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from article Red Sea

Division of the Red Sea into regions representing different stages in the formation of an ocean basin. (After F. Martinez and J. R. Cochran, Structure and tectonics of the northern Red Sea: Catching a continental margin between rifting and drifting,…

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from article Active sound control

Results of a computer simulation of the sound field produced by two sources of spherical sound waves in air that have identical source strengths and are separated by a distance of 10 m. The sources are out of phase and radiate sound at a frequency…

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from article Active sound control

Feed-forward active noise control system. Elements of the system below the broken line are entirely digital, the filter H operating on the input sequence x to produce the output sequence y. The characteristics of the filter are designed by using the…

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from article Active sound control

Active control system for the suppression of propeller-induced aircraft cabin noise. The digital filters H1 and H2 are designed to minimize the sum of the squared error signals e1–e4.

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from article Active sound control

Distribution of sound pressure level (in decibels on an arbitrary scale) at head height in a 48-seat propeller aircraft (a) before and (b) after the use of a multichannel active noise control system consisting of 16 loudspeakers and 32 microphones.…

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from article Active sound control

Multichannel feed forward active control system for suppressing noise from multiple primary sources.

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from article Active sound control

Performance of a multichannel feed forward system for the active suppression of road-induced noise in a small passenger car at a speed of 60 km/h (37 mi/h). Reference signals were taken from six vibration sensors on the vehicle suspension. The…

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from article Deforestation

View of an area of deforestation in Central Kalimantan, Indonesia. In this case, the land is being cleared to develop areas for intensive rice production. (Credit: Australian National University)

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from article Deforestation

The relationship between forest and nonforest (other) land. Preservation of forest lands includes reforestation and natural regeneration. However, deforestation and natural events can lead to nonforest land. Afforestation (the act or process of…

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from article Deforestation

Natural forest areas (in hectares; 1 hectare = 2.47 acres) in various climatic domains (boreal/polar, temperate, subtropical, and tropical) from 1990 to 2015. The data are derived from the Global Forest Resources Assessment 2015 by the Food and…

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from article Deforestation

Former rainforest in northern Queensland, Australia, that was deforested in the early 1900s and is now used for pasture. (Credit: Rodney Keenan)

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from article Deforestation

Aerial view of deforestation in the Amazon region of Brazil. Clearing of trees in the Amazon rainforest has resulted in the elimination of natural resources and numerous species. (Credit: Luoman/Getty Images)

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from article Polaron

An electron self-trapped by the displacements of equilibrium positions of atoms that surround it.

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from article Polaron

Energy levels of quasifree and self-trapped states when the polaron is energetically stable.

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from article Polaron

Polaron mobilities versus inverse temperature.

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from article Ionic crystals

Sodium chloride lattice. The darker circles represent positive ions and the lighter circles negative ions. (After F. Seitz, The Modern Theory of Solids, Dover, 1987)

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from article Ionic crystals

Cesium chloride lattice. (After F. Seitz, The Modern Theory of Solids, Dover, 1987)

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from article Ionic crystals

Wurtzite lattice. (After F. Seitz, The Modern Theory of Solids, Dover, 1987)

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from article Ionic crystals

Zinc blende lattice. (After F. Seitz, The Modern Theory of Solids, Dover, 1987)

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from article Ionic crystals

Calcium fluoride lattice. (After F. Seitz, The Modern Theory of Solids, Dover, 1987)

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from article Ionic crystals

Rutile lattice. (After F. Seitz, The Modern Theory of Solids, Dover, 1987)

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from article Ionic crystals

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from article Basalt

Devils Postpile, Mammoth Lakes, California, United States, which formed about 82,000 years ago, is a great example of columnar basalt. (Credit: U.S. National Park Service)

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from article Basalt

Thin section of upper crust of lava about 3 cm from top; black is microcrystalline groundmass. 0.5 mm = 0.02 in.

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from article Basalt

Thin section of interior of lava shown in Fig. 1, but 7.9 m (26 ft) below the top of the flow. Clear plagioclase crystals are ophitically enclosed in large pyroxene grains up to 1 mm in diameter. Crystals of black magnetite are minor. A few…

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from article Basalt

Growth of crystals as a function of temperature in basalt in Hawaiian lava. °F = (°C × 1.8) + 32.

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from article Basalt

Diagrams illustrating the compositions of basalts in terms of normative mineral formulas. Customarily, CaAl2Si2O8 (anorthite) is grouped together with NaAlSi3O8 (albite), and Fe2SiO4, FeSiO3, and CaFeSi2O6 are grouped with the corresponding Mg…

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from article Vacuum fusion

Vacuum-fusion methods of analysis.

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from article Cohesion (physics)

Calculated pressure-volume curves for molybdenum and xenon at absolute zero. Negative-pressure portions of curves are represented by broken lines because they cannot be directly measured. 1 kilobar = 0.1 GPa; 1 Å3 = 0.001 nm3.

