Urban transportation Planning
An urban transportation system isbasic component of an urban area's social，economic，and physical structure. Not only does the designand performance of a transportation system provide opportunities for mobility，but over the long term，it influences patterns of growth and the level of economic activity through the accessibility it provides to land.Planning for the development or maintenance of the urban transportation system is thus an important activity，both for promoting the efficient movement of people and goods in an urban area and for maintaining the strong supportive role that transportation can play in attaining other community objectives.
There are several basic concepts about an urban transportation system that should be kept in mind. Most important，a transportation system in an urban area is defined as consisting of the facilities and services that allow travel throughout the region，providing opportunities for:(I)mobility to residents of an urban area and movement of goods and (2) accessibility to land .Given this definition，an urban transportation system can be further characterized by three major components:the spatial configuration that permits travel from one location to another;the transportation technologies that provide the means of moving over thesedistances;and the institutional framework that provides for the planning,construction,operation,and maintenance of system facilities.
The Spatial Configuration of a Transportation System
One way to describe the spatial dimension of anurban transportation system is to consider the characteristics of individual trips from anorigin to a destination. For example, atrip can consist of several types of movement undertaken to achieve different objectives.Travelers leaving home might use a local bus system to reach a suburban subway station(a trip collection process)，proceed through the station to the subway platform (a transfer process)，ride the subway to a downtown station (a line-haul process)，and walk to a place of employment (a distribution process). Similarly，one can view a home-to-work trip by car as consisting of similar segments，with the local street system providing the trip collection process, a freeway providing the line-haul capability，a parking lot in the central business district serving as a transfer point，and walking，as before，serving the distribution function.
The facilities andservicesthat provide theseopportunities for travel，when interconnectedtopermit movement from onelocation to another，form a network. Thus，another way ofrepresenting the spatial dimension ofanurban transportation system is as aset of road and transit networks. Even in the smallest urban areas，where mass transit is notavailable，the local street network provides the basic spatial characteristic of the transportation system.
The transportation system of a city can influence the way in which the city's social and economic structure, often called the urban activity system，develops. At the same time，changes in this structure can affect the ability of the transportation system to provide mobility and accessibility. Thus , the transportation system is closely related to the urban activitysystem and; historically, has been an important determinant of urban form.
Because of the relation between transportation and urban activities，many of the methods used by transportation planners depend on estimates of trips generated by specific landuses. The relation also suggests that the options available to public officials dealing withtransportation problems should include not only those related directly to the transportationsystem, but also actions such as zoning that affect the distribution of land use, and thus influence the performance of the transportation system.
The foregoing considerations point to two important principles for transportation planning: The transportation system should be
Considered as an integral part of the social and economic system in an urban area.
Viewed as a set of interconnected facilities and servicesdesigned to provide opportunities for travel from one location to another.
The Technology of Urban Transportation
The technology of urban transportation is closely related to the spatial configuration of the transportation system in that the design transportation networks reflects the speed, operating , and cost characteristics of the vehicle or mode of transportation being used. Technology includes the means of propulsion, type of support，means of guidance，and control technique.
The development and widespreaduse of electric streetcars in urban areas during the late nineteenth century was a technological innovation that initiated the transformation of mostNorth American cities. The advent of the electric streetcar permitted urban areas to
expand beyond the boundaries that had been dictated by previous transportation technologies (e. g.，walking，horse，horsecar)，spawning `streetcar suburbs' with dramatically lower residential densities along streetcar lines radiating from the central city. Whereas many industries had decentralized along railroad lines leading from the central city，and workers initially had to live near these factories,the introductionof streetcars now permitted more distant living.
The success of the streetcar in providing access from selected suburban areas to centralbusiness districts was followed by public acceptance of a second major technological innovation-the automobile，powered by the internal combustion engine. Increasing consumer preferences for lower-density living and for an ability to travel beyond established urban boundaries sparked a phenomenal growth in automobile ownership and usage，beginning in the 1920s .④The automobile continues and accelerated the evolution of urban structure startedby the electric streetcar. Its availability permitted further expansion of urban areas and,more important, provided access to land between the radialstreetcar and railroad lines leading into the central city.
Thetechnology of the internal-combustion engine，however, also led to the decline of other transportationmodes used in urban areas by providing a less expensive and more flexible replacement for rail-based modes. While the automobile provided new opportunities forpersonal mobility and urban growth, motor buses rapidly replaced electric streetcars, to theextent that only five North American cities today still operate large-scale streetcar systems-Boston, Philadelphia, Pittsburgh, Toronto, and San Francisco (although this trend has reversed somewhat in recent years with new `light rail' systems in operation in Edmonton,Calgary, San Diego, and Buffalo). At the same time, the growth of private automobile usehas dramatically reduced theuseof public transportation ingeneral,particularly since the endof World War II. Accordingtothe latest census figures, in1980, 62. 3 million Americansnormally drove alone to work each day, another 19 millioncar-pooled, and 6 million usedpublic transportation.
The technologies and the resulting modes available today for urban transportation arecommon to most cities but are often applied in different ways to serve different purposes. Itshould be noted that certain types of modes are appropriate than others in serving differenttypes of urban trips.
The technological dimension of the urban transportation system suggests a third principle for urban transportation planning:
Transportation planners must consider the transportation system as consisting of different modes ,each having different operational and cost characteristics.
From; Michael D. Meyer and Eric J. Miller "Urban Transportation Planning",1984
Traffic signals
In the United States alone ,some 250,000 intersections have traffic signals , which are defined as all power-operated traffic-control devices except flashers，signs，and markings for directing or warning motorists, cyclists，or pedestrians.
Signals for vehicular，bicycle，and pedestrian control are …pretimed?where specific times intervals are allocated to the various traffic movements and as 'traffic actuated' where time intervals are controlled in whole or in part by traffic demand.
Pretimed Traffic Signals
'Pretimed' traffic signals are set to repeat regularly a given sequence of signal indications for stipulated time intervals through the 24-hr day. They have the advantages of having controllors of lower first cost and that they can be interconnected and coordinated to vehicles to move through a series of intersections with a minimum of stops and other delays.Also, their operation is unaffected by conditions brought on by unusual vehicle behavior such as forced stops，which，with some traffic-actuated signal installations may bring a traffic jam. Their disadvantage is that they cannot adjust to short-time variations in traffic flow and often hold vehicles from one direction when there is no traffic in the other. This results in inconvenience, and sometimes a decrease in capacity.
‘Cycle length’the time required for a complete sequence of indications,ordinarily falls between 30 and 120s. Short cycle lengthsare to be preferred,as the delay to standing vehicles is reduced. With short cycles, however a relatively high percentage of the total time isconsumed in clearing the intersection and starting each succeeding movement. As cycle length increases,the percentage of time lost from these causes decreases. With high volumes of traffic,it may be necessary to increase the cycle length to gain added capacity.
Each traffic lane of a normal signalized intersection can pass roughly one vehicle each
2.1s of green light. The yellow (caution) interval following each green period is usually between 3 and 6s，depending on street width，the needs of pedestrians, and vehicle approachspeed. To determine an approximate cycle division, it is common practice to make short traffic counts during the peak period. Simple computations give the number of vehicles to be accommodated during each signal indication and the minimum green time required to passthem. With modern control equipment, it is possible to change the cycle length and division several times a day, or go to flashing indications to fit the traffic pattern better.
