Uniform sampling of periodic signals using successive conversions

This paper presents a new approach to the generation of uniform sampling signals which is based on multiple signal conversions: from pulse to digital, then from digital to analog and afterwards from analog back to pulse. It is shown that a conventional analog-to-frequency converter is suitable to be used as a controllable pulse generator providing for equidistant sampling pulses the frequency of which is proportional to the sampled signal frequency. This paper describes two methods for designing fast response, jitter-free sampling-time generators allowing accurate, uniform sampling of periodic signals. The prototypes have been built and tested     

New method for reactive power and energy measurement

The properties of an electronic reactive power and energy measurement method based on a frequency-controlled power-to-pulse-rate conversion are analyzed. The reactive power and energy measurements can be efficiently performed by using a simple integrating circuit as a phase shifter, and frequency-controlled analog-to-pulse-rate converter. A low value of the output pulse rate should not be considered as an inherent disadvantage of the method. By introducing a phase-locked loop in order to achieve high pulse-rate output, the benefit of high resolution is added to the method. The improved electronic structure for the measurement can be implemented in the design of reactive power and energy standards. For precision var-hour meters based on the proposed method, it is possible to have an efficient error-checking and adjustment procedure. The proposed method allows reactive power and energy measurement to be made in single- and poly-phase, symmetrical and unsymmetrical, and balanced and unbalanced networks     

Direct ESR and spin trapping methods for the detection and identification of radical fragments in Nafion membranes and model compounds exposed to oxygen radicals

Direct electron spin resonance (ESR) and spin trapping methods are used in our laboratory in order to identify radical fragments in fluorinated membranes (Nafion) used in fuel cells and in model compounds when exposed to reactive oxygen species. Oxygen radicals were generated by the Fenton reaction, by the photo-Fenton method, and by UV-irradiation of aqueous H₂O₂ solutions. Direct ESR detection led to the identification of fluorinated radical fragments in UV-irradiated Nafion neutralized by Cu(II), Fe(II), and Fe(III) cations and exposed to H₂O₂. In Nafion exposed to the Fenton reagent in the presence of DMPO (5,5-dimethyl-1-pyrroline) as the spin trap, radical adducts of hydroxyl and carbon-centered radicals (CCRs) were detected. A fluorinated model compound, perfluro-(2-ethoxyethane) sulfonic acid (CF₃CF₂OCF₂CF₂SO₃H, PFEESA), that mimics the side chain of Nafion was chosen for study, with the goal to shed light on the more complicated degradation processes in the polymeric membranes. Analysis of the spin adducts obtained from UV-irradiated PFEESA in the presence of H₂O₂ and MNP (2-methyl-2-nitrosopropane) as the spin trap suggested that the side chain of Nafion is a possible site of attack by oxygen radicals.     

Policy development in the Netherlands concerning enhanced exposure to natural radiation

Exposure to enhanced natural radiation is treated in terms of the so-called “environmental policy life cycle model”.The integral policy development is described taking into account environmental, economic and social factors. In the present phase, the policy development is focussed on enhanced levels of radioactivity in building materials. In the following phases, attention will be given to the infiltration of radon from the underground, and to possible enhanced natural radiation due to industrial chemical processes. In each phase the decision process concerning regulations is preceded by a corresponding research programme which forms the necessary scientific basis for the specific regulatory choices. A status report closes the contribution.     

Regulation of International Watercourses under the UN/ECE Regional Agreements

Abstract

This article deals with the UN Economic Commission for Europe (UN/ECE) regional agreements, and their use as implementing instruments for protecting and managing international water courses. The background and issues of the regional instruments developed by the UN Economic Commission for Europe are addressed. The contents of the 1992 Helsinki Convention and its implementation are described, as well as the recent development of the Protocol on Water and Health. The relationship to the 1991 Espoo Convention and a comparison with the 1997 UN Convention on the Law of International Watercourses are also included. The potential of the UN/ECE conventions as tools to promote conflict prevention and dispute settlement is discussed. Lessons and conclusions are drawn from the experience on the management of transboundary waters in Europe.     

System for electromotive force standards comparison based on virtual instrument

This paper presents the design and implementation of a virtual instrument (VI) based automated measuring system for electromotive force (EMF) standards comparisons. The VI is designed in the graphical programming language LabVIEW and enables fast and reliable measurement functions, including data acquisition, real-time graphical display, statistical processing, measurement result archiving, and database management. The VI provides low-cost, efficient, and user-friendly comparisons of EMF standards. The emphasis is given to the system optimization in order to minimize measurement uncertainty, and measurement time consumption. Particular attention was paid to the uncertainty consideration on the part of the measurement system itself. Regular application of the automated system for EMF standard cell comparisons accelerated the measurement procedure by more than ten times, and improved significantly the whole measurement process, compared with the previously used one. In addition, type A standard uncertainty is reduced by more than ten times. The Type B standard uncertainty of the EMF standard is estimated.     

Legal implications of exposure to enhanced natural radiation in the context of the euratom directives

The Euratom Directives apply to “enhanced natural radiation” as far as these radiation concerns operations with respect to substances not to “be disregarded as far as radiation protection is concerned” and accordingly it is a subject of the policy of the Member States. In this case application of “enhanced natural radiation” should be subjected to the basic principles of the 1980 Directive. Measures to be taken in national and international context are analysed.