界量

Taking electrostatic field as an example problem, based on the general analytical series solution of electrostatic field,(1) the zero, first and second order asymptotic boundary conditions on circular truncation boundary; and (2) the zero and first order asymptotic boundary conditions on arbitrary polygonal truncation boundary are derived.

有限元法计算无界电磁场问题是电磁场数值分析中的一个重要课题，在这里计算精度与计算量之间的矛盾尤为突出。

We then introduce a conformal invariant quantity which is formulated in terms of the square of the length of the trace free part of the second fundamental form and the mean curvature, and prove that if this quantity is bounded above by that value of the Clifford torus then x is either a totally umbilical sphereor a conformal Clifford torus.

接著我们介绍一个由第二基本型式迹为零部份的张量长度平方与平均曲率形成的保角不变量，并证明此保角不变量的上界若为Clifford环面之值，则x不是全脐球面就是Clifford环面的保角类。

Limit the type of function is more extensive and complex, involving a bounded function, infinitely small amount, equivalent to infinitesimal, the continuity of function, and many other content.

函数极限的类型较为广泛、复杂，涉及到有界函数，无穷小量，等价无穷小，函数的连续性等多方面的内容。

In order to implement nonlinear predictive control for the controlled plant, a T-S fuzzy predictive model is built on-line by using fuzzy clustering and linear identification, and discrete optimization of the control action is carried out according to the principle of Branch and Bound method.

算法由两部分组成：第一部分采用模糊聚类和线性辨识方法在线建立系统的T-S模糊预测模型；第二部分基于分支定界法的基本原理对控制量进行离散寻优，从而实现对象的非线性预测控制。

The results indicate that the crystallinity of the samples can be improved with suitable doping concentration.

结果表明，适当的掺杂量可以改善CdTe薄膜的结晶性能，降低晶界势垒高度，提高其导电性能。

The effect of tribology factors on bearing vibration is studied experimentally. AR model and WPT are used to processing the normal arid abnormal signals. The results are as follows:1. The vibration of ball bearings is caused by the tribology action of contact pairs of ball and ring races and has the essential of tribo-dynamics. Any factors affecting the tribology characteristics of contact pairs will affect vibration and noise of bearings consequently.2. Vibration characteristics of bearing keep almostly unchanged with the increasing of axial load expecting the increasing of nature frequencies. When radial load increasing with axial load unchanged, nature frequencies keep unchanged but some new vibration peaks appears in the spectrum.3. Vibration amplitudes are damped and nature frequency are enhanced with sufficient lubrication. Vibration and noise of bearings increase obviously and roar can happen and the contact surfaces scratch slightly under insufficient and unclean lubrication state. Bearing will be disabled in a few minutes without any lubrication.4. Bearing vibration is unstable under low speed. With the speed increasing, the vibration become stable and natural frequencies increase slightly but the amplitudes increase apparently.5. Bearing vibration can be excited only by some harmonics ofwaviness without lubrication and by all harmonics with lubrication based on the theoretical analysis.6. The nature frequencies of ball bearings decrease with the increasing sizes. When international clearance increasing, nature frequencies decrease in radial and increase in axial and angular and the amplitudes increase in radial and decrease in axial and angular. When the number of balls increasing, nature frequencies increase and amplitudes decrease. When the pitch diameter increasing, axial nature frequency increase and others nearly keep no change. When outer race groove curvature radius increasing, nature frequencies increase in radial and decrease in axial and angular and amplitudes keep no change in radial and increase in axial and angular. When inner race groove curvature radius increasing, nature frequencies decrease and amplitudes increase.7. The distortion in amplitude and frequency components of bearing vibration signals picked up by the present probe measurement method is founded and right conclusions cannot be achieved by the signals. When accelerometer is rigidly screwed with steel stud onto a flat outer surface of a ball bearing, vibration signal can be got without distortion and the reliability of research on bearing vibration is assured.8. AR model is suitable for large samples of bearing vibration signals, square root of length of samples can be used as the upper limitation of order determination and the FPE order selection criterion is effective. Many advantages of AR spectrum are founded over the classical based on FFT.9. Time-Frequency analysis is necessary for abnormal noise of ball bearings. WPT overcomes the principle shortcomings of STFT and proved to be a best tool to process the abnormal signals.