At many intersections，signals must be timed to accommodate pedestrian movements.The Manual recommends that the minimum total time allowed be an initial interval of 4 to 7s for pedestrians to start plus walking time computed at 4 ft/s (1. 2m/s). With separate pedestrian indicators，the WALK indication(lunar white) covers the first of these intervals, and flashing DON'T WALK (Portland orange ) the remainder. The WALK signal flasheswhen there are possible conflicts with vehicles and is steady when there are none. SteadyDON'T WALK tells the pedestrian not to proceed.
If pedestrian control is solely by the vehicle signals，problems develop if the intersection is wide, since the yellow clearance interval will have to be considerably longer than the 3 to 5s needed by vehicles. This will reduce intersection capacity and may call for a longer cycletime.On wide streets having a median at least 6 ft (1. 8m)wide，pedestrians may be stopped there. A separate pedestrian signal activator must be placed on this median if pedestrian push buttons are incorporated into the overall control system.
Coordinated Movement
Fixed-time traffic signals along a street or within an area usually are coordinated to permit compact groups of vehicles called `platoons’to move along together without stopping. Under normal traffic volumes，properly coordinated signals at intervals variously estimatedfrom 2500 ft (0. 76km)to more than a mile (1. 6km) are very effective in producing a smooth flow of traffic. On the other hand，when a street is loaded to capacity，coordination of signals is generally ineffective in producing smooth traffic flow.
Four systems of coordination-simultaneous, alternate，limited progressive, and flexible progressive-have developed over time. The simultaneous system made all color indications on a given street alike at the same time.It produced high vehicle speeds between stops but low
overall speed. Because of this and other faults，it is seldom used today.
The alternate system has all signals change their indication at the same time，but adjacent signals or adjacent groups of signals on a given street show opposite colors. The alternate system works fairly well on a single street that has approximately equal block spacing. It also has been effective for controlling traffic in business districts several blocks on a said,but only when block lengths are approximately equal in both directions. With an areawide alternate system，green and red indications must be of approximately equal length. This cycle division is satisfactory where two major streets intersect but gives too much green time tominor streets crossing major arteries. Other criticisms are that at heavy traffic volumes the later section of the platoon of vehicles is forced to make additional stops，and that adjustments to changing traffic conditions are difficult.
The simple progressive system retains a common cycle length but provides 'go' indications separately at each intersectionto match traffic progression. This permits continuous or nearly continuous flow of vehicle groups at a planned speed in at least one direction and discourages speeding between signals. Flashing lights may be substituted for normal signal indications when traffic becomes light.
The flexible progressive system has a master controller mechanism that directs the controllers for the individual signals. This arrangement not only gives positive coordination between signals，but also makes predetermined changes in cycle length，cycle split，and offsets at intervals during the day. For example，the cycle length of the entire system can be lengthened at peak hours to increase capacity and shortened at other times to decrease delays.
Flashing indications canbe substituted when normal signal control is not needed. Also theoffsets in the timing of successive signalscan be adjusted to favor heavy traffic movements,such as inbound in the morning and outbound in the evening. Again，changes in cycle division at particular intersections can be made. The traffic responsive systemis an advancedflexible progressive system with the capacityto adjust signal settings to measuredtraffic volumes.
Where traffic on heavy-volume or high-speed arteries must be interrupted for relatively light cross traffic，semi-traffic-actuated signals are sometimes used. For them，detectors are placed only on the minor street. The signal indication normally is green on the main road andred on the cross street. On actuation, the indications are reversed for an appropriate
intervalafter which they return to the original colors.
Highway Capacity And Levels of Service
Capacity Defined
Ageneralized definitionof capacity is:The capacity of any elementof the highway system isthe maximum numberof vehicles which has areasonable expectation of passing overthat section (in eitherone orboth directions)during agiven time period under prevailingroadwayand traffic conditions. A sampling of capacitiesfor modern highway elements is asfollows:
Facility Capacityin Passenger Cars Freeways and expressways away from rampsand weaving
2000 sections, per lane per hour
Two-Lane highways, total in both directions, per hour 2000
Three-lane highways, total in each direction, per hour 2000
Twelve-foot lane at signalized intersection, per hour ofgreen
1800
signal time(no interference and ideal progression)
In treating capacity，TRB Circular 212 divides freeways into components: basic freeway segments and those in the zone of influence of weaving areas and ramp junctions. Capacities of expressways，multilane highways，and two- and three-lane facilities also have the two components:basic and those in the zone of influence of intersections. Each of these is treatedseparately below.
Speed-Volume-Capacity Relationships for Basic
Freeway and Multilane Highway Segments
A knowledge of the relationships among speed，volume，and capacity is basic to understanding the place of capacity in highway design and operation. Figurel3.1，which gives such a relationship for a single freeway or expressway lane,is used for illustrative purposes.
If a lone vehicle travels along a traffic lane，the driver is free to proceed at thedesignspeed. This situation is represented at thebeginning of theappropriate curve at theupperleft of Fig.
13.1. But as the number of vehicles in the lane increases,the driver's freedom toselect speed isrestricted. This restriction brings a progressive reduction in speed. For example，many observations have shown that，for a highway designed for 70 mph (113km/h)，when volume reaches 1900passengercars per hour，traffic is slowed to about 43 mph (69km/h). If volumeincreasesfurther, therelatively stablenormal-flow condition usuallyfound at lower volumes is subject to breakdown. Thiszoneof instability is shown by theshaded area on the right side of Fig. 13. 1. One possible consequence is that traffic flow will stabilize at about 2000 vehicles per hour at a velocity of 30 to 40 mph (48 to 64km/h) as shown by the curved solid line on Fig. 13. 1. Often，however , the quality of flow deteriorates and a substantial drop in velocity occurs;in extreme cases vehicles may come to a full stop. In this case the volume of flow quickly decreases as traffic proceeds under a condition known as …forced flow.?V olumes under forced flow are shown by t he dashed curve at the bottom of Fig. 13. 1. Reading from that curve，it can be seen that if the speed falls to 20 mph (32km/h)，the rate of flow will drop to 1700 vehicles per hour; at 10 mph （16km/h) the flow rate is only 1000;and,of course，if vehicles stop，the rate of flow is 0. The result of this reduction in flow rate is that following vehicles all must slow or stop，and the rate of flow falls to the levels shown. Even in those cases where the congestion lasts but a few seconds, additional vehicles are affected after the congestion at the original location has disappeared.A …shock wave’develops which moves along the traffic lane in the direction opposite to that of vehicle travel. Such waves have been observed several miles from the scene of the original point of congestion，with vehicles slowing or stopping and then resuming speed for no apparent reason whatsoever.
Effects of the imposition of speed limits of 60, 50, and 40 mph are suggested by the dotted lines on Fig. 13. 1. A 55-mph (88km/h) curve could also be drawn midway between the60 and 50 mph dotted curves to reflect the effects of the federally imposed 55-mph limit, butthis is conjectural since the level of enforcement varies so widely.
Vehicle spacing，or its reciprocal, traffic density, probably have the greatest effect on capacity since it generates the driver's feeling of freedom or constraint more than any otherfactor. Studies of drivers as they follow other vehicles indicate that the time required to reach a potential collision point，rather than vehicle separation，seems to control behavior. However，this time varies widely among drivers and situations. Field observations have
recorded headways (time between vehicles) ranging from 0. 5 to 2 sec,with an average of about 1. 5s.Thus，the calculated capacity of a traffic lane based on this 1. 5 s average, regardless of speed，will be 2400 vehicles per hour. But even under the best of conditions, occasional gapsin the traffic stream can be expected，so that such high flows are not common. Rather, as noted，they are nearer to 2000 passenger cars per hour.
