Magnesium global development: Outcomes from the TMS 2007 annual meeting

The magnesium industry is experiencing dramatic growth, due in part to the demands of the automotive industry to improve fuel economy and emissions. As a result, the TMS annual magnesium symposium is one of the fastest-growing subject areas at TMS. In addition, TMS is recognized as the global light metals community’s preeminent forum for the presentation of magnesium science and technological issues. As a focal point of the 2007 TMS Annual Meeting in Orlando, Florida, the TMS Magnesium Committee held its first plenary session with expert representatives from around the world. In order to address the surge in magnesium technology in recent years, the TMS Magnesium Globalization plenary session included a variety of subjects that ranged from economic to technical.     

Duality of constrained Voronoi diagrams and Delaunay triangulations

We introduce theconstrained Voronoi diagram of a planar straight-line graph containingn vertices or sites where the line segments of the graph are regarded as obstacles, and show that an extended version of this diagram is the dual of theconstrained Delaunay triangulation. We briefly discussO(n logn) algorithms for constructing the extended constrained Voronoi diagram.This work was partially supported by a grant from the Natural Sciences and Engineering Research Council of Canada.     

Experimental investigation and numerical modelling of transient two-phase flow in a geysering geothermal well

Measurements of the periodic transient flow in a vertical geysering geothermal well are presented. The 70-m deep, 0.1-m internal diameter well taps a hot (about 87 °C) water aquifer rich in dissolved carbon dioxide. Transient pressures measured at various depths show the various flow regimes that develop in the borehole and demonstrate that the periodic flow is caused by the degassing of the water flowing up the well. A one-dimensional numerical model of the flow has been developed. The computed results exhibit the main characteristics of the test measurements. This agreement between model and measurements is considered to support both the numerical model and the conceptual model of the system deduced from the measurements.     

简化混合处理器应用开发 FPGA分担DSP功能降低构建成本

随着大规模现场可编程逻辑阵列(FPGA)的成本降低,加上面向软件的FPGA设计工具的发展,使得FPGA器件获得更多的使用,既能处理过去DSP处理器领域的功能,同时大大降低了专用ASIC方案的风险和前期成本.     

Treatment retention and follow-up outcomes in the Drug Abuse Treatment Outcome Study (DATOS).

Clients in the national Drug Abuse Treatment Outcome Study reported significant overall improvements in drug use and related measures during a 12-month follow-up period. A quasi-experimental design was used to examine the relationship of treatment duration with outcomes in each of the 3 major modalities represented. Client subsamples with longer retention in long-term residential programs and in outpatient methadone treatment had significantly better outcomes than those with shorter lengths of stay (results were inconclusive for outpatient drug-free programs because of sample limitations). This study used several methodological enhancements and showed general continuity of findings on retention effects from previous national evaluations of treatment effectiveness. It supports the need for more careful study of treatment process in relation to outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigations of 3C-SiC inclusions in 4H-SiC epilayers on 4H-SiC single crystal substrates

Synchrotron white beam x-ray topography (SWBXT) and Nomarski optical microscopy (NOM) have been used to characterize 4H-SiC epilayers and to study the character of triangular inclusions therein. 4H-SiC substrates misoriented by a range of angles from (0001), as well as (1 100) and (1120) oriented substrates were used. For epilayers grown on substrates misoriented by 3.5° from (0001) toward <1120>, the triangular inclusions were identified as consisting of two 3C-SiC structural configurations which are related to each other by a 180° rotation about the [111] axis. The epitaxial relationships between the 3C inclusions and the 4H-SiC epilayers (or substrates) were also determined. No evidence was found for the nucleation of 3C-SiC inclusions at superscrew dislocations (along the [0001] axis) in the 4H-SiC substrates. Increasing the off-axis angle of the substrates from 3.5 to 6.5° was found to greatly suppress the formation of the triangular inclusions. In the case of substrates misoriented by 8.0° from (0001) toward <1120>, the triangular inclusions were virtually eliminated. The crystalline quality of 4H-SiC epilayers grown on the substrates misoriented by 8.0° from (0001) was very good. For the (1100) and (1120) samples, there is no indication of 3C-SiC inclusions in the epilayers. Possible formation mechanisms and the morphology of 3C-SiC inclusions are discussed.     

