Thermal Expansion


Thermal expansion is a small, but not always insignificant effect. Typical coefficients are measured in parts per million per kelvin (10-6/K).

Almost all materials expand on heating, the most famous exception being water, which contracts as it is warmed from 0 degrees Celsius to 4 degrees. when water at 00C is heated, it decreases in volume until it reaches 40C. Above 4oC water behaves normally and expands in volume as the temperature is increased. This is referred to as the anomalous behaviour of water.

This is actually a good thing, because as freezing weather sets in, the coldest water, which is about to freeze, is less dense than slightly warmer water, so rises to the top of a lake and the ice begins to form there( on the surface). For almost all other liquids, solidification on cooling begins at the bottom of the container.

Because of the unusual behaviour of water, it is hard for any large body of water to freeze completely. This is made possible, by the layer of ice on the surface, acting as an insulator to reduce the flow of heat out of the water into the cold air.

NOTE: Water expands as it freezes to ice, and this is why pipes break when the water inside them freezes.

Linear Expansivity of Materials.

The coefficient of linear expansion,α is defined as the increase in length per unit length per degree change in temperature, hence

α = ΔL/(LoΔT)

where ΔL is the change in length, Lo is the original length, and ΔT(Tf – Ti) is the change in temperature.

The change in Length,ΔL(L – L0), can be written as:

ΔL = αL0ΔT

where ΔT is the difference between the original temperature and the temperature T, while ΔL is the change in length of the material, and is also equal to how much an Object expands or contracts.

It is customary to choose the standard length Lo to be the length as measured at 0oC.

Then the above equation can be written as

L = Lo (1 +αΔT)

where L is the new Length.

Examples on linear Expansivity

1.An iron of length 50m and at a temperature of 600C is heated to 700C. Calculate its new length .[linear expansivity of iron = 1.2 x 10-5/k]


Lo=50m, Ti= 600oC, Tf= 700oC, L = ?

L = Lo (1 +αΔT) ,

Substituting the given values into the equation,

L = 50 ( 1 + 1.2 x 10-5 x ( 700 – 600))

L = 50 (1 + 1.2 x 10-5 x 100)

L = 50 ( 1 + 0.0012), 50( 1.0012)

     = 50( 1.0012)

L = 50.06m


Principles of Flight


There are four forces acting on the airplane all the time during airplane is flying.The four forces are
(1) Lift, (2) Gravity force or Weight, (3) Thrust, and (4) Drag.
Lift and Drag are considered aerodynamics forces because they exist due to the movement of the Airplane through the Air.

four forces

Lift: is produced by a lower pressure created on the upper surface of an airplane’s wings compared to the pressure on the wing’s lower surfaces,causing the wing to be LIFTED upward. The special shape of the airplane wing (airfoil) is designed so that air flowing over it will have to travel a greater distance and faster resulting in a lower pressure area (see illustration) thus lifting the wing upward. Lift is that force which opposes the force of gravity (or weight).

Lift depends upon:

(1) shape of the airfoil,

(2) the angle of attack,

(3) the area of the surface exposed to the airstream,

(4) the square of the air speed,

(5) the air density.

Weight: The weight acts vertically downward from the center of gravity (CG) of the airplane.

Thrust: is defined as the forward direction pushing or pulling force developed by aircraft engine . This includes reciprocating engines , turbojet engines, turboprop engines.

Drag: is the force which opposes the forward motion of airplane. specifically, drag is a retarding force acting upon a body in motion through a fluid, parallel to the direction of motion of a body. It is the friction of the air as it meets and passes over an airplane and its components. Drag is created by air impact force, skin friction, and displacement of the air.


An airplane has three axes of rotation, namely , the longitudinal axis, the vertical axis, and the lateral axis. see figure below and you will understand what we mean. The simplest way to understand the axes is to think of them as long rods passing through the aircraft where each will intersect the other two. At this point of intersection, called the center of gravity.