The ‘Level of Service’ Concept
As indicated in the discussionof therelationships of speed, volume or density, and vehicle spacing, operating speed goesdownand driver restrictionsbecome greater as traffic volume increase. …Level of service? iscommonly acceptedas a measure of the restrictive effectsof increased volume. Each segment of roadway can be rated at an appropriate level，A to F inclusive，to reflect its condition at the given demand or service volume. Level A representsalmost ideal conditions;Level E is at capacity;Level F indicatesforced flow.
The two best measures for level of service for uninterrupted flow conditions are operating or travel speed and the radio of volume to capacity达到最大限度的广播，called the v/c ratio. For two- and three-lane roads sight distance is also important.
Abbreviated descriptions of operating conditions for the various levels of service are asfollows:
Level A—Free flow; speed controlled by driver's desire，speed limits, or physical roadway conditions.
Level B—Stable flow;operating speeds beginning to be restricted;little or no restrictions on maneuverability from other vehicles.
Level C—Stable flow;speeds and maneuverability more closely restricted.
Level D—Approachesunstable flow;tolerable speeds can be maintained but temporary restrictions to flow cause substantial drops in speed. Little freedom to maneuver，comfort and convenience low.
Level E—V olumes near capacity; speed typically in neighborhood of 30 mph (48km/h);flow unstable;stoppages of momentary duration. Ability to maneuver severely limited.
Level F—Forced flow，low-operating speeds，volumes below capacity; queues formed.
A third measure of level of service suggested in TR
B Circular 212 is traffic density. This is，for a traffic lane，the average number of vehicles occupying a mile (1. 6km) of lane at a given instant.To illustrate，if the average speed is 50 mph，a vehicle is in a given mile for 72 s. If the lane carrying 800 vehicles per hour，average density is then 16 vehicles per mile ;spacing is 330 ft (100m)，center to center. The advantage of the density approach is that the various levels of service can be measured or portrayed in photographs.
From:Clarkson H. Oglesby and R. Gary Hicks “Highway engineering”, 1982
城市交通规划
城市交通系统是市区的社会、经济、和物质结构的一个基本组成部分。一个交通系统的设计和实施不仅为流动性提供机会，并且从长远观点来看，通过它能对土地提供良好使用价值也使经济活动和发展受到益处。这样，为了发展和维护城市交通系统而制定的规划是一项重要的活动，既是为了促进人和货物在市区的有效运转，同时也是为了保持交通在实现其他社团目标方而所能起到的强有力的支援作用。
对于城市交通系统有几个基本概念是应该记住的。最重要的是,一个城市的交通系统被认为是包括交通设施和服务,这两者有助于贯穿全区的出行，并且为以下两方面提供机会:(1)居民的流通量和商品的运转，(2)对于土地的可达性。鉴于这种认识,城市交通系统可以进一步分解为以下三个部分:空间布置,可使一点到另一点的出行成为可能；交通技术,提供两地区运转的手段；机构的机制，提供交通系统设施的规划、建设、运营和维护。
交通系统的空间布置
描述一个城市交通系统的空间尺度的方式是考虑一个人由起点到目的地的出行特点。例如，出行可以包括为达到不同目的的几种类型的流动。离开家的出行者可以乘坐当地的公共汽车而到达另一个郊区地铁车站（出行集合过程），经车站转到地铁站台（换乘过程），乘地铁到达一个商业车站（沿线运行过程），然后步行到工作地点（分散过程）。相似的，人们可以把乘汽车由家到工作地点的出行看作是包括相似的过程，利用当地的街道系统实现出行集合过程，高速公路提供线路的出行能力，在商业中心区的停车场起到换乘点的作用，而步行与前面说的一样，起到分散作用。
当提供这些出行机会的公共设施和服务集合起来,使从一个地点到另一个地点的
运动成为可能时就会形成网络。这样，表示一个城市交通系统的空间尺度的另一种方式是一组道路和公共交通的网络系统。甚至在不能利用公共交通的很小的市区内，当地的街道网络也会提供交通系统的基本空间特征。
城市交通系统将会影响到城市的社会和经济结构（通常被称为城市活动系统）的发展方式。同时,这种结构的变化会影响交通系统提供流动性和可达性的能力。因此,交通系统是与城市活动系统密切相关的;从历史上看,城市交通系统曾经是一个决定城市形态的重要因素。
由于交通和城市活动之间的关系，许多交通规划人员所使用的方法取决于特定的土地利用所产生的出行评估。这个关系还暗示可供与交通问题打交道的政府官员多采用的选择方案。而且也应该包括，例如，影响土地利用分布的区域划分，并因此影响到交通系统特性的一些措施。
上述的考虑指出用于交通规划的两个重要原则：
被认为是市区社会和经济系统的一个完整部分。
被视为目的在于提供从一个地点到另一个地点出行机会的一套互相结合的交通设施和服务。
城市交通的技术
城市交通技术是同交通系统的空间布局紧密相关的，其中交通网设计反映车辆的速度、运行和费用特征所采用的交通模式。技术上包括推进的手段。支撑的类型引导的手段，以及控制技术。
十九世纪晚期，在市区发展和广泛使用有轨电车是一项技术创新，启动了北美大多数城市的转型。有轨电车的出现使城市地区超出了之前运输技术（例如走路、骑马、马车）所限定的界限进行了扩展。产生了大量的居住密度明显很低的位于由市中心辐射出去的电车电车路线沿线的“电车郊区”。与此同时，许多工业也从由市中心延伸出去的提路沿线疏散了，工人们起初需要在这些工厂附近居住，现在引进了电车，住的远也没有什么关系了。
在电车提供由经过挑选的郊区到中心商业区的道路取得成功后，接着是公众对于第二个重大技术革新，即对内燃机为动力的汽车的欢迎。消费者越来越多的对于低密度的居住生活的热爱，以及对于跨越已确定的城市边界出行能力的偏爱，促进了从二十年代开始的汽车购置和使用方便急剧增长。汽车的可用性促使市区进一步扩展，并且更重要的是，汽车为通向市中心的放射状电车线和铁路路线之间地区的可能性提供条件。
然而，由于内燃机技术提供了比有轨交通方式更为廉价的和更为灵活的汽车，从而导致了市区内其他交通方式的衰落。在汽车为个人流通和和城市发展提供了新机会的同时，公共汽车很快取代了电车，以致目前只有五个北美城市还在使用大型电车系统，即波士顿、费城、匹茨堡、多伦多和旧金山（不过近年来这种趋势又有点逆转，新型“轻轨”系统正在埃德蒙顿、卡尔加里、圣地亚哥和布法罗运营）。于此同时，特别是自第二次世界大战结束以来，私人汽车使用的增长，一般来说已显著的使公共交通的使用缩减。根据最近的统计数字，在1980年有六千二百三十万美国人每天是自己驾驶汽车上班，另外有一千九百万人合伙使用汽车，而有六百万人乘用公共交通。
当前可以应用的城市交通技术和交通模式，对于大多数城市来说是通用的，但也常常以不同的方式应用，为不同的目的服务。应当注意到，某些交通方式较其他方式更适合于承担不同类型的城市出行。
城市交通系统的技术方面提出一个用于城市交通规划的第三个原则：
交通规划人员应当认为交通系统包括不同的交通方式，每一个方式具有不同的运营和费用特征。
摘自：迈克尔D.梅耶和艾瑞克J.米勒《城市交通规划》，1984
交通信号
仅在美国，约250000十字路口有交通信号,这被定义为所有除了闪光灯、标志、和标记的用于指导或警告驾驶员、骑自行车的人和行人的电动交通控制装置,。
控制车辆，骑自行车的人和行人的信号是在特定时间间隔分配到各种交通活动的预定时间和在交通运转中控制全部或部分交通需求的的时间间隔。
定时交通信号
