92-629: A kamado ( 竈 , 竃 or 灶 ) is a traditional Japanese wood - or charcoal -fueled cook stove . The precursor of the Kamado was introduced to Japan by Yayoi immigrants from the Korean peninsula during the Kofun period. The name kamado is the Japanese word for "stove" or "cooking range". It means a "place for the cauldron". A movable kamado called "mushikamado" came to the attention of Americans after World War II . It
184-428: A construction material , for making tools and weapons , furniture and paper . More recently it emerged as a feedstock for the production of purified cellulose and its derivatives, such as cellophane and cellulose acetate . As of 2020, the growing stock of forests worldwide was about 557 billion cubic meters. As an abundant, carbon-neutral renewable resource, woody materials have been of intense interest as
276-756: A heat engine . Other times, the heat itself is valued for warmth, cooking , or industrial processes, as well as the illumination that accompanies combustion . Fuels are also used in the cells of organisms in a process known as cellular respiration , where organic molecules are oxidized to release usable energy. Hydrocarbons and related organic molecules are by far the most common source of fuel used by humans, but other substances, including radioactive metals, are also utilized. Fuels are contrasted with other substances or devices storing potential energy , such as those that directly release electrical energy (such as batteries and capacitors ) or mechanical energy (such as flywheels , springs, compressed air, or water in
368-400: A nuclear fission reactor ; nuclear fuel can refer to the material or to physical objects (for example fuel bundles composed of fuel rods ) composed of the fuel material, perhaps mixed with structural, neutron moderating , or neutron reflecting materials. When some of these fuels are struck by neutrons, they are in turn capable of emitting neutrons when they break apart. This makes possible
460-407: A closed forest, and in the manufacture of articles where strength is an important consideration such "second-growth" hardwood material is preferred. This is particularly the case in the choice of hickory for handles and spokes . Here not only strength, but toughness and resilience are important. The results of a series of tests on hickory by the U.S. Forest Service show that: Fuel A fuel
552-453: A factor in Portland cement designs. In addition to the outer ceramic shell, a ceramic or stainless steel bowl inside the unit holds charcoal. One or more grids are suspended over the fire to provide the cooking surface(s) for food. A draft opening in the lower side of the unit provides air to the fuel, as well as a controllable vent in the top of the dome lid for air to exit the cooker. Temperature
644-401: A heavy piece of pine is compared with a lightweight piece it will be seen at once that the heavier one contains a larger proportion of latewood than the other, and is therefore showing more clearly demarcated growth rings. In white pines there is not much contrast between the different parts of the ring, and as a result the wood is very uniform in texture and is easy to work. In hard pines , on
736-405: A large log the sapwood, because of the time in the life of the tree when it was grown, may be inferior in hardness , strength , and toughness to equally sound heartwood from the same log. In a smaller tree, the reverse may be true. In species which show a distinct difference between heartwood and sapwood the natural color of heartwood is usually darker than that of the sapwood, and very frequently
828-400: A log is on the outside, it is more or less knotty near the middle. Consequently, the sapwood of an old tree, and particularly of a forest-grown tree, will be freer from knots than the inner heartwood. Since in most uses of wood, knots are defects that weaken the timber and interfere with its ease of working and other properties, it follows that a given piece of sapwood, because of its position in
920-403: A mixture of propane and butane , both of which are easily compressible gases under standard atmospheric conditions. It offers many of the advantages of compressed natural gas (CNG) but is denser than air, does not burn as cleanly, and is much more easily compressed. Commonly used for cooking and space heating, LP gas and compressed propane are seeing increased use in motorized vehicles. Propane
1012-436: A pivotal part of our contemporary society, with most countries in the world burning fossil fuels in order to produce power, but are falling out of favor due to the global warming and related effects that are caused by burning them. Currently the trend has been towards renewable fuels, such as biofuels like alcohols. Chemical fuels are substances that release energy by reacting with substances around them, most notably by
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#17328524630181104-481: A pretty definite relation between the rate of growth of timber and its properties. This may be briefly summed up in the general statement that the more rapid the growth or the wider the rings of growth, the heavier, harder, stronger, and stiffer the wood. This, it must be remembered, applies only to ring-porous woods such as oak, ash, hickory, and others of the same group, and is, of course, subject to some exceptions and limitations. In ring-porous woods of good growth, it
