparative Study

    CERN Document Server

    Elawady, Yasser H

    2009-01-01

    Laboratory based courses play a critical role in scientific education. Automation is changing the nature of the laboratories, and there is a long running debate about the value of hands on versus simulated and remote laboratories. The remote lab technology has brought a significant improvement in communication within the Academic community and has improved students learning experiences. There are different educational objectives as criteria for judging the laboratories: Hands on advocates emphasize design skills, while remote lab advocates focus on conceptual understanding. Remote laboratories offer all the advantages of the new technology, but are often a poor replacement for real laboratory work. Remote laboratories are similar to simulation techniques in that they require minimal space and time, because the experiments can be rapidly configured and run over the Internet [Web]. But unlike simulations, they provide real data. This paper presents a comparative analysis for the educational objectives of the th...

  4. Simulation study of the high intensity S-Band photoinjector

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiongwei; Nakajima, Kazuhisa [High Energy Accelerator Research Organization, Tsukuba, Ibaraki (Japan)

    2001-10-01

    In this paper, we report the results of simulation study of the high intensity S-Band photoinjector. The aim of the simulation study is to transport high bunch charge with low emittance evolution. The simulation result shows that 7nC bunch with rms emittance 22.3 {pi} mm mrad can be outputted at the exit of photoinjector. (author)

  5. Comparing FDTD and Ray-Tracing Models in Numerical Simulation of HgCdTe LWIR Photodetectors

    Science.gov (United States)

    Vallone, Marco; Goano, Michele; Bertazzi, Francesco; Ghione, Giovanni; Schirmacher, Wilhelm; Hanna, Stefan; Figgemeier, Heinrich

    2016-09-01

    We present a simulation study of HgCdTe-based long-wavelength infrared detectors, focusing on methodological comparisons between the finite-difference time-domain (FDTD) and ray-tracing optical models. We performed three-dimensional simulations to determine the absorbed photon density distributions and the corresponding photocurrent and quantum efficiency spectra of isolated n-on- p uniform-composition pixels, systematically comparing the results obtained with FDTD and ray tracing. Since ray tracing is a classical optics approach, unable to describe interference effects, its applicability has been found to be strongly wavelength dependent, especially when reflections from metallic layers are relevant. Interesting cavity effects around the material cutoff wavelength are described, and the cases where ray tracing can be considered a viable approximation are discussed.

  6. Comparative Study of Rice Morphogenesis wit Different Cultivation Methods

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    [Objective] The aim of this study was to compare the morphological char- acteristics of rice (Oryza sativa L.) with different cultivation methods and investigate the dynamics of organ growth and development characteristics of different rice culti- vars. [Method] Based on continuous field observation and destructive sampling over a growing season, detailed organ morphological data were obtained including leaf length, node number, plant height, tiller number, leaf angle, leaf area and specific leaf weight, to compare organ morphological differences among 4 rice cultivars of Baidao (indica), Jinnanfeng (japonica), 9325 (japonica) and 9915 (japonica) with 3 cultivation methods of field planting in Weigang, pot planting in Weigang, and field planting in Jiangpu. [Result] Maximum leaf length of each node gradually increased at the early growth stage and decreased at the later growth stage, the relationship between maximum leaf length and node position can be described by the equations y=a,,-~ and y=ax+b; node number, growth duration, leaf length and plant height of pot planting rice in Weigang were smaller than that of the other two field planting meth- ods; the relationship between plant height and sunshine duration, plant height and GDD (growing degree days) can be described by the equation y=ax+b, 19.23 ℃.d of GDD (≥10 ≥-d) and 8.12 h of sunshine duration were required to increase 1 cm of plant height; plant height, tiller number, and leaf area of Baidao were higher than that of the other 3 laponica rice cultivars, but the specific leaf weight and leaf angle were smaller. [Conclusion] Comparison of morphological characteristic differ- ences among rice cultivars is an important way to select water-saving and drought- tolerant rice varieties. In this study, the experimental results can be integrated into a rice functional-architectural model to simulate rice organ growth dynamics in a three- dimensional space, thereby providing reference for selecting water

  7. A Comparative Performance Analysis of Routing Protocols in MANET using NS3 Simulator

    Directory of Open Access Journals (Sweden)

    Rakesh Kumar Jha

    2015-03-01

    Full Text Available Due to frequent topology changes and routing overhead, selection of routing protocol in Mobile Ad-hoc Network (MANET is a great challenge. A design issue for an efficient and effective routing protocol is to achieve optimum values of performance parameters under network scenarios. There are various routing protocols available for MANET. This paper involves study of four routing protocols (Ad-hoc On Demand Distance Vector Routing, Optimized Link State Routing, Dynamic Source Routing and Distance Sequenced Distance Vector, and performance comparisons between these routing protocols on the basis of performance metrics (throughput, packet delivery ratio, Packet dropped, jitter and end to end delay measured after simulation of network with the help of NS3 Simulator.

  8. Practical studies on rockfall simulation by DDA

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    In this paper,simulations of real rockfall by discontinuous deformation analysis (DDA) are conducted.In the simulations,the energy losses of rockfall are categorized into three types,i.e.the loss by friction,the loss by collision,and the loss by vegetation.Modeling of the energy loss using absolute parameters is conducted by the DDA method.Moreover,in order to verify the applicability and validity of the proposed DDA,field tests on rockfall and corresponding simulations of rockfall tests by DDA are performe...

  9. Conducting Simulation Studies in the R Programming Environment.

    Science.gov (United States)

    Hallgren, Kevin A

    2013-10-12

    Simulation studies allow researchers to answer specific questions about data analysis, statistical power, and best-practices for obtaining accurate results in empirical research. Despite the benefits that simulation research can provide, many researchers are unfamiliar with available tools for conducting their own simulation studies. The use of simulation studies need not be restricted to researchers with advanced skills in statistics and computer programming, and such methods can be implemented by researchers with a variety of abilities and interests. The present paper provides an introduction to methods used for running simulation studies using the R statistical programming environment and is written for individuals with minimal experience running simulation studies or using R. The paper describes the rationale and benefits of using simulations and introduces R functions relevant for many simulation studies. Three examples illustrate different applications for simulation studies, including (a) the use of simulations to answer a novel question about statistical analysis, (b) the use of simulations to estimate statistical power, and (c) the use of simulations to obtain confidence intervals of parameter estimates through bootstrapping. Results and fully annotated syntax from these examples are provided.

  10. Experiment and Simulation Study on the Amorphous Silicon Photovoltaic Walls

    Directory of Open Access Journals (Sweden)

    Wenjie Zhang

    2014-01-01

    Full Text Available Based on comparative study on two amorphous silicon photovoltaic walls (a-Si PV walls, the temperature distribution and the instant power were tested; and with EnergyPlus software, similar models of the walls were built to simulate annual power generation and air conditioning load. On typical sunshine day, the corresponding position temperature of nonventilated PV wall was generally 0.5~1.5°C higher than that of ventilated one, while the power generation was 0.2%~0.4% lower, which was consistent with the simulation results with a difference of 0.41% in annual energy output. As simulation results, in summer, comparing the PV walls with normal wall, the heat per unit area of these two photovoltaic walls was 5.25 kWh/m2 (nonventilated and 0.67 kWh/m2 (ventilated higher, respectively. But in winter the heat loss of nonventilated one was smaller, while ventilated PV wall was similar to normal wall. To annual energy consumption of heating and cooling, the building with ventilated PV wall and normal wall was also similar but slightly better than nonventilated one. Therefore, it is inferred that, at low latitudes, such as Zhuhai, China, air gap ventilation is suitable, while the length to thickness ratio of the air gap needs to be taken into account.

  11. What Do We Compare When We Compare Religions? Philosophical Remarks on the Psychology of Studying Comparative Religion Abroad

    Science.gov (United States)

    Irvine, Andrew

    2015-01-01

    The issue of comparison is a vexing one in religious and theological studies, not least for teachers of comparative religion in study abroad settings. We try to make familiar ideas fresh and strange, in settings where students may find it hard not to take "fresh" and "strange" as signs of existential threat. The author explores…

  12. A Simulation Study of Paced TCP

    Science.gov (United States)

    Kulik, Joanna; Coulter, Robert; Rockwell, Dennis; Partridge, Craig

    2000-01-01

    In this paper, we study the performance of paced TCP, a modified version of TCP designed especially for high delay- bandwidth networks. In typical networks, TCP optimizes its send-rate by transmitting increasingly large bursts, or windows, of packets, one burst per round-trip time, until it reaches a maximum window-size, which corresponds to the full capacity of the network. In a network with a high delay-bandwidth product, however, Transmission Control Protocol's (TCPs) maximum window-size may be larger than the queue size of the intermediate routers, and routers will begin to drop packets as soon as the windows become too large for the router queues. The TCP sender then concludes that the bottleneck capacity of the network has been reached, and it limits its send-rate accordingly. Partridge proposed paced TCP as a means of solving the problem of queueing bottlenecks. A sender using paced TCP would release packets in multiple, small bursts during a round-trip time in which ordinary TCP would release a single, large burst of packets. This approach allows the sender to increase its send-rate to the maximum window size without encountering queueing bottlenecks. This paper describes the performance of paced TCP in a simulated network and discusses implementation details that can affect the performance of paced TCP.

  13. Simulation studies for multichannel active vibration control

    Science.gov (United States)

    Prakash, Shashikala; Balasubramaniam, R.; Praseetha, K. K.

    2003-10-01

    Traditional approach to vibration control uses passive techniques, which are relatively large, costly and ineffective at low frequencies. Active Vibration Control (AVC) is used to overcome these problems & in AVC additional sources (secondary) are used to cancel vibration from primary source based on the principle of superposition theorem Since the characteristics of the vibration source and environment are time varying, the AVC system must be adaptive. Adaptive systems have the ability to track time varying disturbances and provide optimal control over a much broader range of conditions than conventional fixed control systems. In multi channel AVC vibration fields in large dimensions are controlled & is more complicated. Therefore to actively control low frequency vibrations on large structures, multi channel AVC requires a control system that uses multiple secondary sources to control the vibration field simultaneously at multiple error sensor locations. The error criterion that can be directly measured is the sum of squares of outputs of number of sensors. The adaptive algorithm is designed to minimize this & the algorithm implemented is the "Multiple error LMS algorithm." The best known applications of multiple channel FXLMS algorithm is in real time AVC and system identification. More wider applications are in the control of propeller induced noise in flight cabin interiors. In the present paper the results of simulation studies carried out in MATLAB as well as on TMS320C32 DSP processor will be brought out for a two-channel case.

  14. Aspects of simulation for rectification studies

    Science.gov (United States)

    Mikhail, E. M.; Paderes, F. D., Jr.

    1983-01-01

    The use of mathematical models and simulation is suggested as an aid to rectification. An outline of the factors affecting rectification accuracy is presented along with methods and approaches used for rectifications.

  15. Study Development of the Cardiac Computer Simulations

    Institute of Scientific and Technical Information of China (English)

    VOLKERHellemanns; ZHANGHong; SEKOUSingare; ZHANGZhen-xi; KONGXiang-yun

    2004-01-01

    The technique of computer simulations is a very efficient method in investigating mechanisms of many diseases. This paper reviews how the simulations of the human heart started as a simple mathematical models in the past and developed to the point where genetic information is needed to do suitable work like finding out new medicaments against heart diseases. Also the Influence of the development of computer performance in the future as well as the data presentation is described.

  16. Robust adaptive control of underwater vehicles: A comparative study

    Directory of Open Access Journals (Sweden)

    Thor I. Fossen

    1996-01-01

    Full Text Available Robust adaptive control of underwater vehicles in 6 DOF is analysed in the context of measurement noise. The performance of the adaptive control laws of Sadegh and Harowitz (1990 and Slotine and Benedetto (1990 are compared. Both these schemes require that all states are measured, that is the velocities and positions in surge, sway, heave, roll, pitch and yaw. However, for underwater vehicles it is difficult to measure the linear velocities whereas angular velocity measurements can be obtained by using a 3 axes angular rate sensor. This problem is addressed by designing a nonlinear observer for linear velocity state estimation. The proposed observer requires that the position and the attitude are measured, e.g. by using a hydroacoustic positioning system for linear positions, two gyros for roll and pitch and a compass for yaw. In addition angular rate measurements will be assumed available from a 3-axes rate sensor or a state estimator. It is also assumed that the measurement rate is limited to 2 Hz for all the sensors. Simulation studies with a 3 DOF AUV model are used to demonstrate the convergence and robustness of the adaptive control laws and the velocity state observer.

  17. A framework for the comparative study of language.

    Science.gov (United States)

    Uriagereka, Juan; Reggia, James A; Wilkinson, Gerald S

    2013-07-18

    Comparative studies of language are difficult because few language precursors are recognized. In this paper we propose a framework for designing experiments that test for structural and semantic patterns indicative of simple or complex grammars as originally described by Chomsky. We argue that a key issue is whether animals can recognize full recursion, which is the hallmark of context-free grammar. We discuss limitations of recent experiments that have attempted to address this issue, and point out that experiments aimed at detecting patterns that follow a Fibonacci series have advantages over other artificial context-free grammars. We also argue that experiments using complex sequences of behaviors could, in principle, provide evidence for fully recursive thought. Some of these ideas could also be approached using artificial life simulations, which have the potential to reveal the types of evolutionary transitions that could occur over time. Because the framework we propose has specific memory and computational requirements, future experiments could target candidate genes with the goal of revealing the genetic underpinnings of complex cognition.

