0
Construction
Construction is an industry which builds structures.
1,073 Questions
The term 'provisional sum' is generally well understood in the construction industry. It is used in construction contracts to refer either to work which may or may not be carried out at all, or to work whose content is undefined. In either case, the parties will not attempt to price it accurately when they enter into their contract. Instead, the provisional sum is usually included within the contract price as an approximate guess. The contract normally provides expressly how it is to be dealt with. A common clause provides for the provisional sum to be omitted and an appropriate valuation of the work actually carried out substituted for it.
It is very like an assembly line, where a product is assembled in chronological steps by many people.
Why would a construction worker care about rocks?
Two reasons:
Security of buildings,earthworks, etc. on or inthe rocks, and
Asbuilding materials.
What is the size of 10 drums water tank?
A standard, 55 US gallon / 44 Imperial gallon drum would lead me to believe you would have a 550 US Gallon tank.
The permanent magnet moving coil instrument is the most accurate type for D.C. Measurements. The working principle of these instruments is the same as that of the d'Arsonval type of galvanometers, the difference being that a direct reading instrument is provided with a pointer and a scale
(Fig) Permanent magnet moving coil instrument
Construction of PMMC Instruments
- The constructional features of this instrument are shown in Fig.
- The moving coil is wound with many turns of enameled or silk covered copper wire.
- The coil is mounted on rectangular aluminum former, which is pivoted on jeweled bearings.
- The coils move freely in the field of a permanent magnet.
- Most voltmeter coils are wound on metal frames to provide the required electro-magnetic damping.
- Most ammeter coils, however, are wound on non-magnetic formers, because coil turns are effectively shorted by the ammeter shunt.
- The coil itself, therefore, provides electro magnetic damping.
Magnet Systems
- Old style magnet system consisted of relatively long U shaped permanent magnets having soft iron pole pieces.
- Owing to development of materials like Alcomax and Alnico, which have a high co-ercive force, it is possible to use smaller magnet lengths and high field intensities.
- The flux densities used in PMIMC instruments vary from 0.1 Wb/m to 1 Wb/m.
Control
- When the coil is supported between two jewel bearings two phosphor bronze hairsprings provide the control torque.
- These springs also serve to lead current in and out of the coil. The control torque is provided by the ribbon suspension as shown.
- This method is comparatively new and is claimed to be advantageous as it eliminates bearing friction.
Damping
- Damping torque is produced by movement of the aluminium former moving in the magnetic field of the permanent magnet.
Pointer and Scale
- The pointer is carried by the spindle and moves over a graduated scale.
- The pointer is of lightweight construction and, apart from those used in some inexpensive instruments has the section over the scale twisted to form a fine blade.
- This helps to reduce parallax errors in the reading of the scale. When the coil is supported between two jewel bearings two phosphor bronze hairsprings provide the control torque.
- These springs also serve to lead current in and out of the coil.
Torque Equation.
The torque equation of a moving coil instrument is given by
As the deflection is directly proportional to the current passing through the meter (K and G being constants) we get a uniform (linear) scale for the instrument.
Errors in PMMC Instruments
The main sources of errors in moving coil instruments are due to
- Weakening of permanent magnets due to ageing at temperature effects.
- Weakening of springs due to ageing and temperature effects.
- Change of resistance of the moving coil with temperature.
Advantages and Disadvantages of PMMC Instruments
The main advantages of PMMC instruments are
- The scale is uniformly divided.
- The power consumption is very low
- The torque-weight ratio is high which gives a high accuracy. The accuracy is of the order of generally 2 percent of full-scale deflection.
- Using different values for shunts and multipliers may use a single instrument for many different current and voltage ranges.
- Since the operating forces are large on account of large flux densities, which may be as high as 0.5 Wb/m, the errors due to stray magnetic fields are small.
- Self-shielding magnets make the core magnet mechanism particularly useful in aircraft and aerospace applications.
The chief disadvantages are
- These instruments are useful only for D.C. The torque reverses if the current reverses. If the instrument is connected to a.c., the pointer cannot follow the rapid reversals and the deflection corresponds to mean torque, which is zero. Hence these instruments cannot be used for a.c.
