Inference of critical cod from Charpy V test result

Correlation between the Charpy absorbed energy and critical COD is investigated to obtain a useful method for estimating critical COD from Charpy V data. The round bar tension test, Charpy V-notch test and static 3-point bend test with fatigue notched specimen are carried out using mild steel, 785 MPa grade high strength steel and A5083 aluminum alloy. Correlation is found between W'_c/σ_Y and δ_c as well as between EW'_c/σ_Y² and Eδ_c/σ_Y, where W'_c is the Charpy absorbed energy obtained by considering temperature difference between the Charpy transition temperature and COD transition temperature. The symbols σ_Y, δ_c and E are yield strength, critical COD and Young's modulus, respectively. The correlations are established for various kinds of metals and over a wide temperature range including not only upper shelf range but also the transition range.     

Double exposure stabilization of positive photoresist

Positive photoresists appeared to be the most promising material in VLSI microfabrication for ten or more years from now. Thus, processing know-how needs to be accumulated continuously. This work deals with thermal characteristics of positive photoresist. The following facts were declared experimentally. The quinone diazide, photosensitizer, was thermally decomposed at around 140°C to release N₂. Simultaneously the surface layer of resist film was changed into innert state, called as ‘husk’, with low gas permeability and high chemical resistance. These thermal changes in resist film affect the photoresist to SiO₂ adhesion. In this work a noble process, named double exposure stabilization, is developed to get sufficient chemical resistance and good adhesion simultaneously.     

Electron spin resonance study of defects in CVD-grown 3C-SiC irradiated with 2MeV protons

Electron spin resonance (ESR) was used to study defects induced by 2MeV-proton irradiation in cubic silicon carbide (3C-SiC) epitaxially grown on Si substrates by chemical vapor deposition. A new ESR signal labeled T5 was observed at temperatures lower than ≈100 K in Al doped, p-type 3C-SiC epilayers irradiated. The T5 signal has anisotropic g-values of g₁ = 2.0020 ± 0.0001, g₂ = 2.0007 ± 0.0001,and g₃ = 1.9951 ± 0.0001. The principal axes of the g-tensor were found to be along the 〈100〉 directions, indicating that the T5 center has D₂ symmetry. Isochronal annealing of the irradiated epilayers showed that the T5 center was annealed at temperatures around 150° C. A tentative model is discussed for the T5 center.     

Effect of ion position on single-event transient current

Using focused high-energy microbeams of carbon- and oxygen-ions and a high speed, wide bandwidth measurement system, we found a strong dependence of the collected charge and the transient current waveform on the position of ion incidences. Single-event charge is collected by a diffusion mechanism even when the ion strikes a position about 3 4 μm away from the lateral boundary of the p⁺n-junction area.     

内扩散法Nb3Sn多芯线材的磁化特性研究

研究了内扩散法Ｎｂ３Ｓｎ多芯线材随温度和磁场变化的磁化曲线及磁化率,绘出了磁化量－磁场－温度（Ｍ－Ｈ－Ｔ）的三维临界曲面,归一化后的磁化曲线基本符合Ｋｒａｍｅｒ拟和方程。计算得到的Ｎｂ３Ｓｎ多芯线材有效直径比芯线的原始几何尺寸要大,其原因在于微观结构中存在着“桥梁”,分析表明,多余的磁滞损耗来自于“桥梁”。交流磁化率和Ｘ’和Ｘ″在给定频率和背景磁场下,随交流振幅的变化很小,在给定交流振幅下,随交流     

A Step-Up Phenomenon of the Thyristor Control Circuit with Series RLC Elements

A circuit controlled by thyristors and having series RLC elements gives rise to a step-up phenomenon. The term step-up is defined with respect to the capacitance voltage on steady state operation, i.e., the ratio of the maximum peak value when controlled by thyristers to the peak amplitude when thyristors are short-circuited exceeds unity. The domain of possible step-up voltage is determined by the angle of displacement between current and voltage and damping factor. The step-up voltages appear across each element, i.e., not only across the capacitance, inductance, and resistance but also across the thyristors. The control characteristic has a distinctive hump phenomenon. The interrupted current results in waveform distortion, phase lag, and improved power factor. The difference of characteristics between the peak and rms values of voltages, particularly of inductance and thyristors, is large. The response time, which is evaluated by numbers of half cycles, is large when the step-up ratio becomes large. The output voltage when the circuit is used as a voltage source has a drooping characteristic.     

Improved High-Q Dielectric Resonator with Complex Perovskite Structure

Microwave characteristics of the system Ba(Zn_1/3Ta_2/3)O₃-BaZrO₃ were investigated. Ba(Zn,Ta)O₃ has a perovskite pseudocell and hexagonal superstructure; the superstructure was not formed after addition of BaZrO₃. Both sintering and crystallization of Ba(Zn,Ta)O₃-BaZrO₃ were accelerated compared to those of Ba(Zn,Ta)O₃ alone, and the microwave Q value was also improved. The material optimized for the dielectric resonator, Ba(Ni,Ta)O₃-Ba(Zr,Zn,Ta)O₃, has a dielectric constant of 30, Q value of 10000 at 10 GHz, and temperature coeficient of resonant frequency of 0 ppm/°C.     

Plasma Etching of α-Sialon Ceramics

Plasma etching of β-Si₃N₄, α-sialon/β-Si₃N₄ and α-sialon ceramics were performed with hydrogen glow plasma at 600°C for 10 h. The preferential etching of β-Si₃N₄ grains was observed. The etching rate of α-sialon grains and of the grain-boundary glassy phase was distinctly lower than that of β-Si₃N₄ grains. The size, shape, and distribution of β-Si₃N₄ grains in the α-sialon/β-Si₃N₄ composite ceramics were revealed by the present method.     

The study of surface segregation and the formation of gradient domain structure at the blend of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers and acrylate adhesive copolymers

The effect of siloxane chain length on surface segregation of poly(methyl methacrylate)‐grafted poly(dimethyl siloxane) (PMMA‐g‐PDMS)/poly(2‐ethylhexyl acrylate‐co‐acrylic acid‐co‐vinyl acetate) [P(2EHA‐AA‐VAc)] blends was investigated. The blends of PMMA‐g‐PDMS with P(2EHA‐AA‐VAc) showed surface segregations of PDMS components. The surface enrichments of PDMS in the blends depended significantly on the PDMS chain length. Also, this blend showed the gradient domain structure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 375–380, 2003