实频率灵敏度的唯一性研究

模态参数灵敏度分析的精确算法公式主要有代数法和模态法等,它们每一种方法所求得的灵敏度的正确性在算法的讨论过程中一般都能得到很好的验证,但是对同一系统,不同方法所计算的灵敏度的唯一性问题却从未得到重视。通过讨论可知,即使代数法公式和模态法公式使用不同规范化条件下的实模态来计算实频率灵敏度,它们所获得的数值也是相同的,因此,实频率的灵敏度具有唯一性。

离散传递函数正实性与连续传递函数有限频率正实性的代数判据

正实性是控制理论中最重要的概念之一.许多控制目标的实现皆依赖于某些传递函数的正实性.相比于正实性,有限频率正实性则是较近提出的概念,并且亦在控制理论中找到了大量应用.为了判断离散标量传递函数的正实性和连续标量传递函数的有限频率正实性,本文分别给出了一种易于计算的简洁代数判据.现有的判断连续标量传递函数严格正实性的代数判据可以看作是本文结果的特殊情况.数值算例验证了方法的有效性.

冲击压实工艺对3D打印砂型成形性能影响规律研究

设计制作了一种冲击压实铺粉机构,研究了冲击压实工艺对3D打印砂型成形精度和强度的影响规律,通过理论和实验对比分析了刮板、辊子和冲击压实三种不同铺粉工艺对砂型性能的影响,表明冲击压实工艺所打印砂型具有更高的精度和强度,且能够有效解决铺砂过程中的错层问题,有效改善铺砂质量。

充粘液管材中超声纵向导波的无损检测参数选择

对超声纵向导波在充粘液管材中的传播特性进行了分析。在假设实频率和复波数的基础上,计算了导波的频散曲线,得到并分析了导波在系统中的位移分布曲线和衰减系数分布曲线,以此确定了用各模式检测管材中缺陷的最佳频厚积范围和检测的最佳位置。分析结果表明:频厚积在0.07MHz·mm以下,用L(0,1)模式检测较为理想,检测管内壁缺陷时更灵敏;在0.09～0.16MHz·mm之间用L(0,2)模式检测及在0.18～0.28MHz·mm之间用 L(0,3)模式检测时较为理想。

分数阶RL_βC_α电路特性研究

为探究RLC电路在分数阶下的新特性与新规律,将分数阶电感与电容引入RLC电路。基于分数阶电容与电感定义,推导出分数阶RLC电路阻抗表达式的一般情况;给出纯虚阻抗的满足条件,分析分数阶阶次等系统参数对纯虚阻抗的影响规律;给出分数阶RLC电路短路状态的一般规律与满足条件,推导出短路频率与短路电阻的规律表达式;推导出分数阶RLC电路纯实阻抗电路状态的满足电路频率;给出分数阶RLC电路设计优化举例。研究结果表明,由于分数阶阶次引入,RLC电路设计将展现更多自由度与灵活性。

陶粒、砂填充连续与非连续屏障隔振效果的全尺试验与数值研究

采用全尺试验方法,研究不同材料(陶粒、砂)填充不同类型屏障(连续型、非连续型)的隔振效果。同时,为弥补试验研究的不足,辅以数值研究。为此,在试验研究开展之前,在原场地上进行了面波多通道分析(multi channel analysis of surface waves,简称MASW)试验,以便获得场地的动力学特性,作为数值研究的基础。随后,开展试验工作以便获得场地固定点的传递函数与衰减分贝;并使用数值方法,编制程序计算加速度分量的空间分布场。综合以上两种方法后发现,隔振材料影响在低频处,两者差异不甚明显;在中频处,两者差异开始显现。陶粒的隔振表现接近空沟;在高频处,因土体的阻尼作用明显,材料影响难以表现。综上所述,陶粒的隔振效果远优于砂,整体表现接近空沟。屏障类型影响:当频率为30 Hz时,屏障的作用甚微,分量的空间分布形态以振源为圆心,呈环形分布;频率为50 Hz时,环形分布被屏障打破,其形态由环形变为椭圆形,而短边则指向波阵面方向,令一定强度的分量拒止于屏障的后区域;频率为80 Hz时,土体阻尼作用明显,以致两者差异不甚明显。综上,连续型屏障的隔振效果远优于非连续屏障。材料与屏障类型使用建议:若采用一般性的材料,考虑成本等因素,使用两者皆可;但采用高阻尼材料,考虑隔振效果等因素,则连续型屏障更优。

