1. pointer and reference similarities and difference
2.class hierarchies.
3.constant qualifier.
4. constant object and member functions.
Showing posts with label assignments. Show all posts
Showing posts with label assignments. Show all posts
Friday, December 25, 2009
Wednesday, August 5, 2009
Monday, July 6, 2009
Tuesday, June 23, 2009
Workshop deatils
This is a 20 page pdf document ....
Click HERE or visit the following link
http://www.scribd.com/doc/16733407/Workshop-Record-Details
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Click HERE or visit the following link
http://www.scribd.com/doc/16733407/Workshop-Record-Details
Here's the preview......
Wednesday, March 4, 2009
Sunday, February 22, 2009
Questions for physics assignment for cs
1. explain einsteins coefficiant?
2.basic principles of laser
3.working principle ruby laser
4.working principle helium neon laser
5.explain breifly application of laser
6.holography?recording reconstruction.process in holography?application?
7.optical fibre ?explain application?advantages over conventional transmission lines ?
8.semiconductor injection laser?
9.explain spontaneous emission,stimulated emission
10.explain pumping,metastable level,population inversion..
2.basic principles of laser
3.working principle ruby laser
4.working principle helium neon laser
5.explain breifly application of laser
6.holography?recording reconstruction.process in holography?application?
7.optical fibre ?explain application?advantages over conventional transmission lines ?
8.semiconductor injection laser?
9.explain spontaneous emission,stimulated emission
10.explain pumping,metastable level,population inversion..
Friday, January 16, 2009
Chemistry assisgnment for cs (full)
Cement
In the most general sense of the word, a cement is a binder, a substance which sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term "opus caementicium" to describe masonry which resembled concrete and was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick additives which were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum, cimentum, cäment and cement. Cements used in construction are characterized as hydraulic or non-hydraulic.
The most important use of cement is the production of mortar and concrete - the bonding of natural or artificial aggregates to form a strong building material which is durable in the face of normal environmental effects.
Cement should not be confused with concrete as the term cement explicitly refers to the dry powder substance. Upon the addition of water and/or additives the cement mixture is referred to as concrete, especially if aggregates have been added.
Types of modern cement
Portland cement
Cement is made by heating limestone with small quantities of other materials (such as clay) to 1450°C in a kiln. The resulting hard substance, called ‘clinker’, is then ground with a small amount of gypsum into a powder to make ‘Ordinary Portland Cement’, the most commonly used type of cement (often referred to as OPC).
Portland cement is a basic ingredient of concrete, mortar and most non-speciality grout. The most common use for Portland cement is in the production of concrete. Concrete is a composite material consisting of aggregate (gravel and sand), cement, and water. As a construction material, concrete can be cast in almost any shape desired, and once hardened, can become a structural (load bearing) element. Portland cement may be gray or white.
Portland cement blends
These are often available as inter-ground mixtures from cement manufacturers, but similar formulations are often also mixed from the ground components at the concrete mixing plant.[7]
Portland Blastfurnace Cement contains up to 70% ground granulated blast furnace slag, with the rest Portland clinker and a little gypsum. All compositions produce high ultimate strength, but as slag content is increased, early strength is reduced, while sulfate resistance increases and heat evolution diminishes. Used as an economic alternative to Portland sulfate-resisting and low-heat cements.[8]
Expansive Cements contain, in addition to Portland clinker, expansive clinkers (usually sulfoaluminate clinkers), and are designed to offset the effects of drying shrinkage that is normally encountered with hydraulic cements. This allows large floor slabs (up to 60 m square) to be prepared without contraction joints.
White blended cements may be made using white clinker and white supplementary materials such as high-purity metakaolin.
Colored cements are used for decorative purposes. In some standards, the addition of pigments to produce "colored Portland cement" is allowed. In other standards (e.g. ASTM), pigments are not allowed constituents of Portland cement, and colored cements are sold as "blended hydraulic cements".
Very finely ground cements are made from mixtures of cement with sand or with slag or other pozzolan type minerals which are extremely finely ground. Such cements can have the same physical characteristics as normal cement but with 50% less cement particularly due to their increased surface area for the chemical reaction. Even with intensive grinding they can use up to 50% less energy to fabricate than ordinary Portland cements
Non-Portland hydraulic cements
Pozzolan-lime cements. Mixtures of ground pozzolan and lime are the cements used by the Romans, and are to be found in Roman structures still standing (e.g. the Pantheon in Rome). They develop strength slowly, but their ultimate strength can be very high. The hydration products that produce strength are essentially the same as those produced by Portland cement.
Slag-lime cements. Ground granulated blast furnace slag is not hydraulic on its own, but is “activated” by addition of alkalis, most economically using lime. They are similar to pozzolan lime cements in their properties. Only granulated slag (i.e. water-quenched, glassy slag) is effective as a cement component.
Supersulfated cements. These contain about 80% ground granulated blast furnace slag, 15% gypsum or anhydrite and a little Portland clinker or lime as an activator. They produce strength by formation of ettringite, with strength growth similar to a slow Portland cement. They exhibit good resistance to aggressive agents, including sulfate.
