科技外语教材翻译
Lesson One
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课文：
The Classification of Aircraft
飞行器的分类
Although all airplanes are aircraft, not all aircraft are airplanes. An aircraft is any structure 虽说所有的飞机都是飞行器，但不是所有的飞行器都是飞机。飞行器是指通过空气航that is Intended for navigation through the air and that is supported either by its own buoyancy or 行，由其自身的浮力或者依靠作用在其表面的空气动力支撑的一种结构。
by the dynamic action of the air against its surfaces. A brief look at the various kinds of aircraft is
简单地看一看这些不同种类的航空器，就会对此感到一目了然in order, since you may fly a number of them during your aviation career and since FAA rules for 的，因为在你的航空生涯中你可能驾驶大量的航空器，而且联邦航空局关于飞行员或飞行员pilot or airmen certification are based on aircraft classification. The classification begins with
驾驶证的规定也是以航空器的分类为基础的。分类从种类开始：categories: within a category, specific classes are identified : and within a class, types are 在一种种类中，分为详细的等级：而在一个等级中分为型号。
identified.
Category aircraft that use the same method of staying aloft and use similar means of propulsion 种类利用同一种方法滞留空中和采用类似形式推进力的航空器被归为同一种类。
are grouped into the same category. This is the broadest classification of aircraft. The FAA
这就是航空器最广义的分类。联邦航空局当前认为有四种currently recognizes the four categories of aircraft shown in Figure 1.1: lighter-than-air,
种类的航空器如图1.1所示：轻于空气的（航空器）rotorcraft, glider and airplane.
旋翼式航空器，滑翔器和飞机。
Class Within each category，aircraft with similar operating characteristics are grouped into a
等级在每个种类中，具有类似操纵特性的航空器被分为一个等级，
class ，For instance ，within the airplane category there are four classes: single-engine land, 例如，在飞机种类中有四个等级：单引擎陆地（飞机）single-engine sea, multiengine land, and multiengine sea.
单引擎海上（飞机），多引擎陆地（飞机）和多引擎海上（飞机）。
Type When you refer to a specific make and model of aircraft，you are defining its type.
型号当你谈及一个明确的牌子和样式的航空器时，你指的是它的型号。
Here are some aircraft types you may be familiar with : Cessna 152，Piper Tomahawk，
这里有你熟悉的几种航空器型号：：
BeechBonanza，Boeing 727，McDonnell Douglas DC-10.
The Different Categories and Classes of AirCraft
航空器的不同种类和等级
Lighter-than-air aircraft ascend by displacing a free mass of heavier air with an enclosed mass 轻于空气的（航空器）这种航空器通过用密封的轻型气体团替代自由的重空气团上升。of lighter gas. There are two classes of lighter-than-air aircraft：balloons and airships. Balloons are 有两种轻于空气的航空器：气球和飞艇。气球是驾驭空气气流飘行的无动力的unpowered aircraft that ride air currents. Hot-air balloons were common in the nineteenth century
航空器热气球在19世纪是常见的而今天用于体育运动。and are used today for sport. Airships are powered and have controls to directs their movement.
飞艇有动力并且有操纵装置指引它们的运动。
Inflatable/deflatable airships are called blimps. Dirigibles are airships built on rigid frames;
可充气/可放气飞艇被称作充气的飞艇。飞船是刚性框架构成的飞艇。
the famous German Zeppelins were dirigibles.
著名的德国Zeppelines就是飞船。
A rotorcraft is easily recognized by its large overhead propeller，called a rotor. There are two
旋翼式飞行器通过其巨大的顶部螺旋桨很容易辨认，称作旋翼。有两种的旋翼式飞行classes of rotorcraft：helicopters and gyroplanes. Helicopters have powered rotors that provide 器：直升机和旋翼机。直升机有动力旋翼，它通过空气提供垂直和水both vertical and horizontal motion through the air. On a gyroplane the rotor is freewhiling：
平方向的运动的。在旋翼机上，旋翼是行动自由的：propulsion is provided by an engine and propeller mounted in either a tractor (pulling) or pusher 推进力是通过一个引擎和固定在牵引机或推进器结构上的螺旋桨提供的。configuration.
A glider is an unpowered aircraft with wings and a tail. A sailplane is a high-performance
滑翔机是一种带有机翼和一个尾部的无动力航空器。轻滑翔机是一种高性能滑翔机，能glider capable of remaining aloft on rising air currents. These aircraft can be towed aloft by an 够在上升气流中保持高空飞行。这些航空器能被飞机或绞车拖拽到高处airplane or a winch，or they can be launched over the edge of a cliff. Once aloft，a glider or
，或者它们可以从悬崖上边抛投发射。一旦处在高处，滑翔机或轻sailplane is always coasting down through the air immediately around it. A sailplane pilot stays
滑翔机总是立即沿着它周围的大气向下滑行。轻滑翔机飞行员通过寻找aloft by finding rising air currents produced by the local terrain or weather conditions.
由当地地形或气候条件产生的上升气流来保持高空停留。
An airplane is a powered aircraft with wings and a tail. The airplane category has four
飞机是一种带有机翼和尾部的有动力航空器。飞机种类有四个等级：
classes：single-engine land, single-engine sea, multiengine land, and multiengine sea.
单引擎陆地（飞机），单引擎海上（飞机），多引擎陆地（飞机）和多引擎海上（飞机）。Chapter 2 is devoted to describing airplane and how they fly.
第2章致力于描述飞机和他们是如何飞行的。
These descriptions of category，classes，and type are used by the FAA in defining pilot
种类，等级，和型的这些描述被联邦航空局用在定义飞行员限制方面。
limitations. Your pilot certificate will always specify each category and class of aircraft you may 你的飞行员证书将总是指明你能合法驾驶一种种类和级别的航空器。
legally operate. When you move up to jet-powered aircraft or any aircraft that has a maximum 当你达到驾驶喷气动力的航空器或任何具有超过12，500磅最大起飞重量（大takeoff weight of over 12,500 pounds (about the size of a Lear jet or bigger) you will need a type 约是Lear jet 的尺寸或更大）的航空器时，你将需要你要飞的牌号和样式的型号等级rating in each make and model you fly. The term ―category‖ is also used in another context：In the
“类别“这个词也被应用于另一种情况：在航空器证书certification of aircraft , category refers to the operating limitations or intended use of the aircraft. 方面，“类别“指的是操纵限制或航空器的应用意图。
The aircraft’s Operating Handbook will discuss each category for which it is certified and the
航空器的操作手册将会讨论它所检定的每个种类和遵守的限制。
limitations to be observed.
There is one type of airborne vehicle that is not recognized by the FAA. An ultralight is a 这有一种没有被FAA认可的空运交通工具。超轻型（飞行器）是lightweight，single-person，recreational aircraft like that shown in figure 1.2. The FAA defines 一种重量轻，单人乘，娱乐的航空器，就像图1.2所示。FAA把他们定义为these as ―vehicles‖ and does not regulate their design or construction. You do not need a pilot’s “交通工具”而没有管制它们的设计或结构。你不需要飞行员证书就可以进行驾驶飞行。certificate to fly one.
You will need a pilot’s certificate to fly any kind of airplane ,and you will need training
飞行任何一种飞机你都需要飞行员许可证，而且在你获得许可证之前需要进行培训。before you obtain that certificate.
Lesson Two
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课文
The Parts of an Airplane
飞机的部件
Figure 2.1 shows the basic components of an airplane. Although each manufacturer and each 图 2.1 显示了一个飞机的基本部件。虽然每个制造公司和每个式样都有model have their own design features，these general components are found on every airplane and 他们自己的设计特点，但这些通用部件在每架飞机上都能看到且具有相同的名字。
called by the same names. The entire structure of an airplane is called the airframe.
飞机的整体结构称为机体。
The components of the airframe are ：the wing ，the fuselage ，and the tail assembly ，
飞机的部件是：机翼，飞机机身，和尾部组件
or empennage.
或尾翼组。
Wings are the major characteristic of an airplane. Wings can be mounted above the cabin
机翼是飞机的主要特征。机翼可以安置在机舱的上部（上翼）(high wing)，below the cabin (low wing ) ，or anywhere between (mid wing ). Each manufacturer ，机舱的下部（下翼），或安置在机舱中部的任何位置（中翼）。每个制造公司都有has its own preference. Most modern airplanes are monoplanes：that is ，they have one wing.
它们自己的偏爱。大多数现代飞机都是单翼飞机：即它们有一副机翼。
Airplanes with two wings are called biplanes. There have even been triplanes，the most famous of 有两幅机翼的飞机被称为双翼飞机。甚至有三翼飞机，最著名就是一战中Red Baron 驾which was the Fokker triplanes flown by the Red Baron in World War I.
驶的Fokker三翼飞机。
On the trailing (rearmost) edge of the wing are two sets of movable surfaces. Those farthest 在机翼的最后沿有两套可移动面。距离飞机中心from the center of the airplane (outboard) are called ailerons. The ailerons move when you turn the 线最远的（外侧的）被称为副翼。当你转动操纵盘或来回摆动操纵杆
control wheel or move the control stick side to side. They move in opposite directions ,one going 时副翼就会移动。它们在两个相反方向上运动，一个向上时up while the other goes down . Flaps are the movable surfaces closest to the center (inboard).
而另一个向下。襟翼是靠近中心（内侧的）的可动面。
They are controlled by a lever or switch in the cockpit . Flaps only move downward (sometimes
它们由驾驶座舱内的杠杆或开关控制。襟翼仅仅向下移动（有时也如向下移动backward as well as downward)，and both flaps always move simultaneously.
一样而向后移动），并且两个襟翼总是同时运动。
On most airplanes ,the wings contain the fuel tanks. This is both structurally efficient and 在大多数飞机上，机翼容载油箱。这就是结构的高效性与实用性。practical. The weight of the fuel is distributed along the structure that is doing the lifting , and it 燃油的重量分布于能够产生升力的结构上，从而可使机体的其余部分装载旅客和货leaves the rest of the airframe available for other things , like people and cargo.
物等其他货物。
When you observe an airplane from the front or rear，you will notice that the wings are not 当你从飞机的前面或尾部观察飞机时，你将注意到机翼与地平面并不平行，而是形成一parallel to the ground but form a slight V (see Figure 2.2). This angle is called dihedral. The
个微小的“V”形角。该角称为上反角/下反角。反角的目的purpose of dihedral will be discussed later in this chapter.
将在本章后面讨论。
The fuselage is the body of the airplane. It holds the pilot，passengers，and cargo. The
机身是飞机的躯干部分。它容纳飞行员，乘客，和货物。
fuselage is designed to as small as possible for performance reasons yet spacious enough for
从飞行性能考虑，机身体积尽可能设计小一些，而从舒适角度也应考虑足够的宽敞型。comfort.
