Geostatistical assessment and validation of uncertainty for three-dimensional dioxin data from sediments in an estuarine river

Contaminated sediment management is an urgent environmental and regulatory issue worldwide. Because remediation is expensive, sound quantitative assessments of uncertainty aboutthe spatial distribution of contaminants are critical, butthey are hampered bythe physical complexity of sediment environments. This paper describes the use of geostatistical modeling approaches to quantify uncertainty of 2,3,7,8-tetrachlorodibenzo-p-dioxin concentrations in Passaic River (New Jersey) sediments and to incorporate this information in decision-making processes, such as delineation of contaminated areas and additional sampling needs. First, coordinate transformation and analysis of three-dimensional semivariograms were used to describe and modelthe directional variability accounting forthe meandering course of the river. Then, indicator kriging was employed to provide models of local uncertainty at unsampled locations without requiring a prior transform (e.g. log-normal) of concentrations. Cross-validation results show that the use of probability thresholds leads to more efficient delineation of contaminated areas than a classification based on the exceedence of regulatory thresholds by concentration estimates. Depending on whether additional sampling aims at reducing prediction errors or misclassification rates, the variance of local probability distributions or a measure of the expected closeness to the regulatory threshold can be used to locate candidate locations.     

Bovine somatotropin dose titration in lactating dairy ewes. 3. Treatment interval.

Seventy-four lactating dairy ewes were injected with recombinant bovine somatotropin (bST; sometribove) in a sustained-release formulation. Ewes received 0, 80, 160, or 240 mg of bST/14 d at the end of 2, 4, and 6 wk postlambing, after which injections were withheld for a 28-d period. Response of milk production to bST presented a positive linear contrast and a negative quadratic contrast. After the final injection of bST (d 0), an increase in daily milk production was observed until d +9. A continuous decrease followed with milk production returned to control levels on d +11, +18, and +20, for 80, 160, and 240 mg of bST/14 d. Milk protein content decreased gradually until d +8 before it returned to control levels on d +12, +14 and +14, for 80, 160, and 240 mg of bST/14 d. Levels of bST and IGF-I in plasma presented positive and highly significant linear contrasts and negative quadratics which were significant only for bST. Relative to the evolution of milk production, the evolution of IGF-I levels in plasma was more similar than that of bST, although the correlation of each measure with milk production was high and highly significant. It was concluded that the period between successive injections should be shorter the lower the dose employed; however, a 14-d period seemed to correspond correctly for the dosages and hormone formulation tested.     

Modeling piezoelectric actuators

The piezoelectric actuator (PEA) is a well-known device for managing extremely small displacements in the range from 10 pm to 100 μm. When developing a control system for a piezo-actuated positioning mechanism, the actuator dynamics have to be taken into account. An electromechanical piezo model, based on physical principles, is presented in this paper. In this model, a first-order differential equation is adopted to describe the hysteresis effect, and a partial differential equation is used to describe the mechanical behavior. Since, in practice, a PEA is most often used as an actuator for positioning mechanisms, we considered the influence of such a mechanism on the overall mechanical behavior of PEA and positioning mechanism together. For a well-designed mechanism, the overall mechanical behavior practically equals that of a single mass-spring-damper system, of which the undamped eigenfrequency and the relative damping can be designed favorably. With respect to traditional voltage steering, charge steering has the advantage that no hysteresis is encountered between electrical input and elongation. Electrical steering configurations for both cases of steering are presented. Finally, for the case of charge steering, we derived the total model of a piezo-actuated positioning mechanism. This model is dominated by the mechanical model, which could be designed favorably. Therefore, this model gives a broad range of possibilities for model-based controller design