A new pendulum device to measure contact potential differences

Using a variation of Kelvin's vibrating capacitor technique a new method is described to measure contact potential differences (CPD). The main advantage of this pendulum device is the fact that the variation of CPD, performed, for example, by bombarding the electrode under investigation with an atomic beam, can be measured quasicontinously. The absolute experimental error is?1 meV.     

一种高稳定、高分辨率的光纤位移检测系统

介绍一种大量程、高分辨率、高稳定的光纤传感位移测量系统。该系统基于反射式强度调制机制,由光发射机、传感器、光接收机三部分组成。系统通过采用调制、解调、窄带滤波,信号支路和参考支路双通道相比测量等技术措施,来保证系统的高稳定性和高分辨率。实验还表明测量中应尽量使用朗伯特平面作为光反射面,以解决二次安装的重复性问题。     

Operating mode of high pressure straws with high spatial resolution

The article presents results of studying the operating mode of thin-walled drift tubes (straws) at flushing it with a high-pressure gas mixture, which allowed obtaining extremely high spatial resolution for straw detectors. The results of studying the radiation ageing of straws operating in this mode are also described.     

The miniature light-field camera with high spatial resolution

Optical Review - A light-field camera is an optical system that provides multi-field-angle information in one shot. The microlens array (MLA) in a light-field camera system is the key to provide...     

Extreme ultraviolet radiation for coherent diffractive imaging with high spatial resolution

Using different noble gases,argon,neon and helium,we are able to generate by high-harmonic generation(HHG) just a few harmonic orders in the spectral range 10-35 nm with a photon flux of～2.10 12 photons/(harmonic cm2 s) for argon and～10 10 photons/(harmonic cm2 s) for helium. The few-harmonic-order radiation is used for coherent diffractive imaging directly without any spectral filter. A spatial resolution of～100 nm is achieved using a～30 nm HHG source.     

A mechanical model of vocal-fold collision with high spatial and temporal resolution

The tissue mechanics governing vocal-fold closure and collision during phonation are modeled in order to evaluate the role of elastic forces in glottal closure and in the development of stresses that may be a risk factor for pathology development. The model is a nonlinear dynamic contact problem that incorporates a three-dimensional, linear elastic, finite-element representation of a single vocal fold, a rigid midline surface, and quasistatic air pressure boundary conditions. Qualitative behavior of the model agrees with observations of glottal closure during normal voice production. The predicted relationship between subglottal pressure and peak collision force agrees with published experimental measurements. Accurate predictions of tissue dynamics during collision suggest that elastic forces play an important role during glottal closure and are an important determinant of aerodynamic variables that are associated with voice quality. Model predictions of contact force between the vocal folds are directly proportional to compressive stress (r2 = 0.79), vertical shear stress (r2 = 0.69), and Von Mises stress (r2 = 0.83) in the tissue. These results guide the interpretation of experimental measurements by relating them to a quantity that is important in tissue damage.     

In-duct identification of fluid-borne source with high spatial resolution

Source identification of acoustic characteristics of in-duct fluid machinery is required for coping with the fluid-borne noise. By knowing the acoustic pressure and particle velocity field at the source plane in detail, the sound generation mechanism of a fluid machine can be understood. The identified spatial distribution of the strength of major radiators would be useful for the low noise design. Conventional methods for measuring the source in a wide duct have not been very helpful in investigating the source properties in detail because their spatial resolution is improper for the design purpose. In this work, an inverse method to estimate the source parameters with a high spatial resolution is studied. The theoretical formulation including the evanescent modes and near-field measurement data is given for a wide duct. After validating the proposed method to a duct excited by an acoustic driver, an experiment on a duct system driven by an air blower is conducted in the presence of flow. A convergence test for the evanescent modes is performed to find the necessary number of modes to regenerate the measured pressure field precisely. By using the converged modal amplitudes, very-close near-field pressure to the source is regenerated and compared with the measured pressure, and the maximum error was −16.3 dB. The source parameters are restored from the converged modal amplitudes. Then, the distribution of source parameters on the driver and the blower is clearly revealed with a high spatial resolution for kR<1.84 in which range only plane waves can propagate to far field in a duct. Measurement using a flush mounted sensor array is discussed, and the removal of pure radial modes in the modeling is suggested.     

