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141.
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144.
Impacts of structural-acoustic coupling on the performance of energy density-based active sound transmission control 总被引:2,自引:0,他引:2
S.K. Lau 《Journal of sound and vibration》2003,266(1):147-170
This paper investigates numerically the performance of the active sound transmission control into a rectangular cavity through a flexible panel under the energy density-based error-sensing algorithm. Full coupling between the sound transmitting panel and the enclosed space is considered. A pure vibration actuator, a pure acoustic source and a combined control source system are used as the secondary control source in the active control and their performances are studied. Formulae for the coupled eigenfrequencies of the cavity and the flexible panel are also derived. The strength of the structural-acoustic coupling, the ratio between the first eigenfrequencies of the cavity and the panel and the difference between the excitation frequency and the coupled eigenfrequencies, especially the latter, are found to have crucial impacts on the performance of the active control regardless the type of control source used. 相似文献
145.
Double adaptive notch filter for mechanical grain flow sensors 总被引:2,自引:0,他引:2
Nowadays, commercial combine harvesters are equipped with special sensors for the purposes of precision farming. Sensors are installed to measure the harvested surface and mass flow each second. Hence, grain yield maps are constructed, approximating the actual grain yield on the field before harvesting.Most grain flow sensors are installed on the paddle elevator before storage in the grain tank. At the elevator exit, paddles throw packs of grain against a curved plate on which a force transducer is attached. Therefore, the measured flow signal is heavily disturbed by the paddle rate and resonance frequency of the mechanical sensor.In this study, a computationally cheap method is presented to track both frequencies in the measured flow signal. Based on these frequency trackers, a double notch filter is tuned continuously to remove both disturbances. Moreover, the knowledge about the frequency content can be used to monitor the condition of the mechanical sensor and the paddle elevator. 相似文献
146.
The classical economic order quantity (EOQ) model assumes that items produced are of perfect quality and that the unit cost of production is independent of demand. However, in realistic situations, product quality is never perfect, but is directly affected by the reliability of the production process. In this paper, we consider an EOQ model with imperfect production process and the unit production cost is directly related to process reliability and inversely related to the demand rate. In addition, a numerical example is given to illustrate the developed model. Sensitivity analysis is also performed and discussed. 相似文献
147.
148.
Various problems associated with optimal path planning for mobile observers such as mobile robots equipped with cameras to obtain maximum visual coverage of a surface in the three-dimensional Euclidean space are considered. The existence of solutions to these problems is discussed first. Then, optimality conditions are derived by considering local path perturbations. Numerical algorithms for solving the corresponding approximate problems are proposed. Detailed solutions to the optimal path planning problems for a few examples are given. 相似文献
149.
A pseudopotential depending on an effective core radius is proposed to study the binding energy, equation of state, ion-ion
interaction, phonon dispersion curves (q-space and r-space analysis), mode Grüneisen parameters and dynamical elastic constants
of some fcc f-shell metals La, Yb, Ce and Th. The contribution of the s-like electrons is calculated in the second-order perturbation
theory for the potential while d and f-like electron is taken into account by introducing repulsive short-range Born-Mayer
term. The parameter of the potential is evaluated by zero pressure condition. An excellent agreement between theoretical investigations
and experimental findings is achieved which confirms the present formalism 相似文献
150.
We establish some liminf theorems on the increments of a (N,d)-Gaussian process with the usual Euclidean norm, via estimating upper bounds of large deviation probabilities on the suprema
of the (N,d)-Gaussian process.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献