定时交通信号是设定为在一天二十四小时内规定的时间定期重复一个规定的信号指示。它们有这些优势，包括有低生产成本的控制器，可以联系和协调使车辆以最少的停靠和其他的延迟通过一系列的交叉口。而且，它们的操作不受异常车辆行为引起的状况的的影响，如一些交通信号控制装置可能带来的交通堵塞引起的强迫性停车。它们的劣势是它们无法适应交通流量的变化和在没有其他交通的情况下约束一个方向的车辆。结果是导致交通不便和有时的通行能力下降。
一套完整顺序的“周期时间”通常在30秒到120秒之间。当车辆延迟减少，短循环时间是优先考虑的。然而对于短循环，清理路口和开始每一次顺利的运转消耗的时间
相对较高。当循环周期增加，从这些原因失去的时间减少。对于高流量的交通，可能需要增加循环周期来获得更大的通行能力。
每一个行车道信号正常的路口，一辆车在绿灯下大约2.1秒通过。根据街道宽度、行人需求和车辆靠近速度，每一个绿灯周期后的黄灯（警示）间隔在3秒到6秒之间。要确定一个大致的周期划分，常见的做法是确定高峰期间的短期交通数目。简单的计算给出每一个适应信号指示下车辆数目和车辆通过时最小的绿灯时间。随着现代控制设备，改变循环周期和每天时间次数的划分，或者使闪光信号更好的适应交通模式变的可能。
在许多路口，信号必须被定好来调整行人流动。手册建议行人开始加上步行时间以4英尺每秒（1.2米每秒）计算的最初的间隔允许的最小的总时间是4到7秒。对于单独的行人指示，步行指示（浅白色）包括最开始的时间间隔，禁止通行闪光灯（橘黄色）包括了剩余的时间间隔。当和车辆有可能的冲突步行信号灯闪烁，当没有时步行信号灯不变。禁止通行信号稳定不变时是告诉行人不要继续前行。
如果行人完全由车辆信号控制，如果路口宽问题会变大，因为黄灯间隔将大大高于车辆需要的3到5秒。这将减少交叉路口的通行能力，可能需要一个较长的周期时间。有中线的宽阔街道至少要6英尺（1.8米）宽，行人可能停在那儿。如果行人命令按钮被合并到整体的控制系统，一个单独的行人信号必须放在这个街道中间。
联动移动
一个车道或一个区域的定时交通信号通常联动调来允许一排紧凑的车辆一起移动而不停止。在正常的交通量下，适当的调整从2500英尺（0.76千米）到超过一英里（1.6千米）的各种信号间隔对于形成流畅的交通是非常有效的。另一方面，当一个街道超过了通行能力，调整信号来形成流畅的交通一般是无效的。
四个联动的，同步的，交互的，单一推进式的和弹性连续前进的信号系统随着时间推移已经开发出来。同步的系统使给定的街道在相同的时间内所有的颜色指示相同。它出现在两站之间车速高而整体速度低的街道上。因为这些和其他的错误，今天已经很少使用。
交互式系统在相同的时间有所有的信号转换。但是在一个给定的街道附近的信号灯或者附近的信号群显示互补的颜色。交互式系统在大约相等的街区间隔的信号街上能相当好的工作。它也能有效的在上述说明的商业区控制交通，但是只能当长度在两个方向大约相等时才行。对于全区的交互式系统，绿色指示灯和红色指示灯必须有大约相等的
长度。当两条主要街道相交，但是穿过主要街道的次要街道太多绿灯，这种周期划分是令人满意的。批评是在重交通量下后面区域的一排汽车必须强迫做出额外的停止，而改变交通状况的调整是非常困难的。
简易连续式系统保持一个一般的周期时间，但是在每个交叉路口分别提供“前进”指示来匹配交通进展。这允许在设计速度中的至少一个方向的一组车辆速度连续或接近连续流动，并阻碍了信号之间的超速驾驶。当交通变的轻的时候，闪烁的灯光可以取代正常的信号指示。
弹性连续前进信号系统有一种主控制器装置来指导个别信号控制器。这种布置不仅在信号之间做出了积极协调，而且使预定的周期长度，周期分配，白天的时间间隔偏移的变化。例如，全部系统的周期长度在高峰时段可以延长来提升通行能力或者在其他时间缩短来减少延迟。
当正常的信号控制不需要，闪烁的信号指示可以被代替。而且连续信号偏移的计时可以进行调整来适应重交通，比如早上入境和晚上出境。此外，在特定交叉路口的分配周期可以被计算出来。交通感应系统是一种具有调整交通信号设置来测量交通量的能力的先进弹性连续性系统。
在车流量大或车速高的道路动脉一定被流量和车速相对较轻的交叉路所中断处，半触动式交通信号有时被使用。对于它们，探测器仅被布置在次要街道。正常的信号指示是在主路的绿灯和十字街道的红灯。关于此装置，当它们变回原来的颜色，指示经过一个适当的时间间隔变得相反。
摘自：克拉克森H.奥格尔斯比和R.加里.希克斯《公路工程》，1982
公路通行能力和服务水平
通行能力的定义
道路通行能力的广义定义是：在繁忙的道路和交通条件下公路系统任何元素的通行能力是对在指定的时间通过一断面（一个或两个方向）的最大数量的车辆有一个合理的预期。一个现代公路通行能力的的抽样情况如下：
设施小客车通行能力
远离斜坡和交织路段的高速公路和每小时每个车道的车
2000
流量
两车道公路，每小时两个方向的车流量2000
三车道公路，每小时一个方向的车流量2000
有信号的交叉路口的十二英寸车道，在绿灯条件下每小时
1800
的车流量（没有干扰的理想通行条件下）
关于通行能力处理量，运输交通委员会发布的公路通行能力手册将高速公路划分为以下部分：基本高速公路路段，这些区域有影响的交织地区和砸道连接处，高速公路，多车道公路。两车道和三车道的通行能力同样有两部分组成：基本路段和这些区域有影响作用的交叉路口。
基本高速公路和多车道公路路段
速度，车流量和通行能力的关系
速度，车流量和通行能力之间关系是了解某一地方公路设计和运行能力的基础。图3.1说明了高速公路中速度、车流量和通行能力之间的关系。
如果司机驾驶一辆汽车一直自由的以设计时速独自行驶在一个行车道上，这种情形在左上角的图13.1中以适当的曲线表示出来。但随着车道上车辆数目的增加，司机自由选择速度受到限制。例如，许多研究表明，一个高速公路的设计速度为70英里每小时（113km/h），当车辆容量达到1900辆每小时时，交通速度下降到43英里每小时（69 km /h）。如果车辆数进一步增加，则建立在低车辆数目的相关稳定和正常的流动条件将会被打破。这种不稳定的区域如右侧图13.1阴影区域所示。一个可能的结果是交通流量将如图13.1的实曲线所示以30到40英里每小时（48到64km/h）的速度下稳定在大约2000车辆每小时。然而在通常情况下，车流量的质量恶化，车速大幅度下降；在极端情况下车辆可能完全停止。在这种情况下，车流量迅速下降，这种情况下的交通受益被称为“强制性流动”。强制性流动下的车流量如图13.1下部的虚曲线所示。从曲线上可以看出，如果速度下降到20应力每小时（32km/h），车流量将下降到1700辆每小时，以10英里每小时（16km/h）的流量算只有1000辆车；当然如果车辆停止，车辆流速为0。流速减少的结果是以后的车辆都必须减速或者停止，车辆流速下降到显示的水平。即使在这种情况下，交通拥挤的情况人在持续。短暂时间后，拥挤处原来的车辆离开后，其他的车辆又会受到影响。一个沿着相反车道行驶的车辆的冲击波逐渐形成。这样的冲击波已经在视野里从原来的拥挤点达到几英里。伴随着车辆减速或者停止，而且不会明显恢复原来的速度。
速度限制在60、50和40英里每小时的影响在图13.1中的虚线表示出来。55英里每小时（88km/h）的曲线也可以画在60和50英里每小时的虚线中来反映联邦政府限制的55英里每小时的速度的影响。但是因为执法水平的宽泛和多样性，这只是推测而已。
车辆间距，或者它的倒数，交通密度可能对通行能力有最大的影响，因为它对于司机形成自由或者约束的感觉比其他任何因素都要多。对于司机的研究显示，他们跟随其他车辆以到达一个潜在的碰撞点所需要的时间来控制自己的行为，而不是以汽车分开所需要的时间。不过这个时间点对于不同的司机来说差别非常大。实地观察记录车辆的间隔时间（车与车之间的时间）是从0.5秒到2秒，平均大约是1.5秒。因此，根据这1.5秒平均时间，而不是车速，计算的道路通行能力将会达到2400辆车每小时。但是，即使在最好的交通条件下，车流中的差距也是可能会出现的，所以如此高的车流是不常见的。相反，正如文中所指出的，每小时可以接近2000辆小客车通过。
服务水平的概念
正如讨论中所说明的当交通量增加时速度、流通量、车流密度和行车间距、运行速度下降、延迟增加之间的关系。“服务水平”通常被认为是流通量增加时的延迟性效应的程度。每一个路段可以列出一个合理的水平，包括A级到F级，在给定的要求和服务量下来反映道路的运行质量。A级表示几乎理想的条件，E级表示最大限度的状态，F 级表示车辆强制性的流动。
对于达到车辆不间断流动的服务水平的最好措施是行驶速度，到达最大限度时的播报，v/c率。对于两车道和三车道，道路视距也是非常重要的。
对于各种服务水平的运行条件的简单说明如下：
A级—车辆流通顺畅，车速受司机控制，速度受到限制，或者适应实际道路条件。
B级—车辆流通稳定，运行速度是开始稍有延迟，对于特殊车辆的机动性很少或没有受到限制。
C级—车辆流通稳定，速度和机动性更容易受到限制。
D级—车辆流通不太稳定；可以维持在容忍速度，但是临时性的限制可以引起车流速度大量下降；车辆运行不自由，舒适和方便性低。
E级—交通量接近道路通行能力，车流量不太稳定，车速维持在30英里每小时（48km/h）左右；出现短暂时间的停滞，运行能力受到限制。
F级—车辆流通受到限制，运行速度低，通行能力下降，出现阻塞的长队。
运输研究委员会手册说明的另一种表明服务水平的方法是交通密度。就是对于一
个行车道，在一定的时间内一英里车道上平均的车道数。比如，如果平均速度是50英里每小时，车辆在在一确定的一英里车道上是72s。如果车道上每小时通过800辆汽车每小时，平均车辆密度是16车每英里；车辆中心之间的间隔是330英尺。车辆密度方法的优势是不同的服务水平可以在照片中判断和描述出来。
摘自：克拉克森H.奥格尔斯比和R.加里.希克斯《公路工程》，1982
二○xx 届毕业设计 外文文献翻译
学院：建筑学院 专业：城乡规划 姓名：xxx 学号：xxxxxxxxx 指导教师：xx 完成时间：20xx年x月
绿地，城市持续发展最重要的指标：城市规划效 用研究 Francisco Gómez；José Jabaloyes；Luis Montero； Vicente De Vicente；and Manuel Valcuende 摘要：本篇文章总结了在西班牙城市巴伦西亚开展的一次非常广泛的研究，即绿地在城市舒适度中起到的作用。之前，已经研究出了组成城市环境的环境参数。根据这些值，一系列的舒适指数被分析并被证实，这些指数证明了之前作出的决定中的最佳的行为。同样被研究的还有绿地在公共城市空间中的作用：对太阳辐射的保留度和污染滞留容量。根据绿地的总量，这在公式上达到了舒适指数的极限值，即通过统计相关性，测定出城市达到理论上的舒适所需的绿地的表面积。本篇文章对城市量度的公式进行了更宽泛的分析，通过对空间和环境以更广泛的视角和更丰富的多样性的研究。这三个舒适指数已经被巴伦西亚以最佳的运作状态表现出来了，即达到了统计学上的最确定性。这篇文章最后研究了早前在巴伦西亚进行的绿色规划实验。最终结果考虑到巴伦西亚的学术权威提出的保护许尔塔的建议，正是这个天然商品花园开始了巴伦西亚的形成，接着形成了欧洲地区的战略哲学和欧洲景观风俗。 DOI: 10.1061(ASCE)UP... ? 2011 美国土木工程师协会 关键词：城市规划，植物，树木，应用研究，可持续规划 引言：全球人口城市化速度的增长在最近几年值得注意，这一现象的发生根本上是由于城市为居民提供了更优的基本生活条件，极大地增加了他们的自由度。现实情况是，城市地区表现出越来越多的
