Sharif Digital Repository

Chaotic behavior of bubbles and their random motion because of the effects of an electric field (EF) motivates statistical approaches for investigating electrohydrodynamically (EHD) enhanced heat transfer. A theoretical model for boiling heat transfer under EHD is presented. The model is based on integral balance of momentum, energy, and interfacial area density, and consists of a system of three coupled equations: conservation of void fraction, bubble number density, and momentum of bubbles. Theoretical results are in qualitative agreement with the available experimental observations in the literature. © 2008 by Begell House, Inc  

This paper presents a new statistical based clean algorithm for multiple target detection in noisy environments. For this purpose the variance and average of the ambiguity function as the output of matched filter will be computed. This information used for separating the real targets from the false ones, in noisy environment and heavy clutter up to - 13 dB. © 2006 IEEE  

This paper presents the results of a thorough analysis of applying power quality standards to a granite factory. It explains the procedure of determining power quality indices in a power system. The paper presents the field data and provides the results of statistical analysis in order to extract power quality indices. A comparison against standard limits is also given. The case study gives an overview of power quality in such customers and brings up some practical limitations when applying power quality standards. ©2006 IEEE  

By applying the expectation maximisation algorithm to the maximum likelihood detection of layered space-time codes, the conditional log-likelihood of a single layer is iteratively maximised, rather than maximising the intractable likelihood function of all layers. Computer simulations demonstrate the efficiency of the proposed detection scheme  

In this paper, two different statistical approaches are used for duration prediction of the Farsi language. These two statistical models are Neural Networks (NN) and Classification And Regression Trees (CART). The first step in this work was to create a database and develop a flexible feature extraction and selection module. In the next step, the output of the feature selection module was used to train both models. The results of the trained models are further studied to determine the most important parameters affecting the syllable duration in Farsi, The model accuracy is evaluated by using separate training and test data. In the third step of this work, ah automatic rule generator module... 

To achieve economic stability, distribution Company as an economic institution should be managed by various processes. In this way, knowledge of different processes is the first step. Furthermore, expectations, outputs, requirement data, and sub-processes should be extracted and determined. Accordingly, to assign the performance responsibility of each process, the decision making points must be introduced and, the deviation or change in set-points should be investigated into processes. Also, the performance of processes could be monitored by introducing of the sub-indictors. In this study, a practical method is presented for monitoring of reliability and power loss indices from viewpoint... 

Molecular structural mechanics approach is implemented to investigate vibrational behavior of single-layered graphene sheets. By using the atomistic modeling, mode shapes and natural frequencies are obtained. Vibration analysis is performed under different chirality and boundary conditions. Numerical results from the finite element technique are applied to develop empirical equations via a statistical multiple non-linear regression model. With the proposed empirical equations, fundamental frequencies of single-layered graphene sheets under considered boundary conditions can be predicted within 3 percent accuracy. Copyright © 2007 by ASME  

To make a decision on the nature of a flaw within a pipeline, it is necessary to detect suspicious regions in ultrasonic inspection images reliably and to, derive geometrical parameters such as shape, position and orientation from each measured signal and finally to collate these parameters intelligently by associating each measured signal with a possible flaw type. These two papers present an innovative method of configurable flaw classification and volume estimation in oil pipelines. This method includes: (1) An adaptive thresholding selection for estimation of the area and volume of the flaws, (2) Dynamic detection of interesting points as feature points at different levels of images by... 

Arrays of N weakly coupled oscillators are considered in different configurations. The locking bandwidth for these arrays is defined statistically. Various factors affecting the locking bandwidth and the effect of the coupling network topology on locking bandwidth are studied by solving the dynamic equations of the array numerically. The analytical locking bandwidth for two configurations of arrays is computed and the results are compared with the numerical solution of dynamic equations. © The Institution of Engineering and Technology 2008  

In this paper residual stresses induced by butt metal arc gas welding (MAGW), in accordance with ASTM E837, are determined by hole drilling. The results are analyzed by probabilistic methods. Also, the effect of fatigue life on relaxation of welding residual stress is investigated. The specimens are tested to measure fatigue life and crack growth rates in accordance with ASTM E466 for force controlled amplitude axial fatigue testing. © 2008 Verlag Stahleisen GmbH, Düsseldorf  

A series of low speed wind tunnel tests on a section of a 660 Kw wind turbine blade which is under constructer were conducted to examine the effects of distributed surface contamination on its performance characteristics. At first model was tested in the clean condition and after that it was tested with tree different types of roughness. The data shows that this particular airfoil is very sensitive to the applied surface roughness. For the contaminated model the roughness, 0.5mm height was distributed over the entire upper surface of the airfoil such that the distribution pattern was denser in the vicinity of the leading edge and thinner in the trailing edge area. Statistical data show that... 

