WorldWideScience

Sample records for frost layer presence

  1. Heat transfer and pressure drop amidst frost layer presence for the full geometry of fin-tube heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sung Jool; Choi, Ho Jin; Ha, Man Yeong [Pusan National University, Busan (Korea, Republic of); Kim, Seok Ro; Bang, Seon Wook [Home Appliance Company, LG Electronics, Changwon (Korea, Republic of)

    2010-04-15

    The present study numerically solves the flow and thermal fields in the full geometry of heat exchanger modeling with frost layer presence on the heat exchanger surface. The effects of air inlet velocity, air inlet temperature, frost layer thickness, fin pitch, fin thickness, and heat exchanger shape on the thermo-hydraulic performance of a fin-tube heat exchanger are investigated. Heat transfer rate rises with increasing air inlet velocity and temperature, and decreasing frost layer thickness and fin pitch. Pressure drop rises with increasing air inlet velocity and frost layer thickness, and decreasing fin pitch. The effect of fin thickness on heat transfer and pressure drop is negligible. Based on the present results, we derived the correlations, which express pressure drop and temperature difference between air inlet and outlet as a function of air inlet velocity and temperature, as well as frost layer thickness

  2. Local variation of frost layer thickness and morphology

    Energy Technology Data Exchange (ETDEWEB)

    Qu, Kaiyang; Komori, Satoru [Department of Mechanical Engineering, Kyoto University, Kyoto 606-8501 (Japan); Jiang, Yi [Department of Building Science, School of Architecture, Tsinghua University, Beijing 100084 (China)

    2006-02-15

    Frosting is an important phenomenon encountered in the cryogenic industries in connection with gas coolers, refrigerators, heat pumps, etc. It may adversely affect the performances of those devices. This paper experimentally studied the local frost formation process on a cold surface with natural airflows or forced airflows over it. The frost layer thickness was found to increase stepwise during the frost formation process. This increase pattern was ever indicated only by one literature. The literature attributed the pattern to the melting of frost crystals at the frost surface. However, present observation of the morphology of the frost layer surface suggested that the growth of water drops or ice particles at the initial period caused the first slowly increasing of the frost layer thickness; the following growth of acerose-shaped ice crystals caused the rapidly increasing of the frost layer thickness; thereafter, the column-shaped ice crystals on the surface grew in its length and radius alternatively, which caused the frost layer thickness increasing rapidly and slowly alternatively. (authors)

  3. Effects of fin pitch and array of the frost layer growth on extended surface of a heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Dong Keun; Lee, Kwan Soo [Hanyang Univ., Seoul (Korea, Republic of)

    2003-07-01

    This paper presents the effects of the fin array and pitch on the frost layer growth of a heat exchanger. The numerical results are compared with experimental data of a cold plate to validate the present model, and agree well with experimental data within a maximum error of 8%. The characteristics of the frost formation on staggered fin array are somewhat different from those of in-line array. For fin pitch below 10 mm, the frost layer growth of second fin in the staggered array is affected by that of first fin. The heat transfer of single fin deteriorate with decreasing fin pitch regardless of fin array, however, the thermal performance of a heat exchanger, considering increase of heat surface area, becomes better.

  4. Delayed condensation and frost formation on superhydrophobic carbon soot coatings by controlling the presence of hydrophilic active sites

    Science.gov (United States)

    Esmeryan, Karekin D.; Castano, Carlos E.; Mohammadi, Reza; Lazarov, Yuliyan; Radeva, Ekaterina I.

    2018-02-01

    Condensation frosting is an undesired natural phenomenon that could be impeded efficiently using appropriate wettability and morphologically patterned surfaces. The icephobic properties of carbon soot and the fabrication scalability of its synthesis method are a good foundation for anti-frosting applications; however, the fundamentals of frost growth and spreading on sooted surfaces have not been examined yet. In this study, we investigate the anti-frosting performance of three groups of superhydrophobic soot coatings by means of 16 MHz quartz crystal microbalances (QCMs). The analysis of the real-time sensor signal of each soot coated QCM pattern shows that frost formation and its propagation velocity depend on the quantity of oxygen functionalities and structural defects in the material. In turn, the reduction of both parameters shifts the onset of frost growth to temperatures below  -20 °C, whereas the interdroplet ice bridging is slowed by a factor of four. Moreover, high-resolution scanning electron micrographs of the samples imply delamination upon defrosting of the soot with spherical-like morphology via polar interactions driven mechanism. These results reveal an opportunity for control of frost incipiency on sooted surfaces by adjusting the synthesis conditions and depositing soot coatings with as low as possible content of hydrophilic active sites.

  5. Robert Frost on Writing.

    Science.gov (United States)

    Barry, Elaine

    This book is a collection of Frost's letters, reviews, introductions, lectures, and interviews on writing dating back to 1913. It provides Frost's view of literature, and its relation to language and social order. Part one, "Frost as a Literary Critic," discusses the scope of Frost's criticism and Frost as both critical theorist and…

  6. Crushed aggregates for roads and their properties for frost protection

    Science.gov (United States)

    Kuznetsova, Elena; Willy Danielsen, Svein

    2015-04-01

    of the road system. According to new specification; the size of large stones for this layer should be maximum 0.5 m (longest edge) or ½ layer thickness. And minimum 30% of stones should be less than 90 mm. Fines content (First of all how this materials size will affect heat exchange in the layer, secondly - if the allowable fines content will make the materials frost susceptible. For calculations of frost protection layer thickness the knowledge of thermal conductivity of the aggregate layers is required. Handbook for geotechnical investigations of the soils provides this data for natural gravel which is limited by 0.7 - 1.3 W/mK. But when it comes to the crushed rocks, it can be significantly increased due to the higher conductivity of minerals (especially if they contain high amount of quartz), as well as due to higher effective conductivity. In rock-fill materials, i.e. materials with large particles and low degree of saturation, convection and radiation are the predominant heat transfer mechanisms. Convection and radiation can increase the effective conductivity by factor 2-10. Lebeau and Konrad (2007) showed that convection heat transfer could lead to the formation of undesirable permafrost conditions in toe drains of embankment dams located in Northern Quebec, i.e. in areas where there are no naturally occurring permafrost soils. In a frost design method the required parameter values of crushed rock aggregates are thermal conductivity, density and water content. The heat transfer during the freezing of natural soils is assumed proportional to thermal conductivity of the material. In a coarse-grained material with abundant pore space, convective heat transfer and radiation may be a considerable factor, sometimes even more significant than conduction. Specifications used by pavement engineers in most countries are solely based on grain size distribution and allowable fines content. The presence of fines in these layers can modify their frost susceptibility and

  7. Dedicated Low Latitude Diurnal CO2 Frost Observation Campaigns by the Mars Climate Sounder

    Science.gov (United States)

    Piqueux, S.; Kass, D. M.; Kleinboehl, A.; Hayne, P. O.; Heavens, N. G.; McCleese, D. J.; Schofield, J. T.; Shirley, J. H.

    2017-12-01

    In December 2016 (Ls≈280, MY33) and July 2017 (Ls≈30, MY34), the Mars Climate Sounder (MCS) onboard the Mars Reconnaissance Orbiter (MRO) conducted two distinct observation campaigns. The first one aimed at 1) confirming the presence of low latitude diurnal CO2 frost on Mars, and 2) refining the estimated mass of carbon dioxide condensed at the surface, whereas the second campaign was designed to 3) search for temporally and spatially varying spectral characteristics indicative of frost properties (i.e., crystal size, contamination, etc.) and relationship to the regolith. To meet these goals, MCS acquired thermal infrared observations of the surface and atmosphere at variable local times (≈1.70-3.80 h Local True Solar Time) and in the 10°-50°N latitude band where very low thermal inertia material (<< 100 Jm-2K-1s-0.5) is present. Atmospherically corrected surface brightness temperatures were retrieved in a wavelength region around 32 μm (MCS channel B1) as well as at 12 μm, 16 μm and 22 μm (MCS channels A4, A1, A5) where possible. A preliminary analysis of the data suggests a good general agreement between these new observations and earlier predictions in terms of frost distribution and spectral properties. In addition, pre-frost deposition surface cooling rates are found to be consistent with those predicted by numerical models (i.e., 1-2K per hour). Finally, we observe buffered surface temperatures near the local frost point, indicating a surface emissivity ≈1. (i.e., optically thin frost layers, or dust contaminated frost, or slab-like ice) and no discernable frost metamorphism. We will present a detailed analysis of these new and unique observations, and elaborate on the potential relationship between the regolith and this recurring frost cycle.

  8. Ion acoustic double layers in the presence of plasma source

    International Nuclear Information System (INIS)

    Okuda, H.; Ashour-Abdalla, M.

    1982-01-01

    Steady-state plasma turbulence and the formation of negative potential spikes and double layers in the presence of ion acoustic instabilities have been studied by means of one-dimensional particle simulations in which the velocities of a small fraction of electrons are replaced by the initial drifting Maxwellian at a constant rate. A steady state is found where negative potential spikes appear randomly in space and time giving rise to an anomalous resistivity much greater than previously found. Comparisons of the simulation results with laboratory and space plasmas are discussed

  9. Frost on Utopia Planitia

    Science.gov (United States)

    1977-01-01

    This Viking Lander 2 picture from Utopia Planitia shows the first clear indication of frost accumulation on the Martian surface seen by lander cameras. The picture, looking due north, was obtained with a blue filter at 12:59 p.m. local lander time, Sept. 13, 1977. The season is late winter. Frost appears as a white accumulation around the bottom of rocks, in a trench dug by the lander sampler arm, and in scattered patches on the darker surface. The shadow of the lander, including the camera (center) and the meteorology boom (left), appears in foreground. As the sun moves, the shadow is moving from left to right, exposing areas covered by frost and previously protected from the sun by the lander shadow. (Another image taken one-half hour later suggests the frost patches have become smaller.) Apparently frost, formed during the Martian night, at least partially disappears during the warmer daytime. The composition of the frost, whether carbon dioxide or water or a mixture of the two (CO2 clathrate), is not known. Measurements from the meteorology instrument indicate minimum nighttime temperatures of 160 Kelvin (-171 Fahrenheit). At the time the image was taken, the temperature had risen to 175 Kelvin (-144 Fahrenheit). The atmospheric pressure was 8.835 millibars. This combination of pressure and temperature are inconsistent with carbon dioxide frost formation, but plausible near-surface mechanisms might have resulted in conditions favorable for CO2 frost formation. Viking orbiter thermal mapping and water vapor instruments indicate temperatures might have been slightly lower than measured by the lander, suggesting that the frost is more likely CO2 than H20. A remote, but possible, explanation is that the material is an extremely bright dust deposit. Color images to be taken will be able to discount this interpretation. The mechanism for frost deposition is unknown. Possibilities include formation directly on the surface, precipitation as snow, or material blown to

  10. An improved model for predicting performance of finned tube heat exchanger under frosting condition, with frost thickness variation along fin

    Energy Technology Data Exchange (ETDEWEB)

    Tso, C.P. [Multimedia University, Jalan Ayer Keroh Lama, Melaka (Malaysia). Faculty of Engineering and Technology; Cheng, Y.C.; Lai, A.C.K. [Nanyang Technological University, Singapore (Singapore). School of Mechanical and Aerospace Engineering

    2006-01-15

    Frost accumulation on a heat exchanger, a direct result of combined heat and mass transfer between the moist air flowing across a cold surface, causes heat transfer performance degradation due to the insulating effect of frost layer and the coil blockage as the frost grows. The complex geometry of finned tube heat exchangers leads to uneven wall and air temperature distribution inside the coil, and causes variations of frost growth rate and densification along the coil. In this study, a general distributed model with frost formation was developed. The equations for finned tube heat exchanger were derived in non-steady-state manner and quasi-steady state in the frost model. In order to make the model more realistic, the variation of frost along fin due to uneven temperature distribution was included. The presented model is able to predict the dynamic behavior of an air cooler both under non-frost and frost condition. Comparisons were made based on the frost mass accumulation, pressure drop across coil and energy transfer coefficient, and results were found to agree well with reported experimental results. (author)

  11. Frost Effects Research Facility

    Data.gov (United States)

    Federal Laboratory Consortium — Full-scale study in controlled conditionsThe Frost Effects Research Facility (FERF) is the largest refrigerated warehouse in the United States that can be used for a...

  12. Frost behavior of a fin surface with temperature variation along heat exchanger fins

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jung Soo; Kim, Min Soo; Lee, Kwan Soo [Hanyang Univ., Seoul (Korea, Republic of); Kim, Ook Joong [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of)

    2007-07-01

    This paper presents a mathematical model for predicting the frost behavior formed on heat exchanger fins, considering fin heat conduction under frosting condition. The model is composed of air-side, the frost layer, and fin region, and they are coupled to the frost layer. The frost behavior is more accurately predicted with fin heat conduction considered (Case A) than with a constant fin surface temperature assumed (Case B). The results indicate that the frost thickness and heat transfer rate for Case B are over-predicted in most regions of the fin, as compared to those for Case A. Also, for Case A, the maximum frost thickness varies little with the fin length variations, and the extension of the fin length over 30 mm contributes insignificantly to heat transfer.

  13. Frost evolution in tailings

    International Nuclear Information System (INIS)

    1991-04-01

    A review was carried out on the physical and thermal mechanisms of permafrost evaluation in soils and uranium tailings. The primary mechanism controlling permafrost evolution is conductive heat transfer with the latent heat of fusion of water being liberated as phase change occurs. Depending on the soil properties and freezing rate, pore water can be expelled from the frost front or pore water can migrate towards the frost front. Solute redistribution may occur as the frost front penetrates into the soil. The rate of frost penetration is a function of the thermal properties of the tailings and the climatic conditions. Computer modelling programmes capable of modelling permafrost evolution were reviewed. The GEOTHERM programme was selected as being the most appropriate for this study. The GEOTHERM programme uses the finite element method of thermal analysis. The ground surface temperature is determined by solving the energy balance equations a the ground surface. The GEOTHERM programme was used to simulate the permafrost evolution in the Key Lake Mine tailings located in north central Saskatchewan. The analyses indicated that the existing frozen zones in the tailing pond will eventually thaw if an average snow depth covers the tailings. Hundreds of years are required to thaw the tailings. If minimal snow cover is present the extent of the frozen zone in the tailings will increase

  14. Robert Frost, Teacher.

    Science.gov (United States)

    Vogel, Nancy

    This biography explores poet Robert Frost's techniques as a teacher from the early days of teaching at Pinkerton Academy in Derry, New Hampshire, to his acceptance of a chair at Harvard University and his subsequent associations with numerous other schools. Also examined are his educational practices and philosophy--particularly his life-long…

  15. Tints, Shades and Frost

    Science.gov (United States)

    Sterling, Joan

    2009-01-01

    This article describes a classroom art project inspired by the work of Robert Frost, one of the most acclaimed and beloved American poets of all time. Using tints and shades in a composition, this project demonstrates how quality literature may be incorporated into elementary art lessons in a very useful way, making art an important complement to…

  16. Influences of surface hydrophilicity on frost formation on a vertical cold plate under natural convection conditions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zhongliang; Zhang, Xinghua; Wang, Hongyan; Meng, Sheng; Cheng, Shuiyuan [Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education and Key Laboratory of Heat Transfer and Energy Conversion, Beijing Education Commission, College of Environmental and Energy Engineering, Beijing University of Technology, Pingleyuan 100, Beijing 100022 (China)

    2007-07-15

    Surface hydrophilicity has a strong influence on frost nucleation according to phase transition theory. To study this effect, a close observation of frost formation and deposition processes on a vertical plate was made under free convection conditions. The formation and shape variation of frost crystals during the initial period are described and the frost thickness variation with time on both hydrophobic and plain copper cold surfaces are presented. The various influencing factors are discussed in depth. The mechanism of surface hydrophilicity influence on frost formation was analyzed theoretically. This revealed that increasing the contact angle can increase the potential barrier and restrain crystal nucleation and growth and thus frost deposition. The experimental results show that the initial water drops formed on a hydrophobic surface are smaller and remain in the liquid state for a longer time compared with ones formed on a plain copper surface. It is also observed that the frost layer deposited on a hydrophobic surface is loose and weak. Though the hydrophobic surface can retard frost formation to a certain extent and causes a looser frost layer, our experimental results show that it does not depress the growth of the frost layer. (author)

  17. Frost flowers and sea-salt aerosols over seasonal sea-ice areas in northwestern Greenland during winter–spring

    Directory of Open Access Journals (Sweden)

    K. Hara

    2017-07-01

    Full Text Available Sea salts and halogens in aerosols, frost flowers, and brine play an important role in atmospheric chemistry in polar regions. Simultaneous sampling and observations of frost flowers, brine, and aerosol particles were conducted around Siorapaluk in northwestern Greenland during December 2013 to March 2014. Results show that water-soluble frost flower and brine components are sea-salt components (e.g., Na+, Cl−, Mg2+, K+, Ca2+, Br−, and iodine. Concentration factors of sea-salt components of frost flowers and brine relative to seawater were 1.14–3.67. Sea-salt enrichment of Mg2+, K+, Ca2+, and halogens (Cl−, Br−, and iodine in frost flowers is associated with sea-salt fractionation by precipitation of mirabilite and hydrohalite. High aerosol number concentrations correspond to the occurrence of higher abundance of sea-salt particles in both coarse and fine modes, and blowing snow and strong winds. Aerosol number concentrations, particularly in coarse mode, are increased considerably by release from the sea-ice surface under strong wind conditions. Sulfate depletion by sea-salt fractionation was found to be limited in sea-salt aerosols because of the presence of non-sea-salt (NSS SO42−. However, coarse and fine sea-salt particles were found to be rich in Mg. Strong Mg enrichment might be more likely to proceed in fine sea-salt particles. Magnesium-rich sea-salt particles might be released from the surface of snow and slush layer (brine on sea ice and frost flowers. Mirabilite-like and ikaite-like particles were identified only in aerosol samples collected near new sea-ice areas. From the field evidence and results from earlier studies, we propose and describe sea-salt cycles in seasonal sea-ice areas.

  18. Modelling of frost formation and growth on microstuctured surface

    Science.gov (United States)

    Muntaha, Md. Ali; Haider, Md. Mushfique; Rahman, Md. Ashiqur

    2016-07-01

    Frost formation on heat exchangers is an undesirable phenomenon often encountered in different applications where the cold surface with a temperature below freezing point of water is exposed to humid air. The formation of frost on the heat transfer surface results in an increase in pressure drop and reduction in heat transfer, resulting in a reduction of the system efficiency. Many factors, including the temperature and moisture content of air, cold plate temperature, surface wettability etc., are known to affect frost formation and growth. In our present study, a model for frost growth on rectangular, periodic microgroove surfaces for a range of microgroove dimension (ten to hundreds of micron) is presented. The mathematical model is developed analytically by solving the governing heat and mass transfer equations with appropriate boundary conditions using the EES (Engineering Equation Solver) software. For temperature, a convective boundary condition at frost-air interface and a fixed cold plate surface temperature is used. Instead of considering the saturation or super-saturation models, density gradient at the surface is obtained by considering experimentally-found specified heat flux. The effect of surface wettability is incorporated by considering the distribution of condensed water droplets at the early stage of frost formation. Thickness, density and thermal conductivity of frost layer on the micro-grooved surfaces are found to vary with the dimension of the grooves. The variation of density and thickness of the frost layer on these micro-grooved surfaces under natural convection is numerally determined for a range of plate temperature and air temperature conditions and is compared with experimental results found in the open literature.

  19. Measurements of seasonal frost depth by frost tube in Japan

    Science.gov (United States)

    Harada, K.; Yoshikawa, K.; Iwahana, G.; Stanilovskaya, J. V.; Sawada, Y.; Sone, T.

    2017-12-01

    Since 2011 winter season, frost depths have been measured as an outreach program in Hokkaido, northern part of Japan, where seasonal ground freezing occurs in winter. Frost depths were measured in elementary, junior high and high schools in order to emphasis their interest for earth sciences. At schools, using simple frost tube, measurements were conducted directly once a week by students or teacher during ground freezing under no snow-removal condition. A lecture was made in class and a frost tube was set at schoolyard, as the same tube and protocol as UAF's Permafrost Outreach Program, using clear tube with blue-colored water. In 2011 winter season, we started measurements at three schools, and the number of school extended to 32 in 2016 season, 26 elementary schools, 5 junior high schools and one high school. We visited schools in summer time or just before frost season to talk about the method of measurement, and measurements by students started just after ground freezing. After the end of frozen period, we visited schools again to explain results of each school or another schools in Japan, Alaska, Canada or Russia. The measured frost depths in Hokkaido ranged widely, from only a few centimeter to more than 50 cm. However, some schools had no frost depth due to heavy snow. We confirmed that the frost depth strongly depends on air temperature and snow depth. The lecture was made to student why the frost depth ranged widely, and the effect of snow was explained by using the example of igloo. In order to validate the effect of snow and to compare frost depths, we tried to measure frost depths under snow-removal and no snow-removal conditions at the same elementary school. At the end of December, depths had no significant difference between these conditions, and the difference went to 14 cm after one month, with about 30 cm of snow depth. After these measurements and lectures, students noticed snow has a role as insulator and affects the frost depth.

  20. Effects of Surface Wettability on the Porosity and Wickability of Frost

    Science.gov (United States)

    Witt, Katherine; Ahmadi, Farzad; Boreyko, Jonathan

    2017-11-01

    The wicking of liquids through porous media has been studied for many materials, but never for frost, despite its implications for arctic oil spills and oil-infused surfaces. Here, we characterize silicone oils wicking up frost sheets. A layer of frost was grown on aluminum plates of varying surface wettability: superhydrophilic, hydrophilic, hydrophobic, and superhydrophobic. Once the desired frost thickness was grown, a humidity chamber was used to maintain the frost at the dew point and the bottom of the plate was dipped in a reservoir of fluorescent silicone oil. For all surfaces, the wicking rate of the oil increased with increasing wettability. For the wetting surfaces, this is manifested in the length vs. time data following the classical Washburn equation, exhibiting a power slope of about 1/2 and resulting in a larger effective pore radius with increasing wettability. However, we observed that on the non-wetting surfaces, the discrete distribution of the frosted dew droplets resulted in a new scaling law with a slope much less than 1/2, especially for the superhydrophobic surface which promoted jumping-droplet condensation. This research shows that the wicking of oil up a layer of frost can give insight into the morphology of frost. Conversely, if the underlying wettability of a frost sheet can be controlled, the spread of oil can be widely tuned. This work was supported by a Virginia Space Grant Consortium Undergraduate Research Scholarship (PMPTX7EP).

  1. Robert Frost: Teacher "Earner, Learner, Yearner."

    Science.gov (United States)

    Vogel, Nancy Sue

    An account of Robert Frost's teaching, along with an assessment of it, are presented. Material consulted includes Frost's published letters, prose, and poetry; Lawrance Thompson's authorized biography; Lesley Frost's "New Hampshire's Child: The Derry Journals of Lesley Frost;" and additional sources such as films and periodicals,…

  2. Ion-acoustic double layers in the presence of plasma source

    International Nuclear Information System (INIS)

    Okuda, H.; Ashour-Abdalla, M.

    1981-11-01

    Steady-state plasma turbulence and formation of negative potential spikes and double layers in the presence of ion acoustic instabilities have been studied by means of one-dimensional particle simulations in which velocities of a small fraction of electrons are replaced by the initial drifting Maxwellian at a constant rate. A steady state is found where negative potential spikes appear randomly in space and time giving rise to an anomalous resistivity much greater than previously found. Comparisons of the simulation results with laboratory and space plasmas are discussed

  3. Frost formation on fin-and-tube heat exchangers. Pt. 1. Modeling of frost formation on fin-and-tube heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Seker, D.; Karatas, H. [Arcelik A.S., Istanbul (Turkey); Egrican, N. [Yeditepe University, Istanbul (Turkey)

    2004-06-01

    In this study, the heat and mass transfer characteristics of heat exchangers during frost formation process are analyzed numerically. Unsteady heat and mass transfer coefficients of the air side, heat transfer coefficient of the refrigerant side, air-frost layer interface temperature, the surface efficiency of the heat exchanger and the mass flow rate of the frost accumulated on the heat exchanger surface are calculated. The total conductivity (UA) and pressure drop of the heat exchanger are reported for different air inlet temperature, relative humidity, air mass flow rate and the refrigerant temperature. (author)

  4. Frost as a first wall for the ICF laboratory microfusion facility

    International Nuclear Information System (INIS)

    Orth, C.D.

    1989-01-01

    The authors introduce the concept of using frost as the first wall of the ICF Laboratory Microfusion Facility being designed to produce 200-1000 MJ of thermonuclear yield. They present one design incorporating 2cm of frost deposited at 0.1 g/cm/sup 3/ on an LN-cooled fiber-reinforced polymer substrate. They calculate that such a frost layer will protect the substrate from ablation by target x rays and debris, and from shock-induced spallation. Postshot washdown with water should permit low-activation operation, and should preserve the original wall properties. The authors expect the impact of the frost on laser optics to be minimal, and expect the preshot lifetime of thermally unprotected cryogenic targets to be extended by operating the wall at 100-150 K. Moreover, they believe that such a frost first wall involves little technical risk, and will be inexpensive to construct and operate

  5. Analytical solutions of mushy layer equations describing directional solidification in the presence of nucleation

    Science.gov (United States)

    Alexandrov, Dmitri V.; Ivanov, Alexander A.; Alexandrova, Irina V.

    2018-01-01

    The processes of particle nucleation and their evolution in a moving metastable layer of phase transition (supercooled liquid or supersaturated solution) are studied analytically. The transient integro-differential model for the density distribution function and metastability level is solved for the kinetic and diffusionally controlled regimes of crystal growth. The Weber-Volmer-Frenkel-Zel'dovich and Meirs mechanisms for nucleation kinetics are used. We demonstrate that the phase transition boundary lying between the mushy and pure liquid layers evolves with time according to the following power dynamic law: , where Z1(t)=βt7/2 and Z1(t)=βt2 in cases of kinetic and diffusionally controlled scenarios. The growth rate parameters α, β and ε are determined analytically. We show that the phase transition interface in the presence of crystal nucleation and evolution propagates slower than in the absence of their nucleation. This article is part of the theme issue `From atomistic interfaces to dendritic patterns'.

  6. With Robert Frost in Tesolonia.

    Science.gov (United States)

    Welninski, Virginia

    A teacher's guide and exercises for teaching poetry by Robert Frost to English as a second language students are presented. Suggestions are presented for developing meanings for words and other meaningful units through the use of realia, pictures, demonstrations, definitions, context clues, paraphrasing, completion exercises, solving and creating…

  7. Frost flowers on young Arctic sea ice: The climatic, chemical, and microbial significance of an emerging ice type

    DEFF Research Database (Denmark)

    Barber, D. G.; Ehn, J. K.; Pucko, M.

    2014-01-01

    flowers primarily originated from the surface brine skim. Ikaite crystals were observed to form within an hour in both frost flowers and the thin pond ice. Average ikaite concentrations were 1013 mu molkg(-1) in frost flowers and 1061 mu molkg(-1) in the surface slush layer. Chamber flux measurements...

  8. Evolution of symmetric reconnection layer in the presence of parallel shear flow

    Energy Technology Data Exchange (ETDEWEB)

    Lu Haoyu [Space Science Institute, School of Astronautics, Beihang University, Beijing 100191 (China); Sate Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100190 (China); Cao Jinbin [Space Science Institute, School of Astronautics, Beihang University, Beijing 100191 (China)

    2011-07-15

    The development of the structure of symmetric reconnection layer in the presence of a shear flow parallel to the antiparallel magnetic field component is studied by using a set of one-dimensional (1D) magnetohydrodynamic (MHD) equations. The Riemann problem is simulated through a second-order conservative TVD (total variation diminishing) scheme, in conjunction with Roe's averages for the Riemann problem. The simulation results indicate that besides the MHD shocks and expansion waves, there exist some new small-scale structures in the reconnection layer. For the case of zero initial guide magnetic field (i.e., B{sub y0} = 0), a pair of intermediate shock and slow shock (SS) is formed in the presence of the parallel shear flow. The critical velocity of initial shear flow V{sub zc} is just the Alfven velocity in the inflow region. As V{sub z{infinity}} increases to the value larger than V{sub zc}, a new slow expansion wave appears in the position of SS in the case V{sub z{infinity}} < V{sub zc}, and one of the current densities drops to zero. As plasma {beta} increases, the out-flow region is widened. For B{sub y0} {ne} 0, a pair of SSs and an additional pair of time-dependent intermediate shocks (TDISs) are found to be present. Similar to the case of B{sub y0} = 0, there exists a critical velocity of initial shear flow V{sub zc}. The value of V{sub zc} is, however, smaller than the Alfven velocity of the inflow region. As plasma {beta} increases, the velocities of SS and TDIS increase, and the out-flow region is widened. However, the velocity of downstream SS increases even faster, making the distance between SS and TDIS smaller. Consequently, the interaction between SS and TDIS in the case of high plasma {beta} influences the property of direction rotation of magnetic field across TDIS. Thereby, a wedge in the hodogram of tangential magnetic field comes into being. When {beta}{yields}{infinity}, TDISs disappear and the guide magnetic field becomes constant.

  9. Adsorption Behavior of Vanadium in Presence of alumina with Emphasize on Triple Layer Model Simulation

    International Nuclear Information System (INIS)

    El-Sayed, A.A.

    2006-01-01

    Adsorption behavior of vanadium in alumina colloidal solution as simulation for soil-water and/or sediment - water system was investigated. factors affecting this behavior including Ph, humic acid and alumina concentrations were studied. Three stages of vanadium adsorption on alumina were approved due to Ph changes. The first is increasing adsorption with increasing Ph, in the range 1-3. the second is decreasing adsorption with increasing Ph in the range 6-10. the third is constant adsorption at 100% adsorption in Ph range 3-8 at 10 g/l concentration of alumina. However, at 0.2 g/l, the maximum adsorption of vanadium became less than 100%.The effect of humic acid on the adsorption behavior of vanadium (V) was studied and compared with that of vanadium (IV) . Adsorption behaviors were studied at concentration 4.1 E-4 M for vanadium at 0.1 M ionic strength. Triple layer model was used for simulation of vanadium adsorption behavior in presence of alumina under the same working conditions. the results showed good validation and verification to the data practically found. speciation of vanadium in both homogenous and heterogeneous systems was also studied theoretically so as to verify the most abundant elemental species and its impact on the environment

  10. The effect of stationary and sweeping frequency AC electric fields on frost crystal removal on a cold plate

    Energy Technology Data Exchange (ETDEWEB)

    Tudor, V. [US Naval Academy, Annapolis, MD (United States). Advanced Thermal Systems Laboratory, Mechanical Engineering Department; Ohadi, M. [University of Maryland, College Park, MD (United States). Smart and Small Thermal Systems Laboratory, Mechanical Engineering Department

    2006-06-15

    The effect of stationary and sweeping frequency AC electric fields on frost crystals growth and frost control/removal on a cold plate was studied for the first time in this paper. The main results of this study showed that the presence of AC electric fields can greatly affect both the frost crystals growth pattern and mass accumulation on cold surfaces. The ice surface electrical properties and basic electrostatics were used to explain the main findings in this paper. Up to 46% frost reduction was obtained when the electric field frequency spanned 370Hz to 7.5kHz while the applied voltage was 14.5kV. Two different sets of environmental conditions were tested, which showed that the plate temperature placed an important effect on frost crystals growth under electric fields. An optimum application time of the AC electric fields was found based on least frost mass accumulation on the cold plate. (author)

  11. Anhydrous Ammonia Frost on Titan

    Science.gov (United States)

    Smythe, W. D.; Nelson, R.; Boryta, M. D.

    2009-12-01

    Ammonia has been suggested as a probable source for sustaining Titan's thick nitrogen-dominated atmosphere. Ammonia is believed to be important to maintaining nitrogen in Titan's atmosphere. Ammonia is seen in clouds in the atmospheres of Jupiter and Saturn, but has yet to be detected on any of the satellites. This may be because all forms of NH3 are unstable in the ambient conditions of the satellites surfaces or that its spectral features are altered by other components of the surface, and have not been identified. It has recently been demonstrated[1] that brightening occurs in Titan’s atmosphere that is transient on the time-scale of months. The spectral shape of the brightening is more consistent with that of the transient apparition of a pure ammonia frost than of an ammonia monohydrate or ammonia dihydrate frost. However, the phase behavior of the ammonia water system has peritectics at compositions of 1:1 and 1:2. These hydrate forms would be expected to dominate if the frost, or the reservoir from which the frost was derived had any water present. Physical mechanisms for producing measurable quanitities of anhydrous ammonia can include chemical dehydration or dehydration of the vapor phase - but it is challenging to store significant quantities of the anhydrous material because of the phase behavior in the solid state. [1] Nelson, R.M., et al. Saturn’s Titan: Surface Change, Ammonia, and Implications for Atmospheric and Tectonic Activity., Icarus, 199, pp. 429-441, 2009 This work was performed at JPL under contract to NASA

  12. Optical absorption in silicon layers in the presence of charge inversion/accumulation or ion implantation

    International Nuclear Information System (INIS)

    Alloatti, L.; Lauermann, M.; Koos, C.; Freude, W.; Sürgers, C.; Leuthold, J.

    2013-01-01

    We determine the optical losses in gate-induced charge accumulation/inversion layers at a Si/SiO 2 interface. Comparison between gate-induced charge layers and ion-implanted thin silicon films having an identical sheet resistance shows that optical losses can be significantly lower for gate-induced layers. For a given sheet resistance, holes produce higher optical loss than electrons. Measurements have been performed at λ = 1550 nm

  13. Study of Remontant Raspberry Frost Resistance

    Directory of Open Access Journals (Sweden)

    Pushchina M.Yu.

    2016-08-01

    Full Text Available In this paper we consider the second component of remontant raspberry cold hardiness - frost resistance, namely the ability of this raspberry type to tolerate the lowest temperature. Series of artificial freezing was carried out to check the frost-resistance. According to the data obtained the most frost-resistant varieties of remontant raspberries were detected. The critical low temperature for all studied varieties and forms of remontant raspberries was estimated.

  14. Frost resistance of alpine woody plants

    Directory of Open Access Journals (Sweden)

    Gilbert eNeuner

    2014-12-01

    Full Text Available This report provides a brief review of key findings related to frost resistance in alpine woody plant species, summarizes data on their frost resistance, highlights the importance of freeze avoidance mechanisms, and indicates areas of future research.Freezing temperatures are possible throughout the whole growing period in the alpine life zone. Frost severity, comprised of both intensity and duration, becomes greater with increasing elevation and, there is also a greater probability, that small statured woody plants, may be insulated by snow cover.Several frost survival mechanisms have evolved in woody alpine plants in response to these environmental conditions. Examples of tolerance to extracellular freezing and freeze dehydration, life cycles that allow species to escape frost, and freeze avoidance mechanisms can all be found. Despite their specific adaption to the alpine environment, frost damage can occur in spring, while all alpine woody plants have a low risk of frost damage in winter. Experimental evidence indicates that premature deacclimation in Pinus cembra in the spring, and a limited ability of many species of alpine woody shrubs to rapidly reacclimate when they lose snow cover, resulting in reduced levels of frost resistance in the spring, may be particularly critical under the projected changes in climate.In this review, frost resistance and specific frost survival mechanisms of different organs (leaves, stems, vegetative and reproductive over-wintering buds, flowers and fruits and tissues are compared. The seasonal dynamics of frost resistance of leaves of trees, as opposed to woody shrubs, is also discussed. The ability of some tissues and organs to avoid freezing by supercooling, as visualized by high resolution infrared thermography, are also provided. Collectively, the report provides a review of the complex and diverse ways that woody plants survive in the frost dominated environment of the alpine life zone.

  15. Frost resistance in alpine woody plants.

    Science.gov (United States)

    Neuner, Gilbert

    2014-01-01

    This report provides a brief review of key findings related to frost resistance in alpine woody plant species, summarizes data on their frost resistance, highlights the importance of freeze avoidance mechanisms, and indicates areas of future research. Freezing temperatures are possible throughout the whole growing period in the alpine life zone. Frost severity, comprised of both intensity and duration, becomes greater with increasing elevation and, there is also a greater probability, that small statured woody plants, may be insulated by snow cover. Several frost survival mechanisms have evolved in woody alpine plants in response to these environmental conditions. Examples of tolerance to extracellular freezing and freeze dehydration, life cycles that allow species to escape frost, and freeze avoidance mechanisms can all be found. Despite their specific adaption to the alpine environment, frost damage can occur in spring, while all alpine woody plants have a low risk of frost damage in winter. Experimental evidence indicates that premature deacclimation in Pinus cembra in the spring, and a limited ability of many species of alpine woody shrubs to rapidly reacclimate when they lose snow cover, resulting in reduced levels of frost resistance in the spring, may be particularly critical under the projected changes in climate. In this review, frost resistance and specific frost survival mechanisms of different organs (leaves, stems, vegetative and reproductive over-wintering buds, flowers, and fruits) and tissues are compared. The seasonal dynamics of frost resistance of leaves of trees, as opposed to woody shrubs, is also discussed. The ability of some tissues and organs to avoid freezing by supercooling, as visualized by high resolution infrared thermography, are also provided. Collectively, the report provides a review of the complex and diverse ways that woody plants survive in the frost dominated environment of the alpine life zone.

  16. Antimicrobial Effect of Citrus Aurantifolia Extract on Enterococcus Faecalis Within the Dentinal Tubules in The Presence of Smear Layer

    Directory of Open Access Journals (Sweden)

    Sharifian MR

    2011-12-01

    Full Text Available Background and Aims: Instrumentation of the root canals results in formation of smear layer which covers the dentinal tubules. In infected teeth, it is ideal to achieve a material that has the ability to remove the smear layer besides antimicrobial activity. Therefore, this study was designed to evaluate the antimicrobial effect of Citrus aurantifolia extracts (lime juice and rind extract on Enterococcus faecalis within dentinal tubules in the presence of smear layer.Materials and Methods: One-hundred and forty dentin tubes were prepared from bovine incisors. After removal the smear layer, the specimens were infected with Enterococcus faecalis. Then, the smear layer was reformed. Test solutions were used as the irrigants in study roups as follows: group 1: 5.25% NaOCl; group 2: 17% EDTA; group 3: NaOCl+EDTA; group 4: Lime juice; group 5: ethanolic rind extract of C.aurantifolia; group 6: 96% ethanol. Dentin chips were collected from inner and outer layers of dentinal walls and optical density was measured. The data were analyzed using one-way ANOVA and Tamhane tests.Results: In outer layer of dentin, the efficacy of rind extract was less than that of NaOCl+EDTA (P<0.05. Also Lime juice was less effective than EDTA, NaOCl and NaOCl+EDTA (P<0.05. In inner layer of dentin, Lime juice was significantly less effective than NaOCl and NaOCl+EDTA (P<0.05. The efficacy of rind extract was less than that of NaOCl+EDTA (P<0.05.Conclusion: In the presence of smear layer, the antimicrobial activity of Lime juice was less than that of NaOCl but the efficacy of rind extract was similar to that of NaOCl.

  17. Boundary Layer Adjustments to the Presence of Absorbing Aerosols Inferred from LASIC Field Campaign Observations

    Science.gov (United States)

    Zhang, J.; Zuidema, P.; Delgadillo, R.; Adebiyi, A. A.

    2017-12-01

    Biomass burning aerosols scatter and absorb shortwave radiation efficiently, thereby warming the atmosphere in-situ and cooling the surface below. If the warming stabilizes the atmospheric temperature profile, this will strengthen the low cloud deck. If the absorbing aerosols are mixed into the cloud layer, the cloud response may differ. This study focuses on observations collected by DOE ARM Mobile Facility instruments during the biomass burning season of 2016 and 2017 of the DOE LASIC campaign, or Layered Atlantic Smoke Interactions with Clouds (LASIC), at Ascension Island (8°S, 14°W), located 2,000 km offshore of continental Africa in the trade-wind regime. The subsiding aerosol layer and deepening boundary layer over this location favor the mixing of smoke into the cloud layer and indeed micropulse-derived extinction profiles reveal that aerosol is almost always present near the top of the cloudy boundary layer during July-October, if in varying amounts. When absorbing aerosols are also present near the surface, the boundary layer is deeper and more well-mixed, the diurnal cycle of potential temperature is more prominent, and the cloud top inversion is stronger. The near-surface aerosol loading is not well-correlated with that in the free troposphere, indicating distinct aerosol transport pathways. In this presentation, ERA-Interim reanalysis data will be applied to improve control for meteorological effects, and the cloud adjustments to the smoke-affected thermodynamic structure will be explored.

  18. Frost resistance of building materials

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan De Place

    materials, has been developed.The importance of the pore structure on the development of stresses in the material during freezing is emphasized. To verify the model, experimental investigations are made on various concretes without air-entrainment and brick tiles with different porosities......In this thesis it is shown that the critical degree of saturation is suitable as parameter for the frost resistance of porous building materials. A numerical model for prediction of critical degrees of saturation based on fracture mechanics and phase geometry of two-phase materials, e.g. porous...

  19. Frost Heave in Colloidal Soils

    KAUST Repository

    Peppin, Stephen

    2011-01-01

    We develop a mathematical model of frost heave in colloidal soils. The theory accountsfor heave and consolidation while not requiring a frozen fringe assumption. Two solidificationregimes occur: a compaction regime in which the soil consolidates to accommodate the ice lenses, and a heave regime during which liquid is sucked into the consolidated soil from an external reservoir, and the added volume causes the soil to heave. The ice fraction is found to vary inversely with thefreezing velocity V , while the rate of heave is independent of V , consistent with field and laboratoryobservations. © 2011 Society for Industrial and Applied Mathematics.

  20. Frost damage of concrete subject to confinement

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange

    2016-01-01

    When internal frost damage is observed in real concrete structures, the usual pattern is cracks with a preferred orientation parallel to the exposed surface. When exposing concrete with poor frost resistance to a standardised freeze/thaw test in the laboratory, the orientations of the resulting...

  1. Mechanisms and environmental signals triggering frost hardening ...

    Indian Academy of Sciences (India)

    2004-10-28

    Oct 28, 2004 ... Home; Journals; Journal of Biosciences; Volume 29; Issue 4. Plant resistance to cold stress: Mechanisms and environmental signals triggering frost hardening and dehardening ... Keywords. Cold acclimation of plants; environmental signals; frost hardening; photoperiod; phytochrome; Scots pine ...

  2. OECI TuBaFrost tumor biobanking

    NARCIS (Netherlands)

    Riegman, Peter H. J.; Bosch, Antonio Llombart; Riegman, P. H. J.; Dinjens, W. N. M.; Oomen, M. H. A.; Spatz, A.; Ratcliffe, C.; Knox, K.; Mager, R.; Kerr, D.; Pezzella, F.; van Damme, B.; van de Vijver, M.; van Boven, H.; Morente, M. M.; Alonso, S.; Kerjaschki, D.; Pammer, J.; Lopez-Guerrero, J. A.; Bosch, A. Llombart; Carbone, A.; Gloghini, A.; Teodorovic, I.; Isabelle, M.; Jaminé, D.; Passioukov, A.; Lejeune, S.; Therasse, P.; van Veen, E. B.; Lam, K. H.; Oosterhuis, J. W.

    2008-01-01

    OECI TuBaFrost harbors a complete infrastructure for the exchange of frozen tumor samples between European countries. OECI TuBaFrost consists of: * A code of conduct on how to exchange human residual samples in Europe, * A central database application accessible over the Internet (www.tubafrost.org)

  3. Robert Frost and the Poetry of Physics.

    Science.gov (United States)

    Coletta, W. John; Tamres, David H.

    1992-01-01

    Examines five poems by Robert Frost that illustrate Frost's interest in science. The poems include allusions to renowned physicists, metaphoric descriptions of some famous physics experiments, explorations of complementarity as enunciated by Bohr, and poetic formulations of Heisenberg's uncertainty principle. (20 references) (MDH)

  4. Robert Frost and the Uses of Biography.

    Science.gov (United States)

    Miller, Lewis H., Jr.

    The persona Robert Frost communicated to most of his wide, diverse, and often non-academic audience was that of a rather isolated New England farmer, who--because of his limited experience with city folk and urban living--was untouched and thereby uncorrupted by the ways of the world. In teaching Frost, as in teaching any poet, some sort of…

  5. Size scale dependence of compressive instabilities in layered composites in the presence of stress gradients

    DEFF Research Database (Denmark)

    Poulios, Konstantinos; Niordson, Christian Frithiof

    2016-01-01

    The compressive strength of unidirectionally or layer-wise reinforced composite materials in direction parallel to their reinforcement is limited by micro-buckling instabilities. Although the inherent compressive strength of a given material micro-structure can easily be determined by assessing i...

  6. Growth of thermal oxide layers on GaAs and InP in the presence of ammonium heptamolybdate

    International Nuclear Information System (INIS)

    Mittova, I.Ya.; Lavrushina, S.S.; Afonchikova, A.V.

    2004-01-01

    Processes of thermal oxidation of GaAs and InP in the presence of ammonium heptamolybdate were studied using the methods of X-ray fluorescence analysis and IR spectroscopy at temperatures 480-580 Deg C. It was ascertained that introduction of the activator into the system results in accelerated growth of layers on semiconductors due to participation of anionic component of the chemostimulator in oxidation processes. The activator is integrated into the salts formed [ru

  7. Evaluation of the contact angle and frost resistance of hydrophobised heat-insulating mortars with polystyrene

    Science.gov (United States)

    Barnat-Hunek, Danuta; Łagód, Grzegorz; Klimek, Beata

    2017-07-01

    The aim of the research presented in the paper was to evaluate the feasibility of using hydrophobic preparation based on organosilicon compounds for surface protection on the heat-insulating mortars modified with polystyrene. The work discusses issues related to wettability, absorptivity and frost resistance of the surface layer of mortars. The experimental part pertains to the physical and mechanical properties of polystyrene-modified mortars and the influence of hydrophobic preparation on the contact angle and frost resistance. The frost resistance of mortars was examined following 25 cycles of freezing and thawing. The contact angle of light mortars (θw) was determined before and after the tests of frost resistance, in the function of time using a single measurement liquid. This provided a basis for calculating the surface free energy with Neumann method, characterizing the wettability and adhesion of mortars under normal conditions and with damages resulting from frost weathering. The structure of mortars and the adhesion of lightweight aggregate to cement paste were presented by means of scanning electron microscopy. The studies enabled to determine the hydrophobisation efficiency of heat-insulating mortars with polystyrene. The obtained results confirmed the possibility of producing heat-insulating mortars modified with polystyrene along with proper surface protection against moisture and frost.

  8. Electrical double layer on silver iodide and overcharging in the presence of hydrolyzable cations

    NARCIS (Netherlands)

    Lyklema, J.; Golub, T.P.

    2007-01-01

    Previous studies on the surface charge and electrokinetic charge on silver iodide as a function of the pAg in the presence of some monovalent and trivalent cations as the counterions were extended to include the influence of pH. The main reason for this study was to investigate the possible

  9. Frost risks in the Mantaro river basin

    Directory of Open Access Journals (Sweden)

    G. Trasmonte

    2008-04-01

    Full Text Available As part of the study on the Mantaro river basin's (central Andes of Perú current vulnerability to climate change, the temporal and spatial characteristics of frosts were analysed. These characteristics included intensity, frequency, duration, frost-free periods, area distribution and historical trends. Maps of frost risk were determined for the entire river basin, by means of mathematical algorithms and GIS (Geographic Information Systems tools, using minimum temperature – 1960 to 2002 period, geomorphology, slope, land-use, types of soils, vegetation and life zones, emphasizing the rainy season (September to April, when the impacts of frost on agriculture are most severe. We recognized four categories of frost risks: low, moderate, high and critical. The critical risks (with a very high probability of occurrence were related to high altitudes on the basin (altitudes higher than 3800 m a.s.l., while the low (or null probability of occurring risks were found in the lower zones (less than 2500 m a.s.l.. Because of the very intense agricultural activity and the high sensitivity of the main crops (Maize, potato, artichoke in the Mantaro valley (altitudes between 3100 and 3300 m a.s.l., moderate to high frost risks can be expected, with a low to moderate probability of occurrence. Another significant result was a positive trend of 8 days per decade in the number of frost days during the rainy season.

  10. Characteristics of the surface layer above a row crop in the presence of local advection

    Energy Technology Data Exchange (ETDEWEB)

    Figuerola, P.I. [Universidad de Buenos Aires, Buenos Aires (Argentina)]. E-mail: figuerol@at.fcen.uba.ar; Berliner, P.R. [Blaustein Institute for Desert Research, Ben-Gurion University of the Negev (Israel)

    2006-04-15

    In some arid land, the irrigated fields are not contiguous and are surrounded by large patches of bare land. During the summer time and rainless season, the solar radiation flux is high and the surface temperature during daylight in the dry bare areas, is much higher than that of the air. The sensible heat generated over these areas may be advected to the irrigated fields. The crops are usually planted in rows and the irrigation systems used (trickle) do not wet the whole surface, the dry bare soil between the rows may develop high soil surface temperatures and lead to convective activity inside the canopy above the bare soil. Advection from the surrounding fields and convective activity inside the canopy affect the layer above the crop. We studied the surface layer above an irrigated tomato field planted in Israel's Negev desert. The crop was planted in rows, trickle irrigated and the distance between the outer edges of two adjacent rows was 0.36 m at the time of measurement. The gradients in temperature and water vapor pressure were obtained at various heights above the canopy using a Bowen ratio machine. The residual in the energy balance equation was used as a criterion to determine the equilibrium layer. During the morning, unstable conditions prevail, and the equilibrium layer was between Z/h {approx} 1.9 and 2.4. In some particular circumstances, in the late morning, the bare soil between the rows reached extremely high temperatures and during conditions with low wind speeds free convection was identified. During these hours the residuals of the energy budget to the heights Z/h = 1.5 and 2.4 were significantly different from zero and an extremely large variability was evident for the Z/h = 3.2 layer. Local advection took place during the afternoon resulting in an increase in the stability of the uppermost measured layer and propagated slowly downwards. The equilibrium layer was between Z/h {approx} 1.5 to 2.4. The residuals were significantly different

  11. Frost induced damages within porous materials - from concrete technology to fuel cells technique

    Science.gov (United States)

    Palecki, Susanne; Gorelkov, Stanislav; Wartmann, Jens; Heinzel, Angelika

    2017-12-01

    Porous media like concrete or layers of membrane electrode assemblies (MEA) within fuel cells are affected by a cyclic frost exposure due to different damage mechanisms which could lead to essential degradation of the material. In general, frost damages can only occur in case of a specific material moisture content. In fuel cells, residual water is generally available after shut down inside the membrane i.e. the gas diffusion layer (GDL). During subsequent freezing, this could cause various damage phenomena such as frost heaves and delamination effects of the membrane electrode assembly, which depends on the location of pore water and on the pore structure itself. Porous materials possess a pore structure that could range over several orders of magnitudes with different properties and freezing behaviour of the pore water. Latter can be divided into macroscopic, structured and pre-structured water, influenced by surface interactions. Therefore below 0 °C different water modifications can coexist in a wide temperature range, so that during frost exposure a high amount of unfrozen and moveable water inside the pore system is still available. This induces transport mechanisms and shrinkage effects. The physical basics are similar for porous media. While the freezing behaviour of concrete has been studied over decades of years, in order to enhance the durability, the know-how about the influence of a frost attack on fuel cell systems is not fully understood to date. On the basis of frost damage models for concrete structures, an approach to describe the impact of cyclic freezing and thawing on membrane electrode assemblies has been developed within this research work. Major aim is beyond a better understanding of the frost induced mechanisms, the standardization of a suitable test procedure for the assessment of different MEA materials under such kind of attack. Within this contribution first results will be introduced.

  12. Effect of snow cover on soil frost penetration

    Science.gov (United States)

    Rožnovský, Jaroslav; Brzezina, Jáchym

    2017-12-01

    Snow cover occurrence affects wintering and lives of organisms because it has a significant effect on soil frost penetration. An analysis of the dependence of soil frost penetration and snow depth between November and March was performed using data from 12 automated climatological stations located in Southern Moravia, with a minimum period of measurement of 5 years since 2001, which belong to the Czech Hydrometeorological institute. The soil temperatures at 5 cm depth fluctuate much less in the presence of snow cover. In contrast, the effect of snow cover on the air temperature at 2 m height is only very small. During clear sky conditions and no snow cover, soil can warm up substantially and the soil temperature range can be even higher than the range of air temperature at 2 m height. The actual height of snow is also important - increased snow depth means lower soil temperature range. However, even just 1 cm snow depth substantially lowers the soil temperature range and it can therefore be clearly seen that snow acts as an insulator and has a major effect on soil frost penetration and soil temperature range.

  13. Frost tolerance in wild potatoes : Assessing the predictivity of taxonomic, geographic and ecological factors

    NARCIS (Netherlands)

    Hijmans, R.J.; Jacobs, M.; Bamberg, J.B.; Spooner, D.M.

    2003-01-01

    The use of genetic resources could be more effective and efficient if we were able to predict the presence or absence of useful traits in different populations or accessions. We analyzed the extent to which taxonomic, geographic and ecological factors can predict the presence of frost tolerance in

  14. Improvements in the properties of NbN layers through the presence of small amounts of aluminum during sputtering

    International Nuclear Information System (INIS)

    Haase, E.L.; Ruzicka, J.

    1988-09-01

    Pure phase B1 NbN layers could be sputtered in our laboratory only with a maximum T c of 15.9 K and a residual resistance ratio RRR of c of up to 16.7 K invariably had a large fraction of hexagonal foreign phase. If under similar conditions one sputters layers in the presence of small amounts of Al, one obtains pure B1 phase NbN layers with a maximum T c of 16.9 K. The RRR rises to values of up to 1.16. The specific resistance drops from typical values of around 400 μΩcm to values as low as 73 μΩcm. The width of the X-ray lines drops occasionally, indicating increased grain size. Al acts like a catalyst, being substituted with less than 0.03 at% for a high T c layer. When Al is substituted for Nb in detectable quantities both T c and the lattice parameter drop. To verify the above results the experiment was repeated in a magnetron rather than a RF sputter system with similar outcome. (orig.)

  15. Picocyanobacteria Dominance in Deep Biomass Layers: Relation to Diatom Presence and Episodic Events.

    Science.gov (United States)

    Aguilar, C.; Cuhel, R. L.

    2016-02-01

    In Offshore Marine and Large Lake Waters, most of the biomass and the productivity of phytoplankton occur below surface observation capabilities. Sub-mixed layer phytoplankton populations develop, increase, persist, and decay in relation to physical structure such as pycnocline density gradients interacting with progressively changing light fields. Basin-scale meteorological events and persistence of major invasive species have also left marks on biogeochemical cycling and ecosystem function in Lake Michigan. Among the former are precipitation and turbulence alterations brought on by unusual winter ice cover and a century-scale flood during 2008. Dampened seasonal silicate cycling indicated a basin-wide reduction of diatom production following mussel establishment. Communities in Lake Michigan shifted from diatom and big cell-dominated to small cell picocyanobacteria-dominated phytoplankton. Picocyanobacteria were beneficiaries of profound oligotrophication of the ecosystem starting in 2003. Photosynthetic parameters of pre-2003 Deep Biomass populations dominated by diatoms were systematically different from the cyanobacterial epoch following quagga mussel establishment and increase in depth of 1% incident light to 50-60m. Deep cyanobacterial production has now often been on the same scale as overlying waters. Photophysiology changes in a smooth depth gradient in this clear water as opposed to previous abrupt transition to shade adaptation. Among these many physicochemical permutations, community structure has consistently been a tradeoff between diatoms and picocyanobacteria. Opposing fluctuations of biomass favor one or the other on seasonal time frames of sequential years, with a complete system reset between each (winter mixing). For the Great Flood example, diatom surface blooms increased light extinction and drove the deep biomass maximum up - as populations settled into the pycnocline they had already outcompeted the picocyanobacteria. The opposite was true

  16. Design of UMTRA covers to mitigate the effect of frost penetration

    Energy Technology Data Exchange (ETDEWEB)

    Banani, A.M.; Claire, R.F.

    1994-03-01

    The Uranium Mill Tailings Remedial Action (UMTRA) Project, contracted by the US Department of Energy (DOE), requires construction of disposal cells for residual radioactive materials from abandoned uranium mill tailings. A disposal cell consists of contaminated material placed within a stabilized embankment with a top cover. The embankment and cover should be effective for up to 1000 years, to the extent reasonably achievable, and in any case for at least 200 years. The embankment cover usually consists of a radon/infiltration barrier, a frost barrier and erosion protection layer consisting of bedding and riprap layers. The radon/infiltration barrier and frost barrier are two important elements of the cover systems. A radon/infiltration barrier is designed to reduce the radon emissions from the contaminated materials and to limit the surface water infiltration into the contaminated material. However, a radon/infiltration barrier has to be protected from repeated freeze-thaw cycles to prevent an increase in permeability. Frost penetration depth is site specific and depends on local climatic conditions and soil properties of the cover system. However, placing a frost barrier is not only very costly but also reduces the disposal capacity of the embankment. Recent laboratory test results indicate that freeze-thaw cycles do not significantly effect the permeability of compacted sand-bentonite mixtures. Therefore, radon/infiltration barriers using sand-bentonite mixtures may not require frost barriers for protection against the effects of freeze-thaw. In this paper the design of UMTRA covers is briefly explained; the criteria to determine a 200 year freeze event, and the frost penetration depth are discussed. The results of freeze-thaw permeability tests on compacted clay and sand-bentonite mixtures are also presented.

  17. Determination of tetracyclines in animal feeds in the presence of other drugs by thin-layer chromatography and microbiological method.

    Science.gov (United States)

    Markakis, P K

    1996-01-01

    This method was developed to separate, detect, and quantitate oxytetracycline (OTC) or chlortetracycline hydrochloride (CTC.HCl) in animal feeds in the presence of 11 other drugs: 3 nitrofurans, 2 macrolide antibiotics, 3 sulfonamides, 2 coccidiostatics, and 1 antibacterial growth promoter. OTC or CTC.HCl was separated from coexisting drugs and detected by thin-layer chromatography, then quantitated microbiologically by the agar diffusion method. Analysis of 125 experimental animal feed samples fortified at 5 levels (7.5-400 ppm) with OTC or CTC.HCl and at 1 level (50 ppm) with the rest of the drugs, respectively, gave a limit of quantitation of 1.25 or 0.625 ppm, a recovery of 90.6 or 92.9%, and a coefficient of variation of 2.9-6.1 or 2.3-4.4%.

  18. Frost resistance of fibre reinforced concrete structures

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan De Place

    1999-01-01

    Frost resistance of fibre reinforced concrete with 2.5-4.2% air and 6-9% air (% by volume in fresh concrete) casted in the laboratory and in-situ is compared. Steel fibres with hooked ends (ZP, length 30 mm) and polypropylene fibres (PP, CS, length 12 mm) are applied. It is shown that· addition...... of 0.4-1% by volume of fibres cannot replace air entrainment in order to secure a frost resistant concrete; the minimum amount of air needed to make the concrete frost resistant is not changed when adding fibres· the amount of air entrainment must be increased when fibres are added to establish...

  19. Frost resistance of fibre reinforced concrete structures

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan De Place

    1999-01-01

    of 0.4-1% by volume of fibres cannot replace air entrainment in order to secure a frost resistant concrete; the minimum amount of air needed to make the concrete frost resistant is not changed when adding fibres· the amount of air entrainment must be increased when fibres are added to establish......Frost resistance of fibre reinforced concrete with 2.5-4.2% air and 6-9% air (% by volume in fresh concrete) casted in the laboratory and in-situ is compared. Steel fibres with hooked ends (ZP, length 30 mm) and polypropylene fibres (PP, CS, length 12 mm) are applied. It is shown that· addition...

  20. Power allocation and cooperative jamming for enhancing physical layer security in opportunistic relay networks in the presence of interference

    KAUST Repository

    Abd El-Malek, Ahmed H.

    2017-04-18

    In this paper, the impact of cochannel interference on the secrecy performance of dual-hop decode-and-forward relaying is investigated. In particular, the outage and intercept probabilities are obtained for the opportunistic relay selection (ORS) model in the presence of nonidentical interfering signals under a single/multiple passive eavesdropper(s) attack. Moreover, the proposed work enhances physical layer security performance of ORS model using cooperative jamming (CJ) techniques. Therefore, new closed-form expressions are derived for the intercept and outage probabilities of the CJ-ORS model in the presence of interference over Rayleigh fading channels. Moreover, the analyses are generalized to the case of multiple eavesdroppers where closed-form expressions are derived for the intercept probability. To reveal more insights on the proposed work secrecy performance, asymptotic closed-form expressions for the intercept and outage probabilities are obtained. Using these asymptotic expressions, a power allocation optimization problem is formulated and solved for enhancing the system security. The derived analytical formulas herein are supported by numerical and simulation results to clarify the main contributions of the paper. The results show that, although the cochannel interference increases the system outage probability, it might improve the system secrecy performance. Moreover, the proposed CJ-ORS model is shown to enhance the system secrecy performance compared to ORS model.

  1. Latest results from FROST at Jefferson Lab

    Directory of Open Access Journals (Sweden)

    Ritchie B.G.

    2014-06-01

    Full Text Available The spectrum of broad and overlapping nucleon excitations can be greatly clarified by use of a polarized photon beam incident on a polarized target in meson photoproduction experiments. At Jefferson Lab, a program of such measurements has made use of the Jefferson Lab FROzen Spin Target (FROST. An overview of preliminary results are presented.

  2. Masters of frost; Les maitres du verglas

    Energy Technology Data Exchange (ETDEWEB)

    Leblanc, J.

    2005-05-01

    Research at the University of Quebec at Chicoutimi, an internationally-ranked centre of excellence on research on hoar frost is discussed. Research currently in progress includes projects to characterize the nature of hoar frost on electrical equipment, projects to improve ways of predicting the occurrence of hoar frost, and projects to develop methods for de-icing electrical installations. Based on laboratory observations researchers prepare numerical models and by gaining a better understanding of the weather conditions in a region, they can deduce the probability of frost, and put in place precautionary measures that help to avoid the worst risks. The first type of problems concern the insulators: when first covered with ice they remain functional, but when the ice begins to melt the film of water is likely to conduct current and produce electric arcs. Other problems tend to be mechanical: e.g. the weight of ice on the wires, or asymmetric accumulation of ice, both of these could could cause the network to be dislodged. Projects involving the search for ways and means to de-ice long stretches of cables in winter in difficult-to-access terrain are also the subject of intense investigation.

  3. Latest results from FROST at Jefferson Lab

    Energy Technology Data Exchange (ETDEWEB)

    Ritchie, Barry G. [Arizona State University

    2014-06-01

    The spectrum of broad and overlapping nucleon excitations can be greatly clarified by use of a polarized photon beam incident on a polarized target in meson photoproduction experiments. At Jefferson Lab, a program of such measurements has made use of the Jefferson Lab FROzen Spin Target (FROST). An overview of preliminary results are presented.

  4. Air void structure and frost resistance

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange

    2014-01-01

    This article compiles results from 4 independent laboratory studies. In each study, the same type of concrete is tested at least 10 times, the air void structure being the only variable. For each concrete mix both air void analysis of the hardened concrete and a salt frost scaling test are conduc......This article compiles results from 4 independent laboratory studies. In each study, the same type of concrete is tested at least 10 times, the air void structure being the only variable. For each concrete mix both air void analysis of the hardened concrete and a salt frost scaling test...... is proportional to the product of total air content and specific surface. In all 4 cases, the conclusion is concurrent that the parameter of total surface area of air voids performs equally well or better than the spacing factor when linking air void characteristics to frost resistance (salt frost scaling......). This observation is interesting as the parameter of total surface area of air voids normally is not included in air void analysis. The following reason for the finding is suggested: In the air voids conditions are favourable for ice nucleation. When a capillary pore is connected to an air void, ice formation...

  5. A device for measuring soil frost

    Science.gov (United States)

    James H. Patric; Burley D. Fridley

    1969-01-01

    A water-filled plastic tube buried vertically in the soil in a copper casing permitted repeated observation of frost depth without damaging the sampling site. The device is simple and inexpensive and provides data on soil freezing at least as accurate as direct observation by digging through frozen soil.

  6. Robert Frost and the American College.

    Science.gov (United States)

    Newdick, Robert S.

    1999-01-01

    The life and works of poet Robert Frost are examined for insights into his philosophy concerning higher education, particularly formal education, his own style of teaching, perceptions of the teacher's role within and outside the classroom, and the relationship between student and teacher. (Originally published in 1936) (MSE)

  7. Robert Frost: Rural New England Teacher.

    Science.gov (United States)

    Hiss, Sheila M.

    1989-01-01

    Examines Robert Frost's teaching career, which lasted from 1893 to 1912. Discusses his extreme dislike of teaching, resulting in nervous exhaustion on several occasions, and his teaching innovations, which involved students writing about their own experiences and ideas, and reading aloud for expression and the sound of language. (SV)

  8. COMPARISON OF THE FROST RESISTANCE OF BARLEY ...

    African Journals Online (AJOL)

    Preferred Customer

    immediate recovery of the photosynthetic quantum yield after freezing. Landraces which showed the highest cold tolerance were found to acclimatize best. Key words/phrases: Barley, chlorophyll fluorescence, cold acclimation, Ethiopia, frost tolerance. INTRODUCTION. Barley (Hordeum vulgare L.) is a traditional crop.

  9. Influence of dispersants on aging and frost elastomeric compositions based on butadiene acrylonitrile rubbers

    Directory of Open Access Journals (Sweden)

    R. M. Dolinskaya

    2016-01-01

    Full Text Available The possibility of use of dispergators of various nature for production of rubber technical products with expanded temperature conditions of operation is studied. It is investigated influences of dispergators of Dispergator FL and INT 159 on properties of rubber mixes for receiving products with high resistance to thermal aging or frost resistance. Research of influence of modifiers was conducted for rubber mixes on the basis of butadienenitrile rubbers synthetic (BNRS-18 and BNRS-28. I’s established that at addition of a dispergator of Dispergator FL the indicator of relative deformatstion of compression (RDC and respectively heat stability of rubbers increases. Introduction to structure of elastomeric composition of a dispergator of INT 159 practically doesn’t influence frost resistance, and Dispergator FL worsens her (the coefficient of frost resistance decreases by 15.4–17.8%. Possibly it is connected with the fact that at the lowered temperatures in the presence of Dispergator FL there is a bigger delay of relaxation processes and decrease in energy of the thermal movement of links of macromolecules of rubbers. It becomes insufficient for overcoming of intermolecular interaction in the modified system and commission of conformational transitions of macromolecules under the influence of external loading. Mechanical energy is to a large extent mentioned not on change of a form of macromolecules, and on their mechanodestruction. However, it increases heat stability since it that is higher, than molecular mobility is lower. INT 159 dispergator components, settling down on borders of supramolecular formations of elastomers, increase mobility of links of macromolecules of rubbers, weaken chemical bonds in them, reduce thermal stability, but at the same time INT 159 dispergator practically doesn’t reduce frost resistance therefore it is expedient to apply it when receiving frost-resistant elastomeric composition. Thus, when receiving

  10. Use of Computational Fluid Dynamics for improvement of Balloon Borne Frost Point Hygrometer

    Science.gov (United States)

    Jorge, Teresa; Brunamonti, Simone; Wienhold, Frank G.; Peter, Thomas

    2017-04-01

    In the StratoClim 2016 Balloon Campaign in Nainital (India) during the Asian Summer Monsoon, balloon born payloads containing the EN-SCI CFH - Cryogenic Frost point Hygrometer - were flown to observe water vapor and cloud formation processes in the Upper Troposphere and Lower Stratosphere. Some of the recorded atmospheric water vapor profiles showed unexpected values above the tropopause and were considered contaminated. To interpret these contaminated results and in the scope of the development of a new frost point hygrometer - the Peltier Cooled Frost point Hygrometer (PCFH) - computational fluid dynamic (CFD) simulations with ANSYS Fluent software have been carried out. These simulations incorporate the fluid and thermodynamic characteristics of stratospheric air to predict airflow in the inlet tube of the instrument. An ice wall boundary layer based on the Murphy and Koop 2005 ice-vapor parametrization was created as a cause of the unexpected water vapor. Sensitivity was tested in relation to the CFD mesh, ice wall surface, inlet flow, inlet tube dimension, sensor head location and variation of atmospheric conditions. The development of the PCFH uses the results of this study and other computational fluid dynamic studies concerning the whole instrument boundary layer and heat exchanger design to improve on previous realizations of frost point hygrometers. As a novelty in the field of frost point hygrometry, Optimal Control Theory will be used to optimize the cooling of the mirror by the Peltier element, which will be described in a physical "plant model", since the cooling capacity of a cryogenic liquid will no longer be available in the new instrument.

