Dyson, J. F., Survey, Tex.


One can of course fabricate two-dimensional waveguides. These devices confine light in two transverse directions (x andy). An important example of two-dimensional waveguides is tlie optical fibre, which we will treat directly. Generally, two-dimensional waveguides are of tlie channel variety. An array of two-dimensional waveguide geometries is shown in figure C2.15.13. So far, we have not considered modal interactions in guides, tliat is, tlie coupling of light from one mode to anotlier, or tlie energy transfer between modes. The mode coupling of light is an important tool in optoelectronics. Altliough a full treatment of tliis process is beyond tlie scope of tliis chapter, we will describe one relatively simple device as an example and leave it to tlie reader to survey tlie references for greater detail on a wide variety of stmctures. It should be stated tliat tlie design and fabrication of tliese devices is an exciting area of current research.  [c.2867]

The ideal fractionation yields a series of sharply defined fractions, each distilling at a definite temperature. After each fraction has distilled, the temperature rises rapidly, no liquid being distilled as an intermediate fraction. If the temperature is plotted against the volume of the distillate in such an ideal fractionation, the graph obtained is a series of alternate horizontal and vertical lines resembling a staircase. A more or less sloping break reveals the presence of an intermediate fraction and the amount of such fraction can be used as a qualitative criterion of the performance of different columns. The ultimate aim in the design of efficient fractionating columns is to reduce the proportion of the intermediate fractions to a minimum. The most important factors which influence the separation of mixtures into sharp fractious are the following  [c.95]

A second important need for some guidance system lies in stray electric fields. Clearly, a sufficiently large potential arranged transversely to an ion beam can serve to deflect ions away from the intended direction. Such stray fields can be produced easily by sharp edges or points on the inside of a mass spectrometer and even more so in an ion guide itself. Considerable care is needed in the construction and design of mass spectrometers to reduce these effects to a minimum.  [c.372]

Cubic Boron Nitride (CBN) Wheels. Bonded CBN wheels were introduced to the world market in 1969 and initial reception was poor these wheels were even more expensive than diamond wheels, they were extremely difficult to tme and dress, and they had not found suitable grinding appHcations. Initially CBN was tried on such typical diamond appHcations as carbides and ceramics with very limited success. When it was tried on steel, however, it was phenomenally successfiH. CBN s extremely low wheel wear and its abHity to stay sharp lends itself to computer-aided manufacturing (CAM) (see Computer-aided design and manufacturing (cad/cam)). Japanese engineers, especiaHy, were quick to realize the production advantages in tool grinding, bearings, and auto engine parts. By 1986 Japan consumed over 5 million carats (about one-third of the world production) of CBN (49). Like diamond grit, most CBN intended for resin-bonded appHcations is coated with metal for increased grain retention.  [c.15]

Flumes. Flumes, open channels that have gradual rather than sharp restrictions, are closely analogous to venturi meters for closed pipes. Weirs are analogous to orifice plates. The flume restriction may be produced by a contraction of the sidewalls, by a raised portion of the channel bed (a low broad-crested weir), or by both. One common design is the ParshaH flume shown in Figure 11. Dimensions and capacity tables for ParshaH flumes are available (9). Flumes, widely used in measuring irrigation water, are alternatives to weirs where lower head requirements, higher capacity, and reduced sensitivity to silting are advantageous. Flumes are generally considered more expensive and less accurate than sharp-crested weirs.  [c.62]

Fracture mechanics is a methodology which characterizes the resistance of a material to crack propagation. Provided specific requirements are met, a material property can be measured which describes the performance of the material when a sharp or natural crack is present. This property is called the plane strain fracture toughness and is independent of the specimen geometry used to make the measurement. The measured fracture toughness can then be used ia the design of a component or stmcture to avoid fracture. The concepts of fracture mechanics for britde crack growth were originally proposed ia 1920 (1 3). However, it was not until World War II that the technology was substantially developed. Crack propagation problems were experienced with the Liberty ships constmcted to carry suppHes across the Atlantic ocean. Over a hundred ships fractured ia half and many others had serious cracks, lea ding to extensive research iato brittle fracture ia metals. Later, the development of nuclear power plants and other critical stmctures made accurate predictions of the fracture behavior of thick-waked metal parts essential.  [c.541]

