Applied Mechanics and Materials Vols. 333-335

Abstract: The study analyzed the hourly and daily trends of PM_2.5 concentration and summarized the spatial change in PM_2.5 concentration as well as locations of the concentration hot spots based on data of PM_2.5 concentration, wind speed, and wind direction collected at the air quality monitoring stations in 2010 at Kaohsiung City, Taiwan. Results from the correlation analysis of PM_2.5 concentration suggest that for short-term (1-hr), PM_2.5 concentration could be easily affected by pollution sources around the monitoring stations, due to the atmospheric dispersion, the trends of long-term concentration change among stations were similar (24-hr). The average annual PM_2.5 concentration at Kaohsiung City was 41 μg/m³, and the annual over-standard rate was 13.08% compared with the alert concentration value of 65 μg/m³. The average 24-hr PM_2.5 concentration was the lowest in summer (23 μg/m³) but the highest in winter (62 μg/m³). Concentration change was also the greatest in winter, and nearly 40% of the winter time the concentration was over-standard. Results of this study suggest that higher PM_2.5 concentration would mainly happen with the winter monsoon (north wind), while lower PM_2.5 concentration would mainly happen with the summer monsoon (southwest wind). Furthermore, Daliao and Linyuan monitoring stations at Kaohsiung City are the hot spots with the highest concentration. The results also suggest that the environmental agency should further assess influences from these high PM_2.5 concentration hot spots on local people and formulate effective strategies for pollution emission control.

Abstract: In order to solve the problem of field fault detection for engineering vehicle, we introduce a new networked portable fault diagnostic system based on PDA. The architecture of the system is presented. The system consists of dual-tier architecture. The first tier server is based on the related technical database of engineering vehicles, and the second tier one is the technical information database downloaded from the manufactures technical resources with PDA as the terminal for maintenance technician. The system function includes information query, user interaction, data downloading and uploading as well as network communication. The software platform is composed of Microsoft SQL Server Compact (SQL CE) database, application software on PDA and computer. Meanwhile the hardware platform is mainly composed of desktop PC or dedicated server, PDA mounted with cradle, data acquisition card as well as PCMCIA network adapter and so on. Both wireless communication and USB interface are adopted in the system. It has been used in many military units. The application demonstrates that the PDA-based networked fault diagnosis system of vehicles is beneficial to data query, fault elimination and repair capability of engineering vehicles.

Abstract: Inspired by the personal monitoring method in the anti-collision section drilling, the cluster well anti-collision monitoring and early warning system are developed to prevent the well bore collision in the drilling process. Distance prediction model of the warning system is developed based on the theory of elastic waves in spherical spreading and absorption attenuation. By monitoring the well casing vibration and then the data processing, the relative distance between the drill bit and adjacent well casing is obtained in real time. If the estimating possibility of well collision is occurred, then the alarm is given. The results show that the measurement model was effective in shallow strata for anti-collision warning. The model can improve the effect of present anti-collision monitoring, and provides a guarantee for the safe and efficient drilling.

Abstract: Crack formation is a severe problem concerning steel structures under service loading. Understanding of the mechanism of crack initiation and propagation is therefore critical to structure safety design and maintenance. Although many efforts were put into crack mechanism studying, and some progress has been made in the aspect of crack propagation, the problem of crack initiation i.e. cracking remains left unsolved. In this paper, an inverse modeling method for acoustic emission (AE) source of cracking was proposed for the mechanism revelation. In the method, AE signal was related to crack stress based on the theory of elasto-dynamics; the crack stress was inversely modeled from AE signal by half-space Greens function and procedure of de-convolution. In an application to the AE testing for steel structure cracking, AE source function representing the time history of crack stress was obtained. The crack stress was found to be a step-like function with a pulse, and with it the mechanism of cracking was recovered. The results indicated that, the modeling method is effective for the study on mechanism of cracking.

Abstract: The expert system for fault diagnosis based on classified hierarchical model is addressed so as to improve the maintenance capability of engineering vehicles under complex battle environment. The analysis of fault feature, fault pattern and failure mechanism of the whole machine and its electrical system is accomplished. Furthermore, the structure of classified hierarchical diagnosis model and method of knowledge representation are implemented so that the knowledge base of the fault diagnosis system can be developed. The forward reasoning mechanism of the fault diagnosis expert system is bring forward based on neural network intelligent reasoning that can achieve fuzzy input and multiple fault diagnosis. This work effectively increases the fault maintenance, diagnosis and support capabilities of the military troops.

Abstract: For the improvement of reliability, safety and efficiency advanced methods of fault diagnosis, new technology and method such as expert system become increasingly important for many kinds of fault diagnosis. Thereby, the classification principle of system structure is used to build the hierarchical analysis model of combustion engine. The model is converted to binary fault tree by means of Fault Tree Analytical Method (FTA). Meanwhile, the knowledge base is constructed with production rule and frame representation. Fault diagnosis system is designed on the thought of analytical hierarchy process. Its development is accomplished by Delphi 7.0 language. The work has offered a simple and practical tool to users and brings great convenience to engineering corps.

Abstract: The wear and tear allowances (displacements) of axial thrust bearing in air compressor was diagnosed and predicted, applying the model of artificial neural network (ANN), and compared with the traditional method of diagnosis and prediction. It showed that the results of diagnosis and prediction are more precise than that of traditional method. It can diagnosis and predicts the wear and tear allowances of axial thrust bearing better.

Abstract: In the process of equipment support for diesel engine control system of a certain type of ship, aiming at the problem of fault location of circuit module is complex and low efficient, the circuit module fault tree of control system is established based on fault tree theory. Qualitative and quantitative fault analysis is processed. The control module fault analysis software is researched and developed. The practical application shows that the functional fault control module can be analyzed and diagnosed fast and accurately. And the control module fault can be accurately positioned and processed.

Abstract: In order to solve the problems that diagnosis cycle is very long and diagnostic accuracy is very low dependent on the maintenance man to diagnose fault by experience, an expert system for fault diagnose of a planes airborne electronic devices based on VC++ and CLIPS is proposed. The information exchange is realized between VC++ and CLIPS through writing external function of CLIPS by VC++ platform. The fact base can be generated quickly through acquiring test parameters from test model according to the fault information template base. The expert system established by VC++ platform to write man machine interface codes and load CLIPS to realize fault reasoning can realize the fast fault diagnosis for the airborne electronic devices.

Abstract: Sand production is a serious problem nowadays during the exploitation of oil wells. The mainly research of sand production is focus on the mechanism of sand production and sand prediction, which cant monitor sand production continually and effectively. So a sand monitoring system is needed. The sand monitoring methods mainly contain ultrasonic method and electrical resistant method,but they both have limitations. An intrusive surface vibration sand monitoring system can collect high-frequency vibration signal caused by sand impact using acceleration sensor and then the signal is analyzed in time-domain and frequency domain through special computer software. The system simulates the signal signature of the crude oil in different sand content, velocity of flow and oil temperature under laboratory conditions. The tests show clearly that the s system can perceive the changes in the conditions of fluid.