WorldWideScience

Sample records for passive diffusion tubes

  1. Measurement of Passive Uptake Rates for Volatile Organic Compounds on Commercial Thermal Desorption Tubes and the Effect of Ozone on Sampling

    Energy Technology Data Exchange (ETDEWEB)

    Maddalena, Randy [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Parra, Amanda [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Russell, Marion [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Lee, Wen-Yee [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2013-05-01

    Diffusive or passive sampling methods using commercially filled axial-sampling thermal desorption tubes are widely used for measuring volatile organic compounds (VOCs) in air. The passive sampling method provides a robust, cost effective way to measure air quality with time-averaged concentrations spanning up to a week or more. Sampling rates for VOCs can be calculated using tube geometry and Fick’s Law for ideal diffusion behavior or measured experimentally. There is evidence that uptake rates deviate from ideal and may not be constant over time. Therefore, experimentally measured sampling rates are preferred. In this project, a calibration chamber with a continuous stirred tank reactor design and constant VOC source was combined with active sampling to generate a controlled dynamic calibration environment for passive samplers. The chamber air was augmented with a continuous source of 45 VOCs ranging from pentane to diethyl phthalate representing a variety of chemical classes and physiochemical properties. Both passive and active samples were collected on commercially filled Tenax TA thermal desorption tubes over an 11-day period and used to calculate passive sampling rates. A second experiment was designed to determine the impact of ozone on passive sampling by using the calibration chamber to passively load five terpenes on a set of Tenax tubes and then exposing the tubes to different ozone environments with and without ozone scrubbers attached to the tube inlet. During the sampling rate experiment, the measured diffusive uptake was constant for up to seven days for most of the VOCs tested but deviated from linearity for some of the more volatile compounds between seven and eleven days. In the ozone experiment, both exposed and unexposed tubes showed a similar decline in terpene mass over time indicating back diffusion when uncapped tubes were transferred to a clean environment but there was no indication of significant loss by ozone reaction.

  2. Bromine-quenched high temperature G-M tube with passivated cathode

    International Nuclear Information System (INIS)

    Mitrofanov, N.

    1975-01-01

    A bromine doped self-quenching Geiger-Mueller tube having an operational life expectancy in excess of 1,200 hours at a temperature of 315 0 C is described. The tube comprises a passivated metal coated cathode which is conditioned or aged for operation at room temperature, thus obviating the necessity of thermally cycling the tube at progressively elevated temperatures. Useful metal coatings for the cathode include chromium, platinum, and nickel-copper alloys deposited in a layer less than about 1 mil thick. A method for passivating the metal coated cathode and subsequently conditioning the tube and its contents is disclosed. (auth)

  3. The passive diffusion of Leptospira interrogans

    Science.gov (United States)

    Koens, Lyndon; Lauga, Eric

    2014-12-01

    Motivated by recent experimental measurements, the passive diffusion of the bacterium Leptospira interrogans is investigated theoretically. By approximating the cell shape as a straight helix and using the slender-body-theory approximation of Stokesian hydrodynamics, the resistance matrix of Leptospira is first determined numerically. The passive diffusion of the helical cell is then obtained computationally using a Langevin formulation which is sampled in time in a manner consistent with the experimental procedure. Our results are in excellent quantitative agreement with the experimental results with no adjustable parameters.

  4. The passive diffusion of Leptospira interrogans

    International Nuclear Information System (INIS)

    Koens, Lyndon; Lauga, Eric

    2014-01-01

    Motivated by recent experimental measurements, the passive diffusion of the bacterium Leptospira interrogans is investigated theoretically. By approximating the cell shape as a straight helix and using the slender-body-theory approximation of Stokesian hydrodynamics, the resistance matrix of Leptospira is first determined numerically. The passive diffusion of the helical cell is then obtained computationally using a Langevin formulation which is sampled in time in a manner consistent with the experimental procedure. Our results are in excellent quantitative agreement with the experimental results with no adjustable parameters. (paper)

  5. Single-tube condensation experiment in Passive Auxiliary Feedwater System of APR1400+

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Chang Wook; No, Hee Cheon; Yun, Bong Yo; Jeon, Byong Guk [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2012-05-15

    Conventional Korean nuclear power plants, Advanced Power Reactors (APR), are characterized by an active cooling system. However, Active cooling system may not prevent significant damage without any AC power source available for its operation as vividly illustrated through the recent Fukushima incident. In the APR1400+ to be designed, an independent passive cooling system was added in order to overcome the aforementioned shortcomings. In the Passive Auxiliary Feedwater System (PAFS), gravity force and density difference between steam and water are used. The system comprises of 240 condensation tubes to efficiently remove decay heat. Before applying the PAFS to APR1400+, the system's safety and heat removal performance must be verified. The present study experimentally evaluates the heat removal performance of a single tube in the PAFS. The objectives of SCOP (Single-tube Condensation experiment facility of PAFS) are the evaluation of the heat removal performance in the tube of the PAFS and database construction under various tube designs and test conditions. Reaching these objectives, we developed advanced measurement techniques for the amount of moisture, heat flux, and water film thickness.

  6. [Characterizing the passive opening of the eustachian tube in a hypo-/hyperbaric pressure chamber].

    Science.gov (United States)

    Meyer, M F; Mikolajczak, S; Luers, J C; Lotfipour, S; Beutner, D; Jumah, M D

    2013-09-01

    Beside arbitrary and not arbitrary active pressure equalization systems there is a passive equalization system via the Eustachian tube (ET) at pressure difference between the epipharyngeal space and the middle ear. Aim of this study was to characterize this passive equalization system in a hypobaric/hyperbaric pressure chamber by continuously measuring the tympanic impedance. In contrast to other studies, which are measured only in a hypobaric pressure chamber it is possible to include participants with Eustachian tube dysfunction (ETD). Following a fixed pressure profile 39 participants were exposed to phases of pressure rising and decompression. By continuously measuring the tympanic impedance in the pressure chamber it was possible to measure data of the Eustachian Tube opening Pressure (ETOP), Eustachian Tube closing pressure (ETCP) and Eustachian Tube opening duration (ETOD). In addition it was possible to characterize the gradient of pressure during decompression, while the ET was open. Beside the measurement of the arithmetic average of the ETOP (30.2 ± 15.1 mbar), ETCP (9.1 ± 7.7 mbar) and ETOD (0.65 ± 0.38 s) it was obvious that there are recurrent samples of pressure progression during the phase of tube opening. Generally it is possible to differentiate between the type of complete opening and partial opening. The fundamental characterization of the action of the passive tube opening, including the measurement of the ETOP, ETCP and ETOD, is a first step in understanding the physiological and pathophysiological function of the ET. © Georg Thieme Verlag KG Stuttgart · New York.

  7. Flooding of a large, passive, pressure-tube light water reactor

    International Nuclear Information System (INIS)

    Hejzlar, P.; Todreas, N.E.; Driscoll, M.J.

    1997-01-01

    A reactor concept has been developed which can survive loss of coolant accidents without scram and without replenishing primary coolant inventory, while maintaining safe temperature limits on the fuel and pressure tubes. The proposed concept is a pressure tube type reactor of similar design to CANDU reactors, but differing in three key aspects. First, a solid SiC-coated graphite fuel matrix is used in place of fuel pin bundles to enable the dissipation of decay heat from the fuel in the absence of primary coolant. Second, the heavy water coolant in the pressure tubes is replaced by light water, which also serves as the moderator. Finally, the calandria tank, surrounded by a graphite reflector, contains a low pressure gas instead of heavy water moderator, and this normally-voided calandria is connected to a light water heat sink. The cover gas displaces the light water from the calandria during normal operation, while during loss of coolant or loss of heat sink accidents it allows passive calandria flooding. Calandria flooding also provides redundant and diverse reactor shutdown. This paper describes the thermal hydraulic characteristics of the passively initiated, gravity driven calandria flooding process. Flooding the calandria space with light water is a unique and very important feature of the proposed pressure-tube light water reactor (PTLWR) concept. The flooding of the top row of fuel channels must be accomplished fast enough so that in the total loss of coolant, none of the critical components of the fuel channel, i.e. the pressure tube, the calandria tube, the matrix and the fuel, exceed their design limits. The flooding process has been modeled and shown to be rapid enough to maintain all components within their design limits. (orig.)

  8. Diffusing passive tracers in random incompressible flows: Statistical topography aspects

    International Nuclear Information System (INIS)

    Klyatskin, V.I.; Woyczynski, W.A.; Gurarie, D.

    1996-01-01

    The paper studies statistical characteristics of the passive tracer concentrations and of its spatial gradient, in random incompressible velocity fields from the viewpoint of statistical topography. The statistics of interest include mean values, probability distributions, as well as various functionals characterizing topographic features of tracers. The functional approach is used. We consider the influence of the mean flow (the linear shear flow) and the molecular diffusion coefficient on the statistics of the tracer. Most of our analysis is carried out in the framework of the delta-correlated (in time) approximation and conditions for its applicability are established. But we also consider the diffusion approximation scheme for finite correlation radius. The latter is applied to a diffusing passive tracer that undergoes sedimentation in a random velocity field

  9. Metal diffusion from furnace tubes depends on location

    International Nuclear Information System (INIS)

    Albright, L.F.

    1988-01-01

    Studies of metal samples from an ethylene furnace on the Texas Gulf Coast, using a scanning electron microscope (SEM) and an energy dispersive X-ray analyzer (EDAX), reveal preferential diffusion of chromium, titanium, and aluminum in the coil wall to the surfaces of the tube where they form metal oxides. These elements are gradually depleted from the tube wall. Complicated surface reactions that include the formation of several metal oxides, metal sulfides, and metal-catalyzed coke also occur. Several mechanisms can be postulated as to how metal fines or compounds are formed and transferred in the coil and transfer lines exchanger (TLX) of ethylene units. These surface reactions directly or indirectly affect coke formation in the tube. Finally, creep in the coils is likely a factor in promoting corrosion. Such creep is promoted by variable temperature-time patterns to which a coil is exposed during pyrolysis, and then decoking. Periods of stress and compression occur in the coil walls. Knowledge of the diffusion and reactions that take place can result in better furnace operations and decoking procedures to extend the life of the furnace tubes. In this second installment of a four-part series, photomicrographs of four pyrolysis tube samples from the ethylene furnace indicate that significant differences existed between the outer surfaces, inner surfaces, and cross-sectional areas of the samples. The first installment of the series dealt with coke

  10. A Passive Diffusion Sampler for HT- and HTO-in-Air

    International Nuclear Information System (INIS)

    Surette, R.A.; Nunes, J.C.

    2005-01-01

    Fusion research and tritium removal facilities potentially handle large inventories of tritium gas (HT). If any HT is released into the workplace, a fraction may be converted to tritiated water vapour (HTO). A convenient method to determine the activity concentration of each species is necessary to assess the potential hazard since the radiological hazard of HTO is more than 10 4 that due to HT. Passive samplers for measuring tritiated water vapour (HTO) have been shown to be suitable for use indoors and outdoors. These simple samplers consist of a standard 20-mL liquid scintillation vial with a diffusion orifice that determines the sampling rate.The total tritium samplers described herein are passive or diffusion samplers that contain a small amount of AECL-proprietary wet-proofed catalyst fixed to the underside of the sampling heads to allow conversion of the HT to HTO that is subsequently collected in the sink, (HTO), in the bottom of the sampler. After an appropriate sampling time, liquid scintillation cocktail is added to the vial and the activity collected determined by liquid scintillation analysis. When used in conjunction with the conventional HTO passive sampler the difference between the total and HTO samplers can be used to determine the HT fraction ((HT+HTO) - HTO HT). The sampling rates for the modified diffusion sampler were measured to be 4.6 and 8.1 L/d for HTO and HT, respectively. For a fifteen-minute sampling period, passive samplers can be used to measure tritium activity concentrations from 37 kBq/m 3 to 115 MBq/m 3

  11. Crystalline Silicon Solar Cells with Thin Silicon Passivation Film Deposited prior to Phosphorous Diffusion

    Directory of Open Access Journals (Sweden)

    Ching-Tao Li

    2014-01-01

    Full Text Available We demonstrate the performance improvement of p-type single-crystalline silicon (sc-Si solar cells resulting from front surface passivation by a thin amorphous silicon (a-Si film deposited prior to phosphorus diffusion. The conversion efficiency was improved for the sample with an a-Si film of ~5 nm thickness deposited on the front surface prior to high-temperature phosphorus diffusion, with respect to the samples with an a-Si film deposited on the front surface after phosphorus diffusion. The improvement in conversion efficiency is 0.4% absolute with respect to a-Si film passivated cells, that is, the cells with an a-Si film deposited on the front surface after phosphorus diffusion. The new technique provided a 0.5% improvement in conversion efficiency compared to the cells without a-Si passivation. Such performance improvements result from reduced surface recombination as well as lowered contact resistance, the latter of which induces a high fill factor of the solar cell.

  12. Dynamos driven by poloidal flows in untwisted, curved and flat Riemannian diffusive flux tubes

    International Nuclear Information System (INIS)

    De Andrade, L.C.G.

    2010-01-01

    Recently Vishik anti-fast dynamo theorem has been tested against non-stretching flux tubes (Phys. Plasmas, 15 (2008)). In this paper, another anti dynamo theorem, called Cowling's theorem, which states that axisymmetric magnetic fields cannot support dynamo action, is carefully tested against thick tubular and curved Riemannian untwisted flows, as well as thin flux tubes in diffusive and diffusion less media. In the non-diffusive media Cowling's theorem is not violated in thin Riemann-flat untwisted flux tubes, where the Frenet curvature is negative. Nevertheless the diffusion action in the thin flux tube leads to a dynamo action driven by poloidal flows as shown by Love and Gubbins (Geophysical Res., 23 (1996) 857) in the context of geo dynamos. Actually it is shown that a slow dynamo action is obtained. In this case the Frenet and Riemann curvature still vanishes. In the case of magnetic filaments in diffusive media dynamo action is obtained when the Frenet scalar curvature is negative. Since the Riemann curvature tensor can be expressed in terms of the Frenet curvature of the magnetic flux tube axis, this result can be analogous to a recent result obtained by Chicone, Latushkin and Smith, which states that geodesic curvature in compact Riemannian manifolds can drive dynamo action in the manifold. It is also shown that in the absence of diffusion, magnetic energy does not grow but magnetic toroidal magnetic field can be generated by the poloidal field, what is called a plasma dynamo.

  13. Impurity diffusion, point defect engineering, and surface/interface passivation in germanium

    KAUST Repository

    Chroneos, Alexander I.

    2012-01-26

    In recent years germanium has been emerging as a mainstream material that could have important applications in the microelectronics industry. The principle aim of this study is to review investigations of the diffusion of technologically important p- and n-type dopants as well as surface and interface passivation issues in germanium. The diffusion of impurities in germanium is interrelated to the formation of clusters whenever possible, and possibilities for point defect engineering are discussed in view of recent results. The importance of electrically active defects on the Ge surface and interfaces is addressed considering strategies to suppress them and to passivate the surfaces/interfaces, bearing in mind their importance for advanced devices. © 2012 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Fabrication of fine-grain tantalum diffusion barrier tube for Nb3Sn conductors

    International Nuclear Information System (INIS)

    Hartwig, K. T.; Balachandran, S.; Mezyenski, R.; Seymour, N.; Robinson, J.; Barber, R. E.

    2014-01-01

    Diffusion barriers used in Nb 3 Sn wire are often fabricated by wrapping Ta sheet into a tube with an overlap seam. A common result of such practice is non-uniform deformation in the Ta sheet as it thins by wire drawing because of non-uniform grain size and texture in the original Ta sheet. Seamless Ta tube with a fine-grain and uniform microstructure would be much better for the diffusion barrier application, but such material is expensive and difficult to manufacture. This report presents results on a new fabrication strategy for Ta tube that shows promise for manufacture of less costly tube with an improved microstructure. The fabrication method begins with seam-welded tube but gives a fine-grain uniform microstructure with little difference between the longitudinal seam weld region and the parent metal after post-weld processing. Severe plastic deformation processing (SPD) applied by area reduction extrusion and tube equal channel angular extrusion (tECAE) are used to refine and homogenize the microstructure. Microstructure and mechanical property results are presented for Ta tubes fabricated by this new processing strategy

  15. Fabrication of fine-grain tantalum diffusion barrier tube for Nb3Sn conductors

    Science.gov (United States)

    Hartwig, K. T.; Balachandran, S.; Mezyenski, R.; Seymour, N.; Robinson, J.; Barber, R. E.

    2014-01-01

    Diffusion barriers used in Nb3Sn wire are often fabricated by wrapping Ta sheet into a tube with an overlap seam. A common result of such practice is non-uniform deformation in the Ta sheet as it thins by wire drawing because of non-uniform grain size and texture in the original Ta sheet. Seamless Ta tube with a fine-grain and uniform microstructure would be much better for the diffusion barrier application, but such material is expensive and difficult to manufacture. This report presents results on a new fabrication strategy for Ta tube that shows promise for manufacture of less costly tube with an improved microstructure. The fabrication method begins with seam-welded tube but gives a fine-grain uniform microstructure with little difference between the longitudinal seam weld region and the parent metal after post-weld processing. Severe plastic deformation processing (SPD) applied by area reduction extrusion and tube equal channel angular extrusion (tECAE) are used to refine and homogenize the microstructure. Microstructure and mechanical property results are presented for Ta tubes fabricated by this new processing strategy.

  16. Attenuation of concentration fluctuations of water vapor and other trace gases in turbulent tube flow

    Directory of Open Access Journals (Sweden)

    W. J. Massman

    2008-10-01

    Full Text Available Recent studies with closed-path eddy covariance (EC systems have indicated that the attenuation of fluctuations of water vapor concentration is dependent upon ambient relative humidity, presumably due to sorption/desorption of water molecules at the interior surface of the tube. Previous studies of EC-related tube attenuation effects have either not considered this issue at all or have only examined it superficially. Nonetheless, the attenuation of water vapor fluctuations is clearly much greater than might be expected from a passive tracer in turbulent tube flow. This study reexamines the turbulent tube flow issue for both passive and sorbing tracers with the intent of developing a physically-based semi-empirical model that describes the attenuation associated with water vapor fluctuations. Toward this end, we develop a new model of tube flow dynamics (radial profiles of the turbulent diffusivity and tube airstream velocity. We compare our new passive-tracer formulation with previous formulations in a systematic and unified way in order to assess how sensitive the passive-tracer results depend on fundamental modeling assumptions. We extend the passive tracer model to the vapor sorption/desorption case by formulating the model's wall boundary condition in terms of a physically-based semi-empirical model of the sorption/desorption vapor fluxes. Finally we synthesize all modeling and observational results into a single analytical expression that captures the effects of the mean ambient humidity and tube flow (Reynolds number on tube attenuation.

  17. Modeling of three-dimensional diffusible resistors with the one-dimensional tube multiplexing method

    International Nuclear Information System (INIS)

    Gillet, Jean-Numa; Degorce, Jean-Yves; Meunier, Michel

    2009-01-01

    Electronic-behavior modeling of three-dimensional (3D) p + -π-p + and n + -ν-n + semiconducting diffusible devices with highly accurate resistances for the design of analog resistors, which are compatible with the CMOS (complementary-metal-oxide-semiconductor) technologies, is performed in three dimensions with the fast tube multiplexing method (TMM). The current–voltage (I–V) curve of a silicon device is usually computed with traditional device simulators of technology computer-aided design (TCAD) based on the finite-element method (FEM). However, for the design of 3D p + -π-p + and n + -ν-n + diffusible resistors, they show a high computational cost and convergence that may fail with fully non-separable 3D dopant concentration profiles as observed in many diffusible resistors resulting from laser trimming. These problems are avoided with the proposed TMM, which divides the 3D resistor into one-dimensional (1D) thin tubes with longitudinal axes following the main orientation of the average electrical field in the tubes. The I–V curve is rapidly obtained for a device with a realistic 3D dopant profile, since a system of three first-order ordinary differential equations has to be solved for each 1D multiplexed tube with the TMM instead of three second-order partial differential equations in the traditional TCADs. Simulations with the TMM are successfully compared to experimental results from silicon-based 3D resistors fabricated by laser-induced dopant diffusion in the gaps of MOSFETs (metal-oxide-semiconductor field-effect transistors) without initial gate. Using thin tubes with other shapes than parallelepipeds as ring segments with toroidal lateral surfaces, the TMM can be generalized to electronic devices with other types of 3D diffusible microstructures

  18. Modelling of Condensation in Vertical Tubes for Passive Safety System

    International Nuclear Information System (INIS)

    Papini, D.; Ricotti, M.; Santini, L.; Grgic, D.

    2008-01-01

    Condensation in vertical tubes plays an important role in the performance of heat exchangers in passive safety systems, widely adopted in next generation reactors. Vertical pipe condensers are implemented in the GE-SBWR1000 Isolation Condenser as well as in the Emergency Heat Removal System (EHRS) of the IRIS reactor. The transient and safety analysis is usually carried out by means of best-estimate, thermalhydraulic codes, as RELAP. Suitable heat transfer correlations are required to duly model the two-phase processes. As far as the condensation process is concerned, RELAP5/MOD3.3 adopts the Nusselt correlation to calculate the heat transfer coefficient in laminar conditions and the Shah correlation for turbulent conditions; the maximum of the predictions from laminar and turbulent regimes is used to calculate the condensation heat transfer coefficient. Shah correlation is generally considered as the best empirical correlation for turbulent annular film condensation, but suitable in proper ranges of the various parameters. Nevertheless, recent investigations have pointed out that its validity is highly questionable for high pressure and large diameter tube applications with water, as should be for the utilization for vertical tube condensers in passive safety systems. Thus, a best-estimate model, based on the theory of film condensation on a plain wall, is proposed. Condensate velocity, expressed in terms of Reynolds number, governs the development of three different regime zones: laminar, laminar wavy and turbulent. The best correlation for each regime (Nusselt's for laminar, Kutateladze's for laminar wavy and Chen's for turbulent) is considered and then implemented in RELAP code. Comparison between the Nusselt-Shah and the proposed model shows substantial differences in heat transfer coefficient prediction. Especially, a trend of increasing value of the heat transfer coefficient with tube abscissa (and quality decreasing) is predicted, when turbulence

  19. Evaluation of a passive sampling system of CPVC for nitrogen dioxide in the air

    International Nuclear Information System (INIS)

    Rojas-Bolanos, Omar; Jimenez-Barrantes, Irene

    2012-01-01

    Passive diffusion tubes have been built to determine the concentration of NO 2 in the air with poly tubes (vinyl chloride) chloride (CPVC). The performance has been evaluated during the 2008, through comparisons of their results with the results obtained, using the method modified Griess-Saltzman, recommended by the World Health Organization. The comparison results have shown good agreement between the two methodologies with respect to NO 2 concentrations of 45-85 μg/m''3. Linear regression when used by minimum simple square and ranges test and Wilcoxon signs, no significant differences found between the results provided by both methods. Relative bias calculated in 7 comparisons has varied from -19,05% to 24,44% with an average of 5,76%. The results have indicated that the passive tubes overestimated the concentration of NO 2 ; without however, this bias has not been higher than those reported by other authors. The precision the passive system has been in the field of 5,2% to 10,6%, measured in four tubes through the coefficient of variation, similar to reported by other researchers. (author) [es

  20. Turbulent flux and the diffusion of passive tracers in electrostatic turbulence

    DEFF Research Database (Denmark)

    Basu, R.; Jessen, T.; Naulin, V.

    2003-01-01

    The connection between the diffusion of passive tracer particles and the anomalous turbulent flux in electrostatic drift-wave turbulence is investigated by direct numerical solutions of the 2D Hasegawa-Wakatani equations. The probability density functions for the point-wise and flux surface...

  1. Flooding of a large, passive, pressure-tube LWR

    Energy Technology Data Exchange (ETDEWEB)

    Hejzlar, P.; Todreas, N.E.; Driscoll, M.J. [Massachusetts Institute of Technology, Cambridge, MA (United States)

    1995-09-01

    A reactor concept has been developed which can survive LOCA without scram and without replenishing primary coolant inventory. The proposed concept is a pressure tube type reactor similar to CANDU reactors, but differing in three key aspects: (1) a solid SiC-coated graphite fuel matrix is used in place of fuel pin bundles, (2) the heavy water coolant in the pressure tubes is replaced by light water, and (3) the calandria tank contains a low pressure gas instead of heavy water moderator. The gas displaces the light water from the calandria during normal operation, while during loss of coolant or loss of heat sink accidents, it allows passive calandria flooding. This paper describes the thermal hydraulic characteristics of the gravity driven calandria flooding process. Flooding the calandria space with light water is a unique and very important feature of the proposed pressure-tube LWR concept. The flooding of the top row of fuel channels must be accomplished fast enough so that none of the critical components of the fuel channel exceed their design limits. The flooding process has been modeled and shown to be rapid enough to maintain all components within their design limits. Two other considerations are important. The thermal shock experienced by the calandria and pressure tubes has been evaluated and shown to be within acceptable bounds. Finally, although complete flooding renders the reactor deeply subcritical, various steam/water densities can be hypothesized to be present during the flooding process which could cause reactivity to increase from the initially voided calandria case. One such hypothesis which leads to the maximum possible density of the steam/water mixture in the still unflooded calandria space is entrainment from the free surface. It is shown that the steam/water mixture density yielding the maximum reactivity peak cannot be achieved by entrainment because it exceeds thermohydraulically attainable densities of steam/water by an order of magnitude.

  2. Development of a passive sampler for gaseous mercury

    Science.gov (United States)

    Gustin, M. S.; Lyman, S. N.; Kilner, P.; Prestbo, E.

    2011-10-01

    Here we describe work toward development of the components of a cost effective passive sampling system for gaseous Hg that could be broadly deployed by nontechnical staff. The passive sampling system included an external shield to reduce turbulence and exposure to precipitation and dust, a diffusive housing that directly protects the collection surface during deployment and handling, and a collection surface. A protocol for cleaning and deploying the sampler and an analytical method were developed. Our final design consisted of a polycarbonate external shield enclosing a custom diffusive housing made from expanded PTFE tubing. Two collection surfaces were investigated, gold sputter-coated quartz plates and silver wires. Research showed the former would require extensive quality control for use, while the latter had interferences with other atmosphere constituents. Although the gold surface exhibited the best performance over space and time, gradual passivation would limit reuse. For both surfaces lack of contamination during shipping, deployment and storage indicated that the handling protocols developed worked well with nontechnical staff. We suggest that the basis for this passive sampling system is sound, but further exploration and development of a reliable collection surface is needed.

  3. Hybrid friction diffusion bonding of 316L stainless steel tube-to-tube sheet joints for coil-wound heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Haneklaus, Nils; Cionea, Cristian; Reuven, Rony; Frazer, David; Hosemann, Peter; Peterson, Per F. [Dept of Nuclear Engineering, University of California, Berkeley (United States)

    2016-11-15

    Hybrid friction diffusion bonding (HFDB) is a solid-state bonding process first introduced by Helmholtz-Zentrum Geesthacht to join aluminum tube-to-tube sheet joints of Coil-wound heat exchangers (CWHE). This study describes how HFDB was successfully used to manufacture 316L test samples simulating tube-to-tube sheet joints of stainless steel CWHE for molten salt coolants as foreseen in several advanced nuclear- and thermal solar power plants. Engineering parameters of the test sample fabrication are presented and results from subsequent non-destructive vacuum decay leak testing and destructive tensile pull-out testing are discussed. The bonded areas of successfully fabricated samples as characterized by tube rupture during pull-out tensile testing, were further investigated using optical microscopy and scanning electron microscopy including electron backscatter diffraction.

  4. Heat transfer modelling in the vertical tubes of a natural circulation passive containment loop with noncondensable gas

    International Nuclear Information System (INIS)

    Herranz, L.E.; Munoz-Cobo, J.L.; Tachenko, I.; Sancho, J.; Escriva, A.; Verdu, G.

    1994-01-01

    One of the key safety systems of the Simplified Boiling Water Reactor (SBWR) of General Electric is the Passive Containment Cooling System (PCCS). This system is designed to behave as a heat sink without need of operator actions in case of a reactor accident. Such a function relies on setting up a natural circulation loop between drywell and wetwell. Along this loop heat is removed by condensing the steam coming from the drywell onto the inner surface of externally cooled vertical tubes. Therefore, a successful design of the condenser requires a good knowledge of the local heat transmission coefficients. In this paper a model of steam condensation into vertical tubes is presented. Based on a modified diffusion boundary layer approach for noncondensables, this model accounts for the effect of shear stress caused by the cocurrent steam-gas mixture on the liquid film thickness. An approximate method to calculate film thickness, avoiding iterative algorithms, has been proposed. At present, this model has been implemented in HTCPIPE code and its results are being checked in terms of local heat transfer coefficients against the experimental data available. A good agreement between measurements and predictions is being observed for tests at atmospheric pressure. Further development and validation of the model is needed to consider aspects such as mist formation, wavy flow and high pressure. (author)

  5. Multiple-effect diffusion solar still coupled with a vacuum-tube collector and heat pipe

    KAUST Repository

    Chong, Tze-Ling; Huang, Bin-Juine; Wu, Po-Hsien; Kao, Yeong-Chuan

    2014-01-01

    The present study develops a multiple-effect diffusion solar still (MEDS) with a bended-plate design in multiple-effect diffusion unit (MDU) to solve the peel-off problem of wick material. The MDU is coupled with a vacuum-tube solar collector

  6. Assessment of the numerical diffusion effect in the advection of a passive tracer in BOLCHEM

    International Nuclear Information System (INIS)

    D'Isidoro, M.; Tiesi, A.

    2005-01-01

    The effects of the numerical scheme implemented in the advection equation of BOLCHEM have been quantified with reference to the diffusion of a passive tracer. An equivalent horizontal diffusion coefficient has been measured and is found to be dependent on wind field and resolution

  7. Passivity analysis for uncertain BAM neural networks with time delays and reaction-diffusions

    Science.gov (United States)

    Zhou, Jianping; Xu, Shengyuan; Shen, Hao; Zhang, Baoyong

    2013-08-01

    This article deals with the problem of passivity analysis for delayed reaction-diffusion bidirectional associative memory (BAM) neural networks with weight uncertainties. By using a new integral inequality, we first present a passivity condition for the nominal networks, and then extend the result to the case with linear fractional weight uncertainties. The proposed conditions are expressed in terms of linear matrix inequalities, and thus can be checked easily. Examples are provided to demonstrate the effectiveness of the proposed results.

  8. Continuous 'Passive' Registration of Non-Point Contaminant Loads Via Agricultural Subsurface Drain Tubes

    Science.gov (United States)

    Rozemeijer, J.; Jansen, S.; de Jonge, H.; Lindblad Vendelboe, A.

    2014-12-01

    Considering their crucial role in water and solute transport, enhanced monitoring and modeling of agricultural subsurface tube drain systems is important for adequate water quality management. For example, previous work in lowland agricultural catchments has shown that subsurface tube drain effluent contributed up to 80% of the annual discharge and 90-92% of the annual NO3 loads from agricultural fields towards the surface water. However, existing monitoring techniques for flow and contaminant loads from tube drains are expensive and labor-intensive. Therefore, despite the unambiguous relevance of this transport route, tube drain monitoring data are scarce. The presented study aimed developing a cheap, simple, and robust method to monitor loads from tube drains. We are now ready to introduce the Flowcap that can be attached to the outlet of tube drains and is capable of registering total flow, contaminant loads, and flow-averaged concentrations. The Flowcap builds on the existing SorbiCells, a modern passive sampling technique that measures average concentrations over longer periods of time (days to months) for various substances. By mounting SorbiCells in our Flowcap, a flow-proportional part of the drain effluent is sampled from the main stream. Laboratory testing yielded good linear relations (R-squared of 0.98) between drainage flow rates and sampling rates. The Flowcap was tested in practice for measuring NO3 loads from two agricultural fields and one glasshouse in the Netherlands. The Flowcap registers contaminant loads from tube drains without any need for housing, electricity, or maintenance. This enables large-scale monitoring of non-point contaminant loads via tube drains, which would facilitate the improvement of contaminant transport models and would yield valuable information for the selection and evaluation of mitigation options to improve water quality.

  9. Extraction of thermal Green's function using diffuse fields: a passive approach applied to thermography

    Science.gov (United States)

    Capriotti, Margherita; Sternini, Simone; Lanza di Scalea, Francesco; Mariani, Stefano

    2016-04-01

    In the field of non-destructive evaluation, defect detection and visualization can be performed exploiting different techniques relying either on an active or a passive approach. In the following paper the passive technique is investigated due to its numerous advantages and its application to thermography is explored. In previous works, it has been shown that it is possible to reconstruct the Green's function between any pair of points of a sensing grid by using noise originated from diffuse fields in acoustic environments. The extraction of the Green's function can be achieved by cross-correlating these random recorded waves. Averaging, filtering and length of the measured signals play an important role in this process. This concept is here applied in an NDE perspective utilizing thermal fluctuations present on structural materials. Temperature variations interacting with thermal properties of the specimen allow for the characterization of the material and its health condition. The exploitation of the thermographic image resolution as a dense grid of sensors constitutes the basic idea underlying passive thermography. Particular attention will be placed on the creation of a proper diffuse thermal field, studying the number, placement and excitation signal of heat sources. Results from numerical simulations will be presented to assess the capabilities and performances of the passive thermal technique devoted to defect detection and imaging of structural components.

  10. Drift tube measurements of mobilities and longitudinal diffusion coefficients of ions in gases

    International Nuclear Information System (INIS)

    Chelf, R.D.

    1982-01-01

    The zero-field mobilities of Br - and NH 4+ in O 2 were determined as a function of gas temperature in a high pressure drift tube mass spectrometer. The mobilities and longitudinal diffusion coefficients of the ion-gas combinations Br - in Ne and Kr, Li + in Xe, and Tl/ + in Kr and Xe were determined as a function of E/N, where E is the electric field strength and N is the gas number density in a low pressure drift tube mass spectrometer. The measured longitudinal diffusion coefficients were used for a test and comparison of the generalized Einstein relations of Viehland-Mason and Waldman-Mason theories. The measured mobilities of Br - in Kr and Tl/ + in Kr were used in an iterative-inversion scheme from which the ion-neutral interaction potentials were determined

  11. Evidence for equivalence of diffusion processes of passive scalar and magnetic fields in anisotropic Navier-Stokes turbulence.

    Science.gov (United States)

    Jurčišinová, E; Jurčišin, M

    2017-05-01

    The influence of the uniaxial small-scale anisotropy on the kinematic magnetohydrodynamic turbulence is investigated by using the field theoretic renormalization group technique in the one-loop approximation of a perturbation theory. The infrared stable fixed point of the renormalization group equations, which drives the scaling properties of the model in the inertial range, is investigated as the function of the anisotropy parameters and it is shown that, at least at the one-loop level of approximation, the diffusion processes of the weak passive magnetic field in the anisotropically driven kinematic magnetohydrodynamic turbulence are completely equivalent to the corresponding diffusion processes of passively advected scalar fields in the anisotropic Navier-Stokes turbulent environments.

  12. 3D Numerical Simulation versus Experimental Assessment of Pressure Pulsations Using a Passive Method for Swirling Flow Control in Conical Diffusers of Hydraulic Turbines

    Science.gov (United States)

    TANASA, C.; MUNTEAN, S.; CIOCAN, T.; SUSAN-RESIGA, R. F.

    2016-11-01

    The hydraulic turbines operated at partial discharge (especially hydraulic turbines with fixed blades, i.e. Francis turbine), developing a swirling flow in the conical diffuser of draft tube. As a result, the helical vortex breakdown, also known in the literature as “precessing vortex rope” is developed. A passive method to mitigate the pressure pulsations associated to the vortex rope in the draft tube cone of hydraulic turbines is presented in this paper. The method involves the development of a progressive and controlled throttling (shutter), of the flow cross section at the bottom of the conical diffuser. The adjustable cross section is made on the basis of the shutter-opening of circular diaphragms, while maintaining in all positions the circular cross-sectional shape, centred on the axis of the turbine. The stagnant region and the pressure pulsations associated to the vortex rope are mitigated when it is controlled with the turbine operating regime. Consequently, the severe flow deceleration and corresponding central stagnant are diminished with an efficient mitigation of the precessing helical vortex. Four cases (one without diaphragm and three with diaphragm), are numerically and experimentally investigated, respectively. The present paper focuses on a 3D turbulent swirling flow simulation in order to evaluate the control method. Numerical results are compared against measured pressure recovery coefficient and Fourier spectra. The results prove the vortex rope mitigation and its associated pressure pulsations when employing the diaphragm.

  13. Continuous Passive Sampling of Solutes from Agricultural Subsurface Drainage Tubes

    Science.gov (United States)

    Lindblad Vendelboe, Anders; de Jonge, Hubert; Rozemeijer, Joachim; Wollesen de Jonge, Lis

    2015-04-01

    Agricultural subsurface tube drain systems play an important role in water and solute transport. One study, focusing on lowland agricultural catchments, showed that subsurface tube drainage contributed up to 80% of the annual discharge and 90% of the annual NO3 load from agricultural fields to the receiving water bodies. Knowledge of e.g. nutrient loads and drainage volumes, based on measurements and modelling, are important for adequate water quality management. Despite the importance of tube drain transport of solutes, monitoring data are scarce. This scarcity is a result of the existing monitoring techniques for flow and contaminant load from tube drains being expensive and labor-extensive. The study presented here aimed at developing a cheap, simple, and robust method to monitor solute loads from tube drains. The method is based on the newly developed Flowcap, which can be attached to existing tube drain outlets and can measure total flow, contaminant load and flow-averaged concentrations of solutes in the drainage. The Flowcap builds on the existing Sorbicell principle, a passive sampling system that measures average concentrations over longer periods of time (days to months) for various compounds. The Sorbicell consists of two compartments permeable to water. One compartment contains an adsorbent and one contains a tracer. When water passes through the Sorbicell the compound of interest is absorbed while a tracer is released. Using the tracer loss to calculate the volume of water that has passed the Sorbicell it is possible to calculate the average concentration of the compound. When mounting Sorbicells in the Flowcap, a flow-proportional part of the drainage is sampled from the main stream. To accommodate the wide range of drainage flow rates two Flowcaps with different capacities were tested in the laboratory: one with a capacity of 25 L min-1 (Q25) and one with a capacity of 256 L min-1 (Q256). In addition, Sorbicells with two different hydraulic

  14. Record Charge Carrier Diffusion Length in Colloidal Quantum Dot Solids via Mutual Dot-To-Dot Surface Passivation.

    Science.gov (United States)

    Carey, Graham H; Levina, Larissa; Comin, Riccardo; Voznyy, Oleksandr; Sargent, Edward H

    2015-06-03

    Through a combination of chemical and mutual dot-to-dot surface passivation, high-quality colloidal quantum dot solids are fabricated. The joint passivation techniques lead to a record diffusion length for colloidal quantum dots of 230 ± 20 nm. The technique is applied to create thick photovoltaic devices that exhibit high current density without losing fill factor. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Field evaluation of a tailor-made new passive sampler for the determination of NO2 levels in ambient air.

    Science.gov (United States)

    Ozden, Ozlem; Dogeroglu, Tuncay

    2008-07-01

    This study describes the field evaluation of a tailor-made new glass passive sampler developed for the determination of NO(2), based on the collection on triethanolemine (TEA)-coated fibre filter paper. The sampler has been derived from a Palmes design. The overall uncertainty of the sampler was determined by using Griess-Saltzman ASTM D 1607 standard test method as a reference method. The agreement between the results of the passive sampler and the reference method was +/-7.90% with the correlation coefficient of 0.90. Method precision in terms of coefficient of variance (CV) for three simultaneously applied passive samplers was 8.80%. The uptake rate of NO(2) was found to be 2.49 ml/min in a very good agreement with the value calculated from theory (2.63 ml/min). Sampler detection limit was 1.99 microg/m(3) for an exposure period of 1 week and the sampler can be stored safely for a period of up to 6 weeks before exposure. A comparison of the sampler performance was conducted against a commercially available diffusion tube (Gradko diffusion tube). The results from the applied statistical paired t test indicated that there was no significant difference between the performances of two passive samplers (R (2) > 0.90). Also, another statistical comparison was carried out between the dark and transparent glass passive samplers. The results from the dark-colour sampler were higher than that from the transparent sampler (approximately 25%) during the summer season because of the possible photodegradation of NO(2)-TEA complex.

  16. Reactor core and passive safety systems descriptions of a next generation pressure tube reactor - mechanical aspects

    Energy Technology Data Exchange (ETDEWEB)

    Yetisir, M.; Gaudet, M.; Rhodes, D.; Hamilton, H.; Pencer, J. [Atomic Energy of Canada Limited, Chalk River, ON (Canada)

    2014-07-01

    Canada has been developing a channel-type supercritical water-cooled nuclear reactor concept, often called the Canadian SCWR. The objective of this reactor concept is to meet the technology goals of the Generation IV International Forum (GIF) for the next generation nuclear reactor development, which include enhanced safety features (inherent safe operation and deploying passive safety features), improved resource utilization, sustainable fuel cycle, and greater proliferation resistance than Generation III nuclear reactors. The Canadian SCWR core concept consists of a high-pressure inlet plenum, a separate low-pressure heavy water moderator contained in a calandria vessel, and 336 pressure tubes surrounded by the moderator. The reactor uses supercritical water as a coolant, and a direct steam power cycle to generate electricity. The reactor concept incorporates advanced safety features such as passive core cooling, long-term decay heat rejection to the environment and fuel melt prevention via passive moderator cooling. These features significantly reduce core damage frequency relative to existing nuclear reactors. This paper presents a description of the design concepts for the Canadian SCWR core, reactor building layout and the plant layout. Passive safety concepts are also described that address containment and core cooling following a loss-of coolant accident, as well as long term reactor heat removal at station blackout conditions. (author)

  17. Spiral multiple-effect diffusion solar still coupled with vacuum-tube collector and heat pipe

    KAUST Repository

    Huang, Bin-Juine; Chong, Tze-Ling; Wu, Po-Hsien; Dai, Han-Yi; Kao, Yeong-Chuan

    2015-01-01

    © 2015 Elsevier B.V. A novel solar still with spiral-shape multiple-effect diffusion unit is developed in the present study. The test results of a 14-effect unit coupled with vacuum-tube solar collector (absorber area 1.08m2) show that the highest

  18. A CNT (carbon nanotube) paper as cathode gas diffusion electrode for water management of passive μ-DMFC (micro-direct methanol fuel cell) with highly concentrated methanol

    International Nuclear Information System (INIS)

    Deng, Huichao; Zhang, Yufeng; Zheng, Xue; Li, Yang; Zhang, Xuelin; Liu, Xiaowei

    2015-01-01

    A novel MEA (membrane electrode assembly) structure of passive μ-DMFC (micro-direct methanol fuel cell) controls water management and decreases methanol crossover. The CNT (carbon nanotube) paper replacing CP (carbon paper) as GDL (gas diffusion paper) enhances water back diffusion which passively prevents flooding in the cathode and promotes low methanol crossover. Moreover, the unique structure of CNT paper can also enhance efficiency of oxygen mass transport and catalyst utilization. The passive μ-DMFC with CNT-MEA exhibits significantly higher performance than passive μ-DMFC with CP-MEA and can operate in high methanol concentration, showing the peak power density of 23.2 mW cm −2 . The energy efficiency and fuel utilization efficiency are obviously improved from 11.54% to 22.7% and 36.61%–49.34%, respectively, and the water transport coefficient is 0.47 which is lower than previously reported passive μ-DMFC with CP. - Highlights: • This novel GDL (gas diffusion layer) solves water management and methanol crossover. • This GDL creates a hydraulic pressure in the cathode increasing water back diffusion. • This GDL improves the electrical conductivity and activity of catalyst

  19. Selection of design parameters of diffusion barrier in a passive 222Rn sampler based on activated charcoal adsorption

    International Nuclear Information System (INIS)

    Wei Suxia

    1992-01-01

    A method concerning selection of design parameters of diffusion barrier in a passive 222 Rn sampler based on activated charcoal adsorption. The proper parameter value of diffusion barrier is obtained by means of linearization of 222 Rn adsorption versus the exposure time. Thus, the influence of temperature on measured results may be greatly decreased, and higher sensitivity of the detector may be maintained

  20. Water-storage-tube systems. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Hemker, P.

    1981-12-24

    Passive solar collection/storage/distribution systems were surveyed, designed, fabricated, and mechanically and thermally tested. The types studied were clear and opaque fiberglass tubes, metal tubes with plastic liners, and thermosyphoning tubes. (MHR)

  1. Diffusion of a passive scalar with random advection

    International Nuclear Information System (INIS)

    Molyneux, J.E.; Witten, A.J.

    1980-01-01

    To investigate the instantaneous release of a passive additive into a flow, we assume that the concentration of the additive is governed by the one-dimensional advective diffusion equation in which the advecting flow velocity is a given time-dependent stochastic process. We determine both the one- and two-space-time point probability distributions of the random concentration field. This problem, or more elaborate variations of it, is a rather idealized model for a variety of environmentally important flow situations, for example, the accidental or planned release of a contaminant into a river by a power station, and, as such, it has been investigated by a number of authors. Previous treatments, however, have concentrated on deriving information about the statistical moments of the concentration. Although such information is important, it may be inadequate for accessing the true effects of a flow additive on the environment. Our investigation demonstrates the possibility of obtaining a more complete statistical description

  2. The research activities on in-tube condensation in the presence of noncondensables for passive cooling applications

    Energy Technology Data Exchange (ETDEWEB)

    Tanrikut, A [Turkish Atomic Energy Authority, Ankara (Turkey)

    1996-12-01

    The introduction of nuclear power becomes an attractive solution to the problem of increasing demand for electricity power capacity in Turkey. Thus, Turkey is willing to follow the technological development trends in advanced reactor systems and to participate in joint research studies. The primary objectives of the passive design features are to simplify the design, which assures the minimized demand on operator, and to improve plant safety. To accomplish these features the operating principles of passive safety systems should be well understood by an experimental validation program. Such a validation program is also important for the assessment of advanced computer codes which are currently used for design and licensing procedures. The condensation mode of heat transfer plays an important role for the passive heat removal applications in the current nuclear power plants (e.g. decay heat removal via steam generators in case of loss of heat removal system) and advanced water-cooled reactor systems. But is well established that the presence of noncondensable gases can greatly inhibit the condensation process due to the build-up of noncondensable gas concentration at the liquid/gas interface. The isolation condenser of passive containment cooling system of the simplified boiling water reactors is a typical application area of in-tube condensation in the presence of noncondensable. This paper describes the research activities at the Turkish Atomic Energy Authority concerning condensation in the presence of air, as a noncondensable gas. (author). 9 refs, 6 figs.

  3. The research activities on in-tube condensation in the presence of noncondensables for passive cooling applications

    International Nuclear Information System (INIS)

    Tanrikut, A.

    1996-01-01

    The introduction of nuclear power becomes an attractive solution to the problem of increasing demand for electricity power capacity in Turkey. Thus, Turkey is willing to follow the technological development trends in advanced reactor systems and to participate in joint research studies. The primary objectives of the passive design features are to simplify the design, which assures the minimized demand on operator, and to improve plant safety. To accomplish these features the operating principles of passive safety systems should be well understood by an experimental validation program. Such a validation program is also important for the assessment of advanced computer codes which are currently used for design and licensing procedures. The condensation mode of heat transfer plays an important role for the passive heat removal applications in the current nuclear power plants (e.g. decay heat removal via steam generators in case of loss of heat removal system) and advanced water-cooled reactor systems. But is well established that the presence of noncondensable gases can greatly inhibit the condensation process due to the build-up of noncondensable gas concentration at the liquid/gas interface. The isolation condenser of passive containment cooling system of the simplified boiling water reactors is a typical application area of in-tube condensation in the presence of noncondensable. This paper describes the research activities at the Turkish Atomic Energy Authority concerning condensation in the presence of air, as a noncondensable gas. (author). 9 refs, 6 figs

  4. Passive scalar transport in peripheral regions of random flows

    International Nuclear Information System (INIS)

    Chernykh, A.; Lebedev, V.

    2011-01-01

    We investigate statistical properties of the passive scalar mixing in random (turbulent) flows assuming its diffusion to be weak. Then at advanced stages of the passive scalar decay, its unmixed residue is primarily concentrated in a narrow diffusive layer near the wall and its transport to the bulk goes through the peripheral region (laminar sublayer of the flow). We conducted Lagrangian numerical simulations of the process for different space dimensions d and revealed structures responsible for the transport, which are passive scalar tongues pulled from the diffusive boundary layer to the bulk. We investigated statistical properties of the passive scalar and of the passive scalar integrated along the wall. Moments of both objects demonstrate scaling behavior outside the diffusive boundary layer. We propose an analytic scheme for the passive scalar statistics, explaining the features observed numerically.

  5. Hydrodynamic interaction between bacteria and passive sphere

    Science.gov (United States)

    Zhang, Bokai; Ding, Yang; Xu, Xinliang

    2017-11-01

    Understanding hydrodynamic interaction between bacteria and passive sphere is important for identifying rheological properties of bacterial and colloidal suspension. Over the past few years, scientists mainly focused on bacterial influences on tracer particle diffusion or hydrodynamic capture of a bacteria around stationary boundary. Here, we use superposition of singularities and regularized method to study changes in bacterial swimming velocity and passive sphere diffusion, simultaneously. On this basis, we present a simple two-bead model that gives a unified interpretation of passive sphere diffusion and bacterial swimming. The model attributes both variation of passive sphere diffusion and changes of speed of bacteria to an effective mobility. Using the effective mobility of bacterial head and tail as an input function, the calculations are consistent with simulation results at a broad range of tracer diameters, incident angles and bacterial shapes.

  6. Passivation of phosphorus diffused silicon surfaces with Al2O3: Influence of surface doping concentration and thermal activation treatments

    International Nuclear Information System (INIS)

    Richter, Armin; Benick, Jan; Kimmerle, Achim; Hermle, Martin; Glunz, Stefan W.

    2014-01-01

    Thin layers of Al 2 O 3 are well known for the excellent passivation of p-type c-Si surfaces including highly doped p + emitters, due to a high density of fixed negative charges. Recent results indicate that Al 2 O 3 can also provide a good passivation of certain phosphorus-diffused n + c-Si surfaces. In this work, we studied the recombination at Al 2 O 3 passivated n + surfaces theoretically with device simulations and experimentally for Al 2 O 3 deposited with atomic layer deposition. The simulation results indicate that there is a certain surface doping concentration, where the recombination is maximal due to depletion or weak inversion of the charge carriers at the c-Si/Al 2 O 3 interface. This pronounced maximum was also observed experimentally for n + surfaces passivated either with Al 2 O 3 single layers or stacks of Al 2 O 3 capped by SiN x , when activated with a low temperature anneal (425 °C). In contrast, for Al 2 O 3 /SiN x stacks activated with a short high-temperature firing process (800 °C) a significant lower surface recombination was observed for most n + diffusion profiles without such a pronounced maximum. Based on experimentally determined interface properties and simulation results, we attribute this superior passivation quality after firing to a better chemical surface passivation, quantified by a lower interface defect density, in combination with a lower density of negative fixed charges. These experimental results reveal that Al 2 O 3 /SiN x stacks can provide not only excellent passivation on p + surfaces but also on n + surfaces for a wide range of surface doping concentrations when activated with short high-temperature treatments

  7. An experimental study of high pressure steam condensation in a vertical tube of passive secondary condensation system

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Jae; No, Hee Cheon [KAIST, Taejon (Korea, Republic of)

    1998-07-01

    To investigate the physical parameters of PSCS (Passive Secondary Condensation System) which is a passive residual heat removal system of CP-1300, the high pressure condensation experiments are performed in a small scale experimental facility. The experimental parameters are the local heat flux and the transfer coefficient and the pressure drop in a condensation heat trasnfer. The film condensation heat transfer coefficients in a vertical tube are calculated from the measured wall temperature difference and compared with the analytical models. A new analytical condensation model is developed based on the annular film flow model. The present model gives marginally better results than those from the Shah model in comparison with the experimental data in the database. Also, experimental data are compared with the results of the RELAP5/MOD3.2 thermal hydraulic code. The RELAP5/MOD3.2 underpredicts the condensation heat transfer coefficients of the present experiment by 50 %.

  8. Passive house networks : How can they deliver?

    NARCIS (Netherlands)

    Mlecnik, E.

    2009-01-01

    This paper examines experiences with the diffusion of the passive house concept, applied to the situation of ‘emerging’ countries like Belgium and the Netherlands. Adopter categories considering the passive house concept are defined. A marketing study based on Rogers’ theory of diffusion of

  9. Potential of indirect evaporative passive cooling with embedded tubes in a humid tropical climate : applications in a typical hot humid climate

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Chavez, J.R. [Univ. Autonoma Metropolitana-Azcapotzalco, Mexico City (Mexico). Dept. de Medio Ambiente, Laboratorio de Investigaciones en Arquitectura Bioclimatica; Givoni, B. [California Univ., Los Angeles, CA (United States); BGU, Beer Sheva (Israel); Viveros, O. [Cristobal Colon Univ., Veracruz (Mexico)

    2009-07-01

    The use of passive cooling techniques in buildings in hot and humid regions can reduce energy consumption while increasing thermal comfort for occupants. A study was conducted in the City of Veracruz, Mexico to investigate the performance of tubes embedded in the roof of the Gulf Meteorological Prevision Centre. Two identical insulated experimental cells were used, one serving as the control and the other one as the test unit, where the technique of embedded tubes in the roof was implemented and investigated during a typical overheating season. Results showed that this indirect evaporative cooling system is an effective strategy to reduce indoor temperatures without increasing the indoor humidity in buildings. The indoor maximum temperature was lowered by 2.72 K in the experimental test cell relative to the control unit. In addition, the resulting reduction of radiant temperatures in the test unit improved the thermal comfort of the occupants. It is expected that the implementation of this passive cooling technique will eventually contribute to reduced energy consumption and less use of air-conditioning systems in buildings, and thereby prevent emission of greenhouse gases to the atmosphere. 9 refs., 1 tab., 6 figs.

  10. Passive sampling of DDT, DDE and DDD in sediments: accounting for degradation processes with reaction-diffusion modeling.

    Science.gov (United States)

    Tcaciuc, A Patricia; Borrelli, Raffaella; Zaninetta, Luciano M; Gschwend, Philip M

    2018-01-24

    Passive sampling is becoming a widely used tool for assessing freely dissolved concentrations of hydrophobic organic contaminants in environmental media. For certain media and target analytes, the time to reach equilibrium exceeds the deployment time, and in such cases, the loss of performance reference compounds (PRCs), loaded in the sampler before deployment, is one of the common ways used to assess the fractional equilibration of target analytes. The key assumption behind the use of PRCs is that their release is solely diffusion driven. But in this work, we show that PRC transformations in the sediment can have a measurable impact on the PRC releases and even allow estimation of that compound's transformation rate in the environment of interest. We found that in both field and lab incubations, the loss of the 13 C 2,4'-DDT PRC from a polyethylene (PE) passive sampler deployed at the sediment-water interface was accelerated compared to the loss of other PRCs ( 13 C-labeled PCBs, 13 C-labeled DDE and DDD). The DDT PRC loss was also accompanied by accumulation in the PE of its degradation product, 13 C 2,4'-DDD. Using a 1D reaction-diffusion model, we deduced the in situ degradation rates of DDT from the measured PRC loss. The in situ degradation rates increased with depth into the sediment bed (0.14 d -1 at 0-10 cm and 1.4 d -1 at 30-40 cm) and although they could not be independently validated, these rates compared favorably with literature values. This work shows that passive sampling users should be cautious when choosing PRCs, as degradation processes can affect some PRC's releases from the passive sampler. More importantly, this work opens up the opportunity for novel applications of passive samplers, particularly with regard to investigating in situ degradation rates, pathways, and products for both legacy and emerging contaminants. However, further work is needed to confirm that the rates deduced from model fitting of PRC loss are a true reflection of DDT

  11. Passive heat transfer enhancement in 3D corrugated tube

    DEFF Research Database (Denmark)

    Navickaité, Kristina; Engelbrecht, Kurt; Bahl, Christian

    transfer and fluid flow with a constant wall temperature and total pressure drop. The governing equations for these problems were solved using the Finite Element Method. The results of numerical modelling show significant increase in NTU for double corrugated tubes compared to a circular tube. The friction......An innovative hydraulic design was studied for corrugated tube geometry for a heat exchanger. An ellipse based double corrugation was used as a concept of the geometry. The hydraulic diameter (Dh) is maintained over the tube length while the shape of the cross section varies continuously along...... the flow direction. 38 corrugated tubes with a Dh of 5 mm were studied numerically with corrugation heights from 0.23 to 0.69 mm and corrugation periods from 5 to 50 mm for laminar flow with water. Computational fluid dynamics (CFD) is used as a tool to study the effect of corrugation geometry on heat...

  12. Chemical cleaning specification: few tube test model

    International Nuclear Information System (INIS)

    Hampton, L.V.; Simpson, J.L.

    1979-09-01

    The specification is for the waterside chemical cleaning of the 2 1/4 Cr - 1 Mo steel steam generator tubes. It describes the reagents and conditions for post-chemical cleaning passivation of the evaporator tubes

  13. Mitigation of steam generator tube rupture in a pressurized water reactor with passive safety systems

    Science.gov (United States)

    McDermott, Daniel J.; Schrader, Kenneth J.; Schulz, Terry L.

    1994-01-01

    The effects of steam generator tube ruptures in a pressurized water reactor are mitigated by reducing the pressure in the primary loop by diverting reactor coolant through the heat exchanger of a passive heat removal system immersed in the in containment refueling water storage tank in response to a high feed water level in the steam generator. Reactor coolant inventory is maintained by also in response to high steam generator level introducing coolant into the primary loop from core make-up tanks at the pressure in the reactor coolant system pressurizer. The high steam generator level is also used to isolate the start-up feed water system and the chemical and volume control system to prevent flooding into the steam header. 2 figures.

  14. Passivated emitters in silicon solar cells

    International Nuclear Information System (INIS)

    King, R.R.; Gruenbaum, P.E.; Sinton, R.A.; Swanson, R.M.

    1990-01-01

    In high-efficiency silicon solar cells with low metal contact coverage fractions and high bulk lifetimes, cell performance is often dominated by recombination in the oxide-passivated diffusions on the cell surface. Measurements of the emitter saturation current density, J o , of oxide-passivated, boron and phosphorus diffusions are presented, and from these measurements, the dependence of surface recombination velocity on dopant concentration was extracted. The lowest observed values of J o which are stable under UV light are given for both boron- and phosphorus-doped, oxide-passivated diffusions, for both textured and untextured surfaces. Contour plots which incorporate the above data have been applied to two types of backside-contact solar cells with large area (37.5 cm 2 ) and one-sun efficiencies up to 22.7%

  15. Multipassage diffuser

    International Nuclear Information System (INIS)

    Lalis, A.; Rouviere, R.; Simon, G.

    1976-01-01

    A multipassage diffuser having 2p passages comprises a leak-tight cylindrical enclosure closed by a top cover and a bottom end-wall, parallel porous tubes which are rigidly assembled in sectors between tube plates and through which the gas mixture flows, the tube sectors being disposed at uniform intervals on the periphery of the enclosure. The top tube plates are rigidly fixed to an annular header having the shape of a half-torus and adapted to communicate with the tubes of the corresponding sector. Each passage is constituted by a plurality of juxtaposed sectors in which the mixture circulates in the same direction, the header being divided into p portions limited by radial partition-walls and each constituting two adjacent passages. The diffuser is provided beneath the bottom end-wall with p-1 leak-tight chambers each adapted to open into two different portions of the header, and with two collector-chambers each fitted with a nozzle for introducing the gas mixture and discharging the fraction of the undiffused mixture. By means of a central orifice formed in the bottom end-wall the enclosure communicates with a shaft for discharging the diffused fraction of the gas mixture

  16. A study of swirl flow in draft tubes

    Energy Technology Data Exchange (ETDEWEB)

    Dahlhaug, Ole Gunnar

    1997-12-31

    This thesis presents measurements performed inside conical diffuser and bend, draft tubes of model hydro turbines, and draft tube of a prototype hydro turbine. Experimental results for swirling flow in conical diffuser and bend are presented in three different geometries. The axial velocity decreases at the centre of the tube at high swirl numbers because of an axial pressure gradient set up by the downstream frictional damping of the tangential velocities and the pressure increase downstream of the diffuser. Analytical models of the tangential velocity profiles are found and the radial pressure distribution calculated. Good correlation to the measured pressure distribution was achieved. Diffuser efficiency was calculated based on the equations for velocity and pressure profiles, which gave a qualified estimate of the diffuser hydraulic performance. The calculation shows that the bend reduces the efficiency by more than 30%. For a straight tube followed by a diffuser, numerical calculations were done, using K{epsilon}, RNG and RSM turbulence models for all measured swirl numbers. The K{epsilon} model gave best results for the forced vortex profile at low swirl numbers, while the RSM model gave best results at high swirl number. The turbulent kinetic energy at high swirl numbers gave the largest difference between the calculated and the measured values. Measurements on draft tubes in model turbines show the importance of good draft tube design. Prototype measurements on a Francis turbine show how the outlet draft tube flow should be measured for prototype draft tube evaluation. 54 refs., 118 figs., 2 tabs.

  17. A study of swirl flow in draft tubes

    Energy Technology Data Exchange (ETDEWEB)

    Dahlhaug, Ole Gunnar

    1998-12-31

    This thesis presents measurements performed inside conical diffuser and bend, draft tubes of model hydro turbines, and draft tube of a prototype hydro turbine. Experimental results for swirling flow in conical diffuser and bend are presented in three different geometries. The axial velocity decreases at the centre of the tube at high swirl numbers because of an axial pressure gradient set up by the downstream frictional damping of the tangential velocities and the pressure increase downstream of the diffuser. Analytical models of the tangential velocity profiles are found and the radial pressure distribution calculated. Good correlation to the measured pressure distribution was achieved. Diffuser efficiency was calculated based on the equations for velocity and pressure profiles, which gave a qualified estimate of the diffuser hydraulic performance. The calculation shows that the bend reduces the efficiency by more than 30%. For a straight tube followed by a diffuser, numerical calculations were done, using K{epsilon}, RNG and RSM turbulence models for all measured swirl numbers. The K{epsilon} model gave best results for the forced vortex profile at low swirl numbers, while the RSM model gave best results at high swirl number. The turbulent kinetic energy at high swirl numbers gave the largest difference between the calculated and the measured values. Measurements on draft tubes in model turbines show the importance of good draft tube design. Prototype measurements on a Francis turbine show how the outlet draft tube flow should be measured for prototype draft tube evaluation. 54 refs., 118 figs., 2 tabs.

  18. Diffusion Under Geometrical Constraint

    OpenAIRE

    Ogawa, Naohisa

    2014-01-01

    Here we discus the diffusion of particles in a curved tube. This kind of transport phenomenon is observed in biological cells and porous media. To solve such a problem, we discuss the three dimensional diffusion equation with a confining wall forming a thinner tube. We find that the curvature appears in a effective diffusion coefficient for such a quasi-one-dimensional system. As an application to higher dimensional case, we discuss the diffusion in a curved surface with ...

  19. Preliminary assessment of using tree-tissue analysis and passive-diffusion samplers to evaluate trichloroethene contamination of ground water at Site SS-34N, McChord Air Force Base, Washington, 2001

    Science.gov (United States)

    Cox, S.E.

    2002-01-01

    Two low-cost innovative sampling procedures for characterizing trichloroethene (TCE) contamination in ground water were evaluated for use at McChord Air Force Base (AFB) by the U.S. Geological Survey, in cooperation with the U.S. Air Force McChord Air Force Base Installation Restoration Program, in 2001. Previous attempts to characterize the source of ground-water contamination in the heterogeneous glacial outwash aquifer at McChord site SS-34N using soil-gas surveys, direct-push exploration, and more than a dozen ground-water monitoring wells have had limited success. The procedures assessed in this study involved analysis of tree-tissue samples to map underlying ground-water contamination and deploying passive-diffusion samplers to measure TCE concentrations in existing monitoring wells. These procedures have been used successfully at other U.S. Department of Defense sites and have resulted in cost avoidance and accelerated site characterization. Despite the presence of TCE in ground water at site SS-34N, TCE was not detected in any of the 20 trees sampled at the site during either early spring or late summer sampling. The reason the tree tissue procedure was not successful at the McChord AFB site SS-34N may have been due to an inability of tree roots to extract moisture from a water table 30 feet below the land surface, or that concentrations of TCE in ground water were not large enough to be detectable in the tree tissue at the sampling point. Passive-diffusion samplers were placed near the top, middle, and bottom of screened intervals in three monitoring wells and TCE was observed in all samplers. Concentrations of TCE from the passive-diffusion samplers were generally similar to concentrations found in samples collected in the same wells using conventional pumping methods. In contrast to conventional pumping methods, the collection of ground-water samples using the passive-diffusion samples did not generate waste purge water that would require hazardous

  20. Response to a small external force and fluctuations of a passive particle in a one-dimensional diffusive environment

    Science.gov (United States)

    Huveneers, François

    2018-04-01

    We investigate the long-time behavior of a passive particle evolving in a one-dimensional diffusive random environment, with diffusion constant D . We consider two cases: (a) The particle is pulled forward by a small external constant force and (b) there is no systematic bias. Theoretical arguments and numerical simulations provide evidence that the particle is eventually trapped by the environment. This is diagnosed in two ways: The asymptotic speed of the particle scales quadratically with the external force as it goes to zero, and the fluctuations scale diffusively in the unbiased environment, up to possible logarithmic corrections in both cases. Moreover, in the large D limit (homogenized regime), we find an important transient region giving rise to other, finite-size scalings, and we describe the crossover to the true asymptotic behavior.

  1. On the Aharonov-Bohm diffusion

    International Nuclear Information System (INIS)

    Dasnieres de Veigy, A.; Ouvry, S.; Paris-6 Univ., 75

    1993-07-01

    The diffusion of a charged particle by a singular flux tube is revisited. A simple and rigourous derivation shows that the action of the propagator on an incident plane wave precisely yields the Aharonov-Bohm diffusion amplitude. The forward diffusion is discussed as well as the singularity of the interaction at the position of the flux tube. (orig.)

  2. Two-phase, passive separator-and-filter assembly

    Science.gov (United States)

    Erickson, A. C.; Porter, F. J., Jr.

    1974-01-01

    Assembly separates liquid from gas by passive hydrophilic/hydrophobic material approach. Apparatus is comprised of porous glass hydrophilic tubes. Quantity, lateral size, and pore size of glass tubes are determined by particular design requirements with regard to water rate, water quality contamination level, application endurance life, and operating differential pressure level.

  3. Application of various surface passivation layers in solar cells

    International Nuclear Information System (INIS)

    Lee, Ji Youn; Lee, Soo Hong

    2004-01-01

    In this work, we have used different techniques for surface passivation: conventional thermal oxidation (CTO), rapid thermal oxidation (RTO), and plasma-enhanced chemical vapour deposition (PECVD). The surface passivation qualities of eight different single and combined double layers have been investigated both on phosphorus non-diffused p-type Float Zone (FZ) silicon wafers and on diffused emitters (100 Ω/□ and 40 Ω/□). CTO/SiN 1 passivates very well not only on a non-diffused surface (τ eff = 1361 μs) but also on an emitter (τ eff = 414 μs). However, we concluded that RTO/SiN 1 and RTO/SiN 2 stacks were more suitable than CTO/SiN stacks for surface passivation in solar cells since those stacks had relatively good passivation qualities and suitable optical reflections. RTO/SiN 1 for rear-surface passivation and RTO/SiN 2 for front-surface passivation were applied to the fabrication of solar cells. We achieved efficiencies of 18.5 % and 18.8 % on 0.5 Ω-cm (FZ) silicon with planar and textured front surfaces, respectively. An excellent open circuit voltage (V oc ) of 675.6 mV was obtained for the planar cell.

  4. Short-term diffusive sampler for nitrogen dioxide monitoring in epidemiology

    International Nuclear Information System (INIS)

    Michaud, J.P.; Quackenboss, J.

    1991-01-01

    An automated timed exposure diffusive sampler (TEDS) for sampling nitrogen dioxide (NO 2 ) was developed for use in epidemiological studies. The TEDS sequentially exposes four passive sampling devices (PSD) by microprocessor controlled valves while a pump and air flow guide prevent sampler starvation. Two TEDS units and two portable, real-time NO 2 monitors were tested for accuracy, precision, sensitivity, and linearity of response. The accuracy of the TEDS was within 10 percent of the means of the measured values. The TEDS sensitivity was 20 to 30 ppb-hour for NO 2 . Co-location of the TEDS with a chemiluminescent NO x monitor (EPA reference method) showed a similar responses to ambient NO 2 . TEDS allows better time resolution than traditional diffusive samplers (i.e., Palmes tube) while sharing their ability to sample a variety of gases

  5. dc-plasma-sprayed electronic-tube device

    Science.gov (United States)

    Meek, T.T.

    1982-01-29

    An electronic tube and associated circuitry which is produced by dc plasma arc spraying techniques is described. The process is carried out in a single step automated process whereby both active and passive devices are produced at very low cost. The circuitry is extremely reliable and is capable of functioning in both high radiation and high temperature environments. The size of the electronic tubes produced are more than an order of magnitude smaller than conventional electronic tubes.

  6. Modeling of hydrogen passivation process of silicon for solar cells applications

    International Nuclear Information System (INIS)

    Kuznicki, Z.T.; Ciach, R.; Gorley, P.M.; Voznyy, M.V.

    2001-01-01

    In this paper, results of investigation of evolution equations' system describing hydrogen passivation of silicon are presented. Using Lie group theory the classification of invariant solutions and initial system reduction to systems of ordinary differential equations (ODEs) is carried out for admissible infinitesimal operators under constant hydrogen atoms diffusivity in the sample. Possibility of analytical solution of passivation problem is shown. Analysis of system behavior taking into account diffusion and dissociation mechanisms is performed. It is ascertained that free hydrogen atoms diffusion in the sample and 'defect-hydrogen' dissociation spoil passivation. Analytical dependences obtained make it possible to predict spatial and time defect distribution under hydrogen passivation of silicon depending on experimental conditions

  7. Spiral multiple-effect diffusion solar still coupled with vacuum-tube collector and heat pipe

    KAUST Repository

    Huang, Bin-Juine

    2015-04-01

    © 2015 Elsevier B.V. A novel solar still with spiral-shape multiple-effect diffusion unit is developed in the present study. The test results of a 14-effect unit coupled with vacuum-tube solar collector (absorber area 1.08m2) show that the highest daily pure water production is 40.6kgd-1. The measured highest productivity based on the area of glass cover, solar absorber, and evaporating surface is 34.7, 40.6, and 7.96kgm-2d-1, respectively, which are much higher than the published results. The measured solar distillation efficiency is 2.0-3.5. The performance enhancement results mainly from the lateral diffusion process in the spiraled still cell. The vapor flow generated by heat input can flow freely and laterally through the spiral channel down to the end when solar heat input is high. Besides, the larger evaporating and condensing area at the outer cell may increase heat and mass transfer at the outer cell.