The cross-belt separator is one of the oldest types of separators (10). The feed flows over a conveyor belt, and the magnetics are picked up by another belt perpendicular to the feed belt and moving over the sharp edged upper poles of an electromagnet. The lower poles are situated below the belts and are flat. The disk separator is a modification of the cross-belt and consists of a series of disks containing concentrating grooves and revolving above the feed belt. Electromagnets are used to magnetize the concentrating grooves by induction. This design lends itself to excellent control, sharpness of separation, and selectivity. It is capable of producing a separate middlings product.  [c.410]

The energy audit has seven components as-it-is balance, field survey, equipment tests, checking against optimum design, idea-generation meeting, evaluation, and foUow-up.  [c.94]

Some of the early design hip prostheses, created without a complete understanding of stress forces and anatomical loading characteristics of normal activity, had sharp points at the distal end and along the medial and lateral sides of the stem. Improperly seated, or merely subjected to normal forces, these stems directed concentrated stresses into the interfacing cement. This point loading resulted in cement fracturing into fragments and bone tissue suffering pressure necrosis, resulting in implant failure. More rounded prosthetic designs, and the tools and instmmentation to properly seat them, distribute the load over the widest area. This distribution mimics that of natural bone and prevents pressure necrosis.  [c.189]

The most comprehensive national survey on pesticide in pubHc and private wells has been conducted by the U.S. Environmental Protection Agency beginning in 1985 (11). The purpose of the National Pesticide Survey was both to determine the frequency and concentration of pesticides in drinking water wells nationwide, and to improve understanding of the association of the patterns of pesticide use and the vulnerabiUty of groundwater to contamination. Extensive planning went into the statistical design for the selection of sampling sites and analytical methods for this national survey. Samples were taken from 540 community water wells in all 50 states and from 752 mral domestic wells in 38 states. One hundred and twenty six pesticides and degradation/metabohc products were analyzed in this survey.  [c.214]

Transport Properties. Viscosity, themial conductivity, the speed of sound, and various combinations of these with other properties are called steam transport properties, which are important in engineering calculations. The speed of sound (Fig. 6) is important to choking phenomena, where the flow of steam is no longer simply related to the difference in pressure. Thermal conductivity (Fig. 7) is important to the design of heat-transfer apparatus (see HeaT-EXCHANGETECHNOLOGy). The viscosity, ie, the resistance to flow under pressure, is shown in Figure 8. The sharp declines evident in each of these properties occur at the transition from Hquid to gas phase, ie, from water to steam. The surface tension between water and steam is shown in Figure 9.  [c.352]

A number of good references have been pubUshed on thermoelectric energy conversion, the first in 1957 (1). A thorough survey of the field, together with information on materials properties, is also available (2), as are works on the various approaches to the analysis, design, and constmction of thermoelectric devices (3—6). The most current materials research and device design work is presented aimuaHy in two conferences the International Conference on Thermoelectrics, sponsored by the International Thermoelectric Society, and the Intersociety Energy Conversion Engineering Conference. Work on thermoelectricity takes only a few sessions of this latter conference, which is hosted on a rotating basis by seven cooperating technical societies ACS, American Institute of Aeronautics and Astronautics (AIAA), AIChE, American Nuclear Society (ANS), ASME, Institute of Electrical and Electronics Engineers (IEEE), and SAE.  [c.506]

Turbulent-Bed Design. At the higher gas velocities of the turbulent-bed regime (0.3—1.0 m/s), the distinct bubble phase disappears, and the bulk of the gas flows in a manner described as "In voids which continually coalesce and spHt tracing tortuous passages as they rise through the bed" (57). The surface of the upper bed is considerably more diffuse and has reduced pressure fluctuations and substantially higher entrainment of soflds into the freeboard region. Because of the higher coke-burning capacity requirements and improved contacting efficiency, the vast majority of commercial regenerators are operating in the turbulent-bed regime. In this configuration, the ultimate regeneration capacity is set by the sharp increase in soHd entrainment that occurs as the linear velocity approaches 1.0 m/s and the corresponding effect this air velocity has on the cyclone separation efficiency and dipleg hydraulics (58).  [c.216]

