Applied Mechanics and Materials Vols. 121-126

Abstract: Based on the prevention of gas explosion in colliery, and the risk early-warning theory, the characteristic and reason of gas explosion is analyzed. The accident model is proposed according to gas risk mechanism; then based on the accident risk early warning principle and the organization, combines the minds of safety scientific theory and decision theory, the accident model of early-warning for gas explosion is established. Finally, it analyzes and introduces each element, and indicates the implementation, which provide theory basis for safe early-warning on production.

Abstract: The purpose of this research is to design a negative air ions (NAI) distribution for a house garden in enhancing human health. This study presented an effective approach in integrating air ion monitoring, variograms, Kriging and sprinkler experiment, based on a case study in central Taiwan. Twelve months monitoring of the air ion at thirty sample sites is an effective method for generating spatial and temporal NAI concentrations in the study areas. The measurement results showed that the lowest mean and standard deviation of NAI occurred in January. The highest mean and standard deviation value of NAI occurred in July and June. Factors that impact NAI concentration include types of NAI source, landscape layout, distances to NAI source. The ability of waterfall to generate NAI is larger than sprinkler. The area close to waterfall and far to sprinkler is high NAI concentration. Kriging estimation is useful in evaluating and mapping of spatial negative air ions patterns in a house garden. The maps showed the highest NAI next to the waterfall and lower NAI are the areas next to the entrance of the garden and residence. An experiment found that sprinkler has high ability to generate NAI through the Lenard effect. According to the map which sums up the twelve months NAI concentration, the study garden should set up three sprinklers to increase 5.28 times more NAI concentration, increases 7.56 times of mean NAI when there was any sprinkler. This study provides a hybrid approach to assess and mapping the patterns of negative air ions for future garden design with health concept.

Abstract: Intelligent green buildings are the latest development trend of Taiwan’s building industry. This research focuses on how to control the components and equipments in a building in accordance with the variation of environment and needs of users. In the research, the equipments (heat recovery ventilation, HRV) and components (top windows of ventilation tower) were automatically driven by various environmental sensors installed outdoor and indoor for controlling environmental conditions in real time. Meanwhile, it was helpful to energy saving and indoor environmental health (IEH). S house located in Chiayi of Taiwan is the object of the research. The intelligent environ-control system of S house can be divided into three parts: small weather station monitoring system, intelligent window scenario control system, and indoor monitoring and control system. The points of this research mainly are to construct a overall structure of the intelligent environ-control system, the logic and mechanism of intelligent window scenario control system, essential fresh air calculation, and the judgment on activation and operation of indoor monitoring and control system.

Abstract: Lost foam casting is a relatively new process in commercial terms and is widely used to produce defect free castings owing to its advantages like producing complex shape and acceptable surface finish. In the present research, experimental investigations in lost foam casting of aluminium-silicon cast alloy, LM6, were conducted. The main objective of the study was to evaluate the effect of different sand sizes and pouring temperatures on the porosity of thin-wall castings. A stepped pattern was used in the study and the focus of the investigations was at the thinnest 3 mm section. A full 2-level factorial design experimental technique was employed to plan the experiment and subsequently identify the significant factors which affect the casting porosity. The result shows that increasing in the pouring temperature decreases the porosity in the thin-wall section of casting. Finer sand size is more favourable than coarse size for LFC mould making process.

Abstract: In moving object positioning and tracking, the GPS positioning error is colored noise with time correlations. According to the results of time sequential analyses, the model of the positioning error can be described as a AR(10) model. In order to decrease the computations and realize the real-time positioning and tracking of the moving objects, the AR(10) model is fit to be a 2-order Markov process. The positioning data act as the measurements, the system equations are built, in which the measuring noises have time-correlation. Subtracting the adjacent measurements, the correlated portions of measurements are eliminated, and the differences of the measurements are considered to be the new measurements. The new system equations are rebuilt and the recursive state evaluation algorithm is given, in which the measuring noise is white noise. It avoids higher-order matrix inverse calculations and fewer memories are needed. The simulation results show that the 2-order Markov process can effectively fit to the GPS error model and the precision of the moving object positioning is increased.

Abstract: The dynamic model of planetary gear system was built up with the consideration of the running characteristics of variable speed and variable load of wind turbine transmission system. The expression of dynamic factor which described by external change load and deformation vibration was studied. Then, the response characteristics and dynamic load of planetary gear system of wind turbine have been studied with the consideration of changing external load and time-varying stiffness, mesh phase and nonlinear stiffness of bearing. The results show that: the frequency response of system reflects the low frequency component of external load. The influence of external incentives on sun gear and planet gear is very significant, and the distinguish between low frequency vibration and high frequency vibration is obvious. The flexibility of system has an obvious impact on dynamic load of bearing. The results lay a foundation for strength design and fatigue analysis of wind turbine gearbox.

Abstract: A poorly designed control system can lead to excessive residual vibration and long setting time. This paper investigates the effect of input shaping on control efficiency. To perform this investigation, we design a PD controller combined with input shaping for an inertia plant. We then subject it to four standard types of inputs. The responses of the control systems are described by analytical expressions. The performances of PD control and PD combined with input-shaping control are thoroughly analyzed and compared. Simulation results show that PD feedback control enhanced with input shaping minimizes overshoot and setting time.

Abstract: Micro plasma arc welding (micro PAW) was carried out AM 350 precipitation hardening alloy to produce an edge-joint weld. The application of micro PAW technique was also demonstrated in the present work. The results indicated that the arc voltage increased with increasing quantity of added hydrogen in the argon atmosphere. The collimated shape of low current plasma arc was mainly responsible for the low sensitivity of weld shape to variations in arc length. The edge welded bellows of AM 350 alloys have been successfully welded using the present micro PAW technique.

Abstract: In order to improve the durability of the wood fiber reinforced external wall board, silica fume, a kind of inorganic silica material was added in the board. The properties of the boards containing different amount of silica fume were studied. The durability was effectively characterized by determining the fracture work and bending strength after wetting-drying cycles test of the board. The results showed that the fracture work and bending strength of the board obviously increased when the proportion of silica fume and cement was 1:9~1:3.

Abstract: The sustainable development of human society makes necessary the research on and the use of RAC. For the purpose of enlarging its application range, both lowering cost and enhancing properties of RCA are worth being done. This paper aims at improving RAC’s resistance to permeability and freeze-thaw with a lower addition amount of calcined diatomite compared with silicon fume. Therefore, the main study on effects of calcined diatomite on resistance to permeability and freeze-thaw is carried out through comparison experiments. Research results indicate that the calcined diatomite of 2% added is able to decrease relative penetration coefficient by 59%, the strength loss by 4.9% and the relative strength loss by 3.3%. Obviously, the lower addition of calcined diatomite could achieve good effects, which arrived at the goal of this paper.