1.
Mobile phone signal
–
A mobile phone signal is the signal strength received by a mobile phone from a cellular network. Depending on various factors, such as proximity to a tower, any obstructions such as buildings or trees, most mobile devices use a set of bars of increasing height to display the approximate strength of this received signal to the mobile phone user. In areas, where signal reception would normally be strong, other factors can have an effect on reception or may cause complete failure. In addition, the weather may affect the strength of a signal, due to the changes in radio propagation caused by clouds, precipitation, areas where mobile phones cannot transmit to a nearby mobile site, base station, or repeater are known as dead zones. In these areas, the phone is said to be in a state of outage. Since cell phones rely on radio waves, which travel though the air and are easily attenuated, like other radio transmissions, mobile phone calls can be interrupted by large buildings, terrain, trees, or other objects between the phone and the nearest base. Cellular network providers work continually to improve and upgrade their networks in order to minimize dropped calls, access failures, for mobile virtual network operators, the network quality depends entirely on the host network for the particular handset in question. Some MVNOs use more than one host, which may even have different technologies, Dead zones can be filled-in with microcells, while picocells can handle even smaller areas without causing interference to the larger network. Personal microcells, such as those for a home, are called femtocells, and generally have the range of a cordless phone, a similar system can be set up to perform inmate call capture, which prevents cellphones smuggled into a prison from being used. These still complete calls to or from pre-authorized users such as prison staff and these systems must be carefully designed so as to avoid capturing calls from outside the prison, which would in effect create a dead zone for any passersby outside. In the event of a disaster causing temporary dead zones, a cell on wheels may be brought in until the local infrastructure can be restored. These portable units are used where large gatherings are expected. A dropped call is a terminology used and expressed by wireless mobile phone call subscribers is abruptly cut-off during midconversation. This happens less often today than it would have in the early 1990s, the termination occurs unexpected and is influenced by a number of different reasons such as Dead Zones. In technical circles, it is called an abnormal release, one reason for a call to be dropped may occur when the mobile phone subscriber travels outside the coverage area—the cellular network radio tower. After a telephone connection between two subscribers has been completed, it must remain within range of that subscribers network provider or that connection will lost. Another common reason is occurs when a phone is taken into an area where wireless communication is unavailable, interrupted, interfered with, from the networks perspective, this is the same as the mobile moving out of the coverage area. Occasionally, calls are dropped upon handoff between cells within the providers network
2.
Ka-Bar
–
Additionally, KA-BAR is the trademark and namesake of a related knife manufacturing company, KA-BAR Knives. Inc. of Olean, New York, a subsidiary of the Cutco Corporation, although KA-BAR Knives, Inc. currently makes a wide variety of knives and cutlery, it is best known for the KA-BAR Fighting/Utility knife, which has traditionally used a 7 in. 1095 carbon steel clip point blade and leather-washer handle, the owner of the KA-BAR trademark, the Union Cutlery Co. According to company records, the letter was only partially legible, in 1923, the company adopted the name KA-BAR from the bear story as their trademark. Another criticism was that the Mark Is relatively thin blade was prone to breakage when used for utility tasks such as cutting wire or opening ammunition crates. The Marine Corps authorized limited issuance of a knife with a stiletto blade design, the Marine Raider Stiletto designed by Lt. Col. Clifford H. Shuey. Shueys pattern was essentially a copy of the Fairbairn–Sykes fighting knife with altered material specifications designed to reduce dependence on critical strategic