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Dry Air (dry + air)
Selected AbstractsRotational and Vibrational Temperature Measurements in a High-Pressure Cylindrical Dielectric Barrier Discharge (C-DBD)CONTRIBUTIONS TO PLASMA PHYSICS, Issue 1 2005N. Masoud Abstract The rotational (TR) and vibrational (Tv) temperatures of N2 molecules were measured in a high-pressure cylindrical dielectric barrier discharge (C-DBD) source in Ne with trace amounts (0.02 %) of N2 and dry air excited by radio-frequency (rf) power. Both TR and Tv of the N2 molecules in the C 3,u state were determined from an emission spectroscopic analysis the 2nd positive system (C 3,u , B3,g). Gas temperatures were inferred from the measured rotational temperatures. As a function of pressure, the rotational temperature is essentially constant at about 360 K in the range from 200 Torr to 600 Torr (at 30W rf power) and increases slightly with increasing rf power at constant pressure. As one would expect, vibrational temperature measurements revealed significantly higher temperatures. The vibrational temperature decreases with pressure from 3030 K at 200 Torr to 2270 K at 600 Torr (at 30 W rf power). As a function of rf power, the vibrational temperature increases from 2520 K at 20 W to 2940 K at 60 W (at 400 Torr). Both TR and Tv also show a dependence on the excitation frequency at the two frequencies that we studied, 400 kHz and 13.56 MHz. Adding trace amounts of air instead of N2 to the Ne in the discharge resulted in higher TR and Tv values and in a different pressure dependence of the rotational and vibrational temperatures. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of needle tip distance on barrier discharge and ozone generation for multiple needle-and-plane electrode configurationELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 7 2010Hideki Ueno Abstract The relationship between the barrier discharge characteristics and ozone generation on application of an AC voltage in a triple needle-plane configuration has been investigated for various distances among the triple needle tips (d=0 to 7.0 mm) with a constant distance between the needle tip and the plane (g=3.0 mm) in dry air. The characteristics of the barrier discharge and ozone generation depend on the needle tip distance. It is considered that the influence is caused by the presence of space charge and accumulated charge, as suggested by discharge images taken by a still camera and a CCD camera. The ozone generation efficiency is also estimated from the power consumption and the ozone concentration. It is found that when the distance among the triple needle tips is small, the above influence is strengthened. In this case, the ozone generation efficiency is improved. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(7): 32,41, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10289 [source] Air-Oxidation of a Cu45Zr45Al5Ag5 Bulk Metallic Glass,ADVANCED ENGINEERING MATERIALS, Issue 5 2009Wu Kai This work studied the oxidation behavior of a Ag-containing Cu,Zr,Al-based amorphous alloy (CZA4-BMG) in dry air at 375,500,°C. The oxidation kinetics of CZA4-BMG obeyed a multi-stage parabolic-rate law, and its steady-state oxidation-rate constants were slightly lower than those of Ag-free amorphous alloy (CZA3-BMG) at the temperature below 450,°C, indicating that the addition of Ag played a partly blocking effect in reducing the available cross-sections of the substrate, which in turn reduced inward diffusion of oxygen, thereby leading to the reduction of oxidation rates for CZA4-BMG. [source] Nanoscopic fatigue and stress corrosion crack growth behaviour in a high-strength stainless steel visualized in situ by atomic force microscopyFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 11 2005K. MINOSHIMA ABSTRACT In situ atomic force microscope (AFM) imaging of the fatigue and stress corrosion (SC) crack in a high-strength stainless steel was performed, under both static and dynamic loading. The AFM systems used were (1) a newly developed AFM-based system for analysing the nanoscopic topographies of environmentally induced damage under dynamic loads in a controlled environment and (2) an AFM system having a large sample stage together with a static in-plane loading device. By using these systems, in situ serial clear AFM images of an environmentally induced crack under loading could be obtained in a controlled environment, such as in dry air for the fatigue and in an aqueous solution for the stress corrosion cracking (SCC). The intergranular static SC crack at the free corrosion had a sharp crack tip when it grew straight along a grain boundary. The in situ AFM observations showed that the fatigue crack grew in a steady manner on the order of sub-micrometre. The same result was obtained for the static SC crack under the free corrosion, growing straight along a grain boundary. In these cases, the crack tip opening displacement (CTOD) remained constant. However, as the static SC crack was approaching a triple grain junction, the growth rate became smaller, the CTOD value increased and the hollow ahead of the crack tip became larger. After the crack passed through the triple grain junction, it grew faster with