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friction should be considered early in the system design by reducing it as much as possible through good hardware design. There are, however, cost constraints that may be prohibitive. dither is a simple way to reduce static friction that has been used for a long time. dither can be introduced electronically or mechanically by a vibrator (e.g., in early auto pilots). Recent advances in computer control have also shown the possibility to reduce the effects of friction by estimation and control. Static friction is the friction when sticking. The force required to overcome the static friction and initiate motion is called the break-away force. The maximum friction force typically occurs at a small displacement from the starting point. The main difficulty when modeling the friction is the problem of detecting when the velocity is zero. A remedy for this is found in the model presented by Karnopp.
1- The paragraph is about ———–
1) Reaction force between two surfaces in contact
2) Design methods for reducing the vibration
3) Modeling of dither in mechanical systems
4) Early design of computer control systems
2- The paragraph states that —————-
1) Auto pilot and dither have the same meaning.
2) Auto pilot is an example of using dither.
3) Auto pilot is the only application of using dither.
4) Auto pilot is the earliest system that has used dither.
3- It can be inferred from the paragraph that ————
1) The break-away force is constant.
2) Before sliding, the friction force is constant.
3) There is a pre-sliding displacement between contacting surfaces.
4) Before sliding, the relative displacement between contacting surfaces is zero.
4- Which one of the following sentences is correct?
1) Karnopp has explained the problem of detecting when the velocity is zero.
2) Karnopp has overlooked the problem of detecting when the velocity is zero.
3) Karnopp is the pioneer of the problem of detecting when the velocity is zero.
4) Karnopp has proposed a solution for the problem of detecting when the velocity is zero.
5- The paragraph suggests that ———-
1) Friction has inverse effect on the control system.
2) Friction can be compensated via control design.
3) Control system can eliminate the friction from the system.
4) Control system is used to model and to estimate the friction.
Mechanical engineering plays a dominant role in enhancing safety, economic vitality, enjoyment, and overall quality of life throughout the world. If something moves or uses energy, one will conclude that a mechanical engineer was probably involved in its design or production. At the same time, mechanical engineers are expected to understand and convey the real-world consequences of technological development alternatives to decision-makers and the public. Mechanical engineering is a profession requiring specific skills. These skills are acquired through education, training and experience. A solid foundation in mathematics, basic sciences, and the language arts is of crucial importance. Ability in oral and written communications is important to success in
mechanical engineering studies, and courses in mechanical and technology-related subjects can help students begin to understand the important practicalities of technological projects. While mechanical engineering programs may vary in specific content, and detail, they are linked by a common educational philosophy.
The programs provide a broad-based education with a concentration on fundamentals and basic laws as the major tools required for the professional practice of mechanical engineering.
Employment prospects for mechanical engineers are strong, particularly where local economies are growing. Industrial sectors in which mechanical engineers have
traditionally made substantial contributions are large in number. In addition, the medical and pharmaceutical industries present exciting opportunities for mechanical engineers to join forces with the life sciences. Even the entertainment industry relies heavily on mechanical engineers for special effects and amusement park equipment. The majority of this work is done in companies ranging from large multi-nationals to small local firms. With experience and further education, some
mechanical engineers move into legal or management positions. Others choose the path of scholarly research and teaching. The work of a mechanical engineer is diverse and worldwide, and their careers are marked by an important common factor of continuous learning. One engineer’s new product is another engineer’s new tool.
Mechanical engineers re in the business of advancing the technological state of the art and are doing so at a rapid pace and on a global scale. However, to remain competent and competitive throughout one’s career, they must continuously learn about and use new development in the field. Every project, promotion, and job change produce new learning demands. Engineers who are active in professional societies gain a competitive edge, enhance their knowledge and technical expertise, and acquire leadership skills.
6- All of the following are given in the passage EXEPT …………………..