metals. After their first combat, many Marines in the 2nd Raider Battalion exchanged their Raider stilettos for No.17, in response to a specification requesting a modern individual fighting knife design for the U. S. S. Navy Mark 1 utility knife and existing civilian hunting/utility knives such as Westerns L77 as a basis for further improvements, working with Union Cutlery, USMC Colonel John M. Davis and Major Howard E. The blade, guard, and pommel were coated with a non-reflective matte phosphate finish instead of the polished steel of the original prototype. The design was given the designation of 1219C2, notably, the 1219C2 used a thicker blade stock than that of the USN Mark 1 utility knife, and featured a stout clip point. After extensive trials, the 1219C2 prototype was recommended for adoption, the Marines Quartermaster at the time initially refused to order the knives, but his decision was overruled by the Commandant. The Marine Corps adopted the new knife on November 23,1942, the 1219C2 proved easy to manufacture, the first production run was shipped by Camillus Cutlery Company on January 27,1943. After the U. S. Navy became disenchanted with blade failures on the USN Mark 1 utility knife, the Marine Corps in turn re-designated the 1219C2 as either the USMC Mark 2 Combat Knife, or simply the Knife, Fighting Utility. In naval service, the knife was used as a diving and utility knife from late 1943 onward, though the stacked leather handle tended to rot, the Marine Corps issued USMC Mark 2 combat/fighting utility knife throughout Marine forces, with early deliveries going primarily to elite formations. Marines were often issued knives with U. S. N, Mark 2 markings when Navy-issued Mark 2 knives were all that was available. Unlike the prior Marine Raider stiletto, Marines were taught to use their new knife primarily as a weapon in the initial phases of hand-to-hand combat. After the Second World War, the U. S. Navy, in addition to military contract knives, the knife was produced for the civilian market, and the pattern enjoyed some popularity as a general-purpose hunting and utility knife
3.
Pressure
–
Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure is the relative to the ambient pressure. Various units are used to express pressure, Pressure may also be expressed in terms of standard atmospheric pressure, the atmosphere is equal to this pressure and the torr is defined as 1⁄760 of this. Manometric units such as the centimetre of water, millimetre of mercury, Pressure is the amount of force acting per unit area. The symbol for it is p or P, the IUPAC recommendation for pressure is a lower-case p. However, upper-case P is widely used. The usage of P vs p depends upon the field in one is working, on the nearby presence of other symbols for quantities such as power and momentum. Mathematically, p = F A where, p is the pressure, F is the normal force and it relates the vector surface element with the normal force acting on it. It is incorrect to say the pressure is directed in such or such direction, the pressure, as a scalar, has no direction. The force given by the relationship to the quantity has a direction. If we change the orientation of the element, the direction of the normal force changes accordingly. Pressure is distributed to solid boundaries or across arbitrary sections of normal to these boundaries or sections at every point. It is a parameter in thermodynamics, and it is conjugate to volume. The SI unit for pressure is the pascal, equal to one newton per square metre and this name for the unit was added in 1971, before that, pressure in SI was expressed simply in newtons per square metre. Other units of pressure, such as pounds per square inch, the CGS unit of pressure is the barye, equal to 1 dyn·cm−2 or 0.1 Pa. Pressure is sometimes expressed in grams-force or kilograms-force per square centimetre, but using the names kilogram, gram, kilogram-force, or gram-force as units of force is expressly forbidden in SI. The technical atmosphere is 1 kgf/cm2, since a system under pressure has potential to perform work on its surroundings, pressure is a measure of potential energy stored per unit volume. It is therefore related to density and may be expressed in units such as joules per cubic metre. Similar pressures are given in kilopascals in most other fields, where the prefix is rarely used
4.
