道砟胶固化道床力学特性的离散元分析

为探究道砟胶的使用对有砟轨道道床的影响规律,采用镶嵌式组合颗粒单元构造道砟颗粒,根据相关文献确定道砟胶的黏结模型和刚度模型,利用单轴压缩试验和三点弯曲试验确定道砟胶固化道床的细观力学参数,基于离散元法对道砟胶固化道床开展数值模拟,系统分析道砟胶用量和加胶深度对道砟胶固化道床力学特性的影响。模拟结果表明：随着道砟胶加入量的增大,道床的累积沉降量减小且累积沉降量的振幅减小,道床的刚度逐渐增大且增大趋势逐渐趋于平缓;当道砟胶加入量为48 kg/m3时,道床的累积沉降量最小且刚度最大;随着道砟胶加入深度的增大,道床的累积沉降量减小且累积沉降量的振幅减小,道床的刚度与道砟胶加入深度呈线性关系;道床全部加入道砟胶时道床的沉降量最小且刚度最大。     

Optimization of ballast plan in launch jacket load-out

The calculation of ballast plan in load-out operations is generally performed assuming a rigid barge. This assumption may not be reliable since in reality the barge is flexible. Having incorrect ballast plan may lead to overstressing of the loaded-out structure. We present a method of finding a more accurate ballast plan, taking into account the flexibility of the barge. This method makes use of a multi-objective evolutionary algorithm to find the optimum ballast arrangement at every load-out stage. We model the load-out configuration as a beam on elastic foundation, loaded with distributed trapezoidal loading representing the load from the structure. Minimizing deflection and curvature of the beam, as well as maximizing the ballast transfer efficiency between the load-out stages are chosen as the objectives of the algorithm. It is shown that the proposed method is better than the conventional rigid barge method in terms of minimizing the deflection and curvature as well as maximizing the ballast transfer efficiency.     

地铁线路扣件刚度对钢轨振动与波磨的影响

为探明整体道床轨道区段波磨发生机理及其对轮轨系统参数的影响规律,建立轮对和整体道床轨道三维有限元模型,分析轮轨共振模态与整体道床钢轨振动特性,探讨钢轨扣件刚度和轮对振动模态对整体道床区段钢轨波磨的影响规律.结果 表明:钢轨扣件刚度主要影响钢轨起跳共振频率,而对钢轨pinned-pinned共振频率影响甚微;较低的扣件刚...     

Walking on ballast impacts balance

Railroad workers often perform daily work activities on irregular surfaces, specifically on ballast rock. Previous research and injury epidemiology have suggested a relationship between working on irregular surfaces and postural instability. The purpose of this study was to examine the impact of walking on ballast for an extended duration on standing balance. A total of 16 healthy adult males walked on a 7.62 m × 4.57 m (25 ft × 15 ft) walking surface of no ballast (NB) or covered with ballast (B) of an average rock size of about 1 inch for 4 h. Balance was evaluated using dynamic posturography with the NeuroCom^® Equitest System^? prior to experiencing the NB or B surface and again every 30 min during the 4 h of ballast exposure. Dependent variables were the sway velocity and root-mean-square (RMS) sway components in the medial–lateral and anterior–posterior directions. Repeated measures ANOVA revealed statistically significant differences in RMS and sway velocity between ballast surface conditions and across exposure times. Overall, the ballast surface condition induced greater sway in all of the dynamic posturography conditions. Walking on irregular surfaces for extended durations has a deleterious effect on balance compared to walking on a surface without ballast. These findings of changes in balance during ballast exposure suggest that working on an irregular surface may impact postural control.     

双螺杆挤出机模具过渡和稳流段流场的数值模拟

采用Carreau模型描述熔体的黏度特征,使用POLYFLOW软件数值模拟了异向旋转双螺杆挤出机模具过渡和稳流段的三维等温流场。在不同的工艺参数下,分析比较了模具过渡和稳流段内的速度场、压强场、剪切速率场、剪切应力场以及黏度场。结果表明在模具过渡和稳流段内,螺杆的旋转是该聚合物熔体流变性能的最大影响因素,螺杆头对高黏度熔体的影响范围不大,只限于螺杆头的周围;进入稳流段后,在稳流段作用下熔体的流动逐渐变得稳定均匀;在本文讨论的转速和流量范围内,转速和流量的增加,分别会在不同的区域使熔体受到的剪切速率和剪切应力明显地增大。研究结果为某企业设计双螺杆模具和优化工艺条件提供理论依据。     

