气体作冷却润滑剂的绿色切削试验

为实现绿色切削,研究了无污染、无危害的冷却润滑技术.采用氮气、氧气、二氧化碳气、氩气及过热水蒸气作冷却润滑剂,进行了单因素切削试验.试验结果表明,这些气体冷却润滑剂可以减小切削变形、切削力,降低切削温度,改善加工表面形貌.根据试验结果和冷却润滑作用机理分析可知,气体在切削中具有一定的冷却润滑作用,同时具有来源广泛、无毒害和污染、不用回收处理等绿色特点,故气体具备绿色切削的潜力.     

基于数值模拟的定向连续铸造固液界面位置人工神经网络模型的研究

基于人工神经网络原理及数值模拟技术，对定向凝固连续铸造过程中控制参数的选取进行了研究。利用自行设计的上引式定向凝固连铸机，结合数值模拟，提取了引晶速率、熔体温度、结晶器温度、冷却水温度、冷却水流量、冷却距离等控制参数值及相应目标参数值的固液界面位置。通过归一化处理所得数据，采用BP算法训练网络，对定向凝固连铸控制参数与固液界面位置之间的映射关系进行了函数逼近，建立了固液界面位置神经网络模型，依据该模型，可定量预测定向凝固连铸过程的工艺状态，并可为将来的定向凝固连铸神经网络控制提供可行的控制模型。     

Microwave irradiation under different pH conditions induced a decrease in β-lactoglobulin antigenicity

Whey proteins adjusted at pH values 2, 4.6, 9 and at the natural milk pH (pH 6.8) were subjected to microwave irradiation at 300 W for 20 min or 700 W for 10 min. The protein composition of treated and native whey proteins were evaluated by Lowry’s method and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The ability of treated whey to bind IgG polyclonal antibody was determined by an enzyme-linked immunosorbent assay (ELISA) using sera obtained from rabbit immunized to β-Lactoglobulin (β-Lg). Significantly higher losses in soluble protein concentrations were observed for microwave irradiated whey proteins at pH value 4.6 (35.6% at 300 W and 44.33% at 700 W) (P < 0.0001) compared with those irradiated at the natural milk pH (26% at 300 or 700 W). The electrophoretic patterns of these proteins revealed a considerable decrease in intensity of the band corresponding to α-lactalbumin but only a slight modification was observed for the electrophoretic profiles of β-lactoglobulin. The data obtained with a rabbit anti-β-lactoglobulin immunoglobulin indicated a low antigenic response for microwave-irradiated whey proteins at the natural milk pH (up to 29.32% as well as 300–700 W) (P < 0.001). The lowest antigenicity was observed for samples adjusted to pH 4.6 followed by microwave irradiation at 300 or 700 W (46.99% at 300 W and 41.16% at 700 W) (P < 0.0001).     

GaAs-based materials for heterojunction bipolar transistor's: reliability results and MMIC applications

This paper reports the present status of GaAs based-heterojunction bipolar transistor (HBT) under development at Thales. We have developed a complete GaInP/GaAs-based technological process from material studies to discrete devices and microwave monolithic integrated circuits (MMIC) realisations. This know-how has been transferred recently to Thales/United monolithic semi-conductors. Discrete devices with output power over 1 W and power added efficiency (PAE) over 50% have been obtained at 10 GHz in CW. 8 W MMIC amplifiers have been fabricated using the same unit cells. The first reliability results are promising: more than 6000 h without failure for devices stressed up to 210°C and 40 kA cm⁻². However, it seems that these results can still be improved. Some physical properties of the GaInP/GaAs HBT structures are suspected to have a major impact on the device reliability. The role of key parameters such as hydrogen incorporation in the GaAs base layer or residual strain in the GaInP/GaAs HBT structure has been investigated and its effects on the device characteristics identified. However, the major reliability improvement came from a novel way to passivate the extrinsic base surface. A comparison of the obtained results (device performance and reliability) with some of the best reported values in the literature (HP, TI, Daimler-Benz, etc.) is presented.     

Fabrication of evacuated glazing at low temperature

An indium-based seal augmented with an adhesive, developed to maintain a vacuum between two sheets of glass, avoids the high temperatures required to produce a seal in evacuated glazings to date. An experimentally-validated three-dimensional transient model has been used to predict heat transfer for an indium/adhesive sealed 1 m² area evacuated window with a highly insulating frame. An overall heat loss coefficient of 0.9 W m⁻² K⁻¹, with a midplane value of 0.36 W m⁻² K⁻¹, can be achieved with 0.72 visible transmittance for two 6 mm panes separated by 0.2 mm diameter pillars 40 mm apart. The conduction through a 3 mm edge-seal was 1.14 W m⁻² K⁻¹. Detailed three-dimensional isothermal contour plots through the system are presented.     