Calcium aluminate cements are hydraulic cements made primarily from limestone and bauxite. The active ingredients are monocalcium aluminate CaAl2O4 (CA in Cement chemist notation) and Mayenite Ca12Al14O33 (C12A7 in CCN). Strength forms by hydration to calcium aluminate hydrates. They are well-adapted for use in refractory (high-temperature resistant) concretes, e.g. for furnace linings.
“Natural” Cements correspond to certain cements of the pre-Portland era, produced by burning argillaceous limestones at moderate temperatures. The level of clay components in the limestone (around 30-35%) is such that large amounts of belite (the low-early strength, high-late strength mineral in Portland cement) are formed without the formation of excessive amounts free lime. As with any natural material, such cements have very variable properties.
Geopolymer cements are made from mixtures of water-soluble alkali metal silicates and aluminosilicate mineral powders such as fly ash and metakaolin.
Setting and hardening of cement
When water is mixed with Portland cement, the product sets in a few hours and hardens over a period of weeks. These processes can vary widely depending upon the mix used and the conditions of curing of the product, but a typical concrete sets (i.e. becomes rigid) in about 6 hours, and develops a compressive strength of 8~ MPa in 24 hours. The strength rises to 15~ MPa at 3 days, 23~ MPa at one week, 35~ MPa at 4 weeks, and 41~ MPa at three months. In principle, the strength continues to rise slowly as long as water is available for continued hydration, but concrete is usually allowed to dry out after a few weeks, and this causes strength growth to stop.
Setting and hardening of Portland cement is caused by the formation of water-containing compounds, forming as a result of reactions between cement components and water. Usually, cement reacts in a plastic mixture only at water/cement ratios between 0.25 and 0.75. The reaction and the reaction products are referred to as hydration and hydrates or hydrate phases, respectively. As a result of the reactions (which start immediately), a stiffening can be observed which is very small in the beginning, but which increases with time. The point in time at which it reaches a certain level is called the start of setting. The consecutive further consolidation is called setting, after which the phase of hardening begins.
Stiffening, setting and hardening are caused by the formation of a microstructure of hydration products of varying rigidity which fills the water-filled interstitial spaces between the solid particles of the cement paste, mortar or concrete. The behaviour with time of the stiffening, setting and hardening therefore depends to a very great extent on the size of the interstitial spaces, i. e. on the water/cement ratio. The grain size of the cement and admixtures, e.g. micro silica or nano silica affects the particle distance and therefore the final compressive strength. Typical grain sizes for cement vary between 10 and 20µm. A good mixing and dispersing of all cement and admixture particles is needed to obtain optimal concrete properties after hardening.[4] The hydration products primarily affecting the strength are calcium silicate hydrates ("C-S-H phases"). Further hydration products are calcium hydroxide, sulfatic hydrates (AFm and AFt phases), and related compounds, hydrogarnet, and gehlenite hydrate. Calcium silicates or silicate constituents make up over 70 % by mass of silicate-based cements. The hydration of these compounds and the properties of the calcium silicate hydrates produced are therefore particularly important. Calcium silicate hydrates contain less CaO than the calcium silicates in cement clinker, so calcium hydroxide is formed during the hydration of Portland cement. This is available for reaction with supplementary cementitious materials such as ground granulated blast furnace slag and pozzolans. The simplified reaction of alite with water may be expressed as:
2Ca3OSiO4 + 6H2O → 3CaO.2SiO2.3H2O + 3Ca(OH)2
This is a relatively fast reaction, causing setting and strength development in the first few weeks. The reaction of belite is:
2Ca2SiO4 + 4H2O → 3CaO.2SiO2.3H2O + Ca(OH)2
This reaction is relatively slow, and is mainly responsible for strength growth after one week. Tricalcium aluminate hydration is controlled by the added calcium sulfate, which immediately goes into solution when water is added. Firstly, ettringite is rapidly formed, causing a slowing of the hydration (see tricalcium aluminate):
Ca3(AlO3)2 + 3CaSO4 + 32H2O → Ca6(AlO3)2(SO4)3.32H2O
The ettringite subsequently reacts slowly with further tricalcium aluminate to form "monosulfate" - an "AFm phase":
Ca6(AlO3)2(SO4)3.32H2O + Ca3(AlO3)2 + 4H2O → 3Ca4(AlO3)2(SO4).12H2O
This reaction is complete after 1-2 days. The calcium aluminoferrite reacts slowly due to precipitation of hydrated iron oxide:
2Ca2AlFeO5 + CaSO4 + 16H2O → Ca4(AlO3)2(SO4).12H2O + Ca(OH)2 + 2Fe(OH)3
The pH-value of the pore solution reaches comparably high values and is of importance for most of the hydration reactions.
