Applied Mechanics and Materials Vol. 455

Abstract: In this note, the stability of restricted homological dimensions of complexes over commutative noetherian local ring is discussed. For instance, let R be a Cohen-Macaulay ring and X, Y . If X is bounded below with Gpd, Y is bounded above and =0 for all , then Rfd=Rfd+Rfd.

Abstract: For the frost heave deformation of ground heat exchanger with U-type heat exchanger pipe in subzero condition, a numerical calculation method was proposed by describing constitutive equations and establishing physical model. The finite element simulation study based on ABAQUS code was carried out to explore frost heave deformation behavior of saturated soil and interaction between pipe-soil interfaces ,focuses on the deformation of U-type pipe cause by saturated soil frost heave squeezing under the condition of different cooling rate.The distribution and change law of temperature,displacement, stress and strain on U-type heat exchanger pipe and soil were acquired.

Abstract: The research object is a micro heat exchanger (MHT) applied in chip cooling, a three dimensional simulation model is developed to analyze the transient heat transfer of the exchanger according to both exponential and periodic heat fluxes. Based on the computational results of the profiles of temperature and thermal stress, a comparison of performance of heat exchangers made of copper and silicon nitride compound is carried out. The results indicate that the capability of a copper heat exchanger is better than that of a silicon nitride exchanger under low load working condition due to the excellent thermal conductivity of copper. However, with large load fluctuations, the advantage of structure strength of compound makes the exchanger attractive since it has lower thermal stress and could guarantee a long-term stability. The efforts of this paper are referable for further research and development of micro heat exchangers.

Abstract: In this paper, the feedback control problem is considered for a class of parabolic distributed parameter systems (DPS). By employing a new Lyapunov-Krasovskii functional as well as the linear matrix inequality (LMI), a novel feedback controller is developed, which can guarantee the closed-loop system states uniformly convergent to zero. The stability conditions for closed-loop systems can be easily checked by utilizing the numerically efficient Matlab LMI toolbox. At last, a numerical example shows the effectiveness of the presented LMI-based methods.

Abstract: Detection of Frame difference fails when the human target is stationary in course of moving, this paper presents a method based on combination of adaptive difference and GVF-snake algorithm to solve it. Adaptive differential detection algorithm can accurately extract the target contour, and use it as the initial contour of GVF-snake model which cannot automatically extract it after we got the target. In the process of detection and tracking, calculating GVF field of the whole picture consume too much time, so we use the method of sub-region to improve the real-time. The experimental results show that, the algorithm can provide the actual body contour for GVF-snake model, and effectively track whether the target is stationary or moving.

Abstract: Through analyzing the carrier meter reading system functions, characteristics, composition, Introduced the application of carrier meter reading technology in the power management system. As the carrier meter reading technology continues to improve, electricity management more standardized and scientific, automatic meter reading system technology will be a important means in low voltage automatic management and improving the service level.

Abstract: Jacobian matrix plays a crucial role of kinematic synthesis of a parallel mechanism, however, can not directly be used for its nonhomogeneous physical units. This paper proposes the detailed formulation of the dimensionally homogeneous analytical Jacobian of 3PRS parallel mechanism. After defining a kinematic index and the design variables, the sensitivity that the index varies with dimension parameters is performed. Based on the two chosen case, it is also conducted that the index distributes in the prescribed workspace. Then, the kinematic characteristics of the system are discussed. These results provide the informative insight for choosing the optimal solution of the dimension parameters of 3PRS.

Abstract: Dynamics formulation is a primary task for dynamic optimization, control strategy design and servomotor parameters estimation of the parallel manipulator (PM). In this paper, by using the simple operation form of reciprocal screw and Lie Algebra, the compact expressions of complete Jacobian and Hessian matrix are derived. Then the inverse dynamics of 3PRS parallel manipulator is formulated based on the efficient principle of virtual work. In this model, the generalized forces of both actuation and constraint can be solved. Finally, a numerical simulation example is given to demonstrate this simple yet effective approach.

Abstract: Maximum-likelihood (ML) and its relaxation algorithm are discussed which are used to identify the mathematics model of an Underwater Vehicle (UV). With trial data of zigzag tests, the hydrodynamic derivatives of the UV were estimated, and the better astringency of the relaxation algorithm can be acquired from the contrast between the two methods. A simulation environment based on these parameters is established to verify the validity and effect of these methods. The result shows the model is credible and the methods are very useful for the research of maneuverability and intelligent control of underwater vehicles.

Abstract: This design is a short-range wireless transmission module based on nRF2401, which carries out the data acquisition, short-range wireless transmission, the data display and the port communications between computer and MCU via RS232 serial port. The sensor node circuit based on nRF2401 module was implemented in the paper. The main communication flow chart is described in detail.