Resistivity increase

When a solute elutes from the column, the thermal conductivity of the mobile phase decreases and the temperature of the wire filament, and thus its resistance, increases. A reference cell, through which only the mobile phase passes, corrects for any time-dependent variations in flow rate, pressure, or electrical power, ah of which may lead to a change in the filament s resistance. 

This equation predicts that the height of a theoretical diffusion stage increases, ie, mass-transfer resistance increases, both with bed height and bed diameter. The diffusion resistance for Group B particles where the maximum stable bubble size and the bed height are critical parameters may also be calculated (21). 

Chromium is the most effective addition to improve the resistance of steels to corrosion and oxidation at elevated temperatures, and the chromium—molybdenum steels are an important class of alloys for use in steam (qv) power plants, petroleum (qv) refineries, and chemical-process equipment. The chromium content in these steels varies from 0.5 to 10%. As a group, the low carbon chromium—molybdenum steels have similar creep—mpture strengths, regardless of the chromium content, but corrosion and oxidation resistance increase progressively with chromium content. 

Nickel-based aUoys have superior corrosion resistance to Hon-based aUoys. The only aUoys recommended for hot hydrochloric acid use are Ni—Mo aUoys containing 60—70% Ni and 25—33% Mo. Chlorimet (63 Ni, 32 Mo, 3 Fe) and HasteUoy (60 Ni, 28 Mo, 6 Fe) are found to be stable at aU acid concentrations in the absence of aH and Hon chlorides. Electroless nickel, a Ni—P aUoy containing 2—10% P, shows exceUent resistance to hot hydrogen chloride (71). The corrosion resistance increases with phosphoms content. This coating can be deposited on cast Hon, wrought Hon, mild steel, stainless steels, brass, bron2e, and aluminum (qv). 

The solder and ahoy market, including low melting or fusible ahoys, is a principal user of indium (see SoLDERS AND BRAZING ALLOYS). The addition of indium results in unique properties of solders such as improved corrosion and fatigue resistance, increased hardness, and compatibhity with gold substrates. To fachitate use in various appHcations, indium and its ahoys can be easily fabricated into wine, ribbon, foil, spheres, preforms, solder paste, and powder. 

Rolling resistance increases markedly with rolling velocity. 

Vinyl Acetate—Ethylene Copolymers. In these random copolymers, the ratio of ethylene to vinyl acetate (EVA) is varied from 30—60%. As the vinyl acetate content increases, the oil and heat resistance increases. With higher ethylene content the physical strength, tensile, and tear increases. The polymers are cured with peroxide. The main properties of these elastomers include heat resistance, moderate oil and solvent resistance, low compression set, good weather resistance, high damping, exceUent o2one resistance, and they can be easily colored (see Vinyl polymers, poly(VINYL acetate)). 

The higher chromium—iron alloys were developed in the United States from the early twentieth century on, when the effect of chromium on oxidation resistance at 1090°C was first noticed. Oxidation resistance increased markedly as the chromium content was raised above 20%. For steels containing appreciable quantities of nickel, 20% chromium seems to be the minimum amount necessary for oxidation resistance at 1090°C. 

Increased water resistance Increased tensile strength Increased block resistance Increased solvent resistance Increased adhesion to hydrophilic surfaces... 

Element Solubihty at room temperature, wt % Resistivity increase, fifl-cm) / wt% Electrical conductivity at 0.5 wt %, % lACS... 

Two propylene oxide elastomers have been commercialized, PO—AGE and ECH—PO—AGE. These polymers show excellent low temperature flexibihty and low gas permeabihty. After compounding, PO—AGE copolymer is highly resiUent, and shows excellent flex life and flexibiUty at extremely low temperatures (ca —65°C). It is slightly better than natural mbber in these characteristics. Resistance to oil, fuels, and solvents is moderate to poor. Wear resistance is also poor. Unlike natural mbber, PO—AGE is ozone resistant and resistant to aging at high temperatures. The properties of compounded ECH—PO—AGE he somewhere between those of ECH—EO copolymer and PO—AGE copolymer (22). As the ECH content of the terpolymer increases, fuel resistance increases while low temperature flexibihty decreases. Heat resistance is similar to ECH—EO fuel resistance is similar to polychloroprene. The uncured mbber is soluble in aromatic solvents and ketones. 

