Verbundverhalten von Vollgewindeschrauben in Brettschichtholzbauteilen

Bond behaviour of self‐tapping screws being used as reinforcement in glue‐laminated timber elements – Part 2: Analytical and numerical investigations as well bond model derivation for the calculation of anchorage length In favor of the investigation of bond behaviour, force transfer and anchorage length of self‐tapping screws, several tests have been realized at the Chair of Structures and Structural Design in cooperation with the Institute for Building Material Research of the RWTH Aachen University. The experimental investigations comprise more than 160 pull‐out tests of screws with long embedment length and over 84 load distributions tests. Additionally, several tests displaying the effect of longitudinal cracks in the surrounding wood as well as the effect of the screw tip have been conducted. Through various analyses of the bond behaviour, the experimental investigations form the basis for the calibration and evaluation of the numerical models and allow a prediction of the force transfer of the screws in glue‐laminated elements. Design rules that enable the application of the self‐tapping screws as reinforcement in timber elements have been derived from the knowledge obtained in the experimental and numerical investigations. This paper, which results from a research project funded by the German Research Foundation [1], presents the results of investigations on the bond behavior of self‐tapping screws in glue‐laminated timber elements. Part 1 elaborates on the experimental investigations [2] whereas part 2 illustrates the numerical analyses and presents a bond model, which enables the design of the anchorage length and the safe application of the screws as reinforcement in timber elements.     

Melting and Glass Transformation of One‐Component Systems

Melting of solid chemical elements has recently been explained by electronic transitions. Due to such transitions into higher energy levels the wave‐functions and their local charge distributions are changed. Since the occupation of the electronic states and the corresponding charge distribution change at random with time, the core ions are continuously driven to new positions. If the forces are strong enough and the core ions relax to their new positions within the lifetime of the excited states, the changing arrangement of the core ions corresponds to a melt. These considerations are extended from elements to chemical compounds as one‐component systems. The melting entropy and the specific heat capacities near the melting temperature have been normalised to the number of atoms in the formula unit of the one‐component systems. The heat capacities exceed 3R, which is the value expected for vibrations, and accumulate surprisingly at special values as well as the melting entropies. This seems to support the idea of melting as an electronically induced effect. The distributions of the electronic energy levels in the molten state and in the crystalline solid are different. If the forces of the electronic distribution in the relaxed low energy states of the undercooled melt are too weak to attract the core ions to regular lattice positions, the disorder is frozen‐in during cooling and a glass transition takes place. Sufficiently strong directional bonds between neighbouring ions and low melting entropy per particle favour such a transition.     

胺法气体脱硫胺液中热稳态盐离子的组成分析

建立了两种胺法气体脱硫胺液中热稳态盐的分析方法：离子交换-容量法和固相萃取-离子色谱法，优化了这两种方法的试验条件，并对这两种方法的线性范围、检出限、相对偏差，以及对实际样品的分析进行了对比，结果表明，固相萃取-离子色谱法检出很低，且重复性好；当胺液中的质量分数大于1．0％时，应采用离子交换-容量法，简单快速，当HSS的质量分数小于1．0％时，应采用固相萃取-离子色谱法，比较准确，相对偏差为3．6％。     

Schnelle lokale Raman‐Messung zur Untersuchung von Konzentrationsprofilen bei Mischvorgängen in Mikrokanälen

For the evaluation of mixing processes in microreactors, it is necessary to be able to investigate them in detail. For this purpose, a novel optical measuring system is presented, which allows the visualization of mixing and diffusion‐limited processes as well as concentration differences in fluid films. It consists of focusing optics with a microscope objective. In combination with a Raman spectrometer, various processes such as diffusion in the microreactor can be measured and investigated non‐invasively.