Study on the electronic structures and transport properties of the polyporphyrin nanoribbons with different edge configurations

Combining the density functional theory with the non-equilibrium Green's function, three kinds of polyporphyrin nanoribbons (PPNRs) with different edge configurations have been considered: 1) all carbocyclic eight-membered rings (C8-Rs) located in edge are broken (M1); 2) all C8-Rs located in edge are perfect (M2); 3) partial C8-Rs located in edge are broken, subject to two kinds of configurations, as illustrated by M3 and M4. Calculation results indicate that the completeness of the C8-Rs can influence the electronic structures and transport properties of the nanoribbons. M1 is a nonmagnetic indirect semiconductor, while M2 and M3 are magnetic metals, M4 behaves as the bipolar magnetic semiconductor. Moreover, the spin-dependent transport properties of the two-lead devices based on PPNRs show that the significant spin-filtering effect can be realized in the device with partially broken C8-Rs in edge. Our results indicate that the PPNRs based devices would be suitable for spintronics devices.     

A novel design and micro-fabrication for copper (Cu) electroforming bipolar plates

A novel design and micro-fabrication were developed for micro-proton exchange membrane (PEM) fuel cell stack bipolar plates with cross section of 5 cm² and thickness of about 650 μm. Copper metals were used to make bipolar plates (BPs) by using a LIGA-like micro-fabrication process of deep UV lithography in order to obtain SU-8 resist patterns/and SU-8 mould. Through two-sided exposure and development, copper metal bipolar plates with serpentine (meandering) flow field configurations for a micro PEM fuel cell stack, were fabricated and performance tests through polarization characteristics were conducted; this made it possible for the first time to consider copper sheets as suitable for BPs in micro PEM fuel cell stacks.     

Comparison of 1 MeV electron,Co-60 gamma and 1 MeV proton irradiation effects on silicon NPN transistors

The total dose effects of 1?MeV electrons on the dc electrical characteristics of silicon NPN transistors are investigated in the dose range from 100?krad to 100?Mrad. The different electrical characteristics such as Gummel characteristics, excess base current (ΔI_B), dc current gain (h_FE), transconductance (g_m), displacement damage factor (K) and output characteristics were studied in situ as a function of total dose. A considerable increase in base current (I_B) and a decrease in h_FE, g_m and I_CSat was observed after 1?MeV electron irradiation. The collector–base (C–B) junction capacitance of transistors was measured to estimate the change in the effective carrier concentration. After 1?MeV electron irradiation, a considerable degradation in capacitance was observed. The plot of (1/C²) versus voltage shows that the effective carrier concentration and built-in voltage (V_bi) increase marginally upon 1?MeV electron irradiation. The results of 1?MeV electron irradiation were compared with 1?MeV proton and Co-60 gamma irradiation results in the same dose range. The degradation for 1?MeV electron and Co-60 gamma-irradiated transistors was significantly less when compared to 1?MeV proton-irradiated transistor. The 1?MeV proton, 1?MeV electron and Co-60 gamma-irradiated transistors were subjected to isochronal annealing to analyze the recovery of the electrical parameters.     

Asymptotic Behavior of Global Smooth Solotions to the Euler-Poisson System in Semiconductors

In this paper, we establish the global existence and the asymptotic behavior of smooth solution to the initial-boundary value problem of Euler-Poisson system which is used as the bipolar hydrodynamic model for semiconductors with the nonnegative constant doping profile.     

双极型晶体管在强电磁脉冲作用下的瞬态响应

 利用时域有限差分法,对双极型晶体管在强电磁脉冲作用下的瞬态响应进行了2维数值模拟,分析了器件烧毁过程中电场、电流密度、温度等参数的分布及变化情况,分别观察了低电压和高电压脉冲作用下烧毁过程中热点的形成过程,并得到了器件烧毁所需时间以及能量与脉冲电压幅度之间的关系。在电压脉冲较低时,烧毁点位于通道中靠近集电极的位置,当脉冲电压达到一定幅度的时候,由于发射极与集电极之间发生雪崩击穿,基极和发射极之间电势会抬高,从而引起基极和发射极之间的击穿,形成新的热点,并在电压幅度约高于100 V的情况下会率先达到烧毁温度。随着脉冲电压幅度的增高,晶体管烧毁所需时间呈负指数减少,而所需能量在55~100 V之间接近于线性增长,直到电压幅度约高于100 V时才开始减少。     

基于频分信道双极性光码分多址实现研究

提出了采用光纤法-玻滤波器与电吸收调制器实现频域幅度编解码的频分信道双极性OCDMA系统方案.推导了系统模型理论公式,分析了系统信噪比对接收端探测误差、不同编解码系统和传输信道对系统性能的影响.仿真结果表明：比较高的信噪比有利提高接收端探测效果;系统容纳用户能力增强;系统有良好的相关特性;20 km的SMF搭配300 m的DCF传输系统明显优于20 Km的DSF传输系统.     

Quasineutral limit of bipolar quantum hydrodynamic model for semiconductors

This paper is concerned with the quasineutral limit of the bipolar quantum hydrodynamic model for semiconductors. It is rigorously proved that the strong solutions of the bipolar quantum hydrodynamic model converge to the strong solution of the so-called quantum hydrodynamic equations as the Debye length goes to zero. Moreover, we obtain the convergence of the strong solutions of bipolar quantum hydrodynamic model to the strong solution of the compressible Euler equations with damping if both the Debye length and the Planck constant go to zero simultaneously.     

Multifunctional Organic Emitters for High‐Performance and Low‐Cost Organic Light‐Emitting Didoes

Organic light‐emitting diodes (OLEDs) have great potential applications in display and solid‐state lighting. Stability, cost and high operational efficiency are key issues governing the future commercial application of OLEDs. In this context, searching for multifunctional emitting materials with acceptable light‐emitting and charge‐transporting characteristics has gained increasing attention. For achieving high‐performance and low‐cost OLEDs, the suitable molecular design featured with different electronic and optical nature should be incorporated by combining the advantages of both functional units into the same molecules. This review highlights recent and current advances in developing bifunctional or multifunctional molecules, with the focus on structures, properties, and applications in OLEDs and organic laser.     

Electrochromic sensors: Innovative devices enabled by spectroelectrochemical methods

Electrochromic sensors are electrochemical devices exploiting colour changes as a means to simplify device construction and instrumentation requirements. Despite their advantages, electrochromic sensors have begun to emerge only recently. Mainly based on the works appeared in the literature over the past 2 years, we describe the construction and operation of these devices. A simple framework is proposed to understand and classify these devices more easily. This is based on the sensor architecture, their power source, and how information is displayed. Despite being new, electrochromic sensors are already demonstrated in a number of applications, mostly related to health and point-of-care devices.     

Improving resolution in single-scan 2D spectroscopy

New schemes are introduced that allow one to improve the resolution in the indirect dimension of single-scan ‘ultrafast’ two-dimensional NMR spectra. The methods combine undersampling with band-selective pulses to recover signals that lie outside the detection bandwidth. The efficiency is illustrated for homonuclear total correlation spectroscopy (TOCSY) of quinidine.