A travel flow and mobility framework for visually impaired travellers

A Travel Flow and Mobility Framework for Visually Impaired

Travellers

Simon Harper and Peter Green

Abstract

The aim of this paper is to propose a framework for travel by visually impaired people in order to provide a basis on which to develop future mobility and orientation systems to support such travellers. The ‘travel task’ is reviewed, and then analysed in the context of visual impairment, leading to the development of a simple framework to describe how travel is accomplished. Once this framework has been developed it can be used as a means of examining travel and travel aids for visually impaired people so that inadequacies in the provision of these travel aids can be addressed.

1Introduction

A degree of mobility is essential for many species, as most animals survive through movement to some degree or another, and this is no different for humans and much human activity is accomplished through the ability to travel from one point to another. Travel then is essential not because of the human capacity for mobility, but because of the enabling aspects implicit in this mobility. Most information provided to aid the independent traveller is in the form of visual cues. These cues typically include graphical signs, coloured lights, road markings, printed public transport information etc. These variations in mobility markings for sighted users suggest that travel should not be thought of as a single activity but a sequence of different activities because there has evolved a preferred means of conveying the useful information associated with each of the different travel activities to a user. Alternative forms of information display, catering for different sensory preferences, are however very rare, and hence travellers with visual impairments are at a significant disadvantage with respect to their sighted counterparts. Clearly technological travel aids for visually impaired people could help overcome this disadvantage and so a number of different technologies (both simple and complex) should be implemented to support effective travelling for visually impaired people. However, we believe that it is only possible to make meaningful proposals for such aids if the travel task itself is properly understood in the context of the visually impaired individual. The objective of this paper is then to analyse and suggest a framework for how individuals travel, review travel specifically in the context of people with a visual impairment and make suggestions about travel in the context of the proposed “travel framework”.

2Mobility Primer and Terminology Reference

Travel can be thought of as the whole experience of moving from one place to another regardless of whether the destination is known at the start of travel or if the journey is initially aimless. Conventionally, travel or mobility can be separated into two aspects, those of Orientation and Navigation [7].

?Orientation - can be thought of as knowledge of the basic spatial relationships between objects within the environment [1]. It is used as a term to suggest a comprehension of a travel environment or objects that relate to travel within the environment. How a person is oriented for travel is crucial to successful travelling. Information about position, direction, desired location, route, route planning etc. are all bound up with the concept of orientation.

?Navigation – in contrast, suggests an ability to move within the local environment [10]. This navigation can be either by the use of pre-planning using maps or fore-knowledge, or by navigating 'on-the-fly' and as such a knowledge of immediate objects and obstacles, of the formation of the ground (holes, stairs, flooring etc.), and of dangers both moving and stationary are all required.

3Egocentricity

Because navigation entails some form of mapping and knowledge storage, an understanding of how information is stored and processed in the brain can be useful in mobility research. Cognitive or mental mapping is an abstraction of the real world, covering the mental abilities that allow us to collect, organise, store, recall, and manipulate information about the spatial environment and real world surroundings [9]. In the context of travel, this means everyday spatial environments. Thus information is stored to make sure navigation is possible, (‘how to get there’). In addition, other cognitive knowledge is used to discover ‘where to go’ [8]. Many visually impaired people have a tendency to think of the real world in a ‘egocentric’ manner, such that descriptions of distance and journey become associated with the traveller and not the environment [9]. A sighted person may say “walk to pedestrian crossing and then continue on to the bank” where as a visually impaired person may say “walk 20 metres ahead, then from the tactile surface walk 10 metres to 45 degrees to the right of that position and you are at the Bank”. It can be seen that the specification of distance and direction is far more exacting and the traveller relies on a limited amount of external information in order to reach the destination. Visually impaired travellers also break their journey into shorter stages and orientate themselves within the journey a greater number of times, therefore the mental maps of a visually impaired person have a tendency to be egocentric, exact, and divided into smaller more manageable steps. Tailoring feedback to enhance these traits would therefore enhance the mapping process for visually impaired travellers [9].

