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Selected AbstractsInvasive exotic aoudad (Ammotragus lervia) as a major threat to native Iberian ibex (Capra pyrenaica): a habitat suitability model approachDIVERSITY AND DISTRIBUTIONS, Issue 5 2007Pelayo Acevedo ABSTRACT The introduction of alien species to new environments is one of the main threats to the conservation of biodiversity. One particularly problematic example is that of wild ungulates which are increasingly being established in regions outside their natural distribution range due to human hunting interests. Unfortunately, we know little of the effects these large herbivores may have on the host ecosystems. This study deals with a first comparative analysis of the habitat requirements of two ungulate species that may be facing competition for resources in the south of Europe: the native Iberian ibex (Capra pyrenaica) and the exotic aoudad (Ammotragus lervia). The aoudad is a North African caprid introduced in 1970 as a game species in south-eastern Spain. It has adapted well, and populations have been freely expanding since then. Ecological Niche Factor Analysis is used to describe the realized niche of both species where their distribution ranges merge. Both species occupy marginal areas of rugged terrain in the region. Marginality is higher for the Iberian ibex, which also presents a higher tolerance of secondary environmental gradients than the aoudad. Highly suitable areas for each species are secondarily suitable for the other. Reclassified and cross-tabulated habitat suitability maps showing the areas of potential spatial coexistence and differences in ecological traits between both species are provided. The results obtained do not allow inferring resource competition between these species. However, current aoudad expansion could result in it invading the favoured habitats of the ibex. Inadequate hunting policy and monitoring, and increasing climatic resemblance of the study region to the native aoudad areas, due to a strong desertification process, are facilitating a high rate of expansion. We strongly recommend to eradicate or, at least, monitor these exotic populations, and promote active conservation practices, if one wants to preserve the unique natural resources present in this European region. [source] Screening of the Interactions Between Mg-PSZ and TRIP-Steel and Its Alloys During Sintering,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Christian Weigelt Ceramic,steel compound materials are used in a wide range of applications up to date. Major advantages are the mechanical properties due to the combination of brittle ceramic with tough steel. This study deals with effects of the sintering process on austenitic TRIP-steel/Mg-PSZ composite materials for mechanical load applications. Both, the FeCrNisteel and partially stabilized zirconia offer their special mechanical behavior only in a metastable state. The ability of phase transformation depends mainly on the chemical composition. Mutual interactions of the alloying metals (Cr, Ni, Mn, and Fe) and the ceramic stabilizer (MgO) during sintering may prevent the martensitic phase transformation. This may cause disadvantageous mechanical behavior on mechanical load in use. [source] Deltas in the Abisko area, northern Sweden: the Abiskojokka delta in lake TorneträskGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3-4 2002Hans Andrén Several small river deltas are found within the Abisko area. This study deals with the Abiskojokka delta in Lake Torneträsk. The aim is to describe the recent delta and its morphological development since the middle 1960s. In the apex of the delta, bars consist of boulders and cobbles while the mouth,bars are built by pebbles, gravel and to some extent sand. Birch vegetation is found on the sandy levées while willows and sedges dominate the interlevée basins. Mouth bars close to the lake generally lack vegetation. A comparison of the map in the present study with a map from 1965 shows comparatively small changes since 1964. Similar results are achieved when comparing aerial photographs from 1959 and 2000. Thus, the growth of the Abiskojokka delta is rather small compared to several other deltas in the Scandinavian mountains. This low growth rate is a result of upstream lakes trapping the major part of the fluvial sediments. Therefore, most of the delta sediment is redistributed old glaciofluvial material from the terraces within the Abiskojokka valley. Some material might also emanate from the Abiskojokka canyon. Formation of the main part of the delta is probably associated with the lowering of the Torneträsk ice,lakes, during and after the deglaciation of the region. Although some extreme rainstorm events have occurred in the area during recent decades, the effects of these on the delta are small. The result of such events is, however, visible as deposition of sand and silt on the levées after flooding. On the other hand, the shoreline and the mouth bars are continuously changing due to rather high wave energy especially during northerly winds. Along several mouth bars, spits are formed and reformed due to wave action. Minor changes of, and within, the two main distributaries have also been noticed, especially as bank erosion and redistribution of bars. The project will continue with a survey of the distal slope (foreset slope) of the delta as well as a study (including X,ray radiography) of the bottom sediments in Lake Torneträsk close to the delta front. The upstream deltas within this drainage basin as well as other deltas within the Torneträsk region will be studied. [source] Passive seismic imaging with directive ambient noise: application to surface waves and the San Andreas Fault in