Soon after Portland cement is mixed with water, a brief and intense hydration starts (pre-induction period). Calcium sulfates dissolve completely and alkali sulfates almost completely. Short, hexagonal needle-like ettringite crystals form at the surface of the clinker particles as a result of the reactions between calcium- and sulfate ions with tricalcium aluminate. Further, originating from tricalcium silicate, first calcium silicate hydrates (C-S-H) in colloidal shape can be observed. Caused by the formation of a thin layer of hydration products on the clinker surface, this first hydration period ceases and the induction period starts during which almost no reaction takes place. The first hydration products are too small to bridge the gap between the clinker particles and do not form a consolidated microstructure. Consequently the mobility of the cement particles in relation to one another is only slightly affected, i. e. the consistency of the cement paste turns only slightly thicker. Setting starts after approximately one to three hours, when first calcium silicate hydrates form on the surface of the clinker particles, which are very fine-grained in the beginning. After completion of the induction period, a further intense hydration of clinker phases takes place. This third period (accelerated period) starts after approximately four hours and ends after 12 to 24 hours. During this period a basic microstructure forms, consisting of C-S-H needles and C-S-H leafs, platy calcium hydroxide and ettringite crystals growing in longitudinal shape. Due to growing crystals, the gap between the cement particles is increasingly bridged. During further hydration, the hardening steadily increases, but with decreasing speed. The density of the microstructure rises and the pores fill: the filling of pores causes strength gain.
***************************************************************************************
Lubricants
A lubricant (sometimes referred to as "lube") is a substance (often a liquid) introduced between two moving surfaces to reduce the friction between them, improving efficiency and reducing wear. They also have the function of dissolving foreign particles
One of the single largest applications for lubricants, in the form of motor oil, is to protect the internal combustion engines in motor vehicles and powered equipment
Lubricants perform the following key functions.
* Keep moving parts apart
* Reduce friction
* Transfer heat
* Carry away contaminants & debris
* Transmit power
* Protect against wear
* Prevent corrosion
* Seal for gasses
* Stop the risk of smoke and fire of objects
theory of friction
According to the law of conservation of energy, no energy is destroyed due to friction, though it may be lost to the system of concern. Energy is transformed from other forms into heat. A sliding hockey puck comes to rest because friction converts its kinetic energy into heat. Since heat quickly dissipates, many early philosophers, including Aristotle, wrongly concluded that moving objects lose energy without a driving force.
When an object is pushed along a surface, the energy converted to heat is given by:
where
Fn is the normal force,
μk is the coefficient of kinetic friction,
x is the coordinate along which the object transverses.
Types of lubricants
* Liquid including emulsions and suspensions
* Solid
* Greases
* Adhesive
Liquid lubricants
Liquid lubricants may be characterized in many different ways. One of the most common ways is by the type of base oil used. Following are the most common types.
* Lanolin (wool grease, natural water repellant)
* Water
* Mineral oils
* Vegetable (natural oil)
* Synthetic oils
* Others
Note: although generally lubricants are based on one type of base oil or another, it is quite possible to use mixtures of the base oils to meet performance requirements.
Solid lubricants
Teflon or PTFE
Teflon or PTFE is typically used as a coating layer on, for example, cooking utensils to provide a non-stick surface.
Mineral
Graphite, hexagonal Boron nitride ([3]), Molybdenum disulfide and Tungsten disulfide are examples of materials that can be used as solid lubricants, often to very high temperature. The use of such materials are still restricted by their poor resistance to oxidation (e.g., molybdenum disulfide can only be used up to 350C in air, but 1100C in reducing environments).
In the most general sense of the word, a cement is a binder, a substance which sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term "opus caementicium" to describe masonry which resembled concrete and was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick additives which were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum, cimentum, cäment and cement. Cements used in construction are characterized as hydraulic or non-hydraulic.
The most important use of cement is the production of mortar and concrete - the bonding of natural or artificial aggregates to form a strong building material which is durable in the face of normal environmental effects.
Cement should not be confused with concrete as the term cement explicitly refers to the dry powder substance. Upon the addition of water and/or additives the cement mixture is referred to as concrete, especially if aggregates have been added.
Types of modern cement
Portland cement
Cement is made by heating limestone with small quantities of other materials (such as clay) to 1450°C in a kiln. The resulting hard substance, called ‘clinker’, is then ground with a small amount of gypsum into a powder to make ‘Ordinary Portland Cement’, the most commonly used type of cement (often referred to as OPC).
Portland cement is a basic ingredient of concrete, mortar and most non-speciality grout. The most common use for Portland cement is in the production of concrete. Concrete is a composite material consisting of aggregate (gravel and sand), cement, and water. As a construction material, concrete can be cast in almost any shape desired, and once hardened, can become a structural (load bearing) element. Portland cement may be gray or white.
Portland cement blends
These are often available as inter-ground mixtures from cement manufacturers, but similar formulations are often also mixed from the ground components at the concrete mixing plant.[7]
Portland Blastfurnace Cement contains up to 70% ground granulated blast furnace slag, with the rest Portland clinker and a little gypsum. All compositions produce high ultimate strength, but as slag content is increased, early strength is reduced, while sulfate resistance increases and heat evolution diminishes. Used as an economic alternative to Portland sulfate-resisting and low-heat cements.[8]
Expansive Cements contain, in addition to Portland clinker, expansive clinkers (usually sulfoaluminate clinkers), and are designed to offset the effects of drying shrinkage that is normally encountered with hydraulic cements. This allows large floor slabs (up to 60 m square) to be prepared without contraction joints.
White blended cements may be made using white clinker and white supplementary materials such as high-purity metakaolin.
Colored cements are used for decorative purposes. In some standards, the addition of pigments to produce "colored Portland cement" is allowed. In other standards (e.g. ASTM), pigments are not allowed constituents of Portland cement, and colored cements are sold as "blended hydraulic cements".
