Factors concentration

Division 2. With the advent of higher design pressures the ASME recognized the need for alternative rules permitting thinner walls with adequate safety factors. Division 2 provides for these alternative rules it is more restrictive in both materials and methods of analysis, but it makes use of higher allowable stresses than does Division 1. The maximum allowable stresses were increased from one-fourth to one-third of the ultimate tensile stress or two-thkds of the yield stress, whichever is least for materials at any temperature. Division 2 requkes an analysis of combined stress, stress concentration factors, fatigue stresses, and thermal stress. The same type of materials are covered as in Division 1. 

The iaterrelatioaship of nonalkaline scales (CaSO, CaSO /2H2O, CaSO 2H20) depeads oa temperature and the concentration of CaSO. To assure that no hemihydrate scale forms, MSF operators must mn their plants ia such a manner as to assure that the coaceatratioa of the total dissolved sohds does aot exceed 70,000 ppm at temperatures of 120°C. With average-salinity seawater, plants can operate at a concentration factor of 2, but in the Middle East where water salinity can be as high as 50,000 ppm, the concentration factor should not exceed 1.4. Under no circumstances should the total dissolved soHds exceed 70,000 ppm, ie, twice the concentration of normal seawater at 120°C. 

The optimal conditions for accelerating of investigated reaction by ions Fe(III) and Ag(I) ai e the following pH 5,0 (acetic buffer), Cj. . =l,6T0 M, CpMSA=4T0 M, Cpp =2-10 M. Under these conditions, factors of sensitivity for kinetic determination of metals mentioned above were established as a slope s tangent of the calibration curves that is a plot of reaction velocity (change of optical density of ferroin s solution for 4 minutes) versus analyte s concentration. Factors of sensitivity for determination of Mn(II), Fe(III), Ag(I), Pd(II), Co(II) ai-e 5,5-10" 1,1-10" 2,5-10" 2,0-10" 8,0-10", respectively. 

First procedure consists of several stages. 11-molybdo-bismuthphosphate (MBP) is formed and extracted with butyl acetate, stripped with ammonia or acetate buffer solution and determined in aqueous solution using reaction of MBP with Astro Floxine (AF) or other polymethine dyes. Full separation from molybdate excess is not necessary in this procedure as spectiaim of lA differs considerable from dye spectiaim. Therefore sepai ation is simplified and used only as preconcentration step. Concentration factor 50 and good reproducibility make possible determination of low P(V) concentrations at 10 mol/1 level and lower. 

The possibility of preconcentration of selenium in form of SeO by evaporation of low alkali water solution (for 20-1000 J.g/L) has been investigated. Considerable losses of selenium have been observed during evaporation of acidic and neutral solutions owing to volatility of selenium compounds. During evaporation of low alkali solutions at ph 9-10 there are no losses of selenium. Relative error of selenium determination is 1-2% for 1000 P-g/L solution and 3-5% for 20-100 p.g/L. Concentration factor is 10. 

The possibility of preconcentration of selenium (IV) by coprecipitation with iron (III) hydroxide and lanthanum (III) hydroxide with subsequent determination by flame atomic absorption spectroscopy has been investigated also. The effect of nature and concentration of collector and interfering ions on precision accuracy and reproducibility of analytical signal A has been studied. Application of FefOH) as copreconcentrant leads to small relative error (less than 5%). S, is 0.1-0.2 for 5-100 p.g Se in the sample. Concentration factor is 6. The effect of concentration of hydrochloric acid on precision and accuracy of AAS determination of Se has been studied. The best results were obtained with HCl (1 1). 

Figure 4.20 Values of stress concentration factor, Kt, as a function of radius, r, with 3a limits for a circumferentially notched round bar in tension [d A/(0.5, 0.00266) inches, = 0.00333 inches] (adapted from Haugen, 1980)...

K = actual stress concentration factor for static loading... 

Peterson, R.E., Stress Concentration Factors, John Wiley Son, 1953. 

The parameter (1 -f l ajr ) is commonly termed the stress concentration factor K,) and for a hole where a = r then K, = 3, i.e. the stresses around the periphery of the hole are three times as great as the nominal stress in the material. 

The stress intensity factor is a means of characterising the elastic stress distribution near the crack tip but in itself has no physical reality. It has units of MN and should not be confused with the elastic stress concentration factor (K,) referred to earlier. 

It has been shown that for acrylic, glass-filled nylon and methyl pentene there is reasonable correlation between the reciprocal of the stress concentration factor, K, and impact strength. However, for PVC good correlation could only be achieved if the finite dimensions of the sample were taken into account in the calculation of stress concentration factor. 

