D,L-乳酸、L-乳酸、羟基乙酸的均聚物及共聚物的结晶性能研究

合成了高分子量的聚Ｄ,Ｌ－乳酸、聚Ｌ－乳酸、聚羟基乙酸、Ｄ,Ｌ－乳酸和共聚物以及乙酸和Ｄ,Ｌ－乳酸共聚物。以ＷＡＸＤ、ＦＴ－ＩＲ、ＤＴＡ表征了上述系列聚合物的结晶性能,分析了单体种类和共聚物中单体的比例对聚合物中结晶性能的影响,并对该系列聚合物的晶区结构作了描述。用万能拉力计测试了ＰＬＡ系列聚合物的力学性能,以ＤＴＡ测定了ＰＧＬＡ系列聚合物的热性能,探讨通过调整聚合物的组成以改变其结晶特性来调控聚     

PLGA/PCL复合材料的制备及其性能研究

在聚乳酸-羟基乙酸(PLGA)中加入聚ε-己内酯(PCL)、柠檬酸三丁酯(TBC),通过溶液共混制备了PLGA/PCL共混聚合物,通过静电纺膜及涂膜法制备了不同比表面积的降解膜,并对共混材料力学性能和膜的降解性能进行了研究。结果表明:柠檬酸三丁酯作为增容剂对整个共混聚合物的韧性和强度有明显的影响;当聚乳酸-羟基乙酸和聚ε-己内酯的质量比为80/20、增容剂柠檬酸三丁酯的用量为6%时,所得共混聚合物的断裂伸长率达到130%、冲击强度达到9.55kJ·m-2。相同条件下加入聚ε-己内酯(PCL)的膜的降解性能优于单一的聚乳酸-羟基乙酸(PLGA)膜,静电纺丝膜降解性能优于流延法膜。     

微生物合成的聚羟基链烷酸在细胞内的积聚及提取

综述了以聚β－羟基丁酸为代表的可用作可降解塑料的聚羟基链 细胞内积聚的形态、动力学及其提取技术。     

纤维素改性生物塑料聚羟基脂肪酸酯的研究进展

基于国内外的研究现状,综述了生物塑料聚羟基脂肪酸酯(PHAs)的改性方法以及纤维素改性生物塑料聚羟基脂肪酸酯复合材料的制备工艺。同时,针对每一种纤维素改性生物塑料聚羟基脂肪酸酯复合材料的制备工艺,具体分析了纤维素改性生物塑料聚羟基脂肪酸酯复合材料结构和性能的变化,指出了每种制备工艺的优缺点。纤维素改性生物塑料聚羟基脂肪酸酯复合包装材料将成为今后包装材料领域的研究重点,且实现绿色生产与进一步改善二者复合后的材料性能,将是实现产业化生产的关键。     

可完全生物降解塑料的市场化进展

介绍了目前最具有市场前景的3类可完全生物降解塑料的性能(聚羟基脂肪酸酯、聚丁二酸丁二醇酯和聚乳酸)和国内外市场化进展。     

生物降解材料聚羟基乙酸及其结晶性能研究

聚羟基乙酸(以下简称PGA)是一种单元碳数最少的脂肪族聚酯,集优异的气体阻隔性、生物兼容性和可降解性于一身,极具发展潜力的新型包装材料,也是较重要的医用生物降解材料。采用逐级提高真空度和逐级升温的先进工艺流程,选用高效、环保的新型络合钛溶液作为催化剂,直接缩聚法制备高分子量PGA,研究了PGA在DMSO中重结晶前后的性能特点及对比。     

对聚乙酸乙烯酯乳液木材胶粘剂(白胶)中压缩剪切强度指标检测的探讨

聚乙酸乙烯酯乳液木材胶粘剂在装饰装修中被普遍使用，压缩剪切强度指标直接影响到聚乙酸乙烯酯乳液木材胶粘剂的质量，本文对压缩剪切强度指标的检测提出了更具体的检测操作过程，从而能获得准确的检测结果。     

