Concentration prediction

Report prepared for CMA, Washington, D.C., Indoor DEHP Mir Concentrations Predicted after DEHP Volatilitiesfrom Vinyl Products, Environ. Corp., 1988. 

The primary weakness of the approach is that it does not apply to dense vapor releases, a categoiy which includes most hydrocarbon materials. Furthermore, the concentrations predicted are time-weighted averages, with instantaneous values potentially exceeding the average. Finally, the range of apphcabdity is typically from 0.1 to 10 km downwind from the release. 

No correlation was made initially as to wind direction, nor to probability of any wind direction/weather condition or percent time of occurrence, however, this is certainly an important factor in the probability of the pollutant being at a concentration predicted. The greatest significance is attached to predicting an ultimate ground level concentration from any potential episode. 

We are thus able to find the concentration predicted by this model at any position over the tank surface. Figure 10.74 shows contours of concentration both for the original and modified Verhoff conditions for the operating parameters... 

Hunt, E. R. Jr., Piper, S. C., Nemani, R., Keeling, C. D., Otto, R. D. and Running, S. W. (1996). Global net carbon exchange and intra-annual atmospheric CO2 concentrations predicted by an ecosystem process model and three-dimensional atmospheric transport model. Global Biogeochem. Cycles 10, 431-456. 

Fig. 17 B/E-p dependence of the critical temperatures of liquid-liquid demixing (dashed line) and the equilibrium melting temperatures of polymer crystals (solid line) for 512-mers at the critical concentrations, predicted by the mean-field lattice theory of polymer solutions. The triangles denote Tcol and the circles denote T cry both are obtained from the onset of phase transitions in the simulations of the dynamic cooling processes of a single 512-mer. The segments are drawn as a guide for the eye (Hu and Frenkel, unpublished results)...

Some of the species concentrations predicted by the mathematical model are too small to be physically meaningful. The predicted concentration of H2(aq), for example, is 4 x 10-45 molal. Multiplying this value by Avogadro s number... 

The activities of the free ions remain roughly constant with NaCl concentration, and their concentrations increase only moderately, reflecting the decrease in the B-dot activity coefficients with increasing ionic strength (Fig. 8.3). Formation of the complex species CaCl+ and NaSOj drives the general increase in gypsum solubility with NaCl concentration predicted by the B-dot model. 

Show that, for a first-order reaction [(-rA) = AcA], the outlet concentration predicted by the maximum-mixedness model is... 

In the clinically relevant concentration range56 the relation between the response of the sensor and the viral concentration is linear (a linear fit through the data points in Fig. 10.16a gives a correlation coefficient of 0.98) facilitating easy virus concentration predictions with a calibrated sensor. Furthermore, even at the lowest measured virus concentration (850 particles/ml) a high signal-to-noise ratio of... 

Table 4 Observed sediment toxicity values for H. azteca and C. dilutus and pore water concentrations predicted by equilibrium partitioning [25]...

In general, the Simple Treat model predicted the overall removal of total AHTN and HHCB within a factor of 4 of Artola-Garicano et al. s measured removals for three wastewater treatment plants located in The Netherlands. However, the free AHTN and HHCB concentrations predicted by Simple Treat were inversely related to the measured free concentrations of these compounds [27]. As previously mentioned, the overall removal of AHTN and HHCB measured by Artola-Garicano et al. (14-60%) was significantly less than the overall removal of these compounds measured by Simonich et al. [ 11 ] and Kanda et al. [22] (39-99.9%). 

Virtual sources As indicated above, the gaussian model was formulated for an idealized point source, and such an approach may be unnecessarily conservative (predict an unrealistically large concentration) for a real release. There are formulations for area sources, but such models are more cumbersome than the point source models above. For point source models, methods using a virtual source have been proposed in the past which essentially use the maximum concentration of the real source to determine the location of an equivalent upwind point source that would give the same maximum concentration at the real source. Such an approach will tend to overcompensate and unrealistically reduce the predicted concentration because a real source has lateral and along-wind extent (not a maximum concentration at a point). Consequently, the modeled concentration can be assumed to be bounded above, using the point source formulas in Eq. (23-78) or (23-79), and bounded below by concentrations predicted by using a virtual source approach. 

