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Sample records for carlo optical simulator

  1. Monte Carlo Simulations of Arterial Imaging with Optical Coherence Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Amendt, P.; Estabrook, K.; Everett, M.; London, R.A.; Maitland, D.; Zimmerman, G.; Colston, B.; da Silva, L.; Sathyam, U.

    2000-02-01

    The laser-tissue interaction code LATIS [London et al., Appl. Optics 36, 9068 ( 1998)] is used to analyze photon scattering histories representative of optical coherence tomography (OCT) experiment performed at Lawrence Livermore National Laboratory. Monte Carlo photonics with Henyey-Greenstein anisotropic scattering is implemented and used to simulate signal discrimination of intravascular structure. An analytic model is developed and used to obtain a scaling law relation for optimization of the OCT signal and to validate Monte Carlo photonics. The appropriateness of the Henyey-Greenstein phase function is studied by direct comparison with more detailed Mie scattering theory using an ensemble of spherical dielectric scatterers. Modest differences are found between the two prescriptions for describing photon angular scattering in tissue. In particular, the Mie scattering phase functions provide less overall reflectance signal but more signal contrast compared to the Henyey-Greenstein formulation.

  2. Monte Carlo Simulation of Optical Properties of Wake Bubbles

    Institute of Scientific and Technical Information of China (English)

    CAO Jing; WANG Jiang-An; JIANG Xing-Zhou; SHI Sheng-Wei

    2007-01-01

    Based on Mie scattering theory and the theory of multiple light scattering, the light scattering properties of air bubbles in a wake are analysed by Monte Carlo simulation. The results show that backscattering is enhanced obviously due to the existence of bubbles, especially with the increase of bubble density, and that it is feasible to use the Monte Carlo method to study the properties of light scattering by air bubbles.

  3. Simulation of Astronomical Images from Optical Survey Telescopes using a Comprehensive Photon Monte Carlo Approach

    CERN Document Server

    Peterson, J R; Kahn, S M; Rasmussen, A P; Peng, E; Ahmad, Z; Bankert, J; Chang, C; Claver, C; Gilmore, D K; Grace, E; Hannel, M; Hodge, M; Lorenz, S; Lupu, A; Meert, A; Nagarajan, S; Todd, N; Winans, A; Young, M

    2015-01-01

    We present a comprehensive methodology for the simulation of astronomical images from optical survey telescopes. We use a photon Monte Carlo approach to construct images by sampling photons from models of astronomical source populations, and then simulating those photons through the system as they interact with the atmosphere, telescope, and camera. We demonstrate that all physical effects for optical light that determine the shapes, locations, and brightnesses of individual stars and galaxies can be accurately represented in this formalism. By using large scale grid computing, modern processors, and an efficient implementation that can produce 400,000 photons/second, we demonstrate that even very large optical surveys can be now be simulated. We demonstrate that we are able to: 1) construct kilometer scale phase screens necessary for wide-field telescopes, 2) reproduce atmospheric point-spread-function moments using a fast novel hybrid geometric/Fourier technique for non-diffraction limited telescopes, 3) ac...

  4. Optical coherence tomography: Monte Carlo simulation and improvement by optical amplification

    DEFF Research Database (Denmark)

    Tycho, Andreas

    2002-01-01

    is firmly justified. This is obtained by calculating the heterodyne mixing of the reference and sample beams in a plane conjugate to the discontinuity in the sample probed by the system. Using this approach, a novel expression for the OCT signal is derived, which only depends uopon the intensity...... distribution of the light from the sample and the reference beam. To adequately estimate the intensity distributions, a novel method of modeling a focused Gaussian beam using Monte Carlo simulation is developed. This method is then combined with the derived expression for the OCT signal into a new Monte Carlo...... model of the OCT signal. The OCT signal from a scattering medium are obtained for several beam and sample geometries using the new Monte Carlo model, and when comparing to results of an analytical model based on the extended Huygens-Fresnel principle excellent agreement is obtained. With the greater...

  5. Fast inverse Monte Carlo simulation for extracting the optical properties of cylindrical tissue

    Science.gov (United States)

    Zhao, Huijuan; Zhou, Xiaoqing; Li, Hao; Ma, Jierong; Xu, Kexin

    2009-02-01

    This article aims at the development of the fast inverse Monte Carlo (MC) simulation for the reconstruction of optical properties (absorption coefficient and scattering coefficient ) of cylindrical tissue [1], such as a cervix, from the measurement of near infrared diffuse light on frequency domain. Frequency domain information (amplitude and phase) is extracted from the time domain MC with a modified method. To shorten the computation time in reconstruction of optical properties, efficient and fast forward MC has to be achieved. To do this, firstly, databases of the frequency-domain information under a range of μa and μs were pre-built by combining MC simulation with Lambert-Beer's law. Then, a double polynomial model was adopted to quickly obtain the frequency-domain information in any optical properties. Based on the fast forward MC, the optical properties can be quickly obtained in a nonlinear optimization scheme. Reconstruction resulting from simulated data showed that the developed inverse MC method has the advantages in both the reconstruction accuracy and computation time. The relative errors in reconstruction of the μa and μs are less than +/-6% and +/-12% respectively, while another coefficient (μa or μs) is in a fixed value. When both μa and μs are unknown, the relative errors in reconstruction of the reduced scattering coefficient and absorption coefficient are mainly less than +/-10% in range of 45 properties is less than 0.5 second.

  6. Optical model for port-wine stain skin and its Monte Carlo simulation

    Science.gov (United States)

    Xu, Lanqing; Xiao, Zhengying; Chen, Rong; Wang, Ying

    2008-12-01

    Laser irradiation is the most acceptable therapy for PWS patient at present time. Its efficacy is highly dependent on the energy deposition rules in skin. To achieve optimal PWS treatment parameters a better understanding of light propagation in PWS skin is indispensable. Traditional Monte Carlo simulations using simple geometries such as planar layer tissue model can not provide energy deposition in the skin with enlarged blood vessels. In this paper the structure of normal skin and the pathological character of PWS skin was analyzed in detail and the true structure were simplified into a hybrid layered mathematical model to character two most important aspects of PWS skin: layered structure and overabundant dermal vessels. The basic laser-tissue interaction mechanisms in skin were investigated and the optical parameters of PWS skin tissue at the therapeutic wavelength. Monte Carlo (MC) based techniques were choused to calculate the energy deposition in the skin. Results can be used in choosing optical dosage. Further simulations can be used to predict optimal laser parameters to achieve high-efficacy laser treatment of PWS.

  7. SIMULATION OF ASTRONOMICAL IMAGES FROM OPTICAL SURVEY TELESCOPES USING A COMPREHENSIVE PHOTON MONTE CARLO APPROACH

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, J. R.; Peng, E.; Ahmad, Z.; Bankert, J.; Grace, E.; Hannel, M.; Hodge, M.; Lorenz, S.; Lupu, A.; Meert, A.; Nagarajan, S.; Todd, N.; Winans, A.; Young, M. [Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907 (United States); Jernigan, J. G. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Kahn, S. M.; Rasmussen, A. P.; Chang, C.; Gilmore, D. K. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305 (United States); Claver, C., E-mail: peters11@purdue.edu [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States)

    2015-05-15

    We present a comprehensive methodology for the simulation of astronomical images from optical survey telescopes. We use a photon Monte Carlo approach to construct images by sampling photons from models of astronomical source populations, and then simulating those photons through the system as they interact with the atmosphere, telescope, and camera. We demonstrate that all physical effects for optical light that determine the shapes, locations, and brightnesses of individual stars and galaxies can be accurately represented in this formalism. By using large scale grid computing, modern processors, and an efficient implementation that can produce 400,000 photons s{sup −1}, we demonstrate that even very large optical surveys can be now be simulated. We demonstrate that we are able to (1) construct kilometer scale phase screens necessary for wide-field telescopes, (2) reproduce atmospheric point-spread function moments using a fast novel hybrid geometric/Fourier technique for non-diffraction limited telescopes, (3) accurately reproduce the expected spot diagrams for complex aspheric optical designs, and (4) recover system effective area predicted from analytic photometry integrals. This new code, the Photon Simulator (PhoSim), is publicly available. We have implemented the Large Synoptic Survey Telescope design, and it can be extended to other telescopes. We expect that because of the comprehensive physics implemented in PhoSim, it will be used by the community to plan future observations, interpret detailed existing observations, and quantify systematics related to various astronomical measurements. Future development and validation by comparisons with real data will continue to improve the fidelity and usability of the code.

  8. Channel capacity study of underwater wireless optical communications links based on Monte Carlo simulation

    International Nuclear Information System (INIS)

    Channel capacity of ocean water is limited by propagation distance and optical properties. Previous studies on this problem are based on water-tank experiments with different amounts of Maalox antacid. However, propagation distance is limited by the experimental set-up and the optical properties are different from ocean water. Therefore, the experiment result is not accurate for the physical design of underwater wireless communications links. This letter developed a Monte Carlo model to study channel capacity of underwater optical communications. Moreover, this model can flexibly configure various parameters of transmitter, receiver and channel, and is suitable for physical underwater optical communications links design. (paper)

  9. Peer-to-peer Monte Carlo simulation of photon migration in topical applications of biomedical optics

    Science.gov (United States)

    Doronin, Alexander; Meglinski, Igor

    2012-09-01

    In the framework of further development of the unified approach of photon migration in complex turbid media, such as biological tissues we present a peer-to-peer (P2P) Monte Carlo (MC) code. The object-oriented programming is used for generalization of MC model for multipurpose use in various applications of biomedical optics. The online user interface providing multiuser access is developed using modern web technologies, such as Microsoft Silverlight, ASP.NET. The emerging P2P network utilizing computers with different types of compute unified device architecture-capable graphics processing units (GPUs) is applied for acceleration and to overcome the limitations, imposed by multiuser access in the online MC computational tool. The developed P2P MC was validated by comparing the results of simulation of diffuse reflectance and fluence rate distribution for semi-infinite scattering medium with known analytical results, results of adding-doubling method, and with other GPU-based MC techniques developed in the past. The best speedup of processing multiuser requests in a range of 4 to 35 s was achieved using single-precision computing, and the double-precision computing for floating-point arithmetic operations provides higher accuracy.

  10. Monte Carlo Simulation of Scattered Light with Shear Waves Generated by Acoustic Radiation Force for Acousto-Optic Imaging

    International Nuclear Information System (INIS)

    A Monte Carlo method of multiple scattered coherent light with the information of shear wave propagation in scattering media is presented. The established Monte-Carlo algorithm is mainly relative to optical phase variations due to the acoustic-radiation-force shear-wave-induced displacements of light scatterers. Both the distributions and temporal behaviors of optical phase increments in probe locations are obtained. Consequently, shear wave speed is evaluated quantitatively. It is noted that the phase increments exactly track the propagations of shear waves induced by focus-ultrasound radiation force. In addition, attenuations of shear waves are demonstrated in simulation results. By using linear regression processing, the shear wave speed, which is set to 2.1 m/s in simulation, is estimated to be 2.18 m/s and 2.35 m/s at time sampling intervals of 0.2 ms and 0.5 ms, respectively

  11. Quantum Monte Carlo simulation of suprafluidity with fermions in a two dimensional optical lattice

    International Nuclear Information System (INIS)

    Based on a Projector Quantum Monte Carlo Simulation, we examine the ground state properties of the attractive 2D fermionic Hubbard model. The main focus is on the supersolid phase, where in a periodic system it is known that the superfluid phase coexists with a crystalline structure (CDW-phase) at density n=1. We obtain the conditions for such a phase when the system is confined in a harmonic trap. Furthermore, we consider the BCS-BEC crossover region in a periodic system.

  12. Simulation of diffuse photon migration in tissue by a Monte Carlo method derived from the optical scattering of spheroids.

    Science.gov (United States)

    Hart, Vern P; Doyle, Timothy E

    2013-09-01

    A Monte Carlo method was derived from the optical scattering properties of spheroidal particles and used for modeling diffuse photon migration in biological tissue. The spheroidal scattering solution used a separation of variables approach and numerical calculation of the light intensity as a function of the scattering angle. A Monte Carlo algorithm was then developed which utilized the scattering solution to determine successive photon trajectories in a three-dimensional simulation of optical diffusion and resultant scattering intensities in virtual tissue. Monte Carlo simulations using isotropic randomization, Henyey-Greenstein phase functions, and spherical Mie scattering were additionally developed and used for comparison to the spheroidal method. Intensity profiles extracted from diffusion simulations showed that the four models differed significantly. The depth of scattering extinction varied widely among the four models, with the isotropic, spherical, spheroidal, and phase function models displaying total extinction at depths of 3.62, 2.83, 3.28, and 1.95 cm, respectively. The results suggest that advanced scattering simulations could be used as a diagnostic tool by distinguishing specific cellular structures in the diffused signal. For example, simulations could be used to detect large concentrations of deformed cell nuclei indicative of early stage cancer. The presented technique is proposed to be a more physical description of photon migration than existing phase function methods. This is attributed to the spheroidal structure of highly scattering mitochondria and elongation of the cell nucleus, which occurs in the initial phases of certain cancers. The potential applications of the model and its importance to diffusive imaging techniques are discussed. PMID:24085080

  13. Contrasting properties of gold nanoparticles for optical coherence tomography: phantom, in vivo studies and Monte Carlo simulation

    International Nuclear Information System (INIS)

    The possibility of using silica-gold nanoshells with 150 nm silica core size and 25 nm thick gold shell as contrasting agents for optical coherence tomography (OCT) is analyzed. Experiments on agar biotissue phantoms showed that the penetration of nanoshells into the phantoms increases the intensity of the optical coherence tomography (OCT) signal and the brightness of the corresponding areas of the OCT image. In vivo experiments on rabbit skin demonstrated that the application of nanoshells onto the skin provides significant contrasting of the borders between the areas containing nanoshells and those without. This effect of nanoshells on skin in vivo is manifested by the increase in intensity of the OCT signal in superficial parts of the skin, boundary contrast between superficial and deep dermis and contrast of hair follicles and glands. The presence of nanoshells in the skin was confirmed by electron microscopy. Monte Carlo simulations of OCT images confirmed the possibility of contrasting skin-layer borders and structures by the application of gold nanoshells. The Monte Carlo simulations were performed for two skin models and exhibit effects of nanoparticles similar to those obtained in the experimental part of the study, thus proving that the effects originate exactly from the presence of nanoparticles

  14. Monte Carlo lookup table-based inverse model for extracting optical properties from tissue-simulating phantoms using diffuse reflectance spectroscopy.

    Science.gov (United States)

    Hennessy, Ricky; Lim, Sam L; Markey, Mia K; Tunnell, James W

    2013-03-01

    We present a Monte Carlo lookup table (MCLUT)-based inverse model for extracting optical properties from tissue-simulating phantoms. This model is valid for close source-detector separation and highly absorbing tissues. The MCLUT is based entirely on Monte Carlo simulation, which was implemented using a graphics processing unit. We used tissue-simulating phantoms to determine the accuracy of the MCLUT inverse model. Our results show strong agreement between extracted and expected optical properties, with errors rate of 1.74% for extracted reduced scattering values, 0.74% for extracted absorption values, and 2.42% for extracted hemoglobin concentration values. PMID:23455965

  15. Study of optical clearing in polarization measurements by Monte Carlo simulations with anisotropic tissue-mimicking models.

    Science.gov (United States)

    Chen, Dongsheng; Zeng, Nan; Wang, Yunfei; He, Honghui; Tuchin, Valery V; Ma, Hui

    2016-08-01

    We conducted Monte Carlo simulations based on anisotropic sclera-mimicking models to examine the polarization features in Mueller matrix polar decomposition (MMPD) parameters during the refractive index matching process, which is one of the major mechanisms of optical clearing. In a preliminary attempt, by changing the parameters of the models, wavelengths, and detection geometries, we demonstrate how the depolarization coefficient and retardance vary during the refractive index matching process and explain the polarization features using the average value and standard deviation of scattering numbers of the detected photons. We also study the depth-resolved polarization features during the gradual progression of the refractive index matching process. The results above indicate that the refractive index matching process increases the depth of polarization measurements and may lead to higher contrast between tissues of different anisotropies in deeper layers. MMPD-derived polarization parameters can characterize the refractive index matching process qualitatively. PMID:27240298

  16. Optimization of Monte Carlo simulations

    OpenAIRE

    Bryskhe, Henrik

    2009-01-01

    This thesis considers several different techniques for optimizing Monte Carlo simulations. The Monte Carlo system used is Penelope but most of the techniques are applicable to other systems. The two mayor techniques are the usage of the graphics card to do geometry calculations, and raytracing. Using graphics card provides a very efficient way to do fast ray and triangle intersections. Raytracing provides an approximation of Monte Carlo simulation but is much faster to perform. A program was ...

  17. Comment on "A study on tetrahedron-based inhomogeneous Monte-Carlo optical simulation".

    Science.gov (United States)

    Fang, Qianqian

    2011-01-01

    The Monte Carlo (MC) method is a popular approach to modeling photon propagation inside general turbid media, such as human tissue. Progress had been made in the past year with the independent proposals of two mesh-based Monte Carlo methods employing ray-tracing techniques. Both methods have shown improvements in accuracy and efficiency in modeling complex domains. A recent paper by Shen and Wang [Biomed. Opt. Express 2, 44 (2011)] reported preliminary results towards the cross-validation of the two mesh-based MC algorithms and software implementations, showing a 3-6 fold speed difference between the two software packages. In this comment, we share our views on unbiased software comparisons and discuss additional issues such as the use of pre-computed data, interpolation strategies, impact of compiler settings, use of Russian roulette, memory cost and potential pitfalls in measuring algorithm performance. Despite key differences between the two algorithms in handling of non-tetrahedral meshes, we found that they share similar structure and performance for tetrahedral meshes. A significant fraction of the observed speed differences in the mentioned article was the result of inconsistent use of compilers and libraries. PMID:21559136

  18. Comment on "A study on tetrahedron-based inhomogeneous Monte-Carlo optical simulation".

    Science.gov (United States)

    Fang, Qianqian

    2011-04-19

    The Monte Carlo (MC) method is a popular approach to modeling photon propagation inside general turbid media, such as human tissue. Progress had been made in the past year with the independent proposals of two mesh-based Monte Carlo methods employing ray-tracing techniques. Both methods have shown improvements in accuracy and efficiency in modeling complex domains. A recent paper by Shen and Wang [Biomed. Opt. Express 2, 44 (2011)] reported preliminary results towards the cross-validation of the two mesh-based MC algorithms and software implementations, showing a 3-6 fold speed difference between the two software packages. In this comment, we share our views on unbiased software comparisons and discuss additional issues such as the use of pre-computed data, interpolation strategies, impact of compiler settings, use of Russian roulette, memory cost and potential pitfalls in measuring algorithm performance. Despite key differences between the two algorithms in handling of non-tetrahedral meshes, we found that they share similar structure and performance for tetrahedral meshes. A significant fraction of the observed speed differences in the mentioned article was the result of inconsistent use of compilers and libraries.

  19. Limitations of the commonly used simplified laterally uniform optical fiber probe-tissue interface in Monte Carlo simulations of diffuse reflectance.

    Science.gov (United States)

    Naglič, Peter; Pernuš, Franjo; Likar, Boštjan; Bürmen, Miran

    2015-10-01

    Light propagation models often simplify the interface between the optical fiber probe tip and tissue to a laterally uniform boundary with mismatched refractive indices. Such simplification neglects the precise optical properties of the commonly used probe tip materials, e.g. stainless steel or black epoxy. In this paper, we investigate the limitations of the laterally uniform probe-tissue interface in Monte Carlo simulations of diffuse reflectance. In comparison to a realistic probe-tissue interface that accounts for the layout and properties of the probe tip materials, the simplified laterally uniform interface is shown to introduce significant errors into the simulated diffuse reflectance.

  20. Proton Upset Monte Carlo Simulation

    Science.gov (United States)

    O'Neill, Patrick M.; Kouba, Coy K.; Foster, Charles C.

    2009-01-01

    The Proton Upset Monte Carlo Simulation (PROPSET) program calculates the frequency of on-orbit upsets in computer chips (for given orbits such as Low Earth Orbit, Lunar Orbit, and the like) from proton bombardment based on the results of heavy ion testing alone. The software simulates the bombardment of modern microelectronic components (computer chips) with high-energy (.200 MeV) protons. The nuclear interaction of the proton with the silicon of the chip is modeled and nuclear fragments from this interaction are tracked using Monte Carlo techniques to produce statistically accurate predictions.

  1. ScintSim1: A new Monte Carlo simulation code for transport of optical photons in 2D arrays of scintillation detectors

    OpenAIRE

    Mosleh-Shirazi, Mohammad Amin; Zarrini-Monfared, Zinat; Karbasi, Sareh; Zamani, Ali

    2014-01-01

    Two-dimensional (2D) arrays of thick segmented scintillators are of interest as X-ray detectors for both 2D and 3D image-guided radiotherapy (IGRT). Their detection process involves ionizing radiation energy deposition followed by production and transport of optical photons. Only a very limited number of optical Monte Carlo simulation models exist, which has limited the number of modeling studies that have considered both stages of the detection process. We present ScintSim1, an in-house opti...

  2. Monte Carlo Simulations of the Photospheric Process

    CERN Document Server

    Santana, Rodolfo; Hernandez, Roberto A; Kumar, Pawan

    2015-01-01

    We present a Monte Carlo (MC) code we wrote to simulate the photospheric process and to study the photospheric spectrum above the peak energy. Our simulations were performed with a photon to electron ratio $N_{\\gamma}/N_{e} = 10^{5}$, as determined by observations of the GRB prompt emission. We searched an exhaustive parameter space to determine if the photospheric process can match the observed high-energy spectrum of the prompt emission. If we do not consider electron re-heating, we determined that the best conditions to produce the observed high-energy spectrum are low photon temperatures and high optical depths. However, for these simulations, the spectrum peaks at an energy below 300 keV by a factor $\\sim 10$. For the cases we consider with higher photon temperatures and lower optical depths, we demonstrate that additional energy in the electrons is required to produce a power-law spectrum above the peak-energy. By considering electron re-heating near the photosphere, the spectrum for these simulations h...

  3. Multipurpose Monte Carlo simulator for photon transport in turbid media

    OpenAIRE

    Guerra, Pedro; Aguirre, Juan; Ortuño, Juan E.; María J Ledesma-Carbayo; Vaquero, Juan José; Desco, Manuel; Santos, Andrés

    2009-01-01

    Monte Carlo methods provide a flexible and rigorous solution to the problem of light transport in turbid media, which enable approaching complex geometries for a closed analytical solution is not feasible. The simulator implements local rules of propagation in the form of probability density functions that depend on the local optical properties of the tissue. This work presents a flexible simulator that can be applied in multiple applications related to optical tomography. In particular...

  4. Mean field simulation for Monte Carlo integration

    CERN Document Server

    Del Moral, Pierre

    2013-01-01

    In the last three decades, there has been a dramatic increase in the use of interacting particle methods as a powerful tool in real-world applications of Monte Carlo simulation in computational physics, population biology, computer sciences, and statistical machine learning. Ideally suited to parallel and distributed computation, these advanced particle algorithms include nonlinear interacting jump diffusions; quantum, diffusion, and resampled Monte Carlo methods; Feynman-Kac particle models; genetic and evolutionary algorithms; sequential Monte Carlo methods; adaptive and interacting Marko

  5. Monte carlo simulation for soot dynamics

    KAUST Repository

    Zhou, Kun

    2012-01-01

    A new Monte Carlo method termed Comb-like frame Monte Carlo is developed to simulate the soot dynamics. Detailed stochastic error analysis is provided. Comb-like frame Monte Carlo is coupled with the gas phase solver Chemkin II to simulate soot formation in a 1-D premixed burner stabilized flame. The simulated soot number density, volume fraction, and particle size distribution all agree well with the measurement available in literature. The origin of the bimodal distribution of particle size distribution is revealed with quantitative proof.

  6. Monte Carlo simulation of granular fluids

    OpenAIRE

    Montanero, J. M.

    2003-01-01

    An overview of recent work on Monte Carlo simulations of a granular binary mixture is presented. The results are obtained numerically solving the Enskog equation for inelastic hard-spheres by means of an extension of the well-known direct Monte Carlo simulation (DSMC) method. The homogeneous cooling state and the stationary state reached using the Gaussian thermostat are considered. The temperature ratio, the fourth velocity moments and the velocity distribution functions are obtained for bot...

  7. Adaptive Multilevel Monte Carlo Simulation

    KAUST Repository

    Hoel, H

    2011-08-23

    This work generalizes a multilevel forward Euler Monte Carlo method introduced in Michael B. Giles. (Michael Giles. Oper. Res. 56(3):607–617, 2008.) for the approximation of expected values depending on the solution to an Itô stochastic differential equation. The work (Michael Giles. Oper. Res. 56(3):607– 617, 2008.) proposed and analyzed a forward Euler multilevelMonte Carlo method based on a hierarchy of uniform time discretizations and control variates to reduce the computational effort required by a standard, single level, Forward Euler Monte Carlo method. This work introduces an adaptive hierarchy of non uniform time discretizations, generated by an adaptive algorithmintroduced in (AnnaDzougoutov et al. Raùl Tempone. Adaptive Monte Carlo algorithms for stopped diffusion. In Multiscale methods in science and engineering, volume 44 of Lect. Notes Comput. Sci. Eng., pages 59–88. Springer, Berlin, 2005; Kyoung-Sook Moon et al. Stoch. Anal. Appl. 23(3):511–558, 2005; Kyoung-Sook Moon et al. An adaptive algorithm for ordinary, stochastic and partial differential equations. In Recent advances in adaptive computation, volume 383 of Contemp. Math., pages 325–343. Amer. Math. Soc., Providence, RI, 2005.). This form of the adaptive algorithm generates stochastic, path dependent, time steps and is based on a posteriori error expansions first developed in (Anders Szepessy et al. Comm. Pure Appl. Math. 54(10):1169– 1214, 2001). Our numerical results for a stopped diffusion problem, exhibit savings in the computational cost to achieve an accuracy of ϑ(TOL),from(TOL−3), from using a single level version of the adaptive algorithm to ϑ(((TOL−1)log(TOL))2).

  8. Simulation and the Monte Carlo method

    CERN Document Server

    Rubinstein, Reuven Y

    2016-01-01

    Simulation and the Monte Carlo Method, Third Edition reflects the latest developments in the field and presents a fully updated and comprehensive account of the major topics that have emerged in Monte Carlo simulation since the publication of the classic First Edition over more than a quarter of a century ago. While maintaining its accessible and intuitive approach, this revised edition features a wealth of up-to-date information that facilitates a deeper understanding of problem solving across a wide array of subject areas, such as engineering, statistics, computer science, mathematics, and the physical and life sciences. The book begins with a modernized introduction that addresses the basic concepts of probability, Markov processes, and convex optimization. Subsequent chapters discuss the dramatic changes that have occurred in the field of the Monte Carlo method, with coverage of many modern topics including: Markov Chain Monte Carlo, variance reduction techniques such as the transform likelihood ratio...

  9. Monte Carlo simulation of granular fluids

    CERN Document Server

    Montanero, J M

    2003-01-01

    An overview of recent work on Monte Carlo simulations of a granular binary mixture is presented. The results are obtained numerically solving the Enskog equation for inelastic hard-spheres by means of an extension of the well-known direct Monte Carlo simulation (DSMC) method. The homogeneous cooling state and the stationary state reached using the Gaussian thermostat are considered. The temperature ratio, the fourth velocity moments and the velocity distribution functions are obtained for both cases. The shear viscosity characterizing the momentum transport in the thermostatted case is calculated as well. The simulation results are compared with analytical predictions showing an excellent agreement.

  10. Monte Carlo simulation of photon migration path in turbid media

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A new method of Monte Carlo simulation is developed to simulate the photon migration path in a scattering medium after an ultrashort-pulse laser beam comes into the medium.The most probable trajectory of photons at an instant can be obtained with this method.How the photon migration paths are affected by the optical parameters of the scattering medium is analyzed.It is also concluded that the absorption coefficient has no effect on the most probable trajectory of photons.

  11. Optical Fiber Turbidity Sensor Based on Monte Carlo Simulations%基于蒙特卡罗模拟的光纤浊度传感器

    Institute of Scientific and Technical Information of China (English)

    吴刚; 刘月明; 许宏志; 陈飞华; 黄杰

    2014-01-01

    在后向散射式浊度测量方法的基础上,采用光纤传感技术,设计了一种 Y形光纤束探头结构的浊度传感器,并在光纤束探头前端配置平面镜作为光反射配合目标。根据朗伯比尔定律通过实验研究了消光系数与浊度的线性关系,基于蒙特卡罗法建立了待测液中的光子散射模型,模拟不同检测情形下的传感器接收光强,优化得到光纤束到平面镜的最佳距离。标定接收光强与消光系数的关系曲线用于测量。此法简单高效,能检测消光系数低至0.059 cm-1的水质,平面镜的有效使用将传感器灵敏度提高10倍以上。此传感器可用于便携式检测,结合空分和时分复用技术可实现在线监测。%Based on the backscattering turbidity measurement method,a turbidity sensor with Y-shaped optical fiber bundle probe structure in conj unction with a plane mirror is designed by using the optical fiber sensor technolo-gy.Turbidity is estimated in terms of total interaction coefficient,a parameter that contains strong signature of the turbidity of a solution.A scattered light model based on Monte Carlo simulations is applied to estimate the power collected by the fiber optic probe.The turbidity sensor is simple,and it′s useful for detecting suspended impurities even in small quantities within a liquid,the total interaction coefficient of which is as low as 0.059 cm-1 .With the reasonable use of the mirror,the sensitivity of the sensor is improved more than 10 times.The proposed sensor can be used for the portable measurements and the on-line monitoring can be realized by combining the space-division multiplexing technology and time-division multiplexing technology.

  12. Monte carlo simulations of organic photovoltaics.

    Science.gov (United States)

    Groves, Chris; Greenham, Neil C

    2014-01-01

    Monte Carlo simulations are a valuable tool to model the generation, separation, and collection of charges in organic photovoltaics where charges move by hopping in a complex nanostructure and Coulomb interactions between charge carriers are important. We review the Monte Carlo techniques that have been applied to this problem, and describe the results of simulations of the various recombination processes that limit device performance. We show how these processes are influenced by the local physical and energetic structure of the material, providing information that is useful for design of efficient photovoltaic systems.

  13. Monte Carlo Simulation for Particle Detectors

    CERN Document Server

    Pia, Maria Grazia

    2012-01-01

    Monte Carlo simulation is an essential component of experimental particle physics in all the phases of its life-cycle: the investigation of the physics reach of detector concepts, the design of facilities and detectors, the development and optimization of data reconstruction software, the data analysis for the production of physics results. This note briefly outlines some research topics related to Monte Carlo simulation, that are relevant to future experimental perspectives in particle physics. The focus is on physics aspects: conceptual progress beyond current particle transport schemes, the incorporation of materials science knowledge relevant to novel detection technologies, functionality to model radiation damage, the capability for multi-scale simulation, quantitative validation and uncertainty quantification to determine the predictive power of simulation. The R&D on simulation for future detectors would profit from cooperation within various components of the particle physics community, and synerg...

  14. Modulated pulse bathymetric lidar Monte Carlo simulation

    Science.gov (United States)

    Luo, Tao; Wang, Yabo; Wang, Rong; Du, Peng; Min, Xia

    2015-10-01

    A typical modulated pulse bathymetric lidar system is investigated by simulation using a modulated pulse lidar simulation system. In the simulation, the return signal is generated by Monte Carlo method with modulated pulse propagation model and processed by mathematical tools like cross-correlation and digital filter. Computer simulation results incorporating the modulation detection scheme reveal a significant suppression of the water backscattering signal and corresponding target contrast enhancement. More simulation experiments are performed with various modulation and reception variables to investigate the effect of them on the bathymetric system performance.

  15. Advances in Monte Carlo computer simulation

    Science.gov (United States)

    Swendsen, Robert H.

    2011-03-01

    Since the invention of the Metropolis method in 1953, Monte Carlo methods have been shown to provide an efficient, practical approach to the calculation of physical properties in a wide variety of systems. In this talk, I will discuss some of the advances in the MC simulation of thermodynamics systems, with an emphasis on optimization to obtain a maximum of useful information.

  16. Autocorrelations in hybrid Monte Carlo simulations

    International Nuclear Information System (INIS)

    Simulations of QCD suffer from severe critical slowing down towards the continuum limit. This problem is known to be prominent in the topological charge, however, all observables are affected to various degree by these slow modes in the Monte Carlo evolution. We investigate the slowing down in high statistics simulations and propose a new error analysis method, which gives a realistic estimate of the contribution of the slow modes to the errors. (orig.)

  17. Simulated Annealing using Hybrid Monte Carlo

    OpenAIRE

    Salazar, Rafael; Toral, Raúl

    1997-01-01

    We propose a variant of the simulated annealing method for optimization in the multivariate analysis of differentiable functions. The method uses global actualizations via the hybrid Monte Carlo algorithm in their generalized version for the proposal of new configurations. We show how this choice can improve upon the performance of simulated annealing methods (mainly when the number of variables is large) by allowing a more effective searching scheme and a faster annealing schedule.

  18. Monte Carlo Simulations of Star Clusters

    CERN Document Server

    Giersz, M

    2000-01-01

    A revision of Stod\\'o{\\l}kiewicz's Monte Carlo code is used to simulate evolution of large star clusters. The survey on the evolution of multi-mass N-body systems influenced by the tidal field of a parent galaxy and by stellar evolution is discussed. For the first time, the simulation on the "star-by-star" bases of evolution of 1,000,000 body star cluster is presented. \\

  19. Monte Carlo simulation code modernization

    CERN Document Server

    CERN. Geneva

    2015-01-01

    The continual development of sophisticated transport simulation algorithms allows increasingly accurate description of the effect of the passage of particles through matter. This modelling capability finds applications in a large spectrum of fields from medicine to astrophysics, and of course HEP. These new capabilities however come at the cost of a greater computational intensity of the new models, which has the effect of increasing the demands of computing resources. This is particularly true for HEP, where the demand for more simulation are driven by the need of both more accuracy and more precision, i.e. better models and more events. Usually HEP has relied on the "Moore's law" evolution, but since almost ten years the increase in clock speed has withered and computing capacity comes in the form of hardware architectures of many-core or accelerated processors. To harness these opportunities we need to adapt our code to concurrent programming models taking advantages of both SIMD and SIMT architectures. Th...

  20. Monte Carlo simulations of fluid vesicles

    Science.gov (United States)

    Sreeja, K. K.; Ipsen, John H.; Kumar, P. B. Sunil

    2015-07-01

    Lipid vesicles are closed two dimensional fluid surfaces that are studied extensively as model systems for understanding the physical properties of biological membranes. Here we review the recent developments in the Monte Carlo techniques for simulating fluid vesicles and discuss some of their applications. The technique, which treats the membrane as an elastic sheet, is most suitable for the study of large scale conformations of membranes. The model can be used to study vesicles with fixed and varying topologies. Here we focus on the case of multi-component membranes with the local lipid and protein composition coupled to the membrane curvature leading to a variety of shapes. The phase diagram is more intriguing in the case of fluid vesicles having an in-plane orientational order that induce anisotropic directional curvatures. Methods to explore the steady state morphological structures due to active flux of materials have also been described in the context of Monte Carlo simulations.

  1. Optical monitoring of rheumatoid arthritis: Monte Carlo generated reconstruction kernels

    Science.gov (United States)

    Minet, O.; Beuthan, J.; Hielscher, A. H.; Zabarylo, U.

    2008-06-01

    Optical imaging in biomedicine is governed by the light absorption and scattering interaction on microscopic and macroscopic constituents in the medium. Therefore, light scattering characteristics of human tissue correlate with the stage of some diseases. In the near infrared range the scattering event with the coefficient approximately two orders of magnitude greater than absorption plays a dominant role. When measuring the optical parameters variations were discovered that correlate with the rheumatoid arthritis of a small joint. The potential of an experimental setup for transillumination the finger joint with a laser diode and the pattern of the stray light detection are demonstrated. The scattering caused by skin contains no useful information and it can be removed by a deconvolution technique to enhance the diagnostic value of this non-invasive optical method. Monte Carlo simulations ensure both the construction of the corresponding point spread function and both the theoretical verification of the stray light picture in rather complex geometry.

  2. Hybrid Monte Carlo simulation of polymer chains

    CERN Document Server

    Irbäck, A

    1993-01-01

    We develop the hybrid Monte Carlo method for simulations of single off-lattice polymer chains. We discuss implementation and choice of simulation parameters in some detail. The performance of the algorithm is tested on models for homopolymers with short- or long-range self-repulsion, using chains with $16\\le N\\le 512$ monomers. Without excessive fine tuning, we find that the computational cost grows as $N^{2+z^\\prime}$ with $0.64

  3. Accelerated GPU based SPECT Monte Carlo simulations

    Science.gov (United States)

    Garcia, Marie-Paule; Bert, Julien; Benoit, Didier; Bardiès, Manuel; Visvikis, Dimitris

    2016-06-01

    Monte Carlo (MC) modelling is widely used in the field of single photon emission computed tomography (SPECT) as it is a reliable technique to simulate very high quality scans. This technique provides very accurate modelling of the radiation transport and particle interactions in a heterogeneous medium. Various MC codes exist for nuclear medicine imaging simulations. Recently, new strategies exploiting the computing capabilities of graphical processing units (GPU) have been proposed. This work aims at evaluating the accuracy of such GPU implementation strategies in comparison to standard MC codes in the context of SPECT imaging. GATE was considered the reference MC toolkit and used to evaluate the performance of newly developed GPU Geant4-based Monte Carlo simulation (GGEMS) modules for SPECT imaging. Radioisotopes with different photon energies were used with these various CPU and GPU Geant4-based MC codes in order to assess the best strategy for each configuration. Three different isotopes were considered: 99m Tc, 111In and 131I, using a low energy high resolution (LEHR) collimator, a medium energy general purpose (MEGP) collimator and a high energy general purpose (HEGP) collimator respectively. Point source, uniform source, cylindrical phantom and anthropomorphic phantom acquisitions were simulated using a model of the GE infinia II 3/8" gamma camera. Both simulation platforms yielded a similar system sensitivity and image statistical quality for the various combinations. The overall acceleration factor between GATE and GGEMS platform derived from the same cylindrical phantom acquisition was between 18 and 27 for the different radioisotopes. Besides, a full MC simulation using an anthropomorphic phantom showed the full potential of the GGEMS platform, with a resulting acceleration factor up to 71. The good agreement with reference codes and the acceleration factors obtained support the use of GPU implementation strategies for improving computational efficiency

  4. SU-E-T-590: Optimizing Magnetic Field Strengths with Matlab for An Ion-Optic System in Particle Therapy Consisting of Two Quadrupole Magnets for Subsequent Simulations with the Monte-Carlo Code FLUKA

    International Nuclear Information System (INIS)

    Purpose: Aim of this study was to optimize the magnetic field strengths of two quadrupole magnets in a particle therapy facility in order to obtain a beam quality suitable for spot beam scanning. Methods: The particle transport through an ion-optic system of a particle therapy facility consisting of the beam tube, two quadrupole magnets and a beam monitor system was calculated with the help of Matlab by using matrices that solve the equation of motion of a charged particle in a magnetic field and field-free region, respectively. The magnetic field strengths were optimized in order to obtain a circular and thin beam spot at the iso-center of the therapy facility. These optimized field strengths were subsequently transferred to the Monte-Carlo code FLUKA and the transport of 80 MeV/u C12-ions through this ion-optic system was calculated by using a user-routine to implement magnetic fields. The fluence along the beam-axis and at the iso-center was evaluated. Results: The magnetic field strengths could be optimized by using Matlab and transferred to the Monte-Carlo code FLUKA. The implementation via a user-routine was successful. Analyzing the fluence-pattern along the beam-axis the characteristic focusing and de-focusing effects of the quadrupole magnets could be reproduced. Furthermore the beam spot at the iso-center was circular and significantly thinner compared to an unfocused beam. Conclusion: In this study a Matlab tool was developed to optimize magnetic field strengths for an ion-optic system consisting of two quadrupole magnets as part of a particle therapy facility. These magnetic field strengths could subsequently be transferred to and implemented in the Monte-Carlo code FLUKA to simulate the particle transport through this optimized ion-optic system

  5. Monte Carlo Simulation of an American Option

    Directory of Open Access Journals (Sweden)

    Gikiri Thuo

    2007-04-01

    Full Text Available We implement gradient estimation techniques for sensitivity analysis of option pricing which can be efficiently employed in Monte Carlo simulation. Using these techniques we can simultaneously obtain an estimate of the option value together with the estimates of sensitivities of the option value to various parameters of the model. After deriving the gradient estimates we incorporate them in an iterative stochastic approximation algorithm for pricing an option with early exercise features. We illustrate the procedure using an example of an American call option with a single dividend that is analytically tractable. In particular we incorporate estimates for the gradient with respect to the early exercise threshold level.

  6. Monte Carlo simulations for heavy ion dosimetry

    OpenAIRE

    Geithner, Oksana

    2006-01-01

    Water-to-air stopping power ratio ( ) calculations for the ionization chamber dosimetry of clinically relevant ion beams with initial energies from 50 to 450 MeV/u have been performed using the Monte Carlo technique. To simulate the transport of a particle in water the computer code SHIELD-HIT v2 was used which is a substantially modified version of its predecessor SHIELD-HIT v1. The code was partially rewritten, replacing formerly used single precision variables with double precision variabl...

  7. Sensitivity analysis for oblique incidence reflectometry using Monte Carlo simulations

    DEFF Research Database (Denmark)

    Kamran, Faisal; Andersen, Peter E.

    2015-01-01

    Oblique incidence reflectometry has developed into an effective, noncontact, and noninvasive measurement technology for the quantification of both the reduced scattering and absorption coefficients of a sample. The optical properties are deduced by analyzing only the shape of the reflectance...... profiles. This article presents a sensitivity analysis of the technique in turbid media. Monte Carlo simulations are used to investigate the technique and its potential to distinguish the small changes between different levels of scattering. We present various regions of the dynamic range of optical...... properties in which system demands vary to be able to detect subtle changes in the structure of the medium, translated as measured optical properties. Effects of variation in anisotropy are discussed and results presented. Finally, experimental data of milk products with different fat content are considered...

  8. Probabilistic fire simulator - Monte Carlo simulation tool for fire scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Hostikka, S.; Keski-Rahkonen, O. [VTT Building and Transport, Espoo (Finland)

    2002-11-01

    Risk analysis tool is developed for computing of the distributions of fire model output variables. The tool, called Probabilistic Fire Simulator, combines Monte Carlo simulation and CFAST two-zone fire model. In this work, it is used to calculate failure probability of redundant cables and fire detector activation times in a cable tunnel fire. Sensitivity of the output variables to the input variables is calculated in terms of the rank order correlations. (orig.)

  9. Parallel Monte Carlo simulation of aerosol dynamics

    KAUST Repository

    Zhou, K.

    2014-01-01

    A highly efficient Monte Carlo (MC) algorithm is developed for the numerical simulation of aerosol dynamics, that is, nucleation, surface growth, and coagulation. Nucleation and surface growth are handled with deterministic means, while coagulation is simulated with a stochastic method (Marcus-Lushnikov stochastic process). Operator splitting techniques are used to synthesize the deterministic and stochastic parts in the algorithm. The algorithm is parallelized using the Message Passing Interface (MPI). The parallel computing efficiency is investigated through numerical examples. Near 60% parallel efficiency is achieved for the maximum testing case with 3.7 million MC particles running on 93 parallel computing nodes. The algorithm is verified through simulating various testing cases and comparing the simulation results with available analytical and/or other numerical solutions. Generally, it is found that only small number (hundreds or thousands) of MC particles is necessary to accurately predict the aerosol particle number density, volume fraction, and so forth, that is, low order moments of the Particle Size Distribution (PSD) function. Accurately predicting the high order moments of the PSD needs to dramatically increase the number of MC particles. 2014 Kun Zhou et al.

  10. Quantum Monte Carlo Simulations : Algorithms, Limitations and Applications

    NARCIS (Netherlands)

    Raedt, H. De

    1992-01-01

    A survey is given of Quantum Monte Carlo methods currently used to simulate quantum lattice models. The formalisms employed to construct the simulation algorithms are sketched. The origin of fundamental (minus sign) problems which limit the applicability of the Quantum Monte Carlo approach is shown

  11. Monte Carlo simulations for focusing elliptical guides

    Energy Technology Data Exchange (ETDEWEB)

    Valicu, Roxana [FRM2 Garching, Muenchen (Germany); Boeni, Peter [E20, TU Muenchen (Germany)

    2009-07-01

    The aim of the Monte Carlo simulations using McStas Programme was to improve the focusing of the neutron beam existing at PGAA (FRM II) by prolongation of the existing elliptic guide (coated now with supermirrors with m=3) with a new part. First we have tried with an initial length of the additional guide of 7,5cm and coatings for the neutron guide of supermirrors with m=4,5 and 6. The gain (calculated by dividing the intensity in the focal point after adding the guide by the intensity at the focal point with the initial guide) obtained for this coatings indicated that a coating with m=5 would be appropriate for a first trial. The next step was to vary the length of the additional guide for this m value and therefore choosing the appropriate length for the maximal gain. With the m value and the length of the guide fixed we have introduced an aperture 1 cm before the focal point and we have varied the radius of this aperture in order to obtain a focused beam. We have observed a dramatic decrease in the size of the beam in the focal point after introducing this aperture. The simulation results, the gains obtained and the evolution of the beam size will be presented.

  12. Rare event simulation using Monte Carlo methods

    CERN Document Server

    Rubino, Gerardo

    2009-01-01

    In a probabilistic model, a rare event is an event with a very small probability of occurrence. The forecasting of rare events is a formidable task but is important in many areas. For instance a catastrophic failure in a transport system or in a nuclear power plant, the failure of an information processing system in a bank, or in the communication network of a group of banks, leading to financial losses. Being able to evaluate the probability of rare events is therefore a critical issue. Monte Carlo Methods, the simulation of corresponding models, are used to analyze rare events. This book sets out to present the mathematical tools available for the efficient simulation of rare events. Importance sampling and splitting are presented along with an exposition of how to apply these tools to a variety of fields ranging from performance and dependability evaluation of complex systems, typically in computer science or in telecommunications, to chemical reaction analysis in biology or particle transport in physics. ...

  13. Frequency domain optical tomography using a Monte Carlo perturbation method

    Science.gov (United States)

    Yamamoto, Toshihiro; Sakamoto, Hiroki

    2016-04-01

    A frequency domain Monte Carlo method is applied to near-infrared optical tomography, where an intensity-modulated light source with a given modulation frequency is used to reconstruct optical properties. The frequency domain reconstruction technique allows for better separation between the scattering and absorption properties of inclusions, even for ill-posed inverse problems, due to cross-talk between the scattering and absorption reconstructions. The frequency domain Monte Carlo calculation for light transport in an absorbing and scattering medium has thus far been analyzed mostly for the reconstruction of optical properties in simple layered tissues. This study applies a Monte Carlo calculation algorithm, which can handle complex-valued particle weights for solving a frequency domain transport equation, to optical tomography in two-dimensional heterogeneous tissues. The Jacobian matrix that is needed to reconstruct the optical properties is obtained by a first-order "differential operator" technique, which involves less variance than the conventional "correlated sampling" technique. The numerical examples in this paper indicate that the newly proposed Monte Carlo method provides reconstructed results for the scattering and absorption coefficients that compare favorably with the results obtained from conventional deterministic or Monte Carlo methods.

  14. Monte Carlo simulations for heavy ion dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Geithner, O.

    2006-07-26

    Water-to-air stopping power ratio (s{sub w,air}) calculations for the ionization chamber dosimetry of clinically relevant ion beams with initial energies from 50 to 450 MeV/u have been performed using the Monte Carlo technique. To simulate the transport of a particle in water the computer code SHIELD-HIT v2 was used which is a substantially modified version of its predecessor SHIELD-HIT v1. The code was partially rewritten, replacing formerly used single precision variables with double precision variables. The lowest particle transport specific energy was decreased from 1 MeV/u down to 10 keV/u by modifying the Bethe- Bloch formula, thus widening its range for medical dosimetry applications. Optional MSTAR and ICRU-73 stopping power data were included. The fragmentation model was verified using all available experimental data and some parameters were adjusted. The present code version shows excellent agreement with experimental data. Additional to the calculations of stopping power ratios, s{sub w,air}, the influence of fragments and I-values on s{sub w,air} for carbon ion beams was investigated. The value of s{sub w,air} deviates as much as 2.3% at the Bragg peak from the recommended by TRS-398 constant value of 1.130 for an energy of 50 MeV/u. (orig.)

  15. Monte Carlo Simulation of River Meander Modelling

    Science.gov (United States)

    Posner, A. J.; Duan, J. G.

    2010-12-01

    This study first compares the first order analytical solutions for flow field by Ikeda et. al. (1981) and Johanesson and Parker (1989b). Ikeda et. al.’s (1981) linear bank erosion model was implemented to predict the rate of bank erosion in which the bank erosion coefficient is treated as a stochastic variable that varies with physical properties of the bank (e.g. cohesiveness, stratigraphy, vegetation density). The developed model was used to predict the evolution of meandering planforms. Then, the modeling results were analyzed and compared to the observed data. Since the migration of meandering channel consists of downstream translation, lateral expansion, and downstream or upstream rotations. Several measures are formulated in order to determine which of the resulting planform is closest to the experimental measured one. Results from the deterministic model highly depend on the calibrated erosion coefficient. Since field measurements are always limited, the stochastic model yielded more realistic predictions of meandering planform evolutions. Due to the random nature of bank erosion coefficient, the meandering planform evolution is a stochastic process that can only be accurately predicted by a stochastic model. Quasi-2D Ikeda (1989) flow solution with Monte Carlo Simulation of Bank Erosion Coefficient.

  16. Lattice Monte Carlo simulations of polymer melts

    Science.gov (United States)

    Hsu, Hsiao-Ping

    2014-12-01

    We use Monte Carlo simulations to study polymer melts consisting of fully flexible and moderately stiff chains in the bond fluctuation model at a volume fraction 0.5. In order to reduce the local density fluctuations, we test a pre-packing process for the preparation of the initial configurations of the polymer melts, before the excluded volume interaction is switched on completely. This process leads to a significantly faster decrease of the number of overlapping monomers on the lattice. This is useful for simulating very large systems, where the statistical properties of the model with a marginally incomplete elimination of excluded volume violations are the same as those of the model with strictly excluded volume. We find that the internal mean square end-to-end distance for moderately stiff chains in a melt can be very well described by a freely rotating chain model with a precise estimate of the bond-bond orientational correlation between two successive bond vectors in equilibrium. The plot of the probability distributions of the reduced end-to-end distance of chains of different stiffness also shows that the data collapse is excellent and described very well by the Gaussian distribution for ideal chains. However, while our results confirm the systematic deviations between Gaussian statistics for the chain structure factor Sc(q) [minimum in the Kratky-plot] found by Wittmer et al. [EPL 77, 56003 (2007)] for fully flexible chains in a melt, we show that for the available chain length these deviations are no longer visible, when the chain stiffness is included. The mean square bond length and the compressibility estimated from collective structure factors depend slightly on the stiffness of the chains.

  17. Identification of Logical Errors through Monte-Carlo Simulation

    CERN Document Server

    Emmett, Hilary L

    2010-01-01

    The primary focus of Monte Carlo simulation is to identify and quantify risk related to uncertainty and variability in spreadsheet model inputs. The stress of Monte Carlo simulation often reveals logical errors in the underlying spreadsheet model that might be overlooked during day-to-day use or traditional "what-if" testing. This secondary benefit of simulation requires a trained eye to recognize warning signs of poor model construction.

  18. An empirical formula based on Monte Carlo simulation for diffuse reflectance from turbid media

    Science.gov (United States)

    Gnanatheepam, Einstein; Aruna, Prakasa Rao; Ganesan, Singaravelu

    2016-03-01

    Diffuse reflectance spectroscopy has been widely used in diagnostic oncology and characterization of laser irradiated tissue. However, still accurate and simple analytical equation does not exist for estimation of diffuse reflectance from turbid media. In this work, a diffuse reflectance lookup table for a range of tissue optical properties was generated using Monte Carlo simulation. Based on the generated Monte Carlo lookup table, an empirical formula for diffuse reflectance was developed using surface fitting method. The variance between the Monte Carlo lookup table surface and the surface obtained from the proposed empirical formula is less than 1%. The proposed empirical formula may be used for modeling of diffuse reflectance from tissue.

  19. Monte Carlo Simulation of Solar Reflectances for Cloudy Atmospheres.

    Science.gov (United States)

    Barker, H. W.; Goldstein, R. K.; Stevens, D. E.

    2003-08-01

    Monte Carlo simulations of solar radiative transfer were performed for a well-resolved, large, three-dimensional (3D) domain of boundary layer cloud simulated by a cloud-resolving model. In order to represent 3D distributions of optical properties for 2 × 106 cloudy cells, attenuation by droplets was handled by assigning each cell a cumulative distribution of extinction derived from either a model or an assumed discrete droplet size spectrum. This minimizes the required number of detailed phase functions. Likewise, to simulate statistically significant, high-resolution imagery, it was necessary to apply variance reduction techniques. Three techniques were developed for use with the local estimation method of computing reflectance . First, small fractions of come from numerous, small contributions of computed at each scattering event. Terminating calculation of when it falls below min 103 was found to impact estimates of minimally but reduced computation time by 10%. Second, large fractions of come from infrequent realizations of large . When sampled poorly, they boost Monte Carlo noise significantly. Removing max, storing them in a domainwide reservoir, adding max to local estimates of , and, at simulation's end, distributing the reservoir across the domain in proportion to local , tends to reduce variance much. This regionalization technique works well when the number of photons per unit area is small (nominally 50 000). A value of max 100 reduces variance of greatly with little impact on estimates of . Third, if are computed using exact (e.g., Mie) phase functions for the first N scattering events, and thereafter a blunt-nosed corresponding phase function (e.g., Henyey-Greenstein) is used, production of large is thwarted resulting in reduced variance and time required to achieve accurate estimates of .

  20. Monte Carlo simulation of large electron fields

    Science.gov (United States)

    Faddegon, Bruce A.; Perl, Joseph; Asai, Makoto

    2008-03-01

    Two Monte Carlo systems, EGSnrc and Geant4, the latter with two different 'physics lists,' were used to calculate dose distributions in large electron fields used in radiotherapy. Source and geometry parameters were adjusted to match calculated results to measurement. Both codes were capable of accurately reproducing the measured dose distributions of the six electron beams available on the accelerator. Depth penetration matched the average measured with a diode and parallel-plate chamber to 0.04 cm or better. Calculated depth dose curves agreed to 2% with diode measurements in the build-up region, although for the lower beam energies there was a discrepancy of up to 5% in this region when calculated results are compared to parallel-plate measurements. Dose profiles at the depth of maximum dose matched to 2-3% in the central 25 cm of the field, corresponding to the field size of the largest applicator. A 4% match was obtained outside the central region. The discrepancy observed in the bremsstrahlung tail in published results that used EGS4 is no longer evident. Simulations with the different codes and physics lists used different source energies, incident beam angles, thicknesses of the primary foils, and distance between the primary and secondary foil. The true source and geometry parameters were not known with sufficient accuracy to determine which parameter set, including the energy of the source, was closest to the truth. These results underscore the requirement for experimental benchmarks of depth penetration and electron scatter for beam energies and foils relevant to radiotherapy.

  1. Modelling laser light propagation in thermoplastics using Monte Carlo simulations

    Science.gov (United States)

    Parkinson, Alexander

    Laser welding has great potential as a fast, non-contact joining method for thermoplastic parts. In the laser transmission welding of thermoplastics, light passes through a semi-transparent part to reach the weld interface. There, it is absorbed as heat, which causes melting and subsequent welding. The distribution and quantity of light reaching the interface are important for predicting the quality of a weld, but are experimentally difficult to estimate. A model for simulating the path of this laser light through these light-scattering plastic parts has been developed. The technique uses a Monte-Carlo approach to generate photon paths through the material, accounting for absorption, scattering and reflection between boundaries in the transparent polymer. It was assumed that any light escaping the bottom surface contributed to welding. The photon paths are then scaled according to the input beam profile in order to simulate non-Gaussian beam profiles. A method for determining the 3 independent optical parameters to accurately predict transmission and beam power distribution at the interface was established using experimental data for polycarbonate at 4 different glass fibre concentrations and polyamide-6 reinforced with 20% long glass fibres. Exit beam profiles and transmissions predicted by the simulation were found to be in generally good agreement (R2>0.90) with experimental measurements. The simulations allowed the prediction of transmission and power distributions at other thicknesses as well as information on reflection, energy absorption and power distributions at other thicknesses for these materials.

  2. Public Infrastructure for Monte Carlo Simulation: publicMC@BATAN

    CERN Document Server

    Waskita, A A; Akbar, Z; Handoko, L T; 10.1063/1.3462759

    2010-01-01

    The first cluster-based public computing for Monte Carlo simulation in Indonesia is introduced. The system has been developed to enable public to perform Monte Carlo simulation on a parallel computer through an integrated and user friendly dynamic web interface. The beta version, so called publicMC@BATAN, has been released and implemented for internal users at the National Nuclear Energy Agency (BATAN). In this paper the concept and architecture of publicMC@BATAN are presented.

  3. LASER-DOPPLER VELOCIMETRY AND MONTE-CARLO SIMULATIONS ON MODELS FOR BLOOD PERFUSION IN TISSUE

    NARCIS (Netherlands)

    DEMUL, FFM; KOELINK, MH; KOK, ML; HARMSMA, PJ; GREVE, J; GRAAFF, R; AARNOUDSE, JG

    1995-01-01

    Laser Doppler flow measurements and Monte Carlo simulations on small blood perfusion flow models at 780 nm are presented and compared. The dimensions of the optical sample volume are investigated as functions of the distance of the laser to the detector and as functions of the angle of penetration o

  4. Monte Carlo simulation of neutron scattering instruments

    International Nuclear Information System (INIS)

    A library of Monte Carlo subroutines has been developed for the purpose of design of neutron scattering instruments. Using small-angle scattering as an example, the philosophy and structure of the library are described and the programs are used to compare instruments at continuous wave (CW) and long-pulse spallation source (LPSS) neutron facilities. The Monte Carlo results give a count-rate gain of a factor between 2 and 4 using time-of-flight analysis. This is comparable to scaling arguments based on the ratio of wavelength bandwidth to resolution width

  5. A Monte Carlo approach for simulating the propagation of partially coherent x-ray beams

    DEFF Research Database (Denmark)

    Prodi, A.; Bergbäck Knudsen, Erik; Willendrup, Peter Kjær;

    2011-01-01

    sampling Huygens-Fresnel waves with Monte Carlo methods and is used to propagate each source realization to the detector plane. The sampling is implemented with a modified Monte Carlo ray tracing scheme where the optical path of each generated ray is stored. Such information is then used in the summation......Advances at SR sources in the generation of nanofocused beams with a high degree of transverse coherence call for effective techniques to simulate the propagation of partially coherent X-ray beams through complex optical systems in order to characterize how coherence properties such as the mutual...... of the generated rays at the observation plane to account for coherence properties. This approach is used to simulate simple models of propagation in free space and with reflective and refractive optics. © 2011 COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the...

