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Situ Observations (situ + observation)
Selected AbstractsIn Situ Observation of Dynamic Recrystallization in the Bulk of Zirconium Alloy (Adv. Eng.ADVANCED ENGINEERING MATERIALS, Issue 8 2009Mater. The cover shows the in-situ diffraction setup. A fine synchrotron beam transmits the sample situated in a (heated) load frame and scatters into Debye-Scherrer cones. Large crystallites map onto spots onto the 2D detector rather than continuous rings. In the background, the intensity distribution of one selected reflection - here beta-Zr 110 - is plotted in color scale as a function of azimuthal angle (horizontal axis) and time (vertical axis) revealing the different states during thermo-mechanical processing. More details can be found in the article by K.-D. Liss on page 637. [source] In Situ Observation of Dynamic Recrystallization in the Bulk of Zirconium Alloy,ADVANCED ENGINEERING MATERIALS, Issue 8 2009Klaus-Dieter Liss Dynamic recrystallization and related effects have been followed in situ and in real time while a metal undergoes rapid thermo-mechanical processing. Statistics and orientation correlations of embedded/bulk material grains were deduced from two-dimensional X-ray diffraction patterns and give deep insight into the formation of the microstructure. Applications are relevant in materials design, simulation, and in geological systems. [source] Surface free energies of isotactic polybutene-1 tetragonal and trigonal crystals: the role of conformational entropy of side chainsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Motoi Yamashita Lateral and end surface free energies of melt-crystallized isotactic polybutene-1 (it-PB1) trigonal and tetragonal crystals have been determined by small-angle X-ray scattering and in situ observation of the crystal growth kinetics. The lateral surface free energy , of the trigonal phase is about seven times as large as the value ,Hoff calculated according to Hoffman's equation [Hoffman (1992). Polymer, 33, 2643,2644], while that of the tetragonal phase is roughly in agreement with the estimation. The discrepancy between the values of , and ,Hoff for the trigonal phase can be attributed to the loss of conformational entropy of the ethyl side chains of it-PB1. [source] Determination of ,, solution temperature in Re-rich Ni-base superalloy by small-angle neutron scatteringJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2001Pavel Strunz A harmful segregation of heavy elements (e.g. W, Mo, Re) during solidification of Ni-base superalloys can only be eliminated by using a homogenizing heat treatment, which needs to be carried out in the single-phase (,) field above the ,, solvus temperature but below the solidus temperature. Small-angle neutron scattering (SANS) was employed for in situ observation of the dissolution of precipitates in an Re-rich superalloy. The temperature dependence of the relative volume fraction and the size distribution of smaller ,, precipitates, and the specific surface of large inhomogeneities as well as some other parameters were determined from the two-dimensional scattering curves measured for as-cast and heat-treated samples. Overlap of the incipient melting region with the region where a certain amount of precipitates remained undissolved was observed, thus complicating a determination of the temperature at which all ,, precipitates are already dissolved. Nevertheless, conclusions about the temperature at which the precipitates dissolve and about the temperature at which the incipient melting starts could be formulated. The total scattering probability is suggested as the measure of the overall homogeneity of the distribution of elements in the sample. The temperature dependence of this parameter indicates the optimum solution procedure. [source] Plasticization and spraying of poly (DL-lactic acid) using supercritical carbon dioxide: control of particle sizeJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2004Jianyuan Hao Abstract Exposure of poly(DL-lactic acid) (PDLLA), and related polymers, to supercritical CO2 (scCO2) at or below, physiological temperatures leads to very effective plasticization and liquefying of the polymers. The phenomenon arises from the high solubility and interaction of the scCO2 in the polymer. Under these unique conditions, temperature and solvent labile molecules can be mixed efficiently into the liquefied polymer. This liquefied polymer/drug/CO2 mixture can then be sprayed into a collecting chamber, and during this process particles of drug-loaded polymer are formed. This process is very different from rapid expansion and antisolvent based techniques that have been previously reported. In this article, we describe a method of controlling particle size during the spray process by introducing a backpressure of N2 in the collecting chamber. This backpressure dynamically regulates the loss of CO2 from the issuing polymer/CO2 mixture, leading to control over sprayed particle size. In situ observation of the viscosity of the plasticized polymer indicates that a backpressure of 68 bar or greater is necessary to ensure the production of fine particles. The influences of backpressure and saturation temperature on particle size for the sprayed products are discussed in terms of observed PDLLA/CO2 mixture viscosities. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93: 1083,1090, 2004 [source] In situ observation of water distribution and behaviour in a polymer electrolyte fuel cell by synchrotron X-ray imagingJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2008Taihei Mukaide In situ visualization of the distribution and behaviour of water in a polymer electrolyte fuel cell during power generation has been demonstrated using a synchrotron X-ray imaging technique. Images were recorded using a CCD detector combined with a scintillator (Gd2O2S:Tb) and relay lens system, which were placed at 2.0,m or 2.5,m from the fuel cell. The images were measured continuously before and during power generation, and data on cell performance was recorded. The change of water distribution during power generation was obtained from X-ray images normalized with the initial state of the fuel cell. Compared with other techniques for visualizing the water in fuel cells, this technique enables the water distribution and behaviour in the fuel cell to be visualized during power generation with high spatial resolution. In particular, the effects of the specifications of the gas diffusion layer on the cathode side of the fuel cell on the distribution of water were efficiently identified. This is a very powerful technique for investigating the mechanism of water flow within the fuel cell and the relationship between water behaviour and cell performance. [source] Elastic Indentation Response of Float Glass SurfacesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2010Andrea M. Muller Instrumented Hertzian indentation was used to evaluate the reduced elastic modulus and cone-crack initiation forces for the as-received surfaces of commercial float glasses. Custom-built indentation equipment with the capability of acoustic emission detection was used to monitor continuously the load and depth of penetration at the microscopic scale for forces up to 1 kN. Equipment verification was performed using a reference material, GE 124. The air and tin surfaces of commercial soda,lime,silica and borosilicate float glasses were tested to determine any difference in indentation response for the elastic and fracture behavior of as-received surfaces. Information obtained from the analysis of the load,displacement curves and from the visual inspection of the indentation sites was used to determine the elastic modulus, and the conditions for the onset of cone cracking as a function of surface roughness. The reduced modulus results were verified using additional equipment that allowed the in situ observation of the contact area during loading and unloading. The results showed that there was no difference in the reduced modulus data for the air and tin surfaces for the range of surface displacements studied. The same conclusions were found for cone-cracking loads on as-received surfaces but tests on abraded surfaces showed that the tin surfaces had slightly more resistance to cone cracking than the air surfaces. [source] Colonisation pattern of nonpathogenic Fusarium oxysporum, a potential biological control agent, in roots and rhizomes of tissue cultured Musa plantletsANNALS OF APPLIED BIOLOGY, Issue 1 2006P. Paparu Abstract Under laboratory conditions, nonpathogenic, endophytic Fusarium oxysporum inflicts high mortality among banana weevils and nematodes. Following inoculation into banana (Musa spp.) tissue cultured plants, successful colonisation is necessary for efficient biological control of these pests. The pattern of root and rhizome colonisation by two nonpathogenic Ugandan F. oxysporum strains (V2w2 and III4w1) in cv. Nabusa (AAA-EA) was investigated using light microscopy. Percentage of colonisation in the rhizomes (93%) was higher than in the roots (56%), but hyphal density in the roots (0.30 mm,2) was higher than in the rhizomes (0.21 mm,2). The root bases were better colonised (76%) than root midsections (53%) or tips (39%). Both the strains colonised the roots and the rhizomes, with numerous hyphae infecting the hypodermis but fewer infecting the cortex. Colonisation of vascular tissues was not recorded. Despite the presence of hyphae in intercellular and intracellular spaces of the roots and the rhizomes, normal cell structure was observed. Our