Design optimization of a large scale rooftop photovoltaic system

This paper presents the optimization process of a grid connected photovoltaic (PV) system, which is intended to replace a large-scale thermal solar system on the rooftop of a Federal office building. A PV energy conversion model is described. Based on this model, array surface tilt angle and array size are optimized. The optimization method is based on maximizing the utilization of the array output energy, and, at the same time, minimizing the electricity power sold to grid. An effectiveness factor is introduced that takes into account both of these parameters. The array configuration and the output parameters are determined by comparing several PV modules. A 43.2 kW PV system is designed and operational problems such as harmonic effects and anti-islanding are discussed. Finally, the system performance is simulated and through economic analysis it has shown that the cost of PV system can be recouped in 13 years under the current renewable energy incentive program by the state of Illinois.     

Optimum tilt of solar collector for maximum natural flow

A theoretical treatment to determine the natural flow rate through a flat plate collector having heat losses is made. The governing equations have been expressed in terms of Grashof and Prandtl numbers and a dimensionless heat loss parameter. The method predicts the optimum tilt of the flat plate collector for the maximum draught for a given latitude and insolation. The experimental verification of the theoretical results shows a fair agreement.

A method to calibrate the hot wire anemometer at the desired temperature is evolved for the range of velocities encountered in practice for the flat plate solar collector.     

Dielectric and electro-optical study of ZnO nano rods doped ferroelectric liquid crystals

Addition of Nano rods results change in the dielectric and electro-optical properties of pure Ferroelectric Liquid Crystal (FLC) considerably. The present study is devoted to characterize the dielectric and electro-optical parameters of the FLC nano rods composite system. The size of nano rods is usually much bigger than that of FLC molecules, therefore, when they are doped in different concentrations, in pure FLC, their volume fraction plays considerable role in deciding the molecular dynamics of the resultant composite system. For the lesser concentrations, the nano rods offer mechanical strength to system geometry while at higher concentration of nano rods, they offer additional constraints on the system. In present report both of these aspects have been analyzed and explained.     

Design and validation of a novel multiplex real-time PCR assay for Vibrio pathogen detection

Three species--Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus--account for the majority of vibrio infections in humans. Rapid and accurate identification of Vibrio species has been problematic because phenotypic characteristics are variable within species. Additionally, biochemical identification and confirmation require 2 or more days to complete. Rapid and sensitive molecular techniques for the detection of vibrio pathogens would be useful for the surveillance and management of outbreaks. To facilitate the identification of human-pathogenic species, we designed and validated a highly sensitive, specific, and robust multiplex real-time PCR assay to identify V. cholerae, V. parahaemolyticus, and V. vulnificus using a four-dye configuration in a convenient lyophilized format. Multiple Vibrio strains were sequenced to verify candidate target TaqMan sites. Several individual assays within the multiplex contain multiple primers or probes to ensure detection of polymorphic variants. V. cholerae, V. parahaemolyticus, and V. vulnificus were detected either individually or in mixtures at ≤30 genomic copies. V. cholerae was specifically detected in the presence or absence of Vibrio mimicus. The Vibrio multiplex assay showed 100% specificity to all targets analyzed and no detection of nearest neighbor strains. Each assay exhibited 100% ± 10% efficiency. Multiplex real-time PCR can simplify pathogen detection and reduce costs per test since three species can be analyzed in a single reaction tube. Rapid and accurate detection of pathogenic vibrios in shellfish or seawater samples will improve the microbiological safety of seafood for consumers.     

Doppler-broadened positron annihilation studies in Y-Ba-Cu-O,Tl-Ca-Ba-Cu-O and Bi-Ca-Sr-Cu-O superconductors

Doppler-broadened annihilation radiation spectra have been measured as a function of temperature from 77 K to 300 K, for several high temperature oxide superconductors viz single-phase YBCO, single- and mixed-phase Tl-Ca-Ba-Cu-O and Bi-Ca-Sr-Cu-O compounds. The temperature-dependent parameters extracted respond to a change at the onset of superconducting transition. The observations point to involvement of oxygen valence electrons at the onset of superconducting transition. Also a possible structural change and/or increase in electron density at the oxygen vacancy/defect sites seem to accompany the transition. In addition, the parameters derived are seen to be sensitive to the presence of more than one superconducting phases in mixed phase samples.     

Design of a Multibus-compatible colour graphics subsystem

Colour graphics subsystems can be used in a variety of applications such as high-end business graphics, low-end scientific computations, and for realtime display of process control diagrams. The design of such a subsystem is shown. This subsystem can be added to any Multibus-compatible microcomputer system. The use of an NEC 7220 graphics display controller chip has simplified the design to a considerable extent. CGRAM (CORE graphics on Multibus), a comprehensive subset of the CORE graphics standard package, is supported on the subsystem.     

Active Control of Structures in Nonlinear Response

The need to account for geometric and material nonlinearities in the active control of highly flexible, large, space structures is emphasized herein. The performance index of the control problem is minimized subject to equations of state and costate using a variable metric algorithm. Unlike the conventional techniques for active control, the present algorithm is able to exploit the sparsity and symmetry of the mass and stiffness matrices of the finite element models of structures. The algorithm thus has the potential of being able to control moderately large‐scale, finite element models of highly flexible, large, space structures in a cost‐effective manner. The proposed algorithm is validated in suppressing the nonlinear vibrations of an impulsively loaded, highly flexible beam, and the need for inclusion of nonlinearities is demonstrated.