  6. Rapid Monte Carlo simulation of detector DQE(f)

    Energy Technology Data Exchange (ETDEWEB)

    Star-Lack, Josh, E-mail: josh.starlack@varian.com; Sun, Mingshan; Abel, Eric [Varian Medical Systems, Palo Alto, California 94304-1030 (United States); Meyer, Andre; Morf, Daniel [Varian Medical Systems, CH-5405, Baden-Dattwil (Switzerland); Constantin, Dragos; Fahrig, Rebecca [Department of Radiology, Stanford University, Stanford, California 94305 (United States)

    2014-03-15

    Purpose: Performance optimization of indirect x-ray detectors requires proper characterization of both ionizing (gamma) and optical photon transport in a heterogeneous medium. As the tool of choice for modeling detector physics, Monte Carlo methods have failed to gain traction as a design utility, due mostly to excessive simulation times and a lack of convenient simulation packages. The most important figure-of-merit in assessing detector performance is the detective quantum efficiency (DQE), for which most of the computational burden has traditionally been associated with the determination of the noise power spectrum (NPS) from an ensemble of flood images, each conventionally having 10{sup 7} − 10{sup 9} detected gamma photons. In this work, the authors show that the idealized conditions inherent in a numerical simulation allow for a dramatic reduction in the number of gamma and optical photons required to accurately predict the NPS. Methods: The authors derived an expression for the mean squared error (MSE) of a simulated NPS when computed using the International Electrotechnical Commission-recommended technique based on taking the 2D Fourier transform of flood images. It is shown that the MSE is inversely proportional to the number of flood images, and is independent of the input fluence provided that the input fluence is above a minimal value that avoids biasing the estimate. The authors then propose to further lower the input fluence so that each event creates a point-spread function rather than a flood field. The authors use this finding as the foundation for a novel algorithm in which the characteristic MTF(f), NPS(f), and DQE(f) curves are simultaneously generated from the results of a single run. The authors also investigate lowering the number of optical photons used in a scintillator simulation to further increase efficiency. Simulation results are compared with measurements performed on a Varian AS1000 portal imager, and with a previously published

  7. Stochastic simulation and Monte-Carlo methods; Simulation stochastique et methodes de Monte-Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Graham, C. [Centre National de la Recherche Scientifique (CNRS), 91 - Gif-sur-Yvette (France); Ecole Polytechnique, 91 - Palaiseau (France); Talay, D. [Institut National de Recherche en Informatique et en Automatique (INRIA), 78 - Le Chesnay (France); Ecole Polytechnique, 91 - Palaiseau (France)

    2011-07-01

    This book presents some numerical probabilistic methods of simulation with their convergence speed. It combines mathematical precision and numerical developments, each proposed method belonging to a precise theoretical context developed in a rigorous and self-sufficient manner. After some recalls about the big numbers law and the basics of probabilistic simulation, the authors introduce the martingales and their main properties. Then, they develop a chapter on non-asymptotic estimations of Monte-Carlo method errors. This chapter gives a recall of the central limit theorem and precises its convergence speed. It introduces the Log-Sobolev and concentration inequalities, about which the study has greatly developed during the last years. This chapter ends with some variance reduction techniques. In order to demonstrate in a rigorous way the simulation results of stochastic processes, the authors introduce the basic notions of probabilities and of stochastic calculus, in particular the essential basics of Ito calculus, adapted to each numerical method proposed. They successively study the construction and important properties of the Poisson process, of the jump and deterministic Markov processes (linked to transport equations), and of the solutions of stochastic differential equations. Numerical methods are then developed and the convergence speed results of algorithms are rigorously demonstrated. In passing, the authors describe the probabilistic interpretation basics of the parabolic partial derivative equations. Non-trivial applications to real applied problems are also developed. (J.S.)

  8. Monte Carlo simulations of phosphate polyhedron connectivity in glasses

    Energy Technology Data Exchange (ETDEWEB)

    ALAM,TODD M.

    2000-01-01

    Monte Carlo simulations of phosphate tetrahedron connectivity distributions in alkali and alkaline earth phosphate glasses are reported. By utilizing a discrete bond model, the distribution of next-nearest neighbor connectivities between phosphate polyhedron for random, alternating and clustering bonding scenarios was evaluated as a function of the relative bond energy difference. The simulated distributions are compared to experimentally observed connectivities reported for solid-state two-dimensional exchange and double-quantum NMR experiments of phosphate glasses. These Monte Carlo simulations demonstrate that the polyhedron connectivity is best described by a random distribution in lithium phosphate and calcium phosphate glasses.

  9. Research of Monte Carlo Simulation in Commercial Bank Risk Management

    Institute of Scientific and Technical Information of China (English)

    BeimingXiao

    2004-01-01

    Simulation method is an important-tool in financial risk management. It can simulate financial variable or economic wriable and deal with non-linear or non-nominal issue. This paper analyzes the usage of "Monte Carlo" approach in commercial bank risk management.

  10. Direct Monte Carlo simulation of nanoscale mixed gas bearings

    Directory of Open Access Journals (Sweden)

    Kyaw Sett Myo

    2015-06-01

    Full Text Available The conception of sealed hard drives with helium gas mixture has been recently suggested over the current hard drives for achieving higher reliability and less position error. Therefore, it is important to understand the effects of different helium gas mixtures on the slider bearing characteristics in the head–disk interface. In this article, the helium/air and helium/argon gas mixtures are applied as the working fluids and their effects on the bearing characteristics are studied using the direct simulation Monte Carlo method. Based on direct simulation Monte Carlo simulations, the physical properties of these gas mixtures such as mean free path and dynamic viscosity are achieved and compared with those obtained from theoretical models. It is observed that both results are comparable. Using these gas mixture properties, the bearing pressure distributions are calculated under different fractions of helium with conventional molecular gas lubrication models. The outcomes reveal that the molecular gas lubrication results could have relatively good agreement with those of direct simulation Monte Carlo simulations, especially for pure air, helium, or argon gas cases. For gas mixtures, the bearing pressures predicted by molecular gas lubrication model are slightly larger than those from direct simulation Monte Carlo simulation.

  11. Monte Carlo Simulation in Statistical Physics An Introduction

    CERN Document Server

    Binder, Kurt

    2010-01-01

    Monte Carlo Simulation in Statistical Physics deals with the computer simulation of many-body systems in condensed-matter physics and related fields of physics, chemistry and beyond, to traffic flows, stock market fluctuations, etc.). Using random numbers generated by a computer, probability distributions are calculated, allowing the estimation of the thermodynamic properties of various systems. This book describes the theoretical background to several variants of these Monte Carlo methods and gives a systematic presentation from which newcomers can learn to perform such simulations and to analyze their results. The fifth edition covers Classical as well as Quantum Monte Carlo methods. Furthermore a new chapter on the sampling of free-energy landscapes has been added. To help students in their work a special web server has been installed to host programs and discussion groups (http://wwwcp.tphys.uni-heidelberg.de). Prof. Binder was awarded the Berni J. Alder CECAM Award for Computational Physics 2001 as well ...

  12. Suppression of the initial transient in Monte Carlo criticality simulations

    International Nuclear Information System (INIS)

    Criticality Monte Carlo calculations aim at estimating the effective multiplication factor (k-effective) for a fissile system through iterations simulating neutrons propagation (making a Markov chain). Arbitrary initialization of the neutron population can deeply bias the k-effective estimation, defined as the mean of the k-effective computed at each iteration. A simplified model of this cycle k-effective sequence is built, based on characteristics of industrial criticality Monte Carlo calculations. Statistical tests, inspired by Brownian bridge properties, are designed to discriminate stationarity of the cycle k-effective sequence. The initial detected transient is, then, suppressed in order to improve the estimation of the system k-effective. The different versions of this methodology are detailed and compared, firstly on a plan of numerical tests fitted on criticality Monte Carlo calculations, and, secondly on real criticality calculations. Eventually, the best methodologies observed in these tests are selected and allow to improve industrial Monte Carlo criticality calculations. (author)

  13. Utilising Monte Carlo Simulation for the Valuation of Mining Concessions

    Directory of Open Access Journals (Sweden)

    Rosli Said

    2005-12-01

    Full Text Available Valuation involves the analyses of various input data to produce an estimated value. Since each input is itself often an estimate, there is an element of uncertainty in the input. This leads to uncertainty in the resultant output value. It is argued that a valuation must also convey information on the uncertainty, so as to be more meaningful and informative to the user. The Monte Carlo simulation technique can generate the information on uncertainty and is therefore potentially useful to valuation. This paper reports on the investigation that has been conducted to apply Monte Carlo simulation technique in mineral valuation, more specifically, in the valuation of a quarry concession.

  14. Monte Carlo simulation of electrons in dense gases

    Science.gov (United States)

    Tattersall, Wade; Boyle, Greg; Cocks, Daniel; Buckman, Stephen; White, Ron

    2014-10-01

    We implement a Monte-Carlo simulation modelling the transport of electrons and positrons in dense gases and liquids, by using a dynamic structure factor that allows us to construct structure-modified effective cross sections. These account for the coherent effects caused by interactions with the relatively dense medium. The dynamic structure factor also allows us to model thermal gases in the same manner, without needing to directly sample the velocities of the neutral particles. We present the results of a series of Monte Carlo simulations that verify and apply this new technique, and make comparisons with macroscopic predictions and Boltzmann equation solutions. Financial support of the Australian Research Council.

  15. Two Approaches to Accelerated Monte Carlo Simulation of Coulomb Collisions

    OpenAIRE

    Ricketson, Lee

    2014-01-01

    In plasma physics, the direct simulation of inter-particle Coulomb collisions is often necessary to capture the relevant physics, but presents a computational bottleneck because of the complexity of the process. In this thesis, we derive, test and discuss two methods for accelerating the simulation of collisions in plasmas in certain scenarios. The first is a hybrid fluid-Monte Carlo scheme that reduces the number of collisions that must be simulated. Coupling between the fluid and particl...

  16. Simulate the progress of PGNAA with Monte Carlo

    International Nuclear Information System (INIS)

    A kind of model to simulate bulk coal PGNAA process was set up, and some problems in PGNAA experiments was solved using the MOCA -Monte Carlo software. Analysis of the relationship between the thermal neutron field and the source distance, and the relationship curve with MOCA was obtained, and can be used to design measurement object bucket; simulated bulk coal PGNAA process, and analyzed activated γ spectrum. Through simulating PGNAA process, provide a theoretical basis for a bulk coal PGNAA experiments. (authors)

  17. Guideline of Monte Carlo calculation. Neutron/gamma ray transport simulation by Monte Carlo method

    CERN Document Server

    2002-01-01

    This report condenses basic theories and advanced applications of neutron/gamma ray transport calculations in many fields of nuclear energy research. Chapters 1 through 5 treat historical progress of Monte Carlo methods, general issues of variance reduction technique, cross section libraries used in continuous energy Monte Carlo codes. In chapter 6, the following issues are discussed: fusion benchmark experiments, design of ITER, experiment analyses of fast critical assembly, core analyses of JMTR, simulation of pulsed neutron experiment, core analyses of HTTR, duct streaming calculations, bulk shielding calculations, neutron/gamma ray transport calculations of the Hiroshima atomic bomb. Chapters 8 and 9 treat function enhancements of MCNP and MVP codes, and a parallel processing of Monte Carlo calculation, respectively. An important references are attached at the end of this report.

  18. Monte Carlo simulation of inelastic neutrino scattering in DUMAND

    International Nuclear Information System (INIS)

    Detailed Monte Carlo calculations simulating the detection in the DUMAND 1-km3 optical detector of inelastic neutrino scattering by nucleons at 2 TeV and above show that the measurement of the y distribution is subject to systematic errors due to experimental errors and intrinsic fluctuations which produce errors in the energy determinations of hadronic cascade and muon; uncertainty in the exact amount of antineutrino fraction in the cosmic-ray neutrino flux. The nature of these errors is explored, and methods for removing them from the data developed. The remaining uncertainties are those in the evaluation of the errors in energy determination, and in the antineutrino contamination. It appears that these errors, not statistical ones, will eventually govern the accuracy of the y distributions obtained. Nonetheless, the effect of the boson propagator on the y distribution is so marked that no plausible scenario can be found in which the residual errors cast doubt on whether or not the propagator effect is present

  19. Radiotherapy Monte Carlo simulation using cloud computing technology

    International Nuclear Information System (INIS)

    Cloud computing allows for vast computational resources to be leveraged quickly and easily in bursts as and when required. Here we describe a technique that allows for Monte Carlo radiotherapy dose calculations to be performed using GEANT4 and executed in the cloud, with relative simulation cost and completion time evaluated as a function of machine count. As expected, simulation completion time decreases as 1/n for n parallel machines, and relative simulation cost is found to be optimal where n is a factor of the total simulation time in hours. Using the technique, we demonstrate the potential usefulness of cloud computing as a solution for rapid Monte Carlo simulation for radiotherapy dose calculation without the need for dedicated local computer hardware as a proof of principal.

  20. Monte Carlo Simulation Optimizing Design of Grid Ionization Chamber

    Institute of Scientific and Technical Information of China (English)

    ZHENG; Yu-lai; WANG; Qiang; YANG; Lu

    2013-01-01

    The grid ionization chamber detector is often used for measuring charged particles.Based on Monte Carlo simulation method,the energy loss distribution and electron ion pairs of alpha particle with different energy have been calculated to determine suitable filling gas in the ionization chamber filled with

  1. Monte Carlo simulation of magnetic nanostructured thin films

    Institute of Scientific and Technical Information of China (English)

    Guan Zhi-Qiang; Yutaka Abe; Jiang Dong-Hua; Lin Hai; Yoshitake Yamazakia; Wu Chen-Xu

    2004-01-01

    @@ Using Monte Carlo simulation, we have compared the magnetic properties between nanostructured thin films and two-dimensional crystalline solids. The dependence of nanostructured properties on the interaction between particles that constitute the nanostructured thin films is also studied. The result shows that the parameters in the interaction potential have an important effect on the properties of nanostructured thin films at the transition temperatures.

  2. Quantum Monte Carlo simulation of topological phase transitions

    CERN Document Server

    Yamamoto, Arata

    2016-01-01

    We study the electron-electron interaction effects on topological phase transitions by the ab-initio quantum Monte Carlo simulation. We analyze two-dimensional class A topological insulators and three-dimensional Weyl semimetals with the long-range Coulomb interaction. The direct computation of the Chern number shows the electron-electron interaction modifies or extinguishes topological phase transitions.

  3. Simulating Strongly Correlated Electron Systems with Hybrid Monte Carlo

    Institute of Scientific and Technical Information of China (English)

    LIU Chuan

    2000-01-01

    Using the path integral representation, the Hubbard and the periodic Anderson model on D-dimensional cubic lattice are transformed into field theories of fermions in D + 1 dimensions. These theories at half-filling possess a positive definite real symmetry fermion matrix and can be simulated using the hybrid Monte Carlo method.

  4. Testing Dependent Correlations with Nonoverlapping Variables: A Monte Carlo Simulation

    Science.gov (United States)

    Silver, N. Clayton; Hittner, James B.; May, Kim

    2004-01-01

    The authors conducted a Monte Carlo simulation of 4 test statistics or comparing dependent correlations with no variables in common. Empirical Type 1 error rates and power estimates were determined for K. Pearson and L. N. G. Filon's (1898) z, O. J. Dunn and V. A. Clark's (1969) z, J. H. Steiger's (1980) original modification of Dunn and Clark's…

  5. Monte Carlo Simulations of Impact Ionization Feedback in MOSFET Structures

    OpenAIRE

    Bude, Jeff D.

    1998-01-01

    Although impact ionization feedback is recognized as an important current multiplication mechanism, its importance as a carrier heating mechanism has been largely overlooked. This work emphasizes the inclusion of impact ionization feedback in Monte Carlo device simulations, and its implications for carrier heating in sub-micron CMOS and EEPROM technologies.

  6. Microbial contamination in poultry chillers estimated by Monte Carlo simulations

    Science.gov (United States)

    The risk of microbial contamination during poultry processing may be reduced by the operating characteristics of the chiller. The performance of air chillers and immersion chillers were compared in terms of pre-chill and post-chill contamination using Monte Carlo simulations. Three parameters were u...

  7. Radio emission from cosmic ray air showers : Monte Carlo simulations

    NARCIS (Netherlands)

    Huege, T.; Falcke, H.D.E.

    2005-01-01

    We present time-domain Monte Carlo simulations of radio emission from cosmic ray air showers in the scheme of coherent geosynchrotron radiation. Our model takes into account the important air shower characteristics such as the lateral and longitudinal particle distributions, the particle track lengt

  8. Monte Carlo Simulation on Glueball Search at BESⅢ

    Institute of Scientific and Technical Information of China (English)

    QIN Hu; SHEN Xiao-Yan

    2007-01-01

    The J/ψ radiative decays are suggested as promising modes for glueball search. A full Monte Carlo simulation of J/ψ→γηη and γηη', based on the design of BESⅢ detector, is performed to study the sensitivity of searching for a possible tensor glueball at BESⅢ.

  9. Monte Carlo simulation with the Gate software using grid computing

    International Nuclear Information System (INIS)

    Monte Carlo simulations are widely used in emission tomography, for protocol optimization, design of processing or data analysis methods, tomographic reconstruction, or tomograph design optimization. Monte Carlo simulations needing many replicates to obtain good statistical results can be easily executed in parallel using the 'Multiple Replications In Parallel' approach. However, several precautions have to be taken in the generation of the parallel streams of pseudo-random numbers. In this paper, we present the distribution of Monte Carlo simulations performed with the GATE software using local clusters and grid computing. We obtained very convincing results with this large medical application, thanks to the EGEE Grid (Enabling Grid for E-science), achieving in one week computations that could have taken more than 3 years of processing on a single computer. This work has been achieved thanks to a generic object-oriented toolbox called DistMe which we designed to automate this kind of parallelization for Monte Carlo simulations. This toolbox, written in Java is freely available on SourceForge and helped to ensure a rigorous distribution of pseudo-random number streams. It is based on the use of a documented XML format for random numbers generators statuses. (authors)

  10. Monte Carlo simulations of plutonium gamma-ray spectra

    International Nuclear Information System (INIS)

    Monte Carlo calculations were investigated as a means of simulating the gamma-ray spectra of Pu. These simulated spectra will be used to develop and evaluate gamma-ray analysis techniques for various nondestructive measurements. Simulated spectra of calculational standards can be used for code intercomparisons, to understand systematic biases and to estimate minimum detection levels of existing and proposed nondestructive analysis instruments. The capability to simulate gamma-ray spectra from HPGe detectors could significantly reduce the costs of preparing large numbers of real reference materials. MCNP was used for the Monte Carlo transport of the photons. Results from the MCNP calculations were folded in with a detector response function for a realistic spectrum. Plutonium spectrum peaks were produced with Lorentzian shapes, for the x-rays, and Gaussian distributions. The MGA code determined the Pu isotopes and specific power of this calculated spectrum and compared it to a similar analysis on a measured spectrum

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

    International Nuclear Information System (INIS)

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

  12. Assessing Excel VBA Suitability for Monte Carlo Simulation

    OpenAIRE

    Botchkarev, Alexei

    2015-01-01

    Monte Carlo (MC) simulation includes a wide range of stochastic techniques used to quantitatively evaluate the behavior of complex systems or processes. Microsoft Excel spreadsheets with Visual Basic for Applications (VBA) software is, arguably, the most commonly employed general purpose tool for MC simulation. Despite the popularity of the Excel in many industries and educational institutions, it has been repeatedly criticized for its flaws and often described as questionable, if not complet...

  13. Monte Carlo simulation of virtual Compton scattering below pion threshold

    International Nuclear Information System (INIS)

    This paper describes the Monte Carlo simulation developed specifically for the Virtual Compton Scattering (VCS) experiments below pion threshold that have been performed at MAMI and JLab. This simulation generates events according to the (Bethe-Heitler + Born) cross-section behaviour and takes into account all relevant resolution-deteriorating effects. It determines the 'effective' solid angle for the various experimental settings which are used for the precise determination of the photon electroproduction absolute cross-section

  14. Monte Carlo Simulation of Argon in Nano-Space

    Institute of Scientific and Technical Information of China (English)

    CHEN Min; YANG Chun; GUO Zeng-Yuan

    2000-01-01

    Monte Carlo simulations are performed to investigate the thermodynamic properties of argon confined in nano-scale cubes constructed of graphite walls. A remarkable depression of the system pressures is observed. The simulations reveal that the length-scale of the cube, the magnitude of the interaction between the fluid and the graphite wall and the density of the fluid exhibit reasonable effects on the thermodynamic property shifts of the luid.

  15. Monte Carlo simulations of cold atom ratchets.

    OpenAIRE

    Brown, M.

    2008-01-01

    This thesis reports the theoretical study of several cold atom ratchet systems. In particular the focus of the work is the determination of the ratchet current as a function of the ratchet parameters through analysis of the system symmetries and through numerical simulation. Ratchets are devices that exhibit directed motion in the absence of net forces. It is necessary to drive them away from thermal equilibrium so as to not violate the second law of thermodynamics. Currents are generated whe...

  16. Cosmological Markov Chain Monte Carlo simulation with Cmbeasy

    CERN Document Server

    Müller, C M

    2004-01-01

    We introduce a Markov Chain Monte Carlo simulation and data analysis package for the cosmological computation package Cmbeasy. We have taken special care in implementing an adaptive step algorithm for the Markov Chain Monte Carlo in order to improve convergence. Data analysis routines are provided which allow to test models of the Universe against up-to-date measurements of the Cosmic Microwave Background, Supernovae Ia and Large Scale Structure. The observational data is provided with the software for convenient usage. The package is publicly available as part of the Cmbeasy software at www.cmbeasy.org.

  17. Monte Carlo 2000 Conference : Advanced Monte Carlo for Radiation Physics, Particle Transport Simulation and Applications

    CERN Document Server

    Baräo, Fernando; Nakagawa, Masayuki; Távora, Luis; Vaz, Pedro

    2001-01-01

    This book focusses on the state of the art of Monte Carlo methods in radiation physics and particle transport simulation and applications, the latter involving in particular, the use and development of electron--gamma, neutron--gamma and hadronic codes. Besides the basic theory and the methods employed, special attention is paid to algorithm development for modeling, and the analysis of experiments and measurements in a variety of fields ranging from particle to medical physics.

  18. Martini - Monte Carlo Simulation of Jet Evolution

    International Nuclear Information System (INIS)

    We present the Modular Algorithm for Relativistic Treatment of heavy IoN Interactions (MARTINI), an event generator for the hard and penetrating probes in high energy nucleus-nucleus collisions. The simulation consists of a time evolution model for the soft background, such as hydrodynamics, PYTHIA 8.1 to generate and hadronize the hard partons after the medium evolution, which is based on the McGill-AMY formalism and includes both radiative and elastic processes. MARTINI allows for the generation of full event configurations in the high pT region. We present results for the neutral pion and photon nuclear modification factor in Au + Au collisions at RHIC. (authors)

  19. Meaningful timescales from Monte Carlo simulations of molecular systems

    CERN Document Server

    Costa, Liborio I

    2016-01-01

    A new Markov Chain Monte Carlo method for simulating the dynamics of molecular systems with atomistic detail is introduced. In contrast to traditional Kinetic Monte Carlo approaches, where the state of the system is associated with minima in the energy landscape, in the proposed method, the state of the system is associated with the set of paths traveled by the atoms and the transition probabilities for an atom to be displaced are proportional to the corresponding velocities. In this way, the number of possible state-to-state transitions is reduced to a discrete set, and a direct link between the Monte Carlo time step and true physical time is naturally established. The resulting rejection-free algorithm is validated against event-driven molecular dynamics: the equilibrium and non-equilibrium dynamics of hard disks converge to the exact results with decreasing displacement size.

  20. Monte Carlo Simulations of Neutron Oil well Logging Tools

    International Nuclear Information System (INIS)

    Monte Carlo simulations of simple neutron oil well logging tools into typical geological formations are presented.The simulated tools consist of both 14 MeV pulsed and continuous Am-Be neutron sources with time gated and continuous gamma ray detectors respectively.The geological formation consists of pure limestone with 15% absolute porosity in a wide range of oil saturation.The particle transport was performed with the Monte Carlo N-Particle Transport Code System, MCNP-4B.Several gamma ray spectra were obtained at the detector position that allow to perform composition analysis of the formation.In particular, the ratio C/O was analyzed as an indicator of oil saturation.Further calculations are proposed to simulate actual detector responses in order to contribute to understand the relation between the detector response with the formation composition

  1. Monte Carlo Simulations of Neutron Oil well Logging Tools

    CERN Document Server

    Azcurra, M

    2002-01-01

    Monte Carlo simulations of simple neutron oil well logging tools into typical geological formations are presented.The simulated tools consist of both 14 MeV pulsed and continuous Am-Be neutron sources with time gated and continuous gamma ray detectors respectively.The geological formation consists of pure limestone with 15% absolute porosity in a wide range of oil saturation.The particle transport was performed with the Monte Carlo N-Particle Transport Code System, MCNP-4B.Several gamma ray spectra were obtained at the detector position that allow to perform composition analysis of the formation.In particular, the ratio C/O was analyzed as an indicator of oil saturation.Further calculations are proposed to simulate actual detector responses in order to contribute to understand the relation between the detector response with the formation composition

  2. Monte Carlo simulation of quantum Zeno effect in the brain

    CERN Document Server

    Georgiev, Danko

    2014-01-01

    Environmental decoherence appears to be the biggest obstacle for successful construction of quantum mind theories. Nevertheless, the quantum physicist Henry Stapp promoted the view that the mind could utilize quantum Zeno effect to influence brain dynamics and that the efficacy of such mental efforts would not be undermined by environmental decoherence of the brain. To address the physical plausibility of Stapp's claim, we modeled the brain using quantum tunneling of an electron in a multiple-well structure such as the voltage sensor in neuronal ion channels and performed Monte Carlo simulations of quantum Zeno effect exerted by the mind upon the brain in the presence or absence of environmental decoherence. The simulations unambiguously showed that the quantum Zeno effect breaks down for timescales greater than the brain decoherence time. To generalize the Monte Carlo simulation results for any n-level quantum system, we further analyzed the change of brain entropy due to the mind probing actions and proved ...

  3. A new lattice Monte Carlo method for simulating dielectric inhomogeneity

    Science.gov (United States)

    Duan, Xiaozheng; Wang, Zhen-Gang; Nakamura, Issei

    We present a new lattice Monte Carlo method for simulating systems involving dielectric contrast between different species by modifying an algorithm originally proposed by Maggs et al. The original algorithm is known to generate attractive interactions between particles that have different dielectric constant than the solvent. Here we show that such attractive force is spurious, arising from incorrectly biased statistical weight caused by the particle motion during the Monte Carlo moves. We propose a new, simple algorithm to resolve this erroneous sampling. We demonstrate the application of our algorithm by simulating an uncharged polymer in a solvent with different dielectric constant. Further, we show that the electrostatic fields in ionic crystals obtained from our simulations with a relatively small simulation box correspond well with results from the analytical solution. Thus, our Monte Carlo method avoids the need for the Ewald summation in conventional simulation methods for charged systems. This work was supported by the National Natural Science Foundation of China (21474112 and 21404103). We are grateful to Computing Center of Jilin Province for essential support.

  4. Monte Carlo Simulation of HERD Calorimeter

    CERN Document Server

    Xu, M; Dong, Y W; Lu, J G; Quan, Z; Wang, L; Wang, Z G; Wu, B B; Zhang, S N

    2014-01-01

    The High Energy cosmic-Radiation Detection (HERD) facility onboard China's Space Station is planned for operation starting around 2020 for about 10 years. It is designed as a next generation space facility focused on indirect dark matter search, precise cosmic ray spectrum and composition measurements up to the knee energy, and high energy gamma-ray monitoring and survey. The calorimeter plays an essential role in the main scientific objectives of HERD. A 3-D cubic calorimeter filled with high granularity crystals as active material is a very promising choice for the calorimeter. HERD is mainly composed of a 3-D calorimeter (CALO) surrounded by silicon trackers (TK) from all five sides except the bottom. CALO is made of 9261 cubes of LYSO crystals, corresponding to about 55 radiation lengths and 3 nuclear interaction lengths, respectively. Here the simulation results of the performance of CALO with GEANT4 and FLUKA are presented: 1) the total absorption CALO and its absorption depth for precise energy measure...

  5. Monte Carlo simulations in theoretical physic; Simulations Monte Carlo en physique theorique

    Energy Technology Data Exchange (ETDEWEB)

    Billoire, A.

    1991-12-31

    After a presentation of the MONTE CARLO method principle, the method is applied, first to the critical exponents calculations in the three dimensions ISING model, and secondly to the discrete quantum chromodynamic with calculation times in function of computer power. 28 refs., 4 tabs.

  6. Comparing analytical and Monte Carlo optical diffusion models in phosphor-based X-ray detectors

    Science.gov (United States)

    Kalyvas, N.; Liaparinos, P.

    2014-03-01

    Luminescent materials are employed as radiation to light converters in detectors of medical imaging systems, often referred to as phosphor screens. Several processes affect the light transfer properties of phosphors. Amongst the most important is the interaction of light. Light attenuation (absorption and scattering) can be described either through "diffusion" theory in theoretical models or "quantum" theory in Monte Carlo methods. Although analytical methods, based on photon diffusion equations, have been preferentially employed to investigate optical diffusion in the past, Monte Carlo simulation models can overcome several of the analytical modelling assumptions. The present study aimed to compare both methodologies and investigate the dependence of the analytical model optical parameters as a function of particle size. It was found that the optical photon attenuation coefficients calculated by analytical modeling are decreased with respect to the particle size (in the region 1- 12 μm). In addition, for particles sizes smaller than 6μm there is no simultaneous agreement between the theoretical modulation transfer function and light escape values with respect to the Monte Carlo data.

  7. Monte Carlo simulation of the Neutrino-4 experiment

    Energy Technology Data Exchange (ETDEWEB)

    Serebrov, A. P., E-mail: serebrov@pnpi.spb.ru; Fomin, A. K.; Onegin, M. S.; Ivochkin, V. G.; Matrosov, L. N. [National Research Center Kurchatov Institute, Petersburg Nuclear Physics Institute (Russian Federation)

    2015-12-15

    Monte Carlo simulation of the two-section reactor antineutrino detector of the Neutrino-4 experiment is carried out. The scintillation-type detector is based on the inverse beta-decay reaction. The antineutrino is recorded by two successive signals from the positron and the neutron. The simulation of the detector sections and the active shielding is performed. As a result of the simulation, the distributions of photomultiplier signals from the positron and the neutron are obtained. The efficiency of the detector depending on the signal recording thresholds is calculated.

  8. Monte Carlo simulation of a prototype photodetector used in radiotherapy

    CERN Document Server

    Kausch, C; Albers, D; Schmidt, R; Schreiber, B

    2000-01-01

    The imaging performance of prototype electronic portal imaging devices (EPID) has been investigated. Monte Carlo simulations have been applied to calculate the modulation transfer function (MTF( f )), the noise power spectrum (NPS( f )) and the detective quantum efficiency (DQE( f )) for different new type of EPIDs, which consist of a detector combination of metal or polyethylene (PE), a phosphor layer of Gd sub 2 O sub 2 S and a flat array of photodiodes. The simulated results agree well with measurements. Based on simulated results, possible optimization of these devices is discussed.

  9. Non-analogue Monte Carlo method, application to neutron simulation

    International Nuclear Information System (INIS)

    With most of the traditional and contemporary techniques, it is still impossible to solve the transport equation if one takes into account a fully detailed geometry and if one studies precisely the interactions between particles and matters. Nowadays, only the Monte Carlo method offers such possibilities. However with significant attenuation, the natural simulation remains inefficient: it becomes necessary to use biasing techniques where the solution of the adjoint transport equation is essential. The Monte Carlo code Tripoli has been using such techniques successfully for a long time with different approximate adjoint solutions: these methods require from the user to find out some parameters. If this parameters are not optimal or nearly optimal, the biases simulations may bring about small figures of merit. This paper presents a description of the most important biasing techniques of the Monte Carlo code Tripoli ; then we show how to calculate the importance function for general geometry with multigroup cases. We present a completely automatic biasing technique where the parameters of the biased simulation are deduced from the solution of the adjoint transport equation calculated by collision probabilities. In this study we shall estimate the importance function through collision probabilities method and we shall evaluate its possibilities thanks to a Monte Carlo calculation. We compare different biased simulations with the importance function calculated by collision probabilities for one-group and multigroup problems. We have run simulations with new biasing method for one-group transport problems with isotropic shocks and for multigroup problems with anisotropic shocks. The results show that for the one-group and homogeneous geometry transport problems the method is quite optimal without splitting and russian roulette technique but for the multigroup and heterogeneous X-Y geometry ones the figures of merit are higher if we add splitting and russian roulette

  10. Optical Monte Carlo modeling of a true portwine stain anatomy

    Science.gov (United States)

    Barton, Jennifer K.; Pfefer, T. Joshua; Welch, Ashley J.; Smithies, Derek J.; Nelson, Jerry; van Gemert, Martin J.

    1998-04-01

    A unique Monte Carlo program capable of accommodating an arbitrarily complex geometry was used to determine the energy deposition in a true port wine stain anatomy. Serial histologic sections taken from a biopsy of a dark red, laser therapy resistant stain were digitized and used to create the program input for simulation at wavelengths of 532 and 585 nm. At both wavelengths, the greatest energy deposition occurred in the superficial blood vessels, and subsequently decreased with depth as the laser beam was attenuated. However, more energy was deposited in the epidermis and superficial blood vessels at 532 nm than at 585 nm.

  11. Application of Monte Carlo Simulations to Improve Basketball Shooting Strategy

    CERN Document Server

    Min, Byeong June

    2016-01-01

    The underlying physics of basketball shooting seems to be a straightforward example of the Newtonian mechanics that can easily be traced by numerical methods. However, a human basketball player does not make use of all the possible basketball trajectories. Instead, a basketball player will build up a database of successful shots and select the trajectory that has the greatest tolerance to small variations of the real world. We simulate the basketball player's shooting training as a Monte Carlo sequence to build optimal shooting strategies, such as the launch speed and angle of the basketball, and whether to take a direct shot or a bank shot, as a function of the player's court positions and height. The phase space volume that belongs to the successful launch velocities generated by Monte Carlo simulations are then used as the criterion to optimize a shooting strategy that incorporates not only mechanical, but human factors as well.

  12. Radio emission from cosmic ray air showers: Monte Carlo simulations

    CERN Document Server

    Huege, T; Huege, Tim; Falcke, Heino

    2004-01-01

    We present time-domain Monte Carlo simulations of radio emission from cosmic ray air showers in the scheme of coherent geosynchrotron radiation. Our model takes into account the important air shower characteristics such as the lateral and longitudinal particle distributions, the particle track length and energy distributions, a realistic magnetic field geometry and the shower evolution as a whole. The Monte Carlo approach allows us to retain the full polarisation information and to carry out the calculations without the need for any far-field approximations. We demonstrate the strategies developed to tackle the computational effort associated with the simulation of a huge number of particles for a great number of observer bins and illustrate the robustness and accuracy of these techniques. We predict the emission pattern, the radial and the spectral dependence of the radiation from a prototypical 10^17 eV vertical air shower and find good agreement with our analytical results (Huege & Falcke 2003) and the...

  13. Calculating Variable Annuity Liability 'Greeks' Using Monte Carlo Simulation

    OpenAIRE

    Cathcart, Mark J.; Steven Morrison; McNeil, Alexander J.

    2011-01-01

    Hedging methods to mitigate the exposure of variable annuity products to market risks require the calculation of market risk sensitivities (or "Greeks"). The complex, path-dependent nature of these products means these sensitivities typically must be estimated by Monte Carlo simulation. Standard market practice is to measure such sensitivities using a "bump and revalue" method. As well as requiring multiple valuations, such approaches can be unreliable for higher order Greeks, e.g., gamma. In...

  14. Monte Carlo simulation of hydrogen adsorption on Ni surfaces

    Institute of Scientific and Technical Information of China (English)

    WANG Rui; DENG Hui-qiu; YUAN Xiao-jian; HU Wang-yu

    2007-01-01

    In the present paper the adsorption kinetics of the hydrogen molecule on the(111)and(100)surfaces have been studied with the model proposed by Panczyk and the grand canonical Monte Carlo simulation method.The equilibrium adsorption isotherms are calculated at five different temperatures ranging from 314 K to 376 K and compared with the experimental equilibrium adsorption isotherms.The effects of temperature and pressure on coverage are also analyzed.

  15. Monte Carlo Simulation as a Research Management Tool

    Energy Technology Data Exchange (ETDEWEB)

    Douglas, L. J.

    1986-06-01

    Monte Carlo simulation provides a research manager with a performance monitoring tool to supplement the standard schedule- and resource-based tools such as the Program Evaluation and Review Technique (PERT) and Critical Path Method (CPM). The value of the Monte Carlo simulation in a research environment is that it 1) provides a method for ranking competing processes, 2) couples technical improvements to the process economics, and 3) provides a mechanism to determine the value of research dollars. In this paper the Monte Carlo simulation approach is developed and applied to the evaluation of three competing processes for converting lignocellulosic biomass to ethanol. The technique is shown to be useful for ranking the processes and illustrating the importance of the timeframe of the analysis on the decision process. The results show that acid hydrolysis processes have higher potential for near-term application (2-5 years), while the enzymatic hydrolysis approach has an equal chance to be competitive in the long term (beyond 10 years).

  16. Monte Carlo simulations in small animal PET imaging

    Energy Technology Data Exchange (ETDEWEB)

    Branco, Susana [Universidade de Lisboa, Faculdade de Ciencias, Instituto de Biofisica e Engenharia Biomedica, Lisbon (Portugal)], E-mail: susana.silva@fc.ul.pt; Jan, Sebastien [Service Hospitalier Frederic Joliot, CEA/DSV/DRM, Orsay (France); Almeida, Pedro [Universidade de Lisboa, Faculdade de Ciencias, Instituto de Biofisica e Engenharia Biomedica, Lisbon (Portugal)

    2007-10-01

    This work is based on the use of an implemented Positron Emission Tomography (PET) simulation system dedicated for small animal PET imaging. Geant4 Application for Tomographic Emission (GATE), a Monte Carlo simulation platform based on the Geant4 libraries, is well suited for modeling the microPET FOCUS system and to implement realistic phantoms, such as the MOBY phantom, and data maps from real examinations. The use of a microPET FOCUS simulation model with GATE has been validated for spatial resolution, counting rates performances, imaging contrast recovery and quantitative analysis. Results from realistic studies of the mouse body using {sup -}F and [{sup 18}F]FDG imaging protocols are presented. These simulations include the injection of realistic doses into the animal and realistic time framing. The results have shown that it is possible to simulate small animal PET acquisitions under realistic conditions, and are expected to be useful to improve the quantitative analysis in PET mouse body studies.

  17. Monte Carlo simulations in small animal PET imaging

    International Nuclear Information System (INIS)

    This work is based on the use of an implemented Positron Emission Tomography (PET) simulation system dedicated for small animal PET imaging. Geant4 Application for Tomographic Emission (GATE), a Monte Carlo simulation platform based on the Geant4 libraries, is well suited for modeling the microPET FOCUS system and to implement realistic phantoms, such as the MOBY phantom, and data maps from real examinations. The use of a microPET FOCUS simulation model with GATE has been validated for spatial resolution, counting rates performances, imaging contrast recovery and quantitative analysis. Results from realistic studies of the mouse body using -F and [18F]FDG imaging protocols are presented. These simulations include the injection of realistic doses into the animal and realistic time framing. The results have shown that it is possible to simulate small animal PET acquisitions under realistic conditions, and are expected to be useful to improve the quantitative analysis in PET mouse body studies

  18. Monte Carlo simulation of charge mediated magnetoelectricity in multiferroic bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz-Álvarez, H.H. [Universidad de Caldas, Manizales (Colombia); Universidad Nacional de Colombia Sede Manizales, Manizales, Caldas (Colombia); Bedoya-Hincapié, C.M. [Universidad Nacional de Colombia Sede Manizales, Manizales, Caldas (Colombia); Universidad Santo Tomás, Bogotá (Colombia); Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.co [Universidad Nacional de Colombia Sede Manizales, Manizales, Caldas (Colombia)

    2014-12-01

    Simulations of a bilayer ferroelectric/ferromagnetic multiferroic system were carried out, based on the Monte Carlo method and Metropolis dynamics. A generic model was implemented with a Janssen-like Hamiltonian, taking into account magnetoelectric interactions due to charge accumulation at the interface. Two different magnetic exchange constants were considered for accumulation and depletion states. Several screening lengths were also included. Simulations exhibit considerable magnetoelectric effects not only at low temperature, but also at temperature near to the transition point of the ferromagnetic layer. The results match experimental observations for this kind of structure and mechanism.

  19. Multi-Level Monte Carlo Simulations with Importance Sampling

    OpenAIRE

    Przemyslaw S. Stilger and Ser-Huang Poon

    2013-01-01

    We present an application of importance sampling to multi-asset options under the Heston and the Bates models as well as to the Heston-Hull-White and the Heston-Cox-Ingersoll-Ross models. Moreover, we provide an efficient importance sampling scheme in a Multi-Level Monte Carlo simulation. In all cases, we explain how the Greeks can be computed in the different simulation schemes using the Likelihood Ratio Method, and how combining it with importance sampling leads to a significant variance re...

  20. Monte-Carlo Simulations for the optimisation of a TOF-MIEZE Instrument

    CERN Document Server

    Weber, T; Georgii, R; Häußler, W; Weichselbaumer, S; Böni, P; 10.1016/j.nima.2013.03.010

    2013-01-01

    The MIEZE (Modulation of Intensity with Zero Effort) technique is a variant of neutron resonance spin echo (NRSE), which has proven to be a unique neutron scattering technique for measuring with high energy resolution in magnetic fields. Its limitations in terms of flight path differences have already been investigated analytically for neutron beams with vanishing divergence. In the present work Monte-Carlo simulations for quasi-elastic MIEZE experiments taking into account beam divergence as well as the sample dimensions are presented. One application of the MIEZE technique could be a dedicated NRSE-MIEZE instrument at the European Spallation Source (ESS) in Sweden. The optimisation of a particular design based on Montel mirror optics with the help of Monte Carlo simulations will be discussed here in detail.

  1. Monte Carlo radiative transfer simulation of a cavity solar reactor for the reduction of cerium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Villafan-Vidales, H.I.; Arancibia-Bulnes, C.A.; Dehesa-Carrasco, U. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Privada Xochicalco s/n, Col. Centro, A.P. 34, Temixco, Morelos 62580 (Mexico); Romero-Paredes, H. [Departamento de Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco No.186, Col. Vicentina, A.P. 55-534, Mexico D.F 09340 (Mexico)

    2009-01-15

    Radiative heat transfer in a solar thermochemical reactor for the thermal reduction of cerium oxide is simulated with the Monte Carlo method. The directional characteristics and the power distribution of the concentrated solar radiation that enters the cavity is obtained by carrying out a Monte Carlo ray tracing of a paraboloidal concentrator. It is considered that the reactor contains a gas/particle suspension directly exposed to concentrated solar radiation. The suspension is treated as a non-isothermal, non-gray, absorbing, emitting, and anisotropically scattering medium. The transport coefficients of the particles are obtained from Mie-scattering theory by using the optical properties of cerium oxide. From the simulations, the aperture radius and the particle concentration were optimized to match the characteristics of the considered concentrator. (author)

  2. Pattern Recognition for a Flight Dynamics Monte Carlo Simulation

    Science.gov (United States)

    Restrepo, Carolina; Hurtado, John E.

    2011-01-01

    The design, analysis, and verification and validation of a spacecraft relies heavily on Monte Carlo simulations. Modern computational techniques are able to generate large amounts of Monte Carlo data but flight dynamics engineers lack the time and resources to analyze it all. The growing amounts of data combined with the diminished available time of engineers motivates the need to automate the analysis process. Pattern recognition algorithms are an innovative way of analyzing flight dynamics data efficiently. They can search large data sets for specific patterns and highlight critical variables so analysts can focus their analysis efforts. This work combines a few tractable pattern recognition algorithms with basic flight dynamics concepts to build a practical analysis tool for Monte Carlo simulations. Current results show that this tool can quickly and automatically identify individual design parameters, and most importantly, specific combinations of parameters that should be avoided in order to prevent specific system failures. The current version uses a kernel density estimation algorithm and a sequential feature selection algorithm combined with a k-nearest neighbor classifier to find and rank important design parameters. This provides an increased level of confidence in the analysis and saves a significant amount of time.

  3. Monte Carlo simulation of transition radiation and δ electrons

    International Nuclear Information System (INIS)

    This paper employs Monte Carlo simulations of the performance of a transition radiation detector (TRD). The program has been written for the TRD in the ZEUS spectrometer, which separates electrons from hadrons in the momentum range between 1 GeV/c and 30 GeV/c. Both, total charge method and cluster counting method were simulated taking into account various experimental parameters. In particular, it was found that the cluster counting method relies on a quantitative understanding of the background originating from the production of δ-electrons by charged particles. The results of the Monte Carlo calculations are in agreement with experimental data obtained with prototypes within a systematic uncertainty of 20%. We applied our Monte Carlo program to studies in order to find an optimum layout for the TRD within available space in the ZEUS spectrometer. In this context, the performance of TRD layouts with different geometries and materials has been evaluated comprehensively. The geometry found by optimization promises an improvement on hadron suppression by a factor of about two for both methods compared with present results from test measurements. Applying algorithms for a detailed analysis of the energy and space distributions of the clusters in the TRD, hadrons in the momentum range from 1 to 30 GeV/c can be suppressed to a level of less than 2%. This method of cluster analysing improves the suppression of hadrons by a factor of about two compared to the total charge method. (orig.)

  4. Accelerate Monte Carlo Simulations with Restricted Boltzmann Machines

    CERN Document Server

    Huang, Li

    2016-01-01

    Despite their exceptional flexibility and popularity, the Monte Carlo methods often suffer from slow mixing times for challenging statistical physics problems. We present a general strategy to overcome this difficulty by adopting ideas and techniques from the machine learning community. We fit the unnormalized probability of the physical model to a feedforward neural network and reinterpret the architecture as a restricted Boltzmann machine. Then, exploiting its feature detection ability, we utilize the restricted Boltzmann machine for efficient Monte Carlo updates and to speed up the simulation of the original physical system. We implement these ideas for the Falicov-Kimball model and demonstrate improved acceptance ratio and autocorrelation time near the phase transition point.

  5. Monte Carlo simulation of positronium thermalization in gases

    Directory of Open Access Journals (Sweden)

    Marjanović Srđan D.

    2010-01-01

    Full Text Available In this paper we present the results of Monte Carlo simulations of positronium (Ps swarm thermalization in helium (He and water vapour. We have investigated the temporal evolution of energy and spatial parameters of the swarm and their sensitivity to the shape of the cross-section and the initial energy distribution. Positron anihilation spectroscopy (PAS and positron emission tomography (PET are techniques that depend on anihilation of positronium in materials and tissue. The results obtained point that the Monte Carlo technique shows good agreement with experimental results and is capable of accurately describing the behaviour of Ps particles including the energy, particle lifetime and the moment and location of the anihilation.

  6. Fast Monte Carlo-assisted simulation of cloudy Earth backgrounds

    Science.gov (United States)

    Adler-Golden, Steven; Richtsmeier, Steven C.; Berk, Alexander; Duff, James W.

    2012-11-01

    A calculation method has been developed for rapidly synthesizing radiometrically accurate ultraviolet through longwavelengthinfrared spectral imagery of the Earth for arbitrary locations and cloud fields. The method combines cloudfree surface reflectance imagery with cloud radiance images calculated from a first-principles 3-D radiation transport model. The MCScene Monte Carlo code [1-4] is used to build a cloud image library; a data fusion method is incorporated to speed convergence. The surface and cloud images are combined with an upper atmospheric description with the aid of solar and thermal radiation transport equations that account for atmospheric inhomogeneity. The method enables a wide variety of sensor and sun locations, cloud fields, and surfaces to be combined on-the-fly, and provides hyperspectral wavelength resolution with minimal computational effort. The simulations agree very well with much more time-consuming direct Monte Carlo calculations of the same scene.

  7. On Monte Carlo Simulation and Analysis of Electricity Markets

    International Nuclear Information System (INIS)

    This dissertation is about how Monte Carlo simulation can be used to analyse electricity markets. There are a wide range of applications for simulation; for example, players in the electricity market can use simulation to decide whether or not an investment can be expected to be profitable, and authorities can by means of simulation find out which consequences a certain market design can be expected to have on electricity prices, environmental impact, etc. In the first part of the dissertation, the focus is which electricity market models are suitable for Monte Carlo simulation. The starting point is a definition of an ideal electricity market. Such an electricity market is partly practical from a mathematical point of view (it is simple to formulate and does not require too complex calculations) and partly it is a representation of the best possible resource utilisation. The definition of the ideal electricity market is followed by analysis how the reality differs from the ideal model, what consequences the differences have on the rules of the electricity market and the strategies of the players, as well as how non-ideal properties can be included in a mathematical model. Particularly, questions about environmental impact, forecast uncertainty and grid costs are studied. The second part of the dissertation treats the Monte Carlo technique itself. To reduce the number of samples necessary to obtain accurate results, variance reduction techniques can be used. Here, six different variance reduction techniques are studied and possible applications are pointed out. The conclusions of these studies are turned into a method for efficient simulation of basic electricity markets. The method is applied to some test systems and the results show that the chosen variance reduction techniques can produce equal or better results using 99% fewer samples compared to when the same system is simulated without any variance reduction technique. More complex electricity market models

  8. Review of neutron noise analysis theory by Monte Carlo simulation

    International Nuclear Information System (INIS)

    Some debates on the theory of neutron noise analysis for reactor kinetic parameter measurement were found before 1970 but a report firmly clearing these debates has not been found, and a question was raised when neutron noise experiments for the TRIGA and HANARO reactors in Korea were performed. In order to clarify this question, the neutron noise experiment is simulated by the Monte Carlo method. This simulation confirms that the widely used equation is approximately valid and that the confusion was caused from the explanation on the derivation of the equation. Rossi-α technique is one of the representative methods of noise analyses for the reactor kinetic parameter measurement, but different opinions were raised for the chain reaction related term in the equation. The equation originally derived at the Los Alamos National Laboratory (LANL) has been widely accepted. However, the others were supported by strict mathematics and experiments as well, and the reason of discrepancy has not been clarified. Since it is the problem of basic concept before the effect of neutron energy or geometry is included, the Monte Carlo simulation for the simplest reactor model could clarify it. For this purpose, the experiment measuring the neutron noise is simulated, and it results that the original equation is approximately valid. However, it is judged that the explanation on the equation by the authors derived it for the first time is not so correct, but Orndoff who made the first experiment by the Ross-α technique explained it rather correctly

  9. Neutron stimulated emission computed tomography: a Monte Carlo simulation approach

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, A C [Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Durham, NC 27708 (United States); Harrawood, B P [Duke Advance Imaging Labs, Department of Radiology, 2424 Erwin Rd, Suite 302, Durham, NC 27705 (United States); Bender, J E [Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Durham, NC 27708 (United States); Tourassi, G D [Duke Advance Imaging Labs, Department of Radiology, 2424 Erwin Rd, Suite 302, Durham, NC 27705 (United States); Kapadia, A J [Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Durham, NC 27708 (United States)

    2007-10-21

    A Monte Carlo simulation has been developed for neutron stimulated emission computed tomography (NSECT) using the GEANT4 toolkit. NSECT is a new approach to biomedical imaging that allows spectral analysis of the elements present within the sample. In NSECT, a beam of high-energy neutrons interrogates a sample and the nuclei in the sample are stimulated to an excited state by inelastic scattering of the neutrons. The characteristic gammas emitted by the excited nuclei are captured in a spectrometer to form multi-energy spectra. Currently, a tomographic image is formed using a collimated neutron beam to define the line integral paths for the tomographic projections. These projection data are reconstructed to form a representation of the distribution of individual elements in the sample. To facilitate the development of this technique, a Monte Carlo simulation model has been constructed from the GEANT4 toolkit. This simulation includes modeling of the neutron beam source and collimation, the samples, the neutron interactions within the samples, the emission of characteristic gammas, and the detection of these gammas in a Germanium crystal. In addition, the model allows the absorbed radiation dose to be calculated for internal components of the sample. NSECT presents challenges not typically addressed in Monte Carlo modeling of high-energy physics applications. In order to address issues critical to the clinical development of NSECT, this paper will describe the GEANT4 simulation environment and three separate simulations performed to accomplish three specific aims. First, comparison of a simulation to a tomographic experiment will verify the accuracy of both the gamma energy spectra produced and the positioning of the beam relative to the sample. Second, parametric analysis of simulations performed with different user-defined variables will determine the best way to effectively model low energy neutrons in tissue, which is a concern with the high hydrogen content in

  10. Packaging a free-space intra-chip optical interconnect module: Monte Carlo tolerance study and assembly results

    Science.gov (United States)

    Vervaeke, Michael; Lahti, Markku; Karpinnen, Mikko; Debaes, Christof; Volckaerts, Bart; Karioja, Pentti; Thienpont, Hugo

    2006-04-01

    In this paper we give an overview of the fabrication and assembly induced performance degradation of an intra-multi-chip-module free-space optical interconnect, integrating micro-lenses and a deflection prism above a dense opto-electronic chip. The proposed component is used to demonstrate the capabilities of an accurate micro-optical rapid prototype technique, namely the Deep Proton Writing (DPW). To evaluate the accuracy of DPW and to assess whether our assembly scheme will provide us with a reasonable process yield, we have built a simulation framework combining mechanical Monte Carlo analysis with optical simulations. Both the technological requirements to ensure a high process yield, and the specifications of our in-house DPW technology are discussed. Therefore, we first conduct a sensitivity analysis and we subsequently simulate the effect of combined errors using a Monte Carlo simulation. We are able to investigate the effect of a technology accuracy enhancement on the fabrication and assembly yield by scaling the standard deviation of the errors proportionally to each sensitivity interval. We estimate that 40% of the systems fabricated with DPW will show an optical transmission efficiency above -4.32 dB, which is -3 dB below the theoretical obtainable value. We also discuss our efforts to implement an opto-mechanical Monte Carlo simulator. It enables us to address specific issues not directly related with the micro-optical or DPW components, such as the influence of glueing layers and structures that allow for self-alignment, by combining mechanical tolerancing algorithms with optical simulation software. More in particular we determined that DPW provides ample accuracy to meet the requirements to obtain a high manufacturing yield. Finally, we shortly highlight the basic layout of a completed demonstrator. The adhesive bonding of opto-electronic devices in their package is subject to further improvement to enhance the tilt accuracy of the devices with

  11. Mont Carlo Simulation Program from the World Petroleum Assessment 2000, DDS-60 (emcee.xls)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Monte Carlo programs described in chapter MC, Monte Carlo Simulation Method. Emc2.xls was the program used to calculate the estimates of undiscovered resources for...

  12. Monte Carlo Simulation Program from the World Petroleum Assessment 2000, DDS-60 (Emc2.xls).

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Monte Carlo programs described in chapter MC, Monte Carlo Simulation Method. Emc2.xls was the program used to calculate the estimates of undiscovered resources for...

  13. Monte Carlo Simulation for Statistical Decay of Compound Nucleus

    Directory of Open Access Journals (Sweden)

    Chadwick M.B.

    2012-02-01

    Full Text Available We perform Monte Carlo simulations for neutron and γ-ray emissions from a compound nucleus based on the Hauser-Feshbach statistical theory. This Monte Carlo Hauser-Feshbach (MCHF method calculation, which gives us correlated information between emitted particles and γ-rays. It will be a powerful tool in many applications, as nuclear reactions can be probed in a more microscopic way. We have been developing the MCHF code, CGM, which solves the Hauser-Feshbach theory with the Monte Carlo method. The code includes all the standard models that used in a standard Hauser-Feshbach code, namely the particle transmission generator, the level density module, interface to the discrete level database, and so on. CGM can emit multiple neutrons, as long as the excitation energy of the compound nucleus is larger than the neutron separation energy. The γ-ray competition is always included at each compound decay stage, and the angular momentum and parity are conserved. Some calculations for a fission fragment 140Xe are shown as examples of the MCHF method, and the correlation between the neutron and γ-ray is discussed.

  14. Monte Carlo simulations for design of the KFUPM PGNAA facility

    CERN Document Server

    Naqvi, A A; Maslehuddin, M; Kidwai, S

    2003-01-01

    Monte Carlo simulations were carried out to design a 2.8 MeV neutron-based prompt gamma ray neutron activation analysis (PGNAA) setup for elemental analysis of cement samples. The elemental analysis was carried out using prompt gamma rays produced through capture of thermal neutrons in sample nuclei. The basic design of the PGNAA setup consists of a cylindrical cement sample enclosed in a cylindrical high-density polyethylene moderator placed between a neutron source and a gamma ray detector. In these simulations the predominant geometrical parameters of the PGNAA setup were optimized, including moderator size, sample size and shielding of the detector. Using the results of the simulations, an experimental PGNAA setup was then fabricated at the 350 kV Accelerator Laboratory of this University. The design calculations were checked experimentally through thermal neutron flux measurements inside the PGNAA moderator. A test prompt gamma ray spectrum of the PGNAA setup was also acquired from a Portland cement samp...

  15. Monte Carlo Simulation Tool Installation and Operation Guide

    Energy Technology Data Exchange (ETDEWEB)

    Aguayo Navarrete, Estanislao; Ankney, Austin S.; Berguson, Timothy J.; Kouzes, Richard T.; Orrell, John L.; Troy, Meredith D.; Wiseman, Clinton G.

    2013-09-02

    This document provides information on software and procedures for Monte Carlo simulations based on the Geant4 toolkit, the ROOT data analysis software and the CRY cosmic ray library. These tools have been chosen for its application to shield design and activation studies as part of the simulation task for the Majorana Collaboration. This document includes instructions for installation, operation and modification of the simulation code in a high cyber-security computing environment, such as the Pacific Northwest National Laboratory network. It is intended as a living document, and will be periodically updated. It is a starting point for information collection by an experimenter, and is not the definitive source. Users should consult with one of the authors for guidance on how to find the most current information for their needs.

  16. Monte Carlo simulations and dosimetric studies of an irradiation facility

    Science.gov (United States)

    Belchior, A.; Botelho, M. L.; Vaz, P.

    2007-09-01

    There is an increasing utilization of ionizing radiation for industrial applications. Additionally, the radiation technology offers a variety of advantages in areas, such as sterilization and food preservation. For these applications, dosimetric tests are of crucial importance in order to assess the dose distribution throughout the sample being irradiated. The use of Monte Carlo methods and computational tools in support of the assessment of the dose distributions in irradiation facilities can prove to be economically effective, representing savings in the utilization of dosemeters, among other benefits. One of the purposes of this study is the development of a Monte Carlo simulation, using a state-of-the-art computational tool—MCNPX—in order to determine the dose distribution inside an irradiation facility of Cobalt 60. This irradiation facility is currently in operation at the ITN campus and will feature an automation and robotics component, which will allow its remote utilization by an external user, under REEQ/996/BIO/2005 project. The detailed geometrical description of the irradiation facility has been implemented in MCNPX, which features an accurate and full simulation of the electron-photon processes involved. The validation of the simulation results obtained was performed by chemical dosimetry methods, namely a Fricke solution. The Fricke dosimeter is a standard dosimeter and is widely used in radiation processing for calibration purposes.

  17. Monte Carlo simulation of quantum Zeno effect in the brain

    Science.gov (United States)

    Georgiev, Danko

    2015-12-01

    Environmental decoherence appears to be the biggest obstacle for successful construction of quantum mind theories. Nevertheless, the quantum physicist Henry Stapp promoted the view that the mind could utilize quantum Zeno effect to influence brain dynamics and that the efficacy of such mental efforts would not be undermined by environmental decoherence of the brain. To address the physical plausibility of Stapp's claim, we modeled the brain using quantum tunneling of an electron in a multiple-well structure such as the voltage sensor in neuronal ion channels and performed Monte Carlo simulations of quantum Zeno effect exerted by the mind upon the brain in the presence or absence of environmental decoherence. The simulations unambiguously showed that the quantum Zeno effect breaks down for timescales greater than the brain decoherence time. To generalize the Monte Carlo simulation results for any n-level quantum system, we further analyzed the change of brain entropy due to the mind probing actions and proved a theorem according to which local projections cannot decrease the von Neumann entropy of the unconditional brain density matrix. The latter theorem establishes that Stapp's model is physically implausible but leaves a door open for future development of quantum mind theories provided the brain has a decoherence-free subspace.

  18. Monte Carlo simulation for simultaneous particle coagulation and deposition

    Institute of Scientific and Technical Information of China (English)

    ZHAO; Haibo; ZHENG; Chuguang

    2006-01-01

    The process of dynamic evolution in dispersed systems due to simultaneous particle coagulation and deposition is described mathematically by general dynamic equation (GDE). Monte Carlo (MC) method is an important approach of numerical solutions of GDE. However, constant-volume MC method exhibits the contradictory of low computation cost and high computation precision owing to the fluctuation of the number of simulation particles; constant-number MC method can hardly be applied to engineering application and general scientific quantitative analysis due to the continual contraction or expansion of computation domain. In addition, the two MC methods depend closely on the "subsystem" hypothesis, which constraints their expansibility and the scope of application. A new multi-Monte Carlo (MMC) method is promoted to take account of GDE for simultaneous particle coagulation and deposition. MMC method introduces the concept of "weighted fictitious particle" and is based on the "time-driven" technique. Furthermore MMC method maintains synchronously the computational domain and the total number of fictitious particles, which results in the latent expansibility of simulation for boundary condition, the space evolution of particle size distribution and even particle dynamics. The simulation results of MMC method for two special cases in which analytical solutions exist agree with analytical solutions well, which proves that MMC method has high and stable computational precision and low computation cost because of the constant and limited number of fictitious particles. Lastly the source of numerical error and the relative error of MMC method are analyzed, respectively.

  19. Proceedings of the first symposium on Monte Carlo simulation

    International Nuclear Information System (INIS)

    The first symposium on Monte Carlo simulation was held at Mitsubishi Research Institute, Otemachi, Tokyo, on 10th and 11st of September, 1998. This symposium was organized by Nuclear Code Research Committee at Japan Atomic Energy Research Institute. In the sessions, were presented orally 21 papers on code development, parallel calculation, reactor physics, burn-up, criticality, shielding safety, dose evaluation, nuclear fusion reactor, thermonuclear fusion plasma, nuclear transmutation, electromagnetic cascade, fuel cycle facility. Those presented papers are compiled in this proceedings. The 21 of the presented papers are indexed individually. (J.P.N.)