  8. Process and device for forming imprints on ceramic tubes

    International Nuclear Information System (INIS)

    1985-01-01

    The purpose of the present invention is a process and a device for making imprints on ceramic tubes and these ceramic tubes with imprints. It is known that in uranium enrichment processes by gaseous diffusion, microporous tubes are used to made the diffuser units used for the application of this isotope enrichment process. It is known that these microporous tubes are generally made in two stages. In a first stage, a macroporous ceramic tube called a ''support'' is made. In a second stage, an internal microporous deposit is made which makes it possible to obtain a tube called a ''barrier'' finally having the required porosity to apply the gaseous diffusion enrichment process. The present invention involves the first stage of the manufacturing process of the barriers and, more precisely, a step in the manufacturing process of the supports that makes it possible to improve the efficiency of these barriers

  9. Analysis of airborne pesticides from different chemical classes adsorbed on Radiello® Tenax® passive tubes by thermal-desorption-GC/MS.

    Science.gov (United States)

    Raeppel, Caroline; Fabritius, Marie; Nief, Marie; Appenzeller, Brice M R; Briand, Olivier; Tuduri, Ludovic; Millet, Maurice

    2015-02-01

    An analytical methodology using automatic thermal desorption (ATD) and GC/MS was developed for the determination of 28 pesticides of different chemical classes (dichlobenil, carbofuran, trifluralin, clopyralid, carbaryl, flazasulfuron, mecoprop-P, dicamba, 2,4-MCPA, dichlorprop, 2,4-D, triclopyr, cyprodinil, bromoxynil, fluroxypyr, oxadiazon, myclobutanil, buprofezin, picloram, trinexapac-p-ethyl, ioxynil, diflufenican, tebuconazole, bifenthrin, isoxaben, alphacypermethrin, fenoxaprop and tau-fluvalinate) commonly used in nonagricultural areas in atmospheric samples. This methodology was developed to evaluate the indoor and outdoor atmospheric contamination by nonagricultural pesticides. Pesticides were sampled passive sampling tubes containing Tenax® adsorbent. Since most of these pesticides are polar (clopyralid, mecoprop-P, dicamba, 2,4-MCPA, dichlorprop, 2,4-D, triclopyr, bromoxynil, fluroxypyr, picloram, trinexapac-p-ethyl and ioxynil), a derivatisation step is required. For this purpose, a silylation step using N-(t-butyldimethylsilyl)-N-methyltrifluoroacetamide (MtBSTFA) was added before thermal desorption. This agent was chosen since it delivers very specific ions on electronic impact (m/z = M-57). This method was established with special consideration for optimal thermal desorption conditions (desorption temperature, desorb flow and duration; trap heating duration and flow; outlet split), linear ranges, limits of quantification and detection which varied from 0.005 to 10 ng and from 0.001 to 2.5 ng, respectively, for an uncertainty varied from 8 to 30 %. The method was applied in situ to the analysis of passive tubes exposed during herbicide application to an industrial site in east of France.

  10. Preliminary evaluation, using passive tubes, of carbon monoxide concentrations in outdoor and indoor air at street level shops in Genoa (Italy)

    Science.gov (United States)

    Valerio, Federico; Pala, Mauro; Lazzarotto, Anna; Balducci, Daniele

    Preliminary information on carbon monoxide (CO) concentrations (exposure time: 8 h) both inside and outside 38 randomly selected shops situated on four heavy traffic streets of Genoa was obtained using passive diffusion tubes. Reproducibility and accuracy of this analytical method were tested in real outdoor urban conditions and found within 25%; the detection limit was 1 mgm -3 of CO. The highest mean CO concentrations (15.8 ± 2.2 mgm -3) were found inside shops on Balbi street, a narrow "canyon street". Only in two small shops and two bars (both with many smokers) and in a delicatessen, were indoor CO concentrations significantly higher than outdoor values. The mean outdoor CO concentrations (mgm -3) along the four streets considered (XX Settembre, Balbi, Rolando, Fillak) were 7.4 ± 2.2; 14.5 ± 8.7; 5.8 ± 0.4; 10.5 ± 3.7, respectively. No statistical difference was found, comparing the mean indoor CO concentration with the mean CO outdoor value, measured simultaneously along the sidewalks of each street. CO concentrations in 10 shops without smokers and the nearest outdoor measurements were linearly correlated ( r = 0.99; p statistically significant difference was found comparing indoor CO pollution in shops with smokers (CO: 8.0 ± 5.4) to those without smokers (CO: 7.1 ± 4.6). Forced ventilation, with air intake far from traffic, proved effective in some specific situations in reducing indoor CO concentrations.

  11. Environmental monitoring of tritium in air with passive diffusion samplers

    International Nuclear Information System (INIS)

    Wood, M.J.; Workman, W.J.G.

    1992-01-01

    This paper reports on a field trail in which outdoor air was sampled with an active reference sampler and several passive HTO-in-air samplers simultaneously carried out at Chalk River Laboratories. Both passive and active samplers were changed on an approximately monthly schedule from 1990 September 2 to 1991 April 18. Average temperatures for the sampling intervals ranged from -8.06 degrees C to +15.5 degrees C and HTO-in-air concentrations measured by the active sampler were typically 10 Bq/m 3 . A total of 1290 passive HTO-in-air sampler measurements were made during the seven sampling intervals. The passive samplers used for the field trial were prepared with either tritium-free water or a solution of 50% tritium-free water and 50% ethylene glycol. As expected, the samplers prepared with the water-glycol solution performed more consistently than the samplers prepared with water only. Good agreement between passive and active sampler measurements was observed throughout the field trial

  12. A cheap and simple passive sampler using silicone rubber for the ...

    African Journals Online (AJOL)

    caffeine, personal care products, pharmaceuticals, pesticides and polycyclic aromatic hydrocarbons. Keywords: passive sampler, silicone rubber (PDMS) tubing, GCxGC-TOFMS, ..... concentrations may be derived by using performance reference compounds to determine in situ passive sampler sampling rates followed by ...

  13. Suction forces generated by passive bile bag drainage on a model of post-subdural hematoma evacuation.

    Science.gov (United States)

    Tenny, Steven O; Thorell, William E

    2018-05-05

    Passive drainage systems are commonly used after subdural hematoma evacuation but there is a dearth of published data regarding the suction forces created. We set out to quantify the suction forces generated by a passive drainage system. We created a model of passive drainage after subdural hematoma evacuation. We measured the maximum suction force generated with a bile bag drain for both empty drain tubing and fluid-filled drain tube causing a siphoning effect. We took measurements at varying heights of the bile bag to analyze if bile bag height changed suction forces generated. An empty bile bag with no fluid in the drainage tube connected to a rigid, fluid-filled model creates minimal suction force of 0.9 mmHg (95% CI 0.64-1.16 mmHg). When fluid fills the drain tubing, a siphoning effect is created and can generate suction forces ranging from 18.7 to 30.6 mmHg depending on the relative position of the bile bag and filled amount of the bile bag. The suction forces generated are statistically different if the bile bag is 50 cm below, level with or 50 cm above the experimental model. Passive bile bag drainage does not generate significant suction on a fluid-filled rigid model if the drain tubing is empty. If fluid fills the drain tubing then siphoning occurs and can increase the suction force of a passive bile bag drainage system to levels comparable to partially filled Jackson-Pratt bulb drainage.

  14. Electrochemical dissolution of fresh and passivated chalcopyrite electrodes. Effect of pyrite on the reduction of Fe3+ ions and transport processes within the passive film

    International Nuclear Information System (INIS)

    Olvera, O.G.; Quiroz, L.; Dixon, D.G.; Asselin, E.

    2014-01-01

    Graphical abstract: - Highlights: • FeS 2 increased the dissolution rate of fresh and passivated CuFeS 2 electrodes. • Fe 3+ reduction was the rate controlling step in the dissolution of fresh CuFeS 2 . • Diffusion within the passive film controlled the dissolution rate of passivated CuFeS 2 . - Abstract: The effect of pyrite (FeS 2 ) on the electrochemical dissolution of fresh and passivated chalcopyrite (CuFeS 2 ) electrodes has been studied. Current density values for the dissolution of CuFeS 2 were calculated from EIS measurements. FeS 2 increased the dissolution rate of fresh and passivated CuFeS 2 electrodes indicating that the galvanic effect continued even after the electrode was chemically passivated. The dissolution rate of CuFeS 2 decreased by a factor of 3 after the passivation treatment. Due to the low diffusion rates of ions within the CuFeS 2 passive film and due to an increase in the resistance to the transfer of electrons at the electrode/film interface, the activity of FeS 2 for the reduction of Fe 3+ ions was also reduced by a factor of 2.3 even though FeS 2 was not exposed to any chemical treatment. The results in this work indicate that the dissolution rate of the fresh CuFeS 2 electrode was controlled by the reduction of Fe 3+ ions whereas for the passivated CuFeS 2 electrode the dissolution rate was controlled by diffusion within the passive film

  15. Oxidation mechanism and passive behaviour of nickel in molten carbonate

    Energy Technology Data Exchange (ETDEWEB)

    Vossen, J.P.T. (ECN Fossil Fuels, Petten (Netherlands)); Ament, P.C.H.; De Wit, J.H.W. (Div. of Corrosion, Lab. for Maaterials Sceince, Delft Univ. of Technology, Delft (Netherlands))

    1994-07-01

    The oxidation and passivation mechanism and the passive behaviour of nickel in molten carbonate have been investigated with impedance measurements. The oxidation of nickel proceeds according to a dissolution and reprecipitation process. The slowest steps in the reaction sequence are the dissociation reaction of the carbonate and the diffusion of the formed NiO to the metal surface. In the passive range, dissolution of Ni[sup 2+] proceeds after diffusion of Ni[sup 2+] through the oxide layer. The Ni[sup 2+] is formed at the metal/oxide interface. The slowest process is the diffusion of bivalent nickel ions through the passive scale. The formation of trivalent nickel ions probably takes place at the oxide/melt interface. This reaction is accompanied by the incorporation of an oxygen ion and a nickel vacancy in the NiO lattice. The trivalent nickel ions and the nickel vacancy diffuse to the bulk of the oxide scale. The slowest step in this sequence is the dissociation of the carbonate ions and the incorporation of the oxygen ion in the NiO lattice. 9 figs., 2 tabs., 11 refs.

  16. A passive emergency heat sink for water-cooled reactors with particular application to CANDU reactors

    International Nuclear Information System (INIS)

    Spinks, N.J.

    1996-01-01

    Water in an overhead pool can serve as a general-purpose passive emergency heat sink for water-cooled reactors. It can be used for containment cooling, for emergency depressurization of the heat transport-system, or to receive any other emergency heat, such as that from the CANDU moderator. The passive emergency water system provides in-containment depressurization of steam generators and no other provision is needed for supply of low-pressure emergency water to the steam generators. For containment cooling, the pool supplies water to the tube side of elevated tube banks inside containment. The elevation with respect to the reactor heat source maximizes heat transport, by natural convection, of hot containment gases. This effective heat transport combines with the large heat-transfer coefficients of tube banks, to reduce containment overpressure during accidents. Cooled air from the tube banks is directed past the break in the heat-transport system, to facilitate removal of hydrogen using passive catalytic recombiners. (author)

  17. Evaluation of a Low-Cost Volatile Organic Compound Passive Sampling Method and Laboratory Intercomparison

    Data.gov (United States)

    U.S. Environmental Protection Agency — This project “fenceline Passive Sampler and Sensor Studies” contains information on several related field efforts that examine use of passive sorbent tubes and...

  18. Wave propagation in spatially modulated tubes

    Energy Technology Data Exchange (ETDEWEB)

    Ziepke, A., E-mail: ziepke@itp.tu-berlin.de; Martens, S.; Engel, H. [Institut für Theoretische Physik, Hardenbergstraße 36, EW 7-1, Technische Universität Berlin, 10623 Berlin (Germany)

    2016-09-07

    We investigate wave propagation in rotationally symmetric tubes with a periodic spatial modulation of cross section. Using an asymptotic perturbation analysis, the governing quasi-two-dimensional reaction-diffusion equation can be reduced into a one-dimensional reaction-diffusion-advection equation. Assuming a weak perturbation by the advection term and using projection method, in a second step, an equation of motion for traveling waves within such tubes can be derived. Both methods predict properly the nonlinear dependence of the propagation velocity on the ratio of the modulation period of the geometry to the intrinsic width of the front, or pulse. As a main feature, we observe finite intervals of propagation failure of waves induced by the tube’s modulation and derive an analytically tractable condition for their occurrence. For the highly diffusive limit, using the Fick-Jacobs approach, we show that wave velocities within modulated tubes are governed by an effective diffusion coefficient. Furthermore, we discuss the effects of a single bottleneck on the period of pulse trains. We observe period changes by integer fractions dependent on the bottleneck width and the period of the entering pulse train.

  19. Activities of passive cooling applications and simulation of innovative nuclear power plant design

    International Nuclear Information System (INIS)

    Aglar, F.; Tanrykut, A.

    2002-01-01

    This paper gives a general insight on activities of the Turkish Atomic Energy Authority (TAEA) concerning passive cooling applications and simulation of innovative nuclear power plant design. The condensation mode of heat transfer plays an important role for the passive heat removal application in advanced water-cooled reactor systems. But it is well understood that the presence of noncondesable (NC) gases can greatly inhibit the condensation process due to the build up of NC gas concentration at the liquid/gas interface. The isolation condenser of passive containment cooling system of the simplified boiling water reactors is a typical application area of in-tube condensation in the presence of NC. The test matrix of the experimental investigation undertaken at the METU-CTF test facility (Middle East Technical University, Ankara) covers the range of parameters; Pn (system pressure) : 2-6 bar, Rev (vapor Reynolds number): 45,000-94,000, and Xi (air mass fraction): 0-52%. This experimental study is supplemented by a theoretical investigation concerning the effect of mixture flow rate on film turbulence and air mass diffusion concepts. Recently, TAEA participated to an international standard problem (OECD ISP-42) which covers a set of simulation of PANDA test facility (Paul Scherrer Institut-Switzerland) for six different phases including different natural circulation modes. The concept of condensation in the presence of air plays an important role for performance of heat exchangers, designed for passive containment cooling, which in turn affect the natural circulation behaviour in PANDA systems. (author)

  20. Analyses for passive safety of fusion reactor during ex-vessel loss of coolant accident

    International Nuclear Information System (INIS)

    Honda, Takuro; Okazaki, Takashi; Maki, Koichi; Uda, Tatuhiko; Seki, Yasushi; Aoki, Isao; Kunugi, Tomoaki.

    1995-01-01

    Passive safety of nuclear fusion reactors during ex-vessel Loss-of-Coolant Accidents (LOCAs) in the divertor cooling system has been investigated using a hybrid code, which can treat the interaction of the plasma and plasma facing components (PFCs). The code has been modified to include the impurity emission from PFCs with a diffusion model at the edge plasma. We assumed an ex-vessel LOCA of the divertor cooling system during the ignited operation in International Thermonuclear Experimental Reactor (ITER), in which a carbon-copper brazed divertor plate was employed in the Conceptual Design Activity (CDA). When a double-ended break occurs at the cold leg of the divertor cooling system, the impurity density in the main plasma becomes about twice within 2s after the LOCA due to radiation enhanced sublimation of graphite PFCs. The copper cooling tube of the divertor begins to melt at about 3s after the LOCA, even though the plasma is passively shut down at about 4s due to the impurity accumulation. It is necessary to apply other PFC materials, which can shorten the time period for passive shutdown, or an active shutdown system to keep the reactor structures intact for such rapid transient accident. (author)

  1. Passive Mixing inside Microdroplets

    Directory of Open Access Journals (Sweden)

    Chengmin Chen

    2018-04-01

    Full Text Available Droplet-based micromixers are essential units in many microfluidic devices for widespread applications, such as diagnostics and synthesis. The mixers can be either passive or active. When compared to active methods, the passive mixer is widely used because it does not require extra energy input apart from the pump drive. In recent years, several passive droplet-based mixers were developed, where mixing was characterized by both experiments and simulation. A unified physical understanding of both experimental processes and simulation models is beneficial for effectively developing new and efficient mixing techniques. This review covers the state-of-the-art passive droplet-based micromixers in microfluidics, which mainly focuses on three aspects: (1 Mixing parameters and analysis method; (2 Typical mixing element designs and the mixing characters in experiments; and, (3 Comprehensive introduction of numerical models used in microfluidic flow and diffusion.

  2. Theoretical and computational studies of entangled rod-coil block copolymer diffusion

    Science.gov (United States)

    Wang, Muzhou; Alexander-Katz, Alfredo; Olsen, B. D.

    2012-02-01

    Despite continued interest in the thermodynamics of rod-coil block copolymers for functional nanostructured materials in organic electronics and biomaterials, relatively few studies have investigated the dynamics of these systems which are important for understanding diffusion, mechanics, and self-assembly kinetics. Here, the diffusion of coil-rod-coil block copolymers through entangled melts is simulated using the Kremer-Grest molecular dynamics model, demonstrating that the mismatch between the curvature of the rod and coil blocks results in dramatically slower reptation through the entanglement tube. For rod lengths near the tube diameter, this hindered diffusion is explained by a local curvature-dependent free energy penalty produced by the curvature mismatch, resulting in a rough energy surface as the rod moves along the tube contour. Compared to coil homopolymers which reptate freely along the tube, rod-coil block copolymers undergo an activated diffusion process which is considerably slower as the rod length increases. For large rods, diffusion of the rod through the tube only occurs when the coil blocks occupy straight entanglement tubes, which requires ``arm retraction'' as the dominant relaxation mechanism.

  3. Development of a new passive sampler based on diffusive milligel beads for copper analysis in water

    International Nuclear Information System (INIS)

    Perez, M.; Reynaud, S.; Lespes, G.; Potin-Gautier, M.; Mignard, E.; Chéry, P.; Schaumlöffel, D.; Grassl, B.

    2015-01-01

    A new passive sampler was designed and characterized for the determination of free copper ion (Cu 2+ ) concentration in aqueous solution. Each sampling device was composed of a set of about 30 diffusive milligel (DMG) beads. Milligel beads with incorporated cation exchange resin (Chelex) particles were synthetized using an adapted droplet-based millifluidic process. Beads were assumed to be prolate spheroids, with a diameter of 1.6 mm and an anisotropic factor of 1.4. The milligel was controlled in chemical composition of hydrogel (monomer, cross-linker, initiator and Chelex concentration) and characterized in pore size. Two types of sampling devices were developed containing 7.5% and 15% of Chelex, respectively, and 6 nm pore size. The kinetic curves obtained demonstrated the accumulation of copper in the DMG according to the process described in the literature as absorption (and/or adsorption) and release following the Fick's first law of diffusion. For their use in water monitoring, the typical physico-chemical characteristics of the samplers, i.e. the mass-transfer coefficient (k 0 ) and the sampler-water partition coefficient (K sw ), were determined based on a static exposure design. In order to determine the copper concentration in the samplers after their exposure, a method using DMG bead digestion combined to Inductively Coupled Plasma – Atomic Emission Spectrometry (ICP-AES) analysis was developed and optimized. The DMG devices proved to be capable to absorb free copper ions from an aqueous solution, which could be accurately quantified with a mean recovery of 99% and a repeatability of 7% (mean relative uncertainty). - Highlights: • Controlled geometry of new passive sampler with ellipsoidal shape. • Original manufacturing process based on droplet-based millifluidic device. • Pore size characterization of the sampler. • Mass-transfer and sampler-water partitioning coefficients by static exposure experiments

  4. Development of a new passive sampler based on diffusive milligel beads for copper analysis in water

    Energy Technology Data Exchange (ETDEWEB)

    Perez, M.; Reynaud, S.; Lespes, G.; Potin-Gautier, M. [Université de Pau et des Pays de l’Adour/CNRS UMR IPREM 5254, Hélioparc, 2 av. du Président Angot, 64053 Pau (France); Mignard, E. [CNRS-Solvay-Université Bordeaux, UMR5258, Laboratoire du Futur, 178 Avenue du Dr. A. Schweitzer, 33608 Pessac Cedex (France); Chéry, P. [Bordeaux Science Agro, 1 cours du Général De Gaulle, Gradignan, 33175 (France); Schaumlöffel, D. [Université de Pau et des Pays de l’Adour/CNRS UMR IPREM 5254, Hélioparc, 2 av. du Président Angot, 64053 Pau (France); Grassl, B., E-mail: bruno.grassl@univ-pau.fr [Université de Pau et des Pays de l’Adour/CNRS UMR IPREM 5254, Hélioparc, 2 av. du Président Angot, 64053 Pau (France)

    2015-08-26

    A new passive sampler was designed and characterized for the determination of free copper ion (Cu{sup 2+}) concentration in aqueous solution. Each sampling device was composed of a set of about 30 diffusive milligel (DMG) beads. Milligel beads with incorporated cation exchange resin (Chelex) particles were synthetized using an adapted droplet-based millifluidic process. Beads were assumed to be prolate spheroids, with a diameter of 1.6 mm and an anisotropic factor of 1.4. The milligel was controlled in chemical composition of hydrogel (monomer, cross-linker, initiator and Chelex concentration) and characterized in pore size. Two types of sampling devices were developed containing 7.5% and 15% of Chelex, respectively, and 6 nm pore size. The kinetic curves obtained demonstrated the accumulation of copper in the DMG according to the process described in the literature as absorption (and/or adsorption) and release following the Fick's first law of diffusion. For their use in water monitoring, the typical physico-chemical characteristics of the samplers, i.e. the mass-transfer coefficient (k{sub 0}) and the sampler-water partition coefficient (K{sub sw}), were determined based on a static exposure design. In order to determine the copper concentration in the samplers after their exposure, a method using DMG bead digestion combined to Inductively Coupled Plasma – Atomic Emission Spectrometry (ICP-AES) analysis was developed and optimized. The DMG devices proved to be capable to absorb free copper ions from an aqueous solution, which could be accurately quantified with a mean recovery of 99% and a repeatability of 7% (mean relative uncertainty). - Highlights: • Controlled geometry of new passive sampler with ellipsoidal shape. • Original manufacturing process based on droplet-based millifluidic device. • Pore size characterization of the sampler. • Mass-transfer and sampler-water partitioning coefficients by static exposure experiments.

  5. Streak tube development

    International Nuclear Information System (INIS)

    Hinrichs, C.K.; Estrella, R.M.

    1979-01-01

    A research program for the development of a high-speed, high-resolution streak image tube is described. This is one task in the development of a streak camera system with digital electronic readout, whose primary application is for diagnostics in underground nuclear testing. This program is concerned with the development of a high-resolution streak image tube compatible with x-ray input and electronic digital output. The tube must be capable of time resolution down to 100 psec and spatial resolution to provide greater than 1000 resolution elements across the cathode (much greater than presently available). Another objective is to develop the capability to make design changes in tube configurations to meet different experimental requirements. A demountable prototype streak tube was constructed, mounted on an optical bench, and placed in a vacuum system. Initial measurements of the tube resolution with an undeflected image show a resolution of 32 line pairs per millimeter over a cathode diameter of one inch, which is consistent with the predictions of the computer simulations. With the initial set of unoptmized deflection plates, the resolution pattern appeared to remain unchanged for static deflections of +- 1/2-inch, a total streak length of one inch, also consistent with the computer simulations. A passively mode-locked frequency-doubled dye laser is being developed as an ultraviolet pulsed light source to measure dynamic tube resolution during streaking. A sweep circuit to provide the deflection voltage in the prototype tube has been designed and constructed and provides a relatively linear ramp voltage with ramp durations adjustable between 10 and 1000 nsec

  6. 3D CFD simulations to study the effect of inclination of condenser tube on natural convection and thermal stratification in a passive decay heat removal system

    Energy Technology Data Exchange (ETDEWEB)

    Minocha, Nitin [Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094 (India); Joshi, Jyeshtharaj B., E-mail: jbjoshi@gmail.com [Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094 (India); Department of Chemical Engineering, Institute of Chemical Technology, Matunga, Mumbai 400 019 (India); Nayak, Arun K. [Reactor Engineering Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085 (India); Vijayan, Pallippattu K., E-mail: vijayanp@barc.gov.in [Reactor Engineering Division, Bhabha Atomic Research Center, Trombay, Mumbai 400 085 (India)

    2016-08-15

    Highlights: • Investigation of three-dimensional natural convection and thermal stratification inside large water pool. • Effect of inclination (α) of condenser tube on fluid flow and heat transfer. • The heat transfer was found to be maximum for α = 90° and minimum for α = 15°. • Laminar-turbulent natural convection and heat transfer in the presence of longitudinal vortices. - Abstract: Many advanced nuclear reactors adopt methodologies of passive safety systems based on natural forces such as gravity. In one of such system, the decay heat generated from a reactor is removed by isolation condenser (ICs) submerged in a large water pool called the Gravity Driven Water Pool (GDWP). The objective of the present study was to design an IC for the passive decay heat removal system (PDHRS) for advanced nuclear reactor. First, the effect of inclination of IC tube on three dimensional temperature and flow fields was investigated inside a pilot scale (10 L) GDWP. Further, the knowledge of these fields has been used for the quantification of heat transfer and thermal stratification phenomenon. In a next step, the knowledge gained from the pilot scale GDWP has been extended to design an IC for real size GDWP (∼10,000 m{sup 3}). Single phase CFD simulation using open source CFD code [OpenFOAM-2.2] was performed for different tube inclination angles (α) (w.r.t. to vertical direction) in the range 0° ⩽ α ⩽ 90°. The results indicate that the heat transfer coefficient increases with increase in tube inclination angle. The heat transfer was found to be maximum for α = 90° and minimum for α = 15°. This behavior is due to the interaction between the primary flow (due to pressure gradient) and secondary flow (due to buoyancy force). The primary flow enhanced the fluid sliding motion at the tube top whereas the secondary flow resulted in enhancement in fluid motion along the circumference of tube. As the angle of inclination (α) of the tube was increased, the

  7. Passive Badge Assessment for Long-Term, Low-level Air Monitoring on Submarines: Acrolein Badge Validation

    National Research Council Canada - National Science Library

    Williams, Kimberly P; Rose-Pehrsson, Susan L; Kidwell, David A

    2006-01-01

    .... Passive badge monitors for acrolein detection were tested. Long-term sampling efficiency was evaluated for a 28-day period by comparing the response of the passive badge to an active tube sampling method...

  8. TEPSS - Technology Enhancement for Passive Safety Systems

    International Nuclear Information System (INIS)

    Hart, J.; Slegers, W.J.M.; Boer, S.L. de; Huggenberger, M.; Lopez Jimenez, J.; Munoz-Cabo Gonzalez, J.L.; Reventos Puigjaner, F.

    2000-01-01

    The objective of the TEPSS project was to make significant additions to the technology base of the European Simplified Boiling Water Reactor (ESBWR). The project focused on mixing and stratification phenomena in large water pools, passive decay heat removal from containments, and effects of aerosol deposition inside a passive heat exchanger. The PSI experimental facility LINX (Large-scale Investigation of Natural Circulation and Mixing) has been used to investigate venting of steam and steam-noncondensable gas mixtures into water pools. The test revealed that no significant steam bypass could be detected when injecting a mixture of steam or air and that mixing was very efficient. In addition to the tests, 3-D numerical computations and initial model development have been performed to study the behaviour of bubble plumes in water pools. The major part of the TEPSS project studied selective aspects of the response technology of modem pressure-suppression type containment designs and of passive-type decay heat removal systems. The work included an experimental phase using the large-scale experimental facility PANDA (Passive Nachwaermeabfuhr und Druckabbau), operated by PSI, where eight experiments successfully have been executed to test the performance of the ESBWR containment configuration. The PANDA tests have been analysed successfully using thermalhydraulic system analysis codes and 3-D CFD codes. The AIDA (Aerosol Impaction and Deposition Analysis) experimental facility of PSI has been used to investigate the degradation of passive decay heat removal due to fission product aerosols deposited on the inside surfaces of the PCC (Passive Containment Cooler) heat exchanger tubes. The one test performed revealed that the degradation of the heat transfer in the PCC tubes due to the deposition of aerosols reached about 20%. The test has been analysed using the MELCOR severe accident analysis code. (author)

  9. A passive emergency heat sink for water cooled reactors with particular application to CANDU reg-sign reactors

    International Nuclear Information System (INIS)

    Spinks, N.J.

    1996-01-01

    Water in an overhead pool can serve as a general-purpose passive emergency heat sink for water-cooled reactors. It can be used for containment cooling, for emergency depressurization of the heat transport-system, or to receive any other emergency heat, such as that from the CANDU reg-sign moderator. The passive emergency water system provides in-containment depressurization of steam generators and no other provision is needed for supply of low-pressure emergency water to the steam generators. For containment cooling, the pool supplies water to the tube side of elevated tube banks inside containment. The elevation with respect to the reactor heat source maximizes heat transport, by natural convection, of hot containment gases. This effective heat transport combines with the large heat-transfer coefficients of tube banks, to reduce containment overpressure during accidents. Cooled air from the tube banks is directed past the break in the heat-transport system, to facilitate removal of hydrogen using passive catalytic recombiners

  10. Design and technology parameters influence on durability for heat exchangers tube to tubesheet joints

    Science.gov (United States)

    Ripeanu, R. G.

    2017-02-01

    The main failures of heat exchangers are: corrosion of tubes and jacket, tubes blockage and failures of tube to tubesheet joints also by corrosion. The most critical zone is tube to tubesheet joints. Depending on types of tube to tubesheet joints, in order to better respect conditions of tension and compression, this paper analyses the tubesheet holes shapes, smooth and with a grove, on corrosion behavior. In the case of welding tubes with tubesheet, welding parameters modify corrosion behavior. Were realized welded joints by three welding regimes and tested at corrosion in two media, tap water and industrial water. Were tested also samples made of smooth tubes, finned tubes and tubes coated with a passive product as applied by a heat exchanger manufacturer. For all samples, the roughness parameters were measured, before and after the corrosion tests. The obtained corrosion rates show that stress values and their distribution along the joint modify the corrosion behavior. The optimum welding parameters were established in order to increase the joint durability. The paper has shown that passive product used is not proper chosen and the technology of obtaining rolled thread pipes diminishes tubes’ durability by increasing the corrosion rate.

  11. Passive sampling for the isotopic fingerprinting of atmospheric mercury

    Science.gov (United States)

    Bergquist, B. A.; MacLagan, D.; Spoznar, N.; Kaplan, R.; Chandan, P.; Stupple, G.; Zimmerman, L.; Wania, F.; Mitchell, C. P. J.; Steffen, A.; Monaci, F.; Derry, L. A.

    2017-12-01

    Recent studies show that there are variations in the mercury (Hg) isotopic signature of atmospheric Hg, which demonstrates the potential for source tracing and improved understanding of atmospheric cycling of Hg. However, current methods for both measuring atmospheric Hg and collecting enough atmospheric Hg for isotopic analyses require expensive instruments that need power and expertise. Additionally, methods for collecting enough atmospheric Hg for isotopic analysis require pumping air through traps for long periods (weeks and longer). Combining a new passive atmospheric sampler for mercury (Hg) with novel Hg isotopic analyses will allow for the application of stable Hg isotopes to atmospheric studies of Hg. Our group has been testing a new passive sampler for gaseous Hg that relies on the diffusion of Hg through a diffusive barrier and adsorption onto a sulphur-impregnated activated carbon sorbent. The benefit of this passive sampler is that it is low cost, requires no power, and collects gaseous Hg for up to one year with linear, well-defined uptake, which allows for reproducible and accurate measurements of atmospheric gaseous Hg concentrations ( 8% uncertainty). As little as one month of sampling is often adequate to collect sufficient Hg for isotopic analysis at typical background concentrations. Experiments comparing the isotopic Hg signature in activated carbon samples using different approaches (i.e. by passive diffusion, by passive diffusion through diffusive barriers of different thickness, by active pumping) and at different temperatures confirm that the sampling process itself does not impose mass-independent fractionation (MIF). However, sampling does result in a consistent and thus correctable mass-dependent fractionation (MDF) effect. Therefore, the sampler preserves Hg MIF with very high accuracy and precision, which is necessary for atmospheric source tracing, and reasonable MDF can be estimated with some increase in error. In addition to

  12. Development of More Cost-Effective Methods for Long-Term Monitoring of Soil Vapor Intrusion to Indoor Air Using Quantitative Passive Diffusive-Adsorptive Sampling Techniques

    Science.gov (United States)

    2015-05-01

    ASTM ASTM International ASU Arizona State University ATD automated thermal desorption BENZ Benzene C/Co passive sampler concentration...Protection Agency [USEPA], 1998a, b; California Department of Toxic Substance Control, 2011; ASTM International [ASTM] D7758, 2011). This demonstration... microporous sintered polyethylene, through which the vapors diffuse. Figure 1b. Radiello sampler with regular (white) and low-uptake rate

  13. Probabilistic analysis of degradation incubation time of steam generator tubing materials

    International Nuclear Information System (INIS)

    Pandey, M.D.; Jyrkama, M.I.; Lu, Y.; Chi, L.

    2012-01-01

    The prediction of degradation free lifetime of steam generator (SG) tubing material is an important step in the life cycle management and decision for replacement of steam generators during the refurbishment of a nuclear station. Therefore, an extensive experimental research program has been undertaken by the Canadian Nuclear Industry to investigate the degradation of widely-used SG tubing alloys, namely, Alloy 600 TT, Alloy 690 TT, and Alloy 800. The corrosion related degradations of passive metals, such as pitting, crevice corrosion and stress corrosion cracking (SCC) etc. are assumed to start with the break down of the passive film at the tube-environment interface, which is characterized by the incubation time for passivity breakdown and then the degradation growth rate, and both are influenced by the chemical environment and coolant temperature. Since the incubation time and growth rate exhibit significant variability in the laboratory tests used to simulate these degradation processes, the use of probabilistic modeling is warranted. A pit is initiated with the breakdown of the passive film on the SG tubing surface. Upon exposure to aggressive environments, pitting corrosion may not initiate immediately, or may initiate and then re-passivate. The time required to initiate pitting corrosion is called the pitting incubation time, and that can be used to characterize the corrosion resistance of a material under specific test conditions. Pitting may be the precursor to other corrosion degradation mechanisms, such as environmentally-assisted cracking. This paper will provide an overview of the results of the first stage of experimental program in which samples of Alloy 600 TT, Alloy 690 TT, and Alloy 800 were tested under various temperatures and potentials and simulated crevice environments. The testing environment was chosen to represent layup, startup, and full operating conditions of the steam generators. Degradation incubation times for over 80 samples were

  14. Sudden endotracheal tube block in a patient of Achalasia Cardia

    Directory of Open Access Journals (Sweden)

    Ajit Gupta

    2012-01-01

    Full Text Available Endotracheal tube block due to various mechanical causes such as mucous, blood clot, denture, and ampoules have been reported. A patient of achalasia cardia with chronic passive aspiration pneumonitis developed mucoid mass in the respiratory passage which dislodged during the surgical procedure. The episode occurred almost an hour after induction of anesthesia and the dislodged mucoid mass blocked the lumen of endotracheal tube, leading to hypoxia and impending cardiac arrest. However, the patient was salvaged by replacing the tube.

  15. The influence of geometry and draught shields on the performance of passive samplers.

    Science.gov (United States)

    Hofschreuder, P; van der Meulen, W; Heeres, P; Slanina, S

    1999-04-01

    Passive samplers provide an excellent opportunity to perform indicative measurements or establish a dense network of measuring sites. A drawback compared with conventional active measuring methods is the larger spread of results. This variation can, to a large extent, be attributed to the influence of temperature, sampler geometry and wind on sampling results. A proper design of sampler geometry and optimum choice of draught shield can reduce the influence of wind velocity on a badge type sampler to less than 10%. Wire mesh screens prove to be inadequate in damping turbulence. Filters give good results. Attention should be paid to the size and isolation value of the walls of the sampler to prevent thermal updrafts occurring within the sampler. Tube type samplers are less influenced by wind, provided that turbulence is prevented from influencing diffusion within the sampler.

  16. Deuterium diffusion along the three principal directions in anisotropic Zr–2.5Nb

    Energy Technology Data Exchange (ETDEWEB)

    Khatamian, D., E-mail: khatamiand@aecl.ca

    2013-12-15

    Highlights: •Diffusivity of deuterium in a Zr–2.5Nb plate was measured. •The plate had similar microstructure to that of a CANDU pressure tube. •Diffusion coefficients in the radial direction were 24% less than in the longitudinal direction. •These findings are in close agreement with the theoretical estimates made in the literature. -- Abstract: Pressure tubes of cold-worked Zr–2.5Nb material are used in the CANDU (CANada Deuterium Uranium is a registered trademark of Atomic Energy of Canada Ltd.) reactors to contain the fuel bundles and the heavy water coolant. The pressure tube microstructure consists of α-Zr platelets, with an aspect ratio of 1:5:50 in the radial, transverse and longitudinal directions, surrounded by a thin layer of β-Zr. The diffusivity of hydrogen in β-Zr is higher than in α-Zr. As a result, the diffusivity of hydrogen in the pressure tube material is enhanced compared to unalloyed α-Zr. Due to the anisotropic microstructure of the pressure tube with respect to the β-Zr network, the diffusivity of hydrogen is thought to be different in the three principal pressure tube directions. Measurements made using specimens machined from an 8 mm thick Zr–2.5Nb plate, with a microstructure similar to that of a CANDU pressure tube, suggest the difference between the diffusion constants for deuterium in different directions of an as-installed pressure tube may be as high as 25%.

  17. Subcooled Pool Boiling from Two Tubes of 6 Degree Included Angle in Vertical Alignment

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Myeong-Gie [Andong National University, Andong (Korea, Republic of)

    2015-05-15

    One of the major issues in the design of a heat exchanger is the heat transfer in a tube bundle. The passive condensation heat exchanger (PCHX) adopted in APR+ has U-type tube. The PCHX is submerged in the passive condensation cooling tank (PCCT). The heat exchanging tubes are in vertical alignment and inclined at 3 degrees to prevent water hammer as shown in Fig. 1. For the cases, the upper tube is affected by the lower tube. Therefore, the results for a single tube are not applicable to the design of the PCHX. However, the passive heat exchangers are submerged in the subcooled water under atmospheric pressure. The water temperature in the PCCT rises according to the PAFS actuation and reaches the saturation temperature after more than 2.5 hours. Since this period is very important to maintain reactor integrity, the exact evaluation of heat transfer on the tube bundle is indispensable. Although an experimental study on both subcooled and saturated pool boiling of water was performed to obtain local heat transfer coefficients on a 3 degree inclined tube at atmospheric pressure by Kang, no previous results were treating the bundle effect in the subcooled liquid. The heat transfer on the upper tube is enhanced compared with the single tube. The enhancement of the heat transfer on the upper tube is estimated by the bundle effect ( h{sub r} ). It is defined as the ratio of the heat transfer coefficient ( h{sub b} ) for an upper tube in a bundle with lower tubes activated to that for the same tube activated alone in the bundle. The upper tube within a tube bundle can significantly increase nucleated boiling heat transfer compared to the lower tubes at moderate heat fluxes. Summarizing the published results, it is still necessary to identify effects of liquid subcooling on inclined tubes for application to the PCHX design. Therefore, the present study is aimed to study the variations of pool boiling heat transfer on a tube bundle having a 6 degree included angle in

  18. The diffusion behaviour of hydrogen in a low alloyed carbon steel with respect to the deformation level and to the passivation process in alkaline solutions

    International Nuclear Information System (INIS)

    Juilfs, G.G.

    2001-01-01

    The diffusion behaviour of hydrogen in a low alloyed carbon steel with respect to the deformation level and to the passivation process in alkaline solutions. The influence of plastic strain on the diffusion behaviour of hydrogen in a low alloyed structural steel (FeE 690T) was investigated using the electrochemical permeation technique. The plastic deformation was introduced either by cold rolling or by tensile straining. Specially prepared C(T)-specimen enabled the direct determination of the diffusion coefficient in the highly deformed region ahead of a blunting crack. It was shown, that the apparent diffusion coefficient depends on the plastic strain and on the overall hydrogen concentration, whereas the maximum hydrogen flux remained almost unchanged. These observations are interpreted in terms of variations in the dislocation density, which act as 'sinks' for the diffusable hydrogen atoms. The results are compared with model calculations, that describe the hydrogen transport as a function of the trap density. The comparison of the numerical simulation and the experimental data shows a good agreement over the whole range of plastic strain levels, leading to a trap density of 6.1.10 19 /d 3 . Together with the results of a previous study on the fracture toughness of FeE 690T in the presence of hydrogen the permeation data obtained in this work suggest that the observed influence of deformation rates on the fracture mechanism can be attributed to the reduced mobility of hydrogen atoms in the plastic zone. The assumption that the hydrogen transport during monotonic straining is controlled by diffusion was confirmed by investigations concerning the formation of surface films. Using a potentiodynamic method (cyclovoltammetry) a characterisation of the surface reactions involved in permeation experiments was performed. It was shown that the nature of the passive layers forming on the surface depends on the applied potential, affecting mainly the hydrogen absorption

  19. Investigation of characteristics of passive heat removal system based on the assembled heat transfer tube

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xiang Cheng; Yan, Changqi; Meng, Zhao Ming; Chen, Kailun; Song, Shao Chuang; Yang, Zong Hao; Yu, Jie [Fundamental Science on Nuclear Safety and Simulation Technology Laboratory, Harbin Engineering University, Harbin (China)

    2016-12-15

    To get an insight into the operating characteristics of the passive residual heat removal system of molten salt reactors, a two-phase natural circulation test facility was constructed. The system consists of a boiling loop absorbing the heat from the drain tank, a condensing loop consuming the heat, and a steam drum. A steady-state experiment was carried out, in which the thimble temperature ranged from 450 .deg. C to 700 .deg. C and the system pressure was controlled at levels below 150 kPa. When reaching a steady state, the system was operated under saturated conditions. Some important parameters, including heat power, system resistance, and water level in the steam drum and water tank were investigated. The experimental results showed that the natural circulation system is feasible in removing the decay heat, even though some fluctuations may occur in the operation. The uneven temperature distribution in the water tank may be inevitable because convection occurs on the outside of the condensing tube besides boiling with decreasing the decay power. The instabilities in the natural circulation loop are sensitive to heat flux and system resistance rather than the water level in the steam drum and water tank. RELAP5 code shows reasonable results compared with experimental data.

  20. Investigation of Characteristics of Passive Heat Removal System Based on the Assembled Heat Transfer Tube

    Directory of Open Access Journals (Sweden)

    Xiangcheng Wu

    2016-12-01

    Full Text Available To get an insight into the operating characteristics of the passive residual heat removal system of molten salt reactors, a two-phase natural circulation test facility was constructed. The system consists of a boiling loop absorbing the heat from the drain tank, a condensing loop consuming the heat, and a steam drum. A steady-state experiment was carried out, in which the thimble temperature ranged from 450°C to 700°C and the system pressure was controlled at levels below 150 kPa. When reaching a steady state, the system was operated under saturated conditions. Some important parameters, including heat power, system resistance, and water level in the steam drum and water tank were investigated. The experimental results showed that the natural circulation system is feasible in removing the decay heat, even though some fluctuations may occur in the operation. The uneven temperature distribution in the water tank may be inevitable because convection occurs on the outside of the condensing tube besides boiling with decreasing the decay power. The instabilities in the natural circulation loop are sensitive to heat flux and system resistance rather than the water level in the steam drum and water tank. RELAP5 code shows reasonable results compared with experimental data.

  1. Error in measuring radon in soil gas by means of passive detectors

    International Nuclear Information System (INIS)

    Tanner, A.B.

    1991-01-01

    Passive detection of radon isotopes depends on diffusion of radon atoms from the sites of their generation to the location of the detecting or collecting device. Because some radon decays en route to a passive detector in soil, the radon concentration measured by the detector must be less than the concentration in those soil pores where it is undiminished by diffusion to the detector cavity. The true radon concentration may be significantly underestimated in moist soils. (author)

  2. A thermal mixing model of crossflow in tube bundles for use with the porous body approximation

    International Nuclear Information System (INIS)

    Ashcroft, J.; Kaminski, D.A.

    1996-06-01

    Diffusive thermal mixing in a heated tube bundle with a cooling fluid in crossflow was analyzed numerically. From the results of detailed two-dimensional models, which calculated the diffusion of heat downstream of one heated tube in an otherwise adiabatic flow field, a diffusion model appropriate for use with the porous body method was developed. The model accounts for both molecular and turbulent diffusion of heat by determining the effective thermal conductivity in the porous region. The model was developed for triangular shaped staggered tube bundles with pitch to diameter ratios between 1.10 and 2.00 and for Reynolds numbers between 1,000 and 20,000. The tubes are treated as nonconducting. Air and water were considered as working fluids. The effective thermal conductivity was found to be linearly dependent on the tube Reynolds number and fluid Prandtl number, and dependent on the bundle geometry. The porous body thermal mixing model was then compared against numerical models for flows with multiple heated tubes with very good agreement

  3. Electrical and optical characterization of surface passivation in GaAs nanowires.

    Science.gov (United States)

    Chang, Chia-Chi; Chi, Chun-Yung; Yao, Maoqing; Huang, Ningfeng; Chen, Chun-Chung; Theiss, Jesse; Bushmaker, Adam W; Lalumondiere, Stephen; Yeh, Ting-Wei; Povinelli, Michelle L; Zhou, Chongwu; Dapkus, P Daniel; Cronin, Stephen B

    2012-09-12

    We report a systematic study of carrier dynamics in Al(x)Ga(1-x)As-passivated GaAs nanowires. With passivation, the minority carrier diffusion length (L(diff)) increases from 30 to 180 nm, as measured by electron beam induced current (EBIC) mapping, and the photoluminescence (PL) lifetime increases from sub-60 ps to 1.3 ns. A 48-fold enhancement in the continuous-wave PL intensity is observed on the same individual nanowire with and without the Al(x)Ga(1-x)As passivation layer, indicating a significant reduction in surface recombination. These results indicate that, in passivated nanowires, the minority carrier lifetime is not limited by twin stacking faults. From the PL lifetime and minority carrier diffusion length, we estimate the surface recombination velocity (SRV) to range from 1.7 × 10(3) to 1.1 × 10(4) cm·s(-1), and the minority carrier mobility μ is estimated to lie in the range from 10.3 to 67.5 cm(2) V(-1) s(-1) for the passivated nanowires.

  4. Electropotential measurements of passivation and corrosion of steel coupons

    International Nuclear Information System (INIS)

    Petit, G.S.; Wright, R.R.

    1977-02-01

    There is considerable interest at the Oak Ridge Gaseous Diffusion Plant (ORGDP) in the preparation of mild steel to resist corrosion (passivation) both in moist air and uranium hexafluoride (UF 6 ) environments. Steel prepared by the usual procedures to prevent rusting, such as oiling, plastic coating, painting, or phosphating, cannot be used in the presence of UF 6 . Tests have shown that a chromate treatment or an ammoniacal citrate treatment for passivation are effective. The electropotential behavior of these two passivation treatments is described. The initial electropotential measurement, when compared to that of an unpassivated coupon, gives the electropotential degree in volts of passivation. Continual exposure in the test, when compared to the unpassivated coupon, gives a profile of the durability of the passivation film. The chromate passivation treatment was slightly superior to the citrate passivation

  5. Evaluation Of Gas Diffusion Through Plastic Materials Used In Experimental And Sampling Equipment

    DEFF Research Database (Denmark)

    Kjeldsen, Peter

    1993-01-01

    . Calculations show that diffusion of oxygen through plastic tubing and reactors into anoxic water can be a serious problem for a series of plastic materials. Comparison of the method for turbulent and laminar flow in tubings shows that the difference is insignificant for most cases. Calculations show also......Plastic materials are often used in experimental and sampling equipment. Plastics are not gas tight, since gases are able to diffuse through the walls of tubing and containers made of plastic. Methods for calculating the significance of gas diffusion through the walls of containers and the walls...... of tubings for both turbulent and laminar flow conditions is presented. A more complex model for diffusion under laminar flow conditions is developed. A comprehensive review on gas diffusion coefficients for the main gases (O2, N2, CO2, CH4 etc.) and for a long range of plastic materials is also presented...

  6. Anomalous scaling of passive scalars in rotating flows.

    Science.gov (United States)

    Rodriguez Imazio, P; Mininni, P D

    2011-06-01

    We present results of direct numerical simulations of passive scalar advection and diffusion in turbulent rotating flows. Scaling laws and the development of anisotropy are studied in spectral space, and in real space using an axisymmetric decomposition of velocity and passive scalar structure functions. The passive scalar is more anisotropic than the velocity field, and its power spectrum follows a spectral law consistent with ~ k[Please see text](-3/2). This scaling is explained with phenomenological arguments that consider the effect of rotation. Intermittency is characterized using scaling exponents and probability density functions of velocity and passive scalar increments. In the presence of rotation, intermittency in the velocity field decreases more noticeably than in the passive scalar. The scaling exponents show good agreement with Kraichnan's prediction for passive scalar intermittency in two dimensions, after correcting for the observed scaling of the second-order exponent.

  7. Horizontal Heat Exchanger Design and Analysis for Passive Heat Removal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Vierow, Karen

    2005-08-29

    This report describes a three-year project to investigate the major factors of horizontal heat exchanger performance in passive containment heat removal from a light water reactor following a design basis accident LOCA (Loss of Coolant Accident). The heat exchanger studied in this work may be used in advanced and innovative reactors, in which passive heat removal systems are adopted to improve safety and reliability The application of horizontal tube-bundle condensers to passive containment heat removal is new. In order to show the feasibility of horizontal heat exchangers for passive containment cooling, the following aspects were investigated: 1. the condensation heat transfer characteristics when the incoming fluid contains noncondensable gases 2. the effectiveness of condensate draining in the horizontal orientation 3. the conditions that may lead to unstable condenser operation or highly degraded performance 4. multi-tube behavior with the associated secondary-side effects This project consisted of two experimental investigations and analytical model development for incorporation into industry safety codes such as TRAC and RELAP. A physical understanding of the flow and heat transfer phenomena was obtained and reflected in the analysis models. Two gradute students (one funded by the program) and seven undergraduate students obtained research experience as a part of this program.

  8. Preservative loss from silicone tubing during filling processes.

    Science.gov (United States)

    Saller, Verena; Matilainen, Julia; Rothkopf, Christian; Serafin, Daniel; Bechtold-Peters, Karoline; Mahler, Hanns-Christian; Friess, Wolfgang

    2017-03-01

    Significant loss of preservative was observed during filling of drug products during filling line stops. This study evaluated the losses of three commonly used preservatives in protein drugs, i.e. benzyl alcohol, phenol, and m-cresol. Concentration losses during static incubation were quantified and interpreted with regard to the potential driving forces for the underlying sorption, diffusion, and desorption steps. Partitioning from the solution into the silicone polymer was identified as the most decisive parameter for the extent of preservative loss. Additionally, the influence of tubing inner diameter, starting concentration as well as silicone tubing type was evaluated. Theoretical calculations assuming equilibrium between solution and tubing inner surface and one-directional diffusion following Fick's first law were used to approximate experimental data. Since significant losses were found already after few minutes, adequate measures must be taken to avoid deviations during filling of preservative-containing protein solutions that may impact product quality or antimicrobial efficacy. As a possible alternative to the highly permeable silicone tubing, a specific make of fluoropolymer tubing was identified being suitable for peristaltic pumps and not showing any preservative losses. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Some characteristics of the AEOI [Atomic Energy Organisation of Iran] passive radon diffusion dosimeter

    International Nuclear Information System (INIS)

    Sohrabi, M.; Solaymanian, A.R.

    1988-01-01

    A passive radon diffusion dosimeter was developed for large-scale radon level measurements in Iran. It consists of a plastic cup with a polycarbonate alpha detector in the middle, a plastic tip cover with an opening holding a fiberglass filter and a hard aluminium mesh for protection and support. A new design for our multi-chamber electro-chemical etching (ECE) system was used for multiple foil etching. The effects of pre-etching and ECE times, chamber volume, filter diameter and foil position inside the chamber were investigated. The optimized geometries included 9.5 cm height, 296 cm 3 volume and 2-3 cm filter diameter with the PC foil mounted in the middle. A sensitivity of 0.05±0.007 tracks.cm -2 /Bq.m -3 .day or 1.86±0.28 tracks.cm -2 /pCi.1 -1 .day was obtained at optimized conditions. In this paper, the design and the characteristics of the dosimeter as well as some results of the optimization studies are reported and discussed. (author)

  10. An update on passive correctors for the SSC dipole magnets

    International Nuclear Information System (INIS)

    Green, M.A.

    1991-05-01

    The concept of correction of the magnetization sextupole became a topic of discussion as soon as it was realized that superconductor magnetization could have a serious effect on the SSC beam during injection. Several methods of correction were proposed. These included (1) correction with active bore tube windings like those on the HERA machine which correct out magnetization sextupole and the sextupole due to iron saturation, (2) correction with persistent sextupole windings mounted on the bore tube (3) correction using passive superconductor (4) correction using ferromagnetic material, and (5) correction using oriented magnetized materials. This report deals with the use of passive superconductor to correct the magnetization sextupole. Two basic methods are explored in this report: (1) One can correct the magnetization sextupole by changing the diameter of the superconductor filaments in one or more blocks of the SSC dipole. (2) One can correct the magnetization sextupole and decapole by mounting passive superconducting wires on the inside of the SSC dipole coil bore. In addition, an assessment of the contribution of each conductor in the dipole to the magnetization sextupole and decapole is shown. 38 refs, 25 figs., 15 tabs

  11. Conceptual design of passive containment cooling system with air holdup tanks of improved APR+

    International Nuclear Information System (INIS)

    Jeon, Byong Guk; Cheon No, Hee

    2014-01-01

    In Korea, after the successful validation of passive auxiliary feedwater system (PAFS), a passive containment cooling system (PCCS) gets attention for future development. We suggested PCCS design based on APR+, an advanced PWR developed in Korea, and performed scoping analysis. On the extension of the simple scoping analysis, MARS simulation is performed to incorporate the behavior of water pool outside the containment as well as steam-air mixture inside the containment. Through the simulation we demonstrated the effectiveness of the air holdup tank (AHT). Also we investigated the effect of the models of heat transfer coefficients between steam-air mixture side and water side, and flow instability inside HX tubes. The presence of AHT enables us to reduce the number of required HX tubes more than half through an increase in the heat transfer coefficients due to the reduction of air fraction in the containment. Finally flow instability was observed and mitigated by putting orifice plates at the inlet of tubes, increasing height of return nozzle, and increasing a tube angle. (authors)

  12. Multiple-effect diffusion solar still coupled with a vacuum-tube collector and heat pipe

    KAUST Repository

    Chong, Tze-Ling

    2014-08-01

    The present study develops a multiple-effect diffusion solar still (MEDS) with a bended-plate design in multiple-effect diffusion unit (MDU) to solve the peel-off problem of wick material. The MDU is coupled with a vacuum-tube solar collector to produce a high temperature gradient for high productivity. A heat pipe is used to transfer the solar heat to the MDU. A prototype MEDS-1L was built and tested outdoors. Four performance indexes are proposed for the performance evaluation of MEDS, including daily pure water production per unit area of glass cover, solar absorber, and evaporating surface (Mcov, Msol, Mevp, respectively), and solar distillation efficiency Rcov. The outdoor test results of MEDS-1L show that the solar collector supply temperature Th reaches 100°C at solar radiation 800Wm-2. The highest Mcov is 23.9kgm-2d-1 which is about 29% higher than the basin-type MEDS [11]. The highest value is 25.9kgm-2d-1 for Msol and 2.79kgm-2d-1 for Mevp. The measured Rcov is 1.5-2.44, higher than the basin-type MEDS (1.45-1.88). The Mcov, Msol, Mevp and Rcov of MEDS-1L are all higher than the theoretical calculation of a MEDS with a flat-plate solar collector coupled with a heat pipe (MEDS-FHP) [17].© 2014 Elsevier B.V.

  13. Strengthening the Network for Monitoring Air Quality in the Valle de Aburra with Passive Meters

    International Nuclear Information System (INIS)

    Zapata S, Carmen; Quijano, Ricardo; Vasquez Eliana

    2008-01-01

    This investigation was made by the National University of Colombia in agreement with the Metropolitan Area of the Aburra Valley. The principal objective was to enforcing the monitoring of the quality of the air of the Aburra valley by means of the passive testers of sulfur dioxide, nitrogen dioxide, ozone, volatile organic compounds (BTX) and the rate of particle sedimentation in main road routes. Testers were settled in 15 Stations of the Metropolitan Area for a year. In gas measurement passive tubes of diffusion were used. Settle able particle measurement uses the principle of the gravity and the samples are analyzed by means of total solids. The results of sulfur dioxide and nitrogen do not exceed the Annual Colombian Norm, but in 12 stations of testing the value is surpassed guides of the WHO for nitrogen dioxide. The ozone levels show formation of this one polluting agent in the zones of slope. In 9 stations the Annual Colombian Norm for benzene is exceeded and all the stations the WHO Norm was not fulfilled. The greater rates of particle sedimentation are obtained in the sites of testing influenced by activities of construction and maintenance of ways. The use of passive measurers allows to identify critic zones and to evaluate of simple way the tendencies of atmospheric contamination. We suggest that in Colombia this technique for the measurement of the quality of the air is approved.

  14. Performance behavior of the passive containment cooling system of a natural circulation BWR during postulated accident condition

    International Nuclear Information System (INIS)

    Kumar, Mukesh; Nayak, A.K.; Jain, Vikas; Vijayan, P.K.; Saha, D.; Sinha, R.K.

    2011-01-01

    Passive systems are playing prominent role in the development of innovative nuclear reactor systems due to their simplicity, enhanced safety, reliability and economy. These systems are being considered for normal operation as well as accidental conditions of reactor following a postulated accident scenario to preclude the scenarios arising out of failure of active systems as well as to minimize the operator intervention. Indian innovative reactor AHWR being designed for thorium utilization employs various passive safety concepts. As containment is the ultimate barrier to the release of radioactivity, passive concepts are being employed in BWRs for minimize peak containment pressure in the containment during a postulated accident condition like LOCA. The concept of passive containment cooling system (PCCS) in the AHWR comprises of inclined tube heat exchangers located underneath an elevated pool that removes the heat from the steam-air atmosphere of containment following a LOCA by natural circulation of water inside the tubes. The steam condenses on the external surface of tubes of PCCS in addition to the wall of the containment which in turn depressurizes the containment. This paper deals with the performance assessment of PCCS of AHWR during a postulated design basis LOCA by using the best estimate code RELAP5/Mod3.2. (author)

  15. Chaotic advection, diffusion, and reactions in open flows

    International Nuclear Information System (INIS)

    Tel, Tamas; Karolyi, Gyoergy; Pentek, Aron; Scheuring, Istvan; Toroczkai, Zoltan; Grebogi, Celso; Kadtke, James

    2000-01-01

    We review and generalize recent results on advection of particles in open time-periodic hydrodynamical flows. First, the problem of passive advection is considered, and its fractal and chaotic nature is pointed out. Next, we study the effect of weak molecular diffusion or randomness of the flow. Finally, we investigate the influence of passive advection on chemical or biological activity superimposed on open flows. The nondiffusive approach is shown to carry some features of a weak diffusion, due to the finiteness of the reaction range or reaction velocity. (c) 2000 American Institute of Physics

  16. Sensitivity of the improved Dutch tube diffusion test for detection of ...

    African Journals Online (AJOL)

    The sensitivity of the improved two-tube test for detection of antimicrobial residues in Kenyan milk was investigated by comparison with the commercial Delvo test SP. Suspect positive milk samples (n =244) from five milk collection centers, were analyzed with the improved two-tube and the commercial Delvo SP test as per ...

  17. Random walk of passive tracers among randomly moving obstacles.

    Science.gov (United States)

    Gori, Matteo; Donato, Irene; Floriani, Elena; Nardecchia, Ilaria; Pettini, Marco

    2016-04-14

    This study is mainly motivated by the need of understanding how the diffusion behavior of a biomolecule (or even of a larger object) is affected by other moving macromolecules, organelles, and so on, inside a living cell, whence the possibility of understanding whether or not a randomly walking biomolecule is also subject to a long-range force field driving it to its target. By means of the Continuous Time Random Walk (CTRW) technique the topic of random walk in random environment is here considered in the case of a passively diffusing particle among randomly moving and interacting obstacles. The relevant physical quantity which is worked out is the diffusion coefficient of the passive tracer which is computed as a function of the average inter-obstacles distance. The results reported here suggest that if a biomolecule, let us call it a test molecule, moves towards its target in the presence of other independently interacting molecules, its motion can be considerably slowed down.

  18. Use of passive diffusion sampling method for defining NO2 concentrations gradient in São Paulo, Brazil

    Directory of Open Access Journals (Sweden)

    Meliefste Kees

    2006-06-01

    Full Text Available Abstract Background Air pollution in São Paulo is constantly being measured by the State of Sao Paulo Environmental Agency, however there is no information on the variation between places with different traffic densities. This study was intended to identify a gradient of exposure to traffic-related air pollution within different areas in São Paulo to provide information for future epidemiological studies. Methods We measured NO2 using Palmes' diffusion tubes in 36 sites on streets chosen to be representative of different road types and traffic densities in São Paulo in two one-week periods (July and August 2000. In each study period, two tubes were installed in each site, and two additional tubes were installed in 10 control sites. Results Average NO2 concentrations were related to traffic density, observed on the spot, to number of vehicles counted, and to traffic density strata defined by the city Traffic Engineering Company (CET. Average NO2concentrations were 63μg/m3 and 49μg/m3 in the first and second periods, respectively. Dividing the sites by the observed traffic density, we found: heavy traffic (n = 17: 64μg/m3 (95% CI: 59μg/m3 – 68μg/m3; local traffic (n = 16: 48μg/m3 (95% CI: 44μg/m3 – 52μg/m3 (p Conclusion The differences in NO2 levels between heavy and local traffic sites are large enough to suggest the use of a more refined classification of exposure in epidemiological studies in the city. Number of vehicles counted, traffic density observed on the spot and traffic density strata defined by the CET might be used as a proxy for traffic exposure in São Paulo when more accurate measurements are not available.

  19. Performance of a passive direct ethanol fuel cell

    Science.gov (United States)

    Pereira, J. P.; Falcão, D. S.; Oliveira, V. B.; Pinto, A. M. F. R.

    2014-06-01

    Ethanol emerges as an attractive fuel since it is less toxic and has higher energy density than methanol and can be produced from biomass. Direct ethanol fuel cells (DEFCs) appear as a good choice for producing sustainable energy for portable applications. However, they are still far from attaining acceptable levels of power output, since their performance is affected by the slow electrochemical ethanol oxidation and water and ethanol crossover. In the present work, an experimental study on the performance of a passive DEFC is described. Tailored MEAs (membrane electrode assembly) with different catalyst loadings, anode diffusion layers and membranes were tested in order to select optimal working conditions at high ethanol concentrations and low ethanol crossover. The performance increased with an increase of membrane and anode diffusion layer thicknesses and anode catalyst loading. A maximum power density of 1.33 mW cm-2, was obtained using a Nafion 117 membrane, 4 mg cm-2 of Pt-Ru and 2 mg cm-2 of Pt on the anode and cathode catalyst layers, ELAT as anode diffusion layer, carbon cloth as cathode diffusion layer and an ethanol concentration of 2 M. As far as the authors are aware this is the first work reporting an experimental optimization of passive DEFCs.

  20. Topology Optimization of Passive Micromixers Based on Lagrangian Mapping Method

    Directory of Open Access Journals (Sweden)

    Yuchen Guo

    2018-03-01

    Full Text Available This paper presents an optimization-based design method of passive micromixers for immiscible fluids, which means that the Peclet number infinitely large. Based on topology optimization method, an optimization model is constructed to find the optimal layout of the passive micromixers. Being different from the topology optimization methods with Eulerian description of the convection-diffusion dynamics, this proposed method considers the extreme case, where the mixing is dominated completely by the convection with negligible diffusion. In this method, the mixing dynamics is modeled by the mapping method, a Lagrangian description that can deal with the case with convection-dominance. Several numerical examples have been presented to demonstrate the validity of the proposed method.

  1. Surface protection during plasma hydrogenation for acceptor passivation in InP

    International Nuclear Information System (INIS)

    Lopata, J.; Dautremont-Smith, W.C.; Pearton, S.J.; Lee, J.W.; Ha, N.T.; Luftman, H.S.

    1990-01-01

    Various dielectric and metallic films were examined as H-permeable surface protection layers on InP during H 2 or D 2 plasma exposure for passivation of acceptors in the InP. Plasma deposited SiN x , SiO 2 , and a-Si(H) films ranging in thickness from 85 to 225 angstrom were used to protect p-InP during d 2 plasma exposure at 250 degrees C. Optimum protective layer thicknesses were determined by a trade-off between the effectiveness of the layer to prevent P loss from the wafer surface and the ability to diffuse atomic H or D at a rate greater than or equal to that in the underlying InP. SIMS and capacitance-voltage depth profiling were used to determine the extent of D in-diffusion and acceptor passivation respectively. Sputter deposited W and e-beam evaporated Ti films ∼100 Angstrom thick were also evaluated. The W coated sample yielded similar results to those with dielectric films in that acceptors in p-InP were passivated to a similar depth for the same plasma exposure. The 100 Angstrom Ti film, however, did not allow the D to diffuse into the InP substrate. It is surmised that the Ti film trapped the D, thus preventing diffusion into the substrate

  2. Tracer gas diffusion sampling test plan

    International Nuclear Information System (INIS)

    Rohay, V.J.

    1993-01-01

    Efforts are under way to employ active and passive vapor extraction to remove carbon tetrachloride from the soil in the 200 West Area an the Hanford Site as part of the 200 West Area Carbon Tetrachloride Expedited Response Action. In the active approach, a vacuum is applied to a well, which causes soil gas surrounding the well to be drawn up to the surface. The contaminated air is cleaned by passage through a granular activated carbon bed. There are questions concerning the radius of influence associated with application of the vacuum system and related uncertainties about the soil-gas diffusion rates with and without the vacuum system present. To address these questions, a series of tracer gas diffusion sampling tests is proposed in which an inert, nontoxic tracer gas, sulfur hexafluoride (SF 6 ), will be injected into a well, and the rates of SF 6 diffusion through the surrounding soil horizon will be measured by sampling in nearby wells. Tracer gas tests will be conducted at sites very near the active vacuum extraction system and also at sites beyond the radius of influence of the active vacuum system. In the passive vapor extraction approach, barometric pressure fluctuations cause soil gas to be drawn to the surface through the well. At the passive sites, the effects of barometric ''pumping'' due to changes in atmospheric pressure will be investigated. Application of tracer gas testing to both the active and passive vapor extraction methods is described in the wellfield enhancement work plan (Rohay and Cameron 1993)

  3. Assessing the transport of PAH in the surficial sediment layer by passive sampler approach.

    Science.gov (United States)

    Belles, Angel; Alary, Claire; Criquet, Justine; Ivanovsky, Anastasia; Billon, Gabriel

    2017-02-01

    A new method based on passive samplers has been developed to assess the diffusive flux of fluorene, fluoranthene and pyrene in the sediment bed and across the sediment-water interface. The dissolved compound concentration gradient in the sediment in the vertical direction was measured at the outlet of a storm water pond by using polyethylene strips as passive samplers. Simultaneously, the dissipation of a set of tracer compounds preloaded in the passive samplers was measured to estimate the effective diffusion coefficients of the pollutants in the sediment. Both measurements were used to evaluate the diffusive flux of the compounds according to Fick's first law. The diffusive fluxes of the 3 studied compounds have been estimated with a centimetre-scale resolution in the upper 44cm of the sediment. According to the higher compound diffusion coefficient and the steeper concentration gradient in the surficial sediment layer, the results show that the net flux of compounds near the sediment interface (1cm depth) is on average 500 times higher than in the deep sediment, with average fluxes at 1cm depth on the order of 5, 0.1 and 0.1ng/m 2 /y for fluorene, fluoranthene and pyrene, respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Two-dimensional numerical simulation of boron diffusion for pyramidally textured silicon

    International Nuclear Information System (INIS)

    Ma, Fa-Jun; Duttagupta, Shubham; Shetty, Kishan Devappa; Meng, Lei; Hoex, Bram; Peters, Ian Marius; Samudra, Ganesh S.

    2014-01-01

    Multidimensional numerical simulation of boron diffusion is of great relevance for the improvement of industrial n-type crystalline silicon wafer solar cells. However, surface passivation of boron diffused area is typically studied in one dimension on planar lifetime samples. This approach neglects the effects of the solar cell pyramidal texture on the boron doping process and resulting doping profile. In this work, we present a theoretical study using a two-dimensional surface morphology for pyramidally textured samples. The boron diffusivity and segregation coefficient between oxide and silicon in simulation are determined by reproducing measured one-dimensional boron depth profiles prepared using different boron diffusion recipes on planar samples. The established parameters are subsequently used to simulate the boron diffusion process on textured samples. The simulated junction depth is found to agree quantitatively well with electron beam induced current measurements. Finally, chemical passivation on planar and textured samples is compared in device simulation. Particularly, a two-dimensional approach is adopted for textured samples to evaluate chemical passivation. The intrinsic emitter saturation current density, which is only related to Auger and radiative recombination, is also simulated for both planar and textured samples. The differences between planar and textured samples are discussed

  5. Effect of SiO2 passivation overlayers on hillock formation in Al thin films

    International Nuclear Information System (INIS)

    Kim, Deok-kee

    2012-01-01

    Hillock formation in Al thin films with varying thicknesses of SiO 2 as a passivation layer was investigated during thermal cycling. Based on the stress measurements and the number of hillocks, 250 nm thick SiO 2 was thick enough to suppress the hillock formation and the suppression of hillock at 250 nm passivation and the lack of suppression at thinner passivation is related to the presence/absence of protection against the diffusive flow of atoms from the surrounding area to the surface due to the biaxial compressive stresses present in the film through the weak spots in the passivation layer. The stress state of Al films measured during annealing (the driving force for hillock formation) did not vary much with SiO 2 thickness. A small number of hillocks formed during the plasma enhanced chemical vapor deposition of SiO 2 overlayers at 300 °C. - Highlights: ► We examined the effect of SiO 2 overlayers on hillock formation in Al thin films. ► Thin overlayers were not effective in suppressing diffusive flow to the surface. ► A thick overlayer suppressed the diffusive flow from the interior to the surface. ► The stress state of Al films did not vary much with SiO 2 passivation thickness. ► High mechanical strength provided a large driving force for the large grain growth.