1196-425: A reservoir). The first known use of fuel was the combustion of firewood by Homo erectus nearly two million years ago. Throughout most of human history only fuels derived from plants or animal fat were used by humans. Charcoal , a wood derivative, has been used since at least 6,000 BCE for melting metals. It was only supplanted by coke , derived from coal, as European forests started to become depleted around
1288-918: A self-sustaining chain reaction that releases energy at a controlled rate in a nuclear reactor , or at a very rapid uncontrolled rate in a nuclear weapon . The most common fissile nuclear fuels are uranium-235 ( U) and plutonium-239 ( Pu). The actions of mining, refining, purifying, using, and ultimately disposing of nuclear fuel together make up the nuclear fuel cycle . Not all types of nuclear fuels create energy from nuclear fission. Plutonium-238 and some other elements are used to produce small amounts of nuclear energy by radioactive decay in radioisotope thermoelectric generators and other types of atomic batteries . In contrast to fission, some light nuclides such as tritium ( H) can be used as fuel for nuclear fusion . This involves two or more nuclei combining into larger nuclei. Fuels that produce energy by this method are currently not utilized by humans, but they are
1380-463: A source of energy. The International Energy Agency (IEA) predicts that fossil fuel prices will decline, with oil stabilizing around $ 75 to $ 80 per barrel as electric vehicle adoption surges and renewable energy expands. Additionally, the IEA anticipates a notable increase in liquefied natural gas capacity, enhancing Europe’s energy diversification. The amount of energy from different types of fuel depends on
1472-631: A source of renewable energy. In 2008, approximately 3.97 billion cubic meters of wood were harvested. Dominant uses were for furniture and building construction. Wood is scientifically studied and researched through the discipline of wood science , which was initiated since the beginning of the 20th century. A 2011 discovery in the Canadian province of New Brunswick yielded the earliest known plants to have grown wood, approximately 395 to 400 million years ago . Wood can be dated by carbon dating and in some species by dendrochronology to determine when
1564-460: A source of weakness. In diffuse-porous woods the pores are evenly sized so that the water conducting capability is scattered throughout the growth ring instead of being collected in a band or row. Examples of this kind of wood are alder , basswood , birch , buckeye, maple, willow , and the Populus species such as aspen, cottonwood and poplar. Some species, such as walnut and cherry , are on
1656-564: A tree is first formed as sapwood. The more leaves a tree bears and the more vigorous its growth, the larger the volume of sapwood required. Hence trees making rapid growth in the open have thicker sapwood for their size than trees of the same species growing in dense forests. Sometimes trees (of species that do form heartwood) grown in the open may become of considerable size, 30 cm (12 in) or more in diameter, before any heartwood begins to form, for example, in second growth hickory , or open-grown pines . No definite relation exists between
1748-423: A type of imperfection known as a knot. The dead branch may not be attached to the trunk wood except at its base and can drop out after the tree has been sawn into boards. Knots affect the technical properties of the wood, usually reducing tension strength, but may be exploited for visual effect. In a longitudinally sawn plank, a knot will appear as a roughly circular "solid" (usually darker) piece of wood around which
1840-399: A variety of materials including high fire ceramics, refractory materials, double wall insulated steel, traditional terra cotta, or a mix of Portland cement and crushed lava . Outer surfaces vary from a high gloss ceramic glaze, paint, a textured stucco-like surface or ceramic tiles. Modern ceramic and refractory materials decrease cracking – a common fault in the original design, and still
1932-512: A way to make heavy oil fractions usable as liquid fuels. Many liquid fuels play a primary role in transportation and the economy. Some common properties of liquid fuels are that they are easy to transport and can be handled easily. They are also relatively easy to use for all engineering applications and in home use. Fuels like kerosene are rationed in some countries, for example in government-subsidized shops in India for home use. Conventional diesel
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#17328524630182024-484: A wooden object was created. People have used wood for thousands of years for many purposes, including as a fuel or as a construction material for making houses , tools , weapons , furniture , packaging , artworks , and paper . Known constructions using wood date back ten thousand years. Buildings like the longhouses in Neolithic Europe were made primarily of wood. Recent use of wood has been enhanced by
2116-437: Is a season check in the knot, as is often the case, it will offer little resistance to this tensile stress. Small knots may be located along the neutral plane of a beam and increase the strength by preventing longitudinal shearing . Knots in a board or plank are least injurious when they extend through it at right angles to its broadest surface. Knots which occur near the ends of a beam do not weaken it. Sound knots which occur in