- The cost of these instruments is higher than that of moving iron instruments.
What is footprint in construction?
A footprint, from a construction point of view, is the projected area on the ground or basement, upon witch the construction is to be placed. In other words it is the total consumed horizontal area of the vertical span of the object. An example of this Is the Eiffel Tower. The footprint of the Eiffel Tower is the total square under it, not just the four plates it stands on.
What is the crown in road paving and where is it?
Alright... your interest in paving (and also grading, if you don't realize it) is a bit curious to me, but, to the point..
Roads aren't laid flat. They might appear flat at a glance, but they're not. A lot of factors go into engineering roadways, and that also includes anticipated rainfall/storm surge and drainage. Not laying these roads flat ensures that water runs off the roadways... if it didn't, then it could pool up on the roadways and make them very dangerous to drive. So the idea of not laying a road flat is to prevent things such as hydroplaning in the vehicles traveling on them.
So there'll be a high point in the roadway - that's called the crown. Where it is, exactly, depends on the roadway itself, as well as the factors which go into designing the roadway. Let's say you're driving on a roadway in a mountainous region... for the sake of argument, we'll say it's a road which runs north-south. On the west side of the roadway, you have high ground, while you'll have lower ground on the east side of the roadway. Well, knowing how gravity works, you'll know that the drainage is going to be to the east side of the roadway, so that roadway will be graded so that it slopes downward towards the east side. The crown is going to be the high point on the west side of the roadway in this instance.
Now, if you're traveling along a number of other roads... rural roads on flat land, city/subdivision streets, et. al, you might notice storm drains or ditches on both sides of the roadway. What this means is that drainage is diverted in both directions, so the crown will be more towards the center of the roadway. The caveat to this type of design being that that crown is going to be the weak point of the asphalt mat which is laid on it... if you go down a road with an older asphalt mat, you might notice that crews will come by and do crack seal - pouring tar into cracks which form in the roadway. And you'll often see long lines of this crack sealant right smack in the center of it... that's because a crown set up in this fashion is often the first point at which cracks will form in the asphalt mat.
A typical crown grade will be 2 - 3% - nothing very drastic. Setting up the roadway and crown (and grading out the quarter crown, as well) will be the job of dirt crews, rather than asphalt crews. The dirt crews will start by cutting a rough grade in the vicinity of where the roadway will be. Then they'll take the transit and shoot hubs.. the formula for this, I'm not going to get into right now, because I could show you much easier than I could explain it here. So they'd shoot the hubs, tap them into the grown at the point where the dirt should be, and the graders will cut down the dirt or fill it in and grade it to the top of those hubs, then the grader will cut the grade and ensure that the grade is the appropriate depth below the top of the curb face... so, if there's four inches of asphalt, the grade will be cut four inches below the top of the curb face, and the blade will be angled at whatever the grade of the crown is. The whole process of cutting a grade involves both the blade hand (who runs the grader), and a laborer who'll chase hubs.. they'll ensure each hub is uncovered, signal to the blade hand how far down they need to cut (or how far up they need to fill), etc. They'll also probably have to do various other tasks at given times, such as running the sheep's foot or combo roller, maybe even running a scraper, etc.
What is the construction and working principle of microphone?
Electric energy cause a membrane to move by turning into mechanical energy. The movement of the membrane causes the air pressure to besequentially increased and rarefied. This "train" of increased and rearefied air pressure propagates into the room, and if it strikes our ear drums we perceive it as sound.
What is scarification in road construction?
It is cold planing - or milling - of the asphalt surface. This is done for a number of reasons including the following:
-Removing ruts or bumps or irregularities in a roadway before resurfacing.
-Lowering a road surface that is to be resurfaced or treated so that it fits the profile of adjacent roads.
-Removing existing asphalt that is found to be unacceptable.
Why do you smell gas when Air conditioner is on?
If you're smelling gas with the A/C on that means you have a gas leak in your engine compartment. The gas smell is being sucked into the fresh air intake of your A/C.
