Numerical investigation of bus stop structures in Seoul for the reduction of fine dust entry

Journal of Mechanical Science and Technology - Fences and air curtains can effectively reduce fine dust entry into roadside bus structures, thus decreasing the exposure of passengers to particulate...     

网上实时监测系统设计与实现

网上实时监测系统采用多层结构模式,实现了企业工业控制信息的远程动态显示,文中对软件结构模式进行了分析,详细分析了网上实时监测系统的体系结构,并对系统的设计与实现进行了说明。     

面向机械产品布局设计的特征及组件关系表达

将基于特征设计的思想引入到布局设计中,旨在实现概念设计与详细设计之间有效过渡的特征定义和布局组件关系表达。讨论基于特征的产品设计过程,给出相应的定义、分类规则及其表示方法,同时探讨在布局组件关系清晰表达支持下的基于特征的机械产品布局设计建模过程。这为产品计算机辅助概念设计系统的实现提供初步的理论框架。     

Numerical investigation of prediction performance of design fire curves for a tunnel fire

Journal of Mechanical Science and Technology - The prediction performance of design fire curves is numerically investigated for tunnel fire using the fire dynamics simulator (FDS). A large eddy...     

靶机接收机空中带飞监测仪的研制

本文结合XX系列靶机空中带飞时对接收机信号监测的实际需要。给出了靶机接收机空中带飞监测仪的功能和技术指标,并在此基础上进行了监测仪的软件和硬件设计。     

First real-time detection of surface dust in a tokamak

The first real-time detection of surface dust inside a tokamak was made using an electrostatic dust detector. A fine grid of interlocking circuit traces was installed in the NSTX vessel and biased to 50 V. Impinging dust particles created a temporary short circuit and the resulting current pulse was recorded by counting electronics. The techniques used to increase the detector sensitivity by a factor of ×10,000 to match NSTX dust levels while suppressing electrical pickup are presented. The results were validated by comparison to laboratory measurements, by the null signal from a covered detector that was only sensitive to pickup, and by the dramatic increase in signal when Li particles were introduced for wall conditioning purposes.     

Numerical and experimental investigation of the bell-mouth inlet design of a centrifugal fan for higher internal flow rate

The energy efficiency of a household refrigerator is one of the most critical characteristics considered by manufacturers and consumers. Numerous studies in various fields have been conducted to increase energy efficiency. One of the most efficient methods to reduce the energy consumption of a refrigerator is by improving the performance of fans inside the refrigerator. A number of studies reported various ways to enhance fan performance. However, the majority of these studies focused solely on the fan and did not consider the working environment of the fan, such as the inlet and outlet flow characteristics. The expected performance of fans developed without consideration of these characteristics cannot be determined because complex inlet and outlet flow passage could adversely affect performance. This study investigates the effects of the design of the bell-mouth inlet on the performance of a centrifugal fan in a household refrigerator. In preliminary numerical studies, significant flow loss is identified through the bell-mouth inlet in the target fan system. Several design factors such as tip clearance, inner fence, motor-box struts, and guide vane are proposed to resolve these flow losses. The effects of these factors on fan performance are investigated using computational fluid dynamics techniques to solve incompressible Reynolds-averaged Navier-Stokes equations for predicting the circulating flow of the fan. Experiments are then performed to validate the numerical predictions. Results indicate that four design factors positively affect fan performance in terms of flow rate. The guide vane is the most effective design factor to consider for improving fan performance. Further studies are conducted to investigate the detailed effects of the guide vane by varying its install angle, install location, height, and length. These studies determine the optimum design of the guide vane to achieve the highest performance of the fan and the related flow characteristics around the bell mouth.     

实时监控系统多任务调控策略的设计与实现

工业过程实时监控系统的一个重要特征是多任务性，而多个任务之间协调工作是监控软件设计的关键。该文基于LabVIEW平台提供的优先级设置和执行系统的选择方式，提出了适合于计算机监控系统的多任务调控策略，并讨论了调控策略的设计方法和具体实现。     

An investigation into design and manufacturing of mechanical conveyors systems for food processing

This paper presents the results of a research investigation undertaken to develop methodologies and techniques that will reduce the cost and time of the design, manufacturing and assembly of mechanical conveyor systems used in the food and beverage industry. The improved methodology for design and production of conveyor components is based on the minimisation of materials, parts and costs, using the rules of design for manufacture and design for assembly. Results obtained on a test conveyor system verify the benefits of using the improved techniques. The overall material cost was reduced by 19% and the overall assembly cost was reduced by 20% compared to conventional methods.     

基于组态软件的自动涂布实时监控系统设计

该文提出了一种能对易燃易爆材料自动涂胶系统进行实时监控的方案。监控系统能够对温度、压力、流量、胶层厚度、纠编信息等一系列物理量进行自动显示、越界报警和调节。主要从硬件结构和总体控制两方面做了详细的论述。     

Wearable device for real-time monitoring of human falls

This paper presents a wearable micro-sensing device for monitoring human body falls. It combines micro-sensors and digital data processing technologies, such that in real-time, it can monitor the user to get immediate help by sending an emergency message to an aid station at the moment of falling. The primary feature of this system is the micro sensor, with a horizontal sensor embedded inside a smart coat. Two kinds of micro-sensors are used for the system, one is a micro-mercury switch, and the other is an optical sensor to detect if the wearer is horizontal. With the new algorithms for movement behaviors judgment, the system has the ability to collect, analyze, and transmit data by monitoring the user’s body. In outdoor sports, the system sends information on body position and location, and an emergency message from the user to a specific guard in real-time.     

