基于DPSIR概念模型的黄土丘陵区退耕还林（草）生态环境效应评估

基于DPSIR概念模型，以延安水土保持与生态环境建设试验示范区为实证研究对象，从驱动力、压力、状态、影响、响应5个环节综合对研究区域1999—2009年退耕还林（草）实施的生态环境效应进行评估。结果表明：退耕还林（草）工程实施阶段驱动力值、影响值和生态环境效应值呈现增加趋势，工程结束后均有所降低，而后随时间逐步增加并趋于稳定，压力值随年限总体波动较大，状态值则持续平稳增加。总体而言，工程的实施有效的改善了研究区生态环境状况，水土流失问题也得以改善。研究还发现，输沙模数、降雨量、耕地压力、自然偏离度和人均纯收入等指标是研究区退耕还林（草）工程实施过程中的敏感指标，其对生态环境综合值影响较明显。退耕还林（草）工程通过改变传统的广种薄收耕作观念，发展集水灌溉及大棚等高效设施农业，在促进生态环境恢复的同时提高了当地农民收入，减轻了人类活动对生态环境的压力，调整其朝着与自然环境和谐的方向发展。     

Smooth and highly-crystalline Ag-doped CIGS films sputtered from quaternary ceramic targets

Sputtering with copper indium gallium selenide (CIGS) ceramic targets could produce smooth CIGS thin films that are preferred for preparing two-terminal tandem devices. However, grain sizes prepared in this way are small and device efficiency was low. To increase the grain size, in this report, an Ag layer was pre-sputtered beneath CIGS. The Ag doping layer increased the grain size and improved the crystalline alignment. Consequently, the Ag-doped films exhibited improved charge mobility. From X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy characterizations, we obtained an optimized Ag thickness of 15 nm. Short-circuit current density (J_SC), open-circuit voltage (V_OC), and fill factor (FF) were all improved after doping with 15-nm Ag. Increasing the annealing temperature from 550 °C to 575 °C, the grains was enlarged further, with the power conversion efficiency (PCE) increasing to 14.33% and V_OC to 545 mV. Upon the smooth CIGS film, a thin conformal perovskite layer was fabricated without polishing. This work demonstrates a simple way to fabricate smooth and highly-crystalline CIGS films that can be used for tandem solar cells.     

NSY-3型宽域智能颗粒分析仪

文中对NSY-3型宽域智能颗粒分析仪的原理和特性进行了介绍，并从颗粒分析仪的硬件组成和软件结构两部分着手阐述了颗分系统的设计理念。     

Influence of Grain Bounary on Fatigue Behavior of Ni-base Bicrystals

The influence of the grain boundary on the fatigue behavior was stuied by two three-point-bending (TPB) specimens.One TPB specimen was named Bicrystal 1,whose pre-crack was along the grain boundary and the applied load paralleled to pre-crack direction,while the other TPB specimen was named Bicrystal 2,whose the pre-crack was perpendicular to the grain boundary and the applied load paralleled also to the pre-crack.It was found that the rate of the fatigue crack growth of Bicrystal 1 was about a tenfold higher than that of Bicrystal 2.The fatigue behavior of Bicrystal 2 specimens was dependent on the distance between the crack tip and grain boundary.The crack growth rate was highest when the crack tip was at a critical distance to the grain boundary,while the rate was the lowest when the crack tip reached grain boundary.After the crack was over the grain boundary,the crack growth rate increased.The crystallographic finite element method was applied to analyze the stress and strain structure ahead of the crack,in order to reveal the above characteristics of the fatigue behavior.It is the grain boundary-induced redistribution of stresses near the crack tip that induces the difference of fatigue behavior.     

Influence of Grain Boundary on Fatigue Behavior of Ni-base Bicrystals

The influence of the grain boundary on the fatigue behavior was studied by two three-point-bending (TPB) specimens. One TPB specimen was named Bicrystal 1, whose pre-crack was along the grain boundary and the applied load paralleled to pre-crack direction, while the other TPB specimen was named Bicrystal 2, whose the pre-crack was perpendicular to the grain boundary and the applied load paralleled also to the pre-crack. It was found that the rate of the fatigue crack growth of Bicrystal 1 was about a tenfold higher than that of Bicrystal 2. The fatigue behavior of Bicrystal 2 specimens was dependent on the distance between the crack tip and grain boundary. The crack growth rate was highest when the crack tip was at a critical distance to the grain boundary, while the rate was the lowest when the crack tip reached grain boundary. After the crack was over the grain boundary, the crack growth rate increased. The crystallographic finite element method was applied to analyze the stress and strain structure ahead     