Very finely ground cements are made from mixtures of cement with sand or with slag or other pozzolan type minerals which are extremely finely ground. Such cements can have the same physical characteristics as normal cement but with 50% less cement particularly due to their increased surface area for the chemical reaction. Even with intensive grinding they can use up to 50% less energy to fabricate than ordinary Portland cements
Non-Portland hydraulic cements
Pozzolan-lime cements. Mixtures of ground pozzolan and lime are the cements used by the Romans, and are to be found in Roman structures still standing (e.g. the Pantheon in Rome). They develop strength slowly, but their ultimate strength can be very high. The hydration products that produce strength are essentially the same as those produced by Portland cement.
Slag-lime cements. Ground granulated blast furnace slag is not hydraulic on its own, but is “activated” by addition of alkalis, most economically using lime. They are similar to pozzolan lime cements in their properties. Only granulated slag (i.e. water-quenched, glassy slag) is effective as a cement component.
Supersulfated cements. These contain about 80% ground granulated blast furnace slag, 15% gypsum or anhydrite and a little Portland clinker or lime as an activator. They produce strength by formation of ettringite, with strength growth similar to a slow Portland cement. They exhibit good resistance to aggressive agents, including sulfate.
Calcium aluminate cements are hydraulic cements made primarily from limestone and bauxite. The active ingredients are monocalcium aluminate CaAl2O4 (CA in Cement chemist notation) and Mayenite Ca12Al14O33 (C12A7 in CCN). Strength forms by hydration to calcium aluminate hydrates. They are well-adapted for use in refractory (high-temperature resistant) concretes, e.g. for furnace linings.
“Natural” Cements correspond to certain cements of the pre-Portland era, produced by burning argillaceous limestones at moderate temperatures. The level of clay components in the limestone (around 30-35%) is such that large amounts of belite (the low-early strength, high-late strength mineral in Portland cement) are formed without the formation of excessive amounts free lime. As with any natural material, such cements have very variable properties.
Geopolymer cements are made from mixtures of water-soluble alkali metal silicates and aluminosilicate mineral powders such as fly ash and metakaolin.
Setting and hardening of cement
When water is mixed with Portland cement, the product sets in a few hours and hardens over a period of weeks. These processes can vary widely depending upon the mix used and the conditions of curing of the product, but a typical concrete sets (i.e. becomes rigid) in about 6 hours, and develops a compressive strength of 8~ MPa in 24 hours. The strength rises to 15~ MPa at 3 days, 23~ MPa at one week, 35~ MPa at 4 weeks, and 41~ MPa at three months. In principle, the strength continues to rise slowly as long as water is available for continued hydration, but concrete is usually allowed to dry out after a few weeks, and this causes strength growth to stop.
Setting and hardening of Portland cement is caused by the formation of water-containing compounds, forming as a result of reactions between cement components and water. Usually, cement reacts in a plastic mixture only at water/cement ratios between 0.25 and 0.75. The reaction and the reaction products are referred to as hydration and hydrates or hydrate phases, respectively. As a result of the reactions (which start immediately), a stiffening can be observed which is very small in the beginning, but which increases with time. The point in time at which it reaches a certain level is called the start of setting. The consecutive further consolidation is called setting, after which the phase of hardening begins.
Stiffening, setting and hardening are caused by the formation of a microstructure of hydration products of varying rigidity which fills the water-filled interstitial spaces between the solid particles of the cement paste, mortar or concrete. The behaviour with time of the stiffening, setting and hardening therefore depends to a very great extent on the size of the interstitial spaces, i. e. on the water/cement ratio. The grain size of the cement and admixtures, e.g. micro silica or nano silica affects the particle distance and therefore the final compressive strength. Typical grain sizes for cement vary between 10 and 20µm. A good mixing and dispersing of all cement and admixture particles is needed to obtain optimal concrete properties after hardening.[4] The hydration products primarily affecting the strength are calcium silicate hydrates ("C-S-H phases"). Further hydration products are calcium hydroxide, sulfatic hydrates (AFm and AFt phases), and related compounds, hydrogarnet, and gehlenite hydrate. Calcium silicates or silicate constituents make up over 70 % by mass of silicate-based cements. The hydration of these compounds and the properties of the calcium silicate hydrates produced are therefore particularly important. Calcium silicate hydrates contain less CaO than the calcium silicates in cement clinker, so calcium hydroxide is formed during the hydration of Portland cement. This is available for reaction with supplementary cementitious materials such as ground granulated blast furnace slag and pozzolans. The simplified reaction of alite with water may be expressed as:
2Ca3OSiO4 + 6H2O → 3CaO.2SiO2.3H2O + 3Ca(OH)2
This is a relatively fast reaction, causing setting and strength development in the first few weeks. The reaction of belite is:
2Ca2SiO4 + 4H2O → 3CaO.2SiO2.3H2O + Ca(OH)2
This reaction is relatively slow, and is mainly responsible for strength growth after one week. Tricalcium aluminate hydration is controlled by the added calcium sulfate, which immediately goes into solution when water is added. Firstly, ettringite is rapidly formed, causing a slowing of the hydration (see tricalcium aluminate):
Ca3(AlO3)2 + 3CaSO4 + 32H2O → Ca6(AlO3)2(SO4)3.32H2O
The ettringite subsequently reacts slowly with further tricalcium aluminate to form "monosulfate" - an "AFm phase":
Ca6(AlO3)2(SO4)3.32H2O + Ca3(AlO3)2 + 4H2O → 3Ca4(AlO3)2(SO4).12H2O
This reaction is complete after 1-2 days. The calcium aluminoferrite reacts slowly due to precipitation of hydrated iron oxide:
2Ca2AlFeO5 + CaSO4 + 16H2O → Ca4(AlO3)2(SO4).12H2O + Ca(OH)2 + 2Fe(OH)3
The pH-value of the pore solution reaches comparably high values and is of importance for most of the hydration reactions.