The Axis that extends lengthwise (nose through tail) is call the longitudinal axis, and the rotation about this axis is called “Roll”

The axis that extends crosswise (wing tip through wing tip) is called the lateral axis, and rotation about this axis is called “Pitch”

The axis that passes vertically through the center of gravity (when the aircraft is in level flight ) is called the vertical axis, and rotation about this axis is called “Yaw”


Reference: #thai technics



A Virus is defined as a program inserted into another program. It gets activated by its host program. It replicates itself and spreads to others through floppy transfer. A virus infects data or program every time the user runs the infected program and the virus takes advantages and replicates itself.

There are two types of computer viruses ‘parasitic’ and ‘boot’ virus.

1. A Parasitic virus attaches itself to other programs and is activated when the host program is executed. It tries to get attached to more programs so that chances of getting activated is more. It spreads to other computers when the affected programs are copied. ‘Jerusalem’ and ‘Datacrime’ are parasitic viruses.

2. A Boot virus is designed to enter the boot sector of a floppy disc. It works by replacing the first sector on the disc with part of itself. It hides the rest of itself elsewhere on the disc, with a copy of the first sector. The virus is loaded by the computers built-in start-up program when the machine is switched on. The virus loads, installs itself, hides the rest of itself and then loads the original program. On a hard disc, virus can occupy DOS boot sector or master boot sector.

Some Reported Viruses

3. C-Brain: Amjad and Basit, two pakistani brothers, developed this software in January 1986 to discourage people from buying illegal software at throwaway prices. This was the most famous virus ever found and has a record of damaging few millions of personal computers. This is designed to stay in the boot sector of the disc or near zero sector. The virus enters the machine memory once the PC is booted with the infected floppy.

4. Macmag: This virus attacked Apple Macintosh computers only. Not much damage is reported because of this virus. This was not noticed on any IBM compatible PCs. It displayed a message of peace on the monitor and killed itself.

5. Cascade: This virus attacked IBM PCs and compatibles. The letters on the screen could be seen dropping vertically down to the bottom of screen after the virus picked them off in alphabetical order. This is a sort of parasitic virus. It attaches itself to other programs and gets activated when the host program is executed. It gets copied to other PCs when the programs are copied.

6. Jerusalem: Found in 1987 at Hebrew University, Jerusalem, this virus was designed to activate only on Friday, January 13 and delete all the files executed on that day. This infects the COM and EXE files. This is similar to Cascade virus in that it is parasitic in nature. This virus attaches itself to COM and EXE files to damage the data.

7. Daracrime/Columbus or October the 13th virus: This virus is similar to Jerusalem and was programmed to attack on October 13, 1989. Track zero of computer hard disk is destroyed and the contents of discs are rendered unreadable. This virus enters COM and EXE files and damages the hard disk. An antidote called ‘Vchecker’ was developed by the American Computer Society. Fortunately the virus was located in March 1989 itself and the damage reported after October 13 was minimal.

8. Bomb: This is also know as ‘Logic Bomb’ and ‘Time Bomb’. An event triggered routine in a program that causes a program to crash is defined as a ‘bomb’. Generally, ‘bomb’ is a software inserted in a program by a person working in the company.


Some types of anti virus are;

1.Microsoft Security Essentials: Released by Microsoft in late 2009, Microsoft Security Essentials sports more than a typically verbose Microsoft name: it’s also a really good antivirus. Lightweight enough to run on older machines without crippling their performance, yet competent enough to handle most viruses and malware out there.

2. AVG: Anti Virus Guard has become synonymous with free anti-virus, and there’s a reason for this: AVG offers complete malware protection, with considerably less bloat than the top pay-to-use antivirus clients. And while AVG Free does constantly remind you that you could pay for the professional version of the program, it does this without ever getting in the way of the program’s core purpose: protecting you from viruses.

3. Malwarebytes: This program doesn’t run in your system background and constantly protect you, but when you run into a problem running Malwarebytes will usually take care of what other programs can’t.

