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Process Description of Selection Sort
Introduction
Selection sort is an iterative process in which a list of
unsorted data is placed in either ascending or
descending order. Selection sort gets its name from the way in
which the data are sorted. During each
iteration, the smallest value from a list of unsorted numbers is
selected and then inserted in the front of
the list. As the process continues, the sorted area in the front
of the list gets larger, while the remaining
unsorted area gets smaller. At some point, when all the numbers
from the unsorted list have been
selected and inserted, the list is sorted, and the process is
complete. The selection sort process involves
the following iterative steps: evaluation, identification, and
insertion. See Figure 5.2 for a flowchart of
the process.
Discussion
Evaluation is the scanning process in which the list of numbers
is tested for proper order. This step
normally involves a pass through the list where a series of
comparisons of adjacent numbers determines
whether the list is ordered. If the list is ordered, the process
is complete and ends. If the list is not
ordered, then the lowest value is identified.
Identification is the scanning process by which the lowest value
in the list is located. Normally, the
lowest value is identified by a series of comparisons and swaps.
Once identified, the value can be
inserted.
Insertion is a relocation process in which the lowest value in
the unsorted area of the list is placed or
inserted in the front of the list. On the first iteration, this
value starts the ordered or sorted area of the
list, while the remaining numbers constitute the unsorted or
unordered area of the list. Once the lowest
value has been inserted, the process returns to the evaluating
step, where the iteration continues until
no unordered numbers remain (see Figure 5.3 for an example).
Conclusion
Selection sort is an iterative process in which a list of
unsorted data is placed in either ascending or
descending order. During each iteration, the list is evaluated
to see if it is, in fact, ordered. If not, the
smallest value from a list of unsorted numbers is selected and
then moved to the front of the list. As the
process continues, the sorted area in the front of the list gets
larger, while the remaining unsorted area
gets smaller. At some point, when all the numbers from the
unsorted list have been moved, the list is
sorted and the process is complete. Insertion sort is one of the
many algorithms used by computerprogrammers to sort lists of
data.
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pumped through both the controlled environment and outside the
area. At the same time, the
refrigerant is cycled at strategic points between liquid and
vaporous states. This change in state provides
the means for transferring thermal energy.
The air conditioners operation is centered on four major
components, including the compressor,
condenser coil, expansion valve, and evaporator coil. The
operation of the air conditioner relatesdirectly to these parts and
includes the following steps: compression, condensation, expansion,
and
evaporation. See Figure 5.1.
Discussion
Compression is a fluid- dynamics process in which a given volume
of refrigerant vapor is forced to
occupy a smaller volume of space. Compression occurs when the
compressor forces hot refrigerant
vapor under pressure into the compression chamber. The chamber
is composed of a cylinder/valve
arrangement. The piston draws refrigerant into the cylinder
through an intake; the intake valve closes;
and the piston pushes up into the cylinder, compressing the
refrigerant vapor. The vapor then exits
through an exhaust valve and enters the condenser coil, where
the condensation step occurs.
Condensation is a fluid-dynamics process in which the hot
refrigerant vapors, pumped from the
compressor to the condenser coil, cool and change to liquid. As
this change occurs, the heat of
condensation is released from the refrigerant in the condenser
coil, heating the coil. This heat in turn, is
drawn from the coil by a fan, which passes relatively cooler air
across the coil picking the heat andventing it outside. The
refrigerant liquid then flows through a closed loop to the
expansion valve, where
rapid expansion occurs.
Expansion is a fluid-dynamics process in which the condensed
liquid refrigerant, under relatively high
pressure from the compressor, is forced through an expansion
valve into an area of substantially lower
pressure. The expansion valve acts as nozzle, constricting and
then accelerating the liquid refrigerant
until it passes through a threshold where the constriction is
removed and rapid expansion occurs. At this
point, the expanding refrigerant enters and the evaporator coil,
where it will cool and change state
again.
Evaporation is a fluid-dynamics process in which the rapidly
expanding refrigerant liquid changes to a
vapor. As the liquid enters the evaporator coil, it also enters
an area of substantially lower pressure. As a
result, it vaporizes and in the process absorbs heat. Air in the
controlled environment is circulated across
this coil, which, in turn, absorbs heat from the air. The fan
distributes the resulting cool air throughout
the controlled environment. The refrigerant vapor in then
evaporator coil is then drawn back through
the closed loop to the compressor, At which point the entire
cycle repeats.
Conclusion
The operation of an air conditioner involves four steps. First,
the compressor pumps refrigerant under
pressure into the condenser coil. Here, it is liquefied, giving
up heat that is removed by a fan circulating
air over the condenser coil. The liquid refrigerant moves
through a closed loop, through an expansion
valve, and into the lower- pressure evaporator coil. Here, the
refrigerant changes to a vapor, absorbing
heat from air passing over the evaporator coil. The air then
cools the controlled environment, while the
refrigerant is drawn back into the compressor. At this point the
cycle is complete, and the process
repeats.