  20. Monte Carlo simulation on backward steps of single kinesin molecule

    Institute of Scientific and Technical Information of China (English)

    Wang Hong; Zhang Yong; Dou Shuo-Xing; Wang Peng-Ye

    2008-01-01

    Kinesin is a stepping molecular motor travelling along the microtubule. It moves primarily in the plus end direction of the microtubule and occasionally in the minus-end, backward, direction. Recently, the backward steps of kinesin under different loads and temperatures start to attract interests, and the relations among them are revealed. This paper aims to theoretically understand these relations observed in experiments. After introducing a backward pathway into the previous model of the ATPase cycle of kinesin movement, the dependence of the backward movement on the load and the temperature is explored through Monte Carlo simulation. Our results agree well with previous experiments.

  1. A fitter use of Monte Carlo simulations in regression models

    Directory of Open Access Journals (Sweden)

    Alessandro Ferrarini

    2011-12-01

    Full Text Available In this article, I focus on the use of Monte Carlo simulations (MCS within regression models, being this application very frequent in biology, ecology and economy as well. I'm interested in enhancing a typical fault in this application of MCS, i.e. the inner correlations among independent variables are not used when generating random numbers that fit their distributions. By means of an illustrative example, I provide proof that the misuse of MCS in regression models produces misleading results. Furthermore, I also provide a solution for this topic.

  2. Proceedings of the first symposium on Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-01-01

    The first symposium on Monte Carlo simulation was held at Mitsubishi Research Institute, Otemachi, Tokyo, on 10th and 11st of September, 1998. This symposium was organized by Nuclear Code Research Committee at Japan Atomic Energy Research Institute. In the sessions, were presented orally 21 papers on code development, parallel calculation, reactor physics, burn-up, criticality, shielding safety, dose evaluation, nuclear fusion reactor, thermonuclear fusion plasma, nuclear transmutation, electromagnetic cascade, fuel cycle facility. Those presented papers are compiled in this proceedings. The 21 of the presented papers are indexed individually. (J.P.N.)

  3. Monte-Carlo Simulation on Neutron Instruments at CARR

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The design of high resolution neutron powder diffractometer(HRPD) and two cold neutron guides(CNGs) to be built at China advanced research reactor(CARR) are studied by Monte-Carlo simulation technique.The HRPD instrument is desiged to have a minimum resolution of 0.2% and neutron fluence rate of greater than 106 cm-2 ·s-1 at sample position. The resolution curves, neutron fluence rate and effective neutron beam size at sample position are given. Differences in resolutions and intensity between the

  4. Implict Monte Carlo Radiation Transport Simulations of Four Test Problems

    Energy Technology Data Exchange (ETDEWEB)

    Gentile, N

    2007-08-01

    Radiation transport codes, like almost all codes, are difficult to develop and debug. It is helpful to have small, easy to run test problems with known answers to use in development and debugging. It is also prudent to re-run test problems periodically during development to ensure that previous code capabilities have not been lost. We describe four radiation transport test problems with analytic or approximate analytic answers. These test problems are suitable for use in debugging and testing radiation transport codes. We also give results of simulations of these test problems performed with an Implicit Monte Carlo photonics code.

  5. New electron multiple scattering distributions for Monte Carlo transport simulation

    Energy Technology Data Exchange (ETDEWEB)

    Chibani, Omar (Haut Commissariat a la Recherche (C.R.S.), 2 Boulevard Franz Fanon, Alger B.P. 1017, Alger-Gare (Algeria)); Patau, Jean Paul (Laboratoire de Biophysique et Biomathematiques, Faculte des Sciences Pharmaceutiques, Universite Paul Sabatier, 35 Chemin des Maraichers, 31062 Toulouse cedex (France))

    1994-10-01

    New forms of electron (positron) multiple scattering distributions are proposed. The first is intended for use in the conditions of validity of the Moliere theory. The second distribution takes place when the electron path is so short that only few elastic collisions occur. These distributions are adjustable formulas. The introduction of some parameters allows impositions of the correct value of the first moment. Only positive and analytic functions were used in constructing the present expressions. This makes sampling procedures easier. Systematic tests are presented and some Monte Carlo simulations, as benchmarks, are carried out. ((orig.))

  6. Monte Carlo simulation experiments on box-type radon dosimeter

    Energy Technology Data Exchange (ETDEWEB)

    Jamil, Khalid, E-mail: kjamil@comsats.edu.pk; Kamran, Muhammad; Illahi, Ahsan; Manzoor, Shahid

    2014-11-11

    Epidemiological studies show that inhalation of radon gas ({sup 222}Rn) may be carcinogenic especially to mine workers, people living in closed indoor energy conserved environments and underground dwellers. It is, therefore, of paramount importance to measure the {sup 222}Rn concentrations (Bq/m{sup 3}) in indoors environments. For this purpose, box-type passive radon dosimeters employing ion track detector like CR-39 are widely used. Fraction of the number of radon alphas emitted in the volume of the box type dosimeter resulting in latent track formation on CR-39 is the latent track registration efficiency. Latent track registration efficiency is ultimately required to evaluate the radon concentration which consequently determines the effective dose and the radiological hazards. In this research, Monte Carlo simulation experiments were carried out to study the alpha latent track registration efficiency for box type radon dosimeter as a function of dosimeter’s dimensions and range of alpha particles in air. Two different self developed Monte Carlo simulation techniques were employed namely: (a) Surface ratio (SURA) method and (b) Ray hitting (RAHI) method. Monte Carlo simulation experiments revealed that there are two types of efficiencies i.e. intrinsic efficiency (η{sub int}) and alpha hit efficiency (η{sub hit}). The η{sub int} depends upon only on the dimensions of the dosimeter and η{sub hit} depends both upon dimensions of the dosimeter and range of the alpha particles. The total latent track registration efficiency is the product of both intrinsic and hit efficiencies. It has been concluded that if diagonal length of box type dosimeter is kept smaller than the range of alpha particle then hit efficiency is achieved as 100%. Nevertheless the intrinsic efficiency keeps playing its role. The Monte Carlo simulation experimental results have been found helpful to understand the intricate track registration mechanisms in the box type dosimeter. This paper

  7. Monte Carlo simulation experiments on box-type radon dosimeter

    Science.gov (United States)

    Jamil, Khalid; Kamran, Muhammad; Illahi, Ahsan; Manzoor, Shahid

    2014-11-01

    Epidemiological studies show that inhalation of radon gas (222Rn) may be carcinogenic especially to mine workers, people living in closed indoor energy conserved environments and underground dwellers. It is, therefore, of paramount importance to measure the 222Rn concentrations (Bq/m3) in indoors environments. For this purpose, box-type passive radon dosimeters employing ion track detector like CR-39 are widely used. Fraction of the number of radon alphas emitted in the volume of the box type dosimeter resulting in latent track formation on CR-39 is the latent track registration efficiency. Latent track registration efficiency is ultimately required to evaluate the radon concentration which consequently determines the effective dose and the radiological hazards. In this research, Monte Carlo simulation experiments were carried out to study the alpha latent track registration efficiency for box type radon dosimeter as a function of dosimeter's dimensions and range of alpha particles in air. Two different self developed Monte Carlo simulation techniques were employed namely: (a) Surface ratio (SURA) method and (b) Ray hitting (RAHI) method. Monte Carlo simulation experiments revealed that there are two types of efficiencies i.e. intrinsic efficiency (ηint) and alpha hit efficiency (ηhit). The ηint depends upon only on the dimensions of the dosimeter and ηhit depends both upon dimensions of the dosimeter and range of the alpha particles. The total latent track registration efficiency is the product of both intrinsic and hit efficiencies. It has been concluded that if diagonal length of box type dosimeter is kept smaller than the range of alpha particle then hit efficiency is achieved as 100%. Nevertheless the intrinsic efficiency keeps playing its role. The Monte Carlo simulation experimental results have been found helpful to understand the intricate track registration mechanisms in the box type dosimeter. This paper explains that how radon concentration from the

  8. Monte Carlo simulations of charge transport in heterogeneous organic semiconductors

    Science.gov (United States)

    Aung, Pyie Phyo; Khanal, Kiran; Luettmer-Strathmann, Jutta

    2015-03-01

    The efficiency of organic solar cells depends on the morphology and electronic properties of the active layer. Research teams have been experimenting with different conducting materials to achieve more efficient solar panels. In this work, we perform Monte Carlo simulations to study charge transport in heterogeneous materials. We have developed a coarse-grained lattice model of polymeric photovoltaics and use it to generate active layers with ordered and disordered regions. We determine carrier mobilities for a range of conditions to investigate the effect of the morphology on charge transport.

  9. Polarization Properties of Ferroelectric Superlattice Studied by Monte Carlo Simulation

    Institute of Scientific and Technical Information of China (English)

    Guiwu LU; Hairui XIA; Pijun LIU

    2001-01-01

    The polarization property of a ferroelectric superlattice formed from two alternating materials was studied using Monte Carlo computer simulation. Our study has been developed in a framework of the transverse Ising model with nearest-neighbor interactions. Both the effect of the transverse field and interface coupling strength have been taken into consideration. In view of our results which is in good agreement with previous theoretical results, it is concluded that the Curie temperature of the superlattice increases with the increase of the interface coupling strength JAB.The remanent polarization and saturation coercive force of the superlattice are also presented.

  10. Voxel classification methodology for rapid Monte Carlo simulation of light propagation in complex media

    Institute of Scientific and Technical Information of China (English)

    Nunu Ren; Heng Zhao; Shouping Zhu; Xiaochao Qu; Hongliang Liu; Zhenhua Hu; Jimin Liang; Jie Tian

    2011-01-01

    @@ Monte Carlo (MC) method is a statistical method for simulating photon propagation in media in the optical molecular imaging field.However, obtaining an accurate result using the method is quite time-consuming,especially because the boundary of the media is complex.A voxel classification method is proposed to reduce the computation cost.All the voxels generated by dividing the media are classified into three types (outside, boundary, and inside) according to the position of the voxel.The classified information is used to determine the relative position of the photon and the intersection between photon path and media boundary in the MC method.The influencing factor8 and effectiveness of the proposed method are analyzed and validated by simulation experiments.%Monte Carlo (MC) method is a statistical method for simulating photon propagation in media in the optical molecular imaging field. However, obtaining an accurate result using the method is quite time-consuming,especially because the boundary of the media is complex. A voxel classification method is proposed to reduce the computation cost. All the voxels generated by dividing the media are classified into three types (outside, boundary, and inside) according to the position of the voxel. The classified information is used to determine the relative position of the photon and the intersection between photon path and media boundary in the MC method. The influencing factors and effectiveness of the proposed method are analyzed and validated by simulation experiments.

  11. Momentum transfer Monte Carlo model for the simulation of laser speckle contrast imaging (Conference Presentation)

    Science.gov (United States)

    Regan, Caitlin; Hayakawa, Carole K.; Choi, Bernard

    2016-03-01

    Laser speckle imaging (LSI) enables measurement of relative blood flow in microvasculature and perfusion in tissues. To determine the impact of tissue optical properties and perfusion dynamics on speckle contrast, we developed a computational simulation of laser speckle contrast imaging. We used a discrete absorption-weighted Monte Carlo simulation to model the transport of light in tissue. We simulated optical excitation of a uniform flat light source and tracked the momentum transfer of photons as they propagated through a simulated tissue geometry. With knowledge of the probability distribution of momentum transfer occurring in various layers of the tissue, we calculated the expected laser speckle contrast arising with coherent excitation using both reflectance and transmission geometries. We simulated light transport in a single homogeneous tissue while independently varying either absorption (.001-100mm^-1), reduced scattering (.1-10mm^-1), or anisotropy (0.05-0.99) over a range of values relevant to blood and commonly imaged tissues. We observed that contrast decreased by 49% with an increase in optical scattering, and observed a 130% increase with absorption (exposure time = 1ms). We also explored how speckle contrast was affected by the depth (0-1mm) and flow speed (0-10mm/s) of a dynamic vascular inclusion. This model of speckle contrast is important to increase our understanding of how parameters such as perfusion dynamics, vessel depth, and tissue optical properties affect laser speckle imaging.

  12. Lattice Monte Carlo simulation of Galilei variant anomalous diffusion

    International Nuclear Information System (INIS)

    The observation of an increasing number of anomalous diffusion phenomena motivates the study to reveal the actual reason for such stochastic processes. When it is difficult to get analytical solutions or necessary to track the trajectory of particles, lattice Monte Carlo (LMC) simulation has been shown to be particularly useful. To develop such an LMC simulation algorithm for the Galilei variant anomalous diffusion, we derive explicit solutions for the conditional and unconditional first passage time (FPT) distributions with double absorbing barriers. According to the theory of random walks on lattices and the FPT distributions, we propose an LMC simulation algorithm and prove that such LMC simulation can reproduce both the mean and the mean square displacement exactly in the long-time limit. However, the error introduced in the second moment of the displacement diverges according to a power law as the simulation time progresses. We give an explicit criterion for choosing a small enough lattice step to limit the error within the specified tolerance. We further validate the LMC simulation algorithm and confirm the theoretical error analysis through numerical simulations. The numerical results agree with our theoretical predictions very well

  13. Lattice Monte Carlo simulation of Galilei variant anomalous diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Gang, E-mail: hndzgg@aliyun.com [School of Information System and Management, National University of Defense Technology, Changsha, 410073 (China); Institute of Computer Science, University of Rostock, Albert Einstein Str. 22, Rostock, 18059 (Germany); Bittig, Arne, E-mail: arne.bittig@uni-rostock.de [Institute of Computer Science, University of Rostock, Albert Einstein Str. 22, Rostock, 18059 (Germany); Uhrmacher, Adelinde, E-mail: lin@informatik.uni-rostock.de [Institute of Computer Science, University of Rostock, Albert Einstein Str. 22, Rostock, 18059 (Germany)

    2015-05-01

    The observation of an increasing number of anomalous diffusion phenomena motivates the study to reveal the actual reason for such stochastic processes. When it is difficult to get analytical solutions or necessary to track the trajectory of particles, lattice Monte Carlo (LMC) simulation has been shown to be particularly useful. To develop such an LMC simulation algorithm for the Galilei variant anomalous diffusion, we derive explicit solutions for the conditional and unconditional first passage time (FPT) distributions with double absorbing barriers. According to the theory of random walks on lattices and the FPT distributions, we propose an LMC simulation algorithm and prove that such LMC simulation can reproduce both the mean and the mean square displacement exactly in the long-time limit. However, the error introduced in the second moment of the displacement diverges according to a power law as the simulation time progresses. We give an explicit criterion for choosing a small enough lattice step to limit the error within the specified tolerance. We further validate the LMC simulation algorithm and confirm the theoretical error analysis through numerical simulations. The numerical results agree with our theoretical predictions very well.

  14. Simulating Photon Scattering Effects in Structurally Detailed Ventricular Models Using a Monte Carlo Approach

    Directory of Open Access Journals (Sweden)

    Martin J Bishop

    2014-09-01

    Full Text Available Light scattering during optical imaging of electrical activation within the heart is known to significantlydistort the optically-recorded action potential (AP upstroke, as well as affecting the magnitude of the measured response of ventricular tissue to strong electric shocks. Modelling approaches based on the photondiffusion equation have recently been instrumental in quantifying and helping to understand the origin of the resulting distortion. However, they are unable to faithfully represent regions of non-scattering media, such assmall cavities within the myocardium which are filled with perfusate during experiments. Stochastic Monte Carlo (MC approaches allow simulation and tracking of individual photon `packets' as they propagate through tissuewith differing scattering properties. Here, we present a novel application of the MC method of photon scattering simulation, applied for the first time to the simulation of cardiac optical mapping signals withinunstructured, tetrahedral, finite element computational ventricular models. The method faithfully allows simulation of optical signals over highly-detailed, anatomically-complex MR-based models, includingrepresentations of fine-scale anatomy and intramural cavities. We show that optical action potential upstroke is prolonged close to large subepicardial vessels than further away from vessels, at times having a distinct `humped' morphology.Furthermore, we uncover a novel mechanism by which photon scattering effects around vessels cavities interact with `virtual-electrode' regions of strong de-/hyper-polarised tissue surrounding cavitiesduring shocks, significantly reducing the apparent optically-measured epicardial polarisation. We therefore demonstrate the importance of this novel optical mapping simulation approach along with highly anatomically-detailed models to fully investigate electrophysiological phenomena driven by fine-scale structural heterogeneity.

  15. SIM-RIBRAS: A Monte-Carlo simulation package for RIBRAS system

    Energy Technology Data Exchange (ETDEWEB)

    Leistenschneider, E.; Lepine-Szily, A.; Lichtenthaeler, R. [Departamento de Fisica Nuclear, Instituto de Fisica, Universidade de Sao Paulo (Brazil)

    2013-05-06

    SIM-RIBRAS is a Root-based Monte-Carlo simulation tool designed to help RIBRAS users on experience planning and experimental setup enhancing and caracterization. It is divided into two main programs: CineRIBRAS, aiming beam kinematics, and SolFocus, aiming beam optics. SIM-RIBRAS replaces other methods and programs used in the past, providing more complete and accurate results and requiring much less manual labour. Moreover, the user can easily make modifications in the codes, adequating it for specific requirements of an experiment.

  16. Monte Carlo simulation of zinc protoporphyrin fluorescence in the retina

    Science.gov (United States)

    Chen, Xiaoyan; Lane, Stephen

    2010-02-01

    We have used Monte Carlo simulation of autofluorescence in the retina to determine that noninvasive detection of nutritional iron deficiency is possible. Nutritional iron deficiency (which leads to iron deficiency anemia) affects more than 2 billion people worldwide, and there is an urgent need for a simple, noninvasive diagnostic test. Zinc protoporphyrin (ZPP) is a fluorescent compound that accumulates in red blood cells and is used as a biomarker for nutritional iron deficiency. We developed a computational model of the eye, using parameters that were identified either by literature search, or by direct experimental measurement to test the possibility of detecting ZPP non-invasively in retina. By incorporating fluorescence into Steven Jacques' original code for multi-layered tissue, we performed Monte Carlo simulation of fluorescence in the retina and determined that if the beam is not focused on a blood vessel in a neural retina layer or if part of light is hitting the vessel, ZPP fluorescence will be 10-200 times higher than background lipofuscin fluorescence coming from the retinal pigment epithelium (RPE) layer directly below. In addition we found that if the light can be focused entirely onto a blood vessel in the neural retina layer, the fluorescence signal comes only from ZPP. The fluorescence from layers below in this second situation does not contribute to the signal. Therefore, the possibility that a device could potentially be built and detect ZPP fluorescence in retina looks very promising.

  17. A Monte Carlo simulation of ion transport at finite temperatures

    International Nuclear Information System (INIS)

    We have developed a Monte Carlo simulation for ion transport in hot background gases, which is an alternative way of solving the corresponding Boltzmann equation that determines the distribution function of ions. We consider the limit of low ion densities when the distribution function of the background gas remains unchanged due to collision with ions. Special attention has been paid to properly treating the thermal motion of the host gas particles and their influence on ions, which is very important at low electric fields, when the mean ion energy is comparable to the thermal energy of the host gas. We found the conditional probability distribution of gas velocities that correspond to an ion of specific velocity which collides with a gas particle. Also, we have derived exact analytical formulae for piecewise calculation of the collision frequency integrals. We address the cases when the background gas is monocomponent and when it is a mixture of different gases. The techniques described here are required for Monte Carlo simulations of ion transport and for hybrid models of non-equilibrium plasmas. The range of energies where it is necessary to apply the technique has been defined. The results we obtained are in excellent agreement with the existing ones obtained by complementary methods. Having verified our algorithm, we were able to produce calculations for Ar+ ions in Ar and propose them as a new benchmark for thermal effects. The developed method is widely applicable for solving the Boltzmann equation that appears in many different contexts in physics. (paper)

  18. Monte Carlo simulations of nanoscale focused neon ion beam sputtering.

    Science.gov (United States)

    Timilsina, Rajendra; Rack, Philip D

    2013-12-13

    A Monte Carlo simulation is developed to model the physical sputtering of aluminum and tungsten emulating nanoscale focused helium and neon ion beam etching from the gas field ion microscope. Neon beams with different beam energies (0.5-30 keV) and a constant beam diameter (Gaussian with full-width-at-half-maximum of 1 nm) were simulated to elucidate the nanostructure evolution during the physical sputtering of nanoscale high aspect ratio features. The aspect ratio and sputter yield vary with the ion species and beam energy for a constant beam diameter and are related to the distribution of the nuclear energy loss. Neon ions have a larger sputter yield than the helium ions due to their larger mass and consequently larger nuclear energy loss relative to helium. Quantitative information such as the sputtering yields, the energy-dependent aspect ratios and resolution-limiting effects are discussed.

  19. Methods for variance reduction in Monte Carlo simulations

    Science.gov (United States)

    Bixler, Joel N.; Hokr, Brett H.; Winblad, Aidan; Elpers, Gabriel; Zollars, Byron; Thomas, Robert J.

    2016-03-01

    Monte Carlo simulations are widely considered to be the gold standard for studying the propagation of light in turbid media. However, due to the probabilistic nature of these simulations, large numbers of photons are often required in order to generate relevant results. Here, we present methods for reduction in the variance of dose distribution in a computational volume. Dose distribution is computed via tracing of a large number of rays, and tracking the absorption and scattering of the rays within discrete voxels that comprise the volume. Variance reduction is shown here using quasi-random sampling, interaction forcing for weakly scattering media, and dose smoothing via bi-lateral filtering. These methods, along with the corresponding performance enhancements are detailed here.

  20. Treatment planning in radiosurgery: parallel Monte Carlo simulation software

    Energy Technology Data Exchange (ETDEWEB)

    Scielzo, G. [Galliera Hospitals, Genova (Italy). Dept. of Hospital Physics; Grillo Ruggieri, F. [Galliera Hospitals, Genova (Italy) Dept. for Radiation Therapy; Modesti, M.; Felici, R. [Electronic Data System, Rome (Italy); Surridge, M. [University of South Hampton (United Kingdom). Parallel Apllication Centre

    1995-12-01

    The main objective of this research was to evaluate the possibility of direct Monte Carlo simulation for accurate dosimetry with short computation time. We made us of: graphics workstation, linear accelerator, water, PMMA and anthropomorphic phantoms, for validation purposes; ionometric, film and thermo-luminescent techniques, for dosimetry; treatment planning system for comparison. Benchmarking results suggest that short computing times can be obtained with use of the parallel version of EGS4 that was developed. Parallelism was obtained assigning simulation incident photons to separate processors, and the development of a parallel random number generator was necessary. Validation consisted in: phantom irradiation, comparison of predicted and measured values good agreement in PDD and dose profiles. Experiments on anthropomorphic phantoms (with inhomogeneities) were carried out, and these values are being compared with results obtained with the conventional treatment planning system.

  1. Monte Carlo simulation of electrical corona discharge in air

    Energy Technology Data Exchange (ETDEWEB)

    Settaouti, A.; Settaouti, L. [Electrotechnic Department, University of Sciences and Technology, P.O. Box 1505, El-M' naouar, Oran (Algeria)

    2011-01-15

    Electrical discharges play a key role in technologies; there are many industrial applications where the corona discharge is used. Air as insulator is probably the best compromise solution for many applications. All of this reflects on the great importance of the evaluation of the corona performance characteristics. Numerical simulation of the corona discharge helps to better understand the involved phenomena and optimize the corona devices. This paper is aimed at calculating the corona discharge in negative point-plane air gaps. To describe the non-equilibrium behavior of the electronic avalanches and to simulate the development of corona discharge the method of Monte Carlo has been used. This model provides the spatial-temporal local field and particles charged densities variations as well as the ionization front velocity. (author)

  2. Quantitative application of Monte Carlo simulation in Fire-PSA

    Energy Technology Data Exchange (ETDEWEB)

    Mangs, J.; Hostikka, S.; Korhonen, T. [Valtion Teknillinen Tutkimuskeskus, Espoo (Finland); Keski-Rahkonen, O.

    2007-05-15

    In a power plant a fire cell forms the basic subunit. Since the fire is initially located there, the full-scale time dependent fire simulation and estimation of target response must be performed within the fire cell. Conditional, time dependent damage probabilities in a fire cell can now be calculated for arbitrary targets (component or a subsystem) combining probabilistic (Monte Carlo) and deterministic simulation. For the latter a spectrum from simple correlations up to latest computational fluid dynamics models is available. Selection of the code is made according to the requirements form the target cell. Although calculations are numerically heavy, it is now economically possible and feasible to carry out quantitative fire-PSA for a complete plant iteratively with the main PSA. From real applications examples are shown on assessment of fire spread possibility in a relay room, and potential of fire spread on cables in a tunnel. (orig.)

  3. CORPORATE VALUATION USING TWO-DIMENSIONAL MONTE CARLO SIMULATION

    Directory of Open Access Journals (Sweden)

    Toth Reka

    2010-12-01

    Full Text Available In this paper, we have presented a corporate valuation model. The model combine several valuation methods in order to get more accurate results. To determine the corporate asset value we have used the Gordon-like two-stage asset valuation model based on the calculation of the free cash flow to the firm. We have used the free cash flow to the firm to determine the corporate market value, which was calculated with use of the Black-Scholes option pricing model in frame of the two-dimensional Monte Carlo simulation method. The combined model and the use of the two-dimensional simulation model provides a better opportunity for the corporate value estimation.

  4. Monte Carlo simulation of gamma ray tomography for image reconstruction

    International Nuclear Information System (INIS)

    The Monte Carlo simulations of known density and shape object was validate with Gamma Ray Tomography in static experiments. An aluminum half-moon piece placed inside a steel pipe was the MC simulation test object that was also measured by means of gamma ray transmission. Wall effect of the steel pipe due to irradiation geometry in a single pair source-detector tomography was evaluated by comparison with theoretical data. MCNPX code requires a defined geometry to each photon trajectory which practically prevents this usage for tomography reconstruction simulation. The solution was found by writing a program in Delphi language to create input files automation code. Simulations of tomography data by automated MNCPX code were carried out and validated by experimental data. Working in this sequence the produced data needed a databank to be stored. Experimental setup used a Cesium-137 isotopic radioactive source (7.4 × 109 Bq), and NaI(Tl) scintillation detector of (51 × 51) × 10−3 m crystal size coupled to a multichannel analyzer. A stainless steel tubes of 0,154 m internal diameter, 0.014 m thickness wall. The results show that the MCNPX simulation code adapted to automated input file is useful for generating a matrix data M(θ,t), of a computerized gamma ray tomography for any known density and regular shape object. Experimental validation used RMSE from gamma ray paths and from attenuation coefficient data. (author)

  5. Monte Carlo simulation of x-ray spectra in mammography

    Energy Technology Data Exchange (ETDEWEB)

    Ng, K.P. [Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China). E-mail: benngkp at netvigator.com; Kwok, C.S.; Ng, K.P.; Tang, F.H. [Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China)

    2000-05-01

    A model for generating x-ray spectra in mammography is presented. This model used the ITS version 3 Monte Carlo code for simulating the radiation transport. Various target/filter combinations such as tungsten/aluminium, molybdenum/molybdenum, molybdenum/rhodium and rhodium/rhodium were used in the simulation. Both bremsstrahlung and characteristic x-ray production were included in the model. The simulated x-ray emission spectra were compared with two sets of spectra, those of Boone et al (1997 Med. Phys. 24 1863-74) and IPEM report 78. The {chi}{sup 2} test was used for the overall goodness of fit of the spectral data. There is good agreement between the simulated x-ray spectra and the comparison spectra as the test yielded a probability value of nearly 1. When the transmitted x-ray spectra for specific target/filter combinations were generated and compared with a measured molybdenum/rhodium spectrum and spectra generated in IPEM report 78, close agreement is also observed. This was demonstrated by the probability value for the {chi}{sup 2} test being almost 1 for all the cases. However, minor differences between the simulated spectra and the 'standard' ones are observed. (author)

  6. Monte Carlo simulation of gamma ray tomography for image reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Guedes, Karlos A.N.; Moura, Alex; Dantas, Carlos; Melo, Silvio; Lima, Emerson, E-mail: karlosguedes@hotmail.com [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil); Meric, Ilker [University of Bergen (Norway)

    2015-07-01

    The Monte Carlo simulations of known density and shape object was validate with Gamma Ray Tomography in static experiments. An aluminum half-moon piece placed inside a steel pipe was the MC simulation test object that was also measured by means of gamma ray transmission. Wall effect of the steel pipe due to irradiation geometry in a single pair source-detector tomography was evaluated by comparison with theoretical data. MCNPX code requires a defined geometry to each photon trajectory which practically prevents this usage for tomography reconstruction simulation. The solution was found by writing a program in Delphi language to create input files automation code. Simulations of tomography data by automated MNCPX code were carried out and validated by experimental data. Working in this sequence the produced data needed a databank to be stored. Experimental setup used a Cesium-137 isotopic radioactive source (7.4 × 109 Bq), and NaI(Tl) scintillation detector of (51 × 51) × 10−3 m crystal size coupled to a multichannel analyzer. A stainless steel tubes of 0,154 m internal diameter, 0.014 m thickness wall. The results show that the MCNPX simulation code adapted to automated input file is useful for generating a matrix data M(θ,t), of a computerized gamma ray tomography for any known density and regular shape object. Experimental validation used RMSE from gamma ray paths and from attenuation coefficient data. (author)

  7. 组织光学特性的时间分辨蒙特卡罗仿真研究%Time-Resolved Monte Carlo Simulation for Optical Properties of Tissues

    Institute of Scientific and Technical Information of China (English)

    叶静斋; 陈辉

    2011-01-01

    Reflected, transmitted and scattered light from tissues contains information about tissue properties. Hence, it has potential to be used for noninvasive characterization of biomedical tissues, which can lead to the development of techniques for the early detection of cancer. Time-resolved Monte Carlo model can predict time dependent light distribution in tissues and has advantages of high precision and flexibility and can be used in many tissues. But there are some problems lie in Henyey-Greenstein (HG) phase function used in traditional Monte Carlo model. Thus, Mie phase function based on Mie theory is introduced. Comparison of time-resolved Monte Carlo simulations using several phase functions and experimental data shows that Mie phase function can predict diffuse reflectance of human tissue more real than HG phase function. Nevertheless, because Mie phase function is relative to scattering particle sizes of tissues and the sizes are different, the choice of scattering particle model is difficult when aiming at different particles distribution models.%组织的反射、透射和散射光检测都包含着组织的内部信息,可发展成为无损检测以及癌症早期诊断的重要手段,有着极为重要的意义.时间分辨蒙特卡罗模型能够预测组织的时间分布光学特性,具有精度高、灵活性强的优点,能适用于多种组织.但传统的蒙特卡罗模型中采用的Henyey-Greenstein(HG)相函数存在一些问题.介绍了基于米氏理论的米氏相函数.利用几种相函数进行时间分辨蒙特卡罗仿真并与实验结果进行对比.结果表明,米氏相函数比HG相函数更能真实地体现人体组织的漫反射特性,但由于米氏相函数与组织的散射颗粒尺寸相关,而组织的散射颗粒大小不一,针对不同的组织有不同的颗粒分布模型,因此应用于具体模型时散射颗粒模型的选择会有一些困难.

  8. The impact of Monte Carlo simulation: a scientometric analysis of scholarly literature

    CERN Document Server

    Pia, Maria Grazia; Bell, Zane W; Dressendorfer, Paul V

    2010-01-01

    A scientometric analysis of Monte Carlo simulation and Monte Carlo codes has been performed over a set of representative scholarly journals related to radiation physics. The results of this study are reported and discussed. They document and quantitatively appraise the role of Monte Carlo methods and codes in scientific research and engineering applications.

  9. Monte Carlo simulation of the TRIGA mark 2 criticality experiment

    International Nuclear Information System (INIS)

    The criticality analysis of the TRIGA-2 bench-mark experiment at the Musashi Institute of Technology Research Reactor (MuITR, 100 kW) was performed by the three-dimensional continuous-energy Monte Carlo code (MCNP4A). To minimize errors due to an inexact geometry model, all fresh fuel and control rods as well as vicinity of the core were precisely modeled. Core multiplication factors (Keff) in the initial core critical experiment and in the excess reactivity adjustment for the several fuel-loading patterns as well as the fuel element reactivity worth distributions were used in the validation process of the physical model and neutron cross section data from the ENDF/B-V evaluation. The calculated Keff overestimated the experimental data by 1.0% for both the initial core and the several fuel-loading arrangements (fuel or graphite element was added only to the outer-ring), but the discrepancy increased to 1.8% for the some fuel-loading patterns (graphite element was positioned in the inner-ring). The comparison result of the fuel element worth distribution showed above tendency. Al in all, the agreement between the MCNP predictions and the experimentally determined values is good, which indicates that the Monte Carlo model is enough to simulate criticality of the TRIGA-2 reactor. (author)

  10. IB: A Monte Carlo simulation tool for neutron scattering instrument design under PVM and MPI

    International Nuclear Information System (INIS)

    Design of modern neutron scattering instruments relies heavily on Monte Carlo simulation tools for optimization. IB is one such tool written in C++ and implemented under Parallel Virtual Machine and the Message Passing Interface. The program was initially written for the design and optimization of the EQ-SANS instrument at the Spallation Neutron Source. One of its features is the ability to group simple instrument components into more complex ones at the user input level, e.g. grouping neutron mirrors into neutron guides and curved benders. The simulation engine manages the grouped components such that neutrons entering a group are properly operated upon by all components, multiple times if needed, before exiting the group. Thus, only a few basic optical modules are needed at the programming level. For simulations that require higher computer speeds, the program can be compiled and run in parallel modes using either the PVM or the MPI architectures.

  11. Monte Carlo simulation of the spear reflectometer at LANSCE

    International Nuclear Information System (INIS)

    The Monte Carlo instrument simulation code, MCLIB, contains elements to represent several components found in neutron spectrometers including slits, choppers, detectors, sources and various samples. Using these elements to represent the components of a neutron scattering instrument, one can simulate, for example, an inelastic spectrometer, a small angle scattering machine, or a reflectometer. In order to benchmark the code, we chose to compare simulated data from the MCLIB code with an actual experiment performed on the SPEAR reflectometer at LANSCE. This was done by first fitting an actual SPEAR data set to obtain the model scattering-length-density profile, Β(z), for the sample and the substrate. Then these parameters were used as input values for the sample scattering function. A simplified model of SPEAR was chosen which contained all of the essential components of the instrument. A code containing the MCLIB subroutines was then written to simulate this simplified instrument. The resulting data was then fit and compared to the actual data set in terms of the statistics, resolution and accuracy

  12. Kinetic Monte Carlo simulations of void lattice formation during irradiation

    Science.gov (United States)

    Heinisch, H. L.; Singh, B. N.

    2003-11-01

    Over the last decade, molecular dynamics simulations of displacement cascades have revealed that glissile clusters of self-interstitial crowdions are formed directly in cascades and that they migrate one-dimensionally along close-packed directions with extremely low activation energies. Occasionally, under various conditions, a crowdion cluster can change its Burgers vector and glide along a different close-packed direction. The recently developed production bias model (PBM) of microstructure evolution under irradiation has been structured specifically to take into account the unique properties of the vacancy and interstitial clusters produced in the cascades. Atomic-scale kinetic Monte Carlo (KMC) simulations have played a useful role in understanding the defect reaction kinetics of one-dimensionally migrating crowdion clusters as a function of the frequency of direction changes. This has made it possible to incorporate the migration properties of crowdion clusters and changes in reaction kinetics into the PBM. In the present paper we utilize similar KMC simulations to investigate the significant role that crowdion clusters can play in the formation and stability of void lattices. The creation of stable void lattices, starting from a random distribution of voids, is simulated by a KMC model in which vacancies migrate three-dimensionally and self-interstitial atom (SIA) clusters migrate one-dimensionally, interrupted by directional changes. The necessity of both one-dimensional migration and Burgers vectors changes of SIA clusters for the production of stable void lattices is demonstrated, and the effects of the frequency of Burgers vector changes are described.

  13. Learning About Ares I from Monte Carlo Simulation

    Science.gov (United States)

    Hanson, John M.; Hall, Charlie E.

    2008-01-01

    This paper addresses Monte Carlo simulation analyses that are being conducted to understand the behavior of the Ares I launch vehicle, and to assist with its design. After describing the simulation and modeling of Ares I, the paper addresses the process used to determine what simulations are necessary, and the parameters that are varied in order to understand how the Ares I vehicle will behave in flight. Outputs of these simulations furnish a significant group of design customers with data needed for the development of Ares I and of the Orion spacecraft that will ride atop Ares I. After listing the customers, examples of many of the outputs are described. Products discussed in this paper include those that support structural loads analysis, aerothermal analysis, flight control design, failure/abort analysis, determination of flight performance reserve, examination of orbit insertion accuracy, determination of the Upper Stage impact footprint, analysis of stage separation, analysis of launch probability, analysis of first stage recovery, thrust vector control and reaction control system design, liftoff drift analysis, communications analysis, umbilical release, acoustics, and design of jettison systems.

  14. A generic algorithm for Monte Carlo simulation of proton transport

    Science.gov (United States)

    Salvat, Francesc

    2013-12-01

    A mixed (class II) algorithm for Monte Carlo simulation of the transport of protons, and other heavy charged particles, in matter is presented. The emphasis is on the electromagnetic interactions (elastic and inelastic collisions) which are simulated using strategies similar to those employed in the electron-photon code PENELOPE. Elastic collisions are described in terms of numerical differential cross sections (DCSs) in the center-of-mass frame, calculated from the eikonal approximation with the Dirac-Hartree-Fock-Slater atomic potential. The polar scattering angle is sampled by employing an adaptive numerical algorithm which allows control of interpolation errors. The energy transferred to the recoiling target atoms (nuclear stopping) is consistently described by transformation to the laboratory frame. Inelastic collisions are simulated from DCSs based on the plane-wave Born approximation (PWBA), making use of the Sternheimer-Liljequist model of the generalized oscillator strength, with parameters adjusted to reproduce (1) the electronic stopping power read from the input file, and (2) the total cross sections for impact ionization of inner subshells. The latter were calculated from the PWBA including screening and Coulomb corrections. This approach provides quite a realistic description of the energy-loss distribution in single collisions, and of the emission of X-rays induced by proton impact. The simulation algorithm can be readily modified to include nuclear reactions, when the corresponding cross sections and emission probabilities are available, and bremsstrahlung emission.

  15. Monte Carlo simulations of medium-scale CMB anisotropy

    CERN Document Server

    Kogut, A J

    1996-01-01

    Recent detections of cosmic microwave background (CMB) anisotropy at half-degree angular scales show considerable scatter in the reported amplitude even at similar angular resolution. We use Monte Carlo techniques to simulate the current set of medium-scale CMB observations, including all relevant aspects of sky coverage and measurement technique. The scatter in the reported amplitudes is well within the range expected for the standard cold dark matter (CDM) cosmological model, and results primarily from the restricted sky coverage of each experiment. Within the context of standard CDM current observations of CMB anisotropy support the detection of a ``Doppler peak'' in the CMB power spectrum consistent with baryon density 0.01 < Omega_b < 0.13 (95% confidence) for Hubble constant H_0 = 50 km/s/Mpc. The uncertainties are approximately evenly divided between instrument noise and cosmic variance arising from the limited sky coverage.

  16. Monte Carlo simulations of air showers in atmospheric electric fields

    CERN Document Server

    Buitink, S; Falcke, H; Heck, D; Kuijpers, J

    2009-01-01

    The development of cosmic ray air showers can be influenced by atmospheric electric fields. Under fair weather conditions these fields are small, but the strong fields inside thunderstorms can have a significant effect on the electromagnetic component of a shower. Understanding this effect is particularly important for radio detection of air showers, since the radio emission is produced by the shower electrons and positrons. We perform Monte Carlo simulations to calculate the effects of different electric field configurations on the shower development. We find that the electric field becomes important for values of the order of 1 kV/cm. Not only can the energy distribution of electrons and positrons change significantly for such field strengths, it is also possible that runaway electron breakdown occurs at high altitudes, which is an important effect in lightning initiation.

  17. Monte Carlo simulations of ABC stacked kagome lattice films

    Science.gov (United States)

    Yerzhakov, H. V.; Plumer, M. L.; Whitehead, J. P.

    2016-05-01

    Properties of films of geometrically frustrated ABC stacked antiferromagnetic kagome layers are examined using Metropolis Monte Carlo simulations. The impact of having an easy-axis anisotropy on the surface layers and cubic anisotropy in the interior layers is explored. The spin structure at the surface is shown to be different from that of the bulk 3D fcc system, where surface axial anisotropy tends to align spins along the surface [1 1 1] normal axis. This alignment then propagates only weakly to the interior layers through exchange coupling. Results are shown for the specific heat, magnetization and sub-lattice order parameters for both surface and interior spins in three and six layer films as a function of increasing axial surface anisotropy. Relevance to the exchange bias phenomenon in IrMn3 films is discussed.

  18. Monte Carlo simulations of landmine detection using neutron backscattering imaging

    Energy Technology Data Exchange (ETDEWEB)

    Datema, Cor P. E-mail: c.datema@iri.tudelft.nl; Bom, Victor R.; Eijk, Carel W.E. van

    2003-11-01

    Neutron backscattering is a technique that has successfully been applied to the detection of non-metallic landmines. Most of the effort in this field has concentrated on single detectors that are scanned across the soil. Here, two new approaches are presented in which a two-dimensional image of the hydrogen distribution in the soil is made. The first method uses an array of position-sensitive {sup 3}He-tubes that is placed in close proximity of the soil. The second method is based on coded aperture imaging. Here, thermal neutrons from the soil are projected onto a detector which is typically placed one to several meters above the soil. Both methods use a pulsed D/D neutron source. The Monte Carlo simulation package GEANT 4 was used to investigate the performance of both imaging systems.

  19. Monte Carlo simulations for optimization of neutron shielding concrete

    Science.gov (United States)

    Piotrowski, Tomasz; Tefelski, Dariusz; Polański, Aleksander; Skubalski, Janusz

    2012-06-01

    Concrete is one of the main materials used for gamma and neutron shielding. While in case of gamma rays an increase in density is usually efficient enough, protection against neutrons is more complex. The aim of this paper is to show the possibility of using the Monte Carlo codes for evaluation and optimization of concrete mix to reach better neutron shielding. Two codes (MCNPX and SPOT — written by authors) were used to simulate neutron transport through a wall made of different concretes. It is showed that concrete of higher compressive strength attenuates neutrons more effectively. The advantage of heavyweight concrete (with barite aggregate), usually used for gamma shielding, over the ordinary concrete was not so clear. Neutron shielding depends on many factors e.g. neutron energy, barrier thickness and atomic composition. All this makes a proper design of concrete as a very important issue for nuclear power plant safety assurance.

  20. Effect of doping of graphene structure: A Monte Carlo simulations

    Science.gov (United States)

    Masrour, R.; Jabar, A.

    2016-10-01

    In this work, we have studied the effect of magnetic atom doping of graphene structure using Monte Carlo simulation. The reduced critical temperature with the magnetic atom doping x has been deduced from the thermal variation of magnetization and magnetic susceptibility. The variation of magnetization versus the crystal field of grapheme structure for different x and for different reduced temperatures has been established. We also have measured the coercive field (hC) as a function x in grapheme structure, finding that hC increases with increasing x concentration as predicted experimentally. The doping-induced magnetism in graphene. Magnetically atom doping in graphene systems are potential candidates for application in future spintronic devices, magnetometry requires macroscopic quantities of graphene to detect magnetic moments directly.

  1. Monte Carlo Simulation of Diamond Deposition at Low Temperature

    Institute of Scientific and Technical Information of China (English)

    董丽芳; 张玉红

    2001-01-01

    Diamond deposition at low temperatures is investigated and the relationship between substrate temperature for diamond growth and the energy of the carbonaceous species is given. The electron energy distribution and velocity distribution during the electron assisted chemical vapour deposition have been obtained by using Monte Carlo simulation. The main results obtained are as follows. (1) The substrate temperature for diamond growth will be lower than 800 C when the carbonaceous species on the substrate have mobility energy. For example, if the energy of the carbonaceous species is 0. 75 eV, the substrate temperature will be 380℃-600℃. (2) The greatnumber of atomic H on the substrate is of importance to the growth of diamond films.

  2. Monte Carlo and analytic simulations in nanoparticle-enhanced radiation therapy

    Science.gov (United States)

    Paro, Autumn D; Hossain, Mainul; Webster, Thomas J; Su, Ming

    2016-01-01

    Analytical and Monte Carlo simulations have been used to predict dose enhancement factors in nanoparticle-enhanced X-ray radiation therapy. Both simulations predict an increase in dose enhancement in the presence of nanoparticles, but the two methods predict different levels of enhancement over the studied energy, nanoparticle materials, and concentration regime for several reasons. The Monte Carlo simulation calculates energy deposited by electrons and photons, while the analytical one only calculates energy deposited by source photons and photoelectrons; the Monte Carlo simulation accounts for electron–hole recombination, while the analytical one does not; and the Monte Carlo simulation randomly samples photon or electron path and accounts for particle interactions, while the analytical simulation assumes a linear trajectory. This study demonstrates that the Monte Carlo simulation will be a better choice to evaluate dose enhancement with nanoparticles in radiation therapy.

  3. Characterization of parallel-hole collimator using Monte Carlo Simulation

    International Nuclear Information System (INIS)

    Accuracy of in vivo activity quantification improves after the correction of penetrated and scattered photons. However, accurate assessment is not possible with physical experiment. We have used Monte Carlo Simulation to accurately assess the contribution of penetrated and scattered photons in the photopeak window. Simulations were performed with Simulation of Imaging Nuclear Detectors Monte Carlo Code. The simulations were set up in such a way that it provides geometric, penetration, and scatter components after each simulation and writes binary images to a data file. These components were analyzed graphically using Microsoft Excel (Microsoft Corporation, USA). Each binary image was imported in software (ImageJ) and logarithmic transformation was applied for visual assessment of image quality, plotting profile across the center of the images and calculating full width at half maximum (FWHM) in horizontal and vertical directions. The geometric, penetration, and scatter at 140 keV for low-energy general-purpose were 93.20%, 4.13%, 2.67% respectively. Similarly, geometric, penetration, and scatter at 140 keV for low-energy high-resolution (LEHR), medium-energy general-purpose (MEGP), and high-energy general-purpose (HEGP) collimator were (94.06%, 3.39%, 2.55%), (96.42%, 1.52%, 2.06%), and (96.70%, 1.45%, 1.85%), respectively. For MEGP collimator at 245 keV photon and for HEGP collimator at 364 keV were 89.10%, 7.08%, 3.82% and 67.78%, 18.63%, 13.59%, respectively. Low-energy general-purpose and LEHR collimator is best to image 140 keV photon. HEGP can be used for 245 keV and 364 keV; however, correction for penetration and scatter must be applied if one is interested to quantify the in vivo activity of energy 364 keV. Due to heavy penetration and scattering, 511 keV photons should not be imaged with HEGP collimator

  4. Monte Carlo simulation of ICRF discharge initiation in ITER

    Science.gov (United States)

    Tripský, M.; Wauters, T.; Lyssoivan, A.; Křivská, A.; Louche, F.; Van Schoor, M.; Noterdaeme, J.-M.

    2015-12-01

    Discharges produced and sustained by ion cyclotron range of frequency (ICRF) waves in absence of plasma current will be used on ITER for (ion cyclotron-) wall conditioning (ICWC). The here presented simulations aim at ensuring that the ITER ICRH&CD system can be safely employed for ICWC and at finding optimal parameters to initiate the plasma. The 1D Monte Carlo code RFdinity1D3V was developed to simulate ICRF discharge initiation. The code traces the electron motion along one toroidal magnetic field line, accelerated by the RF field in front of the ICRF antenna. Electron collisions in the calculations are handled by a Monte Carlo procedure taking into account their energies and the related electron collision cross sections for collisions with H2, H2+ and H+. The code also includes Coulomb collisions between electrons and ions (e - e, e - H2+ , e - H+). We study the electron multiplication rate as a function of the RF discharge parameters (i) antenna input power (0.1-5MW), and (ii) the neutral pressure (H2) for two antenna phasing (monopole [0000]-phasing and small dipole [0π0π]-phasing). Furthermore, we investigate the electron multiplication rate dependency on the distance from the antenna straps. This radial dependency results from the decreasing electric amplitude and field smoothening with increasing distance from the antenna straps. The numerical plasma breakdown definition used in the code corresponds to the moment when a critical electron density nec for the low hybrid resonance (ω = ωLHR) is reached. This numerical definition was previously found in qualitative agreement with experimental breakdown times obtained from the literature and from experiments on the ASDEX Upgrade and TEXTOR.

  5. Monte Carlo simulation of transport from an electrothermal vaporizer

    Energy Technology Data Exchange (ETDEWEB)

    Holcombe, James A. [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States)]. E-mail: holcombe@mail.utexas.edu; Ertas, Gulay [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States)

    2006-06-15

    Monte Carlo simulations were developed to elucidate the time and spatial distribution of analyte during the transport process from an electrothermal vaporizer to an inductively coupled plasma. A time-of-flight mass spectrometer was employed to collect experimental data that was compared with the simulated transient signals. Consideration was given to analyte transport as gaseous species as well as aerosol particles. In the case of aerosols, the simulation assumed formation of 5 nm particles and used the Einstein-Stokes equation to estimate the aerosol's diffusion coefficient, which was ca. 1% of the value for free atom diffusion. Desorption conditions for Cu that had been previously elucidated for electrothermal atomic absorption spectrometry were employed for the release processes from the electrothermal vaporizer. The primary distinguishing feature in the output signal to differentiate between gas and aerosol transport was a pronounced, long lived signal after the transient peak if aerosols were transported. Time and spatial distributions of particles within the transport system are presented. This characteristic was supported by independent atomic absorption measurements using a heated (or unheated) quartz T-tube with electrothermal vaporizer introduction.

  6. Scalable Metropolis Monte Carlo for simulation of hard shapes

    Science.gov (United States)

    Anderson, Joshua A.; Eric Irrgang, M.; Glotzer, Sharon C.

    2016-07-01

    We design and implement a scalable hard particle Monte Carlo simulation toolkit (HPMC), and release it open source as part of HOOMD-blue. HPMC runs in parallel on many CPUs and many GPUs using domain decomposition. We employ BVH trees instead of cell lists on the CPU for fast performance, especially with large particle size disparity, and optimize inner loops with SIMD vector intrinsics on the CPU. Our GPU kernel proposes many trial moves in parallel on a checkerboard and uses a block-level queue to redistribute work among threads and avoid divergence. HPMC supports a wide variety of shape classes, including spheres/disks, unions of spheres, convex polygons, convex spheropolygons, concave polygons, ellipsoids/ellipses, convex polyhedra, convex spheropolyhedra, spheres cut by planes, and concave polyhedra. NVT and NPT ensembles can be run in 2D or 3D triclinic boxes. Additional integration schemes permit Frenkel-Ladd free energy computations and implicit depletant simulations. In a benchmark system of a fluid of 4096 pentagons, HPMC performs 10 million sweeps in 10 min on 96 CPU cores on XSEDE Comet. The same simulation would take 7.6 h in serial. HPMC also scales to large system sizes, and the same benchmark with 16.8 million particles runs in 1.4 h on 2048 GPUs on OLCF Titan.

  7. Monte Carlo simulations for design of the KFUPM PGNAA facility

    Energy Technology Data Exchange (ETDEWEB)

    Naqvi, A.A. E-mail: aanaqvi@kfupm.edu.sa; Nagadi, M.M.; Khateeb-ur-Rehman; Maslehuddin, M.; Kidwai, S

    2003-02-01

    Monte Carlo simulations were carried out to design a 2.8 MeV neutron-based prompt gamma ray neutron activation analysis (PGNAA) setup for elemental analysis of cement samples. The elemental analysis was carried out using prompt gamma rays produced through capture of thermal neutrons in sample nuclei. The basic design of the PGNAA setup consists of a cylindrical cement sample enclosed in a cylindrical high-density polyethylene moderator placed between a neutron source and a gamma ray detector. In these simulations the predominant geometrical parameters of the PGNAA setup were optimized, including moderator size, sample size and shielding of the detector. Using the results of the simulations, an experimental PGNAA setup was then fabricated at the 350 kV Accelerator Laboratory of this University. The design calculations were checked experimentally through thermal neutron flux measurements inside the PGNAA moderator. A test prompt gamma ray spectrum of the PGNAA setup was also acquired from a Portland cement sample, using a pulsed beam of 2.8 MeV neutrons. Prompt gamma ray peaks due to the calcium, silicon and iron content of the Portland cement were detected.

  8. Monte Carlo simulations for design of the KFUPM PGNAA facility

    International Nuclear Information System (INIS)

    Monte Carlo simulations were carried out to design a 2.8 MeV neutron-based prompt gamma ray neutron activation analysis (PGNAA) setup for elemental analysis of cement samples. The elemental analysis was carried out using prompt gamma rays produced through capture of thermal neutrons in sample nuclei. The basic design of the PGNAA setup consists of a cylindrical cement sample enclosed in a cylindrical high-density polyethylene moderator placed between a neutron source and a gamma ray detector. In these simulations the predominant geometrical parameters of the PGNAA setup were optimized, including moderator size, sample size and shielding of the detector. Using the results of the simulations, an experimental PGNAA setup was then fabricated at the 350 kV Accelerator Laboratory of this University. The design calculations were checked experimentally through thermal neutron flux measurements inside the PGNAA moderator. A test prompt gamma ray spectrum of the PGNAA setup was also acquired from a Portland cement sample, using a pulsed beam of 2.8 MeV neutrons. Prompt gamma ray peaks due to the calcium, silicon and iron content of the Portland cement were detected

  9. Monte Carlo simulations of intensity profiles for energetic particle propagation

    Science.gov (United States)

    Tautz, R. C.; Bolte, J.; Shalchi, A.

    2016-02-01

    Aims: Numerical test-particle simulations are a reliable and frequently used tool for testing analytical transport theories and predicting mean-free paths. The comparison between solutions of the diffusion equation and the particle flux is used to critically judge the applicability of diffusion to the stochastic transport of energetic particles in magnetized turbulence. Methods: A Monte Carlo simulation code is extended to allow for the generation of intensity profiles and anisotropy-time profiles. Because of the relatively low number density of computational particles, a kernel function has to be used to describe the spatial extent of each particle. Results: The obtained intensity profiles are interpreted as solutions of the diffusion equation by inserting the diffusion coefficients that have been directly determined from the mean-square displacements. The comparison shows that the time dependence of the diffusion coefficients needs to be considered, in particular the initial ballistic phase and the often subdiffusive perpendicular coefficient. Conclusions: It is argued that the perpendicular component of the distribution function is essential if agreement between the diffusion solution and the simulated flux is to be obtained. In addition, time-dependent diffusion can provide a better description than the classic diffusion equation only after the initial ballistic phase.

  10. LSST optical beam simulator

    CERN Document Server

    Tyson, J A; Gilmore, K; Bradshaw, A; Claver, C; Klint, M; Muller, G; Poczulp, G; Resseguie, E

    2014-01-01

    We describe a camera beam simulator for the LSST which is capable of illuminating a 60mm field at f/1.2 with realistic astronomical scenes, enabling studies of CCD astrometric and photometric performance. The goal is to fully simulate LSST observing, in order to characterize charge transport and other features in the thick fully depleted CCDs and to probe low level systematics under realistic conditions. The automated system simulates the centrally obscured LSST beam and sky scenes, including the spectral shape of the night sky. The doubly telecentric design uses a nearly unit magnification design consisting of a spherical mirror, three BK7 lenses, and one beam-splitter window. To achieve the relatively large field the beam-splitter window is used twice. The motivation for this LSST beam test facility was driven by the need to fully characterize a new generation of thick fully-depleted CCDs, and assess their suitability for the broad range of science which is planned for LSST. Due to the fast beam illuminatio...

  11. Quantitative Estimations of Thermal Damage in Skin Tissue Using Monte Carlo Simulation of Polarized Light

    Science.gov (United States)

    Lee, G. W.; Kim, T. H.; Youn, J. I.

    2016-03-01

    Thermal treatment has been used for collagen tightening and tissue contour enhancement. It is important to monitor the condition of collagenous tissue during and immediately after thermal treatment. Collagen denaturation changes the optical properties such as scattering coefficient and anisotropy. In this study, Monte Carlo simulation of polarized light was used to calculate the degree of linear polarization (DOLP) of backscattered light from thermally damaged porcine skin, and the Mueller matrix was calculated to verify the result of DOLP. We observed a decrease in the DOLP and a significant change in the radial distribution of the Mueller matrix elements at temperatures ranging from 55 to 65°C. This could be attributed to the increase in scattering coefficient and decrease in anisotropy caused by thermal denaturation in the tissue. The DOLP method has a potential implementation as a real-time closed-loop feedback system for use in various thermal treatment methods through measuring changes in optical properties of target tissues.

  12. Radiation doses in volume-of-interest breast computed tomography—A Monte Carlo simulation study

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Chao-Jen, E-mail: cjlai3711@gmail.com; Zhong, Yuncheng; Yi, Ying; Wang, Tianpeng; Shaw, Chris C. [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030-4009 (United States)

    2015-06-15

    Purpose: Cone beam breast computed tomography (breast CT) with true three-dimensional, nearly isotropic spatial resolution has been developed and investigated over the past decade to overcome the problem of lesions overlapping with breast anatomical structures on two-dimensional mammographic images. However, the ability of breast CT to detect small objects, such as tissue structure edges and small calcifications, is limited. To resolve this problem, the authors proposed and developed a volume-of-interest (VOI) breast CT technique to image a small VOI using a higher radiation dose to improve that region’s visibility. In this study, the authors performed Monte Carlo simulations to estimate average breast dose and average glandular dose (AGD) for the VOI breast CT technique. Methods: Electron–Gamma-Shower system code-based Monte Carlo codes were used to simulate breast CT. The Monte Carlo codes estimated were validated using physical measurements of air kerma ratios and point doses in phantoms with an ion chamber and optically stimulated luminescence dosimeters. The validated full cone x-ray source was then collimated to simulate half cone beam x-rays to image digital pendant-geometry, hemi-ellipsoidal, homogeneous breast phantoms and to estimate breast doses with full field scans. 13-cm in diameter, 10-cm long hemi-ellipsoidal homogeneous phantoms were used to simulate median breasts. Breast compositions of 25% and 50% volumetric glandular fractions (VGFs) were used to investigate the influence on breast dose. The simulated half cone beam x-rays were then collimated to a narrow x-ray beam with an area of 2.5 × 2.5 cm{sup 2} field of view at the isocenter plane and to perform VOI field scans. The Monte Carlo results for the full field scans and the VOI field scans were then used to estimate the AGD for the VOI breast CT technique. Results: The ratios of air kerma ratios and dose measurement results from the Monte Carlo simulation to those from the physical

  13. Epistemic and systematic uncertainties in Monte Carlo simulation: an investigation in proton Bragg peak simulation

    OpenAIRE

    Maria Grazia PiaINFN Sezione di Genova; Marcia BegalliState University Rio de Janeiro; Anton LechnerVienna University of Technology; Lina QuintieriINFN Laboratori Nazionali di Frascati; Paolo SaraccoINFN Sezione di Genova

    2014-01-01

    The issue of how epistemic uncertainties affect the outcome of Monte Carlo simulation is discussed by means of a concrete use case: the simulation of the longitudinal energy deposition profile of low energy protons. A variety of electromagnetic and hadronic physics models is investigated, and their effects are analyzed. Possible systematic effects are highlighted. The results identify requirements for experimental measurements capable of reducing epistemic uncertainties in the physics models.

  14. Epistemic and systematic uncertainties in Monte Carlo simulation: an investigation in proton Bragg peak simulation

    CERN Document Server

    Pia, Maria Grazia; Lechner, Anton; Quintieri, Lina; Saracco, Paolo

    2010-01-01

    The issue of how epistemic uncertainties affect the outcome of Monte Carlo simulation is discussed by means of a concrete use case: the simulation of the longitudinal energy deposition profile of low energy protons. A variety of electromagnetic and hadronic physics models is investigated, and their effects are analyzed. Possible systematic effects are highlighted. The results identify requirements for experimental measurements capable of reducing epistemic uncertainties in the physics models.