a lower CTOD value; the changes in the CTOD value agreed with those of the crack growth rate. At the cathodic potential, the static SC crack grew in a zigzag path and in an unsteady manner, showing crack growth acceleration and retardation. This unsteady crack growth was considered to be due to the changes in the local hydrogen content near the crack tip. The changes in the CTOD value also agreed with those of the crack growth rate. The CTOD value in the corrosive environment was influenced by the microstructure of the material and the local hydrogen content, showing a larger scatter band, whereas the CTOD value of the fatigue crack in dry air was determined by the applied stress intensity factor, with a smaller scatter band. In addition, the CTOD value in the corrosive environment under both static and dynamic loading was smaller than that of the fatigue crack; the environmentally induced crack had a sharper crack tip than the fatigue crack in dry air. [source] Gaseous diffusion coefficients of methyl bromide and methyl iodide into air, nitrogen, and oxygenHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2009Naoki Matsunaga Abstract The gaseous diffusion coefficients of methyl bromide (CH3Br) and methyl iodide (CH3I) into dry air, nitrogen, and oxygen have been measured in the temperature range 303,453 K and at atmospheric pressure via the Taylor dispersion method. Both for methyl bromide and methyl iodide, the diffusion coefficients do not vary in practice on substituting pure nitrogen or oxygen for dry air. The diffusion coefficients for methyl iodide are systematically smaller than those for methyl bromide by about 11%. For the methyl iodide-oxygen system, the effect of the thermal decomposition of methyl iodide has been observed at 453 K. The present results can be reproduced well by the functional form D = ATB, where D (cm2s,1) is the diffusion coefficient at 101 325 Pa (1 atm) and T (K) is the absolute temperature. The constants A and B are as follows: methyl bromide-(air, nitrogen, oxygen), A = 5.57 × 10,6, B = 1.76; methyl iodide-(air, nitrogen, oxygen), A = 5.26 × 10,6, B = 1.75. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20255 [source] Numerical and experimental investigation of heat and mass transfer in unsaturated porous media with low convective drying intensityHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2008Tao Lu Abstract The heat and mass transfer in an unsaturated wet cylindrical bed packed with quartz particles was investigated theoretically and experimentally for relatively low convective drying rates. The medium was dried by blowing dry air over the top of the porous bed which was insulated by impermeable, adiabatic material on the bottom and sides. Local thermodynamic equilibrium was assumed in the mathematical model describing the multi-phase flow in the unsaturated porous medium using the energy and mass conservation equations for heat and mass transfer during the drying. The drying model included convection and capillary transport of the moisture, and convection and diffusion of the gas. The wet and dry regions were coupled with a dynamic boundary condition at the evaporation front. The numerical results indicated that the drying process could be divided into three periods: the initial temperature rise period, the constant drying rate period, and the reduced drying rate period. The numerical results agreed well with the experimental data, verifying that the mathematical model can evaluate the drying performance of porous media for low drying rates. ©2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(5): 290,312, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20205 [source] A basic study on humidity recovery by using micro-porous media (Effects of thermal condition of fluids and geometrical condition of apparatus on transport performance)HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2006Shixue Wang Abstract Using an experimental apparatus to examine the performance of heat and mass transfer between constant-temperature water and dry air through a porous plate having extremely small pores, the effects of the thermal conditions in the fluids and the geometric condition of the apparatus on moisture transport were measured. The effects of water temperature, thickness of the porous plate, and channel height of the flowing air on moisture transport are noticeable. However, the effect of air temperature in the channel inlet on moisture transport is slight. In addition, in order to evaluate the degree of air humidity absorption, a parameter called the moisture absorption rate was introduced. The moisture absorption rate was shown to decrease with increasing air velocity and varies only slightly for a plate thickness of 1 mm and decreases for a plate thickness of 3.5 mm with increasing water temperature. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(8): 568,581, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20133 [source] Numerical simulation of high-temperature phase change heat storage systemHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 1 2004Yu-Ming Xing Abstract In this paper, numerical results pertaining to cyclic melting and freezing of an encapsulated phase-change material (PCM) have been reported. The cyclic nature of the present problem is relevant to latent heat thermal energy storage system used to power solar Brayton engines in space. In particular, a physical and numerical model of the single-tube phase change heat storage system was developed. A high-temperature eutectic mixture of LiF-CaF2 was used as the PCM and dry air was used as the working fluid. Numerical results were compared with available experimental data. The trends were in close agreement. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(1): 32,41, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10132 [source] Subtropical cold surges: regional aspects and global distributionINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2001René D. Garreaud Abstract Shallow surges of cold dry air are frequently observed to the east of the major mountain ranges, moving from mid-latitudes well into the Tropics in about 4 days. Because of their strong impact on weather, regional aspects of cold surges have received considerable attention, particularly over Southeast Asia, to the east of the Rockies and Mexican Sierras, and to the east of the subtropical Andes. Both observational and numerical studies reveal a similar structure and evolution of cold surges in different regions. These common aspects are reviewed in this work, as well as the mechanisms responsible for the development and subsequent advance of cold surges over the subtropics. Atmospheric reanalysis data are used to document the global distribution of cold surges on the basis of their continental-scale imprints on relevant fields, as well as to estimate their contribution on the regional and global energy balances. It is found that cold surges have a major cooling and drying effect over the regions where they are prevalent (e.g. subtropical South America) and represent a sizeable sink of energy for the Tropics. Copyright © 2001 Royal Meteorological Society [source] EFFECTS OF PRESTORAGE DRY AND HUMID HOT AIR TREATMENTS ON THE QUALITY, TRIGLYCERIDES AND TOCOPHEROL CONTENTS IN ,HASS' AVOCADO FRUITJOURNAL OF FOOD QUALITY, Issue 2 2004J. DE JESUS ORNELAS P. ABSTRACT ,Hass' avocado fruit were heated with dry (50% RH) or moist (95% RH) forced air at 38Cfor 6 h and then stored at 5C and 85% RHfor up to 8 weeks. Fruit were evaluated weekly for quality and for the content of three triglycerides and three tocopherols. Heated fruit had higher weight loss. The nonheated fruit and those heated with dry air displayed the best external quality. Fruit heated with dry air exhibited the best internal quality and the lowest chilling injury incidence. The respiration rate was more intense in fruit heated with moist air. Fruit firmness immediately after harvest was 51N, but decreased to less than 20 N at the end of the storage period in the three treatments. The analysis of triglycerides and tocopherols showed that the 1,2-Dilinoleil-3-Oleil-Glycerol and ,-tocopherol were the most abundant compounds. Therefore, postharvest treatment with dry forced hot air before storage or transport reduces the incidence of chilling injury, and decreases quality deterioration in ,Hass' avocado fruit. [source] Development of a 1-Methylcyclopropene (1-MCP) Sachet Release SystemJOURNAL OF FOOD SCIENCE, Issue 1 2006Younsuk S. Lee ABSTRACT The partitioning of 1-methylcyclopropene (1-MCP) between the gas/polymer matrix was determined for 2 adsorbing agents and 4 sachet materials to estimate the adsorption potential of 1-MCP at 23°C. The release study was performed using a closed system under 2 different environmental conditions, dry air (0% RH) and 90% RH. Sachets made from Tyvek®, paper, low-density polyethylene (LDPE), and polyvinyl acetate (PVA) materials were fabricated to contain silica gel and activated carbon. Activated carbon sachets did not release 1-MCP at either testing condition. Activated carbon had a very strong affinity for 1-MCP. The permeability coefficients of 1-MCP and water in polyethylene and polyvinyl acetate films were determined using a quasi-isostatic method. LDPE sachets containing silica gel had similar 1-MCP release rates at both 0% and 90% RH. PVA sachets containing silica gel had slow release of 1-MCP. The amount of 1-MCP released from PVA sachets containing silica gel at 90% RH was larger than the amount of 1-MCP released at 0% RH. Release of 1-MCP from paper and Tyvek sachets was largely dependent on the sorbate-absorbing ability of the adsorbing agents. [source] Passive-Oxidation Kinetics of SiC MicroparticlesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2004D. Das We investigated the oxidation kinetics of SiC materials in the form of powders (average dimension 4 ,m) in the temperature range 1100°,1500°C in dry air. The oxidation process was monitored through the relative mass gain in a thermobalance. As the specific surface area of the particles was measured, the recorded mass gain could be converted into the corresponding oxide thickness. The oxidation isotherms were fitted to a linear-parabolic equation, and the parabolic rate constant was evaluated. Up to 1400°C, temperature dependence can be described by a single activation energy of 179 kJ/mol, which increases in the 1400°,1500°C