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from article Ordovician

Ordovician, the second period of the Paleozoic Era.

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from article Ordovician

Early Ordovician (Arenig) paleogeography, major rock suites and potential ocean surface currents; based on remanent magnetism data supplemented by plots of the positions of shelf sea carbonates and reefs.

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from article Soil chemistry

Proper soil chemistry helps a green seedling to sprout out from the soil. Soil chemistry controls the availability of plant nutrients within the soil and thus influences plant growth. (Credit: amenic181/Shutterstock)

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from article Soil chemistry

Extensive chemical weathering can remove essential minerals and elements from soil. Typically, only the most insoluble compounds remain in the soil. For example, iron oxides may persist, imparting a reddish-brown color to the soil. (Credit: Stephen…

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from article Soil chemistry

Factors influencing the chemistry of a soil solution. (Credit: Based on an original illustration created by J. F. Hodson)

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from article Walnut

Pith of two species of Juglans: (left) butternut or white walnut (J. cinerea); (right) black walnut (J. nigra). (Photo by Bill Cook, Michigan State University; Bugwood.org)

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from article Walnut

Black walnut (Juglans nigra). (Photo by D. E. Herman, North Dakota State Soil Conservation Committee, U.S. Department of Agriculture–Natural Resources Conservation Service PLANTS Database)

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from article Walnut

Fruits of black walnut (Juglans nigra). (Photo by Rob Routledge, Sault College, Sault Ste. Marie, Ontario, Canada; Bugwood.org)

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from article Walnut

English or Persian walnut (Juglans regia). (Photo by Milan Kořínek)

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from article Walnut

Kernel of English walnut (Juglans regia). (Photo by Piero Amorati, IC Croce, Casalecchio di Reno, Italy; Bugwood.org)

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from article Walnut

Walnut leaf showing symptoms of anthracnose (caused by the fungus Gnomonia leptostyla). (Photo by Pavel Šinkyřík, Czech Republic)

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from article Walnut

Canker disease (caused by the fungus Sirococcus clavigignenti-juglandacearum) on a butternut (Juglans cinerea). (Photo by Mike Ostry, U.S. Department of Agriculture Forest Service)

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from article Comparator

High-gain nonregenerative operational amplifier as voltage comparator.

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from article Comparator

Regenerative operational amplifier as comparator (Schmitt trigger). The input and output voltages are superimposed, showing hysteresis.

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from article Clover

Red clover (Trifolium pratense). (Photo by Tom Heutte, U.S. Department of Agriculture Forest Service)

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from article Clover

White clover (Trifolium repens). (Photo by Pavel Šinkyřík)

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from article Clover

Crimson clover (Trifolium incarnatum). (Photo by Pavel Šinkyřík)

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from article Clover

White sweet clover (Melilotus albus). (Photo by Forest and Kim Starr)

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from article Clover

Leaves of clover affected by leaf spot, which is caused by the fungus Pseudopeziza trifolii. (Photo courtesy of the U.S. Department of Agriculture Cooperative Extension Slide Series, Clemson University)

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from article Decision theory

Decision tree for the problem given in the text. Numbers at nodes represent time past alarm (7:00 A.M.), and numbers at branches refer to the decision mode or state of nature.

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from article Decision theory

From of a decision matrix. Oij = outcome corresponding to the interaction of a strategy (Si) and a state of nature (Nj).

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from article Decision theory

Decision tree structure to determine the subjective utility of lottery outcomes.

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from article Decision theory

Hypothetical subjective utility curves.

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from article Power shovel

Comparison of the boom, dipper handle, and dipper for (a) conventional power shovel, (b) hydraulic backhoe, and (c) hydraulic front shovel. A typical lower frame, crawlers, and machinery frame are shown for the hydraulic shovel.

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from article Magnetic materials

Identification of properties related to the magnetic hysteresis loop. Colored area is the magnetization energy lost in every cycle (hysteresis loss).

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from article Magnetic materials

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from article Magnetic materials

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from article Sewage collection systems

Various pipe shapes. (a) Round. (b) Vertically elongated (ellipse). (c) Pipe-arch. (d) Underpass. (e) Arch. (After American Iron and Steel Institute, Handbook of Steel Drainage and Highway Construction Products, 2d ed., 1971)

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from article Sewage collection systems

Band-coupled pipe joints. (a) Typical band coupling; (b) standard corrugated steel pipe band connectors; (c) band angle connector (after American Iron and Steel Institute, Modern Sewer Design, 1980). (d) Details of an O-ring compression joint for…

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from article Sewage collection systems

Diagram of a mechanical compression water stop and seal. (Link Seal, Thunderline Corp., Wayne, Michigan)