  6. Diffusion in a liquid alloy - theories and experiments

    International Nuclear Information System (INIS)

    Chastang, C.

    1997-01-01

    Different theories concerning the calculation of diffusion coefficients in liquid metals, as well for auto as for hetero-diffusion are presented and some experimental procedures using tracer techniques in shear cells and capillary tubes are described. Diffusion curves are calculated with the TRIO-EF code. Calculated and measured values of diffusion coefficients are compared and discussed with regard to various diffusion mechanisms. Copper gadolinium mixtures have been investigated in more detail. (C.B.)

  7. Diffusion or bulk flow

    DEFF Research Database (Denmark)

    Schulz, Alexander

    2015-01-01

    is currently matter of discussion, called passive symplasmic loading. Based on the limited material available, this review compares the different loading modes and suggests that diffusion is the driving force in apoplasmic loaders, while bulk flow plays an increasing role in plants having a continuous...

  8. High precision optical fiber alignment using tube laser bending

    NARCIS (Netherlands)

    Folkersma, Ger; Römer, Gerardus Richardus, Bernardus, Engelina; Brouwer, Dannis Michel; Herder, Justus Laurens

    2016-01-01

    In this paper, we present a method to align optical fibers within 0.2 μm of the optimal position, using tube laser bending and in situ measuring of the coupling efficiency. For near-UV wavelengths, passive alignment of the fibers with respect to the waveguides on photonic integrated circuit chips

  9. The Role of Surface Passivation in Controlling Ge Nanowire Faceting.

    Science.gov (United States)

    Gamalski, A D; Tersoff, J; Kodambaka, S; Zakharov, D N; Ross, F M; Stach, E A

    2015-12-09

    In situ transmission electron microscopy observations of nanowire morphologies indicate that during Au-catalyzed Ge nanowire growth, Ge facets can rapidly form along the nanowire sidewalls when the source gas (here, digermane) flux is decreased or the temperature is increased. This sidewall faceting is accompanied by continuous catalyst loss as Au diffuses from the droplet to the wire surface. We suggest that high digermane flux and low temperatures promote effective surface passivation of Ge nanowires with H or other digermane fragments inhibiting diffusion and attachment of Au and Ge on the sidewalls. These results illustrate the essential roles of the precursor gas and substrate temperature in maintaining nanowire sidewall passivation, necessary to ensure the growth of straight, untapered, ⟨111⟩-oriented nanowires.

  10. Diffusion welding of ZrO2 solid electrolyte cells

    International Nuclear Information System (INIS)

    Schaefer, W.; Schmidberger, R.

    1980-01-01

    Zirconia based solid-electrolyte-cells can be applied as electrolysis-cells or fuel cells at high temperatures. Scaling up to technical aggregates must be realized by a gastight electrical series-connection of many tubular single cells. A suitable process for connecting single cells is diffusion welding. Starting materials were sintered zirconia-tubes (16 mm diameter, 10 mm length) and gastight interconnecting rings (16 mm diameter, 0.5-2mm length) from gold, platinum or electrically conducting mixed oxides. ZrO 2 -tubes and interconnecting rings were mounted in alternating sequence and diffusion welded under axial pressure at high temperatures. From economic reasons noble metals cannot be used for technical aggregates. The developments were therefore concentrated on the connection with mixed oxides. Optimized welding parameters are: 1400-1500 0 C welding temperature, 2 hours welding time and an axial pressure of approximately 1 Nmm 2 . Up to now gastight tubes consisting of 20 single cells were preparated by diffusion-welding in one step. The process will be further developed for the production of 50-cell-tubes with a total length of about 60 cm. (orig.) [de

  11. A passive sampler for atmospheric ozone

    International Nuclear Information System (INIS)

    Grosjean, D.; Hisham, M.W.M.

    1992-01-01

    A simple, cost-effective passive sampler has been developed for the determination of atmospheric ozone. This passive sampler is based on a colorant which fades upon reaction with ozone, whose concentration can be determined by reflectance measurement of the color change. Direct, on-site measurements are possible, and no chemical analyses are needed. Sampler design and validation studies have been carried out and included quantitative determination of color change vs exposure time (1-8 days), color change vs. ozone concentration (30-350 ppb), and response to changes in sampler configuration that modify the passive sampling rate. With indigo carmine as the colorant, the detection limits are 30 ppb. day and 120 ppb. day using a plastic grid and Teflon filter, respectively, as diffusion barriers. Interferences from nitrogen dioxide, formaldehyde and peroxyacetyl nitrate are 15, 4 and 16%, respectively, thus resulting in a negligible bias when measuring ozone in ambient air

  12. Air enters closed systems not only via plastic tubes

    Energy Technology Data Exchange (ETDEWEB)

    1980-03-01

    Some trouble within the branch was caused by passages of the SHT-interview with Hans Viessmann on the question of guarantee in case of corrosion in heating systems with plastic tubes. The plastic tubes are made responsible for bringing air into the heating system by diffusion, thus causing a danger of corrosion. In this connection, the Thermoval Systemheatings Company, Cologne, makes a statement.

  13. Passive Rocket Diffuser Testing: Reacting Flow Performance of Four Second-Throat Geometries

    Science.gov (United States)

    Jones, Daniel R.; Allgood, Daniel C.; Saunders, Grady P.

    2016-01-01

    Second-throat diffusers serve to isolate rocket engines from the effects of ambient back pressure. As one of the nation's largest rocket testing facilities, the performance and design limitations of diffusers are of great interest to NASA's Stennis Space Center. This paper describes a series of tests conducted on four diffuser configurations to better understand the effects of inlet geometry and throat area on starting behavior and boundary layer separation. The diffusers were tested for a duration of five seconds with a 1455-pound thrust, LO2/GH2 thruster to ensure they each reached aerodynamic steady state. The effects of a water spray ring at the diffuser exits and a water-cooled deflector plate were also evaluated. Static pressure and temperature measurements were taken at multiple axial locations along the diffusers, and Computational Fluid Dynamics (CFD) simulations were used as a tool to aid in the interpretation of data. The hot combustion products were confirmed to enable the diffuser start condition with tighter second throats than predicted by historical cold-flow data or the theoretical normal shock method. Both aerodynamic performance and heat transfer were found to increase with smaller diffuser throats. Spray ring and deflector cooling water had negligible impacts on diffuser boundary layer separation. CFD was found to accurately capture diffuser shock structures and full-flowing diffuser wall pressures, and the qualitative behavior of heat transfer. However, the ability to predict boundary layer separated flows was not consistent.

  14. Effects of curved midline and varying width on the description of the effective diffusivity of Brownian particles

    Science.gov (United States)

    Chávez, Yoshua; Chacón-Acosta, Guillermo; Dagdug, Leonardo

    2018-05-01

    Axial diffusion in channels and tubes of smoothly-varying geometry can be approximately described as one-dimensional diffusion in the entropy potential with a position-dependent effective diffusion coefficient, by means of the modified Fick–Jacobs equation. In this work, we derive analytical expressions for the position-dependent effective diffusivity for two-dimensional asymmetric varying-width channels, and for three-dimensional curved midline tubes, formed by straight walls. To this end, we use a recently developed theoretical framework using the Frenet–Serret moving frame as the coordinate system (2016 J. Chem. Phys. 145 074105). For narrow tubes and channels, an effective one-dimensional description reducing the diffusion equation to a Fick–Jacobs-like equation in general coordinates is used. From this last equation, one can calculate the effective diffusion coefficient applying Neumann boundary conditions.

  15. Statistics of an advected passive scalar

    International Nuclear Information System (INIS)

    Kimura, Y.; Kraichnan, R.H.

    1993-01-01

    An elementary argument shows that non-Gaussian fluctuations in the temperature at a point in space are induced by random advection of a passive temperature field that has a nonlinear mean gradient, whether or not there is molecular diffusion. This is corroborated by exact analysis for the nondiffusive case and by direct numerical simulation for diffusive cases. Eulerian mapping closure gives results close to the simulation data. Non-Gaussian fluctuations of temperature at a point also are induced by a more subtle mechanism that requires both advection and molecular diffusion and is effective even when the statistics are strictly homogeneous. It operates through selectively strong dissipation of regions where intense temperature gradients have been induced by advective straining. This phenomenon is demonstrated by simulations and explored by means of an idealized analytical model

  16. Diffusion-limited mixing by incompressible flows

    Science.gov (United States)

    Miles, Christopher J.; Doering, Charles R.

    2018-05-01

    Incompressible flows can be effective mixers by appropriately advecting a passive tracer to produce small filamentation length scales. In addition, diffusion is generally perceived as beneficial to mixing due to its ability to homogenize a passive tracer. However we provide numerical evidence that, in cases where advection and diffusion are both actively present, diffusion may produce negative effects by limiting the mixing effectiveness of incompressible optimal flows. This limitation appears to be due to the presence of a limiting length scale given by a generalised Batchelor length (Batchelor 1959 J. Fluid Mech. 5 113–33). This length scale limitation may in turn affect long-term mixing rates. More specifically, we consider local-in-time flow optimisation under energy and enstrophy flow constraints with the objective of maximising the mixing rate. We observe that, for enstrophy-bounded optimal flows, the strength of diffusion may not impact the long-term mixing rate. For energy-constrained optimal flows, however, an increase in the strength of diffusion can decrease the mixing rate. We provide analytical lower bounds on mixing rates and length scales achievable under related constraints (point-wise bounded speed and rate-of-strain) by extending the work of Lin et al (2011 J. Fluid Mech. 675 465–76) and Poon (1996 Commun. PDE 21 521–39).

  17. A new passive radon-thoron discriminative measurement system

    International Nuclear Information System (INIS)

    Sciocchetti, G.; Sciocchetti, A.; Giovannoli, P.; DeFelice, P.; Cardellini, F.; Cotellessa, G.; Pagliari, M.

    2010-01-01

    A new passive radon-thoron discriminative measurement system has been developed for monitoring radon and thoron individually. It consists of a 'couple' of passive integrating devices with a CR39 nuclear track detector (NTD). The experimental prototype is based on the application of a new concept of NTD instrument developed at ENEA, named Alpha-PREM, acronym of piston radon exposure meter, which allows controlling the detector exposure with a patented sampling technique (Int. Eu. Pat. and US Pat.). The 'twin diffusion chambers system' was based on two A-PREM devices consisting of the standard device, named NTD-Rn, and a modified version, named NTD-Rn/Tn, which was set up to improve thoron sampling efficiency of the diffusion chamber, without changing the geometry and the start/stop function of the NTD-Rn device. Coupling devices fitted on each device allowed getting a system, which works as a double-chamber structure when deployed at the monitoring position. In this paper both technical and physical aspects are considered. (authors)

  18. A new passive radon-thoron discriminative measurement system.

    Science.gov (United States)

    Sciocchetti, G; Sciocchetti, A; Giovannoli, P; DeFelice, P; Cardellini, F; Cotellessa, G; Pagliari, M

    2010-10-01

    A new passive radon-thoron discriminative measurement system has been developed for monitoring radon and thoron individually. It consists of a 'couple' of passive integrating devices with a CR39 nuclear track detector (NTD). The experimental prototype is based on the application of a new concept of NTD instrument developed at ENEA, named Alpha-PREM, acronym of piston radon exposure meter, which allows controlling the detector exposure with a patented sampling technique (Int. Eu. Pat. and US Pat.). The 'twin diffusion chambers system' was based on two A-PREM devices consisting of the standard device, named NTD-Rn, and a modified version, named NTD-Rn/Tn, which was set up to improve thoron sampling efficiency of the diffusion chamber, without changing the geometry and the start/stop function of the NTD-Rn device. Coupling devices fitted on each device allowed getting a system, which works as a double-chamber structure when deployed at the monitoring position. In this paper both technical and physical aspects are considered.

  19. Analysis of Hydrogen Generation and Accumulation in U-233 Tube Vaults

    International Nuclear Information System (INIS)

    Ally, M.R.; Willis, K.J.

    1999-01-01

    The purpose of the 233 U Safe Storage Program is to enhance the safe storage of 233 U-bearing materials. This report describes the work done at the Oak Ridge National Laboratory's Radiochemical Development Facility (RDF) to address questions related to possible hydrogen generation and accumulation in 233 U tube vaults. The objective of this effort was to verify assumptions in the mathematical model used to estimate the hydrogen content of the gaseous atmosphere that possibly could occur inside the tube vaults in Building 3019 and to evaluate proposed measures for mitigating any hydrogen concerns. A mathematical model was developed using conservative assumptions to evaluate possible hydrogen generation and accumulation in the tube vaults. The model concluded that an equilibrium concentration would be established below the lower flammability limit (LFL) of 4.1% hydrogen. The major assumptions used in the model that were validated are as follows: (1) The shield plug does not form a seal with the tube vault wall, thus allowing the hydrogen gas to diffuse past the shield plug to the upper section of the tube vault. (2) The tube vault end-cap leaks sufficiently to allow air to be drawn into the tube vault by the off-gas system, thereby purging hydrogen from the upper section of the tube vault. (3) Any hydrogen gas generated completely mixes with the other gases present in the lower section of the tube vault and does not stratify beneath the shield plug. (4) The diffusion coefficient determined from the literature for constant diffusion of hydrogen in air is valid. The coefficient is corrected for temperatures from 0 to 25 C. Another assumption used in the model, that hydrogen generated by radiolytic decomposition of hydrogen-bearing materials (e.g., moisture and plastic) leaks from the cans under steady-state condition, as opposed to a sudden release resulting from rupture of the can(s), was beyond the scope of this investigation. Several parameters from the original

  20. YouTube and Video Quizzes

    Directory of Open Access Journals (Sweden)

    Kevin YEE

    2010-04-01

    Full Text Available The Internet sensation YouTube (http://www.youtube.com has become such a force online that it was estimated in 2006 to account for a full tenth of the bandwidth by the entire Internet in the United States (WebProNews, 2007, and to use as much bandwidth in 2007 as the entire Internet had done in 2000 (Carter, 2008. Like many technological tools created with entertainment or profit in mind, YouTube can now be easily and usefully adopted by instructors for educational purposes, and indeed many professors use YouTube in their classroom teaching already (Brooks, 2000. This is especially true for passive uses of YouTube; watching videos that are already online and using them in the classroom experience to support a concept and provide another mechanism for students to connect with the topics. It is fruitful to consider Bloom's Taxonomy of Educational Objectives (Bloom & Krathwohl, 1956 when employing video or any media in the classroom to maximize the intentionality of teaching and learning. The use of video for demonstration or modeling corresponds well to Blooms levels of Knowledge, Comprehension, and Application; while case studies offer a chance to demonstrate Analysis and Synthesis, and perhaps even Evaluation, when comparing a video to information from a text book or other content.

  1. Passivation Using Molecular Halides Increases Quantum Dot Solar Cell Performance.

    Science.gov (United States)

    Lan, Xinzheng; Voznyy, Oleksandr; Kiani, Amirreza; García de Arquer, F Pelayo; Abbas, Abdullah Saud; Kim, Gi-Hwan; Liu, Mengxia; Yang, Zhenyu; Walters, Grant; Xu, Jixian; Yuan, Mingjian; Ning, Zhijun; Fan, Fengjia; Kanjanaboos, Pongsakorn; Kramer, Illan; Zhitomirsky, David; Lee, Philip; Perelgut, Alexander; Hoogland, Sjoerd; Sargent, Edward H

    2016-01-13

    A solution-based passivation scheme is developed featuring the use of molecular iodine and PbS colloidal quantum dots (CQDs). The improved passivation translates into a longer carrier diffusion length in the solid film. This allows thicker solar-cell devices to be built while preserving efficient charge collection, leading to a certified power conversion efficiency of 9.9%, which is a new record in CQD solar cells. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. A population-based exposure assessment methodology for carbon monoxide: Development of a carbon monoxide passive sampler and occupational dosimeter

    Energy Technology Data Exchange (ETDEWEB)

    Apte, Michael G. [Univ. of California, Berkeley, CA (United States)

    1997-09-01

    Two devices, an occupational carbon monoxide (CO) dosimeter (LOCD), and an indoor air quality (IAQ) passive sampler were developed for use in population-based CO exposure assessment studies. CO exposure is a serious public health problem in the U.S., causing both morbidity and mortality (lifetime mortality risk approximately 10{sup -4}). Sparse data from population-based CO exposure assessments indicate that approximately 10% of the U.S. population is exposed to CO above the national ambient air quality standard. No CO exposure measurement technology is presently available for affordable population-based CO exposure assessment studies. The LOCD and IAQ Passive Sampler were tested in the laboratory and field. The palladium-molybdenum based CO sensor was designed into a compact diffusion tube sampler that can be worn. Time-weighted-average (TWA) CO exposure of the device is quantified by a simple spectrophotometric measurement. The LOCD and IAQ Passive Sampler were tested over an exposure range of 40 to 700 ppm-hours and 200 to 4200 ppm-hours, respectively. Both devices were capable of measuring precisely (relative standard deviation <20%), with low bias (<10%). The LOCD was screened for interferences by temperature, humidity, and organic and inorganic gases. Temperature effects were small in the range of 10°C to 30°C. Humidity effects were low between 20% and 90% RH. Ethylene (200 ppm) caused a positive interference and nitric oxide (50 ppm) caused a negative response without the presence of CO but not with CO.

  3. Prediction of Heat Transfer Performance on Horizontal U-Shaped Heat Exchanger in Passive Safety System Using MARS

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Seong-Su; Hong, Soon-Joon [FNC Tech, Yongin (Korea, Republic of); Cho, Hyoung-Kyu; Park, Goon-Cherl [Seoul National University, Seoul (Korea, Republic of)

    2015-10-15

    The design and the safety analysis of the passive safety systems are performed mainly using the best-estimate thermal-hydraulic analysis codes such as RELAP5 and MARS. This study developed the heat transfer model package for the horizontal U-shaped HX submerged in a pool by improving the horizontal in-tube condensation model and developing the outside-tube natural convective nucleate boiling model. This paper presents the HX model package and the validation results against the passive safety system-related experimental data of PASCAL and ATLAS-PAFS. This study developed the heat transfer model package of the horizontal U-shaped HX submerged in a pool in order to obtain a reliable prediction of the HX heat removal performance of the passive safety system, especially PAFS, using MARS. From the validation results, the proposed model package provided the improved prediction of HX performance (condensation, natural convective nucleate boiling, and heat removal rate of the HX) compared to the default model in MARS.

  4. Impurity diffusion, point defect engineering, and surface/interface passivation in germanium

    KAUST Repository

    Chroneos, Alexander I.; Schwingenschlö gl, Udo; Dimoulas, Athanasios Dimoulas

    2012-01-01

    in view of recent results. The importance of electrically active defects on the Ge surface and interfaces is addressed considering strategies to suppress them and to passivate the surfaces/interfaces, bearing in mind their importance for advanced devices

  5. Johnson-Matthey diffuser characterization testing

    International Nuclear Information System (INIS)

    Foster, P. J.; Klein, J. E.; Sessions, H. T.; Morgan, G. A.

    2008-01-01

    A diffuser/permeator commercially fabricated by Johnson-Matthey was purchased for characterization testing at the Savannah River National Laboratory (SRNL). A test system was fabricated to test not only feed and bleed flows and pressures, but also permeate pressure for flows up to 20 sLPM. The tests described in this paper consider the effect of various inert gas types, feed gas compositions, methods for temperature control, and varying tube pressure on permeation of H 2 through the Pd/Ag tubes. (authors)

  6. Trapping of diffusing particles by striped cylindrical surfaces. Boundary homogenization approach

    Science.gov (United States)

    Dagdug, Leonardo; Berezhkovskii, Alexander M.; Skvortsov, Alexei T.

    2015-01-01

    We study trapping of diffusing particles by a cylindrical surface formed by rolling a flat surface, containing alternating absorbing and reflecting stripes, into a tube. For an arbitrary stripe orientation with respect to the tube axis, this problem is intractable analytically because it requires dealing with non-uniform boundary conditions. To bypass this difficulty, we use a boundary homogenization approach which replaces non-uniform boundary conditions on the tube wall by an effective uniform partially absorbing boundary condition with properly chosen effective trapping rate. We demonstrate that the exact solution for the effective trapping rate, known for a flat, striped surface, works very well when this surface is rolled into a cylindrical tube. This is shown for both internal and external problems, where the particles diffuse inside and outside the striped tube, at three orientations of the stripe direction with respect to the tube axis: (a) perpendicular to the axis, (b) parallel to the axis, and (c) at the angle of π/4 to the axis. PMID:26093574

  7. Flame oscillations in tubes with nonslip at the walls

    Energy Technology Data Exchange (ETDEWEB)

    Akkerman, V' yacheslav; Bychkov, Vitaly; Petchenko, Arkady [Institute of Physics, Umeaa University, SE-901 87 Umeaa (Sweden); Eriksson, Lars-Erik [Department of Applied Mechanics, Chalmers University of Technology, 412 96 Goeteborg (Sweden)

    2006-06-15

    A laminar premixed flame front propagating in a two-dimensional tube is considered with nonslip at the walls and with both ends open. The problem of flame propagation is solved using direct numerical simulations of the complete set of hydrodynamic equations including thermal conduction, diffusion, viscosity, and chemical kinetics. As a result, it is shown that flame interaction with the walls leads to the oscillating regime of burning. The oscillations involve variations of the curved flame shape and the velocity of flame propagation. The oscillation parameters depend on the characteristic tube width, which controls the Reynolds number of the flow. In narrow tubes the oscillations are rather weak, while in wider tubes they become stronger with well-pronounced nonlinear effects. The period of oscillations increases for wider tubes, while the average flame length scaled by the tube diameter decreases only slightly with increasing tube width. The average flame length calculated in the present work is in agreement with that obtained in the experiments. Numerical results reduce the gap between the theory of turbulent flames and the experiments on turbulent combustion in tubes. (author)

  8. Passivation Using Molecular Halides Increases Quantum Dot Solar Cell Performance

    KAUST Repository

    Lan, Xinzheng; Voznyy, Oleksandr; Kiani, Amirreza; Garcí a de Arquer, F. Pelayo; Abbas, Abdullah Saud; Kim, Gi-Hwan; Liu, Mengxia; Yang, Zhenyu; Walters, Grant; Xu, Jixian; Yuan, Mingjian; Ning, Zhijun; Fan, Fengjia; Kanjanaboos, Pongsakorn; Kramer, Illan; Zhitomirsky, David; Lee, Philip; Perelgut, Alexander; Hoogland, Sjoerd; Sargent, Edward H.

    2015-01-01

    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Here we report a solution-based passivation scheme is developed featuring the use of molecular iodine and PbS colloidal quantum dots (CQDs). The improved passivation translates into a longer carrier diffusion length in the solid film. This allows thicker solar-cell devices to be built while preserving efficient charge collection, leading to a certified power conversion efficiency of 9.9%, which is a new record in CQD solar cells.

  9. Passivation Using Molecular Halides Increases Quantum Dot Solar Cell Performance

    KAUST Repository

    Lan, Xinzheng

    2015-11-18

    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Here we report a solution-based passivation scheme is developed featuring the use of molecular iodine and PbS colloidal quantum dots (CQDs). The improved passivation translates into a longer carrier diffusion length in the solid film. This allows thicker solar-cell devices to be built while preserving efficient charge collection, leading to a certified power conversion efficiency of 9.9%, which is a new record in CQD solar cells.

  10. Development of a new passive sampler based on diffusive milligel beads for copper analysis in water.

    Science.gov (United States)

    Perez, M; Reynaud, S; Lespes, G; Potin-Gautier, M; Mignard, E; Chéry, P; Schaumlöffel, D; Grassl, B

    2015-08-26

    A new passive sampler was designed and characterized for the determination of free copper ion (Cu(2+)) concentration in aqueous solution. Each sampling device was composed of a set of about 30 diffusive milligel (DMG) beads. Milligel beads with incorporated cation exchange resin (Chelex) particles were synthetized using an adapted droplet-based millifluidic process. Beads were assumed to be prolate spheroids, with a diameter of 1.6 mm and an anisotropic factor of 1.4. The milligel was controlled in chemical composition of hydrogel (monomer, cross-linker, initiator and Chelex concentration) and characterized in pore size. Two types of sampling devices were developed containing 7.5% and 15% of Chelex, respectively, and 6 nm pore size. The kinetic curves obtained demonstrated the accumulation of copper in the DMG according to the process described in the literature as absorption (and/or adsorption) and release following the Fick's first law of diffusion. For their use in water monitoring, the typical physico-chemical characteristics of the samplers, i.e. the mass-transfer coefficient (k0) and the sampler-water partition coefficient (Ksw), were determined based on a static exposure design. In order to determine the copper concentration in the samplers after their exposure, a method using DMG bead digestion combined to Inductively Coupled Plasma - Atomic Emission Spectrometry (ICP-AES) analysis was developed and optimized. The DMG devices proved to be capable to absorb free copper ions from an aqueous solution, which could be accurately quantified with a mean recovery of 99% and a repeatability of 7% (mean relative uncertainty). Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Diffusion on Networks and Diffusion Weighted NMR of the Human Lung

    DEFF Research Database (Denmark)

    Buhl, Niels

    2011-01-01

    of the diffusion propagator to general properties of the underlying graph. Diffusion weighted NMR of the human lung with hyperpolarized noble gases, which over the last decade has been demonstrated to be a very promising way of detecting and quantifying lung diseases like emphysema, represent an obvious...... application of the above mentioned theory, given that the human lung consists of a large network of bifurcating tube like airways. 90-95% of the gas in a human lung resides in the ~30000 pulmonary acini, each of these consists of ~500 airways, which are connected as the edges in a binary tree. We model...... diffusion in the pulmonary acini as diffusion on metric graphs with this structure. The metric graph for each individual pulmonary acinus is embedded in three dimensional space via line segments. By considering an isotropic distribution of acini and a symmetric branching geometry for the line segments...

  12. Antenna for passive RFID tags

    Science.gov (United States)

    Schiopu, Paul; Manea, Adrian; Cristea, Ionica; Grosu, Neculai; Vladescu, Marian; Craciun, Anca-Ileana; Craciun, Alexandru

    2015-02-01

    Minuscule devices, called RFID tags are attached to objects and persons and emit information which positioned readers may capture wirelessly. Many methods of identification have been used, but that of most common is to use a unique serial number for identification of person or object. RFID tags can be characterized as either active or passive [1,2]. Traditional passive tags are typically in "sleep" state until awakened by the reader's emitted field. In passive tags, the reader's field acts to charge the capacitor that powers the badge and this can be a combination of antenna and barcodes obtained with SAW( Surface Acoustic Wave) devices [1,2,3] . The antenna in an RFID tag is a conductive element that permits the tag to exchange data with the reader. The paper contribution are targeted to antenna for passive RFID tags. The electromagnetic field generated by the reader is somehow oriented by the reader antenna and power is induced in the tag only if the orientation of the tag antenna is appropriate. A tag placed orthogonal to the reader yield field will not be read. This is the reason that guided manufacturers to build circular polarized antenna capable of propagating a field that is alternatively polarized on all planes passing on the diffusion axis. Passive RFID tags are operated at the UHF frequencies of 868MHz (Europe) and 915MHz (USA) and at the microwave frequencies of 2,45 GHz and 5,8 GHz . Because the tags are small dimensions, in paper, we present the possibility to use circular polarization microstrip antenna with fractal edge [2].

  13. Characterization of supersonic radiation diffusion waves

    International Nuclear Information System (INIS)

    Moore, Alastair S.; Guymer, Thomas M.; Morton, John; Williams, Benjamin; Kline, John L.; Bazin, Nicholas; Bentley, Christopher; Allan, Shelly; Brent, Katie; Comley, Andrew J.; Flippo, Kirk; Cowan, Joseph; Taccetti, J. Martin; Mussack-Tamashiro, Katie; Schmidt, Derek W.; Hamilton, Christopher E.; Obrey, Kimberly; Lanier, Nicholas E.; Workman, Jonathan B.; Stevenson, R. Mark

    2015-01-01

    Supersonic and diffusive radiation flow is an important test problem for the radiative transfer models used in radiation-hydrodynamics computer codes owing to solutions being accessible via analytic and numeric methods. We present experimental results with which we compare these solutions by studying supersonic and diffusive flow in the laboratory. We present results of higher-accuracy experiments than previously possible studying radiation flow through up to 7 high-temperature mean free paths of low-density, chlorine-doped polystyrene foam and silicon dioxide aerogel contained by an Au tube. Measurements of the heat front position and absolute measurements of the x-ray emission arrival at the end of the tube are used to test numerical and analytical models. We find excellent absolute agreement with simulations provided that the opacity and the equation of state are adjusted within expected uncertainties; analytical models provide a good phenomenological match to measurements but are not in quantitative agreement due to their limited scope. - Highlights: • The supersonic, diffusion of x-rays through sub-solid density materials is studied. • The data are more diffusive and of higher velocity than any prior work. • Scaled 1D analytic diffusion models reproduce the heat front evolution. • Refined radiation transport approximations are tested in numerical simulations. • Simulations match the data if material properties are adjusted within uncertainties

  14. MULTI-PARAMETRIC STUDY OF RISING 3D BUOYANT FLUX TUBES IN AN ADIABATIC STRATIFICATION USING AMR

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-Sykora, Juan; Cheung, Mark C. M. [Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA 94304 (United States); Moreno-Insertis, Fernando [Instituto de Astrofísica de Canarias, E-38200 La Laguna (Tenerife) (Spain)

    2015-11-20

    We study the buoyant rise of magnetic flux tubes embedded in an adiabatic stratification using two-and three-dimensional, magnetohydrodynamic simulations. We analyze the dependence of the tube evolution on the field line twist and on the curvature of the tube axis in different diffusion regimes. To be able to achieve a comparatively high spatial resolution we use the FLASH code, which has a built-in Adaptive Mesh Refinement (AMR) capability. Our 3D experiments reach Reynolds numbers that permit a reasonable comparison of the results with those of previous 2D simulations. When the experiments are run without AMR, hence with a comparatively large diffusivity, the amount of longitudinal magnetic flux retained inside the tube increases with the curvature of the tube axis. However, when a low-diffusion regime is reached by using the AMR algorithms, the magnetic twist is able to prevent the splitting of the magnetic loop into vortex tubes and the loop curvature does not play any significant role. We detect the generation of vorticity in the main body of the tube of opposite sign on the opposite sides of the apex. This is a consequence of the inhomogeneity of the azimuthal component of the field on the flux surfaces. The lift force associated with this global vorticity makes the flanks of the tube move away from their initial vertical plane in an antisymmetric fashion. The trajectories have an oscillatory motion superimposed, due to the shedding of vortex rolls to the wake, which creates a Von Karman street.

  15. MULTI-PARAMETRIC STUDY OF RISING 3D BUOYANT FLUX TUBES IN AN ADIABATIC STRATIFICATION USING AMR

    International Nuclear Information System (INIS)

    Martínez-Sykora, Juan; Cheung, Mark C. M.; Moreno-Insertis, Fernando

    2015-01-01

    We study the buoyant rise of magnetic flux tubes embedded in an adiabatic stratification using two-and three-dimensional, magnetohydrodynamic simulations. We analyze the dependence of the tube evolution on the field line twist and on the curvature of the tube axis in different diffusion regimes. To be able to achieve a comparatively high spatial resolution we use the FLASH code, which has a built-in Adaptive Mesh Refinement (AMR) capability. Our 3D experiments reach Reynolds numbers that permit a reasonable comparison of the results with those of previous 2D simulations. When the experiments are run without AMR, hence with a comparatively large diffusivity, the amount of longitudinal magnetic flux retained inside the tube increases with the curvature of the tube axis. However, when a low-diffusion regime is reached by using the AMR algorithms, the magnetic twist is able to prevent the splitting of the magnetic loop into vortex tubes and the loop curvature does not play any significant role. We detect the generation of vorticity in the main body of the tube of opposite sign on the opposite sides of the apex. This is a consequence of the inhomogeneity of the azimuthal component of the field on the flux surfaces. The lift force associated with this global vorticity makes the flanks of the tube move away from their initial vertical plane in an antisymmetric fashion. The trajectories have an oscillatory motion superimposed, due to the shedding of vortex rolls to the wake, which creates a Von Karman street

  16. Evaluation of a Design Concept for the Combined Air-water Passive Cooling PAFS+

    International Nuclear Information System (INIS)

    Bae, Sung Won; Kwon, Taesoon

    2014-01-01

    The APR+ system provides the Passive Auxiliary Feed-water System (PAFS) for the passive cooling capability. However, the current design requirement for working time for the PAFS is about 8 hours only. Thus, current working time of PAFS can not meet the required 72 hours cooling capability for the long term SBO situation. To meet the 72 hours cooling, the pool capacity should be almost 3∼4 times larger than that of current water cooling tank. In order to continue the PAFS operation for 72 hours, a new passive air-water combined cooling system is proposed. This paper provides the feasibility study on the combined passive air-water cooling system. Figure 1 and 2 show the conceptual difference of the PAFS and combined passive air-water cooling system, respectively. Simple performance evaluation of the passive air cooling heat exchanger has been conducted by the MARS calculation. For the postulated FLB scenario, 4800 heat exchanger tubes and 5 m/s air velocity are not sufficient to sustain the PCCT pool level for 72 hour cooling. Further works on the system design and performance enhancing plan are required to fulfill the 72 hours long term passive cooling

  17. Effect of bio-cover equipped with a novel passive air diffusion system on methane emission reduciton from landfill

    DEFF Research Database (Denmark)

    Lu, W.J.; Mou, Zishen

    2011-01-01

    Based on the aerothermodynamic principles, a kind of breathing bio-cover system was designed to enhance oxygen (O2) supply efficiency and methane (CH4) oxidation capacity. The research showed that O2 concentration (v/v) considerably increased throughout whole profiles of the microcosm (1m) equipped...... with passive air diffusion system (MPADS). When the simulated landfill gas SLFG flow was 771 and 1028 gm−3 d−1, the O2 concentration in MPADS increased gradually and tended to be stable at the atmospheric level after 10 days. The CH4 oxidation rate was 100% when the SLFG flow rate was no more than 1285 gm−3 d......−1, which also was confirmed by the mass balance calculations. The breathing bio-cover system with in situ self-oxygen supply can address the problem of O2 insufficient in conventional landfill bio-cover. The proposed system presents high potential for improving CH4 emission reduction in landfills....

  18. Passive retrieval of Rayleigh waves in disordered elastic media

    International Nuclear Information System (INIS)

    Larose, Eric; Derode, Arnaud; Clorennec, Dominique; Margerin, Ludovic; Campillo, Michel

    2005-01-01

    When averaged over sources or disorder, cross correlation of diffuse fields yields the Green's function between two passive sensors. This technique is applied to elastic ultrasonic waves in an open scattering slab mimicking seismic waves in the Earth's crust. It appears that the Rayleigh wave reconstruction depends on the scattering properties of the elastic slab. Special attention is paid to the specific role of bulk to Rayleigh wave coupling, which may result in unexpected phenomena, such as a persistent time asymmetry in the diffuse regime

  19. Solution of time dependent atmospheric diffusion equation with a proposed diffusion coefficient

    International Nuclear Information System (INIS)

    Mayhoub, A.B.; Essa, KH.S.M.; Aly, SH.

    2004-01-01

    One-dimensional model for the dispersion of passive atmospheric contaminant (not included chemical reactions) in the atmospheric boundary layer is considered. On the basis of the gradient transfer theory (K-theory), the time dependent diffusion equation represents the dispersion of the pollutants is solved analytically. The solution depends on diffusion coefficient K', which is expressed in terms of the friction velocity 'u the vertical coordinate -L and the depth of the mixing layer 'h'. The solution is obtained to either the vertical coordinate 'z' is less or greater than the mixing height 'h'. The obtained solution may be applied to study the atmospheric dispersion of pollutants

  20. An investigation on mechanical property of commercial copper tube to aluminium 2025 tube plate by FWTPET process

    Energy Technology Data Exchange (ETDEWEB)

    Kannan, S., E-mail: kannan.dgl201127@gmail.com [Department of Mechanical Engineering and Mining Machinery Engineering, Indian Institute of Technology (ISM), Dhanbad, Jharkhand 826004 (India); Senthil Kumaran, S., E-mail: sskumaran@ymail.com [Research and Development Center, Department of Mechanical Engineering, RVS Educational Trust' s Group of Institutions, RVS School of Engineering and Technology, Dindigul, Tamilnadu 624005 (India); Kumaraswamidhas, L.A., E-mail: lakdhas1978@gmail.com [Department of Mechanical Engineering and Mining Machinery Engineering, Indian Institute of Technology (ISM), Dhanbad, Jharkhand 826004 (India)

    2016-07-05

    Frictional welding of tube to tube plate by external tool (FWTPET) posses wide spread industrial in mass production process for joint similar and dissimilar materials. Frictional welding process allows welding of some materials that are exceptionally hard to fusion weld. The good quality joint between the tube and tube plate is achieved by selecting the proper process parameter. In this present research, the frictional welding is done between the Aluminium 2025 tube plate and commercial copper tube possessing a clearance fit of 0.1 mm between tube and hole. In this study, two conditions were considered while handing out this experiment. The condiction1 is tube without holes [WOH] and condition 2 is tube with holes [WH] on the tube circumference. In total, twenty seven work pieces have been considered separately for both conditions and the mechanical property such as compression strength and hardness value has been measured for the both set of work piece in two conditions to analysis the joint strength of the welding process. Taguchi L{sub 27} orthogonal array has been used in this process to identify the process parameter which influences the joint strength of the welded samples. ANOVA method is used to calculate the percentage of contribution by each process parameter which influences the better joint strength. Genetic algorithm is used to authenticate the outcome obtained from the both experimental value and optimization value. Scanning Electron Microscope (SEM) and Energy-dispersive X-ray analysis (EDX) has been performed to probe microstructures and chemical compositions for work piece without holes which has higher mechanical property. - Highlights: • FWTPET for dissimilar metals commercial copper tube and Al 2025 tube plate. • The hardness value for tube without holes are 180.988 Hv. • The compression strength for tube without holes are 376.05 MPa. • SEM confirm heat production is done to melt parent metal by diffusion process. • EDX prove no trace

  1. Numerical vs. turbulent diffusion in geophysical flow modelling

    International Nuclear Information System (INIS)

    D'Isidoro, M.; Maurizi, A.; Tampieri, F.

    2008-01-01

    Numerical advection schemes induce the spreading of passive tracers from localized sources. The effects of changing resolution and Courant number are investigated using the WAF advection scheme, which leads to a sub-diffusive process. The spreading rate from an instantaneous source is compared with the physical diffusion necessary to simulate unresolved turbulent motions. The time at which the physical diffusion process overpowers the numerical spreading is estimated, and is shown to reduce as the resolution increases, and to increase as the wind velocity increases.

  2. Final report on development evaluation of Task Group 3 pressure tubes

    International Nuclear Information System (INIS)

    Fleck, R.G.; Price, E.G.; Cheadle, B.A.

    1983-11-01

    This report describes the production and evaluation of pressure tubes manufactured to the recommendations of Task Group 3 (TG3) of the Creep Engineering Design Plan. The Zr-2.5 wt percent Nb tubes were manufactured by modified production route to change their metallurgical structure and so reduce the in-service elongation rates. Three modified routes were investigated and a total of twenty-eight tubes produced. There were no difficulties in manufacture and the tubes satisfied the quality assurance and design specifications of reactor grade tubes. Metallurgical evaluation showed that the expected changes in microstructure had occurred but not to the extent anticipated. The TG3 tubes were found to have comparable properties to current tubes when tested for: tensile strength (irradiated and unirradiated); hydride cracking; stress to reorient hydrides; hydrogen diffusion; flaw tolerance; corrosion (irradiated and unirradiated); wear; rolled joint characteristics; irradiation creep and growth. Lower in-service elongation rates are expected for tubes produced by two of the modified routes

  3. Cathode ray tube screens

    International Nuclear Information System (INIS)

    Cockayne, B.; Robbins, D.J.; Glasper, J.L.

    1982-01-01

    An improved cathode ray tube screen is described which consists of a single- or a poly-crystalline slice of a material such as yttrium aluminium garnet in which dopants such as Tb 3 + , Eu 3 + , Ce 3 + or Tm 3 + are ion implanted to different depths or in different areas of the screen. Annealing the screen removes lattice damage caused by the ion implanting and assists the diffusion of the dopant into the crystal. (U.K.)

  4. Passive Rocket Diffuser Theory: A Re-Examination of Minimum Second Throat Size

    Science.gov (United States)

    Jones, Daniel R.

    2016-01-01

    Second-throat diffusers serve to isolate rocket engines from the effects of ambient back pressure during testing without using active control systems. Among the most critical design parameters is the relative area of the diffuser throat to that of the nozzle throat. A smaller second throat is generally desirable because it decreases the stagnation-to-ambient pressure ratio the diffuser requires for nominal operation. There is a limit, however. Below a certain size, the second throat can cause pressure buildup within the diffuser and prevent it from reaching the start condition that protects the nozzle from side-load damage. This paper presents a method for improved estimation of the minimum second throat area which enables diffuser start. The new 3-zone model uses traditional quasi-one-dimensional compressible flow theory to approximate the structure of two distinct diffuser flow fields observed in Computational Fluid Dynamics (CFD) simulations and combines them to provide a less-conservative estimate of the second throat size limit. It is unique among second throat sizing methods in that it accounts for all major conical nozzle and second throat diffuser design parameters within its limits of application. The performance of the 3-zone method is compared to the historical normal shock and force balance methods, and verified against a large number of CFD simulations at specific heat ratios of 1.4 and 1.25. Validation is left as future work, and the model is currently intended to function only as a first-order design tool.

  5. High-intensity focused ultrasound ablation around the tubing.

    Science.gov (United States)

    Siu, Jun Yang; Liu, Chenhui; Zhou, Yufeng

    2017-01-01

    High-intensity focused ultrasound (HIFU) has been emerging as an effective and noninvasive modality in cancer treatment with very promising clinical results. However, a small vessel in the focal region could be ruptured, which is an important concern for the safety of HIFU ablation. In this study, lesion formation in the polyacrylamide gel phantom embedded with different tubing (inner diameters of 0.76 mm and 3 mm) at varied flow speeds (17-339 cm/s) by HIFU ablation was photographically recorded. Produced lesions have decreased length (~30%) but slightly increased width (~6%) in comparison to that without the embedded tubing. Meanwhile, bubble activities during the exposures were measured by passive cavitation detection (PCD) at the varied pulse repetition frequency (PRF, 10-30 Hz) and duty cycle (DC, 10%-20%) of the HIFU bursts. High DC and low flow speed were found to produce stronger bubble cavitation whereas no significant influence of the PRF. In addition, high-speed photography illustrated that the rupture of tubing was produced consistently after the first HIFU burst within 20 ms and then multiple bubbles would penetrate into the intraluminal space of tubing through the rupture site by the acoustic radiation force. Alignment of HIFU focus to the anterior surface, middle, and posterior surface of tubing led to different characteristics of vessel rupture and bubble introduction. In summary, HIFU-induced vessel rupture is possible as shown in this phantom study; produced lesion sizes and shapes are dependent on the focus alignment to the tubing, flow speed, and tubing properties; and bubble cavitation and the formation liquid jet may be one of the major mechanisms of tubing rupture as shown in the high-speed photography.

  6. Synthesis of barium-strontium titanate hollow tubes using Kirkendall effect

    Science.gov (United States)

    Chen, Xuncai; Im, SangHyuk; Kim, Jinsoo; Kim, Woo-Sik

    2018-02-01

    (BaSr)TiO3 hexagonal hollow tubes was fabricated by a solid-state interfacial reaction including a Kirkendall diffusion. Using a co-precipitation and sol-gel process, a core@shell structure of (BaSr)CO3@TiO2 rods were prepared, and then converted to (BaSr)TiO3 hollow tubes at 750 °C. This was a first achievement of single-phase crystal hollow tube. Here, the inner diameter and wall thickness of hollow tube were about 700 nm and 130 nm, respectively. The fabrication of (BaSr)TiO3 hollow tubes was monitored with scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD) to investigate their formation mechanism. The present synthetic approach would provide a new insight into the design and fabrication of hollow architectures of many perovskite oxides.

  7. Diffusion bonding techniques

    International Nuclear Information System (INIS)

    Peters, R.D.

    1978-01-01

    The applications of diffusion bonding at the General Electric Neutron Devices Department are briefly discussed, with particular emphasis on the gold/gold or gold/indium joints made between metallized alumina ceramic parts in the vacuum switch tube and the crystal resonator programs. Fixtures which use the differential expansion of dissimilar metals are described and compared to one that uses hydraulic pressure to apply the necessary bonding force

  8. Effects of ion acoustic waves on diffusion in a magnetized plasma

    International Nuclear Information System (INIS)

    Watanabe, Yukio; Akazaki, Masanori; Fujiyama, Hiroshi.

    1975-01-01

    This paper describes on the behavior of ion acoustic waves in magnetized plasma. The plasma was produced with a discharge tube placed in an air-core coil. The pressure of argon gas in the discharge tube was 1--10 mTorr. The plasma was entracted along the externally applied magnetic field through a nozzle into a measuring part. The condition of stabilization of drift waves was investigated. Four small glass tubes were placed in contact with the wall of the discharge tube, and the drift wave was remarkably suppressed. Then the ion acoustic waves can be observed. The magnetic field dependence of the frequency of ion acoustic waves was studied. The frequency depends on magnetic field and gas pressure. The magnetic field dependence of the frequency is caused by the variation of electron temperature. The Timofee's theory can explain the magnetic field of generating ion acoustic waves. The ion acoustic waves being excited naturally propagate to the direction of the diamagnetic drift of electrons, and their spectra are monochromatic. The dependence of Dsub(perpendicular), diffusion constant, on magnetic field is explained by two-pole diffusion, and the effect of the monochromatic ion acoustic waves on diffusion is small. (Kato, T.)

  9. Low cost fuel cell diffusion layer configured for optimized anode water management

    Science.gov (United States)

    Owejan, Jon P; Nicotera, Paul D; Mench, Matthew M; Evans, Robert E

    2013-08-27

    A fuel cell comprises a cathode gas diffusion layer, a cathode catalyst layer, an anode gas diffusion layer, an anode catalyst layer and an electrolyte. The diffusion resistance of the anode gas diffusion layer when operated with anode fuel is higher than the diffusion resistance of the cathode gas diffusion layer. The anode gas diffusion layer may comprise filler particles having in-plane platelet geometries and be made of lower cost materials and manufacturing processes than currently available commercial carbon fiber substrates. The diffusion resistance difference between the anode gas diffusion layer and the cathode gas diffusion layer may allow for passive water balance control.

  10. Condensation heat transfer with noncondensable gas for passive containment cooling of nuclear reactors

    Energy Technology Data Exchange (ETDEWEB)

    Leonardi, Tauna [Schlumberger, 14910 Airline Rd., Rosharon, TX 77583 (United States)]. E-mail: Tleonardi@slb.com; Ishii, Mamoru [School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States)]. E-mail: Ishii@ecn.purdue.edu

    2006-09-15

    Noncondensable gases that come from the containment and the interaction of cladding and steam during a severe accident deteriorate a passive containment cooling system's performance by degrading the heat transfer capabilities of the condensers in passive containment cooling systems. This work contributes to the area of modeling condensation heat transfer with noncondensable gases in integral facilities. Previously existing correlations and models are for the through-flow of the mixture of steam and the noncondensable gases and this may not be applicable to passive containment cooling systems where there is no clear passage for the steam to escape. This work presents a condensation heat transfer model for the downward cocurrent flow of a steam/air mixture through a condenser tube, taking into account the atypical characteristics of the passive containment cooling system. An empirical model is developed that depends on the inlet conditions, including the mixture Reynolds number and noncondensable gas concentration.

  11. Automated sample preparation station for studying self-diffusion in porous solids with NMR spectroscopy

    Science.gov (United States)

    Hedin, Niklas; DeMartin, Gregory J.; Reyes, Sebastián C.

    2006-03-01

    In studies of gas diffusion in porous solids with nuclear magnetic resonance (NMR) spectroscopy the sample preparation procedure becomes very important. An apparatus is presented here that pretreats the sample ex situ and accurately sets the desired pressure and temperature within the NMR tube prior to its introduction in the spectrometer. The gas manifold that supplies the NMR tube is also connected to a microbalance containing another portion of the same sample, which is kept at the same temperature as the sample in the NMR tube. This arrangement permits the simultaneous measurement of the adsorption loading on the sample, which is required for the interpretation of the NMR diffusion experiments. Furthermore, to ensure a good seal of the NMR tube, a hybrid valve design composed of titanium, a Teflon® seat, and Kalrez® O-rings is utilized. A computer controlled algorithm ensures the accuracy and reproducibility of all the procedures, enabling the NMR diffusion experiments to be performed at well controlled conditions of pressure, temperature, and amount of gas adsorbed on the porous sample.

  12. Steam condensation heat transfer in the presence of noncondensables in a vertical tube of passive containment cooling system

    International Nuclear Information System (INIS)

    Park, Hyun Sik

    1999-02-01

    A database for laminar condensation heat transfer is constructed from the previous experimental data at various condensation conditions. Based on the database, the condensation models in the standard RELAP5/MOD3.2 code are assessed and improved. Two wall film condensation models, the default and the alternative, are used in RELAP5/MOD3.2. The default model of the laminar film condensation in RELAP5/MOD3.2 does not give any reliable predictions, and its alternative model always predicts higher values than the experimental data. Therefore, it is needed to develop a new correlation based on the experimental data of various operating ranges. A set of condensation experiments in the presence of noncondensable gas in a vertical tube of the passive containment cooling system of the CP-1300 are performed. The experimental results show that the heat transfer coefficients (HTCs) increase as the inlet air mass fraction decreases and the inlet saturated steam temperature decreases. However, the dependence of the inlet mixture Reynolds number on the HTC is small for the operating range. An empirical correlation is developed, and its predictions are compared with experimental data to show good agreement with the standard deviation of 22.3%. The experimental HTCs are also compared with the predictions from the default and the alternative models used in RELAP5/MOD3.2. The experimental apparatus is modeled with two wall-film condensation models in RELAP5/MOD3.2 and the empirical correlation, and simulations are performed for several subtests to be compared with the experimental results. Overall, the simulation results show that the default model of RELAP5/MOD3.2 underpredicts the HTCs, and the alternative model overpredicts them, while the empirical correlation predicts them well throughout the condensing tube. Both the nodalization study and the sensitivity study are also performed. The nodalization study shows that the variation of the node number does not change both modeling

  13. Applied reliability assessment for the passive safety systems of nuclear power plants (NPPs) using system dynamics (SD)

    International Nuclear Information System (INIS)

    Kim, Yun Il; Woo, Tae Ho

    2018-01-01

    The passive system by the free-fall is investigated in the accident of nuclear power plants (NPPs). The complex algorithm of the system dynamics (SD) modeling is done in the passive cooling system. The nuclear passive system by free-fall is successfully modeled for the loss of coolant accident (LOCA). Conventional passive system of gravity or natural circulation is working only when the piping systems is in the good condition. The external coolant supply system is introduced in the case of the piping system failure. The water is poured into the reactor through the guiding piping or tube. If the explosion happens, the coolants could be showering into the reactor core and its building. New kind of passive system is expected successfully in the on-site black out where the drone could be operated by battery or engine.

  14. Experimental studies of thermo-hydraulic processes during passive safety systems operation in new WWER NPP projects

    International Nuclear Information System (INIS)

    Morozov, A.V.; Remizov, O.V.; Kalyakin, D.S.

    2014-01-01

    The results of experimental study of thermal-hydraulic processes during operation of the passive safety systems of WWER reactors of new generation are given. The interaction processes of counter flows of saturated steam and cold water in vertical steam-line of the auxiliary passive core reflood system from secondary hydraulic accumulator are studied. The peculiarities of undeveloped boiling on single horizontal tube heating by steam and steam-gas mixture, which is character for WWER steam generator condensing mode, are investigated [ru

  15. Diffusion transport of nanoparticles at nanochannel boundaries

    International Nuclear Information System (INIS)

    Mahadevan, T. S.; Milosevic, M.; Kojic, M.; Hussain, F.; Kojic, N.; Serda, R.; Ferrari, M.; Ziemys, A.

    2013-01-01

    The manipulation of matter at the nanoscale has unleashed a great potential for engineering biomedical drug carriers, but the transport of nanoparticles (NPs) under nanoscale confinement is still poorly understood. Using colloidal physics to describe NP interactions, we have computationally studied the passive transport of NPs using experimentally relevant conditions from bulk into a nanochannel of 60–90 nm height. NP size, channel height, and the Debye length are comparable so that changes in nanoscale dimensions may induce substantial changes in NP transport kinetics. We show that subtle changes in nanochannel dimensions may alter the energy barrier by about six orders of magnitude resulting in different NP penetration depths and diffusion mechanisms: ballistic, first-order and quasi zero-order transport regimes. The analysis of NP diffusion by continuum methods reveals that apparent diffusivity is reduced by decreasing channel size. The continuum finite element (FE) numerical method reproduced the colloidal model results only when surface interactions were accounted for. These results give a new insight into NP passive transport at the boundaries of nanoconfined domains, and have implications on the design of nanoscale fluidics and NP systems for biomedical and engineering applications.

  16. Analysis of mercury diffusion pumps

    International Nuclear Information System (INIS)

    Dunn, K.A.

    1991-01-01

    Several mercury diffusion pump stages in the Tritium Purification process at the Savannah River Site (SRS) have been removed from service for scheduled preventive maintenance. These stages have been examined to determine if failure has occurred. Evidence of fatigue around the flange portion of the pump has been seen. In addition, erosion and cavitation inside the throat of the venturi tube and corrosion on the other surface of the venturi tube has been observed. Several measures are being examined in an attempt to improve the performance of these pumps. These measures, as well as the noted observations, are described. 4 refs

  17. Device physics underlying silicon heterojunction and passivating-contact solar cells: A topical review

    KAUST Repository

    Chavali, Raghu V. K.; De Wolf, Stefaan; Alam, Muhammad A.

    2018-01-01

    The device physics of commercially dominant diffused-junction silicon solar cells is well understood, allowing sophisticated optimization of this class of devices. Recently, so-called passivating-contact solar cell technologies have become prominent

  18. A condensation experiment in the accumulated conditions of noncondensable gas in a vertical tube

    International Nuclear Information System (INIS)

    Lee, Kwon Yeong; Kim, Moo Hwan

    2005-01-01

    Full text of publication follows: It has been well known that the presence of noncondensable gases in vapors can greatly inhibit the condensation process. Many analytical and experimental studies were conducted to investigate the effect of noncondensable gases on steam condensation for both stagnant and forced-convective situations either over a plate or outside a horizontal tube. Recently, several researches have been performed for the condensation in the presence of noncondensable gases taken place inside the vertical tube in order to give the information to design the passive containment cooling system (PCCS) in Simplified Boiling Water Reactor (SBWR). Generally, the experimental results showed that the heat transfer coefficient depends on inlet noncondensable gas mass fraction, inlet saturated steam temperature related with system pressure and inlet mixture Reynolds number. This research was performed for the System-integrated Modular Advanced ReacTor-Pilot (SMART-P), in which the remaining heat is removed from the core passively by Passive Residual Heat Removal System (PRHRS) condenser in a period of serious accident. The PRHRS is separated from working fluid loop, and pressurized by a nitrogen gas during the normal operation of SMART-P. But when the PRHRS starts operating, the nitrogen gas acts as a noncondensable gas and affects the heat transfer characteristics of the PRHRS. The experimental conditions of this study were almost similar with those of previous researches except the noncondensable gas was accumulated and remained inside the vertical tube. In the previous researches, the noncondensable gas was flowing with constant flow rate. Because of the condensate inside condenser tube, the accumulation of noncondensable gas could be developed inside the vertical tube. At steady-state condition the local temperatures and system pressure were measured to obtain heat transfer characteristics. This study also gave the information about the distribution of the

  19. Effective Drug Delivery in Diffuse Intrinsic Pontine Glioma: A Theoretical Model to Identify Potential Candidates

    Directory of Open Access Journals (Sweden)

    Fatma E. El-Khouly

    2017-10-01

    Full Text Available Despite decades of clinical trials for diffuse intrinsic pontine glioma (DIPG, patient survival does not exceed 10% at two years post-diagnosis. Lack of benefit from systemic chemotherapy may be attributed to an intact bloodbrain barrier (BBB. We aim to develop a theoretical model including relevant physicochemical properties in order to review whether applied chemotherapeutics are suitable for passive diffusion through an intact BBB or whether local administration via convection-enhanced delivery (CED may increase their therapeutic potential. Physicochemical properties (lipophilicity, molecular weight, and charge in physiological environment of anticancer drugs historically and currently administered to DIPG patients, that affect passive diffusion over the BBB, were included in the model. Subsequently, the likelihood of BBB passage of these drugs was ascertained, as well as their potential for intratumoral administration via CED. As only non-molecularly charged, lipophilic, and relatively small sized drugs are likely to passively diffuse through the BBB, out of 51 drugs modeled, only 8 (15%—carmustine, lomustine, erlotinib, vismodegib, lenalomide, thalidomide, vorinostat, and mebendazole—are theoretically qualified for systemic administration in DIPG. Local administration via CED might create more therapeutic options, excluding only positively charged drugs and drugs that are either prodrugs and/or only available as oral formulation. A wide variety of drugs have been administered systemically to DIPG patients. Our model shows that only few are likely to penetrate the BBB via passive diffusion, which may partly explain the lack of efficacy. Drug distribution via CED is less dependent on physicochemical properties and may increase the therapeutic options for DIPG.

  20. Connecting Ellipses to Rectangles in Passive Scalar Transport

    Science.gov (United States)

    Aminian, Manuchehr; Bernardi, Francesca; Camassa, Roberto; Harris, Daniel; McLaughlin, Richard

    2017-11-01

    We study how passive scalar transport in Poiseuille flow is affected by the shape of the pipe cross section. Our previous results have established nontrivial dependence of the skewness of the tracer distribution upon the pipe shape. Previously, we have studied the families of rectangles and ellipses, with the behavior past diffusive timescales primarily depending on aspect ratio, and the type of geometry being secondary. However, at timescales well before the diffusion timescale, the family of ellipses is distinct compared to rectangles. We investigate this phenomenon by studying a collection of exotic cross sections connecting the ellipses and rectangles, using a combination of theoretical and computational tools.

  1. CVD-Based Valence-Mending Passivation for Crystalline-Si Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Meng [Arizona State Univ., Mesa, AZ (United States)

    2015-03-01

    The objective of this project is to investigate a new surface passivation technique, valence-mending passivation, for its applications in crystalline-Si solar cells to achieve significant efficiency improvement and cost reduction. As the enabling technique, the project includes the development of chemical vapor deposition recipes to passivate textured Si(100) and multicrystalline-Si surfaces by sulfur and the characterization of the passivated Si surfaces, including thermal stability, Schottky barrier height, contact resistance and surface recombination. One important application is to replace the Ag finger electrode in Si cells with Al to reduce cost, by ~$0.1/Wp, and allow terawatt-scale deployment of crystalline-Si solar cells. These all-Al Si cells require a low-temperature metallization process for the Al electrode, to be compatible with valence-mending passivation and to prevent Al diffusion into n-type Si. Another application is to explore valence-mending passivation of grain boundaries in multicrystalline Si by diffusing sulfur into grain boundaries, to reduce the efficiency gas between monocrystalline-Si solar cells and multicrystalline-Si cells. The major accomplishments of this project include: 1) Demonstration of chemical vapor deposition processes for valence-mending passivation of both monocrystalline Si(100) and multicrystalline Si surfaces. Record Schottky barriers have been demonstrated, with the new record-low barrier of less than 0.08 eV between Al and sulfur-passivated n-type Si(100) and the new record-high barrier of 1.14 eV between Al and sulfur-passivated p-type Si(100). On the textured p-type monocrystalline Si(100) surface, the highest barrier with Al is 0.85 eV by valence-mending passivation. 2) Demonstration of a low-temperature metallization process for Al in crystalline-Si solar cells. The new metallization process is based on electroplating of Al in a room-temperature ionic liquid. The resistivity of the electroplated Al is ~7×10–6

  2. Rac1 controls epithelial tube length through the apical secretion and polarity pathways

    Directory of Open Access Journals (Sweden)

    Kévin Sollier

    2016-01-01

    Full Text Available The morphometric parameters of epithelial tubes are critical to the physiology and homeostasis of most organs. In addition, many human diseases are associated with tube-size defects. Here, we show that Rac1 limits epithelial tube elongation in the developing fly trachea by promoting Rab5-dependent endocytosis of the apical determinant Crumbs. Rac1 is also involved in a positive feedback loop with the septate junction protein Coracle. Thereby, Rac1 precludes paracellular diffusion and contributes to the septate junction-dependent secretion of the chitin-modifying enzymes Vermiform and Serpentine, which restrict epithelial tube length independently of Crumbs. Thus, Rac1 is a critical component of two important pathways controlling epithelial tube morphogenesis.

  3. Delayed hydrogen cracking test design for pressure tubes

    International Nuclear Information System (INIS)

    Haddad, Roberto; Loberse, Antonio N.; Yawny, Alejandro A.; Riquelme, Pablo

    1999-01-01

    CANDU nuclear power stations pressure tubes of alloy Zr-2,5 % Nb present a cracking phenomenon known as delayed hydrogen cracking (DHC). This is a brittle fracture of zirconium hydrides that are developed by hydrogen due to aqueous corrosion on the metal surface. This hydrogen diffuses to the crack tip where brittle zirconium hydrides develops and promotes the crack propagation. A direct current potential decay (DCPD) technique has been developed to measure crack propagation rates on compact test (CT) samples machined from a non irradiated pressure tube. Those test samples were hydrogen charged by cathodic polarization in an acid solution and then pre cracked in a fatigue machine. This technique proved to be useful to measure crack propagation rates with at least 1% accuracy for DHC in pressure tubes. (author)

  4. Effects of porosity in a model of corrosion and passive layer growth

    Directory of Open Access Journals (Sweden)

    F.D.A. Aarão Reis

    2017-12-01

    Full Text Available We introduce a stochastic lattice model to investigate the effects of pore formation in a passive layer grown with products of metal corrosion. It considers that an anionic species diffuses across that layer and reacts at the corrosion front (metal-oxide interface, producing a random distribution of compact regions and large pores, respectively represented by O (oxide and P (pore sites. O sites are assumed to have very small pores, so that the fraction Φ of P sites is an estimate of the porosity, and the ratio between anion diffusion coefficients in those regions is D_r0 and D_r≪1, significant changes are observed in passive layer growth and corrosion front roughness. For small Φ, a slowdown of the growth rate is observed, which is interpreted as a consequence of the confinement of anions in isolated pores for long times. However, the presence of large pores near the corrosion front increases the frequency of reactions at those regions, which leads to an increase in the roughness of that front. This model may be a first step to represent defects in a passive layer which favor pitting corrosion.

  5. Apparent diffusion coefficient measurement in a moving phantom simulating linear respiratory motion.

    Science.gov (United States)

    Kwee, Thomas C; Takahara, Taro; Muro, Isao; Van Cauteren, Marc; Imai, Yutaka; Nievelstein, Rutger A J; Mali, Willem P T M; Luijten, Peter R

    2010-10-01

    The aim of this study was to examine the effect of simulated linear respiratory motion on apparent diffusion coefficient (ADC) measurements. Six rectangular test tubes (14 × 92 mm) filled with either water, tomato ketchup, or mayonnaise were positioned in a box containing agarose gel. This box was connected to a double-acting pneumatic cylinder, capable of inducing periodic linear motion in the long-axis direction of the magnetic bore (23-mm stroke). Diffusion-weighted magnetic resonance imaging was performed for both the static and moving phantoms, and ADC measurements were made in the six test tubes in both situations. In the three test tubes whose long axes were parallel to the direction of motion, ADCs agreed well between the moving and static phantom situations. However, in two test tubes that were filled with fluids that had a considerably lower diffusion coefficient than the surrounding agarose gel, and whose long axes were perpendicular to the direction of motion, the ADCs agreed poorly between the moving and static phantom situations. ADC measurements of large homogeneous structures are not affected by linear respiratory motion. However, ADC measurements of inhomogeneous or small structures are affected by linear respiratory motion due to partial volume effects.

  6. Apparent diffusion coefficient measurement in a moving phantom simulating linear respiratory motion

    International Nuclear Information System (INIS)

    Kwee, T.C.; Takahara, Taro; Nievelstein, R.A.J.; Mali, W.P.T.M.; Luijten, P.R.; Muro, Isao; Imai, Yutaka; Cauteren, M. Van

    2010-01-01

    The aim of this study was to examine the effect of simulated linear respiratory motion on apparent diffusion coefficient (ADC) measurements. Six rectangular test tubes (14 x 92 mm) filled with either water, tomato ketchup, or mayonnaise were positioned in a box containing agarose gel. This box was connected to a double-acting pneumatic cylinder, capable of inducing periodic linear motion in the long-axis direction of the magnetic bore (23-mm stroke). Diffusion-weighted magnetic resonance imaging was performed for both the static and moving phantoms, and ADC measurements were made in the six test tubes in both situations. In the three test tubes whose long axes were parallel to the direction of motion, ADCs agreed well between the moving and static phantom situations. However, in two test tubes that were filled with fluids that had a considerably lower diffusion coefficient than the surrounding agarose gel, and whose long axes were perpendicular to the direction of motion, the ADCs agreed poorly between the moving and static phantom situations. ADC measurements of large homogeneous structures are not affected by linear respiratory motion. However, ADC measurements of inhomogeneous or small structures are affected by linear respiratory motion due to partial volume effects. (author)

  7. Experimental study of radon and thoron diffusion through barriers

    Energy Technology Data Exchange (ETDEWEB)

    Durcik, M; Havlik, F [Inst. of Preventive and Clinical Medicine, 83301 Bratislava (Slovakia)

    1996-12-31

    The measurement results of diffusion parameters for radon (radon-222) and thoron (radon-220) through barriers, experimental equipment and theoretical background of diffusion are presented in this paper. The diffusion barriers are used for measuring radon and thoron by passive detectors in order to test the reduction techniques in houses. Six samples (filter paper, rubber, polyethylene, glass laminate, polypropylene) were studied for radon diffusion. The thickness barriers were from 0.012 mm to 2 mm, the diffusion area was 16 cm{sup 2} and the volume V{sub 2} was 30 dm{sup 3}. The diffusion constants D were obtained using given expressions and the data from measurements. The procedures used in experiments are useful for study of diffusion ability of radon and thoron in barriers and determination diffusion parameters from short term measurements. (J.K.). 2 figs., 1 tab., 3 refs.

  8. Experimental study of radon and thoron diffusion through barriers

    International Nuclear Information System (INIS)

    Durcik, M.; Havlik, F.

    1995-01-01

    The measurement results of diffusion parameters for radon (radon-222) and thoron (radon-220) through barriers, experimental equipment and theoretical background of diffusion are presented in this paper. The diffusion barriers are used for measuring radon and thoron by passive detectors in order to test the reduction techniques in houses. Six samples (filter paper, rubber, polyethylene, glass laminate, polypropylene) were studied for radon diffusion. The thickness barriers were from 0.012 mm to 2 mm, the diffusion area was 16 cm 2 and the volume V 2 was 30 dm 3 . The diffusion constants D were obtained using given expressions and the data from measurements. The procedures used in experiments are useful for study of diffusion ability of radon and thoron in barriers and determination diffusion parameters from short term measurements. (J.K.). 2 figs., 1 tab., 3 refs

  9. GOTHIC code evaluation of alternative passive containment cooling features

    International Nuclear Information System (INIS)

    Gavrilas, M.; Todreas, E.N.; Driscoll, M.J.

    1996-01-01

    Reliance on passive cooling has become an important objective in containment design. Several reactor concepts have been set forth, which are equipped with entirely passively cooled containments. However, the problems that have to be overcome in rejecting the entire heat generated by a severe accident in a high-rating reactor (i.e. one with a rating greater than 1200 MW e ) have been found to be substantial and without obvious solutions. The GOTHIC code was verified and modified for containment cooling applications; optimal mesh sizes, computational time steps and applicable heat transfer correlations were examined. The effect of the break location on circulation patterns that develop inside the containment was also evaluated. The GOTHIC code was then employed to assess the effectiveness of several original heat rejection features that make it possible to cool high-rating containments. Two containment concepts were evaluated: one for a 1200 MW e new pressure tube light-water reactor, and one for a 1300 MW e pressurized-water reactor. The effectiveness of various containment configurations that include specific pressure-limiting features has been predicted. The best-performance configurations-worst-case-accident scenarios that were examined yielded peak pressures of less than 0.30 MPa for the 1200 MW e pressure tube light-water reactor, and less than 0.45 MPa for the 1300 MW e pressurized-water reactor. (orig.)

  10. Mesoscale Elucidation of Surface Passivation in the Li-Sulfur Battery Cathode.

    Science.gov (United States)

    Liu, Zhixiao; Mukherjee, Partha P

    2017-02-15

    The cathode surface passivation caused by Li 2 S precipitation adversely affects the performance of lithium-sulfur (Li-S) batteries. Li 2 S precipitation is a complicated mesoscale process involving adsorption, desorption and diffusion kinetics, which are affected profoundly by the reactant concentration and operating temperature. In this work, a mesoscale interfacial model is presented to study the growth of Li 2 S film on carbon cathode surface. Li 2 S film growth experiences nucleation, isolated Li 2 S island growth and island coalescence. The slow adsorption rate at small S 2- concentration inhibits the formation of nucleation seeds and the lateral growth of Li 2 S islands, which deters surface passivation. An appropriate operating temperature, especially in the medium-to-high temperature range, can also defer surface passivation. Fewer Li 2 S nucleation seeds form in such an operating temperature range, thereby facilitating heterogeneous growth and potentially inhibiting the lateral growth of the Li 2 S film, which may ultimately result in reduced surface passivation. The high specific surface area of the cathode microstructure is expected to mitigate the surface passivation.

  11. Role of passive valves & devices in poison injection system of advanced heavy water reactor

    International Nuclear Information System (INIS)

    Sapra, M.K.; Kundu, S.; Vijayan, P.K.; Vaze, K.K.; Sinha, R.K.

