1.
Lock (security device)
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A lock is a mechanical or electronic fastening device that is released by a physical object, by supplying secret information, or by a combination thereof. The earliest known lock and key device was discovered in the ruins of Nineveh, Locks such as this were later developed into the Egyptian wooden pin lock, which consisted of a bolt, door fixture, and key. When the key was inserted, pins within the fixture were lifted out of drilled holes within the bolt, when the key was removed, the pins fell part-way into the bolt, preventing movement. The warded lock was also present from antiquity and remains the most recognizable lock, the first all-metal locks appeared between the years 870 and 900, and are attributed to the English craftsmen. It is also said that the key was invented by Theodore of Samos in the 6th century BC, affluent Romans often kept their valuables in secure boxes within their households, and wore the keys as rings on their fingers. The practice had two benefits, It kept the key handy at all times, while signaling that the wearer was wealthy and important enough to have money and jewelry worth securing. The lever tumbler lock, which uses a set of levers to prevent the bolt from moving in the lock, was perfected by Robert Barron in 1778. His double acting lever lock required the lever to be lifted to a height by having a slot cut in the lever. This type of lock is currently used today. The lever tumbler lock was improved by Jeremiah Chubb in 1818. A burglary in Portsmouth Dockyard prompted the British Government to announce a competition to produce a lock that could be opened only with its own key, Chubb was awarded £100 after a trained lock-picker failed to break the lock after 3 months. In 1820, Jeremiah joined his brother Charles in starting their own lock company, the Chubb brothers also received a patent for the first burglar-resisting safe and began production in 1835. The designs of Barron and Chubb were based on the use of levers, but Joseph Bramah. His lock used a key with precise notches along the surface. The lock was at the limits of the manufacturing capabilities of the time and was said by its inventor to be unpickable. Hobbs attempt required some 51 hours, spread over 16 days and this lock design used pins of varying lengths to prevent the lock from opening without the correct key. The modern Yale lock is essentially a developed version of the Egyptian lock. Despite some improvement in key design since, the majority of locks today are variants of the designs invented by Bramah, Chubb
2.
Theft
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In common usage, a theft is the illegal taking of another persons property or services without that persons permission or consent with the intent to deprive the rightful owner of it. The word is used as an informal shorthand term for some crimes against property, such as burglary, embezzlement, larceny, looting, robbery, shoplifting, library theft. In some jurisdictions, theft is considered to be synonymous with larceny, in others, someone who carries out an act of or makes a career of theft is known as a thief. The act of theft is known by other terms such as stealing, thieving. Theft is the name of an offence in California, Canada, England and Wales, Hong Kong, Northern Ireland, the Republic of Ireland. But if she realises the mistake when she gets home and could return the scarf to Y, note that there may be civil liability for the torts of trespass to chattels or conversion in either eventuality. Section 322 of the Criminal Code provides the definition for theft in Canada,322. Because of this, confidential information cannot be the subject of theft and it cannot be converted, not because it is an intangible, but because, save in very exceptional far‑fetched circumstances, the owner would never be deprived of it. However, the theft of trade secrets in certain circumstances does constitute part of the offence of economic espionage, which can be prosecuted under s.19 of the Security of Information Act. Where a motor vehicle is stolen, Section 333.1 provides for a punishment of 10 years for an indictable offence. Theft is a crime with related articles in the Wetboek van Strafrecht, Article 310 prohibits theft, which is defined as taking away any object that belongs to someone else, with the intention to appropriate it illegally. Maximum imprisonment is 4 years or a fine of the fifth category, Article 311 consists of the following, Part 1. Punishable with maximum imprisonment of 6 years or a fine of the category is,1. Theft during certain occasions,3. Theft during night in a residence by someone who is there without knowledge or permission of the owner,4, Theft by 2 or more organized people,5. Theft, where the thief got access by means of violence, climbing in, when theft if committed as in 3 with the situation of 4 and 5, the punishment is a maximum imprisonment of 9 nears or a fine of the fifth category. Article 312 consists of the following, Part 1 prohibits robbery, maximum imprisonment is 9 years or a fine with the fifth category Part 2 allows maximum imprisonment of 12 years or a fine of the fifth category when,1. Robbery was committed during night, in a residence, on the road or moving train,2
3.
