An octane rating, or octane number, is a standard measure of the performance of an engine or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating. In broad terms, fuels with a higher octane rating are used in high performance gasoline engines that require higher compression ratios. In contrast, fuels with lower octane numbers are ideal for diesel engines, because diesel engines do not compress the fuel, but rather compress only air and inject fuel into the air, heated by compression. Gasoline engines rely on ignition of air and fuel compressed together as a mixture, ignited at the end of the compression stroke using spark plugs. Therefore, high compressibility of the fuel matters for gasoline engines. Use of gasoline with lower octane numbers may lead to the problem of engine knocking. In a normal spark-ignition engine, the air-fuel mixture is heated because of being compressed and is triggered to burn by the spark plug. During the combustion process, if the unburnt portion of the fuel in the combustion chamber is heated too much, pockets of unburnt fuel may self-ignite before the main flame front reaches them.
Shockwaves produced by detonation can cause much higher pressures than engine components are designed for, can cause a "knocking" or "pinging" sound. Knocking can cause major engine damage; the most used engine management systems found in automobiles today have a knock sensor that monitors if knock is being produced by the fuel being used. In modern computer-controlled engines, the ignition timing will be automatically altered by the engine management system to reduce the knock to an acceptable level. Octanes are a family of hydrocarbons, they are colorless liquids that boil around 125 °C. One member of the octane family, isooctane, is used as a reference standard to benchmark the tendency of gasoline or LPG fuels to resist self-ignition; the octane rating of gasoline is measured in a test engine and is defined by comparison with the mixture of 2,2,4-trimethylpentane and heptane that would have the same anti-knocking capacity as the fuel under test: the percentage, by volume, of 2,2,4-trimethylpentane in that mixture is the octane number of the fuel.
For example, gasoline with the same knocking characteristics as a mixture of 90% iso-octane and 10% heptane would have an octane rating of 90. A rating of 90 does not mean that the gasoline contains just iso-octane and heptane in these proportions but that it has the same detonation resistance properties; because some fuels are more knock-resistant than pure iso-octane, the definition has been extended to allow for octane numbers greater than 100. Octane ratings are not indicators of the energy content of fuels.. They are only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Where the octane number is raised by blending in ethanol, energy content per volume is reduced. Ethanol BTUs can be compared with gasoline BTUs in heat of combustion tables, it is possible for a fuel to have a Research Octane Number more than 100, because iso-octane is not the most knock-resistant substance available. Racing fuels, avgas, LPG and alcohol fuels such as methanol may have octane ratings of 110 or higher.
Typical "octane booster" gasoline additives include ETBE, isooctane and toluene. Lead in the form of tetraethyllead was once a common additive, but its use for fuels for road vehicles has been progressively phased-out worldwide, beginning in the 1970s; the most common type of octane rating worldwide is the Research Octane Number. RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, comparing the results with those for mixtures of iso-octane and n-heptane. Another type of octane rating, called Motor Octane Number, is determined at 900 rpm engine speed instead of the 600 rpm for RON. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern pump gasoline will be about 8 to 12 octane lower than the RON, but there is no direct link between RON and MON.
Pump gasoline specifications require both a minimum RON and a minimum MON. In most countries in Europe the "headline" octane rating shown on the pump is the RON, but in Canada, the United States and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index, written on pumps as /2, it may sometimes be called the Posted Octane Number. Because of the 8 to 12 octane number difference between RON and MON noted above, the AKI shown in Canada and the United States is 4 to 6 octane numbers lower than elsewhere in the world for the same fuel; this difference between RON and MON is known as the fuel's Sensitivity, is not published for those countries that use the Anti-Knock Index labelling system. See the table in the following section for a comparison. Another type of octane rating, called Observed Road Octane Number, is derived from testing gasolines in real world multi-cylinder engines at wide open throttle, it is still reliable today. The ori
In linguistics, apophony is any sound change within a word that indicates grammatical information. Apophony is exemplified in English as the internal vowel alternations that produce such related words as sing, sung, song rise, risen lie, lay bind, bound weave, wove food, feed blood, bleed brood, breed doom, deem goose, geese tooth, teeth foot, feetThe difference in these vowels marks variously a difference in tense or aspect, part of speech, or grammatical number; that these sound alternations function grammatically can be seen as they are equivalent to grammatical suffixes. Compare the following: The vowel alternation between i and a indicates a difference between present and past tense in the pair sing/sang. Here the past tense is indicated by the vowel a just as the past tense is indicated on the verb jump with the past tense suffix -ed; the plural suffix -s on the word books has the same grammatical function as the presence of the vowel ee in the word geese. Consonants, can alternate in ways that are used grammatically.
