透平机械动叶片的振动状态非接触测量分析

现代工业和生活中广泛使用的透平机械正向着大功率,高负载的趋势发展。透平机械中的叶片长度和叶尖线速度都不断提高。准确地测量叶片实际振动的频率和振幅已成为透平机械的一个重要研究方向。以间断相位法为理论基础的非接触式测量方法具有很强的实际应用价值。利用间断相位法可以得到叶片低阶振动的许多特性,对叶片的设计和安全运行具有很重要的意义。

Imposing Active Sources during High-Frequency Passive Surface-Wave Measurement

Passive surface-wave utilization has been intensively studied as a means of compensating for the short-age of low-frequency information in active surface-wave measurement, In general, passive surface-wave methods cannot provide phase velocities up to several tens of hertz; thus, active surface-wave methods are often required in order to increase the frequency range, To reduce the amount of field work, we pro-pose a strategy for a high-frequency passive surface-wave survey that imposes active sources during con-tinuous passive surface-wave observation; we call our strategy ＂mixed-source surface-wave （MSW） measurement,＂ Short-duration （within 10 min） passive surface waves and mixed-source surface waves were recorded at three sites with different noise levels： namely, inside a school, along a road, and along a railway, Spectral analysis indicates that the high-frequency energy is improved by imposing active sources during continuous passive surface-wave observation, The spatial autocorrelation （SPAC） method and the multichannel analysis of passive surface waves （MAPS） method based on cross-correlations were performed on the recorded time sequences, The results demonstrate the flexibility and applicability of the proposed method for high-frequency phase velocity analysis, We suggest that it will be constructive to perform MSW measurement in a seismic investigation, rather than exclusively performing either active surface-wave measurement or passive surface-wave measurement,

A robust system for real-time pedestrian detection and tracking

A real-time pedestrian detection and tracking system using a single video camera was developed to monitor pedestrians. This system contained six modules: video flow capture, pre-processing, movement detection, shadow removal, tracking, and object classification. The Gaussian mixture model was utilized to extract the moving object from an image sequence segmented by the mean-shift technique in the pre-processing module. Shadow removal was used to alleviate the negative impact of the shadow to the detected objects. A model-free method was adopted to identify pedestrians. The maximum and minimum integration methods were developed to integrate multiple cues into the mean-shift algorithm and the initial tracking iteration with the competent integrated probability distribution map for object tracking. A simple but effective algorithm was proposed to handle full occlusion cases. The system was tested using real traffic videos from different sites. The results of the test confirm that the system is reliable and has an overall accuracy of over 85%.

Event-Related Potentials Measurement of Perception to 3D Motion in Depth

An approach to the direct measure of stereoscopic （3D） videos with different accelerations was presented, using electroen- cephalography （EEG）. In the study, subjects viewed 1-sec-long video clips with a stone ap- proaching straightforward and were required to perceive whether they were able to catch the outline of stone. Peak amplitude of each part was extracted from PO3 electrode located at the occipital region corresponding visual processing and cognition. Three components were conspicuously observed in the periods： 650-800 ms, 800-900 ms and 1150-1250 ms, which were called N310, N480 and N810 in this paper. N310 related to the perception to the initial stage of movement. Movement in- depth could be immediately perceived when initial speed was not less than 3 m/s. N480 related to the perception to acceleration/decel- eration. N810 related to the perception to the point a movement was about to vanish. Sub- jects couldn＇t perceive the outline with the fi- nal speed more than 3 rn/s. For 3 m/s, subjects were in a dilemma to judge with the detecting rate 54%. Together, component analysis com- bined with behavioral results, it was supposed that 3 m/s to be the threshold to completely perceive the outline.

Quantitative Surface Chirality Detection with Sum Frequency Generation Vibrational Spectroscopy： Twin Polarization Angle Approach

Here we report a novel twin polarization angle （TPA） approach in the quantitative chirality detection with the surface sum-frequency generation vibrational spectroscopy （SFG-VS）. Generally, the achiral contribution dominates the surface SFG-VS signal, and the pure chiral signal is usually two or three orders of magnitude smaller. Therefore, it has been difficult to make quantitative detection and analysis of the chiral contributions to the surface SFG- VS signal. In the TPA method, by varying together the polarization angles of the incoming visible light and the sum frequency signal at fixed s or p polarization of the incoming infrared beam, the polarization dependent SFG signal can give not only direct signature of the chiral contribution in the total SFG-VS signal, but also the accurate measurement of the chiral and achiral components in the surface SFG signal. The general description of the TPA method is presented and the experiment test of the TPA approach is also presented for the SFG-VS from the S- and R-limonene chiral liquid surfaces. The most accurate degree of chiral excess values thus obtained for the 2878 cm^-1 spectral peak of the S- and R-limonene liquid surfaces are （23.7±0.4）% and （-25.4±1.3）%, respectively.

Vibration Characteristics of Detached Houses in Japan by Onethird Octave Band Frequency to Environmental Vibration Estimation

In recent years, the complaints against the vibration as environmental pollution tends to increase gradually in Japan. The measurement investigation to demonstrate the actual situation of the environmental vibration was carried out for several years. The measurement manual for each vibration source such as operations of factory machine, construction works, road traffics and railways to unify measurement methods was made at the start. From the measurement investigation, the vibration amplification characteristics of the detached house by one-third octave frequency in Japan was analyzed as a purpose to improve estimated precision of the vibration in a detached house. In this paper, the vibration amplification characteristic expressed at onethird octave band frequency was shown, and the characteristics was arranged about a result measured with 27 detached houses in Japan.

Dynamics of quantum zeno and anti-zeno efects in an open system

We provide a general dynamical approach for the quantum Zeno and anti-Zeno effects in an open quantum system under repeated non-demolition measurements. In our approach the repeated measurements are described by a general dynamical model without the wave function collapse postulation. Based on that model, we further study both the short-time and long-time evolutions of the open quantum system under repeated non-demolition measurements, and derive the measurement-modified decay rates of the excited state. In the cases with frequent ideal measurements at zero-temperature, we re-obtain the same decay rate as that from the wave function collapse postulation （Nature, 2000, 405： 546）. The correction to the ideal decay rate is also obtained under the non-ideal measurements. Especially, we find that the quantum Zeno and anti-Zeno effects are possibly enhanced by the non-ideal natures of measurements. For the open system under measurements with arbitrary period, we generally derive the rate equation for the long-time evolution for the cases with arbitrary temperature and noise spectrum, and show that in the long-time evolution the noise spectrum is effectively tuned by the repeated measurements. Our approach is also able to describe the quantum Zeno and anti-Zeno effects given by the phase modulation pulses, as well as the relevant quantum control schemes.