  18. ULF foreshock under radial IMF: THEMIS observations and global kinetic simulation Vlasiator results compared

    Science.gov (United States)

    Palmroth, Minna; Rami, Vainio; Archer, Martin; Hietala, Heli; Afanasiev, Alexandr; Kempf, Yann; Hoilijoki, Sanni; von Alfthan, Sebastian

    2015-04-01

    For decades, a certain type of ultra low frequency waves with a period of about 30 seconds have been observed in the Earth's quasi-parallel foreshock. These waves, with a wavelength of about an Earth radius, are compressive and propagate with an average angle of 20 degrees with respect of the interplanetary magnetic field (IMF). The latter property has caused trouble to scientists as the growth rate for the instability causing the waves is maximized along the magnetic field. So far, these waves have been characterized by single or multi-spacecraft methods and 2-dimensional hybrid-PIC simulations, which have not fully reproduced the wave properties. Vlasiator is a newly developed, global hybrid-Vlasov simulation, which solves the six-dimensional phase space utilising the Vlasov equation for protons, while electrons are a charge-neutralising fluid. The outcome of the simulation is a global reproduction of ion-scale physics in a holistic manner where the generation of physical features can be followed in time and their consequences can be quantitatively characterised. Vlasiator produces the ion distribution functions and the related kinetic physics in unprecedented detail, in the global scale magnetospheric scale with a resolution of a couple of hundred kilometres in the ordinary space and 20 km/s in the velocity space. We run Vlasiator under a radial IMF in five dimensions consisting of the three-dimensional velocity space embedded in the ecliptic plane. We observe the generation of the 30-second ULF waves, and characterize their evolution and physical properties in time. We compare the results both to THEMIS observations and to the quasi-linear theory. We find that Vlasiator reproduces the foreshock ULF waves in all reported observational aspects, i.e., they are of the observed size in wavelength and period, they are compressive and propagate obliquely to the IMF. In particular, we discuss the issues related to the long-standing question of oblique propagation.

  19. Planar Millimeter-Wave Antennas: A Comparative Study

    Directory of Open Access Journals (Sweden)

    K. Pitra

    2011-04-01

    Full Text Available The paper describes the design and the experimental verification of three types of wideband antennas. Attention is turned to the bow-tie antenna, the Vivaldi antenna and the spiral antenna designed for the operation at millimeter waves. Bandwidth, input impedance, gain, and directivity pattern are the investigated parameters. Antennas are compared considering computer simulations in CST Microwave Studio and measured data.

  20. Simulation Based Studies in Software Engineering: A Matter of Validity

    Directory of Open Access Journals (Sweden)

    Breno Bernard Nicolau de França

    2015-04-01

    Full Text Available Despite the possible lack of validity when compared with other science areas, Simulation-Based Studies (SBS in Software Engineering (SE have supported the achievement of some results in the field. However, as it happens with any other sort of experimental study, it is important to identify and deal with threats to validity aiming at increasing their strength and reinforcing results confidence. OBJECTIVE: To identify potential threats to SBS validity in SE and suggest ways to mitigate them. METHOD: To apply qualitative analysis in a dataset resulted from the aggregation of data from a quasi-systematic literature review combined with ad-hoc surveyed information regarding other science areas. RESULTS: The analysis of data extracted from 15 technical papers allowed the identification and classification of 28 different threats to validity concerned with SBS in SE according Cook and Campbell’s categories. Besides, 12 verification and validation procedures applicable to SBS were also analyzed and organized due to their ability to detect these threats to validity. These results were used to make available an improved set of guidelines regarding the planning and reporting of SBS in SE. CONCLUSIONS: Simulation based studies add different threats to validity when compared with traditional studies. They are not well observed and therefore, it is not easy to identify and mitigate all of them without explicit guidance, as the one depicted in this paper.

  1. Computer Simulation Studies in Condensed-Matter Physics XVII

    Science.gov (United States)

    Landau, D. P.; Lewis, S. P.; Schüttler, H.-B.

    This status report features the most recent developments in the field, spanning a wide range of topical areas in the computer simulation of condensed matter/materials physics. Both established and new topics are included, ranging from the statistical mechanics of classical magnetic spin models to electronic structure calculations, quantum simulations, and simulations of soft condensed matter. The book presents new physical results as well as novel methods of simulation and data analysis. Highlights of this volume include various aspects of non-equilibrium statistical mechanics, studies of properties of real materials using both classical model simulations and electronic structure calculations, and the use of computer simulations in teaching.

  2. Comparing particle-resolved simulation methods for moving particles in a viscous fluid

    Science.gov (United States)

    Wang, Lian-Ping; Gao, Hui; Luo, Li-Shi; Peng, Yan; Yeo, Kyong Min; Maxey, Martin R.

    2008-11-01

    In recent years, quite a few particle-resolved simulation methods have emerged for treating moving solid particles in a viscous fluid. A common advantageous feature shared by these methods is the use of a simple fixed mesh. The no-slip boundary condition on the surface of a particle is handled locally by a consistent coupling or interaction scheme. Here we examine four such methods: lattice Boltzmann equation (LBE) with interpolated bounce back scheme, LBE with immersed boundary method, a hybrid method (Physalis) developed by Prosperetti and co-workers, and a force-coupling method. Our main objective is to inter-compare these methods in terms of accuracy of the simulated flow field, force / torque, and computational efficiency. Two benchmark cases are used: a particle moving in a 3D Couette flow and a 3D flow induced by a spinning sphere at finite Reynolds number. The results are discussed in terms of flow Reynolds number and geometric parameters. We will also comment on the range of relevant physical parameters accessible in these methods.

  3. Filamentous Biopolymers on Surfaces: Atomic Force Microscopy Images Compared with Brownian Dynamics Simulation of Filament Deposition

    Science.gov (United States)

    Mücke, Norbert; Klenin, Konstantin; Kirmse, Robert; Bussiek, Malte; Herrmann, Harald; Hafner, Mathias; Langowski, Jörg

    2009-01-01

    Nanomechanical properties of filamentous biopolymers, such as the persistence length, may be determined from two-dimensional images of molecules immobilized on surfaces. For a single filament in solution, two principal adsorption scenarios are possible. Both scenarios depend primarly on the interaction strength between the filament and the support: i) For interactions in the range of the thermal energy, the filament can freely equilibrate on the surface during adsorption; ii) For interactions much stronger than the thermal energy, the filament will be captured by the surface without having equilibrated. Such a ‘trapping’ mechanism leads to more condensed filament images and hence to a smaller value for the apparent persistence length. To understand the capture mechanism in more detail we have performed Brownian dynamics simulations of relatively short filaments by taking the two extreme scenarios into account. We then compared these ‘ideal’ adsorption scenarios with observed images of immobilized vimentin intermediate filaments on different surfaces. We found a good agreement between the contours of the deposited vimentin filaments on mica (‘ideal’ trapping) and on glass (‘ideal’ equilibrated) with our simulations. Based on these data, we have developed a strategy to reliably extract the persistence length of short worm-like chain fragments or network forming filaments with unknown polymer-surface interactions. PMID:19888472

  4. Filamentous biopolymers on surfaces: atomic force microscopy images compared with Brownian dynamics simulation of filament deposition.

    Directory of Open Access Journals (Sweden)

    Norbert Mücke

    Full Text Available Nanomechanical properties of filamentous biopolymers, such as the persistence length, may be determined from two-dimensional images of molecules immobilized on surfaces. For a single filament in solution, two principal adsorption scenarios are possible. Both scenarios depend primarily on the interaction strength between the filament and the support: i For interactions in the range of the thermal energy, the filament can freely equilibrate on the surface during adsorption; ii For interactions much stronger than the thermal energy, the filament will be captured by the surface without having equilibrated. Such a 'trapping' mechanism leads to more condensed filament images and hence to a smaller value for the apparent persistence length. To understand the capture mechanism in more detail we have performed Brownian dynamics simulations of relatively short filaments by taking the two extreme scenarios into account. We then compared these 'ideal' adsorption scenarios with observed images of immobilized vimentin intermediate filaments on different surfaces. We found a good agreement between the contours of the deposited vimentin filaments on mica ('ideal' trapping and on glass ('ideal' equilibrated with our simulations. Based on these data, we have developed a strategy to reliably extract the persistence length of short worm-like chain fragments or network forming filaments with unknown polymer-surface interactions.

  5. Comparing the performance of 11 crop simulation models in predicting yield response to nitrogen fertilization

    DEFF Research Database (Denmark)

    Salo, T J; Palosuo, T; Kersebaum, K C

    2016-01-01

    , Finland. This is the largest standardized crop model inter-comparison under different levels of N supply to date. The models were calibrated using data from 2002 and 2008, of which 2008 included six N rates ranging from 0 to 150 kg N/ha. Calibration data consisted of weather, soil, phenology, leaf area...... index (LAI) and yield observations. The models were then tested against new data for 2009 and their performance was assessed and compared with both the two calibration years and the test year. For the calibration period, root mean square error between measurements and simulated grain dry matter yields...... mineralization as a function of soil temperature and moisture. Furthermore, specific weather event impacts such as low temperatures after emergence in 2009, tending to enhance tillering, and a high precipitation event just before harvest in 2008, causing possible yield penalties, were not captured by any...

  6. BARRED GALAXY PHOTOMETRY: COMPARING RESULTS FROM THE CANANEA SAMPLE WITH N-BODY SIMULATIONS

    Directory of Open Access Journals (Sweden)

    E. Athanassoula

    2009-01-01

    Full Text Available We compare the results of the photometrical analysis of barred galaxies with those of a similar analysis from N-body simulations. The photometry is for a sample of nine barred galaxies observed in the J and Ks bands with the CANICA near infrared (NIR camera at the 2.1 m telescope of the Observatorio Astrofisico Guillermo Haro (OAGH in Cananea, Sonora, Mexico. The comparison includes radial ellipticity pro les and surface brightness (density for the N-body galaxies pro les along the bar major and minor axes. We nd very good agreement, arguing that the exchange of angular momentum within the galaxy plays a determinant role in the evolution of barred galaxies.

  7. Comparative study of normal and branched alkane monolayer films adsorbed on a solid surface. I. Structure

    DEFF Research Database (Denmark)

    Enevoldsen, Ann Dorrit; Hansen, Flemming Yssing; Diama, A.

    2007-01-01

    The structure of a monolayer film of the branched alkane squalane (C30H62) adsorbed on graphite has been studied by neutron diffraction and molecular dynamics (MD) simulations and compared with a similar study of the n-alkane tetracosane (n-C24H52). Both molecules have 24 carbon atoms along their...

  8. Low-frequency waves at comet 67P/Churyumov-Gerasimenko. Observations compared to numerical simulations

    Science.gov (United States)

    Koenders, C.; Perschke, C.; Goetz, C.; Richter, I.; Motschmann, U.; Glassmeier, K. H.

    2016-10-01

    Context. A new type of low-frequency wave was detected by the magnetometer of the Rosetta Plasma Consortium at the comet during the initial months after the arrival of the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko. This large-amplitude, nearly continuous wave activity is observed in the frequency range from 30 mHz to 80 mHz where 40 mHz to 50 mHz is the dominant frequency. This type of low frequency is not closely related to the gyrofrequency of newborn cometary ions, which differs from previous wave activity observed in the interaction region of comets with the solar wind. Aims: This work aims to reveal a global view on the wave activity region using simulations of the comet-solar wind interaction region. Parameters, such as wavelength, propagation direction, and propagation patterns, are within the focus of this study. While the Rosetta observations only provide local information, numerical simulations provide further information on the global wave properties. Methods: Standard hybrid simulations were applied to the comet-solar wind interaction scenario. In the model, the ions were described as particles, which allows us to describe kinetic processes of the ions. The electrons were described as a fluid. Results: The simulations exhibit a threefold wave structure of the interaction region. A Mach cone and a Whistler wing are observed downstream of the comet. The third kind of wave activity found are low-frequency waves at 97 mHz, which corresponds to the waves observed by Richter et al. (2015, Ann. Geophys., 33, 1031). These waves are caused by the initial pick-up of the cometary ions that are perpendicular to the solar wind flow and in the interplanetary magnetic field direction. The associated electric current becomes unstable. The simulations show that wave activity is only detectable in the + E hemisphere and that the Mach cone and whistler wings need to be distinguished from the newly found instability driven wave activity. The movie associated to

  9. COMPARATIVE ADVERTISING EFFECTIVENESS: A CROSS-CULTURAL STUDY

    OpenAIRE

    KONSOLAKI, KALLIOPI

    2015-01-01

    The lucrative world of comparative advertising has been attractive to marketers, who seek economic types of persuasive communication. Nevertheless, research in the actual effectiveness of comparative advertising has been inconclusive, contradicting, and insufficient. The increasing importance of comparative advertising in the current competitive global environment requires immediate findings about how comparative advertising can work effectively. This study is the first study to develop an in...

  10. Conducting Simulation Studies in the R Programming Environment

    Directory of Open Access Journals (Sweden)

    Kevin A. Hallgren

    2013-10-01

    Full Text Available Simulation studies allow researchers to answer specific questions about data analysis, statistical power, and best-practices for obtainingaccurate results in empirical research. Despite the benefits that simulation research can provide, many researchers are unfamiliar with available tools for conducting their own simulation studies. The use of simulation studies need not be restricted toresearchers with advanced skills in statistics and computer programming, and such methods can be implemented by researchers with a variety of abilities and interests. The present paper provides an introduction to methods used for running simulationstudies using the R statistical programming environment and is written for individuals with minimal experience running simulation studies or using R. The paper describes the rationale and benefits of using simulations and introduces R functions relevant for many simulation studies. Three examples illustrate different applications for simulation studies, including (a the use of simulations to answer a novel question about statistical analysis, (b the use of simulations to estimate statistical power, and (c the use of simulations to obtain confidence intervals of parameter estimates throughbootstrapping. Results and fully annotated syntax from these examples are provided.

  11. [Comparative Migration Studies and Comparative Politics.] Fulbright-Hays Summer Seminars Abroad, 1997 (India).