潜艇应急操纵的建模与仿真

应急模型是潜艇航行训练模拟器中很重要的一部分。该文对潜艇水下潜航状态下会出现的三种紧急状况进行了分析，其中潜艇舱室破损进水是导致潜艇失事的比较严重而常见的情况，文中提出了一种新的潜艇舱室破损进水模型，这种模型考虑了破损位置和面积这些因素。另外，在非常紧急情况下，高压吹除和抛弃压载等措施是挽回潜艇的重要手段，该文也对这两个过程进行了建摸。文章最后对应急过程的几种情况分别进行了仿真分析。结果表明所建立的模型是正确有效的。     

Micro-PIV investigation of the internal flow transitions inside droplets traveling in a rectangular microchannel

This paper discusses the studies on the internal flow field of droplets traveling in a rectangular microchannel by means of microparticle image velocimetry, specifically concentrating on the effects of capillary number, viscosity ratio and interfacial tension. The flow topology is predominantly dependent on the capillary number. It shows that the evident transitions from three pairs of recirculation zones at lower capillary numbers to one pair of recirculation zones near the sidewalls with low velocity in the central area at intermediate capillary numbers, then to a pair of recirculation zones closest to the axial centerline with high velocity in the central area at higher capillary numbers. There are two critical capillary numbers increasing with viscosity ratio in the evolution of flow features. Droplet size only influences two velocity components values other than the flow topology within intervals separated by the critical values. The equilibrium mechanism of viscous friction force and Marangoni stress dominate the internal topological transition in a surfactant added system. The obtained internal fluid phenomena inside droplets are beneficial to provide a guideline for screening of biochemical reaction conditions in the device.     

Stability of continuous welded rail track

As the use of continuous welded rail (CWR) increases in track structures, derailing disasters associated with track buckling also increase in great numbers due to high compressive thermal stress. A three-dimensional CWR track model is developed in the present study to be used for extensive buckling analysis of CWR tracks subjected to temperature load. The analysis model is encoded into a special purpose program using the finite element method. The CWR track model consists of four elements: a mono-symmetric thin-walled open section beam element with 7 degrees of freedom per node to represent the rail; a solid beam-on-elastic-foundation element having 6 degrees of freedom per node to simulate the tie, including vertical and/or longitudinal ballast resistance; an elastic spring element with two nodes and zero length to stand for pad-fastener system; and spring elements for the lateral or longitudinal ballast resistances. Also, two types of significant nonlinearity are included in the track model: the geometric nonlinearity of the rail element, and the materially nonlinear resistance of the ballast. The validity of the present study is strictly verified through a series of comparative analyses with those by others. The nonlinear analysis results have shown that buckling of the track is a three-dimensional problem, and the 2-D rail–tie model and beam model overestimated the CWR track stability.     

Impact of railroad ballast type on frontal plane ankle kinematics during walking

Five healthy male subjects walked on a control surface (level concrete), and two sloped rock surfaces (walking ballast-rock about 1.9 cm across; main line ballast-rock about 3.8 cm across) while their rearfoot motion (defined throughout as ankle inversion/eversion as seen from the frontal plane) was measured to determine if the different walking surfaces caused different ankle kinematics. The ballast was placed in 5m long trays that were tilted 7 degrees in the transverse plane. Rearfoot motion was measured while the subjects walked the length of the respective surfaces wearing work boots. A repeated measures ANOVA and a subsequent multiple comparison test revealed that the rearfoot range of motion was significantly greater walking on the main line ballast than walking on either the walking ballast or the level concrete. Meanwhile, the mean range of rearfoot motion for walking ballast was not significantly different from that resulting from walking on concrete. Variability was more than twice as great walking on main line ballast than walking on level concrete. Rearfoot angular velocities walking on level concrete and walking ballast were not significantly different, but both were significantly less than walking on main line ballast. Results suggested that rearfoot motion could be reduced if railroads placed walking ballast where trainmen have to walk as part of their jobs.     

