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The IIB matrix model has been proposed as a non-perturbative definition of superstring theory since 1996. We study a simplified model that describes the late time behavior of the IIB matrix model non-perturbatively using Monte Carlo methods, and we use the complex Langevin method to overcome the sign problem. We investigate a scenario where the spa...
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... The attenuation in the material of the radioactive source and in the air between the source and detector are neglected. The particles are transferred using the eq. 1 21 : ...
... 1. Based on simple linear congruential generators (LCG) 21 , generate two random numbers Rn1 and Rn2 into the interval (0, 1). ...
تم في البحث الحالي تصميم و كتابة برنامج محاكاة حاسوبي وفقاً لطريقة مونت كارلو ليكون بمثابة نظام عملي إفتراضي بديلاً عن النظام الحقيقي. تم إختبار البرنامج إحصائياً و هندسياً وعددياً لنظام إفتراضي لمصدر مشع- كاشف. تم تنفيذ البرنامج لكاشف آيوديد الصوديوم ولعداد كايكر لمدى من الطاقة يصل إلى 10 MeV. تم استخدام قانون الأعداد الكبيرة (LLN) ونظرية النهاية المركزية (CLT) لاختبار دقة وضبط سير عمل البرنامج والإشارة إلى مدى قرب النتائج من متوسطاتها، وإحصائيًا، إلى أي مدى تميل إلى التوزيع الطبيعي. بشكل عام، أظهرت نتائج عدد من أنواع كفاءة الكاشف توافقاً كبيراً مع النتائج التجريبية المنشورة ونتائج عدد من البرامج العالمية ضمن نسبة خطأ 0,02-5% (أي دقة 95-99,98%) و بمستوى دلالة إحصائية يعكس إحكام خوارزمية المحاكاة. إن التخمين الدقيق والمضبوط للمحاكاة الحالية يمنحها الموثوقية المطلوبة. كما أظهر برنامج المحاكاة الحالي مرونة و فعالية عالية في تصميم أي نظام مصدر- كاشف نووي و تزويد العاملين أو المجربين ذات العلاقة بمؤشرات تساعد في التصميم الأمثل للمنظومة من حيث المكونات و هندسية النظام بأقل مدة زمنية. والتي قد تستغرق من بضعة ثواني الى بضعة دقائق لزمن تنفيذ بإستخدام حاسوب شخصي بمواصفات عادية. على عكس التجارب المختبرية التي قد تستغرق من عدة دقائق الى عدة ساعات. إضافة الى توفير بيئة عمل مثالية خالية من الإشعاع تماما". كما يقدم البرنامج الحالي فهماً عميقاً لما يحدث من تفاعلات في النظام الفيزيائي العملي الحقيقي.
... No variance reduction techniques were used. The statistical uncertainties were 127 estimated by combining the uncertainties from independent runs performed with 128 different random seeds as described by Bielajew (2016). 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t Table 1. ...
Objective: To investigate the influence of different versions of the Monte Carlo codes Geant4 and FLUKA on the calculation of overall response functions f Q of air-filled ionization chambers in clinical proton beams.
Approach: f Q factors were calculated for six plane-parallel and four cylindrical ionization chambers with Geant4 and FLUKA. These factors were compared to already published values that were derived using older versions of these codes.
Main results: Differences in f Q factors calculated with different versions of the same Monte Carlo code can be up to ~1%. Especially for Geant4, the updated version leads to a more pronounced dependence of f Q on proton energy and to smaller f Q factors for high energies.
Significance: Different versions of the same Monte Carlo code can lead to differences in the calculation of f Q factors of up to ~1% without changing the simulation setup, transport parameters, ionization chamber geometry modeling, or employed physics lists. These findings support the statement that the dominant contributor to the overall uncertainty of Monte Carlo calculated f Q factors are type-B uncertainties.
... The function of the rotation matrix R( , ) is to transform the gamma-ray vector components from the local coordinates to the laboratory coordinate system ( x, y,z ) via the azimuthal angle about the positive z-axis, followed by the rotation of the polar angle about yʹ [21]. After the transformation, the three components of the new direction cosine, namely u, v , and w are calculated using Eq. ...
... For the Monte Carlo simulations, the total number and energy albedo are computed by replacing the integrals in Eqs. (21) and (22) with a finite sum and tallying for the particles in all directions and energies, which can be expressed as follows: ...
