Modeling Ultrasonic Pulse-Echo Signals from a Flat-Bottom Hole in Immersion Testing Using a Multi-Gaussian Beam

This paper proposes an ultrasonic measurement model that can predict the pulse-echo signals from a flat-bottom hole in an isotropic, homogeneous solid specimen immersed in water in a computationally efficient manner. To develop such a model, a measurement model approach is adopted based on two important assumptions: the paraxial approximation for the transducer beam and the small flaw assumption for the flat-bottom hole. The modular model that results from these two assumptions contains three terms: a diffraction correction term, a far-field scattering amplitude term and a system efficiency factor term. The diffraction correction is defined based on a multi-Gaussian beam model which allows the rapid evaluation of the wave field incident on the hole. The far-field scattering amplitude of the flat-bottom hole is obtained using the Kirchhoff approximation together with the small flaw assumption. The system efficiency factor is determined by deconvolution of an experimental front surface reflection signal by a reference reflector model. Here, the contribution of each of these three terms to the overall measurement model are described in detail and the accuracy of the proposed model is verified by the comparison of the model-based predictions to experiments.     

Dynamics of a Dual Power-split Transmission Based on Loaded Tooth Contact Analysis

In order to implement the dynamic characteristic of a dual power-split transmission,a dynamic mechanics model is built. Firstly,according to the method of theoretical analysis of the tooth contact analysis ( TCA) and loaded tooth contact analysis ( LTCA) ,the actual meshing process of each gear pairs is simulated, and the time-varying mesh stiffness excitations are obtained,which can improve the numerical precision. Secondly,by using the lumped mass method,the bending-torsional coupling three dimensional dynamic model of the dual power-split transmission is established,and the identical dimensionless equations are deduced by eliminating the effect of rigid displacement and the method of dimensional normalization. Finally,by the method of the fourth order Runge-Kutta algorithm with variable step lengths,the responses of this system in a frequency domain and time domain are obtained,and the dynamic load change characteristics of each gear pairs are analyzed. The results show that the establishment,solution and analysis of the system dynamics model could provide a basis for the dynamic design,and have an important significance for the dynamic efficiency analysis and dynamic performance optimization design of the dual power-split transmission.     

双向晶闸管调光电路

宾馆及民居内的灯光 ,根据不同的需求 ,可以选择不同的调光电路。文章力图将花样繁多的调光电路分类 ,并介绍各类调光电路的用途及优缺点。     

First-Principles Prediction of Superconductivity in Hole Doping of MgCN2

Journal of Superconductivity and Novel Magnetism - Hydrogen-based, boron-based, and carbon-based compounds have been the focus of previous investigations in the process of searching for...     

微孔光纤测头的研制及应用

基于微孔测量中测头不能做得足够小的技术难题,文中提出采用标准多模通信光纤,按特定的工艺技术方法烧熔光纤测球,再进行封装制成测头,应用在微孔测量中。通过对研制成的6φ．1mm光纤测头几何形貌进行实际测量,并应用于φ0．6mm左右小孔孔径的测量分析,标准偏差不超过0．5μm,取得了很好的应用效果。     

Time Domain Analysis of Optical Fiber Probe Signals Measured in a Short Circulating Fluidized Bed Riser

A time domain analysis of electrical signals provided by an optical fiber probe was conducted in order to characterize the local flow dynamics of a short circulating fluidized bed riser with a height of 2.42 m and ID of 82 mm. Experiments were carried out with air, and the bed materials were FCC particles (Geldart A). Probability and standard deviation distribution of signals measured locally at five radial positions and four axial positions are presented. The probability distribution can indicate the uniformity of the flow in terms of solids holdup distribution and can reveal the formation of clusters. Probability distributions indicate that the flux is more uniform in the core region of the reactor and that clusters appear near the wall. The highest value obtained in the standard deviation of the radial distribution suggests greater interaction between particles at that radial position. It was found that for the two lower axial positions, this phenomenon occurs near the wall, and for the two higher positions, the interactions between particles occur both near the wall and in the center due to the exit configuration of the reactor.     

浅谈逐孔起爆技术时间间隔的选取

叙述了逐孔起爆技术机理和优越性,对选取微差间隔时间影响因素进行了分析,推荐了间隔时间的理论计算和经验选取的方法以及国内部分应用单位的实际数据,并对雷管延期精度和窜段问题的原因给予了解析,提出了解决办法的建议.     

微孔光纤测头的研制及应用

基于微孔测量中测头不能做得足够小的技术难题,文中提出采用标准多模通信光纤,按特定的工艺技术方法烧熔光纤测球,再进行封装制成测头,应用在微孔测量中.重点介绍了这种测头的技术参数和成形方法、原理,并对研制的φ0.1 mm光纤测头几何形貌进行实际测量,应用于φ0.6 mm小孔孔径的测量分析,标准偏差不超过0.5μm,取得了很好应用效果.     