Isomerization and Decomposition of Chloromethylacetylene

The isomerization and thermal decomposition of chloromethylacetylene (CMA) has been studied with two shock tube techniques. The first experiment (Jerusalem) utilizes single-pulse shock tube methods to measure the isomerization rate of CMA to chloroallene. In addition, equilibrium constants can be estimated at ∼1200 K. The second experiment (Argonne) monitors Cl-atom formation at temperatures above ∼1150 K. Absolute yield measurements have been performed over the 1200–1700 K range and indicate that two decomposition channels contribute to CMA destruction, namely, Cl fission and HCl elimination. The results show that the branching fraction between processes is temperature dependent. Therefore, direct Cl-atom fission is accompanied by molecular elimination, undoubtedly giving HCl and one or more isomers of C₃H₂. MP2 6–31G(d,p) ab initio electronic structure calculations have been used to determine vibration frequencies and moments of inertia for three C₃H₃Cl isomers. Using these quantities, the experimental equilibrium constants required that ΔH⁰₀(CH₂Cl–C≡CH ⇌ CHCl=C=CH₂) = −;0.24 kcal mole⁻¹. A potential energy surface pertinent to the present system has been constructed, and RRKM calculations have been carried out in order to explain the isomerization rates. The isomerization data can be explained with E₀ = 52.3 kcal mole⁻¹ and 〈ΔE_down〉 = 225 cm⁻¹. Subsequent semi-empirical Troe and RRKM-Gorin modeling of the Cl atom rate data require E₀ = (67.5 ± 0.5) kcal mole⁻¹ with a 〈ΔE_down〉 = (365 ± 90) cm⁻¹. This suggests a heat of formation for propargyl radicals of (79.0 ± 2.5) kcal mole⁻¹.     

Optimization of on-chip ESD protection structures for minimal parasitic capacitance

Diodes are key components in on-chip electrostatic discharge (ESD) protection design. As the operating frequency of the microchip being protected against the ESD continues to increase, the parasitic capacitance associated with the diodes in the ESD structure starts to impose problems for RF operation. This paper presents a systematic approach to optimize the diode structure for minimal parasitic capacitance based on the requirements of breakdown voltage and heat dissipation. Device simulator Atlas with mix-mode simulation capability is calibrated against measurement data and used to carry out the optimization. An optimized diode structure with a parasitic capacitance of less than 30 fF at an operating frequency of 10 GHz and ESD charging voltage of 1 kV has been suggested. Furthermore, a case study to implement and optimize the ESD protection structure based on an existing 0.13-μm CMOS technology has been presented and verified.     

The Cost of Diversity in Textile Finishing

The effect on specific operating and capital costs of textile finishing, incurred by catering for the demands of a wide range of customers in varied styles, is illustrated. The return on investment in a new factory planned to operate under these conditions is realistically examined and a view expressed on the likely pattern of future investment in textile finishing.     

Electrical isolation design rule for GaAs integrated circuitsfabricated on semi-insulating substrates

The characteristics of n-semi-insulating-n (n-si-n) structures that dictate the design rules for electrical isolation between active devices of GaAs integrated circuits fabricated on semi-insulating substrates are studied by one-dimensional and two-dimensional numerical simulations. It is found that the I-V characteristics of these structures are characterized by sharp current-rising regions which result from a potential barrier lowering effect caused by the punchthrough phenomenon. Simplified expressions are derived for quick evaluation of the punchthrough voltages for both one-dimensional and two-dimensional analyses. For a given operating voltage, the one-dimensional calculation gives a larger spacing between n regions in a n-si-n structure for onset of large current flow than does the two-dimensional analysis. Therefore, the spacing obtained from one-dimensional results can be used as a conservative design criterion for device isolation. For more aggressive electrical isolation design, two-dimensional simulation is necessary since it provides more accurate results