Spatia-l temporal variability of soil salt content before and after irrigation in the Yellow River Delta

分别采用传统统计学和地统计学方法,定量分析了灌溉前、后黄河三角洲田块尺度下不同深度土层含盐量的空间变异性并分析空间分布特征。结果表明:除灌溉前0~10 cm土层土壤含盐量呈强变异性外,其余各土层含盐量均表现为中等变异强度;灌溉前土壤盐分主要积聚在0~10 cm和40~60 cm土层,灌溉后主要积聚在40~60 cm土层;灌溉使得0~10 cm和10~20 cm土层土壤含盐量降低,脱盐效果较好;除灌溉后0~10 cm土层的土壤盐分含量呈现弱空间相关性之外,其它土层均呈现强空间相关性;灌溉后与灌溉前相比,除40~60 cm层土壤含盐量外,其余各土层土壤含盐量明显降低、土壤含盐量的等值线密集程度减弱..

Research on voltage-temperature coefficient of high power light-emitting diodes

理论上详细分析了LED正向电压随温度变化的物理机理,并在大的电流范围(0.1~200 mA)和温度范围(60~350 K)内,对AlGaInPI、nGaN材料系功率型LED正向电压随温度的变化关系进行了系统的实验研究。发现在恒定电流下,两者的变化关系可分为高温区和低温区两段。在高温区两者为线性反比关系,并且电压温度系数与正向电流有关,在低温区正向电压随温度减小而突然急剧增大。理论很好地解释了实验结果。The physical mechanism of the forward voltage as a function of the junction temperature in light-emitting diodes(LEDs) was analyzed in detail.And experimental investigation was carried out systematically on the relationship between the forward voltage and the junction temperature in AlGaInP and InGaN high-power LEDs over wide current range(0.1-200 mA) and temperature range(60-350 K).It is discovered that at a constant current,the relationship may be divided into two segments,i.e.in the high temperature region,a linear inverse relationship exists between them and the voltage-temperature coefficient is closely relevant with forward current;while in low temperature region,forward voltage increases drastically as the junction temperature decreases.The experimental results is in good agreement with the theory.国家“863”半导体照明工程资助项目(2006AA03A175);; 福建省重大专项资助项目(2006H0092,2008J0030);; 厦门市重大项目(3502Z20061004

Thermal characteristic analysis of high-power LEDs by structure functions

运用电学法测量功率型lEd冷却瞬态温度曲线,通过数学方法将其转化为积分和微分结构函数来分析器件各区域的热阻和热容,结果发现,各层材料的测量值与理论值基本一致。1μS的瞬态数据采集精度和高的重复性保证了实验结果的准确性和可靠性,运用这种方法比较了3种不同金属芯印刷电路板(MCPCb)对功率型lEd的散热效果,贝格斯Al基板散热性能最好,AnTAl基板次之,普通Al基板最差。研究表明,利用结构函数分析功率型lEd的热特性是一种强有力的方法。The cooling transient temperature curves of high-power LEDs are measured by electritical method.The cumulative and differential structure functions are extracted from these curves to analyse thermal resistances and thermal capacitances of all regimes of high-power LEDs with numeric computational method.It is found out that calculated and measured values of various materials are essentially conformable.The sampling resolution of 1 μs of transient data and high repetition assure the veracity and reliability of experimental result.Subsequently,thermal conduction capabilities of three different metal core printed circuit boards(MCPCBs) with high-power LEDs are compared by this method,and it is discovered that bergquist′s MCPCB has the best thermal conduction capability,ANT′s MCPCB takes second place,and the common MCPCB is the worst.So the structure functions are powerful tools for thermal characteristic analysis of high-power LEDs.国家“863”计划资助项目(2006AA03A175);福建省科技项目(2006H0092;2008J0030);厦门市重大专项资助项目(3502Z20061004

Studies on the purification, characterization and crystallization of FeMoco-deficient nitrogenase MoFe proteins from mutants (UW45, DJ54and DJ35) of Azotobacter vinelandii

