Estimating the Environmental Cost of Shrimp Farming in Coastal Areas of Chittagong and Coxs bazaar in Bangladesh

During the last three decades, shrimp has remained one of the major export items in Bangladesh. It contributes to the development of this country by enhancing export earnings and promoting employment. However, coastal wetlands and agricultural lands are used for shrimp culture, which reduces agricultural opportunity and peasants income, and destroys the mangroves and coastal eco-system. These are the external environmental costs that are not reflected in farmers price and output decisions. This study has aimed to estimate those external environmental costs through the contingent valuation method. The calculated environmental cost of shrimp farming is USD 13.66 per acre per year. Findings suggest that current shrimp production and shrimp price will no longer be optimal once the external costs are internalized. Thus alternative policy recommendations have been proposed so that shrimp farming becomes a sustainable and equitable means of aquaculture.Comment: 28 page

V/F control of Three Phase Induction Motor Drive with Different PWM Techniques

This paper presents a  v/f control of induction motor with different pulse width modulation ( PWM) techniques as sine triangle pulse width modulation ( SPWM), Third-harmonic  pulse width modulation (THPWM) and  Space vector pulse width modulation(SVPWM) using MATLAB SIMULINK. Induction motor modeled in the synchronous q-d reference frame. The performance of IM with full load torque is compared using these techniques for THD, harmonics spectra, utilization of dc supply voltage, fundamental peak of the output voltage and motor speed. The dynamic performance of IM using SVPWM under reference speed and load torque variations is studied also. The results show that the SVPWM is the efficient one because it’s superior performance characteristics. The operation of IM with v/f method for closed loop system is enhancement when SVPWM technique is applied. Keywords: Space vector modulation, SPWM, V/f control, Harmonic injection

MPPT Based on Power Mapping and Frequency Derivative

This article presents a method for harmonic mitigation and maximum power point tracking for a variable-speed grid-connected  wind turbine. The wind energy conversion system consists of a permanent magnet synchronous generator driven by variable-speed wind turbine. The output of the permanent magnet synchronous generator is connected to a single-switch three-phase boost rectifier to generate DC voltage, which feeds a current-controlled inverter to interface the system with the electric utility. The single-switch three-phase boost rectifier is an active power factor correction technique to maintain the power factor at the permanent magnet synchronous generator side to nearly unity and mitigate the permanent magnet synchronous generator current harmonics. To mitigate inverter output current and voltage harmonics, an LCL filter has been used. Acomplete analysis of the harmonic content has been done everywhere in the system. The results show that the proposed maximum power point tracking control strategy succeeded to track the maximum wind power irrespective of the wind speed. This strategy in presence of an LCL filter achieved harmonic mitigation at the permanent magnet synchronous generator and inverter output sides. Keywords: variable-speed wind turbine ; permanent magnet synchronous generator ; maximum power point tracking ; harmonic mitigation ; active power filter.

Analysis of Wind Turbine Driven Permanent Magnet Synchronous Generator under Different Loading Conditions

This paper proposes the configuration of a Wind Turbine generating system equipped with Permanent Magnet Synchronous Generator (PMSG). There are different types of synchronous generators, but the PMSG is chosen which has better performance due to higher efficiency and less maintenance. Since it can be used without a gearbox also implies a reduction of the weight of the nacelle and a reduction of costs. The model includes a wind turbine model, drive train model and PMSG model. The equations that explain their behavior have been introduced. The generator model is established in the d-q synchronous rotating reference frame. The proposed Wind Turbine Generator System (WTGS) has been implemented in MATLAB/SIMULINK software. The PMSG is operating in stand-alone which is loaded with different types of loads. The simulation results indicate the ability of wind driven PMSG to operate over wide range of operating conditions at different loading conditions and show effect of different load types in operation. Keywords: Permanent Magnet Synchronous Generator (PMSG), Wind Turbine, Wind Energy and WTGS MATLAB/SIMULINK

Electrophilically Activated Nitroalkanes in Synthesis of 3,4-Dihydroquinozalines

Nitroalkanes activated with polyphosphoric acid serve as efficient electrophiles in reactions with various nucleophilic amines. Strategically placed second functionality allows for the design of annulation reactions enabling preparation of various heterocycles. This strategy was employed to develop an innovative synthetic approach towards 3,4-dihydroquinazolines from readily available 2-(aminomethyl)anilines

Optimal Choice and Allocation of FACTS Devices for Security-Constrained Economic Dispatch

Flexible AC transmission systems (FACTS) devices have provided new control facilities in power systems. Simultaneous optimization of type, location and parameters for FACTS devices is an important issue when a given number of FACTS devices are applied to the power system with the purpose of increasing system loadability. This paper presents the application of simulated annealing algorism (SA) to find optimal type, location and parameters of FACTS devices to achieve security-constrained economic dispatch (SCED). The overall cost function, which includes generation cost and installation cost of FACTS devices, should be minimized. The SCED constraints are generators, transmission lines and FACTS limits. Two types of FACTS devices are utilized in this study namely STATCOM as a shunt type and TCSC as a series type. In this study simulations were performed on IEEE 14-bus. Results of simulations are encouraging and could efficiently be employed for power system operations. Keywords: Allocation, Security-constrained economic dispatch (SCED), FACTS and simulated annealing (SA)

Structural Transformation of Minimal Spanning Trees in World Commodity Market

We consider structural change of a world trade-flow network for different commodities from 1995 to 2013. A minimum spanning tree is generated from the trade flow data, and we investigate the hierarchical organization of the tree by changing the hub node. Only a few countries are the hub nodes for many of the commodities. We observed the structural transitions, from a chain-like tree (many countries are hub nodes) to a bi-starlike tree (only two countries are hub nodes). In the bi-starlike tree, China and Germany are the only two hub nodes