Nachweis der Firstspaltverpressung bei zerstörungsfreien Schalendickenmessungen an Tunnelinnenschalen

Bisherige Auswertungen bei diversen Tunnelprojekten ergaben, dass bei Tunnelinnenschalen die Firstspaltverpressung nicht immer zerstörungsfrei nachgewiesen wurde. In Bereichen, die beispielsweise durch eine freiliegende Bewehrung in der Firste instand gesetzt werden müssen, ist der Nachweis des Verpressguts von großer Bedeutung. In Laborversuchen wurde an Betonprobekörpern dieser Fragestellung durch Variation verschiedener Einflussgrößen und Parameter experimentell nachgegangen. Im Anschluss daran erfolgte die praktische Umsetzung der Versuchsergebnisse auf einer Tunnelbaustelle im Bereich von detektierten Fehlstellen im Firstbereich. Durch den Einsatz spezieller Verpressgüter und Vorbehandlungen konnte die Tunnelinnenschale mit dem Verpressgut in diesem Bereich zerstörungsfrei einwandfrei nachgewiesen werden. Verification of Ridge‐Gap Grouting by Measuring the Shell Thickness of the Inner Tunnel Layer by Non‐Destructive Testing Previous evaluations of various tunnel projects showed results where the ridge‐gap grouting of the inner tunnel shells was not always been non‐destructively proven. In areas which, for example, have to be repaired through exposed reinforcement in the ridge, the proof of the grouting material is of great importance. This problem was explored experimentally in laboratory tests on concrete test specimens through variation of different actuating variables and parameters. Afterwards, the experimental results were put into practice in areas of detected flaws in the ridge area on a tunnel construction site. The inner tunnel shell with the grouting material could be proved perfectly non‐destructively by using special grouting material and pre‐treatments in this area.     

Chromatin-unstable boar spermatozoa have little chance of reaching oocytes in vivo

In the present study, the prevalence of chromatin instability in the fertilizing-competent sperm population in the porcine oviduct in vivo was examined through qualitative analysis of the chromatin structure status of accessory boar sperm found in in vivo-derived embryos. The binding of chromatin-unstable sperm to oviductal epithelium in vitro was also studied. To examine the sperm chromatin state, a modified fluorescence microscopic sperm chromatin structure assay was used. Among a population of 173 fertile boars, individuals were selected for according to their chromatin status: 25 animals showed more than 5% of chromatin-unstable sperm in their ejaculates, and 7 showed consistently elevated percentages of chromatin-unstable sperm in three successively collected semen samples. A positive correlation was found between incidence of chromatin instability and attached cytoplasmic droplets (r=0.44, P<0.01). Analyses of accessory spermatozoa from in vivo-derived embryos demonstrated that the proportion of chromatin-unstable sperm was significantly (P<0.05) reduced in the population of fertilizing-competent sperm in the oviduct compared with the inseminated sperm. Populations of sperm bound to the oviduct in vitro had significantly (P<0.05) lower percentages of chromatin instability than in the original diluted semen sample. In conclusion, numbers of sperm with unstable chromatin are reduced in the oviductal sperm reservoir, possibly because of associated changes in the plasma membrane that prevent sperm from binding to the oviductal epithelium. We conclude that in vivo the likelihood that sperm with unstable chromatin will reach the egg and fertilize it is low.     

特高压直流输电设备设计综述

高压直流输电已发展成为成熟的技术,典型的电压等级为士500kv。在中国正在运行的几个直流系统中,单条直流系统完整双极的输送容量已达3GW。同时,还有几个电压等级为800kv的UHVDC系统正在建设中,并计划从2009年中期开始陆续投入商业营运。在±800kV直流运行电压基础上,随着通电流能力的不断增加,直流系统的输电能力将会达到双极7．2GW的输送容量。电力技术的长足进步,有赖于强有力的HVDC换流站设备设计的研发工作和长期以来积累的设备制造经验。文章总结了设备设计技术攻关方面的难点,并介绍了UHVDC换流站设备技术的现实情况。     

Influence of vacuum on the porosity and mechanical properties in rotational molding

Rotational molding allows the production of seamless, hollow parts with a high degree of design flexibility. Nevertheless, the process has limitations such as long cycle times as long holding times are necessary to produce components free of air inclusions. Within the scope of this article, an experimental setup was developed to evaluate the possibility and resulting effects of using vacuum in the rotational molding process. For this purpose, trials with different vacuum pressure levels and holding times were carried out and the resulting porosity and surface quality as well as the mechanical properties of the specimens were determined. The investigations showed that the use of vacuum allows a significant reduction in porosity even at low holding times, which can considerably reduce the cycle time of the process. However, the extent of possible time saving is limited by the requirement of a good surface quality, on which the vacuum application shows no effect. Furthermore, the mechanical properties of the parts could be slightly improved by using vacuum. POLYM. ENG. SCI., 59:1544–1551 2019. © 2019 Society of Plastics Engineers     

Study on thermal conductive PA6 composites with 3-dimensional structured boron nitride hybrids

