压电陶瓷已广泛应用于检测、通讯等各个领域.该文采用外差式激光干涉测量法,开展了压电陶瓷振动特性研究.首先给出了激光外差干涉测振仪测试压电陶瓷振动特性的测量方法,并通过实验测得了压电陶瓷片单点振动的频率响应曲线,同时测量了径向直线上若干点的振动频响曲线,进而进行了整个压电陶瓷圆环表面在其谐振频率点的振动测量.实验结果表明,实测压电陶瓷片的谐振频率为30710 Hz,与其产品标定值30000 Hz存在710 Hz偏差.其圆环表面振动的振型具有不对称性,这对压电陶瓷的应用设计提供了指导意义.

针对安钢2800 m3高炉热风炉运行中存在的问题,论述了高炉热风炉智能燃烧系统采用的关键技术及其优势,重点阐述了安钢2800 m3高炉热风炉烧炉自动控制系统改造的具体实施方法及过程,并对改造后取得的效果进行了分析与总结.

An ultraviolet visible (UV-Vis) spectrophotometric and multiwavelength linear regression (MLR) method was developed for eliminating the influence of the surface quality of centrifugal microfluidic chips on the accuracy of their absorbance detection. The regression model is based on scalar scattering theory. The method was validated with cuvettes with different surface quality and Orange G (orange gelb) dye. The coefficients of variation (CVs) of the predicted solution concentration ratios in different cuvettes were < 1%, and the relative errors were < 1.5%. The model was shown to have higher accuracy and precision than that of traditional methods.

In this paper, a phononic crystal (PC) plate with tubular pillars is presented and investigated. The band structures and mode displacement profiles are calculated by using finite element method. The result shows that a complete band gap opens when the ratio of the pillar height to the plate thickness is about 1.6. However, for classic cylinder pillar structures, a band gap opens when the ratio is equal or greater than 3. A tubular pillar design with a void room in it enhances acoustic multiple scattering and gives rise to the opening of the band gap. In order to verify it, a PC structure with double tubular pillars different in size (one within the other) is introduced and a more than 2 times band gap enlargement is observed. Furthermore, the coupling between the resonant mode and the plate mode around the band gap is characterized, as well as the effect of the geometrical parameters on the band gap. The behavior of such structure could be utilized to design a pillar PC with stronger structural stability and to enlarge band gaps.

Phononic crystal cavities with high quality (Q) factors are attractive in both signal processing and sensing applications. In this paper, 2D phononic crystal point defect cavities are fabricated on silicon slabs by micro electromechanical system (MEMS) technologies. An electrode design method is proposed to enhance displacements of the point defect modes. Then the method is applied to design MEMS resonators with different port numbers, among which Q factor as high as 21 300 is obtained in air. Multiport resonators with transmission measurements are proved to be advantageous over one-port resonators with impedance measurements in frequency resolution. A temperature insensitive resonant mass sensor is designed based on a two-port resonator. Two defect modes with strong responses in the two-port resonator are combined to compensate environmental temperature interference. The temperature compensation experiment reveals that temperature interference is effectively compensated from mass measurement and the mass sensitivity of the sensor is 5.4 Hz ng(-1). The conclusion of mode selection or sensing mechanism will help to design resonators or sensors with high performances.

Based on the Euler force induced by the acceleration of compact disk (CD)-like microfluidic chip, this paper presents a novel actuation mechanism for siphon valving. At the preliminary stage of acceleration, the Euler force in the tangential direction of CD-like chip takes the primary place compared with the centrifugal force to function as the actuation of the flow, which fills the siphon and actuates the siphon valving. The Euler force actuation mechanism is demonstrated by the numerical solution of the phase-field based mathematical model for the flow in siphon valve. In addition, experimental validation is implemented in the polymethylmethacrylate-based CD-like microfluidic chip manufactured using CO2 laser engraving technique. To prove the application of the proposed Euler force actuation mechanism, whole blood separation and plasma extraction has been conducted using the Euler force actuated siphon valving. The newly introduced actuation mechanism overcomes the dependence on hydrophilic capillary filling of siphon by avoiding external manipulation or surface treatments of polymeric material. The sacrifice for highly integrated processing in pneumatic pumping technique is also prevented by excluding the volume-occupied compressed air chamber.

This paper presents the topology optimization-based computational design methodology for nanostructures in surface plasmon polaritons. Using the proposed method, nanostructures can be designed solely based on the user’s desired performance specification for the surface plasmon polaritons. This topology optimization-based computational design methodology is implemented based on the material interpolation with hybrid formulation of logarithmic and power law approaches, to mimic the metal surface with exponential decay of the electromagnetic field. The constructed computational design problem is analyzed using the continuous adjoint method, and the filter and projection techniques are utilized to ensure the minimum length scale in the obtained nanostructures. The outlined design methodology is used to investigate the nanostructures for localized surface plasmonic resonances, extraordinary optical transmission, and surface plasmonic cloaking, respectively. For localized surface plasmonic resonances and extraordinary optical transmission, the metallic nanostructures are designed with spectra peaks at the prescribed wavelengths and the shift of the spectra peak is controlled by solving the computational design problem corresponding to a different incident wavelength; for surface plasmonic cloaking, the cloak covered at a curved metal-dielectric interface is designed to bound the surface plasmon polariton at the interface and remove the radiation, where the conventional simple isotropic dielectric readily available in nature is used instead of the material possessing gradient electromagnetic properties with challenges on realization for optical frequencies.

