OBDD-based network reliability calculation

An efficient method for evaluating the terminal-pair reliability based on an edge expansion tree and using an OBDD (ordered binary decision diagram) is presented. The effectiveness of the algorithm is demonstrated on the larger benchmarks collected in previous work. One notable case of the experimental results for a 2×20 lattice network is that the number of nodes in the OBDD is linearly proportional to the number of stages. This is significantly superior to previous algorithms which are based on the sum of disjoint products and has exponential complexity     

Optimization of the host/vector system and culture conditions for production of penicillin acylase in Escherichia coli

Culture performance for the production of penicillin acylase (PAC) in a bioreactor was investigated using HB101 or ATCC11105 as the host and pCLL2902, pCLL3201 or pTrcKnPAC2902 as the expression plasmid. We observed that the production of PAC by HB101 harboring pCLL3201 was, similar to ATCC11105, induced by phenyl acetic acid (PAA) and catabolicaily repressed by glucose, whereas the production of PAC by HB101 harboring pCLL2902 did not require PAA for induction and was not repressed by glucose. PAC activity of HB101 harboring pCLL2902 was significantly higher than that of HB101 harboring pCLL3201. There was no significant effect of host or carbon source on the production of PAC using pCLL2902. The production of PAC by HB101 harboring pTrcKnPAC2902, in which the pac gene expression was controlled by the trc promoter system, was about the same as that by HB101 harboring pCLL2902, when the culture was appropriately induced with isopropyl beta-d-thiogalactopyranoside (IPTG). Therefore, the use of both pCLL2902 and pTrcKnPAC2902 could be expected to be feasible for industrial applications. However, optimization of IPTG induction for HB101 harboring pTrcKnPAC2902 might be required, since formation of inclusion bodies tends to limit the production of PAC in some cases.     

Fabrication of Microcavity Light-Emitting Diodes Using Highly Reflective AlN–GaN and Ta2O 5–SiO2 Distributed Bragg Mirrors

We report the fabrication of microcavity light-emitting diodes (MCLEDs) with high reflectivity and crack-free AlN-GaN distributed Bragg reflector (DBR). The 5lambda microcavity structure consists of an n-type GaN, ten pairs InGaN-GaN multiple quantum wells and p-type GaN sandwiched between the hybrid cavity mode of an AlN-GaN and a Ta₂O₅-SiO₂ DBR. The AlN-GaN DBR has 29 periods with insertion of six AlN-GaN superlattice layers showing a crack-free surface morphology and a high peak reflectivity of 99.4% with a stopband of 21 nm. The output power of MCLED is about 11 W at an injection current of 7 mA. The electroluminescence has a polarization property with a degree of polarization of about 51%.     

新型多线切割机张力控制系统研究

分析了多线切割机的工作原理、组成结构及其工作过程。介绍了多线切割机的总体控制方案,并对多线切割机的张力控制系统进行深入地理论研究,建立了控制系统的运动学和动力学模型。在此基础上,提出了一种PID速度同步跟随控制方案。试验结果表明,该方案可靠、稳定、控制精度高、调整方便。     

Fabrication and properties of PLZT ceramics from spray-dried aqueous solution

PLZT ceramics with the composition of 9/62/38 (La/Zr/Ti) were fabricated from spraydried aqueous solution. Complete crystallization of the spray-dried powder is achieved after 1 hr calcination at 650‡ C as compared to 800‡ C, 1 hr for conventional mixedoxide method. Sintering environment plays an important role in the densification of PLZT ceramics. Densities of the atmosphere sintered samples are much higher than those of normal sintered ones. PLZT ceramics derived from spray-dried powders have properties comparable to those derived from sol-gel ones. The spray-dried method presents a less expensive and more effective approach in the synthesis of PLZT ceramics.     

