考虑路径相关度的PERT网络进度风险的改进算法

提出克服传统计划评审技术(PERT)网络进度风险的局限性进度网络风险概率的改进算法.考虑网络路径之间相关性的约束条件,去除在规定工期内高完工率和高相关性的路径,利用多元正态积分技术,计算PERT网络进度风险概率.算例结果表明:与传统的蒙特卡洛模拟方法相比,该模型能够减少大量的计算时间,且误差较小,可忽略不计.     

搭接网络计划模型分析

对搭接网络计划的计算模型和图示模型进行了较系统的分析,引入了延迟工序和增广网络计划的概念,基于这些概念,讨论了搭接网络计划时间参数的计算模型和双代号搭接时标网络图的生成与判读方法.     

基于Excel的项目计划管理的实现

网络计划技术是用于工程项目计划与控制的一项管理技术,其本质是利用关键路径法(CPM)或计划评审法(PERT)对各项工作安排进行评价和审查.传统解决方法的PERT网络图,对复杂问题求解有很大的局限性.采用线性规划求解的方法,基于Excel对网络计划进行实现和优化,使其作用于更大范围和更复杂场合中.     

双代号搭接网络向VCPM网络转化模型研究

以关键路线法(Critical Path Method,CPM)网络计划图示模型为目标,将双代号搭接网路计划中的搭接关系转化为持续时间不为0的虚工序,即通过增加带持续时间的虚箭线(搭接虚工序)代替搭接关系,把双代号搭接网络转化为VCPM(Virtual Critical Path Method,VCPM)网络.首先将双代号搭接网络中的所有搭接关系转化为结束到开始(Finish-To-Start,FTS)关系;然后在具有搭接关系的实工序之间增加搭接虚工序代替搭接关系构建VCPM网络计划,使其拥有CPM图示模型的直观性;最后其时间参数的计算规则和关键线路的确定以CPM为基础进行改进.     

施工网络计划的Fuzzy方法

采用模糊数学的方法,确定了网络图中工序时间的隶属函数,利用λ-截集时间参数的计算公式,可求得模糊网络各工序λ-截集的时间参数及关键线路的模糊完成期,此方法可行、实用,更接近工程实际,优于传统的PERT法。     

模糊网络计划技术在水利工程施工中的应用研究

基于模糊网络时间参数的加法迭代计算形式及模糊方程解的分层线性规划定义,将三角形模糊数引入工期分析中,对蜀河水电站施工网络进度计划进行分析,得出模糊时间参数、模糊关键线路以及模糊完工期。仿真结果表明,该方法可行且有效,比传统的CPM和PERT方法有了更大的改善。     

应用DBR理论的网络进度计划完工工期仿真

将影响工程项目施工进度的各类风险因素视为影响工程工期中的瓶颈,将鼓-缓冲-绳子(DBR)理论中的“鼓”、“缓冲”、“绳子”3元素加入到传统的计划评估和审查技术(PERT)网络进度计划的编制中;然后,通过识别PERT网络进度计划中的瓶颈工序,制定瓶颈工序的实施计划;最后,通过衡量工序的缓冲时间,计算工程网络进度计划路径的缓冲时间及投料时间,改善工程进度网络图中的工序作业任务活动之间存在的关系及作业活动持续时间的不确定性.算例结果表明:若能够将“鼓”、“缓冲”、“绳子”3元素充分地加以配合,能够达到降低工程施工进度风险的目的.     

PERT方法时间估计问题的探讨

本文根据统计学原理,对PERT方法的时间估计问题进行了分析;利用检验的办法确定了PERT假设前提对工序时间的均值、标准离差及总工期所产生的误差。并提出了减少这些误差的有效方法。     

PERT行为时间参数近似计算公式选优

自 PERT产生以来 ,管理学界出现了许多计算 PERT时间参数的近似公式 ,文章将其中的三点近似公式进行了汇总和对比。通过与 Beta分布系列量化比较发现它们的精度相差较大 ,其中早期 PERT公式有非常差的精度 ,而新出现的一些三点近似公式却有着优异的精度表现。这为 PERT模型时间参数近似计算提供了新的思路     

基于Petri网及矩母函数的计划评审技术

针对经典的计划评审技术不允许网络图中存在回路,而且假定所有活动时间服从β分布,使计划评审技术的使用受到限制的问题,通过将双代号网络映射为基于Petri网的模型,建立了既不改变双代号网络原有特性,又允许回路存在的基于Petri网的计划模型.结合Petri网可达图分析方法,在消减可达图的突发状态的基础上,引入矩母函数计算了PERT模型的性能参数.通过计算实例和仿真实验对比验证了该方法可以用于增强计划评审技术.     

诗与"在"--海德格尔诗学的阐释

海德格尔对荷尔德林诗歌的阐释，目的是进行诗与思的对话，归根结底还是探讨存在。诗与“在”的关系，是海氏诗学框架的核心内容，诗与“在”的关系又进一步引申为艺术与真理的关系，本从真理如何被遮蔽的问题入手，试图读解海德格尔诗学的内涵。艺术是无蔽的真理显明的一种方式，诗是危机的拯救，语言是存在的家园。海德格尔对诗与在的探讨最后又转入了对语言的探讨，无法走出语言的牢笼。只有在实践中，把艺术变成为社会变革的一个因素，才可以解放被传统理性压迫的力量，显现艺术的真理，确立艺术的价值。     

