Dysonian electrical conductivity


For conductive particles smaller than 1 pm, equation 19 should be multiphed by the Cunningham correction factor, (1 + A jDf). For air at room temperature, the molecular mean free path, X, is 0.1 pm, and is 1.72. If the particles to be collected are not electrically conductive, equation 19 should be multiphed by [1 + 2 b — 1/6 + 2)] to correct for the dielectric constant of the material. Equation 19 can be used to predict the relative effect of changes in particle size distribution, gas viscosity, and operating voltage on migration velocity and precipitator efficiency. An interval-integration procedure may be used to calculate average migration velocity for a given particle size distribution, although more often, an average migration velocity is measured experimentally in an existing precipitator for a similar dust. Average migration values are sometimes referred to as drift velocities to distinguish these values from migration velocities which should be related to specific particle sizes. Table 9 fists drift velocities encountered in typical commercial precipitators. Because of the demand for higher efficiency precipitators, drift velocities from less efficient ones must be adjusted for design utilization. To achieve higher  [c.400]

Fluid Properties. A great variety of equipment exists for measuring clean, low viscosity, single-phase fluids at moderate temperatures and pressures. Fluid-related factors that are normally considered are operating pressure, temperature, viscosity, density, corrosive or erosive characteristics, flashing or cavitation tendencies, and fluid compressibiHty. Any extreme fluid characteristic or condition, such as a corrosive nature or high operating temperature, gready reduces the range of available equipment and should be given first consideration in any selection procedure. Other fluid properties important for use of certain meter types are heat capacity, an important consideration for thermal meters, and fluid electrical conductivity, requited for magnetic flow meter operation. In some cases particular fluid requirements may limit the metering choices. An example of this is the requirement for the sanitary design of meters used in food processing (qv).  [c.55]

The function of the MHD combustor is to process fuel, ie, coal oxidizer, ie, preheated air, possibly enriched with oxygen and seed to generate the high temperature electrically conducting working fluid requited for the MHD channel. There are several design requirements (/) highly efficient combustion, ie, high carbon conversion and low heat losses, in order to achieve the temperature (2800—3000 K) required for adequate electrical conductivity (2) innovative wall designs capable of extended life, to contain 500—1000 kPa (5—10 atm) of pressure in the presence of molten slag, seed, and heat fluxes up to 50 W/cm (J) spatially and temporally homogeneous output flow, requiring sophisticated aerothermodynamic design (4) low pressure drop through the combustor, because this directly affects the net power output of the MHD topping cycle (5) effective seed utilization, which means minimizing slag—seed interactions which remove seed from the gas, and attaining uniform seed dispersion (6) electrical isolation of the combustor and its ancillary systems at voltages of 20—40 kV below ground potential, because of the electrical contact of the combustor with the MHD channel (this is particularly challenging for the slag-rejection system) and (7) efficient slag rejection, up to 50 70% of the ash content of the coal burned, as low slag rejection (high ash carry-over) increases seed recovery costs. These design requirements differ sufficiently from those of conventional coal combustors so as to require essentially new technology for the development of MHD coal combustors.  [c.427]

Structural Influence on Optical Properties. Since the formation of these types of charge carriers is essential for electrical conductivity in conjugated organic polymers, an important factor in the stmctural design of conducting polymers is the ease with which they can be oxidized or reduced. The ionization potential of a class of conducting polymers can be altered by modification of the chemical stmcture. Substitution of the polymer with electron-donating groups has been shown to lower the ionization potential for -type doping. The increased electron density along the conjugated system allows for easier removal of electrons during oxidation.  [c.42]

Conductivity. Electrical conductivity is important and should be arranged to be as high as possible. Energy losses and the consequent heating of electrode and electrical connectors are to be avoided. Eor cell design usiag a monopolar electrode configuration, pure electrode materials requite a resistivity of less than Hem (26). This helps not only to avoid energy losses, but also to maintain a uniform current distribution (26,32). Because it iavolves only short current paths through the electrode materials, bipolar design is better for more resistive electrodes such as oxides and conductive polymers.  [c.87]

Design of treatment/recovery Electrical conduction  [c.538]