Growing technology, escalating capability, and increasing complexity in many real world systems demand the applications of multivariate statistical analysis approaches by simulation. In these approaches, generating multivariate random vectors is a crucial part of the system modeling and analyzing. The NORTA algorithm, in which generating the correlation matrices of normal random vectors is the most important task, is one of the most efficient methods in this area. To do this, we need to solve some complicated equations. Many researchers have tried to solve these equations by three general approaches of (1) solving nonlinear equations analytically, (2) solving equations numerically, and (3)... 

Real porous media even though seemingly homogenous and isotropic are most often nonuniform, and the nonuniformity may affect the macroscopic properties of porous media such as permeability, capillary pressure which is a result of the tortuous and circuitous nature of the flow paths in medium. In this study a glass type micromodel is considered as a porous media sample. A four parametric probability density function are used to express pore throat size, pore body size and pores length distributions which are measured using image analysis technique of porous model. The statistical models parameters are calculated by fitting the statistical model to the measured data of pore throat pore body... 

In this paper, a new cache placement scheme is proposed to achieve higher hit ratios with respect to the two conventional schemes namely set-associative and direct mapping. Similar to set-associative, in this scheme, cache space is divided into sets of different sizes. Hence, the length of tag fields associated to each set is also variable and depends on the partition it is in. The proposed mapping function has been simulated with some standard trace files and statistics are gathered and analyzed for different cache configurations. The results reveal that the proposed scheme exhibits a higher hit ratio compared to the two well-known mapping schemes, namely set-associative and direct mapping,... 

Transferring image sequences requires a very high bit-rate on the communication channels. However, if we want to use telephone lines as the means of communication, the bandwidth constraint problems limit the bit-rates, and the optimal exploitation of link and resource are required. The statistical analysis of video signals indicates that there is a strong correlation both between successive picture frames as well as within the picture elements themselves. Theoretically, decorrelation of these signals can lead to bandwidth compression without significantly affecting image resolution. In this research, in order to reduce bit-rate, we propose a new algorithm using Bilinear Transformation... 

This paper assesses the cycles and indices of drought in Iran and prepares general maps of the region, which are affected by droughts with 10- and 30-year reversible periods frequency of 1 and 3 years by utilizing statistical methods. To study the condition of drought, some indices have been applied in Yazd Province over a 48-year statistical period (1925-2000). Then with regard to existing statistics (1998-2001), the effect of drought on various issues during the most recent drought cycle have been assessed. © 2005 Taylor & Francis  

For any respiratory sound analysis or assessment, respiratory flow must also be measured simultaneously with the sounds. However, due to difficulties and/or inaccuracy of the most flow measurement techniques, several researchers have attempted to estimate flow from respiratory sounds. However, all of the proposed methods heavily depend on the availability of different rates of flow for calibration of the model, which makes their use limited by a large degree. In this paper, a robust and novel method for estimating flow using entropy of the band pass filtered tracheal sounds is proposed. The proposed method is independent of the flow rate chosen for calibration; it requires only one breath... 

Pulse Repetition Interval (PRI) Modulation Detection is an important subsystem of a typical electronic warfare support system. In this paper, a robust, fast, and well designed structure for detection of simple and complex PRI modulations based on statistical and sequential analysis of Pulse Repetition Interval (PRI) is proposed. Accuracy and robustness of the technique against electromagnetic noise are demonstrated via simulations  

These two papers present an innovative method of configurable flaw classification and volume estimation in oil pipelines. In part I, the ultrasonic image acquisition system is introduced and surface and volume of the flaw are estimated with fuzzy image processing. A number of real figures illustrate the system performance. The flops calculation reveals that this fuzzy estimator could be integrated in a real time flaw detection system. In part II, at first, the dynamic detection of interesting points, i.e. as feature points at different levels of images, is proposed using wavelet transform. Furthermore, a guided searching strategy is used for the best matching from the coarse level to a fine...