Fast-Fluidized-Bed Design. The fast-fluidized regime (1.0—3.0 m/s superficial velocity) extends into the transport phase, where a sharp increase in the rate of soflds carryover occurs as the transport velocity is approached. In the absence of any soHd recycle, the bed would rapidly disappear. Beyond this velocity, catalyst fed to the base of the regenerator travels upward in a fliUy entrained transport flow. The voidage or density of the resulting suspension is dependent not only on the velocity of the gas but also on the soHd flow rate. If the soHd rate is low, a dilute-phase flow will result. If soflds are fed to the regenerator at a sufficiently high rate, eg, by recirculating the soHd carried over back to the regenerator, then maintaining a relatively large soHd concentration is possible. This condition is referred to as the fast-fluidized bed. At superficial gas velocities substantially higher than the terminal velocity, estabhshing a high soflds concentration, even at high soflds loading (transport regime), becomes increasingly more difficult.  [c.216]

Crystallizers. The basic requirements of a system involving crystallization from solution are as foUows (/) a means of generating supersaturation ia a fashion commensurate with the requirements of produciag a satisfactory crystal size distribution, (2) a vessel to provide sufficient residence time for crystals to grow to a desired size, and (J) mixing to provide a uniform environment for crystal growth. There are numerous manufacturers of crystallization equipment ia addition, many chemical companies design their own crystallizers based on expertise developed within their organizations. Rather than attempt to describe the variety of special crystallizers that can be found ia the marketplace, this section provides a brief general survey of types of crystallizers that use the modes outlined above. Greater detail can be found ia the Hterature (68,69).  [c.356]

D. R. Cox, P/anning of Experiments,]ohxi Wiley Sons, Inc., New York, 1958. This book provides a simple survey of the principles of experimental design and of some of the most usehil experimental schemes. It tries "as far as possible, to avoid statistical and mathematical technicalities and to concentrate on a treatment that will be intuitively acceptable to the experimental worker, for whom the book is primarily intended." As a result, the book emphasizes basic concepts rather than calculations or technical details. Chapters are devoted to such topics as "Some key assumptions," "Randomization," and "Choice of units, treatments, and observations."  [c.524]

Site Selection Factors that must be considered in evaluating potential solid-waste-disposal sites are summarized in Table 25-71. Final selection of a disposal site usually is based on the results of a preliminary site survey, results of engineering design and cost studies, and an environmental-impact assessment.  [c.2252]

B. V. Deijaguin and Z. M. Zorin, Proc. 2nd Int. Congr. Surf. Act., London, 1957, Vol. 2, p. 145.  [c.387]

PiirtDesign. Eor optimum economics and production cycle time, wall thicknesses for ABS parts should be the minimum necessary to satisfy service strength requirements. The typical design range is 0.08 to 0.32 cm, although parts outside this range have been successfliUy molded. A key principle that guides design is avoiding stress concentrators such as notches and sharp edges. Changes ia wall thickness should be gradual, sharp corners should be avoided, and generous radii (25% of the wall thickness) used at wall iatersections with ribs and bosses. To avoid sinks, rib thickness should be between 50 and 75% of the nominal wall. Part-strength at weld lines can be diminished thus welds should be avoided if possible or at least placed ia aoacritical areas of the part (135). Because of polymer orieatatioa, properties such as impact strength vary from poiat to poiat oa the same part and with respect to the flow direction (121). Locations of highest Izod impact strength can be poiats of lowest dart impact strength because of the degree and direction of orientation. ABS suppHers can provide assistance with design of parts upon iaquiry and through design manuals (136). There are a number of special considerations when designing parts for metal plating to optimize the plating process, plate deposition uniformity, and final part quaHty (137). ABS parts can be also designed for soHd—soHd or soHd—foam co-iajection mol ding (138) and for gas-assisted-iajection mol ding (139).  [c.206]