Broad-band NMR with a high spectral and spatial resolution

Spatially selective excitation sequence CARVE (completely arbitrary regional volume excitation) excites signal from an arbitrarily shaped profile (I. Sersa, S. Macura: Magn. Reson. Med.37, 920–931, 1997) by an interleaved sequence of precalculated small tip angle radio-frequency pulses and gradient pulses. Here we propose a spatially selective observation method based on the CARVE principles which is insensitive to the relaxation and the off-resonance effects. The method, CARVED (CARVE detection), excites spins uniformly across the sample and across the spectrum but achieves spatial selectivity by weighted coaddition of the signals after the data acquisition. CARVE-D is suitable for spatially selective high-resolution nuclear magnetic resonance spectroscopy in chemically and geometrically complex systems. The method is analyzed theoretically and demonstrated experimentally on model systems.     

A 2-dimensional detector with high spatial and temporal resolution for metastable rare gas atoms

We describe a detector for metastable rare gas atoms which allows the investigation of transverse atomic beam distributions on the single atom level with lateral dimensions of 1 m, which occur frequently in the field of atom optics. In contrast to existing detection techniques, the conversion step from the metastable atom to an electron is separated from the charge amplification to improve spatial resolution. The conversion is performed at a metal surface, which is followed by an electron-optical system imaging the electron distribution with a proper magnification onto a single electron detection unit. The spatial resolution that we achieve with this technique is on the order of 1 m, the temporal resolution on the order of 1 s. The application of the detector for atom interferometry is discussed. Received: 22 May 1996 / Revised version: 21 June 1996     

用光学多通道分析仪系统作高分辨光谱测量的技术

通常的光多通道分析仪(OMA)存在着同时谱宽与分辨率的矛盾.本文所述方法,在不减小谱宽的前提下,可将该分析仪光谱分辨率提高1～2量级,使之可适用于高分辨率谱研究.     

A novel technique for measuring resistance fluctuations independently of background noise

A novel method is presented for measuring the spectral density of resistance fluctuations without the explicit determination of the voltage background noise (Johnson noise, pre-amplifier noise). The output of a standard ac bridge excited by a single-frequency alternating current is demodulated by two phase-sensitive detectors which operate in quadrature. When the phase difference between excitation and detection is properly set, the real part of the cross-spectral density of the two demodulators shows only the spectral density of the resistance fluctuations and not the disturbing background noise. The feasibility of our new method is demonstrated by measurements of 1/f noise of a thin-film A1 sample.     

Method of measuring the spatial resolution of a photoresist

By analysis of the response of a high-contrast photoresist to sinusoidal illumination, generated interferometrically, one can extract a phenomenological modulation transfer function of the resist material, thereby characterizing its spatial resolution. Deep-ultraviolet interferometric lithography allows the resist response to be quantified at length scales below 100 nm. As an example, the resolution (FWHM) of the commercial resist UVII-HS is found to be approximately 50 nm. This simple method can be applied to materials under development for advanced photolithography with short-wavelength illumination.     

MR imaging of flow with locally high spatial resolution.

Locally focused magnetic resonance imaging (LF MRI) allows imaging with variable spatial resolution within the field of view (FOV). Because LF MRI uses a priori information to provide locally high resolution in regions with rapid spatial variations in intensity (e.g., blood/tissue interface), it allows accurate reproduction of intense sharp edges in the specimen without blurring and truncation artifacts. This study employs LF MRI for 3D imaging of stationary and pulsatile flow. In the implemented version of LF MRI analytically defined basis functions are used to determine image intensity in regions depicted with low or high resolution. It is demonstrated that LF MRI of flow allows a significant (i.e. 3-4 times) reduction in scan time as compared to conventional FT MRI. It is also shown that LF images of pulsatile flow have a decreased appearance of ghosting artifacts as compared to the images reconstructed by using the conventional method.     

