A mill is a device that breaks solid materials into smaller pieces by grinding, crushing, or cutting. Such comminution is an important unit operation in many processes. There are many different types of many types of materials processed in them. Mills were powered by hand, working animal, wind or water. Today they are powered by electricity; the grinding of solid materials occurs through mechanical forces that break up the structure by overcoming the interior bonding forces. After the grinding the state of the solid is changed: the grain size, the grain size disposition and the grain shape. Milling refers to the process of breaking down, sizing, or classifying aggregate material. For instance rock crushing or grinding to produce uniform aggregate size for construction purposes, or separation of rock, soil or aggregate material for the purposes of structural fill or land reclamation activities. Aggregate milling processes are used to remove or separate contamination or moisture from aggregate or soil and to produce "dry fills" prior to transport or structural filling.
Grinding may serve the following purposes in engineering: increase of the surface area of a solid manufacturing of a solid with a desired grain size pulping of resources In spite of a great number of studies in the field of fracture schemes there is no formula known which connects the technical grinding work with grinding results. To calculate the needed grinding work against the grain size changing three semi-empirical models are used; these can be related to the Hukki relationship between particle size and the energy required to break the particles. In stirred mills, the Hukki relationship does not apply and instead, experimentation has to be performed to determine any relationship. Kick for d > 50 mm W K = c k Bond for 50 mm > d > 0.05 mm W B = c B Von Rittinger for d < 0.05 mm W R = c R with W as grinding work in kJ/kg, c as grinding coefficient, dA as grain size of the source material and dE as grain size of the ground material. A reliable value for the grain sizes dA and dE is d80; this value signifies.
The Bond's grinding coefficient for different materials can be found in various literature. To calculate the KICK's and Rittinger's coefficients following formulas can be used c K = 1.151 c B − 0.5 c R = 0.5 c B 0.5 with the limits of Bond's range: upper dBU = 50 mm and lower dBL = 0.05 mm. To evaluate the grinding results the grain size disposition of the source material and of the ground material is needed. Grinding degree is the ratio of the sizes from the grain disposition. There are several definitions for this characteristic value: Grinding degree referring to grain size d80 Z d = d 80, 1 d 80, 2 Instead of the value of d80 d50 or other grain diameter can be used. Grinding degree referring to specific surface Z S = S v, 2 S v, 1 = S m, 2 S m, 1 The specific surface area referring to volume Sv and the specific surface area referring to mass Sm can be found out through experiments. Pretended grinding degree Z a = d 1 a The discharge die gap a of the grinding machine is used for the ground solid matter in this formula.
In materials processing a grinder is a machine for producing fine particle size reduction through attrition and compressive forces at the grain size level. See crusher for mechanisms producing larger particles. In general, grinding processes require a large amount of energy. A typical type of fine grinder is the ball mill. A inclined or horizontal rotating cylinder is filled with balls stone or metal, which grind material to the necessary fineness by friction and impact with the tumblin
Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed through a die of the desired cross-section; the two main advantages of this process over other manufacturing processes are its ability to create complex cross-sections, to work materials that are brittle, because the material only encounters compressive and shear stresses. It forms parts with an excellent surface finish. Drawing is a similar process, which uses the tensile strength of the material to pull it through the die; this limits the amount of change which can be performed in one step, so it is limited to simpler shapes, multiple stages are needed. Drawing is the main way to produce wire. Metal bars and tubes are often drawn. Extrusion may be semi-continuous; the extrusion process can be done with the material cold. Extruded materials include metals, ceramics, modelling clay, foodstuffs; the products of extrusion are called "extrudates". Referred to as "hole flanging", hollow cavities within extruded material cannot be produced using a simple flat extrusion die, because there would be no way to support the centre barrier of the die.
Instead, the die assumes the shape of a block with depth, beginning first with a shape profile that supports the center section. The die shape internally changes along its length into the final shape, with the suspended center pieces supported from the back of the die; the material flows around the fuses together to create the desired closed shape. The extrusion process in metals may increase the strength of the material. In 1797, Joseph Bramah patented the first extrusion process for making pipe out of soft metals, it involved preheating the metal and forcing it through a die via a hand-driven plunger. In 1820 Thomas Burr implemented that process with a hydraulic press. At that time the process was called "squirting". In 1894, Alexander Dick expanded the extrusion process to brass alloys; the process begins by heating the stock material. It is loaded into the container in the press. A dummy block is placed behind it where the ram presses on the material to push it out of the die. Afterward the extrusion is stretched in order to straighten it.