Check the fuel injector "O" rings for leaks. Also the fuel pressure regulator.
Rick
I'm a retired ASE Master/L-1 Technician. I still keep current with the latest automotive technology. Visit my blog for cool articles and TSB's: http://free-auto-repair-advice.blogspot.com
What does 6 ton of rip rap look like?
It looks like a large pile of relatively uniformly sized broken up rock or chunks of concrete. The rocks vary in size from bowling ball size to roughly the size of 2 or 3 drawer file cabinets.
From Wikipedia:
A derrick is a lifting device composed of one mast or pole which is hinged freely at the bottom. It is controlled by lines (usually four of them) powered by some means such as man-hauling or motors, so that the pole can move in all four directions. A line runs up it and over its top with a hook on the end, like with a crane. It is commonly used in docks and on board ships. Some large derricks are mounted on dedicated vessels, and are often known as "floating derricks". Pictures:
http://images.google.se/images?um=1&hl=sv&client=firefox-a&rls=org.mozilla:sv-SE:official&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=oil+derrick&spell=1
What led to construction of the Berlin Wall?
Putting it very simply: the Cold War partitioning of Berlin and the fact that many people in East Berlin were fleeing across the border to West Berlin and freedom. The communist government built the wall to prevent these people from fleeing.
Do you have Volvo dealers in KSA for construction equipments?
Most probably yes. I have known of Komatsu operating through a large local distributor. I am sure even Volvo would have some similar way of operation. All of these leading construction equipment dealers are 100% representatives of their principals. They have strong supply chain network and excellent back office support.
What are minerals that are used as flooring in expensive buildings?
The composite material known as engineered stone uses crushed stone that is bound together by an adhesive such as a polymer resin or cement mix. Marble and quartz are the most common. The historic building "Villa Tugendhat" in Brno, Czech Republic has an onyx wall. The Blush Boutique Nightclub (now closed) in Las Vegas had an onyx dance floor.
What is the difference between a Drivers' License and a Permit?
Drivers license means you can drive alone and you have taken the actual driving portion of the test. Permit is also called your "temps" which means you have to have someone 21 or older in the car with you at all times to help you along your process of learning how to drive. You have to hold these for 6 months before you can get your drivers license. Some state laws may be different about how long you have to hold them or how old you have to be to get them but license = by yourself you are a good driver and took the driving test, permit = You are still learning and not allowed to drive alone
A door salesman would sell doors. Also a door manufacturer would want to sell their product. These should be available at various home improvement and hardware stores.
What is controle of pharmaceutical packaging?
THE MAIN REASON FOR this type of packaging is the ease in which to count them (especially when they are "controlled meds") and also less confusion for people to take them. Each one is numbered and there is less chance that you forget if you took your pill or not. It makes quality control and counting of the meds much easier.
Which came first elevators or skyscrapers?
The answer must include that before skyscrapers, men built what at the time were considered "very tall" buildings between 4 and 10 floors high. They put elevators into these smaller "very tall" buildings. When skyscrapers came later, the concept of elevators simply went along with the concept of extremely tall buildings that tried to reach the sky. So, technically, elevators came before skyscrapers, in numerous small and large towns with what was then "very tall" buildings that were only a fraction of the size of skyscrapers.
Why is hatching used in construction industry drawings?
If I understand your question, hatching is a drawing technique in which the hatching lines are used to delineate and highlight the "cut" "faces" of a cross section of a construction component. j3h.
Why did you choose construction technology and management?
Mainly because I knew they had the potential to make a lot of money and after making a lot of money as an electrician and then suddenly not being able to do it anymore I decided to stay in construction but get into management but originally wanted to get into engineering but was worried about all the math courses and not being able to pass them. Come to find out the 4 year program I started "construction management wound up being the identical program to tht of a civil engineer and after failing a statistics class 3 times I ended up dropping out because after 3 times taking it I still had no clue and the frustration was effecting my work in my other classes. I do know for a fact that an experienced construction manager can make upwards of 300k a year ( that was during a good economy) I would still like to pursue my education goals as a construction manager but with 4 kids and my own business my time to myself is very limited and I just don't have time for it.. I do recomend anyone looking to take construction management classes make sure you are strong in calculus, physics and statistics as I barely made it through them and then the statistics class eventually led to my dropping it all together but hopefully my new business will put me back where I want to be finacially
Explain construction and working of a Solar Cell?