Soon after Portland cement is mixed with water, a brief and intense hydration starts (pre-induction period). Calcium sulfates dissolve completely and alkali sulfates almost completely. Short, hexagonal needle-like ettringite crystals form at the surface of the clinker particles as a result of the reactions between calcium- and sulfate ions with tricalcium aluminate. Further, originating from tricalcium silicate, first calcium silicate hydrates (C-S-H) in colloidal shape can be observed. Caused by the formation of a thin layer of hydration products on the clinker surface, this first hydration period ceases and the induction period starts during which almost no reaction takes place. The first hydration products are too small to bridge the gap between the clinker particles and do not form a consolidated microstructure. Consequently the mobility of the cement particles in relation to one another is only slightly affected, i. e. the consistency of the cement paste turns only slightly thicker. Setting starts after approximately one to three hours, when first calcium silicate hydrates form on the surface of the clinker particles, which are very fine-grained in the beginning. After completion of the induction period, a further intense hydration of clinker phases takes place. This third period (accelerated period) starts after approximately four hours and ends after 12 to 24 hours. During this period a basic microstructure forms, consisting of C-S-H needles and C-S-H leafs, platy calcium hydroxide and ettringite crystals growing in longitudinal shape. Due to growing crystals, the gap between the cement particles is increasingly bridged. During further hydration, the hardening steadily increases, but with decreasing speed. The density of the microstructure rises and the pores fill: the filling of pores causes strength gain.
***************************************************************************************
Lubricants
A lubricant (sometimes referred to as "lube") is a substance (often a liquid) introduced between two moving surfaces to reduce the friction between them, improving efficiency and reducing wear. They also have the function of dissolving foreign particles
One of the single largest applications for lubricants, in the form of motor oil, is to protect the internal combustion engines in motor vehicles and powered equipment
Lubricants perform the following key functions.
* Keep moving parts apart
* Reduce friction
* Transfer heat
* Carry away contaminants & debris
* Transmit power
* Protect against wear
* Prevent corrosion
* Seal for gasses
* Stop the risk of smoke and fire of objects
theory of friction
According to the law of conservation of energy, no energy is destroyed due to friction, though it may be lost to the system of concern. Energy is transformed from other forms into heat. A sliding hockey puck comes to rest because friction converts its kinetic energy into heat. Since heat quickly dissipates, many early philosophers, including Aristotle, wrongly concluded that moving objects lose energy without a driving force.
When an object is pushed along a surface, the energy converted to heat is given by:
where
Fn is the normal force,
μk is the coefficient of kinetic friction,
x is the coordinate along which the object transverses.
Types of lubricants
* Liquid including emulsions and suspensions
* Solid
* Greases
* Adhesive
Liquid lubricants
Liquid lubricants may be characterized in many different ways. One of the most common ways is by the type of base oil used. Following are the most common types.
* Lanolin (wool grease, natural water repellant)
* Water
* Mineral oils
* Vegetable (natural oil)
* Synthetic oils
* Others
Note: although generally lubricants are based on one type of base oil or another, it is quite possible to use mixtures of the base oils to meet performance requirements.
Solid lubricants
Teflon or PTFE
Teflon or PTFE is typically used as a coating layer on, for example, cooking utensils to provide a non-stick surface.
Mineral
Graphite, hexagonal Boron nitride ([3]), Molybdenum disulfide and Tungsten disulfide are examples of materials that can be used as solid lubricants, often to very high temperature. The use of such materials are still restricted by their poor resistance to oxidation (e.g., molybdenum disulfide can only be used up to 350C in air, but 1100C in reducing environments).
Friday, January 9, 2009
Engineering Graphics: TIPS FOR PROJECTION OF SOLIDS
When the axis of the solid inclined any of the projection plane, - First assume the axis is perpendicular to that plane.
- Draw the projection in simple position
- Top view first if the axis is perpendicular to HP
- Front view first if the axis is perpendicular to VP
- Top view first if the axis is perpendicular to HP
- Change position of the view to the given inclination
- Tilt the front view, if the axis inclined to the HP
- Tilt the top view, if the axis inclined to the VP
- Tilt the front view, if the axis inclined to the HP
- Project from this view to get the final view
- Project from the front view, to get the top view if the axis inclined to the HP
- Project from the top view, to get the front view if the axis inclined to the VP
- Project from the front view, to get the top view if the axis inclined to the HP
- Ensure all the points are named in an appropriate manner
- Lower case letters with a (’)dash for the front views
- Lower case letters alone for the top views
Happy Drawing
For More visit the following links::
- Engineering Graphics getting started, Points, Lines…
- Tips for Section of Solids
- Questions on Projections of Solids and Section of Solids
- Projections of Planes
- Projections of Straight Lines - Mid point problem
- Projection of Lines – I (Inclined to only one plane)
- Problems in Projection of Points – 2008-09
- Projection of Points in First Quadrant
- Unit Test Questions 2,3
- Special Questions
Monday, December 22, 2008
Assignments to IT branch
ENGINEERING GRAPHICS
SHEET NO: 2( CONICS)
- The minor axis of an ellipse is 70mm and the distance between its focal points is also 70mm. Using a geometrical construction, draw the ellipse, full size showing all necessary construction lines.
