Relative cost coefficient

Having defined it is necessary to determine the design-dependent factors. The variables, shape complexity, tolerances, etc. modify the relationship between the curves. The relative cost coefficient in Equation (3.1) is one way in which these variables can be expressed. 

This coefficient will determine how much more expensive it will be to produce a component with more demanding features than the ideal design . The characteristics which we have assumed to influence the relative cost coefficient, R, are given below ... 

This was refined on the basis that when a fine surface finish is being produced, fine tolerances could be attained at the same time, and thus it would be somewhat dubious to compound both relative cost coefficients. 

The relative cost coefficient is used to determine how much more expensive it will be to... 

The equation used for the calculation of the relative cost coefficient, is as follows ... 

Some physical properties such as coefficient of thermal expansion and modulus of elasticity of the alloys are given in Table 7.12. Other factors such as resistance to general and pitting corrosion, pitting resistance equivalent number (PREN) and the relative cost ratios are also given in Table 7.12. 

The only meaningful economic comparison considered possible for the experimental apparatus relates the relative cost in additional power to produce a certain increase in heat transfer coefficient by vibration to the cost of increasing the over-all flow velocity. Table I summarizes the power requirements of the experimental apparatus both without vibration and with vibration at resonance for several values of (Re) . Heat transfer coefficients are also shown. 

Element Density, g/cm Electrical resistance, juD. cm at 25°C Sheet resistivity, m 2/sq/25 m Melting point, °C Linear thermal expansion coefficient, ppm/°C Thermal conductivity, W/m-K Relative cost... 

Materials Glasses Metals — Natural Composites Al alloys 5xxx (Al-Mg) Ni alloys 6xxx (Al-Mg-Si) — Mg alloys 7xxx (Al-Zn) Zn alloys 2xxx (Al-Cu) 6066-T4 6162-T5 6162-T6 6463-Tl Coefficient of expansion a — Corrosion, mm-year Cost (relative cost per unit) Fatigue Corrosion fatigue... 

In aerospace applications, the use of nanostructured materials is finalized to a significant improvement of the mechanical properties, Yoimg s modulus, ultimate strength, Poisson coefficient, etc. and reliability. In other sectors (e.g. electronics) the principal requirements are concentrated on the morphology characteristics of employed nanomaterials. In fact, the required quantities are always limited, and concurrent with their availabihty. Instead, for composites and structures, considering the large size of aerospace systems, the quantity and the relative costs represent a critical step. 

Type J thermocouples (Table 11.58) are one of the most common types of industrial thermocouples because of the relatively high Seebeck coefficient and low cost. They are recommended for use in the temperature range from 0 to 760°C (but never above 760°C due to an abrupt magnetic transformation that can cause decalibration even when returned to lower temperatures). Use is permitted in vacuum and in oxidizing, reducing, or inert atmospheres, with the exception of sulfurous atmospheres above 500°C. For extended use above 500°C, heavy-gauge wires are recommended. They are not recommended for subzero temperatures. These thermocouples are subject to poor conformance characteristics because of impurities in the iron. 

ASTM D883 defines a filler as "...a relatively inert material added to a plastic to modify its strength, permanence, working properties, or other quaHties or to lower costs." EiHers (qv) that modify the properties and characteristics of epoxies are employed in epoxy resins for a variety of reasons. Then principal functions are to control viscosity, reduce shrinkage and the coefficient of thermal expansion, effect a cost reduction, and color the epoxy resins. 

A spiral plate exchanger is illustrated in Figure 9.90 in which two fluids flow through the channels formed between the spiral plates. With this form of construction the velocity may be as high as 2.1 m/s and overall transfer coefficients of 2.8 kW/m2 K are frequently obtained. The size can therefore be kept relatively small and the cost becomes comparable or even less than that of shell and tube units, particularly when they are fabricated from alloy steels. 

Phthalocyanine-based dyes are especially useful for CD-R, as the chromophore absorption band falls in the desirable spectral range, and they are noted for excellent photostability. Unlike cyanine dyes, phthalocyanines tend to have very poor solubility, particularly in solvents such as alcohols and aliphatic hydrocarbons (which do not attack polycarbonate and are therefore used for spin coating). Therefore, the main barrier to the wider use of these dyes is the relatively high cost of synthesizing soluble derivatives. Suitable modifications to the Pc core which have been developed, notably by Mitsui Toatsu, are shown in Scheme 7. The bulky R groups reduce undesirable molecular association (which in turn lower the extinction coefficient and hence reflectivity), whereas partial bromination allows fine-tuning of the film absorbance and reflectivity. The metal atom influences the position of the absorption band, the photostability, and the efficiency of the radiationless transition from the excited state.199 This material is marketed by Ciba as Supergreen.204... 

Plate and frame systems offer a great deal of flexibility in obtaining smaller channel dimensions. Equations 4 and 5 show that the Increased hydrodynamic shear associated with relatively thin channels Improves the mass-transfer coefficient. Membrane replacement costs are low but the labor involved is high. For the most-part, plate and frame systems have been troublesome in high-pressure reverse osmosis applications due to the propensity to leak. The most successful plate and frame unit from a commercial standpoint is that manufactured by The Danish Sugar Corporation Ltd. (DDS) (Figure 15). 

Molecular connectivity indices are desirable as potential explanatory variables because they can be calculated for a nominal cost (fractions of a second by computer) and they describe fundamental relationships about chemical structure. That Is, they describe how non-hydrogen atoms of a molecule are "connected". Here we are most concerned with the statistical properties of molecular connectivity Indices for a large set of chemicals In TSCA and the presentation of the results of multivariate analyses using these Indices as explanatory variables to understand several properties important to environmental chemists. We will focus on two properties for which we have a relatively large data base (1) biodegradation as measured by the percentage of theoretical 5-day biochemical oxygen demand (B0D)( 11), and (2) n-octanol/water partition coefficient or hereafter termed log P (12). 

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