The toughness of a material is a design driver in many structures subjected to impact loading. For those materials that must function under a wide range of temperatures, the temperature dependence of the various material properties is often of primary concern. Other structures are subjected to wear or corrosion, so the resistance of a material to those attacks is an important part of the material choice. Thermal and electrical conductivity can be design drivers for some applications, so materials with proper ranges of behavior for those factors must be chosen. Similarly, the acoustical and thermal insulation characteristics of materials often dictate the choice of materials.  [c.390]

Other examples exist where different factors on the list of material selection factors in Figure 7-20 are the design drivers. However, at the time of the initial applications of advanced composite materials, the main issues were simply strength and stiffness. Perhaps a fatigue-life issue could be more important in some applications. Some applications are made despite some disadvantages for composite materials in some of these material selection factors. For example, the electrical conductivity of graphite-epoxy is not sufficient when designing an aircraft subject to a lightning strike (as are all aircraft). All parts of an aircraft must be able to dissipate the electrical charges of lightning strikes. Thus, some supplementary material or electrically conductive material systems must be added to the graphite-epoxy in order to provide the aircraft with appropriate lightning-resistant characteristics.  [c.391]

The toughness of a material is a design driver in many structures subjected to impact loading. For those materials that must function under a wide range of temperatures, the temperature dependence of the various material properties is often of primary concern. Other structures are subjected to wear or corrosion, so the resistance of a material to those attacks is an important part of the material choice. Thermal and electrical conductivity can be design drivers for some applications, so materials with proper ranges of behavior for those factors must be chosen. Similarly, the acoustical and thermal insulation characteristics of materials often dictate the choice of materials.  [c.390]

Other examples exist where different factors on the list of material selection factors in Figure 7-20 are the design drivers. However, at the time of the initial applications of advanced composite materials, the main issues were simply strength and stiffness. Perhaps a fatigue-life issue could be more important in some applications. Some applications are made despite some disadvantages for composite materials in some of these material selection factors. For example, the electrical conductivity of graphite-epoxy is not sufficient when designing an aircraft subject to a lightning strike (as are all aircraft). All parts of an aircraft must be able to dissipate the electrical charges of lightning strikes. Thus, some supplementary material or electrically conductive material systems must be added to the graphite-epoxy in order to provide the aircraft with appropriate lightning-resistant characteristics.  [c.391]

The thermal conductivity, k, varies considerably for different kinds of matter. On an order-of-magni-tude basis, gases will typically have a conductivity range from 0.01 to 0.1 W/(m-K) (0.006 to 0.06 Btu/h-ft-°F), liquids from 0.1 to 10 W/(m—K) (0.06 to 6 Btu/h-ft-°F), nonmetallic solids from 0.1 to 50 W/(m—K) (0.06 to 30 Btu/h-ft-°F), and metallic solids from 10 to 500 W/(m-K) (6 to 300 BtuAi-ft-°F). Obviously, gases are among the lowest conductors of thermal energy, but nonmetallic materials such as foamed plastics and glass wool also have low values of thermal conductivity and are used as insulating materials. Metals are the best conductors of thermal energy. There is also a direct correlation between thermal conductivity and electrical conductivity—that is, the materials that have a high thermal conductivity also have a high electrical conductivity. Conductive heat transfer is an important factor to consider in the design of buildings and in the calculation of building energy loads.  [c.612]

Molybdenum shows good corrosion resistance to zirconia up to 2000° C but above about 1200°C, zirconia becomes electrically conductive and thus care must be taken in the design of high temperature furnaces using zirconia  [c.849]

Over one million air-blown gasifiers were built during World War II to manufacture LHV gas to power vehicles and to generate steam and electric power. Units are available in a variety of designs, some of which have been retrofitted to gas-fired furnaces. Although some research is in progress to refine air-blown wood gasifiers in North America, particularly portable units, most of the research has been conducted in Europe. The Swedish automobile manufacturers, Volvo and Saab, have ongoing programs to develop a standard gasifier design suitable for mass production.  [c.46]

