Electrical properties of CFC- and HCFC-substitutes

Electrical properties of refrigerants are of importance as soon as bushings are surrounded by a refrigerant. This is the case e. g. for hermetic sealed motor compressors as well as for some control devices such as liquid level control units or capacity controls for compressors. This paper presents a survey of existing data for HFC refrigerants and presents new measurements for those HFC blends that have been identified as long term replacements for CFCs and HCFCs. The data collection includes permittivity, electrical conductivity and breakdown voltage. Values are given for the HFC blends R404A, R407C, R410A and R507 as well as for R134a.     

一种运动估计算法的性能评估方法

同时考虑算法的精度和效率,以常用的基于梯度的运动估计算法为例,提出了一种运动估计算法的性能评估方法.在该方法中,以表征算法精度的偏差为横坐标,以表征算法效率的执行时间为纵坐标,构建了一个偏差一时间二维性能评估坐标系,通过设置算法的不同参数,绘制偏差一时间性能评估曲线.性能评估实例表明了所提出的偏差-时间性能评估方法在评估基于梯度的运动估计算法性能时的有效性.     

Investigating the accuracy of evolventometers

Conclusions The measurement results indicate that for checking measuring wheels which are used as standards for grade 5 and 6 wheels (according to GOST 6512-58), as well as for checking involute cams, it is necessary to produce new evolventometers whose kinematic chain must be simple, for instance, as in the Fellow disc instruments. It is also necessary to develop a more reliable method of setting the measuring tip for a given radius of the basic circumference, avoiding the method of setting it by touch.Such instruments are urgently required by the Committee's metrological institutions and plants which are manufacturing high precision wheels, as well as for checking involution cams designed for checking evolventometers.     

Mechanical reliability,how do we advance?

The development of theory and practice for electronic and mechanical reliability is described, and mechanical reliability is seen to be lagging in practice. Theory and practice are described for a project from conception to market feedback for mechanical as well as for electronic reliability. It is noted that for each phase theoretical and practical methods exist for mechanical as well as for electronic reliability analysis. Activities are listed which can strengthen mechanical reliability theory and practice.     

Influence of waveguide material on light emission in luminescent solar concentrators

Five different substrates were tested for their suitability for use as waveguides for luminescent solar concentrators for solar energy applications. The function of such a waveguide is to collect light and to transport it towards a solar cell. In this study the influence of the material of the waveguide on the light emission of the system was investigated. It was determined that the material chosen for the waveguide was not as important as the presence or absence of additives in the waveguide itself. This indicates that economic factors (material cost) and secondary properties such as refractive index, outdoor lifetime and weight are at least as important in the waveguide selection as the nature of the materials used.     

Molecular recognition in chiral discrimination

The importance of obtaining reliable detection systems for enantiomers' assays increases with the necessity of chiral discrimination between the enantiomers of raw materials from the pharmaceutical industry. The utilization of electrochemical sensors in molecular recognition of chiral substances becomes a very accurate and precise alternative for the structural analysis as well as for the chromatographic techniques. The reliability of the response characteristics as well as of the analytical information obtained by using electrochemical sensors is strictly correlated with the design of the sensors. The most reliable design is that of carbon paste based sensors; this design was adopted for the construction of potentiometric, enantioselective membrane electrodes as well as for the construction of the amperometric biosensors, and immunosensors. However, it is also necessary to look for more reliable chiral selectors.     

2D and 3D photonic crystal materials for photocatalysis and electrochemical energy storage and conversion

This perspective reviews recent advances in inverse opal structures, how they have been developed, studied and applied as catalysts, catalyst support materials, as electrode materials for batteries, water splitting applications, solar-to-fuel conversion and electrochromics, and finally as photonic photocatalysts and photoelectrocatalysts. Throughout, we detail some of the salient optical characteristics that underpin recent results and form the basis for light-matter interactions that span electrochemical energy conversion systems as well as photocatalytic systems. Strategies for using 2D as well as 3D structures, ordered macroporous materials such as inverse opals are summarized and recent work on plasmonic–photonic coupling in metal nanoparticle-infiltrated wide band gap inverse opals for enhanced photoelectrochemistry are provided.     

Influence of natural polymer coating on novel colon targeting drug delivery system

A novel colon targeted tablet formulation was developed using natural polysaccharides such as chitosan and guar gum as carriers and diltiazem hydrochloride as model drug. The prepared blend of polymer-drug tablets were coated with two layers, inulin as an inner coat followed by shellac as outer coat and were evaluated for properties such as average weight, hardness and coat thickness. In vitro release studies of prepared tablets were carried out for 2 h in pH 1.2 HCl buffer, 3 h in pH 7.4 phosphate buffer and 6 h in simulated colonic fluid (SCF) in order to mimic the conditions from mouth to colon. It was observed that 4% w/v of rat cecal contents in saline phosphate buffer (SCF) incubated for 24 h provides suitable conditions for in vitro evaluation of the formulations prepared. The drug release from the coated system was monitored using UV/ Visible spectroscopy. In vitro studies revealed that the tablets coated with inulin and shellac have controlled the drug release in stomach and small intestinal environment and released maximum amount of drug in the colonic environment. Among the polymers used, chitosan was found to be the suitable polymer for colon targeting. The study revealed that polysaccharides as carriers and inulin and shellac as coating materials can be used effectively for colon targeting of drugs for treating local as well as systemic disorders.     

