Wichard von Moellendorff

Plastification was in focus of research on metals and alloys in the first third of the 20^th century. Wichard von Moellendorff built up a research laboratory at the “Allgemeine Elektricitätsgesellschaft” (AEG) in Berlin‐Oberschöneweide in the “Kabelwerk Oberspree” (KWO). With systematic investigations on the metallographic and mechanic properties of metals and alloys he made substantial contributions to the scientific discussion of plastification. His results were partially contrary to the current opinion in metal science, but nevertheless true. Together with Czochralski he derived first conceptions on the mechanism for such deformations considering the crystalinity of the metals. After an interruption due to the first world war, Moellendorff started investigations as director of the “Staatliches Materialprüfungsamt” and the “Kaiser‐Wilhelm‐Institut für Metallforschung” on the plastic flow conus of metallic rods during rupture. This process was explained in 1929 by “turning, distortion and shearing of crystallographic planes”. Polanyi at the Kaiser‐Wilhem‐Institut für Faserforschung, was able to explain the mechanism in 1932. Single atoms move step by step through the lattice on inclined positions and form dislocations. Together with neighbored atoms whole plains can be moved with a minimal energy through the crystal. With the dislocation mechanism, hammering, rolling and bending of metals and alloys can be explained. 1933 Polanyi left Nazi‐Germany and became Professor in Manchester, Moellendorff was brave enough to make an affront against the Nazi regime in giving up the membership of the Kaiser‐Wilhelm‐Gesellschaft stating his personal opposition in an official letter which was not widespread behaviour of the German scientific and technical elite.     

COMPONENT ALLEE EFFECTS AND STAGE‐SPECIFIC PREDATION: A BRIEF INSIGHT INTO CONSERVATION AND BIOLOGICAL CONTROL ISSUES

In this paper, we propose a two‐stage structured population model subject to component Allee effects in fecundity and maturation, and with two disturbances (predation only and harvest and predation) acting on both stages. It is shown that this combination leads to a demographic Allee effect—a characteristic that could be exploited in pest biological control, but on the other hand, it represents a bane in conservation biology. The analysis is performed for disturbances with functional responses type 2 and 3, and the models show that they yield qualitatively similar results. This characteristic is discussed from the species conservation and biological control point of view, together with possible extensions of this work.     

基于多分辨分析的沪深股市相关性分析

为了有效地揭示沪深股市不同交易周期股票交易的相关性,本文采用极大重叠离散小波变换,将上证指数和深圳成指高频收益率分解在不同的交易周期上,对各个周期的收益率采用semi-GPD模型作为其边缘分布分别进行拟合,在此基础上采用Copula函数方法建立同周期收益率的联合分布,度量了沪深两市同周期交易的相关性.实证表明,不同交易周期所表现出的相关性存在明显差异,并且随着交易期的增长,沪深两市非对称结构逐步明显。     

Czochralski's creative mistake: a milestone on the way to the Gigabit Era

Much of the rapid change in industry, science, and society is brought about by the meteoric development of the microelectronics industry. Daily life is affected by this development; one has only to think of mobile telephones and the chips on modern credit cards. The raw material for microelectronics is the single crystal of silicon, with very high purity and almost perfect crystal structure. About 95% of the world's current production of silicon single crystals is achieved using the process that Jan Czochralski discovered in 1916. Today, single crystals of silicon can be grown that are up to 2 m long, 300 mm in diameter, and weigh up to 265 kg. The use of magnetic fields has led to significant advances in crystal-drawing technology. Intensive research and development reveals that in addition to the technology, which provides crystals of ever-increasing diameter, defect engineering, and the control of the numerous temperature-dependent reactions of crystal defects, are of paramount importance.     