4Travel and Visual Impairment

Visually impaired people travel a journey in a different way from sighted people using a number of different cues to sighted people. Because the travel task is second nature to most sighted people, and is learnt implicitly from an early age, the actual mechanics of it are often not explicitly considered. When studying travel in the context of a visually impaired person however, knowledge of how visually impaired people actually travel (i.e. without instruction) is important to the creation of a mobility framework. Visually impaired people have no preview of coming objects or obstacles and therefore the use of some type of preview device is important. Major concerns when travelling unassisted are down steps, kerbs, and stairs etc. Hedges, walls and other obstructions are not normally thought of but in the context of visually impaired travel the issue of ‘inside track’obstacles are important and need to be recognised. Consequently the stride length and therefore walking speed of a visually impaired person is less that that of a sighted person, as is the continuity of progress [13]. Body rotation is also used to describe parts of a journey and route descriptions are more complex when given by a blind person. Obstacle information is also more specific and present in greater detail when a visually impaired person describes a route. Moreover, visually impaired people also use simple information more frequently than complex information [1]. The lack of vision, even with a primary assistive mobility device, does limit the travel experience. In studies, many visually impaired people relate that they would normally only travel independently in man-made urban environments (with regular features) and not in countryside environments. In addition to this preference for urban environments, many also stated that they would normally only travel unassisted in areas that were familiar [7]. Any framework for describing the travel and movement of visually impaired people must address these issues (see Table 1).

Table 1: Travel and Mobility Summary

Obstacle Detection and Avoidance

Visually impaired people have limited preview of upcoming objects or obstacles and therefore the use of

some type of preview device is important.

Mental Maps

Although visually impaired people do not exhibit extraordinarily well developed non-visual senses,

studies do show that an increased use of mental maps is present.

Egocentricity

Visually impaired persons use more temporal and egocentric terminology and less spatial and

environmental terminology in defining points than do their sighted counterparts.

Regularity of Environment

The lack of vision, even with a primary assistive mobility device, does limit the travel experience. In

studies, many visually impaired people relate that they would normally only travel independently in man-

made urban environments (with regular features) and not in countryside environments.

Providing Spatial Information

Many congenitally visually impaired people find it difficult to track their position against spatial

information although there is no significant loss of mobility.

5 A Journey Case Study

Most people are able to describe a frequently travelled simple route, however this is not normally done because a sighted individual typically performs the journey without thinking explicitly about the actual route. However if a simple journey is examined then a number of similar parts can be distinguished. These parts are not specific to the journey but to the process of performing the journey and these are of interest. To clarify this concept of a ‘flow of travel’, a short journey will now be described (from the authors office to the train station and into a train. This decomposition is illustrated in Figure 1.) The sequence can be broken down into a series of sub-tasks that represent this ‘flow of travel’. The journey description can now be highlighted within certain relevant contexts to see how the journey breaks down.

Key to Description Breakdown (Contexts)

(print style denotes travel activity)

?Object detection and avoidance

?Waypoint/Orientation point (attempting to provide a regular environment)

?Complex Information Given or processed (adding to the users mental map)

?Direction Information (egocentric spatial information)

?Distance Information (egocentric spatial information)

The starting point and destination are defined implicitly, and any pre-planning is implicit as it is a journey

made many times.

“While all the time making sure I don’t walk into anything or into anybody. Walk from my desk to the

door of my office, open the door and continue a short distance past the lifts until turning right and

proceeding down a long corridor. At the point where I reach a set of double doors I continue through

them and down a flight of stairs, turn 180 degrees and down another flight and then turn 180 degrees and

then down another flight. I am now at ground level and exit the building by walking straight out of the

single door. On the outside I turn right and make for the pedestrian crossing turn left to cross it, and turn

right again to continue about 500m to the train station. I enter through the double doors and move

directly to the electronic departure time display, find the time and platform of the train I wish to

board, and follow the signs to that location. Here I wait until the train has arrived, and then, when the

doors have opened and are clear of disembarking passengers, board it.”

Figure 1: Breaking Down the Travel Task

6The Travel Task Framework (A Flow of Travel)

Currently the travel task is thought of as being grouped into two areas, these being navigation and orientation. It is the contention of this paper that the travel task is far more complex than this, and like Brambring [7] it is considered that a series of interrelated tasks are performed. However, the view proposed here differs somewhat from that of Brambring, who considers travel as being split into a tree of differing tasks (see Figure 2 [7]), in that it is thought that the travel task can be best likened to a looping ‘flow of travel’. This flow of travel can also be analogised to the flow and looping characteristics of control programs running on computer systems. In addition it is suggested

that devices to support travel by visually impaired people should be grouped according to which part of this flow of travel they aid. This will help to show which areas are currently neglected in the provision of primary and secondary electronic travel aids. The framework (see Figure 3) represents a user task analysis model of real-world journeying. The tasks are listed to the left and connected by a thick black line so that the different stages of a journey can be distinguished in the order that they are performed and providing a graphical commentary to the right of each task extends the framework. This commentary groups navigation and orientation objects into memories, obstacles and cues each with a set of associated actions to be performed. These actions are then linked to a method, this means the manner in which this action on this object is supported, and these methods have a number of properties associated with them so that the information returned to the traveller can be examined. For example: it can be seen that a ‘Journey’ task must detect and avoid an obstacle object, this is accomplished by preview and probing methods where both specific and detailed information about the object is returned thereby enabling it to be avoided. As previously stated, travel can be thought of as the whole experience of moving from one place to another regardless of whether the destination is known at the start of travel or if the journey is initially aimless. In this context a successful journey is one in which the desired location or goal is easily reached. Two important areas that assist a traveller in completing a successful journey are preview and external memory (see following section).

