Progress and prospects of group-III nitride semiconductors

We review recent progress in the group-III nitride and related materials, and electronic and optical devices based on them. Blue and UV (e.g. ultra violet) emitters and detectors, and high temperature/high power electronics which has long been coveted are beginning to be realized either in the laboratory or in the commercial arena, due in part to the breathtaking progress made in the last few years in the art and science of GaN, InN, AlN and their salloys. With brief references to the historical aspect of the relevant developments, this review concerns itself primarily with the current status of wide bandgap gallium nitride and related semiconductors from both the materials and devices points of view. Following a discussion of the structural properties of these materials, their electrical and optical properties are described in detail. The available data on metal contacts, the properties of which are indeed very conducive for the devices mentioned, from the points of view of ohmic contacts and Schottky barriers, are elaborated on. Recent progress on processing issues such as etching are reviewed. The review then embarks on an indash;depth discussion and analysis of field effect transistors, bipolar transistors, light emitting diodes, laser and photo detectors.     

Purification and renaturation of recombinant human lymphotoxin (tumour necrosis factor beta) expressed in Escherichia coli as inclusion bodies

High level expression of recombinant human tumour necrosis factor β (rh TNF-β) in Escherichia coli results in the formation of two portions of protein, namely soluble active protein and insoluble protein which is inactive and aggregates in the form of inclusion bodies (IBs). In this study, a procedure for purification and renaturation of rh TNF-β from inclusion bodies has been designed and verified experimentally with a product purity of more than 90% and a recovery of about 30%. The procedure includes washing of IBs with specific wash buffer (Triton X-100/EDTA/lysozyme/PMSF), their solubilization with 8 mol dm^?3 alkaline urea, purification with ion-exchange columns, refolding with renaturation buffer and finally concentration and desalination with an ultrafiltration membrane. The characteristics of the renatured protein were identical with those of purified protein from the soluble fraction as demonstrated by (1) SDS-PAGE, (2) cytotoxic activity on mouse L929 cells, (3) N-terminal amino acid sequence, and (4) gel filtration chromatography.     

Rheology of concentrated solutions of hyperbranched polyesters

The solution rheology of different generations of hyperbranched polyesters in N‐methyl‐2‐pyrrolidinone (NMP) solvent was examined in this study. The solutions exhibited Newtonian behavior over a wide range of polyester concentrations. Also, the relative viscosities of poly(amidoamine) (PAMAM) dendrimers in ethylenediamine were compared with those of the hyperbranched polyesters in NMP. Both types of dendritic polymers have relative viscosities that are exponential functions of their molar fraction in solution. The slopes of these relative viscosity curves show a linear relationship with respect to the generation number. PAMAM dendrimers have the greater slopes for each generation, reflecting their relatively larger intrinsic viscosity values.     

Proposal for st-Routing Protocol

A routing protocol chooses one of the several paths (routes) from a source node to a destination node in the computer network, to send a packet of information. In this paper, we propose a new routing protocol, which we call st-routing protocol, based on st-numbering of a graph. The protocol fits well in noisy environments where robustness of routing using alternative paths is a major issue. The proposed routing protocol provides a systematic way to retry alternative paths without generating any duplicate packets. The protocol works for only those networks that can be represented by biconnected graphs.     

Validation of a Three-Dimensional Computational Fluid Dynamics Model of a Contact Tank

A three-dimensional (3D) computational fluid dynamics (CFD) model of a contact tank is presented in this paper. The model results are compared against 3D velocities and flow through curve (FTC) data, representing a tracer concentration profile, from a 1:8 scale physical model. The objective is to demonstrate that CFD models can simulate both the FTC and the 3D velocity field quite well. Simultaneous validation of velocities and FTC is important in ascertaining the predictive capabilities of CFD models, as physical model studies indicate that different baffle arrangements can lead to similar FTCs. Therefore, a good prediction of only FTC, as presented in previous 3D CFD model studies, does not necessarily imply a correct simulation of the flow field.     

基于不同爆轰产物的格尼速度估算新方法（英）

A new method for prediction of Gurney velocity of explosives is introduced in which energy output is correlated with the heat of detonation, the number of moles of gaseous products of detonation per gram of explosive and the average molecular weight of gaseous products. It is assumed that the CHNO explosive reacts to form products composed of N2 , CO, H2O, CO2, H2,O2 and C（s） as determined by the oxygen balance of the unreacted compound. Good agreement is obtained between measured and calculated values of Gurney velocity as compared to previous correlations which assumed the reaction products to consist of N2 , H2O, CO2 and either C（s） or O2.     

The sinuous antenna-A dual polarized feed for reflector-based searching systems

The sinuous antennas have a numerous applications in military and civil systems such as direction finding systems and reflector feeds due to their superior broadband characteristics and simultaneous polarization capability. In this paper, design, construction and measurements of planar sinuous antennas are investigated for 1–5 GHz frequency range. Feeding sections of this antenna are realized by using microstrip tapered baluns. We have determined the microstrip tapered balun dimensions using Ansoft HFSS-simulation program. The performances of the manufactured antenna are measured using HP vector network analyzer. Polarization patterns and return loss characteristics of the designed antenna that have been measured in anechoic chamber, are presented.