If better properties are required it may be heat treated or cold worked. The extrusion ratio is defined as the starting cross-sectional area divided by the cross-sectional area of the final extrusion. One of the main advantages of the extrusion process is that this ratio can be large while still producing quality parts. Hot extrusion is a hot working process, which means it is done above the material's recrystallization temperature to keep the material from work hardening and to make it easier to push the material through the die. Most hot extrusions are done on horizontal hydraulic presses that range from 230 to 11,000 metric tons. Pressures range from 30 to 700 MPa, therefore lubrication is required, which can be oil or graphite for lower temperature extrusions, or glass powder for higher temperature extrusions; the biggest disadvantage of this process is its cost for its upkeep. The extrusion process is economical when producing between several kilograms and many tons, depending on the material being extruded.
There is a crossover point. For instance, some steels become more economical to roll. Aluminium hot extrusion die Cold extrusion is done at near room temperature; the advantages of this over hot extrusion are the lack of oxidation, higher strength due to cold working, closer tolerances, better surface finish, fast extrusion speeds if the material is subject to hot shortness. Materials that are cold extruded include: lead, aluminum, zirconium, molybdenum, vanadium and steel. Examples of products produced by this process are: collapsible tubes, fire extinguisher cases, shock absorber cylinders and gear blanks. In March 1956, a US Patent was filed for "process for warm extrusion of metal." Patent US3156043 A outlines that a number of important advantages can be achieved with warm extrusion of both ferrous and non-ferrous metals and alloys if a billet to be extruded is changed in its physical properties in response to physical forces by being heated to a temperature below the critical melting point.
Warm extrusion is done above room temperature, but below the recrystallization temperature of the material the temperatures ranges from 800 to 1800 °F. It is used to achieve the proper balance of required forces and final extrusion properties. Friction extrusion was invented at The Welding Institute in the UK and patented in 1991, it was intended as a method for production of homogenous microstructures and particle distributions in metal matrix composite materials. Friction extrusion differs from conventional extrusion in that the charge rotates relative to the extrusion die. An extrusion force is applied so as to push the charge against the die. In practice either the die or the charge may rotate or they may be counter-rotating; the relative rotary motion between the charge and the die has several significant effects on the process. First, the relative motion in the plane of rotation leads to large shear stresses, plastic deformation in the layer of charge in contact with and near the die; this plastic deformation is dissipated by recovery and recrystallization processes
Cream is a dairy product composed of the higher-butterfat layer skimmed from the top of milk before homogenization. In un-homogenized milk, the fat, less dense rises to the top. In the industrial production of cream, this process is accelerated by using centrifuges called "separators". In many countries, it is sold in several grades depending on the total butterfat content, it can be dried to a powder for shipment to distant markets, contains high levels of saturated fat. Cream skimmed from milk may be called "sweet cream" to distinguish it from cream skimmed from whey, a by-product of cheese-making. Whey cream has a lower fat content and tastes more salty, tangy and "cheesy". In many countries, cream is sold fermented: sour cream, crème fraîche, so on. Both forms have many culinary uses in sweet, bitter and tangy dishes. Cream produced by cattle grazing on natural pasture contains some natural carotenoid pigments derived from the plants they eat; this is the origin of butter's yellow color. Cream from goat's milk, or from cows fed indoors on grain or grain-based pellets, is white.