Parkfield, CAGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2009Philippe Roux SUMMARY This study deals with surface waves extracted from microseismic noise in the (0.1,0.2 Hz) frequency band with passive seismic-correlation techniques. For directive noise, we explore the concept of passive seismic-noise tomography performed on three-component sensors from a dense seismic network. From the nine-component correlation tensor, a rotation algorithm is introduced that forces each station pair to re-align in the noise direction, a necessary condition to extract unbiased traveltime from passive seismic processing. After rotation is performed, the new correlation tensor exhibits a surface wave tensor from which Rayleigh and Love waves can be separately extracted for tomography inversion. Methodological aspects are presented and illustrated with group-speed maps for Rayleigh and Love waves and ellipticity measurements made on the San Andreas Fault in the Parkfield area, California, USA. [source] Predicting river water temperatures using the equilibrium temperature concept with application on Miramichi River catchments (New Brunswick, Canada)HYDROLOGICAL PROCESSES, Issue 11 2005Daniel Caissie Abstract Water temperature influences most of the physical, chemical and biological properties of rivers. It plays an important role in the distribution of fish and the growth rates of many aquatic organisms. Therefore, a better understanding of the thermal regime of rivers is essential for the management of important fisheries resources. This study deals with the modelling of river water temperature using a new and simplified model based on the equilibrium temperature concept. The equilibrium temperature concept is an approach where the net heat flux at the water surface can be expressed by a simple equation with fewer meteorological parameters than required with traditional models. This new water temperature model was applied on two watercourses of different size and thermal characteristics, but within a similar meteorological region, i.e., the Little Southwest Miramichi River and Catamaran Brook (New Brunswick, Canada). A study of the long-term thermal characteristics of these two rivers revealed that the greatest differences in water temperatures occurred during mid-summer peak temperatures. Data from 1992 to 1994 were used for the model calibration, while data from 1995 to 1999 were used for the model validation. Results showed a slightly better agreement between observed and predicted water temperatures for Catamaran Brook during the calibration period, with a root-mean-square error (RMSE) of 1·10 °C (Nash coefficient, NTD = 0·95) compared to 1·45 °C for the Little Southwest Miramichi River (NTD = 0·94). During the validation period, RMSEs were calculated at 1·31 °C for Catamaran Brook and 1·55 °C for the Little Southwest Miramichi River. Poorer model performances were generally observed early in the season (e.g., spring) for both rivers due to the influence of snowmelt conditions, while late summer to autumn modelling performances showed better results. Copyright © 2005 John Wiley & Sons, Ltd. [source] Valuation of biodiversity effects from reduced pesticide useINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 2 2006Jesper S. Schou Abstract This study deals with the effects on biodiversity of pesticide-free buffer zones along field margins. Using choice modeling, the majority of respondents to a survey on pesticide use in the environment are willing to accept an increase in the price of bread if the survival of partridge chicks and the number of wild plants increase. The study identifies the need for further empirical work with respect to methodological validation, price estimation, and the use of survey results in policy analysis. In particular, the environmental effects of pesticide use are complex and, therefore, present difficult challenges when presenting information to lay people. Forty-one percent of respondents changed their responses regarding willingness to pay more for bread when references to pesticide use were introduced in the questionnaire. This indicates that scenarios depicting changes in pesticide use can be difficult to present to lay people in an economically rational and well-defined context. Thus, in the study of valuation related to changes in pesticide use, much attention should be devoted to the design and definition of the context. Furthermore, the effects of providing different background information, e.g., with or without the mention of pesticides, should be tested. [source] Non-isothermal plasticity model for cyclic behaviour of soilsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 5 2008L. Laloui Abstract On the one hand, it has been observed that liquefaction-induced shear deformation of soils accumulates in a cycle-by-cycle pattern. On the other hand, it is known that heating could induce plastic hardening. This study deals with the constitutive modelling of the effect that heat may have on the cyclic mechanical properties of cohesive soils, a relatively new area of interest in soil mechanics. In this paper, after a presentation of the thermo-mechanical framework, a non-isothermal plasticity cyclic model formulation is presented and discussed. The model calibration is described based on data from laboratory sample tests. It includes numerical simulations of triaxial shear tests at various constant temperatures. Then, the model predictions are compared with experimental results and discussed in the final section. Both drained and undrained loading conditions are considered. The proposed constitutive model shows good ability to capture the characteristic features of behaviour. Copyright © 2007 John Wiley & Sons, Ltd. [source] Oscillatory flow of a fourth-order fluidINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2009T. Hayat Abstract This study deals with the incompressible flow of a fourth-order fluid over a porous plate oscillating in its own plane. Numerical solution of the nonlinear problem governing the flow is given. The influence of various parameters of interest on the velocity distribution is shown and discussed with the help of several graphs. Copyright © 2008 John Wiley & Sons, Ltd. [source] Higher order finite element methods and multigrid solvers in a benchmark problem for the 3D Navier,Stokes equationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2002Volker John Abstract This paper presents a numerical study of the 3D flow around a cylinder which was defined as a benchmark problem for the steady state Navier,Stokes equations within the DFG high-priority research program flow simulation with high-performance computers by Schafer and Turek (Vol. 52, Vieweg: Braunschweig, 1996). The first part of the study is a comparison of several finite element discretizations with respect to the accuracy of the computed benchmark parameters. It turns out that boundary fitted higher order finite element methods are in general most accurate. Our numerical study improves the hitherto existing reference values for the benchmark parameters considerably. The second part of the study deals with efficient and robust solvers for the discrete saddle point problems. All considered solvers are based on coupled multigrid methods. The flexible GMRES method with a multiple discretization multigrid method proves to be the best solver. Copyright © 2002 John Wiley & Sons, Ltd. [source] Performance of statistical downscaling models in GCM validation and regional climate change estimates: application for Swedish precipitationINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2001Aristita Busuioc Abstract This study deals with an analysis of the performance of a general circulation model (GCM) (HadCM2) in reproducing the large-scale circulation mechanisms controlling Swedish precipitation variability, and in estimating regional climate changes owing to increased CO2 concentration by using canonical correlation analysis (CCA). Seasonal precipitation amounts at 33 stations in Sweden over the period 1899,1990 are used. The large-scale circulation is represented by sea level pressure (SLP) over the Atlantic,European region. The link between seasonal Swedish precipitation and large-scale SLP variability is strong in all seasons, but especially in winter and autumn. For these two seasons, the link is a consequence of the North Atlantic Oscillation (NAO) pattern. In winter, another important mechanism is related to a cyclonic/anticyclonic structure centred over southern Scandinavia. In the past century, this connection has remained almost unchanged in time for all seasons except spring. The downscaling model that is built on the basis of this link is skilful in all seasons, but especially so in winter and autumn. This observed link is only partially reproduced by the HadCM2 model, while large-scale SLP variability is fairly well reproduced in all seasons. A concept about optimum statistical downscaling models for climate change purposes is proposed. The idea is related to the capability of the statistical downscaling model to reproduce low frequency variability, rather than having the highest skill in terms of explained variance. By using these downscaling models, it was found that grid point and downscaled climate signals are similar (increasing precipitation) in summer and autumn, while in winter, the amplitudes of the two signals are different. In spring, both signals show a slight increase in the northern and southern parts of Sweden. Copyright © 2001 Royal Meteorological Society [source] Thermoeconomic analysis of household refrigeratorsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2007Arif Hepbasli Abstract This study deals with thermoeconomic analysis of household refrigerators for providing useful insights into the relations between thermodynamics and economics. In the analysis, the EXCEM method based on the quantities exergy, cost, energy and mass is applied to a household refrigerator using the refrigerant R134a. The performance evaluation of the refrigerator is conducted in terms of exergoeconomic aspects based on the various reference state temperatures ranging from 0 to 20°C. The exergy destructions in each of the components of the overall system are determined for average values of experimentally measured parameters. Exergy efficiencies of the system components are determined to assess their performances and to elucidate potentials for improvement. Thermodynamic loss rate-to-capital cost ratios for each components of the refrigerator are investigated. Correlations are developed to estimate exergy efficiencies and ratios of exergy loss rate-to-capital cost as a function of reference (dead) state temperature. The ratios of exergy loss rates to capital cost values are obtained to vary from 2.949 × 10,4 to 3.468 × 10,4 kW US$,1. The exergy efficiency values are also found to range from 13.69 to 28.00% and 58.15 to 68.88% on the basis of net rational efficiency and product/fuel at the reference state temperatures considered, respectively. It is expected that the results obtained will be useful to those involved in the development of analysis and design methodologies that integrate thermodynamics and economics. Copyright © 2006 John Wiley & Sons, Ltd. [source] Exergetic performance evaluation of a combined heat and power (CHP) system in TurkeyINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2007Ozgur Balli Abstract This study deals with the exergetic performance assessment of a combined heat and power (CHP) system installed