Figure 2: Brambring's General locomotion problems of blind persons.

In the framework we distinguish between, waypoints, orientation points and information points. These are all intended to represent some form of information giving object. A waypoint for instance may be just an arbitrary point (say, where two roads/tracks meet) or it may be a specific point intended to be a waypoint (a beeping sound marker, say). It is however intended that the information point will represent some form of device that gives complex information (for example a timetable, or street map ‘information point’).

Figure 3: A Travel / Mobility Framework

7The Travel Framework in Relation to Travel Aids

7.1Preview and Probing

In real world blind mobility, a lack of preview of upcoming information is one of the major issues to be addressed. Consequently, this preview is supported by both electronic and non-electronic means and travel aids range from the conventional cane and long cane through to laser obstacle

detectors. However, in all cases the travel aid performs a ‘probing’ task such that a limited amount of preview is given [5, 6].

7.2External Memory

Blind mobility solutions exist to accomplish obstacle avoidance and are based on both enhancing preview (as described above), planning to avoid obstacles through knowledge of the environment (orientation), and on navigating oneself around obstacles based on a knowledge of ones orientation within that environment [11]. Planning to avoid obstacles suggests a certain knowledge of an end goal to be achieved, while this is true in many cases it is not always known at the outset, and related travel information may be used in transit as the goal becomes more evident [3, 4].

7.3Cueing

Orientation or 'where-ness' (detecting behaviour, like going round in cicles, direction and distance) is important in blind mobility as it enables travellers to navigate with some degree of accuracy. However, problems exist for visually impaired travellers, because they do not have the luxury of visual cues to base these judgements on. Therefore, the environment must be updated such that cues are provided in an appropriate manner, giving explicit orientation information such that navigational information can be detected.

7.4Feedback

Supporting the general mobility task by providing appropriate explicit feedback, returned implicitly from many objects, is also undertaken by many real world travel aids. Feedback is mainly included as an addition to a travel aid fulfilling a different task, for instance, an obstacle detection device. The premise of these additions is that much feedback is implicit and can be assimilated at speed if the recipient is sighted. This is not the case however, if the recipient has a visual impairment, as the cues, and the complexity of the cues, often depend on the recipient having vision and being able to assimilate this complex visual information quickly [14].

8Conclusion

Applying knowledge about travel and journeys to inform the creation of a mobility framework can enhance the travel experience for visually impaired users by identifying anomalies in the provision of travel aids. The use of egocentric description, accurate journey information, and more frequent orientation points are directly related to the lack of preview found when travelling as a visually impaired user and so these points can then be addressed when creating travel aids. Tools and devices that supplement and enhance the travel information provided by travel aids can then be

created and new devices can be tailored to fill the spaces in the mobility framework left by the current array of travel aids. As can be seen, a journey involves very many complex real-time challenges. However, a dissection of the journey presented in the paper has enabled the formulation of a number of different elements to be identified based on the concepts of mobility and orientation. Although some of the detail will naturally be lost in any attempt to derive a general purpose framework, it is asserted that the ‘Travel Task Framework’ (as described above) represents a concise, understandable and structured basis for any future discussion on individual unassisted travel.

Acknowledgements

The authors would like to thank the support given by the ESPRIT OMI/MODES project in the funding of the POLI project, and Professor Carole Goble and Dr Robert Stevens at the University of Manchester (UK) for discussions pertaining to this paper.

