Lei Hu

Imaging of Transmission Equipment Based on Block Compressed Sensing

Imaging the overhead transmission equipment with high-resolution is very important to intelligent inspection, which is the prerequisites for fault diagnose. The intelligent inspection system often takes traditional imaging process of data acquisition followed by compression, which leads to the waste of image data and memory resources. We adopt an imaging method based on block compressed sensing to image the transmission equipment, the simulation results show that even if we only compressively sampled with 12.5% of the fully acquired image data, the image still can be recovered with high quality.

A New Method for Vibration Signal Analysis Using Time-Frequency Data Fusion Technique

To overcome the inherent deficiencies of conventional time-frequency analysis (TFA) methods, i.e., different TFA methods or the same TFA method with different control parameters will present different results for the same target signal, a novel scheme named as the time-frequency data fusion (TFDF) is developed in this study by extending the idea of data fusion technique. The TFDF technique can present a more accurate time-frequency presentation for the target signal than what can be achieved by any individual TFA method. Therefore, the TFDF has potential to render a significantly improved time-frequency representation and greatly facilitates extracting time-frequency features of target signals. This will promote the applications of TFA in engineering practices and make TFA methods more acceptable to field engineers. The effectiveness of the TFDF technique is validated by three numerical case studies and the analysis of a rubbing-impact signal collected from a rotor test rig.

Comparative Study on Design of Exposed Penstock Laid on Ground Using Chinese and American Specifications

In this paper, differences by using selected three typical specifications—DL/T 5141-2001 (Chinese), ASCE No.79 in the version of 1993(American) and ASCE No.79 in the version of 2012 (American)—in structural design of exposed steel penstock were explored. A practical example about exposed penstock laid on ground applied in hydropower station was also used to analyze specifications clearly. The result shows that the main differences between Chinese and American specifications are allowable stress and load combination. The former is direct factor of calculating exposed penstock shell thickness. Therefore, ASCE No.79 (2012) designs the minimum wall thickness, followed by DL/T 5141-2001 and the last is ASCE No.79 (1993), which is correspondingly contrary to sort by allowable stress. Basically, ASCE No.79 (2012) defines lower safety coefficient for exposed penstock, which is identical with authoritative rules of pressure vessels in the U.S.A and EU. The safety of DL/T 5141-2001 has been proved via rich engineering experience and this specification is recommended for Chinese projects. Besides, ASCE No.79 (2012) is recommended.

Trajectory Planning for the Moving Boundary in Three Dimensional DEM Simulations

The boundary objects moving along a prescribed trajectory commonly appear in the applications of DEM to industrial fields. Generally, a boundary motion can be expressed as the combination of translational and rotational motion through specifying the linear and the angular velocity. However, it is unsuitable to describe the trajectory by this way because of the instantaneously changing location and velocity of the boundary during the simulation. A trajectory planning method is presented to model the arbitrarily complex route where the boundary passes through. This method has been used to predict the digging process of an excavator bucket in this paper. The simulation results show that the complex trajectory of a boundary object can be accurately depicted by the trajectory planning method, and the interaction between the moving boundary and the particle system is reasonable.

Methods to Recognize Special Tags in UHF RFID System

With the emerging of UHF RFID, people pay more and more attention to the recognition and selection of multi-tags. As for the recognition problem, it has already been relatively perfectly solved by anti-collision method. But we still lack mature methods to recognize special tags. This article summarizes and discusses two available solutions: one is to adopt accumulative total count distinguish method; the other is to make use of Low-frequency sensei technology.

A New Method for Extraction of Signals with Higher Order Temporal Structure

This paper addresses the problem of semi-blindly extracting one single desired signal using a priori information about its higher order temporal structure. Our approach is based on the maximization of the auto-correntropy function for a given time delay. Those values provide information which allows the proposed method to adapt a demixing vector to extract the desired signal without the indeterminacy of the permutation problem in blind source separation. Moreover, this method is different from those for Independent Component Analysis that separate all the available sources, which in some problems, is not desirable or computationally possible. Also, the flexibility brought by the Kernel size selection allows the user to choose the range of statistics he is interested in. We show in simulations that correntropy achieve better or equal separation than other linear methods proposed in the literature for source extraction based on temporal structures.

Simulation and Research of the EAF Characteristics under Voltage Flicker Using MATLAB

Ower quality is becoming a more concern of today’s power system engineer due to the rapid growth of non-linear loads, such as power electronic control equipment and electric arc furnace (EAF). Harmonics and voltage flicker are the power quality problems which are introduced to the power system as result of non-linear behavior of the electric arc furnace operation. There are numbers of arc furnace models. This paper presents a time domain model which is used to study its behavior on the power system using MATLAB. To analyze the method, several characteristics for different operating conditions are investigated.

Acoustic Emission Monitoring Technology Used in the Ceramics Grinding Cut Depth Control

Precision grinding on brittle materials accomplished without generating subsurface fracture damage is called ductile-regime grinding. The most important key point for maintaining a ductile material removal regime is to ensure that the cut depth made by grinding process does not exceed the critical cut depth. Through collecting and processing the acoustic emission(AE) signals generated by zirconia (PSZ) ceramic grinding tests, and analyzed the characteristics of AE signals under different grinding parameters. As a result of the experiments described in this paper, it can be concluded that AE signals measured during micro-grinding are sensitive to the changes of cut d- epths. The relationship between AE signals and material removal regime could lead to an in-process sensing strategy of the cut depths for ensuring grinding processes under ductile regime.