Sharif Digital Repository

Sloshing, or liquid free surface oscillation, in containers has many important applications in a variety of engineering fields. The modal method can be used to solve linear sloshing problems and is the most efficient reduced order method that has been used during the previous decade. In the present article, the modal method is used to solve a nonlinear sloshing problem. The method is based on a potential flow solution that implements a two-phase analysis on sloshing in a rectangular container. According to this method, the solution to the mass conservation equation, with a nonpenetration condition at the tank walls, results in velocity potential expansion; this is similar to the mode shapes... 

Aims. Stars twinkle because their light propagates through the atmosphere. The same phenomenon is expected on a longer time scale when the light of remote stars crosses an interstellar turbulent molecular cloud, but it has never been observed at optical wavelengths. The aim of the study described in this paper is to fully simulate the scintillation process, starting from the molecular cloud description as a fractal object, ending with the simulations of fluctuating stellar light curves. Methods. Fast Fourier transforms are first used to simulate fractal clouds. Then, the illumination pattern resulting from the crossing of background star light through these refractive clouds is calculated... 

Aims. Stars twinkle because their light propagates through the atmosphere. The same phenomenon is expected at a longer time scale when the light of remote stars crosses an interstellar molecular cloud, but it has never been observed at optical wavelength. In a favorable case, the light of a background star can be subject to stochastic fluctuations on the order of a few percent at a characteristic time scale of a few minutes. Our ultimate aim is to discover or exclude these scintillation effects to estimate the contribution of molecular hydrogen to the Galactic baryonic hidden mass. This feasibility study is a pathfinder toward an observational strategy to search for scintillation, probing... 

In this article, we have investigated the possibility to distinguish between different galactic models through microlensing parallax studies. We show that a systematic search for parallax effects can be done using the currently running alert systems and complementary photometric telescopes, to distinguish between different lens distance distributions. We have considered two galactic dark compact object distributions, with total optical depths corresponding to the EROS current upper limits. These models correspond to two extreme hypotheses on a three component galactic structure made of a thin disk, a thick disk, and a spherically symmetric halo. Our study shows that for sub-solar mass... 

Improving the sensitivity and the time response of the superconducting transition edge detectors as one of the most promising technologies for millimeter and sub-millimeter wavelength radiation power detection is essential. Having an accurate 3D model for these detectors enables us to design faster detectors with higher sensitivity and detectivity. In this paper, we report on a 3-dimensional finite element model of a current biased superconducting YBa2Cu3O7-x (YBCO) transition-edge detector fabricated by a low-cost Metal-Organic deposition method. The obtained simulation results are in good agreement with the measured response of the detectors. Also, as the simulation results suggest,... 

Over the last two decades there have been numerous reports from different seismically active regions of the world that thermal infrared (TIR) anomalies can be identified around the epicentral areas before major earthquakes [e.g. (Tronin et al., 2002)]. The TIR anomalies reportedly appear as early as 14 to 7 days before the seismic events and affect areas as large as 1000s to 100,000s km2 in size. Our case study for detection of TIRs using NOAA-AVHRR data(Band 4) is an Ms = 5.1 earthquake that occurred on 14th October 2004 near Ravar in Kerman province located in Loot and Tabas deserts, southeast-central Iran. The area is part of the Golbaf-Sirj seismogenic zone. It includes major faults... 

In addition to meeting the real-time constraint, power/energy efficiency and high reliability are two vital objectives for real-time embedded systems. Recently, heterogeneous multicore systems have been considered an appropriate solution for achieving joint power/energy efficiency and high reliability. However, power/energy and reliability are two conflict requirements due to the inherent redundancy of fault-tolerance techniques. Also, because of the heterogeneity of the system, the execution of the tasks, especially real-time tasks, in the heterogeneous system is more complicated than the homogeneous system. The proposed method in this paper employs a passive primary/backup technique to... 

Aims. EROS (Expérience de Recherche d'Objets Sombres) has searched for microlensing toward four directions in the Galactic plane away from the Galactic center. The interpretation of the catalog optical depth is complicated by the spread of the source distance distribution. We compare the EROS microlensing observations with Galactic models (including the Besançon model), tuned to fit the EROS source catalogs, and take into account all observational data such as the microlensing optical depth, the Einstein crossing durations, and the color and magnitude distributions of the catalogued stars. Methods. We simulated EROS-like source catalogs using the HIgh-Precision PARallax COllecting Satellite... 

In recent years, a growing interest in investigation of new energies has been observed. Pressure-retarded osmosis (PRO) could be a feasible source of renewable energy. This study aims to present a model based on the present technology of PRO power plant components for design and economic evaluation of a PRO power plant, and to investigate case studies in order to demonstrate how each main component of a PRO power plant affects the economic evaluation. Therefore, all the mechanisms including intake and outfall systems, pre-treatment system, membrane system, and transportation and generation systems are explicated and meant to present the capability of the model to design the PRO power plant.... 

In recent years, a growing interest in investigation of new energies has been observed. Pressure-retarded osmosis (PRO) could be a feasible source of renewable energy. This study aims to present a model based on the present technology of PRO power plant components for design and economic evaluation of a PRO power plant, and to investigate case studies in order to demonstrate how each main component of a PRO power plant affects the economic evaluation. Therefore, all the mechanisms including intake and outfall systems, pre-treatment system, membrane system, and transportation and generation systems are explicated and meant to present the capability of the model to design the PRO power plant.... 

