
2.1 Software development process Read Online
2.2 Requirements analysis Read Online
2.3 Software design Read Online
2.4 Software construction Read Online
2.5 Software testing Read Online
2.6 Software maintenance Read Online
2.7 Software configuration management Read Online
Virtually all countries now depend on complex computerbased systems. More and more products incorporate computers and controlling software in some form. The software in these systems represents a large and increasing proportion of the total system costs. Therefore, producing software in a costeffective way is essential for the functioning of national and international economies.
Software engineering is an engineering discipline whose goal is the costeffective development of software systems. Software is abstract and intangible. It is not constrained by materials, governed by physical laws or by manufacturing processes. In some ways, this simplifies software engineering as there are no physical limitations on the potential of software. In other ways, however, this lack of natural constraints means that software can easily become extremely complex and hence very difficult to understand.
Software engineering is still a relatively young discipline. The notion of ‘software engineering’ was first proposed in 1968 at a conference held to discuss what was then called the ‘software crisis’. This software crisis resulted directly from the introduction of powerful, third generation computer hardware. Their power made hitherto unrealisable computer applications a feasible proposition. The resulting software was orders of magnitude larger and more complex than previous software systems.
Early experience in building these systems showed that an informal approach to software development was not good enough. Major projects were sometimes years late. They cost much more than originally predicted, were unreliable, difficult to maintain and performed poorly. Software development was in crisis. Hardware costs were tumbling whilst software costs were rising rapidly. New techniques and methods were needed to control the complexity inherent in large software systems.
These techniques have become part of software engineering and are now widely although not universally used. However, there are still problems in producing complex software which meets user expectations, is delivered on time and to budget. Many software projects still have problems and this has led to some commentators (Pressman, 1997) suggesting that software engineering is in a state of chronic affliction.
As our ability to produce software has increased so too has the complexity of the software systems required. New technologies resulting from the convergence of computers and communication systems place new demands on software engineers. For this reason and because many companies do not apply software engineering techniques effectively, we still have problems. Things are not as bad as the doomsayers suggest but there is clearly room for improvement.
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You may think at first that the words "fluid" and "mechanics" should not go together. However, the ways in which fluids (gases and liquids and a few other materials) respond to forces, exert forces, and move from one place to another (their mechanics) are crucially important to many aspects of our experience and our ability to build tools.
Consider, for example, the following areas in which fluid mechanics play an important, if not fundamental, role:
* Meteorology and ocean dynamics (tsunamis, hurricanes, and tornados)
* Fluid flow within living systems (blood flow, lymph flow, air flow)
* Hydraulic machinery (jacks, pumps, lifts, steering mechanisms)
* Chemical processing and piping (pumps, reactors, separators, pipelines)
* Turbomachinery (jet engines, power plants)
* Aeronautical and ship machinery (airplanes, helicopters, boats and ships)
Question: Which of the following is an appropriate unit for fluid density?
Choices:
m[sup]3[/sup]/kg
kg/ft[sup]2[/sup]
mkg/s
lb[sub]m[/sub]/yard[sup]3[/sup]
Question: Ice has a density of 0.91667 g/cm[sup]3[/sup]. Seawater has a surface density of about 1.03 g/cm[sup]3[/sup]. Which of the following best represents the fraction of an iceberg that appears above the water surface according to this data?
Choices:
9%
14%
18%
11%
33%
Question: Which of the following situations might be much better described by compressible flow than incompressible flow?
Choices:
Water flow over Niagra Falls
Air flow over a supersonic plane
Oil flow through a lubrication layer
Air flow in your lungs
Question: For ideal (no frictional losses) flow of an incompressible fluid through a sudden expansion, which of the following best describes how the Bernoulli equation predicts that the pressure will change?
Choices:
The pressure will be lower after the expansion than before.
The pressure will be the same before and after the expansion.
The pressure will be larger after the expansion than before.
The flow will stagnate after the expansion.
Question: Which of the following expresses Reynolds' transport theorem?
Choices:
The volume integral of the derivative of a scalar or vector field over a timedependent volume is equal to the volume integral of the velocity of the field plus the surface integral of the product of the outward boundary speed and the field.
The derivative of the volume integral of a scalar or vector field over a timedependent volume is equal to the volume integral of the derivative of the field plus the surface integral of the product of the outward boundary speed and the field.
The derivative of the volume integral of a scalar or vector field over a timedependent volume is equal to the volume integral of the derivative of the divergence of the field plus the surface integral of the product of the outward boundary speed and the field.
The derivative of the volume integral of a scalar or vector field over a timedependent volume is equal to the volume integral of the derivative of the field plus the volume integral of the product of the outward boundary speed and the field.
Question: Over which of the following length scales is the continuum hypothesis invalid for air at standard temperature and pressure (STP)? I. inches II. 0.1 nanometers III. 10 nanometers IV. 1 micron
Choices:
I and IV only
I only
I, III, and IV only
I, II, III, and IV
Question: Which of the following best describes the continuum hypothesis for a fluid?
Choices:
A fluid deforms continuously.
Fluid properties do not undergo a jump at a boundary.
Pressure changes as a continuous function in space.
The properties of a small averaging volume are the same as those for a macroscopic fluid.
Question: Which of the following are required in order to use Bernoulli's equation? I. Steady flow II. Flow along a streamline III. Inviscid flow IV. Incompressible flow
Choices:
I, II, III, and IV
I and II only
I, II, and III only
II and III only
III and IV only
Question: Which of the following best characterizes a "fluid"?
Choices:
A fluid flows under the influence of a pressure gradient.
A fluid deforms in response to stress.
A fluid has viscosity.
A fluid ceases to flow if there is no pressure gradient.
Question: How high can a 5 hP pump move 5 gal/min of water in Earth's gravity if there are no frictional losses?
Choices:
1.2 m
12 m
120 m
1200 m
Question: Which of the following statements accurately describes Eulerian and Lagrangian mechanics or reference frames?
Choices:
A neutrally buoyant weather balloon makes pressure measurements in an Eulerian reference frame.
An anemometer at the top of Mount Washington makes wind velocity measurements in an Eulerian reference frame.
The fixed laboratory reference frame is a Lagrangian reference frame.
Neither Lagrangian nor Eulerian viewpoints can be exactly correct.