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61.
Throughout much of the parallel processing community there is the sense that writing software for distributed-memory parallel processors Is subject to a ‘no pain—no gain’ rule: that In order to reap the benefits of parallel computation one must first suffer the pain of converting the application to run on a parallel machine. We believe this Is the result of Inadequate programming tools and not a problem Inherent to parallel processing. We will show that one can parallelize real scientific applications and obtain good performance with little effort If the right tools are used. Our vehicle for this demonstration is a 6000-line DNA and protein sequence comparison application that we have implemented in Mental, an object-oriented parallel processing system for both parallel and distributed architectures. We briefly describe the application and present performance information for both the Mentat version and a hand-coded parallel version of the application. 相似文献
62.
将能效标准规定的水冷和风冷螺杆空压机的能效值绘制成曲线,进行取值的变化趋势分析;将水冷输入比功率和风冷输入比功率进行差值对比分析,提出能效标准规定值的欠合理内容,目的在于实现标准取值的合理化。 相似文献
63.
"Reactive-templated grain growth" (RTGG) processing of Bi1/2 Na1/2 TiO3 (BNT)-based ceramics is reported. Molten salt synthesis was used to prepare platelike (∼0.2 μm × 5 μm × 5 μm) Ruddlesden–Popper (Sr3 Ti2 O7 (ST)) and Aurivillius (BaBi2 Nb2 O9 (BBN)) phases which were used as "templates" in studies of RTGG with BNT-based matrixes. A "citrate-gel" route was designed to produce intimately mixed, fine-grain matrixes for these studies. The analytical techniques used were powder X-ray diffraction and microstructural examination of dry-pressed and fired compacts. For mixtures templated with BBN, single-phase perovskite readily formed, and an initially heterogeneous microstructure evolved toward a dense assemblage of anisometric, micrometer-scale grains. Perovskite formation was more sluggish in the mixtures templated with ST, and the final sintered microstructure featured larger, porous grains in an equiaxed, micrometer-scale matrix. A qualitative model, which examined the excess constituents in the matrix after formation of stoichiometric ABO3 perovskite, is proposed to explain the observations. The model predicted an excess of Na2 O and TiO2 in the matrix in the case of BBN templates and only excess TiO2 in the case of ST templates. The results indicate that careful examination of matrix and template chemistry could be important in the selection of systems for RTGG processing. 相似文献
64.
The phase diagram for the CuO-rich part of the La2 O3 ─CuO join was redetermined. La2 Cu2 O5 was found to have a lower limit of stability at 1002°± 5°C and an incongruent melting temperature of ∼1035°C. LagCu7 O19 had both a lower (1012°± 5°C) and an upper (1027°± 5°C) limit of stability. Subsolidus phase relations were studied in the La2 O3 ─CuO─CaO system at 1000°, 1020°, and 1050°C in air. Two ternary phases, La1.9 Ca1.1 Cu2 O5.9 and LaCa2 Cu3 O8.6 , were stable at these temperatures, with three binary phases, Ca2 CuO3 , CaCu2 O3 , and La2 CuO4 . La2 Cu2 O5 and La8 Cu7 O19 were stable only at 1020°C, and did not support solid-solution formation. 相似文献
65.
The electrical properties of ceramic BaTiO3 were investigated by ac impedance spectroscopy over the ranges 25°-330°C and 0.03 Hz-1 MHz. Results are compared with those obtained from fixed-frequency measurements, at 1 kHz and 100 kHz. Fixed-frequency Curie-Weiss plots show deviations from linearity at temperatures well above t c . The ac measurements show that grain boundary impedances influence Curie-Weiss plots in two ways: at high temperatures, they increasingly dominate the fixed-frequency permittivities; at lower temperatures, closer to T c , the high-frequency permittivity contains a contribution from grain boundary effects. Methods for extraction of bulk and grain boundary capacitances from permittivity and electric modulus complex plane plots are discussed. The importance of selecting the appropriate equivalent circuit to model the impedance response is stressed. A constriction impedance model for the grain boundary in BaTiO3 ceramics is proposed: the grain boundary capacitance is neither temperature-independent, nor shows Curie-Weiss behavior. The grain boundary is ferroelectric, similar to the grains, but its impedance is modified by either air gaps or high-impedance electrical inhomogeneity in the region of the necks between grains; the activation energy of the constriction grain boundary impedance differs from that of the bulk, suggesting differences in defect states or impurity levels. 相似文献
66.