    Science.gov (United States)

    Ireland, Patrick

    This paper addresses how the experience of the Fulbright Seminar in India has allowed the participant to enrich his teaching in comparative migration studies and comparative politics. The paper describes specifically how each course has changed as a result of the international experience. The report suggests questions for consideration as the…

  12. Broadcasting simulation case studies to the didactic classroom.

    Science.gov (United States)

    Kalmakis, Karen A; Cunningham, Helene; Lamoureux, Erin T; Ahmed, Elshaymaa M

    2010-01-01

    To explore the potential of using simulation in new ways, it is time to think "outside the lab." To do this, the authors expanded the use of case-study simulations by broadcasting them to classrooms where didactic content could be reinforced with simulation content. Advantages included students' active classroom engagement, simultaneously sharing simulations with many students, modeling students' thinking in clinical situations, and connecting theory to practice.

  13. Three column intermittent simulated moving bed chromatography: 1. Process description and comparative assessment.

    Science.gov (United States)

    Jermann, Simon; Mazzotti, Marco

    2014-09-26

    The three column intermittent simulated moving bed (3C-ISMB) process is a new type of multi-column chromatographic process for binary separations and can be regarded as a modification of the I-SMB process commercialized by Nippon Rensui Corporation. In contrast to conventional I-SMB, this enables the use of only three instead of four columns without compromising product purity and throughput. The novel mode of operation is characterized by intermittent feeding and product withdrawal as well as by partial recycling of the weakly retained component from section III to section I. Due to the smaller number of columns with respect to conventional I-SMB, higher internal flow rates can be applied without violating pressure drop constraints. Therefore, the application of 3C-ISMB allows for a higher throughput whilst using a smaller number of columns. As a result, we expect that the productivity given in terms of throughput per unit time and unit volume of stationary phase can be significantly increased. In this contribution, we describe the new process concept in detail and analyze its cyclic steady state behavior through an extensive simulation study. The latter shows that 3C-ISMB can be easily designed by Triangle Theory even under highly non-linear conditions. The simple process design is an important advantage to other advanced SMB-like processes. Moreover, the simulation study demonstrates the superior performance of 3C-ISMB, namely productivity increases by roughly 60% with respect to conventional I-SMB without significantly sacrificing solvent consumption. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Modeling and comparative study of various detection techniques for FMCW LIDAR using optisystem

    Science.gov (United States)

    Elghandour, Ahmed H.; Ren, Chen D.

    2013-09-01

    In this paper we investigated the different detection techniques especially direct detection, coherent heterodyne detection and coherent homodyne detection on FMCW LIDAR system using Optisystem package. A model for target, propagation channel and various detection techniques were developed using Optisystem package and then a comparative study among various detection techniques for FMCW LIDAR systems is done analytically and simulated using the developed model. Performance of direct detection, heterodyne detection and homodyne detection for FMCW LIDAR system was calculated and simulated using Optisystem package. The output simulated performance was checked using simulated results of MATLAB simulator. The results shows that direct detection is sensitive to the intensity of the received electromagnetic signal and has low complexity system advantage over the others detection architectures at the expense of the thermal noise is the dominant noise source and the sensitivity is relatively poor. In addition to much higher detection sensitivity can be achieved using coherent optical mixing which is performed by heterodyne and homodyne detection.

  15. A simulation tool for brassiness studies.

    Science.gov (United States)

    Gilbert, Joël; Menguy, Ludovic; Campbell, Murray

    2008-04-01

    A frequency-domain numerical model of brass instrument sound production is proposed as a tool to predict their brassiness, defined as the rate of spectral enrichment with increasing dynamic level. It is based on generalized Burger's equations dedicated to weakly nonlinear wave propagation in nonuniform ducts, and is an extension of previous work by Menguy and Gilbert [Acta Acustica 86, 798-810 (2000)], initially limited to short cylindrical tubes. The relevance of the present tool is evaluated by carrying out simulations over distances longer than typical shock formation distances, and by doing preliminary simulations of periodic regimes in a typical brass trombone bore geometry.

  16. Hemispherical sky simulator for daylighting model studies

    Energy Technology Data Exchange (ETDEWEB)

    Selkowitz, S.

    1981-07-01

    The design of a 24-foot-diameter hemispherical sky simulator recently completed at LBL is described. The goal was to produce a facility in which large models could be tested; which was suitable for research, teaching, and design; which could provide a uniform sky, an overcast sky, and several clear-sky luminance distributions, as well as accommodating an artificial sun. Initial operating experience with the facility is described, the sky simulator capabilities are reviewed, and its strengths and weaknesses relative to outdoor modeling tests are discussed.

  17. PERFORMANCE STUDIES OF INTEGRATED FUZZY LOGIC CONTROLLER FOR BRUSHLESS DC MOTOR DRIVES USING ADVANCED SIMULATION MODEL

    National Research Council Canada - National Science Library

    C, Subba Rami Reddy; M, Surya Kalavathi

    2011-01-01

    This paper introduces an Integrated fuzzy logic controller (IFLC) for brushless dc (BLDC) motor drives using advanced simulation model and presents a comparative study of performances of PID controller and IFLC...

  18. Calculating of Dose Distribution in Tongue Brachytherapy by Different Radioisotopes using Monte Carlo Simulation and Comparing by Experimental Data

    Directory of Open Access Journals (Sweden)

    Banafsheh Zeinali Rafsanjani

    2011-06-01

    Full Text Available Introduction: Among different kinds of oral cavity cancers, the frequency of tongue cancer occurrence is more significant. Brachytherapy is the most common method to cure tongue cancers. Long sources are used in different techniques of tongue brachytherapy. The objective of this study is to asses the dose distribution around long sources, comparing different radioisotopes as brachytherapy sources, measuring the homogeneity of delivered dose to treatment volume and also comparing mandible dose and dose of tongue in the regions near the mandible with and without using shield. Material and Method: The Monte Carlo code MCNP4C was used for simulation. The accuracy of simulation was verified by comparing the results with experimental data. The sources like Ir-192, Cs-137, Ra-226, Au-198, In-111 and Ba-131 were simulated and the position of sources was determined by Paris system. Results: The percentage of mandible dose reduction with use of 2 mm Pb shield for the sources mentioned above were: 35.4%, 20.1%, 86.6%, 32.24%, 75.6%, and 36.8%. The tongue dose near the mandible with use of shied did not change significantly. The dose homogeneity from the most to least was obtained from these sources: Cs-137, Au-198, Ir-192, Ba-131, In-111 and Ra-226. Discussion and Conclusion: Ir-192 and Cs-137 were the best sources for tongue brachytherapy treatment but In-111 and Ra-226 were not suitable choices for tongue brachytherapy. The sources like Au-198 and Ba-131 had rather the same performance as Ir-192

  19. Studying Scientific Discovery by Computer Simulation.

    Science.gov (United States)

    1983-03-30

    scientific laws that were induced from data before any theory was available to discover the regularities. To the previous examples, we could add Gregor ...discoveries (excluding those of Mendel and Mendeleev, which we have not simulated) could have been made. The Role of Theory in Law Induction BACON’s

  20. Dynamic rod worth simulation study for a sodium-cooled TRU burner

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Ji; Ha, Pham Nhu Viet, E-mail: phamha@kaeri.re.kr; Lee, Min Jae; Kang, Chang Mu

    2015-12-15

    Highlights: • Dynamic rod worth calculation methodology for a sodium-cooled TRU burner was developed. • The spatial weighting functions were relatively insensitive to control rods position. • The simulated pseudo detector response agreed well with the calculated core power. • The simulated dynamic rod worths compared well against the simulated static values. • Impact of individual detector on the simulated dynamic worth was evaluated. - Abstract: This paper presents a preliminary dynamic rod worth simulation study for a TRU burner core mockup of the PGSFR (Korean Prototype Gen-IV Sodium-cooled Fast Reactor) named BFS-76-1A so as to establish a calculation methodology for evaluating the rod worth of the PGSFR. The simulation method was mainly based on a three-dimensional multi-group nodal diffusion transient code for fast reactors in which the rod drop simulation for the BFS-76-1A was performed and all the fuel assemblies were taken into account for the detector response calculation. Then the dynamic rod worths were inferred from the simulated detector responses using an inverse point kinetics model and compared against the simulated static worths. The results show good agreement between the simulated pseudo detector response and the calculated core power as well as between the simulated dynamic and static rod worths, and thus indicate that the dynamic rod worth simulation method developed in this work can be applied to the rod worth estimation and validation for the PGSFR.

  1. Comparative analysis of mixing distribution in aerobic stirred bioreactor for simulated yeasts and fungus broths.

    Science.gov (United States)

    Cascaval, Dan; Galaction, Anca-Irina; Turnea, Marius

    2007-01-01

    The study on mixing distribution for an aerobic stirred bioreactor and simulated (solutions of carboxymethylcellulose sodium salt), yeasts (S. cerevisiae) and fungus (P. chrysogenum pellets and free mycelia) broths indicated the significant variation of mixing time on the bioreactor height. The experiments suggested the possibility to reach a uniform mixing in whole bulk of the real broths for a certain value of rotation speed or biomass concentration domain. For S. cerevisiae broths the optimum rotation speed increased to 500 rpm with the biomass accumulation from 40 to 150 g/l d.w. Irrespective of their morphology, for fungus cultures the existence of optimum rotation speed (500 rpm) has been recorded only for biomass concentration below 24 g/l d.w. The influence of aeration rate depends on the apparent viscosity/biomass concentration and on the impellers and sparger positions. By increasing the apparent viscosity for simulated broths, or biomass amount for real broths, the shape of the curves describing the mixing time variation is significantly changed for all the considered positions. The intensification of the aeration induced the increase of mixing time, which reached a maximum value, decreasing then, due to the flooding phenomena. This variation became more pronounced at higher viscosities for simulated broths, at higher yeasts concentration, and at lower pellets or filamentous fungus concentration, respectively. By means of the experimental data and using MATLAB software, some mathematical correlations for mixing time have been proposed for each broth and considered position inside the bioreactor. These equations offer a good agreement with the experiment, the maximum deviation being +/-7.3% for S. cerevisiae broths.

  2. Plasma environment of Titan: a 3-D hybrid simulation study

    Directory of Open Access Journals (Sweden)

    S. Simon

    2006-05-01

    Full Text Available Titan possesses a dense atmosphere, consisting mainly of molecular nitrogen. Titan's orbit is located within the Saturnian magnetosphere most of the time, where the corotating plasma flow is super-Alfvénic, yet subsonic and submagnetosonic. Since Titan does not possess a significant intrinsic magnetic field, the incident plasma interacts directly with the atmosphere and ionosphere. Due to the characteristic length scales of the interaction region being comparable to the ion gyroradii in the vicinity of Titan, magnetohydrodynamic models can only offer a rough description of Titan's interaction with the corotating magnetospheric plasma flow. For this reason, Titan's plasma environment has been studied by using a 3-D hybrid simulation code, treating the electrons as a massless, charge-neutralizing fluid, whereas a completely kinetic approach is used to cover ion dynamics. The calculations are performed on a curvilinear simulation grid which is adapted to the spherical geometry of the obstacle. In the model, Titan's dayside ionosphere is mainly generated by solar UV radiation; hence, the local ion production rate depends on the solar zenith angle. Because the Titan interaction features the possibility of having the densest ionosphere located on a face not aligned with the ram flow of the magnetospheric plasma, a variety of different scenarios can be studied. The simulations show the formation of a strong magnetic draping pattern and an extended pick-up region, being highly asymmetric with respect to the direction of the convective electric field. In general, the mechanism giving rise to these structures exhibits similarities to the interaction of the ionospheres of Mars and Venus with the supersonic solar wind. The simulation results are in agreement with data from recent Cassini flybys.

  3. A Comparative Study of Key Management Protocols for WSN

    Directory of Open Access Journals (Sweden)

    Seema Verma

    2014-03-01

    Full Text Available Increased employment of WSN (Wireless Sensor Network in real life applications and their hostile and remote locations accelerate demand of security in WSN. Publicly accessible wireless communication channel also makes WSN vulnerable to numerous security attacks. Scarcity of resources acquaints new sort of challenges and difficulties during implementation of effective security mechanisms. In this paper, we evaluate and compare performance of three different security mechanisms (ECRKS, CKP and AP scheme. ECRKS (Energy-efficient, Connected, Resilient Key pre-distribution Scheme is based upon multi hop communication architecture specifically designed for homogeneous WSN. Clustering based protocols, AP (Asymmetric pre-distribution scheme and CKP (Clustering based Key management Protocol are proposed for heterogeneous WSN. All the above mentioned schemes are simulated in MATLAB to evaluate their effectiveness and suitability for WSN. Simulation result shows that CKP outperforms other two schemes in terms of transmission distance, memory burden, energy dissipation and resilience.

  4. Bias-Correction in Vector Autoregressive Models: A Simulation Study

    Directory of Open Access Journals (Sweden)

    Tom Engsted

    2014-03-01

    Full Text Available We analyze the properties of various methods for bias-correcting parameter estimates in both stationary and non-stationary vector autoregressive models. First, we show that two analytical bias formulas from the existing literature are in fact identical. Next, based on a detailed simulation study, we show that when the model is stationary this simple bias formula compares very favorably to bootstrap bias-correction, both in terms of bias and mean squared error. In non-stationary models, the analytical bias formula performs noticeably worse than bootstrapping. Both methods yield a notable improvement over ordinary least squares. We pay special attention to the risk of pushing an otherwise stationary model into the non-stationary region of the parameter space when correcting for bias. Finally, we consider a recently proposed reduced-bias weighted least squares estimator, and we find that it compares very favorably in non-stationary models.