Numerical and experimental investigation of preform design in non-axisymmetric warm forming

This paper describes a numerical and experimental investigation of preform design in non-axisymmetric warm forming in order to achieve a large reduction in the volume of flash. A titanium TA2 watch-case-like component was used as an example. Sixteen different shapes of hollow preforms were specially designed for finite-element simulation. Their diameters of the center-holes were designed based on the values of the diameters of end-face configurations of punches and ejectors. The corresponding thicknesses of the preforms were determined by the assumption of constant volume. Under the same processing conditions, the diameter of center-hole of the preform should be the inner diameter of ejector such that its volume of flash was able to be greatly reduced to 6% of the volume of the formed component whereas the volume of flash was approximately 25% in the conventional implementation. Experiments were subsequently performed to verify the simulation results. This study rationally demonstrates the success of the preform design for warm forming of non-axisymmetric components, and provides great improvement in the utilization of material in the bulk forming process. Thus, the achievement is a tremendous saving in materials, more than a fourfold, particularly for these rare and expensive alloys.     

低雷诺数涡轮性能计算研究

以某单级涡轮和某两级涡轮为研究对象,基于发展的子午面流线曲率法计算程序,采用四种含雷诺数效应的损失模型,对涡轮气动热力性能进行了数值模拟计算分析,对比分析了各种损失模型在基本假设、损失机理、损失预测、涡轮性能计算方面的差异.论文特别针对低雷诺数工作条件下航空燃气涡轮的性能进行了数值计算,分析研究了雷诺数变化情况下,涡轮性能变化的规律,比较了不同涡轮损失模型对低雷诺数涡轮性能计算的结果.分析结果表明,由于在基本原理和基本假设等方面的差异,不同损失模型的适用条件不同,预测结果差异也较大,在涡轮设计中应特别予以注意.     

Optimization design for a new large-scale eight-link mechanical press

This study proposes a new, large-scale, eight-link mechanical press that consist of four single degree-of-freedom (DOF) planar eight-link mechanisms and has a carrying capacity of 2000 tons. Kinematic analysis of a single DOF planar eight-link mechanism is presented. On the basis of kinematic analysis and the required output displacement curve, a single DOF planar eight-link mechanism is synthesized using differential evolution algorithm. We propose the use of an improved minimum sum of displacement variance (MSDV) cost function to minimize the influence of processing error on the same positions of different single DOF planar eight-link mechanisms. The improved MSDV cost function enables the setting of different weights for different stages with one stroke depending on the importance of each stage. Simulation results show that the designed mechanical press is consistent with the requirements, and that the improved MSDV cost function effectively reduces the influence of machining error.     

航空视频图像实时压缩算法的优化设计

提出了一种针对航空视频图像的编码优化方法,在工控计算机上实现了两路PAL制式彩色视频的同时实时压缩存储.选择离散余弦变换(DCT)去除图像的相关性,在比较各种DCT方法后,对AAN算法进行优化改进,并给出优化的依据,同时优化了可变长编码(VLC)中VLC表的检索方式.通过对视频压缩算法中运算量最大的两个算法模块进行优化改进,在P4 3.0G处理器上实现了8 ms内压缩一帧768×576的彩色图像.算法在32∶1的压缩比下,峰值信噪比(PSNR)为29.47,接近小波压缩算法在该压缩比下的PSNR值,确保了压缩质量.实验结果表明,优化方案在压缩速度、压缩率与压缩质量3者间取得了平衡,能很好地满足航空视频图像实时压缩的需求.     

可卸式防尘盖工装设计分析

叙述了可卸式防尘盖采用两道工序的工装设计适用于中大型防尘盖加工,采用一道工序的工装设计适用于中小型防尘盖的加工。通过对比,分析了两种工装设计的优缺点。     

Application of mobile agents in a web-based real-time monitoring system

Much research has been reported in the area of monitoring real machines using a virtual machining system over the Internet/Intranet. In order to overcome the limitations of net-bandwidth in real-time monitoring tasks, mobile agent technology can be used. This paper proposes a web-based distributed architecture for developing a platform-independent real-time monitoring system. Using this system, users can specify the machining conditions and send the requirements to the central controller. Programs monitoring machining performance can be dispatched from the central controller as mobile agents to the remote hosts where machining signals are sampled from real machines. Finally, an overview of the security issues associated with mobile agents is discussed.     

一种波浪监测系统的硬件设计

海洋状态的实时信息,如海浪波高、方向和周期等海流参数,对于海岸保护、离岸海上活动如钻井平台或船只都具有重要的意义。文章介绍的WaMoS可用于遥控测量海况及表面海流参数。该系统可根据航海的X-波段雷达的信号进行交通控制和导航。     

Application of distributed optical fiber sensor for monitoring the mechanical performance of a driven pile

This paper proposes a special application of Brillouin Optical Time Domain Analysis (BOTDA) sensors for monitoring the mechanical performance of a steel H-pile during driving process in a field in Hong Kong. First, basic calibration and the related installation method of optical fiber sensors (OFS) on pile body were introduced. Second, distributed strain profiles along the H-pile during driving process were successfully obtained from optical fiber sensors. Finally, measured strain distributions of the H-pile subjected to two loading/unloading cycles monitored by OFS were used to interpret field performance of the driven pile. Monitoring results indicate that the vertical load applied on the pile head generated significant compressive deformation, which was however mostly released by the corresponding unloading process. The 1st unloading and 2nd unloading processes released around 66% and 72% of the total compressive pile deformation, respectively. The shear stress levels mobilized between H-pile and surrounding soils were limited after each loading/unloading cycle according to the monitoring results. In addition, loading locations on the driven pile can be clearly identified from strain/stress distribution profiles. It is found from the monitoring study that BOTDA based sensors are more useful than some traditional or other point OFS (such as strain gauges or fiber Bragg grating sensors) to evaluate the average strain distribution of large scale structures.