  11. Presence of a glycine-cysteine-rich beta-protein in the oberhautchen layer of snake epidermis marks the formation of the shedding layer.

    Science.gov (United States)

    Alibardi, Lorenzo

    2014-11-01

    The complex differentiation of snake epidermis largely depends on the variation in the production of glycine-cysteine-rich versus glycine-rich beta-proteins (beta-keratins) that are deposited on a framework of alpha-keratins. The knowledge of the amino acid sequences of beta-proteins in the snake Pantherophis guttatus has allowed the localization of a glycine-cysteine-rich beta-protein in the spinulated oberhautchen layer of the differentiating shedding complex before molting takes place. This protein decreases in the beta-layer and disappears in mesos and alpha-layers. Conversely, while the mRNA for a glycine-rich beta-protein is highly expressed in differentiating beta-cells, the immunolocalization for this protein is low in these cells. This discrepancy between expression and localization suggests that the epitope in glycine-rich beta-proteins is cleaved or modified by posttranslational processes that take place during the differentiation and maturation of the beta-layer. The present study suggests that among the numerous beta-proteins coded in the snake genome to produce epidermal layers with different textures, the glycine-cysteine-rich beta-protein marks the shedding complex formed between alpha- and beta-layers that allows for molting while its disappearance between the beta- and alpha-layers (mesos region for scale growth) is connected to the formation of the alpha-layers.

  12. Frost flower chemical signature in winter snow on Vestfonna ice cap, Nordaustlandet, Svalbard

    Directory of Open Access Journals (Sweden)

    E. Beaudon

    2009-07-01

    Full Text Available The chemistry of snow and ice cores from Svalbard is influenced by variations in local sea ice margin and distance to open water. Snow pits sampled at two summits of Vestfonna ice cap (Nordaustlandet, Svalbard, exhibit spatially heterogeneous soluble ions concentrations despite similar accumulation rates, reflecting the importance of small-scale weather patterns on this island ice cap. The snow pack on the western summit shows higher average values of marine ions and a winter snow layer that is relatively depleted in sulphate. One part of the winter snow pack exhibits a [SO42-/Na+] ratio reduced by two thirds compared with its ratio in sea water. This low sulphate content in winter snow is interpreted as the signature of frost flowers, which are formed on young sea ice when offshore winds predominate. Frost flowers have been described as the dominant source of sea salt to aerosol and precipitation in ice cores in coastal Antarctica but this is the first time their chemical signal has been described in the Arctic. The eastern summit does not show any frost flower signature and we interpret the unusually dynamic ice transport and rapid formation of thin ice on the Hinlopen Strait as the source of the frost flowers.

  13. Frost-proof heat recovery; Frostsikker varmegjenvinning

    Energy Technology Data Exchange (ETDEWEB)

    Groenbaek, Henning; Jenssen, Henning Bent

    2011-07-01

    Technical regulations (TEK10) sets high standards for temperature efficiency of ventilation systems. Heat recovery equipment should be selected from the risk of leakage. Rotating heat exchanger has normally no problem with icing before the temperature approaches -20 C. For the countercurrent heat exchanger bypass-icing is the best method of frost resistant heat exchanger. In addition to selecting the best frost protection method, it is also important how to monitor the formation of ice in the exchanger. The best way is to measure the pressure drop over the heat exchanger. Bypass deicing requires that the unit is designed so that outside air can be led outside heat exchanger and directly to the heater. (AG)

  14. On Medicine and Boundaries: Frost's Mending Wall.

    Science.gov (United States)

    Perlow, Gabriel L; Furman, Andrew C

    2017-07-01

    Published just over a century ago, Robert Frost's Mending Wall stands as one of the most eloquent meditations on boundaries and the complex and nuanced role they play in interpersonal relationships. Often anthologized, and perhaps as often misunderstood, Mending Wall has much to teach medical educators and practicing clinicians about the physician-patient relationship and the evolving dynamic between healer and patient. Remembered mostly for the seemingly contradictory repetition of the adage "Good fences make good neighbors," and the opening "something there is that doesn't love a wall," Frost mischievously navigates through the many meanings and functions of boundaries; how they separate, unite, and ultimately, how they might mend. Mending Wall offers physicians an opportunity to look closely at the barriers and thresholds prevalent in medicine and explore how they both preclude and allow for intimate and healing relationships.

  15. An analytical model for dispersion of material in the atmospheric planetary boundary layer in presence of precipitation

    International Nuclear Information System (INIS)

    Mayhoub, A.B.; Etman, S.M.

    1985-05-01

    An analytical model for the dispersion of particulates and finely divided material released into the atmosphere near the ground is presented. The possible precipitation when the particles are dense enough and large enough to have deposition velocity, is taken into consideration. The model is derived analytically in the mixing layer or Ekman boundary layer where the mixing process is a direct consequence of turbulent and convective motions generated in the boundary layer. (author)

  16. Analysis and Simulation of Frost's Beamformer

    OpenAIRE

    Strupl, M.; Sovka, Pavel

    2003-01-01

    Sensor arrays are often used for a signal separation from noises using the information about the direction of arrival. The aim of this paper is to analyze Frost's beamformer with respect to the speech preprocessing for the hearing impaired people. The frequency response of the system including the background noise attenuation are derived as functions of the direction of arrival. The derivation supposes a uniform linear array of sensors and plane waves. It is shown that the number of possible ...

  17. Genetic engineering: frost damage trial halted.

    Science.gov (United States)

    Budiansky, S

    The University of California at Berkeley has announced the postponement of a planned experiment involving the field testing of bacteria genetically engineered to reduce frost damage to crops. The action came after Jeremy Rifkin, who had earlier filed suit against the National Institutes of Health after its Recombinant DNA Advisory Committee had approved the experiment, threatened to seek a temporary restraining order against the university to halt the experiment.

  18. Frost heave and pipeline upheaval buckling

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, A. C. [University Engineering Department, Cambridge (United Kingdom); Williams, P. J. [Carleton Univ., Geotechnical Science Laboratories, Ottawa, ON (Canada)

    2003-10-01

    The interaction between frost heave and upheaval buckling and the potential effect of these two phenomena on the safety of Arctic pipelines is discussed. When soils freeze, ice forms within the pores between the particles. If the surface is free to move, it heaves, because of the expansion that accompanies freezing. Upheaval buckling occurs in longitudinally constrained buried pipelines which can lead to large upward movements of a pipeline. The driving force for upheaval is the longitudinal compressive force induced by operation of the pipeline. While uniform vertical movement does not affect functionality, movements that induce curvature can overstress a pipeline to a dangerous extent. This paper examines the adverse interaction between the longitudinal variability of frost heave and the propensity of heave-induced overbends, and the conditions under which they might lead to upheaval. Results obtained suggest that discontinuities in frost heave can be sufficient to destabilize a high-pressure pipeline and induce upheaval, even when the original 'as-laid' profile is perfectly straight and level. The heave is most likely to occur in winter, with the upheaval following in the summer when the operating temperature is higher and the uplift resistance is reduced. 27 refs., 2 figs.

  19. Frost heave modelling using porosity rate function

    Science.gov (United States)

    Michalowski, Radoslaw L.; Zhu, Ming

    2006-07-01

    Frost-susceptible soils are characterized by their sensitivity to freezing that is manifested in heaving of the ground surface. While significant contributions to explaining the nature of frost heave in soils were published in late 1920s, modelling efforts did not start until decades later. Several models describing the heaving process have been developed in the past, but none of them has been generally accepted as a tool in engineering applications. The approach explored in this paper is based on the concept of the porosity rate function dependent on two primary material parameters: the maximum rate, and the temperature at which the maximum rate occurs. The porosity rate is indicative of ice growth, and this growth is also dependent on the temperature gradient and the stress state in the freezing soil. The advantage of this approach over earlier models stems from a formulation consistent with continuum mechanics that makes it possible to generalize the model to arbitrary three-dimensional processes, and use the standard numerical techniques in solving boundary value problems. The physical premise for the model is discussed first, and the development of the constitutive model is outlined. The model is implemented in a 2-D finite element code, and the porosity rate function is calibrated and validated. Effectiveness of the model is then illustrated in an example of freezing of a vertical cut in frost-susceptible soil.

  20. Frost Multidimensional Perfectionism Scale: the portuguese version

    Directory of Open Access Journals (Sweden)

    Ana Paula Monteiro Amaral

    2013-01-01

    Full Text Available BACKGROUND: The Frost Multidimensional Perfectionism Scale is one of the most world widely used measures of perfectionism. OBJECTIVE: To analyze the psychometric properties of the Portuguese version of the Frost Multidimensional Perfectionism Scale. METHODS: Two hundred and seventeen (178 females students from two Portuguese Universities filled in the scale, and a subgroup (n = 166 completed a retest with a four weeks interval. RESULTS: The scale reliability was good (Cronbach alpha = .857. Corrected item-total correlations ranged from .019 to .548. The scale test-retest reliability suggested a good temporal stability with a test-retest correlation of .765. A principal component analysis with Varimax rotation was performed and based on the Scree plot, two robust factorial structures were found (four and six factors. The principal component analyses, using Monte Carlo PCA for parallel analyses confirmed the six factor solution. The concurrent validity with Hewitt and Flett MPS was high, as well as the discriminant validity of positive and negative affect (Profile of Mood Stats-POMS. DISCUSSION: The two factorial structures (of four and six dimensions of the Portuguese version of Frost Multidimensional Perfectionism Scale replicate the results from different authors, with different samples and cultures. This suggests this scale is a robust instrument to assess perfectionism, in several clinical and research settings as well as in transcultural studies.

  1. The periglacial engine of mountain erosion – Part 1: Rates of frost cracking and frost creep

    DEFF Research Database (Denmark)

    Andersen, Jane Lund; Egholm, David Lundbek; Knudsen, Mads Faurschou

    2015-01-01

    of the soil mantle strongly modulates the relation between climate and the intensity of mechanical weathering and sediment flux. Our results also point to an offset between the conditions that promote frost cracking and those that promote frost creep, indicating that a stable climate can provide optimal....... Here we investigate the important role that periglacial processes also play in less steep parts of mountain landscapes. Understanding the influences of frost-driven processes in low-relief areas requires a focus on the consequences of an accreting soil mantle, which characterises such surfaces. We......With accelerating climate cooling in the late Cenozoic, glacial and periglacial erosion became more widespread on the surface of the Earth. The resultant shift in erosion patterns significantly changed the large-scale morphology of many mountain ranges worldwide. Whereas the glacial fingerprint...

  2. Changes in phenology and frost risks of

    Directory of Open Access Journals (Sweden)

    Thomas Kartschall

    2015-04-01

    Full Text Available For a retrospective period of 110 years between 1901 and 2010 (observed data, and for the subsequent future period between 2011 and 2100 we calculated the phenological development (bud burst, harvest ripeness, and in particular the spring frost risk (frost after bud burst, as one important derived variable for grapevine (Vitis vinifera L. cv Riesling for the whole of Germany. For the future climate we included two different scenarios (RCP8.5, RCP2.6 each of them containing a triple set with minimum, medium and maximum temperature increase. The time period between 1981 and 2010 as the last three decades in the observed data was chosen as reference. In general we found an acceleration of the phenological development (all main phases mainly beginning in the late 1980s. For the three-decade period between 2031 and 2060 this acceleration will reach 11±3$11\\pm3$ days in the RCP8.5-scenario. The acceleration for the other stages behaved similarly and results in an earlier harvest ripeness of 13±1$13\\pm1$ days. Since a warmer spring in general leads to earlier bud burst, but does not reduce the risk of frost events during this period in the same manner, changes in the risk of spring frost damage were relatively small. For the coming decades this risk will not decrease for all traditional German viticultural regions in the RCP8.5-scenarios; on the contrary, our results suggest it is likely to increase. The results showed an increasing spring frost risk not only for the debated “upcoming” potential viticultural areas in eastern Germany, an effect which will partly also reach the southernmost viticultural areas. This effect in northern and eastern Germany is due to earlier bud burst together with the stronger continental influence, but for the southern and western regions of Germany is mainly due to the even earlier bud burst. This could modify the regionally nuanced character of German wines.

  3. The periglacial engine of mountain erosion – Part 1: Rates of frost cracking and frost creep

    Directory of Open Access Journals (Sweden)

    J. L. Andersen

    2015-10-01

    Full Text Available With accelerating climate cooling in the late Cenozoic, glacial and periglacial erosion became more widespread on the surface of the Earth. The resultant shift in erosion patterns significantly changed the large-scale morphology of many mountain ranges worldwide. Whereas the glacial fingerprint is easily distinguished by its characteristic fjords and U-shaped valleys, the periglacial fingerprint is more subtle but potentially prevails in some mid- to high-latitude landscapes. Previous models have advocated a frost-driven control on debris production at steep headwalls and glacial valley sides. Here we investigate the important role that periglacial processes also play in less steep parts of mountain landscapes. Understanding the influences of frost-driven processes in low-relief areas requires a focus on the consequences of an accreting soil mantle, which characterises such surfaces. We present a new model that quantifies two key physical processes: frost cracking and frost creep, as a function of both temperature and sediment thickness. Our results yield new insights into how climate and sediment transport properties combine to scale the intensity of periglacial processes. The thickness of the soil mantle strongly modulates the relation between climate and the intensity of mechanical weathering and sediment flux. Our results also point to an offset between the conditions that promote frost cracking and those that promote frost creep, indicating that a stable climate can provide optimal conditions for only one of those processes at a time. Finally, quantifying these relations also opens up the possibility of including periglacial processes in large-scale, long-term landscape evolution models, as demonstrated in a companion paper.

  4. Aromatic structure degradation of single layer graphene on an amorphous silicon substrate in the presence of water, hydrogen and Extreme Ultraviolet light

    NARCIS (Netherlands)

    Mund, Baibhav Kumar; Sturm, J.M.; Lee, Christopher James; Bijkerk, Frederik

    2018-01-01

    In this paper we study the reaction of water and graphene under Extreme Ultraviolet (EUV) irradiation and in the presence of hydrogen. In this work, single layer graphene (SLG) on amorphous Si as an underlying substrate was dosed with water (0.75 ML) and exposed to EUV (λ = 13.5 nm, 92 eV) with

  5. Laboratory evaluation of the effect of nitric acid uptake on frost point hygrometer performance

    Directory of Open Access Journals (Sweden)

    T. Thornberry

    2011-02-01

    Full Text Available Chilled mirror hygrometers (CMH are widely used to measure water vapour in the troposphere and lower stratosphere from balloon-borne sondes. Systematic discrepancies among in situ water vapour instruments have been observed at low water vapour mixing ratios (<5 ppm in the upper troposphere and lower stratosphere (UT/LS. Understanding the source of the measurement discrepancies is important for a more accurate and reliable determination of water vapour abundance in this region. We have conducted a laboratory study to investigate the potential interference of gas-phase nitric acid (HNO3 with the measurement of frost point temperature, and consequently the water vapour mixing ratio, determined by CMH under conditions representative of operation in the UT/LS. No detectable interference in the measured frost point temperature was found for HNO3 mixing ratios of up to 4 ppb for exposure times up to 150 min. HNO3 was observed to co-condense on the mirror frost, with the adsorbed mass increasing linearly with time at constant exposure levels. Over the duration of a typical balloon sonde ascent (90–120 min, the maximum accumulated HNO3 amounts were comparable to monolayer coverage of the geometric mirror surface area, which corresponds to only a small fraction of the actual frost layer surface area. This small amount of co-condensed HNO3 is consistent with the observed lack of HNO3 interference in the frost point measurement because the CMH utilizes significant reductions (>10% in surface reflectivity by the condensate to determine H2O.

  6. Frost formation on a plate with different surface hydrophilicity

    Energy Technology Data Exchange (ETDEWEB)

    Hyunuk Lee; Jongmin Shin; Samchul Ha; Bongjun Choi [Digital Appliance Co. Research Lab., L G Electronics Inc., Changwon, Kyoungnam (Korea); Jaekeun Lee

    2004-10-01

    The objectives of this study are to develop frost maps for two different surfaces having two different hydrophilic characteristics and to find ambient conditions associated with the formation of frost structures. Test samples with two different surfaces having dynamic contact angle (DCA) of 23{sup o} and 88{sup o} were installed in a wind tunnel and exposed to a humid airflow. Frost structure is observed with a visualization system in the operating conditions of household refrigerator: airflow temperature in the range of 20 {sup o}C, humidity in the range of 2.64-9.36 g/kg, Reynolds number in the range of 7000-17,000 and cold plate temperature in the range of -11.6 to -28.4 {sup o}C. As a result of this study, frost structures are classified and frost maps are proposed for two different surface hydrophilicities. Surface with low DCA (23{sup o}) shows lower frost thickness and higher frost density than that with high DCA (88{sup o}). It was found that frost structures on surfaces with different DCA are similar. However, low DCA surface at low humidity provides 20-30% denser frost formation due to the shift of areas with different structures. (Author)

  7. Enceladus' near-surface CO2 gas pockets and surface frost deposits

    Science.gov (United States)

    Matson, Dennis L.; Davies, Ashley Gerard; Johnson, Torrence V.; Combe, Jean-Philippe; McCord, Thomas B.; Radebaugh, Jani; Singh, Sandeep

    2018-03-01

    Solid CO2 surface deposits were reported in Enceladus' South Polar Region by Brown et al. (2006). They noted that such volatile deposits are temporary and posited ongoing replenishment. We present a model for this replenishment by expanding on the Matson et al. (2012) model of subsurface heat and chemical transport in Enceladus. Our model explains the distributions of both CO2 frost and complexed CO2 clathrate hydrate as seen in the Cassini Visual and Infrared Mapping Spectrometer (VIMS) data. We trace the journey of CO2 from a subsurface ocean. The ocean-water circulation model of Matson et al. (2012) brings water up to near the surface where gas exsolves to form bubbles. Some of the CO2 bubbles are trapped and form pockets of gas in recesses at the bottom of the uppermost ice layer. When fissures break open these pockets, the CO2 gas is vented. Gas pocket venting is episodic compared to the more or less continuous eruptive plumes, emanating from the "tiger stripes", that are supported by plume chambers. Two styles of gas pocket venting are considered: (1) seeps, and (2) blowouts. The presence of CO2 frost patches suggests that the pocket gas slowly seeped through fractured, cold ice and when some of the gas reached the surface it was cold enough to condense (i.e., T ∼70 to ∼119 K). If the fissure opening is large, a blowout occurs. The rapid escape of gas and drop in pocket pressure causes water in the pocket to boil and create many small aerosol droplets of seawater. These may be carried along by the erupting gas. Electrically charged droplets can couple to the magnetosphere, and be dragged away from Enceladus. Most of the CO2 blowout gas escapes from Enceladus and the remainder is distributed globally. However, CO2 trapped in a clathrate structure does not escape. It is much heavier and slower moving than the CO2 gas. Its motion is ballistic and has an average range of about 17 km. Thus, it contributes to deposits in the vicinity of the vent. Local heat

  8. Grammatical Categories in Robert Frost's Blank Verse: A Quantitative Analysis.

    Science.gov (United States)

    Lyford, Roland Hazen

    Structural linguistic techniques were utilized to categorize the grammatical elements employed by Robert Frost in 46 blank-verse poems. Nineteen main grammatical categories and 26 verb sub-categories based on distinctive selection criteria were devised to examine the range and distribution of Frost's grammatical patterns. Five control poems by E.…

  9. Frost hardiness of tree species is independent of phenology and ...

    Indian Academy of Sciences (India)

    The differences in timing in bud burst between species have been interpreted as an adaptation to late frost events in spring. Thus, it has been suggested that the degree of frost susceptibility of leaves is species-specific and depends on the species' phenology and geographic distribution range. To test for relationships ...

  10. The distribution of water frost on Charon

    Science.gov (United States)

    Buie, Marc W.; Shriver, Scott K.

    1994-01-01

    We present high-spatial-resolution imaging observations of the Pluto-Charon system taken with ProtoCAM on the Infrared Telescope Facility (IRTF). Our dataset consists of measurements from eight nights at widely separated rotational longitudes and covering five wavelengths -- standard J, H, and K, plus two special narrow band filters at 1.5 and 1.75 microns. The relative flux contributions of Pluto and Charon were extracted, when possible, by fitting a two-source Gaussian image model to the observed images. At K, we find the Charon-Pluto magnitude difference to be on average 1.8 mag, somewhat less than the value of 2.2 mag found by Bosh et al. (1992). The average differential magnitude at 1.5 and 1.75 microns is 2.0 and 1.6, respectively. The larger magnitude difference at 1.5 microns is due to a water-frost absorption band on the surface of Charon. Our observations are consistent with a surface of Charon dominated by water frost at all longitudes.

  11. Mathematical modeling of heat transfer between the plant seedling and the environment during a radiation frost

    Directory of Open Access Journals (Sweden)

    Finnikov K.A.

    2010-11-01

    Full Text Available The power of the internal heat source sufficient to maintain a positive temperature of plants during one of the possible form of cold stress - radiation frost was determined with the help of numerical simulation.The simulation of unsteady heat transfer in the soil-plant-air system in the conditions of radiation frost showed that the the ground part of plants is cooling most rapidly, and this process is partially slowed down by the natural-convection heat transfer with warmer air. If the frost is not continuous, the radiative cooling is the main danger for plant. The necessary power of heat-production inside plant that allows it to avoid hypothermia depends both on natural conditions and the size of the plant. For plants with a typical diameter of the stem about 2 mm this heat-production should be from 50 to 100 W / kg. Within 2 hours a total amount of heat about 0.5 MJ / kg in the plant should be allocated. Larger plants will have a smaller surface to mass ratio, and the maintaining of it's temperature will require a lower cost of nutrients per unit, accordingly. Modeling of the influence of plant surface trichomes presence on the process of its cooling showed that the role of trichomes in the protection of plants from hypothermia during radiation frost usually is negative due to the fact that the presence of trichomes increases the radiative heat transfer from the plant and the impediment in air movement near the plant reduces heat flux entering the plant from a warmer air. But in cases where the intensity of heat generation within the plant is sufficient for the maintenance of the plant temperature higher than the air temperature, the presence of trichomes impairs heat transfer from plant to air, and therefore contributes to a better heating of plants.

  12. Transmission line corona losses under hoar frost conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lahti, K.; Nousiainen, K. [Tampere Univ. of Technology (Finland). Power Engineering Group; Lahtinen, M.

    1997-04-01

    Transmission line corona losses under hoar frost conditions were studied in the climate room of the high voltage laboratory of Tampere University of Technology. The measurements were performed using a coaxial measurement arrangement with different bundle and conductor types. The effects of conductor and bundle type, temperature, applied voltage and hoar frost thickness on corona losses were investigated. A two-conductor bundle had corona losses about 2.5--5 times higher than a three-conductor bundle. Relatively thin hoar frosts were used in the tests. Even the thinnest hoar frost resulted in remarkable corona losses and the losses were very sensitive to changes in the hoar frost thickness. The ambient temperature had a strong influence on the measured losses.

  13. Effect of frost on phosphorescence for thermographic phosphor thermometry

    Science.gov (United States)

    Kim, Dong; Kim, Mirae; Kim, Kyung Chun

    2017-12-01

    In this study, we analyzed phosphorescence lifetime and its accuracy by growing frost for thermographic phosphor thermometry in a low-temperature environment. Mg4FGeO6:Mn particles were coated on an aluminum plate and excited with a UV-LED to obtain phosphorescence signals. The surface temperature was maintained at  ‑20, ‑15, ‑10 °C, and the phosphorescence signal was acquired as the frost grew for 3700 s. The lifetime was calculated and compared with the calibration curve under no-frost conditions. The error of the measured lifetime was within 0.7% of that in the no-frost conditions. A 2D surface temperature profile of the target plate was successfully obtained with the frost formation.

  14. Embryonic myocardium shows increased longevity as a functional tissue when cultured in the presence of a noncardiac tissue layer.

    Science.gov (United States)

    Eisenberg, Leonard M; Eisenberg, Carol A

    2006-04-01

    A major aim of regenerative medicine is the construction of bioengineered organs and tissue for transplantation into human patients; yet living tissue is dynamic, and thus arranging cellular and extracellular constituents into an architecture resembling normal adult organs may not be sufficient to maintain tissue stability. In this study, we used cultures of embryonic chick heart tissue as a model to explore how newly formed cardiac tissue constructs can sustain their morphological structure and functional capabilities over extended periods. During the initial days of incubation, embryonic cardiac explants will thrive as beating three-dimensional tissue aggregates. However, within the first week of culture, cardiac aggregates lose their contractile function and flatten. After 2 weeks of incubation, the cardiac cells will have spread out into a homogeneous monolayer and dedifferentiated to a noncardiac phenotype. In contrast, when the embryonic heart tissue was co-cultured with a noncardiac cell layer obtained from adult bone marrow, the cardiac aggregates maintained their contractile function, three-dimensional tissue morphology, and myocyte phenotype for a full month of incubation. The capacity of this noncardiac cell layer to sustain the phenotype and morphology of the cardiac explants was partially replicated by treatment of the heart tissue with conditioned media from bone marrow cells. These findings are discussed in regard to the importance of adjacent cell layers for facilitating organogenesis in the developing embryo and having potential utility in producing stable bioengineered tissue constructs.

  15. Changes in frost days in simulations of twentyfirst century climate

    Energy Technology Data Exchange (ETDEWEB)

    Meehl, G.A.; Tebaldi, C.; Nychka, D. [National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307 (United States)

    2004-10-01

    Global coupled climate model simulations of twentieth and twentyfirst century climate are analyzed for changes in frost days (defined as nighttime minima less than freezing). The model simulations agree with the observed pattern for late twentieth century of a greater decrease of frost days in the west and southwest USA compared to the rest of the country, and almost no change in frost days in fall compared to relatively larger decreases in spring. Associated with general increases of nighttime minimum temperatures, in the future climate with increased greenhouse gases (GHGs) the number of frost days is fewer almost everywhere, but there are greatest decreases over the western parts of the continents. The numbers of frost days are most consistently related to sea level pressure, with more frost days occurring when high pressure dominates on the monthly time scale in association with clearer skies and lower nighttime minimum temperatures. Spatial patterns of relative changes of frost days are indicative of regional scale atmospheric circulation changes that affect nighttime minimum temperatures. Increases of soil moisture and clouds also contribute, but play secondary roles. The linkages among soil moisture, clouds, sea level pressure, and diurnal temperature range are quantified by a statistical multiple regression model. Coefficients for present and future climate are similar among the predictors, indicating physical processes that affect frost days in present and future climates do not appreciably change. Only the intercept changes in association with the significant warming of the mean climate state. This study highlights the fact that, though there is a general decrease in the number of frost days with global warming, the processes that affect the pattern of those changes, and thus the regional changes of frost days, are influenced by several interrelated physical processes, with changes in regional atmospheric circulation generally being most important. (orig.)

  16. Voltammetric Determination of Acetaminophen in the Presence of Codeine and Ascorbic Acid at Layer-by-Layer MWCNT/Hydroquinone Sulfonic Acid-Overoxidized Polypyrrole Modified Glassy Carbon Electrode

    OpenAIRE

    Shahrokhian, Saeed; Saberi, Reyhaneh-Sadat

    2011-01-01

    A very sensitive electrochemical sensor constructed of a glassy carbon electrode modified with a layer-by-layer MWCNT/doped-overoxidized polypyrrole (oppy/MWCNT /GCE) was used for the determination of acetaminophen (AC) in the presence of codeine and ascorbic acid (AA). In comparison to the bare glassy carbon electrode, a considerable shift in the peak potential together with an increase in the peak current was observed for AC on the surface of oppy/MWCNT/GCE, which can be related to the enla...

  17. Part 2. State of the art paper on frost heave : a review of frost heave theory and models

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2005-07-01

    This technical review for a proposed pipeline in the Mackenzie Valley in the Northwest Territories represents the first of 3 reports that document the current state of knowledge about frost heave theory, testing and predictive modelling. The review considers whether frost heave is sufficiently understood and can be controlled to allow for the safe construction and operation of a large diameter chilled gas pipeline. It provides a complete review of frost heavy theory, prediction models acquisition of input data for prediction models, validation of theory and models by laboratory experiments. Details on most of the significant models and experiments were presented on small scale frost heave experiments for northern pipeline design and operation, frost heave prediction models, and frost heave prediction models for buried chilled gas pipelines. The most recent developments applicable to chilled pipelines include the discrete ice lens model, the 2 dimensional rigid ice model, and the development of a 3 dimensional hydrodynamic model. The authors noted that a comprehensive analysis of the pipeline/frost heave problem should consider coupled heat flow and moisture transport in frozen and unfrozen soils; mechanical behaviour of unfrozen soil; moving boundary challenges associated with a moving freezing front and frost heave; growth of pore ice and ice lenses; mechanical behavior of the buried pipe; and pipeline-soil interface behaviour. The other 2 accompanying reports have also been catalogued separately for inclusion in this database. refs., tabs., figs.

  18. A Field and Laboratory Based Assessment of the Potential of High Frequency Ground Penetrating Radar (HFGPR) to Evaluate the Presence and Spatial Variabilty of Hydrophobic Soil Layers

    Science.gov (United States)

    Weirich, F. H.; Neumann, W.; Campbell, D.

    2017-12-01

    The presence of fire related hydrophobic (water repellant) soil layers in a wide range of environmental settings can result in greatly increased rates of storm runoff and erosion. In many situations this can contribute to the generation of debris and/or hyperconcentrated flows. While the role of hydrophobic soils in greatly increasing sediment production in such situations is known, the ability to predict the volume of sediment that will be generated by specific storm events has been limited, in part, by limits on the ability to assess the characteristics of hydrophobic soil layers. At present, the most widely accepted method of assessing the presence, strength, extent and persistence of hydrophobic soil layers requires the performance of an in situ water drop penetration test (WDPT). This approach, while effective on a local site, is labor and time intensive and can be difficult to employ on a watershed or even slope wide basis. As part of a wider research effort to develop more effective methods of evaluating the characteristics of hydrophobic soils a combined field and laboratory based program has been undertaken to evaluate the capability of higher frequency ground penetrating radar (HFGPR) to detect and map out the spatial extent, strength, and persistence of hydrophobic soil layers. This has involved the testing of HFGPR systems at several field site in burnt watersheds in Southern California as well as a program of laboratory tests on samples of fire impacted soils collected from the same watersheds. The field tests were undertaken on sites ranging from a location that had burnt a few weeks earlier to locations where over 5 years had passed since a burn took place. Laboratory samples of soils were taken from the same range of sites and used in the laboratory tests. In parallel with the HFGPR testing WDPT's were used to confirm the findings of the HFGPR approach. Both the field and laboratory results indicate that the use of HFGPR, under appropriate soil

  19. Long-term water absorption tests for frost insulation materials taking into account frost attack

    Directory of Open Access Journals (Sweden)

    Toni A. Pakkala

    2014-01-01

    Full Text Available Water absorption of several different frost insulation materials was tested for four years. The test took into account both immersion and frost attack to materials. On the basis of the research the water absorption on XPS specimens is significantly minor compared to EPS specimens that were studied. The most significant result was that freezing of test specimens did not affect on water absorption of XPS specimens but had a major effect on water absorption of EPS specimens. With frozen EPS specimen the absorption continued increasing even after 48 months of immersion. Presumably the reason for such a behaviour is that the pore structure of EPS is not able to resist the tension caused by freezing water and therefore cracks are formed. Thus, more water absorbs inside the EPS through the cracks and it causes cracking deeper in the specimen which is why absorption increases after every freezing period.

  20. Numerical heat transfer model for frost protection of citrus fruits by water from a spraying system

    Directory of Open Access Journals (Sweden)

    Issa Roy J.

    2012-01-01

    Full Text Available A simplified model is developed to simulate the conditions associated with the protection of fruits from frost damage using water from a spraying system. The model simulates the movement of the solidifying water front on a single fruit, and based on that determines the spray frequency needed for a water film to continuously surround the ice-coated fruit to prevent the fruit temperature from dropping below 0ºC. Simulations are presented for the frost protection of sweet oranges (citrus sinensis. The effect of environmental conditions such as air temperature, air velocity, surface radiation and water film evaporation on the development of the ice layer encasing is considered. Simulations show the effect the encasing ice sheet thickness has on the fruit temperature if water from a spraying system is turned off permanently. Experimental tests are also conducted to determine the change in the thermal properties of citrus sinensis for operating temperatures that range from above freezing to sub-freezing. The results of the experimental tests and the numerical simulations shall lead to a better understanding of fruit protection from frost damage by the application of water from a spraying system.

  1. Experimental and Theoretical Investigations on Frost Heave in Porous Media

    Directory of Open Access Journals (Sweden)

    Feng Ming

    2015-01-01

    Full Text Available For the construction in cold regions, frost heave and thaw settlement are the two factors which must be taken care of. Considered that a saturated soil column was subjected to an overburden pressure to model the ice lens growing process. A typical process, which coupled water, heat, and stress that happened in a saturated freezing soil column, was simulated by the finite element software. We did the numerical simulation under the same conditions as the experiment tests and then compared the results from temperature, frost heave, frozen structure, water content, and water intake. Result shows that the simulation results match well with the experimental results, and the correctness of the mathematical model is validated. On that basis, frost heave amount under different conditions by changing the temperature boundary and loading boundary is obtained. The frost heave has an optimum temperature gradient. Under the optimum value, the frost heave amount increases with increasing temperature gradient. Above the optimum value, frost heave decreases with increasing temperature gradient. Increasing the overburden pressure, frost heave amount always decreases. These results can provide references for the constrictions in cold regions.

  2. [Infrared spectroscopic analysis of Guilin watermelon frost products].

    Science.gov (United States)

    Huang, Dong-lan; Chen, Xiao-kang; Xu, Yong-qun; Sun, Su-qin; Zhou, Qun; Lu, Wen-guan

    2012-08-01

    The objective of the present study is to analyze different products of Guilin watermelon frost by Fourier transform infrared spectroscopy (FTIR), second derivative infrared spectroscopy and two-dimensional correlation spectroscopy (2D-IR) under thermal perturbation. The structural information of the samples indicates that samples from the same factory but of different brands had some dissimilarities in the IR spectra, and the type and content of accessories of them were different compared with conventional IR spectra of samples, peaks at 638 and 616 cm(-1) all arise from anhydrous sodium sulfate in watermelon frost spray and watermelon frost capsule; the characteristic absorption peaks of the sucrose, dextrin or other accessories can be seen clearly in the spectra of watermelon frost throat-clearing buccal tablets, watermelon frost throat tablets and watermelon frost lozenge. And the IR spectra of watermelon frost lozenge is very similar to the IR spectra of sucrose, so it can be easily proved that the content of sucrose in watermelon frost lozenge is high. In the 2D-IR correlation spectra, the samples presented the differences in the position, number and relative intensity of autopeaks and correlation peak clusters. Consequently, the macroscopical fingerprint characters of FTIR, second derivative infrared spectra and 2D-IR spectra can not only provide the information about main chemical constituents in medical materials, but also analyze and identify the type and content of accessories in Guilin watermelon frost. In conclusion, the multi-steps IR macro-fingerprint method is rapid, effective, visual and accurate for pharmaceutical research.

  3. Morphological and genetic perspectives of peach fruit responses to spring frost

    Science.gov (United States)

    Spring frost is one of the most unpredictable cropping factors in many peach production areas. A severe spring frost can wipe out an entire peach crop whereas a mild spring frost may naturally help thinning as is common practice in commercial peach production. The extent of frost damage depends on t...

  4. Cross-Layer Measurement on an IEEE 802.11g Wireless Network Supporting MPEG-2 Video Streaming Applications in the Presence of Interference

    Directory of Open Access Journals (Sweden)

    Alessandro Sona

    2010-01-01

    Full Text Available The performance of wireless local area networks supporting video streaming applications, based on MPEG-2 video codec, in the presence of interference is here dealt with. IEEE 802.11g standard wireless networks, that do not support QoS in according with IEEE 802.11e standard, are, in particular, accounted for and Bluetooth signals, additive white Gaussian noise, and competitive data traffic are considered as sources of interference. The goal is twofold: from one side, experimentally assessing and correlating the values that some performance metrics assume at the same time at different layers of an IEEE 802.11g WLAN delivering video streaming in the presence of in-channel interference; from the other side, deducing helpful and practical hints for designers and technicians, in order to efficiently assess and enhance the performance of an IEEE 802.11g WLAN supporting video streaming in some suitable setup conditions and in the presence of interference. To this purpose, an experimental analysis is planned following a cross-layer measurement approach, and a proper testbed within a semianechoic chamber is used. Valuable results are obtained in terms of signal-to-interference ratio, packet loss ratio, jitter, video quality, and interference data rate; helpful hints for designers and technicians are finally gained.

  5. Presence of Peripheral Neuropathy Is Associated With Progressive Thinning of Retinal Nerve Fiber Layer in Type 1 Diabetes.

    Science.gov (United States)

    Dehghani, Cirous; Srinivasan, Sangeetha; Edwards, Katie; Pritchard, Nicola; Russell, Anthony W; Malik, Rayaz A; Efron, Nathan

    2017-05-01

    Reduced retinal nerve fiber layer (RNFL) thickness has been demonstrated in patients with diabetic peripheral neuropathy (DPN) in cross-sectional studies. This prospective study defines longitudinal alterations to the RNFL thickness in individuals with type 1 diabetes without (DPN-ve) and with (DPN+ve) DPN and in relation to risk factors for nerve damage. A cohort of 105 individuals with type 1 diabetes (20% DPN+ve) with predominantly mild or no retinopathy and no previous retinal photocoagulation underwent spectral-domain optical coherence tomography (SD-OCT) at baseline, 2 years, and 4 years. SD-OCT scans were acquired at 3.45-mm diameter around the optic nerve head and the overall RNFL and RNFL in the nasal, superior, temporal, and inferior quadrants were quantified. By including serial quantified RNFL parameters, linear mixed models were applied to assess the change in RNFL thickness over time and to explore the associations with other clinical variables. There was a significant decline in the overall RNFL thickness (-0.7 μm/y, P = 0.02) and RNFL in the superior quadrant (-1.9 μm/y, P diabetes duration, hemoglobin A1c, lipid profile, blood pressure, cigarette use, alcohol consumption, and body mass index did not show any significant effects (P > 0.05). Individuals with DPN showed a progressive RNFL thinning overall and in the superior quadrant, which was more pronounced in older individuals. There may be common pathways for retinal and peripheral neurodegeneration that are independent of conventional DPN risk factors.

  6. Elephants, fire, and frost can determine community structure and composition in Kalahari Woodlands.

    Science.gov (United States)

    Holdo, Ricardo M

    2007-03-01

    Fire, elephants, and frost are important disturbance factors in many African savannas, but the relative magnitude of their effects on vegetation and their interactions have not been quantified. Understanding how disturbance shapes savanna structure and composition is critical for predicting changes in tree cover and for formulating management and conservation policy. A simulation model was used to investigate how the disturbance regime determines vegetation structure and composition in a mixed Kalahari sand woodland savanna in western Zimbabwe. The model consisted of submodels for tree growth, tree damage caused by disturbance, mortality, and recruitment that were parameterized from field data collected over a two-year period. The model predicts that, under the current disturbance regime, tree basal area in the study area will decline by two-thirds over the next two decades and become dominated by species unpalatable to elephants. Changes in the disturbance regime are predicted to greatly modify vegetation structure and community composition. Elephants are the primary drivers of woodland change in this community at present-day population densities, and their impacts are exacerbated by the effects of fire and frost. Frost, in particular, does not play an important role when acting independently but appears to be a key secondary factor in the presence of elephants and/or fire. Unlike fire and frost, which cannot suppress the woodland phase on their own in this ecosystem, elephants can independently drive the vegetation to the scrub phase. The results suggest that elephant and fire management may be critical for the persistence of certain woodland communities within dry-season elephant habitats in the eastern Kalahari, particularly those dominated by Brachystegia spiciformis and other palatable species.

  7. The potential importance of frost flowers, recycling on snow, and open leads for ozone depletion events

    Directory of Open Access Journals (Sweden)

    M. Piot

    2008-05-01

    > out of the brine layer for the possible acidification of the liquid phase by acid uptake. Our investigation showed that this precipitation is a crucial process for the timing of the bromine explosion in aerosols. Nevertheless, model runs with either 50% precipitation or complete precipitation displayed a relatively weak difference in ozone mixing ratios after four simulated days. By considering conditions typical for "Arctic Haze" pollution events at the start of the run we obtained a low pH in frost flower aerosols due to a greater mixing ratio of SO2, and a strong recycling efficiency via large aerosol number concentration. The aerosol acidification during a haze event most likely intensifies the ozone depletion strength and occurrence. The comparison between our modeled deposition on snow and sampled snow at Barrow (Alaska shows that approximately 75% of deposited bromine may be re-emitted into the gas phase as Br2/BrCl. Among several non-halogen fluxes from the snow, model simulations showed that only HONO affects the chemistry. Finally, we investigated the release of Br2 potentially produced by heterogeneous reactions directly on frost flowers. In this case, we obtained unrealistic results of aerosol compositions and deposition rates on snow compared to observations in the Arctic.

  8. Presidential Green Chemistry Challenge: 1998 Academic Award (Draths and Frost)

    Science.gov (United States)

    Presidential Green Chemistry Challenge 1998 award winners, Dr. Karen M. Draths and Professor John W. Frost, used benign, genetically engineered microbes and sugars (instead of benzene) to synthesize adipic acid and catechol.

  9. Long term pavement performance computed parameter : frost penetration

    Science.gov (United States)

    2008-11-01

    As the pavement design process moves toward mechanistic-empirical techniques, knowledge of seasonal changes in pavement structural characteristics becomes critical. Specifically, frost penetration information is necessary for determining the effect o...

  10. Forecast of frost days based on monthly temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Castellanos, M. T.; Tarquis, A. M.; Corato, M. C.; Saa, A.

    2009-07-01

    Abstract Although frost can cause considerable crop damage, and practices have been developed to mitigate forecasted frost, frost forecasting technologies have not changed for years. This paper reports on a new method based on successive application of two models to forecast the number of monthly frost days for several Community of Madrid (Spain) meteorological stations. The first is an autoregressive integrated moving average (ARIMA) stochastic model that forecasts minimum monthly absolute temperature (t{sub m}in) and average monthly minimum temperature ({mu}{sub t}) following Box and Jenkins methodology. The second model relates monthly temperatures (t{sub m}in, {mu}{sub t}) to the minimum daily temperature distribution during one month. Three ARIMA models were identified. They present the same seasonal behaviour (integrated moving average model) and different non-seasonal part: autoregressive model (Model 1), integrated moving average model (Model 2) and autoregressive and moving average model (Model 3). The results indicate that minimum daily temperature (t{sub d}min) for the meteorological stations studied followed a normal distribution each month with a very similar standard deviation through out the years. This standard deviation obtained for each station and each month could be used as a risk index for cold months. The application of Model 1 to predict minimum monthly temperatures produced the best frost days forecast. This procedure provides a tool for crop managers and crop insurance companies to assess the risk of frost frequency and intensity, so that they can take steps to mitigate frost damage and estimate the damage that frost would cause. (Author) 41 refs.

  11. Building energy efficiency and its effect on the frost insulation

    Energy Technology Data Exchange (ETDEWEB)

    Airaksinen, M., Email: miimu.airaksinen@vtt.fi

    2012-06-15

    The energy efficiency of new buildings has improved significantly and is still improving. As the thermal insulation of the building envelope increases other properties and 'thumb' values might also change. Especially when the thermal transmittance (U-value) of the slab on the ground decreases, the frost insulation should also be reconsidered. The aim of this study is to find out how the frost insulation changes when the base floor and foundation insulation change. (orig.)

  12. Delayed Frost Growth on Jumping-Drop Superhydrophobic Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Boreyko, Jonathan B [ORNL; Collier, Pat [ORNL

    2013-01-01

    Self-propelled jumping drops are continuously removed from a condensing superhydrophobic surface to enable a micrometric steady-state drop size. Here, we report that subcooled condensate on a chilled superhydrophobic surface are able to repeatedly jump off the surface before heterogeneous ice nucleation occurs. Frost still forms on the superhydrophobic surface due to ice nucleation at neighboring edge defects, which eventually spreads over the entire surface via an inter-drop frost wave. The growth of this inter-drop frost front is shown to be up to three times slower on the superhydrophobic surface compared to a control hydrophobic surface, due to the jumping-drop effect dynamically minimizing the average drop size and surface coverage of the condensate. A simple scaling model is developed to relate the success and speed of inter-drop ice bridging to the drop size distribution. While other reports of condensation frosting on superhydrophobic surfaces have focused exclusively on liquid-solid ice nucleation for isolated drops, these findings reveal that the growth of frost is an inter-drop phenomenon that is strongly coupled to the wettability and drop size distribution of the surface. A jumping-drop superhydrophobic condenser was found to be superior to a conventional dropwise condenser in two respects: preventing heterogeneous ice nucleation by continuously removing subcooled condensate, and delaying frost growth by minimizing the success of interdrop ice bridge formation.

  13. A passive solar water heating system for vineyard frost protection

    Energy Technology Data Exchange (ETDEWEB)

    Smyth, M. [Centre for Sustainable Technologies, School of the Built Environment, University of Ulster, Newtownabbey BT37 0QB (Ireland); Skates, H. [Environmental Engineering Research Centre, School of Planning, Architecture and Civil Engineering, Queen' s University, Belfast BT9 5AG (Ireland)

    2009-03-15

    The threat of frost during spring time (after 'bud burst') is an ever present danger to the vineyard owner. To minimise the risk, in addition to good site selection and vineyard management, a number of active frost protection systems are available. Most active methods of frost protection are costly in monetary terms and can also have a detrimental effect on the environment. This work presents the design and performance of a passive solar water heating quilt system under real vineyard operating conditions. Two vineyard sites were selected, and the solar water heating quilt design was evaluated over a three-month period. Detailed measurements of the temperature below and above the soil surface, levels of incident solar radiation and the wind direction and speed were recorded. Field study results indicate that the quilts can improve the solar collection and heat retention of the soil, resulting in increased temperatures during frost events of up to 1 C in air space immediately adjacent to the solar quilts when compared to conditions off the protected area. In addition, the time period during which the frost remains a danger to the vine is also reduced. When heat collection, storage and extraction rates are investigated, simplified calculations indicate that the solar quilt can improve collection by 38.5% over bare soil, resulting in the release of 32% more heat. Extrapolated to vineyard coverage, this could result in an extra 3500 MJ of heat per hectare per (typical frost event condition) day. (author)

  14. Coupling of THALES and FROST using MPI Method

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin Woo; Ryu, Seok Hee; Jung, Chan Do; Jung, Jee Hoon; Um, Kil Sup; Lee, Jae Il [KEPCO Nuclear Fuel, Daejeon (Korea, Republic of)

    2013-10-15

    This paper presents the coupling method between THALES and FROST and the simulation results with the coupled code system. In this study, subchannel analysis code THALES and transient fuel performance code FROST were coupled using MPI method as the first stage of the development of the multi-dimensional safety analysis methodology. As a part of the validation, the CEA ejection accident was simulated using the coupled THALES-FROST code and the results were compared with the ShinKori 3 and 4 FSAR. Comparison results revealed that CHASER using MPI method predicts fuel temperatures and heat flux quantitatively well. Thus it was confirmed that the THALES and FROST are properly coupled. In near future, ASTRA, multi-dimensional core neutron kinetics code, will be linked to THALESFROST code for the detailed three-dimensional CEA ejection analysis. The current safety analysis methodology for a CEA ejection accident based on numerous conservative assumptions with the point kinetics model results in quite adverse consequences. Thus, KNF is developing the multi-dimensional safety analysis methodology to enhance the consequences of the CEA ejection accident. For this purpose, three-dimensional core neutron kinetics code ASTRA, subchannel analysis code THALES, and transient fuel performance analysis code FROST are being coupled using message passing interface(MPI). For the first step, THALES and FROST are coupled and tested.

  15. 3D stability analysis of Rayleigh–Bénard convection of a liquid metal layer in the presence of a magnetic field—effect of wall electrical conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Dimopoulos, Dimitrios; Pelekasis, Nikos A, E-mail: pel@uth.gr [Department of Mechanical and Industrial Engineering, University of Thessaly, Pedion Areos, Volos 38334 (Greece)

    2014-10-01

    Rayleigh–Bénard stability of a liquid metal layer of rectangular cross section is examined in the presence of a strong magnetic field that is aligned with the horizontal direction of the cross section. The latter is much longer than the vertical direction and the cross section assumes a large aspect ratio. The side walls are treated as highly conducting. Linear stability analysis is performed allowing for three-dimensional instabilities that develop along the longitudinal direction. The finite element methodology is employed for the discretization of the stability analysis formulation while accounting for the electrical conductivity of the cavity walls. The Arnoldi method provides the dominant eigenvalues and eigenvectors of the problem. In order to facilitate parallel implementation of the numerical solution at large Hartmann numbers, Ha, domain decomposition is employed along the horizontal direction of the cross section. As the Hartmann number increases a real eigenvalue emerges as the dominant unstable eigenmode, signifying the onset of thermal convection, whose major vorticity component in the core of the layer is aligned with the direction of the magnetic field. Its wavelength along the longitudinal direction of the layer is on the order of twice its height and increases as Ha increases. The critical Grashof was obtained for large Ha and it was seen to scale like Ha {sup 2} signifying the balance between buoyancy and Lorentz forces. For well conducting side walls, the nature of the emerging flow pattern is determined by the combined conductivity of Hartmann walls and Hartmann layers, c{sub H}  + Ha {sup −1}. When poor conducting Hartmann walls are considered, c{sub H} ≪ 1, the critical eigensolution is characterized by well defined Hartmann and side layers. The side layers are characterized by fast fluid motion in the magnetic field direction as a result of the electromagnetic pumping in the vicinity of the Hartmann walls. Increasing the electrical

  16. Suppression of Frost Nucleation Achieved Using the Nanoengineered Integral Humidity Sink Effect.

    Science.gov (United States)

    Sun, Xiaoda; Rykaczewski, Konrad

    2017-01-24

    Inhibition of frost formation is important for increasing efficiency of refrigeration systems and heat exchangers, as well as for preventing the rapid icing over of water-repellant coatings that are designed to prevent accumulation of rime and glaze. From a thermodynamic point of view, this task can be achieved by either increasing hydrophobicity of the surface or decreasing the concentration of water vapor above it. The first approach has been studied in depth, but so far has not yielded a robust solution to the problem of frost formation. In this work, we systematically explore how frost growth can be inhibited by controlling water vapor concentration using bilayer coatings with a porous exterior covering a hygroscopic liquid-infused layer. We lay the theoretical foundation and provide experimental validation of the mass transport mechanism that governs the integral humidity sink effect based on this coating platform as well as reveal intriguing sizing effects about this system. We show that the concentration profile above periodically spaced pores is governed by the sink and source concentrations and two geometrical parameters: the nondimensional pore size and the ratio of the pore spacing to the boundary layer thickness. We demonstrate that when the ratio of the pore spacing to the boundary layer thickness vanishes, as for the nanoporous bilayer coatings, the entire surface concentration becomes uniform and equal to the concentration set by the hygroscopic liquid. In other words, the surface concentration becomes completely independent of the nanopore size. We identified the threshold geometrical parameters for this condition and show that it can lead to a 65 K decrease in the nucleation onset surface temperature below the dew point. With this fundamental insight, we use bilayer coatings to nanoengineer the integral humidity sink effect to provide extreme antifrosting performance with up to a 2 h delay in nucleation onset at 263 K. The nanoporous bilayer

  17. On the Effective Thermal Conductivity of Frost Considering Mass Diffusion and Eddy Convection

    Science.gov (United States)

    Kandula, Max

    2010-01-01

    A physical model for the effective thermal conductivity of water frost is proposed for application to the full range of frost density. The proposed model builds on the Zehner-Schlunder one-dimensional formulation for porous media appropriate for solid-to-fluid thermal conductivity ratios less than about 1000. By superposing the effects of mass diffusion and eddy convection on stagnant conduction in the fluid, the total effective thermal conductivity of frost is shown to be satisfactorily described. It is shown that the effects of vapor diffusion and eddy convection on the frost conductivity are of the same order. The results also point out that idealization of the frost structure by cylindrical inclusions offers a better representation of the effective conductivity of frost as compared to spherical inclusions. Satisfactory agreement between the theory and the measurements for the effective thermal conductivity of frost is demonstrated for a wide range of frost density and frost temperature.

  18. Forecast of Frost Days Based on Monthly Temperatures

    Science.gov (United States)

    Castellanos, M. T.; Tarquis, A. M.; Morató, M. C.; Saa-Requejo, A.

    2009-04-01

    Although frost can cause considerable crop damage and mitigation practices against forecasted frost exist, frost forecasting technologies have not changed for many years. The paper reports a new method to forecast the monthly number of frost days (FD) for several meteorological stations at Community of Madrid (Spain) based on successive application of two models. The first one is a stochastic model, autoregressive integrated moving average (ARIMA), that forecasts monthly minimum absolute temperature (tmin) and monthly average of minimum temperature (tminav) following Box-Jenkins methodology. The second model relates these monthly temperatures to minimum daily temperature distribution during one month. Three ARIMA models were identified for the time series analyzed with a stational period correspondent to one year. They present the same stational behavior (moving average differenced model) and different non-stational part: autoregressive model (Model 1), moving average differenced model (Model 2) and autoregressive and moving average model (Model 3). At the same time, the results point out that minimum daily temperature (tdmin), for the meteorological stations studied, followed a normal distribution each month with a very similar standard deviation through years. This standard deviation obtained for each station and each month could be used as a risk index for cold months. The application of Model 1 to predict minimum monthly temperatures showed the best FD forecast. This procedure provides a tool for crop managers and crop insurance companies to asses the risk of frost frequency and intensity, so that they can take steps to mitigate against frost damage and estimated the damage that frost would cost. This research was supported by Comunidad de Madrid Research Project 076/92. The cooperation of the Spanish National Meteorological Institute and the Spanish Ministerio de Agricultura, Pesca y Alimentation (MAPA) is gratefully acknowledged.

  19. Frost-resistance of red ceramic products

    Directory of Open Access Journals (Sweden)

    Ramires, M. V. V.

    2000-02-01

    Full Text Available The present work is a study about degradation occurring with red ceramics whenever they are exposed to the environmental conditions of a cold and humid climate. Four different types of clay from Rio Grande do Sul were studied: two of them from the Serra Geral formation, and the other two from the formation of Strada Nova, which are commonly used to make roof tiles. The clay was characterised to identify its chemical and mineralogical composition. Also the physical properties were researched. In the ceramic processing, the pressure with four different sintering temperatures (850ºC, 900ºC, 950ºC, and 1000ºC at three different intervals (3, 12, and 24 hours were used. The ceramic materials thus obtained were characterised according to their physical properties (water absorption, total density, porosity, and porous size, and mechanical (mechanical resistance over four points. For the characterisation of the degradation mechanism, some trials were carried out to obtain the coefficient of saturation and on frost and defrost cycles. The microstructural analysis was made with a scanning electronic microscopy. On the basis of the results obtained, a model for the degradation mechanism is presented, and a degradation factor which relates the total volume of mesopores to the standard size of mesopores is suggested. It was concluded that the red ceramic products more prone to be frost-resistant are those presenting a degradation factor below 100.

    Se estudia la degradación que sufre la cerámica roja cuando se expone a la acción de los climas fríos e húmedos. La experimentación se ha realizado con cuatro arcillas de la son expuestas a los climas fríos y húmedos. Se investigaron cuatro diferentes arcillas de la provincia del Rio Grande do Sul, que se emplean tradicionalmente en la fabricación de tejas. Dos de ellas pertenecen a la formación de la Serra Geral y las otras dos de la formación Estrada Nova. La caracterización de las arcillas

  20. Passive anti-frosting surfaces using microscopic ice arrays

    Science.gov (United States)

    Ahmadi, Farzad; Nath, Saurabh; Iliff, Grady; Boreyko, Jonathan

    2017-11-01

    Despite exceptional advances in surface chemistry and micro/nanofabrication, no engineered surface has been able to passively suppress the in-plane growth of frost occurring in humid, subfreezing environments. Motivated by this, and inspired by the fact that ice itself can evaporate nearby liquid water droplets, we present a passive anti-frosting surface in which the majority of the surface remains dry indefinitely. We fabricated an aluminum surface exhibiting an array of small metallic fins, where a wicking micro-groove was laser-cut along the top of each fin to produce elevated water ``stripes'' that freeze into ice. As the saturation vapor pressure of ice is less than that of supercooled liquid water, the ice stripes serve as overlapping humidity sinks that siphon all nearby moisture from the air and prevent condensation and frost from forming anywhere else on the surface. Our experimental results show that regions between stripes remain dry even after 24 hours of operation under humid and supercooled conditions. We believe that the presented anti-frosting technology has the potential to help solve the world's multi-billion dollar frosting problem that adversely affects transportation, power generation, and HVAC systems.

  1. Free convection frost growth in a narrow vertical channel

    Energy Technology Data Exchange (ETDEWEB)

    Tanda, G.; Fossa, M. [Dipartimento di Ingegneria della Produzione, Termoenergetica e Modelli Matematici (DIPTEM), Universita degli Studi di Genova, via all' Opera Pia 15a, I-16145 Genova (Italy)

    2006-06-15

    Processes involving heat transfer from a humid air stream to a cold plate, with simultaneous deposition of frost, are of great importance in a variety of refrigeration equipment. In this work, frost growth on a vertical plate in free convection has been experimentally investigated. The cold plate (0.095m high, 0.282m wide) was placed in a narrow (2.395m high, 0.01m deep) vertical channel open at the top and bottom in order to permit the natural circulation of ambient air. The cold plate temperature and the air relative humidity were varied in the -40 to -4{sup o}C and 31-85% range, respectively, with the air temperature held fixed at 27{sup o}C (+/-1{sup o}C). The main quantities (thickness, temperature and mass of frost, heat flux at the cold plate), measured during the time evolution of the process, are presented as functions of the input parameters (relative humidity and cold plate temperature); in particular, the role exerted by the plate confinement on the frost growth is discussed. Data are recast in order to identify compact parameters able to correlate with good accuracy frost thickness, mass and density data. (author)

  2. Ferromagnetic resonance investigation of physical origins of modification of the perpendicular magnetic anisotropy in Pd/Co layered films in the presence of hydrogen gas

    Science.gov (United States)

    Lueng, C.; Zighem, F.; Faurie, D.; Kostylev, M.

    2017-10-01

    In our work, we study the physical origins of the hydrogen gas induced reduction of the strength of perpendicular magnetic anisotropy (PMA) at the interface of cobalt and palladium layers. To this end, we grow these films on flexible substrates and carry out ferromagnetic resonance (FMR) measurements in the presence of two different stimuli—hydrogen gas and elastic strain. Exposing the samples to H2 results in a downshift of the FMR field. On the contrary, FMR measurements carried out in the presence of an externally applied predominantly tensile elastic stress show an up-shift in the resonance field consistent with negative values of the saturation magnetostriction coefficient for our samples. Qualitative analysis of these results demonstrates that the magneto-elastic contribution to the hydrogen-induced change in PMA is very small and is of the opposite sign to the electronic contribution related to the influence of hydrogen ions on the hybridisation of cobalt and palladium orbitals at the interface.

  3. Langmuir-Blodgett monolayers of cationic dyes in the presence and absence of clay mineral layers: N,N'-dioctadecyl thiacyanine, octadecyl rhodamine B and laponite.

    Science.gov (United States)

    Hussain, Syed Arshad; Schoonheydt, Robert A

    2010-07-20

    Langmuir-Blodgett (LB) films of N,N'-dioctadecyl thiacyanine perchlorate (TC18) and octadecyl rhodamine B chloride (RhB18) and their mixtures in the presence and absence of clay mineral layers were investigated by recording surface pressure-area (pi-A) isotherms and by UV-vis and fluorescence spectroscopies. The pi-A isotherms of TC18, RhB18, and their mixtures are characteristic of liquid expanded state behavior with repulsive interactions between the two cationic dyes. In the presence of laponite, the pi-A isotherms show liquid expanded and condensed-state behavior. In laponite dispersions and in monolayers, TC18 has a strong tendency to aggregate with formation of H- and J- aggregates. The absorption and fluorescence maxima of the monomers in the films are at 435 nm and at 480 nm; H-dimers have an absorption maximum around 410 nm and do not fluoresce. J-dimers are present in all the films with absorption maximum at 461 nm and fluorescence at 463 nm. RhB18 is mainly present as monomers in the LB films with an absorption maximum at 576 nm and fluorescence at 595 nm. Fluorescence resonance energy transfer from TC18 to RhB18 has been observed in clay dispersions and in films with and without laponite. The optimum condition for TC18 --> RhB18 fluorescence energy transfer in the films is 90 mol % TC18 + 10 mol % RhB18.

  4. Frost susceptibility of granular subbase materials contaminated by deicing chemicals

    DEFF Research Database (Denmark)

    Jørgensen, Anders Stuhr; Orlander, Tobias; Doré, Guy

    2013-01-01

    The increase in urban population in arctic areas leads to an increased demand for transportation infrastructures (such as roads and airfields) in the regions. This challenges the road constructions in terms of condition, bearing capacity and maintenance. It is believed that deicing agents used on...... data on the granular subbase material. © 2013 American Society of Civil Engineers....... on roads and airfields enter the granular subbase materials and thereby makes the soil more frost-susceptible. In this project a series of isothermal frost heave tests has been carried out on granular subbase material from the runway at Kuujjuaq Airport, Québec, Canada. The tests have been carried out...... in order to determine the frost susceptibility of the material when it is contaminated by a deicing agent. Two series of three freezing tests with isothermal cooling has been conducted using identical saline gradient added through brine. Two types of cooling ramp, an automatic cooling and a manual cooling...

  5. Heat and mass transfer in the melting of frost

    CERN Document Server

    Mohs, William F

    2015-01-01

    This Brief is aimed at engineers and researchers involved in the refrigeration industry: specifically, those interested in energy utilization and system efficiency. The book presents what the authors believe is the first comprehensive frost melting study involving all aspects of heat and mass transfer. The volume’s description of in-plane and normal digital images of frost growth and melting is also unique in the field, and the digital analysis technique offers an advantage over invasive measurement methods. The scope of book’s coverage includes modeling and experimentation for the frost formation and melting processes. The key sub-specialties to which the book are aimed include refrigeration system analysis and design, coupled heat and mass transfer, and phase-change processes.

  6. Frost sensor for use in defrost controls for refrigeration

    Science.gov (United States)

    French, Patrick D.; Butz, James R.; Veatch, Bradley D.; O'Connor, Michael W.

    2002-01-01

    An apparatus and method for measuring the total thermal resistance to heat flow from the air to the evaporative cooler fins of a refrigeration system. The apparatus is a frost sensor that measures the reduction in heat flow due to the added thermal resistance of ice (reduced conduction) as well as the reduction in heat flow due to the blockage of airflow (reduced convection) from excessive ice formation. The sensor triggers a defrost cycle when needed, instead of on a timed interval. The invention is also a method for control of frost in a system that transfers heat from air to a refrigerant along a thermal path. The method involves measuring the thermal conductivity of the thermal path from the air to the refrigerant, recognizing a reduction in thermal conductivity due to the thermal insulation effect of the frost and due to the loss of airflow from excessive ice formation; and controlling the defrosting of the system.

  7. Spatiotemporal Interaction of Near-Surface Soil Moisture Content and Frost Table Depth in a Discontinuous Permafrost Environment

    Science.gov (United States)

    Guan, X.; Spence, C.; Westbrook, C. J.

    2009-05-01

    The ubiquitous presence of frozen ground in cold regions creates a unique dynamic boundary issue for subsurface water movement and storage. We examined the relationship between ground thaw and spatiotemporal soil moisture patterns at three sites (peatland, wetland and valley) near Yellowknife NT. Thaw depth and near-surface soil moisture were measured along a systematic grid at each site. Energy and water budgets were computed for each site to explain the soil moisture patterns. At the peatland, overall soil moisture decreased through the summer and became more spatially homogeneous with deepened thaw, increased subsurface storage capacity, and drying from evapotranspiration. In the peatland and wetland, accumulated water in depressions maintained soils at higher soil moistures for a longer duration than the hummock tops. The depressions had deeper frost tables than the drier hummock tops because the organic mats covering the hummocks insulated the ground and retarded ground thaw. The wettest soils were often locations of deepest thaw depth due to surface ponding and the transfer of latent heat accompanying surface runoff from upslopes. For example, the 3.3 ha wetland received 3.08x105 m3 of surface inflow from a lake with 2.32 kJm-2 of convective heat available to be transferred into the frozen ground over the study period. Soil moisture patterns also revealed preferential surface and subsurface flow routes. The findings indicate that the presence of frozen ground and differential thawing have a diverse and dynamic relationship with near-surface soil moisture content. When the impermeable boundary is dynamic, and controlled by water and energy fluxes, thicker soil layers are associated with higher moisture. This contrasts findings from temperate regions with a fixed impermeable boundary which show that surface soil moisture content can be lower in areas with thick soil.

  8. Predictive modeling of freezing and thawing of frost-susceptible soils.

    Science.gov (United States)

    2015-09-01

    Frost depth is an essential factor in design of various transportation infrastructures. In frost : susceptible soils, as soils freezes, water migrates through the soil voids below the freezing line : towards the freezing front and causes excessive he...

  9. Analysis of railway subgrade frost heave deformation based on GPS

    Directory of Open Access Journals (Sweden)

    Fuxun Ma

    2016-03-01

    Full Text Available In order to analyze the connection between the railway subgrade frost heave deformation and temperature variation, five GPS stations' data were used to monitor the deformation on a certain section of railway subgrade in northeast China. GAMIT software is used to process the data, providing daily solution, daytime solution and nighttime solution. Vertical trends of these five stations were analyzed to investigate frost heave effect on railway subgrade deformation. The results show that the temperature difference between daytime and night induces stations, significant vertical displacement, and the temperature difference between seasons causes settlement of station which appears linear trend.

