User:Pancho507/sandbox

Rare earths

Perhaps the most important is neodymium, which is used in neodymium magnets inside electric motors for electric vehicles, drones and some wind turbines including gearless wind turbines. Neodymium magnets are the most powerful permanent magnets commercially available besides samarium cobalt which is more expensive [1] and are used in EVs and drone motors due to their high magnetic flux which makes neodymium permanent magnet motors are the most efficient, power dense motors in mass production unlike superconducting motors, and have higher efficiency and power density than other EV motors such as Tesla's induction copper rotor motor in early model S EVs. Many electric aircraft use Neodymium permanent magnets. Neodymium magnets are used in hard drive voice coils, phone vibrators and speakers, CE:YAG and other rare earth phosphors are used in LEDs to convert to blue to white light and are the most common white LEDs, phosphor converted red LEDs with rare earth phosphors are used in some car tail lights Historically phosphors based on non rare earths have lower brightness and thus lower conversion efficiency than those with rare earths, as seen in early fluorescent tubes in the 1930s lamptech UK and early cathode ray tubes. Eventually both cathode ray tubes and fluorescent tubes switched to rare earths which improved their efficiency and brightness.

Open pit mining process

The open pit mining process is usually done as follows

Core drilling is used to locate ore bodies or ore veins just below the surface. This is used during exploratory phases of operation.

The top layer of soil is removed to expose rock. Any vegetation above the rock is removed at this point. This will allow the mine's open pit to be expanded or new ones to be opened.

Vertical holes are drilled into rock.

The vertical holes are filled with an explosive such as ammonium nitrate powder. The holes and the explosive are carefully positioned to allow the creation of benches after the explosive is detonated.

The explosive is detonated, crushing the rock nearby.

A large excavator (such as Komatsu or p and h) is brought into the site of the detonation and scoops up the crush rock and deposits it into large haul trucks.

The trucks then drive to a separation or processing plant nearby within the mine site. There can also be stockpiles of excavated materials on the mine site.

As the excavator removes rock it reveals benches. The ore is usually mined out of the benches using explosives to fracture rock out of the benches and then removing the fractured rock with excavators.

In other words the ore or minerals in the mine are extracted by removing material off the walls of the pit. The material is removed by demolishing the wall with explosives. When the walls are demolished, new rock is exposed to the environment creating a new wall. This new wall becomes visible when an excavator removes the material and dumps it into haul trucks.

The processing plant creates tailings in the form of a slurry which is deposited on a tailings pond known in the industry as a tailings management facility (TMF) or tailings storage facility (TSF) to allow the water in the slurry to evaporate. Once enough of the water has evaporated, the tailings may be moved to piles near the open pit for storage. The TMF is used in a continuous basis.

This is the most common form of open pit mining. Another much less common form, is to use the pit solely to access ore located in the center of the pit.

Min max notation

Min max notation from German article vs Chen notation

High voltage

In power distribution according to IEC 60038, low voltage (LV) is defined as voltages from 100 volts to 1 kilovolt (KV), medium voltage (MV) is defined as voltages from over 1 KV to 35 KV, high voltage (HV) is defined as voltages from above 35 to 230 KV, and extra high voltage (EHV) is defined as voltages above 245 KV. This is a definition that has changed over time and can change among groups of engineers, depending on the country and application. For example medium voltage can be defined as 1 to 75 KV, and ultra high voltage (UHV) can be defined as AC voltages of or over 1000 KV and DC voltages of or over 750 KV. According to the Society of Automotive Engineers (SAE), low voltage is under 30 volts, medium voltage is 30 to 60 volts and high voltage is over 60 volts, and according to the National Electrical Code (NEC) used in buildings in the USA, voltages of up to 30 volts AC or 60 volts DC are considered low voltage, and voltages higher than these are considered high voltage.

History

EUV lithography (EUVL) was first proposed in the mid?-90s, and the first EUVL tools began to be developed shortly afterwards, and were at first expected to be used in mass production a few years later, in the early 2000s. However the challenges of EUVL were much more difficult to overcome than what had been thought. Adoption of EUVL tools was repeatedly delayed; first to 2005? Then to 2008? Then to 2012? then to 2016? It wasn't until 2018? that EUVL tools finally started to be used in integrated circuit chip mass production by samsung, then tsmc, micron, sk hynix and intel. Globafoundries planned to use euvl but it was cancelled together with their 7nm development efforts.

