Parametric programming of CNC machine tools
Directory of Open Access Journals (Sweden)
Gołębski Rafał
2017-01-01
Full Text Available The article presents the possibilities of parametric programming of CNC machine tools for the SINUMERIK 840D sl control system. The kinds and types of the definition of variables for the control system under discussion described. On the example of the longitudinal cutting cycle, parametric programming possibilities are shown. The program’s code and its implementation in the control system is described in detail. The principle of parametric programming in a high-level language is also explained.
PARAMETRIC STUDY OF ELECTRICAL DISCHARGE MACHINING OF AISI 304 STAINLESS STEEL
Directory of Open Access Journals (Sweden)
P. SRINIVASA RAO,
2010-08-01
Full Text Available Electrical discharge machining (EDM is widely used process in the production of mould / dies, aerospace, automobile and electronics industries where intricate complex shapes need to be machined in very hard materials. The selection of the AISI 304 stainless steel was made taking into account its use in almost all industrial applicationsfor approximately 50% of the world’s stainless steel production and consumption. In this work, a study has been carried out on the influence of four design factors: current, open-circuit voltage, servo and dutycycle over material removal rate, tool wear rate, surface roughness and hardness on the die-sinking electrical discharge machining of AISI 304 stainless steel. This has been done using design of experiments (DOE, which allows us to carry out theabove-mentioned analysis performing a relatively small number of experiments. In this case, a 3*24-1 mixed level factorial design, whose resolution is V, has been selected due to the number of factors considered in the study. The resolution of this mixed factorial design allows us to estimate all the main effects, two-factor interactions and pure quadratic effects of the four design factors selected to perform this study.
Modeling of autoresonant control of a parametrically excited screen machine
Abolfazl Zahedi, S.; Babitsky, Vladimir
2016-10-01
Modelling of nonlinear dynamic response of a screen machine described by the nonlinear coupled differential equations and excited by the system of autoresonant control is presented. The displacement signal of the screen is fed to the screen excitation directly by means of positive feedback. Negative feedback is used to fix the level of screen amplitude response within the expected range. The screen is anticipated to vibrate with a parametric resonance and the excitation, stabilization and control response of the system are studied in the stable mode. Autoresonant control is thoroughly investigated and output tracking is reported. The control developed provides the possibility of self-tuning and self-adaptation mechanisms that allow the screen machine to maintain a parametric resonant mode of oscillation under a wide range of uncertainty of mass and viscosity.
Studies on parametric optimization for abrasive water jet machining of Al7075-TiB2 in-situ composite
Kavya, J. T.; Keshavamurthy, R.; Pradeep Kumar, G. S.
2016-09-01
The study focuses on optimization and determination of significant process parameter for Abrasive Water Jet Machining of Al7075-TiB2metal matrix composite. Al-TiB2 metal matrix composite is synthesized by stir casting using in-situ technique. Optimization of machining parameters is done using Taguchi's L25orthogonal array for the experimental trials, with cutting speed, stand-off distance and Abrasive Flow rate as input parameters at five different levels. Analysis Of Variance (ANOVA) method is used for identifying the effect of machining parameters on volumetric material removal rate, surface roughness and dimensional accuracy. Then the results are validated by conducting verification experiments.
Energy Technology Data Exchange (ETDEWEB)
Plodinec, M.J.
1998-11-20
After being filled with glass, DWPF canistered waste forms will be welded closed using an upset resistance welding process. This final closure weld must be leaktight, and must remain so during extended storage at SRS. As part of the DWPF Startup Test Program, a parametric study (DWPF-WP-24) has been performed to determine a range of welder operating parameters which will produce acceptable welds. The parametric window of acceptable welds defined by this study is 90,000 + 15,000 lb of force, 248,000 + 22,000 amps of current, and 95 + 15 cycles* for the time of application of the current.
Parametric Mass Reliability Study
Holt, James P.
2014-01-01
The International Space Station (ISS) systems are designed based upon having redundant systems with replaceable orbital replacement units (ORUs). These ORUs are designed to be swapped out fairly quickly, but some are very large, and some are made up of many components. When an ORU fails, it is replaced on orbit with a spare; the failed unit is sometimes returned to Earth to be serviced and re-launched. Such a system is not feasible for a 500+ day long-duration mission beyond low Earth orbit. The components that make up these ORUs have mixed reliabilities. Components that make up the most mass-such as computer housings, pump casings, and the silicon board of PCBs-typically are the most reliable. Meanwhile components that tend to fail the earliest-such as seals or gaskets-typically have a small mass. To better understand the problem, my project is to create a parametric model that relates both the mass of ORUs to reliability, as well as the mass of ORU subcomponents to reliability.
Parametric Optimization of Nd:YAG Laser Beam Machining Process Using Artificial Bee Colony Algorithm
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Rajarshi Mukherjee
2013-01-01
Full Text Available Nd:YAG laser beam machining (LBM process has a great potential to manufacture intricate shaped microproducts with its unique characteristics. In practical applications, such as drilling, grooving, cutting, or scribing, the optimal combination of Nd:YAG LBM process parameters needs to be sought out to provide the desired machining performance. Several mathematical techniques, like Taguchi method, desirability function, grey relational analysis, and genetic algorithm, have already been applied for parametric optimization of Nd:YAG LBM processes, but in most of the cases, suboptimal or near optimal solutions have been reached. This paper focuses on the application of artificial bee colony (ABC algorithm to determine the optimal Nd:YAG LBM process parameters while considering both single and multiobjective optimization of the responses. A comparative study with other population-based algorithms, like genetic algorithm, particle swarm optimization, and ant colony optimization algorithm, proves the global applicability and acceptability of ABC algorithm for parametric optimization. In this algorithm, exchange of information amongst the onlooker bees minimizes the search iteration for the global optimal and avoids generation of suboptimal solutions. The results of two sample paired t-tests also demonstrate its superiority over the other optimization algorithms.
A Coherent Ising Machine Based On Degenerate Optical Parametric Oscillators
Wang, Zhe; Marandi, Alireza; Wen, Kai; Byer, Robert L.; Yamamoto, Yoshihisa
2014-03-01
A degenerate optical parametric oscillator network is proposed to solve the NP-hard problem of finding a ground state of the Ising model. The underlying operating mechanism originates from the bistable output phase of each oscillator and the inherent preference of the network in selecting oscillation modes with the minimum photon decay rate. Computational experiments are performed on all instances reducible to the NP-hard MAX-CUT problems on cubic graphs of order up to 20. The numerical results reasonably suggest the effectiveness of the proposed network. This project is supported by the FIRST program of Japanese Government. Zhe Wang is also grateful for the support from Stanford Graduate Fellowship.
Institute of Scientific and Technical Information of China (English)
M.M.Kamel; W.A.A.El-Ganaini; Y.S.Hamed
2009-01-01
Ultrasonic machining (USM) is of particular interest for the machining of non-conductive, brittle mate-rials such as engineering ceramics, In this paper, a multi-tool technique is used in USM to reduce the vibration in the tool holder and have reasonable amplitude for the tools. This can be done via dynamic absorbers. The coupling of four non-linear oscillators of the tool holder and tools representing ultrasonic cutting process are investigated. This leads to a four-degree-of-freedom system subjected to multi-external and multi-parametric excitation forces. The aim of this work is to control the tool holder behavior at simultaneous pri-mary, sub-harmonic and internal resonance condition. Mul-tiple scale perturbation method is used to obtain the solution up to the second order approximations. The different reso-nance cases are reported and studied numerically. The stabil-ity of the system is investigated by using both phase-plane and frequency response techniques. The effects of the differ-ent parameters of the tools on the system behavior are studied numerically. Comparison with the available published work is reported.
Song, Dong; Wang, Zhuo; Marmarelis, Vasilis Z; Berger, Theodore W
2009-02-01
This paper presents a synergistic parametric and non-parametric modeling study of short-term plasticity (STP) in the Schaffer collateral to hippocampal CA1 pyramidal neuron (SC) synapse. Parametric models in the form of sets of differential and algebraic equations have been proposed on the basis of the current understanding of biological mechanisms active within the system. Non-parametric Poisson-Volterra models are obtained herein from broadband experimental input-output data. The non-parametric model is shown to provide better prediction of the experimental output than a parametric model with a single set of facilitation/depression (FD) process. The parametric model is then validated in terms of its input-output transformational properties using the non-parametric model since the latter constitutes a canonical and more complete representation of the synaptic nonlinear dynamics. Furthermore, discrepancies between the experimentally-derived non-parametric model and the equivalent non-parametric model of the parametric model suggest the presence of multiple FD processes in the SC synapses. Inclusion of an additional set of FD process in the parametric model makes it replicate better the characteristics of the experimentally-derived non-parametric model. This improved parametric model in turn provides the requisite biological interpretability that the non-parametric model lacks.
Zhang, Xin; Yan, Lin-Feng; Hu, Yu-Chuan; Li, Gang; Yang, Yang; Han, Yu; Sun, Ying-Zhi; Liu, Zhi-Cheng; Tian, Qiang; Han, Zi-Yang; Liu, Le-De; Hu, Bin-Quan; Qiu, Zi-Yu; Wang, Wen; Cui, Guang-Bin
2017-07-18
Current machine learning techniques provide the opportunity to develop noninvasive and automated glioma grading tools, by utilizing quantitative parameters derived from multi-modal magnetic resonance imaging (MRI) data. However, the efficacies of different machine learning methods in glioma grading have not been investigated.A comprehensive comparison of varied machine learning methods in differentiating low-grade gliomas (LGGs) and high-grade gliomas (HGGs) as well as WHO grade II, III and IV gliomas based on multi-parametric MRI images was proposed in the current study. The parametric histogram and image texture attributes of 120 glioma patients were extracted from the perfusion, diffusion and permeability parametric maps of preoperative MRI. Then, 25 commonly used machine learning classifiers combined with 8 independent attribute selection methods were applied and evaluated using leave-one-out cross validation (LOOCV) strategy. Besides, the influences of parameter selection on the classifying performances were investigated. We found that support vector machine (SVM) exhibited superior performance to other classifiers. By combining all tumor attributes with synthetic minority over-sampling technique (SMOTE), the highest classifying accuracy of 0.945 or 0.961 for LGG and HGG or grade II, III and IV gliomas was achieved. Application of Recursive Feature Elimination (RFE) attribute selection strategy further improved the classifying accuracies. Besides, the performances of LibSVM, SMO, IBk classifiers were influenced by some key parameters such as kernel type, c, gama, K, etc. SVM is a promising tool in developing automated preoperative glioma grading system, especially when being combined with RFE strategy. Model parameters should be considered in glioma grading model optimization.
Directory of Open Access Journals (Sweden)
Debkalpa Goswami
2015-03-01
Full Text Available Ultrasonic machining (USM is a mechanical material removal process used to erode holes and cavities in hard or brittle workpieces by using shaped tools, high-frequency mechanical motion and an abrasive slurry. Unlike other non-traditional machining processes, such as laser beam and electrical discharge machining, USM process does not thermally damage the workpiece or introduce significant levels of residual stress, which is important for survival of materials in service. For having enhanced machining performance and better machined job characteristics, it is often required to determine the optimal control parameter settings of an USM process. The earlier mathematical approaches for parametric optimization of USM processes have mostly yielded near optimal or sub-optimal solutions. In this paper, two almost unexplored non-conventional optimization techniques, i.e. gravitational search algorithm (GSA and fireworks algorithm (FWA are applied for parametric optimization of USM processes. The optimization performance of these two algorithms is compared with that of other popular population-based algorithms, and the effects of their algorithm parameters on the derived optimal solutions and computational speed are also investigated. It is observed that FWA provides the best optimal results for the considered USM processes.
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Yoshitaka Haribara
2016-04-01
Full Text Available We present the operational principle of a coherent Ising machine (CIM based on a degenerate optical parametric oscillator (DOPO network. A quantum theory of CIM is formulated, and the computational ability of CIM is evaluated by numerical simulation based on c-number stochastic differential equations. We also discuss the advanced CIM with quantum measurement-feedback control and various problems which can be solved by CIM.
Venkatesan, K.; Ramanujam, R.; Kuppan, P.
2016-04-01
This paper presents a parametric effect, microstructure, micro-hardness and optimization of laser scanning parameters (LSP) on heating experiments during laser assisted machining of Inconel 718 alloy. The laser source used for experiments is a continuous wave Nd:YAG laser with maximum power of 2 kW. The experimental parameters in the present study are cutting speed in the range of 50-100 m/min, feed rate of 0.05-0.1 mm/rev, laser power of 1.25-1.75 kW and approach angle of 60-90°of laser beam axis to tool. The plan of experiments are based on central composite rotatable design L31 (43) orthogonal array. The surface temperature is measured via on-line measurement using infrared pyrometer. Parametric significance on surface temperature is analysed using response surface methodology (RSM), analysis of variance (ANOVA) and 3D surface graphs. The structural change of the material surface is observed using optical microscope and quantitative measurement of heat affected depth that are analysed by Vicker's hardness test. The results indicate that the laser power and approach angle are the most significant parameters to affect the surface temperature. The optimum ranges of laser power and approach angle was identified as 1.25-1.5 kW and 60-65° using overlaid contour plot. The developed second order regression model is found to be in good agreement with experimental values with R2 values of 0.96 and 0.94 respectively for surface temperature and heat affected depth.
Parametric Study Of Window Frame Geometry
DEFF Research Database (Denmark)
Zajas, Jan Jakub; Heiselberg, Per
2013-01-01
This paper describes a parametric study on window frame geometry with the goal of designing frames with very good thermal properties. Three different parametric frame models are introduced, deseribed by a number of variables. In the first part of the study, a process of sensitivity analysis...... is conducted to determine which of the parameters describing the frame have the highest impact on its thermal performance. Afterwards, an optimization process is conducted on each frame in order to optimize the design with regard to three objectives: minimizing the thermal transmittance, maxim izing the net...
Parametric Study Of Window Frame Geometry
DEFF Research Database (Denmark)
Zajas, Jan Jakub; Heiselberg, Per
2013-01-01
This paper describes a parametric study on window frame geometry with the goal of designing frames with very good thermal properties. Three different parametric frame models are introduced, deseribed by a number of variables. In the first part of the study, a process of sensitivity analysis is co...... energy gain factor and minimizing the material use. Since the objectives contradiet each other, it was found that it is not possible to identifY a single solution that satisfies all these goals. lnstead, a compromise between the objectives has to be found....
Parametric study of laser photovoltaic energy converters
Walker, G. H.; Heinbockel, J. H.
1987-01-01
Photovoltaic converters are of interest for converting laser power to electrical power in a space-based laser power system. This paper describes a model for photovoltaic laser converters and the application of this model to a neodymium laser silicon photovoltaic converter system. A parametric study which defines the sensitivity of the photovoltaic parameters is described. An optimized silicon photovoltaic converter has an efficiency greater than 50 percent for 1000 W/sq cm of neodymium laser radiation.
Grasser, L; Parrain, F; Roux, X Le; Gilles, J -P
2008-01-01
Parametric amplification is an interesting way of artificially increasing a MEMS Quality factor and could be helpful in many kinds of applications. This paper presents a theoretical study of this principle, based on Matlab/Simulink simulations, and proposes design guidelines for parametric structures. A new device designed with this approach is presented together with the corresponding FEM simulation results.
Parametric optimization for the production of nanostructure in high carbon steel chips via machining
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M. Ilangkumaran
2015-09-01
Full Text Available Nano crystalline materials are an area of interest for the researchers all over the world due to its superior mechanical properties such as high strength and high hardness. But the cost of nano-crystals is high because of the complexity and cost incurred during its production. This paper focuses on the application of Taguchi method with Fuzzy logic for optimizing the machining parameters of nano-crystalline structured chips production in High Carbon Steel (HCS through machining. An orthogonal array, multi-response performance index, signals to noise ratio and analysis of variance are used to study the machining process with multi-response performance characteristics. The machining parameters namely rake angle, depth of cut, heat treatment, feed and cutting velocity are optimized with considerations of the multi-response performance characteristics. Using the Taguchi and Fuzzy logic method optimum cutting conditions are identified in order to obtain the smallest nanocrystalline structure via machining.
Parametric study of modern airship productivity
Ardema, M. D.; Flaig, K.
1980-01-01
A method for estimating the specific productivity of both hybrid and fully buoyant airships is developed. Various methods of estimating structural weight of deltoid hybrids are discussed and a derived weight estimating relationship is presented. Specific productivity is used as a figure of merit in a parametric study of fully buoyant ellipsoidal and deltoid hybrid semi-buoyant vehicles. The sensitivity of results as a function of assumptions is also determined. No airship configurations were found to have superior specific productivity to transport airplanes.
Energy Technology Data Exchange (ETDEWEB)
Wade, James Rokwel; Tomlinson, Kurt; Bryce, Edwin Anthony
2008-09-01
The charter goal of the Agile Machining and Inspection Thrust Area Team is to identify technical requirements, within the nuclear weapons complex (NWC), for Agile Machining and Inspection capabilities. During FY 2008, the team identified Parametric Technology Corporation (PTC) Pro/CMM as a software tool for use in off-line programming of probing routines--used for measurement--for machining and turning centers. The probing routine would be used for in-process verification of part geometry. The same Pro/CMM program used on the machine tool could also be employed for program validation / part verification using a coordinate measuring machine (CMM). Funding was provided to determine the compatibility of the Pro/CMM probing program with CMM software (Zeiss DMISEngine).
Directory of Open Access Journals (Sweden)
R. K. Arya
2012-12-01
Full Text Available Abstract – In recent few years composite materials have gained pace in engineering application. But they have poor machinability by using conventional machining methods. So it is required to study about these materials for better use in engineering application. To fulfillment of this aim, a study is done by conduct experiments (i.e. Machining on Al/SiC metal matrix composite (MMC. From the non-conventional machining process, Powder Mixed Electrical discharge machining (PMEDM is used to machining of Al/SiC MMC. PMEDM is a technological improvement in conventional EDM, which was previously studied by many researchers to better MRR with good surface roughness (SR. In this study, the controllable machining process parameters (i.e. Peak Current (Ip, Duty Cycle, Powder Concentration (PC, Gap Control and Sensitivity of PMEDM was selected to experimental investigation. The process performance is measured in terms of material removal rate (MRR and surface finish (SR. The research outcome will identify the important parameters and their effect on MRR of Al/SiC MMC in the presence of suspended graphite (Gr powder in a kerosene dielectric of EDM. Response surface methodology (RSM has been used to plan and analyze the experimental results. The experimental results emerged that only sensitivity has non-significant effect on MMR and SR from the selected process parameters, but it gives significant effects with other factors in interaction. Further it found that, the MRR is directly proportional to Ip and inversely proportional to the PC and duty cycle, and the SR improves at lower Ip and optimum range of PC, gap control and duty cycle.
Non-parametric approach to the study of phenotypic stability.
Ferreira, D F; Fernandes, S B; Bruzi, A T; Ramalho, M A P
2016-02-19
The aim of this study was to undertake the theoretical derivations of non-parametric methods, which use linear regressions based on rank order, for stability analyses. These methods were extension different parametric methods used for stability analyses and the result was compared with a standard non-parametric method. Intensive computational methods (e.g., bootstrap and permutation) were applied, and data from the plant-breeding program of the Biology Department of UFLA (Minas Gerais, Brazil) were used to illustrate and compare the tests. The non-parametric stability methods were effective for the evaluation of phenotypic stability. In the presence of variance heterogeneity, the non-parametric methods exhibited greater power of discrimination when determining the phenotypic stability of genotypes.
Studies of nondegenerate, quasi-phase-matched optical parametric amplification
Energy Technology Data Exchange (ETDEWEB)
Lawrence Livermore National Laboratory
2004-03-18
We have performed extensive numerical studies of quasi-phase-matched optical parametric amplification with the aim to improve its nondegenerate spectral bandwidth. Our multi-section fan-out design calculations indicate a 35-fold increase in spectral bandwidth.
Energy Technology Data Exchange (ETDEWEB)
Laroche, E. [Centre National de la Recherche Scientifique (CNRS UMR), Lab. des Sciences de l' Image, de l' Informatique et de la Teledetection, 67 - Illkirch (France); Durieu, C.; Louis, J.P. [Centre National de la Recherche Scientifique (CNRS UPRESA 8029), Lab. d' Electricite, Signaux et Robotique, 94 - Cachan (France)
2002-07-01
Many parametric models of induction machines in sinusoidal mode, some of which account for saturation and iron losses, are available. These models must not only be identifiable, they must also provide for an accurate estimation of physical parameters. In this paper, parameter estimation errors due to measurement noise and model errors are analyzed. The most perturbed cases, such as those neglecting saturation or iron losses, are given special consideration herein. This study allows drawing conclusions as to the practical identifiability of the various models. Results are then used to design optimal experiments in which parameter estimation errors have been minimized. (authors)
Comparative Study of Parametric and Non-parametric Approaches in Fault Detection and Isolation
DEFF Research Database (Denmark)
Katebi, S.D.; Blanke, M.; Katebi, M.R.
This report describes a comparative study between two approaches to fault detection and isolation in dynamic systems. The first approach uses a parametric model of the system. The main components of such techniques are residual and signature generation for processing and analyzing. The second...... approach is non-parametric in the sense that the signature analysis is only dependent on the frequency or time domain information extracted directly from the input-output signals. Based on these approaches, two different fault monitoring schemes are developed where the feature extraction and fault decision...... algorithms employed are adopted from the template matching in pattern recognition. Extensive simulation studies are performed to demonstrate satisfactory performance of the proposed techniques. The advantages and disadvantages of each approach are discussed and analyzed....
Machinability studies on INCONEL 718
Xavior, M. Anthony; Patil, Mahesh; Maiti, Abheek; Raj, Mrinal; Lohia, Nitesh
2016-09-01
The main objective of proposed work is to determine the influence of controllable parameters on machining characteristics of Inconel-718 and to achieve the optimum parameters for sustainable and efficient turning. Understanding the consequences of advanced tool materials together with higher cutting speeds on the formation of residual stresses and therefore the underlying mechanisms of small structural alteration within the subterranean layer thereby becomes terribly crucial for predicting product quality and more optimizing the machining conditions. Controllable cutting parameters such as cutting velocity, feed rate and depth of cut were selected at different level for experimentations in accordance with the Taguchi L9 array method using Minimum Quantity Lubrication (MQL) cutting condition and three different tools namely PVD TiAlN carbide, Cubic boron nitride and ceramic. Extensive study is done on the resulting surface roughness, surface subsurface hardness, tool wear and chip morphology. The results obtained from each of the tool were thoroughly analyzed and finally the optimized parameters are obtained for efficient machining of Inconel 718.
PROCESS UNIFICATION AND FRAME PREPARATION OF MACHINING PARAMETRES FOR ROTATIONAL PARTS
Directory of Open Access Journals (Sweden)
Ersan ASLAN
2005-01-01
Full Text Available Any traditional or computerized metal removal process needs a prototype, a technical drawing and a database for production of a part. Design, process planning and manufacturing problems such as modeling, the necessity data extraction from standard data exchange formats, and part programme preparation for machine tools can be solved by the operators or experts as soon as possible while they occurred in the traditonal approach. In circumstances of the production efforts spent by the computer, all experiences of expert can be saved in a database for foresight of the possible problems. This data can be used at any stage in the product cycle. In this paper, it is presented the results of research efforts which aimed to extract information from the defacto industry standard DXF files to determine features existing on rotational parts to be machined on horizontal machining centers. After process extraction and definition, process unifications and frame preparation for machining parameters of the part are introduced.
Study On Machining Processing Technology Risk Control
Institute of Scientific and Technical Information of China (English)
Li Xiqing
2015-01-01
In the industrial production process,only to ful y guarantee the machining production safety, it can been ensured that the smooth completion of machining process.Under this back ground,in the machining production process,the machinery processing safety would been ful y concerned,several factors, which may lead to the problem of mechanical processing and production process,were analyzed,and the relevant control strategies were researched.In view of this situation,this paper wil specifical y combined with the machining process characteristics to study the machining process manufacturability risk control.
Rocket injector anomalies study. Volume 2: Results of parametric studies
Przekwas, A. J.; Singhal, A. K.; Tam, L. T.
1984-01-01
The employment of a existing computer program to simulate three dimensional two phase gas spray flows in liquid propellant rocket engines. This was accomplished by modification of an existing three dimensional computer program (REFLAN3D) with Euler/Lagrange approach for simulating two phase spray flow, evaporation and combustion. The modified code is referred to as REFLAN3D-SPRAY. Computational studies of the model rocket engine combustion chamber are presented. The parametric studies of the two phase flow and combustion shows qualitatively correct response for variations in geometrical and physical parameters. The injection nonuniformity test with blocked central fuel injector holes shows significant changes in the central flame core and minor influence on the wall heat transfer fluxes.
Directory of Open Access Journals (Sweden)
YOGENDRA TYAGI
2012-08-01
Full Text Available In this paper the drilling of mild steel with the help of CNC drilling machining operation with tool use high speed steel by applying taguchi methodology has been reported. The signal-to-noise ratio applied to find optimum process parameter for CNC drilling machining .A L9 orthogonal array and analysis of variance(ANOVA are applied to study the performance characteristics of machining parameter (spindle speed, feed, depth with consideration of good surface finish as well as high material removal rate(MRR .Surfacefinishing is one of the prime requirements of customers of machining parts .Results obtained by taguchi method and signal-to-noise ratio match closely with (ANOVA and the feed is most effective factor for MRR. And spindle speed is the most effective factor for surface roughness. Multiple regression equation are formulated forestimating predicted value surface roughness and material removal rate
Parametric study for horizontal steam generator modelling
Energy Technology Data Exchange (ETDEWEB)
Ovtcharova, I. [Energoproekt, Sofia (Bulgaria)
1995-12-31
In the presentation some of the calculated results of horizontal steam generator PGV - 440 modelling with RELAP5/Mod3 are described. Two nodalization schemes have been used with different components in the steam dome. A study of parameters variation on the steam generator work and calculated results is made in cases with separator and branch.
Directory of Open Access Journals (Sweden)
M. Kaladhar
2012-08-01
Full Text Available In this work, Taguchi method is applied to determine the optimum process parameters for turning of AISI 304 austenitic stainless steel on CNC lathe. A Chemical vapour deposition (CVD coated cemented carbide cutting insert is used which is produced by DuratomicTM technology of 0.4 and 0.8 mm nose radii. The tests are conducted at four levels of Cutting speed, feed and depth of cut. The influence of these parameters are investigated on the surface roughness and material removal rate (MRR. The Analysis Of Variance (ANOVA is also used to analyze the influence of cutting parameters during machining. The results revealed that cutting speed significantly (46.05% affected the machined surface roughness values followed by nose radius (23.7%. The influence of the depth of cut (61.31% in affecting material removal rate (MRR is significantly large. The cutting speed (20.40% is the next significant factor. Optimal range and optimal level of parameters are also predicted for responses.
Parametric Studies on Star Port Propellant Grain For Ballistic Evaluation
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Himanshu Shekhar
2005-10-01
Full Text Available Star port propellant grains have been extensively studied for their operating as well as geometrical parameters. It is observed that reduced tail-off and better neutrality cannot be achieved simultaneously in a configuration. Parametric study is conducted to know the effect of various parameters of star-shaped propellant grains for ballistic evaluation motor. For reduced tail-off, higher characteristic velocity, lower outer diameter of the star, and lower value of angular fraction is preferred. Star angle, burning rate, and throat diameter have negligible effects on the tail-off factor. For better neutrality, higher value of angular fraction, higher star outer diameter, and star angle near to neutrality, is needed. An alternate configuration is suggested using this parametric study to ascertain least tail-off and enhanced neutrality.
Parametric study of the Venus atmospheric superrotation
Takagi, Masahiro; Matsuda, Yoshihisa
2012-07-01
It has been suggested by Takagi and Matsuda (2007) that the Venus atmospheric superrotation can be generated and maintained by the thermal tides excited by the solar heating at the cloud levels. The superrotation generated by the thermal tide mechanism is supposed to be sensitive to the static stability, initial conditions, vertical distribution of the solar heating, and so on. In the present study, we focus on how the superrotation maintained by the thermal tide mechanism depends on the static stability. The preliminary result shows that the superrotation is maintained in the cases of large static stability, and it fades out with time in the cases of small static stability. The difference may by explained by the dispersion relation of the gravity wave and the thermodynamic balance of the semidiurnal tide. It is also shown that the superrotation faster than 200 m/s is generated in the case included the mean zonal component of the solar heating. It is implied that the deceleration effect of the mean zonal flow due to the thermal tide is canceled by the vertical advection of negative dU/dz above the cloud level, and the momentum is actively exchanged between the cloud and the ground levels because of the vital semidiurnal tide.
Gas Hydrate Growth Kinetics: A Parametric Study
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Remi-Erempagamo Tariyemienyo Meindinyo
2016-12-01
Full Text Available Gas hydrate growth kinetics was studied at a pressure of 90 bars to investigate the effect of temperature, initial water content, stirring rate, and reactor size in stirred semi-batch autoclave reactors. The mixing energy during hydrate growth was estimated by logging the power consumed. The theoretical model by Garcia-Ochoa and Gomez for estimation of the mass transfer parameters in stirred tanks has been used to evaluate the dispersion parameters of the system. The mean bubble size, impeller power input per unit volume, and impeller Reynold’s number/tip velocity were used for analyzing observed trends from the gas hydrate growth data. The growth behavior was analyzed based on the gas consumption and the growth rate per unit initial water content. The results showed that the growth rate strongly depended on the flow pattern in the cell, the gas-liquid mass transfer characteristics, and the mixing efficiency from stirring. Scale-up effects indicate that maintaining the growth rate per unit volume of reactants upon scale-up with geometric similarity does not depend only on gas dispersion in the liquid phase but may rather be a function of the specific thermal conductance, and heat and mass transfer limitations created by the limit to the degree of the liquid phase dispersion is batched and semi-batched stirred tank reactors.
Parametric design study of ``power stick'' and its derivatives
Schock, Alfred; Or, Chuen T.
1995-01-01
The paper addresses some major concerns about the Power Stick concept proposed by Jet Propulsion Laboratory (JPL) personnel, and describes parametric studies of derivative designs to determine to what extent those concerns can be alleviated. The Power Stick and its derivatives are based on the use of the 1-watt(t) Radioisotope Heater Unit (RHU) to power a thermoelectric multicouple. Our study concludes that: (a) while the RHU has been safety-qualified as a low-temperature heater, additional reentry analyses and test would be needed to qualify it as a higher temperature heat source for the Power Stick, (b) even after parametric design optimization, the efficiency of the Power Stick and its derivatives is only 2.2%, and, (c) all generators based on the 1-watt heat source require a thermoelectric multicouple with a large number of extremely thin legs, of very doubtful fabricability.
Parametric studies in elastic stability of nonconservative beams
Directory of Open Access Journals (Sweden)
Nánási T.
2007-11-01
Full Text Available In this paper the nonconservative Beck`s column loaded with follower compressive force is generalized by introduction of the possibility to be subjected to subtangential follower force with excentric point of action. For corresponding boundary eigenvalue problem the frequency equation is derived. Results of parametric studies are presented for the lowest eigencurves, which describe the relation between the compressive load magnitude and the eigenfrequencies and indicate whether stability loss by divergence or by flutter occurs.
Parametric Study Of A Ceramic-Fiber/Metal-Matrix Composite
Murthy, P. L. N.; Hopkins, D. A.; Chamis, C. C.
1992-01-01
Report describes computer-model parametric study of effects of degradation of constituent materials upon mechanical properties of ceramic-fiber/metal-matrix composite material. Contributes to understanding of weakening effects of large changes in temperature and mechanical stresses in fabrication and use. Concerned mainly with influences of in situ fiber and matrix properties upon behavior of composite. Particular attention given to influence of in situ matrix strength and influence of interphase degradation.
Directory of Open Access Journals (Sweden)
S. Chartakom
2008-12-01
Full Text Available Purpose: The objective of this experiment is to obtain the fine surface roughness that is required less final polishing process as well as shortest manufacturing lead time.Design/methodology/approach: the aluminum Alloy 5058, 6163 and 7075 are selected for the experiment on a high speed machine. The machine used for testing is namely Mold Maker 200&2500 which is the high precision machining center. Secondly, the study is emphasizes on the suitable cutting tool and cutting parameters. Accurate surface roughness measured level is an important factor for injection mold making. This section explains the process of surface roughness measurement on the machine, namely MarSurf XCR 20 V1.20-4.Findings: The investigations are shown that the Aluminum graded Al 6163 and Al 7075 can be suitably used for the sport sole mold making in or to obtain the acceptable surface roughness without polishingPractical implications: The method can be adapted for all global shapes of tools, even in the case of complex geometriesOriginality/value: The investigations are shown that the Aluminum Al 6163 and Al 7075 can extremely save machining and polishing time.
Parametric design study of tandem mirror fusion reactors
Energy Technology Data Exchange (ETDEWEB)
Carlson, G.A.
1977-05-27
The parametric design study of the tandem mirror reactor (TMR) is described. The results of this study illustrate the variation of reactor characteristics with changes in the independent design parameters, reveal the set of design parameters which minimizes the cost of the reactor, and show the sensitivity of the optimized design to physics and technological uncertainties. The total direct capital cost of an optimized 1000 MWe TMR is estimated to be $1300/kWe. The direct capital cost of a 2000 MWe plant is less than $1000/kWe.
Parametric Studies of Square Solar Sails Using Finite Element Analysis
Sleight, David W.; Muheim, Danniella M.
2004-01-01
Parametric studies are performed on two generic square solar sail designs to identify parameters of interest. The studies are performed on systems-level models of full-scale solar sails, and include geometric nonlinearity and inertia relief, and use a Newton-Raphson scheme to apply sail pre-tensioning and solar pressure. Computational strategies and difficulties encountered during the analyses are also addressed. The purpose of this paper is not to compare the benefits of one sail design over the other. Instead, the results of the parametric studies may be used to identify general response trends, and areas of potential nonlinear structural interactions for future studies. The effects of sail size, sail membrane pre-stress, sail membrane thickness, and boom stiffness on the sail membrane and boom deformations, boom loads, and vibration frequencies are studied. Over the range of parameters studied, the maximum sail deflection and boom deformations are a nonlinear function of the sail properties. In general, the vibration frequencies and modes are closely spaced. For some vibration mode shapes, local deformation patterns that dominate the response are identified. These localized patterns are attributed to the presence of negative stresses in the sail membrane that are artifacts of the assumption of ignoring the effects of wrinkling in the modeling process, and are not believed to be physically meaningful. Over the range of parameters studied, several regions of potential nonlinear modal interaction are identified.
Tokamak Transmutation of (nuclear) Waste (TTW): Parametric studies
Cheng, E. T.; Krakowski, R. A.; Peng, Y. K. M.
Radioactive waste generated as part of the commercial-power and defense nuclear programs can be either stored or transmuted. The latter treatment requires a capital-intensive neutron source and is reserved for particularly hazardous and long-lived actinide and fission-product waste. A comparative description of fusion-based transmutation is made on the basis of rudimentary estimates of ergonic performance and transmutation capacities versus inventories for both ultra-low aspect-ratio (spherical torus, ST) and conversional (aspect-ratio) tokamak fusion-power-core drivers. The parametric systems studies reported herein provides a preamble to more-detailed, cost-based systems analyses.
Barka, Noureddine
This project involves a study of sensitivity of the hardness profile of cylindrical bars and spur gears heated by induction using finite element models (axisymmetric and 2D) combined with experimental tests. This sensitivity study is considered as the basic step towards the development of prediction models. The study mainly aims at evaluating the effect of material properties and machine parameters on the hardness profile. As the induction heating is very fast, it is reasonable to assume that the material properties are different from those measured under thermodynamic equilibrium conditions. For this reason, the study attempts to measure the effect of variations in material properties on the surface temperature using the axisymmetric model. The results show that the relative magnetic permeability is the property that most significantly influences surface temperatures and the variation of this property has a large effect on the hardness profile. The effects of specific heat and electrical conductivity are rather low, while the thermal conductivity has a negligible effect on the model developed. Moreover, the variation in temperature of austenitizing margins have limited effects on the developed model. Therefore, the use of material properties at thermodynamic equilibrium was sufficient to establish models for predicting trends. Moreover, study of global sensitivity profile of hardness as a function of machine parameters allowed, in the first place, to compare the two cases of heat to medium and high frequency, by applying them to a disc and a gear and determine the effect of the imposed current density and heating time on the hardness profile using the results of the simulations. It appears that the edge effect is smaller in the MF heating case. In addition, the 2D model can confirm that the MF power heat more the tooth root, while the HF power heat the tooth tip region. Finally, the regression models developed were used to estimate surface temperatures and depths
A numerical parametric study on hydrofoil interaction in tandem
Kemal, Omer
2015-01-01
Understanding the effects of the parameters affecting the interaction of tandem hydrofoil system is a crucial subject in order to fully comprehend the aero/hydrodynamics of any vehicle moving inside a fluid. This study covers a parametric study on tandem hydrofoil interaction in both potential and viscous fluids using iterative Boundary Element Method (BEM) and RANSE. BEM allows a quick estimation of the flow around bodies and may be used for practical purposes to assess the interaction inside the fluid. The produced results are verified by conformal mapping and Finite Volume Method (FVM). RANSE is used for viscous flow conditions to assess the effects of viscosity compared to the inviscid solutions proposed by BEM. Six different parameters are investigated and they are the effects of distance, thickness, angle of attack, chord length, aspect ratio and tapered wings. A generalized 2-D code is developed implementing the iterative procedure and is adapted to generate results. Effects of free surface and cavitation are ignored. It is believed that the present work will provide insight into the parametric interference between hydrofoils inside the fluid
A numerical parametric study on hydrofoil interaction in tandem
Directory of Open Access Journals (Sweden)
Kemal Omer
2015-01-01
Full Text Available Understanding the effects of the parameters affecting the interaction of tandem hydrofoil system is a crucial subject in order to fully comprehend the aero/hydrodynamics of any vehicle moving inside a fluid. This study covers a parametric study on tandem hydrofoil interaction in both potential and viscous fluids using iterative Boundary Element Method (BEM and RANSE. BEM allows a quick estimation of the flow around bodies and may be used for practical purposes to assess the interaction inside the fluid. The produced results are verified by conformal mapping and Finite Volume Method (FVM. RANSE is used for viscous flow conditions to assess the effects of viscosity compared to the inviscid solutions proposed by BEM. Six different parameters are investigated and they are the effects of distance, thickness, angle of attack, chord length, aspect ratio and tapered wings. A generalized 2-D code is developed implementing the iterative procedure and is adapted to generate results. Effects of free surface and cavitation are ignored. It is believed that the present work will provide insight into the parametric interference between hydrofoils inside the fluid
A numerical parametric study on hydrofoil interaction in tandem
Directory of Open Access Journals (Sweden)
Omer Kemal Kinaci
2015-01-01
Full Text Available Understanding the effects of the parameters affecting the interaction of tandem hydrofoil system is a crucial subject in order to fully comprehend the aero/hydrodynamics of any vehicle moving inside a fluid. This study covers a parametric study on tandem hydrofoil interaction in both potential and viscous fluids using iterative Boundary Element Method (BEM and RANSE. BEM allows a quick estimation of the flow around bodies and may be used for practical purposes to assess the interaction inside the fluid. The produced results are verified by conformal mapping and Finite Volume Method (FVM. RANSE is used for viscous flow conditions to assess the effects of viscosity compared to the inviscid solutions proposed by BEM. Six different parameters are investigated and they are the effects of distance, thickness, angle of attack, chord length, aspect ratio and tapered wings. A generalized 2-D code is developed implementing the iterative procedure and is adapted to generate results. Effects of free surface and cavitation are ignored. It is believed that the present work will provide insight into the parametric interference between hydrofoils inside the fluid.
A study of hybrid prediction method for ship parametric rolling
Institute of Scientific and Technical Information of China (English)
周耀华; 马宁; 鲁江; 顾民
2016-01-01
The parametric rolling (PR) in the head or following waves has been considered as one of the main stability failure modes in the development of the 2nd generation Intact Stability criterion by the International Maritime Organization (IMO). According to previous studies, the estimation methods of the roll damping affect the prediction of the PR significantly, and most of them are based on experiment data or Ikeda’s empirical formula. The accuracy of the estimation method for the roll damping could be a key aspect for the validity of its prediction for the full scale ship. In this research, a hybrid prediction method is developed for the numerical prediction of the parametric rolling when experiment data are not available for the roll damping. Comparison study is also carried out between the hybrid method and a nonlinear dynamics method, where the roll damping is estimated by the simplified Ikeda’s method and the direct CFD prediction method in a direct non-linear simulation based on the 3-D CFD approach in the model scale. It is shown that the results of the hybrid method are in satisfactory agreements with the model experiment results, and the method can be used for analysis especially at the early design stage where experiment data are often not available.
Experimental study of parametric subharmonic instability for internal waves
Bourget, Baptiste; Joubaud, Sylvain; Odier, Philippe
2013-01-01
Internal waves are believed to be of primary importance as they affect ocean mixing and energy transport. Several processes can lead to the breaking of internal waves and they usually involve non linear interactions between waves. In this work, we study experimentally the parametric subharmonic instability (PSI), which provides an efficient mechanism to transfer energy from large to smaller scales. It corresponds to the destabilization of a primary plane wave and the spontaneous emission of two secondary waves, of lower frequencies and different wave vectors. Using a time-frequency analysis, we observe the time evolution of the secondary waves, thus measuring the growth rate of the instability. In addition, a Hilbert transform method allows the measurement of the different wave vectors. We compare these measurements with theoretical predictions, and study the dependence of the instability with primary wave frequency and amplitude, revealing a possible effect of the confinement due to the finite size of the be...
Parametric scaling study of a magnetically insulated thermionic vacuum switch
Energy Technology Data Exchange (ETDEWEB)
Vanderberg, B.H.; Eninger, J.E. [Royal Inst. of Technology, Stockholm (Sweden). Dept. of Industrial Electrotechnology
1996-02-01
A parametric scaling study is performed on MINOS (Magnetically INsulated Opening Switch), a novel fast ({approximately}100 ns) high-power opening switch concept based on a magnetically insulated thermionic vacuum diode. Principal scaling parameters are the switch dimensions, voltage, current, applied magnetic field, and switching time. The scaling range of interest covers voltages up to 100 kV and currents of several kA. Fundamental scaling properties are derived from models of space-charge flow and magnetic cutoff. The scaling is completed with empirical results from the experimental MX-1 switch operated in an inductive storage pulsed power generator. Results are presented in diagrams showing voltage, current, power, and efficiency relationships and their limitations. The scaling is illustrated by the design of a megawatt average power opening switch for pulsed power applications. Trade-offs in the engineering of this type of switch are discussed.
Parametric study of cantilever walls subjected to seismic loading
Comina, Cesare; Corigliano, Mirko; Foti, Sebastiano; Lai, Carlo G.; Lancellotta, Renato; Leuzzi, Francesco; Nicosia, Giovanni Li Destri; Paolucci, Roberto; Pettiti, Alberto; Psarropoulos, Prodromos N.; Zanoli, Omar
2008-07-01
The design of flexible earth retaining structures under seismic loading is a challenging geotechnical problem, the dynamic soil-structure interaction being of paramount importance for this kind of structures. Pseudo-static approaches are often adopted but do not allow a realistic assessment of the performance of the structure subjected to the seismic motions. The present paper illustrates a numerical parametric study aimed at estimating the influence of the dynamic soil-structure interaction in the design. A series of flexible earth retaining walls have been preliminary designed according to the requirements of Eurocode 7 and Eurocode 8—Part 5; their dynamic behaviour has been then evaluated by means of dynamic numerical simulations in terms of bending moments, accelerations and stress state. The results obtained from dynamic analyses have then been compared with those determined using the pseudo-static approach.
Parametric study on sequential deconvolution for force identification
Lai, Tao; Yi, Ting-Hua; Li, Hong-Nan
2016-09-01
The force identification can be mathematically viewed as the mapping from the observed responses to external forces through a matrix filled with system Markov parameters, which makes it difficult or even impossible for long time duration. A potentially efficient solution is to sequentially perform the identification processing. This paper presents a parametric study on the sequential deconvolution input reconstruction (SDR) method, which was proposed by Bernal. The behavior of the SDR method due to the effects of window parameters, noise levels and sensor configurations is investigated. In addition, a new normalized standard deviation of the reconstruction error over time is derived to cover the effect of only independent noise entries. The sinusoidal and band-limited white noise excitations are tested to be identified with good accuracy even with 10% noise. The simulation results yield various conclusions that may be helpful to engineering practitioners.
Dynamic study of synchronous machine electric drive
Directory of Open Access Journals (Sweden)
Dimitar Spirov
2005-10-01
Full Text Available The dynamic behaviour of the fan blower synchoronous machine drive have been studied in the paper. The equations for the voltages of the synchoronous machine windings are presented in a coordinate system which rotates at the angular speed of the rotor. The mechanical equipment is presented by means of a single-mass dynamic model. The derived system of differential equations is transformed and solved using suitable software product. The results obtained for rotation frequency and electromagnetic torque motor in the courses of different values of rated supply voltage and of different initial resistant moment of the mechanism have been graphically presented. Conclusions from the results obtained have been done.
Learning Machine Learning: A Case Study
Lavesson, N.
2010-01-01
This correspondence reports on a case study conducted in the Master's-level Machine Learning (ML) course at Blekinge Institute of Technology, Sweden. The students participated in a self-assessment test and a diagnostic test of prerequisite subjects, and their results on these tests are correlated with their achievement of the course's learning…
Learning Machine Learning: A Case Study
Lavesson, N.
2010-01-01
This correspondence reports on a case study conducted in the Master's-level Machine Learning (ML) course at Blekinge Institute of Technology, Sweden. The students participated in a self-assessment test and a diagnostic test of prerequisite subjects, and their results on these tests are correlated with their achievement of the course's learning…
Gao, W.; Li, X. R.
2016-07-01
The multi-task learning puts the multiple tasks together to analyse and calculate for discovering the correlation between them, which can improve the accuracy of analysis results. This kind of methods have been widely studied in machine learning, pattern recognition, computer vision, and other related fields. This paper investigates the application of multi-task learning in estimating the effective temperature (T_{eff}), surface gravity (lg g), and chemical abundance ([Fe/H]). Firstly, the spectral characteristics of the three atmospheric physical parameters are extracted by using the multi-task Sparse Group Lasso algorithm, and then the support vector machine is used to estimate the atmospheric physical parameters. The proposed scheme is evaluated on both Sloan stellar spectra and theoretical spectra computed from Kurucz's New Opacity Distribution Function (NEWODF) model. The mean absolute errors (MAEs) on the Sloan spectra are: 0.0064 for lg (T_{eff}/K), 0.1622 for lg (g/(cm\\cdot s^{-2})), and 0.1221 dex for [Fe/H]; The MAEs on synthetic spectra are 0.0006 for lg (T_{eff}/K), 0.0098 for lg (g/(cm\\cdot s^{-2})), and 0.0082 dex for [Fe/H]. Experimental results show that the proposed scheme is excellent for atmospheric parameter estimation.
Study of on-machine error identification and compensation methods for micro machine tools
Wang, Shih-Ming; Yu, Han-Jen; Lee, Chun-Yi; Chiu, Hung-Sheng
2016-08-01
Micro machining plays an important role in the manufacturing of miniature products which are made of various materials with complex 3D shapes and tight machining tolerance. To further improve the accuracy of a micro machining process without increasing the manufacturing cost of a micro machine tool, an effective machining error measurement method and a software-based compensation method are essential. To avoid introducing additional errors caused by the re-installment of the workpiece, the measurement and compensation method should be on-machine conducted. In addition, because the contour of a miniature workpiece machined with a micro machining process is very tiny, the measurement method should be non-contact. By integrating the image re-constructive method, camera pixel correction, coordinate transformation, the error identification algorithm, and trajectory auto-correction method, a vision-based error measurement and compensation method that can on-machine inspect the micro machining errors and automatically generate an error-corrected numerical control (NC) program for error compensation was developed in this study. With the use of the Canny edge detection algorithm and camera pixel calibration, the edges of the contour of a machined workpiece were identified and used to re-construct the actual contour of the work piece. The actual contour was then mapped to the theoretical contour to identify the actual cutting points and compute the machining errors. With the use of a moving matching window and calculation of the similarity between the actual and theoretical contour, the errors between the actual cutting points and theoretical cutting points were calculated and used to correct the NC program. With the use of the error-corrected NC program, the accuracy of a micro machining process can be effectively improved. To prove the feasibility and effectiveness of the proposed methods, micro-milling experiments on a micro machine tool were conducted, and the results
Study on Semi-Parametric Statistical Model of Safety Monitoring of Cracks in Concrete Dams
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Chongshi Gu
2013-01-01
Full Text Available Cracks are one of the hidden dangers in concrete dams. The study on safety monitoring models of concrete dam cracks has always been difficult. Using the parametric statistical model of safety monitoring of cracks in concrete dams, with the help of the semi-parametric statistical theory, and considering the abnormal behaviors of these cracks, the semi-parametric statistical model of safety monitoring of concrete dam cracks is established to overcome the limitation of the parametric model in expressing the objective model. Previous projects show that the semi-parametric statistical model has a stronger fitting effect and has a better explanation for cracks in concrete dams than the parametric statistical model. However, when used for forecast, the forecast capability of the semi-parametric statistical model is equivalent to that of the parametric statistical model. The modeling of the semi-parametric statistical model is simple, has a reasonable principle, and has a strong practicality, with a good application prospect in the actual project.
Bahrami, Sheyda; Shamsi, Mousa
2017-01-01
Functional magnetic resonance imaging (fMRI) is a popular method to probe the functional organization of the brain using hemodynamic responses. In this method, volume images of the entire brain are obtained with a very good spatial resolution and low temporal resolution. However, they always suffer from high dimensionality in the face of classification algorithms. In this work, we combine a support vector machine (SVM) with a self-organizing map (SOM) for having a feature-based classification by using SVM. Then, a linear kernel SVM is used for detecting the active areas. Here, we use SOM for feature extracting and labeling the datasets. SOM has two major advances: (i) it reduces dimension of data sets for having less computational complexity and (ii) it is useful for identifying brain regions with small onset differences in hemodynamic responses. Our non-parametric model is compared with parametric and non-parametric methods. We use simulated fMRI data sets and block design inputs in this paper and consider the contrast to noise ratio (CNR) value equal to 0.6 for simulated datasets. fMRI simulated dataset has contrast 1-4% in active areas. The accuracy of our proposed method is 93.63% and the error rate is 6.37%.
Numerical Analysis of Piles in Layered Soils: A Parametric Study
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Ravi Kumar Reddy C
2015-04-01
Full Text Available In this paper, numerical analysis of a pile-soil interaction problem is presented considering the parameters influencing the axial load-deformation behavior of the pile embedded in a layered soil medium. The analysis is demonstrated with parametric solutions of a pile with underlain model soil strata under the axial force. An attempt is made to ascertain the extent of influence of elastic properties of the pile, geometry of the pile, end conditions of the pile and the elastic properties of the underlain soil strata on the response of the piles under axial loads lying in a model soil layers in terms of the settlement of the pile and the internal deformation of the pile. The study revealed that the increase in modulus of elasticity of pile improves the settlement resistance of the pile, increase in the ratio of cross sectional dimensions causes decrease in the top deformations of the pile, the settlement of the pile reduced to a great extent when the cross section of the pile adopted is non circular instead of circular and increase in the elastic modulii of top and bottom layers of soil has decreased the settlement of the pile to a great extent, but elastic modulus of soil layers other than top and bottom has got negligible influence on the settlement of the pile.
Interactive flutter analysis and parametric study for conceptual wing design
Mukhopadhyay, Vivek
1995-01-01
An interactive computer program was developed for wing flutter analysis in the conceptual design stage. The objective was to estimate the flutter instability boundary of a flexible cantilever wing, when well defined structural and aerodynamic data are not available, and then study the effect of change in Mach number, dynamic pressure, torsional frequency, sweep, mass ratio, aspect ratio, taper ratio, center of gravity, and pitch inertia, to guide the development of the concept. The software was developed on MathCad (trademark) platform for Macintosh, with integrated documentation, graphics, database and symbolic mathematics. The analysis method was based on nondimensional parametric plots of two primary flutter parameters, namely Regier number and Flutter number, with normalization factors based on torsional stiffness, sweep, mass ratio, aspect ratio, center of gravity location and pitch inertia radius of gyration. The plots were compiled in a Vaught Corporation report from a vast database of past experiments and wind tunnel tests. The computer program was utilized for flutter analysis of the outer wing of a Blended Wing Body concept, proposed by McDonnell Douglas Corporation. Using a set of assumed data, preliminary flutter boundary and flutter dynamic pressure variation with altitude, Mach number and torsional stiffness were determined.
Parametric study of the Incompletely Stirred Reactor modeling
Energy Technology Data Exchange (ETDEWEB)
Mobini, K. [Department of Mechanical Engineering, Shahid Rajaee University, Lavizan, Tehran (Iran); Bilger, R.W. [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, Sydney (Australia)
2009-09-15
The Incompletely Stirred Reactor (ISR) is a generalization of the widely-used Perfectly Stirred Reactor (PSR) model and allows for incomplete mixing within the reactor. Its formulation is based on the Conditional Moment Closure (CMC) method. This model is applicable to nonpremixed combustion with strong recirculation such as in a gas turbine combustor primary zone. The model uses the simplifying assumptions that the conditionally-averaged reactive-scalar concentrations are independent of position in the reactor: this results in ordinary differential equations in mixture fraction space. The simplicity of the model permits the use of very complex chemical mechanisms. The effects of the detailed chemistry can be found while still including the effects of micromixing. A parametric study is performed here on an ISR for combustion of methane at overall stoichiometric conditions to investigate the sensitivity of the model to different parameters. The focus here is on emissions of nitric oxide and carbon monoxide. It is shown that the most important parameters in the ISR model are reactor residence time, the chemical mechanism and the core-averaged Probability Density Function (PDF). Using several different shapes for the core-averaged PDF, it is shown that use of a bimodal PDF with a low minimum at stoichiometric mixture fraction and a large variance leads to lower nitric oxide formation. The 'rich-plus-lean' mixing or staged combustion strategy for combustion is thus supported. (author)
Parametric study on patch repaired CFRP laminates using FEA
Energy Technology Data Exchange (ETDEWEB)
Kashfuddoja, M.; Ramji, M. [Indian Institute of Technology. Engineering Optics Lab. Dept. of Mechanical Engineering, Hyderabad (India)
2012-07-01
Carbon fibre reinforced plastic (CFRP) composite laminates have become popular for structural applications as they are lighter, stronger and tougher. Composite structures are also susceptible to damage while in service. For improved service life, the damage needs to be repaired so that repair structure integrity is enhanced. Various parameters like patch size and shape, it's layup sequence and adhesive thickness would influence the performance of the repaired structure. In present work, a parametric study is carried out using finite element analysis (FEA) to investigate the influence of various parameters involved in composite repair. The panel is made of carbon / epoxy composite laminate with stacking sequence of (0/{+-}45/900)s and is subjected to tensile load. Damaged CFRP laminates is repaired by symmetrical patch adhesively bonded over the damaged area. Circular patch of different stacking sequence and size is considered. Influence of adhesive material and it's thickness on repair efficiency is also investigated. The influence of various repair parameters on peel stress is also analysed. (Author)
Parametric Studies for Scenario Earthquakes: Site Effects and Differential Motion
Panza, G. F.; Panza, G. F.; Romanelli, F.
2001-12-01
In presence of strong lateral heterogeneities, the generation of local surface waves and local resonance can give rise to a complicated pattern in the spatial groundshaking scenario. For any object of the built environment with dimensions greater than the characteristic length of the ground motion, different parts of its foundations can experience severe non-synchronous seismic input. In order to perform an accurate estimate of the site effects, and of differential motion, in realistic geometries, it is necessary to make a parametric study that takes into account the complex combination of the source and propagation parameters. The computation of a wide set of time histories and spectral information, corresponding to possible seismotectonic scenarios for different source and structural models, allows us the construction of damage scenarios that are out of reach of stochastic models. Synthetic signals, to be used as seismic input in a subsequent engineering analysis, e.g. for the design of earthquake-resistant structures or for the estimation of differential motion, can be produced at a very low cost/benefit ratio. We illustrate the work done in the framework of a large international cooperation following the guidelines of the UNESCO IUGS IGCP Project 414 "Realistic Modeling of Seismic Input for Megacities and Large Urban Areas" and show the very recent numerical experiments carried out within the EC project "Advanced methods for assessing the seismic vulnerability of existing motorway bridges" (VAB) to assess the importance of non-synchronous seismic excitation of long structures. >http://www.ictp.trieste.it/www_users/sand/projects.html
Hollow cathode modeling: II. Physical analysis and parametric study
Sary, Gaétan; Garrigues, Laurent; Boeuf, Jean-Pierre
2017-05-01
A numerical emissive hollow cathode model which couples plasma and thermal aspects of the NASA NSTAR cathode has been presented in a companion paper and simulation results obtained using the plasma model were compared to experimental data. We now compare simulation results with measurements using the full coupled model. Inside the cathode, the simulated plasma density profile agrees with the experimental data up to the ±50% experimental uncertainty while the simulated emitter temperature differs from measurements by at most 5 K. We then proceed to an analysis of the cathode discharge both inside the cathode where electron emission is dominant and outside in the near plume where electron transport instabilities are important. As observed previously in the literature, the total emitted electron current is much larger (34 {{A}}) than the set discharge current collected at the anode (13 {{A}}) while ionization plays a negligible role. Extracted electrons are emitted from a region much shorter than the full emitter (0.9 {{cm}} versus 2.5 {{cm}}). The influence of an applied axial magnetic field in the plume is also assessed and we observe that it leads to a 10-fold increase of the plasma density 1 cm downstream of the orifice entrance while the simulated discharge potential at the anode is increased from 10 {{V}} up to 35.5 {{V}}. Lastly, we perform a parametric study on both the operating point (discharge current, mass flow rate) and design (inner radius) of the cathode. The simulated useful operating envelope is shown to be limited at low discharge current mostly because of the probable ion sputtering of the emitter and at high discharge current because of emitter evaporation, plasma oscillations and sputtering of the keeper electrode. The behavior of the cathode is also analyzed w.r.t. its internal radius and simulation results show that the useful emitter length scales linearly with the cathode radius.
Parametric study of the fire resistance of simple timber elements
2016-01-01
The graduation thesis presents the influence of fire development on fire resistance of simple timber bearing elements according to SIST EN 1991-1-2 and SIST EN 1995-1-2. The fire analysis of timber bearing elements is divided into three phases. Parametric analysis of influence of certain parameters on fire development is performed in the first phase. On the basis of acquired results second phase follows in which, thermal analysis of timber elements is conducted. Here, charring depths for timb...
Sudhakara, Dara; Prasanthi, Guvvala
2016-08-01
Wire Cut EDM is an unconventional machining process used to build components of complex shape. The current work mainly deals with optimization of surface roughness while machining P/M CW TOOL STEEL by Wire cut EDM using Taguchi method. The process parameters of the Wire Cut EDM is ON, OFF, IP, SV, WT, and WP. L27 OA is used for to design of the experiments for conducting experimentation. In order to find out the effecting parameters on the surface roughness, ANOVA analysis is engaged. The optimum levels for getting minimum surface roughness is ON = 108 µs, OFF = 63 µs, IP = 11 A, SV = 68 V and WT = 8 g.
