主变压器噪声特性分析及复合隔声结构设计*

超高压变电站的主变压器的噪声影响已引起广泛关注。以某典型化设计的500kV变电站A的主变压器为例,进行了现场测试,得到其主变压器噪声能量主要集中在中低频范围内,且具备明显的线谱噪声特征。针对该噪声特点,提出了一种内插微穿孔板的双层带孔板型声学超材料的复合隔声结构。使用传递矩阵理论对该复合结构进行了分析,并在阻抗管中进行了实验验证。实验结果表明：该复合隔声结构具备针对性隔声要求,理论与实验传递损失曲线基本吻合。     

四边简支含多孔材料双层板隔声特性

有限大含多孔材料和空气层复合板结构隔声特性的研究尚不充分。该文旨在研究四边简支边界条件下复合板结构隔声特性。首先基于流体饱和多孔弹性介质的声传播理论计算了声波在多孔介质中的传播波数；继而采用四边简支边界条件下板结构的模态函数，利用模态叠加法和伽辽金法推导了复合板结构隔声系数理论模型，并数值求解复合板隔声量。将理论模型得到的四边简支复合板隔声量与实验结果对比，验证了理论模型的正确性。最后，详细讨论了边界条件、板结构尺寸和多孔材料厚度等主要参数对隔声特性的影响。结果表明：四边简支复合结构隔声特性曲线上“谷值”出现得较少，并且简支复合板隔声特性的第一个“吻合频率”比固支支撑复合板更靠近低频，当频率超过3000 Hz以后，简支和固支边界条件复合板结构隔声特性趋于一致。     

COMPOSITE FIELD THEORY AND THE STRATON MODEL(Ⅱ)

On the basis of previous papers,this work discusses the theory of composite fields composed of colored stratons.Varicus equivalent representations of the S-matrix elements are given.The formulae for the transition matrix elements between states involving baryons in the theory of Straton Model are derived.Finally,the field- current relations are extended to spin 1/2 baryons and their applications are discussed.     

The Schur function realization of vertex operators

We present a realization of untwisted vertex operators in terms of operations on Schur functions. Calculations of matrix elements and traces of products of vertex operators are performed using results from the classical theory of symmetric functions. The concepts of compound, composite and supersymmetric Schur functions naturally appear in this context. Furthermore, a trace formula for a product of vertex operators turns out to be a generalization of a MacDonald identity reformulated in terms of Schur functions.     

Active vibration suppression of multilayered plates integrated with piezoelectric fiber reinforced composites using an efficient finite element model

The active vibration suppression of hybrid composite and fiber metal laminate (FML) plates integrated with piezoelectric fiber reinforced composite (PFRC) sensors and actuators is studied for the first time, using an efficient and advanced layerwise plate theory. Unlike the conventional finite elements, the equipotential condition of electroded surfaces of sensors is satisfied exactly and conveniently using a novel concept of electric node. The effective electromechanical properties of the PFRC laminas are computed using a coupled three-dimensional iso-field micromechanical model. Numerical results are presented for both classical constant gain velocity feedback (CGVF) and optimal control strategies. The instability phenomena in CGVF control with conventionally collocated actuator-sensor pairs, and its remedy with a truly collocated arrangement are illustrated. The effect of segmentation of electrodes on the control response is studied. The segmentation of electrodes leads to a multi-input-multi-output (MIMO) configuration. The effects of piezoelectric fiber orientation, volume fraction and dielectric ratio of PFRC on the control response and the actuation/sensing authority are investigated for cantilever and simply supported plates.     

二维光栅与周期性缝隙阵列组合薄膜结构的杂散光抑制

传统方格型二维光栅与周期性缝隙阵列的组合薄膜结构具有雷达和光学波段双带通的电磁特性. 但由于其杂散光能量集中分布而严重制约它在高精度探测以及成像领域中的应用. 本文提出了一种全新的组合薄膜结构, 即由满足一定约束条件的圆孔型二维光栅和十字缝隙阵列构成. 基于Fraunhofer衍射理论建立组合薄膜结构标量衍射模型, 通过对比两种组合薄膜结构的衍射光分布, 理论分析与实验测试均表明: 圆孔型光栅与十字缝隙阵列组合薄膜结构不仅能够提高其光学透过率, 而且还使其杂散光分布均匀, 降低了其杂散光总比率, 从而有效抑制杂散光, 进一步增强了二维光栅与周期性缝隙阵列组合薄膜结构在实际光学系统中的可靠性. 关键词： 二维光栅 组合薄膜结构 衍射光强 杂散光     

Effective stopping of relativistic composite heavy ions colliding with atoms

A nonperturbative theory of energy loss by relativistic composite heavy highly charged ions colliding with atoms is developed. A simple formula for effective stopping is derived. By composite ions, we mean partially ionized atoms of heavy elements consisting of the ion core and several bound electrons that incompletely neutralize the ion core charge. Such ions, which have, as a rule, a high charge (for example, partly stripped uranium atoms), are used in many experiments performed with modern heavy ion accelerators.     