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SW里的Flow Simulation散热分析实例教程 是一个SIMULATION的插件，我用过的版本中只有2011可以模拟。 大致方法如下：（现在电脑上的是2010，本本上的是2011，在家里了） 1.建模 2.装配 3.编辑材质 ————————分割线——————进入插件 4.进入Simulation功能模块 5.新算例中选择热力 6.设置对流 1.选择产品与空气接触面（多选，也可选择全部然后去掉没用的面） 2.温度开始时开氏的（K），就是热力学温度，开氏温度=摄氏温度+27 3.15°，你要什么样环境温度可以按照这个公式算一下 3.对流系数，不一样的环境系数不一样，老版本的传热学教材里注明，室内的空气的流通量较小，对流系数在5~8W/(m^2·℃，户外在8~15W/(m^2·℃，可根据使用环境进行设置。 7.热量设置，选择光热器件的面。在这里未必要画出LED，因为那样对于新手很难选到LED底部的，可在几班的模型上拉伸出LED底部面积大小的面，最终模拟出来后去加热阻来算LED结温。一般来讲，LED的功率消耗包括发光和产生热两部分的，正常应该是在30%的光+70%的热，光效不一样的话会有很微妙的影响，可忽略不计的，这里我建议不要这么去考虑，如10W的光源就按照产生10W的热去模拟，而不是7W。（此处30%、70%仅限参考） 8.划分网格，网格化分的越精细，模拟会相对精确，流体分析的模拟软件原理是一样的，有时间可以去了解一下。有一些小结构或者比较碎的结构可能造成网格划分失败，多是因为模型的局部有壁厚过薄或者两零件有干涉的情况，好好检查一下。 9.右键---新算例，上面有选项，稳态和瞬态，此处选择稳态，即达到热平衡后的结果。 10.计算模式哪里有三个选项，选择“D”开头的模式，具体名称忘记了。 11.点击运算 12.等··· 13.等··· 14.配置不好或模型较大的用户请重新启动计算机，双击Solidworks，返回到第一步重新开始。 我是这样做的，有高手觉得不妥的话欢迎指导！本打算图文并茂来着，但是电脑在家里，不好意思，就这样将就看吧，要是有什么问题的话，给我留言，但愿对各位有用！ -———————————————————————— 补充： 设置的时候有个接触面的设置，那里会具体到两种材料的接触模式所产生的温差。 我们也可以把整个系统做的具体一点，如集胶体的厚度或硅胶垫的厚度都把它们拉出来，这样会更好一些。

比较PageRank算法和HITS算法的优缺点

题目：请比较PageRank算法和HITS算法的优缺点，除此之外，请再介绍2种用于搜索引擎检索结果的排序算法，并举例说明。 答： 1998年，Sergey Brin和Lawrence Page[1]提出了PageRank算法。该算法基于“从许多优质的网页链接过来的网页，必定还是优质网页”的回归关系，来判定网页的重要性。该算法认为从网页A导向网页B的链接可以看作是页面A对页面B的支持投票，根据这个投票数来判断页面的重要性。当然，不仅仅只看投票数，还要对投票的页面进行重要性分析，越是重要的页面所投票的评价也就越高。根据这样的分析，得到了高评价的重要页面会被给予较高的PageRank值，在检索结果内的名次也会提高。PageRank是基于对“使用复杂的算法而得到的链接构造”的分析，从而得出的各网页本身的特性。 HITS 算法是由康奈尔大学( Cornell University ) 的JonKleinberg 博士于1998 年首先提出。Kleinberg认为既然搜索是开始于用户的检索提问，那么每个页面的重要性也就依赖于用户的检索提问。他将用户检索提问分为如下三种：特指主题检索提问（specific queries，也称窄主题检索提问）、泛指主题检索提问（Broad-topic queries，也称宽主题检索提问）和相似网页检索提问（Similar-page queries）。HITS 算法专注于改善泛指主题检索的结果。 Kleinberg将网页（或网站）分为两类，即hubs和authorities，而且每个页面也有两个级别，即hubs（中心级别）和authorities（权威级别）。Authorities 是具有较高价值的网页，依赖于指向它的页面；hubs为指向较多authorities的网页，依赖于它指向的页面。HITS算法的目标就是通过迭代计算得到针对某个检索提问的排名最高的authority的网页。 通常HITS算法是作用在一定范围的，例如一个以程序开发为主题的网页，指向另一个以程序开发为主题的网页，则另一个网页的重要性就可能比较高，但是指向另一个购物类的网页则不一定。在限定范围之后根据网页的出度和入度建立一个矩阵，通过矩阵的迭代运算和定义收敛的阈值不断对两个向量authority 和hub值进行更新直至收敛。 从上面的分析可见，PageRank算法和HITS算法都是基于链接分析的搜索引擎排序算法，并且在算法中两者都利用了特征向量作为理论基础和收敛性依据。