Parametric Studies of Flow Separation using Air Injection
Zhang, Wei
2004-01-01
Boundary Layer separation causes the airfoil to stall and therefore imposes dramatic performance degradation on the airfoil. In recent years, flow separation control has been one of the active research areas in the field of aerodynamics due to its promising performance improvements on the lifting device. These active flow separation control techniques include steady and unsteady air injection as well as suction on the airfoil surface etc. This paper will be focusing on the steady and unsteady air injection on the airfoil. Although wind tunnel experiments revealed that the performance improvements on the airfoil using injection techniques, the details of how the key variables such as air injection slot geometry and air injection angle etc impact the effectiveness of flow separation control via air injection has not been studied. A parametric study of both steady and unsteady air injection active flow control will be the main objective for this summer. For steady injection, the key variables include the slot geometry, orientation, spacing, air injection velocity as well as the injection angle. For unsteady injection, the injection frequency will also be investigated. Key metrics such as lift coefficient, drag coefficient, total pressure loss and total injection mass will be used to measure the effectiveness of the control technique. A design of experiments using the Box-Behnken Design is set up in order to determine how each of the variables affects each of the key metrics. Design of experiment is used so that the number of experimental runs will be at minimum and still be able to predict which variables are the key contributors to the responses. The experiments will then be conducted in the 1ft by 1ft wind tunnel according to the design of experiment settings. The data obtained from the experiments will be imported into JMP, statistical software, to generate sets of response surface equations which represent the statistical empirical model for each of the metrics as
Directory of Open Access Journals (Sweden)
Ning Ma
2015-11-01
Full Text Available Noncircular holes on the surface of turbine rotor blades are usually machined by electrodischarge machining. A recast layer containing numerous micropores and microcracks is easily generated during the electrodischarge machining process due to the rapid heating and cooling effects, which restrict the wide applications of noncircular holes in aerospace and aircraft industries. Owing to the outstanding advantages of pulse electrochemical machining, electrodischarge machining–pulse electrochemical machining combined technique is provided to improve the overall quality of electrodischarge machining-drilled holes. The influence of pulse electrochemical machining processing parameters on the surface roughness and the influence of the electrodischarge machining–pulse electrochemical machining method on the surface quality and accuracy of holes have been studied experimentally. The results indicate that the pulse electrochemical machining processing time for complete removal of the recast layer decreases with the increase in the pulse electrochemical machining current. The low pulse electrochemical machining current results in uneven dissolution of the recast layer, while the higher pulse electrochemical machining current induces relatively homogeneous dissolution. The surface roughness is reduced from 4.277 to 0.299 µm, and the hole taper induced by top-down electrodischarge machining process was reduced from 1.04° to 0.17° after pulse electrochemical machining. On account of the advantages of electrodischarge machining and the pulse electrochemical machining, the electrodischarge machining–pulse electrochemical machining combined technique could be applied for machining noncircular holes with high shape accuracy and surface quality.
Study of Virtual Machine and its application
Directory of Open Access Journals (Sweden)
Rohaan Chandra
2013-07-01
Full Text Available A virtual machine is software that’s capable of executing programs as if it were a physical machine—it’s a computer within a computer. A virtual machine (VM is a software implemented abstraction of the underlying hardware, which is presented to the application layer of the system. Virtual machines may be based on specifications of a hypothetical computer or emulate the computer architecture and functions of a real world computer.
Study on Simulation of Machining Errors Caused by Cutting Force
Institute of Scientific and Technical Information of China (English)
SHAO Xiaodong; ZHANG Liu; LIN Zhaoxu
2006-01-01
Machining errors caused by cutting force are studied in this paper, and an algorithm to simulate errors is putted forward. In the method, continuous machining process is separated into many machining moments. The deformation of work-piece and cutter at every moment is calculated by finite element method. The machined work-piece is gained by Boolean operation between deformed work-piece and cutter. By analyzing data of final work-piece, machining errors are predicted. The method is proved true by experiment.
Using Phun to Study "Perpetual Motion" Machines
Kores, Jaroslav
2012-01-01
The concept of "perpetual motion" has a long history. The Indian astronomer and mathematician Bhaskara II (12th century) was the first person to describe a perpetual motion (PM) machine. An example of a 13th-century PM machine is shown in Fig. 1. Although the law of conservation of energy clearly implies the impossibility of PM construction, over…
Recovery studies for plutonium machining oil coolant
Energy Technology Data Exchange (ETDEWEB)
Navratil, J. D.; Baldwin, C. E.
1977-04-27
Lathe coolant oil, contaminated with plutonium and having a carbon tetrachloride diluent, is generated in plutonium machining areas at Rocky Flats. A research program was initiated to determine the nature of plutonium in this mixture of oil and carbon tetrachloride. Appropriate methods then could be developed to remove the plutonium and to recycle the oil and carbon tetrachloride. Studies showed that the mixtures of spent oil and carbon tetrachloride contained particulate plutonium and plutonium species that are soluble in water or in oil and carbon tetrachloride. The particulate plutonium was removed by filtration; the nonfilterable plutonium was removed by adsorption on various materials. Laboratory-scale tests indicated the lathe-coolant oil mixture could be separated by distilling the carbon tetrachloride to yield recyclable products.
Using Phun to Study ``Perpetual Motion'' Machines
Koreš, Jaroslav
2012-05-01
The concept of "perpetual motion" has a long history. The Indian astronomer and mathematician Bhaskara II (12th century) was the first person to describe a perpetual motion (PM) machine. An example of a 13th- century PM machine is shown in Fig. 1. Although the law of conservation of energy clearly implies the impossibility of PM construction, over the centuries numerous proposals for PM have been made, involving ever more elements of modern science in their construction. It is possible to test a variety of PM machines in the classroom using a program called Phun2 or its commercial version Algodoo.3 The programs are designed to simulate physical processes and we can easily simulate mechanical machines using them. They provide an intuitive graphical environment controlled with a mouse; a programming language is not needed. This paper describes simulations of four different (supposed) PM machines.4
A Study of the Broadband Parametric Acoustic Array
1982-01-04
parametric array 141 *0 Ia 0 oC ) 0 0 CO U,. U, 4 , a o o co~ cc I U.W D w 0L 0 0 td ~ v*V) - NX ALU AS00 161 JM ZG 142R 6.65 8 00 wo E - rii C 4 Ci ZU Z...sufficiently low that the relative 184 Lim"" 00 d 0C 0000 0~0 aj 0i0 0 c 00 0 CL z1 cV 0> 0 ao - - (L gp-~~~ ccMK iSd ARL:U AS4 9108 VMH cA 185~~ 6.69
Directory of Open Access Journals (Sweden)
Uwe Prells
2000-01-01
Full Text Available The estimation of a model of the foundation of a rotary machine has been recently attempted by using the difference between two sets of response data at some of the bearing locations from two consecutive rundowns of the machine, with and without known unbalance weights at certain positions on the two balance discs of each rotor respectively. However, it would be a great advantage to be able to perform the estimation with a single rundown. Due to practical restrictions in performing such tests (accessibility, costs etc., there are cases in which data for only one rundown are available. In this case, the unbalance configuration is unknown and has, therefore, to be estimated, in addition to the unknown foundation model. Due to the special form of the unbalance force, this overall inverse problem can be solved by eliminating the unbalance configuration from the model estimation process. The remaining equation to estimate the foundation model consists of the projection of the response data, where the associated projector depends on the foundation model parameter. First results using the method, applied to a laboratory test rig and to a commercial turbo-generator, are presented.
Energy Technology Data Exchange (ETDEWEB)
Dutheil, C.
2003-05-15
Soil vapour extraction is a treatment process for soils polluted by volatile organic compounds. Its principle relies on the circulation of gaseous flow in soil by the application of a depression of some hundreds milli-bars. A parametrical study has been led on a soil artificially polluted by tri-chloro-ethene. It shows that the gaseous flow rate has a slight influence on pollutants extraction yield. This is due to rate limited mass transfer processes. Soil moisture plays a negative role on treatment efficiency because of the reduction of the porosity available for the gas circulation. Tests have been performed on a soil polluted by a complex mixture of organic pollutants to elaborate a methodology of technical feasibility assessment. This methodology aims at identifying and limiting risks of site rehabilitation failure. Tests results show that soil vapour extraction was inadequate to treat the soil tested in this study because of the strong affinity between a dense organic phase (grease) and chlorinated solvents. (author)
Communication Studies of DMP and SMP Machines
Sohn, Andrew; Biswas, Rupak; Chancellor, Marisa K. (Technical Monitor)
1997-01-01
Understanding the interplay between machines and problems is key to obtaining high performance on parallel machines. This paper investigates the interplay between programming paradigms and communication capabilities of parallel machines. In particular, we explicate the communication capabilities of the IBM SP-2 distributed-memory multiprocessor and the SGI PowerCHALLENGEarray symmetric multiprocessor. Two benchmark problems of bitonic sorting and Fast Fourier Transform are selected for experiments. Communication-efficient algorithms are developed to exploit the overlapping capabilities of the machines. Programs are written in Message-Passing Interface for portability and identical codes are used for both machines. Various data sizes and message sizes are used to test the machines' communication capabilities. Experimental results indicate that the communication performance of the multiprocessors are consistent with the size of messages. The SP-2 is sensitive to message size but yields a much higher communication overlapping because of the communication co-processor. The PowerCHALLENGEarray is not highly sensitive to message size and yields a low communication overlapping. Bitonic sorting yields lower performance compared to FFT due to a smaller computation-to-communication ratio.
Indian Academy of Sciences (India)
Soumyakant Padhee; Niharranjan Nayak; S K Panda; P R Dhal; S S Mahapatra
2012-04-01
Powder mixed electro-discharge machining (EDM) is being widely used in modern metal working industry for producing complex cavities in dies and moulds which are otherwise difﬁcult to create by conventional machining route. It has been experimentally demonstrated that the presence of suspended particle in dielectric ﬂuid signiﬁcantly increases the surface ﬁnish and machining efﬁciency of EDM process. Concentration of powder (silicon) in the dielectric ﬂuid, pulse on time, duty cycle, and peak current are taken as independent variables on which the machining performance was analysed in terms of material removal rate (MRR) and surface roughness (SR). Experiments have been conducted on an EZNC fuzzy logic Die Sinking EDM machine manufactured by Electronica Machine Tools Ltd. India. A copper electrode having diameter of 25 mm is used to cut EN 31 steel for one hour in each trial. Response surface methodology (RSM) is adopted to study the effect of independent variables on responses and develop predictive models. It is desired to obtain optimal parameter setting that aims at decreasing surface roughness along with larger material removal rate. Since the responses are conﬂicting in nature, it is difﬁcult to obtain a single combination of cutting parameters satisfying both the objectives in any one solution. Therefore, it is essential to explore the optimization landscape to generate the set of dominant solutions. Non-sorted genetic algorithm (NSGA) has been adopted to optimize the responses such that a set of mutually dominant solutions are found over a wide range of machining parameters.
Directory of Open Access Journals (Sweden)
Amlana Panda
2017-01-01
Full Text Available The present study investigates performance and feasibility of application of low cost cemented carbide insert in dry machining of AISI 52100 steel hardened to (55 ± 1 HRC which is rarely researched as far as machining of bearing steel is concerned. Machinability studies i.e. flank wear, surface roughness and morphology analysis of chip has been investigated and statistical regression modeling has been developed. The test has been conducted based on Taguchi L16 OA taking machining parameters like cutting speed, feed and depth of cut. It is observed that uncoated cemented carbide insert performs well at some selected runs (Run 1, 5 and 9 which show its feasibility for hard turning applications. The developed serrated saw tooth chip of burnt blue colour adversely affects the surface quality. Adequacy of the developed statistical regression model has been checked using ANOVA analysis (depending on F value, P value and R2 value and normal probability plot at 95% confidence level. The results of optimal parametric combinations may be adopted while turning hardened AISI 52100 steel under dry environment with uncoated cemented carbide insert.
A Study on Parametric Wave Estimation Based on Measured Ship Motions
DEFF Research Database (Denmark)
Nielsen, Ulrik Dam; Iseki, Toshio
2011-01-01
The paper studies parametric wave estimation based on the ‘wave buoy analogy’, and data and results obtained from the training ship Shioji-maru are compared with estimates of the sea states obtained from other measurements and observations. Furthermore, the estimating characteristics of the param......The paper studies parametric wave estimation based on the ‘wave buoy analogy’, and data and results obtained from the training ship Shioji-maru are compared with estimates of the sea states obtained from other measurements and observations. Furthermore, the estimating characteristics...... of the parametric model are discussed by considering the results of a similar estimation concept based on Bayesian modelling. The purpose of the latter comparison is not to favour the one estimation approach to the other but rather to highlight some of the advantages and disadvantages of the two approaches....
Directory of Open Access Journals (Sweden)
Yun Hsing Cheung
2012-12-01
Full Text Available The three main Value at Risk (VaR methodologies are historical, parametric and Monte Carlo Simulation.Cheung & Powell (2012, using a step-by-step teaching study, showed how a nonparametric historical VaRmodel could be constructed using Excel, thus benefitting teachers and researchers by providing them with areadily useable teaching study and an inexpensive and flexible VaR modelling option. This article extends thatwork by demonstrating how parametric and Monte Carlo Simulation VaR models can also be constructed inExcel, thus providing a total Excel modelling package encompassing all three VaR methods.
MATHEMATICAL MODEL FOR THE STUDY AND DESIGN OF A ROTARY-VANE GAS REFRIGERATION MACHINE
Directory of Open Access Journals (Sweden)
V. V. Trandafilov
2016-08-01
Full Text Available This paper presents a mathematical model of calculating the main parameters the operating cycle, rotary-vane gas refrigerating machine that affect installation, machine control and working processes occurring in it at the specified criteria. A procedure and a graphical method for the rotary-vane gas refrigerating machine (RVGRM are proposed. A parametric study of the main geometric variables and temperature variables on the thermal behavior of the system is analyzed. The model considers polytrope index for the compression and expansion in the chamber. Graphs of the pressure and temperature in the chamber of the angle of rotation of the output shaft are received. The possibility of inclusion in the cycle regenerative heat exchanger is appreciated. The change of the coefficient of performance machine after turning the cycle regenerative heat exchanger is analyzed. It is shown that the installation of a regenerator RVGRM cycle results in increased COP more than 30%. The simulation results show that the proposed model can be used to design and optimize gas refrigerator Stirling.
Beam Dynamics Studies in Recirculating Machines
Pellegrini, Dario; Latina, A
The LHeC and the CLIC Drive Beam share not only the high-current beams that make them prone to show instabilities, but also unconventional lattice topologies and operational schemes in which the time sequence of the bunches varies along the machine. In order to asses the feasibility of these projects, realistic simulations taking into account the most worrisome effects and their interplays, are crucial. These include linear and non-linear optics with time dependent elements, incoherent and coherent synchrotron radiation, short and long-range wakefields, beam-beam effect and ion cloud. In order to investigate multi-bunch effects in recirculating machines, a new version of the tracking code PLACET has been developed from scratch. PLACET2, already integrates most of the effects mentioned before and can easily receive additional physics. Its innovative design allows to describe complex lattices and track one or more bunches accordingly to the machine operation, reproducing the bunch train splitting and recombinat...
Turrin, M.; Stouffs, R.M.F.; Sariyildiz, I.S.
2010-01-01
The paper presents a case study, in which parametric modeling has been used to explore the geometrical design alternatives of a large span roof. Explorative criteria are oriented to the use of on site energy resources, with specific focus on the mitigation of summer discomfort. After broadly
Parametric Study of the Device Angle Dependency of a Single Vortex Generator on a Flat Plate
DEFF Research Database (Denmark)
Fernandez, U.; Réthoré, Pierre-Elouan; Sørensen, Niels N.
. The computational fluid dynamic (CFD) simulations have been com-pared with a wind tunnel experiment, where the corresponding parametric study was per-formed over a single vane mounted on the test section wall in low-speed wind tunnel. In this experiment the flow was recorded using Stereoscopic Particle Image...
Parametric study on coupling loss in subsize ITER Nb3Sn cabled specimen
Nijhuis, Arend; Kate, ten Herman H.J.; Bruzzone, Pierluigi; Bottura, Luca
1996-01-01
The cable in conduit conductors for the various ITER coils are required to function under pulse conditions and fields up to 13 T. A parametric study, restricted to a limited variation of the reference cable lay out, is carried out to clarify the quantitative impact of various cable parameters on the
Parametric-Studies and Data-Plotting Modules for the SOAP
2008-01-01
"Parametric Studies" and "Data Table Plot View" are the names of software modules in the Satellite Orbit Analysis Program (SOAP). Parametric Studies enables parameterization of as many as three satellite or ground-station attributes across a range of values and computes the average, minimum, and maximum of a specified metric, the revisit time, or 21 other functions at each point in the parameter space. This computation produces a one-, two-, or three-dimensional table of data representing statistical results across the parameter space. Inasmuch as the output of a parametric study in three dimensions can be a very large data set, visualization is a paramount means of discovering trends in the data (see figure). Data Table Plot View enables visualization of the data table created by Parametric Studies or by another data source: this module quickly generates a display of the data in the form of a rotatable three-dimensional-appearing plot, making it unnecessary to load the SOAP output data into a separate plotting program. The rotatable three-dimensionalappearing plot makes it easy to determine which points in the parameter space are most desirable. Both modules provide intuitive user interfaces for ease of use.
The Parametrically Forced Pendulum : A Case Study in 1½ Degree of Freedom
Broer, H.W.; Hoveijn, I.; Noort, M. van; Simó, C.; Vegter, G.
2004-01-01
This paper is concerned with the global coherent (i.e., non-chaotic) dynamics of the parametrically forced pendulum. The system is studied in a 1½ degree of freedom Hamiltonian setting with two parameters, where a spatio-temporal symmetry is taken into account. Our explorations are restricted to lar
Preliminary design and parametric study of 1400 m partially earth-anchored cable-stayed bridge
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
The preliminary design and parametric study of 1400 m partially earth-anchored cable-stayed bridge are described. Static per-formance of this new type of bridge is discussed. Compared with fully self-anchored cable-stayed bridge, its advantages in fin-ished state are summarized. Based on numerical calculation, effects of several structural parameters on static performance are presented.
A parametric study of the output of the optically pumped continuous wave CF4 laser
Hartemink, M.; Godfried, H.P.
1993-01-01
A parametric study of laser output versus CF4 pressure and temperature was performed and correlated with a model for the gain in the system, which includes the relevant relaxation processes. Lasing in CF4 was observed at temperatures below 170 K. Cooling the CF4 gas, the output power of the laser in
Energy Technology Data Exchange (ETDEWEB)
Slapa, Rafal Z., E-mail: rz.slapa@gmail.com [Diagnostic Imaging Department, Medical University of Warsaw, Second Faculty of Medicine with English and Physiotherapy Divisions, Warsaw (Poland); Kasperlik–Zaluska, Anna A. [Endocrinology Department, Center for Postgraduate Medical Education, Bielanski Hospital, Warsaw (Poland); Migda, Bartosz [Diagnostic Imaging Department, Medical University of Warsaw, Second Faculty of Medicine with English and Physiotherapy Divisions, Warsaw (Poland); Otto, Maciej [Department of General, Vascular and Transplant Surgery, Medical University of Warsaw, First Faculty of Medicine, Warsaw (Poland); Jakubowski, Wiesław S. [Diagnostic Imaging Department, Medical University of Warsaw, Second Faculty of Medicine with English and Physiotherapy Divisions, Warsaw (Poland)
2015-08-15
Highlights: • Adrenal masses may differ on parametric perfusion ultrasound. • Hyperplastic nodules present distinctive patterns on CEUS in regard to adenomas. • Adrenal lesions perfusion should be further investigated with different modalities. - Abstract: Objectives: To evaluate the possibilities of differentiation of non-malignant adrenal masses with the application of the new technique for the evaluation of enhancement after administration of an ultrasound contrast agent: parametric imaging. Patients and Methods: 34 non-malignant adrenal masses in 29 patients were evaluated in a dynamic examination after the administration of ultrasound contrast agent with parametric imaging. Patterns on parametric imaging of arrival time were evaluated. The final diagnosis was based on CT, MRI, biochemical studies, follow up and/or histopathology examination. Results: The study included: 12 adenomas, 10 hyperplastic nodules, 7 myelolipomas, 3 pheochromocytomas, hemangioma with hemorrhage and cyst. The pattern of peripheral laminar inflow of Sonovue on parametric images of arrival time of was 100% sensitive for hyperplastic nodules and 83% specific in regard to adenomas. Conclusions: Parametric contrast enhanced ultrasound may accurately differentiate hyperplastic adrenal nodules from adenomas and could be complementary to CT or MRI. Incorporation of perfusion studies to CT or MRI could possibly enable one-shop complete characterization of adrenal masses. This could deliver additional information in diagnostics of patients with Conn Syndrome and warrants further studies in this cohort of patients.
Studying depression using imaging and machine learning methods.
Patel, Meenal J; Khalaf, Alexander; Aizenstein, Howard J
2016-01-01
Depression is a complex clinical entity that can pose challenges for clinicians regarding both accurate diagnosis and effective timely treatment. These challenges have prompted the development of multiple machine learning methods to help improve the management of this disease. These methods utilize anatomical and physiological data acquired from neuroimaging to create models that can identify depressed patients vs. non-depressed patients and predict treatment outcomes. This article (1) presents a background on depression, imaging, and machine learning methodologies; (2) reviews methodologies of past studies that have used imaging and machine learning to study depression; and (3) suggests directions for future depression-related studies.
Studies for obtaining a small holle, rapid edm drilling machine
Directory of Open Access Journals (Sweden)
Mihai Şimon
2011-12-01
Full Text Available This paper studies the obtaining of an experimental rapid drilling machine, through EDM process for small holes. The best parameters such as peak current, pulse frequency, duty factor and electrode rotation speed were studied for best machining characteristics. An electrolytic copper rod 0.8 mm diameter was selected as a tool electrode. The experiments generate output responses such as maximum material removal rate (MRR and the dependence with peak current, duty factor and Electrode rotation, parameters. Finally, parameters were optimized for maximum MRR with desired surface roughness value and used for sizing the component for a better small rapid drilling machine.
A Study on the Reliability of a Large Vibration Machine
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
This study aims at the reliability of a large vibration machine ZM2800, including the measurement and analysis of its dynamic load, the stress and reliability analysis of key fragile components as well as the system reliability analysis and calculation of the ma chine. The result of the study provides valuable reference for the evaluation and improve-ment of the structure and performance of the machine.
Electrical discharge machining studies on reactive sintered FeAl
Indian Academy of Sciences (India)
A K Khanra; S Patra; M M Godkhindi
2006-06-01
Electrical discharge machining (EDM) studies on reactive sintered FeAl were carried out with different process parameters. The metal removal rate and tool removal rate were found to increase with the applied pulse on-time. The surface roughness of machined surface also changed with the applied pulse on-time. XRD analysis of machined surface of sintered FeAl showed the formation of Fe3C phase during the EDM process. The debris analysis was used to identify the material removal mechanism occurring during the EDM of sintered FeAl.
Case study of virtual reality in CNC machine tool exhibition
Directory of Open Access Journals (Sweden)
Kao Yung-Chou
2017-01-01
Full Text Available Exhibition and demonstration are generally used in the promotion and sale-assistance of manufactured products. However, the transportation cost of the real goods from the vender factory to the exposition venue is generally expensive for huge and heavy commodity. With the advancement of computing, graphics, mobile apps, and mobile hardware the 3D visibility technology is getting more and more popular to be adopted in visual-assisted communication such as amusement games. Virtual reality (VR technology has therefore being paid great attention in emulating expensive small and/or huge and heavy equipment. Virtual reality can be characterized as 3D extension with Immersion, Interaction and Imagination. This paper was then be focused on the study of virtual reality in the assistance of CNC machine tool demonstration and exhibition. A commercial CNC machine tool was used in this study to illustrate the effectiveness and usability of using virtual reality for an exhibition. The adopted CNC machine tool is a large and heavy mill-turn machine with the width up to eleven meters and weighted about 35 tons. A head-mounted display (HMD was attached to the developed VR CNC machine tool for the immersion viewing. A user can see around the 3D scene of the large mill-turn machine and the operation of the virtual CNC machine can be actuated by bare hand. Coolant was added to demonstrate more realistic operation while collision detection function was also added to remind the operator. The developed VR demonstration system has been presented in the 2017 Taipei International Machine Tool Show (TIMTOS 2017. This case study has shown that young engineers and/or students are very impressed by the VR-based demonstration while elder persons could not adapt themselves easily to the VR-based scene because of eyesight issues. However, virtual reality has successfully being adopted and integrated with the CNC machine tool in an international show. Another machine tool on
Analysis of exergy and parametric study of a v-corrugated solar air heater
Energy Technology Data Exchange (ETDEWEB)
Hedayatizadeh, Mahdi [University of Tabriz, Department of Agricultural Machinery Engineering, Faculty of Agriculture, Tabriz (Iran, Islamic Republic of); University of Birjand, Faculty of Agriculture, P.O. Box 97175/331, Birjand (Iran, Islamic Republic of); Ajabshirchi, Yahya [University of Tabriz, Department of Agricultural Machinery Engineering, Faculty of Agriculture, Tabriz (Iran, Islamic Republic of); Sarhaddi, Faramarz; Farahat, Said [University of Sistan and Baluchestan, Department of Mechanical Engineering, Faculty of Engineering, P.O. Box 98164/161, Zahedan (Iran, Islamic Republic of); Safavinejad, Ali [University of Birjand, Department of Mechanical Engineering, Faculty of Engineering, Birjand (Iran, Islamic Republic of); Chaji, Hossein [University of Tabriz, Department of Agricultural Machinery Engineering, Faculty of Agriculture, Tabriz (Iran, Islamic Republic of); Center of Agriculture and Natural Resources of Khorasan Razavi Province, Ministry of Agriculture, Mashhad (Iran, Islamic Republic of)
2012-07-15
Solar air heater requires investigation for enhancement of solar energy conversion into heat. Different configurations with various artificial roughness geometries are proposed to date. In present study attention is paid on ways leading to more delivery of exergy by a v-corrugated solar air heater through parametric study. Effects of aspect ratio of the collector, inlet air temperature, mass flow rate per collector area etc. are studied. (orig.)
Parametric study on the performance of green residential buildings in China
Xi Wang; Hasim Altan; Jian Kang
2015-01-01
The parametric study of the indoor environment of green buildings focuses on the quantitative and qualitative improvement of residential building construction in China and the achievement of indoor thermal comfort at a low level of energy use. This study examines the effect of the adaptive thermal comfort of indoor environment control in hot summer and cold winter (HSCW) zones. This work is based on a field study of the regional thermal assessment of two typical cases, the results of which ar...
Parametric study on the performance of green residential buildings in China
Xi Wang; Hasim Altan; Jian Kang
2015-01-01
The parametric study of the indoor environment of green buildings focuses on the quantitative and qualitative improvement of residential building construction in China and the achievement of indoor thermal comfort at a low level of energy use. This study examines the effect of the adaptive thermal comfort of indoor environment control in hot summer and cold winter (HSCW) zones. This work is based on a field study of the regional thermal assessment of two typical cases, the results of which ar...
Parametric study of closed wet cooling tower thermal performance
Qasim, S. M.; Hayder, M. J.
2017-08-01
The present study involves experimental and theoretical analysis to evaluate the thermal performance of modified Closed Wet Cooling Tower (CWCT). The experimental study includes: design, manufacture and testing prototype of a modified counter flow forced draft CWCT. The modification based on addition packing to the conventional CWCT. A series of experiments was carried out at different operational parameters. In view of energy analysis, the thermal performance parameters of the tower are: cooling range, tower approach, cooling capacity, thermal efficiency, heat and mass transfer coefficients. The theoretical study included develops Artificial Neural Network (ANN) models to predicting various thermal performance parameters of the tower. Utilizing experimental data for training and testing, the models simulated by multi-layer back propagation algorithm for varying all operational parameters stated in experimental test.
Parametric study on a natural circulation cooled U-battery
Energy Technology Data Exchange (ETDEWEB)
De Zwaan, Sieuwert; Kloosterman, Jan Leen [Delft University of Technology, Delft (Netherlands); Van Uitert, Gert [The Hague (Netherlands)
2008-07-01
A feasibility study has been performed on a natural circulation cooled small nuclear reactor with a molten salt or tin as a coolant. This reactor is called the U-Battery. The study included neutronics calculations to obtain the minimum dimensions required for a critical system during burnup, the calculation of coolant temperature and core temperature reactivity coefficients, and an investigation of the thermal hydraulics to asses the possibilities for natural circulation cooling. For every coolant, core designs are feasible within the dimensions imposed and with natural circulation of the coolant. (authors)
Parametric study and simulation of microbubble column flotation
1991-01-01
A study based on a statistically designed set of experiments (Box-Behnken design) has been conducted to determine the optimum conditions for advanced physical fine coal cleaning using microbubble column flotation. The dependent variables in these experiments were mass yield and product quality (ash, sulfur and btu), while the independent variables were feed solids content, collector dosage, frother dosage, feed rate, aeration rate, and wash water rate. The most important operating parameters ...
The status of parametric studies in radar agriculture
Morain, S. A.
1972-01-01
Outlined is an information system based on the use of remote sensor data and the design, testing, and implementation of interpretation keys for agriculture. The task of crop identification from radar imagery emphasizes dichotomous keys and the effects of frequency, angular and other microwave dependencies of crops for use in discrimination. A mosaic is formulated from imagery and used to study acres in wheat for spread of circular irrigation, spread of crops, and other phenomena.
Energy Technology Data Exchange (ETDEWEB)
Staiger, P.J.; Abbott, J.M.
1980-06-01
The Parametric Study of Potential Early Commercial MHD Power Plants is described and the results of the study are summarized. Two parallel contracted studies were conducted. Each contractor investigated three base cases and parametric variation about these base cases. Each contractor concluded that two of the base cases (a plant using separate firing of an advanced high temperature regenerative air heater with fuel from an advanced coal gasifier and a plant using an intermediate temperature metallic recuperative heat exchanger to heat oxygen enriched combustion air) were comparable in both performance and cost of electricity. The contractors differed in the level of their cost estimates with the capital cost estimates for the MHD topping cycle and the magnet subsystem in particular accounting for a significant part of the difference. The impact of the study on the decision to pursue a course which leads to an oxygen enriched plant as the first commercial MHD plant is described.
Logistic distributed activation energy model--Part 1: Derivation and numerical parametric study.
Cai, Junmeng; Jin, Chuan; Yang, Songyuan; Chen, Yong
2011-01-01
A new distributed activation energy model is presented using the logistic distribution to mathematically represent the pyrolysis kinetics of complex solid fuels. A numerical parametric study of the logistic distributed activation energy model is conducted to evaluate the influences of the model parameters on the numerical results of the model. The parameters studied include the heating rate, reaction order, frequency factor, mean of the logistic activation energy distribution, standard deviation of the logistic activation energy distribution. The parametric study addresses the dependence on the forms of the calculated α-T and dα/dT-T curves (α: reaction conversion, T: temperature). The study results would be very helpful to the application of the logistic distributed activation energy model, which is the main subject of the next part of this series.
Parametric studies on the nanosecond laser micromachining of the materials
Tański, M.; Mizeraczyk, J.
2016-12-01
In this paper the results of an experimental studies on nanosecond laser micromachining of selected materials are presented. Tested materials were thin plates made of aluminium, silicon, stainless steel (AISI 304) and copper. Micromachining of those materials was carried out using a solid state laser with second harmonic generation λ = 532 nm and a pulse width of τ = 45 ns. The effect of laser drilling using single laser pulse and a burst of laser pulses, as well as laser cutting was studied. The influence of laser fluence on the diameter and morphology of a post ablation holes drilled with a single laser pulse was investigated. The ablation fluence threshold (Fth) of tested materials was experimentally determined. Also the drilling rate (average depth per single laser pulse) of holes drilled with a burst of laser pulses was determined for all tested materials. The studies of laser cutting process revealed that a groove depth increases with increasing average laser power and decreasing cutting speed. It was also found that depth of the laser cut grooves is a linear function of number of repetition of a cut. The quantitative influence of those parameters on the groove depth was investigated.
Design and Numerical Parametric Study of Fractal Heat Exchanger
Huang, Zhiwei; Ling, Jiazhen; Hwang, Yunho; Aute, Vikrant; Radermacher, Reinhard
2016-01-01
Air-to-refrigerant heat exchangers are a main component in air-conditioning and heat pump systems and are therefore a topic of major research focus. Such heat exchangers, mainly made of fin-and-tube and microchannels, use fins to augment the heat transfer area of the air-side. Recently it has been shown that finless designs using â‰¤ 1 mm hydraulic diameter bare tubes can deliver better air-side heat transfer performance than conventional heat exchangers. In current study, a novel air-to-refr...
Parametric studies of human thermal mechanisms and measurements.
Thornton, S B; Nair, S S
2000-04-01
A systematic methodology is proposed for mathematically quantifying the effects of measurement inaccuracies due to instrument uncertainty in a human calorimetry project. Human thermal mechanisms are poorly understood at the systems level and this study investigates the importance of these mechanisms quantitatively. The proposed methodology uses sensitivity derivatives combined with sensor accuracies to quantify the effect of each heat transfer mechanism contributing to the errors in the system equations. The method is applicable to any differentiable model to be validated by experimentation. To illustrate the methodology, two example cases, a reclining nude resting subject and a reclining clothed working subject, are analyzed. The calculated expected errors clearly suggest specific modifications.
A parametric study on ice formation inside a spherical capsule
Energy Technology Data Exchange (ETDEWEB)
Ismail, K.A.R.; Silva, T.M. da [Depto. de Engenharia Termica e de Fluidos - FEM-UNICAMP CP: 6122, CEP 13083-970, SP, Campinas (Brazil); Henriquez, J.R. [Depto. de Engenharia Mecanica - DEMEC, UFPE, CEP 50740-530, PE, Recife (Brazil)
2003-09-01
This paper reports the results of a numerical study on the heat transfer during the process of solidification of water inside a spherical capsule. The governing equations of the problem and associated boundary conditions were formulated and solved using a finite difference approach and a moving grid scheme. The model was optimized and the numerical predictions were validated by comparison with experimental results realized by the authors. The model was also used to investigate the effects of the size and material of the shell, initial temperature of the phase change material and the external temperature of the spherical capsule on the solidified mass fraction and the time for the complete solidification. (authors)
Parametric study of turbine NGV blade lean and vortex design
Institute of Scientific and Technical Information of China (English)
Zhang Shaowen; David G. MacManus; Luo Jianqiao
2016-01-01
The effects of blade lean and vortex design on the aerodynamics of a turbine entry nozzle guide vane (NGV) are considered using computational fluid dynamics. The aim of the work is to address some of the uncertainties which have arisen from previous studies where conflicting results have been reported for the effect on the NGV. The configuration was initially based on the energy efficient engine turbine which also served as the validation case for the computational method. A total of 17 NGV configurations were evaluated to study the effects of lean and vortex design on row efficiency and secondary kinetic energy. The distribution of mass flow ratio is introduced as an additional factor in the assessment of blade lean effects. The results show that in the turbine entry NGV, the secondary flow strength is not a dominant factor that determines NGV losses and therefore the changes of loading distribution due to blade lean and the associated loss mecha-nisms should be regarded as a key factor. Radial mass flow redistribution under different NGV lean and twist is demonstrated as an addition key factor influencing row efficiency.
Parametric study of turbine NGV blade lean and vortex design
Directory of Open Access Journals (Sweden)
Zhang Shaowen
2016-02-01
Full Text Available The effects of blade lean and vortex design on the aerodynamics of a turbine entry nozzle guide vane (NGV are considered using computational fluid dynamics. The aim of the work is to address some of the uncertainties which have arisen from previous studies where conflicting results have been reported for the effect on the NGV. The configuration was initially based on the energy efficient engine turbine which also served as the validation case for the computational method. A total of 17 NGV configurations were evaluated to study the effects of lean and vortex design on row efficiency and secondary kinetic energy. The distribution of mass flow ratio is introduced as an additional factor in the assessment of blade lean effects. The results show that in the turbine entry NGV, the secondary flow strength is not a dominant factor that determines NGV losses and therefore the changes of loading distribution due to blade lean and the associated loss mechanisms should be regarded as a key factor. Radial mass flow redistribution under different NGV lean and twist is demonstrated as an addition key factor influencing row efficiency.
Parametric study of solar thermal rocket nozzle performance
Pearson, J. Boise; Landrum, D. Brian; Hawk, Clark W.
1995-01-01
This paper details a numerical investigation of performance losses in low-thrust solar thermal rocket nozzles. The effects of nozzle geometry on three types of losses were studied; finite rate dissociation-recombination kinetic losses, two dimensional axisymmetric divergence losses, and compressible viscous boundary layer losses. Short nozzle lengths and supersonic flow produce short residence times in the nozzle and a nearly frozen flow, resulting in large kinetic losses. Variations in geometry have a minimal effect on kinetic losses. Divergence losses are relatively small, and careful shaping of the nozzle can nearly eliminate them. The boundary layer in these small nozzles can grow to a major fraction of nozzle radius, and cause large losses. These losses are attributed to viscous drag on the nozzle walls and flow blockage by the boundary layer, especially in the throat region. Careful shaping of the nozzle can produce a significant reduction in viscous losses.
Laser produced nanocavities in silica and sapphire: a parametric study
Energy Technology Data Exchange (ETDEWEB)
Hallo, L; Travaille, G; Tikhonchuk, V T; Breil, J [CELIA, Universite Bordeaux I, 351 cours de la Liberation, 33405 Talence (France); Bourgeade, A [CEA - CESTA, BP 2, 3334 Le Barp (France); Nkonga, B [MAB, Universite Bordeaux I, 351 cours de la Liberation, 33405 Talence (France)
2008-05-15
We present a model, that describes a sub-micron cavity formation in a transparent dielectric under a tight focusing of a ultra-short laser pulse. The model solves the full set of Maxwell's equations in the three-dimensional geometry along with non-linear propagation phenomenons. This allows us to initialize hydrodynamic simulations of the sub-micron cavity formation. Cavity characteristics, which depend on 3D energy release and non linear effects, have been investigated and compared with experimental results. For this work, we want to deeply acknowledge the numerical support provided by the CEA Centre de Calcul Recherche et Technologie, whose help guaranteed the achievement of this study.
Experimental study of oil plume stability: Parametric dependences and optimization.
Li, Haoshuai; Shen, Tiantian; Bao, Mutai
2016-10-15
Oil plume is known to interact with density layer in spilled oil. Previous studies mainly focused on tracking oil plumes and predicting their impact on marine environment. Here, simulated experiments are presented that investigated the conditions inducing the formation of oil plume, focusing especially on the effects of oil/water volume ratio, oil/dispersant volume rate, ambient stratification and optimal conditions of oil plume on determining whether a plume will trap or escape. Scenario simulations showed that OWR influences the residence time most, dispersants dosage comes second and salinity least. The optimum residence time starts from 2387s, occurred at approximately condition (OWR, 0.1, DOR, 25.53% and salinity, 32.38). No change in the relative distribution under the more scale tank was observed, indicating these provide the time evolution of the oil plumes.
A Parametric Study of Crack Propagation During Sonic IR Inspection
Chen, J. C.; Kephart, J.; Riddell, W. T.
2006-03-01
We have developed an experiment to study the propagation of synthetic cracks under various controlled conditions during sonic IR inspection. The experiment provides for good repeatability in testing. The parameters of interest include the initial crack length, load history (stress intensity and load ratio) during crack generation, geometry of the crack, material, and also the various conditions involving the ultrasonic source. In general, we find that under typical sonic IR inspection conditions, the initial crack will propagate when subjected to sonic IR testing. The crack growth after each inspection event varies and exhibits a distribution in length of propagation. The results show that the average crack propagation decreases with increasing initial crack length and increasing stress intensity.
Membrane reactor for water detritiation: a parametric study on operating parameters
Energy Technology Data Exchange (ETDEWEB)
Mascarade, J.; Liger, K.; Troulay, M.; Perrais, C. [CEA, DEN, DTN/STPA/LIPC, Centre de Cadarache, Saint-Paul-lez-Durance (France); Joulia, X.; Meyer, X.M. [Universite de Toulouse, INPT, UPS, Laboratoire de Genie Chimique, Toulouse (France); CNRS, Laboratoire de Genie Chimique, Toulouse (France)
2015-03-15
This paper presents the results of a parametric study done on a single stage finger-type packed-bed membrane reactor (PBMR) used for heavy water vapor de-deuteration. Parametric studies have been done on 3 operating parameters which are: the membrane temperature, the total feed flow rate and the feed composition through D{sub 2}O content variations. Thanks to mass spectrometer analysis of streams leaving the PBMR, speciation of deuterated species was achieved. Measurement of the amounts of each molecular component allowed the calculation of reaction quotient at the packed-bed outlet. While temperature variation mainly influences permeation efficiency, feed flow rate perturbation reveals dependence of conversion and permeation properties to contact time between catalyst and reacting mixture. The study shows that isotopic exchange reactions occurring on the catalyst particles surface are not thermodynamically balanced. Moreover, the variation of the heavy water content in the feed exhibits competition between permeation and conversion kinetics.
Parametric study of propeller boss cap fins for container ships
Directory of Open Access Journals (Sweden)
Lim Sang-Seop
2014-06-01
Full Text Available The global price of oil, which is both finite and limited in quantity, has been rising steadily because of the increasing requirements for energy in both developing and developed countries. Furthermore, regulations have been strengthened across all industries to address global warming. Many studies of hull resistance, propulsion and operation of ships have been performed to reduce fuel consumption and emissions. This study examined the design parameters of the propeller boss cap fin (PBCF and hub cap for 6,000TEU container ships to improve the propulsion efficiency. The design parameters of PBCF have been selected based on the geometrical shape. Computational fluid dynamics (CFD analysis with a propeller open water (POW test was performed to check the validity of CFD analysis. The design of experiment (DOE case was selected as a full factorial design, and the experiment was analyzed by POW and CFD analysis. Analysis of variance (ANOVA was performed to determine the correlation among design parameters. Four design alternatives of PBCF were selected from the DOE. The shape of a propeller hub cap was selected as a divergent shape, and the divergent angle was determined by the DOE. Four design alternatives of PBCF were attached to the divergent hub cap, and the POW was estimated by CFD. As a result, the divergent hub cap with PBCF has a negative effect on the POW, which is induced by an increase in torque coefficient. A POW test and cavitation test were performed with a divergent hub cap with PBCF to verify the CFD result. The POW test result showed that the open water efficiency was increased approximately 2% with a divergent hub cap compared to a normal cap. The POW test result was similar to the CFD result, and the divergent hub cap with the PBCF models showed lower open water efficiency. This was attributed to an increase in the torque coefficient just like the CFD results. A cavitation test was performed using the 2 models selected. The test
Parametric Study of Carbon Nanotube Production by Laser Ablation Process
Arepalli, Sivaram; Nikolaev, Pavel; Holmes, William; Hadjiev, Victor; Scott, Carl
2002-01-01
Carbon nanotubes form a new class of nanomaterials that are presumed to have extraordinary mechanical, electrical and thermal properties. The single wall nanotubes (SWNTs) are estimated to be 100 times stronger than steel with 1/6th the weight; electrical carrying capacity better than copper and thermal conductivity better than diamond. Applications of these SWNTs include possible weight reduction of aerospace structures, multifunctional materials, nanosensors and nanoelectronics. Double pulsed laser vaporization process produces SWNTs with the highest percentage of nanotubes in the output material. The normal operating conditions include a green laser pulse closely followed by an infrared laser pulse. Lasers ab late a metal-containing graphite target located in a flow tube maintained in an oven at 1473K with argon flow of 100 sccm at a 500 Torr pressure. In the present work a number of production runs were carried out, changing one operating condition at a time. We have studied the effects of nine parameters, including the sequencing of the laser pulses, pulse separation times, laser energy densities, the type of buffer gas used, oven temperature, operating pressure, flow rate and inner flow tube diameters. All runs were done using the same graphite target. The collected nanotube material was characterized by a variety of analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman and thermo gravimetric analysis (TGA). Results indicate trends that could be used to optimize the process and increase the efficiency of the production process.
Parametric study of radiofrequency helium discharge under atmospheric pressure
Indian Academy of Sciences (India)
SAFDAR HUSSAIN; HAFIZ IMRAN AHMAD QAZI; SHANAWER NIAZ; MANZOOR AHMAD BADAR
2016-12-01
The parameters of radio frequency helium discharge under atmospheric pressure were studied by electrical and optical measurements using high voltage probe, current probe and optical emission spectroscopy. Two discharge modes $\\alpha$ and $\\gamma$ were observed within certain limits. During $\\alpha$ to $\\gamma$ mode transition, a decrease in voltage (280–168 V), current (2.05–1.61 A) and phase angle (76$^{\\rm o}-56^{\\rm o}$) occurred. The discharge parameters such as resistance, reactance, sheath thickness, electron density, excitation temperature and gas temperature were assessed by electrical measurements using equivalent circuit model and optical emission spectroscopy. In $\\alpha$ mode, the discharge current increased from 1.17 to 2.05 A, electron density increased from $0.19 \\times 10^{12} {\\rm to} 0.47 \\times 10^{12} {\\rm cm}^{−3}$ while sheath thickness decreased from 0.40 to 0.25 mm. The excitation temperatures in the $\\alpha$ and $\\gamma$ modes were 3266 and 4500 K respectively, evaluated by Boltzmann’s plot method. The estimated gas temperature increased from 335 K in the α mode to 485 K in the γ mode, suggesting that the radio frequency atmospheric pressure helium discharge can be used for surface treatment applications.
An active debris removal parametric study for LEO environment remediation
Liou, J.-C.
2011-06-01
Recent analyses on the instability of the orbital debris population in the low Earth orbit (LEO) region and the collision between Iridium 33 and Cosmos 2251 have reignited interest in using active debris removal (ADR) to remediate the environment. There are, however, monumental technical, resource, operational, legal, and political challenges in making economically viable ADR a reality. Before a consensus on the need for ADR can be reached, a careful analysis of its effectiveness must be conducted. The goal is to demonstrate the need and feasibility of using ADR to better preserve the future environment and to explore different operational options to maximize the benefit-to-cost ratio. This paper describes a new sensitivity study on using ADR to stabilize the future LEO debris environment. The NASA long-term orbital debris evolutionary model, LEGEND, is used to quantify the effects of several key parameters, including target selection criteria/constraints and the starting epoch of ADR implementation. Additional analyses on potential ADR targets among the existing satellites and the benefits of collision avoidance maneuvers are also included.
Parametric Study of Open Trough Steel Concrete Composite Deck
Directory of Open Access Journals (Sweden)
Merool Devarsh Vakil
2015-01-01
Full Text Available Steel concrete composite deck is used in many parts of the world as fast and economical structural system. Recently the techniques are getting attention in India also. The profile deck is made up of thin cold formed steel sheet which can be formed in any desired shape. In this paper, critical study is made by varying the geometrical and material strength parameters of steel concrete deck. Its effect on flexural resistance and neutral axis location is analyzed. Ductile behavior of deck is another important concern. Here, authors put forward the limiting value of neutral axis for commonly used grades of steel for profile deck, which should be checked to ensure ductile behavior of composite deck. The paper considers variations in concrete thickness, yield strength of material, cylinder strength of concrete for an open trough type profile deck .Analysis of moment of resistance and depth of neutral axis are made as per Euro code EN-1994 assuming full bond between steel and concrete. The results show that there is significant variation in flexural capacity and neutral axis location on varying geometrical and material parameters.
Parametric Studies Of Lightweight Reflectors Supported On Linear Actuator Arrays
Seibert, George E.
1987-10-01
This paper presents the results of numerous design studies carried out at Perkin-Elmer in support of the design of large diameter controllable mirrors for use in laser beam control, surveillance, and astronomy programs. The results include relationships between actuator location and spacing and the associated degree of correctability attainable for a variety of faceplate configurations subjected to typical disturbance environments. Normalizations and design curves obtained from closed-form equations based on thin shallow shell theory and computer based finite-element analyses are presented for use in preliminary design estimates of actuator count, faceplate structural properties, system performance prediction and weight assessments. The results of the analyses were obtained from a very wide range of mirror configurations, including both continuous and segmented mirror geometries. Typically, the designs consisted of a thin facesheet controlled by point force actuators which in turn were mounted on a structurally efficient base panel, or "reaction structure". The faceplate materials considered were fused silica, ULE fused silica, Zerodur, aluminum and beryllium. Thin solid faceplates as well as rib-reinforced cross-sections were treated, with a wide variation in thickness and/or rib patterns. The magnitude and spatial frequency distribution of the residual or uncorrected errors were related to the input error functions for mirrors of many different diameters and focal ratios. The error functions include simple sphere-to-sphere corrections, "parabolization" of spheres, and higher spatial frequency input error maps ranging from 0.5 to 7.5 cycles per diameter. The parameter which dominates all of the results obtained to date, is a structural descriptor of thin shell behavior called the characteristic length. This parameter is a function of the shell's radius of curvature, thickness, and Poisson's ratio of the material used. The value of this constant, in itself
Exergetic performance evaluation and parametric studies of solar air heater
Energy Technology Data Exchange (ETDEWEB)
Gupta, M.K.; Kaushik, S.C. [Centre for Energy Studies, Indian Institute of Technology, Delhi 110016 (India)
2008-11-15
The present study aims to establish the optimal performance parameters for the maximum exergy delivery during the collection of solar energy in a flat-plate solar air heater. The procedure to determine optimum aspect ratio (length to width ratio of the absorber plate) and optimum duct depth (the distance between the absorber and the bottom plates) for maximum exergy delivery has been developed. It is known that heat energy gain and blower work increase monotonically with mass flow rate, while the temperature of air decreases; therefore, it is desirable to incorporate the quality of heat energy collected and the blower work. First it is proved analytically that the optimum exergy output, neglecting blower work, and the corresponding mass flow rate depend on the inlet temperature of air. The energy and exergy output rates of the solar air heater were evaluated for various values of collector aspect ratio (AR) of the collector, mass flow rate per unit area of the collector plate (G) and solar air heater duct depth (H). Results have been presented to discuss the effects of G, AR and H on the energy and exergy output rates of the solar air heater. The energy output rate increases with G and AR, and decreases with H and the inlet temperature of air. The exergy-based evaluation criterion shows that performance is not a monotonically increasing function of G and AR, and a decreasing function of H and inlet temperature of air. Based on the exergy output rate, it is found that there must be an optimum inlet temperature of air and a corresponding optimum G for any value of AR and H. For values of G lesser than optimal corresponding to inlet temperature of air equals to ambient, higher exergy output rate is achieved for the low value of duct depth and high AR in the range of parameters investigated. If G is high, for an application requiring less temperature increase, then either low AR or high H would give higher exergy output rate. (author)
Energy Technology Data Exchange (ETDEWEB)
Choi, Hongyoon; Yoo, Min Young; Cheon, Gi Jeong; Kang, Keon Wook; Chung, Junekey; Lee, Dong Soo [Seoul National Univ., Seoul (Korea, Republic of)
2013-09-15
Basal/acetazolamide stress {sup 99m}Tc-HMPAO single-photon emission computed tomography (SPECT) has been widely used for evaluation of hemodynamics; however, qualitative and subjective visual assessment of cerebrovascular reserve (CVR) has been performed in clinical settings. The aim of this study was to generate parametric CVR images and evaluate its feasibility of quantification. Basal/acetazolamide stress {sup 99m}Tc-HMPAO SPECT data from 17 patients who underwent bypass surgery or percutaneous transluminal angioplasty were used. Spatial normalization was performed and parametric CVR images were generated using relative CVR (rCVR) of each voxel proportional to CVR of the whole brain. Binary parametric maps to show area of relatively reduced CVR were generated also using threshold of rCVR < 90 %. We calculated rCVR of internal carotid artery (ICA) using the parametric CVR images and probabilistic maps for ICA territory. Pre- and postprocedural parametric CVR images were obtained and quantitative rCVRs were compared. The rCVRs were evaluated according to visual grades for regional decreased CVR. Postprocedural rCVR obtained from parametric CVR images increased significantly from preprocedural rCVR. The rCVR was significantly correlated with visual grades of reduced CVR for each side of ICA territories. We generated parametric CVR images for basal/acetazolamide stress {sup 99m}Tc-HMPAO SPECT. As a quantitative measurement, rCVR obtained from the parametric image was feasibly assessed hemodynamic abnormalities with preserved anatomical information.
Directory of Open Access Journals (Sweden)
S.M. Ali
2015-06-01
Full Text Available In this study a parabolic reflector antenna is designed and fabricated for IEEE 802.11a WLAN application. Initially, a single element circular tuning slot coupled Cylindrical Dielectric Resonator Antenna (CDRA feeder is designed and fabricated for a symmetric parabolic reflector. Subsequently, the designed feeder is integrated at the focal point of the parabolic reflector to provide unidirectional radiation pattern with improved gain and sidelobe levels. The measured fractional impedance bandwidth achieved for the proposed antenna is 1.8% for S11<-10 dB from 5.32 to 5.52 GHz. A radiation pattern with broadside radiation and low back radiation has been obtained. A good measurement gain of approximately 13 dB is achieved over the bandwidth by placing CDRA feeder at the focal point of the parabolic reflector. In addition, a comprehensive parametric study has been conducted to realize the effect of slot size and position on the resonance frequency of the designed feeder. Furthermore, a parametric study of various reflector parameters has also been performed to study the effect of size, depth and focal point of the parabolic reflector on gain of the antenna. Important design factors have been identified from the parametric study of the antenna. The experimental and measured results show that the designed antenna is suitable for IEEE WLAN 802.11a wireless application.
Shah, Anoop D; Bartlett, Jonathan W; Carpenter, James; Nicholas, Owen; Hemingway, Harry
2014-03-15
Multivariate imputation by chained equations (MICE) is commonly used for imputing missing data in epidemiologic research. The "true" imputation model may contain nonlinearities which are not included in default imputation models. Random forest imputation is a machine learning technique which can accommodate nonlinearities and interactions and does not require a particular regression model to be specified. We compared parametric MICE with a random forest-based MICE algorithm in 2 simulation studies. The first study used 1,000 random samples of 2,000 persons drawn from the 10,128 stable angina patients in the CALIBER database (Cardiovascular Disease Research using Linked Bespoke Studies and Electronic Records; 2001-2010) with complete data on all covariates. Variables were artificially made "missing at random," and the bias and efficiency of parameter estimates obtained using different imputation methods were compared. Both MICE methods produced unbiased estimates of (log) hazard ratios, but random forest was more efficient and produced narrower confidence intervals. The second study used simulated data in which the partially observed variable depended on the fully observed variables in a nonlinear way. Parameter estimates were less biased using random forest MICE, and confidence interval coverage was better. This suggests that random forest imputation may be useful for imputing complex epidemiologic data sets in which some patients have missing data.
Aerodynamic parametric studies and sensitivity analysis for rotor blades in axial flight
Chiu, Y. D.; Peters, David A.
1991-01-01
The analytical capability is offered for aerodynamic parametric studies and sensitivity analyses of rotary wings in axial flight by using a 3D undistorted wake model in curved lifting line theory. The governing equations are solved by both the Multhopp Interpolation technique and the Vortex Lattice method. The singularity from the bound vortices is eliminated through the Hadamard's finite part concept. Good numerical agreement between both analytical methods and finite differences methods are found. Parametric studies were made to assess the effects of several shape variables on aerodynamic loads. It is found, e.g., that a rotor blade with out-of-plane and inplane curvature can theoretically increase lift in the inboard and outboard regions respectively without introducing an additional induced drag.
Experimental parametric study of servers cooling management in data centers buildings
Nada, S. A.; Elfeky, K. E.; Attia, Ali M. A.; Alshaer, W. G.
2017-01-01
A parametric study of air flow and cooling management of data centers servers is experimentally conducted for different design conditions. A physical scale model of data center accommodating one rack of four servers was designed and constructed for testing purposes. Front and rear rack and server's temperatures distributions and supply/return heat indices (SHI/RHI) are used to evaluate data center thermal performance. Experiments were conducted to parametrically study the effects of perforated tiles opening ratio, servers power load variation and rack power density. The results showed that (1) perforated tile of 25% opening ratio provides the best results among the other opening ratios, (2) optimum benefit of cold air in servers cooling is obtained at uniformly power loading of servers (3) increasing power density decrease air re-circulation but increase air bypass and servers temperature. The present results are compared with previous experimental and CFD results and fair agreement was found.
Parametric theoretical study of a two-stage solar organic Rankine cycle for RO desalination
Energy Technology Data Exchange (ETDEWEB)
Kosmadakis, G.; Manolakos, D.; Papadakis, G. [Department of Natural Resources and Agricultural Engineering, Agricultural University of Athens, 75 Iera Odos Street, 11855 Athens (Greece)
2010-05-15
The present work concerns the parametric study of an autonomous, two-stage solar organic Rankine cycle for RO desalination. The main goal of the current simulation is to estimate the efficiency, as well as to calculate the annual mechanical energy available for desalination in the considered cases, in order to evaluate the influence of various parameters on the performance of the system. The parametric study concerns the variation of different parameters, without changing actually the baseline case. The effect of the collectors' slope and the total number of evacuated tube collectors used, have been extensively examined. The total cost is also taken into consideration and is calculated for the different cases examined, along with the specific fresh water cost (EUR/m{sup 3}). (author)
Institute of Scientific and Technical Information of China (English)
郭莹; 曹巨江; 张科宇
2016-01-01
以面向对象的VB 6.0为开发平台，结合Access建立的标准数据库，控制服务端SolidWorks二次开发接口的A PI函数，调用对象、属性、方法，实现对工业平缝机机壳参数化模块的二次开发。用该方法可以快速、准确、高效地设计出符合用户要求的工业平缝机机壳的三维模型。%The paper proposes a parametric design method of industrial sewing machine casing by use of SolidWorks .This method is based on the object-oriented VB language platform and the standard database established by Access ,to accomplish the secondary development of the parametric design module of the industrial sewing machine casing through controlling API function offered by secondary development interface of server SolidWorks and calling object ,attribute and method .The proposed method can quickly establish the three-dimensional model of the industrial sewing machine casing and it is accurate and efficient to meet the requirements of the user .
CFD Parametric Studies for Global Performance Improvement of Open Refrigerated Display Cabinets
Directory of Open Access Journals (Sweden)
Pedro Dinis Gaspar
2012-01-01
Full Text Available A detailed CFD modelling of an open refrigerated display cabinet has been formulated in a previous study. Some modifications are introduced in order to perform parametric studies dealing with low-cost geometrical and functional characteristics for improvement of the global performance and energy efficiency. The parametric studies are devoted to the analysis of the thermal response and behaviour inside the food conservation space influenced by (1 air flow rate through the evaporator heat exchanger; (2 air curtain behaviour; (3 hole dimensions and distribution of the back panel; (4 discharge and return grilles angles; and (5 flow deflectors inside the internal duct. The analysis of the numerical predictions from the parametric studies allows the development of an optimized model for the conception of an open refrigerated display cabinet with a more adequate configuration. The numerical predictions of the optimized model show lower product temperature and reduced electrical energy consumption, allowing the improvement of the food safety and the energy rationalization of the refrigeration equipment.
Martinelli, M; Ducci, S; Gigan, S; Maitre, A; Fabre, C; Martinelli, Marcello; Treps, Nicolas; Ducci, Sara; Gigan, Sylvain; Maitre, Agnes; Fabre, Claude
2003-01-01
We study experimentally the spatial distribution of quantum noise in the twin beams produced by a type II Optical Parametric Oscillator operating in a confocal cavity above threshold. The measured intensity correlations are at the same time below the standard quantum limit and not uniformly distributed inside the beams. We show that this feature is an unambiguous evidence for the multimode and nonclassical character of the quantum state generated by the device.
Instability strips of main sequence B stars: a parametric study of iron enhancement
Miglio, A; Montalban, J; Dupret, M A
2006-01-01
The discovery of beta Cephei stars in low metallicity environments, as well as the difficulty to theoretically explain the excitation of the pulsation modes observed in some beta Cephei and SPB stars, suggest that the iron opacity ``bump'' provided by standard models could be underestimated. We investigate, by means of a parametric study, the effect of a local iron enhancement on the location of the beta Cephei and SPB instability strips.
Performance comparison and parametric study on spiral groove gas film face seals
Institute of Scientific and Technical Information of China (English)
LIU Yuchuan; SHEN Xinmin; XU Wanfu; WANG Zhili
2004-01-01
Several spiral groove gas film face seals (SGFS) with different layouts are compared quantitatively to analyze their merits and faults and application behaviors. In addition, a parametric study on downstream mode SGFS is conducted to determine its optimal parameters under certain working conditions. In the computation of gas film pressure on the face, finite element method (FEM) is applied to adapt to complicated geometrical boundary.
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.
Marston, C. H.; Alyea, F. N.; Bender, D. J.; Davis, L. K.; Dellinger, T. C.; Hnat, J. G.; Komito, E. H.; Peterson, C. A.; Rogers, D. A.; Roman, A. J.
1980-01-01
The performance and cost of moderate technology coal-fired open cycle MHD/steam power plant designs which can be expected to require a shorter development time and have a lower development cost than previously considered mature OCMHD/steam plants were determined. Three base cases were considered: an indirectly-fired high temperature air heater (HTAH) subsystem delivering air at 2700 F, fired by a state of the art atmospheric pressure gasifier, and the HTAH subsystem was deleted and oxygen enrichment was used to obtain requisite MHD combustion temperature. Coal pile to bus bar efficiencies in ease case 1 ranged from 41.4% to 42.9%, and cost of electricity (COE) was highest of the three base cases. For base case 2 the efficiency range was 42.0% to 45.6%, and COE was lowest. For base case 3 the efficiency range was 42.9% to 44.4%, and COE was intermediate. The best parametric cases in bases cases 2 and 3 are recommended for conceptual design. Eventual choice between these approaches is dependent on further evaluation of the tradeoffs among HTAH development risk, O2 plant integration, and further refinements of comparative costs.
