海南阿陀岭4种加勒比松林分直径分布规律研究

为了给海南省低质低效次生林分的改造经营提供科学、合理的参考依据,利用正态分布、对数正态分布、Weibull分布、Γ分布4种分布函数分别对阿陀岭的4种加勒比松林分的直径分布规律进行了分析研究。结果表明：（1）4种林分的直径分布曲线均为左偏态,林木株数均偏向中小径阶;（2）加勒比松与台湾相思混交林和加勒比松与海南柃混交林用Weibull分布函数拟合的效果更好,加勒比松与浙江润楠混交林用Γ分布函数拟合的效果比较理想,加勒比松纯林用Weibull分布和Γ分布函数拟合效果接近,无显著差异。说明Weibull分布对4种林分的适应性和灵活性最强,正态分布最差,Γ分布和对数正态分布居中。     

河流底泥粒径分形维数与重金属含量相关性——以海南岛南渡江塘柳塘为例

为了揭示河流底泥重金属含量与粒径分形维数、有机质之间的数量关系,借助统计分析和土壤分形维数分析法,分析了南渡江塘柳塘52个底泥样品的粒径分形维数特征;开展了底泥重金属含量与有机质、粒径分形维数的相关性分析、主成分分析及模型回归等。研究结果表明：所调查河流底泥粒径分形维数在2.453~2.971之间,不同粒径分级的分形维数平均值不同;重金属含量与有机质含量、极细砂分形维数、细砂分形维数呈显著的正相关,与粘粒、粉粒分形维数呈负相关,底泥中Zn、Hg受粒径的影响较小。底泥中有机质与粘粒分形维数可作为表征底泥基本理化形状的关键指标。底泥重金属含量（Zn、Hg除外）与有机质存在一元线性数量化关系;底泥重金属（Zn、Hg除外）含量与有机质、粘粒分形维数之间存在二元回归模型的数量化关系,上述模型间的数量化关系对于研究底泥的理化性状有着重要的意义。     

尾矿坝变形细观力学机理的颗粒流数值模拟

以新建四川省盐源县平川铁矿黄草坪尾矿库为工程背景,通过堆坝模型试验与室内土工试验,获得尾矿坝干滩面几何特征、颗粒分布规律及尾矿力学性质。基于离散元理论,采用PFC 2D数值模拟软件进行双轴试验,与土工试验结果对比,得到尾矿细观力学参数,并分析尾矿坝颗粒接触力分布、颗粒位移与坝体结构变形特征。结果显示：1)初期坝中颗粒间接触力较大,形成的力链大致呈45°倾斜向上;坝体尾矿颗粒接触力随着埋深的增加而增大,在基岩凸起处接触力较大且集中。2)初期坝颗粒位移不明显,堆积坝少数尾矿颗粒沿坡面向下滚动,具有较大位移;尾矿堆积坝存在较为典型的滑移面,滑移面上部区域颗粒位移较大。3)初期坝结构变化不明显,尾矿堆积坝中靠近初期坝内坡面附近结构变形显著。     

鼎湖山地区大气颗粒物中水溶性无机盐粒径分布特征

为研究珠江三角洲大气颗粒物的化学组成特征及其来源,2008年10-11月在中科院华南植物研究所鼎湖山区域大气本底观测站对大气中的颗粒物进行了分级（8级）采样,并对各个粒径段颗粒物中水溶性无机盐进行了分析。结果表明,SO42-、NH4+在小于1.1μm的细粒子中出现浓度峰值;Na+和Cl-在1.1-2.1μm出现浓度峰值;NO3-分别在1.1-2.1和3.3-4.7μm出现两个浓度峰值;K+在0.65-1.1和5.8-9μm两个粒径段出现峰值;而Ca2+和Mg2+的浓度峰值则出现在大于9μm粒径段。     