Gamma ray shielding is essential to ensure the safety of personnel and equipment in facilities and environments where radiation exists. The Monte Carlo technique is vital for analyzing the gamma-ray shielding capabilities of materials. In this study, a simple Monte Carlo code, EJUSTCO, is developed to cd simulate gamma radiation transport in shielding materials for academic purposes. The code considers the photoelectric effect, Compton (incoherent) scattering, pair production, and photon annihilation as the dominant interaction mechanisms in the gamma radiation shielding problem. Variance reduction techniques, such as the Russian roulette, survival weighting, and exponential transformation, are incorporated into the code to improve computational efficiency. Predicting the exponential transformation parameter typically requires trial and error as well as expertise. Herein, a deep learning neural network is proposed as a viable method for predicting this parameter for the first time. The model achieves an MSE of 0.00076752 and an R-value of 0.99998. The exposure buildup factors and radiation dose rates due to the passage of gamma radiation with different source energies and varying thicknesses of lead, water, iron, concrete, and aluminum in single-, double-, and triple-layer material systems are validated by comparing the results with those of MCNP, ESG, ANS-6.4.3, MCBLD, MONTEREY MARK (M), PENELOPE, and experiments. Average errors of 5.6%, 2.75%, and 10% are achieved for the exposure buildup factor in single-, double-, and triple-layer materials, respectively. A significant parameter that is not considered in similar studies is the gamma ray albedo. In the EJUSTCO code, the total number and energy albedos have been computed. The results are compared with those of MCNP, FOTELP, and PENELOPE. In general, the EJUSTCO-developed code can be employed to assess the performance of radiation shielding materials because the validation results are consistent with theoretical, experimental, and literary results.
... produce partículas secundarias[15]. En este sentido, el método MC provee una solución a un sistema macroscópico, a través de la simulación de las interacciones microscópicas de sus componentes[16]. Dentro del ámbito de la física médica, las simulaciones Monte Carlo se utilizan como una herramienta para resolver diversos problemas, tales como obtener espectros de salida de unidades de terapia o caracterizar sistemas dosimétricos, por ejemplo. ...
Ionizing radiation transport mechanisms in presence of magnetic fields can be described in terms of formalisms based on the Boltzmann radiation transport equation. However, when the transport occurs not in vacuum but in scattering media the difficulty of its analytical calculation considerably increases because of the random character of the radiation interaction processes with the scattering medium. In this context, the present work proposes and describe a methodology to characterize effects due to strong magnetic fields on electron trajectories by means of numerical techniques, such as Monte Carlo simulation, to be applied to scattering media, typically present in MRI-LINAC devices in radiotherapy situations. The obtained results for air as the scattering material show that variations of the electrons’ trajectories depend jointly on the magnetic field and the interactions with the scattering medium. Increasing the magnetic field intensity enhances the curvature of the trajectories while decreasing the displacement in the radial direction.
... Computers can perform the repetitions if numerous tiny interactions are mathematically modeled. Although the Monte Carlo approach predates computers (more on this later), and they are not required to arrive at a solution, computers make finding a solution considerably faster in most cases [32]. The present study uses Monte Carlo simulations to determine the overall effect of CFP on the confidence intervals of the freight transport sector of seven countries. ...
Freight transportation performs a critical role in the supply networks of the global economy and is heavily influenced by the activities of the industrial and manufacturing sectors, contributing significantly to their global carbon footprint (CFP). This research evaluates the lifecycle-based CFP emissions of freight transport activities in seven selected countries (China, Japan, the United States, Canada, Brazil, Great Britain, and Germany) over fifteen years, considering international trade linkages with the rest of the world. In the literature, most researchers have investigated the CFP of the transportation sector in general or analyzed the CFP of two or three countries, such as the USA and China. However, this research is novel in that it examines the CFP of the freight transport sectors of the seven biggest industrial countries. In addition, a positive relationship was found between the CFP and the gross domestic product (GDP), population, level of urbanization, and area of these countries. Therefore, this study investigates the relationship between global CFP, GDP, population, level of urbanization, and country area. A total of 15 stochastic model-based multi-regional input–output lifecycle assessments were built for each country, comprising 35 key industries. Statistical modeling tools were used to assess carbon emissions. The results show that China is the largest contributor to the freight-related CFP, while the U.S. is the second largest. The manufacture of coke and refined petroleum products represents the dominant sector. In contrast, warehousing and support activities have the most significant contributions in Germany and Great Britain. Land transport and transport via pipelines contribute the most to Canada’s CFP. The results of the regression analysis show that there is a positive relationship between the investigated variables.
... The (t-track) calculation aims to visualize particle trajectories and calculate effective and ambient doses amongst the material, while the (t-cross) tally aims to calculate particle fluence behind shielding. The Monte Carlo method is strongly influenced by historical numbers of particles [17], [31][32][33][34]. Therefore, 10 6 history numbers were used in the current study to reduce uncertainty errors. ...
Neutron encounters difficulties in shielding protection. Thus, many researchers have performed simulation and experimental research on neutron shielding materials. The characteristic of materials is highly dependent on neutron energy. The evaluation of neutron shielding for various materials, such as iron, concrete, aluminum, and borated polyethylene (BPE), was conducted in this paper through simulation using a Monte Carlo code of PHITS 3.27 and calculation via partial density method. A mono-energetic neutron source with an energy of 200 MeV is emitted perpendicular to the shielding material with a thickness of 105 cm. The parameters measured in this analysis include flux, fast neutron removal cross-section, neutron depth dose, ambient dose H*(10) equivalent, and neutron dose reduction factor (RF). Results show that iron is a good material against high-energy neutron and secondary photon radiation at the energy range with the highest removal cross-section and the lowest RF value (0.39), followed by concrete, BPE, and aluminum. The integrated fluence and effective dose profiles were consistent with previous results in the literature. Benchmarking calculation of neutron dose RF was conducted with other publications and was in good agreement within the value range.