混凝土中瞬时爆炸波测试技术及分离的实验研究

为稳定测量混凝土中炮孔周围的爆炸波,对应变片和超动态应变测试系统的频响及最优匹配开展了系统研究,得到了应变片相对误差δ与其允许最高频率fmax之间的关系,测试系统的阶跃信号响应上升时间为0.3μs。基于一维应力波原理,提出了用SHPB技术中透射杆上的应力动态标定试件上输出电压的新方法,得到了爆炸冲击波作用下测试系统的频响和时频分布。针对爆炸波微信号传输中的易受干扰问题,采用了电磁屏蔽等抗干扰技术。用该系统对混凝土模型开展了不耦合装药爆炸波测试,成功测得了23μs内在爆炸近中区激起的爆炸波。通过Rihaczek分布,将爆炸波分离为[(2.3～4.5μs),(0～829 kHz)]的爆炸冲击波区、[(4.5～7.2μs),(0～743 kHz)]的应力波区及[(7.2～24.7μs),(0～514 kHz)]的爆生气体膨胀作用区,并就分离各区作用过程做了分析。     

高精度双测头量块比较仪的研究

研制了一种新型高精度量块比较仪,该比较仪采用上、下双电感测头进行测量.给出了比较仪的总体结构,系统采用数字滤波算法对电感测微仪的随机误差进行处理,在±20μm测量量程内,对比较仪进行了精确标定,编制了测量控制软件.并对该量块比较仪进行了重复性和示值误差测试.实验结果表明其示值误差δ≤±(0.02+0.002L)μm.     

逐孔起爆技术在黄山石灰石矿山中的应用

逐孔起爆技术是近几年发展起来的一种新型起爆技术,一些大型露天矿山已陆续试用.在介绍逐孔起爆技术的基本原理的基础上,介绍了逐孔起爆技术在黄山石灰石矿的设计方法以及在该矿山生产爆破中取得的良好效果.     

纳米粒子晶格畸变率的数量级研究

晶格畸变率是纳米粒子的一个重要参数。用X射线衍射积分宽度法确定了纳米CeO2粒子的晶格畸变率,研究了晶格畸变与晶粒度之间的关系,结合已有资料讨论了纳米粒子晶格畸变率的数量级大小。结果表明,不合理的计算方法可能导致计算出来的晶格畸变值严重失实。     

基于振动噪声信号的齿轮传动系统声压级预测

文中提出一种新的齿轮箱噪声预测方法,它与传统的仅用声压计测量方法不同：该方法采用多个加速度和噪声传感器对齿轮箱进行监测并获取振动和噪声信号;先通过成熟的“以振代噪”技术,计算振动信号的噪声评估向量;然后根据组合预测方法,采用应用线性神经网络算法预测出齿轮箱的声压级,并且通过实验验证其准确性有效性。     

Dipping Process Characteristics Based on Image Processing of Pictures Captured by High-speed Cameras

Nano-Micro Letters - The dipping process was recorded firstly by high-speed camera system; acceleration time, speed, and dipping time were set by the control system of dipping bed, respectively. By...     

露天矿逐孔爆破技术的应用及效果

文章介绍了逐孔起爆技术在部分矿山实际应用的炮孔布置网络和爆破技术效果分析,提出今后需积极探索高精度导爆管雷管孔间延时与孔间应力波幅值叠加原理更好的统一与规范,以推动爆破技术的进步。     

微纳米三坐标测量机接触扫描探头稳定性分析(英文)

对微纳米三坐标测量机(CMM)高精度扫描探头的稳定性进行了分析.该扫描探头由带有球头的光纤探针、悬浮机构、二维角度传感器和微型迈克尔逊干涉仪4部分组成.光纤探针和悬浮片固定在一起,当光纤探针的球头受到触碰时,会带动悬浮机构的悬线发生形变,进而导致贴在悬浮片上的平面反射镜倾斜或在竖直方向上发生位移,前者由二维角度传感器进行感测,后者由微型迈克尔逊干涉仪进行感测.实验结果表明,环境温度的变化是影响探头稳定性的主要因素,探头中机械结构和部件对温度变化的敏感性要远远大于探头中光电器件对温度变化的敏感性.只要将探头放到一个恒温箱中,待恒温箱温度稳定4 h再开始测量,探头即可达到1 nm的分辨力和30nm的测量标准差.     

通孔式金属壳延期电雷管产品研制

通过装填一种通孔式金属壳基础雷管,对其设计原理进行了详细的阐述。与普通结构电雷管进行性能对比,结果表明,在带有通孔后,电雷管延期精度得到提高,点火性能可靠,不干胶密封防水性能有效,产品性能达到国家标准要求。     

Generation of Phase-Modulated Periodic Optical Signals by use of a Polarization Interferometer

Polarization phase-shifting interferometry is an established technique in optical metrology. In the present study it is shown that, by use of this technique, not only is it possible to realize any discrete magnitude of a predetermined phase difference (from 0 to 2pi) between two light beams but also phase-modulated periodic optical signals can be generated simply by rotation of a polarizer or a retarder or both placed at the input of a conventional two-beam interferometer. Some representative linear and nonlinear periodic polarization-induced phase-modulated optical signals are shown. A linear phase modulation of 0-2pi with constant output intensity is obtained in some cases. The Poincaré sphere representation is introduced as a convenient tool for visualizing the dynamics involved in the generation of polarization-phase-modulated waveforms and as a possible aid to intelligent modification of the generated waveform as required. This all-optical technique of continuous and periodic phase variation should prove useful for introducing phase modulation without the need for electro-optic devices.     

Contact Angle and Contact Mechanics of a Glass/Epoxy Interface

An attempt was made to extract the thermodynamic work of adhesion from contact angle measurements and contact mechanics in order to compare it with interfacial toughness values of a glass/epoxy interface. The three probe liquid method, in conjunction with laser goniometry, yielded a value of the work of adhesion of 93 mJ/m². This was an order of magnitude less than the value extracted from the Maugis solution for contacting spheres with surface interactions. These work of adhesion values were both lower than the 1.5 J/m² which was determined in a parallel study of interfacial fracture as a mode-mix independent component of the overall interfacial toughness. Some of the reasons for these differences are explored. This revised version was published online in August 2006 with corrections to the Cover Date.