In physics, and more specifically kinematics, acceleration is the change in velocity over time. Because velocity is a vector, it can change in two ways: a change in magnitude and/or a change in direction. In one dimension, acceleration is the rate at which something speeds up or slows down. However, as a vector quantity, acceleration is also the rate at which direction changes. Acceleration has the dimensions L T-2. In SI units, acceleration is measured in metres per second squared (m/s2).
In common speech, the term acceleration commonly is used for an increase in speed (the magnitude of velocity); a decrease in speed is called deceleration. In physics, a change in the direction of velocity also is an acceleration: for motion on a planar surface, the change in direction of velocity results in centripetal acceleration; whereas the rate of change of speed is a tangential acceleration.
Adaptive control
Adaptive control involves modifying the control law used by a controller to cope with the fact that the parameters of the system being controlled are slowly time-varying or uncertain. For example, as an aircraft flies, its mass will slowly decrease as a result of fuel consumption; we need a control law that adapts itself to such changing conditions. Adaptive control is different from robust control in the sense that it does not need a priori information about the bounds on these uncertain or time-varying parameters; robust control guarantees that if the changes are within given bounds the control law need not be changed, while adaptive control is precisely concerned with control law changes.
Acoustical engineering
Acoustical engineering is the branch of engineering dealing with sound and vibration. It is closely related to acoustics, the science of sound and vibration. Acoustical engineers are typically concerned with:
how to reduce unwanted sounds
how to make useful sounds
using sound as an indication of some other physical property
The art of reducing unwanted sounds is called noise control. Noise control engineers work with engineers in most industries to ensure that their products and processes are quiet. There is also a great deal of work done with the assessment and design of buildings, workplaces, airports, road systems in fact most noise generating or noise sensitive developments. There are many standards and documents stating what levels of performance must be achieved for each condition. The various standards and regulations used in the UK are condensed into The Little Red Book of Acoustics.
The art of producing useful sounds includes the use of ultrasound for medical diagnosis, sonar, and sound reproduction.
A separate and related discipline, audio engineering, is the art of recording and reproducing speech and music for human use.
Aerodynamics
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with the difference being that gas dynamics applies to all gases. Understanding the motion of air (often called a flow field) around an object enables the calculation of forces and moments acting on the object. Typical properties calculated for a flow field include velocity, pressure, density and temperature as a function of position and time. By defining a control volume around the flow field, equations for the conservation of mass, momentum, and energy can be defined and used to solve for the properties. The use of aerodynamics through mathematical analysis, empirical approximation and wind tunnel experimentation form the scientific basis for heavier-than-air flight.
Aerodynamic problems can be identified in a number of ways. The flow environment defines the first classification criterion. External aerodynamics is the study of flow around solid objects of various shapes. Evaluating the lift and drag on an airplane, the shock waves that form in front of the nose of a rocket or the flow of air over a hard drive head are examples of external aerodynamics. Internal aerodynamics is the study of flow through passages in solid objects. For instance, internal aerodynamics encompasses the study of the airflow through a jet engine or through an air conditioning pipe.
The ratio of the problem's characteristic flow speed to the speed of sound comprises a second classification of aerodynamic problems. A problem is called subsonic if all the speeds in the problem are less than the speed of sound, transonic if speeds both below and above the speed of sound are present (normally when the characteristic speed is approximately the speed of sound), supersonic when the characteristic flow speed is greater than the speed of sound, and hypersonic when the flow speed is much greater than the speed of sound. Aerodynamicists disagree over the precise definition of hypersonic flow; minimum Mach numbers for hypersonic flow range from 3 to 12.
The influence of viscosity in the flow dictates a third classification. Some problems involve only negligible viscous effects on the solution, in which case viscosity can be considered to be nonexistent. The approximations to these problems are called inviscid flows. Flows for which viscosity cannot be neglected are called viscous flows.