The tail assembly or empennage consists of two sets of surfaces，usually one horizontal and 尾部集合或尾翼由两组面组成，通常是一组水平的和一组垂直的。
one vertical . (There are airplanes that use a V configuration ，but these are not discussed here to （有一些应用“V”形结构的飞机，但为了减少混乱这些结构在此不加讨论。）reduce confusion . ) The vertical element has a fixed part called the vertical stabilizer and a
垂直部分有一个固定部件，称作垂直安定面，还有一个可移动部分，movable part called the rudder . The rudder is controlled by pedals on the cockpit floor. The
称作方向舵。方向舵是由驾驶座舱地板上的踏板控制的。
horizontal surface usually has a fixed horizontal stabilizer and a movable elevator . On some
水平部分通常有一个固定的水平安定面和一个可移动的升降舵。在某些飞机上airplanes the entire horizontal surface moves，in which case it is called a stabilator . The elevator 整体水平部分可以移动，这种情况下它被称为全动平尾。升降舵或全动or stabilator is controlled by the fore and aft movement of the control wheel or stick.
平尾由驾驶盘或驾驶杆的前后移动来控制。
The engine and propeller on most single-engine airplanes are mounted on the front of the
大部分单发动机飞机上的发动机和螺旋桨被安放在机身前部。
fuselage. This is called the tractor (pulling ) configuration . The protective skin around the engine 这被称为牵引布局。围绕在发动机周围的保护蒙皮称为
is called the cowl. It provides a smooth exterior surface and channels cooling air around the
外罩。它提供光滑的外表面并且引导发动机周围的冷却空气。
engine.
The undercarriage of an airplane is its landing gear. Early airplanes had two main wheels
飞机的起落架是它的着地装置。在早期飞机在机身或机翼下面有两个under the fuselage or wings and a smaller wheel under the tail. Since this was the original method 主轮，在尾部有一个较小的轮子。因为这是原始的设计起落架方法，of designing landing gear , it is called conventional landing gear (see Figure 2.3). Today most
所以它被称为老式/传统起落架（看图2.3）。今天绝大部分飞airplanes are designed with the main wheels farther aft on the fuselage or wing and with a nose
机设计，将主起落架位置设计在机身后部或机翼下，同时用机头的前轮代替了（过去的）wheel rather than a tail wheel. This is the tricycle configuration. Tricycle gear airplanes are easier 尾轮。这就是前三点式起落架设计。前三点式起落架飞机在地面上
to control on the ground，Especially during landing.
较容易控制，特别是在着陆时。
The landing gear on an airplane is either fixed or retractable. Fixed gear is cheaper, easier to 飞机起落架有的是固定的，有的是可回收的。固定的起落架便宜，容易维护，maintain, and foolproof (you don’t have to remember to put it down before landing ).
和无比安全（在着陆前你不必不得不记得放下起落架）。
Aerodynamically, a retractable gear is preferable because with the wheels and struts placed inside 就空气动力学而言，可回收起落架是较优越的，因为当把轮子和支柱放在机翼或机身里时the wing or fuselage , there is less interference with the flow of air.
就减少了对空气流动的干扰。
Lesson Three
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课文
Why Airplanes Fly (I)
飞机为什么能飞
The Forces of Flight
飞行力
An airplane in flight is at the center of a continuous tug-of- war between two pairs of
在飞行状态中，飞机位于两组对抗力（看图3.1）保持平衡的中心点，升力对重力，opposing forces (see Figure 3.1) . Lift opposes weight and thrust opposes drag .
推力对阻力。
Gravity constantly pulls the airplane toward earth . We measure the effects of gravity by the 飞机受到恒定的重力，方向指向地面。我们通过飞行器和它的货物的重量来测量weight of the aircraft and its cargo.
重力的影响。
Thrust is any force acting in the same direction as the airplane flight path (the motion of the 推力是任何与飞机飞行路径（飞机穿过大气的运动）方向相同的力。
airplane through the air). Typically the power plant system (the engine and propeller) provides this
典型地，动力设备系统（发动机和螺旋桨）提供这个力。
force .
Lift and drag are the forces produced by the motion of the airplane through the air. As a pilot, 升力和阻力是飞机穿行大气运动产生的力。作为飞行员，为了合理地应用这些力，你you must understand how these forces are generated in order to use them properly. Lift acts
必须懂得它们是如何产生的。升力垂直perpendicular (at a 90-degree angle) to both the flight path and the wing’s span (the wing-tip to
于（90度角）飞行方向和机翼的跨度方向（翼尖到翼尖的方向）。
wing-tip direction). See Figure 3.2. Drag is any force acting parallel to the flight path but in the 看图3.2。阻力是平行于飞行方向却与飞行方向相反的任何力。opposite direction.
Whenever the airplane is flying at a constant airspeed along a steady flight path (a steady 每当飞机沿着不变航向等速飞行（平稳爬升，平稳下降，或平飞）时，它就是在静态条climb, a steady descent, or straight and level) it is in static flight conditions. In static flight the
件下。在静态飞行中，作用opposing forces on the airplane are balanced：that is ，lift equals weight and thrust equals drag . 在飞机上的对抗力是平衡的：即，升力与重力平衡，推力与阻力平衡。
Whenever an airplane is turning ，changing speed，or changing rate of climb or descent，the
每当飞机转向、变速、或改变爬升或下降速率时，对抗力不再平衡，
opposing forces are not balanced. However , under any changing conditions the airplane is always
然而，在任何变化的条件下，飞机总是在力图均衡相互对抗attempting to equalize the opposing forces and return to static flight.
的力，并恢复到静态飞行的状态。
The Creation of Lift
升力的产生
The actions of the physical forces that support an aircraft in flight are not visible. But rest
飞行中支撑航空器的物质力的作用姿态是不可见的。但是航空器运动时，这些力确保assured that these forces keep an airplane aloft while it moves. Two basic laws of physics,
它能停留空中。物理学的两个基本定律，
Newton’s Third Law of Motion and Bernoulli’s Principle, help explain the phenomenon of flight. 牛顿第三运动定律和伯努利原理，帮助解释飞行现象。
These principles are not difficult to understand when they are explained in practical, flight-related 当这些原理从实践的，相对飞行的角度解释时，它们是不难理解的。
terms.
Newton’s Third Law of Motion states that for every action there is an equal and opposite
牛顿第三运动定律讲述每一个作用都有一个大小相等方向相反的反作用。
reaction. If you could observe the airflow in front of and behind an airplane in flight ，you would 飞行中如果你观察飞机前后的气流，你将看到飞机后面的空气是向下的。
see that the air behind the airplane is redirectedly downward. The downward force caused by the
由机翼引起的向下的力称为下冲气wing is called downwash. The action of redirecting the air down causes the reaction of lifting the 流。转向下降气流的作用引起提升飞机的反作用。
airplane. Only when the mass of air directed down by the wings equals the mass of the airplane 只有当机翼的下推的空气质量力与飞机运动的质量力均等时，飞机才能飞行。
does the airplane fly. Air rushing around and down behind the wings makes an airplane fly.
在机翼后面来回冲撞的空气使飞机得以飞行。
Airfoils Any structure that moves through the air for the purpose of obtaining a useful reaction
翼型为了获得有用的反作用力在空气中运动的任何结构称为翼型。
is called an airfoil . Although airfoils are found in a number of places on an airplane---the wing ，虽说翼型在飞机上许多地方可以看到—机翼，尾翼面，和螺旋桨—但是机tail surfaces ，and propeller –the wing is the most important . The special shape of the wing is the 翼是最重要的地方。机翼特殊的形状是它成功的秘密。secret to its success. Figure 3.4 shows a cross-section of typical airfoil in motion through the air.
图3.4 显示了在空气中运动的典型翼型的横截面。
The airfoil has a rounded leading edge and a sharp trailing edge. The curved shape of the upper
翼型具有圆形的前缘和尖形的后缘。上下面的曲线形状称为曲度弧。and lower surface is called camber. The chord (or chord line ) is a hypothetical straight line that
弦（或弦线）是通过翼型前后缘的一条假象直线。passes through the leading and trailing edges of the airfoil.
Relative Wind and Angle of Attack The stream of air approaching the airfoil is called relative 相对气流和迎角靠近翼型的气流称为相对气流，因为它是运动的气团并wind since it is a moving mass of air and has a direction relative to the airfoil. The direction of the 且相对翼型有一方向。相对气流方向与翼relative wind is exactly opposite that of the flight path of the airfoil. In fact ，relative wind is the 型飞行方向恰恰相反。实际上，相对气流是飞行路result of the flight path. The angle that the relative wind makes with the chord line is called the
径的结果相对气流与弦线的夹角称为迎角。
angle of attack. When describing the magnitude of this angle ，the term low angle of attack means 当描述这个角大小时，低迎角这个术语意味着相对气流与弦线的夹角是小迎a small angle between the relative wind and the chord line. As the angle between the relative wind 角。随着相对气流与弦线夹角的增加，迎and the chord line increases , the angle of attack gets higher.
角变高。
Although these effects hold for every airfoil on the airplane ，the wing is the primary airfoil 尽管这些作用适用于飞机的每个翼型（气动力面），但是，机翼是任何飞行员应该注意of interest to you as a pilot . The wing’s relative wind is a result of the flight path of the entire
的主要翼型(气动力面)。机翼的相对气流是整个飞机飞行路径的结果。
airplane. Realizing this is an important step toward gaining a pilot’s understanding of flight 认识到这一点是飞行员了解飞行力学的重要一步。
mechanics.
Newton’s Law describes the effect the wing has on the air it passed through：the wing
牛顿定律描述了机翼对其周围大气的作用：机翼使气流转向下方。
redirects air downward. It does not ，however ，explain how the wing makes this happen.
然而，它并没有解释机翼如何使这个现象发生的。
Bernoulli’s Principle explains what the wing does to the air to cause it to be redirected downward. 伯努利原理解释了机翼对大气做了什么，并解释了机翼如何使大气转向下方。
Bernoulli’s Principle The eighteenth-century Swiss physicist Daniel Bernoulli discovered that 伯努利原理18世纪瑞士物理学家Daniel Bernoulli 发现如果空气被迫通过一根
if air were forced through a tube with a constriction in it (a venturi tube ) ，the pressure of the air 在里面有约束的管子（文氏管）时，空气的压力在两端时是相同的，但是在有约束处压力减was the same at both ends but less at the constriction. The reason for this ，he theorized ，was that 小。他推理这种现象的原因是空气团为了通过the mass of air had to speed up in order to pass the constriction. The total energy of the air at any 这个约束不得不加速。在管子中任意点空气的总能量是point in the tube must be constant ，because of the conservation energy (a law of physics that
不变的，因为能量守恒（在任何时候都成立的物理定理）。
holds at all times ). Bernoulli then deduced that at the constriction ，more energy was used to
伯努力随后推论在约束处更多的能量用于加速空气分子，留下了较少的能accelerate the air molecules ，leaving less energy to exert pressure on the walls of the tube. He
量向管壁施加压力。
determined that any time the velocity of air is increased，its pressure is decreased. He observed
他确定当空气速度增加时，其压力降低。他发现反之也that the reverse is also true ：when the velocity of air is reduced，its pressure increases. Figure 3.5 成立：当空气速度降低时，其压力增加。图3.5显示了文氏管和压力—速度的关系。shows a venturi tube and these pressure-velocity relationships.
