Fluorine-plasma treated AlGaN/GaN high electronic mobility transistors under off-state overdrive stress

Influences of off-state overdrive stress on the fluorine-plasma treated AlGaN/GaN high-electronic mobility transistors (HEMTs) are experimentally investigated. It is observed that the reverse leakage current between the gate and source decreases after the off-state stress, whereas the current between the gate and drain increases. By analyzing those changes of the reverse currents based on the Frenkel-Poole model, we realize that the ionization of fluorine ions occurs during the off-state stress. Furthermore, threshold voltage degradation is also observed after the off-state stress, but the degradations of AlGaN/GaN HEMTs treated with different F-plasma RF powers are different. By comparing the differences between those devices, we find that the F-ions incorporated in the GaN buffer layer play an important role in averting degradation. Lastly, suggestions to obtain a more stable fluorine-plasma treated AlGaN/GaN HEMT are put forwarded.     

Watt-level,green-pumped optical parametric oscillator based on periodically poled potassium titanyl phosphate with high extraction efficiency

We report a compact, efficient optical parametric oscillator (OPO) based on a periodically poled potassium titanyl phosphate (PPKTP) crystal pumped by a 532 nm laser, which generated 1.51 W of average power at the signal wavelength of 709 nm with the pulse duration of ～ 1.0 ns. The extraction efficiency was up to 59%. To the best of our knowledge, this is the first report on Watt-level green-pumped PPKTP-based singly resonant oscillator OPO (SRO-OPO). The precise build-up time of OPO was determined to be 1.6 ns benefitting from the characteristic of twin-peak pulse profile of pump beam. The spectrum width of the idler was also measured to be 4.2 nm with the central wavelength of 2134 nm at 0.2 nm spectral resolution of optical spectrum analyzer. In addition, the beam quality of M² < 1.9 of generated signal exhibits a good consistency with M² < 1.5 for the pump source.     

新型2-羟乙基苯并[d]异噻唑-3(2H)-酮脂肪酸酯的合成及其抑菌活性

以苯并[d]异噻唑-3(2H)-酮为原料,通过取代与酯化反应合成了9个未见文献报道的了2-{3-氧代苯并[d]异噻唑-2(3H)-基}乙醇脂肪酸酯(4a～4i),其结构经1H NMR,IR和元素分析表征。初步体外抑菌活性测试结果表明,4对六种实验菌均表现出不同程度的抑菌活性,尤其对革兰氏阳性菌,用药量32μg.mL-1时抑菌率在90%以上。     

Electronic Instability of Kagome Metal CsV3Sb5 in the 2×2×2 Charge Density Wave State

Recently discovered kagome metals AV₃Sb₅(A = K,Rb,and Cs) provide an ideal platform to study the correlation among nontrivial band topology,unconventional charge density wave(CDW),and superconductivity.The evolution of electronic structures associated with the change of lattice modulations is crucial for understanding of the CDW mechanism,with the combination of angle-resolved photoemission spectroscopy(ARPES)measurements and density functional theory calculations,we invest...     

光子静质量与库仑定律关系的再论证

文章提出了一种全新的论证库仑定律符合平方反比律为光子静质量等于零的充要条件的方法,从库仑平方反比律的偏移出发,推导出光速随着传播距离的变化规律,从而证明库仑定律符合平方反比律是光子静质量为零的充要条件,并将推导结果与量子场论观点推导结果作出比较.     

对初中代数中整式一章教学的几点体会

初中代数里“整式”这一章是整个代数学的基础,它对学生以后的学习,关系是异常重大的。因此在教学中,必須要求学生要理解透彻,記忆牢固,运用正确,計算熟练。如所周知,在这一章的教学中,教师讲起来,学生多不感到难懂,但一当学生自己动手作起題来,有时就会感到似是而非,沒有把握,乃至錯誤百出。例如,开头时有的学生就不承认a 2a 5b=3a 5b已經算完了;有的认为a~0应等于0,而不应等于1;有的則算出:3x-2(x-5y)=3x-2x-5y,3x-2(x-5y)=3x-6x 30y,x~3·x~2=x~6,x~3y~2 x~2y~3=x~5y~5以及5ab 3ab=Sa2b,5a~2b 3a~2b==8a~4b~2等等錯誤的結果来;甚至有的还长期地把3a~2和(3a)~2,-a~2和(-a)~2,(a b)~2和a~2 b~2混淆不清;或者在教师强調了(a b)~2≠a~2 b~2之后,却連(ab)~2=a~2b~2又不敢承认了。笔者有鑑于此,深     

不同条件下血氨浓度的变化及影响因素

为保证人体中血氨浓度检测结果的准确性,并分析其影响因素,利用美国强生Vitros 250型干化学分析仪,通过比色法对血氨浓度进行检测.对检测结果用统计学软件SPSS 13.0进行计算处理.结果显示:在其它条件一定的情况下,两种温度下血氨浓度的变化不同,随着存放时间的延长,血氨浓度增加.因此对血氨标本应及时送检,检测时间应不超过20min,如不能及时检测,最好放于2-8℃冰箱中保存,但保存时间不应超过2.5h.     

羧甲基壳聚糖与铕、铽配合物的合成和配位机理研究

用羧甲基壳聚糖分别与硝酸铕和硝酸铽反应,制备了羧甲基壳聚糖-铕和羧甲基壳聚糖-铽稀土配合物。用红外光谱和X射线光电子能谱(XPS)等分析测试手段对配合物进行表征。对配合物配位机理进行了初步的研究,配合物中羧甲基壳聚糖中不仅羧基参与了配位,氨基上的N原子和羟基氧原子也参与了配位。     

工业污泥在空气气氛中的燃烧行为：动力学和热力学分析

通过TG分析,研究4种加热速率对空气气氛中污泥燃烧行为的影响。利用FWO和DEAM 2种模型计算污泥燃烧动力学和热力学参数。当升温速率为20 K·min-1时,污泥在空气气氛中的DTG曲线存在一个比较明显的主峰,主要的燃烧阶段发生在433和923 K之间,污泥的质量损失为33.646%。升温速率对污泥燃烧过程基本无影响,4种加热速率下的S、C和Di均随着升温速率的增加而逐渐增加。2种模型计算的Ea平均值分别为53.875和50.298 kJ·mol-1,R~2平均值分别为0.9616和0.9531,表明FWO和DEAM均能很好地估算出污泥燃烧的活化能。     

基于LWT的可见光DCO-OFDM系统

为了解决传统正交频分复用技术峰均比过高、复值型信号结构无法直接应用于强度调制直接检测系统等问题,将提升小波变换(LWT)应用于正交频分复用(OFDM)中,选择正交小波基作为子载波,通过对信号的预测与更新,将信号的高低频分离,并结合可见光通信(VLC)多次反射信道模型,建立了DCO-LWT-OFDM系统模型,推导了LWT...