Comparison of parametric FBP and OS-EM reconstruction algorithm images for PET dynamic study
Energy Technology Data Exchange (ETDEWEB)
Oda, Keiichi; Uemura, Koji; Kimura, Yuichi; Senda, Michio [Tokyo Metropolitan Inst. of Gerontology (Japan). Positron Medical Center; Toyama, Hinako; Ikoma, Yoko
2001-10-01
An ordered subsets expectation maximization (OS-EM) algorithm is used for image reconstruction to suppress image noise and to make non-negative value images. We have applied OS-EM to a digital brain phantom and to human brain {sup 18}F-FDG PET kinetic studies to generate parametric images. A 45 min dynamic scan was performed starting injection of FDG with a 2D PET scanner. The images were reconstructed with OS-EM (6 iterations, 16 subsets) and with filtered backprojection (FBP), and K1, k2 and k3 images were created by the Marquardt non-linear least squares method based on the 3-parameter kinetic model. Although the OS-EM activity images correlated fairly well with those obtained by FBP, the pixel correlations were poor for the k2 and k3 parametric images, but the plots were scattered along the line of identity and the mean values for K1, k2 and k3 obtained by OS-EM were almost equal to those by FBP. The kinetic fitting error for OS-EM was no smaller than that for FBP. The results suggest that OS-EM is not necessarily superior to FBP for creating parametric images. (author)
RFX machine and power supply improvements for RFP advanced studies
Energy Technology Data Exchange (ETDEWEB)
Piovan, R. E-mail: piovan@igi.pd.cnr.it; Gnesotto, F.; Ortolani, S.; Baker, W.; Barana, O.; Bettini, P.; Cavazzana, R.; Chitarin, G.; Dal Bello, S.; De Lorenzi, A.; Fiorentin, P.; Gaio, E.; Grando, L.; Luchetta, A.; Manduchi, G.; Marchiori, G.; Marcuzzi, D.; Masiello, A.; Milani, F.; Peruzzo, S.; Pomaro, N.; Sonato, P.; Taliercio, C.; Toigo, V.; Zaccaria, P.; Zanotto, L.; Zollino, G
2001-10-01
Experimental results and theoretical studies call for Reversed Field Experiment (RFX) machine and power supply improvements to allow studies that go beyond those of a conventional Reversed Field Pinch (RFP) with passively stabilized turbulent MHD dynamo. The new paths opened by recent results in RFX and other RFP machines are introduced; then the goals and the design lines of the technical modifications of RFX, mainly addressed to improve the first wall, the plasma magnetic boundaries and to increase the operational flexibility of the toroidal field circuit power supply, are reported.
Applications of Parametric and Nonparametric Tests for Event Studies on ISE
Handan YOLSAL
2011-01-01
In this study, we conducted a research as to whether splits in shares on the ISE-ON Index at the Istanbul Stock Exchange have had an impact on returns generated from shares between 2005 and 2011 or not using event study method. This study is based on parametric tests, as well as on nonparametric tests developed as an alternative to them. It has been observed that, when cross-sectional variance adjustment is applied to data set, such null hypothesis as “there is no average abnormal return at d...
Humphrey, Joseph W.
1990-01-01
A parametric study has been conducted for an oblique detonation-wave (ODW) 'scramaccelerator' suitable for projectile aerothermodynamics studies in real gas hypersonic test facilities. The results of the present analytical design evaluation indicate that an ODW scramaccelerator using conventional gaseous propellants can accelerate projectiles of 0.1 to 1000 kg masses to speeds in the 6-10 km/sec range. Potential applications for such an accelerator encompass a hypersonic ballistic test range, kinetic energy weapon accelerators, mass drivers to LEO, projectile terminal ballistics testing, projectile/target interaction studies, inertial welders, and shock compactors.
Direct parametric reconstruction in dynamic PET myocardial perfusion imaging: in vivo studies
Petibon, Yoann; Rakvongthai, Yothin; El Fakhri, Georges; Ouyang, Jinsong
2017-05-01
Dynamic PET myocardial perfusion imaging (MPI) used in conjunction with tracer kinetic modeling enables the quantification of absolute myocardial blood flow (MBF). However, MBF maps computed using the traditional indirect method (i.e. post-reconstruction voxel-wise fitting of kinetic model to PET time-activity-curves-TACs) suffer from poor signal-to-noise ratio (SNR). Direct reconstruction of kinetic parameters from raw PET projection data has been shown to offer parametric images with higher SNR compared to the indirect method. The aim of this study was to extend and evaluate the performance of a direct parametric reconstruction method using in vivo dynamic PET MPI data for the purpose of quantifying MBF. Dynamic PET MPI studies were performed on two healthy pigs using a Siemens Biograph mMR scanner. List-mode PET data for each animal were acquired following a bolus injection of ~7-8 mCi of 18F-flurpiridaz, a myocardial perfusion agent. Fully-3D dynamic PET sinograms were obtained by sorting the coincidence events into 16 temporal frames covering ~5 min after radiotracer administration. Additionally, eight independent noise realizations of both scans—each containing 1/8th of the total number of events—were generated from the original list-mode data. Dynamic sinograms were then used to compute parametric maps using the conventional indirect method and the proposed direct method. For both methods, a one-tissue compartment model accounting for spillover from the left and right ventricle blood-pools was used to describe the kinetics of 18F-flurpiridaz. An image-derived arterial input function obtained from a TAC taken in the left ventricle cavity was used for tracer kinetic analysis. For the indirect method, frame-by-frame images were estimated using two fully-3D reconstruction techniques: the standard ordered subset expectation maximization (OSEM) reconstruction algorithm on one side, and the one-step late maximum a posteriori (OSL-MAP) algorithm on the other
Kumar, Sumeet; Heister, Stephen D.; Xu, Xianfan; Salvador, James R.; Meisner, Gregory P.
2013-06-01
A comprehensive numerical model has been proposed to model thermoelectric generators (TEGs) for automotive waste heat recovery. Details of the model and results from the analysis of General Motors' prototype TEG were described in part I of the study. In part II of this study, parametric evaluations are considered to assess the influence of heat exchanger, geometry, and thermoelectric module configurations to achieve optimization of the baseline model. The computational tool is also adapted to model other topologies such as transverse and circular configurations (hexagonal and cylindrical) maintaining the same volume as the baseline TEG. Performance analysis of these different topologies and parameters is presented and compared with the baseline design.
Hashemi-Kia, M.; Toossi, M.
1990-01-01
As a result of this work, a reduction procedure has been developed which can be applied to large finite element model of airframe type structures. This procedure, which is tailored to be used with MSC/NASTRAN finite element code, is applied to the full airframe dynamic finite element model of AH-64A Attack Helicopter. The applicability of the resulting reduced model to parametric and optimization studies is examined. Through application of the design sensitivity analysis, the viability and efficiency of this reduction technique has been demonstrated in a vibration reduction study.
Energy Technology Data Exchange (ETDEWEB)
Kang, Sung Wook; Jang, Beom Seon [Seoul National University, Seoul (Korea, Republic of)
2014-10-15
A three-dimensional numerical model was constructed to analyze the heat transfer of friction stir welding using Fluent and ANSYS multi-physics. The analysis result was used to calculate welding deformation and residual stress. Before the numerical simulation, several simplifying assumptions were applied to the model. Three different methods of heat transfer analysis were employed, and several assumptions were applied to each heat source model. In this work, several parametric studies were performed for certain unspecified variables. The calculated temperature data were compared with experimental data from relevant studies. Additionally, the advantages and disadvantages of the three heat transfer analysis methods were compared.
Manekeller, S.; Leuvenink, Henri; Sitzia, M.; Minor, T.
2005-01-01
The objective of the present study was to evaluate the recently proposed aerobic machine preservation with the noncolloidal HTK solution by comparison with the colloidal Belzer machine perfusion solution (MPS) after procurement of marginal kidneys from non-heart-beating donors. Kidneys were harveste
Manekeller, S; Leuvenink, H; Sitzia, M; Minor, T
2005-01-01
The objective of the present study was to evaluate the recently proposed aerobic machine preservation with the noncolloidal HTK solution by comparison with the colloidal Belzer machine perfusion solution (MPS) after procurement of marginal kidneys from non-heart-beating donors. Kidneys were harveste
Directory of Open Access Journals (Sweden)
Amlana Panda
2016-09-01
Full Text Available Machining of hardened work materials with appropriate levels of process parameters is still a burning issue in manufacturing sectors and challenging. It is because of pressing demand of surface quality which adversely affected by evolution of tool wear. Therefore the present investigation is undertaken to make a decision on parametric optimization of multi-responses such as flank wear and surface roughness during machining hardened AISI 52100 steel (55±1 steel using mixed ceramic insert under dry environment through grey relational analysis combined with Taguchi approach. Also predicted mathematical models of 1st and 2nd order have been developed for responses and checked for its accuracy. Second order mathematical model presented higher R2 value and represents best fit of the model and adequate compared to first order model. Model indicates good correlations between the experimental and predicted results. The proposed grey-based Taguchi methodology has been proved to be efficient for solving multi-attribute decision making problem as a case study in hard machining environment.
Parametric studies on relationships between flutter derivatives of slender bridge (I)
Institute of Scientific and Technical Information of China (English)
Xu Xu
2009-01-01
Relationships between flutter derivatives of slender bridge are investigated based on our previously proposed semi-analytical flutter derivatives of flexible structure.The intrinsic relations are validated with test data of flutter derivatives of two bridges.Changes in flutter derivatives with the aerodynamic center, rotation speed, and angle variation are also studied by using a parametric method. The results show correctness of the proposed expressions of flutter derivatives given by authors in Ref.[1], and indicate that certain relations exist between these derivatives. It is also shown that semi-analytical flutter derivatives are applicable to bridges with a streamlined cross-section.
Energy Technology Data Exchange (ETDEWEB)
GRENARD, C.E.
2000-09-11
Alternative for removing heat from Phase 1, low-activity waste feed double-shell tanks using the ventilation systems have been analyzed for Phase 1 waste feed delivery. The analysis was a parametric study using a model that predicted the waste temperatures for a range of primary and annulus ventilation system flow rates. The analysis was performed to determine the ventilation flow required to prevent the waste temperature from exceeding the Limiting Conditions for Operation limits during normal operation and the Safety Limits during off-normal events.
A Parametric Study for High-Efficiency Gas-Liquid Separator Design
Institute of Scientific and Technical Information of China (English)
2008-01-01
A gas liquid centrifugal separator is widely used in industry on account of its simple geometry and little maintenance. These separators have considerable advantages over filters, scrubbers or precipitators in term of compact design, lower pressure drop and higher capacity. A gas liquid centrifugal separator is a device that utilizes centrifugal forces and low pressure caused by rotational motion to separate liquid from gas by density differences.Efficient and reliable separation is required for the optimum operation. These separators axe often operated at less than peak efficiency due to the entrainment of separated liquid through an outlet pipe which is closely associated with the very complicated flow phenomena involved. Design parameters such as length of the separation space,vane exit angle, inlet to outlet diameter ratio, models for separation efficiency and pressure drop as a function of physical dimensions are not available in literature. This leaves the designer with very little to go on except known designs and experimentation. The aim of present study is to perform a parametric study to get higher efficiency for gas-liquid separator. A parametric study has been carried out with the help of CFD tools to analyze a separation performance of a centrifugal separator by varying the length of separator space. The best design parameters are analyzed based upon obtained results, tangential velocities, vortices, total pressure losses. From the present study several attempts are made to improve the performance of conventional centrifugal separators.
Energy Technology Data Exchange (ETDEWEB)
Ball, J.; Glowa, G.; Wren, J. [Atomic Energy of Canada Limited, Chalk River, Ontario (Canada); Ewig, F. [GRS Koln (Germany); Dickenson, S. [AEAT, (United Kingdom); Billarand, Y.; Cantrel, L. [IPSN (France); Rydl, A. [NRIR (Czech Republic); Royen, J. [OECD/NEA (France)
2001-11-01
This report describes the results of the second phase of International Standard Problem (ISP) 41, an iodine behaviour code comparison exercise. The first phase of the study, which was based on a simple Radioiodine Test Facility (RTF) experiment, demonstrated that all of the iodine behaviour codes had the capability to reproduce iodine behaviour for a narrow range of conditions (single temperature, no organic impurities, controlled pH steps). The current phase, a parametric study, was designed to evaluate the sensitivity of iodine behaviour codes to boundary conditions such as pH, dose rate, temperature and initial I{sup -} concentration. The codes used in this exercise were IODE(IPSN), IODE(NRIR), IMPAIR(GRS), INSPECT(AEAT), IMOD(AECL) and LIRIC(AECL). The parametric study described in this report identified several areas of discrepancy between the various codes. In general, the codes agree regarding qualitative trends, but their predictions regarding the actual amount of volatile iodine varied considerably. The largest source of the discrepancies between code predictions appears to be their different approaches to modelling the formation and destruction of organic iodides. A recommendation arising from this exercise is that an additional code comparison exercise be performed on organic iodide formation, against data obtained front intermediate-scale studies (two RTF (AECL, Canada) and two CAIMAN facility, (IPSN, France) experiments have been chosen). This comparison will allow each of the code users to realistically evaluate and improve the organic iodide behaviour sub-models within their codes. (author)
Parametric study and optimization of a transcritical power cycle using a low temperature source
Energy Technology Data Exchange (ETDEWEB)
Cayer, Emmanuel; Galanis, Nicolas [Universite de Sherbrooke, Genie mecanique, Sherbrooke, QC (Canada); Nesreddine, Hakim [LTE-Hydro-Quebec, 600 av. de la Montagne, Shawinigan, QC (Canada)
2010-04-15
A parametric study and optimization is performed on a transcritical power cycle using six performance indicators: thermal efficiency, specific net output, exergetic efficiency, total UA and surface of the heat exchangers as well as the relative cost of the system. The independent parameters are the maximum temperature and pressure of the cycle as well as the net power output. Results show that it is impossible to simultaneously optimise all six performance indicators, i.e. that the values of the independent parameters are not the same for all the optimizations. The design value for these parameters is therefore a matter of choice, or compromise, among the combinations optimising the performance indicators. For a limited low temperature heat source the parametric studies reveal the existence of a maximum value for the net power output of the system and of another net power output minimising the cost per kW. A comparison of optimised results for three working fluids (CO{sub 2}, ethane, R125) shows that the better fluid depends on the optimised indicator and clearly indicates that a simple first law analysis is not sufficient for the selection of a working fluid. In summary, this paper demonstrates the need to achieve a multi-point optimization and comparison in order to study adequately a transcritical power system. (author)
Free Surface Waves And Interacting Bouncing Droplets: A Parametric Resonance Case Study
Borja, Francisco J.
2013-07-01
Parametric resonance is a particular type of resonance in which a parameter in a system changes with time. A particularly interesting case is when the parameter changes in a periodic way, which can lead to very intricate behavior. This di↵ers from periodic forcing in that solutions are not necessarily periodic. A system in which parametric resonance is realized is when a fluid bath is shaken periodically, which leads to an e↵ective time dependent gravitational force. This system will be used to study the onset of surface waves in a bath with non-uniform topography. A linear model for the surface waves is derived from the Euler equations in the limit of shallow waves, which includes the geometry of the bottom and surface tension. Experiments are performed to compare with the proposed model and good qualitative agreement is found. Another experiment which relies on a shaking fluid bath is that of bouncing fluid droplets. In the case of two droplets the shaking allows for a larger bouncing droplet to attract a smaller moving droplet in a way that creates a bound system. This bound system is studied and shows some analogous properties to quantum systems, so a quantum mechanical model for a two dimensional atom is studied, as well as a proposed model for the droplet-wave system in terms of equations of fluid mechanics.
Pham, Trang Thanh; Liney, Gary; Wong, Karen; Rai, Robba; Lee, Mark; Moses, Daniel; Henderson, Christopher; Lin, Michael; Shin, Joo-Shik; Barton, Michael Bernard
2017-07-04
Response to neoadjuvant chemoradiotherapy (CRT) of rectal cancer is variable. Accurate imaging for prediction and early assessment of response would enable appropriate stratification of management to reduce treatment morbidity and improve therapeutic outcomes. Use of either diffusion weighted imaging (DWI) or dynamic contrast enhanced (DCE) imaging alone currently lacks sufficient sensitivity and specificity for clinical use to guide individualized treatment in rectal cancer. Multi-parametric MRI and analysis combining DWI and DCE may have potential to improve the accuracy of therapeutic response prediction and assessment. This protocol describes a prospective non-interventional single-arm clinical study. Patients with locally advanced rectal cancer undergoing preoperative CRT will prospectively undergo multi-parametric MRI pre-CRT, week 3 CRT, and post-CRT. The protocol consists of DWI using a read-out segmented sequence (RESOLVE), and DCE with pre-contrast T1-weighted (VIBE) scans for T1 calculation, followed by 60 phases at high temporal resolution (TWIST) after gadoversetamide injection. A 3-dimensional voxel-by-voxel technique will be used to produce colour-coded ADC and K(trans) histograms, and data evaluated in combination using scatter plots. MRI parameters will be correlated with surgical histopathology. Histopathology analysis will be standardized, with chemoradiotherapy response defined according to AJCC 7th Edition Tumour Regression Grade (TRG) criteria. Good response will be defined as TRG 0-1, and poor response will be defined as TRG 2-3. The combination of DWI and DCE can provide information on physiological tumour factors such as cellularity and perfusion that may affect radiotherapy response. If validated, multi-parametric MRI combining DWI and DCE can be used to stratify management in rectal cancer patients. Accurate imaging prediction of patients with a complete response to CRT would enable a 'watch and wait' approach, avoiding surgical morbidity
The Parametric Study and Fine-Tuning of Bow-Tie Slot Antenna with Loaded Stub
2017-01-01
A printed Bow-Tie slot antenna with loaded stub is proposed and the effects of changing the dimensions of the slot area, the stub and load sizes are considered in this paper. These parameters have a considerable effect on the antenna characteristics as well as its performance. An in-depth parametric study of these dimensions is presented. This paper proposes the necessary conditions for initial approximation of dimensions needed to design this antenna. In order to achieve the desired performance of the antenna fine tuning of all sizes of these parameters is required. The parametric studies used in this paper provide proper trends for initiation and tuning the design. A prototype of the antenna for 1.7GHz to 2.6GHz band is fabricated. Measurements conducted verify that the designed antenna has wideband characteristics with 50% bandwidth around the center frequency of 2.1GHz. Conducted measurements for reflection coefficient (S11) and radiation pattern also validate our simulation results. PMID:28114354
A parametric study of strength reduction factors for elasto-plastic oscillators
Indian Academy of Sciences (India)
Debasis Karmakar; Vinay K Gupta
2006-08-01
Strength reduction factors (SRFs) continue to play a key role in obtaining design forces from elastic design spectra (via response modiﬁcation factors) in ductility-based earthquake-resistant design. Despite several years of sustained research efforts, it has not been conclusively shown how SRF for a given single-degree-of-freedom structural system depends on various source and site parameters. A parametric study is carried out here for the explicit dependence of SRF spectrum (describing variation of SRF with system period for a given ductility demand) on strong motion duration, earthquake magnitude, geological site conditions, and epicentral distance in case of (non-degrading) elasto-plastic oscillators. For this, scaled response spectra are considered for different combinations of earthquake magnitude, site conditions and epicentral distance, and SRF spectra are generated from 1274 accelerograms recorded in western USA after making those compatible with each of these spectra. It is shown that there is no clear and signiﬁcant dependence of SRF spectrum on strong motion duration. Further, the parametric dependence on earthquake magnitude, site conditions, and epicentral distance broadly conforms to the trends reported by earlier investigations. In particular, this study conﬁrms that the dependence of SRF spectra on earthquake magnitude should not be ignored.
Hybrid Model of Inhomogeneous Solar Wind Plasma Heating by Alfven Wave Spectrum: Parametric Studies
Ofman, L.
2010-01-01
Observations of the solar wind plasma at 0.3 AU and beyond show that a turbulent spectrum of magnetic fluctuations is present. Remote sensing observations of the corona indicate that heavy ions are hotter than protons and their temperature is anisotropic (T(sub perpindicular / T(sub parallel) >> 1). We study the heating and the acceleration of multi-ion plasma in the solar wind by a turbulent spectrum of Alfvenic fluctuations using a 2-D hybrid numerical model. In the hybrid model the protons and heavy ions are treated kinetically as particles, while the electrons are included as neutralizing background fluid. This is the first two-dimensional hybrid parametric study of the solar wind plasma that includes an input turbulent wave spectrum guided by observation with inhomogeneous background density. We also investigate the effects of He++ ion beams in the inhomogeneous background plasma density on the heating of the solar wind plasma. The 2-D hybrid model treats parallel and oblique waves, together with cross-field inhomogeneity, self-consistently. We investigate the parametric dependence of the perpendicular heating, and the temperature anisotropy in the H+-He++ solar wind plasma. It was found that the scaling of the magnetic fluctuations power spectrum steepens in the higher-density regions, and the heating is channeled to these regions from the surrounding lower-density plasma due to wave refraction. The model parameters are applicable to the expected solar wind conditions at about 10 solar radii.
A parametric study of influence of material properties on car cabin environment
Directory of Open Access Journals (Sweden)
Pokorny Jan
2014-03-01
Full Text Available Recently the author presented the paper describing a car cabin heat load model for the prediction of the car cabin environment. The model allowed to simulate a transient behavior of the car cabin, i.e. radiant temperature of surfaces, air temperature and relative humidity. The model was developed in Dymola and was built on the basic principles of thermodynamics and heat balance equations. The model was validated by experiments performed on the Škoda Felicia during various operational conditions. In this paper the authors present a parametric study investigating influence of material properties on a car cabin environment. The Matlab version of the car cabin heat load model has been developed and used. The model was extended by simple graphical user interface and it was deployed into the stand alone executable application. The aim of this parametric study is to identify most important material properties and its effect on the cabin environment during specific operational conditions of car. By means of a sensitive analysis it can identified which material parameters have to be defined precisely and which parameters are not so important for the prediction of the air temperature inside cabin.
Parametric Weight Study of Cryogenic Metallic Tanks for the ``Bimodal'' NTR Mars Vehicle Concept
Kosareo, Daniel N.; Roche, Joseph M.
2006-01-01
A parametric weight assessment of large cryogenic metallic tanks was conducted using the design optimization capabilities in the ANSYS ® finite element analysis code. This analysis was performed to support the sizing of a ``bimodal'' nuclear thermal rocket (NTR) Mars vehicle concept developed at the NASA Glenn Research Center. The tank design study was driven by two load conditions: an in-line, ``Shuttle-derived'' heavy-lift launch with the tanks filled and pressurized, and a burst-test pressure. The main tank structural arrangement is a state-of-the art metallic construction which uses an aluminum-lithium alloy stiffened internally with a ring and stringer framework. The tanks must carry liquid hydrogen in separate launches to orbit where all vehicle components will dock and mate. All tank designs stayed within the available mass and payload volume limits of both the in-line heavy lift and Shuttle derived launch vehicles. Weight trends were developed over a range of tank lengths with varying stiffener cross-sections and tank wall thicknesses. The object of this parametric study was to verify that the proper mass was allocated for the tanks in the overall vehicle sizing model. This paper summarizes the tank weights over a range of tank lengths.
Computerized Simulation of Automotive Air-Conditioning System: A Parametric Study
Directory of Open Access Journals (Sweden)
Haslinda Mohamed Kamar
2013-01-01
Full Text Available This paper presents results of a parametric study performed on an automotive air-conditioning (AAC system of a passenger car. The goals are to assess the effects of varying the volumetric flow rate of supply air, number of occupants, vehicle speed, and the fractional ventilation air intake (XOA, on the dry-bulb temperature and specific humidity of the air inside the passengers cabin, and on the evaporator coil cooling load of the AAC system. Results of the parametric study show that increasing the supply air flow rate reduces the dry-bulb temperature of the cabin air, increases both the specific humidity of the air and the evaporator coil load. Increasing the number of occupants in the passenger cabin causes the cabin air temperature, specific humidity and the evaporator coil load to increase. Increasing the vehicle speed causes the specific humidity of the cabin air and the evaporator coil cooling load to increase but the dry-bulb temperature of the air is not significantly affected. Increasing the fractional fresh air intake (XOA also increases the cabin air specific humidity and the evaporator coil cooling load.
Hybrid Model of Inhomogeneous Solar Wind Plasma Heating by Alfven Wave Spectrum: Parametric Studies
Ofman, L.
2010-01-01
Observations of the solar wind plasma at 0.3 AU and beyond show that a turbulent spectrum of magnetic fluctuations is present. Remote sensing observations of the corona indicate that heavy ions are hotter than protons and their temperature is anisotropic (T(sub perpindicular / T(sub parallel) >> 1). We study the heating and the acceleration of multi-ion plasma in the solar wind by a turbulent spectrum of Alfvenic fluctuations using a 2-D hybrid numerical model. In the hybrid model the protons and heavy ions are treated kinetically as particles, while the electrons are included as neutralizing background fluid. This is the first two-dimensional hybrid parametric study of the solar wind plasma that includes an input turbulent wave spectrum guided by observation with inhomogeneous background density. We also investigate the effects of He++ ion beams in the inhomogeneous background plasma density on the heating of the solar wind plasma. The 2-D hybrid model treats parallel and oblique waves, together with cross-field inhomogeneity, self-consistently. We investigate the parametric dependence of the perpendicular heating, and the temperature anisotropy in the H+-He++ solar wind plasma. It was found that the scaling of the magnetic fluctuations power spectrum steepens in the higher-density regions, and the heating is channeled to these regions from the surrounding lower-density plasma due to wave refraction. The model parameters are applicable to the expected solar wind conditions at about 10 solar radii.
The Parametric Study and Fine-Tuning of Bow-Tie Slot Antenna with Loaded Stub.
Shafiei, M M; Moghavvemi, Mahmoud; Wan Mahadi, Wan Nor Liza
2017-01-01
A printed Bow-Tie slot antenna with loaded stub is proposed and the effects of changing the dimensions of the slot area, the stub and load sizes are considered in this paper. These parameters have a considerable effect on the antenna characteristics as well as its performance. An in-depth parametric study of these dimensions is presented. This paper proposes the necessary conditions for initial approximation of dimensions needed to design this antenna. In order to achieve the desired performance of the antenna fine tuning of all sizes of these parameters is required. The parametric studies used in this paper provide proper trends for initiation and tuning the design. A prototype of the antenna for 1.7GHz to 2.6GHz band is fabricated. Measurements conducted verify that the designed antenna has wideband characteristics with 50% bandwidth around the center frequency of 2.1GHz. Conducted measurements for reflection coefficient (S11) and radiation pattern also validate our simulation results.
Parametric studies of AC plasma display panel cells in complex geometries
Energy Technology Data Exchange (ETDEWEB)
Punset, C.; Boeuf, J.P.; Pitchford, L.C. [Univ. Paul Sabatier, Toulouse (France). CPAT
1996-12-31
The authors have developed a two-dimensional fluid model of AC plasma panel cells. This model was used to study the operation of a plasma panel cell in a barrier rib geometry in single pulse operation. In this communication, they report results from calculations in several different geometries and for a series of applied voltage pulses. The purpose of this work is to study the effect of geometry on the electrical characteristics of AC plasma display panel cells. The calculations reported here are representative of actual device operation. They have also used the model to study the effect of the geometrical parameters of the cell, to optimize the discharge efficiency in producing UV photons and to study cross-talk, i.e., interaction between adjacent cells. The conclusions of these parametric studies will be presented.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The chaotic dynamics of a Duffing oscillator with a parametric force is investigated. By using the direct perturbation technique, we analytically obtain the general solution of the 1st-order equation. Through the boundedness condition of the general solution we get the famous Melnikov function predicting the onset of chaos. When the parametric and external forces are strong, numerical simulations show that increasing the amplitude of the parametric or external force can lead the system into chaos via period doubling.
An Interactive Software for Conceptual Wing Flutter Analysis and Parametric Study
Mukhopadhyay, Vivek
1996-01-01
An interactive computer program was developed for wing flutter analysis in the conceptual design stage. The objective was to estimate the flutter instability boundary of a flexible cantilever wing, when well-defined structural and aerodynamic data are not available, and then study the effect of change in Mach number, dynamic pressure, torsional frequency, sweep, mass ratio, aspect ratio, taper ratio, center of gravity, and pitch inertia, to guide the development of the concept. The software was developed for Macintosh or IBM compatible personal computers, on MathCad application software with integrated documentation, graphics, data base and symbolic mathematics. The analysis method was based on non-dimensional parametric plots of two primary flutter parameters, namely Regier number and Flutter number, with normalization factors based on torsional stiffness, sweep, mass ratio, taper ratio, aspect ratio, center of gravity location and pitch inertia radius of gyration. The parametric plots were compiled in a Vought Corporation report from a vast data base of past experiments and wind-tunnel tests. The computer program was utilized for flutter analysis of the outer wing of a Blended-Wing-Body concept, proposed by McDonnell Douglas Corp. Using a set of assumed data, preliminary flutter boundary and flutter dynamic pressure variation with altitude, Mach number and torsional stiffness were determined.
Polarization effect in parametric amplifier
Institute of Scientific and Technical Information of China (English)
Junhe Zhou; Jianping Chen; Xinwan Li; Guiling Wu; Yiping Wang
2005-01-01
@@ Polarization effect in parametric amplifiers is studied. Coupled equations are derived from the basic propagation equations and numerical solutions are given for both one-wavelength-pump and two-wavelengthpump systems. Several parametric amplifiers driven by pumps at one wavelength and two wavelengths are analyzed and the polarization independent parametric amplifier is proposed.
Cliffe, Matthew J; Goodwin, Andrew L
2013-11-13
We present a detailed study of the mechanism by which the INVERT method (Cliffe et al 2010 Phys. Rev. Lett. 104 125501) guides structure refinement of disordered materials. We present a number of different possible implementations of the central algorithm and explore the question of algorithm weighting. Our analysis includes quantification of the relative contributions of variance and fit-to-data terms during structure refinement, which leads us to study the roles of density fluctuations and configurational jamming in the RMC fitting process. We present a parametric study of the pair distribution function solution space for C60, a-Si and a-SiO2, which serves to highlight the difficulties faced in developing a transferable weighting scheme.
Energy Technology Data Exchange (ETDEWEB)
Silva, Alexandre Alves Sampaio e
1996-07-01
The obtention of the electrical and mechanical parameters of a squirrel-cage induction motor is investigated. Two methods of identification are studied: the reactive power method, used to determine the electrical parameters and an acceleration method on a startup test used to to find the mechanical ones. The method of reactive power is developed by analysing the machine steady state operation. In this analysis, a relationship between the electrical parameters and the reactive power is obtained. A minimization algorithm is used to determine the parameters based on this relationship. The acceleration method uses an acquisition of the transient variables, which is used in a recursive least square method furnishing the mechanical parameters. Both of methods are implemented on a special hardware and software system, consisting of sensors and A/D boards that make a digital acquisition of voltage, current and speed values. The validation procedures for the method and parameters are based on comparing between the real and simulated evaluation of the dynamical behavior of the motor in a startup test. The skin-effect influence over some of the motor parameters was also discussed. (author)
An Experimental Study on Electro Chemical Machining of Microelectrode
Institute of Scientific and Technical Information of China (English)
ZHANG Liao-yuan; LIU Yao
2006-01-01
Puts forward a new method in machining microelectrode by electro chemical machining (ECM) and plastic deformed theory. Theprocedure of this method is to machine the microelectrode according to the basic rule of ECM theory at first. Then, with the change of ECM machining parameters, one of the microelectrode ends is exerted by a load. As a result, the elastic and plastic deformation is produced at the machining section and the microelectrode diameter is reduced.It has been proved that the proposed method can determine the optimum machining parameters to machine the microelectrode of Cu.
Study of CNC Grinding Machining Method About Isometric Polygon Profile
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The formed principle and CNC grinding machining method of isometric polygonal profile are studied deeply and systematically. Equation about section curve of isometric polygon profile is set up by means of geometric principle. With the use of differential geometry theory, the curve is proved to be with geometric feature of convex curve. It is referred to as Isometric Polygonal Curve (IPC), because that is a kind of convex curve on which the distance between any parallel tangent lines is equal. Isometric Poly...
Studies of Machine Learning Photometric Classification of Supernovae
Macaluso, Joseph Nicholas; Cunningham, John; Kuhlmann, Stephen; Gupta, Ravi; Kovacs, Eve
2017-01-01
We studied the use of machine learning for the photometuric classification of Type Ia (SNIa) and core collapse (SNcc) supernovae. We used a combination of simulated data for the Dark Energy survey (DES) and real data from SDSS and chose our metrics to be the sample purity and the efficiency of identifying SNIa supernovae. Our focus was to quantify the effects of varying the training and parameters for random-forest decision-tree algorithms.
Parametric Study on a Horizontal Axis Wind Turbine Proposed for Water Pumping
Directory of Open Access Journals (Sweden)
Dr. Abdullateef A. Jadallah
2014-01-01
Full Text Available Water pumping is considered an economically competitive sustainable process of providing water to communities, rural areas and livestock's. A parametric analysis on HAWT is carried out to explore the influence of the performance parameters on the power generated and withdrawal quantity of water. Effect of wind speed, radius of rotor, ambient condition, well depth, and efficiencies of turbine, generator and the pump were studied and reflected in important generalized performance maps. These performance graphs are valuable in best understanding of on‐design and off‐ design constraints of the horizontal axis wind turbine in water pumping. The blade geometry was also studied. Results showed the reasonable range of wind turbine performance and the corresponding water discharge within the abovementioned constraints. Rating and the effect of pitch angle on discharged water are also presented. Methodology necessary to achieve the abovementioned results is processed by a computer program written in Matlab
Parametric Study and Design Optimization of Centrifugal Pump Impeller-A Review
Directory of Open Access Journals (Sweden)
Vijaypratap R Singh ,
2014-01-01
Full Text Available Centrifugal pumps are widely used for irrigation, water supply plants, steam power plants, sewage, oil refineries, chemical plants, hydraulic power service, food processing factories and mines, because of their suitability in practically any service. Therefore it is necessary to find out the design parameters and working conditions that yield optimal output and maximum efficiency with lowest power consumption. Study indicates that Computational fluid dynamics (CFD analysis is being increasingly applied in the design of centrifugal pumps. With the aid of the CFD approach, the complex internal flows in water pump impellers, can be well predicted, to speed up the pump design procedure. This paper exposes the various research work carried out in this direction especially in the content of parametric study and optimization of centrifugal pump impeller using CFD tool and DoE technique. Literature surveys indicate that very restricted work has been done in this area.
Parametric study on the performance of a heat exchanger with corrugated louvered fins
Energy Technology Data Exchange (ETDEWEB)
Qi, Zhao-gang; Chen, Jiang-ping; Chen, Zhi-jiu [Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, No. 1954, Huashan Rd., Shanghai 200030 (China)
2007-02-15
The Taguchi method is a well-known parametric study tool in engineering quality and experimental design. This study analyzes five experimental factors (flow depth, ratio of fin pitch and fin thickness, tube pitch, number of louvers and angle of louver) affecting the heat transfer and pressure drop of a heat exchanger with corrugated louvered fins using the Taguchi method. Fifteen samples are selected from experimental database and the heat transfer and flow friction characteristics are analyzed. The results show that flow depth, ratio of fin pitch and fin thickness and the number of the louvers are the main factors that influence significantly the thermal hydraulic performance of the heat exchanger with corrugated louvered fins. Therefore, these three factors are considered as the main factors for an optimum design of a heat exchanger. (author)
A parametric simulation study for solvent co-injection process in bitumen deposits
Energy Technology Data Exchange (ETDEWEB)
Yazdani, A.; Alvestad, J.; Kjonsvik, D.; Gilje, E.; Kowalewski, E. [Statoil Canada (Canada)
2011-07-01
The extraction of very large Canadian extra heavy oil and bitumen deposits is facing major challenges, such as energy requirements and access to sustainable water resources. Steam assisted gravity drainage (SAGD) is the most common commercial in-situ recovery process used for the extraction but it has many associated economic and environmental challenges. Moreover, current knowledge of the fundamental physics and mechanics involved in the process is not satisfactory. This paper presents a parametric simulation study for a solvent co-injection (SCI) process in bitumen deposits. This process has the potential to improve the efficiency of steam processes as well as to reduce energy use and CO2 emissions. The study contributes to further understanding of the development process. Several operational and geological parameters were evaluated to assess their impact on SAGD operations. The results demonstrated that the basis for selecting the optimum solvent should not only be mobility improvement capability but should also include other operational and geological conditions.
A PARAMETRIC STUDY ON EXERGETIC ASPECTS OF HYDROGEN ENERGY IN REDUCING FOSSIL FUEL CONSUMPTION
Energy Technology Data Exchange (ETDEWEB)
Adnan Midilli [Energy Division, Mechanical Engineering Department, Nigde University, Nigde (Turkey); Ibrahim Dincer [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, Oshawa, ON (Canada)
2008-09-30
This paper presents a parametric analysis on the exergetic dimension of hydrogen in reducing global fossil fuels consumption. Some key parameters such as fossil fuel based-global waste exergy factor, hydrogen based-global exergetic efficiency, and fossil fuel based-global irreversibility coefficient are proposed and studied in this regard. In order to verify these exergetic parameters, the actual fossil fuel consumption and production data are used as the base data in the analysis. Due to the unavailability of appropriate hydrogen data for the present study, it is assumed that the utilization ratio of hydrogen is practically ranged between 0 and 1. As a result, if exergetic utilization ratio of hydrogen from non-fossil fuel sources at a certain exergetic utilization ratio of fossil fuels increases, the fossil fuel based-global irreversibility coefficient will decrease.
Fall detection using supervised machine learning algorithms: A comparative study
Zerrouki, Nabil
2017-01-05
Fall incidents are considered as the leading cause of disability and even mortality among older adults. To address this problem, fall detection and prevention fields receive a lot of intention over the past years and attracted many researcher efforts. We present in the current study an overall performance comparison between fall detection systems using the most popular machine learning approaches which are: Naïve Bayes, K nearest neighbor, neural network, and support vector machine. The analysis of the classification power associated to these most widely utilized algorithms is conducted on two fall detection databases namely FDD and URFD. Since the performance of the classification algorithm is inherently dependent on the features, we extracted and used the same features for all classifiers. The classification evaluation is conducted using different state of the art statistical measures such as the overall accuracy, the F-measure coefficient, and the area under ROC curve (AUC) value.
Qingsong Xu
2014-01-01
Extreme learning machine (ELM) is a learning algorithm for single-hidden layer feedforward neural network dedicated to an extremely fast learning. However, the performance of ELM in structural impact localization is unknown yet. In this paper, a comparison study of ELM with least squares support vector machine (LSSVM) is presented for the application on impact localization of a plate structure with surface-mounted piezoelectric sensors. Both basic and kernel-based ELM regression models have b...
Experimental Study on Abrasive Water Jet Machining of PZT Ceramic
Dhanawade, Ajit; Upadhyai, Ravi; Rouniyar, Arunkumar; Kumar, Shailendra
2017-07-01
This paper presents research work involved in abrasive water jet machining of PZT ceramic material. Process parameters namely stand-off distance, water pressure and traverse rate are considered in the present study. Response surface methodology approach is used to design the experiments. Relative significance of process parameters and their influence on kerf properties are identified on the basis of analysis of variance. It is found that water pressure and traverse rate are most significant parameters followed by stand-off distance. On the basis of experimental analysis, regression models are developed to predict kerf taper and depth of cut. The models are developed with respect to significant parameters, interaction and quadratic terms. It is found that model predictions are in congruence with experimental results. Multi-response optimization of process parameters is also performed using desirability approach in order to minimize kerf taper and maximize depth of cut. Kerf wall features of machined surfaces are observed using scanning electron microscope. The findings of present study are useful to improve kerf properties in abrasive water jet machining of PZT ceramic materials.
The rise of machine consciousness: studying consciousness with computational models.
Reggia, James A
2013-08-01
Efforts to create computational models of consciousness have accelerated over the last two decades, creating a field that has become known as artificial consciousness. There have been two main motivations for this controversial work: to develop a better scientific understanding of the nature of human/animal consciousness and to produce machines that genuinely exhibit conscious awareness. This review begins by briefly explaining some of the concepts and terminology used by investigators working on machine consciousness, and summarizes key neurobiological correlates of human consciousness that are particularly relevant to past computational studies. Models of consciousness developed over the last twenty years are then surveyed. These models are largely found to fall into five categories based on the fundamental issue that their developers have selected as being most central to consciousness: a global workspace, information integration, an internal self-model, higher-level representations, or attention mechanisms. For each of these five categories, an overview of past work is given, a representative example is presented in some detail to illustrate the approach, and comments are provided on the contributions and limitations of the methodology. Three conclusions are offered about the state of the field based on this review: (1) computational modeling has become an effective and accepted methodology for the scientific study of consciousness, (2) existing computational models have successfully captured a number of neurobiological, cognitive, and behavioral correlates of conscious information processing as machine simulations, and (3) no existing approach to artificial consciousness has presented a compelling demonstration of phenomenal machine consciousness, or even clear evidence that artificial phenomenal consciousness will eventually be possible. The paper concludes by discussing the importance of continuing work in this area, considering the ethical issues it raises
A model for straight and helical solar jets. II. Parametric study of the plasma beta
Pariat, E.; Dalmasse, K.; DeVore, C. R.; Antiochos, S. K.; Karpen, J. T.
2016-11-01
Context. Jets are dynamic, impulsive, well-collimated plasma events that develop at many different scales and in different layers of the solar atmosphere. Aims: Jets are believed to be induced by magnetic reconnection, a process central to many astrophysical phenomena. Within the solar atmosphere, jet-like events develop in many different environments, e.g., in the vicinity of active regions, as well as in coronal holes, and at various scales, from small photospheric spicules to large coronal jets. In all these events, signatures of helical structure and/or twisting/rotating motions are regularly observed. We aim to establish that a single model can generally reproduce the observed properties of these jet-like events. Methods: Using our state-of-the-art numerical solver ARMS, we present a parametric study of a numerical tridimensional magnetohydrodynamic (MHD) model of solar jet-like events. Within the MHD paradigm, we study the impact of varying the atmospheric plasma β on the generation and properties of solar-like jets. Results: The parametric study validates our model of jets for plasma β ranging from 10-3 to 1, typical of the different layers and magnetic environments of the solar atmosphere. Our model of jets can robustly explain the generation of helical solar jet-like events at various β ≤ 1. We introduces the new result that the plasma β modifies the morphology of the helical jet, explaining the different observed shapes of jets at different scales and in different layers of the solar atmosphere. Conclusions: Our results enable us to understand the energisation, triggering, and driving processes of jet-like events. Our model enables us to make predictions of the impulsiveness and energetics of jets as determined by the surrounding environment, as well as the morphological properties of the resulting jets.
Numerical simulations of Kelvin-Helmholtz instability: a two-dimensional parametric study
Tian, Chunlin
2016-01-01
Using two-dimensional simulations, we numerically explore the dependences of Kelvin-Helmholtz instability upon various physical parameters, including viscosity, width of sheared layer, flow speed, and magnetic field strength. In most cases, a multi-vortex phase exists between the initial growth phase and final single-vortex phase. The parametric study shows that the evolutionary properties, such as phase duration and vortex dynamics, are generally sensitive to these parameters except in certain regimes. An interesting result is that for supersonic flows, the phase durations and saturation of velocity growth approach constant values asymptotically as the sonic Mach number increases. We confirm that the linear coupling between magnetic field and Kelvin-Helmholtz modes is negligible if the magnetic field is weak enough. The morphological behaviour suggests that the multi-vortex coalescence might be driven by the underlying wave-wave interaction. Based on these results, we make a preliminary discussion about seve...
Parametric Study of the Elementary Segment of an Antiprismatic Pop-Up Deployable Lattice Column
Directory of Open Access Journals (Sweden)
Friedman Noémi
2014-12-01
Full Text Available In this article the primary segment of an antiprismatic pop-up mast is analyzed, that can be applied for largely flexible architectural designs, like deployable bridges or transportable look-out towers. This deployable column, consisting of rigid plates, rigid and elastic bars, is characterized by its selfdeploying behavior due to the energy accumulated from lengthening the elastic bars during packing. The main goal of this paper is to prepare the analysis of the complex structure by a herein detailed investigation of the behavior of one, basic element of the deployable mast. After the analytical examination of the general behavior of the basic segment a geometrically nonlinear finite element formulation is used to trace the force-displacement diagram. Besides the parametric study, approximations of main mechanical parameters are herein given for facilitating preliminary design of such deployable structures.
Application of parametric equations of motion to study the resonance coalescence in H2(+).
Kalita, Dhruba J; Gupta, Ashish K
2012-12-07
Recently, occurrence of coalescence point was reported in H(2)(+) undergoing multiphoton dissociation in strong laser field. We have applied parametric equations of motion and smooth exterior scaling method to study the coalescence phenomenon of H(2)(+). The advantage of this method is that one can easily trace the different states that are changing as the field parameters change. It was reported earlier that in the parameter space, only two bound states coalesce [R. Lefebvre, O. Atabek, M. Sindelka, and N. Moiseyev, Phys. Rev. Lett. 103, 123003 (2009)]. However, it is found that increasing the accuracy of the calculation leads to the coalescence between resonance states originating from the bound and the continuum states. We have also reported many other coalescence points.
Parametric study of rectangular coil for Eddy Current Testing of lamination
Energy Technology Data Exchange (ETDEWEB)
Wang, Peng Fei; Zeng, Zhi Wei [School of Aerospace Engineering, Xiamen University, Xiamen (China)
2016-04-15
Eddy current testing (ECT) is an important nondestructive testing technology for the inspection of flaws in conductive materials. However, this widely used technology is not suitable for inspecting lamination when a conventional pancake coil is used because the eddy current (EC) generated by the pancake coil is parallel to the lamination and will not be perturbed. A new method using a rectangular coil placed vertical to the work piece is proposed for lamination detection. The vertical sections of the rectangular coil induce ECs that are vertical to the lamination and can be perturbed by the lamination. A parametric study of a rectangular coil by finite element analysis was performed in order to examine the capability of generating vertical EC sent data 1221-1237.
Realistic modelling of the seismic input Site effects and parametric studies
Romanelli, F; Vaccari, F
2002-01-01
We illustrate the work done in the framework of a large international cooperation, showing the very recent numerical experiments carried out within the framework of the EC project 'Advanced methods for assessing the seismic vulnerability of existing motorway bridges' (VAB) to assess the importance of non-synchronous seismic excitation of long structures. The definition of the seismic input at the Warth bridge site, i.e. the determination of the seismic ground motion due to an earthquake with a given magnitude and epicentral distance from the site, has been done following a theoretical approach. In order to perform an accurate and realistic estimate of site effects and of differential motion it is necessary to make a parametric study that takes into account the complex combination of the source and propagation parameters, in realistic geological structures. The computation of a wide set of time histories and spectral information, corresponding to possible seismotectonic scenarios for different sources and stru...
Parametric studies on relationships between flutter derivatives of slender bridge (Ⅱ)
Institute of Scientific and Technical Information of China (English)
Xu xu
2009-01-01
Based on curve fitting of coefficients of three component forces of the Messina Straits Bridge, and the previously proposed semi-analytical expressions of flutter deriva-tives of flexible structure, the change of flutter derivatives of slender bridge cross-section with respect to its aerodynamic center, rotational speed and angle variation is studied using a parametric method. The calculated results are compared with the measured ones, and expressions of flutter derivatives of the Messina Straits Bridge are derived. The in-trinsic relationships existing in flutter derivatives are validated again. It is shown that the influence of the rotational speed on flutter derivatives is not negligible. Therefore, it provides an additional semi-analytical approach for analyzing flutter derivatives of the bridge with streamlined cross-section to get its aerodynamic information.
A study of quasi-mode parametric excitations in lower-hybrid heating of tokamak plasmas
Villalon, E.; Bers, A.
1980-03-01
A detailed linear and non-linear analysis of quasi-mode parametric excitations, relevant to experiments in supplementary heating of tokamak plasmas, is presented. The linear analysis includes the full ion-cyclotron harmonic quasi-mode spectrum, while the nonlinear one, considering depletion of the pump electric field, is applied to the recent Alcator A heating experiment. The quasi-mode excitations are studied independently for the plasma edge and the main bulk of the plasma, and for the two typical regimes in overall density. It is concluded that the excited spectrum has a frequency close to the initial pump frequency, while the wave-number spectrum may be different from the initial linear spectrum.
Hilburger, Mark W.; Starnes, James H., Jr.
2004-01-01
The results of a parametric study of the effects of initial imperfections on the buckling and postbuckling response of three unstiffened thinwalled compression-loaded graphite-epoxy cylindrical shells with different orthotropic and quasi-isotropic shell-wall laminates are presented. The imperfections considered include initial geometric shell-wall midsurface imperfections, shell-wall thickness variations, local shell-wall ply-gaps associated with the fabrication process, shell-end geometric imperfections, nonuniform applied end loads, and variations in the boundary conditions including the effects of elastic boundary conditions. A high-fidelity nonlinear shell analysis procedure that accurately accounts for the effects of these imperfections on the nonlinear responses and buckling loads of the shells is described. The analysis procedure includes a nonlinear static analysis that predicts stable response characteristics of the shells and a nonlinear transient analysis that predicts unstable response characteristics.
Parametric Study and Optimization of Ceiling Fan Blades for Improved Aerodynamic Performance
Directory of Open Access Journals (Sweden)
Ehsan Adeeb
2016-01-01
Full Text Available This paper includes parametric study and optimization of non-linear ceiling fan blades by combining the techniques of Design of Experiments (DOE, Response Surface Methods (RSM and Computational Fluid Dynamics (CFD. Specifically, the nonlinear (elliptical planform shape of ceiling fan blade is investigated in conjunction with blade tip width, root and tip angle of attack. Sixteen cases are designed for three blade ceiling fan using two level full factorial model. The flow field is modeled using Reynolds-Averaged-Navier-Stokes approach. The performance variables used to formulate a multi-objective optimization problem are volumetric flow rate, torque and energy efficiency. Response Surface Method is used to generate the optimized design for non-linear ceiling fan blade profile. The results reveal that the interactions between the design variables play a significant role in determining the performance. It is concluded that the nonlinear forward sweep has a moderate effect on response parameters.
Electron cloud studies for heavy-ion and proton machines
Petrov, F; Weiland, Th
2013-01-01
Electron cloud effects are a known problem in various accelerator facilities around the world. Electron clouds cause instabilities and emittance growth in positron and proton beams as well as in heavy ion beams. Most of the hadron machines experience the build-up of EC due to the multipacting. In LHC and in positron machines production of electrons due to the synchrotron radiation becomes as important as the build-up due to the secondary emission. The main source of seed electrons in heavy ion machines is the residual gas ionization. FAIR facility in Darmstadt will operate with heavy-ion and proton beams. However, the beam parameters are such that the multipacting will start to play a role only for the unconditioned wall with the secondary emission yieldmore than 1.8. In this paperwe study the electron cloud build-up and its effect on the beam stability for FAIR heavy-ion coasting beams. These beams will be used during slow extraction. Electron scattering on the beam ions and its effect on the final neutraliz...
Relational Parametricity for Computational Effects
Møgelberg, Rasmus Ejlers
2009-01-01
According to Strachey, a polymorphic program is parametric if it applies a uniform algorithm independently of the type instantiations at which it is applied. The notion of relational parametricity, introduced by Reynolds, is one possible mathematical formulation of this idea. Relational parametricity provides a powerful tool for establishing data abstraction properties, proving equivalences of datatypes, and establishing equalities of programs. Such properties have been well studied in a pure functional setting. Many programs, however, exhibit computational effects, and are not accounted for by the standard theory of relational parametricity. In this paper, we develop a foundational framework for extending the notion of relational parametricity to programming languages with effects.
Scharfstein, Daniel; McDermott, Aidan; Díaz, Iván; Carone, Marco; Lunardon, Nicola; Turkoz, Ibrahim
2017-05-23
In practice, both testable and untestable assumptions are generally required to draw inference about the mean outcome measured at the final scheduled visit in a repeated measures study with drop-out. Scharfstein et al. (2014) proposed a sensitivity analysis methodology to determine the robustness of conclusions within a class of untestable assumptions. In their approach, the untestable and testable assumptions were guaranteed to be compatible; their testable assumptions were based on a fully parametric model for the distribution of the observable data. While convenient, these parametric assumptions have proven especially restrictive in empirical research. Here, we relax their distributional assumptions and provide a more flexible, semi-parametric approach. We illustrate our proposal in the context of a randomized trial for evaluating a treatment of schizoaffective disorder. © 2017, The International Biometric Society.
MEMS digital parametric loudspeaker
Carreno, Armando Arpys Arevalo
2016-03-23
This paper reports on the design and fabrication of MEMS actuator arrays suitable for Digital Sound reconstruction and Parametric Directional Loudspeakers. Two distinct versions of the device were fabricated: one using the electrostatic principle actuation and the other one, the piezoelectric principle. Both versions used similar membrane dimensions, with a diameter of 500 μm. These devices are the smallest Micro-Machined Ultrasound Transducer (MUT) arrays that can be operated for both modes: Digital Sound Reconstruction and Parametric Loudspeaker. The chips consist of an array with 256 transducers, in a footprint of 12 mm by 12 mm. The total single chip size is: 2.3 cm by 2.3 cm, including the contact pads. © 2016 IEEE.
Study of Parametric Instability of gravitational wave detectors using silicon test masses
Zhang, Jue; Ju, Li; Blair, David
2016-01-01
Parametric instability is an intrinsic risk in high power laser interferometer gravitational wave detectors, in which the optical cavity modes interact with the acoustic modes of the mirrors leading to exponential growth of the acoustic vibration. In this paper, we investigate the potential parametric instability for a proposed next generation gravitational wave detector based on cooled silicon test masses. It is shown that there would be about 2 unstable modes per test mass, with the highest parametric gain of ~76. The importance of developing suitable instability suppression schemes is emphasized.
Monte Carlo study of MLC fields for cobalt therapy machine
Directory of Open Access Journals (Sweden)
Komanduri M Ayyangar
2014-01-01
Full Text Available An automated Multi-Leaf Collimator (MLC system has been developed as add-on for the cobalt-60 teletherapy machines available in India. The goal of the present computational study is to validate the MLC design using Monte Carlo (MC modeling. The study was based on the Kirloskar-supplied Phoenix model machines that closely match the Atomic Energy of Canada Limited (AECL theratron-80 machine. The MLC is a retrofit attachment to the collimator assembly, with 14 non-divergent leaf pairs of 40 mm thick, 7 mm wide, and 150 mm long tungsten alloy plates with rounded edges and 20 mm tongue and 2 mm groove in each leaf. In the present work, the source and collimator geometry has been investigated in detail to arrive at a model that best represents the measured dosimetric data. The authors have studied in detail the proto-I MLC built for cobalt-60. The MLC field sizes were MC simulated for 2 × 2 cm 2 to 14 × 14 cm 2 square fields as well as irregular fields, and the percent depth dose (PDD and profile data were compared with ROPS† treatment planning system (TPS. In addition, measured profiles using the IMATRIXX system‡ were also compared with the MC simulations. The proto-I MLC can define radiation fields up to 14 × 14 cm within 3 mm accuracy. The maximum measured leakage through the leaf ends in closed condition was 3.4% and interleaf leakage observed was 7.3%. Good agreement between MC results, ROPS and IMATRIXX results has been observed. The investigation also supports the hypothesis that optical and radiation field coincidence exists for the square fields studied with the MLC. Plots of the percent depth dose (PDD data and profile data for clinically significant irregular fields have also been presented. The MC model was also investigated to speed up the calculations to allow calculations of clinically relevant conformal beams.
Directory of Open Access Journals (Sweden)
Eloranta Sandra
2011-06-01
Full Text Available Abstract Background When the mortality among a cancer patient group returns to the same level as in the general population, that is, the patients no longer experience excess mortality, the patients still alive are considered "statistically cured". Cure models can be used to estimate the cure proportion as well as the survival function of the "uncured". One limitation of parametric cure models is that the functional form of the survival of the "uncured" has to be specified. It can sometimes be hard to find a survival function flexible enough to fit the observed data, for example, when there is high excess hazard within a few months from diagnosis, which is common among older age groups. This has led to the exclusion of older age groups in population-based cancer studies using cure models. Methods Here we have extended the flexible parametric survival model to incorporate cure as a special case to estimate the cure proportion and the survival of the "uncured". Flexible parametric survival models use splines to model the underlying hazard function, and therefore no parametric distribution has to be specified. Results We have compared the fit from standard cure models to our flexible cure model, using data on colon cancer patients in Finland. This new method gives similar results to a standard cure model, when it is reliable, and better fit when the standard cure model gives biased estimates. Conclusions Cure models within the framework of flexible parametric models enables cure modelling when standard models give biased estimates. These flexible cure models enable inclusion of older age groups and can give stage-specific estimates, which is not always possible from parametric cure models.
Kernel bandwidth estimation for non-parametric density estimation: a comparative study
CSIR Research Space (South Africa)
Van der Walt, CM
2013-12-01
Full Text Available We investigate the performance of conventional bandwidth estimators for non-parametric kernel density estimation on a number of representative pattern-recognition tasks, to gain a better understanding of the behaviour of these estimators in high...
Nonlinear Container Ship Model for the Study of Parametric Roll Resonance
DEFF Research Database (Denmark)
Holden, Christian; Galeazzi, Roberto; Rodríguez, Claudio
2007-01-01
Parametric roll is a critical phenomenon for ships, whose onset may cause roll oscillations up to 40, leading to very dangerous situations and possibly capsizing. Container ships have been shown to be particularly prone to parametric roll resonance when they are sailing in moderate to heavy head...... seas. A Matlab/Simulinkr parametric roll benchmark model for a large container ship has been implemented and validated against a wide set of experimental data. The model is a part of a Matlab/Simulink Toolbox (MSS, 2007). The benchmark implements a 3rd-order nonlinear model where the dynamics of roll...... is strongly coupled with the heave and pitch dynamics. The implemented model has shown good accuracy in predicting the container ship motions, both in the vertical plane and in the transversal one. Parametric roll has been reproduced for all the data sets in which it happened, and the model provides realistic...
Machine Protection Studies for a Crab Cavity in the LHC
Yee-Rendon, B; Baer, T; Barranco, J; Calaga, R; Marsili, A; Tomas, R; Zimmermann, F
2013-01-01
Crab cavities (CCs) apply a transverse kick that rotates the bunches so as to have a head-on collision at the interaction point (IP). Such cavities were successfully used to improve the luminosity of KEKB. They are also a key ingredient of the HL-LHC project to increase the luminosity of the LHC. As CCs can rapidly change the particle trajectories, machine protection studies are required to assess the beam losses due to fast CC failures. In this paper, we discuss the effect of rapid voltage or phase changes in a CC for the HL-LHC layout using measured beam distributions from the present LHC.
Model for straight and helical solar jets. I. Parametric studies of the magnetic field geometry
Pariat, E.; Dalmasse, K.; DeVore, C. R.; Antiochos, S. K.; Karpen, J. T.