A study of a 1-3-2 type piezoelectric composite

A novel 1-3-2 type piezoelectric composite is developed. There are piezoelectric ceramic framework supports at transverse and longitudinal directions in its structure, so it is free from the influence of any outside mechanic impact and environmental temperature change. The sample characteristic is good coherence. It has many advantages, such as a high piezoelectricity, lower density and acoustic impedance matching with water and tissue easily. Based on Newnham's series and parallel theory of composites, the calculation formulae of dielectric and piezoelectric constants of a 1-3-2 type piezoelectric composite are deduced. The sample's characteristics indicate that a 1-3-2 type piezoelectric composite's theoretic calculation values are in good agreement with the measurement results. Element samples have been designed, manufactured and measured. The results indicate that the resonant frequency, resonant impedance, piezoelectricity and static capacity of these samples are stable. It is easy to design sensor array elements using this material.     

Quantifying interference in multipartite quantum systems

The characterization of quantum correlations is crucial to the development of new quantum technologies and to understand how dramatically quantum theory departs from classical physics. Here we systematically study single- and multiparticle interference patterns produced by general two- and three-qubit systems. From this we establish on phenomenological grounds a new type of quantum correlation for these systems, which we name quantum interference, deriving some quantifiers that are given explicitly in terms of the density matrix elements of the complete system. By using these quantifiers, we show that, contrary to our expectations, entanglement is not a required property for a composite quantum system to manifest multiparticle interference.     

旋转超声磨削平行砂轮复合变幅器设计与试验*

为了获得大负载平行砂轮复合变幅器的设计方法,将复合变幅器简化为复合变幅杆与多阶环盘组成。利用Mindlin中厚板理论,求解了各振动环盘的位移、转角、弯矩和剪力解析表达式,并通过复合变幅杆各振动单元间的力、位移的边界条件和连续条件,以及复合变幅杆和环盘两者结构间力与位移的耦合条件,建立了复合变幅器的数学模型和频率方程。针对频率方程进行编程求解 ,设计了平行砂轮复合变幅器。通过有限元仿真分析、实物阻抗特性试验、谐振试验验证。试验结果表明：平行砂轮复合变幅器的试际谐振频率、节圆位置与理论设计的误差小于5%,验证了其理论设计方法的正确性。为研制大负载平行砂轮复合变幅器提供了一种有效的设计方法。     

Spectral finite element based on an efficient layerwise theory for wave propagation analysis of composite and sandwich beams

In this paper, we present a spectral finite element model (SFEM) using an efficient and accurate layerwise (zigzag) theory, which is applicable for wave propagation analysis of highly inhomogeneous laminated composite and sandwich beams. The theory assumes a layerwise linear variation superimposed with a global third-order variation across the thickness for the axial displacement. The conditions of zero transverse shear stress at the top and bottom and its continuity at the layer interfaces are subsequently enforced to make the number of primary unknowns independent of the number of layers, thereby making the theory as efficient as the first-order shear deformation theory (FSDT). The spectral element developed is validated by comparing the present results with those available in the literature. A comparison of the natural frequencies of simply supported composite and sandwich beams obtained by the present spectral element with the exact two-dimensional elasticity and FSDT solutions reveals that the FSDT yields highly inaccurate results for the inhomogeneous sandwich beams and thick composite beams, whereas the present element based on the zigzag theory agrees very well with the exact elasticity solution for both thick and thin, composite and sandwich beams. A significant deviation in the dispersion relations obtained using the accurate zigzag theory and the FSDT is also observed for composite beams at high frequencies. It is shown that the pure shear rotation mode remains always evanescent, contrary to what has been reported earlier. The SFEM is subsequently used to study wavenumber dispersion, free vibration and wave propagation time history in soft-core sandwich beams with composite faces for the first time in the literature.     

Optical measurement on dynamic buckling behavior of stiffened composite panels under in-plane shear

The buckling behavior and failure mode of a composite panel stiffened by I-shaped stringers under in-plane shear is studied using digital fringe projection profilometry. The basic principles of the dynamic phase-shifting technique, multi-frequency phase-unwrapping technique and inverse-phase technique for nonlinear error compensation are introduced. Multi-frequency fringe projection profilometry was used to monitor and measure the change in the morphology of a discontinuous surface of the stiffened composite panel during in-plane shearing. Meanwhile, the strain history of multiple points on the skin was obtained using strain rosettes. The buckling mode and deflection of the panel at different moments were analyzed and compared with those obtained using the finite element method. The experimental results validated the FEM analysis.     

One-dimensional modelling of flame propagation in solid composite fuel with different geometrical configurations

In this paper the propagation of combustion waves in solid composite energetic material consisting of fuel and highly thermal conductive inert elements is investigated using a one-dimensional model with a single step reaction mechanism. The analysis is focused on the study of the effect of the geometrical configuration of the composite material on flame speed and dynamics. Spatial averaging over directions transverse to the propagation direction is performed in such a way as to retain the multidimensional nature of the problem. It is shown that the regimes of combustion depend on the geometry of the composite. The largest possible flame speed enhancement is attained in cases when the heat fluxes along the structural elements are not disrupted. For each configuration selected, there exists an optimal choice of the geometric parameters that maximizes the flame velocity.     