Predictable forms of weirs have been developed that are classified according to the shape of the notch. The discharge of each type can be deterrnined from tables (8) or by actual flow caUbration. Selection of weir type is dependent on the nature of the appHcation. A broad-crested rectangular notch (Fig. 10a) allows streamline development to pass most floating debris and works at lower heads than a sharp-crested weir. Triangular, sharp-crested weirs (Fig. lOd) provide maximum flow range but do not transport floating material. The trape2oidal notch (Fig. 10c) is a combination of the rectangular and triangular forms. In the Cippoletti design, the slope of the ends has a value so that the additional discharge through the triangular portions of the notch exactly compensates for the effects of end contractions. Special forms of notches can be constmcted to simplify the flow head relationship. Figure lOf shows one such form.  [c.62]

Land Availability. The availability of sufficient land suitable for production of land-based biomass can be estimated for the United States by several techniques. One method rebes on the land capabiUties classification scheme developed by the U.S. Department of Agriculture (69), in which land is divided into eight classes. Classes I to III are suited for cultivation of many kinds of crops Class IV is suited only for limited production and Classes V to VIII are useful only for permanent vegetation such as grasses and trees. The U.S. Department of Agriculture surveyed nonfederal land usage for 1987 in terms of these classifications (70). Out of 568 million hm, which corresponds to 60% of the 50-state area, 43% of the land (246.3 x 10 hm ) was in Classes I to III, 13% (75.59 x 10 hm ) in Class IV and 43% (246.3 x 10 hm ) in Classes V to VIII. The actual usage of this land at the time of the survey is shown in Table 25 (70). Table 25 illustrates that of all the land judged suitable for cultivation in Classes I to III, only about one-half of it is actually used as cropland (70), and that the combined areas of pasture, range, and forest lands is about 66% of the total nonfederal lands. There is ample opportunity to produce biomass for energy applications on nonfederal land not used for foodstuffs production. Large areas of land in Classes V to VIII not suited for cultivation, and sizable areas in Classes I to IV not being used for crop production, also would appear to be available for biomass energy applications land used for crop production could be considered for simultaneous or sequential growth of biomass for foodstuffs and energy. Portions of federally owned lands, which are not included in the survey, might also be dedicated to biomass energy applications. Careful design and management of land-based biomass production areas could result in improvement or upgrading of lands to higher land capabiUty classifications.  [c.33]

Scanning Tunneling Microscopy. As of 1995, there are at least two dozen different microscopes based on a very tiny probe that is able to scan a surface at resolutions down to single-atom levels. AH have been developed since 1980, and most after 1985. The proliferation, improvement, and commercialization continues unabated. Only the neat-field scanning optical microscope (NSOM) among the probe instmments uses a light beam, but it dehvets an enlarged image, hence qualifying as a microscope. Many of them ate capable of imaging single atoms. The eadiest of these, the scanning tunneling microscope (STM), was invented in 1981 by IBM (Zbtich) (27). It involves a very sharp Pt—It or W tip scanned only a few tenths of a nm above a conducting surface with a smaH tunneling current. The distance is kept constant by piezoelectric scanning, with an electronic feedback loop to maintain a  [c.332]

Lavoisier checked Ptiesdey s work and recognizing that air contains mainly two gases, named one vital air and the other azote (nitrogen), the latter not supporting life. Later, vital air became oxygen, from the abiUty to form acids ox, ie, sharp (taste) 2in.dgen, to form. In 1777, Lavoisier developed the theory of combustion. His ideas became widely estabhshed and were firmly fixed by his textbook, Ixi Traitu Elumentaire de Chemie (2).  [c.475]