This paper proposes a new model for the longitudinal piezoelectric coefficient (LPC) measurement of the aluminum nitride (AlN) thin film on (100) Si substrate, the AlN thin film is fabricated by the direct-current magnetron sputtering and the piezoelectricity of the AlN thin film is measured by the piezoresponse force microscopy (PFM) in contact mode. In this model, the electric field distribution is taken into account, and the electrostriction displacement caused by the local field concentration is excluded from the measured displacement by the PFM. A LPC value of 4.22 ± 0.34 pm/V is obtained for the clamped AlN thin film by this model, and the deviation between this value and that measured under homogenous field condition is <5.7 %. Therefore, it is reasonable to apply our model to the piezoelectricity characterization of AlN thin films when using the PFM. Furthermore, piezoelectricity of other thin films could also be characterized using this model, which could simplify the measurement process.

This paper presents the topology optimization of steady Navier–Stokes flows with body forces that influence the optimal shape and topology of fluid flows. Based on the implicit expression of the fluid flow with the level set method, an optimization problem is formulated and analyzed using the continuous adjoint method. The shape and topological sensitivities are computed based on the adjoint and asymptotic analysis of the optimization problem. In the optimization procedure, the level set surface is evolved based on the shape sensitivity and nucleated based on the topological sensitivity simultaneously. Three kinds of body forces that are commonly used in the design of fluid devices, i.e. constant, nonuniform, and solution-dependent body forces, are considered in the two-dimensional and three-dimensional numerical examples. Numerical results demonstrate that this method can effectively achieve the topology optimization of the Navier–Stokes flows with body forces.

To adapt to the size of the small satellite,improve the inertia/mass ratio of small satellite attitude control flywheel and lighten the weight of flywheel,a disk brushless DC motor used in flywheel was designed.According to the moment of inertia of the flywheel,the overall structure of the motor was designed and the armature diameter ratio was determined.After analyzing the motor magnetic circuit,the relationship between the magnet size and air gap length was derived.The Finite Element Method(FEM) was used to determine the number of pole pairs and get the method of calculating equivalent air gap flux density.After establishing the relationship between winding parameters and the motor rated data,the formulas of designing winding were proposed.Simulation method was used to analyze the Electromotive Force(EMF) of the motor.A prototype was manufactured with this method and tested.The results show that the maximum error is 6.3%,which proves the correctness of the design method.

Development of sensitive, reliable, high-throughput, label-free detection techniques is an issue with increasing emphasis because the labeling strategies that most of the microarray applications have employed, such as fluorescent, chemiluminescent and radioactive labeling, have synthetic challenges, multiple label issues and may exhibit interference with the binding sites. Label-free detection techniques monitor biomolecular interactions and simplify the bioassays by eliminating the need for secondary reactants. Especially, biosensors based on evanescent waves often have high sensitivities by recording the changes caused by the molecule interaction near the sensor surface within the evanescent field, and moreover they provide quantitative information for the binding kinetics.In this article, we will describe the similarity of sound waves and electromagnetic waves and review the biosensors to which the two types of label-free techniques are related. The theoretical and technical outlines behind the sensing principles, such as the evanescent waves scattering, interference, resonance and tunnel effects, will be summarized. The physical mechanisms to modulate waves by micro/nano structures, which localize the waves, amplify the signal/noise ratio and increase Q factor for high sensitivity and high resolution, will also be discussed. Moreover, the promising acousto-optic sensing mechanism and the possibility of multi-parameter decoupling detection will be mentioned. The potential prospects, merits and challenges of these kinds of biosensors are also indicated.

For BLDC motor with small inductance, the control characteristics and mechanical properties was compared under the PWM drive mode and pulse amplitude modulation (PAM) drive mode. PWM mode has nonlinear control characteristics, and different proportion coefficient should be used in different speed range. PAM drive mode has good linearity, all speed range consistent and the lower power consumption features. But the system structure complexity is increased relatively. The comparison indicates that under PWM and PAM drive mode the system has different performance, and lower power consumption. The actual situation should be considered, when using the two dive mode.

This paper presents a statistical method to estimate the parameters of the brushless dc (BLDC) motor of a flywheel system for energy storage. The principle of the estimation is based on least square estimation under a reasonable constraint. Method is suitable to avoid using complicated test apparatus. Torque constant, static friction coefficient, vicious friction coefficient and inertia moment can be estimated. Furthermore, copper loss, iron loss, mechanical loss and other loss can be computed from these estimation and measurement data. By the proposed method, it is demonstrated experimentally that accuracy estimation can be achieved.

This paper presents the design and analysis of an axial flux permanent-magnet (AFPM) machine for nanosatellites application. It is a miniature axial flux surface mounted permanent magnet flywheel motor, using a printed circuit board (PCB) stator winding. The PCB stator has simplified the design and construction and avoids unnecessary space, since size reduction has become one of the most important aspects of flywheel motor design for nanosatellites. The performances of the machine are estimated by combination method of three-dimensional (3D) electromagnetic finite element analysis (FEA) and approximate theoretical analysis. The back EMF and electromagnetic torque are derived. A comparison between the analysis and experimental measurement results of the prototype machine is also presented. Both simulated and experimental results show that the proposed motor would be an acceptable solution for the nanosatellite applications with advantages such as simple structure and low-cost, as multi-layer circuit board production techniques have made the production of printed circuit coils cheaper and easier.