Erbium-doped fiber amplifier second-order distortion in analog links and electronic compensation

The authors study the second-order distortion when an erbium-doped fiber amplifier (EDFA) is used to amplify the analog optical AM cable TV (CATV) multiple carrier signal from a directly modulated distributed feedback (DFB) semiconductor laser. Experimentally, it was seen that this second order distortion depends critically on the gain of the EDFA fiber amplifier. The authors attribute this distortion to the interaction between the frequency chirping of the DFB laser and the variable gain with wavelength of the amplifier. The authors describe an electronic predistorter that compensates the nonlinearity produced by the DFB-laser-EDFA combination. As a result, the high power advantage of the EDFA can be fully realized in spite of the potential for second-order distortion in the system.<>     

P型硅纳米板压阻特性的理论研究

考虑量子尺寸效应与自旋轨道耦合作用,从含有应变的6×6 Luttinger-Kohn哈密顿量出发,采用有限差分方法建立了p型硅纳米板的能带结构模型.基于硅纳米板压阻特性与其能带结构的相关性,采用改进的压阻理论定量分析了厚度、杂质浓度与温度对其压阻系数的影响.研究结果表明:量子尺寸效应强烈改变了硅纳米板的能带结构,是其压阻系数增大的主要因素,而自旋轨道耦合作用仅对含较高应变的硅纳米板的能带结构有较大影响;硅纳米板的压阻系数具有尺寸效应,随厚度减小而增大,随杂质浓度增加或温度升高而减小.在高简并条件下,硅纳米板的压阻系数与温度无关,完全由杂质浓度的大小控制;在非简并条件下,情况刚好相反.最后,利用施加应力前后空穴等能面形状的变化定性分析了硅纳米板压阻特性的起源.     

Effect of hydroxyl density on condensation behaviors of self-assembled monolayers and performance of pentacene-base organic thin-film transistors

A series of self-assembled monolayers (SAMs), comprising octadecyltrichlorosilane (ODTS), dodecyltrichlorosilane (DDTS), and hexamethyldisilazane (HMDS), were prepared to examine the effects of phase states and condensation behaviors of SAMs on the morphologies and performance of pentacene-based organic field-effect transistors (OFETs) by means of Fourier Transform Infrared (FT-IR) spectrometer, atomic force microscope (AFM), X-ray diffraction (XRD), and semiconductor parameter analyzer. Experimental results reveal that the treatment of SiO₂ substrates with O₂ plasma (denoted as O₂-SiO₂) and the preparation temperature of SAMs dramatically influence the morphologies of SAMs and the performance of corresponding pentacene-based (no purification) OFETs. When the SAMs were prepared at 30 °C, the OFET based on ODTS-treated O₂-SiO₂ substrate had the highest hole mobility, reaching as large as 1.15 cm² V^?1 s^?1, and an on/off current ratio in excess of 10⁵; these values are both much larger than those of a device based on ODTS-modified SiO₂ substrates without O₂ plasma treatment and O₂-SiO₂ substrates modified by ODTS SAMs prepared at other temperatures. OFETs based on O₂-SiO₂ substrates that were modified by DDTS and HMDS SAMs prepared at 4 °C performed best.     

基于ATmega16单片机的微型气象探测系统设计

设计了一种便携式低功耗微型气象探测系统,该系统以低功耗ATmega16单片机作为核心控制部件,采用温湿度传感器、气压传感器以及光强度传感器,进行温度、湿度、气压和光照强度的测量;通过12864液晶、时钟芯片和E2PROM实现数据的显示、存储和查询。实验测试结果表明该微型气象探测系统的测量精度达到了普通气象测量要求,稳定性高。由于该气象探测系统具有微型化、低功耗、实时化和便携式等特点,因而特别适用于小区域的气象监测。     

含磁液磁路系统音圈动力学特性分析

介绍了含磁液磁路系统中音圈的力学特性,一般讨论中该范畴内容常分两大部分:即静力学特性和动力学特性.着重讨论的是含磁液磁路系统音圈的动力学特性并对之进行了分析.