Remarkable improvement in emission efficiency of ZnCdSe/Zn(S)Se LEDs by thermal annealing

Thermal annealing effects on optical and electrical characteristics for p-type and n-type II–VI compound layers (ZnSe, ZnSSe, and MgZnSSe) and on the emission efficiency of ZnCdSe/Zn(S)Se 6 quantum well (QW) light emitting diodes (LEDs) grown by molecular beam epitaxy were investigated. It was clarified that serious degradation of optical and electrical characteristics was not observed up to an annealing temperature of 400°C. In the case of p-MgZnSSe, the maximum permitted annealing temperature was lower than that of Zn(S)Se. The light output of the ZnCdSe/Zn(S)Se multi QW LEDs was enhanced by a factor of three at optimum thermal annealing conditions. The study suggests that this thermal effect for LEDs was produced by the improved crystal quality of ZnCdSe QWs by thermal annealing.     

Modeling of closed-loop voltage-mode controlled interleaved dual boost converter

An extensive small-signal analysis of a voltage-mode controlled interleaved dual boost (IDB) converter operating in continuous current mode based on signal flow graph approach is proposed. Small-signal flow graph is developed, from which open-loop small-signal transfer functions are derived using well known Mason's gain formula. Closed-loop small-signal input-to-output, control-to-output transfer functions are also derived and frequency response characteristics are determined at different duty ratios. Voltage-mode compensator designed using K-factor approach is used for closed-loop operation of IDB converter. Load voltage regulation against supply voltage and load disturbances are demonstrated through experimental results.     

Simultaneous desulfurization and dephosphorization reactions of molten iron by soda ash treatment

Desulfurization and dephosphorization reactions of molten iron by soda ash has been studied on laboratory heats of Fe-C, Fe-C-S, Fe-C-P, and Fe-C-S-P alloys at 1573 and 1623 K. The alloys were melted in helium gas flow and preheated soda ash was added; metal samples were taken at certain time intervals and analyzed for sulfur, phosphorus, and carbon. Evolved gas samples were also taken at certain time intervals and analyzed. The phosphorus and sulfur contents in metals decreased rapidly, reaching the lowest values two to four minutes after the soda ash addition. The degree of desulfurization was generally greater than that of dephosphorization, and both degrees were higher at lower reaction temperature. The major component of evolved gas was CO with small amounts of CO₂. Phosphorus appeared to form a stable phosphate compound with Na₂O, possibly 3Na₂O-P₂O₅, in the slag phase. Soda ash reacts with carbon resulting in decarburization of molten iron and vaporization of sodium; this reaction may cause the fading of soda ash and can be expressed as: Na₂CO₃(1) + (1 +x)C = (1 -xNa₂O(1) + 2xNa(g_ + (2 +xCO(g). For the phosphorus containing melt, the reaction can be expressed as: Na₂CO₃(l) +yC + 2x/3P =x(Na₂O · 1/3P₂O₅)(1) + (2 −y − 8x/3)Na₂O(l) + 2(−l + y + 5x/3)Na(g) + (1 +y)CO(g) and for the sulfur containing melt: Na₂O(l) +C +S = Na₂S(l) + CO(g). Katsumi Mori, Formerly Visiting Associate Research Scientist, University of Michigan, Ann Arbor, MI     

The strategic management and information network system The convenience store net-work

We are living in an advanced information society. The information revolution in computers is going on, among other areas, in the field of marketing. Until now, the term “Information System” has been used in the field of marketing mainly to refer to market research. We need to make the most of this information to aid decision making in new product development and sales promotion. It is fundamental that marketing be consumer oriented. However, the real needs of a contemporary consumer include factors which cannot be revealed by a questionnaire survey. The progresses of computer technology and its reduction in price has enabled the construction of a network system in the distribution stage.

The construction and application of a network system suitable to contemporary marketing management has now become part of the challenge facing business management. They must collect and process distribution information with speed and efficiency. And they must obtain information that is up-to-minute and sufficiently detailed for marketing activity which can then be carried out effectively with small risk. In other words, a company manager who is supported by an information system has come to be able to control in minute detail the information regarding purchase actions of various consumers.     