How does this principle apply to airfoils? The special shape of an airfoil causes the air
这个原理是如何应用于气动力面的呢？气动力面特殊的形状使通过其上面的空气加速，passing over it to speed up while the air below the airfoil is slowed. The change that occurs along 而其下面的空气减速。沿上表面发生的改变是两个
the upper surface is the most significant of the two. The higher-velocity air over the top of the
改变中最明显的。在气动力面上方的高速气流导致机翼上方airfoil results in a large low-pressure area above the wing. The decreased air velocity below the
出现巨大的低压区。气动力面下方的减速空气在机翼下方airfoil creates a smaller higher-pressure area below the wing.
引起较小的高压区。
The large low-pressure area (which could also be called a partial vacuum) pulls the wing up 巨大的低压区（也被称作未尽真空）把机翼向上拖拽进低压区。
into it. The action of pulling up on the wing causes a reaction of pulling down on the passing 将机翼向上拖拽的作用引起了对路过气流向下拖拽的反作用。
airflow. A similar activity is taking place below the wing，but on a much smaller scale. High 类似的活动在机翼下方也发生了，但只是较小范围内。
pressure below the wing acts by pushing it up，causing the reaction of pushing the air down.
机翼下方的高压对机翼产生向上推动的作用，引起对空气向下推的反作用。
The net result is an upward force on the wing called the resultant force. The portion of this 实际的结果是作用在机翼上向上的力，称之为合力。合力垂直于航向（或resultant force that acts perpendicular to the flight path (or relative wind ) is called lift. The
相对气流）的分力被称为升力。
downward force transmitted to the passing airflow is downwash. The most important point to
作用在路过气流上向下的力称为下冲气流。应记住最重要的一点是我们称remember is that the upper surface of the wing produces most of the force we call lift.
为升力的大部分力是由机翼的上表面产生的。
Lesson Four
Text
Why Airplanes Fly (II)
The Creation of Drag
阻力的产生
，you recall，is any force acting parallel to the flight path but in the 诱导阻力。你能记得阻力是与航向平行但方向相反的任何力。
opposite direction. The resultant force created by an airfoil is basically in the correct direction for 有气动力面产生的合力基本上与升力方向一致，但实际上并不是。
lift，but not exactly. Note that the resultant force arrow in Figure 4.1 is not perpendicular to the 注意图4.1中合力的箭头并不与相对气流垂直；
relative wind；it slants slightly toward the direction of the relative wind. Figure 4.2 breaks this 它略略向相对气流方向倾斜。图4.2 把这个力分解成force down into two components and shows that while lift is created (perpendicular to the relative 两部分，并显示出当升力产生时（垂直于相对气流），某个阻力也被升力的产生而诱导产生。wind)，some drag is also induced by the creation of lift. This component of the wing’s resultant
这个机翼的合力的组成部分被称为诱force is called induced drag.
导阻力。
Parasite drag. Any solid object (an airplane ，for instance) that moves through the air must 寄生阻力。任何在空气中运动的固态物（如飞机）在其途中一定会干扰和移动空气分disturb and displace the air molecules along its path. The air molecules resist this disturbance ，子．空气分子抗拒这种扰动，并且抗拒力随着称and the resistance is manifested as a drag force called parasite drag. The amount of parasite drag
作寄生阻力的阻力而显示出来。寄生阻力的大小依赖许多相depends on a number of interacting factors，such as the size of the object，its shape ，and the
互作用的因素，如物体的大小，形状，和表面的粗糙度。
roughness of its surface.
The effective size of an object as it moves through the air is called its frontal area (see Figure 当物体在空气中运动时，它的有效尺寸被称作前视面区域（看图4.3）。
4.3 ). You can visualize frontal area as the shadow an object would cast if a light source came from
你可见的前视面区域看上去就像光源来自于与相对气流同样方向的情况下所产生的投the same direction as the relative wind. A given object’s frontal area can vary depending on its
影。某一物体的前视面向对于风的姿态而变化，正如影子的attitude with respect to the relative wind ，just as the shape of its shadow depends on how it is
形态决定于他相对于光的位置。
presented to the light. A thin board placed edge first into the wind has a small frontal area
(看图4.3（a）)一个薄板首先把边缘放到风中与同一块板把舷侧放到风中相比，前者有一个较小的前视面。
compared to the same board placed broadside into the wind (see Figure 4.3(a)). In general，the
总之，前视面区域larger the frontal area ，the higher the drag force. However ，the shape of the object also has a
越大，阻力值越高。然而，物体的形状对阻力也有很大的影响。powerful effect on drag. A flat plate facing the wind broadside creates a very large drag force，but 面对风舷侧的平面产生非常大的阻力，
if that some frontal area is enclosed in a teardrop shape，the drag is reduced enormously (see
但是若某个前视面是封闭的泪珠状，阻力就被极大地降低（看图4.3（b））。
Figure 4.3(b)). This aspect of parasite drag，Which depends on both frontal area and shape of the 取决于前视面和物体形状的寄生阻力方面被称为形状阻力。
object，is called form drag. Most aircraft have protrusions that add unwanted but necessary frontal
多数飞机具有某些突出物，这些突出物虽属附加物，但却增加了area ，such as radio antennas，wing struts，or fixed landing gear. Aircraft designers often enclose 必不可少的前视面，诸如无线电天线、机翼支柱或固定起落架。飞机设计者经常用称作整流these items in a metal or plastic shroud called a fairing ，which is shaped and oriented to reduce 罩的金属或塑料覆盖物包裹这些突出物，整流罩被设计造型和调整方位来尽可能地降低阻drag as much as possible.
力。
The slowing of air molecules due to skin friction drag is another component of parasite drag 由于蒙皮的磨擦阻力空气分子的减速是寄生阻力的另一种成分（图4.3（c））。(Figure 4.3(c)). Smooth surfaces are obviously better than rough ones. The amount of skin friction 光滑表面明显比粗糙表面好。蒙皮阻力大小与物体整个drag is proportional to the total amount of surface area of the object.
表面区域大小成比例。
When two different shapes are joined together，such as a wing and a fuselage，air may not 在两种不同类型物体连接的情况下，如机翼与机身，空其在连接处不会顺畅流动，这就flow smoothly near the intersection，creating interference drag. Designers often add a specially
产生干扰阻力。设计人员常给连接处增加了一块shaped piece of metal or plastic，called a fillet，to blend the surfaces and reduce the interference 特制形状的金属或塑料件，成为整流包皮，以融合这两个面，从而减少干扰阻力（图4.3（d））drag (Figure 4.3(d)).
Total Drag. The total drag on an airplane in flight is the combination of its induced drag and
总阻力。作用在飞行中飞机上的总阻力是诱导阻力和寄生阻力的合并。
parasite drag.
Factors That Influence Lift and Drag
影响升力和阻力的因素
The aerodynamic forces on an airplane are influenced by four variables:
作用在飞机上的空气动力受四个变量的影响：
1. Its size and shape.
它的尺寸和形状。
2.The density of the air through which it is flying.
它飞行时通过的空气的密度。
3.The angle of attack of its wing.
机翼的迎角。
4.The speed at which it is moving through the air.
它在空气中运动的速度。
Size and Shape. Although the manufacturer determines the basic size and shape of an
尺寸与形状。虽说飞机的基本尺寸与外形由制造商来确定，但飞行员的确有能力应用控airplane, the pilot does have some ability to modify shape by using the control surfaces. A
制面更改形状。
discussion of these controls in detail will take up greater space, so for now we will assume that
这些控制的详细论述将会占据较大篇幅，以至现在我们假设尺寸与形状保持不变。
size and shape remain constant.
Air density. An airplane creates forces by moving air molecules around, so naturally those 空气密度。飞机通过移动周围的空气分子来产生力，因此这些力自然受空气密度的forces are influenced by the density of the air. Density is the number of molecules in a given
影响。密度就是给定空气体积内的分子数。
volume of air. Lift and Drag increase with air density because more molecules are being
升力和阻力随空气密度的增加而增加，因为更多的分子受到影响（所有其它的affected(all other factors being constant). The relationship between air density and the way an
因素是常数）. 空气密度与飞机的运行方式之间的关系是性能的主题airplane performs is the subject of performance, which is not discussed here. We likewise assume 在此不加以讨论。我们同样假设空气密that air density is not changing.
度不变。
Lift and Drag versus angle of attack: stalls. The most direct way a pilot can control lift is through 升力阻力对迎角：失速。飞行员控制升力最直接的方法是通过机翼的迎角。the angle of attack of the wing. Increasing the angle of attack increases lift and induces drag (all
增加迎角能提高升力并减小阻力（所有其它因素不变）。
other things being equal).
There is , however, an upper limit to what the wing can do. Figure 4.4 shows a cross-section 可是机翼能力有其上限。图4.4显示了以增加迎角飞行的of a wing flying at increasing angles of attack. At low angles of attack, the airflow follows the
机翼界面。在低迎角下，气流紧贴机翼表面并有效的改道向airfoil surface closely and is efficiently redirected downward. As the angle of attack increases, the 下。随着迎角的增加，
airflow begins to separate from the upper surface of the airfoil at its trailing edge, and this
气流在后缘处从机翼上表面开始分离，并且该分离产生一个扰流区。
separation produces an area of disturbed air. The separated airflow hinders the creation of
被分离的气流阻碍了洗流的产生并大大地增加了downwash and increases drag significantly. This separation continues to increase as the angle of
阻力。随着迎角的增加这种分离继续增加。
attack increases. When enough lift-producing downwash is replaced by swirling eddies of
当足够的产生升力的洗流被扰动的旋转涡流替代时，升力开始下降。disturbed air, lift begins to decrease. At this point the airfoil is stalled. By definition, a stall occurs
在这一点上机翼失速。按照定义，迎角增大而引when lift decreases as a result of an increase in angle of attack. The angle of attack at which the
起升力减小，这样就产生失速。失速开始时的迎角称作临界迎角。stall begins is called the critical angle of attack.
It must be emphasized that only angle of attack is responsible for the stall process; neither 必须强调仅仅迎角对失速过程有影响；
speed nor the attitude of the aircraft controls it. An airfoil stalls any time the critical angle of attack 速度和飞机飞行姿态都不能控制它。一旦机翼超过临界迎角就发生失速。
is exceeded. A stall can occur at any airspeed and in any aircraft attitude. The only way to recover 失速能在任何飞行速度和任何飞行姿态下发生。从失速中恢复唯一的方法就是from a stall is to reduce the angle of attack.
