The study on the critical temperature, composition, and microstresses in a Nb3Sn layer

Monofilamentary Nb₃Sn wires of large diameter with niobium tube, which were obtained by the method of solid-phase diffusion, are well suited for the study of the distribution of the critical temperature T_c in Nb₃Sn layers. Three regions with different gradients of Sn and Nb concentration and different Cu content can be distinguished in Nb₃Sn layer. In the central part of the layer, the Sn content comprises 24.5 at.% and the gradient of Sn concentration is negligibly small. Measurements on specimens of 1.2 mm in diameter with a slit cut along the cylinder generatrix showed that the critical temperature of the Nb₃Sn region adjacent to Cu(Sn) bronze is lower than the critical temperature of the central part of the layer. Fluctuations of T_c in the central part of the layer exceed the change of T_c related to the gradient of the Sn concentration, which is very small. These fluctuations spread both the R(T) curve and the high-temperature part of the temperature transition registered by the inductive method.     

Anxiety and the Archive: Understanding Plagiarism Detection Services as Digital Archives

Based on a case study of the popular plagiarism detection service Turnitin, particularly its “Legal Document,” this article contends that plagiarism detection services should be viewed as digital archives. Services like Turnitin not only seek to regulate what constitute original texts and appropriate writing practices but also to advance conceptions of the work that archives should do in storing and circulating texts in digital spaces. This article concludes that the services we sometimes use to ensure the integrity of students’ texts can themselves be of questionable integrity—largely through the design of their archives. As increasing numbers of texts take digital form, the problems and promise of digital archives will demand thoughtful responses that do not rush to replace questionable writing and research practices with equally troubling pedagogical and archival ones. These thoughtful responses start with exploring the use of plagiarism detection service archival technology in unadvertised ways.     

Composition and quality attributes of conventionally and organically farmed Pangasius fillets (Pangasius hypophthalmus) on the German market

A range of conventionally and organically farmed Pangasius or sutchi catfish fillets available on the German market were analysed to compare both composition and quality. Differentiation of Pangasius hypophthalmus from Pangasius bocourti was achieved by RFLP-SSCP analysis. The protein content of conventionally farmed fillets ranged between 13.3 and 15.7%, whereas organically produced fillets had significantly higher protein contents of between 17.0 and 17.4%. No difference in the fat content between farming methods was observed, which varied between 1.4 and 3.2%. Polyunsaturated fatty acids represented about 24% of the total fatty acids with a high level of linoleic acid. The comparison of the proximate composition indicated that water was added to most of the conventionally farmed products, in different amounts, as well as water-binding capacity enhancing additives. Differential scanning calorimetry was used to demonstrate the presence of polyphosphate on muscle proteins. Differences in texture, water-binding capacity and colour are discussed.     

Correlation between gas molecular weight, heating value and sonic speed under variable compositions of natural gas

A simulation study of likely uncertainties in molecular weight and heating value of the gas mixture as predicted from measured or calculated sonic speed. The sonic speed, molecular weight and heating value of natural gas were studied as a function of random fluctuation of the gas fractions. A method of sonic speed prediction was developed and used for over 50,000 computer-simulated variants of component concentrations in four- and five-component mixtures. Comparison of the obtained and the reference data on binary (methane–ethane) and multicomponent (Gulf Coast) gas mixtures under standard pressure and moderate temperatures indicates predictability of sonic speed on the basis of the binary virial coefficients, sonic speeds and heat capacities of the pure components. The results for two natural gas mixtures — with and without nonflammable components — are reported. Bivariate distribution and covariance elliptic zone plots are presented for three pairs of dependences of practical interest: molecular weight–sonic speed, heating value–sonic speed and heating value–molecular weight. The correlation coefficients, covariance, and regression equations are given for each pair of variance and mixture.     

铸造锌铝系合金底缩现象探讨

锌铝系合金铸造时出现反常的底部缩孔,而用一般上置式冒口对此类缩孔的补缩效果甚微。由于重力偏析造成的异常成分过冷导致底缩现象,因此针对成因提出消除或减轻底缩的途径。     

挤压铸造高速钢轧辊的研究

高速钢具有硬度高、红硬性好等特点 ,适合于制作轧辊、导辊等高温下工作的部件。高速钢轧辊通常采用离心铸造方法生产 ,由于高速钢中合金元素密度差大 ,轧辊偏析严重 ,高速钢优异的耐磨性发挥不出来。为了克服离心铸造方法的缺点 ,开发了挤压铸造高速钢轧辊技术 ,研究了挤压铸造工艺对高速钢性能的影响。压力、保压时间和压下速度是影响高速钢轧辊缩孔的重要因素。采用浇注温度 1 4 0 0～ 1 4 5 0℃、压力1 5 0 MPa、保压时间 1 2 0～ 1 5 0 s,压下速度 1 4～ 1 6 mm/ s,可获得组织致密、无偏析、加工量少的高速钢轧辊。应用于高速线材轧机预精轧机架 ,使用寿命比高镍铬无限冷硬铸铁轧辊提高 5～ 8倍。     

Crook-County蒙脱石的化学式计算

介绍了用矿物化学成分分析法计算蒙脱石化学式的步骤和结果。Crook-County蒙脱石的化学式为(Si_(3.98)Al_(0.02)~N(Al_(1.63)Mg_(0.15)Fe_(0.22)O_(10)(OH)_2Na_(0.39),分子量为376.7。实验结果表明,此方法的可行性取决于蒙脱石的纯化程度。比较蒙脱石阳离子交换容量的测定值与根据化学式计算值的接近程度,可以对蒙脱石的纯化程度作出评价。     

螺旋钻采煤机在里彦煤矿的应用

对YABSHK-2DM型螺旋钻采煤机的适用条件、应用意义、组成和构造、使用技巧及应用效果进行了论述，指出螺旋钻采煤机适用建筑物下、铁路下、水下的薄煤层“三下”采煤，安全可靠性高，开采成本和劳动强度低，推广前景广阔。     

脱苯沥青的组成,性质及中间相沥青的制备

采用ＧＣ－ＭＳ技术分析了脱苯沥青的组成，该沥青大部分由二环和三环芳烃组成，碳含量接近８５％，且灰分含量低。精制沥青在３８０－４４０℃下处理６０ｍｉｎ，即可得天喹啉不溶物含量为７０．７－９４．４％的中间相沥青，是制备炭的良好原料。