Sharif Digital Repository

The complex dielectric constants of building materials are present in the reflection, transmission and diffraction coefficients of the ray tracing formulation. Any deviation of the dielectric constants included in ray tracing simulation from the actual material properties may be a source of inaccuracy of the simulation results. This paper explores the sensitivity of ray tracing results to the inaccuracy of the dielectric constants of building materials. To do this, the real and imaginary parts of the dielectric constants are considered as random variables to account for the present uncertainty. The propagation of uncertainty in the ray tracing simulation is then obtained by means of the... 

Human tracking is an essential step in many computer vision-based applications. As single view tracking may not be sufficiently robust and accurate, tracking based on multiple cameras has been widely considered in recent years. This paper presents a distributed human tracking method in a smart camera network and introduces a particle filter design based on Histogram of Oriented Gradients (HOG) and color histogram. The proposed adaptive motion model also estimates the target speed from the history of its latest displacement and improves the robustness of the tracker by decreasing the probability of missing targets. In addition, a distributed data fusion method is proposed which fuses the... 

In this paper we study the statistical properties of the Signal to Noise Ratio (SNR) of the dual-hop relaying link in a cooperative wireless communication system in the presence of channel estimation errors for Decode and Forward (DF) relaying protocol. Then for assessment of the system performance the Symbol Error Rate (SER) is considered. Two approaches are introduced for SER calculation from which the second one results in a closed form solution. Finally the second approach is used to find an optimum power allocation scheme for transmission of pilot and data symbols at the source and the relay terminals that results in minimizing the SER and considerable amount of power saving. Also Monte... 

Reliability analysis in FPGA implementation of logic circuits is an important issue in designing fault tolerant systems for faulty environments. In this paper an analytical method is developed for analyzing such systems. This method is based on signal probability propagation of faults from the location of appearance to final outputs of circuit. Single fault model is used for the faults occurred in routes and LUTs. In addition reconvergent fan-outs are handled using 16 correlation coefficients propagation approach. Experimental results show a good agreement between this method and Monte Carlo method for reliability analysis of MCNC benchmarks  

Monte Carlo simulation provides a probabilistic approach to evaluate the physical behavior of infrastructures. Therefore, the performance could be achieved in a more realistic manner. Within this framework, an innovative software code is developed by combining the Monte Carlo and finite difference methods to predict the behavior of embankment dams after impounding. In order to assess the efficiency of the method, the case study of Chahnimeh-4 dam, located at Southeast of Iran, has been investigated in detail. The behavior of this dam is predicted and compared with the field monitoring by using the Kolmogorov-Smirnov test. The results indicate the robustness of the proposed method and it can... 

A new method for modelling and analysis of non-linearity errors caused by the capacitor mismatches and op-amp non-idealities in two-step analogue-to-digital converters (ADCs) is presented. Analytical formulas for estimation of the ADC integral non-linearity (INL) are derived. Using the proposed method, the ADC INL can be calculated in terms of the capacitor mismatches standard deviations. Therefore time-consuming Monte Carlo simulations which are conventionally used to evaluate the effect of random capacitor mismatches on the ADC linearity can be avoided. The effect of op-amp non-idealities, which are frequently examined by the circuit-level simulations, can also be evaluated using the... 

A pipelined architecture is developed for a Sequential Monte Carlo (SMC) receiver that performs joint channel estimation and data detection. The promising feature of the proposed SMC receiver is achieving the near-bound performance in fading channels without using any decision feedback, training or pilot symbols. The proposed architecture exploits the parallelism intrinsic to the algorithm and consists of three blocks, i.e., the SMC core, weight calculator, and resampler. Hardware efficient/parallel architectures for each functional block including the resampling block is developed. The novel feature of the proposed architecture is that makes the execution time of the resampling independent... 

In this paper, the Monte Carlo technique is used to determine the optical detection strategies in three-layered (maternal, amniotic fluid and fetal) tissue model. This model is utilized to estimate the transabdominal optical power and optimum source-detector (S-D) separation. Results based on the launching of 2 million photons with 1 mW optical power showed that the expected optical power output is in the range of 10 -6-10 -10 W/cm 2 depending on S-D separation. Considering the limit of the signal processing methods (such as adaptive noise cancelling) and the use of silicon photodetector, an S-D separation of 4 cm has been selected as a practical compromise between signal level and... 

We use the direct simulation Monte Carlo (DSMC) method and investigate the subsonic rarefied gas flow through micro/nanochannels, imposing a constant pressure ratio and a constant temperature difference between the inflow and wall temperature. We further study the heat transfer characteristics of subsonic nitrogen gas flow under this imposed temperature difference. We show that, specifying a higher temperature magnitude would lead to more rarefactions even imposing a fixed temperature difference. This consequently results in a higher wall heat flux rate for a fixed inflow-wall temperature difference. Our investigating shows that the number of simulated particles need to increase suitably if... 

Microfilters are commonly used to block undesirable particles in the fluid flows and to control the flow patterns in MEMS. The main purpose of this study is to understand the effect of gas type on density, pressure, Mach number, and velocity distributions of fluid flows through a microfilter. The Knudsen number is the slip flow regime passing through the microfilter. We use direct simulation Monte Carlo (DSMC) method to simulate the flow of nitrogen, helium, oxygen, air and methane passing through a specific microfilter. The geometry of microfilter is unique in all cases. Our results confirm that every gas performs a different performance passing through a specific microfilter, and that the... 