聚[9-甲基-9-（8-硫代乙酸辛酯基）-芴]的合成及其金纳米粒子复合物

合成了一种新型的侧链含硫代乙酸辛酯基的聚芴衍生物,聚[9-甲基-9-(8-硫代乙酸辛酯基)-芴](PFMOTA).用这种聚合物修饰金纳米粒子,得到了稳定的PFMOTA/金纳米粒子复合物.采用TEM、GPC、FTIR、UV-vis和PL光谱对聚合物及其修饰的金纳米粒子复合物的结构和性能进行了表征.     

聚羟基乙酸接枝淀粉共聚物的合成和性能

以乙交酯和淀粉为原料,三乙胺为催化剂,在二甲基亚砜介质中合成了聚羟基乙酸接枝淀粉共聚物。讨论了原料配比和反应时间对共聚物接枝率(G)、接枝效率(E)和单体转化率(C)的影响。采用核磁共振谱仪(1H-NM R)、傅立叶变换红外光谱仪(FT-IR)、X射线粉末(多晶)衍射仪(XRD)、差式扫描量热仪(DSC)以及体外降解试验,研究了接枝共聚物的结构和性能。实验结果表明,将乙交酯单体和淀粉接枝共聚,可以得到一类新的可降解聚合物。     

纳米羟基磷灰石/丝素蛋白/聚己内酯复合超细纤维的制备及表征

通过静电纺丝法制备出纳米羟基磷灰石/丝素蛋白/聚己内酯复合超细纤维,利用扫描电镜、红外光谱仪、X射线衍射仪对纳米羟基磷灰石/丝素蛋白/聚己内酯复合超细纤维形貌和结构进行表征,并进行了拉伸测试。结果表明,随着超细纤维中羟基磷灰石含量的增加,纤维的直径逐渐降低,纤维中聚己内酯的结晶逐渐变差。相比于丝素蛋白/聚己内酯超细纤维,含有质量比为30%羟基磷灰石的复合超细纤维仍具有较好的力学性能。体外小鼠成纤维细胞(L929)培养表明,纳米羟基磷灰石/丝素蛋白/聚己内酯复合超细纤维对细胞没有毒性。     

Thermophysical properties of some key solids: An update

In 1985, the CODATA Bulletin published a Report of its Task Group on Thermophysical Properties of Solids which analyzed available data on, and gave recommended values for, the heat capacity of Cu, Fe, W, and Al₂O₃, the thermal expansion of Cu, Si, W, and Al₂O₃, the electrical resistivity of Cu, Fe, Pt, and W, the thermal conductivity of Al, Cu, Fe, and W, and the absolute thermopower of Pb, Cu, Pt, and W. The analysts for the different properties were R. B. Castanet, S. J. Collocott, P. D. Desai, C. Y. Ho, J. G. Hust, R. B. Roberts, C. A. Swenson, and G. K. White. The present paper is an updated version of the earlier report and includes more recent data which change some of the recommended values. notably the heat capacity of Cu and W and the thermal expansion of Si and W.     

Multi-response optimization of the electrical discharge machining of insulating zirconia

In this study, electrical discharge machining has been used to machine insulating zirconia via the assisting electrode method. The process parameter optimization was investigated by combining the Taguchi method with grey relational analysis. The application of Taguchi–grey relational analysis is proven to effectively improve the performance of electrical discharge machining in drilling insulating zirconia. The results of this analysis indicate that the final optimal process parameters are a peak current of 8 A, a pulse duration of 16?µs, a duty cycle of 0.5, and a flushing pressure of 6?MPa. Additionally, the material removal rate, electrode wear rate, and hole taper ratio increase by 39%, 1.5%, and 1.3%, respectively, which improves the grey relational grade by 6.8%. The electrical resistance test confirms that the conductivity of the conductive layer obtained using the final optimal process parameters is better than that of the conductive layer obtained using the initial optimal process parameters. Energy spectrum analysis reveals that the conductive layer is composed of C, Cu, Zn, Zr, and O. Analysis of variance shows that the most significant component of the multi-responses is the peak current, with a 51.4% contribution.     