河南主产烟区土壤颗粒分形特征及对烟叶理化性状的影响

为了研究河南烟区土壤粒径与烟叶品质的关系,在主产烟区选取了26个代表性土样和对应的烤后烟样。建立土壤质量分形模型并计算出烟区耕层土壤分形维数D值。采用多重比较、简单相关分析、通径分析方法分析了土壤分形维数与烟叶主要物理性状、化学成分的相关性。结果表明：①河南主产烟区土壤分形维数最高的地区是洛阳,分形维数为2.818;最低的地区是驻马店,分形维数为2.714,呈现空间异质性。土壤分形维数与黏粒呈极显著正相关,与粗粉粒呈极显著负相关,表现为土壤颗粒越小,土质越粘重,土壤分形维数越大。②烟叶物理性状中叶质重权重为0.2463,与分形维数间接正相关;烟叶化学性状中烟碱权重为0.2214,与分形维数间接负相关。推论河南烟区适宜分形维数为2.752左右,可通过栽培方式培育适宜分形维数。     

循环孔隙水作用下混凝土动态特性试验研究Symbol`@@

对0、10、50次孔隙水循环下不同应变速率(10 -5、10 -4、10 -3、10 -2/s)的混凝土和中低应变速率(10 -4、10 -3/s)下不同孔隙水循环次数(0、10、50、100、200次)的混凝土进行了常三轴压缩试验,试件尺寸为300 mm×600 mm。对循环孔隙水压作用后混凝土的峰值应力物理力学参数的变化规律进行了统计分析,并对混凝土在不同加载速率下的吸能变化规律进行了分析。结果表明：随着应变速率增大,混凝土的峰值应力呈增大趋势,随孔隙水压循环次数的增加,峰值应力大体呈现先增大后减小的阶段性变化;混凝土的吸能能力随加载速率的增加,表现出明显增大的趋势。混凝土的吸能能力随孔隙水压循环次数的增加表现出一定的离散性,但整体上呈先增大后减小的趋势;选用基于Weibull统计理论的混凝土材料分段式动态损伤本构模型对试验数据进行拟合,经验证,此模型与试验结果吻合较好。     

香料植物桂花野生种群分布格局的分形分析

采用分形理论中的计盒维数、信息维数和关联维数对长汀县石峰寨桂花野生种群分布格局的多尺度分布规律进行比较分析。结果表明,桂花野生种群的分布格局具有分形特征,其计盒维数为0.8622～1.0058,信息维数为0.8670～0.9849,关联维数为1.0037～1.0757。桂花种群的计盒维数、信息维数、关联维数相差不大,表明该种群的分布格局强度相对复杂,局域空间占据较强,具有集聚分布的趋势。     

耕作方式对紫色水稻土微团聚体分形特征影响的研究

土壤结构会影响土壤的水、肥、气、热状况,从而影响土壤肥力,而耕作方式会通过影响土壤团聚体状况来影响土壤结构,因此,为研究不同耕作制度对土壤团聚体的影响及土壤质量、结构的定量化描述,以位于西南大学农业部重庆紫色土生态环境重点野外科学观测试验站于1990年设立的长期免耕试验田为研究对象,应用微团聚体粒径分布的分形维数来探讨冬水田平作(DP)、水旱轮作(SH)、垄作免耕(LM)、厢作免耕(XM)和垄作翻耕(LF)等耕作方式对紫色水稻土土壤结构的影响。结果表明,LM、XM、LF和SH耕作方式下各土层的微团聚体含量随粒径的减小而降低,而DP处理下各土层的微团聚体含量随粒径的减小呈先降低后升高的趋势;相关分析表明,2~0.25 mm粒级团聚体含量与土壤中的有机碳、全氮、碱解氮、全磷等土壤养分含量都呈极显著正相关关系,而0.05~0.01 mm和0.01~0.005 mm粒级微团聚体含量都与这几种土壤养分呈显著或者极显著负相关,说明土壤养分主要富含在2~0.25 mm粒级团聚体中;土壤微团聚体分形维数与其各粒级含量极显著相关,微团聚体分形维数以及(< 0.005 mm)/(> 0.005 mm)粒级微团聚体含量比值都可以定量地表征紫色水稻土的结构性状;在0~70 cm土壤深度,LM、XM和LF处理下土壤微团聚体分形维数均极显著低于DP处理,表明垄作或免耕均可以改善土壤结构。     

