Concentration-Dependent Diffusion Coefficients of Binary Gas Mixtures Using a Loschmidt Cell with Holographic Interferometry

An improved experimental setup and data evaluation procedure are presented for a Loschmidt cell combined with interferometry to measure concentration-dependent binary diffusion coefficients. We overcome long-standing discrepancies about the concentration dependence found in the literature. The systematic analysis of the residuals from parameter estimation enabled the improvement of the experimental setup and the identification of relevant fitting parameters. In particular, we found that it is crucial to account for uncertainties (1) in the initial conditions, (2) in the thermal stability of the optical setup, and (3) in camera calibration. The improved experimental setup and data evaluation procedure are validated with diffusion measurements of the system helium–krypton. The concentration dependence of the diffusion coefficient is successfully determined from multiple experiments with gas mixtures of various initial compositions in the half-cells of the Loschmidt cell. The agreement with literature data and the excellent quality of fit allow for high confidence in the results. In Part II of this paper (Wolff et al., in Int J Thermophys, 2018,  https://doi.org/10.1007/s10765-018-2451-7), the improved measurement setup is combined with a refined diffusion model to determine concentration-dependent diffusion coefficients from single measurements of mixing pure gases.     

Investigation of the joining zone of laser welded and cross wedge rolled hybrid parts

Most of today’s technical parts and components are made of monolithic materials. These mono-material components produced in established production processes reach their limits due to their respective material characteristics. Thus, a significant increase in production quality and efficiency can only be achieved by combining different materials in one part. Bulk forming of previously joined semi-finished products to net shape hybrid components that consist of two different materials is a promising method to produce parts with locally optimized characteristics. This new production process chain offers a number of advantages compared to conventional manufacturing technologies. Examples are the production of specific load-adapted forged parts with a high level of material utilization and an impact on the joining zone caused by the following forming process. This paper describes the production process of serially arranged hybrid steel parts, produced by combining a laser welding process with a subsequent cross wedge rolling process. The presented results are only a first approach in order to get first insights in the forming behaviour of laser welded and cross wedge rolled parts. The investigated material combination is C22 (1.0402) and 20MnCr5 (1.7147). This innovative process chain enables the production of hybrid parts. To evaluate the developed process chain, the weld and the joining zone is analysed before and after cross wedge rolling. Main results are that the joining process using laser welding enables a strong bonding between the two materials with a higher hardness in the joining zone than for the individual materials. After the forming process, the bonding of the joining zone is still present, while the hardness decreased but remains higher than of the materials themselves.     

Analysis of Her2/neu membrane protein clusters in different types of breast cancer cells using localization microscopy

The Her2/neu tyrosine kinase receptor is a member of the epidermal growth factor family. It plays an important role in tumour genesis of certain types of breast cancer and its overexpression correlates with distinct diagnostic and therapeutic decisions. Nevertheless, it is still under intense investigation to improve diagnostic outcome and therapy control. In this content, we applied spectral precision distance/position determination microscopy, a technique based on the general principles of localization microscopy in order to study tumour typical conformational changes of receptor clusters on cell membranes. We examined two different mamma carcinoma cell lines as well as cells of a breast biopsy of a healthy donor. The Her2/neu receptor sites were labelled by immunofluorescence using conventional fluorescent dyes (Alexa conjugated antibodies). The characterization of the Her2/neu distribution on plasma membrane sections of 176 different cells yielded a total amount of 20 637 clusters with a mean diameter of 67 nm. Statistical analysis on the single molecule level revealed differences in clustering of Her2/neu between all three different cell lines. We also showed that using spectral precision distance/position determination microscopy, a dual colour reconstruction of the 3D spatial arrangement of Her2/neu and Her3 is possible. This indicates that spectral precision distance/position determination microscopy could be used as an enhanced tool offering additional information of Her2/neu receptor status.     

A precise and robust quartz sensor based on tuning fork technology for (SF6)-gas density control

A novel sensor technology for measuring and monitoring gas density is described. The gas density sensor is self-calibrating and specifically designed to operate as a sulfur hexafluoride (SF₆) monitor and control device in gas insulated high-voltage switchgears (GIS), but can also be applied for density measurement of any kind of gas. It comprises a pair of tuning forks oscillating at their resonance frequency. One oscillator is exposed to the gas to be monitored, the other one is used for comparison and temperature compensation. Exposure to gas leads to a shift in the resonance frequency proportional to the gas density. A density standard based on a combined weight and mass measurement has been performed with a precision better than 0.02%, giving proof of exact sensor calibration. The gas density sensor works with a precision better than 0.5% over a range of 50 kg/m³ SF₆ gas density. Sensor response time is less than 50 ms. The real gas equation of Beattie and Bridgman fits the gauged values with a mean error of 0.125%.     