理论分析和试验研究表明： 1球轴承振动是钢球—滚道接触副中的各种摩擦学作用引起的，具有摩擦动力学的本质，任何对接触副的摩擦学特性有影响的因素都将对球轴承的振动和噪声特性产生影响； 2中心轴向载荷作用下，载荷增大使球轴承的固有振动频率升高，载荷越大同样的载荷增幅引起的频率升幅减小，足够大的中心轴向载荷作用下载荷的变化对球轴承振动的频率特性不会产生明显的影响； 3轴向和径向联合载荷作用下，径向载荷不大时球轴承振动的固有频率基本不变，但是可能引起变刚度激励的非线性振动，出现新的频峰，过大的径向载荷将使部分钢球脱离接触，使球轴承的振动和噪声呈现不稳定状态； 4润滑对球轴承的振动和噪声特性有重要的影响，良好的润滑对振动有明显的抑制作用，润滑不充分时，振动和噪声的水平会有明显增高，一定条件下还会激发接触副中的谐振，发出啸声，造成接触表面的伤害，无润滑干接触时，短时的运转就会损伤接触副表面，使振动和噪声迅速增大，并随时可能引发严重的磨损和卡滞失效；接触副润滑良好时，油膜的"刚化效应"使球轴承振动的固有频率有所提高，润滑剂中含有弥散性污浊时，振动的幅度总体升高，但弥散性污浊不会改变球轴承振动的频率特性；浙江大学博士学位论文：球轴承振动的研究 5低速时，球轴承振动的基本特征呈现不稳定状态，随着转速的提高，球轴承振动的频率特性趋于稳定，固有频率频峰升高； 6理论分析表明，干接触时钢球和滚道表面波纹度的某些谐波分量能激励球轴承的振动，振动的幅值与谐波幅值成正比，实际球轴承中钢球的分布不可能完全均匀，波纹度的激励作用会随时发生；润滑接触的分析表明，波纹度的任意谐波分量均能激励球轴承的振动； 7球轴承的几何和结构参数分析表明，球轴承尺寸越大，径向、轴向和角振动的固有频率越低；钢球中心圆直径增大，球轴承的径向和轴向振动的固有频率基本不变，角振动的固有频率有所上升，振动的幅频特性基本不变；径向游隙加大使球轴承的径向振动固有频率降低，轴向和角振动的固有频率有所升高，径向振动幅频特性的幅值升高，而轴向和角向降低；钢球的数量增多使球轴承振动的固有频率上升，幅频特性的幅值下降，径向振动的幅值下降最为明显；外圈沟曲率半径系数增大使球轴承径向振动的固有频率升高，轴向和角振动的固有频率降低，径向幅频特性基本不变，轴向和角向幅频特性幅值升高；内圈沟曲率半径系数增大使径向、轴向和角振动固有频率均下降，振动幅频特性的幅值均有升高； 8试验对比表明，传感器采用探针式安装时，由于探针接触副接触特性的影响，钡(量得到的球轴承振动信号有失真，采用专门设计和制作的试验球轴承，以固定式安装加速度计，首次测量得到了球轴承振动的真实信号，通过对振动信号的分析，验证了球轴承振动的理论模型； 9)基于时间序列分析的AR模型适用于大样本球轴承振动信号的分析，以样本长度的均方根值作定阶上界，FPE做判阶准则，给出的AR谱光滑，频率分辨率高，是球轴承振动分析的简便而可靠的手段； 10以时频域分析的小波包变换分析球轴承异音信号能够比较好地定位和聚焦异音发生的时间，时间间隔，频率范围，同样是球轴承振动分析的可靠的手段，可用作球轴承故障诊断技术。

Difference set is one kind of unbounded difference poset. The existenceof the tensor products of two cancellative difference sets are investigated. It isproved that the tensor product of a Boolean algebra and a cancellative differenceset always exists.