  5. The importance of being systematically surprisable : Comparative social simulation as experimental technique

    NARCIS (Netherlands)

    Achterkamp, M; Imhof, P

    1999-01-01

    We argue that computer simulation can serve as a functional equivalent for the experimental method in sociology, with respect to theory development. To this end Eve present accounts of experimentation and simulation by experimenting/simulating scientists and sociologists of science. From these analy

  6. Use of wavelets to compare simulated yield patterns for precision agriculture at the field scale

    NARCIS (Netherlands)

    Verhagen, A.; Stein, A.; Epinat, V.

    2000-01-01

    In this paper spatial patterns of simulated water limited potato production for a farm field in the Netherlands are analyzed using wavelets. The simulated yield patterns are decomposed using wavelets into crystals with a varying resolution. These crystals are used to relate the simulated spatial

  7. Using Simulation to Support Novice Teachers' Classroom Management Skills: Comparing Traditional and Alternative Certification Groups

    Science.gov (United States)

    Pankowski, Jennifer; Walker, Joan T.

    2016-01-01

    Drawing from research on situated cognition and the development of expertise and simulations in professional education, we designed two simulation tasks that provided novice teachers with repeated opportunities to deliberately practice managing a classroom under no-fault conditions. The simulations immersed novices in two perennial classroom…

  8. Comparing the effects of real versus simulated violence on dream imagery.

    Science.gov (United States)

    Dale, Allyson; Murkar, Anthony; Miller, Nicolle; Black, Joshua

    2014-08-01

    Participants in the current study were 75 males, including 25 Canadian soldiers, 25 heavy gamers who play military based video games such as "Call of Duty," and a control group comprised of 25 males. One dream per participant was analyzed using Hall and Van de Castle content analysis guidelines, including aggression, threat, and previously established scales for intensity of aggression and emotion. The dreams of soldiers had a higher frequency of both aggression and threat, and were also more intense in aggression and emotion than both the heavy gamers and the controls. These findings suggest that exposure to real life violence and threat (as well as the emotional significance of the experience) is more frequently incorporated into dream imagery than simulated or virtual threat. Limitations and directions for future studies are discussed.

  9. Comparative study of autodyne and heterodyne laser interferometry for imaging

    CERN Document Server

    Lacot, Eric; Roussely, Grégoire; Hugon, Olivier; De Chatellus, Hugues Guillet

    2014-01-01

    For given laser output power, object under investigation and photodiode noise level, we have theoretically compared the signal to noise ratio (SNR) of a heterodyne scanning imager based on a Michelson interferometer and of an autodyne setup based on the Laser Optical Feedback Imaging (LOFI) technique. In both cases, the image is obtained point by point. In the heterodyne configuration, the beating between the reference beam and the signal beam is realized outside the laser cavity (i.e. directly on the detector), while in the autodyne configuration, the wave beating takes place inside the laser cavity and therefore is indirectly detected. In the autodyne configuration, where the laser relaxation oscillations play a leading role, we have compared 1D scans obtained by numerical simulations with different lasers dynamical parameters. Finally we have determined the best laser for LOFI applications and the experimental conditions for which the LOFI detection setup (autodyne interferometer) is competitive comparing ...

  10. Simulation Studies of the Backscattering Signal in HSRL Technique

    CERN Document Server

    Georgakopoulou, Angelika

    2012-01-01

    The technique of High Spectral Resolution Lidar (HSRL) for atmospheric monitoring allows the determination of the aerosol to molecular ratio and can be used in UHECR Observatories using air fluorescence telescopes. By this technique a more accurate estimate of the Cherenkov radiation superimposed to the fluorescence signal can be achieved. A laboratory setup was developed to determine the backscattering coefficients using microparticles diluted in water and diffusion interfaces. In this setup we used a CW SLM laser at 532 nm and a 250 mm Newtonian telescope. Simulations of the above experimental configuration have been made using Scatlab\\c{opyright}, FINESSE\\c{opyright} 0.99.8 and MATLAB\\c{opyright} and are presented in this work. We compare the simulated 2-dimensional Fabry-Perot fringe images of the backscattering signal recorded in the CCD sensor with that of experimental ones. Additionally, we simulated the backscattering of the laser beam by the atmosphere at a height of 2000 m and we have studied the in...

  11. Three-dimensional simulations of gravitationally confined detonations compared to observations of SN 1991T

    Science.gov (United States)

    Seitenzahl, Ivo R.; Kromer, Markus; Ohlmann, Sebastian T.; Ciaraldi-Schoolmann, Franco; Marquardt, Kai; Fink, Michael; Hillebrandt, Wolfgang; Pakmor, Rüdiger; Röpke, Friedrich K.; Ruiter, Ashley J.; Sim, Stuart A.; Taubenberger, Stefan

    2016-07-01

    The gravitationally confined detonation (GCD) model has been proposed as a possible explosion mechanism for Type Ia supernovae in the single-degenerate evolution channel. It starts with ignition of a deflagration in a single off-centre bubble in a near-Chandrasekhar-mass white dwarf. Driven by buoyancy, the deflagration flame rises in a narrow cone towards the surface. For the most part, the main component of the flow of the expanding ashes remains radial, but upon reaching the outer, low-pressure layers of the white dwarf, an additional lateral component develops. This causes the deflagration ashes to converge again at the opposite side, where the compression heats fuel and a detonation may be launched. We first performed five three-dimensional hydrodynamic simulations of the deflagration phase in 1.4 M⊙ carbon/oxygen white dwarfs at intermediate-resolution (2563 computational zones). We confirm that the closer the initial deflagration is ignited to the centre, the slower the buoyant rise and the longer the deflagration ashes takes to break out and close in on the opposite pole to collide. To test the GCD explosion model, we then performed a high-resolution (5123 computational zones) simulation for a model with an ignition spot offset near the upper limit of what is still justifiable, 200 km. This high-resolution simulation met our deliberately optimistic detonation criteria, and we initiated a detonation. The detonation burned through the white dwarf and led to its complete disruption. For this model, we determined detailed nucleosynthetic yields by post-processing 106 tracer particles with a 384 nuclide reaction network, and we present multi-band light curves and time-dependent optical spectra. We find that our synthetic observables show a prominent viewing-angle sensitivity in ultraviolet and blue wavelength bands, which contradicts observed SNe Ia. The strong dependence on the viewing angle is caused by the asymmetric distribution of the deflagration ashes

  12. Comparative study of Trombe wall, water wall and trans wall

    Energy Technology Data Exchange (ETDEWEB)

    Sodha, M.S.; Bansal, N.K.; Singh, S.; Ram, S.; Annamalai, M.; Iyer, M.V.; Nirmala, K.A.; Venkatesh, P.; Prasad, C.R.; Subramani, C.

    1982-01-01

    The thermal performances of three systems viz. Trombe wall: (1) without; and (2) with vents (forced air circulation), water wall and Transwall have been studied analytically interms of heat flux entering the living space (Maintained at 20/sup 0/C) corresponding to the meteriological data on January 19, 1981 at New Delhi (India), a typical cold winter day. Subsequent parametric studies using the simulation indicated that the Transwall system is the more efficient system for the passive heating of buildings.

  13. Comparative studies of methods of obtaining AGW's propagation properties

    Science.gov (United States)

    Lue, H. Y.; Kuo, F. S.

    2012-03-01

    Three among the existing methods of obtaining the properties (intrinsic period, wavelength, propagation direction) of atmospheric gravity waves (AGWs) were compared and studied by numerical method to simulate radar data. Three-dimensional fluctuation velocity satisfying dispersion equation and polarization relation of atmospheric gravity wave were generated, then the numerical data were analysed by these methods to obtain the properties of waves. We found that, hodograph analysis was accurate for a monochromatic wave in obtaining its wave period and propagation direction, but the analysis became erratic for the case of multiple waves' superposition. The error was especially large when data consisted of both upward propagating waves and downward propagating waves. The hodograph method became meaningful again if all the component waves propagated in the same direction and the resulting period was dominantly decided by the lowest frequency wave. Stokes parameters method would obtain statistically meaningful values of wave period and azimuth if the spreading of the azimuths among the component waves did not exceed 90° and the resulting period and azimuth were dominated by the lowest frequency wave component as well, irrespective of the vertical sense of propagation. Another method called phase and group velocity tracing technique was reconfirmed to be meaningful in measuring the characteristic wave period and vertical group and phase velocities of a wave packet: the characteristic wave period and vertical wavelength was dominated by the wave with the highest frequency among the component waves in the wave packet. Based on these numerical results, a composite procedure of data analysis for wave propagation was proposed and an example of real data analysis was presented.

  14. 基于虚拟胃镜的系统反馈自学法与教师指导法的胃镜技能获得的比较研究%The comparative study on gastroscopy skills after virtual reality simulator training by independent and proctored methods

    Institute of Scientific and Technical Information of China (English)

    白杨; 张亚历; 姜泊; 智发朝; 杜庆峰; 刘思德; 张强; 潘德寿; 杜许峰; 蔡建群; 肖冰

    2012-01-01

    目的 拟开展虚拟内镜不同训练模式对胃镜技能建立的作用研究,以期发现最优化的训练模式.方法 将学员分为2组,A组采用自学法,B组教师指导法.训练完成后根据成绩判断哪种训练方法最适合胃镜受训学员.结果 两组在安全性和准确度方面差异无显著性,但在残气量、患者痛苦指数以及操作时间方面,B组训练方法优于A组.结论 推荐教师指导法为虚拟胃镜的训练方法.%[Objective] The aim of this study was to investigate that the role of the different virtual reality simulator training methods during the forming of the gastroscopy skills. [ Methods ] The novice trainees were divided into two groups. Group A accepted the independent training; Group B accepted the proctored training. After finishing the training, scores of two different groups were compared. [ Results ] Results showed there were no significant differences between two groups in terms of safety and accuracy. The significant difference existed in the overinsufflation and patients suffering index and speed. The group B was better than the other group. [ Conclusion ] The proctored methods should be recommended for virtual reality simulator training of gastroscopy skills.

  15. Simulation study of passive target motion analysis

    Institute of Scientific and Technical Information of China (English)

    HU Youfeng; JIAO Binli

    2003-01-01

    In this paper, the problem of underwater passive target motion analysis (TMA) in three dimensions is discussed using the measurements of passive bearings and elevation and frequency on the condition that acoustic source and observer are in different horizontal planes. Simulation results with both of the PLE (pseudo-linear estimation) and MLE (Maximum likelihood estimation) show that the TMA method is effective in oceanic environment. Its error covariance curves tend to its Cramer-Rao lower bounds.

  16. Simulation study on combustion of biomass

    Science.gov (United States)

    Zhao, M. L.; Liu, X.; Cheng, J. W.; Liu, Y.; Jin, Y. A.

    2017-01-01

    Biomass combustion is the most common energy conversion technology, offering the advantages of low cost, low risk and high efficiency. In this paper, the transformation and transfer of biomass in the process of combustion are discussed in detail. The process of furnace combustion and gas phase formation was analyzed by numerical simulation. The experimental results not only help to optimize boiler operation and realize the efficient combustion of biomass, but also provide theoretical basis for the improvement of burner technology.

  17. How Australian and Indonesian Universities Treat Plagiarism: A Comparative Study

    OpenAIRE

    Bambang Yudi Cahyono

    2016-01-01

    This article is a part of a larger study comparing various aspects of policies on plagiarism in two university contexts. It compares policies on plagiarism in universities in Australia and Indonesia. The results of this comparative study showed that Australian and Indonesian universities treat plagiarism differently. Australian universities treat plagiarism explicitly in their university policies. In Australian universities, plagiarism is defined clearly and forms of plagiarism are explained ...

  18. A Comparative Study of the Block Characteristics of Spinal ...

    African Journals Online (AJOL)

    A Comparative Study of the Block Characteristics of Spinal Bupivacaine ... and side effects during and immediately after the surgery were assessed and recorded. ... the study period, group D exhibited significantly lower mean blood pressures ...

  19. Comparative studies of sexual assaults in Canada and in Hong Kong

    OpenAIRE

    Wong, Carol K

    2011-01-01

    Although criminal law involving sexual offence has undergone many legal reforms in both Canada and Hong Kong, there remain numerous socio-cultural factors that maintain the difficulty of achieving successful prosecutions for these offences. This dissertation includes two comparative studies that explore complainant-specific factors that may affect the perception of adult female complainants in real (Study 1) and simulated (Study 2) sexual assault cases. Study 1 reviewed 220 archival rape case...

  20. Experimental and simulation study of capacitively coupled electronegative discharges

    Science.gov (United States)

    Derzsi, Aranka

    2016-09-01

    The application of tailored voltage waveforms, generated by using multiple harmonics of a base frequency, for the excitation of capacitive RF discharges has been recently introduced as a new method to control the ion flux and ion energy distribution at the electrodes. In plasma processing of surfaces complex mixtures of electronegative, reactive gases (e.g. CF4, O2) are usually required. Therefore, the question of whether this new approach to control ion properties can be applied efficiently to such systems is of exceptional importance. Here the electron heating and ionization dynamics, the possibilities and limitations of the efficient control of plasma parameters by voltage waveform tailoring in low-pressure capacitively coupled electronegative discharges are presented. The focus is on geometrically symmetric O2 plasmas, which are investigated by PIC/MCC simulations and experimental methods. O2 discharges driven by impulse-type and sawtooth-type voltage waveforms composed of a maximum of four consecutive harmonics are studied. Experimental results on the dc self-bias voltage, as well as the spatiotemporal distribution of the plasma emission are compared with simulation data for a wide range of operating conditions (fundamental driving frequencies of 5 MHz - 15 MHz, at pressures of 50 mTorr - 700 mTorr). Transitions between electron power absorption due to sheath expansion and the drift-ambipolar mode were induced both by changing the number of harmonics or by changing the gas pressure. A good agreement between simulation and experiment is found, which shows that the collision-reaction model for O2 discharges underlying the simulations describes reasonably the complicated chemistry of oxygen plasmas. An investigation of the dependence of the discharge characteristics on the surface destruction coefficient of the O2(a1Δg) singlet metastable molecules revealed the crucial role of these species, which strongly affects the negative ion balance of the plasma.