减小迎角。
The wing of most airplanes is designed so that stalling occurs progressively rather than all at 大部分飞机机翼设计成失速过程是逐渐的而不是所有的立即失速。
once. The designer’s goal is to make the inboard part of the wing stall first and the tips last (see 设计者的目标是使机翼的内侧部分首先失速而翼尖最后失速（如图4.5所示）。Figure4.5). there are two benefits to this scheme: First, the disturbed air from the stalled inboard 这种方案有两种好处：第一，来自失速内侧机翼的扰流冲击机身和尾翼，在机身wing strikes the fuselage and tail, creating a buffet (noise and shaking) on the airframe. Because it 上产生颤振（噪声和振动）。因为在失速comes early in the stall process, this important warning signal should not be ignored. Second, the 过程中这种重要警告信号来的比较早，所以不应该被忽视。第二，处于control surface on the outboard part of the wing(the ailerons) remain effective even while most of 机翼外侧部分的控制表面（副翼）保持有效工作，甚至大部分机翼已经失速，因此飞行员拥the wing is stalled, so the pilot has control of the airplane as long as aerodynamically possible. A 有对飞机的控制只要空气动力学上可能。
wing’s progressive stall characteristics are built into the design by patterning different shapes of
一种机翼的逐渐失速特征取决于它的设计的形式，可以设计成沿顺着翼展采用不同的翼型，the airfoil along the span of the wing or by building the wing with its tips at a lower angle of
或者把机翼设计成翼稍部分的迎角小于内侧部分的迎角。
attack than the inboard part. Most airplanes have a combination of the two.
大部分飞机共存两种设计形式
Lift and drag versus speed. The most powerful factor in the creation of lift and drag is the speed at 升力和阻力对速度。升力和阻力产生最有力的因素就是飞机在空气中运动的速度。which the airplane moves through the air. If all other variables are held constant, lift and drag vary
如果所有其它的变量保持不变，升力和阻力随着速度with the square of the speed. This means that if speed is doubled, the lift and drag forces increase 的平方变化。就是说如果速度增加到两倍，升力和阻力就要增加四倍。
four times. Conversely , if speed is halved, the aerodynamic forces become one-fourth their 相反，如果速度减半，空气动力变为他们初始值的四分之一。
initial value.
In the real world flying, of course, other variables are not constant. In fact in steady
在真实的飞行世界里，当然，其它的变量不是常数。事实上在稳定飞行中flight(constant speed, no change in altitude), lift is held constant(equal to weight). So let us
（速度恒定，高度不变），升力保持不变（等于重力）。那么让我们来测试一下水平飞行examine the effect of speed on an airplane in level flight.
飞机上的速度的影响
Lift and drag in level flight. As an airplane changes speed., it must simultaneously change its 水平飞行的升力与阻力。当飞机改变速度时，为了保持升力恒定它必须同时改变它的迎角angle of attack in order to keep lift constant. For instance, an increase in speed must be
例如，速度的增加必须与迎角的降低相抵消。counteracted by a decrease in angle of attack. But changes in speed and angle of attack also affect
但是速度和迎角的改变也会影响各种类型的阻the various types of drag.
力。
We know that induced drag changes with angle of attack. Therefore, in level flight, as speed 我们都知道诱导阻力随迎角而改变。因此，在平飞中，速度增加，诱导阻力减小（看图increases, induced drag decreases(see Figure 4.6).
4.6）
Since parasite drag is a function of the number of air molecules being disturbed, it follows that 因为寄生阻力是被干扰空气分子数量的函数，所以寄生阻力随着速度的增加而增加，无parasite drag increases with speed, whether the airplane is in level flight or not.
论飞机是否平飞。
Total drag in level flight is more complicated because induced drag and parasite drag behave 平飞中的总阻力更加复杂，因为诱导阻力和寄生阻力表现不同。
differently. Figure 4.6 shows how each drag force varies with speed. Thrust from the engine is the 图4.6显示每个阻力随速度的变化。发动机的推力是对抗阻力的force that opposes drag. That is why the curve labeled ―total drag‖ in Figure 4.6 has the alternate 力。这就是在图4.6中标有“总阻力”的曲线有“平飞所需推力”替换标label of ―thrust required for level flight.‖
签的原因。
Normally, airplanes in flight move at speeds high enough to make parasite drag the
正常情况下，飞行中的飞机以足够高的速度飞行以至使寄生阻力为占主要作用的predominant drag force. Any increase in speed requires more thrust, and you slow down by
阻力。任何速度增加需要更多的推力，而减速要减小推力。
reducing thrust. Notice that the total drag curve has a characteristic U shape. This indicates that 注意总阻力曲线有一个U型特性。这表明减速降低阻力仅能达到某一点。slowing down reduces drag only to a certain point. The bottom of the U is the point of minimum
U型曲线的最低点就是最小阻力点。drag. If you slow down beyond the point of minimum drag, induced drag predominates. Total drag 如果减速超过最小阻力点，诱导阻力占优势。总阻力现now increases as speed decreases. This means that below a certain speed power must be increased 在随着速度减小而增加。这就是说低于某一速度时为了飞得更慢必须增加推力。
to fly slower! The speed at which minimum drag occurs is typically a few mph faster than normal 最小阻力发生的速度明显比正常起飞速度快。
takeoff speed.
Learning to control an airplane at slow flight speeds is an essential part of flight training.
学习控制低速飞行的飞机是飞行训练的本质部分。
Understanding the drag characteristics of an airplane will simplify the learning process.
了解飞机的阻力特征将会简化知识过程。
Lesson Five
Text
Controlling the airplane in flight
操纵飞行的飞机
Using the Flight Controls.应用飞行操纵装置
The axis of rotation. The flight controls are used by the pilot to position the wing and to move 旋转轴。飞行操纵装置是飞行员用来定位机翼位置和沿着渴望飞行路线运行the airplane along the desired flight path. The motion of any object can be described by its
飞机的。任何物体的运动能用绕三个旋转轴的运动来描述。movement about the three axis of rotation. The point at which the axis meet is called the center of
轴的相交点称作重力中心（CG）。看图5.1。gravity(CG). See Figure 5.1.
The lateral axis and pitch. The lateral axis of rotation can be imagined as a line running from 横轴和俯仰。旋转横轴可假象为一条从翼尖到翼尖并通过重心的直线。
wing tip to wing tip through the center of gravity. Movement about this axis is called pitch and is
关于这个轴的运动称作俯仰并且由尾翼上升controlled by the elevator or stabilator on the tail (see Figure 5.1). when you pull back on the
降舵或全动平尾来控制（看图5.1）。当你向后拉控制轮或控制秆control wheel or stick, the trailing edge of the elevator moves up. This deflects air upward, forcing 时，升降舵的后缘向上移。这就使空气向上偏移，迫使飞机
the tail down and the nose up. Pushing the controls forward lowers the elevator and consequently 尾部向下、头部向上。当向前推动控制装置时，使升降舵降低从而头部向下。
the nose. (―Deflecting the air‖ is a descriptive term, not a literal one. Control surfaces, like the （“使空气转向”是一个描述性的词汇，不是一个准确的词汇。操纵面，就像升降舵一样，elevator , change the shape of the airfoil they are part of. The deflected air is actually the change in 能改变其所在翼型的形状。偏离空气事实上是由于控制运动引起的洗流改变。）
the downwash due to the control movement.) See Figure 5.2. The terms ―raising the nose ‖ and
看图5.2。词汇“升高头部”和“降低头部”
―lowering the nose‖ are conventions adopted from cockpit references.
是采用座舱为参考的习惯。
The vertical axis and yaw. The vertical axis is an imaginary line running through the ceiling 竖轴与偏航。竖轴是一条通过舱顶和机身地板的并且通过重心的假想直线（图and floor of the fuselage, through the center of gravity (Figure 5.1).Rotation about the vertical axis 5.1）。绕竖轴转动称为偏航，并且
is called yaw and is controlled by the rudder on the tail. Pressing on the right rudder pedal deflects 它由尾部的（方向）舵来控制。踩右舵踏板使（方向）舵后缘the trailing edge of the rudder to the right. This redirects the airflow, causing the tail to move to
偏向右方。这个使气流转向，引起尾部向左运动并头部向右运the left and the nose to the right. Pressing the left rudder pedal produces the opposite result.
动。踩左舵踏板产生相反的效果。
The longitudinal axis and roll. The longitudinal axis is an imaginary line running from the 纵轴与滚转。纵轴是一条从机头到机尾并通过重心的假想线（看图5.1）nose to the tail through the center of gravity (see Figure 5.1). Rotation around this axis is called
绕该转动称为滚转并且它由
roll and is controlled by the ailerons on the wings (see Figure 5.3). when the control wheel is
机翼上的副翼来控制（看图5.3）。当转动操纵轮（或来回拉动turned (or the stick is moved from side to side), the ailerons move simultaneously but in opposite 操纵杆）时，副翼同时以相对的方向运动。
directions. To roll right, for example, the control wheel is turned to the right ,which causes the 例如，对向右滚转来说，向右转动操纵轮，引起右副翼向上移动而左副翼向下right aileron to move up and the left aileron down. The aileron that moves down increases lift on 移动。向下移动的副翼在机翼上增加升力，使机翼that wing causing it to rise. The aileron that moves up reduces lift on the wing causing it to
提升。向上移动的副翼在机翼上降低升力，使机翼下降
descend.
There is a simple way to check that the ailerons are moving correctly. Grasp the control wheel, 有一个简单方法来检测副翼的正确运动。抓紧操纵轮或操纵杆
or stick , with your thumb pointing up. When the control is moved left or right , your thumb will 让你的大拇指指向上。当操纵杆向左或向右移动时，你的大拇指将指向向上的point to the up aileron. The other aileron will be down, of course. Study Figure 5.3 until it is
副翼。当然，另一个副翼将是向下。研究图5.3, 很明显这个简单的obvious that this simple check always works.
检测总是很奏效的。
The airplane will continue to roll as long as the ailerons are deflected. The more they are
只要副翼偏斜，飞机将继续滚转。它们偏斜的越多，deflected ,the faster the rate of roll. When the wings reach the angle with the horizon that the pilot 滚转的速率越快。当机翼与地平线形成了飞行员为实施特定机动飞行所需要wants for the particular maneuver he or she is executing , the aileron control must be neutralized 的角度时，副翼操纵必须置于中立位置以阻止滚动。
to stop the rolling motion. Rolling the airplane is called banking, and the angle with the horizon is
滚转飞机称作倾斜，和地平线的夹角称作倾斜角。
called the bank angle. To roll out of an existing bank, the control must be turned opposite the
为了脱离现有倾斜，操纵必须向倾斜相反的方向转动。
direction of bank. For example, to roll level from a right bank , turn the control wheel to the left.