Hinge
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A hinge is a mechanical bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about an axis of rotation. Hinges may be made of material or of moving components. In biology, many joints function as hinges like the elbow joint, there are many types of door hinges. The main types include, Spring hinge which is a hinge made to provide assistance in the closing or the opening of the hinge leaves. A spring is a component of a hinge, that force to secure a hinge closed or keep a hinge opened. Barrel hinge which is a sectional barrel secured by a pivot, pivot hinges which pivot in openings in the floor and the top of the door frame. Also referred to as a double-acting floor hinge and this type is found in ancient dry stone buildings and rarely in old wooden buildings. These are also called haar-hung doors and they are a low cost alternative for use light weight doors. Butt/Mortise hinges usually in threes or fours, which are inset into the door, most residential hinges found in the U. S. are made of steel, although mortise hinges for exterior doors are often made of brass or stainless steel to prevent corrosion. Case hinges Case hinges are similar to a butt hinge however usually more of a nature most commonly used in suitcases, briefcases. Continuous hinges, or piano hinges This type of hinge is also known as a piano hinge and it runs the entire length of the door, panel, or box. Continuous hinges are manufactured with or without holes and these hinges also come in various thicknesses, pin diameters, and knuckle lengths. Concealed hinges Used for furniture doors and they are made of two parts, One part is the hinge cup and the arm, the other part is the mounting plate. Also called cup hinge, or Euro hinge, as they were developed in Europe, most such concealed hinges offer the advantage of full in situ adjustability for standoff distance from the cabinet face as well as pitch and roll by means of two screws on each hinge. Butterfly hinges, or Parliament Hinges These were known as dovetail hinges from the 17th century onwards and can be found on old desks and cabinets from about 1670 until the 18th century. The form of these hinges varied slightly between manufacturers, and their size ranged from the large for heavy doors to the tiniest decorative hinge for use on jewellery boxes. Many hinges of this type were exported to America to support the home trades limited supply and they are still found to be both fairly cheap and decorative, especially on small items
4.
Door
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A door is a moving structure used to block off, and allow access to, an entrance to or within an enclosed space, such as a building or vehicle. Doors normally consist of a panel that swings on hinges on the edge, similar exterior structures to doors are called gates. Typically, doors have a side that faces the inside of a space. In many cases the interior side of a door mostly matches its exterior side, when open, doors admit people, animals, ventilation or light. The door is used to control the atmosphere within a space by enclosing the air drafts. Doors are significant in preventing the spread of fire and they also act as a barrier to noise. Many doors are equipped with locking mechanisms to allow entrance to certain people, as a form of courtesy and civility, people often knock before opening a door and entering a room. Doors are used to screen areas of a building for aesthetics, keeping formal, Doors also have an aesthetic role in creating an impression of what lies beyond. Doors are often endowed with ritual purposes, and the guarding or receiving of the keys to a door, or being granted access to a door can have special significance. Similarly, doors and doorways frequently appear in metaphorical or allegorical situations, literature, the earliest in records are those represented in the paintings of the Egyptian tombs, in which they are shown as single or double doors, each in a single piece of wood. Doors were once believed to be the doorway to the afterlife. The stiles were the boards, one of which, tenoned or hinged, is known as the hanging stile. The horizontal cross pieces are the top rail, bottom rail, the most ancient doors were made timber, such as those referred to in the Biblical depiction of King Solomons temple being in olive wood, which were carved and overlaid with gold. The doors dwelt upon in Homer would appear to have been cased in silver or brass, besides olive wood, elm, cedar, oak and cypress were used. A5, 000-year-old door has been found by archaeologists in Switzerland. All ancient doors were hung by pivots at the top and bottom of the hanging stile which worked in sockets in the lintel and sill and those found at Nippur by Dr. Hilprecht dating from 2000 B. C. were in dolerite. The tenons of the gates at Balawat were sheathed with bronze and these doors or gates were hung in two leaves, each about 8 ft 4 in wide and 27 ft. high, they were encased with bronze bands or strips,10 in. High, covered with decoration of figures, etc
5.
