Applied Mechanics and Materials Vols. 58-60

Abstract: In recent years, the typhoon happens frequently. When typhoon suddenly arrives, the only way to rescue the ship which calls for help in time is to locate the position of the ship in the sea quickly and exactly. But in the ocean, due to the non-ideal channel environment, multipath propagation between accident vessels and monitor stations. All these factors will make the detection of error in measurement of signal characteristics, thus affecting the positioning accuracy. In order to improve the location accuracy of accident vessel in the ocean, two kinds of methods are used. One is to search for realistic channel environmental models for the line-of-sight and the non-line-of-sight propagations to study the characteristics of signal measurements error with good robustness of high-precision positioning algorithms.The other is to analyze the main cause of the different kinds of the measurement errors to find their solutions to decrease the errors.

Abstract: Stewart platforms have recently attracted attention as simulator and machine tools because of their conceptual potentials in high motion dynamics and accuracy combined with high structural rigidity due to their closed kinematic loop. Dynamics design of Stewart platform based on Newton-Euler is presented in this paper firstly. Its aim is to compute the velocity and acceleration according to the index given. Meanwhile, the matching rule is put forward in the design of hydraulic power unit, which requires the power capacity of driving units surround the edge of payload. Based on these principles, optimal driving can be obtained practically. This paper, composed of driving units design and optimization, attempts to ground the foundation on dynamics design and choice in the future.

Abstract: This paper presents an algorithm to develop a mission-based optimal joint space control for a Stewart manipulator. The proposed algorithm consists of two optimization phases. The first phase seeks an inverse kinematic model and controller for the closed loop control of a Stewart manipulator using a feedback value. The second phase optimally tunes the controller called amplitude phase control (apc) in order to meet special mission requirements. Iteration algorithm is used in this phase as the optimization method. The proposed amplitude phase control optimal joint space control shows the capability to reduce the error in tracking the sin signals.

Abstract: Stewart platforms have recently attracted attention as simulator and machine tools because of their conceptual potentials in high motion dynamics and accuracy combined with high structural rigidity due to their closed kinematic loop. This paper, composed of inverse kinematic design and optimization, attempts to ground the foundation on dynamics design and choice in the future.

Abstract: The purpose of this paper is to develop an approach to improve the tracking characteristics of a single axis shaking table actuation system, which is used in active structural control system. Firstly, the process of constructing analytical model of servo-hydraulic actuation system is presented. The proposed model, in the form of the total shaking table transfer function, accounts for the specific physical characteristics of the single axis shaking table. Due to low natural frequency and small hydraulic actuator damping, the single axis shaking table cannot meet the experimental requirement Therefore, three states feedback and three state feed-forward control algorithm based on pole-assignment principle is applied to extend the acceleration bandwidth. Lastly, the shaking table experiments are tested and the experimental results indicate that the controller is effective and reliable.

Abstract: The modulation technologies of L1 signal in GPS/Galileo system have reached many achievements. The chaotic-BOC modulation showed the new usage of signal modulation in Galileo satellite communication. The Lü system (LS) chaos sequence has perfect chaotic characteristic in three -dimension discrete dynamic systems; especially the three-dimension data can be three orthogonal components. From the acquisition and positioning of L1 signal, the chaotic-BOC modulation technology was a right way to choose. The positioning way need the three parameters of the satellite at least here just use the three-dimension chaos system which could be used the three received signals demodulated to get the synchronized signals. These three parts used the Lü system chaotic sequence to solve the spread spectrum communication. Some simulation figure and data illustrated the chaotic system performance which approached to the original PN in GPS/Galileo system. As L1 signal is for civil application and open service, the chaotic way was significant for the future use.

Abstract: Four clusters were classified according to the similarities and dissimilarities of water quality data collected from 1998 to 2008 of the 76 monitoring wells in Pingtung Champaign. The results showed that the groundwater quality of hinterland was better than that of coastal area. Some wells along the coastal areas have already been influenced by seawater intrusion incurring aquifer salinization. The overall grouping accuracy of cluster analysis (CA) for rainy and dry seasons was 95.8% and 97% according to the discriminant analysis, respectively. The results from the back-propagation neural network (BPNN) model showed no significant variations of nitrate (NO₃-N) between the estimated and observed data, however most of the estimated total organic carbon (TOC) data were higher than the observed ones. It meant that the groundwater quality may be susceptible to the impacts of organic pollutants in the future within 90% confidence intervals. The results of this study show that application of CA and BPNN can simplify complex non-linear systems, moreover, groundwater quality can be estimated and modeled via monitoring data over the years. The modeling results can be utilized to frame the corresponding strategies to reduce the monitoring cost and to enhance the cost-effective benefits. The proposed analysis methods can be referred as a management plan for groundwater resources and pollution prevention to achieve the goal of early warning.

Abstract: This study utilizes the river and stream water quality (QUAL2K) model as a tool to simulate and forecast the water quality and then to develop the management strategies for various flow rates above the Kaoping weir of Kaoping River in Taiwan. Model results based on the river assimilative capacity of four various flow rates including Q₉₅, Q₇₅, Q₆₀, and Q₂₅ were conducted to determine the corresponding amounts of pollution reduction. The average pollution reduction ratios of biochemical oxygen demand (BOD₅) and ammonia nitrogen (NH₃-N) should at least reach to 42.0% and 28.3% respectively to meet the restoration goals of Class A water quality standards regulated by Taiwan. The modeling results demonstrate that an increase of water extraction rates in the upstream reaches will have significant adverse effects on the water quality of the Kaoping River. Higher water extraction rates will lower the assimilative capacity that reduces the buffering capacity of river. It also induces that the water quality is susceptible to the impacts of the influent pollutant loads from the tributaries or drainages.

Abstract: This paper firstly analyzed the urgency and technical support of the establishment of a noise monitoring system, then analyzed the three-tiered architecture of the noise monitoring system, and designed the function and database of the system. Based on this, this paper designed and developed the noise monitoring system using the technology of WebGIS, implemented the integration of GIS and noise monitoring system in the Web.

Abstract: Large-scale thermal power units in the main steam temperature as the controlled object with a large delay, large inertia, nonlinear and time-varying characteristics, leads to its control difficult, and make traditional PID control method is difficult to achieved good. Fuzzy systems articulate knowledge, reasoning similar to the human mind the advantages of fuzzy PID control strategy is proposed and used as a powerful mathematical ability of fuzzy PID control system simulation, the result indicate the fuzzy PID algorithm has the ability of fast, immunity, and robust.