Analysis of mesoscopic mechanical dynamic characteristics of ballast bed with under sleeper pads

The meso-dynamical behaviour of a high-speed rail ballast bed with under sleeper pads(USPs)was studied.The geometrically irregular refined discrete element model of the ballast particles was constructed using 3D scanning techniques,and the 3D dynamic model of the rail-sleeper-ballast bed was constructed using the coupled discrete element method-multiflexible-body dynamics(DEM-MFBD)approach.We analyse the meso-mechanical dynamics of the ballast bed with USPs under dynamic load on a train and verify the correctness of the model in laboratory tests.It is shown that the deformation of the USPs increases the contact area between the sleeper and the ballast particles,and subsequently the number of contacts between them.As the depth of the granular ballast bed increases,the contact area becomes larger,and the contact force between the ballast particles gradually decreases.Under the action of the elastic USPs,the contact forces between ballast particles are reduced and the overall vibration level of the ballast bed can be reduced.The settlement of the granular ballast bed occurs mainly at the shallow position of the sleeper bottom,and the installation of the elastic USPs can be effective in reducing the stress on the ballast particles and the settlement of the ballast bed.

Experimental study and numerical simulation of the impact of under-sleeper pads on the dynamic and static mechanical behavior of heavy-haul railway ballast track

Laying the under-sleeper pad(USP)is one of the effective measures commonly used to delay ballast degradation and reduce maintenance workload.To explore the impact of application of the USP on the dynamic and static mechanical behavior of the ballast track in the heavy-haul railway system,numerical simulation models of the ballast bed with USP and without USP are presented in this paper by using the discrete element method(DEM)-multi-flexible body dynamic(MFBD)coupling analysis method.The ballast bed support stiffness test and dynamic displacement tests were carried out on the actual operation of a heavy-haul railway line to verify the validity of the models.The results show that using the USP results in a 43.01%reduction in the ballast bed support stiffness and achieves a more uniform distribution of track loads on the sleepers.It effectively reduces the load borne by the sleeper directly under the wheel load,with a 7.89%reduction in the pressure on the sleeper.Furthermore,the laying of the USP changes the lateral resistance sharing ratio of the ballast bed,significantly reducing the stress level of the ballast bed under train loads,with an average stress reduction of 42.19 kPa.It also reduces the plastic displacement of ballast particles and lowers the peak value of rotational angular velocity by about 50%to 70%,which is conducive to slowing down ballast bed settlement deformation and reducing maintenance costs.In summary,laying the USP has a potential value in enhancing the stability and extending the lifespan of the ballast bed in heavy-haul railway systems.

Development of Ecological Absorbent Core Sanitary Pads in Combination of Kenaf and Chitosan Fibers

The menstrual cycle is always considered as a big nightmare by many women. This research aims to make this process smooth and safe by developing natural sanitary pads which are used to absorb and retain menstrual blood from the body. Some existing sanitary pads contain 90% plastics made of non-woven polypropylene/polyethylene sheets, super absorbent polymers, and polyethylene back sheets that will take up to 600 - 800 years to decompose. So, biodegradable sanitary pads using natural fibers are the best alternative to eliminate the pads which contain non-biodegradable materials. In this research, nonwoven bamboo will be used as the top layer, nonwoven cotton will be used as the second layer, the absorbent core is to be made by the combination of kenaf and chitosan fibers as the third layer, cotton as the fourth layer, and cornstarch-based bioplastic sheets as the bottom layer. These biodegradable natural materials will change the menstrual process into a healthy one as well as create a robust ecological community.