The free-radical chemistry was studied using a zerodimensional box-model based upon the Master Chemical Mechanism (MCM). Two versions of the model were used, with different levels of chemical complexity, to explore the role of hydrocarbons upon free-radical budgets under very clean conditions. The detailed model was constrained to measurements of CO, CH4 and 17 NMHCs, while the simple model contained only the CO and CH4 oxidation mechanisms, together with inorganic chemistry. The OH and HO2 (HOx) concentrations predicted by the two models agreed to within 5-10%. 

Some attempts to exploit sensor dynamics for concentration prediction were carried out in the past. Davide et al. approached the problem using dynamic system theory, applying non-linear Volterra series to the modelling of Thickness Shear Mode Resonator (TSMR) sensors [4], This approach gave rise to non-linear models where the difficulty to discriminate the intrinsic sensor properties from those of the gas delivery systems limited the efficiency of the approach. 

Figure 9.6 Comparison of the equilibrium [equation (9.2.2)] and fractional melting [equation (9.3.15)] models for a bulk solid-liquid partition coefficient Dt of 0.1 (top) and 2 (bottom). Although the concentrations predicted by the two models diverge rapidly for incompatible elements in instantaneous melts, they remain virtually identical for compatible elements.

Dissolved sulfite concentrations predicted from Equation 2 agree with the computerized chemical model to within a relative... 

C(t) modeled according to two-compartment model with zero-order and first-order absorption Pharmacokinetic/pharmacodynamic relationship modeled using Hill model with first-order absorption. Modeled parameters matched experimental parameters when bicompartmental model with zero-order input was used. Linear PKs, anticlockwise hysteresis loop established for all doses studied. Apomorphine and growth hormone concentration predicted with good accuracy... 

In addition to the temporal correlation coefficient, the spatial correlation coefficient was calculated approximately for fixed values of time. Except for one of the mathematical models, all techniques showed a better temporal correlation than spatial correlation. The two correlation coefficients are cross plotted in Figure 5-6. Nappo stressed that correlation coefficients express fidelity in predicting tends, rather than accuracy in absolute concentration predictions. Another measure is used for assessing accuracy in predicting concentrations the ratio of predicted to observed concentration. Nappo averaged this ratio over space and over time and extracted the standard deviation of the data sample for each. The standard deviation expresses consistency of accuracy for each model. For example, a model might have a predicted observed ratio near unity,... 

The full-scale industrial experiment demonstrated the feasibility of a convenient, nonintrusive aconstic chemometric facility for reliable ammonia concentration prediction. The training experimental design spanned the industrial concentration range of interest (0-8%). Two-segment cross-validation (test set switch) showed good accnracy (slope 0.96) combined with a satisfactory RMSEP. It is fully possible to further develop this pilot study calibration basis nntil a fnll industrial model has been achieved. There wonld appear to be several types of analogous chemical analytes in other process technological contexts, which may be similarly approached by acoustic chemometrics. 

One such study details the effects of temperature variation on substrate and metabolite concentration predictions, and used an artificial neural network creating a nonlinear multivariate model to improve concentration predictions. Another study notes the effects of temperature on the mid-infrared spectral data as well, but also noted that the sensor was not affected by reactor operating conditions such as agitation, airflow and backpressure. ... 

Mahmood, 1. (1999) Prediction of clearance, volume of distribution and half-life by allometric scaling and by use of plasma concentrations predicted from pharmacokinetic constants a comparative study. Journal of Pharmacy and Pharmacology, 51, 905-910. 

TABLE 5.2. Concentration Predictions for Four Unknown Samples... 

Concentration, Predicted Concentration, Predicted Concentration, Predicted... 

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