A new equivalent circuit for inverters and its application for the determination of coupling matrix elements of narrow RF bandpass filters

A new equivalent circuit for inverters is presented. Using this circuit, expression for the elements of the coupling matrix of narrow RF band pass filters is derived. The derivation is based on frequency independent coupling assumed in the synthesis of narrow RF band pass filters. Our expression is different from an earlier expression obtained using lumped circuit representations of different types of coupling and their analysis. It is shown that the earlier expression can be derived from our analysis if the coupling is assumed frequency‐variant. Unlike earlier work, our derivation shows how the sign of the coupling coefficient can be obtained. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

The impact of online brand community characteristics on customer engagement: An application of Stimulus-Organism-Response paradigm

The advent of interactive digital platforms has led people to progressively interact on such platforms, urging organizations to create online communities to engage customers with them and with each other to enhance brand loyalty. This study attempts to investigate what motivates customers to engage in these brand communities. Through a questionnaire survey of 430 Facebook users, this study investigates whether and how the unique characteristics (information quality, system quality, virtual interactivity, and rewards) of online brand communities affect customer engagement. The consequent effect of customer engagement on brand loyalty is also examined. This study frames and empirically validates a model for engaging customers with online brand communities on Facebook, considering the moderating role of gender. The Stimulus-Organism-Response paradigm is solicited to justify the theoretical background of this study. The data were analyzed using structure equation modelling. Results reveal that each of the characteristics positively influences customer engagement, with information quality and virtual interactivity bearing the strongest influence. Customer engagement also exhibits a strong positive impact on brand loyalty. This results further reveal that gender gap in the online environment is declining as the impact of all the four characteristics of online brand communities on customer engagement was invariable across male and female members.     

Design and synthesis of non-steroidal diclofenac derivatives as anti-inflammatory drugs

In the course of our studies directed towards the discovery of novel non-steroidal anti-inflammatory agents (NSAIDs), which are expected to have improved drug efficacy and better toxicity profile than diclofenac, we have synthesized new derivatives of diclofenac phosphonates. These phosphonate analogs were efficiently prepared from commercially available 2-hydroxymethylaniline in three steps. The 2-hydroxymethylaniline was converted to the azide in reasonable yield. Click chemistry with a variety of alkynes followed by Arbuzov reaction resulted in a series of triazole based phosphonate products. Our inhibitors are designed to reduce the gastrointestinal bleeding caused by diclofenac by substituting the carboxylic acid group with the phosphonate group and in addition replacing with the triazole ring would allow the flexibility to explore the importance of both hydrophilicity and hydrophobicity of the ring at the active site.     

Titanium machining with new plasma boronized cutting tools

Titanium is a commonly used material in various critical applications such as aerospace and biomedical applications. In this article, for the first time in the literature, development and implementation of a novel plasma boronizing process on Tungsten Carbide (WC) cutting tools is introduced. Plasma boronizing on WC tools is performed with gas combination of 10% BF₃, 40% Argon and 50% H₂ at different temperatures and durations. Performance enhancements of plasma boronized WC tools on Titanium (Ti-6Al-4V) machining are investigated under various cutting conditions. It is found that new plasma boronizing of WC is a very cost effective solution for significantly increasing tool life in Titanium machining.     

Isolation and characterization of pepsin‐solubilized collagen from the integument of sea cucumber (Stichopus vastus)

BACKGROUND: Sea cucumber (Stichopus vastus) is considered an underutilized resource, since only its stomach and intestines are eaten raw as salad in a few countries and the remaining parts, especially the integument rich in collagen, is discarded. Hence a valuable by‐product having potential nutraceutical and pharmaceutical applications is wasted. In the present investigation, pepsin‐solubilized collagen (PSC) from the integument of S. vastus was isolated, purified and characterized. RESULTS: Sodium dodecyl sulfate–polyacrylamide gel electrophoretic analysis showed that the purified collagen was of type I, consisting of three α1 chains of approximately 122 kDa each. The peptide map of PSC digested by V8 protease was different from that of calf skin type I collagen. Fourier transform infrared spectroscopy revealed that the triple helical structure was well preserved in isolated collagen. The denaturation temperature of PSC was 21.23 °C and showed good gel‐forming capability at pH 6.5 and 300 mmol L^?1 NaCl. CONCLUSION: It is inferred that the collagen isolated from S. vastus integument has potential for use as an alternative to land‐based mammalian collagen in food, nutraceuticals and pharmaceutical industries. © 2012 Society of Chemical Industry     

