Alternative comparisons

PARTICULATE EMISSION CONTROL ALTERNATIVES COMPARISON OF "COALTROL" LPA WITH MECHANICAL SYSTEMS ... 

The base plan for an alternative comparison of the type discussed in the preceding paragraph would be the minimum investment which gives the necessary functional results. The alternatives should then be compared with the base plan, and an additional investment would be recommended only if it would give a definite advantage. 

Procedure Experimental design Percentage alternation comparison of choice directions, shown during ... 

An alternative comparison is provided by Reaction 5, where the conjugation energy of the neutral polyene is included on the right-hand side of the equation. 

When the assumption of error-free x-values is not valid, either in method comparisons or, in a conventional calibration analysis, because the standards are unreliable (this problem sometimes arises with solid reference materials), an alternative comparison method is available. This technique is known as the functional relationship by maximum likelihood (FREML) method, and seeks to minimize and estimate both x- and y-dlrection errors. (The conventional least squares approach can be regarded as a special and simple case of FREML.) FREML involves an iterative numerical calculation, but a macro for Minitab now offers this facility (see Bibliography), and provides standard errors for the slope and intercept of the calculated line. The method is reversible (i.e. in a method comparison it does not matter which method is plotted on the x-axis and which on the y-axis), and can also be used in weighted regression calculations (see Section 5.10). 

Analogous to the eluotropic series presented in Table 2, Snyder managed to compare solvents according to their polarity indices P ) [13,14]. In Table 3 an example is given of this alternative comparison, showing the polarity indices (P ) and the selectivity parameters (Xj) of the selected common liquids. 

FRAP is a powerful tool for investigating protein behaviour in nuclei of living cells. FRAP experiments are most informative when an inducible system can be used, allowing to compare protein behaviour in their active and inactive state. Alternatively, comparison of the mobility of functional mutants can be compared with wild type mobility. The possibility to estimate immobile fraction and, moreover, the average duration of immobilisation of individual proteins is very useful in studying the dynamics of nuclear proteins, and specifically those that are involved in DNA transacting processes, transcription, repair... 

Theoretical reaction dynamics can contribute on many levels to our understanding of chemical phenomena. Occasionally, for example, theory can calculate an observable quantity which cannot be measured accurately. Since most dynamics experiments measure relative populations, theory can calibrate them by calculating the absolute cross section for a particular transition. On a more important level, theory contributes to our understanding of chemical phenomena by direct comparison with experiment. Comparisons with approximate calculations are indispensable in determining which aspects of the underlying physics control the reactivity. Alternatively, comparisons with accurate calculations help to ensure that our picture of the chemical reaction is complete. In this dissertation, we develop and apply accurate theoretical methods for describing electronically adiabatic atom—diatom reactive scattering. 

In many process-design calculations it is not necessary to fit the data to within the experimental uncertainty. Here, economics dictates that a minimum number of adjustable parameters be fitted to scarce data with the best accuracy possible. This compromise between "goodness of fit" and number of parameters requires some method of discriminating between models. One way is to compare the uncertainties in the calculated parameters. An alternative method consists of examination of the residuals for trends and excessive errors when plotted versus other system variables (Draper and Smith, 1966). A more useful quantity for comparison is obtained from the sum of the weighted squared residuals given by Equation (1). 

If, however, alternatives are to be compared which are very different in nature, such as a comparison between batch and continuous operation, some allowance for the difference in labor costs must be made. 

The correlation functions provide an alternate route to the equilibrium properties of classical fluids. In particular, the two-particle correlation fimction of a system with a pairwise additive potential detemrines all of its themiodynamic properties. It also detemrines the compressibility of systems witir even more complex tliree-body and higher-order interactions. The pair correlation fiinctions are easier to approximate than the PFs to which they are related they can also be obtained, in principle, from x-ray or neutron diffraction experiments. This provides a useful perspective of fluid stmcture, and enables Hamiltonian models and approximations for the equilibrium stmcture of fluids and solutions to be tested by direct comparison with the experimentally detennined correlation fiinctions. We discuss the basic relations for the correlation fiinctions in the canonical and grand canonical ensembles before considering applications to model systems. 

Smalley R E 1985 Supersonic cluster beams an alternative approach to surface science Comparison of Ab Initio Quantum Chemistry with Experiment for Small Molecules ed R J Bartlett (Boston Reldel)... 

The comparison plot (cf. Section 2.10) is a simple plot of the uptake per unit mass of the experimental material against that of a reference sample at the same relative pressure. It may be regarded as an alternative to the a,-plot, in which the abscissae are actual adsorptions on a sample arbitrarily taken as a standard. 

This is an example of a paired data set since the acquisition of samples over an extended period introduces a substantial time-dependent change in the concentration of monensin. The comparison of the two methods must be done with the paired f-test, using the following null and two-tailed alternative hypotheses... 