Resolution of Optical Isomers), Gakkai Shuppan Senta, Tokyo, Japan, 1989, Chapt. 11, pp. 132—143 Chiral HPLC columns are available from Regis, Spelco, and AST in the United States Merck, Nagel, and Serva in Germany LKB in Sweden and Daisem, Sumitomo, and Toso in Japan.  [c.298]

In 1974 a prosthesis introduced by Howmedica combined a biomechanicaHy high strength material, VitaHum, with a professionally engineered geometry. This prosthesis marked the first design departure from the diamond-shaped cross-sectional geometry previously used. Sharp corners were eliminated and replaced by broad, rounded medial and lateral borders. The total sectional area was much greater than any of the previous hip joint implant stems. The result of these combined factors was decreased unit stresses on the cement mantle. This system also marked the first time surgeons could choose components from a selection large enough to provide fit for most primary and revision total hip replacement patients.  [c.188]

In another elongational rheometer (221), the specimen is suspended on the end of a flexible tape, which is wound onto a wheel turned by a servo-controUed torque motor. This design is the basis for the Gottfert Rheostrain instmment, with which strain rates of 5 x 10 to 2 ate possible.  [c.192]

For mass loadings, particulate matter is withdrawn isokinetically and collected on a glass fiber filter maintained at 120 4° C. The appropriate sampling train is illustrated in Figure 8 (13). The sample no22le is made of stainless steel having a sharp pointed leading edge. The taper is on the outside to provide a constant internal probe diameter. The probe is usually of a buttonhook or elbow design in order to meet alignment requirements. The first two impingers contain a known amount of water, the third is usually empty, and the last contains siUca-gel. Particulate matter, present as soHd or Hquid at the sampling temperature, is collected on a preweighed filter and deterrnined by weighing. Organic condensable matter is collected in the water, extracted with chloroform and then ether, and weighed after evaporation to dryness. The water is also evaporated to dryness and the residue reported as inorganic condensable matter. Particulates are sometimes present in Hquid rather than soHd form, eg, as acid mists (14). An alternative system is available for high volume sampling (15).  [c.301]

Matenals most resistant to detenoration ate chosen, the strength and available shapes of which have a cntical influence upon design. Crevices, areas where water can collect, and sharp edges ate to be avoided, and dissimilat metals must be electrically isolated from one another in order to prevent corrosion of the mote anodic metal. Sharp edges cause paint to draw thin and should be removed by grinding or sanding. Welds have sharp projections that should be removed by grinding. Weld spatter should be scraped or ground from metal surfaces. Outside corners should be rounded, and inside corners should be filled because they provide a collection site for excess paint that may not fully cute. Crevices and pits should be filled with weld metal or caulking because they collect corrosive agents and accelerate deterioration.  [c.363]

The condensate stripper bottoms and the deethanizer bottoms are processed in the depropanizer for a sharp separation of hydrocarbons and and heavier hydrocarbons. The reboiler and tower internals are routinely fouled by nihherlike polymers, and require periodic mechanical cleaning. To minimize this problem, two types of designs are used. In the first design, the bottoms temperature is set low, which results in an operating pressure requiring propylene refrigerant instead of cooling water for the condensation of the overhead product. In the second design, cooling water is used, and a high bottom temperature is required. The latter requires a full spare tower and reboder for continuous operation while the former requires only a spare reboder. A two-tower system is also used to provide the benefits of both approaches, ie, low fouling and low refrigeration, but this option is somewhat more cosdy.  [c.441]

Figure 9-9 shows the cash-flow stages in a project. The expenditure during the research and development stage is normally relatively small. It will usually include some prelimiuaiy process design and a market survey. Once the decision to go ahead with the project has been taken, detailed process-engineering design will commence, and the rate of expenditure starts to increase. The rate is increased still further when equipment is purchased and construction gets under way. There is no return on the investment until the plant is started up. Even during startup, there is some additional expenditure. Once the plant is operating smoothly, an inflow of cash is established. During the early stages of a project, there may be a tax credit because of the existence of expenses without corresponding income.  [c.811]