Thermally reactive aromatic polyamides

2,5-Bis(phenylethynyl)terephthaloyl chloride and 4,6-bis-(phenylethynyl)isophthaloyl chloride were synthesized in a multistep reaction scheme from 2,5-dibromoterephthaldehyde and 4,6-dibromoisophthaldehyde, respectively. Low temperature solution polycondensation of these novel monomers and tolane-2,4′-dicarbonyl chloride with aromatic diamines yielded aromatic polyamides containing phenylethynyl moieties. Inherent viscosities of 0.20–0.51 dL/g were recorded. Attempts to carry out the homopolymerization of 2-(3-aminophenylethynyl)benzoyl chloride hydrochloride under similar conditions led to low molecular weight polyamide. Under differential scanning calorimetry and thermal mechanical analysis, the polyamides exhibited strong exotherms with onset occurring in the 185–225°C range. The exotherms were attributable to intramolecular cycloaddition of phenylethynyl moieties with amide groups to give polybenzalphthalimidine structures. Curing of a pressed pellet specimen for 16 h at 250°C under a nitrogen atmosphere resulted in partial conversion to a polybenzalphthalimidine structure with a concomitant increase in the polymer glass transition temperature. Isothermal aging in air of the cured specimen at 316°C (600°F) led to 25% weight loss after 200 h.     

Low glass transition temperature fluorocarbon ether bibenzoxazole polymers

Fluorocarbon ether bis(o-aminophenol) monomers were prepared by a multistep synthetic route based on the copper-promoted coupling of 4-iodophenyl acetate with 1,8-diiodoperfluoro-3,6-dioxaoctane, 1,11-diiodoperfluoro-3,9-dioxaundecane, 1,14-diiodoperfluoro-5,10-dimethyl-3,-6,9,12-tetraoxatetradecane, and 1,17-diiodoperfluoro-3,6,9,15-tetraoxaheptadecane. Acetic acidpromoted polycyclocondensations of the monomers with long-chain fluorocarbon ether-diimidate esters and -dithioimidate esters led to linear fluorocarbon ether-bibenzoxazole polymers soluble in 1,1,1,3,3,3-hexafluoroisopropanol and 1,1,2-trichloro-1,2,2-trifluoroethane. Polymer structures were verified by elemental and infrared spectral analysis. The polymers were rubbery gums and could be obtained in the inherent viscosity range of 0.20–0.79 dlg^?1. Selection of monomers governed the glass transition temperatures of the resultant polymers. As expected, the polymers exhibited lower glass transition temperatures with increased fluorocarbon ether content, a minimum value of ?58°C being achieved. None of the polymers exhibited crystalline melt temperatures. Based on thermogravimetric analysis data, the thermooxidative stability of the polymers tended to decrease with increased fluorocarbon ether content. Onset of breakdown during thermogravimetric analysis in air occurred in the 350–400°C range. Isothermal aging of the polymers in air indicated good thermooxidative stability at 260°C; only 5% weight loss was recorded after 200 hr.     

Fluorocarbon- containing hydrophobically modified poly(N-isopropylacrylamide)

A fluorocarbon-modified poly(N-isopropylacrylamide) has been synthesized by copolymerization of N-isopropyl acrylamide with a small amount of acrylate or methacrylate containing a perfluoroalkyl group. It was found that the hydrophilicity of macromolecular backbone is an important factor to the solution properties of the copolymers and that hydrophobic association between fluorocarbon groups is stronger than that between the corresponding hydrocarbon analogies. The viscosity of some of the copolymer solutions was very sensitive to temperature. It was dilatant at higher fluorocarbon comonomer content ( > 0.20-1.0 mol%) and was Newtonian at very low fluorocarbon comonomer content (0.03-0.2 mol% ) . Evidence for hydrophobic association of the fluorocarbon groups was obtained from the effects of adding Nad and surfactants on the solution viscosity. The LC-ST properties of these copolymers were studied by DSC method and this was also found to be consistent with hydrophobic association between the fluorocarbo     

高分辨率多光谱数字相机电子学系统的设计

设计了一种基于多光谱技术的机载数字相机电子学系统。它包括时序产生单元、信号处理单元、信号控制单元、数据输出接口单元和数据采集存储单元等几部分。系统具有调光和行频调节功能,用以满足在不同能量状态和不同飞行高度下的成像质量。考虑到机载设备的特殊要求,对其进行了轻量化设计和机载稳定平台设计。它具有实时高速存储和实时采集数据的功能。结果表明,机载数字相机电子学系统的各种功能完全满足设计要求,为实现高分辨率探测提供了保证。