Influence of dynamic strain aging pre-treatment on the low-cycle fatigue behavior of modified 9Cr–1Mo steel

The influence of dynamic strain aging (DSA) pre-treatment on the low-cycle-fatigue (LCF) behavior of modified 9Cr–1Mo steel was investigated at 550 °C. The DSA pre-treatment reduces the fatigue life, which is reflected on the fracture surface as multiple crack initiation. The samples pre-treated by DSA have higher peak tensile stress and positive mean stress effects, which is responsible for the lifetime reduction. The DSA pre-treatment does not change cross-slip mechanisms during mechanical cycling, compared without DSA process, but results in accelerating the microstructure transformation from lath to cells with low dislocation densities, which reduces the number of cycles to failure.     

The protection of bovine skeletal myofibrils from proteolytic damage post mortem by small heat shock proteins

This study aimed to determine how small heat shock proteins (sHSPs) protect myofibrillar proteins from μ-calpain degradation during ageing. Immunoprecipitation experiments with M. longissimus dorsi (LD) from Angus heifers (n = 14) examined the interaction between αβ-crystallin, desmin, titin, HSP20, HSP27 and μ-calpain. Results showed that αβ-crystallin associated with desmin, titin, HSP20, HSP27 and μ-calpain. Exogenous αβ-crystallin reduced desmin and titin degradations in myofibrillar extracts and attenuated μ-calpain activity. In a second experiment, bull LD (n = 94) were aged at − 1.5 °C for up to 28 days post mortem. μ-Calpain autolysed faster in high ultimate pH (pH_u) meat (pH_u ≥ 6.2) and this was concomitant with the more rapid degradation of titin and filamin in this pH_u group. Desmin stability in intermediate pH_u meat (pH_u 5.8 to 6.19) may be due to the protection of myofibril-bound sHSPs combined with the competitive inhibition of μ-calpain by sHSPs.     

Heat recovery from Diesel engines: A thermodynamic comparison between Kalina and ORC cycles

In the context of heat recovery for electric power generation, Kalina cycle (a thermodynamic cycle using as working fluid a mixture of water and ammonia) and Organic Rankine Cycle (ORC) represent two different eligible technologies. In this work a comparison between the thermodynamic performances of Kalina cycle and an ORC cycle, using hexamethyldisiloxane as working fluid, was conducted for the case of heat recovery from two Diesel engines, each one with an electrical power of 8900 kWe. The maximum net electric power that can be produced exploiting the heat source constituted by the exhaust gases mass flow (35 kg/s for both engines, at 346 °C) was calculated for the two thermodynamic cycles. Owing to the relatively low useful power, for the Kalina cycle a relatively simple plant layout was assumed. Supposing reasonable design parameters and a logarithmic mean temperature difference in the heat recovery exchanger of 50 °C, a net electric power of 1615 kW and of 1603 kW respectively for the Kalina and for the ORC cycle was calculated.Although the obtained useful powers are actually equal in value, the Kalina cycle requires a very high maximum pressure in order to obtain high thermodynamic performances (in our case, 100 bar against about 10 bar for the ORC cycle). So, the adoption of Kalina cycle, at least for low power level and medium–high temperature thermal sources, seems not to be justified because the gain in performance with respect to a properly optimized ORC is very small and must be obtained with a complicated plant scheme, large surface heat exchangers and particular high pressure resistant and no-corrosion materials.     

对SAR双通道对消的方位向间歇采样散射波干扰

合成孔径雷达（Synthetic Aperture Radar,SAR）通道对消技术可有效抑制散射波干扰等多种干扰类型,因此本文提出利用方位向间歇采样散射波干扰慢时间间歇性来对抗SAR双通道对消系统的干扰方法.首先详细推导了散射波干扰的SAR双通道对消原理,然后建立了方位向间歇采样散射波干扰模型并分析了该方法对传统SAR成像的干扰效果.在此基础上,分别研究了该干扰方法在双通道对消系统分别采用两种相位补偿条件时的对抗效果.理论与实验分析表明：当采用自动相位搜索算法估计相位进行补偿时,可使得场景对消成像出现类似噪声的混乱明暗斑点,并伴随着未对消的虚假散射场景;当采用准确相位进行补偿时,可在对消成像中形成多个虚假散射场景和对消暗条纹.     

