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A gas flow unified measurement system (UMS-G) for sequential measurement of gas diffusion and gas permeability of geosynthetic clay liners (GCLs) under applied stress conditions (2 to 20 kPa) is described. Measurements made with the UMS-G are compared with measurements made with conventional experimental devices and are found to give similar results. The UMS-G removes the need to rely on two separate systems and increases further the reliability of the gas properties' measurements. This study also shows that the gas diffusion and gas permeability reduce greatly with the increase of both gravimetric water content and apparent degree of saturation. The effect of applied stress on gas diffusion and gas permeability is found to be more pronounced at gravimetric water content greater than 60%. These findings suggest that at a nominal overburden stress of 20 kPa, the GCL used in the present investigation needs to be hydrated to 134% gravimetric water content (65% apparent degree of saturation) before gas diffusion and gas permeability drop to 5.5 x [10.sup.-11] [m.sup.2] x [s.sup.-1] and 8.0 x [10.sup.-13] m x [s.sup.-1], respectively, and to an even higher gravimetric water content (apparent degrees of saturation) at lower stress. Key words: geosynthetic clay liner, gas flow, diffusion, advection, gravimetric water content. Dans le cadre de cette etude, on decrit un systeme de mesure du flux gazeux unifie (UMS-G) afin de mesurer sequentiellement la diffusion gazeuse et la permeabilite au gaz des membranes geosynthetiques d'etancheite d'argile (GCL) soumises des conditions de contrainte (2 20 kPa). Les mesures prises au moyen de l'UMS-G sont comparees aux mesures obtenues au moyen de dispositifs experimentaux courants et il s'avere que les resultats sont semblables. En utilisant l'UMS-G, il n'est plus necessaire d'avoir deux systemes separes et la fiabilite des mesures des proprietes des gaz augmente davantage. De plus cette etude demontre que la diffusion gazeuse et la permeabilite au gaz diminuent considerablement lorsqu'a la fois la teneur en eau gravimetrique et le degre de saturation apparent augmentent. Lorsque la teneur en eau gravimetrique est superieure 60%, on constate que l'effet de la contrainte appliquee sur la diffusion gazeuse et la permeabilite au gaz est plus prononce. Ces resultats suggerent que sous une surcharge de 20 kPa, la GCL utilisee aux fins de cette investigation doit subir une hydratation jusqu'a une teneur en eau gravimetrique de 134% (degre de saturation apparent de 65%) avant que la diffusion gazeuse et la permeabilite au gaz ne baissent jusqu'a 5.5 x [10.sup.-11] [m.sup.2] x [s.sup.-1] et 8.0 x [10.sup.-13] m x [s.sup.-1], respectivement, et jusqu'a une teneur en eau gravimetrique encore plus elevee (degre de saturation apparent) a des contraintes plus faibles. [Traduit par la Redaction] Mots-cles: membrane geosynthetique d'etancheite d'argile (GCL), flux gazeux, diffusion, advection, teneur en eau gravimetrique., Introduction Evaluation of gas migration is important in engineered cover systems of waste containment facilities to prevent or minimize possible contamination of the environment following their closure due to gas [...]

A gas flow regulator for ion propulsion systems on board small satellites is proposed. The device is fabricated by means of micromachining techniques and is made up of a silicon die and a borosilicate glass cover joined together by means of anodic bonding. The fabrication process of two different versions of the device is described. The gas mass flow dependence on both the inlet pressure and the absolute temperature is measured and discussed.

An image processing technique was designed to be utilized in combination with a Fabry-Perot interferometer for time-resolved velocity measurements in gas flows. The method was employed to obtain the Doppler shift in Mie or Rayleigh scattered light from the measurement volume. The technique minimizes the unwanted effects due to the drifting of laser frequency and interferometer alignment. The scattered light is mixed with unshifted light from the interrogation laser for reference before it is passed through the interferometer.

Application of electrothermal launchers for obtaining powder materials coatings with improved values of density and adhesion requires formation of the gas flow region, immediately following behind the shock wave, where microparticles are being caught into acceleration. A method of such region forming by means of the shock wave space and time shaping is presented. The flow dynamics analysis on the basis of a numerical model which was carried out for the case of two gaps in the launcher discharge unit, has shown that it is possible to accelerate microparticles up to very high velocities (2 km/s and higher) with simultaneous control of their temperature and to increase substantially the launcher efficiency. Measurements with the experimental equipment allowed us to determine dynamic parameters of flows, the velocity and extension of the shock-compressed region as well as velocities of the shock-waves and main flow region. Registration of plasma flows radiation spectra permitted to determine their temperature. The obtained experimental results are in good correlation with computer simulation data. Index Terms - Coating, microparticle, flow, electrothermal launcher