  15. Complete Monte Carlo Simulation of Neutron Scattering Experiments

    International Nuclear Information System (INIS)

    The majority of experiments investigating the elastic scattering of fast neutrons were done some 30 years ago. At that time it was not possible to obtain valid corrections for the finite geometry and the finite sample size of the experimental set up, not even having the main frame computers of the Los Alamos National Laboratory at one’s disposal. The reason was not only the limited calculation capacity of those ancient computers but also, to an even higher degree, the lack of powerful Monte Carlo codes and the very limited data base for the isotope in question. The computing power of a present day PC is about ten thousand times that of a super computer of the1970ies. Moreover, most PCs are idle over-night so that using a powerful Monte Carlo program, like MCNPX from Los Alamos, corrections of important scattering experiments can be determined reliably at practically no computer cost. Surely one of the most important experiments is neutron scattering from liquid helium-3, especially considering the expensive and complicated cryogenic target. A complete documentation of such an experiment as performed in the year 1971 at the Los Alamos National Laboratory is available. Therefore it is now possible to perform a thorough simulation of the experiment: starting from the production of mono-energetic neutrons in a gas target, followed by the interaction in the ambient air, and the interaction with the cryostat structure, and finally the scattering medium itself. Another simulation deals with the scattering from hydrogen as a reference measurement. As two thirds of all available differential scattering cross sections of that reaction depend on these measurements the newly arrived at corrections prove to be highly significant because they are smaller by a factor of five. Moreover, it was necessary to simulate another experiment on this reaction, using a white neutron source. This way it was possible to convert the corresponding relative yield excitation functions to

  16. PRIMO: A graphical environment for the Monte Carlo simulation of Varian and Elekta linacs

    OpenAIRE

    Rodriguez, Manuel Jairo; Sempau Roma, Josep; Brualla, Lorenzo

    2013-01-01

    Background: The accurate Monte Carlo simulation of a linac requires a detailed description of its geometry and the application of elaborate variance-reduction techniques for radiation transport. Both tasks entail a substantial coding effort and demand advanced knowledge of the intricacies of the Monte Carlo system being used. Methods: PRIMO, a new Monte Carlo system that allows the effortless simulation of most Varian and Elekta linacs, including their multileaf collimators and electron appli...

  17. Qualitative Simulation of Photon Transport in Free Space Based on Monte Carlo Method and Its Parallel Implementation

    Directory of Open Access Journals (Sweden)

    Xueli Chen

    2010-01-01

    Full Text Available During the past decade, Monte Carlo method has obtained wide applications in optical imaging to simulate photon transport process inside tissues. However, this method has not been effectively extended to the simulation of free-space photon transport at present. In this paper, a uniform framework for noncontact optical imaging is proposed based on Monte Carlo method, which consists of the simulation of photon transport both in tissues and in free space. Specifically, the simplification theory of lens system is utilized to model the camera lens equipped in the optical imaging system, and Monte Carlo method is employed to describe the energy transformation from the tissue surface to the CCD camera. Also, the focusing effect of camera lens is considered to establish the relationship of corresponding points between tissue surface and CCD camera. Furthermore, a parallel version of the framework is realized, making the simulation much more convenient and effective. The feasibility of the uniform framework and the effectiveness of the parallel version are demonstrated with a cylindrical phantom based on real experimental results.

  18. Monte Carlo simulation for dual head gamma camera

    International Nuclear Information System (INIS)

    Monte Carlo (MC) simulation technique was used widely in medical physics applications. In nuclear medicine MC was used to design new medical imaging devices such as positron emission tomography (PET), gamma camera and single photon emission computed tomography (SPECT). Also it can be used to study the factors affecting image quality and internal dosimetry, Gate is on of monte Carlo code that has a number of advantages for simulation of SPECT and PET. There is a limit accessibilities in machines which are used in clinics because of the work load of machines. This makes it hard to evaluate some factors effecting machine performance which must be evaluated routinely. Also because of difficulties of carrying out scientific research and training of students, MC model can be optimum solution for the problem. The aim of this study was to use gate monte Carlo code to model Nucline spirit, medico dual head gamma camera hosted in radiation and isotopes center of Khartoum which is equipped with low energy general purpose LEGP collimators. This was used model to evaluate spatial resolution and sensitivity which is important factor affecting image quality and to demonstrate the validity of gate by comparing experimental results with simulation results on spatial resolution. The gate model of Nuclide spirit, medico dual head gamma camera was developed by applying manufacturer specifications. Then simulation was run. In evaluation of spatial resolution the FWHM was calculated from image profile of line source of Tc 99m gammas emitter of energy 140 KeV at different distances from modeled camera head at 5,10,15,20,22,27,32,37 cm and for these distances the spatial resolution was founded to be 5.76, 7.73, 10.7, 13.8, 14.01,16.91, 19.75 and 21.9 mm, respectively. These results showed a decrement of spatial resolution with increase of the distance between object (line source) and collimator in linear manner. FWHM calculated at 10 cm was compared with experimental results. The

  19. Monte Carlo Simulation and Experimental Characterization of a Dual Head Gamma Camera

    CERN Document Server

    Rodrigues, S; Abreu, M C; Santos, N; Rato-Mendes, P; Peralta, L

    2007-01-01

    The GEANT4 Monte Carlo simulation and experimental characterization of the Siemens E.Cam Dual Head gamma camera hosted in the Particular Hospital of Algarve have been done. Imaging tests of thyroid and other phantoms have been made "in situ" and compared with the results obtained with the Monte Carlo simulation.

  20. On the inclusion of macroscopic theory in Monte Carlo simulation using game theory

    International Nuclear Information System (INIS)

    This paper presents the inclusion of macroscopic damage theory into Monte Carlo particle-range simulation using game theory. A new computer code called RADDI was developed on the basis of this inclusion. Results of Monte Carlo damage simulation after 6.3 MeV proton bombardment of silicon are compared with experimental data of Bulgakov et al. (orig.)

  1. Using Monte Carlo Simulation Technology to Improve Intuitive Effect of Teaching Probability and Mathematical Statistics Course

    Institute of Scientific and Technical Information of China (English)

    万文应; 夏庆

    2015-01-01

    With the illustration of a specific problem, this paper demonstrates that using Monte Carlo Simulation technology will improve intuitive effect of teaching Probability and Mathematical Statistics course, and save instructors’ effort as well.And it is estimated that Monte Carlo Simulation technology will be one of the major teaching methods for Probability and Mathematical Statistics course in the future.

  2. Monte Carlo Simulations of Necrotic Cell Targeted Alpha Therapy

    International Nuclear Information System (INIS)

    Full text: Hypoxic tumour cells are radioresistant and are significant contributors to the locoregional recurrences and distant metastases that mark treatment failure. Due to restricted circulatory supply, hypoxic tumor cells frequently become necrotic and thus necrotic areas often lie near hypoxic tumour areas. In this study we investigate the feasibility of binding an alpha-emitting conjugate to necrotic cells located in the proximity of hypoxic, viable tumour cells. Monte Carlo radiation transport simulations were performed to investigate the dose distribution resulting from the thorium 227 (Th227) decay chain in a representative tumour geometry. The Geant4 software toolkit was used to simulate the decay and interactions of the Th227 decay chain. The distribution of Th227 was based on a study by Thomlinson and Gray of human lung cancer histological samples (Thomlinson RH, Gray LH. Br J Cancer 1955; 9:539). The normalized dose distribution obtained with Geant4 from a cylindrical Th227 source in water is illustrated in Fig. I. The relative contribution of the different decay channels is displayed, together with a profile through the centre of the accumulated dose map. The results support the hypothesis that significant α-particle doses will be deposited in the hypoxic tumor tissue immediately surrounding the necrotic core (where the majority of Th227 will be located). As an internal a-particle generator, the Th227-radioimmunoconjugate shows potential as an efficient hypoxic tumour sterilizer.

  3. Monte Carlo simulation of electron swarms in H2

    International Nuclear Information System (INIS)

    A Monte-Carlo simulation of the motion of an electron swarm in molecular hydrogen was studied in the range E/N = 1.4-170 Td (1 Td = 10-17V/cms2). The simulation was performed for 400-600 electrons at several values of E/N for two different sets of inelastic collision cross sections at high values of E/N. The longitudinal diffusion coefficient Dsub(L), lateral diffusion coefficient D, swarm drift velocity W, average swarm energy epsilon, and the ionization and excitation production coefficients were obtained and compared with experimental results where these are available. It was found that the results obtained differ significantly from the experimental values and this is attributed to the isotopic scattering model used in this work. However, the results lend support to the experimental technique reported by Blevin et al used to determine these transport parameters, and in particular confirm their result that Dsub(L) > D at high values of E/N. (author)

  4. Parallelization of a Monte Carlo particle transport simulation code

    Science.gov (United States)

    Hadjidoukas, P.; Bousis, C.; Emfietzoglou, D.

    2010-05-01

    We have developed a high performance version of the Monte Carlo particle transport simulation code MC4. The original application code, developed in Visual Basic for Applications (VBA) for Microsoft Excel, was first rewritten in the C programming language for improving code portability. Several pseudo-random number generators have been also integrated and studied. The new MC4 version was then parallelized for shared and distributed-memory multiprocessor systems using the Message Passing Interface. Two parallel pseudo-random number generator libraries (SPRNG and DCMT) have been seamlessly integrated. The performance speedup of parallel MC4 has been studied on a variety of parallel computing architectures including an Intel Xeon server with 4 dual-core processors, a Sun cluster consisting of 16 nodes of 2 dual-core AMD Opteron processors and a 200 dual-processor HP cluster. For large problem size, which is limited only by the physical memory of the multiprocessor server, the speedup results are almost linear on all systems. We have validated the parallel implementation against the serial VBA and C implementations using the same random number generator. Our experimental results on the transport and energy loss of electrons in a water medium show that the serial and parallel codes are equivalent in accuracy. The present improvements allow for studying of higher particle energies with the use of more accurate physical models, and improve statistics as more particles tracks can be simulated in low response time.

  5. Monte Carlo simulation of the PEMFC catalyst layer

    Institute of Scientific and Technical Information of China (English)

    WANG Hongxing; CAO Pengzhen; WANG Yuxin

    2007-01-01

    The performance of the polymer electrolyte membrane fuel cell (PEMFC) is greatly controlled by the structure of the catalyst layer.Low catalyst utilization is still a significant obstacle to the commercialization of the PEMFC.In order to get a fundamental understanding of the electrode structure and to find the limiting factor in the low catalyst utilization,it is necessary to develop the mechanical model on the effect of catalyst layer structure on the catalyst utilization and the performance of the PEMFC.In this work,the structure of the catalyst layer is studied based on the lattice model with the Monte Carlo simulation.The model can predict the effects of some catalyst layer components,such as Pt/C catalyst,electrolyte and gas pores,on the utilization of the catalyst and the cell performance.The simulation result shows that the aggregation of conduction grains can greatly affect the degree of catalyst utilization.The better the dispersion of the conduction grains,the larger the total effective area of the catalyst is.To achieve higher utilization,catalyst layer components must be distributed by means of engineered design,which can prevent aggregation.

  6. Monte Carlo Simulations of Cosmic Rays Hadronic Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Aguayo Navarrete, Estanislao; Orrell, John L.; Kouzes, Richard T.

    2011-04-01

    This document describes the construction and results of the MaCoR software tool, developed to model the hadronic interactions of cosmic rays with different geometries of materials. The ubiquity of cosmic radiation in the environment results in the activation of stable isotopes, referred to as cosmogenic activities. The objective is to use this application in conjunction with a model of the MAJORANA DEMONSTRATOR components, from extraction to deployment, to evaluate cosmogenic activation of such components before and after deployment. The cosmic ray showers include several types of particles with a wide range of energy (MeV to GeV). It is infeasible to compute an exact result with a deterministic algorithm for this problem; Monte Carlo simulations are a more suitable approach to model cosmic ray hadronic interactions. In order to validate the results generated by the application, a test comparing experimental muon flux measurements and those predicted by the application is presented. The experimental and simulated results have a deviation of 3%.

  7. Optimizing Muscle Parameters in Musculoskeletal Modeling Using Monte Carlo Simulations

    Science.gov (United States)

    Hanson, Andrea; Reed, Erik; Cavanagh, Peter

    2011-01-01

    Astronauts assigned to long-duration missions experience bone and muscle atrophy in the lower limbs. The use of musculoskeletal simulation software has become a useful tool for modeling joint and muscle forces during human activity in reduced gravity as access to direct experimentation is limited. Knowledge of muscle and joint loads can better inform the design of exercise protocols and exercise countermeasure equipment. In this study, the LifeModeler(TM) (San Clemente, CA) biomechanics simulation software was used to model a squat exercise. The initial model using default parameters yielded physiologically reasonable hip-joint forces. However, no activation was predicted in some large muscles such as rectus femoris, which have been shown to be active in 1-g performance of the activity. Parametric testing was conducted using Monte Carlo methods and combinatorial reduction to find a muscle parameter set that more closely matched physiologically observed activation patterns during the squat exercise. Peak hip joint force using the default parameters was 2.96 times body weight (BW) and increased to 3.21 BW in an optimized, feature-selected test case. The rectus femoris was predicted to peak at 60.1% activation following muscle recruitment optimization, compared to 19.2% activation with default parameters. These results indicate the critical role that muscle parameters play in joint force estimation and the need for exploration of the solution space to achieve physiologically realistic muscle activation.

  8. The Monte Carlo Simulation Method for System Reliability and Risk Analysis

    CERN Document Server

    Zio, Enrico

    2013-01-01

    Monte Carlo simulation is one of the best tools for performing realistic analysis of complex systems as it allows most of the limiting assumptions on system behavior to be relaxed. The Monte Carlo Simulation Method for System Reliability and Risk Analysis comprehensively illustrates the Monte Carlo simulation method and its application to reliability and system engineering. Readers are given a sound understanding of the fundamentals of Monte Carlo sampling and simulation and its application for realistic system modeling.   Whilst many of the topics rely on a high-level understanding of calculus, probability and statistics, simple academic examples will be provided in support to the explanation of the theoretical foundations to facilitate comprehension of the subject matter. Case studies will be introduced to provide the practical value of the most advanced techniques.   This detailed approach makes The Monte Carlo Simulation Method for System Reliability and Risk Analysis a key reference for senior undergra...

  9. Comparison of radiance and polarization values observed in the Mediterranean Sea and simulated in a Monte Carlo model

    DEFF Research Database (Denmark)

    Adams, J.T.; Aas, E.; Højerslev, N.K.;

    2002-01-01

    Measurements of the radiance and degree of polarization made in 1971 in the Mediterranean Sea are presented along with the simulation of all observed quantities by a Monte Carlo technique. It is shown that our independent scattering treatment utilizing a Stokes vector formalism to describe...... the polarization state of the light field produces remarkably good agreement with those values measured in situ. (C) 2002 Optical Society of America...

  10. Monte Carlo Simulation of the Echo Signals from Low-Flying Targets for Airborne Radar

    Directory of Open Access Journals (Sweden)

    Mingyuan Man

    2014-01-01

    Full Text Available A demonstrated hybrid method based on the combination of half-space physical optics method (PO, graphical-electromagnetic computing (GRECO, and Monte Carlo method on echo signals from low-flying targets based on actual environment for airborne radar is presented in this paper. The half-space physical optics method , combined with the graphical-electromagnetic computing (GRECO method to eliminate the shadow regions quickly and rebuild the target automatically, is employed to calculate the radar cross section (RCS of the conductive targets in half space fast and accurately. The direct echo is computed based on the radar equation. The reflected paths from sea or ground surface cause multipath effects. In order to accurately obtain the echo signals, the phase factors are modified for fluctuations in multipath, and the statistical average value of the echo signals is obtained using the Monte Carlo method. A typical simulation is performed, and the numerical results show the accuracy of the proposed method.

  11. Epithelial cancers and photon migration: Monte Carlo simulations and diffuse reflectance measurements

    Science.gov (United States)

    Tubiana, Jerome; Kass, Alex J.; Newman, Maya Y.; Levitz, David

    2015-07-01

    Detecting pre-cancer in epithelial tissues such as the cervix is a challenging task in low-resources settings. In an effort to achieve low cost cervical cancer screening and diagnostic method for use in low resource settings, mobile colposcopes that use a smartphone as their engine have been developed. Designing image analysis software suited for this task requires proper modeling of light propagation from the abnormalities inside tissues to the camera of the smartphones. Different simulation methods have been developed in the past, by solving light diffusion equations, or running Monte Carlo simulations. Several algorithms exist for the latter, including MCML and the recently developed MCX. For imaging purpose, the observable parameter of interest is the reflectance profile of a tissue under some specific pattern of illumination and optical setup. Extensions of the MCX algorithm to simulate this observable under these conditions were developed. These extensions were validated against MCML and diffusion theory for the simple case of contact measurements, and reflectance profiles under colposcopy imaging geometry were also simulated. To validate this model, the diffuse reflectance profiles of tissue phantoms were measured with a spectrometer under several illumination and optical settings for various homogeneous tissues phantoms. The measured reflectance profiles showed a non-trivial deviation across the spectrum. Measurements of an added absorber experiment on a series of phantoms showed that absorption of dye scales linearly when fit to both MCX and diffusion models. More work is needed to integrate a pupil into the experiment.

  12. Characterization of array scintillation detector for follicle thyroid 2D imaging acquisition using Monte Carlo simulation

    International Nuclear Information System (INIS)

    The image acquisition methods applied to nuclear medicine and radiobiology are a valuable research study for determination of thyroid anatomy to seek disorders associated to follicular cells. The Monte Carlo (MC) simulation has also been used in problems related to radiation detection in order to map medical images since the improvement of data processing compatible with personnel computers (PC). This work presents an innovative study to find out the adequate scintillation inorganic detector array that could be coupled to a specific light photo sensor, a charge coupled device (CCD) through a fiber optic plate in order to map the follicles of thyroid gland. The goal is to choose the type of detector that fits the application suggested here with spatial resolution of 10 μm and good detector efficiency. The methodology results are useful to map a follicle image using gamma radiation emission. A source - detector simulation is performed by using a MCNP4B (Monte Carlo for Neutron Photon transport) general code considering different source energies, detector materials and geometries including pixel sizes and reflector types. The results demonstrate that by using MCNP4B code is possible to searching for useful parameters related to the systems used in nuclear medicine, specifically in radiobiology applied to endocrine physiology studies to acquiring thyroid follicles images. (author)

  13. Monte Carlo Simulations of the Response of the MARIE Instrument

    Science.gov (United States)

    Andersen, V.; Lee, K.; Pinsky, L.; Atwell, W.; Cleghorn, T.; Cucinotta, F.; Saganti, P.; Turner, R.; Zeitlin, C.

    2003-01-01

    The MARIE instrument aboard Mars Odyssey functions as a telescope for the detection of charged, energetic, nuclei. The directionality that leads to the telescope description is achieved by requiring coincident signals in two designated detectors in MARIE s silicon detector stack for the instrument to trigger. Because of this, MARIE is actually a bi directional telescope. Triggering particles can enter the detector stack by passing through the lightly shielded front of the instrument, but can also enter the back of the instrument by passing through the bulk of Odyssey. Because of this, understanding how to relate the signals recorded by MARIE to astrophysically important quantities such as particle fluxes or spectra exterior to the spacecraft clearly requires detailed modeling of the physical interactions that occur as the particles pass through the spacecraft and the instrument itself. In order to facilitate in the calibration of the MARIE data, we have begun a program to simulate the response of MARIE using the FLUKA [1] [2] Monte Carlo radiation transport code.

  14. Monte Carlo simulations of ionization potential depression in dense plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Stransky, M., E-mail: stransky@fzu.cz [Department of Radiation and Chemical Physics, Institute of Physics ASCR, Na Slovance 2, 182 21 Prague 8 (Czech Republic)

    2016-01-15

    A particle-particle grand canonical Monte Carlo model with Coulomb pair potential interaction was used to simulate modification of ionization potentials by electrostatic microfields. The Barnes-Hut tree algorithm [J. Barnes and P. Hut, Nature 324, 446 (1986)] was used to speed up calculations of electric potential. Atomic levels were approximated to be independent of the microfields as was assumed in the original paper by Ecker and Kröll [Phys. Fluids 6, 62 (1963)]; however, the available levels were limited by the corresponding mean inter-particle distance. The code was tested on hydrogen and dense aluminum plasmas. The amount of depression was up to 50% higher in the Debye-Hückel regime for hydrogen plasmas, in the high density limit, reasonable agreement was found with the Ecker-Kröll model for hydrogen plasmas and with the Stewart-Pyatt model [J. Stewart and K. Pyatt, Jr., Astrophys. J. 144, 1203 (1966)] for aluminum plasmas. Our 3D code is an improvement over the spherically symmetric simplifications of the Ecker-Kröll and Stewart-Pyatt models and is also not limited to high atomic numbers as is the underlying Thomas-Fermi model used in the Stewart-Pyatt model.

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

    Directory of Open Access Journals (Sweden)

    Hassan Ghodrati

    2014-03-01

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

  16. Monte Carlo simulation algorithm for B-DNA.

    Science.gov (United States)

    Howell, Steven C; Qiu, Xiangyun; Curtis, Joseph E

    2016-11-01

    Understanding the structure-function relationship of biomolecules containing DNA has motivated experiments aimed at determining molecular structure using methods such as small-angle X-ray and neutron scattering (SAXS and SANS). SAXS and SANS are useful for determining macromolecular shape in solution, a process which benefits by using atomistic models that reproduce the scattering data. The variety of algorithms available for creating and modifying model DNA structures lack the ability to rapidly modify all-atom models to generate structure ensembles. This article describes a Monte Carlo algorithm for simulating DNA, not with the goal of predicting an equilibrium structure, but rather to generate an ensemble of plausible structures which can be filtered using experimental results to identify a sub-ensemble of conformations that reproduce the solution scattering of DNA macromolecules. The algorithm generates an ensemble of atomic structures through an iterative cycle in which B-DNA is represented using a wormlike bead-rod model, new configurations are generated by sampling bend and twist moves, then atomic detail is recovered by back mapping from the final coarse-grained configuration. Using this algorithm on commodity computing hardware, one can rapidly generate an ensemble of atomic level models, each model representing a physically realistic configuration that could be further studied using molecular dynamics. © 2016 Wiley Periodicals, Inc. PMID:27671358

  17. Monte Carlo Simulation for the Adsorption of Symmetric Triblock Copolymers

    Institute of Scientific and Technical Information of China (English)

    彭昌军; 李健康; 刘洪来; 胡英

    2004-01-01

    The adsorption behavior of symmetric triblock copolymers, Am/2BnAm/2, from a nonselective solvent at solid-liquid interface has been studied by Monte Carlo simulations on a simple lattice model. Either segment A or segment B is attractive, while the other is non-attractive to the surface. Influences of the adsorption energy,bulk concentration, chain composition and chain length on the microstructure of adsorbed layers are presented.The results show that the total surface coverage and the adsorption amount increases monotonically as the bulk concentration increases. The larger the adsorption energy and the higher the fraction of adsorbing segments, the higher the total surface coverage is exhibited. The product of surface coverage and the proportion of non-attractive segments are nearly independent of the chain length, and the logarithm of the adsorption amount is a linear function of the reciprocal of the reduced temperature. When the adsorption energy is larger, the adsorption amount exhibits a maximum as the fraction of adsorbing segment increases. The adsorption isotherms of copolymers with different length of non-attractive segments can be mapped onto a single curve under given adsorption energy. The adsorption layer thickness decreases as the adsorption energy and the fraction of adsorbing segments increases, but it increhses as the length of non-attractive segments increases. The tails mainly govern the adsorption layer thickness.

  18. Monte Carlo Simulation of SATs in 2D

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    In this paper we use Monte Carlo simulation method to deal with SATs on a square lattice and a triangular lattice in two dimensions in the T→∞ limit.Besides that,the SAT model has been generalized in the coordination number q→∞ limit.The characteristics of SATs in the two limits q=3 and q→∞ have been qualitatively discussed.The obtained results reveal that the SATs have intermediate behaviors between that of SAWs and RWs.The critical exponents of SATs have intermediate behaviors between that of SAWs and RWs.The critical exponents of SATs are monotonous functions of q.With different q,SATs correspondingly belong to different universality classes.For example,on a hexagonal lattice,SATs and SAWs belong to the same universality class;in the limiting situation q→∞,SATs and RWs belong to the same universality class;when q=4 or q=6,SATs and SAWs or RWs belong to the different universality class.

  19. Monte Carlo simulation of electron beam air plasma characteristics

    Institute of Scientific and Technical Information of China (English)

    Deng Yong-Feng; Han Xian-Wei; Tan Chang

    2009-01-01

    A high-energy electron beam generator is used to generate a plasma in atmosphere. Based on a Monte Carlo toolkit named GEANT4,a model including complete physics processes is established to simulate the passage of the electron beam in air. Based on the model,the characteristics of the electron beam air plasma are calculated. The energy distribution of beam electrons (BEs) indicates that high-energy electrons almost reside in the centre region of the beam,but low-energy electrons always live in the fringe area. The energy deposition is calculated in two cases,i.e.,with and without secondary electrons (SEs). Analysis indicates that the energy deposition of Ses accounts for a large part of the total energy deposition. The results of the energy spectrum show that the electrons in the inlet layer of the low-pressure chamber (LPC) are monoenergetic,but the energy spectrum of the electrons in the outlet layer is not pure. The SEs are largely generated at the outlet of the LPC. Moreover,both the energy distribution of Bes and the magnitude of the density of SEs are closely related to the pressure of LPC. Thus,a conclusion is drawn that a low magnitude of LPC pressure is helpful for reducing the energy loss in the LPC and also useful for greatly increasing the secondary electron density in dense air.

  20. Monte Carlo simulation of AB-copolymers with saturating bonds

    CERN Document Server

    Chertovich, A V; Khokhlov, A R; Bohr, J

    2003-01-01

    Structural transitions in a single AB-copolymer chain where saturating bonds can be formed between A-and B-units are studied by means of Monte Carlo computer simulations using the bond fluctuation model. Three transitions are found, coil-globule, coil-hairpin and globule-hairpin, depending on the nature of a particular AB-sequence: statistical random sequence, diblock sequence and 'random-complementary' sequence (one-half of such an AB-sequence is random with Bernoulli statistics while the other half is complementary to the first one). The properties of random-complementary sequences are closer to those of diblock sequences than to the properties of random sequences. The model (although quite rough) is expected to represent some basic features of real RNA molecules, i.e. the formation of secondary structure of RNA due to hydrogen bonding of corresponding bases and stacking interactions of the base pairs in helixes. We introduce the notation of RNA-like copolymers and discuss in what sense the sequences studie...

  1. Catastrophic rupture of lunar rocks - A Monte Carlo simulation

    Science.gov (United States)

    Hoerz, F.; Schneider, E.; Gault, D. E.; Hartung, J. B.; Brownlee, D. E.

    1975-01-01

    A computer model based on Monte Carlo techniques was developed to simulate the destruction of lunar rocks by 'catastrophic rupture' due to meteoroid impact. Energies necessary to accomplish catastrophic rupture were derived from laboratory experiments. A crater-production rate derived from lunar rocks was utilized to calculate absolute time scales. Calculated median survival times for crystalline lunar rocks are 1.9, 4.6, 10.3, and 22 m.y. for rock masses of 10, 100, 1000, and 10,000 g, respectively. Corresponding times of 6, 14.5, 32, and 68 million years are required before the probability of destruction reaches 0.99. These results are consistent with absolute exposure ages measured on returned rocks. Some results also substantiate previous conclusions that the catastrophic-rupture process is significantly more effective in obliterating lunar rocks than mass wasting by single-particle abrasion. The view is also corroborated that most rocks presently on the lunar surface either are exhumed from the regolith or are fragments of much larger boulders rather than primary ejecta excavated from pristine bedrock.

  2. A Monte Carlo simulation approach for flood risk assessment

    Science.gov (United States)

    Agili, Hachem; Chokmani, Karem; Oubennaceur, Khalid; Poulin, Jimmy; Marceau, Pascal

    2016-04-01

    Floods are the most frequent natural disaster and the most damaging in Canada. The issue of assessing and managing the risk related to this disaster has become increasingly crucial for both local and national authorities. Brigham, a municipality located in southern Quebec Province, is one of the heavily affected regions by this disaster because of frequent overflows of the Yamaska River reaching two to three times per year. Since Irene Hurricane which hit the region in 2011 causing considerable socio-economic damage, the implementation of mitigation measures has become a major priority for this municipality. To do this, a preliminary study to evaluate the risk to which this region is exposed is essential. Conventionally, approaches only based on the characterization of the hazard (e.g. floodplains extensive, flood depth) are generally adopted to study the risk of flooding. In order to improve the knowledge of this risk, a Monte Carlo simulation approach combining information on the hazard with vulnerability-related aspects of buildings has been developed. This approach integrates three main components namely hydrological modeling through flow-probability functions, hydraulic modeling using flow-submersion height functions and the study of buildings damage based on damage functions adapted to the Quebec habitat. The application of this approach allows estimating the annual average cost of damage caused by floods on buildings. The obtained results will be useful for local authorities to support their decisions on risk management and prevention against this disaster.

  3. Monte Carlo simulations of ionization potential depression in dense plasmas

    International Nuclear Information System (INIS)

    A particle-particle grand canonical Monte Carlo model with Coulomb pair potential interaction was used to simulate modification of ionization potentials by electrostatic microfields. The Barnes-Hut tree algorithm [J. Barnes and P. Hut, Nature 324, 446 (1986)] was used to speed up calculations of electric potential. Atomic levels were approximated to be independent of the microfields as was assumed in the original paper by Ecker and Kröll [Phys. Fluids 6, 62 (1963)]; however, the available levels were limited by the corresponding mean inter-particle distance. The code was tested on hydrogen and dense aluminum plasmas. The amount of depression was up to 50% higher in the Debye-Hückel regime for hydrogen plasmas, in the high density limit, reasonable agreement was found with the Ecker-Kröll model for hydrogen plasmas and with the Stewart-Pyatt model [J. Stewart and K. Pyatt, Jr., Astrophys. J. 144, 1203 (1966)] for aluminum plasmas. Our 3D code is an improvement over the spherically symmetric simplifications of the Ecker-Kröll and Stewart-Pyatt models and is also not limited to high atomic numbers as is the underlying Thomas-Fermi model used in the Stewart-Pyatt model

  4. Fluid Simulations with Localized Boltzmann Upscaling by Direct Simulation Monte-Carlo

    OpenAIRE

    Degond, Pierre; Dimarco, Giacomo

    2010-01-01

    In the present work, we present a novel numerical algorithm to couple the Direct Simulation Monte Carlo method (DSMC) for the solution of the Boltzmann equation with a finite volume like method for the solution of the Euler equations. Recently we presented in [14],[16],[17] different methodologies which permit to solve fluid dynamics problems with localized regions of departure from thermodynamical equilibrium. The methods rely on the introduction of buffer zones which realize a smooth transi...

  5. Monte Carlo computer simulation of sedimentation of charged hard spherocylinders.

    Science.gov (United States)

    Viveros-Méndez, P X; Gil-Villegas, Alejandro; Aranda-Espinoza, S

    2014-07-28

    In this article we present a NVT Monte Carlo computer simulation study of sedimentation of an electroneutral mixture of oppositely charged hard spherocylinders (CHSC) with aspect ratio L/σ = 5, where L and σ are the length and diameter of the cylinder and hemispherical caps, respectively, for each particle. This system is an extension of the restricted primitive model for spherical particles, where L/σ = 0, and it is assumed that the ions are immersed in an structureless solvent, i.e., a continuum with dielectric constant D. The system consisted of N = 2000 particles and the Wolf method was implemented to handle the coulombic interactions of the inhomogeneous system. Results are presented for different values of the strength ratio between the gravitational and electrostatic interactions, Γ = (mgσ)/(e(2)/Dσ), where m is the mass per particle, e is the electron's charge and g is the gravitational acceleration value. A semi-infinite simulation cell was used with dimensions Lx ≈ Ly and Lz = 5Lx, where Lx, Ly, and Lz are the box dimensions in Cartesian coordinates, and the gravitational force acts along the z-direction. Sedimentation effects were studied by looking at every layer formed by the CHSC along the gravitational field. By increasing Γ, particles tend to get more packed at each layer and to arrange in local domains with an orientational ordering along two perpendicular axis, a feature not observed in the uncharged system with the same hard-body geometry. This type of arrangement, known as tetratic phase, has been observed in two-dimensional systems of hard-rectangles and rounded hard-squares. In this way, the coupling of gravitational and electric interactions in the CHSC system induces the arrangement of particles in layers, with the formation of quasi-two dimensional tetratic phases near the surface. PMID:25084954

  6. Monte Carlo simulation of the neutron monitor yield function

    Science.gov (United States)

    Mangeard, P.-S.; Ruffolo, D.; Sáiz, A.; Madlee, S.; Nutaro, T.

    2016-08-01

    Neutron monitors (NMs) are ground-based detectors that measure variations of the Galactic cosmic ray flux at GV range rigidities. Differences in configuration, electronics, surroundings, and location induce systematic effects on the calculation of the yield functions of NMs worldwide. Different estimates of NM yield functions can differ by a factor of 2 or more. In this work, we present new Monte Carlo simulations to calculate NM yield functions and perform an absolute (not relative) comparison with the count rate of the Princess Sirindhorn Neutron Monitor (PSNM) at Doi Inthanon, Thailand, both for the entire monitor and for individual counter tubes. We model the atmosphere using profiles from the Global Data Assimilation System database and the Naval Research Laboratory Mass Spectrometer, Incoherent Scatter Radar Extended model. Using FLUKA software and the detailed geometry of PSNM, we calculated the PSNM yield functions for protons and alpha particles. An agreement better than 9% was achieved between the PSNM observations and the simulated count rate during the solar minimum of December 2009. The systematic effect from the electronic dead time was studied as a function of primary cosmic ray rigidity at the top of the atmosphere up to 1 TV. We show that the effect is not negligible and can reach 35% at high rigidity for a dead time >1 ms. We analyzed the response function of each counter tube at PSNM using its actual dead time, and we provide normalization coefficients between count rates for various tube configurations in the standard NM64 design that are valid to within ˜1% for such stations worldwide.

  7. Monte Carlo-based simulation of dynamic jaws tomotherapy

    International Nuclear Information System (INIS)

    Purpose: Original TomoTherapy systems may involve a trade-off between conformity and treatment speed, the user being limited to three slice widths (1.0, 2.5, and 5.0 cm). This could be overcome by allowing the jaws to define arbitrary fields, including very small slice widths (<1 cm), which are challenging for a beam model. The aim of this work was to incorporate the dynamic jaws feature into a Monte Carlo (MC) model called TomoPen, based on the MC code PENELOPE, previously validated for the original TomoTherapy system. Methods: To keep the general structure of TomoPen and its efficiency, the simulation strategy introduces several techniques: (1) weight modifiers to account for any jaw settings using only the 5 cm phase-space file; (2) a simplified MC based model called FastStatic to compute the modifiers faster than pure MC; (3) actual simulation of dynamic jaws. Weight modifiers computed with both FastStatic and pure MC were compared. Dynamic jaws simulations were compared with the convolution/superposition (C/S) of TomoTherapy in the ''cheese'' phantom for a plan with two targets longitudinally separated by a gap of 3 cm. Optimization was performed in two modes: asymmetric jaws-constant couch speed (''running start stop,'' RSS) and symmetric jaws-variable couch speed (''symmetric running start stop,'' SRSS). Measurements with EDR2 films were also performed for RSS for the formal validation of TomoPen with dynamic jaws. Results: Weight modifiers computed with FastStatic were equivalent to pure MC within statistical uncertainties (0.5% for three standard deviations). Excellent agreement was achieved between TomoPen and C/S for both asymmetric jaw opening/constant couch speed and symmetric jaw opening/variable couch speed, with deviations well within 2%/2 mm. For RSS procedure, agreement between C/S and measurements was within 2%/2 mm for 95% of the points and 3%/3 mm for 98% of the points, where dose is greater than 30% of the prescription dose (gamma analysis

  8. Monte Carlo simulation on kinetics of batch and semi-batch free radical polymerization

    KAUST Repository

    Shao, Jing

    2015-10-27

    Based on Monte Carlo simulation technology, we proposed a hybrid routine which combines reaction mechanism together with coarse-grained molecular simulation to study the kinetics of free radical polymerization. By comparing with previous experimental and simulation studies, we showed the capability of our Monte Carlo scheme on representing polymerization kinetics in batch and semi-batch processes. Various kinetics information, such as instant monomer conversion, molecular weight, and polydispersity etc. are readily calculated from Monte Carlo simulation. The kinetic constants such as polymerization rate k p is determined in the simulation without of “steady-state” hypothesis. We explored the mechanism for the variation of polymerization kinetics those observed in previous studies, as well as polymerization-induced phase separation. Our Monte Carlo simulation scheme is versatile on studying polymerization kinetics in batch and semi-batch processes.

  9. External individual monitoring: experiments and simulations using Monte Carlo Method

    International Nuclear Information System (INIS)

    In this work, we have evaluated the possibility of applying the Monte Carlo simulation technique in photon dosimetry of external individual monitoring. The GEANT4 toolkit was employed to simulate experiments with radiation monitors containing TLD-100 and CaF2:NaCl thermoluminescent detectors. As a first step, X ray spectra were generated impinging electrons on a tungsten target. Then, the produced photon beam was filtered in a beryllium window and additional filters to obtain the radiation with desired qualities. This procedure, used to simulate radiation fields produced by a X ray tube, was validated by comparing characteristics such as half value layer, which was also experimentally measured, mean photon energy and the spectral resolution of simulated spectra with that of reference spectra established by international standards. In the construction of thermoluminescent dosimeter, two approaches for improvements have. been introduced. The first one was the inclusion of 6% of air in the composition of the CaF2:NaCl detector due to the difference between measured and calculated values of its density. Also, comparison between simulated and experimental results showed that the self-attenuation of emitted light in the readout process of the fluorite dosimeter must be taken into account. Then, in the second approach, the light attenuation coefficient of CaF2:NaCl compound estimated by simulation to be 2,20(25) mm-1 was introduced. Conversion coefficients Cp from air kerma to personal dose equivalent were calculated using a slab water phantom with polymethyl-metacrilate (PMMA) walls, for reference narrow and wide X ray spectrum series [ISO 4037-1], and also for the wide spectra implanted and used in routine at Laboratorio de Dosimetria. Simulations of backscattered radiations by PMMA slab water phantom and slab phantom of ICRU tissue-equivalent material produced very similar results. Therefore, the PMMA slab water phantom that can be easily constructed with low price can

  10. A Fortran-77 program for Monte Carlo simulation of upwelling light from the sea

    Digital Repository Service at National Institute of Oceanography (India)

    Sathe, P.V.; Sathyendranath, S.

    two media separ- ated by a nonflat boundary such as a wind-ruffled sea surface, the Monte Carlo simulation is more effective. The Monte Carlo method is a direct simulation of the actual process of radiation transfer in which a large number... it begins the simulation of radiation transfer. The following are the input parameters which the user controls in every run. (!) Maximum number of photons to be run (2) Solar elevation (3) Fraction of diffuse light present (4) Spectral composition...

  11. Numerical simulation of the blast impact problem using the Direct Simulation Monte Carlo (DSMC) method

    Science.gov (United States)

    Sharma, Anupam; Long, Lyle N.

    2004-10-01

    A particle approach using the Direct Simulation Monte Carlo (DSMC) method is used to solve the problem of blast impact with structures. A novel approach to model the solid boundary condition for particle methods is presented. The solver is validated against an analytical solution of the Riemann shocktube problem and against experiments on interaction of a planar shock with a square cavity. Blast impact simulations are performed for two model shapes, a box and an I-shaped beam, assuming that the solid body does not deform. The solver uses domain decomposition technique to run in parallel. The parallel performance of the solver on two Beowulf clusters is also presented.

  12. Monte Carlo and analytic simulations in nanoparticle-enhanced radiation therapy

    Directory of Open Access Journals (Sweden)

    Paro AD

    2016-09-01

    Full Text Available Autumn D Paro,1 Mainul Hossain,2 Thomas J Webster,1,3,4 Ming Su1,4 1Department of Chemical Engineering, Northeastern University, Boston, MA, USA; 2NanoScience Technology Center and School of Electrical Engineering and Computer Science, University of Central Florida, Orlando, Florida, USA; 3Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabia; 4Wenzhou Institute of Biomaterials and Engineering, Chinese Academy of Science, Wenzhou Medical University, Zhejiang, People’s Republic of China Abstract: Analytical and Monte Carlo simulations have been used to predict dose enhancement factors in nanoparticle-enhanced X-ray radiation therapy. Both simulations predict an increase in dose enhancement in the presence of nanoparticles, but the two methods predict different levels of enhancement over the studied energy, nanoparticle materials, and concentration regime for several reasons. The Monte Carlo simulation calculates energy deposited by electrons and photons, while the analytical one only calculates energy deposited by source photons and photoelectrons; the Monte Carlo simulation accounts for electron–hole recombination, while the analytical one does not; and the Monte Carlo simulation randomly samples photon or electron path and accounts for particle interactions, while the analytical simulation assumes a linear trajectory. This study demonstrates that the Monte Carlo simulation will be a better choice to evaluate dose enhancement with nanoparticles in radiation therapy. Keywords: nanoparticle, dose enhancement, Monte Carlo simulation, analytical simulation, radiation therapy, tumor cell, X-ray 

  13. Litrani a General Purpose Monte-Carlo Program Simulating Light Propagation In Isotropic or Anisotropic Media

    CERN Document Server

    Gentit, François-Xavier

    2001-01-01

    Litrani is a general purpose Monte-Carlo program simulating light propagation in any type of setup describable by the shapes provided by ROOT. Each shape may be made of a different material. Dielectric constant, absorption length and diffusion length of materials may depend upon wavelength. Dielectric constant and absorption length may be anisotropic. Each face of a volume is either partially or totally in contact with a face of another volume, or covered with some wrapping having defined characteristics of absorption, reflection and diffusion. When in contact with another face of another volume, the possibility exists to have a thin slice of width d and index n between the 2 faces. The program has various sources of light: spontaneous photons, photons coming from an optical fibre, photons generated by the crossing of particles or photons generated by an electromagnetic shower. The time and wavelength spectra of emitted photons may reproduce any scintillation spectrum. As detectors, phototubes, APD, or any ge...

  14. Deficiency in Monte Carlo simulations of coupled neutron-gamma-ray fields

    NARCIS (Netherlands)

    Maleka, Peane P.; Maucec, Marko; de Meijer, Robert J.

    2011-01-01

    The deficiency in Monte Carlo simulations of coupled neutron-gamma-ray field was investigated by benchmarking two simulation codes with experimental data. Simulations showed better correspondence with the experimental data for gamma-ray transport only. In simulations, the neutron interactions with m

  15. Suppression of the initial transient in Monte Carlo criticality simulations; Suppression du regime transitoire initial des simulations Monte-Carlo de criticite

    Energy Technology Data Exchange (ETDEWEB)

    Richet, Y

    2006-12-15

    Criticality Monte Carlo calculations aim at estimating the effective multiplication factor (k-effective) for a fissile system through iterations simulating neutrons propagation (making a Markov chain). Arbitrary initialization of the neutron population can deeply bias the k-effective estimation, defined as the mean of the k-effective computed at each iteration. A simplified model of this cycle k-effective sequence is built, based on characteristics of industrial criticality Monte Carlo calculations. Statistical tests, inspired by Brownian bridge properties, are designed to discriminate stationarity of the cycle k-effective sequence. The initial detected transient is, then, suppressed in order to improve the estimation of the system k-effective. The different versions of this methodology are detailed and compared, firstly on a plan of numerical tests fitted on criticality Monte Carlo calculations, and, secondly on real criticality calculations. Eventually, the best methodologies observed in these tests are selected and allow to improve industrial Monte Carlo criticality calculations. (author)

  16. Monte Carlo computer simulation of sedimentation of charged hard spherocylinders

    Energy Technology Data Exchange (ETDEWEB)

    Viveros-Méndez, P. X., E-mail: xviveros@fisica.uaz.edu.mx; Aranda-Espinoza, S. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esq. Paseo, La Bufa s/n, 98060 Zacatecas, Zacatecas, México (Mexico); Gil-Villegas, Alejandro [Departamento de Ingeniería Física, División de Ciencias e Ingenierías, Campus León, Universidad de Guanajuato, Loma del Bosque 103, Lomas del Campestre, 37150 León, Guanajuato, México (Mexico)

    2014-07-28

    In this article we present a NVT Monte Carlo computer simulation study of sedimentation of an electroneutral mixture of oppositely charged hard spherocylinders (CHSC) with aspect ratio L/σ = 5, where L and σ are the length and diameter of the cylinder and hemispherical caps, respectively, for each particle. This system is an extension of the restricted primitive model for spherical particles, where L/σ = 0, and it is assumed that the ions are immersed in an structureless solvent, i.e., a continuum with dielectric constant D. The system consisted of N = 2000 particles and the Wolf method was implemented to handle the coulombic interactions of the inhomogeneous system. Results are presented for different values of the strength ratio between the gravitational and electrostatic interactions, Γ = (mgσ)/(e{sup 2}/Dσ), where m is the mass per particle, e is the electron's charge and g is the gravitational acceleration value. A semi-infinite simulation cell was used with dimensions L{sub x} ≈ L{sub y} and L{sub z} = 5L{sub x}, where L{sub x}, L{sub y}, and L{sub z} are the box dimensions in Cartesian coordinates, and the gravitational force acts along the z-direction. Sedimentation effects were studied by looking at every layer formed by the CHSC along the gravitational field. By increasing Γ, particles tend to get more packed at each layer and to arrange in local domains with an orientational ordering along two perpendicular axis, a feature not observed in the uncharged system with the same hard-body geometry. This type of arrangement, known as tetratic phase, has been observed in two-dimensional systems of hard-rectangles and rounded hard-squares. In this way, the coupling of gravitational and electric interactions in the CHSC system induces the arrangement of particles in layers, with the formation of quasi-two dimensional tetratic phases near the surface.

  17. Simulating rotationally inelastic collisions using a Direct Simulation Monte Carlo method

    CERN Document Server

    Schullian, O; Vaeck, N; van der Avoird, A; Heazlewood, B R; Rennick, C J; Softley, T P

    2015-01-01

    A new approach to simulating rotational cooling using a direct simulation Monte Carlo (DSMC) method is described and applied to the rotational cooling of ammonia seeded into a helium supersonic jet. The method makes use of ab initio rotational state changing cross sections calculated as a function of collision energy. Each particle in the DSMC simulations is labelled with a vector of rotational populations that evolves with time. Transfer of energy into translation is calculated from the mean energy transfer for this population at the specified collision energy. The simulations are compared with a continuum model for the on-axis density, temperature and velocity; rotational temperature as a function of distance from the nozzle is in accord with expectations from experimental measurements. The method could be applied to other types of gas mixture dynamics under non-uniform conditions, such as buffer gas cooling of NH$_3$ by He.

  18. Monte-Carlo Simulator and Ancillary Response Generator of Suzaku XRT/XIS System for Spatially Extended Source Analysis

    CERN Document Server

    Ishisaki, Y; Fujimoto, R; Ozaki, M; Ebisawa, K; Takahashi, T; Ueda, Y; Ogasaka, Y; Ptak, A; Mukai, K; Hamaguchi, K; Hirayama, M; Kotani, T; Kubo, H; Shibata, R; Ebara, M; Furuzawa, A; Iizuka, R; Inoue, H; Mori, H; Okada, S; Yokoyama, Y; Matsumoto, H; Nakajima, H; Yamaguchi, H; Anabuki, N; Tawa, N; Nagai, M; Katsuda, S; Hayashida, K; Bamba, A; Miller, E D; Sato, K; Yamasaki, N Y

    2006-01-01

    We have developed a framework for the Monte-Carlo simulation of the X-Ray Telescopes (XRT) and the X-ray Imaging Spectrometers (XIS) onboard Suzaku, mainly for the scientific analysis of spatially and spectroscopically complex celestial sources. A photon-by-photon instrumental simulator is built on the ANL platform, which has been successfully used in ASCA data analysis. The simulator has a modular structure, in which the XRT simulation is based on a ray-tracing library, while the XIS simulation utilizes a spectral "Redistribution Matrix File" (RMF), generated separately by other tools. Instrumental characteristics and calibration results, e.g., XRT geometry, reflectivity, mutual alignments, thermal shield transmission, build-up of the contamination on the XIS optical blocking filters (OBF), are incorporated as completely as possible. Most of this information is available in the form of the FITS (Flexible Image Transport System) files in the standard calibration database (CALDB). This simulator can also be ut...

  19. Fast photon-boundary intersection computation for Monte Carlo simulation of photon migration

    Science.gov (United States)

    Zhao, Xiaofen; Liu, Hongyan; Zhang, Bin; Liu, Fei; Luo, Jianwen; Bai, Jing

    2013-01-01

    Monte Carlo (MC) method is generally used as a "gold standard" technique to simulate photon transport in biomedical optics. However, it is quite time-consuming since abundant photon propagations need to be simulated in order to achieve an accurate result. In the case of complicated geometry, the computation speed is bound up with the calculation of the intersection between the photon transmission path and media boundary. The ray-triangle-based method is often used to calculate the photon-boundary intersection in the shape-based MC simulation for light propagation, but it is still relatively time-consuming. We present a fast way to determine the photon-boundary intersection. Triangle meshes are used to describe the boundary structure. A line segment instead of a ray is used to check if there exists a photon-boundary intersection, as the next location of the photon in light transports is determined by the step size. Results suggest that by simply replacing the conventional ray-triangle-based method with the proposed line segment-triangle-based method, the MC simulation for light propagation in the mouse model can be speeded up by more than 35%.

  20. On-the-fly nuclear data processing methods for Monte Carlo simulations of fast spectrum systems

    Energy Technology Data Exchange (ETDEWEB)

    Walsh, Jon [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-08-31

    The presentation summarizes work performed over summer 2015 related to Monte Carlo simulations. A flexible probability table interpolation scheme has been implemented and tested with results comparing favorably to the continuous phase-space on-the-fly approach.

  1. Monte Carlo simulation of the standardization of {sup 22}Na using scintillation detector arrays

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Y., E-mail: yss.sato@aist.go.j [National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Quantum Radiation Division, Radioactivity and Neutron Section, Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Murayama, H. [National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage, Chiba 263-8555 (Japan); Yamada, T. [Japan Radioisotope Association, 2-28-45, Hon-komagome, Bunkyo, Tokyo 113-8941 (Japan); National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Quantum Radiation Division, Radioactivity and Neutron Section, Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Tohoku University, 6-6, Aoba, Aramaki, Aoba, Sendai 980-8579 (Japan); Hasegawa, T. [Kitasato University, 1-15-1, Kitasato, Sagamihara, Kanagawa 228-8555 (Japan); Oda, K. [Tokyo Metropolitan Institute of Gerontology, 1-1 Nakacho, Itabashi-ku, Tokyo 173-0022 (Japan); Unno, Y.; Yunoki, A. [National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Quantum Radiation Division, Radioactivity and Neutron Section, Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

    2010-07-15

    In order to calibrate PET devices by a sealed point source, we contrived an absolute activity measurement method for the sealed point source using scintillation detector arrays. This new method was verified by EGS5 Monte Carlo simulation.

  2. Monte Carlo simulation of diffuse attenuation coefficient in presence of non uniform profiles

    Digital Repository Service at National Institute of Oceanography (India)

    Desa, E.S.; Desai, R.G.P.; Desa, B.A.E.

    This paper presents a Monte Carlo simulation of the vertical depth structure of the downward attenuation coefficient (K sub(d)), and the irradiance reflectance (R) for a given profile of chlorophyll. The results are in quantitaive agreement...

  3. Monte-Carlo modelling of multi-conjugate adaptive optics performance on the European Extremely Large Telescope

    CERN Document Server

    Basden, Alastair

    2015-01-01

    The performance of a wide-field adaptive optics system depends on input design parameters. Here we investigate the performance of a multi-conjugate adaptive optics system design for the European Extremely Large Telescope, using an end-to-end Monte-Carlo adaptive optics simulation tool, DASP. We consider parameters such as the number of laser guide stars, sodium layer depth, wavefront sensor pixel scale, number of deformable mirrors, mirror conjugation and actuator pitch. We provide potential areas where costs savings can be made, and investigate trade-offs between performance and cost. We conclude that a 6 laser guide star system using 3 DMs seems to be a sweet spot for performance and cost compromise.

  4. Hybrid Monte-Carlo method for simulating neutron and photon radiography

    International Nuclear Information System (INIS)

    We present a Hybrid Monte-Carlo method (HMCM) for simulating neutron and photon radiographs. HMCM utilizes the combination of a Monte-Carlo particle simulation for calculating incident film radiation and a statistical post-processing routine to simulate film noise. Since the method relies on MCNP for transport calculations, it is easily generalized to most non-destructive evaluation (NDE) simulations. We verify the method's accuracy through ASTM International's E592-99 publication, Standard Guide to Obtainable (E)quivalent Penetrameter Sensitivity for Radiography of Steel Plates [1]. Potential uses for the method include characterizing alternative radiological sources and simulating NDE radiographs

  5. Hybrid Monte-Carlo method for simulating neutron and photon radiography

    Science.gov (United States)

    Wang, Han; Tang, Vincent

    2013-11-01

    We present a Hybrid Monte-Carlo method (HMCM) for simulating neutron and photon radiographs. HMCM utilizes the combination of a Monte-Carlo particle simulation for calculating incident film radiation and a statistical post-processing routine to simulate film noise. Since the method relies on MCNP for transport calculations, it is easily generalized to most non-destructive evaluation (NDE) simulations. We verify the method's accuracy through ASTM International's E592-99 publication, Standard Guide to Obtainable Equivalent Penetrameter Sensitivity for Radiography of Steel Plates [1]. Potential uses for the method include characterizing alternative radiological sources and simulating NDE radiographs.

  6. Simulations of background characteristics of HPGe detectors operating in shallow underground using the Monte Carlo method

    International Nuclear Information System (INIS)

    Monte Carlo codes GEANT 4 and MUSIC have been used to calculate background components of low-level HPGe gamma-ray spectrometers operating in a shallow underground laboratory. The simulated background gamma-ray spectra have been comparable with spectra measured at the Ogoya underground laboratory operating at the depth of 270 m w.e. (water equivalent). The Monte Carlo simulations have proved to be useful approach in estimation of background characteristics of HPGe spectrometers before their construction. (author)

  7. Resolution and intensity in neutron spectrometry determined by Monte Carlo simulation

    DEFF Research Database (Denmark)

    Dietrich, O.W.

    1968-01-01

    The Monte Carlo simulation technique was applied to the propagation of Bragg-reflected neutrons in mosaic single crystals. The method proved to be very useful for the determination of resolution and intensity in neutron spectrometers.......The Monte Carlo simulation technique was applied to the propagation of Bragg-reflected neutrons in mosaic single crystals. The method proved to be very useful for the determination of resolution and intensity in neutron spectrometers....

  8. A geometrical model for the Monte Carlo simulation of the TrueBeam linac

    OpenAIRE

    Rodríguez Niedenführ, Miquel; Sempau Roma, Josep; Fogliata, Antonella; Cozzi, L.; Sauerwein, W.; Brualla, L

    2015-01-01

    Monte Carlo simulation of linear accelerators (linacs) depends on the accurate geometrical description of the linac head. The geometry of the Varian TrueBeam linac is not available to researchers. Instead, the company distributes phase-space files of the flattening-filter-free (FFF) beams tallied at a plane located just upstream of the jaws. Yet, Monte Carlo simulations based on third-party tallied phase spaces are subject to limitations. In this work, an experimentally based geometry develop...

  9. Instantons in Quantum Annealing: Thermally Assisted Tunneling Vs Quantum Monte Carlo Simulations

    Science.gov (United States)

    Jiang, Zhang; Smelyanskiy, Vadim N.; Boixo, Sergio; Isakov, Sergei V.; Neven, Hartmut; Mazzola, Guglielmo; Troyer, Matthias

    2015-01-01

    Recent numerical result (arXiv:1512.02206) from Google suggested that the D-Wave quantum annealer may have an asymptotic speed-up than simulated annealing, however, the asymptotic advantage disappears when it is compared to quantum Monte Carlo (a classical algorithm despite its name). We show analytically that the asymptotic scaling of quantum tunneling is exactly the same as the escape rate in quantum Monte Carlo for a class of problems. Thus, the Google result might be explained in our framework. We also found that the transition state in quantum Monte Carlo corresponds to the instanton solution in quantum tunneling problems, which is observed in numerical simulations.

  10. Monte Carlo molecular simulation of phase-coexistence for oil production and processing

    KAUST Repository

    Li, Jun

    2011-01-01

    The Gibbs-NVT ensemble Monte Carlo method is used to simulate the liquid-vapor coexistence diagram and the simulation results of methane agree well with the experimental data in a wide range of temperatures. For systems with two components, the Gibbs-NPT ensemble Monte Carlo method is employed in the simulation while the mole fraction of each component in each phase is modeled as a Leonard-Jones fluid. As the results of Monte Carlo simulations usually contain huge statistical error, the blocking method is used to estimate the variance of the simulation results. Additionally, in order to improve the simulation efficiency, the step sizes of different trial moves is adjusted automatically so that their acceptance probabilities can approach to the preset values.

  11. Errors associated with metabolic control analysis. Application Of Monte-Carlo simulation of experimental data.

    Science.gov (United States)

    Ainscow, E K; Brand, M D

    1998-09-21

    The errors associated with experimental application of metabolic control analysis are difficult to assess. In this paper, we give examples where Monte-Carlo simulations of published experimental data are used in error analysis. Data was simulated according to the mean and error obtained from experimental measurements and the simulated data was used to calculate control coefficients. Repeating the simulation 500 times allowed an estimate to be made of the error implicit in the calculated control coefficients. In the first example, state 4 respiration of isolated mitochondria, Monte-Carlo simulations based on the system elasticities were performed. The simulations gave error estimates similar to the values reported within the original paper and those derived from a sensitivity analysis of the elasticities. This demonstrated the validity of the method. In the second example, state 3 respiration of isolated mitochondria, Monte-Carlo simulations were based on measurements of intermediates and fluxes. A key feature of this simulation was that the distribution of the simulated control coefficients did not follow a normal distribution, despite simulation of the original data being based on normal distributions. Consequently, the error calculated using simulation was greater and more realistic than the error calculated directly by averaging the original results. The Monte-Carlo simulations are also demonstrated to be useful in experimental design. The individual data points that should be repeated in order to reduce the error in the control coefficients can be highlighted.

  12. Monte Carlo simulation of the seed germination process

    International Nuclear Information System (INIS)

    Paper presented a mathematical model of seed germination process based on the Monte Carlo method and theoretical premises resulted from the physiology of seed germination suggesting three consecutive stages: physical, biochemical and physiological. The model was experimentally verified by determination of germination characteristics for seeds of ground tomatoes, Promyk cultivar, within broad range of temperatures (from 15 to 30 deg C)

  13. Analytical positron range modelling in heterogeneous media for PET Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Lehnert, Wencke; Meikle, Steven R [Discipline of Medical Radiation Sciences, Faculty of Health Sciences, University of Sydney, PO Box 170, Lidcombe NSW 1825 (Australia); Gregoire, Marie-Claude; Reilhac, Anthonin, E-mail: wlehnert@uni.sydney.edu.au [Australian Nuclear Science and Technology Organisation, Lucas Heights NSW 2234 (Australia)

    2011-06-07

    Monte Carlo simulation codes that model positron interactions along their tortuous path are expected to be accurate but are usually slow. A simpler and potentially faster approach is to model positron range from analytical annihilation density distributions. The aims of this paper were to efficiently implement and validate such a method, with the addition of medium heterogeneity representing a further challenge. The analytical positron range model was evaluated by comparing annihilation density distributions with those produced by the Monte Carlo simulator GATE and by quantitatively analysing the final reconstructed images of Monte Carlo simulated data. In addition, the influence of positronium formation on positron range and hence on the performance of Monte Carlo simulation was investigated. The results demonstrate that 1D annihilation density distributions for different isotope-media combinations can be fitted with Gaussian functions and hence be described by simple look-up-tables of fitting coefficients. Together with the method developed for simulating positron range in heterogeneous media, this allows for efficient modelling of positron range in Monte Carlo simulation. The level of agreement of the analytical model with GATE depends somewhat on the simulated scanner and the particular research task, but appears to be suitable for lower energy positron emitters, such as {sup 18}F or {sup 11}C. No reliable conclusion about the influence of positronium formation on positron range and simulation accuracy could be drawn.

  14. Monte Carlo simulation for the electron cascade due to gamma rays in semiconductor radiation detectors

    International Nuclear Information System (INIS)

    A Monte Carlo code was developed for simulating the electron cascade in radiation detector materials. The electron differential scattering cross sections were derived from measured electron energy-loss and optical spectra, making the method applicable for a wide range of materials. The detector resolution in a simplified model system shows dependence on the bandgap, the plasmon strength and energy, and the valence band width. In principle, these parameters could be optimized to improve detector performance. The intrinsic energy resolution was calculated for three semiconductors: silicon (Si), gallium arsenide (GaAs), and zinc telluride (ZnTe). Setting the ionization thresholds for electrons and holes is identified as a critical issue, as this strongly affects both the average electron-hole pair energy w and the Fano factor F. Using an ionization threshold from impact ionization calculations as an effective bandgap yields pair energies that are well matched to measured values. Fano factors of 0.091 (Si), 0.100 (GaAs), and 0.075 (ZnTe) were calculated. The Fano factor calculated for silicon using this model was lower than some results from past simulations and experiments. This difference could be attributed to problems in simulating inter-band transitions and the scattering of low-energy electrons.