Synthesis of a boron-containing conducting polymer from the anodic oxidation of Tris(pyrrolyl)borane

The electrochemical oxidation of Tris(N-pyrrolyl)borane (1) in THF yielded a conducting polymer film with an electron conductivity of ca. 7×10⁻⁴ S cm⁻¹. The coulometric measurements indicated that the three pyrrolyl units were not totally coupled during the electropolymerization reaction. From further UV–VIS and FT-IR spectroscopy data, a structure of poly(1) was then proposed.     

A lateral flow immunoassay for measuring ochratoxin A: Development of a single system for maize,wheat and durum wheat

A quantitative lateral flow immunoassay for the detection of ochratoxin A (OTA) in cereals has been developed. The ready-to-use device includes a nitrocellulose membrane on which capturing reagents are immobilized in spatially confined zones and a conjugate pad on which the antibody labelled with gold nanoparticles is pre-adsorbed. Stabilization of gold labelled antibodies and blocking of non-specific interactions of the nitrocellulose membrane were obtained by using 1% ovalbumin. This, combined with the use of PEG in the extraction of OTA from cereal samples, allows us to level the matrix effects caused by various cereals (maize, wheat and durum wheat). The immunochromatographic assay developed includes a rapid and very simple treatment of samples, which, in addition, does not involve the use of organic solvents and allows the quantitative determination of OTA with limits of detection as low as 1.5 μg kg^?1. The coefficients of inter–assay variations are below 20%, with recoveries which ranged from 87 to 119%. Fifteen maize samples, four wheat and six durum wheat samples were extracted with the aqueous medium and analysed by the developed assay. A good correlation was observed (y = 0.99 x + 0.18, r² = 0.982, n = 25) when data was compared with that obtained through a reference method.     

基于社区结构的复杂网络鲁棒性优化策略

为在复杂网络鲁棒性优化过程中尽可能保留网络初始社区结构,分析重连边策略对网络社区结构的影响,提出一种结合社区结构的复杂网络鲁棒性优化策略.采用Louvain算法确定复杂网络社区结构,利用模拟退火算法提升复杂网络中单个社区的内部鲁棒性,使用改进的智能重连边策略(Smart Rewiring)提升社区间的连接鲁棒性,并通过...     

基于全局最近邻的离群点检测算法

针对全局最近邻离群点检测算法的效率问题,为了能够在数据集中快速准确地检测离群点,运用属性约简技术,将离群点的搜索简约到较小的最具代表性的属性子空间中进行,从而有效降低属性空间搜索的复杂度。在此基础上,通过计算基于近邻的加权离群因子实现离群点的检测并提出了相应的算法。实验表明,该离群点算法具有较好的适应性和有效性。     

Thermal conductivity of polymer composites with close-packed structure of nano and micro fillers

Thermal conductivity of polymer composites with nano and micro fillers has been investigated numerically and experimentally. The nano fillers used were multi-walled carbon nanotubes (MWNTs) and alumina nanoparticles, and the spherical alumina particles were selected as the micro fillers. A periodic unit cell with a random close-packed structure was created using a packing algorithm that treat the micro filler as spheres. Finite element analyses were also performed to predict the potential of nano fillers to enhance thermal conductivity of the composites and to analyze the effect of microstructure of micro fillers. Additionally, the polymer composites with nano and micro fillers were made and the thermal conductivity of the composites were measured. The results showed that the addition of MWNTs to the matrix lead to a large increase in thermal conductivity of the composites. The proposed thermal model predicted a thermal conductivity in good agreement with experiment.     

Simulation of static and kinetic buckling of unstiffened and stiffened cooling tower shells

Natural draught cooling tower shells are loaded mainly by their dead weight and by the wind, which may both cause buckling failure. The present paper compares various numerical procedures to investigate the stability behaviour of cooling tower shells. These are a complete nonlinear analysis, a linear eigenvalue analysis for a stationary non-axisymmetric wind load, and a linear eigenvalue analysis for a wind load, approximated to be axisymmetric. The aim is to evaluate whether a geometrically nonlinear analysis can be replaced by a time-saving classical buckling analysis, probably even for an axisymmetric state of stress. The third procedure, as the most conservative, but a very effective one, will be applied to investigate the mechanical influence of ring stiffners on the buckling behaviour of cooling tower shells. Kinetic instability phenomena will also be examined. The structural improvement resulting from ring stiffeners will be quantified and summarized in design recommendations.