Two cubic pyrochlore phases exist in the system ZnO–Bi2 O3 –Sb2 O5 . Neither has the supposed "ideal" stoichiometry, Zn2 Bi3 Sb3 O14 . One, P 1 , is a solid solution phase, Zn2+ x Bi2.96−( x − y ) Sb3.04− y O14.04+δ where 0< x <0.13(1), 0< y <0.017(2) and a =10.4285(9)−10.451(1) Å. The other, P 2 , is a line phase, Zn2 Bi3.08 Sb2.92 O13.92 with a =10.462(2) Å. Subsolidus phase relations at 950°C involving phases P 1 and P 2 in the ZnO–Bi2 O3 –Sb2 O5 phase diagram have been determined. 相似文献
67.
针对准噶尔盆地西部隆起乌夏断裂带的碳酸氢钠岩层安全钻进问题,开展了碳酸氢钠岩层钻井液体系的研究。由室内研究结果得到,用42%复合盐水溶液作基液配制钻井液,可以抑制碳酸氢钠岩层的溶解,提高钻井液抗CO32-和HCO3-离子污染的能力。性能评价结果表明,该钻井液抗CO32-和HCO3-离子的总浓度在100 000 mg/L以上;该钻井液具有较强的抑制性能和较好的润滑性能,可以抗5%NaCl、5%劣质土或1%Ca2+的污染;膨润土块在该钻井液中热滚后的一次回收率达94.76%,二次回收率达85.28%,配方在不加润滑剂情况下的极压润滑系数为0.168,摩阻系数为0.083 9。指出,现场需根据实际情况适时调整复合盐中各种盐的比例以及复合盐的加量,保证Cl-离子含量不低于160 000 mg/L,将钻井液的pH值控制在9以上,及时补充各处理剂的量。 相似文献
68.
James W. Rosner Alfred E. Thal Jr. Christopher J. West 《Canadian Metallurgical Quarterly》2009,135(8):710-717
The design-build (DB) method for construction project delivery continues to grow in both the private and public sector; additionally, research has shown that the DB method outperforms the design-bid-build (DBB) method. The Air Force has applied the results of these previous research efforts to its military construction (MILCON) program without performing empirical studies to validate the approach. Therefore, the objective of this study was to compare the performance of the DB delivery method with the traditional DBB approach for the Air Force MILCON program. Data related to 835 (278 DB and 557 DBB) MILCON projects for fiscal years 1996–2006 were subsequently analyzed. The DB method had better performance in three of six metrics with the performance being significantly better for cost growth and the number of modifications per million dollars. The traditional DBB method performed significantly better in terms of total project time. Furthermore, the DB method was best suited for various facility types. This study provides empirical evidence of how the DB method provides an advantage over the traditional DBB method for Air Force MILCON projects. 相似文献
69.
70.
Kim Karen Hye-cheon; Bursac Zoran; DiLillo Vicki; White Della Brown; West Delia Smith 《Canadian Metallurgical Quarterly》2009,28(1):131
Objective: Stress has been identified as a significant factor in health and in racial/ethnic health disparities. A potential mediator in these relationships is body weight. Design: Cross-sectional and longitudinal relationships between stress, race, and body weight were examined in an ethnically diverse sample of overweight and obese women with Type 2 diabetes (n = 217) enrolled in a behavioral weight loss program. Main Outcome Measures: Stress (Perceived Stress Scale) was assessed at baseline only and body weight (body mass index) was assessed at baseline and 6 months. Results: Stress was not related to baseline body weight. With every 1 unit lower scored on the baseline stress measure, women lost 0.10 kg ± .04 more at 6 months (p 相似文献