  10. Voltammetric Determination of Acetaminophen in the Presence of Codeine and Ascorbic Acid at Layer-by-Layer MWCNT/Hydroquinone Sulfonic Acid-Overoxidized Polypyrrole Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Saeed Shahrokhian

    2011-01-01

    Full Text Available A very sensitive electrochemical sensor constructed of a glassy carbon electrode modified with a layer-by-layer MWCNT/doped-overoxidized polypyrrole (oppy/MWCNT /GCE was used for the determination of acetaminophen (AC in the presence of codeine and ascorbic acid (AA. In comparison to the bare glassy carbon electrode, a considerable shift in the peak potential together with an increase in the peak current was observed for AC on the surface of oppy/MWCNT/GCE, which can be related to the enlarged microscopic surface area of the electrode. The effect of the experimental conditions on the electrode response, such as types of counter ion, pyrrole and counter ion concentration, potential and number of cycles in the polymerization procedure, amount of MWCNT, and the pH, were investigated. Under the optimized conditions, the calibration curve was obtained over two concentration ranges of 2 × 10−7–6 × 10−6 M and 4 × 10−5–1 × 10−4 M of AC with a linear correlation coefficient (R2 of 0.9959 and 0.9947, respectively. The estimated detection limit (3σ for AC was obtained as 5 × 10−8 M. The developed method was successfully applied to analyze the pharmaceutical preparations of AC, and a recovery of 95% with a relative standard deviation of 0.98% was obtained for AC.

  11. Risk analysis of first and last frost occurrences in central Alborz region, Iran

    NARCIS (Netherlands)

    Rahimi, M.; Khalili, A.; Hajjam, S.; Kamali, G.A.; Stigter, C.J.

    2007-01-01

    Central Alborz is one of the important agricultural regions of Iran. Occurrence of the first frost in fall and the last frost in spring causes damage to the crops in this region every year. Information about the probable dates of frost occurrence helps farmers in preventing or reducing the damages

  12. A method for assessing frost damage risk in sweet cherry orchards of South Patagonia

    NARCIS (Netherlands)

    Cittadini, E.D.; Ridder, de N.; Peri, P.L.; Keulen, van H.

    2006-01-01

    Quantification of frost damage risk is important in planning the development of new orchard areas and for decision-making on design and installation of frost control systems. The objective of this study was to develop a comprehensive method to quantify frost damage risk in different sweet cherry

  13. Experimental study on the effect of frost parameters on domestic refrigerator finned tube evaporator coils

    Energy Technology Data Exchange (ETDEWEB)

    OEzkan, Derya Burcu; OEzil, Eralp [Department of Mechanical Engineering, Yildiz Technical University, 34349 Istanbul (Turkey)

    2006-12-15

    In this study, parameters affecting the frost formation on the evaporator of a refrigerator and the structure of frost were examined. Air velocity measurements both at the air inlet and outlet channels of the evaporator were performed, and the effect of air velocity on frost formation was examined. The rate of evaporation of water inside the refrigerator cabin was also recorded. (author)

  14. Lessons in the Conversation That We Are: Robert Frost's "Death of the Hired Man."

    Science.gov (United States)

    Jost, Walter

    1996-01-01

    Looks at Robert Frost's "The Death of the Hired Man" as a "representative anecdote" for Frost's work, which, taken as a whole, shows readers how to lose themselves among the overlooked places and turnings, the topics and tropes, that make up Frost's rhetorical home, the place of everyday human talk and gossip. (TB)

  15. Water frost and ice - The near-infrared spectral reflectance 0.65-2.5 microns. [observed on natural satellites and other solar system objects

    Science.gov (United States)

    Clark, R. N.

    1981-01-01

    The spectral reflectance of water frost and frost on ice as a function of temperature and grain size is presented with 1-1/2% spectral resolution in the 0.65- to 2.5-micron wavelength region. The well-known 2.0-, 1.65-, and 1.5-micron solid water absorption bands are precisely defined along with the little studied 1.25-micron band and the previously unidentified (in reflectance) 1.04-, 0.90-, and 0.81-micron absorption bands. The 1.5-microns band complex is quantitatively analyzed using a nonlinear least squares algorithm to resolve the band into four Gaussian components as a function of grain size and temperature. It is found that the 1.65-micron component, which was thought to be a good temperature sensor, is highly grain-size dependent and poorly suited to temperature sensing. Another Gaussian component appears to show a dependence of width on grain size while being independent of temperature. The relative apparent band depths are different for frost layers on ice than for thick layers of frost and may explain the apparent band depths seen in many planetary reflectance spectra.

  16. Effect of Postsowing Compaction on Cold and Frost Tolerance of North China Plain Winter Wheat

    Directory of Open Access Journals (Sweden)

    Caiyun Lu

    2017-01-01

    Full Text Available Improper postsowing compaction negatively affects soil temperature and thereby cold and frost tolerance, particularly in extreme cold weather. In North China Plain, the temperature falls to 5 degrees below zero, even lower in winter, which is period for winter wheat growing. Thus improving temperature to promote wheat growth is important in this area. A field experiment from 2013 to 2016 was conducted to evaluate effects of postsowing compaction on soil temperature and plant population of wheat at different stages during wintering period. The effect of three postsowing compaction methods—(1 compacting wheel (CW, (2 crosskill roller (CR, and (3 V-shaped compacting roller after crosskill roller (VCRCR—on winter soil temperatures and relation to wheat shoot growth parameters were measured. Results showed that the highest soil midwinter temperature was in the CW treatment. In the 20 cm and 40 cm soil layer, soil temperatures were ranked in the following order of CW > VCRCR > CR. Shoot numbers under CW, CR, and VCRCR treatments were statistically 12.40% and 8.18% higher under CW treatment compared to CR or VCRCR treatments at the end of wintering period. The higher soil temperature under CW treatment resulted in higher shoot number at the end of wintering period, apparently due to reduced shoot death by cold and frost damage.

  17. Genetic architecture of winter hardiness and frost tolerance in triticale.

    Directory of Open Access Journals (Sweden)

    Wenxin Liu

    Full Text Available Abiotic stress experienced by autumn-sown crops during winter is of great economic importance as it can have a severe negative impact on yield. In this study, we investigated the genetic architecture of winter hardiness and frost tolerance in triticale. To this end, we used a large mapping population of 647 DH lines phenotyped for both traits in combination with genome-wide marker data. Employing multiple-line cross QTL mapping, we identified nine main effect QTL for winter hardiness and frost tolerance of which six were overlapping between both traits. Three major QTL were identified on chromosomes 5A, 1B and 5R. In addition, an epistasis scan revealed the contribution of epistasis to the genetic architecture of winter hardiness and frost tolerance in triticale. Taken together, our results show that winter hardiness and frost tolerance are complex traits that can be improved by phenotypic selection, but also that genomic approaches hold potential for a knowledge-based improvement of these important traits in elite triticale germplasm.

  18. Condensation phenomena and frost problems in the air heat recuperators

    Directory of Open Access Journals (Sweden)

    Adamski Mariusz

    2014-01-01

    Full Text Available Investigation results of condensation phenomena and frost problems in the ventilation heat recuperators are presented. The experiments have been conducted for typical value of indoor temperature 20°C and a large range of humidity values from 20 to 75% and more of an exhausted air. The heat exchanger worked in the real conditions of the winter climate in Bialystok.

  19. Reduced-molecular-weight derivatives of frost grape polysaccharide

    Science.gov (United States)

    A new Type II arabinogalactan was recently described as an abundant gum exudate from stems of wildfrost grape (Vitus riparia Michx.). The purpose of the current study is to more thoroughly characterize the physical properties of this frost grape polysaccharide (FGP), and develop methods to modify th...

  20. Enhancing Perspective, Inviting Response: Multiple Interpretations of a Frost Poem.

    Science.gov (United States)

    Doyle, Brian D.

    1992-01-01

    Asserts that literary criticism and scholarly analyses provide a broad and enriching resource with which to inform instruction and discussion in a pluralistic classroom. Offers examples of a postreading activity based on seven major interpretations of Robert Frost's "Stopping by Woods on a Snowy Evening." Presents follow-up and extension…

  1. In and Outdoor Schooling: Robert Frost and the Classics

    Science.gov (United States)

    Bacon, Helen H.

    1974-01-01

    This is an abridged and modified form of an essay that the author, professor of Greek and Latin at Barnard College, delivered at the Library of Congress symposium held last spring on the hundredth anniversary of Robert Frost's birth. (Editor/RK)

  2. Unsteady boundary layer flow of a nanofluid over a stretching sheet with variable fluid properties in the presence of thermal radiation

    Science.gov (United States)

    Daba, Mitiku; Devaraj, P.

    2016-05-01

    In this paper, we investigated numerically an unsteady boundary layer flow of a nanofluid over a stretching sheet in the presence of thermal radiation with variable fluid properties. Using a set of suitable similarity transformations, the governing partial differential equations are reduced into a set of nonlinear ordinary differential equations. System of the nonlinear ordinary differential equations are then solved by the Keller-box method. The physical parameters taken into consideration for the present study are: Prandtl number Pr, Lewis number Le, Brownian motion parameter N b, thermophoresis parameter N t, radiation parameter N r, unsteady parameter M. In addition to these parameters, two more new parameters namely variable thermophoretic diffusion coefficient parameter e and variable Brownian motion diffusion coefficient parameter β have been introduced in the present study. Effects of these parameters on temperature, volume fraction of the nanoparticles, surface heat and mass transfer rates are presented graphically and discussed briefly. To validate our method, we have compared the present results with some previously reported results in the literature. The results are found to be in a very good agreement.

  3. Development of Some Organs Derived from the Three Embryonic Germ Layer in a Degus Ectopic Pregnancy and Presence of a Cytotrophoblast That Mimics Human Chorionic Placenta

    Directory of Open Access Journals (Sweden)

    C. Bosco

    2014-01-01

    Full Text Available This report describes a case of abdominal pregnancy in an adult female degu from which we recovered two large tissular masses from the peritoneal cavity. The bigger one showed a number of thin vascular connections to the serosa layer of the small intestine. It was also directly connected to the smaller mass by a thin membranous process. The surface of the bigger mass facing the small intestine wall showed the presence of chorionic villous that resembled a villous human chorionic placenta, rather than the hemomonochorial labyrinthine placenta, characteristic of this species. This unusual finding leads us to postulate that in the degu’s uterus the cytotrophoblast is exposed to a number of factors that will activate cascades of cellular and molecular events that ultimately will be signaling the cytotrophoblast to develop into a labyrinthine hemomonochorial placenta. In absence of the proper uterine environment, as is the case of the abdominal pregnancy in the peritoneal cavity reported here, the lack of signaling will lead the cytotrophoblast to develop into a villous chorionic placenta, similar to that observed in human.

  4. Holding emotional and linguistic rulers up to the poetry of Robert Frost.

    Science.gov (United States)

    Whissell, C

    1999-12-01

    The words in a large and representative sample of Robert Frost's poetry were compared with information in several data bases which provided estimates of the poetry's pleasantness, arousal, emotionality, imagery, and linguistic complexity. Findings confirmed that Frost's poetry was linguistically simple and emotionally restrained in comparison to that of his cohort. They also highlighted the increasing variability in Frost's poetry across time and its decreasing imagery. Frost's poetry was more restrained than that of his male cohort but similar to the poetry of his female cohort in its linguistic simplicity. Frost's acknowledged death poems were in fact quite pleasant and passive in emotional tone.

  5. Inhibition of Condensation Frosting by Arrays of Hygroscopic Antifreeze Drops.

    Science.gov (United States)

    Sun, Xiaoda; Damle, Viraj G; Uppal, Aastha; Linder, Rubin; Chandrashekar, Sriram; Mohan, Ajay R; Rykaczewski, Konrad

    2015-12-29

    The formation of frost and ice can have negative impacts on travel and a variety of industrial processes and is typically addressed by dispensing antifreeze substances such as salts and glycols. Despite the popularity of this anti-icing approach, some of the intricate underlying physical mechanisms are just being unraveled. For example, recent studies have shown that in addition to suppressing ice formation within its own volume, an individual salt saturated water microdroplet forms a region of inhibited condensation and condensation frosting (RIC) in its surrounding area. This occurs because salt saturated water, like most antifreeze substances, is hygroscopic and has water vapor pressure at its surface lower than water saturation pressure at the substrate. Here, we demonstrate that for macroscopic drops of propylene glycol and salt saturated water, the absolute RIC size can remain essentially unchanged for several hours. Utilizing this observation, we demonstrate that frost formation can be completely inhibited in-between microscopic and macroscopic arrays of propylene glycol and salt saturated water drops with spacing (S) smaller than twice the radius of the RIC (δ). Furthermore, by characterizing condensation frosting dynamics around various hygroscopic drop arrays, we demonstrate that they can delay complete frosting over of the samples 1.6 to 10 times longer than films of the liquids with equivalent volume. The significant delay in onset of ice nucleation achieved by dispensing propylene glycol in drops rather than in films is likely due to uniform dilution of the drops driven by thermocapillary flow. This transport mode is absent in the films, leading to faster dilution, and with that facilitated homogeneous nucleation, near the liquid-air interface.

  6. Analysis of early-stage frost formation in natural convection over a horizontal cylinder

    Energy Technology Data Exchange (ETDEWEB)

    Tahavvor, Ali R. [School of Engineering, Shiraz University, Shiraz 71348-51154 (Iran); Yaghoubi, Mahmood [School of Engineering, Shiraz University, Shiraz 71348-51154 (Iran); Academy of Sciences (Iran)

    2009-09-15

    Frost growth process on a cold surface consists of two stages: The early-stage or one-dimensional growth of ice columns and multidimensional growth in the form of a porous structure. The transition time which marking these two stages is important for any numerical modeling of frost formation. This paper proposes a mathematical model to predict the transition time and frost properties in natural convection of frost formation over a cooled horizontal cylinder in the first stage of growth period. Comparison is performed among the results of this model and experimental observations reported in the literatures. It is observed that the presented model can be used more efficiently to determine transition time and frost properties in the early-stage of frost formation. Based on the obtained results a new correlation is developed for the duration time of early-stage of frost formation process (transition time) in natural convection. (author)

  7. Frost related dieback in Estonian energy plantations of willows in relation to fertilisation and pathogenic bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Cambours, M.A.; Nejad, P. [Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, Box 7026, 750 07 Uppsala (Sweden); Heinsoo, K. [Institute of Zoology and Botany, Estonian Agricultural University, Riia 181, 51014 Tartu (Estonia); Granhall, U. [Department of Microbiology, Swedish University of Agricultural Sciences, Box 7025, 750 07 Uppsala (Sweden)

    2006-03-15

    Two 9-year old Estonian Salix plantations suffering from dieback were studied: one situated on poor mineral soil and divided into fertilised and unfertilised plots (Saare plantation) and another growing on a well-decomposed and nitrogen-rich organic soil, without fertiliser application (Kambja plantation). Bacteria from internal tissues of visually damaged shoots from seven clones were isolated in spring and autumn. The strains were subsequently biochemically characterised and tested for ice nucleation activity and pathogenicity on Salix. Some strains were also analysed with 16S rRNA. High numbers of culturable bacteria were found, belonging mainly to Erwinia, Sphingomonas, Pseudomonas and Xanthomonas spp. Fertilised plots were significantly more colonised by bacteria than unfertilised plots and also more extensively damaged, showing a lower density of living plants after 7 years of culture. More ice nucleation active (INA) strains were found in Saare fertilised plots and at Kambja than in Saare unfertilised plots. Likewise, most pathogenic strains were isolated from Saare fertilised plots and from Kambja. For some of the willow clones studied, dieback appeared to be related to both clonal frost sensitivity and abundance of INA and pathogenic bacteria. The plantations probably suffered from the presence of high amounts of pathogens and from frost related injuries aggravated by INA bacteria. Most probably the fertilisation at Saare and the nitrogen-rich soil at Kambja created a favourable environment for bacterial development and led to high dieback levels after the first harvest. (author)

  8. Laboratory Evaluation of the Effect of HNO3 Uptake on Frost Point Hygrometer Measurement of Water Vapor under UT/LS Conditions

    Science.gov (United States)

    Thornberry, T.; Gierczak, T.; Gao, R.; Voemel, H.; Watts, L.; Burkholder, J. B.; Fahey, D. W.

    2010-12-01

    Chilled mirror hygrometers (CMH) are widely used to measure water vapor in the troposphere and lower stratosphere from balloon-borne sondes. Systematic discrepancies among in situ water vapor instruments have been observed at low water vapor mixing ratios (CMH under conditions representative of operation in the UT/LS. No detectable interference in the measured frost point temperature was found for HNO3 mixing ratios of up to 2 ppb for exposure times up to 150 minutes. HNO3 was observed to co-condense on the mirror frost, with the adsorbed mass increasing linearly with time at constant exposure levels. Over the duration of a typical balloon sonde ascent (90-120 min), the maximum accumulated HNO3 amounts were comparable to monolayer coverage of the geometric mirror surface area, which likely corresponds to small fractional coverage of the actual frost layer surface area. This small amount of co-condensed HNO3 is consistent with the observed lack of HNO3 interference in the frost point measurement because the CMH utilizes significant reductions (>10%) in surface reflectivity by the condensate for the determination of H2O.

  9. Inverse estimation for the unknown frost geometry on the external wall of a forced-convection pipe

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wen-Lih; Yang, Yu-Ching [Clean Energy Center, Department of Mechanical Engineering, Kun Shan University, Yung-Kang City, Tainan 710-03 (China)

    2009-06-15

    In this study, a conjugate gradient method based inverse algorithm is applied to estimate the unknown frost-layer boundary profile on the external wall of a pipe system using temperature measurements. It is assumed that no prior information is available on the functional form of the unknown profile; hence the procedure is classified as the function estimation in inverse calculation. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The accuracy of the inverse analysis is examined by using simulated exact and inexact temperature measurements. Results show that an excellent estimation on boundary profile can be obtained for the test case considered in this study. (author)

  10. FROST: an ASIC for digital mammography with synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Bergamaschi, A. E-mail: bergamaschi@ts.infn.it; Prest, M.; Vallazza, E.; Arfelli, F.; Dreossi, D.; Longo, R.; Olivo, A.; Pani, S.; Castelli, E

    2003-09-01

    The FRONTier RADiography (FRONTRAD) collaboration is developing a digital system for mammography at the Elettra Synchrotron Light Source in Trieste. The system is based on a silicon microstrip detector array. The ASIC FROST (FRONTRAD Read Out sySTem) was developed as a collaboration between INFN Trieste and Aurelia Microelettronica and is designed to operate in single photon counting mode. FROST provides low-noise and high-gain performances and is able to work at incident photon rates higher than 100 kHz with almost 100% efficiency. The ASIC has been tested and the first images of mammographic test objects will be shown. The acquisition time per breast image should be of about 10 s.

  11. The Physics of Frost Heave and Ice-Lens Growth

    KAUST Repository

    Peppin, Stephen S. L.

    2013-01-01

    The principle cause of frost heave is the formation of segregated ice-ice lenses-in freezing soil columns. Despite much experimental and theoretical work, there remain many questions about the fundamental process by which this occurs. Frost-heave models fall into two main classes: capillary and frozen-fringe models. Which model is appropriate depends on whether there is a frozen fringe; these are difficult to observe but some experimental evidence does exist. Recent advances have revitalized the capillary model, such as the engulfment model and the concept of geometrical supercooling. Key experimental and theoretical challenges remain to be resolved. © Soil Science Society of America 5585 Guilford Rd., Madison, WI 53711 USA. All rights reserved.

  12. H2O frost point detection on Mars

    Science.gov (United States)

    Ryan, J. A.; Sharman, R. D.

    1981-01-01

    The Viking Mars landers contain meteorological instrumentation to measure wind, temperature, and pressure but not atmospheric water content. The landings occurred during local summer, and it was observed that the nocturnal temperature decrease at sensor height (1.6 m) did not exhibit a uniform behavior at either site. It was expected that the rate of decrease would gradually slow, leveling off near sunrise. Instead, a leveling occurred several hours earlier. Temperature subsequently began a more rapid decrease which slowed by sunrise. This suggested that the temperature sensors may be detecting the frost point of water vapor. Analysis of alternative hypotheses demonstrates that none of these are viable candidates. The frost point interpretation is consistent with other lander and orbiter observations, with terrestrial experience, and with modeling of Mars' atmospheric behavior. It thus appears that the meteorology experiment can help provide a basis toward understanding the distribution and dynamics of Martian water vapor.

  13. Full-scale chilled pipeline frost heave testing, Fairbanks, Alaska, USA

    Energy Technology Data Exchange (ETDEWEB)

    Hazen, B. [Northern Engineering and Scientific, Anchorage, AK (United States); Isaacs, R.M. [RMI Associates, Camano Island, WA (United States); Myrick, J.E. [Myrick International, Tyler, TX (United States)

    2010-07-01

    This paper discussed a chilled pipeline frost-heave testing facility that was developed to simulate and record the rate of frost heave and frost-bulb growth for a buried, chilled pipeline in frost-susceptible soil and to determine the effectiveness of different mitigation techniques. The test facility, which was established near Fairbanks, Alaska, in 1979, has 10 test sections using 1.22-metre-diameter pipe. The testing involved un-insulated, insulated, and insulated with over-excavation and gravel berm configurations as well as the frost heave of the chilled pipeline. The test facility was described in detail. Frost heave and frost-bulb growth measurements from the first 10 months of testing were presented, as these are the first data to enter the public domain. The testing was undertaken to investigate the frost-heave relationships between sections, to better understand frost heave in permafrost, to explore possible mitigation options, and to advance the predicative capabilities of frost heave models. 12 refs., 1 tab., 17 figs.

  14. Part 4. Review of centrifuge testing applicability of frost heave

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, V. [Memorial Univ. of Newfoundland, St. John' s, NL (Canada). C-Core; Phillips, R. [Geotechnical Engineering Consultants, Harpenden (United Kingdom); Clark, J. [J.I. Clark and Associates, St. John' s, NL (Canada); Haigh, S. [Cambridge Univ., Cambridge (United Kingdom)

    2005-03-01

    This technical review of a proposed pipeline in the Mackenzie Valley in the Northwest Territories represents the third of 3 reports that document the current state of knowledge about frost heave theory, testing and predictive modelling. It summarizes the applicability of centrifuge testing to northern pipeline frost heave design. The advantages and limitations of this technology were described along with the reduced scale, accelerated time frame and cost effectiveness of centrifuge testing. Centrifuge testing is a viable tool for research into soil-structure interactions in Arctic pipeline design. The technique is also useful where the cost of large-scale testing would be prohibitive. This report describes a series of centrifuge modelling tests that were conducted by C-CORE to determine if the results of full-scale testing at the Calgary test site could be replicated. Work is ongoing for the Gas Research Institute and TransCanada Pipelines to further evaluate centrifuge technology as a tool for predicting the effects of frost heave and evaluating pipeline behaviour under a range of conditions, soil types, trench depths, soil temperature, pipe temperature and supply of water to the freezing front. The results from centrifuge testing were found to be in good agreement with the Calgary test site data, indicating similar patterns of heave displacement and time. It was concluded that centrifuge testing is a quick and cost effective method for testing geotechnical systems. The opportunity exists to extend its use to the prediction of frost heave and the design of Arctic pipelines. The other 2 accompanying reports have also been catalogued separately for inclusion in this database. refs., tabs., figs.

  15. The frost peat production; Routapalaturpeen tuotantoketjun tekniikka, talous ja ympaeristoevaikutukset

    Energy Technology Data Exchange (ETDEWEB)

    Nyroenen, T. [Vapo Oy, Jyvaeskylae (Finland); Leiviskae, V. [Oulu Univ. (Finland). Thule Inst.

    1997-12-01

    The frost peat production means the cutting of frozen peat in the winter time. The aim of this study is to test the possibilities to prolong the peat production season and to produce peat pieces for the horticultural peat industry. In the frost peat production method the frozen peat field is sawed throughout the length and breadth of by a circle saw. The sawed peat pieces are loosened from the field by a so-called `splitter`. The circle saw is equipped with the five circle saw blades (diameter 90 cm). The distance of the blades is adjustable. The splitter is equipped with a horizontal position blade (width 35 cm). The dimensions of the peat pieces are changeable, but from the point of drying the upper limit of the side of the peat cube can be 15-20 cm. The frost peat production method is technically suitable for production of slightly decomposed (H1-5) energy and horticultural peat. The energy peat pieces are allowed to dry up 70-75 % moisture content on the cutting field and then the pieces can be ridged by the screening ridger. If necessary, the ridges can be turned over. In the frost peat production, the conventional sod peat winning machines can be used in the following stages of the working tasks: harrowing, ridging, loading, turning of ridges and stockpiling. The measured output of the circle saw was about 45-50 m{sup 3}/h of energy peat and 58-63 m{sup 3}/h of horticultural peat. The output of the splitter was 120-150 m{sup 3}/h. Theoretically, the output of circle saw and the splitter can easily be doubled. Thereafter the production costs will be about 19 FIM/MWh of energy peat and 18,6 FIM/m{sup 3} of horticultural peat

  16. Strength and Stiffness of Stabilized Alluvial Silt under Frost Actions

    Directory of Open Access Journals (Sweden)

    Haibo Wang

    2017-01-01

    Full Text Available The Yellow River alluvial silt was stabilized into pavement base materials for cold regions. The stabilizing additives were cement, fly ash, and lime, which were included in a range of combinations and dosages when mixed with the silt. Freeze-thaw cyclic impacts were conducted on the treated samples to assess materials performance of withstanding the frost actions. The tests were conducted on samples cured for 7 days to up to 180 days. Test results show that the cement-fly ash-treated samples outperform the other two stabilization categories with respect to material strength and stiffness developed under both normal and frost conditions. Under the normal conditions, the material unconfined compressive (UC strength rises to 3.0 MPa on day 28 depending on the cement and fly ash dosage used. If subjected to frost actions, the fly ash inclusions warrant a residual UC strength value of 1.3 MPa and above. The antifrost performance of the cement-fly ash-treated samples is related to thermal buffer capacity of the fly ash particles. Water adsorption and material soundness results agree with the strength and stiffness development. An optimal dosage was 3–6% for the cement and 0.3 for cement to fly ash mass ratio.

  17. Frost Induces Respiration and Accelerates Carbon Depletion in Trees.

    Directory of Open Access Journals (Sweden)

    Or Sperling

    Full Text Available Cellular respiration depletes stored carbohydrates during extended periods of limited photosynthesis, e.g. winter dormancy or drought. As respiration rate is largely a function of temperature, the thermal conditions during such periods may affect non-structural carbohydrate (NSC availability and, ultimately, recovery. Here, we surveyed stem responses to temperature changes in 15 woody species. For two species with divergent respirational response to frost, P. integerrima and P. trichocarpa, we also examined corresponding changes in NSC levels. Finally, we simulated respiration-induced NSC depletion using historical temperature data for the western US. We report a novel finding that tree stems significantly increase respiration in response to near freezing temperatures. We observed this excess respiration in 13 of 15 species, deviating 10% to 170% over values predicted by the Arrhenius equation. Excess respiration persisted at temperatures above 0 °C during warming and reoccurred over multiple frost-warming cycles. A large adjustment of NSCs accompanied excess respiration in P. integerrima, whereas P. trichocarpa neither excessively respired nor adjusted NSCs. Over the course of the years included in our model, frost-induced respiration accelerated stem NSC consumption by 8.4 mg (glucose eq. cm(-3 yr(-1 on average in the western US, a level of depletion that may continue to significantly affect spring NSC availability. This novel finding revises the current paradigm of low temperature respiration kinetics.

  18. Seasonality of cavitation and frost fatigue in Acer mono Maxim.

    Science.gov (United States)

    Zhang, Wen; Feng, Feng; Tyree, Melvin T

    2017-12-08

    Although cavitation is common in plants, it is unknown whether the cavitation resistance of xylem is seasonally constant or variable. We tested the changes in cavitation resistance of Acer mono before and after a controlled cavitation-refilling and freeze-thaw cycles for a whole year. Cavitation resistance was determined from 'vulnerability curves' showing the percent loss of conductivity versus xylem tension. Cavitation fatigue was defined as a reduction of cavitation resistance following a cavitation-refilling cycle, whereas frost fatigue was caused by a freeze-thaw cycle. A. mono developed seasonal changes in native embolisms; values were relatively high during winter but relatively low and constant throughout the growing season. Cavitation fatigue occurred and changed seasonally during the 12-month cycle; the greatest fatigue response occurred during summer and the weakest during winter, and the transitions occurred during spring and autumn. A. mono was highly resistant to frost damage during the relatively mild winter months; however, a quite different situation occurred during the growing season, as the seasonal trend of frost fatigue was strikingly similar to that of cavitation fatigue. Seasonality changes in cavitation resistance may be caused by seasonal changes in the mechanical properties of the pit membranes. © 2017 John Wiley & Sons Ltd.

  19. CRYOLINK: Monitoring of permafrost and seasonal frost in southern Norway

    Science.gov (United States)

    Farbrot, Herman; Hipp, Tobias; Etzelmüller, Bernd; Humlum, Ole; Isaksen, Ketil; Strand Ødegârd, Rune

    2010-05-01

    The modern southern boundary for Scandinavian permafrost is located in the mountains of Southern Norway. Permafrost and seasonal frost are considered key components of the cryosphere, and the climate-permafrost relation has acquired added importance with the increasing awareness and concern of rising air temperatures. The three-year research project CRYOLINK ("Permafrost and seasonal frost in southern Norway") aims at improving knowledge on past and present ground temperatures, seasonal frost, and distribution of mountain permafrost in Southern Norway by addressing the fundamental problem of heat transfer between the atmosphere and the ground surface. Hence, several shallow boreholes have been drilled in August 2008 in three areas (Juvvass, Jetta and Tron) situated along a west-east transect. On most borehole sites air and ground temperatures are measured. Further, vertical arrays of Miniature Temperature Dataloggers (MTDs; Thermochron iBottons®) at fixed heights above the ground surface have been installed to roughly determine the snow depths at the sites, which is also indicated by digital cameras providing daily pictures of snow and weather conditions. In addition individual MTDs have been placed out to measure ground surface temperature at different aspects and snow settings. This presentation will focus on the field set up and give examples of data obtained from the sites.

  20. Cement mortar-degraded spinney waste composite as a matrix for immobilizing some low and intermediate level radioactive wastes: Consistency under frost attack

    International Nuclear Information System (INIS)

    Eskander, S.B.; Saleh, H.M.

    2012-01-01

    Highlights: ► Spinney fiber is one of the wastes generated from spinning of cotton raw materials. ► Cement mortar composite was hydrated by using the degraded slurry of spinney wastes. ► Frost resistance was assessed for the mortar-degraded spinney waste composite specimens. ► SEM image, FT-IR and XRD patterns were performed for samples subjected to frost attack. - Abstract: The increasing amounts of spinning waste fibers generated from cotton fabrication are problematic subject. Simultaneous shortage in the landfill disposal space is also the most problem associated with dumping of these wastes. Cement mortar composite was developed by hydrating mortar components using the waste slurry obtained from wet oxidative degradation of these spinney wastes. The consistency of obtained composite was determined under freeze–thaw events. Frost resistance was assessed for the mortar composite specimens by evaluating its compressive strength, apparent porosity and mass loss at the end of each period of freeze–thaw up to 45 cycles. Scanning electron microscopy, infrared spectroscopy and X-ray diffraction analyses were performed for samples subjected to frost attack aiming at evaluating the cement mortar in the presence of degraded spinney waste. The cement mortar composite exhibits acceptable resistance and durability against the freeze–thaw treatment that could be chosen in radioactive waste management as immobilizing agent for some low and intermediate level radioactive wastes.

  1. A new model for predicting performance of fin-and-tube heat exchanger under frost condition

    Energy Technology Data Exchange (ETDEWEB)

    Cui, J. [Key Lab. of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024 (China); Li, W.Z., E-mail: wzhongli@dlut.edu.c [Key Lab. of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024 (China); Liu, Y.; Zhao, Y.S. [Key Lab. of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024 (China)

    2011-02-15

    Accurate prediction of frost characteristics has crucial influence on designing effective heat exchangers. In this paper, a new CFD (Computational Fluid Dynamics) model has been proposed to predict the frost behaviour. The initial period of frost formation can be predicted and the influence of surface structure can be considered. The numerical simulations have been carried out to investigate the performance of fin-and-tube heat exchanger under frost condition. The results have been validated by comparison of simulations with the data computed by empirical formulas. The transient local frost formation has been obtained. The average frost thickness, heat exchanger coefficient and pressure drop on air side has been analysed as well. In addition, the influence factors have also been discussed, such as fin pitch, relative humidity, air flow rate and evaporating temperature of refrigerant.

  2. Observed variations in U.S. frost timing linked to atmospheric circulation patterns.

    Science.gov (United States)

    Strong, Courtenay; McCabe, Gregory J

    2017-05-23

    Several studies document lengthening of the frost-free season within the conterminous United States (U.S.) over the past century, and report trends in spring and fall frost timing that could stem from hemispheric warming. In the absence of warming, theory and case studies link anomalous frost timing to atmospheric circulation anomalies. However, recent efforts to relate a century of observed changes in U.S. frost timing to various atmospheric circulations yielded only modest correlations, leaving the relative importance of circulation and warming unclear. Here, we objectively partition the U.S. into four regions and uncover atmospheric circulations that account for 25-48% of spring and fall-frost timing. These circulations appear responsive to historical warming, and they consistently account for more frost timing variability than hemispheric or regional temperature indices. Reliable projections of future variations in growing season length depend on the fidelity of these circulation patterns in global climate models.

  3. Introducing new physical synergism effect arise together presence of multi wall carbon nanotube and Vulcan in the micro porous layer of gas diffusion electrode

    Energy Technology Data Exchange (ETDEWEB)

    Abdullah Mirzaie, R. [Shahid Rajaee Univ., Tehran (Iran, Islamic Republic of). Dept. of Chemistry; Gharibi, H. [Tarbiat Modarres Univ., Tehran (Iran, Islamic Republic of); Javaheri, M. [Tarbiat Modarres Univ., Tehran (Iran, Islamic Republic of). Dept. of Chemistry; Asfa, A. [Shahid Rajaee Univ., Tehran (Iran, Islamic Republic of)

    2009-07-01

    This study investigated the influence of multi-wall carbon nanotube (MWCNT) in fuel cell components. In particular, it examined how vulcanization in the microporous layer affects the performance of the gas-diffusion electrode (GDE) for the cathodic oxygen reduction reaction. Different percentages of MWCNT and Vulcan were used in the microporous layer of the GDE. A porosimeter, scanning electron microscope (SEM) and four probe conductometer was used to study the morphological and physical structure of the fabricated microporous layer. Linear sweep voltametry (LSV), electrochemical impedance spectroscopy (EIS), chronoamperometry and SEM techniques were used to study the electrochemical performance of prepared gas diffusion electrodes for oxygen reduction reaction. The results showed that the combination of MWCNT and Vulcan perturb the morphological structure in the microporous layer. The optimized value of MWCNT in the microporous layer varies with different platinum loading in the reaction layer. The optimized values were found to be 60 wt per cent, 80 wt per cent and 40 wt per cent MWCNT at 0.115 mg per cm{sup 2}, 0.5 mg per cm{sup 2} and 1 mg per cm{sup 2} Pt loading respectively.

  4. Initial discussion on the damage propagation of rock under the frost and thaw condition

    Energy Technology Data Exchange (ETDEWEB)

    Yang, G.; Pu, Y. [Xian University of Science and Technology, Xian (China). Dept. of Civil Engineering

    2002-08-01

    Based on the experimental results obtained from CT scanning of rocks under the condition of frost-and-thaw cycle, the characteristics of damage propagation of three types of rock materials (sandstone, shale and coal) were studied under the conditions of frost-and-thaw cycles. The effect of the number of frost-and-thaw cycles on the damage propagation of rock is emphasised in the discussion. 6 refs., 4 figs., 4 tabs.

  5. Experimental and numerical study on frost heave of saturated rock under uniform freezing conditions

    Science.gov (United States)

    Lv, Zhitao; Xia, Caichu; Li, Qiang

    2018-04-01

    A series of freezing experiments are conducted on saturated sandstone and mortar specimens to investigate the frost heave of saturated rock under uniform freezing conditions. The experimental results show that the frost heave of saturated rock is isotropic under uniform freezing conditions. During the freezing process, three stages are observed in the curves of variation of total frost heaving strain versus time: the thermal contraction stage, the frost heaving stage and the steady stage. Moreover, the amount of final stable frost heave first increases and then decreases with decrease in freezing temperature, and the maximum final stable frost heave occurs at different freezing temperature in saturated sandstone and mortar. Furthermore, a coupled thermal-mechanical (TM) model of frost heave of saturated rock is proposed in which a constraint coefficient \\zeta is used to consider the susceptibility of the internal rock grain structure to the expansion of pore ice. Then, numerical simulations are implemented with COMSOL to solve the governing equations of the TM model. Comparisons of the numerical results with the experimental results are performed to demonstrate the reliability of the model. The influences of elastic modulus and porosity on frost heave are also investigated, and the results show that the total frost heaving strain decreases non-linearly with increasing elastic modulus, and the decrease is significant when the elastic modulus is less than 3000 MPa, or approximately five times the elastic modulus of ice. In addition, the total frost heaving strain increases linearly with increasing porosity. Finally, an empirical equation between total frost heaving strain and freezing temperature is proposed and the equation well describes the variation of total frost heaving strain with freezing temperature.

  6. The first frost in the Pipe Nebula

    Science.gov (United States)

    Goto, Miwa; Bailey, Jeffrey D.; Hocuk, Seyit; Caselli, Paola; Esplugues, Gisela B.; Cazaux, Stephanie; Spaans, Marco

    2018-02-01

    Context. Spectroscopic studies of ices in nearby star-forming regions indicate that ice mantles form on dust grains in two distinct steps, starting with polar ice formation (H2O rich) and switching to apolar ice (CO rich). Aims: We test how well the picture applies to more diffuse and quiescent clouds where the formation of the first layers of ice mantles can be witnessed. Methods: Medium-resolution near-infrared spectra are obtained toward background field stars behind the Pipe Nebula. Results: The water ice absorption is positively detected at 3.0 μm in seven lines of sight out of 21 sources for which observed spectra are successfully reduced. The peak optical depth of the water ice is significantly lower than those in Taurus with the same AV. The source with the highest water-ice optical depth shows CO ice absorption at 4.7 μm as well. The fractional abundance of CO ice with respect to water ice is 16-6+7%, and about half as much as the values typically seen in low-mass star-forming regions. Conclusions: A small fractional abundance of CO ice is consistent with some of the existing simulations. Observations of CO2 ice in the early diffuse phase of a cloud play a decisive role in understanding the switching mechanism between polar and apolar ice formation. Based on data collected by SpeX at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration.Based also on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.The final reduced spectra (FITS format) are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/610

  7. Ice/frost/debris assessment for space shuttle Mission STS-32 (61-C)

    Science.gov (United States)

    Stevenson, Charles G.; Katnik, Gregory N.; Speece, Robert F.

    1986-01-01

    An Ice/Frost/Debris assessment was conducted for Space Shuttle Mission STS-32 (61-C). This assessment begins with debris inspections of the flight elements and launch facilities before and after launch. Ice/Frost formations are calculated during cryogenic loading of the external tank followed by an on-pad assessment of the Shuttle vehicle and pad at T-3 hours in the countdown. High speed films are reviewed after launch to identify Ice/Frost/Debris sources and investigate potential vehicle damage. The Ice/Frost/Debris conditions and their effects on the Space Shuttle are documented.

  8. Anti-icing/frosting and self-cleaning performance of superhydrophobic aluminum alloys

    Science.gov (United States)

    Feng, Libang; Yan, Zhongna; Shi, Xueting; Sultonzoda, Firdavs

    2018-02-01

    Ice formation and frost deposition on cryogenic equipment and systems can result in serious problems and huge economic loss. Hence, it is quite necessary to develop new materials to prevent icing and frosting on cold surfaces in engineering fields. Here, a superhydrophobic aluminum alloy with enhanced anti-frosting, anti-icing, and self-cleaning performance has been developed by a facile one-step method. The anti-frosting/icing performance of superhydrophobic aluminum alloys is confirmed by frosting/icing time delay, consolidating and freezing temperature reduction, and lower amount of frost/ice adhesion. Meanwhile, the excellent self-cleaning performance is authenticated by the fact that simulated pollution particles can be cleaned out by rolling water droplets completely. Finally, based on the classical nucleation theory, anti-icing and anti-frosting mechanisms of the superhydrophobic aluminum alloys are deduced. Results show that grounded on "air cushion" and "heat insulation" effect, a larger nucleation barrier and a lower crystal growth rate can be observed, which, hence, inhibit ice formation and frost deposition. It can be concluded that preparing superhydrophobic surfaces would be an effective strategy for improving anti-icing, anti-frosting, and self-cleaning performance of aluminum alloys.

  9. LOREF: Air cooler optimisation with reduction of ice and frost formation - Optimisation of lamella air-coolers/evaporators of air/water heat pumps - Part 2: mathematical-physical simulation of the lamella air-coolers with condensate and frost formation; LOREF: Luftkuehler-Optimierung mit Reduktion von Eis- und Frostbildung - Optimierung des Lamellenluftkuehlers/Verdampfers von Luft/Wasser-Waermepumpen - Teil 2: mathematisch-physikalische Simulation des Lamellenluftkuehlers mit Kondensat- und Frostbildung

    Energy Technology Data Exchange (ETDEWEB)

    Sahinagic, R.; Gasser, L.; Wellig, B.; Hilfiker, K.

    2008-04-15

    The average coefficient of performance (COP) of air/water heat pumps shall be further improved over the next decade. Its success will strongly depend on two measures: by altering the characteristic of the heat pump through continuous operation instead of on/off operation, and further, by reducing the formation of frost and ice. Frost significantly reduces the air flow, and consequently also the heat and mass transfer in the fin tube evaporator. The formation of frost and ice is influenced by a complex interaction between the fin tube evaporator, the characteristic of the fan and of the heat pump itself. An accurate prediction of these processes is required to optimize the design of the fin tube evaporator in combination with fan and heat pump to further improve the overall efficiency. Based on the theory of simultaneous heat and mass transfer combined with partial condensation and desublimation, a simulation program for the prediction of frost and ice formation has been developed, being valid over the wide range of the ambient air (from -10 {sup o}C to 15 {sup o}C and dry to saturated air). The humidity is deposited either as condensate, frost, ice or as a combination of them on the fins and tubes of the evaporator. It was a major challenge to create a correlation for the physical properties of the frost and ice layer in the unsteady processes. By numerous experiments, four regions of physical properties are distinguished, depending on the temperature at the boundary layer between air and frost or ice: condensate above -2.7 {sup o}C, condensate and ice between -3.5 {sup o}C to -2.7 {sup o}C, ice and frost between -5.2 {sup o}C to -3.5 {sup o}C and frost formed directly by desublimation below -5.2 {sup o}C. A high reliability has been obtained with the mathematical-physical simulation program proven over the entire applicable range of air temperature and humidity, temperature difference for heat transfer, air velocity and geometry of the fin tube evaporator. (author)

  10. Electrical Double-Layer and Ion Bridging Forces between Symmetric and Asymmetric Charged Surfaces in the Presence of Mono- and Divalent Ions

    DEFF Research Database (Denmark)

    Liu, Xiaoyan; Feilberg, Karen Louise; Yan, Wei

    2017-01-01

    charged (3-aminopropyl)trimethoxysilane, and the negatively charged (3-mercaptopropyl)trimethoxysilane. The interactions between the three symmetric systems, as well as between the three asymmetric combinations of surfaces, were measured and compared to calculated electrical double-layer forces....... The results demonstrated that the long-range interactions between the surfaces in all cases were dominated by double-layer forces, while short-range interactions, including adhesion, were dominated by ion bridging forces in the cases where both interaction surfaces favored adsorption of calcium ions...

  11. Frost heaving of planted tree seedlings in the boreal forest of northern Sweden

    International Nuclear Information System (INIS)

    Goulet, France

    2000-01-01

    Frost heaving can be a leading cause of tree seedling mortality in many places in the boreal forest of Northern Sweden. The aim of this investigation was to improve our understanding of frost heaving of planted tree seedlings as related to snow cover, scarification, planting methods and soil types. The thesis is based on a review paper, three field experiments and one laboratory experiment. The experiments focus on different methods to control frost heaving of forest tree seedlings and on a number of factors affecting the extent of frost heaving. The review paper identifies the many aspects of frost heaving of forest tree seedlings and agricultural crops based on an intensive review of the research contributions made during the last century. Even if many investigations have been carried out with the aim to decrease the extent of frost heaving, very little quantitative results are available for tree seedlings. In a field experiment, the choice of planting positions was effective in decreasing frost heaving of planted seedlings following mounding or disc-trenching. Seedlings planted in the depressions were largely affected by frost heaving with a maximal vertical displacement of 5.4 cm while frost heaving did not occur on the top of the mound. On the other hand, the planting time and planting depth had no influence on the extent of frost heaving. In another field experiment the size of the scarified patches was strongly correlated to frost heaving which reached between 7.6 and 11.5 cm in 4 and 8-dm patches compared to between 4.4 and 5.3 in non-scarified soil and in a 1-dm patch. Ground vegetation probably decreases the diurnal temperature variation and the number of freezing-thawing cycles. The duration and magnitude of frost temperatures, the frost hour sum, increased with patch size. The difference between the 8-dm and 1-dm patch increased to 2064 hour-degrees at the end of the winter. In larger patches, the planting depth seemed to be effective in reducing the

  12. Frost heaving of planted tree seedlings in the boreal forest of northern Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Goulet, France

    2000-07-01

    Frost heaving can be a leading cause of tree seedling mortality in many places in the boreal forest of Northern Sweden. The aim of this investigation was to improve our understanding of frost heaving of planted tree seedlings as related to snow cover, scarification, planting methods and soil types. The thesis is based on a review paper, three field experiments and one laboratory experiment. The experiments focus on different methods to control frost heaving of forest tree seedlings and on a number of factors affecting the extent of frost heaving. The review paper identifies the many aspects of frost heaving of forest tree seedlings and agricultural crops based on an intensive review of the research contributions made during the last century. Even if many investigations have been carried out with the aim to decrease the extent of frost heaving, very little quantitative results are available for tree seedlings. In a field experiment, the choice of planting positions was effective in decreasing frost heaving of planted seedlings following mounding or disc-trenching. Seedlings planted in the depressions were largely affected by frost heaving with a maximal vertical displacement of 5.4 cm while frost heaving did not occur on the top of the mound. On the other hand, the planting time and planting depth had no influence on the extent of frost heaving. In another field experiment the size of the scarified patches was strongly correlated to frost heaving which reached between 7.6 and 11.5 cm in 4 and 8-dm patches compared to between 4.4 and 5.3 in non-scarified soil and in a 1-dm patch. Ground vegetation probably decreases the diurnal temperature variation and the number of freezing-thawing cycles. The duration and magnitude of frost temperatures, the frost hour sum, increased with patch size. The difference between the 8-dm and 1-dm patch increased to 2064 hour-degrees at the end of the winter. In larger patches, the planting depth seemed to be effective in reducing the

  13. Statistical Evaluation of Potential Damage to the Al(OH)3 Layer on nTiO2 Particles in the Presence of Swimming Pool and Seawater

    Science.gov (United States)

    Nanosized TiO2 particles (nTiO2) are usually coated with an Al(OH)3 layer when used in sunscreen to shield against the harmful effects of free radicals that are generated when these particles are exposed to UV radiation. Therefore, it is vital to ...

  14. Influence of coffee pruning on the severity of frost damage

    Directory of Open Access Journals (Sweden)

    Armando Androcioli Filho

    2000-01-01

    Full Text Available Frost damages in a field experiment of pruning types and systems for the cultivars of Coffea arabica Catuaí and Mundo Novo, were evaluated at Londrina (23º22’S, 52º10´W, State of Parana, southern Brazil, during the winter of 1990 and 1994. Pruning types evaluated were ‘esqueletamento’ (cutting off all plagiotropic branches at 20-30 cm from the orthotropic branch, ‘decote’ (cutting off the orthotropic branch at 1.5 m and 2.0 m above ground and ‘recepa’ (cutting off the orthotropic branch at 0.8 m above ground, performed on all rows and on alternate rows, and on different sections of the plant. Results indicated that frost damage could increase according to the type and height of pruning. The pruning type ‘esqueletamento’ and prunings at higher levels were more suitable for regions with frost risk. Under severe frost condition, pruning type did not affect the damage in anyone of the treatments evaluated.Foram avaliados os danos causados pelas geadas ocorridas em 1990 e 1994 em cafeeiros de duas cultivares de Coffea arabica L., Catuaí e Mundo Novo, conduzidos em Londrina-PR. Os tipos e sistemas de podas aplicados foram o esqueletamento a 20-30 cm do tronco, decote a 1,5 m e 2,0 m de altura e recepa a 0,80 m de altura. As podas foram feitas em área total e em linhas alternadas e em diferentes partes da planta. Os dados obtidos indicaram que os danos por geada podem ser intensificados em função do tipo e altura da poda. A poda do tipo esqueletamento e as podas altas são mais indicadas para o manejo das lavouras nas regiões mais sujeitas ao fenômeno de geada. No caso de geada severa, todos os cafeeiros foram afetados, independente do tipo de poda.

  15. Frost-bitten foot: dialogues we live by

    OpenAIRE

    Ribeiro, Carlos Augusto; Guimarães, Ana Paula

    2000-01-01

    Ao comparar versões portuguesas e brasileiras de “A Formiguinha e a Neve” (Thompson motivo Z.42: “Stronger and Strongest”: frost-bitten foot” / tipo AaTh 2031, Stronger and Strongest) e inserindo nos nossos passos um texto do Panchatantra (“A história da ratinha”), rumo à interpretação desta história aparentemente simples e infantil, propusémo-nos avançar algumas notas sobre dois tópicos particulares: um relacionado com a linguagem (o quarto passo do nosso artigo); e outro com a filosofia do ...

  16. Analysis of likely Frost Events and day-to-night Variability in near-surface Water Vapor at Gale

    Science.gov (United States)

    Martinez, G.; Fischer, E.; Renno, N. O.; Sebastian, E.; Kemppinen, O.; Bridges, N.; Borlina, C.; Meslin, P. Y.; Genzer, M.; Harri, A. M.; Vicente-Retortillo, A.; de la Torre-Juárez, M.; Ramos, M.; Gomez, F.; Gomez-Elvira, J.

    2015-12-01

    We analyze REMS simultaneous measurements of relative humidity and ground temperature with the highest confidence to identify frost events at Gale crater during the first 1000 sols of the MSL mission. The relative humidity sensor has recently been recalibrated (June 2015), providing relative humidity values slightly lower than those in the previous release (Dec 2014). Here we only use relative humidity data obtained with the latest recalibration parameters. We find that the most likely frost events occurred at four different locations: Dingo Gap during sols 529-535, an unnamed place during sols 554-560, Kimberley during sols 609-617, and an unnamed place during sols 673-676. At these four locations, the terrain features thermal inertia of ~200 SI units, a value much lower than that of 365 ± 50 SI units obtained from satellite measurements at the landing ellipse. We estimate a maximum thickness of the frost layer likely developed at these four locations of the order of tenths of μm, with the precipitable water content (PWC) showing values of a few pr-μm. Since water vapor pressure values derived from REMS measurements present high uncertainties during the daytime, the day-to-night variability in the near-surface water content at Gale cannot be analyzed using only REMS products. By comparing the nighttime PWC values obtained from REMS with the daytime PWC values obtained from satellite, we estimate a day-to-night ratio of the near-surface water vapor pressure at Gale of about 5.

  17. Considering the method of frost resistance determination for Winter Wheat (Triticum aestivum L. varieties

    Directory of Open Access Journals (Sweden)

    Н. І. Рябчун

    2008-04-01

    Full Text Available There is the method represented in the article for frost resistance determination for Winter Wheat (soft and hard varieties by experts’ assessment of varieties submitted for Official Variety Studying. Prescribed temperature limits for artificial freezing of the plants, example varieties for frost-resistance groups, are indicated.

  18. Estimating winter survival of winter wheat by simulations of plant frost tolerance

    NARCIS (Netherlands)

    Bergjord Olsen, A.K.; Persson, T.; Wit, de A.; Nkurunziza, L.; Sindhøj, E.; Eckersten, H.

    2018-01-01

    Based on soil temperature, snow depth and the grown cultivar's maximum attainable level of frost tolerance (LT50c), the FROSTOL model simulates development of frost tolerance (LT50) and winter damage, thereby enabling risk calculations for winter wheat survival. To explore the accuracy of this

  19. Experimental study of frost heaving force based on transient shock response using piezoceramic sensors

    Science.gov (United States)

    Wang, Ruolin; Peng, Tongxiao; Wang, Ming L.

    2016-04-01

    In seasonally frozen soil regions, the frost heaving problem made it difficult to monitor or evaluate the pile safety for long term. So far, no mature tool can be utilized to monitor the frost heaving force, which was unevenly distributed along the pile. In this paper, a piezoceramic sensing based transient excitation response approach was proposed to monitor the frost heaving force in real time. Freeze-thaw cycles can result in great changes of soil engineering properties, including the frost heaving force. So, the freeze-thaw cycle was repeated fourth to study its effect. In the experiment, transient horizontal shock on the top of the pile will be detected by the 6 PZT sensors glued on the pile. The signal data received by the 6 PZT sensors can be used to illustrate the frost heaving force distribution along the pile. Moisture content effect is also one of the important reasons that cause the variation of soil mechanical properties. So three different moisture content (6%, 12%, 18%) testing soil were used in this experiment to detect the variance of the frost heaving force. An energy indicator was developed to quantitatively evaluate the frost heaving force applied on the pile. The experimental results showed that the proposed method was effective in monitoring the uneven distribution of frost heaving force along the pile.

  20. Robert Frost as Teacher. A Poet's Interpretation of the Teacher's Task.

    Science.gov (United States)

    Larson, Mildred

    1979-01-01

    Robert Frost's method of teaching is explained. He saw all education as self-education, not something a teacher can give a student. Frost believed freedom to be a necessity and his method gives the student much freedom while also placing a heavy burden of responsibility on him. (Article originally published in 1951.) (AF)

  1. Experimental and numerical study of frost formation by natural convection over a cold horizontal circular cylinder

    Energy Technology Data Exchange (ETDEWEB)

    Tahavvor, Ali R. [School of Mechanical Engineering, Shiraz University, Shiraz 71348-51154 (Iran); Yaghoubi, Mahmood [School of Mechanical Engineering, Shiraz University, Shiraz 71348-51154 (Iran); Academy of Sciences (Iran)

    2010-11-15

    Frost growth over a cold horizontal circular cylinder by natural convection has been investigated experimentally and numerically. Ambient air relative humidity, temperature and the cold surface temperature have been varied between 30% and 60%, 20 and 35 C and -10 and -4 C respectively. For detail analysis a mathematical model is used to simulate numerically frost formation process. For the first time, multistage modeling and supersaturation assumption is taken into account in the modeling of frost formation under natural convection condition. Comparisons are performed among the results of numerical model and experimental measurements and it is shown that the present model can be used more efficiently to determine frost growth and its properties. Based on the results, new correlations are developed for frost properties. (author)

  2. Numerical and experimental investigation on frosting of energy-recovery ventilator

    Science.gov (United States)

    Bilodeau, Stephane; Mercadier, Yves; Brousseau, Patrick

    Frosting of energy-recovery ventilators results in two major problems: increase of pressure losses and reduction of heat transfer rates. Frost formation of heat and mass exchangers used in these ventilation systems is investigated both experimentally and numerically. A numerical model for the prediction of the thermal behavior of the exchanger is presented. The model is validated with experimental data and is then employed to conduct a parametric study. Results indicate that the absolute humidity is the prevailing parameter for characterizing the frosting phenomenon. A frost-mass-fraction chart is established in terms of the absolute humidity of the warm exhaust stream and of the temperature of the cold supply stream. The effect of time and mass flowrate is also evaluated. The transient three-dimensional model shows that the absolute humidity and the temperature of both air flows vary nonlinearly in the frosted zone.

  3. Micrometeorological and Thermal Control of Frost Flower Growth and Decay on Young Sea Ice

    DEFF Research Database (Denmark)

    Galley, Ryan J.; Else, Brent G. T.; Geilfus, Nicolas-Xavier

    2015-01-01

    and the physical and thermal properties of the sea ice and atmosphere that form, decay and destroy frost flowers on young sea ice. Frost flower formation occurred during a high-pressure system that caused air temperatures to drop to -30°C, with relative humidity of 70% (an under saturated atmosphere), and very......Frost flowers are transient crystal structures that form on new and young sea ice surfaces. They have been implicated in a variety of biological, chemical and physical processes and interactions with the atmosphere at the sea ice surface. We describe the atmospheric and radiative conditions...... calm wind conditions. The sea ice surface temperature at the time of frost flower initiation was 10-13°C warmer than the air temperature. Frost flowers grew on nodules raised above the mean surface height by 5 mm, which were 4-6°C colder than the bare, brine-wetted, highly saline sea ice surface...

  4. Dynamics of frost resistance in various provenances of Abies grandis Lindl.

    Directory of Open Access Journals (Sweden)

    Adam Dolnicki

    2014-01-01

    Full Text Available The frost resistance of one year old needles and shoots of Abies grandis (seven provenances and Abies alba (one provenance was determined using Dexter's method since early autumn till late spring (September-May. Material was collected from trees over ten year old, planted in Beskid Sądecki Range near Krynica, 800 m above sea level. In this study it was found, that in early autumn (September A. grandis develops weaker frost hardiness than Abies alba. In the late autumn and in winter, provenances coming from region II (according to Müller, and especially provenance 12016, are equal in respect to frost hardiness of shoots and needles to Abies alba. Among the provenances from Müller's region I exceptional frost hardiness is displayed by provenance 12005, which is also characterized by fast growth. In spring, Abies alba flushes earlier than A. grandis, which makes it more susceptible to late frosts.

  5. Dispersion Energy Analysis of Rayleigh and Love Waves in the Presence of Low-Velocity Layers in Near-Surface Seismic Surveys

    Science.gov (United States)

    Mi, Binbin; Xia, Jianghai; Shen, Chao; Wang, Limin

    2017-10-01

    High-frequency surface-wave analysis methods have been effectively and widely used to determine near-surface shear (S) wave velocity. To image the dispersion energy and identify different dispersive modes of surface waves accurately is one of key steps of using surface-wave methods. We analyzed the dispersion energy characteristics of Rayleigh and Love waves in near-surface layered models based on numerical simulations. It has been found that if there is a low-velocity layer (LVL) in the half-space, the dispersion energy of Rayleigh or Love waves is discontinuous and ``jumping'' appears from the fundamental mode to higher modes on dispersive images. We introduce the guided waves generated in an LVL (LVL-guided waves, a trapped wave mode) to clarify the complexity of the dispersion energy. We confirm the LVL-guided waves by analyzing the snapshots of SH and P-SV wavefield and comparing the dispersive energy with theoretical values of phase velocities. Results demonstrate that LVL-guided waves possess energy on dispersive images, which can interfere with the normal dispersion energy of Rayleigh or Love waves. Each mode of LVL-guided waves having lack of energy at the free surface in some high frequency range causes the discontinuity of dispersive energy on dispersive images, which is because shorter wavelengths (generally with lower phase velocities and higher frequencies) of LVL-guided waves cannot penetrate to the free surface. If the S wave velocity of the LVL is higher than that of the surface layer, the energy of LVL-guided waves only contaminates higher mode energy of surface waves and there is no interlacement with the fundamental mode of surface waves, while if the S wave velocity of the LVL is lower than that of the surface layer, the energy of LVL-guided waves may interlace with the fundamental mode of surface waves. Both of the interlacements with the fundamental mode or higher mode energy may cause misidentification for the dispersion curves of surface

  6. Dispersion Energy Analysis of Rayleigh and Love Waves in the Presence of Low-Velocity Layers in Near-Surface Seismic Surveys

    Science.gov (United States)

    Mi, Binbin; Xia, Jianghai; Shen, Chao; Wang, Limin

    2018-03-01

    High-frequency surface-wave analysis methods have been effectively and widely used to determine near-surface shear (S) wave velocity. To image the dispersion energy and identify different dispersive modes of surface waves accurately is one of key steps of using surface-wave methods. We analyzed the dispersion energy characteristics of Rayleigh and Love waves in near-surface layered models based on numerical simulations. It has been found that if there is a low-velocity layer (LVL) in the half-space, the dispersion energy of Rayleigh or Love waves is discontinuous and ``jumping'' appears from the fundamental mode to higher modes on dispersive images. We introduce the guided waves generated in an LVL (LVL-guided waves, a trapped wave mode) to clarify the complexity of the dispersion energy. We confirm the LVL-guided waves by analyzing the snapshots of SH and P-SV wavefield and comparing the dispersive energy with theoretical values of phase velocities. Results demonstrate that LVL-guided waves possess energy on dispersive images, which can interfere with the normal dispersion energy of Rayleigh or Love waves. Each mode of LVL-guided waves having lack of energy at the free surface in some high frequency range causes the discontinuity of dispersive energy on dispersive images, which is because shorter wavelengths (generally with lower phase velocities and higher frequencies) of LVL-guided waves cannot penetrate to the free surface. If the S wave velocity of the LVL is higher than that of the surface layer, the energy of LVL-guided waves only contaminates higher mode energy of surface waves and there is no interlacement with the fundamental mode of surface waves, while if the S wave velocity of the LVL is lower than that of the surface layer, the energy of LVL-guided waves may interlace with the fundamental mode of surface waves. Both of the interlacements with the fundamental mode or higher mode energy may cause misidentification for the dispersion curves of surface

  7. Managing potato biodiversity to cope with frost risk in the high Andes: a modeling perspective.

    Science.gov (United States)

    Condori, Bruno; Hijmans, Robert J; Ledent, Jean Francois; Quiroz, Roberto

    2014-01-01

    Austral summer frosts in the Andean highlands are ubiquitous throughout the crop cycle, causing yield losses. In spite of the existing warming trend, climate change models forecast high variability, including freezing temperatures. As the potato center of origin, the region has a rich biodiversity which includes a set of frost resistant genotypes. Four contrasting potato genotypes--representing genetic variability--were considered in the present study: two species of frost resistant native potatoes (the bitter Solanum juzepczukii, var. Luki, and the non-bitter Solanum ajanhuiri, var. Ajanhuiri) and two commercial frost susceptible genotypes (Solanum tuberosum ssp. tuberosum var. Alpha and Solanum tuberosum ssp. andigenum var. Gendarme). The objective of the study was to conduct a comparative growth analysis of four genotypes and modeling their agronomic response under frost events. It included assessing their performance under Andean contrasting agroecological conditions. Independent subsets of data from four field experiments were used to parameterize, calibrate and validate a potato growth model. The validated model was used to ascertain the importance of biodiversity, represented by the four genotypes tested, as constituents of germplasm mixtures in single plots used by local farmers, a coping strategy in the face of climate variability. Also scenarios with a frost routine incorporated in the model were constructed. Luki and Ajanhuiri were the most frost resistant varieties whereas Alpha was the most susceptible. Luki and Ajanhuiri, as monoculture, outperformed the yield obtained with the mixtures under severe frosts. These results highlight the role played by local frost tolerant varieties, and featured the management importance--e.g. clean seed, strategic watering--to attain the yields reported in our experiments. The mixtures of local and introduced potatoes can thus not only provide the products demanded by the markets but also reduce the impact of frosts

  8. Managing potato biodiversity to cope with frost risk in the high Andes: a modeling perspective.

    Directory of Open Access Journals (Sweden)

    Bruno Condori

    Full Text Available Austral summer frosts in the Andean highlands are ubiquitous throughout the crop cycle, causing yield losses. In spite of the existing warming trend, climate change models forecast high variability, including freezing temperatures. As the potato center of origin, the region has a rich biodiversity which includes a set of frost resistant genotypes. Four contrasting potato genotypes--representing genetic variability--were considered in the present study: two species of frost resistant native potatoes (the bitter Solanum juzepczukii, var. Luki, and the non-bitter Solanum ajanhuiri, var. Ajanhuiri and two commercial frost susceptible genotypes (Solanum tuberosum ssp. tuberosum var. Alpha and Solanum tuberosum ssp. andigenum var. Gendarme. The objective of the study was to conduct a comparative growth analysis of four genotypes and modeling their agronomic response under frost events. It included assessing their performance under Andean contrasting agroecological conditions. Independent subsets of data from four field experiments were used to parameterize, calibrate and validate a potato growth model. The validated model was used to ascertain the importance of biodiversity, represented by the four genotypes tested, as constituents of germplasm mixtures in single plots used by local farmers, a coping strategy in the face of climate variability. Also scenarios with a frost routine incorporated in the model were constructed. Luki and Ajanhuiri were the most frost resistant varieties whereas Alpha was the most susceptible. Luki and Ajanhuiri, as monoculture, outperformed the yield obtained with the mixtures under severe frosts. These results highlight the role played by local frost tolerant varieties, and featured the management importance--e.g. clean seed, strategic watering--to attain the yields reported in our experiments. The mixtures of local and introduced potatoes can thus not only provide the products demanded by the markets but also reduce the

  9. Severe soil frost reduced losses of carbon and nitrogen from the forest floor during simulated snowmelt: A laboratory experiment

    Science.gov (United States)

    Andrew B. Reinmann; Pamela H. Templer; John L. Campbell

    2012-01-01

    Considerable progress has been made in understanding the impacts of soil frost on carbon (C) and nitrogen (N) cycling, but the effects of soil frost on C and N fluxes during snowmelt remain poorly understood. We conducted a laboratory experiment to determine the effects of soil frost on C and N fluxes from forest floor soils during snowmelt. Soil cores were collected...

  10. Convective boundary layer flow and heat transfer in a nanofluid in the presence of second order slip, constant heat flux and zero nanoparticles flux

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, M.M., E-mail: mansurdu@yahoo.com [Department of Mathematics and Statistics, College of Science, Sultan Qaboos University, PO Box 36, PC 123 Al-Khod, Muscat (Oman); Al-Rashdi, Maryam H. [Department of Mathematics and Statistics, College of Science, Sultan Qaboos University, PO Box 36, PC 123 Al-Khod, Muscat (Oman); Pop, I. [Department of Mathematics, Faculty of Mathematics and Computer Science, Babeş-Bolyai University, Cluj-Napoca 400084 (Romania)

    2016-02-15

    Highlights: • Convective boundary layer flow and heat transfer in a nanofluid is investigated. • Second order slip increases the rate of shear stress and decreases the rate of heat transfer in a nanofluid. • In nanofluid flow zero normal flux of the nanoparticles at the surface is realistic to apply. • Multiple solutions are identified for certain values of the parameter space. • The upper branch solution is found to be stable, hence physically realizable. - Abstract: In this work, the effects of the second order slip, constant heat flux, and zero normal flux of the nanoparticles due to thermophoresis on the convective boundary layer flow and heat transfer characteristics in a nanofluid using Buongiorno's model over a permeable shrinking sheet is studied theoretically. The nonlinear coupled similarity equations are solved using the function bvp4c using Matlab. Similarity solutions of the flow, heat transfer and nanoparticles volume fraction are presented graphically for several values of the model parameters. The results show that the application of second order slip at the interface is found to be increased the rate of shear stress and decreased the rate of heat transfer in a nanofluid, so need to be taken into account in nanofluid modeling. The results further indicate that multiple solutions exist for certain values of the parameter space. The stability analysis provides guarantee that the lower branch solution is unstable, while the upper branch solution is stable and physically realizable.

