Time-delay spectrometry measurement of magnitude and phase of hydrophone response

A method based on time-delay spectrometry (TDS) was developed for measuring both magnitude and phase response of a hydrophone. The method was tested on several types of hydrophones used in medical ultrasound exposimetry over the range from 5 to 18 MHz. These included polyvinylidene fluoride (PVDF) spot-poled membrane, needle, and capsule designs. One needle hydrophone was designed for high-intensity focused ultrasound (HIFU) applications. The average reproducibility (after repositioning the hydrophone) of the phase measurement was 2.4°. The minimum-phase model, which implies that the phase response is equal to the inverse Hilbert transform of the natural logarithm of the magnitude response, was tested with TDS hydrophone data. Direct TDS-based measurements of hydrophone phase responses agreed well with calculations based on the minimum-phase model, with rms differences of 1.76° (PVDF spot-poled membrane hydrophone), 3.10° (PVDF capsule hydrophone), 3.43° (PVDF needle hydrophone), and 3.36° (ceramic needle hydrophone) over the range from 5 to 18 MHz. Therefore, phase responses for several types of hydrophones may be inferred from measurements of their magnitude responses. Calculation of phase response based on magnitude response using the minimumphase model is a relatively simple and practical alternative to direct measurement of phase.     

Determination of the range of lattice distortion in AIN sintered body by higher order laue zone pattern

To analyse the magnitude and range of lattice distortion which is responsible for the low thermal conductivity in aluminium nitride (AIN) crystal grains, the higher order laue zone (HOLZ) pattern of transmission electron microscopy was used. The HOLZ patterns obtained from various positions in the AIN crystal grain show that the AIN crystal lattice is distorted in the vicinity of the grain-boundary phase, and the magnitude of lattice distortion becomes large as it approaches the grain-boundary phase. Also, the range of distortion extends to approximately 300 nm from the grain-boundary phase.     

Deformation of material with shape memory in the range of martensitic transformations

We investigated experimentally the behavior of material with shape memory upon change of stress in the range of direct and inverse martensitic transformation. The article shows that the magnitude of the phase deformations does not depend on the stresses only but also on the temperature at which they are applied. It was established that a change of stresses in the range of inverse martensitic transformation has barely any influence on the magnitude of strain recovery.Translated from Problemy Proehnosti, No. 12, pp. 57–62, December, 1992.     

Coarse-grained molecular dynamics simulations on size effect of glassy polyethylene particles

The size effect on mechanical properties of glassy polyethylene (PE) nanoscale particles has been investigated by extensive coarse-grained molecular dynamics simulations. The diameter of the PE particles varies in the range of 5-40 nm, we confirm that the particle's behaviour under compressive stress strongly depends on its size-the smaller the particle diameter is, the stiffer the particle behaves. The present mechanical responses of compressed particles are in good agreement with our previous experimental phenomena of micron-sized polymer particles measured by a nanoindentation-based flat punch method. Possible reasons for the size effect are discussed.     

0.1 Hz～50 kHz直线振动幅值和相位国家计量基准系统的研究

描述中国计量科学院在直线振动幅值和相位测量的理论研究和技术实现方面取得的最新进展。简要介绍了国家高、中、低频振动基(副基)准幅相特性测量装置的系统构建、测量原理和技术实现,以及装置达到的主要技术指标。提出振动基(副基)准优化提升中关键的技术创新点,如自主提出了改进的外差正弦逼近法和基于波峰波谷的外差时间间隔法,在压电高频(2kHz～50kHz)振动台上,首次在国内外实现了(1nm～500nm)振幅范围内的纳米级振动传感器灵敏度幅值和相移的测量。中国计量科学研究院(NIM)与德国物理技术研究院(PTB)在10Hz～10kHz范围内开展的标准加速度计灵敏度幅相特性国际双边比对验证了国家基准的测量不确定度。     

Second Harmonic Reflected Light

A review is given of the laws of non-linear optical reflection which govern the direction, polarization and intensity of second harmonic light generated in reflection. The complex non-linear susceptibility of III-V and II-VI piezoelectric compounds has been measured over a range of frequencies and shows characteristic dispersive properties. Both the amplitude and the phase can be determined. When the medium has a centre of inversion, the reflected second harmonic production is several orders of magnitude smaller. The effect has magnetic dipole and electric quadrupole character and has been observed in silicon, germanium and several metals and alloys. In metals the contribution from core electrons and the conduction electron plasma have the same order of magnitude.     

