Die entry losses


Feed purification. Impurities that enter with the feed inevitably cause waste. If feed impurities undergo reaction, then this causes waste from the reactor, as already discussed. If the feed impurity does not undergo reaction, then it can be separated out from the process in a number of ways, as discussed in Sec. 4.1. The greatest source of waste occurs when we choose to use a purge. Impurity builds up in the recycle, and we would like it to build up to a high concentration to minimize waste of feed materials and product in the purge. However, two factors limit the extent to which the feed impurity can be allowed to build up  [c.282]

In the event of a sudden loss of mud In an Interval containing overpressures the mud column in the annulus will drop, thereby reducing the hydrostatic head acting on the formation to the point where formation pressure exceeds mud pressure. Formation fluids (oil, gas or water) can now enter the borehole and travel upwards. In the process the gas will expand considerably but will maintain its initial pressure. The last line of defence leff is the blowout preventer. However, although the BOP will prevent fluid or gas escape to the surface, closing in the well may lead to two potentially disastrous situations  [c.59]

A complicating factor when acquiring downhole data is the contamination of the measured formation by mud filtrate, which is discussed in detail at the end of Section 5.4. During the drilling process mud filtrate will enter the newly penetrated formation to varying degrees. In a highly permeable formation a large quantity of fluid will initially enter the pores. As a result the clay platelets suspended in the mud will quickly accumulate around the borehole wall. The formation effectively filters the penetrating fluid forming a mud cake around the borehole wall which in turn will prevent further invasion. In a less permeable formation this process will take more time and invasion will therefore penetrate deeper into the formation.  [c.131]

This is because no four-indexed two-electron integral like expressions enter into the integrals needed to compute the energy. All such integrals involve p(r) or the product p(/)p(r) because p is itself expanded in a basis (say of M functions), even the term p(r)p(r) scales no worse than tvF. The solution of the KS equations for the KS orbitals ([). involves solving a matrix eigenvalue problem this  [c.2199]

Similar questions can be addressed by the P-RISM (polymer reference interaction site model) theory of Curro and Schweizer [36]. This integral equation theory generalizes the Omstein-Zemike equation to polymeric systems in order to account for the fluid-like packing structure. Details of the molecular architecture enter via the single-chain structure factor. The P-RISM approach yields a detailed description of the phase behaviour and the local structure and has been applied to models with various degrees of structural detail. In the limit that the chains are modelled as infinitely thin Gaussian paths the results are very similar to the Flory-Huggins theory. The theory has been applied to fairly realistic chain models taking the experimentally measured single-chain structure factors as input. More recently, this approach has been applied self-consistently to calculate the change of the molecular confonnation upon blending.  [c.2368]

The transition or d block elements, in which electrons enter inner d orbitals, form a well-defined series with many common and characteristic features. They are all metals those on the right of the block are softer and have lower melting points than those on the left Table 13.2. p. 360). Many are sufficiently resistant to oxidation, corrosion and wear to make them useful in everyday life. They have similar ionisation energies (Figure 1.6), often give ions of variable valency, and readily form complexes (pp. 46. 362) many of which are coloured. However, regular gradations of behaviour, either across a series or down a group are much less apparent than in the typical s and p block elements. The elements at the end of each transition series— copper and zinc in Period 4, silver and cadmium in Period 5 and gold and mercury in Period 6—have d orbitals which are filled. When copper and silver form the copper(I) ion Cu and the silver ion Ag" respectively, and zinc and cadmium the ions Zn " and Cd respectively. the inner d orbitals remain filled. Are these elements and ions properly called transition elements and ions We shall see in Chapters 13 and 14 that their properties are in some respects intermediate between those characteristic of a transition metal and a non-transition metal. Thus zine. for example, is like calcium in some of its compounds but like a transition metal in others. Again, silver has some properties like an alkali metal but also has transition-like properties.  [c.13]

We do not know either side of Eq. (6-33), but we do know that E is to be minimized with respect to some minimization parameters. The only arbitrary parameters we have are the a and aa, which enter into the LCAO. Thus our normal equations are  [c.184]