例如，为了从右倾斜转为水平，就要向左传动操纵轮。
The ailerons are then neutralized when the wings return to level.
当机翼恢复到水平时，那么副翼置于中立。
Coordinated Flight 协调飞行
The ailerons operate by changing the amount of lift on the outboard portion of the wings. Of 副翼操纵伴随着机翼外侧部分的升力大小的改变。
course, lift alone cannot change because induced drag is part of the same force. (Recall that lift
当然，升力不能独自改变因为诱导阻力是同一个力的分力。（回想一下升力和诱导阻力是机and induced drag are two components of the total resultant force created by the wing.) The aileron 翼产生的总合力的两部分。）增加升力的that increases lift also increases drag on that wing tip. At the same time lift and drag are reduced 副翼在那个翼稍上也增加了阻力。同时在另一个翼稍上升力和阻力被降低on the other wing tip. Figure 5.4 shows an airplane beginning to bank to the left. The left aileron is 图5.4显示了飞机开始向左倾斜。左副翼向上，它
up, which reduces the lift and drag on the left wing tip. The right aileron is down, creating more
减小了左翼稍的升力和阻力。右副翼向下，在右翼稍上产生更大的升lift and drag on that wing tip. The changes in lift cause the airplane to bank left as desired;
力和阻力。升力的改变引起飞机向我们渴望的左方倾斜；
however, the changes in drag at the wing tips create a yaw to the right. This unwanted reaction is 然而，翼稍上阻力的改变产生了向右的偏航。这种不被渴望的反应称作called adverse yaw because it always opposes the action of the ailerons. You must add rudder
逆偏航。因为它总是与副翼的作用相反。你必须在这个转向的同input, in the same direction as the turn, to counteract adverse yaw. Entering a right bank, for
一方向加一个偏转方向舵，用来抵消逆偏航。例如，进入右倾斜，instance, you will use right aileron and right rudder until the desired bank is achieved. Then both 你将用右副翼和右方向舵直到获得渴望的倾斜。
controls are neutralized. Rudder input is always required when the ailerons are deflected, both
接着两个操纵置为中立。副翼倾斜时，无论是开始滚转盘旋还是停止滚转盘旋，都需要偏转rolling into and out of turns. Rolling level from a right bank requires left ailerons and left rudder 方向舵。从右倾斜滚转成水平需要左副翼和左方向舵直到机翼水平。until the wings are level. Proper use of the ailerons and rudder results in coordinated flight. When
副翼和方向舵正确的应用导致协调飞行。
pilots refer to flight as ―uncoordinated,‖ they are not maligning the pilot’s physical abilities but
当飞行员谈及飞行“不协调”时，他们不是中伤飞行员的身体能力而是指副翼和方向舵的不referring to improper use of the ailerons and rudder.
正确应用。
Turns and Load Factor
In order for an object in motion to change directions, it must create a force in the direction it 为了使运动的物体改变方向，它必须在它期望去的方向上产生一个力。
wishes to go. An automobile turns because its tires create a sideways force to push it around the 汽车转向是因为它的轮胎产生了一个侧向力，推动它转过角。
corner. An airplane creates this sideway force by banking its wings and redirecting the lift force.
飞机通过倾斜机翼和改变升力方向产生这种侧向力。
The turning force creates an equal and opposite force, called centrifugal force, in accordance with 根据牛顿定律，旋转力产生一个与其大小相等方向相反的力，称作离心力。
Newton’s law. Centrifugal force makes the object return to a straight path when the turning force 当旋转力被撤销时，离心力使物体恢复到直线路径。
is removed. We remember the Wright brothers’ flight in 1903 not because it was the first time a 我们记得1903年莱特的飞行，不是因为一个带有翅膀的机器在上面载有人类winged craft had flown with a human being aboard but because it was the first time any such
的首次飞行，而是因为任何那样人造的带有发动机—用自己的动力的机器的首次飞行。manned craft had flown with an engine—under its own power. Since that time, the growth of
自那次起，在一个非常真实的意aviation has been, in a very real sense, the story of the growth of engine efficiency and reliability. 义上航空的成长已经成为发动机效率和可靠性成长的故事。
Early aircraft engines were big and heavy and produced barely enough power to justify their
早期的飞机发动机是大而笨重，几乎不能产生足够的动力来证明他们在飞机上的重量。weight on the airplane. Since they were industrial rather than aeronautical designs, they sometimes
因为它们（飞机发动机）（起先）是为用于工业而不是为航空设计，所以有时在连接处容易tore themselves from their mountings or imparted such strain on the airplane that the airframe
断裂，或者使飞机承受了巨大的张力，无疑会把机体振得粉碎。
literally shook itself to pieces. All pilot were mechanic because repairs were often made not in
所有的飞行员都是技术人员，因为维修工作经常不在飞机蓬而hangars but in cow pastures or other remote places after a forced landing. It was a colorful and
是在牛的牧地或一次迫降后的另一个遥远的地方。它是一个多彩而浪漫的romantic time , but only for those who survived it. Pilots and designers thought there had to be a 时刻，但仅仅对那些幸存的人来说。飞行员和设计者认为应该有一个好办法。better way. There was , and the modern reciprocating aircraft engine is the result.
这就是，现代的活塞式飞机发动机就是成果。
Today’s pilots need to understand power plant principles and systems in order to operate 为了安全有效地操纵动力设备系统，今天的飞行员需要了解动力设备规章和系统。those systems safely and efficiently. Repairs , fortunately, are the province of airframe and power
幸运的是，维修是机身和动力设备技工们的领域，
plant(A&P) mechanics, FAA certified specialists who meet specific legal and professional
FAA鉴定的具有特定的合法的和职业水准的专业人员。standards. A good pilot is one who not only can fly safely but can converse with these specialists 一个优秀的飞行员不仅能够安全的飞行而且能与这些专业人员进行交流并且能and relay accurate information about power plant system operation.
传达动力设备系统运行的准确信息。
Lesson Seven
Text
The Oil System 供油系统
An engine’s oil system serves two main purposes. It removes internal engine heat,
发动机供油系统服务于两个主要目的。它排除内部发动机的热量，complementing the external cooling systems described above. Oil also coats the moving parts of
补充上面描述的外部冷却系统。油也覆盖发动机的运动部件，
an engine, reducing friction enormously. Without adequate lubrication, an engine will fail within 大量减少摩擦。没有足够的润滑，发动机将在几分钟内瘫痪。minutes. Figure 7.1 shows a typical reciprocating engine oil system. A mechanic or pilot adds oil 图7.1显示了一个典型的活塞式发动机的供油系统。技师或飞行员通过把油放入to the system by putting it into a sump, or reservoir, attached to the lower side of the engine. The
到装在发动机底面的机油箱或储油器而向系统加油。
oil level is read directly from a dipstick, as it is in an automobile.
像在汽车上一样，油面高可直接由量杆读得。
Various types of oil are available for your airplane. Mineral oil (also called non-detergent oil) 各种类型的油应用于你的飞机。矿物油（也称非洗涤性油）是仅在新发动机磨合运转时is typically used only during the break-in period of a new engine. From that point on, ashless
期典型应用。从哪一点以后，无灰烬的dispersant oil (detergent oil) is used. Oil are further categorized by their viscosity, or grade. The
分散剂油（洗涤性油）被应用。根据油的粘性或等级，它们被广泛分类。
Society of Automotive Engineers (SAE) has established the standards for these grades. The higher 汽车工程协会已经为这些等级建立了标准。
the grade, the thicker the oil, so SAE 50 oil is thicker than SAE 20. Aviation oil are identified by
等级越高，油浓度越高，因此SAE50的油要比SAE 20的粘稠。航空机油通过航空等级识aviation grades, which are exactly double the SAE value. For instance, aviation grade 100 is
别，它的等级值恰是SAE值的2倍。例如，航空100等级等与SAE50 equivalent to SAE 50 weight oil. There are even multi-viscosity oil for aircraft; these change their 重量的油。甚至有多粘度机油适应于飞机；根据温度的变化，他们的浓thickness in response to changes in temperature. Automotive oil should never be used in aircraft
度发生变化。汽车机油从不应该应用于飞机发动机上，engines, since the two oils are formulated differently. Refer to your Pilot’s Operating Handbook
因为两种机油表达的方式不同。参考你的关于机油类型和等级的飞行员操for the type and grade of oil to use. If single-viscosity oil is used, you will need to change it when 纵手册进行应用。如果应用单粘度机油，当外界环境变化时你将需要更换机油。the outside climate change.
Aircraft engines use up oil at a regular rate, unlike automobiles, which generally use little oil.
飞机发动机以一定规律速率耗尽机油，不像汽车通常用很少的机油。
It is very important to check the oil level before every flight. Keep in mind that there are no
在每次飞行前检查机油水平高度是非常重要的。要记住空中没有服务站。
service stations in the sky.
An oil pump draws the oil out of the sump through an intake that is screened to trap
油泵通过过滤排污的入口把油从收油池里吸出。
天津科技大学本科毕业设计(论文)任务书
天津科技大学本科毕业设计（论文）任务书 电子信息与自动化学院2007电气工程及其自动化专业 学生学号：07023411 学生姓名：刘广超指导教师姓名: 刘玉良 完成期限：2011 年 3 月1日至2011 年 6 月22日 一、题目名称：连铸坯切割线冷却水PLC控制系统设计 二、设计(论文)内容及要求： 本课题主要内容是应用西门子PLC进行连铸坯自动切割线冷却水供给系统的控制系统设计。具体要求包括： 1）PLC的选型，熟悉西门子PLC硬件配置与软件设计。 2）熟悉连铸坯自动切割线冷却水供给系统，完成PLC冷却水控制系统的工艺路线编制。 3）利用现有的西门子S7-200系列PLC进行连铸坯自动切割线冷却水供给系统硬件设计和梯形图程序设计。在S7-200系列PLC系统中调试通过。 4）写出不少于20000字的毕业设计说明书。 5）完成不少于5000字的外文资料翻译。 6）实习或调研报告，字数不少于2500字。 参考文献: [1] 崔彦彬,孙岩,谭宇硕,基于PLC的锅炉排烟温度控制系统的设计[J],机械设计与制造,2008(5):83-85. [2] 欧元贤,刘旺玉,用PLC实现对焊接机器人的控制[J],机械与电子,2004(12):70-72. [3] 徐德,可编程控制器(PLC)应用技术[M],济南:山东科学技术出版社,2000. [4] 廖常初.PLC编程及应用(第2版)[M].北京:机械工业出版社,2006. [5] 吴迪生,王炎,机器人控制技术[M],北京:机械工业出版社,1988. [6] 陈善本,林涛,智能化焊接机器人技术[M],北京:机械工业出版社,2005.