Euvl allows for a dramatic reduction in mask count and hence process steps for a single layer, when compared with duv krf arf? Excimer laser lithography dual, triple or quadruple pattering, opening the way for an increase in productivity, building layers faster.

9 Japanese companies in the late 90s formed a consortium funded by the japanese goverment's mext program to develop euvl machinery. They all backed out in the mid-2000s and nikon was left developing the technology on its own until at least 2010. This left Asml, which had also started to develop euvl machines in the late 90s, as the sole euvl machine developer and manufacturer worldwide. The japanese were the first, in 2003 to develop a 10khz repetition rate euv laser light source, and had plans to develop an alpha 10w light output euvl tool by 2006. Nikon never released an euvl tool (machine). Canon, which was also a part of the consortium, and also had plans for an EUVL tool, switched its focus to nanoimprint lithography. Gigaphoton also made advances in euv light source technology. Ushio in 2020? Eventually released its own euv light source. A japanese company is the only one worldwide that makes euvl mask inspection machines that can inspect the different layers of euvl masks in 3d without delayering.

Euvl tools require a large co2 laser, the co2 laser generates laser light pulses that then strike a tin droplet as it falls, the droplet is struck twice with separate pulses before it generates euv light. The laser may be in the subfab where it requires its own small cleanroom. The light from the co2 laser is fed into the tool using pipes and mirrors.

Materials

Further information: Compact Cassette tape types and formulations

Magnetic tape consists of a long, narrow strip of material that is flexible to allow it to be wound on a reel. This strip is often made of PET or PEN plastic. This plastic material is coated with a magnetic layer, which is attached to the plastic material using a binder. The magnetic layer often contains finely powdered magnetic material, and the binder also holds the magnetic particles together. The magnetic layer can also be coated with a lubricating mayer made of silicone based materials or dry lubricants such as Teflon, or it may contain pores with lubricant. The binder may also have lubricating properties.

Magnetic domains are like small magnets within a magnetic material. To reduce the size of these magnetic domains and thus improve recording density, the magnetic material is finely powdered. A goal with the evolution from metal particle to barium ferrite to strontium ferrite, is to reduce the size of the magnetic particles, or making more fine powders with them in order to improve recording density. However Coercivity Determines the stability of the information on the magnetic material. With decreasing particle sizes, higher coercivities are required to compensate for small particle sizes and retain information stability. With metal evaporated tape, it becomes possible to have very small magnetic domains. However, these tapes are more fragile, because they do not use a binder and instead the magnetic material often cobalt, sticks directly to the plastic.

There are several kinds of magnetic layers that can be used on a tape. Perhaps the most common is iron oxide, but to increase the information density on the tape, higher coercivity materials with lower particle sizes are used such as chromium dioxide, doping the iron oxide with cobalt, cobalt oxide, needle shaped metal alloy particles, barium ferrite and strontium ferrite, or evaporating an alloy onto the tape using roll to roll physical vapor deposition.

Magnetic tape is often made on PET plastic tape, because it can not be stretched easily and is chemically and dimensionally stable. Alternatively PEN can be used instead of PET as it has superior mechanical properties but is mord expensive. Tape often has an anti curling layer on the back. The magnetic layer on the tape is often made of needle shaped iron oxide particles (with a low coercivity of 400 oersted) together with an acrylic binder,

however higher performance tapes such as those used in videotape such as some vhs tapes, type iv metal cassette tapes and computer tape storage have magnetic chromium dioxide or needle shaped metal particles (the latter of which are coated in a passivation layer), perhaps atop an insulation layer between the pet and magnetic layer to increase performance even further. Lto computer storage used to use metal particles known as metal particulate. and can use barium ferrite or strontium ferrite.

Sole tspes used metal evaporste tape, or cobalt oxides for cassegte tape

Liquid lubricants may be mixed with the binder in addition to the insulator to allow higher writing speeds, useful in videocassette tape and lto tape.

The magnetic layer is applied to the pet as slurry containing magnetic particles suspended in binder and perhaps lubricant that is dried in an inert atmosphere oven to induce polymer cross linking in the binder, adhering the magnetic particles to the pet

leaving pores with lubricant.

