CATALYTIC CONVERTER group: Fuel
economy, Enviromental protection
Old definition:
The Catalytic Converter is one of the most effective
emission control devices available. The Catalytic Converter processes exhaust
to remove pollutants, achieving considerably lower emissions than is possible
with in-cylinder techniques. Vehicles with catalytic converters require
unleaded fuel, since lead forms deposits that poison the catalytic converter by
blocking the access of exhaust gases to the catalyst. The catalytic converter
comprises a ceramic support, a washcoat (usually aluminum oxide) to provide a
very large surface area and a surface layer of precious metals (platinum,
rhodium and palladium are most commonly used) to perform catalyst function.
(A.Faiz, C.Weaver,
M. Walsh, Air pollution from motor vehicles: standards and Technologies for
Controlling Emissions, p.67)
New definition:
A catalyst is a substance that causes a chemical reaction to occur
without undergoing any change to itself. The chemical reaction is one that
normally would not occur at all, or one that occurs at a much faster rate than
normal because of the catalyst. Catalytic converters have been installed on
most cars since 1975, the same time unleaded fuel came into use. The catalytic converter is often called a cat. It is located in front of the
muffler in the exhaust system and looks like a heavy muffler.
A catalytic converter must be hot before it can begin to operate.
Therefore, it is mounted closer to the engine than the muffler so it can be
quickly heated by exhaust. The point where the converter begins to work is
called its light oft temperature,
which is about 500°F. Prior to the invention of the catalytic converter,
exhaust emissions were controlled by engine systems that included leaner
air-fuel mixtures, which resulted in lower performance and fuel economy. The
catalytic converter allowed automotive manufacturers to improve engine
performance and fuel economy and let the convener take care of the emissions.
The catalyst is either monolithic or it has pellets. A monolithic
catalyst is like a big honeycomb (Figure 43.21). It has a thin coating of
platinum and palladium applied to either a ceramic or in monolith coated with
alumina. Alumina is an oxide of aluminum that is very porous. The catalyst's
metals (platinum and palladium) fill the holes in the alumina. Newer catalysts
also include the rare silvery white metal rhodium.
There are three types of catalytic converters:
·
The earliest catalytic converter, called a two-way converter, was designed to oxidize
HC and CO, converting them into H2O and CO2.
·
The three-way
single bed converter oxidizes HC and CO and also reduces harmful NOx
into harmless nitrogen and O2. The NOx portion of the
converter is called a reduction catalyst. The O2 produced in the NOx
portion of the converter aids in oxidizing HC and CO.
·
The three-way
dual bed converter has two chambers. A tube between the two chambers provides
O2 to the rear oxidation chamber, supplied from the air pump (Figure
43.23).
(Tim Gilles, Automotive
Service: Inspection, Maintenance, Repair, pg. 736,737)
My definition is more detailed and makes it easy to
understand why and how this device used by given figures.
ELECTROCHEMICAL DEBURRING group:
Manufacturing/electrochemical mach.
Old
definition:
Electrochemical deburring (ECD) is a
special version of ECM (Fig. 39). ECD was developed to remove burrs and fins or
to round sharp corners. Anodic dissolution occurs on the workpiece burrs in the
presence of a closely placed cathodic tool whose configuration matches the
burred edge. Normally, only a small portion of the cathode is electrically
exposed, so a maximum concentration of the electrolytic action is attained. The
electrolyte flow usually is arranged to carry away any burrs that may break
loose from the workpiece during the cycle.
Voltages are low, current densities are
high, electrolyte flow rate is modest, and electrolyte types are similar to
those used for ECM. The electrode (tool) is stationary, so equipment is simpler
than that used for ECM. Cycle time is short for deburring. Longer cycle time
produces a natural radiusing action.