  1. Large-scale numerical simulations of star formation put to the test: Comparing synthetic images and actual observations for statistical samples of protostars

    CERN Document Server

    Frimann, Søren; Haugbølle, Troels

    2015-01-01

    (abridged) Context: Both observations and simulations of embedded protostars have progressed rapidly in recent years. Bringing them together is an important step in advancing our knowledge about the earliest phases of star formation. Aims: To compare synthetic continuum images and SEDs, created from large-scale numerical simulations, to observational studies - thereby aiding both in the interpretation of observations and test the fidelity of the simulations. Methods: The radiative transfer code RADMC-3D is used to create synthetic continuum images and SEDs of protostellar systems in a large numerical simulation of a molecular cloud. More than 13000 unique radiative transfer models are produced of a variety of different protostellar systems. Results: Over the course of 0.76 Myr more than 500 protostars are formed in the simulation - primarily within two sub-clusters. Synthetic SEDs are used to calculate evolutionary tracers Tbol and Lsmm/Lbol. It is shown that, while the observed distributions of tracers are w...

  2. In situ simulation comparing in-hospital first responder sudden cardiac arrest resuscitation using semiautomated defibrillators and automated external defibrillators.

    Science.gov (United States)

    Kobayashi, Leo; Dunbar-Viveiros, Jennifer A; Sheahan, Bethany A; Rezendes, Megan H; Devine, Jeffrey; Cooper, Mary R; Martin, Peggy B; Jay, Gregory D

    2010-04-01

    Multifaceted approaches using simulation and human factors methods may optimize in-hospital sudden cardiac arrest (SCA) response. The Arrhythmia Simulation/Cardiac Event Nursing Training-Automated External Defibrillator phase (ASCENT-AED) study used in situ medical simulation to compare traditional and AED-supplemented SCA first-responder models. The study was conducted at an academic 719-bed hospital with institutional review board approval. Two simulation scenarios were developed and featured either respiratory arrest with perfusing bradycardia or ventricular fibrillation (VF) arrest. Study floors were equipped with either a semiautomated defibrillator (SD) only (control) or with both SD and AED (experimental); subjects functioned as solitary first responders and did not receive resuscitation training. Fifty nurses were enrolled on control (n=25) and experimental (n=25) floors. The groups' nonblinded performances exhibited the following differences during VF scenario: slower calls for help by the control group [mean time to completion of 25+/-17 seconds versus 18+/-11 seconds for the experimental group (P<0.05)] and fewer subjects in the control group performing chest compressions [44.0% versus experimental group's 95.8% (P<0.001)]. Eighty-eight percent of the control group defibrillated the manikin at an average of 155+/-59 seconds, with 32.0% of those subjects using semiautomated rhythm analysis; 100% (not significant [NS]) of experimental group defibrillated at 154+/-72 seconds (NS) with 100% AED analysis (P<0.001). Fewer control group subjects (28.0%) were observed during the bradycardia scenarios to perform inappropriate chest compressions than the AED-supplemented subjects [69.6% (P=0.01)]; nonindicated defibrillation was delivered during these scenarios by a single subject in the control group. Twenty-eight percent and 72% of VF scenarios were managed appropriately by control and experimental groups, respectively; bradycardia scenarios were managed without

  3. Comparative analysis of different process simulation settings of a micro injection molded part featuring conformal cooling

    DEFF Research Database (Denmark)

    Marhöfer, David Maximilian; Tosello, Guido; Islam, Aminul

    2015-01-01

    different simulation models are established: a version including the part without the surrounding mold block, an advanced version including the mold block and conventional cooling channels, and a third version alike the second with additional conformal cooling for efficient thermal management...... of the implementation of the actual mold block, conventional cooling, and conformal cooling. In the comparison, characteristic quality criteria for injection molding are studied, such as the filling behavior of the cavity, the injection pressure, the temperature distribution, and the resulting part warpage....... Additionally, the analysis of the cooling channels exploiting computational fluid dynamics is introduced as helpful tool for the mold design process. It is observed that the comprehensive implementation of the actual injection molding system and conditions is highly relevant at sub-mm/micro dimensional scales...

  4. Modeling and comparative study of fluid velocities in heterogeneous rocks

    Science.gov (United States)

    Hingerl, Ferdinand F.; Romanenko, Konstantin; Pini, Ronny; Balcom, Bruce; Benson, Sally

    2013-04-01

    Detailed knowledge of the distribution of effective porosity and fluid velocities in heterogeneous rock samples is crucial for understanding and predicting spatially resolved fluid residence times and kinetic reaction rates of fluid-rock interactions. The applicability of conventional MRI techniques to sedimentary rocks is limited by internal magnetic field gradients and short spin relaxation times. The approach developed at the UNB MRI Centre combines the 13-interval Alternating-Pulsed-Gradient Stimulated-Echo (APGSTE) scheme and three-dimensional Single Point Ramped Imaging with T1 Enhancement (SPRITE). These methods were designed to reduce the errors due to effects of background gradients and fast transverse relaxation. SPRITE is largely immune to time-evolution effects resulting from background gradients, paramagnetic impurities and chemical shift. Using these techniques quantitative 3D porosity maps as well as single-phase fluid velocity fields in sandstone core samples were measured. Using a new Magnetic Resonance Imaging technique developed at the MRI Centre at UNB, we created 3D maps of porosity distributions as well as single-phase fluid velocity distributions of sandstone rock samples. Then, we evaluated the applicability of the Kozeny-Carman relationship for modeling measured fluid velocity distributions in sandstones samples showing meso-scale heterogeneities using two different modeling approaches. The MRI maps were used as reference points for the modeling approaches. For the first modeling approach, we applied the Kozeny-Carman relationship to the porosity distributions and computed respective permeability maps, which in turn provided input for a CFD simulation - using the Stanford CFD code GPRS - to compute averaged velocity maps. The latter were then compared to the measured velocity maps. For the second approach, the measured velocity distributions were used as input for inversely computing permeabilities using the GPRS CFD code. The computed

  5. Comparative enzyme inhibitive methanol production by Methylosinus sporium from simulated biogas.

    Science.gov (United States)

    Yoo, Yeon-Sun; Han, Ji-Sun; Ahn, Chang-Min; Kim, Chang-Gyun

    2015-01-01

    Methane in a simulated biogas converting to methanol under aerobic condition was comparatively assessed by inhibiting the activity of methanol dehydrogenase (MDH) of Methylosinus sporium using phosphate, NaCl, NH4Cl or EDTA in their varying concentrations. The highest amount of methane was indistinguishably diverted at the typical conditions regardless of the types of inhibitors: 35°C and pH 7 under a 0.4% (v/v) of biogas, specifically for methanol was obtained for the addition of 40 mM phosphate, 100 mM NaCl, 40 mM NH4Cl or 50 µM EDTA. In other words, 0.71, 0.60, 0.66 and 0.66 mmol methanol was correspondingly generated by the oxidation of 1.3, 0.67, 0.74 and 1.3 mmol methane. It gave a methanol conversion rate of 54.7%, 89.9%, 89.6% and 47.8%, respectively. Among them, the maximum rate of methanol production was observed at 6.25 µmol/mg h for 100 mM NaCl. Regardless of types or concentrations of inhibitors differently used, methanol production could be nonetheless identically maximized when the MDH activity was limitedly hampered by up to 35%.

  6. A Training Transfer Study of Simulation Games

    Science.gov (United States)

    2010-03-01

    protagonist, Ender , was a 12-year-old boy who played video games well. He did so well, in fact, that the government sent him to Battle School for... Ender made a risky move in the game and consequently won the day. Exhausted, he left the simulator to find out the secret of the game and of Battle...the Third Invasion. There were no games , the battles were real, and the only enemy you fought was the buggers. (p. 296) Ender , in fact, had been

  7. Simulation and experimental study of electro-pneumatic valve used in air-powered engine

    Institute of Scientific and Technical Information of China (English)

    Ping-lu CHEN; Xiao-li YU; Lin LIU

    2009-01-01

    To evaluate the performance of newly designed electro-pneumatic valves (EPVs) for the air-powered engine (APE) and study laws of parameters affecting them, a simulation model was established based on the thermodynamics and mechanics theories. Experiments were set up to determine the instantaneous effective orifice area of solenoid valve by the constant volume discharge method. The simulation model was also validated by comparing the measured displacement curve with the simulated displacement curve of the valve in the pressure of 0.16 and 0.49 MPa. Simulation and experimental results showed that maximum working frequency of the designed EPV could reach 30 Hz corresponding to 2000 r/rain of engine rotating speed. Based on simulation results, impacts of temperature and pressure of control air on delay time, full opening/closing time and seating velocity of EPV were analyzed. The simulation model could also act as EPV simulation prototype in designing the air exchange control system of APE.

  8. Global Harmonization of Comparator Products for Bioequivalence Studies.

    Science.gov (United States)

    Gwaza, Luther; Gordon, John; Leufkens, Hubert; Stahl, Matthias; García-Arieta, Alfredo

    2017-05-01

    Comparator products should be the products that were shown to be safe and efficacious in pivotal clinical trials to ensure prescribability of generics. The use of a common comparator ensures switchability between generics. The selection of the comparator is a national responsibility and may be different between countries. This paper discusses the current recommendations on selection of comparators, the associated problems, and the possibility of harmonization. Most countries follow the World Health Organization (WHO) recommendations for selecting comparator products and require the comparator product to be obtained from their national markets to ensure switchability between the local comparator and their generics. These recommendations are only feasible in the few countries where the repetition of the bioequivalence study is economically feasible, but they are impracticable in all other countries. Furthermore, the exclusive use of the local comparator to ensure switchability is ethically and scientifically questionable. The innovator product from well-regulated markets should be the global comparator. This harmonization is feasible as the concept already applies in the WHO prequalification program. It is ineffectual to harmonize only the requirements for performing bioequivalence studies, if such a study has to be repeated for every single country simply because of the different comparator products.

  9. A simulation based engineering method to support HAZOP studies

    DEFF Research Database (Denmark)

    Enemark-Rasmussen, Rasmus; Cameron, David; Angelo, Per Bagge

    2012-01-01

    HAZOP is the most commonly used process hazard analysis tool in industry, a systematic yet tedious and time consuming method. The aim of this study is to explore the feasibility of process dynamic simulations to facilitate the HAZOP studies. We propose a simulation-based methodology to complement...

  10. Simulation study of the plasma brake effect

    CERN Document Server

    Janhunen, Pekka

    2014-01-01

    The plasma brake is a thin negatively biased tether which has been proposed as an efficient concept for deorbiting satellites and debris objects from low Earth orbit. We simulate the interaction with the ionospheric plasma ram flow with the plasma brake tether by a high performance electrostatic particle in cell code to evaluate the thrust. The tether is assumed to be perpendicular to the flow. We perform runs for different tether voltage, magnetic field orientation and plasma ion mass. We show that a simple analytical thrust formula reproduces most of the simulation results well. The interaction with the tether and the plasma flow is laminar when the magnetic field is perpendicular to the tether and the flow. If the magnetic field is parallel to the tether, the behaviour is unstable and thrust is reduced by a modest factor. The case when the magnetic field is aligned with the flow can also be unstable, but does not result in notable thrust reduction. We also fix an error in an earlier reference. According to...

  11. A Simulation Study on A Diesel Engine Assembly Line

    Institute of Scientific and Technical Information of China (English)

    刘庆华; 吴桂花

    2002-01-01

    Nowadays in China, as the economic reform goes further and the central government increasingly demands for raising productivity, more and more state-owned factories begin to turn their heads back to problems arising from their production systems. With the co-operation of Tianjin Diesel Engine Factory, we conducted a simulation study on its diesel engine assembly line, using GPSS as our major simulation language tool. This paper describes the model we constructed, simulation experiments we made on the model, and some conclusions we drew from the simulation study.

  12. Understanding nucleic acid structural changes by comparing wide-angle x-ray scattering (WAXS) experiments to molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Pabit, Suzette A. [School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA; Katz, Andrea M. [School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA; Tolokh, Igor S. [Department of Computer Science, Virginia Tech, Blacksburg, Virginia 24061, USA; Drozdetski, Aleksander [Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA; Baker, Nathan [Pacific Northwest National Laboratory, Richland, Washington 99352, USA; Onufriev, Alexey V. [Department of Computer Science, Virginia Tech, Blacksburg, Virginia 24061, USA; Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA; Pollack, Lois [School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA

    2016-05-24

    Wide-angle x-ray scattering (WAXS) is emerging as a powerful tool for increasing the resolution of solution structure measurements of biomolecules. Compared to its better known complement, small angle x-ray scattering (SAXS), WAXS targets higher scattering angles and can enhance structural studies of molecules by accessing finer details of solution structures. Although the extension from SAXS to WAXS is easy to implement experimentally, the computational tools required to fully harness the power of WAXS are still under development. Currently, WAXS is employed to study structural changes and ligand binding in proteins; however the methods are not as fully developed for nucleic acids. Here, we show how WAXS can qualitatively char- acterize nucleic acid structures as well as the small but significant structural changes driven by the addition of multivalent ions. We show the potential of WAXS to test all-atom molecular dynamics (MD) simulations and to provide insight in understanding how the trivalent ion cobalt(III) hexammine (CoHex) affects the structure of RNA and DNA helices. We find that MD simulations capture the RNA structural change that occurs due to addition of CoHex.