These results show that in the phenylation of thiazole with benzoyl peroxide two secondary reactions enter in competition the attack of thiazole by benzoyloxy radicals, leading to a mixture of thiazolyl benzoates, and the formation of dithiazolyle through attack of thiazole by the thiazolyl radicals resulting from hydrogen abstraction on the substrate and from the dimerization of these radicals. This last reaction is less important than in the case of thiophene but more important than in the case of pyridine (398).  [c.109]

Now consider ions of m/z 100.1 and 100.2. If these are dispersed so as to enter the two elements of Figure 29.3, then the resolution improves to 0.1 mass units, but the number of m/z values that can be measured at the same time falls. In the ten-element array of Figure 29.4, to achieve a mass resolution of 0.1, only the mass range of m/z 100 to 101 would be covered, instead of the range 100 to 110 for unit mass resolution. Because the number of elements in the array does not change, increasing the resolution means that less of the spectrum can be covered. Conversely, the lower the resolution, the greater is the mass range that can be scanned. Thus, arrays can be used to cover wide regions of a mass spectrum at low resolution but only very small regions at high resolution.  [c.209]

After an ion enters one end of the rod assembly, it follows a complicated path before reaching the other end (Figure 49.5). Since there is no accelerating effect of the RF fields along the central axis (z-axis) of the rod assembly, movement of an ion in this direction is not considered further, as it is not a consequence of the inhomogeneous RF fields. Generally, ions enter the rod assembly after having been accelerated sufficiently to have a kinetic energy of about 5 V or less. The drift velocity in the z-direction is given by Equation 49.3, in which an ion of mass m and z charges is either accelerated through an intentionally applied potential of V volts or through an effective V volts caused by natural space-charge effects from following ions.  [c.378]

The vapor pressure ratio measures the intrinsic tendency of component 1 to enter the vapor phase relative to component 2. Likewise, ri measures the tendency of Mi to add to Mi - relative to M2 adding to Mi-. In this sense there is a certain parallel, but it is based on Mi - as a reference radical and hence appears to be less general than the vapor pressure ratio. Note, however, that ri = l/r2 means kn/ki2 = k2i/k22- In this case the ratio of rate constants for monomer 1 relative to monomer 2 is the same regardless of the reference radical examined. This shows the parallelism to be exact.  [c.430]

The low density and high porosity of aerogels lead to several other unique properties. Sound travels ia siUca aerogels at a loagitudiaal velocity of 100—300 m/s (the corresponding value ia ordiaary glass is about 500 m/s) (56). The low souad velocity and low density combine to give a low acoustic impedance, which is the product of the two quantities. SiUca aerogels also have a refractive iadex that is very close to unity, meaning light can enter and leave a piece of aerogel without appreciable reflective losses and refractive effects. And for porosity larger than 0.7, siUca aerogels have a very low dielectric constant (less than 2) (57). FiaaHy, compared to siUca glass, siUca aerogels have an extremely small Young s modulus (lO -10 N /m several orders of magnitude less than nonporous materials), and thus, can be compressed easily (51).  [c.6]

Although molecular recognition, the programmed molecular interaction or binding with a purpose, is difficult to put into numerical values, its fundamental importance in natural sciences with special points of emphasis in molecular biology (1 3) and supramolecular chemistry (8—12) is clear now. Of course, one may say that molecular recognition as itself is old hat, considering the eady lock-and-key principle of Emil Fischer (5) mentioned at the beginning. Nevertheless, molecular recognition has also proved the main portal to enter into the new fascinating technological developments that supramolecular sciences have made available and may further open in the future (205).  [c.195]

Dry— Wet Hardboard. Dry—wet hardboards are the other possible manufacturing alternative. Fiber is processed as in the dry process up through the mat-forming stage. PF binders are used in this system. Then, as the mats are ready to enter the press loader, a large quantity of water is sprayed onto the surface of the mat. This water saturates the top surface of the mat and is sufficient to raise the total moisture content of the mat to 20—40% me, depending on the thickness and density of the product. Thinner, more dense products require more water. The press operates at about 200°C, and as the press closes on the mats, the water is heated to steam. The steam quickly heats and softens the mat, requiring less pressure to compress the mat and produces a hard, dense top surface much like a wet-process surface. However, because there is much less total water in the mat in this system compared to the wet-process system, press cycles are significantly shorter, which produces more product per unit of press surface per unit of time.  [c.389]

