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September 01, 2018
The cathode ray Tube (CRT) is the heart of the C.R.O. the CRT generates the electron beam, accelerates the beam, deflects the beam and also has a screen where beam becomes visible as a spot. The main parts of the CRT are:

1.    Electron Gun
2.    Deflection system
3.    Fluorescent screen
4.    Glass tube or envelope
5.    Base

A schematic diagram of CRT, showing its structure and main components is shown in the figure below.
                                                                                               


Since I want to explain each and every parts of the CRT in detail, I will spilt this topic into 3 parts.

 



 


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September 01, 2018
Integral cycle controllers are converters with the ability to perform direct switching without losses. The process directly converts AC to AC without having to perform the intermediate processes of AC to DC then DC to AC.
The basic integral control cycle is sinusoidal in nature. It operates by combining and eliminating higher frequency half cycles from AC input. The controllers are normally, turned ON of OFF during half cycles where the voltage input is at zero since only the full or half cycles are utilized. Therefore, integral cycle circuits achieve switching at zero voltage without requiring a resonant circuit.
The diagram below shows a simple integral cycle controller. It contains a load and a power switch, which performs the direct conversion. This diagram shows the conversion of source frequency from a factor of three to one.
Power Factor Control                                                                                 
Power factor control, also known as correction of power factor, is the process of reducing the amount of reactive power. The power electronic device used in this case is called a power factor controller (PFC). From the power triangle (which comprises reactive, true and apparent power), the reactive power is at right angle (90°) to the true power and is used to energize the magnetic field. Although reactive power does not have a real value in electronic equipment, the bill for electricity comprises real and reactive power costs. This makes it necessary to have power factor controllers in electronic devices.
Power factor (k) is defined as the ratio of the real power (in kW) to the reactive power (in kVAr). Its value ranges from 0 to 1. If a device has a power factor of 0.8 and above, it is said to be using power efficiently. Incorporating a PFC ensures the power factor ranges from 0.95 to 0.99. Power factor controllers are mainly in industrial equipment to minimize reactive power generated by fluorescent lighting and electric motors.
To ensure power factor is improved without causing harmonic distortion, the conventional capacitors should not be used. Instead, filters (combination of capacitors and reactors) for harmonic suppression are used. The figure below shows a harmonic filter.
The above type of harmonic filter is referred to as a single tuned filter. A quality factor Q of this filter is defined as quality factor of its reactance (XL) at Q (tuning frequency) where Q is given by (nXL/R).

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September 01, 2018
In the UK, turnpikes were an increasingly common way of paying for the maintenance costs of major roads from the early 18thCentury. The UK government allowed private companies, known as Turnpike Trusts, to put up tolls (turnpikes) to collect revenue to upkeep and extend the road system. However, by the 1850s railways took over from turnpikes as the most popular method of transport. The complex and fragmented turnpike system was also seen as an increasing barrier to trade across the UK, and it was effectively abandoned in the late 19th Century as control of the building and maintenance of roads and bridges was given to local government, which collected revenue from local rates and received a subsidy from central government. The development and collapse of the turnpike system provides evidence of the difficulty of finding a single and effective way to fund and operate quasi-public goods.

New technology

The introduction of new technology can often lead to the formation of new markets, and allows existing markets to become complete over time. This occurs for a number of reasons:
1.      New technology can be used to reduce production costs and make it easier for private firms to break-even.
2.      Technology improves the ability of firms to exclude entry to prevent free riders, such as the use of automatic barriers across bridges. Number plate recognition systems can also be used to track and monitor attempts to avoid payments.
3.      Computer systems can be used to enable suppliers to generate and store more knowledge about travellers and about peak flows, and hence reduce information failure, and increase efficiency. For example, cameras and computers can be used to monitor and measure traffic flows over a bridge.
4.      Finally, new technology allows the possibility of creating fast and efficient payment methods, which can avoid the need to queue to have access to public goods.


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September 01, 2018
                   

Cement is a commonly used binding material in the construction. The cement is obtained by burning a mixture of calcareous (calcium) and argillaceous (clay) material at a very high temperature and then grinding the clinker so produced to a fine powder. It was first produced by a mason Joseph Aspdin in England in 1924. He patented it as portland cement.