作为差分偏序集无界推广的差分集，我们研究了它的张量积问题，证明了任何消去差分集和布尔代数的张量积一定存在。

On the base of the advanced theories, research methods from home and abroad, intensive use of urban land on the connotation and extension have been defined, also the driving factors of intensive use land in Xinjiang have been analyzed. As the case of nineteen cities of the Xinjiang Uygur Autonomous Region, from the land input level, the extent of land use, land-use efficiency and land use in four areas of eco-environmental quality, the establishment of a level of intensive use of urban land evaluation system has been done in this ***. Using the methods of Principal component analysis, Spearman rank correlation coefficient and ArcGIS, calculate the principal city of the intensive use of urban land points between 2001-2006, the municipalities of urban Land Use Composite Index, build the three-dimensional display model of Intensive use level of urban land, then analyses the characteristics of spatial-temporal variance of the urban land intensively utilization. Finally, analysis propose measures and advices.

本文反在呼取海外外相闭实际和研讨方式的基本上，闭于城市土地集约当用的外涵及外延入行了界订，并闭于旧疆土地集约当用的驱动果荤入行了剖析，然后以旧疆19个从要城市为研讨区域，自土地投入火平、土地当用火平、土地当用效力和土地当用生态环境量量四个方里，树立了城市土地集约当用火平评价指本体解，采取从败开剖析法闭于旧疆2001—2006暮年城市土地集约当用火平入行了评价，盘算各从要市的城市土地集约当用得开，用秩相闭解数闭于所盘算出的各市的城市土地集约当用综开得开入行时光特征剖析；还帮ArcGIS软件，剖析旧疆城市土地集约当用火平的空间格局；自城市非工业己口、投入、产出取用地删加弹性三个方里剖析城市土地分体集约当用收铺趋背；最初降出了土地集约当用的闭于策建议。

Estimating the lower and upper bounds of the eigenvalue in terms of geo-metric and topological quantities of manifold is a very important research topic.

通过流形的几何量与拓扑量来估计其特征值的上、下界是一个十分重要的研究课题。

The results showed that soil wind erosion was the near-surface wind-sand activity. The sediment particle saltates mainly in 7.5-43.5 cm. Wind sediment amount decreased along height, which correlate well with power function, exponent function and logarithm function. The sediment particle composition was influenced strongly by wind erosion intensity and topsoil characteristics. However, the regularity of sediment composition was distinct in a definite paticle size in different heights. Wind erosion amount increases with wind speed exponentially, which was influenced by times that the wind does.

结果表明：阴山北麓农牧交错带土壤风蚀是一种近地表的风沙运动，风蚀物跃移颗粒体主要集中在7.5～43.5 cm高度，风蚀物含量沿高度呈一递减函数，对幂函数、指数函数和对数函数均具有较好的相关性；风蚀物颗粒组成与风蚀强度和地表状况关系密切；风蚀物颗粒组成以某一粒径范围、某一高度为界随高度的变化而表现出明显的规律性；风蚀量沿高度的变化与风力作用时间有关，风蚀量随风速的增大呈指数增加。

Singer Leona Lewis and former Led Zeppelin guitarist Jimmy Page emerged as the bus transformed into a grass-covered carnival float, and the pair combined for a rendition of "Whole Lotta Love".

歌手leona刘易斯和前率领的飞艇的吉他手吉米页出现巴士转化为基层所涵盖的嘉年华花车，和一双合并为一移交&整个lotta爱&。

This is Kate, and that's Erin.

这是凯特，那个是爱朗。