Analysis of different configurations of flat plate water collectors connected in series

This paper presents the analytical study of flat plate collector based on the computer‐based thermal models considering two different cases, case A (fully covered by glass) and case B (fully covered by photovoltaic (PV) module). These models are developed based on energy balance equations. An analytical expression for characteristic equation for photovoltaic–thermal flat plate collector has been derived as a function of design and climatic parameters. This paper shows the detailed analysis of energy, exergy and electrical energy by varying the number of collectors by considering four weather conditions (A, B, C and D type) for five different cities (New Delhi, Bangalore, Mumbai, Srinagar and Jodhpur) of India. It is observed that the collectors fully covered by PV module combine the production of hot water in addition to electricity generation and it is beneficial in terms of exergy, thermal energy and electrical energy gain. Copyright © 2008 John Wiley & Sons, Ltd.     

Maximum Likelihood Sequence Detection for QPSK on Nonlinear, Band-Limited Channels

A receiver structure based on maximum likelihood sequence estimation (MLSE) for receiving quaternary phase shift keyed signals over band-limited, nonlinear satellite channels, in the presence of additive downlink Gaussian noise, is derived. This work is an extension of work done by Mesiya et al. [2] for binary PSK transmission. Error performance of the receiver at low to moderate signal-to-noise ratios is estimated using computer simulation. For moderate to high signal-to-noise ratios, an upper bound on the probability of symbol error is obtained. A suboptimum receiver structure is then developed and its performance evaluated using computer simulation. It is shown that the performance of the suboptimum receiver is very close to that of the MLSE receiver.     

Microstructural evolution during the supersolidus liquid phase sintering of nickel-based prealloyed powder mixtures

A novel concept for full-density sintering is described. Two prealloyed powders with slight compositional differences are tailored to separate the solidus temperatures into high-melt and low-melt compositions. A mixture of these two powder compositions allows full-density sintering at a temperature between the two solidus temperatures. For these experiments, the two powders were nickel-based alloys, where the low-melt powder contained boron. The mixed powders were sintered at temperatures above the solidus of the low-melt powder to form a transient liquid that promoted rapid densification of the mixture. Microstructure evolution during sintering was assisted using quenching experiments. Variables in this study included the heating rate, peak temperature, hold time, and powder ratio. Interdiffusion between the two powders controls microstructure evolution, with a dominant role associated with boron diffusion and reaction. The transient liquid phase responsible for densification is linked to boron diffusion and subsequent compound precipitation.     

A conformal cylindrical microstrip array for producing omnidirectional radiation pattern

Radiation patterns of rectangular microstrip patches arranged circumferentially on a circular cylinder have been computed. Both the axial patches and circumferential patches have been used. It has been found that the number of circumferential patches required for a given ripple in gain pattern is considerably less, thus simplifying the feed network. Comparison with experimental measurements shows good agreement.     

Microwave-hydrothermal synthesis and characterization of Co-VSB-5 microporous framework

The crystallization of cobalt metal incorporated microporous nickel phosphate framework, Co-VSB-5, with initial Ni/P gel ratio of about 1.0, 1.5 and 2.5, respectively, has been investigated under microwave-hydrothermal conditions. Attempts are made to incorporate metal ion in the range of 2.5–10 atomic % in the VSB-5 framework having varied Ni/P ratio by varying gel pH. The prepared samples were characterized by means of X-ray diffraction, scanning electron microscopy, UV-visible diffuse reflectance spectroscopy (UV-visible DRS), and nitrogen adsorption–desorption measurements at 77 K. The prepared samples are found to be crystalline in nature. The initial gel pH is found to be critical for crystallization of nickel phosphate framework with varied Ni/P ratio. Like wise, isomorphic substitution is favored with an increase in Ni/P gel ratio. The results for UVDRS demonstrated the incorporation of transition metal ions in the octahedral position for nickel sites in VSB-5 framework. The textural properties, such as surface area and micropore volume, of the Co-VSB-5 samples crystallized from initial Ni/P gel ratio of 2.5, were found to lower than those crystallized from initial Ni/P gel ratio of 1.5 at equivalent metal content level. Interestingly, crystallization of framework having micro-mesoporosity is favored with an increase in Ni/P gel ratio. Furthermore, scanning electron microscopy revealed the crystallization of samples with rod shaped morphology irrespective of the nature of metal ion and its concentration from gel comprising of Ni/P of 1.5 and 2.5. The results of UV-Vis DRS demonstrated the incorporation of transition metal ions in the octahedral position for nickel sites in VSB-5 framework.     

Characterization of roadway stormwater system residuals for reuse and disposal options

The chemical characterization of sediments accumulated in catch basins and stormwater ponds provides important information for assessing risks associated with management of these residuals upon removal of accumulated deposits in stormwater systems. In this study, over a period of 15 months, more than 150 residual samples were collected from 77 catch basin units and 22 stormwater ponds from 16 municipalities throughout the state of Florida. Concentrations (mg/kg) of metals and metalloids (arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, and zinc) and trace organics (volatile organics, semi-volatile organics, herbicides, and pesticides) in the sediments were measured. In addition, the synthetic precipitation leaching procedure (SPLP) was utilized to evaluate pollutant leachability risk for a subset of the samples collected. Measured pollutant concentrations were compared to corresponding risk-based guidelines in Florida (i.e., Florida soil cleanup target levels) to assess potential human health risks of beneficial use of these residuals through land application. Leached concentrations were compared to risk-based water quality guidelines (i.e., Florida groundwater cleanup target levels) to examine the potential for groundwater contamination. Although several metals (arsenic, barium, chromium, copper, nickel, lead, and zinc) were routinely detected in the catch basin and stormwater pond sediments, their concentrations were generally lower than the Florida's risk-based cleanup target levels for soils. A small number of organochlorine compounds (e.g., 4,4′-DDE, 4,4′-DDT) were detected, but only in a limited number of the samples (less than 10%); leaching of trace organic pollutants above the Florida risk-based groundwater thresholds was rare. The results suggest that when land-applied or beneficially used, these residuals are not expected to pose a significant threat to human health or the environment and the results of this research will provide stormwater managers and environmental management authorities with a useful resource to examine proper disposal and beneficial use of catch basin and stormwater pond sediments.     

The First Example of Saccharin‐Lithium Bromide Catalysis: Direct Synthesis of N‐Tosylimines from Alcohols

The first procedure to access N‐tosylimines directly from alcohols under mild and neutral conditions is reported. The protocol involves saccharin‐lithium bromide‐catalyzed oxidation of alcohols to aldehydes/ketones with chloramine‐T followed by their condensation with the in situ generated oxidation by‐product p‐toluenesulfonamide in the same reaction vessel to afford N‐tosylimines in 40–90% overall yields. The present work opens up a new and efficient synthetic route to N‐tosyimines directly from alcohols in a one‐pot procedure.