Phase calibration of spatially nonuniform spatial light modulators

A new 512 x 512 pixel phase-only spatial light modulator (SLM) has been found to deviate from being flat by several wavelengths. Also, the retardation of the SLM relative to voltage varies across the device by as much as 0.25 wavelength. The birefringence of each pixel as a function of address voltage is measured from the intensity of the SLM between crossed polarizers. To these responses are added a reference spatial phase measured by phase shifting interferometry for a single address voltage. Fits to the measured data facilitate the compensation of the SLM to a root-mean-square wave-front error of 0.06 wavelength. The application of these corrections to flatten the full aperture of the SLM sharpens the focal plane spot and reduces the distortion of computer-designed diffraction patterns.     

Nonlinear dynamics of a domain boundary in the vicinity of the curie point in ferromagnetics

A rigorous nonlinear solution for a domain boundary with the varying magnitude of the magnetization vector (a Zhirnov domain boundary) has been obtained for ferromagnetics in a magnetic field in the approximation of the Landau second-order phase transitions. The results obtained indicate the efficiency of the nonlocal magnetization reversal mechanism in the range of the Curie temperature.     

Rotation angle measurement based on white-light interferometry with a standard optical flat

We propose a simple white-light interferometric method of measuring a one-dimensional rotation angle with use of an optical plane parallel plate of standard refractive index. The phase change of the interference pattern of the interferometer during the rotation of the flat plate of known refractive index and thickness placed in one of the interferometer's arms is used for determination of the rotation angle. This method has been demonstrated for an accurate angle measurement over the angle range from 0° to 40° within a maximum uncertainty of 0.057°.     

Photonic full-range phase shifter with simultaneous tunable frequency multiplying capability based on a DMZM

In this paper, a novel microwave photonic full-range phase shifter with simultaneous frequency-multiplying capability is proposed. The main device is a dual-drive Mach–Zehnder modulator (DMZM) embedded in a Sagnac loop. Under the assistance of two electrical phase shifters (EPS) and a following polarizer (Pol), the optical carrier is eliminated with desired phase tunable carrier-suppressed double-sideband (CS-DSB) signal reserved. So after photoelectric conversion, the frequency-multiplied phase tunable signals are generated. The frequency multiplication factor (FMF) switching and phase tuning operation of multiplied signals can be achieved easily by adjusting the corresponding EPS. The simulation results show that the proposed structure driven by a 10?GHz RF signal can generate a frequency-doubled signal (20?GHz) or frequency-quadrupled signal (40?GHz) that features full-phase tunable range and flat power response. What is more, the proposed phase shifter has a relatively good robustness to the non-ideal factors, large frequency operation range and good frequency tunable capability.     

Vacuum electric discharge initiated by accelerated nanoparticles

A static breakdown induced by the impact of particles detached from a point anode in a strong electric field, corresponding to the athermal field evaporation threshold, was studied by field ion microscopy. Under these conditions, the particle size threshold for the vacuum discharge initiation decreases by one order of magnitude as compared to the case of flat electrodes and falls within a nanometer range of the average radius of bombarding charged particles. The threshold energies of particles initiating a static electric discharge also exhibit a significant decrease.     

A quasi-optical phase shifter based on an active grating for the 8-mm wavelength range

A new quasi-optical phase shifter for the 8-mm wavelength range, which allows the phase of electromagnetic radiation in a wave beam to be controlled, is described. The phase shifter operation is based on the phenomenon of wave phase variation upon reflection from an active grating that is formed by the layers of plasma in channels of a dielectric plate arranged above a flat metal mirror. It is shown that the phase of the reflected wave can be effectively controlled by changing the grating-mirror distance and the gas pressure in the channels. The experimental data are compared to the results of numerical calculations.     

Quasi-reciprocal mixer as an absolute vector signal standard at microwave frequencies

A reciprocal mixer has the potential to extend an absolute calibration of magnitude and phase relationships at baseband to an absolute calibration at microwave frequencies. Unfortunately, recent publications have shown that mixers are not in general reciprocal devices. The authors' tests have shown that the up- and down-conversion transmission responses for a mixer change with time and temperature. The ratio of the up- and down-conversion transmission responses, however, can be remarkably constant with time and temperature for some mixers. The authors refer to this ratio as the characterised non-reciprocal ratio (CNR) for the mixer. By using a new calibration circuit, they are able to utilise this CNR for a quasi- reciprocal mixer and provide an effective absolute vector calibration standard at microwave frequencies.     

Buckling and large deformation behaviour of composite domes compressed between rigid platens

This paper aims at describing the large deformation behaviour of transversely loaded composite spherical domes. Two distinctive glass fabrics, woven and knitted, embedded in the same thermoplastic matrix, polypropylene, were utilised to produce the composite domes. The doubly curved shells with different number of plies and orientations (radius to thickness ratio in the range of 22–53) were compressed between two rigid flat platens. Load–displacement responses and deformed patterns were examined using experiments and numerical simulations. Because of the large deformation involved, a non-linear stress analysis technique has been adopted to simulate the responses. The loaded domes, both woven and knitted, display rolling-plastic hinge post-buckling response after initial buckling. Some interesting results due to orthotropy have been presented along with comprehensive material characterisations. The numerical simulations have produced very promising matching results.     

