Sample records for stratified charge spark

  1. Combustion characteristics of spark-ignition and pilot flame ignition systems in a model Wankel stratified charge engine

    Muroki, T. [Kanagawa Inst. of Technology, Dept. of Mechanical Engineering, Kanagawa (Japan); Moriyoshi, Y. [Chiba Univ., Dept. of Electronics and Mechanical Engineering, Chiba (Japan)


    In a stratified charge engine, a glow plug pilot flame ignition system has been compared with a spark-ignition system for a model stratified charge Wankel combustion chamber. A motored two-stroke diesel engine was operated as a rapid compression and expansion machine with the cylinder head replaced by a model Wankel combustion chamber designed to simulate the temporal changes of air flow and pressure fields inside the chamber of an actual engine. It was found that the pilot flame ignition system had better ignitability and improved combustion characteristics, especially in the lean mixture range, relative to the spark-ignition system. (Author)

  2. Improving the performance and fuel consumption of dual chamber stratified charge spark ignition engines

    Sorenson, S.C.; Pan, S.S.; Bruckbauer, J.J.; Gehrke, G.R.


    A combined experimental and theoretical investigation of the nature of the combustion processes in a dual chamber stratified charge spark ignition engine is described. This work concentrated on understanding the mixing process in the main chamber gases. A specially constructed single cylinder engine was used to both conduct experiments to study mixing effects and to obtain experimental data for the validation of the computer model which was constructed in the theoretical portion of the study. The test procedures are described. Studies were conducted on the effect of fuel injection timing on performance and emissions using the combination of orifice size and prechamber to main chamber flow rate ratio which gave the best overall compromise between emissions and performance. In general, fuel injection gave slightly higher oxides of nitrogen, but considerably lower hydrocarbon and carbon monoxide emissions than the carbureted form of the engine. Experiments with engine intake port redesign to promote swirl mixing indicated a substantial increase in the power output from the engine and, that an equivalent power levels, the nitric oxide emissions are approximately 30% lower with swirl in the main chamber than without swirl. The development of a computer simulation of the combustion process showed that a one-dimensional combustion model can be used to accurately predict trends in engine operation conditions and nitric oxide emissions even though the actual flame in the engine is not completely one-dimensional, and that a simple model for mixing of the main chamber and prechamber intake gases at the start of compression proved adequate to explain the effects of swirl, ignition timing, overall fuel air ratio, volumetric efficiency, and variations in prechamber air fuel ratio and fuel rate percentage on engine power and nitric oxide emissions. (LCL)

  3. Combustion characteristics of spark ignition and pilot flame ignition systems in a stratified charge Wankel type rotary engine; Sojo kyuki bankerugata rotary kikan ni okeru spark plug tenka to pilot kaen tenka ni yoru nensho tokusei

    Song, Y.; Moriyoshi, Y.; Wada, Y. [Chiba University, Chiba (Japan); Muroki, T. [Kanagawa Institute of Technology, Kanagawa (Japan)


    A pilot flame ignition system, which has superior characteristics in the high ignition energy and the large flame contact area to a conventional spark ignition system, is experimentally examined by the indicated pressure analysis and the high speed direct photography. A model combustion chamber, which simulates a Wankel-type direct injection stratified charge rotary engine, was employed to test the ignition performance of both the pilot flame ignition and spark ignition systems. As a result, it was found that the pilot flame system successfully ignites the very lean charge stratified mixture which the spark system fails to ignite and that the combustion characteristic difference using different ignition systems becomes small as the overall equivalence ratio is increased. 6 refs., 15 figs., 2 tabs.

  4. Fuel Burning Rate Model for Stratified Charge Engine

    SONG Jin'ou; JIANG Zejun; YAO Chunde; WANG Hongfu


    A zero-dimensional single-zone double-curve model is presented to predict fuel burning rate in stratified charge engines, and it is integrated with GT-Power to predict the overall performance of the stratified charge engines.The model consists of two exponential functions for calculating the fuel burning rate in different charge zones.The model factors are determined by a non-linear curve fitting technique, based on the experimental data obtained from 30 cases in middle and low loads.The results show good agreement between the measured and calculated cylinder pressures,and the deviation between calculated and measured cylinder pressures is less than 5%.The zerodimensional single-zone double-curve model is successful in the combustion modeling for stratified charge engines.

  5. Enhanced charge transport kinetics in anisotropic, stratified photoanodes.

    Yazdani, Nuri; Bozyigit, Deniz; Utke, Ivo; Buchheim, Jakob; Youn, Seul Ki; Patscheider, Jörg; Wood, Vanessa; Park, Hyung Gyu


    The kinetics of charge transport in mesoporous photoanodes strongly constrains the design and power conversion efficiencies of dye sensitized solar cells (DSSCs). Here, we report a stratified photoanode design with enhanced kinetics achieved through the incorporation of a fast charge transport intermediary between the titania and charge collector. Proof of concept photoanodes demonstrate that the inclusion of the intermediary not only enhances effective diffusion coefficients but also significantly suppresses charge recombination, leading to diffusion lengths two orders of magnitude greater than in standard mesoporous titania photoanodes. The intermediary concept holds promise for higher-efficiency DSSCs.

  6. Dust particle charge distribution in a stratified glow discharge

    Sukhinin, Gennady I [Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Lavrentyev Ave., 1, Novosibirsk 630090 (Russian Federation); Fedoseev, Alexander V [Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Lavrentyev Ave., 1, Novosibirsk 630090 (Russian Federation); Ramazanov, Tlekkabul S [Institute of Experimental and Theoretical Physics, Al Farabi Kazakh National University, Tole Bi, 96a, Almaty 050012 (Kazakhstan); Dzhumagulova, Karlygash N [Institute of Experimental and Theoretical Physics, Al Farabi Kazakh National University, Tole Bi, 96a, Almaty 050012 (Kazakhstan); Amangaliyeva, Rauan Zh [Institute of Experimental and Theoretical Physics, Al Farabi Kazakh National University, Tole Bi, 96a, Almaty 050012 (Kazakhstan)


    The influence of a highly pronounced non-equilibrium characteristic of the electron energy distribution function in a stratified dc glow discharge on the process of dust particle charging in a complex plasma is taken into account for the first time. The calculated particle charge spatial distribution is essentially non-homogeneous and it can explain the vortex motion of particles at the periphery of a dusty cloud obtained in experiments.

  7. Internal combustion engine using premixed combustion of stratified charges

    Marriott, Craig D.; Reitz, Rolf D. (Madison, WI


    During a combustion cycle, a first stoichiometrically lean fuel charge is injected well prior to top dead center, preferably during the intake stroke. This first fuel charge is substantially mixed with the combustion chamber air during subsequent motion of the piston towards top dead center. A subsequent fuel charge is then injected prior to top dead center to create a stratified, locally richer mixture (but still leaner than stoichiometric) within the combustion chamber. The locally rich region within the combustion chamber has sufficient fuel density to autoignite, and its self-ignition serves to activate ignition for the lean mixture existing within the remainder of the combustion chamber. Because the mixture within the combustion chamber is overall premixed and relatively lean, NO.sub.x and soot production are significantly diminished.

  8. Invited Review. Combustion instability in spray-guided stratified-charge engines. A review

    Fansler, Todd D. [Univ. of Wisconsin, Madison, WI (United States); Reuss, D. L. [Univ. of Michigan, Ann Arbor, MI (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States); Sick, V. [Univ. of Michigan, Ann Arbor, MI (United States); Dahms, R. N. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)


    Our article reviews systematic research on combustion instabilities (principally rare, random misfires and partial burns) in spray-guided stratified-charge (SGSC) engines operated at part load with highly stratified fuel -air -residual mixtures. Results from high-speed optical imaging diagnostics and numerical simulation provide a conceptual framework and quantify the sensitivity of ignition and flame propagation to strong, cyclically varying temporal and spatial gradients in the flow field and in the fuel -air -residual distribution. For SGSC engines using multi-hole injectors, spark stretching and locally rich ignition are beneficial. Moreover, combustion instability is dominated by convective flow fluctuations that impede motion of the spark or flame kernel toward the bulk of the fuel, coupled with low flame speeds due to locally lean mixtures surrounding the kernel. In SGSC engines using outwardly opening piezo-electric injectors, ignition and early flame growth are strongly influenced by the spray's characteristic recirculation vortex. For both injection systems, the spray and the intake/compression-generated flow field influence each other. Factors underlying the benefits of multi-pulse injection are identified. Finally, some unresolved questions include (1) the extent to which piezo-SGSC misfires are caused by failure to form a flame kernel rather than by flame-kernel extinction (as in multi-hole SGSC engines); (2) the relative contributions of partially premixed flame propagation and mixing-controlled combustion under the exceptionally late-injection conditions that permit SGSC operation on E85-like fuels with very low NOx and soot emissions; and (3) the effects of flow-field variability on later combustion, where fuel-air-residual mixing within the piston bowl becomes important.

  9. Numerical Study of Stratified Charge Combustion in Wave Rotors

    Nalim, M. Razi


    A wave rotor may be used as a pressure-gain combustor effecting non-steady flow, and intermittent, confined combustion to enhance gas turbine engine performance. It will be more compact and probably lighter than an equivalent pressure-exchange wave rotor, yet will have similar thermodynamic and mechanical characteristics. Because the allowable turbine blade temperature limits overall fuel/air ratio to sub-flammable values, premixed stratification techniques are necessary to burn hydrocarbon fuels in small engines with compressor discharge temperature well below autoignition conditions. One-dimensional, unsteady numerical simulations of stratified-charge combustion are performed using an eddy-diffusivity turbulence model and a simple reaction model incorporating a flammability limit temperature. For good combustion efficiency, a stratification strategy is developed which concentrates fuel at the leading and trailing edges of the inlet port. Rotor and exhaust temperature profiles and performance predictions are presented at three representative operating conditions of the engine: full design load, 40% load, and idle. The results indicate that peak local gas temperatures will result in excessive temperatures within the rotor housing unless additional cooling methods are used. The rotor itself will have acceptable temperatures, but the pattern factor presented to the turbine may be of concern, depending on exhaust duct design and duct-rotor interaction.

  10. A vacuum spark ion source: High charge state metal ion beams

    Yushkov, G. Yu., E-mail:; Nikolaev, A. G.; Frolova, V. P. [High Current Electronics Institute, Siberian Branch of the Russian Academy of Science, Tomsk 634055 (Russian Federation); Oks, E. M. [High Current Electronics Institute, Siberian Branch of the Russian Academy of Science, Tomsk 634055 (Russian Federation); Tomsk State University of Control System and Radioelectronics, Tomsk 634050 (Russian Federation)


    High ion charge state is often important in ion beam physics, among other reasons for the very practical purpose that it leads to proportionately higher ion beam energy for fixed accelerating voltage. The ion charge state of metal ion beams can be increased by replacing a vacuum arc ion source by a vacuum spark ion source. Since the voltage between anode and cathode remains high in a spark discharge compared to the vacuum arc, higher metal ion charge states are generated which can then be extracted as an ion beam. The use of a spark of pulse duration less than 10 μs and with current up to 10 kA allows the production of ion beams with current of several amperes at a pulse repetition rate of up to 5 pps. We have demonstrated the formation of high charge state heavy ions (bismuth) of up to 15 + and a mean ion charge state of more than 10 +. The physics and techniques of our vacuum spark ion source are described.

  11. A vacuum spark ion source: High charge state metal ion beams

    Yushkov, G. Yu.; Nikolaev, A. G.; Oks, E. M.; Frolova, V. P.


    High ion charge state is often important in ion beam physics, among other reasons for the very practical purpose that it leads to proportionately higher ion beam energy for fixed accelerating voltage. The ion charge state of metal ion beams can be increased by replacing a vacuum arc ion source by a vacuum spark ion source. Since the voltage between anode and cathode remains high in a spark discharge compared to the vacuum arc, higher metal ion charge states are generated which can then be extracted as an ion beam. The use of a spark of pulse duration less than 10 μs and with current up to 10 kA allows the production of ion beams with current of several amperes at a pulse repetition rate of up to 5 pps. We have demonstrated the formation of high charge state heavy ions (bismuth) of up to 15 + and a mean ion charge state of more than 10 +. The physics and techniques of our vacuum spark ion source are described.

  12. Mixture distribution measurement using laser induced breakdown spectroscopy in hydrogen direct injection stratified charge

    Shudo, Toshio [Applied Energy System Group, Division of Energy and Environmental Systems, Hokkaido University, N13 W8 Kita-Ward, Sapporo, Hokkaido 060-8628 (Japan); Oba, Shuji [Mazda Motor Corporation, Hiroshima 730-8670 (Japan)


    Reduction in cooling loss due to the heat transfer from burning gas to the combustion chamber wall is very important for improving the thermal efficiency in hydrogen engines. The previous research has shown that the direct injection stratified charge can be a technique to reduce the cooling loss and improve thermal efficiency in hydrogen combustion. For effective reductions in cooling loss by the stratified charge, it is very important to know the relation between the fuel injection conditions and mixture distribution. The current research employs the laser induced breakdown spectroscopy as a method to measure the hydrogen concentration distribution in the direct injection stratified charge. Measurement of instantaneous local equivalence ratio by the method clears the characteristics of mixture formation in hydrogen direct injection stratified charge. This research also tries to actively control the mixture distribution using a split fuel injection. (author)

  13. Comparaison des performances moteur à charge homogène et moteur à charge stratifiée Performance Comparison Between a Homogeneous-Charge Engine and a Stratified-Charge Engine.

    Raynal B.


    Full Text Available Une évaluation des possibilités théoriques d'amélioration des moteurs actuels, faite par simulation mathématique du fonctionnement d'un moteur à allumage commandé, montre qu'un fonctionnement en mélange homogène pauvre permettrait de réduire de 16 % la consommation sur un cycle ECE chaud. Dans les mêmes conditions d'utilisation, un moteur « à charge stratifiée » idéal donnerait lieu à un gain de 41 %. Des modifications limitées du point de vue technologique ont été apportées à un moteur de série et ont permis d'étendre en mélange pauvre sa zone de fonctionnement. Les gains de consommation réalisés par rapport au moteur standard sont compris entre 5 et 10 %. Le recyclage d'une fraction modérée des gaz d'échappement permet de maintenir les émissions de NO x à moins de 5 g/essai sur cycle ECE, en conservant le gain de consommation précédent. L'analyse des performances d'un moteur Honda CVCC au banc d'essai et sur véhicule montre que les niveaux d'émissions relativement bas de ce type de moteur sont obtenus au prix d'une surconsommation importante par rapport à un véhicule équivalent équipé d'un moteur conventionnel. An evaluation of theoretical possibilities of improving existing engines, obtained by mathematical modelisation of a spark-ignition engine, shows that operating with a homogeneous lean mixture produces a 16 % reduction in consumption for a hot ECE cycle. Under the same running conditions, an ideal strotified-charge engine would produce a gain of 41 %.Limited technological modifications were made in a standard engine sa as ta extend its operating zone using a leon mixture. The consumption gains achieved compared with a standard engine are between 5 and 10%. The recycling of a moderate fraction of the exhaust gases enables NO, emissions ta be maintained at less than 5 g/test for an ECE cycle while preserving the preceding consumption gain.The performance analysis of a Honda C/CC engine on a test

  14. Flow of multiple charged accelerated metal ions from low-inductance vacuum spark

    Gorbunov, S. P.; Krasov, V. P.; Paperny, V. L.; Savyelov, A. S.


    Results of studies of the short-run beams of multiple charged fast ions that have been found earlier by the authors in a low voltage vacuum spark are presented. The ion emission was due to the formation of micropinches in the cathode plasma jet by the action of the self-magnetic field. A relation between the average velocity of the fast ions and that of the bulk of the ions of the cathode jet was obtained over a wide range of the discharge current amplitudes. The total yield of the multiple charged fast ions per pulse Nf was evaluated from the direct collector measurements with regard to a decrease in ion flow due to several reasons. This value was in satisfactory agreement with evaluation that was obtained from the ballistic pendulum measurements and gave Nf ap 5 × 1013-1014 ions per pulse at the average ion charge state of +9 at the maximum of the discharge current Id = 12 kA. Evaluation of current density for these ions gave jf ap 3 mA cm-2 at a distance of about 1 m from the anode.

  15. Flow of multiple charged accelerated metal ions from low-inductance vacuum spark

    Gorbunov, S P [Irkutsk State University, Irkutsk, 664003 (Russian Federation); Krasov, V P [Irkutsk State University, Irkutsk, 664003 (Russian Federation); Paperny, V L [Irkutsk State University, Irkutsk, 664003 (Russian Federation); Savyelov, A S [Moscow Engineering and Physical Institute, Moscow (Russian Federation)


    Results of studies of the short-run beams of multiple charged fast ions that have been found earlier by the authors in a low voltage vacuum spark are presented. The ion emission was due to the formation of micropinches in the cathode plasma jet by the action of the self-magnetic field. A relation between the average velocity of the fast ions and that of the bulk of the ions of the cathode jet was obtained over a wide range of the discharge current amplitudes. The total yield of the multiple charged fast ions per pulse N{sub f} was evaluated from the direct collector measurements with regard to a decrease in ion flow due to several reasons. This value was in satisfactory agreement with evaluation that was obtained from the ballistic pendulum measurements and gave N{sub f} {approx} 5 x 10{sup 13}-10{sup 14} ions per pulse at the average ion charge state of +9 at the maximum of the discharge current I{sub d} 12 kA. Evaluation of current density for these ions gave j{sub f} {approx} 3 mA cm{sup -2} at a distance of about 1 m from the anode.

  16. Homogeneous charge compression ignition (HCCI) - A comparison with spark ignition (SI) operation

    Christensen, Magnus


    Homogeneous Charge Compression Ignition (HCCI) is the third alternative for combustion in engines. Here a homogeneous premixed charge is used as in a spark ignited engine but the charge is compressed to auto-ignition as in a diesel. The characteristics of HCCI was compared to spark ignition (SI) using a 1.6 liter single cylinder engine. Three different fuels were used; isooctane, ethanol and natural gas. HCCI could be used with all three fuels in a single cylinder engine with a fixed compression ratio. Some remarkable results were noted in the experiments. The indicated efficiency of HCCI was much better than for SI operation. The gross indicated efficiency showed values at 50% for the richer cases. This means that the fuel consumption at part load would be reduced to the half compared to SI operation. Very little NO{sub x} was generated with HCCI, only a few ppm. With isooctane, it ranged from 4 to below 1 ppm and with ethanol even lower values. However, HCCI generated more HC and CO. Operation was noisier with HCCI than with SI. Stable and efficient operation with HCCI could be obtained with {lambda} = 3.5 to 9 using isooctane, 3.5 to 6.5 using ethanol, and 2.5 to 3.5 using natural gas. Cycle to cycle variation of combustion was very low. Isooctane could be operated unthrottled without preheating. The selection of the high compression ratio, 21:1, was dependent on the high octane number for natural gas. The attainable IMEP was 5 bar. The limit to make higher IMEP was the rate of combustion. At IMEP 5 bar the main combustion, 10-90% burn duration, took place in less than 2 crank angle degrees (CAD). This is extremely fast and gives very high rate of pressure rise, which leads to noisy operation and high loads on the engine. The lean limit was given by unstable combustion with cycle to cycle variation of combustion, and with high emissions of unburned hydrocarbons and carbon monoxide Examination paper. 15 refs, 38 figs, 1 tab

  17. Charging of dust grains in a nonequilibrium plasma of a stratified glow discharge

    Sukhinin, G. I.; Fedoseev, A. V.


    A theoretical model is presented that describes the charging of dust grains in the positive plasma column of a stratified glow dc discharge in argon. A one-dimensional self-consistent model is used to obtain axial profiles of the electric field, as well as the electron energy distribution function along the axis of the discharge tube. Radial profiles of the electric field are determined in the ambipolar diffusion approximation. It is assumed that, in the radial direction, the electron distribution function depends only on the total electron energy. Two-dimensional distributions of the discharge plasma parameters are calculated and used to determine the potential and charge of a test dust grain at a certain point within the discharge and the electrostatic forces acting on it. It is shown that the grain charge distribution depends strongly on the nonequilibrium electron distribution function and on the nonuniform distribution of the electric field in a stratified glow discharge. A discussion is presented on the suspension of dust grains, the separation of grains by size in the discharge striations, and a possible mechanism for the onset of vortex dust motion at the edge of a dust cloud.

  18. Analysis of flame propagation phenomenon in simplified stratified charge conditions; Tanjunkasareta sojo kyukiba ni okeru kaen denpa gensho no kansatsu

    Moriyoshi, Y.; Morikawa, H. [Chiba University, Chiba (Japan); Kamimoto, T. [Tokyo Institute of Technology, Tokyo (Japan)


    Since the local inhomogeneity of mixture concentration inside the cylinder affects the combustion characteristics, a basic research on combustion phenomenon in stratified charge conditions is required. The authors have made experiments with a constant-volume chamber, which can simulate an idealized stratified charge field by using a removable partition, to obtain the combustion characteristics. Also, numerical calculations are made using some combustion models. As a result, the important feature that the combustion speed is faster in stratified condition than in homogeneous condition can be predicted by the two-step reaction model. 4 refs., 8 figs.

  19. Experimental Investigation of Performance and Emissions of a Stratified Charge CNG Direct Injection Engine with Turbocharger

    Amiruddin Hilmi


    Full Text Available This paper presents the results from 1.6 litre, 4 cylinders stratified charge compressed natural gas (CNG direct injection engine with boosting device. A turbocharger with compressor trim of 40 was used to increase engine output. The engine was tested at wide open throttle (WOT and speed ranging from 1000 to 5000 rpm. Engine performance and emissions data were recorded under steady state condition. Results show turbocharged CNG engine produced an average of 26% increment in brake power and 24% additional maximum brake torque as compared with natural aspirated (NA CNG engine. Turbocharged CNG engine improved brake specific fuel consumption (BSFC and yielded higher fuel conversion efficiency (FCE. Relatively turbocharged CNG engine showed lower emission of hydrocarbon (HC and carbon monoxide (CO throughout tested engine speed. Conversely, the carbon dioxide (CO2 and nitrogen oxide (NOx emission produced were slightly higher compared with NA CNG engine.

  20. Performance and efficiency evaluation and heat release study of a direct-injection stratified-charge rotary engine

    Nguyen, H. L.; Addy, H. E.; Bond, T. H.; Lee, C. M.; Chun, K. S.


    A computer simulation which models engine performance of the Direct Injection Stratified Charge (DISC) rotary engines was used to study the effect of variations in engine design and operating parameters on engine performance and efficiency of an Outboard Marine Corporation (OMC) experimental rotary combustion engine. Engine pressure data were used in a heat release analysis to study the effects of heat transfer, leakage, and crevice flows. Predicted engine data were compared with experimental test data over a range of engine speeds and loads. An examination of methods to improve the performance of the rotary engine using advanced heat engine concepts such as faster combustion, reduced leakage, and turbocharging is also presented.

  1. spark chamber

    A few cosmic rays pass through your body every second of every day, no matter where you are. Look at the spark chamber to your right – every flash is the track made by a cosmic ray from outer space. The spark chamber is filled with a special gas mixture. Cosmic rays knock electrons out of the atoms in the gas. These electrons accelerate towards high voltage metal strips layered throughout the chamber, creating sparks like little bolts of lightning.

  2. spark chamber

    A few cosmic rays pass through your body every second of every day, no matter where you are. Look at the spark chamber to your right – every flash is the track made by a cosmic ray from outer space. The spark chamber is filled with a special gas mixture. Cosmic rays knock electrons out of the atoms in the gas. These electrons accelerate towards high voltage metal strips layered throughout the chamber, creating sparks like little bolts of lightning.

  3. Development of stratified-charge engine by impingement of fuel jet. ; Test results with gasoline fuel. Chokufunshiki shototsu kakusan sojo kyuki kikan no kaihatsu. ; Gasoline nenryo ni yoru jikken kekka

    Kato, S.; Onishi, S. (Japan Clean Engine Lab. Co. Ltd., Ishikawa (Japan))


    Development was made of direct fuel injection stratified-charge method (OSKA nethod), to make the mixture formation in the direct fuel injection engine by having fuel jet positively impinge on the impingement part, installed in the combustion chamber. In the present report, the following conclusion was obtained through experiment on gasoline fuel by a single cylinder engine with a spark ignition method, combined with the OSKA method: High compressive ratio was made adoptable by applying an OSKA method, using a single hole nozzle with low opening pressure. Due to feed air swirl, made unnecessary for the mixture formation, adoption of early injection under the high load, etc., the highest brake mean effective pressure attained to 1.04MPa, which is almost equivalent to that of carburetor type automobile gasoline engine, while the highest brake thermal efficiency did to 37.7%, which is so to that of direct fuel injection diesel engine, equal in volume. Also under the low load, obtained was a high thermal efficiency, nearing that of diesel engine. 8 refs., 9 figs., 2 tabs.

  4. Schlieren-based temperature measurement inside the cylinder of an optical spark ignition and homogeneous charge compression ignition engine.

    Aleiferis, Pavlos; Charalambides, Alexandros; Hardalupas, Yannis; Soulopoulos, Nikolaos; Taylor, A M K P; Urata, Yunichi


    Schlieren [Schlieren and Shadowgraphy Techniques (McGraw-Hill, 2001); Optics of Flames (Butterworths, 1963)] is a non-intrusive technique that can be used to detect density variations in a medium, and thus, under constant pressure and mixture concentration conditions, measure whole-field temperature distributions. The objective of the current work was to design a schlieren system to measure line-of-sight (LOS)-averaged temperature distribution with the final aim to determine the temperature distribution inside the cylinder of internal combustion (IC) engines. In a preliminary step, we assess theoretically the errors arising from the data reduction used to determine temperature from a schlieren measurement and find that the total error, random and systematic, is less than 3% for typical conditions encountered in the present experiments. A Z-type, curved-mirror schlieren system was used to measure the temperature distribution from a hot air jet in an open air environment in order to evaluate the method. Using the Abel transform, the radial distribution of the temperature was reconstructed from the LOS measurements. There was good agreement in the peak temperature between the reconstructed schlieren and thermocouple measurements. Experiments were then conducted in a four-stroke, single-cylinder, optical spark ignition engine with a four-valve, pentroof-type cylinder head to measure the temperature distribution of the reaction zone of an iso-octane-air mixture. The engine optical windows were designed to produce parallel rays and allow accurate application of the technique. The feasibility of the method to measure temperature distributions in IC engines was evaluated with simulations of the deflection angle combined with equilibrium chemistry calculations that estimated the temperature of the reaction zone at the position of maximum ray deflection as recorded in a schlieren image. Further simulations showed that the effects of exhaust gas recirculation and air

  5. A numerical analysis of the effects of a stratified pre-mixture on homogeneous charge compression ignition combustion

    Jamsran, Narankhuu; Lim, Ock Taeck [University of Ulsan, Ulsan (Korea, Republic of)


    We investigated the efficacy of fuel stratification in a pre-mixture of dimethyl ether (DME) and n-butane, which have different autoignition characteristics, for reducing the pressure rise rate (PRR) of homogeneous charge compression ignition engines. A new chemical reaction model was created by mixing DME and n-butane and compared with existing chemical reaction models to verify the effects observed. The maximum PRR depended on the mixture ratio. When DME was charged with stratification and n-butane was charged with homogeneity, the maximum PRR was the lowest among all the mixtures studied. Calculations were performed using CHEMKIN and modified using SENKIN software.

  6. Fastdata processing with Spark

    Karau, Holden


    This book will be a basic, step-by-step tutorial, which will help readers take advantage of all that Spark has to offer.Fastdata Processing with Spark is for software developers who want to learn how to write distributed programs with Spark. It will help developers who have had problems that were too much to be dealt with on a single computer. No previous experience with distributed programming is necessary. This book assumes knowledge of either Java, Scala, or Python.

  7. ElectroSpark Deposition


    ElectroSpark Deposition Hard Chrome Alternatives Team Joint Cadmium Alternatives Team Canadian Hard Chrome Alternatives Team Joint Group on Pollution...00-2007 to 00-00-2007 4. TITLE AND SUBTITLE ElectroSpark Deposition 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...Processes, Inc. ElectroSpark Deposition (ESD) Results of Materials Testing and Technology Insertion January 25, 2007 Advanced Surfaces And Processes, Inc. 3

  8. Spark-hdf5


    The spark-hdf5 package is an extension to the Apache Spark program to allow native access to HDF5 files. It allows users to query the structured files using SQL-like syntax, and can parallelize large queries across several workers.

  9. SparkJet Efficiency

    Golbabaei-Asl, Mona; Knight, Doyle; Anderson, Kellie; Wilkinson, Stephen


    A novel method for determining the thermal efficiency of the SparkJet is proposed. A SparkJet is attached to the end of a pendulum. The motion of the pendulum subsequent to a single spark discharge is measured using a laser displacement sensor. The measured displacement vs time is compared with the predictions of a theoretical perfect gas model to estimate the fraction of the spark discharge energy which results in heating the gas (i.e., increasing the translational-rotational temperature). The results from multiple runs for different capacitances of c = 3, 5, 10, 20, and 40 micro-F show that the thermal efficiency decreases with higher capacitive discharges.

  10. Experimental Study on Stratified and Homogeneous Combustion of a Methanol Direct-Injection Spark-Ignition Engine%甲醇缸内直喷发动机分层燃烧和均质燃烧的试验研究

    李本正; 刘圣华; 农金吉; 宫艳峰


    In a methanol direct-injection spark-ignition (DISI) engine retrofitted from a 4-cylinder diesel engine, the fuel needs to be injected into the cylinder near the end of compression stroke to realize the stratified combustion at partial loads for improving fuel economy. However, at high loads, the fuel needs to be injected into cylinder during intake stroke to realize the homogeneous combustion for achieving high power output. The results show that the methanol DISI engine can operate within the excessive air ratio of 2. 23 and its maximum brake thermal efficiency reaches 35. 3%. The methanol DISI engine exhibits higher power output than that of the original diesel engine. The cyclic variations of imep maintains low under a wide range of operating conditions, which shows a stable combustion. NO_x and soot emissions can be de-creased simultaneously.%在一台4缸柴油机改造的火花点火甲醇缸内直喷发动机上,中低负荷时采用分层燃烧来实现好的燃油经济性,高负荷时采用均质燃烧来获得好的动力性能.试验结果表明,甲醇缸内直喷发动机可以实现过量空气系数为2.23的分层稀薄燃烧;发动机的有效热效率最高可达35.3%,远高于普通汽油机;低速转矩大,动力性超过原机水平;在宽广的转速和负荷范围下平均指示压力的循环变动较小,燃烧稳定性好;该甲醇发动机可以实现NO_x和碳烟的同时降低.

  11. Mars Spark Source Prototype

    Eichenberg, Dennis J.; Lindamood, Glenn R.; Weiland, Karen J.; VanderWal, Randall L.


    The Mars Spark Source Prototype (MSSP) hardware has been developed as part of a proof of concept system for the detection of trace metals such as lead, cadmium, and arsenic in Martian dusts and soils. A spark discharge produces plasma from a soil sample and detectors measure the optical emission from metals in the plasma that will allow their identification and quantification. Trace metal measurements are vital for the assessment of the potential toxicity of the Martian environment for human exploration. The current method of X-ray fluorescence can yield concentrations only of major species. Other instruments are incompatible with the volume, weight, and power constraints for a Mars mission. The instrument will be developed primarily for use in the Martian environment, but would be adaptable for terrestrial use in environmental monitoring. This paper describes the Mars Spark Source Prototype hardware, the results of the characterization tests, and future plans for hardware development.

  12. Generation of nanoparticles by spark discharge

    Tabrizi, N. S.; Ullmann, M.; Vons, V. A.; Lafont, U.; Schmidt-Ott, A.


    The production of nanoparticles by microsecond spark discharge evaporation in inert gas is studied systematically applying transmission electron microscopy, mobility analysis and BET surface area measurement. The method of spark discharge is of special interest, because it is continuous, clean, extremely flexible with respect to material, and scale-up is possible. The particle size distributions are narrow and the mean primary particle size can be controlled via the energy per spark. Separated, unagglomerated particles, 3-12 nm in size, or agglomerates can be obtained depending on the flow rate. The nanoparticulate mass produced is typically 5 g/kWh. A formula is given, which estimates the mass production rate via thermal conductivity, evaporation enthalpy and the boiling point of the material used. We showed that with gas purified at the spot, the method produced gold particles that were so clean that sintering of agglomerated particles occurred at room temperature. The influence of a number of parameters on the primary particle size and mass production rate was studied and qualitatively understood with a model of Lehtinen and Zachariah (J Aerosol Sci 33:357-368, 2002). Surprisingly high charging probabilities for one polarity were obtained. Spark generation is therefore of special interest for producing monodisperse aerosols or particles of uniform size via electrical mobility analysis. Qualitative observations in the present study include the phenomenon of material exchange between the electrodes by the spark, which opens the possibility of producing arbitrary mixtures of materials on a nanoscale. If spark generation of nanoparticles is performed in a standing or almost standing gas, an aerogel of a web-like structure forms between surfaces of different electrical potential.

  13. An Empirical Comparison of Joint and Stratified Frameworks for Studying G × E Interactions: Systolic Blood Pressure and Smoking in the CHARGE Gene-Lifestyle Interactions Working Group.

    Sung, Yun Ju; Winkler, Thomas W; Manning, Alisa K; Aschard, Hugues; Gudnason, Vilmundur; Harris, Tamara B; Smith, Albert V; Boerwinkle, Eric; Brown, Michael R; Morrison, Alanna C; Fornage, Myriam; Lin, Li-An; Richard, Melissa; Bartz, Traci M; Psaty, Bruce M; Hayward, Caroline; Polasek, Ozren; Marten, Jonathan; Rudan, Igor; Feitosa, Mary F; Kraja, Aldi T; Province, Michael A; Deng, Xuan; Fisher, Virginia A; Zhou, Yanhua; Bielak, Lawrence F; Smith, Jennifer; Huffman, Jennifer E; Padmanabhan, Sandosh; Smith, Blair H; Ding, Jingzhong; Liu, Yongmei; Lohman, Kurt; Bouchard, Claude; Rankinen, Tuomo; Rice, Treva K; Arnett, Donna; Schwander, Karen; Guo, Xiuqing; Palmas, Walter; Rotter, Jerome I; Alfred, Tamuno; Bottinger, Erwin P; Loos, Ruth J F; Amin, Najaf; Franco, Oscar H; van Duijn, Cornelia M; Vojinovic, Dina; Chasman, Daniel I; Ridker, Paul M; Rose, Lynda M; Kardia, Sharon; Zhu, Xiaofeng; Rice, Kenneth; Borecki, Ingrid B; Rao, Dabeeru C; Gauderman, W James; Cupples, L Adrienne


    Studying gene-environment (G × E) interactions is important, as they extend our knowledge of the genetic architecture of complex traits and may help to identify novel variants not detected via analysis of main effects alone. The main statistical framework for studying G × E interactions uses a single regression model that includes both the genetic main and G × E interaction effects (the "joint" framework). The alternative "stratified" framework combines results from genetic main-effect analyses carried out separately within the exposed and unexposed groups. Although there have been several investigations using theory and simulation, an empirical comparison of the two frameworks is lacking. Here, we compare the two frameworks using results from genome-wide association studies of systolic blood pressure for 3.2 million low frequency and 6.5 million common variants across 20 cohorts of European ancestry, comprising 79,731 individuals. Our cohorts have sample sizes ranging from 456 to 22,983 and include both family-based and population-based samples. In cohort-specific analyses, the two frameworks provided similar inference for population-based cohorts. The agreement was reduced for family-based cohorts. In meta-analyses, agreement between the two frameworks was less than that observed in cohort-specific analyses, despite the increased sample size. In meta-analyses, agreement depended on (1) the minor allele frequency, (2) inclusion of family-based cohorts in meta-analysis, and (3) filtering scheme. The stratified framework appears to approximate the joint framework well only for common variants in population-based cohorts. We conclude that the joint framework is the preferred approach and should be used to control false positives when dealing with low-frequency variants and/or family-based cohorts.

  14. Stratified charge combustion system using pilot flame ignition. Application to a model combustion chamber of Wankel-type rotary engine; Pilot kaen chakka ni yoru sojo kyuki nensho hoshiki no kenkyu. Wankel gata rotary kikan no model nenshoshitsu ni okeru nensho kaiseki

    Moriyoshi, Y.; Muroki, T.; Song, Y. [Chiba University, Chiba (Japan). Faculty of Engineering


    The ignition mechanism of a pilot flame in a stratified charge mixture was examined using a model combustion chamber of a Wankel-type rotary engine. Experimental study such as LDV measurement, pressure data analysis, high-speed photography and image analysis provides detailed knowledge concerning the stratified charge combustion, which is complemented by theoretical study of the mixture formation process inside the combustion chamber. Characteristics of the pilot flame as an ignition source and the mixture formation inside the model chamber required for enhanced combustion are determined in this study. 6 refs., 11 figs., 2 tabs.

  15. Fast data processing with Spark

    Sankar, Krishna


    Fast Data Processing with Spark - Second Edition is for software developers who want to learn how to write distributed programs with Spark. It will help developers who have had problems that were too big to be dealt with on a single computer. No previous experience with distributed programming is necessary. This book assumes knowledge of either Java, Scala, or Python.

  16. Study of stratified charge wankel rotary engine. (Part 1). ; Summary of the combustion by pilot-burner flame ignition. Sojo kyuki nensho wankel gata kaiten pisuton kikan no kenkyu. (1). ; Pilot kaen chakka ni yoru nensho no gaiyo

    Muroki, T. (Chiba Univ., Chiba (Japan). Faculty of Engineering); Morita, K. (Mazda Motor Corp., Hiroshima (Japan))


    In the U.S.A., the stratified charge wankel rotary engine (hereinafter referred to as DISC-RE) has been developed. This engine uses various kinds of fuel, has a low compression ratio, is equipped with a turbo supercharger, adopts the pilot flame forced ignition system and shows excellent performance. In order to elucidate the basic characteristics of this new internal combustion engine, an experiment was conducted using a single cylinder two cycle diesel engine as a rapid pressure device, to which a modelled combustion chamber was attached. This article is its first report. The main results of the experiment are as follows: It is considered that the combustion process in the modelled combustion chamber used in this study can be made almost similar to the combustion process in the experimental DISC-RE and is sufficient for understanding the basic characteristics of the combustiion. The form of the basic combustion of main fuel is that violent pre-mixed combustion occurs after ignition, then very slow combustion persists for a long time. In order to activate diffuse combustion, it is necessary to facilitate diffusion of the flame of pre-mixed combustion and mixing of fuel and air, and to raise wall temperature of the combustion chamber, etc. 3 refs., 16 figs., 1 tab.

  17. Exergetic Evaluation of Speed and Load Effects in Spark Ignition Engines Évaluation exergétique des effets de la vitesse et de la charge dans les moteurs àallumage par étincelle

    Sezer I.


    Full Text Available This study investigates the effects of various operating conditions in spark ignition engines via an exergy analysis. A thermodynamic cycle model including compression, combustion and expansion processes was used for investigation. Induction and exhaust processes were computed with a simple approximation method. The principles of the second law were applied to the cycle model to perform the exergy analysis. Exergetic variables, i.e., the exergy transfers with heat and work, irreversibilities, thermomechanical exergy, fuel chemical exergy and total exergy were calculated in the exergy analysis. Variation of the exergetic parameters and the distribution of them into the fuel exergy were determined for various operating conditions, i.e., engine speed and load. The first and second law efficiencies and specific fuel consumption were also computed to reveal the optimum operating conditions. The results show that the exergy transfer with heat decreases and the exergy transfer with exhaust gases increases with increasing engine speed. Engine speed of 3 000 rpm gives the maximum exergy transfer as work, the minimum irreversibility and the best efficiency and fuel consumption. Exergy transfers with heat, work and exhaust and irreversibilities increase with increasing engine load. Additionally, the first and second law efficiencies increase and fuel consumption decreases with increasing engine load, so a high engine load gives the best efficiency and fuel consumption. Cette étude examine les effets des différentes conditions de fonctionnement de moteurs à allumage commandé via une analyse exergétique. Un modèle de cycle thermodynamique comprenant les processus de compression, combustion et détente a été utilisé. Les processus d’admission et d’échappement sont modélisés à l’aide d’une méthode simple d’approximation. Les principes de la deuxième loi de la thermodynamique ont été appliqués au modèle de cycle pour effectuer l

  18. The Effect of Spark Timing on the Spark Ignition

    Rafeq A. Khalefa


    Full Text Available  In this work the effect of spark timing on the spark ignition engines is investigated by computer simulation and experimental test for speeds of (1500,2000,2500,3000 and 3500rpm at spark timing of (20o,30o,40o,50o and 60o before TDC for each speed. This is done in order to find a suitable  mathematical expression for spark ignition advancing with respect to the speed of the engine to predict the correct ignition advance  as in real engines .The results showed that the method of using a mathematical expression is more realistic and reasonable  comparing  with the results obtained by other workers. 

  19. Scaling spark on HPC systems

    Chaimov, N; Malony, A.; Canon, S.; C. Iancu; Ibrahim, KZ; Srinivasan, J.


    Copyright © 2016 by the Association for Computing Machinery, Inc. (ACM).We report our experiences porting Spark to large production HPC systems. While Spark performance in a data center installation (with local disks) is dominated by the network, our results show that file system metadata access latency can dominate in a HPC installation using Lustre: it determines single node performance up to 4× slower than a typical workstation. We evaluate a combination of software techniques and hardware...

  20. Arc resistance of laser-triggered spark gaps

    Kushner, M. J.; Kimura, W. D.; Byron, S. R.


    In the use of spark gaps as switching devices, it is desirable to maximize the power delivered to the load and to minimize the power deposited in the switch; that is, it is desirable for the resistance of the switch to be negligible as compared to the load. The hydrodynamic time scale for expansion of the arc in a spark gap and hence for the reduction in its resistance to a small value is tens to hundreds of nanoseconds. Therefore, with current pulses of duration of a few hundred nanoseconds or less, the resistance of the spark gap may be a significant fraction of that of the load. In this paper, we report on measurements that determine the resistance of the arc in a fully diagnosed laser-triggered spark gap. The spark gap switches a 100-ns, 1.5-Ω waterline into a 1.5-Ω load resistor. A capacitive voltage divider housed within the switch enclosure measures the voltage drop across the switch, a current-viewing resistor measures the current, and an interferometer measures the diameter of the plasma column, a value required to calculate its inductance. The resistance of the arc is found to remain in excess of 0.1-0.2 Ω for the duration of the current pulse for a variety of switch gas mixtures. The resistance decreases with increasing charging voltage on the waterline at the time of triggering and decreases with decreasing average molecular weight of the gas mixture in which the arc is sustained.

  1. Underwater spark discharge with long transmission line for cleaning horizontal wells

    Lee, Kern; Chung, Kyoung-Jae; Hwang, Y. S.; Kim, C. Y.


    A transmission line is discussed for application in an underwater spark-discharge technique in the cleaning of a horizontal well by incorporating a power-transmission model into the simulation. The pulsed-spark-discharge technique has been proposed for clogged-well rehabilitation, because it removes incrustations that are attached to well screens by using strong pressure waves that are generated by the rapid expansion of a spark channel. To apply the pulsed-spark-discharge technique to the cleaning of horizontal wells, the coaxial cable between the pulsed power supply and the spark gap as a load needs to be extended to a few hundred meters. Prior to field application, pulsed-spark-discharge experiments were conducted and the role of the transmission line was examined using an improved simulation model. In the model, a non-linear interaction of the spark channel and the capacitor bank is described by the pulse-forming action of the coaxial cable. Based on the accurate physical properties of the water plasma, such as the equation of state and electrical conductivity within the region of interest, the amount of energy contributed to the development of a shock wave was evaluated. The simulation shows that if the initial conditions of the spark channel are the same, no further reduction in strength of the pressure wave occurs, even if the cable length is increased above 50 m. Hence, the degraded peak pressure that was observed in the experiments using the longer cable is attributed to a change in the initial condition of the spark channel. The parametric study suggests that the low initial charging voltage, the high ambient water pressure, and the long cable length yield the low initial spark-channel density, which results in a reduced peak pressure. The simulation of line charging is presented to discuss the principle of disturbing the pre-breakdown process by an extended cable.

  2. Are Crab nanoshots Schwinger sparks?

    Stebbins, Albert [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Yoo, Hojin [Univ. of Wisconsin, Madison, WI (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)


    The highest brightness temperature ever observed are from "nanoshots" from the Crab pulsar which we argue could be the signature of bursts of vacuum e± pair production. If so this would be the first time the astronomical Schwinger effect has been observed. These "Schwinger sparks" would be an intermittent but extremely powerful, ~103 L, 10 PeV e± accelerator in the heart of the Crab. These nanosecond duration sparks are generated in a volume less than 1 m3 and the existence of such sparks has implications for the small scale structure of the magnetic field of young pulsars such as the Crab. As a result, this mechanism may also play a role in producing other enigmatic bright short radio transients such as fast radio bursts.

  3. Efficiency of SparkJet

    Golbabaei-Asl, M.; Knight, D.; Wilkinson, S.


    The thermal efficiency of a SparkJet is evaluated by measuring the impulse response of a pendulum subject to a single spark discharge. The SparkJet is attached to the end of a pendulum. A laser displacement sensor is used to measure the displacement of the pendulum upon discharge. The pendulum motion is a function of the fraction of the discharge energy that is channeled into the heating of the gas (i.e., increasing the translational-rotational temperature). A theoretical perfect gas model is used to estimate the portion of the energy from the heated gas that results in equivalent pendulum displacement as in the experiment. The earlier results from multiple runs for different capacitances of C = 3, 5, 10, 20, and 40(micro)F demonstrate that the thermal efficiency decreases with higher capacitive discharges.1 In the current paper, results from additional run cases have been included and confirm the previous results

  4. Are Crab Nanoshots Schwinger Sparks?

    Stebbins, Albert


    The highest brightness temperature ever observed are from "nanoshots" from the Crab pulsar which we argue could be the signature of bursts of vacuum $e^{\\pm}$ pair production. If so this would be the first time the astronomical Schwinger effect has been observed. These "Schwinger sparks" would be an intermittent but extremely powerful, $\\sim 10^3 L_{\\astrosun}$, 10 PeV $e^{\\pm}$ accelerator in the heart of the Crab. These nanosecond duration sparks are generated in a volume less than $1 m^3$ and the existence of such sparks has implications for the small scale structure of the magnetic field of young pulsars such as the Crab. This mechanism may also play a role in producing other enigmatic bright short radio transients such as fast radio bursts.

  5. Bright Sparks of Our Future!

    Riordan, Naoimh


    My name is Naoimh Riordan and I am the Vice Principal of Rockboro Primary School in Cork City, South of Ireland. I am a full time class primary teacher and I teach 4th class, my students are aged between 9-10 years. My passion for education has developed over the years and grown towards STEM (Science, Technology, Engineering and Mathematics) subjects. I believe these subjects are the way forward for our future. My passion and beliefs are driven by the unique after school programme that I have developed. It is titled "Sparks" coming from the term Bright Sparks. "Sparks" is an after school programme with a difference where the STEM subjects are concentrated on through lessons such as Science, Veterinary Science Computer Animation /Coding, Eco engineering, Robotics, Magical Maths, Chess and Creative Writing. All these subjects are taught through activity based learning and are one-hour long each week for a ten-week term. "Sparks" is fully inclusive and non-selective which gives all students of any level of ability an opportunity to engage into these subjects. "Sparks" is open to all primary students in County Cork. The "Sparks" after school programme is taught by tutors from the different Universities and Colleges in Cork City. It works very well because the tutor brings their knowledge, skills and specialised equipment from their respective universities and in turn the tutor gains invaluable teaching practise, can trial a pilot programme in a chosen STEM subject and gain an insight into what works in the physical classroom.

  6. Fiber laser coupled optical spark delivery system

    Yalin, Azer [Fort Collins, CO; Willson, Bryan [Fort Collins, CO; Defoort, Morgan [Fort Collins, CO; Joshi, Sachin [Fort Collins, CO; Reynolds, Adam [Fort Collins, CO


    A spark delivery system for generating a spark using a laser beam is provided, and includes a laser light source and a laser delivery assembly. The laser delivery assembly includes a hollow fiber and a launch assembly comprising launch focusing optics to input the laser beam in the hollow fiber. The laser delivery assembly further includes exit focusing optics that demagnify an exit beam of laser light from the hollow fiber, thereby increasing the intensity of the laser beam and creating a spark. Other embodiments use a fiber laser to generate a spark. Embodiments of the present invention may be used to create a spark in an engine. Yet other embodiments include collecting light from the spark or a flame resulting from the spark and conveying the light for diagnostics. Methods of using the spark delivery systems and diagnostic systems are provided.

  7. The time response function of spark counters and RPCs

    Gobbi, A. E-mail:; Mangiarotti, A. E-mail:


    The fluctuation theory for the avalanche growth with and without space charge effects is briefly summarized and compared to a broad field of applications. These include spark counters as well as timing and trigger RPCs operated in avalanche mode. A large domain in electrical field strength, pressure, gap size and gas mixture type is covered. A reasonable agreement with the experiment is observed, giving confidence on the validity of both assumptions and treatment of the theory.

  8. Fluttering in Stratified Flows

    Lam, Try; Vincent, Lionel; Kanso, Eva


    The descent motion of heavy objects under the influence of gravitational and aerodynamic forces is relevant to many branches of engineering and science. Examples range from estimating the behavior of re-entry space vehicles to studying the settlement of marine larvae and its influence on underwater ecology. The behavior of regularly shaped objects freely falling in homogeneous fluids is relatively well understood. For example, the complex interaction of a rigid coin with the surrounding fluid will cause it to either fall steadily, flutter, tumble, or be chaotic. Less is known about the effect of density stratification on the descent behavior. Here, we experimentally investigate the descent of discs in both pure water and in a linearly salt-stratified fluids where the density is varied from 1.0 to 1.14 of that of water where the Brunt-Vaisala frequency is 1.7 rad/sec and the Froude number Fr robots for space exploration and underwater missions.

  9. Mars Spark Source Prototype Developed

    Eichenberg, Dennis J.; Lindamood, Glenn R.; VanderWal, Randall L.; Weiland, Karen J.


    The Mars Spark Source Prototype (MSSP) hardware was developed as part of a proof of concept system for the detection of trace metals such as lead, cadmium, and arsenic in Martian dusts and soils. A spark discharge produces plasma from a soil sample, and detectors measure the optical emission from metals in the plasma to identify and quantify them. Trace metal measurements are vital in assessing whether or not the Martian environment will be toxic to human explorers. The current method of x-ray fluorescence can yield concentrations of major species only. Other instruments are incompatible with the volume, weight, and power constraints for a Mars mission. The new instrument will be developed primarily for use in the Martian environment, but it would be adaptable for terrestrial use in environmental monitoring. The NASA Glenn Research Center at Lewis Field initiated the development of the MSSP as part of Glenn's Director's Discretionary Fund project for the Spark Analysis Detection of Trace Metal Species in Martian Dusts and Soils. The objective of this project is to develop and demonstrate a compact, sensitive optical instrument for the detection of trace hazardous metals in Martian dusts and soils.

  10. Lifecycle of laser-produced air sparks

    Harilal, S. S., E-mail:; Brumfield, B. E.; Phillips, M. C. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352 (United States)


    We investigated the lifecycle of laser-generated air sparks or plasmas using multiple plasma diagnostic tools. The sparks were generated by focusing the fundamental radiation from an Nd:YAG laser in air, and studies included early and late time spark dynamics, decoupling of the shock wave from the plasma core, emission from the spark kernel, cold gas excitation by UV radiation, shock waves produced by the air spark, and the spark's final decay and turbulence formation. The shadowgraphic and self-emission images showed similar spark morphology at earlier and late times of its lifecycle; however, significant differences are seen in the midlife images. Spectroscopic studies in the visible region showed intense blackbody-type radiation at early times followed by clearly resolved ionic, atomic, and molecular emission. The detected spectrum at late times clearly contained emission from both CN and N{sub 2}{sup +}. Additional spectral features have been identified at late times due to emission from O and N atoms, indicating some degree of molecular dissociation and excitation. Detailed spatially and temporally resolved emission analysis provides insight about various physical mechanisms leading to molecular and atomic emission by air sparks, including spark plasma excitation, heating of cold air by UV radiation emitted by the spark, and shock-heating.

  11. Flow and mixing of gas in cylinder of a stratified charge engine with two intake valves. Effects of late closing valve timing and intake port configurations; Kyuki nibenshiki sojo kyuki engine no cylinder nai gas ryudo to kongo. Osotoji valve timing oyobi port keijo ni yoru eikyo

    Charoenphonphanich, C.; Niwa, H.; Ennoji, H.; Iijima, T. [Tokai University, Tokyo (Japan)


    A numerical analysis of the flow and mixing of rich mixture and air inducted into the cylinder through each of the two intake ports of a stratified charge engine have been carried out. Numerical calculations were performed by finite volume method for three types of the intake port configurations: inverse V type, parallel type and V type and two types of valve timing; conventional and late closing (Miller cycle). Velocity field, turbulent kinetic energy and distribution of mixture concentration in the cylinder were examined. 3 refs., 10 figs.

  12. Generation of nanoparticles by spark discharge

    Tabrizi, N.S.; Ullmann, M.; Vons, V.A.; Lafont, U.; Schmidt-Ott, A.


    The production of nanoparticles by microsecond spark discharge evaporation in inert gas is studied systematically applying transmission electron microscopy, mobility analysis and BET surface area measurement. The method of spark discharge is of special interest, because it is continuous, clean, extremely flexible with respect to material, and scale-up is possible. The particle size distributions are narrow and the mean primary particle size can be controlled via the energy per spark. Separate...

  13. Plasma spark discharge reactor and durable electrode

    Cho, Young I.; Cho, Daniel J.; Fridman, Alexander; Kim, Hyoungsup


    A plasma spark discharge reactor for treating water. The plasma spark discharge reactor comprises a HV electrode with a head and ground electrode that surrounds at least a portion of the HV electrode. A passage for gas may pass through the reactor to a location proximate to the head to provide controlled formation of gas bubbles in order to facilitate the plasma spark discharge in a liquid environment.

  14. SparkMaster: automated calcium spark analysis with ImageJ.

    Picht, Eckard; Zima, Aleksey V; Blatter, Lothar A; Bers, Donald M


    Ca sparks are elementary Ca-release events from intracellular Ca stores that are observed in virtually all types of muscle. Typically, Ca sparks are measured in the line-scan mode with confocal laser-scanning microscopes, yielding two-dimensional images (distance vs. time). The manual analysis of these images is time consuming and prone to errors as well as investigator bias. Therefore, we developed SparkMaster, an automated analysis program that allows rapid and reliable spark analysis. The underlying analysis algorithm is adapted from the threshold-based standard method of spark analysis developed by Cheng et al. (Biophys J 76: 606-617, 1999) and is implemented here in the freely available image-processing software ImageJ. SparkMaster offers a graphical user interface through which all analysis parameters and output options are selected. The analysis includes general image parameters (number of detected sparks, spark frequency) and individual spark parameters (amplitude, full width at half-maximum amplitude, full duration at half-maximum amplitude, full width, full duration, time to peak, maximum steepness of spark upstroke, time constant of spark decay). We validated the algorithm using images with synthetic sparks embedded into backgrounds with different signal-to-noise ratios to determine an analysis criteria at which a high sensitivity is combined with a low frequency of false-positive detections. Finally, we applied SparkMaster to analyze experimental data of sparks measured in intact and permeabilized ventricular cardiomyocytes, permeabilized mammalian skeletal muscle, and intact smooth muscle cells. We found that SparkMaster provides a reliable, easy to use, and fast way of analyzing Ca sparks in a wide variety of experimental conditions.


    Yakup SEKMEN


    Full Text Available Performance of the spark ignition engines may be increased by changing the geometrical compression ratio according to the amount of charging in cylinders. The designed geometrical compression ratio can be realized as an effective compression ratio under the full load and full open throttle conditions since the effective compression ratio changes with the amount of charging into the cylinder in spark ignition engines. So, this condition of the spark ignition engines forces designers to change their geometrical compression ratio according to the amount of charging into the cylinder for improvement of performance and fuel economy. In order to improve the combustion efficiency, fuel economy, power output, exhaust emissions at partial loads, compression ratio must be increased; but, under high load and low speed conditions to prevent probable knock and hard running the compression ratio must be decreased gradually. In this paper, relation of the performance parameters to compression ratio such as power, torque, specific fuel consumption, cylindir pressure, exhaust gas temperature, combustion chamber surface area/volume ratio, thermal efficiency, spark timing etc. in spark ignition engines have been investigated and using of engines with variable compression ratio is suggested to fuel economy and more clear environment.

  16. Storytelling through animation: Oxford Sparks

    Pyle, D. M.; Cook, A.


    Oxford Sparks is a portal that launched in 2012, with the aim of bringing together resources that have been created across the University of Oxford and elsewhere for the purpose of wider engagement with science. To bring attention to this site, Oxford Sparks developed a set of high-quality short animations, each designed to tell a story relating to a current area of science. These animations have been launched on YouTube, and will shortly be available on iTunesU, and have covered broad areas of science from subduction zones (';Underwater Volcano Disaster'), through the early history of the solar system (';Rogue Planet') to the workings of the Large Hadron Collider (';A quick look around the LHC'). The animations have each been developed in close collaboration with researchers, created by a team with experience of education, engagement and outreach. The two minute scripts are intended to be both widely accessible and viewable as ';stand alone' stories. To this end, the scripts are humorous; while the animations are delightfully quirky, and created by professional animator with a degree-level science background. The animations are also intended to be used as ';lesson starters' in school, and educational activities graded for different age groups are being developed in parallel with the animations. They have been used, successfully, on pre-university summer schools, and in university classes. We are gathering both quantitative (analytics) and qualitative (school teacher and student focus group) feedback to monitor the success of the project, and to understand the strengths and weaknesses of the approach. In the first year since launch, Oxford Sparks animations were viewed over 80,000 times on YouTube, in part due to the surge of interest in the Large Hadron Collider animation after the discovery of the Higgs Boson.

  17. Generation of nanoparticles by spark discharge

    Tabrizi, N.S.; Ullmann, M.; Vons, V.A.; Lafont, U.; Schmidt-Ott, A.