2015-01-01
Context. Jets are dynamic, impulsive, well-collimated plasma events developing at many different scales and in different layers of the solar atmosphere. Aims: Jets are believed to be induced by magnetic reconnection, a process central to many astrophysical phenomena. Studying their dynamics can help us to better understand the processes acting in larger eruptive events (e.g., flares and coronal mass ejections) as well as mass, magnetic helicity, and energy transfer at all scales in the solar atmosphere. The relative simplicity of their magnetic geometry and topology, compared with larger solar active events, makes jets ideal candidates for studying the fundamental role of reconnection in energetic events. Methods: In this study, using our recently developed numerical solver ARMS, we present several parametric studies of a 3D numerical magneto-hydrodynamic model of solar-jet-like events. We studied the impact of the magnetic field inclination and photospheric field distribution on the generation and properties of two morphologically different types of solar jets, straight and helical, which can account for the observed so-called standard and blowout jets. Results: Our parametric studies validate our model of jets for different geometric properties of the magnetic configuration. We find that a helical jet is always triggered for the range of parameters we tested. This demonstrates that the 3D magnetic null-point configuration is a very robust structure for the energy storage and impulsive release characteristic of helical jets. In certain regimes determined by magnetic geometry, a straight jet precedes the onset of a helical jet. We show that the reconnection occurring during the straight-jet phase influences the triggering of the helical jet. Conclusions: Our results allow us to better understand the energization, triggering, and driving processes of straight and helical jets. Our model predicts the impulsiveness and energetics of jets in terms of the surrounding
Sobh, Tarek M.; Tibrewal, Abhilasha
2006-01-01
Operating systems theory primarily concentrates on the optimal use of computing resources. This paper presents an alternative approach to teaching and studying operating systems design and concepts by way of parametrically optimizing critical operating system functions. Detailed examples of two critical operating systems functions using the…
Directory of Open Access Journals (Sweden)
I. K. Romanova
2017-01-01
Full Text Available Bauman Moscow State Technical University, MoscowКалининградский государственный технический университет, КалининградThe article considers practical application aspects of various imaging techniques for parametric analysis of control systems. It is interpreted as a multivariate analysis aimed at studying the influence of external and internal parameters of the system on the quality of its functioning determined by direct and indirect quality criteria. The ultimate goal is to identify regions in the parameter space to provide an appropriate quality of the system. It is noted that visualization is a very important task-supporting aid for a designer to make decision. Stressed that the problem of parametric studies, in most cases, intersects with the major problem of inconsistency of separate partial criteria, i.e., the problem of multi-criteria optimization (MCO. Therefore, the aim of the article was to solve a joint task of visualization and multi-criteria optimization.The article considers traditional types of visualization in deterministic tasks (a 3-D graphics, plotting contour lines, gradient fields, Andrews curves, parallel coordinates, as well as methods used in statistics (graph matrices, etc.. Testing these methods as applied to the practical task of studying a double-circuit stabilization system allowed formulation of requirements for imaging techniques with multiple criteria.Provides a new perspective on using the traditional means to significantly enhance information capacity of imaging. A generic method of visualization is represented as a three-phase study agreed with the task of finding the compromise solutions. The first phase of the research involved identifying the monotony and contra-monotony domains. The second phase was aimed at identifying a region of compromise, or a weak Pareto optimum. The third phase involved the search for a consistent optimum (strong Pareto
A model for straight and helical solar jets: II. Parametric study of the plasma beta
Pariat, E; DeVore, C R; Antiochos, S K; Karpen, J T
2016-01-01
Jets are dynamic, impulsive, well-collimated plasma events that develop at many different scales and in different layers of the solar atmosphere. Jets are believed to be induced by magnetic reconnection, a process central to many astrophysical phenomena. Within the solar atmosphere, jet-like events develop in many different environments, e.g., in the vicinity of active regions as well as in coronal holes, and at various scales, from small photospheric spicules to large coronal jets. In all these events, signatures of helical structure and/or twisting/rotating motions are regularly observed. The present study aims to establish that a single model can generally reproduce the observed properties of these jet-like events. In this study, using our state-of-the-art numerical solver ARMS, we present a parametric study of a numerical tridimensional magnetohydrodynamic (MHD) model of solar jet-like events. Within the MHD paradigm, we study the impact of varying the atmospheric plasma $\\beta$ on the generation and prop...
Parametric Study for Increasing On-Station Duration via Unconventional Aircraft Launch Approach
Kuhl, Christopher A.; Moses, Robert W.; Croom, Mark A.; Sandford, Stephen P.
2004-01-01
The need for better atmospheric predictions is causing the atmospheric science community to look for new ways to obtain longer, higher-resolution measurements over several diurnal cycles. The high resolution, in-situ measurements required to study many atmospheric phenomena can be achieved by an Autonomous Aerial Observation System (AAOS); however, meeting the long on-station time requirements with an aerial platform poses many challenges. Inspired by the half-scale drop test of the deployable Aerial Regional-scale Environmental Survey (ARES) Mars airplane, a study was conducted at the NASA Langley Research Center to examine the possibility of increasing on-station time by launching an airplane directly at the desired altitude. The ARES Mars airplane concept was used as a baseline for Earth atmospheric flight, and parametric analyses of fundamental configuration elements were performed to study their impact on achieving desired on-station time with this class of airplane. The concept involved lifting the aircraft from the ground to the target altitude by means of an air balloon, thereby unburdening the airplane of ascent requirements. The parameters varied in the study were aircraft wingspan, payload, fuel quantity, and propulsion system. The results show promising trends for further research into aircraft-payload design using this unconventional balloon-based launch approach.
Parametric study on the performance of green residential buildings in China
Directory of Open Access Journals (Sweden)
Xi Wang
2015-03-01
Full Text Available The parametric study of the indoor environment of green buildings focuses on the quantitative and qualitative improvement of residential building construction in China and the achievement of indoor thermal comfort at a low level of energy use. This study examines the effect of the adaptive thermal comfort of indoor environment control in hot summer and cold winter (HSCW zones. This work is based on a field study of the regional thermal assessment of two typical cases, the results of which are compared with simulated results of various scenarios of “energy efficiency” strategy and “healthy housing” environmental control. First, the simulated results show that the adaptive thermal comfort of indoor environment control is actually balanced in terms of occupancy, comfort, and energy efficiency. Second, adaptive thermal comfort control can save more energy for heating or cooling than other current healthy housing environmental controls in China׳s HSCW zone. Moreover, a large proportion of energy use is based on the subjective thermal comfort demand of occupants in any building type. Third, the building shape coefficient cannot dominate energy savings. The ratio of the superficial area of a building to the actual indoor floor area has a significant positive correlation with and affects the efficiency of building thermal performance.
Energy Technology Data Exchange (ETDEWEB)
Staunton, R.H.
2004-08-11
The Department of Energy's (DOE) Office of FreedomCAR (Cooperative Automotive Research) and Vehicle Technologies has a strong interest in making rapid progress in permanent magnet (PM) machine development. The program is directing various technology development projects that will advance the technology and lead to request for proposals (RFP) for manufacturer prototypes. This aggressive approach is possible because the technology is clearly within reach and the approach is deemed essential, based on strong market demand, escalating fuel prices, and competitive considerations. In response, this study began parallel development paths that included a literature search/review, development and utilization of multiple parametric models to determine the effects of design parameters, verification of the modeling methodology, development of an interior PM (IPM) machine baseline design, development of alternative machine baseline designs, and cost analyses for several candidate machines. This interim progress report summarizes the results of these activities as of June 2004. This report provides background and summary information for recent machine parametric studies and testing programs that demonstrate both the potential capabilities and technical limitations of brushless PM machines (axial gap and radial gap), the IPM machine, the surface-mount PM machines (interior or exterior rotor), induction machines, and switched reluctance machines. The FreedomCAR program, while acknowledging the progress made by Oak Ridge National Laboratory, Delphi, Delco-Remy International, and others in these programs, has redirected efforts toward a ''short path'' to a marketable and competitive PM motor for hybrid electric vehicle traction applications. The program has developed a set of performance targets for the type of traction machine desired. The short-path approach entails a comprehensive design effort focusing on the IPM machine and meeting the performance
S, Kyriacou; E, Kontoleontos; S, Weissenberger; L, Mangani; E, Casartelli; I, Skouteropoulou; M, Gattringer; A, Gehrer; M, Buchmayr
2014-03-01
An efficient hydraulic optimization procedure, suitable for industrial use, requires an advanced optimization tool (EASY software), a fast solver (block coupled CFD) and a flexible geometry generation tool. EASY optimization software is a PCA-driven metamodel-assisted Evolutionary Algorithm (MAEA (PCA)) that can be used in both single- (SOO) and multiobjective optimization (MOO) problems. In MAEAs, low cost surrogate evaluation models are used to screen out non-promising individuals during the evolution and exclude them from the expensive, problem specific evaluation, here the solution of Navier-Stokes equations. For additional reduction of the optimization CPU cost, the PCA technique is used to identify dependences among the design variables and to exploit them in order to efficiently drive the application of the evolution operators. To further enhance the hydraulic optimization procedure, a very robust and fast Navier-Stokes solver has been developed. This incompressible CFD solver employs a pressure-based block-coupled approach, solving the governing equations simultaneously. This method, apart from being robust and fast, also provides a big gain in terms of computational cost. In order to optimize the geometry of hydraulic machines, an automatic geometry and mesh generation tool is necessary. The geometry generation tool used in this work is entirely based on b-spline curves and surfaces. In what follows, the components of the tool chain are outlined in some detail and the optimization results of hydraulic machine components are shown in order to demonstrate the performance of the presented optimization procedure.
Mutel, Christopher L; de Baan, Laura; Hellweg, Stefanie
2013-06-04
Comprehensive sensitivity analysis is a significant tool to interpret and improve life cycle assessment (LCA) models, but is rarely performed. Sensitivity analysis will increase in importance as inventory databases become regionalized, increasing the number of system parameters, and parametrized, adding complexity through variables and nonlinear formulas. We propose and implement a new two-step approach to sensitivity analysis. First, we identify parameters with high global sensitivities for further examination and analysis with a screening step, the method of elementary effects. Second, the more computationally intensive contribution to variance test is used to quantify the relative importance of these parameters. The two-step sensitivity test is illustrated on a regionalized, nonlinear case study of the biodiversity impacts from land use of cocoa production, including a worldwide cocoa products trade model. Our simplified trade model can be used for transformable commodities where one is assessing market shares that vary over time. In the case study, the highly uncertain characterization factors for the Ivory Coast and Ghana contributed more than 50% of variance for almost all countries and years examined. The two-step sensitivity test allows for the interpretation, understanding, and improvement of large, complex, and nonlinear LCA systems.
Parametric CFD study of micro-energy harvesting in a flow channel exploiting vortex shedding
Koubogiannis, Dimitrios G.
2016-05-01
Miniature energy harvesting devices are increasingly used in various fields. For example, Wireless Sensor Networks have recently made great progress in many applications. However, their main drawback, i.e. the limited duration of operation, poses the requirement for an effective way to recharge their batteries. In this context, the presentwork focuses on the study of micro-energy harvesting from flow by exploiting vortex shedding behind bluff bodies, in order to cause oscillations to a piezoelectric film and generate the required electrical power. To this end, a Computational Fluid Dynamics (CFD) tool is validated on a particular miniature device configuration proposed in the literature and implemented for the numerical simulations of flow around bluff micro-bodies in a very small channel. Aiming to enhance vortex shedding, parametric studies corresponding to different bluff body shapes and arrangements for a fixed Reynolds number are performed, the main parameters involved in the phenomenon are highlighted and the potential for vortex shedding exploitation is qualitatively assessed.
Parametric study on a collocated PZT beam vibration absorber and power harvester
Energy Technology Data Exchange (ETDEWEB)
Huang, Shyh Chin [Mechanical Engineering, Ming Chi University of Technology, New Taipei (China); Tsai, Chao Yang [Mechanical Engineering Army Academy, R.O.C., Taoyuan (China); Liao, Hsiao Hui [LNG Construction and Project Division, CPC Corp., Taipei (China)
2016-11-15
The parametric effects of a PZT beam that is simultaneously used as a vibration absorber and a power harvester were investigated in this study. A cantilever beam paved with PZT layers and with added tip mass has been widely used as a harvester or sometimes as a Dynamic vibration absorber (DVA). However, the beam is rarely considered a collocated device. In this study, the first step was theoretical derivation of a distributed beam covered with bimorph PZT layers. Then, the beam was attached to a 1DOF vibratory main system. Two indicators for vibration absorption and power harvesting were defined. Numerical results demonstrated that the lumped mass ratio favored both of the abilities, but that the DVA mass ratio influenced these two abilities in exactly the opposite way. The conjunction of a harvester circuit into a DVA shifted its resonance frequency up to 5 % (an extreme case of open circuit R→∞). Simultaneous power harvesting diminished the absorption capability up to 35 % for each set of mass ratios. To achieve the maximum degree of power harvesting, a corresponding load resistance that somewhat increases with the lumped mass ratio is applied. Experimental results verified the existence of the best load resistance, but the measured harvested curve was lower than the theoretical calculation because of structure damping and deviations of PZT material properties.
Parametric studies of magnetic-optic imaging using finite-element models
Chao, C.; Udpa, L.; Xuan, L.; Fitzpatrick, G.; Thorne, D.; Shih, W.
2000-05-01
Magneto-optic imaging is a relatively new sensor application of bubble memory technology to NDI. The Magneto-Optic Imager (MOI) uses a magneto-optic (MO) sensor to produce analog images of magnetic flux leakage from surface and subsurface defects. The flux leakage is produced by eddy current induction techniques in nonferrous metals and magnetic yokes are used in ferromagnetic materials. The technique has gained acceptance in the aircraft maintenance industry for use to detect surface-breaking cracks and corrosion. Until recently, much of the MOI development has been empirical in nature since the electromagnetic processes that produce images are rather complex. The availability of finite element techniques to numerically solve Maxwell's equations, in conjunction with MOI observations, allows greater understanding of the capabilities of the instrument. In this paper, we present a systematic set of finite element calculations along with MOI measurements on specific defects to quantify the current capability of the MOI as well as its desired performance. Parametric studies including effects of liftoff and proximity of edges are also studied.—This material is based upon work supported by the Federal Aviation Administration under Contract #DTFA03-98-D-00008, Delivery Order #IA013 and performed at Iowa State University's Center for NDE as part of the Center for Aviation Systems Reliability program.
Solar tower power plant using a particle-heated steam generator: Modeling and parametric study
Krüger, Michael; Bartsch, Philipp; Pointner, Harald; Zunft, Stefan
2016-05-01
Within the framework of the project HiTExStor II, a system model for the entire power plant consisting of volumetric air receiver, air-sand heat exchanger, sand storage system, steam generator and water-steam cycle was implemented in software "Ebsilon Professional". As a steam generator, the two technologies fluidized bed cooler and moving bed heat exchangers were considered. Physical models for the non-conventional power plant components as air- sand heat exchanger, fluidized bed coolers and moving bed heat exchanger had to be created and implemented in the simulation environment. Using the simulation model for the power plant, the individual components and subassemblies have been designed and the operating parameters were optimized in extensive parametric studies in terms of the essential degrees of freedom. The annual net electricity output for different systems was determined in annual performance calculations at a selected location (Huelva, Spain) using the optimized values for the studied parameters. The solution with moderate regenerative feed water heating has been found the most advantageous. Furthermore, the system with moving bed heat exchanger prevails over the system with fluidized bed cooler due to a 6 % higher net electricity yield.
Dimitrakopoulou-Strauss, Antonia; Pan, Leyun; Strauss, Ludwig G
2010-01-01
Dynamic positron emission studies (dPET) with fluorine-18-fluoro-deoxyglucose ((18)F-FDG) were performed in oncologic patients. The primary aim was to evaluate the impact of parametric imaging and assess its feasibility with regard to diagnostics and treatment management. Parametric PET images based on different algorithms have been calculated. Regression-based images, influx images according to Patlak, two-tissue compartment images as well as non-compartmental approaches, based on the fractal dimension, principal component images, and similarity mapping have been used. Our results showed that the use of parametric images is helpful to visualize quantitative parameters of the tracer kinetics and adds a new dimension to the existing conventional PET or PET/computerized tomography (CT) images. Especially, non-compartment models are computationally fast and can be applied in daily routine to gain more detailed information about the distribution of a tracer over time and space. In conclusion, it is our opinion that parametric images will gain increasing importance and find their way into clinical routine due to the improvement of the technical equipment, like computer power, faster data acquisition by new generations of PET/CT scanners and more sophisticated software for data evaluation.
Study of acrylamide level in food from vending machines
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Naceur Haouet
2016-11-01
Full Text Available Acrylamide is a by-product of the Maillard reaction and is potentially carcinogenic to humans. It is found in a number of foods with higher concentrations in carbohydrate-rich foods and moderate levels of protein-rich foods such as meat, fish and seafood. Acrylamide levels in food distributed in vending machines placed in public areas of the city of Perugia were analysed by high-performance liquid chromatography. Samples included five different categories, depending on the characteristics of the products: i potato chips; ii salted bakery products; iii biscuits and wafers; iv sweet bakery products; v sandwiches. A high variability in acrylamide level among different foods and within the same category was detected. Potato chips showed the highest amount of acrylamide (1781±637 μg/kg followed by salted bakery products (211±245 μg/kg, biscuits and wafers (184±254 μg/kg, sweet bakery products (100±72 μg/kg and sandwiches (42±10 μg/kg. In the potato chips and sandwiches categories, all of the samples revealed the presence of acrylamide, while different prevalence was registered in the other foods considered. The data of this study highlight the presence of acrylamide in different foods sold in vending machines and this data could be useful to understand the contribution of this type of consumption to human exposure to this compound.
Directory of Open Access Journals (Sweden)
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.
COMPARATIVE STUDY ON THE TECHNICAL PERFORMANCES OF TWO THICKNESSING MACHINES
Directory of Open Access Journals (Sweden)
Sergiu RĂCĂŞAN
2015-06-01
Full Text Available ract: The paper presents a series of experimental researches on two operating parameters – the energy consumption and the generated noise level – for two thicknessing machines of different generations: MRG8 (production year: 1972 and Felder D963 (production year: 2013. The aim was to highlight some of the developments registered over four decades by this type of woodworking machines. The results show that, in similar operating conditions, the new machine consume less energy and produce lower noise level.
Institute of Scientific and Technical Information of China (English)
Ning WANG; Kui-hua WANG; Wen-bing WU
2013-01-01
In this paper,a model named fictitious soil pile was introduced to solve the boundary coupled problem at the pile tip.In the model,the soil column between pile tip and bedrock was treated as a fictitious pile,which has the same properties as the local soil.The tip of the fictitious soil pile was assumed to rest on a rigid rock and no tip movement was allowed.In combination with the plane strain theory,the analytical solutions of vertical vibration response of piles in a frequency domain and the corresponding semi-analytical solutions in a time domain were obtained using the Laplace transforms and inverse Fourier transforms.A parametric study of pile response at the pile tip and head showed that the thickness and layering of the stratum between pile tip and bedrock have a significant influence on the complex impedances.Finally,two applications of the analytical model were presented.One is to identify the defects of the pile shaft,in which the proposed model was proved to be accurate to identify the location as well as the length of pile defects.Another application of the model is to identify the sediment thickness under the pile tip.The results showed that the sediment can lead to the decrease of the pile stiffness and increase of the damping,especially when the pile is under a low frequency load.
A Parametric Study of Mixing in a Granular Flow a Bi-Axial Spherical Tumbler
Christov, Ivan C; Ottino, Julio M; Sturman, Rob
2015-01-01
We report on a computational parameter space study of mixing protocols for a half-full bi-axial spherical granular tumbler. The quality of mixing is quantified via the intensity of segregation (concentration variance) and computed as a function of three system parameters: angles of rotation about each tumbler axis and the flowing layer depth. Only the symmetric case is considered in which the flowing layer depth is the same for each rotation. We also consider the dependence on $\\bar{R}$, which parametrizes the concentric spheroids ("shells") that comprise the volume of the tumbler. The intensity of segregation is computed over 100 periods of the mixing protocol for each choice of parameters. Each curve is classified via a time constant, $\\tau$, and an asymptotic mixing value, $bias$. We find that most choices of angles and most shells throughout the tumbler volume mix well, with mixing near the center of the tumbler being consistently faster (small $\\tau$) and more complete (small $bias$). We conclude with ex...
Zamboni, Giovanna; Gozzi, Marta; Krueger, Frank; Duhamel, Jean-René; Sirigu, Angela; Grafman, Jordan
2009-01-01
Politics is a manifestation of the uniquely human ability to debate, decide, and reach consensus on decisions affecting large groups over long durations of time. Recent neuroimaging studies on politics have focused on the association between brain regions and specific political behaviors by adopting party or ideological affiliation as a criterion to classify either experimental stimuli or subjects. However, it is unlikely that complex political beliefs (i.e., "the government should protect freedom of speech") are evaluated only on a liberal-to-conservative criterion. Here we used multidimensional scaling and parametric functional magnetic resonance imaging to identify which criteria/dimensions people use to structure complex political beliefs and which brain regions are concurrently activated. We found that three independent dimensions explained the variability of a set of statements expressing political beliefs and that each dimension was reflected in a distinctive pattern of neural activation: individualism (medial prefrontal cortex and temporoparietal junction), conservatism (dorsolateral prefrontal cortex), and radicalism (ventral striatum and posterior cingulate). The structures we identified are also known to be important in self-other processing, social decision-making in ambivalent situations, and reward prediction. Our results extend current knowledge on the neural correlates of the structure of political beliefs, a fundamental aspect of the human ability to coalesce into social entities.
Directory of Open Access Journals (Sweden)
Ellis Thomas L
2011-04-01
Full Text Available Abstract Background Irreversible electroporation (IRE is a new minimally invasive technique to kill undesirable tissue in a non-thermal manner. In order to maximize the benefits from an IRE procedure, the pulse parameters and electrode configuration must be optimized to achieve complete coverage of the targeted tissue while preventing thermal damage due to excessive Joule heating. Methods We developed numerical simulations of typical protocols based on a previously published computed tomographic (CT guided in vivo procedure. These models were adapted to assess the effects of temperature, electroporation, pulse duration, and repetition rate on the volumes of tissue undergoing IRE alone or in superposition with thermal damage. Results Nine different combinations of voltage and pulse frequency were investigated, five of which resulted in IRE alone while four produced IRE in superposition with thermal damage. Conclusions The parametric study evaluated the influence of pulse frequency and applied voltage on treatment volumes, and refined a proposed method to delineate IRE from thermal damage. We confirm that determining an IRE treatment protocol requires incorporating all the physical effects of electroporation, and that these effects may have significant implications in treatment planning and outcome assessment. The goal of the manuscript is to provide the reader with the numerical methods to assess multiple-pulse electroporation treatment protocols in order to isolate IRE from thermal damage and capitalize on the benefits of a non-thermal mode of tissue ablation.
Parametric Study of Strain Rate Effects on Nanoparticle-Reinforced Polymer Composites
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B. Soltannia
2016-01-01
Full Text Available Crashworthiness, energy absorption capacity, and safety are important factors in the design of lightweight vehicles made of fiber-reinforced polymer composite (FRP components. The relatively recent emergence of the nanotechnology industry has presented a novel means to augment the mechanical properties of various materials. As a result, recent attempts have contemplated the use of nanoparticles to further improve the resiliency of resins, especially when resins are used for mating FRP components. Therefore, a comprehensive understanding of the response of nanoreinforced polymer composites, subjected to various rates of loading, is of paramount importance for developing reliable structures. In this paper, the effects of nanoreinforcement on the mechanical response of a commonly used epoxy resin subjected to four different strain rates, are systematically investigated. The results are then compared to those of the neat resin. To characterize the mechanical properties of the nanocomposite, a combination of the strain rate-dependent mechanical (SRDM model of Goldberg and his coworkers and Halpin-Tsai’s micromechanical approach is employed. Subsequently, a parametric study is conducted to ascertain the influences of particle type and their weight percentage. Finally, the numerical results are compared to the experimental data obtained from testing of the neat and the nanoreinforced epoxy resin.
Parametric study for the optimization of ionic liquid pretreatment of corn stover
Energy Technology Data Exchange (ETDEWEB)
Papa, Gabriella [Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Feldman, Taya [Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States); Sale, Kenneth L. [Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States); Adani, Fabrizio [Univ. degli Studi di Milano (Italy); Singh, Seema [Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States); Simmons, Blake A. [Joint BioEnergy Inst. (JBEI), Emeryville, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2017-05-30
A parametric study of the efficacy of the ionic liquid (IL) pretreatment (PT) of corn stover (CS) using 1-ethyl-3-methylimidazolium acetate ([C_{2}C_{1}Im][OAc] ) and cholinium lysinate ([Ch][Lys] ) was conducted. The impact of 50% and 15% biomass loading for milled and non-milled CS on IL-PT was evaluated, as well the impact of 20 and 5 mg enzyme/g glucan on saccharification efficiency. The glucose and xylose released were generated from 32 conditions – 2 ionic liquids (ILs), 2 temperatures, 2 particle sizes (S), 2 solid loadings, and 2 enzyme loadings. Statistical analysis indicates that sugar yields were correlated with lignin and xylan removal and depends on the factors, where S did not explain variation in sugar yields. Both ILs were effective in pretreating large particle sized CS, without compromising sugar yields. The knowledge from material and energy balances is an essential step in directing optimization of sugar recovery at desirable process conditions.
Role of the aperture in Z-scan experiments:A parametric study
Institute of Scientific and Technical Information of China (English)
M. R. Rashidian Vaziri
2015-01-01
In close-aperture Z-scan experiments, a small aperture is conventionally located in the far-field thereby enabling the detection of slight changes in the laser beam profile due to the Kerr-lensing effect. In this work, by numerically solving the Fresnel–Kirchhoff diffraction integrals, the amount of transmitted power through apertures has been evaluated and a parametric study on the role of the various parameters that can infl uence this transmitted power has been done. In order to perform a comprehensive analysis, we have used a nonlinear phase shift optimized for nonlocal nonlinear media in our calculations. Our results show that apertures will result in the formation of symmetrical fl uctuations on the wings of Z-scan transmittance curves. It is further shown that the appearance of these fl uctuations can be ascribed to the natural diffraction of the Gaussian beam as it propagates up to the aperture plane. Our calculations reveal that the nonlocal parameter variations can shift the position of fl uctuations along the optical axis, whereas their magnitude depends on the largeness of the induced nonlinear phase shift. It is concluded that since the mentioned fl uctuations are produced by the natural diffraction of the Gaussian beam itself, one must take care not to mistakenly interpret them as noise and should not expect to eliminate them from experimental Z-scan transmittance curves by using apertures with different sizes.
Energy Technology Data Exchange (ETDEWEB)
Song, Ki Nam; Seo, Jeong Min; Lee, Jin Suk [Korea Atomic Energy Research Institute, Daeduk (Korea, Republic of)
1996-05-01
A formula for the elastic stiffness of the leaf type holddown spring(HDS) assembly with uniformly tapered width from w{sub 0} to w{sub 1} (w{sub 0} , w{sub 1}) has been analytically derived by applying the engineering beam theory and Casiliano`s theory based on strain energy. Elastic stiffnesses for the tapered-width HDSs which are newly designed in the same dimensional design spaces as 14x14 type and 17x17 type KOFA HDS assembly have been estimated form the derived formula and also parametric study of elastic stiffness for their HDSs have been carried out. It is found that elastic stiffnesses of the newly designed tapered-width HDS assemblies have been about 32 {approx} 33 % about higher than those of KOFA holddown spring assemblies, and that effects of axial and shear force on the elastic stiffness have been 0.15 {approx} 0.21 % of the elastic stiffness. Therefore in case that the newly designed tapered-width HDS assemblies have been adapted in KOFA, it is expected that numbers of leaves composing a HDS assembly could be lessened by on due to their having a high elastic stiffness. 13 tabs., 23 figs., 16 refs. (Author) .new.
Near-Sun and 1 AU magnetic field of coronal mass ejections: A parametric study
Patsourakos, S
2016-01-01
Aims. The magnetic field of coronal mass ejections (CMEs) determines their structure, evolution, and energetics, as well as their geoeffectiveness. However, we currently lack routine diagnostics of the near-Sun CME magnetic field, which is crucial for determining the subsequent evolution of CMEs. Methods. We recently presented a method to infer the near-Sun magnetic field magnitude of CMEs and then extrapolate it to 1 AU. This method uses relatively easy to deduce observational estimates of the magnetic helicity in CME-source regions along with geometrical CME fits enabled by coronagraph observations. We hereby perform a parametric study of this method aiming to assess its robustness. We use statistics of active region (AR) helicities and CME geometrical parameters to determine a matrix of plausible near-Sun CME magnetic field magnitudes. In addition, we extrapolate this matrix to 1 AU and determine the anticipated range of CME magnetic fields at 1 AU representing the radial falloff of the magnetic field in t...
MODEL STUDY OF THE DOUBLE FED MACHINE WITH CURRENT CONTROL
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A. S. Lyapin
2016-07-01
Full Text Available The paper deals with modeling results of the double fed induction machine with current control in the rotor circuit. We show the most promising applications of electric drives on the basis of the double fed induction machine and their advantages. We present and consider functional scheme of the electric drive on the basis of the double fed induction machine with current control. Equations are obtained for creation of such machine mathematical model. Expressions for vector projections of rotor current are given. According to the obtained results, the change of the vector projections of rotor current ensures operation of the double fed induction machine with the specified values of active and reactive stator power throughout the variation range of sliding motion. We consider static characteristics of double fed machine with current control. Energy processes proceeding in the machine are analyzed. We confirm the operationpossibility of double fed induction machine with current controlin the rotor circuit with given values of active and reactive stator power. The presented results can be used for creation of mathematical models and static characteristics of double fed machines with current control of various capacities.
Monte Carlo study of MLC fields for cobalt therapy machine
Ayyangar, Komanduri M.; Rani, Roopa A.; Kumar, Anil; Reddy, A. R.
2014-01-01
An automated Multi-Leaf Collimator (MLC) system has been developed as add-on for the cobalt-60 teletherapy machines available in India. The goal of the present computational study is to validate the MLC design using Monte Carlo (MC) modeling. The study was based on the Kirloskar-supplied Phoenix model machines that closely match the Atomic Energy of Canada Limited (AECL) theratron-80 machine. The MLC is a retrofit attachment to the collimator assembly, with 14 non-divergent leaf pairs of 40 mm thick, 7 mm wide, and 150 mm long tungsten alloy plates with rounded edges and 20 mm tongue and 2 mm groove in each leaf. In the present work, the source and collimator geometry has been investigated in detail to arrive at a model that best represents the measured dosimetric data. The authors have studied in detail the proto-I MLC built for cobalt-60. The MLC field sizes were MC simulated for 2 × 2 cm2 to 14 × 14 cm2 square fields as well as irregular fields, and the percent depth dose (PDD) and profile data were compared with ROPS† treatment planning system (TPS). In addition, measured profiles using the IMATRIXX system‡ were also compared with the MC simulations. The proto-I MLC can define radiation fields up to 14 × 14 cm2 within 3 mm accuracy. The maximum measured leakage through the leaf ends in closed condition was 3.4% and interleaf leakage observed was 7.3%. Good agreement between MC results, ROPS and IMATRIXX results has been observed. The investigation also supports the hypothesis that optical and radiation field coincidence exists for the square fields studied with the MLC. Plots of the percent depth dose (PDD) data and profile data for clinically significant irregular fields have also been presented. The MC model was also investigated to speed up the calculations to allow calculations of clinically relevant conformal beams. †Radiation Oncology Planning System (ROPS) is supplied by Tirumala Jyothi Computer Systems described at https
Study on the effect of thermal property of metals in ultrasonic-assisted laser machining
Energy Technology Data Exchange (ETDEWEB)
Lee, Hu Seung; Kim, Gun Woo; Park, Jong Eun [Dept. of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Cho, Sung Hak; Yang, Min Yang; Park, Jong Kweon [Korea Institute of Machinery and Materials, Deajeon (Korea, Republic of)
2015-08-15
The laser machining process has been proposed as an advanced process for the selective fabrication of electrodes without a mask. In this study, we adapt laser machining to metals that have different thermal properties. Based on the results, the metals exhibit a different surface morphology, heat-affected zone (HAZ), and a recast layer around the machined surface according to their thermal conductivity, boiling point, and thermal diffusivity. Then, we apply ultrasonic-assisted laser machining to remove the recast layer. The ultrasonic-assisted laser machining exhibits a better surface quality in metals with higher diffusivity than those having lower diffusivity.
Muon Tracking Studies in a Skew Parametric Resonance Ionization Cooling Channel
Energy Technology Data Exchange (ETDEWEB)
Sy, Amy [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Afanaciev, Andre [George Washington Univ., Washington, DC (United States); Derbenev, Yaroslav S. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Johnson, Rolland [Muons, Inc., Batavia, IL (United States); Morozov, Vasiliy [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
2015-09-01
Skew Parametric-resonance Ionization Cooling (SPIC) is an extension of the Parametric-resonance Ionization Cooling (PIC) framework that has previously been explored as the final 6D cooling stage of a high-luminosity muon collider. The addition of skew quadrupoles to the PIC magnetic focusing channel induces coupled dynamic behavior of the beam that is radially periodic. The periodicity of the radial motion allows for the avoidance of unwanted resonances in the horizontal and vertical transverse planes, while still providing periodic locations at which ionization cooling components can be implemented. A first practical implementation of the magnetic field components required in the SPIC channel is modeled in MADX. Dynamic features of the coupled correlated optics with and without induced parametric resonance are presented and discussed.
Study of parametric instability in gravitational wave detectors with silicon test masses
Zhang, Jue; Zhao, Chunnong; Ju, Li; Blair, David
2017-03-01
Parametric instability is an intrinsic risk in high power laser interferometer gravitational wave detectors, in which the optical cavity modes interact with the acoustic modes of the mirrors, leading to exponential growth of the acoustic vibration. In this paper, we investigate the potential parametric instability for a proposed next generation gravitational wave detector, the LIGO Voyager blue design, with cooled silicon test masses of size 45 cm in diameter and 55 cm in thickness. It is shown that there would be about two unstable modes per test mass at an arm cavity power of 3 MW, with the highest parametric gain of ∼76. While this is less than the predicted number of unstable modes for Advanced LIGO (∼40 modes with max gain of ∼32 at the designed operating power of 830 kW), the importance of developing suitable instability suppression schemes is emphasized.
Institute of Scientific and Technical Information of China (English)
张严心
2015-01-01
As a kind of ancillary translation tool, Machine Translation has been paid increasing attention to and received different kinds of study by a great deal of researchers and scholars for a long time. To know the definition of Machine Translation and to analyse its benefits and problems are significant for translators in order to make good use of Machine Translation, and helpful to develop and consummate Machine Translation Systems in the future.
Study of an NC system of machining crown gears
Xu, Xiaogang; Wang, Huaqing; Yan, Jian; Gao, Shenyou
2005-12-01
Crown gear couplings are usually used in metallurgy and steel rolling equipments, which is manufactured by duplicating processing in common. The method makes the manipulator work hard, and the efficiency is low. The machining precision is limited to the shape of the mold and it is difficult to control the movement of machines table. This work stated an NC system to use hobbing machine. It consists of an industrial control computer, grating sensor, servo- motor and its driver source, servo driver card and other I/O equipments of inputting and outputting. The grating sensor was installed in the axial direction to trace the instantaneous position of gob rest. The radial movement of the machine table was controlled by a servomotor. When the computer captures the axial signal, this system controls the machine table by moving ahead or backwards according to the calculated value of interpolation theory. Thus, two dimensions (axial and radial) associated movement was realized while the crown gear was processed. The feature of the system is that a grating sensor used in the axial direction replaces the servomotor. By making a little change in the mechanism of the machine, NC can be implement and its redesign cost is very low. The design software has an interpolation function for a circular arc and line. The system has been used on a Y1380 gear hobbing machine, and the correlative software of machining crown gear has been designed as well. Satisfactory results have been obtained, showing facility and reliability in practical operation.
Study of the Service Reliability of Machines Based on Safety
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
From the point of safety being the basic requirement of machine operation, equivalent failure number, which is employed to replace the actual statistical failure number, is introduced. Calculating theory of service reliability indexes of machines based on safety is developed. The method proposed in this paper can reflect the damage degree of failure.
Machine Protection Studie for a Crab Cavity in the LHC
Yee-Rendon, B; Baer, T; Barranco, J; Calaga, R; Marsili, A; Tomas, R; Zimmermann, F
2013-01-01
Crab cavities (CCs) apply a transverse kick that rotates the bunches so as to have a head-on collision at the interaction point (IP). Such cavities were successfully used to improve the luminosity of KEKB. They are also a key ingredient of the HL-LHC project to increase the luminosity of the LHC. As CCs can rapidly change the particle trajectories, machine protection studies are required to assess the beam losses due to fast CC failures. In this paper, we discuss the effect of rapid voltage or phase changes in a CC for the HL-LHC layout using measured beam distributions from the present LHC. Presented at IPAC'13 Shanghai, 12-17 May 2013
Kalita, Dhruba J; Rao, Akshay; Rajvanshi, Ishir; Gupta, Ashish K
2011-06-14
We have applied parametric equations of motion (PEM) to study photodissociation dynamics of H(2)(+). The resonances are extracted using smooth exterior scaling method. This is the first application of PEM to non-Hermitian Hamiltonian that includes resonances and the continuum. Here, we have studied how the different resonance states behave with respect to the change in field amplitude. The advantage of this method is that one can easily trace the different states that are changing as the field parameter changes.
Computational parametric study of a Richtmyer-Meshkov instability for an inclined interface.
McFarland, Jacob A; Greenough, Jeffrey A; Ranjan, Devesh
2011-08-01
A computational study of the Richtmyer-Meshkov instability for an inclined interface is presented. The study covers experiments to be performed in the Texas A&M University inclined shock tube facility. Incident shock wave Mach numbers from 1.2 to 2.5, inclination angles from 30° to 60°, and gas pair Atwood numbers of ∼0.67 and ∼0.95 are used in this parametric study containing 15 unique combinations of these parameters. Qualitative results are examined through a time series of density plots for multiple combinations of these parameters, and the qualitative effects of each of the parameters are discussed. Pressure, density, and vorticity fields are presented in animations available online to supplement the discussion of the qualitative results. These density plots show the evolution of two main regions in the flow field: a mixing region containing driver and test gas that is dominated by large vortical structures, and a more homogeneous region of unmixed fluid which can separate away from the mixing region in some cases. The interface mixing width is determined for various combinations of the parameters listed at the beginning of the Abstract. A scaling method for the mixing width is proposed using the interface geometry and wave velocities calculated using one-dimensional gas dynamic equations. This model uses the transmitted wave velocity for the characteristic velocity and an initial offset time based on the travel time of strong reflected waves. It is compared to an adapted Richtmyer impulsive model scaling and shown to scale the initial mixing width growth rate more effectively for fixed Atwood number.
Computational parametric study of a Richtmyer-Meshkov instability for an inclined interface
McFarland, Jacob A.; Greenough, Jeffrey A.; Ranjan, Devesh
2011-08-01
A computational study of the Richtmyer-Meshkov instability for an inclined interface is presented. The study covers experiments to be performed in the Texas A&M University inclined shock tube facility. Incident shock wave Mach numbers from 1.2 to 2.5, inclination angles from 30° to 60°, and gas pair Atwood numbers of ˜0.67 and ˜0.95 are used in this parametric study containing 15 unique combinations of these parameters. Qualitative results are examined through a time series of density plots for multiple combinations of these parameters, and the qualitative effects of each of the parameters are discussed. Pressure, density, and vorticity fields are presented in animations available online to supplement the discussion of the qualitative results. These density plots show the evolution of two main regions in the flow field: a mixing region containing driver and test gas that is dominated by large vortical structures, and a more homogeneous region of unmixed fluid which can separate away from the mixing region in some cases. The interface mixing width is determined for various combinations of the parameters listed at the beginning of the Abstract. A scaling method for the mixing width is proposed using the interface geometry and wave velocities calculated using one-dimensional gas dynamic equations. This model uses the transmitted wave velocity for the characteristic velocity and an initial offset time based on the travel time of strong reflected waves. It is compared to an adapted Richtmyer impulsive model scaling and shown to scale the initial mixing width growth rate more effectively for fixed Atwood number.
Parametric study of transport beam lines for electron beams accelerated by laser-plasma interaction
Scisciò, M.; Lancia, L.; Migliorati, M.; Mostacci, A.; Palumbo, L.; Papaphilippou, Y.; Antici, P.
2016-03-01
In the last decade, laser-plasma acceleration of high-energy electrons has attracted strong attention in different fields. Electrons with maximum energies in the GeV range can be laser-accelerated within a few cm using multi-hundreds terawatt (TW) lasers, yielding to very high beam currents at the source (electron bunches with up to tens-hundreds of pC in a few fs). While initially the challenge was to increase the maximum achievable electron energy, today strong effort is put in the control and usability of these laser-generated beams that still lack of some features in order to be used for applications where currently conventional, radio-frequency (RF) based, electron beam lines represent the most common and efficient solution. Several improvements have been suggested for this purpose, some of them acting directly on the plasma source, some using beam shaping tools located downstream. Concerning the latter, several studies have suggested the use of conventional accelerator magnetic devices (such as quadrupoles and solenoids) as an easy implementable solution when the laser-plasma accelerated beam requires optimization. In this paper, we report on a parametric study related to the transport of electron beams accelerated by laser-plasma interaction, using conventional accelerator elements and tools. We focus on both, high energy electron beams in the GeV range, as produced on petawatt (PW) class laser systems, and on lower energy electron beams in the hundreds of MeV range, as nowadays routinely obtained on commercially available multi-hundred TW laser systems. For both scenarios, our study allows understanding what are the crucial parameters that enable laser-plasma accelerators to compete with conventional ones and allow for a beam transport. We show that suitable working points require a tradeoff-combination between low beam divergence and narrow energy spread.
Parametric study of transport beam lines for electron beams accelerated by laser-plasma interaction
Energy Technology Data Exchange (ETDEWEB)
Scisciò, M.; Antici, P., E-mail: patrizio.antici@polytechnique.edu [INFN-RM1 and SBAI, Università di Roma “La Sapienza,” Via Scarpa 16, 00161 Roma (Italy); INRS-EMT, Université du Québec, 1650 Lionel Boulet, Varennes, Québec J3X 1S2 (Canada); Lancia, L.; Migliorati, M.; Mostacci, A.; Palumbo, L. [INFN-RM1 and SBAI, Università di Roma “La Sapienza,” Via Scarpa 16, 00161 Roma (Italy); Papaphilippou, Y. [CERN, CH 1211 Geneva 23 (Switzerland)
2016-03-07
In the last decade, laser-plasma acceleration of high-energy electrons has attracted strong attention in different fields. Electrons with maximum energies in the GeV range can be laser-accelerated within a few cm using multi-hundreds terawatt (TW) lasers, yielding to very high beam currents at the source (electron bunches with up to tens-hundreds of pC in a few fs). While initially the challenge was to increase the maximum achievable electron energy, today strong effort is put in the control and usability of these laser-generated beams that still lack of some features in order to be used for applications where currently conventional, radio-frequency (RF) based, electron beam lines represent the most common and efficient solution. Several improvements have been suggested for this purpose, some of them acting directly on the plasma source, some using beam shaping tools located downstream. Concerning the latter, several studies have suggested the use of conventional accelerator magnetic devices (such as quadrupoles and solenoids) as an easy implementable solution when the laser-plasma accelerated beam requires optimization. In this paper, we report on a parametric study related to the transport of electron beams accelerated by laser-plasma interaction, using conventional accelerator elements and tools. We focus on both, high energy electron beams in the GeV range, as produced on petawatt (PW) class laser systems, and on lower energy electron beams in the hundreds of MeV range, as nowadays routinely obtained on commercially available multi-hundred TW laser systems. For both scenarios, our study allows understanding what are the crucial parameters that enable laser-plasma accelerators to compete with conventional ones and allow for a beam transport. We show that suitable working points require a tradeoff-combination between low beam divergence and narrow energy spread.
PM Motor Parametric Design Analyses for a Hybrid Electric Vehicle Traction Drive Application
Energy Technology Data Exchange (ETDEWEB)
Staunton, R.H.
2004-10-11
The Department of Energy's (DOE) Office of FreedomCAR (Cooperative Automotive Research) and Vehicle Technologies office has a strong interest in making rapid progress in permanent magnet (PM) machine development. The DOE FreedomCAR program is directing various technology development projects that will advance the technology and hopefully lead to a near-term request for proposals (RFP) for a to-be-determined level of initial production. This aggressive approach is possible because the technology is clearly within reach and the approach is deemed essential, based on strong market demand, escalating fuel prices, and competitive considerations. In response, this study began parallel development paths that included a literature search/review, development and utilization of multiple parametric models, verification of the modeling methodology, development of an interior PM (IPM) machine baseline design, development of alternative machine baseline designs, and cost analyses for several candidate machines. This report summarizes the results of these activities as of September 2004. This report provides background and summary information for recent machine parametric studies and testing programs that demonstrate both the potential capabilities and technical limitations of brushless PM machines (axial gap and radial gap), the IPM machine, the surface-mount PM machines (interior or exterior rotor), induction machines, and switched-reluctance machines. The FreedomCAR program, while acknowledging the progress made by Oak Ridge National Laboratory (ORNL), Delphi, Delco-Remy International, and others in these programs, has redirected efforts toward a ''short path'' to a marketable and competitive PM motor for hybrid electric vehicle (HEV) traction applications. The program has developed a set of performance targets for the type of traction machine desired. The short-path approach entails a comprehensive design effort focusing on the IPM machine and meeting
Nonlinear Container Ship Model for the Study of Parametric Roll Resonance
Directory of Open Access Journals (Sweden)
Christian Holden
2007-10-01
Full Text Available Parametric roll is a critical phenomenon for ships, whose onset may cause roll oscillations up to +-40 degrees, leading to very dangerous situations and possibly capsizing. Container ships have been shown to be particularly prone to parametric roll resonance when they are sailing in moderate to heavy head seas. A Matlab/Simulink parametric roll benchmark model for a large container ship has been implemented and validated against a wide set of experimental data. The model is a part of a Matlab/Simulink Toolbox (MSS, 2007. The benchmark implements a 3rd-order nonlinear model where the dynamics of roll is strongly coupled with the heave and pitch dynamics. The implemented model has shown good accuracy in predicting the container ship motions, both in the vertical plane and in the transversal one. Parametric roll has been reproduced for all the data sets in which it happened, and the model provides realistic results which are in good agreement with the model tank experiments.
Directory of Open Access Journals (Sweden)
H.-W. Wong
2010-04-01
Full Text Available Condensation trails (contrails formed from water vapor emissions behind aircraft engines are the most uncertain components of the aviation impacts on climate change. To gain improved knowledge of contrail and contrail-induced cirrus cloud formation, understanding of contrail ice particle formation immediately after aircraft engines is needed. Despite many efforts spent in modeling the microphysics of ice crystal formation in jet regime (with a plume age <5 s, systematic understanding of parametric effects of variables affecting contrail ice particle formation is still limited. In this work, we apply a microphysical parcel modeling approach to study contrail ice particle formation in near-field aircraft plumes up to 1000 m downstream of an aircraft engine in the soot-rich regime (soot number emission index >1×10^{15} (kg-fuel^{−1} at cruise. The effects of dilution history, ion-mediated nucleation, ambient relative humidity, fuel sulfur contents, and initial soot emissions were investigated. Our simulation results suggest that ice particles are mainly formed by water condensation on emitted soot particles. The growth of ice coated soot particles is driven by water vapor emissions in the first 1000 m and by ambient relative humidity afterwards. The presence of chemi-ions does not significantly contribute to the formation of ice particles in the soot-rich regime, and the effect of fuel sulfur contents is small over the range typical of standard jet fuels. The initial properties of soot emissions play the most critical role, and our calculations suggest that higher number concentration and smaller size of contrail particle nuclei may be able to effectively suppress the formation of contrail ice particles. Further modeling and experimental studies are needed to verify if our findings can provide a possible approach for contrail mitigation.
Directory of Open Access Journals (Sweden)
Alireza Ganjovi
2014-09-01
Full Text Available A kinetic model is used based on Particle in Cell - Monte Carlo Collision (PIC-MCC model, for parametric study of the damage due to partial discharges (PD activity into the surroundings dielectrics of a narrow channel encapsulated within the volume of a dielectric material. The parameters studied are applied electric field, channel dimensions and gas pressure. After employing an electric field across a dielectric material which contains a narrow channel, repeated ionization process starts in the gaseous medium of narrow channel. Charged particles, especially electrons, gain energy from the electric field across narrow channel and cause damage into dielectric surfaces of narrow channel on impact. The dependence of the electron energy distribution function (EEDF on the applied electric field is considered. These estimations are performed based on the number of C-H bond-scissions produced by the impacting electrons of a single PD pulse. Regarding this technique, the consequent damage into the solid dielectric and the time required to increase surface conductivity, is computed. The formation of acid molecules due to interaction of PD pulse with polymer surface in presence of air and humidity causes changes in the surface conductivity of the surrounding dielectrics of the narrow channels. It is observed that the extent of damage caused by a PD is primarily determined by the total number of impacting electrons which are capable of producing bond-scission at the dielectric. Parameters that effectively cause an increase in the number of energetic electrons will increase effective damage as well as surface conductivity of surrounding dielectrics.
Energy Technology Data Exchange (ETDEWEB)
Gaussens, J.; Paillot, H. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1965-07-01
The authors define the notions of use values and price of plutonium. They give a 'simplified parametrized model' simulating the equilibrium of the offer and the demand in time, concerning the plutonium and the price deriving from the relative scarcity of this metal, taking into account the technical and economic operating parameters of the various reactors confronted. This model is simple enough to allow direct computations and establish clear relations between the various parameters. The use of the linear programmes method allows on the other hand a wide extension of the model. This report includes three main parts: I - General description of the study (without detailed calculations) II - Mathematical development of the simplified parametrized model and application (the basic data and the results of the calculations are given) III - Appendices (giving the detailed computations of part II). (authors) [French] Les auteurs definissent les notions de valeurs d'usage et de prix du plutonium. Ils donnent un 'modele parametre simplifie' simulant l'equilibre de l'office et de la demande dans le temps concernant le plutonium et le prix qui decoule de la rarete relative de ce metal, compte tenu des parametres techniques et economiques de fonctionnement des divers reacteurs en presence. Ce modele est suffisamment simple pour permettre des calculs manuels et etablir des liaisons claires entre les divers parametres. L'utilisation de la technique des programmes lineaires permet par ailleurs une extension considerable du modele. Cette note comprend trois parties: I - Expose general de l'etude (sans expose du detail des calculs) II - Developpement mathematique du modele parametre simplifie et application (on precise les donnees de base et le resultat des calculs) III - Annexes (donnant le detail des calculs de la partie II). (auteurs)
Directory of Open Access Journals (Sweden)
H.-W. Wong
2009-10-01
Full Text Available Condensation trails (contrails formed from water vapor emissions behind aircraft engines are the most uncertain components of the aviation impacts on climate change. To gain improved knowledge of contrail and contrail-induced cirrus cloud formation, understanding of contrail ice particle formation immediately after aircraft engines is needed. Despite many efforts spent in modeling the microphysics of ice crystal formation in jet regime (with a plume age <5 s, systematic understanding of parametric effects of variables affecting contrail ice particle formation is still limited. In this work, we apply a one-dimensional modeling approach to study contrail ice particle formation in near-field aircraft plumes up to 1000 m downstream of an aircraft engine in the soot-rich regime (soot number emission index >1×10^{15} (kg-fuel^{−1} at cruise. The effects of ion-mediated nucleation, ambient relative humidity, fuel sulfur content, and initial soot emissions were investigated. Our simulation results suggest that ice particles are mainly formed by water condensation on emitted soot particles. The growth of ice coated soot particles is driven by water vapor emissions in the first 1000 m and by ambient relative humidity afterwards. The presence of chemi-ions does not significantly contribute to the formation of ice particles, and the effect of fuel sulfur content is small over the range typical of standard jet fuels. The initial properties of soot emissions play the most critical role, and our calculations suggest that higher number concentration and smaller size of contrail particle nuclei may be able to effectively suppress the formation of contrail ice particles, providing a possible approach for contrail mitigation.
Fu, F.
2010-01-01
A 3-dimensional finite element model built by the author was used in this paper to analyze the progressive collapse of a multi-storey steel composite frame building. The proposed model can represent the global 3-D behavior of the multi-storey building under the sudden column removal scenarios. Based on this model, parametric studies were carried out to investigate the structural behavior with variations in: strength of structural steel, strength of concrete and reinforcement mesh size. Throug...
2014-01-01
This study aims at providing expertise for preparing public-based flood mapping and estimating flood risks in growing urban areas. To model and predict the magnitude of flood risk areas, an integrated Analytical Hierarchy Process (AHP) and Geographic Information System (GIS) analysis techniques are used for the case of Eldoret Municipality in Kenya. The flood risk vulnerability mapping follows a multi-parametric approach and integrates some of the flooding causative factors such as rainfall d...
Lee, Donghoon; Kim, Ye-seul; Choi, Sunghoon; Lee, Haenghwa; Jo, Byungdu; Choi, Seungyeon; Shin, Jungwook; Kim, Hee-Joung
2017-03-01
The chest digital tomosynthesis(CDT) is recently developed medical device that has several advantage for diagnosing lung disease. For example, CDT provides depth information with relatively low radiation dose compared to computed tomography (CT). However, a major problem with CDT is the image artifacts associated with data incompleteness resulting from limited angle data acquisition in CDT geometry. For this reason, the sensitivity of lung disease was not clear compared to CT. In this study, to improve sensitivity of lung disease detection in CDT, we developed computer aided diagnosis (CAD) systems based on machine learning. For design CAD systems, we used 100 cases of lung nodules cropped images and 100 cases of normal lesion cropped images acquired by lung man phantoms and proto type CDT. We used machine learning techniques based on support vector machine and Gabor filter. The Gabor filter was used for extracting characteristics of lung nodules and we compared performance of feature extraction of Gabor filter with various scale and orientation parameters. We used 3, 4, 5 scales and 4, 6, 8 orientations. After extracting features, support vector machine (SVM) was used for classifying feature of lesions. The linear, polynomial and Gaussian kernels of SVM were compared to decide the best SVM conditions for CDT reconstruction images. The results of CAD system with machine learning showed the capability of automatically lung lesion detection. Furthermore detection performance was the best when Gabor filter with 5 scale and 8 orientation and SVM with Gaussian kernel were used. In conclusion, our suggested CAD system showed improving sensitivity of lung lesion detection in CDT and decide Gabor filter and SVM conditions to achieve higher detection performance of our developed CAD system for CDT.
Refinement of numerical models and parametric study of SOFC stack performance
Burt, Andrew C.
The presence of multiple air and fuel channels per fuel cell and the need to combine many cells in series result in complex steady-state temperature distributions within Solid Oxide Fuel Cell (SOFC) stacks. Flow distribution in these channels, when non-uniform, has a significant effect on cell and stack performance. Large SOFC stacks are very difficult to model using full 3-D CFD codes because of the resource requirements needed to solve for the many scales involved. Studies have shown that implementations based on Reduced Order Methods (ROM), if calibrated appropriately, can provide simulations of stacks consisting of more than 20 cells with reasonable computational effort. A pseudo 2-D SOFC stack model capable of studying co-flow and counter-flow cell geometries was developed by solving multiple 1-D SOFC single cell models in parallel on a Beowulf cluster. In order to study cross-flow geometries a novel Multi-Component Multi-Physics (MCMP) scheme was instantiated to produce a Reduced Order 3-D Fuel Cell Model. A C++ implementation of the MCMP scheme developed in this study utilized geometry, control volume, component, and model structures allowing each physical model to be solved only for those components for which it is relevant. Channel flow dynamics were solved using a 1-D flow model to reduce computational effort. A parametric study was conducted to study the influence of mass flow distribution, radiation, and stack size on fuel cell stack performance. Using the pseudo 2-D planar SOFC stack model with stacks of various sizes from 2 to 40 cells it was shown that, with adiabatic wall conditions, the asymmetry of the individual cell can produce a temperature distribution where high and low temperatures are found in the top and bottom cells, respectively. Heat transfer mechanisms such as radiation were found to affect the reduction of the temperature gradient near the top and bottom cell. Results from the reduced order 3-D fuel cell model showed that greater
Boscolo, Ilario; Stellato, Marco
2012-01-01
The motion of a mass vertically appended to a spring, worldwide used as initiating experiment in a physics undergraduate laboratory, shows generally a complex behaviour owing to the simultaneous action of gravitational, elastic and torsional forces. Moreover, since the friction force, caused by air against the mass movement, has not a simple dependence on the velocity, a further difficulty is added to the study of the motion. The article presents a path to manage the complexity of the experiment maintaining the objective of treating and enlightening the physics of the harmonic motion via the mass-spring experiment. The system is firstly approached as a harmonic oscillator. The notable deviation from that simple dynamics, in particular the parametric oscillation behaviour observed along the lab work, is briefly discussed and modeled at that conjunction. The approach to the parametric behavior is done via the analysis of the motion waveforms.
DEFF Research Database (Denmark)
Niero, M.; Di Felice, F.; Ren, Jingzheng
study of a SME in the wooden pallet sector, investigating to what extent the use of parametric LCI models can be beneficial both in evaluating the environmental impacts of similar products and in providing a preliminary assessment of the potential environmental impacts of new products. We developed...... of elements constituting the wooden pallet, as well as aspects of the manufacturing process, which are information already available to every company. Apart from applicability, the use of an LCI parametric model has also the advantage of flexibility, since the value of the parameters can be easily modified...... in the design process. This modelling approach can be replicated in other manufacturing sectors, provided the products being examined present similar characteristics....
DEFF Research Database (Denmark)
Niero, Monia; Di Felice, F.; Ren, J.
2014-01-01
study of a SME in the wooden pallet sector, investigating to what extent the use of parametric LCI models can be beneficial both in evaluating the environmental impacts of similar products and in providing a preliminary assessment of the potential environmental impacts of new products. We developed...... of elements constituting the wooden pallet, as well as aspects of the manufacturing process, which are information already available to every company. Apart from applicability, the use of an LCI parametric model has also the advantage of flexibility, since the value of the parameters can be easily modified...... in the design process. This modelling approach can be replicated in other manufacturing sectors, provided the products being examined present similar characteristics....
Proton-Ion Medical Machine Study (PIMMS), 2
Bryant, P J; Benedikt, Michael; Crescenti, M; Holy, P; Maier, A T; Pullia, M; Reimoser, S; Rossi, S; Borri, G; Knaus, P; Gramatica, F; Pavlovic, M; Weisser, L
2000-01-01
The Proton-Ion Medical Machine Study (PIMMS) group was formed following an agreement between the Med-AUSTRON (Austria) and the TERA Foundation (Italy) to combine their efforts in the design of a cancer therapy synchrotron capable of accelerating either light ions or protons. CERN agreed to support and host this study in its PS Division. A close collaboration was also set up with GSI (Germany). The study group was later joined by Onkologie-2000 (Czech Republic). Effort was first focused on the theoretical understanding of slow extraction and the techniques required to produce a smooth beam spill for the conformal treatment of complex-shaped tumours with a sub-millimetre accuracy by active scanning with proton and carbon ion beams. Considerations for passive beam spreading were also included for protons. The study has been written in two parts. The more general and theoretical aspects are recorded in Part I and the specific technical design considerations are presented in the present volume, Part II. An accompa...
Proton-Ion Medical Machine Study (PIMMS), 1
Badano, L; Bryant, P J; Crescenti, M; Holy, P; Maier, A T; Pullia, M; Rossi, S; Knaus, P
2000-01-01
The Proton-Ion Medical Machine Study (PIMMS) group was formed following an agreement between the Med-AUSTRON (Austria) and the TERA Foundation (Italy) to combine their efforts in the design of a cancer therapy synchrotron. CERN agreed to host this study in its PS Division and a close collaboration was set up with GSI (Germany). The study group was later joined by Onkologie-2000 (Czech Republic). Effort was first focused on the theoretical understanding of slow extraction and the techniques required to produce a smooth beam spill for the conformal treatment of complex-shaped tumours with a sub-millimetre accuracy by active scanning with proton and carbon ion beams. Considerations for passive scanning were also included. The more general and theoretical aspects of the study are recorded in Part I and the more specific technical design considerations are presented in a second volume Part II. The PIMMS team started their work in January 1996 in the PS Division and continued for a period of three years.
Bencheikh, imane; el hajjaji, souad; abourouh, imane; Kitane, Said; Dahchour, Abdelmalek; El M'Rabet, Mohammadine
2017-04-01
Wastewater treatment is the subject of several studies through decades. Interest is continuously oriented to provide cheaper and efficient methods of treatment. Several methods of treatment exit including coagulation flocculation, filtration, precipitation, ozonation, ion exchange, reverse osmosis, advanced oxidation process. The use of these methods proved limited because of their high investment and operational cost. Adsorption can be an efficient low-cost process to remove pollutants from wastewater. This method of treatment calls for an solid adsorbent which constitutes the purification tool. Agricultural wastes have been widely exploited in this case .As we know the agricultural wastes are an important source of water pollution once discharged into the aquatic environment (river, sea ...). The valorization of such wastes and their use allows the prevention of this problem with an economic and environment benefits. In this context our study aimed testing the wastewater treatment capacity by adsorption onto holocellulose resulting from the valorization of an agriculture waste. In this study, methylene blue (MB) and methyl orange (MO) are selected as models pollutants for evaluating the holocellulose adsorbent capacity. The kinetics of adsorption is performed using UV-visible spectroscopy. In order to study the effect of the main parameters for the adsorption process and their mutual interaction, a full factorial design (type nk) has been used.23 full factorial design analysis was performed to screen the parameters affecting dye removal efficiency. Using the experimental results, a linear mathematical model representing the influence of the different parameters and their interactions was obtained. The parametric study showed that efficiency of the adsorption system (Dyes/ Holocellulose) is mainly linked to pH variation. The best yields were observed for MB at pH=10 and for MO at pH=2.The kinetic data was analyzed using different models , namely , the pseudo
comparative study of moore and mealy machine models adaptation ...