湍流边界层激励下平板振动响应相似性研究

对流激平板的振动试验设计与响应预报作了分析与探讨。验证了湍流脉动压力自功率的归一化方法在不同流体介质间的适用性。对平板流激响应,考虑流体负载并采用模态叠加法进行计算。通过原始模型与缩比模型响应之间的对比,提出一种平板响应间的换算方法。换算结果表明,该方法可以实现同种介质湍流边界层激励下的平板响应之间的换算。对不同外流场介质的平板流激响应,用该方法可实现理论上的换算。该研究结果对水下结构物流激响应预报有实际意义。     

点力和线力作用下的结构振动响应研究

建立了平板结构在点力载荷和线力载荷作用下振动响应的理论模型，应用该模型计算出简支平板在两种载荷作用下的振动响应，然后进行比较分析。通过实验研究了点力载荷与实际惯性激振器产生的线力载荷作用下简支平板振动频响函数的差别。研究表明，点力载荷和线力载荷作用下的振动响应有一定差别，线力作用的圆环直径越大，这种差别越大，且高频段较低频段表现更为明显。     

LF Adaptor Extends Vector Voltmeter Magnitude and Phase Measurements down to 10 Hz

An IC single-sideband modulator is described that allows direct measurement of magnitude and phase of a voltage over 3 decades anywhere in the range 10 Hz to 1 MHz. Two modulators generate a leveled upper-sideband (USB) reference signal about a 1-MHz suppressed carrier acceptable to the HP 8405A vector voltmeter. Another modulator produces a double-sideband (DSB) replica of the output voltage of the test device. The vector voltmeter then measures the magnitude of the upper-sideband reference and test device signals and their phase difference.     

基于激光干涉仪数字信号解码的振动校准方法

提出了一种基于Polytec外差激光干涉仪输出S/PDIF数字信号解码的加速度计校准方法,优化了校准过程,并保障了加速度计的灵敏度幅值与相位校准精度.通过与ISO 16063-11推荐的外差激光干涉法在5 Hz～20 kHz频率范围内的校准结果对比,提出方法的灵敏度幅值相对误差与相位差分别小于0.969％和0.165°...     

Four Voltmeter Vector Impedance Meter Based on Virtual Instrumentation

In this paper, a digital vector impedance half-bridge meter based on virtual instruments is designed, implemented and tested. Here, not only the accuracy of the magnitude of the impedance is considered but, more importantly, its phase measurement accuracy. The meter utilizes a four-voltmeter method which is a basic modification of the well-known three-voltmeter method. The half-bridge is constructed with commercially available data acquisition (DAQ) board in the form of peripheral control interconnect cards incorporated in personal computers. The DAQ board is used only to acquire the voltages instead of using four separate voltmeters, while the excitation signal is produced by an integrated circuit signal generator. The main error in this method arises from the error in measuring the voltage values. Since the resolution of the DAQ board used here is 16 bits; expect that absolute errors due to A/D conversion will be around 0.305 mV for ±10 V range. Detailed error analysis of the method is included in the context of the paper. It is found that the errors in the impedance magnitude is fairly small and relatively less sensitive on the resolution of the voltmeters because of the relative measurements in the half bridge with a precise reference resistance. The original three voltmeter vector impedance meter has relatively large error in the phase especially in the small phase angles. To decrease the phase error to an acceptable range, one has to increase the resolution of the voltmeter appreciably, which makes them expensive. The other solution to reduce the error in the phase angle with less cost is to add a fourth voltmeter which acquires directly the small phase angles. In this case, it is found that, a much lower resolution voltmeter can be utilized while achieving an acceptable measurement accuracy of the impedance.     

An Electronic Multiplier for Accurate Power Measurements

The time division multiplier-type wattmeter is based on a new principle of operation. An operational amplifier operates as an integrator of the sum of Ez (one of the two inputs) and either +E8, or -E8, E8 being an internal standardized voltage. A pulse-width modulation in the form of switch reversals is obtained which differs from balance condition by an amount proportional to Ex. Instantaneous multiplication provides a wattmeter with dc accuracy of ± 0.1 percent up to at least 10 kHz. The output voltage is ± 1 volt for a ± 1-volt input from Ex and Ey. To obtain the required flat frequency characteristics, a coupling transformer and an adjustable resistor are provided. A time constant of 6.8 X 10-9 seconds has been achieved. The voltage signal is readily provided by a precision ratiotran. Errors of ± 0.0001 percent in magnitude and 50 microradians in phase angle are reasonable.