Hot-melt adhesives, normally appHed from an automatic appHcator or a hand-held gun, are extraordinarily useful materials because of rapid bonding characteristics. Problems in using hot-melt adhesives are usually associated with the lack of high temperature performance because, being thermoplastic, they tend to creep under load. Many of these problems can be solved by adding some degree of cross-linking, which must take place after the adhesive has been appHed, not at the temperature at which the adhesive is kept Hquid inside the appHcator. Moisture-curing urethanes have been attempted as cross-linking agents. One of the largest appHcations is in the paperback book industry in the area of book binding. Hot-melt adhesives have also been used in shoe and furniture manufacture where, in the latter case, the problems of creep do enter into the appHcation consideration. Box and carton sealing is a very large use area, as is that of cormgated paper manufacture. Consumer appHcations are growing also.  [c.235]

Although furnace sizes (dimensions for a given MW production) do not vary too widely between principal manufacturers, the type of firing employed by each is generally quite distinctive. This indicates that the furnace size is not strongly controlled by the type of firing system, particularly for pulverized-coal firing (10) (70% through 74-p.m (200 mesh) screen for a mean size of ca 40—50 p.m). The furnace needs to be sufficiendy large to permit the oxygen enough time to penetrate (diffuse through) the blanketing CO2 layer evolving from the burning coal particle. The residual ash particles ate, of course, considerably smaller than the parent coal particle, on the order of a mean size of ca 10 p.m before post-combustion agglomeration. Although flame temperatures should be high for combustion efficiency in order to minimize CO formation and combustible carbon loss, it is further requited that the combustion products (gases) are sufficiently cooled to enter the convection banks below the temperature at which slagging occurs. These contradictory conditions (aside from pollution control requirements) influence the furnace size and have led to solutions such as tangential firing. Another popular and widely appHed solution was the introduction of separate combustion chambers auxiUary to the main furnace. This is generally referred to as cyclone firing or the cyclone furnace (9). This furnace (Fig. 6) is a horizontal, refractory-lined, water-cooled cylinder firing cmshed coal, 95% through a 4.76-mm (4-mesh) screen. Fuel and air are mixed by a swirling (centrifugal) motion which promotes turbulence. The fuel is burned at high heat-release rates in the range of 16.7—30.0 UJ/(m-h)((4.5-8.0) x 10 Btu/(ft -h)) at combustion temperatures in excess of 1649°C. At these temperatures the coal ash content forms a hquid slag film on the water-cooled refractory-lined wall because of the centrifugal force imparted to the coal particles. The gaseous products of combustion ate discharged into the main gas-cooling boiler furnace and the film of molten slag on the walls continually drains away from the burner end and discharges through the tap opening into the main boiler furnace from which it drains into a tank for further disposition. In tangential firing systems, a cyclone (ie, vortex flame) is created in the main furnace, ie, the fuel and air admission system is corner installed. For opposed firing, the fuel-air system is generally designed to impart an initial swid to the reactants before furnace entry.  [c.144]

The manufacturing process utilizes continuous polymerization ia order to minimize cost. A continuous stream of -phenylenediamine solution is impinged on a continuous stream of molten terephthaloyl chloride. Volumetric control is easily achieved because both reactants are in the Hquid state. Residence time ia the mixing apparatus is on the order of 1 s. Next, the reactants enter a high shear, continuous screw mixer, in which the inherent viscosity of the polymer increases to 4-4.5 dL/g. The minimum inherent viscosity required for fiber spinning ia sulfuric acid is 4 dL/g. The residence time is less than 15 s so the polymer solution which enters the third stage is stiH a fluid. The third stage is a high shear, twin-screw mixer with blades positioned for a number of recycle zones within the mixer, thereby achieving lower temperatures, higher residence times, and higher molecular weights.  [c.65]

Among toxic pollutants that may enter the environment, hydraziae is one of the less persistent because it reacts with oxygen and ozone, particularly in the presence of catalytic surfaces such as metals, oxides, etc. The final products of these reactions are innocuous nitrogen and water.  [c.288]