The slurry is made in advance and may include pigments.

The magnetic layer is polished by running the tape through polished pressure rollers to reduce friction between the tape and tape head, giving the tape a mirror finish.

The head usually also has a mirror finish to reduce friction.

Magnetic tape is made in large rolls from which tape reels are made by slitting which is cutting (slitting) the tape from the roll longitudinally into relatively narrow sections as the roll is unwound, the narrow sections are then wound into tape pancakes which are tape reels with hubs but without end caps, which are normally on both ends of the reel to protect the edges of the tape when on the reel.

Metal evaporated tape whose magnetic layer is applied by running the tape through a vacuum chamber where metal is evaporated and condensed on the tape also exists. Some cassette tapes have used type ii cobalt oxide or pseudotype iv ferrocobalt oxide magnetic particles in the magnetic layer.

Barium ferrite is used in lto tapes due to its higher coercivity at a smaller magnetic particle size which allows particles to be closely packed. Strontium ferrite tape was first demonstrated by ibm and fujifilm in 2020 and is expected to replace barium ferrite in the future as it allows for higher capacity lto tapes. Hamr recording has been envisioned for use in high capacity magnetic tape in the future. Giant magnetoresistance tape

History

The first video projectors were crt projectors, which were first used in the 1930s. However because of how CRTs work, there is a limit to their maximum brightness and thus size of images. For example, for higher brightness, higher voltages are required which can be difficult to handle, and because crts work by colliding electrons against phosphor, heat is created in the phosphor which may require cooling, also the phosphor is prone to burn-in.

Thus the eidophor was developed in the 1950s, which strikes electrons in a beam against a plate with oil on the opposite side. The electrons charge the plate electrostatically, changing the direction of reflectivity of the oil and thus controlling the image. The oil side was illuminated by a xenon lamp, which was also a new technology that replaced carbon arc lamps in use in film projectors at the time, the change in direction of reflectivity is similar to how a dlp projector works.

Around the same time, the first color crt projectors were developed. were they large? CRT projectors wouldn't become widely used until the 1980s with the advent of personal computers, since crt projectors are dimmer and better suited for small projection screens. And even then in the 1980s they were used only in relatively small screens such as living rooms and office meeting spaces for displaying TV or computer images.

expand ge talarias in the 70s and 80s used xenon lamps and replaced and were similar to eidophor in working principle and both required a great deal of warmup time talaria 30 min vs eidophor more than an hour, also both suffered from the unique problem of being sensitive to sudden changes in movement: someone bumping into either type of projector would have caused the image to become distorted for 10 minutes. both had similar running costs but talaria was 100 times more long lasting. talarias were brighter but also more complicated than crt projectors of the era, so talarias were only used for large screen, high profile events and in many cases venues had a person dedicated to maintaining and operating it.

But video projectors were still large, so in the 1980s the first modern, tabletop sized projectors were developed. The first was an epson lcd projector with a halogen lamp, similar to those used by slide and overhead projectors. Unlike slide and overhead projectors, these new projectors could change the image instantly and display an image directly from a computer. CRT projectors with similar functionality but larger size (but still tabletop sized) were also developed at this time.

In 1995, uhp ultra high performance, high pressure mercury hpm or ultra high pressure lamps were developed, exclusively with small digital (vs crts which themselves require an analog image input) projection in mind. These could provide a lot of white light in a small and long lasting (compared with earlier halogen) format, finally making them competitive with crts while having the potential to make projectors smaller lighter, brighter (than crts of the same or larger size) and cheaper than earlier larger xenon digital projectors which gave them an advantage over crts. Digital projection delivers digital data to the image generating element such as an lcd, dmd, lcos etc. At the same time dlp technology, which uses a dmd, was developed and the first dlp projectors made.

dlp technology began replacing crts in 1997, and overhead and slide projectors in around the same time. also digital dlp cinema projectors were developed to replace film projectors, but their use would not yet become widespread because of their low resolution of dci 2k (full hd, but with 2048 instead of 1920 horiz pixels) ge talaria, eidophor?

in the 2000s the first ultra short throw projectors were made by japanese companies.

in the 2010s, film projectors were replaced by 4k digital projectors which are usually compliant with the dcp standard.

