A critical assessment of the mechanistic aspects in HAYNES 188 during low-cycle fatigue in the range 25 °C to 1000 °C

The low-cycle fatigue (LCF) behavior of a wrought cobalt-base superalloy, Haynes 188, has been investigated over a range of temperatures between 25 °C and 1000 °C employing a triangular waveform and a constant strain amplitude of ±0.4 pct. Correlations between macroscopic cyclic deformation and fatigue life with the various microstructural phenomena were enabled through scanning electron microscopy (SEM) and transmission electron microscopy (TEM), detailing the crack initiation and propagation modes, deformation substructure, and carbide precipitation. Cyclic stress response varied as a complex function of temperature. Dynamic strain aging (DSA) was found to occur over a wide temperature range between 300 °C and 750 °C. In the DSA domain, the alloy exhibited marked cyclic hardening with a pronounced maximum at 650 °C. Dynamic strain aging has been documented through the occurrence of serrated yielding, inverse temperature dependence of maximum cyclic stress, and cyclic inelastic strain developed at half of the fatigue life. Additionally, the alloy also displayed a negative strain rate sensitivity of cyclic stress in the DSA regime. These macroscopic features in the DSA domain were accompanied by the substructure comprised of coplanar distribution of dislocations associated with the formation of pileups, stacking faults, and very high dislocation density. Toward the end of the DSA domain, dislocation pinning by M₂₃C₆ precipitates occurred predominantly. The deformation behavior below and above the DSA domain has also been investigated in detail. The temperature dependence of LCF life showed a maximum at ≈300 °C. The drastic reduction in life between 300 °C and 850 °C has been ascribed primarily to the deleterious effects of DSA on crack initiation and propagation, while the lower life at temperatures less than 200 °C has been attributed to the combined influence of low ductility and larger cyclic response stress.     

Ion implantation of Si in semi-insulating In0.53Ga0.47As:Fe

Ion implantation of Si in semi-insulating In0.53Ga0.47As:Fe was discussed. Electrical activation of more than 100%, a broad implant profile and an average electron mobility of 3000 cm2/Vs are observed in layers implanted with a dose of 2 × 1013 cm?2 at 260 keV and annealed at 670°C for 15 min. The results of photoluminescence measurements are also presented.     

Brugia pahangi: differential induction and regulation of jird inflammatory responses by life-cycle stages

A novel, miniaturized high-throughput screening format is described for assay of combinatorial libraries generated on beads. This approach, which is ideally suited to encoded libraries synthesized on beads, utilizes the photolytic cleavage of individual compounds into a high-density well array (>6500 wells within a standard 96-well microtiter plate footprint) with well volumes as low as 0.37 microl. As a model study, an encoded dipeptide library (324 members) acylated with isobutyl succinate was assayed using this format to search for potential inhibitors of matrilysin, a member of the matrix metalloproteinase superfamily. In situ release of compounds from solid support was accomplished by photochemical cleavage after beads and enzyme were distributed to the wells. After the addition of a fluorogenic substrate to the array, the extent of enzyme inhibition and identification of active compounds was quantitated by imaging of the fluorescence emission upon uv irradiation. The structure-activity relationship data generated from the identified inhibitors in this study corroborate previous findings, thus validating the utility of this approach as a means of high-throughput screening of bead-based libraries.     

Immune response against the non-repeat region (293-310) of the circumsporozoite protein of Plasmodium vivax

Immunization by peptides based on the repeat sequences of Plasmodium falciparum or P. vivax antigen(s) have shown inconsistent results during clinical trials in humans. This could be attributed to the lack of T-cell help or antigenic polymorphism. Thus, attention has been focused towards the more conserved non-repeat regions. The present study was undertaken to map the antigenic determinant in the vicinity of region II (outside the repeat) of CS protein of P. vivax. The immunogenicity of the peptide was studied alone and after linking with polytuftsin (PT), using alum and Freund's adjuvant, in inbred strains of mice with different genetic backgrounds. The humoral response and antigen induced T-cell proliferation assays clearly demonstrated the immunomodulatory activity of PT. Comparable results were observed with antigen(s) administered either in alum or Freund's adjuvant. The induction of IgG2a and IgG2b antibody isotypes by both, peptide as well as the conjugate, may indicate that the T-helper response involved is of Th1 type. Further the immunofluorescence studies have shown that antibodies recognized the air dried sporozoites of P. cynomolgi. The results thus show that the above sequence has overlapping B and T-cell determinants and that alum can be substituted for Freund's adjuvant in generating an effective immune response.     