刚性圆柱体涡激振动响应模态特性研究

基于改进的尾流振子模型对刚性圆柱体涡激振动响应模态特性进行了研究。建立了刚性圆柱体与尾流振子的耦合模型,对耦合模型进行了线性简化,同时对简化后的模型进行解耦得到圆柱体的模态特性参数。对不同质量比情况下的刚性圆柱体频率、相位角以及主导模态等参数进行了分析。分析结果表明:圆柱体涡激振动响应模态可分为结构模态及流场模态,以流场模态为主导模态;结构模态频率分布在圆柱体固有频率附近,而流场模态频率则分布在斯脱哈尔漩涡泄放频率附近。

Experiment of dynamic property and transient magnetic effects of coal during deformation and fracture

Combining separated SHPB test device of Ф50 mm with ZDKT-type 1 transient magnetic resonance test system, long drop bar of 400 mm was used to impact coal specimens at four different speeds： 1.275, 3.287, 6.251, and 7.404 m/s. The change in waveform, the dynamic mechanical properties, and the generated effect of transient field during the coal deformation and fracture under the loads were discussed and analyzed. While magnetic signals during the coal fracture firstly needed EEMD, decomposition then had a FFT with Data Demon. The main results of the experiment are the following： the main frequency of magnetic signals was between 220 and 450 kHz and the instantaneous frequency during the damage of coal would have the instantaneous jump.

CONSTRUCTION OF THE ENCRYPTION MATRIX BASED ON CHEBYSHEV CHAOTIC NEURAL NETWORKS

The paper proposes a novel algorithm to get the encryption matrix. Firstly, a chaotic sequence generated by Chebyshev chaotic neural networks is converted into a series of low-order integer matrices from which available encryption matrices are selected. Then, a higher order encryption matrix relating real world application is constructed by means of tensor production method based on selected encryption matrices. The results show that the proposed algorithm can produce a "one-time pad cipher" encryption matrix with high security; and the encryption results have good chaos and auto-correlation with the natural frequency of the plaintext being hidden and homogenized.

Study Frequency of Antibiotic Resistance Enzymes in Bacillus Species in Some of Foods

The subject of this study was to survey prevalence Beta lactamase enzyme in Bacillus species isolated from foods in Isfahan city in Iran. This is a laboratory study performed during 2009-2010 years in Isfahan. In this study, 150 samples of food, including juice ketchup, mayonnaise,

Numerical Modeling of the Effect of Crack Parameters on Attenuation Anisotropy

Propagation through stress-aligned fluid-filled cracks and other inclusions have been claimed to be the cause of azimuthal anisotropy observed in the crust and upper mantle.This paper examines the behavior of seismic waves attenuation caused by the internal structure of rock mass,and in particular,the internal geometry of the distribution of fluid-filled openings Systematic research on the effect of crack parameters,such as crack density,crack aspect ratio(the ratio of crack thickness to crack diameter),pore fluid properties(particularly pore fluid velocity),VP/VS ratio of the matrix material and seismic wave frequency on attenuation anisotropy has been conducted based on Hudson's crack theory.The result shows that the crack density,aspect ratio,material filler,seismic wave frequency,and P-wave and shear wave velocity in the background of rock mass,and especially frequency has great effect on attenuation curves.Numerical research can help us know the effect of crack parameters and is a good supplement for laboratory modeling.However,attenuation is less well understood because of the great sensitivity of attenuation to details of the internal geometry.Some small changes in the characteristics of pore fluid viscosity,pore fluids containing gas and liquid phases and pore fluids containing clay can each alter attenuation coefficients by orders of magnitude.Some parameters controlling attenuation are therefore necessary to make reasonable estimations,and anisotropic attenuation is worth studying further.