In addition to selecting compatible metals or electroplates for use with magnesium assembhes, there are several other methods of controlling galvanic corrosion of magnesium parts. One method is to electricady isolate the magnesium component from the cathodic material. In many appHcations, however, this is not a practical alternative due to the mechanical, electrical, or cost requirements. Another alternative is to paint the cathodic material. This provides a barrier against electrolyte contact with the cathode. However, this is not easdy accompHshed in many cases because of the permeabdity of coatings by moisture and the generation of hydrogen and hydroxyl ion [14280-30-9] on the cathode surface. The combined effect is to strip ad but the most alkah-resistant coatings. A third possibdity is a design which prevents pooling of the electrolyte in critical areas of fasteners and interfaces with other cathodic components. This is an effective method of control since it both limits the electrolyte resistance and the duration of its presence because thin films of an aqueous electrolyte have both lower conductivity and higher rates of drying, so that the time of conductivity is minimised in appHcations where exposure to electrolytes is an intermittent event. A final alternative is to use compatible shims or washers in association with joints and fasteners. This control technique works wed where exposure to the electrolyte is again intermittent and surfaces are wed drained. By using a shim or washer that extends 3—6 mm beyond the interface of the cathodic material with the magnesium surface, the electrolyte path is extended to a range where the resistance of typical aqueous salt water electrolytes is sufficiendy high to significantly retard the electrochemical activity. This compatible material may be a nonconductive ceramic, a polymeric material, or a compatible metal, such as an aluminum 5052 or 6061 adoy. The use of an aluminum washer beneath the head of a steel fastener that extends 3—6 mm beyond the radius of the bolt head is a simple effective method of control of the galvanic attack associated with fasteners in magnesium (132—135).  [c.334]

The anisotropy, usually observed in graphite products, is estabUshed in the forming operation. In extmded products, the anisotropic coke particles orient with thek long dimensions parallel to the extmsion dkection. The layer planes of the graphite crystals are predominandy parallel to the long dimension of the coke particle. Accordingly, the highly anisotropic properties of the single crystal are translated, to a greater or lesser degree depending on several factors, to the graphite product. The most important of these factors are coke type, particle size, and the ratio of die-to-mud chamber diameters. The more needlelike the coke particle, the greater the difference is between properties with-grain (parallel to the extmsion dkection) and cross-grain. The use of smaller particles in the mix design also increases this property difference the presence of large particles interferes with the alignment process. As the ratio of mud cylinder-to-die diameter increases, the with-grain to cross-grain ratios of strength and conductivity increase, whereas the with-grain to cross-grain ratios of resistivity and expansion coefficient decrease. Thus anisotropy is increased for the same coke type and mix design when going from a 600 mm diameter die to a 400 mm diameter die on the same extmsion press. As a result of particle orientation in extmded graphitized products, strength. Young s modulus, and thermal conductivity values are greater whereas, electrical resistivity and coefficient of thermal expansion are smaller ki the with-grain dkection than in the two cross-grain dkections.  [c.503]

Electrochemical sensors operate on the principle of controlled change of some electrical parameter, e.g. conductivity, current or voltage, caused by the change of the chemical environment. Specifically, in electrochemical gas sensors the change of conductivity or work function is measured in response to the change of partial pressure of the analyte. Selectivity of the interaction with the analyte in any given application is usually the most important figure of merit for design of a new sensing material. Other parameters that are important for defined practical applications are speed of response and longterm stability. In that respect we have investigated modification of organic semiconductors with room temperature ionic liquids, co-polymerization with polyelectrolytes, grafting and irradiation induced crosslinking to obtain improved performance of solid state sensors based on conjugated conducting polymers.  [c.296]

Type tests are conducted on the first enclosure of each voltage, current rating and fault level to demonstrate compliance with electrical and constructional design parameters. The tests provide a standard reference for any subsequent enclosure with similar ratings and constructional details. The following tests may be conducted to demonstrate verification of the following  [c.421]

Type tests arc conducted on the first assembly (bus system) of each voltage, current rating and fault level to demonstrate compliance with the electrical and constructional design parameters. The tests provide a standard reference for any subsequent assembly with similar ratings and constructional details. Tlie following tests are conducted  [c.953]