report provides the first in situ observation and quantification of endophyte colonisation in banana. The study demonstrated the ability of F. oxysporum strains V2w2 and III4w1 to penetrate intact host tissues and recolonise the host internally upon inoculation, an important step for their suitability as biological control agents. [source] Unravelling the microbial role in ooid formation , results of an in situ experiment in modern freshwater Lake Geneva in SwitzerlandGEOBIOLOGY, Issue 4 2008K. PLEE ABSTRACT The microbial role in the formation of the cortex of low-Mg calcite freshwater ooids in western part of Lake Geneva in Switzerland has been suggested previously, but not demonstrated conclusively. Early work mostly concentrated in hypersaline milieus, and hence little is known about their genesis in freshwater environments. We designed an in situ experiment to mimic the natural process of low-Mg calcite precipitation. A special device was placed in the ooid-rich bank of the lake. It contained frosted glass (SiO2) slides, while quartz (SiO2) is the most abundant mineral composition of ooid nuclei that acted as artificial substrates to favour microbial colonization. Microscopic inspection of the slides revealed a clear seasonal pattern of carbonate precipitates, which were always closely associated with biofilms that developed on the surface of the frosted slides containing extracellular polymeric substance, coccoid and filamentous cyanobacteria, diatoms and heterotrophic bacteria. Carbonate precipitation peaks during early spring and late summer, and low-Mg calcite crystals mostly occur in close association with filamentous and coccoid cyanobacteria (e.g. Tolypothrix, Oscillatoria and Synechococcus, Anacystis, respectively). Further scanning electron microscope inspection of the samples revealed low-Mg calcite with crystal forms varying from anhedral to euhedral rhombohedra, depending on the seasons. Liquid cultures corroborate the in situ observations and demonstrate that under the same physicochemical conditions the absence of biofilms prevents the precipitation of low-Mg calcite crystals. These results illustrate that biofilms play a substantial role in low-Mg calcite ooid cortex formation. It further demonstrates the involvement of microbes in the early stages of ooid development. Combined with ongoing microbial cultures under laboratory-controlled conditions, the outcome of our investigation favoured the hypothesis of external microbial precipitation of low-Mg calcite as the main mechanism involved in the early stage of ooid formation in freshwater Lake Geneva. [source] Spring phenology in boreal Eurasia over a nearly century time scaleGLOBAL CHANGE BIOLOGY, Issue 3 2008NICOLAS DELBART Abstract It has been widely reported that tree leaves have tended to appear earlier in many regions of the northern hemisphere in the last few decades, reflecting climate warming. Satellite observations revealed an 8-day advance in leaf appearance date between 1982 and 1991 in northern latitudes. In situ observations show that leaf appearance dates in Europe have advanced by an average of 6.3 days from 1959 to 1996. Modelling of leaf appearance on the basis of temperature also shows a marked advance in temperate and boreal regions from 1955 to 2002. However, before 1955, reported studies of phenological variations are restricted to local scale. Modelling, ground observations and satellite observations are here combined to analyse phenological variations in Eurasian taiga over nearly a century. The trend observed by remote sensing consists mainly in a shift at the end of the 1980s, reflecting a shift in winter and spring temperature. In western boreal Eurasia, a trend to earlier leaf appearance is evident since the mid-1930s, although it is discontinuous. In contrast, the strong advance in leaf appearance detected over Central Siberia using satellite data in 1982,1991 is strengthened by late springs in 1983,1984; moreover, in this region the green-up timing has displayed successive trends with opposite signs since 1920. Thus, such strong trend is not unusual if considered locally. However, the recent advance is unique in simultaneously affecting most of the Eurasian taiga, the leaf appearance dates after 1990 being the earliest in nearly a century in most of the area. [source] Early findings in comparison of AMSR-E/Aqua L3 global snow water equivalent EASE-grids data with in situ observations for Eastern TurkeyHYDROLOGICAL PROCESSES, Issue 15 2008A. Emre Tekeli Abstract Microwave remote sensing (RS) enables the direct determination of snow water equivalent (SWE), which is an important snow parameter for water resources management. The accuracy of remotely sensed SWE values has always been a concern. Previous studies evaluated global SWE