基于SolidWorks Flow Simulation的比例阀和真空泵的选型与优化

IM 软件世界 · 68 · 在真空泵和罐体之间装一台比例阀，比例阀和真空泵配合可改变抽速，保证罐内恒压。比例阀根据压力变化要求提供维持需要压力，比例阀与真空泵的选型多数靠经验来匹配，往往出现高能耗。通过SolidWorks Flow Simulation 对设备进行分析仿真，通过数据对比最优化的对比例阀与真空泵体的选型。 一、问题的提出 在真空设备和半导体设备中，常常有这样的工艺要求，某罐体内通入恒定流量的气体，并且保证罐体内恒压。通常采用方案是由一支流量计通入恒定流量的气体，出口连接一台真空泵抽气，在真空泵和罐体之间装一台比例阀， 这样比例阀和真空泵配合可改变抽速，保证罐内恒压。 图1 如图1所示是一款真空产品真空气路图，工作顺序如下。（1）首先关闭气动挡板阀-Φ100、电磁阀、流量计和电磁充气阀，比例阀开度100%，打开气动挡板阀-Φ16。基于SolidWorks Flow Simulation的比例阀和真空泵的选型与优化 撰文/北京七星华创电子股份有限公司工业炉分公司 张永军 北京盛维安泰系统技术有限公司 李跃超 （2）然后开启滑阀泵-70L /S 预抽真空，真空度抽至30000Pa 时关闭动挡板阀-Φ16，比例阀开度0%，开启气动挡板阀-Φ100。 （3）真空度抽至2000Pa 时，罗茨泵-300L /S 开启。（4）真空度抽至0.5Pa 时，关闭气动挡板阀-Φ100、罗茨泵-300L /S ，开启电磁阀、流量计，流量计保证0.5L /S 流量的氩气。 （5）达到0.6atm 时开启气动挡板阀-Φ16，比例阀，比例阀和真空泵组成闭环，由PLC 控制其开度。此设备大部分时间在此状况下工作。 在一个实例中，比例阀结构是通径Φ20的蝶阀，阀板在0°～90°转动，以实现0%～100%开启度。在保证0.6atm 恒压时，开启滑阀泵，比例阀开度8%。其8%～100%调节用不到，而且极不灵敏。我们判断比例阀通径选大了。选多大合适呢？结合SolidWorks Flow Simulation 模拟，让我们寻找合适的比例阀通径。 SolidWorks Flow Simulation 是一款比较经典的流体分析软件，它能解决流体流动分析、热分析、共轭传热、瞬态分析，并能作出漂亮视频、图片、图表及报表，且易学易用。除了软件本身向导式的操作流程之外，强大的数 据库可以让使用者减少搜集分析所需数据的工作量。更重要的是与CAD 的无缝集成，可以实现分析结果驱动CAD 参数。使用者无需单独创建流体域，网格划分也极大地减少了使用者的工作量。总之无论是软件的工程化界面，全中文的在线帮助文档，都是使工程师不花费过多的精力在

基于SolidWorksFlowSimulation优化球阀结构

基于SolidWorksFlowSimulation优化球阀结构 摘要：应用SolidWorksFlowSimulation对一款球阀半载及满载状态下的直口型和圆口型两种球体启闭件进行对比，共设计了四个CFD项目：（1）半载+直口型；（2）半载+直口型；（3）半载+圆口型；（4）满载+圆口型。 一、引言 球阀因结构简单、密封性好，而且在一定的公称通径范围内体积较小、重量轻、材料耗用少、安装尺寸小且驱动力矩小，操作简便、易实现快速启闭，是近十几年来发展最快的阀门品种之一。其工作原理是：启闭件（球体）由阀杆带动，并绕方工球阀作轴线作旋转运动的阀门，可用于流体的调节与控制，其中硬密封V 型球阀其V型球芯与堆焊硬质合金的金属阀座之间具有很强的剪切力，特别适用于含纤维、微小固体颗料等介质。球阀的主要特点是本身结构紧凑，适用于水、溶剂、酸和天然气等一般工作介质，而且还适用于工作条件恶劣的介质，如氧气、过氧化氢、甲烷和乙烯等，在各行业得到广泛的应用。 二、项目描述 球阀在使用过程中，通过启闭件的旋转，控制流体的流量。因启闭件长期与流体接触，承受流体的冲压，容易磨损。为提高球阀的使用寿命，有两种方法：（1）选用耐磨性好的材料；（2）优化球阀内部结构，而结构设计是否合理，需要经过物理实验来验证。引入计算流体力学（ComputationalFluidDynamics，CFD）分析后，在做物理实验之前，需要借用流体分析来预测启闭件在使用过程中的与流体间的相互作用，以优化内部结构。为了更好地验证球阀在使用中流量、启闭件阀口状与流体之间的关系，本文以一款球阀为例，设计了四个CFD方案，运用SolidWorksFlowSimulation软件对其阀体进行CFD分析，以对比不同的阀口结构及流量下，各结构内的流体流进球阀内部流体流动状态，以达到优化球阀结构的目的。通过流体分析，可预测不同条件下，流体在球阀内的流动状态，通过对比选择较佳结构设计。此外，球阀的使用者一直有一个误解，认为若流体中夹杂了颗粒，提前过滤流体可有可无，只要增大流体流量，提高流速，就能把杂质冲走。通过粒子示踪等分析，粒子随流体进入球阀后，很难随流体全部带走，因此在球阀使用前，要对流体内的杂质进行过滤，十分必要。 球阀在使用过程中，流量可通过外部控制，为方便理解，按1kg/s为满载，0.5kg/s 为半载进行对比。目前市面上，球体启闭件大致也有两种结构，一种是直口型，一种是圆口型。为更好地进行对比，设计了四个CFD方案，如表1所示。

