Principal factor

These examples are sufficient to illustrate one of the principal factors which should influence the choice of dimensionless parameters. Neglect of these considerations may lead, and indeed sometimes has led, to graphical presentations which are at best clumsy and at worst valueless. 

Capacity Limitations. The fluid flow capacity of a bubble tray may be limited by any of three principal factors. 

The progress of LPG utilization has been closely related to progress in transportation (qv) and storage of this fuel. Large volumes of LPG must be transported from the producing plants to centers of consumption, and transportation costs are a principal factor in the cost of LPG to the consumer. 

In the past, commodity chemicals were generally priced on the basis of ROl. Capital cost was the most critical item, and those elements that ate related to capital cost were the principal factors in the selling price (excluding taw material cost in some cases). On this basis, a satisfactory ROl resulted in acceptable values for other criteria such as ROS or sales margin. Many analysts favor ROS as a benchmark for comparison because it is up to date and simple and because it is increasingly difficult to determine a tme ROl based on what profits might be on plants built under indation and expensive capital and constmction costs. 

MaintainabiUty is a characteristic of design, installation, and operation, usually expressed as the probabiUty that a system can be restored to specified operable conditions within a specified interval of time when maintenance is performed in accordance with prescribed procedures. The ease of fault detection, isolation, and repair are all influenced by system design and are principal factors contributing to maintainabiUty. Also contributing is the supply of spare parts, the supporting repair organization, and preventative maintenance practices. MaintainabiUty must be designed into the equipment. Some factors to consider foUow. 

Module Selection. The choice of the appropriate membrane module for a particular membrane separation balances a number of factors. The principal factors that enter into this decision are Hsted in Table 2. 

Equatioa-of-state theories employ characteristic volume, temperature, and pressure parameters that must be derived from volumetric data for the pure components. Owiag to the availabiHty of commercial iastmments for such measurements, there is a growing data source for use ia these theories (9,11,20). Like the simpler Flory-Huggias theory, these theories coataia an iateraction parameter that is the principal factor ia determining phase behavior ia bleads of high molecular weight polymers. 

Selection of the most suitable machine for a given requirement is an extremely complex process. Added to variations in the properties of the different materials, many of the machines involved have been specifically developed or adapted to perform only particular tasks. The principal factors which must be addressed are toughness/britdeness, hardness, abrasiveness, feed size, cohesity, particle shape and stmcture, heat sensitivity, toxicity, explodability, and specific surface. 

Two principal factors affected the U.S. sulfuric acid industry in the 1980s. The first was the increased availabiUty of recovered sulfur vs Frasch sulfur (see SuLFURREMOVAL AND recovery). This occurred because of environmental concerns and regulations forcing more sulfur to be recovered at refineries, power plants, etc. The effect of this change was that the cost of sulfur in the marketplace became driven largely by the cost of nonsulfur industries, rather than by the traditional discretionary sulfur producers, and tended to stabilize U.S. sulfur prices. 

Piae oil production ia general has continued to decline. One of the principal factors is the decrease ia the amount of piae oil used ia cleaner and disiafectant products. The piae oil content of those products has dropped from 70—90% to 10—30% (116). 

Principal factors that determine the likelihood of toxic effects being produced and their severity include the rates at which the causative substances (patent molecule, toxic metaboUte, or both) teach the tissues and the absolute amounts of materials to which the tissues ate exposed. These determine the dose of material received at the target tissues. 

Dichlorobenzene. T -Dichlorobenzene s largest and growing oudet is in the manufacture of poly(phenylene sulfide) resin (PPS). Other apphcations include room deodorant blocks and moth control, a market which is static and likely to remain unchanged but combined is currently a larger outlet than PPS. Small amounts ofT -dichlorobenzene are used in the production of 1,2,4-trichlorobenzene, dyes, and insecticide intermediates. Exports have been a principal factor in U.S. production with about 25% exported in 1988. 

The principal factors affecting transfer efficiency are the size and shape of the object, the type of apphcation equipment, the air pressure to the spray gun, and the distance of the spray gun from the object. The transfer efficiency becomes lower as the object becomes smaller or more complex. The transfer efficiency increases when the spray gun is brought closer to the object and when the atomizing pressure is reduced. The transfer efficiency of different types of apphcation equipment in descending relative order is manual > electrostatic spray > airless spray > conventional atomized air spray. 

The biochemical basis of penicillin action continues to be an area of active investigation. Penicillins are highly specific inhibitors of enzyme(s) involved in the synthesis of the bacterial cell wall, a structure not present in mammalian cells. Three principal factors are thought to be important for effective antibacterial action by a penicillin ... 

Selection of Equipment The principal factors which influence mixing-equipment choice are (1) the process requirements, (2) the flow properties of the process fluids, (3) equipment costs, and (4) construction materials required. 

The two principal factors governing SCC are tensile stresses and exposure to a specific corrodent. These two factors interact synergistically to produce cracking. Only one factor needs to be removed or sufficiently diminished to prevent cracking. 

It is particularly interesting to consider the influence of the substituents R and Rj in diphenylol alkanes of the type shown in Figure 20.12. Such variations will influence properties because they affect the flexibility of the molecule about the central C-atom, the spatial symmetry of the molecule and also the interchain attraction, the three principal factors determining the physical nature of a high polymer. 

The principal factors which must be accounted for when designing a stack for air pollution control purposes are the dispersion and transport of the pollutants and the performance criteria against which the stack will be compared. These factors include (1) air quality standards, (2) meteorological conditions, and (3) topographical peculiarities. 

Airstream neutralization of acid aerosols by NH3 present in the airway-lumen reduces the health risk associated with acid particles by reducing the acid concentration prior to particle deposition.- In addition, the liquid lining of the respiratory tract probably acts as a chemical buffer," further reducing the health hazard posed by inspired acid particles. Principal factors controlling airstream neutralization of acid aerosols, which is considered to be a diffusion-limited process, are particle surface area, and particle... 

ITowever, most normal somatic cells lack telomerase. Consequently, upon every cycle of cell division when the cell replicates its DNA, about 50-nucleotide portions are lost from the end of each telomere. Thus, over time, the telomeres of somatic cells in animals become shorter and shorter, eventually leading to chromosome instability and cell death. This phenomenon has led some scientists to espouse a telomere theory of aging that implicates telomere shortening as the principal factor in cell, tissue, and even organism aging. Interestingly, cancer cells appear immortal because they continue to reproduce indefinitely. A survey of 20 different tumor types by Geron Corporation of Menlo Park, California, revealed that all contained telomerase activity. 

Polymerization of acrylamide is usually performed in aqueous solutions. The principal factors that determine popularity of this polymerization technique are a high rate of polymer formation and the possibility to obtain a polymer with a large molecular weight. The reason for a specific effect produced by water upon acrylamide polymerization lies in protonation of the macroradical, leading to localization of an unpaired electron, which leads to an increase in the reactivity of the macroradical ... 

The principal factor which runs the process engineering man-hours over expected time for a straight through project is the comparison studies of equipment or process schemes when compared to the relatively simple and limited work after the decisions are made. 

The typical value of porosity for a clean, consolidated, and reasonably uniform sand is 20%. The carbonate rocks (limestone and dolomite) normally exhibit lower values, e.g., 6-8%. These are approximate values and do not fit all situations. The principal factors that complicate intergranular porosity magnitudes are uniformity of grain size, degree of cementation, packing of the grains, and particle shape. 

---