monitoring. However, regional effects such as vegetation, snow grain size, snow density and local meteorological conditions may lead to uncertainties. Thus, regional validation studies that quantify and help to understand these uncertainties and possible error sources are important both for algorithm development and accurate SWE computation. In this study, data of Advanced Microwave Scanning Radiometer (AMSR-E)/Aqua level 3 global SWE Equal Area Scalable Earth (EASE) Grids are compared with ground measurements for 2002,2003 winter period for Eastern Turkey, which includes the headwaters of the Euphrates and Tigris rivers and is fed largely from snowmelt. Thus, accurate determination of SWE is important in optimum resource management for both Turkey and downstream nations. Analyses indicated that AMSR-E generally overestimated SWE in early season. As winter progressed, higher in situ SWE values with respect to AMSR-E were observed which led to underestimation by AMSR-E. The differences between AMSR-E and in situ SWE varied between , 218 and 93 mm. Use of in situ snow densities lead the correlation coefficient between AMSR-E and in situ SWE to increase from 0·10 to 0·32. Underestimation of SWE by AMSR-E occurs after some warm periods, while overestimations occur following refreezing. On rainy days or some days after precipitation within the warm periods, zero AMSR-E SWE values are observed. Copyright © 2008 John Wiley & Sons, Ltd. [source] The role of waves in ice-jam flooding of the Peace-Athabasca DeltaHYDROLOGICAL PROCESSES, Issue 19 2007Spyros Beltaos Abstract Since the late 1960s, a paucity of ice-jam flooding in the lower Peace River has resulted in prolonged dry periods and considerable reduction in the area covered by lakes and ponds that provide habitat for aquatic life in the Peace-Athabasca Delta (PAD) region. To identify the causes of this trend, and to develop mitigation or adaptation strategies under present and future climatic conditions, it is necessary to understand the mechanisms that lead to breakup of the ice cover and jamming within the delta reach of Peace River. Because the lower Peace is extremely flat, the long-period waves caused by spring snowmelt are not generally capable of dislodging the winter ice cover, even under conditions of very high flow. The ice cover decays in place and rubble generation, an essential condition for ice jamming, does not occur. However, major jams do, on occasion, form in the middle section of the river and make their way to the delta via repeated releases and stalls. Each release generates a steep wave which can greatly amplify the hydrodynamic forces that are applied on the ice cover and bring about its dislodgment. This is quantified for the lower Peace River by applying recently developed methodology to local hydrometric data. Detailed in situ observations in the spring of 2003, and additional data from 1997 and 2002, fully corroborate this conclusion. Implications to other flat rivers of northern Canada are discussed. Copyright © 2007 Crown in the right of Canada. Published by John Wiley & Sons, Ltd. [source] Ice regime of the lower Peace River and ice-jam flooding of the Peace-Athabasca DeltaHYDROLOGICAL PROCESSES, Issue 19 2006Spyros Beltaos Abstract The Peace-Athabasca Delta (PAD) in northern Alberta is one of the world's largest inland freshwater deltas, home to large populations of waterfowl, muskrat, beaver, and free-ranging wood bison. Beginning in the mid-1970s, a paucity of ice-jam flooding in the lower Peace River has resulted in prolonged dry periods and considerable reduction in the area covered by lakes and ponds that provide a habitat for aquatic life in the PAD region. Using archived hydrometric data and in situ observations, the ice regime of the lower Peace is described and quantified, setting the stage for identification of the conditions that lead to ice-jam flooding and replenishment of Delta habitat. The first such condition is the occurrence of a mechanical, as opposed to a thermal, breakup event; second, the river flow should be at least 4000 m3/s; and third, an ice jam should form within the last 50 km of the Peace River. The type of breakup event depends on the freeze-up stage and spring flow. The former has increased as a result of flow regulation, and the latter has decreased owing to changing climatic patterns. Both trends tend to inhibit the occurrence of mechanical breakups and contribute to less frequent ice-jam flooding. Potential mitigation strategies are discussed. Copyright © 2006 Crown in the right of Canada. Published by John Wiley & Sons, Ltd. [source] Development of a historical ice database for the study of climate change in CanadaHYDROLOGICAL PROCESSES, Issue 18 2002Frédéric Lenormand Abstract The Canadian government has been compiling various