SolidWorks Flow Simulation在气流纺纱机中的应用

SolidWorks Flow Simulation在气流纺纱机中的应用 一、引言 气流纺纱机又叫转杯纺纱机，气流纺纱有速度大，纱卷大，适应性广，机构简单，不用锭子、钢领、钢丝圈的优点，可成倍地提高细纱的产量。在各种新型纺纱方法与技术中，气流纺纱由于其技术和产品的实用性，得到了大量的推广与应用。气流纺纱的基本工作原理是，将纤维随气流输送到高速回转的转杯内壁，在凝聚槽内形成纱尾，同时被加拈成纱引出，直接绕成筒子。 气流纺纱过程中输入的气流不是单一的空气气体，其中含有大量的纺织纤维，如何使用软件进行可视化的CFD模 拟分析，是非常具有挑战的问题。本文采用专业的计算流体动力学分析软件SolidWorksFlowSimulation对气流纺纱过 程进行数值模拟，分析了内部流体的速度场和压力场分布等，并通过粒子追踪方法，分析了纤维粒子的旋转流动过程。 二、模型组成及分析说明 气流纺纱机的原始模型含有密封垫、轴承、螺栓等部件，非常复杂。为方便计算分析，本文对原始模型进行了简化处理，其结构基本组成及坐标系如图1。 模型由定子、高速转子和外壳三部分组成。其中气流入

口在定子上，直径为1mm，入口流体的质量流率为 0.0002026kg /s，高速转子的转动速度为130000r/min，出 口处的压力边界条件为96325Pa。 首先，使用FlowSimulation分析不含纤维粒子的气体流动，实际问题中纤维对气体的影响忽略不计;然后在该气体流动迹线分析结果的基础上进行纤维粒子流动分析。 三、模型创建 1.初始设置 使用FlowSimulation中提供的自动向导创建功能，进行如下设定，国际制(SI)长度单位为mm，旋转速度单位为r/min，质量流率单位为kg/h;分析类型为内部流动，排除内部没有流动条件的空腔;流体类型为空气;默认初始条件;结果求解精度等级设为4，最小间隙设为1mm，其他默认设置。 2.边界条件 按图1所示设置入口和出口边界条件，入口质量流率为 0.73kg/h(图2)，出口静压为96325Pa(图3)，指定如图4所示的真实壁面旋转条件，指定旋转速度。 3.初始条件 为了加快收敛计算速度，设置壳体内部切向气体初始速度为40m/s。在FlowSimulation中通过设置两个方向的初始条件来实现，此处不再赘述。

pagerank算法实验报告

PageRank算法实验报告 一、算法介绍 PageRank是Google专有的算法，用于衡量特定网页相对于搜索引擎索引中的其他网页而言的重要程度。它由Larry Page 和Sergey Brin在20世纪90年代后期发明。PageRank实现了将链接价值概念作为排名因素。 PageRank的核心思想有2点： 1.如果一个网页被很多其他网页链接到的话说明这个网页比较重要，也就是pagerank值会相对较高； 2.如果一个pagerank值很高的网页链接到一个其他的网页，那么被链接到的网页的pagerank值会相应地因此而提高。 若页面表示有向图的顶点，有向边表示链接，w(i,j)=1表示页面i存在指向页面j的超链接，否则w(i,j)=0。如果页面A存在指向其他页面的超链接，就将A 的PageRank的份额平均地分给其所指向的所有页面，一次类推。虽然PageRank 会一直传递，但总的来说PageRank的计算是收敛的。 实际应用中可以采用幂法来计算PageRank，假如总共有m个页面，计算如公式所示： r=A*x 其中A=d*P+（1-d)*(e*e'/m) r表示当前迭代后的PageRank，它是一个m行的列向量,x是所有页面的PageRank初始值。 P由有向图的邻接矩阵变化而来，P'为邻接矩阵的每个元素除以每行元素之和得到。 e是m行的元素都为1的列向量。 二、算法代码实现

