大陆岩石圈的热-流变底边界——以Kaapvaal、Fennoscandia和Slave克拉通为例

板块构造理论的一个基本假设是相对刚性的岩石圈板块漂浮在相对软弱的软流圈之上作欧拉运动.岩石圈与软流圈间存在边界面称为岩石圈-软流圈边界(LAB).提出一种半解析方法来确定大陆LAB:定义其为有效黏度取极小值所在的深度.该方法得到的LAB,综合考虑了大陆岩石圈地幔介质的热学和流变学性质,故称其为热-流变底部边界.对3个著名克拉通(Kaapvaal,Fennoscandia和Slave)的研究表明:3个克拉通的热-流变底部边界在~250km,与大地电磁测深等其他地球物理方法得到的结果一致.因为热-流变底部边界是从力学的角度来定义的,且提供了岩石圈板块浮于软流圈上运动的极大可能性,因而与板块构造理论的定义更为接近.在该边界及附近,主导的流变机制是湿橄榄石的扩散蠕变,有效黏度极小,差应力小,应变率相对较大.     

影响橄榄石集合体蠕变性质物化因素的研究进展

综述了高温高压条件下岩石和矿物流变性的实验研究结果 ,总结了影响橄榄石集合体流变性能的各种物理和化学因素 .岩石和矿物在高温高压条件下变形的微观机制主要有 2种 :扩散蠕变和位错蠕变 .橄榄石集合体在扩散蠕变机制作用下 ,应变率 ε和差应力之间的关系为线性 ;在位错蠕变机制作用下 ,差应力指数n约等于 3.在相同差应力作用下 ,温度、熔融组分与橄榄石集合体的应变率是正相关的 .含水条件下 ,橄榄石集合体的强度显著降低 .颗粒度对差应力和应变率的影响比较复杂 ,低应变率和小颗粒度对应的差应力指数约等于 1 ;高应变率和粗糙颗粒度时 ,n为 3左右 .     

蠕变对土工格栅加筋砂土地基承载力影响的试验研究

聚丙烯土工格栅加筋技术是一种新型地基处理方法,目前已得到广泛应用.但由于聚丙烯材质问题,土工格栅极易在承载过程中发生蠕变,对土工格栅的加筋效果产生影响.本文进行了 4组平板载荷试验,对不同工况下加筋地基的沉降、土压力分布情况进行分析,并通过扫描电镜对比未蠕变、蠕变后、平板载荷试验后的土工格栅节点及肋条的微观图像,进一步分析蠕变对加筋地基承载性能的影响.结果表明:加筋地基承载性能优于纯砂地基,且随着蠕变应力水平的提高,土工格栅加筋作用逐渐减弱;蠕变使土工格栅存在的缺陷发展成银纹和微裂纹进而影响土工格栅加筋效应.     

云南省弥勒县滑石板水库滑坡滑带土室内流变试验研究

流变是岩土材料的重要特性之一,许多滑坡在破坏前都表现出明显的流变特性.但在实际工程中对于滑带土体流变特性及其所导致的土体强度变化往往没有较实用的分析预测方法.文章以云南省弥勒县滑石板水库滑坡滑带土为研究对象,通过对滑带土进行三轴蠕变试验及松弛试验,得出土体强度参数随时间变化的拟合曲线方程,为预测滑带土的长期强度提供一定理论依据,亦为评价滑坡的长期稳定性及预测滑坡防治工程的长期效果提供一定的理论基础.     

分级加载条件下结构面的流变特性

岩体结构面的蠕变特性研究对解决岩石力学实际问题具有很重要的意义。通过规则齿型结构面在剪切应力条件下的双轴蠕变试验,研究了不同爬坡角的结构面在不同法向应力时的蠕变特性,并根据蠕变试验结果,得到结构面剪切蠕变随法向应力、剪应力、爬坡角的变化规律和时效性。     

深埋隧洞围岩支护设计方法研究

对于深埋隧洞,地应力高,围岩蠕变时间长,若把握不好支护措施的设计,容易造成支护结构的浪费或者围岩发生大的变形甚至坍塌.本文通过平面有限元软件,运用应力折减法得到围岩特征曲线,结合改进的围岩纵向变形曲线及支护特性曲线,运用收敛-约束法分析了围岩-支护的相互作用,得出了不同围岩条件下的最佳支护时机,并结合工程实践进行验证分...     

开采引起的煤岩粘弹塑陛变形数值模拟

为了研究开采引起煤岩的应力和位移变化趋势,分析蠕变特性对煤岩的影响,本文采用国际大型软件ABAQUS,对开采引起的煤岩粘弹塑性变形进行有限元模拟.通过对蠕变模型和非蠕变模型的结果进行对比,说明煤层开采过程中蠕变的影响不可忽略.蠕变模型结果表明:顶板岩层不断发生跨落,呈现低应力区,其垂直位移和蠕变应变最大值分别为4.99米和0.727.煤岩逐渐形成稳定的应力拱,具有的蠕变特性加速了自身的变形,从而起到了卸压的作用.结果与参考文献的现象相吻合,对预防和防治煤等矿山灾害具有重要的现实意义.     