    2014-01-01

    The Advanced Heavy Water Reactor (AHWR) is a 300 MWe pressure tube type boiling light water (H 2 O) cooled, heavy water (D 2 O) moderated reactor. The reactor design is based on well-proven water reactor technologies and incorporates a number of passive safety features such as natural circulation core cooling; direct in-bundle injection of light water coolant during a Loss of Coolant Accident (LOCA) from Advanced Accumulators and Gravity Driven Water Pool by passive means; Passive Decay Heat Removal using Isolation Condensers, Passive Containment Cooling System and Passive Containment Isolation System. In addition to above, there is another passive safety system named as Passive Poison Injection System (PPIS) which is capable of shutting down the reactor for a prolonged time. It is an additional safety system in AHWR to fulfill the shutdown function in the event of failure of wired shutdown systems i.e. primary and secondary shut down systems of the reactor. When demanded, PPIS injects the liquid poison into the moderator by passive means using passive valves and devices. On increase of main heat transport (MHT) system pressure beyond a predetermined value, a set of rupture disks burst, which in-turn actuate the passive valve. The opening of passive valve initiates inrush of high pressure helium gas into poison tanks to push the poison into the moderator system, thereby shutting down the reactor. This paper primarily deals with design and development of Passive Poison Injection System (PPIS) and its passive valves & devices. Recently, a prototype DN 65 size Poison Injection Passive Valve (PIPV) has been developed for AHWR usage and tested rigorously under simulated conditions. The paper will highlight the role of passive valves & devices in PPIS of AHWR. The design concept and test results of passive valves along with rupture disk performance will also be covered. (author)

  12. Advectional enhancement of eddy diffusivity under parametric disorder

    International Nuclear Information System (INIS)

    Goldobin, Denis S

    2010-01-01

    Frozen parametric disorder can lead to the appearance of sets of localized convective currents in an otherwise stable (quiescent) fluid layer heated from below. These currents significantly influence the transport of an admixture (or any other passive scalar) along the layer. When the molecular diffusivity of the admixture is small in comparison to the thermal one, which is quite typical in nature, disorder can enhance the effective (eddy) diffusivity by several orders of magnitude in comparison to the molecular diffusivity. In this paper, we study the effect of an imposed longitudinal advection on the delocalization of convective currents, both numerically and analytically, and report a subsequent drastic boost of the effective diffusivity for weak advection.

  13. High performance passive solar heating system with heat pipe energy transfer and latent heat storage

    NARCIS (Netherlands)

    Dijk, van H.A.L.; Galen, van E; Hensen, J.L.M.; Wit, de M.H.

    1983-01-01

    Preliminar results are reported from a current project on the development of a high performance passive solar heating system. Two special components are introduced: a. A heat pipe as a thermal diode tube for the efficient transfer of collected solar heat from the absorber plate to behind an

  14. Analysis of passive moderator cooling system of Candu-6A reactor at emergency condition

    International Nuclear Information System (INIS)

    Umar, Efrizon; Subki, M. Hadid; Vecchiarelli, Jack

    2001-01-01

    Analysis of passive moderator cooling system subject to in-core LOCA with no emergency core cooling injection has been done. In this study, the new model of passive moderator system has been tested for emergency conditions and CATHENA code Mod-3.5b/Rev1 is used to calculate some parameters of this passive moderator cooling system. This result of simulation show that the proposed moderator cooling system have given satisfactory result, especially for the case with 0.7 m riser diameter and the number of heat exchanger tubes 8100. For PEWS tank containing 3000 m3 of light water initially at 30 0C and a 3641 m2 moderator heat exchanger, the average long-term heat removed rate balances the moderator heat load and the flow through the passive moderator loop remains stable for over 72 hours with no saturated boiling in the calandria and flow instabilities do not develop during long-term period

  15. Gastrostomy Tube (G-Tube)

    Science.gov (United States)

    ... any of these problems: a dislodged tube a blocked or clogged tube any signs of infection (including redness, swelling, or warmth at the tube site; discharge that's yellow, green, or foul-smelling; fever) excessive bleeding or drainage from the tube site severe abdominal pain lasting ...

  16. Model of diffusers / permeators for hydrogen processing

    International Nuclear Information System (INIS)

    Jacobs, W. D.; Hang, T.

    2008-01-01

    Palladium-silver (Pd-Ag) diffusers are mainstays of hydrogen processing. Diffusers separate hydrogen from inert species such as nitrogen, argon or helium. The tubing becomes permeable to hydrogen when heated to more than 250 C and a differential pressure is created across the membrane. The hydrogen diffuses better at higher temperatures. Experimental or experiential results have been the basis for determining or predicting a diffuser's performance. However, the process can be mathematically modeled, and comparison to experimental or other operating data can be utilized to improve the fit of the model. A reliable model-based diffuser system design is the goal which will have impacts on tritium and hydrogen processing. A computer model has been developed to solve the differential equations for diffusion given the operating boundary conditions. The model was compared to operating data for a low pressure diffuser system. The modeling approach and the results are presented in this paper. (authors)

  17. Determination of Matrix Diffusion Properties of Granite

    International Nuclear Information System (INIS)

    Holtta, Pirkko; Siitari-Kauppi, Marja; Huittinen, Nina; Poteri, Antti

    2007-01-01

    Rock-core column experiments were introduced to estimate the diffusion and sorption properties of Kuru Grey granite used in block-scale experiments. The objective was to examine the processes causing retention in solute transport through rock fractures, especially matrix diffusion. The objective was also to estimate the importance of retention processes during transport in different scales and flow conditions. Rock-core columns were constructed from cores drilled into the fracture and were placed inside tubes to form flow channels in the 0.5 mm gap between the cores and the tube walls. Tracer experiments were performed using uranin, HTO, 36 Cl, 131 I, 22 Na and 85 Sr at flow rates of 1-50 μL.min -1 . Rock matrix was characterized using 14 C-PMMA method, scanning electron microscopy (SEM), energy dispersive X-ray micro analysis (EDX) and the B.E.T. method. Solute mass flux through a column was modelled by applying the assumption of a linear velocity profile and molecular diffusion. Coupling of the advection and diffusion processes was based on the model of generalised Taylor dispersion in the linear velocity profile. Experiments could be modelled applying a consistent parameterization and transport processes. The results provide evidence that it is possible to investigate matrix diffusion at the laboratory scale. The effects of matrix diffusion were demonstrated on the slightly-sorbing tracer breakthrough curves. Based on scoping calculations matrix diffusion begins to be clearly observable for non-sorbing tracer when the flow rate is 0.1 μL.min -1 . The experimental results presented here cannot be transferred directly to the spatial and temporal scales that prevail in an underground repository. However, the knowledge and understanding of transport and retention processes gained from this study is transferable to different scales from laboratory to in-situ conditions. (authors)

  18. Thermohydraulic performance comparision of compound inserts for a turbulent flow through a circular tube

    Directory of Open Access Journals (Sweden)

    Kapse Arvind A.

    2017-01-01

    Full Text Available Heat transfer and pressure drop characteristics of three different passive inserts are experimentally investigated for individual and compound insertion. Insert cross-section is altered along the length of test section for compound insertion. Test runs were conducted in a concentric circular tube in tube heat exchanger in the Reynolds number range of 8000 to 32000 with water as a working fluid. Enhancements in Nusselt number and friction factors are reported to be in the range of 38-234% and 55-524%, respectively, over plain tube. The average performance ratios based on equal pumping power are also reported and found in the range of 0.63-1.53. Based on experimental results, optimum combination for compound insertion is proposed.

  19. Integrating Models of Diffusion and Behavior to Predict Innovation Adoption, Maintenance, and Social Diffusion.

    Science.gov (United States)

    Smith, Rachel A; Kim, Youllee; Zhu, Xun; Doudou, Dimi Théodore; Sternberg, Eleanore D; Thomas, Matthew B

    2018-01-01

    This study documents an investigation into the adoption and diffusion of eave tubes, a novel mosquito vector control, during a large-scale scientific field trial in West Africa. The diffusion of innovations (DOI) and the integrated model of behavior (IMB) were integrated (i.e., innovation attributes with attitudes and social pressures with norms) to predict participants' (N = 329) diffusion intentions. The findings showed that positive attitudes about the innovation's attributes were a consistent positive predictor of diffusion intentions: adopting it, maintaining it, and talking with others about it. As expected by the DOI and the IMB, the social pressure created by a descriptive norm positively predicted intentions to adopt and maintain the innovation. Drawing upon sharing research, we argued that the descriptive norm may dampen future talk about the innovation, because it may no longer be seen as a novel, useful topic to discuss. As predicted, the results showed that as the descriptive norm increased, the intention to talk about the innovation decreased. These results provide broad support for integrating the DOI and the IMB to predict diffusion and for efforts to draw on other research to understand motivations for social diffusion.

  20. Effects of roll waves on annular flow heat transfer at horizontal condenser tube

    International Nuclear Information System (INIS)

    Kondo, Masaya; Nakamura, Hideo; Anoda, Yoshinari; Sakashita, Akihiro

    2002-01-01

    Heat removal characteristic of a horizontal in-tube condensation heat exchanger is under investigation to be used for a passive containment cooling system (PCCS) of a next generation-type BWR. Flow regime observed at the inlet of the condenser tube was annular flow, and the local heat transfer rate was ∼20% larger than the prediction by the Dobson-Chato correlation. Roll waves were found to appear on the liquid film in the annular flow. The measured local condensation heat transfer rate was being closely related to the roll waves frequency. Based on these observations, a model is proposed which predicts the condensation heat transfer coefficient for annular flows around the tube inlet. The proposed model predicts well the influences of pressure, local gas-phase velocity and film thickness. (author)

  1. Nitridation of SiO2 for surface passivation

    Science.gov (United States)

    Lai, S. K. C.

    1985-01-01

    An attempt is made to relate the electrical properties of silicon dioxide film to the process history. A model is proposed to explain some of the observed results. It is shown that with our present knowledge of the dielectric, silicon dioxide film shows a lot of promise for its use in surface passivation, both for its resistance to impurity diffusion and for its resistance to radiation damage effects.

  2. Optimization of the Refractive-Index Distribution of Graded-Index Polymer Optical Fiber by the Diffusion-Assisted Fabrication Process

    Science.gov (United States)

    Mukawa, Yoshiki; Kondo, Atsushi; Koike, Yasuhiro

    2012-04-01

    Graded-index polymer optical fiber (GI-POF) is a promising high-speed communication medium for very-short-reach networks, such as home or office networks. The refractive-index distribution of GI-POF needs to be accurately controlled to maximize the bandwidth. We attempted to control the refractive-index distribution by developing a simulation for dopant diffusion. In the rod-in-tube method, GI-POF with an optimal refractive-index distribution was obtained by adjusting the diffusion temperature and the diffusion time, whereas in the coextrusion process, GI-POF with an optimal refractive-index distribution was fabricated by controlling the length of the diffusion tube and the rate of discharge of polymer.

  3. Ellipsometric study of salt film formation during passivation

    Energy Technology Data Exchange (ETDEWEB)

    Wiechmann, Lee Warren [Univ. of Illinois, Urbana-Champaign, IL (United States)

    1979-01-01

    An experimental program was carried out to gain further understanding into the kinetics of salt film formation during repassivation of a corroding metal. Experiments were conducted using an ellipsometer to examine an electrode surface undergoing anodic dissolution and passivation. Because of the constraints of the ellipsometer, the sample had to be mounted vertically. As a consequence natural convection currents had to be taken into account. Calculation showed that the mass transfer limiting current was exceeded by transient currents, indicating that natural convection was present to an extent that could drastically change the system from the diffusion model that was proposed. It was determined that recessing the electrode led to minimized natural convective effects, and to uniform current distribution. The ellipsometer output provided times which were associated with precipitation and dissolution of the salt film. The experimental data was in good agreement with the mathematical model, further strengthening the precipitation-dissolution mechanism of passivation. Furthermore, a dimensionless model was shown capable of a first approximation of the passivation behavior of any metal. Investigations reported here were carried out on iron, nickel, and cobalt.

  4. Research in Hydrogen Passivation of Defects and Impurities in Silicon: Final Report, 2 May 2000-2 July 2003

    International Nuclear Information System (INIS)

    Ashok, S.

    2004-01-01

    This subcontract report describes hydrogenating Si samples by different methods such as low-energy implantation, electron cyclotron resonance (ECR) plasma, and thermal diffusion. The samples were provided through NREL. The experimental work, carried out at Penn State, involved the study of hydrogen interaction with defects, trapping, migration, and formation of complexes. The principal vehicle for the latter study was ion implantation, and the intent to understand mechanisms of defect passivation and activation by hydrogen. NREL implemented a study of hydrogen passivation of impurities and defects in silicon solar cells. The work included theoretical and experimental components performed at different universities. The theoretical studies consisted of the calculation of the structure and parameters related to hydrogen diffusion and interactions of hydrogen with transition-metal impurities in silicon. Experimental studies involved measurements of hydrogen and hydrogen-impurity complexes, and diffusion properties of various species of hydrogen in Si. The experimental work at Penn State included introduction of hydrogen in a variety of PV Si by ECR plasma, low-energy ion implantation, and thermal diffusion. The specific tasks were the evaluation of hydrogen interaction with defects engineered by ion implantation; defect passivation, activation, and migration in hydrogenated Si under thermal anneal; and electrical activity of hydrogen-impurity complexes. Electrical characterization entailed I-V and C-V measurements, spreading resistance, and deep-level transient spectroscopy (DLTS)

  5. Heat transfer behaviors in round tube with conical ring inserts

    International Nuclear Information System (INIS)

    Promvonge, P.

    2008-01-01

    To increase convection heat transfer in a uniform heat flux tube by a passive method, several conical rings used as turbulators are mounted over the test tube. The effects of the conical ring turbulator inserts on the heat transfer rate and friction factor are experimentally investigated in the present work. Conical rings with three different diameter ratios of the ring to tube diameter (d/D = 0.5, 0.6, 0.7) are introduced in the tests, and for each ratio, the rings are placed with three different arrangements (converging conical ring, referred to as CR array, diverging conical ring, DR array and converging-diverging conical ring, CDR array). In the experiment, cold air at ambient condition for Reynolds numbers in a range of 6000-26,000 is passed through the uniform heat flux circular tube. It is found that the ring to tube diameter ratio and the ring arrays provide a significant effect on the thermal performance of the test tube. The experimental results demonstrate that the use of conical ring inserts leads to a higher heat transfer rate than that of the plain surface tube, and the DR array yields a better heat transfer than the others. The results are also correlated in the form of Nusselt number as a function of Reynolds number, Prandtl number and diameter ratio. An augmentation of up to 197%, 333%, and 237% in Nusselt number is obtained in the turbulent flow for the CR, DR and CDR arrays, respectively, although the effect of using the conical ring causes a substantial increase in friction factor

  6. A passive radon dosemeter suitable for workplaces

    International Nuclear Information System (INIS)

    Orlando, C.; Orlando, P.; Patrizii, L.; Tommasino, L.; Tonnarini, S.; Trevisi, R.; Viola, P.

    2002-01-01

    The results obtained in different international intercomparisons on passive radon monitors have been analysed with the aim of identifying a suitable radon monitoring device for workplaces. From this analysis, the passive radon device, first developed for personal dosimetry in mines by the National Radiation Protection Board, UK (NRPB), has shown the most suitable set of characteristics. This radon monitor consists of a diffusion chamber, made of conductive plastic with less than 2 cm height, containing a CR-39 film (Columbia Resin 1939), as track detector. Radon detectors in workplaces may be exposed only during the working hours, thus requiring the storage of the detectors in low-radon zones when not exposed. This paper describes how this problem can be solved. Since track detectors are also efficient neutron dosemeters, care should be taken when radon monitors are used in workplaces, where they may be exposed to neutrons, such as on high altitude mountains, in the surroundings of high energy X ray facilities (where neutrons are produced by (gamma, n) reactions) or around high energy particle accelerators. To this end, the response of these passive radon monitors to high energy neutron fields has been investigated. (author)

  7. Design and fabrication of Sn-Nb-Cu-Ta-C composites for multifilamentary superconducting Nb/sub 3/Sn wires by using the modified tube technique

    Energy Technology Data Exchange (ETDEWEB)

    Glowacki, B A; Kosek, Z M

    1987-10-01

    The factors determining the design and fabrication of Nb/sub 3/Sn multifilamentary wires by the tube technique are discussed. New improved methods of obtaining multifilamentary Nb/sub 3/Sn wires on the basis of both external diffusion and internal diffusion processes, by using the tube technique in a simpler and less expensive way, are presented.

  8. Electrochemical characterization of anode passivation mechanisms in copper electrorefining

    Science.gov (United States)

    Moats, Michael Scott

    Anode passivation can decrease productivity and quality while increasing costs in modern copper electrorefineries. This investigation utilized electrochemical techniques to characterize the passivation behavior of anode samples from ten different operating companies. It is believed that this collection of anodes is the most diverse set ever to be assembled to study the effect of anode composition on passivation. Chronopotentiometry was the main electrochemical technique, employing a current density of 3820 A m-2. From statistical analysis of the passivation characteristics, increasing selenium, tellurium, silver, lead and nickel were shown to accelerate passivation. Arsenic was the only anode impurity that inhibited passivation. Oxygen was shown to accelerate passivation when increased from 500 to 1500 ppm, but further increases did not adversely affect passivation. Nine electrolyte variables were also examined. Increasing the copper, sulfuric acid or sulfate concentration of the electrolyte accelerated passivation. Arsenic in the electrolyte had no effect on passivation. Chloride and optimal concentrations of thiourea and glue delayed passivation. Linear sweep voltammetry, cyclic voltammetry, and impedance spectroscopy provided complementary information. Analysis of the electrochemical results led to the development of a unified passivation mechanism. Anode passivation results from the formation of inhibiting films. Careful examination of the potential details, especially those found in the oscillations just prior to passivation, demonstrated the importance of slimes, copper sulfate and copper oxide. Slimes confine dissolution to their pores and inhibit diffusion. This can lead to copper sulfate precipitation, which blocks more of the surface area. Copper oxide forms because of the resulting increase in potential at the interface between the copper sulfate and anode. Ultimate passivation occurs when the anode potential is high enough to stabilize the oxide film in

  9. Humidity Control System In The Neutron Detector Of Guide Tube

    International Nuclear Information System (INIS)

    Alibasya Harahap, Sentot

    2001-01-01

    The probable symptom neutron detector damage as cause decrease resistivity and corrosion in the electrical terminal, further more occasion to voltage failure and leak current in the isolation. The prevent of voltage failure in detector a needed humidity controller's with dry air supply to guide tube with 2 kg/cm exp.2 air pressure and 7 l/min, air flow as soon as continuity dryer process in the guide tube. Reactor shutdown and operation condition of diffusion rate is 0,476 cm exp.3/year and 6,46 cm exp.3/year

  10. Dynamics of miscible displacements in round tubes

    Energy Technology Data Exchange (ETDEWEB)

    Meiburg, E.; Maxworthy, T.; Chen, C.Y. [Univ. of Southern California, Los Angeles, CA (United States); Petitjeans, P. [Ecole Superieure de Physique et de Chimie Industrielles, Paris (France)

    1995-12-31

    A combined experimental and numerical investigation of miscible two-phase flow in a capillary tube is reported. The fraction of fluid left behind on the wall is obtained as a function of the Peclet, Atwood, and Froude numbers. Scaling arguments are presented for two distinct flow regimes, dominated by diffusion and convection, respectively. In the latter one, an effective surface tension value can be estimated.

  11. Resolvent-based modeling of passive scalar dynamics in wall-bounded turbulence

    Science.gov (United States)

    Dawson, Scott; Saxton-Fox, Theresa; McKeon, Beverley

    2017-11-01

    The resolvent formulation of the Navier-Stokes equations expresses the system state as the output of a linear (resolvent) operator acting upon a nonlinear forcing. Previous studies have demonstrated that a low-rank approximation of this linear operator predicts many known features of incompressible wall-bounded turbulence. In this work, this resolvent model for wall-bounded turbulence is extended to include a passive scalar field. This formulation allows for a number of additional simplifications that reduce model complexity. Firstly, it is shown that the effect of changing scalar diffusivity can be approximated through a transformation of spatial wavenumbers and temporal frequencies. Secondly, passive scalar dynamics may be studied through the low-rank approximation of a passive scalar resolvent operator, which is decoupled from velocity response modes. Thirdly, this passive scalar resolvent operator is amenable to approximation by semi-analytic methods. We investigate the extent to which this resulting hierarchy of models can describe and predict passive scalar dynamics and statistics in wall-bounded turbulence. The support of AFOSR under Grant Numbers FA9550-16-1-0232 and FA9550-16-1-0361 is gratefully acknowledged.

  12. SeZnSb alloy and its nano tubes, graphene composites properties

    Directory of Open Access Journals (Sweden)

    Abhay Kumar Singh

    2013-04-01

    Full Text Available Composite can alter the individual element physical property, could be useful to define the specific use of the material. Therefore, work demonstrates the synthesis of a new composition Se96-Zn2-Sb2 and its composites with 0.05% multi-walled carbon nano tubes and 0.05% bilayer graphene, in the glassy form. The diffused amorphous structure of the multi walled carbon nano tubes and bilayer gaphene in the Se96-Zn2-Sb2 alloy have been analyzed by using the Raman, X-ray photoluminescence spectroscopy, Furrier transmission infrared spectra, photoluminescence, UV/visible absorption spectroscopic measurements. The diffused prime Raman bands (G and D have been appeared for the multi walled carbon nano tubes and graphene composites, while the X-ray photoluminescence core energy levels peak shifts have been observed for the composite materials. Subsequently the photoluminescence property at room temperature and a drastic enhancement (upto 80% in infrared transmission percentage has been obtained for the bilayer graphene composite, along with optical energy band gaps for these materials have been evaluated 1.37, 1.39 and 1.41 eV.

  13. Comprehensive safety analysis code system for nuclear fusion reactors III: Ex-vessel LOCA analyses considering passive safety

    International Nuclear Information System (INIS)

    Honda, T.; Okazaki, T.; Maki, K.; Uda, T.; Seki, Y.; Aoki, I.; Kunugi, T.

    1996-01-01

    Ex-vessel loss-of-coolant accidents (LOCAs) in a fusion reactor have been analyzed to investigate the possibility of passive plasma shutdown. For this purpose, a hybrid code of the plasma dynamics and thermal characteristics of the reactor structures, which has been modified to include the impurity emission from plasma-facing components (PFCs), has been developed. Ex-vessel LOCAs of the cooling system during the ignition operation in the International Thermonuclear Experimental Reactor (ITER), in which graphite PFCs were employed in conceptual design activity, were assumed. When double-ended break occurs at the cold leg of the divertor cooling system, the copper cooling tube begins to melt within 3 s after the LOCA, even though the plasma is passively shut down at nearly 4 s. An active plasma shutdown system will be needed for such rapid transient accidents. On the other hand, when a small (1%) break LOCA occurs there, the plasma is passively shut down at nearly 36 s, which happens before the copper cooling tube begins to melt. When the double-ended break LOCA occurs at the cold leg of the first-wall cooling system, there is enough time (nearly 100 s) to shut down the plasma with a controllable method before the reactor structures are damaged. 21 refs., 8 figs

  14. Effects of Angle of Rotation on Pool Boiling Heat Transfer of V-shape Tube Bundle

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Myeong-Gie [Andong National University, Andong (Korea, Republic of)

    2016-10-15

    The most important facility for the systems is a passive heat exchanger that transfers core decay heat to the cold water in a water storage tank under atmospheric pressure. Since the space for the installation of the heat exchanger is usually limited, developing more efficient heat exchangers is important. In general, pool boiling is generated on the surface of the heat exchanging tube. The major design parameter of the heat exchanger is a tube arrangement. The upper tube is affected by the lower tube and the enhancement of the heat transfer on the upper tube is estimated by the bundle effect. Since heat transfer is related to the conditions of a tube surface, bundle geometries, and a liquid type, lots of studies have been carried out for the combinations of those parameters. An experimental study was performed to investigate the effects of the angle of rotation on pool boiling heat transfer of a V-shape tube bundle. For the test, two smooth stainless steel tubes of 19 mm outside diameter and the water at atmospheric pressure were used. The enhancement of the heat transfer is clearly observed when the angle becomes to 90° where the upper tube has the maximum region of influence by the lower tube. The convective flow and liquid agitation enhance heat transfer while the coalescence of the bubbles deteriorates heat transfer.

  15. Average Natural Convective Heat Transfer of Air-cooled Condensing Heat Exchanger of Emergency Cooldown Tank - Effect of Tube Banks

    International Nuclear Information System (INIS)

    Huh, Seon Jeong; Lee, Hee Joon; Kim, Myoung Jun; Moon, Joo Hyung; Bae, Youngmin; Kim, Young-In

    2016-01-01

    Recently emergency cooldown tank(ECT) is a great concern of passive cooling system for the safety of nuclear reactor. After the operation of a conventional passive cooling system for an extended period, however, the water level falls as a result of the evaporation from the ECT, as steam is emitted from the open top of the tank. In this study, the effect of heat transfer area at the air cooled condensing heat exchanger was investigated by changing 5×5 tube banks into 4×4 and 3×3. Moreover, each of air-side natural convective heat transfer coefficient of tube banks was compared to existing correlations. This study presents the effect of heat transfer area at air-cooled condensing heat exchanger. As heat transfer area decreased, the temperature of outlet increased. In other words, the cooling performance got lower with the decrease of heat transfer area. In addition, the average natural convective heat transfer coefficient was 15.3 W/m"2/K from the 4×4 tube banks, and 4.92 W/m"2/K from the 3×3 tube banks, which had quite a large error more than 46% especially with the value of 4×4 tube banks compared to the value from correlation equation. Therefore, according to this result, it is needed to measure the local heat transfer coefficient of vertical cylinder more elaborately in further study

  16. Average Natural Convective Heat Transfer of Air-cooled Condensing Heat Exchanger of Emergency Cooldown Tank - Effect of Tube Banks

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Seon Jeong; Lee, Hee Joon [Kookmin University, Seoul (Korea, Republic of); Kim, Myoung Jun; Moon, Joo Hyung; Bae, Youngmin; Kim, Young-In [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    Recently emergency cooldown tank(ECT) is a great concern of passive cooling system for the safety of nuclear reactor. After the operation of a conventional passive cooling system for an extended period, however, the water level falls as a result of the evaporation from the ECT, as steam is emitted from the open top of the tank. In this study, the effect of heat transfer area at the air cooled condensing heat exchanger was investigated by changing 5×5 tube banks into 4×4 and 3×3. Moreover, each of air-side natural convective heat transfer coefficient of tube banks was compared to existing correlations. This study presents the effect of heat transfer area at air-cooled condensing heat exchanger. As heat transfer area decreased, the temperature of outlet increased. In other words, the cooling performance got lower with the decrease of heat transfer area. In addition, the average natural convective heat transfer coefficient was 15.3 W/m{sup 2}/K from the 4×4 tube banks, and 4.92 W/m{sup 2}/K from the 3×3 tube banks, which had quite a large error more than 46% especially with the value of 4×4 tube banks compared to the value from correlation equation. Therefore, according to this result, it is needed to measure the local heat transfer coefficient of vertical cylinder more elaborately in further study.

  17. The vascular anatomy of the eustachian tube in the guinea pig.

    Science.gov (United States)

    Voorhees, R L

    1976-08-01

    Vascular anatomy of the eustachian tube has received little attention in the world's medical literature. Forty guinea pigs were perfused with Berlin Blue as a contrast medium and the eustachian tube microvascular architecture visualized through surface preparations. A diffuse, dense two-layered capillary network was found which followed the distribution of mucous glands. Five animals suffering from suppurative otitis media showed marked capillary congestion with increased vessel to tissue density. Relationships to gross arterial and venous supply as found in the human are discussed.

  18. Li4SiO4-Based Artificial Passivation Thin Film for Improving Interfacial Stability of Li Metal Anodes.

    Science.gov (United States)

    Kim, Ji Young; Kim, A-Young; Liu, Guicheng; Woo, Jae-Young; Kim, Hansung; Lee, Joong Kee

    2018-03-14

    An amorphous SiO 2 (a-SiO 2 ) thin film was developed as an artificial passivation layer to stabilize Li metal anodes during electrochemical reactions. The thin film was prepared using an electron cyclotron resonance-chemical vapor deposition apparatus. The obtained passivation layer has a hierarchical structure, which is composed of lithium silicide, lithiated silicon oxide, and a-SiO 2 . The thickness of the a-SiO 2 passivation layer could be varied by changing the processing time, whereas that of the lithium silicide and lithiated silicon oxide layers was almost constant. During cycling, the surface of the a-SiO 2 passivation layer is converted into lithium silicate (Li 4 SiO 4 ), and the portion of Li 4 SiO 4 depends on the thickness of a-SiO 2 . A minimum overpotential of 21.7 mV was observed at the Li metal electrode at a current density of 3 mA cm -2 with flat voltage profiles, when an a-SiO 2 passivation layer of 92.5 nm was used. The Li metal with this optimized thin passivation layer also showed the lowest charge-transfer resistance (3.948 Ω cm) and the highest Li ion diffusivity (7.06 × 10 -14 cm 2 s -1 ) after cycling in a Li-S battery. The existence of the Li 4 SiO 4 artificial passivation layer prevents the corrosion of Li metal by suppressing Li dendritic growth and improving the ionic conductivity, which contribute to the low charge-transfer resistance and high Li ion diffusivity of the electrode.

  19. Numerical study of chemical reactions in a surface microdischarge tube with mist flow based on experiment

    International Nuclear Information System (INIS)

    Shibata, T; Nishiyama, H

    2014-01-01

    Recently, a water treatment method of spraying solution into a discharge region has been developed and shows high energy efficiency. In this study, a simulation model of a water treatment method using a surface microdischarge (SMD) tube with mist flow is proposed for further understanding the detailed chemical reactions. Our model has three phases (plasma, gas and liquid) and three simulation steps. The carrier gas is humid air including 2% or 3% water vapour. The chemical species diffusion characteristics in the SMD tube and the concentrations in a droplet are clarified in a wide pH interval. The simulation results show that the chemical species generated on the SMD tube inner wall are diffused to the central axis and dissolved into fine droplets. Especially, OH radicals dissolve into droplets a few mm away from the SMD tube wall because of acidification of the droplets. Furthermore, the hydrogen peroxide density, which is the most important indicator of a radical reaction in water, is influenced by the initial solution pH. This pH dependence results from ozone self-decomposition in water. (paper)

  20. Numerical study of chemical reactions in a surface microdischarge tube with mist flow based on experiment

    Science.gov (United States)

    Shibata, T.; Nishiyama, H.

    2014-03-01

    Recently, a water treatment method of spraying solution into a discharge region has been developed and shows high energy efficiency. In this study, a simulation model of a water treatment method using a surface microdischarge (SMD) tube with mist flow is proposed for further understanding the detailed chemical reactions. Our model has three phases (plasma, gas and liquid) and three simulation steps. The carrier gas is humid air including 2% or 3% water vapour. The chemical species diffusion characteristics in the SMD tube and the concentrations in a droplet are clarified in a wide pH interval. The simulation results show that the chemical species generated on the SMD tube inner wall are diffused to the central axis and dissolved into fine droplets. Especially, OH radicals dissolve into droplets a few mm away from the SMD tube wall because of acidification of the droplets. Furthermore, the hydrogen peroxide density, which is the most important indicator of a radical reaction in water, is influenced by the initial solution pH. This pH dependence results from ozone self-decomposition in water.

  1. Passive Frequency Selective Surface Array as a Diffuser for Destroying Millimeter Wave Coherence

    Directory of Open Access Journals (Sweden)

    Saiful Islam

    2008-01-01

    Full Text Available This paper presents the design, construction, and testing of grounded frequency selective surface (FSS array as a diffuser for destroying millimeter wave coherence which is used to eliminate speckle in active millimeter wave imaging. To create stochastically independent illumination patterns, we proposed a diffuser based on random-phase distributions obtained by changing the incident frequency. The random-phase diffuser was obtained by mixing up the phase relations between the cells of a deterministic function (e.g., beam splitter. The slot length of FSS is the main design parameter used to optimize the phase shifting properties of the array. The critical parameters of the diffuser array design, such as phase relation with slot lengths, losses, and bandwidth, are discussed. We designed the FSS arrays with finite integral technique (FIT, fabricated by etching technique, and characterized the S-parameters with a free-space MVNA, and measured the radiation patterns with a BWO in motorized setup.

  2. Indoor radon level measurements in Iran using AEOI passive dosimeters

    International Nuclear Information System (INIS)

    Sohrabi, M.; Solaymanian, A.R.

    1988-01-01

    A passive radon diffusion dosimeter was developed at the RPD of AEOI for nationwide indoor radon level measurements. Several parameters of the dosimeter were studied. Radon levels were determined in about 250 houses in Ramsar (a high natural radiation area), Tehran, Babolsar and Gonabad. In this paper, the results of some dosimeter parameters as well as radon levels in indoor air are reported

  3. Offset-gated poly-Si TFTs using in-situ fluorine passivation and excimer laser doping

    International Nuclear Information System (INIS)

    Jung, Sang Hoon; Kim, Cheon Hong; Yoo, Juhn Suk; Han, Min Koo

    2000-01-01

    A new low-temperature poly-Si thin film transistor (TFT) fabrication method employing in-situ fluorine passivation and excimer-laser doping is proposed to fabricate offset-gated poly-Si TFTs. In the new process, the crystallization, the in-situ fluorine passivation of the active layer, and the doping of the source/drain region are performed simultaneously with only one step of excimer laser annealing while the conventional fabrication method requires two laser annealing steps. Employing phosphosilicate glass (PSG) films as a diffusion source, we successfully accomplished excimer laser doping. The subthreshold and the on-state characteristics of the device with in-situ fluorine passivation were considerably improved. This improvement was due to the fluorine passivation effects, which cured dangling bonds and strained bonds in the poly-Si channel, the offset region, and the SiO 2 /poly-Si interface

  4. Offset-gated poly-Si TFTs using in-situ fluorine passivation and excimer laser doping

    CERN Document Server

    Jung, S H; Yoo, J S; Han, M K

    2000-01-01

    A new low-temperature poly-Si thin film transistor (TFT) fabrication method employing in-situ fluorine passivation and excimer-laser doping is proposed to fabricate offset-gated poly-Si TFTs. In the new process, the crystallization, the in-situ fluorine passivation of the active layer, and the doping of the source/drain region are performed simultaneously with only one step of excimer laser annealing while the conventional fabrication method requires two laser annealing steps. Employing phosphosilicate glass (PSG) films as a diffusion source, we successfully accomplished excimer laser doping. The subthreshold and the on-state characteristics of the device with in-situ fluorine passivation were considerably improved. This improvement was due to the fluorine passivation effects, which cured dangling bonds and strained bonds in the poly-Si channel, the offset region, and the SiO sub 2 /poly-Si interface.

  5. Passive sampling methods for contaminated sediments: Scientific rationale supporting use of freely dissolved concentrations

    DEFF Research Database (Denmark)

    Mayer, Philipp; Parkerton, Thomas F.; Adams, Rachel G.

    2014-01-01

    Passive sampling methods (PSMs) allow the quantification of the freely dissolved concentration (Cfree ) of an organic contaminant even in complex matrices such as sediments. Cfree is directly related to a contaminant's chemical activity, which drives spontaneous processes including diffusive upta...

  6. Ocular blood flow decreases during passive heat stress in resting humans.

    Science.gov (United States)

    Ikemura, Tsukasa; Miyaji, Akane; Kashima, Hideaki; Yamaguchi, Yuji; Hayashi, Naoyuki

    2013-12-06

    Heat stress induces various physiological changes and so could influence ocular circulation. This study examined the effect of heat stress on ocular blood flow. Ocular blood flow, end-tidal carbon dioxide (P(ET)CO2) and blood pressure were measured for 12 healthy subjects wearing water-perfused tube-lined suits under two conditions of water circulation: (1) at 35 °C (normothermia) for 30 min and (2) at 50 °C for 90 min (passive heat stress). The blood-flow velocities in the superior temporal retinal arteriole (STRA), superior nasal retinal arteriole (SNRA), and the retinal and choroidal vessels (RCV) were measured using laser-speckle flowgraphy. Blood flow in the STRA and SNRA was calculated from the integral of a cross-sectional map of blood velocity. PETCO2 was clamped at the normothermia level by adding 5% CO2 to the inspired gas. Passive heat stress had no effect on the subjects' blood pressures. The blood-flow velocity in the RCV was significantly lower after 30, 60 and 90 min of passive heat stress than the normothermic level, with a peak decrease of 18 ± 3% (mean ± SE) at 90 min. Blood flow in the STRA and SNRA decreased significantly after 90 min of passive heat stress conditions, with peak decreases of 14 ± 3% and 14 ± 4%, respectively. The findings of this study suggest that passive heat stress decreases ocular blood flow irrespective of the blood pressure or arterial partial pressure of CO2.

  7. Pesticide impact on aquatic invertebrates identified with Chemcatcher® passive samplers and the SPEAR(pesticides) index.

    Science.gov (United States)

    Münze, Ronald; Orlinskiy, Polina; Gunold, Roman; Paschke, Albrecht; Kaske, Oliver; Beketov, Mikhail A; Hundt, Matthias; Bauer, Coretta; Schüürmann, Gerrit; Möder, Monika; Liess, Matthias

    2015-12-15

    Pesticides negatively affect biodiversity and ecosystem function in aquatic environments. In the present study, we investigated the effects of pesticides on stream macroinvertebrates at 19 sites in a rural area dominated by forest cover and arable land in Central Germany. Pesticide exposure was quantified with Chemcatcher® passive samplers equipped with a diffusion-limiting membrane. Ecological effects on macroinvertebrate communities and on the ecosystem function detritus breakdown were identified using the indicator system SPEARpesticides and the leaf litter degradation rates, respectively. A decrease in the abundance of pesticide-vulnerable taxa and a reduction in leaf litter decomposition rates were observed at sites contaminated with the banned insecticide Carbofuran (Toxic Units≥-2.8), confirming the effect thresholds from previous studies. The results show that Chemcatcher® passive samplers with a diffusion-limiting membrane reliably detect ecologically relevant pesticide pollution, and we suggest Chemcatcher® passive samplers and SPEARpesticides as a promising combination to assess pesticide exposure and effects in rivers and streams. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Thermal diffusion of hydrogen in zircaloy-2 containing hydrogen beyond terminal solid solubility

    International Nuclear Information System (INIS)

    Maki, Hideo; Sato, Masao.

    1975-01-01

    The thermal diffusion of hydrogen is one of causes of uneven hydride precipitation in zircaloy fuel cladding tubes that are used in water reactors. In the diffusion model of hydrogen in zircaloy, the effects of the hydride on the diffusibility of hydrogen has been regarded as negligibly small in comparison with that of hydrogen dissolved in the matrix. Contrary to the indications given by this model, phenomena are often encountered that cannot be explained unless hydride platelets have considerable ostensible diffusibility in zircaloy. In order to determine quantitatively the diffusion characteristics of hydrogen in zircaloy, a thermal diffusion experiment was performed with zircaloy-2 fuel cladding tubes containing hydrogen beyond the terminal solid solubility. In this experiment, a temperature difference of 20 0 --30 0 C was applied between the inside and outside surfaces of the specimen in a thermal simulator. To explain the experimental results, a modified diffusion model is presented, in which the effects of stress are introduced into Markowitz's model with the diffusion of hydrogen in the hydride taken into account. The diffusion equation derived from this model can be written in a form that ostensibly represents direct diffusion of hydride in zircaloy. The apparent diffusion characteristics of the hydride at around 300 0 C are Dsub(p)=2.3x10 5 exp(-32,000/RT), (where R:gas constant, T:temperature) and the apparent heat of transport Qsub(p) =-60,000 cal/mol. The modified diffusion model well explains the experimental results in such respects as reaches a steady state after several hours. (auth.)

  9. Personal child and mother carbon monoxide exposures and kitchen levels: methods and results from a randomized trial of woodfired chimney cookstoves in Guatemala (RESPIRE).

    Science.gov (United States)

    Smith, Kirk R; McCracken, John P; Thompson, Lisa; Edwards, Rufus; Shields, Kyra N; Canuz, Eduardo; Bruce, Nigel

    2010-07-01

    During the first randomized intervention trial (RESPIRE: Randomized Exposure Study of Pollution Indoors and Respiratory Effects) in air pollution epidemiology, we pioneered application of passive carbon monoxide (CO) diffusion tubes to measure long-term personal exposures to woodsmoke. Here we report on the protocols and validations of the method, trends in personal exposure for mothers and their young children, and the efficacy of the introduced improved chimney stove in reducing personal exposures and kitchen concentrations. Passive diffusion tubes originally developed for industrial hygiene applications were deployed on a quarterly basis to measure 48-hour integrated personal carbon monoxide exposures among 515 children 0-18 months of age and 532 mothers aged 15-55 years and area samples in a subsample of 77 kitchens, in households randomized into control and intervention groups. Instrument comparisons among types of passive diffusion tubes and against a continuous electrochemical CO monitor indicated that tubes responded nonlinearly to CO, and regression calibration was used to reduce this bias. Before stove introduction, the baseline arithmetic (geometric) mean 48-h child (n=270), mother (n=529) and kitchen (n=65) levels were, respectively, 3.4 (2.8), 3.4 (2.8) and 10.2 (8.4) p.p.m. The between-group analysis of the 3355 post-baseline measurements found CO levels to be significantly lower among the intervention group during the trial period: kitchen levels: -90%; mothers: -61%; and children: -52% in geometric means. No significant deterioration in stove effect was observed over the 18 months of surveillance. The reliability of these findings is strengthened by the large sample size made feasible by these unobtrusive and inexpensive tubes, measurement error reduction through instrument calibration, and a randomized, longitudinal study design. These results from the first randomized trial of improved household energy technology in a developing country and

  10. ToF-SIMS characterization of passivation layers of tubes of steam generators Alloy 690 for the nuclear industry: contribution to the understanding of the mechanisms

    International Nuclear Information System (INIS)

    Mazenc, Arnaud

    2013-01-01

    The nickel release in solution is responsible for part of the radioactive contamination of the primary circuit of the Pressurized Water Reactor (PWR) nuclear power plants. For safety issues, it is very important to limit this contamination. The oxide film formed on the steam generators (SG) tubes surface (in Alloy 690) plays an important role as diffusion barrier in the limitation of this phenomenon. It appears paramount to well control the phenomena of oxide film formation, which themselves are strongly impacted by the materials parameters of the tube (grain size, work hardening, etc.), as well as by the chemical conditions of the primary water (temperature, pH, etc.). The objective of this work is both to finely characterize oxide layer formed on SG tubes and to establish a relationship between corrosion and release. This study was carried out in three parts. The first part consists in the development of an extensive use of the Time of Flight Secondary Ion Mass Spectrometry (ToFSIMS) to characterize the oxide films. This methodology is based on elaboration of reference oxide films by oxidation of metallic samples. The second part of this work is dedicated to the investigation of the influence of three material parameters on the composition and structure of the oxide layer: crystallographic orientation, grain size, and content of chromium intergranular carbide precipitates. Considerable effects are observed for the crystallographic orientation as well as content of precipitates, while the grain size has no influence. Lastly, the last part presents simultaneously the influence of the physicochemical conditions of the primary water on the kinetics of release and the nature of the oxide layer. The temperature and the pH tend to be key parameters influencing corrosion and the release. (author)

  11. A convenient method for calculation of ionic diffusion coefficients for accurate selected ion flow tube mass spectrometry, SIFT-MS

    Science.gov (United States)

    Dryahina, K.; Spanel, P.

    2005-07-01

    A method to calculate diffusion coefficients of ions important for the selected ion flow tube mass spectrometry, SIFT-MS, is presented. The ions, on which this method is demonstrated, include the SIFT-MS precursors H3O+(H2O)0,1,2,3, NO.+(H2O)0,1,2 and O2+ and the product ions relevant to analysis of breath trace metabolites ammonia (NH3+(H2O)0,1,2, NH4+(H2O)0,1,2), acetaldehyde (C2H4OH+(H2O)0,1,2), acetone (CH3CO+, (CH3)2CO+, (CH3)2COH+(H2O)0,1, (CH3)2CO.NO+), ethanol (C2H5OHH+(H2O)0,1,2) and isoprene (C5H7+, C5H8+, C5H9+). Theoretical model of the (12, 4) potential for interaction between the ions and the helium atoms is used, with the repulsive part approximated by the mean hard-sphere cross section and the attractive part describing ion-induced dipole interactions. The reduced zero-field mobilities at 300 K are calculated using the Viehland and Mason theory [L.A. Viehland, S.L. Lin, E.A. Mason, At. Data Nucl. Data Tables, 60 (1995) 37-95], parameterised by a simple formula as a function of the mean hard-sphere cross section, and converted to diffusion coefficients using the Einstein relation. The method is tested on a set of experimental data for simple ions and cluster ions.

  12. Design optimization of hydraulic turbine draft tube based on CFD and DOE method

    Science.gov (United States)

    Nam, Mun chol; Dechun, Ba; Xiangji, Yue; Mingri, Jin

    2018-03-01

    In order to improve performance of the hydraulic turbine draft tube in its design process, the optimization for draft tube is performed based on multi-disciplinary collaborative design optimization platform by combining the computation fluid dynamic (CFD) and the design of experiment (DOE) in this paper. The geometrical design variables are considered as the median section in the draft tube and the cross section in its exit diffuser and objective function is to maximize the pressure recovery factor (Cp). Sample matrixes required for the shape optimization of the draft tube are generated by optimal Latin hypercube (OLH) method of the DOE technique and their performances are evaluated through computational fluid dynamic (CFD) numerical simulation. Subsequently the main effect analysis and the sensitivity analysis of the geometrical parameters of the draft tube are accomplished. Then, the design optimization of the geometrical design variables is determined using the response surface method. The optimization result of the draft tube shows a marked performance improvement over the original.

  13. Coiled Tube Gas Heaters For Nuclear Gas-Brayton Power Conversion

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, Per F.

    2018-03-31

    CTGHs, using methods similar to earlier UCB multi-scale models for PCHEs, which will enable optimization of CTGH designs with respect to the number of manifold pipes, S-CO2 and sodium circulating power, and other design parameters. CTGHs are relatively novel because the tubes loaded in compression as well as the manifold pipes which form the tube sheets. The second major goal of the experimental and modeling effort was to optimize the assembly and heat treatment of the tube-to-tubesheet joints, using a novel tapered joint configuration, and to develop diffusion-bonded joints with high shear strength and creep resistance, as has been done in other applications for tapered plugs. The project would also conduct creep testing of these tubesheet joints in pressurized furnaces under prototypical conditions of stress and temperature, however this was not feasible due to numerous hinderances. Detailed microstructural investigations was conducted on the diffusion bond interface, while the bond strength was evaluated by tensile testing. The mechanical testing quantified the overall strength of the bond and measured the pull out force as well as long term behavior, which complemented the microstructural analysis and gave a complete understanding of the diffusion bond.

  14. Assessment of horizontal in-tube condensation models using MARS code. Part I: Stratified flow condensation

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Seong-Su [Department of Engineering Project, FNC Technology Co., Ltd., Bldg. 135-308, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Department of Nuclear Engineering, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Hong, Soon-Joon, E-mail: sjhong90@fnctech.com [Department of Engineering Project, FNC Technology Co., Ltd., Bldg. 135-308, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Park, Ju-Yeop; Seul, Kwang-Won [Korea Institute of Nuclear Safety, 19 Kuseong-dong, Yuseong-gu, Daejon (Korea, Republic of); Park, Goon-Cherl [Department of Nuclear Engineering, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer This study collected 11 horizontal in-tube condensation models for stratified flow. Black-Right-Pointing-Pointer This study assessed the predictive capability of the models for steam condensation. Black-Right-Pointing-Pointer Purdue-PCCS experiments were simulated using MARS code incorporated with models. Black-Right-Pointing-Pointer Cavallini et al. (2006) model predicts well the data for stratified flow condition. Black-Right-Pointing-Pointer Results of this study can be used to improve condensation model in RELAP5 or MARS. - Abstract: The accurate prediction of the horizontal in-tube condensation heat transfer is a primary concern in the optimum design and safety analysis of horizontal heat exchangers of passive safety systems such as the passive containment cooling system (PCCS), the emergency condenser system (ECS) and the passive auxiliary feed-water system (PAFS). It is essential to analyze and assess the predictive capability of the previous horizontal in-tube condensation models for each flow regime using various experimental data. This study assessed totally 11 condensation models for the stratified flow, one of the main flow regime encountered in the horizontal condenser, with the heat transfer data from the Purdue-PCCS experiment using the multi-dimensional analysis of reactor safety (MARS) code. From the assessments, it was found that the models by Akers and Rosson, Chato, Tandon et al., Sweeney and Chato, and Cavallini et al. (2002) under-predicted the data in the main condensation heat transfer region, on the contrary to this, the models by Rosson and Meyers, Jaster and Kosky, Fujii, Dobson and Chato, and Thome et al. similarly- or over-predicted the data, and especially, Cavallini et al. (2006) model shows good predictive capability for all test conditions. The results of this study can be used importantly to improve the condensation models in thermal hydraulic code, such as RELAP5 or MARS code.

  15. Modeling of Passive Constrained Layer Damping as Applied to a Gun Tube

    Directory of Open Access Journals (Sweden)

    Margaret Z. Kiehl

    2001-01-01

    Full Text Available We study the damping effects of a cantilever beam system consisting of a gun tube wrapped with a constrained viscoelastic polymer on terrain induced vibrations. A time domain solution to the forced motion of this system is developed using the GHM (Golla-Hughes-McTavish method to incorporate the viscoelastic properties of the polymer. An impulse load is applied at the free end and the tip deflection of the cantilevered beam system is determined. The resulting GHM equations are then solved in MATLAB by transformation to the state-space domain.

  16. Development and test evaluation of duplex steam reformer tube

    International Nuclear Information System (INIS)

    Allen, D.C.; Meyer, D.J.; Pflasterer, G.R.

    1980-01-01

    For HTR applications involving a steam reformer (SR), it is uncertain whether an intermediate heat exchanger (IHX) is required. There are several system configurations that could be developed for the application of nuclear heat using the steam reformer reaction. The considerations (advantages vs. disadvantages) for each of the system configurations are summarized. The approach that technically and economically appears to be the most attractive, in studies conducted by General Electric, combines the SR process heat exchanger and the IHX in a single component using a duplex tube. A central question concerning the duplex tube concept is whether the design would provide adequate leak monitoring capability and significant reduction in tritium and hydrogen diffusion, while introducing only a small increase in overall temperature difference from the helium to the process gas. A cooperative GE-KFA effort was undertaken to develop, fabricate, test, and evaluate a duplex steam reformer tube. GE was responsible for the development and fabrication of the tube, and KFA was responsible for testing the tube in the EVA I facility at Juelich. Both GE and KFA are evaluating the thermochemical and metallurgical test data. Actual fabrication of the tube was performed by Foster-Wheeler in accordance with the GE design. This paper reviews the highlights of the fabrication development and preliminary evaluation of the test data

  17. Hydrogen passivation of titanium impurities in silicon: Effect of doping conditions

    Energy Technology Data Exchange (ETDEWEB)

    Santos, P.; Coutinho, J., E-mail: jose.coutinho@ua.pt; Torres, V. J. B. [Department of Physics and I3N, University of Aveiro, Campus Santiago, 3810-193 Aveiro (Portugal); Rayson, M. J. [Department of Chemistry, University of Surrey, Guildford GU2 7XH (United Kingdom); Briddon, P. R. [School of Electrical, Electronic and Computer Engineering, Newcastle University, Newcastle Upon Tyne NE1 7RU (United Kingdom)

    2014-07-21

    While the contamination of solar silicon by fast diffusing transition metals can be now limited through gettering, much attention has been drawn to the slow diffusing species, especially the early 3d and 4d elements. To some extent, hydrogen passivation has been successful in healing many deep centers, including transition metals in Si. Recent deep-level transient spectroscopy (DLTS) measurements concerning hydrogen passivation of Ti revealed the existence of at least four electrical levels related to Ti{sub i}H{sub n} in the upper-half of the gap. These findings challenge the existing models regarding both the current level assignment as well as the structure/species involved in the defects. We revisit this problem by means of density functional calculations and find that progressive hydrogenation of interstitial Ti is thermodynamically stable in intrinsic and n-doped Si. Full passivation may not be possible to attain in p-type Si as Ti{sub i}H{sub 3} and Ti{sub i}H{sub 4} are metastable against dissociation and release of bond-centered protons. All DLTS electron traps are assigned, namely, E40′ to Ti{sub i}H(-/0), E170′ to Ti{sub i}H{sub 3}(0/+), E(270) to Ti{sub i}H{sub 2}(0/+), and E170 to Ti{sub i}H(0/+) transitions. Ti{sub i}H{sub 4} is confirmed to be electrically inert.

  18. Passive decay heat removal by natural circulation

    International Nuclear Information System (INIS)

    Vijayan, P.K.; Venkat Raj, V.; Kakodkar, A.; Mehta, S.K.

    1990-01-01

    The standardised 235 MWe PHWRs being built in India are the pressure tube type, heavy water moderated, heavy water cooled and natural uranium fuelled reactors. Several passive safety features are incorporated in these reactors. These include: (1) Containment pressure reduction and fission product trapping with the help of suppression pool following LOCA. (2) Emergency coolant injection by means of accumulators. (3) Large heat sink provided by the low temperature moderator under accident conditions. (4) Low excess reactivity, through the use of natural uranium fuel and on power fuelling. (5) Residual heat removal by means of natural circulation, etc. of which the last item is the subject matter of this report. (author). 8 refs, 10 figs

  19. Fundamental studies of passivity and passivity breakdown

    International Nuclear Information System (INIS)

    Macdonald, D.D.; Urquidi-Macdonald, M.; Song, H.; Biaggio-Rocha, S.; Searson, P.

    1991-11-01

    This report summarizes the findings of our fundamental research program on passivity and passivity breakdown. During the past three and one half years in this program (including the three year incrementally-funded grant prior to the present grant), we developed and experimentally tested various physical models for the growth and breakdown of passive films on metal surfaces. These models belong to a general class termed ''point defects models'' (PDMs), in which the growth and breakdown of passive films are described in terms of the movement of anion and cation vacancies

  20. Passive behavior of a bulk nanostructured 316L austenitic stainless steel consisting of nanometer-sized grains with embedded nano-twin bundles

    International Nuclear Information System (INIS)

    Li, Tianshu; Liu, Li; Zhang, Bin; Li, Ying; Yan, Fengkai; Tao, Nairong; Wang, Fuhui

    2014-01-01

    Highlights: • Nanometer-grains (NG) and bundles of nano-twins (NT) is synthesized in 316L. • (NG + NT) and NT enhance the concentration of active Fe Fe in the passive film. • (NG + NT) and NT enhance the passive ability. • A Cr 0 -enriched layer forms at the passive film/metal interface. - Abstract: The passive behavior of a bulk nanostructured 316L austenitic stainless steel consisting of nanometer-sized grains (NG) and nano-twin bundles (NT) are investigated. The electrochemical results indicate that the spontaneous passivation ability and growth rate of passive film are improved. The X-ray photoelectron spectroscopy (XPS) shows that a Cr 0 -enriched layer forms at the passive film/metal interface. More nucleation sites afforded by the nanostructures and the enhanced diffusion rate of charged species across the passive film are believed to be responsible for the improved passive ability. The PDM model is introduced to elaborate the microscopic process of passivation

  1. Radon diffusion chamber

    International Nuclear Information System (INIS)

    Pretzsch, G.; Boerner, E.; Lehmann, R.; Sarenio, O.

    1986-01-01

    The invention relates to the detection of radioactive gases emitting alpha particles like radon, thoron and their alpha-decaying daughters by means of a diffusion chamber with a passive detector, preferably with a solid state track detector. In the chamber above and towards the detector there is a single metallized electret with negative polarity. The distance between electret and detector corresponds to the range of the alpha particles of radon daughters in air at the most. The electret collects the positively charged daughters and functions as surface source. The electret increases the sensitivity by the factor 4

  2. In-vitro transdentinal diffusion of monomers from adhesives.

    Science.gov (United States)

    Putzeys, Eveline; Duca, Radu Corneliu; Coppens, Lieve; Vanoirbeek, Jeroen; Godderis, Lode; Van Meerbeek, Bart; Van Landuyt, Kirsten L

    2018-06-01

    Biocompatibility of adhesives is important since adhesives may be applied on dentin near the pulp. Accurate knowledge of the quantity of monomers reaching the pulp is important to determine potential side effects. The aim of this study was to assess the transdentinal diffusion of residual monomers from dental adhesive systems using an in-vitro pulp chamber model. Dentin disks with a thickness of 300 µm were produced from human third molars. These disks were fixed between two open-ended glass tubes, representing an in-vitro pulp chamber. The etch-and-rinse adhesive OptiBond FL and the self-etch adhesive Clearfil SE Bond were applied to the dentin side of the disks, while on in the pulpal side, the glass tube was filled with 600 µL water. The transdentinal diffusion of different monomers was quantified using ultra-performance liquid chromatography-tandem mass spectrometry. The monomers HEMA, CQ, BisGMA, GPDM, 10-MDP and UDMA eluted from the dental materials and were able to diffuse through the dentin disks to a certain extent. Compounds with a lower molecular weight (uncured group: HEMA 7850 nmol and CQ 78.2 nmol) were more likely to elute and diffuse compared to monomers with a higher molecular weight (uncured group: BisGMA 0.42 nmol). When the adhesives were left uncured, diffusion was up to 10 times higher compared to the cured conditions. This in-vitro research resulted in the quantification of various monomers able to diffuse through dentin and therefore contributes to a more detailed understanding about the potential exposure of the dental pulp to monomers from dental adhesives. Biocompatibility of adhesives is important since adhesives may be applied on dentin near the pulp, where tubular density and diameter are greatest. Copyright © 2018. Published by Elsevier Ltd.

  3. Separation of Kr-Xe system by thermal diffusion method

    International Nuclear Information System (INIS)

    Yoshida, Hiroshi; Numata, Kazuyoshi; Matsuda, Yuji; Ouchi, Misao; Naruse, Yuji

    1979-11-01

    Separation experiments of Kr-Xe system were carried out to study the possibility of adapting thermal diffusion method for concentration of krypton in a fuel reprocessing off-gas treatment process. The results are as follows. (1) A batchwise thermal diffusion column of hot tube diameter 21 mm, cold tube diameter 32 mm, effective hight 1000 mm and volume -- 500 CC is the best in separation characteristics and in ease of operation under the different conditions. (2) The overall separation factor increases with increase of the operating temperature in the column with and without reservoir. (3) The optimum operating pressure (about 400 Torr) is independent of the operating conditions such as temperature, reservoir volume and feed gas content. (4) A preliminary design of the Kr-Xe separating plant for a reprocessing plant (1500 ton-U/yr) shows the required number of columns and the total electric power. (author)

  4. Experimental investigation of thermal-hydraulic performance of PCCS with horizontal tube heat exchangers: single U-tube test

    International Nuclear Information System (INIS)

    Nakamura, Hideo; Anoda, Yoshinari; Arai, Kenji; Kurita, Tomohisa

    2000-01-01

    JAERI and JAPC started a cooperative study to verify performance of a PCCS (Passive Containment Cooling System) using horizontal heat exchanger for next-generation BWR in 1998. A test facility with a horizontal single U-tube was constructed in JAERI in 1999 to investigate fundamental condensation behavior under influences of non-condensable gas. Preliminary pre-test analyses were performed using RELAP5/ MOD3.2.1.2 code to expect the experimental outcomes by incorporating a correlation for condensation degradation because of non-condensable gas by Ueno et al. for better prediction. Preliminary results from both experiments (shakedown) and pre-test analyses indicated that the PCCS using horizontal U-tube heat exchanger is promising. Steam generated under assumed severe accident conditions; steam generation rate approx. = 1% core power, non-condensable gas concentration of 1% and simulated containment vessel pressure of 0.7 MPa, was totally condensed with a small differential pressure across inlet and outlet plenum. Experimental data will be accumulated to develop models and correlations for a better prediction of responses of the PCCS using horizontal heat exchanger during postulated severe accidents. (author)

  5. Solar Distillation System Based on Multiple-Effect Diffusion Type Still

    KAUST Repository

    Huang, Bin-Juine; Chong, Tze-Ling; Chang, Hsien-Shun; Wu, Po-Hsien; Kao, Yeong-Chuan

    2014-01-01

    The present study intends to develop a high-performance solar-assisted desalination system (SADS) using multi-effect diffusion type still (MEDS) and the vacuum tube solar collector (VTSC). A MEDS prototype was designed and built. The measured result

  6. A passive decay-heat removal system for an ABWR based on air cooling

    Energy Technology Data Exchange (ETDEWEB)

    Mochizuki, Hiroyasu, E-mail: mochizki@u-fukui.ac.jp [Research Institute of Nuclear Engineering, University of Fukui, 1-2-4 Kanawa-cho, Tsuruga, Fukui 914-0055 (Japan); Yano, Takahiro [School of Engineering, University of Fukui, 1-2-4 Kanawa-cho, Tsuruga, Fukui 914-0055 (Japan)

    2017-01-15

    Highlights: • A passive decay heat removal system for an ABWR is discussed using combined system of the reactor and an air cooler. • Effect of number of pass of the finned heat transfer tubes on heat removal is investigated. • The decay heat can be removed by air coolers with natural convection. • Two types of air cooler are evaluated, i.e., steam condensing and water cooling types. • Measures how to improve the heat removal rate and to make compact air cooler are discussed. - Abstract: This paper describes the capability of an air cooling system (ACS) operated under natural convection conditions to remove decay heat from the core of an Advanced Boiling Water Reactor (ABWR). The motivation of the present research is the Fukushima Severe Accident (SA). The plant suffered damages due to the tsunami and entered a state of Station Blackout (SBO) during which seawater cooling was not available. To prevent this kind of situation, we proposed a passive decay heat removal system (DHRS) in the previous study. The plant behavior during the SBO was calculated using the system code NETFLOW++ assuming an ABWR with the ACS. However, decay heat removal under an air natural convection was difficult. In the present study, a countermeasure to increase heat removal rate is proposed and plant transients with the ACS are calculated under natural convection conditions. The key issue is decreasing pressure drop over the tube banks in order to increase air flow rate. The results of the calculations indicate that the decay heat can be removed by the air natural convection after safety relief valves are actuated many times during a day. Duct height and heat transfer tube arrangement of the AC are discussed in order to design a compact and efficient AC for the natural convection mode. As a result, a 4-pass heat transfer tubes with 2-row staggered arrangement is the candidate of the AC for the DHRS under the air natural convection conditions. The heat removal rate is re-evaluated as

  7. Numerical simulation of condensation phase change flow in an inclined tube with bend

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Jong Chull; Shin, Byung Soo; Do, Kyu Sik [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of); Lee, Yong Kap [Anflux Co., Seoul (Korea, Republic of)

    2012-10-15

    The new PWR design named APR+ incorporates a passive auxiliary feedwater system (PAFS) as shown in Fig.1. The PAFS consists of two separate divisions. Each division is equipped with one passive condensation heat exchanger (PCHX), isolation or drain or vent valves, check valves, instrumentation and control, and pipes. It is aligned to feed condensed water to its corresponding steam generator (SG). During the PAFS normal operation, steam being produced in the SG secondary side by the residual heat moves up due to buoyancy force and then flows into the PCHX where steam is condensed on the inner surface of the tubes of which the outer surfaces are cooled by the water stored in the passive condensation cooling tank (PCCT). The condensate is passively fed into the SG economizer by gravity. Because the thermal hydraulic characteristics in the PCHT determine the condensation mass rate and the possibility of system instability and water hammer, it is important to understand the condensation phase change flow in the PCHT. This paper presents a numerical simulation of the condensation phase change flow in the PCHX adopted for the APR+ PAFS.

  8. Ocular blood flow decreases during passive heat stress in resting humans

    OpenAIRE

    Ikemura, Tsukasa; Miyaji, Akane; Kashima, Hideaki; Yamaguchi, Yuji; Hayashi, Naoyuki

    2013-01-01

    Background Heat stress induces various physiological changes and so could influence ocular circulation. This study examined the effect of heat stress on ocular blood flow. Findings Ocular blood flow, end-tidal carbon dioxide (P ETCO2) and blood pressure were measured for 12 healthy subjects wearing water-perfused tube-lined suits under two conditions of water circulation: (1) at 35°C (normothermia) for 30 min and (2) at 50°C for 90 min (passive heat stress). The blood-flow velocities in the s...

  9. Airway surface irregularities promote particle diffusion in the human lung

    International Nuclear Information System (INIS)

    Martonen, T.; North Carolina Univ., Chapel Hill, NC; Zhang, Z.; Yang, Y.; Bottei, G.

    1995-01-01

    Current NCRP and ICRP particle deposition models employed in risk assessment analyses treat the airways of the human lung as smooth-walled tubes. However, the upper airways of the tracheobronchial (TB) tree are line with cartilaginous rings. Recent supercomputer simulations of in vivo conditions (cited herein), where cartilaginous ring morphologies were based upon fibre-optic bronchoscope examinations, have clearly demonstrated their profound effects upon fluid dynamics. A physiologically based analytical model of fluid dynamics is presented, focusing upon applications to particle diffusion within the TB tree. The new model is the first to describe particle motion while simultaneously simulating effects of wall irregularities, entrance conditions and tube curvatures. This study may explain the enhanced deposition by particle diffusion detected in replica case experiments and have salient implications for the clinically observed preferential distributions of bronchogenic carcinomas associated with inhaled radionuclides. (author)

  10. Criticality safety study of shutdown diffusion cascade coolers

    International Nuclear Information System (INIS)

    Paschal, L.S.; Basoglu, B.; Bentley, C.L.; Dunn, M.E.

    1996-01-01

    Gaseous diffusion plants use cascade coolers in the production of highly enriched uranium (HEU) to remove heat from the enriched stream of UF 6 . The cascade coolers operate like shell and tube heat exchangers with the UF 6 on the shell side and Freon on the tube side. Recirculating cooling water (RCW) in condensers is used to cool the Freon. A criticality safety analysis was previously performed for cascade coolers during normal operation. The purpose of this paper is to evaluate several different hypothetical accidents regarding RCW ingress into the cooler to determine whether criticality safety concerns exist

  11. Spectral Analysis and Computation of Effective Diffusivities for Steady Random Flows

    Science.gov (United States)

    2016-04-28

    even in the motion of sea ice floes influenced by winds and ocean currents. The long time, large scale behavior of such systems is equivalent to an...flow plays a key role in many important processes in the global climate system [55] and Earth’s ecosys- tems [14]. Advection of geophysical fluids...HOMOGENIZATION OF THE ADVECTION-DIFFUSION EQUATION The dispersion of a cloud of passive scalars with density φ diffusing with molecular dif- fusivity ε and

  12. Partitioning of organochlorine pesticides from water to polyethylene passive samplers

    International Nuclear Information System (INIS)

    Hale, Sarah E.; Martin, Timothy J.; Goss, Kai-Uwe; Arp, Hans Peter H.; Werner, David

    2010-01-01

    The mass transfer rates and equilibrium partitioning behaviour of 14 diverse organochlorine pesticides (OCP) between water and polyethylene (PE) passive samplers, cut from custom made PE sheets and commercial polyethylene plastic bags, were quantified. Overall mass transfer coefficients, k O , estimated PE membrane diffusion coefficients, D PE , and PE-water partitioning coefficients, K PE-water, are reported. In addition, the partitioning of three polycyclic aromatic hydrocarbons (PAHs) from water to PE is quantified and compared with literature values. K PE-water values agreed mostly within a factor of two for both passive samplers and also with literature values for the reference PAHs. As PE is expected to exhibit similar sorption behaviour to long-chain alkanes, PE-water partitioning coefficients were compared to hexadecane-water partitioning coefficients estimated with the SPARC online calculator, COSMOtherm and a polyparameter linear free energy relationship based on the Abraham approach. The best correlation for all compounds tested was with COSMOtherm estimated hexadecane-water partitioning coefficients. - The partitioning of organochlorine pesticides between single phase polyethylene passive samplers and water is quantified.

  13. Passive solar technology

    Energy Technology Data Exchange (ETDEWEB)

    Watson, D

    1981-04-01

    The present status of passive solar technology is summarized, including passive solar heating, cooling and daylighting. The key roles of the passive solar system designer and of innovation in the building industry are described. After definitions of passive design and a summary of passive design principles are given, performance and costs of passive solar technology are discussed. Passive energy design concepts or methods are then considered in the context of the overall process by which building decisions are made to achieve the integration of new techniques into conventional design. (LEW).

  14. Numerical investigation of passive heat removal system via steam generator in VVER 1200

    International Nuclear Information System (INIS)

    Dinh Anh Tuan; Duong Thanh Tung; Tran Chi Thanh; Nguyen Van Thai

    2015-01-01

    Passive heat removal system (PHRS) via Steam Generator is an important part in VVER design. In case of Design Basic Accidents such as blackout, failure of feed water supply to steam generator or coolant leakage with failure of emergency core cooling at high pressure. PHRS is designed to remove the residual heat from reactor core through steam generator to heat exchanger which is placed outside reactor vessel. In order to evaluate the passive system, a numerical investigation using a CFD code is performed. However, PHRS has complex geometry for using CFD simulation. Thus, RELAP5 is applied to provide the wall heat flux of tube in the heat exchanger tank. The natural convection in the heat exchanger tank is investigated in this report. Numerical results show temperature and velocity distribution in the heat exchanger tank are calculated with different wall heat flux corresponding to various transient conditions. The calculated results contribute to the capacity analysis of passive heat removal system and giving valuable information for safe operation of VVER 1200. (author)

  15. A passive decay heat removal system for LWRs based on air cooling

    Energy Technology Data Exchange (ETDEWEB)

    Mochizuki, Hiroyasu, E-mail: mochizki@u-fukui.ac.jp [Research Institute of Nuclear Engineering, University of Fukui, 1-2-4 Kanawa-cho, Tsuruga, Fukui 914-0055 (Japan); Yano, Takahiro [Graduate School of Engineering, University of Fukui, 1-2-4 Kanawa-cho, Tsuruga, Fukui 914-0055 (Japan)

    2015-05-15

    Highlights: • A passive decay heat removal system for LWRs is discussed. • An air cooler model which condenses steam is developed. • The decay heat can be removed by air coolers with forced convection. • The dimensions of the air cooler are proposed. - Abstract: The present paper describes the capability of an air cooling system (ACS) to remove decay heat from a core of LWR such as an advanced boiling water reactor (ABWR) and a pressurized water reactor (PWR). The motivation of the present research is the Fukushima severe accident (SA) on 11 March 2011. Since emergency cooling systems using electricity were not available due to station blackout (SBO) and malfunctions, many engineers might understand that water cooling was not completely reliable. Therefore, a passive decay heat removal (DHR) system would be proposed in order to prevent such an SA under the conditions of an SBO event. The plant behaviors during the SBO are calculated using the system code NETFLOW++ for the ABWR and PWR with the ACS. Two types of air coolers (ACs) are applied for the ABWR, i.e., a steam condensing air cooler (SCAC) of which intake for heat transfer tubes is provided in the steam region, and single-phase type of which intake is provided in the water region. The DHR characteristics are calculated under the conditions of the forced air circulation and also the natural air convection. As a result of the calculations, the decay heat can be removed safely by the reasonably sized ACS when heat transfer tubes are cooled with the forced air circulation. The heat removal rate per one finned heat transfer tube is evaluated as a function of air flow rate. The heat removal rate increases as a function of the air flow rate.