2208-401: Is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants . It is an organic material – a natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or more broadly to include
2300-456: Is also greatly increased in strength thereby. Since the latewood of a growth ring is usually darker in color than the earlywood, this fact may be used in visually judging the density, and therefore the hardness and strength of the material. This is particularly the case with coniferous woods. In ring-porous woods the vessels of the early wood often appear on a finished surface as darker than the denser latewood, though on cross sections of heartwood
2392-428: Is an important consideration. The weakening effect is much more serious when timber is subjected to forces perpendicular to the grain and/or tension than when under load along the grain and/or compression . The extent to which knots affect the strength of a beam depends upon their position, size, number, and condition. A knot on the upper side is compressed, while one on the lower side is subjected to tension. If there
2484-467: Is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work . The concept was originally applied solely to those materials capable of releasing chemical energy but has since also been applied to other sources of heat energy, such as nuclear energy (via nuclear fission and nuclear fusion ). The heat energy released by reactions of fuels can be converted into mechanical energy via
2576-406: Is by virtue of the heat retention properties of the ceramic shell with temperatures up to 750 °F (400 °C). Precise control of airflow (and thus temperature) afforded by the vent system means Kamado-style cookers are much like wood-fired ovens and can be used to roast and bake. Kamados may have a rotisserie cradle for crisping the skin of birds and uniform browning. Wood Wood
2668-508: Is controlled by adjusting these two vents, which in most Kamado-style cookers can be monitored through a hole in the lid. Digital temperature control devices can be installed using a small blower to regulate airflow. High-end kamados have layers of insulation that create low-airflow cooking conditions and are self-opening. Mushikamado grills are generally fueled by charcoal but may burn dry twigs, straw or wood. However, attempts have been made to fire them with gas, electricity, or pellets. One of
2760-422: Is dark colored and firm, and consists mostly of thick-walled fibers which form one-half or more of the wood. In inferior oak, this latewood is much reduced both in quantity and quality. Such variation is very largely the result of rate of growth. Wide-ringed wood is often called "second-growth", because the growth of the young timber in open stands after the old trees have been removed is more rapid than in trees in
2852-424: Is decreasing as heating technology and the availability of good quality fuel improves. In some areas, smokeless coal is often the only solid fuel used. In Ireland, peat briquettes are used as smokeless fuel. They are also used to start a coal fire. Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy , usually producing kinetic energy . They must also take
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2944-560: Is difficult to control completely, especially when using mass-produced kiln-dried timber stocks. Heartwood (or duramen ) is wood that as a result of a naturally occurring chemical transformation has become more resistant to decay. Heartwood formation is a genetically programmed process that occurs spontaneously. Some uncertainty exists as to whether the wood dies during heartwood formation, as it can still chemically react to decay organisms, but only once. The term heartwood derives solely from its position and not from any vital importance to
3036-456: Is equivalent to 44 ⁄ 12 (this is the ratio of the molecular/atomic weights) or 3.7 tonnes of CO 2 . Carbon dioxide is one of the greenhouse gases that enhances radiative forcing and contributes to global warming , causing the average surface temperature of the Earth to rise in response, which the vast majority of climate scientists agree will cause major adverse effects . Fuels are
3128-399: Is in the walls, not the cavities. Hence the greater the proportion of latewood, the greater the density and strength. In choosing a piece of pine where strength or stiffness is the important consideration, the principal thing to observe is the comparative amounts of earlywood and latewood. The width of ring is not nearly so important as the proportion and nature of the latewood in the ring. If
3220-486: Is known as secondary growth ; it is the result of cell division in the vascular cambium , a lateral meristem, and subsequent expansion of the new cells. These cells then go on to form thickened secondary cell walls, composed mainly of cellulose , hemicellulose and lignin . Where the differences between the seasons are distinct, e.g. New Zealand , growth can occur in a discrete annual or seasonal pattern, leading to growth rings ; these can usually be most clearly seen on