in 2014? laser illuminated projectors were developed to replace uhp lamps. there are several laser methods but the most common and used in consumer projectors is a spinning phosphor wheel that converts the blue laser into white light, the white light may be asissted by other lasers such a red laser or a red led, a spinning wheel is used to distribute the heat caused by the laser into all of the phosphor in the wheel thus delaying degradation, also ceramic is used in the wheel as it is more heat resistant lasers have longer lifetime, no restrictions on mounting position, lower heat leading to lower ac costs, but rgb laser may color shift over time but this can be corrected with calibration

there are also pure laser projectors such as microvision, but since they project laser light their use has been limited christie rgb rack and barco rgb laser project laser light? r and g or b or some other combination of laser light projected in some other projectors?

For refrigerant article: nontoxic refrigerants did exist but they had a strong odor. Since modern hermetic compressors did not exist, open ones were used which are prone to leaks. so toxic but odorless refrigerants were used. it was thought that since the toxic refrigerants were heavy and thus would fall and stay on the floor in case of a leak, they would be safe in practice?

hydrofluoroolefin: history, synthesis patents? same for cfcs and hcfcs? the need for no odp, low gwp, nontoxic and nonflammable refrigerants and blowing agents to replace earlier cfc, hcfc, and hfcs led to the exploration of alternatives. it was proposed in the 2000s that hfcs should eventually be banned or at least phased down (their use restricted). one of these alternatives is hfos, first synthethized in 2010 at dupont by kostromaris. less than a decade after their first synthesis they began to be adopted in refrigeration.

Early computer monitors were vector, cathode ray tube (CRT) monitors and were rather primitive since there was an urgent need for them. Vector monitors receive relatively simple and small (in RAM) cartessian coordinates from the computer and display and optionally connect them on the screen. In this way graphics could be displayed with very little RAM, but only vector graphics such as text and diagrams could be practically displayed. The path of the electron beam (in the CRT) of a vector monitor varies according to the content it is displaying and is generated on the fly by a vector generator ic. As (video) RAM became available in megabyte quantities due to semiconductor miniaturization advances, vector monitors were abandoned and replaced with raster monitors, which can display more detailed and complex images not practical with vector monitors such as (color and grayscale) photos thus increasing flexibility and quality and with more predictable precision?. The adoption of raster displays was led by Silicon Graphics. Raster graphics have a fixed pattern called a raster so no vector generator is necessary, whose speed and thus image complexity is limited by the speed and miniaturization (number of transistors) of semiconductors? Thus Raster monitors were a large leap and revolution in flexibility and image quality? at the time as they require less advanced ICs while also providing higher flexibility, quality and more predictable precision? Raster graphics require more ram in order to store the color value of every pixel while this was not necessary in vector monitors which only needed to store a set of (fewer) points as cartessian coordinates

CRT computer monitors were replaced with LCD computer monitors in the early 2000s. LCD monitors require much less space in a desk, weigh much less and emit less heat. OLED computer monitors, which offer superior color reproduction and contrast ratios became available in the late 2010s and are more expensive, so they are used in specialized applications such as post-production.

fiber optic cables

the fibers may be organized into ribbons, each consisting of 12 fibers but this amount depends on the cable. this allows for fast mass fusion splicing of cables which reduces the time needed to splice the cables, and allows for faster identification of individual fibers, the ribbons are traditionally rigid and flat and have adhesive along the entire length of the fibers that holds the fibers in the ribbon together. Free form ribbons can change shape, which reduces the space needed for fibers in a cable as it allows for the fibers to be packed in an hexagonal grid, while with traditional ribbons, the ribbons force the fibers to be arranged in a square grid. In a freeform ribbon the glue is only placed at certain intervals along the length of the fibers which allows free form ribbons to be flexible in shape. Fiber optic cables with up to 6912 fibers have been developed by several manufacturers for use in cable ducts. Cables with over 864 fibers, have several groups or tubes of fibers to aid in identification of individual fibers. Each fiber has a thin barrier layer covering the cladding that can be colored to identify the fibers. Fibers can be 250 microns to 200? Microns in diameter 6912 fiber cable fiber diameter