Interdisziplinäre Entwicklung eines künstlichen Kniegelenks (Kniegelenks-Endoprothese) in Kunststoff-Metall-Kombinationsbauweise

Interdisciplinary development of an artificial knee joint endoprosthesis as a “combined plastic-metal-construction” . Endoprostheses for joints of the human locomotor apparatus under certain indications serve as permanent implants for eliminating painful changes of joints (e. g. arthrosis) as well as for restoration of essential joint functions (e. g. knee bending). The complexe correlation of biological-physiological factors and problems concerning materials and nature of load requires the adequate interdisciplinary co-operation of orthopaedic surgeons and engineers. On example of the prototype development of a total prosthesis for the knee joint the biomechanical conditions are sketched by means of the kinematics, statics, dynamics and tribology of normal natural joints (hip and knee) as a basis for the derivation of compensational functions. Already existing models are discussed, and the conception as well as the construction and production of the prototype of an artificial knee joint (“hinge joint-principle”) as a combined “plastic-metal-system” is described.     

先进复合材料的宏微观力学与强韧化设计: 挑战与发展

介绍了在先进复合材料的宏微观力学与强韧化设计领域内的国际发展趋势和国内发展状况、研究的科学意义、主要研究内容和面临的挑战、先进复合材料强韧化机制和原理、复合材料的宏微观力学理论与强韧化设计基本方法、存在的难点问题和发展方向。      

Investigation of tribological and mechanical properties of metal bearings

Copper, aluminum and tin-lead based alloys are widely used as journal bearing materials in tribological applications. Bronze and brass are widely used as journal bearing materials for copper based alloys. Zamacs find applications as journal bearing materials for zinc based alloys, while duralumines are chosen as journal bearing materials for aluminum based alloys. In addition, white metals are widely used as journal bearing materials for tin-lead based alloys. These alloys ensure properties expected from journal bearings. In this study, tribological and mechanical properties of these journal bearings manufactured by metals were investigated. SAE 1050 steel shaft was used as counter abrader. Experiments were carried out in every 30 min for a total of 150 min by using radial journal bearing wear test rig.     

以竹代塑产品在包装领域应用现状

目的 介绍不同种类竹材包装的生产加工方式及其应用,并对以竹代塑产品在包装领域的发展进行展望,以期为以竹代塑产业发展提供借鉴和参考。方法 总结不同以竹代塑产品生产工艺和性能的特点,分析原竹包装和经过化学改性竹包装技术在包装领域的应用现状和存在问题。结果 可以在竹包装材料加工过程中添加功能助剂,或者对竹基材进行物理或化学改性,以及生产设备的机械化和智能化延伸,提升以竹代塑产品的品质和货架期。结论 以竹代塑产品的广泛应用势必会推动以竹代塑产业的可持续高质量发展,为提高竹包装品质和内装产品安全性提供了借鉴和参考。     

N -chloramide modified Nomex? as a regenerable self-decontaminating material for protection against chemical warfare agents

Recent interest in the treatment of textiles for chemical and biological agent defense has led to the creation of materials that contain N-chloramide moieties. These materials have demonstrated efficacy against weaponizable bacteria, mustard, and VX, as well as possessing antimicrobial properties against nuisance organisms that cause conditions such as athlete’s foot or molds. Here, N-chloramides have been attached to Nomex^? intended for use as self-decontaminating regenerable military textiles. The materials were assayed for content of active oxidizing agent, and tested for efficacy against 2-chloroethyl ethyl sulfide and Demeton-S, simulants for mustard and VX, respectively. The decomposition products for each reaction were identified as well as reaction pathways to form each by-product as correlated to analogous products of mustard and VX. Furthermore, the rate constant for the neutralization of each simulant on the reactive material was calculated from data collected by GC-MS and ATR-FTIR real-time studies.     

Using tool life models to minimize processing time on a flexible machine

Economic tool life models are presented for machines with finite capacity tool magazines and variable processing speed capability. Single and multiple part models for minimizing the total throughput time are formulated as nonlinear, integer programs (NLIP). An algorithm is presented for the NLP relaxation and a marginal analysis approach for solving the NLIP is detailed, giving an optimal tool loading policy as well as the processing speeds for each of the part types so as to minimize the makespan. A numerical example illustrates the procedures.     