- Draw an ellipse with major axis 80mm and minor axis 60mm .Also draw one parallel curve, out side the original ellipse, and 18mm away from it.
- Draw an ellipse with major axis AB= 120mm and the minor axis CD = 80mm. the centre lines formed by the major and minor axes intersect at the point ‘O’. Mark the foci of the ellipse on the line AOB. Point P lies on the ellipse such that the angle AOP= 450. Draw the tangent and normal at point P.
- A stone thrown up in the air reaches a maximum height of 120m and falls at a point 90m away, horizontally. Trace the path of the stone, assuming it to be a parabolic. Take a suitable scale.
- A cricket ball is thrown from a building, 7 m high and at the highest point of flight, it just passes over a palm tree 14m high. Draw the path traced by the ball if the distance between the palm tree and building is 3.5 m. use a scale of 1: 100.
- Two points F1 and F2 are located on a plane sheet of paper and are 100mm apart. A point P moves on the sheet such that the difference of its distances from F1 and F2 always remained 50mm. find the locus of P? Draw a tangent and normal to the locus at any general point.
- Two straight lines OA and
SHEET NO 3(MISCELLANEOUS CURVES)
- A circular wheel of 600mm diameter rolls without slipping along a straight surface. Draw the curve traced by a point P on its rim for 1.5 revolutions of the wheel. Name the curve traced.
- A wheel of 50mm diameter rolls without slipping in two straight lines in two stages. For the first half of the revolution of the wheel, it rolls on a vertical line. In the second half it rolls on a line inclined at 40 0 to the vertical. Draw the complete curve traced out by a point P on the circumference initially touching the vertical line in one revolution.
- A motor cyclist drives his motor cycle in a globe of 4m diameter. The diameter of the motor cycle wheel is 80 cm .Draw the locus of a point spot on the circumference of the wheel for one revolution on the maximum diameter path in the globe
- A string is completely wound around the circumference of a semi circular cylinder of 60 mm diameter holding the free end of the string such that the string is all the time held taut, it is unwound completely. Trace the path followed by the free end. Also name the curve
- Draw an Archimedean spiral for 1.5 convolutions .the spiral starts from the pole and its greatest radius is 70mm .Draw the tangent to the curve at appoint 30mm from the pole
- Construct a logarithmic spiral for one convolution given the length of shortest radius as 15mm and the ratio of the lengths of successive radius vectors enclosing an angle of 30 0 as 9:8
Saturday, December 6, 2008
Data Communications basics
Data Communications Basics
Contents(click on the titles below to get detailed notes)
- What is Data Communications?
- Communications Channels
- Serial Communications
- Asynchronous vs. Synchronous Transmission
- The ASCII Character Set
- Parity and Checksums
- Data Compression
- Data Encryption
- Data Storage Technology
- Data Transfer in Digital Circuits
- Transmission over Short Distances (< 2 feet)
- Noise and Electrical Distortion
- Transmission over Medium Distances (<>
- Transmission over Long Distances (<4000 feet)
- Transmission over Very Long Distances (> 4000 feet)
Friday, December 5, 2008
resources for assignments!!
For chemistry .students who got the topic Weston CELL ..
Electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor (a metal or a semiconductor) and an ionic conductor (the electrolyte), and which involve electron transfer between the electrode and the electrolyte or species in solution.
Electrochemical cell
An electrochemical cell is a device used for generating an electromotive force (voltage) and current from chemical reactions. The current is caused by the reactions releasing and accepting electrons at the different ends of a conductor. A common example of an electrochemical cell is a standard 1.5-volt battery. Batteries are composed of usually multiple Galvanic cells.
Wet cell
A wet cell is a galvanic electrochemical cell with a liquid electrolyte. A dry cell, on the other hand, is a cell with a pasty electrolyte. Wet cells were a precursor to dry cells and are commonly used as a learning tool for electrochemistry. It is often built with common laboratory supplies, like beakers, for demonstrations of how electrochemical cells work. A particular type of wet cell known as a concentration cell is important in understanding corrosion. Wet cells may be primary cells (non-rechargeable) or secondary cells (rechargeable).
Primary wet cells
Primary wet cells are the Leclanche cell, Grove cell, Bunsen cell, Chromic acid cell, Clark cell and Weston cell.
Weston cell
The Weston cell, invented by Edward Weston in 1893, is a wet-chemical cell that produces a highly stable voltage suitable as a laboratory standard for calibration of voltmeters. It was adopted as the International Standard for EMF in 1911.
Chemistry
The anode is an amalgam of cadmium with mercury, the cathode is of pure mercury, the electrolyte is a solution of cadmium sulfate and the depolarizer is a paste of mercurous sulfate.