    The production of nanoparticles by microsecond spark discharge evaporation in inert gas is studied systematically applying transmission electron microscopy, mobility analysis and BET surface area measurement. The method of spark discharge is of special interest, because it is continuous, clean, extr

  18. Spark plasma sintering and spark plasma joining of refractory ceramics

    Hoefer, Jeffrey Andrew

    Consolidation of refractory ceramics such as boron carbide (B4C) and silicon carbide (SiC) by conventional sintering techniques (pressure-less sintering, hot pressing, hot isostatic pressing etc.) can prove challenging due to the high temperatures required for sintering. Typically sintering additives are used in order to decrease sintering temperature, but at the sacrifice of purity. Typically B4C requires sintering temperatures above 2000°C without the use of additives, while SiC is generally considered not sinterable without additives, and requires temperatures above 2000°C even with additives. Spark Plasma Sintering (SPS) has emerged as a technology that can reduce the sintering temperature considerably compared to more conventional techniques. The simultaneous application of pressure, heat, and current can reduce sintering temperatures without the use of sintering aids to 1600°C and 2000°C for boron carbide and silicon carbide respectively. One shortcoming of SPS, however, is the difficulty in producing complex shapes. Therefore, for carbide materials such as B4C and SiC, which are difficult to machine, the ability to produce complex shapes is worthy of investigation. One means of creating complex shapes is by joining simple shapes. Joining of monolithic ceramics, in particular SiC, has been achieved, however in all cases an intermediate joining material is used (Ti foil, Silica Powder etc.). Joining of materials using SPS, or as it is called, Spark Plasma Joining, can eliminate the need for an intermediate joining material, producing a high purity and high strength joint. This study investigates SPS of 3 different B4C Powders, as well as SPS joining of simple shape monolithic SiC. Sintering parameters such as temperature, pressure, time, and heating rate are all considered. Influence of sintering parameters on density, grain size, mechanical strength, and joint quality is investigated in detail.

  19. GeoSpark SQL: An Effective Framework Enabling Spatial Queries on Spark

    Zhou Huang


    Full Text Available In the era of big data, Internet-based geospatial information services such as various LBS apps are deployed everywhere, followed by an increasing number of queries against the massive spatial data. As a result, the traditional relational spatial database (e.g., PostgreSQL with PostGIS and Oracle Spatial cannot adapt well to the needs of large-scale spatial query processing. Spark is an emerging outstanding distributed computing framework in the Hadoop ecosystem. This paper aims to address the increasingly large-scale spatial query-processing requirement in the era of big data, and proposes an effective framework GeoSpark SQL, which enables spatial queries on Spark. On the one hand, GeoSpark SQL provides a convenient SQL interface; on the other hand, GeoSpark SQL achieves both efficient storage management and high-performance parallel computing through integrating Hive and Spark. In this study, the following key issues are discussed and addressed: (1 storage management methods under the GeoSpark SQL framework, (2 the spatial operator implementation approach in the Spark environment, and (3 spatial query optimization methods under Spark. Experimental evaluation is also performed and the results show that GeoSpark SQL is able to achieve real-time query processing. It should be noted that Spark is not a panacea. It is observed that the traditional spatial database PostGIS/PostgreSQL performs better than GeoSpark SQL in some query scenarios, especially for the spatial queries with high selectivity, such as the point query and the window query. In general, GeoSpark SQL performs better when dealing with compute-intensive spatial queries such as the kNN query and the spatial join query.

  20. The effect of charge motion on mixture preparation and ignition for spark ignition engines with homogeneous combustion processes. A report of the Institute forInternal Combustion Engines and Automotive Engineering, TU Vienna; Einfluss der Ladungsbewegung auf Gemischbildung und Entzuendung bei Otto-Motoren mit homogenen Brennverfahren. Bericht des Instituts fuer Verbrennungskraftmaschinen und Kraftfahrzeugbau der Technischen Universitaet Wien (IVK)

    Geringer, B. (ed.); Lauer, T.


    The wish to go easy on global oil-resources and the compatibility of environment and traffic are subject of public interest. Therefore, measures must be taken for gasoline engines regarding fuel consumption and CO{sub 2}-emissions. The dethrottling of the intake system by means of residual gas recirculation is a well known measure to reduce the fuel consumption. However, high residual gas concentrations cause a delayed combustion and increased cyclic variations. The specific initiation of charge motion and turbulence in the combustion chamber accelerates and stabilizes the combustion and thus compensates the effects caused by high residual gas concentrations. Because of these complex interactions it is desirable to have the possibility to evaluate the residual gas tolerance of the combustion process at low-load engine operation already during the concept phase. Therefore, it was the aim of this study to develop a method based on numerical simulation that allows a prediction of the combustion stability margin for SI engines with homogeneous combustion for arbitrary in-cylinder flow. Investigations that were carried out with the CFD-method confirmed the acceleration of the combustion with increased turbulence. Further the supporting effect of charge motion on mixture preparation could be pointed out. However, combustion processes with highest swirl-numbers caused a vertical mixture stratification in the combustion chamber with lean mixture at the spark plug resulting in a lower residual gas tolerance. A threshold for a stable combustion could be determined by analyzing the properties of the cylinder charge by means of the flame theory method what further enabled the prediction of the residual gas tolerance of the combustion process and the potential to reduce the fuel consumption. A good correlation between the predicted values of the external residual gas recirculation rate and measurements at the engine test bench could be found. Although improvements of the

  1. Spark discharge in conductive liquid with microbubbles

    Vetchinin, S. P.; Vasilyak, L. M.; Pecherkin, V. Ya; Panov, V. A.; Son, E. E.


    Pulse electrical breakdown in 15% water solution of Isopropyl alcohol with air microbubbles from a pointed anode has been studied experimentally. It is shown, that the breakdown is always initiated from the bright region near the anode (anode “spot”). Detailed investigation into dynamic current-voltage characteristics and synchronized images reveals that it is thermal instability in the near anode region that causes spark channel initiation and development. The breakdown voltage, spark channel propagation speed and short-circuit current increase when the microbubbles are presented in the solution. The spark channel propagation speed is about 4-12 m/s and grows along with microbubbles concentration.

  2. Analysis of cyclic variability in spark-assisted HCCI combustion using a double Wiebe function

    Wagner, Robert M [ORNL; Glewen, William J [ORNL; Edwards, Kevin Dean [ORNL; Daw, C Stuart [ORNL


    A heuristic algorithm based on a double Wiebe function is proposed for estimating the relative importance of distinct combustion modes (propagating flame and compression ignition) occurring within individual combustion cycles as an engine is transitioned from conventional spark-ignited (SI) combustion to homogeneous charge compression ignition (HCCI). The proposed algorithm automates the analysis and categorization of pressure measurements from large numbers of individual cycles, providing new insight into the unstable combustion processes occurring during mode transition. Similar techniques could potentially be utilized for on-line diagnostics and control of the balance between SI and HCCI combustion in spark-assisted HCCI.


    W. Zelinski


    Full Text Available Optoelectronic sparking analyzer provides the possibility to realize a number of algorithms that permit to convert indicated light signals containing information on number of sparkings in the measuring cycle and their intensity divided in ten classes. The paper presents the selected sparking indices converted with the help of a computer and these indices make it possible to evaluate sparking level of separate commutator sectors by calculating average values in the whole measuring cycle of brush-commutator contact in dc machines. The paper also contains limiting values of the presented indices. 

  4. Titian: Data Provenance Support in Spark.

    Interlandi, Matteo; Shah, Kshitij; Tetali, Sai Deep; Gulzar, Muhammad Ali; Yoo, Seunghyun; Kim, Miryung; Millstein, Todd; Condie, Tyson


    Debugging data processing logic in Data-Intensive Scalable Computing (DISC) systems is a difficult and time consuming effort. Today's DISC systems offer very little tooling for debugging programs, and as a result programmers spend countless hours collecting evidence (e.g., from log files) and performing trial and error debugging. To aid this effort, we built Titian, a library that enables data provenance-tracking data through transformations-in Apache Spark. Data scientists using the Titian Spark extension will be able to quickly identify the input data at the root cause of a potential bug or outlier result. Titian is built directly into the Spark platform and offers data provenance support at interactive speeds-orders-of-magnitude faster than alternative solutions-while minimally impacting Spark job performance; observed overheads for capturing data lineage rarely exceed 30% above the baseline job execution time.

  5. Relationship between Electric Spark Sensitivity of Cyclic Nitramines and Their Molecular Electronic Properties

    ZHAO Jian-Ling; ZHI Chun-Yan; ZHAO Feng; FENG Shi-Quan; CHENG Xin-Lu


    On the basis of the structural and electronic properties of 14 different cyclic nitramine molecules, two types of formulas are employed to predict their electric spark sensitivity. One contains the minimum Mulliken charges of nitro group, the ratio of hydrogen to oxygen, and the ratio of carbon to oxygen; the other contains the lowest unoccupied molecular orbital energy, the ratio of hydrogen to oxygen, and the ratio of carbon to oxygen. Using these two types of formulas, we calculate the electric spark sensitivity of these 14 cyclic nitramine molecules, and compare them with the experimental data and previous theoretical values. And our investigations show that the former type of formula is better than the latter on predicting the electric spark sensitivity for cyclic nitramine molecules.

  6. Electromagnetic waves in stratified media

    Wait, James R; Fock, V A; Wait, J R


    International Series of Monographs in Electromagnetic Waves, Volume 3: Electromagnetic Waves in Stratified Media provides information pertinent to the electromagnetic waves in media whose properties differ in one particular direction. This book discusses the important feature of the waves that enables communications at global distances. Organized into 13 chapters, this volume begins with an overview of the general analysis for the electromagnetic response of a plane stratified medium comprising of any number of parallel homogeneous layers. This text then explains the reflection of electromagne

  7. Resistance of a water spark.

    Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Lehr, Jane Marie


    The later time phase of electrical breakdown in water is investigated for the purpose of improving understanding of the discharge characteristics. One dimensional simulations in addition to a zero dimensional lumped model are used to study the spark discharge. The goal is to provide better electrical models for water switches used in the pulse compression section of pulsed power systems. It is found that temperatures in the discharge channel under representative drive conditions, and assuming small initial radii from earlier phases of development, reach levels that are as much as an order of magnitude larger than those used to model discharges in atmospheric gases. This increased temperature coupled with a more rapidly rising conductivity with temperature than in air result in a decreased resistance characteristic compared to preceding models. A simple modification is proposed for the existing model to enable the approximate calculation of channel temperature and incorporate the resulting conductivity increase into the electrical circuit for the discharge channel. Comparisons are made between the theoretical predictions and recent experiments at Sandia. Although present and past experiments indicated that preceding late time channel models overestimated channel resistance, the calculations in this report seem to underestimate the resistance relative to recent experiments. Some possible reasons for this discrepancy are discussed.

  8. Electro-spark deposition technology

    Johnson, R.N. [Pacific Northwest National Lab., Richland, WA (United States)


    Electro-Spark Deposition (ESD) is a micro-welding process that uses short duration, high-current electrical pulses to deposit or alloy a consumable electrode material onto a metallic substrate. The ESD process was developed to produce coatings for use in severe environments where most other coatings fail. Because of the exceptional damage resistance of these coatings, and the versatility of the process to apply a wide variety of alloys, intermetallics, and cermets to metal surfaces, the ESD process has been designated critical to the life and economy of the advanced fossil energy systems as the higher temperatures and corrosive environments exceed the limits of known structural materials to accommodate the service conditions. Developments include producing iron aluminide-based coatings with triple the corrosion resistance of the best previous Fe{sub 3}Al coatings, coatings with refractory metal diffusion barriers and multi layer coatings for achieving functionally gradient properties between the substrate and the surface. A new development is the demonstration of advanced aluminide-based ESD coatings for erosion and wear applications. One of the most significant breakthroughs to occur in the last dozen years is the discovery of a process regime that yields an order of magnitude increase in deposition rates and achievable coating thicknesses. Achieving this regime has required the development of advanced ESD electronic capabilities. Development is now focused on further improvements in deposition rates, system reliability when operating at process extremes, and economic competitiveness.

  9. Cross-correlation spectroscopy study of the transient spark discharge in atmospheric pressure air

    Janda, Mário; Hoder, Tomáš; Sarani, Abdollah; Brandenburg, Ronny; Machala, Zdenko


    A streamer-to-spark transition in a self-pulsing transient spark (TS) discharge of positive polarity in air was investigated using cross-correlation spectroscopy. The entire temporal evolution of the TS was recorded for several spectral bands and lines: the second positive system of N2 (337.1 nm), the first negative system of {{{{N}}}2}+ (391.4 nm), and atomic oxygen (777.1 nm). The results enable the visualization of the different phases of discharge development including the primary streamer, the secondary streamer, and the transition to the spark. The spatio-temporal distribution of the reduced electric field strength during the primary streamer phase of the TS was determined and discussed. The transition from the streamer to the spark proceeds very fast within about 10 ns for the TS with a current pulse repetition rate in the range 8-10 kHz. This is attributed to memory effects, leading to a low net electron attachment rate and faster propagation of the secondary streamer. Gas heating, accumulation of species such as oxygen atoms from the previous TS pulses, as well as generation of charged particles by stepwise ionization seem to play important roles contributing to this fast streamer-to-spark transition.

  10. Stratified medicine and reimbursement issues

    Fugel, Hans-Joerg; Nuijten, Mark; Postma, Maarten


    Stratified Medicine (SM) has the potential to target patient populations who will most benefit from a therapy while reducing unnecessary health interventions associated with side effects. The link between clinical biomarkers/diagnostics and therapies provides new opportunities for value creation to

  11. Cycle-to-cycle fluctuation of combustion in a spark-ignition engine; Hibana tenka engine no nensho hendo

    Hamamoto, Y.; Yoshiyama, S.; Tomita, E.; Hamagami, T. [Okayama University, Okayama (Japan); Otsubo, H. [Yammer Diesel Engine Co. Ltd. Tokyo (Japan)


    In a homogeneous charge spark-ignition engine, the duration of early stage of combustion is a dominant factor for determining the fluctuation of mean effective pressure. And the early stage of combustion varies with the equivalence ratio and turbulence characteristics of the mixture. In this study, the fluctuations of 1% combustion duration and indicated mean effective pressure Pmi were computed as the function of fluctuations both in the equivalence ratio {phi} of the mixture and in the turbulence characteristics of the cylinder charge. And effects of the spark timing {theta}ig and {phi} on the cycle-to-cycle fluctuation in Pmi were investigated. 16 refs., 6 figs.

  12. Electro-spark deposition technology

    Johnson, R.N. [Pacific Northwest Lab., WA (United States)


    Electro-Spark Deposition (ESD) is a micro-welding process that uses short duration, high-current electrical pulses to deposit or alloy a consumable electrode material onto a metallic substrate. The ESD process was developed to produce coatings for use in severe environments where most other coatings fail. Because of the exceptional damage resistance of these coatings, and the versatility of the process to apply a wide variety of alloys, intermetallics, and cermets to metal surfaces, the ESD process has been designated as one of the enabling technologies for advanced energy systems. Developments include producing iron aluminide-based coatings with triple the corrosion resistance of the best previous Fe{sub 3}Al coatings, coatings with refractory metal diffusion barriers and multi layer coatings for achieving functionally gradient properties between the substrate and the surface. One of the most significant breakthroughs to occur in the last dozen years is the discovery of a process regime that promises an order of magnitude increase in deposition rates and achievable coating thicknesses. Since this regime borders on and exceeds the normal operating limits of existing ESD electronic equipment, development is in progress to produce equipment that can consistently and reliably achieve these conditions for a broad range of materials. Progress so far has resulted in a consistent 500% increase in deposition rates, and greater rates still are anticipated. Technology transfer activities are a significant portion of the ESD program effort. Notable successes now include the start-up of a new business to commercialize the ESD technology, the incorporation of the process into the operations of a major gas turbine manufacturer, major new applications in gas turbine blade and steam turbine blade protection and repair, and in military, medical, metal-working, and recreational equipment applications.

  13. Impact of delayed spark restrike on the dynamics of cyclic variability in dilute SI combustion

    Kaul, Brian C [ORNL; Wagner, Robert M [ORNL


    Spark-ignition (SI) engines can derive substantial efficiency gains from operation at high dilution levels. Additionally, the use of exhaust gas recirculation (EGR) for charge dilution also maintains compatibility with three-way catalysts by allowing stoichiometric operation. However, running high dilution levels increases the occurrence of misfires and partial burns, which induce higher levels of cyclic-variability in engine operation. This variability has been shown to have both stochastic and deterministic components. Factors such as in-cylinder turbulence and mixing-variations can be classified as stochastic; while, charge composition is the major source of the deterministic component through its non-linear effect on ignition and flame propagation characteristics. The use of these deterministic components has been previously explored to construct next-cycle control approaches that would allow stable operation near the edge of stability. Building on that work, this paper aims to understand the effect of spark strategies, specifically the use of a second spark (restrike) after the main spark, on engine operation at high dilution levels that were achieved using both excess air (i.e. lean combustion) and EGR.

  14. Comparative study of INPIStron and spark gap

    Han, Kwang S.; Lee, Ja H.


    An inverse pinch plasma switch, INPIStron, was studied in comparison to a conventional spark gap. The INPIStron is under development for high power switching applications. The INPIStron has an inverse pinch dynamics, opposed to Z-pinch dynamics in the spark gap. The electrical, plasma dynamics and radiative properties of the closing plasmas have been studied. Recently the high-voltage pulse transfer capabilities or both the INPIStron and the spark gap were also compared. The INPIStron with a low impedance Z = 9 ohms transfers 87 percent of an input pulse with a halfwidth of 2 mu s. For the same input pulse the spark gap of Z = 100 ohms transfers 68 percent. Fast framing and streak photography, taken with an TRW image converter camera, was used to observe the discharge uniformity and closing plasma speed in both switches. In order to assess the effects of closing plasmas on erosion of electrode material, emission spectra of two switches were studied with a spectrometer-optical multi channel analyzer (OMA) system. The typical emission spectra of the closing plasmas in the INPIStron and the spark gap showed that there were comparatively weak carbon line emission in 658.7 nm and copper (electrode material) line emissions in the INPIStron, indicating low erosion of materials in the INPIStron.

  15. Laser spark distribution and ignition system

    Woodruff, Steven; McIntyre, Dustin L.


    A laser spark distribution and ignition system that reduces the high power optical requirements for use in a laser ignition and distribution system allowing for the use of optical fibers for delivering the low peak energy pumping pulses to a laser amplifier or laser oscillator. An optical distributor distributes and delivers optical pumping energy from an optical pumping source to multiple combustion chambers incorporating laser oscillators or laser amplifiers for inducing a laser spark within a combustion chamber. The optical distributor preferably includes a single rotating mirror or lens which deflects the optical pumping energy from the axis of rotation and into a plurality of distinct optical fibers each connected to a respective laser media or amplifier coupled to an associated combustion chamber. The laser spark generators preferably produce a high peak power laser spark, from a single low power pulse. The laser spark distribution and ignition system has application in natural gas fueled reciprocating engines, turbine combustors, explosives and laser induced breakdown spectroscopy diagnostic sensors.

  16. Electrode Erosion of a High Energy Impulse Spark Gap Switch

    Yao Xueling; Zeng Zhengzhong; Chen Jinliang


    Based on the principle of thermal conduction, three metal alloys (stainless steel,copper-tungsten and graphite) were chosen as the material of the high impulse current discharging switch. Experimental results indicate that the mass loss and surface erosion morphology of the electrode are related with the electrode material (conductivity σ, melting point Tm, density ρ and thermal capacity c) and the impulse transferred charge (or energy) per impulse for the same total impulse transferred charge. The experimental results indicate that the mass loss of stainless steel,copper-tungsten and graphite are 380.10 μg/C, 118.10 μg/C and 81.90 μg/C respectively under the condition of a total impulse transferred charge of 525 C and a transferred charge per impulse of 10.5 C. Under the same impulse transferred charge, the mass loss of copper-tungsten(118.10 μg/C)with the transferred charge per impulse at 10.5 C is far larger than the mass loss (38.61μg/C)at a 1.48 C transferred charge per impulse. The electrode erosion mechanism under high energy impulse arcs is analyzed briefly and it is suggested that by selecting high conductive metal or metal alloy as the electrode material of a high energy impulse spark gap switch and setting high erosion resistance material at the top of the electrode, the mass loss of the electrode can be reduced and the life of the switch prolonged.

  17. Spark - a modern approach for distributed analytics

    CERN. Geneva; Kothuri, Prasanth


    The Hadoop ecosystem is the leading opensource platform for distributed storing and processing big data. It is a very popular system for implementing data warehouses and data lakes. Spark has also emerged to be one of the leading engines for data analytics. The Hadoop platform is available at CERN as a central service provided by the IT department. By attending the session, a participant will acquire knowledge of the essential concepts need to benefit from the parallel data processing offered by Spark framework. The session is structured around practical examples and tutorials. Main topics: Architecture overview - work distribution, concepts of a worker and a driver Computing concepts of transformations and actions Data processing APIs - RDD, DataFrame, and SparkSQL

  18. High performance Spark best practices for scaling and optimizing Apache Spark

    Karau, Holden


    Apache Spark is amazing when everything clicks. But if you haven’t seen the performance improvements you expected, or still don’t feel confident enough to use Spark in production, this practical book is for you. Authors Holden Karau and Rachel Warren demonstrate performance optimizations to help your Spark queries run faster and handle larger data sizes, while using fewer resources. Ideal for software engineers, data engineers, developers, and system administrators working with large-scale data applications, this book describes techniques that can reduce data infrastructure costs and developer hours. Not only will you gain a more comprehensive understanding of Spark, you’ll also learn how to make it sing. With this book, you’ll explore: How Spark SQL’s new interfaces improve performance over SQL’s RDD data structure The choice between data joins in Core Spark and Spark SQL Techniques for getting the most out of standard RDD transformations How to work around performance issues i...

  19. Characteristics of natural gas lean combustion through the compression of quiescent charge in a rapid compression combustor; Kyusoku asshuku nensho sochinai seishi yokongoki asshuku ni okeru tennen gas no kihaku nensho tokusei

    Kataoka, K. [Okayama University of Science, Okayama (Japan); Segawa, D.; Kadota, T.; Hirooka, S. [University of Osaka Prefecture, Osaka (Japan). Faculty of Engineering; Higashino, K. [Osaka Gas Co. Ltd., Osaka (Japan)


    In order to develop a natural gas fueled spark ignition engine with high thermal efficiency and clean exhaust gases, combustion characteristics of natural gas and air mixtures were examined using a rapid compression combustor. We concentrated on lean mixtures because of their potential for high efficiency and low pollutant emissions. To elucidate the effect of compression-induced physical aspects on the combustion process, the charge was kept quiescent before the start of the compression process. The results showed that an increased charge pressure increased the time required for combustion. A high compression ratio or piston speed tended to shorten the combustion time, but their effects were rather weak. An increased humidity in mixtures measurably increased the combustion time. The stratified charge, which was examined using the soap bubble method, markedly improved the combustion process of lean mixtures. 7 refs., 15 figs., 1 tab.

  20. Computer animation of the stratified mixture shape in gasoline direct injection engine

    Sendyka, B.; Pisarczyk, W.; Pajak, M. [Cracow University of Technology (Poland); Lindberg, W. [University of Wyoming (United States)


    The present method of direct fuel injection in Gasoline Direct Injection Engines (GDIE) creates a conical fuel stream, which is inefficient for GDIE. In this paper we analyzed how to achieve stratified conical shape of the rich fuel mixture. The kernel of the rich mixture should be located between the electrodes of the spark plug. This is achieved when the conical stream is bounced back from the surface of the bowl of the piston. The computer animation of the trajectory of the convergent fuel stream was based on equations of the parameters for fuel stream, injection pressure and angle of fuel injector. The presented animation allows us to determine the movement of the stream, from the beginning of injection to the electrodes of the spark plug, where the combustion process of the rich mixture kernel starts. (author)

  1. Optical diagnostics integrated with laser spark delivery system

    Yalin, Azer; Willson, Bryan; Defoort, Morgan; Joshi, Sachin; Reynolds, Adam


    A spark delivery system for generating a spark using a laser beam is provided, and includes a laser light source and a laser delivery assembly. The laser delivery assembly includes a hollow fiber and a launch assembly comprising launch focusing optics to input the laser beam in the hollow fiber. The laser delivery assembly further includes exit focusing optics that demagnify an exit beam of laser light from the hollow fiber, thereby increasing the intensity of the laser beam and creating a spark. Other embodiments use a fiber laser to generate a spark. Embodiments of the present invention may be used to create a spark in an engine. Yet other embodiments include collecting light from the spark or a flame resulting from the spark and conveying the light for diagnostics. Methods of using the spark delivery systems and diagnostic systems are provided.

  2. Processing of bulk Al7075 alloy by spark plasma sintering

    Málek, P.; Molnárová, O.; Cinert, J.; Lukáč, F.; Chráska, T.


    The main advantages of powder metallurgy processing route are the possibility to produce near-net-shape compacts and to minimize the finish machining and material loss. The main problem in particle consolidation process is to suppress porosity, to remove oxide layers, and to retain the microstructure of powder materials. Spark plasma sintering (SPS) combines concurrent uniaxial pressure and direct heating by a pulsed DC current. Sintering occurs at relatively low temperatures for a short time and does not influence significantly the microstructure in the interiors of original powder particles. The efficiency of SPS in producing compacts with low porosity might be dependent on the distribution of particle size in original powder material. The gas atomized Al7075 powder was sieved to several charges and then sintered by SPS. Microstructure of sintered compacts was studied by light and scanning electron microscopy. The phase composition was investigated using X-ray diffraction. The mechanical behaviour was tested by bending tests.

  3. Evaluation of Innovative High Pulse Rate, Purged Spark Gap Concepts


    gugh the switch and the pressure loss through the gas circulation system. The pressure loss is the sum of the losses in the spark gap , flow ducting...developed to solve the mass, momentum, and energy conservation equations which govern the purging process in a spark gap flow channel following arc...formation. [2,3] In this model, gas properties and spark gap flow channel area varied with distance along the flow axis from the spark gap and with

  4. On the physical origin of tails in the time response of spark counters

    Mangiarotti, A


    The time response function of a spark counter is calculated considering that the time delay and its fluctuations originate from the avalanche growth, under space charge effects. The deduced asymmetric time response probability density displays a peak and a tail which both correlate with an increase of the overall time delay. From a comparison to experiment, it is shown that the calculations can reproduce the general trends of the measurements.

  5. On the physical origin of tails in the time response of spark counters

    Mangiarotti, A. E-mail:; Gobbi, A. E-mail:


    The time response function of a spark counter is calculated considering that the time delay and its fluctuations originate from the avalanche growth, under space charge effects. The deduced asymmetric time response probability density displays a peak and a tail which both correlate with an increase of the overall time delay. From a comparison to experiment, it is shown that the calculations can reproduce the general trends of the measurements.

  6. Spark Plasma Sintering of Ultracapacitors

    Hill, Curtis W. [CK Technologies, Camirillo, CA (United States); Boatner, Lynn A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Tucker, Dennis [NASA Johnson Space Center, Houston, TX (United States); Kolopus, James A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cheng, Zhongyang [Auburn Univ., AL (United States)


    A solid-state ultracapacitor module to replace standard electrochemical batteries would achieve major performance gains and mass/volume reduction. This report summarizes a project to evaluate an alternative sintering process to produce a solid-state ultracapacitor to overcome the limitations of both the electrochemical batteries presently in use on spacecraft and of currently available electrochemical ultracapacitors. It will provide a robust energy storage device with higher reliability, wider working temperature range, longer lifetime, and less weight and volume than electrochemical batteries. As modern electronics decrease in size, more efficient and robust remote power is needed. Current state-of-the-art rechargeable batteries cannot be rapidly charged, contain harmful chemicals, and suffer from early wear-out mechanisms. Solid-state ultracapacitors are recyclable energy storage devices that offer the promise of higher power and a greater number of charge/discharge cycles than current rechargeable batteries. In addition, the theoretical energy density when compared to current electrochemical batteries indicates that a significant weight savings is possible. This is a project to develop a very high density solid-state ultracapacitor with giant permittivity and acceptable dielectric loss to overcome the energy-density barrier such that it will be a suitable replacement for batteries.

  7. Modelling Spark Integration in Science Classroom

    Marie Paz E. Morales


    Full Text Available The study critically explored how a PASCO-designed technology (SPARK ScienceLearning System is meaningfully integrated into the teaching of selected topics in Earth and Environmental Science. It highlights on modelling the effectiveness of using the SPARK Learning System as a primary tool in learning science that leads to learning and achievement of the students. Data and observation gathered and correlation of the ability of the technology to develop high intrinsic motivation to student achievement were used to design framework on how to meaningfully integrate SPARK ScienceLearning System in teaching Earth and Environmental Science. Research instruments used in this study were adopted from standardized questionnaires available from literature. Achievement test and evaluation form were developed and validated for the purpose of deducing data needed for the study. Interviews were done to delve into the deeper thoughts and emotions of the respondents. Data from the interviews served to validate all numerical data culled from this study. Cross-case analysis of the data was done to reveal some recurring themes, problems and benefits derived by the students in using the SPARK Science Learning System to further establish its effectiveness in the curriculum as a forerunner to the shift towards the 21st Century Learning.

  8. Vaporization of atherosclerotic plaques by spark erosion

    C.J. Slager (Cornelis); C.E. Essed; J.C.H. Schuurbiers (Johan); N. Bom (Klaas); P.W.J.C. Serruys (Patrick); G.T. Meester (Geert)


    textabstractAn alternative to the laser irradiation of atherosclerotic lesions has been developed. A pulsed electrocardiogram R wave-triggered electrical spark erosion technique is described. Controlled vaporization of fibrous and lipid plaques with minimal thermal side effects was achieved and docu

  9. Generation of Nanoparticles by Spark Discharge

    Salman Tabrizi, N.


    Spark discharge is a method for producing nanoparticles from conductive materials. Besides the general advantages of nanoparticle synthesis in the gas phase, the method offers additional advantages like simplicity, compactness and versatility. The synthesis process is continuous and is performed at

  10. Generation of Nanoparticles by Spark Discharge

    Salman Tabrizi, N.


    Spark discharge is a method for producing nanoparticles from conductive materials. Besides the general advantages of nanoparticle synthesis in the gas phase, the method offers additional advantages like simplicity, compactness and versatility. The synthesis process is continuous and is performed at

  11. Stratified Medicine and Reimbursement Issues

    Hans-Joerg eFugel


    Full Text Available Stratified Medicine (SM has the potential to target patient populations who will most benefit from a therapy while reducing unnecessary health interventions associated with side effects. The link between clinical biomarkers/diagnostics and therapies provides new opportunities for value creation to strengthen the value proposition to pricing and reimbursement (P&R authorities. However, the introduction of SM challenges current reimbursement schemes in many EU countries and the US as different P&R policies have been adopted for drugs and diagnostics. Also, there is a lack of a consistent process for value assessment of more complex diagnostics in these markets. New, innovative approaches and more flexible P&R systems are needed to reflect the added value of diagnostic tests and to stimulate investments in new technologies. Yet, the framework for access of diagnostic–based therapies still requires further development while setting the right incentives and appropriate align stakeholders interests when realizing long- term patient benefits. This article addresses the reimbursement challenges of SM approaches in several EU countries and the US outlining some options to overcome existing reimbursement barriers for stratified medicine.

  12. Suppression of stratified explosive interactions

    Meeks, M.K.; Shamoun, B.I.; Bonazza, R.; Corradini, M.L. [Wisconsin Univ., Madison, WI (United States). Dept. of Nuclear Engineering and Engineering Physics


    Stratified Fuel-Coolant Interaction (FCI) experiments with Refrigerant-134a and water were performed in a large-scale system. Air was uniformly injected into the coolant pool to establish a pre-existing void which could suppress the explosion. Two competing effects due to the variation of the air flow rate seem to influence the intensity of the explosion in this geometrical configuration. At low flow rates, although the injected air increases the void fraction, the concurrent agitation and mixing increases the intensity of the interaction. At higher flow rates, the increase in void fraction tends to attenuate the propagated pressure wave generated by the explosion. Experimental results show a complete suppression of the vapor explosion at high rates of air injection, corresponding to an average void fraction of larger than 30%. (author)

  13. Studies on effect of spark advance angle and spark gap on cycle-by-cycle fluctuations in four stroke spark ignition engine

    Bhaskar, H.B.; Chandrasheaker, T.K. [Sri Siddhartha Inst. of Technology, Maralur, Tumkur (India). Dept. of Mechanical Engineering; Antony, A.J. [Sahyedri Inst. of Technology, Mangalore (India)


    In response to environmental concerns and the depletion of fossil fuels, the automotive industry is striving to increase fuel efficiency and reduce emissions such as soot and nitrous oxides (NOx). This paper focused on the nature of cyclic variability and its manifestation in the characteristics of spark-ignition (SI) engine combustion. Cycle-by-cycle fluctuation is a major phenomenon that limits the range of operating conditions. The parameters affecting cycle-by-cycle fluctuation include mixture distribution, mixture homogeneity, spark intensity, spark timing, spark plug location, spark plug gap, number of spark plugs, swirl, combustion chamber geometry, compression ratio, equivalence ratio, load and speed. The degree to which these parameters influence cycle-by-cycle fluctuations was investigated. The cycle-by-cycle fluctuations in the engine reduces the power output, but increases the engine roughness and emissions. Experiments were carried out on a four stroke single cylinder computerized spark ignition engine. The results revealed the best operating spark gap and advanced spark angle to minimize the cycle-by-cycle fluctuations. The overall engine performance was improved with better drivability. 6 refs., 3 tabs., 10 figs.

  14. Simulation model of stratified thermal energy storage tank using finite difference method

    Waluyo, Joko


    Stratified TES tank is normally used in the cogeneration plant. The stratified TES tanks are simple, low cost, and equal or superior in thermal performance. The advantage of TES tank is that it enables shifting of energy usage from off-peak demand for on-peak demand requirement. To increase energy utilization in a stratified TES tank, it is required to build a simulation model which capable to simulate the charging phenomenon in the stratified TES tank precisely. This paper is aimed to develop a novel model in addressing the aforementioned problem. The model incorporated chiller into the charging of stratified TES tank system in a closed system. The model was developed in one-dimensional type involve with heat transfer aspect. The model covers the main factors affect to degradation of temperature distribution namely conduction through the tank wall, conduction between cool and warm water, mixing effect on the initial flow of the charging as well as heat loss to surrounding. The simulation model is developed based on finite difference method utilizing buffer concept theory and solved in explicit method. Validation of the simulation model is carried out using observed data obtained from operating stratified TES tank in cogeneration plant. The temperature distribution of the model capable of representing S-curve pattern as well as simulating decreased charging temperature after reaching full condition. The coefficient of determination values between the observed data and model obtained higher than 0.88. Meaning that the model has capability in simulating the charging phenomenon in the stratified TES tank. The model is not only capable of generating temperature distribution but also can be enhanced for representing transient condition during the charging of stratified TES tank. This successful model can be addressed for solving the limitation temperature occurs in charging of the stratified TES tank with the absorption chiller. Further, the stratified TES tank can be

  15. Towards spark-proof gaseous pixel detectors

    Tsigaridas, S.; Beuzekom, M. v.; Chan, H. W.; Graaf, H. v. d.; Hartjes, F.; Heijhoff, K.; Hessey, N. P.; Prodanovic, V.


    The micro-pattern gaseous pixel detector, is a promising technology for imaging and particle tracking applications. It is a combination of a gas layer acting as detection medium and a CMOS pixelated readout-chip. As a prevention against discharges we deposit a protection layer on the chip and then integrate on top a micromegas-like amplification structure. With this technology we are able to reconstruct 3D track segments of particles passing through the gas thanks to the functionality of the chip. We have turned a Timepix3 chip into a gaseous pixel detector and tested it at the SPS at Cern. The preliminary results are promising and within the expectations. However, the spark protection layer needs further improvement to make reliable detectors. For this reason, we have created a setup for spark-testing. We present the first results obtained from the lab-measurements along with preliminary results from the testbeam.

  16. Suprathermal electrons in a vacuum spark discharge

    Bashutin, O. A., E-mail:; Savjolov, A. S., E-mail: [National Research Nuclear University MEPhI (Russian Federation)


    Results of experiments on the detection of suprathermal electron beams in the plasma of a highcurrent low-inductance vacuum spark by means of space-resolved spectral X-ray polarimetry are presented. It is shown that the observed polarization of bremsstrahlung may be caused by an ~100-keV electron beam propagating along the discharge axis from the pinching region toward the anode. The influence of the discharge initiation conditions on the parameters of the generated electron beams is analyzed.

  17. SI Engine with repetitive NS spark plug

    Pancheshniy, Sergey; Nikipelov, Andrey; Anokhin, Eugeny; Starikovskiy, Andrey; Laplase Team; Mipt Team; Pu Team


    Now de-facto the only technology for fuel-air mixtures ignition in IC engines exists. It is a spark discharge of millisecond duration in a short discharge gap. The reason for such a small variety of methods of ignition initiation is very specific conditions of the engine operation. First, it is very high-pressure of fuel-air mixture - from 5-7 atmospheres in old-type engines and up to 40-50 atmospheres on the operating mode of HCCI. Second, it is a very wide range of variation of the oxidizer/fuel ratio in the mixture - from almost stoichiometric (0.8-0.9) at full load to very lean (φ = 0.3-0.5) mixtures at idle and/or economical cruising mode. Third, the high velocity of the gas in the combustion chamber (up to 30-50 m/s) resulting in a rapid compression of swirling inlet flow. The paper presents the results of tests of distributed spark ignition system powered by repetitive pulse nanosecond discharge. Dynamic pressure measurements show the increased pressure and frequency stability for nanosecond excitation in comparison with the standard spark plug. Excitation by single nanosecond high-voltage pulse and short train of pulses was examined. In all regimes the nanosecond pulsed excitation demonstrate a better performance.

  18. Relationship between Exploding Bridgewire & Spark Initiation of Low Density PETN

    Lee, Elizabeth; Drake, Rod


    Recent work has shown that the energy delivered after bridgewire burst affects the function time of an EBW detonator. The spark which is formed post bridgewire burst is the means by which the remaining fireset energy is delivered into the detonator. Therefore, by studying the characteristics of spark-gap detonators insight into the contribution of spark initiation to the functioning of EBW detonators may be achieved. Spark initiation of low density explosives consists of; (i) spark formation, (ii) spark interaction with the bed, and (iii) ignition and growth of reaction. Experiments were performed in which beds of an inert simulant were used to study the formation and propagation of sparks. The effect of the spark on inert porous beds was studied over a limited delivered energy range. The disruption of the bed was found to be dependent on the particle size / pore structure of the bed. The effect of spark initiation on a low density PETN bed was then examined, the relationship between delivered energy and function time was found to be the same as for EBW detonators. This necessitated the development of electrical diagnostic techniques to measure the energy delivered to the spark.

  19. Stratified wake of an accelerating hydrofoil

    Ben-Gida, Hadar; Gurka, Roi


    Wakes of towed and self-propelled bodies in stratified fluids are significantly different from non-stratified wakes. Long time effects of stratification on the development of the wakes of bluff bodies moving at constant speed are well known. In this experimental study we demonstrate how buoyancy affects the initial growth of vortices developing in the wake of a hydrofoil accelerating from rest. Particle image velocimetry measurements were applied to characterize the wake evolution behind a NACA 0015 hydrofoil accelerating in water and for low Reynolds number and relatively strong and stably stratified fluid (Re=5,000, Fr~O(1)). The analysis of velocity and vorticity fields, following vortex identification and an estimate of the circulation, reveal that the vortices in the stratified fluid case are stretched along the streamwise direction in the near wake. The momentum thickness profiles show lower momentum thickness values for the stratified late wake compared to the non-stratified wake, implying that the dra...

  20. Life and death of a cardiac calcium spark.

    Stern, Michael D; Ríos, Eduardo; Maltsev, Victor A


    Calcium sparks in cardiac myocytes are brief, localized calcium releases from the sarcoplasmic reticulum (SR) believed to be caused by locally regenerative calcium-induced calcium release (CICR) via couplons, clusters of ryanodine receptors (RyRs). How such regeneration is terminated is uncertain. We performed numerical simulations of an idealized stochastic model of spark production, assuming a RyR gating scheme with only two states (open and closed). Local depletion of calcium in the SR was inevitable during a spark, and this could terminate sparks by interrupting CICR, with or without assumed modulation of RyR gating by SR lumenal calcium. Spark termination by local SR depletion was not robust: under some conditions, sparks could be greatly and variably prolonged, terminating by stochastic attrition-a phenomenon we dub "spark metastability." Spark fluorescence rise time was not a good surrogate for the duration of calcium release. Using a highly simplified, deterministic model of the dynamics of a couplon, we show that spark metastability depends on the kinetic relationship of RyR gating and junctional SR refilling rates. The conditions for spark metastability resemble those produced by known mutations of RyR2 and CASQ2 that cause life-threatening triggered arrhythmias, and spark metastability may be mitigated by altering the kinetics of the RyR in a manner similar to the effects of drugs known to prevent those arrhythmias. The model was unable to explain the distributions of spark amplitudes and rise times seen in chemically skinned cat atrial myocytes, suggesting that such sparks may be more complex events involving heterogeneity of couplons or local propagation among sub-clusters of RyRs.

  1. How stratified is mantle convection?

    Puster, Peter; Jordan, Thomas H.


    We quantify the flow stratification in the Earth's mid-mantle (600-1500 km) in terms of a stratification index for the vertical mass flux, Sƒ (z) = 1 - ƒ(z) / ƒref (z), in which the reference value ƒref(z) approximates the local flux at depth z expected for unstratified convection (Sƒ=0). Although this flux stratification index cannot be directly constrained by observations, we show from a series of two-dimensional convection simulations that its value can be related to a thermal stratification index ST(Z) defined in terms of the radial correlation length of the temperature-perturbation field δT(z, Ω). ST is a good proxy for Sƒ at low stratifications (SƒUniformitarian Principle. The bound obtained here from global tomography is consistent with local seismological evidence for slab flux into the lower mantle; however, the total material flux has to be significantly greater (by a factor of 2-3) than that due to slabs alone. A stratification index, Sƒ≲0.2, is sufficient to exclude many stratified convection models still under active consideration, including most forms of chemical layering between the upper and lower mantle, as well as the more extreme versions of avalanching convection governed by a strong endothermic phase change.

  2. Gas spark switches with increased operating life for Marx generator of lightning test complex

    Bykov, Yu. A.; Krastelev, E. G., E-mail: [Russian Academy of Sciences, Joint Institute for High Temperature (Russian Federation)


    A new design of gas spark switches with an increased operating life and stable dynamic characteristics for the Marx generator of the lightning test complex has been developed. The switches are characterized by the following parameters in the mode of operation: voltage up to 80 kV, discharge current up to 50 kA, flowing charge up to 3.5 C/pulse. An increased operating life is achieved by using torus-shaped electrodes with increased working surface area and a trigger electrode in the form of a thick disk with a hole located between them. Low breakdown delay time and high stability of breakdown voltage under dynamic conditions are provided by gas preionization in the spark gap using UV radiation of an additional corona discharge in the axial region.

  3. Big Data Analytics with Datalog Queries on Spark.

    Shkapsky, Alexander; Yang, Mohan; Interlandi, Matteo; Chiu, Hsuan; Condie, Tyson; Zaniolo, Carlo


    There is great interest in exploiting the opportunity provided by cloud computing platforms for large-scale analytics. Among these platforms, Apache Spark is growing in popularity for machine learning and graph analytics. Developing efficient complex analytics in Spark requires deep understanding of both the algorithm at hand and the Spark API or subsystem APIs (e.g., Spark SQL, GraphX). Our BigDatalog system addresses the problem by providing concise declarative specification of complex queries amenable to efficient evaluation. Towards this goal, we propose compilation and optimization techniques that tackle the important problem of efficiently supporting recursion in Spark. We perform an experimental comparison with other state-of-the-art large-scale Datalog systems and verify the efficacy of our techniques and effectiveness of Spark in supporting Datalog-based analytics.

  4. Spectroscoping analysis of ignition in a spark ignition engine with jet-controlled combustion; Spektroskopische Untersuchung der Entflammung an einem Ottomotor mit strahlgefuehrtem Brennverfahren

    Palaveev, S. [MOT Forschungs- und Entwicklungsgesellschaft fuer Motorentechnik, Optik und Thermodynamik GmbH, Karlsruhe (Germany); Buri, S.; Xander, B.; Spicher, U. [Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Kolbenmaschinen


    The gasoline direct injection engine is one of the most promising strategies today to reduce the fuel consumption and CO{sub 2}-emissions of spark-ignition engines. The commercial launch of that combustion system was possible only through the development of new optical measurement techniques, which have been a major contribution for understanding the basics of the combustion in a stratified mode. In terms of space and time, compared to the homogeneous approach, the air-fuel-ratio for a stratified mode may vary significantly. This fluctuation affects in a critical way the process of ignition and combustion. The knowledge of the air-fuel-ratio in the spark plug area both at time of ignition and in during the combustion is therefore critical for the development of this combustion system and it components. This paper presents the spark-emission spectroscopy as a non invasive optical technique for measuring the air-fuel-ratio {lambda} in the spark gap at time of ignition. (orig.)

  5. Liquid-Arc/Spark-Excitation Atomic-Emission Spectroscopy

    Schlagen, Kenneth J.


    Constituents of solutions identified in situ. Liquid-arc/spark-excitation atomic-emission spectroscopy (LAES) is experimental variant of atomic-emission spectroscopy in which electric arc or spark established in liquid and spectrum of light from arc or spark analyzed to identify chemical elements in liquid. Observations encourage development of LAES equipment for online monitoring of process streams in such industries as metal plating, electronics, and steel, and for online monitoring of streams affecting environment.

  6. Core science: Stratified by a sunken impactor

    Nakajima, Miki


    There is potential evidence for a stratified layer at the top of the Earth's core, but its origin is not well understood. Laboratory experiments suggest that the stratified layer could be a sunken remnant of the giant impact that formed the Moon.

  7. Dual channel formation in a laser-triggered spark gap

    Kushner, M. J.; Kimura, W. D.; Ford, D. H.; Byron, S. R.


    During self-break in spark-gap switches, multiple streamers can form in close proximity to one another. The rate of expansion of these streamers is sufficiently fast that they can interact during the current pulse. To help understand how these closely spaced, expanding spark columns interact, a laser-triggered spark gap has been studied in which two parallel columns (separation 1.3 mm) are simultaneously preionized, resulting in a pair of nearly identical, axisymmetric spark columns. The spark gap (electrode separation 1.2 cm) switches a 100 ns, 40-60 kV, 12-20 kA, 1.5 Ω waterline. Interferograms of the expanding arc channels are obtained with a laser interferometer having a time and spatial resolution of 5 ns and 10 μm, respectively. Voltage and current were measured with an internal capacitive-voltage divider and a current viewing resistor. The interferograms show that for initially identical axisymmetric columns, the individual channels do not merge into a single larger axisymmetric spark column. Instead, regions of high gas density remain inside the combined column long into the recovery period. The columns also do not remain axisymmetric as they grow, indicating a long-range interaction between the channels. The voltage drop and resistance of the dual channel spark gaps changes by less than 15% from that of a single spark channel. A scaling model is presented to explain the resistance measurements and to predict the change in resistance for multichannel spark gaps.

  8. Reliable Field Distortion Spark Gap for Plasma Focus



    A simple,low cost,easily maintained,and reliable field distortion spark gap has been developed to operate at a voltage up to 30 kV.The header construction necessary to attach the spark gap switch to a single 12.5μF,40 kV(10 kJ)capacitor is described.The main features of the spark gap are its wide range of voltage operation,high current capacity,low inductance and long lifetime.The performance of spark gap has been tested in a plasma focus and results are presented in this report.

  9. Inflammation of stratified mixtures in spray guided DI gasoline engines: optimization by application of high speed imaging techniques; Entflammung geschichteter Gemische im strahlgefuehrten Benzin-DI-Motor: Optimierung mit Hilfe von Hochgeschwindigkeits-Visualisierung

    Zimmermann, D.; Kerek, Z.; Wirth, M. [Ford Motor Co. (Germany); Gansert, K.P.; Grzeszik, R.; Storch, A. [Robert Bossch GmbH (Germany); Josefsson, G.; Sandquist, H. [Volvo Car Corp. (Sweden)


    Stratified combustion in spray guided DI gasoline engines is characterized by a maximum of fuel economy potential but also by critical design parameters related to the geometric layout of the combustion system. The relative position between fuel spray and ignition location is essential as well as the dedicated design of the spark plug itself. This could be assessed in multicylinder engine experiments creating the base information for subsequent system component optimizations. The combustion system and component design can be supported to a large extend by in-cylinder investigations of the ignition process. High speed video imaging techniques have been applied in a transparent engine in order to gain a deep understanding of different spark discharge events including successful ignitions as well as misfires. The simultaneous application of imaging and high resolution electrical spark discharge analysis coupled with statistical analysis methods provide valuable insights into the specific conditions of the stratified DI ignition requirements. (orig.)

  10. A Fixpoint Semantics for Stratified Databases



    Przmusinski extended the notion of stratified logic programs,developed by Apt,Blair and Walker,and by van Gelder,to stratified databases that allow both negative premises and disjunctive consequents.However,he did not provide a fixpoint theory for such class of databases.On the other hand,although a fixpoint semantics has been developed by Minker and Rajasekar for non-Horn logic programs,it is tantamount to traditional minimal model semantics which is not sufficient to capture the intended meaning of negation in the premises of clauses in stratified databases.In this paper,a fixpoint approach to stratified databases is developed,which corresponds with the perfect model semantics.Moreover,algorithms are proposed for computing the set of perfect models of a stratified database.

  11. The Electrostatic Spark Sensitiveness of Initiators. Part 4. Initiation of Explosion by Spark Radiation


    including :,ire I. Hardy) Engineer Research and Development Laboratories, Fort Belvoir, Va, U.S.A. (Attn: Dr. Z.V. Harv-alik) Through Frankford...troublesome electrical interference associated with the discharge. The light intensity/time characteristics of sparks were determined using a Mazda 2Ti3

  12. Anticipating change, sparking innovation: framing the future.

    Petersen, Donna J; Finnegan, John R; Spencer, Harrison C


    As the 100th anniversary of the 1915 Welch-Rose report approaches, the Association of Schools and Programs of Public Health (ASPPH) has been pursuing two initiatives to spark innovation in academic partnerships for enhancing population health: (1) Framing the Future: The Second 100 Years of Education for Public Health and (2) Reconnecting Public Health and Care Delivery to Improve the Health of Populations. We describe how ASPPH-member schools and programs accredited by the Council on Education for Public Health, along with their extraordinarily diverse array of partners, are working to improve education that better prepares health professionals to meet 21st-century population health needs.

  13. Relativistic electrons from sparks in the laboratory

    Østgaard, N.; Carlson, B. E.; Nisi, R. S.; Gjesteland, T.; Grøndahl, Ø.; Skeltved, A.; Lehtinen, N. G.; Mezentsev, A.; Marisaldi, M.; Kochkin, P.


    Discharge experiments were carried out at the Eindhoven University of Technology in 2013. The experimental setup was designed to search for electrons produced in meter-scale sparks using a 1 MV Marx generator. Negative voltage was applied to the high voltage (HV) electrode. Five thin (1 mm) plastic detectors (5 cm2 each) were distributed in various configurations close to the spark gap. Earlier studies have shown (for HV negative) that X-rays are produced when a cloud of streamers is developed 30-60 cm from the negative electrode. This indicates that the electrons producing the X-rays are also accelerated at this location, that could be in the strong electric field from counterstreamers of opposite polarity. Comparing our measurements with modeling results, we find that ˜300 keV electrons produced about 30-60 cm from the negative electrode are the most likely source of our measurements. A statistical analysis of expected detection of photon bursts by these fiber detectors indicates that only 20%-45% of the detected bursts could be from soft (˜10 keV) photons, which further supports that the majority of detected bursts are produced by relativistic electrons.

  14. Relativistic electrons from sparks in the laboratory

    Østgaard, N; Nisi, R S; Gjesteland, T; Grøndahl, Ø; Skeltved, A; Lehtinen, N G; Mezentsev, A; Marisaldi, M; Kochkin, P


    Discharge experiments were carried out at the Eindhoven University of Technology in 2013. The experimental setup was designed to search for electrons produced in meter-scale sparks using a 1 MV Marx generator. Negative voltage was applied to the high voltage (HV) electrode. Five thin (1 mm) plastic detectors (5 $\\rm cm^2$ each) were distributed in various configurations close to the spark gap. Earlier studies have shown (for HV negative) that X-rays are produced when a cloud of streamers is developed 30-60 cm from the negative electrode. This indicates that the electrons producing the X-rays are also accelerated at this location, that could be in the strong electric field from counterstreamers of opposite polarity. Comparing our measurements with modeling results, we find that $\\sim$300 keV electrons produced about 30-60 cm from the negative electrode are the most likely source of our measurements. A statistical analysis of expected detection of photon bursts by these fiber detectors indicates that only 20%-4...

  15. Development of a SPARK Training Dataset

    Sayre, Amanda M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Olson, Jarrod R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)


    In its first five years, the National Nuclear Security Administration’s (NNSA) Next Generation Safeguards Initiative (NGSI) sponsored more than 400 undergraduate, graduate, and post-doctoral students in internships and research positions (Wyse 2012). In the past seven years, the NGSI program has, and continues to produce a large body of scientific, technical, and policy work in targeted core safeguards capabilities and human capital development activities. Not only does the NGSI program carry out activities across multiple disciplines, but also across all U.S. Department of Energy (DOE)/NNSA locations in the United States. However, products are not readily shared among disciplines and across locations, nor are they archived in a comprehensive library. Rather, knowledge of NGSI-produced literature is localized to the researchers, clients, and internal laboratory/facility publication systems such as the Electronic Records and Information Capture Architecture (ERICA) at the Pacific Northwest National Laboratory (PNNL). There is also no incorporated way of analyzing existing NGSI literature to determine whether the larger NGSI program is achieving its core safeguards capabilities and activities. A complete library of NGSI literature could prove beneficial to a cohesive, sustainable, and more economical NGSI program. The Safeguards Platform for Automated Retrieval of Knowledge (SPARK) has been developed to be a knowledge storage, retrieval, and analysis capability to capture safeguards knowledge to exist beyond the lifespan of NGSI. During the development process, it was necessary to build a SPARK training dataset (a corpus of documents) for initial entry into the system and for demonstration purposes. We manipulated these data to gain new information about the breadth of NGSI publications, and they evaluated the science-policy interface at PNNL as a practical demonstration of SPARK’s intended analysis capability. The analysis demonstration sought to answer the

  16. Imaging Studies of the Effects of Ethanol/Gasoline Blends on Spark-Assisted HCCI

    Fatouraie, Mohammad; Wooldridge, Margaret


    Spark assist (SA) has been demonstrated to extend the operating limits of homogeneous charge compression ignition (HCCI) modes of engine operation. This experimental investigation focuses on the effects caused by the SA HCCI operation on ignition and combustion properties of 100% indolene and 70% indolene/30% ethanol blends. The spark assist effects are compared to base line HCCI for each blend by varying spark timing at different fuel/air equivalence ratio (φ= 0.4--0.6). High speed imaging is used to understand the effects of flame propagation on heat release rates. Ethanol generally improves engine performance with higher indicated mean effective pressure (IMEP) and higher stability compared to 100% indolene. SA advances phasing within a range of 5 CAD at lower engine speeds (700 rpm) and 11 CAD at higher engine speeds (1200 rpm). SA does not affect heat release rates until immediately (within 5 CAD) prior to autoignition. Unlike previous studies, flames were not observed for all SA conditions. During SA operation, more fuel mass was burned by flame propagation with gasoline compared to E30.

  17. Generation of AuGe nanocomposites by co-sparking technique and their photoluminescence properties

    Kala, Shubhra, E-mail: [National Physical Laboratory (India); Theissmann, Ralf; Kruis, Frank Einar [University of Duisburg-Essen, Institute for Nanostructures and Technology, Faculty of Engineering Science, and CENIDE (Center for Nanointegration Duisburg-Essen) (Germany)


    The feasibility of spark discharge technique for preparing metal-semiconductor nanocomposites is demonstrated. In the AuGe system, Au shows only 10{sup -3} atomic percent solid solubility in Ge, whereas 3.1 at.% Ge is soluble in Au. During the co-sparking, Au is used as anode material; the cathode is composed of Ge. The relative atomic percent of Au and Ge in the initially generated mixture can be changed by changing the charging current to the capacitor used to trigger the sparking. Depending upon the atomic ratio of Au and Ge in the initial mixture, AuGe agglomerates form AuGe composite nanoparticles on subsequent sintering, in which AuGe alloy nanoparticles are found dispersed in a Ge matrix. The size of the dispersed AuGe alloy nanoparticles depend on the relative atomic concentration of Au and Ge in the initial mixture as well as on the sintering temperature. AuGe alloy nanoparticles dispersed in the Ge matrix are observed to exhibit an intense photoluminescence between 550 and 600 nm.

  18. SPARK Peer Helper Program, 1993-94. OER Report.

    Goldberg, Phyllis

    The Peer Helper Program was administered by Substance Prevention, Abuse Rehabilitation, and Knowledge (SPARK). Since its beginning in 1971, SPARK has addressed issues such as drug use, teenage pregnancy, HIV/AIDS, sexual abuse and other forms of violence. The Peer Helper Program was designed to train students in the skills required to assist peers…

  19. A spark-protected high-rate detector

    Fonte, Paulo J R; Costa, L; Ferreira-Marques, R; Mendiratta, S; Peskov, Vladimir; Policarpo, Armando


    We developed a very low resistivity RPC-type detector, the anode of which was a plate made from materials with resistivity up to 5x10 sup 7 OMEGA cm, the cathode being a metallic mesh preceded by a drift region. In such a detector it was actually possible to combine the versatility and high counting-rate capability of metallic PPACs with the extreme robustness and 'protectiveness' of Resistive Plate Chambers. Occasional discharges triggered by large deposits of primary ionisation or by extreme counting rates are quenched by the resistive anode and are constrained to the streamer phase of the sparking process. The study shows that this discharge affects the detector only locally and that the charge released is limited to a few tens of nC. Proportional counting rates up to 10 sup 5 Hz/mm sup 2 were achieved at gains above 10 sup 4. The energy resolution at 6 keV was 20% FWHM. The observed gain-rate trade-off is well described by an analytic model and further improvements may be expected by lowering the resistiv...

  20. A spark-protected high-rate detector

    Fonte, P. E-mail:; Carolino, N.; Costa, L.; Ferreira-Marques, Rui; Mendiratta, S.; Peskov, V.; Policarpo, A


    We developed a very low resistivity RPC-type detector, the anode of which was a plate made from materials with resistivity up to 5x10{sup 7} {omega} cm, the cathode being a metallic mesh preceded by a drift region. In such a detector it was actually possible to combine the versatility and high counting-rate capability of metallic PPACs with the extreme robustness and 'protectiveness' of Resistive Plate Chambers. Occasional discharges triggered by large deposits of primary ionisation or by extreme counting rates are quenched by the resistive anode and are constrained to the streamer phase of the sparking process. The study shows that this discharge affects the detector only locally and that the charge released is limited to a few tens of nC. Proportional counting rates up to 10{sup 5} Hz/mm{sup 2} were achieved at gains above 10{sup 4}. The energy resolution at 6 keV was 20% FWHM. The observed gain-rate trade-off is well described by an analytic model and further improvements may be expected by lowering the resistivity of the anode material. The properties of several custom-made, controllable resistivity, anode materials are described and prospects of improvement in the performance of the detector are discussed. (author)

  1. Calcium sparks in the intact gerbil spiral modiolar artery

    Berge Samantha


    Full Text Available Abstract Background Calcium sparks are ryanodine receptor mediated transient calcium signals that have been shown to hyperpolarize the membrane potential by activating large conductance calcium activated potassium (BK channels in vascular smooth muscle cells. Along with voltage-dependent calcium channels, they form a signaling unit that has a vasodilatory influence on vascular diameter and regulation of myogenic tone. The existence and role of calcium sparks has hitherto been unexplored in the spiral modiolar artery, the end artery that controls blood flow to the cochlea. The goal of the present study was to determine the presence and properties of calcium sparks in the intact gerbil spiral modiolar artery. Results Calcium sparks were recorded from smooth muscle cells of intact arteries loaded with fluo-4 AM. Calcium sparks occurred with a frequency of 2.6 Hz, a rise time of 17 ms and a time to half-decay of 20 ms. Ryanodine reduced spark frequency within 3 min from 2.6 to 0.6 Hz. Caffeine (1 mM increased spark frequency from 2.3 to 3.3 Hz and prolonged rise and half-decay times from 17 to 19 ms and from 20 to 23 ms, respectively. Elevation of potassium (3.6 to 37.5 mM, presumably via depolarization, increased spark frequency from 2.4 to 3.2 Hz. Neither ryanodine nor depolarization changed rise or decay times. Conclusions This is the first characterization of calcium sparks in smooth muscle cells of the spiral modiolar artery. The results suggest that calcium sparks may regulate the diameter of the spiral modiolar artery and cochlear blood flow.