In this case, no end corrections are apphed even though the formula apphes only for sharp-edged weirs. See Schoder and Dawson, Hydraulics, McGraw-Hill, New York, 1934, p. 175, for further details.  [c.898]

Aluminum alloy, copper, copper alloy, nickel, nickel alloy, unalloyed titanium 5(3. No ad(htional requirements. 5fc. No ad(htional requirements except that when the composition of the filler metal is outside the range of composition for the base metal, testing shall be in accordance with column B, item 5. 5. Low-temperature tests such as tensile elongation and sharp-notch tensile strength (compared with unnotched tensile strength) shall have been conducted to provide assurance to the designer that the material and the deposited weld metal are suitable at the design minimum temperatures.  [c.1006]

Vessel Codes Other Than ASME Different design and construction rules are used in other countries. Chemical engineers concerned with pressure vessels outside the United States must become familiar with local pressure-vessel laws and regulations. Boilers and Pressure Vessels, an international survey of design and approval requirements published by the British Standards Institution, May-lands Avenue, Hemel Hempstead, Hertfordshire, England, in 1975, gives pertinent information for 76 political jurisdic tions.  [c.1028]

In some cases, with relatively cold inlet condenser water it has been possible to adjust automatically the steam inlet pressure in response to chilled-water outlet temperatures. In general, however, this type of control is not possible because of the differences in temperature between the flash tank and the condenser. Under usual conditions of warm condenser-water temperatures, the main ejec tors must compress water vapor over a relatively high ratio, requiring an ejector with entirely different operating characteristics. In most cases, when the ejec tor steam pressure is throttled, the capacity of the jet remains almost constant until the steam pressure is reduced to a point at which there is a sharp capacity decrease. At this point, the ejec tors are unstable, and the capacity is severely curtailed. With a sufficient increase in steam pressure, the ejectors will once again become stable and operate at their deign capacity. In effect, steam jets have a vapor-hanming capacity fixed By the pressure at the suction inlet. In order for the ejec tor to operate along its charac teristic pumping curve, it requires a certain minimum steam flow rate which is fixed for any particular pressure in the condenser. (For further information on the design of ejec tors, see Sec. 6)  [c.1123]

Wet Classifiers Closed-circuit wet milling is the rule in large-scale operations because of its greater production and economy, The simplest wet classifier is a settling basin arranged so that the fines do not have time to settle but are drawn off while the thickened coarse product is raked to a central discharge. Examples are the Hardinge Hydro-Classifier and the Dorr thickener. For classification near micrometer size a continuous centrifuge such as the Sharpless siiper-centrifiige or the Bird centrifuge is effective. The separation is not sharp in settlers, and the large space requirement is a detraction. Rake classifiers and screw classifiers are described in Sec, 21, The action is countercurrent, so separation of coarse grains is more effective. Examples are the Hardinge countercurrent (screw) classifier (Fig, 20-42) and the Dorr-Oliver rake classifier (Fig, 20-43), Typical circuits used with these classifiers in cement- and ore-processing plants are shown in Figs, 20-43 and 20-44, Hydrocyclones have Become the most popular wet classifiers in ore operations owing to their compact design and economy of operation. Control is effected by feeding at a constant rate from a sump, in which the hqiiid level is maintained by varying water addition as the slurry feed rate varies (see Fig, 20-45),  [c.1858]

Another factor of importance in dielectrofiltration is the need to have the DEP effect firnoly operative upon all portions of the fluid passing through. Oversight of this factor is a most common cause of incomplete dielectrofiltration. Good dielectrofilter design will emphasize this crucial point. To put this numerically, let us consider the essential field factor for DEP force, namely V( Eo) . Near sharp points, e.g., E, the electric field varies with the radial distance r as E hence our DEP force factor will vaiy as V(E) / In the neigh-  [c.2012]


See pages that mention the term Dyson, J. F., Survey, Tex. : [c.479]    [c.134]    [c.287]    [c.439]    [c.2]    [c.273]    [c.555]    [c.62]    [c.145]    [c.1408]    [c.1430]    [c.2346]    [c.134]    [c.271]   
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