机床颤振的一种新的控制方法

首先评述了目前对机床颤振的各种控制方法,然后提出在线变刀具前、后角抑制颤振的方法,并讨论了这种新方法的抑振原理。试验表明,该方法效果明显。所研制的控制装置结构简单,不需对机床作任何改装,故有可能成为普通车床及数控车床上具有抑制颤振能力的一个功能部件。     

A loss-of-function RNA interference screen for molecular targets in cancer

The pursuit of novel therapeutic agents in cancer relies on the identification and validation of molecular targets. Hallmarks of cancer include self-sufficiency in growth signals and evasion from apoptosis; genes that regulate these processes may be optimal for therapeutic attack. Here we describe a loss-of-function screen for genes required for the proliferation and survival of cancer cells using an RNA interference library. We used a doxycycline-inducible retroviral vector for the expression of small hairpin RNAs (shRNAs) to construct a library targeting 2,500 human genes. We used retroviral pools from this library to infect cell lines representing two distinct molecular subgroups of diffuse large B-cell lymphoma (DLBCL), termed activated B-cell-like DLBCL and germinal centre B-cell-like DLBCL. Each vector was engineered to contain a unique 60-base-pair 'bar code', allowing the abundance of an individual shRNA vector within a population of transduced cells to be measured using microarrays of the bar-code sequences. We observed that a subset of shRNA vectors was depleted from the transduced cells after three weeks in culture only if shRNA expression was induced. In activated B-cell-like DLBCL cells, but not germinal centre B-cell-like DLBCL cells, shRNAs targeting the NF-kappaB pathway were depleted, in keeping with the essential role of this pathway in the survival of activated B-cell-like DLBCL. This screen uncovered CARD11 as a key upstream signalling component responsible for the constitutive IkappaB kinase activity in activated B-cell-like DLBCL. The methodology that we describe can be used to establish a functional taxonomy of cancer and help reveal new classes of therapeutic targets distinct from known oncogenes.     

一种改进的车辆跟驰动力学模型

针对现有跟驰模型存在的不足,文中提出了一种新的优化速度(期望速度)函数,基于“刺激—反应”模式建立了改进的车辆跟驰动力学模型,并运用李亚普诺夫运动稳定性理论对其进行了稳定性分析.最后运用实测数据对模型进行了参数标定和应用性验证.结果表明:改进模型在模拟交通流的启动加速、近似匀速和减速过程方面与实测数据都具有较高的一致性...     

Numerical Investigation of the Impact of Different Configurations and Aspect Ratios on Dense Gas Dispersion in Urban Street Canyons

The dispersion of chlorine gas in urban street canyons was numerically simulated using the fire dynamics simulator, a code developed by the National Institute of Standards and Technology of USA, which uses large eddy simulation coupled with the Smagorinsky sub-grid scale model. The unsteady flow fields were computed by solving the filtered incompressible Navier-Stokes equations under low Mach number ap-proximation by the finite difference method. The studies analyzed the influence of different street canyon configurations and aspect ratios on the flow and chlorine gas dispersion. The geometric configuration and aspect ratio both affect the vortices and the local concentration distributions in street canyons.     

不同轮割制度对内蒙古大针茅草原群落组成的影响

野外试验设计结合室内分析,探讨了以大针茅(Stipa grandis)为建群种的锡林郭勒典型草原区不同轮割制度对割草场产量、物种组成、群落结构及营养状态的影响.一年割2次的利用方式在短期内生物量收获较大,但这种状态较难持续;完全围封不利用也不利于草场恢复;一年割1次的适度刈割制度在当地较为合理,但是连年刈割会导致草场营养贫瘠,植物补偿现象减弱.越高频刈割对大针茅和羊草(Leymus chinensis)种群的影响越严重,产量明显减少,重要值下降,而糙隐子草(Cleistogenes squarrosa)种群则相反;随刈割频度的增高根茎禾草在群落中的相对生物量上升,丛生禾草下降,二者明显互补.刈割对土壤和植物的N素质量分数影响最明显,连续刈割3年的土壤有效N质量分数较对照区降低18.62%,且达到显著水平,有效p,K质量分数也分别下降8.79%和1.93%.     

传感器网络数据流异常数据检测与修正

提出一种通用于传感器网络应用的数据流异常时空综合检测与修正的方法,将基于小波的时域滤噪方法与基于BP神经网络的空域数据融合相结合,并在此基础上提出了基于小波尺度的异常检测与修正方法,通过时间阈值确定数据融合所采用的时间窗口．利用小波变换的时分和频分特性,将异常检测与修正和异常数据持续时间相联系,通过多传感器数据融合的结果对传感器网络异常数据进行修正,从而剔除传感器网络中的异常数据。     

基于贝叶斯网络的钻井作业现场风险评估

针对高投入、高风险和不确定性的钻井作业现场,展开了安全评价研究。提出了一种基于贝叶斯网络定量评
价钻井作业现场风险、寻找风险源的方法。通过分析历史数据与借助专家经验识别不安全因素,将影响钻井作业现场
安全性的32 个因素分为“人的不安全行为”和“物的不安全状态”,同时构建了钻井作业现场安全性的贝叶斯网络拓
扑结构,并进行了概率推理向前预测和向后诊断,定量评估了钻井作业现场安全性,找出了影响最突出的不安全因素。
将其应用于龙岗气田L 井钻井作业现场,得出人为的不安全行为和物的不安全状态概率分别为0.108 和0.165,整个L
井作业现场不安全概率为0.137,并诊断出过程监控缺陷、安全防护设施缺失、作业导致隐患、井控设备缺陷、生产管
理缺陷不安全因素最突出,与现场实际情况一致。该评价方法为现场安全作业提供较为准确的诊断依据。     

陈家山井田煤系地层油气来源研究

从煤系地层的岩性特征入手,从煤岩成分、石油成分、含煤地层及石油的有关地球化学指标等几个方面,阐述了该井田煤系地层的石油来源于三叠系的产油层．并初步总结出煤系地层油气的分布规律．图4,表5,参6     

ELNF归约演算

ＥＬＮＦ演算是在ＬＮＦ演算的基础上扩充而成的函数／逻辑归约演算系统，扩充的主要工作包括逻辑变量、谓词名的引进。提出并描述了逻辑函子ＳＯＬＵＴＩＯＮ和ＰＲＯＶＥ及其归约规则．讨论了ＥＬＮＦ演算的基本概念。为表征ＨＯＲＮ子句提供了一种有效方式。     

时滞控制系统的 PID 参数自整定

针对工业过程中普遍存在的二阶时滞系统，利用开关阶跃响应法辨识被控过程的特征参数，然后用文中所给的整定公式可以非常简单地求出ＰＩＤ参数，经过大量仿真实验，证明了所得出的整定公式的正确性以及控制的鲁棒性