^89Sr放射性核素的活度测量

介绍利用液体烁计数法^89Sr核素进行绝对测量，解决了零几率外推等总理２，合成标准不确定度达到０．６２％，为^89Sr核素的应用提从可靠的测量方法。     

Threshold stress in dispersionally strengthened superplastic Al alloys

It is important for practical applications that some commercial alloys with stabilized finegrained structure should exhibit superplastic behaviour at high temperatures. In this paper the results of impression creep tests conducted on AlMgZn alloys are reported and the strain rate sensitivity and activation enthalpy were determined. The mechanical behaviour of the alloys as a function of the strain rate sensitivity can be divided into three regions. At low and high stresses the strain rate sensitivity parameter is low and the deformation process is not superplastic. Superplastic deformation takes place only at intermediate stresses. The microstructural interpretation of these processes involves, in general, the change of the micromechanisms controlling the different deformation processes. It was determined that by the supposition of a threshold stress depending strongly on temperature, the two regions due to low and intermediate stresses of the deformation can be described by the same constitutive equation.     

Effect of interesterified fat mixtures on certain lipid indices in experimental fat metabolism disturbance

Groups of adult Wistar male and female rats were fed isoenergetically for a three and a six weeks period either with synthetic lipogenic diet containing 5% and 20% fat mixtures (in which sunflower oil and lard were blended according to the ratio of 35:65) or with the same synthetic diet containing the mixture of sunflower oil and interesterified lard in a similar ratio. A control group received a normal diet for 6 weeks, whereas one of the experimental groups (fed with the 20% fat mixture in the lipogenic diet for 6 weeks) was given the normal diet for an additional two weeks period. After the feeding periods had been completed serum HDL-C levels and the total lipid, triglyceride, total cholesterol, free fatty acid levels were determined in serum and liver. The distribution of fatty acids in liver and heart muscle was also evaluated. In comparison to the control values it has been found: 1. Consumption of the lipogenic diet which is known to increase the serum total lipid and total cholesterol content induced in male rats a smaller augmentation in these indices when consuming the 20% fat mixture with a P/S ratio approaching the ideal 1 values, than in case of a 5% fat mixture consumption. In case of female rats, considerable increases of the serum values, could be observed at both fat consumption levels. The serum triglyceride and HDL-C contents decreased for all experimental groups. 2. The total lipid and triglyceride content of the liver increased in a high degree, the fatty liver syndrome was developed--more rapidly in males than in females. The total lipid, triglyceride and total cholesterol contents of the liver of male rats exceeded those of females by 15-30%. 3. The interesterification of the lard component of fat mixture resulted in lipid indices similar to those without interesterification, or in certain cases, they were found to be even slightly more favourable, i.e. the biological effect of the technological change proved to be adequate. 4. After a two weeks regeneration period the serum values of the male rats approached closer the normal control values than those of the females which were decreasing from a very high level but the degree of decrease was greater for them than for the male rats. The lipid content of the liver showed similar values.(ABSTRACT TRUNCATED AT 400 WORDS)     

Lactic acid bacteria profiles and tyramine and tryptamine contents of Turkish tulum cheeses

Tulum cheese, commonly produced in Turkey, is a traditional Turkish dairy product made from raw milk. In this research, 20 samples of tulum cheese were purchased from different markets in Isparta and Ankara (Turkey) and the populations of lactic acid bacteria (LAB) and contents of biogenic amines of Turkish tulum cheeses were investigated. The mean counts of LAB (as log10 cfu/g) were 7.22±0.67 on MRS agar, 6.93±1.77 on M17 agar, 7.28±0.72 on APT agar and 5.98±2.20 on ADA agar. Isolates of LAB obtained from 20 tulum cheeses were characterised as lactobacilli (48.5%), enterococci (32.7%), lactococci (15.8%) and streptococci (3.0%). Lactobacillus paracasei ssp. paracasei, Lactobacillus bifermentans and Enterococcus faecium predominated among the LAB in the samples of tulum cheeses; these organisms represented 30.2% of the isolates. As amino acids, tyrosine and tryptophan were determined in tulum cheeses. Tyramine and tryptamine, biogenic amines, were found at 0.00–329.00 and 0.32–40.44 mg/kg, respectively.     

高压旋喷桩在泵站地基加固中的应用

沙湖泵站经过30多年的运行,总沉降量大,沉降不稳定,不均匀沉降超标,严重影响了泵站的正常运行.通过重新地勘及沉降分析,认为地基承载力不足是泵站地基异常沉降的主要原因.结合泵站情况、地基沉降特点以及施工的便利性,决定采用高压旋喷桩进行加固泵站地基.通过有限元分析了加固前后的沉降变形,结合现场检测,结果表明采用高压旋喷桩加固后,泵站地基沉降满足规范要求,可为类似工程借鉴.