  2. Experimental Validation of a Domestic Stratified Hot Water Tank Model in Modelica for Annual Performance Assessment

    Carmo, Carolina; Dumont, Olivier; Nielsen, Mads Pagh


    coupled with energy system solutions is limited. In this poster, a discretized model of a stratified tank developed in Modelica is presented. The physical phenoma to be considered are the thermal transfers by conduction and convection – stratification, heat loss to ambient, charging and discharging...

  3. The 'electric stroke' and the 'electric spark': anatomists and eroticism at George Baker's electric eel exhibition in 1776 and 1777.

    Plumb, Christopher


    In 1776 and 1777 five living electric eels exhibited in London became a sensational spectacle that appealed to anatomists, electricians and connoisseurs of erotica. George Baker's exhibition made visible the 'electric spark' of the electrical eel and a series of experiments were both witnessed by and participated in by members of the Royal Society and the metropolitan elite. Some participants even grasped the eels firmly in their hands and felt the 'electric stroke' of the eel in addition to observing the spark. In their observation of the electric eel some of these spectators transposed the vivid electric spark from the sphere of electricians and anatomists into that of satirical and erotic literature. Here the erotic electric eel proliferated in the literature and the eel took on quite different connotations that nonetheless were reliant on readers knowledge and experience of the exhibition, experiments and the preoccupations of anatomists. George Baker's electric eel exhibition of 1776 and 1777 is then instructive in exploring the production and circulation of knowledge in Georgian Britain. The story of the electric eel in Georgian culture charts the creation of the electric spark and stroke as objects of observation and encounter, their exhibitionary context, and finally their divergent meanings as the electric eel became erotically charged for a metropolitan masculine elite.

  4. Stably stratified magnetized stars in general relativity

    Yoshida, Shijun; Shibata, Masaru


    We construct magnetized stars composed of a fluid stably stratified by entropy gradients in the framework of general relativity, assuming ideal magnetohydrodynamics and employing a barotropic equation of state. We first revisit basic equations for describing stably-stratified stationary axisymmetric stars containing both poloidal and toroidal magnetic fields. As sample models, the magnetized stars considered by Ioka and Sasaki (2004), inside which the magnetic fields are confined, are modified to the ones stably stratified. The magnetized stars newly constructed in this study are believed to be more stable than the existing relativistic models because they have both poloidal and toroidal magnetic fields with comparable strength, and magnetic buoyancy instabilities near the surface of the star, which can be stabilized by the stratification, are suppressed.

  5. Thermals in stratified regions of the ISM

    Rodriguez-Gonzalez, Ary


    We present a model of a "thermal" (i.e., a hot bubble) rising within an exponentially stratified region of the ISM. This model includes terms representing the ram pressure braking and the entrainment of environmental gas into the thermal. We then calibrate the free parameters associated with these two terms through a comparison with 3D numerical simulations of a rising bubble. Finally, we apply our "thermal" model to the case of a hot bubble produced by a SN within the stratified ISM of the Galactic disk.

  6. On Stratified Vortex Motions under Gravity.


    AD-A156 930 ON STRATIFIED VORTEX MOTIONS UNDER GRAVITY (U) NAVAL i/i RESEARCH LAB WASHINGTON DC Y T FUNG 20 JUN 85 NRL-MIR-5564 UNCLASSIFIED F/G 20/4...Under Gravity LCn * Y. T. Fung Fluid Dynamics Branch - Marine Technologyv Division June 20, 1985 SO Cyk. NAVAL RESEARCH LABORATORY Washington, D.C...DN880-019 TITLE (Include Security Classification) On Stratified Vortex Motions Under Gravity 12 PERSONAL AUTHOR(S) Funa, Y.T. 13a. TYPE OF REPORT 13b

  7. Mixing by microorganisms in stratified fluids

    Wagner, Gregory L; Lauga, Eric


    We examine the vertical mixing induced by the swimming of microorganisms at low Reynolds and P\\'eclet numbers in a stably stratified ocean, and show that the global contribution of oceanic microswimmers to vertical mixing is negligible. We propose two approaches to estimating the mixing efficiency, $\\eta$, or the ratio of the rate of potential energy creation to the total rate-of-working on the ocean by microswimmers. The first is based on scaling arguments and estimates $\\eta$ in terms of the ratio between the typical organism size, $a$, and an intrinsic length scale for the stratified flow, $\\ell = \\left ( \


    A. Rodríguez-González


    Full Text Available We present a model of a “thermal” (i.e., a hot bubble rising within an exponentially stratified region of the ISM. This model includes terms representing the ram pressure braking and the entrainment of environmental gas into the thermal. We then calibrate the free parameters associated with these two terms through a comparison with 3D numerical simulations of a rising bubble. Finally, we apply our “thermal” model to the case of a hot bubble produced by a SN within the stratified ISM of the Galactic disk.

  9. Phase characterisation in spark plasma sintered TiPt alloy

    Chikosha, S


    Full Text Available The conclusions drawn from this presentation are that Spark Plasma Sintering (SPS) of equiatomic BE TiPt powder produces fully sintered specimens, with incomplete homogenisation. There is a need for improved furnace atmosphere control so...

  10. Research of EDM Spark Locations in Die-sinking

    韩强; 何勇; 杨向萍


    Detection of 2-dimention spark locations by electromagnetic detection method in electrical discharge machining (EDM) is studied. The method, which is applied and investigated, is based on the fact that the release of energy from a spark is transformed into electromagnetic wave around the workpiece. A new sensor system composed of high precision linear Hall components and cubic ferrite is used to detect the intensity of magnetic field. Relation equation between the output of the sensor system and 2-dimention spark locations experiment under a spiculate electrode is introduced, and its diagram of curve is drawn. As a result, the information that can be achieved by detecting spark's location gives new possibilities for an extended analysis of the EDM-process.

  11. Exploring the Performance of Spark for a Scientific Use Case

    Sehrish, Saba [Fermilab; Kowalkowski, Jim [Fermilab; Paterno, Marc [Fermilab


    We present an evaluation of the performance of a Spark implementation of a classification algorithm in the domain of High Energy Physics (HEP). Spark is a general engine for in-memory, large-scale data processing, and is designed for applications where similar repeated analysis is performed on the same large data sets. Classification problems are one of the most common and critical data processing tasks across many domains. Many of these data processing tasks are both computation- and data-intensive, involving complex numerical computations employing extremely large data sets. We evaluated the performance of the Spark implementation on Cori, a NERSC resource, and compared the results to an untuned MPI implementation of the same algorithm. While the Spark implementation scaled well, it is not competitive in speed to our MPI implementation, even when using significantly greater computational resources.

  12. Calcium sparks in the heart: dynamics and regulation

    Hoang-Trong TM


    Full Text Available Tuan M Hoang-Trong,1 Aman Ullah,1 M Saleet Jafri1,21Department of Molecular Neuroscience, Krasnow Institute for Advanced Study, George Mason University, Fairfax, VA, USA; 2Biomedical Engineering and Technology, University of Maryland, Baltimore, MD, USAAbstract: Ca2+ plays a central role in the contraction of the heart. It is the bi-directional link between electrical excitation of the heart and contraction. Electrical excitation initiates Ca2+ influx across the sarcolemma and T-tubular membrane that triggered calcium release from the sarcoplasmic reticulum (SR. Ca2+ sparks are the elementary events of calcium release from the SR. Therefore, understanding the dynamics of Ca2+ sparks is essential for understanding the function of the heart. To this end, numerous experimental and computational studies have focused on this topic, exploring the mechanisms of calcium spark initiation, termination, and regulation and what role these play in normal and patho-physiology. The proper understanding of Ca2+ spark regulation and dynamics serves as the foundation for our insights into a multitude of pathological conditions that may develop and that can be the result of structural and/or functional changes at the cellular or subcellular level. Computational modeling of Ca2+ spark dynamics has proven to be a useful tool to understand Ca2+ spark dynamics. This review addresses our current understanding of Ca2+ sparks and how synchronized SR Ca2+ release, in which Ca2+ sparks is a major pathway, is linked to the different cardiac diseases, especially arrhythmias.Keywords: leak, arrhythmia, excitation-contraction coupling, phosphorylation

  13. Electro-Spark Deposited Coatings for Replacement of Chrome Electroplating


    Wear and Corrosion: the Electrospark Deposition Process", published in Proceedings, American Electroplaters and Surface Finishers Society, Jan. 2002. 6...Johnson, R.N., " ElectroSpark Deposition : Principals and Applications", Society of Vacuum Coaters 45th Annual Technical Conference Proceedings, Apr...AD AD-E403 050 Contractor Report ARAET-CR-05002 ELECTRO-SPARK DEPOSITED COATINGS FOR REPLACEMENT OF CHROME PLATING R. N. Johnson J. A. Bailey Pacific

  14. Turbulent Mixing in Stably Stratified Flows


    Liege Colloquium on Ocean Hydrodynamics, volume 46, page 19889898. Elsevier, 1987. R. M. Kerr. Higher-order derivative correlations and the alignment of...19th International Liege Colloquium on Ocean Hydrodynamics, volume 46, pages 3-9. Elsevier, 1988. P. Meunier and G. Spedding. Stratified propelled

  15. Nitrogen transformations in stratified aquatic microbial ecosystems

    Revsbech, Niels Peter; Risgaard-Petersen, N.; Schramm, Andreas


    Abstract  New analytical methods such as advanced molecular techniques and microsensors have resulted in new insights about how nitrogen transformations in stratified microbial systems such as sediments and biofilms are regulated at a µm-mm scale. A large and ever-expanding knowledge base about n...

  16. Electric Spark Sensitivity of Polynitro Compounds. Part V. A Relationship between Electric Spark and Impact Sensitivities of Energetic Materials


    The spark energy, EES, required for 50 percent initiation probability of 41 polynitro compounds was determined. The relationships between the EES values and impact sensitivity, expressed as drop energies Ed of the "first reaction", were established and discussed. The conclusion is made that depending on intermolecular interaction factors in crystals of energetic materials, the mechanism of impact energy transition to the reaction centre of their molecule can be differ from that of transition of energy of electric spark.

  17. Drainage in a model stratified porous medium

    Datta, Sujit S; 10.1209/0295-5075/101/14002


    We show that when a non-wetting fluid drains a stratified porous medium at sufficiently small capillary numbers Ca, it flows only through the coarsest stratum of the medium; by contrast, above a threshold Ca, the non-wetting fluid is also forced laterally, into part of the adjacent, finer strata. The spatial extent of this partial invasion increases with Ca. We quantitatively understand this behavior by balancing the stratum-scale viscous pressure driving the flow with the capillary pressure required to invade individual pores. Because geological formations are frequently stratified, we anticipate that our results will be relevant to a number of important applications, including understanding oil migration, preventing groundwater contamination, and sub-surface CO$_{2}$ storage.

  18. Stably Stratified Flow in a Shallow Valley

    Mahrt, L.


    Stratified nocturnal flow above and within a small valley of approximately 12-m depth and a few hundred metres width is examined as a case study, based on a network of 20 sonic anemometers and a central 20-m tower with eight levels of sonic anemometers. Several regimes of stratified flow over gentle topography are conceptually defined for organizing the data analysis and comparing with the existing literature. In our case study, a marginal cold pool forms within the shallow valley in the early evening but yields to larger ambient wind speeds after a few hours, corresponding to stratified terrain-following flow where the flow outside the valley descends to the valley floor. The terrain-following flow lasts about 10 h and then undergoes transition to an intermittent marginal cold pool towards the end of the night when the larger-scale flow collapses. During this 10-h period, the stratified terrain-following flow is characterized by a three-layer structure, consisting of a thin surface boundary layer of a few metres depth on the valley floor, a deeper boundary layer corresponding to the larger-scale flow, and an intermediate transition layer with significant wind-directional shear and possible advection of lee turbulence that is generated even for the gentle topography of our study. The flow in the valley is often modulated by oscillations with a typical period of 10 min. Cold events with smaller turbulent intensity and duration of tens of minutes move through the observational domain throughout the terrain-following period. One of these events is examined in detail.

  19. Multi Dimensional CTL and Stratified Datalog

    Theodore Andronikos


    Full Text Available In this work we define Multi Dimensional CTL (MD-CTL in short by extending CTL which is thedominant temporal specification language in practice. The need for Multi Dimensional CTL is mainlydue to the advent of semi-structured data. The common path nature of CTL and XPath which provides asuitable model for semi-structured data, has caused the emergence of work on specifying a relation amongthem aiming at exploiting the nice properties of CTL. Although the advantages of such an approach havealready been noticed [36, 26, 5], no formal definition of MD-CTL has been given. The goal of this workis twofold; a we define MD-CTL and prove that the “nice” properties of CTL (linear model checking andbounded model property transfer also to MD-CTL, b we establish new results on stratified Datalog. Inparticular, we define a fragment of stratified Datalog called Multi Branching Temporal (MBT in shortprograms that has the same expressive power as MD-CTL. We prove that by devising a linear translationbetween MBT and MD-CTL. We actually give the exact translation rules for both directions. We furtherbuild on this relation to prove that query evaluation is linear and checking satisfiability, containment andequivalence are EXPTIME–complete for MBT programs. The class MBT is the largest fragment of stratifiedDatalog for which such results exist in the literature.

  20. Thermal mixing in a stratified environment

    Kraemer, Damian; Cotel, Aline


    Laboratory experiments of a thermal impinging on a stratified interface have been performed. The thermal was released from a cylindrical reservoir located at the bottom of a Lucite tank. The stratified interface was created by filling the tank with two different saline solutions. The density of the lower layer is greater than that of the upper layer and the thermal fluid, thereby creating a stable stratification. A pH indicator, phenolphthalein, is used to visualize and quantify the amount of mixing produced by the impingement of the thermal at the interface. The upper layer contains a mixture of water, salt and sodium hydroxide. The thermal fluid is composed of water, sulfuric acid and phenolphthalein. When the thermal entrains and mixes fluid from the upper layer, a chemical reaction takes place, and the resulting mixed fluid is now visible. The ratio of base to acid, called the equivalence ratio, was varied throughout the experiments, as well as the Richardson number. The Richardson number is the ratio of potential to kinetic energy, and is based on the thermal quantities at the interface. Results indicate that the amount of mixing produced is proportional to the Richardson number raised to the -3/2 power. Previous experiments (Zhang and Cotel 1999) revealed that the entrainment rate of a thermal in a stratified environment follows the same power law.

  1. Spark Ignition of Monodisperse Fuel Sprays. Ph.D. Thesis

    Danis, Allen M.; Cernansky, Nicholas P.; Namer, Izak


    A study of spark ignition energy requirements was conducted with a monodisperse spray system allowing independent control of droplet size, equivalent ratio, and fuel type. Minimum ignition energies were measured for n-heptane and methanol sprays characterized at the spark gap in terms of droplet diameter, equivalence ratio (number density) and extent of prevaporization. In addition to sprays, minimum ignition energies were measured for completely prevaporized mixtures of the same fuels over a range of equivalence ratios to provide data at the lower limit of droplet size. Results showed that spray ignition was enhanced with decreasing droplet size and increasing equivalence ratio over the ranges of the parameters studied. By comparing spray and prevaporized ignition results, the existence of an optimum droplet size for ignition was indicated for both fuels. Fuel volatility was seen to be a critical factor in spray ignition. The spray ignition results were analyzed using two different empirical ignition models for quiescent mixtures. Both models accurately predicted the experimental ignition energies for the majority of the spray conditions. Spray ignition was observed to be probabilistic in nature, and ignition was quantified in terms of an ignition frequency for a given spark energy. A model was developed to predict ignition frequencies based on the variation in spark energy and equivalence ratio in the spark gap. The resulting ignition frequency simulations were nearly identical to the experimentally observed values.

  2. The fast algorithm of spark in compressive sensing

    Xie, Meihua; Yan, Fengxia


    Compressed Sensing (CS) is an advanced theory on signal sampling and reconstruction. In CS theory, the reconstruction condition of signal is an important theory problem, and spark is a good index to study this problem. But the computation of spark is NP hard. In this paper, we study the problem of computing spark. For some special matrixes, for example, the Gaussian random matrix and 0-1 random matrix, we obtain some conclusions. Furthermore, for Gaussian random matrix with fewer rows than columns, we prove that its spark equals to the number of its rows plus one with probability 1. For general matrix, two methods are given to compute its spark. One is the method of directly searching and the other is the method of dual-tree searching. By simulating 24 Gaussian random matrixes and 18 0-1 random matrixes, we tested the computation time of these two methods. Numerical results showed that the dual-tree searching method had higher efficiency than directly searching, especially for those matrixes which has as much as rows and columns.

  3. Investigations in the upper load range of stratified operation with injection pressures up to 1000 bar; Untersuchungen im oberen Lastbereich des Schichtbetriebes bei Einspritzdruecken bis 1000 bar

    Buri, Stefan; Busch, Steve; Kubach, Heiko; Spicher, Ulrich [Karlsruhe Univ. (DE). Inst. fuer Kolbenmaschinen (IFKM)


    This paper presents the results of recent research that has been performed on a single-cylinder spray-guided DISI engine at the Institut fuer Kolbenmaschinen. A production multihole injector is used as a baseline and compared with a specially adapted injector at higher injection pressures. Injection pressures of up to 1000 bar are utilized to investigate the combustion and emissions characteristics at the stability limit of stratified combustion. With the modified injector, measurements with the two-color method are applied to analyze this operating condition in terms of soot formation. Included are results for a spark timing variation with 1000 bar injection pressure, an injection pressure variation with constant spark timing, and fuel consumption-optimized engine operating parameters in order to analyze realistic operating points. The benefits of injecting fuel at higher pressures are described, as are the limitations of the experimental setup. (orig.)

  4. Inactivation of Staphylococcus aureus in water by pulsed spark discharge.

    Zheng, Jiansheng


    A pulsed spark plasma discharge system was developed and tested as an energy efficient water sterilization method. A 5 log10 reduction on Staphylococcus aureus concentration of 10(8) CFU/ml was obtained. Complete inactivation was achieved for concentration of 10(6) CFU/ml. Of the various factors generated by an underwater spark discharge, ultraviolet radiation plays a major role. The inactivation was completely suppressed by the addition of 30 mg/L of a soluble sunscreen, Benzophenone-9. Results obtained using the pulsed spark plasma discharge showed that this system has several advantages, such as high energy efficiency, absence of harmful by-products and portability, over the conventional sterilization methods.

  5. Can the inner gap sparking take place in millisecond pulsars?

    Hong-Guang Wang; Guo-Jun Qiao; Ren-Xin Xu


    The inner vacuum gap model has become the foundation stone of most theories on pulsar radio emission. The fundamental picture of this model is the sparking, which was conjectured to be induced by magnetic absorption of background gamma photons. However, a question is, can the sparking be triggered in the millisecond pulsars (MSPs) with magnetic fields (B) only about 10s G? We investigate this problem by including the pair production above the inner gap. Under the assumption that the magnetic field is dipolar, our results show the background gamma-ray emission can not be the key factor that triggers the sparking, at least not in MSPs with B ~ 108 G, if the temperature in the polar cap region is only so high as is observed (< 4 × 106 K). Some other mechanisms are required.

  6. Spark plasma sintering of hydrothermally synthesized bismuth ferrite

    Zorica Branković


    Full Text Available Bismuth ferrite, BiFeO3 (BFO, powder was synthesized by hydrothermal method from Bi(NO33·5 H2O and Fe(NO33·9 H2O as precursors. The synthesized powder was further sintered using spark plasma sintering (SPS. The sintering conditions were optimized in order to achieve high density, minimal amount of secondary phases and improved ferroelectric and magnetic properties. The optimal structure and properties were achieved after spark plasma sintering at 630 °C for 20 min, under uniaxial pressure of 90 MPa. The composition, microstructure, ferroelectric and magnetic properties of the SPS samples were characterized and compared to those of conventionally sintered ceramics obtained from the same powder. Although the samples sintered using conventional method showed slightly lower amount of secondary phases, the spark plasma sintered samples exhibited favourable microstructure and better ferroelectric properties.


    A stratified charge research engine and test stand were designed and built for this work. The primary goal of this project was to evaluate the feasibility of using a removal integral injector ignition source insert which allows a convenient method of charging the relative locat...

  8. Time-lags before breakdown in the DC spark system

    Descoeudres, A


    The voltage time evolution in the DC spark system has been measured together with the current signal during a discharge. The voltage rise-time, given by the circuitry and the HV relay is measured to be of the order of 100 ns. Measurement of the time-lags for breakdown reveals a material dependent behaviour; two populations centered at 0.1 s and at 1.3 ms are detected on stainless steel whereas on tungsten carbide only fast occurring sparks with sharp distribution around 0.1 s are found. The two populations indicate the presence of two different breakdown mechanisms.

  9. Plasma dynamics of a laser filamentation-guided spark

    Point, Guillaume; Carbonnel, Jérôme; Mysyrowicz, André; Houard, Aurélien


    We investigate experimentally the plasma dynamics of a centimeter-scale, laser filamentation-guided spark discharge. Using electrical and optical diagnostics to study monopolar discharges with varying current pulses we show that plasma decay is dominated by free electron recombination if the current decay time is shorter than the recombination characteristic time. In the opposite case, the plasma electron density closely follows the current evolution. We demonstrate that this criterion holds true in the case of damped AC sparks, and that alternative current is the best option to achieve a long plasma lifetime for a given peak current.

  10. Analysis of Plant Breeding on Hadoop and Spark

    Shuangxi Chen


    Full Text Available Analysis of crop breeding technology is one of the important means of computer-assisted breeding techniques which have huge data, high dimensions, and a lot of unstructured data. We propose a crop breeding data analysis platform on Spark. The platform consists of Hadoop distributed file system (HDFS and cluster based on memory iterative components. With this cluster, we achieve crop breeding large data analysis tasks in parallel through API provided by Spark. By experiments and tests of Indica and Japonica rice traits, plant breeding analysis platform can significantly improve the breeding of big data analysis speed, reducing the workload of concurrent programming.

  11. Spark, an application based on Serendipitous Knowledge Discovery.

    Workman, T Elizabeth; Fiszman, Marcelo; Cairelli, Michael J; Nahl, Diane; Rindflesch, Thomas C


    Findings from information-seeking behavior research can inform application development. In this report we provide a system description of Spark, an application based on findings from Serendipitous Knowledge Discovery studies and data structures known as semantic predications. Background information and the previously published IF-SKD model (outlining Serendipitous Knowledge Discovery in online environments) illustrate the potential use of information-seeking behavior in application design. A detailed overview of the Spark system illustrates how methodologies in design and retrieval functionality enable production of semantic predication graphs tailored to evoke Serendipitous Knowledge Discovery in users.

  12. Microstructure of Spark Plasma-Sintered Silicon Nitride Ceramics

    Lukianova, O. A.; Novikov, V. Yu.; Parkhomenko, A. A.; Sirota, V. V.; Krasilnikov, V. V.


    The microstructure and phase composition of the high-content Al2O3-Y2O3-doped spark plasma-sintered silicon nitride were investigated. Fully dense silicon nitride ceramics with a typical α-Si3N4 equiaxed structure with average grain size from 200 to 530 nm, high elastic modulus of 288 GPa, and high hardness of 2038 HV were spark plasma sintered (SPSed) at 1550 °C. Silicon nitride with elongated β-Si3N4 grains, higher hardness of 1800 HV, density of 3.25 g/cm3, and Young's modulus 300 GPa SPSed at 1650 °C was also reviewed.

  13. The fully nonlinear stratified geostrophic adjustment problem

    Coutino, Aaron; Stastna, Marek


    The study of the adjustment to equilibrium by a stratified fluid in a rotating reference frame is a classical problem in geophysical fluid dynamics. We consider the fully nonlinear, stratified adjustment problem from a numerical point of view. We present results of smoothed dam break simulations based on experiments in the published literature, with a focus on both the wave trains that propagate away from the nascent geostrophic state and the geostrophic state itself. We demonstrate that for Rossby numbers in excess of roughly 2 the wave train cannot be interpreted in terms of linear theory. This wave train consists of a leading solitary-like packet and a trailing tail of dispersive waves. However, it is found that the leading wave packet never completely separates from the trailing tail. Somewhat surprisingly, the inertial oscillations associated with the geostrophic state exhibit evidence of nonlinearity even when the Rossby number falls below 1. We vary the width of the initial disturbance and the rotation rate so as to keep the Rossby number fixed, and find that while the qualitative response remains consistent, the Froude number varies, and these variations are manifested in the form of the emanating wave train. For wider initial disturbances we find clear evidence of a wave train that initially propagates toward the near wall, reflects, and propagates away from the geostrophic state behind the leading wave train. We compare kinetic energy inside and outside of the geostrophic state, finding that for long times a Rossby number of around one-quarter yields an equal split between the two, with lower (higher) Rossby numbers yielding more energy in the geostrophic state (wave train). Finally we compare the energetics of the geostrophic state as the Rossby number varies, finding long-lived inertial oscillations in the majority of the cases and a general agreement with the past literature that employed either hydrostatic, shallow-water equation-based theory or

  14. Inverse scattering of dispersive stratified structures

    Skaar, Johannes


    We consider the inverse scattering problem of retrieving the structural parameters of a stratified medium consisting of dispersive materials, given knowledge of the complex reflection coefficient in a finite frequency range. It is shown that the inverse scattering problem does not have a unique solution in general. When the dispersion is sufficiently small, such that the time-domain Fresnel reflections have durations less than the round-trip time in the layers, the solution is unique and can be found by layer peeling. Numerical examples with dispersive and lossy media are given, demonstrating the usefulness of the method for e.g. THz technology.

  15. Topological Structures in Rotating Stratified Flows

    Redondo, J. M.; Carrillo, A.; Perez, E.


    Detailled 2D Particle traking and PIV visualizations performed on a series of large scale laboratory experiments at the Coriolis Platform of the SINTEF in Trondheim have revealed several resonances which scale on the Strouhal, the Rossby and the Richardson numbers. More than 100 experiments spanned a wide range of Rossby Deformation Radii and the topological structures (Parabolic /Eliptic /Hyperbolic) of the quasi-balanced stratified-rotating flows were studied when stirring (akin to coastal mixing) occured at a side of the tank. The strong asymetry favored by the total vorticity produces a wealth of mixing patterns.

  16. Internal combustion engine report: Spark ignited ICE GenSet optimization and novel concept development

    Keller, J.; Blarigan, P. Van [Sandia National Labs., Livermore, CA (United States)


    In this manuscript the authors report on two projects each of which the goal is to produce cost effective hydrogen utilization technologies. These projects are: (1) the development of an electrical generation system using a conventional four-stroke spark-ignited internal combustion engine generator combination (SI-GenSet) optimized for maximum efficiency and minimum emissions, and (2) the development of a novel internal combustion engine concept. The SI-GenSet will be optimized to run on either hydrogen or hydrogen-blends. The novel concept seeks to develop an engine that optimizes the Otto cycle in a free piston configuration while minimizing all emissions. To this end the authors are developing a rapid combustion homogeneous charge compression ignition (HCCI) engine using a linear alternator for both power take-off and engine control. Targeted applications include stationary electrical power generation, stationary shaft power generation, hybrid vehicles, and nearly any other application now being accomplished with internal combustion engines.


    Ruan Fangming; Fujiwara Osamu; Gao Yougang


    Characteristic measurement of contact discharge currents are made through a hand-held metal rod from charged human body. Correlation coefficients are obtained, through Statistic Package for Social Science (SPSS), for various charge voltages, which is based on the effect test of electrode contact approach speeds on discharge current parameters of current peaks, maximum rising slope and spark lengths. Discharge parameters at charge voltage 300V are independent on approach speed. For charge voltages equal to and higher than 500V, the contact approach speed has strong positive correlation with discharge parameters of the peak current and the maximum rising slope, whereas has strong negative correlation with the spark length.

  18. A Model For The Optically Triggered Pseudo-Spark Thyratron Using Local Field And Beam-Bulk Methods

    Pak, Hoyoung; Kushner, Mark J.


    The optically triggered psuedo-spark, also known as the Back-Lit-Thyratron (BLT), is a low pressure plasma switch having an unheated metallic cathode. In this paper, a computer simulation of the BLT is presented consisting of a 2-1/2 dimensional time dependent continuum model for electron and ion transport. The model utilizes both the local field approximation and a beam component for the electron distribution function. We find that switch closure depends critically on the formation of a virtual anode in front of the cathode hole by generation of positive space charge.

  19. Testing of the J-2X Augmented Spark Igniter (ASI) and Its Electronics

    Osborne, Robin


    Reliable operation of the spark ignition system electronics in the J-2X Augmented Spark Igniter (ASI) is imperative in assuring ASI ignition and subsequent Main Combustion Chamber (MCC) ignition events are reliable in the J-2X Engine. Similar to the man-rated J-2 and RS-25 engines, the J-2X ignition system electronics are equipped with spark monitor outputs intended to indicate that the spark igniters are properly energized and sparking. To better understand anomalous spark monitor data collected on the J-2X development engines at NASA Stennis Space Center (SSC), a comprehensive subsystem study of the engine's low- and high-tension spark ignition system electronics was conducted at NASA Marshall Space Flight Center (MSFC). Spark monitor output data were compared to more detailed spark diagnostics to determine if the spark monitor was an accurate indication of actual sparking events. In addition, ignition system electronics data were closely scrutinized for any indication of an electrical discharge in some location other than the firing tip of the spark igniter - a problem not uncommon in the development of high voltage ignition systems.

  20. 46 CFR 30.10-63 - Spark arrester-TB/ALL.


    ... 46 Shipping 1 2010-10-01 2010-10-01 false Spark arrester-TB/ALL. 30.10-63 Section 30.10-63 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY TANK VESSELS GENERAL PROVISIONS Definitions § 30.10-63 Spark arrester—TB/ALL. The term spark arrester means any device, assembly, or method of a...

  1. SparkText: Biomedical Text Mining on Big Data Framework.

    Ye, Zhan; Tafti, Ahmad P; He, Karen Y; Wang, Kai; He, Max M

    Many new biomedical research articles are published every day, accumulating rich information, such as genetic variants, genes, diseases, and treatments. Rapid yet accurate text mining on large-scale scientific literature can discover novel knowledge to better understand human diseases and to improve the quality of disease diagnosis, prevention, and treatment. In this study, we designed and developed an efficient text mining framework called SparkText on a Big Data infrastructure, which is composed of Apache Spark data streaming and machine learning methods, combined with a Cassandra NoSQL database. To demonstrate its performance for classifying cancer types, we extracted information (e.g., breast, prostate, and lung cancers) from tens of thousands of articles downloaded from PubMed, and then employed Naïve Bayes, Support Vector Machine (SVM), and Logistic Regression to build prediction models to mine the articles. The accuracy of predicting a cancer type by SVM using the 29,437 full-text articles was 93.81%. While competing text-mining tools took more than 11 hours, SparkText mined the dataset in approximately 6 minutes. This study demonstrates the potential for mining large-scale scientific articles on a Big Data infrastructure, with real-time update from new articles published daily. SparkText can be extended to other areas of biomedical research.

  2. Meter-scale spark X-ray spectrumstatistics

    Carlson, B E; Kochkin, P; Grondahl, Ø; Nisi, R; Weber, K; Scherrer, Z; LeCaptain, K


    X-ray emission by sparks implies bremsstrahlung from a population of energetic electrons, but the details of this process remain a mystery. We present detailed statistical analysis of X-ray spectra detected by multiple detectors during sparks produced by 1 MV negative high-voltage pulses with 1 $\\mu$s risetime. With over 900 shots, we statistically analyze the signals, assuming that the distribution of spark X-ray fluence behaves as a power law and that the energy spectrum of X-rays detectable after traversing $\\sim$2 m of air and a thin aluminum shield is exponential. We then determine the parameters of those distributions by fitting cumulative distribution functions to the observations. The fit results match the observations very well if the mean of the exponential X-ray energy distribution is 86 $\\pm$ 7 keV and the spark X-ray fluence power law distribution has index -1.29 $\\pm$ 0.04 and spans at least 3 orders of magnitude in fluence.

  3. Direction finding antenna system for spark detection and localization

    Topor, Raluca E.; Bucuci, Stefania C.; Tamas, Razvan D.; Danisor, Alin; Dumitrascu, Ana; Berescu, Serban


    This paper proposes a novel UWB antenna system for spark detection and localization by using the amplitude comparison direction finding (DF) method. The proposed design consists of two identical axially crossed "padlock" shaped UWB antennas, with unbalanced feeding. Simulation results show that such radiating systems can be used for assessing the direction of arrival for short pulses.

  4. Utilization of Alcohol Fuel in Spark Ignition and Diesel Engines.

    Berndt, Don; Stengel, Ron

    These five units comprise a course intended to prepare and train students to conduct alcohol fuel utilization seminars in spark ignition and diesel engines. Introductory materials include objectives and a list of instructor requirements. The first four units cover these topics: ethanol as an alternative fuel (technical and economic advantages,…

  5. Towards a general turbulent combustion model for spark ignition engines

    Naji, H.; Said, R.; Borghi, R.P.


    The prediction of combustion within spark ignition engines needs to take into account the interaction of turbulent fluctuations. Previous attempts at this used a model in which the chemical processes were supposed infinitely fast and the combustion was controlled by turbulent mixing only. This paper describes their progress in extending such models in two directions.

  6. Assembly of optical spark chambers for the experiment Nue


    To continue the research on neutral currents after their discovery in Gargamelle in 1973, the Aachen-Padua Collaboration set up in the neutrino beam of the PS South-East Area, behind Gargamelle, an assembly of 150 optical spark chambers, 2x2 m2 extending over 8 m (experiment T230, Nue). Hans Reithler stands on the right.

  7. Determination of welding spark parameters for cyclone efficiency calculation (rus

    Kitain M.B.


    Full Text Available Importance of the current work is explained by the problem of air purification in the field of breath of the worker and prevention of the fire and the explosion. To solve this problem the authors offer to use Reverse-flow cyclone as precleaner with spark extinguishing option. In case if the dust includes sparks it is very important to insure that the particles with the sparks will be totally collected in the cyclone, so the collection efficiency for such particles will be 100% in the cyclone. For the estimation of the efficiency of gas purification from the dust particles in the cyclones dust particles features should be determinate, that can be done with the satisfactory accuracy only by physical modeling results. The amount of physical experiments was made by the authors. The methods of determination of the geometric diameter and hydraulic size of the particle consisting sparks were offered. The experimental researches showed that the accuracy of using the geometric diameter of such particle is not enough, because the hydrodynamic characteristics of the particles (such as weight, effective diameter, the way of interaction with the environment can be change in the case of moving. At the same time< hydraulic size, determined in the second part of the experiment, consider all these factors and can be used for the estimation of the cyclone efficiency based on the model of turbulent diffusion with the limited velocity.


    Sergey Levchenko


    Full Text Available Spark machining of steel surfaces enhances the subsequent paint coatings adhesion and protective properties. These factors improvement was confirmed at the salt-spray chamber testing and by both adhesion to the surface and depth of corrosion penetration below the paint coating layer measurements.


    I. O. Vakulenko


    Full Text Available Purpose. The purpose of work is an estimation of influence of an electric spark treatment on the state of mouldable superficial coverage of carbon steel. Methodology. The steel of fragment of railway wheel rim served as material for research with chemical composition 0.65% С, 0.67% Mn, 0.3% Si, 0.027% P, 0.028% S. Structural researches were conducted with the use of light microscopy and methods of quantitative metallography. The structural state of the probed steel corresponded to the state after hot plastic deformation. The analysis of hardness distribution in the micro volumes of cathode metal was carried out with the use of microhardness tester of type of PMT-3. An electric spark treatment of carbon steel surface was executed with the use of equipment type of EFI-25M. Findings. After electric spark treatment of specimen surface from carbon steel the forming of multi-layered coverage was observed. The analysis of microstructure found out the existence of high-quality distinctions in the internal structure of coverage metal, depending on the probed area. The results obtained in the process are confirmed by the well-known theses, that forming of superficial coverage according to technology of electric spark is determined by the terms of transfer and crystallization of metal. The gradient of structures on the coverage thickness largely depends on development of structural transformation processes similar to the thermal character influence. Originality. As a result of electric spark treatment on the condition of identical metal of anode and cathode, the first formed layer of coverage corresponds to the monophase state according to external signs. In the volume of coverage metal, the appearance of carbide phase particles is accompanied by the decrease of microhardness values. Practical value. Forming of multi-layered superficial coverage during electric spark treatment is accompanied by the origin of structure gradient on a thickness. The effect

  10. Erosion on spark plug electrodes; Funkenerosion an Zuendkerzenelektroden

    Rager, J.


    Durability of spark plugs is mainly determined by spark gap widening, caused by electrode wear. Knowledge about the erosion mechanisms of spark plug materials is of fundamental interest for the development of materials with a high resistance against electrode erosion. It is therefore crucial to identify those parameters which significantly influence the erosion behaviour of a material. In this work, a reliable and reproducible testing method is presented which produces and characterizes electrode wear under well-defined conditions and which is capable of altering parameters specifically. Endurance tests were carried out to study the dependence of the wear behaviour of pure nickel and platinum on the electrode temperature, gas, electrode gap, electrode diameter, atmospheric pressure, and partial pressure of oxygen. It was shown that erosion under nitrogen is negligible, irrespective of the material. This disproves all common mechanism discussed in the literature explaining material loss of spark plug electrodes. Based on this observation and the variation of the mentioned parameters a new erosion model was deduced. This relies on an oxidation of the electrode material and describes the erosion of nickel and platinum separately. For nickel, electrode wear is caused by the removal of an oxide layer by the spark. In the case of platinum, material loss occurs due to the plasma-assisted formation and subsequent evaporation of volatile oxides in the cathode spot. On the basis of this mechanism a new composite material was developed whose erosion resistance is superior to pure platinum. Oxidation resistant metal oxide particles were added to a platinum matrix, thus leading to a higher erosion resistance of the composite. However, this can be decreased by a side reaction, the separation of oxygen from the metal oxides, which effectively assists the oxidation of the matrix. This reaction can be suppressed by using highly stable oxides, characterized by a large negative Gibbs

  11. Investigations of the causes of hydrocarbon emissions in spark ignition engines with homogeneous charge compression ignition (HCCI). A report of the Institute for Internal Combustion Engines and Automotive Engineering, TU Vienna (IVK); Untersuchung der Ursachen fuer Kohlenwasserstoff-Emissionen beim Ottomotor mit homogener Selbstzuendung (HCCI). Bericht des Instituts fuer Verbrennungskraftmaschinen und Kraftfahrzeugbau derTechnischen Universitaet Wien (IVK)

    Geringer, B. (ed.) [Technische Univ., Vienna (Austria); Loch, A.


    The main aim of research and development in the field of internal combustion engine is to create an engine with low fuel consumption and hence low carbon dioxide emissions to meet future emissions regulations as well as providing a good driving experience. Homogeneous charge compression ignition (HCCI) is an alternative combustion process being currently developed that promises a good fuel consumption rate and low nitrogen oxide emissions for the gasoline engine. The only legally restricted exhaust gas emissions for this combustion process are carbon monoxide (CO) and hydrocarbons (HC). The aim of this research was a better understanding of the causes and sources of hydrocarbon emissions with HCCI using gasoline so as to further reduce hydrocarbon emissions. A description of the HCCI combustion process is followed by a list of the known sources of hydrocarbon emission in conventional gasoline engines and current knowledge of the causes of hydrocarbon emission with HCCI. It is assumed that many of the known causes of hydrocarbon emissions in the conventional gasoline combustion process are the same for HCCI. For this reason, this study focused on combustion and carburation, which is where the combustion processes differ the most. (orig.)

  12. Vehicle driving cycle performance of the spark-less di-ji hydrogen engine

    Boretti, Alberto A. [School of Science and Engineering, University of Ballarat, PO Box663, Ballarat, VIC 3353 (Australia)


    The paper describes coupled CFD combustion simulations and CAE engine performance computations to describe the operation over the full range of load and speed of an always lean burn, Direct Injection Jet Ignition (DI-JI) hydrogen engine. Jet ignition pre-chambers and direct injection are enablers of high efficiencies and load control by quantity of fuel injected. Towards the end of the compression stroke, a small quantity of hydrogen is injected within the spark-less pre-chamber of the DI-JI engine, where it mixes with the air entering from the main chamber and auto-ignites because of the high temperature of the hot glow plug. Then, jets of partially combusted hot gases enter the main chamber igniting there in the bulk, over multiple ignition points, lean stratified mixtures of air and fuel. Engine maps of brake specific fuel consumption vs. speed and brake mean effective pressure are computed first. CAE vehicle simulations are finally performed evaluating the fuel consumption over emission cycles of a vehicle equipped with this engine. (author)

  13. Stratified growth in Pseudomonas aeruginosa biofilms

    Werner, E.; Roe, F.; Bugnicourt, A.;


    In this study, stratified patterns of protein synthesis and growth were demonstrated in Pseudomonas aeruginosa biofilms. Spatial patterns of protein synthetic activity inside biofilms were characterized by the use of two green fluorescent protein (GFP) reporter gene constructs. One construct...... carried an isopropyl-beta-D-thiogalactopyranoside (IPTG)-inducible gfpmut2 gene encoding a stable GFP. The second construct carried a GFP derivative, gfp-AGA, encoding an unstable GFP under the control of the growth-rate-dependent rrnBp(1) promoter. Both GFP reporters indicated that active protein...... of oxygen limitation in the biofilm. Oxygen microelectrode measurements showed that oxygen only penetrated approximately 50 mum into the biofilm. P. aeruginosa was incapable of anaerobic growth in the medium used for this investigation. These results show that while mature P. aeruginosa biofilms contain...

  14. Bayesian Stratified Sampling to Assess Corpus Utility

    Hochberg, J; Thomas, T; Hall, S; Hochberg, Judith; Scovel, Clint; Thomas, Timothy; Hall, Sam


    This paper describes a method for asking statistical questions about a large text corpus. We exemplify the method by addressing the question, "What percentage of Federal Register documents are real documents, of possible interest to a text researcher or analyst?" We estimate an answer to this question by evaluating 200 documents selected from a corpus of 45,820 Federal Register documents. Stratified sampling is used to reduce the sampling uncertainty of the estimate from over 3100 documents to fewer than 1000. The stratification is based on observed characteristics of real documents, while the sampling procedure incorporates a Bayesian version of Neyman allocation. A possible application of the method is to establish baseline statistics used to estimate recall rates for information retrieval systems.

  15. Clustering of floating particles in stratified turbulence

    Boffetta, Guido; de Lillo, Filippo; Musacchio, Stefano; Sozza, Alessandro


    We study the dynamics of small floating particles transported by stratified turbulence in presence of a mean linear density profile as a simple model for the confinement and the accumulation of plankton in the ocean. By means of extensive direct numerical simulations we investigate the statistical distribution of floaters as a function of the two dimensionless parameters of the problem. We find that vertical confinement of particles is mainly ruled by the degree of stratification, with a weak dependency on the particle properties. Conversely, small scale fractal clustering, typical of non-neutral particles in turbulence, depends on the particle relaxation time and is only weakly dependent on the flow stratification. The implications of our findings for the formation of thin phytoplankton layers are discussed.

  16. On turbulence in a stratified environment

    Sarkar, Sutanu


    John Lumley, motivated by atmospheric observations, made seminal contributions to the statistical theory (Lumley and Panofsky 1964, Lumley 1964) and second-order modeling (Zeman and Lumley 1976) of turbulence in the environment. Turbulent processes in the ocean share many features with the atmosphere, e.g., shear, stratification, rotation and rough topography. Results from direct and large eddy simulations of two model problems will be used to illustrate some of the features of turbulence in a stratified environment. The first problem concerns a shear layer in nonuniform stratification, a situation typical of both the atmosphere and the ocean. The second problem, considered to be responsible for much of the turbulent mixing that occurs in the ocean interior, concerns topographically generated internal gravity waves. Connections will be made to data taken during observational campaigns in the ocean.

  17. Stratified scaffold design for engineering composite tissues.

    Mosher, Christopher Z; Spalazzi, Jeffrey P; Lu, Helen H


    A significant challenge to orthopaedic soft tissue repair is the biological fixation of autologous or allogeneic grafts with bone, whereby the lack of functional integration between such grafts and host bone has limited the clinical success of anterior cruciate ligament (ACL) and other common soft tissue-based reconstructive grafts. The inability of current surgical reconstruction to restore the native fibrocartilaginous insertion between the ACL and the femur or tibia, which minimizes stress concentration and facilitates load transfer between the soft and hard tissues, compromises the long-term clinical functionality of these grafts. To enable integration, a stratified scaffold design that mimics the multiple tissue regions of the ACL interface (ligament-fibrocartilage-bone) represents a promising strategy for composite tissue formation. Moreover, distinct cellular organization and phase-specific matrix heterogeneity achieved through co- or tri-culture within the scaffold system can promote biomimetic multi-tissue regeneration. Here, we describe the methods for fabricating a tri-phasic scaffold intended for ligament-bone integration, as well as the tri-culture of fibroblasts, chondrocytes, and osteoblasts on the stratified scaffold for the formation of structurally contiguous and compositionally distinct regions of ligament, fibrocartilage and bone. The primary advantage of the tri-phasic scaffold is the recapitulation of the multi-tissue organization across the native interface through the layered design. Moreover, in addition to ease of fabrication, each scaffold phase is similar in polymer composition and therefore can be joined together by sintering, enabling the seamless integration of each region and avoiding delamination between scaffold layers.

  18. Stratified sampling design based on data mining.

    Kim, Yeonkook J; Oh, Yoonhwan; Park, Sunghoon; Cho, Sungzoon; Park, Hayoung


    To explore classification rules based on data mining methodologies which are to be used in defining strata in stratified sampling of healthcare providers with improved sampling efficiency. We performed k-means clustering to group providers with similar characteristics, then, constructed decision trees on cluster labels to generate stratification rules. We assessed the variance explained by the stratification proposed in this study and by conventional stratification to evaluate the performance of the sampling design. We constructed a study database from health insurance claims data and providers' profile data made available to this study by the Health Insurance Review and Assessment Service of South Korea, and population data from Statistics Korea. From our database, we used the data for single specialty clinics or hospitals in two specialties, general surgery and ophthalmology, for the year 2011 in this study. Data mining resulted in five strata in general surgery with two stratification variables, the number of inpatients per specialist and population density of provider location, and five strata in ophthalmology with two stratification variables, the number of inpatients per specialist and number of beds. The percentages of variance in annual changes in the productivity of specialists explained by the stratification in general surgery and ophthalmology were 22% and 8%, respectively, whereas conventional stratification by the type of provider location and number of beds explained 2% and 0.2% of variance, respectively. This study demonstrated that data mining methods can be used in designing efficient stratified sampling with variables readily available to the insurer and government; it offers an alternative to the existing stratification method that is widely used in healthcare provider surveys in South Korea.

  19. Information content of household-stratified epidemics

    T.M. Kinyanjui


    Full Text Available Household structure is a key driver of many infectious diseases, as well as a natural target for interventions such as vaccination programs. Many theoretical and conceptual advances on household-stratified epidemic models are relatively recent, but have successfully managed to increase the applicability of such models to practical problems. To be of maximum realism and hence benefit, they require parameterisation from epidemiological data, and while household-stratified final size data has been the traditional source, increasingly time-series infection data from households are becoming available. This paper is concerned with the design of studies aimed at collecting time-series epidemic data in order to maximize the amount of information available to calibrate household models. A design decision involves a trade-off between the number of households to enrol and the sampling frequency. Two commonly used epidemiological study designs are considered: cross-sectional, where different households are sampled at every time point, and cohort, where the same households are followed over the course of the study period. The search for an optimal design uses Bayesian computationally intensive methods to explore the joint parameter-design space combined with the Shannon entropy of the posteriors to estimate the amount of information in each design. For the cross-sectional design, the amount of information increases with the sampling intensity, i.e., the designs with the highest number of time points have the most information. On the other hand, the cohort design often exhibits a trade-off between the number of households sampled and the intensity of follow-up. Our results broadly support the choices made in existing epidemiological data collection studies. Prospective problem-specific use of our computational methods can bring significant benefits in guiding future study designs.

  20. Simultaneous equivalence ratio and velocity measurements for non-stationary combustion study in a stratified flow; Mesures couplees de richesse et de vitesse pour la combustion instationnaire en ecoulement stratifie

    Pasquier-Guilbert, N.


    Simultaneous knowledge of local velocity and equivalence ratio is very important in numerous combustion applications and especially for direct injection engines where the flame propagates through a heterogeneous concentration distribution of fuel-air mixture. This study reproduce heterogeneities of equivalence ratio with propane and air in a constant volume combustion vessel. The local influence of velocity and equivalence ratio on the propagation of a spark-ignited flame is studied. To create a stratification, a rich axisymmetric pulsed jet is injected in a leaner chamber and the mixing is ignited. Two optical diagnostics are used simultaneously, PIV for velocity and FARLIF for equivalence ratio, with or without combustion. All properties and range of applications of PIV and FARLIF have been verified. These methods were then used to study the characteristics of stratified combustion. (author)

  1. Experimental Study on Methane Explosion Ignited by Sparks of Cable Bolt Breakage

    MA Wen-ding; XU Jia-lin; ZHANG Shao-hua


    An experimental device was designed for studying methane explosion ignited by sparks of cable bolt breakage. With the methane concentration being in explosion range, a series of experiments were conducted to study the law of spark generation during cable bolt breakage and the probability of methane explosion caused by the spark. The results show that the probability of generating sparks during cable bolt breakage is 50%. The spark generated by the breakage of steel cable bolt strand can't ignite a methane explosion. A detection was carried out using infrared-ray imaging apparatus (IRIA) to measure temperature of the spark generated by cable bolt breakage. It is indicated that the maximum temperature of the spark generated by cable bolt breakage is far less than the required ignition temperature for a methane explosion.

  2. Intermittent hypoxia in rats reduces activation of Ca2+ sparks in mesenteric arteries.

    Jackson-Weaver, Olan; Osmond, Jessica M; Naik, Jay S; Gonzalez Bosc, Laura V; Walker, Benjimen R; Kanagy, Nancy L


    Ca(+) sparks are vascular smooth muscle cell (VSMC) Ca(2+)-release events that are mediated by ryanodine receptors (RyR) and promote vasodilation by activating large-conductance Ca(2+)-activated potassium channels and inhibiting myogenic tone. We have previously reported that exposing rats to intermittent hypoxia (IH) to simulate sleep apnea augments myogenic tone in mesenteric arteries through loss of hydrogen sulfide (H2S)-induced dilation. Because we also observed that H2S can increase Ca(2+) spark activity, we hypothesized that loss of H2S after IH exposure reduces Ca(2+) spark activity and that blocking Ca(2+) spark generation reduces H2S-induced dilation. Ca(2+) spark activity was lower in VSMC of arteries from IH compared with sham-exposed rats. Furthermore, depolarizing VSMC by increasing luminal pressure (from 20 to 100 mmHg) or by elevating extracellular [K(+)] increased spark activity in VSMC of arteries from sham rats but had no effect in arteries from IH rats. Inhibiting endogenous H2S production in sham arteries prevented these increases. NaHS or phosphodiesterase inhibition increased spark activity to the same extent in sham and IH arteries. Depolarization-induced increases in Ca(2+) spark activity were due to increased sparks per site, whereas H2S increases in spark activity were due to increased spark sites per cell. Finally, inhibiting Ca(2+) spark activity with ryanodine (10 μM) enhanced myogenic tone in arteries from sham but not IH rats and blocked dilation to exogenous H2S in arteries from both sham and IH rats. Our results suggest that H2S regulates RyR activation and that H2S-induced dilation requires Ca(2+) spark activation. IH exposure decreases endogenous H2S-dependent Ca(2+) spark activation to cause membrane depolarization and enhance myogenic tone in mesenteric arteries.

  3. Loits skandaalitses gaalal. Sparks Rabarockil. Pärimusmuusika Ait


    Pärnu Kontserdimajas Eesti muusikaauhindade galal üle astunud rockansambel Loits röövis koostöös kultuskirjaniku Sven Kivisildnikuga aasta metal/punk-artisti auhinna, mis pidi minema industrial-metal-artistile Finish Me Off. Ameerika bänd Sparks 14. juunil Järvakandis Rabarockil. Viljandis Tasuja pst.6 avati Eesti Pärimusmuusika Keskuse uus kodu - Pärimusmuusika Ait

  4. Mobile Big Data Analytics Using Deep Learning and Apache Spark

    Alsheikh, Mohammad Abu; Niyato, Dusit; Lin, Shaowei; Tan, Hwee-Pink; Han, Zhu


    The proliferation of mobile devices, such as smartphones and Internet of Things (IoT) gadgets, results in the recent mobile big data (MBD) era. Collecting MBD is unprofitable unless suitable analytics and learning methods are utilized for extracting meaningful information and hidden patterns from data. This article presents an overview and brief tutorial of deep learning in MBD analytics and discusses a scalable learning framework over Apache Spark. Specifically, a distributed deep learning i...




    Full Text Available The hypothesis of the influence of binding energy of metal on the processes of destruction and mass transfer at high-speed machining is considered. Some nonconventional processes of cleaning of intergranularity spaces from waste products at diamond-spark grinding are explained, the approach to assessment of metal resistance in these processes is proposed and eo ipso modern conception of processes in chip formation zone under condition of electric discharge effect is supplemented

  6. Social Media Analytics using Apache Spark Application to Market Research

    Gómez Parada, Mauro


    En este trabajo se intentará generar una herramienta de marketing de la que se pueda obtener información que puede no estar implícita en Instagram con la ayuda de Apache Spark y Apache Cassandra y con la que luego se podrán optimizar las campañas de publicidad que se hagan en esta red social.

  7. The Use of Spark Ignition Engine in Domestic Cogeneration

    Feiza Memet


    Full Text Available Cogeneration plants are strongly sustained by EU energy policies, one of the best beneficiary of this technology being residential buildings. This paper focus on spark ignition engine as a cogeneration application in order to supply energy for domestic consumers. Are considered two aspects of this solution: the energetic aspect and the environmental one. The energetic aspect deals with the energetic ratios, while the environmental aspect refers to the nitrogen oxide and carbon monoxide emissions.

  8. Loits skandaalitses gaalal. Sparks Rabarockil. Pärimusmuusika Ait


    Pärnu Kontserdimajas Eesti muusikaauhindade galal üle astunud rockansambel Loits röövis koostöös kultuskirjaniku Sven Kivisildnikuga aasta metal/punk-artisti auhinna, mis pidi minema industrial-metal-artistile Finish Me Off. Ameerika bänd Sparks 14. juunil Järvakandis Rabarockil. Viljandis Tasuja pst.6 avati Eesti Pärimusmuusika Keskuse uus kodu - Pärimusmuusika Ait

  9. Magnetic flux concentrations from turbulent stratified convection

    Käpylä, P J; Kleeorin, N; Käpylä, M J; Rogachevskii, I


    (abridged) Context: The mechanisms that cause the formation of sunspots are still unclear. Aims: We study the self-organisation of initially uniform sub-equipartition magnetic fields by highly stratified turbulent convection. Methods: We perform simulations of magnetoconvection in Cartesian domains that are $8.5$-$24$ Mm deep and $34$-$96$ Mm wide. We impose either a vertical or a horizontal uniform magnetic field in a convection-driven turbulent flow. Results: We find that super-equipartition magnetic flux concentrations are formed near the surface with domain depths of $12.5$ and $24$ Mm. The size of the concentrations increases as the box size increases and the largest structures ($20$ Mm horizontally) are obtained in the 24 Mm deep models. The field strength in the concentrations is in the range of $3$-$5$ kG. The concentrations grow approximately linearly in time. The effective magnetic pressure measured in the simulations is positive near the surface and negative in the bulk of the convection zone. Its ...

  10. 发动机火花塞积碳问题分析及解决措施%Analysis and Solution to Carbon Deposition of Engine Spark Plug

    付雪超; 马文亮; 李慧军; 由毅


    某车型搭载的1.0L自然吸气式发动机在使用中出现火花塞积碳的问题.为解决此问题,笔者详细分析了可能造成火花塞积碳的原因,并通过试验对比的手段进行了逐一验证.结果表明,造成积碳的原因是火花塞点火能量、工作状态温度偏低,形成的积碳不能燃烧掉.针对该故障原因,提出了延长点火线圈充电时间、优化火花塞尺寸的方案,以提高火花塞点火能量及工作温度.经试验验证,该方案能有效解决火花塞积碳的问题.%The carbon deposition of spark plug for a 1.0L naturally-aspirated engine is found with regard to a specific car on the market.To solve this problem,the cause of carbon deposition of spark plug is particularly analyzed in this article.Furthermore,the validation is performed one by one through test comparison.The result indicates that the carbon deposition attributes to lower ignition energy and operating-state temperature in respect of spark plug,thus leading to non-burning of carbon deposition.In terms of this failure cause,the solution to extend charge time of ignition coil and optimize plug dimensions is presented to enhance the ignition energy of spark plug and operating temperature.This solution can significantly solve the carbon deposition of spark plug via test validation.

  11. Research on retailer data clustering algorithm based on Spark

    Huang, Qiuman; Zhou, Feng


    Big data analysis is a hot topic in the IT field now. Spark is a high-reliability and high-performance distributed parallel computing framework for big data sets. K-means algorithm is one of the classical partition methods in clustering algorithm. In this paper, we study the k-means clustering algorithm on Spark. Firstly, the principle of the algorithm is analyzed, and then the clustering analysis is carried out on the supermarket customers through the experiment to find out the different shopping patterns. At the same time, this paper proposes the parallelization of k-means algorithm and the distributed computing framework of Spark, and gives the concrete design scheme and implementation scheme. This paper uses the two-year sales data of a supermarket to validate the proposed clustering algorithm and achieve the goal of subdividing customers, and then analyze the clustering results to help enterprises to take different marketing strategies for different customer groups to improve sales performance.