Casting (metalworking)
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In metalworking, casting means a process, in which liquid metal is poured into a mold, that contains a hollow cavity of the desired shape, and is then allowed to cool and solidify. The solidified part is known as a casting, which is ejected or broken out of the mold to complete the process. Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods, Casting processes have been known for thousands of years, and widely used for sculpture, especially in bronze, jewellery in precious metals, and weapons and tools. Traditional techniques include casting, plaster mold casting and sand casting. The modern casting process is subdivided into two categories, expendable and non-expendable casting. It is further broken down by the material, such as sand or metal. Expendable mold casting is a classification that includes sand, plastic, shell, plaster. This method of mold casting involves the use of temporary, non-reusable molds, sand casting is one of the most popular and simplest types of casting, and has been used for centuries. Sand casting allows for smaller batches than permanent mold casting and at a reasonable cost. Not only does this method allow manufacturers to create products at a low cost, from castings that fit in the palm of your hand to train beds, it can all be done with sand casting. Sand casting also allows most metals to be cast depending on the type of sand used for the molds, sand casting requires a lead time of days, or even weeks sometimes, for production at high output rates and is unsurpassed for large-part production. Green sand has almost no weight limit, whereas dry sand has a practical part mass limit of 2. Minimum part weight ranges from 0. 075–0.1 kg, the sand is bonded together using clays, chemical binders, or polymerized oils. Sand can be recycled many times in most operations and requires little maintenance, plaster casting is similar to sand casting except that plaster of paris is substituted for sand as a mold material. Plaster casting is an alternative to other molding processes for complex parts due to the low cost of the plaster. The biggest disadvantage is that it can only be used with low melting point non-ferrous materials, such as aluminium, copper, magnesium, and zinc. Shell molding is similar to casting, but the molding cavity is formed by a hardened shell of sand instead of a flask filled with sand. The sand used is finer than sand casting sand and is mixed with a resin so that it can be heated by the pattern, because of the resin and finer sand, it gives a much finer surface finish
6.
Metal
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A metal is a material that is typically hard, opaque, shiny, and has good electrical and thermal conductivity. Metals are generally malleable—that is, they can be hammered or pressed permanently out of shape without breaking or cracking—as well as fusible and ductile, about 91 of the 118 elements in the periodic table are metals, the others are nonmetals or metalloids. Some elements appear in both metallic and non-metallic forms, astrophysicists use the term metal to collectively describe all elements other than hydrogen and helium, the simplest two, in a star. The star fuses smaller atoms, mostly hydrogen and helium, to larger ones over its lifetime. In that sense, the metallicity of an object is the proportion of its matter made up of all chemical elements. Many elements and compounds that are not normally classified as metals become metallic under high pressures, the atoms of metallic substances are typically arranged in one of three common crystal structures, namely body-centered cubic, face-centered cubic, and hexagonal close-packed. In bcc, each atom is positioned at the center of a cube of eight others, in fcc and hcp, each atom is surrounded by twelve others, but the stacking of the layers differs. Some metals adopt different structures depending on the temperature, atoms of metals readily lose their outer shell electrons, resulting in a free flowing cloud of electrons within their otherwise solid arrangement. This provides the ability of metallic substances to easily transmit heat, while this flow of electrons occurs, the solid characteristic of the metal is produced by electrostatic interactions between each atom and the electron cloud. This type of bond is called a metallic bond, Metals are usually inclined to form cations through electron loss, reacting with oxygen in the air to form oxides over various timescales. Examples,4 Na + O2 →2 Na2O2 Ca + O2 →2 CaO4 Al +3 O2 →2 Al2O3, the transition metals are slower to oxidize because they form a passivating layer of oxide that protects the interior. Others, like palladium, platinum and gold, do not react with the atmosphere at all, some metals form a barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny appearance and good conductivity for many decades. The oxides of metals are generally basic, as opposed to those of nonmetals, exceptions are largely oxides with very high oxidation states such as CrO3, Mn2O7, and OsO4, which have strictly acidic reactions. Painting, anodizing or plating metals are good ways to prevent their corrosion, however, a more reactive metal in the electrochemical series must be chosen for coating, especially when chipping of the coating is expected. Water and the two form an electrochemical cell, and if the coating is less reactive than the coatee. Metals in general have high conductivity, high thermal conductivity. Typically they are malleable and ductile, deforming under stress without cleaving, in terms of optical properties, metals are shiny and lustrous. Sheets of metal beyond a few micrometres in thickness appear opaque, although most metals have higher densities than most nonmetals, there is wide variation in their densities, lithium being the least dense solid element and osmium the densest
7.