文献综述城市规划 IMB standardization office【IMB 5AB- IMBK 08- IMB 2C】
浅谈城镇建设存在的问题与未来 姓名：李里 摘要：在阅读多篇文章以后，总结出中国目前新城镇建设存在的普遍问题，由于追求快速城镇化，造成城市建设与城市空间都存在问题，同时建设时并没有考虑保护环境这一方面。目前，生态城市成为最新的城市改造建设模式，取代了传统的城市建设模式。 关键词：城镇建设，生态城市，海绵城市，低碳城市 一、城镇建设存在的问题 目前，新城建设中突出的问题是：新城求洋求新，导致千城一面的城市，形象特色危机；大拆大建导致的生态环境破坏和历史文脉隔断；部分新城人气不足，活力缺少，建设成效与期望差距甚远；过于关注形象和规模，新城认为不足，配套缺失；不够重视经济测算，造成一定的财政负担，前期投入多，后期收效不大。 不少城市的领导为了追求任期业绩，既不尊重投入产出规律，也不考虑经济效果和创新，更不考虑资金的回收问题。对老城区部分青红皂白一律推到重建，这是一种最原始、最不科学、最粗野的城市更新方式，造成一些有保留价值的建筑、设施、古木、风貌等的破坏，是城市的有形和无形资产严重受损，甚至完全消失。城市文脉是一座城市在长期建设中形成的历史的、文化的、特有的、地域的、景观的氛围和环境，是一种历史和文化的积淀。目前，城市中普遍存在着低水平的、低层次的简单城市更新，不注重保护和延续城市的文脉，是城市的文脉收到认为的破坏和割裂。城市正在走向雷同，特有风貌消失。随着世界经济一体化进程的加快和信息、文化、科技各个领域交流的扩大，城市更新改造中大量地运用了新技术、新工艺、新材料、新的设计理念大大促进了城市更新的进程和步伐。但是由于各地“追风”现象十分严重，效仿和追大潮成为时尚，是城市更新中出现了雷同，城市正在被克隆，正在失去领域的、文化的、传统的、多样化的特色，建筑正在失去个性和灵魂。在城市更新改造中，将保护建筑视为获得眼前利益的捷径，千方百计的肆意
吉林化工学院理学院 毕业论文外文翻译English Title（Times New Roman ，三号） 学生学号：08810219 学生姓名：袁庚文 专业班级：信息与计算科学0802 指导教师：赵瑛 职称副教授 起止日期：2012.2.27～2012.3.14 吉林化工学院 Jilin Institute of Chemical Technology
1 外文翻译的基本内容 应选择与本课题密切相关的外文文献（学术期刊网上的），译成中文，与原文装订在一起并独立成册。在毕业答辩前，同论文一起上交。译文字数不应少于3000个汉字。 2 书写规范 2.1 外文翻译的正文格式 正文版心设置为：上边距：3.5厘米，下边距：2.5厘米，左边距：3.5厘米，右边距：2厘米，页眉：2.5厘米，页脚：2厘米。 中文部分正文选用模板中的样式所定义的“正文”，每段落首行缩进2字；或者手动设置成每段落首行缩进2字，字体：宋体，字号：小四，行距：多倍行距1.3，间距：前段、后段均为0行。 这部分工作模板中已经自动设置为缺省值。 2.2标题格式 特别注意：各级标题的具体形式可参照外文原文确定。 1．第一级标题（如：第1章绪论）选用模板中的样式所定义的“标题1”，居左；或者手动设置成字体：黑体，居左，字号：三号，1.5倍行距，段后11磅，段前为11磅。 2．第二级标题（如：1.2 摘要与关键词）选用模板中的样式所定义的“标题2”，居左；或者手动设置成字体：黑体，居左，字号：四号，1.5倍行距，段后为0，段前0.5行。 3．第三级标题（如：1.2.1 摘要）选用模板中的样式所定义的“标题3”，居左；或者手动设置成字体：黑体，居左，字号：小四，1.5倍行距，段后为0，段前0.5行。 标题和后面文字之间空一格（半角）。 3 图表及公式等的格式说明 图表、公式、参考文献等的格式详见《吉林化工学院本科学生毕业设计说明书（论文）撰写规范及标准模版》中相关的说明。
Statistical hypothesis testing Adriana Albu，Loredana Ungureanu Politehnica University Timisoara,adrianaa@aut.utt.ro Politehnica University Timisoara,loredanau@aut.utt.ro Abstract In this article,we present a Bayesian statistical hypothesis testing inspection, testing theory and the process Mentioned hypothesis testing in the real world and the importance of, and successful test of the Notes. Key words Bayesian hypothesis testing; Bayesian inference;Test of significance Introduction A statistical hypothesis test is a method of making decisions using data, whether from a controlled experiment or an observational study (not controlled). In statistics, a result is called statistically significant if it is unlikely to have occurred by chance alone, according to a pre-determined threshold probability, the significance level. The phrase "test of significance" was coined by Ronald Fisher: "Critical tests of this kind may be called tests of significance, and when such tests are available we may discover whether a second sample is or is not significantly different from the first."[1] Hypothesis testing is sometimes called confirmatory data analysis, in contrast to exploratory data analysis. In frequency probability,these decisions are almost always made using null-hypothesis tests. These are tests that answer the question Assuming that the null hypothesis is true, what is the probability of observing a value for the test statistic that is at [] least as extreme as the value that was actually observed?) 2 More formally, they represent answers to the question, posed before undertaking an experiment,of what outcomes of the experiment would lead to rejection of the null hypothesis for a pre-specified probability of an incorrect rejection. One use of hypothesis testing is deciding whether experimental results contain enough information to cast doubt on conventional wisdom. Statistical hypothesis testing is a key technique of frequentist statistical inference. The Bayesian approach to hypothesis testing is to base rejection of the hypothesis on the posterior probability.[3][4]Other approaches to reaching a decision based on data are available via decision theory and optimal decisions. The critical region of a hypothesis test is the set of all outcomes which cause the null hypothesis to be rejected in favor of the alternative hypothesis. The critical region is usually denoted by the letter C. One-sample tests are appropriate when a sample is being compared to the population from a hypothesis. The population characteristics are known from theory or are calculated from the population.