Types of Cement

In addition to ordinary portland cement there are many varieties of cement. Important varieties are briefly explained below:

(i) White Cement:

The cement when made free from colouring oxides of iron, maganese and chlorium results into white cement. In the manufacture of this cement, the oil fuel is used instead of coal for burning. White cement is used for the floor finishes, plastering, ornamental works etc. In swimming pools white cement is used to replace glazed tiles. It is used for fixing marbles and glazed tiles.

(ii) Coloured Cement:

The cements of desired colours are produced by intimately mixing pigments with ordinary cement. The chlorium oxide gives green colour. Cobalt produce blue colour.Iron oxide with different proportion produce brown, red or yellow colour. Addition of manganese dioxide gives black or brown coloured cement. These cements are used for giving finishing touches to floors,walls, window sills, roofs etc.

(iii) Quick Setting Cement:

Quick setting cement is produced by reducing the percentage of gypsum and adding a small amount of aluminium sulphate during the manufacture of cement. Finer grinding also adds to quick setting property. This cement starts setting within 5 minutes after adding water and becomes hard mass within 30 minutes. This cement is used to lay concrete under static or slowly running water.

(iv) Rapid Hardening Cement:

 This cement can be produced by increasing lime content and burning at high temperature while manufacturing cement. Grinding to very fine is also necessary. Though the initial and final setting time of this cement is the same as that of portland cement, it gains strength in early days. This property helps in earlier removal of form works and speed in construction activity.

(v) Low Heat Cement:

 In mass concrete works like construction of dams, heat produced due to hydration of cement will not get dispersed easily. This may give rise to cracks. Hence in such constructions it is preferable to use low heat cement. This cement contains low percentage (5%) of tricalcium aluminate(C3A) and higher percentage (46%) of dicalcium silicate (C2S).

(vi) Pozzolana Cement:

Pozzolana is a volcanic power found in Italy. It can be processed from shales and certain types of clay also. In this cement pozzolana material is 10 to 30 per cent. It can resist action of sulphate. It releases less heat during setting. It imparts higher degree of water tightness. Its tensile strength is high but compressive strength is low. It is used for mass concrete works. It is also used in sewage line works.

(vii) Expanding Cement:

 This cement expands as it sets. This property is achieved by adding expanding medium like sulpho aluminate and a stabilizing agent to ordinary cement. This is used for filling the cracks in concrete structures.

(viii) High Alumina Cement:

 It is manufactured by calcining a mixture of lime and bauxite. It is more resistant to sulphate and acid attack. It develops almost full strength within 24 hours of adding water. It is used for underwater works.
(ix) Blast Furnace Cement:
 In the manufacture of pig iron, slag comes out as a waste product. By grinding clinkers of cement with about 60 to 65 per cent of slag, this cement is produced. The properties of this cement are more or less same as ordinary cement, but it is cheap, since it utilise waste product. This cement is durable but it gains the strength slowly and hence needs longer period of curing.

(x) Acid Resistant Cement:

This cement is produced by adding acid resistant aggregated such as quartz, quartzite, sodium silicate or soluble glass. This cement has good resistance to action of acid and water. It is commonly used in the construction of chemical factories.

(xi) Sulphate Resistant Cement:

 By keeping the percentage of tricalcium aluminate C3A below five per cent in ordinary cement this cement is produced. It is used in the construction of structures which are likely to be damaged by alkaline conditions. Examples of such structures are canals, culverts etc.

(xii) Fly Ash Blended Cement:

 Fly ash is a byproduct in thermal stations. The particles of fly ash are very minute and they fly in the air, creating air pollution problems. Thermal power stations have to spend lot of money to arrest fly ash and dispose safely. It is found that one of the best way to dispose fly-ash is to mix it with cement in controlled condition and derive some of the beneficial effects on cement. Nowadays cement factories produce the fly ash in their own thermal stations or borrow it from other thermal stations and further process it to make it suitable to blend with cement. 20 to 30% fly ash is used for blending.Fly ash blended cements have superior quality of resistance to weathering action. The ultimate strength gained is the same as that with ordinary portland cement. However strength gained in the initial stage is slow.