The first commercially available rf GD sources were based on the Grimm design concept, and enabled both rf and dc operation if parts of the source were interchanged. A leading instrument manufacturer recently introduced a dedicated rf source designed by Marcus [4.180]. The Marcus-type source is operated at pressures similar to those of dc discharge sources but the essential characteristic is the conventional 13.56 MHz radio frequency power applied to the back of the sample by an impedance-matching device. Eor proper operation the sample must be electrically isolated from all metallic parts of the source and ancillary components to reduce rf radiation and conduction losses. In this way the sample no longer acts as the cathode, and the second electrode or counter-electrode (corresponding to the anode in the dc device) is no longer a tube but is represented by the metallic walls of the discharge chamber. The sample area exposed to the discharge is confined by an orifice disk and is much smaller than the counter-electrode, thereby ensuring most of the drop in rf potential occurs at the sample so that no significant sputtering of the counter-electrode occurs.  [c.223]

Joint design must ensure a variety of service criteria such as joint mechanical strength resistance to service environment electrical conductivity, which is of prime importance in soldering of electrical circuitries ease of manufacturing and economics. Compatibhity of the parts to be joined (BM) with the forming braze (FM) is always considered from minimiza tion of mechanical stresses, which may appear after brazing/soldering owing to the difference in coefficient of thermal expansion that always exists between the BM and the FM. These stresses may be very high. Specifics of joint design are avahable for brazing (2) and for soldering of electronic components (1).  [c.246]

Evidence for these species and the associated equilibria comes from a variety of techniques such as vibration spectroscopy, nmr spectroscopy, molecular-weight determinations, radioisotopic exchange using Mg, electrical conductivity, etc. In some cases equilibria can be displaced by crystallization or by the addition of complexing agents such as dioxan (p. 131) or NEt3. The crystal structures of several pertinent adducts have recently been determined (Fig. 5.11). None call for special comment except the curious solvated dimer [EtMg2Cl3(OC4H8)3]2 which features both 5-coordinate trigonal bipyra-midal and 6-coordinate octahedral Mg groups note also that, whilst 4 of the Cl atoms each bridge 2 Mg atoms, the remaining 2 Cl atoms are triply bridging.  [c.132]

THE STATE OF NITRIC ACID IN INERT ORGANIC SOLVENTS The absence of ions in mixtures of acetic acid and nitric acid is shown by their poor electrical conductivity and the Raman spectra of solutions in acetic acid, nitromethane, and chloroform show only the absorptions of the solvent and molecular nitric acid the bands corresponding to the nitronium and nitrate ions cannot be detected. -Although no chemical reaction occurs, measurements of the freezing point and infra-red spectra show that nitric acid forms i i molecular complexes with acetic acid , ether and dioxan. In contrast, the infrared spectrum of nitric acid in chloroform and carbon tetrachloride - is very similar to that of nitric acid vapour, showing that in these cases a close association with the solvent does not occur.  [c.32]

These containers are commonly of a two-piece design body plus end. The body is made from aluminium or tinplate by drawing from a disc and then wall-ironing to stretch and smooth the metal further. The coating is applied by airless spray into the revolving body and must protect the metal from attack by contents which are often acidic. However, once the end is sealed in place, the pack is under carbon dioxide pressure and virtually anaerobic. Under these conditions it has been found that satisfactory protection is obtained from 3-4/tm of a waterborne acrylic-modified epoxy resin clear coating on aluminium. On tinplate, the wall ironing exposes a high proportion of steel and higher coat weights are needed 5 /tm for beer and up to 11 /tm for soft drinks. Coatings must be completely continuous and lacquers are tested for pinholes in an electrical conductivity test. Drying is by con-vected hot air 3 min in the oven, with one minute at the peak temperature around 200°C.  [c.633]

Shields. Power cable (conductor) shields provide a smooth, continuous, conductive, and isopotential interface between the conductor and insulation (Eig. 5). The geometry of the conductor strands permits air gaps between the outer wires of the stranded conductor and the inner surface of the extmded insulation. Without a stress control layer, excessive electric gradients can cause partial discharges within these gaps that harm the insulation. There are two design approaches most shields are either semiconductive shields that use large amounts of carbon black mixed in polymeric-based formulations, or stress-reheving shields that are based on materials with high dielectric constant. Brand names for the latter are Permashield or Emission Shield.  [c.329]

