Ein Statistisch-Rheologisches modell der restfestigkeit geschädigten betons

The residual strength of damaged concrete having a structure similar to a pile of fragments is determined by the frictional resistance to slide of the elements. In the statistical-rheological model this fact is taken into consideration by connecting in parallel extended friction elements. Their load capacity can be expressed by a critical stress which is assumed to be at random in the system and can be described by a steady distribution. A criterion of stability is formulated as an unequation making it possible to compute the stress the system becomes unstable and fail s as well as the total strain at any load. Two examples - the stress-strain relation at elevated temperatures and the restriction of thermal expansion under non-steady state conditions - demonstrate efficiency and bounds of the model.     

X-ray diffraction investigations on evaporated iron films

The structure of thin iron films of thickness about 1500 Å was studied by means of X-ray diffraction analysis. Evaporation and X-ray examination were carried out in the 10^?10 Torr range without exposing the films to the atmosphere using a recently developed ultrahigh vacuum diffraction chamber. The films were deposited onto glass substrates at a rate of 10 Å min^?1 at room temperature and were subsequently annealed at 320°C. They show a (110) fibre texture with a mean crystallite size of the (110)-oriented crystals that was distincly smaller than the film thickness. The lattice parameter was found to be always less than the corresponding value for a bulk iron standard, which can be ascribed to the formation of thermally induced strains.     

Using the Default Option Bias to Influence Decision Making While Driving

Gaining a better understanding of human–computer interaction in multiple-goal environments, such as driving, is critical as people increasingly use information technology to accomplish multiple tasks simultaneously. Extensive research shows that decision biases can be utilized as effective cues to guide user interaction in single-goal environments. This article is a first step toward understanding the effect of decision biases in multiple-goal environments. This study analyzed data from a field experiment during which a comparison was made between drivers’ decisions on parking lots in a single-goal environment and drivers’ decisions in a multiple-goal environment when being exposed to the default option bias. The article shows that the default option bias is effective in multiple-goal environments. The results have important implications for the design of human–computer interaction in multiple-goal environments.     

大型X射线光学仪器:单层镜和多层镜的制造与表征

150~500 mm长度的各种X射线光学元件可用于光束导引,光束调整,以及单色化。本文介绍了两种不同的大型X射线反射镜。第一种为单层反射镜,这种反射镜以2°掠入射角在软X射线区(50~200 eV)起全反射镜作用,可用于自由电子激光器,如德国汉堡的FLASH。第二种是多层镜,由于它的布喇格反射特性,适于作为反射镜以0.4~1°的入射角用于硬X射线区(20~50 keV),如层析光束线的同步辐射存储环中。两种反射镜都用最新物理汽相淀积法制备,并用磁控溅射来实现X射线光学应用所需要的优良光学品质。这一淀积工艺使不同批次的镀膜稳定性良好,有利于实际反射镜在优质衬底上的最后淀积。单层镜和多层镜在它们的相关能量范围内都有很高的反射率,表面粗糙度也很低,且在整个光学波长区这些特性表现均匀。文中所叙相关研究都是借助X射线反射计量(XRR)法,透射电子显微镜(TEM)、光学轮廓仪(OP),以及原子力显微镜(AFM)完成的。     

On the numerical assessment of the safety factor of elastic-plastic structures under variable loading

A finite element method for the shakedown analysis of two-dimensional structures under combined mechanical and thermal loading is presented. Linear elastic-perfectly plastic as well as linear elastic-limited kinematical hardening material behaviour is taken into account. The discretized shakedown problem is solved numerically with the reduced basis technique. A new method for the generation of reduced base vectors is presented. Numerical examples illustrate the proposed method.     

EFFECT OF TEMPERATURE ON WATER SORPTION EQUILIBRIUM OF ONION (ALLIUM CEPA L)

ABSTRACT

Results of the experimental measurement of sorption isotherms at different temperatures obtained by the standard gravimetric method showed the typical sigmoid shape of products rich in carbohydrates. The temperature had the expected effect predicted by the theory of physical adsorption i,e the quantity of sorbed water at a given water activity increased as the temperature decreased. The amount of adsorbed or desorbed water per unit weight of solid depends on the equilibrium temperature. The increase of the temperature results in increase of water activity for the same moisture content which in increases the rates of reactions leading to quality deterioration. As the water activity is raised beyond the intermediate region, water is sorbed by low molecular weight constituents resulting in shifting the isotherm upward. The values of the net isosteric heat of desorption were found to be higher than those or adsorption, which indicates that the binding energy for the latter is higher. At low moisture content the heats of desorption is much higher than that of adsorption.     