  16. Non-destructive measurement methods for large scale gaseous diffusion process equipment

    International Nuclear Information System (INIS)

    Mayer, R.L.; Hagenauer, R.C.; McGinnis, B.R.

    1994-01-01

    Two measurement methods have been developed to measure non-destructively uranium hold-up in gaseous diffusion plants. These methods include passive neutron and passive γ ray measurements. An additional method, high resolution γ ray spectroscopy, provides supplementary information about additional γ ray emitting isotopes, γ ray correction factors, 235 U/ 234 U ratios and 235 U enrichment. Many of these methods can be used as a general purpose measurement technique for large containers of uranium. Measurement applications for these methods include uranium hold-up, waste measurements, criticality safety and nuclear accountability

  17. A simplified counter diffusion method combined with a 1D simulation program for optimizing crystallization conditions.

    Science.gov (United States)

    Tanaka, Hiroaki; Inaka, Koji; Sugiyama, Shigeru; Takahashi, Sachiko; Sano, Satoshi; Sato, Masaru; Yoshitomi, Susumu

    2004-01-01

    We developed a new protein crystallization method has been developed using a simplified counter-diffusion method for optimizing crystallization condition. It is composed of only a single capillary, the gel in the silicon tube and the screw-top test tube, which are readily available in the laboratory. The one capillary can continuously scan a wide range of crystallization conditions (combination of the concentrations of the precipitant and the protein) unless crystallization occurs, which means that it corresponds to many drops in the vapor-diffusion method. The amount of the precipitant and the protein solutions can be much less than in conventional methods. In this study, lysozyme and alpha-amylase were used as model proteins for demonstrating the efficiency of this method. In addition, one-dimensional (1-D) simulations of the crystal growth were performed based on the 1-D diffusion model. The optimized conditions can be applied to the initial crystallization conditions for both other counter-diffusion methods with the Granada Crystallization Box (GCB) and for the vapor-diffusion method after some modification.

  18. Silicon diffusion in aluminum for rear passivated solar cells

    International Nuclear Information System (INIS)

    Urrejola, Elias; Peter, Kristian; Plagwitz, Heiko; Schubert, Gunnar

    2011-01-01

    We show that the lateral spread of silicon in a screen-printed aluminum layer increases by (1.50±0.06) μm/ deg. C, when increasing the peak firing temperature within an industrially applicable range. In this way, the maximum spread limit of diffused silicon in aluminum is predictable and does not depend on the contact area size but on the firing temperature. Therefore, the geometry of the rear side pattern can influence not only series resistance losses within the solar cell but the process of contact formation itself. In addition, too fast cooling lead to Kirkendall void formations instead of an eutectic layer.

  19. Self-diffusion and heterodiffusion in Zr-2.5%Nb α/β interfaces comparison with grain boundary diffusion in α-Zr

    International Nuclear Information System (INIS)

    Iribarren, M.J.; Dyment, F.

    1991-01-01

    Conventional radioactive tracer section techniques were used to make an experimental determination of diffusion parameters for Zr, Nb and Ni along the α/β boundary interfaces of Zr-2.5%Nb and comparing them with those for Zr, Nb and Co in α-Zr grain boundaries. Both determinations were made for a wide range of temperatures, including reactor working temperatures. Different materials were used for this purpose, both specially prepared alloys for diffusion experiments and part of the material from the actual pressure tubes. Different stabilizing thermal treatments were performed and results were analyzed based on the different morphologies obtained. (Author) [es

  20. Diffusion of lithium ions in argon

    International Nuclear Information System (INIS)

    Stefansson, T.

    1983-01-01

    Published measurements of transport coefficients for Li + ions in argon seem to be limited to the mobility and the longitudinal diffusion coefficient in the field-to-density ratio range at and below 200 Td 1-5 . In this paper results are presented from measurements of the transverse diffusion coefficient to mobility ratio (Dsub(T)/μ) for Li + ions in argon in the field-to-density ratio range 10 < E/n < 800 Td. The measurements were made with a drift tube mass spectrometer at a gas temperature of 295 +- 1 K using the modified Townsend method of Skullerud. The experimental curve is compared to a calculation by H.R. Skullerud in the same proceedings. (G.Q.)

  1. Rechargeable biofilm-controlling tubing materials for use in dental unit water lines.

    Science.gov (United States)

    Luo, Jie; Porteous, Nuala; Sun, Yuyu

    2011-08-01

    A simple and practical surface grafting approach was developed to introduce rechargeable N-halamine-based antimicrobial functionality onto the inner surfaces of continuous small-bore polyurethane (PU) dental unit waterline (DUWL) tubing. In this approach, tetrahydrofuran (THF) solution of a free-radical initiator, dicumyl peroxide (DCP), flowed through the PU tubing (inner diameter of 1/16 in., or 1.6 mm) to diffuse DCP into the tubing's inner walls, which was used as initiator in the subsequent grafting polymerization of methacrylamide (MAA) onto the tubing. Upon chlorine bleach treatment, the amide groups of the grafted MAA side chains were transformed into acyclic N-halamines. The reactions were confirmed with attenuated total reflectance infrared (ATR) spectra and iodometric titration. The mechanical properties of the tubing were not significantly affected by the grafting reactions. The biofilm-controlling function of the new N-halamine-based PU tubing was evaluated with Pseudomonas aeruginosa (P. aeruginosa), one of the most isolated water bacteria from DUWLs, in a continuous bacterial flow model. Bacteria culturing and SEM studies showed that the inner surfaces of the new N-halamine-based PU tubing completely prevented bacterial biofilm formation for at least three to four weeks. After that, bacteria began to colonize the tubing surface. However, the lost function was fully regenerated by exposing the tubing inner surfaces to diluted chlorine bleach. The recharging process could be repeated periodically to further extend the biofilm-controlling duration for long-term applications.

  2. Convective and diffusive effects on particle transport in asymmetric periodic capillaries.

    Directory of Open Access Journals (Sweden)

    Nazmul Islam

    Full Text Available We present here results of a theoretical investigation of particle transport in longitudinally asymmetric but axially symmetric capillaries, allowing for the influence of both diffusion and convection. In this study we have focused attention primarily on characterizing the influence of tube geometry and applied hydraulic pressure on the magnitude, direction and rate of transport of particles in axi-symmetric, saw-tooth shaped tubes. Three initial value problems are considered. The first involves the evolution of a fixed number of particles initially confined to a central wave-section. The second involves the evolution of the same initial state but including an ongoing production of particles in the central wave-section. The third involves the evolution of particles a fully laden tube. Based on a physical model of convective-diffusive transport, assuming an underlying oscillatory fluid velocity field that is unaffected by the presence of the particles, we find that transport rates and even net transport directions depend critically on the design specifics, such as tube geometry, flow rate, initial particle configuration and whether or not particles are continuously introduced. The second transient scenario is qualitatively independent of the details of how particles are generated. In the third scenario there is no net transport. As the study is fundamental in nature, our findings could engender greater understanding of practical systems.

  3. Normal and Inverse Diffusive Isotope Fractionation of Deuterated Toluene and Benzene in Aqueous Systems

    DEFF Research Database (Denmark)

    Rolle, Massimo; Jin, Biao

    2017-01-01

    and toluene. Multitracer experiments were carried out in 1-D gel dissection tubes and in a quasi-2-D flow-through porous medium. The experiments allowed us to simultaneously and directly compare the diffusive and dispersive behavior of benzene and toluene. We observed an unexpected, opposite behavior...... of the two monoaromatic hydrocarbons. Toluene showed a normal diffusive isotope effect (DC7D8/DC7H8 = 0.96) with enrichment of the nondeuterated isotopologue in the direction of the diffusive and transverse dispersive fluxes. Conversely, the measured trends for benzene indicate inverse diffusive...

  4. A passive monitor for radon using electrochemical track etch detector

    International Nuclear Information System (INIS)

    Massera, G.E.; Hassib, G.M.; Piesch, E.

    1980-01-01

    A passive, inexpensive monitor for radon detection and dosimetry is described in detail. It consists of a Makrofoil track etch detector inside a diffusion chamber which is sealed by a fibreglass filter through which radon may diffuse while radon daughters and aerosols are retained on the surface of the filter. The α-particle tracks are revealed by etching the Makrofoil in KOH. The lower detection limit of the radon dosimeter is equivalent to a mean dose in the lung of 130 mrem. After an exposure period of 3 months, a mean radon concentration of 0.3 pCi/l can be detected. The instrument is intended for use in a study to measure the long-term radon exposure in buildings in West Germany. (UK)

  5. Influence of microstructure modification on the circumferential creep of Zr–Nb–Sn–Fe cladding tubes

    International Nuclear Information System (INIS)

    Jeong, Gu Beom; Kim, In Won; Hong, Sun Ig

    2016-01-01

    Out-of-reactor, non-irradiated thermal creep performances and lives of annealed and stress-relieved Zr-1.02Nb-0.69Sn-0.12Fe cladding tubes were studied and compared. The creep rates of annealed Zr-1.02Nb-0.69Sn-0.12Fe cladding tubes were appreciably slower than those of stress-relieved annealed counterpart. The stress exponent increased slightly from 5.1 to 6.1 in the stress-relieved cladding to 5.3–6.3 in the annealed cladding. The creep activation energy of the annealed Zr-1.02Nb-0.69Sn-0.12Fe alloy (300–330 kJ/mol) was larger compared to that of the stress-relieved alloy (210–260 kJ/mol). The creep activation energy of annealed alloy is close to that of self-diffusion in α-Zr (336 kJ/mol). The smaller activation energy in the stress-relieved alloy is attributed to the increasing contribution of faster diffusion path such as grain boundaries and dislocations. The presence of dislocation arrays with higher dislocation density and smaller grain size in the stress-relived alloy was confirmed by TEM analysis. The creep rupture time increased dramatically in the annealed Zr–1Nb- 0.7Sn-0.1Fe alloy compared to that of stress-relieved alloy, supporting the decrease of creep rate by annealing. The creep life of Zr-1.02Nb-0.69Sn-0.12Fe claddings can be extended through microstructure modification by annealing at intermediate temperatures in which dislocation creep dominates. - Highlights: • Effect of microstructure modification on creep in Zr–Nb–Sn–Fe tubes was studied. • Creep activation energy in annealed tubes was larger than in stress-relieved tubes. • Lower dislocation density in lager grains was observed after creep in annealed tubes. • Larson–Miller parameter of annealed tube was larger than that of stress-relieved one. • Creep life of tubes was extended through microstructure modification by annealing.

  6. 21 CFR 868.5800 - Tracheostomy tube and tube cuff.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Tracheostomy tube and tube cuff. 868.5800 Section... (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5800 Tracheostomy tube and tube cuff. (a) Identification. A tracheostomy tube and tube cuff is a device intended to be placed into a...

  7. Manufacturing process for cylindrical ceramic tubes with localized imprints and device for application of this process

    International Nuclear Information System (INIS)

    1985-01-01

    This invention involves a process for manufacturing permeable cylindrical ceramic tubes with localized relief such as annular, spiral or simple coiled or double crossed coils or even stipple imprints on their internal face. It is known that one of the techniques for the separation of the mixture of gases with close molecular masses is gaseous diffusion. According to this technique, the gas mixture is circulated under pressure inside tubes constituted by a microporous wall. These tubes, according to a known technique, are constituted by a macroporous ceramic tube, generally called a support, covered on the inside with a microporous layer deposited on this interior wall. The unit constituted by the tube itself or the ''support'' and the microporous layer makes it possible to adapt the total porosity of the covered tube or ''barrier'' in order to obtain an optimal coefficient of gas separation. This technique is used specifically for separation of two gases corresponding to various isotopes of the same simple body. 6 figs

  8. Passive PE Sampling in Support of In Situ Remediation of Contaminated Sediments

    Science.gov (United States)

    2015-08-01

    biodegradation . As discussed in Fernandez et al. (2009b), target compounds like PCBs and PAHs diffuse through the surrounding environmental media... biodegradation . The PE passive sampling technique may also offer significant cost savings per site for sample collection and analysis cost. When compared with...water, detergent), Nitrile gloves, aluminum foil, plastic sheeting, rope, paper towels, garbage bags , bubble wrap, Ziplock bags , and ice. • Non

  9. Tube plug

    International Nuclear Information System (INIS)

    Zafred, P. R.

    1985-01-01

    The tube plug comprises a one piece mechanical plug having one open end and one closed end which is capable of being inserted in a heat exchange tube and internally expanded into contact with the inside surface of the heat exchange tube for preventing flow of a coolant through the heat exchange tube. The tube plug also comprises a groove extending around the outside circumference thereof which has an elastomeric material disposed in the groove for enhancing the seal between the tube plug and the tube

  10. Ultrasonic inspection of tube to tube plate welds

    International Nuclear Information System (INIS)

    Telford, D.W.; Peat, T.S.

    1985-01-01

    To monitor the deterioration of a weld between a tube and tube plate which has been repaired by a repair sleeve inside the tube and brazed at one end to the tube, ultrasound from a crystal at the end of a rod is launched, in the form of Lamb-type waves, into the tube through the braze and allowed to travel along the tube to the weld and be reflected back along the tube. The technique may also be used for the type of heat exchanger in which, during construction, the tubes are welded to the tube plate via external sleeves in which case the ultrasound is used in a similar manner to inspect the sleeve/tube plate weld. an electromagnetic transducer may be used to generate the ultrasound. The ultrasonic head comprising the crystal and an acoustic baffle is mounted on a Perspex (RTM) rod which may be rotated by a stepping motor. Echo signals from the region of deterioration may be isolated by use of a time gate in the receiver. The device primarily detects circumferentially orientated cracks, and may be used in heat exchangers in nuclear power plants. (author)

  11. Perioperative respiratory adverse events in children with active upper respiratory tract infection who received general anesthesia through an orotracheal tube and inhalation agents.

    Science.gov (United States)

    Kim, So Yeon; Kim, Jeong Min; Lee, Jae Hoon; Kang, Young Ran; Jeong, Seung Ho; Koo, Bon-Nyeo

    2013-08-01

    Active upper respiratory tract infection (URI), orotracheal intubation and use of inhalation anesthetics are known risk factors for perioperative respiratory adverse events (RAE). This study investigated the risk factors of perioperative RAE in children with these risk factors. The records of 159 children who underwent general anesthesia with an orotracheal tube and inhalation were reviewed. These patients also had at least one of the following URI symptoms on the day of surgery: clear or green nasal secretion, dry or moist cough, nasal congestion, or fever. RAE such as laryngospasm, bronchospasm, oxygen desaturation and sustained cough were collected before induction, during intubation, during extubation, after extubation and in the postanesthesia care unit. Forty-five patients had RAE. The patients with RAE were younger than those without RAE. There were more passive smokers and a greater number of intubation attempts in patients with RAE than in those without RAE. The type of surgery and type of inhalation agents were not different between patients with and without RAE. Passive smoking was the only independent risk factor for RAE. In children with an active URI using orotracheal tube and inhalation anesthetics, passive smoking is an important risk factor for RAE.

  12. Thermo-structural modelling of a plasma discharge tube for electric propulsion

    International Nuclear Information System (INIS)

    Faoite, D. de; Browne, D.J.; Del Valle Gamboa, J.I.; Stanton, K.T.

    2016-01-01

    Highlights: • Thermo-structural analyses were performed for an electric propulsion space thruster. • Thermal stresses arise primarily from mismatches in thermal expansion coefficients. • Aluminium nitride is a suitable material for a plasma containment tube. • A design is presented allowing a thruster to operate at a power of at least 250 kW. - Abstract: Potential thermal management strategies for the plasma generation section of a VASIMR"® high-power electric propulsion space thruster are assessed. The plasma is generated in a discharge tube using helicon waves. The plasma generation process causes a significant thermal load on the plasma discharge tube and on neighbouring components, caused by cross-field particle diffusion and UV radiation. Four potential cooling system design strategies are assessed to deal with this thermal load. Four polycrystalline ceramics are evaluated for use as the plasma discharge tube material: alumina, aluminium nitride, beryllia, and silicon nitride. A finite element analysis (FEA) method was used to model the steady-state temperature and stress fields resulting from the plasma heat flux. Of the four materials assessed, aluminium nitride would result in the lowest plasma discharge tube temperatures and stresses. It was found that a design consisting of a monolithic ceramic plasma containment tube fabricated from aluminium nitride would be capable of operating up to a power level of at least 250 kW.

  13. State of the Art Report On Condensation Phenomena Within Tubes in the Presence of Noncondensable Gas

    International Nuclear Information System (INIS)

    Polo, J.

    1998-01-01

    Condensation phenomena play an important role in many industrial applications; in particular; the nuclear industry uses such processes in different systems for both operation and safety aspects. Thus most of the engineering safety features in the current Light Water Reactor (LWR) plants as well as in the new advanced/passive type design are based on the condensation phenomena inside tubes to reduce the system pressure and to remove the decay heat released under accidental conditions. Regarding the new advanced/passive plant designs such a systems must ensure their capabilities under severe accident conditions, that means, under the presence of non-condensable gas an even aerosol particles. The presence of even a small quantity of non condensable gas in liquid-vapour has profound influence on the resistance to heat transfer at the liquid-vapour interface leading to reduce in the heat transfer rate. In consequence, the safety analysis of the Simplified Boiling Water Reactor (SBWR) promoted in increase in the modelling, model development and experimental research on the gas mixtures condensing inside vertical tubes. This report summarises the last models developed as well as the experimental findings on such processes. (Author) 51 refs

  14. Intracellular Transport of Cargo in a Sub-diffusive Environment over an Explicit Cytoskeletal Network

    Science.gov (United States)

    Maelfeyt, Bryan; Gopinathan, Ajay

    Intracellular transport occurs in nearly all eukaryotic cells, where materials such as proteins, lipids, carbohydrates, and nucleic acids travel to target locations through phases of passive, diffusion-based transport and active, motor-driven transport along filaments that make up the cell's cytoskeleton.We develop a computational model of the process with explicit cytoskeletal filament networks. In the active transport phase, cargo moves in straight lines along these filaments that are spread throughout the cell. To model the passive transport phase of cargo in the cytoplasm, where anomalous sub-diffusion is thought to take place, we implement a continuous-time random walk. We use this approach to provide a stepping stone to a predictive model where we can determine transport properties over a cytoskeletal network provided by experimental images of real filaments. We illustrate our approach by modeling the transport of insulin out of the cell and determining the impact of network geometry, anomalous sub-diffusion and motor number on the first-passage time distributions for insulin granules reaching their target destinations on the membrane.

  15. A Preliminary Study of Transverse Curvature Effects on Condensation Heat Transfer on Vertical Tube in the Presence of Non-condensable Gas

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Yeon Gun; Kim, Sin [Jeju National Univ., Jeju (Korea, Republic of); Jerng, Dong Wook [Chung Ang Univ., Seoul (Korea, Republic of)

    2013-10-15

    In this study, the effect of the transverse curvature on the condensation HTC on a vertical tube in the presence of air is preliminarily investigated by using the analysis of boundary layer for free convective heat transfer. The results indicate that the heat transfer performance can be enhanced as the outer diameter of condenser tubes is small. To confirm this curvature effect, an experimental program to obtain the condensation heat transfer data for various values of tube diameter is indispensable. Currently, by a joint research project of Jeju National University and Chung-Ang University, a condensation test facility is being designed and constructed to acquire the condensation HTC data as shown in Fig. 3. From a series of experiment on a single vertical tube, the effects of not only the tube diameter but the inclination, the existence of fins and the local velocity of a bulk mixture by natural circulation will be evaluated precisely. An empirical correlation for the condensation heat transfer of a steam-air mixture will also be developed for design optimization and performance evaluation of the PCCS. The Passive Containment Cooling System (PCCS) provides passive means to remove the decay heat and protect the integrity of the containment during severe accidents. Korea, in which all the NPPs employ the concrete containment, may adopt a PCCS using internal condensers. In the event of the loss-of-coolant accident (LOCA), steam released from the reactor coolant system is mixed with air inside the containment and condensed on the outer surface of inclined condenser tubes. It is noted that, among previous theoretical and empirical models for condensation on outer wall in the presence of non-condensable gas, no one took into account the effect of a tube diameter. Though the condensation heat transfer coefficient may vary with transverse curvature of condenser tubes, such a curvature effect has not been reported so far. In this study, a preliminary analysis is conducted

  16. A Preliminary Study of Transverse Curvature Effects on Condensation Heat Transfer on Vertical Tube in the Presence of Non-condensable Gas

    International Nuclear Information System (INIS)

    Lee, Yeon Gun; Kim, Sin; Jerng, Dong Wook

    2013-01-01

    In this study, the effect of the transverse curvature on the condensation HTC on a vertical tube in the presence of air is preliminarily investigated by using the analysis of boundary layer for free convective heat transfer. The results indicate that the heat transfer performance can be enhanced as the outer diameter of condenser tubes is small. To confirm this curvature effect, an experimental program to obtain the condensation heat transfer data for various values of tube diameter is indispensable. Currently, by a joint research project of Jeju National University and Chung-Ang University, a condensation test facility is being designed and constructed to acquire the condensation HTC data as shown in Fig. 3. From a series of experiment on a single vertical tube, the effects of not only the tube diameter but the inclination, the existence of fins and the local velocity of a bulk mixture by natural circulation will be evaluated precisely. An empirical correlation for the condensation heat transfer of a steam-air mixture will also be developed for design optimization and performance evaluation of the PCCS. The Passive Containment Cooling System (PCCS) provides passive means to remove the decay heat and protect the integrity of the containment during severe accidents. Korea, in which all the NPPs employ the concrete containment, may adopt a PCCS using internal condensers. In the event of the loss-of-coolant accident (LOCA), steam released from the reactor coolant system is mixed with air inside the containment and condensed on the outer surface of inclined condenser tubes. It is noted that, among previous theoretical and empirical models for condensation on outer wall in the presence of non-condensable gas, no one took into account the effect of a tube diameter. Though the condensation heat transfer coefficient may vary with transverse curvature of condenser tubes, such a curvature effect has not been reported so far. In this study, a preliminary analysis is conducted

  17. Tube tightness survey during Phenix steam generator operation

    International Nuclear Information System (INIS)

    Cambillard, E.

    1976-01-01

    Phenix steam generators are once-through vessels with single-wall heat-exchange tubes. This design means that any leakage of water into the sodium must be detected as quickly as possible so that the installation can be shut down before extensive damage occurs. The detection of water leaks in Phenix steam generators is based on measurement of the concentration in the sodium, of hydrogen produced by the sodium-water reaction. Since the various modules--evaporators, superheaters, and reheaters--have no free sodium surfaces, detection of hydrogen in argon is not used in Phenix steam generators. The measurement systems employ a probe made of nickel tubes 0.3 mm thick. Hydrogen in the sodium diffuses into a chamber kept under vacuum by an ion pump. The hydrogen pressure in the chamber is measured by a quadrupole mass spectrometer. The nine measurement systems (three per steam generator) are calibrated by injecting hydrogen into the sodium of the secondary circuits. The data-processing computer calculates the hydrogen concentration in the sodium from the spectrometer signals and the probe temperatures, which are not regulated in Phenix; it generates instructions that enable the operator to act if a leak appears. So far, no leaks have been detected. These systems also make it possible to determine rates of hydrogen diffusion caused by corrosion of the steel walls on the water side

  18. Heat Exchanger Tube to Tube Sheet Joints Corrosion Behavior

    Directory of Open Access Journals (Sweden)

    M. Iancu

    2013-03-01

    Full Text Available Paper presents the studies made by the authors above the tube to tube sheet fittings of heat exchanger with fixed covers from hydrofining oil reforming unit. Tube fittings are critical zones for heat exchangers failures. On a device made from material tube and tube sheet at real joints dimensions were establish axial compression force and traction force at which tube is extracted from expanded joint. Were used two shapes joints with two types of fittings surfaces, one with smooth hole of tube sheet and other in which on boring surface we made a groove. From extracted expanded tube zones were made samples for corrosion tests in order to establish the corrosion rate, corrosion potential and corrosion current in working mediums such as hydrofining oil and industrial water at different temperatures. The corrosion rate values and the temperature influence are important to evaluate joints durability and also the results obtained shows that the boring tube sheet shape with a groove on hole tube shape presents a better corrosion behavior then the shape with smooth hole tube sheet.

  19. Superconductivity of powder-in-tube MgB{sub 2} wires

    Energy Technology Data Exchange (ETDEWEB)

    Glowacki, B A; Evetts, J E [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge, CB3 OHE (United Kingdom); Department of Materials Science and Metallurgy, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Majoros, M [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge, CB3 OHE (United Kingdom); Institute of Electrical Engineering, Slovak Academy of Science, Dubravska Cesta 9, Bratislava (Slovakia); Vickers, M [Department of Materials Science and Metallurgy, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Shi, Y [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge, CB3 OHE (United Kingdom); McDougall, I [Oxford Instruments Plc, Eynsham, OX8 ITL (United Kingdom)

    2001-04-01

    A new class of 'powder-in-tube' Mg-B superconducting conductors has been prepared using two different methods: an in situ technique where an Mg + 2B mixture was used as a central conductor core and reacted in situ to form MgB{sub 2}, and an ex situ technique where fully reacted MgB{sub 2} powder was used to fill the metal tube. Conductors were prepared using silver, copper and bimetallic silver/stainless steel tubes. Wires manufactured by the in situ technique, diffusing Mg to B particles experienced {approx}25.5% decrease in density from the initial value after cold deformation, due to the phase transformation from Mg + 2({beta}-B){yields}MgB{sub 2} all with hexagonal structure. A comparative study of the intergranular current and grain connectivity in wires was conducted by AC susceptibility measurements and direct four point transport measurements. Using a SQUID magnetometer, magnetization versus magnetic field (M-H) curves of the round wires before and after sintering and reactive diffusion were measured at 5 K and in magnetic fields up to 5 T to define the J{sub cmag}. The direct current measurements were performed in self field at 4.2 K. A comparison between zero-field-cooled (ZFC) and field-cooled (FC) susceptibility measurements for sintered Ag/MgB{sub 2}, and reacted Cu/Mg + 2B conductors revealed systematic differences in the flux pinning in the wires which is in very good agreement with direct high transport current measurements. (author)

  20. Superconductivity of powder-in-tube MgB{sub 2} wires

    Energy Technology Data Exchange (ETDEWEB)

    Glowacki, B.A.; Evetts, J.E. [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge, CB3 OHE (United Kingdom); Department of Materials Science and Metallurgy, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Majoros, M. [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge, CB3 OHE (United Kingdom); Institute of Electrical Engineering, Slovak Academy of Science, Dubravska Cesta 9, Bratislava (Slovakia); Vickers, M. [Department of Materials Science and Metallurgy, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Shi, Y. [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge, CB3 OHE (United Kingdom); McDougall, I. [Oxford Instruments Plc, Eynsham, OX8 ITL (United Kingdom)

    2001-04-01

    A new class of 'powder-in-tube' Mg-B superconducting conductors has been prepared using two different methods: an in situ technique where an Mg + 2B mixture was used as a central conductor core and reacted in situ to form MgB{sub 2}, and an ex situ technique where fully reacted MgB{sub 2} powder was used to fill the metal tube. Conductors were prepared using silver, copper and bimetallic silver/stainless steel tubes. Wires manufactured by the in situ technique, diffusing Mg to B particles experienced {approx}25.5% decrease in density from the initial value after cold deformation, due to the phase transformation from Mg + 2({beta}-B){yields}MgB{sub 2} all with hexagonal structure. A comparative study of the intergranular current and grain connectivity in wires was conducted by AC susceptibility measurements and direct four point transport measurements. Using a SQUID magnetometer, magnetization versus magnetic field (M-H) curves of the round wires before and after sintering and reactive diffusion were measured at 5 K and in magnetic fields up to 5 T to define the J{sub cmag}. The direct current measurements were performed in self field at 4.2 K. A comparison between zero-field-cooled (ZFC) and field-cooled (FC) susceptibility measurements for sintered Ag/MgB{sub 2}, and reacted Cu/Mg + 2B conductors revealed systematic differences in the flux pinning in the wires which is in very good agreement with direct high transport current measurements. (author)

  1. Adsorption and diffusion of plutonium in soil

    International Nuclear Information System (INIS)

    Relyea, J.F.; Brown, D.A.

    1978-01-01

    The behavior of plutonium in soil--water systems was studied by measuring its apparent diffusion coefficient in the aqueous and solid phases and by finding the adsorption--desorption relationships between soil and solution. Apparent diffusion coefficients of plutonium in soil were measured using a quick-freeze method. Aqueous diffusion was studied in a capillary-tube diffusion cell. Adsorption studies were done by equilibrating a tagged soil--water mixture on a rotary shaker before centrifuging and sampling. As expected from high adsorption coefficients (Kd) (300--10,000), the apparent diffusion coefficients were low compared with normal soil cations (1.4 x 10 -8 cm 2 /sec in a sandy soil to less than 2.4 x 10 -11 cm 2 /sec in a silt loam). The Kd of plutonium in aqueous solution containing the chelate ethylenediaminetetraacetic acid (EDTA) was reduced compared with the Kd in dilute HNO 3 . As the EDTA concentration was increased, the Kd was decreased. The chelate diethylenetriaminepentaacetic acid (DTPA) reduced the Kd more than EDTA at comparable concentrations. The aqueous diffusion coefficients varied from 3.1 x 10 -7 cm 2 /sec in a solution extracted from the silt loam up to 2.7 x 10 -5 cm 2 /sec in a solution extracted from the sandy soil

  2. Tube spacer grid for a heat-exchanger tube bundle

    International Nuclear Information System (INIS)

    Scheidl, H.

    1976-01-01

    A tube spacer grid for a heat-exchanger tube bundle is formed by an annular grid frame having a groove formed in its inner surface in which the interspaced grid bars have their ends positioned and held in interspaced relationship by short sections of tubes passed through holes axially formed in the grid frame so that the tubes are positioned between the ends of the grid bars in the grooves. The tube sections may be cut from the same tubes used to form the tube bundle. 5 claims, 3 drawing figures

  3. Peptide dendrimer-conjugates of ketoprofen: Synthesis and ex vivo and in vivo evaluations of passive diffusion, sonophoresis and iontophoresis for skin delivery.

    Science.gov (United States)

    Hegde, Aswathi R; Rewatkar, Prarthana V; Manikkath, Jyothsna; Tupally, Karnaker; Parekh, Harendra S; Mutalik, Srinivas

    2017-05-01

    The aim of this study was to evaluate skin delivery of ketoprofen when covalently tethered to mildly cationic (2 + or 4 + ) peptide dendrimers prepared wholly by solid phase peptide synthesis. The amino acids glycine, arginine and lysine formed the dendrimer with ketoprofen tethered either to the lysine side-arm (N ε ) or periphery of dendrimeric branches. Passive diffusion, sonophoresis- and iontophoresis-assisted permeation of each peptide dendrimer-drug conjugate (D1-D4) was studied across mouse skin, both in vitro and in vivo. In addition, skin toxicity of dendrimeric conjugates when trialed with iontophoresis or sonophoresis was also evaluated. All dendrimeric conjugates improved aqueous solubility at least 5-fold, compared to ketoprofen alone, while also exhibiting appreciable lipophilicity. In vitro passive diffusion studies revealed that ketoprofen in its native form was delivered to a greater extent, compared with a dendrimer-conjugated form at the end of 24h (Q 24h (μg/cm 2 ): ketoprofen (68.06±3.62)>D2 (49.62±2.92)>D4 (19.20±0.89)>D1 (6.45±0.40)>D3 (2.21±0.19). However, sonophoresis substantially increased the skin permeation of ketoprofen-dendrimer conjugates in 30min (Q 30min (μg/cm 2 ): D4 (122.19±7.14)>D2 (66.74±3.86)>D1 (52.10±3.22)>D3 (41.66±3.22)) although ketoprofen alone again proved superior (Q 30min : 167.99±9.11μg/cm 2 ). Next, application of iontophoresis was trialed and shown to considerably increase permeation of dendrimeric ketoprofen in 6h (Q 6h (μg/cm 2 ): D2 (711.49±39.14)>D4 (341.23±16.43)>D3 (89.50±4.99)>D1 (50.91±2.98), with a Q 6h value of 96.60±5.12μg/cm 2 for ketoprofen alone). In vivo studies indicated that therapeutically relevant concentrations of ketoprofen could be delivered transdermally when iontophoresis was paired with D2 (985.49±43.25ng/mL). Further, histopathological analysis showed that the dendrimeric approach was a safe mode as ketoprofen alone. The present study successfully demonstrates that

  4. Experimental study and modeling of high-temperature oxidation and phase transformation of cladding-tubes made in zirconium alloy

    International Nuclear Information System (INIS)

    Mazeres, Benoit

    2013-01-01

    One of the hypothetical accident studied in the field of the safety studies of Pressurized light Water Reactor (PWR) is the Loss-Of-Coolant-Accident (LOCA). In this scenario, zirconium alloy fuel claddings could undergo an important oxidation at high temperature (T≅ 1200 C) in a steam environment. Cladding tubes constitute the first confinement barrier of radioelements and then it is essential that they keep a certain level of ductility after quenching to ensure their integrity. These properties are directly related to the growth kinetics of both the oxide and the αZr(O) phase and also to the oxygen diffusion profile in the cladding tube after the transient. In this context, this work was dedicated to the understanding and the modeling of the both oxidation phenomenon and oxygen diffusion in zirconium based alloys at high temperature. The numerical tool (EKINOX-Zr) used in this thesis is based on a numerical resolution of a diffusion/reaction problem with equilibrium-conditions on three moving boundaries: gas/oxide, oxide/αZr(O), αZr(O)/βZr. EKINOX-Zr kinetics model is coupled with ThermoCalc software and the Zircobase database to take into account the influence of the alloying elements (Sn, Fe, Cr, Nb) but also the influence of hydrogen on the solubility of oxygen. This study focused on two parts of the LOCA scenario: the influence of a pre-oxide layer (formed in-service) and the effects of hydrogen. Thanks to the link between EKINOX-Zr and the thermodynamic database Zircobase, the hydrogen effects on oxygen solubility limit could be considered in the numerical simulations. Thus, simulations could reproduce the oxygen diffusion profiles measured in pre-hydrided samples. The existence of a thick pre-oxide layer on cladding tubes can induce a reduction of this pre-oxide layer before the growth of a high-temperature one during the high temperature dwell under steam. The first simulations performed using the numerical tool EKINOX-Zr showed that this particular

  5. Influence of screening effect on hydrogen passivation of hole silicon

    International Nuclear Information System (INIS)

    Aleksandrov, O.V.

    2002-01-01

    The simulation of hole silicon passivation during hydrogen diffusion with account of hydrogen-acceptor pairs formation, internal electrical field and screening effect has been carried out. Screening by free carriers of hydrogen and acceptor ions results in shortening their interaction radii and slacking the concentration dependence of hydrogen diffusivity at high level of silicon doping. The consistency of simulated and experimental profiles of holes and hydrogen-acceptor pairs is reached in a broad band of doping levels from 4 x 10 14 to 1.2 x 10 20 cm -3 at the pair binding energy of 0.70-0.79 eV while the radius of the Coulomb interaction of hydrogen and boron ions is equal to 35 A under low doping and decrease with increasing doping level [ru

  6. Outgassing rate of the copper-plated beam tube for ISABELLE

    International Nuclear Information System (INIS)

    Hseuh, H.C.; Gaudet, E.F.

    1981-01-01

    The ultrahigh vacuum system of the intersecting storage accelerator, ISABELLE, will consist of two interlaced rings of stainless steel beam tubes with a circumference 2-1/2 miles each. To obtain a good heat conduction during bakeout and to reduce the resistive wall instability during beam operation, a lmm thick copper coating will be electroplated to the outer surface of this 1.5 mm thick beam tube. To minimize the beam loss due to beam-gas collision, the pressure inside the beam tube is required to be 1 x 10 -11 Torr (N 2 equivalent) or less. To achieve this ultrahigh vacuum, the outgassing rate of the 304 LN stainless steel tubes has been reduced to approx. 1 x 10 -13 Torr. l/cm 2 . sec by vacuum firing at 950 0 C for one hour. However, during acid-bath electroplating of copper, significant amount of hydrogen will be reintroduced and trapped in stainless steel which will substantially increase the outgassing rate (to approx. 2 x 10 -12 Torr . l/cm 2 sec). The outgassing characteristics of these copper-plated beam tubes are studied and discussed within the scope of diffusion and energy of activation. Methods to reduce the outgassing rate to an acceptable level (approx. 1 x 10 -13 Torr . l/cm 2 . sec) are also given

  7. Structure Design and Implementation of the Passive μ-DMFC

    Directory of Open Access Journals (Sweden)

    Xiaowei Liu

    2015-02-01

    Full Text Available A dual-chamber anode structure is proposed in order to solve two performance problems of the conventional passive micro direct methanol fuel cell (μ-DMFC. One of the problems is the unstable performance during long time discharge. The second problem is the short operating time. In this structure, low concentration chamber is filled with methanol solution with appropriate concentration for the μ-DMFC. Pure methanol in high concentration chamber diffuses to the low concentration chamber to keep the concentration of methanol solution suitable for long-term discharge of μ-DMFC. In this study, a Nafion-Polytetrafluoroethylene (PTFE composite membrane is inserted between the two chambers to conduct pure methanol. The experimental results during long-term discharge show that the stable operating time of passive μ-DMFC increases by nearly 2.3 times compared to a conventional one with the same volume. These results could be applied to real products.

  8. Hydrogen passivation of n+p and p+n heteroepitaxial InP solar cell structures

    Science.gov (United States)

    Chatterjee, B.; Ringel, S. A.; Hoffman, R., Jr.

    1995-01-01

    High-efficiency, heteroepitaxial (HE) InP solar cells, grown on GaAs, Si or Ge substrates, are desirable for their mechanically strong, light-weight and radiation-hard properties. However, dislocations, caused by lattice mismatch, currently limit the performance of the HE cells. This occurs through shunting paths across the active photovoltaic junction and by the formation of deep levels. In previous work we have demonstrated that plasma hydrogenation is an effective and stable means to passivate the electrical activity of dislocations in specially designed HE InP test structures. In this work, we present the first report of successful hydrogen passivation in actual InP cell structures grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD). We have found that a 2 hour exposure to a 13.56 MHz hydrogen plasma at 275 C reduces the deep level concentration in HE n+n InP cell structures from as-grown values of approximately 10(exp 15)/cm(exp -3), down to 1-2 x 10(exp 13)/cm(exp -3). The deep levels in the p-type base region of the cell structure match those of our earlier p-type test structures, which were attributed to dislocations or related point defect complexes. All dopants were successfully reactivated by a 400 C, 5 minute anneal with no detectable activation of deep levels. I-V analysis indicated a subsequent approximately 10 fold decrease in reverse leakage current at -1 volt reverse bias, and no change in the forward biased series resistance of the cell structure which indicates complete reactivation of the n+ emitter. Furthermore, electrochemical C-V profiling indicates greatly enhanced passivation depth, and hence hydrogen diffusion, for heteroepitaxial structures when compared with identically processed homoepitaxial n+p InP structures. An analysis of hydrogen diffusion in dislocated InP will be discussed, along with comparisons of passivation effectiveness for n+p versus p+n heteroepitaxial cell configurations. Preliminary hydrogen-passivated

  9. Compositional properties of passivity

    NARCIS (Netherlands)

    Kerber, Florian; van der Schaft, Arjan

    2011-01-01

    The classical passivity theorem states that the negative feedback interconnection of passive systems is again passive. The converse statement, - passivity of the interconnected system implies passivity of the subsystems -, turns out to be equally valid. This result implies that among all feasible

  10. Recovery of deuterium from H-D gas mixture by thermal diffusion in a multi-concentric-tube column device of fixed total sum of column heights with transverse sampling streams

    International Nuclear Information System (INIS)

    Yeh, H.-M.

    2010-01-01

    The effect of the increment in the number of concentric-tube thermal diffusion columns on the recovery of deuterium from H 2 -HD-D 2 system with fixed total sum of column heights, has been investigated. The equations for predicting the degrees of separation in single-column, double-column and triple-column devices have been derived. Considerable improvement in recovery can be achieved if a multi-column device with larger number of column is employed, instead of a single-column device with column height equal to the same total sum of column heights, especially for the case of higher flow-rate operation and larger total sum of column heights.

  11. Modeling cytoskeletal traffic: an interplay between passive diffusion and active transport.

    Science.gov (United States)

    Neri, Izaak; Kern, Norbert; Parmeggiani, Andrea

    2013-03-01

    We introduce the totally asymmetric simple exclusion process with Langmuir kinetics on a network as a microscopic model for active motor protein transport on the cytoskeleton, immersed in the diffusive cytoplasm. We discuss how the interplay between active transport along a network and infinite diffusion in a bulk reservoir leads to a heterogeneous matter distribution on various scales: we find three regimes for steady state transport, corresponding to the scale of the network, of individual segments, or local to sites. At low exchange rates strong density heterogeneities develop between different segments in the network. In this regime one has to consider the topological complexity of the whole network to describe transport. In contrast, at moderate exchange rates the transport through the network decouples, and the physics is determined by single segments and the local topology. At last, for very high exchange rates the homogeneous Langmuir process dominates the stationary state. We introduce effective rate diagrams for the network to identify these different regimes. Based on this method we develop an intuitive but generic picture of how the stationary state of excluded volume processes on complex networks can be understood in terms of the single-segment phase diagram.

  12. Carbon Nano tubes Based Mixed Matrix Membrane for Gas Separation

    International Nuclear Information System (INIS)

    Sanip, S.M.; Ismail, A.F.; Goh, P.S.; Norrdin, M.N.A.; Soga, T.; Tanemura, M.; Yasuhiko, H.

    2011-01-01

    Carbon nano tubes based mixed matrix membrane (MMM) was prepared by the solution casting method in which the functionalized multi walled carbon nano tubes (f-MWNTs) were embedded into the polyimide membrane and the resulting membranes were characterized. The effect of nominal MWNTs content between 0.5 and 1.0 wt % on the gas separation properties were looked into. The morphologies of the MMM also indicated that at 0.7 % loading of f- MWNTs, the structures of the MMM showed uniform finger-like structures which have facilitated the fast gas transport through the polymer matrix. It may also be concluded that addition of open ended and shortened MWNTs to the polymer matrix can improve its permeability by increasing diffusivity through the MWNTs smooth cavity. (author)

  13. Studies on the permeation of hydrogen through steam generator tubes at high temperatures using an electrochemical method

    International Nuclear Information System (INIS)

    Giraudeau, F.; Yang, L.; Steward, F.R.; DeBouvier, O.

    1998-01-01

    The permeation of hydrogen through steam generator tubes at high temperatures (∼ 300 degrees C) has been studied using an electrochemical technique. With this technique, hydrogen is generated on one side of the tube and monitored on the other side. The time for the hydrogen to reach the other side is used to determine the diffusion coefficient of hydrogen in the tube. Boundary conditions at the entry and exit sides have been investigated separately. Preliminary studies were performed on Stainless Steel 316 and Nickel Alloy 800 to better understand the influence of the solution chemistry on the electrochemical evolution of hydrogen. The surface phenomena effect and the trapping effect are discussed to account for differences observed in the permeation response. The hydrogen permeation through oxides at the exit side has been studied. Two nickel alloys (Alloy 800 and Alloy 600), materials widely used for steam generator tubes, have been investigated. The tubes were prefilmed using two different treatments. The oxides were formed in dry air at high temperatures (300 degrees C to 600 degrees C), or in humid gas at 300 degrees C. The diffusion coefficients at 300 degrees C in Stainless Steel 316 and Alloy 800 were determined to be of the order of 10 -6 - 10 -7 cm 2 /s for the bare metal. This is in agreement with results obtained by gas phase permeation techniques in the literature. (author)

  14. Bismuth Passivation Technique for High-Resolution X-Ray Detectors

    Science.gov (United States)

    Chervenak, James; Hess, Larry

    2013-01-01

    The Athena-plus team requires X-ray sensors with energy resolution of better than one part in 3,000 at 6 keV X-rays. While bismuth is an excellent material for high X-ray stopping power and low heat capacity (for large signal when an X-ray is stopped by the absorber), oxidation of the bismuth surface can lead to electron traps and other effects that degrade the energy resolution. Bismuth oxide reduction and nitride passivation techniques analogous to those used in indium passivation are being applied in a new technique. The technique will enable improved energy resolution and resistance to aging in bismuth-absorber-coupled X-ray sensors. Elemental bismuth is lithographically integrated into X-ray detector circuits. It encounters several steps where the Bi oxidizes. The technology discussed here will remove oxide from the surface of the Bi and replace it with nitridized surface. Removal of the native oxide and passivating to prevent the growth of the oxide will improve detector performance and insulate the detector against future degradation from oxide growth. Placing the Bi coated sensor in a vacuum system, a reduction chemistry in a plasma (nitrogen/hydrogen (N2/H2) + argon) is used to remove the oxide and promote nitridization of the cleaned Bi surface. Once passivated, the Bi will perform as a better X-ray thermalizer since energy will not be trapped in the bismuth oxides on the surface. A simple additional step, which can be added at various stages of the current fabrication process, can then be applied to encapsulate the Bi film. After plasma passivation, the Bi can be capped with a non-diffusive layer of metal or dielectric. A non-superconducting layer is required such as tungsten or tungsten nitride (WNx).

  15. Passive ranging using a filter-based non-imaging method based on oxygen absorption.

    Science.gov (United States)

    Yu, Hao; Liu, Bingqi; Yan, Zongqun; Zhang, Yu

    2017-10-01

    To solve the problem of poor real-time measurement caused by a hyperspectral imaging system and to simplify the design in passive ranging technology based on oxygen absorption spectrum, a filter-based non-imaging ranging method is proposed. In this method, three bandpass filters are used to obtain the source radiation intensities that are located in the oxygen absorption band near 762 nm and the band's left and right non-absorption shoulders, and a photomultiplier tube is used as the non-imaging sensor of the passive ranging system. Range is estimated by comparing the calculated values of band-average transmission due to oxygen absorption, τ O 2 , against the predicted curve of τ O 2 versus range. The method is tested under short-range conditions. Accuracy of 6.5% is achieved with the designed experimental ranging system at the range of 400 m.

  16. Thermal characterization of rods, tubes and spheres using pulsed infrared thermography

    International Nuclear Information System (INIS)

    Apinaniz, E; Mendioroz, A; Madariaga, N; Oleaga, A; Celorrio, R; Salazar, A

    2008-01-01

    In this work we analyse the accuracy of an extension of the flash method to measure the thermal diffusivity of rods, tubes and spheres, which was recently proposed by the authors. We have performed measurements in a wide set of calibrated samples of different sizes and we have found that a lower limiting size of the radius can be established for the validity of the method. On the other hand, a procedure to retrieve the thermal conductivity of tubes, based on filling them with a contrast liquid (water), is proposed. Moreover, the thermal contact resistance between the two layers of coated cylinders is also obtained. Measurements on calibrated samples confirm the validity of the two latest methods

  17. Low-wave-number statistics of randomly advected passive scalars

    International Nuclear Information System (INIS)

    Kerstein, A.R.; McMurtry, P.A.

    1994-01-01

    A heuristic analysis of the decay of a passive scalar field subject to statistically steady random advection, predicts two low-wave-number spectral scaling regimes analogous to the similarity states previously identified by Chasnov [Phys. Fluids 6, 1036 (1994)]. Consequences of their predicted coexistence in a single flow are examined. The analysis is limited to the idealized case of narrow band advection. To complement the analysis, and to extend the predictions to physically more realistic advection processes, advection diffusion is simulated using a one-dimensional stochastic model. An experimental test of the predictions is proposed

  18. Introducing passive acoustic filter in acoustic based condition monitoring: Motor bike piston-bore fault identification

    Science.gov (United States)

    Jena, D. P.; Panigrahi, S. N.

    2016-03-01

    Requirement of designing a sophisticated digital band-pass filter in acoustic based condition monitoring has been eliminated by introducing a passive acoustic filter in the present work. So far, no one has attempted to explore the possibility of implementing passive acoustic filters in acoustic based condition monitoring as a pre-conditioner. In order to enhance the acoustic based condition monitoring, a passive acoustic band-pass filter has been designed and deployed. Towards achieving an efficient band-pass acoustic filter, a generalized design methodology has been proposed to design and optimize the desired acoustic filter using multiple filter components in series. An appropriate objective function has been identified for genetic algorithm (GA) based optimization technique with multiple design constraints. In addition, the sturdiness of the proposed method has been demonstrated in designing a band-pass filter by using an n-branch Quincke tube, a high pass filter and multiple Helmholtz resonators. The performance of the designed acoustic band-pass filter has been shown by investigating the piston-bore defect of a motor-bike using engine noise signature. On the introducing a passive acoustic filter in acoustic based condition monitoring reveals the enhancement in machine learning based fault identification practice significantly. This is also a first attempt of its own kind.

  19. Laboratory experiments to characterize radiochloride diffusion in unsaturated soils

    Energy Technology Data Exchange (ETDEWEB)

    Aldaba, D.; Fernandez-Torrent, R.; Rauret, G.; Vidal, M. [Departament de Quimica Analitica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain); Rigol, A. [Departament de Quimica Analitica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain)], E-mail: annarigol@ub.edu

    2010-03-15

    Diffusion transport of {sup 36}Cl was examined in seven soils under unsaturated conditions in tubes packed with two portions of each soil having different {sup 36}Cl activity concentrations. Apparent diffusion coefficients (D{sub a}) derived from diffusion profiles varied within a narrow range (from 3x10{sup -10} to 7x10{sup -10} m{sup 2} s{sup -1}) confirming the minor effect of soil properties on the diffusion of a non-reactive radionuclide like {sup 36}Cl. Instead, packing conditions had a major effect. Solid-liquid distribution coefficients (K{sub d}) derived from D{sub a} (0.02-0.2 L kg{sup -1}) were systematically lower than those obtained from batch experiments (0.6-1.0 L kg{sup -1}), but with a similar variation pattern among soils. The low values of K{sub d} (Cl) confirmed an almost negligible radiochloride-soil interaction.

  20. The effect of roll with passive segment on the planetary rolling process

    Directory of Open Access Journals (Sweden)

    Qing-Ling Zeng

    2015-03-01

    Full Text Available In three-roll planetary rolling process, there is secondary torsion phenomenon that may lead to rolling instability. This article proposed a new idea to alleviate the secondary torsion phenomenon by dividing the secondary torsion segment out of the roll as an independent and passive one. To study the performance of the roll with passive segment, the three-dimensional finite element models of planetary rolling process using actual roll or new roll with passive segment involving elastic–plastic and thermal–mechanical coupling were established by the software ABAQUS/Explicit, and a series of analysis had been done successfully. The rolling temperature and rolling force of planetary mill were in good agreement with the measured results, which indicated that the finite element method would supply important reference merit for three-dimensional thermo-mechanical simulation of the three-roll planetary rolling process. Comparing the simulation results of the two models, the results indicated that the change in the roll structure had just a little influence on the metal deformation, temperature, and rolling force, but it lessened the secondary torsion deformation effectively and improved the outside roundness of the rolled tube slightly. The research provided a new idea for the roll design of three-roll planetary mill (PSW.

  1. Diffusion of protein through the human cornea.

    Science.gov (United States)

    Charalel, Resmi A; Engberg, Kristin; Noolandi, Jaan; Cochran, Jennifer R; Frank, Curtis; Ta, Christopher N

    2012-01-01

    To determine the rate of diffusion of myoglobin and bovine serum albumin (BSA) through the human cornea. These small proteins have hydrodynamic diameters of approximately 4.4 and 7.2 nm, and molecular weights of 16.7 and 66 kDa, for myoglobin and BSA, respectively. Diffusion coefficients were measured using a diffusion chamber where the protein of interest and balanced salt solution were in different chambers separated by an ex vivo human cornea. Protein concentrations in the balanced salt solution chamber were measured over time. Diffusion coefficients were calculated using equations derived from Fick's law and conservation of mass in a closed system. Our experiments demonstrate that the diffusion coefficient of myoglobin is 5.5 ± 0.9 × 10(-8) cm(2)/s (n = 8; SD = 1.3 × 10(-8) cm(2)/s; 95% CI: 4.6 × 10(-8) to 6.4 × 10(-8) cm(2)/s) and the diffusion coefficient of BSA is 3.1 ± 1.0 × 10(-8) cm(2)/s (n = 8; SD = 1.4 × 10(-8) cm(2)/s; 95% CI: 2.1 × 10(-8) to 4.1 × 10(-8) cm(2)/s). Our study suggests that molecules as large as 7.2 nm may be able to passively diffuse through the human cornea. With applications in pharmacotherapy and the development of an artificial cornea, further experiments are warranted to fully understand the limits of human corneal diffusion and its clinical relevance. Copyright © 2012 S. Karger AG, Basel.

  2. Indoor NO/sub 2/ sampling in a large university campus in Benin city, southern Nigeria, using flames diffusion tubes

    International Nuclear Information System (INIS)

    Ukpebor, E.E.; Sadiku, Y.T.; Ahonkhai, S.I.

    2005-01-01

    Monitoring of NO/sub 2/ in different indoor environments (without cooking and with cooking using different fuels) was done. Flames diffusion tubes were used for the monitoring. The sampling duration was two weeks. The highest NO/sub 2/ concentration of 38.61 ppb (73.74 mug/m3) was monitored in the room where the cooking was done with a gas burner. This was followed by the room with firewood cooking, where the concentration was 36.75 ppb (70.19 mug/m3) and the least concentration of 24.05 ppb (46.80 mug/m3) was noted in the room, where kerosene stove was used for cooking. It is of significance to observe that the WHO annual average guideline value of 40 mug/m3 was exceeded in al the rooms where cooking was done. Levels obtained in this study, therefore, suggest a need for precautionary mitigation. However, the outdoor concentration of NO/sub 2/ was almost the same as that obtained indoors in the rooms without cooking. This suggests high penetration indoors of outdoor NO/sub 2/. A background level of 3.40 ppb (6.49 mug/m3) was established for the environment in Ugbowo, Benin City, Nigeria. (author)

  3. CdCl2 passivation of polycrystalline CdMgTe and CdZnTe absorbers for tandem photovoltaic cells

    Science.gov (United States)

    Swanson, Drew E.; Reich, Carey; Abbas, Ali; Shimpi, Tushar; Liu, Hanxiao; Ponce, Fernando A.; Walls, John M.; Zhang, Yong-Hang; Metzger, Wyatt K.; Sampath, W. S.; Holman, Zachary C.

    2018-05-01

    As single-junction silicon solar cells approach their theoretical limits, tandems provide the primary path to higher efficiencies. CdTe alloys can be tuned with magnesium (CdMgTe) or zinc (CdZnTe) for ideal tandem pairing with silicon. A II-VI/Si tandem holds the greatest promise for inexpensive, high-efficiency top cells that can be quickly deployed in the market using existing polycrystalline CdTe manufacturing lines combined with mature silicon production lines. Currently, all high efficiency polycrystalline CdTe cells require a chloride-based passivation process to passivate grain boundaries and bulk defects. This research examines the rich chemistry and physics that has historically limited performance when extending Cl treatments to polycrystalline 1.7-eV CdMgTe and CdZnTe absorbers. A combination of transmittance, quantum efficiency, photoluminescence, transmission electron microscopy, and energy-dispersive X-ray spectroscopy clearly reveals that during passivation, Mg segregates and out-diffuses, initially at the grain boundaries but eventually throughout the bulk. CdZnTe exhibits similar Zn segregation behavior; however, the onset and progression is localized to the back of the device. After passivation, CdMgTe and CdZnTe can render a layer that is reduced to predominantly CdTe electro-optical behavior. Contact instabilities caused by inter-diffusion between the layers create additional complications. The results outline critical issues and paths for these materials to be successfully implemented in Si-based tandems and other applications.

  4. Modeling the transport of organic chemicals between polyethylene passive samplers and water in finite and infinite bath conditions.

    Science.gov (United States)

    Tcaciuc, A Patricia; Apell, Jennifer N; Gschwend, Philip M

    2015-12-01

    Understanding the transfer of chemicals between passive samplers and water is essential for their use as monitoring devices of organic contaminants in surface waters. By applying Fick's second law to diffusion through the polymer and an aqueous boundary layer, the authors derived a mathematical model for the uptake of chemicals into a passive sampler from water, in finite and infinite bath conditions. The finite bath model performed well when applied to laboratory observations of sorption into polyethylene (PE) sheets for various chemicals (polycyclic aromatic hydrocarbons, polychlorinated biphenyls [PCBs], and dichlorodiphenyltrichloroethane [DDT]) and at varying turbulence levels. The authors used the infinite bath model to infer fractional equilibration of PCB and DDT analytes in field-deployed PE, and the results were nearly identical to those obtained using the sampling rate model. However, further comparison of the model and the sampling rate model revealed that the exchange of chemicals was inconsistent with the sampling rate model for partially or fully membrane-controlled transfer, which would be expected in turbulent conditions or when targeting compounds with small polymer diffusivities and small partition coefficients (e.g., phenols, some pesticides, and others). The model can be applied to other polymers besides PE as well as other chemicals and in any transfer regime (membrane, mixed, or water boundary layer-controlled). Lastly, the authors illustrate practical applications of this model such as improving passive sampler design and understanding the kinetics of passive dosing experiments. © 2015 SETAC.

  5. Heat transfer in tube bundles of heat exchangers with flow baffles induced forced mixing

    International Nuclear Information System (INIS)

    AbuRomia, M.M.; Chu, A.W.; Cho, S.M.

    1976-01-01

    Thermal analysis of shell-and-tube heat exchangers is being investigated through geometric modeling of the unit configuration in addition to considering the heat transfer processes taking place within the tube bundle. The governing equations that characterize the heat transfer from the shell side fluid to the tube side fluid across the heat transfer tubewalls are indicated. The equations account for the heat transfer due to molecular conduction, turbulent thermal diffusion, and forced fluid mixing among various shell side fluid channels. The analysis, though general in principle, is being applied to the Clinch River Breeder Reactor Plant-Intermediate Heat Exchanger, which utilizes flow baffles appropriately designed for induced forced fluid mixing in the tube bundle. The results of the analysis are presented in terms of the fluid and tube wall temperature distributions of a non-baffled and baffled tube bundle geometry. The former case yields axial flow in the main bundle region while the latter is associated with axial/cross flow in the bundle. The radial components of the axial/cross flow yield the necessary fluid mixing that results in reducing the thermal unbalance among the heat transfer to the allowable limits. The effect of flow maldistribution, present on the tube or shell sides of the heat exchangers, in altering the temperature field of tube bundles is also noted

  6. A simple modelling of mass diffusion effects on condensation with noncondensable gases for the CATHARE Code

    Energy Technology Data Exchange (ETDEWEB)

    Coste, P.; Bestion, D. [Commissariat a l Energie Atomique, Grenoble (France)

    1995-09-01

    This paper presents a simple modelling of mass diffusion effects on condensation. In presence of noncondensable gases, the mass diffusion near the interface is modelled using the heat and mass transfer analogy and requires normally an iterative procedure to calculate the interface temperature. Simplifications of the model and of the solution procedure are used without important degradation of the predictions. The model is assessed on experimental data for both film condensation in vertical tubes and direct contact condensation in horizontal tubes, including air-steam, Nitrogen-steam and Helium-steam data. It is implemented in the Cathare code, a french system code for nuclear reactor thermal hydraulics developed by CEA, EDF, and FRAMATOME.

  7. Control and optimization of solute transport in a thin porous tube

    KAUST Repository

    Griffiths, I. M.

    2013-03-01

    Predicting the distribution of solutes or particles in flows within porous-walled tubes is essential to inform the design of devices that rely on cross-flow filtration, such as those used in water purification, irrigation devices, field-flow fractionation, and hollow-fibre bioreactors for tissue-engineering applications. Motivated by these applications, a radially averaged model for fluid and solute transport in a tube with thin porous walls is derived by developing the classical ideas of Taylor dispersion. The model includes solute diffusion and advection via both radial and axial flow components, and the advection, diffusion, and uptake coefficients in the averaged equation are explicitly derived. The effect of wall permeability, slip, and pressure differentials upon the dispersive solute behaviour are investigated. The model is used to explore the control of solute transport across the membrane walls via the membrane permeability, and a parametric expression for the permeability required to generate a given solute distribution is derived. The theory is applied to the specific example of a hollow-fibre membrane bioreactor, where a uniform delivery of nutrient across the membrane walls to the extra-capillary space is required to promote spatially uniform cell growth. © 2013 American Institute of Physics.

  8. A DNS study of turbulent mixing of two passive scalars

    International Nuclear Information System (INIS)

    Juneja, A.; Pope, S.B.

    1996-01-01

    We employ direct numerical simulations to study the mixing of two passive scalars in stationary, homogeneous, isotropic turbulence. The present work is a direct extension of that of Eswaran and Pope from one scalar to two scalars and the focus is on examining the evolution states of the scalar joint probability density function (jpdf) and the conditional expectation of the scalar diffusion to motivate better models for multi-scalar mixing. The initial scalar fields are chosen to conform closely to a open-quote open-quote triple-delta function close-quote close-quote jpdf corresponding to blobs of fluid in three distinct states. The effect of the initial length scales and diffusivity of the scalars on the evolution of the jpdf and the conditional diffusion is investigated in detail as the scalars decay from their prescribed initial state. Also examined is the issue of self-similarity of the scalar jpdf at large times and the rate of decay of the scalar variance and dissipation. copyright 1996 American Institute of Physics

  9. Effective diffusion in laminar convective flows

    International Nuclear Information System (INIS)

    Rosenbluth, M.N.; Berk, H.L.; Doxas, I.; Horton, W.

    1987-03-01

    The effective diffusion coefficient D* of a passive component, such as test particles, dye, temperature, magnetic flux, etc., is derived for motion in periodic two-dimensional incompressible convective flow with characteristic velocity v and size d in the presence of an intrinsic local diffusivity D. Asymptotic solutions for effective diffusivity D*(P) in the large P limit, with P ∼ vd/D, is shown to be of the form D* = cDP/sup 1/2/ with c being a coefficient that is determined analytically. The constant c depends on the geometry of the convective cell and on an average of the flow speed along the separatrix. The asymptotic method of evaluation applies to both free boundary and rough boundary flow patterns and it is shown that the method can be extended to more complicated patterns such as the flows generated by rotating cylinders, as in the problem considered by Nadim, Cox, and Brenner [J. Fluid Mech., 164: 185 (1986)]. The diffusivity D* is readily calculated for small P, but the evaluation for arbitrary P requires numerical methods. Monte Carlo particle simulation codes are used to evaluate D* at arbitrary P, and thereby describe the transition for D* between the large and small P limits

  10. An evaluation of designed passive Core Makeup Tank (CMT) for China pressurized reactor (CPR1000)

    International Nuclear Information System (INIS)

    Wang, Mingjun; Tian, Wenxi; Qiu, Suizheng; Su, Guanghui; Zhang, Yapei

    2013-01-01

    Highlights: ► Only PRHRS is not sufficient to maintain reactor safety in case of SGTR accident. ► The Core Makeup Tank (CMT) is designed for CPR1000. ► Joint operation of PRHRS and CMT can keep reactor safety during the SGTR transient. ► CMT is a vital supplement for CPR1000 passive safety system design. - Abstract: Emergency Passive Safety System (EPSS) is an innovative design to improve reliability of nuclear power plants. In this work, the EPSS consists of secondary passive residual heat removal system (PRHRS) and the reactor Core Makeup Tank (CMT) system. The PRHRS, which has been studied in our previous paper, can effectively remove the core residual heat and passively improve the inherent safety by passive methods. The designed CMT, representing the safety improvement for CPR1000, is used to inject cool boron-containing water into the primary system during the loss of coolant accident. In this study, the behaviors of EPSS and transient characteristics of the primary loop system during the Steam Generator Tube Rupture (SGTR) accident are investigated using the nuclear reactor thermal hydraulic code RELAP5/MOD3.4. The results show that the designed CMT can protect the reactor primary loop from boiling and maintain primary loop coolant in single phase state. Both PRHRS and CMT operation ensures reactor safety during the SGTR accident. Results reported in this paper show that the designed CMT is a further safety improvement for CPR1000

  11. Passive sampling and analyses of common dissolved fixed gases in groundwater

    International Nuclear Information System (INIS)

    Spalding, Brian Patrick; Watson, David B.

    2008-01-01

    An in situ passive sampler and gas chromatographic protocol for analysis of the major and several minor fixed gases in groundwater was developed. A gas-tight syringe, mated to a short length of silicone tubing, was equilibrated with dissolved gases in groundwater by immersing in monitoring wells and was used to transport and to inject a 0.5 mL gas sample into a gas chromatograph. Using Ar carrier gas, a HaySep DB porous polymer phase, and sequential thermal conductivity and reductive gas detectors allowed good sensitivity for He, Ne, H2, N2, O2, CO, CH4, CO2, and N2O. Within 4 days of immersion in groundwater, samplers initially filled with either He or air attained the same and constant gas composition at an Oak Ridge, Tennessee, site heavily impacted by uranium, acidity, and nitrate. Between June 2006 and July 2007, 12 permanent groundwater wells were used to test the passive samplers in groundwater contaminated by a group of four closed radioactive wastewater seepage ponds; over a thousand passive gas samples from these wells averaged 56% CO2, 32.4% N2, 2.5% O2, 2.5% N2O, 0.20% CH4, 0.096% H2, and 0.023% CO with an average recovery of 95 14% of the injected gas volume

  12. Diffusion, spread, and migration of botulinum toxin.

    Science.gov (United States)

    Ramirez-Castaneda, Juan; Jankovic, Joseph; Comella, Cynthia; Dashtipour, Khashayar; Fernandez, Hubert H; Mari, Zoltan

    2013-11-01

    Botulinum toxin (BoNT) is an acetylcholine release inhibitor and a neuromuscular blocking agent used for the treatment of a variety of neurologic and medical conditions. The efficacy and safety of BoNT depends on accurate selection and identification of intended targets but also may be determined by other factors, including physical spread of the molecule from the injection site, passive diffusion, and migration to distal sites via axonal or hematogenous transport. The passive kinetic dispersion of the toxin away from the injection site in a gradient-dependent manner may also play a role in toxin spread. In addition to unique properties of the various BoNT products, volume and dilution may also influence local and systemic distribution of BoNT. Most of the local and remote complications of BoNT injections are thought to be due to unwanted spread or diffusion of the toxin's biologic activity into adjacent and distal muscles. Despite widespread therapeutic and cosmetic use of BoNT over more than three decades, there is a remarkable paucity of published data on the mechanisms of distribution and its effects on clinical outcomes. The primary aim of this article is to critically review the available experimental and clinical literature and place it in the practical context. © 2013 International Parkinson and Movement Disorder Society.

  13. Diffusion of hydrogen from plasma source by grain boundaries in EFG silicon

    International Nuclear Information System (INIS)

    Fedotov, A.; Saad, Anis M.H.; Drozdov, N.; Mazanik, A.; Ulyashin, A.; Fahrner, W.R.; Stognii, A.

    2001-01-01

    Diffusion of atomized hydrogen along grain boundaries (GBs) studied by transformation of their electrical activity in p-type silicon bi crystalline samples cut from EFG silicon crystals was investigated. The changes in electrical activity of GBs was estimated relative to both minority (MiC) and majority (MaC) carriers and demonstrated the correlation between the type, structure and thermal pre-history of GBs. It was shown on the base of this study that diffusion along GBs depends essentially on three factors: type of GBs, state of ribbons (as-grown or annealed) and concurrence of grain boundary dangling bonds and boron passivation effects. The model of the longitudinal hydrogen diffusion that explains these results is proposed

  14. Synthesis, characterization and field evaluation of a new calcium-based CO2 absorbent for radial diffusive sampler

    Science.gov (United States)

    Cucciniello, Raffaele; Proto, Antonio; Alfano, Davide; Motta, Oriana

    2012-12-01

    In this paper the use of passive sampling as a powerful approach to monitor atmospheric CO2 is assessed. Suitable substrate based on calcium-aluminium oxide was synthetized according to a process which permits to control the particle size of the CaO/Al based sorbent. The study shows that hydration of substrate is an essential part of the process of CO2 absorption and subsequent conversion to carbonate. X-ray diffraction, thermogravimetric analysis, environmental scanning electron microscopic analysis were used in order to characterize the substrate and to establish the best performances both in terms of particle size and CO2 absorption capacity. Passive samplers for CO2 monitoring were prepared and then tested at laboratory level and in the atmospheric environment. Validation was performed by comparison with an infrared continuous detector. Thermogravimetric analysis results, carried out to evaluate the absorbing capability of this new passive device, were in accordance with data collected at the same time by the active continuous analyser. The diffusive sampling rate and the diffusion coefficient of CO2 respect to this new passive device were also evaluated resulting equal to 47 ± 3 ml min-1 and 0.0509 ± 0.005 cm2 s-1, respectively.

  15. Material Barriers to Diffusive Mixing

    Science.gov (United States)

    Haller, George; Karrasch, Daniel

    2017-11-01

    Transport barriers, as zero-flux surfaces, are ill-defined in purely advective mixing in which the flux of any passive scalar is zero through all material surfaces. For this reason, Lagrangian Coherent Structures (LCSs) have been argued to play the role of mixing barriers as most repelling, attracting or shearing material lines. These three kinematic concepts, however, can also be defined in different ways, both within rigorous mathematical treatments and within the realm of heuristic diagnostics. This has lead to a an ever-growing number of different LCS methods, each generally identifying different objects as transport barriers. In this talk, we examine which of these methods have actual relevance for diffusive transport barriers. The latter barriers are arguably the practically relevant inhibitors in the mixing of physically relevant tracers, such as temperature, salinity, vorticity or potential vorticity. We demonstrate the role of the most effective diffusion barriers in analytical examples and observational data. Supported in part by the DFG Priority Program on Turbulent Superstructures.

  16. Influence of screening effect on hydrogen passivation of hole silicon

    CERN Document Server

    Aleksandrov, O V

    2002-01-01

    The simulation of hole silicon passivation during hydrogen diffusion with account of hydrogen-acceptor pairs formation, internal electrical field and screening effect has been carried out. Screening by free carriers of hydrogen and acceptor ions results in shortening their interaction radii and slacking the concentration dependence of hydrogen diffusivity at high level of silicon doping. The consistency of simulated and experimental profiles of holes and hydrogen-acceptor pairs is reached in a broad band of doping levels from 4 x 10 sup 1 sup 4 to 1.2 x 10 sup 2 sup 0 cm sup - sup 3 at the pair binding energy of 0.70-0.79 eV while the radius of the Coulomb interaction of hydrogen and boron ions is equal to 35 A under low doping and decrease with increasing doping level

  17. Ground state energy of an hydrogen atom confined in carbon nano-structures: a diffusion quantum Monte Carlo study

    International Nuclear Information System (INIS)

    Molayem, M.; Tayebi-Rad, Gh.; Esmaeli, L.; Namiranian, A.; Fouladvand, M. E.; Neek-Amal, M.