基于PADS 2007的PCB设计

目前主流的PCB设计是通过EDA软件完成的,本文通过一个PCB设计实例介绍业界领先的PCB设计软件PADS2007、设计流程及设计效果。

将PADS Power引入EDA技术教学中

高等职业院校在EDA技术课程中,选用的PCB制板软件大多数是Prote l99se和Protel DXP。然而,Mentor Graphics公司的PADS Power随着市场的推广,被越来越多的公司所接受。学校教学内容的设置应紧跟市场和公司的步伐,故将PADS Power软件引入EDA技术教学中,这样不仅丰富了教学内容,而且使学生接触到了市场的主流PCB软件,增加了学生就业竞争力。

基于PADS2004的高速PCB设计

在高速印刷电路板设计过程中,高速电路设计的仿真显示出越来越重要的地位。本文主要介绍了使用PADS2004/hyperLynx软件进行印刷电路板的仿真,通过对高速信号线进行布局布线前仿真和布局布线后仿真,可以发现和解决信号完整性、串扰、EMC等问题。本文还对高速电路设计中电源层分配、时钟设计进行了讨论。

基于随机行走的电源pads分配算法

为了减少芯片上电源网格阻性(IR)压降,提出了一种基于随机行走的电源pads分配算法.该算法由通过随机行走法推导出的节点电源需求评价函数确定部分pads位置,剔除部分候选节点以减小搜索空间,并以候选节点和观察节点为端口建立电源网格宏模型,从而将电路规模降为候选节点和观察节点之和,以逐个pad分配的方法确定剩余pads的位置,以随机行走法结合"滑动窗口"快速计算简化电路中观察节点的最坏压降.对不同电源网格的仿真结果表明,该算法无论在准确性还是效率方面均具有很大的优越性,并且能在二者之间做很好的折衷.

基于PADS软件对高速电路的设计与实现

为了解决高速电路设计中的时序及信号完整性问题,结合PADS软件的主要功能特点,以及高速电路设计的注意事项,以Hi3511模块为例,介绍了使用PADS对布局布线进行的各种规则约定和差分和等长走线等各种强大的功能,进行高速电路设计的方法。并在实际应用中产生了良好的效果。

应用SE-μPADs法检测库尔勒市动物源食品中沙门菌的效果评价

目的:为了快速检测动物性食品中沙门菌的污染。方法:应用国家标准方法和SE-μPADs快速检测方法,对库尔勒市场及屠宰场中的380份样品进行沙门菌检测的评价。结果:国家标准方法中选择性培养基的初筛率为20.00%(76/380),从初筛菌株中分离鉴定出6株沙门菌;SE-μPADs快速检测方法的初筛率为6.58%(25/380),最终分离鉴定出10株沙门菌。SE-μPADs快速检测方法与国家标准方法阳性符合率为100%。库尔勒市场及屠宰场中共检测出10株沙门菌,总检出率为2.63%,而肉样污染率最高,胴体拭子次之,污染率分别达3.66%、3.31%。结论:SE-μPADs快速检测方法的初步应用效果较好,适合推广应用,且库尔勒市应加强对屠宰场及市场上肉品中沙门菌的污染监测。

Comparison Studies on Dynamic Packaging Properties of Corrugated Paperboard Pads

Corrugated paperboard is a kind of inexpensive and environmental-friendly packaging material, and may be made into pads of package cushioning to protect products from shock and vibration damage by isolation during distribution. This article deals with the characterization of dynamic packaging properties of corru-gated paperboard pads, such as dynamic cushioning curves, vibration transmissibility and frequency curves. The main feature of article is the evaluation on the dynamic shock cushioning property and vibration trans-missibility of corrugated paperboard pads by a series of experimental studies on the drop shock tester and vibration tester, the establishment of experimental formulas of dynamic cushioning curves, and the analysis of resonance frequencies and vibration transmissibility. By using the fitting polynomial of curve and method of the least mean square, the experimental formulas with third order polynomial function of dynamic cush-ioning curves for corrugated paperboard pads are obtained. By using linear vibration theory with single de-gree of freedom, the resonance frequencies, vibration transmissibility and damping ratios of corrugated pa-perboard pads at different static loads are acquired. All results show the dynamic properties relevant to de-sign applications of corrugated paperboard pads for protective packaging.