Temporal and spatial vegetation cover changes in Israeli transition zone: AVHRR-based assessment of rainfall impact

The ability of NOAA/AVHRR data to monitor vegetation response to rainfall in three different vegetation zones was assessed along a north-south transect in Israel. The NDVI database was developed from atmospherically- and radiometrically-corrected NDVI composites from observations spanning three years. Three vegetation zones, Mediterranean region, transition zone, and semiarid region, were geographically separated by means of NDVI values. Based on three years of AVHRR observations during a relatively dry year and two years with near average rainfall, the phenological characteristics for all three vegetation zones were very similar and stable. The results showed that only a few AVHRR observations are necessary to monitor the seasonal and spatial variability of vegetation cover in different climatic zones located in Israel. The NDVI of the Israeli transition zone was found to be very sensitive to rainfall. The difference between maximum and minimum NDVI values in rainy season in the transition zone was at least two times higher than that in the Mediterranean and the semiarid regions. This phenomenon can be used as an indicator of any environmental changes in this region.     

Multi-scale,object-based image analysis for mapping geomorphic and ecological zones on coral reefs

Providing accurate maps of coral reefs where the spatial scale and labels of the mapped features correspond to map units appropriate for examining biological and geomorphic structures and processes is a major challenge for remote sensing. The objective of this work is to assess the accuracy and relevance of the process used to derive geomorphic zone and benthic community zone maps for three western Pacific coral reefs produced from multi-scale, object-based image analysis (OBIA) of high-spatial-resolution multi-spectral images, guided by field survey data. Three Quickbird-2 multi-spectral data sets from reefs in Australia, Palau and Fiji and georeferenced field photographs were used in a multi-scale segmentation and object-based image classification to map geomorphic zones and benthic community zones. A per-pixel approach was also tested for mapping benthic community zones. Validation of the maps and comparison to past approaches indicated the multi-scale OBIA process enabled field data, operator field experience and a conceptual hierarchical model of the coral reef environment to be linked to provide output maps at geomorphic zone and benthic community scales on coral reefs. The OBIA mapping accuracies were comparable with previously published work using other methods; however, the classes mapped were matched to a predetermined set of features on the reef.     

An approach to demarcate ground water potential zones through remote sensing and a geographical information system

In order to demarcate the ground water potential zones of Marudaiyar basin different thematic maps such as, lithology, landforms, lineaments and surface water bodies at a 1: 50000 scale were prepared, using remotely-sensed data as well as drainage density and slope classes from Survey of India topographical sheets. In addition, a soil map at 1:50000 scale covering the study area was generated from a 1:250000 scale soil map prepared by the Soil Survey and Landuse Organization by regrouping the soil types based on their hydrological characteristics. All the thematic layers were integrated and analysed using a model developed with logical conditions in the geographical information system (GIS). The ground water potential zones map generated through this model was verified with the yield data to ascertain the validity of the model developed. The verification showed that the ground water potential zones demarcated through the model are in agreement with the bore well yield data collected in the field. Since the present approach was built with logical conditions and reasoning, this approach can be successfully used elsewhere with appropriate modifications. Thus, the above study has clearly demonstrated the capabilities of remote sensing technique and GIS in demarcation of the different ground water potential zones, particularly in such a diverse geological set up.     

Effects of frequency dimming electronic ballast on a high‐pressure mercury thallium iodide discharge

This study focuses on the behavior of a cylindrical metal halide discharge lamp powered by frequency‐controlled electronic ballast. Half‐bridge electronic ballast was designed and achieved.     

Determination of space imagery contrast by a multi-spectral optimized method with AVHRR

Abstract

Satellite data from the Arctic present extensive shaded zones arising from the combination of low Sun elevation and mountainous topography. Field radiometry measurements from training zones on two glaciers in Arctic north-west Svalbard discriminate the different surface states of the glaciers. The SPOT reflectance values have been corrected using the slope orientation and dip parameters from the digital terrain model combined with the corresponding Sun elevation and azimuth. The reflectances of the shaded and illuminated zones have been restored to a new image based on the XS3 versus XS1 bimensional histogram. The pixel values of the new image can distinguish between firn and superimposed ice surface states on the glaciers defined and controlled by field measurements. From the new image a map of the different surface states of the glacier can be produced which is homogeneous in both the shaded and illuminated zones. The boundary between the firn and the superimposed ice can be located on the median and longitudinal profile of the glacier by combining the new image and the digital terrain model. With this method it is possible to locate the boundary between the firn and the superimposed ice and, consequently, the equilibrium line to within 40 m of altitude.     