  15. Monte Carlo simulation for the electron cascade due to gamma rays in semiconductor radiation detectors

    Energy Technology Data Exchange (ETDEWEB)

    Narayan, Raman D.; Miranda, Ryan; Rez, Peter [Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)

    2012-03-15

    A Monte Carlo code was developed for simulating the electron cascade in radiation detector materials. The electron differential scattering cross sections were derived from measured electron energy-loss and optical spectra, making the method applicable for a wide range of materials. The detector resolution in a simplified model system shows dependence on the bandgap, the plasmon strength and energy, and the valence band width. In principle, these parameters could be optimized to improve detector performance. The intrinsic energy resolution was calculated for three semiconductors: silicon (Si), gallium arsenide (GaAs), and zinc telluride (ZnTe). Setting the ionization thresholds for electrons and holes is identified as a critical issue, as this strongly affects both the average electron-hole pair energy w and the Fano factor F. Using an ionization threshold from impact ionization calculations as an effective bandgap yields pair energies that are well matched to measured values. Fano factors of 0.091 (Si), 0.100 (GaAs), and 0.075 (ZnTe) were calculated. The Fano factor calculated for silicon using this model was lower than some results from past simulations and experiments. This difference could be attributed to problems in simulating inter-band transitions and the scattering of low-energy electrons.

  16. Monte Carlo simulation of radiation streaming from a radioactive material shipping cask

    International Nuclear Information System (INIS)

    Simulated detection of gamma radiation streaming from a radioactive material shipping cask have been performed with the Monte Carlo codes MCNP4A and MORSE-SGC/S. Despite inherent difficulties in simulating deep penetration of radiation and streaming, the simulations have yielded results that agree within one order of magnitude with the radiation survey data, with reasonable statistics. These simulations have also provided insight into modeling radiation detection, notably on location and orientation of the radiation detector with respect to photon streaming paths, and on techniques used to reduce variance in the Monte Carlo calculations. 13 refs., 4 figs., 2 tabs

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-02-15

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

  18. SKIRT: the design of a suite of input models for Monte Carlo radiative transfer simulations

    CERN Document Server

    Baes, Maarten

    2015-01-01

    The Monte Carlo method is the most popular technique to perform radiative transfer simulations in a general 3D geometry. The algorithms behind and acceleration techniques for Monte Carlo radiative transfer are discussed extensively in the literature, and many different Monte Carlo codes are publicly available. On the contrary, the design of a suite of components that can be used for the distribution of sources and sinks in radiative transfer codes has received very little attention. The availability of such models, with different degrees of complexity, has many benefits. For example, they can serve as toy models to test new physical ingredients, or as parameterised models for inverse radiative transfer fitting. For 3D Monte Carlo codes, this requires algorithms to efficiently generate random positions from 3D density distributions. We describe the design of a flexible suite of components for the Monte Carlo radiative transfer code SKIRT. The design is based on a combination of basic building blocks (which can...

  19. PASSATA - Object oriented numerical simulation software for adaptive optics

    CERN Document Server

    Agapito, G; Esposito, S

    2016-01-01

    We present the last version of the PyrAmid Simulator Software for Adaptive opTics Arcetri (PASSATA), an IDL and CUDA based object oriented software developed in the Adaptive Optics group of the Arcetri observatory for Monte-Carlo end-to-end adaptive optics simulations. The original aim of this software was to evaluate the performance of a single conjugate adaptive optics system for ground based telescope with a pyramid wavefront sensor. After some years of development, the current version of PASSATA is able to simulate several adaptive optics systems: single conjugate, multi conjugate and ground layer, with Shack Hartmann and Pyramid wavefront sensors. It can simulate from 8m to 40m class telescopes, with diffraction limited and resolved sources at finite or infinite distance from the pupil. The main advantages of this software are the versatility given by the object oriented approach and the speed given by the CUDA implementation of the most computational demanding routines. We describe the software with its...

  20. Estimation of beryllium ground state energy by Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Kabir, K. M. Ariful [Department of Physical Sciences, School of Engineering and Computer Science, Independent University, Bangladesh (IUB) Dhaka (Bangladesh); Halder, Amal [Department of Mathematics, University of Dhaka Dhaka (Bangladesh)

    2015-05-15

    Quantum Monte Carlo method represent a powerful and broadly applicable computational tool for finding very accurate solution of the stationary Schrödinger equation for atoms, molecules, solids and a variety of model systems. Using variational Monte Carlo method we have calculated the ground state energy of the Beryllium atom. Our calculation are based on using a modified four parameters trial wave function which leads to good result comparing with the few parameters trial wave functions presented before. Based on random Numbers we can generate a large sample of electron locations to estimate the ground state energy of Beryllium. Our calculation gives good estimation for the ground state energy of the Beryllium atom comparing with the corresponding exact data.

  1. Monte Carlo simulations of the Galileo energetic particle detector

    International Nuclear Information System (INIS)

    Monte Carlo radiation transport studies have been performed for the Galileo spacecraft energetic particle detector (EPD) in order to study its response to energetic electrons and protons. Three-dimensional Monte Carlo radiation transport codes, MCNP version 4B (for electrons) and MCNPX version 2.2.3 (for protons), were used throughout the study. The results are presented in the form of 'geometric factors' for the high-energy channels studied in this paper: B1, DC2, and DC3 for electrons and B0, DC0, and DC1 for protons. The geometric factor is the energy-dependent detector response function that relates the incident particle fluxes to instrument count rates. The trend of actual data measured by the EPD was successfully reproduced using the geometric factors obtained in this study

  2. OptogenSIM: a 3D Monte Carlo simulation platform for light delivery design in optogenetics.

    Science.gov (United States)

    Liu, Yuming; Jacques, Steven L; Azimipour, Mehdi; Rogers, Jeremy D; Pashaie, Ramin; Eliceiri, Kevin W

    2015-12-01

    Optimizing light delivery for optogenetics is critical in order to accurately stimulate the neurons of interest while reducing nonspecific effects such as tissue heating or photodamage. Light distribution is typically predicted using the assumption of tissue homogeneity, which oversimplifies light transport in heterogeneous brain. Here, we present an open-source 3D simulation platform, OptogenSIM, which eliminates this assumption. This platform integrates a voxel-based 3D Monte Carlo model, generic optical property models of brain tissues, and a well-defined 3D mouse brain tissue atlas. The application of this platform in brain data models demonstrates that brain heterogeneity has moderate to significant impact depending on application conditions. Estimated light density contours can show the region of any specified power density in the 3D brain space and thus can help optimize the light delivery settings, such as the optical fiber position, fiber diameter, fiber numerical aperture, light wavelength and power. OptogenSIM is freely available and can be easily adapted to incorporate additional brain atlases. PMID:26713200

  3. Missile Electro-Optical Countermeasures Simulation Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — This laboratory comprises several hardware-in-the-loop missile flight simulations designed specifically to evaluate the effectiveness of electro-optical air defense...

  4. Fast and scalable algorithm for the simulation of multiple Mie scattering in optical systems.

    Science.gov (United States)

    Kalthoff, Oliver; Kampmann, Ronald; Streicher, Simon; Sinzinger, Stefan

    2016-05-20

    The Monte Carlo simulation of light propagation in optical systems requires the processing of a large number of photons to achieve a satisfactory statistical accuracy. Based on classical Mie scattering, we experimentally show that the independence of photons propagating through a turbid medium imposes a postulate for a concurrent and scalable programming paradigm of general purpose graphics processing units. This ensures that, without rewriting code, increasingly complex optical systems can be simulated if more processors are available in the future. PMID:27411111

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

    CERN Document Server

    Zaidi, H

    1999-01-01

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

  6. A Method for Estimating Annual Energy Production Using Monte Carlo Wind Speed Simulation

    Directory of Open Access Journals (Sweden)

    Birgir Hrafnkelsson

    2016-04-01

    Full Text Available A novel Monte Carlo (MC approach is proposed for the simulation of wind speed samples to assess the wind energy production potential of a site. The Monte Carlo approach is based on historical wind speed data and reserves the effect of autocorrelation and seasonality in wind speed observations. No distributional assumptions are made, and this approach is relatively simple in comparison to simulation methods that aim at including the autocorrelation and seasonal effects. Annual energy production (AEP is simulated by transforming the simulated wind speed values via the power curve of the wind turbine at the site. The proposed Monte Carlo approach is generic and is applicable for all sites provided that a sufficient amount of wind speed data and information on the power curve are available. The simulated AEP values based on the Monte Carlo approach are compared to both actual AEP and to simulated AEP values based on a modified Weibull approach for wind speed simulation using data from the Burfell site in Iceland. The comparison reveals that the simulated AEP values based on the proposed Monte Carlo approach have a distribution that is in close agreement with actual AEP from two test wind turbines at the Burfell site, while the simulated AEP of the Weibull approach is such that the P50 and the scale are substantially lower and the P90 is higher. Thus, the Weibull approach yields AEP that is not in line with the actual variability in AEP, while the Monte Carlo approach gives a realistic estimate of the distribution of AEP.

  7. Comparing statistical data to Monte Carlo simulation - parameter fitting and unfolding

    International Nuclear Information System (INIS)

    The author presents an introduction to the statistical analysis of experimental data by means of Monte Carlo simulations. After a description of the χ2 test of a hypothesis the least-square and maximum-likelihood fits to Monte Carlo distributions are described. Then unfolding is described. Finally confidence intervals are studied, and the computation of upper and lower limits is discussed from a Bayesian point of view. (HSI)

  8. Catfish: A Monte Carlo simulator for black holes at the LHC

    CERN Document Server

    Cavaglià, M; Cremaldi, L; Summers, D

    2006-01-01

    We present a new Fortran Monte Carlo generator to simulate black hole events at CERN's Large Hadron Collider. The generator interfaces to the PYTHIA Monte Carlo fragmentation code. The physics of the BH generator includes, but not limited to, inelasticity effects, exact field emissivities, corrections to semiclassical black hole evaporation and gravitational energy loss at formation. These features are essential to realistically reconstruct the detector response and test different models of black hole formation and decay at the LHC.

  9. Catfish: A Monte Carlo simulator for black holes at the LHC

    Science.gov (United States)

    Cavaglià, M.; Godang, R.; Cremaldi, L.; Summers, D.

    2007-09-01

    We present a new Fortran Monte Carlo generator to simulate black hole events at CERN's Large Hadron Collider. The generator interfaces to the PYTHIA Monte Carlo fragmentation code. The physics of the BH generator includes, but not limited to, inelasticity effects, exact field emissivities, corrections to semiclassical black hole evaporation and gravitational energy loss at formation. These features are essential to realistically reconstruct the detector response and test different models of black hole formation and decay at the LHC.

  10. MOCRA: a Monte Carlo code for the simulation of radiative transfer in the atmosphere.

    Science.gov (United States)

    Premuda, Margherita; Palazzi, Elisa; Ravegnani, Fabrizio; Bortoli, Daniele; Masieri, Samuele; Giovanelli, Giorgio

    2012-03-26

    This paper describes the radiative transfer model (RTM) MOCRA (MOnte Carlo Radiance Analysis), developed in the frame of DOAS (Differential Optical Absorption Spectroscopy) to correctly interpret remote sensing measurements of trace gas amounts in the atmosphere through the calculation of the Air Mass Factor. Besides the DOAS-related quantities, the MOCRA code yields: 1- the atmospheric transmittance in the vertical and sun directions, 2- the direct and global irradiance, 3- the single- and multiple- scattered radiance for a detector with assigned position, line of sight and field of view. Sample calculations of the main radiometric quantities calculated with MOCRA are presented and compared with the output of another RTM (MODTRAN4). A further comparison is presented between the NO2 slant column densities (SCDs) measured with DOAS at Evora (Portugal) and the ones simulated with MOCRA. Both comparisons (MOCRA-MODTRAN4 and MOCRA-observations) gave more than satisfactory results, and overall make MOCRA a versatile tool for atmospheric radiative transfer simulations and interpretation of remote sensing measurements. PMID:22453470

  11. Massively parallel Monte Carlo. Experiences running nuclear simulations on a large condor cluster

    International Nuclear Information System (INIS)

    The trivially-parallel nature of Monte Carlo (MC) simulations make them ideally suited for running on a distributed, heterogeneous computing environment. We report on the setup and operation of a large, cycle-harvesting Condor computer cluster, used to run MC simulations of nuclear instruments ('jobs') on approximately 4,500 desktop PCs. Successful operation must balance the competing goals of maximizing the availability of machines for running jobs whilst minimizing the impact on users' PC performance. This requires classification of jobs according to anticipated run-time and priority and careful optimization of the parameters used to control job allocation to host machines. To maximize use of a large Condor cluster, we have created a powerful suite of tools to handle job submission and analysis, as the manual creation, submission and evaluation of large numbers (hundred to thousands) of jobs would be too arduous. We describe some of the key aspects of this suite, which has been interfaced to the well-known MCNP and EGSnrc nuclear codes and our in-house PHOTON optical MC code. We report on our practical experiences of operating our Condor cluster and present examples of several large-scale instrument design problems that have been solved using this tool. (author)

  12. Monte Carlo simulations of H2 formation on stochastically heated grains

    CERN Document Server

    Cuppen, H M; Morata, O; Herbst, Eric

    2006-01-01

    Continuous-time, random-walk Monte Carlo simulations of H2 formation on grains have been performed for surfaces that are stochastically heated by photons. We have assumed diffuse cloud conditions and used a variety of grains of varying roughness and size based on olivine. The simulations were performed at different optical depths. We confirmed that small grains (r <= 0.02 micron) have low modal temperatures with strong fluctuations, which have a large effect on the efficiency of the formation of molecular hydrogen. The grain size distribution highly favours small grains and therefore H2 formation on these particles makes a large contribution to the overall formation rate for all but the roughest surfaces. We find that at A_V=0 only the roughest surfaces can produce the required amount of molecular hydrogen, but by A_V=1, smoother surfaces are possible alternatives. Use of a larger value for the evaporation energy of atomic hydrogen, but one still consistent with experiment, allows smoother surfaces to prod...

  13. Public repository with Monte Carlo simulations for high-energy particle collision experiments

    CERN Document Server

    Chekanov, S V

    2016-01-01

    Planning high-energy collision experiments for the next few decades requires extensive Monte Carlo simulations in order to accomplish physics goals of these experiments. Such simulations are essential for understanding fundamental physics processes, as well as for setting up the detector parameters that help establish R&D projects required over the next few decades. This paper describes a public repository with Monte Carlo event samples before and after detector-response simulation. The goal of this repository is to facilitate the accomplishment of many goals in planning a next generation of particle experiments.

  14. Monte Carlo simulations of dense gas flow and heat transfer in micro- and nano-channels

    Institute of Scientific and Technical Information of China (English)

    WANG; Moran; LI; Zhixin

    2005-01-01

    The dense gas flow and heat transfer in micro- and nano-channels was simulated using the Enskog simulation Monte Carlo (ESMC) method. The results were compared with those from the direct simulation Monte Carlo (DSMC) method and from the consistent Boltzmann algorithm (CBA). The dense gas flow and heat transfer characteristics were thus analyzed. The results showed that when the gas density was large enough, the finite gas density effect on the flow and heat transfer cannot be ignored, which decreased the skin friction coefficient and changed the heat transfer characteristics on the channel wall surfaces.

  15. Introducing CFD in the optical simulation of linear Fresnel collectors

    Science.gov (United States)

    Moghimi, M. A.; Rungasamy, A.; Craig, K. J.; Meyer, J. P.

    2016-05-01

    This paper seeks to determine whether the Finite Volume method within a commercially available Computational Fluid Dynamics (CFD) solver (ANSYS Fluent) can model radiation with comparable accuracy to a Monte Carlo ray-tracing software package (SolTrace). A detailed investigation was performed into modeling techniques that can be used to significantly reduce the optical errors traditionally associated with CFD modeling of radiation false scattering and ray effect using a simple optical test case. The strategies formulated in the first part of this paper were used to model a variety of Linear Fresnel Collector Concentrating Solar Power Plants. This paper shows that commercial CFD packages yield accurate results for line focusing concentrating solar applications and simple geometries, validating its use in an integrated environment where both optical and thermal performance of these plants can be simulated and optimized.

  16. Numerical investigation of turbomolecular pumps using the direct simulation Monte Carlo method with moving surfaces

    NARCIS (Netherlands)

    Versluis, R.; Dorsman, R.; Thielen, L.; Roos, M.E.

    2009-01-01

    A new approach for performing numerical direct simulation Monte Carlo (DSMC) simulations on turbomolecular pumps in the free molecular and transitional flow regimes is described. The chosen approach is to use surfaces that move relative to the grid to model the effect of rotors and stators on a gas

  17. Monte Carlo simulations to advance characterisation of landmines by pulsed fast/thermal neutron analysis

    NARCIS (Netherlands)

    Maucec, M.; Rigollet, C.

    2004-01-01

    The performance of a detection system based on the pulsed fast/thermal neutron analysis technique was assessed using Monte Carlo simulations. The aim was to develop and implement simulation methods, to support and advance the data analysis techniques of the characteristic gamma-ray spectra, potentia

  18. Monte Carlo simulations of the stability of delta-Pu

    DEFF Research Database (Denmark)

    Landa, A.; Soderlind, P.; Ruban, Andrei

    2003-01-01

    The transition temperature (T-c) for delta-Pu has been calculated for the first time. A Monte Carlo method is employed for this purpose and the effective cluster interactions are obtained from first-principles calculations incorporated with the Connolly-Williams and generalized perturbation methods....... It is found that at T-c similar to 548 K, delta-Pu undergoes transformation from a disordered magnetic state to a structure with an anti ferromagnetic spin alignment that is mechanically unstable with respect to tetragonal distortion. The calculated transition temperature is in good agreement...

  19. Fluid Simulations with Localized Boltzmann Upscaling by Direct Simulation Monte-Carlo

    CERN Document Server

    Degond, Pierre

    2010-01-01

    In the present work, we present a novel numerical algorithm to couple the Direct Simulation Monte Carlo method (DSMC) for the solution of the Boltzmann equation with a finite volume like method for the solution of the Euler equations. Recently we presented in [14],[16],[17] different methodologies which permit to solve fluid dynamics problems with localized regions of departure from thermodynamical equilibrium. The methods rely on the introduction of buffer zones which realize a smooth transition between the kinetic and the fluid regions. In this paper we extend the idea of buffer zones and dynamic coupling to the case of the Monte Carlo methods. To facilitate the coupling and avoid the onset of spurious oscillations in the fluid regions which are consequences of the coupling with a stochastic numerical scheme, we use a new technique which permits to reduce the variance of the particle methods [11]. In addition, the use of this method permits to obtain estimations of the breakdowns of the fluid models less af...

  20. Non-analogue Monte Carlo method, application to neutron simulation; Methode de Monte Carlo non analogue, application a la simulation des neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Morillon, B.

    1996-12-31

    With most of the traditional and contemporary techniques, it is still impossible to solve the transport equation if one takes into account a fully detailed geometry and if one studies precisely the interactions between particles and matters. Only the Monte Carlo method offers such a possibility. However with significant attenuation, the natural simulation remains inefficient: it becomes necessary to use biasing techniques where the solution of the adjoint transport equation is essential. The Monte Carlo code Tripoli has been using such techniques successfully for a long time with different approximate adjoint solutions: these methods require from the user to find out some parameters. If this parameters are not optimal or nearly optimal, the biases simulations may bring about small figures of merit. This paper presents a description of the most important biasing techniques of the Monte Carlo code Tripoli ; then we show how to calculate the importance function for general geometry with multigroup cases. We present a completely automatic biasing technique where the parameters of the biased simulation are deduced from the solution of the adjoint transport equation calculated by collision probabilities. In this study we shall estimate the importance function through collision probabilities method and we shall evaluate its possibilities thanks to a Monte Carlo calculation. We compare different biased simulations with the importance function calculated by collision probabilities for one-group and multigroup problems. We have run simulations with new biasing method for one-group transport problems with isotropic shocks and for multigroup problems with anisotropic shocks. The results show that for the one-group and homogeneous geometry transport problems the method is quite optimal without splitting and russian roulette technique but for the multigroup and heterogeneous X-Y geometry ones the figures of merit are higher if we add splitting and russian roulette technique.

  1. Simulation study of transverse optical klystron radiation

    Institute of Scientific and Technical Information of China (English)

    XuHong-Liang; DiaoCao-Zheng; 等

    1997-01-01

    The radiation from a transverse optical klystron(TOK) is calculated by far field approximation and numerical integration,in which the effects of electron-beam emittance and energy spread are considered.Accurate electron-beam profiles have been experimentally determined and modeled by the Monte Carlo method.The calculated spectra illustrate the emittance of Hefei storage ring imposes on the spontaneous radiation of TOK.

  2. Spatial distribution of reflected gamma rays by Monte Carlo simulation

    International Nuclear Information System (INIS)

    In nuclear facilities, the reflection of gamma rays of the walls and metals constitutes an unknown origin of radiation. These reflected gamma rays must be estimated and determined. This study concerns reflected gamma rays on metal slabs. We evaluated the spatial distribution of the reflected gamma rays spectra by using the Monte Carlo method. An appropriate estimator for the double differential albedo is used to determine the energy spectra and the angular distribution of reflected gamma rays by slabs of iron and aluminium. We took into the account the principal interactions of gamma rays with matter: photoelectric, coherent scattering (Rayleigh), incoherent scattering (Compton) and pair creation. The Klein-Nishina differential cross section was used to select direction and energy of scattered photons after each Compton scattering. The obtained spectra show peaks at 0.511* MeV for higher source energy. The Results are in good agreement with those obtained by the TRIPOLI code [J.C. Nimal et al., TRIPOLI02: Programme de Monte Carlo Polycinsetique a Trois dimensions, CEA Rapport, Commissariat a l'Energie Atomique.

  3. Spatial distribution of reflected gamma rays by Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Jehouani, A. [LPTN, Departement de Physique, Faculte des Sciences Semlalia, B.P. 2390, 40000 Marrakech (Morocco)], E-mail: jehouani@ucam.ac.ma; Merzouki, A. [LPTN, Departement de Physique, Faculte des Sciences Semlalia, B.P. 2390, 40000 Marrakech (Morocco); Remote Sensing and Geomatics of the Environment Laboratory, Ottawa-Carleton Geoscience Centre, Marion Hall, 140 Louis Pasteur, Ottawa, ON, KIN 6N5 (Canada); Boutadghart, F.; Ghassoun, J. [LPTN, Departement de Physique, Faculte des Sciences Semlalia, B.P. 2390, 40000 Marrakech (Morocco)

    2007-10-15

    In nuclear facilities, the reflection of gamma rays of the walls and metals constitutes an unknown origin of radiation. These reflected gamma rays must be estimated and determined. This study concerns reflected gamma rays on metal slabs. We evaluated the spatial distribution of the reflected gamma rays spectra by using the Monte Carlo method. An appropriate estimator for the double differential albedo is used to determine the energy spectra and the angular distribution of reflected gamma rays by slabs of iron and aluminium. We took into the account the principal interactions of gamma rays with matter: photoelectric, coherent scattering (Rayleigh), incoherent scattering (Compton) and pair creation. The Klein-Nishina differential cross section was used to select direction and energy of scattered photons after each Compton scattering. The obtained spectra show peaks at 0.511{sup *} MeV for higher source energy. The Results are in good agreement with those obtained by the TRIPOLI code [J.C. Nimal et al., TRIPOLI02: Programme de Monte Carlo Polycinsetique a Trois dimensions, CEA Rapport, Commissariat a l'Energie Atomique. ].

  4. Spatial distribution of reflected gamma rays by Monte Carlo simulation

    Science.gov (United States)

    Jehouani, A.; Merzouki, A.; Boutadghart, F.; Ghassoun, J.

    2007-10-01

    In nuclear facilities, the reflection of gamma rays of the walls and metals constitutes an unknown origin of radiation. These reflected gamma rays must be estimated and determined. This study concerns reflected gamma rays on metal slabs. We evaluated the spatial distribution of the reflected gamma rays spectra by using the Monte Carlo method. An appropriate estimator for the double differential albedo is used to determine the energy spectra and the angular distribution of reflected gamma rays by slabs of iron and aluminium. We took into the account the principal interactions of gamma rays with matter: photoelectric, coherent scattering (Rayleigh), incoherent scattering (Compton) and pair creation. The Klein-Nishina differential cross section was used to select direction and energy of scattered photons after each Compton scattering. The obtained spectra show peaks at 0.511∗ MeV for higher source energy. The Results are in good agreement with those obtained by the TRIPOLI code [J.C. Nimal et al., TRIPOLI02: Programme de Monte Carlo Polycinśetique à Trois dimensions, CEA Rapport, Commissariat à l'Energie Atomique. [1

  5. Worm Algorithm and Diagrammatic Monte Carlo: A New Approach to Continuous-Space Path Integral Monte Carlo Simulations

    CERN Document Server

    Boninsegni, M; Svistunov, B V

    2006-01-01

    A detailed description is provided of a new Worm Algorithm, enabling the accurate computation of thermodynamic properties of quantum many-body systems in continuous space, at finite temperature. The algorithm is formulated within the general Path Integral Monte Carlo (PIMC) scheme, but also allows one to perform quantum simulations in the grand canonical ensemble, as well as to compute off-diagonal imaginary-time correlation functions, such as the Matsubara Green function, simultaneously with diagonal observables. Another important innovation consists of the expansion of the attractive part of the pairwise potential energy into elementary (diagrammatic) contributions, which are then statistically sampled. This affords a complete microscopic account of the long-range part of the potential energy, while keeping the computational complexity of all updates independent of the size of the simulated system. The computational scheme allows for efficient calculations of the superfluid fraction and off-diagonal correla...

  6. Reliability Assessment of Ultrasonic Nondestructive Inspection Data Using Monte Carlo Simulation

    Science.gov (United States)

    Park, Ik-Keun; Kim, Hyun-Mook

    2003-03-01

    Ultrasonic NDE is one of important technologies in the life-time maintenance of nuclear power plant. Ultrasonic inspection system is consisted of the operator, equipment and procedure. The reliability of ultrasonic inspection system is affected by its ability. The performance demonstration round robin was conducted to quantify the capability of ultrasonic inspection for in-service. The small number of teams who employed procedures that met or exceeded ASME Sec. XI Code requirements detected the piping of nuclear power plant with various cracks to evaluate the capability of detection and sizing. In this paper, the statistical reliability assessment of ultrasonic nondestructive inspection data using Monte Carlo simulation is presented. The results of the probability of detection (POD) analysis using Monte Carlo simulation are compared to these of logistic probability model. In these results, Monte Carlo simulation was found to be very useful to the reliability assessment for the small NDE hit/miss data sets.

  7. In silico radiobiology: Have we reached the limit of Monte Carlo simulations?

    International Nuclear Information System (INIS)

    Monte Carlo radiation transport models are increasingly being used to simulate biological damage. However, such radiation biophysics simulations require realistic molecular models for water, whereas existing Monte Carlo models are limited by their use of atomic cross-sections, which become inadequate for accurately modelling interactions of the very low-energy electrons that are responsible for biological damage. In this study, we borrow theoretical methods commonly employed in molecular dynamics simulations to model the molecular wavefunction of the water molecule as the first step towards deriving new molecular cross-sections. We calculate electron charge distributions for molecular water and find non-negligible differences between the vapor and liquid phases that can be attributed to intermolecular bonding in the condensed phase. We propose that a hybrid Monte Carlo – Molecular Dynamics (MC-MD) approach to modelling radiation biophysics will provide new insights into radiation damage and new opportunities to develop targeted molecular therapy strategies.

  8. Data decomposition of Monte Carlo particle transport simulations via tally servers

    Energy Technology Data Exchange (ETDEWEB)

    Romano, Paul K., E-mail: paul.k.romano@gmail.com [Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 77 Massachusetts Ave., Cambridge, MA 02139 (United States); Siegel, Andrew R., E-mail: siegala@mcs.anl.gov [Argonne National Laboratory, Theory and Computing Sciences, 9700 S Cass Ave., Argonne, IL 60439 (United States); Forget, Benoit, E-mail: bforget@mit.edu [Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 77 Massachusetts Ave., Cambridge, MA 02139 (United States); Smith, Kord, E-mail: kord@mit.edu [Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 77 Massachusetts Ave., Cambridge, MA 02139 (United States)

    2013-11-01

    An algorithm for decomposing large tally data in Monte Carlo particle transport simulations is developed, analyzed, and implemented in a continuous-energy Monte Carlo code, OpenMC. The algorithm is based on a non-overlapping decomposition of compute nodes into tracking processors and tally servers. The former are used to simulate the movement of particles through the domain while the latter continuously receive and update tally data. A performance model for this approach is developed, suggesting that, for a range of parameters relevant to LWR analysis, the tally server algorithm should perform with minimal overhead on contemporary supercomputers. An implementation of the algorithm in OpenMC is then tested on the Intrepid and Titan supercomputers, supporting the key predictions of the model over a wide range of parameters. We thus conclude that the tally server algorithm is a successful approach to circumventing classical on-node memory constraints en route to unprecedentedly detailed Monte Carlo reactor simulations.

  9. In silico radiobiology: Have we reached the limit of Monte Carlo simulations?

    Science.gov (United States)

    Gholami, Y.; Toghyani, M.; Champion, C.; Kuncic, Z.

    2014-03-01

    Monte Carlo radiation transport models are increasingly being used to simulate biological damage. However, such radiation biophysics simulations require realistic molecular models for water, whereas existing Monte Carlo models are limited by their use of atomic cross-sections, which become inadequate for accurately modelling interactions of the very low-energy electrons that are responsible for biological damage. In this study, we borrow theoretical methods commonly employed in molecular dynamics simulations to model the molecular wavefunction of the water molecule as the first step towards deriving new molecular cross-sections. We calculate electron charge distributions for molecular water and find non-negligible differences between the vapor and liquid phases that can be attributed to intermolecular bonding in the condensed phase. We propose that a hybrid Monte Carlo - Molecular Dynamics (MC-MD) approach to modelling radiation biophysics will provide new insights into radiation damage and new opportunities to develop targeted molecular therapy strategies.

  10. Monte-Carlo modelling of multi-object adaptive optics performance on the European Extremely Large Telescope

    Science.gov (United States)

    Basden, A. G.; Morris, T. J.

    2016-09-01

    The performance of a wide-field adaptive optics system depends on input design parameters. Here we investigate the performance of a multi-object adaptive optics system design for the European Extremely Large Telescope, using an end-to-end Monte-Carlo adaptive optics simulation tool, DASP, with relevance for proposed instruments such as MOSAIC. We consider parameters such as the number of laser guide stars, sodium layer depth, wavefront sensor pixel scale, actuator pitch and natural guide star availability. We provide potential areas where costs savings can be made, and investigate trade-offs between performance and cost, and provide solutions that would enable such an instrument to be built with currently available technology. Our key recommendations include a trade-off for laser guide star wavefront sensor pixel scale of about 0.7 arcseconds per pixel, and a field of view of at least 7 arcseconds, that EMCCD technology should be used for natural guide star wavefront sensors even if reduced frame rate is necessary, and that sky coverage can be improved by a slight reduction in natural guide star sub-aperture count without significantly affecting tomographic performance. We find that adaptive optics correction can be maintained across a wide field of view, up to 7 arcminutes in diameter. We also recommend the use of at least 4 laser guide stars, and include ground-layer and multi-object adaptive optics performance estimates.

  11. An Efficient Approach to Ab Initio Monte Carlo Simulation

    CERN Document Server

    Leiding, Jeff

    2013-01-01

    We present a Nested Markov Chain Monte Carlo (NMC) scheme for building equilibrium averages based on accurate potentials such as density functional theory. Metropolis sampling of a reference system, defined by an inexpensive but approximate potential, is used to substantially decorrelate configurations at which the potential of interest is evaluated, thereby dramatically reducing the number needed to build ensemble averages at a given level of precision. The efficiency of this procedure is maximized on-the-fly through variation of the reference system thermodynamic state (characterized here by its inverse temperature \\beta^0), which is otherwise unconstrained. Local density approximation (LDA) results are presented for shocked states in argon at pressures from 4 to 60 GPa. Depending on the quality of the reference potential, the acceptance probability is enhanced by factors of 1.2-28 relative to unoptimized NMC sampling, and the procedure's efficiency is found to be competitive with that of standard ab initio...

  12. Titrating Polyelectrolytes - Variational Calculations and Monte Carlo Simulations

    CERN Document Server

    Jönsson, B; Peterson, C; Sommelius, O; Söderberg, B

    1995-01-01

    Variational methods are used to calculate structural and thermodynamical properties of a titrating polyelectrolyte in a discrete representation. The Coulomb interactions are emulated by harmonic repulsive forces, the force constants being used as variational parameters to minimize the free energy. For the titrating charges, a mean field approach is used. The accuracy is tested against Monte Carlo data for up to 1000 monomers. For an unscreened chain, excellent agreement is obtained for the end-to-end distance and the apparent dissociation constant. With screening, the thermodynamical properties are invariably well described, although the structural agreement deteriorates. A very simple rigid-rod approximation is also considered, giving surprisingly good results for certain properties.

  13. Dynamic Partitioning of GATE Monte-Carlo Simulations on EGEE

    CERN Document Server

    Camarasu-Pop, S; Benoit-Cattin, Hugues; Glatard, Tristan; Sarrut, David; Camarasu-Pop, Sorina

    2010-01-01

    The EGEE Grid offers the necessary infrastructure and resources for reducing the running time of particle tracking Monte-Carlo applications like GATE. However, efforts are required to achieve reliable and efficient execution and to provide execution frameworks to end-users. This paper presents results obtained with porting the GATE software on the EGEE Grid, our ultimate goal being to provide reliable, user-friendly and fast execution of GATE to radiation therapy researchers. To address these requirements, we propose a new parallelization scheme based on a dynamic partitioning and its implementation in two different frameworks using pilot jobs and workflows. Results show that pilot jobs bring strong improvement w.r.t. regular gLite submission, that the proposed dynamic partitioning algorithm further reduces execution time by a factor of two and that the genericity and user-friendliness offered by the workflow implementation do not introduce significant overhead.

  14. New methods for the Monte Carlo simulation of neutron noise experiments in Ads

    International Nuclear Information System (INIS)

    This paper presents two improvements to speed up the Monte-Carlo simulation of neutron noise experiments. The first one is to separate the actual Monte Carlo transport calculation from the digital signal processing routines, while the second is to introduce non-analogue techniques to improve the efficiency of the Monte Carlo calculation. For the latter method, adaptations to the theory of neutron noise experiments were made to account for the distortion of the higher-moments of the calculated neutron noise. Calculations were performed to test the feasibility of the above outlined scheme and to demonstrate the advantages of the application of the track length estimator. It is shown that the modifications improve the efficiency of these calculations to a high extent, which turns the Monte Carlo method into a powerful tool for the development and design of on-line reactivity measurement systems for ADS

  15. PENELOPE, an algorithm and computer code for Monte Carlo simulation of electron-photon showers

    International Nuclear Information System (INIS)

    The FORTRAN 77 subroutine package PENELOPE performs Monte Carlo simulation of electron-photon showers in arbitrary for a wide energy range, from 1 keV to several hundred MeV. Photon transport is simulated by means of the standard, detailed simulation scheme. Electron and positron histories are generated on the basis of a mixed procedure, which combines detailed simulation of hard events with condensed simulation of soft interactions. A simple geometry package permits the generation of random electron-photon showers in material systems consisting of homogeneous bodies limited by quadric surfaces, i.e. planes, spheres, cylinders, etc. This report is intended not only to serve as a manual of the simulation package, but also to provide the user with the necessary information to understand the details of the Monte Carlo algorithm. (Author) 108 refs

  16. Combining cellular automata and Monte Carlo algorithm to simulate three-dimensional grain growth

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; CHEN Ju-hua; GUO Pei-quan; ZHAO Ping

    2006-01-01

    A 3-D simulation of grain growth was conducted by utilizing cellular automata (CA) and Monte Carlo (MC) algorithm. In the simulating procedure, the three-dimensional space is divided into a large number of 2-D isometric planes. Then, each of the planes is divided into identical square cells. Finally, the cellular automata and Monte Carlo algorithm are combined together to simulate the grain growth. Through an evolutionary simulation, the recrystallized microstructure, the grain growth rate and the grain size distribution are acceptably predicted. The simulation routine can be used to simulate the real physical-metallurgy processes and to predict quantitative dynamic information of the evolution of microstructure. Further more, the method is also useful for optimization of materials properties by controlling the microstructure evolution.

  17. PENELOPE, an algorithm and computer code for Monte Carlo simulation of electron-photon showers

    Energy Technology Data Exchange (ETDEWEB)

    Salvat, F.; Fernandez-Varea, J.M.; Baro, J.; Sempau, J.

    1996-07-01

    The FORTRAN 77 subroutine package PENELOPE performs Monte Carlo simulation of electron-photon showers in arbitrary for a wide energy range, from 1 keV to several hundred MeV. Photon transport is simulated by means of the standard, detailed simulation scheme. Electron and positron histories are generated on the basis of a mixed procedure, which combines detailed simulation of hard events with condensed simulation of soft interactions. A simple geometry package permits the generation of random electron-photon showers in material systems consisting of homogeneous bodies limited by quadric surfaces, i.e. planes, spheres, cylinders, etc. This report is intended not only to serve as a manual of the simulation package, but also to provide the user with the necessary information to understand the details of the Monte Carlo algorithm. (Author) 108 refs.

  18. Three Dimension Monte Carlo Simulation of Austenite Grain Growth in CGHAZ of an Ultrafine Grain Steel

    Institute of Scientific and Technical Information of China (English)

    Dong CHEN; Yongping LEI; Xiaoyan LI; Yaowu SHI; Zhiling TIAN

    2003-01-01

    In the present research Monte Carlo technique was used to simulate the grain growth in heat-affected zone(HAZ) of an ultrafine grain steel. An experimental data based (EBD) model proposed by Gao was used to establish the relation between tMCS and real time temperature kinetics in our simulation. The simulations give out the evolution of grain structure and grain size distribution in HAZ of the ultrafine grain steel. A Microsoft Window based on computer program for the simulation of grain growth in the HAZ of weldment in three dimensions has been developed using Monte Carlo technique. For the system, inputting the temperature field data and material properties, the evolution of grain structure, both image of simulated grain structure and numerical datum reflecting grain size distribution can be produced by the program. The system was applied to the ultrafine grain steel welding, and the simulated results show that the ultrafine grain steel has large tendency of grain growth.

  19. Fast Monte Carlo inversion for extracting the optical properties of tubular tissues

    Institute of Scientific and Technical Information of China (English)

    Huijuan Zhao; Xiaoqing Zhou; Julan Liang; Shunqi Zhang

    2008-01-01

    Reconstruction of absorption coefficient μa and scattering coefficient μs is very important for applications of diffuse optical tomography and near infrared spectroscopy. Aiming at the early cancer detection of cervix and stomach, we present a fast inverse Monte-Carlo scheme for extracting μa and μs of a tubular tissue from the measurement on frequency domain. Results show that the computation time for reconstructing one set of μa and μs is less than 1 rain and the relative errors in reconstruction axe less than ±10% for the optical properties of normal cervical tissue and precancerous lesions.

  20. CloudMC: a cloud computing application for Monte Carlo simulation.

    Science.gov (United States)

    Miras, H; Jiménez, R; Miras, C; Gomà, C

    2013-04-21

    This work presents CloudMC, a cloud computing application-developed in Windows Azure®, the platform of the Microsoft® cloud-for the parallelization of Monte Carlo simulations in a dynamic virtual cluster. CloudMC is a web application designed to be independent of the Monte Carlo code in which the simulations are based-the simulations just need to be of the form: input files → executable → output files. To study the performance of CloudMC in Windows Azure®, Monte Carlo simulations with penelope were performed on different instance (virtual machine) sizes, and for different number of instances. The instance size was found to have no effect on the simulation runtime. It was also found that the decrease in time with the number of instances followed Amdahl's law, with a slight deviation due to the increase in the fraction of non-parallelizable time with increasing number of instances. A simulation that would have required 30 h of CPU on a single instance was completed in 48.6 min when executed on 64 instances in parallel (speedup of 37 ×). Furthermore, the use of cloud computing for parallel computing offers some advantages over conventional clusters: high accessibility, scalability and pay per usage. Therefore, it is strongly believed that cloud computing will play an important role in making Monte Carlo dose calculation a reality in future clinical practice.

  1. CloudMC: a cloud computing application for Monte Carlo simulation

    International Nuclear Information System (INIS)

    This work presents CloudMC, a cloud computing application—developed in Windows Azure®, the platform of the Microsoft® cloud—for the parallelization of Monte Carlo simulations in a dynamic virtual cluster. CloudMC is a web application designed to be independent of the Monte Carlo code in which the simulations are based—the simulations just need to be of the form: input files → executable → output files. To study the performance of CloudMC in Windows Azure®, Monte Carlo simulations with penelope were performed on different instance (virtual machine) sizes, and for different number of instances. The instance size was found to have no effect on the simulation runtime. It was also found that the decrease in time with the number of instances followed Amdahl's law, with a slight deviation due to the increase in the fraction of non-parallelizable time with increasing number of instances. A simulation that would have required 30 h of CPU on a single instance was completed in 48.6 min when executed on 64 instances in parallel (speedup of 37 ×). Furthermore, the use of cloud computing for parallel computing offers some advantages over conventional clusters: high accessibility, scalability and pay per usage. Therefore, it is strongly believed that cloud computing will play an important role in making Monte Carlo dose calculation a reality in future clinical practice. (note)

  2. Backscattered radiation into a transmission ionization chamber: measurement and Monte Carlo simulation.

    Science.gov (United States)

    Yoshizumi, Maíra T; Yoriyaz, Hélio; Caldas, Linda V E

    2010-01-01

    Backscattered radiation (BSR) from field-defining collimators can affect the response of a monitor chamber in X-radiation fields. This contribution must be considered since this kind of chamber is used to monitor the equipment response. In this work, the dependence of a transmission ionization chamber response on the aperture diameter of the collimators was studied experimentally and using a Monte Carlo (MC) technique. According to the results, the BSR increases the chamber response of over 4.0% in the case of a totally closed collimator and 50 kV energy beam, using both techniques. The results from Monte Carlo simulation confirm the validity of the simulated geometry.

  3. Instability in the Molecular Dynamics Step of Hybrid Monte Carlo in Dynamical Fermion Lattice QCD Simulations

    CERN Document Server

    Joó, B; Kennedy, A D; Irving, A C; Sexton, J C; Pickles, S M; Booth, S P; Joo, Balint; Pendleton, Brian; Kennedy, Anthony D.; Irving, Alan C.; Sexton, James C.; Pickles, Stephen M.; Booth, Stephen P.

    2000-01-01

    We investigate instability and reversibility within Hybrid Monte Carlo simulations using a non-perturbatively improved Wilson action. We demonstrate the onset of instability as tolerance parameters and molecular dynamics step sizes are varied. We compare these findings with theoretical expectations and present limits on simulation parameters within which a stable and reversible algorithm is obtained for physically relevant simulations. Results of optimisation experiments with respect to tolerance prarameters are also presented.

  4. Particle behavior simulation in thermophoresis phenomena by direct simulation Monte Carlo method

    Science.gov (United States)

    Wada, Takao

    2014-07-01

    A particle motion considering thermophoretic force is simulated by using direct simulation Monte Carlo (DSMC) method. Thermophoresis phenomena, which occur for a particle size of 1 μm, are treated in this paper. The problem of thermophoresis simulation is computation time which is proportional to the collision frequency. Note that the time step interval becomes much small for the simulation considering the motion of large size particle. Thermophoretic forces calculated by DSMC method were reported, but the particle motion was not computed because of the small time step interval. In this paper, the molecule-particle collision model, which computes the collision between a particle and multi molecules in a collision event, is considered. The momentum transfer to the particle is computed with a collision weight factor, where the collision weight factor means the number of molecules colliding with a particle in a collision event. The large time step interval is adopted by considering the collision weight factor. Furthermore, the large time step interval is about million times longer than the conventional time step interval of the DSMC method when a particle size is 1 μm. Therefore, the computation time becomes about one-millionth. We simulate the graphite particle motion considering thermophoretic force by DSMC-Neutrals (Particle-PLUS neutral module) with above the collision weight factor, where DSMC-Neutrals is commercial software adopting DSMC method. The size and the shape of the particle are 1 μm and a sphere, respectively. The particle-particle collision is ignored. We compute the thermophoretic forces in Ar and H2 gases of a pressure range from 0.1 to 100 mTorr. The results agree well with Gallis' analytical results. Note that Gallis' analytical result for continuum limit is the same as Waldmann's result.

  5. MONTE CARLO METHOD AND APPLICATION IN @RISK SIMULATION SYSTEM

    Directory of Open Access Journals (Sweden)

    Gabriela Ižaríková

    2015-12-01

    Full Text Available The article is an example of using the software simulation @Risk designed for simulation in Microsoft Excel spread sheet, demonstrated the possibility of its usage in order to show a universal method of solving problems. The simulation is experimenting with computer models based on the real production process in order to optimize the production processes or the system. The simulation model allows performing a number of experiments, analysing them, evaluating, optimizing and afterwards applying the results to the real system. A simulation model in general is presenting modelling system by using mathematical formulations and logical relations. In the model is possible to distinguish controlled inputs (for instance investment costs and random outputs (for instance demand, which are by using a model transformed into outputs (for instance mean value of profit. In case of a simulation experiment at the beginning are chosen controlled inputs and random (stochastic outputs are generated randomly. Simulations belong into quantitative tools, which can be used as a support for a decision making.

  6. Monte Carlo simulation of photon migration in a cloud computing environment with MapReduce.

    Science.gov (United States)

    Pratx, Guillem; Xing, Lei

    2011-12-01

    Monte Carlo simulation is considered the most reliable method for modeling photon migration in heterogeneous media. However, its widespread use is hindered by the high computational cost. The purpose of this work is to report on our implementation of a simple MapReduce method for performing fault-tolerant Monte Carlo computations in a massively-parallel cloud computing environment. We ported the MC321 Monte Carlo package to Hadoop, an open-source MapReduce framework. In this implementation, Map tasks compute photon histories in parallel while a Reduce task scores photon absorption. The distributed implementation was evaluated on a commercial compute cloud. The simulation time was found to be linearly dependent on the number of photons and inversely proportional to the number of nodes. For a cluster size of 240 nodes, the simulation of 100 billion photon histories took 22 min, a 1258 × speed-up compared to the single-threaded Monte Carlo program. The overall computational throughput was 85,178 photon histories per node per second, with a latency of 100 s. The distributed simulation produced the same output as the original implementation and was resilient to hardware failure: the correctness of the simulation was unaffected by the shutdown of 50% of the nodes. PMID:22191916

  7. Numerical thermalization in particle-in-cell simulations with Monte-Carlo collisions

    International Nuclear Information System (INIS)

    Numerical thermalization in collisional one-dimensional (1D) electrostatic (ES) particle-in-cell (PIC) simulations was investigated. Two collision models, the pitch-angle scattering of electrons by the stationary ion background and large-angle collisions between the electrons and the neutral background, were included in the PIC simulation using Monte-Carlo methods. The numerical results show that the thermalization times in both models were considerably reduced by the additional Monte-Carlo collisions as demonstrated by comparisons with Turner's previous simulation results based on a head-on collision model [M. M. Turner, Phys. Plasmas 13, 033506 (2006)]. However, the breakdown of Dawson's scaling law in the collisional 1D ES PIC simulation is more complicated than that was observed by Turner, and the revised scaling law of the numerical thermalization time with numerical parameters are derived on the basis of the simulation results obtained in this study

  8. Entropic effects in large-scale Monte Carlo simulations

    CERN Document Server

    Predescu, C

    2007-01-01

    The efficiency of Monte Carlo samplers is dictated not only by energetic effects, such as large barriers, but also by entropic effects that are due to the sheer volume that is sampled. The latter effects appear in the form of an entropic mismatch or divergence between the direct and reverse trial moves. We provide lower and upper bounds for the average acceptance probability in terms of the Renyi divergence of order 1/2. We show that the asymptotic finitude of the entropic divergence is the necessary and sufficient condition for non-vanishing acceptance probabilities in the limit of large dimensions. Furthermore, we demonstrate that the upper bound is reasonably tight by showing that the exponent is asymptotically exact for systems made up of a large number of independent and identically distributed subsystems. For the last statement, we provide an alternative proof that relies on the reformulation of the acceptance probability as a large deviation problem. The reformulation also leads to a class of low-varia...

  9. Improvements in Monte Carlo Simulation of Large Electron Fields

    Energy Technology Data Exchange (ETDEWEB)

    Faddegon, Bruce A.; /UC, San Francisco; Perl, Joseph; Asai, Makoto; /SLAC

    2007-11-28

    Two Monte Carlo systems, EGSnrc and Geant4, were used to calculate dose distributions in large electron fields used in radiotherapy. Source and geometry parameters were adjusted to match calculated results with measurement. Both codes were capable of accurately reproducing the measured dose distributions of the 6 electron beams available on the accelerator. Depth penetration was matched to 0.1 cm. Depth dose curves generally agreed to 2% in the build-up region, although there is an additional 2-3% experimental uncertainty in this region. Dose profiles matched to 2% at the depth of maximum dose in the central region of the beam, out to the point of the profile where the dose begins to fall rapidly. A 3%/3mm match was obtained outside the central region except for the 6 MeV beam, where dose differences reached 5%. The discrepancy observed in the bremsstrahlung tail in published results that used EGS4 is no longer evident. The different systems required different source energies, incident beam angles, thicknesses of the exit window and primary foils, and distance between the primary and secondary foil. These results underscore the requirement for an experimental benchmark of electron scatter for beam energies and foils relevant to radiotherapy.

  10. A Monte Carlo simulation model for stationary non-Gaussian processes

    DEFF Research Database (Denmark)

    Grigoriu, M.; Ditlevsen, Ove Dalager; Arwade, S. R.

    2003-01-01

    includes translation processes and is useful for both Monte Carlo simulation and analytical studies. As for translation processes, the mixture of translation processes can have a wide range of marginal distributions and correlation functions. Moreover, these processes can match a broader range of second...... athe proposed Monte Carlo algorithm and compare features of translation processes and mixture of translation processes. Keywords: Monte Carlo simulation, non-Gaussian processes, sampling theorem, stochastic processes, translation processes......A class of stationary non-Gaussian processes, referred to as the class of mixtures of translation processes, is defined by their finite dimensional distributions consisting of mixtures of finite dimensional distributions of translation processes. The class of mixtures of translation processes...

  11. Pipeline integrity management using Monte Carlo simulation; A aplicacao do metodo de Monte Carlo no gerenciamento da integridade de dutos

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Claudio; Costa, Artur; Bittencourt, Euclides [TRANSPETRO - PETROBRAS Transporte, Rio de Janeiro, RJ (Brazil)

    2005-07-01

    Due to the growing relevance of safety and environmental protection policies in PETROBRAS and its subsidiaries, as well as official regulatory agencies and population requirements, integrity management of oil and gas pipelines became a priority activity in TRANSPETRO, involving several sectors of the company's Support Management Department. Inspection activities using intelligent PIGs, field correlations and replacement of pipeline segments are known as high cost operations and request complex logistics. Thus, it is imperative the adoption of management tools that optimize the available resources. This study presents Monte Carlo simulation method as an additional tool for evaluation and management of pipeline structural integrity. The method consists in foreseeing future physical conditions of most significant defects found in intelligent PIG In Line Inspections based on a probabilistic approach. Through Monte Carlo simulation, probability functions of failure for each defect are produced, helping managers to decide which repairs should be executed in order to reach the desired or accepted risk level. The case that illustrates this study refers to the reconditioning of ORSOL 14'' (35,56 mm) pipeline. This pipeline was constructed to transfer petroleum from Urucu's production fields to Solimoes port, in Coari, city in Brazilian Amazon Region. The result of this analysis indicated critical points for repair, in addition to the results obtained by the conventional evaluation (deterministic ASME B-31G method). Due to the difficulties to mobilize staff and execute necessary repairs in remote areas like Amazon forest, the probabilistic tool was extremely useful, improving pipeline integrity level and avoiding future additional costs. (author)

  12. Monte Carlo simulation of secondary electron images for real sample structures in scanning electron microscopy.

    Science.gov (United States)

    Zhang, P; Wang, H Y; Li, Y G; Mao, S F; Ding, Z J

    2012-01-01

    Monte Carlo simulation methods for the study of electron beam interaction with solids have been mostly concerned with specimens of simple geometry. In this article, we propose a simulation algorithm for treating arbitrary complex structures in a real sample. The method is based on a finite element triangular mesh modeling of sample geometry and a space subdivision for accelerating simulation. Simulation of secondary electron image in scanning electron microscopy has been performed for gold particles on a carbon substrate. Comparison of the simulation result with an experiment image confirms that this method is effective to model complex morphology of a real sample.

  13. Monte Carlo simulations of adult and pediatric computed tomography exams: Validation studies of organ doses with physical phantoms

    Energy Technology Data Exchange (ETDEWEB)

    Long, Daniel J.; Lee, Choonsik; Tien, Christopher; Fisher, Ryan; Hoerner, Matthew R.; Hintenlang, David; Bolch, Wesley E. [J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611-6131 (United States); National Cancer Institute, National Institute of Health, Bethesda, Maryland 20892-1502 (United States); J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611-6131 (United States); Department of Radiology, University of Florida, Gainesville, Florida 32610-0374 (United States); J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611-6131 (United States)

    2013-01-15

    Purpose: To validate the accuracy of a Monte Carlo source model of the Siemens SOMATOM Sensation 16 CT scanner using organ doses measured in physical anthropomorphic phantoms. Methods: The x-ray output of the Siemens SOMATOM Sensation 16 multidetector CT scanner was simulated within the Monte Carlo radiation transport code, MCNPX version 2.6. The resulting source model was able to perform various simulated axial and helical computed tomographic (CT) scans of varying scan parameters, including beam energy, filtration, pitch, and beam collimation. Two custom-built anthropomorphic phantoms were used to take dose measurements on the CT scanner: an adult male and a 9-month-old. The adult male is a physical replica of University of Florida reference adult male hybrid computational phantom, while the 9-month-old is a replica of University of Florida Series B 9-month-old voxel computational phantom. Each phantom underwent a series of axial and helical CT scans, during which organ doses were measured using fiber-optic coupled plastic scintillator dosimeters developed at University of Florida. The physical setup was reproduced and simulated in MCNPX using the CT source model and the computational phantoms upon which the anthropomorphic phantoms were constructed. Average organ doses were then calculated based upon these MCNPX results. Results: For all CT scans, good agreement was seen between measured and simulated organ doses. For the adult male, the percent differences were within 16% for axial scans, and within 18% for helical scans. For the 9-month-old, the percent differences were all within 15% for both the axial and helical scans. These results are comparable to previously published validation studies using GE scanners and commercially available anthropomorphic phantoms. Conclusions: Overall results of this study show that the Monte Carlo source model can be used to accurately and reliably calculate organ doses for patients undergoing a variety of axial or helical CT

  14. Construction of the Jacobian matrix for fluorescence diffuse optical tomography using a perturbation Monte Carlo method

    Science.gov (United States)

    Zhang, Xiaofeng

    2012-03-01

    Image formation in fluorescence diffuse optical tomography is critically dependent on construction of the Jacobian matrix. For clinical and preclinical applications, because of the highly heterogeneous characteristics of the medium, Monte Carlo methods are frequently adopted to construct the Jacobian. Conventional adjoint Monte Carlo method typically compute the Jacobian by multiplying the photon density fields radiated from the source at the excitation wavelength and from the detector at the emission wavelength. Nonetheless, this approach assumes that the source and the detector in Green's function are reciprocal, which is invalid in general. This assumption is particularly questionable in small animal imaging, where the mean free path length of photons is typically only one order of magnitude smaller than the representative dimension of the medium. We propose a new method that does not rely on the reciprocity of the source and the detector by tracing photon propagation entirely from the source to the detector. This method relies on the perturbation Monte Carlo theory to account for the differences in optical properties of the medium at the excitation and the emission wavelengths. Compared to the adjoint methods, the proposed method is more valid in reflecting the physical process of photon transport in diffusive media and is more efficient in constructing the Jacobian matrix for densely sampled configurations.

  15. Modeling of hysteresis loops by Monte Carlo simulation

    Science.gov (United States)

    Nehme, Z.; Labaye, Y.; Sayed Hassan, R.; Yaacoub, N.; Greneche, J. M.

    2015-12-01

    Recent advances in MC simulations of magnetic properties are rather devoted to non-interacting systems or ultrafast phenomena, while the modeling of quasi-static hysteresis loops of an assembly of spins with strong internal exchange interactions remains limited to specific cases. In the case of any assembly of magnetic moments, we propose MC simulations on the basis of a three dimensional classical Heisenberg model applied to an isolated magnetic slab involving first nearest neighbors exchange interactions and uniaxial anisotropy. Three different algorithms were successively implemented in order to simulate hysteresis loops: the classical free algorithm, the cone algorithm and a mixed one consisting of adding some global rotations. We focus particularly our study on the impact of varying the anisotropic constant parameter on the coercive field for different temperatures and algorithms. A study of the angular acceptation move distribution allows the dynamics of our simulations to be characterized. The results reveal that the coercive field is linearly related to the anisotropy providing that the algorithm and the numeric conditions are carefully chosen. In a general tendency, it is found that the efficiency of the simulation can be greatly enhanced by using the mixed algorithm that mimic the physics of collective behavior. Consequently, this study lead as to better quantified coercive fields measurements resulting from physical phenomena of complex magnetic (nano)architectures with different anisotropy contributions.

  16. Estimation of optical properties of neuroendocrine pancreas tumor with double-integrating-sphere system and inverse Monte Carlo model.

    Science.gov (United States)

    Saccomandi, Paola; Larocca, Enza Stefania; Rendina, Veneranda; Schena, Emiliano; D'Ambrosio, Roberto; Crescenzi, Anna; Di Matteo, Francesco Maria; Silvestri, Sergio

    2016-08-01

    The investigation of laser-tissue interaction is crucial for diagnostics and therapeutics. In particular, the estimation of tissue optical properties allows developing predictive models for defining organ-specific treatment planning tool. With regard to laser ablation (LA), optical properties are among the main responsible for the therapy efficacy, as they globally affect the heating process of the tissue, due to its capability to absorb and scatter laser energy. The recent introduction of LA for pancreatic tumor treatment in clinical studies has fostered the need to assess the laser-pancreas interaction and hence to find its optical properties in the wavelength of interest. This work aims at estimating optical properties (i.e., absorption, μ a , scattering, μ s , anisotropy, g, coefficients) of neuroendocrine pancreas tumor at 1064 nm. Experiments were performed using two popular sample storage methods; the optical properties of frozen and paraffin-embedded neuroendocrine tumor of the pancreas are estimated by employing a double-integrating-sphere system and inverse Monte Carlo algorithm. Results show that paraffin-embedded tissue is characterized by absorption and scattering coefficients significantly higher than frozen samples (μ a of 56 cm(-1) vs 0.9 cm(-1), μ s of 539 cm(-1) vs 130 cm(-1), respectively). Simulations show that such different optical features strongly influence the pancreas temperature distribution during LA. This result may affect the prediction of therapeutic outcome. Therefore, the choice of the appropriate preparation technique of samples for optical property estimation is crucial for the performances of the mathematical models which predict LA thermal outcome on the tissue and lead the selection of optimal LA settings. PMID:27147075

  17. MONTE CARLO SIMULATION OF METASTABLE OXYGEN PHOTOCHEMISTRY IN COMETARY ATMOSPHERES

    Energy Technology Data Exchange (ETDEWEB)

    Bisikalo, D. V.; Shematovich, V. I. [Institute of Astronomy of the Russian Academy of Sciences, Moscow (Russian Federation); Gérard, J.-C.; Hubert, B. [Laboratory for Planetary and Atmospheric Physics (LPAP), University of Liège, Liège (Belgium); Jehin, E.; Decock, A. [Origines Cosmologiques et Astrophysiques (ORCA), University of Liège (Belgium); Hutsemékers, D. [Extragalactic Astrophysics and Space Observations (EASO), University of Liège (Belgium); Manfroid, J., E-mail: B.Hubert@ulg.ac.be [High Energy Astrophysics Group (GAPHE), University of Liège (Belgium)

    2015-01-01

    Cometary atmospheres are produced by the outgassing of material, mainly H{sub 2}O, CO, and CO{sub 2} from the nucleus of the comet under the energy input from the Sun. Subsequent photochemical processes lead to the production of other species generally absent from the nucleus, such as OH. Although all comets are different, they all have a highly rarefied atmosphere, which is an ideal environment for nonthermal photochemical processes to take place and influence the detailed state of the atmosphere. We develop a Monte Carlo model of the coma photochemistry. We compute the energy distribution functions (EDF) of the metastable O({sup 1}D) and O({sup 1}S) species and obtain the red (630 nm) and green (557.7 nm) spectral line shapes of the full coma, consistent with the computed EDFs and the expansion velocity. We show that both species have a severely non-Maxwellian EDF, that results in broad spectral lines and the suprathermal broadening dominates due to the expansion motion. We apply our model to the atmosphere of comet C/1996 B2 (Hyakutake) and 103P/Hartley 2. The computed width of the green line, expressed in terms of speed, is lower than that of the red line. This result is comparable to previous theoretical analyses, but in disagreement with observations. We explain that the spectral line shape does not only depend on the exothermicity of the photochemical production mechanisms, but also on thermalization, due to elastic collisions, reducing the width of the emission line coming from the O({sup 1}D) level, which has a longer lifetime.

