High-T/sub 0/ strain-compensated InGaAsSb-AlGaAsSb quantum-well lasers emitting at 2.43 /spl mu/m

Strain-compensated InGaAsSb-AlGaAsSb quantum-well (QW) lasers emitting near 2.5 /spl mu/m have been grown by solid-source molecular beam epitaxy. The relatively high arsenic composition causing a tensile strain in the Al/sub 0.25/GaAs/sub 0.08/Sb barriers lowers the valence band edge and the hole energy level, leading to an increased hole confinement and improved laser performance. A 60% external differential efficiency in pulsed mode was achieved for 1000-/spl mu/m-long lasers emitting at 2.43 /spl mu/m. A characteristic temperature T/sub 0/ as high as 163 K and a lasing-wavelength temperature dependence of 1.02 nm//spl deg/C were obtained at room temperature. For 2000 /spl times/ 200 /spl mu/m/sup 2/ broad-area three-QW lasers without lateral current confinement, a low pulsed threshold of 275 A/cm/sup 2/ was measured.     

微胞囊技术及产品F-500多功能灭火剂

介绍了微胞囊技术及产品F-500的灭火原理和优势。     

Information analysis of single photon emission computed tomography with count losses

An analysis is presented of the information transfer from emitter-space to detector-space in single photon emission computed tomography (SPECT) systems. The analysis takes into account the fact that count loss side information is generally not available at the detector. Side information corresponds to the number gamma-rays lost deleted due to lack of interaction with the detector data. It is shown that the information transfer depends on the structure of the likelihood function of the emitter locations associated with the detector data. This likelihood function is the average of a set of ideal-detection likelihood functions, each matched to a particular set of possible deleted gamma-ray paths. A lower bound is derived for the information gain due to incorporating the count loss side information at the detector. This is shown to be significant when the mean emission rate is small or when the gamma-ray deletion probability is strongly dependent on emitter location. Numerical evaluations of the mutual information, with and without side information, associated with information-optimal apertures and uniform parallel-hole collimators are presented.     

Study on heat conduction and adsorption/desorption characteristic of MIL-101/few layer graphene composite

Journal of Porous Materials - Aiming at the poor heat conduction performance of porous MIL-101 applied in adsorption cooling process, few layer graphene (FLG) was selected as a promising thermal...     

Cu2O/Cu Cermet as a Candidate Inert Anode for Al Production

Cu₂O/ x Cu ( x =0–25 wt%) cermets were evaluated as a novel partially inert anode for aluminum (Al) production. The physical and mechanical properties, including the compressive strength, flexural strength, thermal expansion coefficient, thermal conductivity, and dc electrical conductivity were tested at room temperature and at temperatures up to 950°C. The coefficient of thermal expansion, compressive strength, flexural strength, thermal conductivity, and electrical conductivity of Cu₂O/Cu cermets increased with increasing Cu content. High-temperature electrical conductivity measurements showed that with increasing temperature, the electrical conductivity increased when the Cu content was below the percolation threshold, while it decreased when the Cu content was above the percolation threshold. A relatively stable CuAlO₂ layer formed on the cermet surface during electrochemical testing, and the corrosion rate of this anode was estimated to be about 1.8–1.9 cm/year in Al production.     

Preparations and properties of thermosensitive terpolymers of N‐isopropylacrylamide,sodium 2‐acrylamido‐2‐methyl‐propanesuphonate,and N‐tert‐butylacrylamide

Terpolymers based on N‐isopropylacrylamide, sodium 2‐acrylamido‐2‐methyl‐propanesulfonate, and N‐tert‐butylacrylamide were synthesized by free‐radical copolymerization with 2,2′‐azobisisobutyronitrile as an initiator. The lower critical solution temperatures (LCSTs) of the linear polymer aqueous solutions were determined by the measurement of the transmittance on UV at different temperatures. The influence of the polymer concentration, polymer composition, and ionic strength on the LCSTs of the linear polymers was investigated. The LCST decreased with increases in the hydrophobic monomer N‐tert‐butylacrylamide, polymer concentration, and ionic strength. The phase transition became sharp when the polymer concentration and ionic strength increased. Meanwhile, the crosslinked hydrogels were prepared with the same recipe used for the linear terpolymers, but a crosslinker was added to the reaction system. The swelling ratios of the hydrogels at various temperatures and salt solutions were determined. The hydrogels possessed both high swelling ratios and thermosensitivity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

注塑模微机CAD系统

本文介绍了一个微机上运行的注塑模ＣＡＤ系统，此系统主要解决了四个难点，浇注系统设计，冷却系统分析，型腔，型芯的曲面造型设计，装配图和零件工作图的设计绘制，经厂家实际运用证明，该系统使用方便，结果正确，能提高设计效率，降低生产成本。     

Influences of zinc oxide and an organic additive on the electrochemical behavior of pure aluminum in an alkaline solution

The corrosion behavior of pure aluminum in inhibited and uninhibited 4 MKOH was investigated by means of hydrogen collection, polarization curve measurement and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion of pure aluminum was greatly inhibited by the addition of ZnO and dimethyl amine epoxy propane (designated as DE). EIS and EDAX analyses revealed that ZnO produces its effect by depositing on the aluminum surface, which increases the overpotential of hydrogen evolution. It was also found that the addition of DE could greatly improve the deposition of zinc layers.     

Preparation and characterization of polyelectrolyte copolymers containing methyl methacrylate and 2-hydroxyethyl methacrylate. I. Polymers based on methacrylic acid

Acidic polyelectrolyte copolymers containing 2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), and methacrylic acid (MAA) were prepared by free radical polymerization to high conversion in solution. Copolymer yields were obtained by gravimetry (all in the 30–50% range), relative molecular weights estimated by intrinsic viscosity measurements (all in the 50–70 cc/g range), tacticity by ¹³C nuclear magnetic resonance (NMR) spectroscopy (all polymers predominantly syndiotactic with some atactic content), and composition by acid/base titrations in conjunction with ¹H-NMR spectroscopy (all close to the monomer charge ratios). Acid strengths or apparent pKa's were examined as a function of extent of ionization. Measurements performed in water indicated that the compact/extended coil transformation in predominantly syndiotactic polymethacrylic acid occurs also in copolymers of similar tacticity containing moderate to high concentrations of MAA. The apparent pKa of such polymers containing only small amounts of MAA did not vary with extent of ionization, indicating a low degree of interaction between the acid groups. In copolymer pairs containing similar amounts of MAA but differing HEMA and MMA contents, the polymer containing more HEMA appeared the stronger acid, presumably due to a better solvation of that polymer which would increase the net spatial charge–charge separation and decrease cooperative effects that lead to suppressed ionization.     

fMRI-based Decoding of Visual Information from Human Brain Activity: A Brief Review

Machine Intelligence Research - One of the most significant challenges in the neuroscience community is to understand how the human brain works. Recent progress in neuroimaging techniques have...