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多极子声波测井是新一代声波测井技术,偶极子发射换能器制作技术是其关键技术。本文报道了对自行研发的偶极子声波测井换能器的一致性、耐温、指向性等进行的测试分析结果。本文对三个压电弯曲振子的实验测量结果表明,将偶极子声波测井换能器置于硅油中测量的谐振频率要比在空气中测量的谐振频率降低约20%:在室温到150℃范围内,换能器的谐振频率随着温度的升高略有降低;在偶极子声波测井发射换能器的指向性测量曲线中,换能器辐射声波能量最强方向的声压值与其最弱方向的声压值的比值超过12dB;初步现场测量结果说明.本文研制的偶极子声波测井发射换能器能够测得满意的偶极子声波测井波形。 相似文献
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XMAC-Ⅱ是美国阿特拉斯公司新一代交叉偶极子阵列声波测井仪,它可以同时进行偶极子和单极子的测量,提供了测量地层纵波、横波和斯通利波的最好方法,在分析地层各向异性方面也具有独特优势。XMACⅡ对采集到的波形进行全部数字化处理,由于采用了先进的工艺和技术,使该仪器的采集准确性大大提高。在测井过程中可根据实际需要,采集不同的测井数据,这些数据主要包括:声波时差△T,单极全波列,偶极全波列等测井信息。为了使采集到的数据更加准确,必须根据实际情况设置适当的参数,并判断采集到的信息是否正确。本文主要介NXMAC-Ⅱ测井原理及针对不同的参数设置对测井影响方面进行探讨。 相似文献
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近年来远探测测井技术发展迅速,探测范围扩展到几十米,填补了常规声波测井和井间地震之间的探测空白。本文首先介绍了当前油气田对远探测技术的极大需求和广阔的应用前景。然后根据远探测技术的发展过程,介绍电法远探测、单极纵波声波远探测和偶极横波声波远探测技术的原理和各自的使用范围。 相似文献
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交叉偶极阵列声波测井仪是目前主流的先进声波测井设备之一,但在测井过程中难免存在噪声干扰,对测井质量造成不利影响。在利用Matlab对大量实测信号进行时频分析的基础上,针对噪声的规律和特点,提出时域滤波和频域滤波相结合的方案。时域上采取限幅平均滤波法,频域上选择具有线性相位的FIR滤波器。利用Matlab滤波器设计与分析工具箱获取滤波器系数,借助DSP软件开发环境CCS,用汇编语言设计了基于DSP的井下实时FIR数字滤波器。现场测井试验表明,该滤波器对测井信号中存在的噪声具有良好的抑制作用,同时满足测井系统的实时性要求。 相似文献
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偶极声源的指向性是影响声源识别结果的关键因素。目前,偶极声源的识别方法通常是基于声源的指向性信息先验假设,然而在实际偶极声源识别中,很难事先获得声源的指向性信息;此外,声源分布在二维平面上的假设通常不适用于实际的气动系统。为了准确识别指向性信息未知的偶极声源,并获得声源的三维成像结果,提出了一种基于加权迭代L1最小化算法的等效源方法。该方法将声源指向矢量作为未知参数,从测量声压与等效源源强的传递函数中分离出来,并通过加权迭代L1最小化算法将声源指向矢量与等效源源强一起求解出来,进而利用这些求解获得的声源信息进一步预测声场。与以往的偶极声源识别方法不同,该方法可以实现指向性信息未知偶极声源的三维成像。指向性信息未知偶极声源的三组仿真案例和自制类偶极声源的实验研究验证了该方法的有效性和鲁棒性。 相似文献
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本文在电偶极子近似下,对电偶极子的辐射场公式进行了推导,在此基础上,建立了电偶极子近场耦合模型,并借助半波偶极子,对阵面中常见的两种构型,并头和并肩结构的近场耦合效应进行了分析。分析表明,由于偶极辐射的方向性,半波天线的边射性质,并头构型下的近场耦台效应要比并肩构型小近两个数量级。 相似文献
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Stress analysis for a strip of which widths are different at the right and left handsides is carried out for before and after occurrence of a crack at a corner of a step. The strip is analyzed as a thin plate bending problem subject to transverse bending and torsion, and as a plane eleastic problem subject to bending in the plane and uniaxial tension. The rational mapping function of a sum of fractional expressions and complex variable method are used. Stress distribution and stress intensity factors are obtained. 相似文献
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V. L. Sennitskii 《Technical Physics Letters》2005,31(10):856-858
An exact solution is obtained for the problem of interaction between the ideal liquid homogeneously moving at infinity and
streamlining a round cylinder touching a solid wall. 相似文献
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An analytical expression is derived which describes the variation of the thermistor temperature during a relay-effect transient process following an instantaneous change in the supply voltage in an R — RT two-pole network.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 38, No. 3, pp. 465–472, March, 1980. 相似文献
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Methods for imaging a single point source to a line image are discussed, and a design study of single spherical mirror systems that form aberration-free line images is presented. An expression forthe ray density along the line image is derived for such systems in the cases of (i) uniform beam profiles and (ii) Gaussian beam profiles. The resulting ray density profiles are illustrated for single spherical mirror systems over a wide range of design parameters. 相似文献
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C. V. Yogananda 《Acta Mechanica》1969,7(4):299-310
Summary Theoretical expressions for stresses and displacements have been derived for bending under a ring load of a free shell, a shell embedded in a soft medium, and a shell containing a soft core. Numerical work has been done for typical cases with anElliot 803 Digital Computer and influence lines are drawn therefrom.
