Integrated modelling under uncertainty in watershed-level assessment and management.

Uncertainty in water quality model predictions is inevitably high due to natural stochasticity, model uncertainty, and parameter uncertainty. An integrated modelling system (modified-BASINS) under uncertainty is described and demonstrated for use in receiving-water quality prediction and watershed management. A Monte Carlo simulation was used to investigate the effect of various uncertainty types on output prediction. Without pollution control measures in the watershed, the concentrations of total nitrogen (T-N) and total phosphorus (T-P) in the Hwaong Reservoir, considering three uncertainty types, would be less than about 4.4 and 0.23 mg L(-1), respectively, in 2012, with 90% confidence. The effects of two watershed management practices, wastewater treatment plants (WWTP) and constructed wetlands (WETLAND), were evaluated. The combined scenario (WWTP + WETLAND) was the most effective at improving reservoir water quality, bringing concentrations of T-N and T-P in the Hwaong Reservoir to less than 3.4 and 0.14 mg L(-1), 24 and 41% improvements, respectively, with 90% confidence. Overall, the Monte Carlo simulation in the integrated modelling system was practical for estimating uncertainty and reliable in water quality prediction. The approach described here may allow decisions to be made based on the probability and level of risk, and its application is recommended.     

Stable operation range for laser diodes with an integrated passivecavity in the presence of external optical feedback

It is shown that a laser diode with an integrated passive cavity yields higher tolerable levels of feedback from distant reflections than an equivalent long solitary laser diode. To ensure this high tolerance for external feedback, the internal feedback level in the integrated passive cavity must be of the order of about 10%. Then the laser diode remains stable up to external feedback levels in excess of 1% even if the internal reflection phase is not carefully adjusted. External reflections from a cleaved fiber end are then not sufficient to drive the laser into coherence collapse, if realistic coupling efficiencies between laser diode and fiber are taken into account. The low feedback sensitivity is explained by the combination of the long effective length of the laser and a high relaxation resonance frequency. Therefore, quantum-well laser diodes with a long length and a high relaxation resonance frequency are likewise expected to exhibit low feedback sensitivity     

Mutagenicity of ambient aerosol collected in an urban and industrial area of The Netherlands

To investigate the influence of the densely populated and heavily industrialized Rijnmond area of The Netherlands on the genotoxicity of the ambient aerosol, aerosol samples were collected at locations within the area, and at a coastal region located upwind. The mutagenicity of extracts of the samples was compared in the Salmonella/microsome test. The dependence of the effects on sampling time and on sampling location was investigated with the aid of a series of simple mathematical models. These models were also used to estimate the increase in mutagenicity above background levels at the sites in the Rijnmond area due to emissions within that area. Application of the models showed that the clear and significant increases are not merely a result of the additions of mutagens emitted, but that possibly interactions between sampling time- and location-dependent factors play a role. Comparison of the results obtained with the different Ames-test variants (different strains, with and without liver homogenate) indicate that the conclusions concerning the time and location dependence of the effect were not dependent on the variant used.     

Analog and Digital Speed Control of DC Drives Using Proportional-Integral and Integral-Proportional Control Techniques

A comparative study of proportional-integral (P-I) and integral-proportional (I-P) control schemes, for the speed control of a dc drive, using both analog-and microprocessor-based digital circuits, is presented. The often-neglected current response is discussed and results are presented. The speed response to step changes in speed reference and load torque, using both the control schemes, is compared to evaluate the merits of I-P control. A brief discussion of sensitivity to controller gains is also given. It is shown that the I-P control scheme offers some distinctive advantages over P-I control. Experimental and simulation results are also presented.     

Physical modeling of urban air-pollutant transport

Air-pollutant transport within an urban setting is conditioned by local urban geometry, urban-modified meteorological variables, a wide variety of source characteristics and local topography. Extreme complexity and local specificity of the resulting dispersion process requires the use of physical modeling rather than numerical or analytical methods to predict concentration distributions. Serving as an analog computer the boundary-layer wind tunnel provides reliable concentration data which can be applied directly to design and/or decision making.A brief review is made of similarity criteria for simulating physical modeling of the atmospheric boundary-layer and source characteristics in a boundary-layer wind tunnel. Applications to several problems related to stack, vent and automobile emissions are described. Rudimentary portions of a data bank are presented which, with additional data acquisition, can provide a practical method for prediction of automobile exhaust concentrations that will result from proposed freeways or alternative traffic routings.     

Parameters and Technology for Fabricating PIK Reactor Fuel Elements

The construction of the fuel elements of a high-flux PIK research reactor is described. The technological tolerances in the process of fuel-element fabrication are presented. The basic geometric and mass parameters of several standard batches of fabricated fuel elements are determined experimentally. Statistical analysis of the experimental data shows that the deviations in the main parameters fall within the limits of the indicated technological tolerances and are described by a Gaussian distribution to a high degree of accuracy.     

Monitoring, removal and risk assessment of cytostatic drugs in hospital wastewater.

Cytostatic agents are applied in cancer therapy and subsequently excreted into hospital wastewater. As these substances are known to be carcinogenic, mutagenic and toxic for reproduction, they should be removed from wastewater at their source of origin.In this study the fate and effects of the cancerostatic platinum compounds (CPC) cisplatin, carboplatin, oxaliplatin, 5-fluorouracil (5-FU) and the anthracyclines doxorubicin, daunorubicin and epirubicin were investigated in hospital wastewater. Wastewater from the in-patient treatment ward of a hospital in Vienna was collected and monitored for the occurrence of the selected drugs. A calculation model was established to spot the correlation between administered dosage and measured concentrations. To investigate the fate of the selected substances during wastewater treatment, the oncologic wastewater was treated in a pilot membrane bioreactor system (MBR) and in downstream advanced wastewater treatment processes (adsorption to activated carbon and UV-treatment). Genotoxic effects of the oncologic wastewater were assessed before and after wastewater treatment followed by a risk assessment.Monitoring concentrations of the selected cytostatics in the oncologic wastewater were in line with calculated concentrations. Due to different mechanisms (adsorption, biodegradation) in the MBR-system 5 - FU and the anthracyclines were removed < LOD, whereas CPC were removed by 60%. In parallel, genotoxic effects could be reduced significantly by the MBR-system. The risk for humans, the aquatic and terrestrial environment by hospital wastewater containing cytostatic drugs was classified as small in a preliminary risk assessment.