An example is the pattern in English of verb-noun pairs with related meanings but differing in voicing of a postvocalic consonant: Most instances of apophony develop from changes due to phonological assimilation that are grammaticalized when the environment causing the assimilation is lost. Such is the case with English belief/believe. Apophony may involve various types of alternations, including vowels, prosodic elements, smaller features, such as nasality; the sound alternations may be used derivationally. The particular function of a given alternation will depend on the language. Apophony involves vowels. Indo-European ablaut and Germanic umlaut, mentioned above, are well attested examples. Another example is from Dinka: When it comes to plurals, a common vowel alteration in Assyrian Neo-Aramaic is shifting the ɑ sound to e as shown in this table: The vowel alternation may involve more than just a change in vowel quality. In Athabaskan languages, such as Navajo, verbs have series of stems where the vowel alternates indicating a different tense-aspect.
Navajo vowel ablaut, depending on the verb, may be a change in vowel, vowel length, and/or tone. For example, the verb stem -kaah/-ką́ "to handle an open container" has a total of 16 combinations of the 5 modes and 4 aspects, resulting in 7 different verb stem forms. Another verb stem -géésh/-gizh "to cut" has a different set of alternations and mode-aspect combinations, resulting in 3 different forms: Various prosodic elements, such as tone, syllable length, stress, may be found in alternations. For example, Vietnamese has the following tone alternations which are used derivationally: Albanian uses different vowel lengths to indicate number and grammatical gender on nouns: English has alternating stress patterns that indicate whether related words are nouns or verbs; this tends to be the case with words in English that came from Latin: Prosodic alternations are sometimes analyzed as not as a type of apophony but rather as prosodic affixes, which are known, variously, as suprafixes, superfixes, or simulfixes.
Consonant alternation is known as consonant mutation or consonant gradation. Bemba indicates causative verbs through alternation of the stem-final consonant. Here the alternation involves spirantization and palatalization: Celtic languages are well known for their initial consonant mutations. In Indo-European linguistics, ablaut is the vowel alternation that produces such related words as sing, sang and song; the difference in the vowels results from the alternation of the vowel e with the vowel o or with no vowel. To cite a few other examples of Indo-European ablaut, English has a certain class of verbs, called strong verbs, in which the vowel changes to indicate a different grammatical tense-aspect; as the examples above show, a trade in the vowel of the verb stem creates a different verb form. Some of the verbs have a suffix in the past participle form. In Indo-European linguistics, umlaut is the vowel alternation that produces such related words as foot and feet or strong and strength; the difference in the vowels results from the influence of an i or y on the vowel which becomes e.
To cite another example of umlaut, some English weak verbs show umlaut in the present tense. Germanic a-mutation are processes analogous to umlaut but involving the influence of an a or u instead of an i. In Indo-European historical linguistics the terms ablaut and umlaut refer to different phenomena and are not interchangeable. Ablaut is a process that dates back to Proto-Indo-European times, occurs in all Indo-European languages, refers to unpredictable vowel alternations of a specific nature. From an Indo-European perspective, it appears as a variation between o, e, no vowel, although various sound changes result in different vowel alternations appearing in differe
Lumber or timber is a type of wood, processed into beams and planks, a stage in the process of wood production. Lumber is used for structural purposes but has many other uses as well. There are two main types of lumber, it may be surfaced on one or more of its faces. Besides pulpwood, rough lumber is the raw material for furniture-making and other items requiring additional cutting and shaping, it is available in many species hardwoods. Finished lumber is supplied in standard sizes for the construction industry – softwood, from coniferous species, including pine and spruce, hemlock, but some hardwood, for high-grade flooring, it is more made from softwood than hardwoods, 80% of lumber comes from softwood. In the United States milled boards of wood are referred to as lumber. However, in Britain and other Commonwealth nations, the term timber is instead used to describe sawn wood products, like floor boards. In the United States and Canada timber describes standing or felled trees. In Canada, lumber describes cut and surfaced wood.