Functional properties of ceramic-Ag nanocomposite coatings produced by magnetron sputtering

In recent years, the use of nanocomposite materials to functionalize surfaces has been investigated, taking advantage of the complementary properties of the nanocomposite constituents. Among this family of materials, ceramic-Ag coatings have been widely studied due to the large variety of functionalities that silver possesses and the possibility of tuning the coating’s practical features by selecting the proper matrix to support this noble metal. Therefore, this review focuses on the effects of silver nanoparticles on the functional properties of ceramic-Ag nanocomposites. The chemistry, structure, morphology and topography of the coatings are analyzed with respect to the changes produced by the silver nanoparticles’ distribution, amount and sizes and by altering production process variables. To offer a clear understanding of the functionalities of these materials, the optical, electrical, mechanical, tribological, electrochemical and biological properties reported in the last decade are reviewed, focusing on the ability to tune such properties by modifying the silver distribution, morphology and composition. In particular, the surface plasmon resonance, self-lubricating ability and antibacterial effect of silver are covered in detail, establishing their correlation with factors such as silver diffusion, segregation and ionization.     

捷变正弦信号源波形建立时间的精确测量

针对正弦信号源捷变状态切换后的建立时间、开机后波形建立时间以及过载恢复时间等的精确测量问题,提出了一种基于局域波形四参数拟合的测量分析方法,然后将拟合模型参数拓展到全局,进而获得拟合回归波形与过渡过程波形的回归残差波形。该波形的收敛过程反映了正弦波建立过程中的残差收敛变化过程。以它为目标对象,加上主观设定的建立时间的条件判据,可以获得正弦建立时间的起始和终止两个时刻点,最终获得完整的正弦信号建立时间。在两组不同条件下的状态切换实验结果,验证了该方法的有效性和可行性。该方法也可以推广应用到脉冲调频、脉冲调幅、脉冲调相、捷变频信号的建立时间测量评价中。     

Fabrication of continuous slim aluminum fibers using a multi-tooth tool

In this paper, we describe the development of a multi-tooth tool to fabricate continuous, slim aluminum fibers of an equivalent diameter of under 100?µm. Following an analysis of the process of the fabrication of aluminum fibers, we designed a geometric cutting model of the multi-tooth tool with a large inclination as well as the mechanism to form continuous, slim aluminum fibers. We conducted experiments to determine the influence of process parameters on the surface topography and the equivalent diameter of the aluminum fiber. We obtained the continuous, slim aluminum fibers with a micro-fin structure when the cutting speed, cutting depth, and feed rate were in the ranges of 0.08–0.18?mm, 5–15?m/min, and 0.1–0.2?mm/r, respectively. We found that the equivalent diameter of the aluminum fiber gradually increased with decreasing cutting speed, and increasing feed rate and cutting depth. Moreover, the result of a composition analysis indicated that the generated cutting heat had a minimal effect on the oxidation of the aluminum fiber.     

Effect of throat diameters of the ejector on the performance of the refrigeration cycle using a two-phase ejector as an expansion device

This paper is a part in a series that reports on the experimental study of the performance of the two-phase ejector expansion refrigeration cycle. In the present study, three two-phase ejectors are used as an expansion device in the refrigeration cycle. The effects of throat diameter of the motive nozzle, on the coefficient of performance, primary mass flow rate of the refrigerant, secondary mass flow rate of the refrigerant, recirculation ratio, average evaporator pressure, compressor pressure ratio, discharge temperature and cooling capacity, which have never before appeared in open literature, are presented. The effects of the heat sink and heat source temperatures on the system performance are also discussed.     