AC vs DC traction

DC traction motors and thus DC power was used in early electric trains because the smooth acceleration required in trains was easier to achieve when coupled with the technology of the era. The torque and speed of DC scale linearly alongside supply voltage, and efficiency does not vary. Only a mercury arc rectifier in a conversion station or aboard the train (if fed with 16.7hz?), and/or a potentiometer were necessary for smooth speed control. AC traction and thus also AC power began being more widely adopted with the advent of VFD technology, which uses IGBTs to smoothly control motors. AC motors are more efficient, have higher power densities and no brushes to replace or that wear out and create dust, unlike DC motors. However, AC's efficiency varies with load and speed so does their torque? AC is superior to DC. It is more efficient, more power dense and requires less maintenance. Although variacs could have been used earlier in trains to regulate their speed it would have come at the cost of efficiency and heat generaion as the efficiency and thus heat gen of ac depends on the amount of slip between the rotting magnetic field and rotor, variacs only vary voltage and thus field strength, not hertz, so for example it would have resulted in inefficiency when from a standstill, during acceleration, anywhere the motor is not at full speed, variac only regulated voltage and thus field strength when what is necessary is only frequency control

Rhodotron

rhodotron amplifier diacrode

Hfc network

Customers in an HFC network are grouped into service groups. A service group in the context of an HFC network, has a trunk to which all customers connect through distribution taps. The trunk may have distribution amplifiers to extend the length of the trunk which is a single one for downstream and upstream signals, and originates at a fiber, optical node, the node connects through fiber optic to the headend or distribution hub where the signals are converted again into RF in an hfc transmitter receiver like Arris ch3000 and Cisco Prisma II, which emit two RF signals one strictly for downstream and other for upstream then through headend rf management modules like splitters and combiners to join into single cables all services from the hub like video and internet, and then into equipment like I cmts for internet, edge qam for video from other sources and internet from m cmts, and video and internet from a CCAP which is similar to an I cmts but with edge qam functionality For i CMTS vs m CMTS see CMTS I CMTS is monolithic, has in a single box RF outputs for the HFC network and NSI interface M CMTS has a core such as an icmts core, which has an NSI, and it's also connected to edge qams for the RF output for the HFC network M CMTS has extra complexity due to two parts that have to be connected and work together but this way it's more scalable than I cmts

dynamic tracking

many VCRs and VTRs had dynamic tracking heads where the heads were placed on the end of a piezoelectric element, this allowed the heads to more precisely follow the video tracks during slow play and shuttle picture searching

Cellular networks or mobile network s

Mobile phones or cellular phones connect to device technically called an eNodeB for 4g, gNB for 5g, nodeb for 3g, or base transceiver stations or bts for gsm or 2g connections, implemented as either cells which integrated antennas and radios, or as cells with separate antennas and remote radio units, small cells, picocells and femtocells are more likely to be integrated and Metro or macro cells are more likely to be separated and be referred to as radio sites. A Cell or small or metro cell can be self contained, and highly integrated as a single device with an antenna and integrated radio, or instead of a cell, a phone can connect to a larger cellular tower or radio site with antennas, driven by separate, remote radio units or heads, possibly with software defined radio or sdr technologies, that are connected to a providers' network via fiber optics, for example. These cells are spacially distributed in an area to provide consistent coverage to mobile phones, and avoid high power transmission towers which require special permits for operation, as the geographical distribution of the cells allows for each cell to have a low output power.

Distributed antenna systems (DAS), differ from the cell architecture by serving an area with spacially distributed antenna nodes, that are driven by remote radio units (RRUs) or heads (RRHs) located in a central location such as a headend, distribution hub (hub) or central office. These systems can be installed indoors iDAS or outdoors (ODAS). The radiofrequency signals from the RRUs or RRHs is converted to light via a radiofrequency over glass (RFoG) node or transmitter/receiver (platform, optics platform) at the headend and transmitted via optical fiber, to which the antenna nodes are connected via interfaces such as cpri. The antenna nodes have an antenna, a receiver, which converts the light into radiofrequency, and a transmitter, which converts radiofrequency to light. The Radiofrequency from the receiver is fed into an amplifier and into the antenna, and Radiofrequency from the antenna is fed into an amplifier and into a transmitter for conversion into light for transmission over optical fiber to a receiver at the headend, hub or central office.

Cellular gps Ericcson gps Mobile network gps

The radio access network is the access network made up of antennas radios, cells and other components that connect mobile phones to mobile carriers.