  12. Relationship between exploding bridgewire and spark initiation of low density PETN

    Lee, Elizabeth; Drake, Rod


    Recent work has shown that the energy delivered after bridgewire burst affects the function time of an EBW detonator. The spark which is formed post bridgewire burst is the means by which the remaining fireset energy contributes to the reaction. Therefore, by studying the characteristics of spark-gap detonators, insight into the contribution of spark initiation to the functioning of EBW detonators may be achieved. Spark initiation of low density explosives consists of: (i) spark formation, (ii) spark interaction with the bed, and (iii) ignition and growth of reaction. Experiments were performed in which an inert simulant was used to study the formation and propagation of sparks as a function of spark energy. The effect of the spark on inert porous beds was studied over a limited delivered energy range. The disruption of the bed was found to be dependent on the energy delivered. The effect of spark initiation on a low density PETN bed was then examined, the relationship between delivered energy and function time was found to be the same as for EBW detonators.

  13. Breakover mechanism of GaAs photoconductive switch triggering spark gap for high power applications

    Tian, Liqiang; Shi, Wei; Feng, Qingqing


    A spark gap (SG) triggered by a semi-insulating GaAs photoconductive semiconductor switch (PCSS) is presented. Currents as high as 5.6 kA have been generated using the combined switch, which is excited by a laser pulse with energy of 1.8 mJ and under a bias of 4 kV. Based on the transferred-electron effect and gas streamer theory, the breakover characteristics of the combined switch are analyzed. The photoexcited carrier density in the PCSS is calculated. The calculation and analysis indicate that the PCSS breakover is caused by nucleation of the photoactivated avalanching charge domain. It is shown that the high output current is generated by the discharge of a high-energy gas streamer induced by the strong local electric field distortion or by overvoltage of the SG resulting from quenching of the avalanching domain, and periodic oscillation of the current is caused by interaction between the gas streamer and the charge domain. The cycle of the current oscillation is determined by the rise time of the triggering electric pulse generated by the PCSS, the pulse transmission time between the PCSS and the SG, and the streamer transit time in the SG.

  14. Stratified spaces constitute a Fra\\"iss\\'e category

    Mijares, José Gregorio


    We prove that stratified spaces and stratified pseudomanifolds satisfy categorical Fra\\"{\\i}ss\\'e properties. This result was presented for the First Meeting of Logic and Algebra in Bogot\\'a, on Sept. 2010. This article has been submitted to the Revista Colombiana de Matem\\'aticas.

  15. Characterization of a copper spark discharge plasma in argon atmosphere used for nanoparticle generation

    Kohut, Attila; Galbács, Gábor; Márton, Zsuzsanna; Geretovszky, Zsolt


    Spark discharge nanoparticle generation is a dynamically developing application of discharge plasmas. In the present study a spark plasma used for nanoparticle generation is characterized by means of spatially and temporally resolved optical emission spectroscopy (OES) supplemented by fast imaging. The data acquired during the generation of copper nanoparticles in argon ambient is used to describe the spatial and temporal evolution of the species in the spark gap and to derive plasma parameters such as excitation temperature and electron concentration on one hand, and the concentration of the Cu species eroded by a single spark on the other. It is shown that temporally and spatially resolved OES together with a simple equilibrium model are efficient tools to estimate the characteristics of the spark discharge plasma that typically exists in spark discharge nanoparticle generators.

  16. Ca2+ sparks evoked by depolarization of rat ventricular myocytes involve multiple release sites

    ZANGWei-Jin; YUXiao-Jiang; ZANGYi-Min


    AIM:To investigate the fundamental nature of calcium release events (Ca2+‘sparks’) evoked in rat ventricular myocytes during excitation-contraction (E-C) coupling. METHODS: High-resolution line-scan confocal imaging with the fluorescent calcium indicator and patch-clamp techniques were used to study the spontaneous Ca2+ sparks and sparks evoked by depolarization. RESULTS: 1)Line scans oriented along the length of the cell showed that both spontaneous sparks and sparks evoked by depolarization to -35mV appeared to arise at single sites spacing about 1.80μm apart (ie, the sarcomere length), and measurements of their longitudinal spread (full-width at halfmaximal amplitude:FWHM) followed single Gaussian distributions with means of 2.6μm. 2)Different to this,transverse line scans often revealed spontaneous and evoked sparks that appeared to arise near-synchronously from paired sites. Measurements of transverse FWHM of both spontaneous and evoked sparks showed bimodal distributions, which were fit well by the sums of two Gaussian curves with means of 1.8 and 2.9μm for spontaneous sparks and ith means of 1.9 and 3.1 μm for evoked sparks. Relative areas under the two Gaussian curves were 1.73:1 and 1.85:1, respectively, for spontaneous and evoked sparks. CONCLUSIONS: Ca2+ sparks evoked by depolarization are not ′unitary′ events, but often involve multiple sites of origin along Z-lines, as previously shown for spontaneous sparks. Thus, Ca2+ released during sparks directly triggered by influx through L-type Ca2+ channels may, in turn, trigger neighboring sites. The restricted involvement of only a few transverse release sites preserves the essential feature of the ‘local control’ theory of E-C coupling.

  17. Spark Ignition Characteristics of a L02/LCH4 Engine at Altitude Conditions

    Kleinhenz, Julie; Sarmiento, Charles; Marshall, William


    The use of non-toxic propellants in future exploration vehicles would enable safer, more cost effective mission scenarios. One promising "green" alternative to existing hypergols is liquid methane/liquid oxygen. To demonstrate performance and prove feasibility of this propellant combination, a 100lbf LO2/LCH4 engine was developed and tested under the NASA Propulsion and Cryogenic Advanced Development (PCAD) project. Since high ignition energy is a perceived drawback of this propellant combination, a test program was performed to explore ignition performance and reliability versus delivered spark energy. The sensitivity of ignition to spark timing and repetition rate was also examined. Three different exciter units were used with the engine s augmented (torch) igniter. Propellant temperature was also varied within the liquid range. Captured waveforms indicated spark behavior in hot fire conditions was inconsistent compared to the well-behaved dry sparks (in quiescent, room air). The escalating pressure and flow environment increases spark impedance and may at some point compromise an exciter s ability to deliver a spark. Reduced spark energies of these sparks result in more erratic ignitions and adversely affect ignition probability. The timing of the sparks relative to the pressure/flow conditions also impacted the probability of ignition. Sparks occurring early in the flow could trigger ignition with energies as low as 1-6mJ, though multiple, similarly timed sparks of 55-75mJ were required for reliable ignition. An optimum time interval for spark application and ignition coincided with propellant introduction to the igniter and engine. Shifts of ignition timing were manifested by changes in the characteristics of the resulting ignition.

  18. Spark Ignition Characteristics of a LO2/LCH4 Engine at Altitude Conditions

    Kleinhenz, Julie; Sarmiento, Charles; Marshall, William


    The use of non-toxic propellants in future exploration vehicles would enable safer, more cost effective mission scenarios. One promising "green" alternative to existing hypergols is liquid methane/liquid oxygen. To demonstrate performance and prove feasibility of this propellant combination, a 100lbf LO2/LCH4 engine was developed and tested under the NASA Propulsion and Cryogenic Advanced Development (PCAD) project. Since high ignition energy is a perceived drawback of this propellant combination, a test program was performed to explore ignition performance and reliability versus delivered spark energy. The sensitivity of ignition to spark timing and repetition rate was also examined. Three different exciter units were used with the engine's augmented (torch) igniter. Propellant temperature was also varied within the liquid range. Captured waveforms indicated spark behavior in hot fire conditions was inconsistent compared to the well-behaved dry sparks (in quiescent, room air). The escalating pressure and flow environment increases spark impedance and may at some point compromise an exciter.s ability to deliver a spark. Reduced spark energies of these sparks result in more erratic ignitions and adversely affect ignition probability. The timing of the sparks relative to the pressure/flow conditions also impacted the probability of ignition. Sparks occurring early in the flow could trigger ignition with energies as low as 1-6mJ, though multiple, similarly timed sparks of 55-75mJ were required for reliable ignition. An optimum time interval for spark application and ignition coincided with propellant introduction to the igniter and engine. Shifts of ignition timing were manifested by changes in the characteristics of the resulting ignition.

  19. Identification and characterization of calcium sparks in cardiomyocytes derived from human induced pluripotent stem cells.

    Guang Qin Zhang

    Full Text Available INTRODUCTION: Ca2+ spark constitutes the elementary units of cardiac excitation-contraction (E-C coupling in mature cardiomyocytes. Human induced pluripotent stem cell (hiPSC-derived cardiomyocytes are known to have electrophysiological properties similar to mature adult cardiomyocytes. However, it is unclear if they share similar calcium handling property. We hypothesized that Ca2+ sparks in human induced pluripotent stem cell (hiPSCs-derived cardiomyocytes (hiPSC-CMs may display unique structural and functional properties than mature adult cardiomyocytes. METHODS AND RESULTS: Ca2+ sparks in hiPSC-CMs were recorded with Ca2+ imaging assay with confocal laser scanning microscopy. Those sparks were stochastic with a tendency of repetitive occurrence at the same site. Nevertheless, the spatial-temporal properties of Ca2+ spark were analogous to that of adult CMs. Inhibition of L-type Ca2+ channels by nifedipine caused a 61% reduction in calcium spark frequency without affecting amplitude of those sparks and magnitude of caffeine releasable sarcoplasmic reticulum (SR Ca2+ content. In contrast, high extracellular Ca2+ and ryanodine increased the frequency, full width at half maximum (FWHM and full duration at half maximum (FDHM of spontaneous Ca2+ sparks. CONCLUSIONS: For the first time, spontaneous Ca2+ sparks were detected in hiPSC-CMs. The Ca2+ sparks are predominately triggered by L-type Ca2+ channels mediated Ca2+ influx, which is comparable to sparks detected in adult ventricular myocytes in which cardiac E-C coupling was governed by a Ca2+-induced Ca2+ release (CICR mechanism. However, focal repetitive sparks originated from the same intracellular organelle could reflect an immature status of the hiPSC-CMs.

  20. Cavitation Erosion of Electro Spark Deposited Nitinol vs. Stellite Alloy on Stainless Steel Substrate


    EROSION OF ELECTRO SPARK DEPOSITED NITINOL VS. STELLITE® ALLOY ON STAINLESS STEEL SUBSTRATE Theresa A. Hoffard Lean-Miguel San Pedro Mikhail...SUBTITLE 5a. CONTRACT NUMBER CAVITATION EROSION TESTING OF ELECTRO SPARK DEPOSITED NITINOL VS STELLITE® ALLOY ON STAINLESS STEEL SUBTRATE 5b. GRANT...of combining Nitinol (NiTi) superelastic metal alloy with ElectroSpark Deposition (ESD) technology to increase the cavitation erosion resistance of

  1. Workshop on Repetitive Spark Gap Operation Held at Tamarron, Colorado on January 17-19, 1983.


    by Malyuta and Mezhevov (1979) (4) is shown schematically in Fig. 4. in this spark gap , flow of N 2 is fed axially around the first electrode... Gaps -- Flow Diagnostics The types of flow and heat transfer related measurements which have been made in the repetitive spark gap investigations which...spark gap flow physics and its influence on the performance of such switches, (15,26,27) such as is embodied by the studies done at Brown Boveri Research

  2. Measurements of some parameters of thermal sparks with respect to their ability to ignite aviation fuel/air mixtures

    Haigh, S. J.; Hardwick, C. J.; Baldwin, R. E.


    A method used to generate thermal sparks for experimental purposes and methods by which parameters of the sparks, such as speed, size, and temperature, were measured are described. Values are given of the range of such parameters within these spark showers. Titanium sparks were used almost exclusively, since it is particles of this metal which are found to be ejected during simulation tests to carbon fiber composite (CFC) joints. Tests were then carried out in which titanium sparks and spark showers were injected into JP4/(AVTAG F40) mixtures with air. Single large sparks and dense showers of small sparks were found to be capable of causing ignition. Tests were then repeated using ethylene/air mixtures, which were found to be more easily ignited by thermal sparks than the JP4/ air mixtures.

  3. Gas slug ascent through rheologically stratified conduits

    Capponi, Antonio; James, Mike R.; Lane, Steve J.


    Textural and petrological evidence has indicated the presence of viscous, degassed magma layers at the top of the conduit at Stromboli. This layer acts as a plug through which gas slugs burst and it is thought to have a role in controlling the eruptive dynamics. Here, we present the results of laboratory experiments which detail the range of slug flow configurations that can develop in a rheologically stratified conduit. A gas slug can burst (1) after being fully accommodated within the plug volume, (2) whilst its base is still in the underlying low-viscosity liquid or (3) within a low-viscosity layer dynamically emplaced above the plug during the slug ascent. We illustrate the relevance of the same flow configurations at volcanic-scale through a new experimentally-validated 1D model and 3D computational fluid dynamic simulations. Applied to Stromboli, our results show that gas volume, plug thickness, plug viscosity and conduit radius control the transition between each configuration; in contrast, the configuration distribution seems insensitive to the viscosity of magma beneath the plug, which acts mainly to deliver the slug into the plug. Each identified flow configuration encompasses a variety of processes including dynamic narrowing and widening of the conduit, generation of instabilities along the falling liquid film, transient blockages of the slug path and slug break-up. All these complexities, in turn, lead to variations in the slug overpressure, mirrored by changes in infrasonic signatures which are also associated to different eruptive styles. Acoustic amplitudes are strongly dependent on the flow configuration in which the slugs burst, with both acoustic peak amplitudes and waveform shapes reflecting different burst dynamics. When compared to infrasonic signals from Stromboli, the similarity between real signals and laboratory waveforms suggests that the burst of a slug through a plug may represent a viable first-order mechanism for the generation of

  4. Methane metabolism in a stratified boreal lake

    Nykänen, Hannu; Peura, Sari; Kankaala, Paula; Jones, Roger


    Stratified lakes, typical of the boreal zone, are naturally anoxic from their bottoms. In these lakes methanogenesis can account for up to half of organic matter degradation. However, a major part of the methane (CH4) is oxidized in the water column before reaching the atmosphere. Since methanotrophs use CH4 as their sole carbon and energy source, much CH4-derived carbon is incorporated into their biomass. Microbially produced CH4 has strongly negative δ13C compared to other carbon forms in ecosystems, making it possible to follow its route in food webs. However, only a few studies have estimated the amount of this microbial biomass or its carbon stable isotopic composition due to difficulties in separating it from other biomass or from other carbon forms in the water column. We estimated methanotrophic biomass from measured CH4 oxidation, and δ13C of the biomass from measured δ13C values of CH4, DIC, POM and DOC. An estimate of the fraction of methanotrophs in total microbial biomass is derived from bacterial community composition measurements. The study was made in, Alinen Mustajärvi, a small (area 0.75 ha, maximum depth 6.5 m, mean depth 4.2 m,), oligotrophic, mesohumic headwater lake located in boreal coniferous forest in southern Finland. CH4 and DIC concentrations and their δ13C were measured over the deepest point of the lake at 1 m intervals. 13C of DOM and POM were analyzed from composite samples from epi-, meta-, and hypolimnion. Evasion of CH4 and carbon dioxide from the lake surface to the atmosphere was estimated with boundary layer diffusion equations. CH4oxidation was estimated by comparing differences between observed concentrations and CH4potentially transported by turbulent diffusion between different vertical layers in the lake and also by actual methanotrophy measurements and from vertical differences in δ13C-CH4. The estimate of CH4 production was based on the sum of oxidized and released CH4. Molecular microbiology methods were used to

  5. The Universal Aspect Ratio of Vortices in Rotating Stratifi?ed Flows: Experiments and Observations

    Aubert, Oriane; Gal, Patrice Le; Marcus, Philip S


    We validate a new law for the aspect ratio $\\alpha = H/L$ of vortices in a rotating, stratified flow, where $H$ and $L$ are the vertical half-height and horizontal length scale of the vortices. The aspect ratio depends not only on the Coriolis parameter f and buoyancy (or Brunt-Vaisala) frequency $\\bar{N}$ of the background flow, but also on the buoyancy frequency $N_c$ within the vortex and on the Rossby number $Ro$ of the vortex such that $\\alpha = f \\sqrt{[Ro (1 + Ro)/(N_c^2- \\bar{N}^2)]}$. This law for $\\alpha$ is obeyed precisely by the exact equilibrium solution of the inviscid Boussinesq equations that we show to be a useful model of our laboratory vortices. The law is valid for both cyclones and anticyclones. Our anticyclones are generated by injecting fluid into a rotating tank filled with linearly-stratified salt water. The vortices are far from the top and bottom boundaries of the tank, so there is no Ekman circulation. In one set of experiments, the vortices viscously decay, but as they do, they c...

  6. Increasing the isotropic properties of a discharge spark chamber with a large gap

    Nurgozhin, N. N.


    The recording of particle tracks in the form of sparks or streamers running at different angles toward the electric field of the chamber was studied. The investigations were performed with two discharge spark chambers consisting of boxes filled with neon at 1 atm. The spark chambers were powered by a pulse with an amplitude of 300 kV applied from a pulse generator. The recording of particle tracks in the form of sparks took place at track angles smaller than 30 deg with respect to the electrical field. At angle larger than 40 deg the tracks are recorded in the form of streamers. Particle traces with respect to the angle are given.

  7. Oil Coking Prevention Using Electric Water Pump for Turbo-Charge Spark-Ignition Engines

    Han-Ching Lin


    Full Text Available Turbocharger has been widely implemented for internal combustion engine to increase an engine's power output and reduce fuel consumption. However, its operating temperature would rise to 340°C when engine stalls. This higher temperature may results in bearing wear, run-out, and stick, due to oil coking and insufficient lubrication. In order to overcome these problems, this paper employs Electric Water Pump (EWP to supply cool liquid to turbocharger actively when the engine stalls. The system layout, operating timing, and duration of EWP are investigated for obtaining optimal performance. The primarily experimental results show that the proposed layout and control strategy have a lower temperature of 100°C than the conventional temperature 225°C.

  8. Tailored Net-Shape Powder Composites by Spark Plasma Sintering

    Khaleghi, Evan Aryan

    This dissertation investigates the ability to produce net-shape and tailored composites in spark plasma sintering (SPS), with an analysis of how grain growth, densification, and mechanical properties are affected. Using alumina and four progressively anisotropic dies, we studied the impact of specimen shape on densification. We found specimen shape had an impact on overall densification, but no impact on localized properties. We expected areas of the specimen to densify differently, or have higher grain growth, based on current anisotropy in the specimen during sintering, and preliminary results indicated this, but further investigation showed this did not occur. Overall average grain size and porosity decreased as shape complexity increased. In Fe-V-C steel, we mechanical alloyed two rapidly solidified powders, and used spark sintering to retain the properties imparted during the rapid solidification. We noticed VC grains being produced during densification, which improved the final properties. We conducted spark plasma extrusion (SPE) of aluminum to understand the effect on microstructure. We found, through an analysis of the grain structure, that SPE did have a grain deformation potential, and grain size was severely decreased compared to conventional sintering. Dynamic recrystallization did not occur, due to the reduced temperatures we were able to extrude with SPS. Finally, we examined whether there were particular sintering conditions for SPS that reduced the complexity of the grain growth and porosity relationship to one similar to conventional sintering, of the form G = k G0 ε -1/. We found that although a reasonable case could be made for free sintering, as found in the literature, for hot-pressing and SPS the conditions required go against the common knowledge in grain growth and densification kinetics. We were able to fit our data very well to the model, but the correlated results do not make physical sense.

  9. Spark Plasma Sintering of Fuel Cermets for Nuclear Reactor Applications

    Yang Zhong; Robert C. O' Brien; Steven D. Howe; Nathan D. Jerred; Kristopher Schwinn; Laura Sudderth; Joshua Hundley


    The feasibility of the fabrication of tungsten based nuclear fuel cermets via Spark Plasma Sintering (SPS) is investigated in this work. CeO2 is used to simulate fuel loadings of UO2 or Mixed-Oxide (MOX) fuels within tungsten-based cermets due to the similar properties of these materials. This study shows that after a short time sintering, greater than 90 % density can be achieved, which is suitable to possess good strength as well as the ability to contain fission products. The mechanical properties and the densities of the samples are also investigated as functions of the applied pressures during the sintering.

  10. Low temperature spark plasma sintering of YIG powders

    Fernandez-Garcia, L. [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Suarez, M., E-mail: m.suarez@cinn.e [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Fundacion ITMA, Parque Tecnologico de Asturias, 33428, Llanera (Spain); Menendez, J.L. [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain)


    A transition from a low to a high spin state in the magnetization saturation between 1000 and 1100 {sup o}C calcination temperature is observed in YIG powders prepared by oxides mixture. Spark plasma sintering of these powders between 900 and 950 {sup o}C leads to dense samples with minimal formation of YFeO{sub 3}, opening the way to co-sintering of YIG with metals or metallic alloys. The optical properties depend on the sintering stage: low (high) density samples show poor (bulk) optical absorption.

  11. Large aluminium wire spark chambers with magnetostrictive read-out

    Bradamante, Franco; Daum, C; Dechelette, Paul; Fidecaro, Giuseppe; Fidecaro, Maria; Giorgi, M; Penzo, Aldo L; Piemontese, L; Renevey, Max; Schiavon, Paolo; Vascotto, Alessandro


    A set of 1 cm gap wire spark chambers with a sensitive surface of 300 * 100 cm/sup 2/ was constructed for an experiment at the CERN proton synchrotron. The Coulomb scattering was limited by using aluminium wires and by adopting a crossed-wire configuration, which allowed us to minimize the number of chambers for a given number of pairs of coordinates. The wire planes were pulsed by feeding the high voltage from strip-lines along the whole boundary of the chambers. (7 refs).

  12. Low pressure spark gap triggered by an ion diode

    Prono, Daniel S.


    Spark gap apparatus for use as an electric switch operating at high voltage, high current and high repetition rate. Mounted inside a housing are an anode, cathode and ion plate. An ionizable fluid is pumped through the chamber of the housing. A pulse of current to the ion plate causes ions to be emitted by the ion plate, which ions move into and ionize the fluid. Electric current supplied to the anode discharges through the ionized fluid and flows to the cathode. Current stops flowing when the current source has been drained. The ionized fluid recombines into its initial dielectric ionizable state. The switch is now open and ready for another cycle.

  13. Low-pressure spark gap triggered by an ion diode

    Prono, D.S.


    Spark gap apparatus for use as an electric switch operating at high voltage, high current and high repetition rate. Mounted inside a housing are an anode, cathode and ion plate. An ionizable fluid is pumped through the chamber of the housing. A pulse of current to the ion plate causes ions to be emitted by the ion plate, which ions move into and ionize the fluid. Electric current supplied to the anode discharges through the ionized fluid and flows to the cathode. Current stops flowing when the current source has been drained. The ionized fluid recombines into its initial dielectric ionizable state. The switch is now open and ready for another cycle.

  14. Search for an optimum time response of spark counters

    Devismes, A; Kress, T; Gobbi, A; Eschke, J; Herrmann, N; Hildenbrand, K D; Koczón, P; Petrovici, M


    A spark counter of the type developed by Pestov has been tested with the aim of searching for an optimum time response function, changing voltage, content of noble and quencher gases, pressure and energy-loss. Replacing the usual argon by neon has brought an improvement of the resolution and a significant reduction of tails in the time response function. It has been proven that a counter as long as 90 cm can deliver, using neon gas mixture, a time resolution sigma<60 ps with about 1% absolute tail and an efficiency of about 90%.

  15. Spark and HPC for High Energy Physics Data Analyses

    Sehrish, Saba [Fermilab; Kowalkowski, Jim [Fermilab


    A full High Energy Physics (HEP) data analysis is divided into multiple data reduction phases. Processing within these phases is extremely time consuming, therefore intermediate results are stored in files held in mass storage systems and referenced as part of large datasets. This processing model limits what can be done with interactive data analytics. Growth in size and complexity of experimental datasets, along with emerging big data tools are beginning to cause changes to the traditional ways of doing data analyses. Use of big data tools for HEP analysis looks promising, mainly because extremely large HEP datasets can be represented and held in memory across a system, and accessed interactively by encoding an analysis using highlevel programming abstractions. The mainstream tools, however, are not designed for scientific computing or for exploiting the available HPC platform features. We use an example from the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) in Geneva, Switzerland. The LHC is the highest energy particle collider in the world. Our use case focuses on searching for new types of elementary particles explaining Dark Matter in the universe. We use HDF5 as our input data format, and Spark to implement the use case. We show the benefits and limitations of using Spark with HDF5 on Edison at NERSC.

  16. Spark ignition of aviation fuel in isotropic turbulence

    Krisman, Alex; Lu, Tianfeng; Borghesi, Giulio; Chen, Jacqueline


    Turbulent spark ignition occurs in combustion engines where the spark must establish a viable flame kernel that leads to stable combustion. A competition exists between kernel growth, due to flame propagation, and kernel attenuation, due to flame stretch and turbulence. This competition can be measured by the Karlovitz number, Ka, and kernel viability decreases rapidly for Ka >> 1 . In this study, the evolution of an initially spherical flame kernel in a turbulent field is investigated at two cases: Ka- (Ka = 25) and Ka+ (Ka = 125) using direct numerical simulation (DNS). A detailed chemical mechanism for jet fuel (Jet-A) is used, which is relevant for many practical conditions, and the mechanism includes a pyrolysis sub-model which is important for the ignition of large hydrocarbon fuels. An auxiliary non-reacting DNS generates the initial field of isotropic turbulence with a turbulent Reynolds number of 500 (Ka-) and 1,500 (Ka+). The kernel is then imposed at the center of the domain and the reacting DNS is performed. The Ka- case survives and the Ka+ case is extinguished. An analysis of the turbulence chemistry interactions is performed and the process of extinction is described. Department of Energy - Office of Basic Energy Science under Award No. DE-SC0001198.

  17. Intake Manifold Boosting of Turbocharged Spark-Ignited Engines

    Lino Guzzella


    Full Text Available Downsizing and turbocharging is a widely used approach to reduce the fuel consumption of spark ignited engines while retaining the maximum power output. However, a substantial loss in drivability must be expected due to the occurrence of the so-called turbo lag. The turbo lag results from the additional inertia that the turbocharger adds to the system. Supplying air by an additional valve, the boost valve, to the intake manifold can be used to overcome the turbo lag. This turbo lag compensationmethod is referred to as intakemanifold boosting. The aims of this study are to show the effectiveness of intake manifold boosting on a turbocharged spark-ignited engine and to show that intake manifold boosting can be used as an enabler of strong downsizing. Guidelines for the dimensioning of the boost valve are given and a control strategy is presented. The trade-off between additional fuel consumption and the consumption of pressurized air during the turbo lag compensation is discussed. For a load step at 2000 rpm the rise time can be reduced from 2.8 s to 124ms, requiring 11.8 g of pressurized air. The transient performance is verified experimentally by means of load steps at various engine speeds to various engine loads.

  18. Micro Pixel Chamber with resistive electrodes for spark reduction

    Ochi, Atsuhiko; Homma, Yasuhiro; Komai, Hidetoshi; Yamaguchi, Takahiro


    The Micro Pixel Chamber (mu-PIC) using resistive electrodes has been developed and tested. The surface cathodes are made from resistive material, by which the electrical field is reduced when large current is flowed. Two-dimensional readouts are achieved by anodes and pickup electrodes, on which signals are induced. High gas gain (> 60000) was measured using 55Fe (5.9 keV) source, and very intensive spark reduction was attained under fast neutron. The spark rate of resistive mu-PIC was only 10^-4 times less than that of conventional mu-PIC at the gain of 10^4. With these developments, a new MPGD with no floating structure is achieved, with enough properties of both high gain and good stability to detect MIP particles. In addition, mu-PIC can be operated with no HV applied on anodes by using resistive cathodes. Neither AC coupling capacitors nor HV pull up resisters are needed for any anode electrode. Signal readout is drastically simplified by that configuration.

  19. Influence of hydrox on spark ignition engine performance

    Naude, A.F. [University of Pretoria, Pretoria (South Africa). Dept. of Mechanical and Aeronautical Engineering


    A series of experiments were conducted on a Mazda 1600 cc fuel injected engine connected to a Superflow SF901 dynamometer system to examine the influence of small quantities of Hydrox (hydrogen and oxygen), as generated through electrolysis of water, on the performance of a spark ignition engine. The engine was also equipped with a Unichip engine management system in order to enable changes in the spark timing and the amount of fuel injected. Electrolysis was used to generate Hydrox. The process could either be powered from a separate power source or from the engine's alternator. Hydrox was introduced into the engine's intake manifold, and measurements were taken of the engine's performance, emissions and fuel consumption. The authors simulated a typical load condition as experienced for a light passenger car operating at 100 kilometres per hour on the open road. A significant reduction in hydrocarbons at lean air-fuel ratio operation of the engine was observed with the introduction of Hydrox, and there was also a slight improvement in fuel consumption when the electrolysis process was driven by the engine. 2 refs., 1 tab., 5 figs.

  20. Research of an electromagnetically actuated spark gap switch.

    Zhang, Tianyang; Chen, Dongqun; Liu, Jinliang; Wang, Yuwei; Qiu, Yongfeng


    As an important part of pulsed power systems, high-voltage and high-current triggered spark gap switch and its trigger system are expected to achieve a compact structure. In this paper, a high-voltage, high-current, and compact electromagnetically actuated spark gap switch is put forward, and it can be applied as a part of an intense electron-beam accelerator (IEBA). A 24 V DC power supply is used to trigger the switch. The characteristics of the switch were measured for N2 when the gas pressure is 0.10-0.30 MPa. The experimental results showed that the voltage/pressure (V/p) curve of the switch was linear relationship. The operating ranges of the switch were 21%-96%, 21%-95%, 21%-95%, 19%-95%, 17%-95%, and 16%-96% of the switch's self-breakdown voltage when the gas pressures were 0.10, 0.14, 0.18, 0.22, 0.26, and 0.30 MPa, respectively. The switch and its trigger system worked steadily and reliably with a peak voltage of 30 kV, a peak current of 60 kA in the IEBA when the pressure of N2 in the switch was 0.30 MPa.

  1. Dynamic compressive and tensile strengths of spark plasma sintered alumina

    Girlitsky, I.; Zaretsky, E.; Kalabukhov, S.; Dariel, M. P.; Frage, N.


    Fully dense submicron grain size alumina samples were manufactured from alumina nano-powder using Spark Plasma Sintering and tested in two kinds of VISAR-instrumented planar impact tests. In the first kind, samples were loaded by 1-mm tungsten impactors, accelerated to a velocity of about 1 km/s. These tests were aimed at studying the Hugoniot elastic limit (HEL) of Spark Plasma Sintering (SPS)-processed alumina and the decay, with propagation distance, of the elastic precursor wave. In the tests of the second kind, alumina samples of 3-mm thickness were loaded by 1-mm copper impactors accelerated to 100-1000 m/s. These tests were aimed at studying the dynamic tensile (spall) strength of the alumina specimens. The tensile fracture of the un-alloyed alumina shows a monotonic decline of the spall strength with the amplitude of the loading stress pulse. Analysis of the decay of the elastic precursor wave allowed determining the rate of the irreversible (inelastic) strains in the SPS-processed alumina at the initial stages of the shock-induced inelastic deformation and to clarify the mechanisms responsible for the deformation. The 1-% addition of Cr2O3 decreases the HEL of the SPS-processed alumina by 5-% and its spall strength by 50% but barely affects its static properties.

  2. Tangling clustering instability for small particles in temperature stratified turbulence

    Elperin, Tov; Liberman, Michael; Rogachevskii, Igor


    We study particle clustering in a temperature stratified turbulence with small finite correlation time. It is shown that the temperature stratified turbulence strongly increases the degree of compressibility of particle velocity field. This results in the strong decrease of the threshold for the excitation of the tangling clustering instability even for small particles. The tangling clustering instability in the temperature stratified turbulence is essentially different from the inertial clustering instability that occurs in non-stratified isotropic and homogeneous turbulence. While the inertial clustering instability is caused by the centrifugal effect of the turbulent eddies, the mechanism of the tangling clustering instability is related to the temperature fluctuations generated by the tangling of the mean temperature gradient by the velocity fluctuations. Temperature fluctuations produce pressure fluctuations and cause particle clustering in regions with increased pressure fluctuations. It is shown that t...

  3. Effects of rotation on turbulent buoyant plumes in stratified environments

    Fabregat Tomàs, Alexandre; Poje, Andrew C; Özgökmen, Tamay M; Dewar, William K


    We numerically investigate the effects of rotation on the turbulent dynamics of thermally driven buoyant plumes in stratified environments at the large Rossby numbers characteristic of deep oceanic releases...

  4. Action of plasma jets of a low-current spark discharge on microorganisms ( Escherichia coli)

    Baldanov, B. B.; Semenov, A. P.; Ranzhurov, Ts. V.; Nikolaev, E. O.; Gomboeva, S. V.


    High efficiency of bactericide action of cold argon plasma generated by plasma jets of a weak-current spark discharge under atmospheric pressure is demonstrated. It is found that an increase in the time of treatment with plasma jets from a low-current spark discharge makes it possible to effectively inactivate microorganisms over a much larger area.

  5. Spark alloying of VK8 and T15K6 hard alloys

    Kuptsov, S. G.; Fominykh, M. V.; Mukhinov, D. V.; Magomedova, R. S.; Nikonenko, E. A.; Pleshchev, V. P.


    A method is developed to restore the service properties of VK hard alloy plates using preliminary carburizing followed by spark alloying with a VT1-0 alloy. The phase composition is studied as a function of the spark treatment time.

  6. Evaluating the Sustainability of SPARK Physical Education: A Case Study of Translating Research into Practice

    Dowda, Marsha; Sallis, James F.; McKenzie, Thomas L.; Rosengard, Paul; Kohl, Harold W., III


    Dissemination and sustainability of evidence-based physical education programs (PE) has been studied rarely. The sustainability of a health-related PE program (SPARK) was independently evaluated in 111 elementary schools in 7 states. Surveys were mailed to schools that had received SPARK curriculum books, training, and follow-up (response rate =…

  7. 微软启动embeddedSPARK 2010年度挑战赛


    在波士顿嵌入式系统大会(Embedded Systers Conterence (ESC) Boston)的行业演讲中,微软公司(Microsoft Corp)推出了embeddedSPARK 2010年度挑战赛(embedded SPARK 2010 Challenge)。

  8. Calculation of Spark Breakdown or Corona Starting Voltages in Nonuniform Fields

    Pedersen, A.


    The processes leading to a spark breakdown or corona discharge are discussed very briefly. A quantitative breakdown criterion for use in high-voltage design is derived by which spark breakdown or corona starting voltages in nonuniform fields can be calculated. The criterion is applied to the sphere...

  9. Analysis of Spark Plug Gap on Flame Development using Schlieren Technique and Image Processing

    Hii Shu-Yi, Paul; Khalid, Amir; Mohamad, Anuar; Manshoor, Bukhari; Sapit, Azwan; Zaman, Izzuddin; Hashim, Akasha


    Gasoline spark ignition system in cars remains one of the main consumption of fuel in the world nowadays. During combustion process, spark plug is one important key features in a gasoline engine. The incompatibility of spark plug gap width and the fuel used causing backfire and knocking in the combustion engine. Thus, the spark plug gap was studied with focussing in controlling the combustion process to improve the performance of the engine. The main purpose of this research is to investigate the effect of spark plug air gap on flame development. The parameters studied in this research include spark plug air gap width (1.0 mm, 1.2 mm, 1.4 mm, 1.6 mm and 1.8 mm), injection pressure (0.3 MPa, 0.4 MPa, 0.5 MPa and 0.6 MPa) and flame characteristics such as flame front area and the flame intensity. The flame front area of different spark plug gap and injection pressure were investigated through Schlieren photography method. The Schlieren images taken were analysed with the time changes. The experiment results proved that the increase of spark plug gap width will led to better flame development in shorter time while increased the chance of misfire.

  10. Numerical Study on Saltwater Instrusion in a Heterogeneous Stratified Aquifer


    In a costal aquifer, saltwater intrusion is frequently observed due to an excess exploitation. There are many researches focused on the saltwater intrusion. However, there are few researches, which take into consideration the mixing processes in a stratified heterogeneous aquifer. In the present study, a laboratory experiment and numerical simulation are made in order to understand the phenomena in a stratified heterogeneous aquifer. The result of the numerical analysis agrees well with the m...

  11. Simulation of the switching performance of an optically triggered pseudo-spark thyratron

    Pak, Hoyoung; Kushner, Mark J.


    The optically triggered pseudo-spark, also known as the back-lit thyratron, is a low-pressure plasma switch having an unheated metallic cathode, which has performance specifications competitive with conventional hot cathode thyratrons. In this paper a computer simulation of the BLT is presented. The simulation consists of a 2 1/2 -dimensional time-dependent continuum model for electron and ion transport using the local field approximation. The model includes an external circuit, and the user may specify the type of gas, pressure, geometry, and electrode materials. Predictions for the anode delay time are compared to experiment as a function of pressure (p), cathode-anode spacing (d), and trigger fluence. We find that switch closure depends critically on the formation of a virtual anode in front of the cathode hole by generation of positive space charge, and that the anode delay time decreases with increasing p, trigger fluence d, and cathode hole diameter. We also find switch performance is not well characterized by the pd product as in other plasma switches. Rather, we find these quantities depend separately on p and d in a manner which is a function of the geometry of the cathode.


    Szybist, James P [ORNL


    The use of EGR as a diluent allows operation with an overall stoichiometric charge composition, and the addition of cooled EGR results in well-understood thermodynamic benefits for improved fuel consumption. This study investigates the effect of fuel on the combustion and emission response of EGR dilution in spark ignited engines. A 2.0 L GM Ecotec LNF engine equipped with the production side-mounted direct injection (DI) fueling system is used in this study. Ethanol, isooctane and certified gasoline are investigated with EGR from 0% to the EGR dilution tolerance. Constant BMEP at 2000 rpm was operated with varying CA50 from 8 CAD to 16 CAD aTDCf. The results show that ethanol gives the largest EGR tolerance at a given combustion phasing, engine load and speed. The improved EGR dilution tolerance with ethanol is attributed to a faster flame speed, which manifests itself as shorter combustion duration. Data shows that the combustion stability limit occurs at a critical combustion duration that is fuel independent. Due to different flame speeds, this critical combustion duration occurs at different EGR levels for the different fuels.

  13. Surface Characteristics and Electrochemical Impedance Investigation of Spark-Anodized Ti-6Al-4V Alloy

    Garsivaz jazi, M. R.; Golozar, M. A.; Raeissi, K.; Fazel, M.


    In this study, the surface characteristic of oxide films on Ti-6Al-4V alloy formed by an anodic oxidation treatment in H2SO4/H3PO4 electrolyte at potentials higher than the breakdown voltage was evaluated. Morphology of the surface layers was studied by scanning electron microscope. The results indicated that the diameter of pores and porosity of oxide layer increase by increasing the anodizing voltage. The thickness measurement of the oxide layers showed a linear increase of thickness with increasing the anodizing voltage. The EDS analysis of oxide films formed in H2SO4/H3PO4 at potentials higher than breakdown voltage demonstrated precipitation of sulfur and phosphor elements from electrolyte into the oxide layer. X-ray diffraction was employed to exhibit the effect of anodizing voltage on the oxide layer structure. Roughness measurements of oxide layer showed that in spark anodizing, the Ra and Rz parameters would increase by increasing the anodizing voltage. The structure and Corrosion properties of oxide layers were studied using electrochemical impedance spectroscopy (EIS) techniques, in 0.9 wt.% NaCl solution. The obtained EIS spectra and their interpretation in terms of an equivalent circuit with the circuit elements indicated that the detailed impedance behavior is affected by three regions of the interface: the space charge region, the inner compact layer, and outer porous layer.

  14. Automatic code generation in SPARK: Applications of computer algebra and compiler-compilers

    Nataf, J.M.; Winkelmann, F.


    We show how computer algebra and compiler-compilers are used for automatic code generation in the Simulation Problem Analysis and Research Kernel (SPARK), an object oriented environment for modeling complex physical systems that can be described by differential-algebraic equations. After a brief overview of SPARK, we describe the use of computer algebra in SPARK`s symbolic interface, which generates solution code for equations that are entered in symbolic form. We also describe how the Lex/Yacc compiler-compiler is used to achieve important extensions to the SPARK simulation language, including parametrized macro objects and steady-state resetting of a dynamic simulation. The application of these methods to solving the partial differential equations for two-dimensional heat flow is illustrated.

  15. A new spark detection system for the electrostatic septa of the SPS North (experimental) Area

    Barlow, R A; Borburgh, J; Carlier, E; Chanavat, C; Pinget, B


    Electrostatic septa (ZS) are used in the extraction of the particle beams from the CERN SPS to the North Area experimental zone. These septa employ high electric fields, generated from a 300 kV power supply, and are particularly prone to internal sparking around the cathode structure. This sparking degrades the electric field quality, consequently affecting the extracted beam, vacuum and equipment performance. To mitigate these effects, a Spark Detection System (SDS) has been realised, which is based on an industrial SIEMENS S7-400 programmable logic controller and deported Boolean processors modules interfaced through a PROFINET fieldbus. The SDS interlock logic uses a moving average spark rate count to determine if the ZS performance is acceptable. Below a certain spark rate it is probable that the ZS septa tank vacuum can recover, thus avoiding transition into a\

  16. SparkBLAST: scalable BLAST processing using in-memory operations.

    de Castro, Marcelo Rodrigo; Tostes, Catherine Dos Santos; Dávila, Alberto M R; Senger, Hermes; da Silva, Fabricio A B


    The demand for processing ever increasing amounts of genomic data has raised new challenges for the implementation of highly scalable and efficient computational systems. In this paper we propose SparkBLAST, a parallelization of a sequence alignment application (BLAST) that employs cloud computing for the provisioning of computational resources and Apache Spark as the coordination framework. As a proof of concept, some radionuclide-resistant bacterial genomes were selected for similarity analysis. Experiments in Google and Microsoft Azure clouds demonstrated that SparkBLAST outperforms an equivalent system implemented on Hadoop in terms of speedup and execution times. The superior performance of SparkBLAST is mainly due to the in-memory operations available through the Spark framework, consequently reducing the number of local I/O operations required for distributed BLAST processing.

  17. Reduce of Threshold of Laser Inducing Breakdown in Atmosphere by Introducing an Electric Spark

    ZHANG Xian-Bin; SHI Wei; LI Hua


    @@ We report laser-generated plasmas in atmosphere with electrical spark generated by a synchronization circuit.The breakdown thresholds under the conditions that the electrical spark is used and not used are compared.The breakdown threshold has a distinct decrease after the electrical spark is used. Breakdown thresholds as afunction of atmosphere pressure have also been measured at laser wavelengths 532nm and 1064 nm for the laserpulse width of 15ns. We also discuss the principle and performances of the ionized atmosphere by Nd:YAGlaser under the condition of electrical spark introduction. Multiphoton ionization and cascade ionization playimportant roles in the whole process of atmosphere ionization. The free electron induced by electrical spark cansupply the initialization free electron number for multiphoton ionization and cascade ionization. A model forbreakdown in atmosphere, which is in good agreement with the experimental results, is described.

  18. Stabilization of the spark-discharge point on a sample surface by laser irradiation for steel analysis.

    Matsuta, Hideyuki; Kitagawa, Kuniyuki; Wagatsuma, Kazuaki


    A combined technique with laser irradiation is suggested to control spark discharge for analytical use, having a unique feature that firing points of the spark discharge can be fixed by laser irradiation. Because the spark discharge easily initiates at particular surface sites, such as non-metallic inclusions, called selective discharge, the concentration of some elements sometimes deviates from their average one in spark discharge optical emission spectrometry. Therefore, stabilization of firing points on a sample surface could improve the analytical precision.

  19. Ca2+ sparks as a plastic signal for skeletal muscle health, aging, and dystrophy

    Noah WEISLEDER; Jian-jie MA


    Ca2+ sparks are the elementary units of intracellular Ca2+ signaling in striated muscle cells revealed as localized Ca2+ release events from sarcoplasmic reticulum(SR)by confocal microscopy.While Ca2+ sparks are well defined in cardiac muscle,there has been a general belief that these localized Ca2+ release events are rare in intact adult mammalian skeletal muscle.Several laboratories determined that Ca2+ sparks in mammalian skeletal muscle could only be observed in large numbers when the sarcolemmal membranes are permeabilized or the SR Ca2+ content is artificially manipulated,thus the cellular and molecular mechanisms underlying the regulation of Ca2+ sparks in skeletal muscle remain largely unexplored.Recently,we discovered that membrane deformation generated by osmotic stress induced a robust Ca2+ spark response confined in close spatial proximity to the sarcolemmal membrane in intact mouse muscle fibers.In addition to Ca2+ sparks,prolonged Ca2+ transients, termed Ca2+ bursts, are also identified in intact skeletal muscle.These induced Ca2+ release events are reversible and repeatable,revealing a plastic nature in young muscle fibers.In contrast, induced Ca2+ sparks in aged muscle are transient and cannot be re-stimulated.Dystrophic muscle fibers display uncontrolled Ca2+ sparks,where osmotic stress-induced Ca2+ sparks are not reversible and they are no longer spatially restricted to the sarcolemmal membrane.An understanding of the mechanisms that underlie generation of osmotic stressinduced Ca2+ sparks in skeletal muscle and how these mechanisms are altered in pathology, will contribute to our understanding of the regulation of Ca2+ homeostasis in muscle physiology and pathophysiology.

  20. CHARGE syndrome

    Prasad Chitra


    Full Text Available Abstract CHARGE syndrome was initially defined as a non-random association of anomalies (Coloboma, Heart defect, Atresia choanae, Retarded growth and development, Genital hypoplasia, Ear anomalies/deafness. In 1998, an expert group defined the major (the classical 4C's: Choanal atresia, Coloboma, Characteristic ears and Cranial nerve anomalies and minor criteria of CHARGE syndrome. Individuals with all four major characteristics or three major and three minor characteristics are highly likely to have CHARGE syndrome. However, there have been individuals genetically identified with CHARGE syndrome without the classical choanal atresia and coloboma. The reported incidence of CHARGE syndrome ranges from 0.1–1.2/10,000 and depends on professional recognition. Coloboma mainly affects the retina. Major and minor congenital heart defects (the commonest cyanotic heart defect is tetralogy of Fallot occur in 75–80% of patients. Choanal atresia may be membranous or bony; bilateral or unilateral. Mental retardation is variable with intelligence quotients (IQ ranging from normal to profound retardation. Under-development of the external genitalia is a common finding in males but it is less apparent in females. Ear abnormalities include a classical finding of unusually shaped ears and hearing loss (conductive and/or nerve deafness that ranges from mild to severe deafness. Multiple cranial nerve dysfunctions are common. A behavioral phenotype for CHARGE syndrome is emerging. Mutations in the CHD7 gene (member of the chromodomain helicase DNA protein family are detected in over 75% of patients with CHARGE syndrome. Children with CHARGE syndrome require intensive medical management as well as numerous surgical interventions. They also need multidisciplinary follow up. Some of the hidden issues of CHARGE syndrome are often forgotten, one being the feeding adaptation of these children, which needs an early aggressive approach from a feeding team. As the child

  1. SciSpark: In-Memory Map-Reduce for Earth Science Algorithms

    Ramirez, P.; Wilson, B. D.; Whitehall, K. D.; Palamuttam, R. S.; Mattmann, C. A.; Shah, S.; Goodman, A.; Burke, W.


    We are developing a lightning fast Big Data technology called SciSpark based on ApacheTM Spark under a NASA AIST grant (PI Mattmann). Spark implements the map-reduce paradigm for parallel computing on a cluster, but emphasizes in-memory computation, "spilling" to disk only as needed, and so outperforms the disk-based Apache Hadoop by 100x in memory and by 10x on disk. SciSpark extends Spark to support Earth Science use in three ways: Efficient ingest of N-dimensional geo-located arrays (physical variables) from netCDF3/4, HDF4/5, and/or OPeNDAP URLS; Array operations for dense arrays in scala and Java using the ND4S/ND4J or Breeze libraries; Operations to "split" datasets across a Spark cluster by time or space or both. For example, a decade-long time-series of geo-variables can be split across time to enable parallel "speedups" of analysis by day, month, or season. Similarly, very high-resolution climate grids can be partitioned into spatial tiles for parallel operations across rows, columns, or blocks. In addition, using Spark's gateway into python, PySpark, one can utilize the entire ecosystem of numpy, scipy, etc. Finally, SciSpark Notebooks provide a modern eNotebook technology in which scala, python, or spark-sql codes are entered into cells in the Notebook and executed on the cluster, with results, plots, or graph visualizations displayed in "live widgets". We have exercised SciSpark by implementing three complex Use Cases: discovery and evolution of Mesoscale Convective Complexes (MCCs) in storms, yielding a graph of connected components; PDF Clustering of atmospheric state using parallel K-Means; and statistical "rollups" of geo-variables or model-to-obs. differences (i.e. mean, stddev, skewness, & kurtosis) by day, month, season, year, and multi-year. Geo-variables are ingested and split across the cluster using methods on the sciSparkContext object including netCDFVariables() for spatial decomposition and wholeNetCDFVariables() for time-series. The

  2. Joining of beta-SiC by spark plasma sintering

    Grasso, Salvatore [Queen Mary, University of London; Tatarko, Peter [Institute of Physics of Materials, Academy of Sciences of the Czech Republic; Rizzo, S. [Politecnico di Torino; Porwal, Harshit [Queen Mary, University of London; Hu, Chunfeng [Ningbo Institute of Materials Technology & Engineering; Katoh, Yutai [ORNL; Salvo, M [Politecnico di Torino; Reece, Michael John [University of London; Ferraris, Monica [Politecnico di Torino


    Spark plasma sintering (SPS) was employed to join monolithic -SiC with or without titanium as intermediate joining material. Both the localizedand rapid heating contributed to the inherent energy saving of electric current assisted joining technique. The effects of uniaxial pressure and surfacepreparation were analyzed independently with respect to the flexural strength and the morphology of the joints. In particular samples polisheddown to 1 m and joined at 1900 C for 5 min achieved the strength of the as received material. The failure occurred outside the joining interface,confirming the optimum quality of the joint. Pressure in combination with surface preparation was necessary to achieve perfect adhesion and porefree direct joining of SiC. The use of Ti foil as a joining material and pressure allowed joining of unpolished SiC.

  3. Human resource recommendation algorithm based on ensemble learning and Spark

    Cong, Zihan; Zhang, Xingming; Wang, Haoxiang; Xu, Hongjie


    Aiming at the problem of “information overload” in the human resources industry, this paper proposes a human resource recommendation algorithm based on Ensemble Learning. The algorithm considers the characteristics and behaviours of both job seeker and job features in the real business circumstance. Firstly, the algorithm uses two ensemble learning methods-Bagging and Boosting. The outputs from both learning methods are then merged to form user interest model. Based on user interest model, job recommendation can be extracted for users. The algorithm is implemented as a parallelized recommendation system on Spark. A set of experiments have been done and analysed. The proposed algorithm achieves significant improvement in accuracy, recall rate and coverage, compared with recommendation algorithms such as UserCF and ItemCF.

  4. Temperature Control in Spark Plasma Sintering: An FEM Approach

    G. Molénat


    Full Text Available Powder consolidation assisted by pulsed current and uniaxial pressure, namely, Spark Plasma Sintering (SPS, is increasingly popular. One limitation however lies in the difficulty of controlling the sample temperature during compaction. The aim of this work is to present a computational method for the assembly temperature based on the finite elements method (FEM. Computed temperatures have been compared with experimental data for three different dies filled with three materials with different electrical conductivities (TiAl, SiC, Al2O3. The results obtained are encouraging: the difference between computed and experimental values is less than 5%. This allows thinking about this FEM approach as a predictive tool for selecting the right control temperatures in the SPS machine.

  5. Distributed Parallel Endmember Extraction of Hyperspectral Data Based on Spark

    Zebin Wu


    Full Text Available Due to the increasing dimensionality and volume of remotely sensed hyperspectral data, the development of acceleration techniques for massive hyperspectral image analysis approaches is a very important challenge. Cloud computing offers many possibilities of distributed processing of hyperspectral datasets. This paper proposes a novel distributed parallel endmember extraction method based on iterative error analysis that utilizes cloud computing principles to efficiently process massive hyperspectral data. The proposed method takes advantage of technologies including MapReduce programming model, Hadoop Distributed File System (HDFS, and Apache Spark to realize distributed parallel implementation for hyperspectral endmember extraction, which significantly accelerates the computation of hyperspectral processing and provides high throughput access to large hyperspectral data. The experimental results, which are obtained by extracting endmembers of hyperspectral datasets on a cloud computing platform built on a cluster, demonstrate the effectiveness and computational efficiency of the proposed method.

  6. Manifestation of constrained dynamics in a low pressure spark

    Auluck, S K H


    Some features of neutron emission from dense plasma focus suggest that the participating deuterons have energy in the range of 105 eV and have a directionality of toroidal motion. Theoretical models of these devices assume that the plasma evolves through a purely irrotational flow and thus fail to predict such solenoidal flow on the scale of the plasma dimensions. Predictions of a relaxation theory are consistent with experimental data [S K H Auluck, Physics of Plasmas,18, 032508 (2011)], but the assumptions upon which it is based are not compatible with known features of these devices. There is thus no satisfactory theoretical construct which provides the necessity for solenoidal flow in these devices. This paper proposes such theoretical construct, namely, the principle of constrained dynamics, and describes an experiment which provides support for this idea. The experiment consisted of low inductance, self-breaking spark discharge in helium at a pressure ~100 hPa between two pointed electrodes separated by...

  7. The Absence of Plasma in"Spark Plasma Sintering"

    Hulbert, Dustin M.; Anders, Andre; Dudina, Dina V.; Andersson, Joakim; Jiang, Dongtao; Unuvar, Cosan; Anselmi-Tamburini, Umberto; Lavernia, Enrique J.; Mukherjee, Amiya K.


    Spark plasma sintering (SPS) is a remarkable method for synthesizing and consolidating a large variety of both novel and traditional materials. The process typically uses moderate uni-axial pressures (<100 MPa) in conjunction with a pulsing on-off DC current during operation. There are a number of mechanisms proposed to account for the enhanced sintering abilities of the SPS process. Of these mechanisms, the one most commonly put forth and the one that draws the most controversy involves the presence of momentary plasma generated between particles. This study employees three separate experimental methods in an attempt to determine the presence or absence of plasma during SPS. The methods employed include: in-situ atomic emission spectroscopy, direct visual observation and ultra-fast in-situ voltage measurements. It was found using these experimental techniques that no plasma is present during the SPS process. This result was confirmed using several different powders across a wide spectrum of SPS conditions.

  8. Spark plasma sintering of Mn-Al-C hard magnets.

    Pasko, A; LoBue, M; Fazakas, E; Varga, L K; Mazaleyrat, F


    Structural and magnetic characterization of isotropic Mn-Al-C bulk samples obtained by spark plasma sintering (SPS) is reported. This technique, to the best of our knowledge, has not been used for preparation of Mn-Al-based permanent magnets previously. Transformation from the parent -phase to the ferromagnetic τ-phase occurred on heating in the process of sintering. The phase constitution of the melt-spun precursors and consolidated samples was determined by x-ray diffraction. Magnetic hysteresis loops were recorded using a vibrating sample magnetometer. The compositional dependence of the coercivity, magnetization and density of the sintered materials is analysed. To combine good magnetic properties with proper densification, further optimization of the production parameters is necessary.

  9. Low temperature spark plasma sintering of TC4/HA composites

    Huiliang Shao; Lei Cao; Daqian Sun; Zhankui Zhao


    Ti6Al4V/hydroxyapatite composites (TC4/HA) have been prepared by high energy ball milling and low temperature spark plasma sintering at 600 °C, 550 °C, 500 °C and 450 °C, respectively. The sintering temperature of the composites was sharply decreased as the result of the activation and surficial modification effects induced from high energy ball milling. The decomposition and reaction of hydro-xyapatite was successfully avoided, which offers the composites superior biocompatibility. The hydro-xyapatite in the composites was distributed in gap uniformly, and formed an ideal network structure. The lowest hardness, compressive strength and Young's modulus of the composites satisfy the requirements of human bone.

  10. The Absence of Plasma in"Spark Plasma Sintering"

    Hulbert, Dustin M.; Anders, Andre; Dudina, Dina V.; Andersson, Joakim; Jiang, Dongtao; Unuvar, Cosan; Anselmi-Tamburini, Umberto; Lavernia, Enrique J.; Mukherjee, Amiya K.


    Spark plasma sintering (SPS) is a remarkable method for synthesizing and consolidating a large variety of both novel and traditional materials. The process typically uses moderate uni-axial pressures (<100 MPa) in conjunction with a pulsing on-off DC current during operation. There are a number of mechanisms proposed to account for the enhanced sintering abilities of the SPS process. Of these mechanisms, the one most commonly put forth and the one that draws the most controversy involves the presence of momentary plasma generated between particles. This study employees three separate experimental methods in an attempt to determine the presence or absence of plasma during SPS. The methods employed include: in-situ atomic emission spectroscopy, direct visual observation and ultra-fast in-situ voltage measurements. It was found using these experimental techniques that no plasma is present during the SPS process. This result was confirmed using several different powders across a wide spectrum of SPS conditions.

  11. Mechanochemical synthesis and spark plasma sintering of the cerium silicides

    Alanko, Gordon A.; Jaques, Brian; Bateman, Allyssa [Department of Materials Science and Engineering, College of Engineering, Boise State University, 1910 University Drive, Boise, ID 83725 (United States); Butt, Darryl P., E-mail: [Department of Materials Science and Engineering, College of Engineering, Boise State University, 1910 University Drive, Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Boulevard, Idaho Falls, ID 83401 (United States)


    Highlights: • Ce{sub 5}Si{sub 3}, Ce{sub 3}Si{sub 2}, CeSi, CeSi{sub 2−x} and CeSi{sub 2} were mechanochemically synthesized. • Temperature and pressure were monitored to investigate reaction progress. • All syntheses proceeded through a MSR event followed by rapid solid-state diffusion. • Milling time before MSR correlates well with effective heat of formation. • Some synthesized material was densified by spark plasma sintering. - Abstract: The cerium silicides, Ce{sub 5}Si{sub 3}, Ce{sub 3}Si{sub 2}, CeSi, CeSi{sub 2−y}, and CeSi{sub 2−x}, have been prepared from the elements by mechanochemical processing in a planetary ball mill. Preparation of the cerium silicide Ce{sub 5}Si{sub 4} was unsuccessfully attempted and potential reasons for this are discussed. Temperature and pressure of the milling vial were monitored in situ to gain insight into the mechanochemical reaction kinetics, which include a mechanically-induced self-propagating reaction (MSR). Some prepared powders were consolidated by spark plasma sintering to high density. Starting materials, as-milled powders, and consolidated samples were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results obtained help elucidate key questions in mechanochemical processing of intermetallics, showing first phase formation similar to thin films, MSR ignition times that are composition- and milling speed-dependent, and sensitivity of stable compound formation on the impact pressure. The results demonstrate mechanochemical synthesis as a viable technique for rare earth silicides.

