Sharif Digital Repository

Considering the special importance of network flow problems in human life, as well as the complexity of solving these problems in very large scales, there are numerous methods to solve them and the interior point methods are the most important approaches among them. In a number of methods, a preconditioned conjugate gradient solver has been applied for the solution of the Karush-Kuhn-Tucker (KKT) system, in each interior point iteration; therefore, the selection of an appropriate preconditioner is a special issue. In spite of presenting different preconditioners in recent years, discussion and implementation of a particular class of triangulated graph-based preconditioners is our main... 

Here, we first ivestigate some available nonsmooth algorithms indentilying their drawbacks, and then provide some guidelines to avert these drawbacks. We divide the algorithms to two main classes, first order and second order. The main drawback of the second order class of algorithm is that there does not exist any suitable method to approximate the generalized second order derivative. To solve this problem, we construct a uniform approximation for the generalized Hessian matrix of an SC1 function. Using the discrete gradient and the extended second order derivative, we define the discrete Hessian matrix. We construct a sequence of sets, where each set is composed of discrete Hessian... 

Varian Clinac 2100 accelerator head was simulated using EGS5 Monte Carlo code. Phase space method was applied to this simulation. Two phase space plates were used in these simulations; one was inserted before the moveable jaws and the other one was placed after the jaws. The first plate was simulated for energy. And the second plate was to simulate each field size at the set energy. In the phase space method used in the EGS5 code one extracts the particle parametric information from a file as opposed to following the original particles that start at the source point. It is expected that this file to be a replica of the particles that pass the plate and further it should not add any... 

The Wedderburn rank reduction formula and the ABS algorithms are powerful methods for developing matrix factorizations and many fundamental numerical linear algebra processes such as Gramm- Schmidt, conjugate direction and Lanczos methods. Esmaeili, Mahdavi-Amiri and Spedicato introduced a class of integer ABS algorithms for solving linear systems of Diophantine equations. In a recent work, Khorramizadeh and Mahdavi-Amiri have also presented a new class of extended integer ABS algorithms for solving linear Diophantine systems by computing an integer basis for the null space while controlling the growth of intermediate results. Here, we propose new approches to develop a new class of extended... 

In recent years, a strong interplay between quantum mechanics and the physics of waveguide arrays was established based on a formal analogy between atomic and photonic lattices. The study of light evolution in photonic lattices has provided deep insights into the physics of wave function dynamics and, hence, peculiar quantum mechanical features. Arrays of evanescently coupled waveguides is a very versatile model system for discrete physics. Anderson localization and Bloch oscillations are two examples of coherent quantum transport phenomena, which have been investigated in this thesis. In the first part of this thesis, we investigate numerically the effect of long-range interaction on the... 

In this thesis, the optical force acting on the spherical polystyrene particle trapped by optical tweezers is calculated. The calculation is based on the generalized Lorenz-Mie theory. The effect of various parameters on the optical force is also investigated. It is shown that, tuning the different parameters, one can significantly enhance the optical force acting on the trapped particle. Besides, one can achieve a stable 3D trap of a sub-micron particle somewhere far deep inside the sample chamber. Our results indicate that: (1) By obstructing the central region of the incident Gaussian laser beam at the back focal plane of the objective lens, the trap stiffness, the maximum linear force,... 

The main approach of this thesis is to study the performance and efficiency of agricultural biomass derived extractive phases in sample preparation methods. In this regard, different types of agricultural biomasses and various important factors in the production of biochar from biomass were studied by two physical and chemical methods. Accordingly, different types of biochars have been made and applied in different extraction setups along with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and gas chromatography-electron capture (GC-ECD) to detect agricultural pesticides. Also, validated developed methods were used to investigate the safety of some highly... 

This thesis is a survey of results of studies and researches in theory of Division rings and multiplicative groups of division rings and relations between group strcture and algebraic structure of division rings.in this case,we emphesized on study of finitely generated,maximal,nilpotent and soluble subgroups of division rings.we also,study the Valuation theory on division rings and Reduced K-theory of division rings and relations between these theories and group structure of division rings,morever,those which is finite dimensional over their center as vector spaces.at the end,we shortly,study divisible division rings and radicable division rings  

Here, the properties of separability of linkages are studied. In general, a linkage is a simple polygonal chain embedded in 3-space with disjoint, straight-line edges, which are fixed-length bars. The internal vertices are called joints. If the two end points are connected then the linkage is a closed linkage, otherwise it is an open linkage. By imposing restrictions on the way the bars in joints can move, three kinds of linkages as rigid, revolute and flexible can be introduced. A motion in a linkage is the motion of its vertices that preserves the length of the bars, and adheres the restrictions on joints. A collection of linkages are said to be separatable if for any distance d, there is... 

In this research the microstructural, electrical and optical properties of Strontium Titanate and Barium Strontium Titante thin films, fabricated through Pulsed Laser Deposition (PLD), were investigated. X-ray Photoelectron Spectroscopy and X-ray Diffraction study showed that the stoichiometry of the target material was highly preserved by using PLD method. Scanning Electon Microscopy as well as Atomic Force Microscopy depicted that the using of pressed and sintered target is a suitable metod for improving the surface quality of the thin films. Using the pressed target decreased the quality of the thin films and the average roughness of the films increased. The main reason for this... 

