Sharif Digital Repository

There is an importance issue for preservation and survival of ecological systems by vegetation. A study focusing on the hydrodynamics of these complex ecosystems could help to explain the filtering ability of vegetation in wetlands and estuaries. Wetlands assist in flood control, shoreline protection, and groundwater recharge.In addition, they play a purification role, removing sediments and contaminants from polluted waters, nutrient uptake, and oxygen production. Laboratory experiments have been designed to study the influence of marsh vegetation on lateral dispersion. The flow through vegetation is modeled by a circulating flow going through an array of plastic dowels in an experimental... 

The three dimensional resonant interaction between a surface wave and harmonic interfacial waves in a horizontally infinite two-layer fluid was investigated theoretically and experimentally. Initially, both layers assumed to be inviscid, but after obtaining the final equations of the interfacial wave's amplitude, with perturbation, the viscous damping effect, was incorporated in to the interaction equations. It is shown that, surface wave can trigger four opposite- traveling interfacial waves whose amplitudes grow with time. But because of viscosity damping effect, these amplitudes will become constant and won't change with time. The frequencies of the interfacial waves are approximately... 

Recently, a new tool in the study of two-dimensional continuous phase transition was provided by Schramm-Loewner evolution. The main part of SLE is a conformal map which relates growth process of a two-dimensional simple curve to one-dimensional motion on the real axis (so-called Loewner driving function). Time evolution of this map and Loewner driving function is connected via the Loewner differential equation. It turns out that for a certain class of stochastic and conformally invariant curves in two dimensions, the driving function shows Brownian motion in one dimension. Strength point of SLE comes from this fact that all the geometrical properties of such curves is described through a... 

Solar heating in aqautic systems, causes tempreture increasing.This temperature difference will promote an exchange flow between the vegetation and open water. The exchange flow generated by the differential heating and cooling associated with depth variation has also been studied through laboratory experiment and modelling. Differential solar heating can result from shading by rooted emergent aquatic plants, producing a temperature difference between vegetated and unvegetated regions of a surface water body. Horizontal density difference between shaded and open water regions drives currents that carry fluxes between biologically and chemically distinct regions of an aquatic system. Such... 

The heteronuclear complexes [MePt(bhq)(μ-dppy)Au(PPh3)]PF6, 2, [MePt(bhq)(dppy)Tl]PF6, 3 and [Me2Pt2(bhq)2(dppy)2Tl]PF6, 4 in which bhq=benzo{h}quinoline and dppy=2-diphenylphosphinopyridine, were prepared by reaction of the mononuclear complex [MePt(bhq)(dppy)] 1 with 1 equivAuCl(PPh3), 1equiv TlPF6 and 1/2 equiv TlPF6 respectively. All the complexes were fully characterized using multinuclear NMR spectroscopy and ESI-MS spectrometry. In addition molecular structures of complexes 2 and 3 in solid state have been determined by X-ray crystallography that shown strong dative bonds between platinum and gold or thallium atoms. As shown by ESI-MS spectrometry, the Pt-Au bond in complex 2... 

One of the important issues in the fundamental physics is the arrow of time. According to the fundamental theories, motion is symmetry with respect to the passage of time while on a macroscopic level time has direction. In the macroscopic models the arrow of time is provided by the Second Law of Thermodynamics.The thermodynamic arrow is often linked to the cosmological arrow of time, because it is ultimately about the boundary conditions of the early universe.Recently people have tried to suppose this challenge as a fundamental issue and use this as fundamental assumption in their theories.A number of models have attempted to solve the problem based on the concept of information.... 

In this study, the effect of submerged vanes on the bed erosion pattern at a 90° open-channel junction has been evaluated experimentally. In this study, 41 tests have been conducted in four different steps. In each test, the bed surface level has been measured at the end of 1st, 2nd and 24th hour. In the first step, the preliminary tests have been conducted. In this step, six different formations of submerged vanes have been selected and their performance has been evaluated and the most efficient formation, in the field of maximum scour depth reduction, has been selected. In the second step, six different formations of submerged vanes have been selected and their performance has been... 

Multidisciplinary Design Optimization (MDO) has been considered by many researchers, especially in field of aerospace engineering during the last two decades. The goal of MDO is to achieve optimal design of systems considering a variety of disciplines. In this regard, selection of viable disciplines, their codification, structure and interactions, levels of integrity and the optimization approach to be utilized are of importance and challenging.
In this project, MDO external ballistic optimization of the conceptual design of a flying projectile is investigated. The key objectives to be met by optimal design were chosen to be maximizing the payload weight and the covered range. To this... 

Preservation and survival of ecological systems by vegetation is important. A study focusing on the hydrodynamics of these complex ecosystems could help to explain the filtering ability of vegetation in wetlands and estuaries. Wetlands assist in flood control, shoreline protection, and groundwater recharge. In addition, they play a purification role in removing sediments and contaminants from polluted waters, nutrient uptake, and oxygen production.
Laboratory experiments have been designed to study the influence of marsh vegetation on lateral dispersion in flexible vegetation that has been modelled with inclined cylinder. The flow through vegetation is modelled by a circulating flow... 

The theory of resonant wave interaction has found considerable applications in meteorology, oceanography and limnology. It is known that the mechanism serves as an effective means of energy transfer in the atmosphere, oceans and lakes. In this project, the three-dimensional resonant interaction of a surface wave with two pairs of interfacial waves in a stratified fluid is studied theoretically. Witham’s variational method is formulated in order to apply to weak resonant interaction among waves whose amplitudes and phase angles vary slowly with position and time. The method is applied to a surface-interfacial wave interaction in a horizontally infinite two layer fluid. Combination of two... 

In this thesis, we present the results of a laboratory and numerical model study of the exchange flow generated by the temperature gradient between an open water heated by sunlight and a canopy area made of floating vegetation. Particle Image Velocimetry is employed to obtain the structures of the warm flow intruding the canopy at the surface and the bottom cold return flow for different roots length and vegetation density. Following an initial, transient stage of flow build-up governed by a balance between inertia and buoyancy forces, the flow reaches a steady state in the canopy area with a force balance between buoyancy and vegetation drag dominating the flow within roots. At the steady... 

Regardless of the traffic model and its application, an essential input of transportation models is the amount of demand which is usually described using Origin-Destination (O-D) matrix. Many reaserchers have developed different O-D matrix estimation methods using traffic counts, which allow simple data collection as opposed to the costly traditional direct estimation methods based on home and roadside interview. However, Link data is not sufficient to obtain an unique answer. This reaserch tries to estimate O-D matrix by using Automated Vehicle Identification(AVI) data. The research formulates the problem of the estimating O-D matrix as a bi-level problem. The upper level consists of...