temperature range. These results are compared with the oxidation behavior of sintered polycrystalline and monocrystalline SiC materials. [source] Effect of Porosity on the Electrical Properties of Polycrystalline Sodium Niobate: I, Electrical ConductivityJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2003Silvania Lanfredi The electrical behavior of NaNbO3 ceramic samples with different relative densities was investigated by ac impedance spectroscopy in a range of 13 MHz to 10,3 Hz between 400° and 800°C in dry air. Measurements were performed during heating and cooling cycles. The Nyquist impedance diagrams of dense sodium niobate exhibit only one semicircle representing the grain contribution with depression angles as small as 1°, indicating a high homogeneity of the specific electrical properties. In the case of porous samples, the data reveal an additional low-frequency semicircle related to microstructure. For all studied samples, the Arrhenius conductivity plots show a change in the activation energy around 640°C, attributed to the tetragonal-cubic phase transition. The electrical conductivity of porous samples appears to be higher than that of dense ones. [source] Kinetics and Mechanism of Formation of Barium Zirconate from Barium Carbonate and Zirconia PowdersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2003Alberto Ubaldini The formation of BaZrO3 from very fine (70,90 nm) ZrO2 powders and coarser (,1 ,m) BaCO3 powders has been studied in dry and humid air up to 1300°C using TGA/DTA, XRD, SEM, TEM, and EDS microanalysis. In the temperature range 900°,1100°C, barium is rapidly transported at the surface of the ZrO2 particles and reacts, forming BaZrO3. The compound grows as a concentric layer with gradual consumption of the central ZrO2 particle. The overall formation kinetics of BaZrO3 is well described by a diminishing core model, and the most likely rate-determining step is a phase-boundary process at the ZrO2,BaZrO3 moving interface. The size and shape of the final particles is generally determined by the morphology of the starting ZrO2 particles and not by that of the BaCO3. The reaction is faster in humid air than in dry air, and the activation energy decreases from 294 kJ·mol,1 (dry air) to 220 kJ·mol,1 (humid air). When the fraction reacted is >80,90 mol%, the reaction rate rapidly decreases. [source] Tribological characterisation of hard coatings with and without DLC top layer in fretting testsLUBRICATION SCIENCE, Issue 1 2006D. KlaffkeArticle first published online: 14 DEC 200 Abstract The potential of coatings to protect components against wear and to reduce friction has led to a large variety of protective coatings. In order to check the success of coating modifications and to find solutions for different purposes, initial tests with laboratory tribometers are usually done to give information about the performance of a coating. Different Ti-based coatings (TiN, Ti(C,N), and TiAlN) and NiP were tested in comparison to coatings with an additional diamond-like carbon (DLC) top coating. Tests were done in laboratory air at room temperature with oscillating sliding (gross slip fretting) with a ball-on-disc arrangement against a ceramic ball (Al2O3). Special attention was paid to possible effects of moisture (relative humidity). The coefficient of friction was measured on line, and the volumetric wear at the disc was determined after the test from microscopic measurements of the wear scar and additional profiles. The friction and wear behaviour is quite different for the different coatings and depends more or less on the relative humidity. The DLC coating on top of the other coatings reduces friction and wear considerably. In normal and in moist air the coefficient of wear of the DLC top-layer coating is significantly less than 10,6,mm3/Nm and the coefficient of friction is below 0.1. In dry air, however, there is a certain tendency to high wear and high friction. Copyright © 2006 John Wiley & Sons, Ltd. [source] The repeatability of friction and wear results obtained from unlubricated reciprocating sliding testsLUBRICATION SCIENCE, Issue 4 2001D. Klaffke Abstract Laboratory tests can help in the analysis of tribological failures of elements, and improve tribo-systems by choosing appropriate materials. In order to characterise the friction and wear behaviour of candidate materials, various different test methods have been developed in the past and are still in use. One such method is the reciprocating sliding of a ball against a disc. In the work reported here, the repeatability of friction and wear results was evaluated with ten tests under identical conditions with a steel (100Cr6) or alumina (Al2O3) ball against a steel (100Cr6) disc under unlubricated conditions at room temperature. The influence of ambient humidity on friction and wear behaviour was determined in three additional tests in dry and in moist air, respectively. The repeatability of friction coefficient in normal air was better than 5% for alumina/100Cr6 and 12% for 100Cr6/100Cr6, while the repeatability of volumetric wear was slightly better than 10% for alumina/steel, and slightly worse than 10% for steel/steel. For both couples the coefficient of friction