observations on freshwater and coastal sea ice conditions for many years. However, the records are not easily accessible and are dispersed within different government departments. Given this, a major effort was undertaken in order to gather all available observations into a common database,the Canadian Ice Database (CID). This database will respond to the needs for climate monitoring in Canada, the validation and improvement of numerical ice models and the development of new remote-sensing methods. Indeed, several studies have shown that freshwater ice and sea ice are good proxy indicators of climate variability and change. The first version of CID contains in situ observations from 757 sites distributed across Canada, which were originally kept on digital or paper records at the Meteorological Service of Canada Headquarters and the Canadian Ice Service (CIS). The CID holds 63 546 records covering the period from ice season 1822,23 to 2000,01. An analysis of the database allows one to trace the temporal evolution of the ice networks. The freeze-up/break-up network of 2000,01 only represents 4% of what it was in 1985,86. A drastic decline of the ice thickness and the snow on ice network is also observable. In 1997,98, it represented only 10% of the network that existed in 1984,85. The major budget cuts in Canadian government agencies during the late 1980s and the 1990s offer the most plausible explanation for the drastic decline in the ice observation networks. Weekly ice coverage determination on large lakes from satellite imagery by the CIS and the national volunteer ice monitoring program, IceWatch, may provide a means of reviving, at least, the freeze-up/break-up network. Copyright © 2002 John Wiley & Sons, Ltd. [source] The annual cycle and interannual variability of atmospheric pressure in the vicinity of the North PoleINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2003Richard I. Cullather Abstract A comparison of National Centers for Environmental Prediction,National Center for Atmospheric Research reanalysis six-hourly sea-level pressure data with former Soviet drifting station observations over the central Arctic Basin reveals high monthly correlations throughout the period 1950,91, but also a preferred winter season negative bias of about 1.4 hPa. Using the reanalysis, supplemented by Arctic Ocean Buoy Program fields and in situ observations, a generalized depiction of the annual cycle of pressure fields over the Arctic may be constructed. Above the Canada Basin,Laptev Sea side of the Arctic, the annual cycle of surface pressure is dominated by the first harmonic, which has an amplitude of about 5 hPa and maximum pressure occurring in March. Along the periphery of northern Greenland and extending to the North Pole, a weak semiannual cycle is found in surface pressure with maxima in May and November. The presence of the semiannual variation over time is highly variable. Dynamically, this progression of the annual cycle may be attributed to the transfer of atmospheric mass from Eurasia and into the Canadian Archipelago in spring and the reverse condition in autumn. Over the central Arctic Basin, springtime pressure increases result from an enhanced poleward mass transport from Eurasia. An increase of equatorward transport over the Canadian Archipelago in May and June results in central Arctic pressure decreases into summer. A less distinct temporal separation between the poleward Canadian transport and the equatorward Eurasian transport results in the weaker second pressure maximum in autumn. On interannual time-scales, atmospheric mass over the central Arctic is exchanged with the storm track centres of action in the North Atlantic and North Pacific. In particular, the large decrease in central Arctic Basin sea-level pressure during the late 1980s is due to a large transfer of atmospheric mass into the North Pacific. Copyright © 2003 Royal Meteorological Society [source] Evidence for sexual dichromatisms in spawning aggregations of yellowfin grouper Mycteroperca venenosa and tiger grouper Mycteroperca tigris from the southern Gulf of MexicoJOURNAL OF FISH BIOLOGY, Issue 6 2006A. Tuz-Sulub Colour pattern characteristics and gonad histology were used to detect sexual dichromatisms in yellowfin grouper Mycteroperca venenosa and tiger grouper Mycteroperca tigris from the Campeche Bank, Mexico. Specimens were obtained from commercial catches between March and May during 2002 and 2004. All specimens were examined dead. Ninety-seven per cent of males had different sex-associated colour patterns. Male yellowfin grouper displayed a bright yellow blotch on both sides of the lower jaw while females retained a reddish lower jaw. Male tiger grouper had uniform dark pectoral fins while females had bright orange pectoral fins. In