Hydrogen Peroxide Recovery. Hydrogen peroxide formed in the oxidation step is usually recovered by countercurrent extraction of the oxidized working solution, using dernineralized water in Hquid—Hquid sieve tray columns. Working solutions used by the principal producers are less dense than water so these would enter near the base of the column and flow upward as the dispersed phase. Water enters the column at the top and increases in hydrogen peroxide content and density as it flows downward as the continuous phase. AH known principal producers use sieve tray columns having these flow paths for extraction. Dependent on the type and composition of the working solution, concentrations of hydrogen peroxide up to 45 wt % are obtained by extraction. For safety reasons, 45 wt % aqueous hydrogen peroxide extract is a reasonable limit for nonmiscible organic systems (67). The columns and trays are usuaHy constmcted from 304 or 316 stainless steel or low carbon equivalents. Aluminum and high grade aluminum aHoys are also adequate materials. The sieve tray extractor s particular advantages are high throughput, reasonably high tray efficiency, and, because they have no moving parts, they are economically maintained. Rate turndown is about 2 1, limited by the dispersed phase droplet size or tray stabHity. Other extract methods involving use of rotating mechanical devices, packed columns, spray columns, and unfiUed columns have been claimed.  [c.476]

The spray pattern is also important. A soHd cone pattern mixes less well than a hoUow cone, sheet, or multiple jet patterns. Drops that enter along the edge of the spray pattern nearest the exit have less time to heat up and evaporate. Drops that enter along the edges of the spray pattern nearest the walls may not fully evaporate before hitting the walls, resulting in erosion and corrosion of the brick.  [c.57]

Venturi Scrubbers. Venturi scmbbers consist of a convergent section, a throat, and a divergent section. Particulate laden gases enter the convergent section, accelerate to approximately 130 m/s (425 ft/s), and are mixed with water via a spray system at the throat. Smaller (<0.1 fim in dia) particles are removed by diffusion larger particles agglomerate in the water mist. Gases flow to the divergent section where velocities decrease allowing agglomerated particulates to drop out. Approximately 50—70% of particulate matter leaving Hquid waste incinerator furnaces is less than one micrometer in diameter, making removal difficult. To effect higher removal efficiencies, pressure drop between the Venturi inlet and throat is increased to promote greater turbulence and agglomeration. Typical pressure drops range from 2.5 kPa to more than 25 kPa (10—100 in. water). Removal efficiencies are in the 50—99% range depending on particulate size distribution and throat pressure drop. The system can be automated to raise or lower the pressure drop as required removal efficiencies change.  [c.58]

Radicals generated from water-soluble initiator might not enter a micelle (14) because of differences in surface-charge density. It is postulated that radical entry is preceded by some polymerization of the monomer in the aqueous phase. The very short oligomer chains are less soluble in the aqueous phase and readily enter the micelles. Other theories exist to explain how water-soluble radicals enter micelles (15). The micelles are presumed to be the principal locus of particle nucleation (16) because of the large surface area of micelles relative to the monomer droplets.  [c.23]

In any contractual arrangement, each party has a particular set of reasons to enter into the agreement. In a licensing arrangement, the Hcensor holds rights to certain inteUectual property that may be of value the Hcensee would like access to those property rights in order to make, use, or seU products covered by such inteUectual property rights.  [c.106]

Licensee s Perspective. A potential Hcensee maybe interested in entering into a Hcense agreement for a number of reasons. (/) The Hcensee would like the opportunity to augment its own research and development efforts by acquiring technology from other parties through licensing. (2) The Hcensee would like to acquire new ideas which faU into the Hcensee s research or business areas of expertise. (J) The Hcensee wants to avoid Htigation. (4) There is often a window of opportunity via licensing to enter new markets, develop new products, etc, so as to be the first in the marketplace.  [c.106]

Electron Spin Resonance. Instmmentation for esr differs from nmr instmmentation principally as a consequence of the larger gyromagnetic ratio in this experiment. As a result, the external field is typically 0.35 T (3.5 kG). At this field strength the frequency associated with an unpaired electron is about 9.5 GHz (X-band). Systems operating at frequencies up to 34 GHz ( -band) are also available. Fourier transform is becoming commonplace, but CW instmments also are widely used. Microwave radiation at a fixed frequency is produced by a Klystron valve at power levels ranging from less than 0.1 )J.W to several hundred mW and transmitted to the sample via rigid waveguides rather than the coaxial wire. The waveguide terminates in a reflection resonance cavity controlled by a microwave bridge. The function of this cavity is to focus the energy on the sample (see Microwave technology). In comparing systems, reference is made to the Q factor, ie, the ratio of the energy stored in the cavity to the energy lost in a cycle. Q factors of 5000—7000 are common. Esr signals typically become stronger at lower temperatures, and variable temperature systems capable of approaching Hquid helium temperatures are available. Data are plotted in most appHcations as the first derivative spectmm. This presentation is more sensitive to changes in hyperfine stmcture than the absorption mode. Many esr spectrometers are also equipped to connect the electron nuclear double resonance (endor) experiment (9), which requires that the instmments supply rf at both the electron and nuclear frequencies.  [c.402]

