Size-dependent magnetoelectric response of (Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3)-(Ni0.8Zn0.2)Fe2O4 particulate composites

In this paper, we investigated the effect of magnetic grain size on magnetoelectric responses of particulate magnetoelectric 0.7(Bi_0.5Na_0.5TiO₃-Bi_0.5K_0.5TiO₃)-0.3(Ni_0.8Zn_0.2)Fe₂O₄ (BNKT-NZFO) composites. The coexistence of two chemically separated phases was confirmed using x-ray diffraction analysis. The composites had homogeneous microstructure with controlled grain size. The magnetoelectric response of the BNKT-NZFO composites sensitively depended on the grain size of the NZFO phase and the magnetoelectric voltage coefficients presented a marked enhancement of 33% in the engineered grain size range. This result indicated that tailoring the magnetic grain size physically will provide a powerful mean of enhancing magnetoelectric coupling in a two-phase particulate composite, with large potential application in area of magnetic field sensor.     

Modeling and surface texturing on surface roughness in machining LaPO4–Y2O3 composite

In this work, lanthanum phosphate with a 20% yttria (LaPO₄/Y₂O₃) composite prepared by an Aqueous Sol–Gel process is machined using an Abrasive Water Jet Machine (AWJM). The machinability of this composite is studied by varying the input parameters namely Jet Pressure (JP), Stand-Off Distance (SOD), and Traverse Speed (TS) on Surface finish. Garnet of 80 mesh size is used as an abrasive with a flow rate of 85?g/min. The microstructural characterization study reveals the presence of new element YPO₄. This element enhances the machinability and reduced porosity in the composite. Microscopy examinations on the machined surface reveals that partial overlapping at low JP, poor surface finish at high JP and SOD, forged deficiency at maximum SOD and TS. The minimum levels of all input parameters are influenced to obtain acceptable Ra. Atomic Force Microscopy (AFM) on the kerf surface shows micro wear track and peaks. The Multiple Regression Analysis (MRA) is developed for Ra to check the adequacy. From the Analysis of Variance (ANOVA), SOD has a significant effect on Ra with a contribution of 53%. The influence of JP and TS on Ra is found to be 31% and 15%, respectively.     

改性防护蜡对轮胎胎侧胶性能的影响

研究改性防护蜡对轮胎胎侧胶性能的影响。结果表明,与传统防护蜡相比,改性防护蜡异构烷烃质量分数较小,结晶尺寸小且致密程度高。改性防护蜡可在不影响胎侧胶硫化特性和物理性能的前提下,大幅提高胎侧胶抗喷霜性能,保证轮胎表面不受臭氧侵蚀,在防止裂纹产生的同时明显改善成品轮胎外观。     

Agreement and repeatability of four different devices to measure non-invasive tear breakup time (NIBUT)

PurposeSince tear film stability can be affected by fluorescein, the Dry Eye Workshop (DEWSII) recommended non-invasive measurement of tear breakup time (NIBUT). The aim of this study was to investigate the agreement and repeatability of four different instruments in the measurement of NIBUT.Methods72 participants (mean 24.2 ± 3.6 years) were recruited for this multi-centre, cross-sectional study. NIBUT was measured three times from one eye using each of the instruments in randomized order on two separate sessions during a day, separated by at least 2 h. NIBUT was performed at three sites (Switzerland, Germany and UK) using three subjective instruments, Tearscope Plus (Keeler, Windsor, UK) (TS), Polaris (bon Optic, Lübeck, Germany) (POL), EasyTear Viewplus (Easytear, Rovereto, Italy) (ET) and the objective Keratograph 5 M (Oculus Optikgeräte GmbH, Wetzlar, Germany) (KER). As the latter instrument only analyses for 24 s, all data was capped at this value.ResultsNIBUT measurements (average of both sessions) between the four instruments were not statistically significantly different: TS (median 10.4, range 2.0–24.0 s), POL (10.1, 1.0–24.0 s), ET (10.6, 1.0–24.0 s) and KER (11.1, 2.6–24.0 s) (p = 0.949). The objective KER measures were on average (1.2 s ± 9.6 s, 95 % confidence interval) greater than the subjective evaluations of NIBUT with the other instruments (mean difference 0.4 s ± 7.7 s, 95 % confidence interval), resulting in a higher limits of agreement. The slope was -0.08 to 0.11 indicating no bias in the difference between instruments with the magnitude of the NIBUT. Repeated measurements from the two sessions were not significantly different for TS (p = 0.584), POL (p = 0.549), ET (p = 0.701) or KER (p = 0.261).ConclusionsThe four instruments evaluated for their measurement of tear stability were reasonably repeatable and give similar average results.     