Cream is used as an ingredient in many foods, including ice cream, many sauces, stews and some custard bases, is used for cakes. Whipped cream is served as a topping on ice cream sundaes, lassi, sweet pies, blueberries or peaches. Irish cream is an alcoholic liqueur which blends cream with whiskey, honey, wine, or coffee. Cream is used in Indian curries such as masala dishes. Cream is added to coffee in the US and Canada. Both single and double cream can be used in cooking. Double cream or full-fat crème fraîche are used when cream is added to a hot sauce, to prevent any problem with it separating or "splitting". Double cream can be thinned with milk to make an approximation of single cream; the French word crème denotes not only dairy cream, but other thick liquids such as sweet and savory custards, which are made with milk, not cream. Different grades of cream are distinguished by their fat content, whether they have been heat-treated, so on. In many jurisdictions, there are regulations for each type.
The Australia New Zealand Food Standards Code – Standard 2.5.2 – Defines cream as a milk product comparatively rich in fat, in the form of an emulsion of fat-in-skim milk, which can be obtained by separation from milk. Cream must contain no less than 350 g/kg milk fat. Manufacturers labels may distinguish between different fat contents, a general guideline is as follows: Canadian cream definitions are similar to those used in the United States, except for "light cream", low-fat cream with 5% or 6% butterfat. Specific product characteristics are uniform throughout Canada, but names vary by both geographic and linguistic area and by manufacturer: "coffee cream" may be 10% or 18% and "half-and-half" may be 3%, 5%, 6% or 10%, all depending on location and brand. Cream in Canada is defined to be the liquid obtained from milk after separating the various components to increase the milk fat content. Canadian Food and Drug Regulations allow stabilizers and acidity regulators. For heat-treated whipping cream, regulations disallow more than 0.25% skim milk powder, 0.1% glucose solids, 0.005% calcium sulphate, 0.2% microcrystalline cellulose, 0.02% xanthan gum.
The content of milk fat present in canned cream must be displayed as a percentage followed by "milk fat", "B. F", or "M. F". Fat content may be displayed on canned cream in Canada. In France, the use of the term "cream" for food products is defined by the decree 80-313 of April 23, 1980, it specifies the minimum rate of milk fat as well as the rules for pasteurisation or UHT sterilisation. The mention "crème fraîche" can only be used for pasteurised creams conditioned on production site within 24h after pasteurisation. If food additives complying with French and European laws are allowed none will be found in plain "crèmes" and "crèmes fraîches" apart from lactic ferments. Fat is displayed "XX% M. G." for "matière grasse" on packagings. In Japan, cream sold in supermarkets is between 35% and 48% butterfat. Russia, as well as other EAC countries separates cream into two classes: normal and heavy, but the industry has pretty much standardized around the following types: In Sweden, cream is sold as: Matlagningsgrädde, 10–15 % Kaffegrädde, 10-12 %, earlier 12 % Vispgrädde, 36–40 %, the 36 % variant has additives.
Mellangrädde is, nowadays, a less common variant. Gräddfil and Creme Fraiche are two common sour cream products. In Switzerland, the types of cream are defined as follows: Sour cream and crème fraîche are defined as cream soured by bacterial cultures. Thick cream is defined as cream thickened using thickening agents. In the United Kingdom, the types of cream are defined as followed: In the United States, cream is sold as: Most cream products sold in the United States at retail contain the minimum permissible fat content for their product type, e.g. "Half and half" always contains only 10.5% butterfat. Not all grades are defined by all jurisdiction
Butterfat or milkfat is the fatty portion of milk. Milk and cream are sold according to the amount of butterfat they contain; the fatty acids of butterfat are composed as follows: As shown above, the composition of fats in milk is discussed in terms of the fatty acids. Fatty acids do not occur as such in milk. Instead, they are incorporated into compounds called triglycerides. In the U. S. there are federal standards for butterfat content of dairy products. Many other countries have standards for minimum fat levels in dairy products. Commercial products contain the minimum legal amount of fat with any excess being removed to make cream, a valuable commodity. Milks Skim milk contains less than 0.5% fat 0.1% Lowfat milk contains between 0.5–2% fat.
Encyclopædia Britannica, Inc.
