Using three-dimensional discrete element method (DEM) to simulate the vibration of the evaporated pattern casting molding process, accordingly summary the influence law of vibration direction effecting on dry sand filling. The results show that the 3DOF vibration filling effect is best, 2DOF takes second place, 1DOF is the worst. In the 2DOF vibration the YZ direction is best, XY direction worst. Meanwhile Y direction vibration works best in 1DOF vibration, second is X direction, and Z direction gets worst.
In order to study the effect of surface roughness on the Elastohydrodynamic Lubrication (EHL) performance of cylindrical roller bearing, an EHL model of cylindrical roller bearing with three dimensional surface cosine roughness based on finite length line contact theory is established.The EHL performance of cylindrical roller bearing is calculated by the Finite Difference Method (FDM) program, with which the effects of surface cosine roughness amplitude, wavelength and texture angle on EHL performance of cylindrical roller bearing are analyzed.The numerical results show that the roughness amplitude, wavelength and texture angle have great influence on the EHL performance in the contact area.The increase of roughness amplitude and wavelength in a reasonable range is beneficial to the enhancement of EHL performance of the cylindrical roller bearing, and the transverse roughness is more favorable to enhance the bearing capacity and reduce the friction coefficient.
The volume of the transferred gas will be amplified because the gas conducts, a process of free expansion in a container which insulates from heat Because of this the internal energy enthalpy and so on will change as temperature changes To different gas, the reaction will be different Following is my discussion on imaginal gas, van der waals gas, and so on
Severe accuracy loss will happen on the occasion of element distortion, and the program may even fail to finish the calculation when there are elements which are concave. In this study, a novel concave-admissible 8 node quadrilateral plane element is developed within the framework of assumed displacement quasi-conforming method. The B-net method is used for calculation of area integral items and gives results with high precision within convex and even concave quadrangles. Numerical analysis on the element shows its trial functions represent exactly all polynomial terms of order less or equal to 2 in the Cartesian coordinates, which is also proved in numerical experiment described in Fig.1. Numerical results and comparisons with existing elements show that present element exhibits a remarkable robustness and insensitivity with extreme mesh distortions, as well as good accuracy. For the Cook beam problem, satisfactory results can be obtained when the mesh become severely distorted, as shown in Fig. 2. The work described in this abstract is expressed in detail in a full-length paper by Qingyuan Hu, Yang Xia, Ping Hu and Chongjun Li with title “A concave-admissible quadrilateral quasi-conforming plane element using B-net method”, which is under review by European Journal of Mechanics - A/Solids.
Specialized sensory hairs are important biological sensors for arthropods to detect and recognize environmental conditions including acoustic, pressure and airflow signals. However, the present design methodology of such biomimic micro devices are mainly depending on shape mimicking, which greatly restricts their performance. In this paper, a novel genetic algorithm based optimization model for design of piezoelectric functional hair is developed for improving its acoustic pressure or tactile sensitivity. Furthermore, the sensing mechanism of axially polarized piezoelectric hair is explored and the main influencing factors on sensitivity including hair configuration and axial strain distribution are determined. Then, a series of optimized hair configurations are obtained in a specific frequency band from 1 Hz to 500 Hz, whose average sensitivity of 2.21 × 10−3 V Pa−1 is 10 times greater than that of the straight hair of 2.15 × 10−4 V Pa−1 with the same size. For tactile load detection, the output voltage of the optimized hair is about 1.5 times as much as that of the straight hair. The obtained hairs are similar with the spider's trichobothria and tactile hair, which presents an explanation of biological hairs sensitive to dynamic and static loads.
We propose a generalized local $\bar{B}$ framework, addressing locking in degenerated Reissner-Mindlin plate and shell formulations in the context of isogeometric analysis. Parasitic strain components are projected onto the physical space locally, i.e. at the element level, using a least-squares approach. The formulation is general and allows the flexible utilization of basis functions of different order as the projection bases. The present formulation is much cheaper computationally than the global $\bar{B}$ method. Through numerical examples, we show the consistency of the scheme, although the method is not Hu-Washizu variationally consistent. The numerical examples show that the proposed formulation alleviates locking and yields good accuracy for various thicknesses, even for slenderness ratios of $1 \times 10^5$, and has the ability to capture deformations of thin shells using relatively coarse meshes. From the detailed numerical study, it can be opined that the proposed method is less sensitive to locking and mesh distortion.
Multipath effect is the main factor of deteriorating target detection performance in low grazing angle scenario, which results from reflections on the ground/sea surface. Amplitudes of the received signals fluctuate acutely due to the random phase variations of reflected signals along different paths; thereby the performances of target detection and tracking are heavily influenced. This paper deals with target detection in low grazing angle scenario with orthogonal frequency division multiplexing (OFDM) radar. Realistic physical and statistical effects are incorporated into the multipath propagation model. By taking advantage of multipath propagation that provides spatial diversity of radar system and frequency diversity of OFDM waveform, we derive a detection method based on generalized likelihood ratio test (GLRT). Then, we propose an algorithm to optimally design the transmitted subcarrier weights to improve the detection performance. Simulation results show that the detection performance can be improved due to the multipath effect and adaptive OFDM waveform design.
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