System of measurement
–
A system of measurement is a collection of units of measurement and rules relating them to each other. Systems of measurement have historically been important, regulated and defined for the purposes of science and commerce, systems of measurement in modern use include the metric system, the imperial system, and United States customary units. The French Revolution gave rise to the system, and this has spread around the world. In most systems, length, mass, and time are base quantities, later science developments showed that either electric charge or electric current could be added to extend the set of base quantities by which many other metrological units could be easily defined. Other quantities, such as power and speed, are derived from the set, for example. Such arrangements were satisfactory in their own contexts, the preference for a more universal and consistent system only gradually spread with the growth of science. Changing a measurement system has substantial financial and cultural costs which must be offset against the advantages to be obtained using a more rational system. However pressure built up, including scientists and engineers for conversion to a more rational. The unifying characteristic is that there was some definition based on some standard, eventually cubits and strides gave way to customary units to met the needs of merchants and scientists. In the metric system and other recent systems, a basic unit is used for each base quantity. Often secondary units are derived from the units by multiplying by powers of ten. Thus the basic unit of length is the metre, a distance of 1.234 m is 1,234 millimetres. Metrication is complete or nearly complete in almost all countries, US customary units are heavily used in the United States and to some degree in Liberia. Traditional Burmese units of measurement are used in Burma, U. S. units are used in limited contexts in Canada due to the large volume of trade, there is also considerable use of Imperial weights and measures, despite de jure Canadian conversion to metric. In the United States, metric units are used almost universally in science, widely in the military, and partially in industry, but customary units predominate in household use. At retail stores, the liter is a used unit for volume, especially on bottles of beverages. Some other standard non-SI units are still in use, such as nautical miles and knots in aviation. Metric systems of units have evolved since the adoption of the first well-defined system in France in 1795, during this evolution the use of these systems has spread throughout the world, first to non-English-speaking countries, and then to English speaking countries
5.
Metric system
–
The metric system is an internationally agreed decimal system of measurement. Many sources also cite Liberia and Myanmar as the other countries not to have done so. Although the originators intended to devise a system that was accessible to all. Control of the units of measure was maintained by the French government until 1875, when it was passed to an intergovernmental organisation. From its beginning, the features of the metric system were the standard set of interrelated base units. These base units are used to larger and smaller units that could replace a huge number of other units of measure in existence. Although the system was first developed for use, the development of coherent units of measure made it particularly suitable for science. Although the metric system has changed and developed since its inception, designed for transnational use, it consisted of a basic set of units of measurement, now known as base units. At the outbreak of the French Revolution in 1789, most countries, the metric system was designed to be universal—in the words of the French philosopher Marquis de Condorcet it was to be for all people for all time. However, these overtures failed and the custody of the metric system remained in the hands of the French government until 1875. In languages where the distinction is made, unit names are common nouns, the concept of using consistent classical names for the prefixes was first proposed in a report by the Commission on Weights and Measures in May 1793. The prefix kilo, for example, is used to multiply the unit by 1000, thus the kilogram and kilometre are a thousand grams and metres respectively, and a milligram and millimetre are one thousandth of a gram and metre respectively. These relations can be written symbolically as,1 mg =0, however,1935 extensions to the prefix system did not follow this convention, the prefixes nano- and micro-, for example have Greek roots. During the 19th century the prefix myria-, derived from the Greek word μύριοι, was used as a multiplier for 10000, prefixes are not usually used to indicate multiples of a second greater than 1, the non-SI units of minute, hour and day are used instead. On the other hand, prefixes are used for multiples of the unit of volume. The base units used in the system must be realisable. Each of the units in SI is accompanied by a mise en pratique published by the BIPM that describes in detail at least one way in which the base unit can be measured. In practice, such realisation is done under the auspices of a mutual acceptance arrangement, in the original version of the metric system the base units could be derived from a specified length and the weight of a specified volume of pure water
6.