Agricultural engineering
Agricultural engineering is the engineering discipline that applies engineering science and technology to agricultural production and processing. Agricultural engineering combines the disciplines of animal biology, plant biology, and mechanical, civil and chemical engineering principles with a knowledge of agricultural principles
Aircraft Maintenance Engineer
An Aircraft Maintenance Engineer (AME) is a person licenced to ensure that aircraft are airworthy in accordance with local and international aviation standards. The Canadian equivalent to an American Aircraft Maintenance Technician and European's EASA Aircraft Maintenance Technician
All aircraft, with the exception of certain homebuilt and ultralight planes, must carry a valid Certificate of Airworthiness to be legally allowed to fly. In order for this certificate to remain valid, all maintenance on the aircraft must be certified by a licenced AME. All aircraft are maintained periodically in accordance with the Aircraft Maintenance Schedule which comes from the manufacturer of the aircraft and must be approved by local aviation authority. Also, AMEs must rectify defects, which are reported by pilots/cabin crew or found by any maintenance personnel, in accordance with Aircraft Maintenance Manuals (AMM), Illustrated Part Catalogues (IPC), and Wiring Diagram Manuals (WDM). All work performed will be periodically reviewed by Quality Assurance Department (which consists of AMEs as well)if applicable, and with Local Aviation Authority. Also, from time to time, audits are carried out by Quality Assurance Department and Local Aviation Authority on AMEs. Therefore, AMEs carry considerable legal responsibility for ensuring that work has been performed in accordance with the applicable standards of airworthiness.
Architectural engineering
Architectural engineering, also known as Building Engineering, is the application of engineering principles and technology to building design and construction. Definitions of an architectural engineer may refer to:
An engineer in the structural, mechanical, electrical, construction or other engineering fields of building design and construction.
A licensed engineering professional in parts of the United States, where architectural engineering may include complete building design.
In informal contexts, and formally in some places, a professional synonymous with or similar to an architect. In some languages, "architect" is literally translated as "architectural engineer".
Automotive engineering
Modern automotive engineering is a branch of vehicle engineering, incorporating elements of mechanical, electrical, electronic, software and safety engineering as applied to the design, manufacture and operation of motorcycles, automobiles, buses and trucks and their respective engineering subsystems.
Automotive engineers are involved in almost every aspect of designing cars and trucks, from the initial concepts right through to manufacturing them.
Broadly speaking, automotive engineers are separated into three main streams: product engineering, development engineering and manufacturing engineering.
Product engineer (also called design engineer), that would design components/systems (i.e brake engineer and battery engineer). This engineer designs and test a part, seeing that it meets all its requirements (i.e. the shock), performs as required, material meets desired durability and so on.
Development engineer, that engineers the attributes of the automobile. This engineer may provide to the design engineer what spring rate he/she requires to provide the "ride" characteristics required for the automobile to perform as desired, etc.
Manufacturing engineer, determines how to make it.
In Toyota, for example, manufacturing engineering is regarded as a more prestigious career path than designing and developing the cars
Avalanche diode
An avalanche diode is a diode (usually made from silicon, but can be made from another semiconductor) that is designed to go through avalanche breakdown at a specified reverse bias voltage and conduct as a type of voltage reference.
The Zener diode exhibits an apparently similar effect, but its operation is caused by a different mechanism, called Zener breakdown. Both effects are actually present in any such diode, but one usually dominates the other. Zener diodes are typically restricted to a few tens of volts maximum, but silicon avalanche diodes are available with breakdown voltages of over 4000 V.
A common application is protecting electronic circuits against damaging high voltages. The avalanche diode is connected to the circuit so that it is reverse-biased. In other words, its cathode is positive with respect to its anode. In this configuration, the diode is non-conducting and does not interfere with the circuit. If the voltage increases beyond the design limit, the diode suffers avalanche breakdown, causing the harmful voltage to be conducted to earth. When used in this fashion they are often referred to as clamper diodes because they "clamp" the maximum voltage to a predetermined level. Avalanche diodes are normally specified for this role by their clamping voltage VBR and the maximum size of transient they can absorb, specified by either energy (in joules) or i2t. Avalanche breakdown is not destructive, as long as the diode is not allowed to overheat.
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