  13. Comparative study of baseline environmental studies in offshore renewable energies

    Energy Technology Data Exchange (ETDEWEB)

    Huertas-Olivares, C.; Patricio, S.; Neumann, F. [Wave Energy Centre, Lisbon (Portugal); Russell, I. [Wave Dragon (United Kingdom); Sarmento, A. [Instituto Superior Tecnico, Lisbon (Portugal)

    2007-07-01

    The environmental impacts of wave energy projects are not yet fully understood. Only a few Environmental Impact Assessments (EIAs) have been carried out and only for small pilot plants. The assessment of such impacts is a highly complex process, not only because of the medium where these projects are developed but also due to the variety of devices and the different ways in which they interact with the surrounding environment. A further conflict exists with the fact that most EIAs are designed to gain development consent rather than aid environmental protection. This paper presents a comparison of the environmental studies undertaken for several offshore renewable technologies. It concludes by evaluating what environmental factors should be analyzed before the deployment of any wave energy farm, also taking into account the similarities to other marine renewables, mainly offshore wind energy. It aims to establish coherence in this field for future legislation or international standardizations.

  14. Comparing the Pearson and Spearman correlation coefficients across distributions and sample sizes: A tutorial using simulations and empirical data.

    Science.gov (United States)

    de Winter, Joost C F; Gosling, Samuel D; Potter, Jeff

    2016-09-01

    The Pearson product–moment correlation coefficient (rp) and the Spearman rank correlation coefficient (rs) are widely used in psychological research. We compare rp and rs on 3 criteria: variability, bias with respect to the population value, and robustness to an outlier. Using simulations across low (N = 5) to high (N = 1,000) sample sizes we show that, for normally distributed variables, rp and rs have similar expected values but rs is more variable, especially when the correlation is strong. However, when the variables have high kurtosis, rp is more variable than rs. Next, we conducted a sampling study of a psychometric dataset featuring symmetrically distributed data with light tails, and of 2 Likert-type survey datasets, 1 with light-tailed and the other with heavy-tailed distributions. Consistent with the simulations, rp had lower variability than rs in the psychometric dataset. In the survey datasets with heavy-tailed variables in particular, rs had lower variability than rp, and often corresponded more accurately to the population Pearson correlation coefficient (Rp) than rp did. The simulations and the sampling studies showed that variability in terms of standard deviations can be reduced by about 20% by choosing rs instead of rp. In comparison, increasing the sample size by a factor of 2 results in a 41% reduction of the standard deviations of rs and rp. In conclusion, rp is suitable for light-tailed distributions, whereas rs is preferable when variables feature heavy-tailed distributions or when outliers are present, as is often the case in psychological research.

  15. Maier-Saupe model of polymer nematics: Comparing free energies calculated with Self Consistent Field theory and Monte Carlo simulations

    Science.gov (United States)

    Greco, Cristina; Jiang, Ying; Chen, Jeff Z. Y.; Kremer, Kurt; Daoulas, Kostas Ch.

    2016-11-01

    Self Consistent Field (SCF) theory serves as an efficient tool for studying mesoscale structure and thermodynamics of polymeric liquid crystals (LC). We investigate how some of the intrinsic approximations of SCF affect the description of the thermodynamics of polymeric LC, using a coarse-grained model. Polymer nematics are represented as discrete worm-like chains (WLC) where non-bonded interactions are defined combining an isotropic repulsive and an anisotropic attractive Maier-Saupe (MS) potential. The range of the potentials, σ, controls the strength of correlations due to non-bonded interactions. Increasing σ (which can be seen as an increase of coarse-graining) while preserving the integrated strength of the potentials reduces correlations. The model is studied with particle-based Monte Carlo (MC) simulations and SCF theory which uses partial enumeration to describe discrete WLC. In MC simulations the Helmholtz free energy is calculated as a function of strength of MS interactions to obtain reference thermodynamic data. To calculate the free energy of the nematic branch with respect to the disordered melt, we employ a special thermodynamic integration (TI) scheme invoking an external field to bypass the first-order isotropic-nematic transition. Methodological aspects which have not been discussed in earlier implementations of the TI to LC are considered. Special attention is given to the rotational Goldstone mode. The free-energy landscape in MC and SCF is directly compared. For moderate σ the differences highlight the importance of local non-bonded orientation correlations between segments, which SCF neglects. Simple renormalization of parameters in SCF cannot compensate the missing correlations. Increasing σ reduces correlations and SCF reproduces well the free energy in MC simulations.

  16. Development of density plumes of dissolved CO2: Comparing experimental observations with numerical simulations

    Science.gov (United States)

    Kirk, Karen; Vosper, Hayley; Rochelle, Chris; Noy, Dave; Chadwick, Andy

    2014-05-01

    permeability of the system was calculated to be 2.2-2.5 x 10-9 m2, and this used for modelling work. Having experimentally reproduced the transition from diffusion-dissolution to convection-dissolution, and from this determined the system properties, we simulated the process in a numerical flow model. A high resolution model of the Hele-Shaw cell was built using the TOUGH2 flow simulator with the ECO 2N fluid property module, with a permeability of 2.5 x 10-9 m2, and applying laboratory pressure and temperature conditions. Plume development in terms of onset time, sinking rate and wavelength statistics are closely comparable between experiment and model. This suggests therefore that the numerical flow simulator was able to reproduce the critical process of transition from diffusion-dominated to convection-dominated processes in a realistic way. This further increases our confidence in the suitability of numerical models in making predictions of system evolution within CO2 storage schemes.

  17. Energy flux simulation in heterogeneous cropland - a two year study

    Science.gov (United States)

    Klein, Christian; Thieme, Christoph; Biernath, Christian; Heinlein, Florian; Priesack, Eckart

    2016-04-01

    Recent studies show that uncertainties in regional and global climate and weather simulations are partly due to inadequate descriptions of the energy flux exchanges between the land surface and the atmosphere [Stainforth et al. 2005]. One major shortcoming is the limitation of the grid-cell resolution, which is recommended to be about at least 3x3 km² in most models due to limitations in the model physics. To represent each individual grid cell most models select one dominant soil type and one dominant land use type. This resolution, however, is often too coarse in regions where the spatial heterogeneity of soil and land use types are high, e.g. in Central Europe. The relevance of vegetation (e.g. crops), ground cover, and soil properties to the moisture and energy exchanges between the land surface and the atmosphere is well known [McPherson 2007], but the impact of vegetation growth dynamics on energy fluxes is only partly understood [Gayler et al. 2014]. An elegant method to avoid the shortcoming of grid cell resolution is the so called mosaic approach. This approach is part of the recently developed ecosystem model framework Expert-N [Biernath et al. 2013] . The aim of this study was to analyze the impact of the characteristics of five managed field plots, planted with winter wheat, potato and maize on the near surface soil moistures and on the near surface energy flux exchanges of the soil-plant-atmosphere interface. The simulated energy fluxes were compared with eddy flux tower measurements between the respective fields at the research farm Scheyern, North-West of Munich, Germany. To perform these simulations, we coupled the ecosystem model Expert-N to an analytical footprint model [Mauder & Foken 2011] . The coupled model system has the ability to calculate the mixing ratio of the surface energy fluxes at a given point within one grid cell (in this case at the flux tower between the two fields). The approach accounts for the temporarily and spatially

  18. From Comparative Education to Comparative Pedagogy: A Physical Education Case Study

    Science.gov (United States)

    Georgakis, Steve; Graham, Jessica

    2016-01-01

    In the last two decades forces of globalization and the rise of and access to information technology have transformed the nature of educational research. Traditional disciplines such as comparative education have not been immune to these transformational impacts. Although one might expect globalization to promote the study of comparative…

  19. Simulation

    CERN Document Server

    Ross, Sheldon

    2006-01-01

    Ross's Simulation, Fourth Edition introduces aspiring and practicing actuaries, engineers, computer scientists and others to the practical aspects of constructing computerized simulation studies to analyze and interpret real phenomena. Readers learn to apply results of these analyses to problems in a wide variety of fields to obtain effective, accurate solutions and make predictions about future outcomes. This text explains how a computer can be used to generate random numbers, and how to use these random numbers to generate the behavior of a stochastic model over time. It presents the statist

  20. Plasma boundaries at Mars: a 3-D simulation study

    Directory of Open Access Journals (Sweden)

    A. Bößwetter

    2004-12-01

    Full Text Available The interaction of the solar wind with the ionosphere of planet Mars is studied using a three-dimensional hybrid model. Mars has only a weak intrinsic magnetic field, and consequently its ionosphere is directly affected by the solar wind. The gyroradii of the solar wind protons are in the range of several hundred kilometers and therefore comparable with the characteristic scales of the interaction region. Different boundaries emerge from the interaction of the solar wind with the continuously produced ionospheric heavy-ion plasma, which could be identified as a bow shock (BS, ion composition boundary (ICB and magnetic pile up boundary (MPB, where the latter both turn out to coincide. The simulation results regarding the shape and position of these boundaries are in good agreement with the measurements made by Phobos-2 and MGS spacecraft. It is shown that the positions of these boundaries depend essentially on the ionospheric production rate, the solar wind ram pressure, and the often unconsidered electron temperature of the ionospheric heavy ion plasma. Other consequences are rays of planetary plasma in the tail and heavy ion plasma clouds, which are stripped off from the dayside ICB region by some instability.

    Key words. Magnetospheric physics (solar wind interactions with unmagnetized bodies – Space plasma physics (discontinuities; numerical simulation studies

  1. Task Specific Simulations for Medical Training: Fidelity Requirements Compared with Levels of Care

    Science.gov (United States)

    2009-01-01

    the pharmacological responses are simulated. The analysis will also include a discussion on simulating versus replicating human physiology . An initial...systems, such as bleeding, heart rate, blood pressure, etc. An attempt will be made to define a strategy for selecting the correct fidelity of human physiology models as well as ways to reuse existing models.

  2. Simulation Use in Paramedic Education Research (SUPER): A Descriptive Study.

    Science.gov (United States)

    McKenna, Kim D; Carhart, Elliot; Bercher, Daniel; Spain, Andrew; Todaro, John; Freel, Joann

    2015-01-01

    The purpose of this research was to characterize the use of simulation in initial paramedic education programs in order assist stakeholders' efforts to target educational initiatives and resources. This group sought to provide a snapshot of what simulation resources programs have or have access to and how they are used; faculty perceptions about simulation; whether program characteristics, resources, or faculty training influence simulation use; and if simulation resources are uniform for patients of all ages. This was a cross-sectional census survey of paramedic programs that were accredited or had a Letter of Review from the Committee on Accreditation of Educational Programs for the EMS Professions at the time of the study. The data were analyzed using descriptive statistics and chi-square analyses. Of the 638 surveys sent, 389 valid responses (61%) were analyzed. Paramedic programs reported they have or have access to a wide range of simulation resources (task trainers [100%], simple manikins [100%], intermediate manikins [99%], advanced/fully programmable manikins [91%], live simulated patients [83%], computer-based [71%], and virtual reality [19%]); however, they do not consistently use them, particularly advanced (71%), live simulated patients (66%), computer-based (games, scenarios) (31%), and virtual reality (4%). Simulation equipment (of any type) reportedly sits idle and unused in (31%) of programs. Lack of training was cited as the most common reason. Personnel support specific to simulation was available in 44% of programs. Programs reported using simulation to replace skills more frequently than to replace field or clinical hours. Simulation goals included assessment, critical thinking, and problem-solving most frequently, and patient and crew safety least often. Programs using advanced manikins report manufacturers as their primary means of training (87%) and that 19% of faculty had no training specific to those manikins. Many (78%) respondents felt

  3. Scheduling of a computer integrated manufacturing system: A simulation study

    Directory of Open Access Journals (Sweden)

    Nadia Bhuiyan

    2011-12-01

    Full Text Available Purpose: The purpose of this paper is to study the effect of selected scheduling dispatching rules on the performance of an actual CIM system using different performance measures and to compare the results with the literature.Design/methodology/approach: To achieve this objective, a computer simulation model of the existing CIM system is developed to test the performance of different scheduling rules with respect to mean flow time, machine efficiency and total run time as performance measures.Findings: Results suggest that the system performs much better considering the machine efficiency when the initial number of parts released is maximum and the buffer size is minimum. Furthermore, considering the average flow time, the system performs much better when the selected dispatching rule is either Earliest Due Date (EDD or Shortest Process Time (SPT with buffer size of five and the initial number of parts released of eight.Research limitations/implications: In this research, some limitations are: a limited number of factors and levels were considered for the experiment set-up; however the flexibility of the model allows experimenting with additional factors and levels. In the simulation experiments of this research, three scheduling dispatching rules (First In/First Out (FIFO, EDD, SPT were used. In future research, the effect of other dispatching rules on the system performance can be compared. Some assumptions can be relaxed in future work.Practical implications: This research helps to identify the potential effect of a selected number of dispatching rules and two other factors, the number of buffers and initial number of parts released, on the performance of the existing CIM systems with different part types where the machines are the major resource constraints.Originality/value: This research is among the few to study the effect of the dispatching rules on the performance of the CIM systems with use of terminating simulation analysis. This is

  4. Study on the random simulation times of mining engineering reliability

    Institute of Scientific and Technical Information of China (English)

    BI Zhong-wei; DING De-xin; ZHANG Xin-hua

    2005-01-01

    The theory of Monte-Carlo simulation method is that the event happened probability was estimated by happened frequency in the experiments. So it is very important to ascertain the times of simulation. The probability and statistic theory are used to determine the optimal simulation times through strict mathematic reasoning. The study of two cases is made to show the availability of the presented method, and some relative problems were discussed.