  11. Evaluation and improvement of frost durability of clay bricks

    Science.gov (United States)

    Koroth, Surej Raghavan

    In cold regions like Canada, frost action was reported to be the major cause of disintegration of brick veneer. Two approaches to ensure frost durability of clay bricks were studied in this research. One involved the evaluation of durability, while the other studied the improvement of durability through impregnation. In order to carry out these studies, three major objectives were set out for this research. They were: (1) to develop an index to evaluate frost durability, (2) to investigate the feasibility of using nondestructive methods to evaluate durability, and (3) to study the effect of impregnation with different materials on improving durability. It was intended in this research to develop a general durability index for clay bricks, irrespective of the manufacturing process adopted. The performance of the brick was studied using laboratory freeze-thaw test. As the time and facility requirements necessary for the unidirectional freezing test were beyond the constraints which existed in this research, an accelerated omnidirectional freeze-thaw test was used. This fact must be considered while interpreting the results from the freeze-thaw test. The study carried out to compare the performance of existing durability indices showed that they had limitations in reliably assessing durability. Therefore new durability indices were developed based on water absorption properties of bricks. These indices were found to overcome the limitations of existing indices. The feasibility study on nondestructive evaluation of durability was carried out using ultrasonic pulse velocity. New durability provisions were derived based on pulse velocity, using ASTM C216 specifications. At this stage it can be used only along with the ASTM method but it can avoid the time consuming ASTM procedure in many cases. Studies on impregnated bricks showed that there was a general shifting of pore sizes towards lower diameter region. Paraffin impregnated brick showed excellent freeze

  12. Early spring, severe frost events, and drought induce rapid carbon loss in high elevation meadows.

    Directory of Open Access Journals (Sweden)

    Chelsea Arnold

    Full Text Available By the end of the 20th century, the onset of spring in the Sierra Nevada mountain range of California has been occurring on average three weeks earlier than historic records. Superimposed on this trend is an increase in the presence of highly anomalous "extreme" years, where spring arrives either significantly late or early. The timing of the onset of continuous snowpack coupled to the date at which the snowmelt season is initiated play an important role in the development and sustainability of mountain ecosystems. In this study, we assess the impact of extreme winter precipitation variation on aboveground net primary productivity and soil respiration over three years (2011 to 2013. We found that the duration of snow cover, particularly the timing of the onset of a continuous snowpack and presence of early spring frost events contributed to a dramatic change in ecosystem processes. We found an average 100% increase in soil respiration in 2012 and 2103, compared to 2011, and an average 39% decline in aboveground net primary productivity observed over the same time period. The overall growing season length increased by 57 days in 2012 and 61 days in 2013. These results demonstrate the dependency of these keystone ecosystems on a stable climate and indicate that even small changes in climate can potentially alter their resiliency.

  13. Helicity Asymmetry in gamma p -> pi+ n with FROST

    Energy Technology Data Exchange (ETDEWEB)

    Steffen Strauch

    2012-04-01

    The main objective of the FROST experiment at Jefferson Lab is the study of baryon resonances. The polarization observable E for the reaction gamma p to pi+n has been measured as part of this program. A circularly polarized tagged photon beam with energies from 0.35 to 2.35 GeV was incident on a longitudinally polarized frozen-spin butanol target. The final-state pions were detected with the CEBAF Large Acceptance Spectrometer. Preliminary polarization data agree fairly well with present SAID and MAID partial-wave analyses at low photon energies. In most of the covered energy range, however, significant deviations are observed. These discrepancies underline the crucial importance of polarization observables to further constrain these analyses.

  14. Modeling of frost crystal growth over a flat plate using artificial neural networks and fractal geometries

    Science.gov (United States)

    Tahavvor, Ali Reza

    2017-03-01

    In the present study artificial neural network and fractal geometry are used to predict frost thickness and density on a cold flat plate having constant surface temperature under forced convection for different ambient conditions. These methods are very applicable in this area because phase changes such as melting and solidification are simulated by conventional methods but frost formation is a most complicated phase change phenomenon consists of coupled heat and mass transfer. Therefore conventional mathematical techniques cannot capture the effects of all parameters on its growth and development because this process influenced by many factors and it is a time dependent process. Therefore, in this work soft computing method such as artificial neural network and fractal geometry are used to do this manner. The databases for modeling are generated from the experimental measurements. First, multilayer perceptron network is used and it is found that the back-propagation algorithm with Levenberg-Marquardt learning rule is the best choice to estimate frost growth properties due to accurate and faster training procedure. Second, fractal geometry based on the Von-Koch curve is used to model frost growth procedure especially in frost thickness and density. Comparison is performed between experimental measurements and soft computing methods. Results show that soft computing methods can be used more efficiently to determine frost properties over a flat plate. Based on the developed models, wide range of frost formation over flat plates can be determined for various conditions.

  15. Optimum soil frost depth to alleviate climate change effects in cold region agriculture

    Science.gov (United States)

    Yanai, Yosuke; Iwata, Yukiyoshi; Hirota, Tomoyoshi

    2017-03-01

    On-farm soil frost control has been used for the management of volunteer potatoes (Solanum tuberosum L.), a serious weed problem caused by climate change, in northern Japan. Deep soil frost penetration is necessary for the effective eradication of unharvested small potato tubers; however, this process can delay soil thaw and increase soil wetting in spring, thereby delaying agricultural activity initiation and increasing nitrous oxide emissions from soil. Conversely, shallow soil frost development helps over-wintering of unharvested potato tubers and nitrate leaching from surface soil owing to the periodic infiltration of snowmelt water. In this study, we synthesised on-farm snow cover manipulation experiments to determine the optimum soil frost depth that can eradicate unharvested potato tubers without affecting agricultural activity initiation while minimising N pollution from agricultural soil. The optimum soil frost depth was estimated to be 0.28-0.33 m on the basis of the annual maximum soil frost depth. Soil frost control is a promising practice to alleviate climate change effects on agriculture in cold regions, which was initiated by local farmers and further promoted by national and local research institutes.

  16. Optimum soil frost depth to alleviate climate change effects in cold region agriculture.

    Science.gov (United States)

    Yanai, Yosuke; Iwata, Yukiyoshi; Hirota, Tomoyoshi

    2017-03-21

    On-farm soil frost control has been used for the management of volunteer potatoes (Solanum tuberosum L.), a serious weed problem caused by climate change, in northern Japan. Deep soil frost penetration is necessary for the effective eradication of unharvested small potato tubers; however, this process can delay soil thaw and increase soil wetting in spring, thereby delaying agricultural activity initiation and increasing nitrous oxide emissions from soil. Conversely, shallow soil frost development helps over-wintering of unharvested potato tubers and nitrate leaching from surface soil owing to the periodic infiltration of snowmelt water. In this study, we synthesised on-farm snow cover manipulation experiments to determine the optimum soil frost depth that can eradicate unharvested potato tubers without affecting agricultural activity initiation while minimising N pollution from agricultural soil. The optimum soil frost depth was estimated to be 0.28-0.33 m on the basis of the annual maximum soil frost depth. Soil frost control is a promising practice to alleviate climate change effects on agriculture in cold regions, which was initiated by local farmers and further promoted by national and local research institutes.

  17. Influence of aggregate type and chemical admixtures on frost resistance of lightweight mortars

    Science.gov (United States)

    Klimek, Beata; Widomski, Marcin K.; Barnat-Hunek, Danuta

    2017-07-01

    The aim of studies presented in this paper covered analyses of type of lightweight aggregate as well as aeration and hydrophobic admixtures influence on absorbability and frost resistance of heat-insulating mortars applied in the energy-efficient construction. In the presented research, expanded perlite (EP) and expanded clay aggregate (ceramsite) were used as lightweight aggregates. The measurements of the basic mechanical and physical characteristics of tested mortars were performed, including, inter alia, compressive and flexural tensile strength, density, effective (open) and total porosity, absorbability, thermal conductivity as well as frost resistance after 25 cycles of freezing and thawing. Substitution of some part of sand fraction by the lightweight aggregates, expanded clay aggregate or perlite, resulted in changes in physical properties of the tested mortars. The observed decrease in density (specific weight), coefficient of heat transport and strength parameters were simultaneously accompanied by the increase in absorbability. Researches concerning frost resistance of mortars containing ceramsite and perlite showed the improved frost resistance of mortar utilizing perlite. Most of the tested mortars shoved satisfactory frost resistance, only samples of mortar containing ceramsite and aeration admixture were destroyed. The significant influence of aerating admixture on frost resistance of mortars was determined. Hydrophobic siloxanes addition failed to adequately protect the mortars against frost erosion, regardless the type of applied aggregate.

  18. Can the Frost Multidimensional Perfectionism Scale assess perfeccionismo?

    Science.gov (United States)

    Burgess, Alexandra M; DiBartolo, Patricia Marten; Rendón, María Jose

    2017-07-01

    Although culture-based measurement bias threatens the validity of intergroup comparison research, measurement invariance is often assumed rather than demonstrated by researchers who draw conclusions about cross-cultural similarities or differences. The current article investigates the cross-cultural invariance of a popular measure of perfectionism, the Frost Multidimensional Perfectionism Scale (F-MPS; Frost, Marten, Lahart, & Rosenblate, 1990) for a Hispanic/Latina sample. Perfectionism, which encompasses high goal setting and sensitivity to critical evaluation, is a transdiagnostic risk factor for internalizing psychopathology that especially warrants focus among groups burdened by mental health disparities. Multiple samples were used in a series of analyses to construct a baseline first-order measurement model and test for cross-group equivalence. For model development, confirmatory factor analyses (CFAs) were used with 320 female participants (M age = 19.61 years) who identified primarily (n = 301) as European/European American. Measurement invariance testing was conducted with multigroup CFAs using another sample of female adults (n = 574; Mage = 21.21 years), identifying either as European/European American (n = 217) or Hispanic/Latina/Latin American (n = 357). Evidence was found for invariance across the revised F-MPS factor structure, pattern of factor loadings, and factor variances/covariances. Results indicate that predictive relationships may be compared across these groups, but caution is suggested when interpreting raw mean score differences due to intercept nonequivalence. Further, second-order model testing demonstrated support for the bidimensional model of perfectionism cross-culturally. Future research on perfectionism within the Latino/a population is encouraged using this equivalent item set. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  19. Estimation of MHD boundary layer slip flow over a permeable stretching cylinder in the presence of chemical reaction through numerical and artificial neural network modeling

    Directory of Open Access Journals (Sweden)

    P. Bala Anki Reddy

    2016-09-01

    Full Text Available In this paper, the prediction of the magnetohydrodynamic boundary layer slip flow over a permeable stretched cylinder with chemical reaction is investigated by using some mathematical techniques, namely Runge–Kutta fourth order method along with shooting technique and artificial neural network (ANN. A numerical method is implemented to approximate the flow of heat and mass transfer characteristics as a function of some input parameters, explicitly the curvature parameter, magnetic parameter, permeability parameter, velocity slip, Grashof number, solutal Grashof number, Prandtl number, temperature exponent, Schmidt number, concentration exponent and chemical reaction parameter. The non-linear partial differential equations of the governing flow are converted into a system of highly non-linear ordinary differential equations by using the suitable similarity transformations, which are then solved numerically by a Runge–Kutta fourth order along with shooting technique and then ANN is applied to them. The Back Propagation Neural Network is applied for forecasting the desired outputs. The reported numerical values and the ANN values are in good agreement than those published works on various special cases. According to the findings of this study, the ANN approach is reliable, effective and easily applicable for simulating heat and mass transfer flow over a stretched cylinder.

  20. Climate change and spring frost damages for sweet cherries in Germany

    Science.gov (United States)

    Chmielewski, Frank-M.; Götz, Klaus-P.; Weber, Katharina C.; Moryson, Susanne

    2018-02-01

    Spring frost can be a limiting factor in sweet cherry ( Prunus avium L.) production. Rising temperatures in spring force the development of buds, whereby their vulnerability to freezing temperatures continuously increases. With the beginning of blossom, flowers can resist only light frosts without any significant damage. In this study, we investigated the risk of spring frost damages during cherry blossom for historical and future climate conditions at two different sites in NE (Berlin) and SW Germany (Geisenheim). Two phenological models, developed on the basis of phenological observations at the experimental sweet cherry orchard in Berlin-Dahlem and validated for endodormancy release and for warmer climate conditions (already published), were used to calculate the beginning of cherry blossom in Geisenheim, 1951-2015 (external model validation). Afterwards, on the basis of a statistical regionalisation model WETTREG (RCP 8.5), the frequency of frost during cherry blossom was calculated at both sites for historical (1971-2000) and future climate conditions (2011-2100). From these data, we derived the final flower damage, defined as the percentage of frozen flowers due to single or multiple frost events during blossom. The results showed that rising temperatures in this century can premature the beginning of cherry blossom up to 17 days at both sites, independent of the used phenological model. The frequency and strength of frost was characterised by a high temporal and local variability. For both sites, no significant increase in frost frequency and frost damage during blossom was found. In Geisenheim, frost damages significantly decreased from the middle of the twenty-first century. This study additionally emphasises the importance of reliable phenological models which not only work for current but also for changed climate conditions and at different sites. The date of endodormancy release should always be a known parameter in chilling/forcing models.

  1. Numerical Model on Frost Height of Round Plate Fin Used for Outdoor Heat Exchanger of Mobile Electric Heat Pumps

    Directory of Open Access Journals (Sweden)

    Moo-Yeon Lee

    2012-01-01

    Full Text Available The objective of this study is to provide the numerical model for prediction of the frost growth of the round plate fin for the purpose of using it as a round plate fin-tube heat exchanger (evaporator under frosting conditions. In this study, numerical model was considering the frost density change with time, and it showed better agreement with experimental data of Sahin (1994 than that of the Kim model (2004 and the Jonse and Parker model (1975. This is because the prediction on the frost height with time was improved by using the frost thermal conductivity reflecting the void fraction and density of ice crystal with frost growth. Therefore, the developed numerical model could be used for frosting performance prediction of the round plate fin-tube heat exchanger.

  2. The minimum temperatures in the winter 2006/07 in Slovenian frost hollows and cold basins

    Directory of Open Access Journals (Sweden)

    Matej Ogrin

    2007-12-01

    Full Text Available The members of Slovenian Meteorological Forum, Department of Geography at University of Ljubljana and Slovenian Forestry Institute started to measure temperatures in Slovenian frost hollows and cold basins in 2004. The measurements, which improved during the period 2004.2006, continued also in the winter 2006.2007, all together, in more than 30 frost hollows and cold basins Alpine, Dinaridic and even Submediterranean areas. Although the winter 2006/2007 was very mild, minimum temperatures in frost hollow Hribarice fell below -35°C.

  3. Frost susceptibility of sub-base gravel used in Pearl-Chain Bridges: an experimental investigation

    DEFF Research Database (Denmark)

    Lund, Mia Schou Møller; Hansen, Kurt Kielsgaard; Andersen, Iben Brøndum

    2016-01-01

    , no actual frost tests have been carried out to verify this assumption. In the present study, the frost susceptibility of four different Danish gravel materials is categorised from their heave rate. We test two Danish sub-base gravel materials, with particle size distributions of 0–8 mm and 0–31.5 mm......, respectively, and also two modified sub-base gravel materials with increased and reduced fines contents. The fines content of the gravel materials is analysed by laser diffraction, and compared with two common frost susceptibility criteria, Casagrande’s and Schaible’s, and with Danish tender specifications...

  4. Seasonal frost penetration, Sleepers River Research Watershed, Vermont, USA, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — The frost tube network is located within a 3.25-square-mile sub-watershed of the Sleepers River Research Watershed near Danville, Vermont, USA. Tubes were positioned...

  5. Frost sensivity and nutrient status  in a fertilized Norway spruce stand in Denmark

    DEFF Research Database (Denmark)

    Jönsson, Anna Maria; Ingerslev, Morten; Raulund-Rasmussen, Karsten

    2004-01-01

    The aim of this study was to assess the effect of the N, P and K status on frost sensitivity of Norway spruce needles in a fertilization experiment situated in a nutrient poor 29-year-old Picea abies stand in western Denmark. The relative difference in frost sensitivity among trees was assessed...... by an index of injury, based on conductivity measurements of ion leakage from needles. Despite fertilization, all trees indicated N, P and K deficiency. The foliage, collected in late winter, was generally not very frost sensitive, but foliage from trees with the lowest K and P status were more sensitive...... to frost, and the current year needles were more sensitive than the second and third year needles. The advancement of bud burst was assessed in May. Trees with a relatively high N concentration in the current year needles had a more advanced bud burst than trees with a lower N concentration, increasing...

  6. Frost formation and heat transfer on a cold surface in ice fog

    Energy Technology Data Exchange (ETDEWEB)

    Mago, P.J. [Mississippi State University (United States). Department of Mechanical Engineering; Sherif, S.A. [University of Florida, Gainesville (United States). Department of Mechanical and Aerospace Engineering

    2005-06-01

    In this paper a semi-empirical model describing heat and mass transfer on a cold surface in humid air under supersaturated frosting conditions is presented. The lack of psychrometric data in the supersaturated zone of the psychrometric chart has historically impeded the ability of researchers to accurately predict heat and mass transfer in supersaturated air. The work described in this paper has been partially made possible by developing a systematic procedure to compute the properties of supersaturated air, especially in the low temperature zone of the psychrometric chart. Development of such a capability will allow us to predict the amount of frost collected, the frost deposition and heat transfer rates, frost thickness and surface temperature, and other important parameters. (author)

  7. Seasonal frost and soil temperature data, Western Cape Mountains, South Africa, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — Micro-climatic monitoring of air and ground was started in 1990 to evaluate climatic controls on the present-day diurnal soil frost environment in the Western Cape...

  8. Siim Nestor soovitab : Ben Frost ja Alexander Robotnik Eclectical / Siim Nestor

    Index Scriptorium Estoniae

    Nestor, Siim, 1974-

    2007-01-01

    Austraalia muusik ja helilooja Ben Frost projektiga "6 guitars" esinemas festivali Eclectica raames 6. sept. Tartu klubis Rock ja Roll ja itaalia diskor Alexander Robotnik 7. sept. klubis Trehv, esinejatest

  9. Presence Service in IMS

    OpenAIRE

    Petras, David; Baronak, Ivan; Chromy, Erik

    2013-01-01

    This paper describes the presence service, which is located in the IP multimedia subsystem. This service allows making many applications for different groups of people. The paper describes differences between a network without the service and with the service. The biggest change is an increased number of transmitted messages. The presence uses some part of the IP multimedia subsystem control layer, which is shown in communication between the user and the server. The paper deals with the numbe...

  10. Risk Modelling of Late Spring Frost Damage on Fruit Trees, Case Study; Apple Tree, Mashhad Plain

    Directory of Open Access Journals (Sweden)

    M Rahimi

    2012-02-01

    Full Text Available Mashhad plain is one of the most important regions of Apple cultivated areas. Occurring spring late frost creates a lot of damages on bud and decreasing the yield of Apple in this region. Assessment and risk modeling of frost damage would be useful to manage and decrease the damage. The study area is a part of Khorasan Razavi province which is located in Mashhad plain. This region is located in Northeast Iran (36º to 37 º N, 58 º 30' to 60 º E. The area of this region is about 13000 square km which is about one tenth of Khorasan province area. In order to modeling frost damage risk 12 affective parameters including climatological(Minimum temperature, temperature decreasing rate, temperature Increasing rate, Julian days of frost, cumulative degree days, Area under zero line, and frost duration and geographical parameters (Elevation, Longitude, Latitude, Aspect, and slope were selected. 3 damage full radiative frosts were selected in the period of Apple flowering time which was dated 20 April 2003, 8 April 2005, and 28 March 2005. Required meteorological data were collected from 9 meteorological standard stations inside and outside of study area. Linear multiple regression were used to modeling the relationship. The map for each parameter was plotted by using suitable interpolation method including IDW; Spline; Kriging. A grid map was defined with 5 by 5 kilometers to extract enough data for entering to the model. The regression equation was significant at the level of 99% significance. By using this equation the predicted amounts of frost risk damage were calculated for each point of grid and also the map was plotted. The regression equation of observed and predicted frost damage risk was provided by correlation of 0.93 and the error map also was prepared. According to this study in frost of 31 Farvardin 1388 South West parts of the plain estimated as the most frost risk areas by %53.19 and the southeast parts were estimated as the least

  11. Electro-thermal protection system design against atmospheric frost on turbine blades

    Energy Technology Data Exchange (ETDEWEB)

    Noui, M.A.; Perron, J.; Fortin, G. [Quebec Univ., Chicoutimi, PQ (Canada). Anti-Icing Materials International Laboratory

    2010-07-01

    This presentation discussed a research program developed to adapt de-icing thermal heating systems for use in wind turbines. The presence of ice on turbine blades can significantly deteriorate rotor performance. Accumulations of ice can increase the radial load on the turbine blades. The uneven formations of ice can lead to vibrations and the expulsion of pieces of ice into surrounding areas. Ice can also reduce the accuracy of various wind measuring devices. A recent study in Finland showed that turbine heating systems consume 3.6 per cent of annual wind production energy. De-icing systems include protective covers; air inlets; sealing systems; inflation tubes; elastomeric ply; and bond ply. The systems also include blade trailing and loading edges, and blade roots. The energy dissipated by the system's heating element is lost by conduction to the interior of the profile. The research program is now developing a system to improve electrothermal protection against frost that is suitable for turbine blades, as well as a thermal model for simulating its operation in a wind turbine. tabs., figs.

  12. An inverse geometry problem in estimating frost growth on an evaporating tube

    Energy Technology Data Exchange (ETDEWEB)

    Huang, C.H. [Department of Naval Architecture and Marine Engineering, National Cheng Kung University Tainan, Taiwan (Taiwan)

    2002-08-01

    When humid air comes into contact with a surface whose temperature is below the dew point of water vapor in air and also below the freezing point, frost deposition takes place over the surface. The phenomena of the frost growth are very complicated and therefore it is very difficult to model mathematically the behavior of frost growth and predict it. In the present study a transient inverse geometry heat conduction problem (shape identification problem) is solved using the conjugate gradient method (CGM) and boundary element method (BEM)-based inverse algorithm to estimate the unknown irregular frost thickness and shape. Results obtained by using the CGM to estimate the frost growth are justified based on the numerical experiments. It is concluded that the accurate frost shape can be estimated by the CGM except for the initial and final time. The reason and improvement of this singularity are addressed. Finally the effects of reducing the number of sensors and increasing the measurement errors on the inverse solutions are discussed. (orig.)

  13. Metal stress consequences on frost hardiness of plants at northern high latitudes: a review and hypothesis

    Energy Technology Data Exchange (ETDEWEB)

    Taulavuori, Kari [Department of Biology, University of Oulu, PO Box 3000, FIN-90014, Oulu (Finland)]. E-mail: kari.taulavuori@oulu.fi; Prasad, M.N.V. [Department of Plant Sciences, University of Hyderabad, Hyderabad 500 046, Andhra Pradesh (India); Taulavuori, Erja [Department of Biology, University of Oulu, PO Box 3000, FIN-90014, Oulu (Finland); Laine, Kari [Department of Biology, University of Oulu, PO Box 3000, FIN-90014, Oulu (Finland)

    2005-05-01

    This paper reviews the potential of trace/heavy metal-induced stress to reduce plant frost hardiness at northern high latitudes. The scientific questions are first outlined prior to a brief summary of heavy metal tolerance. The concepts of plant capacity and survival adaptation were used to formulate a hypothesis, according to which heavy metal stress may reduce plant frost hardiness for the following reasons: (1) Heavy metals change membrane properties through impaired resource acquisition and subsequent diminution of the cryoprotectant pool. (2) Heavy metals change membrane properties directly through oxidative stress, i.e. an increase of active oxygen species. (3) The involved co-stress may further increase oxidative stress. (4) The risk of frost injury increases due to membrane alterations. An opposite perspective was also discussed: could metal stress result in enhanced plant frost hardiness? This phenomenon could be based on the metabolism (i.e. glutathione, polyamines, proline, heat shock proteins) underlying a possible general adaptation syndrome of stress (GAS). As a result of the review it was suggested that metal-induced stress seems to reduce rather than increase plant frost hardiness. - Metal stress may reduce plant frost hardiness.

  14. The vulnerability of silver fir populations to damage from late frosts

    Directory of Open Access Journals (Sweden)

    Klisz Marcin

    2016-03-01

    Full Text Available The aim of the study was to determine the vulnerability of selected silver fir populations to damage from late frost in the climatic conditions of south-eastern Poland. To determine the vulnerability of apical and lateral shoots to damage caused by late frosts, we observed four test plots in 2009 and 2014, each containing progenies of selected seed stands. Our statistical analyses were based on a model incorporating the following variables: site, year, type of frost damage, population as well as the possible interaction between these variables. Significant differences between the populations were found in terms of their sensitivity to damage from low temperature occurring during the growth period. Furthermore, we indirectly demonstrated differences in the severity of late frost on the experimental plots, as well as the intensity and variability of late frost shoot damage. Based on these results, we divided the studied populations into two groups of low (EF, KRA1 and NAR and high (LES2 and BAL2 sensitivity to late frost damage.

  15. Delayed frost formation on hybrid nanostructured surfaces with patterned high wetting contrast

    Science.gov (United States)

    Hou, Youmin; Zhou, Peng; Yao, Shuhuai

    2014-11-01

    Engineering icephobic surfaces that can retard the frost formation and accumulation are important to vehicles, wind turbines, power lines, and HVAC systems. For condensation frosting, superhydrophobic surfaces promote self-removal of condensed droplets before freezing and consequently delay the frost growth. However, a small thermal fluctuation may lead to a Cassie-to-Wenzel transition, and thus dramatically enhance the frost formation and adhesion. In this work, we investigated the heterogeneous ice nucleation on hybrid nanostructured surfaces with patterned high wetting contrast. By judiciously introducing hydrophilic micro-patches into superhydrophobic nanostructured surface, we demonstrated that such a novel hybrid structure can efficiently defer the ice nucleation as compared to a superhydrophobic surface with nanostructures only. We observed efficient droplet jumping and higher coverage of droplets with diameter smaller than 10 μm, both of which suppress frost formation. The hybrid surface avoids the formation of liquid-bridges for Cassie-to-Wenzel transition, therefore eliminating the `bottom-up' droplet freezing from the cold substrate. These findings provide new insights to improve anti-frosting and anti-icing by using heterogeneous wettability in multiscale structures.

  16. Metal stress consequences on frost hardiness of plants at northern high latitudes: a review and hypothesis

    International Nuclear Information System (INIS)

    Taulavuori, Kari; Prasad, M.N.V.; Taulavuori, Erja; Laine, Kari

    2005-01-01

    This paper reviews the potential of trace/heavy metal-induced stress to reduce plant frost hardiness at northern high latitudes. The scientific questions are first outlined prior to a brief summary of heavy metal tolerance. The concepts of plant capacity and survival adaptation were used to formulate a hypothesis, according to which heavy metal stress may reduce plant frost hardiness for the following reasons: (1) Heavy metals change membrane properties through impaired resource acquisition and subsequent diminution of the cryoprotectant pool. (2) Heavy metals change membrane properties directly through oxidative stress, i.e. an increase of active oxygen species. (3) The involved co-stress may further increase oxidative stress. (4) The risk of frost injury increases due to membrane alterations. An opposite perspective was also discussed: could metal stress result in enhanced plant frost hardiness? This phenomenon could be based on the metabolism (i.e. glutathione, polyamines, proline, heat shock proteins) underlying a possible general adaptation syndrome of stress (GAS). As a result of the review it was suggested that metal-induced stress seems to reduce rather than increase plant frost hardiness. - Metal stress may reduce plant frost hardiness

  17. Plant safety margin against frost damages has declined in Switzerland over the last four decades

    Science.gov (United States)

    Vitasse, Yann; Schneider, Léonard; Klein, Geoffrey; Rixen, Christian; Rebetez, Martine

    2017-04-01

    Winters and early springs have become warmer over the last decades which has in turn promoted earlier plant development in temperate regions. While temperatures will on average continue to increase in the coming decades due to the rise of greenhouse gases concentration in the atmosphere, there is no consensus about how the occurrence of late spring frosts will change. If the frequency and the severity of late spring frosts remain unchanged in the future or advance less than vegetation onset, vulnerable plant organs (young leaves, flowers or dehardened buds) may be more exposed to frost damage. Here we analyzed long-term series of temperature data during the period 1975-2016 at 50 locations in Switzerland. We used different thresholds of growing degree days (GDD) as a proxy for spring phenology of fruit trees based on long-term series of phenological observations. Finally, we tested whether the time lag between the date when the GDD is reached and the latest occurrence of frost has changed over the study period. Overall we found that the safety margin against potential frost damage to plants has slightly decreased during the study period, irrespective of elevation (from 203 to 2283 m). Our results suggest that the cost for preventing frost damages on fruit trees could increase in the coming decades and the introduction of new varieties of fruit trees adapted to warmer climate should be carefully considered as they generally exhibit earlier spring phenology.

  18. CO2 Frost Phenomenon for Binary System of Methane-Carbon Dioxide Mixtures

    Directory of Open Access Journals (Sweden)

    Gede Wibawa

    2015-12-01

    Full Text Available In the present study, the CO2 frost phenomenon of CH4-CO2 mixtures has been observed for the rational design of CO2 removal from natural gas using a controlled freeze out area. The CO2 frost conditions were estimated using the ZNE method and process simulation software (Aspen HYSYS® v7.3. The experiment was carried out using a double pipe heat exchanger (DPHE with the concentration of CO2 in the gas mixture at 5 and 10% and pressure of the gas mixture from 1 to 20 bar. The equilibrium temperature predictions of the ZNE method and the process simulation software only had a slight difference, with a magnitude deviation of less than 1% for pressures below 20 bar and 3% for pressures in the range of 20-30 bar, respectively. In the experimental study, CO2 frost formation was detected at pressures of 1, 5, 10 and 20 bar. The locations of the initial CO2 frost formation were determined using a pressure drop indicator associated with the predicted frost temperatures obtained from the ZNE method and the process simulation software. For all studied variables, the locations of initial CO2 frost formation were found at 0.887-1.531 m from the inlet.

  19. Modeling of a domestic frost-free refrigerator

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, J.K.; Ram Gopal, M.; Chakraborty, S. [Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

    2007-03-15

    In the present study, a comprehensive thermo-fluidic model is developed for a domestic frost-free refrigerator. The governing equations, coupled with pertinent boundary conditions, are solved by employing a conservative control volume formulation, in the environment of a three-dimensional unstructured mesh. Experiments are also conducted to validate the results predicted by the present computational model. It is found that the computational and experimental results qualitatively agree with each other, although certain discrepancies can be observed in terms of the exact numerical values obtained. For the freezer compartment, the computationally predicted temperatures are somewhat higher than the experimental ones, whereas for the refrigerating compartment, the computed temperatures are lower than the corresponding experimental observations. The difference between experimental and computational results may be attributed to the lack of precise data on the airflow rates and the unaccounted heat transfer rates through the door gaskets and the compressor. From the heat transfer and fluid flow analysis, certain modifications in the design are also suggested, so as to improve the performance of the refrigerator. (author)

  20. Use of LST images from MODIS/AQUA sensor as an indication of frost occurrence in RS

    OpenAIRE

    Débora de S. Simões; Denise C. Fontana; Matheus B. Vicari

    2015-01-01

    ABSTRACTAlthough frost occurrence causes severe losses in agriculture, especially in the south of Brazil, the data of minimum air temperature (Tmin) currently available for monitoring and predicting frosts show insufficient spatial distribution. This study aimed to evaluate the MDY11A1 (LST – Land Surface Temperature) product, from the MODIS sensor on board the AQUA satellite as an estimator of frost occurrence in the southeast of the state of Rio Grande do Sul, Brazil. LST images from ...

  1. Use of LST images from MODIS/AQUA sensor as an indication of frost occurrence in RS

    OpenAIRE

    Simões, Débora de S.; Fontana, Denise C.; Vicari, Matheus B.

    2015-01-01

    ABSTRACTAlthough frost occurrence causes severe losses in agriculture, especially in the south of Brazil, the data of minimum air temperature (Tmin) currently available for monitoring and predicting frosts show insufficient spatial distribution. This study aimed to evaluate the MDY11A1 (LST – Land Surface Temperature) product, from the MODIS sensor on board the AQUA satellite as an estimator of frost occurrence in the southeast of the state of Rio Grande do Sul, Brazil. LST images from the ni...

  2. Statistical analysis of high order moments is a turbulent boundary layer with strong density differences; Analyse statistique des moments d'ordre eleve dans une couche limite turbulente en presence de differences de densite importantes

    Energy Technology Data Exchange (ETDEWEB)

    Soudani, A. [Batna Univ., Dept. de Physique, Faculte des Sciences (Algeria); Bessaih, R. [Mentouri-Constantine Univ., Dept. de Genie Mecanique, Faculte des Sciences de l' Ingenieur (Algeria)

    2004-12-01

    The study of turbulent boundary layer with strong differences of density is important for the understanding of practical situations occurring for example in the cooling of turbine blades through the tangential injection of a different gas or in combustion. In order to study the fine structure of wall turbulence in the presence of significant variations of density, a statistical analysis of the experimental data, obtained in a wind tunnel, is carried out. The results show that the relaxation of the skewness factor of u'(S{sub u'}) is carried out more quickly in the external layer than close to the wall, as well for the air injection as for the helium injection. S{sub u'} grows close to the injection slot in an appreciable way and this increase is accentuated for the air injection than for the helium injection. This growth of the skewness factor close to the injection slot can be explained by the increase in the longitudinal convective flux of turbulent energy in this zone. The results show for the distribution of the flatness factor F{sub u'} that there is no significant effect of the density gradient on the intermittent structure of the instantaneous longitudinal velocity in the developed zone, x/{delta} {>=} 5. The statistical analysis carried out in this study shows that the helium injection in the boundary layer generates more violent ejections than in the case of air injection. This result is confirmed by the significant contribution of the ejections to turbulent mass flux.

  3. Use of the delayed luminescence test for evaluation of changes in frost-resistance of winter wheat

    Directory of Open Access Journals (Sweden)

    Aleksander Brzóstowicz

    2013-12-01

    Full Text Available The influence of frost hardening conditions on the frost-resistance of three winter wheat cultivars ('Mironowska 808', 'Grana' and 'Maris Huntsman' was studied. Frost resistance was measured periodically during the autumn and winter season by the delayed luminescence method. Parallelly an electrical conductivity test was performed for comparison. It was found that the temperature which delayed luminescence reaches its maximum (tN correlates with (t50 obtained by the conductometric method. The differences in response of particular cultivars to frost and hardening conditions are described.

  4. Frost sensitivity of various deciduous plant species during leaf development in spring

    Science.gov (United States)

    Estrella, Nicole; Heinzmann, Verena; Menzel, Annette

    2017-04-01

    Frost damage in deciduous woody plants is a major climate component affecting fitness and distribution of species. It is a trade-off between early bud burst enlarging the potential growing season and frost risk for deciduous plants in many regions. In a warming world observed earlier budburst may lead to an increased risk of spring frost damage caused by higher variability in temperatures (IPCC 2007). Lenz et al. (2013) showed that leaves are in general more sensitive to frost in later leaf development stages. But still there is little knowledge on stages of leaf development and their susceptibility to frost damage in many deciduous species. Additionally there might be variation with plant traits or different strategies within specific groups of species. Frost risk minimization can also be achieved by variability in bud burst within a specimen. Therefore, in this study we observed more than 174 individual plant specimen of 96 deciduous woody plant species growing in a comparable microclimate outside on the campus of the Technical University of Munich in Freising, southern Germany. Their phenology was intensively studied from 12th of March to 4th of May, including variation within a specimen. Several times twigs for the frost experiment were cut in different stages of leaf development and exposed to freezing temperatures of -4 and -6°C in two lab freezers. Since the leaf development in spring 2015 started comparably late, too many species emerged simultaneously leading to some capacity problems in the freezers. Nevertheless, our results still reveal novel aspects concerning leaf development and frost sensitivity. The phenological development proceeded in general from outside to inside of the crown (59%), in 33% of the cases all over the plant simultaneously. Sporadic, inside to outside or vertical development characteristics occurred in rare cases (8%). Mixed model analysis indicated impacts on phenology by plant family, natural origin, pollination mode, and

  5. Community impacts of mid-May frost event during an anomalously warm spring

    Science.gov (United States)

    Hufkens, K.; Sonnentag, O.; Keenan, T. F.; Richardson, A. D.; Melaas, E. K.; Bailey, A.; O'Keefe, J.; Friedl, M. A.

    2011-12-01

    Global land and ocean surface temperatures of 2010 have gone on record as one of the warmest of the last 131 years. In the northeastern US extraordinarily warm spring temperatures were recorded, averaging +3 °C above the long term mean, causing very early leaf development. However, the entire northeastern US region was hit by a severe frost event. Leveraging the coincidence of an anomalously warm spring and a late spring frost event we assess species specific responses of these combined extremes for three northern hardwood species(sugar maple, American beech, yellow birch) across an elevational gradient. We integrated ground observations with satellite and near-surface remote sensing data to address the following questions: 1) How did different species respond to a gradient in altitude / freezing temperatures? 2) How does phenological strategy influence this response? 3) To what extent were regional effects measurable? 4) How did the late spring frost event alter the carbon balance of a northern hardwood forest? 5) Finally, what changes do we foresee in community ecology? Our results show an early onset for all species, triggered by the anomalously warm spring. However, the three species responded differently to a late spring frost event. Where both yellow birch and American beech remained largely unaffected by frost, by comparison, sugar maple showed severe frost damage with increasing altitude resulting in leaf loss and delayed canopy development. Conservative estimates of gross carbon exchange losses due to the frost event ranged from 63 g C m-2 to 156 g C m-2, or ~5% to ~13 % of the annual gross carbon exchange of a northern hardwood forest. Our results suggest that the additional pressure on forest succession at high altitude range margins due to late spring frost events may provide a competitive advantage for yellow birch and American beech, at the expense of sugar maple. Consequently, a late spring frost does not only affect the short term carbon balance

  6. Potential sea salt aerosol sources from frost flowers in the pan-Arctic region

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Li [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Now at Department of Earth System Science, University of California, Irvine California USA; Russell, Lynn M. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Burrows, Susannah M. [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA

    2016-09-23

    In order to better represent observed wintertime aerosol concentrations at Barrow, Alaska, we implemented an observationally-based parameterization for estimating sea salt production from frost flowers in the Community Earth System Model (CESM). In this work, we evaluate the potential influence of this sea salt source on the pan-Arctic (60ºN-90ºN) climate. Results show that frost flower salt emissions substantially increase the modeled surface sea salt aerosol concentration in the winter months when new sea ice and frost flowers are present. The parameterization reproduces both the magnitude and seasonal variation of the observed submicron sea salt aerosol concentration at surface in Barrow during winter much better than the standard CESM simulation without a frost-flower salt particle source. Adding these frost flower salt particle emissions increases aerosol optical depth by 10% and results in a small cooling at surface. The increase in salt particle mass concentrations of a factor of 8 provides nearly two times the cloud condensation nuclei concentration, as well as 10% increases in cloud droplet number and 40% increases in liquid water content near coastal regions adjacent to continents. These cloud changes reduce longwave cloud forcing by 3% and cause a small surface warming, increasing the downward longwave flux at the surface by 2 W m-2 in the pan-Arctic under the present-day climate.

  7. An experimental study of the correlation for predicting the frost height in applying the photoelectric technology

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, J.; Wang, W.; Guo, Q.C.; Zhao, Y.H. [Department of Building Environment and Facility Engineering, College of Architecture and Civil Engineering, Beijing University of Technology, No.100 Pingleyuan, Chaoyang District, Beijing 100124 (China)

    2010-08-15

    It is found that the photoelectric technology is suitable for the accurate measurement of the frost height. The objectives of this paper are to experimentally investigate the correspondence between the output signal of the photoelectric sensor and the frost height, and then develop a generalized correlation to predict the frost height directly and accurately. The experiments are conducted in a wide range of operating conditions for air temperature 17.7 C-27.2 C, relative humidity 21.6% RH to 64.9% RH, air velocity 0.5 m/s to 4.5 m/s and cold surface temperature -10.5 C to -6.5 C. Based on 21 groups of experiments with total 600 data, a linear correlation with a relative deviation of {+-}10% is setup. Further validation of this correlation is conducted by comparing the predicted results with 4 additional experiments, and approximately 95% of the predicted frost heights are consistent with the measured data within a relative deviation of {+-}10%. These results indicate that the photoelectric technology can predict the frost height directly. The application of the proposed correlation to provide defrost control strategy is also discussed in this paper. (author)

  8. Future bloom and blossom frost risk for Malus domestica considering climate model and impact model uncertainties.

    Directory of Open Access Journals (Sweden)

    Holger Hoffmann

    Full Text Available The future bloom and risk of blossom frosts for Malus domestica were projected using regional climate realizations and phenological ( = impact models. As climate impact projections are susceptible to uncertainties of climate and impact models and model concatenation, the significant horizon of the climate impact signal was analyzed by applying 7 impact models, including two new developments, on 13 climate realizations of the IPCC emission scenario A1B. Advancement of phenophases and a decrease in blossom frost risk for Lower Saxony (Germany for early and late ripeners was determined by six out of seven phenological models. Single model/single grid point time series of bloom showed significant trends by 2021-2050 compared to 1971-2000, whereas the joint signal of all climate and impact models did not stabilize until 2043. Regarding blossom frost risk, joint projection variability exceeded the projected signal. Thus, blossom frost risk cannot be stated to be lower by the end of the 21st century despite a negative trend. As a consequence it is however unlikely to increase. Uncertainty of temperature, blooming date and blossom frost risk projection reached a minimum at 2078-2087. The projected phenophases advanced by 5.5 d K(-1, showing partial compensation of delayed fulfillment of the winter chill requirement and faster completion of the following forcing phase in spring. Finally, phenological model performance was improved by considering the length of day.

  9. Statistical-Synoptic Analysis of the Atmosphere Thickness Pattern of Iran’s Pervasive Frosts

    Directory of Open Access Journals (Sweden)

    Iman Rousta

    2016-08-01

    Full Text Available The present study aimed at analyzing the synoptic pattern of atmospheric thickness of winter pervasive frosts in Iran. To this end, the data related to the daily minimum temperature of a 50-year period (1961–2010 were gathered from 451 synoptic and climatology stations. Then, the instances in which the temperature was below 0 °C for at least two consecutive days and this phenomenon covered at least 50% of the entirety of Iran were selected. Subsequently, the atmosphere thickness pattern was extracted for these days, with the representative day being identified and analyzed through cluster analysis. The results showed that the Siberian high pressure plays a significant role in the occurrence of pervasive frosts in Iran. In some other cases, the northeast–southwest direction of this pattern leads to its combination with the East Europe high pressure, causing widespread frosts in Iran. Furthermore, the interaction between counter clockwise currents in this system and the clockwise currents in the Azores high pressure tongue directs cold weather from northern parts of Europe toward Iran. The formation of blocking systems leads to the stagnation of cold weather over Iran, a phenomenon that results in significant reduction of temperature and severe frosts in these areas. In addition, the omega pattern (the fifth pattern and Deep Eastern European trough and polar low pressure pattern (the fourth pattern were the most dominant and severe frost patterns in Iran respectively.

  10. Restoring sedges and mosses into frost heaving iron fens, San Juan Mountains, Colorado

    Directory of Open Access Journals (Sweden)

    R.A. Chimner

    2011-08-01

    Full Text Available Rare iron fens in the San Juan Mountains of Colorado are frequently in poor condition due to mining, roads and ditches, which have left much of the fen completely bare of vegetation. Natural revegetation is slow to occur in the bare areas because of severe frost heave in the cold mountain climate. Therefore, experimental revegetation plots were conducted in a factorial design with mulching and no mulching, crossed with moss diaspores, sedge transplants, and moss and sedge combined. Mulching influenced surface soil temperatures by reducing the midday highs and increasing the night-time lows, which decreased the frequency and amount of frost heave. Peat moisture also modified frost heave, with the greatest frost heaving occurring near 75 % peat moisture content (water table 10–20 cm below the surface and the least when soils were either wetter or drier. Moss survival was dependent on mulch, with no moss surviving in plots without mulch. Mulching also increased sedge transplant survival. In summary, mulching significantly increased the success of vegetation restoration efforts for frost heave areas in mountain fens.

  11. Short communication. Harvest time in hedgerow Arbequina olive orchards in areas with early frosts

    Energy Technology Data Exchange (ETDEWEB)

    Gracia, P.; Sanchez-Gimeno, A. C.; Benito, M.; Oria, R.; Lasa, J. M.

    2012-11-01

    The shortening of harvest time attained in hedgerow olive (Olea europaea L.) orchards represents an advantage for the adoption of this cropping system in areas that are prone to suffer frost during the harvest period. To establish an optimal harvesting window, we carried out a study of the fruit ripening process on a hedgerow orchard of Arbequina olive trees, located in Zaragoza (Spain). From 2007 to 2009, oil accumulation on the fruit (% of dry weight) and oil yield (grams of oil per 100 fruits) were monitored, from early September to late November. Over the three years both variables peaked around November 15th, indicating that Arbequina reached full ripening earlier than has been reported previously for this variety. In two of the three seasons the orchard suffered several frosts during November. Long term climatic data from this area indicated that the risk of early frosts (< -2 degree centigrade) increases as November progresses with a high risk after November 20{sup t}h. In conclusion, the optimal harvesting period for Arbequina in this area should not extend beyond November 20{sup t}h. A rapid harvesting before this date is advisable to avoid the risk of damage caused by early frost in Zaragoza. Hedgerow planting provides an additional advantage in frost-prone areas, because mechanization of operations permits a short harvest period, easier to fit into the optimal harvesting window. (Author) 20 refs.

  12. Presence Service in IMS

    Directory of Open Access Journals (Sweden)

    David Petras

    2013-01-01

    Full Text Available This paper describes the presence service, which is located in the IP multimedia subsystem. This service allows making many applications for different groups of people. The paper describes differences between a network without the service and with the service. The biggest change is an increased number of transmitted messages. The presence uses some part of the IP multimedia subsystem control layer, which is shown in communication between the user and the server. The paper deals with the number of generated messages depending on the behaviour of the users. This is described by a mathematical model using discrete Markov chains.

  13. Performance tests of air source heat pumps under frosting conditions. Quality of results

    Science.gov (United States)

    Fahlen, P.

    This report focuses on the analysis of uncertainties in research regarding air-source heat pumps. The principles recommended by the Western European Calibration Conference (WECC) are applied and the generated information is condensed in the form of uncertainty budgets. The ensuring discussion, and the Measurement Assurance Program that was applied during the research work are also relevant to general testing of cooling coils, e.g. for air source heat pumps. The general conclusion of the analysis is that the method of determining frost mass by continuous weighing and frost density by inference from pressure drop considerations, which is presented in the report, has the potential to produce results with an accuracy on a par with the best previously used techniques to investigate frosting and defrosting phenomena. Furthermore, the methodology has the distinct advantage of yielding online measuring possibilities and being much less time consuming than traditional techniques.

  14. Frost Growth CFD Model of an Integrated Active Desiccant Rooftop Unit

    Energy Technology Data Exchange (ETDEWEB)

    Geoghegan, Patrick J [ORNL; Petrov, Andrei Y [ORNL; Vineyard, Edward Allan [ORNL; Zaltash, Abdolreza [ORNL; Linkous, Randall Lee [ORNL

    2008-01-01

    A frost growth model is incorporated into a Computational Fluid Dynamics (CFD) simulation of a heat pump by means of a user-defined function in FLUENT, a commercial CFD code. The transient model is applied to the outdoor section of an Integrated Active Desiccant Rooftop (IADR) unit in heating mode. IADR is a hybrid vapor compression and active desiccant unit capable of handling 100% outdoor air (dedicated outdoor air system) or as a total conditioning system, handling both outdoor air and space cooling or heating loads. The predicted increase in flow resistance and loss in heat transfer capacity due to frost build-up are compared to experimental pressure drop readings and thermal imaging. The purpose of this work is to develop a CFD model that is capable of predicting frost growth, an invaluable tool in evaluating the effectiveness of defrost-on-demand cycles.

  15. The application of photo-coupler for frost detecting in an air-source heat pump

    Energy Technology Data Exchange (ETDEWEB)

    Byun, Ju-Suk; Lee, Jinho [School of Mechanical Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Jeon, Chang-Duk [Department of Mechanical Engineering, Chungju National University, Chung-Buk 380-702 (Korea, Republic of); Jung, Ji-Hoon [Piping Engineering Team, Plant Engineering Center, Daelim Industrial Company, Seoul 150-010 (Korea, Republic of)

    2006-03-15

    This experimental study is carried out to investigate reliability and effectiveness of a new method of using photo-coupler for detecting frost formation in an air source heat pump, and further to determine the most efficient initiation point of the defrost cycle. This new method of using photo-coupler as a frost sensing device is evaluated by comparing its performance with conventional time control defrost system in which defrost cycle is set to start at predetermined interval, e.g. about at every 1-1.5h. Results indicate that overall heating capacity of photo-coupler detection method (case IV) is 5.5% higher than that of time control method. It is also shown that for maximum efficiency the defrost cycle must be initiated before the frost build-up area exceeds 45% of total front surface of the outdoor coil. (author)

  16. Delineation of frost characteristics on cold walls by using a new formula for psychrometrics demarcation boundary

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Ahmed Hamza H. [Department of Mechanical Engineering, Faculty of Engineering, Assiut University, Assiut 71516 (Egypt)

    2009-06-15

    In this study, a direct formula that predicts either the frost formation on cold walls is correspondence to psychrometric-subsaturated or supersaturated regions is presented. The developed formula uses the data of the entering air dry-bulb temperature and absolute humidity, and the absolute humidity of the air at saturation corresponding to the coil surface temperature. Cases studies of demarcation criteria for frost formation on evaporator coil using experimental measured data, and on walls of cold storage freezer using measured data from literature are used to validate the formula and it is found that results are completely matches to the graphic plot of the data on the psychrometric chart. In case of cold storage freezers, the result clearly shows that a greater demarcation criteria value indicates frost formation under sever condition that is characterized as snow-like with low density and thermal conductivity. (author)

  17. Simulating the Probability of Grain Sorghum Maturity before the First Frost in Northeastern Colorado

    Directory of Open Access Journals (Sweden)

    Gregory S. McMaster

    2016-09-01

    Full Text Available Expanding grain sorghum [Sorghum bicolor (L. Moench] production northward from southeastern Colorado is thought to be limited by shorter growing seasons due to lower temperatures and earlier frost dates. This study used a simulation model for predicting crop phenology (PhenologyMMS to estimate the probability of reaching physiological maturity before the first fall frost for a variety of agronomic practices in northeastern Colorado. Physiological maturity for seven planting dates (1 May to 12 June, four seedbed moisture conditions affecting seedling emergence (from Optimum to Planted in Dust, and three maturity classes (Early, Medium, and Late were simulated using historical weather data from nine locations for both irrigated and dryland phenological parameters. The probability of reaching maturity before the first frost was slightly higher under dryland conditions, decreased as latitude, longitude, and elevation increased, planting date was delayed, and for later maturity classes. The results provide producers with estimates of the reliability of growing grain sorghum in northeastern Colorado.

  18. Superabsorbent Polymers as a Means of Improving Frost Resistance of Concrete

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange; Jensen, Ole Mejlhede; Laustsen, Sara

    2015-01-01

    on how SAP influences concrete frost resistance. Moreover, it also presented a larger experimental study on the topic. The conclusions that were drawn from the experimental study were in line with the extract of the pool of results from the literature, first of all that SAP addition can improve frost......Superabsorbent polymer (SAP) was introduced in cementitious materials about 15 years ago. Since then, several studies on the frost resistance of concrete with SAP have been published. However, an up-to-date review across the different studies is missing. This paper presented a literature review...... resistance of concrete. The improvement was attributed to voids created by SAP. As was clearly demonstrated in the paper, it was crucial to document the void structure of the hardened concrete. Other factors than SAP could lead to void formation. For example, residue of surfactant on SAP particles...

  19. North Polar Surfaces of the Uranian Moons: Coated with CO2 Frost?

    Science.gov (United States)

    Cartwright, Richard; Emery, Joshua; Rivkin, Andy; Trilling, David; Pinilla-Alonso, Noemi

    2014-12-01

    We propose to investigate the near-surface composition of the Uranian moons Ariel, Umbriel, Titania, and Oberon by using the Infrared Array Camera (IRAC) onboard the Spitzer Space Telescope. Previous IRAC observations of these objects in Program 71 (2003 - 2005) indicate that the surfaces of their southern hemispheres are dominated by pure water ice (sub-observer latitudes 7 - 18 degree S). The observations we propose here are of these objects' now observable northern hemispheres (sub-observer latitudes 25 - 33 degree N). Unlike the Program 71 observations, which collected data near the end of southern summer when any seasonal CO2 frost would have migrated to the winter hemisphere, we are proposing to observe these moons at the beginning of northern summer when seasonal CO2 frost should still be present. Therefore, the 2015 - 2016 Cycle 11 opportunity window represents an ideal time frame to search for seasonal CO2 frost on these objects.

  20. Void structure of concrete with superabsorbent polymers and its relation to frost resistance of concrete

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange; Jensen, Ole Mejlhede; Laustsen, Sara

    2013-01-01

    Superabsorbent polymers (SAP) can be used to control air void formation in concrete. However, due to surfactant left on suspension polymerized SAP particles during production, they may not only create SAP voids but also entrain extra air. In the present investigation, a method is tested to remove...... surfactant prior to concrete mixing. The method comprises rinsing of the SAP with ethanol. This effectively removes the surfactant. Freeze-thaw testing of concrete with rinsed and non-rinsed SAP shows that for equal dosages of SAP, the extra air entrained due to surfactant is considerable and can make...... the difference between poor and satisfactory frost-resistance. Furthermore, the results indicate that voids created directly by SAP protect concrete against frost deterioration just like other air voids; if the concrete contains enough SAP voids, these alone can provide sufficient frost resistance. © 2013 RILEM....

  1. PERSEPSI BERKEHIDUPAN BERMASYARAKAT MENURUT PUISI “MENDING WALL” KARYA ROBERT FROST: SUATU TINJAUAN STILISTIKA

    Directory of Open Access Journals (Sweden)

    Jumino Jumino

    2015-06-01

    Full Text Available Human beings are one the best living creatures God created in the world. While living, as their existence, they have duties to do as individual creature,  as social creature, and as God creature. Each existence has its consequences. Through his poem “Mending Wall”, Robert Frost views human existence as social creature that needs relations to the others surrounding. One of human relations happens is described by two opposing characters on human beings within the poem. To make the poem more interested and challenging, Frost applied stylistic writing by choosing good diction and image of words used packed in some figurative language. The figurative language involves personification, metaphor, and symbol. In this article, the writer analyzes the elements of stylistics used by Frost in the poem “Mending Wall”.

  2. Influence of low temperature and frost duration on Phytophthora alni subsp. alni viability

    Energy Technology Data Exchange (ETDEWEB)

    Cerny, K.; Filipova, N.; Strnadova, V.

    2012-11-01

    Limits on the survival of P. alni subsp. alni (PAA) due to low temperature can be expected based on previously published laboratory and field studies. This study presents a laboratory experiment to test the influence of low temperature and frost duration on PAA viability. Ten PAA isolates were incubated at different temperatures (-0.1, -2.5, -5.0, -7.5, and -10.0 degree centigrade) and frost durations (0 - 7, 14, 21, and 28 days). A regression analysis confirmed the significant influence of both factors (low temperature and frost duration, and their interaction) on the survival of the pathogen under laboratory conditions. The survival and failure time analysis showed that the survival of the pathogen differs significantly after mild frost (all the isolates tested survived temperatures between -0.1 and -5.0 degree centigrade during the entire testing period) and heavy frost (the pathogen died after 21 days of incubation at -7.5 degree centigrade and after 2 days at -10.0 degree centigrade). Moreover, the viability of the pathogen decreased significantly if the temperature of -5.0 degree centigrade was maintained for at least 1 week and the temperature of -7.5 degree centigrade persisted in laboratory conditions for at least 4 days. The results of the study proved the pathogen to be very sensitive to heavy frost. The low-temperature limits for PAA occur regularly in Central Europe in January. It is probable that these temperatures can reduce PAA populations in diseased black alder stems. The climate change characterised by increases in the lowest minimum winter temperatures in Central Europe (as hypothesised by IPCC) may pose a significant risk for affected alder population in the area. (Author) 21 refs.

  3. Chlorophyll fluorescence as a parameter for frost hardiness in winter wheat. A comparison with other hardiness parameters.

    NARCIS (Netherlands)

    Clement, JMAM; vanHasselt, PR

    1996-01-01

    Frost hardiness of winter wheat leaves (Triticum aestivum L. cv. Urban) was measured during an eight weeks hardening period using chlorophyll fluorescence. Determination of frost induced damage after freezing, measured as the decrease of photochemical capacity of photosystem II (F-V/F-M =

  4. The influence of thermal inertia on temperatures and frost stability on Triton

    Science.gov (United States)

    Spencer, John R.; Moore, Jeffrey M.

    1992-01-01

    It is presently argued, in view of (1) a thermal inertia model for the surface of Triton which (like previous ones) predicts a monotonic recession of permanent N2 deposits toward the poles and very little seasonal N2 frost in the southern hemisphere, and (2) new spectroscopic evidence for nonvolatile CO2 on Triton's bright southern hemisphere, that much of that bright southern material is not N2. Such bright southern hemisphere volatiles may allow the formation of seasonal frosts, thereby helping to explain the observed spectroscopic changes of Triton during the last decade.

  5. Io meteorology - How atmospheric pressure is controlled locally by volcanos and surface frosts

    Science.gov (United States)

    Ingersoll, Andrew P.

    1989-01-01

    The present modification of the Ingersoll et al. (1985) hydrodynamic model of the SO2 gas sublimation-driven flow from the day to the night side of Io includes the effects of nonuniform surface properties noted in observational studies. Calculations are conducted for atmospheric pressures, horizontal winds, sublimation rates, and condensation rates for such surface conditions as patchy and continuous frost cover, volcanic venting, surface temperature discontinuities, subsurface cold trapping, and the propagation of insolation into the frost. While pressure is found to follow local vapor pressure away from the plumes, it becomes higher inside them.

  6. Designing a Frost Forecasting Service for Small Scale Tea Farmers in East Africa

    Science.gov (United States)

    Adams, E. C.; Nyaga, J. W.; Ellenburg, W. L.; Limaye, A. S.; Mugo, R. M.; Flores Cordova, A. I.; Irwin, D.; Case, J.; Malaso, S.; Sedah, A.

    2017-12-01

    Kenya is the third largest tea exporter in the world, producing 10% of the world's black tea. Sixty percent of this production occurs largely by small scale tea holders, with an average farm size of 1.04 acres, and an annual net income of 1,075. According to a recent evaluation, a typical frost event in the tea growing region causes about 200 dollars in losses which can be catastrophic for a small holder farm. A 72-hour frost forecast would provide these small-scale tea farmers with enough notice to reduce losses by approximately $80 annually. With this knowledge, SERVIR, a joint NASA-USAID initiative that brings Earth observations for improved decision making in developing countries, sought to design a frost monitoring and forecasting service that would provide farmers with enough lead time to react to and protect against a forecasted frost occurrence on their farm. SERVIR Eastern and Southern Africa, through its implementing partner, the Regional Centre for Mapping of Resources for Development (RCMRD), designed a service that included multiple stakeholder engagement events whereby stakeholders from the tea industry value chain were invited to share their experiences so that the exact needs and flow of information could be identified. This unique event allowed enabled the design of a service that fit the specifications of the stakeholders. The monitoring service component uses the MODIS Land Surface Temperature product to identify frost occurrences in near-real time. The prediction component, currently under testing, uses the 2-m air temperature, relative humidity, and 10-m wind speed from a series of high-resolution Weather Research and Forecasting (WRF) numerical weather prediction model runs over eastern Kenya as inputs into a frost prediction algorithm. Accuracy and sensitivity of the algorithm is being assessed with observations collected from the farmers using a smart phone app developed specifically to report frost occurrences, and from data shared through

  7. David Sanders. A Divided Poet: Robert Frost, North of Boston, and the Drama of Disappearance.

    Directory of Open Access Journals (Sweden)

    Tatiani G. Rapatzikou

    2012-03-01

    Full Text Available David Sanders in his monograph entitled A Divided Poet: Robert Frost, North of Boston, and the Drama of Disappearance (2011 sheds light on the dilemmas, doubts and personal conflicts Frost confronted while composing his poetic collection North of Boston in which some of his most well-known lyrics, such as “Mending Wall,” “After Apple-Picking,” and “The Wood-Pile,” are contained. This book should be considered alongside a number of other publications either in monograph or essay form that app...

  8. Robert Frost's "The road not taken", Childhood, psychoanalytic symbolism, and creativity.

    Science.gov (United States)

    Glenn, J

    2001-01-01

    Robert Frost, often regarded as a folksy farmer-poet, was also a more profound, even terrifying, creator. His poem "The Road Not Taken" reveals his delight in multiple meanings, his ambivalence, and his penchant for misleading his readers. He denied that the poem proclaimed his striving for the unconventional and asserted that it was meant to tease his friend Edward Thomas for his compulsive indecisiveness. This essay also notes the unconscious meanings of the poem, including Frost's reactions to losing his close friend, his own indecisiveness, his conflict between heterosexual and homosexual object choices, his need for a "secret sharer," and his attachments.

  9. Frost heave modelling of buried pipelines using non-linear Fourier finite elements

    International Nuclear Information System (INIS)

    Wan, R. G.; You, R.

    1998-01-01

    Numerical analysis of the response of a three-dimensional soil-pipeline system in a freezing environment using non-linear Fourier finite elements was described as an illustration of the effectiveness of this technique in analyzing plasticity problems. Plastic deformations occur when buried pipeline is under the action of non-uniform frost heave. The three-dimensional frost heave which develops over time including elastoplastic deformations of the soil and pipe are computed. The soil heave profile obtained in the numerical analysis was consistent with experimental findings for similar configurations. 8 refs., 8 figs

  10. In live interaction, does familiarity promote attraction or contempt? Reply to Norton, Frost, and Ariely (2011).

    Science.gov (United States)

    Reis, Harry T; Maniaci, Michael R; Caprariello, Peter A; Eastwick, Paul W; Finkel, Eli J

    2011-09-01

    In this reply, we address and refute each of Norton, Frost, and Ariely's (see record 2011-18560-001) specific objections to the conclusion that, ceteris paribus, familiarity breeds liking in live interaction. In particular, we reiterate the importance of studying live interaction rather than decontextualized processes. These rebuttals notwithstanding, we concur with Norton et al.'s call for an integrative model that encompasses both Norton, Frost, and Ariely's (see record 2006-23056-008) results and ours (see record 2011-04644-001), and we point readers toward a description of a possible model presented in our original article. PsycINFO Database Record (c) 2011 APA, all rights reserved.

  11. Climate warming and the risk of frost damage to boreal forest trees : identification of critical ecophysiological traits

    Energy Technology Data Exchange (ETDEWEB)

    Hanninen, H. [Helsinki Univ., Helsinki (Finland). Plant Ecophysiology and Climate Change Group

    2006-07-15

    Eco-physiological traits critical to the occurrence of frost damage in trees in the boreal zone were identified. Two computer simulations were used to examine why 1 simulation predicted heavy frost damage as a consequence of climate warming, while another closely related model did not. The 2 models were developed and parametrized to predict the annual cycle of frost hardiness of trees in central Finland. Model{sub 1} was developed for a theoretical generalized tree species. Model{sub 2} was developed and parametrized to predict needle frost hardiness of Scots pine. Four conceptual traits were used to describe the environmental regulation of ontogenetic development during the ontogenetic phases of growth, lignification, rest and quiescence. The cycle of frost hardiness was developed as a 2-step process. Annual ontogenetic development was modelled with air temperature and night length as the driving forces. The rate of frost hardening and dehardening was then modelled as a function of air temperature, night length and the prevailing phase of the annual ontogenetic cycle. The process was carried out in both models by calculating the rate of change of frost hardiness as a first-order dynamic process. Examination of the risk of frost damage was based on mean values rather than the corresponding maxima of needle damage over the 92 cycles examined. The modelling comparison indicated that the response rates of ontogenetic development during quiescence to air temperature is a critical trait for the risk of frost damage following climate warming. It was suggested that determining the form of the non-linear response is crucial to the assessment of climate warming impacts. Results indicated that predictions of the risk of increased frost damage to trees in response to climate warming remain equivocal. It was concluded that further experimental work with a variety of tree species is needed. 57 refs., 1 tab., 7 figs.

  12. Transcriptome profiling of fully open flowers in a frost-tolerant almond genotype in response to freezing stress.

    Science.gov (United States)

    Hosseinpour, Batool; Sepahvand, Sadegh; Kamali Aliabad, Kazem; Bakhtiarizadeh, MohammadReza; Imani, Ali; Assareh, Reza; Salami, Seyed Alireza

    2018-02-01

    Spring frost is a major limiting abiotic stress for the cultivation of almonds [Prunus dulcis (Mill.)] in Mediterranean areas or the Middle East. Spring frost, in particular, damages almond fully open flowers, resulting to significant reduction in yield. Little is known about the genetic factors expressed after frost stress in Prunus spp. as well as in almond fully open flowers. Here, we provide the molecular signature of pistils of fully open flowers from a frost-tolerant almond genotype. The level of frost tolerance in this genotype was determined for all three flowering stages and was confirmed by comparing it to two other cultivars using several physiological analyses. Afterwards, comprehensive expression profiling of genes expressed in fully open flowers was performed after being exposed to frost temperatures (during post-thaw period). Clean reads, 27,104,070 and 32,730,772, were obtained for non-frost-treated and frost-treated (FT) libraries, respectively. A total of 62.24 Mb was assembled, generating 50,896 unigenes and 66,906 transcripts. Therefore, 863 upregulated genes and 555 downregulated genes were identified in the FT library. Functional annotation showed that most of the upregulated genes were related to various biological processes involved in responding to abiotic stress. For the first time, a highly expressed cold-shock protein was identified in the reproductive organ of fruit trees. The expression of six genes was validated by RT-PCR. As the first comprehensive analysis of open flowers in a frost-tolerant almond genotype, this study represents a key step toward the molecular breeding of fruit tree species for frost tolerance.

  13. Effect of adsorption of Pb(II) and Cd(II) ions in the presence of EDTA on the characteristics of electrical double layers at the ion exchanger/NaCl electrolyte solution interface.

    Science.gov (United States)

    Kołodyńska, Dorota; Skwarek, Ewa; Hubicki, Zbigniew; Janusz, Władysław

    2009-05-15

    The main propose of this work was to describe the basic parameters of electrical double layer structures of the ion exchanger/NaCl before and after the sorption process of Pb(II) and Cd(II) ions from aqueous solutions in the presence of the complexing agent EDTA (ethylenediaminetetraacetic acid). In the studies the following ion exchangers were used: cation exchangers Micro-ionex (in the H(+) and NH(+)(4) forms), Dowex 50W x 4 (in the H(+) form), and Dowex 50W x 12 (in the H(+) form); anion exchangers Dowex 1 x 4 (in the Cl(-) form) and Dowex 1 x 8 (in the Cl(-) form). Study of the physicochemical properties of the sample surface was carried out. The influence of ionic strength, pH, and solution interface was investigated. Electrophoretic mobility, surface charge density, and parameters for different concentrations of the electrolytes under question were presented. pH was changed from 3 to 10. The studies were carried out for the M(II)-EDTA = 1:1 system. The effects of the concentration of the solution containing the above-noted complexes and of the ion exchange/solution phase contact time on sorption capacities of the ion exchangers under consideration were studied. Kinetic parameters of the sorption process were also determined.

  14. On the need for data for the verification of service life models for frost damage

    DEFF Research Database (Denmark)

    Geiker, Mette Rica; Engelund, Sven

    1999-01-01

    The purpose of this paper is to draw the attention to the need for the verification of service life models for frost attack on concrete and the collection of relevant data. To illustrate the type of data needed the paper presents models for internal freeze/thaw damage (internal cracking including...