In the United Kingdom, the word lumber is used in relation to wood and has several other meanings, including unused or unwanted items. Referring to wood, Timber is universally used instead. Remanufactured lumber is the result of secondary or tertiary processing/cutting of milled lumber, it is lumber cut for industrial or wood-packaging use. Lumber is cut by ripsaw or resaw to create dimensions that are not processed by a primary sawmill. Resawing is the splitting of 1-inch through 12-inch hardwood or softwood lumber into two or more thinner pieces of full-length boards. For example, splitting a ten-foot 2×4 into two ten-foot 1×4s is considered resawing. Structural lumber may be produced from recycled plastic and new plastic stock, its introduction has been opposed by the forestry industry. Blending fiberglass in plastic lumber enhances its strength and fire resistance. Plastic fiberglass structural lumber can have a "class 1 flame spread rating of 25 or less, when tested in accordance with ASTM standard E 84," which means it burns slower than all treated wood lumber.
Logs are converted into timber by being hewn, or split. Sawing with a rip saw is the most common method, because sawing allows logs of lower quality, with irregular grain and large knots, to be used and is more economical. There are various types of sawing: Plain sawn – A log sawn through without adjusting the position of the log and the grain runs across the width of the boards. Quarter sawn and rift sawn – These terms have been confused in history but mean lumber sawn so the annual rings are reasonably perpendicular to the sides of the lumber. Boxed heart – The pith remains within the piece with some allowance for exposure. Heart center – the center core of a log. Free of heart center – A side-cut timber without any pith. Free of knots – No knots are present. Dimensional lumber is lumber, cut to standardized width and depth, specified in inches. Carpenters extensively use dimensional lumber in framing wooden buildings. Common sizes include 2×4, 2×6, 4×4; the length of a board is specified separately from the width and depth.
It is thus possible to find 2×4s that are four and twelve feet in length. In Canada and the United States, the standard lengths of lumber are 6, 8, 10, 12, 14, 16, 18, 20, 22 and 24 feet. For wall framing, "stud" or "precut" sizes are available, are used. For an eight-, nine-, or ten-foot ceiling height, studs are available in 92 5⁄8 inches, 104 5⁄8 inches, 116 5⁄8 inches; the term "stud" is used inconsistently to specify length. Under the prescription of the Method of Construction issued by the Southern Song government in the early 12th century, timbers were standardized to eight cross-sectional dimensions. Regardless of the actual dimensions of the timber, the ratio between width and height was maintained at 1:1.5. Units are in Song Dynasty inches. Timber smaller than the 8th class were called "unclassed"; the width of a timber is referred to as one "timber", the dimensions of other structural components were quoted in multiples of "timber". The dimensions of timbers in similar application show a gradual diminution from the Sui Dyansty to the modern era.
The length of a unit of dimensional lumber is limited by the height and girth of the tree it is milled from. In general the maximum length is 24 ft. Engineered wood products, manufactured by binding the strands, fibers, or veneers of wood, together with adhesives, to form composite materials, offer more flexibility and greater structural strength than typical wood building materials. Pre-cut studs save a framer much time, because they are pre-cut by the manufacturer for use in 8-, 9-
Grade–Ruan is a civil parish on the Lizard peninsula in Cornwall, United Kingdom ten miles south of Falmouth. It is a rural parish bounded by the sea. Grade–Ruan civil parish encompasses part of Goonhilly Downs and the major settlements are Ruan Minor, St Ruan and Cadgwith; the parish was formed in 1934 because falling population necessitated merging the ecclesiastical parishes of Grade, Ruan Major and Ruan Minor. All three were in the Hundred of Kerrier. Cadgwith was in Grade parish and in Ruan Minor parish; the population of Grade–Ruan has increased steadily. There is a school in the parish, Grade Ruan CE Primary School, situated in Ruan Minor. Grade–Ruan lies within the Cornwall Area of Outstanding Natural Beauty. A third of Cornwall has AONB designation, with the same status and protection as a National Park; the parish churches of the three former parishes are St Grada at Grade, the churches of Ruan Major and Ruan Minor, the latter two dedicated to St Rumonus. All three have towers though Ruan Minor Church tower is small.
Ruan Major Church was altered by Edmund Sedding in 1867 and is now a ruin. The church of Ruan Major lay within the manor of Winnianton; the church of St Rumon in Ruan Major is a grade. The church of Ruan Minor lay within the manor of Winnianton; the church is a small 15th century building and has a Norman piscina. Erisey Manor House is a Grade II listed farmhouse; the oldest part is part of a house built in an E shape in 1620. The 1620 house was built by Richard Erisey. James Erisey was born at an earlier Erisey House.
