热晕小尺度不稳定性实验研究

本文报导了STRS不稳定性的模拟实验结果,研究了正弦强度分布的小尺度扰动源在热晕介质中传播的不稳定性发展情况,对不同扰动空间周期、不同光功率下小尺度不稳定性的增长做了一些实验研究,证实了激光在介质传播中,热晕将导致小尺度不稳定性的指数增长。     

底部气流对CO2激光切割硅钢切口质量的影响

激光切割相对冲压及线切割工艺具有自由度大、加工效率高、不会影响铁心质量等优点,但由于残渣及切口粗糙问题一定程度上影响了激光切割硅钢片的质量和应用范围.通过采用在工件底部增设辅助侧吹喷嘴,控制熔渣流向,保证成品切割质量激光切割工艺,试验证明,合理控制工艺参量,可获得良好效果.利用有限元法进一步对工件底部气流状况进行了数值模拟,分析了流动过程中在不同的角度和流速下光斑移动和气流场变化的情况,初步确定工件底部侧吹气流以20°吹入的辅助侧吹工艺,为进一步合理控制熔渣流向获得光滑的精细切口提供了实践和理论依据.     

一维有序聚苯胺纳米阵列的制备及电化学储能性能

以导电玻璃FTO为基底电极, 在硫酸溶液中, 分别研究了苯胺单体浓度和恒定电流大小对聚苯胺(PANI)形貌的影响; 同时恒定苯胺单体的浓度和工作电流, 探究了不同类型的质子酸对PANI阵列形貌的影响. 结果表明, 采用恒电流方法可以制备出一维有序PANI纳米线阵列, 而且当苯胺的浓度为0.1 mol/L, 恒电流法的工作电流密度为0.03 mA/cm²时, 所制备的PANI纳米线阵列形貌最佳; 当用HCl, HNO₃和对甲苯磺酸(p-TSA)作为合成PANI的支持液时, 得到树桩状的PANI 纳米结构, 不能得到均一的纳米线阵列结构. 电化学性能测试结果表明, 制备的最佳形貌PANI纳米线阵列的比电容值可达560 F/g; 循环1000周后电容损失率为11%.     

Improved Harmonic Incompatibility Removal for Susceptibility Mapping via Reduction of Basis Mismatch

In quantitative susceptibility mapping (QSM), the background field removal is an essential data acquisition step because it has a significant effect on the restoration quality by generating a harmonic incompatibility in the measured local field data. Even though the sparsity based first generation harmonic incompatibility removal (1GHIRE) model has achieved the performance gain over the traditional approaches, the 1GHIRE model has to be further improved as there is a basis mismatch underlying in numerically solving Poisson’s equation for the background removal. In this paper, we propose the second generation harmonic incompatibility removal (2GHIRE) model to reduce a basis mismatch, inspired by the balanced approach in the tight frame based image restoration. Experimental results shows the superiority of the proposed 2GHIRE model both in the restoration qualities and the computational efficiency.     

Preconcentration of trace elements from natural water with palladium precipitation

Palladium salts can be used as a coprecipitation carrier for the preconcentration of trace elements from natural water prior to their measurement by atomic spectrometry (AAS). The palladium is subsequently reduced by the introduction of hydrogen gas into the sample solution. The procedure is applied to the determination of Cu, Pb and Cd in seawater (enrichment factor 50) and synthetic water samples. Operating conditions have been optimized for the analysis of real samples. With the technique established an enrichment factor (500 fold) is feasible in synthetic samples. The recoveries of Cu, Cd and Pb from seawater are 95, 103 and 100%, respectively. This simple and rapid method can be applied in a wide pH-range and with complex matrices.     

Immersogeometric thermal analysis of flows inside buildings with reconfigurable components

Journal of Thermal Analysis and Calorimetry - The design and operation of energy sustainable buildings rely on the comprehensive understanding of how ventilation flows are influenced by different...     

Thiocyanation of Allylic Alcohols Promoted by Trifluoroacetic Acid

A rapid and efficient acid-promoted strategy to access allylic thiocyanates using allylic alcohols as substrates and easily-available NH₄SCN as the thiocyanate source is presented under metal- and oxidant-free conditions. Through screening of various kinds of acids, organic and strong trifluoroacetic acid (TFA) was found most effective. Testing of substrates showed that the strategy has remarkable functional group tolerance. A possible mechanism is provided, and the gram-scale experiment demonstrate that this novel protocol has potential industrial application value.