  15. Leaf fall, humus depth, and soil frost in a northern hardwood forest

    Science.gov (United States)

    George Hart; Raymond E. Leonard; Robert S. Pierce

    1962-01-01

    In the mound-and-depression microtopography of the northern hardwood forest, leaves are blown off the mounds and collect in the depressions. This influence of microtopography on leaf accumulation is responsible for much of the variation in humus depth; and this, in turn, affects the formation and depth of soil frost.

  16. Man, Nature, and Art in Robert Frost's Poetry | Elimimian | Lwati: A ...

    African Journals Online (AJOL)

    ... and it is along these three aesthetic trajectories that this essay will be divided and addressed. In discussing these areas, an attempt will be made to examine the diversity of Frost's lyricism, the poet's sense of Romanticism, and the particular rhetorical and poetic devices which he employs to elucidate or illuminate his work.

  17. Eucalypts and Their Potential for Invasiveness Particularly in Frost-Prone Regions

    Directory of Open Access Journals (Sweden)

    Trevor H. Booth

    2012-01-01

    Full Text Available Eucalypts are being considered for biofuel production in the Lower Coastal Plain of the United States. The evolution of eucalypts in Australia has equipped some species to be successful in plantations and has also influenced their potential as invasive species. More than 200 eucalypt species have been evaluated in many countries around the world. Generally eucalypts have proved to have limited invasive potential for a number of reasons, including their poor dispersal capabilities. Two regions with climates similar to the Lower Coastal Plain of the United States are identified in Argentina and China. Frosts, particularly sudden frosts, are an important limitation for eucalypts in these regions, so existing plantations are very limited. However, invasive eucalypts do not appear to be a major problem in other regions of either country. The use of carefully selected frost-tolerant species and the development of genetically modified eucalypts may now open up more frost-affected areas for eucalypt plantations. Some control actions may be necessary and research needs are outlined, but it is concluded that experience in other regions around the world suggests that eucalypts are likely to be a relatively low risk as invasive species in the Lower Coastal Plain.

  18. Prediction of long-term frost heave of chilled gas pipelines by centrifuge modeling

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, V.; Clark, J.; Hawlader, B. [Memorial Univ. of Newfoundland, St. John' s, NL (Canada). C-Core; Zhou, J. [TransCanada PipeLines Ltd., Calgary, AB (Canada)

    2004-07-01

    The behaviour of pipelines operating under harsh northern conditions has been studied at full-scale test facilities since the 1970s in order to develop and calibrate various theories and analytical models. The studies have addressed the issue of predicting frost heave of chilled pipelines. The use of chilled gas transmission for northern pipelines is touted as being an effective solution to preserve permafrost and to increase throughput. Frost heave occurs in soil as in-situ pore water freezes and additional free water advances to the freezing front leading to the formation of ice lenses. The amount of heave depends on soil type, cooling rate, thermal gradient and availability of a water source. The extent of deformation of both frozen and unfrozen soil also plays a role in the amount of heave. In recent years, centrifuge modeling of frost heave processes have provided useful information. Small-scale models have been constructed and tested under increased gravitational acceleration to replicate full-scale conditions. The key benefits are the reduced scale and time effects used in the modeling of the frost heave, allowing for sequential studies on soil types, pipe temperatures, groundwater and climatic conditions. This paper presented an interpretation of test results. Comparison with full-scale test sites has shown promising results, but some further verification exercises are warranted, particularly in the design methodology that allows for reliable and accurate prediction of pipeline behaviour as it passes through discontinuous permafrost or changing soil type. 14 refs., 2 tabs., 9 figs.

  19. Development of frost tolerance in winter wheat as modulated by differential root and shoot temperature

    NARCIS (Netherlands)

    Windt, C.W.; van Hasselt, P.R

    Winter wheat plants (Triticum aestivum L. cv. Urban), grown in nutrient solution, were exposed to differential shoot/root temperatures (i.e., 4/4, 4/20, 20/4 and 20/20 degrees C) for six weeks. Leaves grown at 4 degrees C showed an increase in frost tolerance from - 4 degrees C down to -11 degrees

  20. Expression of dehydrin 5 during the development of frost tolerance in barley (Hordeum vulgare)

    Czech Academy of Sciences Publication Activity Database

    Kosová, K.; Holková, L.; Prášil, I.T.; Prášilová, P.; Bradáčová, M.; Vítámvás, P.; Čapková, Věra

    2008-01-01

    Roč. 165, č. 11 (2008), s. 1142-1151 ISSN 0176-1617 R&D Projects: GA MZe QF3191; GA MZe 1G57060 Institutional research plan: CEZ:AV0Z50380511 Keywords : Cold acclimation * Dehydrin 5 * Frost tolerance Subject RIV: GE - Plant Breeding Impact factor: 2.437, year: 2008

  1. Variation in damage from growing-season frosts among open-pollinated families of red alder.

    Science.gov (United States)

    Kevin C. Peeler; Dean S. DeBell

    1987-01-01

    Repeated growing-season frosts during late April and early May 1985 caused extensive damage to red alder (Alnus rubra Bong.) seedlings in a newly planted research trial in western Washington. About two-thirds of the seedlings were severely damaged (entire stem damaged or necrotic). Such damage varied by family, from 50 percent of seedlings in the...

  2. Bacterial stem blight of alfalfa: A disease that increases frost damage

    Science.gov (United States)

    Alfalfa producers count on the first harvest in late spring to deliver the highest tonnage and best quality of forage of the year. A late frost can significantly reduce both yield and quality. Losses are due not only to the physical damage from freezing of the alfalfa stem and leaves but also from d...

  3. Some relationships among air, snow, and soil temperatures and soil frost

    Science.gov (United States)

    George Hart; Howard W. Lull

    1963-01-01

    Each winter gives examples of the insulating properties of snow cover. Seeds and soil fauna are protected from the cold by snow. Underground water pipes are less likely to freeze under snow cover. And, according to many observers, the occurrence, penetration, and thaw of soil frost are affected by snow cover. The depth of snow necessary to protect soil from freezing...

  4. Portrayal of Realism and Rationalism in the Selected Poems of Robert Frost

    Directory of Open Access Journals (Sweden)

    Sathi Veerraghava Reddy

    2014-06-01

    Full Text Available Robert Frost (1874-1963 is a famous American Poet. As most of his poems are autobiographical in subject, it is evident that he has been mostly influenced by the environment around him in composing his masterpieces. Frost’s themes are very simple in the surface meaning endowed with an easily understandable diction and a liberal style of writing. Yet, a careful study of his works vividly reveals his greatness as a ‘true’ judge of various critical aspects associated with the everyday experiences of the humans. His major characters- the narrators in “Stopping by Woods on a Snowy Evening”, “Mending wall” and “The Road not Taken” are viewed as the real people with real struggles in real life. It is seen that Frost’s poetry is highly connotative and the same reader can interpret the poetry of Robert Frost in multiple ways in multiple settings. The present article aims at critically examining Frost’s ‘realistic’ and ‘rationalistic’ approaches in the elevation of human nature under the broad spectrum of human life. This article also aims at proving that no poem of Frost ends in an absolute imagination because Frost himself seems to believe in realism as the ultimate fate of the individuals though fancy and imagination provides a temporary relief to the disturbed soul.

  5. Cryoprotectants are metabolic fuels during long term frost exposure in the earthworm Dendrobaena octaedra

    DEFF Research Database (Denmark)

    Jørgensen, S.; Overgaard, J.; Holmstrup, M.

    2008-01-01

    Ectothermic animals that live in the subarctic and temperate regions must have strategies to deal with periods of frost during winter. The earthworm Dendrobaena octaedra is a freeze tolerant species that accumulates large concentrations of the cryoprotectant glucose upon ice formation in the extr...... as anaerobic fuel source than as a cryoprotectant....

  6. Snow and frost measurements in a watershed-management research program

    Science.gov (United States)

    Richard S. Sartz

    1957-01-01

    I am going to tell you about our snow and frost work on the Hubbard Brook Experimental Forest in the White Mountains of New Hampshire. Hubbard Brook is one of several experimental areas scattered throughout the country on which personnel of the United States Forest Service are seeking to learn how different kinds of forests and methods of managing them affect...

  7. Frost hardiness of introduced sea buckthorn (Hippophae rhamnoides L. genotypes in Central Russia

    Directory of Open Access Journals (Sweden)

    Ozherelieva Zoya

    2016-04-01

    Full Text Available Sea buckthorn (Hippophae rhamnoides L. genotypes of different ecological and geographical origins were tested. Frost hardiness extent was determined during winter by artificial freezing, which allowed identify varietal differences in frost hardiness of buds and tissues of sea buckthorn shoots. In order to identify differences in adaptation to low temperature we determined the fractional composition of water in annual shoots; and proline and malone dialdehyde concentration and total amylase activity in bark of shoots of female and male genotypes. In December, the sea buckthorn genotypes were in deep dormancy, when maximum frost hardiness of buds and tissues of annual shoots occurred. During the next months, the frost hardiness of buds and shoot tissues decreased during the state of exogenous dormancy. The performed experiment gave an opportunity to select hardy genotypes ‘Kenigsbergskaya’, ‘Surpriz Baltiki’, B 23-34, and ‘Prima Dona’ for use in further breeding, as they had demonstrated stable hardiness during the whole winter period according to all of the components of winter hardiness.

  8. Frost Damage Detection in Sugarcane Crop Using Modis Images and Srtm Data

    Science.gov (United States)

    Rudorff, B.; Alves de Aguiar, D.; Adami, M.

    2011-12-01

    Brazil is the largest world producer of sugarcane which is used to produce almost equal proportions of either sugar (food) or ethanol (biofuel). In recent years sugarcane crop production has increased fast to meet the growing market demand for sugar and ethanol. This increase has been mainly due to expansion in crop area, but sugarcane production is also subjected to several factors that influence both the agricultural crop yield (tons of stalks/ha) and the industrial yield (kg of sugar/ton of stalks). Sugarcane is a semi-perennial crop that experiences major growth during spring and summer seasons with large demands for water and high temperatures to produce good stalk formation (crop yield). The harvest is performed mainly during fall and winter seasons when water availability and temperature should be low in order to accumulate sucrose in the stalks (industrial yield). These favorable climatic conditions for sugarcane crop are found in several regions in Brazil, particularly in São Paulo state, which is the major sugarcane producer in Brazil being responsible for almost 60% of its production. Despite the favorable climate in São Paulo state there is a certain probability of frost occurrence from time to time that has a negative impact on sugarcane crop, particularly on industrial yield, reducing the amount of sugar in the stalks; having consequences on price increase and product shortage. To evaluate the impact of frost on sugarcane crop, in the field, on a state level, is not a trivial task; however, this information is relevant due to its direct impact on the consumer market. Remote sensing images allow a synoptic view and present great potential to monitor large sugarcane plantations as has been done since 2003 in São Paulo state by the Canasat Project with Landsat type images (http://www.dsr.inpe.br/laf/canasat/en/). Images acquired from sensors with high temporal resolution such as MODIS (Moderate-Resolution Imaging Spectroradiometer) present the

  9. Evaluation and refinement of sprinkler application rate models used in frost protection

    Energy Technology Data Exchange (ETDEWEB)

    Perry, K.B.

    1979-01-01

    Two models of the sprinkled orchard which predict the application rates required for successful frost protection were evaluated. A Sprinkling Application Rate (SPAR79) model, used the heat budget approach to determine the rate of heat lost by the plant part through radiative, convective, and latent heat transfer processes at the actual plant part temperature and at the plant part's critical temperature. The difference between these two rates of heat loss is the rate at which heat must be added by the latent heat of fusion liberated as the applied water freezes. This model added consideration of humidity and ice accumulation to a refinement of the heat budget configuration of earlier models. It showed that humidity is not a contributing factor in the determination of application rates. Ice accumulation was shown to decrease the required application rate by 67% when it increased the characteristic plant part size from 0.2 to 2.0 cm. A distribution factor, a component of a factor previously only estimated, was shown to increase by 30% (from 1.0 to 1.3) as blossom and leaf development progressed. Pulsed sprinkling for frost protection was carried out during six frost nights. Blossom temperatures, application rate, pulsing cycle, wind speed and air temperature were simultaneously recorded. These observations illustrated that in order to provide adequate protection an appropriate application rate and pulsing cycle must be provided by the model. It was concluded that by varying the distribution factor through the growing season and varying the application rate through a single frost night by pulsing, according to atmospheric parameters and ice accumulation, a significant decrease in amount of water applied may be realized. This decrease in water applied will alleviate ice buildup, water cost, soil drainage and nutrient leaching problems associated with sprinkling for frost protection.

  10. FROST - FReezing Of coated and uncoated duST particles

    Science.gov (United States)

    Wex, H.

    2009-04-01

    In April 2008, the measurement campaign FROST (FReezing Of coated and uncoated duST particles) was conducted at the ACCENT (Atmospheric Composition Change - the European NeTwork of excellence) infrastructure site LACIS (Leipzig Aerosol Cloud Interaction Simulator). During the campaign, size selected coated and uncoated Arizona Test Dust (ATD) particles were characterized with respect to shape, chemical composition, hygroscopic growth and activation, and their ability to act as IN (Ice Nuclei). The ATD particles were dispersed by means of a fluidized bed generator. Coatings were applied in different furnaces, operated at different temperatures. The coatings were either succinic acid, sulphuric acid, or ammonium sulphate. A DMA (Differential Mobility Analyzer) was used for selecting particles with a mobility diameter of 300 nm. The following measurements were done: Three AMS (Aerosol Mass Spectrometers, e.g. Schneider et al. (2005) and references therein) were used to determine particle composition. Particles were collected on grids for subsequent TEM (Transmission Electron Micoscropy) analysis. Hygroscopic growth factors were determined by means of a HH-TDMA (High Humidity Tandem Differential Mobility Analyzer) that measured up to relative humidities (RH) of 98% (Hennig et al. (2005)). The critical super-saturations needed for the activation of the investigated particles into cloud droplets were measured with a continuous flow CCNc (Cloud Condensation Nucleus counter) from DMT (Droplet Measurement Technologies, Roberts and Nenes (2005)). The LACIS flow tube was extended to a length of 8 m, so LACIS could be used to examine the immersion freezing behaviour of the coated and uncoated ATD particles. By a bulk analysis and by the AMS measurements, the ATD particles were found to contain water soluble material, however in small quantities. By means of the online AMS measurements, it was possible to distinguish between thin and thick H2SO4 coatings. For the thin coatings

  11. Stabilization of Leidenfrost vapour layer by textured superhydrophobic surfaces.

    Science.gov (United States)

    Vakarelski, Ivan U; Patankar, Neelesh A; Marston, Jeremy O; Chan, Derek Y C; Thoroddsen, Sigurdur T

    2012-09-13

    In 1756, Leidenfrost observed that water drops skittered on a sufficiently hot skillet, owing to levitation by an evaporative vapour film. Such films are stable only when the hot surface is above a critical temperature, and are a central phenomenon in boiling. In this so-called Leidenfrost regime, the low thermal conductivity of the vapour layer inhibits heat transfer between the hot surface and the liquid. When the temperature of the cooling surface drops below the critical temperature, the vapour film collapses and the system enters a nucleate-boiling regime, which can result in vapour explosions that are particularly detrimental in certain contexts, such as in nuclear power plants. The presence of these vapour films can also reduce liquid-solid drag. Here we show how vapour film collapse can be completely suppressed at textured superhydrophobic surfaces. At a smooth hydrophobic surface, the vapour film still collapses on cooling, albeit at a reduced critical temperature, and the system switches explosively to nucleate boiling. In contrast, at textured, superhydrophobic surfaces, the vapour layer gradually relaxes until the surface is completely cooled, without exhibiting a nucleate-boiling phase. This result demonstrates that topological texture on superhydrophobic materials is critical in stabilizing the vapour layer and thus in controlling--by heat transfer--the liquid-gas phase transition at hot surfaces. This concept can potentially be applied to control other phase transitions, such as ice or frost formation, and to the design of low-drag surfaces at which the vapour phase is stabilized in the grooves of textures without heating.

  12. Stabilization of Leidenfrost vapour layer by textured superhydrophobic surfaces

    KAUST Repository

    Vakarelski, Ivan Uriev

    2012-09-12

    In 1756, Leidenfrost observed that water drops skittered on a sufficiently hot skillet, owing to levitation by an evaporative vapour film. Such films are stable only when the hot surface is above a critical temperature, and are a central phenomenon in boiling. In this so-called Leidenfrost regime, the low thermal conductivity of the vapour layer inhibits heat transfer between the hot surface and the liquid. When the temperature of the cooling surface drops below the critical temperature, the vapour film collapses and the system enters a nucleate-boiling regime, which can result in vapour explosions that are particularly detrimental in certain contexts, such as in nuclear power plants. The presence of these vapour films can also reduce liquid-solid drag. Here we show how vapour film collapse can be completely suppressed at textured superhydrophobic surfaces. At a smooth hydrophobic surface, the vapour film still collapses on cooling, albeit at a reduced critical temperature, and the system switches explosively to nucleate boiling. In contrast, at textured, superhydrophobic surfaces, the vapour layer gradually relaxes until the surface is completely cooled, without exhibiting a nucleate-boiling phase. This result demonstrates that topological texture on superhydrophobic materials is critical in stabilizing the vapour layer and thus in controlling-by heat transfer-the liquid-gas phase transition at hot surfaces. This concept can potentially be applied to control other phase transitions, such as ice or frost formation, and to the design of low-drag surfaces at which the vapour phase is stabilized in the grooves of textures without heating. © 2012 Macmillan Publishers Limited. All rights reserved.

  13. Greenhouse gas fluxes in a drained peatland forest during spring frost-thaw event

    Directory of Open Access Journals (Sweden)

    M. K. Pihlatie

    2010-05-01

    Full Text Available Fluxes of greenhouse gases (GHG carbon dioxide (CO2, methane (CH4 and nitrous oxide (N2O were measured during a two month campaign at a drained peatland forest in Finland by the eddy covariance (EC technique (CO2 and N2O, and automatic and manual chambers (CO2, CH4 and N2O. In addition, GHG concentrations and soil parameters (mineral nitrogen, temperature, moisture content in the peat profile were measured. The aim of the measurement campaign was to quantify the GHG fluxes during freezing and thawing of the top-soil, a time period with potentially high GHG fluxes, and to compare different flux measurement methods. The forest was a net CO2 sink during the two months and the fluxes of CO2 dominated the GHG exchange. The peat soil was a small sink of atmospheric CH4 and a small source of N2O. Both CH4 oxidation and N2O production took place in the top-soil whereas CH4 was produced in the deeper layers of the peat, which were unfrozen throughout the measurement period. During the frost-thaw events of the litter layer distinct peaks in CO2 and N2O emissions were observed. The CO2 peak followed tightly the increase in soil temperature, whereas the N2O peak occurred with a delay after the thawing of the litter layer. CH4 fluxes did not respond to the thawing of the peat soil. The CO2 and N2O emission peaks were not captured by the manual chambers and hence we conclude that high time-resolution measurements with automatic chambers or EC are necessary to quantify fluxes during peak emission periods. Sub-canopy EC measurements and chamber-based fluxes of CO2 and N2O were comparable, although the fluxes of N2O measured by EC were close to the detection limit of the system. We conclude

  14. Black frost. Icing of wind turbine blades endangers stability and safety; Schwarzer Frost. Wenn Eis die Stand- und Verkehrssicherheit von Windkraftanlagen gefaehrdet

    Energy Technology Data Exchange (ETDEWEB)

    Lucks, Christoph [Windcomp GmbH, Hamburg (Germany)

    2010-02-15

    Sailors used to fear icing of sails and ropes from freezing mist and rain. They called it ''black frost'', and this is the same phenomenon that also endangers wind turbine safety. Weather conditions that cause rain to freeze have a characteristic temperature stratification, i.e. moist and warm air over cold ground level air. So far, icing has not caused significant damage in Germany, but this does not mean that it is not a problem. The contribution goes into the causes of icing and the prevention of ice formation. (orig.)

  15. Frost Monitoring and Forecasting Using MODIS Land Surface Temperature Data and a Numerical Weather Prediction Model Forecasts for Eastern Africa

    Science.gov (United States)

    Kabuchanga, Eric; Flores, Africa; Malaso, Susan; Mungai, John; Sakwa, Vincent; Shaka, Ayub; Limaye, Ashutosh

    2014-01-01

    Frost is a major challenge across Eastern Africa, severely impacting agricultural farms. Frost damages have wide ranging economic implications on tea and coffee farms, which represent a major economic sector. Early monitoring and forecasting will enable farmers to take preventive actions to minimize the losses. Although clearly important, timely information on when to protect crops from freezing is relatively limited. MODIS Land Surface Temperature (LST) data, derived from NASA's Terra and Aqua satellites, and 72-hr weather forecasts from the Kenya Meteorological Service's operational Weather Research Forecast model are enabling the Regional Center for Mapping of Resources for Development (RCMRD) and the Tea Research Foundation of Kenya to provide timely information to farmers in the region. This presentation will highlight an ongoing collaboration among the Kenya Meteorological Service, RCMRD, and the Tea Research Foundation of Kenya to identify frost events and provide farmers with potential frost forecasts in Eastern Africa.

  16. Physical, rheological, functional and film properties of a novel emulsifier: Frost grape polysaccharide (FGP) from Vitis riparia Michx

    Science.gov (United States)

    A novel emulsifier, Frost grape polysaccharide (FGP), isolated from natural exudate of the species Vitis riparia Michx, was physically and rheologically characterized. The determination of the physical, structural, thermodynamic, emulsification, film, and rheological properties of FGP provide essent...

  17. Use of LST images from MODIS/AQUA sensor as an indication of frost occurrence in RS

    Directory of Open Access Journals (Sweden)

    Débora de S. Simões

    2015-10-01

    Full Text Available ABSTRACTAlthough frost occurrence causes severe losses in agriculture, especially in the south of Brazil, the data of minimum air temperature (Tmin currently available for monitoring and predicting frosts show insufficient spatial distribution. This study aimed to evaluate the MDY11A1 (LST – Land Surface Temperature product, from the MODIS sensor on board the AQUA satellite as an estimator of frost occurrence in the southeast of the state of Rio Grande do Sul, Brazil. LST images from the nighttime overpass of the MODIS/AQUA sensor for the months of June, July and August from 2006 to 2012, and data from three conventional weather stations of the National Institute of Meteorology (INMET were used. Consistency was observed between Tmin data measured in weather stations and LST data obtained from the MODIS sensor. According to the results, LSTs below 3 ºC recorded by the MODIS/AQUA sensor are an indication of a favorable scenario to frost occurrence.

  18. EVALUATION OF FROST HEAVE ON WASTE TRANSFER LINES WITH SHALLOW DEPTHS IN DST (DOUBLE SHELL TANK) FARMS

    Energy Technology Data Exchange (ETDEWEB)

    HAQ MA

    2009-05-12

    The purpose of this document is to evaluate the effect of frost heave on waste transfer lines with shallow depths in DST farms. Because of the insulation, well compacted sandy material around waste transfer lines, the type of sandy and gravel soil, and relatively low precipitation at Hanford site, it is concluded that waste transfer lines with one foot of soil covers (sandy cushion material and insulation) are not expected to undergo frost heave damaging effects.

  19. Development and Sensitivity Analysis of a Frost Risk model based primarily on freely distributed Earth Observation data

    Science.gov (United States)

    Louka, Panagiota; Petropoulos, George; Papanikolaou, Ioannis

    2015-04-01

    The ability to map the spatiotemporal distribution of extreme climatic conditions, such as frost, is a significant tool in successful agricultural management and decision making. Nowadays, with the development of Earth Observation (EO) technology, it is possible to obtain accurately, timely and in a cost-effective way information on the spatiotemporal distribution of frost conditions, particularly over large and otherwise inaccessible areas. The present study aimed at developing and evaluating a frost risk prediction model, exploiting primarily EO data from MODIS and ASTER sensors and ancillary ground observation data. For the evaluation of our model, a region in north-western Greece was selected as test site and a detailed sensitivity analysis was implemented. The agreement between the model predictions and the observed (remotely sensed) frost frequency obtained by MODIS sensor was evaluated thoroughly. Also, detailed comparisons of the model predictions were performed against reference frost ground observations acquired from the Greek Agricultural Insurance Organization (ELGA) over a period of 10-years (2000-2010). Overall, results evidenced the ability of the model to produce reasonably well the frost conditions, following largely explainable patterns in respect to the study site and local weather conditions characteristics. Implementation of our proposed frost risk model is based primarily on satellite imagery analysis provided nowadays globally at no cost. It is also straightforward and computationally inexpensive, requiring much less effort in comparison for example to field surveying. Finally, the method is adjustable to be potentially integrated with other high resolution data available from both commercial and non-commercial vendors. Keywords: Sensitivity analysis, frost risk mapping, GIS, remote sensing, MODIS, Greece

  20. Frost retardation of an air-source heat pump by the hot gas bypass method

    Energy Technology Data Exchange (ETDEWEB)

    Byun, Ju-Suk [Yonsei Center for Clean Technology, Yonsei University, Seoul 120-749 (Korea); Lee, Jinho [School of Mechanical Engineering, Yonsei University, Seoul 120-749 (Korea); Jeon, Chang-Duk [Department of Mechanical Engineering, Chungju National University, Chung-Buk 380-702 (Korea)

    2008-03-15

    This study is concerned with a hot gas (refrigerant) bypass method to retard the formation and propagation of frost in an air-source heat pump. The feasibility of the hot gas bypass method was investigated experimentally and the method's performance is compared with that of a normal, 1.12 kW capacity air-source heat pump system with no defrost equipment such as an electric resistance heater. Results indicate that the hot gas bypass method is useful for retarding the formation and growth of frost at the outdoor coil. The best performance is shown under a bypass refrigerant flow rate of 0.2 kg/min (20% of the whole system refrigerant flow rate). During 210 min of heat pump operation, the hot gas bypass method improved COP and heating capacity at an average of 8.5% and 5.7%, respectively, relative to the normal system. (author)

  1. USE OF PHASE CHANGE MATERIAL (PCM FOR FROST PREVENTION IN A MODEL GREENHOUSE

    Directory of Open Access Journals (Sweden)

    Ahmet KÜRKLÜ

    1997-02-01

    Full Text Available In this study, the possibility of using phase change materials to prevent occurrance of frost in greenhouses during winter was investigated. The melting and freezing temperatures of the PCM were about 8 oC and 4 oC, respectively.The air temperature difference between the PCM and the control greenhouses was about 2oC on average during the day and night time, PCM greenhouse having the higher temperature at night and lower temperature during the day. Frost was prevented on 7 out of 9 occasions, though the temperature difference between the greenhouses was small for some of these days. Solar fraction stored by the PCM store was about 30 %.

  2. Development and application of a forecasting system to avoid spring frost damage in chiana valley

    Directory of Open Access Journals (Sweden)

    Gaetano Zipoli

    2011-02-01

    Full Text Available Late frost is one of the more serious adversity for Italian agriculture. Several methods have been developed to protect cultivations, but their application results particularly effective (also from an economic point of view only if supported by forecasting systems during the more susceptible period of the year. On these basis a forecasting system of late frost in Val di Chiana (an area in central Italy mainly cultivated with cereals and high quality fruits was developed. The system consists in an empirical model, based on a preventive agroclimatic analysis of the area to identify night cooling dynamics (for several meteorological conditions in the spring. A network of 10 thermohygrometric stations was installed in the area integrating the information obtained by a local agrometeorological station network. The final product was a forecasting bulletin emitted every three hours beginning from the 13:00 p.m. A validation of the system was performed for 2006 to verify the forecast skill.

  3. Development and application of a forecasting system to avoid spring frost damage in chiana valley

    Directory of Open Access Journals (Sweden)

    Simone Orlandini

    Full Text Available Late frost is one of the more serious adversity for Italian agriculture. Several methods have been developed to protect cultivations, but their application results particularly effective (also from an economic point of view only if supported by forecasting systems during the more susceptible period of the year. On these basis a forecasting system of late frost in Val di Chiana (an area in central Italy mainly cultivated with cereals and high quality fruits was developed. The system consists in an empirical model, based on a preventive agroclimatic analysis of the area to identify night cooling dynamics (for several meteorological conditions in the spring. A network of 10 thermohygrometric stations was installed in the area integrating the information obtained by a local agrometeorological station network. The final product was a forecasting bulletin emitted every three hours beginning from the 13:00 p.m. A validation of the system was performed for 2006 to verify the forecast skill.

  4. Comparison of heat pump performance using fin-and-tube and microchannel heat exchangers under frost conditions

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Liang-Liang [Institute of Refrigeration and Cryogenics, Shanghai Jiaotong University, Shanghai 200240 (China); Yang, Liang [Institute of Refrigeration and Cryogenics, Shanghai Jiaotong University, Shanghai 200240 (China); China R and D Center, Carrier Corporation, 3239 Shen Jiang Road, Pudong, Shanghai 201206 (China); Zhang, Chun-Lu [China R and D Center, Carrier Corporation, 3239 Shen Jiang Road, Pudong, Shanghai 201206 (China)

    2010-04-15

    Vapor compression heat pumps are drawing more attention in energy saving applications. Microchannel heat exchangers can provide higher performance via less core volume and reduce system refrigerant charge, but little is known about their performance in heat pump systems under frosting conditions. In this study, the system performance of a commercial heat pump using microchannel heat exchangers as evaporator is compared with that using conventional finned-tube heat exchangers numerically and experimentally. The microchannel and finned-tube heat pump system models used for comparison of the microchannel and finned-tube evaporator performance under frosting conditions were developed, considering the effect of maldistribution on both refrigerant and air sides. The quasi-steady-state modeling results are in reasonable agreement with the test data under frost conditions. The refrigerant-side maldistribution is found remarkable impact on the microchannel heat pump system performance under the frost conditions. Parametric study on the fan speed and the fin density under frost conditions are conducted as well to figure out the best trade-off in the design of frost tolerant evaporators. (author)

  5. Frosted branch angiitis, neuroretinitis as initial ocular manifestation in Behçet disease

    OpenAIRE

    Al-Mujaini, Abdullah; Wali, Upender K

    2011-01-01

    Behçet disease is an idiopathic, multisystem disorder characterized by recurrent episodes of orogenital ulceration and vasculitis of the veins and arteries of all calibers. Ocular involvement may affect the conjunctiva, sclera, uveal tract, vitreous, blood vessels, and retina. Many theories have pointed toward an autoimmune response behind its pathogenesis, which may be triggered by exposure to an infectious agent. Frosted branch angiitis is characterized by vascular inflammation, sheathing, ...

  6. Frost-Resistant Plants Selection Peculiarities at Winter Wheat (Triticum aestivum L. Varieties Breeding

    Directory of Open Access Journals (Sweden)

    М. П. Чебаков

    2009-12-01

    Full Text Available Giving regard to the main elements of Winter Wheat varieties assessment when selecting frost resistant plants and taking into account genetic potential of the parents, date of hybrids sowing and their assessment by the speed of spring vegetation, it is possible in the sense of successful breeding to derive the most steady genotypes by the specified characteristics starting from F1. hybrids.

  7. Frost formation and defrost control parameters for open multideck refrigerated food display cabinets

    Energy Technology Data Exchange (ETDEWEB)

    Tassou, S.A.; Datta, D. [Brunel Univ., Dept. of Mechanical Engineering, Uxbridge (United Kingdom); Marriott, D. [Safeway Stores plc, Hayes (United Kingdom)

    2001-04-03

    In order to achieve the required air and product temperatures in refrigerated food display cabinets, the evaporator coils, which are normally located in the base of the cabinets, operate at temperatures below the freezing point of water. The air which is circulated over the evaporator coil is cooled below its dew point and water vapour present in the air condenses and eventually freezes on the coil surface. With continuous operation of the coil, frost will accumulate on the coil surface leading to a decrease both in the air flowrate and in the overall heat transfer coefficient. In order to maintain satisfactory performance, evaporator coils are defrosted periodically. Although different defrost control strategies can be employed, for simplicity and cost considerations, defrosting in supermarket refrigeration systems is usually controlled by a pre-set time cycle. It is widely acknowledge, however, that time-based defrost may cause a number of unnecessary defrost cycles and this reduces the energy efficiency of the refrigeration systems as well as the accuracy of temperature control of the cabinets. Implementing defrost only when it is needed or on 'demand' should reduce the number of defrost cycles and lead to savings in energy and improved product quality. This paper reports on field and experimental investigations on the processes of frosting and defrosting of medium-temperature display cabinet evaporator coils. The results show that for medium-temperature refrigeration applications where the environment temperature is kept reasonably constant, the store humidity is the primary parameter influencing the rate of frost formation. Using relative humidity as a control parameter the defrost frequency can be reduced considerably without affecting cabinet performance and product integrity. Alongside the effect of relative humidity, the paper also considers the effects of other performance parameters on the processes of frosting and defrosting such as cooling

  8. Frost heave and northern pipelines, state of the art and status of research : three contributing studies

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence, D.E.; Smith, S.L.; Burgess, M.M. (comps.) [Natural Resources Canada, Ottawa, ON (Canada). Geological Survey of Canada

    2005-07-01

    Three review studies were conducted in response to the renewed interest in building a large diameter buried chilled natural gas pipeline in the Mackenzie Valley, Northwest Territories, to transport gas from the Beaufort/Mackenzie Delta to southern markets. The 3 review studies were commissioned by the Geological Survey of Canada to document the current state of knowledge about frost heave theory, testing and predictive modelling. The usefulness of this knowledge to the design, construction and operation of a buried chilled gas pipeline was also evaluated. The studies addressed one of the primary technical and engineering design issues that must be considered in the design of northern pipelines, that of the development of a frost bulb around buried chilled pipelines, and the associated heave of frost-susceptible soil and stresses imposed on the pipeline. The issue of differential heave is of particular concern. The information gathered from this study can be used to form the basis for the regulatory review process. This open file report provides a summary of the 3 studies. The 3 individual commissions reports were catalogued separately for inclusion in this database. refs., tabs., figs.

  9. Frosted branch angiitis, neuroretinitis as initial ocular manifestation in Behçet disease

    Directory of Open Access Journals (Sweden)

    Abdullah Al-Mujaini

    2011-01-01

    Full Text Available Behçet disease is an idiopathic, multisystem disorder characterized by recurrent episodes of orogenital ulceration and vasculitis of the veins and arteries of all calibers. Ocular involvement may affect the conjunctiva, sclera, uveal tract, vitreous, blood vessels, and retina. Many theories have pointed toward an autoimmune response behind its pathogenesis, which may be triggered by exposure to an infectious agent. Frosted branch angiitis is characterized by vascular inflammation, sheathing, retinal edema, and retinal hemorrhages. The disease may be idiopathic in a majority of the cases or may be associated with ocular and systemic pathology. Association between Behηet disease, Frosted branch angiitis, and neuroretinitis is not reported in literature. This uncommon combination reflects the varied systemic and ocular manifestations in Behηet disease, especially in patients who are not diagnosed and treated in time. We hereby report a case of bilateral frosted branch angiitis and neuroretinitis in a young male from Middle-east, suffering from Behçet disease.

  10. Climate Change and Crop Exposure to Adverse Weather: Changes to Frost Risk and Grapevine Flowering Conditions.

    Directory of Open Access Journals (Sweden)

    Jonathan R Mosedale

    Full Text Available The cultivation of grapevines in the UK and many other cool climate regions is expected to benefit from the higher growing season temperatures predicted under future climate scenarios. Yet the effects of climate change on the risk of adverse weather conditions or events at key stages of crop development are not always captured by aggregated measures of seasonal or yearly climates, or by downscaling techniques that assume climate variability will remain unchanged under future scenarios. Using fine resolution projections of future climate scenarios for south-west England and grapevine phenology models we explore how risks to cool-climate vineyard harvests vary under future climate conditions. Results indicate that the risk of adverse conditions during flowering declines under all future climate scenarios. In contrast, the risk of late spring frosts increases under many future climate projections due to advancement in the timing of budbreak. Estimates of frost risk, however, were highly sensitive to the choice of phenology model, and future frost exposure declined when budbreak was calculated using models that included a winter chill requirement for dormancy break. The lack of robust phenological models is a major source of uncertainty concerning the impacts of future climate change on the development of cool-climate viticulture in historically marginal climatic regions.

  11. Frost for the trees: Did climate increase erosion in unglaciated landscapes during the late Pleistocene?

    Science.gov (United States)

    Marshall, Jill A; Roering, Joshua J; Bartlein, Patrick J; Gavin, Daniel G; Granger, Darryl E; Rempel, Alan W; Praskievicz, Sarah J; Hales, Tristram C

    2015-11-01

    Understanding climatic influences on the rates and mechanisms of landscape erosion is an unresolved problem in Earth science that is important for quantifying soil formation rates, sediment and solute fluxes to oceans, and atmospheric CO2 regulation by silicate weathering. Glaciated landscapes record the erosional legacy of glacial intervals through moraine deposits and U-shaped valleys, whereas more widespread unglaciated hillslopes and rivers lack obvious climate signatures, hampering mechanistic theory for how climate sets fluxes and form. Today, periglacial processes in high-elevation settings promote vigorous bedrock-to-regolith conversion and regolith transport, but the extent to which frost processes shaped vast swaths of low- to moderate-elevation terrain during past climate regimes is not well established. By combining a mechanistic frost weathering model with a regional Last Glacial Maximum (LGM) climate reconstruction derived from a paleo-Earth System Model, paleovegetation data, and a paleoerosion archive, we propose that frost-driven sediment production was pervasive during the LGM in our unglaciated Pacific Northwest study site, coincident with a 2.5 times increase in erosion relative to modern rates. Our findings provide a novel framework to quantify how climate modulates sediment production over glacial-interglacial cycles in mid-latitude unglaciated terrain.

  12. Changing risk of spring frost damage in grapevines due to climate change? A case study in the Swiss Rhone Valley

    Science.gov (United States)

    Meier, Michael; Fuhrer, Jürg; Holzkämper, Annelie

    2018-01-01

    Late spring frost is a severe risk during early plant development. It may cause important economic damage to grapevine production. In a warming climate, late frost risk either could decline due to the reduction in frost days and an advancement of the last day of frost or increase due to a more pronounced shift forward of the start of the active growing period of the plants. These possibilities were analyzed in a case study for two locations in the lower Swiss Rhone Valley (Sion, Aigle) where viticulture is an important part of agriculture. Twelve phenology models were calibrated for the developmental stage BBCH09 (bud burst) using measured or reconstructed temperature data for two vineyards in Changins (1958 to 2012) and Leytron (1977 to 2014) together with observed phenological data. The day of year (DOY) for BBCH09 was then modelled for the years 1951 to 2050 using the best performing phenology model in combination with ten downscaled and bias-corrected climate scenarios. A 100-day period starting with BBCH09 was defined, during which daily mean and minimum temperatures were used to calculate three frost risk indices in each year. These indices were compared between the periods 1961-1990 (reference) and 2021-2050 (climate change scenario). Based on the average of the ensemble of climate model chains, BBCH09 advanced by 9 (range 7-11) (Aigle) and 7 (range 5-8) (Sion) days between the two time periods, similar to the shift in the last day of frost. The separate results of the different model chains suggest that, in the near future, late spring frost risk may increase or decrease, depending on location and climate change projections. While for the reference, the risk is larger at the warmer site (Sion) compared to that at the cooler site (Aigle), for the period 2021-2050, small shifts in both phenology and occurrence of frost (i.e., days with daily minimum temperature below 0 °C) lead to a small decrease in frost risk at the warmer but an increase at the cooler

  13. The effect of watermelon frost on prostaglandin E2 (PGE2 in inflamed pulp tissue (in vitro study

    Directory of Open Access Journals (Sweden)

    Dennis Dennis

    2009-06-01

    Full Text Available Background: Pulp inflammation can be marked by the increase of prostaglandin E2(PGE2 level compared to normal pulp. The increase of PGE2 may lead to vasodilatation, increase of vascular permeability, pain and bone resorption. Watermelon frost has been well known in Chinese society for pain relief and inflammation in oral cavity and teeth. Purpose: The aim of this study was to investigate that watermelon frost can be used to decrease the PGE2 level. Method: 27 samples of pulp tissues used in this in-vitro study, were extirpated from the patients’ teeth with symptomatic irreversible pulpitis referred to clinic of Conservative Dentistry, RSPGM Faculty of Dentistry, USU. Trial materials were applied to 27 samples i.e. watermelon frost as a trial material and commercial watermelon frost and eugenol to observe their effect on PGE2. PGE2 level of each material was detected through ELISA method by measuring and comparing the absorbance reading of the wells of the samples against standards with a micro plate reader at W1 = 650 nm and W2 = 490 nm. Result: The result showed the biggest effect was found in the third group (eugenol, mean 4.6933, followed by the first group (watermelon frost as a trial material, mean 18,1578 then the second group (commercial watermelon frost, mean 82,2689. OneWay ANOVA revealed that there were significant differences among all trial materials (p < 0.001 on PGE2 level. Conclusion: This study demonstrated that watermelon frost can be used to decrease the PGE2 level in inflamed pulp tissue and led to the acceptance of traditional medicine and natural products as an alternative form of dental care.

  14. Experiments in Ice Contaminant Remanent Magnetization of Dusty Frost Deposits

    Science.gov (United States)

    Grossman, Y.; Aharonson, O.; Shaar, R.

    2017-12-01

    Sedimentary rocks can acquire magnetization in the presence of an external field as grains settle out of suspension in a water column - a process known as Depositional Remanent Magnetization (DRM). In analogy with this, here we propose and experimentally demonstrate a new mechanism for acquisition of magnetization by ice and particulate mixtures which we term Ice Contaminant Remanent Magnetization (ICRM). This phenomenon results from the settling of atmospheric dust containing magnetic particles (e.g. magnetite or other iron oxides). Upon freezing, magnetic dust particles assume a preferential orientation that depends on the external planetary field, resulting in bulk magnetization of the dusty ice. Hence over geologic timescales, the ice stratigraphy is expected to record the geomagnetic history. To test this hypothesis, we designed a set of experiments in which mixtures of ice and dust were deposited in a controlled ambient magnetic field environment. We measured the ratio between the volume normalized magnetization of the dusty ice (m) and the applied field (H) during deposition of the mixture, which is expressed as the effective ICRM susceptibility: m=χICRMH. A magnetic field was applied by a 3-axis Helmholtz coil at the Weizmann Simulating Planetary Ices & Environments Laboratory, and the frozen samples were analyzed in a 2G-Entreprises SQUID Rock Magnetometer at the Hebrew University Institute for Earth Sciences. We measured a clear correlation in amplitude and direction between the ambient magnetic field applied during deposition and the remanent magnetic moment of the resulting samples. We studied various concentrations and particle sizes (diameters 5 µm to 50 µm) of iron and magnetite particles. Effective bulk susceptibilities show a range of values, starting from 10-3 and up to values that saturate the analytical instrument. Our preliminary results indicate that natural ice deposits may acquire variable magnetization due to ICRM, which may in turn be

  15. Comparing Stage Presence and Virtual Reality Presence

    Directory of Open Access Journals (Sweden)

    Sebastian Xavier Samur

    2016-05-01

    Full Text Available Reflecting on the impending release of new Head Mounted Display virtual reality (VR technologies, the article examines definitions and techniques for digital presence, and compares them with research into stage presence. It opens with an outline of definitions of digital presence, comparing them with Cormac Power’s fictional, auratic, and literal modes of presence in performance. The article then looks at techniques used in VR and on stage to achieve presence. Finally, performance examples that use virtual reality technologies are presented. The article concludes that even if the technology falls short, discourse on digital presence is useful in providing insights into presence on stage.

  16. Seasonal to Decadal Variations of Water Vapor in the Tropical Lower Stratosphere Observed with Balloon-Borne Cryogenic Frost Point Hygrometers

    Science.gov (United States)

    Fujiwara, M.; Voemel, H.; Hasebe, F.; Shiotani, M.; Ogino, S.-Y.; Iwasaki, S.; Nishi, N.; Shibata, T.; Shimizu, K.; Nishimoto, E.; hide

    2010-01-01

    We investigated water vapor variations in the tropical lower stratosphere on seasonal, quasi-biennial oscillation (QBO), and decadal time scales using balloon-borne cryogenic frost point hygrometer data taken between 1993 and 2009 during various campaigns including the Central Equatorial Pacific Experiment (March 1993), campaigns once or twice annually during the Soundings of Ozone and Water in the Equatorial Region (SOWER) project in the eastern Pacific (1998-2003) and in the western Pacific and Southeast Asia (2001-2009), and the Ticosonde campaigns and regular sounding at Costa Rica (2005-2009). Quasi-regular sounding data taken at Costa Rica clearly show the tape recorder signal. The observed ascent rates agree well with the ones from the Halogen Occultation Experiment (HALOE) satellite sensor. Average profiles from the recent five SOWER campaigns in the equatorial western, Pacific in northern winter and from the three Ticosonde campaigns at Costa Rica (10degN) in northern summer clearly show two effects of the QBO. One is the vertical displacement of water vapor profiles associated with the QBO meridional circulation anomalies, and the other is the concentration variations associated with the QBO tropopause temperature variations. Time series of cryogenic frost point hygrometer data averaged in a lower stratospheric layer together with HALOE and Aura Microwave Limb Sounder data show the existence of decadal variations: The mixing ratios were higher and increasing in the 1990s, lower in the early 2000s, and probably slightly higher again or recovering after 2004. Thus linear trend analysis is not appropriate to investigate the behavior of the tropical lower stratospheric water vapor.

  17. Frost stress evolution and winter pea ideotype in the context of climate warming at a regional scale

    Directory of Open Access Journals (Sweden)

    Castel Thierry

    2017-01-01

    Full Text Available Pea (Pisum sativum L. is an important crop in temperate regions for its high seed protein concentration that is particularly sensitive to abiotic stresses. The abrupt temperature increase known as the “1987/1988 temperature regime shift” that occurs over Europe is questioning how winter pea will perform in the changing climate. This study assessed the winter frost damage evolution along from 1961 to 2015 in Burgundy-Franche-Comté by using: (1 daily observed and gridded regional temperature data and (2 a validated crop winter frost stress model calibrated for pea. This study shows a global decrease of the frost stress nevertheless resulting from a subtle balance between the decrease in its intensity and the increase of the number of events. The frost stress evolution patterns with warming depend on both plant frost resistance level and acclimation rate and are still sensitive to winter climate fluctuations. This study provides relevant information for breeding performant winter crop ideotypes able to moderate detrimental effects of climate change and offering new cropping opportunities in temperate regions.

  18. THE EFFECT OF CULTIVAR AND BEARING TREE ON BUD DIFFERENTIATION, FROST DAMAGE AND FRUIT SET IN APPLE

    Directory of Open Access Journals (Sweden)

    Nikola Pavičić

    2004-06-01

    Full Text Available After severe winter frost, an examination was initiated of frost damage suffered by Idared and Golden Delicious clone B. The cultivars differed significantly in the differentiation intensity, the hare of damaged differentiated buds, but not in share of damaged undifferentiated buds. In both cultivars the bud damage was more intensive on long bearing wood than on spur, regardless differentiation grade. The interaction between the cultivar and the bearing wood was insignificant. The flower bud differentiation was better in Idared, but it also suffered more frost damage than the Golden Delicious clone B with differentiated buds, but not than that with undifferentiated buds. In both cultivars frost damage increases with increase of differentiated flower buds (R2=0.759; P≤0.001. The fruit set was within the limits of expectation only on the spurs of the Golden Delicious clone B, which showed strong tendency towards fruit set on long bearing shoots. In 2000, the yield of the cultivars was almost equal, as the result of thinning due to the frost damage on Idared.

  19. Changes of Frost Damage and Treeline Advance for Swiss Stone Pine in the Calimani Mts. (Eastern Carpathians, Romania

    Directory of Open Access Journals (Sweden)

    KERN, Zoltán

    2008-01-01

    Full Text Available Checking the tree-ring structure of 39 living and 9 crossdated dead samples of Swissstone pine (Pinus cembra L. collected from the upper timberline of the CalimaniMts. we haveidentified 59 frost rings over the past 250 years. We found concentrated occurrence of frost events inthree decades: in the 1790s, 1810s and 1910s. No frost ring was observed in two bidecadal periods:1750-1770 and 1850-1870. Out of the analysed interval 1963-2004 is the longest period without frostring occurrence. After 1920 both frequency and severity of frost events seem to decrease compared tothe prior 170 years. We determined the altitude of highest growing stone pine individuals in theBradului Ciont–Pietrosu region in June, 2006. Individuals were sorted into tree-form or bush-likemorphological groups. Mean elevation data of the groups were corrected by an estimated constant biasof GPS measurements (-30 m. Comparing the corrected values to early 20th century inventory data65 m and 95 m upward migration was determined for treeline and boundary of bush-like occurence,respectively. The parallel results suggest that the 20th century advance of the upper forest limit wasdue to the decrease of frost stress at the zone of timberline.

  20. Recent changes in frost days events characteristics in Uruguay-Southeastern South America.

    Science.gov (United States)

    Renom, Madeleine; De Mello, Santiago

    2015-04-01

    There are few studies about extreme temperature events in Southeastern South America as is it mentioned in the SREX report (2009), although these events generate human health impacts and big economical looses. Southeastern South America is one of the major agricultural production regions worldwide. Particularly in Uruguay, agricultural production represents a high percentage of the GDP and, in the last 15 years there has been a significant increase in the area used for that economic activity. Although frost is not always is considered as an extreme event it causes, in the case of Uruguay, an impact on society, energy consumption and agricultural losses. Previous studies have shown a negative trend in the occurrence of cold nights (TN10) during winter (June-July-August) and autumn (March-April-May) in Uruguay. This work try to determine if these trends affects the occurrences and characteristics of frost days (Tmin< 0°C). Based on a high-quality daily minimum temperature for 11 meteorological stations that cover the period 1950-2009, we analyzed different features of frost days. Long term trends do not present a clear spatial behaviour suggesting that there is a not clear relationship between the percentile based index (TN10) and a fixed index (FD). At monthly scale, May and September show a negative trend, although these months present a low number of cases that difficult the statistical treatment. It is noticeable that from a decadal point of view the last decade (2000-2009) was the decade with fewer occurrences comparing with the rest, while the 90's is the decade that presents more cases. We also analyzed changes in frost period (FP) which commonly extends from May to September. In general all the stations present a decrease in the FP in accordance with the negative trend detected at monthly scale, suggesting a warming in autumn and spring time. Although we detected different behaviour in two stations, one located inner land and the other located on the

  1. Investigation of Frost Tolerance of Flower in Two Iranian Cornelian Cherry Clones

    Directory of Open Access Journals (Sweden)

    Z. Samiee Rad

    2013-10-01

    Full Text Available In many areas, low temperature is an important environmental limiting factor in production and distribution of horticultural trees and plants. This study was conducted to study the frost tolerance of main local clones of cornelian cherry in Tarom Sofla region, Qazvin, Iran. Cold treatments at 5 levels (+4, +2, 0, -2 and -4 ˚C at two cooling periods (3 and 5 hours were arranged as a factorial experiment, based on completely randomized design with 4 replications, at flowering stage of Golabie Siah (black pear and Paeizi (autumn clones in 2009-2010. For each treatment, the electrical conductivity (EC and acidity (pH were measured just after shaking (t=0, every 3 hours in the first 24 hours, and once daily in the 2nd to 8th day. After a week, the samples were autoclaved at 105˚C for 4 minutes and the changes were recorded. Results showed that the range of EC in flower was 92.2-846.2 µS/cm, and the range of pH varied from 6.4 to 7.7. Based on the results, the effect of frost intensity on EC changes was ascending, and on pH was slowly ascending and sometimes fixed. The highest value of EC due to destruction of tissues, as an index of frost damage of the flower, was obtained at +4 ˚C. Therefore, tolerance range of cornelian cherry flower has been estimated to be more than +4 ˚C.

  2. Prediction of Frost Risks and Plagues using WRF model: a Port Wine region case study

    Science.gov (United States)

    Rodrigues, M. A.; Rocha, A.; Monteiro, A.; Quénol, H.; de Freitas, J. R.

    2012-04-01

    In viticulture where the quality of the wine, the selection of the grapevines or even the characteristics of the farming soil, also depending from local soil features like topography, proximity of a river or water body, will act locally on the weather. Frosts are of significant concern to growers of many cultures crops such as winegrapes. Because of their high latitude and some altitude, the vineyards of the Demarcated Douro Region (DDR) are subjected to the frost, which cause serious damages. But the hazards of vineyard don't confine to the incidents of the fortuitous and meteorological character. The illnesses and plagues affect frequently the vineyards of Demarcated Douro Region due, namely to the weather, to the high power of the regional stocks, to the dense vegetation badly drained and favourable to the setting of numberless fungi, viruses and/or poisonous insects. In the case of DDR it is worth noticing the meteorological conditions due to the weather characteristics. Although there are several illnesses and plagues the most important enemies for the vine in the DDR are the mildew, oidium, grey rottenness, grape moth,. . . , if the climatic conditions favour their appearance and development. For this study, we selected some months for different periods, at the 16 weather stations of the Region of Douro. We use the Weather Research and Forecast Model (WRF) to study and possibly predict the occurrence of risk and plagues (mildew) episodes. The model is first validated with the meteorological data obtained at the weather stations. The knowledge of frost and plagues occurrence allows one to decrease its risks not only by selecting the cultural species and varieties but also the places of growth and the planting and sowing dates.

  3. Assessing Wheat Frost Risk with the Support of GIS: An Approach Coupling a Growing Season Meteorological Index and a Hybrid Fuzzy Neural Network Model

    Directory of Open Access Journals (Sweden)

    Yaojie Yue

    2016-12-01

    Full Text Available Crop frost, one kind of agro-meteorological disaster, often causes significant loss to agriculture. Thus, evaluating the risk of wheat frost aids scientific response to such disasters, which will ultimately promote food security. Therefore, this paper aims to propose an integrated risk assessment model of wheat frost, based on meteorological data and a hybrid fuzzy neural network model, taking China as an example. With the support of a geographic information system (GIS, a comprehensive method was put forward. Firstly, threshold temperatures of wheat frost at three growth stages were proposed, referring to phenology in different wheat growing areas and the meteorological standard of Degree of Crop Frost Damage (QX/T 88-2008. Secondly, a vulnerability curve illustrating the relationship between frost hazard intensity and wheat yield loss was worked out using hybrid fuzzy neural network model. Finally, the wheat frost risk was assessed in China. Results show that our proposed threshold temperatures are more suitable than using 0 °C in revealing the spatial pattern of frost occurrence, and hybrid fuzzy neural network model can further improve the accuracy of the vulnerability curve of wheat subject to frost with limited historical hazard records. Both these advantages ensure the precision of wheat frost risk assessment. In China, frost widely distributes in 85.00% of the total winter wheat planting area, but mainly to the north of 35°N; the southern boundary of wheat frost has moved northward, potentially because of the warming climate. There is a significant trend that suggests high risk areas will enlarge and gradually expand to the south, with the risk levels increasing from a return period of 2 years to 20 years. Among all wheat frost risk levels, the regions with loss rate ranges from 35.00% to 45.00% account for the largest area proportion, ranging from 58.60% to 63.27%. We argue that for wheat and other frost-affected crops, it is

  4. Development of a Frost Risk Assessment Tool in Agriculture for a Mediterranean ecosystem Utilizing MODIS satellite observations Geomatics and Surface Data

    Science.gov (United States)

    Louka, Panagiota; Papanikolaou, Ioannis; Petropoulos, George; Migiros, George; Tsiros, Ioannis

    2014-05-01

    Frost risk in Mediterranean countries is a critical factor in agricultural planning and management. Nowadays, the rapid technological developments in Earth Observation (EO) technology have improved dramatically our ability to map the spatiotemporal distribution of frost conditions over a given area and evaluate its impacts on the environment and society. In this study, a frost risk model for agricultural crops cultivated in a Mediterranean environment has been developed, based primarily on Earth Observation (EO) data from MODIS sensor and ancillary spatial and point data. The ability of the model to predict frost conditions has been validated for selected days on which frost conditions had been observed for a region in Northwestern Greece according to ground observations obtained by the Agricultural Insurance Organization (ELGA). An extensive evaluation of the frost risk model predictions has been performed herein to evaluate objectively its ability to predict the spatio-temporal distribution of frost risk in the studied region, including comparisons against physiographical factors of the study area. The topographical characteristics that were taken under consideration were latitude, altitude, slope steepness, topographic convergence and the extend of the areas influenced by water bodies (such as lake and sea) existing in the study area. Additional data were also used concerning land use data and vegetation classification (type and density). Our results showed that the model was able to produce reasonably the spatio-temporal distribution of the frost conditions in our study area, following largely explainable patterns in respect to the study site and local weather conditions characteristics. All in all, the methodology implemented herein proved capable in obtaining rapidly and cost-effectively cartography of the frost risk in a Mediterranean environment, making it potentially a very useful tool for agricultural management and planning. The model presented here has

  5. Tolerância de frutos de pessegueiro a geadas Fruit frost tolerance in peach

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    André Paulo Assmann

    2008-12-01

    Full Text Available Este trabalho teve como objetivo avaliar a tolerância de frutos de pessegueiro aos danos ocasionados pela geada. A geada ocorreu no dia 5 de setembro de 2006, sendo que a temperatura mínima, a 1,5 m do solo, foi de - 1,06ºC. Foram avaliados 28 genótipos de pessegueiro em diferentes estádios fenológicos. O delineamento experimental foi o inteiramente casualizado, com três repetições (plantas de pessegueiro, procedendo-se à avaliação em seis ramos por planta. No dia em que ocorreu a geada, foram mensurados o número de frutos por ramo, diâmetro sutural médio dos frutos, número total de gemas vegetativas, percentual de brotação e percentual de brindilas formadas a partir das gemas brotadas. Uma segunda avaliação foi realizada 15 dias após a primeira, para avaliar o percentual de queda de frutos e o diâmetro sutural médio dos frutos remanescentes. Genótipos bem enfolhados e cujos frutos apresentavam endocarpo endurecido, no momento da ocorrência da geada, foram tolerantes ao dano ocasionado pelo frio; frutos com diâmetro sutural inferior a 20 mm foram suscetíveis à geada, enquanto frutos com diâmetro sutural superior a 30 mm apresentaram boa tolerância, independentemente do genótipo avaliado.The aim of this work was to evaluate the fruit damage tolerance in different peach tree genotypes after natural freeze. The frost happened on September 5, 2006, and the minimum temperature, 1.5 meters over soil, was -1.06ºC. Twenty- eight peach tree genotypes, in different stages of development, were evaluated, in a completely random design, in three replication (plants and six branches by plants. Immediately after frost, we measured the number of fruits per branches, average fruit suture diameter, percentage of sprouts and percentage of twigs in formation. A second evaluation was accomplished fifteen days after the first one in order to assess the percentage of fruit drop and the average remaining fruit suture diameter. Genotypes

  6. CLAS+FROST: new generation of photoproduction experiments at Jefferson Lab

    Energy Technology Data Exchange (ETDEWEB)

    Eugene Pasyuk

    2009-12-01

    A large part of the experimental program in Hall B of the Jefferson Lab is dedicated to baryon spectroscopy. Photoproduction experiments are essential part of this program. CEBAF Large Acceptance Spectrometer (CLAS) and availability of circularly and linearly polarized tagged photon beams provide unique conditions for this type of experiments. Recent addition of the Frozen Spin Target (FROST) gives a remarkable opportunity to measure double and triple polarization observables for different pseudo-scalar meson photoproduction processes. For the first time, a complete or nearly complete experiment becomes possible and will allow model independent extraction of the reaction amplitude. An overview of the experiment and its current status is presented.

  7. Experiences with hoar-frost and its monitoring in Western Bohemia, Czech Republic

    Energy Technology Data Exchange (ETDEWEB)

    Sulan, J. [Czech Hydrometeorological Inst., Pilsen (Czech Republic). Regional Branche Pilsen

    2004-07-01

    At this study data from winter season 2002/2003 were used to find basic statistics about conditions suitable for hoar-frost deposition. Simple criterion according to Norrman (2002) was applied and important role of screening and sheltering effect was confirmed. The most critical place with the longest time of suitable conditions was found on sheltered and screened site in elevation 550 m above sea level on highway D5 near the border crossing Rozvadov - Waidhause. This result confirms the judgment from thermal mapping according to which this stretch is one of the most critical places of Czech highway network at all. (orig.)

  8. Determination of E and G Observables in n Photoproduction on the CLAS Frozen Spin Target (FROST)

    Energy Technology Data Exchange (ETDEWEB)

    Senderovich, Igor [University of Connecticut, Storrs, CT (United States); Morrison, Brian T. [Arizona State University, Tempe, AZ (United States); Dugger, Michael R. [Arizona State University, Tempe, AZ (United States); Ritchie, Barry G. [Arizona State University, Tempe, AZ (United States); Tucker, Ross J. [Arizona State University, Tempe, AZ (United States)

    2014-01-01

    Polarization observables are vital for disentangling overlapping resonances in the baryon spectrum. Extensive data have been collected at Jefferson Lab in Hall B with circularly and linearly polarized tagged photon beam incident on longitudinally polarized protons provided by the Frozen Spin Target (FROST). The focus of the described work is on η photoproduction, which acts as an "isospin filter", isolating the N*(I = 1/2) resonances. Preliminary results for the double-polarization observables E and G are presented. There are currently no data on these in the world database for η photoproduction.

  9. Prediction of frost location using machine learning and wireless sensor networks

    OpenAIRE

    Diedrichs, Ana

    2014-01-01

    The damage caused by the frost takes place when the temperatures are below than a tolerable limit for the plants. Each phenological state, e.g owering, has a variable cold hardiness, so the lethal temperature is also variable. Freezing climatic events are the most dangerous, because they affect a large land surface. Mendoza is not an exception. According to the Instituto Nacional de Vitivinicultura (INV), in 2013 the loss of the vine crop reached up to 27%. Big part of that loss of yield was ...

  10. Simulating transmission and control of Taenia solium infections using a reed-frost stochastic model

    DEFF Research Database (Denmark)

    Kyvsgaard, Niels Chr.; Johansen, Maria Vang; Carabin, Hélène

    2007-01-01

    The transmission dynamics of the human-pig zoonotic cestode Taenia solium are explored with both deterministic and stochastic versions of a modified Reed-Frost model. This model, originally developed for microparasitic infections (i.e. bacteria, viruses and protozoa), assumes that random contacts...... humans eating under-cooked pork meat harbouring T. solium metacestodes. Deterministic models of each scenario were first run, followed by stochastic versions of the models to assess the likelihood of infection elimination in the small population modelled. The effects of three groups of interventions were...

  11. Remedial measures to tame the frost heaves at gas distribution stations in west-east gas pipeline

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Daoming; Gong, Jing [Beijing Key Laboratory of Urban Oil and Gas Distribution Technology, China University of Petroleum (China); Wang, Xiaoping; Li, Kai; Jiang, Yongtao [West-East Gas Pipeline Company (China)

    2010-07-01

    In China, a pipeline running 3900 kilometers from Xinjiang to the Yangtze River Delta area and with a capacity of 12 billion cubic meters of gas annually was put into operation in 2004. Due to subfreezing gas temperatures, the distribution stations have since then suffered from frost heaves. One method to address this issue could be to install gas-fueled heaters, however, that would imply important additional costs as well as problems in acquiring land. The aim of this paper is to present and compare different methods to deal with the frost heaves issue. Soil replacement with a water mitigation technique was found to be the best option based on geotechnical survey, calculations and data; this technique was successfully applied to several distribution stations with different water tables. A frost heaves mitigation method was developed herein and proved to be more cost effective than gas-fueled heaters.

  12. Drought and frost tolerance in rhododendron collection of the Mlyňany Arboretum (Slovakia: a screening for future climate

    Directory of Open Access Journals (Sweden)

    Ferus Peter

    2017-12-01

    Full Text Available Rhododendrons are jewels of the Mlyňany Arboretum, Institute of Forest Ecology of the Slovak Academy of Sciences (IFE SAS. Blossoming in May, they attract thousands of visitors. But recently these woody plants have much suffered from climatic extremes such as summer droughts and winter frosts, associated with the advancing climate change. To assess the rhododendron collection’s stability, its drought and frost injury level were tested in field, in summer 2015 and winter 2017, respectively. The tested parameters were: leaf wilting and electrolyte leakage combined with shrub leaf area, insolation level and overall health state. We found that the drought effect was strong or very strong in only ca. 30% rhododendron species and ca. 10% rhododendron cultivars, and that around 60% shrubs showed no or only moderate symptoms of water deficit. The drought injury level was only associated with the genotype. The most tolerant / sensitive genotypes, commonly occurring in the park, were: R. catawbiense, R. ponticum, R. smirnowii, cv. ‘Boursault’, cv. ‘Cunningham’s White’ and cv. ‘Purpureum Elegans’ / R. fortunei and cv. ‘Tamarindos’. On the other hand, the most frequent response to frost in the observed rhododendron genotypes was moderate injury (28 and 37% for species and cultivars, respectively, nevertheless more than 18% species and almost 6% cultivars exhibited strong frost damage. Despite absence of significant differences in the factor-response between the species, we may suggest this decreasing sequence of the genotypes ordered according to their frost resistance: genotypes: cv. ‘Cunningham’s White’ > R. decorum > R. fortunei and cv. ‘Duke of York’ > R. smirnowii > cvs. ‘Purpureum Elegans’ and ‘Tamarindos’ > R. macrophyllum and cv. ‘Nova Zembla’ > R. catawbiense > R. ponticum. These results have been compared with similar works in rhododendron species/cultivars as well as suggested species drought/frost

  13. There is no direct relationship between N-status and frost hardiness in needles of NH3-exposed Scots pine seedlings

    NARCIS (Netherlands)

    Clement, JMAM; Venema, JH; Van Hasselt, PR

    2000-01-01

    The effect of short-term atmospheric ammonia deposition on frost hardening of needles of three-month-old seedlings of Scots pine (Pinus sylvestris L.) was studied. Plants were frost hardened under short day and moderate temperature conditions in the laboratory during exposure to gaseous NH3

  14. Robert Frost's Chicken Feathers and Other Lectures from the 1968 Augustana College NDEA English Institute. Augustana College Press Monograph Series No. 1.

    Science.gov (United States)

    Huseboe, Arthur R., Ed.

    The four lectures in this publication were composed with the common concern for making the study of high school English more effective and more delightful. Papers are (1) "Robert Frost's Chicken Feathers" by C. W. Geyer (discusses the influence of oral folklore and humor on Frost's poetry); (2) "Nature in Literature" by Gerhard T. Alexis; (3)…

  15. Winter frost resistance of Pinus cembra measured in situ at the alpine timberline as affected by temperature conditions.