An analytic and experimental investigation into gaseous flow with slight rarefaction through long microchannels is undertaken. A two-dimensional (2-D) analysis of the Navier-Stokes equations with a first-order slip-velocity boundary condition demonstrates that both compressibility and rarefied effects are present in long microchannels. By undertaking a perturbation expansion in [Epsilon], the height-to-length ratio of the channel, and using the ideal gas equation of state, it is shown that the zeroth-order analytic solution for the streamwise mass flow corresponds well with the experimental results. Also, the effect of slip upon the pressure distribution is derived, and it is obtained that this slip velocity leads directly to a wall-normal migration of mass. The fabrication of wafer-bonded microchannels that possess well-controlled surface structure is described, and a means for accurately measuring the mass flow through the channels is presented. Experimental results obtained with this mass-flow measurement technique for streamwise helium mass flow through microchannels 52.25-[[micro]meter] wide, 1.33-[[micro]meter] deep, and 7500-[[micro]meter] long for a pressure range of 1.6-4.2 atmospheres (outlet pressures at atmospheric) are presented and shown to compare favorably with the analysis. [147] Index Terms - Fluid flow measurement, microelectromechanical devices, perturbation methods, rarefied gas dynamics.

An experimental study revealed the velocities of atomic hydrogen and helium in an arcjet thruster to be similar, thereby implying velocity measurements near the exit plane to be representative of the average mass velocity. This suggests that species specific velocity-measurement strategies are versatile in quantifying velocity measures of the related species near the exit plane.

For the first time, to the best of our knowledge, two-dimensional instantaneous measurements of the flow velocity and the gas temperature have been performed in a turbulent flame with simultaneous use of particle image velocimetry and planar filtered Rayleigh scattering. These single-shot measurements provide simultaneous information on the local flame structure (curvature and temperature gradients) and on the local flow conditions (vortices, flow divergences, and strain rates). The applicability of the technique is demonstrated in a turbulent lean [CH.sub.4]-air V flame. OCIS codes: 120.1740, 120.6780, 290.5850, 290.5870.

Oxygen laser-induced fluorescence was studied experimentally to quantify significant error and uncertainty sources and to evaluate the technique feasibility for gas temperature measurements in the 1-6-atm, 300-500-K regime. The dominant uncertainty source is quantum noise. For low-speed flows, the dominant error source is nonlinear process errors originating from oxygen ion fluorescence and saturation. For flows where the pressure is unknown or variable, collisional quenching may introduce an additional error up to 3 K/atm. For high-speed flows above 300 K, the dominant error source is the slow vibrational relaxation time of oxygen molecules. The optimum experimental conditions are determined by budgeting the allowable temperature inaccuracy to various uncertainty and error sources. In general, the nonlinear process errors limit the laser fluence that may be used, and the quantum noise determines the minimum number of laser shots per measurement.

Images show how an ionization cloud forms at the needle electrode, how the cloud evolves into a shell, and how one or more streamers emerge from this shell and propagate. Index Terms--Gas discharges, pulsed corona, streamer inception, streamer propagation.

The high-voltage (HV) nanosecond discharge in wide pressure range develops in the form of the streamer discharge. Intensified charge-coupling device images of the discharge development and propagation in pure air are presented. For cathode-directed streamer, the area of streamer branching is obtained as well as dependence between branching intensity and discharge parameters. The streamer structure has been measured when the streamer was initiated by a long HV pulse. Index Terms--Branching, nanosecond pulsed discharge, streamer.

The paper presents the constructive details and functioning principle of an electronic volumetric flow meter for gases, which exploits the properties of magnetic fluids and has no moving mechanical components. It is a bidirectional flow meter, operating both in static and in moving conditions. The flow meter has a sensing unit, which consists of two sensors, one for differential pressure and an other for acceleration or inclination angle and of a tubular measuring element, as well as an electronic measuring system. Details are given on the hydrodynamic-electronic correction mechanism, which eliminates the influences of inclinations and accelerations on the volumic flow signal, followed by a description of the main features of the electronic system. The experiments performed showed the possibility of metering even very small gas volumes, such as 0.1 [cm.sup.3] at a flow rate of 50 [cm.sup.3]/min. The metering at higher flow rate values, up to 100 [m.sup.3]/h, needed only the insert of the measuring element corresponding to the requested flow rate domain.

Researchers have figured out a new way to accelerate crude oil flow using electric and magnetic pulses, which could help harvest crude oil buried in fields deep below the seafloor. The new method d is based on the simple concept of sending a magnetic or electric pulse through the pipeline and into the oil that causes the wax-like molecules in the crude oil to cluster together into a smaller number of large particles, which makes it flow more easily.