文献信息 文献标题：Exploring Environmental Colour Design in Urban Contexts （城市环境色彩设计初探） 文献作者：Galyna McLellan, Mirko Guaralda 文献出处：《The Journal of Public Space》,2018,3(1):93-102 字数统计：英文3636单词，20879字符；中文7078汉字 外文文献 Exploring Environmental Colour Design in Urban Contexts Abstract The increasing complexity of urban colour and growing recognition of its psychological effects prompts rethinking of the current conceptual and methodological approaches to environmental colour design. Contemporary designers are challenged to understand how evolving colour knowledge can be integrated with the fundamentals of colour design. This paper aims to elaborate on the concept of environmental colour composition (ECC) and outlines an alternative approach to colour design in urban environments. A better understanding of the dynamic relationships between the tangible and perceptual elements of an ECC can bring new meaning to the consideration of colour as an integral component of city design. The proposed concepts of environmental colour events and scenarios provide a foundation for both further theoretical inquiry and practical application of synthesised colour knowledge in the design of urban environments. Keywords:environmental colour composition, environmental colour design, colour event, colour scenario ‘What is the colour of your favourite public place?’ Surprisingly, this simple question often causes confusion among many interviewees. Indeed, the complexity and ambiguity of visual information presented to viewers in a contemporary urban space make it difficult to determine what the prevailing spatial colour is. However,
毕业论文（设计）外文翻译 题目：中国上市公司偏好股权融资：非制度性因素 系部名称：经济管理系专业班级:会计082班 学生姓名：任民学号： 200880444228 指导教师：冯银波教师职称:讲师 年月日
译文： 中国上市公司偏好股权融资：非制度性因素 国际商业管理杂志 2009.10 摘要：本文把重点集中于中国上市公司的融资活动，运用西方融资理论，从非制度性因素方面，如融资成本、企业资产类型和质量、盈利能力、行业因素、股权结构因素、财务管理水平和社会文化，分析了中国上市公司倾向于股权融资的原因，并得出结论，股权融资偏好是上市公司根据中国融资环境的一种合理的选择。最后，针对公司的股权融资偏好提出了一些简明的建议。 关键词：股权融资，非制度性因素，融资成本 一、前言 中国上市公司偏好于股权融资，根据中国证券报的数据显示，1997年上市公司在资本市场的融资金额为95.87亿美元，其中股票融资的比例是72.5％，，在1998年和1999年比例分别为72.6％和72.3％，另一方面，债券融资的比例分别是17.8％，24.9％和25.1％。在这三年，股票融资的比例，在比中国发达的资本市场中却在下跌。以美国为例，当美国企业需要的资金在资本市场上，于股权融资相比他们宁愿选择债券融资。统计数据显示，从1970年到1985年，美日企业债券融资占了境外融资的91.7％，比股权融资高很多。阎达五等发现，大约中国3/4的上市公司偏好于股权融资。许多研究的学者认为，上市公司按以下顺序进行外部融资：第一个是股票基金，第二个是可转换债券，三是短期债务，最后一个是长期负债。许多研究人员通常分析我国上市公司偏好股权是由于我们国家的经济改革所带来的制度性因素。他们认为，上市公司的融资活动违背了西方古典融资理论只是因为那些制度性原因。例如，优序融资理论认为，当企业需要资金时，他们首先应该转向内部资金（折旧和留存收益），然后再进行债权融资，最后的选择是股票融资。在这篇文章中，笔者认为，这是因为具体的金融环境激活了企业的这种偏好，并结合了非制度性因素和西方金融理论，尝试解释股权融资偏好的原因。
软件专业毕业论文外文文献中英文翻译 Object landscapes and lifetimes Tech nically, OOP is just about abstract data typing, in herita nee, and polymorphism, but other issues can be at least as importa nt. The rema in der of this sect ion will cover these issues. One of the most importa nt factors is the way objects are created and destroyed. Where is the data for an object and how is the lifetime of the object con trolled? There are differe nt philosophies at work here. C++ takes the approach that con trol of efficie ncy is the most importa nt issue, so it gives the programmer a choice. For maximum run-time speed, the storage and lifetime can be determined while the program is being written, by placing the objects on the stack (these are sometimes called automatic or scoped variables) or in the static storage area. This places a priority on the speed of storage allocatio n and release, and con trol of these can be very valuable in some situati ons. However, you sacrifice flexibility because you must know the exact qua ntity, lifetime, and type of objects while you're writing the program. If you are trying to solve a more general problem such as computer-aided desig n, warehouse man ageme nt, or air-traffic con trol, this is too restrictive. The sec ond approach is to create objects dyn amically in a pool of memory called the heap. In this approach, you don't know un til run-time how many objects you n eed, what their lifetime is, or what their exact type is. Those are determined at the spur of the moment while the program is runnin g. If you n eed a new object, you simply make it on the heap at the point that you n eed it. Because the storage is man aged dyn amically, at run-time, the amount of time required to allocate storage on the heap is sig ni fica ntly Ion ger tha n the time to create storage on the stack. (Creat ing storage on the stack is ofte n a si ngle assembly in structio n to move the stack poin ter dow n, and ano ther to move it back up.) The dyn amic approach makes the gen erally logical assumpti on