As shown in the illustration, the cell is set up in an H-shaped glass vessel with the cadmium amalgam in one leg and the pure mercury in the other. Electrical connections to the cadmium amalgam and the mercury are made by platinum wires fused through the lower ends of the legs.
Unsaturated Weston cells, such as this example, are the most common voltage standards in normal laboratory use. This specimen represents a style going back to at least 1929. These cells show a small temperature coefficient and so are normally preferred over the saturated Weston cell. However their e.m.f. decreases by about 0.08 mv per year, and thus must be calibrated periodically against a saturated Weston cell at a defined temperature. The Weston cell may be diagramed as:
Cd(Hg) | CdSO4(aq), Hg2SO4 | Hg.
Unsaturated Weston cells, such as this example, are the most common voltage standards in normal laboratory use. This specimen represents a style going back to at least 1929. These cells show a small temperature coefficient and so are normally preferred over the saturated Weston cell. However their e.m.f. decreases by about 0.08 mv per year, and thus must be calibrated periodically against a saturated Weston cell at a defined temperature. The Weston cell may be diagramed as:
Cd(Hg) | CdSO4(aq), Hg2SO4 | Hg.
Weston invented and patented the saturated cadmium cell in 1893. It had the advantage of being less temperature sensitive than the previous standard, the Clark cell. It also had the advantage of producing a voltage very near to one volt: 1.0183 V. In 1911 the Weston Saturated Cadmium Cell became the International Standard for electromotive force. Weston waved his patent rights shortly afterword so anyone was allowed to manufacture it.
Back in the early days of electrical measurement technology, a special type of battery known as a mercury standard cell was popularly used as a voltage calibration standard. The output of a mercury cell was 1.0183 to 1.0194 volts DC (depending on the specific design of cell), and was extremely stable over time. Advertised drift was around 0.004 percent of rated voltage per year. Mercury standard cells were sometimes known as Weston cells or cadmium cells.
Disadvantages
Unfortunately, mercury cells were rather intolerant of any current drain and could not even be measured with an analog voltmeter without compromising accuracy. Manufacturers typically called for no more than 0.1 mA of current through the cell, and even that figure was considered a momentary, or surge maximum! Consequently, standard cells could only be measured with a potentiometric (null-balance) device where current drain is almost zero. Short-circuiting a mercury cell was prohibited, and once short-circuited, the cell could never be relied upon again as a standard device.
Now electrical assignment working of single phase meter.
Construction of induction type energy meter
Induction type energy meter essentially consists of following components
(a) Driving system (b) Moving system (c) Braking system and (d) Registering system.
• Driving system: The construction of the electro magnet system is shown in Fig. 44.1(a) and it consists of two electromagnets, called “shunt” magnet and “series” magnet, of laminated construction.
A coil having large number of turns of fine wire is wound on the middle limb of the shunt magnet. This coil is known as “pressure or voltage” coil and is connected across the supply mains. This voltage coil has many turns and is arranged to be as highly inductive as possible. In other words, the voltage coil produces a high ratio of inductance to resistance. This causes the current, and therefore the flux, to lag the supply voltage by nearly090. An adjustable copper shading rings are provided on the central limb of the shunt magnet to make the phase angle displacement between magnetic field set up by shunt magnet and supply voltage is approximately090. The copper shading bands are also called the power factor compensator or compensating loop. The series electromagnet is energized by a coil, known as “current” coil which is connected in series with the load so that it carry the load current. The flux produced by this magnet is proportional to, and in phase with the load current.
• Moving system: The moving system essentially consists of a light rotating aluminium disk mounted on a vertical spindle or shaft. The shaft that supports the aluminium disk is connected by a gear arrangement to the clock mechanism on the front of the meter to provide information that consumed energy by the load. The time varying (sinusoidal) fluxes produced by shunt and series magnet induce eddy currents in the aluminium disc. The interaction between these two magnetic fields and eddy currents set up a driving torque in the disc. The number of rotations of the disk is therefore proportional to the energy consumed by the load in a certain time interval and is commonly measured in killowatt-hours (Kwh).
• Braking system: Damping of the disk is provided by a small permanent magnet, located diametrically opposite to the a.c magnets. The disk passes between the magnet gaps. The movement of rotating disc through the magnetic field crossing the air gap sets up eddy currents in the disc that reacts with the magnetic field and exerts a braking torque. By changing the position of the brake magnet or diverting some of the flux there form, the speed of the rotating disc can be controlled.
• Registering or Counting system: The registering or counting system essentially consists of gear train, driven either by worm or pinion gear on the disc shaft, which turns pointers that indicate on dials the number of times the disc has turned. The energy meter thus determines and adds together or integrates all the instantaneous power values so that total energy used over a period is thus known. Therefore, this type of meter is also called an “integrating” meter.
Basic operation
Induction instruments operate in alternating-current circuits and they are useful only when the frequency and the supply voltage are approximately constant. The most commonly used technique is the shaded pole induction watt-hour meter, shown in fig.44.1 (b).
(a) Driving system (b) Moving system (c) Braking system and (d) Registering system.
• Driving system: The construction of the electro magnet system is shown in Fig. 44.1(a) and it consists of two electromagnets, called “shunt” magnet and “series” magnet, of laminated construction.