Use of wireless sensor networks (WSNs) to record environmental data such as temperature, sound level, and light intensity has grown dramatically. The specification of the locations of sensors is important. Using tools such as global positioning system (GPS) to find the location of sensors is not economical. Sensors can record their distances from neighboring sensors. On the other hand, the locations of some sensors are fixed. In wireless sensor network localization (SNL), we want to find the location of sensors using the available information. An approach for solving the SNL problem is to model the problem as an optimization problem and use an interior point method for its solution. Interior... 

In order to achieve a compromised solution for a multi-objective problem, we make use of the Tchebycheff norm to minimize the distance from the current estimate of the objectives from the ideal point. Solutions obtained from the Tchebycheff approach are weakly efficient for multi-objective problems. For a better solution, the augmented weighted Tchebycheff norm has been proposed. Here, we use the satisficing tradeoff algorithm to solve the augmented weighted Tchebycheff problems. Since the supplier selection problem is usually a multi objective problem, we use the augmented weighted Tchebycheff method for obtaining its solutions. Numerical results are presented illustrating the performance... 

In the modern world, steganography is an image processing technique, revealing to be a suitable process for information hiding. In most cases, steganography has shown to be more effective than cryptography techniques. Recently, there have been attempts to improve the stego-image quality and hiding capacity by introducing new methods. Here, we inspect the advantages and disadvantages of some new steganography methods for digital images. The implemented methods are color and grayscale image steganography with OPVSP algorithm, BRL and GRL methods, and the simple LSB method with OPAP algorithm. Here, we compare the implementation results of these methods using MATLAB 7.4.0, with other common... 

We study wavelet transformation for use in pattern recognition. Feature extraction is a crucial processing step for pattern recognition. Feature extraction is based on finding mathematical methods for reducing dimensionality of pattern representation. Two most important features to be extracted are edges and textures. Edges and textures are not absolute concepts and change with scale. Moreover, local characteristics of edges are needed. In recent decades, wavelet transformation as a mathematical tool has captured the attention of many scientists in signal processing and mathematics. Wavelet basis can provide efficient and useful description of a function or signal since it has local... 

Linear and nonlinear problems on integer and real numbers constitute very important optimization problems. Recently, methods have been developed using pumps to solve this type of problem. Feasibility pumps usually produce random perturbations. In this method,the generated random perturbations are replaced by a penalty framework and feasibility pumps are introduced as methods of displacement. Feasibility pump algorithms on 0-1 are used to solve these problems and the alternating direction methods are used. A convergence theorem is presented for the alternate direction method based on the penalty.New changes to the feasibility pumps and existing algorithms for solving linear and nonlinear... 

Civil engineering structures and infrastructures including buildings and bridges are exposed to various externally applied loadings such as traffic, wind and earthquake during their operational lifetime. In this regards, structural static/dynamic displacement monitoring and their charactristics by mounted transducers is the mostly utilized and popular strategy. This may provide quantitative information for both structural safety evaluation and maintenance purposes. Such practice, however, is highly expensive to be operateddue to wiring, power signal transmission issues, limitations of sensor configuration to capture the entire structural response, and so forth. In addition, this may affect... 

Here, we explain an algorithm, recently introduced in the literature, for the personalized nurse scheduling problem. In this algorithm the authors focus on the deterministic counterpart of the specific problem that has been described in the second international nurse rostering competition. One specificity of this version is that most constraints are soft, meaning that they can be violated at the price of a penalty. The problem is modeled as an integer program (IP) and is solved using a branch-and-price procedure. In this model, each column of the IP corresponds to a rotation, i.e., a sequence of consecutive working days for a nurse. In contrast, classical models involve individual nurse... 

The Transparent electrode (transparent conductive layer) is an essential component of electro-optical devices, especially screens, solar cells and touch screens. Today, most semiconductor oxides such as ITO are used for this purpose, which have problems such as inflexibility, high cost, environmental degradation and ion penetration in organic displays. In this research, the design, simulation and fabrication of a transparent electrode with a network of metal nanowires with low resistance between cross fibers and high aspect ratio during the production stages of polymer mold, metal coating and characterization has been done. Using the reducing atmosphere in the sputtering chamber, the... 

Physical and chemical properties of tungsten oxide thin films change reversibly while exposure to hydrogen gas. This property is called gasochromic. To enhance optical properties of such films, nanostructured, amorphous and porous thin films of (WO3)1-x(MeO)x (MeO= TiO2, MoO3, NiO; x=0.09, 0.17, 0.23, 0.29, 0.33) were fabricated by Pulsed Laser Deposition. Molar percentage of Me/W (Me= Ti, Mo and Ni) was changed in films with respect to targets; for Ti and Ni always a reduction, but for Mo an enhancement for low percentages was observed. The reason is the existence of thermal ablation mechanism during deposition, in the other word is different vapor pressure effect. An increment in x for...