Multicore platforms provide a great opportunity for implementation of fault-tolerance techniques to achieve high reliability in real-time embedded systems. Passive redundancy is well-suited for multicore platforms and a well-established technique to tolerate transient and permanent faults. However, it incurs significant power overheads, which go wasted in fault-free execution scenarios. Meanwhile, due to the Thermal Design Power (TDP) constraint, in some cases, it is not feasible to simultaneously power on all cores on a multicore platform. Since TDP is the maximum sustainable power that a chip can consume, violating TDP makes some cores automatically restart or significantly reduce their... 

This paper is concerned with the existence of positive solution to a class of singular fourth order elliptic equation of Kirchhoff type (Formula Presented.)▵2u-λM(‖∇u‖2)▵u-μ|x|4u=h(x)uγ+k(x)uα,under Navier boundary conditions, u= ▵u= 0. Here Ω⊂ RN, N≥ 1 is a bounded C4-domain, 0 ∈ Ω, h(x) and k(x) are positive continuous functions, γ∈ (0 , 1) , α∈ (0 , 1) and M: R+→ R+ is a continuous function. By using Galerkin method and sharp angle lemma, we will show that this problem has a positive solution for m0 and 0 < μ< μ∗. Here μ∗=(N(N-4)4)2 is the best constant in the Hardy inequality. Besides, if μ= 0 , λ> 0 and h, k are Lipschitz functions, we show that this problem has a positive smooth... 

We present a combined trust region-line search structured algorithm for solving constrained nonlinear least-squares problems. The approach is based on adaptive structured scheme due to Mahdavi-Amiri and Bartels of the exact penalty method of Coleman and Conn for nonlinearly constrained optimization problems. The structured adaptation also makes use of the ideas of Nocedal and Overton for handling quasi-Newton updates of projected Hessians. For robustness, we propose a new penalty parameter updating strategy and a specific line search strategy within the trust region, taking account of the least-squares objective and special structured considerations for the approximate projected... 

Due to increasing demand for natural gas, storage plan development in order to cope with seasonal gas fluctuations and ensure constant gas supply during a year, has recently become highly indispensable. However, developing underground gas storage (UGS) facility is so costly which may sometimes discourage the investment.One of the main cost items while fulfilling a UGS project can be attributed to cushion gas; this is part of gas inventory which remainspermanently in the storage field in order to maintain pressure and provide adequate deliverability rate during production cycles.For this reason, UGS in low quality gas reservoirs has been recentlyproposed. In such a case, native reservoir gas... 

This study presents an analytical approach for proper selection of output functions to be regulated for the Vienna rectifier such that the resultant closed-loop systems are minimum phase. Specifically, two different adaptive control methodologies based on the input-output linearisation are developed and categorised. In the first category, three output functions are introduced and imposed to be zero by using three dynamic feedback laws. On the basis of states to be regulated, four different cases are studied and it is shown that only one of these cases results in a one-dimensional zero dynamics with an asymptotically stable equilibrium point. In the second category, two output functions are... 

A new method to evaluate the steady state performance of a three-phase self excited induction generator based on conductance minimization is proposed. It can be simply used to take series compensation into account. Among the priorities of this method are the absence of convergence problem and flexibility. Simple methods to find the frequency and magnetizing reactance have been proposed. Simulation results show the efficiency of this method  

By development of ocean exploration, autonomous vehicles are employed to perform on-water and underwater tasks. Using an extended Kalman filter, Inertial Navigation System/Doppler Velocity Log (INS/DVL) integrated systems are trying to navigate in oceans and underwater environments when Global Positioning System (GPS) signals are not accessible. The dependency of DVL signals on acoustic environments may cause any DVL malfunction due to sea creatures or strong wave-absorbing material. In this paper, an improved version of evolutionary TS-fuzzy (eTS) is proposed in order to predict DVL sensor outputs at DVL malfunction moment, by utilizing an artificial intelligent (AI) aided integrated... 

The physics and modes of radiation in structures exhibiting extraordinary transmission (ET) can be best studied using Green's function formalism. In this article, we find the electromagnetic response to local excitation of a canonical structure exhibiting ET, and investigate the role of complex waves. The structure is a perfectly conducting slab having a finite or infinite number of through-slits. The solution breaks up the field into even and odd modes, and solves for the fields of the structure with a finite number of slits, by setting up an integral equation. The solution is then extended to find Greens' function of the infinitely periodic structure. The dispersion relations of the... 

We revisit the classical edge coloring problem for general graphs in the streaming model. In this model, the input graph is presented as a stream of edges, and the algorithm must report colors assigned to the edges in a streaming fashion, using a memory of size O(n polylog n) on graphs of up to O(n2) edges. In ESA 2019 and SOSA 2021, two elegant randomized algorithms were presented for this problem in the adversarial edge arrival model, where the latest one colors any input graph using O(Δ2/s) colors with high probability in O (ns) space. In this short note, we propose two extremely simple streaming algorithms that achieve the same color and space bounds deterministically. Besides being... 

Introduction: Due to the importance of laser light penetration and propagation in biological tissues, many researchers have proposed several numerical methods such as Monte Carlo, finite element and green function methods. Among them, the Monte Carlo method is an accurate method which can be applied for different tissues. However, because of its statistical nature, Monte Carlo simulation requires a large number of photon pockets to be traced, so it is computationally expensive and time-consuming. Although other numerical methods based on the diffusion method are fast, they have two important limitations: first, they are not valid near the bounder of sample and source, and second, their...