  12. What sparks interest in science? A naturalistic inquiry

    Jackson, Julie Kay Cropper

    This study examined how career scientists became interested in science. Eight practicing scientists were asked a focus question, "What sparked your interest in science?" Their responses recorded during personal interviews and reported in correspondence frame this qualitative study. Analysis of the data revealed a variety of influences. The influences were coded, arranged into lists, and grouped by theme. A total of 18 themes emerged from the data. Five of the emerging themes were common across all of the participants. They were the influence of a family member, the influence of a teacher, being naturally curious, being interested in science, and reading books, magazines, and/or encyclopedias. Five themes were common among 5 to 7 participants. These themes included visiting museums, having broad exposure, enjoyment of mathematics, enjoying being outside, and freedom to play and explore. Eight themes were common among 2 to 4 of the participants. They were financial incentive, influence of religion, participation in science fairs, influence of the manned space program, having a scientist in the family, having the opportunity to teach others, not seeing self as a scientist, and first generation college graduate. The emerging themes were compared and contrasted with historical and contemporary literature. Vocational psychology's leading career choice and development literature was also aligned with the emerging themes. Data from this study supports tenets of Trait and Factor Theory, Developmental Theory, and Social Learning Theory. Reported data also supports the proposed movement toward a unified theory of career choice and development. A combination of personality traits, developmental stages, self-efficacy, and learning experiences influenced the vocational decisions of the scientists who participated in this study. The study concludes with suggestions for sparking and sustaining interest in science that people responsible for preparing future scientists may find

  13. Charged Leptons

    Albrecht, J; Babu, K; Bernstein, R H; Blum, T; Brown, D N; Casey, B C K; Cheng, C -h; Cirigliano, V; Cohen, A; Deshpande, A; Dukes, E C; Echenard, B; Gaponenko, A; Glenzinski, D; Gonzalez-Alonso, M; Grancagnolo, F; Grossman, Y; Harnik, R; Hitlin, D G; Kiburg, B; Knoepfe, K; Kumar, K; Lim, G; Lu, Z -T; McKeen, D; Miller, J P; Ramsey-Musolf, M; Ray, R; Roberts, B L; Rominsky, M; Semertzidis, Y; Stoeckinger, D; Talman, R; Van De Water, R; Winter, P


    This is the report of the Intensity Frontier Charged Lepton Working Group of the 2013 Community Summer Study "Snowmass on the Mississippi", summarizing the current status and future experimental opportunities in muon and tau lepton studies and their sensitivity to new physics. These include searches for charged lepton flavor violation, measurements of magnetic and electric dipole moments, and precision measurements of the decay spectrum and parity-violating asymmetries.

  14. Laser interferometric measurements of a laser-preionization-triggered spark column

    Kimura, W. D.; Kushner, M. J.; Crawford, E. A.; Byron, S. R.


    A KrF laser (248 nm) is used to volume preionization trigger a 40-100 kV, greater than 10-kA, 100-ns spark gap switch. This method of triggering creates reproducible and axisymmetric spark columns having low temperature and spatial jitter. A short pulse (less than 5 ns) tunable dye laser and a Mach-Zehnder interferometer are used to obtain spatial and temporal measurements of the spark column. The spatial resolution of the interferograms is better than 5 microns. The fringe shifts of the interferograms are used to calculate the electron and heavy particle density distributions within the spark column as a function of time during the spark. Results are presented for sparks in 5 percent SF6/20 percent N2/75 percent He and 1 percent Xe/99 percent H2 gas mixtures. dc and pulsed self-breakdown voltages are also measured in order to provide a reference for the laser-triggered results. Data on laser-triggering reliability and spark breakdown delay time are also presented.

  15. FTIR Analysis of Flowing Afterglow from a High-Frequency Spark Discharge

    White, Allen; Hieftje, Gary M.; Ray, Steve; Pfeuffer, Kevin


    Plasmas are often used as ionization sources for ambient mass spectrometry (AMS). Here, the flowing afterglow of a novel high-energy spark discharge system, operated in nitrogen at high repetition rates, is investigated as a source for AMS. The spark discharge here is the same as that of an automobile ignition circuit.Combustion in automobile engines is initiated by a spark ignition system that is designed to deliver short-duration,high-voltage sparks to multiple engine cylinders. The arrangement utilized in this study is a modified discharge configuration designed to produce similarly short-duration, high-voltage discharges. It consists of an automotive ignition coil that is activated by a spark initiation circuit that discharges in turn into a cell with neutral gas input flow and ultimately into the collection orifice of a mass spectrometer. The discharge voltage is approximately 40kV at 800 Hz. High-frequency spark discharges in a nitrogen flow produce reagent ions such as NO+. In order to better evaluate the effectiveness of the discharge in producing reagent ions, an FTIR is utilized to measure IR active species such as nitric oxide, hydroxide, ozone, and water in the afterglow of the spark discharge during variation of discharge parameters. Time-resolved IR emission spectra provide additional insight into the reagent ion production mechanisms.

  16. Calcium Hex aluminate reaction sintering by Spark Plasma Sintering; Sinterizacion reactiva de Hexaluminato de Calcio mediante Spark Plasma Sintering

    Iglesia, P. G. de la; Garcia-Moreno, O.; Torrecillas, R.; Menendez, J. L.


    Calcium hex aluminate (CaAl{sub 1}2O{sub 1}9) is the most alumina-rich intermediate compound of the CaO-Al{sub 2}O{sub 3} system. The formation of this aluminate is produced by the reaction between calcium oxide and alumina with the consequent formation of intermediates compounds with lower alumina content with increasing temperature (CaAl{sub 2}O{sub 4}, CaAl4O{sub 7}). In this study we studied the variation of sintering parameters for obtaining dense and pure calcium hex aluminate by reaction sintering by Spark Plasma Sintering (SPS). A mixing of Al{sub 2}O{sub 3} and CaCO{sub 3} were used as reactive. Final densities close to the theoretical and phase transformation over 93% were achieved by this method. (Author) 22 refs.

  17. Stability of stratified two-phase flows in horizontal channels

    Barmak, Ilya; Ullmann, Amos; Brauner, Neima; Vitoshkin, Helen


    Linear stability of stratified two-phase flows in horizontal channels to arbitrary wavenumber disturbances is studied. The problem is reduced to Orr-Sommerfeld equations for the stream function disturbances, defined in each sublayer and coupled via boundary conditions that account also for possible interface deformation and capillary forces. Applying the Chebyshev collocation method, the equations and interface boundary conditions are reduced to the generalized eigenvalue problems solved by standard means of numerical linear algebra for the entire spectrum of eigenvalues and the associated eigenvectors. Some additional conclusions concerning the instability nature are derived from the most unstable perturbation patterns. The results are summarized in the form of stability maps showing the operational conditions at which a stratified-smooth flow pattern is stable. It is found that for gas-liquid and liquid-liquid systems the stratified flow with smooth interface is stable only in confined zone of relatively lo...

  18. Background Oriented Schlieren in a Density Stratified Fluid

    Verso, Lilly


    Non-intrusive quantitative fluid density measurements methods are essential in stratified flow experiments. Digital imaging leads to synthetic Schlieren methods in which the variations of the index of refraction are reconstructed computationally. In this study, an important extension to one of these methods, called Background Oriented Schlieren (BOS), is proposed. The extension enables an accurate reconstruction of the density field in stratified liquid experiments. Typically, the experiments are performed by the light source, background pattern, and the camera positioned on the opposite sides of a transparent vessel. The multi-media imaging through air-glass-water-glass-air leads to an additional aberration that destroys the reconstruction. A two-step calibration and image remapping transform are the key components that correct the images through the stratified media and provide non-intrusive full-field density measurements of transparent liquids.

  19. Background oriented schlieren in a density stratified fluid

    Verso, Lilly; Liberzon, Alex


    Non-intrusive quantitative fluid density measurement methods are essential in the stratified flow experiments. Digital imaging leads to synthetic schlieren methods in which the variations of the index of refraction are reconstructed computationally. In this study, an extension to one of these methods, called background oriented schlieren, is proposed. The extension enables an accurate reconstruction of the density field in stratified liquid experiments. Typically, the experiments are performed by the light source, background pattern, and the camera positioned on the opposite sides of a transparent vessel. The multimedia imaging through air-glass-water-glass-air leads to an additional aberration that destroys the reconstruction. A two-step calibration and image remapping transform are the key components that correct the images through the stratified media and provide a non-intrusive full-field density measurements of transparent liquids.

  20. SINDA/FLUINT Stratified Tank Modeling for Cryrogenic Propellant Tanks

    Sakowski, Barbara


    A general purpose SINDA/FLUINT (S/F) stratified tank model was created to simulate self-pressurization and axial jet TVS; Stratified layers in the vapor and liquid are modeled using S/F lumps.; The stratified tank model was constructed to permit incorporating the following additional features:, Multiple or singular lumps in the liquid and vapor regions of the tank, Real gases (also mixtures) and compressible liquids, Venting, pressurizing, and draining, Condensation and evaporation/boiling, Wall heat transfer, Elliptical, cylindrical, and spherical tank geometries; Extensive user logic is used to allow detailed tailoring - Don't have to rebuilt everything from scratch!!; Most code input for a specific case is done through the Registers Data Block:, Lump volumes are determined through user input:; Geometric tank dimensions (height, width, etc); Liquid level could be input as either a volume percentage of fill level or actual liquid level height

  1. Numerical Simulation on Stratified Flow over an Isolated Mountain Ridge

    LI Ling; Shigeo Kimura


    The characteristics of stratified flow over an isolated mountain ridge have been investigated numerically. The two-dimensional model equations, based on the time-dependent Reynolds averaged NavierStokes equations, are solved numerically using an implicit time integration in a fitted body grid arrangement to simulate stratified flow over an isolated ideally bell-shaped mountain. The simulation results are in good agreement with the existing corresponding analytical and approximate solutions. It is shown that for atmospheric conditions where non-hydrostatic effects become dominant, the model is able to reproduce typical flow features. The dispersion characteristics of gaseous pollutants in the stratified flow have also been studied. The dispersion patterns for two typical atmospheric conditions are compared. The results show that the presence of a gravity wave causes vertical stratification of the pollutant concentration and affects the diffusive characteristics of the pollutants.

  2. Stability of stratified two-phase flows in inclined channels

    Barmak, Ilya; Ullmann, Amos; Brauner, Neima


    Linear stability of stratified gas-liquid and liquid-liquid plane-parallel flows in inclined channels is studied with respect to all wavenumber perturbations. The main objective is to predict parameter regions in which stable stratified configuration in inclined channels exists. Up to three distinct base states with different holdups exist in inclined flows, so that the stability analysis has to be carried out for each branch separately. Special attention is paid to the multiple solution regions to reveal the feasibility of non-unique stable stratified configurations in inclined channels. The stability boundaries of each branch of steady state solutions are presented on the flow pattern map and are accompanied by critical wavenumbers and spatial profiles of the most unstable perturbations. Instabilities of different nature are visualized by streamlines of the neutrally stable perturbed flows, consisting of the critical perturbation superimposed on the base flow. The present analysis confirms the existence of ...

  3. Numerical contribution to the characterisation and predictive calculation of mixture formation and combustion in a jet-guided direct-injected spark ignition engine[Dissertation 14937]; Numerischer Beitrag zur Charakterisierung und Vorausberechnung der Gemischbildung und Verbrennung in einem direkteingespritzten, strahlgefuehrten Ottomotor

    Koch, T.


    The present thesis deals with the thermodynamic, physical and chemical processes inside a jet-guided direct injected spark ignition engine. The main focus on the investigations has been set on the phenomena of mixture formation and combustion. The objective of this work was the development of a physically based, fast model to predict the heat release and pressure evolution. Therefore, numerous fundamental investigations were carried out prior to defining the basis of the phenomenological approach. The dominating influence of the fuel injection has been investigated with extensive three-dimensional simulations of the two-phase flow for quiescent laboratory conditions subsequently experimentally validated as well as for the engine applications. Spray penetration, the evaporation rate and the turbulence influence of the hollow-cone spray have been of particular importance. Comprehensive mainly optically based experiments have also been performed in parallel within the scope of a second thesis. The synergetic combination of numerical with experimental investigations yielded insights into key phenomena and led to a detailed understanding of the relevant combustion-related process. The phenomenological modeling of the determining process of injection, fuel evaporation, mixture formation, ignition, heat release and NO formation has been performed by concentrating on the most significant individual physical phenomena. Thereby the focus has been on the formulation of the combustion by a superposition of a premixed and mixing controlled approach. The newly developed model has been tested for numerous operating conditions in stratified as well as homogenous charge. Additionally, multidimensional operating maps have been simulated which serve as a basis for complete vehicle-cycle computations. (author)

  4. Experimental evaluation of a spark-ignited engine using biogas as fuel

    Juan Miguel Mantilla González


    Full Text Available Different CH4 and CO2 mixtures were used as fuel in this work; they were fed into a spark-ignited engine equipped with devices allowing spark advance, gas delivery and gas consumption to be measured. Engine bench-tests re-vealed changes in the main operation parameters and emissions. The results showed that increasing CO2 percen-tage in the mixture increased the spark angle, reduced maximum power and torque and reduced exhaust emissions (by 90% in some cases when DAMA resolution 1015/2005 was applied. The main components to be considered when an engine of this type operates with gas fuel were also recognised.

  5. A time-varying copula mixture for hedging the clean spark spread with wind power futures

    Christensen, Troels Sønderby; Pircalabu, Anca; Høg, Esben


    trading in the spot clean spark spread and wind power futures. To facilitate hedging decisions, we propose a time-varying copula mixture for the joint behavior of the spot clean spark spread and the daily wind index. The model describes the data surprisingly well, both in terms of the marginals...... and the dependence structure, while being straightforward and easy to implement. Based on Monte Carlo simulations from the proposed model, the results indicate that significant benefits can be achieved by using wind power futures to hedge the spot clean spark spread. Moreover, a comparison study shows...

  6. Interface behavior of tungsten coating on stainless steel by electro spark deposition

    Wang Yuangang


    Full Text Available A new method of electro spark deposition method was put forward, which was based on the theory of electro spark deposition by changing the polarity in the liquid. Tungsten coating layers was produced on surface of Stainless Steel by electro spark deposition. The micro hardness, microstructure, chemical composition and phases of the coating layer were examined by means of hardness test, scanning electron microscopy (SEM and energy dispersive spectrometer (EDS analysis. The results showed that there was tungsten coating in the surface, which was discontinuous. Microhardness of the coating layer was about 3 times more than that of the substrate. The combination between coating layer and substrate was metallurgical bond.

  7. The secular and the supernatural: madness and psychiatry in the short stories of Muriel Spark.

    Beveridge, A W


    Edinburgh-born Muriel Spark is one of modern Scotland's greatest writers. Examination of her work reveals that the subjects of madness and psychiatry are recurrent themes in her writing. She herself had a mental breakdown when she was a young woman and she took an interest in the world of psychiatry and psychoanalysis. In her short stories, Spark approaches the subject of madness in a variety of ways: she relates it to the supernatural; to writing fiction; and to religion. She frequently juxtaposes secular and supernatural explanations of mental disturbance. Spark adopts a sceptical and, at times, mocking view of psychiatrists and psychiatric treatment. Both psychoanalysis and pills are seen as problematic.

  8. Charging of aerosol and nucleation in atmospheric pressure electrical discharges

    Borra, J. P.


    The paper focuses on applications of atmospheric pressure plasmas (dc corona, streamer, spark and ac dielectric barrier discharges (DBDs)) in aerosol processes for materials and environment. Since aerosol kinematics depends mainly on electric forces acting on charged particles, the two mechanisms of aerosol charging by the collection of ions are presented in corona, post-corona and DBDs. In such defined charging conditions, field and diffusion charging laws are depicted, with respect to applications of controlled kinematics of charged aerosol. Then key parameters controlling the formation by nucleation and the growth by coagulation of particles in plasmas are presented. Sources of vapor leading to nucleated nanoparticles are depicted in atmospheric pressure electrical discharges: (i) when filamentary dc streamer and spark as well as ac-DBDs interact with metal or dielectric surfaces and (ii) when discharges induce reactions with gaseous precursors in volume. In both cases, condensable gaseous species are produced, leading to nano-sized particles by physical and chemical routes of nucleation. The composition, size and structure of primary nanoparticles as well as the final size of agglomerates are related to plasma parameters (energy, number per unit surface and time and thermal gradients around each filament as well as the transit time).

  9. Linear Inviscid Damping for Couette Flow in Stratified Fluid

    Yang, Jincheng


    We study the inviscid damping of Coutte flow with an exponentially stratified density. The optimal decay rates of the velocity field and density are obtained for general perturbations with minimal regularity. For Boussinesq approximation model, the decay rates we get are consistent with the previous results in the literature. We also study the decay rates for the full equations of stratified fluids, which were not studied before. For both models, the decay rates depend on the Richardson number in a very similar way. Besides, we also study the inviscid damping of perturbations due to the exponential stratification when there is no shear.

  10. Bases of Schur algebras associated to cellularly stratified diagram algebras

    Bowman, C


    We examine homomorphisms between induced modules for a certain class of cellularly stratified diagram algebras, including the BMW algebra, Temperley-Lieb algebra, Brauer algebra, and (quantum) walled Brauer algebra. We define the `permutation' modules for these algebras, these are one-sided ideals which allow us to study the diagrammatic Schur algebras of Hartmann, Henke, Koenig and Paget. We construct bases of these Schur algebras in terms of modified tableaux. On the way we prove that the (quantum) walled Brauer algebra and the Temperley-Lieb algebra are both cellularly stratified and therefore have well-defined Specht filtrations.

  11. How to Demonstrate the Voltage on a charged object in Physics Laboratory

    Baddi, Raju


    Common Objects like a comb or a pen get charged when rubbed against something like human hair or garment clothing. Charged objects exhibit noticeable attractive or repulsive force lifting small pieces of paper or pushing/pulling a suspended light object charged with the same/opposite(uncharged) polarity respectively. This indicates the strong electrical nature of charged objects. Flashes due to spark between oppositely charged objects can be seen in total darkness. Implying a large potential difference between these charged objects which is not possible at lower voltages. This article describes a method to measure the voltage on commonly charged objects with respect to earth using simple instrumentation based on capacitors and CMOS voltmeter. Once the potential difference is known the average charge on the object can be calculated as well. The article also suggests a simple femto-farad capacitance meter for electrostatics work.

  12. Time-resolved spark-source mass spectroscopy: the effect of spark duration on relative sensitivity factors, ion intensity and precision of analysis

    Franklin, James Curry [Univ. of Tennessee, Knoxville, TN (United States)


    A radio-frequency, high-voltage spark ion source in conjunction with a double-focusing mass spectrometer has been used to measure the relative sensitivity factors for several elements in matrices of tin, iron, beryllium oxide, uranium, and steels. The sensitivity factors were examined for concentration and matrix effects. No significant variations were found for the concentration ranges studied, but there were very large sensitivity variations with changes in the matrix type. In order to accomplish this study, circuits were designed and installed to synchronize the ion-beam chopping circuits with the radio-frequency spark pulses so that time-resolved spectra were obtained at different periods in the spark pulse.

  13. Automatic code generation in SPARK: Applications of computer algebra and compiler-compilers

    Nataf, J.M.; Winkelmann, F.


    We show how computer algebra and compiler-compilers are used for automatic code generation in the Simulation Problem Analysis and Research Kernel (SPARK), an object oriented environment for modeling complex physical systems that can be described by differential-algebraic equations. After a brief overview of SPARK, we describe the use of computer algebra in SPARK's symbolic interface, which generates solution code for equations that are entered in symbolic form. We also describe how the Lex/Yacc compiler-compiler is used to achieve important extensions to the SPARK simulation language, including parametrized macro objects and steady-state resetting of a dynamic simulation. The application of these methods to solving the partial differential equations for two-dimensional heat flow is illustrated.

  14. Hot wire and spark pyrolysis as simple new routes to silicon nanoparticle synthesis

    Scriba, MR


    Full Text Available gases, silane and diborane or silane and phosphine were used. While hot wire pyrolysis always results in multifaceted particles, those produced by spark pyrolysis are spherical. Electrical resistance measurements of compressed powders showed that boron...

  15. Analysis of Discharge Spark Energy in Buck Converter of a Continuous Mode of Inductive Current

    CUI Bao-chun; CHENG Hong; WANG Cong; LU Huan-yu; SHI Yun


    The basic idea of intrinsically safe circuit and the discharge spark in the Buck converter in the explosive atmospheres were introduced. The Buck converter is the main topological structure of the switch type of intrinsically safe circuit, which has two working modes: continuous inductive current (CCM - continuous conduction mode) and discrete inductance current (DCM - discontinuous conduction mode). The operating state of the continuous inductive current mode is analyzed in detail and the energy of discharge spark in various operating modes is discussed. The total energy will decrease with the increase of switch frequency, in a switching cycle; the discharge spark energy has a maximum and a minimum value. Therefore, the Buck converter has smaller discharge spark energy than the linear power circuit and the switch type of intrinsically safe circuit can enhance the output power and the conversion efficiency of the intrinsically safe power.

  16. Aspects of the bioethanol use at the turbocharged spark ignition engine

    Obeid Zuhair


    Full Text Available In the actual content of pollution regulations for the automotives, the use of alternative fuels becomes a priority of the thermal engine scientific research domain. From this point of view bioethanol can represents a viable alternative fuel for spark ignition engines offering the perspective of pollutant emissions reduction and combustion improvement. The paper presents results of the experimental investigations of a turbo-supercharged spark ignition engine (developed from a natural admission spark ignition engine fuelled with gasoline fuelled with bioethanol-gasoline blends. The engine is equipped with a turbocharger for low pressure supercharging, up till 1.4 bar. An correlation between air supercharging pressure-compression ratio-dosage-spark ignition timing-brake power is establish to avoid knocking phenomena at the engine operate regime of full load and 3000 min-1. The influences of the bioethanol on pollutant emissions level are presented.

  17. Spark PRM: Using RRTs within PRMs to efficiently explore narrow passages

    Shi, Kensen


    © 2014 IEEE. Probabilistic RoadMaps (PRMs) have been successful for many high-dimensional motion planning problems. However, they encounter difficulties when mapping narrow passages. While many PRM sampling methods have been proposed to increase the proportion of samples within narrow passages, such difficult planning areas still pose many challenges. We introduce a novel algorithm, Spark PRM, that sparks the growth of Rapidly-expanding Random Trees (RRTs) from narrow passage samples generated by a PRM. The RRT rapidly generates further narrow passage samples, ideally until the passage is fully mapped. After reaching a terminating condition, the tree stops growing and is added to the roadmap. Spark PRM is a general method that can be applied to all PRM variants. We study the benefits of Spark PRM with a variety of sampling strategies in a wide array of environments. We show significant speedups in computation time over RRT, Sampling-based Roadmap of Trees (SRT), and various PRM variants.

  18. Analysis of photonic band-gap structures in stratified medium

    Tong, Ming-Sze; Yinchao, Chen; Lu, Yilong;


    Purpose - To demonstrate the flexibility and advantages of a non-uniform pseudo-spectral time domain (nu-PSTD) method through studies of the wave propagation characteristics on photonic band-gap (PBG) structures in stratified medium Design/methodology/approach - A nu-PSTD method is proposed...

  19. Plane Stratified Flow in a Room Ventilated by Displacement Ventilation

    Nielsen, Peter Vilhelm; Nickel, J.; Baron, D. J. G.


    The air movement in the occupied zone of a room ventilated by displacement ventilation exists as a stratified flow along the floor. This flow can be radial or plane according to the number of wall-mounted diffusers and the room geometry. The paper addresses the situations where plane flow...

  20. Bacterial production, protozoan grazing and mineralization in stratified lake Vechten.

    Bloem, J.


    The role of heterotrophic nanoflagellates (HNAN, size 2-20 μm) in grazing on bacteria and mineralization of organic matter in stratified Lake Vechten was studied.Quantitative effects of manipulation and fixation on HNAN were checked. Considerable losses were caused by centrifugation, even at low spe

  1. Population dynamics of sinking phytoplankton in stratified waters

    Huisman, J.; Sommeijer, B.P.


    We analyze the predictions of a reaction-advection-diffusion model to pinpoint the necessary conditions for bloom development of sinking phytoplanktonspecies in stratified waters. This reveals that there are two parameter windows that can sustain sinking phytoplankton, a turbulence window and atherm

  2. Gravity-induced stresses in stratified rock masses

    Amadei, B.; Swolfs, H.S.; Savage, W.Z.


    This paper presents closed-form solutions for the stress field induced by gravity in anisotropic and stratified rock masses. These rocks are assumed to be laterally restrained. The rock mass consists of finite mechanical units, each unit being modeled as a homogeneous, transversely isotropic or isotropic linearly elastic material. The following results are found. The nature of the gravity induced stress field in a stratified rock mass depends on the elastic properties of each rock unit and how these properties vary with depth. It is thermodynamically admissible for the induced horizontal stress component in a given stratified rock mass to exceed the vertical stress component in certain units and to be smaller in other units; this is not possible for the classical unstratified isotropic solution. Examples are presented to explore the nature of the gravity induced stress field in stratified rock masses. It is found that a decrease in rock mass anisotropy and a stiffening of rock masses with depth can generate stress distributions comparable to empirical hyperbolic distributions previously proposed in the literature. ?? 1988 Springer-Verlag.

  3. Dispersion of (light) inertial particles in stratified turbulence

    van Aartrijk, M.; Clercx, H.J.H.; Armenio, Vincenzo; Geurts, Bernardus J.; Fröhlich, Jochen


    We present a brief overview of a numerical study of the dispersion of particles in stably stratified turbulence. Three types of particles arc examined: fluid particles, light inertial particles ($\\rho_p/\\rho_f = \\mathcal{O}(1)$) and heavy inertial particles ($\\rho_p/\\rho_f \\gg 1$). Stratification

  4. The dynamics of small inertial particles in weakly stratified turbulence

    van Aartrijk, M.; Clercx, H.J.H.

    We present an overview of a numerical study on the small-scale dynamics and the large-scale dispersion of small inertial particles in stably stratified turbulence. Three types of particles are examined: fluid particles, light inertial particles (with particle-to-fluid density ratio 1Ͽp/Ͽf25) and

  5. Characterization of Inlet Diffuser Performance for Stratified Thermal Storage

    Cimbala, John M.; Bahnfleth, William; Song, Jing


    Storage of sensible heating or cooling capacity in stratified vessels has important applications in central heating and cooling plants, power production, and solar energy utilization, among others. In stratified thermal storage systems, diffusers at the top and bottom of a stratified tank introduce and withdraw fluid while maintaining a stable density gradient and causing as little mixing as possible. In chilled water storage applications, mixing during the formation of the thermocline near an inlet diffuser is the single greatest source of thermal losses. Most stratified chilled water storage tanks are cylindrical vessels with diffusers that are either circular disks that distribute flow radially outward or octagonal rings of perforated pipe that distribute flow both inward and outward radially. Both types produce gravity currents that are strongly influenced by the inlet Richardson number, but the significance of other parameters is not clear. The present investigation considers the dependence of the thermal performance of a perforated pipe diffuser on design parameters including inlet velocity, ambient and inlet fluid temperatures, and tank dimensions for a range of conditions representative of typical chilled water applications. Dimensional analysis is combined with a parametric study using results from computational fluid dynamics to obtain quantitative relationships between design parameters and expected thermal performance.

  6. Global and Partial Errors in Stratified and Clustering Sampling

    Giovanna Nicolini; Anna Lo Presti


    In this paper we split up the sampling error occurred in stratified and clustering sampling, called global error and measured by the variance of estimator, in many partial errors each one referred to a single stratum or cluster. In particular, we study, for clustering sampling, the empirical distribution of the homogeneity coefficient that is very important for settlement of partial errors.

  7. Non-local effects in a stratified glow discharge with dust particles

    Sukhinin, G I; Fedoseev, A V [Institute of Thermophysics SB RAS, Lavrentyev Ave., 1, Novosibirsk, 630090 (Russian Federation); Ramazanov, T S; Amangaliyeva, R Zh; Dosbalayev, M K; Jumabekov, A N [Institute of Experimental and Theoretical Physics, Al Farabi Kazakh National University, Tole Bi, 96a, Almaty, 050012 (Kazakhstan)], E-mail:


    The work is aimed at describing non-local effects in the positive column of a low-pressure stratified dc glow discharge in argon with dust particles in a vertical cylindrical discharge tube. Numerical calculations of plasma parameters in the axis of the discharge tube were performed with the help of a hybrid model based on the solution of a non-local Boltzmann equation for electron energy distribution function (EEDF). Axial distributions of optical emission from striations with dust particles were measured experimentally. Negatively charged dust particles in a low-pressure stratified gas discharge should levitate at the anode-side branch of an electric field distribution above its maximum. At the same time the experiments showed that the dust particles levitate at the cathode side of a stratum. This paradox is explained by the fact that in a low-pressure striated discharge the optical emission distribution is displaced relative to the electric field distribution that was shown both by numerical simulations and experimental measurements.

  8. Analyzing large data sets from XGC1 magnetic fusion simulations using apache spark

    Churchill, R. Michael [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)


    Apache Spark is explored as a tool for analyzing large data sets from the magnetic fusion simulation code XGCI. Implementation details of Apache Spark on the NERSC Edison supercomputer are discussed, including binary file reading, and parameter setup. Here, an unsupervised machine learning algorithm, k-means clustering, is applied to XGCI particle distribution function data, showing that highly turbulent spatial regions do not have common coherent structures, but rather broad, ring-like structures in velocity space.

  9. Breakdown characteristics in DC spark experiments of copper focusing on purity and hardness

    Yokoyama, Kazue; Higashi, Yasuo; Higo, Toshi; Matsumoto, Shuji; Santiago-Kern, Ana Rocia; Pasquino, Chiara; Calatroni, Sergio; Wuensch, Walter


    The breakdown characteristics related to the differences in purity and hardness were investigated for several types of copper using a DC spark test system. Three types of oxygen-free copper (OFC) materials, usual class 1 OFC 7-nine large-grain copper and 6-nine hot-isotropic-pressed (HIP) copper with/without diamond finish, were tested with the DC spark test system. The measurements of the beta, breakdown fields, and breakdown probability are presented and discussed in this paper.

  10. SparkSQL:基于内存的大数据处理引擎

    高彦杰; 陈冠诚



  11. RS Components发布具三维功能的DesignSpark PCB升级版


    RSComponents宣布推出其免费印制电路板(PCB)设计软件包DesignSpark PCB第二版。在与Number One Systems合作的情况下,DesignSpark PCB的新特性包括PCB布局的独特三维可视化以及提升的资料库管理功能。

  12. Benefits and applications of laser-induced sparks in real scale model measurements

    Gómez-Bolaños, Javier; Delikaris-Manias, Symeon; Pulkki, Ville Topias


    The characteristics of using a laser-induced spark as a monopole source in scale model measurements were assessed by comparison with an electric spark and a miniature spherical loudspeaker. Room impulse responses of first order directivity sources were synthesized off-line using six spatially dis...... to synthesize room responses of directional sources, e.g., to obtain directional information about reflections inside scale models....

  13. Flash (Ultra-Rapid) Spark-Plasma Sintering of Silicon Carbide

    Eugene A. Olevsky; Stephen M. Rolfing; Maximenko, Andrey L.


    A new ultra-rapid process of flash spark plasma sintering is developed. The idea of flash spark plasma sintering (or flash hot pressing - FHP) stems from the conducted theoretical analysis of the role of thermal runaway phenomena for material processing by flash sintering. The major purpose of the present study is to theoretically analyze the thermal runaway nature of flash sintering and to experimentally address the challenge of uncontrollable thermal conditions by the stabilization of the f...

  14. Thermoelectric and mechanical properties of melt spun and spark plasma sintered n-type Yb- and Ba-filled skutterudites

    Salvador, James R., E-mail: [General Motors Research and Development Center, 30500 Mound Road, Warren, MI 48090 (United States); Waldo, Richard A.; Wong, Curtis A. [General Motors Research and Development Center, 30500 Mound Road, Warren, MI 48090 (United States); Tessema, Misle [Optimal Inc., 14492 Sheldon Road, Suite 300, Plymouth, MI 48170 (United States); Brown, David N.; Miller, David J. [Molycorp Inc. Research and Development Center, 61 Science Park Road, 01-17 Galen, Singapore 117252 (Singapore); Wang, Hsin; Wereszczak, Andrew A.; Cai, Wei [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)


    Highlights: • N-type double filled skutterudites can be formed by a combination of melt spinning and spark plasma sintering, obviating annealing steps. • The consolidated billets have thermoelectric properties that are comparable to those produced using more time and energy intensive powder metallurgical methods. • We demonstrate that the here described preparation route is scalable to 80 g billets as evidenced by the comparable nature of the transport properties of specimens cuts from large samples to those of smaller lab-scale specimens. -- Abstract: Here we present thermoelectric and mechanical properties of n-type filled-skutterudites produced by a combination of melt spinning of pre-melted charges with subsequent consolidation by spark plasma sintering, a process we refer to as MS-SPS. This combination of processing steps leads to phase-pure n-type filled-skutterudites and obviates more energy and time intensive annealing steps. We show that both the thermoelectric properties and the tensile fracture strength compare favorably to materials made by traditional methods. The process is scalable to at least 80 g billets, such that the transport properties measured on test bars harvested from these larger billets compare favorably to those measured on lab-scale billets (5 g total billet mass). ZT values approaching 1.1 at 750 K were observed in materials made by MS-SPS. In addition, the tensile fracture strength of test bars cut from an 80 g billet is ∼128 MPa at room temperature and decreases with increasing temperature. Fractography of the test bars reveals that the majority failed due to surface and edge flaws with few failures due to volume type flaws. This indicates that the powder metallurgical methods employed to produce these samples is mature.

  15. Devices to improve the performance of a conventional two-stroke spark ignition engine

    Poola, R. B.; Nagalingam, B.; Gopalakrishnan, K. V.


    This paper presents research efforts made in three different phases with the objective of improving the fuel economy of and reducing exhaust emissions from conventional, carbureted, two-stroke spark ignition (SI) engines, which are widely employed in two-wheel transportation in India. A review concerning the existing two-stroke engine technology for this application is included. In the first phase, a new scavenging system was developed and tested to reduce the loss of fresh charge through the exhaust port. In the second phase, the following measures were carried out to improve the combustion process: (1) using an in-cylinder catalyst, such as copper, chromium, and nickel, in the form of coating; (2) providing moderate thermal insulation in the combustion chamber, either by depositing thin ceramic material or by metal inserts; (3) developing a high-energy ignition system; and (4) employing high-octane fuel, such as methanol, ethanol, eucalyptus oil, and orange oil, as a blending agent with gasoline. Based on the effectiveness of the above measures, an optimized design was developed in the final phase to achieve improved performance. Test results indicate that with an optimized two-stroke SI engine, the maximum percentage improvement in brake thermal efficiency is about 31%, together with a reduction of 3400 ppm in hydrocarbons (HC) and 3% by volume of carbon monoxide (CO) emissions over the normal engine (at 3 kW, 3000 rpm). Higher cylinder peak pressures (3-5 bar), lower ignition delay (2-4 degrees CA), and shorter combustion duration (4-10 degrees CA) are obtained. The knock-limited power output is also enhanced by 12.7% at a high compression ratio (CR) of 9:1. The proposed modifications in the optimized design are simple, low-cost, and easy to adopt for both production and existing engines.

  16. Detection bots using Spark Streaming%基于Spark Strea ming的僵尸主机检测算法

    张蕾; 李井泉; 曲武; 白涛


    The wide use of broadband Internet connections has given rise to a new threat against Internet service providers and end users as well.Botnets are vast networks of compromised hosts under the control of single masters who possess the ability to launch large-scale malicious activities such as spamming,DDoS attacks,identity theft,and phishing with privacy-violating spyware and other forms of malicious software.This paper’s goal is to introduce a novel distributed algorithm for malicious (potential bots)activity recognition based on network traffic statistics generated by IPFIX,where IPFIX related is correlated as the host IPFIX graph structure,and a feature extraction method based on the spark streaming is leveraged for exacting im-plicit characteristics.Furthermore,in order to verify the validity of the algorithm,this paper established an IPFIXScanner de-tection prototype system.Scalability and robustness were the main principles during the design of the system architecture.The experimental results show that the IPFIXScanner is able to detect botnet participant computers (bots)with the help of novel features originating from various local networks,while the algorithms provide utmost anonymity to network operators,and has approximate linear speedup.It proves the feasibility of applying spark streaming engine to distributed bots detection.%随着宽带互联网的广泛应用,产生了同时针对互联网服务提供商和用户的新型威胁,僵尸网络。僵尸网络通过多类传播和感染程序,构建一个可一对多控制的网络,操控大量僵尸主机发起DDoS攻击、发送垃圾邮件、偷窃敏感数据和钓鱼等恶意行为。基于一种分布式实时处理框架,提出一种分布式的僵尸主机检测算法。该算法能够充分利用网络流量的统计数据IPFIX,在无须深度包解析的情况下,能够识别僵尸主机行为。同时,使用该算法实现了IPFIXScanner原型系统。系统的鲁棒性和可

  17. A new spark detection system for the electrostatic septa of the SPS North (experimental) Area

    Barlow, R A; Borburgh, J; Carlier, E; Chanavat, C; Fowler, T; Pinget, B


    Electrostatic septa (ZS) are used in the extraction of the particle beams from the CERN SPS to the North Area experimental zone. These septa employ high electric fields, generated from a 300 kV power supply, and are particularly prone to internal sparking around the cathode structure. This sparking degrades the electric field quality, consequently affecting the extracted beam, vacuum and equipment performance. To mitigate these effects, a Spark Detection System (SDS) has been realised, which is based on an industrial SIEMENS S7-400 programmable logic controller and deported Boolean processor modules interfaced through a PROFINET fieldbus. The SDS interlock logic uses a moving average spark rate count to determine if the ZS performance is acceptable. Below a certain spark rate it is probable that the ZS septa tank vacuum can recover, thus avoiding transition into a state where rapid degradation would occur. Above this level an interlock is raised and the high voltage is switched off. Additionally, all spark si...

  18. Utilization of waste glycerin to fuelling of spark ignition engines

    Stelmasiak, Z.; Pietras, D.


    The paper discusses a possibilities of usage a simple alcohols to fuelling of spark ignition engines. Methanol and blends of methanol with glycerin, being a waste product from production of bio-components to fuels based on rapeseed oil, have been used in course of the investigations. The main objective of the research was to determine possibilities of utilization of glycerin to blending of engine fuels. The investigations have been performed using the Fiat 1100 MPI engine. Parameters obtained with the engine powered by pure methanol and by methanol- glycerin mixtures with 10÷30%vol content of glycerin were compared to parameters of the engine fuelled conventionally with the E95 gasoline. The investigations have shown increase of overall efficiency of the engine run on pure methanol with 2.5÷5.0%, and run on the mixture having 10% addition of glycerin with 2.0÷7.8%. Simultaneously, fuelling of the engine with the investigated alcohols results in reduced concentration of toxic components in exhaust gases like: CO, THC and NOx, as well as the greenhouse gas CO2.

  19. Reactive Spark Plasma Sintering: Successes and Challenges of Nanomaterial Synthesis

    Dina V. Dudina


    Full Text Available Spark plasma sintering (SPS, initially developed as an advanced sintering technique for consolidating nanopowders into nanostructured bulk materials, has been recently looked at in much broader perspective and gained a strong reputation of a versatile method of solid state processing of metals, ceramics, and composites. The powders in the SPS-dies experience the action of pulsed electric current and uniaxial pressure; they are heated at very high rates unachievable in furnace heating and sintered within shorter times and at lower temperatures than in conventional methods. The principle of SPS and convenient design of the facilities make it attractive for conducting solid state synthesis. In this paper, based on our own results and the literature data, we analyze the microstructure formation of the products of chemical reactions occurring in the SPS in an attempt to formulate the requirements to the microstructure parameters of reactant mixtures and SPS conditions that should be fulfilled in order to produce a nanostructured material. We present successful syntheses of nanostructured ceramics and metal matrix composite with nanosized reinforcements in terms of microstructure stability and attractive properties of the materials and discuss the challenges of making a dense nanostructured material when reaction and densification do not coincide during the SPS. In the final part of the paper, we provide an outlook on the further uses of reactive SPS in the synthesis of nanostructured materials.

  20. Electro-spark deposited coatings for protection of materials

    Johnson, R.N. [Battelle Pacific Northwest Lab., Richland, WA (United States)


    Electro-Spark Deposition (ESD) is a micro-welding process that uses short duration, high-current electrical pulses to deposit or alloy a consumable electrode material onto a metallic substrate. The coating is fused (metallurgically bonded) to the substrate with such a low total heat input that the bulk substrate material remains at or near ambient temperature. Rapid solidification of the deposit typically results in an extremely fine-grained deposit that may be amorphous for some materials. Nearly any electrically conductive metal, alloy or cermet can be applied to metallic substrates. The ESD process allows multi-layer coatings to be built-up using different materials to create graded structures or surface compositions that would be difficult to achieve by other means. A series of iron-aluminide coatings based on Fe{sub 3}Al and FeAl in combination with refractory metal diffusion-barrier coatings and supplementary additions of other elements are in corrosion testing at ANL. The most recent FeAl coatings are showing a factor of three better corrosion performance than the best previous coatings. Technology transfer activities are a significant portion of the ESD program effort. Notable successes now include the start-up of a new business to commercialize the ESD technology, major new applications in gas turbine engines and steam turbine blade coatings, and in military, medical, metal-working, and recreational equipment applications.

  1. Numerical simulation of spark ignition engine using OpenFOAM®

    B.T. Kannan


    Full Text Available The present work is the numerical investigation of Spark Ignition (SI engines using an open source Computational Fluid Dynamics (CFD tool. Investigations on the usage of OpenFOAM® CFD tool has been carried out for the simulation of SI engines using engineFoam solver. Four-valve pent roof type engine is chosen for the present simulations. The standard k–ɛ turbulence model is used along with the Reynolds Averaged Navier Stokes (RANS equations for simulating the flow field. Energy equation and transport equation for regress variable is solved along with the momentum equations. Xi model is used for the transport and Gulder's correlation is used for laminar flame speed. Unstrained model is used for calculating the laminar flame speed velocity. Two simulations are carried out one with cold flow and the other with combustion. For combustion analysis, Iso-octane fuel is used. Average cylinder pressure is tracked for different Crank Angles (CA from −180 to 60. The temperature contours are plotted on a vertical plane inside the cylinder to indicate the rise in temperature due to combustion. The results indicate that the open source CFD code can be an ideal choice for engine designers.

  2. Dynamic yield and tensile strengths of spark plasma sintered alumina

    Girlitsky, I.; Zaretsky, E.; Kalabukhov, S.; Dariel, M.; Frage, N.


    Fully dense alumina samples with 0.6 μm grain size were produced from alumina powder using Spark Plasma Sintering and tested in two types of VISAR-instrumented planar impact tests. In the tests of the first type the samples of 0.28 to 6-mm thickness were loaded by 1-mm tungsten impactors accelerated up to a velocity of about 1 km/s. These tests were aimed to study the Hugoniot elastic limit (HEL) of the SPS-processed alumina and the decay of the elastic precursor wave with propagation distance. In the second type of test the samples of ~3-mm thickness were loaded by 1-mm copper impactors accelerated up to velocities 100-1000 m/s. These tests were aimed to study the dynamic tensile (spall) strength of the alumina. The data on tensile fracture of the alumina demonstrate a monotonic decline of the spall strength with the amplitude of the loading stress pulse. The data on the decay of the elastic precursor wave allows for determining the rates of the irreversible (inelastic) strains in the SPS-processed alumina at the initial stages of shock-induced inelastic deformation and, thus, to derive some conclusions concerning the mechanisms responsible of the deformation.

  3. Experimental Investigation of Augmented Spark Ignition of a LO2/LCH4 Reaction Control Engine at Altitude Conditions

    Kleinhenz, Julie; Sarmiento, Charles; Marshall, William


    The use of nontoxic propellants in future exploration vehicles would enable safer, more cost-effective mission scenarios. One promising green alternative to existing hypergols is liquid methane (LCH4) with liquid oxygen (LO2). A 100 lbf LO2/LCH4 engine was developed under the NASA Propulsion and Cryogenic Advanced Development project and tested at the NASA Glenn Research Center Altitude Combustion Stand in a low pressure environment. High ignition energy is a perceived drawback of this propellant combination; so this ignition margin test program examined ignition performance versus delivered spark energy. Sensitivity of ignition to spark timing and repetition rate was also explored. Three different exciter units were used with the engine s augmented (torch) igniter. Captured waveforms indicated spark behavior in hot fire conditions was inconsistent compared to the well-behaved dry sparks. This suggests that rising pressure and flow rate increase spark impedance and may at some point compromise an exciter s ability to complete each spark. The reduced spark energies of such quenched deliveries resulted in more erratic ignitions, decreasing ignition probability. The timing of the sparks relative to the pressure/flow conditions also impacted the probability of ignition. Sparks occurring early in the flow could trigger ignition with energies as low as 1 to 6 mJ, though multiple, similarly timed sparks of 55 to 75 mJ were required for reliable ignition. Delayed spark application and reduced spark repetition rate both correlated with late and occasional failed ignitions. An optimum time interval for spark application and ignition therefore coincides with propellant introduction to the igniter.

  4. A stratified layer of light elements at the top of the outer core

    McDonough, W. F.; Buffett, B. A.; Cormier, V. F.; Cottaar, S.; Day, E. A.; Dou, S.; French, S. W.; Irving, J. C.; Kavner, A.; Panning, M. P.; Parai, R.; Rose, I.


    Earth’s core is thought to have formed from sinking metal diapirs that segregated at mid-mantle conditions. Consequently, the core and mantle may not be in chemical equilibrium. Recent experiments suggest that at the pressures and temperatures of the core, lower mantle oxides and silicates may have an increased solubility in iron. Geodynamic calculations predict that if a core/mantle chemical reaction delivers a flux of oxygen to the core, a low-density, stratified layer, estimated to be 60-70 km thick, may form at the top of the core. Seismological, geochemical, and mineral physics data pertinent to the conditions at the top of the core combined with geodynamic models provide critical tests of the stratified outer core hypothesis. A linear combination of normal mode observations with a composite sensitivity restricted to VP in the outermost outer core is inverted. Travel time measurements of SmKS and PmKP are obtained from seismograms stacked over dense arrays. Forward modeling tests the sensitivity of these different data to predicted seismic models, and aids in identifying features that might mask the signal, e.g., topography on the core-mantle boundary, ultra-low velocity zones, and heterogeneities in the lowermost mantle. Chemical and isotopic ratios are used to consider the residual products of putative core-mantle exchange events, together with mass and charge balance, and allow to assess compositional constraints on both the core and mantle. Development of a stable, stratified O-enriched layer at the top of the outer core over Earth history may ultimately limit chemical communication between the mantle and the rest of the outer core. Implications for movement of siderophile trace elements (e.g. W, P and Pb) across the CMB over time are evaluated. Mineral physics estimates of high pressure and temperature equations of state of relevant mantle and core materials provide data to calculate density and sound velocities at outer core conditions to predict

  5. Analyzing of the Inspiration of America SPARK Curriculum for Chinese PE%浅析美国 SPARK 课程对我国体育教学的启示



    SPARK 课程国内外的研究现状进行分析和总结,了解 SPARK 课程目前国内的研究成果和国外的实践研究和课程开展情况,探讨美国 SPARK 课程对我国体育课程的启示。%This paper analyzes and summarizes the current situation of study on SPARK curriculum at home and abroad, tries to understand the present domestic research results , foreign practice research and curriculum development of SPARK curriculum , discusses the inspiration of America SPARK curriculum for PE curriculum in China.

  6. SciSpark's SRDD : A Scientific Resilient Distributed Dataset for Multidimensional Data

    Palamuttam, R. S.; Wilson, B. D.; Mogrovejo, R. M.; Whitehall, K. D.; Mattmann, C. A.; McGibbney, L. J.; Ramirez, P.


    Remote sensing data and climate model output are multi-dimensional arrays of massive sizes locked away in heterogeneous file formats (HDF5/4, NetCDF 3/4) and metadata models (HDF-EOS, CF) making it difficult to perform multi-stage, iterative science processing since each stage requires writing and reading data to and from disk. We have developed SciSpark, a robust Big Data framework, that extends ApacheTM Spark for scaling scientific computations. Apache Spark improves the map-reduce implementation in ApacheTM Hadoop for parallel computing on a cluster, by emphasizing in-memory computation, "spilling" to disk only as needed, and relying on lazy evaluation. Central to Spark is the Resilient Distributed Dataset (RDD), an in-memory distributed data structure that extends the functional paradigm provided by the Scala programming language. However, RDDs are ideal for tabular or unstructured data, and not for highly dimensional data. The SciSpark project introduces the Scientific Resilient Distributed Dataset (sRDD), a distributed-computing array structure which supports iterative scientific algorithms for multidimensional data. SciSpark processes data stored in NetCDF and HDF files by partitioning them across time or space and distributing the partitions among a cluster of compute nodes. We show usability and extensibility of SciSpark by implementing distributed algorithms for geospatial operations on large collections of multi-dimensional grids. In particular we address the problem of scaling an automated method for finding Mesoscale Convective Complexes. SciSpark provides a tensor interface to support the pluggability of different matrix libraries. We evaluate performance of the various matrix libraries in distributed pipelines, such as Nd4jTM and BreezeTM. We detail the architecture and design of SciSpark, our efforts to integrate climate science algorithms, parallel ingest and partitioning (sharding) of A-Train satellite observations from model grids. These

  7. Spark Heat Transfer Measurements in Flowing Gases Résumé des transferts de chaleur entre une étincelle d'allumage et des écoulements gazeux

    Verhoeven D.


    Full Text Available Using a technique based on holographic interferometry, the total energy transferred from a spark to the surrounding gases was measured for a number of spark plug electrode geometries, flow velocities, gas pressures and coil charge times. A standard automotive ignition coil was used. For the combinations of parameter values studied, we observed spark efficiencies(ratio of the energy in the gas heated by the spark to the electrical energy supplied to the spark plug of from 20 to 60 percent. For realistic engine conditions we estimate the quantity of energy transferred to the gas by our ignition system to be roughly 30 mJ. We show how these measurements of total energy transferred to the gas can be used to estimate the spark power vs. time characteristic of a standard inductive ignition system. À partir de techniques basées sur l'interférométrie holographique, l'énergie totale transférée par une étincelle aux gaz environnants a été mesurée en faisant varier la géométrie des électrodes de la bougie d'allumage, la vitesse des gaz, la pression et le temps de charge de la bobine, cette dernière étant un modèle standard pour automobile. Pour les différentes combinaisons et valeurs des paramètres étudiés, il a été observé une variation du rendement d'étincelle(rapport entre l'énergie transmise aux gaz par l'étincelle à l'énergie électrique fournie à la bougie allant de 20 à 60 %. Pour des conditions réelles de fonctionnement dans un moteur, on peut estimer que l'énergie transmise aux gaz par le système d'allumage est voisine de 30 mJ. Il est aussi montré comment ces mesures de l'énergie totale transférée aux gaz, peuvent être exploitées pour caractériser en fonction du temps, la puissance transmise dans l'étincelle générée par un système standard d'allumage inductif.

  8. Study of MRI in Stratified Viscous Plasma Configuration

    Carlevaro, Nakia; Renzi, Fabrizio


    We analyze the morphology of the Magneto-rotational Instability (MRI) for a stratified viscous plasma disk configuration in differential rotation, taking into account the so-called corotation theorem for the background profile. In order to select the intrinsic Alfv\\'enic nature of MRI, we deal with an incompressible plasma and we adopt a formulation of the perturbation analysis based on the use of the magnetic flux function as a dynamical variable. Our study outlines, as consequence of the corotation condition, a marked asymmetry of the MRI with respect to the equatorial plane, particularly evident in a complete damping of the instability over a positive critical height on the equatorial plane. We also emphasize how such a feature is already present (although less pronounced) even in the ideal case, restoring a dependence of the MRI on the stratified morphology of the gravitational field.

  9. FC-normal and extended stratified logic program

    许道云; 丁德成


    This paper investigates the consistency property of FC-normal logic program and presentsan equivalent deciding condition whether a logic program P is an FC-normal program. The decidingcondition describes the characterizations of FC-normal program. By the Petri-net presentation ofa logic program, the characterizations of stratification of FC-normal program are investigated. Thestratification of FC-normal program motivates us to introduce a new kind of stratification, extendedstratification, over logic program. It is shown that an extended (locally) stratified logic program isan FC-normal program. Thus, an extended (locally) stratified logic program has at least one stablemodel. Finally, we have presented algorithms about computation of consistency property and a fewequivalent deciding methods of the finite FC-normal program.

  10. Turbulent thermal diffusion in strongly stratified turbulence: theory and experiments

    Amir, G; Eidelman, A; Elperin, T; Kleeorin, N; Rogachevskii, I


    Turbulent thermal diffusion is a combined effect of the temperature stratified turbulence and inertia of small particles. It causes the appearance of a non-diffusive turbulent flux of particles in the direction of the turbulent heat flux. This non-diffusive turbulent flux of particles is proportional to the product of the mean particle number density and the effective velocity of inertial particles. The theory of this effect has been previously developed only for small temperature gradients and small Stokes numbers (Phys. Rev. Lett. {\\bf 76}, 224, 1996). In this study a generalized theory of turbulent thermal diffusion for arbitrary temperature gradients and Stokes numbers has been developed. The laboratory experiments in the oscillating grid turbulence and in the multi-fan produced turbulence have been performed to validate the theory of turbulent thermal diffusion in strongly stratified turbulent flows. It has been shown that the ratio of the effective velocity of inertial particles to the characteristic ve...

  11. Numerical Simulation of Wakes in a Weakly Stratified Fluid

    Rottman, James W; Innis, George E; O'Shea, Thomas T; Novikov, Evgeny


    This paper describes some preliminary numerical studies using large eddy simulation of full-scale submarine wakes. Submarine wakes are a combination of the wake generated by a smooth slender body and a number of superimposed vortex pairs generated by various control surfaces and other body appendages. For this preliminary study, we attempt to gain some insight into the behavior of full-scale submarine wakes by computing separately the evolution the self-propelled wake of a slender body and the motion of a single vortex pair in both a non-stratified and a stratified environment. An important aspect of the simulations is the use of an iterative procedure to relax the initial turbulence field so that turbulent production and dissipation are in balance.

  12. Helicity dynamics in stratified turbulence in the absence of forcing

    Rorai, C; Pouquet, A; Mininni, P D


    A numerical study of decaying stably-stratified flows is performed. Relatively high stratification and moderate Reynolds numbers are considered, and a particular emphasis is placed on the role of helicity (velocity-vorticity correlations). The problem is tackled by integrating the Boussinesq equations in a periodic cubical domain using different initial conditions: a non-helical Taylor-Green (TG) flow, a fully helical Beltrami (ABC) flow, and random flows with a tunable helicity. We show that for stratified ABC flows helicity undergoes a substantially slower decay than for unstratified ABC flows. This fact is likely associated to the combined effect of stratification and large scale coherent structures. Indeed, when the latter are missing, as in random flows, helicity is rapidly destroyed by the onset of gravitational waves. A type of large-scale dissipative "cyclostrophic" balance can be invoked to explain this behavior. When helicity survives in the system it strongly affects the temporal energy decay and t...

  13. Axisymmetric modes in vertically stratified self-gravitating discs

    Mamatsashvili, George


    We perform linear analysis of axisymmetric vertical normal modes in stratified compressible self-gravitating polytropic discs in the shearing box approximation. We study specific dynamics for subadiabatic, adiabatic and superadiabatic vertical stratifications. In the absence of self-gravity, four well-known principal modes can be identified in a stratified disc: acoustic p-, surface gravity f-, buoyancy g- and inertial r-modes. After characterizing modes in the non-self-gravitating case, we include self-gravity and investigate how it modifies the properties of these modes. We find that self-gravity, to a certain degree, reduces their frequencies and changes the structure of the dispersion curves and eigenfunctions at radial wavelengths comparable to the disc height. Its influence on the basic branch of the r-mode, in the case of subadiabatic and adiabatic stratifications, and on the basic branch of the g-mode, in the case of superadiabatic stratification (which in addition exhibits convective instability), do...

  14. Elementary stratified flows with stability at low Richardson number

    Barros, Ricardo [Mathematics Applications Consortium for Science and Industry (MACSI), Department of Mathematics and Statistics, University of Limerick, Limerick (Ireland); Choi, Wooyoung [Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, New Jersey 07102-1982 (United States)


    We revisit the stability analysis for three classical configurations of multiple fluid layers proposed by Goldstein [“On the stability of superposed streams of fluids of different densities,” Proc. R. Soc. A. 132, 524 (1931)], Taylor [“Effect of variation in density on the stability of superposed streams of fluid,” Proc. R. Soc. A 132, 499 (1931)], and Holmboe [“On the behaviour of symmetric waves in stratified shear layers,” Geophys. Publ. 24, 67 (1962)] as simple prototypes to understand stability characteristics of stratified shear flows with sharp density transitions. When such flows are confined in a finite domain, it is shown that a large shear across the layers that is often considered a source of instability plays a stabilizing role. Presented are simple analytical criteria for stability of these low Richardson number flows.

  15. Experiments on the dryout behavior of stratified debris beds

    Leininger, Simon; Kulenovic, Rudi; Laurien, Eckart [Stuttgart Univ. (Germany). Inst. of Nuclear Technology and Energy Systems (IKE)


    In case of a severe accident with loss of coolant and core meltdown a particle bed (debris) can be formed. The removal of decay heat from the debris bed is of prime importance for the bed's long-term coolability to guarantee the integrity of the RPV. In contrast to previous experiments, the focus is on stratified beds. The experiments have pointed out that the bed's coolability is significantly affected.

  16. Computation of mixing in large stably stratified enclosures

    Zhao, Haihua

    This dissertation presents a set of new numerical models for the mixing and heat transfer problems in large stably stratified enclosures. Basing on these models, a new computer code, BMIX++ (Berkeley mechanistic MIXing code in C++), was developed by Christensen (2001) and the author. Traditional lumped control volume methods and zone models cannot model the detailed information about the distributions of temperature, density, and pressure in enclosures and therefore can have significant errors. 2-D and 3-D CFD methods require very fine grid resolution to resolve thin substructures such as jets, wall boundaries, yet such fine grid resolution is difficult or impossible to provide due to computational expense. Peterson's scaling (1994) showed that stratified mixing processes in large stably stratified enclosures can be described using one-dimensional differential equations, with the vertical transport by free and wall jets modeled using standard integral techniques. This allows very large reductions in computational effort compared to three-dimensional numerical modeling of turbulent mixing in large enclosures. The BMIX++ code was developed to implement the above ideas. The code uses a Lagrangian approach to solve 1-D transient governing equations for the ambient fluid and uses analytical models or 1-D integral models to compute substructures. 1-D transient conduction model for the solid boundaries, pressure computation and opening models are also included to make the code more versatile. The BMIX++ code was implemented in C++ and the Object-Oriented-Programming (OOP) technique was intensively used. The BMIX++ code was successfully applied to different types of mixing problems such as stratification in a water tank due to a heater inside, water tank exchange flow experiment simulation, early stage building fire analysis, stratification produced by multiple plumes, and simulations for the UCB large enclosure experiments. Most of these simulations gave satisfying

  17. A statistical mechanics approach to mixing in stratified fluids

    Venaille, A.; Gostiaux, L.; Sommeria, J.