三、心得体会 在完成算法的过程中，我有以下几点体会： 1、在动手实现的过程中，先将算法的思想和思路理解清楚，对于后续动手实现 有很大帮助。 2、在实现之前，对于每步要做什么要有概念，然后对于不会实现的部分代码先 查找相应的用法，在进行整体编写。 3、在实现算法后，在寻找数据验证算法的过程中比较困难。作为初学者，对于 数据量大的数据的处理存在难度，但数据量的数据很难寻找，所以难以进行实例分析。

(免费版)SolidWorksFlowSimulation的滤清器过滤效果分析

基于SolidWorksFlowSimulation的滤清器过滤效果分析 发表时间： 2014-2-18 作者: 陈璟*梁健*周金卿*邓昌建来源: 万方数据 关键字: SolidWorks Flow Simulation 滤清器过滤效果分析 应用SolidWorks软件的Flow Simulation插件对一款典型的发动机滤板式滤清器核心部件进行CFD分析。通过流体动力学仿真分析，可以直观地得到滤清器内部空气的流线分布，获得内部流体速度场切片云图。通过粒子轨迹示踪法，模拟三种不同粒径的杂质在滤清器内部的运动过程，可预测该款滤板式滤清器对气流中不同粒径杂质过滤效果，以便于下一步对产品结构进行优化设计。 发动机在工作时，需吸入大量空气，若空气中含有灰尘等杂质将会加剧发动机内部零件的磨损；若空气中曲轴润滑油的油滴随空气流入发动机内，则这些油滴混在燃油内与空气一起发生燃烧反应，会导致大量浓烟。因此，为了最大限度地避免这些现象，必须在发动机前安装空气滤清器。 本文所涉及的模型，是一款典型空气滤清器的核心部件，该部件有一个入口，一个出口，内置一块滤板，其中该内置滤板通过改变气流路径来分离出空气中的油滴等杂质。 本文采用专业的计算流体动力学分析软件SolidWorks Flow Simulation对气流经过滤清器过程进行数值模拟，通过粒子追踪方法，评估了该滤清器对三种尺寸（8μm、13μm和18μm）油滴等杂质的过滤效果。 本文CFD分析的目标是，评估该结构的滤清器对不同尺寸油滴等杂质过滤效果，并用 P=1-Moutlet/Minlet来计算预测的过滤量。其中：Moutlet及Minlet分别表示流经入口及出口的质量流量。 一、模型简化及数值模拟假设 1.简化模型创建 空气滤清器的原始模型含有缸套、密封垫、活塞环及螺栓等部件，比较复杂。为方便计算分析，本文对原始模型进行了简化处理，其基本结构组成及坐标系如图1所示。 图1 滤清器模型结构 模型由壳体、入口、出口和滤板四部分组成。滤板将壳体分隔成左右腔室，入口和出口皆在壳体上，壳体腔内高200mm，内径为80mm，入口和出口直径均为14mm，流体经入口进入第一腔室，遇到滤板阻隔，整体向下流动，从相通处流至第二腔室，再经出口流出。其中流体经入口的质量流率为0.0001kg/s，沿法向进气，出口处边界条件为默认数值：101325Pa和293.15K。

PageRank算法的核心思想

如何理解网页和网页之间的关系，特别是怎么从这些关系中提取网页中除文字以外的其他特性。这部分的一些核心算法曾是提高搜索引擎质量的重要推进力量。另外，我们这周要分享的算法也适用于其他能够把信息用结点与结点关系来表达的信息网络。 今天，我们先看一看用图来表达网页与网页之间的关系，并且计算网页重要性的经典算法：PageRank。 PageRank 的简要历史 时至今日，谢尔盖·布林（Sergey Brin）和拉里·佩奇（Larry Page）作为Google 这一雄厚科技帝国的创始人，已经耳熟能详。但在1995 年，他们两人还都是在斯坦福大学计算机系苦读的博士生。那个年代，互联网方兴未艾。雅虎作为信息时代的第一代巨人诞生了，布林和佩奇都希望能够创立属于自己的搜索引擎。1998 年夏天，两个人都暂时离开斯坦福大学的博士生项目，转而全职投入到Google 的研发工作中。他们把整个项目的一个总结发表在了1998 年的万维网国际会议上（WWW7，the seventh international conference on World Wide Web）（见参考文献[1]）。这是PageRank 算法的第一次完整表述。 PageRank 一经提出就在学术界引起了很大反响，各类变形以及对PageRank 的各种解释和分析层出不穷。在这之后很长的一段时间里，PageRank 几乎成了网页链接分析的代名词。给你推荐一篇参考文献[2]，作为进一步深入了解的阅读资料。

