Use of166mHo for calibration of gamma-ray spectrometers with semiconductor detectors

Translated from Atomnaya Énergiya, Vol. 67, No. 3, pp. 215–216, September, 1989.     

Removal of nitrates from groundwater through the use of artificial wetlands

Intensive fertilizer use has led to nitrate contamination of groundwater in many areas. This article examines the possibility of removing nitrates through the construction of artificial wetlands. A pilot study conducted in Denmark has found that the method is effective and economical, at least for small waterworks, though further treatment is necessary before an acceptable microbiological water quality is attained.     

On the construction of the reachability domain in one nonlinear problem

An algorithm for construction of the reachability domain by the given time instant ? for a nonlinear third order system under the condition of preliminary approach to a predefined point is proposed. All possible cases of location of this point in the motion plane of the system for different values of the time instant ? are studied.     

Influence of coherent structures on mass transfer near stagnation region in agitated small tanks

Electrochemical method is applied to study coherent structures in a complex three-dimensional flow generated by a rotating magnetic rod. In order to detect these structures, the power spectral density (PSD) analysis of the limiting diffusion current fluctuations is provided. This analysis reveals the existence of resonance frequencies when the probe is located in the very vicinity of the stirrer. The main resonance is related to the mechanical excitation frequency. The detailed analysis of the PSD curves points out some mechanisms of development of turbulence as sub-harmonics and non-linear interactions. For different locations of the probe and different angular rates of the stirrer Ω, a similarity of the energy repartition is obtained when the PSD is plotted versus the adimensional frequency f/Ω. Flow visualization by laser tomography is also provided and the local secondary flow past the electrode probe is sketched. The laser Doppler velocimetry (LDV) at a given location in a horizontal z-plane indicates a tornado wise mean flow structure.     

Changes in Lake Ontario Total Phosphorus Concentrations 1976–1978

An apparent decrease in total phosphorus concentrations of approximately 4.l μgP/L has been reported recently for the spring values of 1977 and 1978 in Lake Ontario. Investigation of the loading reduction for this period independent of sedimentation factors can account for only 10% of the change. The results indicate that changes in the sedimentation rate of total phosphorus during this period offer an explanation for the majority of the change in concentration.