Grading in civil engineering and landscape architectural construction is the work of ensuring a level base, or one with a specified slope, for a construction work such as a foundation, the base course for a road or a railway, or landscape and garden improvements, or surface drainage. The earthworks created for such a purpose are called the sub-grade or finished contouring. In the case of gravel roads and earthworks for certain purposes, grading forms not just the base but the cover and surface of the finished construction, is called finished grade, it is done using heavy machinery like bulldozers and excavators to prepare an area and using a grader for a finer finish. In the environmental design professions grading and regrading are a specifications and construction component in landscape design, landscape architecture, architecture projects, it is used for buildings or outdoor amenities regarding foundations and footings, slope terracing and stabilizing, aesthetic contouring, directing surface runoff drainage of stormwater and domestic/irrigation runoff flows.
Matusik, John. "Grading and Earthworks" in The Land Development Handbook, 2004. Gravel Roads Construction and Maintenance Guide, Federal Highway Administration and the South Dakota Local Technical Assistance Program, 2015. "How to Grade Gravel Roads" in Gravel Roads, Soil Stabilization, Soil-Sement® by Frank Elswick, 2017. Recommended Practices Manual: A Guideline for Maintenance and Service of Unpaved Roads, Choctawhatchee and Yellow Rivers Watershed Management Authority, 2000
Metamorphism is the change of minerals or geologic texture in pre-existing rocks, without the protolith melting into liquid magma. The change occurs due to heat and the introduction of chemically active fluids; the chemical components and crystal structures of the minerals making up the rock may change though the rock remains a solid. Changes at or just beneath Earth's surface due to weathering or diagenesis are not classified as metamorphism. Metamorphism occurs between diagenesis, melting; the geologists who study metamorphism are known as "metamorphic petrologists." To determine the processes underlying metamorphism, they rely on statistical mechanics and experimental petrology. Three types of metamorphism exist: contact and regional. Metamorphism produced with increasing pressure and temperature conditions is known as prograde metamorphism. Conversely, decreasing temperatures and pressure characterize retrograde metamorphism. Metamorphic rocks can change without melting. Heat causes atomic bonds to break, the atoms move and form new bonds with other atoms, creating new minerals with different chemical components or crystalline structures, or enabling recrystallization.
When pressure is applied, somewhat flattened grains that orient in the same direction have a more stable configuration. The temperature lower limit on what is considered to be a metamorphic process is considered to be 100 – 200 °C; the upper boundary of metamorphic conditions is related to the onset of melting processes in the rock. The maximum temperature for metamorphism is 700 – 900 °C, depending on the pressure and on the composition of the rock. Migmatites are rocks formed at this upper limit, which contains pods and veins of material that has started to melt but has not segregated from the refractory residue. Since the 1980s it has been recognized that rocks are dry enough and of a refractory enough composition to record without melting "ultra-high" metamorphic temperatures of 900 – 1100 °C; the metamorphic process has to be over pressure of at least 100 mega pascals but below 300 mega pascals, the depth of 100 mega pascals varies depending on what type of rock is applying pressure. Regional or Barrovian metamorphism covers large areas of continental crust associated with mountain ranges those associated with convergent tectonic plates or the roots of eroded mountains.
Conditions producing widespread regionally metamorphosed rocks occur during an orogenic event. The collision of two continental plates or island arcs with continental plates produce the extreme compressional forces required for the metamorphic changes typical of regional metamorphism; these orogenic mountains are eroded, exposing the intensely deformed rocks typical of their cores. The conditions within the subducting slab as it plunges toward the mantle in a subduction zone produce regional metamorphic effects, characterized by paired metamorphic belts; the techniques of structural geology are used to unravel the collisional history and determine the forces involved. Regional metamorphism can be described and classified into metamorphic facies or metamorphic zones of temperature/pressure conditions throughout the orogenic terrane. Contact metamorphism occurs around intrusive igneous rocks as a result of the temperature increase caused by the intrusion of magma into cooler country rock; the area surrounding the intrusion where the contact metamorphism effects are present is called the metamorphic aureole.
Contact metamorphic rocks are known as hornfels. Rocks formed by contact metamorphism may not present signs of strong deformation and are fine-grained. Contact metamorphism is greater adjacent to the intrusion and dissipates with distance from the contact; the size of the aureole depends on the heat of the intrusion, its size, the temperature difference with the wall rocks. Dikes have small aureoles with minimal metamorphism whereas large ultramafic intrusions can have thick and well-developed contact metamorphism; the metamorphic grade of an aureole is measured by the peak metamorphic mineral which forms in the aureole. This is related to the metamorphic temperatures of pelitic or aluminosilicate rocks and the minerals they form; the metamorphic grades of aureoles are sillimanite hornfels, pyroxene hornfels. Magmatic fluids coming from the intrusive rock may take part in the metamorphic reactions. An extensive addition of magmatic fluids can modify the chemistry of the affected rocks. In this case the metamorphism grades into metasomatism.
