[en] The quality of water in 1 421 drinking—water wells was monitored in a nationwide well water study. Samples were taken once from all wells, and during three seasons from 421 wells. The wells were selected in such a way that the sample would be as representative as possible of the quality of the drinking—water in households’ own wells in ru— ral areas. The study comprised general water quality parameters, influence of sampling season, and factors related to the type, the condition and the pollution of the wells. In part of the well waters selenium, radioactivity and pesticides were determined. The effect of plumbing materials on the quality of water was also examined. The health—based criteria of the quality of drinking—water were not met in 50 — 70 % of the well waters monitored, depending upon the sampling time. The most common defects were the occurrence of bacteria indicating faecal pollution (2— 25 %) and a high concentration of nitrate (11 — 13 %) and fluoride (7 — 16 %). The tar— get values set for the other properties affecting the usableness of water were not met in 80 % of the well waters examined. The most common defects in this respect were the turbidity and the colour of water (40 — 50 %), the occurrence of iron (20 — 25 %) and manganese (20 %), and a low ph value. Depending upon the area, only 11 — 15 % of the wells met all the criteria related to the corrosive effect of the water. About 17 % of the households in the study suffered from periodical or continuous insufficiency of water. The types of well were dug wells with concrete sink rings in 72 %, and drilled bedrock wells in 20 % of te cases. The rest were spring wells or dug wells with stone walls. The condition of a well was, according 10 the judgement of the sampler, good in 58 %, satisfactory in 36 % and poor in 6 % of the households. Seasonal variation could be seen mainly in the occurrence of faecal bacteria. Distinct differences in the quality of water appeared owing to geological circumstances, geographic location and land use. Fluorides occurred in higher concentrations in South—Eastern Finland, and pH value, alcalinity and hardness were higher in the coastal than inland area. The influence of the see could be seen as higher sodium and chloride concentrations. Higher concentrations of organic matter were found in Ostrobothnia. The concentrations of selenium in the wells were far below the health—based limit value but the variation range of the results was wide. Selenium in well waters may occur because of general pollution such as use of fertilizers and, locally, it may come from the bedrock. Pesticides were found only in one well in the study. The values of radio— activity found in this study were on average lower than those in earlier studies of the Finnish Centre for Radiation and Nuclear Safety. (author)

[en] The quality of water in 1 421 drinking-water wells was monitored in a nationwide well water study. Samples were taken once from all wells, and during three seasons from 421 wells. The wells were selected in such a way that me sample would be as representative as possible of the quality of the drinking-water in households' own wells in rural areas. The study comprised general water quality parameters, influence of sampling season, and factors related to the type, the condition and the pollution of the wells. In part of the well waters selenium, radioactivity and pesticides were determined. The effect of plumbing materials on the quality of water was also examined. (33 refs., 148 figs., 71 tabs.)

[en] The rolling contact fatigue (RCF) behavior of tungsten carbide (WC) based cermet coatings (WC-12% Co) deposited by plasma and HVOF spraying was studied. The RCF testing was carried out with a two-roll configuration testing machine under unlubricated rolling conditions without sliding. Loads applied in the tests resulted to Hertzian contact pressures of 420--600 MPa. The influence of spraying method on the RCF behavior of the coatings was studied as a function of Hertzian contact stress. Plasma sprayed coating showed severe surface roughening and subsurface cracking of the coating under all studied load levels. HVOF sprayed coating behavior was clearly different from the plasma coating with smaller structural changes. HVOF coating retained its original surface roughness but vertical cracks penetrating the coating appeared in this coating

[en] Time- and space-resolved magnetic (B-dot) probe measurements in combination with measurements of the plasma parameters were carried out to investigate the relationship between the formation and propagation of helicon modes and the radio frequency (rf) power deposition in the core of a helicon plasma. The Poynting flux and the absorbed power density are deduced from the measured rf magnetic field distribution in amplitude and phase. Special attention is devoted to the helicon absorption under linear and nonlinear conditions. The present investigations are attached to recent observations in which the nonlinear nature of the helicon wave absorption has been demonstrated by showing that the strong absorption of helicon waves is correlated with parametric excitation of electrostatic fluctuations.