3312-431: Is laid down on the outside of the wood previously formed, it follows that unless a tree materially increases its production of wood from year to year, the rings must necessarily become thinner as the trunk gets wider. As a tree reaches maturity its crown becomes more open and the annual wood production is lessened, thereby reducing still more the width of the growth rings. In the case of forest-grown trees so much depends upon
3404-470: Is more complex. The water conducting capability is mostly taken care of by vessels : in some cases (oak, chestnut, ash) these are quite large and distinct, in others ( buckeye , poplar , willow ) too small to be seen without a hand lens. In discussing such woods it is customary to divide them into two large classes, ring-porous and diffuse-porous . In ring-porous species, such as ash, black locust, catalpa , chestnut, elm , hickory, mulberry , and oak,
3496-558: Is now found in the US as a Kamado-style cooker or barbecue grill . The mushikamado is a round clay pot with a removable domed clay lid and is typically found in Southern Japan. The kanji character for kamado is 竈 . The kanji character may be the best name to use when searching for information about traditional unmovable kamados. Elsewhere, the word kamado has become a generic term for ceramic or unfired-clay cookstoves. Mushikamado are made from
3588-399: Is similar to gasoline in that it is a mixture of aliphatic hydrocarbons extracted from petroleum . Kerosene is used in kerosene lamps and as a fuel for cooking, heating, and small engines. Natural gas , composed chiefly of methane , can only exist as a liquid at very low temperatures (regardless of pressure), which limits its direct use as a liquid fuel in most applications. LP gas is
3680-431: Is the rule. Some others never form heartwood. Heartwood is often visually distinct from the living sapwood and can be distinguished in a cross-section where the boundary will tend to follow the growth rings. For example, it is sometimes much darker. Other processes such as decay or insect invasion can also discolor wood, even in woody plants that do not form heartwood, which may lead to confusion. Sapwood (or alburnum )
3772-409: Is the third most commonly used motor fuel globally. Fuel gas is any one of a number of fuels that are gaseous under ordinary conditions. Many fuel gases are composed of hydrocarbons (such as methane or propane ), hydrogen , carbon monoxide , or mixtures thereof. Such gases are sources of potential heat energy or light energy that can be readily transmitted and distributed through pipes from
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3864-413: Is the younger, outermost wood; in the growing tree it is living wood, and its principal functions are to conduct water from the roots to the leaves and to store up and give back according to the season the reserves prepared in the leaves. By the time they become competent to conduct water, all xylem tracheids and vessels have lost their cytoplasm and the cells are therefore functionally dead. All wood in
3956-400: Is then known as the latewood or summerwood. There are major differences, depending on the kind of wood. If a tree grows all its life in the open and the conditions of soil and site remain unchanged, it will make its most rapid growth in youth, and gradually decline. The annual rings of growth are for many years quite wide, but later they become narrower and narrower. Since each succeeding ring
4048-461: Is usually the latewood in which the thick-walled, strength-giving fibers are most abundant. As the breadth of ring diminishes, this latewood is reduced so that very slow growth produces comparatively light, porous wood composed of thin-walled vessels and wood parenchyma. In good oak, these large vessels of the earlywood occupy from six to ten percent of the volume of the log, while in inferior material they may make up 25% or more. The latewood of good oak
4140-1006: Is widespread public debate about how carbon neutral these fuels are. Fossil fuels are hydrocarbons , primarily coal and petroleum ( liquid petroleum or natural gas ), formed from the fossilized remains of ancient plants and animals by exposure to high heat and pressure in the absence of oxygen in the Earth's crust over hundreds of millions of years. Commonly, the term fossil fuel also includes hydrocarbon-containing natural resources that are not derived entirely from biological sources, such as tar sands . These latter sources are properly known as mineral fuels . Fossil fuels contain high percentages of carbon and include coal, petroleum, and natural gas. They range from volatile materials with low carbon: hydrogen ratios like methane , to liquid petroleum to nonvolatile materials composed of almost pure carbon, like anthracite coal. Methane can be found in hydrocarbon fields, alone, associated with oil, or in
4232-401: The grain of the rest of the wood "flows" (parts and rejoins). Within a knot, the direction of the wood (grain direction) is up to 90 degrees different from the grain direction of the regular wood. In the tree a knot is either the base of a side branch or a dormant bud. A knot (when the base of a side branch) is conical in shape (hence the roughly circular cross-section) with the inner tip at