    Science.gov (United States)

    Buchner, Othmar; Neuner, Gilbert

    2011-11-01

    Winter frost resistance (WFR), midwinter frost hardening and frost dehardening potential of Pinus cembra L. were determined in situ by means of a novel low-temperature freezing system at the alpine timberline ecotone (1950 m a.s.l., Mt Patscherkofel, Innsbruck, Austria). In situ liquid nitrogen (LN₂)-quenching experiments should check whether maximum WFR of P. cembra belonging to the frost hardiest conifer group, being classified in US Department of Agriculture climatic zone 1, suffices to survive dipping into LN₂ (-196 °C). Viability was assessed in a field re-growth test. Maximum in situ WFR (LT₅₀) of leaves was cembra was higher than that obtained on detached twigs, as reported earlier. In situ LN₂-quenching experiments were lethal in all cases even when twigs of P. cembra were exposed to an in situ frost hardening treatment (12 days at -20 °C followed by 3 days at -50 °C) to induce maximum WFR. Temperature treatments applied in the field significantly affected the actual WFR. In January a frost hardening treatment (21 days at -20 °C) led to a significant increase of WFR (buds: -62 °C to cembra was not at its specific maximum WFR. In contrast, simulated warm spells in late winter led to premature frost dehardening (buds: -32.6 °C to -10.2 °C; leaves: -32.7 to -16.4 °C) followed by significantly earlier bud swelling and burst in late winter. Strikingly, both temperature treatments, either increased air temperature (+10.1 °C) or increased soil temperature (+6.5 °C), were similarly effective. This high readiness to frost harden and deharden in winter in the field must be considered to be of great significance for future winter survival of P. cembra. Determination of WFR in field re-growth tests appears to be a valuable tool for critically judging estimates of WFR obtained on detached twigs in an ecological context.

  16. Material and fin pitch effect on frosting CO2 in a fin-and-tube heat exchanger

    Science.gov (United States)

    Bassila, Joseph; Toubassy, Joseph; Danlos, Amélie; Descombes, Georges; Clodic, Denis

    2017-02-01

    Cryo Pur technology uses cryogenic separation to remove water vapor and carbon dioxide from biogas, in order to obtain bio-methane. To cool down the biogas at a very low temperature, a fin-and-tube heat exchanger is designed. In order to improve the fin-and-tube heat exchanger performance, a model is developed to investigate the material and fin pitch on frosting carbon dioxide. This paper will study the effect of the tubes and the fins material, and the fin pitch effect. The purpose is to extend the duration of a frosting cycle.

  17. Frost Growth and Densification on a Flat Surface in Laminar Flow with Variable Humidity

    Science.gov (United States)

    Kandula, M.

    2012-01-01

    Experiments are performed concerning frost growth and densification in laminar flow over a flat surface under conditions of constant and variable humidity. The flat plate test specimen is made of aluminum-6031, and has dimensions of 0.3 mx0.3 mx6.35 mm. Results for the first variable humidity case are obtained for a plate temperature of 255.4 K, air velocity of 1.77 m/s, air temperature of 295.1 K, and a relative humidity continuously ranging from 81 to 54%. The second variable humidity test case corresponds to plate temperature of 255.4 K, air velocity of 2.44 m/s, air temperature of 291.8 K, and a relative humidity ranging from 66 to 59%. Results for the constant humidity case are obtained for a plate temperature of 263.7 K, air velocity of 1.7 m/s, air temperature of 295 K, and a relative humidity of 71.6 %. Comparisons of the data with the author's frost model extended to accommodate variable humidity suggest satisfactory agreement between the theory and the data for both constant and variable humidity.

  18. Model prediction of frost tolerance as related to winter survival of wheat in Finnish field trials

    Directory of Open Access Journals (Sweden)

    A.K. BERGJORD

    2008-12-01

    Full Text Available The model FROSTOL simulates course of frost tolerance in winter wheat on a daily basis from sowing on as affected by soil temperature (2 cm, snow cover, phenological development, and a genotypic maximum level of frost tolerance (LT50. A series of cultivar trials in Finland was used to evaluate the model's ability to estimate plant survival in natural field environments during winters with differing weather conditions. Recorded survival was compared with number of intersections between the curves of simulated LT50 and the soil temperature curve for each field. A cumulative stress level (CSL was calculated based both on number of intersections and FROSTOL simulated stress levels. The correlation between CSL and field recordings was quite low. While the field trials characterize a general ability to stand various types of winter stress, FROSTOL estimates damage caused by the soil temperature regime only. However, FROSTOL simulations seemed to correspond reasonably well to field observations when low temperature was the eventual cause of damage.

  19. ASSESSMENT OF CERAMIC TILE FROST RESISTANCE BY MEANS OF THE FREQUENCY INSPECTION METHOD

    Directory of Open Access Journals (Sweden)

    MICHAL MATYSÍK

    2011-06-01

    Full Text Available The paper presents some results of our experimental analysis of ceramic cladding element frost resistance, particular attention being paid to the application of the frequency inspection method. Three different sets of ceramic tiles of the Ia class to EN 14 411 B standard made by various manufacturers have been analyzed. The ceramic tiles under investigation have been subjected to freeze-thaw-cycle-based degradation in compliance with the relevant ČSN EN ISO 10545-12 standard. Furthermore, accelerated degradation procedure has been applied to selected test specimens, consisting in reducing the temperature of water soaked ceramic tiles in the course of the degradation cycles down –70°C. To verify the correctness of the frequency inspection results, additional physical properties of the ceramic tiles under test have been measured, such as, the ceramic tile strength limit, modulus of elasticity and modulus of deformability, resulting from the flexural tensile strength tests, integrity defect and surface micro-geometry tracking. It has been proved that the acoustic method of frequency inspection is a sensitive indicator of the structure condition and can be applied to the ceramic cladding element frost resistance and service life prediction assessment.

  20. Screening of plant resources with anti-ice nucleation activity for frost damage prevention.

    Science.gov (United States)

    Suzuki, Shingo; Fukuda, Satoshi; Fukushi, Yukiharu; Arakawa, Keita

    2017-11-01

    Previous studies have shown that some polyphenols have anti-ice nucleation activity (anti-INA) against ice-nucleating bacteria that contribute to frost damage. In the present study, leaf disk freezing assay, a test of in vitro application to plant leaves, was performed for the screening of anti-INA, which inhibits the ice nucleation activity of an ice-nucleating bacterium Erwinia ananas in water droplets on the leaf surfaces. The application of polyphenols with anti-INA, kaempferol 7-O-β-glucoside and (-)-epigallocatechin gallate, to the leaf disk freezing assay by cooling at -4--6 °C for 3 h, revealed that both the compounds showed anti-INAs against E. ananas in water droplets on the leaf surfaces. Further, this assay also revealed that the extracts of five plant leaves showed high anti-INA against E. ananas in water droplets on leaf surfaces, indicating that they are the candidate resources to protect crops from frost damage.

  1. CO2 capture at low temperatures (30-80 °C) and in the presence of water vapor over a thermally activated Mg-Al layered double hydroxide.

    Science.gov (United States)

    Torres-Rodríguez, Daniela A; Lima, Enrique; Valente, Jaime S; Pfeiffer, Heriberto

    2011-11-10

    The carbonation process of a calcined Mg-Al layered double hydroxide (LDH) was systematically analyzed at low temperatures, varying the relative humidity. Qualitative and quantitative experiments were performed. In a first set of experiments, the relative humidity was varied while maintaining a constant temperature. Characterization of the rehydrated products by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and solid-state NMR revealed that the samples did not recover the LDH structure; instead hydrated MgCO(3) was produced. The results were compared with similar experiments performed on magnesium oxide for comparison purposes. Then, in the second set of experiments, a kinetic analysis was performed. The results showed that the highest CO(2) capture was obtained at 50 °C and 70% of relative humidity, with a CO(2) absorption capacity of 2.13 mmol/g.

  2. Experimental study of no-frost refrigerator. Part 1: heat transfer through the walls; Estudo experimental de um refrigerador no-frost. Parte 1: transferencia de calor atraves das paredes

    Energy Technology Data Exchange (ETDEWEB)

    Goncalves, Joaquim Manoel [Escola Tecnica Federal de Santa Catarina, Sao Jose, SC (Brazil)]. E-mail: joaquim@nrva.ufsc.br; Melo, Claudio; Vieira, Luis Antonio Torquato [Santa Catarina Univ., Florianopolis, SC (Brazil). Dept. de Engenharia Mecanica

    2000-07-01

    This paper approaches the heat transfer in permanent regimen trough the walls of a no-frost refrigerator with two compartments with forced internal ventilation. The presented methodology allows the determination of thermal resistances of the walls externally. Also, the heating effect due to the compressor, the condenser and the air distribution between the compartments are investigated.

  3. EVIDENCE FOR FRESH FROST LAYER ON THE BARE NUCLEUS OF COMET HALE-BOPP AT 32 AU DISTANCE

    Energy Technology Data Exchange (ETDEWEB)

    Szabo, Gyula M.; Kiss, Laszlo L.; Pal, Andras; Kiss, Csaba; Sarneczky, Krisztian [MTA CSFK, Konkoly Observatory, Konkoly Thege Miklos ut 15-17, H-1121 Budapest (Hungary); Juhasz, Attila; Hogerheijde, Michiel R. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)

    2012-12-10

    Here, we report that the activity of comet Hale-Bopp ceased between late 2007 and 2009 March, at about 28 AU distance from the Sun. At that time, the comet resided at a distance from the Sun that exceeded the freeze-out distance of regular comets by an order of magnitude. A Herschel Space Observatory PACS scan was taken in mid-2010, in the already inactive state of the nucleus. The albedo has been found to be surprisingly large (8.1% {+-} 0.9%), which exceeds the value known for any other comets. With re-reduction of archive Hubble Space Telescope images from 1995 and 1996, we confirm that the pre-perihelion albedo resembled that of an ordinary comet and was smaller by a factor of two than the post-activity albedo. Our further observations with the Very Large Telescope also confirmed that the albedo increased significantly by the end of the activity. We explain these observations by proposing gravitational redeposition of icy grains toward the end of the activity. This is plausible for such a massive body in a cold environment, where gas velocity is lowered to the range of the escape velocity. These observations also show that giant comets are not just the upscaled versions of the comets we know but can be affected by processes that are yet to be fully identified.

  4. The interplay between inner and outer frost damage and its implication for accelerated freeze-thaw testing

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange

    2014-01-01

    In the present project salt frost scaling was registered during an accelerated freeze-thaw test (CEN/TS 12390-9). After the test, inner damage was evaluated by observing the crack patterns on fluorescence impregnated plane sections. The results indicate that the developments of inner and outer...

  5. Bacterial blight (Pseudomonas pisi Sackett) of peas in South Africa, with special reference to frost as a predisposing factor

    NARCIS (Netherlands)

    Boelema, B.H.

    1972-01-01

    In the beginning of the nineteen fifties bacterial blight caused much damage to pea crops in South Africa, particularly to those grown for seed production. A study has been made of the causal organism and the conditioning factors of the disease, special attention being paid to frost as a

  6. Influence of frost damage and sample preconditioning on the porosity characterization of cement based materials using low temperature calorimetry

    DEFF Research Database (Denmark)

    Wu, Min; Fridh, Katja; Johannesson, Björn

    2015-01-01

    Low temperature calorimetry (LTC) can be used to study the meso-porosity of cement based materials. The influence of frost damage on the meso-porosity determination by LTC was explored on a model material MCM-41 and two cement pastes by conducting repeated cycles of freezing and melting measureme...

  7. Experimental investigation of the effect of air velocity on a unit cooler under frosting condition: a case study

    Science.gov (United States)

    Bayrak, Ergin; Çağlayan, Akın; Konukman, Alp Er S.

    2017-10-01

    Finned tube evaporators are used in a wide range of applications such as commercial and industrial cold/freezed storage rooms with high traffic loading under frosting conditions. In this case study, an evaporator with an integrated fan was manufactured and tested under frosting conditions by only changing the air flow rate in an ambient balanced type test laboratory compared to testing in a wind tunnel with a more uniform flow distribution in order to detect the effect of air flow rate on frosting. During the test, operation was performed separately based on three different air flow rates. The parameters concerning test operation such as the changes of air temperature, air relative humidity, surface temperature, air-side pressure drop and refrigerant side capacity etc. were followed in detail for each air flow rate. At the same time, digital images were captured in front of the evaporator; thus, frost thicknesses and blockage ratios at the course of fan stall were determined by using an image-processing technique. Consequently, the test and visual results showed that the trendline of air-side pressure drop increased slowly at the first stage of test operations, then increased linearly up to a top point and then the linearity was disrupted instantly. This point speculated the beginning of defrost operation for each case. In addition, despite detecting a velocity that needs to be avoided, a test applied at minimum air velocity is superior to providing minimum capacity in terms of loss of capacity during test operations.

  8. Increasing the frost resistance of ‘Golden Delicious’, ‘Gala’ and ‘Šampion’ apple cultivars

    Directory of Open Access Journals (Sweden)

    Łysiak Grzegorz P.

    2016-12-01

    Full Text Available The aim of this research was the evaluation of whether the application of 5-ALA, which has potential as a plant growth stimulating agent with indirect anti-stress activity, can limit the damage caused by low temperatures in winter. The research was conducted on frost-sensitive apple cultivars for three years in an orchard and in a laboratory. During the vegetative seasons of each year, the trees of three apple cultivars (‘Golden Delicious’, ‘Gala’ and ‘Šampion’ were subject to 5-ALA foliar application. Three times during each winter following the field application, apple shoots were taken to the laboratory and frozen at −20°C, −25°C and −30°C. After incubation, the damage to the sensitive parts of the shoots was evaluated. The application had a positive effect on the frost resistance of all cultivars, most often at the end of dormancy, which is especially noteworthy because frost damage occurs most frequently during this period. Positive effects of the application were found in most of the experiment combinations of cultivar, year, freezing date and shoot part. Additionally, the positive influence of 5-ALA application on frost resistance was found to increase with each year of the research.

  9. Promoting sustainable potato agriculture in the Andean region by supplemental calcium nutrition and breeding for frost tolerance

    Science.gov (United States)

    Collaborative research in Peru sought to promote sustainable potato production and, mitigate adverse impacts of climate change through two approaches: first calcium amendments to increase crop yield and, second to enhance frost tolerance in native potatoes. All the multi-year, multi-location experim...

  10. Frost drought in conifers at the alpine timberline: xylem dysfunction and adaptations.

    Science.gov (United States)

    Mayr, Stefan; Hacke, Uwe; Schmid, Peter; Schwienbacher, Franziska; Gruber, Andreas

    2006-12-01

    Drought stress can cause xylem embolism in trees when the water potential (psi) in the xylem falls below specific vulnerability thresholds. At the alpine timberline, frost drought is known to cause excessive winter embolism unless xylem vulnerability or transpiration is sufficiently reduced to avoid critical psi. We compared annual courses of psi and embolism in Picea abies, Pinus cembra, Pinus mugo, Larix decidua, and Juniperus communis growing at the timberline vs. low altitude. In addition, vulnerability properties and related anatomical parameters as well as wood density (D(t)) and wall reinforcement (wall thickness related to conduit diameter) were studied. This allowed an estimate of stress intensities as well as a detection of adaptations that reduce embolism formation. At the alpine timberline, psi was lowest during winter with corresponding embolism rates of up to 100% in three of the conifers studied. Only Pinus cembra and Larix decidua avoided winter embolism due to moderate psi. Minor embolism was observed at low altitude where the water potentials of all species remained within a narrow range throughout the year. Within species, differences in psi50 (psi at 50% loss of conductivity) at high vs. low altitude were less than 1 MPa. In Picea abies and Pinus cembra, psi50 was more negative at the timberline while, in the other conifer species, psi50 was more negative at low altitude. Juniperus communis exhibited the lowest (-6.4 +/- 0.04 MPa; mean +/- SE) and Pinus mugo the highest psi50 (-3.34 +/- 0.03 MPa). In some cases, D(t) and tracheid wall reinforcement were higher than in previously established relationships of these parameters with psi50, possibly because of mechanical demands associated with the specific growing conditions. Conifers growing at the alpine timberline were exposed to higher drought stress intensities than individuals at low altitude. Frost drought during winter caused high embolism rates which were probably amplified by freeze

  11. Borehole Heat Exchanger Systems: Hydraulic Conductivity and Frost-Resistance of Backfill Materials

    Science.gov (United States)

    Anbergen, Hauke; Sass, Ingo

    2016-04-01

    constant radial stress boundary conditions (sigma 2 = sigma 3 = constant) • radial freezing from inside out, following the in-situ freezing direction The results differ substantially from prior test procedures (such as standardized frost tests for concrete or soft soils). Concentric frost-induced cracking was observed. The cracking pattern is in good agreement with cryostatic suction processes and frost heave in fine grained soils. The hydraulic conductivity of the system depends on the composition of the grout. With the developed testing device (and procedure) a unified and independent assessment and quality control becomes feasible. Adequate materials for advanced shallow geothermal systems can be clearly identified.

  12. Applying Fibre-Optic Distributed Temperature Sensing to Near-surface Temperature Dynamics of Broadacre Cereals During Radiant Frost Events.

    Science.gov (United States)

    Stutsel, B.; Callow, J. N.

    2017-12-01

    Radiant frost events, particularly those during the reproductive stage of winter cereal growth, cost growers millions of dollars in lost yield. Whilst synoptic drivers of frost and factors influencing temperature variation at the landscape scale are relatively well understood, there is a lack of knowledge surrounding small-scale temperature dynamics within paddocks and plot trials. Other work has also suggested a potential significant temperature gradient (several degrees) vertically from ground to canopy, but this is poorly constrained experimentally. Subtle changes in temperature are important as frost damage generally occurs in a very narrow temperature range (-2 to -5°C). Once a variety's damage threshold is reached, a 1°C difference in minimum temperature can increase damage from 10 to 90%. This study applies Distributed Temperature Sensing (DTS) using fibre optics to understand how minimum temperature evolves during a radiant frost. DTS assesses the difference in attenuation of Raman scattering of a light pulse travelling along a fibre optic cable to measure temperature. A bend insensitive multimode fibre was deployed in a double ended duplex configuration as a "fence" run through four times of sowing at a trial site in the Western Australian Wheatbelt. The fibre optic fence was 160m long and 800mm tall with the fibre optic cable spaced 100mm apart vertically, and calibrated in ambient water ( 10 to 15oC) and a chilled glycol ( -8 to-10 oC) baths. The temperature measurements had a spatial resolution of 0.65m and temporal resolution of 60s, providing 2,215 measurements every minute. The results of this study inform our understanding of the subtle temperature changes from the soil to canopy, providing new insight into how to place traditional temperature loggers to monitor frost damage. It also addresses questions of within-trial temperature variability, and provides an example of how novel techniques such as DTS can be used to improve the way temperature

  13. The role of the observed tropical convection in the generation of frost events in the southern cone of South America

    Directory of Open Access Journals (Sweden)

    G. V. Müller

    2008-06-01

    Full Text Available Based on previous results obtained from observations and linear wave theory analysis, the hypothesis that large-scale patterns can generate extreme cold events in southeast South America through the propagation of remotely excited Rossby waves was already suggested. This work will confirm these findings and extend their analysis through a series of numerical experiments using a primitive equation model where waves are excited by a thermal forcing situated in positions chosen according to observed convection anomalies over the equatorial region. The basic state used for these experiments is a composite of austral winters with maximum and minimum frequency of occurrence of generalized frosts that can affect a large area known as the Wet Pampas located in the central and eastern part of Argentina. The results suggest that stationary Rossby waves may be one important mechanism linking anomalous tropical convection with the extreme cold events in the Wet Pampas. The combination of tropical convection and a specific basic state can generate the right environment to guide the Rossby waves trigged by the tropical forcing towards South America. Depending on the phase of the waves entering the South American continent, they can favour the advection of anomalous wind at low levels from the south carrying cold and dry air over the whole southern extreme of the continent, producing a generalized frost in the Wet Pampa region. On the other hand, when a basic state based on the composites of minimum frosts is used, an anomalous anticyclone over the southern part of the continent generates a circulation with a south-southeast wind which brings maritime air and therefore humidity over the Wet Pampas region, creating negative temperature anomalies only over the northeastern part of the region. Under these conditions even if frosts occur they would not be generalized, as observed for the other basic state with maximum frequency of occurrence of generalized frosts.

  14. Spatial and temporal variation in weather events critical for boreal agriculture: III Frost and winter time fluctuation

    Directory of Open Access Journals (Sweden)

    Pirjo Peltonen-Sainio

    2016-03-01

    Full Text Available In the boreal zone of Europe, differences between the four seasons are considerable. Also, the within-season variation in climatic conditions is substantial. This has many impacts on agriculture that are exceptional when compared to any other environmental zone in Europe. All the meteorological data were based on weather observations made by the Finnish Meteorological Institute. Likelihood (% for soil frost (≤ 0 °C at 20 cm soil depth at nine weather stations, and late snow cover (> 1 cm (10 km × 10 km grid were estimated for late spring. Probabilities (% of night frost at the ground surface (March-September were calculated at nine weather stations by frequencies of the lowest observed night-time temperature: a between –2 and –5 °C (mild, b ≤ –5 °C (moderate and c ≤ –9 °C (severe. Also, the probabilities (% of night frost in mid-summer were estimated (≤ –1 °C for at least five hours. Furthermore, a significant shift from mild to below-freezing conditions was measured in winter as a period of at least ten days with daily maximum temperatures above 0°C followed by at least a 10-day period with daily mean temperatures below –5°C in order to characterize high fluctuating winter conditions. All these except late snow cover constitute high risks to crop production. Deep soil frost may postpone sowings, while in advanced springs, night frost may cause damage. For winter crops and perennials, shifts from mild to cold spells outside the growing season are particularly detrimental. Again the data may have many other applications beyond the assessments highlighted in this paper.

  15. The role of the observed tropical convection in the generation of frost events in the southern cone of South America

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, G.V. [Centro de Investigacion Cientifica y de Transferencia Tecnologica a la Produccion (CICYTTP/CONICET), Diamante (Argentina); Ambrizzi, T. [Universidade de Sao Paulo (Brazil). Dept. de Ciencias Atmosfericas; Ferraz, S.E. [Universidade Federal de Santa Maria/CRSPE-INPE (Brazil). Dept. de Fisica

    2008-07-01

    Based on previous results obtained from observations and linear wave theory analysis, the hypothesis that large-scale patterns can generate extreme cold events in southeast South America through the propagation of remotely excited Rossby waves was already suggested. This work will confirm these findings and extend their analysis through a series of numerical experiments using a primitive equation model where waves are excited by a thermal forcing situated in positions chosen according to observed convection anomalies over the equatorial region. The basic state used for these experiments is a composite of austral winters with maximum and minimum frequency of occurrence of generalized frosts that can affect a large area known as the Wet Pampas located in the central and eastern part of Argentina. The results suggest that stationary Rossby waves may be one important mechanism linking anomalous tropical convection with the extreme cold events in the Wet Pampas. The combination of tropical convection and a specific basic state can generate the right environment to guide the Rossby waves trigged by the tropical forcing towards South America. Depending on the phase of the waves entering the South American continent, they can favour the advection of anomalous wind at low levels from the south carrying cold and dry air over the whole southern extreme of the continent, producing a generalized frost in the Wet Pampa region. On the other hand, when a basic state based on the composites of minimum frosts is used, an anomalous anticyclone over the southern part of the continent generates a circulation with a south-southeast wind which brings maritime air and therefore humidity over the Wet Pampas region, creating negative temperature anomalies only over the northeastern part of the region. Under these conditions even if frosts occur they would not be generalized, as observed for the other basic state with maximum frequency of occurrence of generalized frosts. (orig.)

  16. Electrical heating tapes for hot water piping and frost protection; Elektrische Heizbaender fuer Warmwasserleitungen und Frostschutz

    Energy Technology Data Exchange (ETDEWEB)

    Nipkow, J.

    2003-07-01

    This leaflet issued by the Swiss Federal Office of Energy and professional plumbing and installation associations presents information and recommendations on the use of electrical heating tapes in sanitary installations and rainwater piping. The considerable amount of electrical power needed for the operation of these heating tapes is discussed and methods of reducing consumption by the use efficient controllers are described. It is further mentioned that the correct design and planning of sanitary installations can help reduce the necessity for the use of heating tapes. Cost comparisons are made between heat-tape and circulation-based solutions for different heat sources. Tips are provided on installation details. Frost protection for piping in unheated rooms and for rainwater down-pipes is also discussed.

  17. Performance analysis of a no-frost hybrid air conditioning system with integrated liquid desiccant dehumidification

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Li; Dang, Chaobin; Hihara, Eiji [Department of Human and Engineered Environmental Studies, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-Shi, Chiba 277-8563 (Japan)

    2010-01-15

    This paper reports a performance analysis for a hybrid air conditioning system. In this system, the sensible heat load is primarily treated by a vapor compression heat hump; the latent heat load is treated by a liquid dehumidification system that uses a lithium chloride solution as a desiccant. In addition, by decreasing the humidity ratio of air flowing through the outdoor heat exchanger of the vapor compression heat pump, frosting can be retarded. The overall system performance was evaluated by a cycle simulation conducted both in summer and winter modes. Compared to a traditional air conditioning system, the hybrid air conditioning system improves the coefficient of performance (COP) by approximately 20% and 100% in summer and winter, respectively. (author)

  18. Frost protection for wind energy installations; Frostschutz fuer Windenergieanlagen. Eisfreie Oberflaechen der Natur abgeschaut

    Energy Technology Data Exchange (ETDEWEB)

    Siegmann, K.; Meola, G.; Hirayama, M.

    2009-07-01

    This article discusses how naidered intural materials can be used to prevent wind energy installations in exposed alpine locations from icing up. The problems encountered with wind turbines in Scandinavia and in the Swiss Alps due to icing-up are discussed. The mechanisms involved in the formation of hoar frost and clear ice on the rotors of the wind turbines are discussed. Techniques and materials for fighting the icing-up of the rotors are examined. Various special 'ice-phobic' coatings for the rotor blades are listed and discussed. These must adhere to the rotor blades but be repellent to ice. Teflon is quoted as being the most tested material. So-called 'anti-freeze' proteins that can be found in fish and insects are also being examined as a possible coating for the rotors.

  19. Vineyards sheltered against frost; Des vignes a l'abri du gel

    Energy Technology Data Exchange (ETDEWEB)

    Sagot, F.

    2004-05-01

    Vine growers of the Chablis region (northern Bourgogne area, France) have used fire-baskets and paraffin candles during decades to protect their vineyards against spring frosts. An innovative solution based on heating cables has been proposed by Electricite de France (EdF) to replace these old systems. The Ni-Cu resistive wire of these cables is covered by a first PVC sheath and by a second UV-resistant high density polyethylene sheath. A control wire is also included in the cable to detect any accidental cut. The operating cost of the system is comprised between 50 and 70 euros/h for a 10000 m{sup 2} parcel and reaches a greater efficiency than classical systems with 95% of buds protected. Short article. (J.S.)

  20. Jet impingement heat transfer in a frost-free refrigerator: The influence of confinement

    Energy Technology Data Exchange (ETDEWEB)

    Imraan, M.; Sharma, R.N. [Department of Mechanical Engineering, The University of Auckland, 20 Symonds Street, Private Bag 92019, Auckland (New Zealand)

    2009-05-15

    Heat transfer characteristics of a slot air jet (width w) impinging on a circular cylinder (diameter d = w) located 5d from the jet exit in a confined space have been studied for Reynolds number (based on cylinder diameter and mean jet velocity) in the range of 1000-12,000. This situation is found in a frost-free refrigerator, amongst other rapid food refrigeration applications. The results reveal that the slot jet impinging on a circular cylinder in a confined space yields heat transfer rates that are between those for the corresponding uniform cross-flow (lower limit) and slot jet impingement on a non-confined cylinder (upper limit) cases. A dimensionless confinement spacing H/d = 10 was found at which the heat transfer rate was a minimum. CFD analysis revealed that this was due to periodic jet flapping and generation of large flow structures between the cylinder and the confining wall. (author)

  1. Monuments to Academic Carelessness: The Self-fulfilling Prophecy of Katherine Frost Bruner.

    Science.gov (United States)

    Rekdal, Ole Bjørn

    2014-09-01

    In 1942, Katherine Frost Bruner published an article titled "Of psychological writing: Being some valedictory remarks on style." It was published in Journal of Abnormal and Social Psychology , the journal for which she served as editorial assistant between 1937 and 1941. Her collection of advice to writing scholars has been widely quoted, including by several editions of The Publication Manual of the American Psychological Association . The most frequently quoted message in Bruner's article deals with the importance of making sure that references in academic texts are complete and accurate. Exploring the citation history of this particular message reveals an ironic point: the great majority of those who have quoted Bruner's words on reference accuracy have not done so accurately. The case may serve as a reminder of the importance of the basic academic principle of striving to use primary sources. The most startling finding in this study is how frequently this principle is violated, even by authors who advise and educate academic writers.

  2. Characterization of sound emitted by wind machines used for frost control

    Energy Technology Data Exchange (ETDEWEB)

    Gambino, V.; Gambino, T. [Aercoustics Engineering Ltd., Toronto, ON (Canada); Fraser, H.W. [Ontario Ministry of Agriculture, Food and Rural Affairs, Vineland, ON (Canada)

    2007-07-01

    Wind machines are used in Niagara-on-the-Lake to protect cold-sensitive crops against cold injury during winter's extreme cold temperatures,spring's late frosts and autumn's early frosts. The number of wind machines in Ontario has about doubled annually from only a few in the late 1990's, to more than 425 in 2006. They are not used for generating power. Noise complaints have multiplied as the number of wind machines has increased. The objective of this study was to characterize the sound produced by wind machines; learn why residents are annoyed by wind machine noise; and suggest ways to possibly reduce sound emissions. One part of the study explored acoustic emission characteristics, the sonic differences of units made by different manufacturers, sound propagation properties under typical use atmospheric conditions and low frequency noise impact potential. Tests were conducted with a calibrated Larson Davis 2900B portable spectrum analyzer. Sound was measured with a microphone whose frequency response covered the range 4 Hz to 20 kHz. The study examined and found several unique acoustic properties that are characteristic of wind machines. It was determined that noise from wind machines is due to both aerodynamic and mechanical effects, but aerodynamic sounds were found to be the most significant. It was concluded that full range or broadband sounds manifest themselves as noise components that extend throughout the audible frequency range from the bladepass frequency to upwards of 1000 Hz. The sound spectrum of a wind machine is full natural tones and impulses that give it a readily identifiable acoustic character. Atmospheric conditions including temperature, lapse rate, relative humidity, mild winds, gradients and atmospheric turbulence all play a significant role in the long range outdoor propagation of sound from wind machines. 6 refs., 6 figs.

  3. Pharmacological evaluation for anticancer and immune activities of a novel polysaccharide isolated from Boletus speciosus Frost.

    Science.gov (United States)

    Hou, Yiling; Ding, Xiang; Hou, Wanru; Song, Bo; Wang, Ting; Wang, Fang; Li, Jian; Zeng, Yichun; Zhong, Jie; Xu, Ting; Zhu, Hongqing

    2014-04-01

    The fungal polysaccharides have been revealed to exhibit a variety of biological activities, including antitumor, immune-stimulation and antioxidation activities. In the present study, the immune and anticancer activities of a novel polysaccharide, BSF-A, isolated from Boletus speciosus Frost was investigated. The inhibitory rate of S180 tumors in mice treated with 40 mg/kg BSF-A reached 62.449%, which was the highest rate from the three doses administered; this may be comparable to mannatide. The antitumor activity of BSF-A is commonly considered to be a consequence of the stimulation of the cell-mediated immune response, as it may significantly promote the macrophage cells in the dose range of 100-400 µg/ml in vitro. The levels of the cytokines, IL-6, IL-1β and TNF-α, and nitric oxide, induced by BSF-A treatment at varying concentrations in the macrophage cells were similar to the levels in the cells treated with lipopolysaccharide. There was weak expression of the TNF-α, IL-6, IL-1β and inducible nitric oxide synthase mRNA in the untreated macrophages, but this increased significantly in a dose-dependent manner in the BSF-A-treated cells. BSF-A also had a time- and dose-dependent effect on the growth inhibition of the Hep-2 cells, with the concentration of 400 µg/ml having the highest inhibitory rate. A quantitative PCR array analysis of the gene expression profiles indicated that BSF-A had anticancer activities that affected cell apoptosis in the Hep-2 cells. The results obtained in the present study indicated that the purified polysaccharide of Boletus speciosus Frost is a potential source of natural anticancer substances.

  4. Effects of Spring Late Frost on Black Seed (Nigella sativa L. under Controlled Conditions

    Directory of Open Access Journals (Sweden)

    T Khorsandi

    2015-04-01

    Full Text Available In many years plant growth strongly affected by late spring frost. In order to evaluate the effects of late frost on Black Seed plants, a factorial experiment based on completely randomized design with three replications was carried out in college of agriculture, Ferdowsi University of Mashhad and five Black Seed ecotypes (Birjsnd, Sabzewar, Ferdows, Gonabad and Neyshabour after two months growth and hardening in natural environment, were exposed to seven temperatures (0, -1.5, -3, -4.5, -6, -7.5 and -9°C in termogradient freezer. For determining cold stress damages, Lethal Temperature (LT for 50% of plants according to the Electrolyte Leakage percentage (LT50el, LT for 50% of plants according to the Survival percentage (LT50su, LT for 50% of plants according to the plant necrose in Test Tube (LT50tt and Reduced Dry Matter Temperature 50 (RDMT50 were measured. Ability of plants for recovery was recorded based on leaf number and leaf area, plant dry weight and cold damage percentage of leaves. According to the LT50tt, LT50su and RDMT50 Black Seed plants can tolerated cold stress in range between -5.7 to -9.0 °C and Sabzewar and Ferdows ecotypes had the most and the least cold tolerance, respectively. At the point of ability of plants for recovery, Ferdows ecotype had the least and Sabzewar and Neyshabour ecotypes had the best plant recovery. Moreover there were high correlations between LT50tt and LT50 based on electrolyte leakage, survival and RDMT50. Electrolyte leakage and visual scoring of cold damage in test tube are rapid methods, so for assessing cold tolerance in plants LT50el and LT50tt indeces may be useful.

  5. Temporal and Spatial Variations of the First and Last Frost Date During 1961-2013 in Henan Prouince and Their Responses to Climate Changes

    Directory of Open Access Journals (Sweden)

    YAN Jun-hui

    2015-10-01

    Full Text Available In this study, the annual first and last frost date for each station was defined on the basis of daily minimum ground temperature at 17 meteorological stations over the period from 1961 to 2013 in Henan Province. The spatial and temporal changes of first and last frost date, as well as their responses to seasonal temperature variations, were analyzed. The results showed that: The regional mean first frost date showed a significantly delaying trend, with a linear trend of 2.2 d·10 a-1 during the most recent 53 years. The strongest delaying regions occurred in western mountain areas, with the maximum value in Lushi(4.0 d·10 a-1. However, the regional mean last frost date indicated a notably advancing trend, with a linear trend of 2.3 d·10 a-1 over the period from 1961 to 2013. The greatest advancing regions were detected in central and southern Henan, with the maximum value in Zhumadian(4.9 d·10 a-1. The regional mean first and last frost dates were significantly correlated with seasonal mean temperatures. The regression coefficient between first (last frost date and seasonal mean temperature was 6.5 d·℃-1(-3.5 d·℃-1, representing that the first(last frost day was delayed(advanced by 6.5(3.5 days if spring temperature (mean temperature of February, March, and April increased by 1.0 ℃, suggesting that the first frost date was more sensitive to climate change than last frost date in the context of global warming background.

  6. Physical Layer Network Coding

    DEFF Research Database (Denmark)

    Fukui, Hironori; Yomo, Hironori; Popovski, Petar

    2013-01-01

    /receive interference. The way to deal with this problem in distributed wireless networks is usage of MAC-layer mechanisms that make a spatial reservation of the shared wireless medium, similar to the well-known RTS/CTS in IEEE 802.11 wireless networks. In this paper, we investigate two-way relaying in presence...

  7. Presence of Social Presence during Disasters

    DEFF Research Database (Denmark)

    Mukkamala, Alivelu Manga; Beck, Roman

    2017-01-01

    During emergencies, affected people use social media platforms for interaction and collaboration. Social media is used to ask for help, provide moral support, and to help each other, without direct face-to-face interactions. From a social presence point of view, we analyzed Twitter messages to un...

  8. IA method for measuring the amount of hoar frost formation in the recuperation channels of ventilation systems using the adjustable mathematical model of this process

    Directory of Open Access Journals (Sweden)

    Shilin Aleksandr

    2017-01-01

    Full Text Available The paper presents a method for measuring the amount of hoar frost formation in the recuperation channels of ventilation systems using the adjustable mathematical model of the hoar frost process. The principle is based on the fact that the contour of the adjustment of the hoar frost model is included in the measurement in accordance with the measured pressure drop, which is proportional to the amount of hoar frost. Unlike the known measurement methods, it is proposed to use the state variables of the mathematical model as the measured value. These state variables are not subject to non-deterministic interferences and random influences. The paper presents simulation results confirming the adequacy of the dynamic model. In conclusion, an example of the use of a recuperation channel in the defrost management system is given.

  9. Simulated Frosts At Different Phenological Stages of the Potato Crop and Their Impact On Yields Cv Ccompis: Preliminary Studies

    International Nuclear Information System (INIS)

    Fairlie, T. E.; Ortega, A

    1994-01-01

    The frost damages on the potato crop were simulated through an experiment in the Jiscuani community, in Southern Peru, Puno. Five levels of foliar damage (0, 25, 50, 75 and 100%) in different phenological stages were evaluated for their impact on tuber yield. The most significant phenological damages resulted at plant germination and at the early stolon formation, when foliar damage was higher than 50%. Moreover, the greatest effect on yield was caused at flowering stage (100 days after planting), recording reductions from 15 to 55 % at the different damage levels. The methodology for the frost simulation, cutting foliar sections according damage levels and making further rubbing on foliar area was apparently adequate. (author) [es

  10. Frost damage of bricks composing a railway tunnel monument in Central Japan: field monitoring and laboratory simulation

    Directory of Open Access Journals (Sweden)

    C. Thomachot

    2005-01-01

    Full Text Available Bricks of tunnels and bridges of Usui Pass railway (Japan exposed to north are subject to frost damage. Average depth of erosion due to detachment of angular blocks is around 1-1.5 cm. In order to assess this weathering and to understand its mechanism, an experimental study was carried out in the field and laboratory. Field monitoring showed the combination of seasonal and diurnal freezing with a maximum of heave when the freezing front reached 5 cm depth. Bricks taken from the site were submitted to unidirectional freezing at capillary and vacuum saturation in the laboratory. Results showed that frost damage of bricks was favoured by high saturation level and repetition of freeze-thaw cycles.

  11. The effects of frost thickness on the heat transfer of finned tube heat exchanger subject to the combined influence of fan types

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jeng-Min; Hsieh, Wen-Chien; Ke, Xin-Ji [Department of Refrigeration, Air Conditioning National Chin-Yi University of Technology, Taichung County, Taiping City 411 (China); Wang, Chi-Chuan [Energy and Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu 310 (China)

    2008-05-15

    This study conducts a numerical study concerning the effect of frost thickness on the heat transfer performance of a four rows plate finned tube heat exchanger. Calculations are made under constant air volume and variable air volume conditions. It is found that the initial surge of heat transfer rate in the frosted finned tube heat exchanger is mainly associated with the critical radius effect rather than the surface roughness. The frost thermal conductivity plays an important role in the surge phenomenon. There is hardly any initial surge when frost thermal conductivity is below 0.1 W m{sup -1} K{sup -1}. It is also recommended that a refrigerator should defrost when half of a single flow channel area is blocked by frost. The calculations also reveal that a centrifugal fan is recommended with a small fin-pitch heat exchanger. However, if a long term operation at a thick frost situation is unavoidable, an axial fan should be selected. There is no great difference between selection of an axial fan or centrifugal fan for a larger fin pitch heat exchanger. (author)

  12. An Experimental Investigation On Minimum Compressive Strength Of Early Age Concrete To Prevent Frost Damage For Nuclear Power Plant Structures In Cold Climates

    Energy Technology Data Exchange (ETDEWEB)

    Koh, Kyungtaek; Kim, Dogyeum; Park, Chunjin; Ryu, Gumsung; Park, Jungjun; Lee, Janghwa [Korea Institute Construction Technology, Goyang (Korea, Republic of)

    2013-06-15

    Concrete undergoing early frost damage in cold weather will experience significant loss of not only strength, but also of permeability and durability. Accordingly, concrete codes like ACI-306R prescribe a minimum compressive strength and duration of curing to prevent frost damage at an early age and secure the quality of concrete. Such minimum compressive strength and duration of curing are mostly defined based on the strength development of concrete. However, concrete subjected to frost damage at early age may not show a consistent relationship between its strength and durability. Especially, since durability of concrete is of utmost importance in nuclear power plant structures, this relationship should be imperatively clarified. Therefore, this study verifies the feasibility of the minimum compressive strength specified in the codes like ACI-306R by evaluating the strength development and the durability preventing the frost damage of early age concrete for nuclear power plant. The results indicate that the value of 5 MPa specified by the concrete standards like ACI-306R as the minimum compressive strength to prevent the early frost damage is reasonable in terms of the strength development, but seems to be inappropriate in the viewpoint of the resistance to chloride ion penetration and freeze-thaw. Consequently, it is recommended to propose a minimum compressive strength preventing early frost damage in terms of not only the strength development, but also in terms of the durability to secure the quality of concrete for nuclear power plants in cold climates.

  13. An Experimental Investigation On Minimum Compressive Strength Of Early Age Concrete To Prevent Frost Damage For Nuclear Power Plant Structures In Cold Climates

    International Nuclear Information System (INIS)

    Koh, Kyungtaek; Kim, Dogyeum; Park, Chunjin; Ryu, Gumsung; Park, Jungjun; Lee, Janghwa

    2013-01-01

    Concrete undergoing early frost damage in cold weather will experience significant loss of not only strength, but also of permeability and durability. Accordingly, concrete codes like ACI-306R prescribe a minimum compressive strength and duration of curing to prevent frost damage at an early age and secure the quality of concrete. Such minimum compressive strength and duration of curing are mostly defined based on the strength development of concrete. However, concrete subjected to frost damage at early age may not show a consistent relationship between its strength and durability. Especially, since durability of concrete is of utmost importance in nuclear power plant structures, this relationship should be imperatively clarified. Therefore, this study verifies the feasibility of the minimum compressive strength specified in the codes like ACI-306R by evaluating the strength development and the durability preventing the frost damage of early age concrete for nuclear power plant. The results indicate that the value of 5 MPa specified by the concrete standards like ACI-306R as the minimum compressive strength to prevent the early frost damage is reasonable in terms of the strength development, but seems to be inappropriate in the viewpoint of the resistance to chloride ion penetration and freeze-thaw. Consequently, it is recommended to propose a minimum compressive strength preventing early frost damage in terms of not only the strength development, but also in terms of the durability to secure the quality of concrete for nuclear power plants in cold climates

  14. Frost-related dieback of Swedish and Estonian Salix plantations due to pathogenic and ice nucleation-active bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Cambours, M.A.

    2004-07-01

    During the past decade, important dieback has been observed in short-rotation forestry plantations of Salix viminalis and S. dasyclados in Sweden and Estonia, plantations from which the isolation of ice nucleation-active (INA) and pathogenic bacteria has also been reported. This thesis investigates the connection between bacterial infection and frost as a possible cause for such damage, and the role played by internal and external factors (e.g. plant frost sensitivity, fertilisation) in the dieback observed. Bacterial floras isolated from ten Salix clones growing on fertilised/unfertilised mineral soil or nitrogen-rich organic soil, were studied. Culturable bacterial communities present both in internal necrotic tissues and on the plant surface (i.e. epiphytes) were isolated on two occasions (spring and autumn). The strains were biochemically characterised (with gram, oxidase and fluorescence tests), and tested for ice nucleation-activity. Their pathogenic properties were studied with and without association to a freezing stress. Certain strains were eventually identified with BIOLOG plates and 16S rRNA analysis. A high number of culturable bacterial strains was found in the plant samplings, belonging mainly to Erwinia and Sphingomonas spp.; pathogenic and INA communities being mostly Erwinia-, Sphingomonas- and Xanthomonas-like. The generally higher plant dieback noted in the field on nutrient-rich soils and for frost sensitive clones was found connected to higher numbers of pathogenic and INA bacteria in the plants. We thus confirm Salix dieback to be related to a synergistic effect of frost and bacterial infection, possibly aggravated by fertilisation.

  15. Frost stress evolution and winter pea ideotype in the context of climate warming at a regional scale

    OpenAIRE

    Castel Thierry; Lecomte Christophe; Richard Yves; Lejeune-Hénaut Isabelle; Larmure Annabelle

    2017-01-01

    Pea (Pisum sativum L.) is an important crop in temperate regions for its high seed protein concentration that is particularly sensitive to abiotic stresses. The abrupt temperature increase known as the “1987/1988 temperature regime shift” that occurs over Europe is questioning how winter pea will perform in the changing climate. This study assessed the winter frost damage evolution along from 1961 to 2015 in Burgundy-Franche-Comté by using: (1) daily observed and gridded regional temperature ...

  16. Digital Image Sensor-Based Assessment of the Status of Oat (Avena sativa L.) Crops after Frost Damage

    OpenAIRE

    Isidro Villegas-Romero; Matilde Santos; Antonia Macedo-Cruz; Gonzalo Pajares

    2011-01-01

    The aim of this paper is to classify the land covered with oat crops, and the quantification of frost damage on oats, while plants are still in the flowering stage. The images are taken by a digital colour camera CCD-based sensor. Unsupervised classification methods are applied because the plants present different spectral signatures, depending on two main factors: illumination and the affected state. The colour space used in this application is CIELab, based on the decomposition of the colou...

  17. Water relation response to soil chilling of six olive (Olea europaea L.) cultivars with different frost resistance

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Lopez, D.; Gijon, M. C.; Marino, J.; Moriana, A.

    2010-07-01

    The relationship between the water relations of six olive cultivars exposed to different soil temperatures (14 0.1, 9.9 0.1 and 5.8 0.2 degree centigrade) and their inherent frost resistance (as determined by two different methods) was investigated. Soil chilling was achieved by introducing pots of olive plants into water baths. The water relations of these plants were compared to those of plants kept under conditions of room temperature. The cultivars Frantoio, Picual and Changlot Real began to show significant dehydration below 14 degree centigrade, while Cornicabra, Arbequina and Ascolana Tenera showed this below 10 degree centigrade. This response is probably due to delayed stomatal closure. Only Cornicabra and Picual showed a significant reduction in leaf conductance (below 10 degree centigrade and 6 degree centigrade respectively). This absence of stomatal control led to a significantly greater dehydration in Ascolana Tenera. These variations in response to the soil chilling temperature suggest that different mechanisms may be at work, and indicate that would be necessary to study the influence of rootstock in the frost resistance of olive plants. The variations recorded grouped the cultivars as either resistant (Cornicabra), tolerant (Picual, Ascolana Tenera and Arbequina), or sensitive (Frantoio and Changlot Real). This classification is in line with the frost resistance reported for these cultivars in the literature, and with the results obtained in the present work using the stomatal density and ion leakage methods of determining such resistance. (Author) 40 refs.

  18. Significance of frost action and surface soil characteristics to wind erosion at Rocky Flats, Colorado. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Caine, N.

    1978-09-01

    This study of the potential links between soil freezing and wind erosion was conducted at Rocky Flats during 4 winters. Most of the study has involved the conditions leading to the growth of segregation ice in the surface soil and the ground heave which that produces. This occurs about 15 times in the average winter at Rocky Flats, always on a diurnal cycle. Such frost action is preferentially distributed in time and space and cannot be estimated from air temperatures alone. November and March are the months of most frequent frost heave, and then only in the days following precipitation or snowmelt. The most marked frost effects are found on exposed interfluve and hillcrest situations, where there are patches of bare soil. Almost no effects are found on the valley floors. Soil disturbance by segregation ice leads to a marked decrease in soil bulk density, and presumably in soil strength though this change has not been quantitatively defined. However, this does not lead to wind erosion of the soil at the study site because that surface is more influenced by the vegetation cover than by the soil characteristics.

  19. Physical and eco-physiological aspects in forecasting and crop protection of fruit trees from late frost

    International Nuclear Information System (INIS)

    Zinoni, Franco; Antolini, Gabriele; Palara, Ugo; Rossi, Federica; Reggidori, Giampiero

    2005-01-01

    Late frosts represent for fruit production one of the most relevant natural hazards worldwide, considering severity and extent of damage, whose occurrence is constantly increasing, concomitantly to the increase of climate variability. Therefore, impacts on affected farms and local economy are often devastating, but information about how to protect plants from freezing is relatively limited. The research in the field of forecast, risk hazard assessment and protection is directed towards the reduction of the risk level, acting together with new trends in selection of resistant cvs. Crop vulnerability is jointly determined by genetic peculiarities of the various species and cvs, but a determinant role is played by phenology and agronomic practices. The orchard structural features, tree canopy characteristics and tree arrangement in rows are determinant in conditioning energy and radiation exchanges between soil and the surrounding atmosphere, thus on the exchange processes that are responsible of radiation frosts, mainly occurring in Spring, when plant sensibility is at its maximum. The knowledge of local meteorology, together with the weather reports, which can forecast risk situations, should support the acquisition of passive protection systems and to improve the active ones. The correct evaluation of frost risk holds a great importance in fruit orchard programming and in the choice of protection systems and, therefore, the drawing up of risk maps which correlate the topographical characteristics of soil with the tolerance level of the different fruit tree species [it

  20. Penetration of chlorides in hardened concrete during frost salt scaling cycles

    Directory of Open Access Journals (Sweden)

    Moral N.

    2010-06-01

    Full Text Available Sixty samples from three concrete mixes (same components were prepared and subjected to frost salt scaling cycles. A set of 20 samples from the same mix was tested according to the French standard XP P18-420. Another set was exposed to different chloride concentrations. Different numbers of freeze/thaw cycles were applied to the last set. The mass of scaled-off particles follows a lognormal distribution. Despite high standard deviation, this scaling test enables to separate high resistant from very low resistant concrete. A combined analysis reveals that the scaling and the chloride penetration front are independent from a phenomenological point of view and that the chloride concentration on the exposed surface directly influences the amount of scaled mass according to the typical pessimum effect. These results raise two main questions: is the amount of chloride on the surface solution a direct or indirect parameter and what happens to this pessimum effect if we take into account the scaling test dispersion?

  1. Advances in control of frost on evaporator coils with an applied electric field

    Energy Technology Data Exchange (ETDEWEB)

    Tudor, V. [Advanced Thermal Research Laboratory, Mechanical Engineering Department, US Naval Academy, Annapolis, MD 21402 (United States); Ohadi, M. [Smart and Small Thermal Systems Laboratory, Mechanical Engineering Department, University of Maryland, College park, MD 20742 (United States); Salehi, M.A.; Lawler, J.V. [ATEC Inc., College Park, MD 20742 (United States)

    2005-10-01

    This paper introduces an innovative technique on use of an applied electric field for control of frost over evaporator coils with fin density and geometric configuration of interest to freezer/refrigerator applications. The technique discussed in this paper, referred to as the 'dielectric barrier discharge' (DBD) method, may be particularly suitable for application in evaporator coils with high fin density. Experiments conducted with a small-scale laboratory test-module, as well as a full-scale supermarket evaporator are presented. The DBD technique is based on generating localized non-resistive heating within fins of an evaporator coil via application of a high-voltage, alternating current through electrodes. Our experiments demonstrate that the defrosting time using DBD is substantially shorter than conventional techniques, while the energy consumption associated with the process is less than one half of the corresponding energy of the electrical resistance heating methods. Basic operational principles of the technique, its advantages and limitations when compared to conventional electrical defrosting techniques are discussed and presented for the first time in this paper. (author)

  2. Growth of C02 frost thickness near Chasma Borealis during northern winter and spring.

    Energy Technology Data Exchange (ETDEWEB)

    Feldman, W. C. (William C.); Boynton, W. V. (William V.); Prettyman, T. H. (Thomas H.); Kelly, N.; Maurice, S. (Sylvestre)

    2003-01-01

    Epithermal neutron fluxes measured using the Neutron Spectrometer component of the Mars OdysscNGamma-Ray Spectrometer suite of instruments were studied to determ i ne the spatial and temporal dependence of CO2 frost cover of the nor t h polar cap for L, between 329 and 99 arcoccntric longitude. This time period spans the la t e northern xvinter through summer solstice . In the absence of a CO, cuvcr, the entire basement terrain p o l eward of about +55 latitude is vm, rich in I1 :0 . The consequent enhanced abundance of hydrogen in near-surface soils leads to an anomaluusly low flux of oumardly leaking cpithcrmal ncutrons, wh i ch is a prominent signatu r e of epi t hermal neutron maps measured after about L, = 90 . Because the epithermal neutron flux rises monotonically w i t h increasing thickness of t h e CO . fros t cover, it provides a robust measure of the CO2 thickness in space and time .

  3. Study of polydiethylsiloxane-based ferrofluid with excellent frost resistance property

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Y.X. [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Zhuang, L. [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)], E-mail: stszhl@mail.sysu.edu.cn; Shen, H. [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Zhang, W. [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Shao, Z.J. [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

    2009-03-15

    The polydiethylsiloxane-based ferrofluid was prepared by dispersing finely divided magnetic Fe{sub 3}O{sub 4} particles which are modified with oleoyl sarcosine and lauroyl sarcosine. The optimized experiment parameters including molar ratio of surfactant to Fe{sub 3}O{sub 4} (1:5), temperature (80 deg. C), stirring rate (300 RPM), the surfactant content of lauroyl sarcosine (0 to 33 mol%) and the modification time (25 min) were obtained by the orthogonal test. The magnetic liquid was characterized by a transmission electron microscope (TEM), infrared (IR) spectrometer, X-ray diffractometer (XRD), thermogravimetry (TG), vibrating sample magnetometer (VSM) and differential scanning calorimetry (DSC). It is indicated that the surfactant is mainly bonded to the surface of Fe{sub 3}O{sub 4} nanoparticles through covalent bond between carboxylate (COO{sup -}) and Fe atom. The modified magnetic particles are equally dispersed into the carrier and remain stable below -12 deg. C over 4 months. The ferrofluids exhibit excellent frost resistance property and distinctly reduced temperature coefficient of viscosity compared with polydimethylsiloxane-based ferrofluids and hydrocarbon-based ferrofluids, respectively. The saturation magnetization could reach up to 27.7 emu/g.

  4. Cryosorption of helium on argon frost TFTR [Tokamak Fusion Test Reactor] neutral beamlines

    International Nuclear Information System (INIS)

    Kamperschroer, J.H.; Cropper, M.B.; Dylla, H.F.

    1989-11-01

    Helium pumping on argon frost has been investigated on TFTR neutral beam injectors and shown to be viable for limited helium beam operation. Maximum pumping speeds are ∼ 25% less than those measured for pumping of deuterium. Helium pumping efficiency is low, > 20 argon atoms are required to pump each helium atom. Adsorption isotherms are exponential and exhibit a two-fold increase in adsorption capacity as the cryopanel temperature is reduced from 4.3 K to 3.7 K. Pumping speed was found to be independent of cryopanel temperature over the temperature range studied. After pumping a total of 2000 torr-l of helium, the beamline base pressure rose to 2x10 -5 torr from an initial value of 10 -8 torr. Accompanying this three order of magnitude increase in pressure was a modest 40% decrease in pumping speed. The introduction of 168 torr-l of deuterium prior to helium injection reduced the pumping speed by a factor of two with no decrease in adsorption capacity. 29 refs., 7 figs

  5. Cryosorption of helium on argon frost in Tokamak Fusion Test Reactor neutral beamlines

    International Nuclear Information System (INIS)

    Kamperschroer, J.H.; Cropper, M.B.; Dylla, H.F.; Garzotto, V.; Dudek, L.E.; Grisham, L.R.; Martin, G.D.; O'Connor, T.E.; Stevenson, T.N.; von Halle, A.; Williams, M.D.; Kim, J.

    1990-01-01

    Helium pumping on argon frost has been investigated on Tokamak Fusion Test Reactor (TFTR) neutral beam injectors and shown to be viable for limited helium beam operation. Maximum pumping speeds are ∼25% less than those measured for pumping of deuterium. Helium pumping efficiency is low, >20 argon atoms are required to pump each helium atom. Adsorption isotherms are exponential and exhibit a twofold increase in adsorption capacity as the cryopanel temperature is reduced from 4.3 K to 3.7 K. Pumping speed was found to be independent of cryopanel temperature over the temperature range studied. After pumping a total of 2000 Torr l of helium, the beamline base pressure rose to 2x10 -5 Torr from an initial value of 10 -8 Torr. Accompanying this three order of magnitude increase in pressure was a modest 40% decrease in pumping speed. The introduction of 168 Torr l of deuterium prior to helium injection reduced the pumping speed by a factor of two with no decrease in adsorption capacity

  6. Psychometric proprieties of the portuguese version of the frost multidimensional perfectionism scale

    Directory of Open Access Journals (Sweden)

    Marco Estêvão Coreia

    2017-01-01

    Full Text Available Perfectionism is defined as the desire to achieve the highest standards of performance, in combination with unduly critical evaluations of one’s performance. This study was designed to analyse the psychometric proprieties of the Portuguese version of the Frost Multidimensional Perfectionism Scale through confirmatory factor analysis in two different samples (calibration with 350 adolescent athletes and validation with 206 adolescent athletes. The confirmatory factor analysis suggested that after dropping items with low factor loadings, the six-factor model showed good fit (χ 2 = 292.83, B-S p < 0.001; χ 2/d f = 1.693, PCFI = 0.79, PGFI = 0.70, CFI = 0.96, GFI = 0.93, RMSEA = 0.045. All constructs presented good internal consistency, convergent and discriminant validity. A multi-group analysis exposed the cross validity of the model. The correlations between perfectionism, fear of failure and sport anxiety measures revealed evidence of its concurrent validity, providing evidence for the proposed model. Overall, the results of the present study provided evidence for these instruments’ validity and reliability, however further investigations are required.

  7. Investigation the Frost Resistance of Vegetative and Reproductive Buds of Pear Cultivars in Mashhad Climate Condition

    Directory of Open Access Journals (Sweden)

    shadan khorshidi

    2017-02-01

    Full Text Available Introduction: Most deciduous trees need low temperature to break flower bud dormancy. One of the most important abiotic stresses is low temperature which limits production of temperate fruits. Pear production has been considerably reduced in recent years. Important pear cultivars show different levels of resistance to cold. Cold compatibility followed by resistance increase is controlled genetically and contains several mechanisms which lead to production of different metabolites such as: polypeptides, amino acids and sugars. The object of this research was to evaluate the frost resistance of different ‘Dare Gazi’ genotypes and other pear cultivars in Mashhad climate condition. Materials and Methods: This study was conducted to investigate the frost resistance of 23 ‘Dare Gazi’ pear genotypes and nine other cultivars include: ‘William’s’, ‘Bell de june’, ‘Spadona’, ‘Koshia’, ‘Domkaj’, ‘Torsh’, ‘Sebri’ and ‘Tabrizi’. Plant material contained vegetative and reproductive buds of one-year-old shoot samples which were collected from 25-year old trees on March 2014, four days after winter cold (-6.6 °C in three directions of trees and sent to the laboratory. Frost damages of vegetative and reproductive buds were investigated based on visual observations (%, electrolyte leakage (EC and proline content. EC was measured with a Metrohm 644 digital conductivity meter and proline content was measured based on Bates et al. (1973 method, using acid ninhydrin. The experiment was performed on completely randomized experimental design with three replications. Statistical analysis was carried out using MSTAT-C and Excel software. Mean values were compared using the least significance difference test (LSD at 1% levels. Cluster analysis was conducted by SPSS 16 program. Results and Discussion: Highest EC of reproductive buds was observed in ‘Dare Gazi’ 10, 19, ‘Tabrizi’ and ‘Torsh’ whereas ‘Dare Gazi’ 8, 18

  8. Freezing pattern and frost killing temperature of apple (Malus domestica) wood under controlled conditions and in nature.

    Science.gov (United States)

    Pramsohler, Manuel; Hacker, Jürgen; Neuner, Gilbert

    2012-07-01

    The freezing pattern and frost killing temperatures of apple (Malus domestica Borkh.) xylem were determined by differential thermal analysis and infrared differential thermal analysis (IDTA). Results from detached or attached twigs in controlled freezing experiments and during natural field freezing of trees were compared. Non-lethal freezing of apoplastic water in apple xylem as monitored during natural winter frosts in the field occurred at -1.9 ± 0.4 °C and did not change seasonally. The pattern of whole tree freezing was variable and specific to the environmental conditions. On detached twigs high-temperature freezing exotherms (HTEs) occurred 2.8 K below the temperature observed under natural frosts in the field with a seasonal mean of -4.7 ± 0.5 °C. Microporous apple xylem showed freezing without a specific pattern within a few seconds in IDTA images during HTEs, which is in contrast to macroporous xylem where a 2D freezing pattern mirrors anatomical structures. The pith tissue always remained unfrozen. Increasing twig length increased ice nucleation temperature; for increased twig diameter the effect was not significant. In attached twigs frozen in field portable freezing chambers, HTEs were recorded at a similar mean temperature (-4.6 ± 1.0 °C) to those for detached twigs. Upon lethal intracellular freezing of apple xylem parenchyma cells (XPCs) low-temperature freezing exotherms (LTEs) can be recorded. Low-temperature freezing exotherms determined on detached twigs varied significantly between a winter minimum of -36.9 °C and a summer maximum -12.7 °C. Within the temperature range wherein LTEs were recorded by IDTA in summer (-12.7 ± 0.5 to -20.3 ± 1.1 °C) various tiny clearly separated discontinuous freezing events could be detected similar to that in other species with contrasting XPC anatomy. These freezing events appeared to be initially located in the primary and only later in the secondary xylem. During the LTE no

  9. Atmospheric circulation associated with extreme generalized frosts persistence in central-southern South America

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Gabriela V. [Centro de Investigaciones Cientificas y Transferencia de Tecnologia a la Produccion, Diamante (CICYTTTP-CONICET), Diamante, Entre Rios (Argentina); Berri, Guillermo J. [Servicio Meteorologico Nacional - CONICET, Buenos Aires (Argentina)

    2012-03-15

    Generalized frosts (GF) in central-southern South America have a strong impact due to their spatial extension, and they are especially important when they become persistent. This paper aims at identifying the atmospheric circulation features that determine the extreme GF persistence, i.e. very persistent and without persistence, and the differences between them, during the 1961-1990 winters. Since the GF without persistence group outnumbers the other one, two subgroups are composed with events selected from winters with maximum and minimum frequency of GF occurrence, respectively. Additionally, the individual event of July 1988 within the very persistent GF group is analyzed due to its exceptional persistence. GF persistence is mainly conditioned by two large-scale dynamic factors. One is the Rossby wave train propagation across the Pacific Ocean, and the other one is the location with respect to the continent and the magnitude of the confluence in the jet entrance region in subtropical latitudes. A predominantly meridional Rossby wave train propagation with a confluence region to the west of the continent prior to the event favors GF with intermediate (null) persistence depending on the greater (lesser) jet acceleration. This is conditioned by the magnitude of the confluence, which, in turn, depends on the disposition of the wave train propagation pattern. Instead, an essentially zonal propagation with a confluence region to the east of the continent favors the GF persistence for several days, yet if there is no confluence the event does not persist. The greatest persistence of an event combines the confluence/diffluence of the jet entrance/exit region, which depends on the disposition with respect to the continent of the zonally propagating Rossby wave trains. (orig.)

  10. Validation of Aura Microwave Limb Sounder stratospheric water vapor measurements by the NOAA frost point hygrometer

    Science.gov (United States)

    Hurst, Dale F.; Lambert, Alyn; Read, William G.; Davis, Sean M.; Rosenlof, Karen H.; Hall, Emrys G.; Jordan, Allen F.; Oltmans, Samuel J.

    2017-01-01

    Differences between stratospheric water vapor measurements by NOAA frost point hygrometers (FPHs) and the Aura Microwave Limb Sounder (MLS) are evaluated for the period August 2004 through December 2012 at Boulder, Colorado, Hilo, Hawaii, and Lauder, New Zealand. Two groups of MLS profiles coincident with the FPH soundings at each site are identified using unique sets of spatiotemporal criteria. Before evaluating the differences between coincident FPH and MLS profiles, each FPH profile is convolved with the MLS averaging kernels for eight pressure levels from 100 to 26 hPa (~16 to 25 km) to reduce its vertical resolution to that of the MLS water vapor retrievals. The mean FPH – MLS differences at every pressure level (100 to 26 hPa) are well within the combined measurement uncertainties of the two instruments. However, the mean differences at 100 and 83 hPa are statistically significant and negative, ranging from −0.46 ± 0.22 ppmv (−10.3 ± 4.8%) to −0.10 ± 0.05 ppmv (−2.2 ± 1.2%). Mean differences at the six pressure levels from 68 to 26 hPa are on average 0.8% (0.04 ppmv), and only a few are statistically significant. The FPH – MLS differences at each site are examined for temporal trends using weighted linear regression analyses. The vast majority of trends determined here are not statistically significant, and most are smaller than the minimum trends detectable in this analysis. Except at 100 and 83 hPa, the average agreement between MLS retrievals and FPH measurements of stratospheric water vapor is better than 1%. PMID:28845378

  11. Agricultural losses related to frost events: use of the 850 hPa level temperature as an explanatory variable of the damage cost

    Science.gov (United States)

    Papagiannaki, K.; Lagouvardos, K.; Kotroni, V.; Papagiannakis, G.

    2014-09-01

    The objective of this study is the analysis of damaging frost events in agriculture, by examining the relationship between the daily minimum temperature in the lower atmosphere (at an isobaric level of 850 hPa) and crop production losses. Furthermore, the study suggests a methodological approach for estimating agriculture risk due to frost events, with the aim of estimating the short-term probability and magnitude of frost-related financial losses for different levels of 850 hPa temperature. Compared with near-surface temperature forecasts, temperature forecasts at the level of 850 hPa are less influenced by varying weather conditions or by local topographical features; thus, they constitute a more consistent indicator of the forthcoming weather conditions. The analysis of the daily monetary compensations for insured crop losses caused by weather events in Greece shows that, during the period 1999-2011, frost caused more damage to crop production than any other meteorological phenomenon. Two regions of different geographical latitudes are examined further, to account for the differences in the temperature ranges developed within their ecological environment. Using a series of linear and logistic regressions, we found that minimum temperature (at an 850 hPa level), grouped into three categories according to its magnitude, and seasonality, are significant variables when trying to explain crop damage costs, as well as to predict and quantify the likelihood and magnitude of damaging frost events.

  12. Significance of frost action and surface soil characteristics to wind erosion at Rocky Flats, Colorado. Third progress report, October 1, 1976--June 30, 1977

    Energy Technology Data Exchange (ETDEWEB)

    Caine, N.; Morin, P.; Nicholas, R.M.

    1977-01-01

    This report summarizes information on soil frost effects collected on Rocky Flats during the 1976 and 1977 winter. The work has continued on two scales as in the previous two winters. Empirical surveys along 4 line transects during the second half of the winter support earlier conclusions that the frost susceptibility of the Rocky Flats soils is well keyed to topography. This has been used in testing a mapping procedure for potential soil frost activity in the entire Rocky Flats area. Instrumental records of weather and soil conditions have been maintained throughout the winter at the Lindsay Ranch study site, northwest of the Rocky Flats Plant. During the winter, 9 frost heave events have been recorded and are described here. This represents a low frequency of soil disturbance by frost and is accounted for by the drought conditions on the Colorado Piedmont during 1976 and 1977. Even the events which occurred were of relatively slight magnitude, a further reflection of the lack of soil moisture during the period.

  13. Presence While Watching Movies

    Directory of Open Access Journals (Sweden)

    Tom Troscianko

    2011-05-01

    Full Text Available “Presence” is the illusion of being in a mediated experience rather than simply being an observer. It is a concept often applied to the question of realism of virtual environments. However, it is equally applicable to the act of watching a movie. A movie provides a markedly different visual environment to that given by the natural world—particularly because of frequent edits. And yet, the audience in a movie achieves high levels of presence. We investigate the relationship between presence and the optical and temporal parameters of movies. We find effects of mean shot length, colour/b&w, and 3D/2D. We find that short shots, while being unnatural, are associated with high levels of presence. We consider why such artificial stimuli should appear so real and immersive.

