Author Keywords: trimethylaluminium hydrolysate; stereoregular; poly(propylene oxide); fractionation; end-group analysis; cyclic oligomers 相似文献
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21.
内建自测试(Built-in Self Test,BIST)是测试片上系统(System on- Chip,SoC)中嵌入式存储器的重要技术;但是,利用BIST技术采用多种算法对嵌入式存储器进行测试仍面临诸多挑战;对此,提出了一种基于SoC的可以带有多种测试算法的嵌入式DRAM存储器BIST设计,所设计的测试电路可以复用状态机的状态,利用循环移位寄存器(Cyclic Shift Register,CSR)产生操作命令,利用地址产生电路产生所需地址;通过对3种BIST电路支持的算法,全速测试,面积开销3个方面的比较,表明提出的嵌入式DRAM存储器BIST设计在测试时间,测试故障覆盖率和测试面积开销等各方面都取得了较好的性能. 相似文献
22.
The effect of thermal shock on the spalling of oxides from the surfaces of several commercial alloys was determined. The average cooling rate was varied from approximately 240°C/sec to less than 1.0°C/sec during cyclic oxidation tests in air. The tests consisted of 100 cycles of 1 hr at the maximimum temperature (1100 or 1200°C). The alloys were HOS-875, TD-Ni, TD-NiCrAl, In-601, In-702, and B-1900 plus Hf. All of these alloys exhibited partial spalling within the oxide rather than total oxide loss down to bare metal. Thermal shock resulted in deformation of the metal, which in turn resulted, in most cases, in change of the oxide failure mode from compressive to tensile. Tensile failures were characterized by cracking of the oxide and little loss, while compressive failures were characterized by explosive loss of platelets of oxide. This behavior was confirmed by examination of mechanically stressed oxide scales. The thermally shocked oxides spalled less than the slow-cooled samples with the exception of TD-NiCrAl. This material failed in a brittle manner rather than by plastic deformation. The HOS-875 and the TD-Ni did not spall during either type of cooling. Thus, the effect of thermal shock on spalling is determined, in large part, by the mechanical properties of the metal. 相似文献
23.
Partially stereoregular poly(propylene oxide) samples were synthesized via reactions catalysed by a preformed analytically defined trimethylaluminium hydrolysate. These samples were fractionated into two contrastingly different fractions.
1. (i) D-polymers: This fraction constituted the major part (up to 90%). It mainly contained cyclic low molecular weight oligomers (MW < 1000). The linear chains found in D-polymers had hydroxyl end groups. No double bonds could be detected spectroscopically.
2. (ii) K-polymers: This fraction was high molecular weight stereoregular polymer. Stepwise thermal precipitation from dilute isooctane solution of K-polymers yielded a succession of fractions which differed in melting point. It appears that the phase equilibria during the thermal precipitations were not controlled by the molecular weights of species.
24.
花岗岩残积土在华南、东南沿海、南岳、新疆等地区广泛分布,前人的研究多集中在结构性及微观特性上,后循环加载、位移演化、土壤密度等因素对筋-土界面的剪切特性及加筋作用效果的影响评估研究较少。从循环试验剪切刚度这一重要参数入手,以加载次数、加载频率值、位移振幅值、土壤重度值为自变量,应用控制变量法,通过设计循环直剪试验,得到加筋花岗岩残积土的剪切应力与剪切位移、垂直位移与剪切位移关系曲线进行观察对比,结果表明:花岗岩残积土土工格栅界面剪切刚度受位移半振幅、土壤干重度影响很大,受加载频率影响很小,循环加载并没有弱化后循环界面剪切强度,剪切位移与位移半振幅呈负相关关系。 相似文献
25.
循环结构在C程序设计中占据重要的位置,是教学中的重点,同时也是教学中的难点。在教学中,如何使学生建立“循环”的概念、理解“循环”的含义、设计“循环”算法、实现“循环”功能,是教学设计的重点。通过对循环结构教学设计,理清教学思路,明确教学目标,化解教学难点、突出教学重点,寓趣味性、目标性于教学中,采用了项目引导、任务驱动、演示法、分析法、讨论法等多种教学方法,调动学生学习的积极性,培养学生程序设计能力。 相似文献
26.
具有层状结构的磷酸锆α-Zr(HPO4)2·H2O通过粉末X-射线衍射(XRD),振动光谱(红外IR和拉曼光谱Raman),热分析仪(TG),透射电子显微镜(TEM),扫描电子显微镜(SEM)和BET氮气吸附等手段进行了表征.所制备的α-Zr(HPO4)2·H2O的BET表面积为12.29 m^2/g.研究了α-Zr(HPO4)2·H2O的插入行为,与四甲基溴化铵和十六烷基三甲基溴化铵的插入反应表明插入是完全的,层间距分别增加了0.46 nm和1.68 nm,且插入化合物的荧光性质在室温被检测. 相似文献
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Branched-chain/cyclic alkanes have been obtained, by solvent extraction and molecular-sieve adsorption, from a UK low-temperature (Rexco) coal tar, a USA fluidized-bed pyrolysis (FMC COED) coal tar, and a novel supercritical-gas-extract of a Turkish (Elbistan) lignite. Mass spectrometry (with gas chromatography and field-desorption) established the presence of mono-, di (including sesquiterpanes), tri-, tetra- (steranes only), and pentacyclic (triterpanes only) alkanes, including several steranes and triterpanes not previously reported as coal-tar constituents. The potential of cyclic alkanes as geochemical markers, even for commercial coal products subjected to appreciable heat treatment, is demonstrated by the identification of C12, C13, C15 and C16 dicyclics (including isoprenoid alkanes), C17-C26 tricyclics, and C27 and C29 hopane-type pentacyclics (triterpanes) in FMC, and of C16-C38 monocyclics, C34-C36 dicyclics, C22-C36 tricyclics, C27-C30 tetracyclics (steranes), and C27, C29, C30, C31, C32, and C33 hopane-type pentacyclics (triterpanes) in Rexco tar. Tetra- and pentacyclic alkanes were also preserved in the lignite extract. 相似文献
30.
Julian Chojnowski 《Journal of Inorganic and Organometallic Polymers》1991,1(3):299-323
Some basic aspects of the kinetics and mechanisms of anionic and cationic ring-opening polymerization of cyclic siloxanes are discussed in connection with their use in polymer synthesis. The emphasis is put on the polymerization of strained ring monomers, such as cyclic trisiloxanes, since these provide the possibility of tailoring the polymer structure. Much attention is devoted to association phenomena and to oligomer formation processes.This review is from the Second International Topical Workshop, Advances in Silicon-Based Polymer Science. 相似文献