    2006-01-01

    Using the diffusion quantum monte Carlo method, the ground state energy of an Hydrogen atom confined in a carbon nano tube and a C60 molecule is calculated. For Hydrogen atom confined in small diameter tubes, the ground state energy shows significant deviation from a free Hydrogen atom, while with increasing the diameter this deviation tends to zero.

  18. Passive sampling of ambient ozone by solid phase microextraction with on-fiber derivatization

    International Nuclear Information System (INIS)

    Lee, I-S.; Tsai, S.-W.

    2008-01-01

    The solid phase microextraction (SPME) device with the polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber was used as a passive sampler for ambient ozone. Both O-2,3,4,5,6-(pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) and 1,2-di-(4-pyridyl)ethylene (DPE) were loaded onto the fiber before sampling. The SPME fiber assembly was then inserted into a PTFE tubing as a passive sampler. Known concentrations of ozone around the ambient ground level were generated by a calibrated ozone generator. Laboratory validations of the SPME passive sampler with the direct-reading ozone monitor were performed side-by-side in an exposure chamber at 25 deg. C. After exposures, pyriden-4-aldehyde was formed due to the reaction between DPE and ozone. Further on-fiber derivatizations between pyriden-4-aldehyde and PFBHA were followed and the derivatives, oximes, were then determined by portable gas chromatography with electron capture detector. The experimental sampling rate of the SPME ozone passive sampler was found to be 1.10 x 10 -4 cm 3 s -1 with detection limit of 58.8 μg m -3 h -1 . Field validations with both SPME device and the direct-reading ozone monitor were also performed. The correlations between the results from both methods were found to be consistent with r = 0.9837. Compared with other methods, the current designed sampler provides a convenient and sensitive tool for the exposure assessments of ozone

  19. A Study on the Characteristics of Design Variables for IRSS Diffuser

    Science.gov (United States)

    Cho, Yong-Jin; Ko, Dae-Eun

    2017-11-01

    In modern naval ships, infrared signature suppression systems (IRSS) are installed to decrease the temperature of waste gas generated in propulsion engine and the metallic surface temperature of heated exhaust pipes. Generally, IRSS is composed of eductor, mixing tube, and diffuser. Diffuser serves to reduce the temperature by creating an air film using the pressure difference between internal gas and external air. In this study, design variables were selected by analyzing the diffuser and the characteristics of design variables that affect the performance of diffuser were examined using Taguchi experiment method. For the diffuser performance analysis, a heat flow analysis technique established in previous research was used. The IRSS performance evaluation was carried out based on the average area value of the metal surface temperature and the temperature of the exhaust gas at the outlet of the diffuser, which are variables directly related to the intensity of infrared signature in naval ships. It was verified that the exhaust gas temperature is greatly affected by changes in the diameter of the diffuser outlet, and the metal surface temperature of diffuser is greatly affected by changes in the number of diffuser rings.

  20. Tube holding system

    International Nuclear Information System (INIS)

    Cunningham, R.C.

    1978-01-01

    A tube holding rig is described for the lateral support of tubes arranged in tight parcels in a heat exchanger. This tube holding rig includes not less than two tube supporting assemblies, with a space between them, located crosswise with respect to the tubes, each supporting assembly comprising a first set of parallel components in contact with the tubes, whilst a second set of components is also in contact with the tubes. These two sets of parts together define apertures through which the tubes pass [fr

  1. Simulation of steam condensation in the presence of noncondensable gases in horizontal condenser tubes using RELAP5 for advanced nuclear reactors

    International Nuclear Information System (INIS)

    Macedo, Luiz Alberto; Torres, Walmir Maximo

    2009-01-01

    Horizontal heat exchangers are used in advanced light water nuclear reactors in their passive cooling systems, such as residual heat removal (RHRS) and passive containment cooling system (PCCS). Condensation studies of steam and noncondensable gases mixtures in these heat exchangers are very important due to the phenomena multidimensional nature and the condensate stratification effects. This work presents a comparison between simulation results and experimental data in steady state conditions for some inlet pressure, steam and noncondensable gases (air) inlet mass fractions. The test section is three meters long and consists of two concentric tubes containing pressure, temperature and flow rate sensors. The internal tube, called condenser, contains steam-air mixture flow and external tube is a counter current cooler with water flow rate at low temperature. This test section was modeled and simulations were performed with RELAP5 code. Experimental tests were carried out for 200 to 400 kPa inlet pressure and 5, 10, 15 and 20% of inlet air mass fractions. Comparisons between experimental data and simulation results are presented for 200 and 400 kPa pressure conditions and showed good agreement. However, for 400 kPa inlet steam pressure and inlet air mass fractions above 5%, the simulated temperatures are lower than the experimental data at the final third from the inlet condenser tube, indicating a code overestimation of heat transfer coefficient. New correlations for heat transfer coefficient in these steam-air conditions must be theoretical and experimentally studied and implemented in RELAP5 code for better representing the condensation phenomena. (author)

  2. Design and Computational Fluid Dynamics Optimization of the Tube End Effector for Reactor Pressure Vessel Head Type VVER-1000

    International Nuclear Information System (INIS)

    Novosel, D.

    2006-01-01

    In this paper is presented development and optimization of the tube end effector design which should consist of 4 ultrasonic transducers, 4 Eddy Current's transducers and Radiation Proof Dot Camera. Basically, designing was conducted by main input requests, such as: inner diameter of a tested reactor pressure vessel head penetration tube, dimensions of a transducers and maximum allowable vertical movement of a manipulator connection rod in order to cover all inner tube surface. As is obvious, for ultrasonic testing should be provided the thin layer of liquid material (in our case water was chosen) which is necessary to make physical contact between transducer surface and investigated inner tube surface. By help of Computational Fluid Dynamics, determined were parameters of geometry, as the most important factor of transducer housing, hydraulically parameters for water supply and primary drain together implemented into this housing, movement of the end effectors (vertical and cylindrical) and finally, necessary equipment which has to provide all hydraulically and pneumatic requirements. As the cylindrical surface of the inner tube diameter was liquefied and contact between transducer housing and tested tube wasn't ideally covered, water leakage could occur in downstream direction. To reduce water leakage, which is highly contaminated, developed was second water drain by diffuser assembly which is driven by Venturi pipe, commercially called vacuum generator. Using the Computational Fluid Dynamic, obtained was optimized geometry of diffuser control volume with the highest efficiency, in other words, unobstructed fluid flux. Afterwards, the end effectors system was synchronized to the existing operable system for NDT methods all invented and designed by INETEC. (author)

  3. Transport logistics in pollen tubes.

    Science.gov (United States)

    Chebli, Youssef; Kroeger, Jens; Geitmann, Anja

    2013-07-01

    Cellular organelles move within the cellular volume and the effect of the resulting drag forces on the liquid causes bulk movement in the cytosol. The movement of both organelles and cytosol leads to an overall motion pattern called cytoplasmic streaming or cyclosis. This streaming enables the active and passive transport of molecules and organelles between cellular compartments. Furthermore, the fusion and budding of vesicles with and from the plasma membrane (exo/endocytosis) allow for transport of material between the inside and the outside of the cell. In the pollen tube, cytoplasmic streaming and exo/endocytosis are very active and fulfill several different functions. In this review, we focus on the logistics of intracellular motion and transport processes as well as their biophysical underpinnings. We discuss various modeling attempts that have been performed to understand both long-distance shuttling and short-distance targeting of organelles. We show how the combination of mechanical and mathematical modeling with cell biological approaches has contributed to our understanding of intracellular transport logistics.

  4. Normal and Inverse Diffusive Isotope Fractionation of Deuterated Toluene and Benzene in Aqueous Systems

    DEFF Research Database (Denmark)

    Rolle, Massimo; Jin, Biao

    2017-01-01

    Diffusive isotope fractionation of organic contaminants in aqueous solution is difficult to quantify, and only a few experimental data sets are available for compounds of environmental interest. In this study, we investigate diffusive fractionation of perdeuterated and nondeuterated benzene...... and toluene. Multitracer experiments were carried out in 1-D gel dissection tubes and in a quasi-2-D flow-through porous medium. The experiments allowed us to simultaneously and directly compare the diffusive and dispersive behavior of benzene and toluene. We observed an unexpected, opposite behavior...... of the two monoaromatic hydrocarbons. Toluene showed a normal diffusive isotope effect (DC7D8/DC7H8 = 0.96) with enrichment of the nondeuterated isotopologue in the direction of the diffusive and transverse dispersive fluxes. Conversely, the measured trends for benzene indicate inverse diffusive...

  5. Error quantification of the axial nodal diffusion kernel of the DeCART code

    International Nuclear Information System (INIS)

    Cho, J. Y.; Kim, K. S.; Lee, C. C.

    2006-01-01

    This paper is to quantify the transport effects involved in the axial nodal diffusion kernel of the DeCART code. The transport effects are itemized into three effects, the homogenization, the diffusion, and the nodal effects. A five pin model consisting of four fuel pins and one non-fuel pin is demonstrated to quantify the transport effects. The transport effects are analyzed for three problems, the single pin (SP), guide tube (GT) and control rod (CR) problems by replacing the non-fuel pin with the fuel pin, a guide-tube and a control rod pins, respectively. The homogenization and diffusion effects are estimated to be about -4 and -50 pcm for the eigenvalue, and less than 2 % for the node power. The nodal effect on the eigenvalue is evaluated to be about -50 pcm in the SP and GT problems, and +350 pcm in the CR problem. Regarding the node power, this effect induces about a 3 % error in the SP and GT problems, and about a 20 % error in the CR problem. The large power error in the CR problem is due to the plane thickness, and it can be decreased by using the adaptive plane size. From the error quantification, it is concluded that the homogenization and the diffusion effects are not controllable if DeCART maintains the diffusion kernel for the axial solution, but the nodal effect is controllable by introducing the adaptive plane size scheme. (authors)

  6. Anomalous behavior of the diffusion coefficient in thin active films

    International Nuclear Information System (INIS)

    Basu, Abhik; Joanny, Jean-Francois; Prost, Jacques; Jülicher, Frank

    2012-01-01

    Inspired by recent experiments in cell biology, we elucidate the visco-elastic properties of an active gel by studying the dynamics of a small tracer particle inside it. In a stochastic hydrodynamic approach for an active gel of finite thickness L, we calculate the mean square displacement of a particle. These particle displacements are governed by fluctuations in the velocity field. We characterize the short-time behavior when the gel is a solid as well as the limit of long times when the gel becomes a fluid and the particle shows simple diffusion. Active stresses together with local polar order give rise to velocity fluctuations that lead to characteristic behaviors of the diffusion coefficient that differ fundamentally from those found in a passive system: the diffusion coefficient can depend on system size and diverges as L approaches an instability threshold. Furthermore, the diffusion coefficient becomes independent of the particle size in this case. (paper)

  7. HF electronic tubes. Technologies, grid tubes and klystrons

    International Nuclear Information System (INIS)

    Lemoine, Th.

    2009-01-01

    This article gives an overview of the basic technologies of electronic tubes: cathodes, electronic optics, vacuum and high voltage. Then the grid tubes, klystrons and inductive output tubes (IOT) are introduced. Content: 1 - context and classification; 2 - electronic tube technologies: cathodes, electronic optics, magnetic confinement (linear tubes), periodic permanent magnet (PPM) focussing, collectors, depressed collectors; 3 - vacuum technologies: vacuum quality, surface effects and interaction with electrostatic and RF fields, secondary emission, multipactor effect, thermo-electronic emission; 4 - grid tubes: operation of a triode, tetrodes, dynamic operation and classes of use, 'common grid' and 'common cathode' operation, ranges of utilisation and limitations, operation of a tetrode on unadjusted load, lifetime of a tetrode, uses of grid tubes; 5 - klystrons: operation, impact of space charge, multi-cavity klystrons, interaction efficiency, extended interaction klystrons, relation between interaction efficiency, perveance and efficiency, ranges of utilization and power limitations, multi-beam klystrons and sheet beam klystrons, operation on unadjusted load, klystron band pass and lifetime, uses; 6 - IOT: principle of operation, ranges of utilisation and limitations, interaction efficiency and depressed collector IOT, IOT lifetime and uses. (J.S.)

  8. High-Performance Quantum Dot Thin-Film Transistors with Environmentally Benign Surface Functionalization and Robust Defect Passivation.

    Science.gov (United States)

    Jung, Su Min; Kang, Han Lim; Won, Jong Kook; Kim, JaeHyun; Hwang, ChaHwan; Ahn, KyungHan; Chung, In; Ju, Byeong-Kwon; Kim, Myung-Gil; Park, Sung Kyu

    2018-01-31

    The recent development of high-performance colloidal quantum dot (QD) thin-film transistors (TFTs) has been achieved with removal of surface ligand, defect passivation, and facile electronic doping. Here, we report on high-performance solution-processed CdSe QD-TFTs with an optimized surface functionalization and robust defect passivation via hydrazine-free metal chalcogenide (MCC) ligands. The underlying mechanism of the ligand effects on CdSe QDs has been studied with hydrazine-free ex situ reaction derived MCC ligands, such as Sn 2 S 6 4- , Sn 2 Se 6 4- , and In 2 Se 4 2- , to allow benign solution-process available. Furthermore, the defect passivation and remote n-type doping effects have been investigated by incorporating indium nanoparticles over the QD layer. Strong electronic coupling and solid defect passivation of QDs could be achieved by introducing electronically active MCC capping and thermal diffusion of the indium nanoparticles, respectively. It is also noteworthy that the diffused indium nanoparticles facilitate charge injection not only inter-QDs but also between source/drain electrodes and the QD semiconductors, significantly reducing contact resistance. With benign organic solvents, the Sn 2 S 6 4- , Sn 2 Se 6 4- , and In 2 Se 4 2- ligand based QD-TFTs exhibited field-effect mobilities exceeding 4.8, 12.0, and 44.2 cm 2 /(V s), respectively. The results reported here imply that the incorporation of MCC ligands and appropriate dopants provide a general route to high-performance, extremely stable solution-processed QD-based electronic devices with marginal toxicity, offering compatibility with standard complementary metal oxide semiconductor processing and large-scale on-chip device applications.

  9. Development of safety evaluation technique of steam generator tubes for the next generation

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Hyuk Sang; Kim, I. S.; Ann, Se Jin; Lee, S. J.; Seo, M. S.; Lee, Y. H.; Kim, J. H.; Hong, J. G. [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    2000-02-15

    Subject 1 - a technique for predicting the SCC susceptibility of steam generator tube material based on the repassivation kinetics was developed and the effects of Pb in the repassivation rate and SCC susceptibility rate of tube material was investigated with this technique. An alloy with a higher slope value of log i(t) vs. q(t) plot based on the current transient curve obtained by scratch test and a lower slope value log i(t) vs. l/q(t) plot (cBV) is repassivated faster with a more protective passive film and it can be predicted that it will show higher resistance to SCC. With PbO addition in all solution studied (pH 4, pH 10, Cl- containing pH 4), alloy 690TT showed decreased repassivation rate. So it can be predict that PbO addition lower the resistance of SCC of steam generator tune material. Subject 2 - SG wear testing of tube and support materials has been conducted at various load and sliding amplitude in air environment. The results showed effect of normal load and sliding amplitude on SG tube wear damage. It was also shown that, for predominantly sliding motion, the SG wear coefficient of work-rate model is lower for Inconel 690TT compared with inconel 600MA. SG tube wear data show that, for work-rates ranging from 4 to 25mW, average tube wear coefficient of 43.76{approx}54.05 X 10{sup 15} Pa{sup -1} for Inconel 600MA and 26.88{approx}33.94 X 10{sup -15} Pa{sup 1} for Inconel 690TT against 405 and 409 stainless steels.

  10. Passive measurement of flux nucleation in the current-induced resistive state of type I superconductors

    International Nuclear Information System (INIS)

    Selig, K.P.; Chimenti, D.E.; Huebener, R.P.

    1978-01-01

    Flux-tube nucleation rates have been measured in the current-induced resistive state of type I superconducting In films between 1.5 and 2.0 K by a completely passive technique. Indication of periodic nucleation is observed only in narrow regions of sample voltage drop, whose position is a sensitive function of temperature. Frequency bandwidth measurements of the nucleation rate yield a spectral purity of one part in 10 4 within the narrow regions where an experimental signal can be detected. (orig.) [de

  11. Multi-walled carbon nano-tubes for energy storage and production applications

    International Nuclear Information System (INIS)

    Andrews, R.; Jacques, D.; Likpa, S.; Qian, D.; Rantell, T.; Anthony, J.

    2005-01-01

    Full text of publication follows: Since their discovery, carbon nano-tubes have been proposed as candidate materials for a broad range of applications, including high strength composites, molecular electronics, and energy storage. In many cases, nano-tubes have been proposed to replace traditional carbon materials, such as activated carbons in energy storage devices. In other cases, novel applications have been proposed, such as the use of carbon nano-tube arrays in photovoltaic devices. The use of multi-walled carbon nano-tubes in energy storage devices has generated great interest due to their high inherent conductivity, layered structure, and high surface area per volume compared to traditional graphitic materials. However as produced nano-tubes do not possess ideal properties, and exhibit only modest charge storage. We have explored the charge storage abilities of nano-tubes with varying morphologies (fullerenic versus stacked cones), nano-tubes containing N or B dopants, as well as various post-treatments of the nano-tubes. The use of nano-tubes in charge storage devices will be described, as well as modification of the nano-tube surfaces or morphology to improve this performance. The synthesis of nano-tubes with several differing hetero-atom dopants will also be described, as well as the effect of heat treatment on these structures. One of the most significant problems in organic photovoltaics is the typically low charge-carrier mobility in organic thin films which, coupled with short exciton diffusion lengths, means that photo-generated charge-carrier pairs are more likely to re-combine than reach an electrode to generate current. Two organic systems with high charge-carrier mobilities are carbon nano-tubes (here, MWNTs) and acene-based organic semiconductors. We believe that blended devices based on MWNTs and organic semiconductors could lead to the next class of efficient, flexible and inexpensive organic photovoltaic systems. We have developed methods to

  12. An Isotope Study of Hydrogenation of poly-Si/SiOx Passivated Contacts for Si Solar Cells: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Schnabel, Manuel; Nemeth, William; van de Loo, Bas, W.H.; Macco, Bart; Kessels, Wilhelmus, M.M.; Stradins, Paul; Young, David, L.

    2017-06-26

    For many years, the record Si solar cell efficiency stood at 25.0%. Only recently have several companies and institutes managed to produce more efficient cells, using passivated contacts of made doped poly-Si or a-Si:H and a passivating intrinsic interlayer in all cases. Common to these designs is the need to passivate the layer stack with hydrogen. In this contribution, we perform a systematic study of passivated contact passivation by hydrogen, using poly-Si/SiOx passivated contacts on n-Cz-Si, and ALD Al2O3 followed by a forming gas anneal (FGA) as the hydrogen source. We study p-type and n-type passivated contacts with implied Voc exceeding 690 and 720 mV, respectively, and perform either the ALD step or the FGA with deuterium instead of hydrogen in order to separate the two processes via SIMS. By examining the deuterium concentration at the SiOx in both types of samples, we demonstrate that the FGA supplies negligible hydrogen species to the SiOx, regardless of whether the FGA is hydrogenated or deuterated. Instead, it supplies the thermal energy needed for hydrogen species in the Al2O3 to diffuse there. Furthermore, the concentration of hydrogen species at the SiOx can saturate while implied Voc continues to increase, showing that the energy from the FGA is also required for hydrogen species already at the SiOx to find recombination-active defects to passivate.

  13. Computational Fluid Dynamic Investigation of Loss Mechanisms in a Pulse-Tube Refrigerator

    International Nuclear Information System (INIS)

    Martin, K; Esguerra, J; Dodson, C; Razani, A

    2015-01-01

    In predicting Pulse-Tube Cryocooler (PTC) performance, One-Dimensional (1-D) PTR design and analysis tools such as Gedeon Associates SAGE® typically include models for performance degradation due to thermodynamically irreversible processes. SAGE®, in particular, accounts for convective loss, turbulent conductive loss and numerical diffusion “loss” via correlation functions based on analysis and empirical testing.In this study, we compare CFD and SAGE® estimates of PTR refrigeration performance for four distinct pulse-tube lengths. Performance predictions from PTR CFD models are compared to SAGE® predictions for all four cases. Then, to further demonstrate the benefits of higher-fidelity and multidimensional CFD simulation, the PTR loss mechanisms are characterized in terms of their spatial and temporal locations. (paper)

  14. Thermal Sizing of Heat Exchanger Tubes for Air Natural Convective Cooling System of Emergency Cooling Tank

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Myoung Jun; Lee, Hee Joon [Kookmin Univ., Seoul (Korea, Republic of); Moon, Joo Hyung; Bae, Youngmin; Kim, Youngin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    For the long operation of secondary passive cooling system, however, water level goes down by evaporation in succession at emergency cooling tank. At the end there would be no place to dissipate heat from condensation heat exchanger. Therefore, steam cooling heat exchanger is put on the top of emergency cooling tank to maintain appropriate water level by collecting evaporating steam. Steam cooling heat exchanger is installed inside an air chimney and evaporated steam is cooled down by air natural convection. In this study, thermal sizing of steam cooling heat exchanger under air natural convection was conducted by TSCON program for the design of experimental setup as shown in Fig. 2. Thermal sizing of steam cooling heat exchanger tube under air natural convection was conducted by TSCON program for the design of experimental setup. 25 - 1' tubes which has a length 1687 mm was determined as steam cooling heat exchanger at 2 kW heat load and 100 liter water pool in emergency cooling tank (experimental limit condition). The corresponding width of two tubes is 50 mm and has 5 by 5 tube array for heat exchanger.

  15. Thermal Sizing of Heat Exchanger Tubes for Air Natural Convective Cooling System of Emergency Cooling Tank

    International Nuclear Information System (INIS)

    Kim, Myoung Jun; Lee, Hee Joon; Moon, Joo Hyung; Bae, Youngmin; Kim, Youngin

    2014-01-01

    For the long operation of secondary passive cooling system, however, water level goes down by evaporation in succession at emergency cooling tank. At the end there would be no place to dissipate heat from condensation heat exchanger. Therefore, steam cooling heat exchanger is put on the top of emergency cooling tank to maintain appropriate water level by collecting evaporating steam. Steam cooling heat exchanger is installed inside an air chimney and evaporated steam is cooled down by air natural convection. In this study, thermal sizing of steam cooling heat exchanger under air natural convection was conducted by TSCON program for the design of experimental setup as shown in Fig. 2. Thermal sizing of steam cooling heat exchanger tube under air natural convection was conducted by TSCON program for the design of experimental setup. 25 - 1' tubes which has a length 1687 mm was determined as steam cooling heat exchanger at 2 kW heat load and 100 liter water pool in emergency cooling tank (experimental limit condition). The corresponding width of two tubes is 50 mm and has 5 by 5 tube array for heat exchanger

  16. Effects of Dihedral Angle on Pool Boiling Heat Transfer from Two Tubes in Vertical Alignment

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Myeong-Gie [Andong National University, Andong (Korea, Republic of)

    2014-10-15

    One of the major issues in pool boiling heat transfer is a tube arrangement. The upper tube is affected by the lower tube and the enhancement of the heat transfer on the upper tube is estimated by the bundle effect ( h{sub r} ). It is defined as the ratio of the heat transfer coefficient ( h{sub b} ) for an upper tube in a bundle with lower tubes activated to that for the same tube activated alone in the bundle. Since heat transfer is related with the conditions of a tube surface, bundle geometries, and a liquid type, lots of studies have been carried out for the combinations of those parameters. The most effective parameter must be the tube pitch. Many researchers have been investigated its effect on heat transfer enhancement for the tube bundles and the tandem tubes. The heat transfer on the upper tube of the tubes is enhanced compared with the single tube. The upper tube within a tube bundle can significantly increase nucleate boiling heat transfer compared to the lower tubes at moderate heat fluxes. At high heat fluxes these influences disappear and the data merge onto the pool boiling curve of a single tube. It was explained that the major influential factor is the convective effects due to the fluid velocity and the rising bubbles. They used microstructure-R134a or FC-3184 combinations and identified that the increase in the heat flux of the lower tube decreased the superheat ( ∆T{sub sat} ) of the upper tube. The passive condensers adopted in SWR1000 and APR+ has U-type tubes. Those tubes are slightly inclined from the horizontal to prevent the occurrence of the water hammer. Since the pitch between the upper and lower tubes is varying along the tube length, the results for the fixed pitch are not applicable to the analysis of these condensers. Although there are lots of studies introducing results for the effects of inclination angle on pool boiling heat transfer, no results are treating the angle between two tubes. Therefore, the present study is aimed

  17. ESTIMATION OF TURBULENT DIFFUSIVITY WITH DIRECT NUMERICAL SIMULATION OF STELLAR CONVECTION

    Energy Technology Data Exchange (ETDEWEB)

    Hotta, H.; Iida, Y.; Yokoyama, T., E-mail: hotta.h@eps.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2012-05-20

    We investigate the value of horizontal turbulent diffusivity {eta} by numerical calculation of thermal convection. In this study, we introduce a new method whereby the turbulent diffusivity is estimated by monitoring the time development of the passive scalar, which is initially distributed in a given Gaussian function with a spatial scale d{sub 0}. Our conclusions are as follows: (1) assuming the relation {eta} = L{sub c} v{sub rms}/3, where v{sub rms} is the root-mean-square (rms) velocity, the characteristic length L{sub c} is restricted by the shortest one among the pressure (density) scale height and the region depth. (2) The value of turbulent diffusivity becomes greater with the larger initial distribution scale d{sub 0}. (3) The approximation of turbulent diffusion holds better when the ratio of the initial distribution scale d{sub 0} to the characteristic length L{sub c} is larger.

  18. Two passive groundwater treatment installations at DOE facilities

    International Nuclear Information System (INIS)

    Barton, W.D.; Craig, P.M.; Stone, W.C.

    1997-01-01

    Groundwater is being successfully treated by reactive media at two DOE sites. Passive treatment utilizing containerized treatment media has been installed on a radioactive groundwater seep at Oak Ridge National Lab, Oak Ridge, Tennessee, and on a TCE plume at the Portsmouth Gaseous Diffusion Plant in Piketon, Ohio. In both applications, flow is conducted by gravity through canisters of reactive treatment media. The canister-based treatment installation at ORNL utilizes a natural sodium-chabazite zeolite to remove radiological cations (Sr, Cs) from contaminated groundwater at greater than 99.9% efficiency. Portsmouth is currently conducting tests on three different types of treatment media for reductive dehalogenation of TCE

  19. Evaluation of a Simple, Small-Plot Meteorological Technique for Measurement of Ammonia Emission: Feasibility, Costs, and Recommendations

    DEFF Research Database (Denmark)

    Pedersen, Simon Vilms; di Perta, Ester Scotto; Hafner, Sasha D.

    2018-01-01

    are regularly developed, and their efficacy needs to be tested using accurate methods. To date, a major obstacle to many available emission measurement techniques is the requirement of large plot sizes of homogeneous surface characteristics, which particularly is a challenge to the number of plot......-level replicates that can be carried out on a field providing uniform surface characteristics throughout. The objectives of this research were to test three different methods for measuring NH3 flux when applied to small plots (methods and to determine...... techniques, wind tunnels measuring gas-phase ammonia using ALPHA passive diffusion samplers and a flux chamber method using Dräger tubes for measurements of ammonia concentration (DTM) were used. As an inexpensive alternative small-plot method, we studied the feasibility of applying ALPHA passive diffusion...

  20. Tube to tube excursive instability - sensitivities and transients

    International Nuclear Information System (INIS)

    Brown, M.; Layland, M.W.

    1980-01-01

    A simple basic analysis of excursive instability in a boiler tube shows how it depends upon operating conditions and physical properties. A detailed mathematical model of an AGR boiler is used to conduct a steady state parameter sensitivity survey. It is possible from this basis to anticipate the effects of changes in operating conditions and changes in design parameters upon tube to tube stability. Dynamic responses of tubes operating near the stability threshold are examined using a mathematical model. Simulated excursions are triggered by imparting small abrupt pressure changes on the boiler inlet pressure. The influences of the magnitude of the pressure change, waterside friction factor and gas side coupling between tubes are examined. (author)

  1. Relative distance between tracers as a measure of diffusivity within moving aggregates

    Science.gov (United States)

    Pönisch, Wolfram; Zaburdaev, Vasily

    2018-02-01

    Tracking of particles, be it a passive tracer or an actively moving bacterium in the growing bacterial colony, is a powerful technique to probe the physical properties of the environment of the particles. One of the most common measures of particle motion driven by fluctuations and random forces is its diffusivity, which is routinely obtained by measuring the mean squared displacement of the particles. However, often the tracer particles may be moving in a domain or an aggregate which itself experiences some regular or random motion and thus masks the diffusivity of tracers. Here we provide a method for assessing the diffusivity of tracer particles within mobile aggregates by measuring the so-called mean squared relative distance (MSRD) between two tracers. We provide analytical expressions for both the ensemble and time averaged MSRD allowing for direct identification of diffusivities from experimental data.

  2. Tube-support response to tube-denting evaluation. Volume 1. Final report

    International Nuclear Information System (INIS)

    Anderson, P.L.; Hall, J.F.; Shah, P.K.; Wills, R.L.

    1983-05-01

    The response of the tube supports is one of the important considerations of tube denting in a steam generator. Investigations have indicated that damaged tube supports have the potential to distort and damage tubes. This investigation considers the response to tube denting of the Combustion Engineering type tube supports. Drilled support plates and eggcrate tube supports are tested in a model steam generator in which tube denting is induced. The experimental data is used to verify and refine analytical predictor models developed using finite element techniques. It was found that analytical models underpredicted the deformations of the tube supports and appropriate modifications to enhance the predictive capability are identified. Non-destructive examination methods are evaluated for application to operating steam generators. It was found that the standard eddy current and profilometry techniques are acceptable methods for determining tube deformations, but these techniques are not adequate to assess tube support damage. Radiography is judged to be the best available means of determining the extent and progression of damage in tube supports

  3. Measuring Charge Carrier Diffusion in Coupled Colloidal Quantum Dot Solids

    KAUST Repository

    Zhitomirsky, David

    2013-06-25

    Colloidal quantum dots (CQDs) are attractive materials for inexpensive, room-temperature-, and solution-processed optoelectronic devices. A high carrier diffusion length is desirable for many CQD device applications. In this work we develop two new experimental methods to investigate charge carrier diffusion in coupled CQD solids under charge-neutral, i.e., undepleted, conditions. The methods take advantage of the quantum-size-effect tunability of our materials, utilizing a smaller-bandgap population of quantum dots as a reporter system. We develop analytical models of diffusion in 1D and 3D structures that allow direct extraction of diffusion length from convenient parametric plots and purely optical measurements. We measure several CQD solids fabricated using a number of distinct methods and having significantly different doping and surface ligand treatments. We find that CQD materials recently reported to achieve a certified power conversion efficiency of 7% with hybrid organic-inorganic passivation have a diffusion length of 80 ± 10 nm. The model further allows us to extract the lifetime, trap density, mobility, and diffusion coefficient independently in each material system. This work will facilitate further progress in extending the diffusion length, ultimately leading to high-quality CQD solid semiconducting materials and improved CQD optoelectronic devices, including CQD solar cells. © 2013 American Chemical Society.

  4. Reaction-diffusion systems in intracellular molecular transport and control.

    Science.gov (United States)

    Soh, Siowling; Byrska, Marta; Kandere-Grzybowska, Kristiana; Grzybowski, Bartosz A

    2010-06-07

    Chemical reactions make cells work only if the participating chemicals are delivered to desired locations in a timely and precise fashion. Most research to date has focused on active-transport mechanisms, although passive diffusion is often equally rapid and energetically less costly. Capitalizing on these advantages, cells have developed sophisticated reaction-diffusion (RD) systems that control a wide range of cellular functions-from chemotaxis and cell division, through signaling cascades and oscillations, to cell motility. These apparently diverse systems share many common features and are "wired" according to "generic" motifs such as nonlinear kinetics, autocatalysis, and feedback loops. Understanding the operation of these complex (bio)chemical systems requires the analysis of pertinent transport-kinetic equations or, at least on a qualitative level, of the characteristic times of the constituent subprocesses. Therefore, in reviewing the manifestations of cellular RD, we also describe basic theory of reaction-diffusion phenomena.

  5. Condenser tube buckling within tube-tubesheet joints

    International Nuclear Information System (INIS)

    Willertz, L.E.; Kalnins, A.; Updike, D.P.

    1991-01-01

    The problem of the appearance of protrusions, or bumps, in the interior of roller-expanded tubes within a tubesheet is addressed. Such bumps have been observed in condensers of power plants. A brief history of the reported occurrences of the bumps is given. The hypothesis is advanced that the mechanics of the formation of the bumps is similar to a buckling problem that has 'bifurcation at infinity'. Following this hypothesis, a two-dimensional physical model is developed, and the application of this model to study a three-dimensional bump is proposed. It is proposed in this paper that an initial deviation from the circular shape of the tube required to produce a bump. It is shown that without such a deviation the tubes cannot buckle. An experiment with short tube segments has been performed that verifies some of the features of the observed condenser tube bumps. Exactly what force produced the initial deviation for the observed bumps is still unknown. Available evidence implicates the hydro-laser jet that is used in the cleaning of tubes and tubesheets. A scenario of how a bump could have been produced by the hydro-laser jet is proposed. (author)

  6. Structural integrity evaluations of CANDU pressure tubes

    International Nuclear Information System (INIS)

    Radu, Vasile

    2003-01-01

    The core of a CANDU-6 pressurized heavy water reactor consists of some hundred horizontal pressure tubes that are manufactured from a Zr-2.5%Nb alloy and which contain the fuel bundles. These tubes are susceptible to a damaging phenomenon known as Delayed Hydride Cracking (DHC). The Zr-2.5%Nb alloy is susceptible to DHC phenomenon when there is diffusion of hydrogen atoms to a service-induced flaws, followed by the hydride platelets formation on the certain crystallographic planes in the matrix material. Finally, the development of hydride regions at the flaw-tip will happened. These hydride regions are able to fracture under stress-temperature conditions (DHC initiation) and the cracks can extend and grow by DHC mechanism. Some studies have been focused on the potential to initiate DHC at the blunt flaws in a CANDU reactor pressure tube and a methodology for structural integrity evaluation was developed. The methodology based on the Failure Assessment Diagrams (FAD's) consists in an integrated graphical plot, where the fracture failure and plastic collapse are simultaneously evaluated by means of two non-dimensional variables (K r and L r ). These two variables represent the ratio of the applied value of either stress or stress intensity factor and the resistance parameter of corresponding magnitude (yield stress or fracture toughness, respectively). Once the plotting plane is determined by the variables K r and L r , the procedure defines a critical failure line that establishes the safe area. The paper will demonstrate the possibility to perform structural integrity evaluations by means of Failure Assessment Diagrams for flaws occurring in CANDU pressure tubes. (author)

  7. Combined natural convection and surface radiation in the annular region between a volumetrically heated inner tube and a finite conducting outer tube

    International Nuclear Information System (INIS)

    Gianoulakis, S.; Klein, D.E.

    1993-01-01

    Buoyancy-driven natural-convection heat transfer in enclosures has been the subject of considerable research with applications to electronic packaging, solar collectors, and shipping containers for spent nuclear fuel. A numerical study has been carried out to predict combined natural-convection and radiation heat transfer in the annular region between concentric tubes. The inner tube was volumetrically heated. Both tubes were of finite conductance. The surfaces of the annular region were diffuse and gray. The gas in the annulus was assumed to be nonparticipating. A newly developed hybrid finite element finite difference method was used for the study. This method combines finite element discretization of geometries with finite difference discretized solution procedures for the governing differential equations. This study examined the effects of surface radiative properties and material conductivities on the temperature and velocity fields and on local heat transfer rates. Fluid Raleigh numbers ranging from 10 3 to 10 7 , ratios of solid to fluid region thermal conductivities ranging from 10 to 10 4 , and surface total hemispherical emissivities ranging from 0.0 to 1.0 were examined in this study. It was found that the heat transfer across the annulus was dominated by conduction and radiation for the lower Raleigh number flows. As the fluid Raleigh number increased, convection became a primary mode of heat transfer. As the surface emissivity was increased in the annulus, the average Nusselt number on the inner tube surface decreased

  8. Five years of nitrogen dioxide measurement with diffusion tube samplers at over 1000 sites in the UK

    Science.gov (United States)

    Stevenson, Ken; Bush, Tony; Mooney, Diane

    In 1993, a large (>1000 monitoring sites) co-ordinated monitoring network for nitrogen dioxide, using diffusion tube samplers, was established in urban areas throughout the UK. The primary aim of this network is to assess the spatial and temporal distribution of NO 2 throughout the UK and highlight areas of high concentration which may require more detailed monitoring with automatic analysers. This paper presents a summary of the results for the first 5-years of monitoring, 1993-1997 inclusive. The network has shown that highest concentrations occur in London and urban areas of Yorkshire and Humberside and the East and West Midlands of the UK. Averaged over the whole of the UK, NO 2 concentrations have been remarkably similar for most of the 5 years, though a significant decrease was observed at urban background locations in 1997. Overall, average NO 2 concentrations during 1997 were 23 ppb at kerbside locations and 13 ppb at urban background locations. The results of the network have been used by the Department of Environment, Transport and the Regions as one of the criteria for the selection of priority areas for expansion of the UK Automatic Urban Network in recent years. Extensive quality assurance and control procedures incorporated into the network ensure that the estimated accuracy of the data is broadly comparable with the accuracy requirement for indicative monitoring specified in the EU "daughter" Directive for NO2 (±25%) . The complete dataset of results for the network can be found on the world wide web at http://www.environment.detr.gov.uk/airq/aqinfo.htm.

  9. Passive film growth on carbon steel and its nanoscale features at various passivating potentials

    International Nuclear Information System (INIS)

    Li, Yuan; Cheng, Y. Frank

    2017-01-01

    Highlights: • Imaged the topography of passivated steel at various film-forming potentials. • Characterized the nanoscale features of passive films. • Determined the composition of passive films formed at various potentials. - Abstract: In this work, the passivation and topographic sub-structure of passive films on a carbon steel in a carbonate/bicarbonate solution was characterized by electrochemical measurements, atomic force microscopy and X-ray photoelectron spectroscopy. When passivating at a potential near the active-passive transition, the film contains the mixture of Fe_3O_4, Fe_2O_3 and FeOOH, with numerous nanoscale features. As the film-forming potential shifts positively, the passive film becomes more compact and the nanoscale features disappear. When the film is formed at a passive potential where the oxygen evolution is enabled, the content of FeOOH in the film increases, resulting in an amorphous topography and reduced corrosion resistance.

  10. Corrosion evaluation of heat recovery steam generator superheater tube in two methods of testing: Tafel polarization and electrochemical impedance spectroscopy (EIS)

    Science.gov (United States)

    Santoso, Rio Pudjidarma; Riastuti, Rini

    2018-05-01

    The purpose of this research is to evaluate the corrosion process which occurs on the water side of Heat Recovery Steam Generator (HRSG) superheater tube. The tube was 13CrMo44 and divided into 3 types of specimen: new tube, used tube (with oxide layer on surface), cleaned-used tube (without oxide layer on surface). The evaluation of corrosion parameters wasperformed using deaerated ultra-high purity water (boiler feed water) in two methods of testing: Tafel polarization and Electrochemical Impedance Spectroscopy (EIS). Tafel polarization was excellent as its capability to show the value of corrosion current and the corrosion rate explicitly, on the other hand, EIS was excellent as its capability to explain for corrosion mechanism on metal interface in detail. Both methods showed that the increase of electrolyte temperature from 25°C to 55°C would increase the corrosion rate with the mechanism of decreasing polarization resistance due to thinning out the passive film thickness and enlarge the area of reduction reaction of cathode. Magnetite oxide scale which is laid on the surface of used tube specimen shows protective nature to reduce the corrosion rate, and clear up this oxide would increase the corrosion rate back as new tube.

  11. Importance of passive diffusion in the uptake of polychlorinated biphenyls by phagotrophic protozoa

    Energy Technology Data Exchange (ETDEWEB)

    Kujawinski, E.B.; Farrington, J.W.; Moffett, J.W.

    2000-05-01

    Unicellular protozoan grazers represent a size class of organisms where a transition in the mechanism of chlorobiphenyl (CB) introduction, from diffusion through surface membranes to ingestion of contaminated prey, could occur. This study compares the relative importance of these two processes in the overall uptake of polychlorinated biphenyls by protists. Uptake rates and steady-state concentrations were compared in laboratory cultures of grazing and nongrazing protozoa. These experiments were conducted with a 10-{micro}m marine scuticociliate (Uronema sp.), bacterial prey (Halomonas halodurans), and a suite of 21 CB congeners spanning a range of aqueous solubilities. The dominant pathway of CB uptake by both grazing and nongrazing protozoa was diffusion. Organic-carbon-normalized CB concentrations (in the protozoan cell) were equivalent in grazing and nongrazing protozoa for all congeners studied. Rate constants for uptake into and loss from the protozoan cell were independently determined by using [3,3{prime}, 4,4{prime}-{sup 14}C]tetrachlorobiphenyl (IUPAC no. 77), 0.38 {+-} 0.03 min{sup {minus}1} and (1.1 {+-} 0.1) x 10{sup {minus}5} (g of organic carbon){minus}{sup {minus}1} min{sup {minus}1}, respectively. Magnitudes of the uptake and loss processes were calculated and compared by using a numerical model. The model result was consistent with data from the bioaccumulation experiment and supported the hypothesis that diffusive uptake is faster than ingestive uptake in phagotrophic unicellular protozoa.

  12. Use of passive sampling for atmospheric tritium monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Caldeira Ideias, P.; Pierrard, O.; Tournieux, D. [Institut de Radioprotection et de Surete Nucleaire - IRSN (France); Tenailleau, L. [Marine nationale (France)

    2014-07-01

    Tritium is one of the most important radionuclide in environmental radiological monitoring. In French civil and military nuclear facilities, the releases levels are between 100 to 100 000 higher than any other radionuclide (rare gas excluded). Moreover these levels will probably increase in the next decades. With an average energy of 6 keV, the beta particle from tritium radioactive decay is difficult to detect and quantify within the environmental levels. To monitor the tritium in the air, French actors (authorities, operator, and experts) commonly use atmospheric bubblers and water vapour condensers. This type of sampling approach is time-consuming and very costly. To simplify and complete these methods, the Institute for Radiological Protection and Nuclear Safety (IRSN), had developed an atmospheric tritium monitoring device based on passive sampling. The passive sampler developed consists in a small container designed with a patented specific geometry and filled with 13X molecular sieve. This system is based on free diffusion flow principle (Fick's law). The driving force is the partial pressure gradient existing between the environmental atmosphere and the passive sampler. The constancy of the sampling rate for different moisture conditions assures the representativeness of the proposed device. The desorption bench developed specifically allows the recovery of 99% of the water vapour sampled in the molecular sieve. More than 99% of the sampled tritium (HTO) activity is recovered in the range between 0 and 100 Bq.L{sup -1}. Above 100 Bq.L{sup -1} to 25 k Bq.L{sup -1} (max tested activity), it was verified that no more than 3% of the tritium remains in the molecular sieve.. Thus, the use of passive sampler provides: - a representative sampling method, - a good detection limit (0,01 Bq.m{sup -3}), - no electric power supply needs, - a wide range of sampling duration (1 day to 1 month), - a low-cost method for monitoring. Different performance tests were

  13. Passive film growth on carbon steel and its nanoscale features at various passivating potentials

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yuan; Cheng, Y. Frank, E-mail: fcheng@ucalgary.ca

    2017-02-28

    Highlights: • Imaged the topography of passivated steel at various film-forming potentials. • Characterized the nanoscale features of passive films. • Determined the composition of passive films formed at various potentials. - Abstract: In this work, the passivation and topographic sub-structure of passive films on a carbon steel in a carbonate/bicarbonate solution was characterized by electrochemical measurements, atomic force microscopy and X-ray photoelectron spectroscopy. When passivating at a potential near the active-passive transition, the film contains the mixture of Fe{sub 3}O{sub 4}, Fe{sub 2}O{sub 3} and FeOOH, with numerous nanoscale features. As the film-forming potential shifts positively, the passive film becomes more compact and the nanoscale features disappear. When the film is formed at a passive potential where the oxygen evolution is enabled, the content of FeOOH in the film increases, resulting in an amorphous topography and reduced corrosion resistance.

  14. Passivity-based design of robust passive damping for LCL-filtered voltage source converters

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Blaabjerg, Frede; Loh, Poh Chiang

    2015-01-01

    Passive damping is proven as a robust stabilizing technique for LCL-filtered voltage source converters. However, conventional design methods of passive dampers are based on the passive components only, while the inherent damping effect of time delay in the digital control system is overlooked....... In this paper, a frequency-domain passivity-based design approach is proposed, where the passive dampers are designed to eliminate the negative real part of the converter output admittance with closed-loop current control, rather than shaping the LCL-filter itself. Thus, the influence of time delay...... in the current control is included, which allows a relaxed design of the passive damper with the reduced power loss and improved stability robustness against grid parameters variations. Design procedures of two commonly used passive dampers with LCL-filtered VSCs are illustrated. Experimental results validate...

  15. Localization of protein aggregation in Escherichia coli is governed by diffusion and nucleoid macromolecular crowding effect.

    Directory of Open Access Journals (Sweden)

    Anne-Sophie Coquel

    2013-04-01

    Full Text Available Aggregates of misfolded proteins are a hallmark of many age-related diseases. Recently, they have been linked to aging of Escherichia coli (E. coli where protein aggregates accumulate at the old pole region of the aging bacterium. Because of the potential of E. coli as a model organism, elucidating aging and protein aggregation in this bacterium may pave the way to significant advances in our global understanding of aging. A first obstacle along this path is to decipher the mechanisms by which protein aggregates are targeted to specific intercellular locations. Here, using an integrated approach based on individual-based modeling, time-lapse fluorescence microscopy and automated image analysis, we show that the movement of aging-related protein aggregates in E. coli is purely diffusive (Brownian. Using single-particle tracking of protein aggregates in live E. coli cells, we estimated the average size and diffusion constant of the aggregates. Our results provide evidence that the aggregates passively diffuse within the cell, with diffusion constants that depend on their size in agreement with the Stokes-Einstein law. However, the aggregate displacements along the cell long axis are confined to a region that roughly corresponds to the nucleoid-free space in the cell pole, thus confirming the importance of increased macromolecular crowding in the nucleoids. We thus used 3D individual-based modeling to show that these three ingredients (diffusion, aggregation and diffusion hindrance in the nucleoids are sufficient and necessary to reproduce the available experimental data on aggregate localization in the cells. Taken together, our results strongly support the hypothesis that the localization of aging-related protein aggregates in the poles of E. coli results from the coupling of passive diffusion-aggregation with spatially non-homogeneous macromolecular crowding. They further support the importance of "soft" intracellular structuring (based on

  16. Turbulent diffusion of small particles

    International Nuclear Information System (INIS)

    Margolin, L.G.

    1977-11-01

    The diffusion of small, spherical, rigid particles suspended in an incompressible turbulent fluid, but not interacting with each other, was studied. As a stochastic process, the turbulent fluid velocity field is assumed to be homogeneous, isotropic and stationary. Assuming the Stokes regime, a particle of equation of motion is used which includes only the effects of Stokes drag and a virtual mass force and an exact solution is found for the particle velocity correlation function, for all times and initial conditions, in terms of a fluid velocity correlation function measured along the motion of the particle. This shows that for times larger than a certain time scale, the particle velocity correlation becomes stationary. The effect of small shears in the fluid velocity was considered, under the additional restrictions of a certain high frequency regime for the turbulence. The shears convected past the particle much faster than the growth of the boundary layer. New force terms due to the presence of such shears are calculated and incorporated into the equation of motion. A perturbation solution to this equation is constructed, and the resultant particle velocity correlation function and diffusion coefficient are calculated. To lowest order, the particle diffusivity is found to be unaltered by the presence of small mean flow shears. The last model treated is one in which particles traverse a turbulent fluid with a large mean velocity. Among other restrictions, linearized form drag is assumed. The diffusion coefficient for such particles was calculated, and found to be much smaller than the passive scalar diffusion coefficient. This agrees within 5 percent with the experimental results of Snyder and Lumley

  17. Development and first experimental results of the KERENA Passive Outflow Reducer

    Energy Technology Data Exchange (ETDEWEB)

    Dumond, Julien; Maisberger, Fabian [AREVA NP GmbH (Germany); Class, Andreas [Karlsruher Institut fuer Technologie (Germany)

    2012-11-01

    Increased safety and reduced costs are achieved in the boiling water reactor KERENA with a smart combination of active and passive safety systems. One of these passive systems is the Emergency Condenser (EC). The EC passively removes excess heat and in particular the decay heat from the Reactor Pressure Vessel (RPV) during transients and Loss of Coolant Accidents (LOCA) without supplementary water inventory loss. The EC passively becomes active when the water level in the condenser tubes falls so that steam gets in contact with the cold condenser surface. This is triggered by a transient or a loss of coolant involving drop in RPV water level. The condensate returns to the RPV through the EC condensate return line. A break of the EC return line must be considered as a design accident. The Passive Outflow Reducer (POR) is positioned in the reactor nozzle at the end of the EC condensate return line to limit the loss of coolant passively without moving part in this scenario before other passive and active systems fill up the core with coolant. The requirements on the POR are conflicting. On the one hand, the mass flow leaving the RPV has to be limited in case of the break of the EC condensate return line. On the other hand, the flow resistance from the EC to the RPV should not decrease EC heat removal capacity. Furthermore, the component must be compact (l < 1m) and easily manufactured. In the framework of the PhD a new POR design composed of 37 parallel doublenozzle channels (Figure 1) has been developed. The development of this POR design is described in chapter 1. The system was first designed to meet LOCA requirement (section 1.1) in LOCA direction (red arrow on Figure 1) with system-code and then optimized to minimize flow resistance in EC direction (blue arrow on Figure 1) with commercial CFD software (section 1.2). Both requirements can be achieved with one single pipe but the component would be much too long (about 6 meters). To assure compactness of the

  18. Development and first experimental results of the KERENA Passive Outflow Reducer

    International Nuclear Information System (INIS)

    Dumond, Julien; Maisberger, Fabian; Class, Andreas

    2012-01-01

    Increased safety and reduced costs are achieved in the boiling water reactor KERENA with a smart combination of active and passive safety systems. One of these passive systems is the Emergency Condenser (EC). The EC passively removes excess heat and in particular the decay heat from the Reactor Pressure Vessel (RPV) during transients and Loss of Coolant Accidents (LOCA) without supplementary water inventory loss. The EC passively becomes active when the water level in the condenser tubes falls so that steam gets in contact with the cold condenser surface. This is triggered by a transient or a loss of coolant involving drop in RPV water level. The condensate returns to the RPV through the EC condensate return line. A break of the EC return line must be considered as a design accident. The Passive Outflow Reducer (POR) is positioned in the reactor nozzle at the end of the EC condensate return line to limit the loss of coolant passively without moving part in this scenario before other passive and active systems fill up the core with coolant. The requirements on the POR are conflicting. On the one hand, the mass flow leaving the RPV has to be limited in case of the break of the EC condensate return line. On the other hand, the flow resistance from the EC to the RPV should not decrease EC heat removal capacity. Furthermore, the component must be compact (l < 1m) and easily manufactured. In the framework of the PhD a new POR design composed of 37 parallel doublenozzle channels (Figure 1) has been developed. The development of this POR design is described in chapter 1. The system was first designed to meet LOCA requirement (section 1.1) in LOCA direction (red arrow on Figure 1) with system-code and then optimized to minimize flow resistance in EC direction (blue arrow on Figure 1) with commercial CFD software (section 1.2). Both requirements can be achieved with one single pipe but the component would be much too long (about 6 meters). To assure compactness of the

  19. Numerical studies on heat transfer and pressure drop characteristics of flat finned tube bundles with various fin materials

    Science.gov (United States)

    Peng, Y.; Zhang, S. J.; Shen, F.; Wang, X. B.; Yang, X. R.; Yang, L. J.

    2017-11-01

    The air-cooled heat exchanger plays an important role in the field of industry like for example in thermal power plants. On the other hand, it can be used to remove core decay heat out of containment passively in case of a severe accident circumstance. Thus, research on the performance of fins in air-cooled heat exchangers can benefit the optimal design and operation of cooling systems in nuclear power plants. In this study, a CFD (Computational Fluid Dynamic) method is implemented to investigate the effects of inlet velocity, fin spacing and tube pitch on the flow and the heat transfer characteristics of flat fins constructed of various materials (316L stainless steel, copper-nickel alloy and aluminium). A three dimensional geometric model of flat finned tube bundles with fixed longitudinal tube pitch and transverse tube pitch is established. Results for the variation of the average convective heat transfer coefficient with respect to cooling air inlet velocity, fin spacing, tube pitch and fin material are obtained, as well as for the pressure drop of the cooling air passing through finned tube. It is shown that the increase of cooling air inlet velocity results in enhanced average convective heat transfer coefficient and decreasing pressure drop. Both fin spacing and tube pitch engender positive effects on pressure drop and have negative effects on heat transfer characteristics. Concerning the fin material, the heat transfer performance of copper-nickel alloy is superior to 316L stainless steel and inferior to aluminium.

  20. Fast fracture of a zirconium alloy pressure tube: cause and implications

    International Nuclear Information System (INIS)

    Price, E.G.; Cheadle, B.A.

    1985-12-01

    The cause of the unstable fracture of a Zircaloy-2 pressure tube in the core of a CANDU reactor is reviewed. Failure was associated with the presence of brittle zones of zirconium hydride which developed as a result of thermal gradient induced hydrogen diffusion. Unstable fracture occurred when the partial thickness crack reached an unstable length and the crack ran 2 meters along the tube and terminated by circumferential tearing. The partial thickness defect initiated and propagated to an unstable length by delayed hydride cracking is high compared to fatigue progression and increases exponentially with temperature. Delayed hydride cracking can be prevented by reducing residual stresses to a minimum and by high standards of non-destructive testing that ensures freedom from unacceptable defects. Future prevention of fast fracture is based upon the inspection of a limited number of fuel channels for the presence of defects and for conditions which can cause hydride build-up together with the periodic removal of Zr-2.5wt% Nb tubes to monitor their condition

  1. Chest tube insertion

    Science.gov (United States)

    Chest drainage tube insertion; Insertion of tube into chest; Tube thoracostomy; Pericardial drain ... Be careful there are no kinks in your tube. The drainage system should always sit upright and be placed ...

  2. Vibro-impact responses of a tube with tube--baffle interaction

    International Nuclear Information System (INIS)

    Shin, Y.S.; Sass, D.E.; Jendrzejczyk, J.A.

    1978-01-01

    The relatively small, inherent tube-to-baffle hole clearances associated with manufacturing tolerances in heat exchangers affect the vibrational characteristics and the response of the tube. Numerical studies were made to predict the vibro-impact response of a tube with tube-baffle interaction. The finite element method has been employed with a non-linear elastic contact spring-dashpot to model the effect of the relative approach between the tube and the baffle plate. The coupled equations of motion are directly integrated with a proportional system damping represented by a linear combination of mass and stiffness. Lumped mass approach with explicit time integration scheme was found to be a suitable choice for tube-baffle impacting analysis. Fourier analyses indicate that the higher mode contributions to the tube response are significant for strong tube-baffle impacting. The contact damping forces are negligible compared with the contact spring forces. The numerical analysis results are in reasonably good agreement with those of the experiments

  3. Passivity and Evolutionary Game Dynamics

    KAUST Repository

    Park, Shinkyu; Shamma, Jeff S.; Martins, Nuno C.

    2018-01-01

    This paper investigates an energy conservation and dissipation -- passivity -- aspect of dynamic models in evolutionary game theory. We define a notion of passivity using the state-space representation of the models, and we devise systematic methods to examine passivity and to identify properties of passive dynamic models. Based on the methods, we describe how passivity is connected to stability in population games and illustrate stability of passive dynamic models using numerical simulations.

  4. Passivity and Evolutionary Game Dynamics

    KAUST Repository

    Park, Shinkyu

    2018-03-21

    This paper investigates an energy conservation and dissipation -- passivity -- aspect of dynamic models in evolutionary game theory. We define a notion of passivity using the state-space representation of the models, and we devise systematic methods to examine passivity and to identify properties of passive dynamic models. Based on the methods, we describe how passivity is connected to stability in population games and illustrate stability of passive dynamic models using numerical simulations.

  5. Developing a passive trap for diffusive atmospheric {sup 14}CO{sub 2} sampling

    Energy Technology Data Exchange (ETDEWEB)

    Walker, Jennifer C.; Xu, Xiaomei [Department of Earth System Science, University of California, Irvine, Irvine, CA (United States); Fahrni, Simon M. [Department of Earth System Science, University of California, Irvine, Irvine, CA (United States); Institute of Particle Physics, ETH, Zurich (Switzerland); Lupascu, Massimo [Department of Earth System Science, University of California, Irvine, Irvine, CA (United States); Department of Geography, National University of Singapore (Singapore); Czimczik, Claudia I. [Department of Earth System Science, University of California, Irvine, Irvine, CA (United States)

    2015-10-15

    {sup 14}C-CO{sub 2} measurement is an unique tool to quantify source-based emissions of CO{sub 2} for both the urban and natural environments. Acquiring a sample that temporally integrates the atmospheric {sup 14}C-CO{sub 2} signature that allows for precise {sup 14}C analysis is often necessary, but can require complex sampling devices, which can be difficult to deploy and maintain, especially for multiple locations. Here we describe our progress in developing a diffusive atmospheric CO{sub 2} molecular sieve trap, which requires no power to operate. We present results from various cleaning procedures, and rigorously tested for blank and memory effects. Traps were tested in the environment along-side conventional sampling flasks for accuracy. Results show that blank and memory effects can be minimized with thorough cleaning and by avoiding overheating, and that diffusively collected air samples agree well with traditionally canister-sampled air.

  6. Performance test of passive radon–thoron discriminative detectors on environmental parameters

    International Nuclear Information System (INIS)

    Sorimachi, Atsuyuki; Tokonami, Shinji; Omori, Yasutaka; Ishikawa, Tetsuo

    2012-01-01

    This paper describes how humidity, wind and ambient aerosols in air influence the detection responses of passive detectors. Two types of alpha track detectors based on a passive radon ( 222 Rn)–thoron ( 220 Rn) discriminative measurement technique were used: the Raduet and Radopot detectors that were developed and calibrated by the National Institute of Radiological Sciences, Japan. The initial experiment showed that the infiltration rate of 220 Rn onto sponges with a high air exchange rate for the Raduet detectors was one third lower than that onto filters for the Radopot detectors. Little distinct dependence on humidity was observed for the 222 Rn detection responses of both detectors. For 220 Rn, the detection responses of both detectors for the high air exchange rate seemed to decrease slightly at high humidity conditions. The 220 Rn detection responses of the Radopot detectors had little influence from wind speed. The 220 Rn detection responses of the Raduet detectors for the high air exchange rate seemed to decrease at low wind speeds. Furthermore, there was little difference between the detection responses in the presence and absence of ambient aerosol particles because the ambient aerosols were filtered out during their passive diffusion through the sponges and filters for the Raduet and Radopot detectors, respectively.

  7. Robust Mpc for Actuator–Fault Tolerance Using Set–Based Passive Fault Detection and Active Fault Isolation

    Directory of Open Access Journals (Sweden)

    Xu Feng

    2017-03-01

    Full Text Available In this paper, a fault-tolerant control (FTC scheme is proposed for actuator faults, which is built upon tube-based model predictive control (MPC as well as set-based fault detection and isolation (FDI. In the class of MPC techniques, tubebased MPC can effectively deal with system constraints and uncertainties with relatively low computational complexity compared with other robust MPC techniques such as min-max MPC. Set-based FDI, generally considering the worst case of uncertainties, can robustly detect and isolate actuator faults. In the proposed FTC scheme, fault detection (FD is passive by using invariant sets, while fault isolation (FI is active by means of MPC and tubes. The active FI method proposed in this paper is implemented by making use of the constraint-handling ability of MPC to manipulate the bounds of inputs.

  8. Phase transitions, melting dynamics, and solid-state diffusion in a nano test tube.

    Science.gov (United States)

    Holmberg, Vincent C; Panthani, Matthew G; Korgel, Brian A

    2009-10-16

    Confined nanoscale geometry greatly influences physical transformations in materials. The electron microscope enables direct visualization of these changes. We examined the evolution of a germanium (Ge) nanowire attached to a gold (Au) nanocrystal as it was heated to 900 degrees C. The application of a carbon shell prevented changes in volume and interfacial area during the heating cycle. Au/Ge eutectic formation was visualized, occurring 15 degrees C below the bulk eutectic temperature. Capillary pressure pushed the melt into the cylindrical neck of the nanowire, and Ge crystallized in the spherical tip of the carbon shell. Solid-state diffusion down the length of the confined Ge nanowire was observed at temperatures above 700 degrees C; Au diffusion was several orders of magnitude slower than in a bulk Ge crystal.

  9. Some characteristics of the Atomic Energy Organization of Iran (AEOI) passive radon diffusion dosimeter for indoor exposure determination of public in Iran

    International Nuclear Information System (INIS)

    Sohrabi, M.; Solaymanian, A.R.

    1989-01-01

    A Passive Radon diffusion dosimeter (PRDD) was developed at the Radiation Protection Department of the Atomic Energy Organization of Iran (AEOI) for large scale radon level measurements in Iran. It consists of a plastic cup with a polycarbonate alpha detector in the middle, a plastic top cover with an opening holding a fiberglass filter and a hard aluminium mesh for protection and support. A new design of our multi-chamber system was used for multiple foil etching. The effects of pre-etching and ECE times, chamber volume, filter diameter and foil position inside the chamber were investigated. The optimized geometries include 9.5 cm height, 269 cm 3 volume and 2-3 cm filter diameter with the polycarbonate foil mounted in the middle. A sensitivity of 0.05+-0.007 tracks cm -2 /Bq.m -3 day or 1.96+-0.28 tracks cm -2 /pCi.1 -1 day was obtained at optimized conditions. The characteristics of the dosimeter as well as some preliminary results of indoor radon level measurements for determination of public exposure in 250 houses in different cities of Iran including Tehran, Ramsar, Babolsar and Gonabad are presented. The highest radon levels were found in high natural areas of Ramsar

  10. Numerical modeling of condensation from vapor-gas mixtures for forced down flow inside a tube

    International Nuclear Information System (INIS)

    Yuann, R.Y.; Schrock, V.E.; Chen, Xiang, M.

    1995-01-01

    Laminar film condensation is the dominant heat transfer mode inside tubes. In the present paper direct numerical simulation of the detailed transport process within the steam-gas core flow and in the condensate film is carried out. The problem was posed as an axisymmetric two dimensional (r, z) gas phase inside an annular condensate film flow with an assumed smooth interface. The fundamental conservation equations were written for mass, momentum, species concentration and energy in the gaseous phase with effective diffusion parameters characterizing the turbulent region. The low Reynolds number two equation κ-ε model was employed to determine the eddy diffusion coefficients. The liquid film was described by similar formulation without the gas species equation. An empirical correlation was employed to correct for the effect of film waviness on the interfacial shear. A computer code named COAPIT (Condensation Analysis Program Inside Tube) was developed to implement numerical solution of the fundamental equations. The equations were solved by a marching technique working downstream from the entrance of the condensing section. COAPIT was benchmarked against experimental data and overall reasonable agreement was found for the key parameters such as heat transfer coefficient and tube inner wall temperature. The predicted axial development of radial profiles of velocity, composition and temperature and occurrence of metastable vapor add insight to the physical phenomena

  11. Numerical modeling of condensation from vapor-gas mixtures for forced down flow inside a tube

    Energy Technology Data Exchange (ETDEWEB)

    Yuann, R Y [Taiwan Power Company, Taipei (Taiwan, Province of China); Schrock, V E [Univ. of California, Berkeley, CA (United States); Chen, Xiang

    1995-09-01

    Laminar film condensation is the dominant heat transfer mode inside tubes. In the present paper direct numerical simulation of the detailed transport process within the steam-gas core flow and in the condensate film is carried out. The problem was posed as an axisymmetric two dimensional (r, z) gas phase inside an annular condensate film flow with an assumed smooth interface. The fundamental conservation equations were written for mass, momentum, species concentration and energy in the gaseous phase with effective diffusion parameters characterizing the turbulent region. The low Reynolds number two equation {kappa}-{epsilon} model was employed to determine the eddy diffusion coefficients. The liquid film was described by similar formulation without the gas species equation. An empirical correlation was employed to correct for the effect of film waviness on the interfacial shear. A computer code named COAPIT (Condensation Analysis Program Inside Tube) was developed to implement numerical solution of the fundamental equations. The equations were solved by a marching technique working downstream from the entrance of the condensing section. COAPIT was benchmarked against experimental data and overall reasonable agreement was found for the key parameters such as heat transfer coefficient and tube inner wall temperature. The predicted axial development of radial profiles of velocity, composition and temperature and occurrence of metastable vapor add insight to the physical phenomena.

  12. Laser-beam-induced current mapping evaluation of porous silicon-based passivation in polycrystalline silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Rabha, M. Ben; Bessais, B. [Laboratoire de Nanomateriaux et des Systemes pour l' Energie, Centre de Recherches et des Technologies de l' Energie - Technopole de Borj-Cedria BP 95, 2050 Hammam-Lif (Tunisia); Dimassi, W.; Bouaicha, M.; Ezzaouia, H. [Laboratoire de photovoltaique, des semiconducteurs et des nanostructures, Centre de Recherches et des Technologies de l' Energie - Technopole de Borj-Cedria BP 95, 2050 Hammam-Lif (Tunisia)

    2009-05-15

    In the present work, we report on the effect of introducing a superficial porous silicon (PS) layer on the performance of polycrystalline silicon (pc-Si) solar cells. Laser-beam-induced current (LBIC) mapping shows that the PS treatment on the emitter of pc-Si solar cells improves their quantum response and reduce the grain boundaries (GBs) activity. After the porous silicon treatment, mapping investigation shows an enhancement of the LBIC and the internal quantum efficiency (IQE), due to an improvement of the minority carrier diffusion length and the passivation of recombination centers at the GBs as compared to the reference substrate. It was quantitatively shown that porous silicon treatment can passivate both the grains and GBs. (author)

  13. Passive neutron design study for 200-L waste drums

    International Nuclear Information System (INIS)

    Menlove, H.O.; Beddingfield, D.B.; Pickrell, M.M.

    1997-09-01

    We have developed a passive neutron counter for the measurement of plutonium in 200-L drums of scrap and waste. The counter incorporates high efficiency for the multiplicity counting in addition to the traditional coincidence counting. The 252 Cf add-a-source feature is used to provide an accurate assay over a wide range of waste matrix materials. The room background neutron rate is reduced by using 30 cm of external polyethylene shielding and the cosmic-ray background is reduced by statistical filtering techniques. Monte Carlo Code calculations were used to determine the optimum detector design, including the gas pressure, size, number, and placement of the 3 He tubes in the moderator. Various moderators, including polyethylene, plastics, teflon, and graphite, were evaluated to obtain the maximum efficiency and minimum detectable mass of plutonium

  14. Impact of xylomethazoline on eustachian tube function in healthy participants.

    Science.gov (United States)

    Meyer, Moritz F; Mikolajczak, Stefanie; Korthäuer, Christine; Jumah, Masen D; Hahn, Moritz; Grosheva, Maria; Lüers, Jan-Christoffer; Hüttenbrink, Karl-Bernd; Beutner, Dirk

    2015-06-01

    The use of decongestants is common in otitis media eustachian tube (ET) dysfunction. However, the underlying mechanism and the type of action on the complex middle ear pressure equalization system are poorly understood. Here, by use of the pressure chamber, we investigated the impact of intranasal decongestive therapy (xylomethazoline) on ET function. Thirty healthy participants (60 ears) were exposed to a predetermined profile of phases of compression and decompression in a hypobaric and hyperbaric pressure chamber. ET opening pressure, ET opening duration, ET opening frequency, and ET closing pressure were determined before and after intranasal application of xylomethazoline. A significantly higher number of ET openings (ET opening frequency) in passive equalization condition could be measured after application of decongestants than before. No significant difference could be found in the values of ET opening pressure, ET opening duration, and ET closing pressure parameters before in comparison with the values after application of xylomethazoline. We conclude that xylomethazoline might only have a minor effect during active and passive middle ear pressure equalization. Larger cohorts and targeted application of decongestants should be tested to confirm these preliminary data and to find new evidence on the effects of decongestants.

  15. Pressure tube reactor

    International Nuclear Information System (INIS)

    Susuki, Akira; Murata, Shigeto; Minato, Akihiko.

    1993-01-01

    In a pressure tube reactor, a reactor core is constituted by arranging more than two units of a minimum unit combination of a moderator sealing pipe containing a calandria tube having moderators there between and a calandria tube and moderators. The upper header and a lower header of the calandria tank containing moderators are communicated by way of the moderator sealing tube. Further, a gravitationally dropping mechanism is disposed for injecting neutron absorbing liquid to a calandria gas injection portion. A ratio between a moderator volume and a fuel volume is defined as a function of the inner diameter of the moderator sealing tube, the outer diameter of the calandria tube and the diameter of fuel pellets, and has no influence to intervals of a pressure tube lattice. The interval of the pressure tube lattice is enlarged without increasing the size of the pressure tube, to improve production efficiency of the reactor and set a coolant void coefficient more negative, thereby enabling to improve self controllability and safety. Further, the reactor scram can be conducted by injecting neutron absorbing liquid. (N.H.)

  16. French Fries, Dialysis Tubing & Computer Models: Teaching Diffusion & Osmosis through Inquiry & Modeling

    Science.gov (United States)

    Friedrichsen, Patricia Meis; Pallant, Amy

    2007-01-01

    Can eating large amounts of sugarless candy and gum lead to diarrhea? How does Milk of Magnesia work? How does penicillin kill bacteria? These are some of the questions that students answer in this series of lessons on diffusion and osmosis. To begin the unit, students predict the results of a demonstration involving the relationship between…

  17. Device physics underlying silicon heterojunction and passivating-contact solar cells: A topical review

    KAUST Repository

    Chavali, Raghu V. K.

