NMR Fingerprinting of Chemical Changes in Asphalt Fractions on Oxidation

Abstract

The composition of asphalt has been the subject of much study because such data are required in determining its performance-related properties. A problem inherent in studying asphalt composition is its chemical complexity; however, the characterization of asphalt can be better achieved by separating into fractions. In this work, the chemical property of commercial-grade asphalt obtained from BAPCO refinery, Bahrain (BH), was carried out. The rolling thin-film oven (RTFO), used for short-term aging, and pressurized aging vessel (PAV), used for long-term aging, ASTM D4124 (1991) method was used to separate fresh and aged asphalt into four generic fractions such as asphaltenes, polar aromatics, naphthene aromatics, and saturates. The Corbett fractionation procedure was used to separate fresh and aged asphalt into four generic fractions such as asphaltenes, polar aromatics, naphthene aromatics, and saturates. Nuclear magnetic resonance (NMR) was employed to fingerprint the chemical changes that occurred in asphalt during the aging processes. NMR measurements of asphalt fractions showed that during aging, isomerization and dehydrogenation types of reactions took place. Significant differences were observed between the structure and composition of fresh and aged fractions of asphalt. Results from NMR spectrometry provided significant information concerning the chemical transformations that occurred during the aging processes.     

CO_2 激光切割金属材料的工艺参数与性能关系的研究

本文研究了用 CO_2激光切割金属材料时,切割工艺参数对热影响区显微组织及力学状况的影响和相互关系.结果得出,激光切割淬火回火态金属材料时,热影响区由表及里出现三层不同的显微组织,即白亮的熔化层,相变硬化层(它由白色的淬火层和灰色的回火层组成),以及黑色的回火层.对各层形成的原因及其显微硬度,残余应力场的分布进行了分析试验结果说明,对一些特殊性能下使用的金属材料,既须考虑切割参数对切割表面质量的影响,还须考虑它们对热影响区显微组织和力学状态的影响.不同材料应根据情况选用优选工艺参数.     

利用软件线程集成技术实现硬件到软件的转移

该文介绍了线程集成，一种在通用单片微处理器或微控制器上低耗并行执行的新方法，后级编译技术有效地插入多个控制线程，并提供细粒度的多个线程而不用上下文切换的方法，这样允许用软件完成实时的功能来代替专用外围硬件。该文研究了在主线程中集成实时客户线程时的代码转移，生成的集成线程能满足所有的实时性，线程集成的概念和代码转移被应用到实际中来检验这种方法的可行性。     

壁面凸体层流绕流流场的数值计算

采用贴体坐标变换方法将直角坐标系中不规则的流动区域变换成规则的计算区域．对求解原始变量（ｕｋ，ｐ）的ＳＩＭＰＬＥＲ方法进行了改进，应用有限分析法给出了由正常网格求解原始变量的选代方法．然后计算了台阶绕流和任意凸体绕流的流速、压力场．计算结果表明该方法简单有效，压力、速度收敛效果好，计算精度较高．可以用于计算各种流动区域的流场．     

A survey of database design transformations based on the Entity-Relationship model

At present, the Entity-Relationship (ER) model is the most important paradigm for conceptual database design. Since the model was introduced in the mid-seventies, a large body of literature has been published on transforming conceptual ER schemas or diagrams into logical data models. The purpose of this paper is to survey this literature. A first focus is on transformation approaches from the ER model to traditional data models, i.e. to the relational, the network, or the hierarchical model; this is then complemented by a discussion of more recent transformations to object-oriented models. A second focus is on considering the process of reverse engineering, i.e. transformations from a logical model back into the ER model; finally, an overview of direct transformations between various logical data models is presented.     

Phase transformations in thermally exposed Au-Al ball bonds

Gold-aluminum ball bonds were thermally exposed at constant elevated temperatures, and the resultant phase transformations studied in detail. The as-bonded microstructure of a Au-Al ball bond essentially consisted of a reaction zone (termed “alloyed zone” (AZ) in the as-bonded condition) between the Au bump and the bonded Al metallization. It is the growth of the reaction zone between the Au bump and the bonded Al metallization and also the nonbonded Al metallization during thermal exposure that gave rise to the various phase transformations. Au₄Al, Au₈Al₃, and Au₂Al are the predominant phases that grew across the ball bond until the bonded Al metallization is available to take part in the interdiffusion reactions. After the complete consumption of the bonded Al metallization, the Au-Al phases reverse transformed resulting in the formation of the Au₄Al phase in the entire reaction zone across the ball bond (RZ-A). The lateral interdiffusion reactions resulted in the nucleation and the growth of all of the Au-Al phases given by the phase diagram. Kidson’s analysis and Tu et al.’s treatment were extended to a five-phase binary system to explain the phase transformations in thermally exposed Au-Al ball bonds. It is possible for all of the Au-Al phases to grow across a ball bond uninhibited as long as the bonded metallization is available. However, the supply limitation of the bonded metallization gives rise to reverse transformations where Al-rich phases transform to Au-rich phases and eventually result in the formation of the Au₄Al phase in the entire RZ-A. If infinite time is allowed, Au₄Al would dissolve; the extent of which is dependent on the solubility of Al in Au. No supply of Au lateral to the bond causes the reverse transformation of the Au₄Al phase, giving rise to the lateral growth of the remaining Au-Al phases. If infinite time is allowed, the lateral phase transformations would result in the formation of a phase that is dependant on the relative proportion of Au and Al present in the nonbonded metallization (NBM) and Au₄Al below the void line. Hence, the presence of a phase in a particular location of a ball bond is dependent on the time and temperature of thermal exposure.     

Specific Features of Thermochemical Processes in High‐Temperature Coke of Polymer Composite Materials

The temperature fields in coked layers of polymer composite materials (fiberglass plastics) under hightemperature heating and subsequent cooling in a cold oxidizer flow are experimentally studied. Based on the analysis of experimental data and numerical research, it is shown that exothermal chemical reactions can proceed in the coked layer of fiberglass plastics, which creates conditions for maintaining high temperatures in the compositecoke layer during a rather long time.     

Modular analysis and design of log-domain circuits based on LIN↔ELIN transformations

We systematized and developed some procedures for the modular design of externally-linear internally nonlinear (ELIN) circuits resulting in a general LIN↔ELIN transformation procedure. This one was also extended to analysis of these types of circuits. The procedure is exemplified on log-domain circuits. In the design one starts with the linear block diagram (LIN) described by transfer functions and one substitutes directly each linear building block by a corresponding nonlinear one. The parameters of each nonlinear component depend on the given parameters of its linear correspondent. Input F ⁻¹ and output F blocks are added. In the analysis one identifies the nonlinear basic circuit components and each of them is substituted by its corresponding linear building block. Input and output F ⁻¹-F cells are removed. The ideal transfer function can be calculated on the linear block diagram now. The LIN↔ELIN transformations make a direct connection between equivalent linear and ELIN circuits, simplify their design and analysis procedures and permit the development of CAD procedures.     

灰色Verhulst 预测模型的数乘特性

为揭示灰色Verhulst模型的建模精度在系统原始特征序列数乘变换前后的变化规律,降低其建模复杂性,研究了灰色Verhulst模型的建模参数在系统原始特征序列经过数乘变换前后的量化关系以及数乘变换对该模型建模精度的影响程度.研究结果表明,灰色Verhulst模型的建模精度与系统原始数据序列的数乘变换无关.利用数乘变换能降低原始数据的量级,简化建模过程,而不会改变灰色Verhulst模型的建模精度.