To develop thermally conductive PA6 composites with the aim of decreasing filler content, structure-complexed fillers were fabricated. This research presented an effective approach by noncovalent functionalization of poly(dopamine) (PDA) followed by silver nanoparticles decoration to fabricate 3-dimensional (3-D) structured boron nitride hybrids (BN@PDA@AgNPs). BN hybrids were then introduced into PA6 to prepare thermally conductive PA6 composites. The results demonstrated that PA6/BN hybrids (PMB) composites exhibited higher thermal conducivity compared with PA6/BN composites, which revealed more effective construction of thermal conductive network in the composites with the addition of 3-D structured fillers. The effects of BN hybrids with different loadings on thermal stability, mechanical property, as well as electrical resistance of the composites were also analyzed. Overall, the prepared PMB composites exhibited outstanding performance in thermal conductivity, thermal stability, mechanical property, while retaining good electrical insulating property, which showed a potential application in electronic packaging fields. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47630.     

Proxies and measurement techniques for mineral dust in Antarctic ice cores

To improve quantitative interpretation of ice core aeolian dust records, a systematic methodological comparison was made. This involved methods for water-insoluble particle counting (Coulter counter and laser-sensing particle detector), soluble ion analysis (ion chromatography and continuous flow analysis), elemental analysis (inductively coupled plasma mass spectroscopy at pH 1 and after full acid digestion), and water-insoluble elemental analysis (proton induced X-ray emission). Antarctic ice core samples covering the last deglaciation from the EPICA Dome C (EDC) and the EPICA Dronning Maud Land (EDML) cores were used. All methods correlate very well among each other, but the ratios of glacial age to Holocene concentrations, which are typically a factor approximately 100, differ between the methods by up to a factor of 2 with insoluble particles showing the largest variability. The recovery of ICP-MS measurements depends on the digestion method and is differentfor different elements and during different climatic periods. EDC and EDML samples have similar dust composition, which suggests a common dust source or a common mixture of sources for the two sites. The analyzed samples further reveal a change of dust composition during the last deglaciation.     

Improvement of multicrystalline silicon solar cells by a low temperature anneal after emitter diffusion

The influence of an annealing step at about 500 °C after emitter diffusion of multicrystalline solar cells is investigated. Neighboring wafers from a silicon ingot were processed using different annealing durations and temperatures. The efficiency of the cells was measured and detailed light beam induced current measurements were performed. These show that mainly areas with high contents of precipitates near the crucible walls are affected by the anneal. An efficiency increase from 14.5 to 15.4% by a 2 h anneal at 500 °C was observed. The effect seems to be more likely external than internal gettering. Copyright © 2010 John Wiley & Sons, Ltd.     

苏黎世联邦理工学院模式:建构以设计为中心的师资结构

通过阐述设计与研究的关系、机构与教学组织、师资任用与评价、师资引进4个方面介绍了苏黎世联邦理工学院模式的建筑教育和师资建设.建筑学教学的核心目标是学生设计能力的培养,而知识和研究是其必要保障,应该在认识设计与研究明确差异的基础上,构建适合的组织机构、教学计划、师资引进和评价体系.只有人尽其才、各尽所能才能促进教师和院系的长远发展.     

Analysis of the Processing-Pressure Dependent Refractive Index of Polycarbonate by Transmission Measurements of Glass-Filled Specimen

In this study, the influence of pressure during processing on the refractive index (RI) of polycarbonate (PC) was investigated by transmission measurements on glass-filled samples with a spectrometer. In order to isolate the pressure dependence of the RI from other influencing parameters such as cooling rate, orientation and stress states, the samples were prepared in a pressure-specific volume-Temperature (pvT) instrument under constant cooling rate and temperature history and without shear effects. Subsequently, the RI was determined at the intersection of the dispersion curves of the glass and the polymer by evaluating the wavelength of the maximal transmission of the samples. The mean RI over the entire cross section of the sample is determined by the transmission measurements without complex sample preparation. The investigations show that the RI of PC increases by 3.26 E-6 per bar with increasing pressure. POLYM. ENG. SCI., 60:512–516, 2020. © 2019 The Authors. Polymer Engineering & Science published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers.     

C/C-SiC component for metallic phase change materials

Thanks to their high energy density and thermal conductivity, metallic Phase Change Materials (mPCM) have shown great potential to improve the performance of thermal energy storage systems. However, the commercial application of mPCM is still limited due to their corrosion behavior with conventional container materials. This work first addresses on a fundamental level, whether carbon-based composite-ceramics are suitable for corrosion critical components in a thermal storage system. The compatibility between the mPCM AlSi₁₂ and the Liquid Silicon Infiltration (LSI)-based carbon fiber reinforced silicon carbide (C/C-SiC) composite is then investigated via contact angle measurements, microstructure analysis, and mechanical testing after exposure. The results reveal that the C/C-SiC composite maintains its mechanical properties and microstructure after exposure in the strongly corrosive mPCM. Based on these results, efforts were made to design and manufacture a container out of C/C-SiC for the housing of mPCM in vehicle application. The stability of the component filled with mPCM was proven nondestructively via computer tomography (CT). Successful thermal input- and output as well as thermal storage ability were demonstrated using a system calorimeter under conditions similar to the application. The investigated C/C-SiC composite has significant application potential as a structural material for thermal energy storage systems with mPCM.