Most of the separators used as of this writing (ca 1995) are the high tension or electrodynamic type (Eig. 17a), based on the principle of corona discharge in an ionizing field utilizing the focusing or the beam-type electrode design (2,6). The particle stream is fed on to a rotating metal dmm or rotor which is grounded. Particles enter a field of charged ionizing electrode assembly which spans the entire length of the dmm and suppHed with a d-c voltage of up to 50 kV and a negative polarity (current flow is usually 5—15 mA/m rotor length). The electrode assembly itself comprises a fine wire electrode to produce the ionizing field and a large-diameter electrode to produce a dense non discharging field. Particles are charged by ion bombardment. Particles that have high conductivity lose their charge to the grounded dmm and therefore are thrown from the dmm surface by centrifugal force and aided by a non discharging static electrode that is placed after the ionizing electrode. Particles having low conductivity and nonconductors retain their charge and are  [c.410]

In the acid-leaching process, the oxide ore is leached with sulfuric acid at elevated temperature and pressure, which causes nickel, but not iron, to enter into solution. The leach solution is purified, foHowed by reaction with hydrogen sulfide and subsequent precipitation of nickel and cobalt sulfides.  [c.3]

The model child mold used during this investigations (fig. 4) enables to simulate problems like they oecure in the field of light metal casting of rims in the automobile industry. The casted test part eonsists of four spokes which are arranged in angles of 30°, 60° and 90° to each other. The strong material accumulation in the eenter area of the casted test part and the erass change of cross sections make a casting free of defects more difficult. The test child mold have the dimensions of 300mm width,  [c.12]

Jn several papers [102-105] JB presented the results of their calculations on CH2, CHj, and BH2. We find their study of the X Ai, state of BH2 particularly interesting [104], because this system was treated also by Brommer and HCR [94]. The results of JB et al. are of comparable accuracy with those by HCR like the latter authors, JB were forced to modify their original ab initio potentials slightly to improve the agreement with the available experimental data. An attempt was undertaken to make a direct comparison of both approaches, but it did not lead to a final conclusion, because of difficulties in transforming the HCR potentials into the fomi they enter within the JB algorithms. Let us note that both works confirmed the conclusion of our old ab initio study [33] that the assignment of the bands observed in the of A Bi X Ai absorption spectium, made by Herzberg and Johns [37], was not correct.  [c.515]

The neighborhoods of the atoms directly bonded to tbe chiral center must be defined. The neighborhood of an atom A. dircetly bonded to the ehiral eenter, is dc-fned as the set of atoms whose distance (in number of bonds) to A is less than their distance to any of the other three atoms bonded to the chiral center (Figure 8-9. In cyclic structures different neighborhoods can overlap.  [c.421]

After a chemical is released and distributed in the environment it might enter our model fish through its gUls or to some e3rtent also through food. Then it is distributed in the body (mainly between the aqueous phase, storage hpids, and membrane lipids). At the same time metabolism and excretion processes take place. Metabolism leads in most cases to less toxic compounds, but in some cases the contrary can happen the product of metabolism is more toxic than the mother compound. Thus, this possibility needs to be kept in mind too, if compounds are tested in vivo. The fraction of the compound (and of possible metabolites) reaching the target(s) then causes the adverse effect. Therefore, if toxicity data are modeled,  [c.504]