that objects tend to be complicated, so the extra overhead of finding storage and releas ing that storage will not have an importa nt impact on the creati on of an object .In additi on, the greater flexibility is esse ntial to solve the gen eral program ming problem. Java uses the sec ond approach, exclusive". Every time you want to create an object, you use the new keyword to build a dyn amic in sta nee of that object. There's ano ther issue, however, and that's the lifetime of an object. With Ian guages that allow objects to be created on the stack, the compiler determines how long the object lasts and can automatically destroy it. However, if you create it on the heap the compiler has no kno wledge of its lifetime. In a Ianguage like C++, you must determine programmatically when to destroy the
本科毕业设计（论文） 外文翻译 专业名称：土木工程 年级班级： 学生姓名： 指导教师： 二○年月日
Urban transportation Planning An urban transportation system is basic component of an urban area's social，economic，and physical structure. Not only does the design and performance of a transportation system provide opportunities for mobility，but over the long term，it influences patterns of growth and the level of economic activity through the accessibility it provides to land. Planning for the development or maintenance of the urban transportation system is thus an important activity，both for promoting the efficient movement of people and goods in an urban area and for maintaining the strong supportive role that transportation can play in attaining other community objectives. There are several basic concepts about an urban transportation system that should be kept in mind. Most important，a transportation system in an urban area is defined as consisting of the facilities and services that allow travel throughout the region，providing opportunities for:(I)mobility to residents of an urban area and movement of goods and (2) accessibility to land .Given this definition，an urban transportation system can be further characterized by three major components: the spatial configuration that permits travel from one location to another; the transportation technologies that provide the means of moving over these distances; and the institutional framework that provides for the planning, construction, operation, and maintenance of system facilities. The Spatial Configuration of a Transportation System One way to describe the spatial dimension of an urban transportation system is to consider the characteristics of individual trips from an origin to a destination. For example, a trip can consist of several types of movement undertaken to achieve different objectives. Travelers leaving home might use a local bus system to reach a suburban subway station(a trip collection process)，proceed through the station to the subway platform (a transfer process)，ride the subway to a downtown station (a line-haul process)，and walk to a place of employment (a distribution process). Similarly，one can view a home-to-work trip by car as consisting of similar segments，with the local street system providing the trip collection process, a freeway providing the line-haul capability，a parking lot in the central business district serving as a transfer point，and walking，as before，serving the distribution function. The facilities and services that provide these opportunities for travel，when
毕业设计（论文）外文文献翻译 文献、资料中文题目：气候学知识在城市规划中的应用文献、资料英文题目： 文献、资料来源： 文献、资料发表（出版）日期： 院（部）： 专业： 班级： 姓名： 学号： 指导教师： 翻译日期： 2017.02.14
气候学知识在城市规划中的应用 埃利亚松Ingegaè编写 哥德堡大学气候学在自然地理学、地球科学研究中心 瑞典哥德堡Box 460，S-405,30 收稿于1999年7月19日，修稿于1999年11月1日，发行于1999年11月23日 摘要 城市景观创造的气候会反过来影响城市，这是一既成事实；例如：人类的舒适性，空气质量以及能量消耗。然而尽管理论上如此，人们往往认为气象因素对于城市规划实施的实际操作影响很小。其原因是一重要的课题，因为答案要求之于气候学家，规划者和规划过程中。目前研究的主要目标旨在探讨如何以及何时使用气候变化知识在城市化过程中。该研究策略是由跨学科研究团体及气候学家和规划者策划的。案例研究包括不同的采访技巧以及历史数据，这是由在瑞典的三个直辖市从事城市规划工作的各种参与者提供的。研究表明，城市规划者对气候方面较感兴趣，但对气象信息的使用却是杂乱无章，从而结果得出气候学对城市规划影响较低。低冲击是由于几个可能与五个解释变量：概念和基于知识、技术、政策、组织和市场有关。这次讨论提出了某些方面的一些关键的结论,旨在解决这些限制。城市气候学家满足规划者需求驱动的需要提供好的参数,合适的方法和工具是很重要的。城市气候学家也鼓励规划者、决策者和公众提高对城市气候重要性的认识。然而,随着规划是一项政治活动并非总是基于甚至关系到科学知识,一些确定的约束只能通过中和在社会环境的规划制度能力的改善。 关键词:城市气候;城市结构;土地利用;环境规划 1、介绍 1.1、城市气候——简短背景 城市景观为当地创造了一个不同于周围的乡村景观的气候。最证据确凿的是城市热岛效应，研究表明城乡在晴朗和平静的夜晚存在12℃的温差（奥科；1981）。然而城市土地利用变化常常与由一个温暖与寒冷地区拼接的独特的城市土地利用的变化作比较；例如，在公园和建筑物周围能产生的内部城市温度差异高达7℃（斯普瑞肯?史密斯、奥科；1998）。街道几何也是非常重要的城市温度场。天空视角系数（SVF），图1已表明城市温度与其表面温度有关，而不是空气温度(Baè rring et al., 1985;Eliasson, 1992, 1994)。然而对于一个城市的平均SVF已被证明不同城市与最大城市热岛(空气温度)有良好的相关性(Oke, 1981; Park, 1987)。城市中的物质（沥青、砖块、玻璃等）的热特性不同于与在农村发现的物质（树、草、裸露的土壤等）。一般来说，建筑材料在城市中的运用会通过它们储存热量的特性来加剧城市的热岛效应。奥科认为材料和结构的多样性同样是热岛效应的两个主要原因。其他一
