模块化可靠性系统的Signature计算方法研究

系统Signature是体现结构设计优良性的一组向量,描述系统设计对系统故障率的影响,在诸如系统可靠性指标分析、系统设计、系统寿命比较、寿命极限行为以及系统设计优化等方面展现出了强大的功能,成为可靠性研究领域越来越强有力的研究工具。而如何求解一个系统的Signature往往成为分析的关键一步,当系统庞大而复杂时,Signature计算难度将随着元件数目的增加呈指数增加,出现维数爆炸问题,这无疑对后续的分析造成巨大的障碍. 本文为了解决此问题,建立了基于模块化思想的系统Signature求解方法,并给出了基于模块化思想的模块化串、并联系统与模块化备份系统的求解方法,对比于传统算法,运用模块化思想大大减少了计算Signature的复杂度,能够有效减小计算量,缩减计算时间,并拓展了可求解Signature的系统范围。     

A combined tryptic peptide and winged peptide internal standard approach for the determination of α‐lactalbumin in dairy products by ultra high performance liquid chromatography with tandem mass spectrometry

A robust ultra high performance liquid chromatography with tandem mass spectrometry method at peptide level was established for measuring α‐lactalbumin in various dairy products. An isotope‐labeled winged peptide (VKKILDKVG*I NYW*L AHKALCSEKL) with extra amino acids of the sequence of signature peptide concatenated at each end as the internal standard was spiked in samples to participate in the whole tryptic digestion process. The peptide VG*I NYW*L AHK that resulted from the isotope‐labeled winged peptide was used as the final isotopically labeled internal standard of the α‐lactalbumin signature peptide (VGINYWLAHK) during the quantitative analysis. The contents of α‐lactalbumin in samples were calculated based on the equimolar relationship between the α‐lactalbumin protein and signature peptide. The optimized molar ratio of trypsin to protein (1:60) and enzymatic digestion time (5 h) could not only improve the digestion efficiency and reduce the cost, but also minimize the period of sample pretreatment. Considering the robustness of the current method using the isotopically labeled internal standard and acceptable measurement cost, its application may promote the development of nutrient investigation and quality control of α‐lactalbumin in dairy products. This protein analysis method might provide a new reference strategy for food analysis and quantitative protein analysis.     

Weakly hyperbolic involutions

Pfister’s Local–Global Principle states that a quadratic form over a (formally) real field is weakly hyperbolic (i.e. represents a torsion element in the Witt ring) if and only if its total signature is zero. This result extends naturally to the setting of central simple algebras with involution. The present article provides a new proof of this result and extends it to the case of signatures at preorderings. Furthermore the quantitative relation between nilpotence and torsion is explored for quadratic forms as well as for central simple algebras with involution.     

A variant of Digital Signature Algorithm

In this paper we present a variant of the Digital Signature Algorithm based on a factorization problem and two discrete logarithm problems. We prove that our signature scheme is at least as secure as the original Digital Signature Algorithm and withstands all known attacks.      

An Infrared Image Synthesis Model for High-Speed Targets

Although a number of infrared models are available for synthesizing the infrared image of static objects, they fail to simulate the infrared signature of targets flying at high speed. This paper presents an infrared image synthesis model for such kind of targets. Within this model, we account for not only all forms of heat transfer inside the targets but also the dynamic interaction between the target's surface and the surrounding air-flow. The heat transfer process between the target's surface and the air-flow is carefully analyzed based on the principles of infrared physics, aerodynamics and heat transfer, and a term due to aerodynamic heating is incorporated into our new model. Experimental results illustrate the potential of the model     

The behavior of warm standby components with respect to a coherent system

This paper is concerned with a coherent system consisting of active components and equipped with warm standby components. In particular, we study the random quantity which denotes the number of surviving warm standby components at the time of system failure. We represent the distribution of the corresponding random variable in terms of system signature and discuss its potential utilization with a certain optimization problem.     

Measurement of the directional emittance of polycrystalline beryllium oxide

The spectral emittance of polycrystalline beryllium oxide has been measured at four different angles from 0° to 75°, at a temperature of 150°C. From the spectral measurements the average band emittance in the 8–13 μm window has been calculated. The results show that the band emittance decreases from 0.44 at the angle of 0°, down to 0.23 at an angle 75° off the normal. The low band emittance is caused by a strong reststrahlen band in the wavelength region 9.2–14 μm. This reststrahlen band has been modelled by a Lorentz one-oscillator model. Experiment and calculations show that this band of low emittance increases its width towards shorter wavelengths at inclined angles and covers almost the entire upper atmospheric window 8–13 μm at the angle of 75°.     

The use of a thermostable signature amidase in the resolution of the bicyclic synthon (rac)-γ-lactam

The resolution of the bicyclic synthon (rac)-γ-lactam (2-azabicyclo[2.2.1]hept-5-en-3-one) is an important step in the synthesis of a group of chemotherapuetic agents known as carbocyclic nucleosides. The archaeon Sulfolobus solfataricus MT4 produces a thermostable γ-lactamase that has a high sequence homology to the signature amidase family of enzymes. It shows similar inhibition patterns of amidases towards benzonitrile, phenylmethylsulfonyl fluoride and heavy metals such as Hg²⁺, and is activated by thiol reagents. The enzyme selectively cleaves the (+)-enantiomer from a racemic mix of γ-lactam. It also exhibits general amidase activity by cleaving linear and branched aliphatic and aromatic amides. The enzyme catalyses the synthesis of benzoic hydrazide from benzamide preferentially to benzamide cleavage in the presence of excess hydrazine. This enzyme has potential for use in industrial biotransformations in the production of both carbocyclic nucleosides and hydrazides.