Monte Carlo simulation applied in total reflection X-ray fluorescence: Preliminary results

The X-ray Fluorescence (XRF) analysis is a technique for the qualitative and quantitative determination of chemical constituents in a sample. This method is based on detection of the characteristic radiation intensities emitted by the elements of the sample, when properly excited. A variant of this technique is the Total Reflection X-ray Fluorescence (TXRF) that utilizes electromagnetic radiation as excitation source. In total reflection of X-ray, the angle of refraction of the incident beam tends to zero and the refracted beam is tangent to the sample support interface. Thus, there is a minimum angle of incidence at which no refracted beam exists and all incident radiation undergoes total reflection. In this study, we evaluated the influence of the energy variation of the beam of incident x-rays, using the MCNPX code (Monte Carlo NParticle) based on Monte Carlo method. © 2013 AIP Publishing LLC.

Estudo de Monte Carlo da produção de nova ressonância neutra decaindo em dois bósons vetoriais no experimento CMS

Pós-graduação em Física - IFT

Cálculo das funções de anisotropia e radial de dose para braquiterapia com semente de 192Ir em diferentes materiais de interesse em radiologia com o auxílio do programa baseado no método de Monte Carlo MCNPX

The brachytherapy braquiterapia is an x-ray modality radiotherapy in which stamped or halfstamped radioactive sources in format of seeds are used, wires or to one short distance, in contact or implanted to the fabric to be treated. All the treatment modalities require a previous planning. The formalism recommended for calculation of dose was considered by the AAPM for the first TG-43 Report. In it distributions of dose of isolated seeds measured and calculated by Monte Carlo method in water instead of with models half-empiricists. In this work we in accordance with present some preliminary results of the calculation of functions of radial anisotropy and of dose in the distance for seed of 192Ir, wide used in brachytherapy treatments of high tax of dose (HDR), with the aid of the program based on the Monte Carlo method MCNPX v2.50 (Mount Carlo N ParticleeXtended). The materials chosen in the simulation beyond water, had been MS20 and estriado muscle

A simulação de Monte Carlo como instrumento fundamental para a análise de viabilidade econômica: a implementação de uma fundição de ferro em uma empresa metalúrgica

In uncertainly economic scenarios, an economic feasibility analysis must be done to accept a project based on investment criteria, such as NPV and IRR, mainly because the shareholders tend to invest their budget in a project if it has a great chance to return their investments. The studied company outsources all of its foundry services, what makes it very dependent of its suppliers, because the products have a lower quality level, long delivery periods and high prices. Therefore, this work will analyze the project of building an iron-casting foundry to decrease the dependence of its suppliers. In order to develop this research, all needed data related to the construction of the foundry and sales were collected to create deterministic and probabilistic (Monte Carlo Simulation) cash flows using MsExcel® and Oracle's Crystal Ball® software. As a result, the project was found to be risky by the NPV and IRR in the case of this new production line supplying only the internal needs. However, when the company offers its services to the foundry market, the project turns to be feasible

Estudo do método Monte Carlo e sua aplicação no modelo SIR

In this work we present a discussion and the results of the simulation of disease spread using the Monte Carlo method. The dissemination model is the SIR model and presents as main characteristic the disease evolution among individuals of the population subdivided into three groups: susceptible (S), infected (I) and recovered (R). The technique used is based on the introduction of transition probabilities S-> I and I->R to do the spread of the disease, they are governed by a Poisson distribution. The simulation of the spread of disease was based on the randomness introduced, taking into account two basic parameters of the model, the power of infection and average time of the disease. Considering appropriate values of these parameters, the results are presented graphically and analysis of these results gives information on a group of individuals react to the changes of these parameters and what are the chances of a disease becoming a pandemic

A Monte Carlo study of the anisotropic N=3 Ashkin-Teller model

The phase diagram of an asymmetric N = 3 Ashkin-Teller model is obtained by a numerical analysis which combines Monte Carlo renormalization group and reweighting techniques. Present results reveal several differences with those obtained by mean-field calculations and a Hamiltonian approach. In particular, we found Ising critical exponents along a line where Goldschmidt has located the Kosterlitz-Thouless multicritical point. On the other hand, we did find nonuniversal exponents along another transition line. Symmetry breaking in this case is very similar to the N = 2 case, since the symmetries associated to only two of the Ising variables are broken. However, for large values of the coupling constant ratio XW = W/K, when the only broken symmetry is of a hidden variable, we detected first-order phase transitions giving evidence supporting the existence of a multicritical point, as suggested by Goldschmidt, but in a different region of the phase diagram. © 2002 Elsevier Science B.V. All rights reserved.

Using the Ferrenberg-Swendsen Monte Carlo method for nonuniversal exponents

We use the method of Monte Carlo evolution in the coupling constant space of Ferrenberg and Swendsen to evaluate the nonuniversal exponent η* associated to a linear defect in a 2d Ising model. © 1989.

