Pseudomorphic InP HEMTs with dry-etched source vias having 190 mWoutput power and 40% PAE at V-band

We report state-of-the-art V-band power performance of 0.15-μm gate length InGaAs/InAlAs/InP HEMT's which have 15 μm×23 μm dry-etched through-substrate source vias (substrate thickness 50 μm). The 500-μm wide InP HEMT's were measured in fixture at 60 GHz and demonstrated an output power of 190 mW with 40% power-added efficiency (PAE) and 6.8 dB power gain at an input power of 16 dBm. These results represent the best combination of power and PAE reported to date at this frequency for any solid state device. The results are achieved through optimization of the InP-based heterostructure which incorporates a graded pseudomorphic InGaAs channel and a graded pseudomorphic InAlAs Schottky barrier layer, and the use of 15 μm×23 μm dry-etched through-substrate source vias     

New molecular prognostic markers in gastric carcinoma

Many molecular events have been reported as prognostic factors in gastric cancer. Amplifications of K-sam and c-met genes are often associated with poorly differentiated adenocarcinoma, while ERBB2 genes are amplified in well--differentiated adenocarcinomas of the stomach. Alterations of tumor suppressor regulators confer progression of gastric cancer. On the other hand, multi autocrine loops of growth factors/receptors in gastric cancer cells play a key role in the progression and metastasis of cancer cells. The overexpression of K-sam gene, occurs in 31.9% of gastric cancers, and the prognosis of patients with overexpression of K-sam gene is poorer than those without it. Multivariate analysis reveals that the overexpression of K-sam gene is an important factor for prognosis, lymphnode metastasis and the depth of tumor invasion of gastric carcinomas.     

Transient Tests on a Voltage-Regulated Controlled-Current PWM Converter

The controlled-current PWM converter has the capability of delivering near sinusoidal current waveforms with unity and even leading power factors. This paper describes its transient characteristics when operated with a simple proportional feedback control to ensure regulated dc voltage output. Experimental tests show that it has fast step response and that it survives abnormal operational conditions such as brown-outs and loss of a single phase.     

An integrated switched-capacitor signal processing design system

A CAD system integrating switched-capacitor network function synthesis, circuit synthesis, and layout is presented. The tool addresses the design of programmable gain, cosine, interpolation, and arbitrary transfer functions in addition to canonical filter structures. Amplifier design is based on numerical optimization of highly accurate analytic models derived with the aid of symbolic-mathematics-based model development aids. The physical design of the filter is created by a general-purpose switched-capacitor circuit synthesizer. The tool makes it possible to synthesize a complete switched-capacitor signal path with full handcrafted quality in a single day. Examples taken from actual IC designs illustrate the utility and accuracy of the various functions     

Studies on semiconductor optical amplifiers for line capacityexpansion in photonic space-division switching system

The problems associated with introducing traveling wave amplifiers (TWAs) to photonic space-division (SD) switching systems are examined. Experiments were carried out to clarify the TWA noise effect and interference between cascaded TWAs, using about 10-dB gain TWA modules. Possibility of a 128-line photonic SD switching system, using current polarization-independent LiNbO₃ 8×8 switch matrices, has been shown through the experiments. The possible line capacity value of the photonic SD switching system with TWAs is examined theoretically. It is shown that the expected line capacity value for such a switching system exceeds 10³     

Large-scale fabrication of Ag nanoparticles in PVP nanofibres and net-like silver nanofibre films by electrospinning

Heat treatment of various compositions of AgNO(3)-doped polyvinylpyrrolidone (PVP) composite nanofibres fabricated by electrospinning produced two kinds of silver species: (i) Ag nanoparticles dispersed in PVP nanofibres, when the loading of AgNO(3) was 5?wt%, and (ii)?a net-like silver nanofibre film when the loading of AgNO(3) was five times greater than that of PVP in the composite nanofibres. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible absorption spectroscopy, FT-IR spectra, powder x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were used to characterize the silver nanoparticles and nanofibres. The formation mechanisms are discussed based on the redox reaction between AgNO(3) and PVP during heat treatment; essentially, the weight ratios of AgNO(3) to PVP determined the types of morphologies, from Ag nanoparticles to silver nanofibre film. The present results may find some potential application in the design of new composite materials in the dielectric and electronics areas.     