TCA法脱除榛子壳多糖中蛋白质的工艺研究

以废弃的榛子壳为主要原料,先采用水浴浸提的方法对榛子壳的多糖进行提取,再对榛子壳粗多糖溶液进行脱蛋白处理,然后用紫外分光光度计对其进行蛋白吸光度的测定;采用单因素试验和响应面试验,探讨榛子壳粗多糖脱蛋白的研究。三氯乙酸(TCA)法对榛子壳粗多糖溶液进行脱蛋白试验,结果表明三氯乙酸法脱蛋白的最佳工艺参数为三氯乙酸质量分数4.2%,静置时间20.11 min,样液与TCA的体积比2.03∶1;在此条件下得到榛子壳粗多糖中蛋白的脱除率为77.21%,与模型的预测值79.62%基本吻合,说明响应曲面所得数据可靠。     

DEM模拟解析二元混合颗粒粒径偏析分布规律

颗粒粒径偏析分布是高炉炉顶布料过程中不可避免的现象,易造成炉喉处局部料层的空隙度降低和压差升高,影响煤气流的均匀分布,继而间接影响炉况的顺行。通过DEM离散单元法模拟研究二元混合颗粒的偏析分布规律,同时,提出一个偏析指数T,用以表征粒径偏析分布的相对程度。研究结果表明：同一T值图中,相邻区域颗粒的T值相差越大,则该区域颗粒的粒径偏析程度越大;不同T值图中,所有相邻T值之差的平均绝对值越大,则颗粒堆积整体粒径偏析程度越为严重。     

Quantitative modeling and application of CNC machine failure distribution curve

To quantitatively study the distribution curve of CNC machines, the Weibull linear regression using the failure data of CNC machines is analyzed. As the result of analyzing WPP(Weibull probability plot), the failure rate distribution curve which includes early failure period and random failure period is established by piecewise twofold Weibull model. The establish method of the model and the process of parameter estimated by maximum likelihood are explained. The correctness of the model is verified by comparing the lasting time of early failure period with the actual situation. The optimization warranty of CNC machines is obtained by an object function which is established by the model.     

一维稳态流非饱和土渗透系数垂直分布模型及其线性简化

渗透系数是控制地下水流动的重要参数,对渗透系数的空间分布规律进行研究具有重要的意义。基于Gardner模型获取了一维稳态流非饱和土渗透系数沿垂直分布模型,该模型用指数函数描述,受饱和渗透系数和无量纲的深度与流动率等因素的控制;该模型表明一维稳态流条件下均质典型土类的渗透系数其沿垂直方向变化趋势主要受比流量与饱和渗流系数的负数值二者之间的相对大小影响。分别采用泰勒级数方法和以地下水位处及地表处的渗透系数作为控制条件方法对一维稳态流非饱和土渗透系数沿垂直分布模型进行线性近似简化。采用泰勒级数方法获取的简化模型其计算误差随无量纲的深度增大而增大。简化后的模型具有形式简单、参数少等特点。通过算例对比简化模型与原模型的差异,计算结果表明:采用以地下水位处及地表处的渗透系数作为控制条件的方法进行线性近似简化的模型计算误差比采用泰勒级数方法获得的线性近似简化模型的计算误差小。     

Application of the Weibull Distribution for the Recognition of Transformer PD Phenomena

The problem of identification of partial discharge phenomena occurring in a transformer insulating system is addressed. Under the assumption that different PD sources can produce pulse of different PD distributions, five typical artificial defects have been designed to compare the PD distributions coming from different sources, such as internal voids, surface and corona discharges. In this aim, Weibull distribution has been introduced to estimate the parameters and the least square methods (LSM) have been used to estimate the parameters. The goodness of fit to a Weibull distribution is checked by the Cramer-von-Mises (CVM) test. It is shown that the probability function fits well the partial discharge height distribution. By this way,different discharge sources can be distinguished. by Weibull parameter. In addition, the recognition of two or more PD phenomena simultaneously active is approached by means of an additive Weibull distribution. It allows quantities related to each of the two or more superimposed PD phenomena to be estimated, according to the Weibull parameters and the standard mean quantities.     