1) Mechanical engineers are born with a natural distinctive talent
2) Mechanical engineering is a profession requiring particular skills
3) Mechanical engineering influences almost every aspect of our daily life
4) Some mechanical engineers move into legal or management positions
7- According to the passage, mechanical engineering programs ……………………
1) have fixed content and detail
2) influence the political movements
3) have a dim employment prospect
4) share the same educational philosophy
8- The phrase “this work” in line 20 refers to ………………………. .
1) medical industry
2) mechanical engineering
3) amusement park industry
4) pharmaceutical industry
9- In can be inferred from the sentence “One engineer’s
new product is another engineer’s new tool” that ————
1) mechanical engineering is rapidly and globally advancing
2) there is a competition throughout an engineer’s career
3) every new product causes promotion and new learning demand for another engineer
4) a new product of an engineer is an opportunity of new development in the field
10- Reading the passage, one can come to the conclusion that mechanical engineering is —– .
1) a field of study touching every aspect of life
2) a technical expertise with a concentration on fundamentals
3) a life-long process to gain a competitive edge
4) a profession requiring ability in oral and written communication
Imagine a day without mechanical engineering. You wake up in a cold room because, without modern heating systems, every tree within 100 miles has already been burned. Stumbling over your cat, which you did not see because you can’t switch on the lights, since electric generators were never invented, you decided to take a refreshing shower. Turning on the water, you are rudely reminded that hot water is available only at luxurious spas that import wood. Thank goodness for those clever chemical and electrical engineers, that develop battery powered transistors radio. After 15 minutes of squeakily music (Oh, yeah, mechanical engineers also design music speakers), you decide to get breakfast. After getting on your bicycle (You still call it a bicycle, although it rides more like a tank because its inflexible materials weigh 50 pounds, and it has no gearing), you struggle to the local café, dreaming of a more automated way of driving around or even flying through the air. The morning has left you dark and cranky, especially when you realize that the rest of the day has much more of the same in store for you.
You dream of whirling machine that quietly sort, wash,dry, and fold clothes neatly, and flying machines that can outrun an echo in a canyon and others that are faster than a shooting star. You dream of tiny robots that probe and fix the heart, mind, and body-healing breaks, blocks, andbruises. It would take diverse communities of dedicated men and women who are bound together by the common goal of making life safer, healthier, more hospitable, and more fun. You realize that, like the pyramid builders or an army of ants, these engineers would get little individual recognition or appreciation. Engineers express love with better vacuum cleaners, more efficient power tools, and cleaner wastewater treatment plants. Their inventions are not always artistic, but neither is raw sewage thrown from a second-storey window. In a wordy world where talk is cheap, engineering has a concreteness and usefulness that is not easily faked. After a day without mechanical engineers, it makes you wonder what life would be like without even higher-priced professionals, such as lawyers ,real estate brokers, or baseball players.
11- The passage suggests that ————-.
1) human needs mechanical engineers to generate electricity
2) other professionals enable mechanical engineers to earn money
3) it is mechanical engineer’s dream that led to inventions
4) human’s life heavily depends on mechanical engineering
12- The word “cranky” in line 12 is closest in meaning to – ———— .
1) gloomy
2) moody
3) unpleasant
4) unaffected
13- It can be understood that during life without
mechanical engineering —-
1) it takes 15 minutes to arrive at work by a bicycle
2) drivers communities of professional are bound together
3) individuals are more hospitable, confident, and healthier
4) 50- pound bicycles are among the heavy vehicles to be used
14- The word “it” in line 23 refers to ———— .
1) life without mechanical engineering
2) a day without mechanical engineering
3) a day without mechanical engineering and the trained
4) life without mechanical engineering and other trained professionals
Vibration is the motion of a particle or a body or system of connected displaced from a position of equilibrium. Most vibrations are undesirable in machines and structures because they produce increased stresses, energy losses, cause added wear, increase bearing loads, induce fatigue, create passenger discomfort in vehicles, and absorb energy from the system. Rotating machine parts need careful balancing in order to prevent damage from vibrations.