For the purposes of performing an impact test on a material it is proposed to use an elastic stress concentration factor of 3.5. If the notch tip radius is to be 0.25 mm estimate a suitable notch depth. 

The second special case is an orthotropic lamina loaded at angle a to the fiber direction. Such a situation is effectively an anisotropic lamina under load. Stress concentration factors for boron-epoxy were obtained by Greszczuk [6-11] in Figure 6-7. There, the circumferential stress around the edge of the circular hole is plotted versus angular position around the hole. The circumferential stress is normalized by a , the applied stress. The results for a = 0° are, of course, identical to those in Figure 6-6. As a approaches 90°, the peak stress concentration factor decreases and shifts location around the hole. However, as shown, the combined stress state at failure, upon application of a failure criterion, always occurs near 0 = 90°. Thus, the analysis of failure due to stress concentrations around holes in a lamina is quite involved. 

Fracture is caused by higher stresses around flaws or cracks than in the surrounding material. However, fracture mechanics is much more than the study of stress concentration factors. Such factors are useful in determining the influence of relatively large holes in bodies (see Section 6.3, Holes in Laminates), but are not particularly helpful when the body has sharp notches or crack-like flaws. For composite materials, fracture has a new dimension as opposed to homogeneous isotropic materials because of the presence of two or more constituents. Fracture can be a fracture of the individual constituents or a separation of the interface between the constituents. 

The stress-intensity factors are quite different from stress concentration factors. For the same circular hole, the stress concentration factor is 3 under uniaxial tension, 2 under biaxiai tension, and 4 under pure shear. Thus, the stress concentration factor, which is a single scalar parameter, cannot characterize the stress state, a second-order tensor. However, the stress-intensity factor exists in all stress components, so is a useful concept in stress-type fracture processes. For example. 

The amount of bleed-off required would depend on the nature of the make-up water and the type of conditioning chemicals used. The specialist tower manufacturer, conditioning chemical supplier or water-treatment consultant will advise the maximum concentration factor (the ratio of circulating water concentration to make-up water concentration) which can be allowed. The necessary bleed-off is then given by ... 

Concentration factor the ratio of concentration locally to that in the bulk solution. 

The three principal concentration mechanisms postulated as being responsible for on-load corrosion processes by Mann are dry-out, concentration in crevices, and concentration in porous deposits. (Clean boiler tube surfaces on which high-pressure water is boiled under forced convection do not develop concentration factors of more than about two.)... 

In these ways, then, concentration factors of up to five orders of magnitude may be developed, depending upon the circumstances. Despite much work in this area, theory has not yet developed to the stage where accurate predictions can be made reliably, but the state of the art is such that semi-quantitative assessments can be of considerable value in interpreting occurrences. 

For both coordinated and congruent control, the pH depends upon the phosphate concentration and the sodium to phosphate ratio. Generally, however, phosphates are unsuitable for use at boiler pressures above 100 bar as their low solubility and high concentration factors developed lead to corrosive conditions. 

Discussion. Because of the specific nature of atomic absorption spectroscopy (AAS) as a measuring technique, non-selective reagents such as ammonium pyrollidine dithiocarbamate (APDC) may be used for the liquid-liquid extraction of metal ions. Complexes formed with APDC are soluble in a number of ketones such as methyl isobutyl ketone which is a recommended solvent for use in atomic absorption and allows a concentration factor of ten times. The experiment described illustrates the use of APDC as a general extracting reagent for heavy metal ions. 

Process Cost (US per thousand m3 of culture) Concentration factor... 

In addition to expressing the spectral data as projections onto the spectral factors (basis vectors), we express the concentration data as projections onto the concentration factors (basis vectors). 

On a rank-by-rank (i.e. factor-by-factor) basis, we rotate, or perturb, each pair of factors, (1 spectral factor and its corresponding concentration factor) towards each other to maximize the fit of the linear regression between the projections of the spectra onto the spectral factor with the projections of the concentrations onto the concentration factor. 

The prediction step for PLS is also slightly different than for PCR. It is also done on a rank-by-rank basis using pairs of special and concentration factors. For each component, the projection of the unknown spectrum onto the first spectral factor is scaled by a response coefficient to become a corresponding projection on the first concentration factor. This yields the contribution to the total concentration for that component that is captured by the first pair of spectral and concentration factors. We then repeat the process for the second pair of factors, adding its concentration contribution to the contribution from the first pair of factors. We continue summing the contributions from each successive factor pair until all of the factors in the basis space have been used. 

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