African Journals Online (AJOL)
user
Information and Communications Technology has influenced the need for automated machines that can carry out important production ... enjoys a reputation for improving or eliminating uneven skin tone ..... Information Management Vol. 5, pp.
Study on full automatic arc welding machine for spherical tank
Institute of Scientific and Technical Information of China (English)
蒋力培; 张甲英; 俞建荣
2002-01-01
A full automatic welding machine for spherical tanks' all position multi-layer welds has been developed. This machine is mainly composed of a two-dimension seam tracking system based on microcomputer's memory and a welding tractor as well as rail. The main features of the machine are: while welding the first layer of a seam, its microcomputer system can analyze and store the tracing information from a two-dimension sensor, and control the welding head device to realize two-dimension real time tracing; while welding the second layer up to the top layer of the seam, it can realize two-dimension tracing based on the memorial data, automatically determine the layer number and continually sway the welding head. The welding test shows that the machine has good tracing and welding behavior, and is suitable for spherical tank's all position multi-layer welds.
Conceptual Study of Permanent Magnet Machine Ship Propulsion Systems
1977-12-01
thyristors and can be either water or air cooled. The machine-cycloconverter, many-phase or parallel three-phase connection design offers a drive system with characteristics well matched to a ship propulsion system.
About Bifurcational Parametric Simplification
Gol'dshtein, V; Yablonsky, G
2015-01-01
A concept of "critical" simplification was proposed by Yablonsky and Lazman in 1996 for the oxidation of carbon monoxide over a platinum catalyst using a Langmuir-Hinshelwood mechanism. The main observation was a simplification of the mechanism at ignition and extinction points. The critical simplification is an example of a much more general phenomenon that we call \\emph{a bifurcational parametric simplification}. Ignition and extinction points are points of equilibrium multiplicity bifurcations, i.e., they are points of a corresponding bifurcation set for parameters. Any bifurcation produces a dependence between system parameters. This is a mathematical explanation and/or justification of the "parametric simplification". It leads us to a conjecture that "maximal bifurcational parametric simplification" corresponds to the "maximal bifurcation complexity." This conjecture can have practical applications for experimental study, because at points of "maximal bifurcation complexity" the number of independent sys...
Directory of Open Access Journals (Sweden)
H. AHMADI
2015-03-01
Full Text Available In the present paper, a set of parametric FE stress analyses is carried out for two-planar welded tubular DKT-joints under two different axial load cases. Analysis results are used to present general remarks on the effect of geometrical parameters on the stress concentration factors (SCFs at the inner saddle, outer saddle, crown toe, and crown heel positions on the main (outer brace. Based on the results of finite element analyses which are verified against the experimental data, a complete set of SCF database is constructed. Then a new set of SCF parametric equations is developed through nonlinear regression analysis for the fatigue design of two-planar DKT-joints under axial loads. An assessment study of these equations is conducted against the experimental data and the satisfaction of criteria regarding the acceptance of parametric equations is checked. Significant effort has been devoted by researchers to the study of SCFs in various uni-planar tubular connections. Nevertheless, for multi-planar joints covering the majority of practical applications, very few investigations have been reported due to the complexity and high cost involved.
Study the effect of cryogenic cooling on orthogonal machining Process
Directory of Open Access Journals (Sweden)
Arvind Kaushal
2016-06-01
Full Text Available In present scenario , all the manufacturing organization aims to maximize the productivity of organization in respect of all the aspect of manufacturing process, in case of machining process, it associated with various factors which affect the productivity directly in sense of tool life . Temperature, cutting forces, shear angle, work-piece surface finishing & accuracy, amount of power consumed in machining process and other thing also. All the factors might be optimized by applying effective and efficient amount of coolant throughout the process, to get desired efficiency of process. A coolant play a vital role in machining operation but which must have specific properties which have been reviewed in previous article of various student , research scholars , scientist and industrial candidates .in this research paper , we were focusing on the effect of cryogenic cooling on cutting temperature , cutting forces , chip behavior , shear angle , when alloy steel EN-8 and aluminum alloy 6061-T89 was machined by carbide cutting tool (coated & uncoated & applying liquid nitrogen as a coolant and observed that temperature was decreased during the machining process about 16% to 27% and cutting forces improved to 13%when the machining was performed , the same without cooling of EN-8 alloy, similarly on the other hand in case of aluminum alloy 6061-T89 , temperature was decreased to 25% to 37% and cutting force improved to 9% .
The numerical model for parametric studies of forest haul roads pavements
Directory of Open Access Journals (Sweden)
Lenka Ševelová
2010-01-01
Full Text Available Forest roads pavement structures are considered to be low volume roads. These roads serve as a mean of transport of wood and people. Besides they are currently often used for recreational purpose. The construction of the pavements should be suitable for forest transportation irrespective of their low bearing capacity. These pavement structures are very specific for special unbound materials that are used in their construction. To meet the requirements of the pavement designs and simulation analysis the FEM model in the software ANSYS was created.This paper compares two material models used for the description of the behaviour of unbound materials. The first is linear elastic according to Hook theory (H model and the second one is nonlinear plastic model Drucker-Prager (D–P model. ANSYS software has been used to create flexible model based on the parametrers of variable principle. The flexible model is parametric to realize repeated calculations useful for optimization analysis.
Numerical study of a parametric parabolic equation and a related inverse boundary value problem
Mustonen, Lauri
2016-10-01
We consider a time-dependent linear diffusion equation together with a related inverse boundary value problem. The aim of the inverse problem is to determine, based on observations on the boundary, the nonhomogeneous diffusion coefficient in the interior of an object. The method in this paper relies on solving the forward problem for a whole family of diffusivities by using a spectral Galerkin method in the high-dimensional parameter domain. The evaluation of the parametric solution and its derivatives is then completely independent of spatial and temporal discretizations. In the case of a quadratic approximation for the parameter dependence and a direct solver for linear least squares problems, we show that the evaluation of the parametric solution does not increase the complexity of any linearized subproblem arising from a Gauss-Newtonian method that is used to minimize a Tikhonov functional. The feasibility of the proposed algorithm is demonstrated by diffusivity reconstructions in two and three spatial dimensions.
Parametric and Non-Parametric System Modelling
DEFF Research Database (Denmark)
Nielsen, Henrik Aalborg
1999-01-01
considered. It is shown that adaptive estimation in conditional parametric models can be performed by combining the well known methods of local polynomial regression and recursive least squares with exponential forgetting. The approach used for estimation in conditional parametric models also highlights how....... For this purpose non-parametric methods together with additive models are suggested. Also, a new approach specifically designed to detect non-linearities is introduced. Confidence intervals are constructed by use of bootstrapping. As a link between non-parametric and parametric methods a paper dealing with neural...... the focus is on combinations of parametric and non-parametric methods of regression. This combination can be in terms of additive models where e.g. one or more non-parametric term is added to a linear regression model. It can also be in terms of conditional parametric models where the coefficients...
A Non Parametric Study of the Volatility of the Economy as a Country Risk Predictor
Costanzo, Sabatino; Dominguez, Ramses; Moreno, William
2007-01-01
This paper intends to explain Venezuela's country spread behavior through the Neural Networks analysis of a monthly economic activity general index of economic indicators constructed by the Central Bank of Venezuela, a measure of the shocks affecting country risk of emerging markets and the U.S. short term interest rate. The use of non parametric methods allowed the finding of non linear relationship between these inputs and the country risk. The networks performance was evaluated using the method of excess predictability.
Parametric study on performance of bridge retrofitted by unseating prevention devices
Institute of Scientific and Technical Information of China (English)
Kuang-Yen Liu; Kuo-Chun Chang
2006-01-01
Over the past decade, seismically induced damage to bridges has been widely reported following major earthquakes such as the 1994 Northridge, 1995 Kobe and 1999 Chi-Chi events. Since these earthquakes, restrainers and stoppers have been installed on bridges to prevent unseating and excessive displacements, respectively. Alternatively, column jacketing has also been proven to be effective. However, the enhanced shear strength may result in extra retrofitting works on the footing. For bridges damaged in the Chi-Chi earthquake, investigations revealed that most bridge columns experienced none-to-minor damage in the longitudinal direction. The reason for this unexpected performance was the construction practice of using a rubber bearing, which is an unbolted design that may slide under large lateral forces. In this paper,parametric studies on simply-supported bridges retrofitted by a restrainer or concrete shear key along the longitudinal and transverse axes were carried out. The research focuses on finding suitable combinations of the design force and gap spacing so the restrainer and concrete shear key can be used as an unseating prevention device, with respect to the allowable column damage in terms of displacement ductility under near-fault type earthquakes. A two-lane PCI-girder bridge was selected as the benchmark model. In the longitudinal direction, a total of nine combinations considering yielding strength and gap spacing for the restrainer were analyzed; while parameters for the concrete shear key were divided into three shear force levels and three gap spacings. In the transverse direction, a similar approach was adapted, except smaller gap spacing was used. For each of the above mentioned earthquakes, seven input ground motions were selected and their PGAs were adjusted to 0.36g and 0.45g as the Design earthquake and Maximum Considerable Earthquake, respectively. Based on the results of nonlinear time history analyses, proper parameters to design the
Parametric study and performance analysis of hybrid rocket motors with double-tube configuration
Yu, Nanjia; Zhao, Bo; Lorente, Arnau Pons; Wang, Jue
2017-03-01
The practical implementation of hybrid rocket motors has historically been hampered by the slow regression rate of the solid fuel. In recent years, the research on advanced injector designs has achieved notable results in the enhancement of the regression rate and combustion efficiency of hybrid rockets. Following this path, this work studies a new configuration called double-tube characterized by injecting the gaseous oxidizer through a head end injector and an inner tube with injector holes distributed along the motor longitudinal axis. This design has demonstrated a significant potential for improving the performance of hybrid rockets by means of a better mixing of the species achieved through a customized injection of the oxidizer. Indeed, the CFD analysis of the double-tube configuration has revealed that this design may increase the regression rate over 50% with respect to the same motor with a conventional axial showerhead injector. However, in order to fully exploit the advantages of the double-tube concept, it is necessary to acquire a deeper understanding of the influence of the different design parameters in the overall performance. In this way, a parametric study is carried out taking into account the variation of the oxidizer mass flux rate, the ratio of oxidizer mass flow rate injected through the inner tube to the total oxidizer mass flow rate, and injection angle. The data for the analysis have been gathered from a large series of three-dimensional numerical simulations that considered the changes in the design parameters. The propellant combination adopted consists of gaseous oxygen as oxidizer and high-density polyethylene as solid fuel. Furthermore, the numerical model comprises Navier-Stokes equations, k-ε turbulence model, eddy-dissipation combustion model and solid-fuel pyrolysis, which is computed through user-defined functions. This numerical model was previously validated by analyzing the computational and experimental results obtained for
Impact of the HEALTHY Study on Vending Machine Offerings in Middle Schools
Hartstein, Jill; Cullen, Karen W.; Virus, Amy; El Ghormli, Laure; Volpe, Stella L.; Staten, Myrlene A.; Bridgman, Jessica C.; Stadler, Diane D.; Gillis, Bonnie; McCormick, Sarah B.; Mobley, Connie C.
2011-01-01
Purpose/Objectives: The purpose of this study is to report the impact of the three-year middle school-based HEALTHY study on intervention school vending machine offerings. There were two goals for the vending machines: serve only dessert/snack foods with 200 kilocalories or less per single serving package, and eliminate 100% fruit juice and…
Mukherjee, Sananda
In recent years, there has been great interest in the potential of green roofs as an alternative roofing option to reduce the energy consumed by individual buildings as well as mitigate large scale urban environmental problems such as the heat island effect. There is a widespread recognition and a growing literature of measured data that suggest green roofs can reduce building energy consumption. This thesis investigates the potential of green roofs in reducing the building energy loads and focuses on how the different parameters of a green roof assembly affect the thermal performance of a building. A green roof assembly is modeled in Design Builder- a 3D graphical design modeling and energy use simulation program (interface) that uses the EnergyPlus simulation engine, and the simulated data set thus obtained is compared to field experiment data to validate the roof assembly model on the basis of how accurately it simulates the behavior of a green roof. Then the software is used to evaluate the thermal performance of several green roof assemblies under three different climate types, looking at the whole building energy consumption. For the purpose of this parametric simulation study, a prototypical single story small office building is considered and one parameter of the green roof is altered for each simulation run in order to understand its effect on building's energy loads. These parameters include different insulation thicknesses, leaf area indices (LAI) and growing medium or soil depth, each of which are tested under the three different climate types. The energy use intensities (EUIs), the peak and annual heating and cooling loads resulting from the use of these green roof assemblies are compared with each other and to a cool roof base case to determine the energy load reductions, if any. The heat flux through the roof is also evaluated and compared. The simulation results are then organized and finally presented as a decision support tool that would
Scala, Antonio; Festa, Gaetano; Vilotte, Jean-Pierre
2017-01-01
Earthquake ruptures often develop along faults separating materials with dissimilar elastic properties. Due to the broken symmetry, the propagation of the rupture along the bimaterial interface is driven by the coupling between interfacial sliding and normal traction perturbations. We numerically investigate in-plane rupture growth along a planar interface, under slip weakening friction, separating two dissimilar isotropic linearly elastic half-spaces, and we perform a parametric study of the classical Prakash-Clifton regularisation, for different material contrasts. In particular the mesh-dependence and the regularisation-dependence of the numerical solutions are analysed in this parameter space. When the regularisation involves a slip-rate dependent relaxation time, a characteristic sliding distance is identified below which numerical solutions no longer depend on the regularisation parameter, i.e. they are physically well-posed solutions. Such regularisation provides an adaptive high-frequency filter of the slip-induced normal traction perturbations, following the dynamic shrinking of the dissipation zone during the acceleration phase. In contrast, a regularisation involving a constant relaxation time leads to numerical solutions that always depend on the regularisation parameter since it fails in adapting to the shrinking of the process zone. Dynamic regularisation is further investigated using a non-local regularisation based on a relaxation time that depends on the dynamic length of the dissipation zone. Such reformulation is shown to provide similar results as the dynamic time scale regularisation proposed by Prakash-Clifton when the slip rate is replaced by the maximum slip rate along the sliding interface. This leads to the identification of a dissipative length scale associated with the coupling between interfacial sliding and normal traction perturbations, together with a scaling law between the maximum slip rate and the dynamic size of the process zone
Parametric Study of the Effect of Burnable Poison Rods for PWR Burnup Credit
Energy Technology Data Exchange (ETDEWEB)
Wagner, J.C.
2001-09-28
The Interim Staff Guidance on burnup credit (ISG-8) issued by the United States Nuclear Regulatory Commission's (U.S. NRC) Spent Fuel Project Office recommends restricting the use of burnup credit to assemblies that have not used burnable absorbers. This recommended restriction eliminates a large portion of the currently discharged spent fuel assemblies from cask loading, and thus severely limits the practical usefulness of burnup credit. In the absence of readily available information on burnable poison rod (BPR) design specifications and usage in U.S. pressurized-water-reactors (PWRs), and the subsequent reactivity effect of BPR exposure on discharged spent nuclear fuel (SNF), NRC staff has indicated a need for additional information in these areas. In response, this report presents a parametric study of the effect of BPR exposure on the reactivity of SNF for various BPR designs, fuel enrichments, and exposure conditions, and documents BPR design specifications. Trends in the reactivity effects of BPRs are established with infinite pin-cell and assembly array calculations with the SCALE and HELIOS code packages, respectively. Subsequently, the reactivity effects of BPRs for typical initial enrichment and burnup combinations are quantified based on three-dimensional (3-D) KENO V.a Monte Carlo calculations with a realistic rail-type cask designed for burnup credit. The calculations demonstrate that the positive reactivity effect due to BPR exposure increases nearly linearly with burnup and is dependent on the number, poison loading, and design of the BPRs and the initial fuel enrichment. Expected typical reactivity increases, based on one-cycle BPR exposure, were found to be less than 1% {Delta}k. Based on the presented analysis, guidance is offered on an appropriate approach for calculating bounding SNF isotopic data for assemblies exposed to BPRs. Although the analyses do not address the issue of validation of depletion methods for assembly designs with BPRs
Aircraft Trajectory Optimization Using Parametric Optimization Theory
Valenzuela Romero, Alfonso
2012-01-01
In this thesis, a study of the optimization of aircraft trajectories using parametric optimization theory is presented. To that end, an approach based on the use of predefined trajectory patterns and parametric optimization is proposed. The trajectory pat
Directory of Open Access Journals (Sweden)
Kühnast, Corinna
2008-04-01
Full Text Available Background: Although non-normal data are widespread in biomedical research, parametric tests unnecessarily predominate in statistical analyses. Methods: We surveyed five biomedical journals and – for all studies which contain at least the unpaired t-test or the non-parametric Wilcoxon-Mann-Whitney test – investigated the relationship between the choice of a statistical test and other variables such as type of journal, sample size, randomization, sponsoring etc. Results: The non-parametric Wilcoxon-Mann-Whitney was used in 30% of the studies. In a multivariable logistic regression the type of journal, the test object, the scale of measurement and the statistical software were significant. The non-parametric test was more common in case of non-continuous data, in high-impact journals, in studies in humans, and when the statistical software is specified, in particular when SPSS was used.
Parametric Matching of Drivetrain For Parallel Hybrid Electric Vehicle
National Research Council Canada - National Science Library
Zhang Zhongwei; Yu Hao; Li Yingli
2013-01-01
...; this thesis presents a simulation analysis of the PHEV and the influence on vehicle characteristic by component parameters of drivetrain, and studies the parametric choice and proper parametric...
Study on Measuring System of Casing Machine Based on PLC
Directory of Open Access Journals (Sweden)
Huiqiang Wang
2014-05-01
Full Text Available According to the technology requirements of measurement for animal casing, in this paper, we use PLC and touch screen as the control core, the electromechanical integration design ideas to research the methods and principles for casing measure, and analyze the mechanical structures and mechanical characteristics of casing machine. As the control core, the programmable logic controller (PLC ensures that the whole control system has high precision, high stability, high reliability during the operation time. Through PLC and touch screen well match with PLC which make the casing machine more convenient to operate the whole system. The configuration software form has a brief and intuitive interface on touch screen which makes it easy to use. The mechanical structure and control system of this casing machine are more stable, more reliable and with high anti-interference ability, and satisfies various requirements for animal casings, easy and convenient to operate.
Spectroscopic ellipsometric study of Ge nanocrystals embedded in SiO{sub 2} using parametric models
Energy Technology Data Exchange (ETDEWEB)
Petrik, P.; Fried, M. [Research Institute for Technical Physics and Materials Science, Budapest (Hungary); Dana, A.; Aydinli, A. [Institute of Materials Science and Nanotechnology, Bilkent University, Ankara (Turkey); Foss, S.; Finstad, T.G. [University of Oslo, Department of Physics, Blindern, Oslo (Norway); Basa, P.
2008-05-15
Ge-rich SiO{sub 2} layers on top of Si substrates were deposited using plasma enhanced chemical vapour deposition. Ge nanocrystals embedded in the SiO{sub 2} layers were formed by high temperature annealing. The samples were measured and evaluated by spectroscopic ellipsometry. Effective medium theory (EMT) and parametric semiconductor models have been used to model the dielectric function of the layers. Systematic dependences of the layer thickness and the oscillator parameters have been found on the annealing temperature (nanocrystal size). (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Parametric study of friction stir spot welding of aluminium alloy 5754
Directory of Open Access Journals (Sweden)
D. Klobčar
2014-01-01
Full Text Available The paper presents a parametric analysis of friction stir spot welding (FSSW of aluminium alloy 5754 in a lap joint. Experimental plan was done according to the response surface methodology (RSM, where tool rotation speed varied between 988 and 3511 rpm, plunge rate between 24,4 and 150 mm/min and dwell time between 1 and 3,5s. The plunge depth was held constant at 0,4 mm. The welds were tensile-shear tested and the microstructure was analysed. Mathematical models describing the relationship between welding parameters and spot strength, axial force and rotational moment were developed and the optimal FSSW parameters were found.
Parametric study of single expansion ramp nozzles at subsonic/transonic speeds
Capone, F. J.; Re, R. J.; Bare, E. A.; Maclean, M. K.
1987-01-01
The Langley Research Center has conducted a parametric investigation to determine the aeropropulsive characteristics of single expansion ramp nozzles (SERN). The SERN is a nonaxisymmetric, variable-area, internal/external expansion exhaust nozzle. Internal nozzle parameters that were varied included upper ramp length, ramp chordal angle, lower flap length, flap angle and the axial and vertical locations of nozzle throat. Convergent-divergent and convergent nozzles were included in this investigation which was conducted in the Langley 16-Foot Transonic Tunnel at Mach numbers from 0.6 to 1.2 and at nozzle pressure ratios up to 12.0.
Parametric study of the cost estimate for ultra precision RF components
Turunen, Joni; Osterberg, Kenneth; Makinen, Saku
2011-01-01
The purpose of this thesis was to find out how the shape accuracy and surface roughness of an RF disk affect the machining time of a disk and the cost of the accelerating structures. The disks in question are part of a future Compact Linear Collider (CLIC) project. This thesis was made because the price of a single disk is a major cost driver of the CLIC project. The cost of a disk is composed mainly of the time consuming ultra precise machining with expensive diamond tools. The surface roughness Ra 25 nm and shape accuracy 5 μm requirements are the reason for the need of ultra precision. The total number of disks to be produced for CLIC at 3 TeV center-of-mass energy is roughly 4.1 million, thus the project is a typical example of mass production where learning curves can be applied. Based on the theoretical calculations, changing the surface roughness Ra from 25 nm to 100 nm decreases the total ultra precise machining from 644 minutes to 311 minutes with current tooling and machining parameters. The effect...
Residual stress determination in PECVD TiN coatings by X-ray diffraction: a parametric study
DEFF Research Database (Denmark)
Thomsen, N.B.; Horsewell, Andy; Mogensen, K.S.
1998-01-01
The main objective of this research is to study the residual macroscopic stress in titanium-nitride, TiN, coatings deposited onto a tool steer substrate. The measurements were performed with a theta-theta decoupled X-ray diffractometer. The coatings were manufactured using an industrial pulsed......-DC plasma-enhanced chemical vapour deposition (PECVD) technique. The coatings were characterized in terms of microstructure, mechanical and tribological properties. A parametric study of the deposition parameters was performed. Process pressure, bias voltage, temperature and partial gas flows (argon...
EXPERIMENTAL STUDY OF THE DYNAMICS OF CENTRIFUGAL CASTING MACHINES FOR PRODUCTION OF MILL ROLLS
Directory of Open Access Journals (Sweden)
P. G. Anofriev
2017-06-01
Full Text Available Purpose. The main purpose of experimental studies is to establish the adequacy of the developed mathematical models of machine fluctuations and the actual parameters of machine vibration. Almost all casting machines for the production of mill rolls have a unique design and performances. The additional aim of this work is to compare the vibration level of the casting machine with the requirements of the current vibration standards for new technological machines. Frequency analysis of the oscillations allows establishing defects in workmanship, errors of rotating parts installation and their influence on the dynamics of the machine. Methodology. Measurement of vibration parameters was performed on the moving parts of roller bearings of the machine. To measure the amplitudes of accelerations in three mutually perpendicular directions piezoelectric sensors with magnetic mount were used. Electrical signals from the sensors were recorded on magnetic tape. Further analysis of the oscillations was carried out and visualized using specialized frequency analyzer. The frequency analyzer implements the algorithm of fast Fourier transformation and/or integration of sensor input signal. After the first integration the data for plotting the vibration velocity spectrogram were obtained and as a result of the second integration there are the data of vibration displacements spectrogram of the machine supports. Findings. The results of experimental studies of centrifugal casting machine vibrations for the production of two-layer rolls were presented. There were obtained and analyzed the spectrograms of accelerations, velocities and displacements of moving parts of the upper and lower roller supports. The work of the machine is associated with the calculated values passing of critical frequencies and the short-term development of resonance oscillations of the rotor and roller bearings. Originality. For the first time the author obtained the frequency spectra of
Studies of the Twin Helix Parametric-resonance Ionization Cooling Channel with COSY INFINITY
Energy Technology Data Exchange (ETDEWEB)
J.A. Maloney, K.B. Beard, R.P. Johnson, A. Afanasev, S.A. Bogacz, Y.S. Derbenev, V.S. Morozov, B. Erdelyi
2012-07-01
A primary technical challenge to the design of a high luminosity muon collider is an effective beam cooling system. An epicyclic twin-helix channel utilizing parametric-resonance ionization cooling has been proposed for the final 6D cooling stage. A proposed design of this twin-helix channel is presented that utilizes correlated optics between the horizontal and vertical betatron periods to simultaneously focus transverse motion of the beam in both planes. Parametric resonance is induced in both planes via a system of helical quadrupole harmonics. Ionization cooling is achieved via periodically placed wedges of absorbing material, with intermittent rf cavities restoring longitudinal momentum necessary to maintain stable orbit of the beam. COSY INFINITY is utilized to simulate the theory at first order. The motion of particles around a hyperbolic fixed point is tracked. Comparison is made between the EPIC cooling channel and standard ionization cooling effects. Cooling effects are measured, after including stochastic effects, for both a single particle and a distribution of particles.
Ning Ma; Xiaolong Yang; Mingqian Gao; Jinlong Song; Ganlin Liu; Wenji Xu
2015-01-01
Noncircular holes on the surface of turbine rotor blades are usually machined by electrodischarge machining. A recast layer containing numerous micropores and microcracks is easily generated during the electrodischarge machining process due to the rapid heating and cooling effects, which restrict the wide applications of noncircular holes in aerospace and aircraft industries. Owing to the outstanding advantages of pulse electrochemical machining, electrodischarge machining–pulse electrochemic...
Lua, Yuan J.; Liu, Wing K.; Belytschko, Ted
1992-01-01
A stochastic damage model for predicting the rupture of a brittle multiphase material is developed, based on the microcrack-macrocrack interaction. The model, which incorporates uncertainties in locations, orientations, and numbers of microcracks, characterizes damage by microcracking and fracture by macrocracking. A parametric study is carried out to investigate the change of the stress intensity at the macrocrack tip by the configuration of microcracks. The inherent statistical distribution of the fracture toughness arising from the intrinsic random nature of microcracks is explored using a statistical approach. For this purpose, a computer simulation model is introduced, which incorporates a statistical characterization of geometrical parameters of a random microcrack array.
Schroeder, J C; Tolbert, P E; Eisen, E A; Monson, R R; Hallock, M F; Smith, T J; Woskie, S R; Hammond, S K; Milton, D K
1997-05-01
Machining fluids are diverse products that contain numerous additives and contaminants, including polycyclic aromatic hydrocarbons. Studies treating machining fluids as an aggregate exposure have found both positive and negative associations with lung cancer. In this nested case-control study of automotive workers (667 cases and 3,041 matched controls), individual estimates of exposure quantity and duration for specific classes of machining fluids were derived. An inverse dose-response relationship was found between synthetic machining fluids and lung cancer mortality, with an odds ratio of 0.6 (95% CI = 0.4, 0.8) for the highest level of lifetime exposure. The relationship was strongest for recent exposures. There was little evidence of an association with soluble or straight oil machining fluids. Risks were inconsistently elevated in workers exposed to aluminum. Results from this study provide strong evidence that exposure to machining fluids is not associated with an increased risk of lung cancer mortality in automotive workers.
Parametric study on phase separation of binary mixtures in a lid driven cavity: A DPD study
Gidituri, Harinadha; Anand, Vijay; Panchagnula, Mahesh; Vedantam, Srikanth
2016-11-01
We investigate the phase separation behavior of binary mixtures in two dimensional periodic and lid driven cavity domains using dissipative particle dynamics (DPD). The effect of DPD parameters like repulsion coefficient, dissipative coefficient, cut-off radius, and weight function exponent on domain size growth has been studied. The phase separation is delayed for low values of repulsion coefficient. Under these conditions, a few clusters of the dispersed phase are distributed in a continuous phase. This is because of weak inter-particle repulsion. As we increase the repulsion coefficient value, this behavior disappears. The domain growth rate is also observed to increase with an increase in the value of the dissipation coefficient as well as cut-off radius. Finally, the dynamics of phase separation in the lid driven cavity problem are significantly different when compared to that in the periodic domain, due to the formation of a stable vortex in the cavity. The vortex results in a dynamic equilibrium between clustering and separation. The distribution of cluster sizes is studied as a function of the driven cavity parameters.
Study on Applying Hybrid Machine Learning into Family Apparel Expenditure
Institute of Scientific and Technical Information of China (English)
SHEN Lei
2008-01-01
Hybrid Machine Learning (HMD is a kind of advanced algorithm in the field of intelligent information process.It combines the induced learning based-on decision-making tree with the blocking neural network.And it provides a useful intelligent knowledge-based data mining technique.Its core algorithm is ID3 and Field Theory based ART (FTART).The paper introduces the principals of hybrid machine learning firstly, and then applies it into analyzing family apparel expenditures and their influencing factors systematically.Finally, compared with those from the traditional statistic methods, the results from HML is more friendly and easily to be understood.Besides, the forecasting by HML is more correct than by the traditional ways.
Study on Support Vector Machine Based on 1-Norm
Institute of Scientific and Technical Information of China (English)
PAN Mei-qin; HE Guo-ping; HAN Cong-ying; XUE Xin; SHI You-qun
2006-01-01
The model of optimization problem for Support Vector Machine(SVM) is provided, which based on the definitions of the dual norm and the distance between a point and its projection onto a given plane. The model of improved Support Vector Machine based on 1-norm (1 - SVM) is provided from the optimization problem, yet it is a discrete programming. With the smoothing technique and optimality knowledge, the discrete programming is changed into a continuous programming. Experimental results show that the algorithm is easy to implement and this method can select and suppress the problem features more efficiently.Illustrative examples show that the 1 - SVM deal with the linear or nonlinear classification well.
Study of Machining Error Forecast in NC Lathe
Institute of Scientific and Technical Information of China (English)
LIU Jiwei; ZHANG Ying; YANG Zheqing
2006-01-01
This paper brings forward a kind of machining error forecast principle in NC lathe simulation system. It combines the method of math, dynamic, material and mechanism, etc, sums up the factors which can affect the machining error, coalescent knowledge of mechanism manufacture technique and interconvert characteristic, mapped the change of physics factor in cutting process into virtual manufacture system by mathematical model. On the platform of Windows 2000 and Visual C++, applying program is developed by use of C++. The lean warehouse of MATLAB is transferred in order to command MATLAB on the language platform of MATLAB, and then the curve of the results is drawn by the outcome of calculation, which is based on the mathematical model in order to manifest the simulation results in the pattern of data and curve.
Cohen, D; Cohen, Doron; Heller, Eric J.
2000-01-01
We consider a classically chaotic system that is described by an Hamiltonian ${\\cal H}(Q,P;x)$ where x is a constant parameter. Our main interest is in the case of a gas-particle inside a cavity, where $x$ controls a deformation of the boundary or the position of a `piston'. The quantum-eigenstates of the system are $|n(x)>$. We describe how the parametric kernel $P(n|m)= ||^2$ evolves as a function of $\\delta x=x{-}x_0$. We explore both the perturbative and the non-perturbative regimes, and discuss the capabilities and the limitations of semiclassical as well as of random-waves and random-matrix-theory (RMT) considerations.
A Conceptual Wing Flutter Analysis Tool for Systems Analysis and Parametric Design Study
Mukhopadhyay, Vivek
2003-01-01
An interactive computer program was developed for wing flutter analysis in the conceptual design stage. The objective was to estimate flutt er instability boundaries of a typical wing, when detailed structural and aerodynamic data are not available. Effects of change in key flu tter parameters can also be estimated in order to guide the conceptual design. This userfriendly software was developed using MathCad and M atlab codes. The analysis method was based on non-dimensional paramet ric plots of two primary flutter parameters, namely Regier number and Flutter number, with normalization factors based on wing torsion stiffness, sweep, mass ratio, taper ratio, aspect ratio, center of gravit y location and pitch-inertia radius of gyration. These parametric plo ts were compiled in a Chance-Vought Corporation report from database of past experiments and wind tunnel test results. An example was prese nted for conceptual flutter analysis of outer-wing of a Blended-Wing- Body aircraft.
Zhou, Lim Yi; Shan, Fam Pei; Shimizu, Kunio; Imoto, Tomoaki; Lateh, Habibah; Peng, Koay Swee
2017-08-01
A comparative study of logistic regression, support vector machine (SVM) and least square support vector machine (LSSVM) models has been done to predict the slope failure (landslide) along East-West Highway (Gerik-Jeli). The effects of two monsoon seasons (southwest and northeast) that occur in Malaysia are considered in this study. Two related factors of occurrence of slope failure are included in this study: rainfall and underground water. For each method, two predictive models are constructed, namely SOUTHWEST and NORTHEAST models. Based on the results obtained from logistic regression models, two factors (rainfall and underground water level) contribute to the occurrence of slope failure. The accuracies of the three statistical models for two monsoon seasons are verified by using Relative Operating Characteristics curves. The validation results showed that all models produced prediction of high accuracy. For the results of SVM and LSSVM, the models using RBF kernel showed better prediction compared to the models using linear kernel. The comparative results showed that, for SOUTHWEST models, three statistical models have relatively similar performance. For NORTHEAST models, logistic regression has the best predictive efficiency whereas the SVM model has the second best predictive efficiency.
Institute of Scientific and Technical Information of China (English)
林作铨; 李未
1995-01-01
Parametric logic is introduced. The language, semantics and axiom system of parametric logic are defined. Completeness theorem of parametric logic is provided. Parametric logic has formal ability powerful enough to capture a wide class of logic as its special cases, and therefore can be viewed as a uniform basis for modern logics.
Mohr, C; Leyendecker, S; Helmchen, C
2008-02-01
Little is known regarding how cognitive strategies help to modulate neural responses of the human brain in ongoing pain syndromes to alleviate pain. Under pathological pain conditions, any self-elicited contact with usually non-painful stimuli may become painful. We examined whether the human brain is capable of dissociating self-controlled from externally administered thermal hyperalgesia in the experimental capsaicin model. Using functional magnetic resonance imaging, 17 male subjects were investigated in a parametric design with heat stimuli at topically capsaicin-sensitized skin. In contrast to external stimulation, self-administered pain was controllable. For both conditions application trials without noticeable thermal stimulation were introduced and used as high-level baseline (HLB) to account for the capsaicin-induced ongoing pain and other covariables. Following subtraction of the HLB, the anterior insula and the anterior cingulate cortex (ACC) but not the somatosensory cortices maintained parametric neural responses to thermal hyperalgesia. A stronger pain-related activity increase during self-administered stimuli was observed in the posterior insula. In contrast, prefrontal cortex showed stronger increases to uncontrollable external heat stimuli. In the state of ongoing pain (capsaicin), pain-intensity-encoding regions (anterior insula, ACC) but not those with sensory discriminative functions (SI, SII) showed graded, pain-intensity-related neural responses in thermal hyperalgesia. Some areas were able to dissociate between self- and externally administered stimuli in thermal hyperalgesia, which might be related to differences in perceived controllability. Thus, neural mechanisms maintain the ability to dissociate external from self-generated states of injury in thermal hyperalgesia. This may help to understand how cognitive strategies potentially alleviate chronic pain syndromes.
Airy beam optical parametric oscillator.
Aadhi, A; Chaitanya, N Apurv; Jabir, M V; Vaity, Pravin; Singh, R P; Samanta, G K
2016-05-04
Airy beam, a non-diffracting waveform, has peculiar properties of self-healing and self-acceleration. Due to such unique properties, the Airy beam finds many applications including curved plasma wave-guiding, micro-particle manipulation, optically mediated particle clearing, long distance communication, and nonlinear frequency conversion. However, many of these applications including laser machining of curved structures, generation of curved plasma channels, guiding of electric discharges in a curved path, study of nonlinear propagation dynamics, and nonlinear interaction demand Airy beam with high power, energy, and wavelength tunability. Till date, none of the Airy beam sources have all these features in a single device. Here, we report a new class of coherent sources based on cubic phase modulation of a singly-resonant optical parametric oscillator (OPO), producing high-power, continuous-wave (cw), tunable radiation in 2-D Airy intensity profile existing over a length >2 m. Based on a MgO-doped periodically poled LiNbO3 crystal pumped at 1064 nm, the Airy beam OPO produces output power more than 8 W, and wavelength tunability across 1.51-1.97 μm. This demonstration gives new direction for the development of sources of arbitrary structured beams at any wavelength, power, and energy in all time scales (cw to femtosecond).
Directory of Open Access Journals (Sweden)
Bilel Jarraya
2014-03-01
Full Text Available Bank efficiency scores usually serve as a tool for comparing institutions with each other while allowing us to quantify sub-optimal decision-making unit choices. In the case of inter-country comparisons, such differences can also arise because of macro-economic heterogeneity between countries. Previous studies estimated a common technology limit for a sample of banking institutions in different countries. The contribution of our paper is that we employ a parametric approach to specify meta-frontiers and to study the effect of macro-economic heterogeneity on banking technology development. First, we use a parametric directional distance function to specify the appropriate technology frontier for each nation and the meta-technology frontier that includes all country-specific frontiers. Then, we define the directional technology gap ratio referring to the inefficiency scores evaluated from meta-technology and country-specific technology frontiers. The estimated parameters are more significant in our model than in the general model, also called the common frontier model. Comparing the results of our model to those of common frontiers, we find a substantial variation not only in inefficiency scores but also in countries’ rankings. While resorting to a pooled linear regression model, we demonstrate that the assessed technology gap ratio exhibits a significant association with inflation rates and per capita GDP. This result proves the influence of macro-economic heterogeneity on banks’ efficiency and technological development.
Zhang, Guojun; Guo, Jianwen; Ming, Wuyi; Huang, Yu; Shao, Xinyu; Zhang, Zhen
2014-01-01
Nano-electrical discharge machining (nano-EDM) is an attractive measure to manufacture parts with nanoscale precision, however, due to the incompleteness of its theories, the development of more advanced nano-EDM technology is impeded. In this paper, a computational simulation model combining the molecular dynamics simulation model and the two-temperature model for single discharge process in nano-EDM is constructed to study the machining mechanism of nano-EDM from the thermal point of view. The melting process is analyzed. Before the heated material gets melted, thermal compressive stress higher than 3 GPa is induced. After the material gets melted, the compressive stress gets relieved. The cooling and solidifying processes are also analyzed. It is found that during the cooling process of the melted material, tensile stress higher than 3 GPa arises, which leads to the disintegration of material. The formation of the white layer is attributed to the homogeneous solidification, and additionally, the resultant residual stress is analyzed.
Energy Technology Data Exchange (ETDEWEB)
Al Mamon, Abdulla; Das, Sudipta [Visva-Bharati, Department of Physics, Santiniketan (India)
2015-06-15
In this present work, we try to build up a cosmological model using a non-canonical scalar field within the framework of a spatially flat FRW space-time. In this context, we have considered four different parametrizations of the equation of state parameter of the non-canonical scalar field. Under this scenario, analytical solutions for various cosmological parameters have been found out. It has been found that the deceleration parameter shows a smooth transition from a positive value to some negative value which indicates that the universe was undergoing an early deceleration followed by late time acceleration which is essential for the structure formation of the universe. With these four parametrizations, the future evolution of the models are also discussed. It has been found that one of the models (Generalized Chaplygin gas model, GCG) mimics the concordance ΛCDM in the near future, whereas two other models (CPL and JBP) diverge due to future singularity. Finally, we have studied these theoretical models with the latest datasets from SN Ia + H(z) + BAO/CMB. (orig.)
The impact of machine learning techniques in the study of bipolar disorder: A systematic review.
Librenza-Garcia, Diego; Kotzian, Bruno Jaskulski; Yang, Jessica; Mwangi, Benson; Cao, Bo; Pereira Lima, Luiza Nunes; Bermudez, Mariane Bagatin; Boeira, Manuela Vianna; Kapczinski, Flávio; Passos, Ives Cavalcante
2017-07-18
Machine learning techniques provide new methods to predict diagnosis and clinical outcomes at an individual level. We aim to review the existing literature on the use of machine learning techniques in the assessment of subjects with bipolar disorder. We systematically searched PubMed, Embase and Web of Science for articles published in any language up to January 2017. We found 757 abstracts and included 51 studies in our review. Most of the included studies used multiple levels of biological data to distinguish the diagnosis of bipolar disorder from other psychiatric disorders or healthy controls. We also found studies that assessed the prediction of clinical outcomes and studies using unsupervised machine learning to build more consistent clinical phenotypes of bipolar disorder. We concluded that given the clinical heterogeneity of samples of patients with BD, machine learning techniques may provide clinicians and researchers with important insights in fields such as diagnosis, personalized treatment and prognosis orientation. Copyright © 2017 Elsevier Ltd. All rights reserved.
A Study on Automatic Scoring for Machine Translation Systems
Institute of Scientific and Technical Information of China (English)
Yao Jianmin(姚建民); Zhang Jing; Zhao Tiejun; Li Sheng
2004-01-01
String similarity measures of edit distance, cosine correlation and Dice coefficient are adopted to evaluate machine translation results. Experiment shows that the evaluation method distinguishes well between "good" and "bad" translations. Another experiment manifests a consistency between human and automatic scorings of 6 general-purpose MT systems. Equational analysis validates the experimental results. Although the data and graphs are very promising, correlation coefficient and significance tests at 0.01 level are made to ensure the reliability of the results. Linear regression is made to map the automatic scoring results to human scorings.
Study on the all position automatic pipeline backing weld machine
Institute of Scientific and Technical Information of China (English)
Tang Deyu; Feng Biao; Li Chunrun; Niu Huli; Zhang Yongsheng; Zhang Jianhu
2008-01-01
As a result of the lower backing weld efficiency, the applying of automatic welding is seriously limited. So a kind of special automatic welder is designed and manufactured for backing weld. This paper introduces the character of the assembled pulse CO2 arc welding machine which has strong penetrability. It specifies the technology of controlling the parameters of all position automatic welding by computer and multi-axis controller. Moreover typical welding proce-dure parameters are provided. It is proved by examination that the economical and practical equipment and technology are suitable for the long-distance transmission pipeline, and it has a good foreground of spreading and applying.
Directory of Open Access Journals (Sweden)
Milutin G. Jovanović
2006-12-01
Full Text Available The brushless doubly-fed machine (BDFM allows the use of a partially rated inverter and represents an attractive cost-effective candidate for variable speed applications with limited speed ranges. In its induction machine form (BDFIM, the BDFM has significant rotor losses and poor efficiency due to the cage rotor design which makes the machine dynamic models heavily parameter dependent and the resulting controller configuration complicated and difficult to implement. A reluctance version of the BDFM, the brushless doubly-fed reluctance machine (BDFRM, ideally has no rotor losses, and therefore offers the prospect for higher efficiency and simpler control compared to the BDFIM. A detailed study of this interesting and emerging machine is very important to gain a thorough understanding of its unusual operation, control aspects and compromises between optimal performance and the size of the inverter and the machine. This paper will attempt to address these issues specifically concentrating on developing conditions for various control properties of the machine such as maximum power factor, maximum torque per inverter ampere and minimum copper losses, as well as analysing the associated trade-offs.
Study on the nano machining process with a vibrating AFM tip on the polymer surface
Energy Technology Data Exchange (ETDEWEB)
Liu Weitao [State Key Laboratory of Robotics and Systems, Robotics Institute, Harbin Institute of Technology, Harbin 150080 (China); Center for Precision Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001 (China); Yan Yongda, E-mail: yanyongda@yahoo.com.cn [State Key Laboratory of Robotics and Systems, Robotics Institute, Harbin Institute of Technology, Harbin 150080 (China); Center for Precision Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001 (China); Hu Zhenjiang; Zhao Xuesen; Yan Jiucun; Dong Shen [Center for Precision Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001 (China)
2012-01-15
The polymer has been proved to be nano machined by a vibrating tip in tapping mode of Atomic Force Microscope (AFM). The force between the tip and the surface is an important factor which determines success of the machining process. Controlling this force with high accuracy is the foundation of nanomachining in AFM tapping mode. To achieve a deeper understanding on this process, the tip is modeled as a driving oscillator with damping. Factors affecting the nano machining process are studied. The Hertz elastic contact theory is used to calculate the maximum contact pressure applied by the tip which is employed as a criterion to judge the deformation state of the sample. The simulation results show that: The driven amplitude can be used as a main parameter of controlling the machined depth. Sharper tips and harder cantilevers should be used for successful nanomachining with the vibrating tip. Under the same conditions, a larger tip radius will not only result in the machining error, but also lead to failure of the nanomachining process. The higher driving frequency will lead to a larger tapping force. However it cannot be used as a parameter to control the machined depth because of its narrow variation range. But it is a main error source for the nanomachining process in AFM tapping mode. Moreover, a larger Young's modulus polymer sample will induce a smaller machined depth, a larger maximum contact pressure and a bigger tapping force.
Parametric versus non-parametric simulation
Dupeux, Bérénice; Buysse, Jeroen
2014-01-01
Most of ex-ante impact assessment policy models have been based on a parametric approach. We develop a novel non-parametric approach, called Inverse DEA. We use non parametric efficiency analysis for determining the farm’s technology and behaviour. Then, we compare the parametric approach and the Inverse DEA models to a known data generating process. We use a bio-economic model as a data generating process reflecting a real world situation where often non-linear relationships exist. Results s...
Study on Surface Engineering of Normalized Steels Subjected To Machine
Institute of Scientific and Technical Information of China (English)
Hardening
2004-01-01
Engineering the surfaces of components to improve the life and performance of parts used in automotive and aerospace engineering is the active area of research. Suitable Thermal/Mechanical/Thermo mechanical surface engineering treatments will produce extensive rearrangement of atoms in metals and alloys and corresponding marked variations in Physical, Chemical and Mechanical properties. Among the more important of these treatments are heat treatment processes such as hardening by Quenching, Induction hardening and Case Carburizing which rely on phase transformations to produce desired changes in mechanical properties. Other processes where phase transformation occur are casting, welding and machining etc. [1] Phase transformation may be homogeneous or heterogeneous. Homogeneous involves rearrangements in the structure of the material taking place simultaneously in all parts of the solid, while the heterogeneous transformation involves structural changes which are more localized. Alternatively they could be called as Isothermal and Nonisothermal transformation. But irrespective of the classification, these transformations alter the structure of the material giving rise to changes in the mechanical and physical properties of the processed material. It is of interest to review some consequences of surface modification in isothermal (Normalizing) and nonisothermal transformations (Machining) of low carbon steels.
Energy Technology Data Exchange (ETDEWEB)
Li, Haiqing; Li, Yuxin; Yin, Bo; Tang, Weijun; Yu, Xiangrong; Geng, Daoying [Huashan Hospital, Department of Radiology, Fudan University, Shanghai (China); Chen, Yan [Fudan University, Department of Neurology, Huashan Hospital, Shanghai (China); Huang, Weiyuan [People' s Hospital of Hainan Province, Department of Radiology, Haikou, Hainan Province (China); Zhang, Biyun [Nanjing University of Traditional Chinese Medicine, Department of radiotherapy, Affiliated Jiangsu Province Hospital of Traditional Chinese Medicine, Nanjing (China)
2015-09-15
To investigate functional cerebral abnormalities in patients with amyotrophic lateral sclerosis (ALS) using functional magnetic resonance imaging (fMRI) during action observation. Thirty patients with ALS and 30 matched healthy controls underwent fMRI with an experimental paradigm while observing a video of repetitive flexion-extension of the fingers at three frequency levels or three complexity levels, alternated with periods of a static hand. A parametric analysis was applied to determine the effects of each of the two factors. Action observation activated similar neural networks as the research on execution of action in the ALS patients and healthy subjects in several brain regions related to the mirror-neuron system (MNS). In the ALS patients, in particular, the dorsal lateral premotor cortex (dPMC), inferior parietal gyrus (IPG), and SMA, were more activated compared with the activation in the controls. Increased activation within the primary motor cortex (M1), dPMC, inferior frontal gyrus (IFG), and superior parietal gyrus (SPG) mainly correlated with hand movement frequency/complexity in the videos in the patients compared with controls. The findings indicated an ongoing compensatory process occurring within the higher order motor-processing system of ALS patients, likely to overcome the loss of function. (orig.)
Machine learning patterns for neuroimaging-genetic studies in the cloud
Da Mota, Benoit; Tudoran, Radu; Costan, Alexandru; Varoquaux, Gaël; Brasche, Goetz; Conrod, Patricia; Lemaitre, Herve; Paus, Tomas; Rietschel, Marcella; Frouin, Vincent; Poline, Jean-Baptiste; Antoniu, Gabriel; Thirion, Bertrand
2014-01-01
Brain imaging is a natural intermediate phenotype to understand the link between genetic information and behavior or brain pathologies risk factors. Massive efforts have been made in the last few years to acquire high-dimensional neuroimaging and genetic data on large cohorts of subjects. The statistical analysis of such data is carried out with increasingly sophisticated techniques and represents a great computational challenge. Fortunately, increasing computational power in distributed architectures can be harnessed, if new neuroinformatics infrastructures are designed and training to use these new tools is provided. Combining a MapReduce framework (TomusBLOB) with machine learning algorithms (Scikit-learn library), we design a scalable analysis tool that can deal with non-parametric statistics on high-dimensional data. End-users describe the statistical procedure to perform and can then test the model on their own computers before running the very same code in the cloud at a larger scale. We illustrate the potential of our approach on real data with an experiment showing how the functional signal in subcortical brain regions can be significantly fit with genome-wide genotypes. This experiment demonstrates the scalability and the reliability of our framework in the cloud with a 2 weeks deployment on hundreds of virtual machines. PMID:24782753
DEFF Research Database (Denmark)
Jakobsen, M. D.; Sundstrup, E.; Andersen, C. H.
2014-01-01
Objective The aim of this study was to evaluate muscle activity during hamstring rehabilitation exercises performed in training machine compared with elastic resistance. Design Six women and 13 men aged 28-67 yrs participated in a crossover study. Electromyographic (EMG) activity was recorded...... in the biceps femoris and the semitendinosus during the concentric and the eccentric phase of hamstring curls performed with TheraBand elastic tubing and Technogym training machines and normalized to maximal voluntary isometric contraction-EMG (normalized EMG). Knee joint angle was measured using electronic...... inclinometers. Results Training machines and elastic resistance showed similar high levels of muscle activity (biceps femoris and semitendinosus peak normalized EMG >80%). EMG during the concentric phase was higher than during the eccentric phase regardless of exercise and muscle. However, compared with machine...
Toll, T. A.
1980-01-01
A parametric analysis was made to investigate the relationship between current cargo airplanes and possible future designs that may differ greatly in both size and configuration. The method makes use of empirical scaling laws developed from statistical studies of data from current and advanced airplanes and, in addition, accounts for payload density, effects of span distributed load, and variations in tail area ratio. The method is believed to be particularly useful for exploratory studies of design and technology options for large airplanes. The analysis predicts somewhat more favorable variations of the ratios of payload to gross weight and block fuel to payload as the airplane size is increased than has been generally understood from interpretations of the cube-square law. In terms of these same ratios, large all wing (spanloader) designs show an advantage over wing-fuselage designs.
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
2016-01-01
Heat transfer and pressure loss characteristics of a fin and tube heat exchanger are numerically investigated based on parametric fin geometry. The cross-flow type heat exchanger with circular tubes and rectangular fin profile is selected as a reference design. The fin geometry is varied using...... a design aspect ratio as a variable parameter in a range of 0.1-1.0 to predict the impact on overall performance of the heat exchanger. In this paper, geometric profiles with a constant thickness of fin base are studied. Three-dimensional, steady state CFD model is developed using commercially available...... are determined. The best performed geometric fin profile based on the higher heat transfer and lower pressure loss is predicted. The study provides insights into the impact of fin geometry on the heat transfer performance which help escalate the understanding of heat exchanger designing and manufacturing...
Specimen Machining for the Study of the Effect of Swelling on CGR in PWR Environment.
Energy Technology Data Exchange (ETDEWEB)
Teysseyre, Sebastien Paul [Idaho National Lab. (INL), Idaho Falls, ID (United States)
2015-06-01
This report describes the preparation of ten specimens to be used for the study of the effect of swelling on the propagation of irradiation assisted stress corrosion cracking cracks. Four compact tension specimens, four microscopy plates and two tensile specimens were machined from a AISI 304 material that was irradiated up to 33 dpa. The specimens had been machined such as to represent the behavior of materials with 3.7%swelling and <2% swelling.
Institute of Scientific and Technical Information of China (English)
HOU Xinyi; JIANG Xiaomei; GAO Jianmin; YIN Yafang
2006-01-01
The research method in this paper is based on the standard of American Society for Testing and Materials (ASTM), Planing and sanding are selected to study the machining properties of E. Urophylla × E. Grandis plantation wood. Moreover, the reasons for machining defects are analyzed. The results show E. Urophylla × E. Grandis planted in south China is a good species with a great potential for solid wood utilization.
Atomic structure of machined semiconducting chips: An x-ray absorption spectroscopy study
Energy Technology Data Exchange (ETDEWEB)
Paesler, M.; Sayers, D.
1988-12-01
X-ray absorption spectroscopy (XAS) has been used to examine the atomic structure of chips of germanium that were produced by single point diamond machining. It is demonstrated that although the local (nearest neighbor) atomic structure is experimentally quite similar to that of single crystal specimens information from more distant atoms indicates the presence of considerable stress. An outline of the technique is given and the strength of XAS in studying the machining process is demonstrated.
Chen, Kan; Stafford, Frank P.
A case study of machine vision was conducted to identify and analyze the employment effects of high technology in general. (Machine vision is the automatic acquisition and analysis of an image to obtain desired information for use in controlling an industrial activity, such as the visual sensor system that gives eyes to a robot.) Machine vision as…
Directory of Open Access Journals (Sweden)
Kristiansen Ivar S
2011-08-01
Full Text Available Abstract Background To preserve patient anonymity, health register data may be provided as binned data only. Here we consider as example, how to estimate mean survival time after a diagnosis of metastatic colorectal cancer from Norwegian register data on time to death or censoring binned into 30 day intervals. All events occurring in the first three months (90 days after diagnosis were removed to achieve comparability with a clinical trial. The aim of the paper is to develop and implement a simple, and yet flexible method for analyzing such interval censored and truncated data. Methods Considering interval censoring a missing data problem, we implement a simple multiple imputation strategy that allows flexible sensitivity analyses with respect to the shape of the censoring distribution. To allow identification of appropriate parametric models, a χ2-goodness-of-fit test--also imputation based--is derived and supplemented with diagnostic plots. Uncertainty estimates for mean survival times are obtained via a simulation strategy. The validity and statistical efficiency of the proposed method for varying interval lengths is investigated in a simulation study and compared with simpler alternatives. Results Mean survival times estimated from the register data ranged from 1.2 (SE = 0.09 to 3.2 (0.31 years depending on period of diagnosis and choice of parametric model. The shape of the censoring distribution within intervals did generally not influence results, whereas the choice of parametric model did, even when different models fit the data equally well. In simulation studies both simple midpoint imputation and multiple imputation yielded nearly unbiased analyses (relative biases of -0.6% to 9.4% and confidence intervals with near-nominal coverage probabilities (93.4% to 95.7% for censoring intervals shorter than six months. For 12 month censoring intervals, multiple imputation provided better protection against bias, and coverage probabilities
Directory of Open Access Journals (Sweden)
Alexandros Arsalis
2016-08-01
Full Text Available In this study a small-scale, completely autonomous combined cooling, heating, and power (CCHP system is coupled to a photovoltaic (PV subsystem, to investigate the possibility of reducing fuel consumption. The CCHP system generates electrical energy with the use of a simple gas turbine cycle, with a rated nominal power output of 1 MWe. The nominal power output of the PV subsystem is examined in a parametric study, ranging from 0 to 600 kWe, to investigate which configuration results in a minimum lifecycle cost (LCC for a system lifetime of 20 years of service. The load profile considered is applied for a complex of households in Nicosia, Cyprus. The solar data for the PV subsystem are taken on an hourly basis for a whole year. The results suggest that apart from economic benefits, the proposed system also results in high efficiency and reduced CO2 emissions. The parametric study shows that the optimum PV capacity is 300 kWe. The minimum lifecycle cost for the PV-assisted CCHP system is found to be 3.509 million €, as compared to 3.577 million € for a system without a PV subsystem. The total cost for the PV subsystem is 547,445 €, while the total cost for operating the system (fuel is 731,814 € (compared to 952,201 € for a CCHP system without PVs. Overall the proposed system generates a total energy output of 210,520 kWh (during its whole lifetime, which translates to a unit cost of 17 €/kWh.
Directory of Open Access Journals (Sweden)
P. Karthik
2015-12-01
Full Text Available The present study aimed to perform the parametric analysis on thermo-hydraulic performance of a compact heat exchanger using computational fluid dynamics (CFD. The analysis has been carried out at different frontal air velocities by varying the geometrical parameters such as fin pitch, transverse tube pitch, longitudinal tube pitch, louver pitch and louver angle. The air side performance of the heat exchanger has been evaluated by calculating Colburn factor (j and Fanning friction factor (f. The comparison of CFD results with the experimental data exhibited a good agreement and the influence of various geometrical parameters for the selected range of values on the pressure drop, heat transfer coefficient and goodness factor was analyzed. The results obtained from the analysis will be very useful to optimize the louvered fin and flat tube compact heat exchanger for better thermo-hydraulic performance analysis without the need of time consuming and expensive experimentation.
Zhang, Xiaojing; Musson-Genon, Luc; Dupont, Eric; Milliez, Maya; Carissimo, Bertrand
2014-05-01
A detailed numerical simulation of a radiation fog event with a single column model is presented, which takes into account recent developments in microphysical parametrizations. One-dimensional simulations are performed using the computational fluid dynamics model Code_Saturne and the results are compared to a very detailed in situ dataset collected during the ParisFog campaign, which took place near Paris, France, during the winter 2006-2007. Special attention is given to the detailed and complete diurnal simulations and to the role of microphysics in the fog life cycle. The comparison between the simulated and the observed visibility, in the single-column model case study, shows that the evolution of radiation fog is correctly simulated. Sensitivity simulations show that fog development and dissipation are sensitive to the droplet-size distribution through sedimentation/deposition processes but the aerosol number concentration in the coarse mode has a low impact on the time of fog formation.
Imani, Farhad; Ghavidel, Sahar; Abolmaesumi, Purang; Khallaghi, Siavash; Gibson, Eli; Khojaste, Amir; Gaed, Mena; Moussa, Madeleine; Gomez, Jose A.; Romagnoli, Cesare; Cool, Derek W.; Bastian-Jordan, Matthew; Kassam, Zahra; Siemens, D. Robert; Leveridge, Michael; Chang, Silvia; Fenster, Aaron; Ward, Aaron D.; Mousavi, Parvin
2016-03-01
Recently, multi-parametric Magnetic Resonance Imaging (mp-MRI) has been used to improve the sensitivity of detecting high-risk prostate cancer (PCa). Prior to biopsy, primary and secondary cancer lesions are identified on mp-MRI. The lesions are then targeted using TRUS guidance. In this paper, for the first time, we present a fused mp-MRI-temporal-ultrasound framework for characterization of PCa, in vivo. Cancer classification results obtained using temporal ultrasound are fused with those achieved using consolidated mp-MRI maps determined by multiple observers. We verify the outcome of our study using histopathology following deformable registration of ultrasound and histology images. Fusion of temporal ultrasound and mp-MRI for characterization of the PCa results in an area under the receiver operating characteristic curve (AUC) of 0.86 for cancerous regions with Gleason scores (GSs)>=3+3, and AUC of 0.89 for those with GSs>=3+4.