一．棕色固氮菌突变种UW45、缺失nifH（DJ54）和缺失nifE(DJ35)突变种的钼铁蛋白的纯化、特性鉴定及结晶研究 棕色固氮菌突变种UW45的菌体破碎后，所得粗提物经两次DEAE 52柱层析后得到部分纯的nifB- MoFe蛋白和Fe蛋白。再经Sephacryl S-300和 DEAE柱的进一步纯化，便使nifB- MoFe蛋白基本达到SDS凝胶电泳纯。SDS-PAGE结果表明，nifB- MoFe蛋白具有与野生型棕色固氮菌（OP）MoFe蛋白相同的亚基种类和组成。此粗提物可为用NMF抽提的 OP MoFe蛋白的FeMoco激活，所得Fe蛋白具有与OP Fe蛋白相似的互补活性，可使OP MoFe的比活性达到2192 nmol C2H2/min/mg蛋白。FeMoco可使无互补活性的 nifB- MoFe蛋白与nifB- Fe蛋白组成具有可观放氢活性的固氮酶，使FeMoco显出的比活性接近文献报道的还原乙炔的最高值。对nifB- MoFe蛋白的结晶及晶体生长进行了的研究，初步探讨了结晶溶液各组分的种类和浓度、结晶方法和实验操作等与能否出现晶体及晶体的数目、大小、质量、形状和出晶时间等的相互关系。在结晶实验时，一次就得到了国内外尚未报道的该蛋白的短斜四棱柱的棕色晶体。目前所得的最大的晶体的二维边长都为0.1mm。初步结果表明，这种晶体可能就是nifB- MoFe蛋白的晶体。 从棕色固氮菌突变种DJ54中得到了ΔnifH MoFe蛋白；并参与了棕色固氮菌突变种DJ35的ΔnifE MoFe蛋白的分离纯化，所用方法与nifB- MoFe蛋白的分离纯化相似。对这两种突变种蛋白的特性和结晶进行了初步研究。在结晶实验时，也是一次就得到了国内外尚未报道的ΔnifH MoFe蛋白和ΔnifEMoFe蛋白的晶体。 二．新型固氮酶MnFe蛋白和CrFe蛋白的特性与结晶研究 在已有的工作基础上，分离纯化了几批MnFe蛋白和CrFe蛋白，并用部分纯的nifB- Fe蛋白进行活性互补，分别测定了MnFe蛋白和CrFe蛋白的底物还原活性。不断优化MnFe蛋白和CrFe蛋白晶体生长条件，获得了晶质良好的MnFe蛋白和CrFe蛋白的较大晶体。 在2001年的“神舟2号”飞船搭载实验中，MnFe蛋白的出晶率达到100%，所获得的晶体也比地面对照略厚些。继续进行MnFe蛋白和CrFe蛋白的空间计划的地面匹配实验，以满足对蛋白质样品的要求，以保证宇宙飞船“神舟3号”的蛋白质搭载实验获得更好的结果

提高中国软件产业自主创新能力的科技政策思考

当前中国软件产业发展面临着难得的机遇和广阔的市场空间,快速提升中国软件产业自主创新能力是促进中国软件产业发展的关键,也是促进经济可持续发展的必由之路。是促进软件企业联盟,增加软件研发投入力度,营造自主创新的外部环境等措施

西北实业公司火炮的模仿与制造——以晋造36式75毫米火炮为例

文章以晋造36式75毫米山炮制造的技术史为视角,利用档案和工业遗存,考察西北实业公司火炮制造历史,探究了36式山炮仿制的原因和过程。分析了钢铁材料的来源和火炮制造标准的形成,整理出制造工序和加工设备,考证了施耐德产来复线机的技术特点和引进过程,并对其中所折射出的民国时期我国火炮制造的特点进行了讨论

The Effect of Global Value Chain Embeddedness on Productivity: An Analysis of its Impact and Mechanism

