基于MOCCII多功能二阶电流模式滤波器设计

文中提出了一种基于M OCC II(多端输出第二代电流传输器)的单输入三输出二阶滤波器电路模型,由该模型可得出几种不同的滤波器电路,每种滤波器电路都由四个M OCC II、两个接地电容和电阻组成。不但能同时实现二阶高通滤波、低通滤波和带通滤波功能,还可以通过对输出端的直接组合,实现带阻和全通滤波功能及其他任意形式的二阶信号传输功能。滤波器的角频率和品质因数独立可调,应用非常灵活。与同类滤波电路相比较,该电路不但结构简单,而且使用灵活,有利于集成。同时,对其中一种滤波器的滤波特性进行了测试,实验结果表明,滤波器的滤波性能良好,电路模型完全正确。     

Superhydrophobic Flexible Supercapacitors Formed by Integrating Hydrogel with Functional Carbon Nanomaterials

Main observation and conclusion With the rapid development of the wearable electronics,the flexible supercapacitor with high energy density has attracted more a...     

声表面波射频识别系统的FMCW信号源设计

频率调制连续波(FMCW)的产生(即FMCW信号源)是声表面波射频识别系统频域采样阅读器的重要组成部分。为了满足扫频速度、带宽和线性度等要求,采用直接数字频率合成器(DDS)与锁相环(PLL)混频,并结合IQ调制的方式设计了超高频FMCW信号源。实际制作了信号源电路,DDS芯片输出I、Q两路正交信号,并分别以差分形式传输至IQ调制芯片进行上变频。测试了DDS输出信号的差分、正交特性,分别对信号源产生的单频信号和扫频信号进行了测试。最后搭建系统对声表面波标签进行测试。测试结果表明信号源设计的有效性。     

雪崩击穿条件下4.5kV IGBT器件的背面优化研究

The static avalanche breakdown behavior of 4.5 kV high-voltage IGBT is studied by theory analysis and experiment. The avalanche breakdown behaviors of the 4.5 kV IGBTs with different backside structures are investigated and compared by using the curve tracer. The results show that the snap back behavior of the breakdown waveform is related to the bipolar PNP gain, which leads to the deterioration of the breakdown voltage. There are two ways to optimize the backside structure, one is increasing the implant dose of the N C buffer layer, the other is decreasing the implant dose of the P C collector layer. It is found that the optimized structure is effective in suppressing the snap back behavior and improving the breakdown characteristic of high voltage IGBT.     

对变压器局部放电及其现场试验的相关问题的分析及处理

本文研究了电力变压器产生局部放电的现象以及这种现象为什么会发生的原因;一旦这种现象产生以后可能带来的危害。同时本文还研究了在实验中出现的几种关于变压器局部放电的故障类型,此外,还对这种非正常放电产生的原因以及这种非正常放电的可能性。最后,本文通过实验研究指出,在进行变压器的生产中要对装配工艺进行严格的把关,以确保变压器的质量。     

Chemical composition and in vitro evaluation of the cytotoxic and antioxidant activities of supercritical carbon dioxide extracts of pitaya (dragon fruit) peel

Background

Hylocereus polyrhizus and Hylocereus undatus are two varieties of the commonly called pitaya fruits, and pitaya fruits have gained popularity in many countries all over the world. However, studies on chemical composition and the nutritional quality of pitaya flesh peel are limited.

Results

Extracts of pitaya (H. polyrhizus and H. undatus) peel were extracted by supercritical carbon dioxide extraction, and analyzed by gas chromatography–mass spectrometry analysis. Their cytotoxic and antioxidant activities were investigated. The main components of H. polyrhizus extract were β-amyrin (15.87%), α-amyrin (13.90%), octacosane (12.2%), γ-sitosterol (9.35%), octadecane (6.27%), 1-tetracosanol (5.19%), stigmast-4-en-3-one (4.65%), and campesterol (4.16%), whereas H. undatus were β-amyrin (23.39%), γ-sitosterol (19.32%), and octadecane (9.25%), heptacosane (5.52%), campesterol (5.27%), nonacosane (5.02%), and trichloroacetic acid, hexadecyl ester (5.21%). Both of the two extracts possessed good cytotoxic activities against PC3, Bcap-37, and MGC-803 cells (IC₅₀ values ranging from 0.61 to 0.73 mg/mL), and the activities of their main components were also studied. Furthermore, these extracts also presented some radical scavenging activities, with IC₅₀ values of 0.83 and 0.91 mg/mL, respectively.

Conclusion

This paper provides evidence for studying the chemical composition of supercritical carbon dioxide extracts of pitaya peel and their biological activity.     

天然气管道泄漏可调谐二极管激光遥感探测的研究

天然气管道泄漏不仅造成经济损失而且是危险之源。传统的天然气管道泄漏检测技术效率低、速度慢,难以满足实际应用的需要。近年来以近红外二极管激光吸收光谱为基础的光学传感器由于具有灵敏度高、体积小、重量轻和无需维护等优点而得到了广泛的应用。文章以可调谐二极管激光吸收光谱和谐波探测技术为基础进行天然气管道泄漏遥感探测技术的研究,采用二次谐波与一次谐波信号的比值作为系统浓度标定,结果显示浓度与比值之间具有较好的一致性。文章还就不同地形散射体对探测结果的影响进行了测量和分析,实验结果表明二次谐波与一次谐波信号比值标定技术对便携式二极管激光光学测量能够很好的满足实际应用的需要。