Pyrolytic oil from fluidised bed pyrolysis of oil palm shell and itscharacterisation

Biomass in the form of oil palm shellwas pyrolysed in an externally heated 5 cm diameter, 30 cm high fluidised bed pyrolysis reactorwith nitrogen as the fluidising gas and silica sand as the bed material. The pyrolysis oil wascollected in a series of condenser and ice-cooled collectors. The char was collected separatelywhile the gases were flared. The effects of process conditions, like fluidised bed reactortemperature, feed size and fluidisation gas flow rate on the product yields were studied. Theproduct yields were found to be significantly influenced by the process conditions. Thecomposition of oil was determined at fluidised bed temperature of 500°C at which the liquidproduct yield was maximum. The oil was analysed by Fourier Transform infra-red (FTIR)spectroscopy and gas chromatography/mass spectrometry (GC/MS) techniques. In addition, thephysical properties of the oil were determined. The results showed that the oil was highlyoxygenated containing a high fraction of phenol-based compounds. Detailed analysis of the oilshowed that there was no concentration of biologically active polycyclic aromatic species in theoil. A brief preliminary economic analysis is presented at the end of the paper (see Appendix). ©1999 Elsevier Science Ltd. All rights reserved.     

Effects of species and moisture content on penetration of liquid in laser incised lumber by the passive impregnation method

Penetration of liquid by passive impregnation method for Douglas-fir (Pseudotsuga menziesii Franco), sugi (Cryptomeria japonica D. Don) and Japanese larch (Larix leptolepis Gordon) was studied. Effects of initial moisture content of sugi (16, 43 and 70% moisture content) on liquid penetration were also studied. Dried Douglas-fir (mc=14%) and sugi (mc=16%), and green Japanese larch (mc=45%) and sugi (mc=70%) were treated by passive impregnation method for penetration analysis. It was observed that dried sugi had the highest level of liquid penetration both in length (170 mm) and width (8 mm) for all measured sections followed by green sugi, green Japanese larch and dried Douglas-fir. In case of different initial moisture content, the highest absorption (624 kg/m³) and penetration (maximum 87 and 96% at cross and longitudinal surfaces, respectively) was observed for sugi having the lowest initial moisture content under the same passive impregnation conditions. Absorption and penetration decreased with the increase of initial moisture content for sugi. These results could help in designing incising pattern and density, as well as solving the problems related to high initial moisture content of wood for passive impregnation.     

Technical appraisal of solar home systems in Bangladesh: A field investigation

Solar Home System (SHS) based rural electrification has experienced a considerable growth in Bangladesh since the start of the Rural Electrification and Renewable Energy Development Project (REREDP) in 2003. The initial target of 50,000 SHS installations in off-grid areas was achieved within 2.5 years, 3 years ahead of schedule. After achieving a revised target of 200,000 SHSs, ahead of schedule in early 2009, a new target of 1 million SHS installations by 2012 was set. The installation of about 0.5 million systems by March 2010 indicates that the current target may well be achieved before the deadline. The size of the SHS market and its impact on the regeneration of the rural economy make it necessary to investigate the quality and reliability of the installed SHSs, if the continued success of the initiative is to be maintained. This paper reports on the findings from a field-based technical appraisal of SHS installations in Bangladesh. Sixty geographically dispersed installation sites were visited. Physical characteristics of the SHSs and their system components were tested to ascertain compliance with and deviations from the approved specifications. Despite the overwhelming success of the REREDP project, the study revealed various shortcomings. Notable among these are: incompatible and sub-optimal component configurations, faulty installations and a lack of effective quality assurance mechanism. The findings are contextualized and the ways to address the identified shortcomings are discussed.     

Physico-mechanical properties of chemically treated coir reinforced polypropylene composites

The physico-mechanical properties of coir reinforced polypropylene (PP) composites been investigated. In order to attain improved mechanical properties of the composites coir was chemically treated with o-hydroxybenzene diazonium salt. Both raw and treated coir samples were utilized for the fabrication of the composites. The mechanical properties of the composites prepared from chemically treated coir are found to be much better compared to those of untreated ones. Tensile strengths of the composites of both raw and chemically treated coir-PP composites showed a decreasing trend with increasing filler content. However, the values for the chemically treated coir-PP composites at all mixing ratios are found to be higher than that of neat PP. The surface morphologies of the fractured surfaces of the composites were recorded using scanning electron microscopy (SEM) to gain information about the fiber–matrix interfacial adhesion in the composites.