固溶处理对2205双相不锈钢组织及钝化膜特性的影响

用不同温度对2205双相不锈钢进行固溶处理,利用定量金相法及硬度法、电化学极化试验、电化学阻抗谱试验的方法研究固溶温度与2205双相不锈钢微观组织和钝化膜特性之间的关系。结果表明,当固溶温度为950 ℃时,有σ相存在,分布于铁素体/奥氏体晶界,当固溶温度为1000 ℃时,σ相消失,铁素体相比例随固溶温度的升高而升高,奥氏体相比例则呈相反规律;电化学试验和阻抗谱试验结果显示,材料在950 ℃时钝化膜稳定性和耐蚀性能最差,在1050 ℃时钝化膜稳定性和耐蚀性能最好。     

基于优化遗传算法改进的小波网络预测锰系磷化膜的耐蚀性

针对小波网络训练速率较慢、结构不易确定等问题,结合实验选取的因素(包括输入参数和输出结果),通过仿真确定了小波网络的结构为3-7-1。接着,利用优化遗传算法对小波网络进行改进,修正其初始权值和因子。通过仿真证实了改进的小波网络具备更强的寻优能力和更快的收敛速率。最后,利用改进的小波网络预测锰系磷化膜的耐蚀性。结果表明:改进的小波网络可以更好地拟合样本数据,能够进行较准确的预测。     

基于复合相变材料的梯级组合蓄热特性研究

针对潜热蓄热装置内部相变材料（PCM）导热系数偏小，蓄热速率过低的问题，对基于复合相变材料的两级串联式梯级蓄热装置的相变过程进行了数值研究。通过对不同热物性PCM工况的对比与分析，得到了装置在不同工况下的蓄热特性。结果表明，存在最佳的热扩散系数，使固定熔点的PCM实现“均匀等速相变”。同时，增大PCM的热扩散系数可以有效降低加热面温度，但随着热扩散系数的增大，加热面温度降低幅度减小。通过分析Stefan数，得到了装置最佳的参数，使工况蓄热效果最佳。最后，通过Stefan数为2.88时的实验工况验证了相关规律的正确性。     

海绵负载纳米Al2O3复合吸附剂去除水中硒研究

研究制备了海绵负载纳米Al2O3微球的复合吸附剂(NAS),并用于对Se(Ⅳ)和Se(Ⅵ)的吸附。结果表明,合成的纳米Al2O3微球(NAO)的平均尺寸为200~400 nm,在海绵上负载NAO会使其分散性更好。当NAO负载量分别为80 mg/g和60 mg/g时,NAS对Se(Ⅳ)和Se(Ⅵ)的吸附性能为佳,分别需要60、120 min达到平衡,适应pH为2~5;两者均符合准2级动力学模型;NAS对Se(Ⅳ)、Se(Ⅵ)的最大吸附容量分别为137.2、143.9 mg/g,能很好地与Freundlich模型拟合,说明NAS表面不均匀,且属于多层吸附。经过2次的循环,对Se(Ⅳ)和Se(Ⅵ)的去除率有所降低,但均仍保持在一定的水平,说明NAS可再生循环利用。NAS作为一种新型吸附剂去除水中Se具有较好的应用前景。     

A large-grain-size thick-film polycrystalline diamond detector for x-ray detection

A diamond film with a size of 6 × 6 × 0.5 mm³ is fabricated by electron-assisted chemical vapor deposition. Raman spectrum analysis, x-ray diffraction and scanning electron microscope images confirm the high purity and large grain size, which is larger than 300 μm. Its resistivity is higher than ${10}^{12}\,{\rm{\Omega }}\cdot {\rm{cm}}.$ Interlaced-finger electrodes are imprinted onto the diamond film to develop an x-ray detector. Ohmic contact is confirmed by checking the linearity of its current–voltage curve. The dark current is lower than 0.1 nA under an electric field of 30 kV cm⁻¹. The time response is 220 ps. The sensitivity is about 125 mA W⁻¹ under a biasing voltage of 100 V. A good linear radiation dose rate is also confirmed. This diamond detector is used to measure x-ray on a Z-pinch, which has a double-layer 'nested tungsten wire array'. The pronounced peaks in the measured waveform clearly characterize the x-ray bursts, which proves the performance of this diamond detector.