Energy Technology Data Exchange (ETDEWEB)
Chitty, Walter-John [CEA, DSM, IRAMIS, Laboratoire Pierre Suee, F-91191 Gif-sur-Yvette cedex (France); Dillmann, Philippe [CEA, DSM, IRAMIS, Laboratoire Pierre Suee, F-91191 Gif-sur-Yvette cedex (France); Institut de Recherches sur les Archeomateriaux, LMC UMR5060 CNRS (France)], E-mail: philippe.dillmann@cea.fr; L' Hostis, Valerie [CEA, DEN, DPC, SCCME, Laboratoire d' Etude du Comportement des Betons et des Argiles, F-91191 Gif-sur-Yvette (France); Millard, Alain [CEA, DEN, DM2S, SEMT, Laboratoire de Modelisation, Systemes et Simulation, F-91191 Gif-sur-Yvette (France)
2008-11-15
The prediction of long-term behaviour of reinforced concrete structures involved in the nuclear industry requires a phenomenological modelling of the rebars corrosion processes. Previous analytical characterisation of archaeological artefacts allowed to identify a typical layout constituted of four layers (the metal, the dense product layer, the transformed medium and the binder). Additional experiments leaded to identify the long-term corrosion mechanisms. Following these results, this paper proposes an analytical model of long-term corrosion of rebars embedded in concrete. This modelling is considering the kinetic of oxygen diffusion through the system and its consumption at the metal/dense product layer interface as a function of concrete water saturation degree. Corrosion products thicknesses estimated with the model are then compared to corrosion product thicknesses measured on archaeological artefacts. A parametric study is performed and demonstrates that the oxygen diffusivity and the kinetic constant of the cathodic reaction affect in a wide range the model results.
Dereux, A.; Hassan, K.; Weeber, J.-C.; Djellali, N.; Bozhevolnyi, S. I.; Tsilipakos, O.; Pitilakis, A.; Kriezis, E.; Papaioannou, S.; Vyrsokinos, K.; Pleros, N.; Tekin, T.; Baus, M.; Kalavrouziotis, D.; Giannoulis, G.; Avramopoulos, H.
2011-01-01
Surface plasmons polaritons are electromagnetic waves propagating along the surface of a conductor. Surface plasmons photonics is a promising candidate to satisfy the constraints of miniaturization of optical interconnects. This contribution reviews an experimental parametric study of dielectric loaded surface plasmon waveguides ring resonators and add-drop filters within the perspective of the recently suggested hybrid technology merging plasmonic and silicon photonics on a single board (European FP7 project PLATON "Merging Plasmonic and Silicon Photonics Technology towards Tb/s routing in optical interconnects"). Conclusions relevant for dielectric loaded surface plasmon switches to be integrated in silicon photonic circuitry will be drawn. They rely on the opportunity offered by plasmonic circuitry to carry optical signals and electric currents through the same thin metal circuitry. The heating of the dielectric loading by the electric current enables to design low foot-print thermo-optical switches driving the optical signal flow.
Directory of Open Access Journals (Sweden)
C. Negulescu
2010-09-01
Full Text Available The aim of this paper is to propose a simplified methodology to evaluate the mechanical performances of buildings exposed to landslide hazard, by using procedures inspired from the seismic risk analysis, such as the Capacity Spectrum Method (ATC 40, 1996. Landslide hazard involves so many aspects, that quantitative vulnerability assessment requires to consider one basic scenario at a time, i.e. one typology for the landslide hazard and one for the structural element considered. In this paper, we propose to assess vulnerability for simple one bay-one storey reinforced concrete (RC frame structures subjected to differential settlements, using 2-D parametric nonlinear static time-history analyses. After a short review of methods used in practice to estimate building deformations induced by ground movements (e.g. differential settlements, we present the parametric studies carried out to identify the most relevant parameters, in order to predict the structural damage, as well as the methodology to develop analytical fragility curves, that can be used to quantitatively evaluate the structural vulnerability in landslide risk analyses. Different types of parameters that could influence structural behaviour have been examined in this analysis: foundation type (i.e. different combinations of links, cross-section geometry, section reinforcement degree, displacement magnitudes and displacement inclination angles. We show that the magnitude and inclination angle of displacements can be used as two relevant parameters for this type of landslide scenario. Based on these results, some simulations are conducted using the software SeismoStruct (SeismoSoft, 2003, and the proposed structural damage levels consider the local strain limits of steel and concrete constitutive materials. Some preliminary fragility curves are proposed with respect to the magnitude of differential ground displacement. It can be seen that the curves corresponding to limit states LS2
Negulescu, C.; Foerster, E.
2010-09-01
The aim of this paper is to propose a simplified methodology to evaluate the mechanical performances of buildings exposed to landslide hazard, by using procedures inspired from the seismic risk analysis, such as the Capacity Spectrum Method (ATC 40, 1996). Landslide hazard involves so many aspects, that quantitative vulnerability assessment requires to consider one basic scenario at a time, i.e. one typology for the landslide hazard and one for the structural element considered. In this paper, we propose to assess vulnerability for simple one bay-one storey reinforced concrete (RC) frame structures subjected to differential settlements, using 2-D parametric nonlinear static time-history analyses. After a short review of methods used in practice to estimate building deformations induced by ground movements (e.g. differential settlements), we present the parametric studies carried out to identify the most relevant parameters, in order to predict the structural damage, as well as the methodology to develop analytical fragility curves, that can be used to quantitatively evaluate the structural vulnerability in landslide risk analyses. Different types of parameters that could influence structural behaviour have been examined in this analysis: foundation type (i.e. different combinations of links), cross-section geometry, section reinforcement degree, displacement magnitudes and displacement inclination angles. We show that the magnitude and inclination angle of displacements can be used as two relevant parameters for this type of landslide scenario. Based on these results, some simulations are conducted using the software SeismoStruct (SeismoSoft, 2003), and the proposed structural damage levels consider the local strain limits of steel and concrete constitutive materials. Some preliminary fragility curves are proposed with respect to the magnitude of differential ground displacement. It can be seen that the curves corresponding to limit states LS2 (moderate damage) and
Luo, Zhiwen; Li, Yuguo
2011-10-01
This paper reports the results of a parametric CFD study on idealized city models to investigate the potential of slope flow in ventilating a city located in a mountainous region when the background synoptic wind is absent. Examples of such a city include Tokyo in Japan, Los Angeles and Phoenix in the US, and Hong Kong. Two types of buoyancy-driven flow are considered, i.e., slope flow from the mountain slope (katabatic wind at night and anabatic wind in the daytime), and wall flow due to heated/cooled urban surfaces. The combined buoyancy-driven flow system can serve the purpose of dispersing the accumulated urban air pollutants when the background wind is weak or absent. The microscopic picture of ventilation performance within the urban structures was evaluated in terms of air change rate (ACH) and age of air. The simulation results reveal that the slope flow plays an important role in ventilating the urban area, especially in calm conditions. Katabatic flow at night is conducive to mitigating the nocturnal urban heat island. In the present parametric study, the mountain slope angle and mountain height are assumed to be constant, and the changing variables are heating/cooling intensity and building height. For a typical mountain of 500 m inclined at an angle of 20° to the horizontal level, the interactive structure is very much dependent on the ratio of heating/cooling intensity as well as building height. When the building is lower than 60 m, the slope wind dominates. When the building is as high as 100 m, the contribution from the urban wall flow cannot be ignored. It is found that katabatic wind can be very beneficial to the thermal environment as well as air quality at the pedestrian level. The air change rate for the pedestrian volume can be as high as 300 ACH.
Parametrizing Algebraic Curves
Lemmermeyer, Franz
2011-01-01
We present the technique of parametrization of plane algebraic curves from a number theorist's point of view and present Kapferer's simple and beautiful (but little known) proof that nonsingular curves of degree > 2 cannot be parametrized by rational functions.
Mabied, Ahmed F; Müller, Melanie; Dinnebier, Robert E; Nozawa, Shunsuke; Hoshino, Manabu; Tomita, Ayana; Sato, Tokushi; Adachi, Shin-ichi
2012-08-01
The [4π + 4π] photodimerization process of the 9-substituted anthracene derivative crystalline 9-methylanthracene (9-MA) was investigated using time-resolved X-ray powder diffraction. The study was carried out in-situ using a CCD area detector. Sequential and parametric Rietveld refinement was applied for quantitative phase analysis. The results of traditional sequential Rietveld refinement showed that the evolution of the dimerization process can be described using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. The parameters of the JMAK equation were obtained successfully by parametric Rietveld refinement and suggest that the reaction follows heterogeneous nucleation and one-dimensional growth with a decreasing nucleation rate.
Parametric Methods for Order Tracking Analysis
DEFF Research Database (Denmark)
Jensen, Tobias Lindstrøm; Nielsen, Jesper Kjær
2017-01-01
Order tracking analysis is often used to find the critical speeds at which structural resonances are excited by a rotating machine. Typically, order tracking analysis is performed via non-parametric methods. In this report, however, we demonstrate some of the advantages of using a parametric method...... for order tracking analysis. Specifically, we show that we get a much better time and frequency resolution, obtain a much more robust and accurate estimate of the RPM profile, and are able to perform accurate order tracking analysis even without the tachometer signal....
Directory of Open Access Journals (Sweden)
Srisawat Supsomboon
2014-01-01
Full Text Available The purpose of this study was to increase the quality of product by focusing on the machine efficiency improvement. The principle of the reliability centered maintenance (RCM was applied to increase the machine reliability. The objective was to create preventive maintenance plan under reliability centered maintenance method and to reduce defects. The study target was set to reduce the Lead PPM for a test machine by simulating the proposed preventive maintenance plan. The simulation optimization approach based on evolutionary algorithms was employed for the preventive maintenance technique selection process to select the PM interval that gave the best total cost and Lead PPM values. The research methodology includes procedures such as following the priority of critical components in test machine, analyzing the damage and risk level by using Failure Mode and Effects Analysis (FMEA, calculating the suitable replacement period through reliability estimation, and optimizing the preventive maintenance plan. From the result of the study it is shown that the Lead PPM of test machine can be reduced. The cost of preventive maintenance, cost of good product, and cost of lost product were decreased.
Machining studies of die cast aluminum alloy-silicon carbide composites
Sornakumar, Thambu; Kathiresan, Marimuthu
2010-10-01
Metal matrix composites (MMCs) with high specific stiffness, high strength, improved wear resistance, and thermal properties are being increasingly used in advanced structural, aerospace, automotive, electronics, and wear applications. Aluminum alloy-silicon carbide composites were developed using a new combination of the vortex method and the pressure die-casting technique in the present work. Machining studies were conducted on the aluminum alloy-silicon carbide (SiC) composite work pieces using high speed steel (HSS) end-mill tools in a milling machine at different speeds and feeds. The quantitative studies on the machined work piece show that the surface finish is better for higher speeds and lower feeds. The surface roughness of the plain aluminum alloy is better than that of the aluminum alloy-silicon carbide composites. The studies on tool wear show that flank wear increases with speed and feed. The end-mill tool wear is higher on machining the aluminum alloy-silicon carbide composites than on machining the plain aluminum alloy.
Werler, Marc; Maas, Ulrich
2016-01-01
A novel extension of a rapid compression machine (RCM), namely a Rapid Compression Expansion Machine (RCEM), is described and its use for studying chemical kinetics is demonstrated. Like conventional RCMs, the RCEM quickly compresses a fuel/air mixture by pushing a piston into a cylinder; the resulting high temperatures and pressures initiate chemical reactions. In addition, the machine can rapidly expand the compressed gas in a controlled way by pulling the piston outwards again. This freezes chemical activity after a pre-defined reaction duration, and therefore allows a convenient probe sampling and ex-situ gas analysis of stable species. The RCEM therefore is a promising instrument for studying chemical kinetics, including also partially reacted fuel/air mixtures. The setup of the RCEM, its experimental characteristics and its use for studying chemical reactions are outlined in detail. To allow comparisons of RCEM results with predictions of chemical reaction mechanisms, a simple numerical model of the RCE...
On Parametric (and Non-Parametric Variation
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Neil Smith
2009-11-01
Full Text Available This article raises the issue of the correct characterization of ‘Parametric Variation’ in syntax and phonology. After specifying their theoretical commitments, the authors outline the relevant parts of the Principles–and–Parameters framework, and draw a three-way distinction among Universal Principles, Parameters, and Accidents. The core of the contribution then consists of an attempt to provide identity criteria for parametric, as opposed to non-parametric, variation. Parametric choices must be antecedently known, and it is suggested that they must also satisfy seven individually necessary and jointly sufficient criteria. These are that they be cognitively represented, systematic, dependent on the input, deterministic, discrete, mutually exclusive, and irreversible.
Jakobsen, Markus Due; Sundstrup, Emil; Andersen, Christoffer H; Persson, Roger; Zebis, Mette K; Andersen, Lars L
2014-04-01
The aim of this study was to evaluate muscle activity during hamstring rehabilitation exercises performed in training machine compared with elastic resistance. Six women and 13 men aged 28-67 yrs participated in a crossover study. Electromyographic (EMG) activity was recorded in the biceps femoris and the semitendinosus during the concentric and the eccentric phase of hamstring curls performed with TheraBand elastic tubing and Technogym training machines and normalized to maximal voluntary isometric contraction-EMG (normalized EMG). Knee joint angle was measured using electronic inclinometers. Training machines and elastic resistance showed similar high levels of muscle activity (biceps femoris and semitendinosus peak normalized EMG >80%). EMG during the concentric phase was higher than during the eccentric phase regardless of exercise and muscle. However, compared with machine exercise, slightly lower (P knee joint angle for the semitendinosus and the biceps femoris during the concentric and the eccentric phase, respectively. Perceived loading (Borg CR10) was significantly higher (P exercise performed with elastic resistance induces similar peak hamstring muscle activity but slightly lower EMG values at more extended knee angles and with higher perceived loading as hamstring curls using training machines.
Applying machine learning to identify autistic adults using imitation: An exploratory study.
Li, Baihua; Sharma, Arjun; Meng, James; Purushwalkam, Senthil; Gowen, Emma
2017-01-01
Autism spectrum condition (ASC) is primarily diagnosed by behavioural symptoms including social, sensory and motor aspects. Although stereotyped, repetitive motor movements are considered during diagnosis, quantitative measures that identify kinematic characteristics in the movement patterns of autistic individuals are poorly studied, preventing advances in understanding the aetiology of motor impairment, or whether a wider range of motor characteristics could be used for diagnosis. The aim of this study was to investigate whether data-driven machine learning based methods could be used to address some fundamental problems with regard to identifying discriminative test conditions and kinematic parameters to classify between ASC and neurotypical controls. Data was based on a previous task where 16 ASC participants and 14 age, IQ matched controls observed then imitated a series of hand movements. 40 kinematic parameters extracted from eight imitation conditions were analysed using machine learning based methods. Two optimal imitation conditions and nine most significant kinematic parameters were identified and compared with some standard attribute evaluators. To our knowledge, this is the first attempt to apply machine learning to kinematic movement parameters measured during imitation of hand movements to investigate the identification of ASC. Although based on a small sample, the work demonstrates the feasibility of applying machine learning methods to analyse high-dimensional data and suggest the potential of machine learning for identifying kinematic biomarkers that could contribute to the diagnostic classification of autism.
Ali, Habiba I; Jarrar, Amjad H; Abo-El-Enen, Mostafa; Al Shamsi, Mariam; Al Ashqar, Huda
2015-05-28
Increasing the healthfulness of campus food environments is an important step in promoting healthful food choices among college students. This study explored university students' suggestions on promoting healthful food choices from campus vending machines. It also examined factors influencing students' food choices from vending machines. Peer-led semi-structured individual interviews were conducted with 43 undergraduate students (33 females and 10 males) recruited from students enrolled in an introductory nutrition course in a large national university in the United Arab Emirates. Interviews were audiotaped, transcribed, and coded to generate themes using N-Vivo software. Accessibility, peer influence, and busy schedules were the main factors influencing students' food choices from campus vending machines. Participants expressed the need to improve the nutritional quality of the food items sold in the campus vending machines. Recommendations for students' nutrition educational activities included placing nutrition tips on or beside the vending machines and using active learning methods, such as competitions on nutrition knowledge. The results of this study have useful applications in improving the campus food environment and nutrition education opportunities at the university to assist students in making healthful food choices.
The upgraded Large Plasma Device, a machine for studying frontier basic plasma physics.
Gekelman, W; Pribyl, P; Lucky, Z; Drandell, M; Leneman, D; Maggs, J; Vincena, S; Van Compernolle, B; Tripathi, S K P; Morales, G; Carter, T A; Wang, Y; DeHaas, T
2016-02-01
In 1991 a manuscript describing an instrument for studying magnetized plasmas was published in this journal. The Large Plasma Device (LAPD) was upgraded in 2001 and has become a national user facility for the study of basic plasma physics. The upgrade as well as diagnostics introduced since then has significantly changed the capabilities of the device. All references to the machine still quote the original RSI paper, which at this time is not appropriate. In this work, the properties of the updated LAPD are presented. The strategy of the machine construction, the available diagnostics, the parameters available for experiments, as well as illustrations of several experiments are presented here.
A Case Study of Employing A Single Server Nonpreemptive Priority Queuing Model at ATM Machine
Abdullah Furquan; Abdullah Imran
2015-01-01
This paper discusses a case study of employing a single server nonpreemptivepriorityqueuing model [1]at ATM machine which originally operates on M/M/1 model. In this study we have taken two priority classes of people in following order:- .Priority class 1- woman .Priority class 2- man Sometimea long queue is formed at ATMmachine (single server)but the bank management don’t have enough money to invest on installing new ATM machine.In this situation we want to apply single ser...
Directory of Open Access Journals (Sweden)
Debkalpa Goswami
2014-01-01
Full Text Available Electrochemical micromachining (EMM appears to be a very promising micromachining process for having higher machining rate, better precision and control, reliability, flexibility, environmental acceptability, and capability of machining a wide range of materials. It permits machining of chemically resistant materials, like titanium, copper alloys, super alloys and stainless steel to be used in biomedical, electronic, micro-electromechanical system and nano-electromechanical system applications. Therefore, the optimal use of an EMM process for achieving enhanced machining rate and improved profile accuracy demands selection of its various machining parameters. Various optimization tools, primarily Derringer’s desirability function approach have been employed by the past researchers for deriving the best parametric settings of EMM processes, which inherently lead to sub-optimal or near optimal solutions. In this paper, an attempt is made to apply an almost new optimization tool, i.e. differential search algorithm (DSA for parametric optimization of three EMM processes. A comparative study of optimization performance between DSA, genetic algorithm and desirability function approach proves the wide acceptability of DSA as a global optimization tool.
Varela, J; Moncuquet, M
2016-01-01
The aim of this study is to simulate the interaction of the solar wind with the Hermean magnetosphere when the interplanetary magnetic field is weak, performing a parametric study for all the range of hydrodynamic values of the solar wind predicted on Mercury for the ENLIL + GONG WSA + Cone SWRC model: density from $12$ to $180$ cm$^{-3}$, velocity from $200$ to $500$ km/s and temperatures from $2 \\cdot 10^4$ to $18 \\cdot 10^4$ K, and compare the results with a real MESSENGER orbit as reference case. We use the code PLUTO in spherical coordinates and an asymmetric multipolar expansion for the Hermean magnetic field. The study shows for all simulations a stand off distance larger than the Mercury radius and the presence of close magnetic field lines on the day side of the planet, so the dynamic pressure of the solar wind is not high enough to push the magnetopause on the planet surface if the interplanetary magnetic field is weak. The simulations with large dynamic pressure lead to a large compression of the H...
Scott, Serena J.; Salgaonkar, Vasant; Prakash, Punit; Burdette, E. Clif; Diederich, Chris J.
2017-03-01
Preferential acoustic absorption and heating of bone can significantly impact interstitial ultrasound ablation of tumors within or bordering the spine. Furthermore, intervening cortical bone may provide acoustic and thermal insulation that can protect sensitive structures nearby, such as the spinal cord. The objectives of this study are firstly, to apply parametric and patient-specific models to theoretically assess the feasibility of interstitial ultrasound ablation of tumors within and near the spine, and secondly, to identify potential energy delivery strategies, safety criteria, advantages, and disadvantages of interstitial ultrasound in this setting. Transient biothermal models using previously validated approximations for power deposition within bone from interstitial sources were employed. Multilayered axisymmetric models were used to perform a parametric assessment of the impact of tumor dimensions, attenuation (dependent on residual bone content), perfusion, and maximum temperature thresholds on necessary treatment parameters and on treatment effectiveness. 3D patient-specific finite element models were generated based on segmented CT scans for nine representative patient cases selected to bracket a range of clinical interest, with tumors in or near the vertebrae, sacrum, and ilium. Tumors were 10-27 mm in diameter, 10-43 mm long, and 0-14 mm from the spinal canal. Paraspinal tumors, osteolytic vertebral tumors, and a mixed osteolytic/osteoblastic iliac bone tumor were considered. 7 MHz (1.5 mm OD) and 3.0 MHz (3.2 mm OD) applicators with an array of 1-4 tubular transducers (0.5 -1.5 cm long, 150-360° sector angles), were applied in various implant configurations. Variable thicknesses of bone insulating critical anatomy from the tumor and insulation of the spinal cord with injected carbon dioxide were also investigated for definition of safety margins and possible protection of critical structures. 6-44 mm diameter osteolytic tumors surrounded by bone and
Experimental Study of Machinability in Mill-grinding of SiCp/Al Composites
Institute of Scientific and Technical Information of China (English)
LI Jianguang; DU Jinguang; YAO Yingxue; HAO Zhaopeng; LIU Xiao
2014-01-01
An attempt was made to investigate the machinability of SiCp/Al composites based on the experimental study using mill-grinding processing method. The experiments were carried out on a high-speed CNC machining center using integrated abrasive cutting tool. The effects of combined machining parameters, e g, cutting speed (vs), feed rate (vf), and depth of cut (ap), with the same change of material removal rate (MRR) on the mill-grinding force and surface roughness (Ra) were investigated. The formation mechanism of typical machined surface defects was analyzed by SEM. The experimental results reveal that with the same change of material removal rate, lower mill-grinding force values can be gained by increasing depth of cut and feed rate simultaneously at higher cutting speed. With the same change of MRR value, lower surface roughness values can be gained by increasing the feed rate at higher cutting speed, rather than just increasing the depth of cut, or increasing the feed rate and depth of cut simultaneously. The machined surface of SiCp/Al composites reveals typical defects which can influence surface integrity.
End mill tools integration in CNC machining for rapid manufacturing processes: simulation studies
Directory of Open Access Journals (Sweden)
Muhammed Nafis Osman Zahid
2015-01-01
Full Text Available Computer numerical controlled (CNC machining has been recognized as a manufacturing process that is capable of producing metal parts with high precision and reliable quality, whereas many additive manufacturing methods are less capable in these respects. The introduction of a new layer-removal methodology that utilizes an indexing device to clamp the workpiece can be used to extend CNC applications into the realm of rapid manufacturing (CNC-RM processes. This study aims to improve the implementation of CNC machining for RM by formulating a distinct approach to integrate end mill tools during finishing processes. A main objective is to enhance process efficiency by minimizing the staircasing effect of layer removal so as to improve the quality of machined parts. In order to achieve this, different types of end mill tools are introduced to cater for specific part surfaces during finishing operations. Virtual machining simulations are executed to verify the method and the implications. The findings indicate the advantages of the approach in terms of cutting time and excess volume left on the parts. It is shown that using different tools for finishing operations will improve the capabilities of CNC machining for rapid manufacturing applications.
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Mat Deris Ashanira
2016-01-01
Full Text Available Electric Discharge Machining (EDM is one of the modern machining which is capable in handling hard and difficult-to-machine material. The successful of EDM basically depends on its performances such as surface roughness (Ra, material removal rate (MRR, electrode wear rate (EWR and dimensional accuracy (DA. Ra is considered as the most important performance due to it role as a technological quality measurement for a product and also a factor that significantly affects the manufacturing process. This paper presents the experimental study of surface roughness in die sinking EDM using stainless steel SS316L with copper impregnated graphite electrode. The machining experimental is conducted based on the two levels full factorial design of design of experiment (DOE with five machining parameters which are peak current, servo voltage, servo speed, pulse on time and pulse off time. The results were analyzed using grey relational analysis (GRA and it was found that pulse on time and servo voltage give the most influence to the Ra value.
Machinability Study of Hybrid Nanoclay-Glass Fibre Reinforced Polyester Composites
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P. Prabhu
2013-01-01
Full Text Available Glass fibre reinforced polyester composites (GRP and hybrid nanoclay and glass fibre reinforced polyester nanocomposites (CGRP are fabricated by vacuum assisted resin infusion technique. The optimum mechanical properties are obtained for CGRP with 3 wt.% nanoclay. Three types of drills (carbide twist drill D 5407060, HSS twist drill BS-328, and HSS end mill (4 flutes “N”-type end mill RH-helical flute of 6 mm diameters are used to drill holes on GRP and CGRP. Three different speeds (600, 852, and 1260 rpm and two different feeds (0.045, 0.1 mm/rev are selected as process parameters. The effect of process parameter on thrust force and delamination during drilling CGRP is analyzed for optimizing the machining parameters. The delamination factor is low for the optimum process parameter (feed = 0.1 mm/rev and speed 852 rpm. Microstructural analysis confirms that at higher feeds, delamination is low for CGRP drilled with carbide tools. In order to analyze the effect of nanoclay in CGRP on tool wear, 200 holes were drilled on CGRP samples with 3 wt.% nanoclay, and the tool wear is analyzed under optimized parametric condition. Tool wear is high in HSS twist drill compared with carbide drill. The presence of nanoclay also accelerates the tool wear.
Study of the Induction Machine Unsymmetrical Condition Using In Total Fluxes Equations
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SIMION, A.
2010-02-01
Full Text Available On the basis of the mathematical model, called in total fluxes in a previous paper, and which is proper for the analysis of transient operation of the two-phase induction machine, one obtains the symmetrical steady-state equations, which are valid for three-phase machines, as well. The obtained mathematical expressions are much more simple and easier to use than the consecrated ones, which are generally applied in scientific literature. Moreover, considerations are to be made upon the space-time rotational vectors, emphasizing their importance in understanding the physical phenomena that characterize induction machines. The use of these space vectors is further tested out for the study of unsymmetrical supply, which gives a much faster method in obtaining the electromagnetic torque expression. Finally, the results are compared with the ones that come out from the traditional methods, more exactly, the symmetric component method.
Xiong, Yuan
2017-05-02
This study presents an experimental work investigating the controlling parameters on the formation of an electrically-induced inner toroidal vortex (ITV) near a nozzle rim in small, laminar nonpremixed coflow flames, when an alternating current is applied to the nozzle. A systematic parametric study was conducted by varying the flow parameters of the fuel and coflowing-air velocities, and the nozzle diameter. The fuels tested were methane, ethylene, ethane, propane, n-butane, and i-butane, each representing different ion-generation characteristics and sooting tendencies. The results showed that the fluid dynamic effects on ITV formation were weak, causing only mild variation when altering flow velocities. However, increased fuel velocity resulted in increased polycyclic aromatic hydrocarbon (PAH) formation, which promoted ITV formation. When judging the ITV-formation tendency based on critical applied voltage and frequency, it was qualitatively well correlated with the PAH concentration and the relative location of PAHs to the nozzle rim. The sooting tendency of the fuels did not affect the results much. A change in the nozzle diameter highlighted the importance of the relative distance between the PAH zone and the nozzle rim, indicating the role of local electric-field intensity on ITV formation. Detailed onset conditions, characteristics of near-nozzle flow patterns, and PAH distributions are also discussed.
Zhu, Xiaowei; Iungo, G. Valerio; Leonardi, Stefano; Anderson, William
2017-02-01
For a horizontally homogeneous, neutrally stratified atmospheric boundary layer (ABL), aerodynamic roughness length, z_0, is the effective elevation at which the streamwise component of mean velocity is zero. A priori prediction of z_0 based on topographic attributes remains an open line of inquiry in planetary boundary-layer research. Urban topographies - the topic of this study - exhibit spatial heterogeneities associated with variability of building height, width, and proximity with adjacent buildings; such variability renders a priori, prognostic z_0 models appealing. Here, large-eddy simulation (LES) has been used in an extensive parametric study to characterize the ABL response (and z_0) to a range of synthetic, urban-like topographies wherein statistical moments of the topography have been systematically varied. Using LES results, we determined the hierarchical influence of topographic moments relevant to setting z_0. We demonstrate that standard deviation and skewness are important, while kurtosis is negligible. This finding is reconciled with a model recently proposed by Flack and Schultz (J Fluids Eng 132:041203-1-041203-10, 2010), who demonstrate that z_0 can be modelled with standard deviation and skewness, and two empirical coefficients (one for each moment). We find that the empirical coefficient related to skewness is not constant, but exhibits a dependence on standard deviation over certain ranges. For idealized, quasi-uniform cubic topographies and for complex, fully random urban-like topographies, we demonstrate strong performance of the generalized Flack and Schultz model against contemporary roughness correlations.
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Peyman Kor
2016-12-01
Full Text Available The deposition of asphaltenes on the inner wall of oil wells and pipelines causes flow blockage and significant production loss in these conduits. The major underlying mechanism(s for the deposition of asphaltene particles from the oil stream are still under investigation as an active research topic in the literature. In this work, a new deposition model considering both diffusional and inertial transport of asphaltene toward the tubing surface was developed. Model predictions were compared and verified with two sound experimental data available in the literature to evaluate the model's performance. A parametric study was done using the validated model in order to investigate the effect of the asphaltene particle size, flow velocity and oil viscosity on the magnitude of asphaltene deposition rate. Results of the study revealed that increasing the oil velocity causes more drag force on wall's inner surface; consequently, particles tend to transport away from the surface and the rate of asphaltene deposition is decreased. In addition, the developed model predicts that at low fluid velocity (∼0.7 m/s, the less viscous oil is more prone to asphaltene deposition problem.
The Dynamic Study of the Weft Insertion of Air Jet Weaving Machines
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Gabriella Oroszlány
2010-10-01
Full Text Available The application of the air jet loom is widespread in the textile industry because ofits high productivity, convenient controllability, high filling insertion rate, low noise andlow vibration levels. Air stream in confusor guides can be classified into two types. A weftyarn ejected with high speed air flow is given the drag force caused by friction between theweft yarn and the air flow. In this article we show the study of the dynamics of the type Pair jet weaving machines and the definition of the skin friction coefficient for multifilamentweft. We have given a calculation procedure for the dynamic description of the insertionprocess of weaving machines marked P.
Comparative aspects about the studying methods of cast irons machinability, based on the tool wear
Carausu, C.; Pruteanu, O.
2016-08-01
The paper presents some considerations of the authors, regarding the studying methods of the cast irons machinability, based on the tools wear on drilling operations. Are described the conditions in which the experimental researches were conducted, intended to offer an overview on drilling machinability of some cast irons categories. It is presented a comparison between long-term methods and short-term methods, for determining the optimal speed chipping of a grey cast iron with lamellar graphite, with average values of tensile strength. Are described: the research methodology, obtained results and conclusions drawn after the results analysis.
Machine Learning Approaches for High-resolution Urban Land Cover Classification: A Comparative Study
Energy Technology Data Exchange (ETDEWEB)
Vatsavai, Raju [ORNL; Chandola, Varun [ORNL; Cheriyadat, Anil M [ORNL; Bright, Eddie A [ORNL; Bhaduri, Budhendra L [ORNL; Graesser, Jordan B [ORNL
2011-01-01
The proliferation of several machine learning approaches makes it difficult to identify a suitable classification technique for analyzing high-resolution remote sensing images. In this study, ten classification techniques were compared from five broad machine learning categories. Surprisingly, the performance of simple statistical classification schemes like maximum likelihood and Logistic regression over complex and recent techniques is very close. Given that these two classifiers require little input from the user, they should still be considered for most classification tasks. Multiple classifier systems is a good choice if the resources permit.
A comparison study of two Tricept units for reconfigurable parallel kinematic machines
Institute of Scientific and Technical Information of China (English)
Shi Junshan; Tang Xiaoqiang; Lin Chunshen; Wang Liping
2005-01-01
This paper presents a comparison study of workspace and dexterity of two Tricept units for Reconfigurable Parallel Kinematic Machines (RPKMs). The modular leg of RPKMs is designed and the RPKMs can be built by changing the setting of modules. A compositive kinematic model is developed accordingly. The inverse kinematics and Jacobian of these two Tricept units are analyzed. Considering workspace volume and dexterity, the effects of geometric size of some modules on the two Tricept units are discussed. In the end, comparison results of these two Tricept units are given. The comparison of two kinds of Parallel Kinematic Machines (PKMs) can be of help in the design and configuration planning of the RPKMs.
Parametric functional principal component analysis.
Sang, Peijun; Wang, Liangliang; Cao, Jiguo
2017-03-10
Functional principal component analysis (FPCA) is a popular approach in functional data analysis to explore major sources of variation in a sample of random curves. These major sources of variation are represented by functional principal components (FPCs). Most existing FPCA approaches use a set of flexible basis functions such as B-spline basis to represent the FPCs, and control the smoothness of the FPCs by adding roughness penalties. However, the flexible representations pose difficulties for users to understand and interpret the FPCs. In this article, we consider a variety of applications of FPCA and find that, in many situations, the shapes of top FPCs are simple enough to be approximated using simple parametric functions. We propose a parametric approach to estimate the top FPCs to enhance their interpretability for users. Our parametric approach can also circumvent the smoothing parameter selecting process in conventional nonparametric FPCA methods. In addition, our simulation study shows that the proposed parametric FPCA is more robust when outlier curves exist. The parametric FPCA method is demonstrated by analyzing several datasets from a variety of applications. © 2017, The International Biometric Society.
Xie, Hong-Bo; Huang, Hu; Wu, Jianhua; Liu, Lei
2015-02-01
We present a multiclass fuzzy relevance vector machine (FRVM) learning mechanism and evaluate its performance to classify multiple hand motions using surface electromyographic (sEMG) signals. The relevance vector machine (RVM) is a sparse Bayesian kernel method which avoids some limitations of the support vector machine (SVM). However, RVM still suffers the difficulty of possible unclassifiable regions in multiclass problems. We propose two fuzzy membership function-based FRVM algorithms to solve such problems, based on experiments conducted on seven healthy subjects and two amputees with six hand motions. Two feature sets, namely, AR model coefficients and room mean square value (AR-RMS), and wavelet transform (WT) features, are extracted from the recorded sEMG signals. Fuzzy support vector machine (FSVM) analysis was also conducted for wide comparison in terms of accuracy, sparsity, training and testing time, as well as the effect of training sample sizes. FRVM yielded comparable classification accuracy with dramatically fewer support vectors in comparison with FSVM. Furthermore, the processing delay of FRVM was much less than that of FSVM, whilst training time of FSVM much faster than FRVM. The results indicate that FRVM classifier trained using sufficient samples can achieve comparable generalization capability as FSVM with significant sparsity in multi-channel sEMG classification, which is more suitable for sEMG-based real-time control applications.
Ivanova, Violeta M.; Sousa, Rita; Murrihy, Brian; Einstein, Herbert H.
2014-06-01
This paper presents results from research conducted at MIT during 2010-2012 on modeling of natural rock fracture systems with the GEOFRAC three-dimensional stochastic model. Following a background summary of discrete fracture network models and a brief introduction of GEOFRAC, the paper provides a thorough description of the newly developed mathematical and computer algorithms for fracture intensity, aperture, and intersection representation, which have been implemented in MATLAB. The new methods optimize, in particular, the representation of fracture intensity in terms of cumulative fracture area per unit volume, P32, via the Poisson-Voronoi Tessellation of planes into polygonal fracture shapes. In addition, fracture apertures now can be represented probabilistically or deterministically whereas the newly implemented intersection algorithms allow for computing discrete pathways of interconnected fractures. In conclusion, results from a statistical parametric study, which was conducted with the enhanced GEOFRAC model and the new MATLAB-based Monte Carlo simulation program FRACSIM, demonstrate how fracture intensity, size, and orientations influence fracture connectivity.
Chakraborty, Pritam; Biner, S. Bulent
2015-10-01
Ferritic-martensitic steels are currently being considered as structural materials in fusion and Gen-IV nuclear reactors. These materials are expected to experience high dose radiation, which can increase their ductile to brittle transition temperature and susceptibility to failure during operation. Hence, to estimate the safe operational life of the reactors, precise evaluation of the ductile to brittle transition temperatures of ferritic-martensitic steels is necessary. Owing to the scarcity of irradiated samples, particularly at high dose levels, micro-mechanistic models are being employed to predict the shifts in the ductile to brittle transition temperatures. These models consider the ductile damage evolution, in the form of nucleation, growth and coalescence of voids; and the brittle fracture, in the form of probabilistic cleavage initiation, to estimate the influence of irradiation on the ductile to brittle transition temperature. However, the assessment of irradiation dependent material parameters is challenging and influences the accuracy of these models. In the present study, the effects of irradiation on the overall flow stress and ductile damage behavior of two ferritic-martensitic steels is parametrically investigated. The results indicate that the ductile damage model parameters are mostly insensitive to irradiation levels at higher dose levels though the resulting flow stress behavior varies significantly.
Rozendaal, Rodger A.
1986-01-01
The Variable Sweep Transition Flight Experiment (VSTFE) was initiated to establish a boundary-layer transition data base for laminar flow wing design. For this experiment, full-span upper-surface gloves will be fitted to a variable sweep F-14 aircraft. The results of two initial tasks are documented: a parametric pressure distribution/boundary-layer stability study and the design of an upper-surface glove for Mach 0.8. The first task was conducted to provide a data base from which wing-glove pressure distributions could be selected for glove designs. Boundary-layer stability analyses were conducted on a set of pressure distributions for various wing sweep angles, Mach numbers, and Reynolds number in the range of those anticipated for the flight-test program. The design procedure for the Mach 0.8 glove is described, and boundary-layer stability calculations and pressure distributions are presented both at design and off-design conditions. Also included is the analysis of the clean-up glove (smoothed basic wing) that will be flight-tested initially and the analysis of a Mach 0.7 glove designed at the NASA Langley Research Center.
Kratz, Jonathan L.; Chapman, Jeffryes W.; Guo, Ten-Huei
2017-01-01
The efficiency of aircraft gas turbine engines is sensitive to the distance between the tips of its turbine blades and its shroud, which serves as its containment structure. Maintaining tighter clearance between these components has been shown to increase turbine efficiency, increase fuel efficiency, and reduce the turbine inlet temperature, and this correlates to a longer time-on-wing for the engine. Therefore, there is a desire to maintain a tight clearance in the turbine, which requires fast response active clearance control. Fast response active tip clearance control will require an actuator to modify the physical or effective tip clearance in the turbine. This paper evaluates the requirements of a generic active turbine tip clearance actuator for a modern commercial aircraft engine using the Commercial Modular Aero-Propulsion System Simulation 40k (C-MAPSS40k) software that has previously been integrated with a dynamic tip clearance model. A parametric study was performed in an attempt to evaluate requirements for control actuators in terms of bandwidth, rate limits, saturation limits, and deadband. Constraints on the weight of the actuation system and some considerations as to the force which the actuator must be capable of exerting and maintaining are also investigated. From the results, the relevant range of the evaluated actuator parameters can be extracted. Some additional discussion is provided on the challenges posed by the tip clearance control problem and the implications for future small core aircraft engines.
Directory of Open Access Journals (Sweden)
Nancy K. Dess
2013-11-01
Full Text Available Naïve humans and rats voluntarily consume little ethanol at concentrations above ~6% due to its aversive flavor. Developing procedures that boost intake of ethanol or ethanol-paired flavors facilitates research on neural mechanisms of ethanol-associated behaviors and helps identify variables that modulate ethanol intake outside of the lab. The present study explored the impact on consumption of ethanol and ethanol-paired flavors of nutritionally significant parametric variations: ethanol vehicle (gelatin or solution, with or without polycose; ethanol concentration (4% or 10%; and feeding status (chow deprived or ad lib. during flavor conditioning and flavor preference testing. Individual differences were modeled by testing rats of lines selectively bred for high (HiS or low (LoS saccharin intake. A previously reported preference for ethanol-paired flavors was replicated when ethanol had been drunk during conditioning. However, indifference or aversion to ethanol-paired flavors generally obtained when ethanol had been eaten in gelatin during conditioning, regardless of ethanol concentration, feeding status, or caloric value of the vehicle. Modest sex and line variations occurred. Engaging different behavioral systems when eating gelatin, rather than drinking solution, may account for these findings. Implications for parameter selection in future neurobiological research and for understanding conditions that influence ethanol intake outside of the lab are discussed.
Kari, Otto K; Rojalin, Tatu; Salmaso, Stefano; Barattin, Michela; Jarva, Hanna; Meri, Seppo; Yliperttula, Marjo; Viitala, Tapani; Urtti, Arto
2017-04-01
When nanocarriers are administered into the blood circulation, a complex biomolecular layer known as the "protein corona" associates with their surface. Although the drivers of corona formation are not known, it is widely accepted that this layer mediates biological interactions of the nanocarrier with its surroundings. Label-free optical methods can be used to study protein corona formation without interfering with its dynamics. We demonstrate the proof-of-concept for a multi-parametric surface plasmon resonance (MP-SPR) technique in monitoring the formation of a protein corona on surface-immobilized liposomes subjected to flowing 100 % human serum. We observed the formation of formulation-dependent "hard" and "soft" coronas with distinct refractive indices, layer thicknesses, and surface mass densities. MP-SPR was also employed to determine the affinity (K D ) of a complement system molecule (C3b) with cationic liposomes with and without polyethylene glycol. Tendency to create a thick corona correlated with a higher affinity of opsonin C3b for the surface. The label-free platform provides a fast and robust preclinical tool for tuning nanocarrier surface architecture and composition to control protein corona formation.
Metal matrix composites synthesis, wear characteristics, machinability study of MMC brake drum
Natarajan, Nanjappan; Davim, J Paulo
2015-01-01
This book is dedicated to composite materials, presenting different synthesis processes, composite properties and their machining behaviour. The book describes also the problems on manufacturing of metal matrix composite components. Among others, it provides procedures for manufacturing of metal matrix composites and case studies.
LENUS (Irish Health Repository)
Mourao-Miranda, J
2012-05-01
To date, magnetic resonance imaging (MRI) has made little impact on the diagnosis and monitoring of psychoses in individual patients. In this study, we used a support vector machine (SVM) whole-brain classification approach to predict future illness course at the individual level from MRI data obtained at the first psychotic episode.
Machine-induced Background Simulation Studies for LHC Run 1, Run 2 and HL-LHC
Kwee-Hinzmann, Regina; Bruce, Roderik; Cerutti, Francesco; Esposito, Luigi Salvatore; Gibson, Stephen; Lechner, Anton; Garcia Morales, Hector; Yin Vallgren, Christina
2017-01-01
The study of machine-induced background to the experiments is vital for several reasons. Too much background can be an issue for operation and the difficult part is to judge when exactly “too much” is attained. It is a complex topic as experiments are directly or indirectly affected by conditions all around the LHC ring e.g. collimation settings and vacuum quality. A detailed study of background can also help understanding the machine better to identify potential issues and complemented by dedicated machine tests. Finally such a study is relevant for the experiments to analyse the characteristics of machine background to make sure not to count it into a new physics signal. This report summarises simulation results of three background sources, local beam-gas, beam-halo from the betatron collimation in IR7 and for the first time beam-halo from momentum collimation in IR3. Two of the most dominant sources, local beam-gas and betatron halo, have been systematically studied for LHC Run 1 and Run 2 cases, and ...
Giammichele, N; Fontaine, G; Brassard, P
2016-01-01
We present a prescription for parametrizing the chemical profile in the core of white dwarfs in the light of the recent discovery that pulsation modes may sometimes be deeply confined in some cool pulsating white dwarfs. Such modes may be used as unique probes of the complicated chemical stratification that results from several processes that occurred in previous evolutionary phases of intermediate-mass stars. This effort is part of our ongoing quest for more credible and realistic seismic models of white dwarfs using static, parametrized equilibrium structures. Inspired from successful techniques developed in design optimization fields (such as aerodynamics), we exploit Akima splines for the tracing of the chemical profile of oxygen (carbon) in the core of a white dwarf model. A series of tests are then presented to better seize the precision and significance of the results that can be obtained in an asteroseismological context. We also show that the new parametrization passes an essential basic test, as it ...
Validity of Parametrized Quark Propagator
Institute of Scientific and Technical Information of China (English)
ZHUJi-Zhen; ZHOULi-Juan; MAWei-Xing
2005-01-01
Based on an extensively study of the Dyson-Schwinger equations for a fully dressed quark propagator in the “rainbow”approximation, a parametrized fully dressed quark propagator is proposed in this paper. The parametrized propagator describes a confining quark propagator in hadron since it is analytic everywhere in complex p2-plane and has no Lemmann representation. The validity of the new propagator is discussed by comparing its predictions on selfenergy functions A/(p2), Bl(p2) and effective mass M$(p2) of quark with flavor f to their corresponding theoretical results produced by Dyson-Schwinger equations. Our comparison shows that the parametrized quark propagator is a good approximation to the fully dressed quark propagator given by the solutions of Dyson-Schwinger equations in the rainbow approximation and is convenient to use in any theoretical calculations.
Validity of Parametrized Quark Propagator
Institute of Scientific and Technical Information of China (English)
ZHU Ji-Zhen; ZHOU Li-Juan; MA Wei-Xing
2005-01-01
Based on an extensively study of the Dyson-Schwinger equations for a fully dressed quark propagator in the "rainbow" approximation, a parametrized fully dressed quark propagator is proposed in this paper. The parametrized propagator describes a confining quark propagator in hadron since it is analytic everywhere in complex p2-plane and has no Lemmann representation. The validity of the new propagator is discussed by comparing its predictions on selfenergy functions Af(p2), Bf(p2) and effective mass Mf(p2) of quark with flavor f to their corresponding theoretical results produced by Dyson-Schwinger equations. Our comparison shows that the parametrized quark propagator is a good approximation to the fully dressed quark propagator given by the solutions of Dyson-Schwinger equations in the rainbow approximation and is convenient to use in any theoretical calculations.
A parametric study on unbalanced three phase islanded microgrids with inverter interfaced units
DEFF Research Database (Denmark)
Sanseverino, Eleonora Riva; Quang, Ninh Nguyen; Zizzo, Gaetano;
2013-01-01
In this paper, the solution of the power flow for unbalanced three phase microgrids systems is proposed. The study aims at the integration of inverter interfaced units using the control law used for primary voltage and frequency regulation, so as to take into account possible small variations...... of these parameters to account for sudden load changes. The proposed study deals with unbalanced systems which is the typical case of small distribution systems and shows how the power losses term varies as the regulators parameters vary as well, thus showing that these are sensitive parameters that could have...... an important role in optimal management of such systems....
Beam dynamics studies and parametric characterization of a standing wave electron linac
Dash, R.; Mondal, J.; Sharma, A.; Mittal, K. C.
2013-07-01
This paper presents the results of electron beam tracking simulations for a 30 MeV standing wave electron linac at Electron Beam Centre Kharghar, Navi Mumbai, India. For the pulsed mode operation of the present linac preferential operation parameters have been determined from the results of beam dynamics studies. This electron accelerator is a general purpose facility for generation of Bremsstrahlung X-rays and neutron scattering experiments. This electron accelerator-based experimental neutron facility will be used for measurement of neutron cross-section (n,γ), (n, xn) and (n, f) reactions at different energies for various materials and material irradiation studies.
Directory of Open Access Journals (Sweden)
KUSTOV A.I.
2012-01-01
Full Text Available Dependences of physical-mechanical properties from structural parameters of material play very important role. The paper deals with the perspectives of the application of acoustic microscopy methods for studying the changes of physical - mechanical properties of materials in a condensed state under external influence. The basic principles of the methods as well as the results of the experiments of studying the structure of materials in a condensed state and its transformation upon changing the composition and types of thermomechanical treatment are given in the article. The high sensitivity to non-heterogeneity and defects upon acoustic visualization and in the regime of determining physic-mechanical properties are demonstrated.
Parametric study of radiative heat transfer in arrays of fixed discrete surfaces
Energy Technology Data Exchange (ETDEWEB)
Antoniak, Z.I.; Palmer, B.J.; Drost, M.K. [Pacific Northwest Lab., Richland, WA (United States); Welty, J.R. [Oregon State Univ., Corvallis, OR (United States)
1996-02-01
The parameter space for study of radiative transfer in and through arrays of regular elements is extremely large. The present study has developed a number of correlations, based on MCLITE code results for simple geometric elements. These correlations can guide a designer of heat exchangers in optimizing performance. When the incident radiation is diffuse, these correlations are fairly accurate. When the incident radiation is collimated, and strikes the array at some arbitrary angle, the correlations are less accurate. For detailed analysis of heat exchanger performance there is no substitute for exercising a code such as MCLITE. 4 refs., 3 figs., 3 tabs.
Parametric Study of the Roundhead for the New Port of La Coruna at Punta Langosteira
DEFF Research Database (Denmark)
Burcharth, H. F.; Haagensen, Per
The Port of La Coruna, Spain is to be expanded by a new port at Punta Langosteria. The Port Authority of La Coruna has by contract of October 28, 2002, retained the Hydraulic and Coastal Engineering Laboratory at Aalborg University, Denmark, to make a systematic model test study of the breakwater...
A Parametric Study of Stability of Geotextile-Reinforced Soil Above an Underground Cavity
DEFF Research Database (Denmark)
poor, Abbas Tahmasebi; Noorzad, R.; Shooshpasha, E.;
2012-01-01
A study based on two-dimensional finite element analyses under plane strain condition was performed by PLAXIS code to investigate the behavior of geotextilereinforced soil above an underground cavity. The effects of depth of single layer, tensile stiffness, number and length of reinforcement laye...
Wind‐gust parametrizations at heights relevant for wind energy: a study based on mast observations
DEFF Research Database (Denmark)
Suomi, I.; Vihma, T.; Gryning, Sven-Erik;
2013-01-01
gustiness conditions were studied using observations from two coastal/archipelago weather masts in the Gulf of Finland (northern Europe) with observation heights between 30 and 143 m. Only moderate and strong wind cases were addressed. Both masts were located over relatively flat terrain but the local...
Parametric study of multiple configurations of pico hydrokinetic turbines using CFD
Directory of Open Access Journals (Sweden)
Yogaraja Balakrishnan
2016-01-01
Full Text Available This paper aims to study the river flow characteristics over pico hydrokinetic turbines with variation of arrangement using computational fluid dynamics (CFD software. This study is required to obtain the optimum spacing and angle between the turbines which leads to higher turbine effective utilisation and performance in terms of power generated. In this study, a river model is created in CFD software to simulate the water flow over the turbines as they are placed in a river to obtain the water flow characteristic. Different types of array arrangements are simulated in the river model. Multiple turbines are used to accumulate more power. The turbine model which consists of eight turbines is arranged in series with different spacing, ranging from a size of diameter (1D to four times diameter (4D of turbine is simulated to identify the optimum spacing between the turbines. Then, the simulation is continued using a sufficient spacing of 0.5D with angles ranging of 10° to 60° from datum of original position to minimise the disruption of the aquatic environment. The velocity profiles of each turbine are obtained and analysed. The 4D spacing and 40° angle displayed higher average velocities compared to other arrangements. Thus, from this study, the 4D and 40° are deduced as the optimum spacing and angle, respectively.
A parametric study of a solar calcinator using computational fluid dynamics
Energy Technology Data Exchange (ETDEWEB)
Fidaros, D.K.; Baxevanou, C.A.; Vlachos, N.S. [University of Thessaly, Volos (Greece). Laboratory of Fluid Mechanics and Turbomachines, Department of Mechanical and Industrial Engineering
2007-11-15
In this work a horizontal rotating solar calcinator is studied numerically using computational fluid dynamics. The specific solar reactor is a 10 kW model designed and used for efficiency studies. The numerical model is based on the solution of the Navier-Stokes equations for the gas flow, and on Lagrangean dynamics for the discrete particles. All necessary mathematical models were developed and incorporated into a computational fluid dynamics model with the influence of turbulence simulated by a two-equation (RNG k-{epsilon}) model. The efficiency of the reactor was calculated for different thermal inputs, feed rates, rotational speeds and particle diameters. The numerically computed degrees of calcination compared well with equivalent experimental results. (author)
Parametric Study of Pulse-Combustor-Driven Ejectors at High-Pressure
Yungster, Shaye; Paxson, Daniel E.; Perkins, Hugh D.
2015-01-01
Pulse-combustor configurations developed in recent studies have demonstrated performance levels at high-pressure operating conditions comparable to those observed at atmospheric conditions. However, problems related to the way fuel was being distributed within the pulse combustor were still limiting performance. In the first part of this study, new configurations are investigated computationally aimed at improving the fuel distribution and performance of the pulse-combustor. Subsequent sections investigate the performance of various pulse-combustor driven ejector configurations operating at highpressure conditions, focusing on the effects of fuel equivalence ratio and ejector throat area. The goal is to design pulse-combustor-ejector configurations that maximize pressure gain while achieving a thermal environment acceptable to a turbine, and at the same time maintain acceptable levels of NOx emissions and flow non-uniformities. The computations presented here have demonstrated pressure gains of up to 2.8%.
Quasi-Dimensional Modelling and Parametric Studies of a Heavy-Duty HCCI Engine
Directory of Open Access Journals (Sweden)
Sunil Kumar Pandey
2011-01-01
Full Text Available A quasi-dimensional modelling study is conducted for the first time for a heavy duty, diesel-fuelled, multicylinder engine operating in HCCI mode. This quasidimensional approach involves a zero-dimensional single-zone homogeneous charge compression ignition (HCCI combustion model along with a one-dimensional treatment of the intake and exhaust systems. A skeletal chemical kinetic scheme for n-heptane was used in the simulations. Exhaust gas recirculation (EGR and compression ratio (CR were the two parameters that were altered in order to deal with the challenges of combustion phasing control and operating load range extension. Results from the HCCI mode simulations show good potential when compared to conventional diesel performance with respect to important performance parameters such as peak firing pressure, specific fuel consumption, peak pressure rise, and combustion noise. This study shows that HCCI combustion mode can be employed at part load of 25% varying the EGR rates between 0 and 60%.
Parametric Study of Two-Body Floating-Point Wave Absorber
Institute of Scientific and Technical Information of China (English)
Atena Amiri; Roozbeh Panahi; Soheil Radfar
2016-01-01
In this paper, we present a comprehensive numerical simulation of a point wave absorber in deep water. Analyses are performed in both the frequency and time domains. The converter is a two-body floating-point absorber (FPA) with one degree of freedom in the heave direction. Its two parts are connected by a linear mass-spring-damper system. The commercial ANSYS-AQWA software used in this study performs well in considering validations. The velocity potential is obtained by assuming incompressible and irrotational flow. As such, we investigated the effects of wave characteristics on energy conversion and device efficiency, including wave height and wave period, as well as the device diameter, draft, geometry, and damping coefficient. To validate the model, we compared our numerical results with those from similar experiments. Our study results can clearly help to maximize the converter’s efficiency when considering specific conditions.
Directory of Open Access Journals (Sweden)
Erica Claustro
2013-06-01
Full Text Available This paper is an investigation of the Melbourne Recital Centre as a case study to define the parameters necessary for good acoustical quality as it relates to the Binaural Quality Index and determining the intimacy of the hall by its initial time delay gap. The Melbourne Recital Centre, designed by Ashton Raggatt McDougall Architects, is a significant case study, as its design was driven by the acoustic requirements of reflection and diffusion through Odeon Acoustical Software. It achieves the same acoustical quality of older, ornately designed shoebox concert halls, from the perspective of contemporary design and fabrication tools and techniques. The sleek design of the Melbourne Recital Centre successfully reflects sound waves in low, mid, and high frequencies due to corresponding wall panel differentiation in the corresponding scales, as engineered by Arup Acoustics.
Parametric Study of Square Concrete Filled Steel Tube Columns Subjected To Concentric Loading
Directory of Open Access Journals (Sweden)
Bhushan H. Patil
2014-08-01
Full Text Available The Concrete Filled Steel Tube (CFST member has many advantages compared with the conventional concrete structural member. This study presents on the behaviour of concrete-filled steel tube (CFST columns under axial load by changing parameters. The parameters are thickness of steel tube, Grade of concrete and length of column. The study was conducted using ANSYS 13 finite element software. All the columns are 60 X 60 mm in size. The thickness of the tube is taken as 2, 3, 4, 5 and 6 mm for thickness variation. The grades of concrete infill are M25, M30, M40, M50, M60 and M70 used for grade variation. Lengths of columns are taken as 900, 1200, 1500, 1800, 2100, and 2400 mm for length variation. Buckling load is compared with Euro code 4 (1994.
Directory of Open Access Journals (Sweden)
Srivathsa B.
2015-12-01
Full Text Available Thermal barrier coatings (TBCs are widely used on different hot components of gas turbine engines such as blades and vanes. Although, several mechanisms for the failure of the TBCs have been suggested, it is largely accepted that the durability of these coatings is primarily determined by the residual stresses that are developed during the thermal cycling. In the present study, the residual stress build-up in an electron beam physical vapour deposition (EB-PVD based TBCs on a coupon during thermal cycling has been studied by varying three parameters such as the cooling rate, TBC thickness and substrate thickness. A two-dimensional thermomechanical generalized plane strain finite element simulations have been performed for thousand cycles. It was observed that these variations change the stress profile significantly and the stress severity factor increases non-linearly. Overall, the predictions of the model agree with reported experimental results and help in predicting the failure mechanisms.
Parametric Study of the Scavenging Process in Marine Two-Stroke Diesel Engines
DEFF Research Database (Denmark)
Andersen, Fredrik Herland; Mayer, Stefan
2015-01-01
in axial velocity and the formation ofcentral recirculation zones, known as vortex breakdown. Thispaper will present a CFD analysis of the scavenging process ina MAN B&W two-stroke diesel engine. The study include aparameter sweep where the operating conditions such as airamount, port timing and scavenging...... pressure are varied. TheCFD model comprise the full geometry from scavenge receiverto exhaust receiver. Asymmetric inlet and outlet conditions isincluded as well as the dynamics of a moving piston and valve.Time resolved boundary conditions corresponding tomeasurements from an operating, full scale...... production, engineas well as realistic initial conditions are used in the simulations.The CFD model provides a detailed description of the incylinderflow from exhaust valve opening (EVO) to exhaustvalve closing (EVC). The study reveals a close couplingbetween the volume flow (delivery ratio) and the in...
Energy Technology Data Exchange (ETDEWEB)
Poletiko, C.; Hueber, C. [Inst. de Protection et de Surete Nucleaire, C.E. Cadarache, St. Paul-lez-Durance (France); Fabre, B. [CISI, C.E. Cadarache, St. Paul-lez-Durance (France)
1996-12-01
In case of severe nuclear accident, radioactive material may be released into the environment. Among the fission products involved, are the very volatile iodine isotopes. However, the chemical forms are not well known due to the presence of different species in the containment with which iodine may rapidly react to form aerosols, molecular iodine, hydroiodic acid and iodo-organics. Tentative explanations of different mechanisms were performed through benchscale tests. A series of tests has been performed at AEA Harwell (GB) to study parameters such as pH, dose rate, concentration, gas flow rate, temperature in relation to molecular iodine production, under dynamic conditions. Another set of tests has been performed in AECL Whiteshell (CA) to study the behaviour of painted coupons, standing in gas phase or liquid phase or both, with iodine compounds under radiation. The purpose of our paper is to synthesize the data and compare the results to the IODE code calculation. Some parameters of the code were studied to fit the experimental result the best. A law, concerning the reverse reaction of iodide radiolytic oxidation, has been proposed versus: pH, concentrations and gas flow-rate. This law does not apply for dose rate variations. For the study of painted coupons, it has been pointed out that molecular iodine tends to be adsorbed or chemically absorbed on the surface in gas phase, but the mechanism should be more sophisticated in the aqueous phase. The iodo-organics present in liquid phase tend to be partly or totally destroyed by oxidation under radiation (depending upon the dose delivered). These points are discussed. (author) 18 figs., 3 tabs., 15 refs.
Parametric study of the Noble's action potential model for cardiac Purkinje fibers
Energy Technology Data Exchange (ETDEWEB)
Wang, P.K.C. [Department of Electrical Engineering, University of California, Los Angeles, CA 90095-1594 (United States); Kogan, B.Y. [Department of Computer Science, University of California, Los Angeles, CA 90095-1594 (United States)]. E-mail: kogan@cs.ucla.edu
2007-08-15
The effect of parameter variation on repolarization processes in the Noble model (Hodjkin-Huxley type) for action potential (AP) generation in Purkinje cells is studied using a combination of computer simulation and nonlinear dynamic system theory including Hopf bifurcation analysis. Both the original Noble model and a simplified Noble model are used in this study. It is shown that these models have similar qualitative dynamic behavior in the presence of parameter variations. In particular, it is demonstrated that both normal and abnormal modes of cell performance can be obtained by varying the potassium and anion conductances. The abnormal mode (cardiac arrest) may play a significant role in disorganizing the electrical activities in the heart muscles. The existence of Hopf bifurcation with respect to variations in the anion conductance and fixed values of potassium conductances is studied in detail. The regions corresponding to spontaneous AP excitation, and various types of cardiac arrest in the ion-conductance parameter space of both full and simplified Noble models with and without external stimuli are mapped out using computer simulation.