  5. Studies of climate dynamics with innovative global-model simulations

    Science.gov (United States)

    Shi, Xiaoming

    Climate simulations with different degrees of idealization are essential for the development of our understanding of the climate system. Studies in this dissertation employ carefully designed global-model simulations for the goal of gaining theoretical and conceptual insights into some problems of climate dynamics. Firstly, global warming-induced changes in extreme precipitation are investigated using a global climate model with idealized geography. The precipitation changes over an idealized north-south mid-latitude mountain barrier at the western margin of an otherwise flat continent are studied. The intensity of the 40 most intense events on the western slopes increases by about ~4°C of surface warming. In contrast, the intensity of the top 40 events on the eastern mountain slopes increases at about ~6°C. This higher sensitivity is due to enhanced ascent during the eastern-slope events, which can be explained in terms of linear mountain-wave theory relating to global warming-induced changes in the upper-tropospheric static stability and the tropopause level. Dominated by different dynamical factors, changes in the intensity of extreme precipitation events over plains and oceans might differ from changes over mountains. So the response of extreme precipitation over mountains and flat areas are further compared using larger data sets of simulated extreme events over the two types of surfaces. It is found that the sensitivity of extreme precipitation to increases in global mean surface temperature is 3% per °C lower over mountains than over the oceans or the plains. The difference in sensitivity among these regions is not due to thermodynamic effects, but rather to differences between the gravity-wave dynamics governing vertical velocities over the mountains and the cyclone dynamics governing vertical motions over the oceans and plains. The strengthening of latent heating in the storms over oceans and plains leads to stronger ascent in the warming climate

  6. Computational lfuid dynamics simulation of intracranial aneurysms - comparing size and shape

    Institute of Scientific and Technical Information of China (English)

    Zifeng Yang; Hongtao Yu; George P Huang; Ryan Schwieterman; Bryan Ludwig

    2015-01-01

    Objective:To study the hemodynamics of an anatomic internal carotid artery aneurysm derived from a patient-specific model and then manipulate into two phantom morphologies: one growing uniformly by size and the other changing shape unevenly. Methods: The computational model of the saccular, internal carotid artery, aneurysm was constructed from 3D rotational, digitally subtracted, catheter angiography images. Computational fluid dynamics simulations were performed under pulsatile cardiac flow conditions. Velocity vectors, streamlines, pressure, and wall shear stress (WSS) and its variance distributions were quantitatively visualized. Results: The maximum pressure andWSS from the time-averaged distribution on the inside saccular surface of the original case are 415.38 and 17.61 Pa. In contrast, the bi-lobed shape gives rise to higher peak values of pressure (461.00 Pa) andWSS (33.20 Pa) on the saccular dome. Conversely, the evenly enlarged aneurysm actually results in a slightly lower peak pressure (399.58 Pa) and drastically decreasedWSS (9.81 Pa). Conclusions:The current study indicates that the size of the aneurysm should not be the only determining factor for the rupture risk consideration, the irregularity of the aneurysm shape and the corresponding aberrant hemodynamics might be a more important factor to consider for risk assessment.

  7. A COMPARATIVE STUDY OF SPECTRAL METHODS WITH SEA WAVE DATA

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Two spectral methods are used to study sea wave data.Firstly, the estimated results calculated by the sequency spectrum method and frequency spectrum method are compared, and then the differences between the two methods are discussed.Furthermore, compared with frequency spectral analysis, sequency spectral analysis has many advantages: faster calculating speed, convenient use and high distinguishability.

  8. A comparative study between dissipative particle dynamics and molecular dynamics for simple- and complex-geometry flows.

    Science.gov (United States)

    Keaveny, Eric E; Pivkin, Igor V; Maxey, Martin; Em Karniadakis, George

    2005-09-08

    The purpose of this study is to compare the results from molecular-dynamics and dissipative particle dynamics (DPD) simulations of Lennard-Jones (LJ) fluid and determine the quantitative effects of DPD coarse graining on flow parameters. We illustrate how to select the conservative force coefficient, the cut-off radius, and the DPD time scale in order to simulate a LJ fluid. To show the effects of coarse graining and establish accuracy in the DPD simulations, we conduct equilibrium simulations, Couette flow simulations, Poiseuille flow simulations, and simulations of flow around a periodic array of square cylinders. For the last flow problem, additional comparisons are performed against continuum simulations based on the spectral/hp element method.

  9. Comparative study of two linearization methods for time intervals generation of SVPWM technique

    Directory of Open Access Journals (Sweden)

    Khaled N. Faris

    2016-12-01

    In this paper a comparative study for two linearization methods are carried out for generating the time intervals of SVPWM technique. The proposed linearization methods achieve a minimum computational time rather than the trigonometric sine function which is considered the base for the time interval calculations of the SVPWM technique. The first linearization method is based on the first order equation, and the second method is the (Takagi–Sugeno fuzzy modeling system. The comparative study includes the accuracy of the two models, also a simulation model is carried out for current THD estimation using the two proposed methods compared with the current THD generated by SVPWM based on the trigonometric sine function.

  10. A Theoretical Study of Subsurface Drainage Model Simulation of ...

    African Journals Online (AJOL)

    A Theoretical Study of Subsurface Drainage Model Simulation of Drainage Flow and ... of subsurface drain spacing, evapotranspiration and irrigation water quality on ... The study was carried out on a conceptual uniform homogenous irrigated ...

  11. Religious Confession and Symptom Severity: A Prospective Comparative Study.

    Science.gov (United States)

    Rana, Madiha; Rana, Majeed; Herzberg, Philipp Y; Krause, Christin

    2015-12-01

    Little research has been done on comparing confessions regarding mental health. In the present study, 320 people (78 Buddhists, 77 Catholics, 89 Protestants and 79 Muslims) were compared in terms of their symptom severity. Buddhists and Protestants had lower scores than Catholics and Muslims for obsessive-compulsive behavior and hostility. Muslim group had the highest comparative scores for psychoticism. Buddhists and Protestants had comparatively low scores for paranoid ideation and overall symptom severity, with Catholics and Muslims having high ones. Results reveal that confession should be taken in account in psychological research and diagnosis, since it is explicitly associated with psychological well-being.

  12. Simulation and Comparative Practical Performance Analysis Of A Stand-Alone PV Power System in Gökçeada

    Directory of Open Access Journals (Sweden)

    Mete Çubukçu

    2013-05-01

    Full Text Available This study simulates and analyzes the practical performance of a 2 kW stand-alone PV power system located in Gökçeada/Turkey. System performance was calculated both by simulation and real life measurements. Although the total system efficiency and the performance ratio is simulated 5 % and 41 %, these values are calculated averagely during the real-life monitoring period as 4 % and % 32.4 respectively. The results were reported using the international evaluation parameters. The main reasons of the difference between the simulated and practical calculated values are the partial shadow effects and the limited energy generation due to the low load demand.

  13. Parameter ranking of stock market dynamics: a comparative study of ...

    African Journals Online (AJOL)

    ... a comparative study of the mathematical models of competition and mutualistic interactions. ... Open Access DOWNLOAD FULL TEXT ... Our approach also permits us to gain some useful insights into the ability of the model to reflect what is ...

  14. A prospective, randomized multicenter study comparing APD and CAPD treatment

    DEFF Research Database (Denmark)

    Bro, S; Bjorner, J B; Tofte-Jensen, P

    2000-01-01

    OBJECTIVE: The goals for maintenance dialysis treatment are to improve patient survival, reduce patient morbidity, and improve patient quality of life. This is the first randomized prospective study comparing automated peritoneal dialysis (APD) and continuous ambulatory peritoneal dialysis (CAPD)...

  15. 424 Comparative Studies on the Larvicidal Action of Novaluron ...

    African Journals Online (AJOL)

    FIRST LADY

    2011-01-18

    Jan 18, 2011 ... Comparative Studies on the Larvicidal Action of Novaluron. (Mosquiron. ® .... leguminous seeds and grains against Aedes aegypti and Culex pipens pallens ..... New classification for the composite genus Aedes. (Diptera: ...

  16. A Comparative Kinetic Study of Acidic Hydrolysis of Wastes ...

    African Journals Online (AJOL)

    A Comparative Kinetic Study of Acidic Hydrolysis of Wastes Cellulose from Agricultural Derived Biomass. ... fuels and chemicals offers potential economical, environmental and strategic ... Keywords: Agricultural wastes; cellulose; acid hydrolysis; first-order rate kinetics; activation energy, Arrhenius equation ... Article Metrics.

  17. A COMPARATIVE STUDY OF ALGORITHMS FOR LAND COVER CHANGE

    Data.gov (United States)

    National Aeronautics and Space Administration — A COMPARATIVE STUDY OF ALGORITHMS FOR LAND COVER CHANGE SHYAM BORIAH*, VARUN MITHAL, ASHISH GARG, VIPIN KUMAR, MICHAEL STEINBACH, CHRIS POTTER, AND STEVE KLOOSTER*...

  18. Comparative studies on the mineralization of furfural urea and urea ...

    African Journals Online (AJOL)

    Comparative studies on the mineralization of furfural urea and urea fertilizers in ... conducted to evaluate the effects of furfural urea as a slow release N fertilizer in ... The controlled or slow availability supplies N continuously over an extended ...

  19. Comparative study of the nutritional composition of matured green ...

    African Journals Online (AJOL)

    Comparative study of the nutritional composition of matured green and red fruits of ... Journal of Agriculture, Forestry and the Social Sciences ... It is still green when matured and turn from yellow to red if left for sometime after reaching maturity.

  20. SIMULATION STUDY OF GENERALIZED PREDICTIVE CONTROL FOR TURBINE POWER

    Institute of Scientific and Technical Information of China (English)

    Shi Xiaoping; Li Dongmei

    2004-01-01

    A GPC (generalized predictive control) law is developed to control the power of a turbine, after transforming the nonlinear mathematical model of the power regulation system into a CARIMA(controlled auto-regressive integrated moving average) form. The effect of the new control law is compared with a traditional PID (proportional, integral and differential) control law by numerical simulation. The simulation results verify the effectiveness, the correctness and the advantage of the new control scheme.

  1. Teacher Leader Human Relations Skills: A Comparative Study

    Science.gov (United States)

    Roby, Douglas E.

    2012-01-01

    In this study, 142 graduate school teachers working in schools throughout southwestern Ohio assessed their human relation skills. A human relations survey was used for the study, and results were compared with colleagues assessing the teachers in the study. The survey was developed using a Likert-type scale, and was based on key elements affecting…

  2. Teacher Leader Human Relations Skills: A Comparative Study

    Science.gov (United States)

    Roby, Douglas E.

    2012-01-01

    In this study, 142 graduate school teachers working in schools throughout southwestern Ohio assessed their human relation skills. A human relations survey was used for the study, and results were compared with colleagues assessing the teachers in the study. The survey was developed using a Likert-type scale, and was based on key elements affecting…

  3. A Comparative Study of English and Chinese Taboos

    Institute of Scientific and Technical Information of China (English)

    SONG Li-xian; PENG Jian-wu

    2016-01-01

    As a very common language phenomenon in English and Chinese culture, taboo exists in almost every aspects of daily life. Taboo is a relatively sensitive topic and it has distinctive national features and profound cultural connotations. The compara-tive study of English and Chinese taboos is an important subject in intercultural communication, which is easy to be overlooked. The short knowledge of taboo is a great barrier in intercultural communication, therefore, making a comparative study of linguis-tic taboos becomes imperative.

  4. Comparative Analysis and Simulation of Diode Clamped & Cascaded H-Bridge Multilevel Inverter using SPWM Technique

    Directory of Open Access Journals (Sweden)

    Mohit Jain

    2015-01-01

    Full Text Available Multilevel inverters have become more popular over the years in high power medium voltage applications without the use of a transformer and with promise of less disturbance & reduced harmonic distortion. In this paper, two types of multilevel converter in three phase configuration, cascaded H-Bridge multilevel inverter (CMLI and diode clamped multilevel inverter (DCMLI of 5 and 7-level are modelled and compared in the case of feeding of a three phase squirrel cage induction motor. Here, carrier based sinusoidal pulse width modulation (SPWM technique is used as the modulation strategy. These modulation strategy include phase disposition technique (PD, phase opposition disposition technique (POD, and an alternative phase opposition disposition technique (APOD. A detailed study of the modulation technique has been carried out through MATLAB/SIMULINK for both multilevel converters and a comparative evaluation between DCMLI and CMLI using SPWM technique in terms of THD%.

  5. Simulation studies of polymer electrolytes for battery applications

    Energy Technology Data Exchange (ETDEWEB)

    Halley, J.W.; Nielsen, B.

    1998-07-01

    The authors report modeling studies of polyethylene oxide which are carried out with the goal of elucidating the mechanisms of ion conduction in the temperature range of interest to battery applications. They review the previous work in which the amorphous regions of the polymer between its glass and melting temperatures is modeled by a molecular dynamics algorithm in which the model system is polymerized from a model monomeric liquid. They described new work in which the hydrogen centers are added to the model in order to permit comparison with recent neutron work. They compare the simulations of frequency dependent conductivity with experiment and end with a brief discussion of possibilities for improved conductivity which the current understanding suggests.

  6. First studies of T-station alignment with simulated data

    CERN Document Server

    Nicolas, L; Hicheur, A; Hulsbergen, W; Needham, M; Raven, G

    2008-01-01

    The alignment of the tracking stations using tracks fitted using standard LHCb track fit is studied. The procedure is presented together with two examples using simulated data. The first scenario presents the alignment of the IT and OT layers using beam-gas events at 450~GeV with no magnetic field. The second scenario is the alignment of the OT layers and IT boxes, layers and ladders with magnet-on data using minimum bias events at nominal energy. The results are validated by refitting J/$\\psi$ tracks using the misaligned geometry compared to the re-aligned case as well as the default. It is shown that after alignment the J $\\psi$ mass resolution is degraded by at most 3~\\%.