Despite the fact that control charts are able to trigger a signal when a process has changed, it does not indicate when the process change has begun. The time difference between the changing point and a signal of a control chart could cause confusions on the sources of the problems. Knowing the exact time of a process change would help to reduce the time for identification of the special cause. In this article, a model for the change-point problem is first introduced and a maximum-likelihood estimator (MLE) is applied when a linear trend disturbance is present. Then, Monte Carlo simulation is applied in order to evaluate the accuracy and the precision performances of the proposed... 

Motivated by numerous applications in Monte Carlo techniques and as of late, in deriving non dominated solutions in multi-objective optimization problems, this article addresses generating uniform random variables (λi, λi ≥ 0, i = 1,..., n) over a simplex in ℝ2 (n ≥ 2), i.e., Σi=1 n λi = 1. In this article, first, conditional distribution of λi where Σi=1 n λi = 1 is derived and then inverse method is applied to generate random variables  

The time-dependent diffusion of neutrons in a spheroid as a function of the focal distance has been studied. The solution is based on an orthogonal basis and an extrapolation distanced related boundary condition for the spheroidal geometry. It has been shown that spheres and disks are two limiting cases for the spheroids, for which there is a smooth transition for the systems properties between these two limits. Furthermore, it is demonstrated that a slight deformation from a sphere does not affect the fundamental mode properties, to the first order. The calculations for both multiplying and non-multiplying media have been undertaken, showing good agreement with direct Monte Carlo... 

As a primary step of establishment of an extensive air shower array consisting 20 scintillation detectors we optimized an individual detector. Square shaped scintillators are placed under a metal pyramid Light Enclosure with a photomultiplier tube (PMT) at the vertex of it. A set of experiments are performed to optimize the height of light enclosures by comparing 4 different heights 0.1, 0.2, 0.3 and 0.4 m. These experiments are supported by a Monte Carlo simulation of detection process. In this article, by considering experimental and simulation results we concluded that 20 cm is an optimum height for light enclosures  

Many of the physical macroscopic quantities could be explained as the result of a collection of microscopic particles which act independent of each-other, in a linear fashion. Since the physical laws of the interaction of these particles with their surrounding medium are non-deterministic, one could think of these particles as the generators of a linear stochastic field. In this paper, we have introduced a derivation which has yielded an equation for the spatiotemporal correlations in such a field. The derivation is simple and extendable to include the behavior of many physical particles. A simple numerical algorithm has been devised to solve the obtained initial value integrodifferential... 

The Ensemble Kalman Filter (EnKF) is a Monte Carlo based method to assimilate the measurement data sequentially in time. Although, EnKF has some advantages over the other Kalman based methods to deal with non-linear and/or high dimensional reservoir models, it also suffers from deficiency in estimation of non-Gaussian parameters. In this work, we propose a re-parameterization method to handle non-Gaussian parameters via Ensemble Kalman Filter framework. For this purpose, concept of cumulative distribution function transformation has been used. In addition, the statistics of prior information have been aggregated in the state vector in order to capture the prior uncertainties of non-Gaussian... 

Orbit determination (OD) problem utilizing onboard sensors is a key requirement for many current and future space missions. Though there exists ample research and work on this subject, a novel algorithm is presented in this paper for the nonlinear problem of OD. In this regard, initially a new cubature-quadrature particle filter (CQPF) that uses the square-root cubature-quadrature Kalman filter (SR-CQKF) to generate the importance proposal distribution is developed. The developed CQPF scheme avoids the limitation of the standard particle filter (PF) concerning new measurements. Subsequently, CQPF is enhanced to take advantage of the relative entropy (Kullback-Leibler Distance) criterion to... 

In this paper, the development of the MCNPX-ESUT (MCNPX-Energy Engineering of Sharif University of Technology) computer code for simulation of neutron/gamma pulse height distribution is reported. Since liquid organic scintillators like NE-213 are well suited and routinely used for spectrometry in mixed neutron/gamma fields, this type of detectors is selected for simulation in the present study. The proposed algorithm for simulation includes four main steps. The first step is the modeling of the neutron/gamma particle transport and their interactions with the materials in the environment and detector volume. In the second step, the number of scintillation photons due to charged particles such... 

In this article, a double-max multivariate exponentially weighted moving average (DM-MEWMA) chart is proposed to jointly monitor the parameters of a multivariate multistage auto-correlated (MMAP) process. While the process is assumed to work in a linear state-space form, two modified statistics are combined into a novel statistic to monitor the mean vector and the covariance matrix of the MMAP simultaneously. Besides, prior knowledge of variation propagation is used so that the chart has both a fault identification power and capability of working with the sample size of one. A statistical test shows that the two proposed statistics are independent of the process dimension. Monte Carlo... 

Determining the shape factor is essential for solving radiative heat transfer problems. An important case that has various applications in the heat power plant systems is calculation of the configuration factor between the fins and the in-plane parallel semi-cylinder. In the present work, Monte Carlo method, Cross string method, and analytical solutions were implemented for this problem. Several simulations were performed by varying semi-cylinders radius and different lengths of the fin. Also, the influence of the number of emitting rays and the number of strips was studied. Considering a fin between two tubes, it is found that calculating the view factor between one tube and a fin is...