    2018-01-15

    The device physics of commercially dominant diffused-junction silicon solar cells is well understood, allowing sophisticated optimization of this class of devices. Recently, so-called passivating-contact solar cell technologies have become prominent, with Kaneka setting the world\\'s silicon solar cell efficiency record of 26.63% using silicon heterojunction contacts in an interdigitated configuration. Although passivating-contact solar cells are remarkably efficient, their underlying device physics is not yet completely understood, not in the least because they are constructed from diverse materials that may introduce electronic barriers in the current flow. To bridge this gap in understanding, we explore the device physics of passivating contact silicon heterojunction (SHJ) solar cells. Here, we identify the key properties of heterojunctions that affect cell efficiency, analyze the dependence of key heterojunction properties on carrier transport under light and dark conditions, provide a self-consistent multiprobe approach to extract heterojunction parameters using several characterization techniques (including dark J-V, light J-V, C-V, admittance spectroscopy, and Suns-Voc), propose design guidelines to address bottlenecks in energy production in SHJ cells, and develop a process-to-module modeling framework to establish the module\\'s performance limits. We expect that our proposed guidelines resulting from this multiscale and self-consistent framework will improve the performance of future SHJ cells as well as other passivating contact-based solar cells.

  18. Vertical steam generator with slab-type tube-plate with even tube bundle washing

    International Nuclear Information System (INIS)

    Manek, O.; Masek, V.; Motejl, V.; Quitta, R.

    1980-01-01

    A shielding plate supporting the tubes attached to the tube plate of a vertical steam generator is mounted above the tube plate. Tube sleeves are designed with a dimensional tolerance relative to the heat transfer tubes and the sleeve end and the tube plate end. A separate space is thus formed above the tube plate in which circulation or feed water is introduced to flow between the branch and the heat transfer tube. This provides intensive washing of heat transfer tubes at a critical point and prevents deposit formation, thus excluding heat transfer tube failures. (J.B.)

  19. Comparative Measurements of Radon Concentration in Soil Using Passive and Active Methods in High Level Natural Radiation Area (HLNRA of Ramsar

    Directory of Open Access Journals (Sweden)

    Amanat B

    2013-12-01

    Full Text Available Background: Radon and its daughters are amongst the most important sources of natural exposure in the world. Soil is one of the signifcant sources of radon/thoron due to both radium and thorium so that the emanated thoron from it may cause in creased uncertainties in radon measurements. Recently, a diffusion chamber has been designed and optimized for passive discriminative measurements of radon/thoron concentrations in soil. Objective: In order to evaluate the capability of the passive method, some com parative measurements (with active methods have been performed. Method: The method is based upon measurements by a diffusion chamber, includ ing two Lexan polycarbonate SSNTDs, which can discriminate the emanated radon/ thorn from the soil by delay method. The comparative measurements have been done in ten selected points of HLNRA of Ramsar in Iran. The linear regression and cor relation between the results of two methods have been studied. Results: The results show that the radon concentrations are within the range of 12.1 to 165 kBq/m3 values. The correlation between the results of active and passive methods was measured by 0.99 value. As well, the thoron concentrations have been measured between 1.9 to 29.5 kBq/m3 values at the points. Conclusion: The sensitivity as well as the strong correlation with active mea surements shows that the new low-cost passive method is appropriate for accurate seasonal measurements of radon and thoron concentration in soil.

  20. Carbon nano tubes -Buckypaper- radiation studies for medical physics application

    Energy Technology Data Exchange (ETDEWEB)

    Alanazi, A.; Alkhorayef, M.; Dalton, A.; Bradley, D. A. [University of Surrey, Department of Physics, College for Nuclear and Radiation Physics, Guildford, Surrey GR2 7XH (United Kingdom); Alzimami, K. [King Saud University, Department of Radiological Sciences, P. O. Box 10219, Riyadh 11433 (Saudi Arabia); Abuhadi, N., E-mail: a.alanazi@surrey.ac.uk [Jazan University, Faculty of Medical Applied Sciences, Diagnostic Radiology Department, P. O. Box 114, Jazan (Saudi Arabia)

    2015-10-15

    Radiation dosimetry underpins safe and effective clinical applications of radiation. Many materials have been used to measure the radiation dose deposited in human tissue, their radiation response requiring the application of correction factors to account for various influencing factors, including sensitivity to dose and energy dependence. In regard to the latter, account needs to be taken of difference from the effective atomic number of human tissue, soft or calcified. Graphite ion chambers and semiconductor diode detectors have been used to make measurements in phantoms but these active devices represent a clear disadvantage when considered for in vivo dosimetry. In both circumstances, dosimeters with atomic number similar to human tissue are needed. Carbon nano tubes have properties that potentially meet the demand, requiring low voltage in active devices and an atomic number similar to adipose tissue. In this study, single-wall carbon nano tubes buckypaper has been used to measure the beta particle dose deposited from a strontium-90 source, the medium displaying thermoluminescence at potentially useful sensitivity. As an example, the samples show a clear response for a dose of 2 Gy. This finding suggests that carbon nano tubes can be used as a passive dosimeter specifically for the high levels of radiation exposures used in radiation therapy. Furthermore, the finding points towards further potential applications such as for space radiation measurements, not least because the medium satisfies a demand for light but strong materials of minimal capacitance. (Author)

  1. Carbon nano tubes -Buckypaper- radiation studies for medical physics application

    International Nuclear Information System (INIS)

    Alanazi, A.; Alkhorayef, M.; Dalton, A.; Bradley, D. A.; Alzimami, K.; Abuhadi, N.

    2015-10-01

    Radiation dosimetry underpins safe and effective clinical applications of radiation. Many materials have been used to measure the radiation dose deposited in human tissue, their radiation response requiring the application of correction factors to account for various influencing factors, including sensitivity to dose and energy dependence. In regard to the latter, account needs to be taken of difference from the effective atomic number of human tissue, soft or calcified. Graphite ion chambers and semiconductor diode detectors have been used to make measurements in phantoms but these active devices represent a clear disadvantage when considered for in vivo dosimetry. In both circumstances, dosimeters with atomic number similar to human tissue are needed. Carbon nano tubes have properties that potentially meet the demand, requiring low voltage in active devices and an atomic number similar to adipose tissue. In this study, single-wall carbon nano tubes buckypaper has been used to measure the beta particle dose deposited from a strontium-90 source, the medium displaying thermoluminescence at potentially useful sensitivity. As an example, the samples show a clear response for a dose of 2 Gy. This finding suggests that carbon nano tubes can be used as a passive dosimeter specifically for the high levels of radiation exposures used in radiation therapy. Furthermore, the finding points towards further potential applications such as for space radiation measurements, not least because the medium satisfies a demand for light but strong materials of minimal capacitance. (Author)

  2. Fate of the herbicides 2,4,5-T, atrazine, and DNOC in a shallow, anaerobic aquifer investigated by in situ passive diffusive emitters and laboratory batch experiments

    DEFF Research Database (Denmark)

    Arildskov, N.P.; Pedersen, Philip Grinder; Albrechtsen, Hans-Jørgen

    2001-01-01

    simultaneously with tritiated water (HTO) as tracer in the depth interval 3 to 4 rubs (meters below surface) by use of passive diffusive emitters. Atrazine and 2,4,5-T were persistent during the approximately 18 days residence time in the aquifer. In contrast, DNOC was rapidly removed from the water phase...... to 4 rubs and from 8 to 9 rubs. In these incubations, formation of Fe2+ and depletion of sulfate showed iron and sulfate reduction in sediment from 3 to 3.5 rubs and sulfate reduction in 3.5 to 4 rubs sediment. In sediment from 8 to 9 rubs, the dominant redox process was methane formation. In sediment...... first-order kinetics, and when normalized to the sediment/water-ratio, the field and laboratory derived rate constants compared well. The DNOC degradation in the methanogenic incubations (8 to 9 rubs) was up to 50 times faster than in the sediments from 3 to 4 rubs, likely due to the low redox potential....

  3. Active and passive transport of cargo in a corrugated channel: A lattice model study

    Science.gov (United States)

    Dey, Supravat; Ching, Kevin; Das, Moumita

    2018-04-01

    Inside cells, cargos such as vesicles and organelles are transported by molecular motors to their correct locations via active motion on cytoskeletal tracks and passive, Brownian diffusion. During the transportation of cargos, motor-cargo complexes (MCCs) navigate the confining and crowded environment of the cytoskeletal network and other macromolecules. Motivated by this, we study a minimal two-state model of motor-driven cargo transport in confinement and predict transport properties that can be tested in experiments. We assume that the motion of the MCC is directly affected by the entropic barrier due to confinement if it is in the passive, unbound state but not in the active, bound state where it moves with a constant bound velocity. We construct a lattice model based on a Fokker Planck description of the two-state system, study it using a kinetic Monte Carlo method and compare our numerical results with analytical expressions for a mean field limit. We find that the effect of confinement strongly depends on the bound velocity and the binding kinetics of the MCC. Confinement effectively reduces the effective diffusivity and average velocity, except when it results in an enhanced average binding rate and thereby leads to a larger average velocity than when unconfined.

  4. Slow positron studies of hydrogen activation/passivation on SiO2/Si(100) interfaces

    International Nuclear Information System (INIS)

    Lynn, K.G.; Asoka-Kumar, P.

    1991-01-01

    The hydrogen atoms are one of the most common impurity species found in semiconductor systems owing to its large diffusivity, and are easily incorporated either in a controlled process like in ion implantation or in an uncontrolled process like the one at the fabrication stage. Hydrogen can passivate dangling bonds and dislocations in these systems and hence can be used to enhance the electrical properties. In a SiO 2 /Si system, hydrogen can passivate electronic states at the interface and can alter the fixed or mobile charges in the oxide layer. Since hydrogen is present in almost all of the environments of SiO 2 /Si wafer fabrication, the activation energy of hydrogen atoms is of paramount importance to a proper understanding of SiO 2 /Si based devices and has not been measured on the technologically most important Si(100) face. There are no direct, nondestructive methods available to observe hydrogen injection into the oxide layer and subsequent diffusion. This study uses the positrons as a ''sensitive'', nondestructive probe to observe hydrogen interaction in the oxide layer and the interface region. We also describe a new way of characterizing the changes in the density of the interface states under a low-temperature annealing using positrons. 9 refs., 6 figs

  5. Slow positron studies of hydrogen activation/passivation on SiO2/Si(100) interfaces

    Science.gov (United States)

    Lynn, K. G.; Asoka-Kumar, P.

    The hydrogen atoms are one of the most common impurity species found in semiconductor systems owing to its large diffusivity, and are easily incorporated either in a controlled process like in ion implantation or in an uncontrolled process like the one at the fabrication stage. Hydrogen can passivate dangling bonds and dislocations in these systems and hence can be used to enhance the electrical properties. In a SiO2/Si system, hydrogen can passivate electronic states at the interface and can alter the fixed or mobile charges in the oxide layer. Since hydrogen is present in almost all of the environments of SiO2/Si wafer fabrication, the activation energy of hydrogen atoms is of paramount importance to a proper understanding of SiO2/Si based devices and has not been measured on the technologically most important Si(100) face. There are no direct, nondestructive methods available to observe hydrogen injection into the oxide layer and subsequent diffusion. The positrons are used as a 'sensitive', nondestructive probe to observe hydrogen interaction in the oxide layer and the interface region. A new way is described of characterizing the changes in the density of the interface states under a low temperature annealing using positrons.

  6. Characterizing the active opening of the eustachian tube in a hypobaric/hyperbaric pressure chamber.

    Science.gov (United States)

    Mikolajczak, Stefanie; Meyer, Moritz Friedo; Hahn, Moritz; Korthäuer, Christine; Jumah, Masen Dirk; Hüttenbrink, Karl-Bernd; Grosheva, Maria; Luers, Jan Christoffer; Beutner, Dirk

    2015-01-01

    Active and passive opening of the Eustachian tube (ET) enables direct aeration of the middle ear and a pressure balance between middle ear and the ambient pressure. The aim of this study was to characterize standard values for the opening pressure (ETOP), the opening frequency (ETOF), and the opening duration (ETOD) for active tubal openings (Valsalva maneuver, swallowing) in healthy participants. In a hypobaric/hyperbaric pressure chamber, 30 healthy participants (19 women, 11 men; mean age, 25.57 ± 3.33 years) were exposed to a standardized profile of compression and decompression. The pressure values were recorded via continuous impedance measurement during the Valsalva maneuver and swallowing. Based on the data, standard curves were identified and the ETOP, ETOD, and ETOF were determined. Recurring patterns of the pressure curve during active tube opening for the Valsalva maneuver and for active swallowing were characterized. The mean value for the Valsalva maneuver for ETOP was 41.21 ± 17.38 mbar; for the ETOD, it was 2.65 ± 1.87 seconds. In the active pressure compensation by swallowing, the mean value for the ETOP was 29.91 ± 13.07 mbar; and for the ETOD, it was 0.82 ± 0.53 seconds. Standard values for the opening pressure of the tube and the tube opening duration for active tubal openings (Valsalva maneuver, swallowing) were described, and typical curve gradients for healthy subjects could be shown. This is another step toward analyzing the function of the tube in compression and decompression.

  7. Use of CATHENA to model calandria-tube/moderator heat transfer after pressure-tube/calandria-tube ballooning contact

    International Nuclear Information System (INIS)

    Fan, H.Z.; Bilanovic, Z.; Nitheanandan, T.

    2004-01-01

    A study was performed to assess the effect of the calandria-tube/moderator heat transfer after pressure-tube/calandria tube ballooning contact using CATHENA. Results of this study indicated that the analytical tool, CATHENA, can be applied for pool boiling heat transfer on the external surface of a large diameter tube, such as the calandria tube used in CANDU reactors. The methodology in such CANDU-generic study can be used to simulate the tube surface with multiple boiling regimes and to assess the benefits of closely coupling thermalhydraulics modelling and fuel/fuel channel behaviour modelling. CATHENA (Canadian Algorithm for THErmalhydraulic Network Analysis) is a one-dimensional, two-fluid thermalhydraulic simulation code designed by AECL to analyse two-phase flow and heat transfer in piping networks. The detailed heat transfer package in CATHENA allows a connection to be established from the multiple solid surfaces of tubes to the surrounding large amount of moderator water, which acts as a heat sink during a postulated loss of coolant event. The generalized heat transfer package within CATHENA allows the tube walls to be divided into several layers in the radial direction and several sectors in the circumferential direction, to account for heat transfer conditions in these two directions. The CATHENA code with the generalized heat transfer package is capable of capturing key pool-boiling phenomena such as nucleate, transition and film boiling heat transfer as well as an ability to model the rewet phenomenon to some extent. A CATHENA input model was generated and used in simulations of selected contact boiling experiment test cases. The transient wall temperatures have been calculated in different portions of the calandria tube. By using this model an adequate agreement was achieved between CATHENA calculation and experimental measurement The CATHENA code enables one to investigate the transient and local thermal-mechanical behaviour of the calandria tube

  8. Wet effluent diffusion denuder: The tool for determination of monoterpenes in forest

    Czech Academy of Sciences Publication Activity Database

    Křůmal, Kamil; Mikuška, Pavel; Večeřová, Kristýna; Urban, Otmar; Pallozzi, E.; Večeřa, Zbyněk

    2016-01-01

    Roč. 153, JUN (2016), s. 260-267 ISSN 0039-9140 R&D Projects: GA MŠk(CZ) LO1415 Institutional support: RVO:68081715 ; RVO:67179843 Keywords : diffusion denuder * monoterpene * biogenic volatile organic compounds * tenax tubes Subject RIV: CB - Analytical Chemistry , Separation; EH - Ecology, Behaviour (UEK-B) Impact factor: 4.162, year: 2016

  9. Wet effluent diffusion denuder: The tool for determination of monoterpenes in forest

    Czech Academy of Sciences Publication Activity Database

    Křůmal, Kamil; Mikuška, Pavel; Večeřová, Kristýna; Urban, Otmar; Pallozzi, E.; Večeřa, Zbyněk

    2016-01-01

    Roč. 153, JUN (2016), s. 260-267 ISSN 0039-9140 R&D Projects: GA MŠk(CZ) LO1415 Institutional support: RVO:68081715 ; RVO:67179843 Keywords : diffusion denuder * monoterpene * biogenic volatile organic compounds * tenax tubes Subject RIV: CB - Analytical Chemistry, Separation; EH - Ecology, Behaviour (UEK-B) Impact factor: 4.162, year: 2016

  10. Rigorous upper bounds for transport due to passive advection by inhomogeneous turbulence

    International Nuclear Information System (INIS)

    Krommes, J.A.; Smith, R.A.

    1987-05-01

    A variational procedure, due originally to Howard and explored by Busse and others for self-consistent turbulence problems, is employed to determine rigorous upper bounds for the advection of a passive scalar through an inhomogeneous turbulent slab with arbitrary generalized Reynolds number R and Kubo number K. In the basic version of the method, the steady-state energy balance is used as a constraint; the resulting bound, though rigorous, is independent of K. A pedagogical reference model (one dimension, K = ∞) is described in detail; the bound compares favorably with the exact solution. The direct-interaction approximation is also worked out for this model; it is somewhat more accurate than the bound, but requires considerably more labor to solve. For the basic bound, a general formalism is presented for several dimensions, finite correlation length, and reasonably general boundary conditions. Part of the general method, in which a Green's function technique is employed, applies to self-consistent as well as to passive problems, and thereby generalizes previous results in the fluid literature. The formalism is extended for the first time to include time-dependent constraints, and a bound is deduced which explicitly depends on K and has the correct physical scalings in all regimes of R and K. Two applications from the theory of turbulent plasmas ae described: flux in velocity space, and test particle transport in stochastic magnetic fields. For the velocity space problem the simplest bound reproduces Dupree's original scaling for the strong turbulence diffusion coefficient. For the case of stochastic magnetic fields, the scaling of the bounds is described for the magnetic diffusion coefficient as well as for the particle diffusion coefficient in the so-called collisionless, fluid, and double-streaming regimes

  11. Diffusive flux in a model of stochastically gated oxygen transport in insect respiration

    Energy Technology Data Exchange (ETDEWEB)

    Berezhkovskii, Alexander M. [Mathematical and Statistical Computing Laboratory, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, Maryland 20892 (United States); Shvartsman, Stanislav Y. [Department of Chemical and Biological Engineering and Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544 (United States)

    2016-05-28

    Oxygen delivery to insect tissues is controlled by transport through a branched tubular network that is connected to the atmosphere by valve-like gates, known as spiracles. In certain physiological regimes, the spiracles appear to be randomly switching between open and closed states. Quantitative analysis of this regime leads a reaction-diffusion problem with stochastically switching boundary condition. We derive an expression for the diffusive flux at long times in this problem. Our approach starts with the derivation of the passage probability for a single particle that diffuses between a stochastically gated boundary, which models the opening and closing spiracle, and the perfectly absorbing boundary, which models oxygen absorption by the tissue. This passage probability is then used to derive an expression giving the diffusive flux as a function of the geometric parameters of the tube and characteristic time scales of diffusion and gate dynamics.

  12. Improvement of pump tubes for gas guns and shock tube drivers

    Science.gov (United States)

    Bogdanoff, D. W.

    1990-01-01

    In a pump tube, a gas is mechanically compressed, producing very high pressures and sound speeds. The intensely heated gas produced in such a tube can be used to drive light gas guns and shock tubes. Three concepts are presented that have the potential to allow substantial reductions in the size and mass of the pump tube to be achieved. The first concept involves the use of one or more diaphragms in the pump tube, thus replacing a single compression process by multiple, successive compressions. The second concept involves a radical reduction in the length-to-diameter ratio of the pump tube and the pump tube piston. The third concept involves shock heating of the working gas by high explosives in a cyclindrical geometry reusable device. Preliminary design analyses are performed on all three concepts and they appear to be quite feasible. Reductions in the length and mass of the pump tube by factors up to about 11 and about 7, respectively, are predicted, relative to a benchmark conventional pump tube.

  13. Concept research on general passive system

    International Nuclear Information System (INIS)

    Han Xu; Yang Yanhua; Zheng Mingguang

    2009-01-01

    This paper summarized the current passive techniques used in nuclear power plants. Through classification and analysis, the functional characteristics and inherent identification of passive systems were elucidated. By improving and extending the concept of passive system, the general passive concept was proposed, and space and time relativity was discussed and assumption of general passive system were illustrated. The function of idealized general passive system is equivalent with the current passive system, but the design of idealized general passive system is more flexible. (authors)

  14. Experimental design and analysis for irradiation of SiC/SiC composite tubes under a prototypic high heat flux

    Science.gov (United States)

    Petrie, Christian M.; Koyanagi, Takaaki; McDuffee, Joel L.; Deck, Christian P.; Katoh, Yutai; Terrani, Kurt A.

    2017-08-01

    The purpose of this work is to design an irradiation vehicle for testing silicon carbide (SiC) fiber-reinforced SiC matrix composite cladding materials under conditions representative of a light water reactor in order to validate thermo-mechanical models of stress states in these materials due to irradiation swelling and differential thermal expansion. The design allows for a constant tube outer surface temperature in the range of 300-350 °C under a representative high heat flux (∼0.66 MW/m2) during one cycle of irradiation in an un-instrumented ;rabbit; capsule in the High Flux Isotope Reactor. An engineered aluminum foil was developed to absorb the expansion of the cladding tubes, due to irradiation swelling, without changing the thermal resistance of the gap between the cladding and irradiation capsule. Finite-element analyses of the capsule were performed, and the models used to calculate thermal contact resistance were validated by out-of-pile testing and post-irradiation examination of the foils and passive SiC thermometry. Six irradiated cladding tubes (both monoliths and composites) were irradiated and subsequently disassembled in a hot cell. The calculated temperatures of passive SiC thermometry inside the capsules showed good agreement with temperatures measured post-irradiation, with two calculated temperatures falling within 10 °C of experimental measurements. The success of this design could lead to new opportunities for irradiation applications with materials that suffer from irradiation swelling, creep, or other dimensional changes that can affect the specimen temperature during irradiation.

  15. Experimental design and analysis for irradiation of SiC/SiC composite tubes under a prototypic high heat flux

    Energy Technology Data Exchange (ETDEWEB)

    Petrie, Christian M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Koyanagi, Takaaki [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); McDuffee, Joel L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Deck, Christian P. [General Atomics, San Diego, CA (United States); Katoh, Yutai [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Terrani, Kurt A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-05-04

    The purpose of this work is to design an irradiation vehicle for testing silicon carbide (SiC) fiber-reinforced SiC matrix composite cladding materials under conditions representative of a light water reactor in order to validate thermo-mechanical models of stress states in these materials due to irradiation swelling and differential thermal expansion. The design allows for a constant tube outer surface temperature in the range of 300–350 °C under a representative high heat flux (~0.66 MW/m2) during one cycle of irradiation in an un-instrumented “rabbit” capsule in the High Flux Isotope Reactor. An engineered aluminum foil was developed to absorb the expansion of the cladding tubes, due to irradiation swelling, without changing the thermal resistance of the gap between the cladding and irradiation capsule. Finite-element analyses of the capsule were performed, and the models used to calculate thermal contact resistance were validated by out-of-pile testing and post-irradiation examination of the foils and passive SiC thermometry. Six irradiated cladding tubes (both monoliths and composites) were irradiated and subsequently disassembled in a hot cell. The calculated temperatures of passive SiC thermometry inside the capsules showed good agreement with temperatures measured post-irradiation, with two calculated temperatures falling within 10 °C of experimental measurements. Furthermore, the success of this design could lead to new opportunities for irradiation applications with materials that suffer from irradiation swelling, creep, or other dimensional changes that can affect the specimen temperature during irradiation.

  16. Production of ceramic-metal joints for high-vacuum applications and development of simulation program for discharge tube

    Energy Technology Data Exchange (ETDEWEB)

    Kang, S. H.; Chung, K. H. [Seoul National University, Seoul (Korea)

    2000-04-01

    To develop a ceramic-metal jointed tube for high-vacuum applications, metalizing process and active metal brazing were investigated. Active metal brazing was adopted as a joining process to produce a high-vacuum tube which had high joint strength and reliability. A possibility for the development of new composition of Mo-Mn paste was studied. Also, to improve the strength and reliability of active metal brazed joint, TiN coating was introduced as a diffusion barrier. It was revealed that TiN coating could improve the joint strength and reliability. 100mm {phi} tube joint was produced using incusil ABA brazing alloy. The strength and reliability of manufactured tube showed higher value than commercial one. The electric field distribution in ceramic tube under high voltage was analyzed. Two dimensional electric field distribution was investigated under the existence of charged particles. From this result, electric field distribution at the surface of ceramic tube and the location of high electric field was predicted. Finally, Arc discharge was simulated to analyze the effect of arc discharge on the discharge tube wall. The maximum temperature of arc was 12000-13000K. The wall temperature was increased 100-170K by the arc discharge. 45 refs., 57 figs., 4 tabs. (Author)

  17. Damage detection and isolation via autocorrelation: a step toward passive sensing

    Science.gov (United States)

    Chang, Y. S.; Yuan, F. G.

    2018-03-01

    Passive sensing technique may eliminate the need of expending power from actuators and thus provide a means of developing a compact and simple structural health monitoring system. More importantly, it may provide a solution for monitoring the aircraft subjected to environmental loading from air flow during operation. In this paper, a non-contact auto-correlation based technique is exploited as a feasibility study for passive sensing application to detect damage and isolate the damage location. Its theoretical basis bears some resemblance to reconstructing Green's function from diffusive wavefield through cross-correlation. Localized high pressure air from air compressor are randomly and continuously applied on the one side surface of the aluminum panels through the air blow gun. A laser Doppler vibrometer (LDV) was used to scan a 90 mm × 90 mm area to create a 6 × 6 2D-array signals from the opposite side of the panels. The scanned signals were auto-correlated to reconstruct a "selfimpulse response" (or Green's function). The premise for stably reconstructing the accurate Green's function requires long sensing times. For a 609.6 mm × 609.6 mm flat aluminum panel, the sensing times roughly at least four seconds is sufficient to establish converged Green's function through correlation. For the integral stiffened aluminum panel, the geometrical features of the panel expedite the formation of the diffusive wavefield and thus shorten the sensing times. The damage is simulated by gluing a magnet onto the panels. Reconstructed Green's functions (RGFs) are used for damage detection and damage isolation based on an imaging condition with mean square deviation of the RGFs from the pristine and the damaged structure and the results are shown in color maps. The auto-correlation based technique is shown to consistently detect the simulated damage, image and isolate the damage in the structure subjected to high pressure air excitation. This technique may be transformed into

  18. In planta passive sampling devices for assessing subsurface chlorinated solvents.

    Science.gov (United States)

    Shetty, Mikhil K; Limmer, Matt A; Waltermire, Kendra; Morrison, Glenn C; Burken, Joel G

    2014-06-01

    Contaminant concentrations in trees have been used to delineate groundwater contaminant plumes (i.e., phytoscreening); however, variability in tree composition hinders accurate measurement of contaminant concentrations in planta, particularly for long-term monitoring. This study investigated in planta passive sampling devices (PSDs), termed solid phase samplers (SPSs) to be used as a surrogate tree core. Characteristics studied for five materials included material-air partitioning coefficients (Kma) for chlorinated solvents, sampler equilibration time and field suitability. The materials investigated were polydimethylsiloxane (PDMS), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polyoxymethylene (POM) and plasticized polyvinyl chloride (PVC). Both PDMS and LLDPE samplers demonstrated high partitioning coefficients and diffusivities and were further tested in greenhouse experiments and field trials. While most of the materials could be used for passive sampling, the PDMS SPSs performed best as an in planta sampler. Such a sampler was able to accurately measure trichloroethylene (TCE) and tetrachloroethylene (PCE) concentrations while simultaneously incorporating simple operation and minimal impact to the surrounding property and environment. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Role of Passive Safety Features in Prevention And Mitigation of Severe Plant Conditions in Indian Advanced Heavy Water Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Vikas; Nayak, A.; Dhiman, M.; Kulkarni, P. P.; Vijayan, P. K.; Vaze, K. K. [Bhabha Atomic Research Centre, Mumbai (India)

    2013-10-15

    Pressing demands of economic competitiveness, the need for large-scale deployment, minimizing the need of human intervention, and experience from the past events and incidents at operating reactors have guided the evolution and innovations in reactor technologies. Indian innovative reactor 'AHWR' is a pressure-tube type natural circulation based boiling water reactor that is designed to meet such requirements, which essentially reflect the needs of next generation reactors. The reactor employs various passive features to prevent and mitigate accidental conditions, like a slightly negative void reactivity coefficient, passive poison injection to scram the reactor in event of failure of the wired shutdown systems, a large elevated pool of water as a heat sink inside the containment, passive decay heat removal based on natural circulation and passive valves, passive ECC injection, etc. It is designed to meet the fundamental safety requirements of safe shutdown, safe decay heat removal and confinement of activity with no impact in public domain, and hence, no need for emergency planning under all conceivable scenarios. This paper examines the role of the various passive safety systems in prevention and mitigation of severe plant conditions that may arise in event of multiple failures. For the purpose of demonstration of the effectiveness of its passive features, postulated scenarios on the lines of three major severe accidents in the history of nuclear power reactors are considered, namely; the Three Mile Island (TMI), Chernobyl and Fukushima accidents. Severe plant conditions along the lines of these scenarios are postulated to the extent conceivable in the reactor under consideration and analyzed using best estimate system thermal-hydraulics code RELAP5/Mod3.2. It is found that the various passive systems incorporated enable the reactor to tolerate the postulated accident conditions without causing severe plant conditions and core degradation.

  20. ROLE OF PASSIVE SAFETY FEATURES IN PREVENTION AND MITIGATION OF SEVERE PLANT CONDITIONS IN INDIAN ADVANCED HEAVY WATER REACTOR

    Directory of Open Access Journals (Sweden)

    VIKAS JAIN

    2013-10-01

    Full Text Available Pressing demands of economic competitiveness, the need for large-scale deployment, minimizing the need of human intervention, and experience from the past events and incidents at operating reactors have guided the evolution and innovations in reactor technologies. Indian innovative reactor ‘AHWR’ is a pressure-tube type natural circulation based boiling water reactor that is designed to meet such requirements, which essentially reflect the needs of next generation reactors. The reactor employs various passive features to prevent and mitigate accidental conditions, like a slightly negative void reactivity coefficient, passive poison injection to scram the reactor in event of failure of the wired shutdown systems, a large elevated pool of water as a heat sink inside the containment, passive decay heat removal based on natural circulation and passive valves, passive ECC injection, etc. It is designed to meet the fundamental safety requirements of safe shutdown, safe decay heat removal and confinement of activity with no impact in public domain, and hence, no need for emergency planning under all conceivable scenarios. This paper examines the role of the various passive safety systems in prevention and mitigation of severe plant conditions that may arise in event of multiple failures. For the purpose of demonstration of the effectiveness of its passive features, postulated scenarios on the lines of three major severe accidents in the history of nuclear power reactors are considered, namely; the Three Mile Island (TMI, Chernobyl and Fukushima accidents. Severe plant conditions along the lines of these scenarios are postulated to the extent conceivable in the reactor under consideration and analyzed using best estimate system thermal-hydraulics code RELAP5/Mod3.2. It is found that the various passive systems incorporated enable the reactor to tolerate the postulated accident conditions without causing severe plant conditions and core degradation.

  1. Ethanol Dehydration by Evaporation and Diffusion in an Inert Gas Layer

    Energy Technology Data Exchange (ETDEWEB)

    In-Sick, Chung; Kyu-Min, Song [Korea Advanced Institute of Science and Technology, Taejeon (Korea, Republic of); Won-Hi, Hong; Ho-Nam, Chang [Korea Advanced Institute of Science and Technology, Taejeon (Korea, Republic of)

    1994-08-01

    Ethanol dehydration of azeotropic mixture was performed by using diffusion distillation apparatus consisting of a wetted-wall column with two concentric tubes. Ethanol-water mixtures evaporated below the boiling point was separated during the diffusion through the gap filled with an inert gas. As the temperature difference between evaporation part and condensation part was increased, the total flux increased but the selectivity decreased. The effect of the annular width on the selectivity was not significant but the total flux was decreased with decreases in the annular width. Inert gas has an effect on the diffusivity of evaporated gas components. The total flux in case of helium as inert gas was larger than that in case of air but the selectivity in case of using helium was lower. (author). 14 refs. 1 tab. 12 figs.

  2. Surface Passivation in Empirical Tight Binding

    OpenAIRE

    He, Yu; Tan, Yaohua; Jiang, Zhengping; Povolotskyi, Michael; Klimeck, Gerhard; Kubis, Tillmann

    2015-01-01

    Empirical Tight Binding (TB) methods are widely used in atomistic device simulations. Existing TB methods to passivate dangling bonds fall into two categories: 1) Method that explicitly includes passivation atoms is limited to passivation with atoms and small molecules only. 2) Method that implicitly incorporates passivation does not distinguish passivation atom types. This work introduces an implicit passivation method that is applicable to any passivation scenario with appropriate parameter...

  3. Solution of the atmospheric diffusion equation with a realistic diffusion coefficient and time dependent mixing height

    International Nuclear Information System (INIS)

    Mayhoub, A.B.; Etman, S.M.

    1997-01-01

    One dimensional model for the dispersion of a passive atmospheric contaminant (neglecting chemical reactions) in the atmospheric boundary layer is introduced. The differential equation representing the dispersion of pollutants is solved on the basis of gradient-transfer theory (K- theory). The present approach deals with a more appropriate and realistic profile for the diffusion coefficient K, which is expressed in terms of the friction velocity U, the vertical coordinate z and the depth of the mixing layer h, which is taken time dependent. After some mathematical simplification, the equation analytic obtained solution can be easily applied to case study concerning atmospheric dispersion of pollutants

  4. Vibro-impact responses of a tube with tube--baffle interaction. [LMFBR

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Y S; Sass, D E; Jendrzejczyk, J A

    1978-01-01

    The relatively small, inherent tube-to-baffle hole clearances associated with manufacturing tolerances in heat exchangers affect the vibrational characteristics and the response of the tube. Numerical studies were made to predict the vibro-impact response of a tube with tube-baffle interaction. The finite element method has been employed with a non-linear elastic contact spring-dashpot to model the effect of the relative approach between the tube and the baffle plate. The coupled equations of motion are directly integrated with a proportional system damping represented by a linear combination of mass and stiffness. Lumped mass approach with explicit time integration scheme was found to be a suitable choice for tube-baffle impacting analysis. Fourier analyses indicate that the higher mode contributions to the tube response are significant for strong tube-baffle impacting. The contact damping forces are negligible compared with the contact spring forces. The numerical analysis results are in reasonably good agreement with those of the experiments.

  5. Diffusive-light invisibility cloak for transient illumination

    Science.gov (United States)

    Orazbayev, B.; Beruete, M.; Martínez, A.; García-Meca, C.

    2016-12-01

    Invisibility in a diffusive-light-scattering medium has been recently demonstrated by employing a scattering-cancellation core-shell cloak. Unlike nondiffusive cloaks, such a device can be simultaneously macroscopic, broadband, passive, polarization independent, and omnidirectional. Unfortunately, it has been verified that this cloak, as well as more sophisticated ones based on transformation optics, fail under pulsed illumination, invalidating their use for a variety of applications. Here, we introduce a different approach based on unimodular transformations that enables the construction of unidirectional diffusive-light cloaks exhibiting a perfect invisibility effect, even under transient conditions. Moreover, we demonstrate that a polygonal cloak can extend this functionality to multiple directions with a nearly ideal behavior, while preserving all other features. We propose and numerically verify a simple cloak realization based on a layered stack of two isotropic materials. The studied devices have several applications not addressable by any of the other cloaks proposed to date, including shielding from pulse-based detection techniques, cloaking undesired scattering elements in time-of-flight imaging or high-speed communication systems for diffusive environments, and building extreme optical security features. The discussed cloaking strategy could also be applied to simplify the implementation of thermal cloaks.

  6. Passive Education

    Science.gov (United States)

    Bojesen, Emile

    2018-01-01

    This paper does not present an advocacy of a passive education as opposed to an active education nor does it propose that passive education is in any way 'better' or more important than active education. Through readings of Maurice Blanchot, Jacques Derrida and B.S. Johnson, and gentle critiques of Jacques Rancière and John Dewey, passive…

  7. Bender/Coiler for Tubing

    Science.gov (United States)

    Stoltzfus, J. M.

    1983-01-01

    Easy-to-use tool makes coils of tubing. Tubing to be bend clamped with stop post. Die positioned snugly against tubing. Operator turns handle to slide die along tubing, pushing tubing into spiral groove on mandrel.

  8. Properties of the chalcogenide–carbon nano tubes and graphene composite materials

    International Nuclear Information System (INIS)

    Singh, Abhay Kumar; Kim, JunHo; Park, Jong Tae; Sangunni, K.S.

    2015-01-01

    Highlights: • Chalcogenides. • Melt quenched. • Composite materials. • Multi walled carbon nano tubes. • Bilayer graphene. - Abstract: Composite can deliver more than the individual elemental property of the material. Specifically chalcogenide- multi walled carbon nano tubes and chalcogenide- bilayer graphene composite materials could be interesting for the investigation, which have been less covered by the investigators. We describe micro structural properties of Se 55 Te 25 Ge 20, Se 55 Te 25 Ge 20 + 0.025% multi walled carbon nano tubes and Se 55 Te 25 Ge 20 + 0.025% bilayer graphene materials. This gives realization of the alloying constituents inclusion/or diffusion inside the multi walled carbon nano tubes and bilayer graphene under the homogeneous parent alloy configuration. Raman spectroscopy, X-ray photoelectron spectroscopy, UV/Visible spectroscopy and Fourier transmission infrared spectroscopy have also been carried out under the discussion. A considerable core energy levels peak shifts have been noticed for the composite materials by the X-ray photoelectron spectroscopy. The optical energy band gaps are measured to be varied in between 1.2 and 1.3 eV. In comparison to parent (Se 55 Te 25 Ge 20 ) alloy a higher infrared transmission has been observed for the composite materials. Subsequently, variation in physical properties has been explained on the basis of bond formation in solids

  9. Hydrogenation of passivated contacts

    Energy Technology Data Exchange (ETDEWEB)

    Nemeth, William; Yuan, Hao-Chih; LaSalvia, Vincenzo; Stradins, Pauls; Page, Matthew R.

    2018-03-06

    Methods of hydrogenation of passivated contacts using materials having hydrogen impurities are provided. An example method includes applying, to a passivated contact, a layer of a material, the material containing hydrogen impurities. The method further includes subsequently annealing the material and subsequently removing the material from the passivated contact.

  10. Steam generator tube extraction

    International Nuclear Information System (INIS)

    Delorme, H.

    1985-05-01

    To enable tube examination on steam generators in service, Framatome has now developed a process for removing sections of steam generator tubes. Tube sections can be removed without being damaged for treating the tube section expanded in the tube sheet

  11. Conceptual mechanical design for a pressure-tube type supercritical water-cooled reactor

    Energy Technology Data Exchange (ETDEWEB)

    Yetisir, M.; Diamond, W.; Leung, L.K.H.; Martin, D.; Duffey, R. [Atomic Energy of Canada Limited, Chalk River, ON (Canada)

    2011-07-01

    This paper presents a conceptual mechanical design for a heavy-water-moderated pressure-tube supercritical water (SCW) reactor, which has evolved from the well-established CANDU nuclear reactor. As in the current designs, the pressure-tube SCW reactor uses a calandria vessel and, as a result, many of today's technologies (such as the shutdown safety systems) can readily be adopted with small changes. Because the proposed concept uses a low-pressure moderator, it does not require a pressure vessel that is subject to the full SCW pressure and temperature conditions. The proposed design uses batch refueling and hence, the reactor core is orientated vertically. Significant simplifications result in the design with the elimination of on line fuelling systems, fuel channel end fittings and fuel channel closure seals and thus utilize the best features of Light Water Reactor (LWR) and Heavy Water Reactor (HWR) technologies. The safety goal is based on achieving a passive 'no core melt' configuration for the channels and core, so the mechanical features and systems directly reflect this desired attribute. (author)

  12. Conceptual mechanical design for a pressure-tube type supercritical water-cooled reactor

    International Nuclear Information System (INIS)

    Yetisir, M.; Diamond, W.; Leung, L.K.H.; Martin, D.; Duffey, R.

    2011-01-01

    This paper presents a conceptual mechanical design for a heavy-water-moderated pressure-tube supercritical water (SCW) reactor, which has evolved from the well-established CANDU nuclear reactor. As in the current designs, the pressure-tube SCW reactor uses a calandria vessel and, as a result, many of today's technologies (such as the shutdown safety systems) can readily be adopted with small changes. Because the proposed concept uses a low-pressure moderator, it does not require a pressure vessel that is subject to the full SCW pressure and temperature conditions. The proposed design uses batch refueling and hence, the reactor core is orientated vertically. Significant simplifications result in the design with the elimination of on line fuelling systems, fuel channel end fittings and fuel channel closure seals and thus utilize the best features of Light Water Reactor (LWR) and Heavy Water Reactor (HWR) technologies. The safety goal is based on achieving a passive 'no core melt' configuration for the channels and core, so the mechanical features and systems directly reflect this desired attribute. (author)

  13. Sustainability of the prevention of passive infant smoking within well-baby clinics.

    Science.gov (United States)

    Crone, M R; Verlaan, M; Willemsen, M C; van Soelen, P; Reijneveld, S A; Sing, R A Hira; Paulussen, T G W M

    2006-04-01

    This study assessed the antecedents of continued use of an education program to prevent passive smoking in infants. It consists of a booklet for parents and a manual for health professionals describing a five-step procedure for discussing passive smoking. A questionnaire was sent to 67 managers, 670 nurses, and 335 physicians working in well-baby clinics (response rate: 70%, 53%, 47% respectively). Questions concerned the completeness of use, level of institutionalization, and characteristics of the organization, the user, and the dissemination strategy. Seventy-one percent of nurses and 42% of physicians worked with the program. They foremost provided the first three steps of the five-step procedure. Physicians' completeness of use was related to their perceived responsibility in providing this education, and nurses' use was related to their perceived self-efficacy, responsibility, training attendance, participation in the adoption decision, and level of institutionalization. Diffusion efforts should focus on improving the completeness of use and level of institutionalization.

  14. Passive safety; Passive Sicherheit

    Energy Technology Data Exchange (ETDEWEB)

    Rueckert, J. [Skoda Auto a.s., Mlada Boleslav (Czech Republic). Interieurentwicklung und Versuche; Hau, M. [Skoda Auto a.s., Mlada Boleslav (Czech Republic). Koordination der Fahrzeugsicherung

    2004-05-01

    The specifications for passive safety are partly based on the legal requirements for all export markets combined with the strict internal standards of Volkswagen Group. The Euro NCAP tests and their precisely defined testing methods using the new point assessment are very important. (orig.)

  15. The use of twisted tapes for the enhancement of heat transfer outside tube bundles

    International Nuclear Information System (INIS)

    Mansur, Sergio-Said

    1993-01-01

    A numerical and experimental investigation of the thermohydraulics of tubular heat exchangers equipped with twisted tapes outside the tubes was carried out. Experimental data for the pressure drop and flow velocity as well as flow visualization data were obtained using a simulated exchanger made of plexiglas. A porous medium type of model allowed for the numerical evaluation of the heat transfer and pressure drop in this unique geometry exchanger. The model was used on the TRIO computer code, developed by the Commissariat a l'Energie Atomique, CEA - France. The experimental data allowed for the evaluation of the flow distribution throughout the exchanger and for the determination of parameters entering the numerical model. The appropriateness of the latter for the macroscopic description of the flow was confirmed by extensive comparison with the experimental data. A comparative analysis of different types of configurations of this exchanger revealed satisfactory performance levels for the exchanger presently investigated. Finally, the flow visualization data were used to qualitatively infer the main aspects of the turbulent diffusion along the tube bundle. The twisted tapes were observed to enhance the fluid mixing process, thus providing for a more effective diffusion of momentum, mass and energy. (author) [fr

  16. Comparative assessment of condensation models for horizontal tubes

    International Nuclear Information System (INIS)

    Schaffrath, A.; Kruessenberg, A.K.; Lischke, W.; Gocht, U.; Fjodorow, A.

    1999-01-01

    The condensation in horizontal tubes plays an important role e.g. for the determination of the operation mode of horizontal steam generators of VVER reactors or passive safety systems for the next generation of nuclear power plants. Two different approaches (HOTKON and KONWAR) for modeling this process have been undertaken by Forschungszentrum Juelich (FZJ) and University for Applied Sciences Zittau/Goerlitz (HTWS) and implemented into the 1D-thermohydraulic code ATHLET, which is developed by the Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH for the analysis of anticipated and abnormal transients in light water reactors. Although the improvements of the condensation models are developed for different applications (VVER steam generators - emergency condenser of the SWR1000) with strongly different operation conditions (e.g. the temperature difference over the tube wall in HORUS is up to 30 K and in NOKO up to 250 K, the heat flux density in HORUS is up to 40 kW/m 2 and in NOKO up to 1 GW/m 2 ) both models are now compared and assessed by Forschungszentrum Rossendorf FZR e.V. Therefore, post test calculations of selected HORUS experiments were performed with ATHLET/KONWAR and compared to existing ATHLET and ATHLET/HOTKON calculations of HTWS. It can be seen that the calculations with the extension KONWAR as well as HOTKON improve significantly the agreement between computational and experimental data. (orig.) [de

  17. Optimization and evaluation of multi-bed adsorbent tube method in collection of volatile organic compounds

    Science.gov (United States)

    Ho, Steven Sai Hang; Wang, Liqin; Chow, Judith C.; Watson, John G.; Xue, Yonggang; Huang, Yu; Qu, Linli; Li, Bowei; Dai, Wenting; Li, Lijuan; Cao, Junji

    2018-04-01

    The feasibility of using adsorbent tubes to collect volatile organic compounds (VOCs) has been demonstrated since the 1990's and standardized as Compendium Method TO-17 by the U.S. Environmental Protection Agency (U.S EPA). This paper investigates sampling and analytical variables on concentrations of 57 ozone (O3) precursors (C2-C12 aliphatic and aromatic VOCs) specified for the Photochemical Assessment Monitoring Station (PAMS). Laboratory and field tests examined multi-bed adsorbent tubes containing a sorbate combination of Tenax TA, Carbograph 1 TD, and Carboxen 1003. Analyte stabilities were influenced by both collection tube temperature and ambient O3 concentrations. Analytes degraded during storage, while blank levels were elevated by passive adsorption. Adsorbent tube storage under cold temperatures (- 10 °C) in a preservation container filled with solid silica gel and anhydrous calcium sulfate (CaSO4) ensured sample integrity. A high efficiency (> 99%) O3 scrubber (i.e., copper coil tube filled with saturated potassium iodide [KI]) removed O3 (i.e., air stream with a sampling capacity of 30 h. Water vapor scrubbers interfered with VOC measurements. The optimal thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) desorption time of 8 min was found at 330 °C. Good linearity (R2 > 0.995) was achieved for individual analyte calibrations (with the exception of acetylene) for mixing ratios of 0.08-1.96 ppbv. The method detection limits (MDLs) were below 0.055 ppbv for a 3 L sample volume. Replicate analyses showed relative standard deviations (RSDs) of < 10%, with the majority of the analytes within < 5%.

  18. Feeding tube - infants

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/007235.htm Feeding tube - infants To use the sharing features on this page, please enable JavaScript. A feeding tube is a small, soft, plastic tube placed ...

  19. Passive House Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Strom, I.; Joosten, L.; Boonstra, C. [DHV Sustainability Consultants, Eindhoiven (Netherlands)

    2006-05-15

    PEP stands for 'Promotion of European Passive Houses' and is a consortium of European partners, supported by the European Commission, Directorate General for Energy and Transport. In this working paper an overview is given of Passive House solutions. An inventory has been made of Passive House solutions for new build residences applied in each country. Based on this, the most common basic solutions have been identified and described in further detail, including the extent to which solutions are applied in common and best practice and expected barriers for the implementation in each country. An inventory per country is included in the appendix. The analysis of Passive House solutions in partner countries shows high priority with regard to the performance of the thermal envelope, such as high insulation of walls, roofs, floors and windows/ doors, thermal bridge-free construction and air tightness. Due to the required air tightness, special attention must be paid to indoor air quality through proper ventilation. Finally, efficient ((semi-)solar) heating systems for combined space and DHW heating still require a significant amount of attention in most partner countries. Other basic Passive House solutions show a smaller discrepancy with common practice and fewer barriers have been encountered in partner countries. In the next section, the general barriers in partner countries have been inventoried. For each type of barrier a suggested approach has been given. Most frequently encountered barriers in partner countries are: limited know-how; limited contractor skills; and acceptation of Passive Houses in the market. Based on the suggested approaches to overcoming barriers, this means that a great deal of attention must be paid to providing practical information and solutions to building professionals, providing practical training to installers and contractors and communication about the Passive House concept to the market.

  20. Limited Mouth Opening Secondary to Diffuse Systemic Sclerosis

    Directory of Open Access Journals (Sweden)

    Tomoko Wada

    2013-01-01

    Full Text Available Systemic sclerosis (SSc is a relatively rare condition with an immunologically mediated pathogenesis. For reasons that are not clearly understood, dense collagen is deposited in the connective tissues of the body in extraordinary amounts. Although its dramatic effects are seen in association with the skin, the disease is often quite serious with visceral organ involvement. We describe a case of limited mouth opening secondary to diffuse SSc, improvement in mouth opening with passive jaw stretch exercises, and the challenges involved in performing dental procedures for such patients.

  1. ALD TiO x as a top-gate dielectric and passivation layer for InGaZnO115 ISFETs

    Science.gov (United States)

    Pavlidis, S.; Bayraktaroglu, B.; Leedy, K.; Henderson, W.; Vogel, E.; Brand, O.

    2017-11-01

    The suitability of atomic layer deposited (ALD) titanium oxide (TiO x ) as a top gate dielectric and passivation layer for indium gallium zinc oxide (InGaZnO115) ion sensitive field effect transistors (ISFETs) is investigated. TiO x is an attractive barrier material, but reports of its use for InGaZnO thin film transistor (TFT) passivation have been conflicting thus far. In this work, it is found that the passivated TFT’s behavior depends on the TiO x deposition temperature, affecting critical device characteristics such as threshold voltage, field-effect mobility and sub-threshold swing. An O2 annealing step is required to recover TFT performance post passivation. It is also observed that the positive bias stress response of the passivated TFTs improves compared the original bare device. Secondary ion mass spectroscopy excludes the effects of hydrogen doping and inter-diffusion as sources of the temperature-dependent performance change, therefore indicating that oxygen gettering induced by TiO x passivation is the likely source of oxygen vacancies and, consequently, carriers in the InGaZnO film. It is also shown that potentiometric sensing using ALD TiO x exhibits a near Nernstian response to pH change, as well as minimizes V TH drift in TiO x passivated InGaZnO TFTs immersed in an acidic liquid. These results add to the understanding of InGaZnO passivation effects and underscore the potential for low-temperature fabricated InGaZnO ISFETs to be used as high-performance mobile chemical sensors.

  2. THE USE OF PASSIVE SOLAR HEATING SYSTEMS AS PART OF THE PASSIVE HOUSE

    Directory of Open Access Journals (Sweden)

    Bryzgalin Vladislav Viktorovich

    2018-05-01

    Full Text Available Subject: systems of passive solar heating, which can, without the use of engineering equipment, capture and accumulate the solar heat used for heating buildings. Research objectives: study of the possibility to reach the passive house standard (buildings with near zero energy consumption for heating in climatic conditions of Russia using the systems of passive solar heating in combination with other solutions for reduction of energy costs of building developed in the past. Materials and methods: search and analysis of literature, containing descriptions of various passive solar heating systems, examples of their use in different climatic conditions and the resulting effect obtained from their use; analysis of thermophysical processes occurring in these systems. Results: we revealed the potential of using the solar heating systems in the climatic conditions of parts of the territories of the Russian Federation, identified the possibility of cheaper construction by the passive house standard with the use of these systems. Conclusions: more detailed analysis of thermophysical and other processes that take place in passive solar heating systems is required for creation of their computational models, which will allow us to more accurately predict their effectiveness and seek the most cost-effective design solutions, and include them in the list of means for achieving the passive house standard.

  3. A didactically novel derivation of the telegraph equation to describe sound propagation in rigid tubes

    International Nuclear Information System (INIS)

    Till, Bernie C; Driessen, Peter F

    2014-01-01

    Starting from first principles, we derive the telegraph equation to describe the propagation of sound waves in rigid tubes by using a simple approach that yields a lossy transmission line model with frequency-independent parameters. The approach is novel in the sense that it has not been found in the literature or textbooks. To derive the lossy acoustic telegraph equation from the lossless wave equation, we need only to relax the assumption that the dynamical variables are constant over the entire cross-sectional area of the tube. In this paper, we do this by introducing a relatively narrow boundary layer at the wall of the tube, over which the dynamical variables decrease linearly from the constant value to zero. This allows us to make very simple corrections to the lossless case, and to express them in terms of two parameters, namely the viscous diffusion time constant and the thermal diffusion time constant. The coefficients of the resulting telegraph equation are frequency-independent. A comparison with the telegraph equation for the electrical transmission line establishes precise relationships between the electrical circuit elements and the physical properties of the fluid. These relationships are thus proven a posteriori rather than asserted a priori. In this way, we arrive at an instructive and useful derivation of the acoustic telegraph equation, which takes viscous damping and thermal dissipation into account, and is accessible to students at the undergraduate level. This derivation does not resort to the combined heavy machinery of fluid dynamics and thermodynamics, does not assume that the waveforms are sinusoidal, and does not assume any particular cross-sectional shape of the tube. Surprisingly, we have been unable to find a comparable treatment in the standard introductory physics and acoustics texts, or in the literature. (paper)

  4. Passive solar construction handbook

    Energy Technology Data Exchange (ETDEWEB)

    Levy, E.; Evans, D.; Gardstein, C.

    1981-08-01

    Many of the basic elements of passive solar design are reviewed. The unique design constraints presented in passive homes are introduced and many of the salient issues influencing design decisions are described briefly. Passive solar construction is described for each passive system type: direct gain, thermal storage wall, attached sunspace, thermal storage roof, and convective loop. For each system type, important design and construction issues are discussed and case studies illustrating designed and built examples of the system type are presented. Construction details are given and construction and thermal performance information is given for the materials used in collector components, storage components, and control components. Included are glazing materials, framing systems, caulking and sealants, concrete masonry, concrete, brick, shading, reflectors, and insulators. The Load Collector Ratio method for estimating passive system performance is appended, and other analysis methods are briefly summarized. (LEW)

  5. Eustachian tube patency

    Science.gov (United States)

    Eustachian tube patency refers to how much the eustachian tube is open. The eustachian tube runs between the middle ear and the throat. It controls the pressure behind the eardrum and middle ear space. This helps keep ...

  6. Adhesion of volatile propofol to breathing circuit tubing.

    Science.gov (United States)

    Lorenz, Dominik; Maurer, Felix; Trautner, Katharina; Fink, Tobias; Hüppe, Tobias; Sessler, Daniel I; Baumbach, Jörg Ingo; Volk, Thomas; Kreuer, Sascha

    2017-08-21

    Propofol in exhaled breath can be measured and may provide a real-time estimate of plasma concentration. However, propofol is absorbed in plastic tubing, thus estimates may fail to reflect lung/blood concentration if expired gas is not extracted directly from the endotracheal tube. We evaluated exhaled propofol in five ventilated ICU patients who were sedated with propofol. Exhaled propofol was measured once per minute using ion mobility spectrometry. Exhaled air was sampled directly from the endotracheal tube and at the ventilator end of the expiratory side of the anesthetic circuit. The circuit was disconnected from the patient and propofol was washed out with a separate clean ventilator. Propofol molecules, which discharged from the expiratory portion of the breathing circuit, were measured for up to 60 h. We also determined whether propofol passes through the plastic of breathing circuits. A total of 984 data pairs (presented as median values, with 95% confidence interval), consisting of both concentrations were collected. The concentration of propofol sampled near the patient was always substantially higher, at 10.4 [10.25-10.55] versus 5.73 [5.66-5.88] ppb (p tubing was 4.58 [4.48-4.68] ppb, 3.46 [3.21-3.73] in the first hour, 4.05 [3.77-4.34] in the second hour, and 4.01 [3.36-4.40] in the third hour. Out-gassing propofol from the breathing circuit remained at 2.8 ppb after 60 h of washing out. Diffusion through the plastic was not observed. Volatile propofol binds or adsorbs to the plastic of a breathing circuit with saturation kinetics. The bond is reversible so propofol can be washed out from the plastic. Our data confirm earlier findings that accurate measurements of volatile propofol require exhaled air to be sampled as close as possible to the patient.

  7. Computer modelling of eddy current probes for ISI of pressure tube/calandria tube assemblies in PHWRs

    International Nuclear Information System (INIS)

    Rao, B.P.C.; Shyamsunder, M.T.; Bhattacharya, D.K.; Raj, Baldev

    1992-01-01

    Non-destructive Evaluation (NDE) plays a major role in ensuring the safe and reliable operation of PHWRs which are the mainstay of India's nuclear power programme. An important in-service inspection (ISI) requirement in these reactors is carried out through Eddy Current Testing (ECT) of the pressure tube (PT)/calandria tube (CT) assemblies. The material of construction of these assemblies is zircaloy-2. The two main objectives of this ISI are the detection of garter spring between CT and PT and the profiling of gap between CT and PT. The paper discusses the work carried out at the authors' laboratory on the development of ECT probes for ISI of PT/CT assemblies. Emphasis has been given on the work done on the design and optimisation of the probes using computer modeling. A 2-D finite element code has been developed for this purpose. The code is developed around a diffusion equation which can be derived from Maxwell's equations governing the electromagnetic phenomenon. An axisymmetry has been considered, since the probes are bobbin type. Results of impedance plane outputs obtained by modelling and those by experiments using actual probes have shown good matching. Salient features of an indigenously developed interactive PC based data acquisition, analysis and retrieval system to cater to ISI of PC/CT assemblies are described. (author). 10 refs., 7 figs

  8. Effect of tube-support interaction on the dynamic responses of heat exchanger tubes

    International Nuclear Information System (INIS)

    Shin, Y.S.; Jendrzejczyk, J.A.; Wambsganss, M.W.

    1977-01-01

    Operating heat exchangers have experienced tube damages due to excessive flow-induced vibration. The relatively small inherent tube-to-baffle hole clearances associated with manufacturing tolerances in heat exchangers affect the tube vibrational characteristics. In attempting a theoretical analysis, questions arise as to the effects of tube-baffle impacting on dynamic responses. Experiments were performed to determine the effects of tube-baffle impacting in vertical/horizontal tube orientation, and in air/water medium on the vibrational characteristics (resonant frequencies, mode shapes, and damping) and displacement response amplitudes of a seven-span tube model. The tube and support conditions were prototypic, and overall length approximately one-third that of a straight tube segment of the steam generator designed for the CRBR. The test results were compared with the analytical results based on the multispan beam with ''knife-edge'' supports

  9. 2.5 MWT Heat Exchanger Designs for Passive DHRS in PGSFR

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dehee; Eoh, Jaehyuk; Lee, Tae-Ho [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    Decay Heat Removal System (DHRS) of PGSFR consists of two passive DHRS (PDHRS) trains and two active DHRS (ADHRS) trains. Recently, total heat removal capacity of the DHRS in the PGSFR has increased to 10 MWT from 4 MWT reflecting safety analysis results. Consequently, DHRS components including heat exchangers, dampers, electro-magnetic pump, fan, piping, expansion tank and stack have been newly designed. In this work, physical models and correlations to design two main components of the PDHRS, decay heat exchanger (DHX) and natural-draft sodium-to-air heat exchanger (AHX), are introduced and designed data are presented. Physical models and correlations applied for heat exchangers in the PDHRS design were introduced and design works using the SHXSA and AHXSA codes has been completed for 2.5 MWT decay heat removal capability. DHX and AHX are designed utilizing SHXSA and AHXSA codes, respectively. Those design codes have capability of thermal sizing and performance analysis for the shell-and-tube type and counter-current flow heat exchanger unit. Since both SHXSA and AHXSA codes are similar, following description is focused on the SHXSA code. A single flow channel associated with an individual heat transfer tube is basically considered for thermal sizing and then the calculation results and design variables regarding heat transfer and pressure drop, etc. are extended to whole tubes. Various correlations of heat transfer and pressure loss for the shell- and tubeside flows were implemented in the computer codes. The analysis domain is discretized into several control volumes and heat transfer and pressure losses are calculated in each control volume.

  10. Annular gap measurement between pressure tube and calandria tube by eddy current technique

    International Nuclear Information System (INIS)

    Bhole, V.M.; Rastogi, P.K.; Kulkarni, P.G.

    1992-01-01

    In pressurised heavy water reactor (PHWR) major distinguishing feature is that there are number of identical fuel channels in the reactor core. Each channel consists of pressure tube of Zr-2.5 Nb or zircaloy-2 through which high temperature, high pressure primary coolant is passing. The pressure tube contains fuel. Surrounding the pressure tube there is low pressure, cool heavy water (moderator). The moderator is thermally separated from coolant by the tube which is nominally concentric with pressure tube called calandria tube. There are four garter springs in the annular gap between pressure tube and calandria tube. During the life of the reactor there are number of factors by which the pressure tube sags, most important factors are irradiation creep, thermal creep, fuel load etc. Because of the sag of pressure tube it can touch the calandria tube resulting in formation of cold spot. This leads to hydrogen concentration at that spot by which the material at that place becomes brittle and can lead to catastrophic failure of pressure tube. There is no useful access for measurement of annular gap either through the gas annular space or from exterior of calandria tube. So the annular gap was measured from inside surface of pressure tube which is accessible. Eddy current technique was used for finding the gap. The paper describe the details of split coil design of bobbin probe, selection of operating point on normalised impedance diagram by choosing frequency. Experimental results on full scale mock up, and actual gap measurement in reactor channel, are also given. (author). 7 figs

  11. Categorising YouTube

    DEFF Research Database (Denmark)

    Simonsen, Thomas Mosebo

    2011-01-01

    This article provides a genre analytical approach to creating a typology of the User Generated Content (UGC) of YouTube. The article investigates the construction of navigation processes on the YouTube website. It suggests a pragmatic genre approach that is expanded through a focus on YouTube......’s technological affordances. Through an analysis of the different pragmatic contexts of YouTube, it is argued that a taxonomic understanding of YouTube must be analysed in regards to the vacillation of a user-driven bottom-up folksonomy and a hierarchical browsing system that emphasises a culture of competition...... and which favours the already popular content of YouTube. With this taxonomic approach, the UGC videos are registered and analysed in terms of empirically based observations. The article identifies various UGC categories and their principal characteristics. Furthermore, general tendencies of the UGC within...

  12. Pressure tube type reactors

    International Nuclear Information System (INIS)

    Komada, Masaoki.

    1981-01-01

    Purpose: To increase the safety of pressure tube type reactors by providing an additional ECCS system to an ordinary ECCS system and injecting heavy water in the reactor core tank into pressure tubes upon fractures of the tubes. Constitution: Upon fractures of pressure tubes, reduction of the pressure in the fractured tubes to the atmospheric pressure in confirmed and the electromagnetic valve is operated to completely isolate the pressure tubes from the fractured portion. Then, the heavy water in the reactor core tank flows into and spontaneously recycles through the pressure tubes to cool the fuels in the tube to prevent their meltdown. By additionally providing the separate ECCS system to the ordinary ECCS system, fuels can be cooled upon loss of coolant accidents to improve the safety of the reactors. (Moriyama, K.)

  13. EXPERIMENTAL INVESTIGATION OF THE CONVECTIVE HEAT TRANSFER IN A SPIRALLY COILED CORRUGATED TUBE WITH RADIANT HEATING

    Directory of Open Access Journals (Sweden)

    Milan Đorđević

    2017-12-01

    Full Text Available The Archimedean spiral coil made of a transversely corrugated tube was exposed to radiant heating in order to represent a heat absorber of the parabolic dish solar concentrator. The main advantage of the considered innovative design solution is a coupling effect of the two passive methods for heat transfer enhancement - coiling of the flow channel and changes in surface roughness. The curvature ratio of the spiral coil varies from 0.029 to 0.234, while water and a mixture of propylene glycol and water are used as heat transfer fluids. The unique focus of this study is on specific boundary conditions since the heat flux upon the tube external surfaces varies not only in the circumferential direction, but in the axial direction as well. Instrumentation of the laboratory model of the heat absorber mounted in the radiation field includes measurement of inlet fluid flow rate, pressure drop, inlet and outlet fluid temperature and 35 type K thermocouples welded to the coil surface. A thermal analysis of the experimentally obtained data implies taking into consideration the externally applied radiation field, convective and radiative heat losses, conduction through the tube wall and convection to the internal fluid. The experimental results have shown significant enhancement of the heat transfer rate compared to spirally coiled smooth tubes, up to 240% in the turbulent flow regime.

  14. Tube-in-shell heat exchangers

    International Nuclear Information System (INIS)

    Richardson, J.

    1976-01-01

    Tube-in-shell heat exchangers normally comprise a bundle of parallel tubes within a shell container, with a fluid arranged to flow through the tubes in heat exchange with a second fluid flowing through the shell. The tubes are usually end supported by the tube plates that separate the two fluids, and in use the tube attachments to the tube plates and the tube plates can be subject to severe stress by thermal shock and frequent inspection and servicing are required. Where the heat exchangers are immersed in a coolant such as liquid Na such inspection is difficult. In the arrangement described a longitudinally extending central tube is provided incorporating axially spaced cylindrical tube plates to which the opposite ends of the tubes are attached. Within this tube there is a tubular baffle that slidably seals against the wall of the tube between the cylindrical tube plates to define two co-axial flow ducts. These ducts are interconnected at the closed end of the tube by the heat exchange tubes and the baffle comprises inner and outer spaced walls with the interspace containing Ar. The baffle is easily removable and can be withdrawn to enable insertion of equipment for inspecting the wall of the tube and tube attachments and to facilitate plugging of defective tubes. Cylindrical tube plates are believed to be superior for carrying pressure loads and resisting the effects of thermal shock. Some protection against thermal shock can be effected by arranging that the secondary heat exchange fluid is on the tube side, and by providing a thermal baffle to prevent direct impingement of hot primary fluid on to the cylindrical tube plates. The inner wall of the tubular baffle may have flexible expansible region. Some nuclear reactor constructions incorporating such an arrangement are described, including liquid metal reactors. (U.K.)

  15. Studies on hydrogen separation membrane for IS process. Membrane preparation with porous α-alumina tube

    International Nuclear Information System (INIS)

    Hwang, Gab-Jin; Onuki, Kaoru; Shimizu, Saburo

    1998-01-01

    It was investigated the preparation technique of hydrogen separation membrane to enhance the decomposition ratio of hydrogen iodide in the thermochemical IS process. Hydrogen separation membranes based on porous α-alumina tubes having pore size of 100 nm and 10 nm were prepared by chemical vapor deposition using tetraethylorthosilicate (TEOS) as the Si source. In the hydrogen separation membrane, its pore was closed by the deposited silica and then the permeation of gas was affected by the hindrance diffusion. At 600degC, the selectivity ratios (H 2 /N 2 ) were 5.2 and 160 for the membranes based on porous α-alumina tube having pore size of 100 nm and 10 nm, respectively. (author)

  16. Heat exchanger tube tool

    International Nuclear Information System (INIS)

    Gugel, G.

    1976-01-01

    Certain types of heat-exchangers have tubes opening through a tube sheet to a manifold having an access opening offset from alignment with the tube ends. A tool for inserting a device, such as for inspection or repair, is provided for use in such instances. The tool is formed by a flexible guide tube insertable through the access opening and having an inner end provided with a connector for connection with the opening of the tube in which the device is to be inserted, and an outer end which remains outside of the chamber, the guide tube having adequate length for this arrangement. A flexible transport hose for internally transporting the device slides inside of the guide tube. This hose is long enough to slide through the guide tube, into the heat-exchanger tube, and through the latter to the extent required for the use of the device. The guide tube must be bent to reach the end of the heat-exchanger tube and the latter may be constructed with a bend, the hose carrying anit-friction elements at interspaced locations along its length to make it possible for the hose to negotiate such bends while sliding to the location where the use of the device is required

  17. Observation of "YouTube" Language Learning Videos ("YouTube" LLVS)

    Science.gov (United States)

    Alhamami, Munassir

    2013-01-01

    This paper navigates into the "YouTube" website as one of the most usable online tools to learn languages these days. The paper focuses on two issues in creating "YouTube" language learning videos: pedagogy and technology. After observing the existing "YouTube" LLVs, the study presents a novel rubric that is directed…

  18. An automatic measuring system for mapping of spectral and angular dependence of direct and diffuse solar radiation; Et automatisk maalesystem for kartlegging av vinkel- og spektralfordeling av direkte og diffus solstraaling

    Energy Technology Data Exchange (ETDEWEB)

    Grandum, Oddbjoern

    1997-12-31

    In optimizing solar systems, it is necessary to know the spectral and angular dependence of the radiation. The general nonlinear character of most solar energy systems accentuates this. This thesis describes a spectroradiometer that will measure both the direct component of the solar radiation and the angular dependence of the diffuse component. Radiation from a selected part of the sky is transported through a movable set of tube sections on to a stationary set of three monochromators with detectors. The beam transport system may effectively be looked upon as a single long tube aimed at a particular spot in the sky. The half value of the effective opening angle is 1.3{sup o} for diffuse radiation and 2.8{sup o} for direct radiation. The whole measurement process is controlled and operated by a PC and normally runs without manual attention. The instrument is built into a caravan. The thesis describes in detail the experimental apparatus, calibration and measurement accuracies. To map the diffuse radiation, one divides the sky into 26 sectors of equal solid angle. A complete measurement cycle is then made at a random point within each sector. These measurements are modelled by fitting to spherical harmonics, enforcing symmetry around the solar direction and the horizontal plane. The direct radiation is measured separately. Also the circumsolar sector is given special treatment. The measurements are routinely checked against global radiation measured in parallel by a standard pyranometer, and direct solar radiation by a pyrheliometer. An extensive improvement programme is being planned for the instrument, including the use of a photomultiplier tube to measure the UV part of the spectrum, a diode array for the 400-1100 nm range, and use of a Ge diode for the 1000-1900 nm range. 78 refs., 90 figs., 31 tabs.

  19. Surface Passivation in Empirical Tight Binding

    Science.gov (United States)

    He, Yu; Tan, Yaohua; Jiang, Zhengping; Povolotskyi, Michael; Klimeck, Gerhard; Kubis, Tillmann

    2016-03-01

    Empirical Tight Binding (TB) methods are widely used in atomistic device simulations. Existing TB methods to passivate dangling bonds fall into two categories: 1) Method that explicitly includes passivation atoms is limited to passivation with atoms and small molecules only. 2) Method that implicitly incorporates passivation does not distinguish passivation atom types. This work introduces an implicit passivation method that is applicable to any passivation scenario with appropriate parameters. This method is applied to a Si quantum well and a Si ultra-thin body transistor oxidized with SiO2 in several oxidation configurations. Comparison with ab-initio results and experiments verifies the presented method. Oxidation configurations that severely hamper the transistor performance are identified. It is also shown that the commonly used implicit H atom passivation overestimates the transistor performance.