Vibration occurs when a system is displaced from a position of stable equilibrium. The system tends to return to this equilibrium position under the action of restoring
forces (such as the elastic forces, as for a mass attached to a spring, or gravitational forces, as for a simple pendulum). (2 examples of elastic and gravitational forces) The system keeps moving back and forth across its position of equilibrium. A system is a combination of elements intended to act together to accomplish an objective. For example, an automobile is a system whose elements are the wheels, suspension, car body, and so forth. A static element is one whose output at any given time depends only on the input at that time (synchronous)
while a dynamic element is one whose present output depends on past inputs. In the same way we also speak of static and dynamic systems. A static system contains all elements while a dynamic system contains at least one dynamic element.
A physical system undergoing a time-varying interchange or dissipation of energy among or within its elementary storage or dissipative devices is said to be in a dynamic state. All of the elements in general are called passive, i.e., they are incapable of generating net energy. A dynamic system composed of a finite number of storage elements is said to be lumped or discrete, while a system containing
elements, which are dense in physical space, is called continuous. The analytical description of the dynamics of the discrete case is a set of ordinary differential equations, while for the continuous case it is a set of partial (not complete) differential equations. The analytical formation of a dynamic system depends upon the kinematic or geometric constraints and the physical laws governing the behavior of the system.
16- Which of the following statements is NOT mentioned in the passage?
1) A dynamic system is contingent upon the constraints of a number of discrete and continuous elements.
2) A static element is pertinent to synchronous rotation while a dynamic element is based on past inputs that may turn into and output.
3) The dynamic of the discrete case require more kinematic or geometric constraints when compared to the increasingly volatile continuous case.
4) A static system is made up of all involving elements while a dynamic system calls for at least one time-varying element.
17- Mechanical vibrations can cause the following damages except ———— .
1) higher efficiency
2) noise
3) distruction
4) discomfort
18- Which of the following best describes a dynamic system:
1) All of the passive elements, in general, are called dynamic.
2) Modeling of a discrete dynamic system involves partial differential equations.
3) Modeling of a dynamic system involves kinematic constraints.
4) A dynamic system is one that changes with time.
19- The passage suggests that which of the following needed to take place in order for the machines parts to act together:
1) Vibration occurs when a system is displaced from a position of stable equilibrium
2) The system tends to return to this equilibrium position under the action of dissipative devices.
3) A system is a combination of elements intended to act together to accomplish an objective.
4) Rotating machine parts need careful balancing in order to prevent damage from vibration.
20- The word dissipation as it is used in this passage isclosest in meaning to:
1) dissemination
2) consumption
3) distribution
4) contemplation
In conventionally engineered structures there is a tendency for overdesigning, usually for meeting safety requirements. Ideally, one would like to have “passive design for purpose, and adaptive design for crises”. By contrast, the usual conventional approach is to ensure that the passive structure is adequate for crises also, thus entailing higher costs due to over-designing. Some examples wherein, ideally, adaptive action should come into play only for crisis or special situation are buildings in earthquake zones, aircrafts during take-off and landing, and vehicles in crashes. A smart configuration would be that in which normal loads are taken care of in normal conditions and suitable actuation systems are activated to tackle abnormal loads. Even for normal loads, corrosion and other aging effects can render the orginal passive desgn unsuitable (even unsafe) with the passage of time. If continuous monitoring can be bult into the design through distributed embedded sensors, timely re-pairs can be taken up, thus saving costs and ensuring a higher degree of safety.
Two types of smartness in structures can be distinguished:
closed-loop and open-loop. A closed-loop smart structure senses the changes to diagnose the nature of the problem, takes action to mitigate the problem, and also stores the date of the episode for future reference. Open-loop smartness means that the design is such that structural integrity is enhanced only when needed, and the structure relapses to its normal state when there is no need to enhanced integrity. Smart bridges are a particularly attractive proposition. Bridges involve an enormous amount of investment on construction, maintenance, repair, upgrade, and finally replacement. Possible vehicular accidents, earthquakes, and terrorism are
additional problems to contend with. Embedding optical fibres (fibers) as distributed sensors at the construction stage itself is not a very costly proposition. On-line
monitoring and processing of the vast amount of sensor data is again not a difficult thing to do by present-day standards. And the overall advantages in terms of lower
maintenance costs, higher safety and security, and avoidance of inconvenience caused by closure for repair work can be enormous, not to mention the prevention of disasters like bridge collapses.