Aplicação da Simulação de Monte Carlo no estudo de testes de fadiga em rodas agrícolas

Due to the increasing demand from clients and the search for better performances in the heavy vehicles industry, a progressive evolution in technology in a general way was needed. This paper uses a scientific method to validate, prior to its manufacture, the project of an agricultural wheel for sugar cane harvesters. Monte Carlo Simulation is used in conjunction with Finite Elements Method, in order to simulate the wheel's behavior in a cornering test, identify possible failure regions and get an estimate for its life under fatigue. To this end, test conditions according to EUWA Standards were simulated and obeyed, relevant to fatigue. Simulation results were interesting, according to industry experts involved in the project and manufacture of the product in question, and have provided important elements for the decision making regarding improvements that could be made on the product project before its execution

Forward energy flow, central charged-particle multiplicities, and pseudorapidity gaps in W and Z boson events from pp collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Measurement of the inclusive production cross sections for forward jets and for dijet events with one forward and one central jet in pp collisions at root s=7 TeV

The inclusive production cross sections for forward jets, as well for jets in dijet events with at least one jet emitted at central and the other at forward pseudorapidities, are measured in the range of transverse momenta p(T) = 35-150 GeV/c in proton-proton collisions at root s = 7 TeV by the CMS experiment at the LHC. Forward jets are measured within pseudorapidities 3.2<|eta|<4.7, and central jets within the |eta|<2.8 range. The double differential cross sections with respect to pt and eta are compared to predictions from three approaches in perturbative quantum chromodynamics: (i) next-to-leading-order calculations obtained with and without matching to parton-shower Monte Carlo simulations, (ii) PYTHIA and HERWIG parton-shower event generators with different tunes of parameters, and (iii) CASCADE and HEJ models, including different non-collinear corrections to standard single-parton radiation. The single-jet inclusive forward jet spectrum is well described by all models, but not all predictions are consistent with the spectra observed for the forward-central dijet events.

Theoretical studies of liquids by computer simulations: the water-acetone mixture.

Monte Carlo simulation results for pure liquid acetone and water-acetone mixtures calculated in the isothermal and isobaric (NPT) ensemble at T=298K and p=1.0atm are presented. The TIP4P model was used for water and optimized potential for liquid simulation (OPLS) force field parameters used for acetone. The results obtained for the average configurational energy as a function of the mole fraction are in good accord with experimental data. Energy partitioning and co-ordination numbers results calculated for equimolar water-acetone solution are compared to similar data obtained for other water-organic liquid mixtures. These results show an increase in water-water interaction energy and co-ordination numbers when the interaction between water and organic liquid molecules decrease. Distribution functions for pure liquid acetone and water-acetone mixtures are presented. Dipole-dipole angular correlation functions obtained for pure liquid acetone show a predominance of dimers with parallel alignment of dipole moments. Radial distribution functions from water-acetone interaction show characteristic features of hydrogen bonded liquids. Radial and angular distribution functions for water-water correlation calculated in pure water and in equimolar water-acetone mixture are compared, showing very similar features in both systems. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Comparison of SRIM, MCNPX and GEANT simulations with experimental data for thick Al absorbers

Proton computerized tomography deals with relatively thick targets like the human head or trunk. In this case precise analytical calculation of the proton final energy is a rather complicated task, thus the Monte Carlo simulation stands out as a solution. We used the GEANT4.8.2 code to calculate the proton final energy spectra after passing a thick Al absorber and compared it with the same conditions of the experimental data. The ICRU49, Ziegler85 and Ziegler2000 models from the low energy extension pack were used. The results were also compared with the SRIM2008 and MCNPX2.4 simulations, and with solutions of the Boltzmann transport equation in the Fokker-Planck approximation. (C) 2009 Elsevier Ltd. All rights reserved.

Comparison of GEANT4 simulations with experimental data for thick al absorbers

Proton beams in medical applications deal with relatively thick targets like the human head or trunk. Therefore, relatively small differences in the total proton stopping power given, for example, by the different models provided by GEANT4 can lead to significant disagreements in the final proton energy spectra when integrated along lengthy proton trajectories. This work presents proton energy spectra obtained by GEANT4.8.2 simulations using ICRU49, Ziegler1985 and Ziegler2000 models for 19.68MeV protons passing through a number of Al absorbers with various thicknesses. The spectra were compared with the experimental data, with TRIM/SRIM2008 and MCNPX2.4.0 simulations, and with the Payne analytical solution for the transport equation in the Fokker-Plank approximation. It is shown that the MCNPX simulations reasonably reproduce well all experimental spectra. For the relatively thin targets all the methods give practically identical results but this is not the same for the thick absorbers. It should be noted that all the spectra were measured at the proton energies significantly above 2MeV, i.e., in the so-called Bethe-Bloch region. Therefore the observed disagreements in GEANT4 results, simulated with different models, are somewhat unexpected. Further studies are necessary for better understanding and definitive conclusions. © 2009 American Institute of Physics.

Reactive power support pricing of distributed generators with primary energy source uncertainty

In this paper, a novel methodology to price the reactive power support ancillary service of Distributed Generators (DGs) with primary energy source uncertainty is shown. The proposed methodology provides the service pricing based on the Loss of Opportunity Costs (LOC) calculation. An algorithm is proposed to reduce the uncertainty present in these generators using Multiobjective Power Flows (MOPFs) implemented in multiple probabilistic scenarios through Monte Carlo Simulations (MCS), and modeling the time series associated with the generation of active power from DGs through Markov Chains (MC). © 2011 IEEE.