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41.
Schutte JF Reinbolt JA Fregly BJ Haftka RT George AD 《International journal for numerical methods in engineering》2004,61(13):2296-2315
Present day engineering optimization problems often impose large computational demands, resulting in long solution times even on a modern high-end processor. To obtain enhanced computational throughput and global search capability, we detail the coarse-grained parallelization of an increasingly popular global search method, the particle swarm optimization (PSO) algorithm. Parallel PSO performance was evaluated using two categories of optimization problems possessing multiple local minima-large-scale analytical test problems with computationally cheap function evaluations and medium-scale biomechanical system identification problems with computationally expensive function evaluations. For load-balanced analytical test problems formulated using 128 design variables, speedup was close to ideal and parallel efficiency above 95% for up to 32 nodes on a Beowulf cluster. In contrast, for load-imbalanced biomechanical system identification problems with 12 design variables, speedup plateaued and parallel efficiency decreased almost linearly with increasing number of nodes. The primary factor affecting parallel performance was the synchronization requirement of the parallel algorithm, which dictated that each iteration must wait for completion of the slowest fitness evaluation. When the analytical problems were solved using a fixed number of swarm iterations, a single population of 128 particles produced a better convergence rate than did multiple independent runs performed using sub-populations (8 runs with 16 particles, 4 runs with 32 particles, or 2 runs with 64 particles). These results suggest that (1) parallel PSO exhibits excellent parallel performance under load-balanced conditions, (2) an asynchronous implementation would be valuable for real-life problems subject to load imbalance, and (3) larger population sizes should be considered when multiple processors are available. 相似文献
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我们曾报道了某些芳香族氨羧酸类化合物的促排效果,并讨论了它们的结构与促排效果之间的关系。这些化合物的特点是对钍和稀土核素铈(~(144)Ce)都有较好的促排效果,有的化合物对钍促排效果优于811或相似于811。但在药理试验中观察到有的化合物毒性和稳定性未达理想要求,所以对一些效果较好的化合物进行结构改造,以图获得高效低毒且又稳定的药物。8102为1,2-二羟基3,6-双甲基亚胺基二乙酸的衍化物,是近年来经结构改造后较为理想的促排药物之一。本文主要报道8102对钍的促排疗效。 相似文献
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<正>近日,瓜子二手车联合《互联网周刊》发布了“2022年9月新车商线上销量排行榜”。9月是传统的二手车消费旺季,随着流通便利政策和购车利好的落地,政策组合拳效应持续发挥,消费者购车意愿加速释放。目前,新车商依托线上平台打开卖车新增量,覆盖全国的线上销售拓宽了增收渠道,二手车销售情况持续向好。榜单数据显示,9月新车商线上平均销量环比增长近70%,销量TOP20新车商线上平均销量环比增长近100%,增幅领跑行业。 相似文献
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Reversed-phase, packed capillary liquid chromatography interfaced by electrospray ionization to mass spectrometry was explored as an analytical method for determination of metabolites in microscale tissue samples using single islets of Langerhans as a model system. With the use of a 75 microm inner diameter column coupled to a quadrupole ion trap mass spectrometer in full scan mode, detection limits of 0.1-33 fmol were achieved for glycoloytic and tricarboxylic acid cycle metabolites. Reproducible processing of islets for analysis with little loss of metabolites was performed by rapid freezing followed by methanol-water extraction. The method yielded 20 microL of extract of which just 15 nL was injected suggesting the potential for performing multiple assays on the same islet. Approximately 200 presumed metabolites could be detected, of which 22 were identified by matching retention times and MS/MS spectra to standards. Relative standard deviations for peak detection was from 7 to 18% and was unaffected by storage for up to 11 days. The method was used to detect changes in metabolism associated with increasing extracellular islet glucose concentration from 3 to 20 mM yielding results largely consistent with known metabolism of islets. Because most previous studies of islet metabolism have only observed a few compounds at once and require far more tissue, this measurement method represents a significant advance for studies of metabolism of islets and other microscale samples. 相似文献
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本工作研究了一种含钇的、在较低温一次烧结的SrTiO3 GBBL电容器材料,该材料具有制备工艺简单、有效介电常数频散较小、损耗较低等优点. 相似文献
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Marginean I Kelly RT Prior DC LaMarche BL Tang K Smith RD 《Analytical chemistry》2008,80(17):6573-6579
A detailed characterization of a conventional low-flow electrospray ionization (ESI) source for mass spectrometry (MS) using solution compositions typical of reversed-phase liquid chromatography is reported. Contrary to conventional wisdom, the pulsating regime consistently provided better ESI-MS performance than the cone-jet regime for the interface and experimental conditions studied. This observation is supported by additional measurements showing that a conventional heated capillary interface affords more efficient sampling and transmission for the charged aerosol generated by a pulsating electrospray. The pulsating electrospray provided relatively constant MS signal intensities over a wide range of voltages, while the signal decreased slightly with increasing voltage for the cone-jet electrospray. The MS signal also decreased with increasing emitter-interface distance for both pulsating and cone-jet electrosprays due to the expansion of the charged aerosol plume. At flow rates below 100 nL/min, the MS signal increased with increasing flow rate due to increased number of gas-phase ions produced. At flow rates greater than 100 nL/min, the signal reached a plateau due to decreasing ionization efficiency at larger flow rates. These results suggest approaches for improving MS interface performance for low-flow (nano- to micro-) electrosprays. 相似文献