4. AVAST: This is one of the top free anti-viruses on the market, and for good reason: it’s remarkably complete. Expect great all-around protection, including against trojans and spyware. You can also expect constant reminders that there’s a free version you can upgrade to, on your desktop and in your inbox. Still, the protection is solid.

5. Comodo Firewall + Antivirus: Comodo is best known for its free firewall, but it also offers a bundled firewall and antivirus program. While the Comodo firewall isn’t the easiest to use, and the antivirus doesn’t include protection for non-virus forms of  malware, this one’s worth mentioning if you’re looking for a free securitysuite which includes both a firewall and anti-virus protection.




How to Use Lemon to produce Electricity:
Introduction: The construction and working of the lemon
experiment can be compared to a conventional
battery having electrodes and electrolyte. “Lemon
battery”, as the experiment is popularly known,
requires two external metal electrodes in the same
way; however the electrolyte is supplied by the
lemon itself.
Two electrodes ( a zinc nail and a Copper Coin ),
A Juicy Lemon , which serve as Electrolyte,
A Voltmeter to measure the Current generated,
And a Wire.
In a conventional battery, the two electrodes are
two different metal pieces (Usually copper and
zinc), submerged in an acidic solution (electrolyte)
and connected through an external wiring to a
voltmeter or a small bulb. Similarly, for a “lemon
battery” experiment, two different metals in the
form of a zinc nail and a copper coin are inserted
into a juicy lemon. The lemon battery is also
known as a voltaic battery which produces
electricity by converting chemical energy to
electrical energy.
The juice of lemon is acidic in nature
and works as a powerful electrolyte. The lemon
itself serves as a reservoir for transfer of electrons
to and from the electrodes. When the two
electrodes, copper and zinc, are suspended in the
acidic lemon juice, the atomic structure of the
atoms of both the electrodes starts breaking,
resulting in production of individual electrons.
Note that electricity will be
generated only when the battery circuit gets
completed by external wiring. Also, it is not the
lemon which is the source of energy, but the
chemical change in the zinc that produces
electricity. The zinc electrode, when inside the
lemon, gets oxidized by releasing electrons and
goes to a lower energy state. This leads to the
transfer of electrons from a high energy state
electrode to a low energy state electrode. Thus,
lemon just serves as an environment for the
generation of electricity; however doesn’t produce
any electrons on its own.
Key Note: The voltage produced by a single lemon is very
small. However, a series of lemons can be used to
increase the voltage of the whole battery. A series
involving four lemon batteries can easily light an







Please comment if you find this article helpful.

The Penalty for Ignorance is Lack


A hydraulic device is a device that uses liquids to transmit pressure equally from one point to another.

Hydraulic machines are machinery and tools that use liquid fluid power to do simple work. Heavy equipment is a common example.
In this type of machine, hydraulic fluid is transmitted throughout the machine to various hydraulic motors and hydraulic cylinders and becomes pressurised according to the resistance present. The fluid is controlled directly or automatically by control valves and distributed through hoses and tubes.

NOTE: Hydraulic machinery is operated by the use of hydraulics, where a liquid is the powering medium.

It is important that a hydraulic system contains no air bubbles. You may have heard about the need to “bleed the air out of the brake lines” of you car. If there is an air bubble in the system, then the force applied to the first piston gets used compressing the air in the bubble rather than moving the second piston, which has a big effect on the efficiency of the system.

Some examples of hydraulic devices include:
Jaws of life,
Metal shears,
Car crushers,
Automobile brakes,
Garbage compactors,
Log splitters,
Zero radius lawn tractors,
Bobcat tractors.

The Penalty for Ignorance is Lack


A gear or cogwheel is a rotating machine part having cut teeth, or cogs , which mesh with another toothed part to transmit torque , in most cases with teeth on the one gear being of identical shape, and often also with that shape on the other gear.
Nearly all mechanical devices rely on some form of gearing, and the key to a reliable gear is a good and appropriate design taking into account such factors as strength, wear resistance, noise, and fatigue resistance.