situ observations of live fishes at fishing sites showed the lower jaw and pectoral fin colourations to be clearly visible underwater at a depth of 35 m. All males of both species and most females (80% yellowfin grouper and 98% tiger grouper) were sexually active and probably caught during their spawning season. This suggests that distinct colourations observed for male M. venenosa and M. tigris may be seasonal displays associated with spawning. Both the lower jaw and pectoral fin colourations were still visible in dead fishes after several days on ice. Differences observed for ray length of exserted vertical fins in tiger grouper specimens were probably not a sex-associated characteristic. [source] Tolerance of Pinus taeda and Pinus serotina to low salinity and flooding: Implications for equilibrium vegetation dynamicsJOURNAL OF VEGETATION SCIENCE, Issue 1 2008Benjamin Poulter Abstract Questions: 1. Do pine seedlings in estuarine environments display discrete or continuous ranges of physiological tolerance to flooding and salinity? 2. What is the tolerance of Pinus taeda and P. serotina to low salinity and varying hydrologic conditions? 3. Are the assumptions for ecological equilibrium met for modeling plant community migration in response to sea-level rise? Location: Albemarle Peninsula, North Carolina, USA. Methods: In situ observations were made to quantify natural pine regeneration and grass cover along a salinity stress gradient (from marsh, dying or dead forest, to healthy forest). A full-factorial greenhouse experiment was set up to investigate mortality and carbon allocation of Pinus taeda and P. serotina to low-salinity conditions and two hydrology treatments over 6 months. Treatments consisted of freshwater and two salinity levels (4 ppt and 8 ppt) under either permanently flooded or periodically flushed hydrologic conditions. Results: Natural pine regeneration was common (5,12 seedlings per m2) in moderate to well-drained soils where salinity concentrations were below ca. 3.5 ppt. Pine regeneration was generally absent in flooded soils, and cumulative mortality was 100% for 4 and 8 ppt salinity levels under flooded conditions in the greenhouse study. Under weekly flushing conditions, mortality was not significantly different between 0 and 4 ppt, confirming field observations. Biomass accumulation was higher for P. taeda, but for both pine species, the root to shoot ratio was suppressed under the 8 ppt drained treatment, reflecting increased below-ground stress. Conclusions: While Pinus taeda and P. serotina are commonly found in estuarine ecosystems, these species display a range of physiological tolerance to low-salinity conditions. Our results suggest that the rate of forest migration may lag relative to gradual sea-level rise and concomitant alterations in hydrology and salinity. Current bioclimate or landscape simulation models assume discrete thresholds in the range of plant tolerance to stress, especially in coastal environments, and consequently, they may overestimate the rate, extent, and timing of plant community response to sea-level rise. [source] Formation of TiC core-graphitic mantle grains from CO gasMETEORITICS & PLANETARY SCIENCE, Issue 5 2006Yuki KIMURA 1996). Carbonaceous materials can be formed from C2H2 and its derivatives, as well as from CO gas. In this paper, we will demonstrate that large-cage-structure carbon particles can be produced from CO gas by the Boudouard reaction. Since the sublimation temperature for such fullerenes is low, the large cages can be deposited onto previously nucleated TiC and produce TiC core-graphitic mantle spherules. New constraints for the formation conditions and the time scale for the formation of TiC core-graphitic mantle spherules are suggested by the results of this study. In particular, TiC core-graphitic mantle grains that are found in primitive meteorites that have never experienced hydration could be mantled by fullerenes or carbon nanotubes rather than by graphite. In situ observations of these grains in primitive anhydrous meteoritic matrix could confirm or refute this prediction and would demonstrate that the graphitic mantle on such grains is a metamorphic feature due to interaction of the presolar fullerenes with water within the meteorite matrix. [source] Kinetic measurements from in situ TEM observationsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 3 2009Renu Sharma Abstract Environmental transmission or scanning transmission electron microscope is ideally suited to observe gas solid interactions at nanoscale. It is shown that the time and temperature resolved data, obtained from in situ observations, can be used to obtain reaction rates and understand the kinetics of the processes. Low or high magnification images provide the change in length, area