Savanna and tropical rainforest biomass estimation and spatialization using JERS-1 data

The objective of this study is to show the relation among backscatter signals of JERS-1 images and biophysical parameters (biomass values) of forest and savanna formations. Two contact zones involving these vegetation units in Brazilian Amazonia (Roraima and Mato Grosso States) were selected. A regression model was applied during the analysis of these two variables, based on the best fit function and taking into account the data dispersion. Maps were generated showing biomass spatialization of the vegetation typology found in the study areas. The importance of this study is the innovation referring to the joint analysis of JERS-1 data of these two contact zones in Amazonia, representing both an abrupt contact and a smooth contact along a transition zone of savanna/tropical rainforests formations.     

Assimilation of GOES-derived solar insolation into a mesoscale model for studies of cloud shading effects

Cloud cover is capable of generating mesoscale temperature gradients by shading the surface. The purposes of this paper are to utilize GOES visible imagery to assimilate cloud shading elTects into a mesoscale model and to examine the ability of a realistic treatment of moving and changing cloud fields to produce boundary layer convergence zones which may lead to preferred areas of deep convective development. A simplified version of the radiative model of Gautier et Ill. is used to convert hourly gridded GOES brightness data into surface insolation for assimilation into the mesoscale model. The conversion process is presented in detail so that readers may duplicate the assimilation scheme. A case in the Texas Panhandle on 24 and 25 April 1982 is studied. Results of the modelling study show that cloud shading produces (a) a much more complicated surface temperature field, (b) a large change in the planetary boundary layer depth, and (c) substantial boundary layer convergence zones compared to a simulation without cloud shading. These mesoscale effects, in association with synoptic-scale instability, may be important in thunderstorm and severe weather development. The techniques utilized for assimilating satellite-derived insolation may be especially important in after-the-fact mesoscale modelling of air pollution cases and in field studies.     

汽车用氙气前照灯电子镇流器的设计

采用PIC16F785单片机进行控制,设计并实现了一种新型的汽车用氙气前照灯镇流器。针对当前汽车用氙气前照灯镇流器产品效率低、可靠性差等方面的不足,采用单芯片控制、平面变压器、软开关和全贴片等技术,大幅度提高产品的可靠性,效率提高了4%。实验结果证明了该设计的可行性和有效性。     

Weighing lexical information for software clustering in the context of architecture recovery

In this paper, we present a software clustering approach that leverages the information conveyed by the zone in which each lexeme appears in the classes of object oriented systems. We define six zones in the source code: Class Name, Attribute Name, Method Name, Parameter Name, Comment, and Source Code Statement. These zones may convey information with different levels of relevance, and so their contribution should be differently weighed according to the software system under study. To this aim, we define a probabilistic model of the lexemes distribution whose parameters are automatically estimated by the Expectation-Maximization algorithm. The weights of the zones are then exploited to compute similarities among source code classes, which are then grouped by a k-Medoid clustering algorithm. To assess the validity of our solution in the software architecture recovery field, we applied our approach to 19 software systems from different application domains. We observed that the use of our probabilistic model and the defined zones improves the quality of clustering results so that they are close to a theoretical upper bound we have proved.     

船舶压载系统仿真软件研究与设计

为了对船舶压载水系统的运行过程进行动态仿真与研究，建立了整个船舶压载水系统的仿真模型。具体地，依据工程流体力学的知识，并利用功率键合图的方式，建立了包括管网和基本元件的仿真模型。借助第三方的COM组件VisualGraph，利用VisualC#开发出压载水系统的动态仿真与监控软件。仿真软件将泵、阀、船舱等元件模块化，通过编辑等操作构建具体拓扑结构。操作员可以在此基础上进行压载舱注水、排水等仿真操作，同时对液位变化、泵阀开启、报警等情况进行监控。     

Modelling the sensitivity to various factors of shipborne pollutant discharges

Most of the marine pollution attributable to ship actions is associated with the illicit discharge of oily residues or ballast water, in what is commonly termed operational pollution. In the particular case of ballast water, careless disposal can lead to severe ecological damage, including the irreversible establishment of communities of invasive species. In its 2004 Convention on ballast water management, the International Maritime Organisation defined the measures to be followed to prevent these environmental issues, including the exchange with mid-oceanic water at a minimum distance from the shore. This paper uses two numerical models to analyse the effects of several factors on the dilution of a discharge from a ship moving in the Spanish Mediterranean waters, in order to determine under which conditions the environmental impact of the discharge will be minimum. The results highlight the dual role played by a freshwater plume, which may contribute either to decrease or to enhance the onshoreward transport of the discharged substance, and the relevance of the ship's speed in determining the dilution rates.