               Meshing Gears

Two or more gears working in a sequence (train) are called a gear train or, in many cases, a transmission ; such gear arrangements can produce a
mechanical advantage through a gear ratio and thus may be considered a
simple machine. Geared devices can change the speed, torque, and direction of a power source. The most common situation is for a gear to mesh with another gear; however, a gear can also mesh with a non-rotating toothed part, called a rack, thereby producing
translation instead of rotation.

1-Bevel gear:
These gears have teeth cut on a cone instead of a cylinder blank. They are used in pairs to transmit rotary motion and torque where the bevel gear shafts are at right angles (90 degree) to each other.
2-Crossed helical gear
These gears also transmit rotary motion and torque through a right angle. The teeth of a helical gear are inclined at an angle to the axis of rotation of the gear.
3-Worm and worm wheel
A gear which has one tooth is called worm. The tooth is in the form of a screw thread. A worm wheel meshes with the worm. The worm wheel is a helical gear with teeth inclined to that they can engage with the tread like worm. Like the cross helical gears, the worm and the worm wheel transmit torque and rotary motion through a right angle. The worm always drives the worm wheel and never the other way round. The mechanism locks if the worm wheel tries to drive the worm. Worm mechanism is very quiet running.
4-Helical gear
The gear is used for application that requires very quite and smooth running, at high rotational velocities. Parallel helical gears have their teeth inclined at a small angle to their axis of rotation. Each tooth is part of a spiral or helix. The helical gears have splines cut in their center holes. The gear can move along a splined shaft, although they rotate with the shaft. Double helical gears give an efficient transfer of torque and smooth motion at very high rotational velocities.
5-Spiral bevel gears
When it is necessary to transmit quietly and smoothly a large torque through a right angle at high velocities, spiral bevel gears can be used. Spiral bevel gears have teeth cut in helix spiral form on the surface of a cone. They are quieter running than straight bevel gears and have a longer life. Spiral bevel gears are used in motorcar axle gearboxes.
6-Internal gears
It is possible to cut gear teeth on the face of a gear wheel. Also, gear teeth can be cut the inclined of a gear ring. Internal gears have better load carrying capacity than external spur gear. They are safer in use because the teeth are guarded.
         Reference: Wikipedia ,

The Penalty for Ignorance is Lack


Renewable energy is the  energy that comes from resources which are naturally replenished on a human timescale, such as sunlight , wind , rain ,
tides, waves , and geothermal heat. Renewable energy replaces conventional fuels in four distinct areas: electricity generation , air and water heating/cooling, motor fuels , and rural energy services.

Renewable energy resources are always available to be tapped, and will not run out.
Renewable energy includes Biomass, Wind, Hydro-power, Geothermal and Solar sources .

SOLAR ENERGY: This form of energy relies on the nuclear fusion power from the core of the Sun. This energy can be collected and converted in a few different ways. The range is from solar water heating with solar collectors or attic cooling with solar attic fans for domestic use to the complex technologies of direct conversion of sunlight to electrical energy using mirrors and boilers or photovoltaic cells. Unfortunately these are currently insufficient to fully power our modern society.
WIND POWER: The movement of the atmosphere is driven by differences of temperature at the Earth’s surface due to varying temperatures of the Earth’s surface when lit by sunlight. Wind energy can be used to pump water or generate electricity, but requires extensive areal coverage to produce significant amounts of energy.
HYDROELECTRIC ENERGY : This form uses the gravitational potential of elevated water that was lifted from the oceans by sunlight. It is not strictly speaking renewable since all reservoirs eventually fill up and require very expensive excavation to become useful again. At this time, most of the available locations for hydroelectric dams are already used in the developed world.
BIOMASS : Biomass is the term for energy from plants. Energy in this form is very commonly used throughout the world. Unfortunately the most popular is the burning of trees for cooking and warmth. This process releases copious amounts of carbon dioxide gases into the atmosphere and is a major contributor to unhealthy air in many areas. Some of the more modern forms of biomass energy are methane generation and production of alcohol for automobile fuel and fueling electric power plants.