4324-429: The resin which increases the strength when dry. Such resin-saturated heartwood is called "fat lighter". Structures built of fat lighter are almost impervious to rot and termites , and very flammable. Tree stumps of old longleaf pines are often dug, split into small pieces and sold as kindling for fires. Stumps thus dug may actually remain a century or more since being cut. Spruce impregnated with crude resin and dried
4416-441: The stoichiometric ratio , the chemically correct air and fuel ratio to ensure complete combustion of fuel, and its specific energy , the energy per unit mass. 1 MJ ≈ 0.28 kWh ≈ 0.37 HPh . (The fuel-air ratio (FAR) is the reciprocal of the air-fuel ratio (AFR).) λ is the air-fuel equivalence ratio, and λ =1 means that it is assumed that the fuel and the oxidising agent (oxygen in air) are present in exactly
4508-464: The 18th century. Charcoal briquettes are now commonly used as a fuel for barbecue cooking. Crude oil was distilled by Persian chemists , with clear descriptions given in Arabic handbooks such as those of Muhammad ibn Zakarīya Rāzi . He described the process of distilling crude oil/petroleum into kerosene , as well as other hydrocarbon compounds, in his Kitab al-Asrar ( Book of Secrets ). Kerosene
4600-558: The absorption of a proton or neutron . In most stars the fuel is provided by hydrogen, which can combine to form helium through the proton-proton chain reaction or by the CNO cycle . When the hydrogen fuel is exhausted, nuclear fusion can continue with progressively heavier elements, although the net energy released is lower because of the smaller difference in nuclear binding energy. Once iron-56 or nickel-56 nuclei are produced, no further energy can be obtained by nuclear fusion as these have
4692-433: The addition of steel and bronze into construction. The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevailing climate at the time a tree was cut. Wood, in the strict sense, is yielded by trees , which increase in diameter by the formation, between the existing wood and the inner bark , of new woody layers which envelop the entire stem, living branches, and roots. This process
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#17328524630184784-418: The annual rings of growth and the amount of sapwood. Within the same species the cross-sectional area of the sapwood is very roughly proportional to the size of the crown of the tree. If the rings are narrow, more of them are required than where they are wide. As the tree gets larger, the sapwood must necessarily become thinner or increase materially in volume. Sapwood is relatively thicker in the upper portion of
4876-568: The area around modern Baku , Azerbaijan . These fields were described by the Arab geographer Abu al-Hasan 'Alī al-Mas'ūdī in the 10th century, and by Marco Polo in the 13th century, who described the output of those wells as hundreds of shiploads. With the development of the steam engine in the United Kingdom in 1769, coal came into more common use, the combustion of which releases chemical energy that can be used to turn water into steam. Coal
4968-449: The border between the two classes, forming an intermediate group. In temperate softwoods, there often is a marked difference between latewood and earlywood. The latewood will be denser than that formed early in the season. When examined under a microscope, the cells of dense latewood are seen to be very thick-walled and with very small cell cavities, while those formed first in the season have thin walls and large cell cavities. The strength
5060-458: The cell walls are composed of micro-fibrils of cellulose (40–50%) and hemicellulose (15–25%) impregnated with lignin (15–30%). In coniferous or softwood species the wood cells are mostly of one kind, tracheids , and as a result the material is much more uniform in structure than that of most hardwoods . There are no vessels ("pores") in coniferous wood such as one sees so prominently in oak and ash, for example. The structure of hardwoods
5152-435: The central portion one-fourth the height of the beam from either edge are not serious defects. Knots do not necessarily influence the stiffness of structural timber; this will depend on the size and location. Stiffness and elastic strength are more dependent upon the sound wood than upon localized defects. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to
5244-427: The claims for ceramic construction is it does not affect flavor (no metallic taste) and, for the same reasoning, lump wood charcoal produces little ash and is preferred. Mushikamado is designed to steam rice and it is used by Japanese families for ceremonial occasions. It is versatile and can be used for grilling and smoking. Flat-bread, such as pizza , can be cooked on a flat ceramic or stone tray (pizza stone). This
5336-445: The competition of the trees in their struggle for light and nourishment that periods of rapid and slow growth may alternate. Some trees, such as southern oaks , maintain the same width of ring for hundreds of years. On the whole, as a tree gets larger in diameter the width of the growth rings decreases. As a tree grows, lower branches often die, and their bases may become overgrown and enclosed by subsequent layers of trunk wood, forming
5428-433: The contrast is conspicuous (see section of yew log above). This is produced by deposits in the heartwood of chemical substances, so that a dramatic color variation does not imply a significant difference in the mechanical properties of heartwood and sapwood, although there may be a marked biochemical difference between the two. Some experiments on very resinous longleaf pine specimens indicate an increase in strength, due to