A coil having large number of turns of fine wire is wound on the middle limb of the shunt magnet. This coil is known as “pressure or voltage” coil and is connected across the supply mains. This voltage coil has many turns and is arranged to be as highly inductive as possible. In other words, the voltage coil produces a high ratio of inductance to resistance. This causes the current, and therefore the flux, to lag the supply voltage by nearly090. An adjustable copper shading rings are provided on the central limb of the shunt magnet to make the phase angle displacement between magnetic field set up by shunt magnet and supply voltage is approximately090. The copper shading bands are also called the power factor compensator or compensating loop. The series electromagnet is energized by a coil, known as “current” coil which is connected in series with the load so that it carry the load current. The flux produced by this magnet is proportional to, and in phase with the load current.
• Moving system: The moving system essentially consists of a light rotating aluminium disk mounted on a vertical spindle or shaft. The shaft that supports the aluminium disk is connected by a gear arrangement to the clock mechanism on the front of the meter to provide information that consumed energy by the load. The time varying (sinusoidal) fluxes produced by shunt and series magnet induce eddy currents in the aluminium disc. The interaction between these two magnetic fields and eddy currents set up a driving torque in the disc. The number of rotations of the disk is therefore proportional to the energy consumed by the load in a certain time interval and is commonly measured in killowatt-hours (Kwh).
• Braking system: Damping of the disk is provided by a small permanent magnet, located diametrically opposite to the a.c magnets. The disk passes between the magnet gaps. The movement of rotating disc through the magnetic field crossing the air gap sets up eddy currents in the disc that reacts with the magnetic field and exerts a braking torque. By changing the position of the brake magnet or diverting some of the flux there form, the speed of the rotating disc can be controlled.
• Registering or Counting system: The registering or counting system essentially consists of gear train, driven either by worm or pinion gear on the disc shaft, which turns pointers that indicate on dials the number of times the disc has turned. The energy meter thus determines and adds together or integrates all the instantaneous power values so that total energy used over a period is thus known. Therefore, this type of meter is also called an “integrating” meter.
Basic operation
Induction instruments operate in alternating-current circuits and they are useful only when the frequency and the supply voltage are approximately constant. The most commonly used technique is the shaded pole induction watt-hour meter, shown in fig.44.1 (b).
The rotating element is an aluminium disc, and the torque is produced by the interaction of eddy currents generated in the disc with the imposed magnetic fields that are produced by the voltage and current coils of the energy meter.
Let us consider a sinusoidal flux ()tφ is acting perpendicularly to the plane of the aluminium disc, the direction of eddy current by Lenz’s law is indicated in figure Fig.44.2. It is now quite important to investigate whether any torque will develope in aluminium disc by interaction of a sinusoidally varying flux ei()tφ and the eddy currents induced by itself.0daveeeeTIIIIφφφφβ∞∠=∞�� (44.1)
where φ and eI are expressed in r.m.s and 0β�� (because the reactance of the aluminium disc is nearly equal to zero). Therefore, the interaction of a sinusoidally varying flux ()tφ and its own eddy currentei (induced) cannot produce torque any on the disc.
So in all induction instruments we have two fluxes produce by currents flowing in the windings of the instrument. These fluxes are alternating in nature and so they induce emfs in a aluminium disc or a drum provided for the purpose. These emfs in turn circulate eddy currents in the disc.
As in an energy meter instrument, we have two fluxes and two eddy currents and therefore two torques are produced by
i) are shown in fig.44.3.
Let us consider a sinusoidal flux ()tφ is acting perpendicularly to the plane of the aluminium disc, the direction of eddy current by Lenz’s law is indicated in figure Fig.44.2. It is now quite important to investigate whether any torque will develope in aluminium disc by interaction of a sinusoidally varying flux ei()tφ and the eddy currents induced by itself.0daveeeeTIIIIφφφφβ∞∠=∞�� (44.1)
where φ and eI are expressed in r.m.s and 0β�� (because the reactance of the aluminium disc is nearly equal to zero). Therefore, the interaction of a sinusoidally varying flux ()tφ and its own eddy currentei (induced) cannot produce torque any on the disc.
So in all induction instruments we have two fluxes produce by currents flowing in the windings of the instrument. These fluxes are alternating in nature and so they induce emfs in a aluminium disc or a drum provided for the purpose. These emfs in turn circulate eddy currents in the disc.
As in an energy meter instrument, we have two fluxes and two eddy currents and therefore two torques are produced by
i) are shown in fig.44.3.
()()()()()()()cos(,)cos(,)cos()cos(180)cos()cos()2coscosdavshrmsseshrmssesermsshsermsshshrmssesermsshTIIIIIIVkVkkIkZZkkVIZθααθθαθααθ⎡⎤∞Φ∠Φ−Φ∠Φ⎣⎦⎡⎤∞Φ+−Φ+−⎣⎦⎡⎤′′∞++−⎢⎥⎣⎦′⎛⎞∞⎜⎟⎝⎠ ∞ cosVIθ = power in the circuit
where ,,,,,shseshseIIVandIΦΦ are all expressed as r.m.s.
where ,,,,,shseshseIIVandIΦΦ are all expressed as r.m.s.
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