in Eskisehir city of Turkey. Quantitative exergy balance for each component and the whole CHP system was considered, while exergy consumptions in the system were determined. The performance characteristics of this CHP system were evaluated using exergy analysis method. The exergetic efficiency of the CHP system was accounted for 38.16% with 49 880 kW as electrical products. The exergy consumption occurred in this system amounted to 80 833.67 kW. The ways of improving the exergy efficiency of this system were also analysed. As a result of these, a simple way of increasing the exergy efficiency of the available CHP system was suggested that the valves-I,III and the MPSC could be replaced by a 3500 kW-intermediate pressure steam turbine (IPST). If the IPST is installed to the CHP system (called the modified CHP (MCHP) system), the exergetic efficiency of the MCHP system is calculated to be 40.75% with 53 269.53 kW as electrical products. The exergy consumption is found to be 77 444.14 kW in the MCHP system. Copyright © 2006 John Wiley & Sons, Ltd. [source] Assessment of the energy and exergy utilization efficiencies in the Turkish agricultural sectorINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2006Zafer Utlu Abstract This study deals with evaluating the energy and exergy utilization efficiencies in the Turkish agricultural sector over a 12-year period from 1990 to 2001. In the energy and exergy analyses, two main energy sources, namely fuels and electricity, are taken into consideration, while the sectoral energy and exergy efficiencies are compared for this period. These main energy sources include diesel for tractors and other vehicles, and electricity for pumps. Overall energy utilization efficiencies are obtained to vary between 29.1 and 41.1%, while overall exergy utilization efficiencies are found to range from 27.9 to 37.4% in the analysed years, respectively. It may be concluded that the present technique proposed here may be used as a useful tool in analysing and evaluating the energy and exergy utilization efficiencies, identifying energy efficiency and/or energy conservation opportunities and dictating the energy strategies of countries. Copyright © 2005 John Wiley & Sons, Ltd. [source] Forecasting total and industrial sector electricity demand based on genetic algorithm approach: Turkey case studyINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2005Harun Kemal Ozturk Abstract This study deals with estimation of the total and industrial sector electricity consumption based on genetic algorithm (GA) approach, and then proposes two scenarios to project future consumptions. Total electricity consumption is estimated based on gross national product (GNP), population, import and export figures of Turkey. Industrial sector electricity is calculated based on the GNP, import and export figures. Three forms of the genetic algorithm electricity demand (GAED) models for the total and two forms for the industrial electricity consumption are developed. The best-fit GAED model in terms of total minimum relative average errors between observed and estimated values is selected for future demand estimation. ,High- and low-growth scenarios' are proposed for predicting the future electricity consumption. Results showed that the GAED estimates the electricity demand in comparison with the other electricity demand projections. The GAED model plans electricity demand of Turkey until 2020. Copyright © 2005 John Wiley & Sons, Ltd. [source] Energy and exergy analysis of Salihli geothermal district heating system in Manisa, TurkeyINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2005Leyla Ozgener Abstract This study deals with an energy and exergy analysis of Salihli geothermal district heating system (SGDHS) in Manisa, Turkey. In the analysis, actual system data are used to assess the district heating system performance, energy and exergy efficiencies, specific exergy index, exergetic improvement potential and exergy losses. Energy and exergy losses throughout the SGDHS are quantified and illustrated in the flow diagram. The exergy losses in the system, particularly due to the fluid flow, take place in the pumps and the heat exchanger, as well as the exergy losses of the thermal water (e.g. geothermal fluid) and the natural direct discharge of the system. As a result, the total exergy losses account for 2.22, 17.88 and 20.44%, respectively, of the total exergy input to the entire SGDHS. The overall energy and exergy efficiencies of the SGDHS components are also studied to evaluate their individual performances and determined to be 55.5 and 59.4%, respectively. Copyright © 2005 John Wiley & Sons, Ltd. [source] Reignition phenomenon of high-speed hydrogen jet diffusion flameINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2002Shuichi Torii Abstract An experimental study deals with a high-speed hydrogen jet diffusion flame ejected vertically upward from a straight circular nozzle. Consideration is given to the reignition phenomenon that occurs after blow-off of the main flame. The Schlieren technique and image-processing method with the aid of the high-speed video camera are employed to visualize the flame shape, particularly the flame base near the nozzle tip and to investigate the time history of the flame morphology. It is found that: (i) the flame reignition phenomenon of hydrogen jet diffusion flames appears only in a certain region of mass flow rates; (ii) the small-sized flame-let remains in the vicinity of the nozzle rim at the mass flow rates that the reignition occurs; (iii) a further increase in mass flow rates makes the flame-let extinguish and no reignition occurs; (iv) the time interval of flame reignition extends with an increase in mass flow rates; and (v) the flow rates of the onset and end of the reignition and the existence of flame-let formed near the nozzle rim are affected by the rim thickness of the fuel nozzle. Copyright © 2002 John Wiley & Sons, Ltd. [source] Sensitivity analysis on stochastic equilibrium transportation networks using genetic algorithmJOURNAL OF ADVANCED TRANSPORTATION, Issue 3 2004Halim Ceylan Abstract This study deals with the sensitivity analysis of an equilibrium transportation networks using genetic algorithm approach and uses the bi-level iterative sensitivity algorithm. Therefore, integrated Genetic Algorithm-TRANSYT and Path Flow Estimator (GATPFE) is developed for signalized road networks for various level of perceived travel time in order to test the sensitivity of perceived travel time error in an urban stochastic road networks. Level of information provided to drivers correspondingly affects the signal timing parameters and hence the Stochastic User Equilibrium (SUE) link flows. When the information on road system is increased, the road users try to avoid conflicting links. Therefore, the stochastic equilibrium assignment concept tends to be user equilibrium. The GATPFE is used to solve the bi-level problem, where the Area Traffic Control (ATC) is the upper-level and the SUE assignment is the lower-level. The GATPFE is tested for six-junction network taken from literature. The results show that the integrated GATPFE can be applied to carry out sensitivity analysis at the equilibrium network design problems for various level of information and it simultaneously optimize the signal timings (i.e. network common cycle time, signal stage and offsets between junctions). [source] Impact behavior of hybrid composite platesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2010Metin Sayer Abstract This experimental study deals with the impact response of hybrid composite laminates. Two different hybrid composite laminates, aramid/glass and aramid/carbon, and two different stacking sequences, such as [0/0/90/90]A+ [90/90/0/0]G for AG1 and [0/90/±45]A+ [±45/90/0]G for AG2 and so on (see Table I), were chosen for impact testing. The impact energy was gradually increased until complete perforation took place, and an energy profiling method (EPM) was used to identify the perforation thresholds of composites. The damaged samples were visually inspected. The images of the several samples subjected to various impact energies were registered and used for comparison and identifying damage mechanisms. The perforation thresholds for [0/90/±45]s aramid/glass and aramid/carbon laminates were found to be approximately 5% higher than those for their counterparts with the [0/0/90/90]s stacking sequence. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Effect of xylanase on ozone bleaching kinetics and properties of Eucalyptus kraft pulpJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2003M Blanca Roncero Abstract Environmental pressure has led the pulp and paper industry to develop new technologies in order to reduce or suppress the presence of various pollutants in effluents from bleaching plants. One of the choices for this purpose is enzyme-based biotechnology. This study deals with the effect of using a xylanase-based enzymatic pretreatment, in a TCF (Totally Chlorine Free) sequence, on the properties of the resulting paper pulps. The hexenuronic acid content in the pulp and the physical properties of the paper were also studied. The performance of the xylanase was analysed through kinetic studies on ozone bleaching. The enzymatic pretreatment results in easier bleaching and delignification of the pulp, causing a bleach-boosting effect. The decreased consumption of reagent is related to a decreased content of hexenuronic groups. The physical properties of the treated pulp are similar to those of untreated pulps. Cellulose degradation, delignification and chromophores' removal show first-order kinetics. Enzyme pretreatment leads to differences between the kinetic constants of cellulose degradation and chromophores' removal, due to an increased accessibility to bleaching agents. The xylanase treatment leads to a lower floor kappa number (IK,) during the ozone stage. Copyright © 2003 Society of Chemical Industry [source] Community life as a motive for migration from the urban center to the rural periphery in IsraelJOURNAL OF COMMUNITY PSYCHOLOGY, Issue 6 2010Sara Arnon A white house topped by a red roof, set in a garden, surrounded by a lawn dotted with trees and shrubs,this is not just a child's naive drawing. It is the aspiration of many in the modern world, Israelis among them. This case study deals with the inner migration of families, mainly from the urban center of Israel, to rural communities in its northern periphery. It is also an opportunity to examine counter-urbanization characteristics and motivations, which contribute to our understanding of the role of community in this process. © 2010 Wiley Periodicals, Inc. [source] INFLUENCE OF FLOW REGIMES ON TEMPERATURE HETEROGENEITIES WITHIN A SCRAPED SURFACE HEAT EXCHANGERJOURNAL OF FOOD PROCESS ENGINEERING, Issue 3 2000ERIC DUMONT ABSTRACT In industrial applications, fluids processed in scraped surface heat exchangers often show large temperature heterogeneities at the exchanger outlet. Our study deals with the thermal evolution of model fluids, Newtonian and non-Newtonian in heating or cooling conditions and allows us to link the phenomena of appearance and disappearance of temperature heterogeneities with the changes in the flow pattern within the exchanger. Based on literature data dedicated to scraped surface heat exchangers as well as to annular spaces without blades, we have shown that thermally homogeneous products can be obtained when