PageRank 的基本原理 我在这里先介绍一下PageRank 的最基本形式，这也是布林和佩奇最早发表PageRank 时的思路。 首先，我们来看一下每一个网页的周边结构。每一个网页都有一个“输出链接”（Outlink）的集合。这里，输出链接指的是从当前网页出发所指向的其他页面。比如，从页面A 有一个链接到页面B。那么B 就是A 的输出链接。根据这个定义，可以同样定义“输入链接”（Inlink），指的就是指向当前页面的其他页面。比如，页面C 指向页面A，那么C 就是A 的输入链接。 有了输入链接和输出链接的概念后，下面我们来定义一个页面的PageRank。我们假定每一个页面都有一个值，叫作PageRank，来衡量这个页面的重要程度。这个值是这么定义的，当前页面I 的PageRank 值，是I 的所有输入链接PageRank 值的加权和。 那么，权重是多少呢？对于I 的某一个输入链接J，假设其有N 个输出链接，那么这个权重就是N 分之一。也就是说，J 把自己的PageRank 的N 分之一分给I。从这个意义上来看，I 的PageRank，就是其所有输入链接把他们自身的PageRank 按照他们各自输出链接的比例分配给I。谁的输出链接多，谁分配的就少一些；反之，谁的输出链接少，谁分配的就多一些。这是一个非常形象直观的定义。

基于SOLIDWORKSFlowSimulation工业除尘设备导流板设计

基于SOLIDWORKS Flow Simulation I业除尘设备导流板设 基于SOLIDWORKS Flow Simulation T业除尘设备导流板设计撰文/陕西 美徳资讯有限公司李鹏DS SOLIDWORKS彭军 一.问题的提出燃煤锅炉、冶金行业、化工行业等工业设备在工作过程中产生的尾气中含有大量的颗粒污染物（硫化合物如二氧化硫;氮化合物如和N02;碳的氧化物CO和C02;碳氢化合物和卤素的化合物等），这些有害的粉尘及气体如果直接排到大气中就会形成雾霾。所以工业尾气在排放到大气之前就需要进行化学处理，也就是在会产生有害气体及粉尘的工业设备上增加除尘设备（图Do 除尘设备的除尘效果是工业设备需要考虑的重中之中。一般工业除尘主要是减少尾气中的固体颗粒物和有害气体，有害气体通过化学反应减少，固体颗粒物通过电场、水雾等方法排出设备。 有害气体能够最大化地进行化学反应直接影响除尘效果，在工业上一般采用使有害气体通过蜂窝状载体催化剂（图2和图3）,在有害气体通过催化剂的瞬间进行化学反应以达到除尘的效果。如何能使有害气体充分地与催化剂发生化学反应将是除尘的核心，如果有害气体与催化剂接触不均匀，除尘效果不好，工业设备排出的烟气一般都是高温、大流量，含有粉尘的气体。如果烟气流畅不均匀将会使催化剂不能完全反应，流速快的地方发生化学反应快，流速慢的地方发生化学反应慢, 烟气中的粉尘也会山于流场不均匀或发生紊流造成对蜂窝催化剂的磨损或粉尘堆积，造成催化剂的浪费及除尘效率低下（图4和图5）。

二.流场优化及导流板设计烟气在进入除尘设备时，山于流速较快、烟道曲直，烟气必然会产生流畅不均匀和紊流等现象（图 4、图5）。为了使烟气均匀地流入除尘设备，就需要在除尘设备进气口加上导 流板。导流板的设计乎工计算难度较大，凭经验结果不准确，需要多次样机试制才能完成，设计周期较长，成本增加。如果使用SOLIDWORKS Flow SimulationCFD 软件可以非常容易解决此问题。 使用SOLIDffORKS Flow Simulation设计?导流板步骤如下。第一步: 使用SOLIDWORKS建立除尘设备主要结构（图6）。 第二步: 使用SOLIDffORKS Flow Simulation建立流场仿真模型。 （1）通过没有导流板时的流场分布图（图 4、图5）可以看到流场分布极不均匀，需要设讣导流板;导流板的设讣可在SOLIDWORKS中初步设计（图7）。 （2）建立CFD工程算例。通过SOLIDWORKSFlow Simulation向导可以完成工 程算例的75%的设置: 定义工程名称、使用的3D模型、工程算例所使用的单位系统、工程算例的类型（内流还是外流）、流体的介质（空气）和默认网格类型（图8，图12）。 （3）定义边界条件。 ◎定义入口体积流: 模拟烟气从入口进入，烟气温度350?,速度75m2/so ◎定义出口圧力: 3000Pa负压，模拟风机的作用（图13）。