The Penalty for Ignorance is Lack


1) Wood is used in making furniture. Furniture are movable objects intended to support activities such as: seating and sleeping. Examples of furniture include: tables, beds, chairs e.t.c
2) Wood is used in Building Construction. Wood is a major component in building , used in roofing, flooring, doors, windows, window frame.
3) Wood is used in making the handle of implement like plough, sickle, cutlass, e.t.c
4) Wood is used in making pulp and paper.
5) Lorry bodies are made of Wood.

1) Ceramics are used in making bricks. Bricks are used for building purposes because they are cheap and durable.
2) Porcelain made from ceramics are used to store chemicals; because they are resistant to attack of chemicals
3) Ceramics are used in making electrical insulators; because of their high electrical resistance and a good insulating property.
4) Ceramics are used in making tiles.
5) Ceramics are used in the construction of furnaces and oven.


1) Metals are used in making household utensils.
2) Metals are used in making vehicle and ship parts.
3) Lead is used in making Batteries of vehicles.
4) High Carbon steel are used in making cutting tools , for example files, knives , drills e.t.c
5) Crankshaft, connecting rods are made of medium carbon steel.
6) Gears , screws are made of low carbon steel.


1) Glass are used in making eye glasses , mug, and flower vases.
2) They are used in making doors, windows and mirror.
3) Television and Computer screen are made of glass.

The Penalty for Ignorance is Lack



The term “plastics” includes materials composed of
various elements such as carbon, hydrogen,
oxygen, nitrogen, chlorine, and sulfur. Plastics
typically have high molecular weight, meaning each
molecule can have thousands of atoms bound
together. Naturally occurring materials, such as
wood, horn and rosin, are also composed of
molecules of high molecular weight. The
manufactured or synthetic plastics are often
designed to mimic the properties of natural
materials. Plastics, also called polymers, are
produced by the conversion of natural products or
by the synthesis from primary chemicals generally
coming from oil, natural gas, or coal.
Most plastics are based on the carbon atom.
Silicones, which are based on the silicon atom, are
an exception. The carbon atom can link to other
atoms with up to four chemical bonds. When all of
the bonds are to other carbon atoms, diamonds or
graphite or carbon black soot may result. For
plastics the carbon atoms are also connected to
the aforementioned hydrogen, oxygen, nitrogen,
chlorine, or sulfur. When the connections of atoms
result in long chains, like pearls on a string of
pearls, the polymer is called a thermoplastic.
Thermoplastics are characterized by being
meltable. The thermoplastics all have repeat units,
the smallest section of the chain that is identical.
We call these repeat units unit cells. The vast
majority of plastics, about 92%, are


A Thermoset is a polymer that solidifies or “sets”
irreversibly when heated or cured. Similar to the
relationship between a raw and a cooked egg, a
cooked egg cannot revert back to its original form
once heated, and a thermoset polymer can’t be
softened once “set”. Thermosets are valued for
their durability and strength and are used
extensively in automobiles and construction
including applications such as adhesives, inks, and
coatings. The most common thermoset is the
rubber truck and automobile tire. Some examples
of thermoset plastics and their product applications
• Mattresses
• Cushions
• Insulation
Unsaturated Polyesters:
• Boat hulls
• Bath tubs and shower stalls
• Furniture
• Adhesive glues
• Coating for electrical devices
• Helicopter and jet engine blades
Phenol Formaldehyde:
• Oriented strand board
• Plywood
• Electrical appliances
• Electrical circuit boards and switches
A Thermoplastic is a polymer in which the
molecules are held together by weak secondary
bonding forces that soften when exposed to heat
and return to its original condition when cooled
back down to room temperature. When a
thermoplastic is softened by heat, it can then be
shaped by extrusion, molding, or pressing. Ice
cubes are common household items which
exemplify the thermoplastic principle. Ice will melt
when heated but readily solidifies when cooled.
Like a polymer, this process may be repeated
numerous times. Thermoplastics offer versatility
and a wide range of applications. They are
commonly used in food packaging because they
can be rapidly and economically formed into any
shape needed to fulfill the packaging function.
Examples include milk jugs and carbonated soft
drink bottles. Other examples of thermoplastics
• Packaging
• Electrical insulation
• Milk and water bottles
• Packaging film
• House wrap
• Agricultural film
• Carpet fibers
• Automotive bumpers
• Microwave containers
• External prostheses
Polyvinyl Chloride (PVC):
• Sheathing for electrical cables
• Floor and wall coverings
• Siding
• Automobile instrument panels


