哈里伯顿声幅变密度测井仪的维修与改进

通过分析哈里伯顿声幅变密度测井仪的电路原理、声系结构以及仪器整体联接存在的问题 ,找出下井仪器不能正常工作的原因 ,提出了相应的改进方法。

声速测井中盲区问题的若干讨论

声速测井作为最重要的常规测井项目之一,在剖面岩性定性识别、孔隙度定量计算、岩石力学参数计算及流体性质判别,尤其是含气层定性识别等方面具有独到优势,一度成为各大油田测井的必测项目之一。双发双收声系因为具有井眼补偿功能而成为当前国内外声波测井仪器的主流声系结构,但经过理论推导与实践证明,该声系结构在软地层测量应用中有可能存在盲区,扩大时差测量误差。双发四收声系随之产生,在一定程度上消除了盲区的影响。为深入探讨盲区厚度的受控因素,本文首先推导了双发双收声系结构在软地层中盲区厚度的计算公式,证明了盲区厚度与接收器间距和探测地层第一临界角大小有关。在此基础上,构想了一种兼具井眼补偿与盲区消除功能的双发三收声系结构,弥补了传统双发双收声系在软地层测井应用中的不足。在保证纵向分辨率相同的前提下,从盲区产生难易程度和最短仪器长度两方面对双发双收、双发三收和双发四收三种声系结构进行了比较分析,最终认为双发三收声系结构综合优势突出,具有一定的实际应用价值。

The similitude research on underwater complex shell-structure based on SEA

In this paper, the vibration arid sound radiation of the underwater complexshell-structure which is the cylindrical shell with hemi-spherical shell on the ends are studied bystatistical energy analysis (SEA). The whole shell-structure is divided into the four subsystems,and the SEA physical model and power flow balance equations among these subsystems are established.The similitude relations of input power, coupling loss factor and modal density of the subsystemsbetween the complex shell-structure and its scaled-down model are analyzed. According to thesimilitude theory and power flow balance equations, when the immerged shell-structures are excited,the similar relations of spatially averaged vibration response and underwater radiating sound powerare established for the complex shell-structure and its scaled-down model.

CYLINDER-SPHERE 3-DOF ULTRASONIC MOTOR AND ITS CONTROL

A three degree-of-freedom (DOF) ultrasonic motor (USM) with a cylinder-shaped stator and a spherical rotor is introduced, which uses one first order longitudinal and two second order bending nature vibration modes of the cylinder. Control strategies for the two DOF trajectory following are studied and applied to the prototype USM. Vibration amplitude control is employed for speed regulation. The first trajectory following strategy is a step-by-step interpolation. The second strategy is vector decomposition control. Three pulse width modulation (PWM) methods for the exciting voltage regulation are investigated. These methods are compared and verified by several experiments. The key is to keep the phase differences of the three vibration constants and small exciting voltage distortion while the exciting voltages are changed for simplifing the control process and obtaining good control performance. The vector control method has advantages of small trajectory following error, smooth moving and low noise.

Improved ultrasonic differentiation model for structural coal types based on neural network

In order to solve the difficulty of detailed recognition of subdivisions of structural coal types,a differentiation model that combines BP neural network with an ultrasonic reflection method is proposed.Structural coal types are recognized based on a suitable consideration of ultrasonic speed,an ultrasonic attenuation coefficient,characteristics of ultrasonic transmission and other parameters relating to structural coal types.We have focused on a computational model of ultrasonic speed,attenuation coefficient in coal and differentiation algorithm of structural coal types based on a BP neural network.Experiments demonstrate that the model can distinguish structural coal types effectively.It is important for the improved ultrasonic differentiation model to predict coal and gas outbursts.

Structural-acoustic coupling characteristics of honeycomb sandwich plate based on parameter sensitivity analysis

The structural-acoustic coupling model for isotropic thin elastic plate was extended to honeycomb sandwich plate(HSP) by applying Green function method.Then an equivalent circuit model of the weakly-strongly coupled system was proposed.Based on that,the estimation formulae of the coupled eigenfrequency were derived.The accuracy of the theoretical predictions was checked against experimental data,with good agreement achieved.Finally,the effects of HSP design parameters on the system coupling degree,the acoustic cavity eigenfrequency,and sound pressure response were analyzed.The results show that mechanical and acoustical characteristics of HSP can be improved by increasing the thickness of face sheet and reducing the mass density of material.

Hilbert-Huang transform based noise filtering for the identification of structural systems

This paper proposes an enhanced noise filtering technique to the Hilbert-Huang transformation technology for the identification of structural systems using vibration measurements. The Hilbert-Huang transformation technology is a set of superior algorithms non-stationary signals and also for analyzing non-linear and offers increased accuracy for linear and stationary signals. However, the signals are filtered by reconstruction from ＂＇selected＂ intrinsic mode functions （IMFs）, derived from the original signal through the empirical mode decomposition method. The proposed filtering technique offers the criterion for selecting the IMFs using the orthogonalization coefficient. In addition, a simple free vibration modal analysis has been resolved for the evaluation of the modal damping ratio. Through the enhanced filtering, it is possible to increase the accuracy for the estimation of the time-varying system＇s natural frequency and the damping ratio, indicative of the degree of damage, which helps an effective design of a control system.

Echo-state-network classification based multi-services awareness in high-speed optical passive networks

With the challenge of great growing of services diversity,service-oriented supporting ability is required by current high-speed passive optical network( PON). Aimed at enhancing the quality of service( Qo S) brought by diversified-services,this study proposes an echo state network( ESN)based multi-service awareness mechanism in 10-Gigabite ethernet passive optical network( 10GEPON). In the proposed approach,distributed architecture is adopted to realize this ESN based multi-service awareness. According to the network architecture of 10G-EPON,where a main ESN is running in OLT and a number of ESN agents works in ONUs. The main-ESN plays the main function of service-awareness from the total view of various kinds of services in 10G-EPON system,by full ESN training. Then,the reservoir information of well-trained ESN in OLT will be broadcasted to all ONUs and those ESN agents working in ONUs are allowed to conduct independent service-awareness function. Thus,resources allocation and transport policy are both determined only in ONUs. Simulation results show that the proposed mechanism is able to better support the ability of multiple services.

An FBG acoustic emission source locating system based on PHAT and GA

Using the acoustic emission locating technology to monitor the health of the structure is important for ensuring the continuous and healthy operation of the complex engineering structures and large mechanical equipment. In this paper, four fiber Bragg grating(FBG) sensors are used to establish the sensor array to locate the acoustic emission source. Firstly, the nonlinear locating equations are established based on the principle of acoustic emission, and the solution of these equations is transformed into an optimization problem. Secondly, time difference extraction algorithm based on the phase transform(PHAT) weighted generalized cross correlation provides the necessary conditions for the accurate localization. Finally, the genetic algorithm(GA) is used to solve the optimization model. In this paper, twenty points are tested in the marble plate surface, and the results show that the absolute locating error is within the range of 10 mm, which proves the accuracy of this locating method.