基于粒度的本体模块抽取算法研究

本体模块的抽取是解决本体复用问题的关键技术.分析了本体模块抽取的相关研究现状,提出一种基于粒度抽取本体模块的算法.该算法利用WordNet和本体上下文来得到可表示本体结构中粒度特征的一组介于0和1之间的实数值,即本体中概念词和关系词的分面权值,使本体模块的边界得到合理的区分.实验表明,该算法能够有效地抽取出符合指定粒度参数的本体模块.     

L-谷氨酰胺冷却结晶工艺探索

采用冷却结晶方法对L-谷氨酰胺进行重结晶,探索了在冷却结晶方法下开始降温温度对最终产品粒度及晶形的影响,并利用粒度分析仪及检测显微镜分析得到结晶产品的粒度分布及晶形,从而确定了最佳降温温度为30℃。     

在荷载作用下低强度岩体的蠕变损伤特性初探

低强度岩体在荷载影响下的蠕变损伤发展过程是一个复杂的裂隙发生扩展过程,通过采用实时成像技术得到当轴向荷载达到极限强度附近时,岩石微破裂聚集形成裂隙,蠕变率在短时间增加,产生更大的塑性变形,当轴向荷载达到极限强度附近时,在相对小的荷载作用下微损伤发生蠕变。当荷载比较大的时候,岩石直接进入加速蠕变阶段,立即发生破坏。通过实时成像技术对低强度岩体的蠕变微分析得到一些对荷载影响下低强度岩体稳定性分析有益的结果。     

Yield and rheological properties of exopolysaccharide from a local isolate: Xanthomonas axonopodis pv. vesicatoria

BackgroundThe aim of the present study was to evaluate gum productivity of a local strain, Xanthomonas axonopodis pv. vesicatoria, isolated from pepper plant, and its rheological behavior for the first time compared to the standard strain, Xanthomonas campestris DSM 19000 (NRRL B-1459). The influence of operational conditions (agitation rate and inoculum volume) on gum production and rheological properties of gums from the Xanthomonas strains were investigated.ResultsThe isolated strain of Xanthomonas showed similar xanthan yield compared to the standard strain. Furthermore, this study clearly confirmed that gum yield depended on bacterial strain, agitation rate, and inoculum size. The most suitable conditions for the gum production in an orbital shaker in terms of agitation rate and inoculum size were 180 rpm and 5%, respectively, resulting in an average production of 10.96 and 11.19 g/L for X. axonopodis pv.vesicatoria and X. campestris DSM 19000, respectively. Regarding the rheological properties, Ostwald-de-Waele and power law models were used to describe flow and oscillatory behavior of the gum solutions, respectively. Consistency of the novel gum solution remarkably was much higher than the commercial xanthan gum solution. Flow and oscillatory behavior and their temperature ramps showed that weak gel-like structure could be obtained with less gum concentrations when the novel gum was used.ConclusionTherefore, yield and technological properties of the aqueous solutions of the exopolysaccharide synthesized by X. axonopodis pv. vesicatoria were observed to be more suitable for industrial production.     

上市高新企业高管薪酬及其效应的实证研究

高新企业是人力资本密集型企业,薪酬是发挥其人力资本优势的主要激励手段,高管人员的薪酬是公司治理机制的核心内容之一。本研究对上市高新产业企业的高管的薪酬进行了实证研究,发现对上市高新产业企业高管的薪酬水平有显著影响的因素是公司的规模、业绩、公司所处的经济区域以及公司的最大股东的持股比例,其中,公司的规模对高管的薪酬的影响最大。对高管的持股比例有显著影响的因素是公司的规模、业绩及公司的最大股东的持股比例。独立董事在董事会所占的比例、监事会规模并不影响高管的薪酬。高管的薪酬和公司的业绩显著正相关,高管的薪酬水平、持股比例和高管的薪酬差距明显影响着公司的业绩。本研究证实了高新企业高管薪酬的效应,建议对高新企业高管人员实行以市场为导向、以公司的业绩为驱动的薪酬制度,在规范的基础上大力推行股票期权计划,适当提高高管团队的薪酬差距,进一步完善高新企业的治理结构。     

Mathematical model of pulsatile flow of non-Newtonian fluid in tubes of varying cross-sections and its implications to blood flow