(Kutz
M., Mechanical engineers’ handbook 3rd edition: Manufacturing and management,
p. 228)
New definition:
Electrochemical deburring (ECD) is a
deburring process which uses electrical energy to remove burrs in a very
localized area, as opposed to thermal energy machining which provides general
deburring. The part to be deburred is placed in a non-metallic fixture which
positions an electrode in close proximity to the burrs. The workpiece is
charged positively (anode). the electrode is charged negatively (cathode), and
an electrolytic so-lution is directed under pressure to the gap between the
electrode and the burr. This flow of electrolyte precedes the applica-tion of
the current in order to flush out any loose chips which probably would cause a
short in the system that could damage the part. the tooling, or the equipment
As the burr dissolves, a very controlled radius is formed. The process is
consistent from part to part.
The process always requires fixturing to
establish the anode—cathode relationship. A typical fixture consists of a
plastic locator which holds the part and insulates (masks) areas of the part
which do not require ECD. The fixture also positions a highly conductive
electrode, designed with a contour that con-forms to the desired dimensions of
the area to be deburred. The locator and electrode direct the flow of
electrolyte. The vari-ables of voltage, current, electrolyte flow, and cycle
time provide precise control of the ECD process. 
Fig. 21.1. How electrochemical debumng
works. A. DEBURRING of a workpiece by electrolytic means relies upon
ndeplating" the anodically connected workpiece, using a cathodically
connected tool, both immersed in electrolyte such as salt water. B. WORKPIECE
with a burr. C. WORKPIECE mounted on anode connection in a tank of electrolyte.
D. CYLINDRICAL brass tool has slots to cause turbulence, and is connected to
negative lead.
(James
A. Brown, Modern manufacturing processes,pg. 160)
My
definition became more rich with the visual explanations about the process
PIEZO VELOCITY SENSOR group: Control
old definition is not exist
New definition:
Typically piezoelectric
sensors accomplish a velocity output measurement by applying a filter to an
accelerometer that acts as an integrator circuit. Fig. 4 shows the estimated
sensor dynamics of a PCB sensor that was used successfully in a control
circuit. The vertical line at 2.5 Hz indicates the lower bandwidth of the
sensor. The straight line in each graph represents the relationship of velocity
to acceleration if an infinite sensor bandwidth was possible. It should be
noted that the magnitude is reasonably predicted at frequencies above the lower
bandwidth line. This might imply that a good measure of velocity can be
achieved for frequencies above the lower bandwidth. When used in a control
configuration, the phase is more important than the amplitude. If this sensor
were to be used to measure resonant frequencies near the lower limit of the
bandwidth, the phase would be about 66 degrees instead of 90 degrees. At 66
degrees, the projection on to the imaginary axis (sin(33)=0.55) would be only
55% of the actual velocity, whereas, at 2x the lower bandwidth, the projection
on to the imaginary axis would be about (sin(66) = 0.91) 91% of the actual
velocity. This has proven to be an acceptable distortion of the actual
velocity. It is therefore recommended that piezoelectric velocity sensors only
be used to control floors with fundamental natural frequencies at least 2x the
lower limit of the sensor bandwidth.
(Tom
Proulx, Dynamics of Civil Structures, Volume 4: Proceedings of the 28th IMac,
pg.192,193)
There is no older definition to compare, but I faund my
definition is enoug to explain the device.
SHEAR JOINT group: Manufacturing /welding
Old definition:
The shear joint is used in
welding semicrystalline materials that have a sharp and narrow melting point.
Energy directors are not useful with crystalline materials because material
displaced from the energy director either degrades or recrystallizes before it
can flow across the joint interface and form a weld. The small, initial contact
area of the shear joint is the first to melt during welding; melting then
continues along the vertical walls as the parts telescope together in a
smearing action that eliminates exposure to air and premature solidification.
Strong hermetic seals can be obtained. Rigid side wall support is necessary to
prevent deflection during welding, and the walls of the bottom section must be
supported by the holding fixture. The top part of the joint should be as
shallow as possible, similar to a lid, but of sufficient structural integrity
to withstand internal deflection. Shear joints provide part alignment and a
uniform contact area.