农村社会养老保险的现状、问题与对策研究社会保障对国家安定和经济发展具有重要作用，“城乡二元经济”现象日益凸现，农村社会保障问题客观上成为社会保障体系中极为重要的部分。建立和完善农村社会保障制度关系到农村乃至整个社会的经济发展，并且对我国和谐社会的构建至关重要。我国农村社会保障制度尚不完善，因此有必要加强对农村独立社会保障制度的构建，尤其对农村养老制度的改革，建立健全我国社会保障体系。从户籍制度上看，我国居民养老问题可分为城市居民养老和农村居民养老两部分。对于城市居民我国政府已有比较充足的政策与资金投人，使他们在物质和精神方面都能得到较好地照顾，基本实现了社会化养老。而农村居民的养老问题却日益突出，成为摆在我国政府面前的一个紧迫而又棘手的问题。 一、我国农村社会养老保险的现状 关于农村养老，许多地区还没有建立农村社会养老体系，已建立的地区也存在很多缺陷，运行中出现了很多问题，所以完善农村社会养老保险体系的必要性与紧迫性日益体现出来。 （一）人口老龄化加快 随着城市化步伐的加快和农村劳动力的输出，越来越多的农村青壮年人口进入城市，年龄结构出现“两头大，中间小”的局面。中国农村进入老龄社会的步伐日渐加快。第五次人口普查显示：中国65岁以上的人中农村为5938万，占老龄总人口的67.4%.在这种严峻的现实面前，农村社会养老保险的徘徊显得极其不协调。 （二）农村社会养老保险覆盖面太小 中国拥有世界上数量最多的老年人口，且大多在农村。据统计，未纳入社会保障的农村人口还很多，截止2000年底，全国7400多万农村居民参加了保险，占全部农村居民的11.18%，占成年农村居民的11.59%.另外，据国家统计局统计，我国进城务工者已从改革开放之初的不到200万人增加到2003年的1.14亿人。而基本方案中没有体现出对留在农村的农民和进城务工的农民给予区别对待。进城务工的农民既没被纳入到农村养老保险体系中，也没被纳入到城市养老保险体系中，处于法律保护的空白地带。所以很有必要考虑这个特殊群体的养老保险问题。
本科毕业设计（论文）中英文对照翻译 院（系部）电气工程与自动化 专业名称电子信息工程 年级班级 04级7班 学生姓名 指导老师
Infrared Remote Control System Abstract Red outside data correspondence the technique be currently within the scope of world drive extensive usage of a kind of wireless conjunction technique,drive numerous hardware and software platform support. Red outside the transceiver product have cost low, small scaled turn, the baud rate be quick, point to point SSL, be free from electromagnetism thousand Raos etc.characteristics, can realization information at dissimilarity of the product fast, convenience, safely exchange and transmission, at short distance wireless deliver aspect to own very obvious of advantage.Along with red outside the data deliver a technique more and more mature, the cost descend, red outside the transceiver necessarily will get at the short distance communication realm more extensive of application. The purpose that design this system is transmit cu stomer’s operation information with infrared rays for transmit media, then demodulate original signal with receive circuit. It use coding chip to modulate signal and use decoding chip to demodulate signal. The coding chip is PT2262 and decoding chip is PT2272. Both chips are made in Taiwan. Main work principle is that we provide to input the information for the PT2262 with coding keyboard. The input information was coded by PT2262 and loading to high frequent load wave whose frequent is 38 kHz, then modulate infrared transmit dioxide and radiate space outside when it attian enough power. The receive circuit receive the signal and demodulate original information. The original signal was decoded by PT2272, so as to drive some circuit to accomplish
Riverfront Landscape Design for London 2012 Olympic Park Client: Olympic Delivery Authority Location: London, UK Project Credit: Atkins Text: Mike McNicholas, Project Director, Atkins How do you plant along a river's edge, knowing that millions of people could be passing through thesite in the near future? How do you design, create and maintain the surrounding wetlands, knowing that man-made wet woodland is very rare and transitionalby nature? How do you ensurethat the habitat being created remains viable and sustainable in the long-term? Atkins’engineers of the wetlands and river edges on the London 2012 Olympic Park were tasked with fi nding answers to all of these questions. Covering more than 246 hectares of formerly derelict industrial land, London’s new Olympic Park for the London 2012 Olympic and Paralympic Games is one of Europe’s biggest-ever urban greening projects. Rivers and wetlands are at the heart of the vision for the new park, which lies in east London’s Lower Lee Valley. Th e landscape that’s now emerging will provide a backdrop for the main action of
毕业论文外文资料翻译题目(宋体三号，居中) 学院(全称，宋体三号，居中) 专业(全称，宋体三号，居中) 班级(宋体三号，居中) 学生(宋体三号，居中) 学号(宋体三号，居中) 指导教师(宋体三号，居中) 二〇一〇年月日(宋体三号，居中，时间与开题时间一致)
（英文原文装订在前）
Journal of American Chemical Society, 2006, 128(7): 2421-2425. (文献翻译必须在中文译文第一页标明文献出处：即文章是何期刊上发表的，X年X 卷X期，格式如上例所示，四号，右对齐，杂志名加粗。) [点击输入译文题目-标题1，黑体小二] [点击输入作者，宋体小四] [点击输入作者单位，宋体五号] 摘要[点击输入，宋体五号] 关键词[点击输入，宋体五号] 1[点击输入一级标题-标题2，黑体四号] [点击输入正文，宋体小四号，1.25倍行距] 1.1[点击输入二级标题-标题3，黑体小四] [点击输入正文，宋体小四，1.25倍行距] 1.1.1[点击输入三级标题-标题4，黑体小四] [点击输入正文，宋体小四，1.25倍行距] 说明： 1.外文文章必须是正规期刊发表的。 2.翻译后的中文文章必须达到2000字以上，并且是一篇完整文章。 3.必须要有外文翻译的封面，使用学校统一的封面； 封面上的翻译题目要写翻译过来的中文题目； 封面上时间与开题时间一致。 4.外文原文在前，中文翻译在后； 5.中文翻译中要包含题目、摘要、关键词、前言、全文以及参考文献，翻译要条理
清晰，中文翻译要与英文一一对应。 6.翻译中的中文文章字体为小四，所有字母、数字均为英文格式下的，中文为宋体， 标准字符间距。 7.原文中的图片和表格可以直接剪切、粘贴，但是表头与图示必须翻译成中文。 8.图表必须居中，文章段落应两端对齐、首行缩进2个汉字字符、1.25倍行距。 例如： 图1. 蛋白质样品的PCA图谱与8-卟啉识别排列分析(a)或16-卟啉识别排列分析(b)。为了得到b 的 数据矩阵，样品用16-卟啉识别排列分析来检测，而a 是通过捕获首八卟啉接收器数据矩阵从 b 中 萃取的。