Nomenclature A (),B () Functions of - a, t Mean radius and thickness of the shell - E S , S Young's modulus andPoisson's ratio of the shell - G c , c Shear modulus andPoisson's ratio of the casting or core - I 0 (r),I 1 (r) ModifiedBessel functions of the first kind and order zero and one respectively - K 0 (r),K 1 (r) ModifiedBessel functions of the second kind and order zero and one respectively - p Ring load, lb/in - U, W Displacement components in the casing or core in thez andr direction - u, w Displacement components of a middle surface point in the shell - r , rz Radial and shearing stress components - Independent variable of infinite integrals - k [3(1–S 2)a 2/t 2]1/4 With 13 Figures 相似文献
Einflußlinien für die Biegung einer freien Schale, einer Schale in einer weichen Bettung und einer Schale mit weichem Kern
Zusammenfassung Für die Biegung einer freien Schale, einer weich gebetteten Schale und einer Schale mit weichem Kern unter einer Ringlast werden Ausdrücke für die Spannungen und Verschiebungen hergeleitet. Die Ergebnisse wurden für einige typische Fälle mit einem DigitalrechnerElliot 803 numerisch ausgewertet. Die sich ergebenden Einflußlinien wurden graphisch dargestellt.
Nomenclature A (),B () Functions of - a, t Mean radius and thickness of the shell - E S , S Young's modulus andPoisson's ratio of the shell - G c , c Shear modulus andPoisson's ratio of the casting or core - I 0 (r),I 1 (r) ModifiedBessel functions of the first kind and order zero and one respectively - K 0 (r),K 1 (r) ModifiedBessel functions of the second kind and order zero and one respectively - p Ring load, lb/in - U, W Displacement components in the casing or core in thez andr direction - u, w Displacement components of a middle surface point in the shell - r , rz Radial and shearing stress components - Independent variable of infinite integrals - k [3(1–S 2)a 2/t 2]1/4 With 13 Figures 相似文献
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Failure analysis is carried out on a fractured hub obtained from a diesel generator of a high-speed motor ship. Macrofractography, microfractography, standard optical metallography, material characterization techniques, and numerical modeling were used to verify the findings of the current investigation. Cracking initiation is attributed to fretting fatigue caused by a modification performed in the vicinity of the fractured hub. Operational vibrations contributed to the propagation of the cracks as typical fatigue cracks until final fracture. 相似文献
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A. M. Kudin G. I. Barenblatt V. N. Kalashnikov S. A. Vlasov V. S. Belokon' 《Journal of Engineering Physics and Thermophysics》1973,25(6):1567-1569
Results are shown pertaining to the action of jets of dilute polymer solutions on solid barriers. The piercing of a barrier is explained by the viscoelastic properties of aggregates which, during an impact, behave like solid particles.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 25, No. 6, pp. 1090–1094, December, 1973. 相似文献
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In our paper (Annals of Operations Research, 193:71–90, 2012) we introduced a special kind of k?1-width junction tree, called k-th order cherry tree in order to approximate a joint probability distribution. The approximation is the best if the Kullback–Leibler divergence between the true joint probability distribution and the approximating one is minimal. Finding the best approximating k?1-width junction tree probability distribution is NP-complete if 2<k<d?1, where d is the dimension of the joint probability distribution (see Karger and Srebro in 12th ACM-SIAM Symposium on Discrete Algorithms (SODA), 2001, Malvestuto in Kybernetika 48:825–844, 2012). In Broad Research in Artificial Intelligence and Neuroscience (BRAIN), special issue on complexity in sciences and artificial intelligence, pp. 40–45, 2010 we also proved that the best approximating k?1-width junction tree probability distribution can be embedded into a k-th order cherry tree probability distribution. We introduce here a greedy algorithm resulting very good approximations in reasonable computing time. We prove then that if the Markov network which encodes the conditional independences of the multivariate probability distribution fulfills some requirements then our greedy algorithm is able to find the true probability distribution. Our algorithm uses just the k-th order marginal probability distributions as input. We compare the results of the greedy algorithm proposed in this paper with the greedy algorithm proposed by Malvestuto (IEEE Trans. Syst. Man Cybern. 21:1287–1294, 1991). 相似文献