Adaptronic structure is another term used for smart structures. In the years to come, we shall see an increasing trend to incorporate smartness into the design of even ordinary items of use. Rogers has given a particularly vivid description of the nature of structural designs of the future: Adaptronic structures must, as their basic premise, be designed for a given prupose; and, by the transduction
of energy, must be able to modify their behavirour to create an envelope of utility. As an example, a ladder that is overloaded could use electrical energy to stiffen or strengthen itself while alerting the user that the ladder is overloaded. The overload response should also be based upon the actual ‘life experience’ of the ladder to account for aging or a damaged rung; therefore, the ladder must determine its current state of health and use this information as the metric for when the ladder has been overloaded. At some point of time, the ladder will then announce its retirement, as it can no longer perform even minimal tasks.
21- The author of the text would probably agree with which of the following statements?
1) A smart configuration saves costs while ensuring a higher degree of safety.
2) Passive structure is cost-effective and adequate for crises.
3) Over-designing is adequate for meeting safety requirements.
4) Adaptive design entailing over-designing is activated to tackle crises.
22- Closed- loop smartness means the design is such that ———-.
1) prevents corrosion or other aging-effects
2) monitors and repairs the damages caused
3) diverges from its normal state when the trend wears off
4) records the dynamics and episodes
23- The author of the passage would probably consider
which one of the following most analogous to adaptive action for crisis or special situations?
1) optical fibres
2) bridge collapses
3) smart bridges
4) embedded sensors
24- As used in the passage, the phrase “contend with”
most nearly means:
1) compete with
2) cope with
3) extirpate on
4) predicate on
25- A ladder as an adaptronic structure can ——–
1) overload itself like and open-loop structure.
2) Alert the user about possible damages.
3) Increase its rigidity using electrical energy.
4) act as a smart structure to reconfigure itself for various loading conditions
26- Smart bridges are designed to ———
1) modify and behave as an envelope of utility
2) house distributed sensor for health monitoring purposes
3) be adaptive in harsh conditions.
4) increase safety and maintenance costs
Suspension systems are important subsystems of most wheeled vehicles. A vehicle suspension system performs two major tasks. It should isolate the vehicle body from external road disturbances for the sake of passenger comfort, while retaining a firm contact between the road and the tire. Road disturbances have the characteristics of large magnitude in low-frequency disturbances (e.g., hills) and small magnitude in high- frequency disturbances (e.g., road roughness). A basic automobile suspension that is known as a passive suspension system consists of an energy storing element, normally a spring, and an energy dissipating element, normally a shock absorber. The main weakness of the passive suspension is that is unable to improve both ride comfort and safety factor simultaneously. In the passive suspension system, there is always a trade-off between vehicle ride comfort and safety factor.
27- The paragraph is about:
1) Automobile vibration
2) Guidance of the automobile
3) Road design for vehicles
4) Energy dissipation by an automobile
28- Which one of the following sentences is true about the road disturbances?
1) Hills and road roughness have the same characteristics.
2) Road disturbance mean hills and road roughness.
3) Road roughness is an example of the high frequency disturbance.
4) Road roughness is a characteristic of the high frequency disturbance.
29- The paragraph states that in passive suspension system:
1) Safety factor and ride comfort are independent.
2) Ride comfort and safety factor have positive correlation on each other.
3) Ride comfort has positive impact of the safety of the car.
4) To improve the ride comfort, the safety factor must be sacrificed, and vice versa.
30- It can be inferred from the paragraph that:
1) The car suspension system has role on the stability of the vehicle.
2) The car suspension system is used to store energy.
3) The passenger has to control the car suspension system.
4) The car suspension system affects the road disturbances.
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