Encyclopædia Britannica, Inc. is a Scottish-founded, now American company best known for publishing the Encyclopædia Britannica, the world's oldest continuously published encyclopedia. The company was founded in Edinburgh, Scotland, in the 18th century, in the atmosphere of the Scottish Enlightenment. A printer, Colin Macfarquhar, an engraver, Andrew Bell, formed a partnership to create a new book that would embody the new spirit of scholarship. William Smellie was engaged to edit the original three-volume work, published one volume at a time beginning in 1768; the encyclopaedia's reputation grew throughout the publication of its subsequent volumes. The 11th edition was published in 1910/11. In 1920, the trademark and publication rights were sold to Sears Roebuck, which held them until 1943, when ownership passed to William Benton; the 12th edition was published in 1921/22, the 13th edition was published in 1926. A revised 14th edition was published in 1929. By the mid-1930s, the company headquarters had moved to Chicago, United States, the editorial staff were now no longer disbanded after the completion of a new edition, but kept on as a permanent editorial department, to keep pace with the rapid increase in knowledge at the time.
Starting in 1936, a new printing of the encyclopaedia was published each year, incorporating the latest changes and updates. In 1938, the first edition of the Britannica Book of the Year appeared; this annual supplement is still published today. William Benton published the Britannica from 1943 until his death in 1973. Benton acquired Electrical Research Products Inc. Classroom renamed it Encyclopædia Britannica Films. After the death of Benton's widow Helen Benton in 1974, the Benton Foundation continued to manage the Britannica until it was sold to Jacqui Safra in 1996. In 1947, Britannica released a compendium of World War II in 4 volumes. In 1952, Britannica published the landmark set Great Books of the Western World, a 54-volume set of the "great books" of Western culture. Publishing rights to Compton's Encyclopedia were acquired by Encyclopædia Britannica, Inc. in 1961. Merriam-Webster Inc. has been a subsidiary of Encyclopædia Britannica Inc. since 1964. On March 9, 1976 the U. S. Federal Trade Commission entered an opinion and order enjoining Encyclopædia Britannica, Inc. from using a) deceptive advertising practices in recruiting sales agents and obtaining sales leads, b) deceptive sales practices in the door-to-door presentations of its sales agents.
Jacqui Safra gained ownership in 1996. Under Safra's ownership the company has experienced some financial woes with freelance contributors waiting up to six months for payment and staff going years without pay raises, according to a report in the New York Post. Cost-cutting measures have included mandates to use copyright free photos. Britannica in December 2002 told employees it would raise the contribution paid into their 401 accounts eliminated them entirely. A company spokesman said: "We've had some cost reductions and belt-tightening but we're not going into details… We're a held company." History of the Encyclopædia Britannica Encyclopædia Britannica Ultimate Reference Suite Encyclopædia Britannica Online Merriam-Webster Inc. "Encyclopædia Britannica May Refer to ‘For Sale’ to Raise Capital," Portland Oregonian, April 7, 1995 Richard A. Melcher, "Dusting Off the Britannica," Business Week, October 20, 1997 Robert McHenry, “The Building of Britannica Online” Steve Barth, "Britannica on the Virtual Bookshelf," Knowledge Management Magazine Dorothy Auchter, "The Evolution of Encyclopædia Britannica," Reference Services Review 27, no. 3: 297 Sydney Morning Herald online Company website Encyclopædia Britannica Corporate, “Company History”
A homogenizer is a piece of laboratory or industrial equipment used for the homogenization of various types of material, such as tissue, food and many others. Many different models have been developed using various physical technologies for disruption; the mortar and pestle used for thousands of years, is a standard tool in modern laboratories. More modern solutions are based on blender type of instruments, bead mills, ultrasonic treatment, rotor-stator mechanical, high pressure, many other physical forces. There are many different names for the same piece of mechanical homogenizing equipment, including Cell Lysor, High Shear Mixer, Polytron, Rotor Stator Homogenizer, Sonicator or Tissue Tearor. Cell fractionation is done by homogenizer to release the organelles from cell. Whereas older technologies just focused on the disruption of the material, newer technologies address quality or environmental aspects, such as cross-contamination, risk of infection, or noise. Homogenization is a common sample preparation step prior to the analysis of nucleic acids, cells, metabolism and many other targets.