is lowest in moist air and about 50% higher in dry air. The coefficient of wear is also least in moist air and higher by a factor of 3(5) in dry air for tests with a 100Cr6 (alumina) ball. [source] Novel Biomembrane-Mimicking Polymer Surface with Environmental ResponsivenessMACROMOLECULAR RAPID COMMUNICATIONS, Issue 17 2005Hong Tan Abstract Summary: In this article, we designed and synthesized novel segmented poly(carbonate urethane)s containing both hydrophobic fluorinated alkyl group and hydrophilic phosphatidylcholine polar head groups on the side chain. The contact angle measurement, XPS, together with ATR-IR investigation indicated a reversible overturn of the phosphatidylcholine groups with the movement of the hydrophobic fluorinated alkyl groups when the samples were treated in dry air or water. The change in environment from air to water induced a reorganization of the surface in order to minimize the interfacial free energy, resulting in a macroscopic change of surface wettability. The good environmental responsiveness of such biomembrane-mimicking films may find successful applications as biomaterials. Environmentally responsive surface using FPCPCU50 as an example; FPCPCU50 coated on aligned carbon nanotube film and dried in vacuum at 50,°C for 7 h and sample c treated in hot water at 80,°C for 1 h. [source] Effectiveness of platinum and iridium in improving the resistance of Ni-Al to thermal cycling in air,steam mixturesMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 6 2008R. Kartono Abstract The aim of this work was to assess the value of platinum and iridium additions, with and without hafnium, to binary Ni-Al alloys, intended to act as models for aluminide coatings. Attention was focused on a (,,+,,,) Ni-22Al alloy, but comparisons were made with , -Ni-50Al. All compositions are given in at%. Alloys were exposed to flowing gases at a total pressure of 1 bar for one thousand 1 h cycles at 1200,°C. Compared to binary Ni-Al alloys, the Pt-modified alloys performed much better (with or without Hf) in dry air. Thermal cycling in air,+,12% H2O led to more rapid weight losses, due to enhanced spalling. Again, the addition of Pt was beneficial, but weight losses were still significant in the absence of Hf additions. A Ni-22Al-15Pt,+,Hf alloy slowly lost weight by scale spallation over 1000 cycles, but a Ni-22Al-30Pt,+,Hf alloy resisted weight loss. Partial substitution of Ir for Pt was beneficial in both wet and dry air. However, in the case of wet air, Hf additions were necessary to prevent slow spallation losses. [source] Optimisation of in-service performance of boiler steels by modelling high-temperature corrosionMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 3 2006L. Heikinheimo Abstract The main objective of the EU OPTICORR project is the optimisation of in-service performance of boiler steels by modelling high-temperature corrosion, the development of a life-cycle approach (LCA) for the materials in energy production, particularly for the steels used in waste incinerators and co-fired boiler plants. The expected benefits of this approach for safe and cost effective energy production are: - control and optimisation of in-service performance of boiler materials, - understanding of high-temperature corrosion and oxidation mechanisms under service conditions, - improvement of reliability to prevent the failure of components and plant accidents and - expanding the limits of boiler plant materials by corrosion simulations for flexible plant operation conditions (steel, fuel, temperature etc.). The technical aim of the EU OPTICORR project is the development of modelling tools for high-temperature oxidation and corrosion specifically in boiler conditions with HCl- and SO2 -containing combustion gases and Cl-containing salts. The work necessitates thermodynamic data collection and processing. For development and modelling, knowledge about the corrosion mechanisms and exact data are needed. The kinetics of high-temperature oxidation and corrosion are determined from laboratory thermo-gravimetric tests (TG) and multi-sample exposure tests. The materials studied are typical boiler tubes and fin-steels: ferritic alloys, the austenitic steel T347 and the Ni-based alloy Inconel 625. The exposure gases are dry air, air with 15 vol-% H2O, and with 2000 ppm HCl and 200 ppm SO2. The salt deposits used are based on KCl-ZnCl2 and Ca, Na, K, Pb, Zn-sulfates. The test temperatures for exposures with deposits are 320 and 420°C and, for gas exposures, 500 to 600°C. At present the tools being developed are ChemSheet based programmes with a kinetic module and easy-to-use interface and a more sophisticated numerical finite-difference-based diffusion calculation programme, InCorr, developed for prediction of inward corrosion and internal corrosion. The development of modelling tools for oxidation and high-temperature corrosion was started with thermodynamic data collection for relevant systems and thermodynamic mappings. Further, there are needs to develop the simulation model and tool for salt-induced hot corrosion based on the ChemSheet approach. Also, the work on modelling and simulating with the InCorr kinetic modelling tool will be continued to