Design mechanisms and constraints

This paper describes a model of design, which takes a different perspective in that it emphasises mechanisms and constraints. The model accommodates design-related activities from the enterprise level through to activities of individuals (e.g. decision-making processes), and provides a holistic treatment of existing design methods. It is suggested that the output of a design stage is not so much the input to the next, as the provider of constraints. Consequently, the creative component of design is not concentrated in one task, with the others being technician tasks: instead each of the tasks augments the design in a creative way. A degree of commonality was observed across different domains and stages of design, which leads to the proposal of a generic design activity (GDA), that can be used in diverse design situations. Sub-activities within the GDA were identified as the generation of candidate solutions, solution assessment, solution selection, implementation, and retrieval of design intent. It is suggested that one of the limitations of many design tools, especially artificial intelligence, is the reliance on on complete problem and constraint specification. In real situations, designers have to determine constraints from incomplete and qualitative specifications, using subjective processes. Furthermore, they subsequently have to negotiate with others for the relaxation of constraints, as the design space may be over-constrained. This negotiation involves interaction with others, and adds the organisational behaviour factors to the design process. Decision-making during design needs to be able to accommodate multiple viewpoints, cope with uncertainty of analysis (incompleteness of knowledge), propagate uncertain variables, and accommodate varying degrees of information abstraction. Other areas of design that may benefit for additional research are identified. This work was performed at the Department of Mechanical Engineering, University of Canterbury, New Zealand. Submitted to Research in Engineering Design     

An alternative method of estimating uncertainty

A method of estimating the uncertainty of the result of a measurement is proposed, which is more universal, simple, and accurate than the law of the spread of uncertainty. The method is based on the traditional experimental approach to estimating the variance, on the introduction of the idea of introduced uncertainty and a proof of its close connection with the precision of the measurements. __________ Translated from Izmeritel’naya Tekhnika, No. 5, pp. 15–18, May, 2007.     

Condition, safety and cost profiles for deteriorating structures with emphasis on bridges

After an enormous investment in construction of highway networks undertaken in the second half of the 20th century, the highway networks of most European and North American countries are now completed or close to completion. As a result, the need in funding changed from building new highway structures to repair, rehabilitation, and replacement the existing ones. In this paper, a model for analyzing the evolution in time of probabilistic performance indicators of existing structures, in terms of condition, safety, and cost under no maintenance, preventive maintenance, and essential maintenance, is presented. This model integrates the current practice in bridge management systems based on visual inspections (condition index) with structural assessment (safety index) during the lifetime of existing structures. The proposed model allows the consideration of uncertainties in the performance deterioration process, times of application of maintenance actions, and in the effects of maintenance actions on the condition, safety, and life-cycle cost of structures by defining all parameters involved in the model as random variables. Interaction between condition and safety profiles is defined through probabilistic and deterministic relations. The probabilistic characteristics of the condition, safety, and cost profiles of deteriorating structures are computed by Monte-Carlo simulation. Several realistic examples, based on data on highway bridge components gathered in the United Kingdom, are presented.     

Impacts of layout,surface condition and alloying elements on diffusion welding of micro process devices

The formation of a monolithic part during diffusion bonding is accompanied by the diffusion of atoms across the bonding planes. At sufficient low roughness, it mainly depends on the temperature and dwell time. At the same time, the diffusion process competes against grain growth. By adjusting an appropriate level of bearing pressure, it is possible to control deformation taking into account additional parameters resulting from mechanical microstructures and the design and aspect ratio of the part. Furthermore, material properties, such as the content of alloying elements, the degree of cold work hardening and the grain size, have an impact on diffusion and deformation behavior. Also the surface condition of mating surfaces is important to diffusion kinetics and the quality of the joint. Especially passivation layers of corrosion‐resistant alloys, such as stainless steels and nickel‐based alloys, impair diffusion. In contrast to this, cold work hardening at low depth below the surface, e. g. by means of a blasting processes, may facilitate formation of a good bond and help to limit grain size. For oxide dispersion‐strengthened materials, additional impacts on diffusion bonding behavior applies.