Sharif Digital Repository

In the present study, an adaptive sliding mode control method was employed to control a fish robotic system using hardware in the loop methodology. Up to now, few researches have focused on autonomous control of fish robot in dynamic environments which may be the result of difficulties in modeling of hydrodynamic effects on fish robot. Therefore, following the introduction of the nonlinear model for the robot, elongated body theory, suggested by Lighthill, was used to analyze fish movements. Then, kinematics control to track desired trajectories was designed for under-actuated model of robot. Adaptive sliding mode controller, capable of adapting according to changes and uncertainties, was... 

Herein we report for the first time on efficient and environmentally friendly bioenergy production from bacteriorhodopsin (bR) and green florescent protein (GFP) as co-sensitizers. bR as a transmembrane protein, acts like a light-driven proton pump in Halobacterium salinarum, converting light energy into a proton gradient. Employing GFP beside bR can enhance the photo-bioenergy production efficiency in two aspects: GFP can increase short circuit current by improvement in light absorption either by extending the sensitizingspectrumor making fluorescence in absorption region of bR. It can also enhance open circuit voltage more than 150 mV by improvement in photoelectrode converging and... 

The main objective of this paper is to provide comparative quantitative examinations on the capabilities of two-dimensional horizontal and pseudo-three-dimensional (3D) modelling approaches for simulating spatial and temporal variability of the flow and salinity in Lake Urmia, Iran. The water quality in the lake has been an environmentally important subject partly because this shallow hypersaline aquatic ecosystem is considered to be one of the largest natural habitats of a unique multicellular organism, Artemia urmiana. This brine shrimp is the major food source for many of the protected and rare shorebirds that visit the lake. A.urmiana can grow and survive in certain ranges of salinity,... 

Tapered circular cylinders are employed in a variety of ocean engineering applications. While being geometrically simple, this configuration creates a complex flow pattern in the near wake of the structure. Most previous experimental studies on tapered circular cylinders were dealing with stationary cylinders to explore the wake flow field and vortex shedding patterns past the cylinder. Few studies paid attentions to the vortex induced vibration of the tapered cylinders. This paper reports some results from in-water towing-tank experiments on the vortex-excited vibrations of tapered circular cylinders in a uniform flow. Cylinders with different mean diameters (28 and 78 mm), mass ratios (6.1... 

The aim of this paper is to introduce a novel approach, called Endurance Wave Analysis (EWA), for non-linear dynamic analysis and assessment of offshore structures subjected to irregular wave forces. This is, in fact, an extension of the Endurance Time Analysis (ETA) already presented by previous researchers for the seismic assessment of onshore structures. With the EWA method, the offshore structure is simulated under a predefined Intensifying Wave Train Function (IWTF), corresponding to a gradually deteriorating sea state at a specific site. The function is designed so that the roughness of the sea state represented by them increases over the time and even goes well beyond the design sea... 

Urmia Lake, located in a closed basin in north-west Iran, is the largest lake (5000-6000 km2) in the Middle East. It is very saline with total dissolved salts reaching 200 g/l compared with a normal seawater salinity of about 35 g/l. The construction of a causeway, which was initiated in 1979 but then abandoned until the early 2000s, is near completion and will provide road access between the western and eastern provinces. The causeway has an opening 1.25 km long and divides Urmia Lake into a northern and southern basin and restricts water exchange. The flow and salinity regimes are affected by the presence of this new causeway, and there are concerns over the well being of the Artemia... 

This paper introduces a novel methodology for design and assessment of offshore structures exposed to irregular sea waves. For this, Constrained NewWave (CNW) is integrated with the Endurance Time Analysis (ETA) methodology, which is basically developed for the performance based analysis of onshore structures to earthquake loads. In this approach, the offshore structure is simulated in time-domain under a set of calibrated intensifying wave functions. They are devised to represent a gradually increasing roughness of the sea state by time. A performance index such as base shear, drift or stress in a critical structural members are monitored until they reach to a predefined maximum value. A... 

Underwater surface of man-made structures is quickly covered by unwanted aquatic organisms. They change the flow regime around the structure. Despite the important contributions of previous studies on the vortex induced vibration (VIV) of bluff bodies, the flow induced vibration of non-stationary cylinders covered by marine fouling appears not to have received due attentions in the literature. The current paper reports on an attempt for better understanding the marine fouling effects on the VIV of circular cylinders. A structured review of the literature related to the fluid structure interactions in marine fouled cylinders is first presented. Results of an experimental study on the VIV of... 

Effects of suppression devices on the vortex induced vibration (VIV) of inclined cylinders appear not to have received previous due attentions. The current paper reports the results of some towing tank experiments on the vortex induced cross-flow vibrations of bare and helically straked cylinders in vertical and inclined arrangements. Rigid test cylinders were mounted on a single degree of freedom elastic support. The inclination angles examined were θ=0°, ±20° and ±45°. The Reynolds number ranged from 4000 to 45. 000 and the reduced velocity from 1 to 16. With all tests the mass ratio and the mass-damping parameters were kept constant.Test results on "inclined bare" and "inclined helically... 

In this paper we study the optical bistability in a double coupler fiber ring resonator which consists of an erbium doped fiber amplifier (EDFA) in half part of the fiber ring and a quantum dot doped fiber (QDF) saturable absorber in the other half. The bistability is provided by the QDF section of the ring resonator. The EDFA is employed to reduce the switching power. The transmitted and reflected bistability characteristics are investigated. It is shown that the switching power for this new bistable device is less than 10 mW  

This paper models and analyses the dynamic response of a synchronous generator driven off-grid micro hydro power system using Simulink tool of MATLAB software. The results are assessed from various perspectives including regulation through no load to full load and overload scenarios under normal and abnormal operating conditions. The investigation under the normal conditions of no load, linearly changing load and full load divulges that the system operates in a satisfactory manner as generator voltage and frequency remain approximately constant at 1 pu. However, at full load generator voltage and frequency drop 3% and 0.5% respectively from its nominal values but remain within prescribed... 

This paper models and analyses the dynamic response of a synchronous generator driven off-grid micro hydro power system using Simulink tool of MATLAB software. The results are assessed from various perspectives including regulation through no load to full load and overload scenarios under normal and abnormal operating conditions. The investigation under the normal conditions of no load, linearly changing load and full load divulges that the system operates in a satisfactory manner as generator voltage and frequency remain approximately constant at 1 pu. However, at full load generator voltage and frequency drop 3% and 0.5% respectively from its nominal values but remain within prescribed... 

Endurance Wave Analysis (EWA) is a novel, simple, economical but yet reliable method for the integrity assessment of offshore platforms against extreme irregular waves. The current paper presents a framework for the probabilistic assessment of offshore platforms based on EWA. The stochastic nature and the uncertainties in the ocean waves were taken into account by introducing a set of artificial, random and gradually intensifying wave trains. To simulate other uncertainties in the loading and the strength of the structure a Latin Hypercube Sampling (LHS) type of Monte Carlo Simulation (MCS) was employed. The EWA methodology and different structural performance criteria were considered. The... 

This in-water experimental study deals with the effects of the after-body on the FIV response of round and sharp edge cylinders. Different circular, square, diamond, and right-angle isosceles triangular cross-sections are investigated. The triangular cylinder is examined in four different symmetrical and unsymmetrical configurations with respect to the incident flow. The current towing tank experiments form a basis for the feasibility study of the isosceles triangular cylinders for FIV energy converters. The results indicate that the cylinders with a flat side perpendicular to the flow have a galloping type of response. In contrast, the cylinders with a sharp vertex pointing the flow show a...