基于加权最小二乘法的供水管网节点流量校核

管网水力模型是实现供水系统现代化管理的重要工具,要使水力模型能比较准确地反映管网真实运行状态,达到预期使用目的,其中的参数需要校核。将管网节点流量校核作为优化问题,采用加权最小二乘法逐步迭代求解,与已有研究相比,采用矩阵分析法推导供水管网雅克比矩阵解析式,引入水量分配矩阵聚合节点流量,将欠定问题转化为超定,提高了校核的计算效率和结果的可靠性。采用简单管网阐明了雅克比矩阵的计算、节点流量的聚合及梯度向量的构造,利用实际管网验证了方法的实用性。     

CFD-DEM Simulation to Study the Filtration Characteristic of the Fine Particle in the Filter Media

The gas-solid two-phase flow characteristics of fine particles in the filter media were simulated based on CFD-DEM (Discrete Element Method) in this study, and the particle group, particle size distribution, and the rebound effect between particles, particle and fiber were taken into account the calculations. Additionally, the movement characteristics of the particle group and the deposition form of the fine particles in the fibrous filtration were analyzed. The results indicate that it is convenient and feasible to simulate the filtration process of the filter media as well as the deposition process and form of the fine particle on the media surface using CFD-DEM, and the simulation results are consistent with the experimental observations in the literature. The surface filtration has larger contribution to the filtration process, and most of the particles are captured by the media surface. Meanwhile, parts of smaller particles that enter into the media are captured by the depth filtration. A larger number of particles are collected by the particle-particle capture mechanism. The filtration efficiencies of the filter media are varied with the particle systems, and for the model of the filter media in this study, the filtration efficiency of the multi-particle system is about 20% higher than that of the single-particle one.     

Reliability model for Subsystems of CNC machine tool with small samples

Many subsystems in CNC machine tool have only a few failures, so they are small samples. In this case, classical reliability modeling method often has large errors. For the failure data of small sample, maximum likelihood estimation method is used to estimate the Weibull distribution model parameters of time between failures of the subsystems. Then, the Weibull distribution model parameters are modified by parameter bias correction method. Finally, the effect of bias correction parametersis tested by the D test and the error area ratio test method. The test results show that the modified models are better.     

Simple Shear Test of Interface between Sand and Structure under High Stress

By using a simple shear apparatus that is developed from RMT-150B,a series of simple shear tests of interface between saturated sand and structure under high normal stress were carried out to study constitutive law and shearing stiffness of interface to provide some theoretical evidences for design and calculation of projects concerned with mechanical problem of interface.In test,sand was consolidated in upper shearing box firstly,then,shear was started and testing data was recorded under high and constant normal stress.During the process,sand can deform relatively freely.It is shown that the relation curve between shear stress and shear displacement under high normal stress in simple shear tests is different from that in direct shear tests,and the complete shearing deformation process of interface under high stress can be described as a nonlinear elastic-perfect plastic form;Weibull distribution with three parameters can overcome the mathematical deficiencies of hyperbola in NEPP.The new model which is established by substituting Weibull distribution for the hyperbola of NEPP better agrees with the testing data.The regressive results of the initial shearing stiffness demonstrate that the linear function is slightly better than power function to express the relation between the initial shearing stiffness and normal stress.Based on the new interface model,the formula of tangential shearing stiffness is proposed,meantime,the change trend of tangential shearing stiffness of the new model is compared with that of NEPP.     

区域经济系统的分形特征及规模分布

将分形方法引入区域经济系统中,从Zipf定则的理论出发,推导出Zipf公式是Hausdorff（豪斯道夫）维数的特例。以黑龙江省粮食生产经济系统为例,定量地分析了近四年黑龙江省粮食生产经济系统中各要素的规模分布现状和发展趋势：由分维整体结果看,规模分布是分散的;由分维值的变化趋势来看,差异在减小,规模分布趋于集中。表明Hausdorff（豪斯道夫）维数能更深刻地反映粮食生产经济要素规模分布的复杂变化,并为了解和指导区域经济发展提供了新的方法和依据。