Taylor vortices appear in the exchanger. Studies done on the exchanger with and without blades show that the thermal behavior is basically the same for both geometries but with a difference in critical Taylor numbers value for change in heat transfer regime. The presence of blades promotes the appearance of instabilities at lower values of generalized Taylor number (Tag= 10 with blades; Tag= 39 without blades). It shows as well, that the value of critical Taylor number in scraped surface heat exchanger closely depends upon the flow-rate even for very low values for Reaxg (Reaxg < <1). [source] Effect of sample size on microwave power absorption within dielectric materials: 2D numerical results vs. closed-form expressionsAICHE JOURNAL, Issue 6 2009S. Curet Abstract This study deals with the analytical and numerical solutions of the heat source term because of microwave heating for high and low dielectric materials in 1D and 2D configurations. The authors compare closed-form expressions dedicated to microwave power calculation to numerical simulations. A comprehensive and accurate analysis of the microwave power reflected from the surface of the sample is also carried out during microwave heating. The influence of sample length is studied using an original numerical procedure. The study highlights that 1D closed-form expressions can be extended to 2D configurations in the case of sufficiently high dielectric properties. Examples of heating rate during 2D microwave heating in TE10 mode are finally presented. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Identification of acrylic consolidants in wood by Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2006Martina Ohlídalová Abstract Consolidation is an important conservation treatment of damaged wooden historical monuments. Successful consolidation is based on sufficient penetration of the consolidant into the wood. For this reason, it is very important to prove the presence of the consolidant in wood. In this study, Raman spectroscopy was used for identification of acrylic consolidants in wood. Prior to the measurement, it was necessary to find the most suitable settings of instrumental parameters of the Raman spectrometer. It was necessary to suppress the fluorescence of the wood itself, as well as the fluorescence of the acrylic consolidants used, as much as possible. Another task was to find the most suitable measuring area from the point of view of the wooden microstructure. This study deals with developing a methodology that examines acrylates in wood that can be successfully used to examine the penetration of acrylate consolidants in wood. Copyright © 2006 John Wiley & Sons, Ltd. [source] System thinking skills at the elementary school levelJOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 5 2010Orit Ben-Zvi Assaraf Abstract This study deals with the development of system thinking skills at the elementary school level. It addresses the question of whether elementary school students can deal with complex systems. The sample included 40 4th grade students from one school in a small town in Israel. The students studied an inquiry-based earth systems curriculum that focuses on the hydro-cycle. The program involved lab simulations and experiments, direct interaction with components and processes of the water cycle in the outdoor learning environment and knowledge integration activities. Despite the students' minimal initial system thinking abilities, most of them made significant progress with their ability to analyze the hydrological earth system to its components and processes. As a result, they recognized interconnections between components of a system. Some of the students reached higher system thinking abilities, such as identifying interrelationships among several earth systems and identifying hidden parts of the hydrological system. The direct contact with real phenomena and processes in small scale scenarios enabled these students to create a concrete local water cycle, which could later be expanded into large scale abstract global cycles. The incorporation of outdoor inquiry-based learning with lab inquiry-based activities and knowledge integration assignments contributed to the 4th grade students' capacity to develop basic system thinking abilities at their young age. This suggests that although system thinking is regarded as a high order thinking skill, it can be developed to a certain extent in elementary school. With a proper long-term curriculum, these abilities can serve as the basis for the development of higher stages of system thinking at the junior,high/middle school level. © 2009 Wiley Periodicals, Inc. J Res Sci Teach 47: 540,563, 2010 [source] Habitat restriction in Mammillaria pectinifera, a threatened endemic Mexican cactusJOURNAL OF VEGETATION SCIENCE, Issue 6 2003José Alejandro Zavala-Hurtado Dávila-Aranda et al. (1993) Abstract. This study deals with the habitat restriction of Mammillaria pectinifera, a threatened cactus species, confined to a few low density localities of the Tehuacán valley in tropical Mexico. We analysed the patterns of presence/absence of M. pectinifera in relation to the presence/absence of 48 other plant species, and the variation of environmental factors in 120 sampling plots. A Principal Components Analysis revealed a clear segregation between plots with and without individuals of M. pectinifera. A classification analysis resulted in four groups: two with low prevalence and two with high prevalence of M. pectinifera. Paired comparisons between plots with and without M. pectinifera allowed the characterization of its patterns of occurrence related to the variation of environmental factors. M. pectinifera was found on deep alkaline soils with relatively high surface