Discovering and developing any new medicine is a long and expensive process. A nev compound must not only produce the desired response with minimal side-effects bu must also be demonstrably better than existing therapies. Two key steps in many dru discovery programmes are the identification of hit molecules ( hits ) and lead serie ( leads ). A hit is a molecule that has some reproducible activity in a biological assay, t lead series comprises a set of related molecules that usually share some common structura feature, and which show some variation in the activity as the structure is modified. Thi gives one confidence that further synthetic modification to the lead series (termed lea., optimisation) has a good chance of resulting in a drug candidate with the desired potenc and selectivity, lack of toxicity and the appropriate characteristics to enable it to reach it target in vivo. Such a drug candidate will then enter the early stages of developmeni where further large-scale investigations are undertaken.  [c.657]

A Shortcut. The spreadsheet Excel (Appendix A) is available on many microcomputer systems. It is designed for business applications, not science, but it can be useful for handling large data sets. In this problem, we have a set of 14 Cp values at conesponding T values and we would like to enter CpjT and T values into the program. Canying out the repeated divisions by hand calculator is not very time-consuming or eiTor-prone for this small problem, but it would be in a research project generating hundreds of data points.  [c.25]

Procedure. Cany out SCF calculations for ethylene, 1,3-butadiene, 1,3,5-hexa-tiiene, and 1,3,5,7-octatetraene using Program SCF. The program prints a series of prompts. You will need to designate the number of molecules to be run in any series, for example, by answering NMOLS with 001. You will need to tell how many molecular orbitals will be calculated and how many are filled, for example, 004002 for 1,3-butadiene. You will need to specify the geometry by giving the x-coordinates of all atoms in the molecule followed by the y-coordinates. The molecule is assumed to be planar hence, the z-coordinates are all 0. Unformatted inputs are separated by commas, for example, 0,1.4,2.1,3.5 for the x-coordinates of butadiene and 0,0,1.2,1.2 for the y-coordinates. Following this, the atoms are numbered in the same order as the coordinates were entered, obviously, 1,2,3,4 in this case. Use commas to separate unformatted entries. At this point, the coordinates are automatically printed out as an input check. The number of derivatives is asked, NDER . For now, we are only interested in the parent compound enter 0001. After more output, you are asked for OPTIONS For now, ehoose 0000. Designators like 13 are input formats (Chiriian, 1981). 13 signifies an integer in the r ightmost position in a field of 3 digits, for example, 001.  [c.257]

Frequently, the object of distillation of a solid under reduced pressure is to remove foreign colouring matter, tar and other non-volatile solids without appreciable loss of material—a process which is generally more effective and more economical than several crystallisations from a solvent the purity of the distillate may be more easily ascertained by a melting point determination. In such circumstances, a thermometer is unnecessary and the two-bulb flask, depicted in Fig. II, 19, 4, may be employed rubber stoppers are used, and both the solid and the apparatus must be dry. It is usually advisable to heat the flask with a rather large free flame and to maintain a rotary motion round the walls less bumping occurs than when the flask is heated from the bottom. If there is considerable frothing at the start, the flame should be directed at the upper walls and neck of the flask. If the solid tends to solidify in the side arm, it may be melted by the application of a free flame. When the distillation is complete, air is allowed to enter the apparatus, the contents of the receiving bulb are melted and poured out into a convenient receptacle.  [c.107]

This also brings up the essential relationship of science and its historical perspective. We can never talk about science without putting it into a time frame. August Comte wrote, L histoire de la science c est la science meme — The history of science is really science itself. When we look back in time early scientists (savants) long believed that the earth was the center of the universe and that it was flat. They even warned that approaching its edges would put one at risk of falling off. However strange this may be for us today, they were interpreting the limited knowledge they had at the time. We may pride ourselves on what we consider our advanced knowledge as we enter the twenty-first century, but I am sure future generations will look back at us and say how ignorant and naive we were. As Einstein said, One thing I have learned in a long life is that all of our science, measured against reality,  [c.5]

The simple expression l/p(Hg) — l/p(F) where p(Hg) and p(F) are" the respective densities of a solid obtained by immersion at atmospheric pressure in mercury and in another suitable fluid F, gives a value of the total pore volume of the solid.Since, by the Washburn equation (3.77), mercury at atmospheric pressure cannot enter pores of radius below 7-5 pm (p. 176), l/p(Hg) gives the volume of the solid itself plus that of virtually the whole of the pore system fluid F on the other hand can enter all pores of diameter greater than a (a = molecular diameter of F). l/p(F) will therefore give the true volume of the solid plus that of all pores of diameter less than [c.187]