环境科学专业就业前景
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毕业设计外文翻译资料
外文出处： 《Exploiting Software How to Break Code》By Greg Hoglund, Gary McGraw Publisher : Addison Wesley Pub Date : February 17, 2004 ISBN : 0-201-78695-8 译文标题： JDBC接口技术 译文： JDBC是一种可用于执行SQL语句的JavaAPI（ApplicationProgrammingInterface应用程序设计接口）。它由一些Java语言编写的类和界面组成。JDBC为数据库应用开发人员、数据库前台工具开发人员提供了一种标准的应用程序设计接口，使开发人员可以用纯Java语言编写完整的数据库应用程序。 一、ODBC到JDBC的发展历程 说到JDBC，很容易让人联想到另一个十分熟悉的字眼“ODBC”。它们之间有没有联系呢？如果有，那么它们之间又是怎样的关系呢？ ODBC是OpenDatabaseConnectivity的英文简写。它是一种用来在相关或不相关的数据库管理系统（DBMS）中存取数据的，用C语言实现的，标准应用程序数据接口。通过ODBCAPI，应用程序可以存取保存在多种不同数据库管理系统（DBMS）中的数据，而不论每个DBMS使用了何种数据存储格式和编程接口。 1．ODBC的结构模型 ODBC的结构包括四个主要部分：应用程序接口、驱动器管理器、数据库驱动器和数据源。应用程序接口：屏蔽不同的ODBC数据库驱动器之间函数调用的差别，为用户提供统一的SQL编程接口。 驱动器管理器：为应用程序装载数据库驱动器。 数据库驱动器：实现ODBC的函数调用，提供对特定数据源的SQL请求。如果需要，数据库驱动器将修改应用程序的请求，使得请求符合相关的DBMS所支持的文法。 数据源：由用户想要存取的数据以及与它相关的操作系统、DBMS和用于访问DBMS的网络平台组成。 虽然ODBC驱动器管理器的主要目的是加载数据库驱动器，以便ODBC函数调用，但是数据库驱动器本身也执行ODBC函数调用，并与数据库相互配合。因此当应用系统发出调用与数据源进行连接时，数据库驱动器能管理通信协议。当建立起与数据源的连接时，数据库驱动器便能处理应用系统向DBMS发出的请求，对分析或发自数据源的设计进行必要的翻译，并将结果返回给应用系统。 2．JDBC的诞生 自从Java语言于1995年5月正式公布以来，Java风靡全球。出现大量的用java语言编写的程序，其中也包括数据库应用程序。由于没有一个Java语言的API，编程人员不得不在Java程序中加入C语言的ODBC函数调用。这就使很多Java的优秀特性无法充分发挥，比如平台无关性、面向对象特性等。随着越来越多的编程人员对Java语言的日益喜爱，越来越多的公司在Java程序开发上投入的精力日益增加，对java语言接口的访问数据库的API 的要求越来越强烈。也由于ODBC的有其不足之处，比如它并不容易使用，没有面向对象的特性等等，SUN公司决定开发一Java语言为接口的数据库应用程序开发接口。在JDK1．x 版本中，JDBC只是一个可选部件，到了JDK1．1公布时，SQL类包（也就是JDBCAPI）
毕业设计外文翻译附原文
外文翻译 专业机械设计制造及其自动化学生姓名刘链柱 班级机制111 学号1110101102 指导教师葛友华
外文资料名称： Design and performance evaluation of vacuum cleaners using cyclone technology 外文资料出处：Korean J. Chem. Eng., 23(6), (用外文写) 925-930 (2006) 附件： 1.外文资料翻译译文 2.外文原文
应用旋风技术真空吸尘器的设计和性能介绍 吉尔泰金，洪城铱昌，宰瑾李， 刘链柱译 摘要：旋风型分离器技术用于真空吸尘器 - 轴向进流旋风和切向进气道流旋风有效地收集粉尘和降低压力降已被实验研究。优化设计等因素作为集尘效率，压降，并切成尺寸被粒度对应于分级收集的50％的效率进行了研究。颗粒切成大小降低入口面积，体直径，减小涡取景器直径的旋风。切向入口的双流量气旋具有良好的性能考虑的350毫米汞柱的低压降和为1.5μm的质量中位直径在1米3的流量的截止尺寸。一使用切向入口的双流量旋风吸尘器示出了势是一种有效的方法，用于收集在家庭中产生的粉尘。 摘要及关键词：吸尘器; 粉尘; 旋风分离器 引言 我们这个时代的很大一部分都花在了房子，工作场所，或其他建筑，因此，室内空间应该是既舒适情绪和卫生。但室内空气中含有超过室外空气因气密性的二次污染物，毒物，食品气味。这是通过使用产生在建筑中的新材料和设备。真空吸尘器为代表的家电去除有害物质从地板到地毯所用的商用真空吸尘器房子由纸过滤，预过滤器和排气过滤器通过洁净的空气排放到大气中。虽然真空吸尘器是方便在使用中，吸入压力下降说唱空转成比例地清洗的时间，以及纸过滤器也应定期更换，由于压力下降，气味和细菌通过纸过滤器内的残留粉尘。 图1示出了大气气溶胶的粒度分布通常是双峰形，在粗颗粒（>2.0微米）模式为主要的外部来源，如风吹尘，海盐喷雾，火山，从工厂直接排放和车辆废气排放，以及那些在细颗粒模式包括燃烧或光化学反应。表1显示模式，典型的大气航空的直径和质量浓度溶胶被许多研究者测量。精细模式在0.18?0.36 在5.7到25微米尺寸范围微米尺寸范围。质量浓度为2?205微克，可直接在大气气溶胶和 3.85至36.3μg/m3柴油气溶胶。
天津科技大学外文翻译
从传统ASP到https://www.wendangku.net/doc/962359012.html, 摘要： https://www.wendangku.net/doc/962359012.html,是微软公司应对网络应用程序发展的新产品。在https://www.wendangku.net/doc/962359012.html,内部的革新对于这个产品导致了重大的工业普及意义。因此对于https://www.wendangku.net/doc/962359012.html,的教育有一个增长的需求。网络应用程序的发展是大学生在大学三年级时的本科课程。为了满足工业产业和大学生的需求，我们已经改变了从传统ASP到https://www.wendangku.net/doc/962359012.html,这个课程的焦点。这篇论文报告了这个改变。https://www.wendangku.net/doc/962359012.html,有重大意义的产品特点和对于改变的动机在其中被讨论。在这个过程中，遇到的问题和一些有用的网上学习资源在论文中被描述。 关键词：网络应用程序的发展，传统ASP，https://www.wendangku.net/doc/962359012.html,，移动，https://www.wendangku.net/doc/962359012.html, 1.介绍 https://www.wendangku.net/doc/962359012.html,不仅仅是ASP的一个新版本。它为移动窗口应用到网络应用程序提供了革新。网络服务和微软网络框架已经使愿景成为了一个现实，就是让它作为下一代计算机信息计算处理的平台。伴随着服务器端控件、网页表单和代码隐藏（代码后置）等一系列技术的的应用，我们可以通过完整的面向对象的编制程序设计（OOP）模型发展网络应用程序。这就有助于人们了解https://www.wendangku.net/doc/962359012.html,,以及使https://www.wendangku.net/doc/962359012.html,在行业中普及。这个行业的项目工程是新西兰国立理工学院（UNITEC）计算机系统学士学位（BCS）的最后的课程，这是大学生们从事现一个现实的真正的工作的工程项目。在我们学校我们已经观察到一个快速增长、快速成长的https://www.wendangku.net/doc/962359012.html,的相关产业的项目工程。 这个网络应用程序开发（The Web Application Development）论文是本科大学生大学三年级的课程。它最初提供使用的是ASP 2.0和应用服务器平台（ColdFusion）。为了满足来自产业行业和大学生们的需求情况，我们已经改变了课程的教学内容，它们包括https://www.wendangku.net/doc/962359012.html,、Visual https://www.wendangku.net/doc/962359012.html, (https://www.wendangku.net/doc/962359012.html,) 、和应用服务器平台（ColdFusion）。这些改变已经从2003年的第一学期就开始了。 这篇论文将要调查https://www.wendangku.net/doc/962359012.html,的产品功能，以及说明解释为什么https://www.wendangku.net/doc/962359012.html, 的产品功能是独一无二的。有关迁移到https://www.wendangku.net/doc/962359012.html,的动机我们进行了讨论并进行了分析。我们分析了在我们学校有关https://www.wendangku.net/doc/962359012.html,的产品行业工程项目的当前的发展形势，还分析了对我们的学生的短期的调查结果，以及分析了https://www.wendangku.net/doc/962359012.html,是否是一个更好的工具对于教育教学。有关迁移到https://www.wendangku.net/doc/962359012.html,遇到的问题也被讨论，同时也提出了一些对学习有用的资源。通过预知可知，对于那些想要打算去介绍引进https://www.wendangku.net/doc/962359012.html,的老师来说是很有帮助的。 2.为什么使用https://www.wendangku.net/doc/962359012.html,是特别的？ 在互联网上有许多文章是论述https://www.wendangku.net/doc/962359012.html,超过传统的动态服务器网页 (ASP)的优势。例如，https://www.wendangku.net/doc/962359012.html,引进了一个综合的完整的开发环境（IDE），，一个单
毕业设计外文翻译原文.