Schlieren visualization of ultrasonic wave fields with high spatial resolution

The visualization of ultrasonic wave fields in optically transparent liquids using the acousto-optic interaction is a well proven tool for the experimental investigation of wave propagation including wave field interaction effects with certain discontinuities and obstacles like reflection, refraction, and diffraction effects as well as for transducer testing and design. For high resolution visualization of wave fields including pulsed waveforms, pulsed light sources and sensitive optical imaging sensors with certain specifications are needed. In this paper the technical requirements of optical and electronic components for high resolution visualization of ultrasound wave fields will be presented. Also, specifications and operation results of a new designed, inexpensive Schlieren optical system will be presented, which is capable of pulsed wave field visualization in the MHz frequency range. The spatial resolution is high enough, not only for accurate beam shape and wave pattern visualization, but also for a gray-scaled display of wave amplitudes including amplitude zero crossings in ultrasound pulses. Consequently, ultrasonic wavelengths can be visualized quantitatively as well as wavelength changes of the ultrasound pulses while traveling through transparent media with different sound velocities. Results to be presented will include 2 MHz and 10 MHz experiments using single transducers as well as linear arrays of commercial medical scanners during their standard operation showing the system beamforming characteristics.     

无序高空间分辨率影像快速拼接方法

遥感影像拼接技术作为影像成图的重要手段,一直是遥感领域研究的热点。在保证拼接精度的同时,如何提高拼接效率,成为低空遥感技术应急应用的难点。针对低空航空遥感影像成像姿态变化剧烈、数据量大等特点,提出针对无序影像改进的基于稀疏矩阵的光束平差SURF拼接算法,即对无序影像进行特征选取和匹配,自行判断相邻和相间位置信息,配准平差中引入稀疏矩阵进行加速。方法在保证精度的同时,极大提高了航空相机影像拼接算法的速度,能很好地解决无人机影像高建筑物的拼接错位问题。无人机倾斜数据集拼接和航空相机影像拼接的结果验证了利用本算法进行高空间分辨率影像拼接的精度和效率。     

High vacuum ionization chamber with high spatial resolution for monitoring synchrotron radiation beams

The possibility of using an ionization chamber with a cutting collectorin vacuum (10⁻⁴–10⁻⁵ Pa) for online monitoring of the position of a synchrotron radiation (SR) beam is studied experimentally The possibility of measuring the vertical position of the SR beam with a precision of up to several micrometers is demonstrated in the high vacuum conditions of an open channel in the VEPP-4M storage ring (in the absence of a beryllium window). Two such ionization chambers operating synchronously and situated one after another can serve as a basis for the SR beam stabilization system in neighboring channels.     

A device for measuring tactile spatiotemporal sensitivity

A tactile stimulator array constructed from 88 piezoelectric ceramic plates is described. The array can produce sinusoidal traveling waves with arbitrary temporal frequency, spatial wavelength, and amplitude. Detection thresholds were measured for five temporal frequencies (1, 4, 16, 64, and 256 Hz) and five spatial wavelengths (1.81, 3.62, 7.23, 14.5, and infinity mm), and were plotted as a three-dimensional, spatiotemporal threshold surface. Detection thresholds were also measured using a conventional vibrator and a large circular contactor simulating the infinite wavelength stimulus produced by the array. The results describe the spatial and temporal frequency sensitivity of the P and NP I cutaneous receptor populations.     

A highly-sensitive automatic transient laser-induced breakdown spectroscopy system with high temporal and spatial resolution

A highly-sensitive automatic transient laser-induced breakdown spectroscopy(LIBS) system is designed and integrated.It successfully avoids the delay time selecting problem in the conventional LIBS system,and realizes the LIBS data acquisition with high spatiotemporal resolution automatically.Multiple transient spectra can be obtained in each measurement,which will provide more information for spectral research.The water-vapour and liquid-water Raman scattering spectra are captured by this system,and the comparison of experimental water-vapour Raman scattering spectrum with theoretical data verifies the reliability of the LIBS system.Based on this system,the air laser induced air breakdown spectra are captured and analysed.The system is also useful for the research on water-vapour Raman Lidar remote sensing.