stoniness and high water retention capacity, showing low species richness compared with plots where it was absent. The limited distribution of M. pectinifera in the Tehuacán Valley seems to be related to particular requirements of this species, being restricted to certain suitable habitat patches. Nevertheless, it is likely that other aspects, such as poor dispersal and establishment abilities, or biotic interactions could be associated with the observed patterns. [source] Spatial dynamics of regeneration in a conifer/broad-leaved forest in northern JapanJOURNAL OF VEGETATION SCIENCE, Issue 5 2000Yasuhiro Kubota Ohwi (1972) Abstract. This study deals with stand dynamics over a 6-yr period in a conifer/broad-leaved mixed forest in Hokkaido, northern Japan. The annual rates of gap formation and recovery were 81.3 m2/ha and 66.7 m2/ha, respectively and turnover time of the canopy was 125 yr. The recruitment processes of the component species in this cool-temperate forest were governed by different canopy types: gap, canopy edge and closed canopy. Magnolia obovata regenerated in canopy edges, and Acer mono and Prunus ssiori regenerated in canopy edges and gaps. The results suggested that the mosaic structure made up of closed canopy, canopy edge and gap was related to various regeneration niches. Abies sachalinensis had high mortality rates, initiating gap expansion. The transition probabilities from closed canopy or canopy edge to gap for deciduous broad-leaved trees were lower than for A. sachalinensis, which implies that the difference in degeneration patterns of conifer and broad-leaved canopies contributes to the heterogeneity of spatial structure in the mixed forests. Spatial dynamics were determined by a combination of gap expansion by A. sachalinensis (neighbour-dependent disturbance) and gap formation by deciduous broad-leaved trees (random disturbance). [source] Input and SLA: Adults' Sensitivity to Different Sorts of Cues to French GenderLANGUAGE LEARNING, Issue S1 2005Susanne E. Carroll All second language (L2) learning theories presuppose that learners learn the target language from the speech signal (or written material, when learners are reading), so an understanding of learners' ability to detect and represent novel patterns in linguistic stimuli will constitute a major building block in an adequate theory of second language acquisition (SLA) input. Pattern detection, a mainstay of current connectionist modeling of language learning, presupposes a sensitivity to particular properties of the signal. Learning abstract grammatical knowledge from the signal presupposes, as well, the capacity to map phonetic properties of the signal onto properties of another type (segments and syllables, morpheme categories, and so on). Thus, even seemingly "simple" grammatical phenomena may embody complex structural knowledge and be instantiated by a plethora of diverse cues. Moreover, cues have no a priori status; a phenomenon of a given sort takes on a value as a cue when acquisition of the grammatical system reveals it to be useful. My study deals with initial sensitivity to cues to gender attribution in French. Andersen (1984) asked: "What's gender good for anyway?" One answer comes from a number of studies, done mostly in the last 20 years, of gender processing by both monolingual and bilingual speakers (among many others, Bates, Devescovi, Hernandez, & Pizzamiglio, 1996; Bates & Liu, 1997; Friederici & Jacobsen, 1990; Grosjean, Dommergues, Cornu, Guillemon, & Besson, 1994; Guillemon & Grosjean, 2001; Taft & Meunier, 1998). These studies provide evidence that in monolinguals and early (but not late) L2 learners, prenominal morphosyntactic exponents of gender prime noun activation and speed up noun recognition. Over the same period, a growing number of studies detailing the course of L2 gender acquisition for a variety of different target languages and learner types (e.g., Bartning, 2000; Chini, 1995; Dewaele & Véronique, 2000; Granfeldt, 2003; Hawkins & Franceschina, 2004) have provided support for the hypothesis that developmental paths differ for early and later learners of gender. Yet despite its obvious importance to SLA theorizing, few studies have dealt directly with adult learners' ability to detect and analyze potential cues to gender at the initial stage of exposure to the L2 (and this despite considerable discussion in recent years of the nature of the "initial state" of L2 learning). The study reported on in this article, which was actually conducted in the late 1980s, was an attempt to shed some light on what the beginning learner can do with the gender attribution problem. This study was, at that time, and is even now, an anomaly; most research dealing with "input" provided descriptions of what people say to learners, not what learners can perceive and represent. Indeed, most studies that shed light on the initial analytical capacities of absolute beginners were concerned with "perceptual" learning, that is, with the acquisition of phonetic or phonological distinctions (e.g., Broselow, Hurtig, & Ringen's [1987] study of tone learning or various studies on the perception of the /r/ vs. /l/ phonemes in American English by Japanese speakers). In this update, it is therefore worth mentioning Rast's (2003) dissertation and Rast and Dommergues (2003), which is based on it, which examined the results of the first 8 hr of instructed learning of Polish by francophone adults. My study asked if anglophone adults, with little or no prior exposure to French, given auditory stimuli, were equally sensitive to phonological, morphosyntactic, or semantic cues to French gender classes. The issue of what learners can detect in the signal and encode is an empirical one. I presented 