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Microfluidic chip for performing multiphase (liquid/gas) reactions with heterogeneous catalysis. (a) Photograph of chip. This system was used for the hydrogenation of alkenes to form alkanes. The channel structures are in silicon. The heater and…

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from article Microfluidics

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from article Microfluidics

Flow profiles at a solid boundary (a) with no slip and (b) with slip.

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from article Microfluidics

Flows in microchannels. (a) Diagram of a section of a microchannel with a square cross section. (b) Flow profile of a pressure-driven flow and (c) an electroosmotic flow in a channel. The two series of fluorescent micrographs show the evolution of a…

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from article Microfluidics

Passive micromixer. (a) Section of a microchannel with grooves in the form of asymmetric herringbones on the bottom wall; the grooves lead to mixing in pressure-driven flows through the channel. One mixing cycle is made up of two regions of…

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from article Fat and oil (food)

Olive oil and other sources of healthy fats in food. Cocoa butter in dark chocolate is a mixture of fatty acids. (Credit: Lumus Photography/iStock/Getty Images)

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from article Fat and oil (food)

Refining process for fats and oils. RBD = refined, bleached, and deodorized.

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from article Air cooling

Schematic view of simple evaporative air cooler.

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from article Air cooling

Schematic of air washer.

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from article Air cooling

Typical extended-surface air-cooling coil.

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from article Air cooling

Air cooling by circulating ice-cooled water.

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from article Air cooling

Air cooling by circulating water that is cooled, in turn, by evaporation in flash tank.

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from article Hoisting machine

Mechanical advantage of pulley systems.

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from article Hoisting machine

Powered and hand winches. (a) Heavy-duty single-drum winch. (b) Wire-rope hand winch. 4500 lb = 2042 kg.

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from article Hoisting machine

Chain hand hoists. (a) Lever (ratchet). (b) Differential. (c) Worm gear. (d) Spur gear.

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from article Hoisting machine

Hoists. (a) Chain. (b) Roller chain.

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from article Hoisting machine

Four types of jib cranes. (a) Wall crane. (b) Pillar crane. (c) Movable hydraulic crane. (d) Crane truck.

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from article Hoisting machine

Basic types of overhead-traveling cranes. (a) Traveling gantry cranes. (b) Cantilever crane. (c) Top-running crane. (d) Underhung crane.

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from article Extraterrestrial intelligence

A portion of the Allen Telescope Array used by the SETI Institute in its search for extraterrestrial intelligence. (Credit: Seth Shostak/SETI Institute)

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from article Extraterrestrial intelligence

The Green Bank Telescope, which has a collecting dish area that covers more than 9300 m2. (Credit: NRAO/AUI/NSF)

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from article Extraterrestrial intelligence

The traditional Drake equation, appearing in full in the top row with its terms explained, offers a rough way to calculate the number of technologically advanced civilizations in our home galaxy, the Milky Way. The bottom row offers a variation on…

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from article Motor

Cutaway view of a single-phase motor. (Emerson Motor Division)

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from article Motor

Elements of an electric motor. (After G. McPherson and R. D. Laramore, An Introduction of Electrical Machines and Transformers, 2d ed., Wiley, New York, 1989)

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from article Motor

Disassembled universal motor. (Emerson Motor Division)

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from article Motor

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from article Motor

Comparison between a conventional synchronous motor an HTS synchronous motor.

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from article Motor

Cutaway view of 5-MW HTS motor built by American Superconductor (AMSC) for the Office of Naval Research (ONR).

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from article Motor

AMSC/ONR 5-MW HTS motor.

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from article Motor

Single-phase universal or dc motor control using half- and full-wave (ac) controls, with and without voltage feedback. (a) Half-wave circuit. (b) Full-wave circuit. (c) Half-wave circuit with voltage feedback. (d) Full-wave circuit with voltage…

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from article Motor

Half-wave and full-wave cycloconverters with graphical symbols for simplified representation. (a) Half-wave cycloconverter (exclusive of triggering of silicon controlled rectifier gates). (b) Full-wave cycloconverter (exclusive of silicon controlled…

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from article Motor

Rectifier-inverter circuitry for variable voltage/frequency control of three-phase motors. (a) Block diagram of rectifier-inverter. (b) Three-phase full-wave controlled rectifier. (c) Basic inverter dc to three-phase ac for phase-shift voltage…

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from article Motor

Speed control of wound-rotor induction motor by static variation of external rotor resistance, using a high-frequency thyristor-controlled chopper circuit.

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from article Motor

Closed-loop control of a wound-rotor induction motor by a static cascade drive system.

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from article Motor

Full-wave thyristor rectifier and autosequentially commutated current-source inverter.

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from article Motor

Closed-loop control of a squirrel-cage induction motor using a current-source inverter with a current-regulating loop and a voltage-regulating loop.