Poor performance can result from fan inlet eccentric or spinning dow, and discharge ductwork that does not permit development of hiU fan pressure. Sometimes inlet restrictions starve a fan and limit performance. To obtain rated performance, the air must enter the fan uniformly over the inlet area without rotation or unusual turbulence. This allows all portions of the fan wheel to do equal work. If more air is distributed to one side of the wheel, such as with an elbow on the inlet, the work performed by the lightiy loaded portions of the wheel is reduced and capacity is decreased by 5—10%. The use of an inlet box duct on a fan can reduce capacity by as much as 25% unless there are turning vanes in the duct. Use of the vanes reduces the capacity loss to around 5%.  [c.107]

In order for a soHd to bum it must be volatilized, because combustion is almost exclusively a gas-phase phenomenon. In the case of a polymer, this means that decomposition must occur. The decomposition begins in the soHd phase and may continue in the Hquid (melt) and gas phases. Decomposition produces low molecular weight chemical compounds that eventually enter the gas phase. Heat from combustion causes further decomposition and volatilization and, therefore, further combustion. Thus the burning of a soHd is like a chain reaction. For a compound to function as a flame retardant it must intermpt this cycle in some way. There are several mechanistic descriptions by which flame retardants modify flammabiUty. Each flame retardant actually functions by a combination of mechanisms. For example, metal hydroxides such as Al(OH)2 decompose endothermically (thermal quenching) to give water (inert gas dilution). In addition, in cases where up to 60 wt % of Al(OH)2 may be used, such as in polyolefins, the physical dilution effect cannot be ignored.  [c.465]

Channeling is a phenomenon of implantation where impacting ions enter into ordered open spaces, called channels, in the crystal lattice. Channels allow the implanted ion to avoid nuclear collisions and travel further into the lattice than would an ion that collided with atoms in the lattice. Channels can be planar or axial. The primary energy loss in channeled ions is from electron scattering. Channeling can affect the degree of control of the doping profile, especially when dealing with shallow junctions. Consequendy, wafers are tilted to avoid channeling, typically at a 7° angle (30).  [c.350]

The intermediates are blended in large blenders. Surprisingly, it is important to avoid formulations of the blend which have the stoichiometric cation phosphate ratio and hahde phosphate ratio for two reasons. First, the NH Cl and Sb202 powders react to form volatile antimony oxychloride compounds, hence an excess of these species is required. If the chloride drops below the stoichiometry due to this volatilization then some calcium orthophosphate is formed and the Mn activator ions enter this undesired phase giving the cake a pink color. On the other hand a large excess of the chloride results in greater losses due to volatilization and some additional sintering. The losses due to volatilization depend on the amount of excess chloride, the final temperature of synthesis, cake depth, etc. A loosely fitting cover for the cmcible in which the blend is fired must be used to prevent variation in the stoichiometry due to volatilization. The second important consideration in the blend formulation is the use of slightly less CaCO than is required to meet the stoichiometry of the material. The phase diagram indicates that for such a blend composition a small amount of the calcium pyrophosphate phase is formed. The activator Mn ions do not enter this relatively inert second phase however, a large excess of this phase generally results in excessive sintering and shrinkage resulting in a hard cake which is difficult to process further. If on the other hand the amount of the pyrophosphate phase formed is too Httle or does not exist at all then the cake is very soft and there is a risk of forming Cap2 and CaO as undesired second phases due to normal weighing errors in manufacturing. Typically the blend is formulated to give 1—3 wt % of the calcium pyrophosphate phase.  [c.288]

The methylphosphonates differ from the phosphodiesters and phosphorothiolates in that the methyl derivatives are uncharged and are thus less water soluble. Moreover, compared to the naturally occurring phosphodiesters, the methylphosphonates form slightly less stable duplexes with complementary DNA and RNA sequences. This effect has been ascribed to the iaevitable chiraUty problem that is, if one isomer biads less well, the overall binding is decreased. Methylphosphonates can enter cell membranes by a passive mechanism and are completely resistant to nucleases.  [c.263]


See pages that mention the term Die entry losses : [c.1579]    [c.1583]    [c.1744]    [c.2424]    [c.271]    [c.623]    [c.552]    [c.105]    [c.278]   
Plastics engineering Изд.3 (2002) -- [ c.360 , c.382 ]