Nanosecond Passive Voltage Probes

Passive voltage probes with megohm input impedance at dc are traditionally understood as RC compensated dividers, but this is inadequate even for system rise times as slow as 100 ns. Qualitative understanding of faster probes is generally in terms of resistive damping of resonances, but this has been notably successful in practice only with the use of resistive conductor probe cable as introduced by Kobbe. This paper demonstrates that nanosecond probes can be understood and designed for a systematic transmission line viewpoint. The properties of the resistive conductor probe cable as a transmission line are an essential feature, and the original motivation for the use of resistive cable as damping of a resonance is seen to be largely irrelevant for nanosecond probes.     

Replica-based crack inspection

Surface replication has been proposed as a method for crack detection in space-shuttle main engine flowliner slots. The results of a feasibility study show that examination of surface replicas with a scanning electron microscope can result in the detection of cracks as small as 0.005 inch, and surface flaws as small as 0.001 inch, for the flowliner material.     

On-line coupling of capillary gel electrophoresis with electrospray mass spectrometry for oligonucleotide analysis

Homooligodeoxyribonucleotides differing one nucleotide in length from 12- to 15-mer and from 17- to 20-mer were separated by size with capillary gel electrophoresis (CGE) using an entangled polymer solution in coated capillaries. The resolved components were analyzed by on-line coupling of CGE with electrospray mass spectrometry (ES-MS), denoted as CGE/ES-MS, in the full-scan negative ion detection mode. Baseline separation was achieved for the 12-15-mer oligonucleotide mixtures. Both synthetic phosphodiester oligonucleotide mixtures as well as their phosphorothioate analogues, serving as model compounds for antisense oligonucleotides, could be analyzed by on-line CGE/ES-MS coupling. Terminally phosphorylated and nonphosphorylated synthetic failure sequences could be electrophoretically separated and mass spectrometically characterized as well. This methodology might be a useful tool for synthesis control of phosphodiester oligonucleotides as well as for analysis of phosphorothioate analogues as they are used in antisense drug development.     

III-V nitrides—important future electronic materials

The present stage of development for the AlN-GaN-InN class of III-V nitrides is reviewed, with emphasis on the electronic properties of the materials. We also briefly cover the most important types of device structures presently under study, as well as application areas for III-nitride devices now foreseen. A brief overview of the main growth techniques is presented, since a further development of the growth of these materials is indeed the key towards a desired substantial improvement in material quality. This is needed both for the establishment of definite data for physical parameters, as well as for the proper functioning of most devices. The basic band structure as well as excitonic properties are briefly discussed. It is pointed out that these materials are in most cases excitonic at room temperature, for bulk as well as for quantum structures. Doping and properties of donors and acceptors are highlighted, here, in particular, the parameters for shallow acceptors, such as their binding energies, are far from well known. There is no complete picture of the identification of characteristic optical spectra (such as bound exciton spectra) with specific donors and acceptors. The properties of defects, in particular dislocations which are very abundant in the heteroepitaxial material studied today, are discussed. Dislocations may not themselves be severe recombination centers, and the degradation of active devices via dislocation climb seems to be absent in III-nitrides. The progress in the area of heterostructures and quantum wells based on the AlGaN/GaN and the InGaN/GaN systems is reviewed, in relation to the present strong development of related devices. An interesting observation is the importance of the piezoelectric effect, due to a strong built-in strain in most structures. Application areas cover a very broad range in optoelectronics, but also high frequency power devices, with applications for example in satellite communication systems.     

Deformation and life assessment of high temperature materials under creep fatigue loading

The knowledge of mechanical long term behaviour under static and cyclic loading for high temperature components requires methodologies for life assessment in order to employ the full potential of materials. A phenomenological life time prediction concept which was developed for multi‐stage creep fatigue loading demonstrates the applicability of rules for synthesis of stress strain path and relaxation including an internal stress concept, as well as mean stress effects. Further, a creep fatigue interaction concept which was also developed covers a wide range of creep dominant loading as well as fatigue dominant loading. Service‐type experiments conducted at different strain rates and hold times for verification purposes demonstrate the acceptability of life prediction method for variation of conventional 1 %Cr‐steels as well as modern high chromium 9‐10 %Cr‐steels. Generally, the service life of components is influenced by multi‐axial behaviour. Multi‐axial experiments with e.g. notched specimens and with cruciform specimens accompanied by advanced methods for calculation of stress strain path and life time prediction stress conditions are of future interest.     

Statistical Analysis and Robust Optimization of Forming Processes and Forming-to-Crash Process Chains

In this paper, a novel strategy for statistical analysis and multi-objective robust design-parameter optimization of forming processes as well as forming-to-crash process chains is discussed and results presented for a ZStE340 metal blank of a B-pillar. The strategy comprises both physical experiments and numerical simulation and is built upon a novel material and damage model as well as several software tools which allow for an efficient sensitivity, stability and robustness analysis, even for simulation results on highly resolved grids.