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from article Motor

Field and armature circuits of a dc motor. M = motor; Vt = terminal voltage across the armature; Ia = armature current; Ra = armature winding resistance; Rax = external resistance in armature circuit; Vf = voltage across the field; If = field…

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from article Motor

Chopper control of dc motors. (a) Symbolic representation of a chopper. (b) Basic chopper circuit. (c) Constant-frequency, variable-pulse-width waveform. (d) Variable-frequency, constant-pulse-width waveform. (e) Variable-frequency,…

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from article Motor

Single-phase converters and their quadrant operations. (a) Half-wave converter. (b) Semiconverter. (c) Full converter. (D) Dual converter. (e) Waveforms in a dc motor controlled by a single-phase half-wave converter. e = voltage at dc terminals; Ia…

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from article Sound-reproducing system

Loudspeakers influence the sound of recordings while they are being made, and then those recordings are used to evaluate other audio products, including loudspeakers. Subjective evaluation, used alone, is a flawed process.

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from article Sound-reproducing system

Some important reference sound levels relating to what is recorded and what is heard.

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from article Sound-reproducing system

Just-audible deviations in a measured frequency response when the program material is a complex orchestration in a reverberant space. From left to right are shown deviations caused by a high-Q, a medium-Q, and a low-Q resonance. The magnitudes of…

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from article Sound-reproducing system

Evolution of multichannel audio. (a) Two-channel stereophonic reproduction. (b) Quadraphonics. (c) 5.1-channel “home theater.” The larger loudspeaker symbol is a subwoofer. (d) 7.1-channel multichannel movie and music entertainment system.

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from article Chemical dynamics

Schematic of a molecular-beam experiment; the entire apparatus is under high vacuum.

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from article Chemical dynamics

Contour map of the DCl intensity. (a) Center-of-mass angular distribution of DCl from the reaction D + Cl2. (b) Angular distribution of Cl atoms from photodissociation of Cl2 molecules. Broken lines correspond to the second Cl atom.

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from article Chemical dynamics

Two-dimensional projection of CH3+ ions produced by ionizing CH3 radicals from CH3I dissociation. (Credit: Reprinted with permission from P. L. Houston, Snapshots of chemistry: Product imaging of molecular reactions, Acc. Chem. Res., 28:453–460,…

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from article Chemical dynamics

Schematic molecular-potential surfaces for ICN in the stable ground state (lower) and unstable excited state (upper). (Credit: Reprinted with permission from A. H. Zewail, Femtochemistry: Atomic-scale dynamics of the chemical bond, J. Phys. Chem. A,…

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from article Chemical dynamics

Fluorescence signals versus time delay for excitation of CN at 389.7, 389.8, 390.4, and 391.4 nm (from top to bottom). The longest wavelength excites CN when the reaction is nearly over, but the shortest excites CN when the reaction has just…

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from article Chemical dynamics

Contour plot of the potential-energy surface for the reaction F + H2 → HF + H, with a typical reactive trajectory indicated.

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from article Orion Nebula

Orion Nebula and its neighborhood. (a) Visual-wavelength view of the Orion Nebula obtained by taking a time exposure on a photographic plate with the 4-m-diameter (158-in.) telescope on Kitt Peak, Arizona (National Optical Astronomy Observatories).…

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from article Orion Nebula

Closeup view of the Trapezium stars obtained with the Planetary Camera on the Hubble Space Telescope. The field-of-view shown is 35 arcseconds of each side. Most faint stars have tails pointing away from the brightest star. These low-mass stars are…

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from article Orion Nebula

Hubble Space Telescope image showing the inner portion of the Orion Nebula in the light of doubly ionized oxygen (blue), atomic hydrogen (green) and singly ionized nitrogen (red). (C. R. O'Dell and S. K. Wong, Rice University; NASA)

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from article Orion Nebula

Hubble Space Telescope image showing closeups of several disks and ionized structures surrounding low-mass stars embedded within the Orion Nebula. The stars located near the Trapezium stars exhibit bright comet-shaped regions of gas expanding away…

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from article Petroleum products

Chemical engineer examining a petroleum sample. (Credidt: Shutterstock/Elnur)

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from article Ferroelectrics

Domain configurations (simplified) encountered in ferroelectric crystals. (a) First class. (b) Second class.

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from article Ferroelectrics

Ferroelectric domains in BaTiO3 photographed through a polarizing microscope. Ferroelectric domains range from macroscopic to submicroscopic size.

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from article Ferroelectrics

Net polarization P of a ferroelectric crystal versus externally applied electric field E.

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from article Ferroelectrics

Circuit for the display of ferroelectric hysteresis loops on an oscilloscope.

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from article Ferroelectrics

Dependence upon temperature of the spontaneous polarization of some ferroelectrics. °F = (K × 1.8) − 459.67. °C = K − 273.15.

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from article Ferroelectrics

Anomalous temperature dependence of relative dielectric constant of ferroelectrics at transition temperature. °F = (K × 1.8) − 459.67. °C = K − 273.15.