The effects of rheological behavior of blood and pulsatility on flow through an artery with stenosis have been investigated. Blood has been represented by a non-Newtonian fluid obeying Herschel–Bulkley equation. Using the Reynolds number as the perturbation parameter, a perturbation technique is adopted to solve the resulting quasi-steady non-linear coupled implicit system of differential equations. Analytical expressions for velocity distribution, wall shear stress, volumetric flow rate and the mean flow resistance have been obtained. It is observed that the wall shear stress and flow resistance increase for increasing value of yield stress with other parameters held fixed. One of the remarkable results of the present analysis is not only to bring out the effect of the size of the stenosis but also to study the influence of the shape of the stenosis. The change in the shape of the stenosis brings out a significant change in the value of flow resistance but it has no effect on the variation of wall shear stress except shifting the point (where it attains its maximum value) towards downstream. It is pertinent to point out that pulsatile flow of Newtonian fluid, Bingham plastic fluid and Power-law fluid become particular cases of the present model. The present approach has general validity in comparison with many mathematical models developed by others and may be applied to any mathematical model by taking into account of any type of rheological property of blood. The obtained velocity profiles have been compared with the experimental data and it is observed that blood behaves like a Herschel–Bulkley fluid rather than Power-law and Bingham fluids. Finally, some biorheological applications of the present model have briefly been discussed.     

微槽群相变式微冷系统的换热特性实验

本文对用于大功率电子器件冷却的微槽群相变微冷系统的冷却工质液位高度、蒸发元件表面微槽群尺寸及横向微槽的采用等因素对整个微冷系统散热性能的影响进行了实验研究。在其它条件保持不变的情况下，对液位高度变化、微槽群尺寸及横向微槽的采用对微冷系统散热影响进行了讨论，并确定了该微冷系统的最佳液位参数和最佳尺寸参数。     

项目选择与确定过程中的风险管理研究

组织战略目标导向的项目选择与确定过程存在较高的风险性,已成为困扰管理决策者的首要问题。在此,给出了项目选择与确定过程以及风险管理的过程,简要论述了项目的战略意义与项目r失败的问题;提出了在项目选择与项目确定阶段,充分考虑项目特点的客观性风险因素与主观性风险因素的识别与量化理念;给出了项目选择与确定过程中风险管理原则以及风险控制的具体措施。     

广东省省属研究机构参与区域科研平台建设的研究

科研创新平台的建设是实现核心技术竞争力的保证.分析了广东省省属研究机构参与本区域各类科研创新平台建设的现状和存在的主要问题,并提出了解决问题的建议.     

分散聚合法制备微米级PMMA微球的研究

采用分散聚合法合成了微米级聚甲基丙烯酸甲酯(PMMA)微球，对影响粒径及其分布的各种因素，如单体、引发剂、稳定剂、分散介质以及反应温度等进行了考察，探讨了分散聚合法制备单分散大粒径微球的机理。研究结果表明：增加单体和引发剂浓度，微球的粒径增大，分散性变宽；增加稳定剂的量，微球的粒径减小，分散性变窄；此外分散介质的极性和反应温度的影响也很明显。通过合理调节各种影响因素可制备理想粒径和粒径分布的PMMA微球。     

Viscoelasticity of blood and viscoelastic blood analogues for use in polydymethylsiloxane in vitro models of the circulatory system

The non-Newtonian properties of blood are of great importance since they are closely related with incident cardiovascular diseases. A good understanding of the hemodynamics through the main vessels of the human circulatory system is thus fundamental in the detection and especially in the treatment of these diseases. Very often such studies take place in vitro for convenience and better flow control and these generally require blood analogue solutions that not only adequately mimic the viscoelastic properties of blood but also minimize undesirable optical distortions arising from vessel curvature that could interfere in flow visualizations or particle image velocimetry measurements. In this work, we present the viscoelastic moduli of whole human blood obtained by means of passive microrheology experiments. These results and existing shear and extensional rheological data for whole human blood in the literature enabled us to develop solutions with rheological behavior analogous to real whole blood and with a refractive index suited for PDMS (polydymethylsiloxane) micro- and milli-channels. In addition, these blood analogues can be modified in order to obtain a larger range of refractive indices from 1.38 to 1.43 to match the refractive index of several materials other than PDMS.     

Characterising and evaluating information seeking behaviour in a digital environment: Spotlight on the ‘bouncer’

The paper delineates and explains an emerging, but significant, form of digital information seeking behaviour among information consumers, which the authors have called ‘bouncing’. The evidence for this behaviour has emerged from five years of deep log analysis studies – an advanced form of transaction log analysis – of a wide range of users of digital information resources. Much of the evidence and discussion provided comes from the scholarly communication field. Two main bouncing metrics were applied in the log studies: site penetration, which is the number of items or pages viewed in a session, and return visits. The evidence shows that (1) a high proportion of people view just a few items or pages during a visit to a site and, (2) a high proportion of visitors either do not come back to the site or they did so infrequently. Typically those who penetrated a site least tended to return the least frequently. These people are termed ‘bouncers’. They bounce into the site and then bounce out again, presumably, to another site, as a high proportion of them do not appear to come back again. Possible explanations – negative and positive, for the form of behaviour are discussed.