If a standard method is available, the performance of a new method can be evaluated by comparing results with those obtained with an approved standard method. The comparison should be done at a minimum of three concentrations to evaluate the applicability of the new method for different amounts of analyte. Alternatively, we can plot the results obtained by the new method against those obtained by the approved standard method. A linear regression analysis should give a slope of 1 and ay-intercept of 0 if the results of the two methods are equivalent. 

Individual comparisons using Fisher s least significant difference test are based on the following null hypothesis and one-tailed alternative hypothesis... 

Dual viscous-flow reservoir inlet. An inlet having two reservoirs, used alternately, each having a leak that provides viscous flow. This inlet is used to obtain precise comparisons of isotope ratios in two samples. 

Comparing two or more complex alternatives is more difficult than examining equipment capacity or first cost. Characteristics of alternatives should be weighted for relative importance and measured on a common scale to aEow proper evaluation. Many characteristics such as first cost, capacity, space requirement, and annual energy use can be measured objectively and used for system comparisons. Experience has shown that items such as maintenance expense, component life, and downtime can also be rehably estimated. Other factors, eg, system maintainabEity, flexibEity, and comfort, are more arbitrary. 

R. L. WooUey and H. M. Simmons, "Hydrogen Storage in Vehicles—An Operational Comparison of Alternative Prototypes," Society of Automotive Engineers FuelandEubricantsMeeting St. Louis, Mo., 1976. 

Noise. Technical differences exist between personal noise dosimeters and high accuracy sound level meters and these may alter the usual preference for personal monitors. But it is exposure to noise rather than general room noise that must be estimated for comparison with noise exposure criteria, the logarithmic expression and alternative means of summation (3 vs 5 db doubling) compHcate statistics. Exposure criteria for both dose and peak exposure must be evaluated, and space and time variabiUty of noise intensity can be immense. 

If possible comparisons are focused on energy systems, nuclear power safety is also estimated to be superior to all electricity generation methods except for natural gas (30). Figure 3 is a plot of that comparison in terms of estimated total deaths to workers and the pubHc and includes deaths associated with secondary processes in the entire fuel cycle. The poorer safety record of the alternatives to nuclear power can be attributed to fataUties in transportation, where comparatively enormous amounts of fossil fuel transport are involved. Continuous or daily refueling of fossil fuel plants is required as compared to refueling a nuclear plant from a few tmckloads only once over a period of one to two years. This disadvantage appHes to solar and wind as well because of the necessary assumption that their backup power in periods of no or Httie wind or sun is from fossil-fuel generation. Now death or serious injury has resulted from radiation exposure from commercial nuclear power plants in the United States (31). 

Preferably the transferring lab provides a sample which has already been analyzed, with the certainty of the results being known (41). This can be either a reference sample or a sample spiked to simulate the analyte. An alternative approach is to compare the test results with those made using a technique of known accuracy. Measurements of the sample are made at the extremes of the method as well as the midpoint. The cause of any observed bias, the statistical difference between the known sample value and the measured value, should be determined and eliminated (42). When properly transferred, the method allows for statistical comparison of the results between the labs to confirm the success of the transfer. 

The sweetness of fmctose is 1.3—1.8 times that of sucrose (10). This property makes fmctose attractive as an alternative for sucrose and other commercially available sweeteners. Fmctose is probably sweetest ia comparison with sucrose when cold and freshly made up ia low concentrations at a slightly acidic pH (5). This relative sweetness difference is commonly attributed to changes ia fmctose stmcture when cold ( P-D-fmctopyranose(l), sweet) as compared to the stmcture when the sweetener is warm ( P-D-fmctofuranose (2), less sweet). Based on nmr spectroscopy and sensory panel evaluation of sweetness, however, it has been observed that the absolute sweetness of fmctose is the same at 5°C as at 50°C, and is not dependent on anomeric distribution (11). Rather, it maybe the sweetness of sucrose, which changes with temperature, that gives fmctose sweetness the appearance of becoming sweeter at low temperatures. 

A procedure to measure both types of nitrogen oxide compounds at the same time involves development of a pink color by mixing FeSO with sulfuric acid, followed by measurement or comparison of color intensity. This general type of procedure and the possible alternatives ate discussed in References 148—150. 

The concentration of dissolved ionic substances can be roughly estimated by multiplying the specific conductance by an empirical factor of 0.55—0.9, depending on temperature and soluble components. Since specific conductance is temperature dependent, all samples should be measured at the same temperature. Alternatively, an appropriate temperature-correction factor obtained by comparisons with known concentrations of potassium chloride may be used. Instmments are available that automatically correct conductance measurements for different temperatures. 

Whenever an economic evaluation is undertaken, a corresponding problem definition should be provided as the basis on which the evaluation is made. This definition, sometimes called an economic scope, should clearly differentiate between specifications that have actually been selected and features that have been assumed for the evaluation. In a comparison of alternatives, all of the assumptions, data, and conditions must be consistent, reaUstic, and devoid of bias. 

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