Radiation-induced reactions of ring-substituted polystyrenes analyzed by radiolysis of low molecular-weight model compounds

Radiation-induced reactions of polystyrene derivatives have been studied by the radiolysis of ring-substituted isopropylbenzene derivatives, i. e., 4-amino. 4-hydroxy, 4-methoxy, 4-methyl, 4-chloromethyl, 4-chloro, and 4-acetyl derivatives. Low-temperature ESR analyses measured at 77 K indicate that. In general, the a-position is the most sensitive site to radiation and that thus a-radicals are produced through a-hydrogen removal. However, among these derivatives, the amino, acetyl, chloromethyl, and. chloro derivatives undergo different reactions from the other derivatives. A phCO? CH₃ cleavage from the- acetyl derivative and N? H cleavage from the amino derivative occur, and chlorine removal takes place from the chloro-methyl and chloro derivatives. Final products detected by gas chromatography-mass spectrometry indicate not only that radiation-induced free radical recombination occurs. but also that if chlorine is produced by radiation, hydrogen abstraction by radiation-induced chlorine takes place prior to the free radical recombination. The susceptibility of each derivative to hydrogen abstraction by radiation-induced active chlorine increases, as the electron-donation of ring-substituents is increased. Based on the clarified reaction mechanism, the design of polystyrene derivatives as resist materials is discussed and two new types of resist systems are described. One is a new chloromethylstyrene based blend resist, which is formulated from poly(4-meth-oxystyrene) and poly(4-chloromethylstyrene). The other is a new non-swelling alkaline developable negative resist, which is formulated from poly(4-hydroxystyrene) and a chlorine-releasing compound.     

Effect of impurity hydrogen on the deformation and fracture in an Al-5 mass Pct Mg alloy

Air-melted and argon-melted Al-5 mass pct Mg alloy specimens containing impurity hydrogen of 0.27 and 0.04 mass ppm, respectively, were tensile-tested at ambient temperature. The ductility and fracture processes were compared in the two specimens, and hydrogen evolution behavior during the test was also compared using a special testing machine equipped with a mass spectrometer and ultra high vacuum chamber. The air-melted specimen, containing a higher amount of hydrogen, had less reduction in area (RA) and a higher amount of evolved hydrogen gas on fracture. This implied that the impurity hydrogen was in the transgranular voids, which appeared as dimples on the fracture surface. Fracture process analysis involving fractography, load-displacement curve analysis, and optical microscopy on a cross section of the deformed test piece demonstrated that the impurity hydrogen reduces nonuniform elongation by accelerating the nucleation of transgranular voids produced under triaxial tensile stress after necking. Hydrogen evolution was also detected corresponding to each load drop in the serrated flow of the air-melted specimen, supporting the idea that hydrogen atoms are transported with moving dislocations.     

类金刚石纤维砂轮的开发及其磨削特性

为了获得高精度加工表面，最近磨具市场上有一种Al2O3纤维砂轮问世^[1]。该砂轮克服了磨粒砂轮中磨粒易于脱落的缺点，但其硬度仍受到一定限制。近十年来，由于类金刚石薄膜具有接近金刚石的硬度、高耐磨性和很低的摩擦系数等优良的机械、物理、化学和光电特性，因而被广泛地应用于精密零部件和涂附刃具的制造^[2]。如果能将类金刚石薄膜形成类金刚石纤维，然后将其代替Al2O3纤维作为磨料，就可以满足纤维砂轮的硬度要求。因此，1999年以来，日本山口胜美教授和中国魏源迁教授成功地将类金刚石纤维植入基体并与树脂结合剂结合，开发了一种类金刚石纤维砂轮^[3-5]。该砂轮中的类金刚石纤维按同一方向排列且与砂轮磨削面相垂直，纤维的端部可用作为切削刃。为了考察这种新型砂轮的磨削特性，本文作者对难加工材料如模具钢SKD11及硬脆材料如硅片、光学玻璃、石英和大理石进行了大量的磨削试验。试验结果表明能获得纳米级加工表面，例如被磨硅片和模具钢的表面粗糙度分别为Ra2nm(Ryl5nm)和Ra2nm(Ry23nm)。