Martensitic transformations in a skeleton-type TiC/TiNi composite

The temperature kinetics of martensitic transformations in a skeleton-type TiC/TiNi composite with micron-sized structural constituents was studied. The composite is fabricated using a unique technique. Heat treatment and a change in the chemical composition of the titanium carbide are shown to affect the transformation temperatures. This effect is related to the redistribution of the chemical elements between the carbide and metallic components of the composite; as a result, the titanium nickelide becomes enriched in nickel.     

Exclusive processes in position space and the pion distribution amplitude

We suggest to carry out lattice calculations of current correlators in position space, sandwiched between the vacuum and a hadron state (e.g. pion), in order to access hadronic light-cone distribution amplitudes (DAs). In this way the renormalization problem for composite lattice operators is avoided altogether, and the connection to the DA is done using perturbation theory in the continuum. As an example, the correlation function of two electromagnetic currents is calculated to the next-to-next-to-leading order accuracy in perturbation theory and including the twist-four corrections. We argue that this strategy is fully competitive with direct lattice measurements of the moments of the DA, defined as matrix elements of local operators, and offers new insight in the space-time picture of hard exclusive reactions. PACS  12.38.-t, 14.20.Dh; 13.40.Gp     

Study of 1-3-2 type piezoelectric composite transducer array

Based on a new structure of precise location and decoupling between the transducer elements, high frequency underwater transmission transducer arrays with 4 elements and 8 elements serried uniform linear array were studied, using novel 1-3-2 type piezoelectric composite as the sensing material. There are ceramic framework supports in the transverse and longitudinal directions in 1-3-2 type piezoelectric composite structure; the transducer is free from the influence of outside mechanical impact and the environment temperature change. Transducer and array samples have been designed, fabricated and measured. The resonant frequency is 150 kHz, resonant transmission response greater than 160 dB, and bandwidth is from 140 kHz to 160 kHz. The results indicate that, the transducer array has wide bandwidth, high sensitivity, stabile performance, and good coherence.     

Dynamic stiffness matrix of thin-walled composite I-beam with symmetric and arbitrary laminations

For the spatially coupled free vibration analysis of thin-walled composite I-beam with symmetric and arbitrary laminations, the exact dynamic stiffness matrix based on the solution of the simultaneous ordinary differential equations is presented. For this, a general theory for the vibration analysis of composite beam with arbitrary lamination including the restrained warping torsion is developed by introducing Vlasov's assumption. Next, the equations of motion and force–displacement relationships are derived from the energy principle and the first order of transformed simultaneous differential equations are constructed by using the displacement state vector consisting of 14 displacement parameters. Then explicit expressions for displacement parameters are derived and the exact dynamic stiffness matrix is determined using force–displacement relationships. In addition, the finite-element (FE) procedure based on Hermitian interpolation polynomials is developed. To verify the validity and the accuracy of this study, the numerical solutions are presented and compared with analytical solutions, the results from available references and the FE analysis using the thin-walled Hermitian beam elements. Particular emphasis is given in showing the phenomenon of vibrational mode change, the effects of increase of the modulus and the bending–twisting coupling stiffness for beams with various boundary conditions.     

利用含多孔介质微穿孔周期结构增强声吸收

为获得理想吸声性能,提出了一种由多孔材料,微穿孔板及空气层构成的周期复合结构,并利用微穿孔板理论和等效流体多孔材料模型,结合等效电路法进行了分析。结果表明,复合结构显著增强了微穿孔板结构的中低频吸声性能,但其高频性能较单独多孔材料差;采用合适填充比例并联布置多种多孔材料,可适当调节复合结构的吸声性能。此外,周期复合结构的堆叠层数N≥1时,相对单层复合结构,中低频吸声带宽提升至少40%(≥380 Hz);相对多层微穿孔板结构,增大N对相应中低频吸声带宽提升不低于30%(≥300 Hz)。总体上,文中周期复合结构可显著增强传统微穿孔结构的中低频性能,是一种简单高效的中低频宽频降噪方案。      

Study on the prestressed sandwich piezoelectric ceramic ultrasonic transducer of torsional-flexural composite vibrational mode

Based on the classical torsional and flexural vibrational theory of a slender rod, the prestressed sandwich torsional-flexural composite mode piezoelectric ceramic ultrasonic transducer is studied. This type of transducer consists of the slender metal rods and the longitudinally and tangentially polarized piezoelectric ceramic rings. The resonance frequency equations for the torsional and flexural vibrations in the transducers are derived. The simultaneous resonance of the torsional and flexural vibrations in the transducer is acquired by correcting the length of the metal slender rods resulting from the piezoelectric ceramic elements. The experimental results show that the measured resonance frequencies of the transducers are in good agreement with the computed ones, and the measured resonance frequencies of the torsional and the flexural vibrations in the composite transducers are also in good agreement with each other.