... Figura 1 mostra o resultado do método direto aplicado no caso de uma distribuição normal com domínio [a,b]. Figura 1 -O inverso da função cumulativa de probabilidade de uma distribuição normal típica.Fonte:Bielajew (2001). ...
... então x é aceito, se não for esse o caso, rejeitar (região sombreada acima de ( ) / ( ) na Figura 2) e voltar ao passo 2.Claramente, esse método é limitado a valores finitos de a e b.Figura 2 -A distribuição de probabilidade da distribuição normal típica escalada pelo método de rejeição.Fonte:Bielajew (2001). ...
... Accurate characterization and quantification of such short-term dose enhancement have been very challenging. However, some MC [51,55,57] and experimental [54,57,60] approaches have provided preliminary information about some key issues such as correlation with radiation properties and NP concentration. ...
... The radiation transport, accounting for scattering and absorption interactions, is described by the main Boltzmann transport equation (BTE) [60]. However, analytic solutions to the BTE are commonly difficult to achieve or non-available in most practical cases. ...
Nanoparticles have proven to be biocompatible and suitable for many biomedical applications. Currently, hyperthermia cancer treatments based on Fe nanoparticle infusion excited by alternating magnetic fields are commonly used. In addition to this, MRI-based image-guided radiotherapy represents, nowadays, one of the most promising accurate radiotherapy modalities. Hence, assessing the feasibility of combining both techniques requires preliminary characterization of the corresponding dosimetry effects. The present work reports on a theoretical and numerical simulation feasibility study aimed at pointing out preliminary dosimetry issues. Spatial dose distributions incorporating magnetic nanoparticles in MRI-based image-guided radiotherapy have been obtained by Monte Carlo simulation approaches accounting for all relevant radiation interaction properties as well as charged particles coupling with strong external magnetic fields, which are representative of typical MRI-LINAC devices. Two main effects have been evidenced: local dose enhancement (up to 60% at local level) within the infused volume, and non-negligible changes in the dose distribution at the interfaces between different tissues, developing to over 70% for low-density anatomical cavities. Moreover, cellular uptakes up to 10% have been modeled by means of considering different Fe nanoparticle concentrations. A theoretical temperature-dependent model for the thermal enhancement ratio (TER) has been used to account for radiosensitization due to hyperthermia. The outcomes demonstrated the reliability of the Monte Carlo approach in accounting for strong magnetic fields and mass distributions from patient-specific anatomy CT scans to assess dose distributions in MRI-based image-guided radiotherapy combined with magnetic nanoparticles, while the hyperthermic radiosensitization provides further and synergic contributions.
... Monte Carlo criticality calculations use a convergence method analogous to the power iteration method used by deterministic methods. 1 Starting from a guess neutron fission source and fundamental eigenvalue, a transport calculation is performed in order to obtain the next step's fission source and eigenvalue. The process is repeated until convergence is reached by some chosen measure. ...
A novel source convergence acceleration method for Monte Carlo eigenvalue calculations is proposed in this paper. The method consists of simulating the bulk of the inactive cycles with online-generated multigroup cross sections. Then the active cycles are simulated with continuous-energy cross sections to preserve full fidelity. The method was implemented in the Monte Carlo code SCONE and tested on several three-dimensional full-length assembly models. In some cases, the same multigroup cross sections were used for several spatially separated materials in order to limit statistical uncertainties. The method was shown to accelerate calculations by a factor of 2.5 to 5 at the cost of a slightly increased standard deviation in the flux distribution estimated across several independent simulations. The memory usage due to storing multigroup cross sections does not seem to be prohibitive for practical applications.
... The critical thickness problem in the reflected system with tetra-anisotropic scattering was solved by Koklu and Ozer. Rashidian Maleki presented a Monte Carlo method to solve the slab albedo problem with linearly anisotropic scattering, in which by sampling the scattering cosine and then rotating the coordinate systems (Bielajew, 2001) the direction of the scattered neutron was calculated. ...
Different types of deterministic solution methods were used to solve neutron transport equations corresponding to half-space and slab albedo problems. In these types of solution methods, in addition to the error of the numerical solutions, the obtained results contain truncation and discretization errors. In the present work, a non-analog Monte Carlo method is provided to simulate the half-space and slab albedo problems with Inönü and Anlı-Güngör strongly anisotropic scattering functions. For each scattering function, the sampling method of the direction of the scattered neutrons is presented. The effects of different beams with different angular dependencies and the effects of different scattering parameters on the reflection probability are investigated using the developed Monte Carlo method. The validity of the Monte Carlo method is also confirmed through the comparison with the published data.