  14. Proteins Involved in Distinct Phases of Cold Hardening Process in Frost Resistant Winter Barley (Hordeum vulgare L. cv Luxor

    Directory of Open Access Journals (Sweden)

    Radovan Hynek

    2013-04-01

    Full Text Available Winter barley is an economically important cereal crop grown in higher latitudes and altitudes where low temperatures represent an important environmental constraint limiting crop productivity. In this study changes in proteome of leaves and crowns in a frost tolerant winter barley cv. Luxor in relation to short and long term periods of cold followed by a brief frost treatment were studied in order to disclose proteins responsible for the cold hardening process in distinct plant tissues. The mentioned changes have been monitored using two dimensional difference gel electrophoresis (2D-DIGE with subsequent peptide-mapping protein identification. Regarding approximately 600–700 distinct protein spots detected on 2D gels, there has been found at least a two-fold change after exposure to low temperatures in about 10% of proteins in leaves and 13% of proteins in crowns. Protein and nitrogen metabolic processes have been influenced by low temperature to a similar extent in both tissues while catabolism, carbohydrate metabolism and proteins involved in stress response have been more affected in crowns than in leaves. The range of changes in protein abundance was generally higher in leaves and chloroplast proteins were frequently affected which suggests a priority to protect photosynthetic apparatus. Overall, our data proved existence of slightly different response strategies to low temperature stress in crowns and leaves, i.e., tissues with different biological role. Moreover, there have been found several proteins with large increase in accumulation, e.g., 33 kDa oxygen evolving protein of photosystem II in leaves and “enhanced disease susceptibility 1” in crowns; these proteins might have potential to indicate an enhanced level of frost tolerance in barley.

  15. Capturing Online Presence

    DEFF Research Database (Denmark)

    de Bakker, Frank; Hellsten, Lina

    2013-01-01

    an important channel for CSR debate. In this paper, we present an explorative study of activist groups’ online presence via their websites and propose a combination of methods to study both the structural positioning of websites (hyperlink network analysis) and the meanings in these websites (semantic co-word...... activist networks’ online presence can provide insights into the tactics these networks apply to achieve institutional change on CSR issues. Meanwhile, we identify some notable differences between styles and word use in the two organisations’ websites. We conclude with a set of suggestions for future...

  16. The presence of ADHD

    DEFF Research Database (Denmark)

    Breining, Sanni Nørgaard

    2014-01-01

    This paper uses high quality register-data to study the spillover effects on firstborns from having a younger sibling suffering from ADHD. Using OLS and cousin fixed effects analyses it is found that the educational outcomes of healthy firstborn children are significantly reduced by the presence...

  17. Connected media and presence

    NARCIS (Netherlands)

    Kort, J.; Nefs, H.T.; Gullström, C.; Greef, T.J. de; Parnes, P.

    2013-01-01

    Effective design of shared mediated spaces, information and connectedness requires theory and practice from a range of disciplines such as found in European projects like Together Anywhere, Together Anytime (TA2) and the EIT ICT Labs Mediating Presence activity. Building on this work we continue to

  18. Frost, defrost, and refrost and its impact on the air-side thermal-hydraulic performance of louvered-fin, flat-tube heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Y.; Zhong, Y.; Hrnjak, P.S.; Jacobi, A.M. [Department of Mechanical and Industrial Engineering, University of Illinois, 1206 West Green Street, Urbana, IL 61801 (United States)

    2006-11-15

    The thermal-hydraulic performance under conditions of an initial frost growth on the air-side surface, and for subsequent 'refrosting' after a defrost period is experimentally studied for folded-louvered-fin, microchannel heat exchangers. In total, five heat exchangers are considered; the thermal performances during one frost-growth cycle for four different fin geometries are compared in terms of overall heat transfer coefficient, pressure drop, and j and f factors; the defrost and refrost characteristics of two heat exchangers are compared to explore geometry effects. Typically, the performance under refrosting conditions becomes periodic and repeatable after the third or fourth refrosting cycle. The allowable frost growth period (before a defrost is required), the defrost requirement, and the thermal-hydraulic performance depend on heat exchanger geometry for the specimens used in this study. (author)

  19. Recent Divergences Between Stratospheric Water Vapor Measurements by Aura MLS and Frost Point Hygrometers

    Science.gov (United States)

    Hurst, D. F.; Rosenlof, K. H.; Davis, S. M.; Hall, E. G.; Jordan, A. F.; Read, W. G.; Voemel, H.; Selkirk, H. B.

    2015-12-01

    A recent comparison of stratospheric water vapor measurements by the Aura Microwave Limb Sounder (MLS) and frost point hygrometers (FPs) during 2004-2012 reported agreement better than 1% from 68 to 26 hPa, small but statistically significant biases at 83 and 100 hPa, and no compelling evidence of long-term linear trends in FP-MLS differences [Hurst et al., 2014]. A previous comparison [Voemel et al., 2007] also found good agreement above 83 hPa. Recently it has become evident that differences between FP and MLS stratospheric water vapor measurements have widened during the last 5 years at two Northern Hemisphere (NH) mid-latitude sounding sites. Here we examine differences between coincident MLS and FP measurements of stratospheric water vapor at five sounding sites: two in the NH mid-latitudes (Boulder, Colorado and Lindenberg, Germany), two in the tropics (San Jose, Costa Rica and Hilo, Hawaii), and one in the SH mid-latitudes (Lauder, New Zealand). Analyses of the Boulder and Lindenberg data reveal reasonably uniform breakpoints in the timeseries of FP-MLS differences throughout the stratosphere, indicating that trends after mid-2010 are statistically different from trends before mid-2010. At Boulder and Lindenberg the post-breakpoint trends are statistically significant and fairly consistent over eight MLS retrieval pressures (100-26 hPa), averaging -0.08 ± 0.02 and -0.05 ± 0.02 ppmv per year, respectively (Figure 1). These translate to mean changes in stratospheric FP-MLS differences of -0.42 ± 0.08 ppmv (-10 ± 2%) and -0.23 ± 0.08 ppmv (-6 ± 2%) between mid-2010 and mid-2015. Breakpoints for the eight MLS pressure levels above Lauder are less uniform than for the two NH sites, however forced breakpoints of mid-2010 produce a mean stratospheric trend of -0.05 ± 0.02 ppmv per year in the FP-MLS differences. Breakpoints for the two tropical sites are inconsistent, as are the trend results with forced breakpoints of mid-2010. Hurst, D.F., et al., (2014

  20. Urbanization may reduce the risk of frost damage to spring flowers: A case study of two shrub species in South Korea.

    Directory of Open Access Journals (Sweden)

    Hyeon-Ju Gim

    Full Text Available Regional warming, owing to urbanization, leads to earlier spring phenological events and may expose plants to hard freeze damage. This study examined the influence of urbanization on the risk of frost damage to spring flowers in South Korea from 1973 to 2015. For the analysis period, we categorized 25 cities into two groups: those showing rapid population growth (rPG ≥ 200,000, including 13 cities, and those showing no or decreased population growth (nPG, including 12 cities. We then investigated the time from the last frost dates (LFDs in spring to the first flowering dates (FFDs for each group. The rPG group experienced significant spring warming of 0.47°C per decade, resulting in earlier LFDs and FFDs. For this group, the advancement of LFD was more rapid than that of FFD, and the days between these two dates increased from 0.42 to 0.47 days per decade, implying a reduced risk of frost damage. Spring warming and the advancement of FFDs and LFDs were relatively small for the nPG group, and the LFDs were rather delayed. Consequently, the days between LFDs and FFDs were reduced from -1.05 to -1.67 days per decade, indicating an increased risk of frost damage. The contrasting changes in the frost-damage risk between the two city groups can be attributed to distinct urban warming at night, which makes the LFDs substantially earlier in the rPG group. Therefore, this study suggests that the warming associated with urbanization may lessen the risk of spring frost damage to plants in rapidly growing urban areas.

  1. Urbanization may reduce the risk of frost damage to spring flowers: A case study of two shrub species in South Korea.

    Science.gov (United States)

    Gim, Hyeon-Ju; Ho, Chang-Hoi; Kim, Jinwon; Lee, Eun Ju

    2018-01-01

    Regional warming, owing to urbanization, leads to earlier spring phenological events and may expose plants to hard freeze damage. This study examined the influence of urbanization on the risk of frost damage to spring flowers in South Korea from 1973 to 2015. For the analysis period, we categorized 25 cities into two groups: those showing rapid population growth (rPG) ≥ 200,000, including 13 cities, and those showing no or decreased population growth (nPG), including 12 cities. We then investigated the time from the last frost dates (LFDs) in spring to the first flowering dates (FFDs) for each group. The rPG group experienced significant spring warming of 0.47°C per decade, resulting in earlier LFDs and FFDs. For this group, the advancement of LFD was more rapid than that of FFD, and the days between these two dates increased from 0.42 to 0.47 days per decade, implying a reduced risk of frost damage. Spring warming and the advancement of FFDs and LFDs were relatively small for the nPG group, and the LFDs were rather delayed. Consequently, the days between LFDs and FFDs were reduced from -1.05 to -1.67 days per decade, indicating an increased risk of frost damage. The contrasting changes in the frost-damage risk between the two city groups can be attributed to distinct urban warming at night, which makes the LFDs substantially earlier in the rPG group. Therefore, this study suggests that the warming associated with urbanization may lessen the risk of spring frost damage to plants in rapidly growing urban areas.

  2. The influence of KJ, CuSO4, and Mg(ClO32 on defoliation and subsequent frost resistance and growth of apple trees in nurseries

    Directory of Open Access Journals (Sweden)

    Alina Basak

    2015-06-01

    Full Text Available In most cases 2-year-old trees of 3 cultivars responded better to defoliants than 1-year-old ones. Spraying with defoliants on September 25 - 28 was more effective than spraying 10 days earlier. There was also more bark injury in the autumn, and more frost injury on trees defoliated on the ealier date. Mg(ClO32 seemed to be the best defoliant but markedly decreased the frost resistance of McIntosh trees. Defoliants investigated may be applied to limited extent to 2-year-old trees but not to 1-year-old ones.

  3. Performance investigation of a novel frost-free air-source heat pump water heater combined with energy storage and dehumidification

    International Nuclear Information System (INIS)

    Wang, Fenghao; Wang, Zhihua; Zheng, Yuxin; Lin, Zhang; Hao, Pengfei; Huan, Chao; Wang, Tian

    2015-01-01

    Highlights: • Experiments are carried out to investigate a novel frost-free ASHPWH system. • Dynamic characteristics of the system are studied at different ambient conditions. • Test results confirm the expected potential to control the frost-free process. • The COP increased 17.9% and 3.4% respectively in comparison with RCD at −3 °C and 3 °C. - Abstract: Air-source heat pump (ASHP) often operates with substantial frost formation on the outdoor heat exchanger at low ambient temperature in winter, it insulates the finned surface and also reduces heat transfer rate, leading to performance degradation or even shutdown of ASHP systems. Although several defrosting methods have been reported, the frosting and defrosting processes reduced energy efficiency and resulted in, in some cases, heat pump breakdown. To solve this problem, a novel frost-free air-source heat pump water heater (ASHPWH) system has been developed, which coupled with an extra heat exchanger coated by a solid desiccant (EHECSD) with an energy storage device (ESD). Based on the previous studies, a further analysis and comprehensive research on the novel frost-free ASHPWH system is presented in this paper. The dynamic characteristics of the novel system are investigated experimentally in different ambient conditions. An experimental setup and experimental procedures are described in detail. Thereafter, the dehumidification efficiency and regeneration efficiency of EHECSD, suction and discharge pressures of the compressor, the temperature of PCM are evaluated during the heating and regeneration modes respectively. Results indicate that the system can keep the evaporator frost-free for 32, 34, 36 min during heating mode at the ambient temperatures of −3 °C, 0 °C and 3 °C and 85% RH. Compared with the reverse-cycle defrosting (RCD), COP of the frost-free ASHPWH are 17.9% and 3.4% higher at the ambient temperature of −3 °C and 3 °C respectively. With this innovative technology, it has

  4. A Combined Field/Laboratory Method for Assessment of Frost Tolerance with Freezing Tests and Chlorophyll Fluorescence

    Directory of Open Access Journals (Sweden)

    Franz-W. Badeck

    2015-03-01

    Full Text Available Recent progress in genotyping allows for studies of the molecular genetic basis of cold resistance in cereals. However, as in many other fields of molecular genetic analysis, phenotyping for high numbers of genotypes is still a major bottleneck. The use of chlorophyll fluorescence measurements as an indicator for freezing stress is a well established and rapid method for evaluation of frost tolerance. In order to extend the applicability of this technique beyond plants grown under controlled conditions in growth chambers and sacrificed for the test, here we study its applicability for leaves harvested from field trials during winter and subjected to freezing tests. Such an approach allows for simultaneous studies of the advancement of cold hardening and other components of winter survival apart from frost tolerance. It is shown that cutting or senescence of cut leaves does not have adverse effects on the outcome of subsequent freezing stress tests. The time requirements for field sampling and laboratory testing on high numbers of genotypes allow for the application of the proposed approach for genotyping/phenotyping studies.

  5. Algebraic modeling and thermodynamic design of fan-supplied tube-fin evaporators running under frosting conditions

    International Nuclear Information System (INIS)

    Ribeiro, Rafael S.; Hermes, Christian J.L.

    2014-01-01

    In this study, the method of entropy generation minimization (i.e., design aimed at facilitating both heat, mass and fluid flows) is used to assess the evaporator design (aspect ratio and fin density) considering the thermodynamic losses due to heat and mass transfer, and viscous flow processes. A fully algebraic model was put forward to simulate the thermal-hydraulic behavior of tube-fin evaporator coils running under frosting conditions. The model predictions were validated against experimental data, showing a good agreement between calculated and measured counterparts. The optimization exercise has pointed out that high aspect ratio heat exchanger designs lead to lower entropy generation in cases of fixed cooling capacity and air flow rate constrained by the characteristic curve of the fan. - Highlights: • An algebraic model for frost accumulation on tube-fin heat exchangers was advanced. • Model predictions for cooling capacity and air flow rate were compared with experimental data, with errors within ±5% band. • Minimum entropy generation criterion was used to optimize the evaporator geometry. • Thermodynamic analysis led to slender designs for fixed cooling capacity and fan characteristics

  6. Aggregate-cement paste transition zone properties affecting the salt-frost damage of high-performance concretes

    International Nuclear Information System (INIS)

    Cwirzen, Andrzej; Penttala, Vesa

    2005-01-01

    The influence of the cement paste-aggregate interfacial transition zone (ITZ) on the frost durability of high-performance silica fume concrete (HPSFC) has been studied. Investigation was carried out on eight non-air-entrained concretes having water-to-binder (W/B) ratios of 0.3, 0.35 and 0.42 and different additions of condensed silica fume. Studies on the microstructure and composition of the cement paste have been made by means of environmental scanning electron microscope (ESEM)-BSE, ESEM-EDX and mercury intrusion porosimetry (MIP) analysis. The results showed that the transition zone initiates and accelerates damaging mechanisms by enhancing movement of the pore solution within the concrete during freezing and thawing cycles. Cracks filled with ettringite were primarily formed in the ITZ. The test concretes having good frost-deicing salt durability featured a narrow transition zone and a decreased Ca/Si atomic ratio in the transition zone compared to the bulk cement paste. Moderate additions of silica fume seemed to densify the microstructure of the ITZ

  7. Role of Changes in Cell Fatty Acids Composition in the Increasing of Frost Resistance of Winter Wheat Suspension Culture

    Directory of Open Access Journals (Sweden)

    I.V. Lyubushkina

    2013-11-01

    Full Text Available Influences of low temperatures (4 and 8 ° С on the frost tolerance and fatty acid compositions of cells in a winter wheat suspension culture have been studied. It has been found that treatment of the culture with 4 °C (7 days did not protect cells from subsequent freezing temperature action (-8 °С, 6 h and was not accompanied significant changes in the fatty acid composition. On the contrary, the treatment of the culture with the temperature 8 °C (7 days prevented the death caused by freezing temperature and the content of saturated fatty acids decreased: pentadecanoic acid (by 35,0%, palmitic acid (by 19,9% and stearic acid (by 65,4%, and the content of α-linolenic acid increased by 94%. That was the cause of the double bond index (DBI increase by 16%. The role of fatty acids composition changes in the process of increasing frost tolerance in plants are discussed.

  8. On Multiple-Layered Vortices

    Science.gov (United States)

    Rossow, Vernon J.

    2011-01-01

    As part of an ongoing effort to find ways to make vortex flow fields decompose more quickly, photographs and observations are presented of vortex flow fields that indicate the presence of multiple layers of fluid rotating about a common axis. A survey of the literature indicates that multiple-layered vortices form in waterspouts, tornadoes and lift-generated vortices of aircraft. An explanation for the appearance of multiple-layered structures in vortices is suggested. The observations and data presented are intended to improve the understanding of the formation and persistence of vortex flow fields.

  9. Wall Layers

    Science.gov (United States)

    1992-01-14

    Mathematical Sciences Institute. Ithaca, NY: Cornell. Guckenheimer, J. & Labouriau, 1. 1990. Bifurcation of the Hodgkin - Huxley equations: a new vt.vist. In...olm es -____ II_ John Guckenheimer Avwi tI.,,ti 1it y ’odes ,Av9L! an.,I/or Dist Special •D L 2 Narrative Philip Holmes is continuing to study the...not localized in spae like the structur observed in the turbulent baft y layer. Wavelet bases, having compact support, seem much more appropriate. J

  10. PresenceRemote

    DEFF Research Database (Denmark)

    Sokoler, Tomas; Svensson, Marcus Sanchez

    2008-01-01

    This paper reports on our early experiences with the design of Social TV for senior citizens. Even though there seems to be a straight forward match between new interactive TV technologies on the rise and the notion of supporting social interaction amongst elderly TV viewers it is not at all clea...... for unarticulated intentions of use in our design of Social TV. The ‘PresenceRemote’ is an enhanced TV remote control making it possible for you to notice others and be noticed by peers within your local neighborhood as you watch TV....

  11. PresenceRemote

    DEFF Research Database (Denmark)

    Sokoler, Tomas; Svensson, Marcus Sanchez

    2008-01-01

    This paper reports on our early experiences with the design of Social TV for senior citizens. Even though there seems to be a straight forward match between new interactive TV technologies on the rise and the notion of supporting social interaction amongst elderly TV viewers it is not at all clea...... for unarticulated intentions of use in our design of Social TV. The ‘PresenceRemote’ is an enhanced TV remote control making it possible for you to notice others and be noticed by peers within your local neighborhood as you watch TV.......This paper reports on our early experiences with the design of Social TV for senior citizens. Even though there seems to be a straight forward match between new interactive TV technologies on the rise and the notion of supporting social interaction amongst elderly TV viewers it is not at all clear...

  12. Short-term exposure to atmospheric ammonia does not affect frost hardening of needles from three- and five-year-old Scots pine trees

    NARCIS (Netherlands)

    Clement, J.M A M; van Hasselt, P.R; van Eerden, L.J.M.; Dueck, T.A.

    The effect of atmospheric ammonia on frost hardening of needles from 3- and 5-year-old Scots pine trees was investigated. Trees were exposed to various concentrations of NH(3) during different hardening stages under laboratory conditions and in experiments with open-top chambers under a natural

  13. An Approximate Method of Calculation of Relative Humidity Required to Prevent Frosting on Inside of Aircraft Pressure Cabin Windows, Special Report

    Science.gov (United States)

    Jones, Alun R.

    1940-01-01

    This report has been prepare in response to a request for information from an aircraft company. A typical example was selected for the presentation of an approximate method of calculation of the relative humidity required to prevent frosting on the inside of a plastic window in a pressure type cabin on a high speed airplane. The results of the study are reviewed.

  14. The Influence of the Antarctic Oscillation (AAO on Cold Waves and Occurrence of Frosts in the State of Santa Catarina, Brazil

    Directory of Open Access Journals (Sweden)

    Maikon Passos A. Alves

    2017-03-01

    Full Text Available This paper examines the relationship between the Antarctic Oscillation (AAO, cold waves and occurrence of frosts in the state of Santa Catarina, Brazil, during the winter quarter. Research on this topic can assist different spheres of society, such as public health and agriculture, since cold waves can influence and/or aggravate health problems and frosts can inflict economic losses especially in the agricultural sector. For the purpose of this paper, cold wave is considered as the event in which the daily average surface air temperature was at least two standard deviations below the average value of the series on the day and for two consecutive days or more. The data on the average air temperature and frost occurrences are provided by the Company of Agricultural Research and Rural Extension of Santa Catarina/Center for Environmental Information and Hydrometeorology (EPAGRI/CIRAM. The AAO was subjected to statistical analysis using significance tests for the averages (Student’s t-test and variances (F-test with a significance level of α = 5%. The results show that cold waves are unevenly distributed in the agroecological zones of Santa Catarina. It is found that the AAO is associated with the occurrence of frosts (in the agroecological zones represented by the municipalities of Itajaí and São José in the state of Santa Catarina.

  15. Influence of wind velocity fluctuation on air temperature difference between the fan and ground levels and the effect of frost protective fan operation

    International Nuclear Information System (INIS)

    Araki, T.; Matsuo, K.; Miyama, D.; Sumikawa, O.; Araki, S.

    2008-01-01

    We invested the influence of wind velocity fluctuation on air temperature difference between the fan (4.8 m) and ground levels (0.5 m) and the effect of frost protective fan operation in order to develop a new method to reduce electricity consumption due to frost protective fan operation. The results of the investigations are summarized as follows: (1) Air temperature difference between the fan (4.8 m) and ground levels (0.5 m) was decreased following an increase in wind velocity, and the difference was less than 1°C for a wind velocity more than 3.0 m/s at a height of 6.5 m. (2) When the wind velocity was more than 2-3 m/s, there was hardly any increase in the temperature of the leaves. In contrast, when the wind velocity was less than 2-3 m/s, an increase in the temperature of the leaves was observed. Based on these results, it is possible that when the wind velocity is greater than 2-3 m, it prevents thermal inversion. Therefore, there would be no warmer air for the frost protective fan to return to the tea plants and the air turbulence produced by the frost protective fan would not reach the plants under the windy condition

  16. Use of H2Ri wicking fabric to prevent frost boils in the Dalton Highway Beaver Slide area, Alaska final report.

    Science.gov (United States)

    2012-08-01

    Many roads in Alaska, such as the Dalton Highway, experience degradation during spring thaw due to the downslope running of shallow groundwater. The water flow : down the slope and pools up in the road embankments, where it freezes, causing frost boi...

  17. Comparisons of temperature, pressure and humidity measurements by balloon-borne radiosondes and frost point hygrometers during MOHAVE-2009

    Directory of Open Access Journals (Sweden)

    D. F. Hurst

    2011-12-01

    Full Text Available We compare coincident, in situ, balloon-borne measurements of temperature (T and pressure (P by two radiosondes (Vaisala RS92, Intermet iMet-1-RSB and similar measurements of relative humidity (RH by RS92 sondes and frost point hygrometers. Data from a total of 28 balloon flights with at least one pair of radiosondes are analyzed in 1-km altitude bins to quantify measurement differences between the sonde sensors and how they vary with altitude. Each comparison (T, P, RH exposes several profiles of anomalously large measurement differences. Measurement difference statistics, calculated with and without the anomalous profiles, are compared to uncertainties quoted by the radiosonde manufacturers. Excluding seven anomalous profiles, T differences between 19 pairs of RS92 and iMet sondes exceed their measurement uncertainty limits (2 σ 31% of the time and reveal a statistically significant, altitude-independent bias of 0.5 ± 0.2 °C. Similarly, RS92-iMet P differences in 22 non-anomalous profiles exceed their uncertainty limits 23% of the time, with a disproportionate 83% of the excessive P differences at altitudes >16 km. The RS92-iMet pressure differences increase smoothly from −0.6 hPa near the surface to 0.8 hPa above 25 km. Temperature and P differences between all 14 pairs of RS92 sondes exceed manufacturer-quoted, reproducibility limits (σ 28% and 11% of the time, respectively. About 95% of the excessive T differences are eliminated when 5 anomalous RS92-RS92 profiles are excluded. Only 5% of RH measurement differences between 14 pairs of RS92 sondes exceed the manufacturer's measurement reproducibility limit (σ. RH measurements by RS92 sondes are also compared to RH values calculated from frost point hygrometer measurements and coincident T measurements by the radiosondes. The influences of RS92-iMet Tand P differences on RH values and water vapor mixing

  18. On the marine atmospheric boundary layer characteristics over Bay ...

    Indian Academy of Sciences (India)

    Usually over tropical regions, marine lower atmosphere is characterized by different regions such as surface layer, mixed layer (ML), transition layer, cloud layer, and trade wind inversion. The cause of the trade wind inversion is the presence of the descending limb of the Hadley cell circulation. The trade wind inversion, acts ...

  19. MITRE sensor layer prototype

    Science.gov (United States)

    Duff, Francis; McGarry, Donald; Zasada, David; Foote, Scott

    2009-05-01

    The MITRE Sensor Layer Prototype is an initial design effort to enable every sensor to help create new capabilities through collaborative data sharing. By making both upstream (raw) and downstream (processed) sensor data visible, users can access the specific level, type, and quantities of data needed to create new data products that were never anticipated by the original designers of the individual sensors. The major characteristic that sets sensor data services apart from typical enterprise services is the volume (on the order of multiple terabytes) of raw data that can be generated by most sensors. Traditional tightly coupled processing approaches extract pre-determined information from the incoming raw sensor data, format it, and send it to predetermined users. The community is rapidly reaching the conclusion that tightly coupled sensor processing loses too much potentially critical information.1 Hence upstream (raw and partially processed) data must be extracted, rapidly archived, and advertised to the enterprise for unanticipated uses. The authors believe layered sensing net-centric integration can be achieved through a standardize-encapsulate-syndicateaggregate- manipulate-process paradigm. The Sensor Layer Prototype's technical approach focuses on implementing this proof of concept framework to make sensor data visible, accessible and useful to the enterprise. To achieve this, a "raw" data tap between physical transducers associated with sensor arrays and the embedded sensor signal processing hardware and software has been exploited. Second, we encapsulate and expose both raw and partially processed data to the enterprise within the context of a service-oriented architecture. Third, we advertise the presence of multiple types, and multiple layers of data through geographic-enabled Really Simple Syndication (GeoRSS) services. These GeoRSS feeds are aggregated, manipulated, and filtered by a feed aggregator. After filtering these feeds to bring just the type

  20. Aclimatação ao frio e dano por geada em canola Acclimatization to cold and frost-injury in canola

    Directory of Open Access Journals (Sweden)

    Genei Antonio Dalmago

    2010-09-01

    Full Text Available O objetivo deste trabalho foi avaliar a influência da aclimatação ao frio sobre o dano causado pela geada em diferentes estádios fenológicos de genótipos de canola. Foram realizados cinco experimentos em ambiente controlado, em 2006, 2007 e 2008. Os fatores avaliados foram: genótipos, aclimatação (com; sem, intensidades de geada, estádios de desenvolvimento de plantas, regimes de aclimatação e regimes de geada. As variáveis avaliadas foram: queima de folhas, massa de matéria seca, estatura de plantas, duração de subperíodo, componentes de rendimento e rendimento de grãos. A aclimatação ao frio, antes da geada, resultou em menor queima de folhas e maior massa de matéria seca, em comparação a plantas não aclimatadas. As geadas foram prejudiciais a partir de -6°C no início do ciclo de desenvolvimento, principalmente em plantas não aclimatadas, e a partir de -4ºC na floração, com redução do número de síliquas e do número de grãos por síliqua. A aclimatação após as geadas não contribuiu para a tolerância da canola a esse evento. Geadas consecutivas não acarretaram maior prejuízo à canola. A aclimatação de plantas de canola antes da geada reduz os danos, principalmente quando a geada ocorre no início do desenvolvimento das plantas.The objective of this work was to evaluate the influence of cold acclimatization on frost damage at different phenological stages of canola genotypes. Five experiments were carried out under controlled conditions, in 2006, 2007, and 2008. The evaluated factors were: genotypes, acclimatization (with; without, frost gradient, plant developmental stages, acclimatization regimes and frost regimes. The evaluated variables were: leaf scorching symptoms, dry weight, plant height, length of subperiod, yield components and grain yield. The acclimatization before frost resulted in lesser leaf scorching symptoms and higher dry matter in comparison to plants not acclimated. Frosts were

  1. The Impact of Blended Learning on Social Presence, Cognitive Presence, Teaching Presence, and Perceived Learning

    Science.gov (United States)

    Harrell, Kyleigh Blackwell

    2017-01-01

    The quantitative study examined how blended learning influences high school learners' social presence, cognitive presence, teacher presence, and perceived learning in comparison to online instruction. The study answered the following research questions: (a) Do differences exist among the social presence, cognitive presence, and teaching presence…

  2. Role of planting stock size and fertilizing in initial growth performance of rowan (Sorbus aucuparia L. reforestation in a mountain frost hollow

    Directory of Open Access Journals (Sweden)

    Ivan Kuneš

    2014-08-01

    Full Text Available The aim of study: (1 to compare the survival rate, growth performance and nutrition of large and common-sized planting stock of rowan (Sorbus aucuparia L. on a frost-exposed site and (2 to assess whether fertilizing had any effect on the plantations.Area of study: The Jizera Mts., an area heavily disturbed by air pollution situated on the Czech-Polish border close to GermanyMaterials and methods: Two types of planting stock were tested in a mountain frost hollow on an acidic mountain humic podsol: (a the bare-rooted saplings 131–140 cm tall and (b common-sized containerized transplants 26–35 cm. One half of the saplings and common-sized transplants were left untreated and the other half were fertilized with a low dose (30 g per tree of a slow release fertilizer based on methylene urea and potassium magnesium phosphate. Growth performance and nutrition of plantations were investigated.Main results: Due to serious deformations and stem breakages inflicted by snow and frost, the prospects of common-sized transplants seem much worse than those of saplings. The height growth of saplings was significantly more rapid than that of common-sized transplants. As for growth, neither the saplings nor common-sized transplants did significantly respond to fertilizing. The effects of fertilizing on nutrition of rowans were unconvincing. The extreme temperature events during growth seasons and snow deformations in winters might be the decisive factors influencing growth performance of rowans under referred conditions.Research highlights: On the frost-exposed sites, the height of taller saplings might partly compensate for a missing shelter of forest stand since the terminal leaders are above ground-frost zone.Key words: mountain ash; sapling; common-sized transplants; nutritional status; temperature.Abbreviations: CS – Control Saplings; CT – Control Transplants; FS – Fertilized Saplings; FT – Fertilized Transplants

  3. Physical, Rheological, Functional, and Film Properties of a Novel Emulsifier: Frost Grape Polysaccharide from Vitis riparia Michx.

    Science.gov (United States)

    Hay, William T; Vaughn, Steven F; Byars, Jeffrey A; Selling, Gordon W; Holthaus, Derek M; Price, Neil P J

    2017-10-04

    A novel emulsifier, Frost grape polysaccharide (FGP), isolated from natural exudate of the species Vitis riparia Michx, was physically and rheologically characterized. The determination of the physical, structural, thermodynamic, emulsification, film, and rheological properties of FGP provide essential details for the commercial adoption of this novel plant polysaccharide. FGP is capable of producing exceptionally stable emulsions when compared with the industrially ubiquitous gum arabic (GA). The FGP isolate contained a negligible amount of nitrogen (0.03%), indicating that it does not contain an associated glycoprotein, unlike GA. Solutions of FGP have a high degree of thermostability, displaying no loss in viscosity with temperature cycling and no thermal degradation when held at 90 °C. FGP is an excellent film former, producing high tensile strength films which remain intact at temperatures up to 200 °C. This work identified a number of potential food and pharmaceutical applications where FGP is significantly superior to GA.

  4. Multifunctional layered magnetic composites

    Science.gov (United States)

    Siglreitmeier, Maria; Wu, Baohu; Kollmann, Tina; Neubauer, Martin; Nagy, Gergely; Schwahn, Dietmar; Pipich, Vitaliy; Faivre, Damien; Zahn, Dirk; Fery, Andreas

    2015-01-01

    Summary A fabrication method of a multifunctional hybrid material is achieved by using the insoluble organic nacre matrix of the Haliotis laevigata shell infiltrated with gelatin as a confined reaction environment. Inside this organic scaffold magnetite nanoparticles (MNPs) are synthesized. The amount of MNPs can be controlled through the synthesis protocol therefore mineral loadings starting from 15 wt % up to 65 wt % can be realized. The demineralized organic nacre matrix is characterized by small-angle and very-small-angle neutron scattering (SANS and VSANS) showing an unchanged organic matrix structure after demineralization compared to the original mineralized nacre reference. Light microscopy and confocal laser scanning microscopy studies of stained samples show the presence of insoluble proteins at the chitin surface but not between the chitin layers. Successful and homogeneous gelatin infiltration in between the chitin layers can be shown. The hybrid material is characterized by TEM and shows a layered structure filled with MNPs with a size of around 10 nm. Magnetic analysis of the material demonstrates superparamagnetic behavior as characteristic for the particle size. Simulation studies show the potential of collagen and chitin to act as nucleators, where there is a slight preference of chitin over collagen as a nucleator for magnetite. Colloidal-probe AFM measurements demonstrate that introduction of a ferrogel into the chitin matrix leads to a certain increase in the stiffness of the composite material. PMID:25671158

  5. Multifunctional layered magnetic composites

    Directory of Open Access Journals (Sweden)

    Maria Siglreitmeier

    2015-01-01

    Full Text Available A fabrication method of a multifunctional hybrid material is achieved by using the insoluble organic nacre matrix of the Haliotis laevigata shell infiltrated with gelatin as a confined reaction environment. Inside this organic scaffold magnetite nanoparticles (MNPs are synthesized. The amount of MNPs can be controlled through the synthesis protocol therefore mineral loadings starting from 15 wt % up to 65 wt % can be realized. The demineralized organic nacre matrix is characterized by small-angle and very-small-angle neutron scattering (SANS and VSANS showing an unchanged organic matrix structure after demineralization compared to the original mineralized nacre reference. Light microscopy and confocal laser scanning microscopy studies of stained samples show the presence of insoluble proteins at the chitin surface but not between the chitin layers. Successful and homogeneous gelatin infiltration in between the chitin layers can be shown. The hybrid material is characterized by TEM and shows a layered structure filled with MNPs with a size of around 10 nm. Magnetic analysis of the material demonstrates superparamagnetic behavior as characteristic for the particle size. Simulation studies show the potential of collagen and chitin to act as nucleators, where there is a slight preference of chitin over collagen as a nucleator for magnetite. Colloidal-probe AFM measurements demonstrate that introduction of a ferrogel into the chitin matrix leads to a certain increase in the stiffness of the composite material.

  6. Intercropping frost-sensitive legume crops with winter oilseed rape reduces weed competition, insect damage, and improves nitrogen use efficiency

    Directory of Open Access Journals (Sweden)

    Cadoux Stéphane

    2015-05-01

    Full Text Available Mixing plant species in agroecosystems is highlighted as an agroecological solution to reduce pesticides and fertilizers while maintaining profitability. In the French context, intercropping frost-sensitive legume crops with winter oilseed rape is potentially interesting and began to be implemented by farmers. In this study we aimed at measuring the services and disservices of this intercrop with three different legume mixtures, in terms of growth and yield for rapeseed, ground cover of weeds in autumn and damage caused by rape winter stem weevil. The experiment was carried out at four sites from 2011 to 2014. We showed higher total aerial dry weights and total aerial nitrogen contents in the intercrops compared to sole winter oilseed rape in November. The companion plants contributed to the control of weeds and the mitigation of rape winter stem weevil damage, notably through the increase in the total aerial weight. In spring, after destruction of the companion plants, the intercrops had partially compensated a reduction in the N fertilization rate (–30 kg per hectare in terms of aerial nitrogen content in rapeseed, with no consequences on the yield which was maintained or even increased. There were probably other interactions such as an improvement in rapeseed root exploration. The consequences were an increase in the nitrogen use efficiency in intercrops. The intercrop with faba bean and lentil showed the best results in terms of autumn growth, weed control, reduction in rape winter stem weevil damage, and rapeseed N content in spring and yield. Intercropping frost-sensitive legume crops with winter oilseed rape is thus a promising way to reconcile yield and reduction in pesticides and fertilizer use and perhaps to benefit more widely to the cropping system.

  7. Efficacy of cervicothoracic sympathectomy versus conservative management in patients suffering from incapacitating raynaud,s syndrome after frost bite

    International Nuclear Information System (INIS)

    Khan, M.I.; Rehman, A.; Tariq, M.; Sheen, S.N.

    2008-01-01

    Raynaud's syndrome is a known complication of cold injuries. Stress, smoking and metabolic diseases may further aggravate the disease course. The purpose of this study was to determine the efficacy of Cervico-thoracic sympathectomy as compared to conservative management in severe Raynaud's syndrome after frostbite. This non-randomized controlled trial was conducted at Railway Hospital, Rawalpindi and Islamic International Medical Complex, Islamabad between January 1999 and June 2006. All patients sustained severe cold trauma in the mountain ridges of Himalayas in Kashmir. In all cases, an informed consent was obtained from patients and families. All operations performed were free of charges. Out of the total 48 patients who developed incapacitating Raynaud's syndrome of the upper limbs after frost bite, 17 patients underwent thoracic sympathectomy through anterior supraclavicular route. Remaining 31 patients were treated conservatively and were placed in the control group. Data was collected on pre-designed proforma and assessed using SPSS (version 11). Chi-square test was applied to assess the effectiveness of the two treatment modalities. All operated cases initially showed improvement in symptoms and incapacitation. Among sympathectomised patients, 11 patients became symptom free and 3 patients showed mild but improved symptoms. Two patients after initial transient improvement developed incapacitating symptoms requiring further treatment, one patient developed gangrene of distal phalanx nine month after sympathectomy requiring amputation of the finger. Frequency of attacks and duration between the attacks reduced in all operated patients of cervical sympathectomy (p<0.05) as compared to conservative management. Cervical sympathectomy is a very effective modality of treatment in patients having severe Raynaud's disease of upper limbs secondary to frost bite. (author)

  8. Layering and Ordering in Electrochemical Double Layers

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yihua [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States; Kawaguchi, Tomoya [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States; Pierce, Michael S. [Rochester Institute of Technology, School of Physics and Astronomy, Rochester, New York 14623, United States; Komanicky, Vladimir [Faculty of Science, Safarik University, 041 54 Kosice, Slovakia; You, Hoydoo [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States

    2018-02-26

    Electrochemical double layers (EDL) form at electrified interfaces. While Gouy-Chapman model describes moderately charged EDL, formation of Stern layers was predicted for highly charged EDL. Our results provide structural evidence for a Stern layer of cations, at potentials close to hydrogen evolution in alkali fluoride and chloride electrolytes. Layering was observed by x-ray crystal truncation rods and atomic-scale recoil responses of Pt(111) surface layers. Ordering in the layer is confirmed by glancing-incidence in-plane diffraction measurements.

  9. Investigations on the formation of frost on lamella heat-exchangers used in heat pumps; LOREF: Luftkuehler-Optimierung mit Reduktion von Eis- und Frostbildung. Untersuchung der Frostbildung fuer Lamellenluftkuehler von Waermepumpen

    Energy Technology Data Exchange (ETDEWEB)

    Sahinagic, R.; Imholz, M.; Berlinger, L.; Huber, H.; Hilfiker, K. [Hochschule fuer Technik und Architektur (HTA) Lucerne, Institut fuer Produktentwicklung, Thermische Verfahren und Anlagen (TVA), Horw (Switzerland)

    2004-07-01

    This comprehensive final report presents the results of the LOREF project carried out at the University of Applied Science in Horw, Switzerland, on the formation of frost on lamella air-coolers used in heat pumps. The report presents the results of extensive tests on the formation of frost on the lamella of the heat exchangers used in air-water heat pumps. The mathematical relationships and the theory behind the formation of frost on cooled surfaces are discussed in detail. The results of numerical simulations and practical tests are presented. The practical tests involved the observation of ice and frost formation on various surface forms. The results of the physical tests and observations are quoted in detail. The mathematical modelling method used and the associated results are discussed. The report is rounded off with an appendix containing tables, diagrams and photos.

  10. Removal of surgical smear layer.

    Science.gov (United States)

    Fabiani, Cristiano; Franco, Vittorio; Covello, Francesco; Brambilla, Eugenio; Gagliani, Massimo M

    2011-06-01

    During apicoectomy and retrograde cavity preparation, a smear layer, which contains microorganisms and necrotic pulpal tissues, is formed on the dentinal surfaces cut by the instruments. Bacteria can survive and proliferate inside or below the smear layer. The purpose of this study was to evaluate in vitro two different procedures for the removal of the smear layer in retrocavities prepared with ultrasonic retrotips. Twenty-eight single-rooted teeth were cleaned, shaped, and obturated with gutta-percha and sealer. The apical 3 mm of each root were cut with a carbide bur, and retrograde cavities were prepared with ProUltra ultrasonic retrotips (Maillefer Dentsply, Baillagues, Switzerland) at a depth of 3 mm. Teeth in group A were treated with a gel of 35% orthophosphoric acid for 15 seconds, and teeth in group B were treated with a gel of 24% EDTA at a neutral pH for 2 minutes. The samples were prepared for scanning electron microscopic observation and scored for the presence of the smear layer on the retrocavity walls. Eighty percent of the teeth in group A showed an optimal degree of cleanliness of the walls, with dentinal tubules completely open. The majority of analyzed samples coming from group B showed dentinal tubules covered with the smear layer. The analysis of the samples showed that orthophosphoric acid is more effective than EDTA in removing surgical smear layer even with less time of action. Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  11. Snippets from the past: the evolution of Wade Hampton Frost's epidemiology as viewed from the American Journal of Hygiene/Epidemiology.

    Science.gov (United States)

    Morabia, Alfredo

    2013-10-01

    Wade Hampton Frost, who was a Professor of Epidemiology at Johns Hopkins University from 1919 to 1938, spurred the development of epidemiologic methods. His 6 publications in the American Journal of Hygiene, which later became the American Journal of Epidemiology, comprise a 1928 Cutter lecture on a theory of epidemics, a survey-based study of tonsillectomy and immunity to Corynebacterium diphtheriae (1931), 2 papers from a longitudinal study of the incidence of minor respiratory diseases (1933 and 1935), an attack rate ratio analysis of the decline of diphtheria in Baltimore (1936), and a 1936 lecture on the age, time, and cohort analysis of tuberculosis mortality. These 6 American Journal of Hygiene /American Journal of Epidemiology papers attest that Frost's personal evolution mirrored that of the emerging "early" epidemiology: The scope of epidemiology extended beyond the study of epidemics of acute infectious diseases, and rigorous comparative study designs and their associated quantitative methods came to light.

  12. A GIS analysis of the relationship between sinkholes, dry-well complaints and groundwater pumping for frost-freeze protection of winter strawberry production in Florida.

    Science.gov (United States)

    Aurit, Mark D; Peterson, Robert O; Blanford, Justine I

    2013-01-01

    Florida is riddled with sinkholes due to its karst topography. Sometimes these sinkholes can cause extensive damage to infrastructure and homes. It has been suggested that agricultural practices, such as sprinkler irrigation methods used to protect crops, can increase the development of sinkholes, particularly when temperatures drop below freezing, causing groundwater levels to drop quickly during groundwater pumping. In the strawberry growing region, Dover/Plant City, Florida, the effects have caused water shortages resulting in dry-wells and ground subsidence through the development of sinkholes that can be costly to maintain and repair. In this study, we look at how frost-freeze events have affected West Central Florida over the past 25 years with detailed comparisons made between two cold-years (with severe frost-freeze events) and a warm year (no frost-freeze events). We analyzed the spatial and temporal correlation between strawberry farming freeze protection practices and the development of sinkholes/dry well complaints, and assessed the economic impact of such events from a water management perspective by evaluating the cost of repairing and drilling new wells and how these compared with using alternative crop-protection methods. We found that the spatial distribution of sinkholes was non-random during both frost-freeze events. A strong correlation between sinkhole occurrence and water extraction and minimum temperatures was found. Furthermore as temperatures fall below 41°F and water levels decrease by more than 20 ft, the number of sinkholes increase greatly (N >10). At this time alternative protection methods such as freeze-cloth are cost prohibitive in comparison to repairing dry wells. In conclusion, the findings from this study are applicable in other agricultural areas and can be used to develop comprehensive water management plans in areas where the abstraction of large quantities of water occur.

  13. A GIS analysis of the relationship between sinkholes, dry-well complaints and groundwater pumping for frost-freeze protection of winter strawberry production in Florida.

    Directory of Open Access Journals (Sweden)

    Mark D Aurit

    Full Text Available Florida is riddled with sinkholes due to its karst topography. Sometimes these sinkholes can cause extensive damage to infrastructure and homes. It has been suggested that agricultural practices, such as sprinkler irrigation methods used to protect crops, can increase the development of sinkholes, particularly when temperatures drop below freezing, causing groundwater levels to drop quickly during groundwater pumping. In the strawberry growing region, Dover/Plant City, Florida, the effects have caused water shortages resulting in dry-wells and ground subsidence through the development of sinkholes that can be costly to maintain and repair. In this study, we look at how frost-freeze events have affected West Central Florida over the past 25 years with detailed comparisons made between two cold-years (with severe frost-freeze events and a warm year (no frost-freeze events. We analyzed the spatial and temporal correlation between strawberry farming freeze protection practices and the development of sinkholes/dry well complaints, and assessed the economic impact of such events from a water management perspective by evaluating the cost of repairing and drilling new wells and how these compared with using alternative crop-protection methods. We found that the spatial distribution of sinkholes was non-random during both frost-freeze events. A strong correlation between sinkhole occurrence and water extraction and minimum temperatures was found. Furthermore as temperatures fall below 41°F and water levels decrease by more than 20 ft, the number of sinkholes increase greatly (N >10. At this time alternative protection methods such as freeze-cloth are cost prohibitive in comparison to repairing dry wells. In conclusion, the findings from this study are applicable in other agricultural areas and can be used to develop comprehensive water management plans in areas where the abstraction of large quantities of water occur.

  14. Association analysis of frost tolerance in rye using candidate genes and phenotypic data from controlled, semi-controlled, and field phenotyping platforms

    Directory of Open Access Journals (Sweden)

    Li Yongle

    2011-10-01

    Full Text Available Abstract Background Frost is an important abiotic stress that limits cereal production in the temperate zone. As the most frost tolerant small grain cereal, rye (Secale cereale L. is an ideal cereal model for investigating the genetic basis of frost tolerance (FT, a complex trait with polygenic inheritance. Using 201 genotypes from five Eastern and Middle European winter rye populations, this study reports a multi-platform candidate gene-based association analysis in rye using 161 single nucleotide polymorphisms (SNPs and nine insertion-deletion (Indel polymorphisms previously identified from twelve candidate genes with a putative role in the frost responsive network. Results Phenotypic data analyses of FT in three different phenotyping platforms, controlled, semi-controlled and field, revealed significant genetic variations in the plant material under study. Statistically significant (P ScCbf15 and one in ScCbf12, all leading to amino acid exchanges, were significantly associated with FT over all three phenotyping platforms. Distribution of SNP effect sizes expressed as percentage of the genetic variance explained by individual SNPs was highly skewed towards zero with a few SNPs obtaining large effects. Two-way epistasis was found between 14 pairs of candidate genes. Relatively low to medium empirical correlations of SNP-FT associations were observed across the three platforms underlining the need for multi-level experimentation for dissecting complex associations between genotypes and FT in rye. Conclusions Candidate gene based-association studies are a powerful tool for investigating the genetic basis of FT in rye. Results of this study support the findings of bi-parental linkage mapping and expression studies that the Cbf gene family plays an essential role in FT.

  15. Development of a program for estimating air-to-air sensible heat recovery energy savings reduction due to frost control and comparison with EE4

    Energy Technology Data Exchange (ETDEWEB)

    Ball, I. [GES Technologies Inc., Montreal, PQ (Canada)

    2006-07-01

    Air-to-air heat recovery is an important energy savings measure for new or existing buildings. However, frost formation in cold climates limits the use of air-to-air heat recovery for HVAC applications. This study examined the methodology for estimating heat recovery energy savings in the program EE4, the main building energy modelling tool used in Canada. The EE4 is used together with the Modeling National Energy Building code to evaluate building energy performance for the Commercial Building Incentive Program. It is the basis for calculating the resulting financial incentives for building owners. The main objective of the study was to present a more realistic algorithm for estimating energy savings in relation to sensible air-to-air heat recovery accounting for two types of conventional frost control methods: face and bypass and outdoor air preheat. This algorithm was developed into a computer program called HRSIM that performs hourly calculations and contains an option for air-to-air heat recovery. Results from the simulations demonstrate that when accounting for frost control, the annual energy savings calculated in EE4 were 10 to 53 per cent higher than with HRSIM. 6 refs., 1 tab., 7 figs.

  16. Effects of mid-season frost and elevated growing season temperature on stomatal conductance and specific xylem conductivity of the arctic shrub, Salix pulchra

    Energy Technology Data Exchange (ETDEWEB)

    Gorsuch, D. M.; Oberbauer, S. F. [Florida International Univ., Dept. of Biological Sciences, Miami, FL (United States)

    2002-10-01

    It is hypothesized that because deciduous plants have a growth season limited in length and also have generally larger conduit volumes, they are more likely to be injured by freeze-thaw induced cavitation during the growing season. To test this hypothesis, the deciduous arctic shrub, Salix pulchra, was grown in simulated Alaskan summer temperatures and at five degrees C above the ambient simulation in controlled environments. Specific hydraulic conductivity and leaf stomatal conductance were measured in plants grown at both temperatures before and after freeze treatment simulating a mid-season frost. Before freeze treatment specific hydraulic conductivity was 2.5 times higher and stomatal conductance was 1.3 times higher in plants grown at elevated temperature. After freeze treatment reduction in hydraulic conductivity and stomatal conductance was 3.5 and 1.8 times higher in the plants grown at the higher temperature than plants grown at ambient temperature. Plants grown at the higher temperature also had larger vessel diameters and higher vessel densities than ambient-grown plants. These results suggest that higher growing season temperatures will make arctic deciduous shrubs more susceptible to frost damage. The implication of these results for plant growth in the arctic tundra is that while climate warming favours plants with larger vessels and higher specific xylem conductivity over plants with lower values, this competitive advantage may be lost if there is an increase in the risk of frost during the growing season. 43 refs., 5 figs.

  17. [Ability of winter wheat plants to become hardened against frost related to peculiarities of carbon dioxide exchange, biomass synthesis, and various forms of water-soluble carbohydrates].

    Science.gov (United States)

    Klimov, S V; Burakhanova, E A; Alieva, G P; Suvorova, T A

    2010-01-01

    The donor-acceptor relation (DAR) in a plant under cold exposure to frost was studied in the plants of winter wheat (Triticum aestivum L.) Mironovskaya 808 cultivar and its allocytoplasmatic hybrid containing alien cytoplasm of goat grass (Aegilops ovata L.) and grown in a water culture until phenophase, from two leaves until branching. The alteration of DAR was processed by treatment of plant with solutions of diuron and paraquat the photosynthesis inhibitors, keeping plants in the dark, changing from mixotrophic to autotrophic nutrient, and also through the exchange of nutrient solution to distillate water. Determination of frost-resistance on the basis of survival percentage among frozen plants is more significant (R = 0.701-0.999) and related to the frost-resistance of leaves, the correlation P/Rd between speeds of true photosynthesis at light saturation (P) and plant dark respiration (Rd), the approximate speed of dry plant biomass alteration, the total content of water-soluble sugars, and the ratio of di- and monosaccharides (sucrose, glucose + fructose) in leaves. The importance of all the indexes mentioned above for acquiring resistance to low temperatures in plants is discussed in the present article.

  18. Significance of frost action and surface soil characteristics to wind erosion at Rocky Flats, Colorado. Second progress report, October 1, 1975--May 30, 1976

    Energy Technology Data Exchange (ETDEWEB)

    Caine, N.; Morin, P.

    1976-01-01

    This report summarizes information on soil frost effects collected on Rocky Flats during the 1975-1976 winter. On a broad scale, work on soil textures at and just below the ground surface corroborates the conclusion reached earlier that the general frost susceptibility of the Rocky Flats soils is quite well keyed to topography. This is incorporated into a mapping procedure for potential soil frost activity which is applied to the northwestern part of the Rocky Flats area. On a site scale, instrumental records of weather conditions and soil responses have been maintained from October, 1975, to May, 1976, at the Lindsay Ranch study site, northwest of the Rocky Flats Plant. During that period, 33 needle ice events have been observed and recorded and are described in this report. A preliminary examination of wind data for the same period suggests that the soil in areas of natural vegetation on the site are not exposed to wind action. If, however, they were exposed, winds capable of eroding them are common.

  19. Prediction of Frost-Heaving Behavior of Saline Soil in Western Jilin Province, China, by Neural Network Methods

    Directory of Open Access Journals (Sweden)

    Xudong Zhang

    2017-01-01

    Full Text Available In this study, backpropagation neural network (BPNN and generalized regression neural network (GRNN approaches are used to predict the frost-heaving ratio (FR of the saline soil specimen collected from Nong’an, Western Jilin, China. Four variables, namely, water content (WC, compactness, temperature, and content of soluble salts (CSS, are considered in predicting FR. A total of 360 pieces of data, collected from the experimental results, in which 30 pieces of data were selected randomly as the testing set data and the rest of the data were treated as the training set data, are applied to develop the prediction models. The predicted data from the models are compared with the experimental data. Then, the results of the two approaches are compared to obtain a relatively reliable model. Results indicate that the prediction model for the FR of saline soil in Nong’an can be successfully established using the GRNN method. Four new GRNN models are constructed for sensitivity analysis to assess the influence degree of the influencing factors, and the results indicate that water content is the most influential variable in the FR of the saline soil specimen, whereas content of soluble salts is the least influential variable.

  20. Prolongation of soil frost resulting from reduced snow cover increases nitrous oxide emissions from boreal forest soil

    Energy Technology Data Exchange (ETDEWEB)

    Maljanen, M.; Martikainen, P.J. (Univ. of Kuopio, Dept. of Environmental Science (Finland)); Alm, J.; Repo, T. (Finnish Forest Research Inst., Joensuu Research Centre (Finland))

    2010-07-01

    Emission rates of the greenhouse gas, nitrous oxide (N{sub 2}O), from northern upland forest soils are generally low. According to recent climate scenarios, the snow cover in the boreal region is predicted to decrease and which will result in lower soil temperatures. In this study, we investigated whether lower soil temperatures during winter can also trigger N{sub 2}O emissions from boreal forest soils with originally low N{sub 2}O emissions, as has earlier been shown for northern agricultural soils with higher N{sub 2}O emissions. We measured the N{sub 2}O emissions from a spruce forest in eastern Finland where the soil temperature was changed by manipulating snow-pack thickness and using insulating covers. The effects of the treatments on methane (CH{sub 4}) and carbon dioxide (CO{sub 2}) fluxes were also studied for comparative purposes. The results show that there can be an increase in N{sub 2}O emissions and CO{sub 2} production rate from boreal upland forest soils resulting from a thinner snow cover that causes a prolongation of soil frost. Reducing the snow pack thickness had only minor effects on the CH{sub 4} fluxes. (orig.)

  1. Rule-based Mamdani-type fuzzy modelling of thermal performance of fintube evaporator under frost conditions

    Directory of Open Access Journals (Sweden)

    Ozen Dilek Nur

    2016-01-01

    Full Text Available Frost formation brings about insulating effects over the surface of a heat exchanger and thereby deteriorating total heat transfer of the heat exchanger. In this study, a fin-tube evaporator is modeled by making use of Rule-based Mamdani-Type Fuzzy (RBMTF logic where total heat transfer, air inlet temperature of 2 °C to 7 °C and four different fluid speed groups (ua1=1; 1.44; 1.88 m s-1, ua2=2.32; 2.76 m s-1, ua3=3.2; 3.64 m s-1, ua4=4.08; 4.52; 4.96 m s-1 for the evaporator were taken into consideration. In the developed RBMTF system, outlet parameter UA was determined using inlet parameters Ta and ua. The RBMTF was trained and tested by using MATLAB® fuzzy logic toolbox. R2 (% for the training data and test data were found to be 99.91%. With this study, it has been shown that RBMTF model can be reliably used in determination of a total heat transfer of a fin-tube evaporator.

  2. Digital Image Sensor-Based Assessment of the Status of Oat (Avena sativa L. Crops after Frost Damage

    Directory of Open Access Journals (Sweden)

    Isidro Villegas-Romero

    2011-06-01

    Full Text Available The aim of this paper is to classify the land covered with oat crops, and the quantification of frost damage on oats, while plants are still in the flowering stage. The images are taken by a digital colour camera CCD-based sensor. Unsupervised classification methods are applied because the plants present different spectral signatures, depending on two main factors: illumination and the affected state. The colour space used in this application is CIELab, based on the decomposition of the colour in three channels, because it is the closest to human colour perception. The histogram of each channel is successively split into regions by thresholding. The best threshold to be applied is automatically obtained as a combination of three thresholding strategies: (a Otsu’s method, (b Isodata algorithm, and (c Fuzzy thresholding. The fusion of these automatic thresholding techniques and the design of the classification strategy are some of the main findings of the paper, which allows an estimation of the damages and a prediction of the oat production.

  3. Digital image sensor-based assessment of the status of oat (Avena sativa L.) crops after frost damage.

    Science.gov (United States)

    Macedo-Cruz, Antonia; Pajares, Gonzalo; Santos, Matilde; Villegas-Romero, Isidro

    2011-01-01

    The aim of this paper is to classify the land covered with oat crops, and the quantification of frost damage on oats, while plants are still in the flowering stage. The images are taken by a digital colour camera CCD-based sensor. Unsupervised classification methods are applied because the plants present different spectral signatures, depending on two main factors: illumination and the affected state. The colour space used in this application is CIELab, based on the decomposition of the colour in three channels, because it is the closest to human colour perception. The histogram of each channel is successively split into regions by thresholding. The best threshold to be applied is automatically obtained as a combination of three thresholding strategies: (a) Otsu's method, (b) Isodata algorithm, and (c) Fuzzy thresholding. The fusion of these automatic thresholding techniques and the design of the classification strategy are some of the main findings of the paper, which allows an estimation of the damages and a prediction of the oat production.

  4. FUD - SALA. Stabilization of unbound layers on a road section; FUD - SALA. Provstraecka med stabilisering av obundna lager

    Energy Technology Data Exchange (ETDEWEB)

    Svedberg, Bo; Ekdahl, Peter; Macsik, Josef; Maijala, Aino; Lahtinen, Pentti; Hermansson, Aake; Knutsson, Sven; Edeskaer, Tommy

    2008-06-15

    Stabilization of unbound layers is a method that enables the properties of road structures to be improved, for example the layer modulus of the sub base, by addition of binders. Traditional binders are cement, Merit 5000 (fine ground slag cement), lime and bitumen. The method is commonly in practice in Europe and has been also used occasionally for public roads in Sweden. Today there are examples where fly ashes (bio and coal based) have been used as binders in smaller roads for example in the counties of Uppsala, Soedermanland and also for other paved areas for heavy vehicles in the county of Vaestmanland and in Finland. These examples have mainly been carried out using an empirical approach. The objective of the project is to develop two applications as a base for full scale demonstration. One of them is a paved road and the other one is a private road with gravel as wearing course. The binders used are cement, Merit and fly-ash. Two sections of a road were used a reference. The work indicates that stabilization of unbound layers will improve the bearing capacity of the road construction significantly although the total depth of the structure is reduced. The design of the road structure was carried out in a conservative manner as there were no basis for a precise determination of the layer modulus. The developed applications are not frost lifting although their insulating properties are low and about the same as fine grained silt. The durability against frost and thaw cycles has been assessed and is expected to be acceptable. The fly ashes used will need addition of cement and Merit to perform well in frost and thaw tests. Applying both applications will result in a reduced depth of the structure and the sub-base layers can nearly be excluded. Life cycle cost calculations indicate that the cost of investment for a road construction using a stabilized layer are slightly higher than the cost of investment for the reference construction. This is probably due to the

  5. Presence of nitrites, nitrates, nitrosamines in the eggs of Intensively ...

    African Journals Online (AJOL)

    In this study, the presence and concentrations of nitrosamines and their precursors (nitrates and nitrites) in raw table eggs obtained from four layer-farms in Abeokuta, were analysed. Nitrosamines are highly toxic and carcinogenic group of chemicals that have the potential to be formed in the body through a process called ...

  6. Non-stationary temporal characterization of the temperature profile of a soil exposed to frost in south-eastern Canada

    Directory of Open Access Journals (Sweden)

    F. Anctil

    2008-05-01

    Full Text Available The objective of this work was to compare time and frequency fluctuations of air and soil temperatures (2-, 5-, 10-, 20- and 50-cm below the soil surface using the continuous wavelet transform, with a particular emphasis on the daily cycle. The analysis of wavelet power spectra and cross power spectra provided detailed non-stationary accounts with respect to frequencies (or periods and to time of the structure of the data and also of the relationships that exist between time series. For this particular application to the temperature profile of a soil exposed to frost, both the air temperature and the 2-cm depth soil temperature time series exhibited a dominant power peak at 1-d periodicity, prominent from spring to autumn. This feature was gradually damped as it propagated deeper into the soil and was weak for the 20-cm depth. Influence of the incoming solar radiation was also revealed in the wavelet power spectra analysis by a weaker intensity of the 1-d peak. The principal divergence between air and soil temperatures, besides damping, occurred in winter from the latent heat release associated to the freezing of the soil water and the insulation effect of snowpack that cease the dependence of the soil temperature to the air temperature. Attenuation and phase-shifting of the 1-d periodicity could be quantified through scale-averaged power spectra and time-lag estimations. Air temperature variance was only partly transferred to the 2-cm soil temperature time series and much less so to the 20-cm soil depth.

  7. Recent divergences in stratospheric water vapor measurements by frost point hygrometers and the Aura Microwave Limb Sounder

    Science.gov (United States)

    Hurst, Dale F.; Read, William G.; Vömel, Holger; Selkirk, Henry B.; Rosenlof, Karen H.; Davis, Sean M.; Hall, Emrys G.; Jordan, Allen F.; Oltmans, Samuel J.

    2017-01-01

    Balloon-borne frost point hygrometers (FPs) and the Aura Microwave Limb Sounder (MLS) provide high-quality vertical profile measurements of water vapor in the upper troposphere and lower stratosphere (UTLS). A previous comparison of stratospheric water vapor measurements by FPs and MLS over three sites - Boulder, Colorado (40.0° N); Hilo, Hawaii (19.7° N); and Lauder, New Zealand (45.0° S) - from August 2004 through December 2012 not only demonstrated agreement better than 1% between 68 and 26 hPa but also exposed statistically significant biases of 2 to 10% at 83 and 100 hPa (Hurst et al., 2014). A simple linear regression analysis of the FP-MLS differences revealed no significant long-term drifts between the two instruments. Here we extend the drift comparison to mid-2015 and add two FP sites - Lindenberg, Germany (52.2° N), and San José, Costa Rica (10.0° N) - that employ FPs of different manufacture and calibration for their water vapor soundings. The extended comparison period reveals that stratospheric FP and MLS measurements over four of the five sites have diverged at rates of 0.03 to 0.07 ppmv year−1 (0.6 to 1.5% year−1) from ~2010 to mid-2015. These rates are similar in magnitude to the 30-year (1980–2010) average growth rate of stratospheric water vapor (~ 1% year−1) measured by FPs over Boulder (Hurst et al., 2011). By mid-2015, the FP–MLS differences at some sites were large enough to exceed the combined accuracy estimates of the FP and MLS measurements. PMID:28966694

  8. Stationary Double Layers in a Collisionless Magnetoplasma

    DEFF Research Database (Denmark)

    Noriyoshi, Sato; Mieno, Tetsu; Hatakeyama, Rikizo

    1983-01-01

    Stationary double layers are generated in a magnetoplasma by applying potential differences between two heated plates on which the plasma is produced by surface ionization. By measuring the double-layer formation process, a localized potential drop is found to be formed initially in front...... of the plate on the low-potential side, being accompanied with current limitation. This localized potential drop moves along the plasma column, but finally stops and results in the formation of the stationary double layer in the presence of sufficient plasma supply from the plate on the high-potential side....

  9. Conserved S-Layer-Associated Proteins Revealed by Exoproteomic Survey of S-Layer-Forming Lactobacilli

    Science.gov (United States)

    Johnson, Brant R.; Hymes, Jeffrey; Sanozky-Dawes, Rosemary; Henriksen, Emily DeCrescenzo

    2015-01-01

    The Lactobacillus acidophilus homology group comprises Gram-positive species that include L. acidophilus, L. helveticus, L. crispatus, L. amylovorus, L. gallinarum, L. delbrueckii subsp. bulgaricus, L. gasseri, and L. johnsonii. While these bacteria are closely related, they have varied ecological lifestyles as dairy and food fermenters, allochthonous probiotics, or autochthonous commensals of the host gastrointestinal tract. Bacterial cell surface components play a critical role in the molecular dialogue between bacteria and interaction signaling with the intestinal mucosa. Notably, the L. acidophilus complex is distinguished in two clades by the presence or absence of S-layers, which are semiporous crystalline arrays of self-assembling proteinaceous subunits found as the outermost layer of the bacterial cell wall. In this study, S-layer-associated proteins (SLAPs) in the exoproteomes of various S-layer-forming Lactobacillus species were proteomically identified, genomically compared, and transcriptionally analyzed. Four gene regions encoding six putative SLAPs were conserved in the S-layer-forming Lactobacillus species but not identified in the extracts of the closely related progenitor, L. delbrueckii subsp. bulgaricus, which does not produce an S-layer. Therefore, the presence or absence of an S-layer has a clear impact on the exoproteomic composition of Lactobacillus species. This proteomic complexity and differences in the cell surface properties between S-layer- and non-S-layer-forming lactobacilli reveal the potential for SLAPs to mediate intimate probiotic interactions and signaling with the host intestinal mucosa. PMID:26475115

  10. Effect of extra-fine slag replacement on carbonation and frost salt scaling resistance of mortars[ACI SP-234-8

    Energy Technology Data Exchange (ETDEWEB)

    Copuroglu, O.; Fraaij, A.; Schlangen, E. [Delft Univ. of Technology, Delft (Netherlands). Dept. of Civil Engineering; Bijen, J. [INTRON (Netherlands)

    2006-07-01

    This study examined the effects of extra-fine slag (EFS) on the carbonation and frost salt scaling resistance of mortars at different replacement levels for 2 types of cements. In the first part of the examination, EFS replaced a certain amount of European CEM 3/B cement composed of 67 per cent slag with ordinary fineness. The second part examined the effect of EFS on microstructure and frost salt scaling resistance of mortars at different replacement levels in European normal portland cement CEM 1 32,5R. The average Blaine fineness of EFS was 500 m{sup 2}/kg. The water to cement ratio was maintained at 0.45. The carbonation resistance and pore structure of the cement mortars was examined. Carbonation resistance was measured using the phenolphthalein method after accelerated carbonation tests in a 3 per cent carbon dioxide chamber. Mercury intrusion porosimetry was used to study the pore structures. The chemical and physical properties of this cement were presented along with the obtained cement blends. The first part of the study showed that increasing the average fineness and total amount of slag results in a higher degrees of water uptake compared to the control sample. Therefore, it was claimed that the critical amount of normal portland cement clinker is important in terms of carbonation and frost salt scaling durability. It was concluded that an increasing EFS content lowers the scaling resistance. The effect is most evident when the replacement percentage is increased from 50 to 75 per cent. It was suggested that future studies should focus on the content of normal portland cement clinker, the hydration rate of clinker and slag, as well as the related activation of the slag. 10 refs., 5 tabs., 12 figs.

