基于模糊控制的齿轮传动系统振动主动控制与仿真

基于集中质量法建立了由一对渐开线直齿圆柱齿轮组成的传动系统3自由度数学模型.采用一种主动控制结构,使主动控制力以更直接的方式来控制齿轮啮合点由于传动误差而引起的振动.通过压电堆作动器输出的位移控制齿轮轴的弯曲振动,以抑制齿轮传动误差,进而达到控制齿轮传动系统振动噪声的目的.在Matlab/Simulink环境中设计模糊...     

四维空间相交定理的几何证明

为解决研究四维空间几何元素相交时思维图象的困难，对四维空间中的相交定理用几何的方法进行了证明，并配以直观图。     

二阶线性中立型微分差分方程非振动解的类型与判别

本文讨论了二阶线性中立型微分差分方程d~2/dt~2[x(t)-cx(t-τ)]+px(t-σ)=0的非振动解的所有类型及其判别。     

Melt Quality Evaluation of Ductile Iron by Pattern Recognition of Thermal Analysis Cooling Curves

The melt quality of ductile iron can be related to the melt's thermal analysis cooling curve. The freezing zone of the thermal analysis cooling curve was found to indicate the melt quality of the ductile iron. A comprehensive difference parameter, Ω, of the thermal analysis cooling curves was found to be related to the properties of ductile iron melts such as composition, temperature, and graphite morphology. As Ω ap- proached O, the thermal analysis cooling curves were found to come together with all the properties indicat- ing melt quality about the same. A database of thermal analysis cooling curves related to the properties of the ductile iron melts was set up as a basis for a method to accurately evaluate the melt quality of ductile iron by pattern recognition of thermal analysis cooling curves. The quality of a ductile iron melt can then be immediately determined by comparing its thermal analysis cooling curve freezing zone shape to those in the database.     

Apolipoprotein E controls cerebrovascular integrity via cyclophilin A

Human apolipoprotein E has three isoforms: APOE2, APOE3 and APOE4. APOE4 is a major genetic risk factor for Alzheimer's disease and is associated with Down's syndrome dementia and poor neurological outcome after traumatic brain injury and haemorrhage. Neurovascular dysfunction is present in normal APOE4 carriers and individuals with APOE4-associated disorders. In mice, lack of Apoe leads to blood-brain barrier (BBB) breakdown, whereas APOE4 increases BBB susceptibility to injury. How APOE genotype affects brain microcirculation remains elusive. Using different APOE transgenic mice, including mice with ablation and/or inhibition of cyclophilin A (CypA), here we show that expression of APOE4 and lack of murine Apoe, but not APOE2 and APOE3, leads to BBB breakdown by activating a proinflammatory CypA-nuclear factor-κB-matrix-metalloproteinase-9 pathway in pericytes. This, in turn, leads to neuronal uptake of multiple blood-derived neurotoxic proteins, and microvascular and cerebral blood flow reductions. We show that the vascular defects in Apoe-deficient and APOE4-expressing mice precede neuronal dysfunction and can initiate neurodegenerative changes. Astrocyte-secreted APOE3, but not APOE4, suppressed the CypA-nuclear factor-κB-matrix-metalloproteinase-9 pathway in pericytes through a lipoprotein receptor. Our data suggest that CypA is a key target for treating APOE4-mediated neurovascular injury and the resulting neuronal dysfunction and degeneration.     

特殊索赔下离散时间延迟更新过程的期望贴现罚金函数

离散时间更新风险过程下所获得的结果一般都具有递归的属性而易于程序化,因此不但具有独立的研究意义,还可以作为连续时间更新过程相关结果的近似和上下界估计.研究具有一般索赔间隔时间的离散时间延迟更新过程,在索赔额服从几何分布时,利用Lundberg基本方程的根及期望贴现罚金函数所满足的更新方程,获得了期望贴现罚金函数的显示表达.     

支持追责和用户撤销的属性基加密方案

针对当前属性基加密系统中用户与中心滥用密钥以及用户解密权限的撤销问题, 提出一种支持追责和用户撤销的属性基加密方案. 该方案使用“不动点”作为密钥拥有者的标识符, 实现了对恶意用户的身份追踪; 通过用户与中心交互生成解密密钥, 解决了半信任中心滥用密钥的问题; 利用完全子集方案和自更新加密方案实现了用户的即时撤销, 并达到了前向/后向安全性; 同时使用Paillier加密体制, 避免了追踪过程中的存储代价. 该方案无需在系统建立阶段预先确定属性个数, 且在标准模型下被证明是选择明文安全的.     

回采面上隅角埋管抽放采空区瓦斯数值模拟

针对中小型高瓦斯矿井的实际情况,采用数值模拟确定提高瓦斯抽放效率的方案.按照渗流力学的方法将采空区视为连续的渗流空间,采用GAMB IT建立采空区计算几何模型.确定了冒落带的孔隙率和黏性系数.采用FLUENT软件对采空区瓦斯涌出量及埋管抽放瓦斯进行数值模拟,得到了采空区沿工作面走向、倾向和竖向3个不同方向上瓦斯浓度的分布规律,以及埋管抽放采空区瓦斯的最佳参数.模拟结果表明,在抽放管路压力为-100Pa时,抽放管路内和上隅角瓦斯浓度随着抽放位置的变化呈现规律性.当抽放位置距底板垂高2m、沿倾斜方向距回风巷道1m、沿走向深入采空区4m时,瓦斯抽放效果最佳,上隅角瓦斯浓度降至1.1%.上隅角区域采取封堵措施后,上隅角瓦斯浓度降至0.7%.     

含钛高强钢中夹杂物析出行为研究

以不同钛含量(0.032%~0.153%)的高强钢为研究对象,利用SEM、EDS等对钢中氧化物及氮化物夹杂的形貌、组成、数量及尺寸分布进行表征,结合热力学与动力学计算,对TiN的析出行为进行分析。结果表明,当钢中Ti含量较低(0.032%)时,冶炼过程会形成富含MgAl_2O_4的多边形高熔点固态夹杂,易造成水口堵塞;当Ti含量大于0.106%时,钢中形成了富含TiAl_2O_5的液态球形夹杂,可通过上浮去除,不易堵塞水口;Ca处理能将低钛钢中的夹杂改性为低熔点的铝酸钙,不仅降低了水口堵塞风险,还能还原夹杂物中的Ti,提高Ti的收得率。含钛高强钢中夹杂物平均尺寸为1~2μm,氮化物平均尺寸为1~3μm,其均随着Ti含量的增加而稍有增加。当Ti含量小于0.04%时,将钢中N含量控制在0.0018%以下,能有效减小TiN的析出尺寸;当Ti含量大于0.1%时,实际工业生产中很难阻止TiN的液析,但可通过提高钢中细小氧化物的数量,来细化TiN的尺寸。     

国营林场总收入GM（1,1）及预测分析

运用GM(1,1)模型及灰色系统预测技术,对福建省国营卫闽林场未来若干年内总收入进行动态预测,并对结果予以分析与讨论。