论优化施工现场管理

施工现场管理效果的好坏直接影响工程项目的质量、进度和效益.因此,只有不断优化项目施工现场,提高项目的现场管理水平,企业才能在市场竞争中获得份额,本文从施工现场管理的基本定义出发,并重点论述了项目现场的优化管理.     

Combined heuristics for determining order quantity under time-varying demands

The time-varying demands for a certain period are often assumed to be less than the basic economic order quantity （EOQ） so that total replenishment quantity rather than economic order quantity is normally considered by most of the heuristics. This acticle focuses on a combined heuristics method for determining order quantity under generalized time-varying demands. The independent policy （IP）, abnormal independent policy （AIP） and dependent policies are studied and compared. Using the concepts of normal/abnormal periods and the properties of dependent policies, a dependent policy-based heuristics （DPH） is proposed for solving the order quantity problems with a kind of time-varying demands pattern under which the first period is normal. By merging the Silver-Meal （S-M） heuristics and the dependent policy-based heuristics （DPH）, a combined heuristics （DPH/S-M） is developed for solving order quantity problems with generalized time-varying demands. The experimentation shows that （1） for the problem with one normal period, no matter which position the normal period stands, the DPH/S-M could not guarantee better than the S-M heuristics, however it is superior to the S-M heuristics in the case that the demands in the abnormal periods are in descending order, and （2） The DPH/S-M is superior to the S-M heuristics for problems with more than one normal period, and the more the number of normal periods, the greater the improvements.     

股权结构与科技型中小企业创新基于创业板上市公司的实证研究

科技型中小企业的创新关乎中国创新驱动发展战略能否成功.股权结构会影响企业创新行为,股权集中可以使大股东有足够的实力与动力监督管理层,却又可能导致大股东掏空等私利行为;股权制衡可以防止大股东权力滥用,却又带来更多的决策成本,降低大股东工作积极性.基于此,研究选取2011～2018年709个创业板上市企业为样本,实证研究发现,股权集中度与创业板企业的创新绩效正相关,股权制衡度与之负相关,进一步分析发现在成立时间较短的企业、第1大股东绝对控股的企业中尤为如此.研究丰富了股权结构及企业创新影响因素研究,而且对现实中科技型中小企业的公司治理提供新思路.     

Opposite effects of fear conditioning and extinction on dendritic spine remodelling

It is generally believed that fear extinction is a form of new learning that inhibits rather than erases previously acquired fear memories. Although this view has gained much support from behavioural and electrophysiological studies, the hypothesis that extinction causes the partial erasure of fear memories remains viable. Using transcranial two-photon microscopy, we investigated how neural circuits are modified by fear learning and extinction by examining the formation and elimination of postsynaptic dendritic spines of layer-V pyramidal neurons in the mouse frontal association cortex. Here we show that fear conditioning by pairing an auditory cue with a footshock increases the rate of spine elimination. By contrast, fear extinction by repeated presentation of the same auditory cue without a footshock increases the rate of spine formation. The degrees of spine remodelling induced by fear conditioning and extinction strongly correlate with the expression and extinction of conditioned fear responses, respectively. Notably, spine elimination and formation induced by fear conditioning and extinction occur on the same dendritic branches in a cue- and location-specific manner: cue-specific extinction causes formation of dendritic spines within a distance of two micrometres from spines that were eliminated after fear conditioning. Furthermore, reconditioning preferentially induces elimination of dendritic spines that were formed after extinction. Thus, within vastly complex neuronal networks, fear conditioning, extinction and reconditioning lead to opposing changes at the level of individual synapses. These findings also suggest that fear memory traces are partially erased after extinction.     

欧拉弯曲梁三次 Hermite 区间样条多小波有限元分析

基于小波多辨分析思想,选择三次Hermite区间样条函数作为多小波尺度基函数,用于构建梁单元多尺度位移近似空间;由最小势能原理,推导出欧拉弯曲梁有限元平衡方程.结果表明:该小波单元可通过改变多小波尺度函数的尺度来重新划分网格,从而可自由调节小波单元的计算精度;其计算精度与采用具有相同网格划分的任意多个传统欧拉弯曲梁单元求解的精度完全相同;该小波单元更加清晰地反映了小波有限元与传统有限元之间的关联.     

能量输入对煤泥浮选过程的影响

为研究煤泥浮选指标与能量输入的关系,针对细粒级为主导的难选煤泥,建立浮选能量输入测试系统,设计在浮选机轴转速分别为1 500,1 800和2 100 r/min时的浮选速度试验,并对不同浮选能量输入条件下的产品进行粒度分析、密度分析和扫描电镜分析。研究结果表明:随着浮选的进行,煤泥的可浮性越来越差,单位精煤可燃体回收率上浮所需要的能量越来越大;当转速为1 500 r/min,精煤灰分含量(质量分数)为13.27%,可燃体回收率为73.35%时,需消耗能量0.18 W;在相同的精煤灰分含量下,当转速为2 100 r/min时,精煤可燃体回收率为81.01%时需消耗能量0.73 W;在低转速下单位能耗所获取的精煤可燃体回收率比高转速下的高,但在相同浮选时间内,高转速下能获得更高的精煤可燃体回收率;在相同条件下,增加浮选过程能量输入能够提高精煤质量或可燃体回收率;在低能量输入条件下,损失的精煤主要是粗粒级的煤岩连生体,粗颗粒连生体和煤岩解离较好的微细粒煤粒需在高能量输入条件才能回收,但同时伴随着异质细泥对精煤的污染。     

材料组成对镁铝尖晶石化行为的影响

以菱镁石、轻烧氧化镁和工业氧化铝细粉为原料,采用半干压法成型,在不同温度下煅烧处理,研究材料组成对镁铝尖晶石化行为的影响。结果表明,富铝尖晶石的尖晶石化反应滞后于富镁尖晶石,两类尖晶石化反应完成温度相差约100℃;富铝尖晶石的尖晶石化反应分两步进行,即在形成理论尖晶石的基础上再固溶氧化铝,最终形成富铝尖晶石;富铝尖晶石烧结程度较富镁尖晶石的低,形成较小的晶粒和气孔。     

我国戊型肝炎全病毒抗原抗HEV·IgM酶联诊断盒的临床应用

我国戊型肝炎全病毒抗原抗ＨＥＶ·ＩｇＭ酶联诊断盒的临床应用廖绵初，干侣仙，黄如统，李晓萸，李德荣（厦门大学抗癌研究中心）（军事医学科学院五所）赵炳华（浙江医科大学第一附属医院）从１９８９年正式确立戊型肝炎ＨｅｐａｔｉｔｉｓＥ以来，许多国家都研制其诊断...     

双退缩非线性抛物型方程的比较原理及其应用

建立双退缩非线性抛物型方程的比较原理并用以证明一类双退缩抛物型方程初边值问题解唯一且在有很时间内耗竭。