Energy Technology Data Exchange (ETDEWEB)
Amharrak, H., E-mail: hicham.amharrak@im2np.fr [Aix Marseille Université, CNRS, Université de Toulon, IM2NP UMR 7334, 13397, Marseille (France); Reynard-Carette, C. [Aix Marseille Université, CNRS, Université de Toulon, IM2NP UMR 7334, 13397, Marseille (France); Lyoussi, A. [CEA, DEN, DER, Instrumentation Sensors and Dosimetry Laboratory, Cadarache, F-13108 Saint Paul lez Durance (France); Carette, M.; Brun, J.; De Vita, C. [Aix Marseille Université, CNRS, Université de Toulon, IM2NP UMR 7334, 13397, Marseille (France); Fourmentel, D.; Villard, J-F. [CEA, DEN, DER, Instrumentation Sensors and Dosimetry Laboratory, Cadarache, F-13108 Saint Paul lez Durance (France)
2015-11-01
The nuclear heating measurements in Material Testing Reactors (MTRs) are crucial for the study of nuclear materials and fuels under irradiation. The reference measurements of this nuclear heating are especially performed by a differential calorimeter including a graphite sample material and two calorimetric cells. Then these measurements are used for other experimental conditions in order to predict the nuclear heating and thermal conditions induced in the irradiation devices. This paper will present simulations with MCNP5 Monte-Carlo transport code (using ENDF/B-VI nuclear data library) to evaluate the nuclear heating inside the calorimeter during irradiation campaigns of the CARMEN-1P mock-up inside OSIRIS reactor periphery (MTR based on Saclay, France). The whole complete geometry of the sensor has been considered. The calculation method corresponds to a calculation in two steps. Consequently, we used as an input source in the model, the neutron and photon spectra calculated in various experimental locations tested during the irradiation campaign (H9, H10, H11, D9). After a description of the differential calorimeter sensor, the MCNP5 model used for the calculations of nuclear heating inside the calorimeter elements is introduced by two quantities: KERMA and energy deposition rate per mass unit. The Charged Particle Equilibrium (CPE) inside the calorimeter elements is studied. The contribution of prompt gamma and neutron is determined. A comparison between this total nuclear heating calculation and the experimental results in a graphite sample will be made. Then parametric studies performed on the influence of the various calorimeter components on the nuclear heating are presented and discussed. The studies of the influence of the nature of materials, the sensor jacket, the source type and the comparison of the results obtained for the two calorimetric cells leads to some proposals for the sensor improvement.
Pavement Subgrade Performance Study in the Danish Road Testing Machine
DEFF Research Database (Denmark)
Ullidtz, Per; Ertman Larsen, Hans Jørgen
1997-01-01
Most existing pavement subgrade criteria are based on the AASHO Road Test, where only one material was tested and for only one climatic condition. To study the validity of these criteria and to refine the criteria a co-operative research program entitled the "International Pavement Subgrade Perfo...
Asselin, Marie-Claude; Cunningham, Vincent J.; Amano, Shigeko; Gunn, Roger N.; Nahmias, Claude
2004-03-01
A non-invasive alternative to arterial blood sampling for the generation of a blood input function for brain positron emission tomography (PET) studies is presented. The method aims to extract the dimensions of the blood vessel directly from PET images and to simultaneously correct the radioactivity concentration for partial volume and spillover. This involves simulation of the tomographic imaging process to generate images of different blood vessel and background geometries and selecting the one that best fits, in a least-squares sense, the acquired PET image. A phantom experiment was conducted to validate the method which was then applied to eight subjects injected with 6-[18F]fluoro-L-DOPA and one subject injected with [11C]CO-labelled red blood cells. In the phantom study, the diameter of syringes filled with an 11C solution and inserted into a water-filled cylinder were estimated with an accuracy of half a pixel (1 mm). The radioactivity concentration was recovered to 100 ± 4% in the 8.7 mm diameter syringe, the one that most closely approximated the superior sagittal sinus. In the human studies, the method systematically overestimated the calibre of the superior sagittal sinus by 2-3 mm compared to measurements made in magnetic resonance venograms on the same subjects. Sources of discrepancies related to the anatomy of the blood vessel were found not to be fundamental limitations to the applicability of the method to human subjects. This method has the potential to provide accurate quantification of blood radioactivity concentration from PET images without the need for blood samples, corrections for delay and dispersion, co-registered anatomical images, or manually defined regions of interest.
Energy Technology Data Exchange (ETDEWEB)
Nordstroem, T.; Kilpinen, P.; Hupa, M. [Aabo Akademi, Turku (Finland). Combustion Chemistry Group
1996-12-31
The objective of this work has been to investigate the soot formation in a blast furnace fired with heavy fuel oil, using detailed kinetic modelling. This work has been concentrated on parameter studies that could explain under which conditions soot is formed and how that formation could be avoided. The parameters investigated were temperature, pressure, stoichiometric ratio, pyrolysis gas composition and reactor model. The calculations were based on a reaction mechanism that consists of 100 species and 446 reactions including polyaromatic hydrocarbons (PAM) up to 7 aromatic rings SULA 2 Research Programme; 4 refs.
Parametric Study of the Scavenging Process in Marine Two-Stroke Diesel Engines
DEFF Research Database (Denmark)
Andersen, Fredrik Herland; Mayer, Stefan
2015-01-01
Large commercial ships such as container vesselsand bulk carriers are propelled by low-speed, uniflowscavenged two-stroke diesel engines. The integral in-cylinderprocess in this type of engine is the scavenging process,where the burned gas from the combustion process isevacuated through the exhaust...... in axial velocity and the formation ofcentral recirculation zones, known as vortex breakdown. Thispaper will present a CFD analysis of the scavenging process ina MAN B&W two-stroke diesel engine. The study include aparameter sweep where the operating conditions such as airamount, port timing and scavenging...
Application of program LAURA to perfect gas shock tube flows: A parametric study
Mitterer, K. F.; Mitcheltree, R. A.; Gnoffo, P. A.
1992-01-01
The Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) was originally developed to solve steady-flow problems. The desire to validate the algorithm with shock tube experimental data motivated the development of a time-accurate version of the LAURA code. The current work presents a test of the Algorithm. Computational results are compared with the exact solution for a simple shock tube case. The parameters examined are Courant number, relaxation sweeps, grid spacing, and the inviscid relaxation factor. The results of the study indicate that LAURA is capable of producing accurate solutions when appropriate values are used for each parameter.
Parametric Study of the Absorption Cross-Section for a Moderately Conducting Thin Cylinder.
Gurton, Kristan Peter
A system has been developed to measure the absorption cross section of a single carbon fiber at 35 GHz as a function of length, orientation, and diameter. Typical lengths considered ranged from 1 to 20 mm, and diameters ranged from 3 to 8 um. The results were compared with the modified integral equation calculations of Waterman and Pedersen that describe the scattering and absorption behavior for a wire of finite length and conductivity. Good agreement was found for all lengths, orientations, and diameters studied.
Parametric study of the absorption cross section for a moderately conducting thin cylinder
Gurton, Kristan P.; Bruce, Charles W.
1995-05-01
A system has been developed to measure the absorption cross section for a single carbon fiber at 35 GHz as a function of length, orientation, and diameter. Typical lengths of the fibers considered ranged from 1 to 20 mm, and diameters ranged from 3 to 8 mu m. The results were compared with the modified integral equation calculations of Waterman and Pedersen that describe the scattering and absorption behavior for a wire of finite length and conductivity. Good agreement was found for all lengths, orientations, and diameters studied.
Energy Technology Data Exchange (ETDEWEB)
Wang, Baoming; Li, Jun; Qi, Yabing; Jia, Xuhong; Luo, Jianhong [Department of Chemical Engineering, Sichuan University, Chengdu 610065 (China)
2012-10-15
In order to purify phosphoric acid, the suspension melt crystallization process was studied. The suspension crystallization experiments were carried out with 80, 84 and 88 wt% phosphoric acid melt at the cooling rates of 0.05, 0.1 and 0.2 K/min, respectively. Sweating experiments were executed for various crystals obtained in suspension crystallization step. The purification effects of the sweating parameters including sweating time, initial inclusion amount and initial impurity content were studied. The inclusion fraction increases with the increase in cooling rate. The inclusion fraction of the crystals which were formed with feed concentration of 84 wt% phosphoric acid melt is lowest among the three feed concentrations. Different impurities have different purification performances during sweating. High inclusion amount and low impurity concentration favor the purification of H{sub 3}PO{sub 4}.0.5H{sub 2}O crystals during sweating. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Directory of Open Access Journals (Sweden)
Ravi Teja Vedula
2017-01-01
Full Text Available Biacetyl phosphorescence has been the commonly used molecular tagging velocimetry (MTV technique to investigate in-cylinder flow evolution and cycle-to-cycle variations in an optical engine. As the phosphorescence of biacetyl tracer deteriorates in the presence of oxygen, nitrogen was adopted as the working medium in the past. Recently, nitrous oxide MTV technique was employed to measure the velocity profile of an air jet. The authors here plan to investigate the potential application of this technique for engine flow studies. A possible experimental setup for this task indicated different permutations of image signal-to-noise ratio (SNR and laser line width. In the current work, a numerical analysis is performed to study the effect of these two factors on displacement error in MTV image processing. Also, several image filtering techniques were evaluated and the performance of selected filters was analyzed in terms of enhancing the image quality and minimizing displacement errors. The flow displacement error without image preprocessing was observed to be inversely proportional to SNR and directly proportional to laser line width. The mean filter resulted in the smallest errors for line widths smaller than 9 pixels. The effect of filter size on subpixel accuracy showed that error levels increased as the filter size increased.
Deyglun, Clément; Carasco, Cédric; Pérot, Bertrand
2014-06-01
The detection of Special Nuclear Materials (SNM) by neutron interrogation is extensively studied by Monte Carlo simulation at the Nuclear Measurement Laboratory of CEA Cadarache (French Alternative Energies and Atomic Energy Commission). The active inspection system is based on the Associated Particle Technique (APT). Fissions induced by tagged neutrons (i.e. correlated to an alpha particle in the DT neutron generator) in SNM produce high multiplicity coincidences which are detected with fast plastic scintillators. At least three particles are detected in a short time window following the alpha detection, whereas nonnuclear materials mainly produce single events, or pairs due to (n,2n) and (n,n'γ) reactions. To study the performances of an industrial cargo container inspection system, Monte Carlo simulations are performed with the MCNP-PoliMi transport code, which records for each neutron history the relevant information: reaction types, position and time of interactions, energy deposits, secondary particles, etc. The output files are post-processed with a specific tool developed with ROOT data analysis software. Particles not correlated with an alpha particle (random background), counting statistics, and time-energy resolutions of the data acquisition system are taken into account in the numerical model. Various matrix compositions, suspicious items, SNM shielding and positions inside the container, are simulated to assess the performances and limitations of an industrial system.
Wu, Zhiliang; Wang, Shuxin; Zhang, Lianhong; Hu, S. Jack
This paper presents an analytical model of the electrical contact resistance between the carbon paper gas diffusion layers (GDLs) and the graphite bipolar plates (BPPs) in a proton exchange membrane (PEM) fuel cell. The model is developed based on the classical statistical contact theory for a PEM fuel cell, using the same probability distributions of the GDL structure and BPP surface profile as previously described in Wu et al. [Z. Wu, Y. Zhou, G. Lin, S. Wang, S.J. Hu, J. Power Sources 182 (2008) 265-269] and Zhou et al. [Y. Zhou, G. Lin, A.J. Shih, S.J. Hu, J. Power Sources 163 (2007) 777-783]. Results show that estimates of the contact resistance compare favorably with experimental data by Zhou et al. [Y. Zhou, G. Lin, A.J. Shih, S.J. Hu, J. Power Sources 163 (2007) 777-783]. Factors affecting the contact behavior are systematically studied using the analytical model, including the material properties of the two contact bodies and factors arising from the manufacturing processes. The transverse Young's modulus of chopped carbon fibers in the GDL and the surface profile of the BPP are found to be significant to the contact resistance. The factor study also sheds light on the manufacturing requirements of carbon fiber GDLs for a better contact performance in PEM fuel cells.
Energy Technology Data Exchange (ETDEWEB)
Wu, Zhiliang; Wang, Shuxin; Zhang, Lianhong [School of Mechanical Engineering, Tianjin University, Tianjin 300072 (China); Hu, S. Jack [Department of Mechanical Engineering, The University of Michigan, Ann Arbor, MI 48109-2125 (United States)
2009-04-15
This paper presents an analytical model of the electrical contact resistance between the carbon paper gas diffusion layers (GDLs) and the graphite bipolar plates (BPPs) in a proton exchange membrane (PEM) fuel cell. The model is developed based on the classical statistical contact theory for a PEM fuel cell, using the same probability distributions of the GDL structure and BPP surface profile as previously described in Wu et al. [Z. Wu, Y. Zhou, G. Lin, S. Wang, S.J. Hu, J. Power Sources 182 (2008) 265-269] and Zhou et al. [Y. Zhou, G. Lin, A.J. Shih, S.J. Hu, J. Power Sources 163 (2007) 777-783]. Results show that estimates of the contact resistance compare favorably with experimental data by Zhou et al. [Y. Zhou, G. Lin, A.J. Shih, S.J. Hu, J. Power Sources 163 (2007) 777-783]. Factors affecting the contact behavior are systematically studied using the analytical model, including the material properties of the two contact bodies and factors arising from the manufacturing processes. The transverse Young's modulus of chopped carbon fibers in the GDL and the surface profile of the BPP are found to be significant to the contact resistance. The factor study also sheds light on the manufacturing requirements of carbon fiber GDLs for a better contact performance in PEM fuel cells. (author)
Parametric Study of Defect Detection in Pipes with Bend Using Guided Ultrasonic Waves
Directory of Open Access Journals (Sweden)
Jack Tan Jin
2016-01-01
Full Text Available The propagation behaviour of guided ultrasonic waves in a steel pipe with welded bend is studied by finite element simulation. The effectiveness of the longitudinal L(0,2 and torsional T(0,1 guided waves in detecting circumferential cut near the weld is investigated. In order to identify the presence of the defect, the reflection strength due to the cut is studied. The geometry of the weld is constructed based on common V-bevel butt joints and the anisotropy of the 316L stainless steel weld is included to correctly predict the scattering of ultrasonic waves. The finite element model is built to allow high accuracy. Detection of small circumferential cut (up to 60° circumferential extent can be achieved with longitudinal L(0,2 mode. Detection of moderate to large circumferential cut can be achieved by torsional T(0,1 or longitudinal L(0,2 modes, with T(0,1 mode preferred due to its less mode conversion to higher order modes.
Parametric Study on the Influence of Warping Deformation upon Natural Frequencies of Die Springs
Directory of Open Access Journals (Sweden)
Ying Hao
2016-01-01
Full Text Available The free vibrational characteristics of die springs are examined by Riccati transfer matrix method in this study. The warping deformation of spring’s cross section, as a new design factor, is incorporated into the differential equation of motion. Numerical simulations show that the warping deformation is a significant role of the behavior of natural frequencies of die springs and should be considered carefully. Approximately 40% of the errors may occur if warping is neglected. The change laws of warping effect with the parameter variations of springs are also explored, including the height-to-width ratio of the cross section, the cylinder diameter, the helix pitch angle, and the number of coils. The warping effect exhibits the most remarkable changes with the variation in the height-to-width ratio of the cross section. However, this effect is not fairly sensitive to the changes in other parameters, and it is particularly significant when the cross section is relatively narrow regardless of the changes in other parameters. This study evidently answers the key scientific question: “under what working condition should the warping effect be considered or ignored?” The analysis results can be used to guide spring designers in engineering.
Motuku, M.; Vaidya, U. K.; Janowski, G. M.
1999-10-01
Low velocity impact response of glass reinforced polymer composites, which have the potential to self-repair both micro- and macro-damage, has been investigated. This class of material falls under the category of passive smart polymer composites. The self-repairing mechanism is achieved through the incorporation of hollow fibers in addition to the normal solid reinforcing fibers. The hollow fibers store the damage-repairing solution or chemicals that are released into the matrix or damaged zone upon fiber failure. Plain-weave S-2 glass fabric reinforcement, vinyl ester 411-C50 and EPON-862 epoxy resin systems were considered for this study. Different tubing materials were investigated for potential use as storage materials for the repairing chemicals instead of the actual hollow repair fibers and included borosilicate glass micro-capillary pipets, flint glass pasteur pipets, copper tubing and aluminum tubing. composite panels were fabricated by using a vacuum assisted resin transfer molding process. The present investigation addressed fabrication of self-repairing composite panels and some of the parameters that influence the response of self-repairing composites to impact loading. Specific issues addressed by this study include: the processing quality; the selection of storage material for the repairing solution; release and transportation of the repairing solution; the effect of the number, type and spatial distribution of the repairing tubes, specimen thickness, matrix material and impact energy level.
Sanz-Douglass, Gabriela J.
Traditional aircraft composite stiffened panels are designed to avoid buckling of the skin at service loads, to prevent initiation and growth of delamination damages. In stitched composites, the stitching provides reinforcement against delamination; therefore, the structure can be designed for operation in a post buckled state with local skin buckling. The novel stitched stiffened composite panel concept titled Pultruded-Rod Stiffened Efficient Unitized Structure, PRSEUS, was designed specifically for operating in the postbuckling regime, yet the nonlinear postbuckling behavior of PRSEUS has not been explored fully. This thesis presents a finite element analysis based trade study to understand influence of frame stiffener design variables on the nonlinear postbuckling response of the PRSEUS panel concept. The trade study allowed exploration of the design space as a first step towards design optimization. It also allowed discovery of some of the challenges of post processing that must be addressed to enable an automated surrogate based design optimization of the PRESUS stiffened panel concept for operation in postbuckling regimes.
Nickfarjam, Abolfazl; Firoozabadi, S Mohammad P
2014-08-01
Irreversible electroporation (IRE) is a new tumour ablation method used in cancer treatment procedures. In a successful IRE treatment it is crucial to impose minimum thermal damage to the tumour and its surrounding healthy tissue, while subjecting the entire tumour to a strong electric field. Here we present a 3D model of a subcutaneous tumour in a four-layer skin using a geometry-based finite element approach. Four common needle electrode configurations were studied in this paper. The study evaluated six essential factors which are important in the electrical and thermal distributions in tumour and normal tissue. The results revealed that a hexagonal 3 × 3 geometry provides the maximum electrical coverage of the tumour, compared to other electrode configurations. However, in some cases the hexagonal 2 × 2 geometry can ablate the entire tumour with less damage to normal tissue. We found that the deeper insertion of 2- and 4-electrode geometries can lead to more damage to healthy tissue. The results also indicate that the insertion of the electrodes into tumour tissue can increase thermal damage dramatically due to existing large electrical conductivity. These findings suggest that needle electrodes should not be placed within the tumour tissue if the goal is to prevent thermal damage. This method can be used as a trade-off between electric field coverage in tumour tissue and thermal damage to both tumour and normal tissue.
Machining Performance Study on Metal Matrix Composites-A Response Surface Methodology Approach
Directory of Open Access Journals (Sweden)
A. Srinivasan
2012-01-01
Full Text Available Problem statement: Metal Matrix Composites (MMC have become a leading material among composite materials and in particular, particle reinforced aluminum MMCs have received considerable attention due to their excellent engineering properties. These materials are known as the difficult-to-machine materials because of the hardness and abrasive nature of reinforcement element-like Alumina (Al2O3. Approach: In this study, an attempt has been made to model the machinability evaluation through the response surface methodology in machining of homogenized 10% micron Al2O3 LM25 Al MMC manufactured through stir casting method. Results: The combined effects of three machining parameters including cutting speed (s, feed rate (f and depth of cut (d on the basis of three performance characteristics of tool wear (VB, surface Roughness (Ra and cutting Force (Fz were investigated. The contour plots were generated to study the effect of process parameters as well as their interactions. Conclusion: The process parameters are optimized using desirability-based approach response surface methodology.
Study of cutting forces in machining of magnesium composite by response surface methodology
Directory of Open Access Journals (Sweden)
M. Saravanakumar
2015-01-01
Full Text Available Metal Matrix composites (MMCs has many excellent engineering properties like good strength to weight ratio, stiffness and increased wear resistance etc., These properties are the main requirements in aerospace, automotive industries and hence the MMCs are extensively used in these industries. This paper presents the detailed experimental study on cutting forces and surface roughness aspects in turning of 5% Graphite reinforced AZ91D Magnesium alloy metal matrix composite (AZ91D Magnesium alloy matrix + 5 % Graphite reinforcement. The stir casting process under inert atmosphere is followed for synthesis of the composite. The turning process is followed using Tungsten carbide cutting tool, in a lathe. The effect of machining parameters viz., cutting speed, feed rate and depth of cut, on the cutting forces and surface roughness (Ra achieved during the machining are analysed and modelled through the response surface methodology (RSM. Study of effect of machining parameters and their interactions are carried out by using the surface, contour plots of RSM. The experimental result shows that the most significant machining parameter affecting surface roughness and cutting forces is cutting speed. The experimental results and predicted values are observed as in good agreement.
Observation of Parametric Instability in Advanced LIGO
Evans, Matthew; Fritschel, Peter; Miller, John; Barsotti, Lisa; Martynov, Denis; Brooks, Aidan; Coyne, Dennis; Abbott, Rich; Adhikari, Rana; Arai, Koji; Bork, Rolf; Kells, Bill; Rollins, Jameson; Smith-Lefebvre, Nicolas; Vajente, Gabriele; Yamamoto, Hiroaki; Derosa, Ryan; Effler, Anamaria; Kokeyama, Keiko; Betzweiser, Joseph; Frolov, Valera; Mullavey, Adam; O`Reilly, Brian; Dwyer, Sheila; Izumi, Kiwamu; Kawabe, Keita; Landry, Michael; Sigg, Daniel; Ballmer, Stefan; Massinger, Thomas J; Staley, Alexa; Mueller, Chris; Grote, Hartmut; Ward, Robert; King, Eleanor; Blair, David; Ju, Li; Zhao, Chunnong
2015-01-01
Parametric instabilities have long been studied as a potentially limiting effect in high-power interferometric gravitational wave detectors. Until now, however, these instabilities have never been observed in a kilometer-scale interferometer. In this work we describe the first observation of parametric instability in an Advanced LIGO detector, and the means by which it has been removed as a barrier to progress.
Inhaled air quality with desk incorporated personalized ventilation (PV): parametric study
DEFF Research Database (Denmark)
Bolashikov, Zhecho Dimitrov; Nagano, Hideaki; Melikov, Arsen Krikor
manikin was seated with abdomen pressed against the table edge. The amount of clean air inhaled by the manikin was measured under numerous experiments studying different combinations of personalized airflow rates (isothermal) - 2, 4, 6, 8 and 10 L/s, widths of the two jets - 0.03 and 0.06 m, posture...... of the manikin - seated with the abdomen pressed against the table edge, moved backwards from or leaned over the table. The best performance was achieved with the 0.06 m openings: 85% of PV air was inhaled by the occupant at 10 L/s. The portion of clean PV air inhaled by the manikin was 80% when it was bent over...
Parametrical analysis on the diffuse ceiling ventilation by experimental and numerical studies
DEFF Research Database (Denmark)
Zhang, Chen; Kristensen, Martin Heine; Jensen, Jakob Sølund;
2016-01-01
This paper aims to investigate the performance of diffuse ceiling ventilation in a classroom. An experimental study is carried out in a test chamber to examine the impact of diffuse ceiling opening area on the system cooling capacity and thermal comfort. The results indicate that diffuse ceiling...... ventilation provides a satisfied thermal comfort level in the occupied zone even under a high ventilation rate and a high heat load condition. A design chart method is adopted to compare different diffuse ceiling configurations, and the results indicate that the system with a 18% diffuse ceiling opening area....... The numerical results reveal that even distribution of heat sources gives a lower draught risk environment than centralized distribution. In addition, there is a significant increase on the draught risk with increase of room height....
A parametric study of a thick, incompressible flow over a curved surface
Directory of Open Access Journals (Sweden)
Valeriu DRAGAN
2011-12-01
Full Text Available The purpose of this paper is to investigate the lift phenomenon produced by the Coanda effect when a fluid flows over a curved surface. A secondary goal was to quantify and to integrate it on super circulation wing aircraft configurations. Therefore we have conducted a series of CFD studies, varying the fluid velocity and measuring the pressure gradient over the super circulated curved ramp. The results showed that thick jets provide the anticipated lift force which is proportional to the flow velocity. Although in this case the ratio between the Coanda lift and the thrust of the jet itself is less than 10% on average. The immediate interpretation is that, by using thick jets we can increase the lift generated by the SCW aircraft bearing in mind that the main lift is not generated by this effect but rather by diversion of the jet downwards.
Efficiency and comfort of knee braces: A parametric study based on computational modelling
Pierrat, Baptiste; Calmels, Paul; Navarro, Laurent; Avril, Stéphane
2014-01-01
Knee orthotic devices are widely proposed by physicians and medical practitioners for preventive or therapeutic objectives in relation with their effects, usually known as to stabilize joint or restrict ranges of motion. This study focuses on the understanding of force transfer mechanisms from the brace to the joint thanks to a Finite Element Model. A Design Of Experiments approach was used to characterize the stiffness and comfort of various braces in order to identify their mechanically influent characteristics. Results show conflicting behavior: influent parameters such as the brace size or textile stiffness improve performance in detriment of comfort. Thanks to this computational tool, novel brace designs can be tested and evaluated for an optimal mechanical efficiency of the devices and a better compliance of the patient to the treatment.
Parametric study of power absorption from electromagnetic waves by small ferrite spheres
Englert, Gerald W.
1989-01-01
Algebraic expressions in terms of elementary mathematical functions are derived for power absorption and dissipation by eddy currents and magnetic hysteresis in ferrite spheres. Skin depth is determined by using a variable inner radius in descriptive integral equations. Numerical results are presented for sphere diameters less than one wavelength. A generalized power absorption parameter for both eddy currents and hysteresis is expressed in terms of the independent parameters involving wave frequency, sphere radius, resistivity, and complex permeability. In general, the hysteresis phenomenon has a greater sensitivity to these independent parameters than do eddy currents over the ranges of independent parameters studied herein. Working curves are presented for obtaining power losses from input to the independent parameters.
Parametric Study of the Effect of Membrane Tension on Sunshield Dynamics
Ross, Brian; Johnston, John D.; Smith, James
2002-01-01
The NGST sunshield is a lightweight, flexible structure consisting of pretensioned membranes supported by deployable booms. The structural dynamic behavior of the sunshield must be well understood in order to predict its influence on observatory performance. A 1/10th scale model of the sunshield has been developed for ground testing to provide data to validate modeling techniques for thin film membrane structures. The validated models can then be used to predict the behaviour of the full scale sunshield. This paper summarizes the most recent tests performed on the 1/10th scale sunshield to study the effect of membrane preload on sunshield dynamics. Topics to be covered include the test setup, procedures, and a summary of results.
Shock Wave Observation in Narrow Tubes for a Parametric Study on Micro Wave Rotor Design
Institute of Scientific and Technical Information of China (English)
Koji Okamoto; Mikiya Araki
2008-01-01
Wave rotor is expected to improve the performance of micro gas turbines drastically. In the wave rotor design, the rotor speed is determined principally by the tube length. Therefore, a longer tube is preferable for miniaturized wave rotors to avoid the difficulty in bearings and lubrication system, while it may yield thicker wall boundary layer, shock wave dissipation and so on. In the present study, an experimental apparatus was built to visualize the wave rotor internal flow dynamics in a narrow tube by schlieren method and Laser Doppler Anemometry. In addition, different lengths of the tube were adopted and compared to investigate the effect of wall friction. Finally, 2D numerical simulation was performed and the results were compared with those of experiments.
A parametric study on the dynamic behavior of porous bronze at various strain rates
Zhang, Yue; Hu, Jianxing; Lei, Jianyin; Wang, Zhihua; Zhao, Longmao
2016-10-01
An experimental investigation on the porous bronze at various strain rates is firstly carried out in this study to explore the effects of relative density and strain rate in the mechanical behavior. Furthermore, a multi-parameter constitutive model of describing the rate-dependent behavior for porous bronze is developed. The parameters in the constitutive model are density dependent, and the specific forms of these parameters as functions of relative density are obtained. It can be concluded from the test results and constitutive model that the high relative density leads to increase in yield strength and energy absorption capacity of the materials and the strain rate also has positive effects on the yield strength and energy absorption capacity of porous bronze.
A parametric study on the use of passive fire protection in FPSO topside module
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Friebe Martin
2014-12-01
Full Text Available Fire is a continuous threat to FPSO topside modules as large amounts of oil and gas are passing through the modules. As a conventional measure to mitigate structural failure under fire, passive fire protection (PFP coatings are widely used on main structural members. However, an excessive use of PFP coatings can cause considerable cost for material purchase, installation, inspection and maintenance. Long installation time can be a risk since the work should be done nearly at the last fabrication stage. Thus, the minimal use of PFP can be beneficial to the reduction of construction cost and the avoidance of schedule delay. This paper presents a few case studies on how different applications of PFP have influence on collapse time of a FPSO module structure. A series of heat analysis and thermal elasto-plastic FE analysis are performed for different PFP coatings and the resultant collapse time and the amount of PFP coatings are compared with each other.
A parametric study on the use of passive fire protection in FPSO topside module
Friebe, Martin; Jang, Beom-Seon; Jim, Yanlin
2014-12-01
Fire is a continuous threat to FPSO topside modules as large amounts of oil and gas are passing through the modules. As a conventional measure to mitigate structural failure under fire, passive fire protection (PFP) coatings are widely used on main structural members. However, an excessive use of PFP coatings can cause considerable cost for material purchase, installation, inspection and maintenance. Long installation time can be a risk since the work should be done nearly at the last fabrication stage. Thus, the minimal use of PFP can be beneficial to the reduction of construction cost and the avoidance of schedule delay. This paper presents a few case studies on how different applications of PFP have influence on collapse time of a FPSO module structure. A series of heat analysis and thermal elasto-plastic FE analysis are performed for different PFP coatings and the resultant collapse time and the amount of PFP coatings are compared with each other.
Iwakami, Wakana; Yamada, Shoichi
2013-01-01
The systematic research of flow patterns behind the accretion shock wave is conducted using three-dimensional hydrodynamics simulations for core-collapse supernovae in this study. Changing the accretion rate and neutrino luminosity, the steady solutions of the one-dimensional irrotational accretion flow passing through the spherical shock wave are evolved by imposing a random perturbation with 1% amplitude at the onset of the simulations. Depending on the accretion rate and neutrino luminosity, various flow patterns appear behind the shock wave. We classified them into the three fundamental flow patterns: (1) sloshing motion, (2) spiral motion, (3) multiple high-entropy bubbles, and the two anomalous flow patterns: (4) spiral motion with buoyant bubbles, and (5) spiral motion with pulsating rotational velocity. The sloshing and spiral motions tend to be dominant in the higher accretion rate and lower neutrino luminosity, and the generations of multiple buoyant bubbles tend to prevail in the lower accretion ra...
Exergetic and Parametric Study of a Solar Aided Coal-Fired Power Plant
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Eric Hu
2013-03-01
Full Text Available A solar-aided coal-fired power plant realizes the integration of a fossil fuel (coal or gas and clean energy (solar. In this paper, a conventional 600 MW coal-fired power plant and a 600 MW solar-aided coal-fired power plant have been taken as the study case to understand the merits of solar-aided power generation (SAPG technology. The plants in the case study have been analyzed by using the First and Second Laws of Thermodynamics principles. The solar irradiation and load ratio have been considered in the analysis. We conclude that if the solar irradiation was 925 W/m2 and load ratio of the SAPG plant was 100%, the exergy efficiency would be 44.54% and the energy efficiency of the plant (46.35%. It was found that in the SAPG plant the largest exergy loss was from the boiler, which accounted for about 76.74% of the total loss. When the load ratio of the unit remains at 100%, and the solar irradiation varies from 500 W/m2 to 1,100 W/m2, the coal savings would be in the range of 8.6 g/kWh to 15.8 g/kWh. If the solar irradiation were kept at 925 W/m2 while the load ratio of the plant changed from 30% to 100%, the coal savings could be in the range of 11.99 g/kWh to 13.75 g/kWh.
Stoja, Endri; Hoxha, Julian; Domnori, Elton; Pajewski, Lara; Frezza, Fabrizio
2017-04-01
In this study the electromagnetic field scattered by a buried object is obtained by use of a commercial full-wave frequency-domain solver which implements the Finite Element Method (FEM). The buried object is supposed to have different simple shapes and material composition such as a cylinder or cylindrical shell modelling for example a void in concrete or a poly-vinyl chloride (PVC) pipeline, respectively. Material properties available in literature are correctly modelled by data interpolation. The model is excited by a linearly-polarized plane wave impinging normally on the interface between air and soil/cement half-space. Comparison with simulation data provided by another simulator implementing the finite-difference time domain (FDTD) technique in the case of a simple buried perfect electric cylinder allows for FEM data validation. We further study the properties and the spatial variation of the scattered fields in different contexts by varying the geometrical and material properties of the model relative to the impinging wave characteristics. The aim is to clearly determine the conditions under which detection is possible. Moreover, by application of signal processing techniques to scattered field data, the position, shape, and object orientation recognition problems are considered. Results from different DSP algorithms are compared with the goal to find the best performing one relative to the context. Performance is evaluated in terms of detection success and resolving ability. The use of ground penetrating radar (GPR) techniques in the field of Civil Engineering offers inspection capabilities in the structure with no destructive intervention. Acknowledgement This abstract is a contribution to COST Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar", www.GPRadar.eu, www.cost.eu.
Dhote, Yogesh; Thombre, Shashikant
2016-10-01
This paper presents the thermal performance of the proposed double flow natural convection solar air heater with in-built liquid (oil) sensible heat storage. Unused engine oil was used as thermal energy storage medium due to its good heat retaining capacity even at high temperatures without evaporation. The performance evaluation was carried out for a day of the month March for the climatic conditions of Nagpur (India). A self reliant computational model was developed using computational tool as C++. The program developed was self reliant and compute the performance parameters for any day of the year and would be used for major cities in India. The effect of change in storage oil quantity and the inclination (tilt angle) on the overall efficiency of the solar air heater was studied. The performance was tested initially at different storage oil quantities as 25, 50, 75 and 100 l for a plate spacing of 0.04 m with an inclination of 36o. It has been found that the solar air heater gives the best performance at a storage oil quantity of 50 l. The performance of the proposed solar air heater is further tested for various combinations of storage oil quantity (50, 75 and 100 l) and the inclination (0o, 15o, 30o, 45o, 60o, 75o, 90o). It has been found that the proposed solar air heater with in-built oil storage shows its best performance for the combination of 50 l storage oil quantity and 60o inclination. Finally the results of the parametric study was also presented in the form of graphs carried out for a fixed storage oil quantity of 25 l, plate spacing of 0.03 m and at an inclination of 36o to study the behaviour of various heat transfer and fluid flow parameters of the solar air heater.
DEFF Research Database (Denmark)
Chen, Zhe; Blaabjerg, Frede; Iov, Florin
2005-01-01
A direct phase model of synchronous machines implemented in MA TLAB/SIMULINK is presented. The effects of the machine saturation have been included. Simulation studies are performed under various conditions. It has been demonstrated that the MATLAB/SIMULINK is an effective tool to study the complex...
DEFF Research Database (Denmark)
Chen, Zhe; Blaabjerg, Frede; Iov, Florin
2005-01-01
A direct phase model of synchronous machines implemented in MA TLAB/SIMULINK is presented. The effects of the machine saturation have been included. Simulation studies are performed under various conditions. It has been demonstrated that the MATLAB/SIMULINK is an effective tool to study the complex...
Parametric study of ion heating in a burnout device (HIP-1)
Sigman, D. R.; Reinmann, J. J.; Lauver, M. R.
1974-01-01
Results of further studies on the Lewis Research Center hot-ion plasma source (HIP-1) are reported. Changes have been made in both the electrode geometry and materials to produce higher ion temperatures. Ion temperature increased significantly with increased vacuum pumping speed. The best ion temperatures achieved, so far, for H(+), D(+), and He(+) plasmas are estimated to be equal to, or greater than 0.6, equal to, or greater than 0.9, and equal to, greater than 2.0 keV, respectively. Electrode pairs produced high ion temperatures whether on the magnetic axis or off it by 5.5 cm. Multiple sources, one on-axis and one off-axis, were run simultaneously from a single power supply by using independent gas feed rates. A momentum analyzer has been added to the charge-exchange neutral particle analyzer to identify particles according to mass, as well as energy. Under any given plasma condition, the higher mass ions have higher average energies but not by as much as the ratio of their respective masses.
Parametric Study on Dynamic Response of Fiber Reinforced Polymer Composite Bridges
Directory of Open Access Journals (Sweden)
Woraphot Prachasaree
2015-01-01
Full Text Available Because of high strength and stiffness to low self-weight ratio and ease of field installation, fiber reinforced polymer (FRP composite materials are gaining popularity as the materials of choice to replace deteriorated concrete bridge decks. FRP bridge deck systems with lower damping compared to conventional bridge decks can lead to higher amplitudes of vibration causing dynamically active bridge deck leading serviceability problems. The FRP bridge models with different bridge configurations and loading patterns were simulated using finite element method. The dynamic response results under varying FRP deck system parameters were discussed and compared with standard specifications of bridge deck designs under dynamic loads. In addition, the dynamic load allowance equation as a function of natural frequency, span length, and vehicle speed was proposed in this study. The proposed dynamic load allowance related to the first flexural frequency was presented herein. The upper and lower bounds’ limits were established to provide design guidance in selecting suitable dynamic load allowance for FRP bridge systems.
Iannaccone, F; Debusschere, N; De Bock, S; De Beule, M; Van Loo, D; Vermassen, F; Segers, P; Verhegghe, B
2014-03-01
Carotid artery stenting is emerging as an alternative technique to surgery for the treatment of symptomatic severe carotid stenosis. Clinical and experimental evidence demonstrates that both plaque morphology and biomechanical changes due to the device implantation can be possible causes of an unsuccessful treatment. In order to gain further insights of the endovascular intervention, a virtual environment based on structural finite element simulations was built to emulate the stenting procedure on generalized atherosclerotic carotid geometries which included a damage model to quantify the injury of the vessel. Five possible lesion scenarios were simulated by changing both material properties and vascular geometrical features to cover both presumed vulnerable and stable plaques. The results were analyzed with respect to lumen gain and wall stresses which are potentially related to the failure of the procedure according to previous studies. Our findings show that an elliptic lumen shape and a thinner fibrous cap with an underlying lipid pool result in higher stenosis reduction, while large calcifications and fibrotic tissue are more prone to recoil. The shielding effect of a thicker fibrous cap helps to reduce local compressive stresses in the soft plaque. The presence of a soft plaque reduces the damage in the healthy vascular structures. Contrarily, the presence of hard plaque promotes less damage volume in the fibrous cap and reduces stress peaks in this region, but they seem to increase stresses in the media-intima layer. Finally the reliability of the achieved results was put into clinical perspective.
Parametric studies of an active solar water heating system with various types of PVT collectors
Indian Academy of Sciences (India)
Roonak Daghigh; Mohd Hafidz Ruslan; Kamaruzzaman Sopian
2015-10-01
This study simulated active photovoltaic thermal solar collectors (PV/T) for hot water production using TRNSYS. The PV/T collectors consist of the amorphous, monocrystalline and polycrystalline. The long-term performances for the glazed and unglazed PV/T collectors were also evaluated. In this simulation, the design parameters used were collector area of 4 m2, collector slope angle of 15 degree and mass flow rate to the collector area ratio of 8–20 kg/hm2. In addition the tank height between 0.9 m to 1.1 m for unglazed PV/T collectors and 0.9 m to 1 m for glazed collectors, as well as the storage tank volume between 200 and 300 L has been used. The climate parameters used were solar radiation levels range of 4–4.9 kWh/m2, the mean ambient temperature in the range of 25–28°C. The results of the simulation indicated that there was an increase in solar fraction and electrical power output of the active PV/T hot water system.
Directory of Open Access Journals (Sweden)
Awais Bokhari
2015-09-01
Full Text Available The depleting fossil fuel reserves and increasing environmental concerns have continued to stimulate research into biodiesel as a green fuel alternative produced from renewable resources. In this study, Kapok (Ceiba pentandra oil methyl ester was produced by using microwave-assisted technique. The optimum operating conditions for the microwave-assisted transesterification of Kapok seed oil including temperature, catalyst loading, methanol to oil molar ratio, and irradiation time were investigated by using Response Surface Methodology (RSM based on Central Composite Design (CCD. A maximum conversion of 98.9 % was obtained under optimum conditions of 57.09 °C reaction temperature, 2.15 wt% catalyst (KOH loading, oil to methanol molar ratio of 1:9.85, and reaction time of 3.29 min. Fourier Transform Infra-Red (FT-IR spectroscopy was performed to verify the conversion of the fatty acid into methyl esters. The properties of Kapok oil methyl ester produced under the optimum conditions were characterized and found in agreement with the international ASTM D 6751 and EN 14214 standards.
Parametric study on the effect of rainfall pattern to slope stability
Directory of Open Access Journals (Sweden)
Hakim Sagitaningrum Fathiyah
2017-01-01
Full Text Available Landslide in Indonesia usually occurs during the rainy seasons. Previous studies showed that rainfall infiltration has a great effect on the factor of safety (FS of slopes. This research focused on the effect of rainfall pattern on the FS of unsaturated slope with different slope angle i.e.: 30°, 45°, and 60°. Three different rainfall patterns, which are normal, advanced, and delayed were considered in the analysis. The effects of low or high hydraulic conductivity of the soil are also observed. The analyses were conducted with SEEP/W for the seepage and SLOPE/W for the slope stability. It is found that the lowest FS for gentle slope is reached under the application of advanced rainfall pattern and the lowest FS for steep slope is reached under the application of delayed rainfall pattern. Reduction of FS is known to be the largest for gentle slope rather than steep slope due to negative pore water pressure reduction and the rising of ground water level. The largest FS reduction caused by rainfall was achieved for gentle slope under advanced rainfall pattern.
Kiliç, Mehtap Gülsün; Hoşten, Cetin; Demirci, Sahinde
2009-11-15
This paper attempts to compare electrocoagulation using aluminum anodes and stainless steel cathodes with conventional coagulation by aluminum sulfate dosing on aqueous suspensions of ultrafine quartz. Several key parameters affecting the efficiency of electrocoagulation and coagulation were investigated with laboratory scale experiments in search of optimal parameter values. Optimal values of the parameters were determined on the basis of the efficiency of turbidity removal from ultrafine quartz suspensions. The parameters investigated in the study were suspension pH, electrical potential, current density, electrocoagulation time, and aluminum dosage. A comparison between electrocoagulation and coagulation was made on the basis of total dissolved aluminum, revealing that electrocoagulation and coagulation were equally effective at the same aluminum dosage for the removal of quartz particles from suspensions. Coagulation, however, was more effective in a wider pH range (pH 6-9) than electrocoagulation which yielded optimum effectiveness in a relatively narrower pH range around 9, where, in both methods, these pH values corresponded to near-zero zeta potentials of quartz particles. Furthermore, experimental results confirmed that electrocoagulation could display some pH buffering capacity. The kinetics of electrocoagulation was very fast (<10 min) in approaching a residual turbidity, which could be modeled with a second-order rate equation.
A Parametric Study on Using Active Debris Removal to Stabilize the Future LEO Debris Environment
Liou, J.C.
2010-01-01
Recent analyses of the instability of the orbital debris population in the low Earth orbit (LEO) region and the collision between Iridium 33 and Cosmos 2251 have reignited the interest in using active debris removal (ADR) to remediate the environment. There are; however, monumental technical, resources, operational, legal, and political challenges in making economically viable ADR a reality. Before a consensus on the need for ADR can be reached, a careful analysis of the effectiveness of ADR must be conducted. The goal is to demonstrate the feasibility of using ADR to preserve the future environment and to guide its implementation to maximize the benefit-cost ratio. This paper describes a comprehensive sensitivity study on using ADR to stabilize the future LEO debris environment. The NASA long-term, orbital debris evolutionary model, LEGEND, is used to quantify the effects of many key parameters. These parameters include (1) the starting epoch of ADR implementation, (2) various target selection criteria, (3) the benefits of collision avoidance maneuvers, (4) the consequence of targeting specific inclination or altitude regimes, (5) the consequence of targeting specific classes of vehicles, and (6) the timescale of removal. Additional analyses on the importance of postmission disposal and how future launches might affect the requirements to stabilize the environment are also included.
A Parametric Study on Using Active Debris Removal for LEO Environment Remediation
2010-01-01
Recent analyses on the instability of the orbital debris population in the low Earth orbit (LEO) region and the collision between Iridium 33 and Cosmos 2251 have reignited the interest in using active debris removal (ADR) to remediate the environment. There are; however, monumental technical, resource, operational, legal, and political challenges in making economically viable ADR a reality. Before a consensus on the need for ADR can be reached, a careful analysis of its effectiveness must be conducted. The goal is to demonstrate the need and feasibility of using ADR to better preserve the future environment and to guide its implementation to maximize the benefit-to-cost ratio. This paper describes a new sensitivity study on using ADR to stabilize the future LEO debris environment. The NASA long-term orbital debris evolutionary model, LEGEND, is used to quantify the effects of several key parameters, including target selection criteria/constraints and the starting epoch of ADR implementation. Additional analyses on potential ADR targets among the currently existing satellites and the benefits of collision avoidance maneuvers are also included.
A Parametric Study for Regenerative Ammonia-Based Scrubbing for the Capture of CO2
Energy Technology Data Exchange (ETDEWEB)
Resnik, K.P.; Garber, W.; Hreda, D.C.; Yeh, J.T.; Pennline, H.W.
2006-09-01
A continuous gas and liquid flow, regenerative scrubbing process for CO2 capture is currently being demonstrated at the bench-scale level. An aqueous ammonia-based solution captures CO2 from simulated flue gas in an absorber and releases a nearly pure stream of CO2 in the regenerator. After the regeneration, the solution of ammonium compounds is recycled to the absorber. The design of the continuous flow unit was based on earlier exploratory results from a semi-batch reactor, where a CO2 and N2 gas mixture flowed through a well-mixed batch of ammonia-based solution. Recently, a series of tests have been conducted on the continuous unit to observe the effect of various parameters on CO2 removal efficiency and regenerator effectiveness within the flow system. The parameters that were studied include absorber temperature, regenerator temperature, initial NH3 concentration, simulated flue gas flow rate, liquid solvent inventory in the flow system, and height of the packed-bed absorber. Results from this current testing campaign conducted in the continuous scrubbing unit as well as test results from a 5-cycle semi-batch reactor will be discussed.
Uncertainties in volcanic plume modeling: a parametric study using FPLUME model
Macedonio, Giovanni; Costa, Antonio; Folch, Arnau
2016-04-01
Tephra transport and dispersal models are commonly used for volcanic hazard assessment and tephra dispersal (ash cloud) forecasts. The proper quantification of the parameters defining the source term in the dispersal models, and in particular the estimation of the mass eruption rate, plume height, and particle vertical mass distribution, is of paramount importance for obtaining reliable results in terms of particle mass concentration in the atmosphere and loading on the ground. The study builds upon numerical simulations of using FPLUME, an integral steady-state model based on the Buoyant Plume Theory, generalized in order to account for volcanic processes (particle fallout and re-entrainment, water phase changes, effects of wind, etc). As reference cases for strong and weak plumes, we consider the cases defined during the IAVCEI Commission on tephra hazard modeling inter-comparison exercise. The goal was to explore the leading order role of each parameter in order to assess which should be better constrained to better quantify the eruption source parameters for use by the dispersal models. Moreover, a sensitivity analysis investigates the role of wind entrainment and intensity, atmospheric humidity, water phase changes, and particle fallout and re-entrainment. Results show that the leading-order parameters are the mass eruption rate and the air entrainment coefficient, specially for weak plumes.
Snorradóttir, Bergthóra S; Jónsdóttir, Fjóla; Sigurdsson, Sven Th; Másson, Már
2014-08-01
A model is presented for transdermal drug delivery from single-layered silicone matrix systems. The work is based on our previous results that, in particular, extend the well-known Higuchi model. Recently, we have introduced a numerical transient model describing matrix systems where the drug dissolution can be non-instantaneous. Furthermore, our model can describe complex interactions within a multi-layered matrix and the matrix to skin boundary. The power of the modelling approach presented here is further illustrated by allowing the possibility of a donor solution. The model is validated by a comparison with experimental data, as well as validating the parameter values against each other, using various configurations with donor solution, silicone matrix and skin. Our results show that the model is a good approximation to real multi-layered delivery systems. The model offers the ability of comparing drug release for ibuprofen and diclofenac, which cannot be analysed by the Higuchi model because the dissolution in the latter case turns out to be limited. The experiments and numerical model outlined in this study could also be adjusted to more general formulations, which enhances the utility of the numerical model as a design tool for the development of drug-loaded matrices for trans-membrane and transdermal delivery.
Parametric modal transition systems
DEFF Research Database (Denmark)
Beneš, Nikola; Křetínský, Jan; Larsen, Kim Guldstrand;
2011-01-01
Modal transition systems (MTS) is a well-studied specification formalism of reactive systems supporting a step-wise refinement methodology. Despite its many advantages, the formalism as well as its currently known extensions are incapable of expressing some practically needed aspects in the refin......Modal transition systems (MTS) is a well-studied specification formalism of reactive systems supporting a step-wise refinement methodology. Despite its many advantages, the formalism as well as its currently known extensions are incapable of expressing some practically needed aspects...... in the refinement process like exclusive, conditional and persistent choices. We introduce a new model called parametric modal transition systems (PMTS) together with a general modal refinement notion that overcome many of the limitations and we investigate the computational complexity of modal refinement checking....
A parametric study of dispersion processes in semi-enclosed basins
Energy Technology Data Exchange (ETDEWEB)
Buffoni, G. [ENEA, Centro Ricerche S. Teresa, La Spezia (Italy). Dipt. di Innovazione; Bellucci, A.; Zambianchi, E. [Istituto Universitario Navale, Neapel (Italy); Griffa, A. [Consiglio Nazionale delle Ricerche, La Spezia (Italy)
1999-07-01
The dispersion processes in semi-enclosed basins with stationary flows have been studied by means of an Eulerian advection-diffusion model. Special interest have been given to quantities which characterize the macroscopic state of the system: the normalized total quantity C(t) (C (0) = 1) of a tracer inside the basin, and its residence time T. Also the principal eigenvalue {tau}{sub 0} of the advection-diffusion problem has been considered, since for stationery flows C (t) attains, for time t long enough, an exponential decay shape C{sub 0}exp (-t/{tau}{sub 0} ). The focus is one the comparison between cases where the flow is rotational with re circulations, represented by a flow with a gyre at the outflow. The sensitivity of the results to a number of parameters, including initial and boundary conditions and the eddy diffusivity coefficient, have been studied. It is found that for small Peclet numbers, when the flow is highly diffusive, the results do not depend strongly on the flow structure. {tau}{sub 0} tends to a constant limit (dependent on the boundary conditions) at decreasing Peclet number, and T is approximated by T asymptotically equal to {tau}{sub 0}. For high Peclet numbers, instead, the rotational and irrotational cases are qualitatively different. For rotational flows, {tau}{sub 0}, tends to zero at increasing Peclet number, and T tends toward the advective time scale. For flows with re circulations, in which the tracer tends to be trapped inside the gyre, {tau}{sub 0} increases at increasing Peclet numbers and T asymptotically equal to {tau}{sub 0}, for all initial and boundary conditions. The values of T and {tau}{sub 0} do not change significantly in the range of realistic Peclet numbers considered. This suggests that, for flows with re circulations, the macroscopic dispersion properties depend only weakly on the eddy diffusion coefficient. [Italian] Processi di dispersione in bacini semi-chiusi caratterizzati da flussi stazionari sono stati
Parametric study of the partial oxidation of propane over nickel and platinum based catalysts
Mukka, Mayuri
Hydrogen production though the partial oxidation of propane over 1%Pt/CeO 2 and 1%Ni/CeO2 catalysts was studied in a fixed-bed reactor. The purpose of the experiments was to study the pathways, priority and the sequence of reactions which occur over each catalyst system. A temperature of 600°C and O2/C3H8 ratio of 1.78 was used for all the runs. The space velocity was varied by varying the flowrates (100, 200, 300, 400 sccm), and also the catalyst loadings. Seven species were found at the outlet of the reactor (C3H8, O2, H2, CO, CO2, H2O and C3H 6). All the species except H2O were analyzed quantitatively by the gas chromatograph. The following reactions can occur during the process at 600°C: total oxidation, partial oxidation, steam reforming, dry reforming, water gas shift, dehydrogenation and water formation. Of these, a Gaussian elimination process yields four independent reactions. This results in ten sets of possible independent reactions. For each set, a material balance on the six outlet compositions allows the calculation of rates of each of the four reactions in the set. Sets containing negative rates for irreversible reactions are discarded. To confirm the validity of sets containing dry reforming, steam reforming and water gas shift, these reactions were carried out over the catalysts at the experimentally determined outlet conditions for the propane partial oxidation process. For the 1%Ni/CeO2 catalyst, both dry and steam reforming reactions were favorable, but the water gas shift reaction was not favorable. The activities of the 1%Pt/CeO2 catalyst for dry reforming and steam reforming were insignificant. The water gas shift reaction was not conducted over the 1%Pt/CeO2 catalyst as no feasible set contained this reaction. These results, coupled with the effect of weight hourly space velocity, allows us to evaluate the relative importance of each reaction in each allowable set as a function of contact time. The results indicate that the pathways
A parametric study of dispersion processes in semi-enclosed basins
Energy Technology Data Exchange (ETDEWEB)
Buffoni, G. [ENEA, Centro Ricerche S. Teresa, La Spezia (Italy). Dipt. di Innovazione; Bellucci, A.; Zambianchi, E. [Istituto Universitario Navale, Neapel (Italy); Griffa, A. [Consiglio Nazionale delle Ricerche, La Spezia (Italy)
1999-07-01
The dispersion processes in semi-enclosed basins with stationary flows have been studied by means of an Eulerian advection-diffusion model. Special interest have been given to quantities which characterize the macroscopic state of the system: the normalized total quantity C(t) (C (0) = 1) of a tracer inside the basin, and its residence time T. Also the principal eigenvalue {tau}{sub 0} of the advection-diffusion problem has been considered, since for stationery flows C (t) attains, for time t long enough, an exponential decay shape C{sub 0}exp (-t/{tau}{sub 0} ). The focus is one the comparison between cases where the flow is rotational with re circulations, represented by a flow with a gyre at the outflow. The sensitivity of the results to a number of parameters, including initial and boundary conditions and the eddy diffusivity coefficient, have been studied. It is found that for small Peclet numbers, when the flow is highly diffusive, the results do not depend strongly on the flow structure. {tau}{sub 0} tends to a constant limit (dependent on the boundary conditions) at decreasing Peclet number, and T is approximated by T asymptotically equal to {tau}{sub 0}. For high Peclet numbers, instead, the rotational and irrotational cases are qualitatively different. For rotational flows, {tau}{sub 0}, tends to zero at increasing Peclet number, and T tends toward the advective time scale. For flows with re circulations, in which the tracer tends to be trapped inside the gyre, {tau}{sub 0} increases at increasing Peclet numbers and T asymptotically equal to {tau}{sub 0}, for all initial and boundary conditions. The values of T and {tau}{sub 0} do not change significantly in the range of realistic Peclet numbers considered. This suggests that, for flows with re circulations, the macroscopic dispersion properties depend only weakly on the eddy diffusion coefficient. [Italian] Processi di dispersione in bacini semi-chiusi caratterizzati da flussi stazionari sono stati
Parametric Study on the Tensile Properties of Ni-Based Alloy for a VHTR
Kim, Dong-Jin; Jung, Su Jin; Mun, Byung Hak; Kim, Sung Woo; Lim, Yun Soo
2015-01-01
A very high-temperature reactor (VHTR) has been studied among generation IV nuclear power plants owing to its many advantages such as high-electric efficiency and massive hydrogen production. The material used for the heat exchanger should sustain structural integrity for its life even though the material is exposed to a harsh environment at 1223 K (950 °C) in an impure helium coolant. Therefore, an enhancement of the material performance at high temperature gives a margin in determining the operating temperature and life time. This work is an effort to find an optimum combination of alloying elements and processing parameters to improve the material performance. The tensile property and microstructure for nickel-based alloys fabricated in a laboratory were evaluated as a function of the heat treatment, cold working, and grain boundary strengthener using a tension test at 1223 K (950 °C), scanning electron microscopy, and transmission electron microscopy. Elongation to rupture was increased by additional heat treatment and cold working, followed by additional heat treatment in the temperature range from 1293 K to 1383 K (1020 °C to 1110 °C) implying that the intergranular carbide contributes to grain boundary strengthening. The temperature at which the grain boundary is improved by carbide decoration was higher for a cold-worked specimen, which was described by the difference in carbide stability and carbide formation kinetics between no cold-worked and cold-worked specimens. Zr and Hf played a scavenging effect of harmful elements causing an increase in ductility.
Directory of Open Access Journals (Sweden)
Mohamed Hamdi
2008-01-01
Full Text Available The so-called Flameless Oxidation is a novel combustion mode, in which combustion products are re-circulated and mixed into the fresh incoming fuel and air streams. This reduces the concentration of the reactants and thereby reducing the reaction rate through avoiding the formation of sharp high temperature zones in the combustion chamber. Flameless combustion has been acknowledged as one of the most interesting combustion technologies to meet both the targets of high energy efficiency and low pollutant emissions. This technology has already been successfully applied and exploited in industrial burners. The present investigation is concerned with the application of the flameless combustion mode to an adiabatic combustor, typically used in gas turbine engines. Detailed chemical kinetics calculations, by means of a specific zero-dimensional loop reactor model, have been performed to analyze its chemical aspects. The model simulates the combustor by a number of reactors that represent different zones in the combustion chamber. The main objective of this study is to increase the understanding of NOx formation from flameless mode, where currently very few experimental data are available. The investigation is focused on a comparison of the influence of pressure, residence time and temperature on the NOx and CO emissions, using two reaction mechanisms of the C/H/O/N system: the Miller-Bowman mechanism and the GRI_MECH3.0 mechanism. Simulation results clearly illustrate that even at high operating temperatures and pressures, NOx emissions could be reduced by flameless combustion to very low levels. A comparison between the predictions obtained by using the two chemical kinetics mechanisms is presented and discussed. It is shown that the predictions of the Miller-Bowman mechanism deviate from the predictions of the GRI3.0 mechanism in many aspects, especially as related to NOx emission results.
Energy Technology Data Exchange (ETDEWEB)
Curtis, C.W.; Guin, J.A.; Tsai, K.J.; Pass, M.C.
1984-01-01
This study has investigated the combined hydroprocessing of coal with petroleum solvents consisting of heavy and reduced crudes and residua to determine the feasibility of simultaneous upgrading of both materials to lighter products. Six hydrogen-rich heavy petroleum materials have been processed with Illinois No. 6 coal at 400/sup 0/C and 425/sup 0/C for 30 minutes under three reaction conditions: a N/sub 2/ atmosphere, a H/sub 2/ atmosphere and a H/sub 2/ atmosphere using hydrotreating extrudates. Liquefaction of bituminous coal can be achieved in the petroleum solvents with coal conversion being dependent upon the reaction conditions. Noncatalytic coal conversions of 45 to 50% are achieved in a H/sub 2/ atmosphere. Addition of a catalyst increases conversion to near 70%. Only approximately 35% conversion is obtained in a N/sub 2/ atmosphere. In the catalytic environment substantial conversions to pentane soluble material occur. Hydrotreatment and extraction of the solvent prior to coprocessing increases the amount of coal conversion and, in some cases, increases the amount of pentane soluble material produced. The influence of the solvent appears to be related to the molecular weight, viscosity and Conradson Carbon number of the petroleum materials. Evaluation of the reaction parameters of temperature, hydrogen pressure, time and catalyst extrudate size for coprocessing has been undertaken. Based on the production of pentane soluble oil and coal conversion, feasible parameters are established: 425/sup 0/C, 1250 psig H/sub 2/ pressure at ambient temperature, long reaction time and a hydrogenation catalyst with a small particle size. Combined processing is shown to be sensitive to catalyst extrudate size, with powdered catalyst giving substantially more oil yield and coal conversion than the extrudates. 6 references, 11 figures, 4 tables.