If the intruded rock is rich in carbonate the result is a skarn. Fluorine-rich magmatic waters which leave a cooling granite may form greisens within and adjacent to the contact of the granite. Metasomatic altered aureoles can localize the deposition of metallic ore minerals and thus are of economic interest. A special type of contact metamorphism, associated with fossil fuel fires, is known as pyrometamorphism. Hydrothermal metamorphism is the result of the interaction of a rock with a high-temperature fluid of variable composition; the difference in composition between an existing rock and the invading fluid triggers a set of metamorphic and metasomatic reactions. The hydrothermal fluid may be magmatic, circulating ocean water. Convective circulation of hydrothermal fluids in the ocean floor basalts produces extensive hydrothermal metamorphism adjacent to spreading centers and other submarine volcanic areas
In geology, a graded bed is one characterized by a systematic change in grain or clast size from one side of the bed to the other. Most this takes the form of normal grading, with coarser sediments at the base, which grade upward into progressively finer ones. Graded beds represent depositional environments which decrease in transport energy as time passes, but these beds can form during rapid depositional events, they are best represented in turbidite strata, where they indicate a sudden strong current that deposits heavy, coarse sediments first, with finer ones following as the current weakens. They can form in terrestrial stream deposits. In reverse or inverse grading the bed coarsens upwards; this type of grading is uncommon but is characteristic of sediments deposited by grain flow and debris flow. It is observed in Aeolian processes; these deposition processes are examples of granular convection. Graded bedding is a sorting of particles according to clast size and shape on a lithified horizontal plane.
The term is an explanation as to. Stratification on a lateral plane is the physical result of active depositing of different size materials. Density and gravity forces in the downward movement of these materials in a confined system result in a separating of the detritus settling with respect to size. Thus, higher-porosity clasts form at the top and denser, less porous clasts are consolidated on the bottom, in what is called normal grading. Grades of the bedding material are determined by precipitation of solid components compared to the viscosity of the medium in which the particles precipitate. Steno’s Principle of Original Horizontality explains that rock layers form in horizontal layers over an underdetermined time scale and depth. Nicholas Steno first published his hypothesis in 1669 after recognizing that fossils were preserved in layers of rock. For materials to settle in stratified layers the defining quality is periodicity. There must be repeated depositional events with changes in precipitation of materials over time.
The thickness of graded beds ranges from 1 millimeter to multiple meters. There is no set time limit. Uniformity of size and shape of materials within the bed form must be present on a present or horizontal plane. Weathering: the chemical or physical forces breaking apart the solid materials that are transported. Erosion: The movement of material due to weathering forces that have freed materials for movement. Deposition: The material settles on a horizontal plane either through chemical or physical precipitation. Note: The secondary processes of compaction and lithification help to hold a stratified bed in place. In aeolian or fluid depositional environments, where there is a decrease in transport energy over time, the bedding material is sorted more uniformly, according to the normal grading scale; as water or air slows, the turbidity decreases. The suspended load of the detritus precipitate. In times of fast movement the bedding may be poorly sorted on the deposition surface and thus is not graded because of the quick movement of the material.
In broad channels with decreasing slopes, slow-moving water can carry large amounts of detritus over a large area. Thus, graded beds form at points with decreased slopes in wide areas with less bounding of energy current flows; the energy decreases. Turbid sediments precipitate in concordant shapes in layers. Changes in currents or physical deformation in the environment can be determined upon observation and monitoring of a depositional surface or lithologic sequence with unconformities above or below a graded bed. Detrital sedimentary graded beds are formed from erosional and weathering forces. Graded beds formed from detrital materials are composed of sand, clay. After lithification, shale and sandstone are formed from the detrital deposits. Clastic formations are of organic sources, such as biochemical chert, which forms from siliceous marine organism decay and diagenesis. Organic sedimentation of parent material from decaying plant matter in bogs or swamps can result in a graded bedding complex.
This activity leads after thousands of years. Limestone is more than 95% biogenic in origin, it is made from the deposition of carbonate fossils of marine organisms. Bio erosion caused by animals, such as bivalves and sponges change the marine substrate, resulting in layered bedding planes, due to their sifting of bed material in search of food. Organic clastic bedding can become millions of years under pressure. A favored explanation is kinetic sieving. Clastic rock Monroe, James S. and Reed Wicander. The Changing Earth: Exploring Geology and Evolution, 2nd ed. Belmont: West Publishing Company, 1997. ISBN 0-314-09577-2 pp. 114