  18. QCDMPI - pure QCD Monte Carlo simulation code with MPI

    International Nuclear Information System (INIS)

    QCDMPI is a pure QCD simulation code with MPI calls. QCDMPI is very portable because; - you can simulate any-dimensional QCD, - on any-dimensional partitioning, - on any number of processors, - with rather small working area. Also by this program, you can get two performances, - calculation (link update time) - communication (MB/sec). In this paper, outline of QCDMPI is reported. Comparison of the performances on several parallel machines; AP1000, AP1000+, AP3000, Cenju-3, Paragon, SR2201 and Workstation Cluster, is also reported. (orig.)

  19. Quantum Monte Carlo Simulations of Adulteration Effect on Bond Alternating Spin=1/2 Chain

    Science.gov (United States)

    Zhang, Peng; Xu, Zhaoxin; Ying, Heping; Dai, Jianhui; Crompton, Peter

    The S=1/2 Heisenberg chain with bond alternation and randomness of antiferromagnetic (AFM) and ferromagnetic (FM) interactions is investigated by quantum Monte Carlo simulations of loop/cluster algorithm. Our results have shown interesting finite temperature magnetic properties of this model. The relevance of our study to former investigation results is discussed.

  20. Estimating Rare Event Probabilities in Large Scale Stochastic Hybrid Systems by Sequential Monte Carlo Simulation

    NARCIS (Netherlands)

    Blom, H.A.P.; Krystul, J.; Bakker, G.J.

    2006-01-01

    We study the problem of estimating small reachability probabilities for large scale stochastic hybrid processes through Sequential Monte Carlo (SMC) simulation. Recently, [Cerou et al., 2002, 2005] developed an SMC approach for diffusion processes, and referred to the resulting SMC algorithm as an I

  1. Multiple molecular dynamics time-scales in Hybrid Monte Carlo fermion simulations

    OpenAIRE

    PEARDON, MICHAEL JAMES; SEXTON, JAMES CHRISTOPHER

    2003-01-01

    PUBLISHED A scheme for separating the high- and low-frequency molecular dynamics modes in Hybrid Monte Carlo (HMC) simulations of gauge theories with dynamical fermions is presented. The algorithm is tested in the Schwinger model with Wilson fermions. MP is grateful to Enterprise-Ireland for support under grant SC/01/306.

  2. Monte Carlo Simulation for Moderator of Compact D-T Neutron Generator

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    In order to study the neutron moderation of D-T neutron generator, moderators with diffident materials and structures are predicted by Monte Carlo simulations. Neutron generator is simplified as the diameter 20 cm, length 25 cm cylinder. The target is very

  3. Monte Carlo simulation of hydrogen physisorption in K-doped single walled carbon nanotube array

    International Nuclear Information System (INIS)

    Properties of hydrogen physisorption in K-doped single walled carbon nanotube array (SWCNTA) are investigated in detail by grand canonical Monte Carlo simulation. The optimization of hydrogen storage capacity at 293 K and 10 MPa as a function of K-doping schemes, K atoms' doped-sites, and SWCNTA configuration is discussed.

  4. Towards integration of compositional risk analysis using Monte Carlo simulation and security testing

    OpenAIRE

    Viehmann, Johannes

    2014-01-01

    This short paper describes ongoing efforts to combine concepts of security risk analysis with security testing into a single process. Using risk analysis artefact composition and Monte Carlo simulation to calculate likelihood values, the method described here is intended to become applicable for complex large scale systems with dynamically changing probability values.

  5. Monte Carlo simulation - a powerful tool to support experimental activities in structure reliability

    Energy Technology Data Exchange (ETDEWEB)

    Yuritzinn, T. [CEA Saclay, Dept. de Mecanique et de Technologie (DRN/DMT/SEMT/LISN), 91 - Gif-sur-Yvette (France); Chapuliot, S. [CEA Saclay, Dept. Modelisation de Systemes et Structures (DM2S/SEMT), 91 - Gif sur Yvette (France); Eid, M. [CEA Saclay, Dept. de Mecanique et de Technologie (DRN/DMT/SERMA/LCA), 91 - Gif-sur-Yvette (France); Masson, R.; Dahl, A.; Moinereau, D. [Electricite de France (EDF), 75 - Paris (France)

    2003-07-01

    Monte-Carlo Simulation (MCS) can have different uses in supporting structure reliability investigations and assessments. In this paper we focus our interest on the use of MCS as a numerical tool to support the fitting of the experimental data related to toughness experiments. (authors)

  6. Exploring uncertainty in glacier mass balance modelling with Monte Carlo simulation

    NARCIS (Netherlands)

    Machguth, H.; Purves, R.S.; Oerlemans, J.; Hoelzle, M.; Paul, F.

    2008-01-01

    By means of Monte Carlo simulations we calculated uncertainty in modelled cumulative mass balance over 400 days at one particular point on the tongue of Morteratsch Glacier, Switzerland, using a glacier energy balance model of intermediate complexity. Before uncertainty assessment, the model was tun

  7. Simulating Scintillator Light Collection Using Measured Optical Reflectance

    Energy Technology Data Exchange (ETDEWEB)

    Janecek, Martin; Moses, William

    2010-01-28

    To accurately predict the light collection from a scintillating crystal through Monte Carlo simulations, it is crucial to know the angular distribution from the surface reflectance. Current Monte Carlo codes allow the user to set the optical reflectance to a linear combination of backscatter spike, specular spike, specular lobe, and Lambertian reflections. However, not all light distributions can be expressed in this way. In addition, the user seldom has the detailed knowledge about the surfaces that is required for accurate modeling. We have previously measured the angular distributions within BGO crystals and now incorporate these data as look-up-tables (LUTs) into modified Geant4 and GATE Monte Carlo codes. The modified codes allow the user to specify the surface treatment (ground, etched, or polished), the attached reflector (Lumirror(R), Teflon(R), ESR film, Tyvek(R), or TiO paint), and the bonding type (air-coupled or glued). Each LUT consists of measured angular distributions with 4o by 5o resolution in theta and phi, respectively, for incidence angles from 0? to 90? degrees, in 1o-steps. We compared the new codes to the original codes by running simulations with a 3 x 10 x 30 mm3 BGO crystal coupled to a PMT. The simulations were then compared to measurements. Light output was measured by counting the photons detected by the PMT with the 3 x 10, 3 x 30, or 10 x 30 mm2 side coupled to the PMT, respectively. Our new code shows better agreement with the measured data than the current Geant4 code. The new code can also simulate reflector materials that are not pure specular or Lambertian reflectors, as was previously required. Our code is also more user friendly, as no detailed knowledge about the surfaces or light distributions is required from the user.

  8. Numerical simulations of blast-impact problems using the direct simulation Monte Carlo method

    Science.gov (United States)

    Sharma, Anupam

    There is an increasing need to design protective structures that can withstand or mitigate the impulsive loading due to the impact of a blast or a shock wave. A preliminary step in designing such structures is the prediction of the pressure loading on the structure. This is called the "load definition." This thesis is focused on a numerical approach to predict the load definition on arbitrary geometries for a given strength of the incident blast/shock wave. A particle approach, namely the Direct Simulation Monte Carlo (DSMC) method, is used as the numerical model. A three-dimensional, time-accurate DSMC flow solver is developed as a part of this study. Embedded surfaces, modeled as triangulations, are used to represent arbitrary-shaped structures. Several techniques to improve the computational efficiency of the algorithm of particle-structure interaction are presented. The code is designed using the Object Oriented Programming (OOP) paradigm. Domain decomposition with message passing is used to solve large problems in parallel. The solver is extensively validated against analytical results and against experiments. Two kinds of geometries, a box and an I-shaped beam are investigated for blast impact. These simulations are performed in both two- and three-dimensions. A major portion of the thesis is dedicated to studying the uncoupled fluid dynamics problem where the structure is assumed to remain stationary and intact during the simulation. A coupled, fluid-structure dynamics problem is solved in one spatial dimension using a simple, spring-mass-damper system to model the dynamics of the structure. A parametric study, by varying the mass, spring constant, and the damping coefficient, to study their effect on the loading and the displacement of the structure is also performed. Finally, the parallel performance of the solver is reported for three sample-size problems on two Beowulf clusters.

  9. Dosimetry in small-animal CT using Monte Carlo simulations

    International Nuclear Information System (INIS)

    Small-animal computed tomography (micro-CT) imaging devices are increasingly being used in biological research. While investigators are mainly interested in high-contrast, low-noise, and high-resolution anatomical images, relatively large radiation doses are required, and there is also growing concern over the radiological risk from preclinical experiments. This study was conducted to determine the radiation dose in a mouse model for dosimetric estimates using the GEANT4 application for tomographic emission simulations (GATE) and to extend its techniques to various small-animal CT applications. Radiation dose simulations were performed with the same parameters as those for the measured micro-CT data, using the MOBY phantom, a pencil ion chamber and an electrometer with a CT detector. For physical validation of radiation dose, absorbed dose of brain and liver in mouse were evaluated to compare simulated results with physically measured data using thermoluminescent dosimeters (TLDs). The mean difference between simulated and measured data was less than 2.9% at 50 kVp X-ray source. The absorbed doses of 37 brain tissues and major organs of the mouse were evaluated according to kVp changes. The absorbed dose over all of the measurements in the brain (37 types of tissues) consistently increased and ranged from 42.4 to 104.0 mGy. Among the brain tissues, the absorbed dose of the hypothalamus (157.8–414.30 mGy) was the highest for the beams at 50–80 kVp, and that of the corpus callosum (11.2–26.6 mGy) was the lowest. These results can be used as a dosimetric database to control mouse doses and preclinical targeted radiotherapy experiments. In addition, to accurately calculate the mouse-absorbed dose, the X-ray spectrum, detector alignment, and uncertainty in the elemental composition of the simulated materials must be accurately modeled

  10. Dosimetry in small-animal CT using Monte Carlo simulations

    Science.gov (United States)

    Lee, C.-L.; Park, S.-J.; Jeon, P.-H.; Jo, B.-D.; Kim, H.-J.

    2016-01-01

    Small-animal computed tomography (micro-CT) imaging devices are increasingly being used in biological research. While investigators are mainly interested in high-contrast, low-noise, and high-resolution anatomical images, relatively large radiation doses are required, and there is also growing concern over the radiological risk from preclinical experiments. This study was conducted to determine the radiation dose in a mouse model for dosimetric estimates using the GEANT4 application for tomographic emission simulations (GATE) and to extend its techniques to various small-animal CT applications. Radiation dose simulations were performed with the same parameters as those for the measured micro-CT data, using the MOBY phantom, a pencil ion chamber and an electrometer with a CT detector. For physical validation of radiation dose, absorbed dose of brain and liver in mouse were evaluated to compare simulated results with physically measured data using thermoluminescent dosimeters (TLDs). The mean difference between simulated and measured data was less than 2.9% at 50 kVp X-ray source. The absorbed doses of 37 brain tissues and major organs of the mouse were evaluated according to kVp changes. The absorbed dose over all of the measurements in the brain (37 types of tissues) consistently increased and ranged from 42.4 to 104.0 mGy. Among the brain tissues, the absorbed dose of the hypothalamus (157.8-414.30 mGy) was the highest for the beams at 50-80 kVp, and that of the corpus callosum (11.2-26.6 mGy) was the lowest. These results can be used as a dosimetric database to control mouse doses and preclinical targeted radiotherapy experiments. In addition, to accurately calculate the mouse-absorbed dose, the X-ray spectrum, detector alignment, and uncertainty in the elemental composition of the simulated materials must be accurately modeled.

  11. Crossed source-detector geometry for a novel spray diagnostic: Monte Carlo simulation and analytical results.

    Science.gov (United States)

    Berrocal, Edouard; Churmakov, Dmitry Y; Romanov, Vadim P; Jermy, Mark C; Meglinski, Igor V

    2005-05-01

    Sprays and other industrially relevant turbid media can be quantitatively characterized by light scattering. However, current optical diagnostic techniques generate errors in the intermediate scattering regime where the average number of light scattering is too great for the single scattering to be assumed, but too few for the diffusion approximation to be applied. Within this transitional single-to-multiple scattering regime, we consider a novel crossed source-detector geometry that allows the intensity of single scattering to be measured separately from the higher scattering orders. We verify Monte Carlo calculations that include the imperfections of the experiment against analytical results. We show quantitatively the influence of the detector numerical aperture and the angle between the source and the detector on the relative intensity of the scattering orders in the intermediate single-to-multiple scattering regime. Monte Carlo and analytical calculations of double light-scattering intensity are made with small particles that exhibit isotropic scattering. The agreement between Monte Carlo and analytical techniques validates use of the Monte Carlo approach in the intermediate scattering regime. Monte Carlo calculations are then performed for typical parameters of sprays and aerosols with anisotropic (Mie) scattering in the intermediate single-to-multiple scattering regime. PMID:15881059

  12. Optical eye simulator for laser dazzle events.

    Science.gov (United States)

    Coelho, João M P; Freitas, José; Williamson, Craig A

    2016-03-20

    An optical simulator of the human eye and its application to laser dazzle events are presented. The simulator combines optical design software (ZEMAX) with a scientific programming language (MATLAB) and allows the user to implement and analyze a dazzle scenario using practical, real-world parameters. Contrary to conventional analytical glare analysis, this work uses ray tracing and the scattering model and parameters for each optical element of the eye. The theoretical background of each such element is presented in relation to the model. The overall simulator's calibration, validation, and performance analysis are achieved by comparison with a simpler model based uponCIE disability glare data. Results demonstrate that this kind of advanced optical eye simulation can be used to represent laser dazzle and has the potential to extend the range of applicability of analytical models. PMID:27140558

  13. Monnte Carlo Simulation of Kinetics of Ammonia Oxidative Decomposition over the Commercial Propylene Ammoxidation Catalyst(Mo-Bi)

    Institute of Scientific and Technical Information of China (English)

    罗正鸿; 詹晓力; 等

    2003-01-01

    Monte Carlo method is applied to investigate the kinetics of ammonia oxidative decomposition over the commercial propylene ammoxidation catalyst(Mo-Bi).The simulation is quite in agreement with experimetal results.Monte Carlo simulation proves that the process of ammonia oxidation decomposition is a two-step reaction.

  14. Application of Macro Response Monte Carlo method for electron spectrum simulation

    International Nuclear Information System (INIS)

    During the past years several variance reduction techniques for Monte Carlo electron transport have been developed in order to reduce the electron computation time transport for absorbed dose distribution. We have implemented the Macro Response Monte Carlo (MRMC) method to evaluate the electron spectrum which can be used as a phase space input for others simulation programs. Such technique uses probability distributions for electron histories previously simulated in spheres (called kugels). These probabilities are used to sample the primary electron final state, as well as the creation secondary electrons and photons. We have compared the MRMC electron spectra simulated in homogeneous phantom against the Geant4 spectra. The results showed an agreement better than 6% in the spectra peak energies and that MRMC code is up to 12 time faster than Geant4 simulations

  15. Monte Carlo study of skin optical clearing to enhance light penetration in the tissue: implications for photodynamic therapy of acne vulgaris

    Science.gov (United States)

    Bashkatov, Alexey N.; Genina, Elina A.; Tuchin, Valery V.; Altshuler, Gregory B.; Yaroslavsky, Ilya V.

    2008-06-01

    Result of Monte Carlo simulations of skin optical clearing is presented. The model calculations were carried out with the aim of studying of spectral response of skin under immersion liquids action and calculation of enhancement of light penetration depth. In summary, we have shown that: 1) application of glucose, propylene glycol and glycerol produced significant decrease of light scattering in different skin layers; 2) maximal clearing effect will be obtained in case of optical clearing of skin dermis, however, absorbed light fraction in skin dermis changed insignificantly, independently on clearing agent and place it administration; 3) in contrast to it, the light absorbed fraction in skin adipose layer increased significantly in case of optical clearing of skin dermis. It is very important because it can be used for development of optical methods of obesity treatment; 4) optical clearing of superficial skin layers can be used for decreasing of power of light radiation used for treatment of acne vulgaris.

  16. Monte Carlo simulation of a single detector unit for the neutron detector array NEDA

    OpenAIRE

    Jaworski, G.; Palacz, M.; Nyberg, Johan; De Angelis, G.; de France, G; Nitto, A. Di; Egea, J.; Erduran, M. N.; Ertürk, S.; Farnea, E.; Gadea, A.; V González; Gottardo, A.(Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Legnaro, I-35020, Italy); Hüyük, T.; Kownacki, J.

    2012-01-01

    A study of the dimensions and performance of a single detector of the future neutron detector array NEDA was performed by means of Monte Carlo simulations, using GEANT4. Two different liquid scintillators were evaluated: the hydrogen based BC501A and the deuterated BC537. The efficiency and the probability that one neutron will trigger a signal in more than one detector were investigated as a function of the detector size. The simulations were validated comparing the results to experimental m...

  17. Monte Carlo simulations of mesoscale fracture modelling of concrete with random aggregates and pores

    OpenAIRE

    Wang XF, Yang ZJ, Yates JR, Jivkov AP, Zhang Ch

    2015-01-01

    A procedure for generating two-dimensional heterogeneous meso-scale concrete samples is developed, in which the multi-phasic features including the shape, size, volume fraction and spatial distribution of aggregates and pores are randomised. Zero-thickness cohesive interface elements with softening traction–separation relations are pre-inserted within solid element meshes to simulate complex crack initiation and propagation. Extensive Monte Carlo simulations (MCS) of uniaxial tension tests ...

  18. KMCLib: A general framework for lattice kinetic Monte Carlo (KMC) simulations

    OpenAIRE

    Leetmaa, Mikael; Skorodumova, Natalia V.

    2014-01-01

    KMCLib is a general framework for lattice kinetic Monte Carlo (KMC) simulations. The program can handle simulations of the diffusion and reaction of millions of particles in one, two, or three dimensions, and is designed to be easily extended and customized by the user to allow for the development of complex custom KMC models for specific systems without having to modify the core functionality of the program. Analysis modules and on-the-fly elementary step diffusion rate calculations can be i...

  19. 1D Monte-Carlo simulation of charge accumulation process inside Teflon film

    OpenAIRE

    Watanabe, Rikio; Ota, Masahiro; Tanaka, Yasuhiro; Tomita, Nobuyuki; 渡辺 力夫; 大田 真広; 田中 康寛; 冨田 信之

    2005-01-01

    The charge accumulation processes inside a Teflon film are investigated with one-dimensional Monte-Carlo simulation. Elastic and inelastic scattering processes are considered in the collisions between electrons and atoms consisting of Teflon (CF4). Electron-phonon interaction and trapping effect are also included in the estimation of total cross section. A case of 20 keV electron irradiation is tested and charge accumulation process is successfully simulated. The electric field is also calcul...

  20. Monte Carlo Simulation of Linear Polymer Thermal Depolymerization under Isothermal and Dynamic Modes

    OpenAIRE

    Bystritskaya, Elena V.; Karpukhin, Oleg N.; Kutsenova, Alla V.

    2011-01-01

    Kinetics of linear polymer thermal depolymerization under isothermal and dynamic TGA modes was simulated by the Monte Carlo method. The simulation was carried out on model arrays having the same initial degree of polymerization = 1 0 0 and different width (polydispersity index, P D I = / = 1 ∼ 3 ) at three constant temperatures and five heating rates. Kinetics of the process in both modes is described by the Avrami equation, the exponent in which decreasing as the distribution wid...

  1. Colloidal nanoparticles trapped by liquid-crystal defect lines: A lattice Monte Carlo simulation

    Science.gov (United States)

    Jose, Regina; Skačej, Gregor; Sastry, V. S. S.; Žumer, Slobodan

    2014-09-01

    Lattice-based Monte Carlo simulations are performed to study a confined liquid crystal system with a topological disclination line entangling a colloidal nanoparticle. In our microscopic study the disclination line is stretched by moving the colloid, as in laser tweezing experiments, which results in a restoring force attempting to minimize the disclination length. From constant-force simulations we extract the corresponding disclination line tension, estimated as ˜50 pN, and observe its decrease with increasing temperature.

  2. A Paradox of Decreasing Entropy in Multiscale Monte Carlo Grain Growth Simulations

    OpenAIRE

    Esche, Sven K.; Michael Nosonovsky

    2008-01-01

    Grain growth in metals is driven by random thermal fluctuations and increases the orderliness of the system. This random process is usually simulated by the Monte Carlo (MC) method and Cellular Automata (CA). The increasing orderliness results in an entropy decrease, thus leading to a paradoxical apparent violation of the second law of thermodynamics. In this paper, it is shown that treating the system as a multiscale system resolves this paradox. MC/CA simulations usually take into considera...

  3. Validation of GEANT4 Monte Carlo Simulation Code for 6 MV Varian Linac Photon Beam

    International Nuclear Information System (INIS)

    The head of a clinical linear accelerator based on the manufacturer detailed information is simulated by using GEANT4. Percentage Depth Dose (PDD) and flatness symmetry (lateral dose profiles) in water phantom were evaluated. Comparisons between experimental and simulated data were carried out for two field sizes; 5 × 5, and 10 ×10 cm2. The obtained results indicated that GEANT4 code is a promising and validated Monte Carlo program for using in radiotherapy applications

  4. A Monte Carlo Simulation of the Flow Network Reliability using Importance and Stratified Sampling

    OpenAIRE

    Bulteau, Stéphane; El Khadiri, Mohamed

    1997-01-01

    We consider the evaluation of the flow network reliability parameter. Because the exact evaluation of this parameter has exponential time complexity- , simulation methods are used to derive an estimate. In this paper, we use the state space decomposition methodology of Doulliez and Jamoulle for constructing a new simulation method which combines the importance and the stratified Monte Carlo principles. We show that the related estimator belongs to the variance-reduction family. By numerical c...

  5. A Bifurcation Monte Carlo Scheme for Rare Event Simulation

    CERN Document Server

    Liu, Hongliang

    2016-01-01

    The bifurcation method is a way to do rare event sampling -- to estimate the probability of events that are too rare to be found by direct simulation. We describe the bifurcation method and use it to estimate the transition rate of a double well potential problem. We show that the associated constrained path sampling problem can be addressed by a combination of Crooks-Chandler sampling and parallel tempering and marginalization.

  6. Subroutines to Simulate Fission Neutrons for Monte Carlo Transport Codes

    OpenAIRE

    Lestone, J. P.

    2014-01-01

    Fortran subroutines have been written to simulate the production of fission neutrons from the spontaneous fission of 252Cf and 240Pu, and from the thermal neutron induced fission of 239Pu and 235U. The names of these four subroutines are getnv252, getnv240, getnv239, and getnv235, respectively. These subroutines reproduce measured first, second, and third moments of the neutron multiplicity distributions, measured neutron-fission correlation data for the spontaneous fission of 252Cf, and meas...

  7. Quantifying the Effect of Undersampling in Monte Carlo Simulations Using SCALE

    Energy Technology Data Exchange (ETDEWEB)

    Perfetti, Christopher M [ORNL; Rearden, Bradley T [ORNL

    2014-01-01

    This study explores the effect of undersampling in Monte Carlo calculations on tally estimates and tally variance estimates for burnup credit applications. Steady-state Monte Carlo simulations were performed for models of several critical systems with varying degrees of spatial and isotopic complexity and the impact of undersampling on eigenvalue and flux estimates was examined. Using an inadequate number of particle histories in each generation was found to produce an approximately 100 pcm bias in the eigenvalue estimates, and biases that exceeded 10% in fuel pin flux estimates.

  8. Monte Carlo Molecular Simulation with Isobaric-Isothermal and Gibbs-NPT Ensembles

    KAUST Repository

    Du, Shouhong

    2012-05-01

    This thesis presents Monte Carlo methods for simulations of phase behaviors of Lennard-Jones fluids. The isobaric-isothermal (NPT) ensemble and Gibbs-NPT ensemble are introduced in detail. NPT ensemble is employed to determine the phase diagram of pure component. The reduced simulation results are verified by comparison with the equation of state by by Johnson et al. and results with L-J parameters of methane agree considerably with the experiment measurements. We adopt the blocking method for variance estimation and error analysis of the simulation results. The relationship between variance and number of Monte Carlo cycles, error propagation and Random Number Generator performance are also investigated. We review the Gibbs-NPT ensemble employed for phase equilibrium of binary mixture. The phase equilibrium is achieved by performing three types of trial move: particle displacement, volume rearrangement and particle transfer. The simulation models and the simulation details are introduced. The simulation results of phase coexistence for methane and ethane are reported with comparison of the experimental data. Good agreement is found for a wide range of pressures. The contribution of this thesis work lies in the study of the error analysis with respect to the Monte Carlo cycles and number of particles in some interesting aspects.

  9. Massive Parallelism of Monte-Carlo Simulation on Low-End Hardware using Graphic Processing Units

    Energy Technology Data Exchange (ETDEWEB)

    Mburu, Joe Mwangi; Hah, Chang Joo Hah [KEPCO International Nuclear Graduate School, Ulsan (Korea, Republic of)

    2014-05-15

    Within the past decade, research has been done on utilizing GPU massive parallelization in core simulation with impressive results but unfortunately, not much commercial application has been done in the nuclear field especially in reactor core simulation. The purpose of this paper is to give an introductory concept on the topic and illustrate the potential of exploiting the massive parallel nature of GPU computing on a simple monte-carlo simulation with very minimal hardware specifications. To do a comparative analysis, a simple two dimension monte-carlo simulation is implemented for both the CPU and GPU in order to evaluate performance gain based on the computing devices. The heterogeneous platform utilized in this analysis is done on a slow notebook with only 1GHz processor. The end results are quite surprising whereby high speedups obtained are almost a factor of 10. In this work, we have utilized heterogeneous computing in a GPU-based approach in applying potential high arithmetic intensive calculation. By applying a complex monte-carlo simulation on GPU platform, we have speed up the computational process by almost a factor of 10 based on one million neutrons. This shows how easy, cheap and efficient it is in using GPU in accelerating scientific computing and the results should encourage in exploring further this avenue especially in nuclear reactor physics simulation where deterministic and stochastic calculations are quite favourable in parallelization.

  10. Reliability Assessment of Active Distribution System Using Monte Carlo Simulation Method

    Directory of Open Access Journals (Sweden)

    Shaoyun Ge

    2014-01-01

    Full Text Available In this paper we have treated the reliability assessment problem of low and high DG penetration level of active distribution system using the Monte Carlo simulation method. The problem is formulated as a two-case program, the program of low penetration simulation and the program of high penetration simulation. The load shedding strategy and the simulation process were introduced in detail during each FMEA process. Results indicate that the integration of DG can improve the reliability of the system if the system was operated actively.

  11. Geometry navigation acceleration based on automatic neighbor search and oriented bounding box in Monte Carlo simulation

    International Nuclear Information System (INIS)

    Geometry navigation plays the most fundamental role in Monte Carlo particle transport simulation. It's mainly responsible for locating a particle inside which geometry volume it is and computing the distance to the volume boundary along the certain particle trajectory during each particle history. Geometry navigation directly affects the run-time performance of the Monte Carlo particle transport simulation, especially for large scale complicated systems. Two geometry acceleration algorithms, the automatic neighbor search algorithm and the oriented bounding box algorithm, are presented for improving geometry navigation performance. The algorithms have been implemented in the Super Monte Carlo Calculation Program for Nuclear and Radiation Process (SuperMC) version 2.0. The FDS-II and ITER benchmark models have been tested to highlight the efficiency gains that can be achieved by using the acceleration algorithms. The exact gains may be problem dependent, but testing results showed that runtime of Monte Carlo simulation can be considerably reduced 50%∼60% with the proposed acceleration algorithms. (author)

  12. Worm algorithm and diagrammatic Monte Carlo: A new approach to continuous-space path integral Monte Carlo simulations

    Science.gov (United States)

    Boninsegni, M.; Prokof'Ev, N. V.; Svistunov, B. V.

    2006-09-01

    A detailed description is provided of a new worm algorithm, enabling the accurate computation of thermodynamic properties of quantum many-body systems in continuous space, at finite temperature. The algorithm is formulated within the general path integral Monte Carlo (PIMC) scheme, but also allows one to perform quantum simulations in the grand canonical ensemble, as well as to compute off-diagonal imaginary-time correlation functions, such as the Matsubara Green function, simultaneously with diagonal observables. Another important innovation consists of the expansion of the attractive part of the pairwise potential energy into elementary (diagrammatic) contributions, which are then statistically sampled. This affords a complete microscopic account of the long-range part of the potential energy, while keeping the computational complexity of all updates independent of the size of the simulated system. The computational scheme allows for efficient calculations of the superfluid fraction and off-diagonal correlations in space-time, for system sizes which are orders of magnitude larger than those accessible to conventional PIMC. We present illustrative results for the superfluid transition in bulk liquid He4 in two and three dimensions, as well as the calculation of the chemical potential of hcp He4 .

  13. Worm algorithm and diagrammatic Monte Carlo: A new approach to continuous-space path integral Monte Carlo simulations

    International Nuclear Information System (INIS)

    A detailed description is provided of a new worm algorithm, enabling the accurate computation of thermodynamic properties of quantum many-body systems in continuous space, at finite temperature. The algorithm is formulated within the general path integral Monte Carlo (PIMC) scheme, but also allows one to perform quantum simulations in the grand canonical ensemble, as well as to compute off-diagonal imaginary-time correlation functions, such as the Matsubara Green function, simultaneously with diagonal observables. Another important innovation consists of the expansion of the attractive part of the pairwise potential energy into elementary (diagrammatic) contributions, which are then statistically sampled. This affords a complete microscopic account of the long-range part of the potential energy, while keeping the computational complexity of all updates independent of the size of the simulated system. The computational scheme allows for efficient calculations of the superfluid fraction and off-diagonal correlations in space-time, for system sizes which are orders of magnitude larger than those accessible to conventional PIMC. We present illustrative results for the superfluid transition in bulk liquid 4He in two and three dimensions, as well as the calculation of the chemical potential of hcp 4He

  14. Optical simulations for Ambilight TV systems

    Science.gov (United States)

    Bruyneel, Filip; Lanoye, Lieve

    2012-06-01

    Ambilight is a unique Philips feature, where RGB LEDs are used to create a dynamic light halo around the television. This extends the screen and hence increases the viewing experience, as it draws the viewer more into the action on the screen. The feature receives very positive consumer feedback. However, implementing Ambilight in the increasingly stringent design boundary conditions of a slim and thin TV set is a challenging task. Optical simulations play a vital role in each step of the Ambilight development. Ranging from prototype to final product, we use simulations, next to prototyping, to aid the choice of LEDs, optical materials and optical systems during different phases of the design process. Each step the impact of the optical system on the mechanical design and TV set dimensions needs to be taken into account. Moreover, optical simulations are essential to guarantee the required optical performance given a big spread in LED performance, mechanical tolerances and material properties. Next to performance, optical efficiency is also an important parameter to evaluate an optical design, as it establishes the required number of LEDs and the total LED power. As such optical efficiency defines the thermal power which needs to be dissipated by the LED system. The innovation roadmap does not stop here. For future systems we see a miniaturization trend, where smaller LED packages and smaller dies are used. This evolution makes the impact of mechanical tolerances on the optical design more severe. Consequentially, this approach poses a whole new challenge to the way we use optical simulations in our design process.

  15. PhyloSim - Monte Carlo simulation of sequence evolution in the R statistical computing environment

    Directory of Open Access Journals (Sweden)

    Massingham Tim

    2011-04-01

    Full Text Available Abstract Background The Monte Carlo simulation of sequence evolution is routinely used to assess the performance of phylogenetic inference methods and sequence alignment algorithms. Progress in the field of molecular evolution fuels the need for more realistic and hence more complex simulations, adapted to particular situations, yet current software makes unreasonable assumptions such as homogeneous substitution dynamics or a uniform distribution of indels across the simulated sequences. This calls for an extensible simulation framework written in a high-level functional language, offering new functionality and making it easy to incorporate further complexity. Results PhyloSim is an extensible framework for the Monte Carlo simulation of sequence evolution, written in R, using the Gillespie algorithm to integrate the actions of many concurrent processes such as substitutions, insertions and deletions. Uniquely among sequence simulation tools, PhyloSim can simulate arbitrarily complex patterns of rate variation and multiple indel processes, and allows for the incorporation of selective constraints on indel events. User-defined complex patterns of mutation and selection can be easily integrated into simulations, allowing PhyloSim to be adapted to specific needs. Conclusions Close integration with R and the wide range of features implemented offer unmatched flexibility, making it possible to simulate sequence evolution under a wide range of realistic settings. We believe that PhyloSim will be useful to future studies involving simulated alignments.

  16. Monte Carlo simulation of carbon ion radiotherapy for Human Eye

    CERN Document Server

    Pang, Chengguo; Yao, Zeen; Xu, Junkui; Li, Wuyuan; Yuan, Jiao

    2014-01-01

    Carbon ion is the mostly common used particle in heavy ion radiotherapy. In this paper, carbon ion dose in tumor treatment for human eye was simulated with FLUKA code, 80 MeV/u carbon beam was irradiated into the human eye from two directions, The first is from the lateral-forward direction which was a typical therapeutic condition, maximum dose was deposited in the tumor volume. The second one was that beam irradiated into eyes from the forward direction which may cause certain medical accident. The calculated results are compared with other reports. The agreement indicates that this method can be used for treatment plan in heavy ion radiotherapy.

  17. Diffusion microscopist simulator - The development and application of a Monte Carlo simulation system for diffusion MRI

    International Nuclear Information System (INIS)

    Diffusion magnetic resonance imaging (dMRI) has made a significant breakthrough in neurological disorders and brain research thanks to its exquisite sensitivity to tissue cyto-architecture. However, as the water diffusion process in neuronal tissues is a complex biophysical phenomena at molecular scale, it is difficult to infer tissue microscopic characteristics on a voxel scale from dMRI data. The major methodological contribution of this thesis is the development of an integrated and generic Monte Carlo simulation framework, 'Diffusion Microscopist Simulator' (DMS), which has the capacity to create 3D biological tissue models of various shapes and properties, as well as to synthesize dMRI data for a large variety of MRI methods, pulse sequence design and parameters. DMS aims at bridging the gap between the elementary diffusion processes occurring at a micrometric scale and the resulting diffusion signal measured at millimetric scale, providing better insights into the features observed in dMRI, as well as offering ground-truth information for optimization and validation of dMRI acquisition protocols for different applications. We have verified the performance and validity of DMS through various benchmark experiments, and applied to address particular research topics in dMRI. Based on DMS, there are two major application contributions in this thesis. First, we use DMS to investigate the impact of finite diffusion gradient pulse duration (delta) on fibre orientation estimation in dMRI. We propose that current practice of using long delta, which is enforced by the hardware limitation of clinical MRI scanners, is actually beneficial for mapping fibre orientations, even though it violates the underlying assumption made in q-space theory. Second, we employ DMS to investigate the feasibility of estimating axon radius using a clinical MRI system. The results suggest that the algorithm for mapping the direct microstructures is applicable to dMRI data acquired from

  18. Diagnostic x-ray dosimetry using Monte Carlo simulation

    International Nuclear Information System (INIS)

    An Electron Gamma Shower version 4 (EGS4) based user code was developed to simulate the absorbed dose in humans during routine diagnostic radiological procedures. Measurements of absorbed dose using thermoluminescent dosimeters (TLDs) were compared directly with EGS4 simulations of absorbed dose in homogeneous, heterogeneous and anthropomorphic phantoms. Realistic voxel-based models characterizing the geometry of the phantoms were used as input to the EGS4 code. The voxel geometry of the anthropomorphic Rando phantom was derived from a CT scan of Rando. The 100 kVp diagnostic energy x-ray spectra of the apparatus used to irradiate the phantoms were measured, and provided as input to the EGS4 code. The TLDs were placed at evenly spaced points symmetrically about the central beam axis, which was perpendicular to the cathode-anode x-ray axis at a number of depths. The TLD measurements in the homogeneous and heterogenous phantoms were on average within 7% of the values calculated by EGS4. Estimates of effective dose with errors less than 10% required fewer numbers of photon histories (1x107) than required for the calculation of dose profiles (1x109). The EGS4 code was able to satisfactorily predict and thereby provide an instrument for reducing patient and staff effective dose imparted during radiological investigations. (author)

  19. MULTILEVEL MONTE CARLO (MLMC) SIMULATIONS: PERFORMANCE RESULTS FOR SPE10 (XY SLICES)

    Energy Technology Data Exchange (ETDEWEB)

    Kalchev, Delyan [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Vassilevski, Panayot S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-02-26

    In this report we first describe a generic multilevel Monte Carlo method and then illustrate its superior performance over a traditional single-level Monte Carlo method for second order elliptic PDEs corresponding to two-dimensional layers in (x, y)-direction of the Tenth SPE Comparative Solution project (SPE 10) which gives high-contrast permeability coefficients. The SPE10 data set is used as a coarse level in the Monte Carlo method and the respective permeability coefficient k (provided in the SPE10 dataset) is used as a mean in the simulation. The actual coefficients are drawn based on a KL-expansion assuming that the log-mean is perturbed by a log-normal distributed samples.

  20. Synchrotron stereotactic radiotherapy: dosimetry by Fricke gel and Monte Carlo simulations.

    Science.gov (United States)

    Boudou, Caroline; Biston, Marie-Claude; Corde, Stéphanie; Adam, Jean-François; Ferrero, Claudio; Estève, François; Elleaume, Hélène

    2004-11-21

    Synchrotron stereotactic radiotherapy (SSR) consists in loading the tumour with a high atomic number element (Z), and exposing it to monochromatic x-rays from a synchrotron source (50-100 keV), in stereotactic conditions. The dose distribution results from both the stereotactic monochromatic x-ray irradiation and the presence of the high Z element. The purpose of this preliminary study was to evaluate the two-dimensional dose distribution resulting solely from the irradiation geometry, using Monte Carlo simulations and a Fricke gel dosimeter. The verification of a Monte Carlo-based dosimetry was first assessed by depth dose measurements in a water tank. We thereafter used a Fricke dosimeter to compare Monte Carlo simulations with dose measurements. The Fricke dosimeter is a solution containing ferrous ions which are oxidized to ferric ions under ionizing radiation, proportionally to the absorbed dose. A cylindrical phantom filled with Fricke gel was irradiated in stereotactic conditions over several slices with a continuous beam (beam section = 0.1 x 1 cm2). The phantom and calibration vessels were then imaged by nuclear magnetic resonance. The measured doses were fairly consistent with those predicted by Monte Carlo simulations. However, the measured maximum absolute dose was 10% underestimated regarding calculation. The loss of information in the higher region of dose is explained by the diffusion of ferric ions. Monte Carlo simulation is the most accurate tool for dosimetry including complex geometries made of heterogeneous materials. Although the technique requires improvements, gel dosimetry remains an essential tool for the experimental verification of dose distribution in SSR with millimetre precision.

  1. PRIMO. A graphical environment for the Monte Carlo simulation of Varian and Elekta linacs

    International Nuclear Information System (INIS)

    Background: The accurate Monte Carlo simulation of a linac requires a detailed description of its geometry and the application of elaborate variance-reduction techniques for radiation transport. Both tasks entail a substantial coding effort and demand advanced knowledge of the intricacies of the Monte Carlo system being used. Methods: PRIMO, a new Monte Carlo system that allows the effortless simulation of most Varian and Elekta linacs, including their multileaf collimators and electron applicators, is introduced. PRIMO combines (1) accurate physics from the PENELOPE code, (2) dedicated variance-reduction techniques that significantly reduce the computation time, and (3) a user-friendly graphical interface with tools for the analysis of the generated data. PRIMO can tally dose distributions in phantoms and computerized tomographies, handle phase-space files in IAEA format, and import structures (planning target volumes, organs at risk) in the DICOM RT-STRUCT standard. Results: A prostate treatment, conformed with a high definition Millenium multileaf collimator (MLC 120HD) from a Varian Clinac 2100 C/D, is presented as an example. The computation of the dose distribution in 1.86 x 3.00 x 1.86 mm3 voxels with an average 2 % standard statistical uncertainty, performed on an eight-core Intel Xeon at 2.67 GHz, took 1.8 h - excluding the patient-independent part of the linac, which required 3.8 h but it is simulated only once. Conclusion: PRIMO is a self-contained user-friendly system that facilitates the Monte Carlo simulation of dose distributions produced by most currently available linacs. This opens the door for routine use of Monte Carlo in clinical research and quality assurance purposes. It is free software that can be downloaded from http://www.primoproject.net. (orig.)

  2. Measurement and Monte Carlo simulation of 6 MV X-rays for small radiation fields

    International Nuclear Information System (INIS)

    In order to obtain basic data for treatment plan in radiosurgery, we measured small fields of 6 MV X-rays and compared the measured data with our Monte Carlo simulations for the small fields. The small fields of 1.0, 2.0 and 3.0 cm in diameter were used in this study. Percentage depth dose (PDD) and beam profiles of those fields were measured and calculated. A small semiconductor detector, water phantoms, and a remote control system were used for the measurement. Monte Carlo simulations were performed using the EGS4 code with the input data prepared for the energy distribution of 6MV X-rays, beam divergence, circular fields and the geometry of the water phantoms. In the case of PDD values, the calculated values were lower than the measured values for all fields and depths, with the differences being 0.3 to 5.7% at the depths of 2.0 to 20.0 cm and 0.0 to 8.9% at the surface regions. As a result of the analysis of beam profiles for all field sizes at a depth of 10cm in water phantom, the measured 90% dose widths were in good agreement with the calculated values, however, the calculated penumbra radii were 0.1cm shorter than measured values. The measured PDDs and beam profiles agreement with the Monte Carlo calculations approximately. However, it is different when it comes to calculations in the area of phantom surface and penumbra because the Monte Carlo calculations were performed under the simplified geometries. Therefore, we have to study how to include the actual geometries and more precise data for the field area in Monte Carlo calculations. The Monte Carlo calculations will be used as a useful tool for the very complicated conditions in measurement and verification

  3. Monte Carlo simulations of a novel Micromegas 2D array for proton dosimetry

    Science.gov (United States)

    Dolney, D.; Ainsley, C.; Hollebeek, R.; Maughan, R.

    2016-02-01

    Modern proton therapy affords control of the delivery of radiotherapeutic dose on fine length and temporal scales. The authors have developed a novel detector technology based on Micromesh Gaseous Structure (Micromegas) that is uniquely tailored for applications using therapeutic proton beams. An implementation of a prototype Micromegas detector for Monte Carlo using Geant4 is presented here. Comparison of simulation results with measurements demonstrates agreement in relative dose along the proton longitudinal dose profile to be 1%. The effect of a radioactive calibration source embedded in the chamber gas is demonstrated by measurements and reproduced by simulations, also at the 1% level. Our Monte Carlo simulations are shown to reproduce the time structure of ionization pulses produced by a double-scattering delivery system.

  4. A Monte Carlo simulation for kinetic chemotaxis models: an application to the traveling population wave

    CERN Document Server

    Yasuda, Shugo

    2015-01-01

    A Monte Carlo simulation for the chemotactic bacteria is developed on the basis of the kinetic modeling, i.e., the Boltzmann transport equation, and applied to the one-dimensional traveling population wave in a micro channel.In this method, the Monte Carlo method, which calculates the run-and-tumble motions of bacteria, is coupled with a finite volume method to solve the macroscopic transport of the chemical cues in the field. The simulation method can successfully reproduce the traveling population wave of bacteria which was observed experimentally. The microscopic dynamics of bacteria, e.g., the velocity autocorrelation function and velocity distribution function of bacteria, are also investigated. It is found that the bacteria which form the traveling population wave create quasi-periodic motions as well as a migratory movement along with the traveling population wave. Simulations are also performed with changing the sensitivity and modulation parameters in the response function of bacteria. It is found th...

  5. Comparison of Geant4-DNA simulation of S-values with other Monte Carlo codes

    Energy Technology Data Exchange (ETDEWEB)

    André, T. [Université Bordeaux 1, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); Morini, F. [Research Group of Theoretical Chemistry and Molecular Modelling, Hasselt University, Agoralaan Gebouw D, B-3590 Diepenbeek (Belgium); Karamitros, M. [Université Bordeaux 1, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, INCIA, UMR 5287, F-33400 Talence (France); Delorme, R. [LPSC, Université Joseph Fourier Grenoble 1, CNRS/IN2P3, Grenoble INP, 38026 Grenoble (France); CEA, LIST, F-91191 Gif-sur-Yvette (France); Le Loirec, C. [CEA, LIST, F-91191 Gif-sur-Yvette (France); Campos, L. [Departamento de Física, Universidade Federal de Sergipe, São Cristóvão (Brazil); Champion, C. [Université Bordeaux 1, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); Groetz, J.-E.; Fromm, M. [Université de Franche-Comté, Laboratoire Chrono-Environnement, UMR CNRS 6249, Besançon (France); Bordage, M.-C. [Laboratoire Plasmas et Conversion d’Énergie, UMR 5213 CNRS-INPT-UPS, Université Paul Sabatier, Toulouse (France); Perrot, Y. [Laboratoire de Physique Corpusculaire, UMR 6533, Aubière (France); Barberet, Ph. [Université Bordeaux 1, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); and others

    2014-01-15

    Monte Carlo simulations of S-values have been carried out with the Geant4-DNA extension of the Geant4 toolkit. The S-values have been simulated for monoenergetic electrons with energies ranging from 0.1 keV up to 20 keV, in liquid water spheres (for four radii, chosen between 10 nm and 1 μm), and for electrons emitted by five isotopes of iodine (131, 132, 133, 134 and 135), in liquid water spheres of varying radius (from 15 μm up to 250 μm). The results have been compared to those obtained from other Monte Carlo codes and from other published data. The use of the Kolmogorov–Smirnov test has allowed confirming the statistical compatibility of all simulation results.

  6. Sampling of transport coefficients in steady state Townsend Monte Carlo simulation

    International Nuclear Information System (INIS)

    In this paper a complete and consistent set of equations for sampling of the data in steady state Townsend (SST) Monte Carlo simulations (MCS) is developed. Standard implementation of a Monte Carlo simulation code for time of flight (TOF) allows us to add SST sampling. Membrane's sampling has an advantage in obtaining spatial variation of properties with high spatial resolution but with a problem in poor statistics for low energy electrons that move perpendicular to the field axis. The box sampling overcomes this problem but suffers from a poorer statistics than membrane sampling. The results show the effect of non-conservative collisions in the difference between SST and TOF results. In addition the internal consistency between two methods of SST sampling is very good. The present paper also gives a complete set of equations for conversion between the two types of experiments TOF and SST. Our simulation provided us also with a way to test the conversion formulae and their convergence

  7. MCViNE -- An object oriented Monte Carlo neutron ray tracing simulation package

    CERN Document Server

    Lin, Jiao Y Y; Granroth, Garrett E; Abernathy, Douglas L; Lumsden, Mark D; Winn, Barry; Aczel, Adam A; Aivazis, Michael; Fultz, Brent

    2015-01-01

    MCViNE (Monte-Carlo VIrtual Neutron Experiment) is a versatile Monte Carlo (MC) neutron ray-tracing program that provides researchers with tools for performing computer modeling and simulations that mirror real neutron scattering experiments. By adopting modern software engineering practices such as using composite and visitor design patterns for representing and accessing neutron scatterers, and using recursive algorithms for multiple scattering, MCViNE is flexible enough to handle sophisticated neutron scattering problems including, for example, neutron detection by complex detector systems, and single and multiple scattering events in a variety of samples and sample environments. In addition, MCViNE can take advantage of simulation components in linear-chain-based MC ray tracing packages widely used in instrument design and optimization, as well as NumPy-based components that make prototypes useful and easy to develop. These developments have enabled us to carry out detailed simulations of neutron scatteri...

  8. Subroutines to Simulate Fission Neutrons for Monte Carlo Transport Codes

    CERN Document Server

    Lestone, J P

    2014-01-01

    Fortran subroutines have been written to simulate the production of fission neutrons from the spontaneous fission of 252Cf and 240Pu, and from the thermal neutron induced fission of 239Pu and 235U. The names of these four subroutines are getnv252, getnv240, getnv239, and getnv235, respectively. These subroutines reproduce measured first, second, and third moments of the neutron multiplicity distributions, measured neutron-fission correlation data for the spontaneous fission of 252Cf, and measured neutron-neutron correlation data for both the spontaneous fission of 252Cf and the thermal neutron induced fission of 235U. The codes presented here can be used to study the possible uses of neutron-neutron correlations in the area of transparency measurements and the uses of neutron-neutron correlations in coincidence neutron imaging.

  9. Monte Carlo simulation of MOSFET dosimeter for electron backscatter using the GEANT4 code.

    Science.gov (United States)

    Chow, James C L; Leung, Michael K K

    2008-06-01

    The aim of this study is to investigate the influence of the body of the metal-oxide-semiconductor field effect transistor (MOSFET) dosimeter in measuring the electron backscatter from lead. The electron backscatter factor (EBF), which is defined as the ratio of dose at the tissue-lead interface to the dose at the same point without the presence of backscatter, was calculated by the Monte Carlo simulation using the GEANT4 code. Electron beams with energies of 4, 6, 9, and 12 MeV were used in the simulation. It was found that in the presence of the MOSFET body, the EBFs were underestimated by about 2%-0.9% for electron beam energies of 4-12 MeV, respectively. The trend of the decrease of EBF with an increase of electron energy can be explained by the small MOSFET dosimeter, mainly made of epoxy and silicon, not only attenuated the electron fluence of the electron beam from upstream, but also the electron backscatter generated by the lead underneath the dosimeter. However, this variation of the EBF underestimation is within the same order of the statistical uncertainties as the Monte Carlo simulations, which ranged from 1.3% to 0.8% for the electron energies of 4-12 MeV, due to the small dosimetric volume. Such small EBF deviation is therefore insignificant when the uncertainty of the Monte Carlo simulation is taken into account. Corresponding measurements were carried out and uncertainties compared to Monte Carlo results were within +/- 2%. Spectra of energy deposited by the backscattered electrons in dosimetric volumes with and without the lead and MOSFET were determined by Monte Carlo simulations. It was found that in both cases, when the MOSFET body is either present or absent in the simulation, deviations of electron energy spectra with and without the lead decrease with an increase of the electron beam energy. Moreover, the softer spectrum of the backscattered electron when lead is present can result in a reduction of the MOSFET response due to stronger

  10. MCNPX Monte Carlo burnup simulations of the isotope correlation experiments in the NPP Obrigheim

    Energy Technology Data Exchange (ETDEWEB)

    Cao Yan, E-mail: ycao@anl.go [Nuclear Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Gohar, Yousry [Nuclear Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Broeders, Cornelis H.M. [Forschungszentrum Karlsruhe, Institute for Neutron Physics and Reactor Technology, P.O. Box 3640, 76021 Karlsruhe (Germany)

    2010-10-15

    This paper describes the simulation work of the Isotope Correlation Experiment (ICE) using the MCNPX Monte Carlo computer code package. The Monte Carlo simulation results are compared with the ICE-Experimental measurements for burnup up to 30 GWD/t. The comparison shows the good capabilities of the MCNPX computer code package for predicting the depletion of the uranium fuel and the buildup of the plutonium isotopes in a PWR thermal reactor. The Monte Carlo simulation results show also good agreements with the experimental data for calculating several long-lived and stable fission products. However, for the americium and curium actinides, it is difficult to judge the predication capabilities for these actinides due to the large uncertainties in the ICE-Experimental data. In the MCNPX numerical simulations, a pin cell model is utilized to simulate the fuel lattice of the nuclear power reactor. Temperature dependent libraries based on JEFF3.1 nuclear data files are utilized for the calculations. In addition, temperature dependent libraries based ENDF/B-VII nuclear data files are utilized and the obtained results are very close to the JEFF3.1 results, except for {approx}10% differences in the prediction of the minor actinide isotopes buildup.

  11. Dosimetry in radiotherapy and brachytherapy by Monte-Carlo GATE simulation on computing grid; Dosimetrie en radiotherapie et curietherapie par simulation Monte-Carlo GATE sur grille informatique

    Energy Technology Data Exchange (ETDEWEB)

    Thiam, Ch.O

    2007-10-15

    Accurate radiotherapy treatment requires the delivery of a precise dose to the tumour volume and a good knowledge of the dose deposit to the neighbouring zones. Computation of the treatments is usually carried out by a Treatment Planning System (T.P.S.) which needs to be precise and fast. The G.A.T.E. platform for Monte-Carlo simulation based on G.E.A.N.T.4 is an emerging tool for nuclear medicine application that provides functionalities for fast and reliable dosimetric calculations. In this thesis, we studied in parallel a validation of the G.A.T.E. platform for the modelling of electrons and photons low energy sources and the optimized use of grid infrastructures to reduce simulations computing time. G.A.T.E. was validated for the dose calculation of point kernels for mono-energetic electrons and compared with the results of other Monte-Carlo studies. A detailed study was made on the energy deposit during electrons transport in G.E.A.N.T.4. In order to validate G.A.T.E. for very low energy photons (<35 keV), three models of radioactive sources used in brachytherapy and containing iodine 125 (2301 of Best Medical International; Symmetra of Uro- Med/Bebig and 6711 of Amersham) were simulated. Our results were analyzed according to the recommendations of task group No43 of American Association of Physicists in Medicine (A.A.P.M.). They show a good agreement between G.A.T.E., the reference studies and A.A.P.M. recommended values. The use of Monte-Carlo simulations for a better definition of the dose deposited in the tumour volumes requires long computing time. In order to reduce it, we exploited E.G.E.E. grid infrastructure where simulations are distributed using innovative technologies taking into account the grid status. Time necessary for the computing of a radiotherapy planning simulation using electrons was reduced by a factor 30. A Web platform based on G.E.N.I.U.S. portal was developed to make easily available all the methods to submit and manage G

  12. Monte-Carlo modelling of multi-object adaptive optics performance on the European Extremely Large Telescope

    CERN Document Server

    Basden, Alastair

    2016-01-01

    The performance of a wide-field adaptive optics system depends on input design parameters. Here we investigate the performance of a multi-object adaptive optics system design for the European Extremely Large Telescope, using an end-to-end Monte-Carlo adaptive optics simulation tool, DASP, with relevance for proposed instruments such as MOSAIC. We consider parameters such as the number of laser guide stars, sodium layer depth, wavefront sensor pixel scale, actuator pitch and natural guide star availability. We provide potential areas where costs savings can be made, and investigate trade-offs between performance and cost, and provide solutions that would enable such an instrument to be built with currently available technology. Our key recommendations include a trade-off for laser guide star wavefront sensor pixel scale of about 0.7 arcseconds per pixel, and a field of view of at least 7 arcseconds, that EMCCD technology should be used for natural guide star wavefront sensors even if reduced frame rate is nece...

  13. Computer simulation of the collision frequency of two particles in optical tweezers

    Institute of Scientific and Technical Information of China (English)

    Xu Sheng-Hua; Li Yin-Mei; Lou Li-Ren; Sun Zhi-Wei

    2005-01-01

    Optical tweezers have been successfully used in the study of colloid science. In most applications people are concerned with the behaviour of a single particle held in the optical tweezers. Recently, the ability of the optical tweezers to simultaneously hold two particles has been used to determine the stability ratio of colloidal dispersion. This new development stimulates the efforts to explore the characteristics of a two-particle system in the optical tweezers.An infinite spherical potential well has been used to estimate the collision frequency for two particles in the optical trap based on a Monte Carlo simulation. In this article, a more reasonable harmonic potential, commonly accepted for the optical tweezers, is adopted in a Monte Carlo simulation of the collision frequency. The effect of hydrodynamic interaction of particles in the trap is also considered. The simulation results based on this improved model show quantitatively that the collision frequency drops down sharply at first and then decreases slowly as the distance between the two particles increases. The simulation also shows how the collision frequency is related to the stiffness of the optical tweezers.

  14. Monte Carlo simulation: tool for the calibration in analytical determination of radionuclides; Simulacion Monte Carlo: herramienta para la calibracion en determinaciones analiticas de radionucleidos

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, Jorge A. Carrazana; Ferrera, Eduardo A. Capote; Gomez, Isis M. Fernandez; Castro, Gloria V. Rodriguez; Ricardo, Niury Martinez, E-mail: cphr@cphr.edu.cu [Centro de Proteccion e Higiene de las Radiaciones (CPHR), La Habana (Cuba)

    2013-07-01

    This work shows how is established the traceability of the analytical determinations using this calibration method. Highlights the advantages offered by Monte Carlo simulation for the application of corrections by differences in chemical composition, density and height of the samples analyzed. Likewise, the results obtained by the LVRA in two exercises organized by the International Agency for Atomic Energy (IAEA) are presented. In these exercises (an intercomparison and a proficiency test) all reported analytical results were obtained based on calibrations in efficiency by Monte Carlo simulation using the DETEFF program.

  15. Toward a Monte Carlo program for simulating vapor-liquid phase equilibria from first principles

    Energy Technology Data Exchange (ETDEWEB)

    McGrath, M; Siepmann, J I; Kuo, I W; Mundy, C J; Vandevondele, J; Sprik, M; Hutter, J; Mohamed, F; Krack, M; Parrinello, M

    2004-10-20

    Efficient Monte Carlo algorithms are combined with the Quickstep energy routines of CP2K to develop a program that allows for Monte Carlo simulations in the canonical, isobaric-isothermal, and Gibbs ensembles using a first principles description of the physical system. Configurational-bias Monte Carlo techniques and pre-biasing using an inexpensive approximate potential are employed to increase the sampling efficiency and to reduce the frequency of expensive ab initio energy evaluations. The new Monte Carlo program has been validated through extensive comparison with molecular dynamics simulations using the programs CPMD and CP2K. Preliminary results for the vapor-liquid coexistence properties (T = 473 K) of water using the Becke-Lee-Yang-Parr exchange and correlation energy functionals, a triple-zeta valence basis set augmented with two sets of d-type or p-type polarization functions, and Goedecker-Teter-Hutter pseudopotentials are presented. The preliminary results indicate that this description of water leads to an underestimation of the saturated liquid density and heat of vaporization and, correspondingly, an overestimation of the saturated vapor pressure.

  16. Noninvasive optical measurement of bone marrow lesions: a Monte Carlo study on visible human dataset

    Science.gov (United States)

    Su, Yu; Li, Ting

    2016-03-01

    Bone marrow is both the main hematopoietic and important immune organ. Bone marrow lesions (BMLs) may cause a series of severe complications and even myeloma. The traditional diagnosis of BMLs rely on mostly bone marrow biopsy/ puncture, and sometimes MRI, X-ray, and etc., which are either invasive and dangerous, or ionizing and costly. A diagnosis technology with advantages in noninvasive, safe, real-time continuous detection, and low cost is requested. Here we reported our preliminary exploration of feasibility verification of using near-infrared spectroscopy (NIRS) in clinical diagnosis of BMLs by Monte Carlo simulation study. We simulated and visualized the light propagation in the bone marrow quantitatively with a Monte Carlo simulation software for 3D voxelized media and Visible Chinese Human data set, which faithfully represents human anatomy. The results indicate that bone marrow actually has significant effects on light propagation. According to a sequence of simulation and data analysis, the optimal source-detector separation was suggested to be narrowed down to 2.8-3.2cm, at which separation the spatial sensitivity distribution of NIRS cover the most region of bone marrow with high signal-to-noise ratio. The display of the sources and detectors were optimized as well. This study investigated the light transport in spine addressing to the BMLs detection issue and reported the feasibility of NIRS detection of BMLs noninvasively in theory. The optimized probe design of the coming NIRS-based BMLs detector is also provided.

  17. Monte Carlo simulation for the micellar behavior of amphiphilic comb-like copolymers

    Institute of Scientific and Technical Information of China (English)

    冯莺; 隋家贤; 赵季若; 陈欣方

    2000-01-01

    Micellar behaviors in 2D and 3D lattice models for amphiphilic comb-like copolymers in water phase and in water/oil mixtures were simulated. A dynamical algorithm together with chain reptation movements was used in the simulation. Three-dimension displaying program was pro-grammed and free energy was estimated by Monte Carlo technigue. The results demonstrate that reduced interaction energy influences morphological structures of micelle and emulsion ??stems greatly; 3D simulation showing can display more direct images of morphological structures; the amphiphilic comb-like polymers with a hydrophobic main chain and hydrophilic side chains have lower energy in water than in oil.