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from article Ferroelectrics

Schematic representation of the reversal of the spontaneous polarization by a mechanical shear stress T in KH2PO4 and Rochelle salt.

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from article Ferroelectrics

Crystal lattice of BaTiO3. Arrows indicate displacements of the ions when crystal becomes polarized.

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from article Ferroelectrics

Anomalous temperature dependence of relative dielectric constant of antiferroelectric crystals. Note increase as transition temperature is approached and drop when antipolarization occurs. °F = (K × 1.8) − 459.67. °C = K − 273.15.

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from article Ferroelectrics

Polarization P of antiferroelectric PbZrO3 versus externally applied electric field E. Strong fields “switch” the antiferroelectric crystal into a ferroelectric state, as shown here schematically.

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from article Micro-electro-mechanical systems (MEMS)

Silicon etching processes. (a) Isotropic etching. (b) Anisotropic crystal etching. (c) Vertical anisotropic etching.

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from article Micro-electro-mechanical systems (MEMS)

Basic surface micromachining process. (a) Thermal oxidation of silicon. (b) Silicon dioxide patterning. (c) Polysilicon deposition. (d) Polysilicon patterning. (e) Release etching of silicon dioxide to render the mechanical structure.

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from article Micro-electro-mechanical systems (MEMS)

Surface-micromachined pressure transducer.

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from article Micro-electro-mechanical systems (MEMS)

Surface-micromachined movable mirror array. (E. Garcia, Sandia National Laboratories)

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from article Micro-electro-mechanical systems (MEMS)

Torsional ratcheting actuator fabricated by surface micromachining. (a) Overview. (b) Close-up. (J. Jakubczala, Sandia National Laboratories)

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from article Micro-electro-mechanical systems (MEMS)

Magnetic 1 × 2 optical fiber switch fabricated by deep-x-ray lithography. Total device size is approximately 4 mm × 4 mm. (Henry Guckel, University of Wisconsin)

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from article Gravitational radiation

Volume rendering of the gravitational radiation generated during the merger of a binary black hole system. The red spheres represent the horizons of the black holes. The color map shows positive wave amplitudes in yellow/red and negative amplitudes…

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from article Gravitational radiation

Effect of a gravitational wave, passing in a direction perpendicular to the plane of the paper, on a ring of test particles. The ring is distorted into an ellipse, elongated in one direction in one half-cycle of the wave, and elongated in the…

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from article Gravitational radiation

Orbital decay of the binary pulsar PSR 1913+16, discovered by Russell Hulse and Joseph Taylor in 1974. Data points show the measured change in the orbit (the periastron is the minimum separation of the pulsar from the center of mass of the binary…

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from article Gravitational radiation

The gravitational-wave signal GW150914, recorded by the LIGO detectors at Hanford, Washington, and Livingston, Louisiana, on September 14, 2015. The thick orange and blue lines show the data from the Hanford and Livingston detectors, respectively,…

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from article Microwave impedance measurement

Microwave system, with complex traveling-wave amplitudes a and b that are generally used to describe the electric and magnetic fields.

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from article Microwave impedance measurement

Two-port network showing (a) the voltages and currents used in y-parameter definitions, and (b) the incident and reflected complex-wave amplitudes used in scattering-parameter definitions.

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from article Microwave impedance measurement

Directional coupler which forms the basic element of a microwave reflectometer.

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from article Microwave impedance measurement

Basic circuit for a network analyzer.

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from article Microwave impedance measurement

Geometric construction used with six-port reflectometer to determine the complex reflection coefficient from the intersection of three circles.

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from article Microwave impedance measurement

Basic circuit for a multistate reflectometer.

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from article Microwave impedance measurement

Basic elements of a time-domain reflectometer.

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from article Kirchhoff's laws of electric circuits

Circuit demonstrating Kirchhoff's current law.

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from article Kirchhoff's laws of electric circuits

Simple loop to show Kirchhoff's voltage law.

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from article Kirchhoff's laws of electric circuits

Two-loop network demonstrating the application of Kirchhoff's voltage law.

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from article Organic reaction mechanism

Potential energy–reaction coordinate diagram for a typical nucleophilic substitution reaction that proceeds by the SN 2 mechanism. Ea = activation energy.

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from article Septic tank

Section of a typical septic tank for on-site residential wastewater treatment.

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from article Alternating-current circuit theory

Direct-current circuit.

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from article Alternating-current circuit theory

Sinusoidal waveforms. (a) Simple sinusoid without phase shift (b) Sinusoid with phase shift.

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from article Alternating-current circuit theory

Phasors. (a) Simple phasor. (b) Phasor with phase shift. (c) Voltage and current phasors. (d) Phasor for the sum of two voltages.

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from article Alternating-current circuit theory

Complex numbers. (a) The number z = x + j\,y = r ejθ. (b) Its complex conjugate z* = x − j y = r ejθ. (c) Multiplication of z by ± j, equivalent to rotation through 90°.

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from article Alternating-current circuit theory