Software Defined Traffic Engineering for Improving Quality of Service

The Software Defined Networking(SDN) paradigm separates the control plane from the packet forwarding plane, and provides applications with a centralized view of the distributed network state. Thanks to the flexibility and efficiency of the traffic flow management, SDN based traffic engineering increases network utilization and improves Quality of Service(QoS). In this paper, an SDN based traffic scheduling algorithm called CATS is proposed to detect and control congestions in real time. In particular, a new concept of aggregated elephant flow is presented. And then a traffic scheduling optimization model is formulated with the goal of minimizing the variance of link utilization and improving QoS. We develop a chaos genetic algorithm to solve this NP-hard problem. At the end of this paper, we use Mininet, Floodlight and video traces to simulate the SDN enabled video networking. We simulate both the case of live video streaming in the wide area backbone network and the case of video file transferring among data centers. Simulation results show that the proposed algorithm CATS effectively eliminates network congestions in subsecond. In consequence, CATS improves the QoS with lower packet loss rate and balanced link utilization.

Experimental and simulation research on the influence of voltage amplitude,frequency and carrier gas flow rate on the performance of FAIMS

A micro sensor chip of High-field Asymmetric Waveform Ion Mobility Spectrometry(FAIMS) was designed and fabricated by inductively coupled plasma(ICP) etching on the both sides of silicon and double silicon-glass bonding,with dimensions of 18.8 mm×12.4 mm×1.2mm.The sample ions were created at ambient pressure by VUV lamp ion source,which was equipped with a 10.6 eV photo discharge lamp(λ=116.5 nm).The 2-pentanone was adopted to illustrate the influences of high-field rectangular asymmetric waveform voltage amplitude,frequency and carrier gas flow rate on the performance of FAIMS sensor chip.The experiment results showed that with the frequency or carrier gas flow rate increasing,or voltage amplitude decreasing,the FAIMS sensitivity increases,and that the resolution decreases with the increasing of the frequency or flow rate.The FAIMS simulation results based on the SIMION software was in agreement with the experimental results.The FAIMS detection sensitivity experiment showed that the FAIMS sensor chip can detect positive and negative ions simultaneously,and has detection sensitivity as low as 0.1 ppm for acetic acid.

The effects of attached flexible tail length on the flow structure of an oscillating cylinder

Particle Imaging Velocimetry （PIV） is utilized to investigate the flow structures of an oscillating cylinder attached to a flexible tail. At the same oscillation frequency and amplitude, the mean streamwise velocity along the wake central-line and the mean vertical velocity around the trailing edge of the flexible tail can be greatly increased with the tail length. Meanwhile, the longer the flexible tail is, the larger its deformation is. In order to study the influence of flexible tail length on the wake pattern of the experimental model, the relationships between the swirling strength Aci of vortex structure near the tail end and the velocity of tail trailing edge have been revealed. Moreover, the convection tracks and the Aci of vortex cores for different flexible tails are discussed.

Shape change induced by g_(9/2) rotational alignment in ^(84,86)Mo

Neutron-deficient Z ≈ N nuclei84,86Mo have been investigated using pairing-deformation self-consistent cranked shell modelcalculations up to spin I > 20 . Our calculations are in good agreement with the experimental data, indicating γ-soft triaxial shapesat low rotational frequency and well-deformed triaxial-oblate shapes at high rotational frequency for both nuclei. The shape changeis due to the alignments of the g9/2protons and g9/2neutrons.

The electromagnetic wave experiment for CSES mission： Search coil magnetometer

The seismic activities on the Earth can produce a disturbance of the electromagnetic field and particles in the ionosphere. The search coil magnetometer(SCM) mounted on China Seismo-Electromagnetic satellite(CSES) is designed to measure the magnetic field fluctuation of low frequency electromagnetic waves in the frequency range of 10 Hz–20 k Hz. The SCM comprises a three-axis search coil sensor mounted on a 4.5 m boom and an electronic box inside satellite module. The sampling rate of the SCM is 51.2 k Hz and the time resolution of the power spectrum density(PSD) is 2 s. The frequency resolution is 12.5 Hz.There are three operation modes: survey, detailed survey and calibration. In the survey mode, the SCM can provide a PSD in the whole frequency range of 10 Hz–20 k Hz and wave forms in the low frequency range below 2 k Hz while in the detailed survey mode the SCM can provide both PSD and wave forms in the whole frequency range of 10 Hz–20 k Hz. The sensitivity of the SCM instrument is 5.0×10^(-4) n T Hz^(-1/2) at 10 Hz, 5.0×10^(–5) n T Hz^(-1/2) at 200 Hz, 3.4×10^(-5) n T Hz^(-1/2) at 2 k Hz and 1.1×10^(-4) n T Hz^(-1/2) at 20 k Hz. The telemetry rate is ~0.85 Mbps in the survey mode and ~3.0 Mbps in the detailed survey mode. The phase difference between three axes can be made generally with a precision of less than 1.0°. The dynamic range of the SCM instrument is over 100 d B. The orthogonality of three mechanical axes of search coil senor is better than 0.13°. The performance of SCM can satisfy the requirement of scientific objectives of CSES mission.