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September 01, 2018
If the pressure in the suction line of the pump is less than the vapour pressure of the fluid, it results in the formation of bubbles and collapsing of those bubbles at the ‘eye of the impeller’ and that is termed as cavitation.
The pressure in the suction line can drop due to serval reasons.
●     The suction line has too many turns and bends (avoid that, talk to layout and piping engineers)
●     Plugged strainer or filter in the suction line (ensure the line is clean, maintenance is necessary)
●     Rusted Pipe results in friction losses (keep an eye on those and change if necessary)
●     Low level in the suction vessel (make sure that it operates at operating set point or close to it)
●     Damaged fittings over a period and so forth


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September 01, 2018
Anti-Braking System is a safety system that allows the wheels on a motor vehicle to continue interacting tractively with the road surface as directed by driver steering inputs while braking, preventing the wheels from locking up (that is, ceasing rotation) and therefore avoiding skidding.  A skidding wheel (where the tire contact patch is sliding relative to the road) has lesstraction than a non-skidding wheel. If you have been stuck on ice, you know that if your wheels are spinning you have no traction. This is because the contact patch is sliding relative to the ice. By keeping the wheels from skidding while you slow down, anti-lock brakes benefit you in two ways: You'll stop faster, and you'll be able to steer while you stop.
There are four main components to an ABS system:
a)    Speed sensors
      b)  Pump                   
      c)  Valves
      d)  Controller
Speed Sensors- The anti-lock braking system needs some way of knowing when a wheel is about to lock up. The speed sensors, which are located at each wheel, or in some cases in the differential, provide this information.
Valves- There is a valve in the brake line of each brake controlled by the ABS. On some systems, the valve has three positions:
· In position one, the valve is open; pressure from the master cylinder is passed right through to the brake.
· In position two, the valve blocks the line, isolating that brake from the master cylinder. This prevents the pressure from rising further should the driver push the brake pedal harder.
·   In position three, the valve releases some of the pressure from the brake.

Pump- Since the valve is able to release pressure from the brakes, there has to be some way to put that pressure back. That is what the pump does; when a valve reduces the pressure in a line, the pump is there to get the pressure back up.
Controller- The controller is a computer in the car. It watches the speed sensors and controls the valves.
An ABS generally offers improved vehicle control and decreases stopping distances on dry and slippery surfaces for many drivers; however, on loose surfaces like gravel or snow-covered pavement, an ABS can significantly increase braking distance, although still improving vehicle control.




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September 01, 2018

HOW DO YOU MOVE ABOUT IN SPACE?

A spacecraft uses most of its energy getting up into space. With no drag to overcome once in orbit, the spacecraft can then “coast” without expending any more energy. But how can you change a spacecraft’s course? Move it from one orbit to another? Or bring it back to Earth?
View of the Space Shuttle Discovery as photographed during the survey operation performed by the crew on the International Space Station.  As part of the survey and part of every mission's activities, the orbiter performed a back-flip for the rendezvous pitch maneuver.
Credit: NASA

HOW DO ROCKETS HELP YOU MANEUVER IN ORBIT?

Speeding up and slowing down in orbit works just opposite to what you might expect. The larger a spacecraft's orbit, the slower the spacecraft travels.  So if you wanted to pass a spacecraft just ahead of you, you would have to fire a thruster in a forward direction. This would decrease your orbital energy and drop you into a lower orbit, where you would travel faster! The "passing lane" in orbit is always lower.

HOW DO ROCKETS HELP YOU MANEUVER IN OPEN SPACE?

Once you are far from a planet, say, while flying between Earth and Jupiter, mid-course corrections are fairly straight-forward. To speed up, you fire a rear-facing thruster. To slow down, you fire a forward-facing thruster. To alter your course, you fire a thruster in a sideward direction. To rotate your spacecraft, you fire a pair of sideward-pointed thrusters located near opposite sides of the spacecraft. To stop rotating, you fire thrusters aimed in the opposite direction.

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