Integrated Topping Cycle. The objective of the integrated topping cycle program was to build and test, for a total of 1000 hours, an integrated coal-fired MHD flow train consisting of a combustor, no22le, channel, associated power conditioning equipment, and diffuser. The flow train and the operating conditions are intended to be prototypical of hardware for commercial plants, so that design and operating data can be used to project component performance, lifetime, and reUabiUty in commercial plants. The flow train operated at 50 MW. The program was conducted by a team led by TRW, Inc., and included Textron Defense Systems and Westinghouse Electric Corp. The integrated topping cycle operation followed an earlier program of component testing at the CDIF, and concluded in 1993, when program binding was terrninated, with over 500 hours of accumulated operating time, of which over 300 hours were at design power-generating conditions (152,153).  [c.436]

Much research involving monitoring of thermal effects at power stations was conducted ia the 1970s and 1980s. The increased knowledge gained and more stringent regulations led to approaches for using biological requirements of aquatic organisms plus local environmental characteristics of the rivers, lakes, and estuaries used for cooling to design nondamaging cooling systems specific for a site. Because the rate of increase in demand for electricity and development of new generating stations also diminished, new power plants were evaluated more thoroughly and located in less susceptible environments. Approaches for regulatory thermal power stations that evolved by the mid-1980s were still in practice as of 1997 (see Power generation).  [c.472]

If used for flammable liquid spills, which might involve a second phase such as spill control granules or debris, these pose numerous design problems including static, electrical classification, chemical compatibility and industrial hygiene relative to the exhaust. Commercial designs for Class I Group D gas and Class II Groups E-G dust atmospheres are typically air operated via a venturi, so contain no electrical drives. Hoses both for air supply from a grounded air supply outlet, and for liquid recovery, are conductive with additionally static dissipative hose fabric (about 10 2-m). Eilters are also static dissipative. The design is such that all parts are continuously bonded and grounded. Normally the ground continuity is established at prescribed check points before each use. Eloat or similar mechanisms are employed to cut off suction once the recovery tank has reached capacity level, although additional precautions may be needed to avoid overflow via either siphoning (if the recovery hose is completely submerged in liquid) or if defoaming agents are not used where appropriate. Eor flammable liquid spills in particular, measures should be taken to ensure personnel are not a source of ignition (4-3.1).  [c.157]

Often, complex apparatus and systems, process piping arrangements and even support structures utilize different metals, alloys or other materials. These are often employed in corrosive or conductive environments and, in practice, the contact of dissimilar materials cannot be avoided totally. It is important that the designer minimize the damaging effects of corrosion by optimizing the compatibility of materials either by selection or arrangement in the overall design. Compatible materials are those that will not cause an uneconomic breakdown within the system, even though they are utilized together in a particular medium in appropriate relative sizes and compositions. In addition to material influences on each other by virtue of inherent or induced differences of electric potentiality, adverse chemical reactions can occur as a result of changes in materials caused by environmental variations. All these possibilities must be examined thoroughly by the designer.  [c.36]

This report provides an aging assessment of electric motors and was conducted under the auspices of the USNRC NPAR. Pertinent failure-related information was derived from LERs, IPRDS, NPRDS, and NPE including failure modes, mechanisms, and causes for motor problems. In addition, motor design and materials of construction were reviewed to identify age-sensitive components. The study included consideration of the seismic susceptibility of age-degraded motor components to externally-induced vibrational effects.  [c.98]

Increasing awareness of the cost-effectiveness of electroplating processes has led to critical appraisals being made of cell design, not only to improve the product through improved efficiency and economics of the process itself, typically through the costs of electricity. Thus the use of more conductive solutions, combined with minimisation of the anode-cathode spacing can yield a 40% saving in electrical power. However, not all of this saving is necessarily desirable if chemical costs thereby increase and the peripheral cost of solution heating has also to be increased. Similarly, improved agitation and filtration may also be considered for optimisation studies. This chemical engineering approach has found increasing value, not least in the development of new types of plating cell specifically for metal recovery from trade effluent, dragouts and rinses " . In fact the number of new designs far outnumbers the number of optimising and independent assessment studies so that it is not possible to name a best-buy , and time is needed for commercial realities to eventually declare a winner, albeit not on entirely objective terms.  [c.378]


See pages that mention the term Dysonian electrical conductivity : [c.1942]    [c.174]    [c.494]    [c.164]    [c.124]    [c.119]   
The science and technology of carbon nanotubes (1999) -- [ c.110 ]