or volume with time at constant temperature and pressure conditions during nitridation of Cu,Cr thin films, deposition of Au particles, growth of Si nanowire and carbon nanotubes. Effect of electron beam is estimated by making observations with and without constant electron beam exposure. Quantitative electron energy loss spectroscopy is employed to measure the reduction rate of Ce+4 in pure ceria, mixed oxides (ceria-zirconia) and catalyst (Rh-ceria-zirconia) powders. Microsc. Res. Tech. 2009. © 2009 Wiley-Liss, Inc. [source] Tensile properties and damage behaviors of glass-bead-filled modified polyphenylene oxide under large strainPOLYMER COMPOSITES, Issue 6 2001C. P. Tsui Based on Continuum Damage Mechanics (CDM), a damage model for glass-bead-filled modified polyphenylene oxide (GB/PPO) has been proposed to describe its damage behavior at various levels of tensile strain by considering the reduction of effective loading area. Hence, an equation for prediction of effective elastic modulus of the damaged GB/PPO composites in terms of the three principal true strains was derived. The tensile properties and damage behaviors of the GB/PPO composites with different volume percentages of glass beads were investigated using standard tensile tests and load-unload tests, respectively. The addition of glass beads increases Young's modulus of PPO but has a weakening effect on its tensile strength. A maximum value of tensile work to break and tensile strain at break was found when 5 vol% of glass beads with a mean diameter of 11 ,m was blended with PPO. These results were justified through microscopic examination of the fracture surfaces of the tensile specimens by using a scanning electron microscope (SEM). In - situ observations of the strain damage processes were made through the SEM equipped with a tensile stage to determine the strain at fully debonding of glass beads. The volumetric strain of GB/PPO composites increases because of microcavitation during strain damage. In general, the prediction for the effective elastic modulus of the damaged GB/PPO composites at different true strains is slightly higher than the experimental results. The damage evolution rates after fully debonding of glass beads from the matrix are close to those predicted by the proposed damage model. [source] An easterly tip jet off Cape Farewell, Greenland.THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 645 2009I: Aircraft observations Abstract An easterly tip jet event off Cape Farewell, Greenland, is described and analysed in considerable detail. In Part I of this study (this paper) comprehensive aircraft-based observations are described, while in Part II of this study numerical simulations and a dynamical analysis are presented. The easterly tip jet of 21 February 2007 took place during the Greenland Flow Distortion experiment. It resulted through the interaction of a barotropic synoptic-scale low pressure system in the central North Atlantic and the high topography of southern Greenland. In situ observations reveal a jet core at the coast with peak winds of almost 50 m s,1, about 600,800 m above the sea surface, and of 30 m s,1 at 10 m. The depth of the jet increased with wind speed from ,1500 m to ,2500 m as the peak winds increased from 30 to 50 m s,1. The jet accelerated and curved anticyclonically as it reached Cape Farewell and the end of the barrier. The easterly tip jet was associated with a tongue of cold and dry air along the coast of southeast Greenland, general cloud cover to the east, and cloud streets to the south of Cape Farewell. Precipitation was observed during the low-level components of the flight. The very high wind speeds generated a highly turbulent atmospheric boundary layer and resulted in some of the highest surface wind stresses ever observed over the ocean. Copyright © 2009 Royal Meteorological Society [source] The relative impact of meteorological observations in the Norwegian regional model as determined using an energy norm-based approachATMOSPHERIC SCIENCE LETTERS, Issue 1 2010Andrea Storto Abstract The sensitivity of the forecasts to different observation groups is evaluated by comparing moist total energy norm-based cost functions within the HARMONIE/Norway regional model. We quantify the quality loss associated to each observation type. The use of a localisation operator has allowed us to obtain results for the whole domain and for the area of continental Norway only, as well as for different vertical sub-regions of the atmosphere. Results show a prominent role of in situ observations for short-range forecasts, while for medium-range forecasts microwave satellite observations result in the largest impact, especially the AMSU-A channels peaking within the troposphere. 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