直流稳压电源轻松做

电源是电路的核心,是电子电路制作过程中必不可少的设备。一个好的直流稳压电源能让电路制作事半功倍,效果显著。一般直流稳压电源由变压器、整流、滤波、稳压等几个部分组成。本文介绍了一种简单实用的直流稳压电源的制作。     

Cubic polynomial patches through geodesics

We consider patches that contain any given 3D polynomial curve as a pregeodesic (i.e. geodesic up to reparametrization). A curve is a pregeodesic if and only if its rectifying plane coincides with the tangent plane to the surface, we use this fact to construct ruled cubic patches through pregeodesics and bicubic patches through pairs of pregeodesics. We also discuss the G¹ connection of (1,k) patches with abutting pregeodesics.     

趋于理想的全波整流电路

本文分析了整流电路的非线性问题,设计了改进型精密全波整流电路。该电路采取以恒流源为整流负载等有关措施,使整流二极管的正向导通压降为一常数。分析和实验均表明,该电路的非线性误差趋近于零,消除了二极管“死区”的影响,并有较好的温度稳定性。     

Experimental and physical approaches on a novel semiconducting-ionic membrane fuel cell

Semiconducting-ionic membranes (SIMs) have exhibited significant superiority to replace the conventional ionic electrolytes in solid oxide fuel cells (SOFCs). One interesting phenomenon is that the SIMs can successfully avoid the underlying short-circuiting issue and power losses while bringing significantly enhanced power output. It is crucial to understand the physics in such devices as they show distinct electrochemical processes with conventional fuel cells. We first presented experimental studies of a SIM fuel cell based on a composite of semiconductor LiCo_0.8Fe_0.2O₂ (LCF) and ionic conductor Sm-doped CeO₂ (SDC), which achieved a remarkable power density of 1150 mW cm^?2 at 550 °C along with a high open circuit voltage (OCV) of 1.04 V. Then, for the first time we used a physical model via combining a semiconductor-ionic contact junction with a rectifying layer which blocks the electron leakage to describe such unique SIM device and excellent performance. Current and power are the most important characteristics for the device, by introducing the rectifying layer we described the SIM physical nature and new device process. This work presented a new view on advanced SIM SOFC science and technology from physics.     

Epitaxial growth and rectification characteristics of double perovskite oxide La2NiMnO6 films on Nb-SrTiO3 single crystal substrates

High-quality thin films of double perovskite La₂NiMnO₆ (LNMO) were epitaxially grown on Nb-doped SrTiO₃ (NSTO) substrates by pulsed laser deposition. The films were found to undergo a ferromagnetic-to-paramagnetic transition at ~ 280 K, which is consistent with the literature report. In the electrical measurements, typical rectifying behavior was observed in the LNMO/NSTO heterojunction. The diffusion voltage (V_D) increases linearly with temperature (T) during cooling until T = 170 K. At T < 170 K, V_D increases at a higher rate and the V_D-T relationship becomes non-linear. A disordered phase related spin polarization was used to understand such behaviors in the heterojunctions.     

A simple organic diode structure with strong rectifying characteristics

A simple organic diode structure has been made based on N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine (NPB)/Fullerene (C₆₀) heterojunction. Ultraviolet photoelectron spectroscopy measurements show an energy level alignment at the heterojunction as such that no potential barrier near this heterojunction to hinder the formation of charge transfer excitons, which recombines at a very fast rate. This fast exciton recombination at this heterojunction makes NPB/C₆₀ behave like an ideal Ohmic contact and thus leads to an extremely high 7.8 × 10⁴ rectifying ratio from the electrode/organic contacts.     

X-band circularly polarized rectennas for microwave power transmission applications

Circularly polarized rectennas operating at X-band are studied in this paper. The quasi-square patches fed by aperture coupling are used as the circularly polarized receiving antennas, which are easily matched and integrated with the circuits of rectennas. The： double-layer structure not only minimizes the size of the rectennas but also decreases the effects of the circuits on the antenna. The receiving elements have broader bandwidth and higher gain than the single-layer patches. Two rectennas operating at 10GHz are designed, fabricated and measured. The voltage of 3.86V on a load of 200Ω is measured and a high RF-DC conversion efficiency of 75% is obtained at 9.98GHz. It is convenient for this kind of rectennas to form large arrays for high power applications.     

牵引变电站用整流器设计

本文介绍了专为地铁、轻轨供电而设计制造的牵引变电站用整流器,详细描述了12脉波整流器原理、元件选择、电路保护设计。应用图形编程软件LabVIEW作为与上位计算机的通信软件。     

HPS整流管芯片散热效率计算仿真研究

针对传统散热效率计算方法存在计算时间过长、计算效率过低以及计算误差偏高等问题,提出了一种新的散热效率计算方法———基于傅里叶导热方程的散热效率计算方法。通过对高功率半导体整流管芯片进行分析,引用傅里叶导热方程计算出整流管芯片的传热热阻,根据传热热阻随着温度的变化,获取高功率半导体整流管芯片散热系数。根据高功率半导体整流管芯片散热系数,构建高功率半导体整流管芯片散热模型,利用建立的模型分析转速、冷气流入口的压力和速度以及冷却孔的分布等对转子温度场的以及散热效率的影响,优化散热路径,完成高功率半导体整流管芯片散热计算。实验结果表明,所提方法有效减少了计算时间,提高了计算效率,与此同时,降低了计算误差,使计算结果更为准确。     

Current saturation effect for pentacene-based static induction transistor under negative drain-source and gate voltages

Usually, the drain-source current (I_DS) increases with positive drain-source voltage (V_DS) for pentacene-based organic static induction transistor (OSIT) ITO(Source)/Pentacene/Al(Gate)/Pentacene/Au(Drain) and it shows an inherent rectifying property under negative gate voltages (V_G), i.e. the slope of I_DS vs. V_DS curve increases with V_DS but without any current saturation effect. In this paper, we investigated the electrical characteristics of pentacene-based OSIT ITO/Pentacene(80 nm)/Al(15 nm)/Pentacene(80 nm)/Au under negative V_DS and V_G, and found that I_DS changed from rectifying property to saturation effect when the magnitude of negative V_DS was increased from 0 V to −6 V under negative V_G, and the turn-on voltage (V_ON) moved to larger negative voltages when the magnitude of negative V_G increased and the movement step of V_ON gets smaller after keeping the device for a long time, and the possible mechanisms for such a kind of current modulation were discussed.