Directory of Open Access Journals (Sweden)
Paul Richmond
Full Text Available High performance computing on the Graphics Processing Unit (GPU is an emerging field driven by the promise of high computational power at a low cost. However, GPU programming is a non-trivial task and moreover architectural limitations raise the question of whether investing effort in this direction may be worthwhile. In this work, we use GPU programming to simulate a two-layer network of Integrate-and-Fire neurons with varying degrees of recurrent connectivity and investigate its ability to learn a simplified navigation task using a policy-gradient learning rule stemming from Reinforcement Learning. The purpose of this paper is twofold. First, we want to support the use of GPUs in the field of Computational Neuroscience. Second, using GPU computing power, we investigate the conditions under which the said architecture and learning rule demonstrate best performance. Our work indicates that networks featuring strong Mexican-Hat-shaped recurrent connections in the top layer, where decision making is governed by the formation of a stable activity bump in the neural population (a "non-democratic" mechanism, achieve mediocre learning results at best. In absence of recurrent connections, where all neurons "vote" independently ("democratic" for a decision via population vector readout, the task is generally learned better and more robustly. Our study would have been extremely difficult on a desktop computer without the use of GPU programming. We present the routines developed for this purpose and show that a speed improvement of 5x up to 42x is provided versus optimised Python code. The higher speed is achieved when we exploit the parallelism of the GPU in the search of learning parameters. This suggests that efficient GPU programming can significantly reduce the time needed for simulating networks of spiking neurons, particularly when multiple parameter configurations are investigated.
Richmond, Paul; Buesing, Lars; Giugliano, Michele; Vasilaki, Eleni
2011-05-04
High performance computing on the Graphics Processing Unit (GPU) is an emerging field driven by the promise of high computational power at a low cost. However, GPU programming is a non-trivial task and moreover architectural limitations raise the question of whether investing effort in this direction may be worthwhile. In this work, we use GPU programming to simulate a two-layer network of Integrate-and-Fire neurons with varying degrees of recurrent connectivity and investigate its ability to learn a simplified navigation task using a policy-gradient learning rule stemming from Reinforcement Learning. The purpose of this paper is twofold. First, we want to support the use of GPUs in the field of Computational Neuroscience. Second, using GPU computing power, we investigate the conditions under which the said architecture and learning rule demonstrate best performance. Our work indicates that networks featuring strong Mexican-Hat-shaped recurrent connections in the top layer, where decision making is governed by the formation of a stable activity bump in the neural population (a "non-democratic" mechanism), achieve mediocre learning results at best. In absence of recurrent connections, where all neurons "vote" independently ("democratic") for a decision via population vector readout, the task is generally learned better and more robustly. Our study would have been extremely difficult on a desktop computer without the use of GPU programming. We present the routines developed for this purpose and show that a speed improvement of 5x up to 42x is provided versus optimised Python code. The higher speed is achieved when we exploit the parallelism of the GPU in the search of learning parameters. This suggests that efficient GPU programming can significantly reduce the time needed for simulating networks of spiking neurons, particularly when multiple parameter configurations are investigated.
DEFF Research Database (Denmark)
Niero, M.; Di Felice, F.; Ren, Jingzheng;
to consider changes in the design of the wooden pallets. Based on the results of the application of the LCI parametric model to a selection of different wooden pallets, we further determined numerical correlations between the environmental impacts and the most significant inventory parameters, i.e. mass...
A parametric study of assembly pressure, thermal expansion, and membrane swelling in PEM fuel cells
Directory of Open Access Journals (Sweden)
Maher A.R. Sadiq Al-Baghdadi
2016-01-01
Full Text Available Proton Exchange membrane (PEM fuel cells are still undergoing intense development, and the combination of new and optimized materials, improved product development, novel architectures, more efficient transport processes, and design optimization and integration are expected to lead to major gains in performance, efficiency, durability, reliability, manufacturability and cost-effectiveness. PEM fuel cell assembly pressure is known to cause large strains in the cell components. All components compression occurs during the assembly process of the cell, but also during fuel cell operation due to membrane swelling when absorbs water and cell materials expansion due to heat generating in catalyst layers. Additionally, the repetitive channel-rib pattern of the bipolar plates results in a highly inhomogeneous compressive load, so that while large strains are produced under the rib, the region under the channels remains approximately at its initial uncompressed state. This leads to significant spatial variations in GDL thickness and porosity distributions, as well as in electrical and thermal bulk conductivities and contact resistances (both at the ribe-GDL and membrane-GDL interfaces. These changes affect the rates of mass, charge, and heat transport through the GDL, thus impacting fuel cell performance and lifetime. In this paper, computational fluid dynamics (CFD model of a PEM fuel cell has been developed to simulate the pressure distribution inside the cell, which are occurring during fuel cell assembly (bolt assembling, and membrane swelling and cell materials expansion during fuel cell running due to the changes of temperature and relative humidity. The PEM fuel cell model simulated includes the following components; two bi-polar plates, two GDLs, and, an MEA (membrane plus two CLs. This model is used to study and analyses the effect of assembling and operating parameters on the mechanical behaviour of PEM. The analysis helped identifying critical
Parametric study of Fischer-Tropsch synthesis in supercritical phase carbon dioxide
Gautam, Jitendra
The results from studies on Fischer Tropsch synthesis wherein syngas was dissolved in CO2 are presented. The syngas generally used was typical of that obtained from coal gasification, i.e. CO:H2 of one. Under these conditions Co-based catalysts without any water gas shift catalyst does not perform well while Fe -- based catalysts have been found to be useful. However, the Fe based catalysts have a propensity towards CO2 selectivity via the primary FT reaction, Boudouard reaction and the water gas shift reaction. The use of CO2 as a solvent was found to suppress the CO2 and CH4 selectivity while enhancing the hydrocarbon selectivity and CO conversion when FT synthesis was conducted using coal derived syngas on Fe-Zn-K catalysts. The effects were found to be significantly pronounced at pressures higher than or equal to 1200 psig. It should be noted that CO2 is supercritical at pressures higher than 1070 psig and 31.4 °C. The effect of CO2 partial pressure, reactor pressure, reaction temperature, catalyst loading and H 2:CO ratio in syngas on the liquid product distribution was evaluated. Some of the notable findings include product tenability by varying temperature and pressure as well as varying the CO2 partial pressure and the syngas composition. Increasing the reactor pressure was found to favor longer chain growth. In addition, it was noted that the ratio between CO2:syngas in the reaction mixture is an important factor in the liquid product distribution. A higher value of the ratio is seen to favor hydrocarbon synthesis, while a lower value of the ratio favors oxygenate production particularly pentanols and butanols. In addition, the data on the once through fractionation of the products utilizing the solubilities in supercritical CO2 and pressure tuning were encouraging. It was found that the products can be easily fractionated into narrow carbon chain length distributions downstream of the reactor by simply reducing the pressures in each collection vessel. It
Karthick, S. K.; Rao, Srisha M. V.; Jagadeesh, G.; Reddy, K. P. J.
2016-07-01
We use the rectangular gaseous supersonic ejector as a platform to study the mixing characteristics of a confined supersonic jet. The entrainment ratio (ER) of the ejector, the non-mixed length (LNM), and potential core length (LPC) of the primary supersonic jet are measures to characterize mixing within the supersonic ejector. Experiments are carried out on a low area ratio rectangular supersonic ejector with air as the working fluid in both primary and secondary flows. The design Mach number of the nozzle (MPD = 1.5-3.0) and primary flow stagnation pressure (Pop = 4.89-9.89 bars) are the parameters that are varied during experimentation. Wall static pressure measurements are carried out to understand the performance of the ejector as well as to estimate the LNM (the spatial resolution is limited by the placement of pressure transducers). Well-resolved flow images (with a spatial resolution of 50 μm/pixel and temporal resolution of 1.25 ms) obtained through Planar Laser Mie Scattering (PLMS) show the flow dynamics within the ejector with clarity. The primary flow and secondary flow are seeded separately with acetone that makes the LNM and LPC clearly visible in the flow images. These parameters are extracted from the flow images using in-house image processing routines. A significant development in this work is the definition of new scaling parameters within the ejector. LNM, non-dimensionalized with respect to the fully expanded jet height hJ, is found to be a linear function of the Mach number ratio (Mach number ratio is defined as the ratio of design Mach number (MPD) and fully expanded Mach number (MPJ) of the primary jet). This definition also provides a clear demarcation of under-expanded and over-expanded regimes of operation according to [MPD/MPJ] > 1 and [MPD/MPJ] < 1, respectively. It is observed that the ER increased in over-expanded mode (to 120%) and decreased in under-expanded mode (to 68%). Similarly, LNM decreased (to 21.8%) in over-expanded mode
Controlling Parametric Resonance
DEFF Research Database (Denmark)
Galeazzi, Roberto; Pettersen, Kristin Ytterstad
2012-01-01
Parametric resonance is a resonant phenomenon which takes place in systems characterized by periodic variations of some parameters. While seen as a threatening condition, whose onset can drive a system into instability, this chapter advocates that parametric resonance may become an advantage if t...
Directory of Open Access Journals (Sweden)
Eloranta Sandra
2012-06-01
Full Text Available Abstract Background Relative survival is commonly used for studying survival of cancer patients as it captures both the direct and indirect contribution of a cancer diagnosis on mortality by comparing the observed survival of the patients to the expected survival in a comparable cancer-free population. However, existing methods do not allow estimation of the impact of isolated conditions (e.g., excess cardiovascular mortality on the total excess mortality. For this purpose we extend flexible parametric survival models for relative survival, which use restricted cubic splines for the baseline cumulative excess hazard and for any time-dependent effects. Methods In the extended model we partition the excess mortality associated with a diagnosis of cancer through estimating a separate baseline excess hazard function for the outcomes under investigation. This is done by incorporating mutually exclusive background mortality rates, stratified by the underlying causes of death reported in the Swedish population, and by introducing cause of death as a time-dependent effect in the extended model. This approach thereby enables modeling of temporal trends in e.g., excess cardiovascular mortality and remaining cancer excess mortality simultaneously. Furthermore, we illustrate how the results from the proposed model can be used to derive crude probabilities of death due to the component parts, i.e., probabilities estimated in the presence of competing causes of death. Results The method is illustrated with examples where the total excess mortality experienced by patients diagnosed with breast cancer is partitioned into excess cardiovascular mortality and remaining cancer excess mortality. Conclusions The proposed method can be used to simultaneously study disease patterns and temporal trends for various causes of cancer-consequent deaths. Such information should be of interest for patients and clinicians as one way of improving prognosis after cancer is
Energy Technology Data Exchange (ETDEWEB)
Thorwarth, Daniela [Tuebingen Univ. (Germany). Section for Biomedical Physics; Notohamiprodjo, Mike [Tuebingen Univ. (Germany). Dept. of Diagnostic and Interventional Radiology; Zips, Daniel; Mueller, Arndt-Christan [Tuebingen Univ. (Germany). Dept. of Radiation Oncology
2017-05-01
To increase tumour control probability (TCP) in prostate cancer a method was developed integrating multi-parametric functional and biological information into a dose painting treatment plan aiming focal dose-escalation to tumour sub-volumes. A dose-escalation map was derived considering individual, multi-parametric estimated tumour aggressiveness. Multi-parametric functional imaging (MRI, Choline-/PSMA-/FMISO-PET/CT) was acquired for a high risk prostate cancer patient with a high level of tumour load (cT3b cN0 cM0) indicated by subtotal involvement of prostate including the right seminal vesicle and by PSA-level >100. Probability of tumour presence was determined by a combination of multi-parametric functional image information resulting in a voxel-based map of tumour aggressiveness. This probability map was directly integrated into dose optimization in order to plan for inhomogeneous, biological imaging based dose painting. Histograms of the multi-parametric prescription function were generated in addition to a differential histogram of the planned inhomogeneous doses. Comparison of prescribed doses with planned doses on a voxel level was realized using an effective DVH, containing the ratio of prescribed vs. planned dose for each tumour voxel. Multi-parametric imaging data of PSMA, Choline and FMISO PET/CT as well as ADC maps derived from diffusion weighted MRI were combined to an individual probability map of tumour presence. Voxel-based prescription doses ranged from 75.3 Gy up to 93.4 Gy (median: 79.6 Gy), whereas the planned dose painting doses varied only between 72.5 and 80.0 Gy with a median dose of 75.7 Gy. However, inhomogeneous voxel-based dose prescriptions can only be implemented into a treatment plan until a certain level. Multi-parametric probability based dose painting in prostate cancer is technically and clinically feasible. However, detailed calibration functions to define the necessary probability functions need to be assessed in future
Setup Time Reduction On Solder Paste Printing Machine – A Case Study
Directory of Open Access Journals (Sweden)
Rajesh Dhake
2013-06-01
Full Text Available Lean manufacturing envisages the reduction of the seven deadly wastes referred to as MUDA. Setup time forms a major component of the equipment downtime. It leads to lower machine utilization and restricts the output and product variety. This necessitates the requirement for quick setups. Single Minute Exchange of Die philosophy (a lean manufacturing tool here after referred as “SMED” is one of the important tool which aims at quick setups driving smaller lot sizes, lower production costs, improve productivity in terms of increased output, increased utilization of machine and labor hours, make additional capacity available (often at bottleneck resources, reduce scrap and rework, and increase flexibility[3]. This paper focuses on the application of Single Minute Exchange of Die[1] and Quick Changeover Philosophy[2] for reducing setup time on Solder Past Printing Machine (bottleneck machine in a electronic speedo-cluster manufacturing company. The four step SMED philosophy was adopted to effect reduction in setup time. The initial step was gathering information about the present setup times and its proportion to the total productive time. A detailed video based time study of setup activities was done to classify them into external and internal setup activities in terms of their need (i.e. preparation, replacement or adjustment, time taken and the way these could be reduced, simplified or eliminated. The improvements effected were of three categories viz., mechanical, procedural and organizational. The paper concludes by comparing the present and proposed (implemented methods of setup procedures.
Machining Duplex Stainless Steel: Comparative Study Regarding End Mill Coated Tools
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Ronny M. Gouveia
2016-10-01
Full Text Available The difficulties in the machining of duplex stainless steel are well known. However, research on this matter is rather limited. Suppliers offer quite different cutting tools for the same raw material, with end mills of two, three or even four knives and a huge number of distinct coatings, some of them under commercial brands, making it difficult to assess the advantages they offer. Furthermore, there is a remarkable difference among the several types of duplex stainless steel available nowadays on the market. The present work intends to assess the machining performance of different tools, analyzing the behavior and wear mechanisms with two different cutting lengths, keeping constant the machining trajectory. Some other parameters were also kept constant, such as cutting speed, depth of cut and cutting width, as well as feed per tooth. The machining process was carried out under lubricated conditions, using an emulsion of 5% oil in water. Tools provided with a different number of teeth and surface coatings were tested, analyzing the wear behavior of each cutting length using scanning electron microscopy, trying to identify wear performance and how each coating contributes to increased tool life. The surfaces produced were also analyzed by means of profilometry measurements, correlating tool wear and part surface roughness. This comparative study allows determining the advantages of different tools relative to others, based on coatings and tool geometry.
Karsi, Redouane; Zaim, Mounia; El Alami, Jamila
2017-07-01
Thanks to the development of the internet, a large community now has the possibility to communicate and express its opinions and preferences through multiple media such as blogs, forums, social networks and e-commerce sites. Today, it becomes clearer that opinions published on the web are a very valuable source for decision-making, so a rapidly growing field of research called “sentiment analysis” is born to address the problem of automatically determining the polarity (Positive, negative, neutral,…) of textual opinions. People expressing themselves in a particular domain often use specific domain language expressions, thus, building a classifier, which performs well in different domains is a challenging problem. The purpose of this paper is to evaluate the impact of domain for sentiment classification when using machine learning techniques. In our study three popular machine learning techniques: Support Vector Machines (SVM), Naive Bayes and K nearest neighbors(KNN) were applied on datasets collected from different domains. Experimental results show that Support Vector Machines outperforms other classifiers in all domains, since it achieved at least 74.75% accuracy with a standard deviation of 4,08.
Experimental study on bearing preload optimum of machine tool spindle
Xu, Tao; Xu, Guanghua; Zhang, Qin; Hua, Cheng; Zhang, Hu; Jiang, Kuosheng
2012-05-01
An experimental study is conducted to investigate the possibility and the effect of temperature rise and vibration level of bearing by adjusting axial preloads and radial loads in spindle bearing test rig. The shaft of the test rig is driven by a motorized high speed spindle at the range of 0~20000 rpm. The axial preloads and radial loads on bearings are controlled by using hydraulic pressure which can be adjusted automatically. Temperature rise and radial vibration of test bearings are measured by thermocouples and Polytec portable laser vibrometer PDV100. Experiment shows that the temperature rise of bearings is nonlinear varying with the increase of radial loads, but temperature rise almost increases linearly with the increase of axial preload and rotating speed. In this paper, an alternate axial preload is used for bearings. When the rotating speed passes through the critical speed of the shaft, axial preload of bearings will have a remarkable effect. The low preload could reduce bearing vibration and temperature rise for bearings as well. At the others speed, the high preload could improve the vibration performance of high speed spindle and the bearing temperature was lower than that of the constant pressure preload spindle.
Man or machine? An experimental study of prehospital emergency amputation.
Leech, Caroline; Porter, Keith
2016-09-01
Prehospital emergency amputation is a rare procedure, which may be necessary to free a time-critical patient from entrapment. This study aimed to evaluate four techniques of cadaveric lower limb prehospital emergency amputation. A guillotine amputation of the distal femur was undertaken in fresh frozen self-donated cadavers. A prehospital doctor conducted a surgical amputation with Gigli saw or hacksaw for bone cuts and firefighters carried out the procedure using the reciprocating saw and Holmatro device. The primary outcome measures were time to full amputation and the number of attempts required. The secondary outcomes were observed quality of skin cut, soft tissue cut and CT assessment of the proximal bone. Observers also noted the potential risks to the rescuer or patient during the procedure. All techniques completed amputation within 91 s. The reciprocating saw was the quickest technique (22 s) but there was significant blood spattering and continuation of the cut to the surface under the leg. The Holmatro device took less than a minute. The quality of the proximal femur was acceptable with all methods, but 5 cm more proximal soft tissue damage was made by the Holmatro device. Emergency prehospital guillotine amputation of the distal femur can effectively be performed using scalpel and paramedic shears with bone cuts by the Gigli saw or fire service hacksaw. The reciprocating saw could be used to cut bone if no other equipment was available but carried some risks. The Holmatro cutting device is a viable option for a life-threatening entrapment where only firefighters can safely access the patient, but would not be a recommended primary technique for medical staff. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/
Directory of Open Access Journals (Sweden)
DUMITRACHE Petru
2011-11-01
Full Text Available The objective of this paper is the highlighting of the main aspects that be considered in parametric modelling of the ROPS/FOPS protective structures in order to study of their behaviour using finite element method. In first part of the paper are presented, briefly, the main reference documents governing the mechanical protection of the human operator of machinery and equipment construction. Also, is presented the scheme of the optimization process of protective structures using CAD and FEA platforms. Next, is presented a parametric analysis of the protective structures geometry, in order to determine the main geometric parameters that define the geometry of these structures. These geometrical parameters are used in a case study where the geometry for a protective structure was generated using a CAD platform. In final part of the article are to present conclusions.
Directory of Open Access Journals (Sweden)
Ali Zare
2011-10-01
Full Text Available Survival analysis is a set of methods used for analysis of the data which exist until the occurrence of an event. This study aimed to compare the results of the use of the semi-parametric Cox model with parametric models to determine the factors influencing the length of stay of patients in the inpatient units of Women Hospital in Tehran, Iran. In this historical cohort study all 3421 charts of the patients admitted to Obstetrics, Surgery and Oncology units in 2008 were reviewed and the required patient data such as medical insurance coverage types, admission months, days and times, inpatient units, final diagnoses, the number of diagnostic tests, admission types were collected. The patient length of stay in hospitals leading to recoverys was considered as a survival variable. To compare the semi-parametric Cox model and parametric (including exponential, Weibull, Gompertz, log-normal, log-logistic and gamma models and find the best model fitted to studied data, Akaike's Information Criterion (AIC and Cox-Snell residual were used. P<0.05 was considered as statistically significant. AIC and Cox-Snell residual graph showed that the gamma model had the lowest AIC (4288.598 and the closest graph to the bisector. The results of the gamma model showed that factors affecting the patient length of stay were admission day, inpatient unit, related physician specialty, emergent admission, final diagnosis and the number of laboratory tests, radiographies and sonographies (P<0.05. The results showed that the gamma model provided a better fit to the studied data than the Cox proportional hazards model. Therefore, it is better for researchers of healthcare field to consider this model in their researches about the patient length of stay (LOS if the assumption of proportional hazards is not fulfilled.
Acomi, Nicoleta; Ancuţa, Cristian; Andrei, Cristian; Boştinǎ, Alina; Boştinǎ, Aurel
2016-12-01
Ships are mainly built to sail and transport cargo at sea. Environmental conditions and state of the sea are communicated to vessels through periodic weather forecasts. Despite officers being aware of the sea state, their sea time experience is a decisive factor when the vessel encounters severe environmental conditions. Another important factor is the loading condition of the vessel, which triggers different behaviour in similar marine environmental conditions. This paper aims to analyse the behaviour of a port container vessel in severe environmental conditions and to estimate the potential conditions of parametric roll resonance. Octopus software simulation is employed to simulate vessel motions under certain conditions of the sea, with possibility to analyse the behaviour of ships and the impact of high waves on ships due to specific wave encounter situations. The study should be regarded as a supporting tool during the decision making process.
Biological parametric mapping with robust and non-parametric statistics.
Yang, Xue; Beason-Held, Lori; Resnick, Susan M; Landman, Bennett A
2011-07-15
Mapping the quantitative relationship between structure and function in the human brain is an important and challenging problem. Numerous volumetric, surface, regions of interest and voxelwise image processing techniques have been developed to statistically assess potential correlations between imaging and non-imaging metrices. Recently, biological parametric mapping has extended the widely popular statistical parametric mapping approach to enable application of the general linear model to multiple image modalities (both for regressors and regressands) along with scalar valued observations. This approach offers great promise for direct, voxelwise assessment of structural and functional relationships with multiple imaging modalities. However, as presented, the biological parametric mapping approach is not robust to outliers and may lead to invalid inferences (e.g., artifactual low p-values) due to slight mis-registration or variation in anatomy between subjects. To enable widespread application of this approach, we introduce robust regression and non-parametric regression in the neuroimaging context of application of the general linear model. Through simulation and empirical studies, we demonstrate that our robust approach reduces sensitivity to outliers without substantial degradation in power. The robust approach and associated software package provide a reliable way to quantitatively assess voxelwise correlations between structural and functional neuroimaging modalities. Copyright © 2011 Elsevier Inc. All rights reserved.
Schmidt, Andreas; Lausch, Angela; Vogel, Hans-Jörg
2016-04-01
Diffuse reflectance spectroscopy as a soil analytical tool is spreading more and more. There is a wide range of possible applications ranging from the point scale (e.g. simple soil samples, drill cores, vertical profile scans) through the field scale to the regional and even global scale (UAV, airborne and space borne instruments, soil reflectance databases). The basic idea is that the soil's reflectance spectrum holds information about its properties (like organic matter content or mineral composition). The relation between soil properties and the observable spectrum is usually not exactly know and is typically derived from statistical methods. Nowadays these methods are classified in the term machine learning, which comprises a vast pool of algorithms and methods for learning the relationship between pairs if input - output data (training data set). Within this pool of methods a Gaussian Process Regression (GPR) is newly emerging method (originating from Bayesian statistics) which is increasingly applied to applications in different fields. For example, it was successfully used to predict vegetation parameters from hyperspectral remote sensing data. In this study we apply GPR to predict soil organic carbon from soil spectroscopy data (400 - 2500 nm). We compare it to more traditional and widely used methods such as Partitial Least Squares Regression (PLSR), Random Forest (RF) and Gradient Boosted Regression Trees (GBRT). All these methods have the common ability to calculate a measure for the variable importance (wavelengths importance). The main advantage of GPR is its ability to also predict the variance of the target parameter. This makes it easy to see whether a prediction is reliable or not. The ability to choose from various covariance functions makes GPR a flexible method. This allows for including different assumptions or a priori knowledge about the data. For this study we use samples from three different locations to test the prediction accuracies. One
When Machines Design Machines!
DEFF Research Database (Denmark)
2011-01-01
Until recently we were the sole designers, alone in the driving seat making all the decisions. But, we have created a world of complexity way beyond human ability to understand, control, and govern. Machines now do more trades than humans on stock markets, they control our power, water, gas...... and food supplies, manage our elevators, microclimates, automobiles and transport systems, and manufacture almost everything. It should come as no surprise that machines are now designing machines. The chips that power our computers and mobile phones, the robots and commercial processing plants on which we...... depend, all are now largely designed by machines. So what of us - will be totally usurped, or are we looking at a new symbiosis with human and artificial intelligences combined to realise the best outcomes possible. In most respects we have no choice! Human abilities alone cannot solve any of the major...
Vi, Peter
2006-11-15
A field study with a before-and-after experimental design was conducted to evaluate the potential reduction in the risk of musculoskeletal injuries to rodworkers when using an automatic rebar-tying machine. Eleven rodworkers participated in this experiment. All dependent variables (trunk posture, rebar-tying time and responses to a usability questionnaire) were first measured before introducing the rebar-tying machine and then after 3 months of usage all dependent variables were measured again. The results of the study indicated that working with a rebar-tying machine significantly reduced the magnitude, frequency and duration of exposure to awkward trunk posture. Tying time was reduced when participants used the machine. The usability questionnaire indicated that most participants preferred to use the rebar-tying machine for ground-level rebar construction. The field study also revealed that the rebar-tying machine is not limited to the reinforcing trade. The machine can be used for other purposes, such as tying electrical conduit and attaching radiant heat tube to steel mesh. Based on trunk posture exposure, rebar-tying time, usability and transferability, it is concluded that the rebar-tying machine can be an effective tool to reduce the frequency and duration of severe trunk flexion, improve usability and increase productivity among concrete reinforcement workers.
Form, William; McMillen, David Byron
1983-01-01
Data from the first national study of technological change show that proportionately more women than men operate machines, are more exposed to machines that have alienating effects, and suffer more from the negative effects of technological change. (Author/SSH)
Ali, Ishtiaq; 10.5121/ijnsa.2011.3101
2011-01-01
The interest in virtualization has been growing rapidly in the IT industry because of inherent benefits like better resource utilization and ease of system manageability. The experimentation and use of virtualization as well as the simultaneous deployment of virtual software are increasingly getting popular and in use by educational institutions for research and teaching. This paper stresses on the potential advantages associated with virtualization and the use of virtual machines for scenarios, which cannot be easily implemented and/or studied in a traditional academic network environment, but need to be explored and experimented by students to meet the raising needs and knowledge-base demanded by the IT industry. In this context, we discuss various aspects of virtualization - starting from the working principle of virtual machines, installation procedure for a virtual guest operating system on a physical host operating system, virtualization options and a performance study measuring the throughput obtained ...
Using machine-coded event data for the micro-level study of political violence
Directory of Open Access Journals (Sweden)
Jesse Hammond
2014-07-01
Full Text Available Machine-coded datasets likely represent the future of event data analysis. We assess the use of one of these datasets—Global Database of Events, Language and Tone (GDELT—for the micro-level study of political violence by comparing it to two hand-coded conflict event datasets. Our findings indicate that GDELT should be used with caution for geo-spatial analyses at the subnational level: its overall correlation with hand-coded data is mediocre, and at the local level major issues of geographic bias exist in how events are reported. Overall, our findings suggest that due to these issues, researchers studying local conflict processes may want to wait for a more reliable geocoding method before relying too heavily on this set of machine-coded data.
End mill tools integration in CNC machining for rapid manufacturing processes: simulation studies
Muhammed Nafis Osman Zahid; Keith Case; Darren Watts
2015-01-01
Computer numerical controlled (CNC) machining has been recognized as a manufacturing process that is capable of producing metal parts with high precision and reliable quality, whereas many additive manufacturing methods are less capable in these respects. The introduction of a new layer-removal methodology that utilizes an indexing device to clamp the workpiece can be used to extend CNC applications into the realm of rapid manufacturing (CNC-RM) processes. This study aims to improve the imple...
End mill tools integration in CNC machining for rapid manufacturing processes: simulation studies
Muhammed Nafis Osman Zahid; Keith Case; Darren Watts
2015-01-01
Computer numerical controlled (CNC) machining has been recognized as a manufacturing process that is capable of producing metal parts with high precision and reliable quality, whereas many additive manufacturing methods are less capable in these respects. The introduction of a new layer-removal methodology that utilizes an indexing device to clamp the workpiece can be used to extend CNC applications into the realm of rapid manufacturing (CNC-RM) processes. This study aims to improve the imple...
Deflecting cavity dynamics for time-resolved machine studies of SXFEL user facility
Song, Minghao; Liu, Bo; Wang, Dong
2016-01-01
Radio frequency deflectors are widely used for time-resolved electron beam energy, emittance and radiation profile measurements in modern free electron laser facilities. In this paper, we present the beam dynamics aspects of the deflecting cavity of SXFEL user facility, which is located at the exit of the undulator. With a targeted time resolution around 10 fs, it is expected to be an important tool for time-resolved commissioning and machine studies for SXFEL user facility.
Ahoughalandari, Bahar; Cabral, Alexandre R
2017-05-01
The efficiency of methane oxidation in passive methane oxidation biosystems (PMOBs) is influenced by, among other things, the intensity and distribution of the CH4 loading at the base of the methane oxidation layer (MOL). Both the intensity and distribution are affected by the capillary barrier that results from the superposition of the two materials constituting the PMOB, namely the MOL and the gas distribution layer (GDL). The effect of capillary barriers on the unsaturated flow of water has been well documented in the literature. However, its effect on gas flow through PMOBs is still poorly documented. In this study, sets of numerical simulations were performed to evaluate the effect of unsaturated hydraulic characteristics of the MOL material on the value and distribution of moisture and hence, the ease and uniformity in the distribution of the upward flow of biogas along the GDL-MOL interface. The unsaturated hydraulic parameters of the materials used to construct the experimental field plot at the St-Nicephore landfill (Quebec, Canada) were adopted to build the reference simulation of the parametric study. The behavior of the upward flow of biogas for this particular material was analyzed based on its gas intrinsic permeability function, which was obtained in the laboratory. The parameters that most influenced the distribution and the ease of biogas flow at the base of the MOL were the saturated hydraulic conductivity and pore size distribution of the MOL material, whose effects were intensified as the slope of the interface increased. The effect of initial dry density was also assessed herein. Selection of the MOL material must be made bearing in mind that these three parameters are key in the effort to prevent unwanted restriction in the upward flow of biogas, which may result in the redirection of biogas towards the top of the slope, leading to high CH4 fluxes (hotspots). In a well-designed PMOB, upward flow of biogas across the GDL-MOL interface is
Rotary ultrasonic machining of CFRP composites: a study on power consumption.
Cong, W L; Pei, Z J; Deines, T W; Srivastava, Anil; Riley, L; Treadwell, C
2012-12-01
Carbon fiber reinforced plastic (CFRP) composites are very difficult to machine. A large number of holes need to be drilled in CFRP for many applications. Therefore, it is important to develop cost-effective drilling processes. CFRP has been drilled by rotary ultrasonic machining (RUM) successfully. The literature has reports about the effects of input variables on output variables (including cutting force, torque, surface roughness, tool wear, and workpiece delamination) in RUM of CFRP. However, there are no reports on power consumption in RUM of CFRP. This paper reports the first study on power consumption in RUM of CFRP. It reports an experimental investigation on effects of input variables (ultrasonic power, tool rotation speed, feedrate, and type of CFRP) on power consumption of each component (including ultrasonic power supply, spindle motor, coolant pump, and air compressor) and the entire RUM system.
Directory of Open Access Journals (Sweden)
Hassan Bakhshandeh Amnieh
2016-06-01
Full Text Available Technological progress in tunneling has led to modern and efficient tunneling methods in vast underground spaces even under inappropriate geological conditions. Identification and access to appropriate and sufficient geological hazard data are key elements to successful construction of underground structures. Choice of the method, excavation machine, and prediction of suitable solutions to overcome undesirable conditions depend on geological studies and hazard analysis. Identifying and investigating the ground hazards in excavating urban tunnels by an EPB machine could augment the strategy for improving soil conditions during excavation operations. In this paper, challenges such as geological hazards, abrasion of the machine cutting tools, clogging around these tools and inside the chamber, diverse work front, severe water level fluctuations, existence of water, and fine-grained particles in the route were recognized in a study of Tehran subway line 7, for which solutions such as low speed boring, regular cutter head checks, application of soil improving agents, and appropriate grouting were presented and discussed. Due to the presence of fine particles in the route, foam employment was suggested as the optimum strategy where no filler is needed.
Marçais, J.; Gupta, H. V.; De Dreuzy, J. R.; Troch, P. A. A.
2016-12-01
Geomorphological structure and geological heterogeneity of hillslopes are major controls on runoff responses. The diversity of hillslopes (morphological shapes and geological structures) on one hand, and the highly non linear runoff mechanism response on the other hand, make it difficult to transpose what has been learnt at one specific hillslope to another. Therefore, making reliable predictions on runoff appearance or river flow for a given hillslope is a challenge. Applying a classic model calibration (based on inverse problems technique) requires doing it for each specific hillslope and having some data available for calibration. When applied to thousands of cases it cannot always be promoted. Here we propose a novel modeling framework based on coupling process based models with data based approach. First we develop a mechanistic model, based on hillslope storage Boussinesq equations (Troch et al. 2003), able to model non linear runoff responses to rainfall at the hillslope scale. Second we set up a model database, representing thousands of non calibrated simulations. These simulations investigate different hillslope shapes (real ones obtained by analyzing 5m digital elevation model of Brittany and synthetic ones), different hillslope geological structures (i.e. different parametrizations) and different hydrologic forcing terms (i.e. different infiltration chronicles). Then, we use this model library to train a machine learning model on this physically based database. Machine learning model performance is then assessed by a classic validating phase (testing it on new hillslopes and comparing machine learning with mechanistic outputs). Finally we use this machine learning model to learn what are the hillslope properties controlling runoffs. This methodology will be further tested combining synthetic datasets with real ones.
Er, Füsun; Iscen, Pınar; Sahin, Sevki; Çinar, Nilgun; Karsidag, Sibel; Goularas, Dionysis
2017-08-01
This study aims to examine the distinguishability of age-related cognitive decline (ARCD) from dementias based on some neurocognitive tests using machine learning. 106 subjects were divided into four groups: ARCD (n=30), probable Alzheimer's disease (AD) (n=20), vascular dementia (VD) (n=21) and amnestic mild cognitive impairment (MCI) (n=35). The following tests were applied to all subjects: The Wechsler memory scale-revised, a clock-drawing, the dual similarities, interpretation of proverbs, word fluency, the Stroop, the Boston naming (BNT), the Benton face recognition, a copying-drawings and Öktem verbal memory processes (Ö-VMPT) tests. A multilayer perceptron, a support vector machine and a classification via regression with M5-model trees were employed for classification. The pairwise classification results show that ARCD is completely separable from AD with a success rate of 100% and highly separable from MCI and VD with success rates of 95.4% and 86.30%, respectively. The neurocognitive tests with the higher merit values were Ö-VMPT recognition (ARCD vs. AD), Ö-VMPT total learning (ARCD vs. MCI) and semantic fluency, proverbs, Stroop interference and naming BNT (ARCD vs. VD). The findings show that machine learning can be successfully utilized for distinguishing ARCD from dementias based on neurocognitive tests. Copyright © 2017 Elsevier Ltd. All rights reserved.
Maloney, J A; Derbenev, Ya S; Afanasev, A; Johnson, R P; Ankenbrandt, C A; Yoshikawa, C; Yonehara, K; Neuffer, D; Erdelyi, B
2014-01-01
Muon colliders have been proposed for the next generation of particle accelerators that study high-energy physics at the energy and intensity frontiers. In this paper we study a possible implementation of muon ionization cooling, Parametric-resonance Ionization Cooling (PIC), in the twin helix channel. The resonant cooling method of PIC offers the potential to reduce emittance beyond that achievable with ionization cooling with ordinary magnetic focusing. We examine optimization of a variety of parameters, study the nonlinear dynamics in the twin helix channel and consider possible methods of aberration correction.
Wang, Ying; Feng, Chenglian; Liu, Yuedan; Zhao, Yujie; Li, Huixian; Zhao, Tianhui; Guo, Wenjing
2017-02-01
Transition metals in the fourth period of the periodic table of the elements are widely widespread in aquatic environments. They could often occur at certain concentrations to cause adverse effects on aquatic life and human health. Generally, parametric models are mostly used to construct species sensitivity distributions (SSDs), which result in comparison for water quality criteria (WQC) of elements in the same period or group of the periodic table might be inaccurate and the results could be biased. To address this inadequacy, the non-parametric kernel density estimation (NPKDE) with its optimal bandwidths and testing methods were developed for establishing SSDs. The NPKDE was better fit, more robustness and better predicted than conventional normal and logistic parametric density estimations for constructing SSDs and deriving acute HC5 and WQC for transition metals in the fourth period of the periodic table. The decreasing sequence of HC5 values for the transition metals in the fourth period was Ti > Mn > V > Ni > Zn > Cu > Fe > Co > Cr(VI), which were not proportional to atomic number in the periodic table, and for different metals the relatively sensitive species were also different. The results indicated that except for physical and chemical properties there are other factors affecting toxicity mechanisms of transition metals. The proposed method enriched the methodological foundation for WQC. Meanwhile, it also provided a relatively innovative, accurate approach for the WQC derivation and risk assessment of the same group and period metals in aquatic environments to support protection of aquatic organisms.
Piattelli, Maurizio; Scarano, Antonio; Paolantonio, Michele; Iezzi, Giovanna; Petrone, Giovanna; Piattelli, Adriano
2002-01-01
The aim of the present study was a comparison of implants' responses to a machined surface and to a surface sandblasted with hydroxyapatite (HA) particles (resorbable blast material [RBM]). Threaded machined and RBM, grade 3, commercially pure, titanium, screw-shaped inplants were used in this study. Twenty-four New Zealand white mature male rabbits were used. The inplants were inserted into the articular femoral knee joint according to a previously described technique. Each rabbit received 2 inplants, 1 test (RBM) and 1 control (machined). A total of 48 implants (24 control and 24 test) were inserted. The rabbits were anesthetized with intramuscular injections of fluanisone (0.7 mg/ kg body weight) and diazepam (1.5 mg/kg b.wt.), and local anesthesia was given using 1 mL of 2% lidocaine/adrenalin solution. Two rabbits died in the postoperative course. Four animals were euthanatized with an overdose of intravenous pentobarbital after 1, 2, 3, and 4 weeks; 6 rabbits were euthanatized after 8 weeks. A total of 44 implants were retrieved. The specimens were processed with the Precise 1 Automated System to obtain thin ground sections. A total of 3 slides were obtained for each implant. The slides were stained with acid and basic fuchsin and toluidine blue. The slides were observed in normal transmitted light under a Leitz Laborlux microscope, and histomorphometric analysis was performed. With the machined implants, it was possible to observe the presence of bone trabeculae near the implant surface at low magnification. At higher magnification many actively secreting alkaline phosphatasepositive (ALP+) osteoblasts were observed. In many areas, a not yet mineralized matrix was present. After 4 to 8 weeks, mature bone appeared in direct contact with the implant surface, but in many areas a not yet mineralized osteoid matrix was interposed between the mineralized bone and implant surface. In the RBM implants, many ALP+ osteoblasts were present and in direct contact with
Cohen; Heller
2000-03-27
We consider a classically chaotic system that is described by a Hamiltonian H(Q,P;x), where x is a constant parameter. Specifically, we discuss a gas particle inside a cavity, where x controls a deformation of the boundary or the position of a "piston." The quantum eigenstates of the system are |n(x)>. We describe how the parametric kernel P(nmid R:m) = ||(2) evolves as a function of deltax = x-x(0). We explore both the perturbative and the nonperturbative regimes, and discuss the capabilities and the limitations of semiclassical as well as random waves and random-matrix-theory considerations.
Mytidis, Antonis; Panagopoulos, Orestis P; Whiting, Bernard
2015-01-01
This is a follow-up sensitivity study on r-mode gravitational wave signals from newborn neutron stars illustrating the applicability of machine learning algorithms for the detection of long-lived gravitational-wave transients. In this sensitivity study we examine three machine learning algorithms (MLAs): artificial neural networks (ANNs), support vector machines (SVMs) and constrained subspace classifiers (CSCs). The objective of this study is to compare the detection efficiency that MLAs can achieve with the efficiency of conventional detection algorithms discussed in an earlier paper. Comparisons are made using 2 distinct r-mode waveforms. For the training of the MLAs we assumed that some information about the distance to the source is given so that the training was performed over distance ranges not wider than half an order of magnitude. The results of this study suggest that machine learning algorithms are suitable for the detection of long-lived gravitational-wave transients and that when assuming knowle...
Institute of Scientific and Technical Information of China (English)
Zhao Xiufen; Yin Guofu; Tian Guiyun; Yin Ying
2008-01-01
Automatic identification of flaws is very important for ultrasonic nondestructive testing and evaluation of large shaft. A novel automatic defect identification system is presented. Wavelet packet analysis (WPA) was applied to feature extraction of ultrasonic signal, and optimal Support vector machine (SVM) was used to perform the identification task. Meanwhile, comparative study on convergent velocity and classified effect was done among SVM and several improved BP network models. To validate the method, some experiments were performed and the results show that the proposed system has very high identification performance for large shafts and the optimal SVM processes better classification performance and spreading potential than BP manual neural network under small study sample condition.
Pasetti Monizza, G.; Matt, D. T.; Benedetti, C.
2016-11-01
According to Wortmann classification, the Building Industry (BI) can be defined as engineer-to-order (ETO) industry: the engineering-process starts only when an order is acquired. This definition implies that every final product (building) is almost unique’ and processes cannot be easily standardized or automated. Because of this, BI is one of the less efficient industries today’ mostly leaded by craftsmanship. In the last years’ several improvements in process efficiency have been made focusing on manufacturing and installation processes only. In order to improve the efficiency of design and engineering processes as well, the scientific community agrees that the most fruitful strategy should be Front-End Design (FED). Nevertheless, effective techniques and tools are missing. This paper discusses outcomes of a research activity that aims at highlighting whether Parametric and Generative Design techniques allow reducing wastes of resources and improving the overall efficiency of the BI, by pushing the Digitalization of design and engineering processes of products. Focusing on the Glued-Laminated-Timber industry, authors will show how Parametric and Generative Design techniques can be introduced in a standard supply-chain system, highlighting potentials and criticism on the supply-chain system as a whole.
Dai, Houfu; Chen, Genyu; Zhou, Cong; Fang, Qihong; Fei, Xinjiang
2017-01-01
Three-dimension molecular dynamics (MD) simulations is employed to investigate the ultraprecision machining of single crystal silicon with structured nanoscale diamond tool fabricated by laser. The advantages and disadvantages of diamond machining using structured tools are discussed in comparison with those of using non-structured tools. The von Mises stress distribution, hydrostatic stress distribution, atomic displacement, stress, the radial distribution function, cutting forces, frictional coefficient, subsurface temperature and potential energy during the nanometric machining process are studied. A theoretical analysis model is also established to investigate the subsurface damage mechanism by analyzing the distribution of residual stress during the nanoscale machining process. The results show that a structured nanoscale tool in machining brittle material silicon causes a smaller hydrostatic stress, a less compressive normal stress σxx and σyy , a lower temperature and a smaller cutting force. However, the structured nanoscale tool machining results in smaller chip volume and more beta-silicon phase. Besides, the friction coefficient for tool with V-shape groove is smaller than those for non-structured tools and other structured nanoscale tools. This means that the tool with V-shape groove can reduce the resistance to cutting during the nanoscale machining process. In addition, the results also point out that the potential energy of subsurface atoms and the number of other atoms for pyramid-structured tool are much smaller than those of using non-structured tools and other structured nanoscale tools.
A Generic Synthesis Algorithm for Well-Defined Parametric Design
Schotborgh, W.O.; Kokkeler, F.G.M.; Tragter, H.; Bomhoff, M.J.; Houten, van F.J.A.M.
2008-01-01
This paper aims to improve the way synthesis tools can be built by formalizing: 1) the design artefact, 2) related knowledge and 3) an algorithm to generate solutions. This paper focuses on well-defined parametric engineering design, ranging from machine elements to industrial products. A design art
Comparison of reliability techniques of parametric and non-parametric method
Directory of Open Access Journals (Sweden)
C. Kalaiselvan
2016-06-01
Full Text Available Reliability of a product or system is the probability that the product performs adequately its intended function for the stated period of time under stated operating conditions. It is function of time. The most widely used nano ceramic capacitor C0G and X7R is used in this reliability study to generate the Time-to failure (TTF data. The time to failure data are identified by Accelerated Life Test (ALT and Highly Accelerated Life Testing (HALT. The test is conducted at high stress level to generate more failure rate within the short interval of time. The reliability method used to convert accelerated to actual condition is Parametric method and Non-Parametric method. In this paper, comparative study has been done for Parametric and Non-Parametric methods to identify the failure data. The Weibull distribution is identified for parametric method; Kaplan–Meier and Simple Actuarial Method are identified for non-parametric method. The time taken to identify the mean time to failure (MTTF in accelerating condition is the same for parametric and non-parametric method with relative deviation.
Institute of Scientific and Technical Information of China (English)
王朝琴; 王小荣; 田亚平
2014-01-01
By thoroughly analyzing present status of CNC parametric programming,a general parametric programming template (GPPT)oriented 3-axis CNC milling machine with FANUC 0i system was proposed. Many CNC functions such as polar programming (G16/G15),coordinate rotation (G68/G69)and local coordinate (G52)were integrated into one program with the characteristic of structured program. The GPPT could be used to generate feature-based program easily. Practical applications of the GPPT show that it can solve the vast majority of part/feature programming.%通过深入分析数控加工参数化编程现状，提出一个面向3轴数控铣床的通用参数化编程模板。该模板将数控编程中常用功能如极坐标编程（G16/G15）、坐标系旋转（G68/G69）和局部坐标系（G52）等集成在一个程序中，具有结构化程序特点。用该模板易于编制基于特征的参数化程序。实际应用表明，3轴数控铣床通用参数化编程模板可解决绝大部分零件/特征的编程。
Machine Learning Data Imputation and Classification in a Multicohort Hypertension Clinical Study.
Seffens, William; Evans, Chad; Taylor, Herman
2015-01-01
Health-care initiatives are pushing the development and utilization of clinical data for medical discovery and translational research studies. Machine learning tools implemented for Big Data have been applied to detect patterns in complex diseases. This study focuses on hypertension and examines phenotype data across a major clinical study called Minority Health Genomics and Translational Research Repository Database composed of self-reported African American (AA) participants combined with related cohorts. Prior genome-wide association studies for hypertension in AAs presumed that an increase of disease burden in susceptible populations is due to rare variants. But genomic analysis of hypertension, even those designed to focus on rare variants, has yielded marginal genome-wide results over many studies. Machine learning and other nonparametric statistical methods have recently been shown to uncover relationships in complex phenotypes, genotypes, and clinical data. We trained neural networks with phenotype data for missing-data imputation to increase the usable size of a clinical data set. Validity was established by showing performance effects using the expanded data set for the association of phenotype variables with case/control status of patients. Data mining classification tools were used to generate association rules.
Investigation for parametric vibration of rolling mill
Institute of Scientific and Technical Information of China (English)
唐华平; 丁睿; 吴运新; 钟掘
2002-01-01
The vibration unsteady condition of rolling mill caused by flexural vibration of strip has been investigated. The parametric flexural vibration equation of rolled strip has been established. The parametric flexural vibration stability of rolled strip has been studied and the regions of stability and unstability have been determined based on Floquet theory and perturbation method. The flexural-vibration of strip is unstable when the frequency of variable tension is two times as the natural frequency of flexural-vibration strip. The characteristic of current in a temp driving motor's main loop has been studied and tested, it has been proved that there are 6 harmonic component and 12 harmonic component in main loop of driving motor electricity. The vertical vibration of working roller has been tested, the test result approves that the running unsteady is caused by parametric vibration. It attaches importance to the parametric vibration of rolling mill.
Slocum, Alexander H
1992-01-01
This book is a comprehensive engineering exploration of all the aspects of precision machine design - both component and system design considerations for precision machines. It addresses both theoretical analysis and practical implementation providing many real-world design case studies as well as numerous examples of existing components and their characteristics. Fast becoming a classic, this book includes examples of analysis techniques, along with the philosophy of the solution method. It explores the physics of errors in machines and how such knowledge can be used to build an error budget for a machine, how error budgets can be used to design more accurate machines.
Study on the Fruit Grading Recognition System Based on Machine Vision
Directory of Open Access Journals (Sweden)
Huan Ma
2015-07-01
Full Text Available The study proposed that the current development of fruit industry requires the fast and efficient methods to test the varieties of fruits, which can combine the image processing and computer machine vision technology together to be applied in the field of fruit varieties detection, so as to be consistent with this new trend. At present, the determination of these traits were mainly depended on visual grading and manual measurement, which existed the problems such as: slow speed, low accuracy and poor objectivity and so on.
Statistical Capability Study of a Helical Grinding Machine Producing Screw Rotors
Holmes, C. S.; Headley, M.; Hart, P. W.
2017-08-01
Screw compressors depend for their efficiency and reliability on the accuracy of the rotors, and therefore on the machinery used in their production. The machinery has evolved over more than half a century in response to customer demands for production accuracy, efficiency, and flexibility, and is now at a high level on all three criteria. Production equipment and processes must be capable of maintaining accuracy over a production run, and this must be assessed statistically under strictly controlled conditions. This paper gives numerical data from such a study of an innovative machine tool and shows that it is possible to meet the demanding statistical capability requirements.
Automated Generation of Machine Verifiable and Readable Proofs: A Case Study of Tarski's Geometry
Stojanovic Durdevic, Sana; Narboux, Julien; Janicic, Predrag
2015-01-01
International audience; The power of state-of-the-art automated and interactive the-orem provers has reached the level at which a significant portion of non-trivial mathematical contents can be formalized almost fully automat-ically. In this paper we present our framework for the formalization of mathematical knowledge that can produce machine verifiable proofs (for different proof assistants) but also human-readable (nearly textbook-like) proofs. As a case study, we focus on one of the twent...
Institute of Scientific and Technical Information of China (English)
HOU Xinyi; JIANG Xiaomei; GAO Jianmin; YIN Yafang
2006-01-01
The research method of this paper is based on the standards of American Society for Testing and Materials(ASTM).Four items that contain boring,mortising,shaping and turning are selected to study the machining properties of E. urophylla×E. grandis plantation wood.The reasons for machining defects are analyzed.The result shows that E.urophylla×E.grandis planted in South China is a good species with great potential for solid wood utilization.
A Case Study of Employing A Single Server Nonpreemptive Priority Queuing Model at ATM Machine
Directory of Open Access Journals (Sweden)
Abdullah Furquan
2015-08-01
Full Text Available This paper discusses a case study of employing a single server nonpreemptivepriorityqueuing model [1]at ATM machine which originally operates on M/M/1 model. In this study we have taken two priority classes of people in following order:- .Priority class 1- woman .Priority class 2- man Sometimea long queue is formed at ATMmachine (single serverbut the bank management don’t have enough money to invest on installing new ATM machine.In this situation we want to apply single server nonpreemptive priority queuing model.The security guard at the ATM will divide the customers in two category and arrange the customers in the above said priority order Thuspriority class 1 people willreceive theatm service ahead of priority class 2 people.This will reduce the waiting time of priority class 1 people. Of course by doing this the waiting time of priority class 2will increase. This is ok as long as the increment in waiting time of priority class2 people is reasonable and within the tolerable limitof priority class 2people.This will be true when percentage of priority class 1 people is relatively less as compared to priority class 2 people To know the attitude and tolerable limit of priority class 2 people towards the single server non preemtive priority model a sample survey has been done on the incomingpriority class 2 population at the atm machine.Against this background, the queuing process is employed with emphasis to Poisson distribution to assess the waiting time. The data for this study was collected from primary source and is limited to ATM service point of state bank of India located at Ramesh chowk, Aurangabad, bihar, India.. The assistance of three colleague was sought in collecting the data. The Interarrival time and service time data was collected during busy working hours (i.e. 10.30am to 4:00pm during the first 60 days. A sample survey was done to know the attitude and tolerable limit of priority class 2people towards the single server
Programmatic Formation: Practical Applications of Parametric Design
Madkour, Yehia; Erhan, Halil; Neumann, Oliver
2009-01-01
Programmatic Formation explores design as a responsive process.The study we present engages the complexity of the surroundings using parametric and generative design methods. It illustrates that responsiveness of designs can be achieved beyond geometric explorations.The parametric models can combine and respond simultaneously to design and its programmatic factors, such as performance-sensitive design-decisions, and constraints.We demonstrate this through a series of case st...
Goswami, D.; Chakraborty, S.
2014-11-01
Laser machining is a promising non-contact process for effective machining of difficult-to-process advanced engineering materials. Increasing interest in the use of lasers for various machining operations can be attributed to its several unique advantages, like high productivity, non-contact processing, elimination of finishing operations, adaptability to automation, reduced processing cost, improved product quality, greater material utilization, minimum heat-affected zone and green manufacturing. To achieve the best desired machining performance and high quality characteristics of the machined components, it is extremely important to determine the optimal values of the laser machining process parameters. In this paper, fireworks algorithm and cuckoo search (CS) algorithm are applied for single as well as multi-response optimization of two laser machining processes. It is observed that although almost similar solutions are obtained for both these algorithms, CS algorithm outperforms fireworks algorithm with respect to average computation time, convergence rate and performance consistency.
Overview of Sustainability Studies of CNC Machining and LAM of Stainless Steel
Nyamekye, Patricia; Leino, Maija; Piili, Heidi; Salminen, Antti
Laser additive manufacturing (LAM), known also as 3D printing, is a powder bed fusion (PBF) type of additive manufacturing (AM) technology used to fabricate metal parts out of metal powder. The development of the technology from building prototype parts to functional parts has increased remarkably in 2000s. LAM of metals is promising technology that offers new opportunities to manufacturing and to resource efficiency. However, there is only few published articles about its sustainability. Aim in this study was to create supply chain model of LAM and CNC machining and create a methodology to carry out a life cycle inventory (LCI) data collection for these techniques. The methodology of the study was literature review and scenario modeling. The acquisition of raw material, production phase and transportations were used as basis of comparison. The modelled scenarios were fictitious and created for industries, like aviation and healthcare that often require swift delivery as well as customized parts. The results of this study showed that the use of LAM offers a possibility to reduce downtime in supply chains of spare parts and reduce part inventory more effectively than CNC machining. Also the gap between customers and business is possible to be shortened with LAM thus offering a possibility to reduce emissions due to less transportation. The results also indicated weight reduction possibility with LAM due to optimized part geometry which allow lesser amount of metallic powder to be used in making parts.
First principles study and empirical parametrization of twisted bilayer MoS2 based on band-unfolding
Tan, Yaohua; Chen, Fan W.; Ghosh, Avik W.
2016-09-01
We explore the band structure and ballistic electron transport in twisted bilayer MoS2 using the density functional theory. The sphagetti like bands are unfolded to generate band structures in the primitive unit cell of the original 2H MoS2 bilayer and projected onto the original bands of an individual layer. The corresponding twist angle dependent bandedges are extracted from the unfolded band structures. Based on a comparison within the same primitive unit cell, an efficient two band effective mass model for indirect ΓV and ΛC valleys is created and parametrized by fitting to the unfolded band structures. With the two band effective mass model, we calculate transport properties—specifically, the ballistic transmission in arbitrarily twisted bilayer MoS2 .
Directory of Open Access Journals (Sweden)
Shahryar Garmsiri
2014-04-01
Full Text Available The potential benefits are examined of the “Power-to-Gas” (P2G scheme to utilize excess wind power capacity by generating hydrogen (or potentially methane for use in the natural gas distribution grid. A parametric analysis is used to determine the feasibility and size of systems producing hydrogen that would be injected into the natural gas grid. Specifically, wind farms located in southwestern Ontario, Canada are considered. Infrastructure requirements, wind farm size, pipeline capacity, geographical dispersion, hydrogen production rate, capital and operating costs are used as performance measures. The model takes into account the potential production rate of hydrogen and the rate that it can be injected into the local gas grid. “Straw man” systems are examined, centered on a wind farm size of 100 MW integrating a 16-MW capacity electrolysis system typically producing 4700 kg of hydrogen per day.
Parametric methods for spatial point processes
DEFF Research Database (Denmark)
Møller, Jesper
(This text is submitted for the volume ‘A Handbook of Spatial Statistics' edited by A.E. Gelfand, P. Diggle, M. Fuentes, and P. Guttorp, to be published by Chapmand and Hall/CRC Press, and planned to appear as Chapter 4.4 with the title ‘Parametric methods'.) 1 Introduction This chapter considers...... inference procedures for parametric spatial point process models. The widespread use of sensible but ad hoc methods based on summary statistics of the kind studied in Chapter 4.3 have through the last two decades been supplied by likelihood based methods for parametric spatial point process models....... The increasing development of such likelihood based methods, whether frequentist or Bayesian, has lead to more objective and efficient statistical procedures. When checking a fitted parametric point process model, summary statistics and residual analysis (Chapter 4.5) play an important role in combination...
La Barbera, Luigi; Costa, Francesco; Villa, Tomaso
2016-02-01
The International Standardization Organization (ISO) 12189 standard was recently introduced to preclinically evaluate and compare the mechanical properties of posterior stabilization devices. This scenario presents some new significant steps ahead over the vertebrectomy model recommended by American Society for Testing and Materials (ASTM) F1717 standard: the modular anterior support allows for describing a closer scenario to the effective clinical use as well as to test very flexible and dynamic posterior stabilization devices. Despite these significant advantages, ISO 12189 received little attention in the literature. Anatomical parameters depending on the spinal level were compared to the published data or original measurements on biplanar stereoradiography on 13 patients. Other mechanical variables, describing the test set-up design, were considered and all parameters were investigated using a numerical parametric finite element model. Stress values were calculated by also considering their worst-case combination. The standard set-up represents quite well the anatomy of an instrumented average thoracolumbar segment. The parametric comparative analysis demonstrates a significant (even beyond +350%) maximum increase in the stress on the device, compared to the standard currently in use. The anterior support stiffness plays the most detrimental effect (maximum stress increases up to 396%). The initial precompression step has an important role in determining the final stress values achieved at peak load (up to +76%). Moreover, when combining these two contributions, an even higher stress increase may be achieved (up to 473%). Despite the other anatomical parameters playing a secondary role, their worst-case combination demonstrates that a device could potentially undergo higher stresses than those reached according to standard suggestions (maximum increase of 22.4% at L1). Any user/designer should be aware of these effects when using ISO 12189 standard for the
Institute of Scientific and Technical Information of China (English)
陈晋; 王震; 邵元海
2012-01-01
The pretreatment process of twin support vector machine based on Parametric-margin has been improved, principal component analysis to reduce the dimensionality of the data is used in the data preprocessing stage. The twin support vector machines based on principal component analysis speeds up the training process. Experiments on public available datasets show excellent classification ability. Dimensionality reduction of the high-dimensional dataset is also more successful. Finally, this algorithm is applied on handwritten numeral recognition. The experimental results show the effective of our algorithm.%改进了基于参数化间隔的双子支持向量机算法的预处理过程，在数据预处理阶段使用了主成分分析法对数据进行降维，提出了基于主成分分析的参数化间隔双子支持向量机，从而加快了整个算法的训练速度．公共数据库上的实验结果显示了该算法的优秀分类能力，对高维数据集的降维效果也比较成功．最后，将这种算法应用到手写体数字识别技术上，实验结果显示出该算法较好的分类性能．