Optimum blank design of an automobile sub-frame Jong-Yop Kim a ,Naksoo Kim a,*,Man-Sung Huh b a Department of Mechanical Engineering,Sogang University,Shinsu-dong 1,Mapo-ku,Seoul 121-742,South Korea b Hwa-shin Corporation,Young-chun,Kyung-buk,770-140,South Korea Received 17July 1998 Abstract A roll-back method is proposed to predict the optimum initial blank shape in the sheet metal forming process.The method takes the difference between the ?nal deformed shape and the target contour shape into account.Based on the method,a computer program composed of a blank design module,an FE-analysis program and a mesh generation module is developed.The roll-back method is applied to the drawing of a square cup with the ˉange of uniform size around its periphery,to con?rm its validity.Good agreement is recognized between the numerical results and the published results for initial blank shape and thickness strain distribution.The optimum blank shapes for two parts of an automobile sub-frame are designed.Both the thickness distribution and the level of punch load are improved with the designed blank.Also,the method is applied to design the weld line in a tailor-welded blank.It is concluded that the roll-back method is an effective and convenient method for an optimum blank shape design.#2000Elsevier Science S.A.All rights reserved. Keywords:Blank design;Sheet metal forming;Finite element method;Roll-back method
毕业设计(论文)外文资料翻译〔含原文〕
南京理工大学 毕业设计(论文)外文资料翻译 教学点：南京信息职业技术学院 专业：电子信息工程 姓名：陈洁 学号： 014910253034 外文出处：《 Pci System Architecture 》 (用外文写) 附件： 1.外文资料翻译译文；2.外文原文。 指导教师评语： 该生外文翻译没有基本的语法错误，用词准确，没 有重要误译，忠实原文；译文通顺，条理清楚，数量与 质量上达到了本科水平。 签名： 年月日 注：请将该封面与附件装订成册。
附件1：外文资料翻译译文 64位PCI扩展 1.64位数据传送和64位寻址：独立的能力 PCI规范给出了允许64位总线主设备与64位目标实现64位数据传送的机理。在传送的开始，如果回应目标是一个64位或32位设备，64位总线设备会自动识别。如果它是64位设备，达到8个字节（一个4字）可以在每个数据段中传送。假定是一串0等待状态数据段。在33MHz总线速率上可以每秒264兆字节获取（8字节／传送＊33百万传送字／秒），在66MHz总线上可以528M字节／秒获取。如果回应目标是32位设备，总线主设备会自动识别并且在下部4位数据通道上（AD[31::00]）引导，所以数据指向或来自目标。 规范也定义了64位存储器寻址功能。此功能只用于寻址驻留在4GB地址边界以上的存储器目标。32位和64位总线主设备都可以实现64位寻址。此外，对64位寻址反映的存储器目标（驻留在4GB地址边界上）可以看作32位或64位目标来实现。 注意64位寻址和64位数据传送功能是两种特性，各自独立并且严格区分开来是非常重要的。一个设备可以支持一种、另一种、都支持或都不支持。 2.64位扩展信号 为了支持64位数据传送功能，PCI总线另有39个引脚。 ●REQ64#被64位总线主设备有效表明它想执行64位数据传送操作。REQ64#与FRAME#信号具有相同的时序和间隔。REQ64#信号必须由系统主板上的上拉电阻来支持。当32位总线主设备进行传送时，REQ64#不能又漂移。 ●ACK64#被目标有效以回应被主设备有效的REQ64#（如果目标支持64位数据传送），ACK64#与DEVSEL#具有相同的时序和间隔（但是直到REQ64#被主设备有效，ACK64#才可被有效）。像REQ64#一样，ACK64#信号线也必须由系统主板上的上拉电阻来支持。当32位设备是传送目标时，ACK64#不能漂移。 ●AD[64::32]包含上部4位地址／数据通道。 ●C/BE#[7::4]包含高4位命令/字节使能信号。 ●PAR64是为上部4个AD通道和上部4位C/BE信号线提供偶校验的奇偶校验位。 以下是几小结详细讨论64位数据传送和寻址功能。 3.在32位插入式连接器上的64位卡
天津科技大学__数据库系统试卷(A)及答案
A．数据库文件 B．索引文件 C．日志文件 D．备注文件 10.若系统在运行过程中，由于某种硬件故障，使存储在外存上的数据 部分损失或全部损失，这种情况称为（ C ）。 A．事务故障 B．系统故障 C．介质故障 D．运行故障 11.关于“死锁”，下列说法中正确的是（ D ）。 A．死锁是操作系统中的问题，数据库操作中不存在 B．在数据库操作中防止死锁的方法是禁止两个用户同时操作数据库C．当两个用户竞争相同资源时不会发生死锁 D．只有出现并发操作时，才有可能出现死锁 12.并发操作会带来哪些数据不一致性（ D ）。 A．丢失修改、不可重复读、脏读、死锁 B．不可重复读、脏读、死锁 C．丢失修改、脏读、死锁 D．丢失修改、不可重复读、脏读 13.从一个数据库文件中取出满足某个条件的所有记录的操作是 （A ）。 A．选择 B．连接 C．投影 D．复制 14.如果事务T获得了数据项Q上的排它锁，则T对Q（ C ）。 A. 只能读不能写 B. 只能写不能读 C. 既可读又可写 D. 不能读也不能写 15.对数据对象施加封锁，避免死锁的方法没有采用以下（C ）策略。 A．顺序封锁法 B．一次封锁法 D．两段锁 二、判断题（请判断下面说法是否正确，并在答题纸相应 位置填写√或×，每题1分，共10分） 1.（ X ）数据库系统的数据独立性是指不会因为存储策略的变化而 影响存储结构。 2.（ X ）规范化主要的理论依据是关系代数理论。 3.（ X ）把低一级的关系模式分解为若干个高一级的关系模式，其 目的是为了消除插入异常、删除异常和数据不一致。 4.（ X ）如果两个实体之间具有M : N 联系，则将它们转换为关系 模型的结果是两个表。 5.（ X ）在数据库三级模式结构中，外模式的个数与用户个数相同。 6.（ X ）关系模式R，S 具有共同的属性X，且X是R的主码，则X 称为S的外部码。 7.（ X ）数据冗余引起的问题主要是花费空间。
英文翻译与英文原文.陈--
翻译文献：INVESTIGATION ON DYNAMIC PERFORMANCE OF SLIDE UNIT IN MODULAR MACHINE TOOL （对组合机床滑台动态性能的调查报告） 文献作者：Peter Dransfield, 出处：Peter Dransfield, Hydraulic Control System-Design and Analysis of TheirDynamics, Springer-Verlag, 1981 翻译页数：p139—144 英文译文： 对组合机床滑台动态性能的调查报告 【摘要】这一张纸处理调查利用有束缚力的曲线图和状态空间分析法对组合机床滑台的滑动影响和运动平稳性问题进行分析与研究，从而建立了滑台的液压驱动系统一自调背压调速系统的动态数学模型。通过计算机数字仿真系统，分析了滑台产生滑动影响和运动不平稳的原因及主要影响因素。从那些中可以得出那样的结论，如果能合理地设计液压缸和自调背压调压阀的结构尺寸. 本文中所使用的符号如下： s1-流源，即调速阀出口流量； S el—滑台滑动摩擦力 R一滑台等效粘性摩擦系数： I1—滑台与油缸的质量 12—自调背压阀阀心质量 C1、c2—油缸无杆腔及有杆腔的液容； C2—自调背压阀弹簧柔度； R1, R2自调背压阀阻尼孔液阻， R9—自调背压阀阀口液阻 S e2—自调背压阀弹簧的初始预紧力； I4, I5—管路的等效液感 C5、C6—管路的等效液容： R5, R7-管路的等效液阻； V3, V4—油缸无杆腔及有杆腔内容积； P3, P4—油缸无杆腔及有杆腔的压力 F—滑台承受负载， V—滑台运动速度。本文采用功率键合图和状态空间分折法建立系统的运动数学模型，滑台的动态特性可以能得到显著改善。
毕业设计外文翻译
毕业设计（论文） 外文翻译 题目西安市水源工程中的 水电站设计 专业水利水电工程 班级 学生 指导教师 2016年
研究钢弧形闸门的动态稳定性 牛志国 河海大学水利水电工程学院，中国南京，邮编210098 nzg_197901@https://www.wendangku.net/doc/962359012.html,，niuzhiguo@https://www.wendangku.net/doc/962359012.html, 李同春 河海大学水利水电工程学院，中国南京，邮编210098 ltchhu@https://www.wendangku.net/doc/962359012.html, 摘要 由于钢弧形闸门的结构特征和弹力，调查对参数共振的弧形闸门的臂一直是研究领域的热点话题弧形弧形闸门的动力稳定性。在这个论文中，简化空间框架作为分析模型，根据弹性体薄壁结构的扰动方程和梁单元模型和薄壁结构的梁单元模型，动态不稳定区域的弧形闸门可以通过有限元的方法，应用有限元的方法计算动态不稳定性的主要区域的弧形弧形闸门工作。此外，结合物理和数值模型，对识别新方法的参数共振钢弧形闸门提出了调查，本文不仅是重要的改进弧形闸门的参数振动的计算方法，但也为进一步研究弧形弧形闸门结构的动态稳定性打下了坚实的基础。 简介 低举升力，没有门槽，好流型，和操作方便等优点，使钢弧形闸门已经广泛应用于水工建筑物。弧形闸门的结构特点是液压完全作用于弧形闸门，通过门叶和主大梁，所以弧形闸门臂是主要的组件确保弧形闸门安全操作。如果周期性轴向载荷作用于手臂，手臂的不稳定是在一定条件下可能发生。调查指出:在弧形闸门的20次事故中，除了极特殊的破坏情况下，弧形闸门的破坏的原因是弧形闸门臂的不稳定;此外，明显的动态作用下发生破坏。例如:张山闸，位于中国的江苏省，包括36个弧形闸门。当一个弧形闸门打开放水时，门被破坏了，而其他弧形闸门则关闭，受到静态静水压力仍然是一样的，很明显，一个动态的加载是造成的弧形闸门破坏一个主要因素。因此弧形闸门臂的动态不稳定是造成弧形闸门(特别是低水头的弧形闸门)破坏的主要原是毫无疑问。
天津科技大学食品学院复试全接触
天津科技大学2011年食品学院复试全接触 --特别感谢刘同学 10年考研学长的复试经验贴给迷茫的我带来了不少帮助和信心，结束了两天的复试，晚上闲下来给12年考研的童鞋们也唠唠我的复试，把学长的热心接力棒传下去，希望给12年的考生们带来一点帮助。 言归正传，我第一志愿是食品科学专业。调剂的有没有来我不清楚，第一志愿是去了129个人参加复试。我们的复试时间定在4月9号，10号。9号上午报名审核，主要内容包括复试通知书盖章（复试通知书自己从网上下载），复试考试缴费（90大洋），学院审核（包括身份证、学生证、本科在校成绩单、四六级证书、政审表，原件和复印件都要准备好）。9号下午就面试了，它怎么安排的我也没细看，学院有帖通知，我就查好了自己面试和笔试的时间，考场。下面面试和笔试分两个部分说，便于大家了解。 一、面试 1、面试的老师一共分6个组，除了第一组叫号填表的老师，其余的每一组都是两个老师。 第一组的老师就是负责叫号和填表，填表就是问你是否服从调剂，是否愿意念专业硕士，还有你有没有选好的导师，这些都是要填的。 2、第二组的老师问的是专业的问题，问我的是面包的加工工艺，面包是怎么上色的，澄清型果汁和浑浊型果汁的工艺区别，商业灭菌的概念。 3、第三组也是一个老师，是个南方银，说话特别快，因为听不太懂我就特别认真的盯着老师的眼睛，一丝不苟的听，把老师看的都不好意思了，一个劲的挠头。他问我平时查什么外文文献，我说我用过几次springer，老师问我那看什么纸 质的外文期刊，我说试的看过，看不懂！他还问我用过什么检测的仪器，我说知道气相色谱，但没见过。还问怎么把水加热到115度，还问了类似于GMP之类的专业英文缩写，我不认识。这一组答的最糟，不过大家好像都差不多。
工程造价外文翻译(有出处)
预测高速公路建设项目最终的预算和时间 摘要 目的——本文的目的是开发模型来预测公路建设项目施工阶段最后的预算和持续的时间。 设计——测算收集告诉公路建设项目，在发展预测模型之前找出影响项目最终的预算和时间，研究内容是基于人工神经网络(ANN)的原理。与预测结果提出的方法进行比较,其精度从当前方法基于挣值。 结果——根据影响因素最后提出了预算和时间，基于人工神经网络的应用原理方法获得的预测结果比当前基于挣值法得到的结果更准确和稳定。 研究局限性/意义——因素影响最终的预算和时间可能不同,如果应用于其他国家,由于该项目数据收集的都是泰国的预测模型,因此,必须重新考虑更好的结果。 实际意义——这项研究为用于高速公路建设项目经理来预测项目最终的预算和时间提供了一个有用的工具，可为结果提供早期预算和进度延误的警告。 创意/价值——用ANN模型来预测最后的预算和时间的高速公路建设项目,开发利用项目数据反映出持续的和季节性周期数据, 在施工阶段可以提供更好的预测结果。 关键词：神经网、建筑业、预测、道路、泰国 文章类型：案例研究 前言 一个建设工程项普遍的目的是为了在时间和在预算内满足既定的质量要求和其他规格。为了实现这个目标,大量的工作在施工过程的管理必须提供且不能没有计划地做成本控制系统。一个控制系统定期收集实际成本和进度数据,然后对比与计划的时间表来衡量工作进展是否提前或落后时间表和强调潜在的问题(泰克兹,1993)。成本和时间是两个关键参数，在建设项目管理和相关参数的研究中扮演着重要的角色，不断提供适当的方法和
工具，使施工经理有效处理一个项目，以实现其在前期建设和在施工阶段的目标。在施工阶段,一个常见的问题要求各方参与一个项目，尤其是一个所有者,最终项目的预算到底是多少?或什么时候该项目能被完成？ 在跟踪和控制一个建设项目时，预测项目的性能是非常必要的。目前已经提出了几种方法,如基于挣值技术、模糊逻辑、社会判断理论和神经网络。将挣值法视为一个确定的方法，其一般假设，无论是性能效率可达至报告日期保持不变，或整个项目其余部分将计划超出申报日期（克里斯坦森，1992；弗莱明和坎普曼，2000 ；阿萨班尼，1999；维卡尔等人，2000）。然而，挣值法的基本概念在研究确定潜在的进度延误、成本和进度的差异成本超支的地区。吉布利（1985）利用平均每个成本帐户执行工作的实际成本，也称作单位收入的成本，其标准差来预测项目完工成本。各成本帐户每月的进度是一个平均平稳过程标准偏差，显示预测模型的可靠性，然而，接受的单位成本收益在每个报告期在变化。埃尔丁和休斯（1992）和阿萨班尼（1999）利用分解组成成本的结构来提高预测精度。迪克曼和Al-Tabtabai（1992）基于社会判断理论提出了一个方法，该方法在预测未来的基础上的一组线索，源于人的判断而不是从纯粹的数学算法。有经验的项目经理要求基于社会判断理论方法的使用得到满意的结果。Moselhi等人（2006）应用“模糊逻辑”来预测潜在的成本超支和对建设工程项目的进度延迟。该方法的结果在评估特定时间状态的项目和评价该项目的利润效率有作用。这有助于工程人员所完成的项目时间限制和监控项目预算。Kaastra和博伊德（1996）开发的“人工神经网络”,此网络作为一种有效的预测工具，可以利用过去“模式识别”工作和显示各种影响因素的关系，然后预测未来的发展趋势。罗威等人（2006）开发的成本回归模型能在项目的早期阶段估计建筑成本。总共有41个潜在的独立变量被确定，但只有四个变量：总建筑面积，持续时间，机械设备，和打桩，是线性成本的关键驱动因素，因为它们出现在所有的模型中。模型提出了进一步的洞察了施工成本和预测变量的各种关系。从模型得到的估计结果可以提供早期阶段的造价咨询（威廉姆斯（2003））——最终竞标利用回归模型预测的建设项目成本。 人工神经网络已被广泛用在不同的施工功能中，如估价、计划和产能预测。神经网络建设是Moselhi等人（1991）指出，由Hegazy（1998）开发了一个模型，该模型考虑了项目的外在特征，估计加拿大的公路建设成本： ·项目类型 ·项目范围