Extrusion – This continuous process is used to
produce films, sheet, profiles, tubes, and pipes.
Plastic material as granules, pellets, or powder, is
first loaded into a hopper and then fed into a long
heated chamber through which it is moved by the
action of a continuously revolving screw. The
chamber is a cylinder and is referred to as an
extruder. Extruders can have one or two revolving
screws. The plastic is melted by the mechanical
work of the screw and the heat from the extruder
wall. At the end of the heated chamber, the molten
plastic is forced out through a small opening
called a die to form the shape of the finished
product. As the plastic is extruded from the die, it
is fed onto a conveyor belt for cooling or onto
rollers for cooling or by immersion in water for
cooling. The operation’s principle is the same as
that of a meat mincer but with added heaters in the
wall of the extruder and cooling of the product.
Examples of extruded products include lawn
edging, pipe, film, coated paper, insulation on
electrical wires, gutter and down spouting, plastic
lumber, and window trim. Thermoplastics are
processed by continuous extrusion. Thermoset
elastomer can be extruded into weatherstripping
by adding catalysts to the rubber material as it is
fed into the extruder.

Calendering – This continuous process is an
extension of film extrusion. The still warm
extrudate is chilled on polished, cold rolls to
create sheet from 0.005 inches thick to 0.500
inches thick. The thickness is well maintained and
surface made smooth by the polished rollers.
Calendering is used for high output and the ability
to deal with low melt strength. Heavy polyethylene
films used for construction vapor and liquid
barriers are calendered. High volume PVC films are
typically made using calendars.

Film Blowing – This process continuously
extrudes vertically a ring of semi-molten polymer
in an upward direction, like a fountain. A bubble of
air is maintained that stretches the plastic axially
and radially into a tube many times the diameter of
the ring. The diameter of the tube depends on the
plastic being processed and the processing
conditions. The tube is cooled by air and is nipped
and wound continuously as a flattened tube. The
tube can be processed to form saleable bags or
slit to form rolls of film with thicknesses of 0.0003
to 0.005 inches thick. Multiple layers of different
resins can be used to make the tube.

Injection Molding – This process can produce
intricate three-dimensional parts of high quality
and great reproducibility. It is predominately used
for thermoplastics but some thermosets and
elastomers are also processed by injection
molding. In injection molding plastic material is
fed into a hopper, which feeds into an extruder. An
extruder screw pushes the plastic through the
heating chamber in which the material is then
melted. At the end of the extruder the molten
plastic is forced at high pressure into a closed
cold mold. The high pressure is needed to be sure
the mold is completely filled. Once the plastic
cools to a solid, the mold opens and the finished
product is ejected. This process is used to make
such items as butter tubs, yogurt containers, bottle
caps, toys, fittings, and lawn chairs. Special
catalysts can be added to create the thermoset
plastic products during the processing, such as
cured silicone rubber parts. Injection molding is a
discontinuous process as the parts are formed in
molds and must be cooled or cured before being
removed. The economics are determined by how
many parts can be made per cycle and how short
the cycles can be.

