Donor–acceptor copolymers based on benzo[1,2-b:4,5-b′]dithiophene and pyrene-fused phenazine for high-performance polymer solar cells

Two novel donor–acceptor (D–A)-type conjugated polymers of PTTPPz-BDT and PTTPPz-BDTT were successfully synthesized by Stille coupling polymerization, in which 7,8-dialkoxy benzo[1,2-b:4,5-b′]dithiophene (BDT) and 7,8-bithienyl benzo[1,2-b:4,5-b′]dithiophene (BDTT) were used as donor units, thiophene and pyrene-fused phenazine (PPz) were employed as π-bridges and acceptor units, respectively. High carrier mobilities, broad absorption spectra, narrow optical band gaps, and low HOMO energy levels were observed for both polymers. Furthermore, high-efficiency photovoltaic performance with power conversion efficiency (PCE) over 4.25% was exhibited in their polymer solar cells (PSCs) using [6,6]-phenyl-C₇₁-butyric-acid-methyl-ester (PC₇₁BM) as acceptor. The maximum PCE of 4.86% with short-circuit current density of 11.10 mA cm⁻² and fill factor of 62.5% was obtained in the PTTPPz-BDTT based cell. These results indicate that incorporating large planar PPz moiety into D–A-type copolymer is an efficient approach to improve photovoltaic performance for PSCs.     

Novel polycrystalline silicon thin film transistors prepared by deposition from Si2H6 and subsequent annealing by NH3 plasma

This work investigated the channel layer of polycrystalline silicon (poly-Si) thin film transistors (TFTs) prepared by amorphous silicon (a-Si) films deposited using Si₂H₆ gas. The recrystallization of channel layers, source/drain, gate electrodes and post implant anneal were performed at the same time. Due to the larger grain size, the device has higher field effect mobility than SiH₄ deposited devices. These devices were also subsequently passivated by NH₃ plasma. The NH₃ plasma significantly improves the n-channel devices; however, the improvement of p-channel devices is limited. Especially, the threshold voltage of n-channel devices is significantly shifted toward the negative gate voltage than the shift magnitude of p-channel devices. To investigate the band gap width and Fermi level by determining the leakage activation energy, it is found that the channel film is changed slightly from p-type to n-type. These results may be attributed to the donor effect by NH₃ plasma passivation.     

发动机润滑系统典型组成部件工作性能的试验研究

在各自专用试验台上，参照相应标准规范要求，分别对发动机润滑系统典型组成部件机油泵、机油滤清器和机油冷却器的工作性能进行了试验研究。试验重点考察了机油温度、机油泵转速以及出油压力等因素对机油泵供油特性的影响，分析了在各种温度下机油流经滤清器和冷却器时机油流量与其所产生的压降之间的关系。研究结果可以为发动机润滑系统设计和分析提供参考。     

Combustion and emission characteristics of a two-stroke diesel engine operating on alcohol

Though, as a renewable energy resource, alcohol fuel has many advantages in China, it is difficult for diesel engines to operate on alcohol due to its low cetane number and high latent heat of vaporization. This paper proposes an approach to its ignition problem by combining internal exhaust gas recirculation (EGR) with injection of small diesel fuel. Based on this approach, a two-stroke single-cylinder diesel engine was developed. Preliminary studies demonstrated that the engine can run on alcohol with almost zero level of smoke and low exhaust gas temperature, and that the engine operating on alcohol has lower nitrogen oxide (NO_x) emissions and 2–3% higher effective thermal efficiency than that operating on diesel fuel in moderate and high load zones.     

一种国外火电厂烟气脱硫系统成本估算模型介绍

近些年来,随着能源与电力行业的快速发展,导致了大量SO2污染物的排放,因此必须推广烟气脱硫技术以减小SO2的排放。介绍国外的一种根据初投资和运行维护费用对新建电厂和原有电厂增加脱硫系统的成本估算模型。此模型可以初步评价机组FGD(FlueGasDesulfurization)建设的经济性,估算初投资、运行和维护成本,从而为电厂脱硫的预可行性研究提供参考。     

Sol-gel processed silica/titania/ÿ-Glycidoxypropyltrimethoxysilane composite materials for photonic applications

Silica/titania/?-Glycidoxypropyltrimethoxysilane composite materials processed by the sol-gel technique were studied for photonic applications. Waveguide thin films with thickness more than 1.7 μm were prepared by the sol-gel spin coating technique and low temperature heat treatment from this high titanium content composite materials. The films were analyzed by atomic force microscopy (AFM), ellipsometry, differential thermal analysis (DTA), thermal gravimetric analysis (TGA), UV-visible spectroscopy (UV-VIS), and Fourier transform infrared (FT-IR) spectroscopy. It was observed that the film becomes thinner as the titanium contents increase. A change of the refractive index through the range 1.52–1.61 at the optical wavelength of 633 nm was achieved by varying the molar ratio between silica and titanium. A dense, low absorption, and high transparency in the visible range waveguide films could be obtained at a low temperature. It was also noted that organic compounds in the film would decompose in the temperature range from 200°C to 480°C. Accordingly, purely inorganic silica-titania films with a thickness of about 0.7 μm could also be obtained by a single-coating process, when the film was baked at a temperature of 500°C or higher. The waveguides properties and photonic applications of the composite material solgel films were also investigated.     

WCDMA与GPRS技术浅析

主要介绍了WCDMA技术与GPRS技术的基本概念,并对二者进行了比较,指出在向第三代移动通信系统(3rdGeneration,简称为3G)过渡的时代,这两种技术各有所长,必将有一番大的较量。     

LTE系统中Turbo译码的改进算法

LTE系统对可靠通信提出了更高的要求,这在一定程度上依赖于信道编码的性能。针对LTE系统中的Turbo译码算法进行了研究,在Max-Log-MAP和Log-MAP算法的基础上提出了一种改进算法。理论分析和仿真结果表明,这种改进算法的性能有进一步提升,并且更加易于硬件实现,具有较低的复杂度。     

计算层析成像光谱仪中二元光学元件的研究

报道了用二元光学技术制作的二维位相型衍射光栅作为计算层析成像光谱仪中的光谱元件.对该光谱元件衍射阵列的强度分布、衍射效率以及各衍射级效率对波长的响应曲线进行了实验检测.结果表明,实验与理论相一致.     

Friction modeling and adaptive compensation using a relay feedbackapproach

In this paper, the application of a dual-relay feedback approach toward modeling of frictional effects in servomechanisms is addressed. The friction model consists of Coulomb and viscous friction components, both of which can be automatically extracted from suitably designed relay experiments. At the same time, the dynamical model of the servomechanical system can be obtained from the experiments. Thus, a proportional-integral-derivative feedback motion controller and a feedforward friction compensator can be automatically tuned in this manner. The friction model obtained is also directly applicable to initialization of an adaptive control scheme proposed. Results from simulation and experiments are presented to illustrate the practical appeal of the proposed method