外文翻译原文
204/JOURNAL OF BRIDGE ENGINEERING/AUGUST1999
JOURNAL OF BRIDGE ENGINEERING /AUGUST 1999/205 ends.The stress state in each cylindrical strip was determined from the total potential energy of a nonlinear arch model using the Rayleigh-Ritz method. It was emphasized that the membrane stresses in the com-pression region of the curved models were less than those predicted by linear theory and that there was an accompanying increase in ?ange resultant force.The maximum web bending stress was shown to occur at 0.20h from the compression ?ange for the simple support stiffness condition and 0.24h for the ?xed condition,where h is the height of the analytical panel.It was noted that 0.20h would be the optimum position for longitudinal stiffeners in curved girders,which is the same as for straight girders based on stability requirements.From the ?xed condition cases it was determined that there was no signi?cant change in the membrane stresses (from free to ?xed)but that there was a signi?cant effect on the web bend-ing stresses.Numerical results were generated for the reduc-tion in effective moment required to produce initial yield in the ?anges based on curvature and web slenderness for a panel aspect ratio of 1.0and a web-to-?ange area ratio of 2.0.From the results,a maximum reduction of about 13%was noted for a /R =0.167and about 8%for a /R =0.10(h /t w =150),both of which would correspond to extreme curvature,where a is the length of the analytical panel (modeling the distance be-tween transverse stiffeners)and R is the radius of curvature.To apply the parametric results to developing design criteria for practical curved girders,the de?ections and web bending stresses that would occur for girders with a curvature corre-sponding to the initial imperfection out-of-?atness limit of D /120was used.It was noted that,for a panel with an aspect ratio of 1.0,this would correspond to a curvature of a /R =0.067.The values of moment reduction using this approach were compared with those presented by Basler (Basler and Thurlimann 1961;Vincent 1969).Numerical results based on this limit were generated,and the following web-slenderness requirement was derived: 2 D 36,500a a =1?8.6?34 (1) ? ??? t R R F w ?y where D =unsupported distance between ?anges;and F y =yield stress in psi. An extension of this work was published a year later,when Culver et al.(1973)checked the accuracy of the isolated elas-tically supported cylindrical strips by treating the panel as a unit two-way shell rather than as individual strips.The ?ange/web boundaries were modeled as ?xed,and the boundaries at the transverse stiffeners were modeled as ?xed and simple.Longitudinal stiffeners were modeled with moments of inertias as multiples of the AASHO (Standard 1969)values for straight https://www.wendangku.net/doc/962359012.html,ing analytical results obtained for the slenderness required to limit the plate bending stresses in the curved panel to those of a ?at panel with the maximum allowed out-of-?atness (a /R =0.067)and with D /t w =330,the following equa-tion was developed for curved plate girder web slenderness with one longitudinal stiffener: D 46,000a a =1?2.9 ?2.2 (2) ? ? ? t R f R w ?b where the calculated bending stress,f b ,is in psi.It was further concluded that if longitudinal stiffeners are located in both the tension and compression regions,the reduction in D /t w will not be required.For the case of two stiffeners,web bending in both regions is reduced and the web slenderness could be de-signed as a straight girder panel.Eq.(1)is currently used in the ‘‘Load Factor Design’’portion of the Guide Speci?cations ,and (2)is used in the ‘‘Allowable Stress Design’’portion for girders stiffened with one longitudinal stiffener.This work was continued by Mariani et al.(1973),where the optimum trans-verse stiffener rigidity was determined analytically. During almost the same time,Abdel-Sayed (1973)studied the prebuckling and elastic buckling behavior of curved web panels and proposed approximate conservative equations for estimating the critical load under pure normal loading (stress),pure shear,and combined normal and shear loading.The linear theory of shells was used.The panel was simply supported along all four edges with no torsional rigidity of the ?anges provided.The transverse stiffeners were therefore assumed to be rigid in their directions (no strains could be developed along the edges of the panels).The Galerkin method was used to solve the governing differential equations,and minimum eigenvalues of the critical load were calculated and presented for a wide range of loading conditions (bedding,shear,and combined),aspect ratios,and curvatures.For all cases,it was demonstrated that the critical load is higher for curved panels over the comparable ?at panel and increases with an increase in curvature. In 1980,Daniels et al.summarized the Lehigh University ?ve-year experimental research program on the fatigue behav-ior of horizontally curved bridges and concluded that the slen-derness limits suggested by Culver were too severe.Equations for ‘‘Load Factor Design’’and for ‘‘Allowable Stress Design’’were developed (respectively)as D 36,500a =1?4?192(3)? ?t R F w ?y D 23,000a =1?4 ?170 (4) ? ? t R f w ?b The latter equation is currently used in the ‘‘Allowable Stress Design’’portion of the Guide Speci?cations for girders not stiffened longitudinally. Numerous analytical and experimental works on the subject have also been published by Japanese researchers since the end of the CURT project.Mikami and colleagues presented work in Japanese journals (Mikami et al.1980;Mikami and Furunishi 1981)and later in the ASCE Journal of Engineering Mechanics (Mikami and Furunishi 1984)on the nonlinear be-havior of cylindrical web panels under bending and combined bending and shear.They analyzed the cylindrical panels based on Washizu’s (1975)nonlinear theory of shells.The governing nonlinear differential equations were solved numerically by the ?nite-difference method.Simple support boundary condi-tions were assumed along the curved boundaries (top and bot-tom at the ?ange locations)and both simple and ?xed support conditions were used at the straight (vertical)boundaries.The large displacement behavior was demonstrated by Mi-kami and Furunishi for a range of geometric properties.Nu-merical values of the load,de?ection,membrane stress,bend-ing stress,and torsional stress were obtained,but no equations for design use were presented.Signi?cant conclusions include that:(1)the compressive membrane stress in the circumfer-ential direction decreases with an increase in curvature;(2)the panel under combined bending and shear exhibits a lower level of the circumferential membrane stress as compared with the panel under pure bending,and as a result,the bending moment carried by the web panel is reduced;and (3)the plate bending stress under combined bending and shear is larger than that under pure bending.No formulations or recommendations for direct design use were made. Kuranishi and Hiwatashi (1981,1983)used the ?nite-ele-ment method to demonstrate the elastic ?nite displacement be-havior of curved I-girder webs under bending using models with and without ?ange rigidities.Rotation was not allowed (?xed condition)about the vertical axis at the ends of the panel (transverse stiffener locations).Again,the nonlinear distribu-