Blow Molding – Blow molding is a process used in
conjunction with extrusion or injection molding. In
one form, extrusion blow molding, the die forms a
continuous semi-molten tube of thermoplastic
material. A chilled mold is clamped around the
tube and compressed air is then blown into the
tube to conform the tube to the interior of the mold
and to solidify the stretched tube. Overall, the goal
is to produce a uniform melt, form it into a tube
with the desired cross section and blow it into the
exact shape of the product. This process is used
to manufacture hollow plastic products and its
principal advantage is its ability to produce hollow
shapes without having to join two or more
separately injection molded parts. This method is
used to make items such as commercial drums
and milk bottles. Another blow molding technique
is to injection mold an intermediate shape called a
preform and then to heat the preform and blow the
heat-softened plastic into the final shape in a
chilled mold. This is the process to make
carbonated soft drink bottles.

Expanded Bead Blowing – This process begins
with a measured volume of beads of plastic being
placed into a mold. The beads contain a blowing
agent or gas, usually pentane, dissolved in the
plastic. The closed mold is heated to soften the
plastic and the gas expands or blowing agent
generates gas. The result is fused closed cell
structure of foamed plastic that conforms to a
shape, such as expanded polystyrene cups.
Styrofoam™ expanded polystyrene thermal
insulation board is made in a continuous extrusion
process using expanded bead blowing.

Rotational Molding – Rotational molding consists
of a mold mounted on a machine capable of
rotating on two axes simultaneously. Solid or
liquid resin is placed within the mold and heat is
applied. Rotation distributes the plastic into a
uniform coating on the inside of the mold then the
mold is cooled until the plastic part cools and
hardens. This process is used to make hollow
configurations. Common rotationally molded
products include shipping drums, storage tanks
and some consumer furniture and toys.

Compression Molding – This process has a
prepared volume of plastic placed into a mold
cavity and then a second mold or plug is applied
to squeeze the plastic into the desired shape. The
plastic can be a semi-cured thermoset, such as an
automobile tire, or a thermoplastic or a mat of
thermoset resin and long glass fibers, such as for
a boat hull. Compression molding can be
automated or require considerable hand labor.

Transfer molding is a refinement of compression
molding. Transfer molding is used to encapsulate
parts, such as for semi-conductor manufacturing
The formation of plywood or oriented strand board
using thermoset adhesives is a variant of
compression molding. The wood veneer or strands
are coated with catalyzed thermoset phenol
formaldehyde resin and compressed and heated to
cause the thermoset plastic to form into a rigid,
non-melting adhesive.

Casting – This process is the low pressure, often
just pouring, addition of liquid resins to a mold.
Catalyzed thermoset plastics can be formed into
intricate shapes by casting. Molten polymethyl
methacrylate thermoplastic can be cast into slabs
to form windows for commercial aquariums.
Casting can make thick sheet, 0.500 inches to
many inches thick.

Thermoforming – Films of thermoplastic are
heated to soften the film, and then the soft film is
pulled by vacuum or pushed by pressure to
conform to a mold or pressed with a plug into a
mold. Parts are thermoformed either from cut
pieces for thick sheet, over 0.100 inches, or from
rolls of thin sheet. The finished parts are cut from
the sheet and the scrap sheet material recycled for
manufacture of new sheet. The process can be
automated for high volume production of clamshell
food containers or can be a simple hand labor
process to make individual craft items.