某铜铁矿尾矿库废水神经网络预测研究

金属矿山尾矿库废水中含有H^ 、CN^-和多种金属离子，是矿区及其流域酸性污染和金属污染的主要污染源。在收集某铜铁矿尾矿库废水14年水质监测资料基础上，运用人工神经网络的改进BP算法对其8项水质指标进行了分析、分类和仿真预测，揭示了该矿尾矿库废水的污染特性，查清了主要污染物。     

基于流固热耦合的油气两相动压密封追随动态特性

为提升油气两相动压密封的运转稳定性和抗干扰能力,研究其密封补偿环的响应运动,揭示油气两相动压密封的追随动态特性, 考虑温度、变形对密封环和流体膜的综合作用,采用MATLAB软件建立密封环与流体膜的流固热耦合有限元分析模型. 计算流体膜的动态刚度和阻尼系数,求解油气两相动压密封的受迫振动模型,分析补偿环的响应运动. 讨论转速、压差、油气比、弹簧刚度和O形圈阻尼对密封补偿环响应运动角向振幅和轴向振幅的影响,分析密封的追随动态特性. 结果表明:提高转速和油气比有利于提高密封的追随动态特性;压差、弹簧刚度和O形圈阻尼的增大不利于密封补偿环的追随响应运动,其中弹簧刚度和O形圈阻尼增大前期,补偿环响应振幅变化不敏感,增大后期,补偿环响应振幅急剧降低. 研究结果为油气两相动压密封的补偿机构优化和动态性能研究提供理论支撑,并得到基于流固热耦合的油气两相动压密封追随动态特性求解方法.     

基于无线传感器网络节点的无线防误锁具设计

无线传感器网络使用电池供电,能量十分有限,其功耗问题严重制约了无线传感器网络的发展与应用。结合无线防误锁具,从硬件选型和低功耗软件设计两个方面设计无线传感器网络节点,降低功耗,延长网络的使用寿命。     

基于果蝇算法的开关磁阻电机多目标优化研究

针对采用传统算法对开关磁阻电机(SRM)本体进行多目标优化时存在算法复杂、调节参数多、计算量大且易陷入局部最优解等问题,提出一种基于果蝇算法(FOA)的SRM本体多目标优化设计方法。利用极限学习机算法建立SRM非参数模型,采用FOA算法对其进行优化,实现了SRM定转子极弧的全局最优设计,最后对该优化算法的效果进行了仿真验证,同时与传统粒子群优化算法(PSO)进行了对比分析,结果表明,FOA算法不仅获得了较PSO算法更好的转矩波动系数和效率指标,而且具有参数设置少、收敛速度快且不易陷入局部最优解等特点,具有较好的应用价值。     

Structural and ion transport properties of [(AgI)x(AgBr)0.4−x](LiPO3)0.6 and (AgBr)x(LiPO3)(1−x) solid electrolytes

The (AgBr)_x(LiPO₃)_(1−x) (x=0.4 and 0.5) and [(AgI)_x(AgBr)_0.4−x](LiPO₃)_0.6 (x=0.1, 0.2, and 0.3) superionic electrolytes have been prepared by conventional melt quenching using a twin roller. These electrolytes are characterized by X-ray diffraction, SEM, and energy dispersive X-ray analysis (EDAX) for structural investigation. Electrical characterizations have been carried out by the AC impedance analysis. The conductivity of LiPO₃ glassy system at room temperature is improved by doping with the silver bromide (AgBr)_x(LiPO₃)_(1−x) and the mixture of silver iodide, silver bromide (AgI-AgBr-LiPO₃ system) up to 10⁻⁵ and 10⁻³ Ω⁻¹ cm⁻¹, respectively (improvements by four or five orders of magnitude). The frequency response of ionic conductivity has been analyzed by universal dynamic response model (Jonscher's law) and AC conductivity data are fitted using the Jonscher's power law. The conductivity values obtained by the power law and impedance plots are comparable. The frequency exponent (n) has a value between 0 and 1. The AgI-AgBr-LiPO₃ system shows the mixed alkali effect. Summerfield scaling master curve is temperature dependent, which may be due to the contribution of the both lithium and silver ions to ionic conduction.