Reliability Evaluation of CRH_(3C) Brake Pads Based on Bayes Method

In the reliability life evaluation of CRH_(3C) brake pads,the evaluation model of reliability life is put forward based on the Bayes method in the small sample. The correctness of evaluation model is validated by comparing and analyzing with the evaluation results based on Bootstrap simulation. Also by comparing the result with the semi-empirical method,the life evaluation results of the brake pads which are based on the Bayes method are more actual. The results which are based on the Bayes method can provide the theoretical basis and guidance for the repair and replacement of brake pads.

从ORCAD原理图文件到PADS2000 PCB文件的转换过程

本文详细说明了从ORCAD原理图文件转换成PADS2000PCB文件的过程。

Assessment of pressure generated by catamenial pads in genital and behind-the-knee sites <i>in vivo</i>

We conducted an in vivo pilot study to evaluate the pressure exerted by a feminine hygiene pad worn in the traditional way in the genital area and behind the knee, as measured using a novel pressure sensor device. The purpose was to determine whether pressure measured behind the knee correlated with genital pressure, thereby showing that behind-the-knee pressure measurements could be extrapolated to genital pressures recorded under clinical in-use conditions. Four female volunteers wore each of 3 currently marketed feminine hygiene pads and the sensors on the genital area and behind the knee while walking, sitting, and standing for approximately 2 minutes of each activity. Four participants completed the walking and sitting portions of the study and three completed the walking, sitting, and standing portions. The pressure data collected for all 3 pads in both the genital and BTK locations were similar inn both clinical tests. The preliminary results obtained in this clinical pilot study successfully confirm that pressure exerted from feminine hygiene pads in the BTK clinical test model is very similar to real product wear conditions.

Rock Magnetic Characterization of Fine Particles from Car Engines, Brake Pads and Tobacco: An Environmental Pilot Study on Oahu, Hawaii, USA

Today, it is well known that small airborne particles are very harmful to human health. For the first time in Hawaii we have conducted an environmental pilot study of fine magnetic particles on the island of Oahu, Hawaii, of particulate matter (PM) PM = 60, PM = 10, and PM = 2.5. In order to do a rock magnetic characterization we have performed low field susceptibility vs. temperature [k-T] experiments to determine the Curie points of small particles collected from exhaust pipes, as well as from brake pads of four different types of car engines using gasoline octane ratings of 87, 89, and 92. The Curie point determinations are very well defined and range from 292°C through 393°C and up to 660°C. In addition, we have conducted magnetic granulometry experiments on raw tobacco, burnt tobacco ashes, as well as on automotive engine exhaust, and brake pads in question. The results of the experiments show ferro and ferrimagnetic hysteresis loops with magnetic grain sizes ranging from superparamagnetic-multidomain [SP-MD], multidomain [MD] and pseudo-single domain [PSD] shown on the modified Day et al., diagram of Dunlop (2002). Thus far, the results we have obtained from this pilot study are in agreement with other studies conducted from cigarette ashes from Bulgaria. Our results could be correlated to the traffic-related PM in Rome, Italy where the SP fraction mainly occurs as coating of MD particles originated by localized stress in the oxidized outer shell surrounding the un-oxidized core of magnetite-like grains. All these magnetic particles have been reported to be very harmful to our human bodies (i.e. brain, lungs, heart, liver etc.).

Importance of Well Spacing and Orientation for Multi-Lateral Pads on Production: Learnings from Production Analysis and Numerical Modelling of the Mannville Coal Measures, South Central Alberta