联合收割机清粮筛的运动仿真与优化

清粮筛筛面的运动状态是影响清粮性能的关键因素.为了优化清粮筛机构的工作参数(结构参数和运动参数),提高清粮性能,运用CAD/CAE运动学仿真软件对清粮筛进行了3D建模和运动仿真分析,考察了筛面加速度的变化规律.仿真结果表明:在相同的变动比例下,筛面的加速度对连杆长度的变化最为敏感;曲柄的转速对筛面的加速度也有重要的影响.因此选择连杆长度和曲柄转速作为关键参数,以振动最小和筛面加速度最大为优化的目标.经优化:该机构在谷物清选时, 清粮筛的其他结构参数不变,连杆LAB =0.46 m、曲柄转速n= 330 r/min为最佳.     

High-speed μc-Si films deposition and large-grain poly-Si films deposition by surface wave discharge

Microcrystalline silicon (μc-Si) and polycrystalline silicon (poly-Si) films are deposited by surface wave (SW) discharge at 2.45 GHz in H₂/SiH₄ gas. This high density SW plasma at relatively low pressures (4-60 Pa) enables strong dissociation of feedstock gas. The films deposited on substrate are investigated by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The SW discharge in 10% SiH₄ at total pressure of ∼ 30 Pa gives μc-Si films on a substrate at 250 °C, at a fairly high deposition rate of 4-20 nm/s, with a crystalline volume fraction of 0.5-0.8 and a grain size of 10-40 nm. Furthermore, poly-Si film with crystalline volume fraction of > 99% is deposited at higher substrate temperature (400 °C) in 2% SiH₄ discharge at lower pressure (4 Pa). X-ray diffraction and SEM results revealed that the grain size of poly-Si films is as large as 600 nm, which is almost 6 times larger than previously reported values.     

Dependence of photovoltaic parameters on grain size and density of states in n-i-p and p-i-n polycrystalline silicon solar cells

One-dimensional modeling of polycrystalline silicon (pc-Si) p⁺-i-n⁺ and n⁺-i-p⁺ homojunctions under AM1.5 light is presented. Single-crystalline grains separated by amorphous silicon transition zones are introduced to model the pc-Si structure. The usual density of states (DOS) with exponential band-tails and Gaussian-distributed deep levels is assumed in these transition regions. Effects of the grain size, the thickness of the undoped region and the DOS on the photovoltaic characteristics are presented. The calculation enables us to understand the very poor performance of the solar cells based on solid-phase-crystallized polysilicon processed at low temperature (< 600 °C). It gives the minimum value of the grain size and the maximum DOS to obtain acceptable photovoltaic performance.     

本征纳米硅薄膜的微结构表征

采用PECVD技术,在玻璃衬底上低温沉积了优质本征纳米硅薄膜,并利用Raman光谱对其微结构作了表征。研究结果表明,硅烷浓度、衬底温度Ts对表征纳米硅薄膜微结构的晶化率和平均晶粒尺寸参数影响很大。SiH4浓度越低,越有利于晶化,对应的晶化率拐点温度越低。平均晶粒尺寸、晶化率随衬底温度的升高具有相似的变化规律,谱中出现的拐点温度一致,暗示它们之间存在紧密的联系。从薄膜生长角度对该实验结果作了合理解释。     

Differences in Yields,Residue Composition and N Mineralization Dynamics of Bt and Non-Bt Maize

Cultivation of genetically modified crops may have several direct and indirect effects on soil ecosystem processes, such as soil nitrogen (N) transformations. Field studies were initiated in Northeast Missouri in 2002 and 2003 to determine grain and biomass yields and the effects of application of crop residues from five Bt maize hybrids and their respective non-Bt isolines on soil inorganic N under tilled and no-till conditions in a maize-soybean rotation. A separate aerobic incubation study examined soil N mineralization from residue components (leaves, stems, roots) of one Bt maize hybrid and its non-Bt isoline in soils of varying soil textural class. Three Bt maize hybrids produced 13–23% greater grain yields than the non-Bt isolines. Generally no differences in leaf and stem tissues composition and biomass was observed between Bt and non-Bt maize varieties. Additionally, no differences were observed in cumulative N mineralization from Bt and non-Bt maize residues, except for non-Bt maize roots that mineralized 2.7 times more N than Bt maize roots in silt loam soil. Incorporation of Bt residues in the field did not significantly affect soil inorganic N under tilled or no-till conditions. Overall Bt and non-Bt maize residues did not differ in their effect on N dynamics in laboratory and field studies.