5520-600: The correct proportions so that they are both fully consumed in the reaction. Nuclear fuel is any material that is consumed to derive nuclear energy . In theory, a wide variety of substances could be a nuclear fuel, as they can be made to release nuclear energy under the right conditions. However, the materials commonly referred to as nuclear fuels are those that will produce energy without being placed under extreme duress. Nuclear fuel can be "burned" by nuclear fission (splitting nuclei apart) or fusion (combining nuclei together) to derive nuclear energy. "Nuclear fuel" can refer to
5612-593: The earliest fuel employed by humans is wood. Evidence shows controlled fire was used up to 1.5 million years ago at Swartkrans , South Africa. It is unknown which hominid species first used fire, as both Australopithecus and an early species of Homo were present at the sites. As a fuel, wood has remained in use up until the present day, although it has been superseded for many purposes by other sources. Wood has an energy density of 10–20 MJ / kg . Recently biofuels have been developed for use in automotive transport (for example bioethanol and biodiesel ), but there
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#17328524630185704-415: The end of a log, but are also visible on the other surfaces. If the distinctiveness between seasons is annual (as is the case in equatorial regions, e.g. Singapore ), these growth rings are referred to as annual rings. Where there is little seasonal difference growth rings are likely to be indistinct or absent. If the bark of the tree has been removed in a particular area, the rings will likely be deformed as
5796-403: The exact mechanisms determining the formation of earlywood and latewood. Several factors may be involved. In conifers, at least, rate of growth alone does not determine the proportion of the two portions of the ring, for in some cases the wood of slow growth is very hard and heavy, while in others the opposite is true. The quality of the site where the tree grows undoubtedly affects the character of
5888-634: The form of methane clathrates . Fossil fuels formed from the fossilized remains of dead plants by exposure to heat and pressure in the Earth's crust over millions of years. This biogenic theory was first introduced by German scholar Georg Agricola in 1556 and later by Mikhail Lomonosov in the 18th century. It was estimated by the Energy Information Administration that in 2007 primary sources of energy consisted of petroleum 36.0%, coal 27.4%, natural gas 23.0%, amounting to an 86.4% share for fossil fuels in primary energy consumption in
5980-420: The fuel itself, or to physical objects (for example bundles composed of fuel rods ) composed of the fuel material, mixed with structural, neutron moderating , or neutron-reflecting materials. Nuclear fuel has the highest energy density of all practical fuel sources. The most common type of nuclear fuel used by humans is heavy fissile elements that can be made to undergo nuclear fission chain reactions in
6072-431: The generation of renewable energy is therefore under way to help meet increased energy needs. The burning of fossil fuels produces around 21.3 billion tonnes (21.3 gigatonnes ) of carbon dioxide (CO 2 ) per year, but it is estimated that natural processes can only absorb about half of that amount, so there is a net increase of 10.65 billion tonnes of atmospheric carbon dioxide per year (one tonne of atmospheric carbon
6164-505: The grain. In some decorative applications, wood with knots may be desirable to add visual interest. In applications where wood is painted , such as skirting boards, fascia boards, door frames and furniture, resins present in the timber may continue to 'bleed' through to the surface of a knot for months or even years after manufacture and show as a yellow or brownish stain. A knot primer paint or solution (knotting), correctly applied during preparation, may do much to reduce this problem but it
6256-412: The greater the water content, the greater its softening effect. The moisture in wood can be measured by several different moisture meters . Drying produces a decided increase in the strength of wood, particularly in small specimens. An extreme example is the case of a completely dry spruce block 5 cm in section, which will sustain a permanent load four times as great as a green (undried) block of
6348-459: The highest nuclear binding energies. Any nucleii heavier than Fe and Ni would thus absorb energy instead of giving it off when fused. Therefore, fusion stops and the star dies. In attempts by humans, fusion is only carried out with hydrogen ( H (deuterium) or H (tritium)) to form helium-4 as this reaction gives out the most net energy. Electric confinement ( ITER ), inertial confinement (heating by laser) and heating by strong electric currents are
6440-407: The larger vessels or pores (as cross sections of vessels are called) are localized in the part of the growth ring formed in spring, thus forming a region of more or less open and porous tissue. The rest of the ring, produced in summer, is made up of smaller vessels and a much greater proportion of wood fibers. These fibers are the elements which give strength and toughness to wood, while the vessels are