Steel
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Steel is an alloy of iron and other elements, primarily carbon, that is widely used in construction and other applications because of its high tensile strength and low cost. Steels base metal is iron, which is able to take on two forms, body centered cubic and face centered cubic, depending on its temperature. It is the interaction of those allotropes with the elements, primarily carbon. In the body-centred cubic arrangement, there is an atom in the centre of each cube. Carbon, other elements, and inclusions within iron act as hardening agents that prevent the movement of dislocations that otherwise occur in the lattices of iron atoms. The carbon in steel alloys may contribute up to 2. 1% of its weight. Steels strength compared to pure iron is possible at the expense of irons ductility. With the invention of the Bessemer process in the mid-19th century and this was followed by Siemens-Martin process and then Gilchrist-Thomas process that refined the quality of steel. With their introductions, mild steel replaced wrought iron, further refinements in the process, such as basic oxygen steelmaking, largely replaced earlier methods by further lowering the cost of production and increasing the quality of the product. Today, steel is one of the most common materials in the world and it is a major component in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons. Modern steel is generally identified by various grades defined by assorted standards organizations, the noun steel originates from the Proto-Germanic adjective stakhlijan, which is related to stakhla. The carbon content of steel is between 0. 002% and 2. 1% by weight for plain iron–carbon alloys and these values vary depending on alloying elements such as manganese, chromium, nickel, iron, tungsten, carbon and so on. Basically, steel is an alloy that does not undergo eutectic reaction. In contrast, cast iron does undergo eutectic reaction, too little carbon content leaves iron quite soft, ductile, and weak. Carbon contents higher than those of steel make an alloy, commonly called pig iron, while iron alloyed with carbon is called carbon steel, alloy steel is steel to which other alloying elements have been intentionally added to modify the characteristics of steel. Common alloying elements include, manganese, nickel, chromium, molybdenum, boron, titanium, vanadium, tungsten, cobalt, and niobium. Additional elements are important in steel, phosphorus, sulfur, silicon, and traces of oxygen, nitrogen, and copper. Alloys with a higher than 2. 1% carbon content, depending on other element content, cast iron is not malleable even when hot, but it can be formed by casting as it has a lower melting point than steel and good castability properties
8.
Wolverhampton
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Wolverhampton is a city and metropolitan borough in the West Midlands, England. At the 2011 census, it had a population of 249,470, the demonym for people from the city is Wulfrunian. Historically part of Staffordshire, the city is named after Wulfrun, prior to the Norman Conquest, the areas name appears only as variants of Heantune or Hamtun, the prefix Wulfrun or similar appearing in 1070 and thereafter. Alternatively, the city may have earned its name from Wulfereēantūn after the Mercian King. The variation Wolveren Hampton is seen in records, e. g. in 1381. The city grew initially as a market town specialising in the woollen trade, in the Industrial Revolution, it became a major centre for coal mining, steel production, lock making and the manufacture of cars and motorcycles. The economy of the city is based on engineering, including a large aerospace industry. A local tradition states that King Wulfhere of Mercia founded an abbey of St Mary at Wolverhampton in 659, the Mercians and West Saxons claimed a decisive victory and the field of Woden is recognised by numerous place names in Wednesfield. In 985, King Ethelred the Unready granted lands at a place referred to as Heantun to Lady Wulfrun by royal charter and this became the site for the current St. Peters Church. A statue of Lady Wulfrun, sculpted by Sir Charles Wheeler, Wolverhampton is recorded in the Domesday Book in 1086 as being in the Hundred of Seisdon and the county of Staffordshire. The lords of the manor are listed as the canons of St Mary, with the tenant-in-chief being Samson, Wolverhampton at this date is a large settlement of fifty households. In 1179, there is mention of a market held in the town and this charter for a weekly market held on a Wednesday was eventually granted on 4 February 1258 by Henry III. From the 16th century onwards, Wolverhampton became home to a number of industries including lock and key making and iron. Wolverhampton suffered two Great Fires, the first in April 1590, and the second in September 1696, both fires started in todays Salop Street. The first fire lasted for five days and left nearly 700 people homeless and this second fire led to the purchase of the first fire engine within the city in September 1703. There is also evidence that Wolverhampton may have been the location of the first working Newcomen Steam Engine in 1712. In Victorian times, Wolverhampton grew to be a town mainly due to the huge amount of industry that occurred as a result of the abundance of coal. The remains of this wealth can be seen in houses such as Wightwick Manor and The Mount
9.