SI units
–
The International System of Units is the modern form of the metric system, and is the most widely used system of measurement. It comprises a coherent system of units of measurement built on seven base units, the system also establishes a set of twenty prefixes to the unit names and unit symbols that may be used when specifying multiples and fractions of the units. The system was published in 1960 as the result of an initiative began in 1948. It is based on the system of units rather than any variant of the centimetre-gram-second system. The motivation for the development of the SI was the diversity of units that had sprung up within the CGS systems, the International System of Units has been adopted by most developed countries, however, the adoption has not been universal in all English-speaking countries. The metric system was first implemented during the French Revolution with just the metre and kilogram as standards of length, in the 1830s Carl Friedrich Gauss laid the foundations for a coherent system based on length, mass, and time. In the 1860s a group working under the auspices of the British Association for the Advancement of Science formulated the requirement for a coherent system of units with base units and derived units. Meanwhile, in 1875, the Treaty of the Metre passed responsibility for verification of the kilogram, in 1921, the Treaty was extended to include all physical quantities including electrical units originally defined in 1893. The units associated with these quantities were the metre, kilogram, second, ampere, kelvin, in 1971, a seventh base quantity, amount of substance represented by the mole, was added to the definition of SI. On 11 July 1792, the proposed the names metre, are, litre and grave for the units of length, area, capacity. The committee also proposed that multiples and submultiples of these units were to be denoted by decimal-based prefixes such as centi for a hundredth, on 10 December 1799, the law by which the metric system was to be definitively adopted in France was passed. Prior to this, the strength of the magnetic field had only been described in relative terms. The technique used by Gauss was to equate the torque induced on a magnet of known mass by the earth’s magnetic field with the torque induced on an equivalent system under gravity. The resultant calculations enabled him to assign dimensions based on mass, length, a French-inspired initiative for international cooperation in metrology led to the signing in 1875 of the Metre Convention. Initially the convention only covered standards for the metre and the kilogram, one of each was selected at random to become the International prototype metre and International prototype kilogram that replaced the mètre des Archives and kilogramme des Archives respectively. Each member state was entitled to one of each of the prototypes to serve as the national prototype for that country. Initially its prime purpose was a periodic recalibration of national prototype metres. The official language of the Metre Convention is French and the version of all official documents published by or on behalf of the CGPM is the French-language version
7.
Pascal (unit)
–
The pascal is the SI derived unit of pressure used to quantify internal pressure, stress, Youngs modulus and ultimate tensile strength. It is defined as one newton per square meter and it is named after the French polymath Blaise Pascal. Common multiple units of the pascal are the hectopascal which is equal to one millibar, the unit of measurement called standard atmosphere is defined as 101,325 Pa and approximates to the average pressure at sea-level at the latitude 45° N. Meteorological reports typically state atmospheric pressure in hectopascals, the unit is named after Blaise Pascal, noted for his contributions to hydrodynamics and hydrostatics, and experiments with a barometer. The name pascal was adopted for the SI unit newton per square metre by the 14th General Conference on Weights, one pascal is the pressure exerted by a force of magnitude one newton perpendicularly upon an area of one square metre. The unit of measurement called atmosphere or standard atmosphere is 101325 Pa and this value is often used as a reference pressure and specified as such in some national and international standards, such as ISO2787, ISO2533 and ISO5024. In contrast, IUPAC recommends the use of 100 kPa as a standard pressure when reporting the properties of substances, geophysicists use the gigapascal in measuring or calculating tectonic stresses and pressures within the Earth. Medical elastography measures tissue stiffness non-invasively with ultrasound or magnetic resonance imaging, in materials science and engineering, the pascal measures the stiffness, tensile strength and compressive strength of materials. In engineering use, because the pascal represents a small quantity. The pascal is also equivalent to the SI unit of energy density and this applies not only to the thermodynamics of pressurised gases, but also to the energy density of electric, magnetic, and gravitational fields. In measurements of sound pressure, or loudness of sound, one pascal is equal to 94 decibels SPL, the quietest sound a human can hear, known as the threshold of hearing, is 0 dB SPL, or 20 µPa. The airtightness of buildings is measured at 50 Pa, the units of atmospheric pressure commonly used in meteorology were formerly the bar, which was close to the average air pressure on Earth, and the millibar. Since the introduction of SI units, meteorologists generally measure pressures in hectopascals unit, exceptions include Canada and Portugal, which use kilopascals. In many other fields of science, the SI is preferred, many countries also use the millibar or hectopascal to give aviation altimeter settings. In practically all fields, the kilopascal is used instead. Centimetre of water Metric prefix Orders of magnitude Pascals law