Mechanical properties of laser-pressure-welded joint between dissimilar galvannealed steel and pure aluminium

Dissimilar metal joints of Zn-coated Galvannealed steel (GA steel) and commercially available pure aluminium (A1050) sheets were produced by changing the laser power and the roller pressure by the laser pressure welding method. By this method, the YAG laser beam was irradiated into a flare groove made by these dissimilar metal sheets. In addition, the laser beam was scanned at various frequencies and patterns through the fθ lens using two-dimensional scanning mirrors. Then the sheets were pressed by the pressure rolls to be joined.

The compound layers in the weld interface were observed by an optical microscope and the layer thicknesses were measured. The thicknesses ranged from 7 to 20 μm. The mechanical properties of the welded joints were evaluated by the tensile-shear test and peel test. In the tensile-shear test, the strengths of the joints produced under the most welding conditions were so high that the fracture occurred through the base aluminium sheet. In the peel test of the specimens subjected to a laser beam of 1200–1400 W power under roller pressure of 2.94 kN, the specimen fracture took place in the base aluminium sheet. Even if the compound layer was thick, high joint strength was obtained. On the other hand, the specimen fractured in the weld interface at a laser power of 1500 W. The results of X-ray diffraction on the peel test specimen surface identified that the intermetallic compound on the GA steel side was Fe₂Al₅Zn_0.4. Moreover, the aluminium parts adhering to the GA steel side were confirmed. These results suggest that the fracture in the peel test occurred between the compound layer and A1050 and partly in the base aluminium. A micro-Vickers hardness test was performed to examine the hardness distribution in the compound layer. The hardness values near A1050 and GA steel were about 100 and 470 Hv, respectively, which suggests that the compound layer should not necessarily consist of brittle intermetallic compounds. It is therefore concluded that laser pressure welding could produce high strength joints of GA steel and A1050 dissimilar materials.     

铁基合金的液相扩散焊接

本文介绍了用于航天工业的铁基合金－Ｉｎｃｏｌｏｙ８００液相扩散焊接技术，探讨了中间夹层的选择及母材表面合金化的手段，观察分析了焊缝组织及其机械性能。研究表明，中间夹层选择的成功与否是影响液相扩散焊接的主要因素之一。通过试验，找出了中间夹层中硼，碳，硅三种元素的最佳添加量。试验证明，采用激光喷镀法使母材表面合金化的手段是可行的，但镀层底部局部起伏不平导致焊缝形成生成相影响了焊缝的机械性能，通过各种方     

Rapid Formation of α-Al2O3 Scale on an Fe–Al Alloy by Pure-Metal Coatings at 900 °C

Rapid formation of an α-Al₂O₃ scale on Fe–50 at.%Al by pure metal thin coatings of Ni, Al, Ti, Cr or Fe was investigated, and the effects of those elements on Al₂O₃-scale evolution were assessed. The oxidation behavior of samples with and without coatings could be divided into two groups: the samples with/without Ni and Al, and those with Ti, Cr and Fe. The mass gains of samples coated with Al and Ni were almost the same as that of non-coated Fe–50 at.%Al alloy. The mass gains of samples coated with Ti, Cr, and Fe were much lower than that of the Fe–50 at.%Al alloy. A stable α-Al₂O₃ scale was found to develop from the beginning of oxidation on the samples coated with Ti, Cr and Fe. However metastable θ-Al₂O₃ remained after long-time oxidation of non-coated and Ni- and Al-coated samples. The direct α-Al₂O₃ scale formation on the samples with Cr or Fe coatings was speculated to be due to sympathetic nucleation of α-Al₂O₃ on the surface of Al-supersaturated Fe₂O₃ for Fe-coated sample, and composition changes from (Cr,Al)₂O₃ to (Al,Cr)₂O₃ for the Cr-coated sample. Initial formation of an oxide having a corundum structure was inferred to provide a nucleation site for precipitation of α-Al₂O₃ without prior formation of a metastable Al₂O₃ scale.