    Predicting how much mixing occurs when a given amount of energy is injected into a Boussinesq fluid is a longstanding problem in stratified turbulence. The huge number of degrees of freedom involved in those processes renders extremely difficult a deterministic approach to the problem. Here we present a statistical mechanics approach yielding prediction for a cumulative, global mixing efficiency as a function of a global Richardson number and the background buoyancy profile.

  18. Corticosteroids and pediatric septic shock outcomes: a risk stratified analysis.

    Sarah J Atkinson

    Full Text Available The potential benefits of corticosteroids for septic shock may depend on initial mortality risk.We determined associations between corticosteroids and outcomes in children with septic shock who were stratified by initial mortality risk.We conducted a retrospective analysis of an ongoing, multi-center pediatric septic shock clinical and biological database. Using a validated biomarker-based stratification tool (PERSEVERE, 496 subjects were stratified into three initial mortality risk strata (low, intermediate, and high. Subjects receiving corticosteroids during the initial 7 days of admission (n = 252 were compared to subjects who did not receive corticosteroids (n = 244. Logistic regression was used to model the effects of corticosteroids on 28-day mortality and complicated course, defined as death within 28 days or persistence of two or more organ failures at 7 days.Subjects who received corticosteroids had greater organ failure burden, higher illness severity, higher mortality, and a greater requirement for vasoactive medications, compared to subjects who did not receive corticosteroids. PERSEVERE-based mortality risk did not differ between the two groups. For the entire cohort, corticosteroids were associated with increased risk of mortality (OR 2.3, 95% CI 1.3-4.0, p = 0.004 and a complicated course (OR 1.7, 95% CI 1.1-2.5, p = 0.012. Within each PERSEVERE-based stratum, corticosteroid administration was not associated with improved outcomes. Similarly, corticosteroid administration was not associated with improved outcomes among patients with no comorbidities, nor in groups of patients stratified by PRISM.Risk stratified analysis failed to demonstrate any benefit from corticosteroids in this pediatric septic shock cohort.

  19. On the Impact of Bootstrap in Stratified Random Sampling

    LIU Cheng; ZHAO Lian-wen


    In general the accuracy of mean estimator can be improved by stratified random sampling. In this paper, we provide an idea different from empirical methods that the accuracy can be more improved through bootstrap resampling method under some conditions. The determination of sample size by bootstrap method is also discussed, and a simulation is made to verify the accuracy of the proposed method. The simulation results show that the sample size based on bootstrapping is smaller than that based on central limit theorem.

  20. Stability of stratified two-phase flows in inclined channels

    Barmak, I.; Gelfgat, A. Yu.; Ullmann, A.; Brauner, N.


    Linear stability of the stratified gas-liquid and liquid-liquid plane-parallel flows in the inclined channels is studied with respect to all wavenumber perturbations. The main objective is to predict the parameter regions in which the stable stratified configuration in inclined channels exists. Up to three distinct base states with different holdups exist in the inclined flows, so that the stability analysis has to be carried out for each branch separately. Special attention is paid to the multiple solution regions to reveal the feasibility of the non-unique stable stratified configurations in inclined channels. The stability boundaries of each branch of the steady state solutions are presented on the flow pattern map and are accompanied by the critical wavenumbers and the spatial profiles of the most unstable perturbations. Instabilities of different nature are visualized by the streamlines of the neutrally stable perturbed flows, consisting of the critical perturbation superimposed on the base flow. The present analysis confirms the existence of two stable stratified flow configurations in a region of low flow rates in the countercurrent liquid-liquid flows. These configurations become unstable with respect to the shear mode of instability. It was revealed that in slightly upward inclined flows the lower and middle solutions for the holdup are stable in the part of the triple solution region, while the upper solution is always unstable. In the case of downward flows, in the triple solution region, none of the solutions are stable with respect to the short-wave perturbations. These flows are stable only in the single solution region at low flow rates of the heavy phase, and the long-wave perturbations are the most unstable ones.

  1. Thermal stratification built up in hot water tank with different inlet stratifiers

    Dragsted, Janne; Furbo, Simon; Dannemand, Mark


    H is a rigid plastic pipe with holes for each 30 cm. The holes are designed with flaps preventing counter flow into the pipe. The inlet stratifier from EyeCular Technologies ApS is made of a flexible polymer with openings all along the side and in the full length of the stratifier. The flexibility...... in order to elucidate how well thermal stratification is established in the tank with differently designed inlet stratifiers under different controlled laboratory conditions. The investigated inlet stratifiers are from Solvis GmbH & Co KG and EyeCular Technologies ApS. The inlet stratifier from Solvis Gmb...... of the stratifier prevents counterflow. The tests have shown that both types of inlet stratifiers had an ability to create stratification in the test tank under the different test conditions. The stratifier from EyeCular Technologies ApS had a better performance at low flows of 1-2 l/min and the stratifier...

  2. Diesel engines vs. spark ignition gasoline engines -- Which is ``greener``?

    Fairbanks, J.W. [Dept. of Energy, Washington, DC (United States)


    Criteria emissions, i.e., NO{sub x}, PM, CO, CO{sub 2}, and H{sub 2}, from recently manufactured automobiles, compared on the basis of what actually comes out of the engines, the diesel engine is greener than spark ignition gasoline engines and this advantage for the diesel engine increases with time. SI gasoline engines tend to get out of tune more than diesel engines and 3-way catalytic converters and oxygen sensors degrade with use. Highway measurements of NO{sub 2}, H{sub 2}, and CO revealed that for each model year, 10% of the vehicles produce 50% of the emissions and older model years emit more than recent model year vehicles. Since 1974, cars with SI gasoline engines have uncontrolled emission until the 3-way catalytic converter reaches operating temperature, which occurs after roughly 7 miles of driving. Honda reports a system to be introduced in 1998 that will alleviate this cold start problem by storing the emissions then sending them through the catalytic converter after it reaches operating temperature. Acceleration enrichment, wherein considerable excess fuel is introduced to keep temperatures down of SI gasoline engine in-cylinder components and catalytic converters so these parts meet warranty, results in 2,500 times more CO and 40 times more H{sub 2} being emitted. One cannot kill oneself, accidentally or otherwise, with CO from a diesel engine vehicle in a confined space. There are 2,850 deaths per year attributable to CO from SI gasoline engine cars. Diesel fuel has advantages compared with gasoline. Refinery emissions are lower as catalytic cracking isn`t necessary. The low volatility of diesel fuel results in a much lower probability of fires. Emissions could be improved by further reducing sulfur and aromatics and/or fuel additives. Reformulated fuel has become the term covering reducing the fuels contribution to emissions. Further PM reduction should be anticipated with reformulated diesel and gasoline fuels.

  3. What sparks the radio-loud phase of nearby quasars?

    Coziol, Roger; Andernach, Heinz; Torres-Papaqui, Juan Pablo; Ortega-Minakata, René Alberto; Moreno del Rio, Froylan


    To better constrain the hypotheses proposed to explain why only a few quasars are radio loud (RL), we compare the characteristics of 1958 nearby (z ≤ 0.3) SDSS (Sloan Digital Sky Survey) quasars, covered by the FIRST (Faint Images of the Radio Sky at Twenty-centimeters) and NVSS (NRAO VLA Sky Survey) radio surveys. Only 22 per cent are RL with log (L1.4 GHz) ≥ 22.5 W Hz-1, the majority being compact (C), weak radio sources (WRS), with log (L1.4 GHz) radio morphologies: 3 per cent have a core and a jet (J), 2 per cent have a core with one lobe (L), and 10 per cent have a core with two lobes (T), the majority being powerful radio sources (PRS), with log (L1.4 GHz) ≥ 24.5 W Hz-1. In general, RL quasars have higher bolometric luminosities and ionization powers than radio-quiet (RQ) quasars. The WRS have comparable black hole (BH) masses as the RQ quasars, but higher accretion rates or radiative efficiencies. The PRS have higher BH masses than the WRS, but comparable accretion rates or radiative efficiencies. The WRS also have higher FWHM_{[O iii]} than the PRS, consistent with a coupling of the spectral characteristics of the quasars with their radio morphologies. Inspecting the SDSS images and applying a neighbour search algorithm reveal no difference between the RQ and RL quasars of their host galaxies, environments, and interaction. Our results prompt the conjecture that the phenomenon that sparks the RL phase in quasars is transient, intrinsic to the active galactic nuclei, and stochastic, due to the chaotic nature of the accretion process of matter on to the BHs.

  4. Review: Fuel Volatility Standards and Spark-Ignition Vehicle Driveability

    Yanowitz, Janet; McCormick, Robert L.


    We've put spark-ignition engine fuel standards in place in order to ensure acceptable hot and cold weather driveability (HWD and CWD). Vehicle manufacturers and fuel suppliers have developed systems that meet our driveability requirements so effectively that drivers overwhelmingly find that their vehicles reliably start up and operate smoothly and consistently throughout the year. For HWD, fuels that are too volatile perform more poorly than those that are less volatile. Vapor lock is the apparent cause of poor HWD, but there is conflicting evidence in the literature as to where in the fuel system it occurs. Most studies have found a correlation between degraded driveability and higher dry vapor pressure equivalent or lower TV/L = 20, and less consistently with a minimum T50. For CWD, fuels with inadequate volatility can cause difficulty in starting and rough operation during engine warmup. The Driveability Index (DI)-a function of T10, T50, and T90-is well correlated with CWD in hydrocarbon fuels. For ethanol-containing fuels, a correction factor to the DI equation improves the correlation with CWD, although the best value for that factor has still not been determined. Ethanol increases the heat of vaporization. But, this is likely insignificant for E15 and lower concentration fuels. The impact of ethanol on driveability is likely due to its direct effect on vapor pressure at cold temperatures. For E51-E83 or flex-fuel blends, ASTM sets a minimum vapor pressure; however, published data suggest that a correction for the amount of ethanol in the fuel is needed to accurately predict CWD, possibly because ethanol has a higher lower-flammability limit.

  5. Nanosecond repetitively pulsed discharges in air at atmospheric pressure—the spark regime

    Pai, David Z.; Lacoste, Deanna A.; Laux, Christophe O.


    Nanosecond repetitively pulsed (NRP) spark discharges have been studied in atmospheric pressure air preheated to 1000 K. Measurements of spark initiation and stability, plasma dynamics, gas temperature and current-voltage characteristics of the spark regime are presented. Using 10 ns pulses applied repetitively at 30 kHz, we find that 2-400 pulses are required to initiate the spark, depending on the applied voltage. Furthermore, about 30-50 pulses are required for the spark discharge to reach steady state, following initiation. Based on space- and time-resolved optical emission spectroscopy, the spark discharge in steady state is found to ignite homogeneously in the discharge gap, without evidence of an initial streamer. Using measured emission from the N2 (C-B) 0-0 band, it is found that the gas temperature rises by several thousand Kelvin in the span of about 30 ns following the application of the high-voltage pulse. Current-voltage measurements show that up to 20-40 A of conduction current is generated, which corresponds to an electron number density of up to 1015 cm-3 towards the end of the high-voltage pulse. The discharge dynamics, gas temperature and electron number density are consistent with a streamer-less spark that develops homogeneously through avalanche ionization in volume. This occurs because the pre-ionization electron number density of about 1011 cm-3 produced by the high frequency train of pulses is above the critical density for streamer-less discharge development, which is shown to be about 108 cm-3.

  6. Stratified source-sampling techniques for Monte Carlo eigenvalue analysis.

    Mohamed, A.


    In 1995, at a conference on criticality safety, a special session was devoted to the Monte Carlo ''Eigenvalue of the World'' problem. Argonne presented a paper, at that session, in which the anomalies originally observed in that problem were reproduced in a much simplified model-problem configuration, and removed by a version of stratified source-sampling. In this paper, stratified source-sampling techniques are generalized and applied to three different Eigenvalue of the World configurations which take into account real-world statistical noise sources not included in the model problem, but which differ in the amount of neutronic coupling among the constituents of each configuration. It is concluded that, in Monte Carlo eigenvalue analysis of loosely-coupled arrays, the use of stratified source-sampling reduces the probability of encountering an anomalous result over that if conventional source-sampling methods are used. However, this gain in reliability is substantially less than that observed in the model-problem results.

  7. Stability of stratified two-phase flows in horizontal channels

    Barmak, I.; Gelfgat, A.; Vitoshkin, H.; Ullmann, A.; Brauner, N.


    Linear stability of stratified two-phase flows in horizontal channels to arbitrary wavenumber disturbances is studied. The problem is reduced to Orr-Sommerfeld equations for the stream function disturbances, defined in each sublayer and coupled via boundary conditions that account also for possible interface deformation and capillary forces. Applying the Chebyshev collocation method, the equations and interface boundary conditions are reduced to the generalized eigenvalue problems solved by standard means of numerical linear algebra for the entire spectrum of eigenvalues and the associated eigenvectors. Some additional conclusions concerning the instability nature are derived from the most unstable perturbation patterns. The results are summarized in the form of stability maps showing the operational conditions at which a stratified-smooth flow pattern is stable. It is found that for gas-liquid and liquid-liquid systems, the stratified flow with a smooth interface is stable only in confined zone of relatively low flow rates, which is in agreement with experiments, but is not predicted by long-wave analysis. Depending on the flow conditions, the critical perturbations can originate mainly at the interface (so-called "interfacial modes of instability") or in the bulk of one of the phases (i.e., "shear modes"). The present analysis revealed that there is no definite correlation between the type of instability and the perturbation wavelength.

  8. Continuous Dependence on the Density for Stratified Steady Water Waves

    Chen, Robin Ming; Walsh, Samuel


    There are two distinct regimes commonly used to model traveling waves in stratified water: continuous stratification, where the density is smooth throughout the fluid, and layer-wise continuous stratification, where the fluid consists of multiple immiscible strata. The former is the more physically accurate description, but the latter is frequently more amenable to analysis and computation. By the conservation of mass, the density is constant along the streamlines of the flow; the stratification can therefore be specified by prescribing the value of the density on each streamline. We call this the streamline density function. Our main result states that, for every smoothly stratified periodic traveling wave in a certain small-amplitude regime, there is an L ∞ neighborhood of its streamline density function such that, for any piecewise smooth streamline density function in that neighborhood, there is a corresponding traveling wave solution. Moreover, the mapping from streamline density function to wave is Lipschitz continuous in a certain function space framework. As this neighborhood includes piecewise smooth densities with arbitrarily many jump discontinues, this theorem provides a rigorous justification for the ubiquitous practice of approximating a smoothly stratified wave by a layered one. We also discuss some applications of this result to the study of the qualitative features of such waves.

  9. Survival analysis of cervical cancer using stratified Cox regression

    Purnami, S. W.; Inayati, K. D.; Sari, N. W. Wulan; Chosuvivatwong, V.; Sriplung, H.


    Cervical cancer is one of the mostly widely cancer cause of the women death in the world including Indonesia. Most cervical cancer patients come to the hospital already in an advanced stadium. As a result, the treatment of cervical cancer becomes more difficult and even can increase the death's risk. One of parameter that can be used to assess successfully of treatment is the probability of survival. This study raises the issue of cervical cancer survival patients at Dr. Soetomo Hospital using stratified Cox regression based on six factors such as age, stadium, treatment initiation, companion disease, complication, and anemia. Stratified Cox model is used because there is one independent variable that does not satisfy the proportional hazards assumption that is stadium. The results of the stratified Cox model show that the complication variable is significant factor which influent survival probability of cervical cancer patient. The obtained hazard ratio is 7.35. It means that cervical cancer patient who has complication is at risk of dying 7.35 times greater than patient who did not has complication. While the adjusted survival curves showed that stadium IV had the lowest probability of survival.

  10. Internal combustion engines a detailed introduction to the thermodynamics of spark and compression ignition engines, their design and development

    Benson, Rowland S


    Internal Combustion of Engines: A Detailed Introduction to the Thermodynamics of Spark and Compression Ignition Engines, Their Design and Development focuses on the design, development, and operations of spark and compression ignition engines. The book first describes internal combustion engines, including rotary, compression, and indirect or spark ignition engines. The publication then discusses basic thermodynamics and gas dynamics. Topics include first and second laws of thermodynamics; internal energy and enthalpy diagrams; gas mixtures and homocentric flow; and state equation. The text ta

  11. Modeling calcium wave based on anomalous subdiffusion of calcium sparks in cardiac myocytes.

    Xi Chen

    Full Text Available Ca(2+ sparks and Ca(2+ waves play important roles in calcium release and calcium propagation during the excitation-contraction (EC coupling process in cardiac myocytes. Although the classical Fick's law is widely used to model Ca(2+ sparks and Ca(2+ waves in cardiac myocytes, it fails to reasonably explain the full-width at half maximum(FWHM paradox. However, the anomalous subdiffusion model successfully reproduces Ca(2+ sparks of experimental results. In this paper, in the light of anomalous subdiffusion of Ca(2+ sparks, we develop a mathematical model of calcium wave in cardiac myocytes by using stochastic Ca(2+ release of Ca(2+ release units (CRUs. Our model successfully reproduces calcium waves with physiological parameters. The results reveal how Ca(2+ concentration waves propagate from an initial firing of one CRU at a corner or in the middle of considered region, answer how large in magnitude of an anomalous Ca(2+ spark can induce a Ca(2+ wave. With physiological Ca(2+ currents (2pA through CRUs, it is shown that an initial firing of four adjacent CRUs can form a Ca(2+ wave. Furthermore, the phenomenon of calcium waves collision is also investigated.

  12. Parameter sensitivity analysis of stochastic models provides insights into cardiac calcium sparks.

    Lee, Young-Seon; Liu, Ona Z; Hwang, Hyun Seok; Knollmann, Bjorn C; Sobie, Eric A


    We present a parameter sensitivity analysis method that is appropriate for stochastic models, and we demonstrate how this analysis generates experimentally testable predictions about the factors that influence local Ca(2+) release in heart cells. The method involves randomly varying all parameters, running a single simulation with each set of parameters, running simulations with hundreds of model variants, then statistically relating the parameters to the simulation results using regression methods. We tested this method on a stochastic model, containing 18 parameters, of the cardiac Ca(2+) spark. Results show that multivariable linear regression can successfully relate parameters to continuous model outputs such as Ca(2+) spark amplitude and duration, and multivariable logistic regression can provide insight into how parameters affect Ca(2+) spark triggering (a probabilistic process that is all-or-none in a single simulation). Benchmark studies demonstrate that this method is less computationally intensive than standard methods by a factor of 16. Importantly, predictions were tested experimentally by measuring Ca(2+) sparks in mice with knockout of the sarcoplasmic reticulum protein triadin. These mice exhibit multiple changes in Ca(2+) release unit structures, and the regression model both accurately predicts changes in Ca(2+) spark amplitude (30% decrease in model, 29% decrease in experiments) and provides an intuitive and quantitative understanding of how much each alteration contributes to the result. This approach is therefore an effective, efficient, and predictive method for analyzing stochastic mathematical models to gain biological insight.

  13. Sparking connections: An exploration of adolescent girls' relationships with science

    Wheeler, Kathryn A.

    Despite progress in narrowing the gender gap, fewer women than men pursue science careers. Adolescence is a critical age when girls' science interest is sparked or smothered. Prior research provides data on who drops out of the "science pipeline" and when, but few studies examine why and how girls disconnect from science. This thesis is an in-depth exploratory study of adolescent girls' relationships with science based on a series of interviews with four middle-class Caucasian girls---two from public schools, two homeschooled. The girls' stones about their experiences with, feelings about, and perspectives on science, the science process, and their science learning environments are examined with a theoretical and analytic approach grounded in relational psychology. The potential link between girls' voices and their involvement in science is investigated. Results indicate that girls' relationships with science are multitiered. Science is engaging and familiar in the sense that girls are curious about the world, enjoy learning about scientific phenomena, and informally use science in their everyday fives. However, the girls in this study differentiated between the science they do and the field of science, which they view as a mostly male endeavor (often despite real life experiences to the contrary) that uses rather rigid methods to investigate questions of limited scope and interest. In essence, how these girls defined science defined their relationship with science: those with narrow conceptions of science felt distant from it. Adolescent girls' decreased involvement in science activities may be a relational act---a move away from a patriarchical process, pedagogy, and institution that does not resonate with their experiences, questions, and learning styles. Girls often feel like outsiders to science; they resist considering science careers when they have concerns that implicitly or explicitly, doing so would involve sacrificing their knowledge, creativity, or

  14. Development And Testing Of Biogas-Petrol Blend As An Alternative Fuel For Spark Ignition Engine



    Full Text Available Abstract This research is on the development and testing of a biogas-petrol blend to run a spark ignition engine. A2080 ratio biogaspetrol blend was developed as an alternative fuel for spark ignition engine test bed. Petrol and biogas-petrol blend were comparatively tested on the test bed to determine the effectiveness of the fuels. The results of the tests showed that biogas petrol blend generated higher torque brake power indicated power brake thermal efficiency and brake mean effective pressure but lower fuel consumption and exhaust temperature than petrol. The research concluded that a spark ignition engine powered by biogas-petrol blend was found to be economical consumed less fuel and contributes to sanitation and production of fertilizer.

  15. Reliable prediction of electric spark sensitivity of nitramines: a general correlation with detonation pressure.

    Keshavarz, Mohammad Hossein; Pouretedal, Hamid Reza; Semnani, Abolfazl


    For nitramines, a general correlation has been introduced to predict electric spark sensitivity through detonation pressure. New method uses maximum obtainable detonation pressure as a fundamental relation so that it can be corrected for some nitramines which have some specific molecular structure. There is no need to use crystal density and heat of formation of nitramine explosives for predicting detonation pressure and electric spark sensitivity. The predicted electric spark sensitivities are compared with calculated results on the basis of quantum mechanical computations for some nitramines that latter can be applied. The root mean square (rms) deviations from experiment for new method and the predicted results of complicated quantum mechanical method are 1.18 and 3.49J, respectively.

  16. Apparatus for atmospheric pressure pin-to-hole spark discharge and uses thereof

    Dobrynin, Danil V.; Fridman, Alexander; Cho, Young I.; Fridman, Gregory; Friedman, Gennady


    Disclosed herein are atmospheric pressure pin-to-hole pulsed spark discharge devices and methods for creating plasma. The devices include a conduit for fluidically communicating a gas, a plasma, or both, therethrough, portion of the conduit capable of being connected to a gas supply, and a second portion of the conduit capable of emitting a plasma; a positive electrode comprising a sharp tip; and a ground plate electrode. Disclosed are methods for treating a skin ulcer using non-thermal plasma include flowing a gas through a cold spark discharge zone simultaneously with the creation of a pulsed spark discharge to give rise to a non-thermal plasma emitted from a conduit, the non-thermal plasma comprising NO; and contacting a skin ulcer with said non-thermal plasma for sufficient time and intensity to give rise to treatment of the skin ulcer.

  17. Magnetic Field in the Gravitationally Stratified Coronal Loops

    B. N. Dwivedi; A. K. Srivastava


    We study the effect of gravitational stratification on the estimation of magnetic fields in the coronal loops. By using the method of MHD seismology of kink waves for the estimation of magnetic field of coronal loops, we derive a new formula for the magnetic field considering the effect of gravitational stratification. The fast-kink wave is a potential diagnostic tool for the estimation of magnetic field in fluxtubes. We consider the eleven kink oscillation cases observed by TRACE between July 1998 and June 2001. We calculate magnetic field in the stratified loops (str) and compare them with the previously calculated absolute magnetic field (abs). The gravitational stratification efficiently affects the magnetic field estimation in the coronal loops as it affects also the properties of kink waves. We find ≈22% increment in the magnetic field for the smallest ( = 72 Mm) while ≈42% increment in the absolute magnetic field for the longest ( = 406 Mm) coronal loops. The magnetic fields str and abs also increase with the number density, if the loop length does not vary much. The increment in the magnetic field due to gravitational stratification is small at the lower number densities, however, it is large at the higher number densities. We find that damping time of kink waves due to phase-mixing is less in the case of gravitationally stratified loops compared to nonstratified ones. This indicates the more rapid damping of kink waves in the stratified loops. In conclusion, we find that the gravitational stratification efficiently affects the estimation of magnetic field and damping time estimation especially in the longer coronal loops.

  18. Experimental Study of Fluorine Transport Rules in Unsaturated Stratified Soil

    ZHANG Hong-mei; SU Bao-yu; LIU Peng-hua; ZHANG Wei


    With the aid of soil column test models, the transport rules of fluorine contaminants in unsaturated stratified soils are discussed. Curves of F- concentrations at different times and sites in the unsaturated stratified soil were obtained under conditions of continuous injection of fluoride contaminants and water. Based on the analysis of the actual observation data, the values between computed results and observed data were compared. It is shown that the chemical properties of fluorine ions are active. The migration process of fluorine ions in soils is complex. Because of the effect of adsorption and desorption, the curve of the fluorine ion breakthrough curve is not symmetric. Its concentration peak value at each measuring point gradually decays. The tail of the breakthrough curve is long and the process of leaching and purifying using water requires considerable time. Along with the release of OHˉ in the process of fluorine absorption, the pH value of the soil solution changed from neutral to alkalinity during the test process. The first part of the breakthrough curve fitted better than the second part. The main reason is that fluorine does not always exist in the form of fluorinions in groundwater. Given the long test time, fluorinions possibly react with other ions in the soil solution to form complex water-soluble fluorine compounds. Only the retardation factor and source-sink term have been considered in our numerical model, which may leads to errors of computed values. But as a whole the migration rules of fluorine ions are basically correct, which indicates that the established numerical model can be used to simulate the transport rules of fluorine contaminants in unsaturated stratified soils.

  19. Stratified spin-up in a sliced, square cylinder

    Munro, R. J. [Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Foster, M. R. [Department of Mathematical Sciences, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)


    We previously reported experimental and theoretical results on the linear spin-up of a linearly stratified, rotating fluid in a uniform-depth square cylinder [M. R. Foster and R. J. Munro, “The linear spin-up of a stratified, rotating fluid in a square cylinder,” J. Fluid Mech. 712, 7–40 (2012)]. Here we extend that analysis to a “sliced” square cylinder, which has a base-plane inclined at a shallow angle α. Asymptotic results are derived that show the spin-up phase is achieved by a combination of the Ekman-layer eruptions (from the perimeter region of the cylinder's lid and base) and cross-slope-propagating stratified Rossby waves. The final, steady state limit for this spin-up phase is identical to that found previously for the uniform depth cylinder, but is reached somewhat more rapidly on a time scale of order E{sup −1/2}Ω{sup −1}/log (α/E{sup 1/2}) (compared to E{sup −1/2}Ω{sup −1} for the uniform-depth cylinder), where Ω is the rotation rate and E the Ekman number. Experiments were performed for Burger numbers, S, between 0.4 and 16, and showed that for S≳O(1), the Rossby modes are severely damped, and it is only at small S, and during the early stages, that the presence of these wave modes was evident. These observations are supported by the theory, which shows the damping factors increase with S and are numerically large for S≳O(1)

  20. Comparison of hospital-wide and age and location - stratified antibiograms of S. aureus, E. coli, and S. pneumoniae: age- and location-stratified antibiograms


    Background Antibiograms created by aggregating hospital-wide susceptibility data from diverse patients can be misleading. To demonstrate the utility of age- and location-stratified antibiograms, we compared stratified antibiograms for three common bacterial pathogens, E. coli, S. aureus, and S. pneumoniae. We created stratified antibiograms based on patient age (/=65 years), and inpatient or outpatient location using all 2009 E. coli and S. aureus, and all 2008–2009 S. pneumoniae isolates sub...

  1. Electromagnetic fields due to dipole antennas over stratified anisotropic media.

    Kong, J. A.


    Solutions to the problem of radiation of dipole antennas in the presence of a stratified anisotropic media are facilitated by decomposing a general wave field into transverse magnetic (TM) and transverse electric (TE) modes. Employing the propagation matrices, wave amplitudes in any region are related to those in any other regions. The reflection coefficients, which embed all the information about the geometrical configuration and the physical constituents of the medium, are obtained in closed form. In view of the general formulation, various special cases are discussed.

  2. Instabilities developed in stratified flows over pronounced obstacles

    Varela, J.; Araújo, M.; Bove, I.; Cabeza, C.; Usera, G.; Martí, Arturo C.; Montagne, R.; Sarasúa, L. G.


    In the present work we study numerical and experimentally the flow of a two-layer stratified fluid over a topographic obstacle. The problem reflects a wide number of oceanographic and meteorological situations, where the stratification plays an important role. We identify the different instabilities developed by studying the pycnocline deformation due to a pronounced obstacle. The numerical simulations were made using the model caffa3D.MB which works with a numerical model of Navier-Stokes equations with finite volume elements in curvilinear meshes. The experimental results are contrasted with numerical simulations. Linear stability analysis predictions are checked with particle image velocimetry (PIV) measurements.

  3. Stratified waveguide grating coupler for normal fiber incidence.

    Wang, Bin; Jiang, Jianhua; Chambers, Diana M; Cai, Jingbo; Nordin, Gregory P


    We propose a new stratified waveguide grating coupler (SWGC) to couple light from a fiber at normal incidence into a planar waveguide. SWGCs are designed to operate in the strong coupling regime without intermediate optics between the fiber and the waveguide. Two-dimensional finite-difference time-domain simulation in conjunction with microgenetic algorithm optimization shows that approximately 72% coupling efficiency is possible for fiber (core size of 8.3 microm and delta=0.36%) to slab waveguide (1.2-microm core and delta=3.1%) coupling. We show that the phase-matching and Bragg conditions are simultaneously satisfied through the fundamental leaky mode.

  4. Magnetorotational instability in weakly ionised, stratified accretion discs

    Salmeron, Roberto Aureliano; Salmeron, Raquel; Wardle, Mark


    The magnetorotational instability (MRI) (Balbus and Hawley 1991, Hawley and Balbus 1991) transports angular momentum radially outwards in accretion discs through the distortion of the magnetic field lines that connect fluid elements. In protostellar discs, low conductivity is important, especially in the inner regions (Gammie 1996, Wardle 1997). As a result, low k modes are relevant and vertical stratification is a key factor of the analysis. However, most models of the MRI in these environments have adopted either the ambipolar diffusion or resistive approximations and have not simultaneously treated stratification and Hall conductivity. We present here a linear analysis of the MRI, including the Hall effect, in a stratified disc.

  5. ClimateSpark: An In-memory Distributed Computing Framework for Big Climate Data Analytics

    Hu, F.; Yang, C. P.; Duffy, D.; Schnase, J. L.; Li, Z.


    Massive array-based climate data is being generated from global surveillance systems and model simulations. They are widely used to analyze the environment problems, such as climate changes, natural hazards, and public health. However, knowing the underlying information from these big climate datasets is challenging due to both data- and computing- intensive issues in data processing and analyzing. To tackle the challenges, this paper proposes ClimateSpark, an in-memory distributed computing framework to support big climate data processing. In ClimateSpark, the spatiotemporal index is developed to enable Apache Spark to treat the array-based climate data (e.g. netCDF4, HDF4) as native formats, which are stored in Hadoop Distributed File System (HDFS) without any preprocessing. Based on the index, the spatiotemporal query services are provided to retrieve dataset according to a defined geospatial and temporal bounding box. The data subsets will be read out, and a data partition strategy will be applied to equally split the queried data to each computing node, and store them in memory as climateRDDs for processing. By leveraging Spark SQL and User Defined Function (UDFs), the climate data analysis operations can be conducted by the intuitive SQL language. ClimateSpark is evaluated by two use cases using the NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) climate reanalysis dataset. One use case is to conduct the spatiotemporal query and visualize the subset results in animation; the other one is to compare different climate model outputs using Taylor-diagram service. Experimental results show that ClimateSpark can significantly accelerate data query and processing, and enable the complex analysis services served in the SQL-style fashion.

  6. Streamer-to-spark transition initiated by a nanosecond overvoltage pulsed discharge in air

    Lo, A.; Cessou, A.; Lacour, C.; Lecordier, B.; Boubert, P.; Xu, D. A.; Laux, C. O.; Vervisch, P.


    This study is focused on the streamer-to-spark transition generated by an overvoltage nanosecond pulsed discharge under atmospheric pressure air in order to provide a quantitative insight into plasma-assisted ignition. The discharge is generated in atmospheric pressure air by the application of a positive high voltage pulse of 35 kV to pin-to-pin electrodes and a rise time of 5 ns. The generated discharge consists of a streamer phase with high voltage and high current followed by a spark phase characterized by a low voltage and a decreasing current in several hundreds of nanosecond. During the streamer phase, the gas temperature measured by optical emission spectroscopy related to the second positive system of nitrogen shows an ultra-fast gas heating up to 1200 K at 15 ns after the current rise. This ultra-fast gas heating, due to the quenching of electronically excited species by oxygen molecules, is followed by a quick dissociation of molecules and then the discharge transition to a spark. At this transition, the discharge contracts toward the channel axis and evolves into a highly conducting thin column. The spark phase is characterized by a high degree of ionization of nitrogen and oxygen atoms shown by the electron number density and temperature measured from optical emission spectroscopy measurements of N+ lines. Schlieren imaging and optical emission spectroscopy techniques provide the time evolution of the spark radius, from which the initial pressure in the spark is estimated. The expansion of the plasma is adiabatic in the early phase. The electronic temperature and density during this phase allows the determination of the isentropic coefficient. The value around 1.2-1.3 is coherent with the high ionization rate of the plasma in the early phase. The results obtained in this study provide a database and the initial conditions for the validation of numerical simulations of the ignition by plasma discharge.

  7. SciDB versus Spark: A Preliminary Comparison Based on an Earth Science Use Case

    Clune, T.; Kuo, K. S.; Doan, K.; Oloso, A.


    We compare two Big Data technologies, SciDB and Spark, for performance, usability, and extensibility, when applied to a representative Earth science use case. SciDB is a new-generation parallel distributed database management system (DBMS) based on the array data model that is capable of handling multidimensional arrays efficiently but requires lengthy data ingest prior to analysis, whereas Spark is a fast and general engine for large scale data processing that can immediately process raw data files and thereby avoid the ingest process. Once data have been ingested, SciDB is very efficient in database operations such as subsetting. Spark, on the other hand, provides greater flexibility by supporting a wide variety of high-level tools including DBMS's. For the performance aspect of this preliminary comparison, we configure Spark to operate directly on text or binary data files and thereby limit the need for additional tools. Arguably, a more appropriate comparison would involve exploring other configurations of Spark which exploit supported high-level tools, but that is beyond our current resources. To make the comparison as "fair" as possible, we export the arrays produced by SciDB into text files (or converting them to binary files) for the intake by Spark and thereby avoid any additional file processing penalties. The Earth science use case selected for this comparison is the identification and tracking of snowstorms in the NASA Modern Era Retrospective-analysis for Research and Applications (MERRA) reanalysis data. The identification portion of the use case is to flag all grid cells of the MERRA high-resolution hourly data that satisfies our criteria for snowstorm, whereas the tracking portion connects flagged cells adjacent in time and space to form a snowstorm episode. We will report the results of our comparisons at this presentation.

  8. A-Stratified Computerized Adaptive Testing with Unequal Item Exposure across Strata.

    Deng, Hui; Chang, Hua-Hua

    The purpose of this study was to compare a proposed revised a-stratified, or alpha-stratified, USTR method of test item selection with the original alpha-stratified multistage computerized adaptive testing approach (STR) and the use of maximum Fisher information (FSH) with respect to test efficiency and item pool usage using simulated computerized…

  9. Tabitha Sparks, The Doctor in the Victorian Novel : Family Practices

    Escuret, Annie


    Tabitha Sparks’s The Doctor in the Victorian Novel: Family Practices looks at the trajectory of the figure of the doctor in Victorian literature, examining its evolution from the mid-1820s to the turn of the century. For Sparks, the doctor is, indeed, both a barometer of the evolution of the medical profession and of the Victorian novel. It is, in particular, through the variations of the marriage-plot that Spark traces the impact of the medical figure, oscillating between an index of social ...

  10. Welding of titanium and nickel alloy by combination of explosive welding and spark plasma sintering technologies

    Malyutina, Yu. N., E-mail:; Bataev, A. A., E-mail:; Shevtsova, L. I., E-mail: [Novosibirsk State Technical University, Novosibirsk, 630073 (Russian Federation); Mali, V. I., E-mail:; Anisimov, A. G., E-mail: [Lavrentyev Institute of Hydrodynamics SB RAS, Novosibirsk, 630090 (Russian Federation)


    A possibility of titanium and nickel-based alloys composite materials formation using combination of explosive welding and spark plasma sintering technologies was demonstrated in the current research. An employment of interlayer consisting of copper and tantalum thin plates makes possible to eliminate a contact between metallurgical incompatible titanium and nickel that are susceptible to intermetallic compounds formation during their interaction. By the following spark plasma sintering process the bonding has been received between titanium and titanium alloy VT20 through the thin powder layer of pure titanium that is distinguished by low defectiveness and fine dispersive structure.

  11. Welding of titanium and nickel alloy by combination of explosive welding and spark plasma sintering technologies

    Malyutina, Yu. N.; Bataev, A. A.; Mali, V. I.; Anisimov, A. G.; Shevtsova, L. I.


    A possibility of titanium and nickel-based alloys composite materials formation using combination of explosive welding and spark plasma sintering technologies was demonstrated in the current research. An employment of interlayer consisting of copper and tantalum thin plates makes possible to eliminate a contact between metallurgical incompatible titanium and nickel that are susceptible to intermetallic compounds formation during their interaction. By the following spark plasma sintering process the bonding has been received between titanium and titanium alloy VT20 through the thin powder layer of pure titanium that is distinguished by low defectiveness and fine dispersive structure.

  12. Capacitive Gap Distance Control in Pin-Plane electrode DC Spark Systems at CERN



    Capacitive inter-electrode gap distance measurement and control has been implemented into DC Spark System II, used by the DC Spark Study to conduct vacuum electrical breakdown experiments as a complement to breakdown experiments in RF accelerating structures. The implemented system is described, along with the calibration measurements needed for its use. Sources of experimental uncertainty in gap distance were investigated. It was found that the lowest relative uncertainty of gap distance the system is capable of achieving is 3%, or an absolute uncertainty of about 1 μm for a 30 μm gap.

  13. Numerical simulation and analysis of energy loss in a nanosecond spark gap switch

    Lavrinovich, I. V.; Oreshkin, V. I.


    A system of differential equations for the RLC circuit of a capacitor-switch assembly was derived being supplemented with an equation for the spark resistance of the switch in accordance with the Braginsky model. The parameters that affect the solutions of equations for the circuit with parallel or series connection of several capacitor-switch assemblies to a common inductive load were determined. Based on numerical solution of the system of equations, a dependence of the energy ES released in the spark within the first halfperiod on the discharge circuit and switch parameters was found.

  14. The concept of isochoric central spark ignition and its fuel gain in inertial fusion

    Kuzmin, A D


    One of the best methods in inertial confinement fusion (ICF) is the concept of central spark ignition, consisting of two distinct regions named as hot and cold regions and formed by hydro-dynamical implosion of fuel micro-sphere central spark ignition method in inertial fusion and fuel pellet design condition in fusion power plant has been investigated and fuel gain for isochoric model in this method is calculated. We have shown the effects of different physical parameters of inertial fusion on fuel gain and optimized limit for fuel density and fuel pellet radius has been calculated.

  15. Microwaves spark emission spectroscopy for the analysis of cations: A simple form of atomic emission spectroscopy

    Zahid Hussain; Khalid Mohammed Khan; Khadim Hussain; Sadam Hussain; Shahnaz Perveen


    A novel method for the cation analysis was investigated. The analysis is based on the sparking of the salts of metals in a microwave oven after placing in a graphite cell. The graphite cell absorbs microwaves and produces high temperature which converts the salt into light emitting species. The colour of light was found to dependent on the nature of cation, however, the intensity of the emitted light was found to be depending upon the form and shape of the graphite assembly in addition to the concentration of the salt. This communication presents explanation for all these observations and for the systematic and quantitative analysis using microwave spark emission technique.

  16. Impulse tests on distribution transformers protected by means of spark gaps

    Pykaelae, M.L.; Palva, V. [Helsinki Univ. of Technology, Otaniemi (Finland). High Voltage Institute; Niskanen, K. [ABB Corporate Research, Vaasa (Finland)


    Distribution transformers in rural networks have to cope with transient overvoltages, even with those caused by the direct lightning strokes to the lines. In Finland the 24 kV network conditions, such as wooden pole lines, high soil resistivity and isolated neutral network, lead into fast transient overvoltages. Impulse testing of pole-mounted distribution transformers ({<=} 200 kVA) protected by means of spark gaps were studied. Different failure detection methods were used. Results can be used as background information for standardization work dealing with distribution transformers protected by means of spark gaps. (orig.) 9 refs.

  17. Multifurcation Assembly of Charged Aerosols and Its Application to 3D Structured Gas Sensors.

    Bae, Yongjun; Pikhitsa, Peter V; Cho, Hyesung; Choi, Mansoo


    Multifurcated assemblies composed of charged nanoparticles (NPs) are fabricated by using spark discharge and manipulating the electric field. The multifurcated structure of the assembly of NPs and spontaneous interconnections between the near structures are described. The gas sensor with the tetrafurcated-NP-assembled structure demonstrates ≈200% enhanced response to 100 ppm CO at 300 °C. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. 基于 Spark 的社交网络特性分析%Analysis of the Characteristics of Social Network Based on Spark

    邢立国; 吕琼帅


    With the continued penetration of the Internet,social network has developed rapidly,and become a research focus. In the era of big data,social networks have the characteristics of a great amount of data which traditional analytical techniques can not handle with. This paper analyzes the characteristics of social networks with Spark distribution computing system.%随着互联网对社会的持续渗透,社交网络得到了迅猛发展,也成为研究的一个热点。在大数据时代,社交网络具有数据量极大的特点,传统的分析技术不能胜任。利用 Spark 分布式计算系统,进行了社交网络的特性分析。

  19. Effect of Spark Motor Program on the development of gross motor skills in intellectually disabled educable boys

    Hashem Faal Moganloo


    Results: Spark Program caused significant changes in all the variables of the study, except speed and agility, in the experimental group after 24 sessions. The changes included: agility and speed (P=0.731, balance (P=0, strength (P=0.002, and bilateral coordination (P=0. Conclusion: Spark Motor Program can improve gross motor skills in intellectually disabled educable students.

  20. CHARGE Association

    Semanti Chakraborty


    Full Text Available We present here a case of 17-year-old boy from Kolkata presenting with obesity, bilateral gynecomastia, mental retardation, and hypogonadotrophic hypogonadism. The patient weighed 70 kg and was of 153 cm height. Facial asymmetry (unilateral facial palsy, gynecomastia, decreased pubic and axillary hair, small penis, decreased right testicular volume, non-palpable left testis, and right-sided congenital inguinal hernia was present. The patient also had disc coloboma, convergent squint, microcornea, microphthalmia, pseudohypertelorism, low set ears, short neck, and choanalatresia. He had h/o VSD repaired with patch. Laboratory examination revealed haemoglobin 9.9 mg/dl, urea 24 mg/dl, creatinine 0.68 mg/dl. IGF1 77.80 ng/ml (decreased for age, GH <0.05 ng/ml, testosterone 0.25 ng/ml, FSH-0.95 ΅IU/ml, LH 0.60 ΅IU/ml. ACTH, 8:00 A.M cortisol, FT3, FT4, TSH, estradiol, DHEA-S, lipid profile, and LFT was within normal limits. Prolactin was elevated at 38.50 ng/ml. The patient′s karyotype was 46XY. Echocardiography revealed ventricularseptal defect closed with patch, grade 1 aortic regurgitation, and ejection fraction 67%. Ultrasound testis showed small right testis within scrotal sac and undescended left testis within left inguinal canal. CT scan paranasal sinuses revealed choanalatresia and deviation of nasal septum to the right. Sonomammography revealed bilateral proliferation of fibroglandular elements predominantly in subareoalar region of breasts. MRI of brain and pituitary region revealed markedly atrophic pituitary gland parenchyma with preserved infundibulum and hypothalamus and widened suprasellar cistern. The CHARGE association is an increasingly recognized non-random pattern of congenital anomalies comprising of coloboma, heart defect, choanal atresia, retarded growth and development, genital hypoplasia, ear abnormalities, and/or deafness. [1] These anomalies have a higher probability of occurring together. In this report, we have

  1. Sequential stratified sampling belief propagation for multiple targets tracking


    Rather than the difficulties of highly non-linear and non-Gaussian observation process and the state distribution in single target tracking, the presence of a large, varying number of targets and their interactions place more challenge on visual tracking. To overcome these difficulties, we formulate multiple targets tracking problem in a dynamic Markov network which consists of three coupled Markov random fields that model the following: a field for joint state of multi-target, one binary process for existence of individual target, and another binary process for occlusion of dual adjacent targets. By introducing two robust functions, we eliminate the two binary processes, and then apply a novel version of belief propagation called sequential stratified sampling belief propagation algorithm to obtain the maximum a posteriori (MAP) estimation in the dynamic Markov network. By using stratified sampler, we incorporate bottom-up information provided by a learned detector (e.g. SVM classifier) and belief information for the messages updating. Other low-level visual cues (e.g. color and shape) can be easily incorporated in our multi-target tracking model to obtain better tracking results. Experimental results suggest that our method is comparable to the state-of-the-art multiple targets tracking methods in several test cases.

  2. Penetrative convection in stratified fluids: velocity and temperature measurements

    M. Moroni


    Full Text Available The flux through the interface between a mixing layer and a stable layer plays a fundamental role in characterizing and forecasting the quality of water in stratified lakes and in the oceans, and the quality of air in the atmosphere. The evolution of the mixing layer in a stably stratified fluid body is simulated in the laboratory when "Penetrative Convection" occurs. The laboratory model consists of a tank filled with water and subjected to heating from below. The methods employed to detect the mixing layer growth were thermocouples for temperature data and two image analysis techniques, namely Laser Induced Fluorescence (LIF and Feature Tracking (FT. LIF allows the mixing layer evolution to be visualized. Feature Tracking is used to detect tracer particle trajectories moving within the measurement volume. Pollutant dispersion phenomena are naturally described in the Lagrangian approach as the pollutant acts as a tag of the fluid particles. The transilient matrix represents one of the possible tools available for quantifying particle dispersion during the evolution of the phenomenon.


    Bobileva Tatiana Nikolaevna


    Full Text Available Almost all subsurface rocks used as foundations for various types of structures are stratified. Such heterogeneity may cause specific behaviour of the materials under strain. Differential equations describing the behaviour of such materials contain rapidly fluctuating coefficients, in view of this, solution of such equations is more time-consuming when using today’s computers. The method of asymptotic averaging leads to getting homogeneous medium under study to averaged equations with fixed factors. The present article is concerned with stratified soil mass consisting of pair-wise alternative isotropic elastic layers. In the results of elastic modules averaging, the present soil mass with horizontal rock stratification is simulated by homogeneous transversal-isotropic half-space with isotropy plane perpendicular to the standing axis. Half-space is loosened by a vertical alveole of circular cross-section, and virgin ground is under its own weight. For horizontal parting planes of layers, the following two types of surface conditions are set: ideal contact and backlash without cleavage. For homogeneous transversal-isotropic half-space received with a vertical alveole, the analytical solution of S.G. Lekhnitsky, well known in scientific papers, is used. The author gives expressions for stress components and displacements in soil mass for different marginal conditions on the alveole surface. Such research problems arise when constructing and maintaining buildings and when composite materials are used.

  4. Stability of steam-water countercurrent stratified flow

    Lee, S C


    Two flow instabilities which limit the normal condensation processes in countercurrent stratified steam-water flow have been identified experimentally: flooding and condensation-induced waterhammer. In order to initiate condensation-induced waterhammer in nearly horizontal or moderately-inclined steam/subcooled-water flow, two conditions, the appearance of a wavy interface and complete condensation of the incoming steam, are necessary. Analyses of these conditions are performed on a basis of flow stability and heat transfer considerations. Flooding data for several inclinations and channel heights are collected. Effects of condensation, inclination angle and channel height on the flooding characteristics are discussed. An envelope theory for the onset of flooding in inclined stratified flow is developed, which agrees well with the experimental data. Some empirical information on basic flow parameters, such as mean film thickness and interfacial friction factor required for this theory are measured. The previous viewpoints on flooding appear not to conflict with the present experimental data in nearly horizontal flow but the flooding phenomena in nearly vertical flow appear to be more complicated than those described by these viewpoints because of liquid droplet entrainment.

  5. Strongly Stratified Turbulence Wakes and Mixing Produced by Fractal Wakes

    Dimitrieva, Natalia; Redondo, Jose Manuel; Chashechkin, Yuli; Fraunie, Philippe; Velascos, David


    This paper describes Shliering and Shadowgraph experiments of the wake induced mixing produced by tranversing a vertical or horizontal fractal grid through the interfase between two miscible fluids at low Atwood and Reynolds numbers. This is a configuration design to models the mixing across isopycnals in stably-stratified flows in many environmental relevant situations (either in the atmosphere or in the ocean. The initial unstable stratification is characterized by a reduced gravity: g' = gΔρ ρ where g is gravity, Δρ being the initial density step and ρ the reference density. Here the Atwood number is A = g' _ 2 g . The topology of the fractal wake within the strong stratification, and the internal wave field produces both a turbulent cascade and a wave cascade, with frecuen parametric resonances, the envelope of the mixing front is found to follow a complex non steady 3rd order polinomial function with a maximum at about 4-5 Brunt-Vaisalla non-dimensional time scales: t/N δ = c1(t/N) + c2g Δρ ρ (t/N)2 -c3(t/N)3. Conductivity probes and Shliering and Shadowgraph visual techniques, including CIV with (Laser induced fluorescence and digitization of the light attenuation across the tank) are used in order to investigate the density gradients and the three-dimensionality of the expanding and contracting wake. Fractal analysis is also used in order to estimate the fastest and slowest growing wavelengths. The large scale structures are observed to increase in wave-length as the mixing progresses, and the processes involved in this increase in scale are also examined.Measurements of the pointwise and horizontally averaged concentrations confirm the picture obtained from past flow visualization studies. They show that the fluid passes through the mixing region with relatively small amounts of molecular mixing,and the molecular effects only dominate on longer time scales when the small scales have penetrated through the large scale structures. The Non

  6. Preliminary investigation into the simulation of a laser-induced plasma by means of a floating object in a spark gap

    West, NJ


    Full Text Available In this research, an orthogonally laser-triggered spark gap is investigated. The laser beam is directed in the region of a 30mm spark gap at 90 degrees to the gap and focused on the axis. The influence of plasma position within the spark gap...

  7. Preparing Magnetocaloric LaFeSi Uniform Microstructures by Spark Plasma Sintering

    Vicente, N.; Ocanã, J.; Neves Bez, Henrique


    Spark Plasma Sintering (SPS) of LaFeSi alloy powders was conducted to prepare magnetocaloric La-Fe-Si-based uniform microstructures. Two electrically insulating discs made of alumina were interposed between the punches and powder sample inhibiting the flow of electric current across the powder......’s microhardness by means of ANOVA statistics....

  8. Influence of spark plasma sintering and baghdadite powder on mechanical properties of hydroxyapatite

    Khandan, A.; Karamian, E.; Mehdikhani-Nahrkhalaji, M.; Mirmohammadi, H.; Farzadi, A.; Ozada, N.; Heidarshenas, B.; Zamani, K.


    Since hydroxyapatite-based materials have similar composition and crystallinity as natural calcified tissues, can be used for bone/tissue engineering. In the present study a novel nanocomposite based on bioceramics such as Natural Hydroxyapatite (NHA) and Baghdadite (BAG), was sintered by spark plas

  9. Towards the Industrial Application of Spark Ablation for Nanostructured Functional Materials

    Pfeiffer, T.V.


    Nanostructuring of functional materials is an essential part in the design of energy related devices – but the industrial tools we have to make these materials are lacking. This dissertation explores the green, flexible, and scalable spark discharge process for the fabrication of complex




    The article presents the investigation results of the biological stability of the waste and regenerated lubricating oil Mysella-40, designed for high-speed engines with spark ignition. Biocides were prepared to protect the oil from microbial destruction. It was found that the use of biocides in the recommended concentration has no negative effect on the basic performance of the lubricating oil.

  11. Damping Resonant Current in a Spark-Gap Trigger Circuit to Reduce Noise


    gap (multichannel linear spark-gap) switched system based on a quarter-module of AFRL’s Shiva Star Capacitor Bank. For this, the noise interferes... Shiva Star Capacitor Bank. For this, the noise interferes with an unintegrated measurement needed of the loads local electric field. The noise source

  12. Dependence of Nanoparticles Synthesis Energy Consumption in the Gas Spark Discharge on Circuit Parameters

    D.A. Mylnikov


    Full Text Available In this paper, we study the specific energy of titanium dioxide nanoparticles synthesis in a spark discharge in the air by varying the parameters of a discharge circuit. The dependence shows a maximum at a capacitor voltage of about 2 kV and a monotonic decrease with increasing voltage.

  13. Towards the Industrial Application of Spark Ablation for Nanostructured Functional Materials

    Pfeiffer, T.V.


    Nanostructuring of functional materials is an essential part in the design of energy related devices – but the industrial tools we have to make these materials are lacking. This dissertation explores the green, flexible, and scalable spark discharge process for the fabrication of complex nanostructu

  14. Sparking Passion: Engaging Student Voice through Project-Based Learning in Learning Communities

    Ball, Christy L.


    How do we confront entrenched educational practices in higher education that lead to student demotivation, poor retention, and low persistence? This article argues that project-based learning that situates student voice and capacity at the center of culturally-responsive curriculum has the potential to spark student passion for problem-solving…

  15. 75 FR 62853 - Reno-Sparks Indian Colony Liquor Control Ordinance


    ...-Mart Superstore to sell liquor on tribal lands, which will general millions of dollars in sales revenue and increase funding for essential government services provided by the Reno-Sparks Indian Colony. The ordinance will increase the ability of the tribal government to control the distribution and possession of...

  16. Knock Detection in Spark Ignition Engines Base on Complementary Ensemble Empirical Mode Decomposition-Hilbert Transform

    Fengrong Bi


    Full Text Available In spark ignition engines, knock onset limits the maximum spark advance. An inaccurate identification of this limit penalises the fuel conversion efficiency. Thus knock feature extraction is the key of closed-loop control of ignition in spark ignition engine. This paper reports an investigation of knock detection in spark ignition (SI engines using CEEMD-Hilbert transform based on the engine cylinder pressure signals and engine cylinder block vibration signals. Complementary Ensemble Empirical Mode Decomposition (CEEMD was used to decompose the signal and detect knock characteristic. Hilbert transform was used to analyze the frequency information of knock characteristic. The result shows that, for both of cylinder pressure signals and vibration signals, the CEEMD algorithm could extract the knock characteristic, and the Hilbert transform result shows that the energy of knock impact areas has the phenomenon of frequency concentration in both cylinder pressure signal and cylinder block vibration signal. At last, the knock window is then determined, based on which a new knock intensity evaluation factor K is propose, and it can accurately distinguish between heavy knock, light knock, and normal combustion three states.

  17. Enhancement of flame development by microwave-assisted spark ignition in constant volume combustion chamber

    Wolk, Benjamin


    The enhancement of laminar flame development using microwave-assisted spark ignition has been investigated for methane-air mixtures at a range of initial pressures and equivalence ratios in a 1.45. l constant volume combustion chamber. Microwave enhancement was evaluated on the basis of several parameters including flame development time (FDT) (time for 0-10% of total net heat release), flame rise time (FRT) (time for 10-90% of total net heat release), total net heat release, flame kernel growth rate, flame kernel size, and ignitability limit extension. Compared to a capacitive discharge spark, microwave-assisted spark ignition extended the lean and rich ignition limits at all pressures investigated (1.08-7.22. bar). The addition of microwaves to a capacitive discharge spark reduced FDT and increased the flame kernel size for all equivalence ratios tested and resulted in increases in the spatial flame speed for sufficiently lean flames. Flame enhancement is believed to be caused by (1) a non-thermal chemical kinetic enhancement from energy deposition to free electrons in the flame front and (2) induced flame wrinkling from excitation of flame (plasma) instability. The enhancement of flame development by microwaves diminishes as the initial pressure of the mixture increases, with negligible flame enhancement observed above 3. bar. © 2013 The Combustion Institute.

  18. Flash (Ultra-Rapid) Spark-Plasma Sintering of Silicon Carbide

    Olevsky, Eugene A.; Rolfing, Stephen M.; Maximenko, Andrey L.


    A new ultra-rapid process of flash spark plasma sintering is developed. The idea of flash spark plasma sintering (or flash hot pressing - FHP) stems from the conducted theoretical analysis of the role of thermal runaway phenomena for material processing by flash sintering. The major purpose of the present study is to theoretically analyze the thermal runaway nature of flash sintering and to experimentally address the challenge of uncontrollable thermal conditions by the stabilization of the flash sintering process through the application of the external pressure. The effectiveness of the developed FHP technique is demonstrated by the few seconds-long consolidation of SiC powder in an industrial spark plasma sintering device. Specially designed sacrificial dies heat the pre-compacted SiC powder specimens to a critical temperature before applying any voltage to the powder volume and allowing the electrode-punches of the SPS device setup to contact the specimens and pass electric current through them under elevated temperatures. The experimental results demonstrate that flash sintering phenomena can be realized using conventional SPS devices. The usage of hybrid heating SPS devices is pointed out as the mainstream direction for the future studies and utilization of the new flash hot pressing (ultra-rapid spark plasma sintering) technique.

  19. Spark Ignition of Combustible Vapor in a Plastic Bottle as a Demonstration of Rocket Propulsion

    Mattox, J. R.


    I report an innovation that provides a compelling demonstration of rocket propulsion, appropriate for students of physics and other physical sciences. An electrical spark is initiated from a distance to cause the deflagration of a combustible vapor mixed with air in a lightweight plastic bottle that is consequently propelled as a rocket by the…

  20. High thermoelectric performance of reduced lanthanide molybdenum oxides densified by spark plasma sintering

    Xu, Jianxiao Jackie; Sonne, Monica; Yanangiya, Shun-ichi


    Four highly reduced molybdenum oxides LnMo8O14 (Ln = La, Ce, Nd and Sm) containing bicapped Mo8 clusters were synthesized via solid state reaction followed by spark plasma sintering. The thermoelectric properties were investigated, and NdMo8O14 exhibits the best performance with the maximum power...

