Ab Initio Based Understanding of the Segregation and Diffusion Mechanisms of Hydrogen in Steels

A microscopic understanding of the processes that lead to hydrogen embrittlement is of critical importance for developing new generations of high-strength steels. With this article, we provide an overview of insights that can be gained from ab initio based methods when investigating the segregation and diffusion mechanisms of hydrogen in steels. We first discuss the solubility and diffusion behavior of hydrogen in the ferrite, austenite, and martensite phases. We consider not only defect-free bulk phases but also the influence of alloying elements and geometric defects such as vacancies and grain boundaries. In the second part, the behavior of hydrogen in the presence of precipitates, the solubility, the surface absorption, and the influence of hydrogen on the interface cohesion are studied. Finally, we provide simulation results for the interaction of hydrogen with dislocations. For all these applications, we will comment on advantages and shortcomings of ab initio methods and will demonstrate how the obtained data and insights can complement experimental approaches to extract general trends and to identify causes of hydrogen embrittlement.     

Structural investigation of PEG-fibrinogen conjugates

Controllable bio-synthetic polymeric hydrogels made from fibrinogen-poly(ethylene glycol) adducts have been successfully employed in tissue engineering. The structural consequences of PEG conjugation to fibrinogen (i.e., PEGylation) in such a hydrogel network are not fully understood. The current investigation details the structural alterations caused to the reduced fibrinogen polypeptides by the covalent attachment of linear or branched PEG chains. The structure of PEGylated fibrinogen polypeptides were comprehensively characterized using small angle X-ray scattering, light scattering, and cryo-transmission electron microscopy. These characterizations concur that the bio-synthetic hybrids self-assemble into elongated objects, having a protein core of about 50 Å in diameter decorated with multiple PEG chains. Conjugates with branched PEG chains were shorter, and have lower average molecular weight compared to conjugates with linear chains. The diameter of the protein core of both samples was similar, suggesting a tail-to-head aggregation of the PEGylated fibrinogen polypeptide. A more complete understanding of this unique structural arrangement can provide further insight into the full extent of biofunctional accessibility in a biomaterial that combines the advantages of synthetic polymers with bioactive proteins.     

Measurement design for evaluation of measurement results characterized by dispersion

A measurement-design procedure for evaluation of measurement results characterized by dispersion is proposed. Russia. Translated from Izmeritel’naya Tekhnika, No. 12, pp. 12–15, December, 1999.     

Not every domain of a plain decompressor contains the domain of a prefix-free one

C. Calude, A. Nies, L. Staiger, and F. Stephan posed the following question about the relation between plain and prefix Kolmogorov complexities (see their paper in DLT 2008 conference proceedings): does the domain of every optimal decompressor contain the domain of some optimal prefix-free decompressor? In this paper we provide a negative answer to this question.     

满足个人和企业对嵌入式平台的需求

危机中寻找亮点 在全球经济衰退背景中,依然能看到很多积极信号,在特定部门中还存在着极大的发展和增长潜力,例如:上网本的季度增长率达160%,3G业务美国第一次超越了欧洲,数字音乐也在蓬勃发展(苹果公司业务超过了沃尔玛),互联网市场增长率达20%,游戏机市场增长率19%,网络电视也在快速成长.在企业用户端,POS设备越来越精良.     

Technological features of a process and equipment for superplastic rolling of axially symmetric heat-resistant alloy components of rotors for modern aircraft engines

Scientific bases of a technology for superplastic roll forming of axially symmetric parts of gas turbine engines that are made of heat-resistant alloys are described. It is shown that a formed microcrystal structure allows their deformation under conditions of superplasticity, thereby providing changes in physical and mechanical and processing properties. Parts manufactured by superplastic rolling feature a highly homogeneous microstructure over the entire volume and isotropic mechanical properties or an optimized gradient microstructure allowing for nonuniform temperature and power loading in the process of operation. Technological features of the equipment for superplastic roll forming of discs for motors and requirements for the equipment and the control system are described and methods of calculation of major unit strength are covered.     

Measurement planning for quality assurance with allowance for systematic error

We present a procedure for choosing optimal measurement plans for quality assurance with allowance for systematic error in the measurements. Translated from Izmeritel'naya Tekhnika, No. 8, pp. 3–9, August, 1998.     

Novel nonlinear-modulation acoustic technique for crack detection

Novel nonlinear-modulation methods for crack detection are discussed. The approach is based on the so-called cross-modulation effect consisting of the modulation transfer from an intensive, initially slowly amplitude-modulated stronger (pump) excitation to the probe signal. Advantage of this technique is a very flexible choice of the operation frequencies, since their ratio for both carriers and the modulation may be rather arbitrary. This in its turn allows one to effectively use the sample resonances in order to achieve the necessary level of the pump excitation and to ameliorate conditions for detection of the modulation sidelobes for the probe wave. Unlike higher harmonic-generation methods the initial nonlinear distortions of the pump and probe excitations (e.g. due to nonlinearities in the electronics) are not critical for this technique. In the paper we summarise results of recent test experiments that indicated high sensitivity of the new technique.