The modelling results from numerical simulations of the Early Cretaceous, Mannville coal measures with anisotropic permeability provide insights into development strategies not readily visualized or otherwise intuitive. The complex relationships between water and gas production, the contribution from multiple coal seams as well as from organic rich shales, and the impact of well interference combined with anisotropic fracture permeability are investigated through a series of numerical simulations of four well-pads (on the corners of a square mile of land with decreasing well spacing from 1, 3, to 4 laterals per pad). After 25 years of production, the two pads with optimally-oriented laterals with respect to the fracture permeability anisotropy produce 61% of the recovered gas for the 1 lateral/pad model, 52% for the 3 laterals/pad model, and 50% for the 4 laterals/pad model. Downspacing has a greater impact on increasing the gas production from pads with the poorly-oriented main laterals than from the pads with the optimally-oriented main laterals. The cumulative gas production at the end of the 25 year history is 4.2% higher for an optimally-oriented pad (pad1) and 1.1× higher for a poorly-oriented pad (pad3) for a model with 4 laterals/pad than 3 laterals/pad and an optimally-oriented pad is 1.1% higher for an optimally-oriented pad and 1.5× higher for a poorly-oriented pad for a model with 3 laterals/pad than 1 lateral/pad. Although downspacing from 3 to 4 laterals/pad has a greater impact on increasing the cumulative gas production from optimally-oriented pads than downspacing from 1 to 3 laterals/pad, the lower impact on poorly-oriented pads results in a lower total increase the cumulative gas production from the four pads. At the end of the 25-year production history, 9.0% more gas is recovered for the 4 lateral/pad model than the 3 lateral/pad model, which predicts 1.2× more gas than the 1 lateral/pad model. The recovered shale gas exceeds the recovered coal gas after ~7 years of production. The higher contribution of produced coal gas predicted due to downspacing results from a higher contribution of recovered gas from the main coal seam, while the contribution from the minor coal seams is lower. Downspacing has a minimal impact on the cumulative water production;after 25 years of production a difference of 1.0% is predicted between models with 4 and 3 laterals/pad and 1.7% between models with 1 and 3 laterals/pad. While downspacing increases the cumulative water production for the poorly-oriented pads (1.1× for 3 to 4 laterals/pad and 1.3× for 3 to 1 lateral/pad after 25 years), the cumulative water production for the optimally-oriented pads is lower over the majority of the production history (after ~4 years and 3.2% lower after 25 years for 3 to 4 laterals/pad and after ~6 months and 1.1× lower after 25 years for 1 to 3 laterals/pad).

Mentor Graphics新型PADS和XPI工具满足当今设计需要

近日,Mentor Graphics在京举办PCB Forum（印制电路板论坛）,公司SDD部门业务发展经理David Wiens介绍了PCB设计的新理念及其创新产品。PADS重新定义PCB市场格局不久前,Mentor宣布以较低价位推出三款全新PADS系列产品。

PADS for DOS自动布线示例

PADS for DOS的布线功能十分强大。印制板设计的一般过程有设置系统参数、建立图稿、元器件布局、布线、印制板图输出。根据不同的情况,布线又分为手工布线和自动布线,下面以一个典型例子说明一下自动布线方法。

PADS电路及印制板设计软件使用入门(二)

一、放置元器件在主菜单下点取[F2 Add Part],信息栏显示: Name of part type for new part(CR=＊)> 其含意为输入新元件的型号名称,用键盘输入DIODE回车,屏幕上工作区内出现一个反白的被框住的元件,同时功能栏内也出现下级菜单,其中[F2 Ro-tate]可将元件逆时针旋转 90°,[F3 Mirror X]可将元件沿X方向作镜向处理,[F4 Mirror Y]可将元件沿Y方向作镜向处理,根据需要,将元件作旋转、镜向处理后移到合适位置。点鼠标左键放置,若输入元件错误。

PADS电路及印制板设计软件使用入门(一)

PADS俗称“比思”软件是一款功能强大、操作简便的电路及印制板辅助设计软件,深受一些电子厂家的钟受。就我个人的使用体会,我觉得它提供了一些十分独特的功能,给人一种平实朴素的感觉,但由于国内电子刊物上对此极少介绍,导致电子爱好者对它的了解远远不及PROTEL。为此,本文以一个具体的电路为例,简要地介绍采用PADS系统进行电路原理图的绘制,直到印制板的设计以及输出的全过程,希望能对朋友们有所帮助。

PADS电路及印制板设计软件简介

PADS软件通称“比思”。本刊早在1995年就介绍过,但当时这种软件流行甚少,没有为广大读者所关注。在“比思”日益推广的今天,介绍当今的PADS,是一件有益之事。明年年初开始,本刊还要连载它的使用方法。