  1. Large-scale virtual screening on public cloud resources with Apache Spark.

    Capuccini, Marco; Ahmed, Laeeq; Schaal, Wesley; Laure, Erwin; Spjuth, Ola


    Structure-based virtual screening is an in-silico method to screen a target receptor against a virtual molecular library. Applying docking-based screening to large molecular libraries can be computationally expensive, however it constitutes a trivially parallelizable task. Most of the available parallel implementations are based on message passing interface, relying on low failure rate hardware and fast network connection. Google's MapReduce revolutionized large-scale analysis, enabling the processing of massive datasets on commodity hardware and cloud resources, providing transparent scalability and fault tolerance at the software level. Open source implementations of MapReduce include Apache Hadoop and the more recent Apache Spark. We developed a method to run existing docking-based screening software on distributed cloud resources, utilizing the MapReduce approach. We benchmarked our method, which is implemented in Apache Spark, docking a publicly available target receptor against [Formula: see text]2.2 M compounds. The performance experiments show a good parallel efficiency (87%) when running in a public cloud environment. Our method enables parallel Structure-based virtual screening on public cloud resources or commodity computer clusters. The degree of scalability that we achieve allows for trying out our method on relatively small libraries first and then to scale to larger libraries. Our implementation is named Spark-VS and it is freely available as open source from GitHub ( abstract.

  2. Spark plasma-sintered Sn-based intermetallic alloys and their Li-storage studies

    Nithyadharseni, P


    Full Text Available In the present study, SnSb, SnSb/Fe, SnSb/Co, and SnSb/Ni alloy powders processed by co-precipitation were subjected to spark plasma-sintering (SPS) at 400 °C for 5 min. The compacts were structurally and morphologically characterized by X...

  3. The SPARK Programs: A Public Health Model of Physical Education Research and Dissemination

    McKenzie, Thomas L.; Sallis, James F.; Rosengard, Paul; Ballard, Kymm


    SPARK [Sports, Play, and Active Recreation for Kids], in its current form, is a brand that represents a collection of exemplary, research-based, physical education and physical activity programs that emphasize a highly active curriculum, on-site staff development, and follow-up support. Given its complexity (e.g., multiple school levels, inclusion…

  4. Hydrodynamics of stratified epithelium: steady state and linearized dynamics

    Yeh, Wei-Ting


    A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue is assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description for tissue dynamics at long-wavelength, long-time limit is developed, and the analysis reveals important insight for the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface could enhance small perturbations. This destabilizing mechanism is general for continuous self-renewal multi-layered tissues, it could be related to the origin of certain tissue morphology and developing pattern.

  5. Hydrodynamics of stratified epithelium: Steady state and linearized dynamics

    Yeh, Wei-Ting; Chen, Hsuan-Yi


    A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue are assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description of tissue dynamics at the long-wavelength, long-time limit is developed, and the analysis reveals important insights into the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface enhances small perturbations. This destabilizing mechanism is general for continuous self-renewal multilayered tissues; it could be related to the origin of certain tissue morphology, tumor growth, and the development pattern.

  6. Local Radiation MHD Instabilities in Magnetically Stratified Media

    Tao, Ted


    We study local radiation magnetohydrodynamic instabilities in static, optically thick, vertically stratified media with constant flux mean opacity. We include the effects of vertical gradients in a horizontal background magnetic field. Assuming rapid radiative diffusion, we use the zero gas pressure limit as an entry point for investigating the coupling between the photon bubble instability and the Parker instability. Apart from factors that depend on wavenumber orientation, the Parker instability exists for wavelengths longer than a characteristic wavelength lambda_{tran}, while photon bubbles exist for wavelengths shorter than lambda_{tran}. The growth rate in the Parker regime is independent of the orientation of the horizontal component of the wavenumber when radiative diffusion is rapid, but the range of Parker-like wavenumbers is extended if there exists strong horizontal shear between field lines (i.e. horizontal wavenumber perpendicular to the magnetic field). Finite gas pressure introduces an additio...

  7. The Risk-Stratified Osteoporosis Strategy Evaluation study (ROSE)

    Rubin, Katrine Hass; Holmberg, Teresa; Rothmann, Mette Juel


    The risk-stratified osteoporosis strategy evaluation study (ROSE) is a randomized prospective population-based study investigating the effectiveness of a two-step screening program for osteoporosis in women. This paper reports the study design and baseline characteristics of the study population....... 35,000 women aged 65-80 years were selected at random from the population in the Region of Southern Denmark and-before inclusion-randomized to either a screening group or a control group. As first step, a self-administered questionnaire regarding risk factors for osteoporosis based on FRAX......(®) was issued to both groups. As second step, subjects in the screening group with a 10-year probability of major osteoporotic fractures ≥15 % were offered a DXA scan. Patients diagnosed with osteoporosis from the DXA scan were advised to see their GP and discuss pharmaceutical treatment according to Danish...

  8. Short-wave vortex instability in stratified flow

    Bovard, Luke


    In this paper we investigate a new instability of the Lamb-Chaplygin dipole in a stratified fluid. Through numerical linear stability analysis, a secondary peak in the growth rate emerges at vertical scales about an order of magnitude smaller than the buoyancy scale $L_{b}=U/N$ where $U$ is the characteristic velocity and $N$ is the Brunt-V\\"{a}is\\"{a}l\\"{a} frequency. This new instability exhibits a growth rate that is similar to, and even exceeds, that of the zigzag instability, which has the characteristic length of the buoyancy scale. This instability is investigated for a wide range of Reynolds $Re=2000-20000$ and horizontal Froude numbers $F_{h}=0.05-0.2$, where $F_{h}=U/NR$, $Re=UR/\

  9. A study of stratified gas-liquid pipe flow

    Johnson, George W.


    This work includes both theoretical modelling and experimental observations which are relevant to the design of gas condensate transport lines. Multicomponent hydrocarbon gas mixtures are transported in pipes over long distances and at various inclinations. Under certain circumstances, the heavier hydrocarbon components and/or water vapour condense to form one or more liquid phases. Near the desired capacity, the liquid condensate and water is efficiently transported in the form of a stratified flow with a droplet field. During operating conditions however, the flow rate may be reduced allowing liquid accumulation which can create serious operational problems due to large amounts of excess liquid being expelled into the receiving facilities during production ramp-up or even in steady production in severe cases. In particular, liquid tends to accumulate in upward inclined sections due to insufficient drag on the liquid from the gas. To optimize the transport of gas condensates, a pipe diameters should be carefully chosen to account for varying flow rates and pressure levels which are determined through the knowledge of the multiphase flow present. It is desirable to have a reliable numerical simulation tool to predict liquid accumulation for various flow rates, pipe diameters and pressure levels which is not presently accounted for by industrial flow codes. A critical feature of the simulation code would include the ability to predict the transition from small liquid accumulation at high flow rates to large liquid accumulation at low flow rates. A semi-intermittent flow regime of roll waves alternating with a partly backward flowing liquid film has been observed experimentally to occur for a range of gas flow rates. Most of the liquid is transported in the roll waves. The roll wave regime is not well understood and requires fundamental modelling and experimental research. The lack of reliable models for this regime leads to inaccurate prediction of the onset of

  10. Turbulent reconnection of magnetic bipoles in stratified turbulence

    Jabbari, Sarah; Mitra, Dhrubaditya; Kleeorin, Nathan; Rogachevskii, Igor


    We consider strongly stratified forced turbulence in a plane-parallel layer with helicity and corresponding large-scale dynamo action in the lower part and nonhelical turbulence in the upper. The magnetic field is found to develop strongly concentrated bipolar structures near the surface. They form elongated bands with a sharp interface between opposite polarities. Unlike earlier experiments with imposed magnetic field, the inclusion of rotation does not strongly suppress the formation of these structures. We perform a systematic numerical study of this phenomenon by varying magnetic Reynolds number, scale separation ratio, and Coriolis number. We also focus on the formation of the current sheet between bipolar regions where reconnection of oppositely oriented field lines occurs. We determine the reconnection rate by measuring either the inflow velocity in the vicinity of the current sheet or by measuring the electric field in the reconnection region. We demonstrate that for small Lundquist number, S1000, the...

  11. Direct simulation of the stably stratified turbulent Ekman layer

    Coleman, G. N.; Ferziger, J. H.; Spalart, P. R.


    The Navier-Stokes equations and the Boussinesq approximation were used to compute a 3D time-dependent turbulent flow in the stably stratified Ekman layer over a smooth surface. The simulation data are found to be in very good agreement with atmospheric measurements when nondimensionalized according to Nieuwstadt's local scaling scheme. Results suggest that, when Reynolds number effects are taken into account, the 'constant Froud number' stable layer model (Brost and Wyngaard, 1978) and the 'shearing length' stable layer model (Hunt, 1985) for the dissipitation rate of turbulent kinetic energy are both valid. It is concluded that there is good agreement between the direct numerical simulation results and large-eddy simulation results obtained by Mason and Derbyshire (1990).

  12. Inertial modes of non-stratified superfluid neutron stars

    Prix, R; Andersson, N


    We present results concerning adiabatic inertial-mode oscillations of non-stratified superfluid neutron stars in Newtonian gravity, using the anelastic and slow-rotation approximations. We consider a simple two-fluid model of a superfluid neutron star, where one fluid consists of the superfluid neutrons and the second fluid contains all the comoving constituents (protons, electrons). The two fluids are assumed to be ``free'' in the sense that vortex-mediated forces like mutual friction or pinning are absent, but they can be coupled by the equation of state, in particular by entrainment. The stationary background consists of the two fluids rotating uniformly around the same axis with potentially different rotation rates. We study the special cases of co-rotating backgrounds, vanishing entrainment, and the purely toroidal r-modes, analytically. We calculate numerically the eigenfunctions and frequencies of inertial modes in the general case of non co-rotating backgrounds, and study their dependence on the relat...

  13. Magnetorotational instability in stratified, weakly ionised accretion discs

    Salmeron, Roberto Aureliano; Salmeron, Raquel; Wardle, Mark


    We present a linear analysis of the vertical structure and growth of the magnetorotational instability in stratified, weakly ionised accretion discs, such as protostellar and quiescent dwarf novae systems. The method includes the effects of the magnetic coupling, the conductivity regime of the fluid and the strength of the magnetic field, which is initially vertical. The conductivity is treated as a tensor and assumed constant with height. We obtained solutions for the structure and growth rate of global unstable modes for different conductivity regimes, strengths of the initial magnetic field and coupling between ionised and neutral components of the fluid. The envelopes of short-wavelenght perturbations are determined by the action of competing local growth rates at different heights, driven by the vertical stratification of the disc. Ambipolar diffusion perturbations peak consistently higher above the midplane than modes including Hall conductivity. For weak coupling, perturbations including the Hall effec...

  14. Second order closure for stratified convection: bulk region and overshooting

    Biferale, L; Sbragaglia, M; Scagliarini, A; Toschi, F; Tripiccione, R


    The parameterization of small-scale turbulent fluctuations in convective systems and in the presence of strong stratification is a key issue for many applied problems in oceanography, atmospheric science and planetology. In the presence of stratification, one needs to cope with bulk turbulent fluctuations and with inversion regions, where temperature, density -or both- develop highly non-linear mean profiles due to the interactions between the turbulent boundary layer and the unmixed -stable- flow above/below it. We present a second order closure able to cope simultaneously with both bulk and boundary layer regions, and we test it against high-resolution state-of-the-art 2D numerical simulations in a convective and stratified belt for values of the Rayleigh number, up to Ra = 10^9. Data are taken from a Rayleigh-Taylor system confined by the existence of an adiabatic gradient.

  15. Oxygenation of Stratified Reservoir Using Air Bubble Plume

    Schladow, S. G.


    Excess nutrients loading from urban area and watershed into lakes and reservoirs increases the content of organic matter, which, through decomposition, needs increased dissolve oxygen (DO). Many eutrophic reservoirs and lakes cannot meet the DO requirement during stratified season and suffers from the hypolimnetic anoxia. As a result, benthic sediment produces anoxic products such as methane, hydrogen sulphide, ammonia, iron, manganese, and phosphorus. In order to address the hypolimnetic anoxia, oxygen is artificially supplied into reservoir using an aeration system (i.e., bubbler). The most common result of lake/reservoir aeration is to destratify the reservoir so that the water body may completely mix under natural phenomena and remain well oxygenated throughout. Other advantages of destratification are: (1) allows warm- water fish to inhabit the entire reservoir, (2) suppress the nutrient release from sediment, and (3) decreases the algal growth by sending them to the darker zone. A one-dimensional reservoir-bubbler model is developed and applied to examine the effects of an aeration system on mixing and dissolved oxygen dynamics in the Upper Peirce Reservoir, Singapore. After introduction of the aeration system in the reservoir, it was found that the hypolimnetic DO increased significantly, and the concentration of algae, soluble manganese and iron substantially reduced. It is found that the reservoir-bubbler model predicts the mixing (temperature as mixing parameter) and dissolved oxygen concentration in the reservoir with acceptable accuracy. It is shown in terms of bubbler mechanical efficiency (i.e., operating cost) and total DO contribution from the aeration system into the reservoir that the selections of airflow rate per diffuser, air bubble radius, and total number of diffusers are important design criteria of a bubbler system. However, the overall bubbler design also depends on the reservoir size and stratified area of interest, ambient climate, and

  16. Nonlinear gravity-wave interactions in stratified turbulence

    Remmel, Mark; Sukhatme, Jai; Smith, Leslie M.


    To investigate the dynamics of gravity waves in stratified Boussinesq flows, a model is derived that consists of all three-gravity-wave-mode interactions (the GGG model), excluding interactions involving the vortical mode. The GGG model is a natural extension of weak turbulence theory that accounts for exact three-gravity-wave resonances. The model is examined numerically by means of random, large-scale, high-frequency forcing. An immediate observation is a robust growth of the so-called vertically sheared horizontal flow (VSHF). In addition, there is a forward transfer of energy and equilibration of the nonzero-frequency (sometimes called "fast") gravity-wave modes. These results show that gravity-wave-mode interactions by themselves are capable of systematic interscale energy transfer in a stratified fluid. Comparing numerical simulations of the GGG model and the full Boussinesq system, for the range of Froude numbers ( Fr) considered (0.05 ≤ Fr ≤ 1), in both systems the VSHF is hardest to resolve. When adequately resolved, VSHF growth is more vigorous in the GGG model. Furthermore, a VSHF is observed to form in milder stratification scenarios in the GGG model than the full Boussinesq system. Finally, fully three-dimensional nonzero-frequency gravity-wave modes equilibrate in both systems and their scaling with vertical wavenumber follows similar power-laws. The slopes of the power-laws obtained depend on Fr and approach -2 (from above) at Fr = 0.05, which is the strongest stratification that can be properly resolved with our computational resources.

  17. Visualization periodic flows in a continuously stratified fluid.

    Bardakov, R.; Vasiliev, A.


    To visualize the flow pattern of viscous continuously stratified fluid both experimental and computational methods were developed. Computational procedures were based on exact solutions of set of the fundamental equations. Solutions of the problems of flows producing by periodically oscillating disk (linear and torsion oscillations) were visualized with a high resolutions to distinguish small-scale the singular components on the background of strong internal waves. Numerical algorithm of visualization allows to represent both the scalar and vector fields, such as velocity, density, pressure, vorticity, stream function. The size of the source, buoyancy and oscillation frequency, kinematic viscosity of the medium effects were traced in 2D an 3D posing problems. Precision schlieren instrument was used to visualize the flow pattern produced by linear and torsion oscillations of strip and disk in a continuously stratified fluid. Uniform stratification was created by the continuous displacement method. The buoyancy period ranged from 7.5 to 14 s. In the experiments disks with diameters from 9 to 30 cm and a thickness of 1 mm to 10 mm were used. Different schlieren methods that are conventional vertical slit - Foucault knife, vertical slit - filament (Maksoutov's method) and horizontal slit - horizontal grating (natural "rainbow" schlieren method) help to produce supplementing flow patterns. Both internal wave beams and fine flow components were visualized in vicinity and far from the source. Intensity of high gradient envelopes increased proportionally the amplitude of the source. In domains of envelopes convergence isolated small scale vortices and extended mushroom like jets were formed. Experiments have shown that in the case of torsion oscillations pattern of currents is more complicated than in case of forced linear oscillations. Comparison with known theoretical model shows that nonlinear interactions between the regular and singular flow components must be taken

  18. Workplace Charging. Charging Up University Campuses

    Giles, Carrie [ICF International, Fairfax, VA (United States); Ryder, Carrie [ICF International, Fairfax, VA (United States); Lommele, Stephen [National Renewable Energy Lab. (NREL), Golden, CO (United States)


    This case study features the experiences of university partners in the U.S. Department of Energy's (DOE) Workplace Charging Challenge with the installation and management of plug-in electric vehicle (PEV) charging stations.

  19. Optimizing R with SparkR on a commodity cluster for biomedical research.

    Sedlmayr, Martin; Würfl, Tobias; Maier, Christian; Häberle, Lothar; Fasching, Peter; Prokosch, Hans-Ulrich; Christoph, Jan


    Medical researchers are challenged today by the enormous amount of data collected in healthcare. Analysis methods such as genome-wide association studies (GWAS) are often computationally intensive and thus require enormous resources to be performed in a reasonable amount of time. While dedicated clusters and public clouds may deliver the desired performance, their use requires upfront financial efforts or anonymous data, which is often not possible for preliminary or occasional tasks. We explored the possibilities to build a private, flexible cluster for processing scripts in R based on commodity, non-dedicated hardware of our department. For this, a GWAS-calculation in R on a single desktop computer, a Message Passing Interface (MPI)-cluster, and a SparkR-cluster were compared with regards to the performance, scalability, quality, and simplicity. The original script had a projected runtime of three years on a single desktop computer. Optimizing the script in R already yielded a significant reduction in computing time (2 weeks). By using R-MPI and SparkR, we were able to parallelize the computation and reduce the time to less than three hours (2.6 h) on already available, standard office computers. While MPI is a proven approach in high-performance clusters, it requires rather static, dedicated nodes. SparkR and its Hadoop siblings allow for a dynamic, elastic environment with automated failure handling. SparkR also scales better with the number of nodes in the cluster than MPI due to optimized data communication. R is a popular environment for clinical data analysis. The new SparkR solution offers elastic resources and allows supporting big data analysis using R even on non-dedicated resources with minimal change to the original code. To unleash the full potential, additional efforts should be invested to customize and improve the algorithms, especially with regards to data distribution. Copyright © 2016 The Authors. Published by Elsevier Ireland Ltd.. All

  20. Formation of a spark discharge in an inhomogeneous electric field with current limitation by a large ballast Resistance

    Baldanov, B. B., E-mail: [Russian Academy of Sciences, Institute of Physical Material Science, Siberian Branch (Russian Federation)


    Results of studies of a spark discharge initiated in argon in a point–plane electrode gap with limitation of the discharge current by a large ballast resistance are presented. It is shown that the current flowing through the plasma channel of such a low-current spark has the form of periodic pulses. It is experimentally demonstrated that, when a low-current spark transforms into a constricted glow discharge, current pulses disappear, the spatial structure of the cathode glow changes abruptly, and a brightly glowing positive plasma column forms in the gap.

  1. Stratified flows with variable density: mathematical modelling and numerical challenges.

    Murillo, Javier; Navas-Montilla, Adrian


    Stratified flows appear in a wide variety of fundamental problems in hydrological and geophysical sciences. They may involve from hyperconcentrated floods carrying sediment causing collapse, landslides and debris flows, to suspended material in turbidity currents where turbulence is a key process. Also, in stratified flows variable horizontal density is present. Depending on the case, density varies according to the volumetric concentration of different components or species that can represent transported or suspended materials or soluble substances. Multilayer approaches based on the shallow water equations provide suitable models but are not free from difficulties when moving to the numerical resolution of the governing equations. Considering the variety of temporal and spatial scales, transfer of mass and energy among layers may strongly differ from one case to another. As a consequence, in order to provide accurate solutions, very high order methods of proved quality are demanded. Under these complex scenarios it is necessary to observe that the numerical solution provides the expected order of accuracy but also converges to the physically based solution, which is not an easy task. To this purpose, this work will focus in the use of Energy balanced augmented solvers, in particular, the Augmented Roe Flux ADER scheme. References: J. Murillo , P. García-Navarro, Wave Riemann description of friction terms in unsteady shallow flows: Application to water and mud/debris floods. J. Comput. Phys. 231 (2012) 1963-2001. J. Murillo B. Latorre, P. García-Navarro. A Riemann solver for unsteady computation of 2D shallow flows with variable density. J. Comput. Phys.231 (2012) 4775-4807. A. Navas-Montilla, J. Murillo, Energy balanced numerical schemes with very high order. The Augmented Roe Flux ADER scheme. Application to the shallow water equations, J. Comput. Phys. 290 (2015) 188-218. A. Navas-Montilla, J. Murillo, Asymptotically and exactly energy balanced augmented flux

  2. Deep silicon maxima in the stratified oligotrophic Mediterranean Sea

    Y. Crombet


    Full Text Available The silicon biogeochemical cycle has been studied in the Mediterranean Sea during late summer/early autumn 1999 and summer 2008. The distribution of nutrients, particulate carbon and silicon, fucoxanthin (Fuco, and total chlorophyll-a (TChl-a were investigated along an eastward gradient of oligotrophy during two cruises (PROSOPE and BOUM encompassing the entire Mediterranean Sea during the stratified period. At both seasons, surface waters were depleted in nutrients and the nutriclines gradually deepened towards the East, the phosphacline being the deepest in the easternmost Levantine basin. Following the nutriclines, parallel deep maxima of biogenic silica (DSM, fucoxanthin (DFM and TChl-a (DCM were evidenced during both seasons with maximal concentrations of 0.45 μmol L−1 for BSi, 0.26 μg L−1 for Fuco, and 1.70 μg L−1 for TChl-a, all measured during summer. Contrary to the DCM which was a persistent feature in the Mediterranean Sea, the DSM and DFMs were observed in discrete areas of the Alboran Sea, the Algero-Provencal basin, the Ionian sea and the Levantine basin, indicating that diatoms were able to grow at depth and dominate the DCM under specific conditions. Diatom assemblages were dominated by Chaetoceros spp., Leptocylindrus spp., Pseudonitzschia spp. and the association between large centric diatoms (Hemiaulus hauckii and Rhizosolenia styliformis and the cyanobacterium Richelia intracellularis was observed at nearly all sites. The diatom's ability to grow at depth is commonly observed in other oligotrophic regions and could play a major role in ecosystem productivity and carbon export to depth. Contrary to the common view that Si and siliceous phytoplankton are not major components of the Mediterranean biogeochemistry, we suggest here that diatoms, by persisting at depth during the stratified period, could contribute to a

  3. Fishing and the oceanography of a stratified shelf sea

    Sharples, Jonathan; Ellis, Jim R.; Nolan, Glenn; Scott, Beth E.


    Fishing vessel position data from the Vessel Monitoring System (VMS) were used to investigate fishing activity in the Celtic Sea, a seasonally-stratifying, temperate region on the shelf of northwest Europe. The spatial pattern of fishing showed that three main areas are targeted: (1) the Celtic Deep (an area of deeper water with fine sediments), (2) the shelf edge, and (3) an area covering several large seabed banks in the central Celtic Sea. Data from each of these regions were analysed to examine the contrasting seasonality of fishing activity, and to highlight where the spring-neap tidal cycle appears to be important to fishing. The oceanographic characteristics of the Celtic Sea were considered alongside the distribution and timing of fishing, illustrating likely contrasts in the underlying environmental drivers of the different fished regions. In the central Celtic Sea, fishing mainly occurred during the stratified period between April and August. Based on evidence provided in other papers of this Special Issue, we suggest that the fishing in this area is supported by (1) a broad increase in primary production caused by lee-waves generated by seabed banks around spring tides driving large supplies of nutrients into the photic zone, and (2) greater concentrations of zooplankton within the region influenced by the seabed banks and elevated primary production. In contrast, while the shelf edge is a site of elevated surface chlorophyll, previous work has suggested that the periodic mixing generated by an internal tide at the shelf edge alters the size-structure of the phytoplankton community which fish larvae from the spawning stocks along the shelf edge are able to exploit. The fishery for Nephrops norvegicus in the Celtic Deep was the only one to show a significant spring-neap cycle, possibly linked to Nephrops foraging outside their burrows less during spring tides. More tentatively, the fishery for Nephrops correlated most strongly with a localised shift in

  4. SciSpark: Highly Interactive and Scalable Model Evaluation and Climate Metrics

    Wilson, B. D.; Palamuttam, R. S.; Mogrovejo, R. M.; Whitehall, K. D.; Mattmann, C. A.; Verma, R.; Waliser, D. E.; Lee, H.


    Remote sensing data and climate model output are multi-dimensional arrays of massive sizes locked away in heterogeneous file formats (HDF5/4, NetCDF 3/4) and metadata models (HDF-EOS, CF) making it difficult to perform multi-stage, iterative science processing since each stage requires writing and reading data to and from disk. We are developing a lightning fast Big Data technology called SciSpark based on ApacheTM Spark under a NASA AIST grant (PI Mattmann). Spark implements the map-reduce paradigm for parallel computing on a cluster, but emphasizes in-memory computation, "spilling" to disk only as needed, and so outperforms the disk-based ApacheTM Hadoop by 100x in memory and by 10x on disk. SciSpark will enable scalable model evaluation by executing large-scale comparisons of A-Train satellite observations to model grids on a cluster of 10 to 1000 compute nodes. This 2nd generation capability for NASA's Regional Climate Model Evaluation System (RCMES) will compute simple climate metrics at interactive speeds, and extend to quite sophisticated iterative algorithms such as machine-learning based clustering of temperature PDFs, and even graph-based algorithms for searching for Mesocale Convective Complexes. We have implemented a parallel data ingest capability in which the user specifies desired variables (arrays) as several time-sorted lists of URL's (i.e. using OPeNDAP, or local files). The specified variables are partitioned by time/space and then each Spark node pulls its bundle of arrays into memory to begin a computation pipeline. We also investigated the performance of several N-dim. array libraries (scala breeze, java jblas & netlib-java, and ND4J). We are currently developing science codes using ND4J and studying memory behavior on the JVM. On the pyspark side, many of our science codes already use the numpy and SciPy ecosystems. The talk will cover: the architecture of SciSpark, the design of the scientific RDD (sRDD) data structure, our

  5. Laser diagnostic and plasma technological fundamentals of emission and fuel consumption reduction in DI internal combustion engines. Investigation of a plasma ignition system for DI spark ignition engines. Final report; Laserdiagnostische und plasmatechnologische Grundlagen zur Verminderung von Emissionen und Kraftstoffverbrauch von DI-Verbrennungsmotoren. Untersuchung eines Plasmazuendsystems fuer DI-Ottomotoren. Abschlussbericht

    Lepperhoff, G.; Geiger, J.; Wolters, P.; Boewing, R.; Neff, W.


    Misfire in stratified DI spark ignition engines may result from cyclic variations of the mixture near the spark plugs. More stable ignition is expected from an initiation of inflammation in a volume range which is significantly larger than the ignition spark of a transistor coil ignition system. the research project investigated the interdependence between electric power supply and the development and propagation of the plasma on a plasma spark plug in space and time. Goals of development are: Development of a system for test stand testing (no electromagnetic interference in the electronic system of the test stand; long-term stability and low variation of the ignition energy; low electrode wear); higher thermal efficiency than conventional transistor coil ignition systems; improved ignition of slow-reacting mixtures with ignition energies below 120 mJ; 'remote' inflammation across a gap of several mm inside the combustion space. [German] Bei geschichtet betriebenen DI-Ottomotoren koennen zyklische Schwankungen in der Gemischzusammensetzung in Zuendkerzennaehe zu Verbrennungsaussetzern fuehren. Durch die Initiierung der Entflammung in einem Volumenbereich, der im Vergleich zum Zuendfunken einer Transistorspulenzuendung (TSZ) deutlich groesser ist, wird eine stabilere Verbrennungseinleitung erwartet. In diesem Forschungsvorhaben liegt der Schwerpunkt auf der Untersuchung des Zusammenhangs zwischen der elektrischen Leistungseinkopplung und der zeitlich-raeumlichen Entstehung und Ausbreitung des Plasmas an einer Plasmazuendkerze. Die wesentlichen Ziele sind: - Darstellung eines pruefstandtauglichen Systems fuer den Betrieb an DI-Ottomotoren (keine elektromagnetische Stoerung der Pruefstandelektronik; Langzeitstabilitaet der Zuendenergie bei kleiner Schwankungsbreite; niedriger Verschleiss der Elektroden) - hoeherer thermischer Wirkungsgrad als konventionelle Transistorspulenzuendungen - verbesserte Zuendung reaktionstraeger Gemische mit Zuendenergien <120 m

  6. Turbulence comes in bursts in stably stratified flows

    Rorai, C; Pouquet, A


    There is a clear distinction between simple laminar and complex turbulent fluids. But in some cases, as for the nocturnal planetary boundary layer, a stable and well-ordered flow can develop intense and sporadic bursts of turbulent activity which disappear slowly in time. This phenomenon is ill-understood and poorly modeled; and yet, it is central to our understanding of weather and climate dynamics. We present here a simple model which shows that in stably stratified turbulence, the stronger bursts can occur when the flow is expected to be more stable. The bursts are generated by a rapid non-linear amplification of energy stored in waves, and are associated with energetic interchanges between vertical velocity and temperature (or density) fluctuations. Direct numerical simulations on grids of 2048^3 points confirm this somewhat paradoxical result of measurably stronger events for more stable flows, displayed not only in the temperature and vertical velocity derivatives, but also in the amplitude of the field...

  7. DNS of stratified spatially-developing turbulent thermal boundary layers

    Araya, Guillermo; Castillo, Luciano; Jansen, Kenneth


    Direct numerical simulations (DNS) of spatially-developing turbulent thermal boundary layers under stratification are performed. It is well known that the transport phenomena of the flow is significantly affected by buoyancy, particularly in urban environments where stable and unstable atmospheric boundary layers are encountered. In the present investigation, the Dynamic Multi-scale approach by Araya et al. (JFM, 670, 2011) for turbulent inflow generation is extended to thermally stratified boundary layers. Furthermore, the proposed Dynamic Multi-scale approach is based on the original rescaling-recycling method by Lund et al. (1998). The two major improvements are: (i) the utilization of two different scaling laws in the inner and outer parts of the boundary layer to better absorb external conditions such as inlet Reynolds numbers, streamwise pressure gradients, buoyancy effects, etc., (ii) the implementation of a Dynamic approach to compute scaling parameters from the flow solution without the need of empirical correlations as in Lund et al. (1998). Numerical results are shown for ZPG flows at high momentum thickness Reynolds numbers (~ 3,000) and a comparison with experimental data is also carried out.

  8. Stratified patterns of divorce: Earnings, education, and gender

    Amit Kaplan


    Full Text Available Background: Despite evidence that divorce has become more prevalent among weaker socioeconomic groups, knowledge about the stratification aspects of divorce in Israel is lacking. Moreover, although scholarly debate recognizes the importance of stratificational positions with respect to divorce, less attention has been given to the interactions between them. Objective: Our aim is to examine the relationship between social inequality and divorce, focusing on how household income, education, employment stability, relative earnings, and the intersection between them affect the risk of divorce in Israel. Methods: The data is derived from combined census files for 1995-2008, annual administrative employment records from the National Insurance Institute and the Tax Authority, and data from the Civil Registry of Divorce. We used a series of discrete-time event-history analysis models for marital dissolution. Results: Couples in lower socioeconomic positions had a higher risk of divorce in Israel. Higher education in general, and homogamy in terms of higher education (both spouses have degrees in particular, decreased the risk of divorce. The wife's relative earnings had a differential effect on the likelihood of divorce, depending on household income: a wife who outearned her husband increased the log odds of divorce more in the upper tertiles than in the lower tertile. Conclusions: Our study shows that divorce indeed has a stratified pattern and that weaker socioeconomic groups experience the highest levels of divorce. Gender inequality within couples intersects with the household's economic and educational resources.

  9. Self-Knowledge and Risk in Stratified Medicine.

    Hordern, Joshua


    This article considers why and how self-knowledge is important to communication about risk and behaviour change by arguing for four claims. First, it is doubtful that genetic knowledge should properly be called 'self-knowledge' when its ordinary effects on self-motivation and behaviour change seem so slight. Second, temptations towards a reductionist, fatalist, construal of persons' futures through a 'molecular optic' should be resisted. Third, any plausible effort to change people's behaviour must engage with cultural self-knowledge, values and beliefs, catalysed by the communication of genetic risk. For example, while a Judaeo-Christian notion of self-knowledge is distinctively theological, people's self-knowledge is plural in its insight and sources. Fourth, self-knowledge is found in compassionate, if tense, communion which yields freedom from determinism even amidst suffering. Stratified medicine thus offers a newly precise kind of humanising health care through societal solidarity with the riskiest. However, stratification may also mean that molecularly unstratified, 'B' patients' experience involves accentuated suffering and disappointment, a concern requiring further research.

  10. [Phylogenetic diversity of bacteria in soda lake stratified sediments].

    Tourova, T P; Grechnikova, M A; Kuznetsov, V V; Sorokin, D Yu


    Various previously developed techniques for DNA extraction from the samples with complex physicochemical structure (soils, silts, and sediments) and modifications of these techniques developed in the present work were tested. Their usability for DNA extraction from the sediments of the Kulunda Steppe hypersaline soda lakes was assessed, and the most efficient procedure for indirect (two-stage) DNA extraction was proposed. Almost complete separation of the cell fraction was shown, as well as the inefficiency of nested PCR for analysis of the clone libraries obtained from washed sediments by amplification of the 16S rRNA gene fragments. Analysis of the clone library obtained from the cell fractions of stratified sediments (upper, medium, and lower layers) revealed that in the sediments of Lake Gorchina-3 most eubacterial phylotypes belonged to the class Clostridia, phylum Firmicutes. They were probably specific for this habitatand formed a new, presently unknown high-rank taxon. The data obtained revealed no pronounced stratification of the spe- cies diversity of the eubacterial component of the microbial community inhabiting the sediments (0-20 cm) in the inshore zone of Lake Gorchina-3.

  11. Stratified Flow Past a Hill: Dividing Streamline Concept Revisited

    Leo, Laura S.; Thompson, Michael Y.; Di Sabatino, Silvana; Fernando, Harindra J. S.


    The Sheppard formula (Q J R Meteorol Soc 82:528-529, 1956) for the dividing streamline height H_s assumes a uniform velocity U_∞ and a constant buoyancy frequency N for the approach flow towards a mountain of height h, and takes the form H_s/h=( {1-F} ) , where F=U_{∞}/Nh. We extend this solution to a logarithmic approach-velocity profile with constant N. An analytical solution is obtained for H_s/h in terms of Lambert-W functions, which also suggests alternative scaling for H_s/h. A `modified' logarithmic velocity profile is proposed for stably stratified atmospheric boundary-layer flows. A field experiment designed to observe H_s is described, which utilized instrumentation from the spring field campaign of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program. Multiple releases of smoke at F≈ 0.3-0.4 support the new formulation, notwithstanding the limited success of experiments due to logistical constraints. No dividing streamline is discerned for F≈ 10, since, if present, it is too close to the foothill. Flow separation and vortex shedding is observed in this case. The proposed modified logarithmic profile is in reasonable agreement with experimental observations.

  12. Large eddy simulation of unsteady lean stratified premixed combustion

    Duwig, C. [Division of Fluid Mechanics, Department of Energy Sciences, Lund University, SE 221 00 Lund (Sweden); Fureby, C. [Division of Weapons and Protection, Warheads and Propulsion, The Swedish Defense Research Agency, FOI, SE 147 25 Tumba (Sweden)


    Premixed turbulent flame-based technologies are rapidly growing in importance, with applications to modern clean combustion devices for both power generation and aeropropulsion. However, the gain in decreasing harmful emissions might be canceled by rising combustion instabilities. Unwanted unsteady flame phenomena that might even destroy the whole device have been widely reported and are subject to intensive studies. In the present paper, we use unsteady numerical tools for simulating an unsteady and well-documented flame. Computations were performed for nonreacting, perfectly premixed and stratified premixed cases using two different numerical codes and different large-eddy-simulation-based flamelet models. Nonreacting simulations are shown to agree well with experimental data, with the LES results capturing the mean features (symmetry breaking) as well as the fluctuation level of the turbulent flow. For reacting cases, the uncertainty induced by the time-averaging technique limited the comparisons. Given an estimate of the uncertainty, the numerical results were found to reproduce well the experimental data in terms both of mean flow field and of fluctuation levels. In addition, it was found that despite relying on different assumptions/simplifications, both numerical tools lead to similar predictions, giving confidence in the results. Moreover, we studied the flame dynamics and particularly the response to a periodic pulsation. We found that above a certain excitation level, the flame dynamic changes and becomes rather insensitive to the excitation/instability amplitude. Conclusions regarding the self-growth of thermoacoustic waves were drawn. (author)

  13. Economic evaluation in stratified medicine: methodological issues and challenges

    Hans-Joerg eFugel


    Full Text Available Background: Stratified Medicine (SM is becoming a practical reality with the targeting of medicines by using a biomarker or genetic-based diagnostic to identify the eligible patient sub-population. Like any healthcare intervention, SM interventions have costs and consequences that must be considered by reimbursement authorities with limited resources. Methodological standards and guidelines exist for economic evaluations in clinical pharmacology and are an important component for health technology assessments (HTAs in many countries. However, these guidelines have initially been developed for traditional pharmaceuticals and not for complex interventions with multiple components. This raises the issue as to whether these guidelines are adequate to SM interventions or whether new specific guidance and methodology is needed to avoid inconsistencies and contradictory findings when assessing economic value in SM.Objective: This article describes specific methodological challenges when conducting health economic (HE evaluations for SM interventions and outlines potential modifications necessary to existing evaluation guidelines /principles that would promote consistent economic evaluations for SM.Results/Conclusions: Specific methodological aspects for SM comprise considerations on the choice of comparator, measuring effectiveness and outcomes, appropriate modelling structure and the scope of sensitivity analyses. Although current HE methodology can be applied for SM, greater complexity requires further methodology development and modifications in the guidelines.


    Jabbari, Sarah; Brandenburg, Axel; Kleeorin, Nathan; Mitra, Dhrubaditya; Rogachevskii, Igor, E-mail: [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)


    Recent work by Mitra et al. (2014) has shown that in strongly stratified forced two-layer turbulence with helicity and corresponding large-scale dynamo action in the lower layer, and nonhelical turbulence in the upper, a magnetic field occurs in the upper layer in the form of sharply bounded bipolar magnetic spots. Here we extend this model to spherical wedge geometry covering the northern hemisphere up to 75° latitude and an azimuthal extent of 180°. The kinetic helicity and therefore also the large-scale magnetic field are strongest at low latitudes. For moderately strong stratification, several bipolar spots form that eventually fill the full longitudinal extent. At early times, the polarity of spots reflects the orientation of the underlying azimuthal field, as expected from Parker’s Ω-shaped flux loops. At late times their tilt changes such that there is a radial field of opposite orientation at different latitudes separated by about 10°. Our model demonstrates the spontaneous formation of spots of sizes much larger than the pressure scale height. Their tendency to produce filling factors close to unity is argued to be reminiscent of highly active stars. We confirm that strong stratification and strong scale separation are essential ingredients behind magnetic spot formation, which appears to be associated with downflows at larger depths.

  15. Local properties of countercurrent stratified steam-water flow

    Kim, H J


    A study of steam condensation in countercurrent stratified flow of steam and subcooled water has been carried out in a rectangular channel/flat plate geometry over a wide range of inclination angles (4/sup 0/-87/sup 0/) at several aspect ratios. Variables were inlet water and steam flow rates, and inlet water temperature. Local condensation rates and pressure gradients were measured, and local condensation heat transfer coefficients and interfacial shear stress were calculated. Contact probe traverses of the surface waves were made, which allowed a statistical analysis of the wave properties. The local condensation Nusselt number was correlated in terms of local water and steam Reynolds or Froude numbers, as well as the liquid Prandtl number. A turbulence-centered model developed by Theofanous, et al. principally for gas absorption in several geometries, was modified. A correlation for the interfacial shear stress and the pressure gradient agreed with measured values. Mean water layer thicknesses were calculated. Interfacial wave parameters, such as the mean water layer thickness, liquid fraction probability distribution, wave amplitude and wave frequency, are analyzed.

  16. Stratifying the Risk of Venous Thromboembolism in Otolaryngology

    Shuman, Andrew G.; Hu, Hsou Mei; Pannucci, Christopher J.; Jackson, Christopher R.; Bradford, Carol R.; Bahl, Vinita


    Objective The consequences of perioperative venous thromboembolism (VTE) are devastating; identifying patients at risk is an essential step in reducing morbidity and mortality. The utility of perioperative VTE risk assessment in otolaryngology is unknown. This study was designed to risk-stratify a diverse population of otolaryngology patients for VTE events. Study Design Retrospective cohort study. Setting Single-institution academic tertiary care medical center. Subjects and Methods Adult patients presenting for otolaryngologic surgery requiring hospital admission from 2003 to 2010 who did not receive VTE chemoprophylaxis were included. The Caprini risk assessment was retrospectively scored via a validated method of electronic chart abstraction. Primary study variables were Caprini risk scores and the incidence of perioperative venous thromboembolic outcomes. Results A total of 2016 patients were identified. The overall 30-day rate of VTE was 1.3%. The incidence of VTE in patients with a Caprini risk score of 6 or less was 0.5%. For patients with scores of 7 or 8, the incidence was 2.4%. Patients with a Caprini risk score greater than 8 had an 18.3% incidence of VTE and were significantly more likely to develop a VTE when compared to patients with a Caprini risk score less than 8 (P otolaryngology patients for 30-day VTE events and allows otolaryngologists to identify patient subgroups who have a higher risk of VTE in the absence of chemoprophylaxis. PMID:22261490

  17. Mixing efficiency of turbulent patches in stably stratified flows

    Garanaik, Amrapalli; Venayagamoorthy, Subhas Karan


    A key quantity that is essential for estimating the turbulent diapycnal (irreversible) mixing in stably stratified flow is the mixing efficiency Rf*, which is a measure of the amount of turbulent kinetic energy that is irreversibly converted into background potential energy. In particular, there is an ongoing debate in the oceanographic mixing community regarding the utility of the buoyancy Reynolds number (Reb) , particularly with regard to how mixing efficiency and diapycnal diffusivity vary with Reb . Specifically, is there a universal relationship between the intensity of turbulence and the strength of the stratification that supports an unambiguous description of mixing efficiency based on Reb ? The focus of the present study is to investigate the variability of Rf* by considering oceanic turbulence data obtained from microstructure profiles in conjunction with data from laboratory experiments and DNS. Field data analysis has done by identifying turbulent patches using Thorpe sorting method for potential density. The analysis clearly shows that high mixing efficiencies can persist at high buoyancy Reynolds numbers. This is contradiction to previous studies which predict that mixing efficiency should decrease universally for Reb greater than O (100) . Funded by NSF and ONR.

  18. Simulation and study of stratified flows around finite bodies

    Gushchin, V. A.; Matyushin, P. V.


    The flows past a sphere and a square cylinder of diameter d moving horizontally at the velocity U in a linearly density-stratified viscous incompressible fluid are studied. The flows are described by the Navier-Stokes equations in the Boussinesq approximation. Variations in the spatial vortex structure of the flows are analyzed in detail in a wide range of dimensionless parameters (such as the Reynolds number Re = Ud/ ν and the internal Froude number Fr = U/( Nd), where ν is the kinematic viscosity and N is the buoyancy frequency) by applying mathematical simulation (on supercomputers of Joint Supercomputer Center of the Russian Academy of Sciences) and three-dimensional flow visualization. At 0.005 < Fr < 100, the classification of flow regimes for the sphere (for 1 < Re < 500) and for the cylinder (for 1 < Re < 200) is improved. At Fr = 0 (i.e., at U = 0), the problem of diffusion-induced flow past a sphere leading to the formation of horizontal density layers near the sphere's upper and lower poles is considered. At Fr = 0.1 and Re = 50, the formation of a steady flow past a square cylinder with wavy hanging density layers in the wake is studied in detail.

  19. Numerical simulation of charge stratifications to improve combustion and NO formation of lean-burn SI engines

    Zhijun PENG


    The influences of charge stratification on spark ignition (SI) engine combustion and NO emission were analyzed using a phenomenological model. The mixture in the cylinder was divided spherically into three parts: a central core with a stoichiometric air-fuel charge, a dilution region without any combustible charge, and a mixing region lying between the core and the dilution region.Three mixture stratification parameters such as the extent of dilution in the mixing region, the extent of combustible charge in the mixing region, and the gradient of stratification in the mixing region were investigated. The results indicate that the extent of combustible charge in the mixing region could reduce in-cylinder NO formation significantly, compared with the extent of dilution in the mixing region. As long as the degree of dilution in the mixing region is within the dilution limit of the combustible charge, the gradient of dilution has little effect on combustion and NO formation.

  20. Battery charging system

    Carollo, J.A.; Kalinsky, W.A.


    A battery charger utilizes three basic modes of operation that includes a maintenance mode, a rapid charge mode and time controlled limited charging mode. The device utilizes feedback from the battery being charged of voltage, current and temperature to determine the mode of operation and the time period during which the battery is being charged.

  1. Gas mixtures for spark gap closing switches with emphasis on efficiency of operation

    Christophorou, L. G.; McCorkle, D. L.; Hunter, S. R.

    The efficient operation of a spark gap closing switch requires a gaseous medium with large breakdown strength, low conduction voltage, and a short formative time lag. Gas properties necessary to achieve these requirements are identified and discussed. Based on available knowledge of such properties, a number of binary (e.g., c-C4F8, or 1-C3F6, or n-C4F10, or C3F8, or C6F6 in Ar or He or H2) and ternary gas mixtures (e.g., c-C4F8, or n-C4F10, or C3F8 in Ar or He + C2H2 or another low ionization onset additive) have been identified which may be suitable for use in spark gap closing switches.

  2. submitter Triggering of a pressurized spark gap by a laser beam

    Deutsch, F


    A delay line was discharged into a terminating resistor by a spark gap of coaxial design. The spark gap was triggered by a focused laser beam, introduced along the axis; a Q-switched ruby laser giving pulses of 20 ns duration and up to 50 MW power was used. The range of operation of the gap, formative time of the breakdown and jitter were investigated for different gases at pressures above atmospheric, gap widths of 4-10 mm and voltages of up to 120 kv. Mixtures of argon and nitrogen were found to have certain advantages, such as a low threshold for ionization by the laser beam, sufficient dielectric strength, low values of the formative-time jitter and chemical inertness. Formative times of down to about 1 ns and jitters below 1 ns were found. The laser power can be relatively low (0centerdot5-5 MW). An explanation for the breakdown mechanism is proposed.

  3. A Feature Selection Method for Large-Scale Network Traffic Classification Based on Spark

    Yong Wang


    Full Text Available Currently, with the rapid increasing of data scales in network traffic classifications, how to select traffic features efficiently is becoming a big challenge. Although a number of traditional feature selection methods using the Hadoop-MapReduce framework have been proposed, the execution time was still unsatisfactory with numeral iterative computations during the processing. To address this issue, an efficient feature selection method for network traffic based on a new parallel computing framework called Spark is proposed in this paper. In our approach, the complete feature set is firstly preprocessed based on Fisher score, and a sequential forward search strategy is employed for subsets. The optimal feature subset is then selected using the continuous iterations of the Spark computing framework. The implementation demonstrates that, on the precondition of keeping the classification accuracy, our method reduces the time cost of modeling and classification, and improves the execution efficiency of feature selection significantly.

  4. Performances Evaluation of a Novel Hadoop and Spark Based System of Image Retrieval for Huge Collections

    Luca Costantini


    Full Text Available A novel system of image retrieval, based on Hadoop and Spark, is presented. Managing and extracting information from Big Data is a challenging and fundamental task. For these reasons, the system is scalable and it is designed to be able to manage small collections of images as well as huge collections of images. Hadoop and Spark are based on the MapReduce framework, but they have different characteristics. The proposed system is designed to take advantage of these two technologies. The performances of the proposed system are evaluated and analysed in terms of computational cost in order to understand in which context it could be successfully used. The experimental results show that the proposed system is efficient for both small and huge collections.

  5. Tantalum-Tungsten Oxide Thermite Composite Prepared by Sol-Gel Synthesis and Spark Plasma Sintering

    Cervantes, O; Kuntz, J; Gash, A; Munir, Z


    Energetic composite powders consisting of sol-gel derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition tested and results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High Pressure Spark Plasma Sintering (HPSPS) technique, on the sol-gel derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The sol-gel derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta - WO{sub 3}) energetic composite was consolidated to a density of 9.17{sup -3} or 93% relative density. In addition those parts were consolidated without significant pre-reaction of the constituents, thus the sample retained its stored chemical energy.

  6. Gaseous photomultipliers with solid photocathodes for the detection of sparks, flames and dangerous gases

    Carlson, P.; Francke, T.; Lund-Jensen, B.; Peskov, V. E-mail:


    In many applications, it is necessary to detect sparks or flames in daylight conditions or in illuminated areas. Most flames emit strongly in the ultraviolet spectrum (180-280 nm), and this property can be used for reliable identification of flames. We have developed new spark and flame detectors based on gaseous photomultipliers with CsI, CuI or CsTe photocathodes. A modified version of the detector can also detect smoke and dangerous vapors. These detectors are able to perform complex monitoring and detection functions. Some of their advantages are: low cost, high sensitivity, large output signal and operation under battery power. Gaseous photomultipliers can be position sensitive and, if necessary, be used in combination with various optical systems, for example for monitoring flames from space.

  7. Heat treatment process of new NdFeB magnet prepared by spark plasma sintering

    李涛; 岳明; 张久兴; 王公平; 肖耀福; 王润


    In recent years, spark plasma sintering technique(SPS) has been a focus in the field of material preparation due to its advantages. SPS technique is first introduced for preparation of high quality NdFeB magnets. The effects of heat treatment process on the magnetic properties of SPS NdFeB magnet were investigated. Meanwhile, the effects of heat treatment process on the microstructure, tropism and dimensional precision of the SPS NdFeB magnets were also studied. The high quality NdFeB magnets with fine grains were prepared under proper heat treatment process. The results show that the magnetic properties of SPS NdFeB can be further improved through proper heat treatment process. Meanwhile, the experiment also demonstrates that it is feasible to prepare near-net-shape NdFeB magnets with fine grains and high magnetic property by spark plasma sintering.

  8. Structural, Mechanical and Tribological Properties of Spark Plasma Sintered Ti6Al4V Alloy

    Mróz A.


    Full Text Available The influence of spark plasma sintering parameters on the structural, mechanical and tribological characteristics of the Ti6Al4V alloy, which is used as implant material in biomedical engineering, was investigated. The experimental data confirm that full density and attractive mechanical properties can be obtained using the spark plasma sintering method. Tribological tests, performed in dry conditions, allowed the authors to indicate the most suitable sintering parameters. The material characterized by the highest wear resistance was selected for further tribological testing in articulation with UHMWPE in simulated body fluids. Although the weight of the polymeric material articulating against the sintered Ti6Al4V was slightly higher compared to the UHMWPE articulating against the reference material (Ti6Al4V rod, the friction coefficient was lower.

  9. Fabrication, spark plasma consolidation, and thermoelectric evaluation of nanostructured CoSb3

    Khan, A.; Saleemi, M.; Johnsson, M.


    Nanostructured powders of thermoelectric (TE) CoSb3 compounds were synthesized using a chemical alloying method. This method involved co-precipitation of oxalate precursors in aqueous solution with controlled pH, followed by thermochemical treatments including calcination and reduction to produce...... stoichiometric nanostructured CoSb3. Moreover, CoSb 3 nanoparticles were consolidated by spark plasma sintering (SPS) with a very brief processing time. Very high compaction densities (>95%) were achieved and the grain growth was almost negligible during consolidation. An iterative procedure was developed...... to maintain pre-consolidation particle size and to compensate Sb evaporation during reduction. Significant changes in particle size and morphology were observed, and the post-reduction cooling was found to be an important stage in the process. The spark plasma sintering (SPS) parameters were optimized...

  10. Radiation-MHD simulations for the development of a spark discharge channel.

    Niederhaus, John Henry; Jorgenson, Roy E.; Warne, Larry K.; Chen, Kenneth C.


    The growth of a cylindrical s park discharge channel in water and Lexan is studied using a series of one - dimensional simulations with the finite - element radiation - magnetohydrodynamics code ALEGRA. Computed solutions are analyzed in order to characterize the rate of growth and dynamics of the spark c hannels during the rising - current phase of the drive pulse. The current ramp rate is varied between 0.2 and 3.0 kA/ns, and values of the mechanical coupling coefficient K p are extracted for each case. The simulations predict spark channel expansion veloc ities primarily in the range of 2000 to 3500 m/s, channel pressures primarily in the range 10 - 40 GPa, and K p values primarily between 1.1 and 1.4. When Lexan is preheated, slightly larger expansion velocities and smaller K p values are predicted , but the o verall behavior is unchanged.

  11. 火花放电等离子体射流实验研究%Experimental Investigation on Spark Discharge Plasma Jet

    刘汝兵; 孙伟; 牛中国; 王萌萌; 杨欢; 林麒


    A spark discharge plasma jet generator has been designed to obtain higher energy zero net mass flux jet,which can generate continuous jet flow at higher average speed and operate at normal atmospheric pres⁃sure with frequency up to 9kHz. The structure of the generator was described and the discharge phenomenon of the plamsa jet was researched to find the mechanism in which how the plamsa jet generates the continuous jet flow at higher average speed. The average speed of the plamsa jet flow was measured by a pitot tube , to investi⁃gate how the electrical parameters and the gap between the two electrodes affect the average speed of the jet flow from the generator. The axial jet velocity distribution and the jet flow characteristics charts of the spark discharge plasma jet have been obtained as well. The experimental results show that the jet flow speed of the spark dis⁃charge plasma jet generator may reach more than 40m/s continuously, which raises with the increasing of the loading voltage,and there exists the best gap between the two electrodes as well as the loading voltage frequency for a given jet generator.%提出一种火花放电等离子体射流发生器,可获得能量较高的零质量射流。其工作频率可达9kHz,可在大气压下产生持续的平均速度较高的射流。详细阐述了该射流发生器结构;通过对其放电形态的研究,探讨了产生射流的机理;利用皮托管测量了射流平均速度,研究了发生器电极间距及外加电参数对射流平均速度的影响,测量了射流平均速度轴向分布;得到了该等离子体射流发生器的射流特性曲线。实验结果表明,该发生器产生的持续射流平均速度可达40m/s以上;增大加载电压还可提高射流速度;对给定的射流发生器,存在最佳电极间距和电压频率。

  12. Germination of embryos from stratified and non-stratified seeds and growth of apple seedlings (Malus domestica Borkh cv. "Antonówka"

    Jerzy Czerski


    Full Text Available The germination of whole seeds, the seeds without coat and isolated embryos of apple cv. "Antonówka Zwykła" after 90 days of cold-stratification was compared with the germination of embryos isolated from non-stratified seeds. They were germinated under 16hrs during a day at temperature 25°C and 20°C during the night. It has been found that after 2 weeks whole stratified seeds germinated in 5 per cent, seeds without coat in 25 per cent and isolated embryos in 98 per cent. Isolated embryos from nun-stratified seeds, after 2 weeks, germinated in the range from 75 to 88 per cent. The results indicate the similar germination ability of embryos isolated from nun-stratified seeds. The seedling populations obtained from embryo's stratified and non-stratified seeds were fully comparable and they evaluated: 1 a wide range of individual differences within population, 2 a similar number of seedlings in each class of shoot length, 3 a similar morphological habitus in each class of shoot length, 4 a similar fresh leaf weight and whole plant increment.

  13. Development of High Efficiency Clean Combustion Engine Designs for Spark-Ignition and Compression-Ignition Internal Combustion Engines

    Marriott, Craig; Gonzalez, Manual; Russell, Durrett


    This report summarizes activities related to the revised STATEMENT OF PROJECT OBJECTIVES (SOPO) dated June 2010 for the Development of High-Efficiency Clean Combustion engine Designs for Spark-Ignition and Compression-Ignition Internal Combustion Engines (COOPERATIVE AGREEMENT NUMBER DE-FC26-05NT42415) project. In both the spark- (SI) and compression-ignition (CI) development activities covered in this program, the goal was to develop potential production-viable internal combustion engine system technologies that both reduce fuel consumption and simultaneously met exhaust emission targets. To be production-viable, engine technologies were also evaluated to determine if they would meet customer expectations of refinement in terms of noise, vibration, performance, driveability, etc. in addition to having an attractive business case and value. Prior to this activity, only proprietary theoretical / laboratory knowledge existed on the combustion technologies explored The research reported here expands and develops this knowledge to determine series-production viability. Significant SI and CI engine development occurred during this program within General Motors, LLC over more than five years. In the SI program, several engines were designed and developed that used both a relatively simple multi-lift valve train system and a Fully Flexible Valve Actuation (FFVA) system to enable a Homogeneous Charge Compression Ignition (HCCI) combustion process. Many technical challenges, which were unknown at the start of this program, were identified and systematically resolved through analysis, test and development. This report documents the challenges and solutions for each SOPO deliverable. As a result of the project activities, the production viability of the developed clean combustion technologies has been determined. At this time, HCCI combustion for SI engines is not considered production-viable for several reasons. HCCI combustion is excessively sensitive to control variables

  14. Abnormal Ca2+ spark/STOC coupling in cerebral artery smooth muscle cells of obese type 2 diabetic mice.

    Angélica Rueda

    Full Text Available Diabetes is a major risk factor for stroke. However, the molecular mechanisms involved in cerebral artery dysfunction found in the diabetic patients are not completely elucidated. In cerebral artery smooth muscle cells (CASMCs, spontaneous and local increases of intracellular Ca2+ due to the opening of ryanodine receptors (Ca2+ sparks activate large conductance Ca2+-activated K+ (BK channels that generate spontaneous transient outward currents (STOCs. STOCs have a key participation in the control of vascular myogenic tone and blood pressure. Our goal was to investigate whether alterations in Ca(2+ spark and STOC activities, measured by confocal microscopy and patch-clamp technique, respectively, occur in isolated CASMCs of an experimental model of type-2 diabetes (db/db mouse. We found that mean Ca(2+ spark amplitude, duration, size and rate-of-rise were significantly smaller in Fluo-3 loaded db/db compared to control CASMCs, with a subsequent decrease in the total amount of Ca(2+ released through Ca(2+ sparks in db/db CASMCs, though Ca(2+ spark frequency remained. Interestingly, the frequency of large-amplitude Ca(2+ sparks was also significantly reduced in db/db cells. In addition, the frequency and amplitude of STOCs were markedly reduced at all voltages tested (from -50 to 0 mV in db/db CASMCs. The latter correlates with decreased BK channel β1/α subunit ratio found in db/db vascular tissues. Taken together, Ca(2+ spark alterations lead to inappropriate BK channels activation in CASMCs of db/db mice and this condition is aggravated by the decrease in the BK β1 subunit/α subunit ratio which underlies the significant reduction of Ca(2+ spark/STOC coupling in CASMCs of diabetic animals.

  15. About the constructive and functional particularities of spark ignition engines with gasoline direct injection: experimental results

    Niculae, M.; Ivan, F.; Neacsu, D.