88 adult English speakers with highly patterned data in list form, namely, auditory sequences of [Det + N]French + translation equivalentEnglish forms. The patterns, all true generalizations, were drawn from linguistic descriptions of French. These cues are believed by grammarians of the language to be "psychologically real" to native speakers. I then measured in 3 different ways what my participants had acquired. Given the extreme limitations on the input (no visual supports to identify referents of names), the participants performed pretty well. Moreover, they proved to be highly sensitive to "natural" semantic and morphological patterns and could generalize accurately from learned instances to novel exemplars. These patterns, however, are not directly instantiated in the speech signal; they are abstractions imposed on the stimuli by human linguistic cognition. Moreover, although it would be inaccurate to describe the learning patterns as "transfer"(because English nouns have no gender feature), prior knowledge seemed to be implicated in the results. Above all, these Anglophones appear to perceive the gender learning problem as a semantic one and to make use of "top-down" information in solving it. It follows that the pattern detection that they can do when listening to speech is clearly biased by what they already know. These results, therefore, provide support for hypotheses that the initial state is to be defined in terms of the transfer of first language (L1) grammatical knowledge and/or the transfer of L1-based processing procedures. [source] Variations in Grain Size Analysis with a Time-of-Transition Laser Sizer (Galai CIS-50) using a Gravitational Flow SystemPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 6 2004Björn Bohling Abstract This study deals with grain size analysis with a Laser Sizer Galai CIS-50. This device utilizes the time-of-transition method and is equipped with a module for measurements in the range 0.5 to 150,,m along with a gravitational flow system. Experiments were conducted using natural marine sediments. The aim was to determine possible explanations for discrepancies in the measured results that occurred between different operators of the Galai CIS-50. These discrepancies may be due to differences in the technique of inserting a sub-sample into the measurement system. Furthermore, the influence of the sample concentration and the flow velocity in the device's liquid flow cell is considered, since these factors can act as potential sources of inaccuracies and errors in the experimental setup. Strong variations in the results occurred, which were mainly due to problems in the detection of particles >20,,m. In the range>20,,m gaps appeared in the registration of the size distribution. An improvement in reproducibility was achieved by using a pipette instead of a beaker for the insertion step. Nevertheless, the standard deviation for mean grain sizes of natural marine sediments obtained with the Galai CIS-50 is still about 20%. [source] Instrumentation for Simultaneous Gas and Particle Velocity Measurements at Mach,5,PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 6 2002Francis Micheli Abstract This study deals with re-entry vehicles passing through high-altitude clouds of ice particles. The particles disturb the flow field and are erosive, thereby increasing the turbulent heat flux considerably. Measurements were performed in a blow-down wind tunnel to analyze the effects of a particle field on the flow. The wind tunnel flow was seeded by two aerosols. The first was used for LDV flow velocity measurements. Its size was checked by the analysis of its passage through a plane shock wave. The second aerosol was made of uniform micro-spheres of 200,,m diameter, used to simulated the water droplets. The velocity, feeding and scattering of the latter aerosol need to be accurately measured. The velocities of the flow field and of the micro-spheres were measured simultaneously by laser velocimetry. This paper describes the instruments used to seed, ascertain and measure this flow with two aerosols. [source] Role of the interphase in the flow stability of reactive coextruded multilayer polymersPOLYMER ENGINEERING & SCIENCE, Issue 4 2009Khalid Lamnawar Coextrusion technologies are commonly used to produce multilayered composite sheets or films for a large range of applications from food packaging to optics. The contrast of rheological properties between layers can lead to interfacial instabilities. Important theoretical and experimental advances regarding theses defects have, during the last decades, been made using a mechanical and numerical approach. This study deals with the influence of the physicochemical affinity between the neighboring layers on interfacial instabilities for functionalized incompatible polymers. It was experimentally confirmed, in this case, that weak disturbance can be predicted by considering an interface of nonzero thickness (corresponding to an interdiffusion/reaction zone interphase) instead of a purely geometrical interface between the two reactive layers. According to the rheological investigations, an experimental strategy was here formulated to investigate the parameters that controlled the stability of the reactive multilayer flows. The role of the viscosity ratio, elasticity ratio, and layer ratio of the stability of the interface was also investigated coupling to the reaction rate/compatibilization phenomenon. Hence, based on this analysis, guidelines for a stable coextrusion of reactive functionalized polymers can be provided coupling the classical parameters and the physicochemical affinity at the polymer/polymer interface. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] | ||||||||||||||||||||||||||||