旋转机械无线监测中的多普勒效应

由于应用无线通信技术对旋转机械进行状态监测时,无线设备安装在转轴上随轴高速旋转,无线设备之间的相对位置发生变化,因此会产生多普勒效应,影响无线通信。针对这一问题,首先,提出了两种无线设备安装方式;然后,建立了旋转运动中无线设备的多普勒频移理论模型,并分析了影响无线通信的因素;最后,对水润滑轴承水膜压力进行无线监测试验,引入误码率和丢包率研究了其与轴转速之间的关系,并对多普勒频移理论模型进行验证。理论与试验分析结果表明:多普勒频移与无线设备摆动圆直径、轴转速以及电磁波入射角密切相关,尤以转速影响为甚;在433 MHz通信频率下,无线监测方法不能很好地用于转速接近或超过10kr/min的旋转机械;转速对丢包率的影响大于误码率,丢包率为误码率的2~3倍。     

Quantitative assessment of rockfall hazard in post-landslide high rock slope through terrestrial laser scanning

Bulletin of Engineering Geology and the Environment - Post-landslide high slopes have always been at increased risk for rockfall disasters, posing a considerable threat to the slope toe area and...     

感温光纤检测装置的设计与实现

分布式感温光纤测温系统在电缆隧道在线监测中被广泛运用,为确保其有效性,需定期对感温光纤进行加热检测.运用单片机、云服务器、手机App设计一套检测装置,实现对感温光纤的远程控制加热检测.     

Three-dimensional Numerical Study of Laminar Confined Slot Jet Impingement Cooling using Slurry of Nano—encapsulated Phase Change Material

This Article presents a three dimensional numerical model investigating thermal performance and hydrodynamics features of the confined slot jet impingement using slurry of Nano Encapsulated Phase Change Material (NEPCM) as a coolant. The slurry is composed of water as a base fluid and n-octadecane NEPCM particles with mean diameter of 100nm suspended in it. A single phase fluid approach is employed to model the NEPCM slurry.The thermo physical properties of the NEPCM slurry are computed using modern approaches being proposed recently and governing equations are solved with a commercial Finite Volume based code. The effects of jet Reynolds number varying from 100 to 600 and particle volume fraction ranging from 0% to 28% are considered. The computed results are validated by comparing Nusselt number values at stagnation point with the previously published results with water as working fluid. It was found that adding NEPCM to the base fluid results with considerable amount of heat transfer enhancement.The highest values of heat transfer coefficients are observed at H/W=4 and C_m=0.28. However, due to the higher viscosity of slurry compared with the base fluid, the slurry can produce drastic increase in pressure drop of the system that increases with NEPCM particle loading and jet Reynolds number.     

Fast slicing orientation determining and optimizing algorithm for least volumetric error in rapid prototyping

Rapid prototyping fabricates physical prototypes from three-dimensional designing models using the additive process with layers. Aims at reducing the inevitable volumetric error induced in phrase of model slicing which impacts the shape accuracy of fabricated entity, a fast determining scheme of optimal slicing orientation for least volumetric error is proposed. The work analyses the staircase effect between two consecutive layers, then infers a direct computing formula of volume deviation of a whole model. Introduces the term of area weighted normal to express the significant effect of facet area on volumetric error and converts the optimal orientation determining problem to the least absolute deviation linear regression issue. Employs prominent components analysis on weighted normal set to obtain an approximate orientation efficiently, then optimizes the solution through few searchings in neighboring orientation space. The validity and efficiency of the algorithm are evaluated on several examples. Results demonstrate that proposed algorithm consumes less than 32 % of computation load and adaptively obtains the optimal slicing orientation.     

传统戏台与地方戏曲文化的关联性研究——以湘赣地区传统戏台为例

由于戏台的独特属性，使得戏台形态与戏曲文化之间存在的互动关系，应当成为研究的重要组成部分。以湘赣地区传统戏台为例，从共性与个性两个层面，对传统戏台的形态特征以及与之相关的戏曲文化因素进行梳理，就相互之间的关联性进行系统性研究，探讨戏台形态的内涵，为戏台和戏曲的双重保护提供互补思路，为同类保护提供示范，促进实现物质和非物质文化遗产的双向保护，探寻历史文化遗产的研究理论和操作体系的途径，推进兼具时代性与地域性的文化开发与利用。     

Geometrical effect on laminar mixed convection in the entrance region of shrouded arrays of heated rectangular blocks

Abstract

The effect of geometric parameter on laminar mixed convection in the entrance region of shrouded arrays of heated rectangular blocks is approached numerically for large Prandtl number fluid. The problem considered is related to convective cooling of electronic components mounted on horizontal circuit boards. Typical development of streamline and isotherm, block wall temperature distribution, and local Nusselt number are presented. It is found that the secondary flow leads to a significant enhancement in heat transfer. The multiple eddies above the block, induced by the combined geometric and buoyancy effect, lead to a more uniform block wall temperature distribution and then reduce the magnitude of the highest wall temperature.