PMNT粉体的溶胶-凝胶法制备研究

以硝酸铅、六水合硝酸镁、草酸铌、钛酸丁酯为前驱体原料,去离子水、乙二醇为溶剂,柠檬酸为螯合剂,铅、镁、铌、钛离子比为1：（1-x）/3：2（1-x）/3：x,其化学式为（1-x）Pb（Mg1/3Nb2/3）O3-xPbTiO3,采用溶胶-凝胶法经1150℃焙烧制备得到了单一相钙钛矿结构的PMNT粉末.     

时域Rankine源法求解有限水深船舶在规则波中的水底压力变化

应用势流理论中的Rankine源面元法和时域步进法,求解了有限水深船舶在规则波中运动的水底压力变化。将速度势分解成基本势、局部势和记忆势,以叠模解作为基本势对自由表面条件和物面条件进行了线性化,通过在水底布置面元来满足水底条件。利用研制的水底压力-水面波浪测量系统,测量了不同入射波船模表面波形与水底压力的时历曲线,理论计算与实验结果符合较好,验证了自编程序的正确性。通过对比二者的等高线图发现,水底压力与表面波形的峰谷有较好的一致性,并且压力较波形更为平滑。     

Equivalent method for accurate solution to linear interval equations

Based on linear interval equations, an accurate interval finite element method for solving structural static problems with uncertain parameters in terms of optimization is discussed.On the premise of ensuring the consistency of solution sets, the original interval equations are equivalently transformed into some deterministic inequations.On this basis, calculating the structural displacement response with interval parameters is predigested to a number of deterministic linear optimization problems.The results are proved to be accurate to the interval governing equations.Finally, a numerical example is given to demonstrate the feasibility and efficiency of the proposed method.     

Characteristics and threshold voltage model of GaN-based FinFET with recessed gate

In this work, AlGaN/GaN FinFETs with different fin widths have been successfully fabricated, and the recessed-gate FinFETs are fabricated for comparison. The recessed-gate FinFETs exhibit higher transconductance value and positive shift of threshold voltage. Moreover, with the fin width of the recessed-gate FinFETs increasing, the variations of both threshold voltage and the transconductance increase. Next, transfer characteristics of the recessed-gate FinFETs with different fin widths and recessed-gate depths are simulated by Silvaco software. The relationship between the threshold voltage and the AlGaN layer thickness has been investigated. The simulation results indicate that the slope of threshold voltage variation reduces with the fin width decreasing. Finally, a simplified threshold voltage model for recessed-gate FinFET is established,which agrees with both the experimental results and simulation results.     

Vertical polarization-induced doping InN/InGaN heterojunction tunnel FET with hetero T-shaped gate

A novel vertical InN/InGaN heterojunction tunnel FET with hetero T-shaped gate as well as polarization-doped source and drain region (InN-Hetero-TG-TFET) is proposed and investigated by Silvaco-Atlas simulations for the first time. Compared with the conventional physical doping TFET devices, the proposed device can realize the P-type source and N-type drain region by means of the polarization effect near the top InN/InGaN and bottom InGaN/InN heterojunctions respectively, which could provide an effective solution of random dopant fluctuation (RDF) and the related problems about the high thermal budget and expensive annealing techniques due to ion-implantation physical doping. Besides, due to the hetero T-shaped gate, the improvement of the on-state performance can be achieved in the proposed device. The simulations of the device proposed here in this work show I_ON of 4.45×10^-5 A/μm, I_ON/I_OFF ratio of 10¹³, and SS_avg of 7.5 mV/dec in InN-Hetero-TG-TFET, which are better than the counterparts of the device with a homo T-shaped gate (InN-Homo-TG-TFET) and our reported lateral polarization-induced InN-based TFET (PI-InN-TFET). These results can provide useful reference for further developing the TFETs without physical doping process in low power electronics applications.     

奇异三阶微分方程边值问题的正解

讨论了奇异三阶微分方程边值问题的正解存在性.通过与一个线性算子相关的第一特征值的讨论,运用不动点指数定理,得到了正解存在的结果.其中允许h(t)在t=0和t=1处奇异.     

城市表层土壤重金属污染分析模型

本文先利用Matlab做出各种重金属元素浓度的空间分布图,初步得到土壤重金属污染的状况.接着用内梅罗污染指数法定量的确定土壤重金属污染最严重的地区,并用主成分分析法进行了验证.最后利用灰色-灾变与回归预测的组合模型解决了地质环境的演变问题.     

Fabrication and characterization of V-gate AlGaN/GaN high-electron-mobility transistors

V-gate GaN high-electron-mobility transistors (HEMTs) are fabricated and investigated systematically. A V-shaped recess geometry is obtained using an improved Si3N4 recess etching technology. Compared with standard HEMTs, the fabricated V-gate HEMTs exhibit a 17% higher peak extrinsic transconductance due to a narrowed gate foot. Moreover, both the gate leakage and current dispersion are dramatically suppressed simultaneously, although a slight degradation of frequency response is observed. Based on a two-dimensional electric field simulation using Silvaco "ATLAS" for both standard HEMTs and V-gate HEMTs, the relaxation in peak electric field at the gate edge is identified as the predominant factor leading to the superior performance of V-gate HEMTs.     

古典Adams谱序列中的一个非平凡乘积元

证明了古典Adams谱序列中的乘积元b_0~2β_s∈Ext_A~(s+4,t(s))(Z_p,Z_p)的非平凡性,其中p≥11,2≤sp-2,t(s)=2(p-1)[(s+2)p+(s-1)]+(s-2).     

染料敏化太阳能电池中花青素与β-胡萝卜素天然染料共敏化的研究

从高原格桑花和胡萝卜中提取天然染料花青素和β-胡萝卜素作为敏化剂,并组装染料敏化太阳能电池(DSC).研究了提取的天然染料的光吸收性能、主要成分和共敏化方式,讨论了花青素和β-胡萝卜素的共敏化形式、比例、浓度和时间对DSC光电性能的影响.研究发现,花青素和β-胡萝卜素混合敏化时表现出明显的共敏化作用,而分层敏化时则共敏效果不明显.当花青素含量逐渐降低时,共敏化电池的短路电流和光电转换效率表现出先增大后减小的趋势,且共敏化的最佳体积比为1∶1,同时发现共敏化时间比通常少很多,最佳敏化时间为15min.最佳共敏化条件下组装的DSC的短路电流密度为0.725 mA/cm2,光电转换效率为0.267;,相比于花青素和β-胡萝卜素单独敏化时组装的DSC,短路电流分别提高了60;和505;,光电转换效率分别提高了51;和480;,这主要得益于共敏化后拓宽的光谱吸收范围.