Development of a multilayer interference simulation program for MSS systems

This paper discusses the development of a multilayer interference analysis and simulation program which is used to evaluate interference between non-geostationary and geostationary satellites. In addition to evaluating interference, this program can be used in the development of sharing criteria and coordination among various Mobile Satellite Services (MSS) systems. A C++/Windows implementation of this program, called Globalstar Interference Simulation Program (GISP), has been developed

Semi-exact local absorbing boundary condition for seismic wave simulation

An absorbing boundary condition is necessary in seismic wave simulation for eliminating the unwanted artificial reflections from model boundaries. Existing boundary condition methods often have a trade-off between numerical accuracy and computational efficiency. We proposed a local absorbing boundary condition for frequency-domain finite-difference modelling. The proposed method benefits from exact local plane-wave solution of the acoustic wave equation along predefined directions that effectively reduces the dispersion in other directions. This method has three features: simplicity, accuracy and efficiency. Numerical simulation demonstrated that the proposed method has higher efficiency than the conventional methods such as the second-order absorbing boundary condition and the perfectly matched layer (PML) method. Meanwhile, the proposed method shared the same low-cost feature as the first-order absorbing boundary condition method

Molecular identification and phylogeny of Nerita᾽s species on rocky shores of the Northern Persian Gulf

Neritas are among the most dominant groups of Gastropoda in the Persian Gulf. There is no previous study in relation to molecular and phylogeny of Neritas in the study area. The molecular identification of Nerita species have been studied for the first time in the northern rocky coastal zones of Persian Gulf during 2013 and 2014. After morphological identifications of species, DNA extraction, amplifying partial of cytochrome oxidase COI and 16S rRNA and sequencing procedure were done in the laboratory. In this study, 6 COI and 6 16S rRNA sequences, belonging to 3 species, were obtained. Also, phylogeny analyses with drawing phylogeny trees of Maximum Likelihood and Bayesian were done using MEGA6 and BEAST softwares. Morphological and molecular identification results were similar for 2 species and dissimilar for one species. This discrepancy shows that a combination of morphological and molecular studies is more reliable for species identification than either of them solely. The results also showed that Nerita species are monophyletic

Quasi Self-Excited DFIG-Based Wind Energy Conversion System

This article introduces a new configuration of the doubly-fed induction generator (DFIG) based wind energy conversion system (WECS) employing only a reduced-size rotor side converter (RSC) in tandem with a supercapacitor. In the proposed structure, the grid side converter (GSC) utilized in conventional DFIG-based WECSs is successfully eliminated. This is accomplished by employing the hydraulic transmission system (HTS) as a continuously variable and shaft decoupling transmission unit. This transforms the conventional constant-ratio drives by providing an opportunity to control the power flow through the generator's rotor circuit regardless of the wind turbine's shaft speed. This feature of HTS can be utilized to control the RSC power and ultimately regulate the supercapacitor voltage without a need for GSC. The proposed system is investigated and simulated in MATLAB Simulink at various wind speeds to validate the results and demonstrate the dynamic performance of the system

Polynomial modeling for time-varying systems based on a particle swarm optimization algorithm

In this paper, an effective particle swarm optimization (PSO) is proposed for polynomial models for time varying systems. The basic operations of the proposed PSO are similar to those of the classical PSO except that elements of particles represent arithmetic operations and variables of time-varying models. The performance of the proposed PSO is evaluated by polynomial modeling based on various sets of time-invariant and time-varying data. Results of polynomial modeling in time-varying systems show that the proposed PSO outperforms commonly used modeling methods which have been developed for solving dynamic optimization problems including genetic programming (GP) and dynamic GP. An analysis of the diversity of individuals of populations in the proposed PSO and GP reveals why the proposed PSO obtains better results than those obtained by GP

Estimation of Post-Stack R-Factors Across Multiple Fields and Production Scenarios

The detection of pressure build-up by time-shift during injection requires a rock physics model that accurately captures strain-induced velocity changes. The post-stack R-factor model, introduced by Hatchell and Bourne (2005) and Røste et al. (2005), is generally presumed to possess a constant spatially invariant R, and in previous work has been estimated for production only, However, when this model is applied to injection, there are discrepancies between predicted and observed time-shifts. To understand this further, we attempt to estimate four distinct R-values (R+OB, R-OB, R+UB and R-UB) within both overburden and underburden layers, for injection and production zones. We calibrate these R-values in three distinct fields in the North Sea. According to our results, a fixed R-factor appears insufficient, and a spatially variable R-factor is necessary. There is some indication of differences between injection and production scenarios. A negative R-factor is also observed in the underburden of injection zones within chalk reservoirs, which indicates signal complexity and unknown causative physical mechanisms for the underburden time-shifts when compared to the overburden

Basic model and governing equation of solar cells used in power and control applications

This paper provides an overview of modeling of a group of commercially available solar cells to ease the study of solar powered electric systems. The models solar cells can be accurately used to predict the behavior of the system operation under different conditions

A New Method for Solving 3D Elliptic Problem with Dirichlet or Neumann Boundary Conditions Using Finite Difference Method

Abstract In this paper, a new algorithm for solving general three dimensional linear Elliptic types P.D.E.'s applying finite difference method is introduced. In this method, the boundary conditions are considered as auxiliary equations coupling with the main equations to constitute a system of linear equations, using suitable finite difference partial derivatives. The mesh points are also generated simply by proposed algorithm. This algorithm can perform numbering of mesh points, generating matrix coefficient, and right hand side vector by a special automatic procedure. Numerical experiments are presented to show performance, reliability and efficiency of proposed algorithm