High performance cooling of a HVDC converter using a fatty acid ester-based phase change dispersion in a heat sink with double-layer oblique-crossed ribs

The paper concerns with a high performance cooling method for a HVDC converter using fatty acid ester-based phase change dispersion (PCD) in a heat sink with double-layer oblique-crossed ribs. Thermo-physical properties of PCDs were first characterized under both solid and liquid states, and the cooling performance of the heat exchanger was then experimentally examined, by heating two copper blocks clamped closely to the aluminium heating surfaces. A three-dimensional Euler-Euler multiphase approach was further performed to evaluate the thermal performance under different operating conditions including heating power, flowrate and PCD concentration. The results showed that the viscosity of PCD can be a 100 times that of water, but the increased pumping power was only ~17.01% on average. The use of the PCD achieved a lower temperature of heat sink and fluid than that of water under the same set of conditions due to the latent heat of the PCM, thus enabling a safer and cooler environment for temperature-sensitive HVDC components such as insulated gate bipolar transistors (IGBT). An optimal set of working conditions was proposed and a flowrate of 8 L/min under a heating power of 1.1 kW and a PCM concentration of 25% was recommended for industrial cooling operations.     

Bemessung von Grundbauwerken aus Stahlbeton nach DIN 1054 (01.03)

Design of Foundation Construction made of Reinforced Concrete according to DIN 1054 (01.03) Other than the idea given in DIN 1054 (draft november 1976) the scope of the revised draft of january 2003 clearly also refers to the stability as well as the serviceability of construction and structural members concerning ground and foundation work. However, the design concepts proposed in this contribution, do not completely correspond to other regulations of the new “Generation of Standards”, in particular to the rules for the design of concrete structural members (DIN 1045‐1, part 1‐4, DIN 1055‐100, DIN Fachberichte 100‐104). This leads to interpretation possibilities for the interface between both standards. In the following the main features and differences of both standards are introduced and application rules are proposed. Furthermore, the application of the new “Generation of Standards” is presented within the example of a tunnel structure in mining construction. These results are compared to the results according to the standards which have been valid so far (DIN 1045 (07.88), DIN 1054 (11.76), ZTV‐Tunnel part I).     

基于机器学习的传统建筑聚落历史风貌保护生成设计方法——以罗马Termini火车站周边地块城市更新设计为例

本文关注在传统建筑聚落的历史风貌保护或更新设计中,如何依靠计算机信息技术获得不依赖于人的主观判断的传统空间形态构成规则,建立数字化生成设计工具,来解答传统建筑聚落历史文化信息的精确传承和创新利用的问题。文中介绍了人工智能领域中的数据挖掘和机器学习对以上问题的解决可能,并结合案例介绍了"基于案例学习"等技术工具在城市历史地段城市更新设计中的应用成果。探索了基于知识发现的生成设计工具对传统建筑聚落历史风貌保护所起到的作用。     

Strain rate sensitivity of titanium matrix composites under tensile loading

Titanium matrix composites continuously reinforced by silicon carbide fibres are considered as key technology for a new generation of aero engines. High specific strength and stiffness promise significant weight savings and performance improvements. Impact loading may be one critical aspect in the design of rotating compressor components with titanium matrix composites. On the other hand the strength increases at high strain rates. Considering this additional loading capability enables a design closer to the edge. Therefore, the strength to strain rate relation needs to be examined. This paper presents results of high strain rate tests at the fly wheel device. Loadings resulting in strain rates from quasistatic loading to 740 1/s were applied. The results are discussed and the mechanism of energy consumption was investigated by determination of the plastic deformed length by scanning electron microscopy.     

A tilting device for three-dimensional microscopy: Application to in situ imaging of interphase cell nuclei

The resolution of an optical microscope is considerably less in the direction of the optical axis (z) than in the focal plane (x-y plane). This is true of conventional as well as confocal microscopes. For quantitative microscopy, for instance studies of the three-dimensional (3-D) organization of chromosomes in human interphase cell nuclei, the 3-D image must be reconstructed by a point spread function or an optical transfer function with careful consideration of the properties of the imaging system. To alleviate the reconstruction problem, a tilting device was developed so that several data sets of the same cell nucleus under different views could be registered. The 3-D information was obtained from a series of optical sections with a Zeiss transmission light microscope Axiomat using a stage with a computer-controlled stepping motor for movement in the z-axis. The tilting device on the Axiomat stage could turn a cell nucleus through any desired angle and also provide movement in the x-y direction. The technique was applied to 3-D imaging of human lymphocyte cell nuclei, which were labelled by in situ hybridization with the DNA probe pUC 1.77 (mainly specific for chromosome 1). For each nucleus, 3-D data sets were registered at viewing angles of 0°, 90° and 180°; the volumes and positions of the labelled regions (spots) were calculated. The results also confirm that, in principle, any angle of a 2p geometry can be fixed for data acquisition with a high reproducibility. This indicates the feasibility of axiotomographical microscopy of cell nuclei.