本文采用2000-2006年中国工业企业数据库、中国海关进出口数据库的微观企业数据以及2001-2011年世界投入产出数据库(WIOD)与中国工业企业数据库的合并数据,考察了全球价值链嵌入的生产率改善效应。我们发现,参与全球价值链可以有效提高中国企业的生产效率,且全球价值链嵌入与企业的生产效率改进存在"倒U型"关系。同时,企业参与全球价值链会通过中间品效应、大市场效应以及竞争效应改善其生产率。经验研究结论支持了上述3个全球价值链的生产率改善机制,但随着中国企业与发达国家的技术距离缩短,上述3个机制的改善效应会逐渐消失或减弱,从而可能面临价值链"低端锁定"风险。此外,全球价值链嵌入的生产率效应在国有企业和加工贸易企业中不显著。Based on the firm-level data of ＂Annual Surveys of Industrial Firms from the National Bu- reau of Statistics （NBS） of China＂, ＂Chinese Customs Transaction-level Trade Data＂ from 2000 to 2006, the merged data of ＂World Input-Output Database＂ （ WIOD ）, and ＂Chinese Industrial Firm Database＂ from 2001 to 2011, this paper examines the productivity effect of the global value chain embeddedness. We find that participation in the global value chain can effectively improve the productivity of firms, and the GVC embeddedness and productivity improvement have an inverted ＂U-shape＂ relationship. Meanwhile, firms can gain productivity improvement from participating GVC through the intermediate effect, the big market effect and the competition effect. Empirical results support the above three productivity improvement mechanisms. However, when the technology gap between our firms and the ones in developed countries is shortened, the improvement through the above three mechanisms disappears or diminishes, in which situa- tion firms face the risk of ＂Low-end Locking Dilemma＂ of GVC. In addition, the productivity effects of GVC embeddedness on state-owned firms and processing-trade firms are not as significant as those of other firms and industries.国家自然科学基金项目(71503048)；国家自然科学基金面上项目(71673083)；霍英东教育基金会第十四届高等院校青年教师基金基础性研究课题(141085)的资助

Conformal Predictor Based Syndrome Differentiation for Traditional Chinese Chronic Fatigue Diagnosis

构建中医证素组合智能诊断模型需要特殊的域预测分类器而非传统的点预测分类器.引入一致性预测器(COnfOrMAl PrEdICTOr,CP),以算法随机性水平值为证素的重要性度量,以算法风险水平为阈值进行域预测输出,以中医慢性疲劳样本集为研究对象,随机森林(rAndOM fOrEST,rf)等传统机器学习算法被嵌入到CP框架中计算样本奇异值.实验结果表明,CP-rf模型不仅拟合率比其他域预测分类器高,还对阈值具有很好的鲁棒性,克服了阈值对预测域的波动性,解决了中医多证素组合诊断关键的技术难题之一,同时CP-rf模型的预测域错误率能够被算法风险水平阈值所校准,表明其阈值具有明确的统计意义和可解释性,能够被中医医生所接受.Syndrome differentiation in traditional Chinese medicine(TCM)which identifies the combination of some selected syndrome factors as the diagnosis for the patient falls into the region prediction rather than point prediction.In this study,conformal predictor(CP)is introduced in the literature of syndrome differentiation diagnosis which provides algorithms randomness level as the importance of syndrome factor and applies the significance level to serve as the threshold.The study aims to the chronic fatigue(CF) dataset in TCM,for which many novel machine learning algorithms,such as random forest(RF),have been plugged into the framework of CP to compute the nonconformity score of the example.The experimental results show that CP-RF highlights not only significantly high matching ratio beyond other region classifiers but robust to threshold value as well.The latter overcomes the fluctuation of region prediction derives from different threshold values and solves one of the most critical challenges in TCM.Moreover,the error rate of CP-RF is hedged by the significance level,which illustrates statistically interpretability and is easy to acceptance by TCM practitioners.福建省自然科学基金(2012J01274); 华侨大学高层次人才科研项目(09BS515