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由聚(琥珀酰亚胺-乳酸)的碱溶液水解反应制备了含有亲水性羧基的聚(天冬氨酸-co-乳酸)(PAL)。用IR、NMR、DSC、元素分析等方法表征了PAL的组成和结构。结果表明,PAL中的聚乳酸链段为间同立构或无规立构,由此推断丙交酯在开环聚合反应时发生了酯交换或链转移反应,导致聚乳酸链段产生消旋现象;聚合反应机理是羟基引发的聚合,获得了无定型态聚合物PAL。由于共聚反应中丙交酯熔体的蒸发损耗,合成的PAL中聚天冬氨酸的含量高于理论值。 相似文献
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在微波辐射作用下,以辛酸亚锡为催化剂,胆固醇为共引发剂引发L-丙交酯开环聚合制备了一组胆固醇-(L-乳酸)n低聚物(C-LAn),采用红外光谱、核磁共振氢谱、凝胶渗透色谱、差示扫描量热法、偏光显微镜和小角X射线衍射研究了产物的结构与性能。结果表明,C-LAn低聚物的相对分子质量可以通过改变n(胆固醇)∶n(L-丙交酯)值进行调控,其结构是由胆固醇端基和聚乳酸螺旋链构成的层状结构;C-LAn低聚物兼有结晶性和液晶性,且受低聚物分子中聚(L-乳酸)链段的长度影响,随着聚(L-乳酸)链段增长,低聚物呈现液晶态的温度区间变窄、温度升高。 相似文献
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以2-苄基三硫代碳酸酯基乙醇为引发剂,在辛酸亚锡催化下引发丙交酯(LA)开环聚合,合成大分子链转移剂PLA macro-CTA,加入第二单体聚甲基丙烯酸N,N-二甲氨基乙酯(DMAEMA),通过可逆-加成-断裂链转移(RAFT)自由基聚合,得到两亲性嵌段共聚物PLA-b-PDMAEMA。采用核磁共振光谱(1 HNMR和13 CNMR)、红外光谱(FT-IR)及凝胶色谱(GPC)对合成的共聚物化学结构进行表征,并通过接触角测试和热重分析(TGA)对其进行性能测试。结果表明成功合成了嵌段共聚物且分子量分布指数较窄;引入PDMAEMA链段后聚乳酸的热稳定性和亲水性得到提高。 相似文献
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Production planning and scheduling are becoming the core of production management, which support the decision of a petrochemical company. The optimization of production planning and scheduling is attempted by every refinery because it gains additional profit and stabilizes the daily production. The optimization problem considered in industry and academic research is of different levels of realism and complexity, thus increasing the gap. Operation research with mathematical programming is a conventional approach used to address the planning and scheduling problem. Additionally, modeling the processes, objectives, and constraints and developing the optimization algorithms are significant for industry and research. This paper introduces the perspective of production planning and scheduling from the development viewpoint. 相似文献
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目的 探索江门世遗文化的传承、发展和转化的新思路,践行国家在《粤港澳大湾区发展规划》纲要中要求江门承担与港澳地区文化创意合作与开发任务的分工。方法 与澳门高校紧密合作,开展专业培训课程,以开平碉楼为例,从人文视角开展设计研究,梳理开平碉楼的文化脉络,把世遗文化的元素和其背后的文化融入文创产品中,提升文创产品的附加值,推动当地文创产业结构的变革。结果 两地高校构建了稳定的科研团队,开设长期有效的设计培训课程,与景区建立了研究协作关系,帮助景区构建了一套产销研的商业模式。结论 以跨区域高校合作为平台,以文创产品为抓手,依托江澳两地的资源优势,可以构建江门世遗文化全新的品牌形象,最终推动开平世遗文化的活化。 相似文献
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Error and uncertainty in modeling and simulation 总被引:1,自引:0,他引:1
William L. Oberkampf Sharon M. DeLand Brian M. Rutherford Kathleen V. Diegert Kenneth F. Alvin 《Reliability Engineering & System Safety》2002,75(3)
This article develops a general framework for identifying error and uncertainty in computational simulations that deal with the numerical solution of a set of partial differential equations (PDEs). A comprehensive, new view of the general phases of modeling and simulation is proposed, consisting of the following phases: conceptual modeling of the physical system, mathematical modeling of the conceptual model, discretization and algorithm selection for the mathematical model, computer programming of the discrete model, numerical solution of the computer program model, and representation of the numerical solution. Our view incorporates the modeling and simulation phases that are recognized in the systems engineering and operations research communities, but it adds phases that are specific to the numerical solution of PDEs. In each of these phases, general sources of uncertainty, both aleatory and epistemic, and error are identified. Our general framework is applicable to any numerical discretization procedure for solving ODEs or PDEs. To demonstrate this framework, we describe a system-level example: the flight of an unguided, rocket-boosted, aircraft-launched missile. This example is discussed in detail at each of the six phases of modeling and simulation. Two alternative models of the flight dynamics are considered, along with aleatory uncertainty of the initial mass of the missile and epistemic uncertainty in the thrust of the rocket motor. We also investigate the interaction of modeling uncertainties and numerical integration error in the solution of the ordinary differential equations for the flight dynamics. 相似文献