(Plastics Design Library, Handbook of Plastics Joining: A Practical
Guide, p.49)
New definition:
Shear joints are typically
used for applications that require a hermetic seal It should be noted that
hcmictic scals can also be achieved with energy director joints. hut the shear
joint is usually preferred. Figure 8.16 shows a typical cross section of a
shear joint along with recommended dimensions. Table 8.6 lists some of the
advantages and disadvantages of shear joints.
It should be noted that one major
disadvantages of the shear joint is the relatively high dimensional tolerance
that is required to obtain a uniform weld. Therefore, when the part size
increases, the shear joint is not generally recommended. Another disadvantage
of the shear joint is that complex fixture design may be needed when part
geometry cannot provide sufficient support for the shear joint. This is due to
the fact that without providing support over the entire part. the part can
deflect outwards as the upper part shears into the lower part. This will reduce
the actual interference and result in poor welds. If the fixture provides
uniform support over the entire weld surface, it is usually Important that the
fixture incorporates moving parts to allow removal of the assembled parts at
the end of the weld cycle. (inc solution to this problem is to use a double
shear joint, as seen in Fig. 8.17. which also shows other variations to shear
joint design. Table 8.7 provides general guide-lines for the dimensions and
tolerances of shear joints for different part sizes.
(Avraham
Benatar, Plastics and composites welding handbook, 10. Cilt, pg. 161,162)
My definition fulfills the missing of the older
definition by well explanation of process and added figures.
COST TRADE-OFFS group: Project management
Old definition:
The importance of
marketing orientation for business success has been well documented. How management
allocates scarce resources to the product, price, promotion, and place
components of the marketing mix will determine a company's market share and
profitability. Management can improve a firm's competitive position by spending
more effectively and efficiently to the individual components of marketing mix,
and/or efficiency. The cost trade-offs that management must make. The objective
is to allocate recources to product, price, promotion, and place in a manner
that will lead to the greatest long-run profits.
(J. A. Tompkins, J. D. Smith,
Warehouse Management Handbook, p.184)
New definition:
The decision to introduce
new technology into a space mission involves intelligent, thorough cost/risk
trade-off assessments that must be conducted at the system level. These
assessments must include accurate estimates of the nonrecurring costs
associated with development and space qualification. An up-front mission
philosophy that governs trade-off decisions should be articulated. In all
cases, available off-the-shelf technologies must be included in the trade-off
considerations.
Cost trade-off studies at
the program level could also consider technology and hardware from the growing
commercial space infrastructure. For example, infrastructure costs, such as
launch, mission ground control, and retrieval and distribution of scientific
data—the life-cycle costs—can often be lowered signifi-cantly by using
commercially available products and services instead of duplicat-ing them
in-house. The recent DOD experience of introducing commercial off-the-shelf
elements into military specification systems is also relevant.
Figure 3.4 Visualizing a Time/Cost Trade-Off
The graph shows the range
of cost versus-time solutions for a given project scope. For any project, there
are three critical data points:
1. The earliest finish
date of the last activity
2. The latest allowable
finish date of the last activity
3. The least cost to
accomplish all the work required
By extension, we can find
a point that describes the late finish and last dollar. This point is the
sponsor's expectation that she or he will receive the final product or service
on or before a given date and at a cost not to exceed some predefined amount.
The area between any point on the time/cost trade-off line and the outer limits
of the project is a manage-ment reserve or contingency for the project manager.
(Larry Richman, Improving Your Project Management Skills, pg.36,37)
(National Research Council
(U.S.). Committee on Technology for Space Science and Applications of the
Aeronautics and Space Engineering Board, Reducing the costs of space science research
missions, pg.11,43)
In older definition it is not clear what is mentioned
about the subject. But my definition explains the word graphically. On the
other hand I am not satisfacted about my defibition about its being
understandable.
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