demonstrate the use of the tool for various steels and alloys in defined combustion environments. [source] The influence of an upper-level frontal zone on the Mack Lake Wildfire environmentMETEOROLOGICAL APPLICATIONS, Issue 2 2007Tarisa Zimet Abstract Meteorological assessment of wildland fire danger has traditionally involved the identification of several synoptic weather types empirically determined to influence wildfire spread. Specifically, in the Great Lakes Region, high wildfire danger is often witnessed in association with northwesterly synoptic-scale flow aloft. Such synoptic-scale flow is regularly associated with the development of upper-level frontal zones also known as upper-level jet/front systems, which are often characterised by intrusions of stratospheric air into the troposphere. The notion that upper-frontal development can play an important role in promoting wildfire spread is advanced through interrogation of the output from a fine-scale numerical simulation of a documented explosive wildfire case; the Mack Lake Fire of May 1980. The Mack Lake case was characterised by a developing upper-level front embedded within a shortwave trough in the vicinity of the fire location. The upper-level front originated in northwesterly flow in central Canada as an upper-tropospheric ridge amplified over western North America. A thermally indirect circulation at the jet exit region both contributed to the intensification of the front and was associated with a maximum in quasi-geostrophic descent at mid-levels upstream of the fire region. The subsidence ushered dry air from the middle and upper-troposphere downward along sloping isentropes adiabatically warming and drying it along the way. A well-developed dry air intrusion associated with the operation of these processes extended to nearly the 750 hPa level far downstream from the actual upper-frontal zone supplying the fire environment with dry air that originated in the upper-troposphere/lower stratosphere. The organised subsidence was also responsible for downward advection of high momentum air from within the frontal zone into the fire environment, further influencing the wildfire spread. We conclude that upper-frontal processes, characteristic of northwesterly synoptic-scale flow, are likely a contributing factor to the prevalence of wildfire spread under such synoptic-scale conditions. Copyright © 2007 Royal Meteorological Society [source] Use of METEOSAT water-vapour images for the diagnosis of a vigorous stratospheric intrusion over the central MediterraneanMETEOROLOGICAL APPLICATIONS, Issue 3 2000K Lagouvardos The diagnosis of a vigorous dry intrusion over the central Mediterranean is performed using water-vapour images from METEOSAT. This dry intrusion was located on the rear side of a cold front (propagating from Italy to Greece) and played an important role in the onset of thunderstorms over the western Greek coasts. A combination of satellite imagery and potential vorticity analyses showed that the dry air originated in the lower-stratospheric and higher-tropospheric layers. The interaction of the dry air with the moist air masses within the warm conveyor belt ahead of the cold front (overrun of warm air by low equivalent potential temperature air) produced a potentially unstable region over the area of reported thunderstorms. Copyright © 2000 Royal Meteorological Society [source] Temperature dependence of thermally-carbonized porous silicon humidity sensorPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2005M. Björkqvist Abstract Thermal carbonization of porous silicon (PS) at 820 °C under acetylene atmosphere is an appropriate method for humidity sensing purposes. It produces stable and hydrophilic surface still maintaining originally large specific surface area of PS. We report the temperature dependence of various electrical param- eters measured for the thermally-carbonized PS humidity sensor. Capacitance of the sensor in dry air (6 RH%) is almost constant at various temperatures, whereas in higher relative humidity values, the temperature dependence becomes evident. The resistance variation of the sensor is less dependent on RH as the temperature increases. While the capacitance showed linear behavior as a function of temperature, the resistance had a clear non-linear temperature dependence. In order to get information about the effects of frequency on capacitance values, we measured a phase angle and admittance of the sensor as a function of frequency at three different temperatures in low and high humidity. According to these results, it is preferable to operate this sensor construction using low frequency (<1 kHz). (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mechanical and tribological characterization of CNx films deposited by d.c. magnetron sputteringPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2007L. Ipaz Abstract Carbon nitride (CNx) thin films were deposited onto silicon and steel substrates at 400 °C from a carbon target by d.c. magnetron sputtering system. The composition, structural, and mechanical properties of deposited films were investigated as a function of argon/nitrogen concentration and sputtering power, by means of Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy (RS), and nanoindentation. The EDS and Elastic Forward Analisys Analysis (EFA) showed that the nitrogen concentration in the CNx deposited films varied between 16% and 28% at depending on nitrogen concentrations in argon/nitrogen gas mixture, and deposition power. FTIR analysis indicated the presence of 2266 and 2278 cm,1 stretching peaks associated with CN triple bonds of nitriles and isocyanides, 1640 cm,1 and 1545 cm,1 associated with the C=C and C=N bonds. The thickness of the CNx deposited films varied between 0.4 and 0.8 µm at different sputtering powers. The hardness and Young's modulus were investigated by depth sensing nanoindentation method. The obtained hardness and Young's modulus increased from 4 to 17 GPa, and from 50 to 170 GPa, respectively; when the nitrogen content in the deposited films diminished between 28 and 12%. On the other hand, the friction and wear tests were done using a pin-on-disc tribometer. The friction tests showed values of 0.05 and 0.4 in dry air and humid atmosphere; respectively. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Polycrystalline sputtered Cd(Zn, Mn)Te films for top cells in PV tandem structuresPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2004Sung Hyun Lee Abstract The CdTe-ZnTe or CdTe,MnTe alloy system is evaluated for application in high efficiency polycrystalline thin film multijunction solar cells. CdZnTe alloy films with 1.6 and 1.7 eV band gap and CdMnTe with 1.6 and 1.8 eV were deposited by RF magnetron sputtering from targets made of mixed powders of CdTe and ZnTe (25% and 40%) or MnTe (13% and 25%), respectively. Without postdeposition treatment, however, both of these alloy films exhibit quite low photovoltaic performance when used to make cells with CdS as the heterojunction partner. Therefore, we have searched for an appropriate postdeposition treatment to improve the efficiency of these alloy films. As-grown films have been postdeposition treated with vapors of chlorine-containing materials such as HCl gas, CdCl2, ZnCl2 or MnCl2 in dry air or H2+Ar atmosphere. When the CdCl2 + ZnCl2 or MnCl2 vapor was used, the ratio of CdCl2 to ZnCl2 or MnCl2 was adjusted to match the stoichiometry of alloy films. The temperature of the treatment was chosen to represent conditions employed for those alloy films/CdS structures. As a result, the postdeposition treated CdZnTe and CdMnTe cell efficiency can be improved by a factor of over 100. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] An easterly tip jet off Cape Farewell, Greenland.THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 645 2009I: Aircraft observations Abstract An easterly tip jet event off Cape Farewell, Greenland, is described and analysed in considerable detail. In Part I of this study (this paper) comprehensive aircraft-based observations are described, while in Part II of this study numerical simulations and a dynamical analysis are presented. The easterly tip jet of 21 February 2007 took place during the Greenland Flow Distortion experiment. It resulted through the interaction of a barotropic synoptic-scale low pressure system in the central North Atlantic and the high topography of southern Greenland. In situ observations reveal a jet core at the coast with peak winds of almost 50 m s,1, about 600,800 m above the sea surface, and of 30 m s,1 at 10 m. The depth of the jet increased with wind speed from ,1500 m to ,2500 m as the peak winds increased from 30 to 50 m s,1. The jet accelerated and curved anticyclonically as it reached Cape Farewell and the end of the barrier. The easterly tip jet was associated with a tongue of cold and dry air along the coast of southeast Greenland, general cloud cover to the east, and cloud streets to the south of Cape Farewell. Precipitation was observed during the low-level components of the flight. The very high wind speeds generated a highly turbulent atmospheric boundary layer and resulted in some of the highest surface wind stresses ever observed over the ocean. Copyright © 2009 Royal Meteorological Society [source] Towards a consistent numerical compressible non-hydrostatic model using generalized Hamiltonian toolsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 635 2008Almut Gassmann Abstract A set of compressible non-hydrostatic equations for a turbulence-averaged model atmosphere comprising dry air and water in three phases plus precipitating fluxes is presented, in which common approximations are introduced in such a way that no inconsistencies occur in the associated budget equations for energy, mass and Ertel's potential vorticity. These conservation properties are a prerequisite for any climate simulation or NWP model. It is shown that a Poisson bracket form for the ideal fluid part of the full-physics equation set can be found, while turbulent friction and diabatic heating are added as separate ,dissipative' terms. This Poisson bracket is represented as a sum of a two-fold antisymmetric triple bracket (a Nambu bracket represented as helicity bracket) plus two antisymmetric brackets (so-called mass and thermodynamic brackets of the Poisson type). The advantage of this approach is that the given conservation properties and the