[en] Two Rolling Contact Fatigue (RCF) test systems have been developed in order to compare coatings according to their service lives under high-load rolling contact. Experimental testing facilities of the three-roller and the two-roller type RCF test equipment are presented and problems involved with testing of thermally sprayed coatings are discussed. The aim of this three-year-project is to study reasons for development of coating micropitting and delamination of high-velocity oxyfuel (HVOF) and detonation gun sprayed coatings. Some observations of rolling contact fatigue behavior of detonation gun sprayed WC+12% Co coating subjected to a nearly pure rolling line contact at cyclic Hertzian stress level of approximately 410 MPa are made, but interpreting the results requires still more work

[en] Laser induced fluorescence spectroscopy based on single-photon absorption can be calibrated by a comparative Rayleigh scattering measurement performed under identical excitation and detection conditions with a reference gas of known Rayleigh scattering cross-section. For light atoms, however, the excitation wavelengths are located in the VUV spectral range and are difficult to generate. Furthermore, VUV radiation is strongly absorbed in air, many other gases and at elevated pressure even in the investigated medium itself (optical thickness). Two-photon Absorption Laser Induced Fluorescence spectroscopy (TALIF) circumvents these problems. The excitation is, however, much less efficient, and focused laser radiation is used in most cases to generate a measurable TALIF signal. Good spatial resolution - determined by the focal dimensions - is an additional welcome consequence. The applicability of Rayleigh calibration is lost due to the nonlinear character of the excitation process. So-called ''flow tube reactions'' which generate well-defined atomic densities with the aid of titration methods can be applied as reference sources in this situation. This procedure requires that the reference source can be attached to the experimental chamber in accordance with the vacuum requirements

[en] The atmospheric pressure plasma jet is a capacitively coupled radio frequency discharge (13.56 MHz) running with a high helium flux (2 m³ h^-1) between concentric electrodes. Small amounts (0.5%) of admixed molecular oxygen do not disturb the homogeneous plasma discharge. The jet effluent leaving the discharge through the ring-shaped nozzle contains high concentrations of radicals at a low gas temperature-the key property for a variety of applications aiming at treatment of thermally sensitive surfaces. We report on absolute atomic oxygen density measurements by two-photon absorption laser-induced fluorescence (TALIF) spectroscopy in the jet effluent. Calibration is performed with the aid of a comparative TALIF measurement with xenon. An excitation scheme (different from the one earlier published) providing spectral matching of both the two-photon resonances and the fluorescence transitions is applied

[en] A global model of a homogeneous plasma bulk oscillating between electron-free radio-frequency (rf) sheaths is developed. Particle and power balance, including ohmic heating loss for bulk-electrons and ions in the sheaths, yield the bulk electron temperature and density. Explicit time dependence of the reduced bulk electric field and correspondingly of the total ionization rate and electron transport coefficients is accounted for. Results for a gas mixture of 0.5 vol% oxygen in helium at atmospheric pressure within a 1 mm discharge gap as a function of the 13.56 MHz rf power density are presented and compared with a semi-kinetic 1D-fluid simulation. The quality of agreement is critically analyzed and correlated with the individual global model assumptions. (fast track communication)

[en] A micro atmospheric pressure plasma jet (μ-APPJ) has been designed providing excellent access for optical diagnostics and a simple geometry ideally suited for modeling and simulation. The plasma jet is a homogeneous non-equilibrium discharge at ambient pressure. It operates with a noble base gas and a volume-percentage admixture of a molecular gas. Laser spectroscopy and optical emission spectroscopy can be applied in the discharge volume and the effluent region. Applications of the discharge are mainly based on reactive species in the effluent. The effluent region of the discharge operated in helium with an oxygen admixture has been investigated. Highly reactive ground state atomic oxygen as measured by absolutely calibrated two-photon laser induced fluorescence spectroscopy (TALIF) is observed up to several centimeters away from the nozzle in the effluent. Detailed understanding of the underlying transport mechanisms requires investigations of both the discharge volume and the effluent region. (author)

[en] The two-photon resonances of atomic hydrogen (λ=2x205.1 nm), atomic nitrogen (λ=2x206.6 nm) and atomic oxygen (λ=2x225.6 nm) are investigated together with two selected transitions in krypton (λ=2x204.2 nm) and xenon (λ=2x225.5 nm). The natural lifetimes of the excited states, quenching coefficients for the most important collisions partners, and the relevant ratios of the two-photon excitation cross sections are measured. These data can be applied to provide a calibration for two-photon laser-induced fluorescence measurements based on comparisons with spectrally neighbouring noble gas resonances. (author)