Regulation of canonical Wnt/β-catenin pathway in the nucleus

Canonical Wnt/β-catenin pathway plays a central role in development, homeostasis, as well as tumorigenesis. The regulation of the pathway involves various and complicated mechanisms, including the extracellular, intracellular and endonuclear regulation. As the key component of the pathway, the Lefl/Tcfs-β-catenin complex is also the key target of regulation in the nucleus. In the current review, we are going to summarize the regulators in the nucleus which can modify the transcrip- tional activity of the Wnt/β-catenin pathway.     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

论信托财产的人格性

信托财产是信托关系的基本要素,由于信托的特殊性,信托财产与传统民法的财产有很大区别,正确给信托财产定位,是信托业得以健康发展的核心问题。信托财产的特性在于其人格性,而这种人格性的赋予是以交易成本最小化为动因,尽管信托财产人格性设计对受益人的利益有偏袒,但从社会成本而言,其目的在于促使交易成本最小化,当然,对信托财产的人格性不能绝对化,由于利益平衡的需求,往往在特定情况下对信托财产予以人格否认。     

卤素离子在多晶铜电极表面的微分电容研究

本文通过测量金属晶体电极表面的微分电容研究了金属电极表面在金属与水溶液界面上的吸附能力,以及金属与吸附质之间的相互作用。文中论述了多晶铜电极在(0.5-x)mNaClO_4+xmNaBr的一系列不同x值的溶液中的微分电容测量值及微分电容-电位曲线,证明了F~-和ClO_4~-离子在多晶铜电极表面是非常弱的吸附,Br~-离子在多晶铜电极表面具有特定的吸附,每条电容-电位曲线有一个凸起的峰。在峰所对应的位能值,金属表面对阴离子的吸附能力强,证实金属-吸附质之间的相互作用强,吸附的阴离子在过渡层中散射导电电子的能力也强。对于相同阴离子和金属的体系,其微分电容与吸附质的浓度、电压、溶液的pH值和表面的非均匀性等因素密切有关。研究证明,金属晶体电极表面在电解质溶液中的微分电容的变化规律类似于表面电反射信号的强弱变化规律,微分电容大小取决于金属-吸附质之间的电荷转移程度。     

气体对阴离子表活剂压裂液破胶实验研究

阴离子表活剂压裂液是新型清洁压裂液,原油和地层水对其破胶机理与实验研究已相当充分,但气体对其破胶作用至今研究很少.为解决阴离子表活剂压裂液在压裂应用中的障碍,研究采用一套实用的实验流程,评价了天然气、氮气、二氧化碳三种常见气体对阴离子表活剂压裂液的影响.实验证明,三种不同的气体对阴离子表活剂压裂液的降粘幅度存在较大的差别,其中,二氧化碳气体对阴离子清洁压裂液降粘幅度最大,可使交联液体彻底破胶,天然气对阴离子型表活剂压裂液降粘幅度较小,氮气对阴离子压裂液的粘度几乎没有影响,氮气和天然气可以使液体泡沫化,从而有利于返排.实验结果为优化压裂设计提供了依据,可有效提高现场压裂施工成功率.     

多腔速调管主要性能指标简化分析

介绍了速调管在我国的发展现状和几种不同结构的多腔速调管的主要特性比较,并给出了小信号条件下速调管的各种主要特性的简化分析方法.在这种简化分析方法中,把多腔速调管看作是几个双腔速调管的级联,并且没有考虑非线性、空间电荷效应和相对论效应等带来的影响,目的是阐述基本原理和基本分析方法.     

DEM/CFD modelling of the deposition of dilute granular systems in a vertical container

Deposition of granular materials into a container is a general industrial packing process. In this study, the deposition behaviour of dilute granular mixtures consisting of two types of particles that were of the same particle size but different particle densities in the presence of air was numerically analyzed using a coupled discrete element method （DEM） and computational fluid dynamics （CFD）. Bilayer granular mixtures with light particles at bottom and heavy particles at top were first simulated. It was found that the presence of air significantly affected the flow behaviour of the bilayer mixtures. For the system with a relatively low initial void fraction, the air entrapped inside the container escaped through the dilated zones induced due to the friction between the powder bed and wall surfaces. The escaping air streams entrained light particles that were originally located at the bottom of the granular system. Consequently, these light particles were migrated to the top of the granular bed at the end of deposition process. More light particles were migrated when the deposition distance was increased. For the system with a high initial void fraction, some light particles penetrated into the top layer of heavy particles and created a mixing zone. Deposition of random mixtures with different initial void fractions was also investigated and the influence of initial void fraction on the segregation behaviour was explored as well. It was found that the increase of void fraction promoted segregation during the deposition in air. It was demonstrated that, for granular mixtures consisting of particles of different air sensitivities, the presence of air had a significant impact on the mixing and segregation behaviour during the deposition.     

Using new fusion operations to improve trust expressiveness of subjective logic

Subjective logic provides a means to describe the trust relationship of the real world.However,existing fusion operations it offers treat fused opinions equally,which makes it impossible to deal with the weighted opinions effectively.A.Jφsang presents a solution,which combines the discounting operator and the fusion operator to produce the consensus to the problem.In this paper,we prove that this approach is unsuitable to deal with the weighted opinions because it increases the uncertainty of the consensus.To address the problem,we propose two novel fusion operators that are capable of fusing opinions according to the weight of opinion in a fair way,and one of the strengths of them is improving the trust expressiveness of subjective logic.Furthermore,we present the justification on their definitions with the mapping between the evidence space and the opinion space.Comparisons between existing operators and the ones we proposed show the effectiveness of our new fusion operations.