structure of the brackets provide a good strategy for the construction of their discrete analogues. It is shown how discrete brackets are constructed to retain their antisymmetric properties throughout the spatial discretisation process, and a method is demonstrated how the time scheme can also be incorporated in this philosophy. Copyright © 2008 Royal Meteorological Society [source] Convective mixing in a tropopause foldTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 599 2004H. J. Reid Abstract We present a case study of the passage of a tropopause fold over the UK behind a cold front, with emphasis on the mixing caused by convection extending into the fold. The event took place on 15,16 January 1999, and was the subject of intensive observations using the Met Office C130 aircraft and the mesosphere,stratosphere,troposphere (MST) radar at Aberystwyth. Here we concentrate on radar and satellite observations during the afternoon of 16 January, when the surface cold front had passed over the UK. A tongue of moist air moved north-eastwards over Wales at 700 hPa at this time, which, because of the very dry air in the fold above, resulted in potential instability. The resulting convection was clearly observed in NOAA satellite images. The MST radar depicted the passage of the cold front and tropopause fold as a layer of high-echo power and vertical wind shear ascending with time. Spectral widths showed the fold to be free of turbulence until 1200 UTC on 16 January, when convection was observed reaching into the frontal zone and generating turbulence. Eddy dissipation and diffusivity rates of 8.6 mW kg,1 and 8.5 m2s,1, respectively, were derived for this event. To place these figures in context, they are compared with corresponding rates derived for sixteen other passages of tropopause folds over the radar, each resulting from shear rather than convective instability. The convective event is found to be comparable to the strongest shear events, and to correspond to moderate turbulence as experienced by an aircraft. This process is of potential importance for atmospheric chemistry because it mixes boundary layer air directly with stratospheric air over a timescale of 1,2 hours. Copyright © 2004 Royal Meteorological Society [source] Six-year follow-up of an intervention to improve the management of preschool children with asthmaACTA PAEDIATRICA, Issue 12 2009Carl-Axel Hederos Abstract Aims:, In a randomized controlled study involving 60 preschool children with asthma, an intervention with extra information and support to parents in the form of group discussions was performed. An earlier follow-up after 18 months revealed an improved adherence and a reduction of exacerbation days. This is a 6-year follow-up. Methods:, Fifty-four children performed clinical examinations, blood tests, measurements of exhaled nitric oxide, spirometry, bronchial provocation with dry air and skin prick tests. Data from the patients' records and questionnaires were obtained. Results:, Twenty-nine per cent had no current signs of asthma, whereas 43% exhibited persistent and 28% intermittent asthma. The burden on the healthcare system was minimal. Intermittent inhaled corticosteroid (ICS) therapy was used by 81%. The intervention group (IG) had fewer contacts with nurses. Their parents had a better quality of life. Interviewing children separately contributed in identification of children needing treatment. More children in the IG had to restart ICS as they had signs of worse asthma control. Conclusion:, Straightforward and timely support to parents of children with asthma can have long-term positive effects by strengthening the ability of parents to treat their children at home, although parents may also develop an underestimation of mild symptoms. It is important to directly ask children about their disease and to maintain regular follow-up visits. [source] Visco-elastic changes of vocal fold mucosa related to high and low relative air humidityCLINICAL OTOLARYNGOLOGY, Issue 4 2000R.J.B. Hemler Objective. To study the effects of high and low relative air humidity (RH) on the visco-elastic properties of the vocal fold cover. Materials and methods. The vocal fold mucosa of sheep larynges was microdissected. The mucosal specimens were attached on one side to an oscillator and on the other side to a force transducer. A sinusoidal oscillation (stress) was applied to the specimen and the transduced force (strain) was recorded in two different conditions of a continuous passing airflow: either dry air (RH = 0%) or humid air (RH = 100%). Of the recorded stress and strain curves the gain and phase-shift between the curves were computed and from these parameters stiffness and viscosity were calculated. In both air conditions the deep surface of the specimen was in contact with a saline bath. Results. Stiffness and viscosity both increased significantly more in dry air than in humid air. This increased stiffness and viscosity returned to baseline values after rehydration. Conclusion. We conclude that these findings indicate that changes in the RH of the airflow passing over the vocal cords influences the visco-elastic properties of the vocal cord cover. [source] | |||||||||||||||||||||||||