  11. Predicting the presence and cover of management relevant invasive plant species on protected areas.

    Science.gov (United States)

    Iacona, Gwenllian; Price, Franklin D; Armsworth, Paul R

    2016-01-15

    Invasive species are a management concern on protected areas worldwide. Conservation managers need to predict infestations of invasive plants they aim to treat if they want to plan for long term management. Many studies predict the presence of invasive species, but predictions of cover are more relevant for management. Here we examined how predictors of invasive plant presence and cover differ across species that vary in their management priority. To do so, we used data on management effort and cover of invasive plant species on central Florida protected areas. Using a zero-inflated multiple regression framework, we showed that protected area features can predict the presence and cover of the focal species but the same features rarely explain both. There were several predictors of either presence or cover that were important across multiple species. Protected areas with three days of frost per year or fewer were more likely to have occurrences of four of the six focal species. When invasive plants were present, their proportional cover was greater on small preserves for all species, and varied with surrounding household density for three species. None of the predictive features were clearly related to whether species were prioritized for management or not. Our results suggest that predictors of cover and presence can differ both within and across species but do not covary with management priority. We conclude that conservation managers need to select predictors of invasion with care as species identity can determine the relationship between predictors of presence and the more management relevant predictors of cover. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Basic Ozone Layer Science

    Science.gov (United States)

    Learn about the ozone layer and how human activities deplete it. This page provides information on the chemical processes that lead to ozone layer depletion, and scientists' efforts to understand them.

  13. VSWI Wetlands Advisory Layer

    Data.gov (United States)

    Vermont Center for Geographic Information — This dataset represents the DEC Wetlands Program's Advisory layer. This layer makes the most up-to-date, non-jurisdictional, wetlands mapping avaiable to the public...

  14. Frost resistant air-entrained concrete (XF3) with fly ash in hydraulic engineering; Frostbestaendige Luftporenbetone (XF3) mit Flugasche im Wasserbau

    Energy Technology Data Exchange (ETDEWEB)

    Brandl, J. [Max Boegl GmbH und Co. KG, Neumarkt (Germany)

    2008-07-01

    The Isar canal was refurbished in order to fulfil the requirements regarding frost resistance in the area of the changing water levels. Fly ash concretes from 80 to 120 kg fly ash per m{sup 3} concrete had been produced with which the air content was generated by addition of an air entraining agent. The fly ash concrete with air voids produced by using air entraining agents is resistant to freeze thaw changes and fulfils the requirements for a concrete of the exposure class XF3. (orig.)

  15. Layer-by-layer cell membrane assembly

    Science.gov (United States)

    Matosevic, Sandro; Paegel, Brian M.

    2013-11-01

    Eukaryotic subcellular membrane systems, such as the nuclear envelope or endoplasmic reticulum, present a rich array of architecturally and compositionally complex supramolecular targets that are as yet inaccessible. Here we describe layer-by-layer phospholipid membrane assembly on microfluidic droplets, a route to structures with defined compositional asymmetry and lamellarity. Starting with phospholipid-stabilized water-in-oil droplets trapped in a static droplet array, lipid monolayer deposition proceeds as oil/water-phase boundaries pass over the droplets. Unilamellar vesicles assembled layer-by-layer support functional insertion both of purified and of in situ expressed membrane proteins. Synthesis and chemical probing of asymmetric unilamellar and double-bilayer vesicles demonstrate the programmability of both membrane lamellarity and lipid-leaflet composition during assembly. The immobilized vesicle arrays are a pragmatic experimental platform for biophysical studies of membranes and their associated proteins, particularly complexes that assemble and function in multilamellar contexts in vivo.

  16. In The Presence of Technology

    DEFF Research Database (Denmark)

    Nortvig, Anne-Mette

    In a hybrid synchronous classroom that includes both on line and on campus students, technology plays a big part in the teaching. This paper attempts to analyse and discuss how the transparency of technology affects opportunities for the students to interact and for the teacher to be present in d...... of disembodied presence and presents different learning design experiments that have been developed in a physiotherapy e-learning program to deal with the experience of disembodied presence and to thematise the role of technology....

  17. Double layers in space

    International Nuclear Information System (INIS)

    Carlqvist, P.

    1982-01-01

    For more than a decade it has been realised that electrostatic double layers are likely to occur in space. The author briefly discusses the theoretical background of such double layers. Most of the paper is devoted to an account of the observational evidence for double layers in the ionosphere and magnetosphere of the Earth. Several different experiments are reviewed including rocket and satellite measurements and ground based observations. It is concluded that the observational evidence for double layers in space is very strong. The experimental results indicate that double layers with widely different properties may exist in space. (Auth.)

  18. Family presence during cardiopulmonary resuscitation.

    Science.gov (United States)

    Jabre, Patricia; Belpomme, Vanessa; Azoulay, Elie; Jacob, Line; Bertrand, Lionel; Lapostolle, Frederic; Tazarourte, Karim; Bouilleau, Guillem; Pinaud, Virginie; Broche, Claire; Normand, Domitille; Baubet, Thierry; Ricard-Hibon, Agnes; Istria, Jacques; Beltramini, Alexandra; Alheritiere, Armelle; Assez, Nathalie; Nace, Lionel; Vivien, Benoit; Turi, Laurent; Launay, Stephane; Desmaizieres, Michel; Borron, Stephen W; Vicaut, Eric; Adnet, Frederic

    2013-03-14

    The effect of family presence during cardiopulmonary resuscitation (CPR) on the family members themselves and the medical team remains controversial. We enrolled 570 relatives of patients who were in cardiac arrest and were given CPR by 15 prehospital emergency medical service units. The units were randomly assigned either to systematically offer the family member the opportunity to observe CPR (intervention group) or to follow standard practice regarding family presence (control group). The primary end point was the proportion of relatives with post-traumatic stress disorder (PTSD)-related symptoms on day 90. Secondary end points included the presence of anxiety and depression symptoms and the effect of family presence on medical efforts at resuscitation, the well-being of the health care team, and the occurrence of medicolegal claims. In the intervention group, 211 of 266 relatives (79%) witnessed CPR, as compared with 131 of 304 relatives (43%) in the control group. In the intention-to-treat analysis, the frequency of PTSD-related symptoms was significantly higher in the control group than in the intervention group (adjusted odds ratio, 1.7; 95% confidence interval [CI], 1.2 to 2.5; P=0.004) and among family members who did not witness CPR than among those who did (adjusted odds ratio, 1.6; 95% CI, 1.1 to 2.5; P=0.02). Relatives who did not witness CPR had symptoms of anxiety and depression more frequently than those who did witness CPR. Family-witnessed CPR did not affect resuscitation characteristics, patient survival, or the level of emotional stress in the medical team and did not result in medicolegal claims. Family presence during CPR was associated with positive results on psychological variables and did not interfere with medical efforts, increase stress in the health care team, or result in medicolegal conflicts. (Funded by Programme Hospitalier de Recherche Clinique 2008 of the French Ministry of Health; ClinicalTrials.gov number, NCT01009606.).

  19. Elevated CO{sub 2} and development of frost hardiness in Norway spruce (picea abies (L.) Karst.); Oekt CO{sub 2} og utvikling av frostherdighet i gran

    Energy Technology Data Exchange (ETDEWEB)

    Dalen, Lars Sandved

    1998-09-01

    This thesis discusses controlled laboratory experiments carried out to study the effects of CO{sub 2} pollution on Norwegian spruce. It was found that elevated CO{sub 2} increased height growth and biomass production. It slightly increased frost hardiness, but only at high nitrogen values. There was no evidence of adverse effects of elevated CO{sub 2} on the phenology of bud set and the development of frost hardiness. Although not statistically significant, there seemed to be a consistently higher concentration of soluble carbohydrates in one-season-old Norway spruce seedlings treated with elevated CO{sub 2}. This was not found in three-year-old seedlings grown in open top chambers, possibly indicating a down-regulation of photosynthesis or a transition from free to predetermined growth, and change in allocation of photosynthates with age. Treatment with high or low concentrations of CO{sub 2} and nitrogen fertilizer did not affect apoplastic chitinolytic activity during cold acclimation, nor were there any effects on antifreeze activity in these apoplastic extracts from cold acclimated needles. 149 refs., 21 figs., 8 tabs.

  20. Modeling the summertime Arctic cloudy boundary layer

    Energy Technology Data Exchange (ETDEWEB)

    Curry, J.A.; Pinto, J.O. [Univ. of Colorado, Boulder, CO (United States); McInnes, K.L. [CSIRO Division of Atmospheric Research, Mordialloc (Australia)

    1996-04-01

    Global climate models have particular difficulty in simulating the low-level clouds during the Arctic summer. Model problems are exacerbated in the polar regions by the complicated vertical structure of the Arctic boundary layer. The presence of multiple cloud layers, a humidity inversion above cloud top, and vertical fluxes in the cloud that are decoupled from the surface fluxes, identified in Curry et al. (1988), suggest that models containing sophisticated physical parameterizations would be required to accurately model this region. Accurate modeling of the vertical structure of multiple cloud layers in climate models is important for determination of the surface radiative fluxes. This study focuses on the problem of modeling the layered structure of the Arctic summertime boundary-layer clouds and in particular, the representation of the more complex boundary layer type consisting of a stable foggy surface layer surmounted by a cloud-topped mixed layer. A hierarchical modeling/diagnosis approach is used. A case study from the summertime Arctic Stratus Experiment is examined. A high-resolution, one-dimensional model of turbulence and radiation is tested against the observations and is then used in sensitivity studies to infer the optimal conditions for maintaining two separate layers in the Arctic summertime boundary layer. A three-dimensional mesoscale atmospheric model is then used to simulate the interaction of this cloud deck with the large-scale atmospheric dynamics. An assessment of the improvements needed to the parameterizations of the boundary layer, cloud microphysics, and radiation in the 3-D model is made.

  1. Carbon nanofiber growth on thin rhodium layers

    NARCIS (Netherlands)

    Chinthaginjala, J.K.; Unnikrishnan, S.; Smithers, Mark A.; Smithers, M.A.; Kip, Gerhardus A.M.; Lefferts, Leonardus

    2012-01-01

    A thinlayer of carbon nanofibers (CNFs) was synthesized on a thin polycrystalline rhodium (Rh) metal layer by decomposing ethylene in the presence of hydrogen. Interaction of Rh crystals with carbon results in fragmentation and formation of Rh-nanoparticles, facilitating CNF growth. CNFs are

  2. Coatings to prevent frost

    DEFF Research Database (Denmark)

    Lusada, Ricardo; Holberg, Stefan; Bennedsen, Jeanette Marianne Dalgaard

    2016-01-01

    at temperatures just below 0°C, for example at −4°C, is low. Freezing of a single drop on aluminum leads, however, to instant freezing of the complete surface. On hydrophobic coatings, such a freezing drop is isolated; the frozen area grows slowly. At −4°C surface temperature in a +12°C/90% relative humidity...... direction. Although the airflow compromised the anti-ice properties to some extent, the application of the hydrophobic coating in a heat recovery ventilation experiment extended the time interval between defrosting cycles by a factor of 2.3....

  3. Ciemat Relational Capital: Institutional Presence

    International Nuclear Information System (INIS)

    Vaquero Ortiz, E. M.; González Pineda, L. M.; Cascante Díaz, E.

    2015-01-01

    The resources in any organization for its activity development can be divided into two main groups: tangible assets and intangible assets. In recent decades there has been a recognition of the importance of the intangible assets as value generators for the development and growth of organizations. And the so called Relational Capital is among them Relational Capital arises from the relationship processes that an organization maintains with external agents. Thus, in the case of a public research institution, such as CIEMAT, it includes the relations with projects financing organizations, with partners and with customers (both public and private entities which are serviced), as well as the institutional presence understood as the participation in discussion and coordination forums (foundations, associations, committees…). This report presents a study of CIEMAT institutional presence in the year 2015.

  4. Breathing life into social presence

    DEFF Research Database (Denmark)

    Cowley, Stephen; Fester, Marie-Theres

    2018-01-01

    Whilst many studies focus on human-to-media interactions, this paper turns to how a multimodal medium influences human-to-human contact. By bringing together both radical embodied cognitive science (Chemero 2009) and dialogism (Linell 2009), the paper develops an anti-representationalist approach...... to the concept of social presence. We use an exploratory study of close friendships that maintain their interaction through the use of the mobile instant messaging service WhatsApp. In so doing, we describe texting as language-activity where people engage with each other by using resources from body, environment...... attention to this kind of heightened social presence that we choose to call “co-imagining”....

  5. Influência de M/C (M = Mo, Cu, Fe e W incorporado à camada difusora do eletrodo de difusão de gás frente à reação de oxidação de hidrogênio na presença de CO The effect of M/C (M = Mo, Cu, Fe and W in the diffusion layer of gas diffusion electrodes on the hydrogen oxidation reaction in the presence of carbon monoxide

    Directory of Open Access Journals (Sweden)

    Luis Gustavo da Silva Pereira

    2007-01-01

    Full Text Available The performance of proton exchange membrane fuel cells (PEMFC with Pt-based anodes is drastically lowered when CO-containing hydrogen is used to feed the system, because of the strong adsorption of CO on platinum. In the present work the effects of the presence of a conversion layer of CO to CO2 composed by several M/C materials (where M = Mo, Cu, Fe and W in gas diffusion anodes formed by Pt catalysts were investigated. The diffusion layers formed by Mo/C e W/C show good CO-tolerance, and this was attributed to the CO removal by parallel occurrence of the water-gas shift reaction and the so-called bifunctional mechanism.

  6. Multi-layers castings

    Directory of Open Access Journals (Sweden)

    J. Szajnar

    2010-01-01

    Full Text Available In paper is presented the possibility of making of multi-layers cast steel castings in result of connection of casting and welding coating technologies. First layer was composite surface layer on the basis of Fe-Cr-C alloy, which was put directly in founding process of cast carbon steel 200–450 with use of preparation of mould cavity method. Second layer were padding welds, which were put with use of TIG – Tungsten Inert Gas surfacing by welding technology with filler on Ni matrix, Ni and Co matrix with wolfram carbides WC and on the basis on Fe-Cr-C alloy, which has the same chemical composition with alloy, which was used for making of composite surface layer. Usability for industrial applications of surface layers of castings were estimated by criterion of hardness and abrasive wear resistance of type metal-mineral.

  7. A double layer review

    International Nuclear Information System (INIS)

    Block, L.P.

    1977-06-01

    A review of the main results on electrostatic double layers (sometimes called space charge layers or sheaths) obtained from theory, and laboratory and space experiments up to the spring of 1977 is given. By means of barium jets and satellite probes, double layers have now been found at the altitudes, earlier predicted theoretically. The general potential distribution above the auroral zone, suggested by inverted V-events and electric field reversals, is corroborated. (author)

  8. Layered plasma polymer composite membranes

    Science.gov (United States)

    Babcock, Walter C.

    1994-01-01

    Layered plasma polymer composite fluid separation membranes are disclosed, which comprise alternating selective and permeable layers for a total of at least 2n layers, where n is .gtoreq.2 and is the number of selective layers.

  9. Electroless atomic layer deposition

    Science.gov (United States)

    Robinson, David Bruce; Cappillino, Patrick J.; Sheridan, Leah B.; Stickney, John L.; Benson, David M.

    2017-10-31

    A method of electroless atomic layer deposition is described. The method electrolessly generates a layer of sacrificial material on a surface of a first material. The method adds doses of a solution of a second material to the substrate. The method performs a galvanic exchange reaction to oxidize away the layer of the sacrificial material and deposit a layer of the second material on the surface of the first material. The method can be repeated for a plurality of iterations in order to deposit a desired thickness of the second material on the surface of the first material.

  10. Astronomy: Ozone-like layer in an exoplanet atmosphere

    Science.gov (United States)

    Heng, Kevin

    2017-08-01

    The nature of exoplanetary atmospheres is hotly debated. The thermal spectrum of an exoplanet called a hot Jupiter reveals the presence of an analogue of Earth's ozone layer, although its composition is unknown. See Letter p.58

  11. Sonic Virtuality, Environment, and Presence

    DEFF Research Database (Denmark)

    Grimshaw, Mark

    2018-01-01

    The article presents a brief introduction to the concept of sonic virtuality, a view of sound as a multi-modal, emergent perception that provides a framework that has since been used to provide an explanation of the formation of environments. Additionally, the article uses such concepts to explain...... the phenomenon of presence, not only in virtual worlds but also in actual worlds. The view put forward is that environment is an emergent perception, formed from the hypothetical modelling of salient worlds of sensory things, and it is in the environment that we feel present. The article ends with some thoughts...

  12. Family presence at resuscitation attempts.

    Science.gov (United States)

    Jaques, Helen

    UK resuscitation guidelines suggest that parents and carers should be allowed to be present during a resuscitation attempt in hospital but no guidance is available regarding family presence when resuscitation takes place out of hospital. A new research study has suggested that relatives who were offered the opportunity to witness resuscitation were less likely to develop symptoms of post-traumatic stress disorder than those who were not given the chance. This article summarises the results of this study and provides an expert commentary on its conclusions.

  13. Electronic properties of bilayer phosphorene quantum dots in the presence of perpendicular electric and magnetic fields

    Science.gov (United States)

    Li, L. L.; Moldovan, D.; Xu, W.; Peeters, F. M.

    2017-10-01

    Using the tight-binding approach, we investigate the electronic properties of bilayer phosphorene (BLP) quantum dots (QDs) in the presence of perpendicular electric and magnetic fields. Since BLP consists of two coupled phosphorene layers, it is of interest to examine the layer-dependent electronic properties of BLP QDs, such as the electronic distributions over the two layers and the so-produced layer-polarization features, and to see how these properties are affected by the magnetic field and the bias potential. We find that in the absence of a bias potential only edge states are layer polarized while the bulk states are not, and the layer-polarization degree (LPD) of the unbiased edge states increases with increasing magnetic field. However, in the presence of a bias potential both the edge and bulk states are layer polarized, and the LPD of the bulk (edge) states depends strongly (weakly) on the interplay of the bias potential and the interlayer coupling. At high magnetic fields, applying a bias potential renders the bulk electrons in a BLP QD to be mainly distributed over the top or bottom layer, resulting in layer-polarized bulk Landau levels (LLs). In the presence of a large bias potential that can drive a semiconductor-to-semimetal transition in BLP, these bulk LLs exhibit different magnetic-field dependences, i.e., the zeroth LLs exhibit a linearlike dependence on the magnetic field while the other LLs exhibit a square-root-like dependence.

  14. The Frequency of Growing Season Frost in the Subalpine Environment (Medicine Bow Mountains, Southeastern Wyoming), The Interaction of Leaf Morphology and Infrared Radiational Cooling and the Effects of Freezing on Native Vegetation

    Science.gov (United States)

    1995-05-01

    inexpensive heated thermistor anemometer. Agric For Meteorol 8:395-405 Billings WD 1969. Vegetational pattern near timberline as affected by fire -snowdrift...Morawetz W and Gottsberger G 1977. Frost damage of cerrado plants in Botucatu, Brazil, as related to the geographical distribution of the species

  15. The Tebuconazole-based Protectant of Seeds “Bunker” Induces the Synthesis of Dehydrins During Cold Hardening and Increases the Frost Resistance of Wheat Seedlings

    Directory of Open Access Journals (Sweden)

    A.V. Korsukova

    2015-12-01

    Full Text Available Triazole derivatives are widely used in agriculture for seed protectant of cereals against seed and soil infection. Triazole derivatives can have an effect on the biochemical and physiological functions of plants. The tebuconazole-based protectant of seeds «Bunker» (content of tebuconazole 60 grams per liter, g/L is a systemic fungicide of preventive and therapeutic action. The effect of the seed treatment by «Bunker» preparation on the shoot growth and cell viability coleoptile, synthesis of dehydrins in shoots and frost resistance etiolated winter and spring wheat seedlings has been studied. It has been shown that treatment of winter and spring wheat seed by «Bunker» preparation induces similar concentration-dependent inhibition of the coleoptiles length. At the recommended dose (0,5 liter per tonne of seeds, L/t growth inhibition was 28 - 30%, at a concentration of 1 L/t – 33 - 36%, at a concentration of 1,5 L/t – 40 - 42%, at a concentration of 3 L/t – 43 - 47%, at a concentration of 4 L/t – 48 - 51% and at 5 L/t – 53 - 56%. The treatment of wheat seed by «Bunker» preparation had no phytotoxic effect on coleoptile cells in any of the studied concentrations, on the contrary, with increasing concentration of preparation observed the increase in cell viability, as measured by recovery of 2,3,5-triphenyltetrazolium chloride. We can assume that having retardant properties, tebuconazole not only inhibits the growth of plants, but also delays their aging. The treatment of seed protectant at a concentration of 1.5 L/t induced synthesis of the dehydrins with molecular masses about 19, 21, 22, 25 and 27 kD in winter wheat shoots and 18,6, 27 and 28,5 kD in spring wheat shoots during cold hardening. Among identified dehydrins the dehydrin of 27 kD is most significantly induced both in winter and spring wheat. The treatment of seed protectant «Bunker» in the same concentration increased the frost resistance of winter and spring wheat

  16. Synthesis of frost-like CuO combined graphene-TiO{sub 2} by self-assembly method and its high photocatalytic performance

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Dinh Cung Tien [Department of Advanced Materials Science & Engineering, Hanseo University, Seosan, Chungnam, 356-706 (Korea, Republic of); Cho, Kwang-Youn [Korea Institutes of Ceramic Engineering and Technology, Soho-ro, Jinju-Si, Gyeongsangnam-do (Korea, Republic of); Oh, Won-Chun, E-mail: wc_oh@hanseo.ac.kr [Department of Advanced Materials Science & Engineering, Hanseo University, Seosan, Chungnam, 356-706 (Korea, Republic of)

    2017-08-01

    Highlights: • The frost-like CuO nanoparticles (3–5 nm) combined with the small TiO{sub 2} rods (50–100 nm) are expected to have a high charge transfer effect from TiO{sub 2} to CuO. • In this study, ·OH and h{sup +} play a major role in the photocatalytic reaction than O{sub 2}·{sup –} or both hydroxyl and holes are the active species responsible under visible light irradiation. • The photocatalytic degradation of rhodamine B (RhB), methylene blue trihydrate (MB), and reactive black B (RBB) in an aqueous solution under visible light irradiation was observed by UV spectrophotometry after measurement of the decrease of their concentrations. CuO-graphene-TiO{sub 2} is expected to become a new potential material for photodegradation activity with excellent photodegradation. - Graphical abstract: TEM image of CuO-graphene (a and b), and CuO-graphene-TiO{sub 2} (c and d) composites. - Abstract: A novel material, frost-like CuO combined-graphene-TiO{sub 2} composite, was successfully synthesized using a self-assembly method. During the reaction, the loading of CuO and TiO{sub 2} nanoparticles on graphene sheets was achieved. The obtained CuO-graphene-TiO{sub 2} composite photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), and X-ray photoelectron spectroscopy (XPS). The frost-like CuO nanoparticles combined with the small TiO{sub 2} rods were successfully loaded on the transparent graphene sheets. The photocatalytic degradation of rhodamine B (RhB), methylene blue trihydrate (MB), and reactive black B (RBB) in an aqueous solution under visible light irradiation was observed by UV spectrophotometry after measurement of the decrease of their concentrations. Through the photocatalytic test and TOC results, the CuO-graphene-TiO{sub 2} is expected to

  17. Stable Boundary Layer Issues

    NARCIS (Netherlands)

    Steeneveld, G.J.

    2012-01-01

    Understanding and prediction of the stable atmospheric boundary layer is a challenging task. Many physical processes are relevant in the stable boundary layer, i.e. turbulence, radiation, land surface coupling, orographic turbulent and gravity wave drag, and land surface heterogeneity. The

  18. Double layer formation

    International Nuclear Information System (INIS)

    Singh, N.

    1982-01-01

    Results from several numerical simulations of the formation of double layers in plasmas with a constant potential drop across them are presented. Here the emphasis is mainly on plasma processes during the formation of double layers. The recurring formation of double layers, their propagation and associated current interruptions are observed when the electron current injected into the simulation region from the low potential side exceeds the electron thermal current. This recurring process is stopped (or delayed) when the electron current recuperation is inhibited by a small magnetic force on the electrons. The motion of double layers is examined and it is found that the motion is caused by the interruption of the ion current from the high potential side. The subsequent recovery of this current renders the double layer stationary. (author)

  19. Development of boundary layers

    International Nuclear Information System (INIS)

    Herbst, R.

    1980-01-01

    Boundary layers develop along the blade surfaces on both the pressure and the suction side in a non-stationary flow field. This is due to the fact that there is a strongly fluctuating flow on the downstream blade row, especially as a result of the wakes of the upstream blade row. The author investigates the formation of boundary layers under non-stationary flow conditions and tries to establish a model describing the non-stationary boundary layer. For this purpose, plate boundary layers are measured, at constant flow rates but different interferent frequency and variable pressure gradients. By introducing the sample technique, measurements of the non-stationary boundary layer become possible, and the flow rate fluctuation can be divided in its components, i.e. stochastic turbulence and periodical fluctuation. (GL) [de

  20. Improved electron transport layer

    DEFF Research Database (Denmark)

    2012-01-01

    The present invention provides: a method of preparing a coating ink for forming a zinc oxide electron transport layer, comprising mixing zinc acetate and a wetting agent in water or methanol; a coating ink comprising zinc acetate and a wetting agent in aqueous solution or methanolic solution......; a method of preparing a zinc oxide electron transporting layer, which method comprises: i) coating a substrate with the coating ink of the present invention to form a film; ii) drying the film; and iii) heating the dry film to convert the zinc acetate substantially to ZnO; a method of preparing an organic...... photovoltaic device or an organic LED having a zinc oxide electron transport layer, the method comprising, in this order: a) providing a substrate bearing a first electrode layer; b) forming an electron transport layer according to the following method: i) coating a coating ink comprising an ink according...

  1. Oxygen inhibition layer of composite resins: effects of layer thickness and surface layer treatment on the interlayer bond strength.

    Science.gov (United States)

    Bijelic-Donova, Jasmina; Garoushi, Sufyan; Lassila, Lippo V J; Vallittu, Pekka K

    2015-02-01

    An oxygen inhibition layer develops on surfaces exposed to air during polymerization of particulate filling composite. This study assessed the thickness of the oxygen inhibition layer of short-fiber-reinforced composite in comparison with conventional particulate filling composites. The effect of an oxygen inhibition layer on the shear bond strength of incrementally placed particulate filling composite layers was also evaluated. Four different restorative composites were selected: everX Posterior (a short-fiber-reinforced composite), Z250, SupremeXT, and Silorane. All composites were evaluated regarding the thickness of the oxygen inhibition layer and for shear bond strength. An equal amount of each composite was polymerized in air between two glass plates and the thickness of the oxygen inhibition layer was measured using a stereomicroscope. Cylindrical-shaped specimens were prepared for measurement of shear bond strength by placing incrementally two layers of the same composite material. Before applying the second composite layer, the first increment's bonding site was treated as follows: grinding with 1,000-grit silicon-carbide (SiC) abrasive paper, or treatment with ethanol or with water-spray. The inhibition depth was lowest (11.6 μm) for water-sprayed Silorane and greatest (22.9 μm) for the water-sprayed short-fiber-reinforced composite. The shear bond strength ranged from 5.8 MPa (ground Silorane) to 36.4 MPa (water-sprayed SupremeXT). The presence of an oxygen inhibition layer enhanced the interlayer shear bond strength of all investigated materials, but its absence resulted in cohesive and mixed failures only with the short-fiber-reinforced composite. Thus, more durable adhesion with short-fiber-reinforced composite is expected. © 2014 Eur J Oral Sci.

  2. Roughness effects on the double-layer charge capacitance : the case of Helmholtz layer induced roughness attenuation

    NARCIS (Netherlands)

    Palasantzas, G.; Backx, G.M.E.A.

    2003-01-01

    For electrical double layers, the presence of a Helmholtz layer could lead to electrode roughness attenuation. The latter is assumed of self-affine type which is characterized by the roughness amplitude w, the correlation length xi, and the roughness exponent H. For sufficiently rough metal

  3. Monitoring presence of chemical agents

    International Nuclear Information System (INIS)

    Preston, J.M.

    1984-01-01

    The specification describes a case for use with a hand-portable chemical agent detector for continuously monitoring an atmosphere for the presence of predetermined chemical agents. The detector having means for ionizing air samples and providing at an output terminal electrical signals representative of the mobility spectrum of ionized chemical vapours produced by the ionizing means. The case comprises means for defining a chamber in the case for supporting and removably enclosing the detector, means for communicating ambient atmosphere to the chamber, electrical circuit means in the case, the circuit means being adapted to be detachably connected to the detector output terminal when the detector is positioned in the chamber and being responsive to the electrical signals for producing an alarm signal when the signals detect a chemical agent concentration in the atmosphere exceeding a predetermined concentration level, and alarm means responsive to the alarm signal. (author)

  4. Measurements of the air flow field in the freezer compartment of a top-mount no-frost refrigerator: the effect of temperature

    Energy Technology Data Exchange (ETDEWEB)

    Lacerda, V.T.; Melo, C.; Barbosa, J.R.Jr. [Federal University of Santa Catarina, Florianopolis, SC (Brazil). Department of Mechanical Engineering; Duarte, P.O.O. [Multibras Eletrodomesticos S.A., Whirlpool Corporation, Joinville, SC (Brazil)

    2005-08-01

    The energy consumption of a household refrigerator is closely related to the distributions of temperature inside its compartments, Since, such distributions are dependent on the chilled air circulating inside the refrigerator, its energy consumption can be reduced and its efficiency improved through optimization of the air flow fields inside the compartments. In this work, particle image velocimetry (PIV) was used to measure velocity fields inside the freezer compartment of a commercial top-mount no-frost refrigerator at two critical vertical sections at three different temperatures levels. To perform the tests, a commercial unit was equipped with two specially constructed insulated windows which enables clear visualization of the flow field under real operating conditions. The results show that significant changes in the air flow distribution occur when the temperature is reduced. (author)

  5. A study of the air-side heat transfer and pressure drop characteristics of tube-fin 'no-frost' evaporators

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, Jader R. Jr.; Melo, Claudio; Hermes, Christian J.L.; Waltrich, Paulo J. [POLO - National Institute of Science and Technology of Refrigeration and Thermophysics, Federal University of Santa Catarina, 88040-900, Florianopolis, SC (Brazil)

    2009-09-15

    A study is presented on the influence of the air flow rate and surface geometry on the thermal-hydraulic performance of commercial tube-fin 'no-frost' evaporators. A specially constructed wind-tunnel calorimeter was used in the experiments from which data on the overall thermal conductance, pressure drop, Colburn j-factor and Darcy friction factor, f, were extracted. Eight different evaporator samples with distinct geometric characteristics, such as number of tube rows, number of fins and fin pitch were tested. Semi-empirical correlations for j and f are proposed in terms of the air-side Reynolds number and the finning factor. A discussion is presented on the performance of the evaporators with respect to specific criteria such as the pumping power as a function of heat transfer capacity and the volume of material in each evaporator. (author)

  6. High levels of nucleotide diversity and fast decline of linkage disequilibrium in rye (Secale cereale L. genes involved in frost response

    Directory of Open Access Journals (Sweden)

    Korzun Viktor

    2011-01-01

    Full Text Available Abstract Background Rye (Secale cereale L. is the most frost tolerant cereal species. As an outcrossing species, rye exhibits high levels of intraspecific diversity, which makes it well-suited for allele mining in genes involved in the frost responsive network. For investigating genetic diversity and the extent of linkage disequilibrium (LD we analyzed eleven candidate genes and 37 microsatellite markers in 201 lines from five Eastern and Middle European rye populations. Results A total of 147 single nucleotide polymorphisms (SNPs and nine insertion-deletion polymorphisms were found within 7,639 bp of DNA sequence from eleven candidate genes, resulting in an average SNP frequency of 1 SNP/52 bp. Nucleotide and haplotype diversity of candidate genes were high with average values π = 5.6 × 10-3 and Hd = 0.59, respectively. According to an analysis of molecular variance (AMOVA, most of the genetic variation was found between individuals within populations. Haplotype frequencies varied markedly between the candidate genes. ScCbf14, ScVrn1, and ScDhn1 were dominated by a single haplotype, while the other 8 genes (ScCbf2, ScCbf6, ScCbf9b, ScCbf11, ScCbf12, ScCbf15, ScIce2, and ScDhn3 had a more balanced haplotype frequency distribution. Intra-genic LD decayed rapidly, within approximately 520 bp on average. Genome-wide LD based on microsatellites was low. Conclusions The Middle European population did not differ substantially from the four Eastern European populations in terms of haplotype frequencies or in the level of nucleotide diversity. The low LD in rye compared to self-pollinating species promises a high resolution in genome-wide association mapping. SNPs discovered in the promoters or coding regions, which attribute to non-synonymous substitutions, are suitable candidates for association mapping.

  7. Mitochondrial energy-dissipating systems (alternative oxidase, uncoupling proteins, and external NADH dehydrogenase) are involved in development of frost-resistance of winter wheat seedlings.

    Science.gov (United States)

    Grabelnych, O I; Borovik, O A; Tauson, E L; Pobezhimova, T P; Katyshev, A I; Pavlovskaya, N S; Koroleva, N A; Lyubushkina, I V; Bashmakov, V Yu; Popov, V N; Borovskii, G B; Voinikov, V K

    2014-06-01

    Gene expression, protein synthesis, and activities of alternative oxidase (AOX), uncoupling proteins (UCP), adenine nucleotide translocator (ANT), and non-coupled NAD(P)H dehydrogenases (NDex, NDPex, and NDin) were studied in shoots of etiolated winter wheat (Triticum aestivum L.) seedlings after exposure to hardening low positive (2°C for 7 days) and freezing (-2°C for 2 days) temperatures. The cold hardening efficiently increased frost-resistance of the seedlings and decreased the generation of reactive oxygen species (ROS) during further cold shock. Functioning of mitochondrial energy-dissipating systems can represent a mechanism responsible for the decrease in ROS under these conditions. These systems are different in their response to the action of the hardening low positive and freezing temperatures. The functioning of the first system causes induction of AOX and UCP synthesis associated with an increase in electron transfer via AOX in the mitochondrial respiratory chain and also with an increase in the sensitivity of mitochondrial non-phosphorylating respiration to linoleic and palmitic acids. The increase in electron transfer via AOX upon exposure of seedlings to hardening freezing temperature is associated with retention of a high activity of NDex. It seems that NDex but not the NDPex and NDin can play an important role in maintaining the functional state of mitochondria in heterotrophic tissues of plants under the influence of freezing temperatures. The involvement of the mitochondrial energy-dissipating systems and their possible physiological role in the adaptation of winter crops to cold and frost are discussed.

  8. Arctic microbial and next-generation sequencing approach for bacteria in snow and frost flowers: selected identification, abundance and freezing nucleation

    Science.gov (United States)

    Mortazavi, R.; Attiya, S.; Ariya, P. A.

    2015-06-01

    During the spring of 2009, as part of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) campaign in Barrow, Alaska, USA, we examined the identity, population diversity, freezing nucleation ability of the microbial communities of five different snow types and frost flowers. In addition to the culturing and gene-sequence-based identification approach, we utilized a state-of-the-art genomic next-generation sequencing (NGS) technique to examine the diversity of bacterial communities in Arctic samples. Known phyla or candidate divisions were detected (11-18) with the majority of sequences (12.3-83.1%) belonging to one of the five major phyla: Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Cyanobacteria. The number of genera detected ranged from, 101-245. The highest number of cultivable bacteria was observed in frost flowers (FFs) and accumulated snow (AS) with 325 ± 35 and 314 ± 142 CFU m L-1, respectively; and for cultivable fungi 5 ± 1 CFU m L-1 in windpack (WP) and blowing snow (BS). Morphology/elemental composition and ice-nucleating abilities of the identified taxa were obtained using high resolution electron microscopy with energy-dispersive X-ray spectroscopy and ice nucleation cold-plate, respectively. Freezing point temperatures for bacterial isolates ranged from -20.3 ± 1.5 to -15.7 ± 5.6 °C, and for melted snow samples from -9.5 ± 1.0 to -18.4 ± 0.1 °C. An isolate belonging to the genus Bacillus (96% similarity) had ice nucleation activity of -6.8 ± 0.2 °C. Comparison with Montreal urban snow, revealed that a seemingly diverse community of bacteria exists in the Arctic with some taxa possibly originating from distinct ecological environments. We discuss the potential impact of snow microorganisms in the freezing and melting process of the snowpack in the Arctic.

  9. Evaporating brine from frost flowers with electron microscopy and implications for atmospheric chemistry and sea-salt aerosol formation

    Czech Academy of Sciences Publication Activity Database

    Yang, X.; Neděla, Vilém; Runštuk, Jiří; Ondrušková, G.; Krausko, J.; Vetráková, L'.; Heger, D.

    2017-01-01

    Roč. 17, č. 10 (2017), s. 6291-6303 ISSN 1680-7316 R&D Projects: GA ČR(CZ) GA14-22777S Institutional support: RVO:68081731 Keywords : experimental-computational approach * aqueous-solutions * boundary-layer * blowing snow * spectroscopic properties * low-temperatures Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering OBOR OECD: Meteorology and atmospheric sciences Impact factor: 5.318, year: 2016

  10. Layered inorganic solids

    Czech Academy of Sciences Publication Activity Database

    Čejka, Jiří; Morris, R. E.; Nachtigall, P.; Roth, Wieslaw Jerzy

    2014-01-01

    Roč. 43, č. 27 (2014), s. 10274-10275 ISSN 1477-9226 Institutional support: RVO:61388955 Keywords : layered inorganic solids * physical chemistry * catalysis Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.197, year: 2014

  11. The Bottom Boundary Layer

    Science.gov (United States)

    Trowbridge, John H.; Lentz, Steven J.

    2018-01-01

    The oceanic bottom boundary layer extracts energy and momentum from the overlying flow, mediates the fate of near-bottom substances, and generates bedforms that retard the flow and affect benthic processes. The bottom boundary layer is forced by winds, waves, tides, and buoyancy and is influenced by surface waves, internal waves, and stratification by heat, salt, and suspended sediments. This review focuses on the coastal ocean. The main points are that (a) classical turbulence concepts and modern turbulence parameterizations provide accurate representations of the structure and turbulent fluxes under conditions in which the underlying assumptions hold, (b) modern sensors and analyses enable high-quality direct or near-direct measurements of the turbulent fluxes and dissipation rates, and (c) the remaining challenges include the interaction of waves and currents with the erodible seabed, the impact of layer-scale two- and three-dimensional instabilities, and the role of the bottom boundary layer in shelf-slope exchange.

  12. Layered Fault Management Architecture

    National Research Council Canada - National Science Library

    Sztipanovits, Janos

    2004-01-01

    ... UAVs or Organic Air Vehicles. The approach of this effort was to analyze fault management requirements of formation flight for fleets of UAVs, and develop a layered fault management architecture which demonstrates significant...

  13. Addressing Ozone Layer Depletion

    Science.gov (United States)

    Access information on EPA's efforts to address ozone layer depletion through regulations, collaborations with stakeholders, international treaties, partnerships with the private sector, and enforcement actions under Title VI of the Clean Air Act.

  14. the Martian atmospheric boundary layer

    DEFF Research Database (Denmark)

    Petrosyan, A.; Galperin, B.; Larsen, Søren Ejling

    2011-01-01

    The planetary boundary layer (PBL) represents the part of the atmosphere that is strongly influenced by the presence of the underlying surface and mediates the key interactions between the atmosphere and the surface. On Mars, this represents the lowest 10 km of the atmosphere during the daytime...... atmosphere. To date, this region of the atmosphere has been studied directly, by instrumented lander spacecraft, and from orbital remote sensing, though not to the extent that is necessary to fully constrain its character and behavior. Current data strongly suggest that as for the Earth's PBL, classical...... of the modeling techniques used for the PBL on Earth are also being applied to the Martian PBL, including novel uses of very high resolution large eddy simulation methods. We conclude with those aspects of the PBL that require new measurements in order to constrain models and discuss the extent to which...

  15. Magnetic and magnetoresistance studies of nanometric electrodeposited Co films and Co/Cu layered structures: Influence of magnetic layer thickness

    International Nuclear Information System (INIS)

    Zsurzsa, S.; Péter, L.; Kiss, L.F.; Bakonyi, I.

    2017-01-01

    The magnetic properties and the magnetoresistance behavior were investigated for electrodeposited nanoscale Co films, Co/Cu/Co sandwiches and Co/Cu multilayers with individual Co layer thicknesses ranging from 1 nm to 20 nm. The measured saturation magnetization values confirmed that the nominal and actual layer thicknesses are in fairly good agreement. All three types of layered structure exhibited anisotropic magnetoresistance for thick magnetic layers whereas the Co/Cu/Co sandwiches and Co/Cu multilayers with thinner magnetic layers exhibited giant magnetoresistance (GMR), the GMR magnitude being the largest for the thinnest Co layers. The decreasing values of the relative remanence and the coercive field when reducing the Co layer thickness down to below about 3 nm indicated the presence of superparamagnetic (SPM) regions in the magnetic layers which could be more firmly evidenced for these samples by a decomposition of the magnetoresistance vs. field curves into a ferromagnetic and an SPM contribution. For thicker magnetic layers, the dependence of the coercivity (H c ) on magnetic layer thickness (d) could be described for each of the layered structure types by the usual equation H c =H co +a/d n with an exponent around n=1. The common value of n suggests a similar mechanism for the magnetization reversal by domain wall motion in all three structure types and hints also at the absence of coupling between magnetic layers in the Co/Cu/Co sandwiches and Co/Cu multilayers. - Highlights: • Electrodeposited nanoscale Co films and Co/Cu layered structures. • Co layer thickness (d) dependence of coercivity (H c ) and magnetoresistance. • H c depends on Co layer thickness according to H c =H co +a/d n with n around 1. • The common n value suggests a similar mechanism of magnetization reversal. • The common n value suggests the absence of coupling between magnetic layers.

  16. Magnetic and magnetoresistance studies of nanometric electrodeposited Co films and Co/Cu layered structures: Influence of magnetic layer thickness

    Energy Technology Data Exchange (ETDEWEB)

    Zsurzsa, S., E-mail: zsurzsa.sandor@wigner.mta.hu; Péter, L.; Kiss, L.F.; Bakonyi, I.

    2017-01-01

    The magnetic properties and the magnetoresistance behavior were investigated for electrodeposited nanoscale Co films, Co/Cu/Co sandwiches and Co/Cu multilayers with individual Co layer thicknesses ranging from 1 nm to 20 nm. The measured saturation magnetization values confirmed that the nominal and actual layer thicknesses are in fairly good agreement. All three types of layered structure exhibited anisotropic magnetoresistance for thick magnetic layers whereas the Co/Cu/Co sandwiches and Co/Cu multilayers with thinner magnetic layers exhibited giant magnetoresistance (GMR), the GMR magnitude being the largest for the thinnest Co layers. The decreasing values of the relative remanence and the coercive field when reducing the Co layer thickness down to below about 3 nm indicated the presence of superparamagnetic (SPM) regions in the magnetic layers which could be more firmly evidenced for these samples by a decomposition of the magnetoresistance vs. field curves into a ferromagnetic and an SPM contribution. For thicker magnetic layers, the dependence of the coercivity (H{sub c}) on magnetic layer thickness (d) could be described for each of the layered structure types by the usual equation H{sub c}=H{sub co}+a/d{sup n} with an exponent around n=1. The common value of n suggests a similar mechanism for the magnetization reversal by domain wall motion in all three structure types and hints also at the absence of coupling between magnetic layers in the Co/Cu/Co sandwiches and Co/Cu multilayers. - Highlights: • Electrodeposited nanoscale Co films and Co/Cu layered structures. • Co layer thickness (d) dependence of coercivity (H{sub c}) and magnetoresistance. • H{sub c} depends on Co layer thickness according to H{sub c}=H{sub co}+a/d{sup n} with n around 1. • The common n value suggests a similar mechanism of magnetization reversal. • The common n value suggests the absence of coupling between magnetic layers.

  17. Stability of mixing layers

    Science.gov (United States)

    Tam, Christopher; Krothapalli, A

    1993-01-01

    The research program for the first year of this project (see the original research proposal) consists of developing an explicit marching scheme for solving the parabolized stability equations (PSE). Performing mathematical analysis of the computational algorithm including numerical stability analysis and the determination of the proper boundary conditions needed at the boundary of the computation domain are implicit in the task. Before one can solve the parabolized stability equations for high-speed mixing layers, the mean flow must first be found. In the past, instability analysis of high-speed mixing layer has mostly been performed on mean flow profiles calculated by the boundary layer equations. In carrying out this project, it is believed that the boundary layer equations might not give an accurate enough nonparallel, nonlinear mean flow needed for parabolized stability analysis. A more accurate mean flow can, however, be found by solving the parabolized Navier-Stokes equations. The advantage of the parabolized Navier-Stokes equations is that its accuracy is consistent with the PSE method. Furthermore, the method of solution is similar. Hence, the major part of the effort of the work of this year has been devoted to the development of an explicit numerical marching scheme for the solution of the Parabolized Navier-Stokes equation as applied to the high-seed mixing layer problem.

  18. Layered tin dioxide microrods

    International Nuclear Information System (INIS)

    Duan Junhong; Huang Hongbo; Gong Jiangfeng; Zhao Xiaoning; Cheng Guangxu; Yang Shaoguang

    2007-01-01

    Single-crystalline layered SnO 2 microrods were synthesized by a simple tin-water reaction at 900 deg. C. The structural and optical properties of the sample were characterized by x-ray powder diffraction, energy-dispersive x-ray spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy, Raman scattering and photoluminescence (PL) spectroscopy. High resolution transmission electron microscopy studies and selected area electron diffraction patterns revealed that the layered SnO 2 microrods are single crystalline and their growth direction is along [1 1 0]. The growth mechanism of the microrods was proposed based on SEM, TEM characterization and thermodynamic analysis. It is deduced that the layered microrods grow by the stacking of SnO 2 sheets with a (1 1 0) surface in a vapour-liquid-solid process. Three emission peaks at 523, 569 and 626 nm were detected in room-temperature PL measurements

  19. Layered Systems Engineering Engines

    Science.gov (United States)

    Breidenthal, Julian C.; Overman, Marvin J.

    2009-01-01

    A notation is described for depicting the relationships between multiple, contemporaneous systems engineering efforts undertaken within a multi-layer system-of-systems hierarchy. We combined the concepts of remoteness of activity from the end customer, depiction of activity on a timeline, and data flow to create a new kind of diagram which we call a "Layered Vee Diagram." This notation is an advance over previous notations because it is able to be simultaneously precise about activity, level of granularity, product exchanges, and timing; these advances provide systems engineering managers a significantly improved ability to express and understand the relationships between many systems engineering efforts. Using the new notation, we obtain a key insight into the relationship between project duration and the strategy selected for chaining the systems engineering effort between layers, as well as insights into the costs, opportunities, and risks associated with alternate chaining strategies.

  20. Craters and Layers

    Science.gov (United States)

    2006-01-01

    11 March 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some typical relations between impact craters and light-toned, layered rock on Mars. The larger circular feature at the north (top) end of the image marks the location of a filled, buried crater on intermountain terrain north of Hellas Planitia. The larger crater at the southeast (lower right) corner formed by meteor impact into the layered material in which the buried crater is encased. The layered rock, in this case, has a light tone similar to the sedimentary rocks being explored by the Mars Exploration Rover, Opportunity, thousands of kilometers away in Sinus Meridiani. Location near: 24.9oS, 299.3oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  1. Inference of polymer adsorption from electrical double layer measurements : the silver iodide-polyvinyl alcohol system

    NARCIS (Netherlands)

    Koopal, L.K.

    1978-01-01

    The purpose of this study was to investigate how the double layer properties of charged particles are modified by the presence of adsorbed polymer molecules and to obtain information on the conformation of the polymer layer from the observed alterations in the double layer

  2. Frictional properties of the end-grafted polymer layer in presence of salt solution

    Science.gov (United States)

    Raftari, Maryam; Zhang, Zhenyu; Leggett, Graham J.; Geoghegan, Mark

    2012-02-01

    We have studied the frictional behaviour of grafted poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) films using friction force microscopy (FFM). The films were prepared on native oxide-terminated silicon substrates using the technique of atom transfer radical polymerization (ATRP). These brushes had constant grafting density (1.18 nm2), and of a thickness of ˜66 nm, as measured by ellipsometry. We show that single asperity contact mechanics (Johnson-Kendall-Roberts (JKR) and Derjaguin-M"uller-Toporov (DMT) models) as well as a linear (Amontons) relation between applied load and frictional load all apply to these systems depending on the concentration of salt and the nature of the FFM probe. Measurements were made using gold-coating and polymer functionalized silicon nitride triangular probes. Polymer functionalized probe included growth the PDMAEMA with same method on tips. The frictional behaviour are investigated between PDMAEMA and gold coated and PDMAEMA tips immersed in different concentrations of KCl, KBr and KI.

  3. Layered semiconductor neutron detectors

    Science.gov (United States)

    Mao, Samuel S; Perry, Dale L

    2013-12-10

    Room temperature operating solid state hand held neutron detectors integrate one or more relatively thin layers of a high neutron interaction cross-section element or materials with semiconductor detectors. The high neutron interaction cross-section element (e.g., Gd, B or Li) or materials comprising at least one high neutron interaction cross-section element can be in the form of unstructured layers or micro- or nano-structured arrays. Such architecture provides high efficiency neutron detector devices by capturing substantially more carriers produced from high energy .alpha.-particles or .gamma.-photons generated by neutron interaction.

  4. Layers in Crater Wall

    Science.gov (United States)

    2004-01-01

    22 January 2004 This January 2004 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows three distinct bands of layered material exposed in the wall of a south, middle-latitude meteor impact crater wall. Talus--debris shed from erosion of the wall--has piled up on the slopes below the layered outcrop. This picture is located near 45.5oS, 85.9oW, and covers an area 3 km (1.9 mi) wide. Sunlight illuminates the scene from the right/lower right.

  5. Demonstration cultivation of Salix in northern Sweden with a focus on frost resistance; Demonstrationsodling av Salix i Norrland med frosttolerans i fokus

    Energy Technology Data Exchange (ETDEWEB)

    Soederstroem, Yvonne

    2010-06-15

    This project is part of the Thermal Engineering Research Association's (Vaermeforsk) programme 'Crops from field to energy production' and the goal is to convince growers to begin cultivating Salix in the northern part of Sweden. The project will demonstrate whether it is possible to grow Salix and examine what type of Salix (the report refers to the different types as Tora, Karin and Gudrun) is most frost-resistant and resistant to insects, fungal infections and animals. The project is aimed primarily at landowners and energy companies. The results showed that growth at the demonstration plots was moderate and the establishment rate was considered good. Growth has been uneven across the fields. At Eriksgaard, about 75% of the plants survived the winter. Survival was determined by the number of plants missing and dead. Additional plants were planted at the sites in 2009. No major insect or leaf fungus attacks were noted at either Eriksgaard or Soergaard, but they both experienced grazing from deer and elk. The rating showed that the herbicide treatment was not sufficient on the demonstration fields. For this reason, a comparison of average lengths was performed of Gudrun in Bodum, where the weeds had not grown as much. The comparison showed that the difference in growth was not significant in the autumn 2008, but the plants in Bodum had grown more by autumn 2009. Topping was not performed in the spring 2009 so that the plants would have an opportunity to grow higher than the weeds and the plants would have an opportunity to have a growth spurt. A comparison of Tora, Karin and Gudrun in Roedoen showed moderate growth for the three types. There were variations in the rows and across the field, mostly for Tora and Karin. Gudrun had lower, but more consistent growth across the field. During the summer 2009, survival was rated for the plants in Roedoen. This rating showed that 90% of Tora, 60% of Karin and 70% of Gudrun had survived the winter. The Salix

  6. Comparative Analysis of Transcriptomes of Macrophage Revealing the Mechanism of the Immunoregulatory Activities of a Novel Polysaccharide Isolated fromBoletus speciosusFrost.

    Science.gov (United States)

    Ding, Xiang; Zhu, Hongqing; Hou, Yiling; Hou, Wanru; Zhang, Nan; Fu, Lei

    2017-01-01

    The mechanism of the immunoregulatory activities of polysaccharide is still not clear. Here, we performed the B-cell, T-cell, and macrophage cell proliferation, the cell cycle analysis of macrophage cells, sequenced the transcriptomes of control group macrophages, and Boletus speciosus Frost polysaccharide (BSF-1) group macrophages using Illumina sequencing technology to identify differentially expressed genes (DEGs) to determine the molecular mechanisms of immunomodulatory activity of BSF-1 in macrophages. These results suggested that BSF-1 could promote the proliferation of B-cell, T-cell, and macrophages, promote the proliferation of macrophage cells by abolishing cell cycle arrests in the G0/G1 phases, and promote cell cycle progression in S-phase and G2/M phase, which might induce cell division. A total of 12,498,414 and 11,840,624 bp paired-end reads were obtained for the control group and BSF-1 group, respectively, and they corresponded to a total size of 12.5 G bp and 11.8 G bp, respectively, after the low-quality reads and adapter sequences were removed. Approximately 81.83% of the total number of genes (8,257) were expressed reads per kilobase per million mapped reads (RPKM ≥1) and more than 1366 genes were highly expressed (RPKM >60) in the BSF-1 group. A gene ontology-enrichment analysis generated 13,042 assignments to cellular components, 13,094 assignments to biological processes, and 13,135 assignments to molecular functions. A Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that the mitogen-activated protein kinase (MAPK) signaling pathways are significantly enriched for DEGs between the two cell groups. An analysis of transcriptome resources enabled us to examine gene expression profiles, verify differential gene expression, and select candidate signaling pathways as the mechanisms of the immunomodulatory activity of BSF-1. Based on the experimental data, we believe that the significant antitumor activities of BSF-1 in

  7. Comparative Analysis of Transcriptomes of Macrophage Revealing the Mechanism of the Immunoregulatory Activities of a Novel Polysaccharide Isolated from Boletus speciosus Frost

    Science.gov (United States)

    Ding, Xiang; Zhu, Hongqing; Hou, Yiling; Hou, Wanru; Zhang, Nan; Fu, Lei

    2017-01-01

    Background: The mechanism of the immunoregulatory activities of polysaccharide is still not clear. Materials and Methods: Here, we performed the B-cell, T-cell, and macrophage cell proliferation, the cell cycle analysis of macrophage cells, sequenced the transcriptomes of control group macrophages, and Boletus speciosus Frost polysaccharide (BSF-1) group macrophages using Illumina sequencing technology to identify differentially expressed genes (DEGs) to determine the molecular mechanisms of immunomodulatory activity of BSF-1 in macrophages. Results: These results suggested that BSF-1 could promote the proliferation of B-cell, T-cell, and macrophages, promote the proliferation of macrophage cells by abolishing cell cycle arrests in the G0/G1 phases, and promote cell cycle progression in S-phase and G2/M phase, which might induce cell division. A total of 12,498,414 and 11,840,624 bp paired-end reads were obtained for the control group and BSF-1 group, respectively, and they corresponded to a total size of 12.5 G bp and 11.8 G bp, respectively, after the low-quality reads and adapter sequences were removed. Approximately 81.83% of the total number of genes (8,257) were expressed reads per kilobase per million mapped reads (RPKM ≥1) and more than 1366 genes were highly expressed (RPKM >60) in the BSF-1 group. A gene ontology-enrichment analysis generated 13,042 assignments to cellular components, 13,094 assignments to biological processes, and 13,135 assignments to molecular functions. A Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that the mitogen-activated protein kinase (MAPK) signaling pathways are significantly enriched for DEGs between the two cell groups. Conclusion: An analysis of transcriptome resources enabled us to examine gene expression profiles, verify differential gene expression, and select candidate signaling pathways as the mechanisms of the immunomodulatory activity of BSF-1. Based on the experimental data, we

  8. High enthalpy hypersonic boundary layer flow

    Science.gov (United States)

    Yanow, G.

    1972-01-01

    A theoretical and experimental study of an ionizing laminar boundary layer formed by a very high enthalpy flow (in excess of 12 eV per atom or 7000 cal/gm) with allowance for the presence of helium driver gas is described. The theoretical investigation has shown that the use of variable transport properties and their respective derivatives is very important in the solution of equilibrium boundary layer equations of high enthalpy flow. The effect of low level helium contamination on the surface heat transfer rate is minimal. The variation of ionization is much smaller in a chemically frozen boundary layer solution than in an equilibrium boundary layer calculation and consequently, the variation of the transport properties in the case of the former was not essential in the integration. The experiments have been conducted in a free piston shock tunnel, and a detailed study of its nozzle operation, including the effects of low levels of helium driver gas contamination has been made. Neither the extreme solutions of an equilibrium nor of a frozen boundary layer will adequately predict surface heat transfer rate in very high enthalpy flows.

  9. Layers in Melas Chasma

    Science.gov (United States)

    2006-01-01

    [figure removed for brevity, see original site] Click on image for larger annotated version This scene of layered deposits is from Melas Chasma, part of the Valles Marineris valley network. The area consists of a series of plateaus and cliffs that form a step-like terrain similar to the Grand Staircase-Escalante region of southwest Utah. The upper-right half of the image covers the highest plateau, and lower cliffs and plateaus step down in elevation toward the lower left of the image. Dunes of dark sand commonly cover the flat plateaus and distinct layers of bedrock are exposed in the cliffs. The orientations of these layers may help scientists to understand how the layers formed and the kind of environment that the layers formed in. Black rectangles on the left side of the image are areas where the image data was lost during transmission from Mars Reconnaissance Orbiter to Earth. This subscene [above] shows a series of boulder tracks on the left side of the image. The boulders fell from the cliffs above and left behind a series of small depressions. Each depression was made as the boulder bounced and rolled along the surface. In many cases, the tracks can be followed to the specific boulder that made them. Also visible in this subscene are cross-sections through the layered bedrock. This bedrock likely formed through settling of sand-sized particles out of the air or out of a body of water that has since drained away. These layers are 'cross-bedded', which means that subsequent layers are not parallel to each other but are instead oriented at an angle to other layers. The fact that these layers are cross-bedded indicates that the sand-sized particles were moved horizontally along the surface as they settled, just like sand dunes or ripples at the bottom of a stream. The size and shape of these cross-beds may help scientists to determine if the layers formed underwater or on land. Image PSP_001377_1685 was taken by the High Resolution Imaging Science Experiment

  10. Black layers on historical architecture.

    Science.gov (United States)

    Toniolo, Lucia; Zerbi, Carlotta M; Bugini, Roberto

    2009-03-01

    separation is particularly evident in 'recent' crust, where the sulphation process is more active. Black compact deposits show a higher porosity than black crusts because gypsum is not coming from the chemical corrosion of the substrate but from outside; actually, in the former case, the substrate is sound. Encrustations show a highly regular crystal organisation of gypsum (close packed tabular crystals) that cannot be traced back to casual atmospheric deposit or to corrosion of the substrate but rather to the crystallisation of a solution coming from an external source. Also in this case, the marble is sound; evidence of the effect of some protection treatment is pointed out. In spite of the apparent similarity of the examined samples, analytical results have evidenced three main types of black crusts: black crust with decayed substrate, compact deposit and black encrustation showing a sound substrate underneath. Experimental evidence of calcite grains sulphation in progress, taking place according to a model recently proposed, has been observed. Sulphation process is prevented where particular conservation treatments had been applied in the past. New experimental studies can be focussed to understand the specific conditions (measurements of micro-climatic and thermodynamic parameters) and mechanisms for black crusts formation in situ. The problem of the kinetic of the sulphation process of marble, the assessment of black layers formation in the case of different carbonate stone materials and the study of acid attack in presence of surface protecting layers deserve further investigation.

  11. BILATERAL KEY COMPARISON SIM.T-K6.5 ON HUMIDITY STANDARDS IN THE DEW/FROST-POINT TEMPERATURE RANGE FROM −30 °C TO +20 °C

    Science.gov (United States)

    Meyer, C.W.; Solano, A.

    2016-01-01

    A Regional Metrology Organization (RMO) Key Comparison of dew/frost point temperatures over the range −30 °C TO +20 °C was carried out by the National Institute of Standards and Technology (NIST, USA) and the Laboratorio Costarricense de Metrología (LACOMET, Costa Rica), between February 2015 and August 2015. The results of this comparison are reported here, along with descriptions of the humidity laboratory standards for NIST and LACOMET and the uncertainty budget for these standards. This report also describes the protocol for the comparison and presents the data acquired. The results are analyzed, determining the degree of equivalence between the dew/frost-point standards of NIST and LACOMET. PMID:28066029

  12. Asymmetric polymeric membranes containing a metal-rich dense layer with a controlled thickness and method of making same

    KAUST Repository

    Peinemann, Klaus-Viktor

    2016-01-21

    A structure, and methods of making the structure are provided in which the structure can include: a membrane having a first layer and a second layer, the first layer comprising polymer chains formed with coordination complexes with metal ions, and the second layer consisting of a porous support layer formed of polymer chains substantially, if not completely, lacking the presence of metal ions. The structure can be an asymmetric polymeric membrane containing a metal-rich layer as the first layer. In various embodiments the first layer can be a metal-rich dense layer. The first layer can include pores. The polymer chains of the first layer can be closely packed. The second layer can include a plurality of macro voids and can have an absence of the metal ions of the first layer.

  13. Layer-Cake Earth

    Science.gov (United States)

    Tedford, Rebecca; Warny, Sophie

    2006-01-01

    In this article, the authors offer a safe, fun, effective way to introduce geology concepts to elementary school children of all ages: "coring" layer cakes. This activity introduces the concepts and challenges that geologists face and at the same time strengthens students' inferential, observational, and problem-solving skills. It also addresses…

  14. Layered double hydroxides

    DEFF Research Database (Denmark)

    López Rayo, Sandra; Imran, Ahmad; Hansen, Hans Chr. Bruun

    2017-01-01

    A novel zinc (Zn) fertilizer concept based on Zn doped layered double hydroxides (Zn-doped Mg-Fe-LDHs) has been investigated. Zn-doped Mg-Fe-LDHs were synthetized, their chemical composition was analyzed and their nutrient release was studied in buffered solutions with different pH values. Uptake...

  15. Physical layer network coding

    DEFF Research Database (Denmark)

    Fukui, Hironori; Popovski, Petar; Yomo, Hiroyuki

    2014-01-01

    Physical layer network coding (PLNC) has been proposed to improve throughput of the two-way relay channel, where two nodes communicate with each other, being assisted by a relay node. Most of the works related to PLNC are focused on a simple three-node model and they do not take into account...

  16. Our Shrinking Ozone Layer

    Indian Academy of Sciences (India)

    Depletion of the Earth's ozone layer is one of the major environmental concerns for the new millennium having serious implications on human health, agriculture and cli- mate. In the past decades, research by the international scientific community has been directed towards under- standing the impact of human interference ...

  17. Reflection of presence: toward more natural and responsive telecollaboration

    Science.gov (United States)

    Agamanolis, Stefan; Westner, Alex; Bove, V. Michael, Jr.

    1998-02-01

    THe purpose of reflection of presence is to create a framework for a telepresence environment that intelligently responds and adapts itself to its inhabitants in order to enhance interpersonal communication or also reflections of the other remotely-located participants, just as if every one is standing in the same room looking at each other through a real mirror. Using visual and auditory cues, segmented images of participants are dynamically layered into a single display using varying transparency, position and scale to reflect center of attention and degree of presence. Wireless tangible interfaces allow participants to customize their shared space and collaboratively manipulate and annotate media objects in the background. The system is novel in that it is implemented totally as a set of cooperating scripts instead of through a low-level programming language, enabling rapid experimental changes in the behavior of the prototype.

  18. Effects of spring frosts in selected apple and pear orchards in the Lublin region in the years 2000, 2005 and 2007. Part I. Experiment at EF Felin. Part II. Selected production orchards

    Directory of Open Access Journals (Sweden)

    Tomasz Lipa

    2012-12-01

    Full Text Available Data concerning the effect of spring frosts on the survival of flower buds of several apple and pear cultivars, as well as on the damage caused by spring frosts to apple fruit are presented in the present paper. Observations were conducted in experimental and commercial orchards in the Lublin area in the years 2000, 2005 and 2007. The lowest temperature in spring in the consecutive years occurred on the following dates: 2000 - 3rd and 4th May, 2005 - 1st April and 22nd May, and 2007 - 2nd and 4th May. The most serious damages of buds were found in apple trees of Red Boskoop, Rubin and Jonagold cvs. grown in the experimental orchard in Felin (Lublin (this was an average value for the years 2000 and 2007, whereas the buds of the late flowering cultivars of Golden Delicious Smoothee, Royal Gala and Ligol survived with significantly lesser damages. These observations generally confirmed those made in commercial orchards in 2005 and 2007, in which buds of cv. Elise also showed high resistance to spring frosts. Pear trees of cv. Concorde showed low damage to flower buds in 2007 and produced a reasonably good crop. Fruits of cv. Jonagold and its mutations Wilmuta, Jonica, Decosta and Rubinstar proved to be very sensitive to spring frosts, as well as fruits of cv. Lired. The positive influence of the Polish rootstock P60 on flower bud survival was observed in the year 2000. However, this was not confirmed in 2007, thus further observations are necessary to check these effects.

  19. Double layers - theory and experiment

    International Nuclear Information System (INIS)

    Torven, S.

    1980-06-01

    A survey is given of recent investigations of electric double layers in low density plasmas. The existence of double layers is now well established in both magnetized and unmagnetized plasmas. Laboratory experiments and numerical simulations show that double layers coexist with waves and fluctuations as expected in view of the particle beams which are formed in the layer. Under certain conditions the level of the fluctuations is small and experimental results then compare favourably with stationary double layer models. Significant progress on layer formation processes has been made, but further investigations are required to predict under what conditions double layers will form in different types of plasmas. (author)

  20. Variability of the Mixed-Layer Height Over Mexico City

    Science.gov (United States)

    García-Franco, J. L.; Stremme, W.; Bezanilla, A.; Ruiz-Angulo, A.; Grutter, M.

    2018-02-01

    The diurnal and seasonal variability of the mixed-layer height in urban areas has implications for ground-level air pollution and the meteorological conditions. Measurements of the backscatter of light pulses with a commercial lidar system were performed for a continuous period of almost six years between 2011 and 2016 in the southern part of Mexico City. The profiles were temporally and vertically smoothed, clouds were filtered out, and the mixed-layer height was determined with an ad hoc treatment of both the filtered and unfiltered profiles. The results are in agreement when compared with values of mixed-layer height reconstructed from, (i) radiosonde data, and (ii) surface and vertical column densities of a trace gas. The daily maxima of the mean mixed-layer height reach values > 3 km above ground level in the months of March-April, and are clearly lower (pollution episodes and the height of the mixed layer. The growth rate of the convective mixed-layer height has a seasonal behaviour, which is characterized together with the mixed-layer-height anomalies. A clear residual layer is evident from the backscattered signals recorded in days with specific atmospheric conditions, but also from the cloud-filtered mean diurnal profiles. The occasional presence of a residual layer results in an overestimation of the reported mixed-layer height during the night and early morning hours.