Mechanical Strength and Failure Characteristics of Cast Mg-9 pctAl-1 pctZn Alloys Produced by a Heated-Mold Continuous Casting Process: Tensile Properties

The mechanical properties and failure characteristics of a cast Mg alloy (AZ91: Mg-Al_8.9-Zn_0.6-Mn_0.2) produced by a heated-mold continuous casting process (HMC) are investigated. In a modification of the original HMC process, the cooling of the liquid alloy by direct water spray is carried out in an atmosphere of high-purity argon gas. The HMC-AZ91 alloy exhibits excellent mechanical properties (high strength and high ductility) that are about twice as high as those for the same alloy produced by conventional gravity casting. The increased material strength and ductility of the HMC sample are attributed to nanoscale and microscale microstructural characteristics. The fine grains and tiny spherical eutectic structures (e.g., Mg₁₇Al₁₂ and Al₆Mn) distributed randomly in the matrix of the HMC alloy result in resistance to dislocation movement, leading to high tensile strength. Basal slip on (0001) planes in the relatively organized crystal orientation of the HMC alloy, as well as grain boundary sliding through tiny spherical eutectic structures, results in high ductility. Details of the failure mechanism under static loading in the HMC alloy are also discussed using failure models.     

Four-channel arrayed polarization independent EA modulator with anIPF carrier operating at 10 Gb/s

We have developed a four-channel 10-Gb/s electroabsorption modulator array. We have introduced an innovative technique with an impedance-matched film (IPF) carrier to feed the electrical driving signal. The IPF carrier is made of an insulating polyimide film on which a coplanar waveguide is formed. We have achieved 10-Gb/s operation for all channels with clear eye opening and with negligibly small crosstalk. Polarization independence is confirmed for each arrayed channel     

SOLVENT EXTRACTION OF CHROMIUM(Vl) BY 3-(4-PYRIDYL)-l,5-DIPHENYL PENTANE

The distribution equilibrium of Cr(VI) between an aqueous sulfuric acid solution of potassium bichromate and a nitrobenzene solution of 3-(4-pyridyl)-l,5-diphenyl pentane (PDPP or B) has been studied. Hydrogen chromate ion among several ionic species of Cr(VI) in the aqueous solution is extractable in the present system. The chromium concentration in the organic phase is correlated with the concentrations of hydrogen chromate and hydrogen ion in the aqueous phase with PDPP in the organic phase. The interfacial reaction rate is also obtained and it gives the equilibrium relation by equating the extraction rate with the stripping rate. Results of the freezing point depression of the organic solution and the interfacial tension, obtained for the present system, indicate that the Cr(VT)-PDPP complex in the organic phase might be the aggregation of several molecules of chromate acid and PDPP, and that the complex is surface active. A Cr(VI)-PDPP complex adsorbed at the liquid-liquid interface reacts with hydrogen chromate ion in the aqueous phase consecutively.     

Second order asymptotic efficlency in terms of the asymptotic variance of seqrential estimation procedures in the presence of nrisance parameters

In the presence of nuisance parameters, the Bhattacharyya type bound for the asymptotic variance of estimation procedures is obtained. It is shown that the modified maximum likelihood (ML) estimation procedures together with any stopping rule does not attain the bound. Further it is shown that the modified ML estimation procedure with the appropriate stopping rule is second order asymptotically efficient in some class of estimation procedures in the sense that it attains the lower bound for the asymptotic variance in the class.     

Fluorescent SiC and its application to white light-emitting diodes

Fluorescent-SiC(f-SiC),which contains donor and acceptor impurities with optimum concentrations, has high conversion efficiency from NUV to visible light caused by donor-acceptor-pair(DAP) recombination. This material can be used as a substrate for a near UV light-emitting diode(LED) stack,and leads to monolithic white LED device with suitable spectral property for general lighting applications.In this paper,we describe basic technologies of the white LED,such as optical properties of f-SiC substrate,and epitaxial growth of NUV stack on the f-SiC substrate.     

Employee self-enhancement motives and job performance behaviors: Investigating the moderating effects of employee role ambiguity and managerial perceptions of employee commitment.

This study examined the effects of employee self-enhancement motives on job performance behaviors (organizational citizenship behaviors and task performance) and the value of these behaviors to them. The authors propose that employees display job performance behaviors in part to enhance their self-image, especially when their role is not clearly defined. They further argue that the effects of these behaviors on managerial reward recommendation decisions should be stronger when managers believe the employees to be more committed. The results from a sample of 84 working students indicate that role ambiguity moderated the effects of self-enhancement motives on job performance behaviors and that managerial perceptions of an employee's commitment moderated the effects of those organizational citizenship behaviors that are aimed at other individuals on managers' reward allocation decisions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Crystalline orientation dependence of electrical properties of Mn Germanide/Ge(1 1 1) and (0 0 1) Schottky contacts

We have investigated the crystalline orientation dependence of the electrical properties of Mn germanide/Ge(1 1 1) and (0 0 1) Schottky contacts. We prepared epitaxial and polycrystalline Mn₅Ge₃ layers on Ge(1 1 1) and (0 0 1) substrates, respectively. The Schottky barrier height (SBH) estimated from the current density-voltage characteristics for epitaxial Mn₅Ge₃/Ge(1 1 1) is as low as 0.30 eV, while the SBH of polycrystalline Mn₅Ge₃/Ge(0 0 1) is higher than 0.56 eV. On the other hand, the SBH estimated from capacitance-voltage characteristics are higher than 0.6 eV for both samples. The difference of these SBHs can be explained by the local carrier conduction through the small area with the low SBH regions in the epitaxial Mn₅Ge₃/Ge(1 1 1) contact. This result suggests the possibility that the lowering SBH takes place due to Fermi level depinning in epitaxial germanide/Ge(1 1 1) contacts.     

Full-color reflective liquid-crystal display using internal-reflection inverted-scattering (IRIS) mode

Abstract— We developed a bright full-color reflective LCD which employs a newly developed IRIS mode, a scattering PDLC, and a MIM active matrix with two processes. The full-color IRIS LCD provides high efficiency for ambient light and good color representation characteristics for battery-driven low-power applications.