6532-468: The main source of fuel for stars . Fusion fuels are light elements such as hydrogen whose nucleii will combine easily. Energy is required to start fusion by raising the temperature so high that nuclei can collide together with enough energy that they stick together before repelling due to electric charge. This process is called fusion and it can give out energy. In stars that undergo nuclear fusion, fuel consists of atomic nuclei that can release energy by
6624-480: The moisture content of the air) retains 8–16% of the water in the cell walls, and none, or practically none, in the other forms. Even oven-dried wood retains a small percentage of moisture, but for all except chemical purposes, may be considered absolutely dry. The general effect of the water content upon the wood substance is to render it softer and more pliable. A similar effect occurs in the softening action of water on rawhide, paper, or cloth. Within certain limits,
6716-542: The other hand, the latewood is very dense and is deep-colored, presenting a very decided contrast to the soft, straw-colored earlywood. It is not only the proportion of latewood, but also its quality, that counts. In specimens that show a very large proportion of latewood it may be noticeably more porous and weigh considerably less than the latewood in pieces that contain less latewood. One can judge comparative density, and therefore to some extent strength, by visual inspection. No satisfactory explanation can as yet be given for
6808-404: The plant overgrows the scar. If there are differences within a growth ring, then the part of a growth ring nearest the center of the tree, and formed early in the growing season when growth is rapid, is usually composed of wider elements. It is usually lighter in color than that near the outer portion of the ring, and is known as earlywood or springwood. The outer portion formed later in the season
6900-605: The point in stem diameter at which the plant's vascular cambium was located when the branch formed as a bud. In grading lumber and structural timber , knots are classified according to their form, size, soundness, and the firmness with which they are held in place. This firmness is affected by, among other factors, the length of time for which the branch was dead while the attaching stem continued to grow. Knots materially affect cracking and warping, ease in working, and cleavability of timber. They are defects which weaken timber and lower its value for structural purposes where strength
6992-452: The point of origin directly to the place of consumption. Fuel gas is contrasted with liquid fuels and from solid fuels, though some fuel gases are liquefied for storage or transport. While their gaseous nature can be advantageous, avoiding the difficulty of transporting solid fuel and the dangers of spillage inherent in liquid fuels, it can also be dangerous. It is possible for a fuel gas to be undetected and collect in certain areas, leading to
7084-509: The popular methods. Most transportation fuels are liquids, because vehicles usually require high energy density . This occurs naturally in liquids and solids. High energy density can also be provided by an internal combustion engine . These engines require clean-burning fuels. The fuels that are easiest to burn cleanly are typically liquids and gases. Thus, liquids meet the requirements of being both energy-dense and clean-burning. In addition, liquids (and gases) can be pumped, which means handling
7176-779: The process of combustion . Chemical fuels are divided in two ways. First, by their physical properties, as a solid, liquid or gas. Secondly, on the basis of their occurrence: primary (natural fuel) and secondary (artificial fuel) . Thus, a general classification of chemical fuels is: Solid fuel refers to various types of solid material that are used as fuel to produce energy and provide heating , usually released through combustion. Solid fuels include wood , charcoal , peat , coal , hexamine fuel tablets , and pellets made from wood (see wood pellets ), corn , wheat , rye and other grains . Solid-fuel rocket technology also uses solid fuel (see solid propellants ). Solid fuels have been used by humanity for many years to create fire . Coal
7268-411: The properties of the wood. Certain rot-producing fungi impart to wood characteristic colors which thus become symptomatic of weakness. Ordinary sap-staining is due to fungal growth, but does not necessarily produce a weakening effect. Water occurs in living wood in three locations, namely: In heartwood it occurs only in the first and last forms. Wood that is thoroughly air-dried (in equilibrium with
7360-468: The reverse is commonly true. Otherwise the color of wood is no indication of strength. Abnormal discoloration of wood often denotes a diseased condition, indicating unsoundness. The black check in western hemlock is the result of insect attacks. The reddish-brown streaks so common in hickory and certain other woods are mostly the result of injury by birds. The discoloration is merely an indication of an injury, and in all probability does not of itself affect