Study of the cavity-magnon-polariton transmission line shape

We experimentally and theoretically investigate the microwave transmission line shape of the cavity-magnon-polariton(CMP)created by inserting a low damping magnetic insulator into a high quality 3D microwave cavity. While fixed field measurements are found to have the expected Lorentzian characteristic, at fixed frequencies the field swept line shape is in general asymmetric. Such fixed frequency measurements demonstrate that microwave transmission can be used to access magnetic characteristics of the CMP,such as the field line width H. By developing an effective oscillator model of the microwave transmission we show that these line shape features are general characteristics of harmonic coupling. At the same time, at the classical level the underlying physical mechanism of the CMP is electrodynamic phase correlation and a second model based on this principle also accurately reproduces the experimental line shape features. In order to understand the microscopic origin of the effective coupled oscillator model and to allow for future studies of CMP phenomena to extend into the quantum regime, we develop a third, microscopic description,based on a Green's function formalism. Using this method we calculate the transmission spectra and find good agreement with the experimental results.

Numerical simulation of drop oscillation in AC electrowetting

In this paper,a "macroscopic-scale" numerical method for drop oscillation in AC electrowetting is presented.The method is based on a high-fidelity moving mesh interface tracking(MMIT) approach and a "microscopic model" for the moving contact line.The contact line model developed by Ren et al.[Phys Fluids,2010,22:102103] is used in the simulation.To determine the slip length in this model,we propose a calibration procedure using the experimental data of drop spreading in DC electrowetting.In the simulation,the frequency of input AC voltage varies in a certain range while the root-mean-square value remains fixed.The numerical simulation is validated against the experiment and it shows that the predicted resonance frequencies for different oscillation modes agree reasonably well with the experiment.The origins of discrepancy between simulation and experiment are analyzed in the paper.Further investigation is also conducted by including the contact angle hysteresis into the contact line model to account for the "stick-slip" behavior.A noticeable improvement on the prediction of resonance frequencies is achieved by using the hysteresis model.

Study of TiO_2 thin films on Si substrate by the photoacoustic elastic bending method

The quantitative photoacoustic investigation of different TiO2 thin films on Si substrates is presented using the elastic bending method. Photoacoustic signal amplitude and phase spectra versus modulation frequency were measured and analyzed using different sample thicknesses. Within the proposed method particular attention is given to the analysis of optical, thermal, elastic and structural sample parameters. Considerable focus is devoted to the fitting procedure of experimental results using the two-layer sample theoretical model. Characteristics of previously developed photoacoustic apparatus are discussed, attempting to search the ideal experimental conditions which can provide a good signal-to-noise ratio and sensitivity.

Analog Processing Based Vibration Measurement Technique Using Michelson Interferometer

A Michelson interferometer based sensor, to monitor the displacement and vibration of a surface, is presented. The interference signals detected in quadrature are processed using analog electronics to find the direction of the motion of a vibrating surface in real-time. The complete instrumentation and signal processing are implemented for the interpretation of the amplitude as well as positive and negative excursion of the vibration cycles. This new technique is simpler as compared to the techniques commonly used in the interferometer based vibration sensors. Using this technique, we have measured mechanical vibrations having a magnitude of the order of nanometers and frequency in the range of 50Hz to 500Hz. By making small changes in the electronic circuit, the technique can be implemented for the extended range of the vibration frequencies and amplitude.