England
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England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west, the Irish Sea lies northwest of England and the Celtic Sea lies to the southwest. England is separated from continental Europe by the North Sea to the east, the country covers five-eighths of the island of Great Britain in its centre and south, and includes over 100 smaller islands such as the Isles of Scilly, and the Isle of Wight. England became a state in the 10th century, and since the Age of Discovery. The Industrial Revolution began in 18th-century England, transforming its society into the worlds first industrialised nation, Englands terrain mostly comprises low hills and plains, especially in central and southern England. However, there are uplands in the north and in the southwest, the capital is London, which is the largest metropolitan area in both the United Kingdom and the European Union. In 1801, Great Britain was united with the Kingdom of Ireland through another Act of Union to become the United Kingdom of Great Britain and Ireland. In 1922 the Irish Free State seceded from the United Kingdom, leading to the latter being renamed the United Kingdom of Great Britain, the name England is derived from the Old English name Englaland, which means land of the Angles. The Angles were one of the Germanic tribes that settled in Great Britain during the Early Middle Ages, the Angles came from the Angeln peninsula in the Bay of Kiel area of the Baltic Sea. The earliest recorded use of the term, as Engla londe, is in the ninth century translation into Old English of Bedes Ecclesiastical History of the English People. According to the Oxford English Dictionary, its spelling was first used in 1538. The earliest attested reference to the Angles occurs in the 1st-century work by Tacitus, Germania, the etymology of the tribal name itself is disputed by scholars, it has been suggested that it derives from the shape of the Angeln peninsula, an angular shape. An alternative name for England is Albion, the name Albion originally referred to the entire island of Great Britain. The nominally earliest record of the name appears in the Aristotelian Corpus, specifically the 4th century BC De Mundo, in it are two very large islands called Britannia, these are Albion and Ierne. But modern scholarly consensus ascribes De Mundo not to Aristotle but to Pseudo-Aristotle, the word Albion or insula Albionum has two possible origins. Albion is now applied to England in a poetic capacity. Another romantic name for England is Loegria, related to the Welsh word for England, Lloegr, the earliest known evidence of human presence in the area now known as England was that of Homo antecessor, dating to approximately 780,000 years ago. The oldest proto-human bones discovered in England date from 500,000 years ago, Modern humans are known to have inhabited the area during the Upper Paleolithic period, though permanent settlements were only established within the last 6,000 years
10.
Combination lock
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A combination lock is a type of locking device in which a sequence of numbers or symbols is used to open the lock. Types range from inexpensive three-digit luggage locks to high-security safes, unlike a regular padlock, combination locks do not use keys. The earliest known combination lock was excavated in a Roman period tomb on the Kerameikos, attached to a small box, it featured several dials instead of keyholes. In 1206, the Muslim engineer Al-Jazari documented a combination lock in his book al-Ilm Wal-Amal al-Nafi Fi Sinaat al-Hiyal, muhammad al-Astrulabi also made combination locks, two of which are kept in Copenhagen and Boston Museums. Gerolamo Cardano later described a combination lock in the 16th century, one of the simplest types of combination lock, often seen in low-security bicycle locks and in briefcases, uses several rotating discs with notches cut into them. The lock is secured by a pin with several teeth on it which hook into the rotating discs, when the notches in the discs align with the teeth on the pin, the lock can be opened. This lock is considered to be one of the least secure types of combination lock, opening one in this fashion depends on slight irregularities in the machining of the parts. Unless the lock is machined precisely, when the pin is pulled outward and this disc is then rotated until a slight click is heard, indicating that the tooth has settled into the notch. The procedure is repeated for the discs, resulting in an open lock. Combination locks found on padlocks, lockers, or safes may use a dial which interacts with several parallel discs or cams. Customarily, a lock of this type is opened by rotating the dial clockwise to the first numeral, counterclockwise to the second, and so on in an alternating fashion until the last numeral is reached. The cams typically have an indentation or notch, and when the combination is entered. Depending on the quality of the lock, some single-dial combination locks can also be defeated relatively easily, typical padlocks are manufactured with generous tolerances, allowing two, three or even more digits of play in the correct access sequence. Given a 60-number dial with three cams and three digits of play, the space is reduced from 60 ×60 ×60 to 20 ×20 ×20. Additionally, if testing the mechanism to open the lock does not modify the state of the lock, the first two digits are entered normally once, then, starting from the second digit, the dial is rotated sequentially through the digits, testing the lock on each. The reduced search time would be × 60², a reduction of nearly 82% from 360 hours to 65 hours and this strategy can be extended to the second digit as well, slightly reducing the search time further.78 hours. This is still significantly better security than multiple-dial locks and many keyed locks, inexpensive padlocks are often also susceptible to direct mechanical attacks, such as the use of a padlock shim which can release the shackle without entering a combination. This weakness reduces the number of possible combinations from 64,000 to a mere 100, in 1978 a combination lock which could be set by the user to a sequence of his own choosing was invented by Andrew Elliot Rae
11.