Thermal Methods Level-measuring systems may be based on the difference in thermal characteristics oetween the fluids, such as temperature or thermal conductivity. A fixed-point level sensor based on the difference in thermal conductivity between two fluids consists of an electrically heated thermistor inserted into the vessel. The temperature of the thermistor and consequently its electrical resistance increase as the thermal conductivity of the fluid in which it is immersed decreases. Since the thermal conductivity of liquids is markedly higher than that of vapors, such a device can be used as a point level detector for liquid-vapor interface. 

Temperature The level of the temperature measurement (4 K, 20 K, 77 K, or higher) is the first issue to be considered. The second issue is the range needed (e.g., a few degrees around 90 K or 1 to 400 K). If the temperature level is that of air separation or liquefact-ing of natural gas (LNG), then the favorite choice is the platinum resistance thermometer (PRT). Platinum, as with all pure metals, has an electrical resistance that goes to zero as the absolute temperature decreases to zero. Accordingly, the lower useful limit of platinum is about 20 K, or liquid hydrogen temperatures. Below 20 K, semiconductor thermometers (germanium-, carbon-, or silicon-based) are preferred. Semiconductors have just the opposite resistance-temperature dependence of metals—their resistance increases as the temperature is lowered, as fewer valence electrons can be promoted into the conduction band at lower temperatures. Thus, semiconductors are usually chosen for temperatures from about 1 to 20 K. 

Data from precoat tests, however, generally produce filtrate cui-ves with much steeper slopes. The precoat bed has a greater resistance than most filter fabrics, and the particles which are separated on a continuous precoat usually form a cake which has a relatively low resistance when compared to that of the precoat bed. Once the thickness of the deposited solids becomes significant, their resistance increases. Thus, at very short form times, the slope of the filtrate cui ve... 

When the product layer is porous the reaction will continue but at decreasing rate as the diffusional resistance increases with increasing conversion. Then,... 

Electrical re.slstance probe.s. These probes are the next most common type of corrosion probes after coupons. This type of probe measures changes in the electrical resistance as a thin strip of metal gets thinner with ongoing corrosion. As the metal gets thinner, its resistance increases. This technique was developed in the 1950s by Dravinieks and Cataldi and has undergone many improvements since then. 

The system resistance increases and discharge reduces at the same rated speed This condition refers to point B, to which the earlier point A, has now shifted. The system now operates at a higher head f/j2. whereas the actual head has not increased. This condition has occurred due to higher system resistance offered by the throttle. The pump and the prime-mover efficieticy will now reduce to 73 7r from its original 8.3%. 

The system aluminum/water belongs to group II where represents the pitting potential and lies between -0.8 and -1.0 V according to the material and the medium [22,23,36,39,42]. Since alkali ions are necessary as opposite ions to the OH ions in alkalization, the resistance increases with a decrease in alkali ion concentration (see Fig. 2-11). In principle, however, active aluminum cannot be protected cathodically [see the explanation of Eq. (2-56)]. 

Since the Wenner formula [Eq. (24-41)] was deduced for hemispherical electrodes, measuring errors appear for spike electrodes. To avoid errors in excess of 5%, the depth of penetration must be less than a 5. Soil resistivity increases greatly under frost conditions. While electrodes can be driven through thin layers of frost, soil resistivity measurements deeper than 20 cm in frozen ground are virtually impossible. 

Increased anode resistance Increase rectifier voltage, check anode bed... 

The ac resistance increase due to skin effect given above should be considered as a minimum. When wires are placed next to one another and placed in layers within a transformer, the near field magnetic effects between wires further crowd the current density into even smaller areas within the wire s cross-section. For instance, when wires are wound next to one another, the current is pushed away from the points of contact along the surfaces of the wires to areas orthogonal to the winding plane. When layers are placed on top of one another the inner layers show much greater degradation in apparent resistance than do the outermost layers. 

Polycarbonates with superior notched impact strength, made by reacting bisphenol A, bis-phenol S and phosgene, were introduced in 1980 (Merlon T). These copolymers have a better impact strength at low temperatures than conventional polycarbonate, with little or no sacrifice in transparency. These co-carbonate polymers are also less notch sensitive and, unlike for the standard bis-phenol A polymer, the notched impact strength is almost independent of specimen thickness. Impact resistance increases with increase in the bis-phenol S component in the polymer feed. Whilst tensile and flexural properties are similar to those of the bis-phenol A polycarbonate, the polyco-carbonates have a slightly lower deflection temperature under load of about 126°C at 1.81 MPa loading. 

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