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from article Sewage collection systems

Some typical sewer manholes with standard 24-in. (61-cm) cover and frame. (a) Inside drop. (b) Outside drop. (c) Unit for a large sewer. (After R. L. Linsley and J. B. Franzini, Water Resources Engineering, 3d ed., McGraw-Hill, 1979)

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from article Sewage collection systems

Drop manhole detail. (a) Vertical section. (b) Horizontal section (A-A in part a). (After National Clay Pipe Institute, Clay Pipe Engineering Manual, 1962)

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from article Sewage collection systems

Typical house sewer connection. (After Metcalf & Eddy, Inc., and G. Tchobanoglous, Wastewater Engineering: Collection and Pumping of Wastewater, McGraw-Hill, 1981)

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from article Sewage collection systems

Typical stormwater street inlets. (a) Gutter. (b) Curb. (c) Combination; grate placed directly in front of curb opening and depressed. (d) Multiple; undepressed. (After Joint Committee of American Society of Civil Engineers and Water Pollution…

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from article Sewage collection systems

Typical catch basin with removable hood trap for cleanout. (Neenah Foundry Co., Neenah, Wisconsin)

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from article Sewage collection systems

Typical contract plan and profile sheet for sewer lateral. (a) Plan. (b) Profile; numbers on horizontal axis refer to sites with same numbers in part a. MH = manhole. Sta = Station. Inv. El. = Invert elevation. RCP = reinforced concrete pipe. S =…

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from article Sewage collection systems

Hydraulic profile for uniform flow condition, showing values at points U and D.

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from article Sewage collection systems

Hydraulic element graphs for conditions of partial flow in terms of full section. (a) Pipe-arch section. (b) Circular section. (After American Iron and Steel Institute, Modern Sewer Design, 1980)

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from article Engineering

Test firing of NASA’s 3D-printed rocket engine nozzle. 3D printing allows engineers to test new prototypes, including objects designed with multiple materials, speeding the development process and time. (Credit: NASA/MSFC/David Olive)

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from article Granite

Granite. (Credit: paylessimages/Getty Images)

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from article Granite

Classification of granitic rocks by the IUGS scheme. All proportions are by volume percentages.

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from article Turboprop

Typical turboprop configurations. (a) Fixed-turbine turboprop. (b) Free-turbine turboprop. (c) Offset-gearbox turboprop. (d) Counterrotating turboprop. (e) Unducted fan, an ungeared, counterrotating, pusher turboprop. (After R. C. Hawkins, Unducted…

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from article Turboprop

Typical turboprop installations. (a) Conventional tractor-type single-rotation turboprop (Saab Corp.). (b) Unducted fan, a pusher-type counterrotating turboprop (GE Aircraft Engines).

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from article Thermostat

Typical heat-cool thermostat. (Honeywell Inc.)

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from article Thermostat

Comparison of temperature variations using a timed on-off thermostat with and without heat anticipation.

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from article South America

Map of South America.

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from article South America

Andes Mountains, Chile. The Andes, which parallel the Pacific coast, constitute one of the Earth's most majestic features. Only the Himalayas exceed them in elevation and mass. (United Press International)

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from article South America

Representative view of the hilly uplands and low mountain country of the Guiana Highlands. One of five waterfalls on the Canaima River, Gran Sabana in southern Venezuela. (Venezuelan Information Service)

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from article South America

Uplifted beaches on desert coast, east side of San Juan Bay, Departmento de Ica, Peru. The sea cliff is about 100 ft (30 m) high. Each horizontal line represents a former beach. (Photograph by F. Atchley)

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from article South America

Port of Matarani on the desert coast of southern Peru. This oblique aerial view looks coastwise southward over one of the world's driest and most barren coastal zones. (Servicio Aerofotográfico Nacional)

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from article Quark

An illustration of two hadrons interacting to form a so-called pentaquark, an association of four quarks and one antiquark. The hadron at left is a meson composed of a quark and antiquark, while the hadron at right is a three-quark baryon. The…

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from article Quark

Depiction of the three generations of quarks. (Credit: Fermilab)

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from article Bridge

Corpus Christi Harbor Bridge, a through-arch bridge, Corpus Christi, Texas, USA. (Credit: Brian Kanof/McGraw-Hill Education)

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from article Bridge

Typical bridge elevation.

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from article Bridge

Cast-in-place concrete deck under construction. (Courtesy of Lian Duan)

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from article Bridge

A typical steel-grid bridge deck.

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from article Bridge

Typical components of orthotropic deck bridges with (a) open ribs and (b) closed ribs. (From M. S. Troitsky, Orthotropic Steel Deck Bridges, 2d ed., JFL Arch Welding Foundation, Cleveland, OH, 1987. Courtesy of The James F. Lincoln Arc Welding…

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from article Bridge