  7. LCIO - A persistency framework for linear collider simulation studies

    Energy Technology Data Exchange (ETDEWEB)

    Graf, Norman

    2003-06-17

    Almost all groups involved in linear collider detector studies have their own simulation software framework. Using a common persistency scheme would allow to easily share results and compare reconstruction algorithms. We present such a persistency framework, called LCIO (Linear Collider I/O). The framework has to fulfill the requirements of the different groups today and be flexible enough to be adapted to future needs. To that end we define an ''abstract object persistency layer'' that will be used by the applications. A first implementation, based on a sequential file format (SIO) is completely separated from the interface, thus allowing support to additional formats if necessary. The interface is defined with the AID (Abstract Interface Definition) tool from freehep.org that allows creation of Java and C++ code synchronously. In order to make use of legacy software a Fortran interface is also provided. We present the design and implementation of LCIO.

  8. A simulation based engineering method to support HAZOP studies

    DEFF Research Database (Denmark)

    Enemark-Rasmussen, Rasmus; Cameron, David; Angelo, Per Bagge

    2012-01-01

    HAZOP is the most commonly used process hazard analysis tool in industry, a systematic yet tedious and time consuming method. The aim of this study is to explore the feasibility of process dynamic simulations to facilitate the HAZOP studies. We propose a simulation-based methodology to complement...... the conventional HAZOP procedure. The method systematically generates failure scenarios by considering process equipment deviations with pre-defined failure modes. The effect of failure scenarios is then evaluated using dynamic simulations -in this study the K-Spice® software used. The consequences of each failure...... model as case study....

  9. Computer simulation studies of pulsed Doppler signals from vortices

    Institute of Scientific and Technical Information of China (English)

    CHEN Sizhong; WANG Yuanyuan; WANG Weiqi

    2001-01-01

    A computer simulation method for pulsed Doppler signals from vortices was proposed to generate simulated vortex Doppler signals under various given circumstances. The relative waveforms, such as the maximum frequency waveform, the mean frequency waveform and the bandwidth waveform, were obtained using the short time Fourier analysis of those simulated signals. The relations were studied between several spectrum parameters obtained from these waveforms and given simulation conditions, such as the position and the size of the sample volume, the distance between two vortices, the free stream velocity and the maximum tangent velocity of the vortex. The sensitive parameters were found to detect vortices using the pulsed Doppler techniques.

  10. Comparative study of bowtie and patient scatter in diagnostic CT

    Science.gov (United States)

    Prakash, Prakhar; Boudry, John M.

    2017-03-01

    A fast, GPU accelerated Monte Carlo engine for simulating relevant photon interaction processes over the diagnostic energy range in third-generation CT systems was developed to study the relative contributions of bowtie and object scatter to the total scatter reaching an imaging detector. Primary and scattered projections for an elliptical water phantom (major axis set to 300mm) with muscle and fat inserts were simulated for a typical diagnostic CT system as a function of anti-scatter grid (ASG) configurations. The ASG design space explored grid orientation, i.e. septa either a) parallel or b) parallel and perpendicular to the axis of rotation, as well as septa height. The septa material was Tungsten. The resulting projections were reconstructed and the scatter induced image degradation was quantified using common CT image metrics (such as Hounsfield Unit (HU) inaccuracy and loss in contrast), along with a qualitative review of image artifacts. Results indicate object scatter dominates total scatter in the detector channels under the shadow of the imaged object with the bowtie scatter fraction progressively increasing towards the edges of the object projection. Object scatter was shown to be the driving factor behind HU inaccuracy and contrast reduction in the simulated images while shading artifacts and elevated loss in HU accuracy at the object boundary were largely attributed to bowtie scatter. Because the impact of bowtie scatter could not be sufficiently mitigated with a large grid ratio ASG, algorithmic correction may be necessary to further mitigate these artifacts.

  11. Is it Trauma- or Fantasy-based? Comparing dissociative identity disorder, post-traumatic stress disorder, simulators, and controls.

    Science.gov (United States)

    Vissia, E M; Giesen, M E; Chalavi, S; Nijenhuis, E R S; Draijer, N; Brand, B L; Reinders, A A T S

    2016-08-01

    The Trauma Model of dissociative identity disorder (DID) posits that DID is etiologically related to chronic neglect and physical and/or sexual abuse in childhood. In contrast, the Fantasy Model posits that DID can be simulated and is mediated by high suggestibility, fantasy proneness, and sociocultural influences. To date, these two models have not been jointly tested in individuals with DID in an empirical manner. This study included matched groups [patients (n = 33) and controls (n = 32)] that were compared on psychological Trauma and Fantasy measures: diagnosed genuine DID (DID-G, n = 17), DID-simulating healthy controls (DID-S, n = 16), individuals with post-traumatic stress disorder (PTSD, n = 16), and healthy controls (HC, n = 16). Additionally, personality-state-dependent measures were obtained for DID-G and DID-S; both neutral personality states (NPS) and trauma-related personality states (TPS) were tested. For Trauma measures, the DID-G group had the highest scores, with TPS higher than NPS, followed by the PTSD, DID-S, and HC groups. The DID-G group was not more fantasy-prone or suggestible and did not generate more false memories. Malingering measures were inconclusive. Evidence consistently supported the Trauma Model of DID and challenges the core hypothesis of the Fantasy Model. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  12. Nuclear wasteform materials: Atomistic simulation case studies

    Energy Technology Data Exchange (ETDEWEB)

    Chroneos, A., E-mail: alex.chroneos@open.ac.uk [Materials Engineering, The Open University, Milton Keynes MK7 6AA (United Kingdom); Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Institute of Materials Science, NCSR Demokritos, GR-15310 Athens (Greece); Rushton, M.J.D. [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Jiang, C. [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Tsoukalas, L.H. [Department of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States)

    2013-10-15

    Ever increasing global energy demand combined with a requirement to reduce CO{sub 2} emissions has rekindled an interest in nuclear power generation. In order that nuclear energy remains publicly acceptable and therefore a sustainable source of power it is important that nuclear waste is dealt with in a responsible manner. To achieve this, improved materials for the long-term immobilisation of waste should be developed. The extreme conditions experienced by nuclear wasteforms necessitate the detailed understanding of their properties and the mechanisms acting within them at the atomic scale. This latter issue is the focus of the present review. Atomic scale simulation techniques can accelerate the development of new materials for nuclear wasteform applications and provide detailed information on their physical properties that cannot be easily accessed by experiment. The present article introduces examples of how atomic scale, computational modelling techniques have led to an improved understanding of current nuclear wasteform materials and also suggest how they may be used in the development of new wasteforms.

  13. Laboratory analogues simulating Titan's atmospheric aerosols: Compared chemical compositions of grains and thin films

    Science.gov (United States)

    Carrasco, Nathalie; Jomard, François; Vigneron, Jackie; Etcheberry, Arnaud; Cernogora, Guy

    2016-09-01

    Two sorts of solid organic samples can be produced in laboratory experiments simulating Titan's atmospheric reactivity: grains in the volume and thin films on the reactor walls. We expect that grains are more representative of Titan's atmospheric aerosols, but films are used to provide optical indices for radiative models of Titan's atmosphere. The aim of the present study is to address if these two sorts of analogues are chemically equivalent or not, when produced in the same N2-CH4 plasma discharge. The chemical compositions of both these materials are measured by using elemental analysis, XPS analysis and Secondary Ion Mass Spectrometry. The main parameter probed is the CH4/N2 ratio to explore various possible chemical regimes. We find that films are homogeneous but significantly less rich in nitrogen and hydrogen than grains produced in the same experimental conditions. This surprising difference in their chemical compositions could be explained by the efficient etching occurring on the films, which stay in the discharge during the whole plasma duration, whereas the grains are ejected after a few minutes. The higher nitrogen content in the grains possibly involves a higher optical absorption than the one measured on the films, with a possible impact on Titan's radiative models.

  14. Sustaining and Improving Study Abroad Experiences Through Comparative Evaluation.

    Science.gov (United States)

    Johanson, Linda S

    Researchers have related participation in study abroad experiences to many positive outcomes for nursing students; however, educators are faced with the task of not only developing meaningful study abroad opportunities but sustaining and improving them as well. Educators can evaluate repeat study abroad programs by comparing experiences, looking for trends, and conjecturing rationales. To illustrate this process, an example of a study abroad opportunity that has been repeated over 11 years is presented. The first six years have been compared to the most recent five years, revealing three categories of change for evaluation and the resulting course improvements.

  15. What Every Social Studies Teacher Should Know about Simulations

    Science.gov (United States)

    Wright-Maley, Cory

    2015-01-01

    Simulations are of growing interest within the social studies in terms of research and practice. Although the findings of early research were unfavorable to simulations in terms of student learning, recent research has revealed new and interesting findings related to different domains of student learning that earlier research did not. In light of…

  16. Simulation Studies of Stratum Corneum Lipid Mixtures

    OpenAIRE

    Das, C; Noro, MG; Olmsted, PD

    2009-01-01

    We present atomistic molecular dynamics results for fully hydrated bilayers composed of ceramide NS-24:0, free fatty acid 24:0 and cholesterol, to address the effect of the different components in the stratum corneum (the outermost layer of skin) lipid matrix on its structural properties. Bilayers containing ceramide molecules show higher in-plane density and hence lower rate of passive transport compared to phospholipid bilayers. At physiological temperatures, for all composition ratios expl...

  17. Comparative Study of Copyright Trade between China and UK

    Directory of Open Access Journals (Sweden)

    Liu Ting

    2013-10-01

    Full Text Available This study aims to promote the development of Chinese copyright trade by comparing copyright trade between China and UK and finding out on which aspects China lags behind UK. With the deepening of Chinese reform and opening up, China has improved its copyright system and accelerated the development of our copyright trade. However, there still is a big gap compared with UK and other developed countries. Based on the comparative study of copyright trade between UK and China, we draw a conclusion so as to promote the development of China's copyright trade. We mainly adopted comparative research method, statistical research method and Empirical research methods in this study. The results show there is a big gap between China and UK on legal system, management of intellectual property right and main information channels etc. China still has a long way to go.

  18. SIMULATION STUDY AND IMPLEMENTATION ON ROUTING PROTOCOLS IN MANET

    Directory of Open Access Journals (Sweden)

    Anju Yadav

    2012-09-01

    Full Text Available Ad-hoc networks are characterized by a lack of infrastructure, and by a random and quickly changing network topology; thus the need for a robust dynamic routing protocol that can accommodate such an environment. Consequently, many routing algorithms have come in toexistence to satisfy the needs of communications in such networks. This article presents a simulation study and comparison the performance between two categories of routing protocols, table-driven (Proactive and on-demand (Reactive routing protocols, this two categories were illustrated by using two different examples ofrouting protocols, first example is DSDV (Destination Sequenced Distance-Vector from the Proactive family and the second example isAODV (Ad Hoc On-Demand Distance Vector and DSR (Dynamic Source Routing Protocol from the Reactive family. Both protocols weresimulated by using NS-2 (network simulator-2 package. Both routing protocols were compared in terms of average throughput (packets delivery ratio while varying data rate, TCP types ,maximumpackets in queue and number of packet drop while varying data rate by using the Trace file. For the same queue length DSDV performsbetter than AODV. AODV is preferred due to its more efficient use of bandwidth.

  19. Simulation Studies of Satellite Laser CO2 Mission Concepts

    Science.gov (United States)

    Kawa, Stephan Randy; Mao, J.; Abshire, J. B.; Collatz, G. J.; Sun X.; Weaver, C. J.

    2011-01-01

    Results of mission simulation studies are presented for a laser-based atmospheric CO2 sounder. The simulations are based on real-time carbon cycle process modeling and data analysis. The mission concept corresponds to ASCENDS as recommended by the US National Academy of Sciences Decadal Survey. Compared to passive sensors, active (lidar) sensing of CO2 from space has several potentially significant advantages that hold promise to advance CO2 measurement capability in the next decade. Although the precision and accuracy requirements remain at unprecedented levels of stringency, analysis of possible instrument technology indicates that such sensors are more than feasible. Radiative transfer model calculations, an instrument model with representative errors, and a simple retrieval approach complete the cycle from "nature" run to "pseudodata" CO2. Several mission and instrument configuration options are examined, and the sensitivity to key design variables is shown. Examples are also shown of how the resulting pseudo-measurements might be used to address key carbon cycle science questions.

  20. Impact of coronary tortuosity on coronary pressure: numerical simulation study.

    Directory of Open Access Journals (Sweden)

    Yang Li

    Full Text Available BACKGROUND: Coronary tortuosity (CT is a common coronary angiographic finding. Whether CT leads to an apparent reduction in coronary pressure distal to the tortuous segment of the coronary artery is still unknown. The purpose of this study is to determine the impact of CT on coronary pressure distribution by numerical simulation. METHODS: 21 idealized models were created to investigate the influence of coronary tortuosity angle (CTA and coronary tortuosity number (CTN on coronary pressure distribution. A 2D incompressible Newtonian flow was assumed and the computational simulation was performed using finite volume method. CTA of 30°, 60°, 90°, 120° and CTN of 0, 1, 2, 3, 4, 5 were discussed under both steady and pulsatile conditions, and the changes of outlet pressure and inlet velocity during the cardiac cycle were considered. RESULTS: Coronary pressure distribution was affected both by CTA and CTN. We found that the pressure drop between the start and the end of the CT segment decreased with CTA, and the length of the CT segment also declined with CTA. An increase in CTN resulted in an increase in the pressure drop. CONCLUSIONS: Compared to no-CT, CT can results in more decrease of coronary blood pressure in dependence on the severity of tortuosity and severe CT may cause myocardial ischemia.