7452-575: The risk of a gas explosion . For this reason, odorizers are added to most fuel gases so that they may be detected by a distinct smell. The most common type of fuel gas in current use is natural gas . Biofuel can be broadly defined as solid, liquid, or gas fuel consisting of, or derived from biomass . Biomass can also be used directly for heating or power—known as biomass fuel . Biofuel can be produced from any carbon source that can be replenished rapidly e.g. plants. Many different plants and plant-derived materials are used for biofuel manufacture. Perhaps
7544-453: The same size will. The greatest strength increase due to drying is in the ultimate crushing strength, and strength at elastic limit in endwise compression; these are followed by the modulus of rupture, and stress at elastic limit in cross-bending, while the modulus of elasticity is least affected. Wood is a heterogeneous , hygroscopic , cellular and anisotropic (or more specifically, orthotropic ) material. It consists of cells, and
7636-494: The same type of tissue elsewhere, such as in the roots of trees or shrubs. In a living tree, it performs a mechanical-support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients among the leaves , other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, woodchips , or fibers . Wood has been used for thousands of years for fuel , as
7728-499: The shape of their container; the fumes of liquid fuels are flammable, not the fluids. Most liquid fuels in widespread use are derived from the fossilized remains of dead plants and animals by exposure to heat and pressure inside the Earth's crust. However, there are several types, such as hydrogen fuel (for automotive uses), ethanol , jet fuel and bio-diesel , which are all categorized as liquid fuels. Emulsified fuels of oil in water, such as orimulsion , have been developed as
7820-430: The tree, may well be stronger than a piece of heartwood from the same tree. Different pieces of wood cut from a large tree may differ decidedly, particularly if the tree is big and mature. In some trees, the wood laid on late in the life of a tree is softer, lighter, weaker, and more even textured than that produced earlier, but in other trees, the reverse applies. This may or may not correspond to heartwood and sapwood. In
7912-445: The tree. This is evidenced by the fact that a tree can thrive with its heart completely decayed. Some species begin to form heartwood very early in life, so having only a thin layer of live sapwood, while in others the change comes slowly. Thin sapwood is characteristic of such species as chestnut , black locust , mulberry , osage-orange , and sassafras , while in maple , ash , hickory , hackberry , beech , and pine, thick sapwood
8004-416: The trunk of a tree than near the base, because the age and the diameter of the upper sections are less. When a tree is very young it is covered with limbs almost, if not entirely, to the ground, but as it grows older some or all of them will eventually die and are either broken off or fall off. Subsequent growth of wood may completely conceal the stubs which will remain as knots. No matter how smooth and clear
8096-418: The wood formed, though it is not possible to formulate a rule governing it. In general, where strength or ease of working is essential, woods of moderate to slow growth should be chosen. In ring-porous woods, each season's growth is always well defined, because the large pores formed early in the season abut on the denser tissue of the year before. In the case of the ring-porous hardwoods, there seems to exist
8188-550: The world. Non-fossil sources in 2006 included hydroelectric 6.3%, nuclear 8.5%, and others ( geothermal , solar , tidal , wind , wood , waste ) amounting to 0.9%. World energy consumption was growing about 2.3% per year. Fossil fuels are non-renewable resources because they take millions of years to form, and reserves are being depleted much faster than new ones are being made. So we must conserve these fuels and use them judiciously. The production and use of fossil fuels raise environmental concerns. A global movement toward
8280-438: Was also produced during the same period from oil shale and bitumen by heating the rock to extract the oil, which was then distilled. Rāzi also gave the first description of a kerosene lamp using crude mineral oil, referring to it as the "naffatah". The streets of Baghdad were paved with tar , derived from petroleum that became accessible from natural fields in the region. In the 9th century, oil fields were exploited in
8372-592: Was later used to drive ships and locomotives . By the 19th century, gas extracted from coal was being used for street lighting in London. In the 20th and 21st centuries, the primary use of coal is to generate electricity , providing 40% of the world's electrical power supply in 2005. Fossil fuels were rapidly adopted during the Industrial Revolution , because they were more concentrated and flexible than traditional energy sources, such as water power. They have become
8464-409: Was the fuel source which enabled the Industrial Revolution , from firing furnaces , to running steam engines . Wood was also extensively used to run steam locomotives . Both peat and coal are still used in electricity generation today. The use of some solid fuels (e.g. coal) is restricted or prohibited in some urban areas, due to unsafe levels of toxic emissions. The use of other solid fuels as wood
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