  20. Determination of molecular diffusion coefficient in n-alkane binary mixtures: empirical correlations.

    Science.gov (United States)

    De Mezquia, D Alonso; Bou-Ali, M Mounir; Larrañaga, M; Madariaga, J A; Santamaría, C

    2012-03-08

    In this work we have measured the molecular diffusion coefficient of the n-alkane binary series nC(i)-nC(6), nC(i)-nC(10), and nC(i)-nC(12) at 298 K and 1 atm and a mass fraction of 0.5 by using the so-called sliding symmetric tubes technique. The results show that the diffusion coefficient at this concentration is proportional to the inverse viscosity of the mixture. In addition, we have also measured the diffusion coefficient of the systems nC(12)-nC(6), nC(12)-nC(7), and nC(12)-nC(8) as a function of concentration. From the data obtained, it is shown that the diffusion coefficient of the n-alkane binary mixtures at any concentration can be calculated from the molecular weight of the components and the dynamic viscosity of the corresponding mixture at 50% mass fraction.

  1. The role of the velocity gradient in laminar convective heat transfer through a tube with a uniform wall heat flux

    International Nuclear Information System (INIS)

    Wang Liangbi; Zhang Qiang; Li Xiaoxia

    2009-01-01

    This paper aims to contribute to a better understanding of convective heat transfer. For this purpose, the reason why thermal diffusivity should be placed before the Laplacian operator of the heat flux, and the role of the velocity gradient in convective heat transfer are analysed. The background to these analyses is that, when the energy conservation equation of convective heat transfer is used to explain convective heat transfer there are two points that are difficult for teachers to explain and for undergraduates to understand: thermal diffusivity is placed before the Laplacian operator of temperature; on the wall surface (the fluid side) the velocity is zero, a diffusion equation of temperature is gained from energy conservation equation, however, temperature cannot be transported. Consequently, the real physical meaning of thermal diffusivity is not clearly reflected in the energy conservation equation, and whether heat transfer occurs through a diffusion process or a convection process on the wall surface is not clear. Through a simple convective heat transfer case: laminar convective heat transfer in a tube with a uniform wall heat flux on the tube wall, this paper explains these points more clearly. The results declare that it is easier for teachers to explain and for undergraduates to understand these points when a description of heat transfer in terms of the heat flux is used. In this description, thermal diffusivity is placed before the Laplacian operator of the heat flux; the role of the velocity gradient in convective heat transfer appears, on the wall surface, the fact whether heat transfer occurs through a diffusion process or a convection process can be explained and understood easily. The results are not only essential for teachers to improve the efficiency of university-level physics education regarding heat transfer, but they also enrich the theories for understanding heat transfer

  2. Direct media exposure of MEMS multi-sensor systems using a potted-tube packaging concept

    DEFF Research Database (Denmark)

    Hyldgård, Anders; Birkelund, Karen; Janting, Jakob

    2008-01-01

    in the filling material is measured. The packaging concept is used to encapsulate a microfabricated multi-sensor (measuring temperature, water conductivity, pressure and light intensity). The direct exposure of the sensors results in high sensitivity and fast response time. The design of an elongated multi-sensor......A packaging concept for Data Storage Tags is presented. A potted-tube packaging concept, using a polystyrene tube and different epoxies as filling material that allows for direct sensor exposure is investigated. The curing temperature, water uptake and the diffusion coefficient for water...... is described and effectiveness of the packaging is demonstrated with the precise measurement of water conductivity using the packaged multi-sensor. The packaging concept is very promising for high accuracy measurements in harsh environments....

  3. Passive-solar construction handbook

    Energy Technology Data Exchange (ETDEWEB)

    Levy, E.; Evans, D.; Gardstein, C.

    1981-02-01

    Many of the basic elements of passive solar design are reviewed. Passive solar construction is covered according to system type, each system type discussion including a general discussion of the important design and construction issues which apply to the particular system and case studies illustrating designed and built examples of the system type. The three basic types of passive solar systems discussed are direct gain, thermal storage wall, and attached sunspace. Thermal performance and construction information is presented for typical materials used in passive solar collector components, storage components, and control components. Appended are an overview of analysis methods and a technique for estimating performance. (LEW)

  4. Passivity and passivity breakdown of 304L stainless steel in hot and concentrated nitric acid

    International Nuclear Information System (INIS)

    Gillard-Tcharkhtchi, Elsa

    2014-01-01

    The objective of this study is to characterize the oxidation behavior of 304L stainless steel (SS) in representative conditions of spent nuclear fuel reprocessing, i.e. in hot and concentrated nitric acid. In these conditions the SS electrochemical potential is in the passive domain and its corrosion rate is low. However when the media becomes more aggressive, the potential may be shifted towards the trans-passive domain characterized with a high corrosion rate. Passivity and passivity breakdown in the trans-passive domain are of a major interest for the industry. So as to characterize these phenomenons, this work was undertaken with the following representative conditions: a 304L SS from an industrial sheet was studied, the media was hot and concentrated HNO 3 , long term tests were performed. First, the surface of an immersed 304L SS was characterized with several complementary techniques from the micro to the nanometer scale. Then oxidation kinetics was studied in the passive and in the trans-passive domain. The oxidation behavior was studied thanks to weight loss determination and surface analysis. Finally, oxidation evolution as a function of the potential was studied from the passive to the trans-passive domain. In particular, this allowed us to obtain the anodic curve of 304L SS in hot and concentrated and to define precisely the 304L SS limits of in such conditions. (author) [fr

  5. Field monitoring of volatile organic compounds using passive air samplers in an industrial city in Japan

    International Nuclear Information System (INIS)

    Kume, Kazunari; Ohura, Takeshi; Amagai, Takashi; Fusaya, Masahiro

    2008-01-01

    Highly portable, sensitive, and selective passive air samplers were used to investigate ambient volatile organic compound (VOC) levels at multiple sampling sites in an industrial city, Fuji, Japan. We determined the spatial distributions of 27 species of VOCs in three campaigns: Mar (cold season), May (warm season), and Nov (mild season) of 2004. In all campaigns, toluene (geometric mean concentration, 14.0 μg/m 3 ) was the most abundant VOC, followed by acetaldehyde (4.76 μg/m 3 ), and formaldehyde (2.58 μg/m 3 ). The spatial distributions for certain VOCs showed characteristic patterns: high concentrations of benzene and formaldehyde were typically found along major roads, whereas high concentrations of toluene and tetrachloroethylene (PCE) were usually found near factories. The spatial distribution of PCE observed was extremely consistent with the diffusion pattern calculated from Pollutant Release and Transfer Register data and meteorological data, indicated that passive air samplers are useful for determining the sources and distributions of ambient VOCs. - Passive air samplings with hood are useful for determining the identities, sources, and distributions of ambient VOC pollutants

  6. Resistance of Incoloy 800 steam generator tube to pitting corrosion in PWR secondary water at 250°C

    International Nuclear Information System (INIS)

    Schvartzman, Mônica M.A.M.; Albuquerque, Adriana Silva de; Esteves, Luiza; Rabello, Emerson G.; Mansur, Fábio Abud

    2017-01-01

    The steam generator (SG) is one of the main components of a PWR, so the performance of this type of nuclear power plant depends to a large extent on the trouble-free operation of SGs. Its degradation significantly affects the overall plant performance. Alloy 800NG (Incoloy® 800) is a nickel-iron-chromium alloy used for steam generator tubes in PWRs due to their high strength, good workability and resistance to corrosion. This behavior is attributed to the protective oxide film formed on the metal surface by contact with the high temperature pressurized water. However, chloride is one of major SG impurities that cause the breakdown of the passive film and initiate localized corrosion in passive metals as Alloy 800NG. The aim of this study is to provide information about the pitting corrosion behavior of the Incoloy® 800 steam generator tube under normal secondary circuit parameters (250 deg C and 5 MPa) and abnormal conditions of operation (presence of chloride ions in the secondary water). For this, optical microscopy, XRD and EDS analysis and electrochemical tests have been carried out under simulated PWR secondary water operating conditions. The susceptibility to pitting corrosion was evaluated using electrochemical tests and the oxide layer formed on material was examined by means of scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS) analyses. (author)

  7. Resistance of Incoloy 800 steam generator tube to pitting corrosion in PWR secondary water at 250°C

    Energy Technology Data Exchange (ETDEWEB)

    Schvartzman, Mônica M.A.M. [Pontifícia Universidade Católica de Minas Gerais (PUC-Minas), Belo Horizonte, MG (Brazil); Albuquerque, Adriana Silva de; Esteves, Luiza; Rabello, Emerson G.; Mansur, Fábio Abud, E-mail: monicacdtn@gmail.com, E-mail: asa@cdtn.br, E-mail: luiza.esteves@cdtn.br, E-mail: egr@cdtn.br, E-mail: fametalurgica@gmail.com [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2017-07-01

    The steam generator (SG) is one of the main components of a PWR, so the performance of this type of nuclear power plant depends to a large extent on the trouble-free operation of SGs. Its degradation significantly affects the overall plant performance. Alloy 800NG (Incoloy® 800) is a nickel-iron-chromium alloy used for steam generator tubes in PWRs due to their high strength, good workability and resistance to corrosion. This behavior is attributed to the protective oxide film formed on the metal surface by contact with the high temperature pressurized water. However, chloride is one of major SG impurities that cause the breakdown of the passive film and initiate localized corrosion in passive metals as Alloy 800NG. The aim of this study is to provide information about the pitting corrosion behavior of the Incoloy® 800 steam generator tube under normal secondary circuit parameters (250 deg C and 5 MPa) and abnormal conditions of operation (presence of chloride ions in the secondary water). For this, optical microscopy, XRD and EDS analysis and electrochemical tests have been carried out under simulated PWR secondary water operating conditions. The susceptibility to pitting corrosion was evaluated using electrochemical tests and the oxide layer formed on material was examined by means of scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS) analyses. (author)

  8. Numerical investigation of the heat transfer of a ferrofluid inside a tube in the presence of a non-uniform magnetic field

    Science.gov (United States)

    Hariri, Saman; Mokhtari, Mojtaba; Gerdroodbary, M. Barzegar; Fallah, Keivan

    2017-02-01

    In this article, a three-dimensional numerical investigation is performed to study the effect of a magnetic field on a ferrofluid inside a tube. This study comprehensively analyzes the influence of a non-uniform magnetic field in the heat transfer of a tube while a ferrofluid (water with 0.86 vol% nanoparticles (Fe3O4) is let flow. The SIMPLEC algorithm is used for obtaining the flow and heat transfer inside the tube. The influence of various parameters, such as concentration of nanoparticles, intensity of the magnetic field, wire distance and Reynolds number, on the heat transfer is investigated. According to the obtained results, the presence of a non-uniform magnetic field significantly increases the Nusselt number (more than 300%) inside the tube. Also, the magnetic field induced by the parallel wire affects the average velocity of the ferrofluid and forms two strong eddies in the tube. Our findings show that the diffusion also raises as the concentration of the nanoparticle is increased.

  9. Passive films at the nanoscale

    International Nuclear Information System (INIS)

    Maurice, Vincent; Marcus, Philippe

    2012-01-01

    Highlights: ► Nanoscale data on growth, structure and local properties of passive films reviewed. ► Preferential role of defects of passive films on the corrosion resistance emphasized. ► Effect of grain boundaries on local electronic properties shown by new data. ► Use of atomistic modeling to test mechanistic hypotheses illustrated. - Abstract: The nanometer scale chemical and structural aspects of ultrathin oxide passive films providing self-protection against corrosion to metals and alloys in aqueous environments are reviewed. Data on the nucleation and growth of 2D anodic oxide films, details on the atomic structure and nanostructure of 3D passive films, the preferential role of surface step edges in dissolution in the passive state and the preferential role of grain boundaries of the passive films in passivity breakdown are presented. Future perspectives are discussed, and exemplified by new data obtained on the relationship between the nanostructure of oxide passive films and their local electronic properties. Atomistic corrosion modeling by ab initio density functional theory (DFT) is illustrated by the example of interactions of chloride ions with hydroxylated oxide surfaces, including the role of surface step edges. Data obtained on well-defined substrate surfaces with surface analytical techniques are emphasized.

  10. Helically coiled tube heat exchanger

    International Nuclear Information System (INIS)

    Harris, A.M.

    1981-01-01

    In a heat exchanger such as a steam generator for a nuclear reactor, two or more bundles of helically coiled tubes are arranged in series with the tubes in each bundle integrally continuing through the tube bundles arranged in series therewith. Pitch values for the tubing in any pair of tube bundles, taken transverse to the path of the reactor coolant flow about the tubes, are selected as a ratio of two unequal integers to permit efficient operation of each tube bundle while maintaining the various tube bundles of the heat exchanger within a compact envelope. Preferably, the helix angle and tube pitch parallel to the path of coolant flow are constant for all tubes in a single bundle so that the tubes are of approximately the same length within each bundle

  11. Categorising YouTube

    OpenAIRE

    Simonsen, Thomas Mosebo

    2011-01-01

    This article provides a genre analytical approach to creating a typology of the User Generated Content (UGC) of YouTube. The article investigates the construction of navigation processes on the YouTube website. It suggests a pragmatic genre approach that is expanded through a focus on YouTube’s technological affordances. Through an analysis of the different pragmatic contexts of YouTube, it is argued that a taxonomic understanding of YouTube must be analysed in regards to the vacillation of a...

  12. Passivation Of High-Temperature Superconductors

    Science.gov (United States)

    Vasquez, Richard P.

    1991-01-01

    Surfaces of high-temperature superconductors passivated with native iodides, sulfides, or sulfates formed by chemical treatments after superconductors grown. Passivating compounds nearly insoluble in and unreactive with water and protect underlying superconductors from effects of moisture. Layers of cuprous iodide and of barium sulfate grown. Other candidate passivating surface films: iodides and sulfides of bismuth, strontium, and thallium. Other proposed techniques for formation of passivating layers include deposition and gas-phase reaction.

  13. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... YouTube Videos » NEI YouTube Videos: Amblyopia Listen NEI YouTube Videos YouTube Videos Home Age-Related Macular Degeneration ... Retinopathy of Prematurity Science Spanish Videos Webinars NEI YouTube Videos: Amblyopia Embedded video for NEI YouTube Videos: ...

  14. Effect of Tube Pitch on Pool Boiling Heat Transfer of Vertical Tube Bundle

    International Nuclear Information System (INIS)

    Kang, Myeong Gie

    2016-01-01

    Summarizing the previous results it can be stated that heat transfer coefficients are highly dependent on the tube pitch and the heat flux of the relevant tube. The published results are mostly about the horizontal tubes. However, there are many heat exchangers consisting of vertical tubes like AP600. Therefore, the focus of the present study is an identification of the effects of a tube pitch as well as the heat flux of a relevant tube on the heat transfer of a tube bundle installed vertically. When the heat flux is increased many bubbles are generating due to the increase of the nucleation sites. The bubbles become coalescing with the nearby bubbles and generates big bunches of bubbles on the tube surface. This prevents the access of the liquid to the surface and deteriorates heat transfer. The bubble coalescence is competing with the mechanisms enhancing heat transfer. The pitch was varied from 28.5 mm to 95 mm and the heat flux of the nearby tube was changed from 0 to 90kW/m"2. The enhancement of the heat transfer is clearly observed when the heat flux of the nearby tube becomes larger and the heat flux of the upper tube is less than 40kW/m"2. The effect of the tube pitch on heat transfer is negligible as the value of DP/ is increased more than 4.

  15. Measure Guideline: Passive Vents

    Energy Technology Data Exchange (ETDEWEB)

    Berger, David [Consortium for Advanced Residential Buildings, Norwalk, CT (United States); Neri, Robin [Consortium for Advanced Residential Buildings, Norwalk, CT (United States)

    2016-02-05

    This document addresses the use of passive vents as a source of outdoor air in multifamily buildings. The challenges associated with implementing passive vents and the factors affecting performance are outlined. A comprehensive design methodology and quantified performance metrics are provided. Two hypothetical design examples are provided to illustrate the process. This document is intended to be useful to designers, decision-makers, and contractors implementing passive ventilation strategies. It is also intended to be a resource for those responsible for setting high-performance building program requirements, especially pertaining to ventilation and outdoor air. To ensure good indoor air quality, a dedicated source of outdoor air is an integral part of high-performance buildings. Presently, there is a lack of guidance pertaining to the design and installation of passive vents, resulting in poor system performance. This report details the criteria necessary for designing, constructing, and testing passive vent systems to enable them to provide consistent and reliable levels of ventilation air from outdoors.

  16. Importance of Passive Diffusion in the Uptake of Polychlorinated Biphenyls by Phagotrophic Protozoa†

    OpenAIRE

    Kujawinski, Elizabeth B.; Farrington, John W.; Moffett, James W.

    2000-01-01

    Unicellular protozoan grazers represent a size class of organisms where a transition in the mechanism of chlorobiphenyl (CB) introduction, from diffusion through surface membranes to ingestion of contaminated prey, could occur. This study compares the relative importance of these two processes in the overall uptake of polychlorinated biphenyls by protists. Uptake rates and steady-state concentrations were compared in laboratory cultures of grazing and nongrazing protozoa. These experiments we...

  17. VFLOW2D - A Vorte-Based Code for Computing Flow Over Elastically Supported Tubes and Tube Arrays

    Energy Technology Data Exchange (ETDEWEB)

    WOLFE,WALTER P.; STRICKLAND,JAMES H.; HOMICZ,GREGORY F.; GOSSLER,ALBERT A.

    2000-10-11

    A numerical flow model is developed to simulate two-dimensional fluid flow past immersed, elastically supported tube arrays. This work is motivated by the objective of predicting forces and motion associated with both deep-water drilling and production risers in the oil industry. This work has other engineering applications including simulation of flow past tubular heat exchangers or submarine-towed sensor arrays and the flow about parachute ribbons. In the present work, a vortex method is used for solving the unsteady flow field. This method demonstrates inherent advantages over more conventional grid-based computational fluid dynamics. The vortex method is non-iterative, does not require artificial viscosity for stability, displays minimal numerical diffusion, can easily treat moving boundaries, and allows a greatly reduced computational domain since vorticity occupies only a small fraction of the fluid volume. A gridless approach is used in the flow sufficiently distant from surfaces. A Lagrangian remap scheme is used near surfaces to calculate diffusion and convection of vorticity. A fast multipole technique is utilized for efficient calculation of velocity from the vorticity field. The ability of the method to correctly predict lift and drag forces on simple stationary geometries over a broad range of Reynolds numbers is presented.

  18. Scottish Passive House: Insights into Environmental Conditions in Monitored Passive Houses

    Directory of Open Access Journals (Sweden)

    Janice Foster

    2016-04-01

    Full Text Available Climate change and sustainability legislation in recent years has led to significant changes in construction approaches in the UK housing sector. This has resulted in the adoption of new building typologies, including the German Passivhaus (Passive House standard. This standard aims to improve occupant comfort and energy efficiency, potentially changing the ways in which homes operate and how occupants interact with them. With increasing construction of low energy dwellings, there is an emerging gap in knowledge in relation to occupant health and wellbeing, thermal comfort, and indoor air quality (IAQ. Using data collected from a two year Building Performance Evaluation (BPE study funded by Innovate UK, the environmental data (temperature, relative humidity and carbon dioxide concentrations from five Certified Passive House homes in Scotland was compared. The results demonstrate problems with overheating with peak temperatures exceeding 30 °C. Imbalanced mechanical ventilation with heat recovery (MVHR systems were identified in 80% of the dwellings and inadequate IAQ was found due to poor ventilation. Only one of the Passive Houses studied exhibited thermal conditions and IAQ which were, on the whole within Passive House parameters. This paper outlines the insights and the main issues of Scottish Passive House in the broader context of sustainability.

  19. Optimizing Tube Precurvature to Enhance Elastic Stability of Concentric Tube Robots.

    Science.gov (United States)

    Ha, Junhyoung; Park, Frank C; Dupont, Pierre E

    2017-02-01

    Robotic instruments based on concentric tube technology are well suited to minimally invasive surgery since they are slender, can navigate inside small cavities and can reach around sensitive tissues by taking on shapes of varying curvature. Elastic instabilities can arise, however, when rotating one precurved tube inside another. In contrast to prior work that considered only tubes of piecewise constant precurvature, we allow precurvature to vary along the tube's arc length. Stability conditions for a planar tube pair are derived and used to formulate an optimal design problem. An analytic formulation of the optimal precurvature function is derived that achieves a desired tip orientation range while maximizing stability and respecting bending strain limits. This formulation also includes straight transmission segments at the proximal ends of the tubes. The result, confirmed by both numerical and physical experiment, enables designs with enhanced stability in comparison to designs of constant precurvature.

  20. CANDU passive shutdown systems

    Energy Technology Data Exchange (ETDEWEB)

    Hart, R S; Olmstead, R A [AECL CANDU, Sheridan Park Research Community, Mississauga, ON (Canada)

    1996-12-01

    CANDU incorporates two diverse, passive shutdown systems, independent of each other and from the reactor regulating system. Both shutdown systems function in the low pressure, low temperature, moderator which surrounds the fuel channels. The shutdown systems are functionally different, physically separate, and passive since the driving force for SDS1 is gravity and the driving force for SDS2 is stored energy. The physics of the reactor core itself ensures a degree of passive safety in that the relatively long prompt neutron generation time inherent in the design of CANDU reactors tend to retard power excursions and reduces the speed required for shutdown action, even for large postulated reactivity increases. All passive systems include a number of active components or initiators. Hence, an important aspect of passive systems is the inclusion of fail safe (activated by active component failure) operation. The mechanisms that achieve the fail safe action should be passive. Consequently the passive performance of the CANDU shutdown systems extends beyond their basic modes of operation to include fail safe operation based on natural phenomenon or stored energy. For example, loss of power to the SDS1 clutches results in the drop of the shutdown rods by gravity, loss of power or instrument air to the injection valves of SDS2 results in valve opening via spring action, and rigorous self checking of logic, data and timing by the shutdown systems computers assures a fail safe reactor trip through the collapse of a fluctuating magnetic field or the discharge of a capacitor. Event statistics from operating CANDU stations indicate a significant decrease in protection system faults that could lead to loss of production and elimination of protection system faults that could lead to loss of protection. This paper provides a comprehensive description of the passive shutdown systems employed by CANDU. (author). 4 figs, 3 tabs.

  1. Stable isotope enrichment by thermal diffusion

    International Nuclear Information System (INIS)

    Vasaru, Gheorghe

    2003-01-01

    Thermal diffusion (TD) in both gaseous and liquid phase has been the subject of extensive experimental and theoretical investigations, especially after the invention by K. Clusius and G. Dickel of the thermal diffusion column, sixty years ago. This paper gives a brief overview of the most important applications and developments of this transport phenomenon for enrichment of 13 C and of some noble gases isotopes in our institute. The results of calculations of the transport coefficients H and K for a concentric tube type TD column, operated with methane as process gas, are presented. Static separation factor at equilibrium vs gas pressure has been calculated for various molecular models. The experimental separation factors for different gas pressure were found to be consistent with those calculated for the inverse power repulsion model and the Lennard-Jones model. The most important characteristics of a seven-stage cascade consisting of 19 TD columns of concentric tube type are given. This system has been constructed and successfully operated at a temperature of 673 K and produces an enrichment of methane of natural isotopic 13 C abundance, up to the concentration of 25% 13 CH 4 . Enrichment of the noble gases isotopes implies: - a . Enrichment of 20 Ne and 22 Ne in a eight-stage cascade consisting of 8 TD columns; - b. enrichment of 46 Ar in a seven-stage cascade consisting of TD columns and finally; - c. enrichment of 78 Kr and 86 Kr in a fifteen-stage cascade, consisting of 35 TD columns. For all these installations we have adopted TD columns of hot wire type (4 m in length), operated at a temperature of 1073 K. (author)

  2. Population synthesis and x-ray properties of passively evolving galaxies

    International Nuclear Information System (INIS)

    Renzini, A.

    1989-01-01

    In this review some evolutionary processes in galaxies will be considered which may be less exciting than other phenomena such as starburst activities, galactic interactions, merging, or cannibalism. The discussion will rather be restricted to passively evolving stellar populations, i.e. to what may happen when all giant molecular clouds have blown away, when every shower of star formation has ceased, and stars just shine, age, and eventually die. Only this passive evolution is in fact subject to laws that - at least in principle - can be rigorously formulated, while star formation processes, because of the prominent role played by chaotic hydrodynamics, rather resemble meteorological events. In Section 2 some fundamental properties of simple stellar populations are introduced. These can be regarded as the basic laws controlling the evolution of stellar populations, once that they have condensed from the diffused medium. In Section 3 the primary requirements that acceptable evolutionary population synthesis should fulfil are then briefly recalled, and, finally, in Section 4 some of the basic laws are put at play in an attempt to discuss the evolution over cosmological times of the X-ray properties of elliptical galaxies. (author)

  3. Hybrid heat pipe based passive cooling device for spent nuclear fuel dry storage cask

    International Nuclear Information System (INIS)

    Jeong, Yeong Shin; Bang, In Cheol

    2016-01-01

    Highlights: • Hybrid heat pipe was presented as a passive cooling device for dry storage cask of SNF. • A method to utilize waste heat from spent fuel was suggested using hybrid heat pipe. • CFD analysis was performed to evaluate the thermal performance of hybrid heat pipe. • Hybrid heat pipe can increase safety margin and storage capacity of the dry storage cask. - Abstract: Conventional dry storage facilities for spent nuclear fuel (SNF) were designed to remove decay heat through the natural convection of air, but this method has limited cooling capacity and a possible re-criticality accident in case of flooding. To enhance the safety and capacity of dry storage cask of SNF, hybrid heat pipe-based passive cooling device was suggested. Heat pipe is an excellent passive heat transfer device using the principles of both conduction and phase change of the working fluid. The heat pipe containing neutron absorber material, the so-called hybrid heat pipe, is expected to prevent the re-criticality accidents of SNF and to increase the safety margin during interim and long term storage period. Moreover, a hybrid heat pipe with thermoelectric module, a Stirling engine and a phase change material tank can be used for utilization of the waste heat as heat-transfer medium. Located at the guide tube or instrumentation tube, hybrid heat pipe can remove decay heat from inside the sealed metal cask to outside, decreasing fuel rod temperature. In this paper, a 2-step analysis was performed using computational fluid dynamics code to evaluate the heat and fluid flow inside a cask, which consisted of a single spent fuel assembly simulation and a full-scope dry cask simulation. For a normal dry storage cask, the maximum fuel temperature is 290.0 °C. With hybrid heat pipe cooling, the temperature decreased to 261.6 °C with application of one hybrid heat pipe per assembly, and to 195.1 °C with the application of five hybrid heat pipes per assembly. Therefore, a dry

  4. The density and velocity of plasma bullets propagating along one dielectric tube

    Directory of Open Access Journals (Sweden)

    Longfei Ji

    2015-08-01

    Full Text Available This study shows that the propagation of plasma bullets along one dielectric tube is strongly affected by many discharge parameters, such as the waveform of applied voltage (AC or pulsed DC, peak voltage, He flow rate, and the frequency of AC voltage. Analysis indicates that the density and velocity of plasma bullets are mainly determined by the electric field at the front of plasma bullets. These discharge parameters may significantly influence the distribution of plasma potential along the tube, thus control the electric field at the front of plasma bullets and their propagation. An increase in the pulsed DC voltage with its rise time of <40-50 ns can lead to an obvious improvement in the electric field at the front of plasma bullets, resulting in generation of a plasma in the high density gas and a fast propagation of plasma bullets. He flowing through the tube can contribute to the surface diffusion of charged species, and greatly increase the electric field at the front of plasma bullets. During the propagation of plasma bullets, their density is decreased due to the surface recombination of charged species, such as electrons and ions.

  5. Techniques for active passivation

    Science.gov (United States)

    Roscioli, Joseph R.; Herndon, Scott C.; Nelson, Jr., David D.

    2016-12-20

    In one embodiment, active (continuous or intermittent) passivation may be employed to prevent interaction of sticky molecules with interfaces inside of an instrument (e.g., an infrared absorption spectrometer) and thereby improve response time. A passivation species may be continuously or intermittently applied to an inlet of the instrument while a sample gas stream is being applied. The passivation species may have a highly polar functional group that strongly binds to either water or polar groups of the interfaces, and once bound presents a non-polar group to the gas phase in order to prevent further binding of polar molecules. The instrument may be actively used to detect the sticky molecules while the passivation species is being applied.

  6. Memory effects on adsorption tubes for mercury vapor measurement in ambient air: elucidation, quantification, and strategies for mitigation of analytical bias.

    Science.gov (United States)

    Brown, Richard J C; Kumar, Yarshini; Brown, Andrew S; Kim, Ki-Hyun

    2011-09-15

    The short- and long-term memory effects associated with measurements of mercury vapor in air using gold-coated silica adsorption tubes have been described. Data are presented to quantify these effects and to determine their dependence on certain relevant measurement parameters, such as number of heating cycles used for each analysis, age of adsorption tube, mass of mercury on adsorption tube, and the length of time between analyses. The results suggest that the long-term memory effect is due to absorption of mercury within the bulk gold in the adsorption tube, which may only be fully liberated by allowing enough time for this mercury to diffuse to the gold surface. The implications of these effects for air quality networks making these measurements routinely has been discussed, and recommendations have been made to ensure any measurement bias is minimized.

  7. A Method to Establishing Tube Plugging Criterion for Heat Exchangers with Straight Tubes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyungnam [KHNP CRI, Daejeon (Korea, Republic of)

    2016-10-15

    The difference of thermal expansion coefficients between the shell and tube materials causes the stress in axial direction of tube. Because of the axial stress due to thermal load, the straight tubes are used for heat exchangers operated in low temperature such as CCW (Component Cooling Water) heat exchangers and condensers. It is inevitable for the materials of the components to be degraded as the power plants become older. The degradation accompanies increasing maintenance cost as well as creating safety issues. The materials and wall thickness of heat exchanger tubes in nuclear power plants are selected to withstand system temperature, pressure, and corrosion. There are many codes and standards to be referred for calculating the minimum thickness of the heat exchanger tube in the designing stage. However, the codes and standards related to show the tube plugging criteria may not exist currently. In this paper, a method to establish the tube plugging criteria of BOP heat exchangers, which is based on the USNRC Regulatory Guide 1.121, is introduced and the tube plugging criteria for the TPCCW heat exchanger of Yonggwang NPP No. 1 and 2. A method to establish the tube plugging criteria of heat exchangers with straight tubes are introduced based on the USNRC Regulatory Guide 1.121. As an example, the tube plugging criterion for the CCW heat exchanger of a nuclear power plant is provided.

  8. Investigation of the diffusion behavior of sodium in Cu(In,Ga)Se{sub 2} layers

    Energy Technology Data Exchange (ETDEWEB)

    Laemmle, Anke, E-mail: anke.laemmle@zsw-bw.de; Wuerz, Roland; Powalla, Michael [Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden Württemberg, Industriestraße 6, 70565 Stuttgart (Germany); Schwarz, Torsten; Cojocaru-Mirédin, Oana; Choi, Pyuck-Pa [Max-Planck-Institut für Eisenforschung, Max-Planck-Str. 1, 40237 Düsseldorf (Germany)

    2014-04-21

    Sodium diffusion in Cu(In,Ga)Se{sub 2} (CIGS) layers was investigated over a temperature range from 157 °C to 400 °C. The diffusion profiles were measured by secondary ion mass spectrometry. Sodium ions diffused from a sodium fluoride (NaF) layer on the CIGS surface into the CIGS layer. From Na diffusion profiles, the diffusion along grain boundaries could be distinguished from the diffusion into the grain interior. Atom-probe tomography measurements reveal that even at a low temperature of 157 °C bulk diffusion of sodium into CIGS occurs. Based on this data, the slower diffusion coefficient in the volume can be described by the Arrhenius equation D{sub Na}{sup V} = 9.7 × 10{sup −9} exp(−0.36 eV/k{sub B}T) cm{sup 2} s{sup −1} and the fast diffusion along the grain boundaries by D{sub Na}{sup GB} = 6.5 × 10{sup −9} exp(−0.21 eV/k{sub B}T) cm{sup 2} s{sup −1}. Hence, we propose that sodium ions do not only passivate grain boundaries, but also act as dopants in the CIGS bulk.

  9. Canning by the diffusion caused by a heated die; Gainage par diffusion par filiere chauffante

    Energy Technology Data Exchange (ETDEWEB)

    Gauthron, M [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    In this process, the uranium fuel is clad with a zirconium can by passing the element through a die. The operation takes place at a temperature varying between 500 and 1000 deg. C. The heating is obtained by passing low voltage electric current through the can. This process differs from the co-extrusion process in that the uranium is not deformed. The uranium is therefore machined to the final dimensions before canning, it can also be hollow. Two types of processes can be adopted for the extrusion: a) Process in which the binding of the can to the uranium is obtained without diffusion (here the can is at high temperature - subsequently cooled - and the uranium is at a low temperature); b) Process in which uranium-zirconium diffusion is initiated. No matter which process is adopted the element is subsequently heat treated in an over at 800 deg. C in order to obtain the final diffusion. The quality of this diffusion is dependent on the initial state of the surfaces and on the degree of vacuum maintained during the operation. (author) [French] Dans ce procede, la gaine zirconium est plaquee sur le combustible uranium par passage dans une filiere. L'operation a lieu a chaud, a une temperature variant entre 500 et 1000 deg. C. Le chauffage est assure par passage d'un courant basse tension dans la gaine. A la difference du procede de cofilage, l'uranium ne subit pas de deformation durant l'operation. Il est donc prealablement usine aux cotes definitives et peut etre creux. Deux processus sont possibles pendant le passage dans la filiere: a) Obtention d'un frettage de la gaine sur l'uranium sans diffusion (avec une gaine a haute temperature et un tube d'uranium a basse temperature, eventuellement refroidi); b) Obtention d'un commencement de diffusion uranium-zirconium. Quelque soit le processus adopte, la cartouche est ensuite traitee dans un four a 800 deg. C pour obtenir la diffusion definitive. La qualite de celle-ci depend essentiellement des etats de surface initiaux

  10. Advanced diffusion system for low contamination in-line rapid thermal processing of silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Biro, D.; Preu, R.; Schultz, O.; Peters, S.; Huljic, D.M.; Zickermann, D.; Schindler, R.; Luedemann, R.; Willeke, G. [Fraunhofer Institute for Solar Energy Systems ISE, Freiburg (Germany)

    2002-10-01

    A novel diffusion system for in-line rapid thermal diffusion is presented. The lamp-heated furnace has a low thermal mass and a metal free transport system based on the walking beam principle. The furnace has been used to process first solar cells with lightly and highly doped emitters respectively. Solar cells with shallow lightly doped emitters show that the emitters processed in the new device can be well passivated. Shallow emitters with sheet resistances of up to 40/sq. have been contacted successfully by means of screen printing and firing through a SiN{sub x} antireflection coating. (author)

  11. Integral nuclear power reactor with natural coolant circulation. Investigation of passive RHR system

    International Nuclear Information System (INIS)

    Samoilov, O.B.; Kuul, V.S.; Malamud, V.A.; Tarasov, G.I.

    1996-01-01

    The development of a small power (up to 240 MWe) integral PWR for nuclear co-generation power plants has been carried out. The distinctive features of this advanced reactor are: primary circuit arrangement in a single pressure vessel; natural coolant circulation; passive safety systems with self-activated control devices; use of a second (guard) vessel housing the reactor; favourable conditions for the most severe accident management. A passive steam condensing channel has been developed which is activated by the direct action of the primary circuit pressure without an automatic controlling action or manual intervention for emergency cooling of an integral reactor with an in-built pressurizer. In an emergency situation as pressure rises in the reactor a self-activated device blows out non-condensable gases from the condenser tube bundle and returns them in the steam-condensing mode of the operation with the returing primary coolant condensate into the reactor. The thermo-physical test facility is constructed and the experimental development of the steam-condensing channels is performed aiming at the verification of mathematical models for these channels operation in integral reactors both at loss-of-heat removal and LOCA accidents. (orig.)

  12. Automation in tube finishing bay

    International Nuclear Information System (INIS)

    Bhatnagar, Prateek; Satyadev, B.; Raghuraman, S.; Syama Sundara Rao, B.

    1997-01-01

    Automation concept in tube finishing bay, introduced after the final pass annealing of PHWR tubes resulted in integration of number of sub-systems in synchronisation with each other to produce final cut fuel tubes of specified length, tube finish etc. The tube finishing bay which was physically segregated into four distinct areas: 1. tube spreader and stacking area, 2. I.D. sand blasting area, 3. end conditioning, wad blowing, end capping and O.D. wet grinding area, 4. tube inspection, tube cutting and stacking area has been studied

  13. Comparison of Active and Passive Humidifiers on Mechanical Ventilation

    Directory of Open Access Journals (Sweden)

    H. Dilek Mersin Özcanoğlu

    2010-12-01

    Full Text Available Objective: To research the effectiveness on humidifying, respiratory mechanics, bacterial colonization and infection rates of continuous usage for 96 hours of active and passive humidifiers which are used for heating and moisturizing the inspired gases in patients under mechanical ventilation. Materials and Methods: Adult patients who are expected to support at least 4 days under mechanical ventilation, excluding patients with primary lung disease and sepsis, are included in the research. Patients are separated in two groups as a passive humidifier group (heat moisture exchange filter (n=16 and an active humidifier group (n=14. In passive humidifier group, humidifier is used continuously for 96 hours without change. In active humidifier group moisturizing is obtained by using sterile distilled water in heated humidifier. Patients whose demographic characteristics were recorded and first 24 hour APACHE II scores were calculated, were taking chest X-Ray’s daily. Respiratory mechanics measurements were recorded twice a day which were watched in Servo300A ventilators respiratory mechanics monitor, in patients under volume controlled ventilation. The amount of moisture and liquidity of the secretion in endotracheal tube were recorded and scored visually. The endotracheal aspiration samples at the beginning and at the end of 96th hour and respiratory circuits ventilator side sample taken at 96th hour were studied microbiologically. Cultures and colonial counts were studied at Cerrahpasa Medical Faculty Microbiology Laboratory. Results: There were no significant difference in two groups by demographic data, APACHE II scores and illness diagnoses. In passive humidifier group, respiratory mechanics showed no significant difference between the beginning and the 4th day (p>0.05. In active humidifier group when MAP, PEEPtot, EEF, Rins, Rexp values showed no significant difference between the beginning and the 4th day but PIP values showed significant

  14. Development of a simple method for the immobilization of anti-thyroxine antibody on polystyrene tubes for use in the measurement of total thyroxine in serum

    International Nuclear Information System (INIS)

    Rani Gnanasekar; Shalaka Paradkar; Vijay Kadwad; Ketaki Bapat; Grace Samuel; Sachdev, S.S.; Sivaprasad, N.

    2015-01-01

    We describe a simple method for the immobilisation of anti-thyroxine antibody on to the surface of polystyrene tubes and a simple assay format for the quantitative estimation of total thyroxine in serum. The immobilisation of anti-thyroxine antibody was achieved through passive adsorption of normal rabbit gamma globulin and anti-rabbit antibody raised in goat, as immune bridges. This procedure ensured minimum utilisation of primary and secondary antibody as neat sera without precipitation or affinity purification. The developed assay system using these antibody coated tubes covers a range of 0-240 ng/mL of thyroxine with intra and inter assay variations of less than 10 %. (author)

  15. Assessment of RELAP5/MOD3.3 condensation models for the tube bundle condensation in the PCCS of ESBWR

    International Nuclear Information System (INIS)

    Zhou, W.; Wolf, B.; Revankar, S.T.

    2011-01-01

    The passive containment condenser system (PCCS) in an ESBWR reactor consists of vertical tube bundle submerged in a large pool of water. The condensation model for the PCCS in a thermalhydraulics code RELAP5/MOD3.3 consists of the default Nusselt model and an alternate condensation model from UCB condensation correlation. An assessment of the PCCS condensation model in RELAP5/MOD3.3 was carried out using experiments conducted on a single tube and tube bundle PCCS tests at Purdue University. The experimental conditions were simulated with the default and the alternate condensation models in the REALP5/MOD3.3 beta version of the code. The default model and the UCB model (alternate model) give quite different results on condensation heat transfer for the PCCS. The default model predicts complete condensation well whereas the UCB model predicts the through flow condensation well. Based on this study it was found that none of the models in REALP5 can predict complete condensation as well as the through flow condensation well. (author)

  16. Assessment of RELAP5/MOD3.3 condensation models for the tube bundle condensation in the PCCS of ESBWR

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, W., E-mail: wenzzhou@cityu.edu.hk [Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong (China); Wolf, B. [Purdue University, West Lafayette, IN 47907 (United States); Revankar, S. [Purdue University, West Lafayette, IN 47907 (United States); POSTECH, Pohang (Korea, Republic of)

    2013-11-15

    The passive containment condenser system (PCCS) in an ESBWR reactor consists of vertical tube bundle submerged in a large pool of water. The condensation model for the PCCS in a thermalhydraulics code RELAP5/MOD3.3 consists of the default Nusselt model and an alternate condensation model from UCB condensation correlation. An assessment of the PCCS condensation model in RELAP5/MOD3.3 was carried out using experiments conducted on a single tube and tube bundle PCCS tests at Purdue University. The experimental conditions were simulated with the default and the alternate condensation models in the REALP5/MOD3.3 beta version of the code. The default model and the UCB model (alternate model) give quite different results on condensation heat transfer for the PCCS. The default model predicts complete condensation well whereas the UCB model predicts the through flow condensation well. Based on this study it was found that none of the models in REALP5 can predict complete condensation as well as the through flow condensation well.

  17. CRL X-ray tube

    International Nuclear Information System (INIS)

    Kolchevsky, N.N.; Petrov, P.V.

    2015-01-01

    A novel types of X-ray tubes with refractive lenses are proposed. CRL-R X-ray tube consists of Compound Refractive Lens- CRL and Reflection X-ray tube. CRL acts as X-ray window. CRL-T X-ray consists of CRL and Transmission X-ray tube. CRL acts as target for electron beam. CRL refractive lens acts as filter, collimator, waveguide and focusing lens. Properties and construction of the CRL X-ray tube are discussed. (authors)

  18. Wire-in-tube structure fabricated by single capillary electrospinning via nanoscale Kirkendall effect: the case of nickel-zinc ferrite.

    Science.gov (United States)

    Fu, Jiecai; Zhang, Junli; Peng, Yong; Zhao, Changhui; He, Yongmin; Zhang, Zhenxing; Pan, Xiaojun; Mellors, Nigel J; Xie, Erqing

    2013-12-21

    Wire-in-tube structures have previously been prepared using an electrospinning method by means of tuning hydrolysis/alcoholysis of a precursor solution. Nickel-zinc ferrite (Ni0.5Zn0.5Fe2O4) nanowire-in-nanotubes have been prepared as a demonstration. The detailed nanoscale characterization, formation process and magnetic properties of Ni0.5Zn0.5Fe2O4 nanowire-in-nanotubes has been studied comprehensively. The average diameters of the outer tubes and inner wires of Ni0.5Zn0.5Fe2O4 nanowire-in-nanotubes are around 120 nm and 42 nm, respectively. Each fully calcined individual nanowire-in-nanotube, either the outer-tube or the inner-wire, is composed of Ni0.5Zn0.5Fe2O4 monocrystallites stacked along the longitudinal direction with random orientation. The process of calcining electrospun polymer composite nanofibres can be viewed as a morphologically template nucleation and precursor diffusion process. This allows the nitrates precursor to diffuse toward the surface of the nanofibres while the oxides (decomposed from hydroxides and nitrates) products diffuse to the core region of the nanofibres; the amorphous nanofibres transforming thereby into crystalline nanowire-in-nanotubes. In addition, the magnetic properties of the Ni0.5Zn0.5Fe2O4 nanowire-in-nanotubes were also examined. It is believed that this nanowire-in-nanotube (sometimes called core-shell) structure, with its uniform size and well-controlled orientation of the long nanowire-in-nanotubes, is particularly attractive for use in the field of nano-fluidic devices and nano-energy harvesting devices.

  19. Photovoltaic characteristics of diffused P/+N bulk GaAs solar cells

    Science.gov (United States)

    Borrego, J. M.; Keeney, R. P.; Bhat, I. B.; Bhat, K. N.; Sundaram, L. G.; Ghandhi, S. K.

    1982-01-01

    The photovoltaic characteristics of P(+)N junction solar cells fabricated on bulk GaAs by an open tube diffusion technique are described in this paper.Spectral response measurements were analyzed in detail and compared to a computer simulation in order to determine important material parameters. It is projected that proper optimization of the cell parameters can increase the efficiency of the cells from 12.2 percent to close to 20 percent.

  20. Location and optimization analysis of capillary tube network embedded in active tuning building wall

    International Nuclear Information System (INIS)

    Niu, Fuxin; Yu, Yuebin

    2016-01-01

    In this study, a building wall with a thermal tuning function is further investigated. This design turns the building wall from a passive thermal system to an active system. A capillary tube network is installed inside the wall to manipulate the thermodynamics and realize more flexibility and potentials of the wall. This novel building wall structure performs efficiently in terms of building load reduction and supplementary heating and cooling, and the structure is convenient for applying low grade or natural energy with a wider temperature range. The capillary tube network's location inside the wall greatly impacts the thermal and energy performance of the building wall. The effects of three locations including external, middle and internal side are analyzed. The results indicate that the internal wall surface temperature can be neutralized from the ambient environment when the embedded tubes are fed with thermal water. The wall can work with a wide range of water temperature and the optimal location of the tube network is relatively constant in different modes. Power benefit with the wall changes from 2 W to 39 W when the outdoor air temperature changes, higher in summer than in winter. - Highlights: • A building wall with a tuning function is proposed using a capillary pipe network. • Low-grade thermal water can be used to actively manipulate the thermal mass. • Location of the capillary network is investigated to maximize the performance. • The innovation can potentially lower down the grade of energy use in buildings.

  1. Transport of lead to crack tips in steam generator tubes

    International Nuclear Information System (INIS)

    Adler, G.D.; Marks, C.R.; Fruzzetti, K.

    2009-01-01

    The mechanisms by which lead is transported from its ultimate source to steam generator tubes and into cracks are not well understood and, to date, a comprehensive evaluation of possible mechanisms has not previously been performed. Specifically, local lead concentrations up to 20 wt. percent have been measured at crack tips, and it is not fully understood how lead concentrations of this magnitude occur, since lead concentrations in SG feedwater are typically quite low (on the order of a few parts per trillion). Additionally, there is evidence that at secondary side conditions, lead is essentially entirely adsorbed onto solid surfaces. Furthermore, if lead were present in the liquid phase, it would not be expected to be in a form that would facilitate concentration in a crevice (crack) by electrochemical means. There has previously been some speculation that lead transport to crack tips may occur through surface diffusion of adsorbed species. It has also been postulated that lead transport may occur via diffusion through the oxide layer along crack walls or via diffusion of lead out of the bulk Alloy 600 to grain boundaries exposed to secondary water by advancing cracks. However, there have been no critical evaluations of these hypotheses. With the current state of knowledge, it is difficult for utilities to determine whether additional efforts to further reduce the inventory of lead in the secondary system are justified. Furthermore, specific sources of lead that are especially likely to accelerate SCC cannot be identified (e.g., significant masses of lead are present in SG deposits, but it is not known if this lead can be transported to crack tips). The work presented in this paper quantitatively evaluates (based on the published literature, not new experimental work) a number of hypothesized lead transport mechanisms, including: Liquid phase diffusion; Electrochemically influenced diffusion of cations and anions; Bulk alloy diffusion; Surface diffusion; Solid

  2. Pediatric cuffed endotracheal tubes

    Directory of Open Access Journals (Sweden)

    Neerja Bhardwaj

    2013-01-01

    Full Text Available Endotracheal intubation in children is usually performed utilizing uncuffed endotracheal tubes for conduct of anesthesia as well as for prolonged ventilation in critical care units. However, uncuffed tubes may require multiple changes to avoid excessive air leak, with subsequent environmental pollution making the technique uneconomical. In addition, monitoring of ventilatory parameters, exhaled volumes, and end-expiratory gases may be unreliable. All these problems can be avoided by use of cuffed endotracheal tubes. Besides, cuffed endotracheal tubes may be of advantage in special situations like laparoscopic surgery and in surgical conditions at risk of aspiration. Magnetic resonance imaging (MRI scans in children have found the narrowest portion of larynx at rima glottides. Cuffed endotracheal tubes, therefore, will form a complete seal with low cuff pressure of <15 cm H 2 O without any increase in airway complications. Till recently, the use of cuffed endotracheal tubes was limited by variations in the tube design marketed by different manufacturers. The introduction of a new cuffed endotracheal tube in the market with improved tracheal sealing characteristics may encourage increased safe use of these tubes in clinical practice. A literature search using search words "cuffed endotracheal tube" and "children" from 1980 to January 2012 in PUBMED was conducted. Based on the search, the advantages and potential benefits of cuffed ETT are reviewed in this article.

  3. Amorphous silicon oxide layers for surface passivation and contacting of heterostructure solar cells of amorphous and crystalline silicon; Amorphe Siliziumoxidschichten zur Oberflaechenpassivierung und Kontaktierung von Heterostruktur-Solarzellen aus amorphen und kristallinem Silizium

    Energy Technology Data Exchange (ETDEWEB)

    Einsele, Florian

    2010-02-05

    Atomic hydrogen plays a dominant role in the passivation of crystalline silicon surfaces by layers of amorphous silicon. In order to research into this role, this thesis presents the method of hydrogen effusion from thin amorphous films of silicon (a-Si:H) and silicon oxide (a-SiO{sub x}:H). The oxygen concentration of the sub-stoichiometric a-SiO{sub x}:H films ranges up to 10 at.-%. The effusion experiment yields information about the content and thermal stability of hydrogen and about the microstructure of the films. A mathematical description of the diffusion process of atomic hydrogen yields an analytical expression of the effusion rate R{sub E} depending on the linearly increasing temperature in the experiment. Fitting of the calculated effusion rates R{sub E} to measured effusion spectra yields the diffusion coefficient of atomic hydrogen in a-SiO{sub x}:H. With increasing oxygen concentration, the diffusion coefficient of hydrogen in the a-SiO{sub x}:H films decreases. This is attributed to an increasing Si-H bond energy due to back bonded oxygen, resulting in a higher stability of hydrogen in the films. This result is confirmed by an increasing thermal stability of the p-type c-Si passivation with a-SiO{sub x}:H of increasing oxygen concentrations up to 5 at.-%. The passivation reaches very low recombination velocities of S < 10 cm/s at the interface. However, for higher oxygen concentrations up to 10 at.-%, the passivation quality decreases significantly. Here, infrared spectroscopy of Si-H vibrational modes and hydrogen effusion show an increase of hydrogen-rich interconnected voids in the films. This microstructure results in a high amount of molecular hydrogen (H{sub 2}) in the layers, which is not suitable for the saturation of c-Si interface defects. Annealing of the films at temperatures around 400 C leads to a release of H{sub 2} from the voids, as a result of which Si-Si bonds in the material reconstruct. Subsequently, hydrogen migration in the

  4. Passive cavitation imaging with ultrasound arrays.

    Science.gov (United States)

    Salgaonkar, Vasant A; Datta, Saurabh; Holland, Christy K; Mast, T Douglas

    2009-12-01

    A method is presented for passive imaging of cavitational acoustic emissions using an ultrasound array, with potential application in real-time monitoring of ultrasound ablation. To create such images, microbubble emissions were passively sensed by an imaging array and dynamically focused at multiple depths. In this paper, an analytic expression for a passive image is obtained by solving the Rayleigh-Sommerfield integral, under the Fresnel approximation, and passive images were simulated. A 192-element array was used to create passive images, in real time, from 520-kHz ultrasound scattered by a 1-mm steel wire. Azimuthal positions of this target were accurately estimated from the passive images. Next, stable and inertial cavitation was passively imaged in saline solution sonicated at 520 kHz. Bubble clusters formed in the saline samples were consistently located on both passive images and B-scans. Passive images were also created using broadband emissions from bovine liver sonicated at 2.2 MHz. Agreement was found between the images and source beam shape, indicating an ability to map therapeutic ultrasound beams in situ. The relation between these broadband emissions, sonication amplitude, and exposure conditions are discussed.

  5. Expansion of passive safety function

    International Nuclear Information System (INIS)

    Inai, Nobuhiko; Nei, Hiromichi; Kumada, Toshiaki.

    1995-01-01

    Expansion of the use of passive safety functions is proposed. Two notions are presented. One is that, in the design of passive safety nuclear reactors where aversion of active components is stressed, some active components are purposely introduced, by which a system is built in such a way that it behaves in an apparently passive manner. The second notion is that, instead of using a passive safety function alone, a passive safety function is combined with some active components, relating the passivity in the safety function with enhanced controllability in normal operation. The nondormant system which the authors propose is one example of the first notion. This is a system in which a standby safety system is a portion of the normal operation system. An interpretation of the nondormant system via synergetics is made. As an example of the second notion, a PIUS density lock aided with active components is proposed and is discussed

  6. Numerical simulation of cavitation surge and vortical flows in a diffuser with swirling flow

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Bin; Wang, Jiong; Xiao, L. Z.; Long, X. [Wuhan University, Hubei (China); Luo, X. [Tsinghua University, Beijing (China); Miyagawa, K. [Waseda University, Tokyo (Japan); Tsujimoto, Yoshinobu [Osaka University, Osaka (Japan)

    2016-06-15

    The strong swirling flow at the exit of the runner of a Francis turbine at part load causes flow instabilities and cavitation surges in the draft tube, deteriorating the performance of the hydraulic power system. The unsteady cavitating turbulent flow in the draft tube is simplified and modeled by a diffuser with swirling flow using the Scale-adaptive simulation method. Unsteady characteristics of the vortex rope structure and the underlying mechanisms for the interactions between the cavitation and the vortices are both revealed. The generation and evolution of the vortex rope structures are demonstrated with the help of the iso-surfaces of the vapor volume fraction and the Qcriterion. Analysis based on the vorticity transport equation suggests that the vortex dilatation term is much larger along the cavity interface in the diffuser inlet and modifies the vorticity field in regions with high density and pressure gradients. The present work is validated by comparing two types of cavitation surges observed experimentally in the literature with further interpretations based on simulations.

  7. Constructing passive houses

    Energy Technology Data Exchange (ETDEWEB)

    Oehler, S. [Oehler Faigle Archkom Solar Architektur, Bretten (Germany)

    2005-07-01

    Everybody can learn to build energy-efficient. It needs theoretical and practical experience. 1997 we built the first freestanding Passive House in Europe, the Passive House Oehler. There had been a lot of questions, starting with the insecurity, whether the calculation program of the Passive House Institute, the PHPP, is working properly in our case. Nobody knew at that time because nobody tried it out before. It took us a lot of time to find out and every detail of the construction hat to be invented to meet the very high demand of thermal quality. All the following houses needed less time and had fewer open questions, adding one piece of experience with every building. 2002 we realised the biggest Passive House, the office building Energon Ulm with 420 working spaces. In the meantime we have learned a lot like how to produce prefabricated timber elements for the facades, providing good insulation, air tightness and avoiding serious thermal bridges. We have proofed, that any kind of building type can be a Passive House. And with increasing experience the freedom of design and construction is growing. Even the economical efficiency increased. The Energon Ulm is providing a much better indoor climate than any other office building and was build 10 % cheaper than an average German office building. At present the Passive House Standard is the most efficient solution for the user to live in the desired comfort zone between 20 C and 25 C. This zone of individual feeling-well can be described with the term ''operative temperature''. This term is defined by factors like air temperature, radiation temperature of warm and cold surfaces, air speed and humidity. The result of all these factors has to be within 18 C to 25 C without accepting one of the factors getting extreme.

  8. GOTHIC Simulation of Passive Containment Cooling System

    International Nuclear Information System (INIS)

    Ha, Huiun; Kim, Hangon

    2013-01-01

    The performance of this system depends on the condensation of steam moving downward inside externally cooled vertical tubes. AES-2006: During a DBA, heat is removed by internally cooled vertical tubes, which are located in containment. We are currently developing the conceptual design of Innovative PWR, which is will be equipped with various passive safety features, including PCCS. We have plan to use internal heat exchanger (HX) type PCCS with concrete containment. In this case, the elevation of HXs is important to ensure the heat removal during accidents. In general, steam is lighter than air mixture in containment. So, steam may be collected at the upper side of containment. It means that higher elevation of HXs, larger heat removal efficiency of those. So, the aim of the present paper is to give preliminary study on variation of heat removal performance according to elevation of HXs. With reference to the design specification of the current reactors including APR+, we had determined conceptual design of PCCS. Using it, we developed a GOTHIC model of the APR1400 containment was adopted PCCS. This calculation model is described herein and representative results of calculation are presented. APR 1400 GOTHIC model was developed for PCCS performance calculation and sensitivity test according to installation elevation of PCCXs. Calculation results confirm that PCCS is working properly. It is found that the difference due to the installation elevation of PCCXs is insignificant at this preliminary analysis, however, further studies should be performed to confirm final performance of PCCS according to the installation elevation. These insights are important for developing the PCCS of Innovative PWR

  9. GOTHIC Simulation of Passive Containment Cooling System

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Huiun; Kim, Hangon [Korea Hydro and Nuclear Power Co. Ltd., Daejeon (Korea, Republic of)

    2013-05-15

    The performance of this system depends on the condensation of steam moving downward inside externally cooled vertical tubes. AES-2006: During a DBA, heat is removed by internally cooled vertical tubes, which are located in containment. We are currently developing the conceptual design of Innovative PWR, which is will be equipped with various passive safety features, including PCCS. We have plan to use internal heat exchanger (HX) type PCCS with concrete containment. In this case, the elevation of HXs is important to ensure the heat removal during accidents. In general, steam is lighter than air mixture in containment. So, steam may be collected at the upper side of containment. It means that higher elevation of HXs, larger heat removal efficiency of those. So, the aim of the present paper is to give preliminary study on variation of heat removal performance according to elevation of HXs. With reference to the design specification of the current reactors including APR+, we had determined conceptual design of PCCS. Using it, we developed a GOTHIC model of the APR1400 containment was adopted PCCS. This calculation model is described herein and representative results of calculation are presented. APR 1400 GOTHIC model was developed for PCCS performance calculation and sensitivity test according to installation elevation of PCCXs. Calculation results confirm that PCCS is working properly. It is found that the difference due to the installation elevation of PCCXs is insignificant at this preliminary analysis, however, further studies should be performed to confirm final performance of PCCS according to the installation elevation. These insights are important for developing the PCCS of Innovative PWR.

  10. Simulation of the migration in fracutred rock by a model based on capillary tubes

    International Nuclear Information System (INIS)

    Dahlbom, P.

    1992-05-01

    In this paper the ability of a model based upon capillary tubes to reproduce the hydrodynamic dispersion in connection with flow of contaminated groundwater in fractured rock is investigated. It is assumed that the cross sectional areas are circular and that the flow is laminar. The molecular diffusion is neglected as well as the impact of variations in velocity over the cross-sectional area. It is assumed that the cross sectional areas in an ensemble of tubes belong to a gamma distribution. The velocity differences between tubes having different cross sectional area cause hydrodynamic dispersion. The model is applied to field tracer experiments at two sites. It is shown that the mean size of the cavities is smaller at a large depth and that the distribution is more narrow. The parameter in the gamma distribution has to be given different values to reproduce the breakthrough course at the different sites. It is also pointed out that there is no general relation between conductivity of a porous medium and its porosity without consideration of the pore size distribution. (au)

  11. Pressure tube type research reactor

    International Nuclear Information System (INIS)

    Ueda, Hiroshi.

    1976-01-01

    Object: To prevent excessive heat generation due to radiation of a pressure tube vessel. Structure: A pressure tube encasing therein a core comprises a dual construction comprising inner and outer tubes coaxially disposed. High speed cooling water is passed through the inner tube for cooling. In addition, in the outer periphery of said outer tube there is provided a forced cooling tube disposed coaxially thereto, into which cooling fluid, for example, such as moderator or reflector is forcibly passed. This forced cooling tube has its outer periphery surrounded by the vessel into which moderator or reflector is fed. By the provision of the dual construction of the pressure tube and the forced cooling tube, the vessel may be prevented from heat generation. (Ikeda, J.)

  12. Optimization of drift gases for accuracy in pressurized drift tubes

    CERN Document Server

    Kirchner, J J; Dinner, A R; Fidkowski, K J; Wyatt, J H

    2001-01-01

    Modern detectors such as ATLAS use pressurized drift tubes to minimize diffusion and achieve high coordinate accuracy. However, the coordinate accuracy depends on the exact knowledge of converting measured times into coordinates. Linear space-time relationships are best for reconstruction, but difficult to achieve in the $E \\propto \\frac{1}{r}$ field. Previous mixtures, which contained methane or other organic quenchers, are disfavored because of ageing problems. From our studies of nitrogen and carbon dioxide, two mixtures with only small deviations from linearity were determined and measured. Scaling laws for different pressures and magnetic fields are also given.

  13. Optimization of drift gases for accuracy in pressurized drift tubes

    International Nuclear Information System (INIS)

    Kirchner, J.J.; Becker, U.J.; Dinner, R.B.; Fidkowski, K.J.; Wyatt, J.H.

    2001-01-01

    Modern detectors such as ATLAS use pressurized drift tubes to minimize diffusion and achieve high coordinate accuracy. However, the coordinate accuracy depends on the exact knowledge of converting measured times into coordinates. Linear space-time relationships are best for reconstruction, but difficult to achieve in the E∝1/r field. Previous mixtures, which contained methane or other organic quenchers, are disfavored because of ageing problems. From our studies of nitrogen and carbon dioxide, two mixtures with only small deviations from linearity were determined and measured. Scaling laws for different pressures and magnetic fields are also given

  14. Electrochemical behavior of tube-fin assembly for an aluminum automotive condenser with improved corrosion resistance

    Science.gov (United States)

    Pech-Canul, M. A.; Guía-Tello, J. C.; Pech-Canul, M. I.; Aguilar, J. C.; Gorocica-Díaz, J. A.; Arana-Guillén, R.; Puch-Bleis, J.

    An aluminum automotive condenser was designed to exhibit high corrosion resistance in the seawater acetic acid test (SWAAT) combining zinc coated microchannel tubes and fins made with AA4343/AA3003(Zn)/AA4343 brazing sheet. Electrochemical measurements in SWAAT solution were carried out under laboratory conditions using tube-fin assembly and individual fin and tube samples withdrawn from the condenser core. The aim was to gain information on the protective role of the zinc sacrificial layer and about changes in corrosion behavior as a function of immersion time. External corrosion of the tube-fin system was simulated by immersion of mini-core samples under open circuit conditions. The corrosion rate increased rapidly during the first 6 h and slowly afterwards. The short time behavior was related to the dissolution of the oxide film and fast dissolution of the outermost part of the zinc diffusion layer. With the aid of cross-sectional depth corrosion potential profiles, it was shown that as the sacrificial layer gets dissolved, the surface concentration of zinc decreases and the potential shifts to less negative values. The results of galvanic coupling of tube and fins in a mini-cell showed that the tube became the anode while the fins exhibited cathodic behavior. An evolution in the galvanic interaction was observed, due to the progressive dissolution of the sacrificial zinc layer. The difference of uncoupled potentials between tube and fins decreased from 71 mV to 32 mV after 84 h of galvanic coupling. At the end of such period there was still a part of the zinc sacrificial layer remaining which would serve for protection of the tube material for even longer periods and there were indications of slight corrosion in the fins.

  15. Electrochemical behavior of tube-fin assembly for an aluminum automotive condenser with improved corrosion resistance

    Directory of Open Access Journals (Sweden)

    M.A. Pech-Canul

    Full Text Available An aluminum automotive condenser was designed to exhibit high corrosion resistance in the seawater acetic acid test (SWAAT combining zinc coated microchannel tubes and fins made with AA4343/AA3003(Zn/AA4343 brazing sheet. Electrochemical measurements in SWAAT solution were carried out under laboratory conditions using tube-fin assembly and individual fin and tube samples withdrawn from the condenser core. The aim was to gain information on the protective role of the zinc sacrificial layer and about changes in corrosion behavior as a function of immersion time. External corrosion of the tube-fin system was simulated by immersion of mini-core samples under open circuit conditions. The corrosion rate increased rapidly during the first 6 h and slowly afterwards. The short time behavior was related to the dissolution of the oxide film and fast dissolution of the outermost part of the zinc diffusion layer. With the aid of cross-sectional depth corrosion potential profiles, it was shown that as the sacrificial layer gets dissolved, the surface concentration of zinc decreases and the potential shifts to less negative values. The results of galvanic coupling of tube and fins in a mini-cell showed that the tube became the anode while the fins exhibited cathodic behavior. An evolution in the galvanic interaction was observed, due to the progressive dissolution of the sacrificial zinc layer. The difference of uncoupled potentials between tube and fins decreased from 71 mV to 32 mV after 84 h of galvanic coupling. At the end of such period there was still a part of the zinc sacrificial layer remaining which would serve for protection of the tube material for even longer periods and there were indications of slight corrosion in the fins. Keywords: Aluminum, Automotive, Corrosion, Galvanic, Zn coating

  16. The passive of reflexive verbs in Icelandic

    Directory of Open Access Journals (Sweden)

    Hlíf Árnadóttir

    2011-10-01

    Full Text Available The Reflexive Passive in Icelandic is reminiscent of the so-called New Passive (or New Impersonal in that the oblique case of a passivized object NP is preserved. As is shown by recent surveys, however, speakers who accept the Reflexive Passive do not necessarily accept the New Passive, whereas conversely, speakers who accept the New Passive do also accept the Reflexive Passive. Based on these results we suggest that there is a hierarchy in the acceptance of passive sentences in Icelandic, termed the Passive Acceptability Hierarchy. The validity of this hierarchy is confirmed by our diachronic corpus study of open access digital library texts from Icelandic journals and newspapers dating from the 19th and 20th centuries (tímarit.is. Finally, we sketch an analysis of the Reflexive Passive, proposing that the different acceptability rates of the Reflexive and New Passives lie in the argument status of the object. Simplex reflexive pronouns are semantically dependent on the verbs which select them, and should therefore be analyzed as syntactic arguments only, and not as semantic arguments of these verbs.

  17. Magnetic shielding of an inhomogeneous magnetic field source by a bulk superconducting tube

    International Nuclear Information System (INIS)

    Hogan, K; Fagnard, J-F; Wéra, L; Vanderheyden, B; Vanderbemden, P

    2015-01-01

    Bulk type-II irreversible superconductors can act as excellent passive magnetic shields, with a strong attenuation of low frequency magnetic fields. Up to now, the performances of superconducting magnetic shields have mainly been studied in a homogenous magnetic field, considering only immunity problems, i.e. when the field is applied outside the tube and the inner field should ideally be zero. In this paper, we aim to investigate experimentally and numerically the magnetic response of a high-T c bulk superconducting hollow cylinder at 77 K in an emission problem, i.e. when subjected to the non-uniform magnetic field generated by a source coil placed inside the tube. A bespoke 3D mapping system coupled with a three-axis Hall probe is used to measure the magnetic flux density distribution outside the superconducting magnetic shield. A finite element model is developed to understand how the magnetic field penetrates into the superconductor and how the induced superconducting shielding currents flow inside the shield in the case where the emitting coil is placed coaxially inside the tube. The finite element modelling is found to be in excellent agreement with the experimental data. Results show that a concentration of the magnetic flux lines occurs between the emitting coil and the superconducting screen. This effect is observed both with the modelling and the experiment. In the case of a long tube, we show that the main features of the field penetration in the superconducting walls can be reproduced with a simple analytical 1D model. This model is used to estimate the maximum flux density of the emitting coil that can be shielded by the superconductor. (paper)

  18. Passive control of thermoacoustic instabilities in swirl-stabilized combustion at elevated pressures

    Directory of Open Access Journals (Sweden)

    L Justin Williams

    2016-09-01

    Full Text Available In this study, a porous insert is placed at the dump plane of a swirl-stabilized lean premixed combustor to passively suppress thermoacoustic instabilities. The diffuser-shaped annular ring of porous inert material influences the turbulent flow field directly, including recirculation zones and vortical and/or shear layer structures to passively control the acoustic performance of the combustor. The porous inert material is made of silicon carbide–hafnium carbide coated, high-strength, high-temperature-resistant open-cell foam materials. In this study, the porous insert concept is investigated at above-ambient operating pressures to demonstrate its suitability for practical combustion applications. Experiments are conducted in quartz and metal combustors, without and with the porous insert while varying operating pressure, equivalence ratio, and reactant flow rate. Measurements show that the porous insert, and consequent changes in the combustor flow field, decrease the sound pressure levels at the frequency of combustion instability at all operating conditions investigated in this study. The porous insert also decreases the broadband combustion noise, i.e. the measured sound pressure levels over a wide frequency range.

  19. Technique employed to seal a tube leaking in a heat exchanger of the tube type by explosives with supporting means for the adjacent tubes

    International Nuclear Information System (INIS)

    Larson, G.C.

    1978-01-01

    This invention concerns the technique employed to seal a tube leaking in a heat exchanger of the tube and tube plate type by detonating metal plugs activated by an explosive and inserted in both ends of the tube. It refers in particular to an apparatus and process in which the deformation or distortion of the adjacent tubes and tube plate ties under the effect of the explosive forces is significantly reduced [fr

  20. A novel rumor diffusion model considering the effect of truth in online social media

    Science.gov (United States)

    Sun, Ling; Liu, Yun; Zeng, Qing-An; Xiong, Fei

    2015-12-01

    In this paper, we propose a model to investigate how truth affects rumor diffusion in online social media. Our model reveals a relation between rumor and truth — namely, when a rumor is diffusing, the truth about the rumor also diffuses with it. Two patterns of the agents used to identify rumor, self-identification and passive learning are taken into account. Combining theoretical proof and simulation analysis, we find that the threshold value of rumor diffusion is negatively correlated to the connectivity between nodes in the network and the probability β of agents knowing truth. Increasing β can reduce the maximum density of the rumor spreaders and slow down the generation speed of new rumor spreaders. On the other hand, we conclude that the best rumor diffusion strategy must balance the probability of forwarding rumor and the probability of agents losing interest in the rumor. High spread rate λ of rumor would lead to a surge in truth dissemination which will greatly limit the diffusion of rumor. Furthermore, in the case of unknown λ, increasing β can effectively reduce the maximum proportion of agents who do not know the truth, but cannot narrow the rumor diffusion range in a certain interval of β.