单纵模671nm红光激光器

利用全波片和Nd:YVO4激光器的偏振特性构成双折射滤光片,使用I类临界相位匹配LBO作为倍频晶体,在注入泵浦功率2.7W的情况下获得149mW的671nm单纵模红光输出,光-光转换率5.6%,该结构简单、紧凑,适合用于中低功率激光器。     

双侧风险度量方法及其在投资组合优化模型中的应用

现有的资产风险度量方法不能合理的反映收益的向上波动给投资者带来的风险感受,针对这一不足,本文提出了一种新的风险度量方法,这一方法综合考虑了投资者对于损失的规避和对超额收益的偏好,能够更为真实的反映投资者对于资产收益双侧波动的不同风险感受.同时本文结合新的风险度量方法给出了投资组合优化模型,并对模型的解从不同角度进行了分析.研究结果表明,新的风险度量方法可以为投资者提供更有效的投资决策依据,并且投资者的风险态度对于投资组合有效前沿和最优投资组合都有显著的影响.     

随机利息力下的一类年金的时间价值

对于年金的时间价值的研究,往往假定利率在整个期间内是固定不变的,但事实上,由于受到多种因素的影响,利率通常具有不确定性.因此,本文采用可逆MA(1)模型对随机利息力进行建模,在此基础上,研究了期末付虹式年金和期末付平顶虹式年金的时间价值问题,给出了上述两种形式年金现值的期望和方差的递推公式.通过数值仿真分析了相关参数对...     

圆柱装药在偏心定向起爆时水中近场压力特性

对UHL-5装药在侧向9点偏心定向起爆和几何中心点起爆时的水下爆炸近场峰值压力分布特性进行实验研究和数值模拟,得到2种起爆条件下不同距离与方位角测点处冲击波峰值压力和侧向9点起爆时的定向增益区域.结果表明,对于5 kg圆柱形UHL-5装药,采用侧向9点偏心定向起爆方式时,在爆距750 mm、方位角90°范围内的流场区域...     

Synthesis of new cyclotriphosphazene derivatives bearing Schiff bases and their thermal and absorbance properties

In this study, a series of cyclotriphosphazene derivatives containing a Schiff base (3a–3d) were synthesized by the reactions of hexachlorocyclotriphosphazene (1) with bis-aryl Schiff bases ( 2a – 2d ) having different terminal groups (H, F, Cl, and Br). The products ( 3a – 3d ) were characterized by elemental and mass analyses, FT-IR, and ¹ H, ¹³ C, and ³¹ P NMR spectroscopies. Furthermore, the structure of compound 3a was also determined by X-ray crystallography. The thermal behaviors and the spectral properties of the new cyclotriphosphazene compounds ( 3a – 3d ) were investigated and the results were compared in the series.     

Biosynthesis of silver nanoparticles using Onosma sericeum Willd. and evaluation of their catalytic properties and antibacterial and cytotoxic activity

In this study, silver nanoparticle (AgNP) synthesis was carried out using Onosma sericeum Willd. aqueous extract for the first time, with a simple, economical, and green method without the need for any other organic solvent or external reducing or stabilizing agent. A variety of AgNPs, all of different particle sizes, were synthesized by controlling the silver ion concentration, extract volume, temperature, and pH. It was determined that the optimum conditions for AgNP synthesis were 1 mM AgNO3, pH 8, 25 °C, 20 g/200 mL extract, silver nitrate, and extract ratio 5:1 (v/v). The AgNPs were defined using UV-Vis spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The particle size distribution and zeta potential measurements of the AgNPs were measured using the dynamic light scattering (DLS) technique. It was determined that the AgNPs with a particle size of less than 10 nm showed a higher catalytic effect in the reduction of 2-nitrobenzenamine. It was also found that these nanoparticles had a cytotoxic effect on the MCF-7 breast cancer cell line depending on dosage and time. The resulting IC50 values were between 76.63 µg/mL and 169.77 µg/mL. Furthermore, the biosynthesized AgNPs showed effective antibacterial activity against the Acinetobacter baumannii bacteria. The results of the study showed that synthesized AgNPs can have a promising role in biomedical and nanobiotechnology applications.     

Study of the THGEM detector with a reflective CsI photocathode

The THGEM detector without and with a CsI has been tested successfully. The optimal parameters of THGEM have been determined from eight samples. The UV photoelectric effect of the CsI photocathode is observed. The changing tendency related to the extraction efficiency (ε_extr) versus the extraction electric field is measured, and several electric fields influencing the anode current are adjusted to adapt to the THGEM detector with a reflective CsI photocathode.     

基于单色捕捉技术的透平导叶传热系数测量

采用窄带热敏液晶瞬态单色捕捉技术测量叶片全表面传热系数,以预先加热被测叶片并在主流中快速冷却的方法引入温度阶跃,利用3台3CCD（电荷耦合元件）相机对叶片表面的不同区域进行图像采集记录,将图像坐标转换至叶片空间坐标,通过后处理得到叶片表面传热系数。由实验结果分析可知,叶片前缘区域传热系数最大值位于加速最剧烈处,在吸力面...     

SnO_2/石墨纳米片复合电极及其在超级电容器中的应用

在电场的作用下对石墨棒进行电化学剥离,使其表面形成相互平行排列,且垂直于石墨棒基底的二维(2D)石墨纳米片阵列(GNSA).然后通过阴极还原电沉积法制备Sn O2/石墨纳米片阵列(Sn O2/GNSA)复合电极.采用场发射扫描电镜(FE-SEM)、X射线衍射(XRD)和傅里叶变换红外(FT-IR)光谱对其形貌和结构进行了表征.电化学测试表明该复合电极具有优异的超电容性能,在0.5 mol·L-1Li NO3电解质中,扫描速率为5 m V·s-1,电位窗口为1.4 V时,比电容达4015 F·m-2.由Sn O2/GNSA复合电极和相同电解质组装成的对称型超级电容器,在扫描速率为5 m V·s-1时,其电位窗口可增至1.8 V,能量密度达到0.41 Wh·m-2,循环5000圈后其比电容仍保持为初始比电容的81%.