    The paper aims to analyze and compare the environmental performances between a gasoline direct engine and a multi-point injection engine. There are analyzed the stages of emission formation during the New European Driving Cycle. The paper points out the dynamic, economic and environmental performances of spark ignition engines equipped with a GDI systems. Reason why, we believe the widespread implementation of this technology is today an immediate need.

  16. Microsoft BizSpark in Portugal : how to enhance entrepreneurship through the creation of shared value

    Gonçalves, Mariana Duarte de Oliveira


    Over the years we have seen a growing awareness of consumers and investors concerning companies’ good practices. Corporate Social Responsibility has been gaining ground and has now become part of several companies’ strategic plan as a means of creating a win-win situation for themselves and for society through the creation of Shared Value. In this context, we thought it pertinent to introduce BizSpark, a global Microsoft’s three-year program that supports technological startups by providin...

  17. The laser welding of iridium-platinum tips to spark plug electrodes

    Antoszewski, Bogdan; Tofil, Szymon


    The paper presents selected results of model and technological experiments of welding iridium-platinum tips to spark plug electrodes. Variants of welding technology included different ways of preparing materials and the use of different Nd: YAG lasers (Rofin BLS 720 and Rofin Integral). The results of technological tests were verified by the metallographic evaluation of joints. Performance tests when powered by biogas were conducted for selected variants of welding.

  18. Master Sintering Surface: A practical approach to its construction and utilization for Spark Plasma Sintering prediction

    Pouchly V.


    Full Text Available The sintering is a complex thermally activated process, thus any prediction of sintering behaviour is very welcome not only for industrial purposes. Presented paper shows the possibility of densification prediction based on concept of Master Sintering Surface (MSS for pressure assisted Spark Plasma Sintering (SPS. User friendly software for evaluation of the MSS is presented. The concept was used for densification prediction of alumina ceramics sintered by SPS.

  19. Ca2+ sparks and Ca2+ glows in superior cervical ganglion neurons

    Li-jun YAO; Cai-hong WU; Jie LIU; Zhuan ZHOU; He-ping CHENG; Gang WANG; Kun-fu OU-YANG; Chao-liang WEI; Xian-hua WANG; Shi-rong WANG; Wei YAO; Hong-ping HUANG; Jian-hong LUO


    Aim: Ca2+ release from the endoplasmic reticulum (ER) is an integral component of neuronal Ca2+ signaling. The present study is to investigate properties of local Ca2+ release events in superior cervical ganglion (SCO) neurons. Methods: Primary cultured SCO neurons were prepared from neonatal rats (P3-P7). Low concentration of caffeine was used to induce Ca2+ release from the ER Ca2+ store, and intracellular Ca2+ was recorded by high-resolution line scan confocal imaging and the Ca2+ indicator Fluo-4. Results: Two populations of local Ca2+ release events with distinct temporal characteristics were evoked by 1.5 mmol/L caffeine near the surface membrane in the soma and the neurites of SCG neurons. Brief events similar to classic Ca2+ sparks lasted a few hundreds of milliseconds, whereas long-lasting events displayed duration up to tens of seconds. Typical somatic and neurite sparks were of 0.3- and 0.52-fold increase in local Fluo-4 fluorescence, respectively. Typical Ca2+ glows were brighter (△F/F0 approximately 0.6), but were highly confined in space. The half maximum of full duration of neurite sparks was much longer than those in the soma (685 vs 381 ms). Conclusion: Co-existence of Ca2+ sparks and Ca2+ glows in SCG neurons indicates distinctive local regulation of Ca2+ release kinetics. The local Ca2+ signals of variable, site-specific temporal length may bear important implications in encoding a "memory" of the trigger signal.

  20. Reactive Spark Plasma Sintering (SPS) of Nitride Reinforced Titanium Alloy Composites (Postprint)


    ies on in situ alloying and reactions during the SPS process. A recent study on SPS processing of hafnium carbide (HfC) starting from a blend of...AFRL-RX-WP-JA-2014-0177 REACTIVE SPARK PLASMA SINTERING (SPS) OF NITRIDE REINFORCED TITANIUM ALLOY COMPOSITES (POSTPRINT) Jaimie S...SINTERING (SPS) OF NITRIDE REINFORCED TITANIUM ALLOY COMPOSITES (POSTPRINT) 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT

  1. Method for operating a spark-ignition, direct-injection internal combustion engine

    Narayanaswamy, Kushal; Koch, Calvin K.; Najt, Paul M.; Szekely, Jr., Gerald A.; Toner, Joel G.


    A spark-ignition, direct-injection internal combustion engine is coupled to an exhaust aftertreatment system including a three-way catalytic converter upstream of an NH3-SCR catalyst. A method for operating the engine includes operating the engine in a fuel cutoff mode and coincidentally executing a second fuel injection control scheme upon detecting an engine load that permits operation in the fuel cutoff mode.


    Can ÇINAR


    Full Text Available In this study, the effects of intake valve lift variation on engine performance have been investigated experimentally. An alternative prototype has been designed and constructed for variable valve systems. A fourstroke, single cylinder, spark ignition engine has been used for experiments. The effects of four different intake valve lift value (6.5 mm, 5 mm, 4 mm and 3 mm on volumetric efficiency, engine torque, specific fuel consumption and exhaust emissions have been investigated.

  3. Structure and properties of nanocrystalline rare earth bulks prepared by spark plasma sintering

    卢年端; 宋晓艳; 刘雪梅; 张久兴


    A series of rare earth bulks with the ultrafine nanocrystalline structure were prepared by applying an "oxygen-free" (an environmental oxygen concentration less than 0.5 ppm) in-situ synthesis system, where the inert-gas condensation was combined with the spark plasma sintering technology into an entirely closed system. The thermal and mechanical properties of the prepared ultrafine nanocrystalline bulks were characterized and compared with those of the raw polycrystalline bulks. It was found that the speci...

  4. Biospark: scalable analysis of large numerical datasets from biological simulations and experiments using Hadoop and Spark.

    Klein, Max; Sharma, Rati; Bohrer, Chris H; Avelis, Cameron M; Roberts, Elijah


    Data-parallel programming techniques can dramatically decrease the time needed to analyze large datasets. While these methods have provided significant improvements for sequencing-based analyses, other areas of biological informatics have not yet adopted them. Here, we introduce Biospark, a new framework for performing data-parallel analysis on large numerical datasets. Biospark builds upon the open source Hadoop and Spark projects, bringing domain-specific features for biology.

  5. Experimental determination of the filling coefficient for an aspirated spark-ignition engine

    Raţiu, S.; Alexa, V.; Kiss, I.; Cioată, V.


    This study aims at determining, by experiment, the filling coefficient of a spark-ignition, normal aspirated engine, with carburettor. For this purpose, a pilot plant was designed for measuring the pressure at various points on the route, simulating a stationary air flow regime by means of a vacuum pump. Measurements were made for various lifting heights of the intake valve and various opening positions of the throttle body, thus highlighting how their influence on the pressure loss and on the filling coefficient.

  6. Cavity Ignition in Supersonic Flow by Spark Discharge and Pulse Detonation


    constant volume, through a detonation , or some combination. While a deflagration (flame) through constant volume combustion can provide rapid heat release...significantly disrupted, and the detonation was able to ignite and burn most of the fuel within the cavity. This led to decreased heat release in regime IV...locate/proci of the Combustion InstituteCavity ignition in supersonic flow by spark discharge and pulse detonation Timothy M. Ombrello a,⇑, Campbell D

  7. Sensitivity of Lead Azide to Electric Spark (Chuvstvitelnost Azida Svintsa k Elektricheskoi Iskre)


    On supplying a voltage pulse to the Incendiary electrode of the triple - electrode v.clay P, it operated, one of the specimen electrodes got connected...azide to electric spark. Substances which can cover particles of explosive materials (paraffin, ceresin, wax, castor oil, camphor , etc.) are often...modern concepts, excitation of explosion in an explo- sive material leads to the formation of "hot points " and to thermal trigger- ing. Increase of

  8. Flow system for liquid sample introduction in arc/spark excitation sources

    Bellato, CR; Pasquini, C


    A flow system based on the monosegmented flow analysis (MSFA) approach is described for delivery of liquid samples to arc/spark excitation sources commonly used in spectrographs. A Carl Zeiss PGS-2 spectrograph, previously-automated in the laboratory by replacing its photographic plate detection system with a photodiode array, was employed, The sample is introduced via an injection port into the path to the excitation source, where the liquid sample plug (typically 50 mu l) is passed through ...

  9. Different Boosting Systems and their Control Strategies for a Spark Ignition Internal Combustion Engine

    Bolehovský Ondřej; Macek Jan


    This research uses 1-D simulation in GT-Power for evaluation of boosting systems for a spark ignition engine. Exhaust gas driven (waste-gated turbocharger) and mechanical driven (Roots blower) boosting systems are assessed in both steady state and transient modes in terms of performance, efficiency, fuel consumption, drivability, energy distribution and other aspects that influence gas exchange phase. Moreover, different boost control strategies, particularly at partial load, are also evaluat...

  10. High-efficiency synthesis of nanoparticles in a repetitive multigap spark discharge generator

    Ivanov, V. V.; Efimov, A. A.; Mylnikov, D. A.; Lizunova, A. A.; Bagazeev, A. V.; Beketov, I. V.; Shcherbinin, S. V.


    We describe a method of obtaining aerosol nanoparticles in a repetitive spark discharge generator with 12 interelectrode gaps between tin electrodes, which operates at a pulse repetition frequency of 2.5 kHz. During synthesis of tin oxide nanoparticles in air, the mass productivity of the gas discharge generator reaches up to 9 g/h for primary particles with characteristic sizes within 5-10 nm and agglomerate size on the order of 50 nm.

  11. Impulse Breakdown Characteristics In Air In The Presence Of A Local Spark

    Settaouti, Abdelrahmane [عبد الرحمن ساتوتو


    In this paper, we study the flashover phenomena in air gaps containing floating metallic objects. The effect of a local spark on the impulse breakdown characteristics of a model gap arrangement which simulating a gas insulated switch (GIS) has been experimentally investigated. The three electrode gap consists of two conical rods facing each other together with a ground plane (or conical rod with the angle of the tip being varied). One of the horizontal rods is energized and one is left floati...

  12. Localized intracellular calcium signaling in muscle: calcium sparks and calcium quarks.

    Niggli, E


    Subcellularly localized Ca2+ signals in cardiac and skeletal muscle have recently been identified as elementary Ca2+ signaling events. The signals, termed Ca2+ sparks and Ca2+ quarks, represent openings of Ca2+ release channels located in the membrane of the sarcoplasmic reticulum (SR). In cardiac muscle, the revolutionary discovery of Ca2+ sparks has allowed the development of a fundamentally different concept for the amplification of Ca2+ signals by Ca(2+)-induced Ca2+ release. In such a system, a graded amplification of the triggering Ca2+ signal entering the myocyte via L-type Ca2+ channels is accomplished by a recruitment process whereby individual SR Ca2+ release units are locally controlled by L-type Ca2+ channels. In skeletal muscle, the initial SR Ca2+ release is governed by voltage-sensors but subsequently activates additional Ca2+ sparks by Ca(2+)-induced Ca2+ release from the SR. Results from studies on elementary Ca2+ release events will improve our knowledge of muscle Ca2+ signaling at all levels of complexity, from the molecule to normal cellular function, and from the regulation of cardiac and skeletal muscle force to the pathophysiology of excitation-contraction coupling.

  13. Effect of biofuel E85 combustion on fuel consumption in spark-ignition engines

    Adam Polcar


    Full Text Available Biofuels represent an alternative source of energy that should gradually decrease our dependence on crude oil. A rapid development of their use in combustion engines is above all the consequence of their very positive balance of emissions. The possibility of use of biofuels in conventional combustion engines is given by their physico-chemical properties. Bioethanol is one of biofuels that can be used in spark-ignition engines. However, because of its lower heating value, it is necessary to change the mixing ratio fuel/air. The aim of this paper is to evaluate the effect of combustion of a mixture of bioethanol with gasoline (in the ratio 85:15 on fuel consumption in the spark-ignition engine. Experimental measurements were performed using a six-cylinder spark-ignition Peugeot engine with the overall volume of 2.946 cm3, which was equipped with a multi-hole system of indirect injection. Obtained results indicated that the combustion of E85 biofuel markedly increased the reduction of specific fuel consumption (corrected to atmospheric conditions. As compared with gasoline Natural 95, the actual volume consumption of E85 biofuel increased under the maximum engine load in average by 30.4 %. In spite of a relatively high consumption of E85 biofuel the total costs associated with running of a modified engine were lower than those of the engine combusting gasoline Natural 95.

  14. Investigation of the energy dependence of breakdown properties with a DC spark setup

    Hansen, Anita; Calatroni, S


    The Compact LInear Collider (CLIC) study is a site independent feasibility study aiming at the development of a realistic technology at an affordable cost for a future linear electron-positron collider. The European Organization for Nuclear Research (CERN) is one of the collaborators for the CLIC study.The CLIC Test Facility (CTF3) positioned at CERN provides testing of this technology, including the testing of the proposed radio-frequency (RF) structures in a two-beam concept to produce the necessary accelerating electric field as high as 100 MV/m to reach the goal of a nominal total energy of 3 TeV. One problem at such high accelerating fields is electrical discharges, i.e. sparks, damaging the inside of the RF structures as well as deflecting the trajectories of accelerated particles. A Direct Current (DC) spark test setup is in use at CERN to aid the understanding of electrical discharges under vacuum conditions, also called vacuum arcs. In contrast to the more complex CTF3 setup, the DC spark setup is si...

  15. A multi-platform evaluation of the randomized CX low-rank matrix factorization in Spark

    Gittens, Alex; Kottalam, Jey; Yang, Jiyan; Ringenburg, Michael, F.; Chhugani, Jatin; Racah, Evan; Singh, Mohitdeep; Yao, Yushu; Fischer, Curt; Ruebel, Oliver; Bowen, Benjamin; Lewis, Norman, G.; Mahoney, Michael, W.; Krishnamurthy, Venkat; Prabhat, Mr


    We investigate the performance and scalability of the randomized CX low-rank matrix factorization and demonstrate its applicability through the analysis of a 1TB mass spectrometry imaging (MSI) dataset, using Apache Spark on an Amazon EC2 cluster, a Cray XC40 system, and an experimental Cray cluster. We implemented this factorization both as a parallelized C implementation with hand-tuned optimizations and in Scala using the Apache Spark high-level cluster computing framework. We obtained consistent performance across the three platforms: using Spark we were able to process the 1TB size dataset in under 30 minutes with 960 cores on all systems, with the fastest times obtained on the experimental Cray cluster. In comparison, the C implementation was 21X faster on the Amazon EC2 system, due to careful cache optimizations, bandwidth-friendly access of matrices and vector computation using SIMD units. We report these results and their implications on the hardware and software issues arising in supporting data-centric workloads in parallel and distributed environments.

  16. 5-Hydroxytryptamino-induced calcium sparks in cultured rat stomach fundus smooth muscle cells

    ZHANG; Xiaoling; (张小玲); YAN; Hongtao; (阎宏涛); YAN; Yang; (闫炀)


    With a new fluorescence probe of Ca2+, STDIn-AM, 5-hydroxytryptamino (5-HT)-induced spontaneous calcium release events (calcium sparks) in cultured rat stomach fundus smooth muscle cells (SFSMC) are investigated by laser scanning confocal microscope. The mechanisms of initiation of Ca2+ sparks, propagating Ca2+ waves and their relation to E-C coupling are discussed. After the extracellular [Ca2+] is increased to 10 mmol/L, addition of 5-HT causes hot spots throughout the cytoplasm, which is brighter near the plasmalemma. The amplitude of the event is at least two times greater than the standard deviation of fluorescence intensity fluctuations measured in the neighboring region and the duration of the Ca2+ signal is over 100 ms. The results suggest that 5-HT acts by the way of 5-HT2 receptors on SFSMC, then through 5-HT2 receptors couples IP3/Ca2+ and DG/PKC double signal transduction pathways to cause Ca2+ release from intracellular Ca2+ stores and followed Ca2+ influx possibly through calcium release-activated calcium influx. The acceptor of activated 5-HT2 can also cause membrane depolarization, which then stimulates the L-type Ca2+ channels leading to Ca2+ influx. Thenthe local Ca2+ entry mentioned above activates ryanodine-sensitive Ca2+ releasechannels (RyR) on sarcoplasmic reticulum (SR) to cause local Ca2+ release events (Ca2+ sparks) through calcium-induced calcium release (CICR).

  17. Numerical study on the combustion process of a biogas spark-ignition engine

    Carrera José L.


    Full Text Available The fuel called biogas is obtained through anaerobic digestion of different types of organic waste, providing a way to tap the energy stored in organic matter. The use of this fuel is also attractive from the standpoint of global warming because its application does not register a net emission of carbon dioxide into the atmosphere. One possible use for this fuel is to feed the spark-ignition internal combustion engines. In the present, there is little information available about the process of combustion in internal combustion engines fueled by biogas. The combustion process of an internal combustion engine ignition powered by biogas is characterized in terms of the duration of combustion, i.e., depending on the time elapsed while the reactants (methane and oxygen are transformed into products (mainly carbon dioxide and water. This study numerically evaluates the way in which the geometrical parameters such as the compression ratio and operating parameters like engine speed, the excess air, the time of spark timing and carbon dioxide content of biogas affect the evolution of the combustion process. To carry out this study, a five factors and two levels experiment was designed and conducted, based on which, the most influential parameters were identified. Equations expressing the combustion characteristic parameters, as a function of the geometric and operation parameters of a spark ignited engines, are delivered as a result.

  18. Consolidation of W–Ta composites: Hot isostatic pressing and spark and pulse plasma sintering

    Dias, M., E-mail: [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Guerreiro, F. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Correia, J.B. [LNEG, Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 1649-038 Lisboa (Portugal); Galatanu, A. [National Institute of Materials Physics, Atomistilor 105 bis Bucharest-Magurele, 077125 Ilfov (Romania); Rosiński, M. [Warsaw University of Technology, Faculty of Materials Science and Engineering, Warsaw (Poland); Monge, M.A.; Munoz, A. [Departamento de Física, Univerdidad Carlos III de Madrid, Avd. de la Universidad 30, 28911 Madrid (Spain); Alves, E. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Carvalho, P.A. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); CeFEMA, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)


    Highlights: • Consolidation of W–Ta composites using three techniques: HIP, SPS and PPS. • Comparison of consolidation methods in terms of W–Ta interdiffusion and densification. • Microstructure analysis in terms of oxides formation. - Abstract: Composites consisting of tantalum fiber/powder dispersed in a nanostructured W matrix have been consolidated by spark and pulse plasma sintering as well as by hot isostatic pressing. The microstructural observations revealed that the tungsten–tantalum fiber composites consolidated by hot isostatic pressing and pulse plasma sintering presented a continuous layer of Ta{sub 2}O{sub 5} phase at the W/Ta interfaces, while the samples consolidated by spark plasma sintering evidenced a Ta + Ta{sub 2}O{sub 5} eutectic mixture due to the higher temperature of this consolidation process. Similar results have been obtained for the tungsten–tantalum powder composites. A (W, Ta) solid solution was detected around the prior nanostructured W particles in tungsten–tantalum powder composites consolidated by spark and pulse plasma sintering. Higher densifications were obtained for composites consolidated by hot isostatic pressing and pulse plasma sintering.


    Scott A. Socolofsky; Brian C. Crounse; E. Eric Adams


    Two-phase plumes play an important role in the more practical scenarios for ocean sequestration of CO{sub 2}--i.e. dispersing CO{sub 2} as a buoyant liquid from either a bottom-mounted or ship-towed pipeline. Despite much research on related applications, such as for reservoir destratification using bubble plumes, our understanding of these flows is incomplete, especially concerning the phenomenon of plume peeling in a stratified ambient. To address this deficiency, we have built a laboratory facility in which we can make fundamental measurements of plume behavior. Although we are using air, oil and sediments as our sources of buoyancy (rather than CO{sub 2}), by using models, our results can be directly applied to field scale CO{sub 2} releases to help us design better CO{sub 2} injection systems, as well as plan and interpret the results of our up-coming international field experiment. The experimental facility designed to study two-phase plume behavior similar to that of an ocean CO{sub 2} release includes the following components: 1.22 x 1.22 x 2.44 m tall glass walled tank; Tanks and piping for the two-tank stratification method for producing step- and linearly-stratified ambient conditions; Density profiling system using a conductivity and temperature probe mounted to an automated depth profiler; Lighting systems, including a virtual point source light for shadowgraphs and a 6 W argon-ion laser for laser induced fluorescence (LIF) imaging; Imaging system, including a digital, progressive scanning CCD camera, computerized framegrabber, and image acquisition and analysis software; Buoyancy source diffusers having four different air diffusers, two oil diffusers, and a planned sediment diffuser; Dye injection method using a Mariotte bottle and a collar diffuser; and Systems integration software using the Labview graphical programming language and Windows NT. In comparison with previously reported experiments, this system allows us to extend the parameter range of

  20. A modification of the method of Carey and Sparks (1986) to estimate eruption column height from maximum clast dispersal

    Espindola, J.


    The method of Carey and Sparks (1986) has been widely applied to estimate the hight of eruptive columns from the dispersal of the maximum clast size. These authors presented curves of maximum downwind range versus crosswind range for different clast diameters and wind speeds obtained from the numerical solution of a column model developed by Sparks(1986). An improved model of eruptive column was later developed by Woods (1988). In this work we present the results of the simulation of clast dispersal following the procedure of Carey and Sparks (1986) and the eruption column of Woods (1988). The numerical calculations were carried out with a code that computes the height of the column and the vertical velocity, the density and the radius along the column. The code determines then the support envelopes for a given clast size and their fall, after leaving the column, are computed from the equations of motion with viscous friction. For the same downwind and crosswind ranges, this method yields column heights about 10% smaller than the method of Carey and Sparks and about 20% higher wind velocities. The height of the crater above sea level plays also a small role in the results. We present comparisons for the 1982 eruption columns from El Chichon volcano. References Carey S and RSJ Sparks (1986) Bull. Volcanol. 48: 109-125 Sparks RSJ (1986) Bull. Volcanol. 48: 3-15 Woods AW (1988) Bull. Volcanol. 50: 169-193

  1. Role of Ryanodine Receptor Subtypes in Initiation and Formation of Calcium Sparks in Arterial Smooth Muscle: Comparison with Striated Muscle

    Maik Gollasch


    Full Text Available Calcium sparks represent local, rapid, and transient calcium release events from a cluster of ryanodine receptors (RyRs in the sarcoplasmic reticulum. In arterial smooth muscle cells (SMCs, calcium sparks activate calcium-dependent potassium channels causing decrease in the global intracellular [Ca2+] and oppose vasoconstriction. This is in contrast to cardiac and skeletal muscle, where spatial and temporal summation of calcium sparks leads to global increases in intracellular [Ca2+] and myocyte contraction. We summarize the present data on local RyR calcium signaling in arterial SMCs in comparison to striated muscle and muscle-specific differences in coupling between L-type calcium channels and RyRs. Accordingly, arterial SMC Cav1.2 L-type channels regulate intracellular calcium stores content, which in turn modulates calcium efflux though RyRs. Downregulation of RyR2 up to a certain degree is compensated by increased SR calcium content to normalize calcium sparks. This indirect coupling between Cav1.2 and RyR in arterial SMCs is opposite to striated muscle, where triggering of calcium sparks is controlled by rapid and direct cross-talk between Cav1.1/Cav1.2 L-type channels and RyRs. We discuss the role of RyR isoforms in initiation and formation of calcium sparks in SMCs and their possible molecular binding partners and regulators, which differ compared to striated muscle.

  2. Combustion characteristics of turbo charged DISI-engines

    Hoffmeyer, Henrik


    In spite of progress in the development of alternative powertrain systems and energy sources, the internal combustion and all its derivates still are and will be the main powertrain for automobiles. In SI-engines, several approaches compete with each other like the controlled auto ignition (CAI or HCCI), throttle-free load control using variable valvetrains, stratified mixture formation with lean engine operation or highly turbo charged downsizing concepts all combined with gasoline direct injection. The presented work makes a contribution for a deeper understanding of the combustion process of a turbo charged direct injection engine operating with external EGR as well as lean stratified mixture. Using detailed test bench investigations and introducing a new optical measurement tool, the combustion process is described in detail focusing on the occurrence of non-premixed combustion phenomena. The influence of engine parameters like global and local air-/fuel ratio, external EGR and fuel rail pressure as well as the influence of fuel parameters are discussed giving a characterization of the combustion process of stratified engine operation. Furthermore, the influences of non-inert exhaust gas components on engine knock tendency are investigated using external EGR with an EGR catalyst. Opposing the results to numerical analysis, combustion characteristics of turbo charged DISI-engines are presented. (orig.)

  3. High ion charge states in a high-current, short-pulse, vacuum ARC ion sources

    Anders, A.; Brown, I.; MacGill, R.; Dickinson, M. [Lawrence Berkeley National Lab., CA (United States)


    Ions of the cathode material are formed at vacuum arc cathode spots and extracted by a grid system. The ion charge states (typically 1-4) depend on the cathode material and only little on the discharge current as long as the current is low. Here the authors report on experiments with short pulses (several {mu}s) and high currents (several kA); this regime of operation is thus approaching a more vacuum spark-like regime. Mean ion charge states of up to 6.2 for tungsten and 3.7 for titanium have been measured, with the corresponding maximum charge states of up to 8+ and 6+, respectively. The results are discussed in terms of Saha calculations and freezing of the charge state distribution.

  4. A model for evaluating the ballistic resistance of stratified packs

    Pirvu, C.; Georgescu, C.; Badea, S.; Deleanu, L.


    Models for evaluating the ballistic performance of stratified packs are useful in reducing the time for laboratory tests, understanding the failure process and identifying key factors to improve the architecture of the packs. The authors present the results of simulating the bullet impact on a packs made of 24 layers, taking into consideration the friction between layers (μ = 0.4) and the friction between bullet and layers (μ = 0.3). The aim of this study is to obtain a number of layers that allows for the bullet arrest in the packs and to have several layers undamaged in order to offer a high level of safety for this kind of packs that could be included in individual armors. The model takes into account the yield and fracture limits of the two materials the bullet is made of and those for one layer, here considered as an orthotropic material, having maximum equivalent plastic strain of 0.06. All materials are considered to have bilinear isotropic hardening behavior. After documentation, the model was designed as isothermal because thermal influence of the impact is considered low for these impact velocities. The model was developed with the help of Ansys 14.5. Each layer has 200 mm × 200 × 0.35 mm. The bullet velocity just before impact was 400 m/s, a velocity characterizing the average values obtained in close range with a ballistic barrel and the bullet model is following the shape and dimensions of the 9 mm FMJ (full metal jacket). The model and the results concerning the number of broken layers were validated by experiments, as the number of broken layers for the actual pack (made of 24 layers of LFT SB1) were also seven...eight. The models for ballistic impact are useful when they are particularly formulated for resembling to the actual system projectile - target.

  5. Internal and vorticity waves in decaying stratified flows

    Matulka, A.; Cano, D.


    Most predictive models fail when forcing at the Rossby deformation Radius is important and a large range of scales have to be taken into account. When mixing of reactants or pollutants has to be accounted, the range of scales spans from hundreds of Kilometers to the Bachelor or Kolmogorov sub milimiter scales. We present some theoretical arguments to describe the flow in terms of the three dimensional vorticity equations, using a lengthscale related to the vorticity (or enstrophy ) transport. Effect of intermittent eddies and non-homogeneity of diffusion are also key issues in the environment because both stratification and rotation body forces are important and cause anisotropy/non-homogeneity. These problems need further theoretical, numerical and observational work and one approach is to try to maximize the relevant geometrical information in order to understand and therefore predict these complex environmental dispersive flows. The importance of the study of turbulence structure and its relevance in diffusion of contaminants in environmental flows is clear when we see the effect of environmental disasters such as the Prestige oil spill or the Chernobil radioactive cloud spread in the atmosphere. A series of Experiments have been performed on a strongly stratified two layer fluid consisting of Brine in the bottom and freshwater above in a 1 square meter tank. The evolution of the vortices after the passage of a grid is video recorded and Particle tracking is applied on small pliolite particles floating at the interface. The combination of internal waves and vertical vorticity produces two separate time scales that may produce resonances. The vorticity is seen to oscilate in a complex way, where the frecuency decreases with time.

  6. The nonlinear evolution of modes on unstable stratified shear layers

    Blackaby, Nicholas; Dando, Andrew; Hall, Philip


    The nonlinear development of disturbances in stratified shear flows (having a local Richardson number of value less than one quarter) is considered. Such modes are initially fast growing but, like related studies, we assume that the viscous, non-parallel spreading of the shear layer results in them evolving in a linear fashion until they reach a position where their amplitudes are large enough and their growth rates have diminished sufficiently so that amplitude equations can be derived using weakly nonlinear and non-equilibrium critical-layer theories. Four different basic integro-differential amplitude equations are possible, including one due to a novel mechanism; the relevant choice of amplitude equation, at a particular instance, being dependent on the relative sizes of the disturbance amplitude, the growth rate of the disturbance, its wavenumber, and the viscosity of the fluid. This richness of choice of possible nonlinearities arises mathematically from the indicial Frobenius roots of the governing linear inviscid equation (the Taylor-Goldstein equation) not, in general, differing by an integer. The initial nonlinear evolution of a mode will be governed by an integro-differential amplitude equations with a cubic nonlinearity but the resulting significant increase in the size of the disturbance's amplitude leads on to the next stage of the evolution process where the evolution of the mode is governed by an integro-differential amplitude equations with a quintic nonlinearity. Continued growth of the disturbance amplitude is expected during this stage, resulting in the effects of nonlinearity spreading to outside the critical level, by which time the flow has become fully nonlinear.

  7. A new scoring system to stratify risk in unstable angina

    Salzberg Simón


    Full Text Available Abstract Background We performed this study to develop a new scoring system to stratify different levels of risk in patients admitted to hospital with a diagnosis of unstable angina (UA, which is a complex syndrome that encompasses different outcomes. Many prognostic variables have been described but few efforts have been made to group them in order to enhance their individual predictive power. Methods In a first phase, 473 patients were prospectively analyzed to determine which factors were significantly associated with the in-hospital occurrence of refractory ischemia, acute myocardial infarction (AMI or death. A risk score ranging from 0 to 10 points was developed using a multivariate analysis. In a second phase, such score was validated in a new sample of 242 patients and it was finally applied to the entire population (n = 715. Results ST-segment deviation on the electrocardiogram, age ≥ 70 years, previous bypass surgery and troponin T ≥ 0.1 ng/mL were found as independent prognostic variables. A clear distinction was shown among categories of low, intermediate and high risk, defined according to the risk score. The incidence of the triple end-point was 6 %, 19.2 % and 44.7 % respectively, and the figures for AMI or death were 2 %, 11.4 % and 27.6 % respectively (p Conclusions This new scoring system is simple and easy to achieve. It allows a very good stratification of risk in patients having a clinical diagnosis of UA. They may be divided in three categories, which could be of help in the decision-making process.

  8. Assessing iron dynamics in the release from a stratified reservoir

    Ashby, S.L.; Faulkner, S.P.; Gambrell, R.P.; Smith, B.A.


    Field and laboratory studies were conducted to describe the fate of total, dissolved, and ferrous (Fe2.) iron in the release from a stratified reservoir with an anoxic hypolimnion. Concentrations of total iron in the tail water indicated a first order removal process during a low flow release (0.6 m3sec1), yet negligible loss was observed during a period of increased discharge (2.8 m 3 sec-1). Dissolved and ferrous iron concentrations in the tailwater were highly variable during both release regimes and did not follow responses based on theoretical predictions. Ferrous iron concentrations in unfiltered samples were consistently greater than concentrations observed in samples filtered separately through 0.4, 0.2, and 0.1 ??m filters. Total iron removal in laboratory studies followed first order kinetics, but was twice that rate (0.077 mg.L-1 .hr 1) observed during low flow discharge in the tailwater (0.036 mg. L1 .hr1). Dissolved and ferrous iron losses in laboratory studies were rapid (???75% in the first 15 minutes and 95% within 1 hour), followed theoretical predictions, and were much faster than observations in the tailwater (???30% within the first hour). The presence of particulate forms of ferrous iron in the field and differences in removal rates observed in field and laboratory studies indicate a need for improved field assessment techniques and consideration of complexation reactions when assessing the dynamics of iron in reservoir releases and downstream impacts as a result of operation regimes. ?? Copyright by the North American Lake Management Society 2004.

  9. Interfacial instabilities in a stratified flow of two superposed fluids

    Schaflinger, Uwe


    Here we shall present a linear stability analysis of a laminar, stratified flow of two superposed fluids which are a clear liquid and a suspension of solid particles. The investigation is based upon the assumption that the concentration remains constant within the suspension layer. Even for moderate flow-rates the base-state results for a shear induced resuspension flow justify the latter assumption. The numerical solutions display the existence of two different branches that contribute to convective instability: long and short waves which coexist in a certain range of parameters. Also, a range exists where the flow is absolutely unstable. That means a convectively unstable resuspension flow can be only observed for Reynolds numbers larger than a lower, critical Reynolds number but still smaller than a second critical Reynolds number. For flow rates which give rise to a Reynolds number larger than the second critical Reynolds number, the flow is absolutely unstable. In some cases, however, there exists a third bound beyond that the flow is convectively unstable again. Experiments show the same phenomena: for small flow-rates short waves were usually observed but occasionally also the coexistence of short and long waves. These findings are qualitatively in good agreement with the linear stability analysis. Larger flow-rates in the range of the second critical Reynolds number yield strong interfacial waves with wave breaking and detached particles. In this range, the measured flow-parameters, like the resuspension height and the pressure drop are far beyond the theoretical results. Evidently, a further increase of the Reynolds number indicates the transition to a less wavy interface. Finally, the linear stability analysis also predicts interfacial waves in the case of relatively small suspension heights. These results are in accordance with measurements for ripple-type instabilities as they occur under laminar and viscous conditions for a mono-layer of particles.

  10. Magnetoacoustic Waves in Stratified Atmospheres with a Magnetic Null Point

    Tarr, Lucas A.; Linton, Mark; Leake, James E.


    Magnetic fields strongly modify the propagation of MHD waves from the photosphere to the low corona, as can be shown exactly for the most simple case of a uniform magnetic field and isothermally stratrified atmosphere. For slightly more realistic scenarios, where both the atmospheric parameters and the magnetic field vary spatially, the linear MHD equations typically cannot be solved analytically. We use the Lagrangian Remap code--a nonlinear, shock-capturing MHD code--to study the propagation of initially acoustic wavepackets through a model 2D atmosphere that includes a gravitationally stratified chromosphere, transition region, and low corona. The magnetic field is formed by three photospheric concentrations and includes a single magnetic null point, resulting in an inhomogeneous system with a magnetic dome topology. A portion of an introduced wavepacket will refract toward the null due to the varying Alfven speed. Waves incident on the equipartition contour surrounding the null, where the sound and Alfven speeds coincide, partially transmit, reflect, and mode convert between branches of the local dispersion relation. Outward propagating slow modes generated during conversion become strongly concentrated along the set of field lines passing near the null. Acoustic energy is beamed back downwards towards each photospheric foot point, and upwards along one separatrix that exits the top of the numerical domain. Changes in the dominant restoring force for the wavepacket, between the Lorentz and pressure gradient forces, lead to a buildup of current density along topologically important features of the system (the null point and its four separatrices) and can drive reconnection at the null point itself. Ohmic dissipation of the currents locally heats the plasma. We find that the amount of current accumulation depends on where the centroid of a wavepacket initial crosses the photosphere, but does not simply coincide with regions of open versus closed magnetic field or

  11. Stability characteristics of jets in linearly-stratified, rotating fluids

    Chen, Rui-Rong; Boyer, Don L.; Tao, Lijun

    A series of laboratory experiments are conducted concerning an azimuthal jet of a linearly stratified rotating fluid in a cylindrical geometry. The jet is characterized by vertical and horizontal shear and the question of the stability of the flow is considered experimentally. The jet is driven by a source-sink method characterized by a volume flow rate of strength Q. BecauseQ has no direct geophysical significance a combined external set of dimensionless parameters is introduced. These include the Rossby, Richardson and Ekman numbers, the jet aspect ratio and two geometrical parameters. A RossbyRo against RichardsonRi number flow regime diagram is presented which shows that the wave mode of the instability generally decreases with increasingRo andRi, for fixedRi andRo, respectively. In accordance with Killworth's (1980) linear stability analysis, the wave mode for smallRi (Ri ⪉ 15) depends principally onRi with the instability being largely a baroclinic one. For largerRi(Ri ⪉ 100), again as predicted by Killworth's theory, the wave mode depends primarily onRo, the instability being a barotropic one. The regime diagram can be used to estimate the wave-length of jet instabilities in the atmosphere and oceans. These estimates suggest that the wave-lengths decrease with increasing jet velocity, decreasing jet width (equivalent to increasing horizontal shear) and increasing vertical shear, other parameters being fixed. An azimuthal topography aligned along the jet has the tendency to stabilize the jet in the sense that the amplitude of the instability is shown to be dramatically smaller in the presence of the topography, other parameters being fixed. The topography also tends to increase the wave-length of the instability. A scaling analysis is advanced, and supporting experimental data presented, relating the external and internal parameters utilized.

  12. Magnetic charge quantisation and fractionally charged quarks

    Hooft, G. 't


    If magnetic monopoles with Schwinger's value of the magnetic charge would exist then that would pose serious restrictions on theories with fractionally charged quarks, even if they are confined. Weak and electromagnetic interactions must be unified with color, leading to a Weinberg angle w close to

  13. Distribution of vaccine/antivirals and the 'least spread line' in a stratified population

    Goldstein, E.; Apolloni, A.; Lewis, B.; Miller, J. C.; Macauley, M.; Eubank, S.; Lipsitch, M.; Wallinga, J.


    We describe a prioritization scheme for an allocation of a sizeable quantity of vaccine or antivirals in a stratified population. The scheme builds on an optimal strategy for reducing the epidemic's initial growth rate in a stratified mass-action model. The strategy is tested on the EpiSims network

  14. Implementing content constraints in alpha-stratified adaptive using a shadow test approach

    Linden, van der Wim J.; Chang, Hua-Hua


    The methods of alpha-stratified adaptive testing and constrained adaptive testing with shadow tests are combined. The advantages are twofold: First, application of the shadow test approach allows the implementation of any type of constraint on item selection in alpha-stratified adaptive testing. Sec

  15. Implementing Content Constraints in Alpha-Stratified Adaptive Testing Using a Shadow Test Approach. Research Report.

    van der Linden, Wim J.; Chang, Hua-Hua

    The methods of alpha-stratified adaptive testing and constrained adaptive testing with shadow tests are combined in this study. The advantages are twofold. First, application of the shadow test allows the researcher to implement any type of constraint on item selection in alpha-stratified adaptive testing. Second, the result yields a simple set of…

  16. Experimental Validation of a Domestic Stratified Hot Water Tank Model in Modelica for Annual Performance Assessment

    Carmo, Carolina; Dumont, Olivier; Nielsen, Mads Pagh


    The use of stratified hot water tanks in solar energy systems - including ORC systems - as well as heat pump systems is paramount for a better performance of these systems. However, the availability of effective and reliable models to predict the annual performance of stratified hot water tanks c...

  17. Lessons for molecular diagnostics in oncology from the Cancer Research UK Stratified Medicine Programme.

    Lindsay, Colin R; Shaw, Emily; Walker, Ian; Johnson, Peter W M


    The implementation of stratified medicine in modern cancer care presents substantial opportunity to refine diagnosis and treatment but also numerous challenges. Through experience in a UK tumor profiling initiative, we have gained valuable insights into the complexities and possible solutions for routine delivery of stratified cancer medicine.

  18. Optimal stratification of item pools in α-stratified computerized adaptive testing

    Chang, Hua-Hua; Linden, van der Wim J.


    A method based on 0-1 linear programming (LP) is presented to stratify an item pool optimally for use in α-stratified adaptive testing. Because the 0-1 LP model belongs to the subclass of models with a network flow structure, efficient solutions are possible. The method is applied to a previous item

  19. Numerical Investigation of Effective Heat Conductivity of Fluid in Charging Process of Thermal Storage Tank

    Taheri, H.; Schmidt, F. P.; Gabi, M.


    This paper presents a numerical case study of heat transfer mechanisms during the charging process of a stratified thermal storage tank applied in a specific adsorption heat pump cycle. The effective thermal conductivity of the heat transfer fluid during the charging process is analyzed through CFD simulations using Unsteady Reynolds-averaged Navier-Stokes equations (URANS). The aim of the study is to provide an equivalent thermal conductivity for a one-dimensional storage tank model to be us...

  20. Linear shaped charge

    Peterson, David; Stofleth, Jerome H.; Saul, Venner W.


    Linear shaped charges are described herein. In a general embodiment, the linear shaped charge has an explosive with an elongated arrowhead-shaped profile. The linear shaped charge also has and an elongated v-shaped liner that is inset into a recess of the explosive. Another linear shaped charge includes an explosive that is shaped as a star-shaped prism. Liners are inset into crevices of the explosive, where the explosive acts as a tamper.

  1. Indications for tonsillectomy stratified by the level of evidence

    Windfuhr, Jochen P.


    Background: One of the most significant clinical trials, demonstrating the efficacy of tonsillectomy (TE) for recurrent throat infection in severely affected children, was published in 1984. This systematic review was undertaken to compile various indications for TE as suggested in the literature after 1984 and to stratify the papers according to the current concept of evidence-based medicine. Material and methods: A systematic Medline research was performed using the key word of “tonsillectomy“ in combination with different filters such as “systematic reviews“, “meta-analysis“, “English“, “German“, and “from 1984/01/01 to 2015/05/31“. Further research was performed in the Cochrane Database of Systematic Reviews, National Guideline Clearinghouse, Guidelines International Network and BMJ Clinical Evidence using the same key word. Finally, data from the “Trip Database” were researched for “tonsillectomy” and “indication“ and “from: 1984 to: 2015“ in combination with either “systematic review“ or “meta-analysis“ or “metaanalysis”. Results: A total of 237 papers were retrieved but only 57 matched our inclusion criteria covering the following topics: peritonsillar abscess (3), guidelines (5), otitis media with effusion (5), psoriasis (3), PFAPA syndrome (6), evidence-based indications (5), renal diseases (7), sleep-related breathing disorders (11), and tonsillitis/pharyngitis (12), respectively. Conclusions: 1) The literature suggests, that TE is not indicated to treat otitis media with effusion. 2) It has been shown, that the PFAPA syndrome is self-limiting and responds well to steroid administration, at least in a considerable amount of children. The indication for TE therefore appears to be imbalanced but further research is required to clarify the value of surgery. 3) Abscesstonsillectomy as a routine is not justified and indicated only for cases not responding to other measures of treatment, evident complications

  2. Discharge current distribution in stratified soil under impulse discharge

    Eniola Fajingbesi, Fawwaz; Shahida Midi, Nur; Elsheikh, Elsheikh M. A.; Hajar Yusoff, Siti


    The mobility of charge particles traversing a material defines its electrical properties. Soil (earth) have long been the universal grounding before and after the inception of active ground systems for electrical appliance purpose due to it semi-conductive properties. The soil can thus be modelled as a single material exhibiting semi-complex inductive-reactive impedance. Under impulse discharge such as lightning strikes to soil this property of soil could result in electric potential level fluctuation ranging from ground potential rise/fall to electromagnetic pulse coupling that could ultimately fail connected electrical appliance. In this work we have experimentally model the soil and lightning discharge using point to plane electrode setup to observe the current distribution characteristics at different soil conductivity [mS/m] range. The result presented from this research indicate above 5% shift in conductivity before and after discharge which is significant for consideration when dealing with grounding designs. The current distribution in soil have also be successfully observed and analysed from experimental result using mean current magnitude in relation to electrode distance and location, current density variation with depth all showing strong correlation with theoretical assumptions of a semi-complex impedance material.

  3. Transport Phenomena in Stratified Multi-Fluid Flow in the Presence and Absence of Gravity

    Chigier, Norman; Humphrey, William


    Experiments are being conducted to study the effects of buoyancy on planar density-stratified shear flows. A wind tunnel generates planar flows separated by an insulating splitter plate, with either flow heated, which emerge from a two-dimensional nozzle. The objective is to isolate and define the effect of gravity and buoyancy on a stratified shear layer. To this end, both stably and unstably stratified layers will be investigated. This paper reports on the results of temperature and velocity measurements across the nozzle exit plane and downstream along the nozzle center plane.

  4. Efficiency evaluation of the DISC (direct-injection stratified charge), DHC (dilute homogeneous charge), and DI Diesel engines (direct-injection diesel)

    Hane, G.J.


    The thermodynamic laws governing the Otto and diesel cycle engines and the possible approaches that might be taken to increase the delivered efficiency of the reciprocating piston engine are discussed. The generic aspects of current research are discussed and typical links between research and the technical barriers to the engines' development are shown. The advanced engines are discussed individually. After a brief description of each engine and its advantages, the major technical barriers to their development are discussed. Also included for each engine is a discussion of examples of the linkages between these barriers and current combustion and thermodynamic research. For each engine a list of questions is presented that have yet to be resolved and could not be resolved within the scope of this study. These questions partially indicate the limit to the state of knowledge regarding efficiency characteristics of the advanced engine concepts. The major technical barriers to each of the engines and their ranges of efficiency improvement are summarized.

  5. Electrodynamics of Radiating Charges

    Øyvind Grøn


    Full Text Available The theory of electrodynamics of radiating charges is reviewed with special emphasis on the role of the Schott energy for the conservation of energy for a charge and its electromagnetic field. It is made clear that the existence of radiation from a charge is not invariant against a transformation between two reference frames that has an accelerated motion relative to each other. The questions whether the existence of radiation from a uniformly accelerated charge with vanishing radiation reaction force is in conflict with the principle of equivalence and whether a freely falling charge radiates are reviewed. It is shown that the resolution of an electromagnetic “perpetuum mobile paradox” associated with a charge moving geodetically along a circular path in the Schwarzschild spacetime requires the so-called tail terms in the equation of motion of a charged particle.

  6. Processing of pure titanium containing titanium-based reinforcing ceramics additives using spark plasma sintering

    Mondiu Olayinka DUROWOJU


    Full Text Available The densification behaviour, microstructural changes and hardness characteristics during spark plasma sintering of CP-Ti reinforced with TiC, TiN, TiCN and TiB2 were investigated. Commercially pure Ti powders were dry mixed with varied amounts (2.5 and 5 wt. % of the ceramic additives using a T2F Turbula mixer for 5 h and at a speed of 49 rpm. The blended composite powders were then sintered using spark plasma sintering system (model HHPD-25 from FCT Germany at a heating rate of 100oC min-1, dwell time of 5 min and sintering temperature of 950ºC. The sintering of CP-Ti was used as a base study to select the proper spark plasma sintering temperature for full density. Densification was monitored through analysis of the recorded punch displacement and the measured density of the sintered samples using Archimedes method. High densities ranging from 97.8% for 5% TiB2 addition to 99.6% for 5% TiCN addition were achieved at a relatively low temperature of 950°C. Microstructural analyses show a uniform distribution of the additives and finer structure showing their inhibitive effect on grain growth. An improved hardness was observed in all the cases with highest values obtained with TiCN as a result of the combined effect of TiC and TiN. A change in the fracture mode from trans granular to intergranular was also observed.

  7. Fabrication and Characterization of Surrogate Fuel Particles Using the Spark Erosion Method

    Metzger, Kathryn E.

    In light of the disaster at the Fukushima Daiichi Nuclear Plant, the Department of Energy's Advanced Fuels Program has shifted its interest from enhanced performance fuels to enhanced accident tolerance fuels. Dispersion fuels possess higher thermal conductivities than traditional light water reactor fuel and as a result, offer improved safety margins. The benefits of a dispersion fuel are due to the presence of the secondary non-fissile phase (matrix), which serves as a barrier to fission products and improves the overall thermal performance of the fuel. However, the presence of a matrix material reduces the fuel volume, which lowers the fissile content of dispersion. This issue can be remedied through the development of higher density fuel phases or through an optimization of fuel particle size and volume loading. The latter requirement necessitates the development of fabrication methods to produce small, micron-order fuel particles. This research examines the capabilities of the spark erosion process to fabricate particles on the order of 10 μm. A custom-built spark erosion device by CT Electromechanica was used to produce stainless steel surrogate fuel particles in a deionized water dielectric. Three arc intensities were evaluated to determine the effect on particle size. Particles were filtered from the dielectric using a polycarbonate membrane filter and vacuum filtration system. Fabricated particles were characterized via field emission scanning electron microscopy (FESEM), laser light particle size analysis, energy-dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD), and gas pycnometry. FESEM images reveal that the spark erosion process produces highly spherical particles on the order of 10 microns. These findings are substantiated by the results of particle size analysis. Additionally, EDS and XRD results indicate the presence of oxide phases, which suggests the dielectric reacted with the molten debris during particle formation.

  8. Conversion of a diesel engine to a spark ignition natural gas engine



    Requirements for alternatives to diesel-fueled vehicles are developing, particularly in urban centers not in compliance with mandated air quality standards. An operator of fleets of diesel- powered vehicles may be forced to either purchase new vehicles or equip some of the existing fleets with engines designed or modified to run on alternative fuels. In converting existing vehicles, the operator can either replace the existing engine or modify it to burn an alternative fuel. Work described in this report addresses the problem of modifying an existing diesel engine to operate on natural gas. Tecogen has developed a technique for converting turbocharged automotive diesel engines to operate as dedicated spark-ignition engines with natural gas fuel. The engine cycle is converted to a more-complete-expansion cycle in which the expansion ratio of the original engine is unchanged while the effective compression ratio is lowered, so that engine detonation is avoided. The converted natural gas engine, with an expansion ratio higher than in conventional spark- ignition natural gas engines, offers thermal efficiency at wide-open- throttle conditions comparable to its diesel counterpart. This allows field conversion of existing engines. Low exhaust emissions can be achieved when the engine is operated with precise control of the fuel air mixture at stoichiometry with a 3-way catalyst. A Navistar DTA- 466 diesel engine with an expansion ratio of 16.5 to 1 was converted in this way, modifying the cam profiles, increasing the turbocharger boost pressure, incorporating an aftercooler if not already present, and adding a spark-ignition system, natural gas fuel management system, throttle body for load control, and an electronic engine control system. The proof-of-concept engine achieved a power level comparable to that of the diesel engine without detonation. A conversion system was developed for the Navistar DT 466 engine. NOx emissions of 1.5 g/bhp-h have been obtained.

  9. Laser-induced spark ignition of H2/O2/Ar mixtures


    Laser-induced spark ignition of hydrogen-oxygen-argon mixtures was experimentally investigated using a Q-swiched Nd:YAG laser to break down the gas at 532 nm. The laser-based high-speed schlieren system was employed to record flame front evolution for the gas mixtures with different initial pressure or laser output energy or argon dilution. The results show that the breakdown of the gas leads to the generation of ellipsoidal plasma. The rarefaction waves create the toroidal rings at the leading and trailing edges of the plasma, which provides a reasonable explanation for inward wrinkle of the plasma and the resultant flame. The toroidal rings at leading edge decays more rapidly and a gas lobe is generated that moves towards the laser. The hot gas in the plasma induces the generation of the spark kernel. Affected by the very weak shock wave or compression waves reflected off the wall, the initial laminar flame decelerates. The arc flame front interactions with the wall, reversed shock wave or compression waves, rarefaction waves, etc. induce the transition from laminar flame to turbulent one. These induce the transition from laminar flame to turbulent flame. For stoichiometric hydrogen-oxygen mixtures diluted by 76.92% argon at an initial pressure of 53.33 kPa, the minimum output energy of the laser is 15 mJ for successful laser-induced spark ignition. With increasing initial pressure or the output energy of the laser, or decreasing argon dilution, the speed of the flame front increases.

  10. The potential of rapid cooling spark plasma sintering for metallic materials

    Faming Zhang


    Full Text Available Spark plasma sintering (SPS is a remarkable technique for consolidating a large variety of advanced materials with rapid heating rates. However, adjusting the cooling rates has so far faced limitations. This communication discusses the potentials of SPS integrated with a novel gas quenching system that can allow metallic materials to be sintered and rapidly quenched directly after the sintering step, saving energy and costs. Results on numerical simulations of rapid cooling-SPS and the mechanical properties and microstructures of Ti6Al4V alloy are discussed; exhibiting the feasibility of this rapid cooling SPS technique and the major implications for the field of SPS and metallic powder consolidation.

  11. A compact spark pre-ionized pulser sustainer TE–CO2 laser

    N S Benerji; Neeraj Varshnay; Lala Abhinandan; U Nundy


    A compact spark pre-ionized pulser sustainer TE–CO2 laser that can produce an output energy of one joule with an overall efficiency of 12.4% is presented. Optical pulses have durations of 7.15 s FWHM. Here, the laser uses all solid-state excitation (ASSE) circuit and the discharge formed between two uniform field electrodes placed 1.5 cm apart ultimately leads to a discharge volume of 50 cm × 1.5 cm × 1.5 cm.

  12. Spark Ignition of Combustible Vapor in a Plastic Bottle as a Demonstration of Rocket Propulsion

    Mattox, J. R.


    I report an innovation that provides a compelling demonstration of rocket propulsion, appropriate for students of physics and other physical sciences. An electrical spark is initiated from a distance to cause the deflagration of a combustible vapor mixed with air in a lightweight plastic bottle that is consequently propelled as a rocket by the release of combustion products, i.e., a "whoosh rocket." My recommendation is that the standard fuel for pedagogical whoosh demonstrations be isopropanol, and the recommended vessel is the 3.8-L high-density polyethylene (HDPE) bottle.

  13. X-rays from negative laboratory sparks in air: Influence of the anode geometry

    Hettiarachchi, Pasan; Rahman, Mahbubur; Cooray, Vernon; Dwyer, Joseph


    In this experimental work, the influence of the grounded anode geometry is studied on the X-ray production from the laboratory sparks in air at atmospheric pressure when a negative impulse voltage is applied to a high voltage rod which served as a cathode. The result shows that the smaller the diameter of the anode, the higher the energy of X-ray bursts. This observation can be explained by the mechanism that the encounter of negative and positive streamer fronts just before the final breakdown is the event that accelerates electrons to X-ray generating energies, but may not be the only mechanism that generates X-rays.

  14. Construction and performance of large wire spark chambers with magnetostrictive read-out

    Grayer, G; Dietl, H; Hyams, Bernard David; Jones, C; Koch, W; Lorenz, E; Lütjens, G; Männer, W; Meissburger, J; Stierlin, U; Weilhammer, P


    Describes the construction and performance of wire spark chambers having an active area of 3.60*0.90 m/sup 2/, a gap of 10 mm, and a wire spacing of 1 mm. Magnetostrictive read-out from both planes gives two coordinate values per chamber. Chambers of this type, together with smaller ones of similar construction, have been part of a magnet spectrometer which performed reliably between May 1970 and May 1971; during this time they were pulsed approximately 10/sup 7/ times. (9 refs).

  15. Nuclear Rocket Ceramic Metal Fuel Fabrication Using Tungsten Powder Coating and Spark Plasma Sintering

    Barnes, M. W.; Tucker, D. S.; Hone, L.; Cook, S.


    Nuclear thermal propulsion is an enabling technology for crewed Mars missions. An investigation was conducted to evaluate spark plasma sintering (SPS) as a method to produce tungsten-depleted uranium dioxide (W-dUO2) fuel material when employing fuel particles that were tungsten powder coated. Ceramic metal fuel wafers were produced from a blend of W-60vol% dUO2 powder that was sintered via SPS. The maximum sintering temperatures were varied from 1,600 to 1,850 C while applying a 50-MPa axial load. Wafers exhibited high density (>95% of theoretical) and a uniform microstructure (fuel particles uniformly dispersed throughout tungsten matrix).

  16. Spark Plasma Sintering of high-strength ultrafine-grained tungsten carbide

    Nokhrin, A. V.; Chuvil'deev, V. N.; Blagoveshchenskiy, Yu V.; Boldin, M. S.; Sakharov, N. V.; Isaeva, N. V.; Popov, A. A.; Lantcev, E. A.; Belkin, O. A.; Smirnova, E. S.


    The paper dwells on the research conducted into high-rate consolidation of pure tungsten carbide nanopowders using the Spark Plasma Sintering. Studies included the effect that the original size of WC nanoparticles and their preparation modes have on density, structure parameters, and mechanical properties of tungsten carbide. It has been found that materials that show abnormal grain growth during sintering have lower values of sintering activation energy as compared to materials the structure of which is more stable during high-rate heating. A qualitative model is proposed that explains this effect through the dependence of the grain boundary diffusion coefficient on the grain boundary migration rate.

  17. Surprising synthesis of nanodiamond from single-walled carbon nanotubes by the spark plasma sintering process

    Mirzaei, Ali; Ham, Heon; Na, Han Gil; Kwon, Yong Jung; Kang, Sung Yong; Choi, Myung Sik; Bang, Jae Hoon; Park, No-Hyung; Kang, Inpil; Kim, Hyoun Woo


    Nanodiamond (ND) was successfully synthesized using single-walled carbon nanotubes (SWCNTs) as a pure solid carbon source by means of a spark plasma sintering process. Raman spectra and X-ray diffraction patterns revealed the generation of the cubic diamond phase by means of the SPS process. Lattice-resolved TEM images confirmed that diamond nanoparticles with a diameter of about ˜10 nm existed in the products. The NDs were generated mainly through the gas-phase nucleation of carbon atoms evaporated from the SWCNTs. [Figure not available: see fulltext.

  18. An assessment of combustion products of spark ignition engines supplied by ethanol - gasoline blends

    Uzuneanu, K.; Golgotiu, E.


    The causes of environmental pollution by internal combustion engines arise from the use of fuels containing bounded carbon, from the fact that combustion takes place on a cyclic basis and at high temperature. The first and the last causes are directly related to the fuel and therefore there is in principle a possibility to reduce pollution by acting upon the fuel used. The present paper deals with the comparison of the level of combustion products of a spark ignition engine supplied by gasoline and by a mixture of 10 % ethanol - 90% gasoline.


    Karel Vokurka


    Full Text Available The surface temperatures of the plasma core in the final stages of the first contraction phase of spark-generated bubbles oscillating under ordinary laboratory conditions in a large expanse of water are determined experimentally. The measurement method is based on an analysis of the optical radiation from the bubbles and on the assumption that the plasma core is radiating as a black-body. It is found that the maximum surface temperatures of the plasma core range 4300–8700 K.

  20. Performance and emissions analysis on using acetone–gasoline fuel blends in spark-ignition engine


    In this study, new blended fuels were formed by adding 3–10 vol. % of acetone into a regular gasoline. According to the best of the author's knowledge, it is the first time that the influence of acetone blends has been studied in a gasoline-fueled engine. The blended fuels were tested for their energy efficiencies and pollutant emissions using SI (spark-ignition) engine with single-cylinder and 4-stroke. Experimental results showed that the AC3 (3 vol.% acetone + 97 vol.% gasoline) blended fu...