Energy and emissions forecast of China over a long-time horizon

Forecasts of energy demand, the fuel mix meeting that demand and the associated emissions are a key requirement for informed energy planning and policy decisions to ensure energy security and address climate change. While there have been many studies on China focusing on the short and medium term (to 2020 and 2050) there is little in the literature focusing on the long term (to 2100). This paper seeks to address those gaps on sectoral energy demands and emissions on long term by following a two-stage approach. It develops key energy indicators on useful energy demand, transport mobility and end use fuel demand for various sectors. The main drivers of these indicators are socio-economic parameters. The indicators are used to project energy service demands and emissions forward for China in TIMES G5 model at least cost approach. The results from this reference scenario suggest that China will require approximately 4 Gtoe of primary energy, by the end of the 21st century to deliver 3 Gtoe final energy consumption, 10 PWh of electricity generation, 1.3 Gtoe of energy imports, which will results in 10 Gt CO₂ emissions.     

Ionic liquid based absorption chillers for usage of low grade waste heat in industry

The standard working pairs for absorption chillers, ammonia/water and water/lithium bromide show problematic behaviours like crystallisation and corrosiveness. Because of their convenient solving properties and their low vapour pressure, ionic liquids are a new promising class of sorbents for absorption cooling purposes. In this study, the working pairs water/1,3‐dimethylimidazolium dimethylphosphate ([MMIM][DMP]) and water/1‐ethyl‐3‐methylimidazolium dimethylphosphate ([EMIM][DMP]) are implemented in AspenPlus. The performance of a single effect cycle with these pairs is simulated and compared to results of a cycle with water/LiBr. For [EMIM][DMP] a coefficient of performance (COP) comparable to that of LiBr or even higher (up to 0.85) is found. [MMIM][DMP] shows a smaller maximum COP but a largely wider operating temperature range than LiBr. Results are compared with those of other groups, discrepancies discussed and improvements suggested. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and Characterization of Ferrocene-Containing Hyperbranched Poly(aroylarylene)s

Ferrocene-containing hyperbranched poly(aroylarylene)s are prepared in satisfactory yields by one-pot copolycyclotrimerization of bis(aroylacetylene)s with a ferrocene-containing monoyne. The ferrocene content of the polymers can be varied by changing the monomer feed ratio, and copolymers with up to 41 mol% of ferrocene moiety can be readily prepared. All the polymers are thermally stable, losing little of their weights when heated to 340 °C. This article is dedicated to Professor Didier Astruc.     

Fracture mechanics analysis of stable crack growth under sustained load and instability of circumferential cracks in straight water-steam pipes

In order to determine the component behaviour of pipes made from X 20 CrMoV 121 steel for the water-steam circulation system of a helium-cooled high-temperature reactor component, tests were carried out under load conditions similar to the case of emergency cooling. The aim of the tests was to determine the stable and unstable crack growth in the less tough weld filler metal of girt-welded pipes of 18·5 mm wall thickness and 400 mm inside diameter. The tests were carried out with weld filler metals of two different toughnessesSuch stable crack growth could be of particular importance in the case of residual heat removal. For this reason two tests were carried out on pipes with a circumferential crack under sustained load.In the second part of the test programme pipes with defects were loaded under sustained internal pressure, and additionally an increasing bending moment was applied. The aim of this investigation was to determine the boundary conditions for failure occurring by leak or by fracture with regard to the different toughness of the weld filler metal.The fracture mechanics analysis was carried out using a modified version of the flow-stress criterion for circumferential cracks (Batelle approach) and using also the so-called ‘effective fracture toughness’ $\text{K}{}_{\mathrm{<mtext>eff</mtext>}}$.The investigation has revealed that the component toughness is adequately high and component failure by fracture is not expected. The experimental results can be described theoretically using either the Battelle approach or the formulae of linear-elastic fracture mechanics if the data obtained in the test characterising component behaviour (flow stress or effective toughness) are used as a basis. The results show that an evaluation of component behaviour using $\text{K}{}_{\mathrm{<mtext>Jo</mtext>}}$ values determined by CT specimens according to the $\text{J}$ integral procedure is too conservative.