  18. Monte Carlo Simulation on Coordinated Movement of Kinesin and Dynein Motors

    Institute of Scientific and Technical Information of China (English)

    WANG Hong; DOU Shuo-Xing; WANG Peng-Ye

    2008-01-01

    Kinesin and dynein are two important classes of molecular motors which are responsible for active organelle trafficking and cell division.They call work together to carry a cargo,moving along the microtubule in a coordinated way.We use Monte Carlo method to simulate the dynamics of this coordinated movement.Based on four essential assumptions,our simulations reproduce some features of the recent in vivo experiments.The fast moving speed of the cargo js simulated and the speed distribution is presented.

  19. Impact of Weather Conditions on the Construction of the Terminal - Monte Carlo Simulation

    Directory of Open Access Journals (Sweden)

    Tatjana Stanivuk

    2013-03-01

    Full Text Available A simulation model is developed for the potential planned Patagonia and Tierra del Fuego terminals. The purpose is to identify reliability and availability of loading operations at the terminal. The harsh weather conditions, technical reliability and concurrent traffic affect LNG (Liquefied Natural Gas Carriers during approaching or loading. Probabilistic simulation method is created and Monte Carlo simulations are carried out for several cases, with varied production, number of jetties and terminal storage. The results indicate high importance of weather restrictions and are used to present a recommendation with two loading jetties and a larger volume of storage capacity.

  20. A Monte Carlo simulation of the packing and segregation of spheres in cylinders

    Directory of Open Access Journals (Sweden)

    C. R. A. ABREU

    1999-12-01

    Full Text Available In this work, the Monte Carlo method (MC was extended to simulate the packing and segregation of particles subjected to a gravitational field and confined inside rigid walls. The method was used in systems containing spheres inside cylinders. The calculation of void fraction profiles in both the axial and radial directions was formulated, and some results are presented. In agreement with experimental data, the simulations show that the packed beds present structural ordering near the cylindrical walls up to a distance of about 4 particle diameters. The simulations also indicate that the presence of the cylindrical wall does not seem to have a strong effect on the gravitational segregation phenomenon.

  1. Monte Carlo simulation by GEANT 4 and GESPECOR of in situ gamma-ray spectrometry measurements.

    Science.gov (United States)

    Chirosca, Alecsandru; Suvaila, Rares; Sima, Octavian

    2013-11-01

    The application of GEANT 4 and GESPECOR Monte Carlo simulation codes for efficiency calibration of in situ gamma-ray spectrometry was studied. The long computing time required by GEANT 4 prevents its use in routine simulations. Due to the application of variance reduction techniques, GESPECOR is much faster. In this code specific procedures for incorporating the depth profile of the activity were implemented. In addition procedures for evaluating the effect of non-homogeneity of the source were developed. The code was validated by comparison with test simulations carried out with GEANT 4 and by comparison with published results. PMID:23566809

  2. Number of iterations needed in Monte Carlo Simulation using reliability analysis for tunnel supports

    Directory of Open Access Journals (Sweden)

    E. Bukaçi

    2016-06-01

    Full Text Available There are many methods in geotechnical engineering which could take advantage of Monte Carlo Simulation to establish probability of failure, since closed form solutions are almost impossible to use in most cases. The problem that arises with using Monte Carlo Simulation is the number of iterations needed for a particular simulation.This article will show why it’s important to calculate number of iterations needed for Monte Carlo Simulation used in reliability analysis for tunnel supports using convergence – confinement method. Number if iterations needed will be calculated with two methods. In the first method, the analyst has to accept a distribution function for the performance function. The other method suggested by this article is to calculate number of iterations based on the convergence of the factor the analyst is interested in the calculation. Reliability analysis will be performed for the diversion tunnel in Rrëshen, Albania, by using both methods mentioned and results will be confronted

  3. Modeling weight variability in a pan coating process using Monte Carlo simulations.

    Science.gov (United States)

    Pandey, Preetanshu; Katakdaunde, Manoj; Turton, Richard

    2006-10-06

    The primary objective of the current study was to investigate process variables affecting weight gain mass coating variability (CV(m) ) in pan coating devices using novel video-imaging techniques and Monte Carlo simulations. Experimental information such as the tablet location, circulation time distribution, velocity distribution, projected surface area, and spray dynamics was the main input to the simulations. The data on the dynamics of tablet movement were obtained using novel video-imaging methods. The effects of pan speed, pan loading, tablet size, coating time, spray flux distribution, and spray area and shape were investigated. CV(m) was found to be inversely proportional to the square root of coating time. The spray shape was not found to affect the CV(m) of the process significantly, but an increase in the spray area led to lower CV(m) s. Coating experiments were conducted to verify the predictions from the Monte Carlo simulations, and the trends predicted from the model were in good agreement. It was observed that the Monte Carlo simulations underpredicted CV(m) s in comparison to the experiments. The model developed can provide a basis for adjustments in process parameters required during scale-up operations and can be useful in predicting the process changes that are needed to achieve the same CV(m) when a variable is altered.

  4. Exploring fluctuations and phase equilibria in fluid mixtures via Monte Carlo simulation

    Science.gov (United States)

    Denton, Alan R.; Schmidt, Michael P.

    2013-03-01

    Monte Carlo simulation provides a powerful tool for understanding and exploring thermodynamic phase equilibria in many-particle interacting systems. Among the most physically intuitive simulation methods is Gibbs ensemble Monte Carlo (GEMC), which allows direct computation of phase coexistence curves of model fluids by assigning each phase to its own simulation cell. When one or both of the phases can be modelled virtually via an analytic free energy function (Mehta and Kofke 1993 Mol. Phys. 79 39), the GEMC method takes on new pedagogical significance as an efficient means of analysing fluctuations and illuminating the statistical foundation of phase behaviour in finite systems. Here we extend this virtual GEMC method to binary fluid mixtures and demonstrate its implementation and instructional value with two applications: (1) a lattice model of simple mixtures and polymer blends and (2) a free-volume model of a complex mixture of colloids and polymers. We present algorithms for performing Monte Carlo trial moves in the virtual Gibbs ensemble, validate the method by computing fluid demixing phase diagrams, and analyse the dependence of fluctuations on system size. Our open-source simulation programs, coded in the platform-independent Java language, are suitable for use in classroom, tutorial, or computational laboratory settings.

  5. GPU-accelerated Monte Carlo simulation of particle coagulation based on the inverse method

    Science.gov (United States)

    Wei, J.; Kruis, F. E.

    2013-09-01

    Simulating particle coagulation using Monte Carlo methods is in general a challenging computational task due to its numerical complexity and the computing cost. Currently, the lowest computing costs are obtained when applying a graphic processing unit (GPU) originally developed for speeding up graphic processing in the consumer market. In this article we present an implementation of accelerating a Monte Carlo method based on the Inverse scheme for simulating particle coagulation on the GPU. The abundant data parallelism embedded within the Monte Carlo method is explained as it will allow an efficient parallelization of the MC code on the GPU. Furthermore, the computation accuracy of the MC on GPU was validated with a benchmark, a CPU-based discrete-sectional method. To evaluate the performance gains by using the GPU, the computing time on the GPU against its sequential counterpart on the CPU were compared. The measured speedups show that the GPU can accelerate the execution of the MC code by a factor 10-100, depending on the chosen particle number of simulation particles. The algorithm shows a linear dependence of computing time with the number of simulation particles, which is a remarkable result in view of the n2 dependence of the coagulation.

  6. The proton therapy nozzles at Samsung Medical Center: A Monte Carlo simulation study using TOPAS

    Science.gov (United States)

    Chung, Kwangzoo; Kim, Jinsung; Kim, Dae-Hyun; Ahn, Sunghwan; Han, Youngyih

    2015-07-01

    To expedite the commissioning process of the proton therapy system at Samsung Medical Center (SMC), we have developed a Monte Carlo simulation model of the proton therapy nozzles by using TOol for PArticle Simulation (TOPAS). At SMC proton therapy center, we have two gantry rooms with different types of nozzles: a multi-purpose nozzle and a dedicated scanning nozzle. Each nozzle has been modeled in detail following the geometry information provided by the manufacturer, Sumitomo Heavy Industries, Ltd. For this purpose, the novel features of TOPAS, such as the time feature or the ridge filter class, have been used, and the appropriate physics models for proton nozzle simulation have been defined. Dosimetric properties, like percent depth dose curve, spreadout Bragg peak (SOBP), and beam spot size, have been simulated and verified against measured beam data. Beyond the Monte Carlo nozzle modeling, we have developed an interface between TOPAS and the treatment planning system (TPS), RayStation. An exported radiotherapy (RT) plan from the TPS is interpreted by using an interface and is then translated into the TOPAS input text. The developed Monte Carlo nozzle model can be used to estimate the non-beam performance, such as the neutron background, of the nozzles. Furthermore, the nozzle model can be used to study the mechanical optimization of the design of the nozzle.

  7. Realistic PET Monte Carlo Simulation With Pixelated Block Detectors, Light Sharing, Random Coincidences and Dead-Time Modeling

    OpenAIRE

    Guérin, Bastein; Fakhri, Georges El

    2008-01-01

    We have developed and validated a realistic simulation of random coincidences, pixelated block detectors, light sharing among crystal elements and dead-time in 2D and 3D positron emission tomography (PET) imaging based on the SimSET Monte Carlo simulation software. Our simulation was validated by comparison to a Monte Carlo transport code widely used for PET modeling, GATE, and to measurements made on a PET scanner.

  8. A Unified Microscopic-Macroscopic Monte Carlo Simulation of Gas-Grain Chemistry in Cold Dense Interstellar Clouds

    OpenAIRE

    Chang, Qiang; Herbst, Eric

    2012-01-01

    For the first time, we report a unified microscopic-macroscopic Monte Carlo simulation of gas-grain chemistry in cold interstellar clouds in which both the gas-phase and the grain surface chemistry are simulated by a stochastic technique. The surface chemistry is simulated with a microscopic Monte Carlo method in which the chemistry occurs on an initially flat surface. The surface chemical network consists of 29 reactions initiated by the accreting species H, O, C, and CO. Four different mode...

  9. Using hybrid implicit Monte Carlo diffusion to simulate gray radiation hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Cleveland, Mathew A., E-mail: cleveland7@llnl.gov; Gentile, Nick

    2015-06-15

    This work describes how to couple a hybrid Implicit Monte Carlo Diffusion (HIMCD) method with a Lagrangian hydrodynamics code to evaluate the coupled radiation hydrodynamics equations. This HIMCD method dynamically applies Implicit Monte Carlo Diffusion (IMD) [1] to regions of a problem that are opaque and diffusive while applying standard Implicit Monte Carlo (IMC) [2] to regions where the diffusion approximation is invalid. We show that this method significantly improves the computational efficiency as compared to a standard IMC/Hydrodynamics solver, when optically thick diffusive material is present, while maintaining accuracy. Two test cases are used to demonstrate the accuracy and performance of HIMCD as compared to IMC and IMD. The first is the Lowrie semi-analytic diffusive shock [3]. The second is a simple test case where the source radiation streams through optically thin material and heats a thick diffusive region of material causing it to rapidly expand. We found that HIMCD proves to be accurate, robust, and computationally efficient for these test problems.

  10. Simulation of the functioning of a gamma camera using Monte Carlo method; Simulacion del funcionamiento de una camara gamma mediante metodo Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Oramas Polo, I.

    2014-07-01

    This paper presents the simulation of the gamma camera Park Isocam II by Monte Carlo code SIMIND. This simulation allows detailed assessment of the functioning of the gamma camera. The parameters evaluated by means of the simulation are: the intrinsic uniformity with different window amplitudes, the system uniformity, the extrinsic spatial resolution, the maximum rate of counts, the intrinsic sensitivity, the system sensitivity, the energy resolution and the pixel size. The results of the simulation are compared and evaluated against the specifications of the manufacturer of the gamma camera and taking into account the National Protocol for Quality Control of Nuclear Medicine Instruments of the Cuban Medical Equipment Control Center. The simulation reported here demonstrates the validity of the SIMIND Monte Carlo code to evaluate the performance of the gamma camera Park Isocam II and as result a computational model of the camera has been obtained. (Author)

  11. Prediction of beam hardening artefacts in computed tomography using Monte Carlo simulations

    Science.gov (United States)

    Thomsen, M.; Knudsen, E. B.; Willendrup, P. K.; Bech, M.; Willner, M.; Pfeiffer, F.; Poulsen, M.; Lefmann, K.; Feidenhans'l, R.

    2015-01-01

    We show how radiological images of both single and multi material samples can be simulated using the Monte Carlo simulation tool McXtrace and how these images can be used to make a three dimensional reconstruction. Good numerical agreement between the X-ray attenuation coefficient in experimental and simulated data can be obtained, which allows us to use simulated projections in the linearisation procedure for single material samples and in that way reduce beam hardening artefacts. The simulations can be used to predict beam hardening artefacts in multi material samples with complex geometry, illustrated with an example. Linearisation requires knowledge about the X-ray transmission at varying sample thickness, but in some cases homogeneous calibration phantoms are hard to manufacture, which affects the accuracy of the calibration. Using simulated data overcomes the manufacturing problems and in that way improves the calibration.

  12. MONTE CARLO SIMULATION OF SPIN-POLARIZED SECONDARY ELECTRONS FROM IRON

    Institute of Scientific and Technical Information of China (English)

    X. Sun; Z.J. Ding; H.M Li; K. Salma; Z.M. Zhang; W.S. Tan

    2005-01-01

    A Monte Carlo model considering the electron spin direction and spin asymmetry has been developed. The energy distribution of the secondary electron polarization and the primary energy dependence of the polarization from Fe are studied. The simulation results show that:(1) the intensity of the spin-up secondary electrons is larger thanvthat of thevspin-down secondary electrons, suggesting the secondary electrons are spin polarized; (2) the spin polarization of secondary electrons with nearly zero kinetic energy is higher than the average valance spin polarization, Pb=27% for Fe. With increasing kinetic energy, the spin polarization of the secondary electrons decreases to the value of Pb remaining constant at higher kinetic energies;(3) the spin polarization increases with an increase in the primary energy and reaches a saturation value at higher primary energy in both the Monte Carlo simulation and experimental results.

  13. Fe-Al alloy surface tension and expansion coefficient of the Monte Carlo simulation

    International Nuclear Information System (INIS)

    Using the new modified analytical EAM and the Monte Carlo method, and constructing a new system and surface, the liquid surface tension was calculated. According to a given temperature alloy free energy minima, the coefficient of linear expansion of the Fe-Al alloy is simulated. The method and the results discussed, we give the mathematical relationship between the liquid surface tension and the temperature of the three kinds of Fe-Al alloy. The results of the simulation are in good agreement with existing experimental data in the low temperature zone, however, the result is a little lower than the experimental results in the high temperature zone. So the calculation result shows that the Monte Carlo method is very effective in the Fe-Al alloy and the method is right and reliable here. (authors)

  14. Unusual adsorption site behavior in PCN-14 metal-organic framework predicted from Monte Carlo simulation.

    Science.gov (United States)

    Lucena, Sebastião M P; Mileo, Paulo G M; Silvino, Pedro F G; Cavalcante, Célio L

    2011-12-01

    The adsorption equilibrium of methane in PCN-14 was simulated by the Monte Carlo technique in the grand canonical ensemble. A new force field was proposed for the methane/PCN-14 system, and the temperature dependence of the molecular siting was investigated. A detailed study of the statistics of the center of mass and potential energy showed a surprising site behavior with no energy barriers between weak and strong sites, allowing open metal sites to guide methane molecules to other neighboring sites. Moreover, this study showed that a model assuming weakly adsorbing open metal clusters in PCN-14, densely populated only at low temperatures (below 150 K), can explain published experimental data. These results also explain previously observed discrepancies between neutron diffraction experiments and Monte Carlo simulations.

  15. Monte Carlo Simulation of Laser-Ablated Particle Splitting Dynamic in a Low Pressure Inert Gas

    Science.gov (United States)

    Ding, Xuecheng; Zhang, Zicai; Liang, Weihua; Chu, Lizhi; Deng, Zechao; Wang, Yinglong

    2016-06-01

    A Monte Carlo simulation method with an instantaneous density dependent mean-free-path of the ablated particles and the Ar gas is developed for investigating the transport dynamics of the laser-ablated particles in a low pressure inert gas. The ablated-particle density and velocity distributions are analyzed. The force distributions acting on the ablated particles are investigated. The influence of the substrate on the ablated-particle velocity distribution and the force distribution acting on the ablated particles are discussed. The Monte Carlo simulation results approximately agree with the experimental data at the pressure of 8 Pa to 17 Pa. This is helpful to investigate the gas phase nucleation and growth mechanism of nanoparticles. supported by the Natural Science Foundation of Hebei Province, China (No. A2015201166) and the Natural Science Foundation of Hebei University, China (No. 2013-252)

  16. The analog linear interpolation approach for Monte Carlo simulation of PGNAA: The CEARPGA code

    Science.gov (United States)

    Zhang, Wenchao; Gardner, Robin P.

    2004-01-01

    The analog linear interpolation approach (ALI) has been developed and implemented to eliminate the big weight problem in the Monte Carlo simulation code CEARPGA. The CEARPGA code was previously developed to generate elemental library spectra for using the Monte Carlo - library least-squares (MCLLS) approach in prompt gamma-ray neutron activation analysis (PGNAA). In addition, some other improvements to this code have been introduced, including (1) adopting the latest photon cross-section data, (2) using an improved detector response function, (3) adding the neutron activation backgrounds, (4) generating the individual natural background libraries, (5) adding the tracking of annihilation photons from pair production interactions outside of the detector and (6) adopting a general geometry package. The simulated result from the new CEARPGA code is compared with those calculated from the previous CEARPGA code and the MCNP code and experimental data. The new CEARPGA code is found to give the best result.

  17. Monte Carlo simulation of pulse pile-up effect in gamma spectrum of a PGNAA system

    Science.gov (United States)

    Mowlavi, Ali Asghar; Hadizadeh Yazdi, Mohammad Hadi

    2011-12-01

    We have applied a pile-up Monte Carlo simulation code on gamma spectrum of a prompt gamma neutron activation analysis (PGNAA) system. The code has been run in nonparalyzable mode for a specific geometry of a PGNAA system with 241Am-9Be source and NaI(Tl) detector to obtain the distortion due to “pile-up” in the pulse height of gamma spectrum. The results show that the main background in the nitrogen region of interest (ROI) is due to two pile-ups. We have also evaluated the variation of count rate and total photon sampling over the Monte Carlo spectra. At high count rates, not only the nitrogen ROI but also carbon ROI, and hydrogen peak are disturbed strongly. Comparison between the results of simulations and the experimental spectra has shown a good agreement. The code could be used for other source setups and different gamma detection systems.

  18. Monte Carlo simulation of pulse pile-up effect in gamma spectrum of a PGNAA system

    Energy Technology Data Exchange (ETDEWEB)

    Mowlavi, Ali Asghar, E-mail: amowlavi@sttu.ac.ir [Physics Department, School of Sciences, Sabzevar Tarbiat Moallem University, Sabzevar (Iran, Islamic Republic of); TRIL, ICTP, Trieste (Italy); Hadizadeh Yazdi, Mohammad Hadi [Physics Department, School of Sciences, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of)

    2011-12-21

    We have applied a pile-up Monte Carlo simulation code on gamma spectrum of a prompt gamma neutron activation analysis (PGNAA) system. The code has been run in nonparalyzable mode for a specific geometry of a PGNAA system with {sup 241}Am-{sup 9}Be source and NaI(Tl) detector to obtain the distortion due to 'pile-up' in the pulse height of gamma spectrum. The results show that the main background in the nitrogen region of interest (ROI) is due to two pile-ups. We have also evaluated the variation of count rate and total photon sampling over the Monte Carlo spectra. At high count rates, not only the nitrogen ROI but also carbon ROI, and hydrogen peak are disturbed strongly. Comparison between the results of simulations and the experimental spectra has shown a good agreement. The code could be used for other source setups and different gamma detection systems.

  19. Monte Carlo simulation of pulse pile-up effect in gamma spectrum of a PGNAA system

    International Nuclear Information System (INIS)

    We have applied a pile-up Monte Carlo simulation code on gamma spectrum of a prompt gamma neutron activation analysis (PGNAA) system. The code has been run in nonparalyzable mode for a specific geometry of a PGNAA system with 241Am-9Be source and NaI(Tl) detector to obtain the distortion due to “pile-up” in the pulse height of gamma spectrum. The results show that the main background in the nitrogen region of interest (ROI) is due to two pile-ups. We have also evaluated the variation of count rate and total photon sampling over the Monte Carlo spectra. At high count rates, not only the nitrogen ROI but also carbon ROI, and hydrogen peak are disturbed strongly. Comparison between the results of simulations and the experimental spectra has shown a good agreement. The code could be used for other source setups and different gamma detection systems.

  20. Domain-growth kinetics and aspects of pinning: A Monte Carlo simulation study

    DEFF Research Database (Denmark)

    Castán, T.; Lindgård, Per-Anker

    1991-01-01

    By means of Monte Carlo computer simulations we study the domain-growth kinetics after a quench across a first-order line to very low and moderate temperatures in a multidegenerate system with nonconserved order parameter. The model is a continuous spin model relevant for martensitic transformati......By means of Monte Carlo computer simulations we study the domain-growth kinetics after a quench across a first-order line to very low and moderate temperatures in a multidegenerate system with nonconserved order parameter. The model is a continuous spin model relevant for martensitic...... transformations, surface reconstructions, and magnetic transitions. No external impurities are introduced, but the model has a number of intrinsic, annealable pinning mechanisms, which strongly influences the growth kinetics. It allows a study of pinning effects of three kinds: (a) pinning of domain walls...

  1. The effect of variability in body segment parameters on joint moment using Monte Carlo simulations.

    Science.gov (United States)

    Nguyen, Tam C; Reynolds, Karen J

    2014-01-01

    This study used Monte Carlo methods to simulate the effects of variability and uncertainty in inertial body segment parameters (BSPs) on joint torques calculated using inverse dynamics. The average and standard deviation values of BSPs from previously published studies were used as inputs into the Monte Carlo simulation. Data from five groups were evaluated: cadaveric subjects; living subjects (Caucasian only); female living subjects (Caucasian only); male living subjects (Caucasian only); and living subjects (non-Caucasian). The differences in BSPs observed between the different groups were statistically significant; however, using BSP variability data from these groups made little difference to the calculated joint torques. This suggests that for slow and repeatable movement such as walking, BSPs have little effect on joint moments, except for the swing phase. Even then, the magnitude of difference in the swing phase due to variability in BSPs is not much greater than the inter-trial variability. As expected, distal BSPs have little effect on proximal joint moment.

  2. A Pipelined and Parallel Architecture for Quantum Monte Carlo Simulations on FPGAs

    Directory of Open Access Journals (Sweden)

    Akila Gothandaraman

    2010-01-01

    Full Text Available Recent advances in Field-Programmable Gate Array (FPGA technology make reconfigurable computing using FPGAs an attractive platform for accelerating scientific applications. We develop a deeply pipelined and parallel architecture for Quantum Monte Carlo simulations using FPGAs. Quantum Monte Carlo simulations enable us to obtain the structural and energetic properties of atomic clusters. We experiment with different pipeline structures for each component of the design and develop a deeply pipelined architecture that provides the best performance in terms of achievable clock rate, while at the same time has a modest use of the FPGA resources. We discuss the details of the pipelined and generic architecture that is used to obtain the potential energy and wave function of a cluster of atoms.

  3. Magnetic properties of a ferromagnetic thin film with four spin interaction: A Monte Carlo simulation study

    International Nuclear Information System (INIS)

    Monte Carlo simulation has been used to study the critical behaviors and the magnetic properties of a ferromagnetic thin Ising film with a plaquette four spin interaction. The effects of the ratio rs=Js/J of the surface exchange interaction to the bulk one and the four spin interaction on phase diagrams are investigated. A number of characteristic behaviors have been found, which include the first- and second-order phase transitions, thus also the tricritical points, triple point and isolated critical point. - Highlights: ► The magnetic behavior of an Ising ferromagnetic film has been studied using Monte Carlo simulation. ► The effects of the four spin interaction on the phase diagrams have been examined. ► The thermal variations of magnetizations have been investigated. ► The dependence of the total susceptibility on the temperature is investigated

  4. Monte Carlo simulations of CsI(Tl) scintillation crystals for use in a three-dimensional megavoltage CT scanner

    Energy Technology Data Exchange (ETDEWEB)

    Mosleh-Shirazi, M.A. (Joint Department of Physics, Institute of Cancer Research and Royal Marsden Hospital, Downs Road, Sutton, Surrey SM2 5PT (United Kingdom)); Swindell, W. (Joint Department of Physics, Institute of Cancer Research and Royal Marsden Hospital, Downs Road, Sutton, Surrey SM2 5PT (United Kingdom)); Evans, P.M. (Joint Department of Physics, Institute of Cancer Research and Royal Marsden Hospital, Downs Road, Sutton, Surrey SM2 5PT (United Kingdom))

    1994-09-01

    A Monte Carlo model has been devised for a study of the effects of various scintillation crystal parameters on light irradiance upon a remote lens. The purpose of these simulations is to optimise the design of the scintillation crystal array for our 3-D megavoltage CT scanner. The scanner will be attached to the gantry of a linear accelerator and will be implemented to measure and reduce errors in patient positioning during a course of cancer treatment with radiotherapy. The scintillator studied here is CsI(Tl) irradiated with 6 MV X-rays. The angular distributions of light emerging from crystals coated with specular and lambertian reflectors are compared. The effect of crystal size on the light output of crystals coated with the above reflectors is shown. The relative dependence of light output (to a remote lens) on crystal optical attenuation length and coating reflectivity is demonstrated. Comparison with some experimental data is also included. ((orig.))

  5. SKIRT: The design of a suite of input models for Monte Carlo radiative transfer simulations

    Science.gov (United States)

    Baes, M.; Camps, P.

    2015-09-01

    The Monte Carlo method is the most popular technique to perform radiative transfer simulations in a general 3D geometry. The algorithms behind and acceleration techniques for Monte Carlo radiative transfer are discussed extensively in the literature, and many different Monte Carlo codes are publicly available. On the contrary, the design of a suite of components that can be used for the distribution of sources and sinks in radiative transfer codes has received very little attention. The availability of such models, with different degrees of complexity, has many benefits. For example, they can serve as toy models to test new physical ingredients, or as parameterised models for inverse radiative transfer fitting. For 3D Monte Carlo codes, this requires algorithms to efficiently generate random positions from 3D density distributions. We describe the design of a flexible suite of components for the Monte Carlo radiative transfer code SKIRT. The design is based on a combination of basic building blocks (which can be either analytical toy models or numerical models defined on grids or a set of particles) and the extensive use of decorators that combine and alter these building blocks to more complex structures. For a number of decorators, e.g. those that add spiral structure or clumpiness, we provide a detailed description of the algorithms that can be used to generate random positions. Advantages of this decorator-based design include code transparency, the avoidance of code duplication, and an increase in code maintainability. Moreover, since decorators can be chained without problems, very complex models can easily be constructed out of simple building blocks. Finally, based on a number of test simulations, we demonstrate that our design using customised random position generators is superior to a simpler design based on a generic black-box random position generator.

  6. Monte-Carlo simulation of backscattered electrons in Auger electron spectroscopy. Part 1: Backscattering factor calculation

    Energy Technology Data Exchange (ETDEWEB)

    Tholomier, M.; Vicario, E.; Doghmane, N.

    1987-10-01

    The contribution of backscattered electrons to Auger electrons yield was studied with a multiple scattering Monte-Carlo simulation. The Auger backscattering factor has been calculated in the 5 keV-60 keV energy range. The dependence of the Auger backscattering factor on the primary energy and the beam incidence angle were determined. Spatial distributions of backscattered electrons and Auger electrons are presented for a point incident beam. Correlations between these distributions are briefly investigated.

  7. Parallel J-W Monte Carlo Simulations of Thermal Phase Changes in Finite-size Systems

    CERN Document Server

    Radev, R

    2002-01-01

    The thermodynamic properties of 59 TeF6 clusters that undergo temperature-driven phase transitions have been calculated with a canonical J-walking Monte Carlo technique. A parallel code for simulations has been developed and optimized on SUN3500 and CRAY-T3E computers. The Lindemann criterion shows that the clusters transform from liquid to solid and then from one solid structure to another in the temperature region 60-130 K.

  8. REX: A Monte Carlo simulation of thick gas target resonant scattering reactions

    Energy Technology Data Exchange (ETDEWEB)

    Curtis, N., E-mail: n.curtis@bham.ac.uk; Walshe, J.

    2015-10-11

    A Monte Carlo code has been developed to simulate resonant scattering reactions using the thick gas target technique in inverse kinematics. Results are presented for the {sup 4}He({sup 20}Ne,α){sup 20}Ne reaction at 70 MeV, and compared to an experimental measurement which utilised an array of segmented silicon strip detectors. In the case studied, angular straggling in the chamber window is found to dominate the excitation energy resolution.

  9. Monte Carlo simulation of the three-dimensional XY model with bilinear-biquadratic exchange interaction

    OpenAIRE

    Nagata, H; Žukovič, M.; Idogaki, T.

    2013-01-01

    The three-dimensional XY model with bilinear-biquadratic exchange interactions $J$ and $J'$, respectively, has been studied by Monte Carlo simulations. From the detailed analysis of the thermal variation of various physical quantities, as well as the order parameter and energy histogram analysis, the phase diagram including two different ordered phases has been determined. There is a single phase boundary from a paramagnetic to a dipole-quadrupole ordered phase, which is of second order in a ...

  10. Deposition at glancing angle, surface roughness, and protein adsorption: Monte Carlo simulations.

    Science.gov (United States)

    Zhdanov, Vladimir P; Rechendorff, Kristian; Hovgaard, Mads B; Besenbacher, Flemming

    2008-06-19

    To generate rough surfaces in Monte Carlo simulations, we use the 2 + 1 solid-on-solid model of deposition with rapid transient diffusion of newly arrived atoms supplied at glancing angle. The surfaces generated are employed to scrutinize the effect of surface roughness on adsorption of globular and anisotropic rodlike proteins. The obtained results are compared with the available experimental data for Ta deposition at glancing angle and for the bovine serum albumin and fibrinogen uptake on the corresponding Ta films.

  11. A Monte Carlo Simulation for the Ion Transport in Glow Discharges with Dusts

    Institute of Scientific and Technical Information of China (English)

    SUN Ai-Ping; PU Wei; QIU Xiao-Ming

    2001-01-01

    We use the Monte Carlo method to simulate theion transport in the rf parallel plate glow discharge with a negative-voltage pulse connected to the electrode. It is found that self-consistent field, dust charge, dust concentration,and dust size influence the energy distribution and the density of the ions arriving at the target, and in particular, the latter two make significant influence. As dust concentration or dust size increases, the number of ions arriving at the target reduces greatly.

  12. Risk Analysis of Tilapia Recirculating Aquaculture Systems: A Monte Carlo Simulation Approach

    OpenAIRE

    Kodra, Bledar

    2007-01-01

    Risk Analysis of Tilapia Recirculating Aquaculture Systems: A Monte Carlo Simulation Approach Bledar Kodra (ABSTRACT) The purpose of this study is to modify an existing static analytical model developed for a Re-circulating Aquaculture Systems through incorporation of risk considerations to evaluate the economic viability of the system. In addition the objective of this analysis is to provide a well documented risk based analytical system so that individuals (investors/lenders) c...

  13. Dielectric constant of the polarizable dipolar hard sphere fluid studied by Monte Carlo simulation and theories

    OpenAIRE

    M. Valiskó; D. Boda

    2005-01-01

    A systematic Monte Carlo (MC) simulation and perturbation theoretical (PT) study is reported for the dielectric constant of the polarizable dipolar hard sphere (PDHS) fluid. We take the polarizability of the molecules into account in two different ways. In a continuum approach we place the permanent dipole of the molecule into a sphere of dielectric constant ε∞ in the spirit of Onsager. The high frequency dielectric constant ε∞ is calculated from the Clausius-Mosotti relation, while the diele...

  14. The use of Monte Carlo simulations for seismic hazard assessment in the U.K.

    OpenAIRE

    R. M. W. Musson

    2000-01-01

    The input required for a seismic hazard study using conventional Probabilistic Seismic Hazard assessment (PSHA) methods can also be used for probabilistic analysis of hazard using Monte Carlo simulation methods. This technique is very flexible, and seems to be under-represented in the literature. It is very easy to modify the form of the seismicity model used, for example, to introduce non-Poissonian behaviour, without extensive reprogramming. Uncertainty in input parameters can also be model...

  15. Local and chain dynamics in miscible polymer blends: A Monte Carlo simulation study

    OpenAIRE

    Luettmer-Strathmann, Jutta; Mantina, Manjeera

    2005-01-01

    Local chain structure and local environment play an important role in the dynamics of polymer chains in miscible blends. In general, the friction coefficients that describe the segmental dynamics of the two components in a blend differ from each other and from those of the pure melts. In this work, we investigate polymer blend dynamics with Monte Carlo simulations of a generalized bond-fluctuation model, where differences in the interaction energies between non-bonded nearest neighbors distin...

  16. TITAN: a computer program for accident occurrence frequency analyses by component Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Nomura, Yasushi [Department of Fuel Cycle Safety Research, Nuclear Safety Research Center, Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan); Tamaki, Hitoshi [Department of Safety Research Technical Support, Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan); Kanai, Shigeru [Fuji Research Institute Corporation, Tokyo (Japan)

    2000-04-01

    In a plant system consisting of complex equipments and components for a reprocessing facility, there might be grace time between an initiating event and a resultant serious accident, allowing operating personnel to take remedial actions, thus, terminating the ongoing accident sequence. A component Monte Carlo simulation computer program TITAN has been developed to analyze such a complex reliability model including the grace time without any difficulty to obtain an accident occurrence frequency. Firstly, basic methods for the component Monte Carlo simulation is introduced to obtain an accident occurrence frequency, and then, the basic performance such as precision, convergence, and parallelization of calculation, is shown through calculation of a prototype accident sequence model. As an example to illustrate applicability to a real scale plant model, a red oil explosion in a German reprocessing plant model is simulated to show that TITAN can give an accident occurrence frequency with relatively good accuracy. Moreover, results of uncertainty analyses by TITAN are rendered to show another performance, and a proposal is made for introducing of a new input-data format to adapt the component Monte Carlo simulation. The present paper describes the calculational method, performance, applicability to a real scale, and new proposal for the TITAN code. In the Appendixes, a conventional analytical method is shown to avoid complex and laborious calculation to obtain a strict solution of accident occurrence frequency, compared with Monte Carlo method. The user's manual and the list/structure of program are also contained in the Appendixes to facilitate TITAN computer program usage. (author)

  17. Direct Measurement of Power Dissipated by Monte Carlo Simulations on CPU and FPGA Platforms

    DEFF Research Database (Denmark)

    Albicocco, Pietro; Papini, Davide; Nannarelli, Alberto

    In this technical report, we describe how power dissipation measurements on different computing platforms (a desktop computer and an FPGA board) are performed by using a Hall effectbased current sensor. The chosen application is a Monte Carlo simulation for European option pricing which is a popu...... is a popular algorithm used in financial computations. The Hall effect probe measurements complement the measurements performed on the core of the FPGA by a built-in Xilinx power monitoring system....

  18. Risk analysis and Monte Carlo simulation applied to the generation of drilling AFE estimates

    International Nuclear Information System (INIS)

    This paper presents a method for developing an authorization-for-expenditure (AFE)-generating model and illustrates the technique with a specific offshore field development case study. The model combines Monte Carlo simulation and statistical analysis of historical drilling data to generate more accurate, risked, AFE estimates. In addition to the general method, two examples of making AFE time estimates for North Sea wells with the presented techniques are given

  19. Monte Carlo simulation of inclusive pionic reaction around resonance and higher energy perspectives

    International Nuclear Information System (INIS)

    We describe all the inclusive pionic reactions in a variety of nuclei around the resonance region by means of a microscopic many-body calculation that evaluates reaction probabilities, followed by a Monte Carlo simulation which follows the evolution of the pions. We also make an intrusion into the higher energy domain by paying attention to the absorption mechanisms and their repercussions in exclusive single-charge exchange reactions. 27 refs., 11 figs

  20. Stochastic method for accommodation of equilibrating basins in kinetic Monte Carlo simulations

    OpenAIRE

    Van Siclen, Clinton DeW.

    2008-01-01

    A computationally simple way to accommodate 'basins' of trapping sites in standard kinetic Monte Carlo simulations is presented. By assuming the system is effectively equilibrated in the basin, the residence time (time spent in the basin before escape) and the probabilities for transition to states outside the basin may be calculated. This is demonstrated for point defect diffusion over a periodic grid of sites containing a complex basin.

  1. Monte Carlo Simulations of Type Ia Supernova Observations in Supernova Surveys

    OpenAIRE

    Li, Weidong; Filippenko, Alexei V.; Riess, Adam G.

    2000-01-01

    We have performed Monte Carlo simulations of type Ia supernova (SN Ia) surveys to quantify their efficiency in discovering peculiar overluminous and underluminous SNe Ia. We determined how the type of survey (magnitude-limited, distance-limited, or a hybrid) and its characteristics (observations frequency and detection limit) affect the discovery of peculiar SNe Ia. We find that there are strong biases against the discovery of peculiar SNe Ia introduced by at least four observational effects:...

  2. Polypeptide-Nanoparticle Interactions and Corona Formation Investigated by Monte Carlo Simulations

    OpenAIRE

    Carnal, Fabrice; Clavier, Arnaud; Stoll, Serge

    2016-01-01

    Biomacromolecule activity is usually related to its ability to keep a specific structure. However, in solution, many parameters (pH, ionic strength) and external compounds (polyelectrolytes, nanoparticles) can modify biomacromolecule structure as well as acid/base properties, thus resulting in a loss of activity and denaturation. In this paper, the impact of neutral and charged nanoparticles (NPs) is investigated by Monte Carlo simulations on polypeptide (PP) chains with primary structure bas...

  3. Topological excitations and Monte-Carlo simulation of the Abelian-Higgs model

    International Nuclear Information System (INIS)

    The phase structure and topological excitations, in particular the magnetic monopole current density, are investigated in a Monte-Carlo simulation of the lattice version of the four-dimensional Abelian-Higgs model. The monopole current density is found to be large in the confinement phase and rapidly decreasing in the Coulomb and Higgs phases. This result supports the view that confinement is neglected with the condensation of monopole-antimonopole pairs

  4. Comparison of multiple-gate MOSFET architectures using Monte Carlo simulation

    OpenAIRE

    Saint-Martin, J.; Bournel, A.; Dollfus, P.

    2005-01-01

    Multiple-gate SOI MOSFETs with gate length equal to 25 nm are compared using device Monte Carlo simulation. In such architectures, the short channel effects may be controlled with much less stringent body and oxide thickness requirements than in single-gate MOSFET. Our results highlight that planar double-gate MOSFET is a good candidate to obtain both high current drive per unit-width and weak subthreshold leakage with large integration density and aggressive delay time, compared to non plana...

  5. PeneloPET, a Monte Carlo PET simulation tool based on PENELOPE: features and validation

    Energy Technology Data Exchange (ETDEWEB)

    Espana, S; Herraiz, J L; Vicente, E; Udias, J M [Grupo de Fisica Nuclear, Departmento de Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid, Madrid (Spain); Vaquero, J J; Desco, M [Unidad de Medicina y CirugIa Experimental, Hospital General Universitario Gregorio Maranon, Madrid (Spain)], E-mail: jose@nuc2.fis.ucm.es

    2009-03-21

    Monte Carlo simulations play an important role in positron emission tomography (PET) imaging, as an essential tool for the research and development of new scanners and for advanced image reconstruction. PeneloPET, a PET-dedicated Monte Carlo tool, is presented and validated in this work. PeneloPET is based on PENELOPE, a Monte Carlo code for the simulation of the transport in matter of electrons, positrons and photons, with energies from a few hundred eV to 1 GeV. PENELOPE is robust, fast and very accurate, but it may be unfriendly to people not acquainted with the FORTRAN programming language. PeneloPET is an easy-to-use application which allows comprehensive simulations of PET systems within PENELOPE. Complex and realistic simulations can be set by modifying a few simple input text files. Different levels of output data are available for analysis, from sinogram and lines-of-response (LORs) histogramming to fully detailed list mode. These data can be further exploited with the preferred programming language, including ROOT. PeneloPET simulates PET systems based on crystal array blocks coupled to photodetectors and allows the user to define radioactive sources, detectors, shielding and other parts of the scanner. The acquisition chain is simulated in high level detail; for instance, the electronic processing can include pile-up rejection mechanisms and time stamping of events, if desired. This paper describes PeneloPET and shows the results of extensive validations and comparisons of simulations against real measurements from commercial acquisition systems. PeneloPET is being extensively employed to improve the image quality of commercial PET systems and for the development of new ones.

  6. Monte Carlo simulation of a clearance box monitor used for nuclear power plant decommissioning.

    Science.gov (United States)

    Bochud, François O; Laedermann, Jean-Pascal; Bailat, Claude J; Schuler, Christoph

    2009-05-01

    When decommissioning a nuclear facility it is important to be able to estimate activity levels of potentially radioactive samples and compare with clearance values defined by regulatory authorities. This paper presents a method of calibrating a clearance box monitor based on practical experimental measurements and Monte Carlo simulations. Adjusting the simulation for experimental data obtained using a simple point source permits the computation of absolute calibration factors for more complex geometries with an accuracy of a bit more than 20%. The uncertainty of the calibration factor can be improved to about 10% when the simulation is used relatively, in direct comparison with a measurement performed in the same geometry but with another nuclide. The simulation can also be used to validate the experimental calibration procedure when the sample is supposed to be homogeneous but the calibration factor is derived from a plate phantom. For more realistic geometries, like a small gravel dumpster, Monte Carlo simulation shows that the calibration factor obtained with a larger homogeneous phantom is correct within about 20%, if sample density is taken as the influencing parameter. Finally, simulation can be used to estimate the effect of a contamination hotspot. The research supporting this paper shows that activity could be largely underestimated in the event of a centrally-located hotspot and overestimated for a peripherally-located hotspot if the sample is assumed to be homogeneously contaminated. This demonstrates the usefulness of being able to complement experimental methods with Monte Carlo simulations in order to estimate calibration factors that cannot be directly measured because of a lack of available material or specific geometries. PMID:19359851

  7. Patient-specific CT dose determination from CT images using Monte Carlo simulations

    Science.gov (United States)

    Liang, Qing

    Radiation dose from computed tomography (CT) has become a public concern with the increasing application of CT as a diagnostic modality, which has generated a demand for patient-specific CT dose determinations. This thesis work aims to provide a clinically applicable Monte-Carlo-based CT dose calculation tool based on patient CT images. The source spectrum was simulated based on half-value layer measurements. Analytical calculations along with the measured flux distribution were used to estimate the bowtie-filter geometry. Relative source output at different points in a cylindrical phantom was measured and compared with Monte Carlo simulations to verify the determined spectrum and bowtie-filter geometry. Sensitivity tests were designed with four spectra with the same kVp and different half-value layers, and showed that the relative output at different locations in a phantom is sensitive to different beam qualities. An mAs-to-dose conversion factor was determined with in-air measurements using an Exradin A1SL ionization chamber. Longitudinal dose profiles were measured with thermoluminescent dosimeters (TLDs) and compared with the Monte-Carlo-simulated dose profiles to verify the mAs-to-dose conversion factor. Using only the CT images to perform Monte Carlo simulations would cause dose underestimation due to the lack of a scatter region. This scenario was demonstrated with a cylindrical phantom study. Four different image extrapolation methods from the existing CT images and the Scout images were proposed. The results show that performing image extrapolation beyond the scan region improves the dose calculation accuracy under both step-shoot scan mode and helical scan mode. Two clinical studies were designed and comparisons were performed between the current CT dose metrics and the Monte-Carlo-based organ dose determination techniques proposed in this work. The results showed that the current CT dosimetry failed to show dose differences between patients with the same

  8. APPLICATION OF QUEUING THEORY TO AUTOMATED TELLER MACHINE (ATM FACILITIES USING MONTE CARLO SIMULATION

    Directory of Open Access Journals (Sweden)

    UDOANYA RAYMOND MANUEL

    2014-04-01

    Full Text Available This paper presents the importance of applying queuing theory to the Automated Teller Machine (ATM using Monte Carlo Simulation in order to determine, control and manage the level of queuing congestion found within the Automated Teller Machine (ATM centre in Nigeria and also it contains the empirical data analysis of the queuing systems obtained at the Automated Teller Machine (ATM located within the Bank premises for a period of three (3 months. Monte Carlo Simulation is applied to this study in order to review the queuing congestion and queuing discipline at the Automated Teller Machine facilities or Automated Teller Machine service centers, and also estimate the arrival time, waiting time and service time of each customer found during the peak hours and off peak hours. An experiment was been carried out with the aid of a stop watch, recording material, etc on order to obtain the time in which every customer spends at the Automated Teller Machine (ATM service centre from the time of arrival to the time of departure. The model contains five servers which are heavily congested during the peak hours and during the off peak hours, servers are found being idle. Policy recommendations that could be use to manage and control the high level of queuing congestion at Automated Teller Machine (ATM centers were made using the statistical results presented by Monte Carlo simulation software attached to this work, such results include having not more than 15 customers within 1 hour, etc.

  9. Modeling Replenishment of Ultrathin Liquid Perfluoropolyether Z Films on Solid Surfaces Using Monte Carlo Simulation

    Directory of Open Access Journals (Sweden)

    M. S. Mayeed

    2014-01-01

    Full Text Available Applying the reptation algorithm to a simplified perfluoropolyether Z off-lattice polymer model an NVT Monte Carlo simulation has been performed. Bulk condition has been simulated first to compare the average radius of gyration with the bulk experimental results. Then the model is tested for its ability to describe dynamics. After this, it is applied to observe the replenishment of nanoscale ultrathin liquid films on solid flat carbon surfaces. The replenishment rate for trenches of different widths (8, 12, and 16 nms for several molecular weights between two films of perfluoropolyether Z from the Monte Carlo simulation is compared to that obtained solving the diffusion equation using the experimental diffusion coefficients of Ma et al. (1999, with room condition in both cases. Replenishment per Monte Carlo cycle seems to be a constant multiple of replenishment per second at least up to 2 nm replenished film thickness of the trenches over the carbon surface. Considerable good agreement has been achieved here between the experimental results and the dynamics of molecules using reptation moves in the ultrathin liquid films on solid surfaces.

  10. Numerical simulation of LIGO input optics

    Science.gov (United States)

    None, Shivanand; Jamal, Nafis; Yoshida, Sanichiro

    2005-11-01

    Numerical analysis has been carried out to understand the performance of the Input Optics used in the first generation of LIGO (Laser Interferometer Gravitational-wave Observatory) detector. The input optics is a subsystem consisting of a mode cleaner and mode-matching telescope, where all the optics are suspended and installed in vacuum. Using the end-to-end package (LIGO programming language), computer codes have been made to simulate the input optics. Giving realistic seismic noise to the suspension point of the optics and using the length sensing/alignment sensing control for the mode cleaner, the performance of the input optics has been simulated under various scenarios such as with an order of magnitude higher seismic noise than the normal level, and with/without the alignment sensing control feedback from the arm cavity to the mode-matching telescope. The results are assessed in terms of the beam pointing fluctuation of the laser beam going into the arm cavities, and its influence on the optical coupling to the arm cavities and the noise level at the gravitational wave port signal.

  11. Monte Carlo simulations for the optimisation of low-background Ge detector designs

    Energy Technology Data Exchange (ETDEWEB)

    Hakenmueller, Janina; Heusser, Gerd; Maneschg, Werner; Schreiner, Jochen; Simgen, Hardy; Stolzenburg, Dominik; Strecker, Herbert; Weber, Marc; Westernmann, Jonas [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); Laubenstein, Matthias [Laboratori Nazionali del Gran Sasso, Via G. Acitelli 22, 67100 Assergi L' Aquila (Italy)

    2015-07-01

    Monte Carlo simulations for the low-background Ge spectrometer Giove at the underground laboratory of MPI-K, Heidelberg, are presented. In order to reduce the cosmogenic background at the present shallow depth (15 m w.e.) the shielding of the spectrometer includes an active muon veto and a passive shielding (lead and borated PE layers). The achieved background suppression is comparable to Ge spectrometers operated in much greater depth. The geometry of the detector and the shielding were implemented using the Geant4-based toolkit MaGe. The simulations were successfully optimised by determining the correct diode position and active volume. With the help of the validated Monte Carlo simulation the contribution of the single components to the overall background can be examined. This includes a comparison between simulated results and measurements with different fillings of the sample chamber. Having reproduced the measured detector background in the simulation provides the possibility to improve the background by reverse engineering of the passive and active shield layers in the simulation.

  12. Direct simulation Monte Carlo investigation of the Rayleigh-Taylor instability

    Science.gov (United States)

    Gallis, M. A.; Koehler, T. P.; Torczynski, J. R.; Plimpton, S. J.

    2016-08-01

    The Rayleigh-Taylor instability (RTI) is investigated using the direct simulation Monte Carlo (DSMC) method of molecular gas dynamics. Here, fully resolved two-dimensional DSMC RTI simulations are performed to quantify the growth of flat and single-mode perturbed interfaces between two atmospheric-pressure monatomic gases as a function of the Atwood number and the gravitational acceleration. The DSMC simulations reproduce many qualitative features of the growth of the mixing layer and are in reasonable quantitative agreement with theoretical and empirical models in the linear, nonlinear, and self-similar regimes. In some of the simulations at late times, the instability enters the self-similar regime, in agreement with experimental observations. For the conditions simulated, diffusion can influence the initial instability growth significantly.

  13. Monte Carlo simulations of multiple scattering effects in laser assisted free-free scattering experiments

    Science.gov (United States)

    Deharak, B. A.; Savich, J. L.; Roberts, H. M.; Brown, E. G.; McGill, M. R.; Kim, B. N.; Weaver, C. M.; Martin, N. L. S.

    2016-05-01

    We have conducted a series of Monte Carlo simulations of laser assisted free-free scattering experiments. The simulations make use of Kroll-Watson approximation to account for the effects of the laser field on the scattering process. The parameters for these simulations are believed to mimic the experimental conditions of the work reported by Wallbank and Holmes, particularly the target number density. The simulations account for the effects multiple scattering (i.e., the scattering of a single incident electron from multiple target atoms). We present a comparison of the results of these simulations to the experimental results of Wallbank and Holmes. This work was supported by the National Science Foundation under Grants Nos. PHY-0855040 (NLSM) and PHY-1402899 (BAd).

  14. A GAMOS plug-in for GEANT4 based Monte Carlo simulation of radiation-induced light transport in biological media

    OpenAIRE

    Glaser, Adam K.; Kanick, Stephen C.; Zhang, Rongxiao; Arce, Pedro; Pogue, Brian W.

    2013-01-01

    We describe a tissue optics plug-in that interfaces with the GEANT4/GAMOS Monte Carlo (MC) architecture, providing a means of simulating radiation-induced light transport in biological media for the first time. Specifically, we focus on the simulation of light transport due to the Čerenkov effect (light emission from charged particle’s traveling faster than the local speed of light in a given medium), a phenomenon which requires accurate modeling of both the high energy particle and subsequen...

  15. Commissioning of a Varian Clinac iX 6 MV photon beam using Monte Carlo simulation

    Science.gov (United States)

    Dirgayussa, I. Gde Eka; Yani, Sitti; Rhani, M. Fahdillah; Haryanto, Freddy

    2015-09-01

    Monte Carlo modelling of a linear accelerator is the first and most important step in Monte Carlo dose calculations in radiotherapy. Monte Carlo is considered today to be the most accurate and detailed calculation method in different fields of medical physics. In this research, we developed a photon beam model for Varian Clinac iX 6 MV equipped with MilleniumMLC120 for dose calculation purposes using BEAMnrc/DOSXYZnrc Monte Carlo system based on the underlying EGSnrc particle transport code. Monte Carlo simulation for this commissioning head LINAC divided in two stages are design head Linac model using BEAMnrc, characterize this model using BEAMDP and analyze the difference between simulation and measurement data using DOSXYZnrc. In the first step, to reduce simulation time, a virtual treatment head LINAC was built in two parts (patient-dependent component and patient-independent component). The incident electron energy varied 6.1 MeV, 6.2 MeV and 6.3 MeV, 6.4 MeV, and 6.6 MeV and the FWHM (full width at half maximum) of source is 1 mm. Phase-space file from the virtual model characterized using BEAMDP. The results of MC calculations using DOSXYZnrc in water phantom are percent depth doses (PDDs) and beam profiles at depths 10 cm were compared with measurements. This process has been completed if the dose difference of measured and calculated relative depth-dose data along the central-axis and dose profile at depths 10 cm is ≤ 5%. The effect of beam width on percentage depth doses and beam profiles was studied. Results of the virtual model were in close agreement with measurements in incident energy electron 6.4 MeV. Our results showed that photon beam width could be tuned using large field beam profile at the depth of maximum dose. The Monte Carlo model developed in this study accurately represents the Varian Clinac iX with millennium MLC 120 leaf and can be used for reliable patient dose calculations. In this commissioning process, the good criteria of dose

  16. Commissioning of a Varian Clinac iX 6 MV photon beam using Monte Carlo simulation

    International Nuclear Information System (INIS)

    Monte Carlo modelling of a linear accelerator is the first and most important step in Monte Carlo dose calculations in radiotherapy. Monte Carlo is considered today to be the most accurate and detailed calculation method in different fields of medical physics. In this research, we developed a photon beam model for Varian Clinac iX 6 MV equipped with MilleniumMLC120 for dose calculation purposes using BEAMnrc/DOSXYZnrc Monte Carlo system based on the underlying EGSnrc particle transport code. Monte Carlo simulation for this commissioning head LINAC divided in two stages are design head Linac model using BEAMnrc, characterize this model using BEAMDP and analyze the difference between simulation and measurement data using DOSXYZnrc. In the first step, to reduce simulation time, a virtual treatment head LINAC was built in two parts (patient-dependent component and patient-independent component). The incident electron energy varied 6.1 MeV, 6.2 MeV and 6.3 MeV, 6.4 MeV, and 6.6 MeV and the FWHM (full width at half maximum) of source is 1 mm. Phase-space file from the virtual model characterized using BEAMDP. The results of MC calculations using DOSXYZnrc in water phantom are percent depth doses (PDDs) and beam profiles at depths 10 cm were compared with measurements. This process has been completed if the dose difference of measured and calculated relative depth-dose data along the central-axis and dose profile at depths 10 cm is ≤ 5%. The effect of beam width on percentage depth doses and beam profiles was studied. Results of the virtual model were in close agreement with measurements in incident energy electron 6.4 MeV. Our results showed that photon beam width could be tuned using large field beam profile at the depth of maximum dose. The Monte Carlo model developed in this study accurately represents the Varian Clinac iX with millennium MLC 120 leaf and can be used for reliable patient dose calculations. In this commissioning process, the good

  17. Commissioning of a Varian Clinac iX 6 MV photon beam using Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Dirgayussa, I Gde Eka, E-mail: ekadirgayussa@gmail.com; Yani, Sitti; Haryanto, Freddy, E-mail: freddy@fi.itb.ac.id [Institut Teknologi Bandung, Jl. Ganesha 10, 40132 (Indonesia); Rhani, M. Fahdillah [Tang Tock Seng Hospital (Singapore)

    2015-09-30

    Monte Carlo modelling of a linear accelerator is the first and most important step in Monte Carlo dose calculations in radiotherapy. Monte Carlo is considered today to be the most accurate and detailed calculation method in different fields of medical physics. In this research, we developed a photon beam model for Varian Clinac iX 6 MV equipped with MilleniumMLC120 for dose calculation purposes using BEAMnrc/DOSXYZnrc Monte Carlo system based on the underlying EGSnrc particle transport code. Monte Carlo simulation for this commissioning head LINAC divided in two stages are design head Linac model using BEAMnrc, characterize this model using BEAMDP and analyze the difference between simulation and measurement data using DOSXYZnrc. In the first step, to reduce simulation time, a virtual treatment head LINAC was built in two parts (patient-dependent component and patient-independent component). The incident electron energy varied 6.1 MeV, 6.2 MeV and 6.3 MeV, 6.4 MeV, and 6.6 MeV and the FWHM (full width at half maximum) of source is 1 mm. Phase-space file from the virtual model characterized using BEAMDP. The results of MC calculations using DOSXYZnrc in water phantom are percent depth doses (PDDs) and beam profiles at depths 10 cm were compared with measurements. This process has been completed if the dose difference of measured and calculated relative depth-dose data along the central-axis and dose profile at depths 10 cm is ≤ 5%. The effect of beam width on percentage depth doses and beam profiles was studied. Results of the virtual model were in close agreement with measurements in incident energy electron 6.4 MeV. Our results showed that photon beam width could be tuned using large field beam profile at the depth of maximum dose. The Monte Carlo model developed in this study accurately represents the Varian Clinac iX with millennium MLC 120 leaf and can be used for reliable patient dose calculations. In this commissioning process, the good

  18. Research of Monte Carlo method used in simulation of different maintenance processes

    International Nuclear Information System (INIS)

    The paper introduces two kinds of Monte Carlo methods used in equipment life process simulation under the least maintenance: condition: method of producing the interval of lifetime, method of time scale conversion. The paper also analyzes the characteristics and the using scope of the two methods. By using the conception of service age reduction factor, the model of equipment's life process under incomplete maintenance condition is established, and also the life process simulation method applicable to this situation is invented. (authors)

  19. Monte Carlo simulation of a gas measurement beacon: computation and validation, ASGA/VGM beacon

    International Nuclear Information System (INIS)

    The author reports a Monte Carlo simulation of a gas measurement sensor (ASGA or Ventilation Gas Monitor) used to monitor and detect radioactivity in the ventilation of the CERN's LHC (Large Hadron Collider). He recalls the performance required for these beacons, and the different factors governing their detection threshold. He discusses the possibilities offered by the GEANT4 code to model and simulation the beacon physics, and to generate events. Results are obtained in terms of spectrum of deposited energy. The author reports the sensitivity determination

  20. Application of direct simulation Monte Carlo method for analysis of AVLIS evaporation process

    International Nuclear Information System (INIS)

    The computation code of the direct simulation Monte Carlo (DSMC) method was developed in order to analyze the atomic vapor evaporation in atomic vapor laser isotope separation (AVLIS). The atomic excitation temperatures of gadolinium atom were calculated for the model with five low lying states. Calculation results were compared with the experiments obtained by laser absorption spectroscopy. Two types of DSMC simulations which were different in inelastic collision procedure were carried out. It was concluded that the energy transfer was forbidden unless the total energy of the colliding atoms exceeds a threshold value. (author)

  1. Corsika+Herwig Monte Carlo Simulation of Neutrino Induced Atmospheric Air Showers

    CERN Document Server

    Ambrosio, M; Selva, A D; Miele, G; Pastor, S; Pisanti, O; Rosa, L

    2003-01-01

    High-energy neutrino astronomy represents an open window both on astrophysical mechanisms of particle acceleration and on fundamental interactions. The possibility of detecting them in large earth-based apparatus, like AUGER, AMANDA, ANTARES, is quite challenging. In view of this, the capability of generating reliable simulations of air showers induced by neutrinos is mandatory in the analysis of experimental data. In this paper we describe preliminary results towards the development of a new version of the Monte Carlo CORSIKA, capable of handling neutrinos too as primary particles. In our approach the first interaction of the primary neutrino is simulated in CORSIKA with a call to the HERWIG event generator.

  2. Monte Carlo simulations of neutron-scattering instruments using McStas

    DEFF Research Database (Denmark)

    Nielsen, K.; Lefmann, K.

    2000-01-01

    Monte Carlo simulations have become an essential tool for improving the performance of neutron-scattering instruments, since the level of sophistication in the design of instruments is defeating purely analytical methods. The program McStas, being developed at Rise National Laboratory, includes an...... extension language that makes it easy to adapt it to the particular requirements of individual instruments, and thus provides a powerful and flexible tool for constructing such simulations. McStas has been successfully applied in such areas as neutron guide design, flux optimization, non-Gaussian resolution...

