Applied Mechanics and Materials Vol. 607

Abstract: In order to effectively extract nonstationary and nonlinear fault signature of hydropower units’ signals, a new method, based on Hilbert–Huang transform (HHT), is proposed. This method is used to carry out EMD (Empirical Mode Decomposition) analysis and Hilbert transform of signals firstly and then extract Hilbert spectrum to provide a basis for signal feature extraction. The vibration signal of upper brackets in hydropower units has been put forward with experimental analysis. The results suggest that the EMD can decompose vibration components in different frequency domain, which has intuitive physical meaning. Moreover, Hilbert spectrum also has a good resolution in time domain and frequency domain. Thus, HHT can be used to depict the fault signals effectively and lay the foundation of the fault pattern recognition.

Abstract: In the field of computer vision research, object feature detection and matching algorithm become a hot. Aiming at SIFT algorithm and SURF algorithm cannot meet the needs of real-time application, a feature point detection and matching algorithm based on orient FAST detector and rotation BRIEF descriptor is used. The experiments demonstrate that, this method not only remains the advantages of SURF but also improves the detection speed, and it can fully applicable to the field of computer vision to detect moving targets.

Abstract: The polyurethane sheet is an important part of automotive interior trim. For a long time, the measurement and recording are both accomplished by hand. It has problems such as low measuring precision, low working efficiency. Accordance with the existed problem of polyurethane sheet measurement, we developed an online measurement for polyurethane sheet and code-spurting system. The system measures the thickness through two channels using laser displacement sensors. PLC collects data and controls the alarm device. Weighing is completed by belt scale and weighing instrument PT650D. Host computer software communicates with slave computer through serial interface. It not only makes data processing and storage function true, but also can make database operations such as data query, statistics and so on. In order to be convenient for quality tracing, the system sets and prints a number for each block. It also can print irregular information such as thickness and weight.

Abstract: Visibility monitoring under foggy condition is very essential to traffic safety on expressway. The definition and influence factor of visibility are summarized. The main advantages and disadvantages of three common methods- transmission method, scattering method, digital imaging method and related visibility meters are analyzed and compared here. The domestic and foreign status and trends of visibility research on foggy expressway are mainly introduced from thick fog forecast, warning and monitoring system, visibility detection device. Aiming at the existing problems of visibility monitoring in expressway, some suggestions for improvement are put forward at last.

Abstract: Annual average daily traffic (AADT) serves the important basic data in transportation sector. Future level of service is forecasted, based on design traffic volume. AADT is used as design traffic which is the basic traffic volume in transportation plan. But AADT is estimated using short duration traffic counts at most sites because permanent traffic counts are installed at limited sites. A various of methodologis about short duration traffic counts are used to estimate AADT. This study compared with typical short duration traffic counts methodologies in USA and Korea. Short duration traffic counts in USA typically are defined as stations where 24-hour, 48-hour of data is collected. In Korea, short duration traffic counts are collected at one day (24-hour) or two days (not two consecutive days). So this study compared among each short duration traffic counts methodology: one day (24-hour), two consecutive days (48-hour), not two consecutive days (twice per year). Short duration traffic counts surveyed twice per year is the best method to reduce AADT estimation error among analyzed methodologies. The analysis found that in case adjustment factor is applied to estimate AADT, AADT estimation error is further lowered.

Abstract: This study investigates the characteristics of eye movements by operating flat knitting machine. For the objective evaluation purpose of the flat knitting machine operation interface, we arrange participants finish operation tasks on the interface, then use eye tracker to analyze and evaluate the layout design. Through testing of the different layout designs, we get fixation sequences, the count of fixation, heat maps, and fixation length. The results showed that the layout design could significantly affect the eye-movement, especially the fixation sequences and the heat maps, the count of fixation and fixation length are always impacted by operation tasks. Overall, data obtained from eye movements can not only be used to evaluate the operation interface, but also significantly enhance the layout design of the flat knitting machine.

Abstract: Edges of images contain important information such as form, size, and location of objects. Thus, edge detection is an extremely important factor in image processing. In order to detect such edges, much research has been carried out, and edge detectors such as Sobel, Prewitt, Robert, Canny, and Laplacian of Gaussian (“LoG”) are universally used. This Research compares and analyzes the crack extraction function of each edge detector to automatically detect cracks occurring in concrete structures. In order to do this, simulated crack samples of various widths and contrasts were produced and attached to concrete walls, and crack images were taken from different distances. Cracks were extracted from the images taken using edge detectors like Sobel, Prewitt, Robert, Canny, and LoG, and the crack extraction performance of the edge detectors used were compared and analyzed based on the photographed distance.

Abstract: Dynamic strain acquisition technology is becoming increasingly important in industrial production. Compared with the static strain acquisition technology,the dynamic stain acquisition technology provided a much wider range of frequencies from 0~100KHz which required a much more accurate data acquisition system. This paper proposed an accurate data acquisition system which included electric bridge、constant current source、signal amplifier and anti-aliasing filter. This system has largely suppressed noise and increased the performance of the dynamic strain acquisition.

Abstract: Set the alarm value in the condition monitoring system of hydropower unit to monitor unit state parameters, if the difference between the two values exceeds the safety threshold, the alarm works, it is an effective method. Now the state parameters alarm values are set up mainly for the stable operation area in the unit condition monitoring system, which were not suit for low load conditions and in the process of load. To realize the full condition dynamic alarm of hydroelectric generating units, they are two ways: (1), build unit state parameter prediction model, compared predict values with the measured values. (2), set the alarm line, when the measured value exceeds the alarm line, the alarm works,. These two methods are considered the working condition head and output .This paper introduces several different alarm line settings, such as line alarm, partition line alarm, dynamic alarm curve and dynamic alarm surface.

Abstract: Energy consumption is a main area in wireless sensor network researching. Interior monitoring system is designed by organized ZigBee wireless network. Address assignment mechanism is put forward and the result about sensor nodes is displayed. Aiming at the problems of LEACH algorithm that all nodes will be assigned cluster head, this paper proposes the algorithm that cluster head projected in first every round is effective until the next round so that reducing energy consumption in competition about cluster head. Through the simulation test, network address assignment is normal, data can be displayed through LED, and network telecommunication is stable.