In the field of optics, a homogenizer is an optical device that makes the light beam from a laser or lamp source more uniform in its intensity across its cross-section to enable the light source to provide a more uniform illumination on a surface. Use of a homogenizer in an illumination system is important in consumer applications such as light projectors for movies and industrial applications such as imaging equipment for microlithography for production of semiconductor microchips; such homogenizers are called beam homogenizers or beam uniformizers. The main principle in their design approach is to divide the light beam cross-section-wise into multiple segments and overlap these segments of different intensities into a recombined beam of improved uniformity. A variety of optical homogenization devices have been developed, including fly's-eye lens arrays and solid light tunnels, beam-folding wedged mirrors and split prisms. Homogenization French pressure cell press Cell disruption Ultrasonic homogenizer
Water is a transparent, tasteless and nearly colorless chemical substance, the main constituent of Earth's streams and oceans, the fluids of most living organisms. It is vital for all known forms of life though it provides no calories or organic nutrients, its chemical formula is H2O, meaning that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. Water is the name of the liquid state of H2O at standard ambient pressure, it forms precipitation in the form of rain and aerosols in the form of fog. Clouds are formed from suspended droplets of its solid state; when finely divided, crystalline ice may precipitate in the form of snow. The gaseous state of water is water vapor. Water moves continually through the water cycle of evaporation, condensation and runoff reaching the sea. Water covers 71% of the Earth's surface in seas and oceans. Small portions of water occur as groundwater, in the glaciers and the ice caps of Antarctica and Greenland, in the air as vapor and precipitation.
Water plays an important role in the world economy. 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a major source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers and canals. Large quantities of water and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a wide variety of chemical substances. Water is central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, sport fishing, diving; the word water comes from Old English wæter, from Proto-Germanic *watar, from Proto-Indo-European *wod-or, suffixed form of root *wed-. Cognate, through the Indo-European root, with Greek ύδωρ, Russian вода́, Irish uisce, Albanian ujë; the identification of water as a substance Water is a polar inorganic compound, at room temperature a tasteless and odorless liquid, nearly colorless with a hint of blue.
This simplest hydrogen chalcogenide is by far the most studied chemical compound and is described as the "universal solvent" for its ability to dissolve many substances. This allows it to be the "solvent of life", it is the only common substance to exist as a solid and gas in normal terrestrial conditions. Water is a liquid at the pressures that are most adequate for life. At a standard pressure of 1 atm, water is a liquid between 0 and 100 °C. Increasing the pressure lowers the melting point, about −5 °C at 600 atm and −22 °C at 2100 atm; this effect is relevant, for example, to ice skating, to the buried lakes of Antarctica, to the movement of glaciers. Increasing the pressure has a more dramatic effect on the boiling point, about 374 °C at 220 atm; this effect is important in, among other things, deep-sea hydrothermal vents and geysers, pressure cooking, steam engine design. At the top of Mount Everest, where the atmospheric pressure is about 0.34 atm, water boils at 68 °C. At low pressures, water cannot exist in the liquid state and passes directly from solid to gas by sublimation—a phenomenon exploited in the freeze drying of food.
At high pressures, the liquid and gas states are no longer distinguishable, a state called supercritical steam. Water differs from most liquids in that it becomes less dense as it freezes; the maximum density of water in its liquid form is 1,000 kg/m3. The density of ice is 917 kg/m3. Thus, water expands 9% in volume as it freezes, which accounts for the fact that ice floats on liquid water; the details of the exact chemical nature of liquid water are not well understood. Pure water is described as tasteless and odorless, although humans have specific sensors that can feel the presence of water in their mouths, frogs are known to be able to smell it. However, water from ordinary sources has many dissolved substances, that may give it varying tastes and odors. Humans and other animals have developed senses that enable them to evaluate the potability of water by avoiding water, too salty or putrid; the apparent color of natural bodies of water is determined more by dissolved and suspended solids, or by reflection of the sky, than by water itself.
Light in the visible electromagnetic spectrum can traverse a couple meters of pure water without significant absorption, so that it looks transparent and colorless. Thus aquatic plants and other photosynthetic organisms can live in water up to hundreds of meters deep, because sunlight can reach them. Water vapour is invisible as a gas. Through a thickness of 10 meters or more, the intrinsic color of water is visibly turquoise, as its absorption spectrum has