Reference: American Chemistry Council, Plastics Industry
Producer Statistics Group, 2005


GSM networks consist of thee major systems: SS,
which is known to be The Switching System; BSS,
which is also called The Base Station; and the
Operation and Support System for GSM networks.
Below all three systems are defined in details with
sub systems of each system.
The Switching System
The Switching system is very operative system in
which many crucial operations are conducted, SS
systems holds five databases with in it which
performs different functions. If we talk about major
tasks of SS system it performs call processing and
subscriber related functions. These five databases
from SS systems are HLR, MSC, VLR, AUC and EIR.
Let’s study each database in detail and learn what
functions this little systems performs.
HLR- Home Location Register:
HLR is database, which holds very important
information of subscribers. It is mostly known for
storing and managing information of subscribers. It
contains subscriber service profile, status of
activities, information about locations and
permanent data of all sorts. When new connections
are purchased, these subscribers are registered in
HLR of mobile phone companies.
MSC- Mobile Services Switching Center:
MSC is also important part of SS, it handles
technical end of telephony.It is build to perform
switching functionality of the entire system. It’s
most important task is to control the calls to and
from other telephones, which means it controls
calls from same networks and calls from other
networks. Toll ticketing, common channel
signaling, network interfacing etc are other tasks
which MSC is responsible for.
VLR- Visitor Location Register:
VLR performs very dynamic tasks; it is database
which stores temporary data regarding subscribers
which is needed by Mobile Services Switching
Center-MSC VLR is directly connected to MSC,
when subscribe moves to different MSC location,
Visitor location register – VLR integrates to MSC of
current location and requests the data about
subscriber or Mobile station ( MS ) from the Home
Location Register –HLR. When subscriber makes a
call the Visitor location register-VLR will have
required information for making call already and it
will not required to connect to Home Register
Location – HRL again.
AUC- Authentication Center:
AUC is small unit which handles the security end
of the system. Its major task is to authenticate and
encrypt those parameters which verify user’s
identification and hence enables the confidentiality
of each call made by subscriber. Authentication
center – AUC makes sure mobile operators are
safe from different frauds most likely to happen
when hackers are looking for even smallest loop
wholes in systems.
EIR – Equipment Identity Register:
EIR is another important database which holds
crucial information regarding mobile equipments.
EIR helps in restricting for calls been stolen,
malfunctioning of any MS, or unauthorized access.
AUC – Authentication center and EIR- Equipment
Identity registers are either Stand-alone nodes or
some times work together as combined AUC/EIR
nodes for optimum performance.
The Base Station System (BSS)
The base station system have very important role
in mobile communication. BSS are basically out
door units which consist of iron rods and are
usually of high length. BSS are responsible for
connecting subscribers (MS) to mobile
networks.All the communication is made in Radio
transmission.The Base station System is further
divided in two systems. These two systems, they
are BSC, and BTS. Let’s study these two systems
in detail.
BTS – The Base Transceiver Station:
Subscriber, MS (Mobile Station) or mobile phone
connects to mobile network through BTS; it
handles communication using radio transmission
with mobile station. As name suggests, Base
transceiver Station is the radio equipment which
receive and transmit voice data at the same time.
BSC control group of BTSs.
BSC – The Base Station Controller:
The Base Station normally controls many cells, it
registers subscribers, responsible for MS
handovers etc. It creates physical link between
subscriber (MS) and BTS , then manage and
controls functions of it. It performs the function of
high quality switch by handover over the MS to
next BSC when MS goes out of the current range
of BTS, it helps in connecting to next in range BTS
to keep the connection alive within the network. It
also performs functions like cell configuration data,
control radio frequency in BTS. Data moves to
MSC-Mobile switching center after BSC done
processing it. MSC is switching center which acts
as bridge between different mobile networks.

Architecture and Working of GSM Networks

The Operation and Support System (OSS)
OMC- Operations and maintenance center is
designed to connect to equipment of MSC- Mobile
Switching Center and BSC-Base Station Controller.
The implementation of OMC is called OSS-The
Operations and Support System.OSS helps in
mobile networks to monitor and control the
complex systems.The basic reason for developing
operation and support system is to provide
customers a cost effective support and solutions. It
helps in managing, centralizing, local and regional
operational activities required for GMS networks.
Maintaining mobile network organization, provide
overview of network, support and maintenance
activities are other important aspects of Operation
and Support System

The Penalty for Ignorance is Lack