无角化

Part II, the artificial boundary condition and its numerical methods based on natural boundary reduction for a hyperbolic initial boundary value problem in an infinite domain with a concave angle is investigated.

第二部分，研究一类具有凹角的无界外区域的双曲型初边值问题基于自然边界归化的人工边界条件及其数值方法。

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。

Finally, the boundary feedback control of the undamped Euler-Bernoulli beamwith both ends free is concerned.

最后，对两端自由的变系数无阻尼Euler-Bernoulli梁采用旋转角、角速度和位移、速度的线性边界反馈指数稳定化问题进行了讨论。

Symmetrical six-horn nickel diselenide nanostars were firstly synthesized with selenium powder as precursor but without any external reducing agents. Each nanostar consisted of a central core and six symmetrical nanohorns.

以硒粉为硒源，在无外加还原剂的条件下首次合成了六角星状二硒化镍纳米晶，每个纳米星具有一个中心核和六个对称纳米角。

Stems angular, glabrous. Radical leaves: stipules brown, membranous, abaxially glabrous; petiole glabrous; leaf blade with 7–9 pairs of leaflets; leaflets petiolulate, green on both surfaces, fasciated or fasciated lanceolate, 5–7 × 1.5–1.7 cm, both surfaces glabrous, base subcordate to obliquely truncate or rounded, margin acutely incised serrate, apex rounded to acute; cauline leaves: stipules green, falcate, herbaceous, margin incised serrate; leaf blade resembling that of radical leaves but leaflets fewer and narrower higher up stem.

茎具角，无毛；胚根叶：托叶使成褐色，膜，背面无毛；叶柄无毛；叶片具7-9对小叶；具小叶柄的小叶，绿色在两面，扁化或者扁化， 5-7 * 1.5-1.7 厘米，两面无毛，基部近心形在斜截形或圆形，边缘尖锐锐裂状锯齿，先端圆形的到锐尖；茎生叶托叶绿色，镰刀形，草本，给锐裂状锯齿镶边；叶片象胚根叶的那但是高的更少和狭窄的小叶向上茎。

Results The hEFs were successfully isolated and cultivated from gonadal ridges and dorsal mesenteries of human embryos. They could be passaged beyond the 25th generation. The biologic characteristics of the cells did not change, even in high-passage cells or frozen-thawed cells. The cells expressed prolyl 4-hydroxylase β, but not cytokeratin-4, which was similar to the fibroblasts. The cultured cells expressed bFGF and LIF.

结果：从人胚胎生殖腺嵴和肠背系膜中成功地分离培养出hEFs，该细胞可传25代以上，且经过传代及冻存复苏后生物学特性无改变；hEFs表达脯氨酰4-羟化酶β亚单位，不表达细胞角蛋白4，确定其为成纤维细胞；该成纤维细胞表达bFGF和LIF。

This report presents a case of fully edentulism with severe resorbed ridge and lack of keratinized mucosa over mandibular left alveolar ridge area.

本病例报告为一全口无牙的患者，下颚左侧齿槽嵴严重吸收且缺乏角化黏膜。

Resut: the results of 21 cases of stomach malignant stromal tumors immunohistochemical were positive.the great mass of ck and ema were negative.among the 21 cases,3 patients of extensive metastasis were dead after operation,2 patients were given polypectomy,but they recured after operation 8 months and 9 months.one of them was operated again and lived 1 year,16 patients were disease-free survival 3 to 6 years.

结果：21例免疫组化结果示cd34均为阳性，而上皮指标细胞角蛋白和膜上皮抗体大部分阴性；其中3例广泛转移者于术后4～6月死亡，姑息性切除2例，术后8月及9月均复发，其中1例再次手术，存活1年，其余16例均无瘤生存，生存期为3至6年。

I didn't watch TV last night, because it .

昨晚我没有看电视，因为电视机坏了。

Since this year, in a lot of villages of Beijing, TV of elevator liquid crystal was removed.

今年以来，在北京的很多小区里，电梯液晶电视被撤了下来。