  3. Monte Carlo simulation of spectrum changes in a photon beam due to a brass compensator

    Energy Technology Data Exchange (ETDEWEB)

    Custidiano, E.R., E-mail: ernesto7661@gmail.com [Department of Physics, FaCENA, UNNE, Av., Libertad 5470, C.P.3400, Corrientes (Argentina); Valenzuela, M.R., E-mail: meraqval@gmail.com [Department of Physics, FaCENA, UNNE, Av., Libertad 5470, C.P.3400, Corrientes (Argentina); Dumont, J.L., E-mail: Joseluis.Dumont@elekta.com [Elekta CMS Software, St.Louis, MO (United States); McDonnell, J., E-mail: josemc@express.com.ar [Cumbres Institute, Riobamba 1745, C.P.2000, Rosario, Santa Fe (Argentina); Rene, L, E-mail: luismrene@gmail.com [Radiotherapy Center, Crespo 953, C.P.2000, Rosario, Santa Fe (Argentina); Rodriguez Aguirre, J.M., E-mail: juakcho@gmail.com [Department of Physics, FaCENA, UNNE, Av., Libertad 5470, C.P.3400, Corrientes (Argentina)

    2011-06-15

    Monte Carlo simulations were used to study the changes in the incident spectrum when a poly-energetic photon beam passes through a static brass compensator. The simulated photon beam spectrum was evaluated by comparing it against the incident spectra. We also discriminated the changes in the transmitted spectrum produced by each of the microscopic processes. (i.e. Rayleigh scattering, photoelectric effect, Compton scattering, and pair production). The results show that the relevant process in the energy range considered is the Compton Effect, as expected for composite materials of intermediate atomic number and energy range considered.

  4. Mercedes-Benz water molecules near hydrophobic wall: Integral equation theories vs Monte Carlo simulations

    Science.gov (United States)

    Urbic, T.; Holovko, M. F.

    2011-10-01

    Associative version of Henderson-Abraham-Barker theory is applied for the study of Mercedes-Benz model of water near hydrophobic surface. We calculated density profiles and adsorption coefficients using Percus-Yevick and soft mean spherical associative approximations. The results are compared with Monte Carlo simulation data. It is shown that at higher temperatures both approximations satisfactory reproduce the simulation data. For lower temperatures, soft mean spherical approximation gives good agreement at low and at high densities while in at mid range densities, the prediction is only qualitative. The formation of a depletion layer between water and hydrophobic surface was also demonstrated and studied.

  5. Mercedes–Benz water molecules near hydrophobic wall: Integral equation theories vs Monte Carlo simulations

    Science.gov (United States)

    Urbic, T.; Holovko, M. F.

    2011-01-01

    Associative version of Henderson-Abraham-Barker theory is applied for the study of Mercedes–Benz model of water near hydrophobic surface. We calculated density profiles and adsorption coefficients using Percus-Yevick and soft mean spherical associative approximations. The results are compared with Monte Carlo simulation data. It is shown that at higher temperatures both approximations satisfactory reproduce the simulation data. For lower temperatures, soft mean spherical approximation gives good agreement at low and at high densities while in at mid range densities, the prediction is only qualitative. The formation of a depletion layer between water and hydrophobic surface was also demonstrated and studied. PMID:21992334

  6. Analysis of skin tissues spatial fluorescence distribution by the Monte Carlo simulation

    CERN Document Server

    Churmakov, D Y; Piletsky, S A; Greenhalgh, D A

    2003-01-01

    A novel Monte Carlo technique of simulation of spatial fluorescence distribution within the human skin is presented. The computational model of skin takes into account the spatial distribution of fluorophores, which would arise due to the structure of collagen fibres, compared to the epidermis and stratum corneum where the distribution of fluorophores is assumed to be homogeneous. The results of simulation suggest that distribution of auto- fluorescence is significantly suppressed in the near-infrared spectral region, whereas the spatial distribution of fluorescence sources within a sensor layer embedded in the epidermis is localized at an effective depth.

  7. Monte Carlo simulations of the luminosity function of hot white dwarfs

    CERN Document Server

    Torres, S; Krzesinski, J; Kleinman, S J

    2012-01-01

    We present a detailed Monte Carlo simulation of the population of the hot branch of the white dwarf luminosity function. We used the most up-to-date stellar evolutionary models and we implemented a full description of the observational selection biases. Our theoretical results are compared with the luminosity function of hot white dwarfs obtained from the Sloan Digital Sky Survey (SDSS), for both DA and non-DA white dwarfs. For non-DA white dwarfs we find an excellent agreement with the observational data, while for DA white dwarfs our simulations show some discrepancies with the observations for the brightest luminosity bins, those corresponding to L>= 10 L_sun.

  8. Experimental results and Monte Carlo simulations of a landmine localization device using the neutron backscattering method

    Energy Technology Data Exchange (ETDEWEB)

    Datema, C.P. E-mail: c.datema@iri.tudelft.nl; Bom, V.R.; Eijk, C.W.E. van

    2002-08-01

    Experiments were carried out to investigate the possible use of neutron backscattering for the detection of landmines buried in the soil. Several landmines, buried in a sand-pit, were positively identified. A series of Monte Carlo simulations were performed to study the complexity of the neutron backscattering process and to optimize the geometry of a future prototype. The results of these simulations indicate that this method shows great potential for the detection of non-metallic landmines (with a plastic casing), for which so far no reliable method has been found.

  9. Kinetic Monte Carlo simulation of formation of microstructures in liquid droplets

    Energy Technology Data Exchange (ETDEWEB)

    Block, M [Institut fuer Theoretische Physik, Technische Universitaet Berlin, D-10623 Berlin (Germany); Kunert, R [Institut fuer Theoretische Physik, Technische Universitaet Berlin, D-10623 Berlin (Germany); Schoell, E [Institut fuer Theoretische Physik, Technische Universitaet Berlin, D-10623 Berlin (Germany); Boeck, T [Institut fuer Kristallzuechtung Berlin, D-12489 Berlin (Germany); Teubner, Th [Institut fuer Kristallzuechtung Berlin, D-12489 Berlin (Germany)

    2004-11-01

    We study the deposition of indium droplets on a glass surface and the subsequent formation of silicon microcrystals inside these droplets. Kinetic Monte Carlo methods are used to analyse the influence of growth temperature, flux of incoming particles, surface coverage, and in particular an energy parameter simulating the surface tension, upon the morphology of growth. According to the experimental conditions of crystallization, a temperature gradient and diffusion in spherical droplets are included. The simulations explain the formation of silicon crystal structures in good agreement with the experiment. The dependence of their shape and the conditions of formation on the growth parameters are investigated in detail.

  10. MONTE-CARLO SIMULATION FOR ATOMIC DEPOSITION OF AMORPHOUS ELECTROLESS Ni80P20 COATING

    Institute of Scientific and Technical Information of China (English)

    K.S. Guan; H.R. Bai; Z.W. Wang; Y.S. Yin

    2002-01-01

    Atomic growth process and structure of Amorphous Electroless Coating have beenstudied, using Monte-Carlo simulation method. The simulation results of amorphousNi80P20 coating show that PDFs are in accordance with practical values. The mi-grations of adatoms in coating's growth are different from that of solidification ofamorphous materials. In some cases, the migrated adatoms in the process of growthof amorphous coating are not enough to occupy all vacancies and traps, so the amor-phous coating is micro-porous. The immovable probability k and the largest migrationdistance of adatoms, which lie on the electroless bath components, affect the PDF,volume density and microporosity remarkably.

  11. Grand canonical Monte Carlo simulations of hydrogen adsorption in carbon cones

    International Nuclear Information System (INIS)

    The Monte Carlo method in its grand ensemble variant (GCMC) is used in order to study the hydrogen adsorption (77 K) characteristics of novel carbon structures, namely Carbon Cones (CCs). CCs are conical shaped curved graphitic sheets, with five different apex angles. CC structures with correct bonding topology were developed via atomistic-molecular simulations, while GCMC simulations of hydrogen adsorption were carried out on the five different apex angle structures. Emphasis has been given on the adsorption properties inside the cones and it was found that cone tips are characterized by enhanced adsorbability. The results were also compared with similar calculations on carbon nanotubes.

  12. Monte Carlo Simulation on Energy Deposition of Low-Energy Electrons in Liquid Water

    Institute of Scientific and Technical Information of China (English)

    TAN Zhen-Yu; XIA Yue-Yuan; ZHAO Ming-Wen; LIU Xiang-Dong; HUANG Bo-Da; LI Feng; JI Yan-Ju

    2005-01-01

    @@ A Monte Carlo approach to simulate the transport and energy deposition of low energy electrons (E0 ≤ 10 keV) in liquid water is presented. The elastic scattering of electrons is described by Mott cross section, which is derivedfrom the relativistic wave equation of Dirac. The inelastic scattering model of electrons is b~ed on the dielectric response theory with exchange effect included. A new method of sampling various inelaltic scattering events is proposed in the simulation. Using the approach stated, the spatial distribution of inel~tic scattering events and energy deposition of electrons in liquid water are computed and the results are compared with other theoretical studies.

  13. A new Monte-Carlo based simulation for the CryoEDM experiment

    OpenAIRE

    Raso-Barnett, Matthew

    2015-01-01

    This thesis presents a new Monte-Carlo based simulation of the physics of ultra-cold neutrons (UCN) in complex geometries and its application to the CryoEDM experiment. It includes a detailed description of the design and performance of this simulation along with its use in a project to study the magnetic depolarisation time of UCN within the apparatus due to magnetic impurities in the measurement cell, which is a crucial parameter in the sensitivity of a neutron electricdipole-moment (nEDM) ...

  14. Algorithm and application of Monte Carlo simulation for multi-dispersive copolymerization system

    Institute of Scientific and Technical Information of China (English)

    凌君; 沈之荃; 陈万里

    2002-01-01

    A Monte Carlo algorithm has been established for multi-dispersive copolymerization system, based on the experimental data of copolymer molecular weight and dispersion via GPC measurement. The program simulates the insertion of every monomer unit and records the structure and microscopical sequence of every chain in various lengths. It has been applied successfully for the ring-opening copolymerization of 2,2-dimethyltrimethylene carbonate (DTC) with (-caprolactone (ε-CL). The simulation coincides with the experimental results and provides microscopical data of triad fractions, lengths of homopolymer segments, etc., which are difficult to obtain by experiments. The algorithm presents also a uniform frame for copolymerization studies under other complicated mechanisms.

  15. Theory and Monte-Carlo simulation of adsorbates on corrugated surfaces

    DEFF Research Database (Denmark)

    Vives, E.; Lindgård, P.-A.

    1993-01-01

    Phase transitions in systems of adsorbed molecules on corrugated surfaces are studied by means of Monte Carlo simulation. Particularly, we have studied the phase diagram of D2 on graphite as a function of coverage and temperature. We have demonstrated the existence of an intermediate gamma......-phase between the commensurate and incommensurate phase stabilized by defects. Special attention has been given to the study of the epitaxial rotation angles of the different phases. Available experimental data is in agreement with the simulations and with a general theory for the epitaxial rotation which takes...

  16. On grain growth kinetics in two-phase polycrystalline materials through Monte Carlo simulation

    Indian Academy of Sciences (India)

    K R Phaneesh; Anirudh Bhat; Gautam Mukherjee; K T Kashyap

    2013-08-01

    Monte Carlo Potts model simulation was carried out on a 2D square lattice for various surface fractions of second phase particles for over 50,000 iterations. The observations are in good agreement with known theoretical and experimental results with respect to both growth kinetics as well as grain size distribution. Further, the average grain size and the largest grain size were computed for various surface fractions which have indicated normal grain growth and microstructure homogeneity. The surface fraction of the second phase particles interacting with the grain boundaries (), hitherto not computed through the simulation route, is shown to vary inversely as the average grain size due to Zener pinning.

  17. Monte Carlo simulation methodology for the reliabilty of aircraft structures under damage tolerance considerations

    Science.gov (United States)

    Rambalakos, Andreas

    Current federal aviation regulations in the United States and around the world mandate the need for aircraft structures to meet damage tolerance requirements through out the service life. These requirements imply that the damaged aircraft structure must maintain adequate residual strength in order to sustain its integrity that is accomplished by a continuous inspection program. The multifold objective of this research is to develop a methodology based on a direct Monte Carlo simulation process and to assess the reliability of aircraft structures. Initially, the structure is modeled as a parallel system with active redundancy comprised of elements with uncorrelated (statistically independent) strengths and subjected to an equal load distribution. Closed form expressions for the system capacity cumulative distribution function (CDF) are developed by expanding the current expression for the capacity CDF of a parallel system comprised by three elements to a parallel system comprised with up to six elements. These newly developed expressions will be used to check the accuracy of the implementation of a Monte Carlo simulation algorithm to determine the probability of failure of a parallel system comprised of an arbitrary number of statistically independent elements. The second objective of this work is to compute the probability of failure of a fuselage skin lap joint under static load conditions through a Monte Carlo simulation scheme by utilizing the residual strength of the fasteners subjected to various initial load distributions and then subjected to a new unequal load distribution resulting from subsequent fastener sequential failures. The final and main objective of this thesis is to present a methodology for computing the resulting gradual deterioration of the reliability of an aircraft structural component by employing a direct Monte Carlo simulation approach. The uncertainties associated with the time to crack initiation, the probability of crack detection, the

  18. MCViNE - An object oriented Monte Carlo neutron ray tracing simulation package

    Science.gov (United States)

    Lin, Jiao Y. Y.; Smith, Hillary L.; Granroth, Garrett E.; Abernathy, Douglas L.; Lumsden, Mark D.; Winn, Barry; Aczel, Adam A.; Aivazis, Michael; Fultz, Brent

    2016-02-01

    MCViNE (Monte-Carlo VIrtual Neutron Experiment) is an open-source Monte Carlo (MC) neutron ray-tracing software for performing computer modeling and simulations that mirror real neutron scattering experiments. We exploited the close similarity between how instrument components are designed and operated and how such components can be modeled in software. For example we used object oriented programming concepts for representing neutron scatterers and detector systems, and recursive algorithms for implementing multiple scattering. Combining these features together in MCViNE allows one to handle sophisticated neutron scattering problems in modern instruments, including, for example, neutron detection by complex detector systems, and single and multiple scattering events in a variety of samples and sample environments. In addition, MCViNE can use simulation components from linear-chain-based MC ray tracing packages which facilitates porting instrument models from those codes. Furthermore it allows for components written solely in Python, which expedites prototyping of new components. These developments have enabled detailed simulations of neutron scattering experiments, with non-trivial samples, for time-of-flight inelastic instruments at the Spallation Neutron Source. Examples of such simulations for powder and single-crystal samples with various scattering kernels, including kernels for phonon and magnon scattering, are presented. With simulations that closely reproduce experimental results, scattering mechanisms can be turned on and off to determine how they contribute to the measured scattering intensities, improving our understanding of the underlying physics.

  19. Constraining physical parameters of ultra-fast outflows in PDS 456 with Monte Carlo simulations

    Science.gov (United States)

    Hagino, K.; Odaka, H.; Done, C.; Gandhi, P.; Takahashi, T.

    2014-07-01

    Deep absorption lines with extremely high velocity of ˜0.3c observed in PDS 456 spectra strongly indicate the existence of ultra-fast outflows (UFOs). However, the launching and acceleration mechanisms of UFOs are still uncertain. One possible way to solve this is to constrain physical parameters as a function of distance from the source. In order to study the spatial dependence of parameters, it is essential to adopt 3-dimensional Monte Carlo simulations that treat radiation transfer in arbitrary geometry. We have developed a new simulation code of X-ray radiation reprocessed in AGN outflow. Our code implements radiative transfer in 3-dimensional biconical disk wind geometry, based on Monte Carlo simulation framework called MONACO (Watanabe et al. 2006, Odaka et al. 2011). Our simulations reproduce FeXXV and FeXXVI absorption features seen in the spectra. Also, broad Fe emission lines, which reflects the geometry and viewing angle, is successfully reproduced. By comparing the simulated spectra with Suzaku data, we obtained constraints on physical parameters. We discuss launching and acceleration mechanisms of UFOs in PDS 456 based on our analysis.

  20. Nonequilibrium candidate Monte Carlo is an efficient tool for equilibrium simulation

    Energy Technology Data Exchange (ETDEWEB)

    Nilmeier, J. P.; Crooks, G. E.; Minh, D. D. L.; Chodera, J. D.

    2011-10-24

    Metropolis Monte Carlo simulation is a powerful tool for studying the equilibrium properties of matter. In complex condensed-phase systems, however, it is difficult to design Monte Carlo moves with high acceptance probabilities that also rapidly sample uncorrelated configurations. Here, we introduce a new class of moves based on nonequilibrium dynamics: candidate configurations are generated through a finite-time process in which a system is actively driven out of equilibrium, and accepted with criteria that preserve the equilibrium distribution. The acceptance rule is similar to the Metropolis acceptance probability, but related to the nonequilibrium work rather than the instantaneous energy difference. Our method is applicable to sampling from both a single thermodynamic state or a mixture of thermodynamic states, and allows both coordinates and thermodynamic parameters to be driven in nonequilibrium proposals. While generating finite-time switching trajectories incurs an additional cost, driving some degrees of freedom while allowing others to evolve naturally can lead to large enhancements in acceptance probabilities, greatly reducing structural correlation times. Using nonequilibrium driven processes vastly expands the repertoire of useful Monte Carlo proposals in simulations of dense solvated systems.

  1. Monte Carlo simulations of star clusters - II. Tidally limited, multi-mass systems with stellar evolution

    CERN Document Server

    Giersz, M

    2000-01-01

    A revision of Stod\\{'o}{\\l}kiewicz's Monte Carlo code is used to simulate evolution of large star clusters. A survey of the evolution of N-body systems influenced by the tidal field of a parent galaxy and by stellar evolution is presented. The results presented are in good agreement with theoretical expectations and the results of other methods (Fokker-Planck, Monte Carlo and N-body). The initial rapid mass loss, due to stellar evolution of the most massive stars, causes expansion of the whole cluster and eventually leads to the disruption of less bound systems ($W_0=3$). Models with larger $W_0$ survive this phase of evolution and then undergo core collapse and subsequent post-collapse expansion, like isolated models. The expansion phase is eventually reversed when tidal limitation becomes important. The results presented are the first major step in the direction of simulating evolution of real globular clusters by means of the Monte Carlo method.

  2. Auxiliary-Field Quantum Monte Carlo Simulations of Neutron Matter in Chiral Effective Field Theory

    CERN Document Server

    Wlazłowski, G; Moroz, S; Bulgac, A; Roche, K J

    2014-01-01

    We present variational Monte Carlo calculations of the neutron matter equation of state using chiral nuclear interactions. The ground-state wavefunction of neutron matter, containing non-perturbative many-body correlations, is obtained from auxiliary-field quantum Monte Carlo simulations of up to about 340 neutrons interacting on a 10^3 discretized lattice. The evolution Hamiltonian is chosen to be attractive and spin-independent in order to avoid the fermion sign problem and is constructed to best reproduce broad features of chiral nuclear forces. This is facilitated by choosing a lattice spacing of 1.5 fm, corresponding to a momentum-space cutoff of 414 MeV/c, a resolution scale at which strongly repulsive features of nuclear two-body forces are suppressed. Differences between the evolution potential and the full chiral nuclear interaction are then treated perturbatively. Our results for the equation of state are compared to previous quantum Monte Carlo simulations which employed chiral two-body forces at n...

  3. Million-Body Star Cluster Simulations: Comparisons between Monte Carlo and Direct N-body

    Science.gov (United States)

    Rodriguez, Carl L.; Morscher, Meagan; Wang, Long; Chatterjee, Sourav; Rasio, Frederic A.; Spurzem, Rainer

    2016-08-01

    We present the first detailed comparison between million-body globular cluster simulations computed with a Hénon-type Monte Carlo code, CMC, and a direct N-body code, NBODY6++GPU. Both simulations start from an identical cluster model with 106 particles, and include all of the relevant physics needed to treat the system in a highly realistic way. With the two codes "frozen" (no fine-tuning of any free parameters or internal algorithms of the codes) we find good agreement in the overall evolution of the two models. Furthermore, we find that in both models, large numbers of stellar-mass black holes (>1000) are retained for 12 Gyr. Thus, the very accurate direct N-body approach confirms recent predictions that black holes can be retained in present-day, old globular clusters. We find only minor disagreements between the two models and attribute these to the small-N dynamics driving the evolution of the cluster core for which the Monte Carlo assumptions are less ideal. Based on the overwhelming general agreement between the two models computed using these vastly different techniques, we conclude that our Monte Carlo approach, which is more approximate, but dramatically faster compared to the direct N-body, is capable of producing an accurate description of the long-term evolution of massive globular clusters even when the clusters contain large populations of stellar-mass black holes.

  4. Dose perturbation in the presence of metallic implants: treatment planning system versus Monte Carlo simulations

    Science.gov (United States)

    Wieslander, Elinore; Knöös, Tommy

    2003-10-01

    An increasing number of patients receiving radiation therapy have metallic implants such as hip prostheses. Therefore, beams are normally set up to avoid irradiation through the implant; however, this cannot always be accomplished. In such situations, knowledge of the accuracy of the used treatment planning system (TPS) is required. Two algorithms, the pencil beam (PB) and the collapsed cone (CC), are implemented in the studied TPS. Comparisons are made with Monte Carlo simulations for 6 and 18 MV. The studied materials are steel, CoCrMo, Orthinox® (a stainless steel alloy and registered trademark of Stryker Corporation), TiAlV and Ti. Monte Carlo simulated depth dose curves and dose profiles are compared to CC and PB calculated data. The CC algorithm shows overall a better agreement with Monte Carlo than the PB algorithm. Thus, it is recommended to use the CC algorithm to get the most accurate dose calculation both for the planning target volume and for tissues adjacent to the implants when beams are set up to pass through implants.

  5. Applying Monte Carlo Simulation to Biomedical Literature to Approximate Genetic Network.

    Science.gov (United States)

    Al-Dalky, Rami; Taha, Kamal; Al Homouz, Dirar; Qasaimeh, Murad

    2016-01-01

    Biologists often need to know the set of genes associated with a given set of genes or a given disease. We propose in this paper a classifier system called Monte Carlo for Genetic Network (MCforGN) that can construct genetic networks, identify functionally related genes, and predict gene-disease associations. MCforGN identifies functionally related genes based on their co-occurrences in the abstracts of biomedical literature. For a given gene g , the system first extracts the set of genes found within the abstracts of biomedical literature associated with g. It then ranks these genes to determine the ones with high co-occurrences with g . It overcomes the limitations of current approaches that employ analytical deterministic algorithms by applying Monte Carlo Simulation to approximate genetic networks. It does so by conducting repeated random sampling to obtain numerical results and to optimize these results. Moreover, it analyzes results to obtain the probabilities of different genes' co-occurrences using series of statistical tests. MCforGN can detect gene-disease associations by employing a combination of centrality measures (to identify the central genes in disease-specific genetic networks) and Monte Carlo Simulation. MCforGN aims at enhancing state-of-the-art biological text mining by applying novel extraction techniques. We evaluated MCforGN by comparing it experimentally with nine approaches. Results showed marked improvement. PMID:26415184

  6. Entanglement and the fermion sign problem in auxiliary field quantum Monte Carlo simulations

    Science.gov (United States)

    Broecker, Peter; Trebst, Simon

    2016-08-01

    Quantum Monte Carlo simulations of fermions are hampered by the notorious sign problem whose most striking manifestation is an exponential growth of sampling errors with the number of particles. With the sign problem known to be an NP-hard problem and any generic solution thus highly elusive, the Monte Carlo sampling of interacting many-fermion systems is commonly thought to be restricted to a small class of model systems for which a sign-free basis has been identified. Here we demonstrate that entanglement measures, in particular the so-called Rényi entropies, can intrinsically exhibit a certain robustness against the sign problem in auxiliary-field quantum Monte Carlo approaches and possibly allow for the identification of global ground-state properties via their scaling behavior even in the presence of a strong sign problem. We corroborate these findings via numerical simulations of fermionic quantum phase transitions of spinless fermions on the honeycomb lattice at and below half filling.

  7. Gamma irradiator dose mapping: a Monte Carlo simulation and experimental measurements

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Rogerio R.; Ribeiro, Mariana A.; Grynberg, Suely E.; Ferreira, Andrea V.; Meira-Belo, Luiz Claudio, E-mail: rrr@cdtn.b, E-mail: marianaalmeida@ufmg.b, E-mail: seg@cdtn.b, E-mail: avf@cdtn.b, E-mail: lcmb@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Sousa, Romulo V.; Sebastiao, Rita de C.O., E-mail: romuloverdolin@yahoo.com.b, E-mail: ritacos@ufmg.b [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Inst. de Ciencias Exatas. Dept. de Quimica

    2009-07-01

    Gamma irradiator facilities can be used in a wide range of applications such as biological and chemical researches, food treatment and sterilization of medical devices and products. Dose mapping must be performed in these equipment in order to establish plant operational parameters, as dose uniformity, source utilization efficiency and maximum and minimum dose positions. The isodoses curves are generally measured using dosimeters distributed throughout the device, and this procedure often consume a large amount of dosimeters, irradiation time and manpower. However, a detailed curve doses identification of the irradiation facility can be performed using Monte Carlo simulation, which reduces significantly the monitoring with dosimeters. The present work evaluates the absorbed dose in the CDTN/CNEN Gammacell Irradiation Facility, using the Monte Carlo N-particles (MCNP) code. The Gammacell 220, serial number 39, was produced by Atomic Energy of Canada Limited and was loaded with sources of {sup 60}Co. Dose measurements using TLD and Fricke dosimeters were also performed to validate the calculations. The good agreement of the results shows that Monte Carlo simulations can be used as a predictive tool of irradiation planning for the CDTN/CNEN Gamma Cell Irradiator. (author)

  8. Development of a space radiation Monte Carlo computer simulation based on the FLUKA and ROOT codes

    CERN Document Server

    Pinsky, L; Ferrari, A; Sala, P; Carminati, F; Brun, R

    2001-01-01

    This NASA funded project is proceeding to develop a Monte Carlo-based computer simulation of the radiation environment in space. With actual funding only initially in place at the end of May 2000, the study is still in the early stage of development. The general tasks have been identified and personnel have been selected. The code to be assembled will be based upon two major existing software packages. The radiation transport simulation will be accomplished by updating the FLUKA Monte Carlo program, and the user interface will employ the ROOT software being developed at CERN. The end-product will be a Monte Carlo-based code which will complement the existing analytic codes such as BRYNTRN/HZETRN presently used by NASA to evaluate the effects of radiation shielding in space. The planned code will possess the ability to evaluate the radiation environment for spacecraft and habitats in Earth orbit, in interplanetary space, on the lunar surface, or on a planetary surface such as Mars. Furthermore, it will be usef...

  9. Monte Carlo simulation of mixed neutron-gamma radiation fields and dosimetry devices

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Guoqing

    2011-12-22

    Monte Carlo methods based on random sampling are widely used in different fields for the capability of solving problems with a large number of coupled degrees of freedom. In this work, Monte Carlos methods are successfully applied for the simulation of the mixed neutron-gamma field in an interim storage facility and neutron dosimeters of different types. Details are discussed in two parts: In the first part, the method of simulating an interim storage facility loaded with CASTORs is presented. The size of a CASTOR is rather large (several meters) and the CASTOR wall is very thick (tens of centimeters). Obtaining the results of dose rates outside a CASTOR with reasonable errors costs usually hours or even days. For the simulation of a large amount of CASTORs in an interim storage facility, it needs weeks or even months to finish a calculation. Variance reduction techniques were used to reduce the calculation time and to achieve reasonable relative errors. Source clones were applied to avoid unnecessary repeated calculations. In addition, the simulations were performed on a cluster system. With the calculation techniques discussed above, the efficiencies of calculations can be improved evidently. In the second part, the methods of simulating the response of neutron dosimeters are presented. An Alnor albedo dosimeter was modelled in MCNP, and it has been simulated in the facility to calculate the calibration factor to get the evaluated response to a Cf-252 source. The angular response of Makrofol detectors to fast neutrons has also been investigated. As a kind of SSNTD, Makrofol can detect fast neutrons by recording the neutron induced heavy charged recoils. To obtain the information of charged recoils, general-purpose Monte Carlo codes were used for transporting incident neutrons. The response of Makrofol to fast neutrons is dependent on several factors. Based on the parameters which affect the track revealing, the formation of visible tracks was determined. For

  10. Monte Carlo simulation of mixed neutron-gamma radiation fields and dosimetry devices

    International Nuclear Information System (INIS)

    Monte Carlo methods based on random sampling are widely used in different fields for the capability of solving problems with a large number of coupled degrees of freedom. In this work, Monte Carlos methods are successfully applied for the simulation of the mixed neutron-gamma field in an interim storage facility and neutron dosimeters of different types. Details are discussed in two parts: In the first part, the method of simulating an interim storage facility loaded with CASTORs is presented. The size of a CASTOR is rather large (several meters) and the CASTOR wall is very thick (tens of centimeters). Obtaining the results of dose rates outside a CASTOR with reasonable errors costs usually hours or even days. For the simulation of a large amount of CASTORs in an interim storage facility, it needs weeks or even months to finish a calculation. Variance reduction techniques were used to reduce the calculation time and to achieve reasonable relative errors. Source clones were applied to avoid unnecessary repeated calculations. In addition, the simulations were performed on a cluster system. With the calculation techniques discussed above, the efficiencies of calculations can be improved evidently. In the second part, the methods of simulating the response of neutron dosimeters are presented. An Alnor albedo dosimeter was modelled in MCNP, and it has been simulated in the facility to calculate the calibration factor to get the evaluated response to a Cf-252 source. The angular response of Makrofol detectors to fast neutrons has also been investigated. As a kind of SSNTD, Makrofol can detect fast neutrons by recording the neutron induced heavy charged recoils. To obtain the information of charged recoils, general-purpose Monte Carlo codes were used for transporting incident neutrons. The response of Makrofol to fast neutrons is dependent on several factors. Based on the parameters which affect the track revealing, the formation of visible tracks was determined. For

  11. Free-space laser optical link simulation software

    OpenAIRE

    Vergaz Benito, Ricardo

    2008-01-01

    GDAF (Displays and Photonics Applications Group) in Electronics Technology Department at University Carlos III de Madrid develops a hardware-software application for a communications free-space optical link, in a Project with INSA corp. It aims to substitute the usual radio frequencies link, because of the increasing of bandwidth and the guarantee of privacity. Optics and electronics collaboration is searched.

  12. New techniques in Monte Carlo simulation: experience with a prototype of generic programming application to Geant4 physics processes

    CERN Document Server

    Pia, Maria Grazia; Begalli, Marcia; Quintieri, Lina; Saracco, Paolo; Sudhakar, Manju; Weidenspointner, Georg; Zoglauer, Andreas

    2010-01-01

    An investigation is in progress to evaluate extensively and quantitatively the possible benefits and drawbacks of new programming paradigms in a Monte Carlo simulation environment, namely in the domain of physics modeling. The prototype design and extensive benchmarks, including a variety of rigorous quantitative metrics, are presented. The results of this research project allow the evaluation of new software techniques for their possible adoption in Monte Carlo simulation on objective, quantitative ground.

  13. MUSIC -- An Automated Scan for Deviations between Data and Monte Carlo Simulation

    CERN Document Server

    CMS Collaboration

    We present a model independent analysis approach, systematically scanning the data for deviations from the Monte Carlo expectation. Such an analysis can contribute to the understanding of the detector and the tuning of the event generators. Due to the minimal theoretical bias this approach is sensitive to a variety of models, including those not yet thought of. Events are classified into event classes according to their particle content (muons, electrons, photons, jets and missing transverse energy). A broad scan of various distributions is performed, identifying significant deviations from the Monte Carlo simulation. We outline the importance of systematic uncertainties, which are taken into account rigorously within the algorithm. Possible detector effects and generator issues, as well as models involving supersymmetry and new heavy gauge bosons have been used as an input to the search algorithm. %Several models involving supersymmetry, new heavy gauge bosons and leptoquarks, as well as possible detector ef...

  14. An analysis on the theory of pulse oximetry by Monte Carlo simulation

    Science.gov (United States)

    Fan, Shangchun; Cai, Rui; Xing, Weiwei; Liu, Changting; Chen, Guangfei; Wang, Junfeng

    2008-10-01

    The pulse oximetry is a kind of electronic instrument that measures the oxygen saturation of arterial blood and pulse rate by non-invasive techniques. It enables prompt recognition of hypoxemia. In a conventional transmittance type pulse oximeter, the absorption of light by oxygenated and reduced hemoglobin is measured at two wavelength 660nm and 940nm. But the accuracy and measuring range of the pulse oximeter can not meet the requirement of clinical application. There are limitations in the theory of pulse oximetry, which is proved by Monte Carlo method. The mean paths are calculated in the Monte Carlo simulation. The results prove that the mean paths are not the same between the different wavelengths.

  15. Simulation model based on Monte Carlo method for traffic assignment in local area road network

    Institute of Scientific and Technical Information of China (English)

    Yuchuan DU; Yuanjing GENG; Lijun SUN

    2009-01-01

    For a local area road network, the available traffic data of traveling are the flow volumes in the key intersections, not the complete OD matrix. Considering the circumstance characteristic and the data availability of a local area road network, a new model for traffic assignment based on Monte Carlo simulation of intersection turning movement is provided in this paper. For good stability in temporal sequence, turning ratio is adopted as the important parameter of this model. The formulation for local area road network assignment problems is proposed on the assumption of random turning behavior. The traffic assignment model based on the Monte Carlo method has been used in traffic analysis for an actual urban road network. The results comparing surveying traffic flow data and determining flow data by the previous model verify the applicability and validity of the proposed methodology.

  16. Implementation of 3D Lattice Monte Carlo Simulation on a Cluster of Symmetric Multiprocessors

    Institute of Scientific and Technical Information of China (English)

    雷咏梅; 蒋英; 等

    2002-01-01

    This paper presents a new approach to parallelize 3D lattice Monte Carlo algorithms used in the numerical simulation of polymer on ZiQiang 2000-a cluster of symmetric multiprocessors(SMPs).The combined load for cell and energy calculations over the time step is balanced together to form a single spatial decomposition.Basic aspects and strategies of running Monte Carlo calculations on parallel computers are studied.Different steps involved in porting the software on a parallel architecture based on ZiQiang 2000 running under Linux and MPI are described briefly.It is found that parallelization becomes more advantageous when either the lattice is very large or the model contains many cells and chains.

  17. Improving the efficiency of Monte Carlo simulations of systems that undergo temperature-driven phase transitions

    Science.gov (United States)

    Velazquez, L.; Castro-Palacio, J. C.

    2013-07-01

    Recently, Velazquez and Curilef proposed a methodology to extend Monte Carlo algorithms based on a canonical ensemble which aims to overcome slow sampling problems associated with temperature-driven discontinuous phase transitions. We show in this work that Monte Carlo algorithms extended with this methodology also exhibit a remarkable efficiency near a critical point. Our study is performed for the particular case of a two-dimensional four-state Potts model on a square lattice with periodic boundary conditions. This analysis reveals that the extended version of Metropolis importance sampling is more efficient than the usual Swendsen-Wang and Wolff cluster algorithms. These results demonstrate the effectiveness of this methodology to improve the efficiency of MC simulations of systems that undergo any type of temperature-driven phase transition.

  18. Monte Carlo simulation to investigate the formation of molecular hydrogen and its deuterated forms

    CERN Document Server

    Sahu, DIpen; Majumdar, Liton; Chakrabarti, Sandip K

    2015-01-01

    $H_2$ is the most abundant interstellar species. Its deuterated forms ($HD$ and $D_2$) are also significantly abundant. Huge abundances of these molecules could be explained by considering the chemistry occurring on the interstellar dust. Because of its simplicity, Rate equation method is widely used to study the formation of grain-surface species. However, since recombination efficiency of formation of any surface species are heavily dependent on various physical and chemical parameters, Monte Carlo method would be best method suited to take care of randomness of the processes. We perform Monte Carlo simulation to study the formation of $H_2$, $HD$ and $D_2$ on interstellar ices. Adsorption energies of surface species are the key inputs for the formation of any species on interstellar dusts but binding energies of deuterated species are yet to known with certainty. A zero point energy correction exists between hydrogenated and deuterated species which should be considered while modeling the chemistry on the ...

  19. A new Monte Carlo code for absorption simulation of laser-skin tissue interaction

    Institute of Scientific and Technical Information of China (English)

    Afshan Shirkavand; Saeed Sarkar; Marjaneh Hejazi; Leila Ataie-Fashtami; Mohammad Reza Alinaghizadeh

    2007-01-01

    In laser clinical applications, the process of photon absorption and thermal energy diffusion in the target tissue and its surrounding tissue during laser irradiation are crucial. Such information allows the selection of proper operating parameters such as laser power, and exposure time for optimal therapeutic. The Monte Carlo method is a useful tool for studying laser-tissue interaction and simulation of energy absorption in tissue during laser irradiation. We use the principles of this technique and write a new code with MATLAB 6.5, and then validate it against Monte Carlo multi layer (MCML) code. The new code is proved to be with good accuracy. It can be used to calculate the total power bsorbed in the region of interest. This can be combined for heat modelling with other computerized programs.

  20. Study of the inactive layer of a germanium detector: experimental and Monte Carlo simulation treatments

    Energy Technology Data Exchange (ETDEWEB)

    Zevallos-Chavez, Juan Y.; Pires, Carlos Augusto; Zahn, Guilherme Soares [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)]. E-mail: juan@if.usp.br; Genezini, Frederico Antonio [Centro Regional de Ciencias Nucleares (CRCN), Recife, PE (Brazil)). E-mail: Cruz, Manoel Tiago F. da (Sao Paulo Univ., SP (Brazil). Inst. de Fisica

    2005-07-01

    The detection efficiency of a Germanium detector was measured in the energy range of 80 keV up to 1 MeV. A model function to fit the efficiency data was used, containing an absorbing window factor. The results were compared with a Monte Carlo simulation of the photon interactions where, the nominal dimensions were varied in order to check the low-energy behavior of the efficiency curve. The Monte Carlo results showed to be in good agreement with the experimental ones when the nominal dimensions of the crystal, except for its dead layer thickness, were used. This difference in the dead layer was attributed to its non-uniformity. (author)

  1. Power-feedwater temperature operating domain for Sbwr applying Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Aguilar M, L. A.; Quezada G, S.; Espinosa M, E. G.; Vazquez R, A.; Varela H, J. R.; Cazares R, R. I.; Espinosa P, G., E-mail: sequega@gmail.com [Universidad Autonoma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco No. 186, Col. Vicentina, 09340 Mexico D. F. (Mexico)

    2014-10-15

    In this work the analyses of the feedwater temperature effects on reactor power in a simplified boiling water reactor (Sbwr) applying a methodology based on Monte Carlo simulation is presented. The Monte Carlo methodology was applied systematically to establish operating domain, due that the Sbwr are not yet in operation, the analysis of the nuclear and thermal-hydraulic processes must rely on numerical modeling, with the purpose of developing or confirming the design basis and qualifying the existing or new computer codes to enable reliable analyses. The results show that the reactor power is inversely proportional to the temperature of the feedwater, reactor power changes at 8% when the feed water temperature changes in 8%. (Author)

  2. On the Self-Consistent Event Biasing Schemes for Monte Carlo Simulations of Nanoscale MOSFETs

    CERN Document Server

    Islam, Sharnali; Ahmed, Shaikh

    2009-01-01

    Different techniques of event biasing have been implemented in the particle-based Monte Carlo simulations of a 15nm n-channel MOSFET. The primary goal is to achieve enhancement in the channel statistics and faster convergence in the calculation of terminal current. Enhancement algorithms are especially useful when the device behavior is governed by rare events in the carrier transport process. After presenting a brief overview on the Monte Carlo technique for solving the Boltzmann transport equation, the basic steps of deriving the approach in presence of both the initial and the boundary conditions have been discussed. In the derivation, the linearity of the transport problem has been utilized first, where Coulomb forces between the carriers are initially neglected. The generalization of the approach for Hartree carriers has been established in the iterative procedure of coupling with the Poisson equation. It is shown that the weight of the particles, as obtained by biasing of the Boltzmann equation, survive...

  3. Accurate and precise determination of critical properties from Gibbs ensemble Monte Carlo simulations

    Energy Technology Data Exchange (ETDEWEB)

    Dinpajooh, Mohammadhasan [Department of Chemistry and Chemical Theory Center, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455 (United States); Bai, Peng; Allan, Douglas A. [Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, Minnesota 55455 (United States); Siepmann, J. Ilja, E-mail: siepmann@umn.edu [Department of Chemistry and Chemical Theory Center, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455 (United States); Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, Minnesota 55455 (United States)

    2015-09-21

    Since the seminal paper by Panagiotopoulos [Mol. Phys. 61, 813 (1997)], the Gibbs ensemble Monte Carlo (GEMC) method has been the most popular particle-based simulation approach for the computation of vapor–liquid phase equilibria. However, the validity of GEMC simulations in the near-critical region has been questioned because rigorous finite-size scaling approaches cannot be applied to simulations with fluctuating volume. Valleau [Mol. Simul. 29, 627 (2003)] has argued that GEMC simulations would lead to a spurious overestimation of the critical temperature. More recently, Patel et al. [J. Chem. Phys. 134, 024101 (2011)] opined that the use of analytical tail corrections would be problematic in the near-critical region. To address these issues, we perform extensive GEMC simulations for Lennard-Jones particles in the near-critical region varying the system size, the overall system density, and the cutoff distance. For a system with N = 5500 particles, potential truncation at 8σ and analytical tail corrections, an extrapolation of GEMC simulation data at temperatures in the range from 1.27 to 1.305 yields T{sub c} = 1.3128 ± 0.0016, ρ{sub c} = 0.316 ± 0.004, and p{sub c} = 0.1274 ± 0.0013 in excellent agreement with the thermodynamic limit determined by Potoff and Panagiotopoulos [J. Chem. Phys. 109, 10914 (1998)] using grand canonical Monte Carlo simulations and finite-size scaling. Critical properties estimated using GEMC simulations with different overall system densities (0.296 ≤ ρ{sub t} ≤ 0.336) agree to within the statistical uncertainties. For simulations with tail corrections, data obtained using r{sub cut} = 3.5σ yield T{sub c} and p{sub c} that are higher by 0.2% and 1.4% than simulations with r{sub cut} = 5 and 8σ but still with overlapping 95% confidence intervals. In contrast, GEMC simulations with a truncated and shifted potential show that r{sub cut} = 8σ is insufficient to obtain accurate results. Additional GEMC simulations for hard

  4. Simulation and study on the γ response spectrum of BGO detector by the application of monte carlo code MOCA

    International Nuclear Information System (INIS)

    Application of Monte Carlo method to build spectra library is useful to reduce experiment workload in Prompt Gamma Neutron Activation Analysis (PGNAA). The new Monte Carlo Code MOCA was used to simulate the response spectra of BGO detector for gamma rays from 137Cs, 60Co and neutron induced gamma rays from S and Ti. The results were compared with general code MCNP, show that the agreement of MOCA between simulation and experiment is better than MCNP. This research indicates that building spectra library by Monte Carlo method is feasible. (authors)

  5. Direct simulation Monte Carlo calculation of rarefied gas drag using an immersed boundary method

    Science.gov (United States)

    Jin, W.; Kleijn, C. R.; van Ommen, J. R.

    2016-06-01

    For simulating rarefied gas flows around a moving body, an immersed boundary method is presented here in conjunction with the Direct Simulation Monte Carlo (DSMC) method in order to allow the movement of a three dimensional immersed body on top of a fixed background grid. The simulated DSMC particles are reflected exactly at the landing points on the surface of the moving immersed body, while the effective cell volumes are taken into account for calculating the collisions between molecules. The effective cell volumes are computed by utilizing the Lagrangian intersecting points between the immersed boundary and the fixed background grid with a simple polyhedra regeneration algorithm. This method has been implemented in OpenFOAM and validated by computing the drag forces exerted on steady and moving spheres and comparing the results to that from conventional body-fitted mesh DSMC simulations and to analytical approximations.

  6. Introduction to Computational Physics and Monte Carlo Simulations of Matrix Field Theory

    CERN Document Server

    Ydri, Badis

    2015-01-01

    This book is divided into two parts. In the first part we give an elementary introduction to computational physics consisting of 21 simulations which originated from a formal course of lectures and laboratory simulations delivered since 2010 to physics students at Annaba University. The second part is much more advanced and deals with the problem of how to set up working Monte Carlo simulations of matrix field theories which involve finite dimensional matrix regularizations of noncommutative and fuzzy field theories, fuzzy spaces and matrix geometry. The study of matrix field theory in its own right has also become very important to the proper understanding of all noncommutative, fuzzy and matrix phenomena. The second part, which consists of 9 simulations, was delivered informally to doctoral students who are working on various problems in matrix field theory. Sample codes as well as sample key solutions are also provided for convenience and completness. An appendix containing an executive arabic summary of t...

  7. Monte Carlo simulation of thermodynamic properties for two-dimensional Lennard-Jones fluids

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Canonical ensemble Monte Carlo simulations have been carried out to investigate the thermodynamic properties of two-dimensional fluids subjected to truncated Lennard-Jones 12-6 potential. The simulations of thermodynamic states sweep across liquid-vapor regime over a wide range of thermodynamic conditions. Simulated isotherms behave van der Waals loop-like characteristics in the liquid-vapor phase-transition region. It suggests a continuous isothermal phase transition in the case of micro system, in which the system size prohibits phase separation. Two-dimensional dimensionless van der Waals equation of states has been obtained from theoretical analysis. By fitting simulated data to this equation, temperature-dependent parameters in the equation have been determined.

  8. Ab-initio molecular dynamics simulation of liquid water by Quantum Monte Carlo

    CERN Document Server

    Zen, Andrea; Mazzola, Guglielmo; Guidoni, Leonardo; Sorella, Sandro

    2014-01-01

    Despite liquid water is ubiquitous in chemical reactions at roots of life and climate on earth, the prediction of its properties by high-level ab initio molecular dynamics simulations still represents a formidable task for quantum chemistry. In this article we present a room temperature simulation of liquid water based on the potential energy surface obtained by a many-body wave function through quantum Monte Carlo (QMC) methods. The simulated properties are in excellent agreement with recent neutron scattering and X-ray experiments, particularly concerning the position of the oxygen-oxygen peak in the radial distribution function, at variance of previous Density Functional Theory attempts. Given the excellent performances of QMC on large scale supercomputers, this work opens new perspectives for predictive and reliable ab-initio simulations of complex chemical systems.

  9. Kontrola tačnosti rezultata u simulacijama Monte Karlo / Accuracy control in Monte Carlo simulations

    Directory of Open Access Journals (Sweden)

    Nebojša V. Nikolić

    2010-04-01

    Full Text Available U radu je demonstrirana primena metode automatizovanog ponavljanja nezavisnih simulacionih eksperimenata sa prikupljanjem statistike slučajnih procesa, u dostizanju i kontroli tačnosti simulacionih rezultata u simulaciji sistema masovnog opsluživanja Monte Karlo. Metoda se zasniva na primeni osnovnih stavova i teorema matematičke statistike i teorije verovatnoće. Tačnost simulacionih rezultata dovedena je u direktnu vezu sa brojem ponavljanja simulacionih eksperimenata. / The paper presents an application of the Automated Independent Replication with Gathering Statistics of the Stochastic Processes Method in achieving and controlling the accuracy of simulation results in the Monte Carlo queuing simulations. The method is based on the application of the basic theorems of the theory of probability and mathematical statistics. The accuracy of the simulation results is linked with a number of independent replications of simulation experiments.

  10. Monte Carlo simulation of the image formation process in portal imaging

    International Nuclear Information System (INIS)

    We have written Monte Carlo programs to simulate the formation of radiological images. Our code is used to propagate a simulated x-ray fluence through each component of an existing video-based portal imaging system. This simulated fluence consists of a 512x512 pixel image containing both contrast-detail patterns as well as checker patterns to assess spatial resolution of the simulated portal imager. All of the components of the portal imaging system were modeled as a cascade of eight linear stages. Using this code, one can assess the visual impact of changing components in the imaging chain by changing the appropriate probability density function. Virtual experiments were performed to assess the visual impact of replacing the lens and TV camera by an amorphous silicon array, and the effect of scattered radiation on portal images

  11. Ab initio molecular dynamics simulation of liquid water by quantum Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Zen, Andrea, E-mail: a.zen@ucl.ac.uk [Dipartimento di Fisica, “La Sapienza” - Università di Roma, piazzale Aldo Moro 5, 00185 Rome (Italy); London Centre for Nanotechnology, University College London, London WC1E 6BT (United Kingdom); Luo, Ye, E-mail: xw111luoye@gmail.com; Mazzola, Guglielmo, E-mail: gmazzola@phys.ethz.ch; Sorella, Sandro, E-mail: sorella@sissa.it [SISSA–International School for Advanced Studies, Via Bonomea 26, 34136 Trieste (Italy); Democritos Simulation Center CNR–IOM Istituto Officina dei Materiali, 34151 Trieste (Italy); Guidoni, Leonardo, E-mail: leonardo.guidoni@univaq.it [Dipartimento di Fisica, “La Sapienza” - Università di Roma, piazzale Aldo Moro 5, 00185 Rome (Italy); Dipartimento di Scienze Fisiche e Chimiche, Università degli Studi dell’ Aquila, via Vetoio, 67100 L’ Aquila (Italy)

    2015-04-14

    Although liquid water is ubiquitous in chemical reactions at roots of life and climate on the earth, the prediction of its properties by high-level ab initio molecular dynamics simulations still represents a formidable task for quantum chemistry. In this article, we present a room temperature simulation of liquid water based on the potential energy surface obtained by a many-body wave function through quantum Monte Carlo (QMC) methods. The simulated properties are in good agreement with recent neutron scattering and X-ray experiments, particularly concerning the position of the oxygen-oxygen peak in the radial distribution function, at variance of previous density functional theory attempts. Given the excellent performances of QMC on large scale supercomputers, this work opens new perspectives for predictive and reliable ab initio simulations of complex chemical systems.

  12. Development of an optimized Compton suppression gamma-ray spectrometric system using Monte Carlo simulation.

    Science.gov (United States)

    Choi, Y; Lee, K B; Kim, K J; Han, J; Yi, E S

    2016-03-01

    We have chosen to establish the Compton Suppression Spectrometer (CSS) for low activity environmental samples with a high purity germanium (HPGe) primary detector and a removable plug-in detector (NaI(Tl)) surrounded with a cylindrical annulus guard detector (NaI(Tl)). Monte Carlo simulation with PENELOPE (PENetration and Energy LOss of Positrons and Electrons) is used to determine the optimal geometry of the CSS. To verify a correlation between experiment and simulation, the energy distribution of (137)Cs and (60)Co point sources is measured and simulated for each condition. The CSS parameters are studied to determine optimal detector geometry and Compton Suppression Factor (CSF). The timing resolution of the CSS was found to be 44ns (FWHM), which is an outstanding result in the semiconductor-based gamma-ray spectrometry. All measured values of CSF agree within 5% with the values obtained from the simulation. The optimum geometry and CSF values are discussed. PMID:26778448

  13. Automatic variance reduction for Monte Carlo simulations via the local importance function transform

    Energy Technology Data Exchange (ETDEWEB)

    Turner, S.A.

    1996-02-01

    The author derives a transformed transport problem that can be solved theoretically by analog Monte Carlo with zero variance. However, the Monte Carlo simulation of this transformed problem cannot be implemented in practice, so he develops a method for approximating it. The approximation to the zero variance method consists of replacing the continuous adjoint transport solution in the transformed transport problem by a piecewise continuous approximation containing local biasing parameters obtained from a deterministic calculation. He uses the transport and collision processes of the transformed problem to bias distance-to-collision and selection of post-collision energy groups and trajectories in a traditional Monte Carlo simulation of ``real`` particles. He refers to the resulting variance reduction method as the Local Importance Function Transform (LIFI) method. He demonstrates the efficiency of the LIFT method for several 3-D, linearly anisotropic scattering, one-group, and multigroup problems. In these problems the LIFT method is shown to be more efficient than the AVATAR scheme, which is one of the best variance reduction techniques currently available in a state-of-the-art Monte Carlo code. For most of the problems considered, the LIFT method produces higher figures of merit than AVATAR, even when the LIFT method is used as a ``black box``. There are some problems that cause trouble for most variance reduction techniques, and the LIFT method is no exception. For example, the author demonstrates that problems with voids, or low density regions, can cause a reduction in the efficiency of the LIFT method. However, the LIFT method still performs better than survival biasing and AVATAR in these difficult cases.

  14. Automatic variance reduction for Monte Carlo simulations via the local importance function transform

    International Nuclear Information System (INIS)

    The author derives a transformed transport problem that can be solved theoretically by analog Monte Carlo with zero variance. However, the Monte Carlo simulation of this transformed problem cannot be implemented in practice, so he develops a method for approximating it. The approximation to the zero variance method consists of replacing the continuous adjoint transport solution in the transformed transport problem by a piecewise continuous approximation containing local biasing parameters obtained from a deterministic calculation. He uses the transport and collision processes of the transformed problem to bias distance-to-collision and selection of post-collision energy groups and trajectories in a traditional Monte Carlo simulation of ''real'' particles. He refers to the resulting variance reduction method as the Local Importance Function Transform (LIFI) method. He demonstrates the efficiency of the LIFT method for several 3-D, linearly anisotropic scattering, one-group, and multigroup problems. In these problems the LIFT method is shown to be more efficient than the AVATAR scheme, which is one of the best variance reduction techniques currently available in a state-of-the-art Monte Carlo code. For most of the problems considered, the LIFT method produces higher figures of merit than AVATAR, even when the LIFT method is used as a ''black box''. There are some problems that cause trouble for most variance reduction techniques, and the LIFT method is no exception. For example, the author demonstrates that problems with voids, or low density regions, can cause a reduction in the efficiency of the LIFT method. However, the LIFT method still performs better than survival biasing and AVATAR in these difficult cases

  15. Tomographic image of prompt gamma ray from boron neutron capture therapy: A Monte Carlo simulation study

    International Nuclear Information System (INIS)

    The resulting neutron captures in 10B are used for radiation therapy. The occurrence point of the characteristic 478 keV prompt gamma rays agrees with the neutron capture point. If these prompt gamma rays are detected by external instruments such as a gamma camera or single photon emission computed tomography (SPECT), the therapy region can be monitored during the treatment using images. A feasibility study and analysis of a reconstructed image using many projections (128) were conducted. The optimization of the detection system and a detailed neutron generator simulation were beyond the scope of this study. The possibility of extracting a 3D BNCT-SPECT image was confirmed using the Monte Carlo simulation and OSEM algorithm. The quality of the prompt gamma ray SPECT image obtained from BNCT was evaluated quantitatively using three different boron uptake regions and was shown to depend on the location and size relations. The prospects for obtaining an actual BNCT-SPECT image were also estimated from the quality of the simulated image and the simulation conditions. When multi tumor regions should be treated using the BNCT method, a reasonable model to determine how many useful images can be obtained from SPECT can be provided to the BNCT facilities based on the preceding imaging research. However, because the scope of this research was limited to checking the feasibility of 3D BNCT-SPECT image reconstruction using multiple projections, along with an evaluation of the image, some simulation conditions were taken from previous studies. In the future, a simulation will be conducted that includes optimized conditions for an actual BNCT facility, along with an imaging process for motion correction in BNCT. Although an excessively long simulation time was required to obtain enough events for image reconstruction, the feasibility of acquiring a 3D BNCT-SPECT image using multiple projections was confirmed using a Monte Carlo simulation, and a quantitative image analysis was

  16. Monte Carlo simulation of radiative processes in electron-positron scattering

    International Nuclear Information System (INIS)

    The Monte Carlo simulation of scattering processes has turned out to be one of the most successful methods of translating theoretical predictions into experimentally meaningful quantities. It is the purpose of this thesis to describe how this approach can be applied to higher-order QED corrections to several fundamental processes. In chapter II a very brief overview of the currently interesting phenomena in e+- scattering is given. It is argued that accurate information on higher-order QED corrections is very important and that the Monte Carlo approach is one of the most flexible and general methods to obtain this information. In chapter III the author describes various techniques which are useful in this context, and makes a few remarks on the numerical aspects of the proposed method. In the following three chapters he applies this to the processes e+e- → μ+μ-(γ) and e+e- → qanti q(sigma). In chapter IV he motivates his choice of these processes in view of their experimental and theoretical relevance. The formulae necessary for a computer simulation of all quantities of interest, up to order α3, is given. Chapters V and VI describe how this simulation can be performed using the techniques mentioned in chapter III. In chapter VII it is shown how additional dynamical quantities, namely the polarization of the incoming and outgoing particles, can be incorporated in our treatment, and the relevant formulae for the example processes mentioned above are given. Finally, in chapter VIII the author presents some examples of the comparison between theoretical predictions based on Monte Carlo simulations as outlined here, and the results from actual experiments. (Auth.)

  17. Srna-Monte Carlo codes for proton transport simulation in combined and voxelized geometries

    International Nuclear Information System (INIS)

    This paper describes new Monte Carlo codes for proton transport simulations in complex geometrical forms and in materials of different composition. The SRNA codes were developed for three dimensional (3D) dose distribution calculation in proton therapy and dosimetry. The model of these codes is based on the theory of proton multiple scattering and a simple model of compound nucleus decay. The developed package consists of two codes: SRNA-2KG and SRNA-VOX. The first code simulates proton transport in combined geometry that can be described by planes and second order surfaces. The second one uses the voxelized geometry of material zones and is specifically adopted for the application of patient computer tomography data. Transition probabilities for both codes are given by the SRNADAT program. In this paper, we will present the models and algorithms of our programs, as well as the results of the numerical experiments we have carried out applying them, along with the results of proton transport simulation obtained through the PETRA and GEANT programs. The simulation of the proton beam characterization by means of the Multi-Layer Faraday Cup and spatial distribution of positron emitters obtained by our program indicate the imminent application of Monte Carlo techniques in clinical practice. (author)

  18. Ge(Li) intrinsic efficiency calculation using Monte Carlo simulation for γ radiation transport

    International Nuclear Information System (INIS)

    To solve a radiation transport problem by using Monte Carlo simulation method, the evolution of a large number of radiations must be simulated and also the analysis of their history must be done. The evolution of a radiation starts by the radiation emission, followed by the radiation unperturbed propagation in the medium between the successive interactions and then the radiation parameters modification in the points where interactions occur. The goal of this paper consists in the calculation of the total detection efficiency and the intrinsic efficiency for a coaxial Ge(Li) detector, using Monte Carlo method in order to simulate the γ radiation transport. A Ge(Li) detector with 106 cm3 active volume and γ photons with energies in 50 keV - 2 MeV range, emitted by a point source situated on the detector axis, were considered. Each γ photon evolution is simulated by an analogue process step-by-step until the photon escapes from the detector or is completely absorbed in the active volume of the detector. (author)

  19. Srna - Monte Carlo codes for proton transport simulation in combined and voxelized geometries

    Directory of Open Access Journals (Sweden)

    Ilić Radovan D.

    2002-01-01

    Full Text Available This paper describes new Monte Carlo codes for proton transport simulations in complex geometrical forms and in materials of different composition. The SRNA codes were developed for three dimensional (3D dose distribution calculation in proton therapy and dosimetry. The model of these codes is based on the theory of proton multiple scattering and a simple model of compound nucleus decay. The developed package consists of two codes: SRNA-2KG and SRNA-VOX. The first code simulates proton transport in combined geometry that can be described by planes and second order surfaces. The second one uses the voxelized geometry of material zones and is specifically adopted for the application of patient computer tomography data. Transition probabilities for both codes are given by the SRNADAT program. In this paper, we will present the models and algorithms of our programs, as well as the results of the numerical experiments we have carried out applying them, along with the results of proton transport simulation obtained through the PETRA and GEANT programs. The simulation of the proton beam characterization by means of the Multi-Layer Faraday Cup and spatial distribution of positron emitters obtained by our program indicate the imminent application of Monte Carlo techniques in clinical practice.

  20. Kinetic Monte Carlo Simulation of Cation Diffusion in Low-K Ceramics

    Science.gov (United States)

    Good, Brian

    2013-01-01

    Low thermal conductivity (low-K) ceramic materials are of interest to the aerospace community for use as the thermal barrier component of coating systems for turbine engine components. In particular, zirconia-based materials exhibit both low thermal conductivity and structural stability at high temperature, making them suitable for such applications. Because creep is one of the potential failure modes, and because diffusion is a mechanism by which creep takes place, we have performed computer simulations of cation diffusion in a variety of zirconia-based low-K materials. The kinetic Monte Carlo simulation method is an alternative to the more widely known molecular dynamics (MD) method. It is designed to study "infrequent-event" processes, such as diffusion, for which MD simulation can be highly inefficient. We describe the results of kinetic Monte Carlo computer simulations of cation diffusion in several zirconia-based materials, specifically, zirconia doped with Y, Gd, Nb and Yb. Diffusion paths are identified, and migration energy barriers are obtained from density functional calculations and from the literature. We present results on the temperature dependence of the diffusivity, and on the effects of the presence of oxygen vacancies in cation diffusion barrier complexes as well.