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New measurements are reported for the density and viscosity of tetralin and trans-decalin. The density was determined from room temperature to 60°C for tetralin and to 95°C for trans-decalin. The kinematic viscosity was measured up to temperatures slightly above 100°C. Our results improve upon the values recommended by the American Petroleum Institute for these liquids. 相似文献
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Ravinder Koul 《工程教育杂志》2018,107(2):219-237
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Masao Doyama 《Bulletin of Materials Science》1999,22(3):723-728
By making a step on one surface (
) of a rectangular small paralellepiped copper crystal, dislocations could be created by the molecular dynamic method. The
dislocation created was not a complete edge dislocation but a pair of Heidenreich-Shockley partial dislocations. Each time
a dislocation was created, the stress on the surface was released. Small copper crystals having a notch were pulled (until
fracture), compressed and buckled by use of the molecular dynamic method. An embedded atom potential was used to represent
the interaction between atoms. Dislocations were created near the tip of the notch. A very sharp yield stress was observed.
The results of high speed deformations of pure silicon small crystals using the molecular dynamics are presented. The results
suggest that plastic deformation may be possible for the silicon with a high speed deformation even at room temperature. Another
small size single crystal, the same size and the same surfaces, was compressed using molecular dynamic method. The surfaces
are {110}, {112} and {111}. The compressed direction was [111]. It was found that silicon crystals are possible to be compressed
with a high speed deformation. This may suggest that silicon may be plastically deformed with high speed deformation. 相似文献
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SMC/BMC废弃物对工业及环境造成了很大影响,指出了SMC/BMC回收再利用的紧迫性。通过对目前国际上SMC/BMC回收再利用的3种典型途径优缺点的对比,参照国外SMC/BMC回收再利用的先进方法,对我国SMC/BMC回收再利用提供了可行的建议. 相似文献
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Albert C. Parr 《Journal of research of the National Institute of Standards and Technology》2001,106(1):151-186
The national measurement system for photometric and radiometric quantities is presently based upon techniques that make these quantities traceable to a high-accuracy cryogenic radiometer. The redefinition of the candela in 1979 provided the opportunity for national measurement laboratories to base their photometric measurements on optical detector technology rather than on the emission from high-temperature blackbody optical sources. The ensuing technical developments of the past 20 years, including the significant improvements in cryogenic radiometer performance, have provided the opportunity to place the fundamental maintenance of photometric quantities upon absolute detector based technology as was allowed by the 1979 redefinition. Additionally, the development of improved photodetectors has had a significant impact on the methodology in most of the radiometric measurement areas. This paper will review the status of the NIST implementation of the technical changes mandated by the 1979 redefinition of the candela and its effect upon the maintenance and dissemination of optical radiation measurements. 相似文献