Bank vault
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A bank vault is a secure space where money, valuables, records, and documents are stored. It is intended to protect their contents from theft, unauthorized use, fire, natural disasters, unlike safes, vaults are an integral part of the building within which they are built, using armored walls and a tightly fashioned door closed with a complex lock. Historically, strongrooms were built in the basement of a bank where the ceilings were vaulted, modern bank vaults typically contain many safe deposit boxes, as well as places for teller cash drawers, and other valuable assets of the bank or its customers. They are also common in buildings where valuables are kept such as post offices, grand hotels, rare book libraries. Vault technology developed in a type of race with bank robbers. As burglars came up with new ways to break into vaults, modern vaults may be armed with a wide array of alarms and anti-theft devices. Some nineteenth- and early-twentieth-century vaults were built so well that today they are almost impossible to destroy and these older vaults were typically made with steel-reinforced concrete. The walls were usually at least 1 ft thick, and the door itself was typically 3.5 ft thick, total weight ran into the hundreds of tons. Today vaults are made thinner, lighter materials that, while still secure, are easier to dismantle than their earlier counterparts. The need for secure storage stretches far back in time, the earliest known locks were made by the Egyptians. Ancient Romans used a sophisticated locking system, called warded locks. Warded locks had special notches and grooves that made picking them more difficult, Lock technology advanced independently in ancient India, Russia, and China, where the combination lock is thought to have originated. In the United States, most banks relied on small iron safes fitted with a key lock up until the middle of the nineteenth century, after the Gold Rush of 1849, unsuccessful prospectors turned to robbing banks. The prospectors would often break into the bank using a pickax, the safe was usually small enough that the thief could get it out a window, and take it to a secluded spot to break it open. Banks demanded more protection and safe makers responded by designing larger, heavier safes, Safes with a key lock were still vulnerable through the key hole, and bank robbers soon learned to blast off the door by pouring explosives in this opening. In 1861, inventor Linus Yale Jr. introduced the combination lock. Bankers quickly adopted Yales lock for their safes, but bank robbers came up with ways to get past the new invention. It was possible to use force to punch the combination lock through the door, other experienced burglars learned to drill holes into the lock case and use mirrors to view the slots in the combination wheels inside the mechanism
12.
HVAC
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Heating, ventilation and air conditioning is the technology of indoor and vehicular environmental comfort. Its goal is to provide comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, Refrigeration is sometimes added to the fields abbreviation as HVAC&R or HVACR, or ventilating is dropped as in HACR. Ventilation removes unpleasant smells and excessive moisture, introduces outside air, keeps interior building air circulating, ventilation includes both the exchange of air to the outside as well as circulation of air within the building. It is one of the most important factors for maintaining acceptable indoor air quality in buildings, methods for ventilating a building may be divided into mechanical/forced and natural types. HVAC systems can be used in domestic and commercial environments. HVAC systems can provide ventilation, reduce air infiltration, and maintain pressure relationships between spaces, the means of air delivery and removal from spaces is known as room air distribution. In modern buildings the design, installation, and control systems of functions are integrated into one or more HVAC systems. For very small buildings, contractors normally estimate the capacity, engineer, for larger buildings, building service designers, mechanical engineers, or building services engineers analyze, design, and specify the HVAC systems. Specialty mechanical contractors then fabricate and commission the systems, Building permits and code-compliance inspections of the installations are normally required for all sizes of building. HVAC is based on inventions and discoveries made by Nikolay Lvov, Michael Faraday, Willis Carrier, Edwin Ruud, Reuben Trane, James Joule, William Rankine, Sadi Carnot, heaters are appliances whose purpose is to generate heat for the building. This can be done via central heating, such a system contains a boiler, furnace, or heat pump to heat water, steam, or air in a central location such as a furnace room in a home, or a mechanical room in a large building. The heat can be transferred by convection, conduction, or radiation, heaters exist for various types of fuel, including solid fuels, liquids, and gases. Another type of source is electricity, normally heating ribbons composed of high resistance wire. This principle is used for baseboard heaters and portable heaters. Electrical heaters are used as backup or supplemental heat for heat pump systems. The heat pump gained popularity in the 1950s in Japan and the United States, heat pumps can extract heat from various sources, such as environmental air, exhaust air from a building, or from the ground. In the case of heated water or steam, piping is used to transport the heat to the rooms, most modern hot water boiler heating systems have a circulator, which is a pump, to move hot water through the distribution system
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