How A Photovoltic Cell Works ----
Return Photovoltaics
The "photovoltaic effect" is the basic physical process through which a PV cell converts sunlight into electricity. Sunlight is composed of photons, or particles of solar energy. These photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum. When photons strike a PV cell, they may be reflected or absorbed, or they may pass right through. Only the absorbed photons generate electricity. When this happens, the energy of the photon is transferred to an electron in an atom of the cell (which is actually a semiconductor). With its newfound energy, the electron is able to escape from its normal position associated with that atom to become part of the current in an electrical circuit. By leaving this position, the electron causes a "hole" to form. Special electrical properties of the PV cell-a built-in electric field-provide the voltage needed to drive the current through an external load (such as a light bulb).
p-Types, n-Types, and the Electric Field
To induce the electric field within a PV cell, two separate semiconductors are sandwiched together. The "p" and "n" types of semiconductors correspond to "positive" and "negative" because of their abundance of holes or electrons (the extra electrons make an "n" type because an electron actually has a negative charge). Although both materials are electrically neutral, n-type silicon has excess electrons and p-type silicon has excess holes. Sandwiching these together creates a p/n junction at their interface, thereby creating an electric field. When the p-type and n-type semiconductors are sandwiched together, the excess electrons in the n-type material flow to the p-type, and the holes thereby vacated during this process flow to the n-type. (The concept of a hole moving is somewhat like looking at a bubble in a liquid. Although it's the liquid that is actually moving, it's easier to describe the motion of the bubble as it moves in the opposite direction.) Through this electron and hole flow, the two semiconductors act as a battery, creating an electric field at the surface where they meet (known as the "junction"). It's this field that causes the electrons to jump from the semiconductor out toward the surface and make them available for the electrical circuit. At this same time, the holes move in the opposite direction, toward the positive surface, where they await incoming electrons. Making n and p Material The most common way of making p-type or n-type silicon material is to add an element that has an extra electron or is lacking an electron. In silicon, we use a process called "doping." We'll use silicon as an example because crystalline silicon was the semiconductor material used in the earliest successful PV devices, it's still the most widely used PV material, and, although other PV materials and designs exploit the PV effect in slightly different ways, knowing how the effect works in crystalline silicon gives us a basic understanding of how it works in all devices. Absorption and Conduction In a PV cell, photons are absorbed in the p layer. It's very important to "tune" this layer to the properties of the incoming photons to absorb as many as possible and thereby free as many electrons as possible. Another challenge is to keep the electrons from meeting up with holes and "recombining" with them before they can escape the cell. To do this, we design the material so that the electrons are freed as close to the junction as possible, so that the electric field can help send them through the "conduction" layer (the n layer) and out into the electric circuit. By maximizing all these characteristics, we improve the conversion efficiency* of the PV cell.
To make an efficient solar cell, we try to maximize absorption, minimize reflection and recombination, and thereby maximize conduction. *The conversion efficiency of a PV cell is the proportion of sunlight energy that the cell converts to electrical energy. This is very important when discussing PV devices, because improving this efficiency is vital to making PV energy competitive with more traditional sources of energy (e.g., fossil fuels). Naturally, if one efficient solar panel can provide as much energy as two less-efficient panels, then the cost of that energy (not to mention the space required) will be reduced. For comparison, the earliest PV devices converted about 1%-2% of sunlight energy into electric energy. Today's PV devices convert 7%-17% of light energy into electric energy. Of course, the other side of the equation is the money it costs to manufacture the PV devices. This has been improved over the years as well. In fact, today's PV systems produce electricity at a fraction of the cost of early PV systems.
dugouts
What is the meaning of construction line?
A construction line is a line very lightly drawn and is used as a guide to help draw all other lines and shapes properly.
