bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of the Rheocasting Process and of the SLS Layer on the Fatigue Behavior of 357 Aluminum Alloy
Authors: Abou Antoun Alain , Brochu Myriam , Möller Heinrich
Published: September 2014

Two objectives were targeted: 1) compare the high cycle fatigue behavior of rheocast aluminum alloy 357 prepared by the swirl enthalpy equilibration device (SEED) and by the Council for Scientific and Industrial Research (CSIR) process, and 2) study the effect of surface liquid segregation (SLS) on the fatigue behavior of the CSIR material. Rectangular hourglass specimens machined from rheocast plates were tested at four stress amplitudes in axial fatigue with a stress ratio of R = -1 and a frequency of 20 Hz. Results obtained for SLS free specimens show that the SEED and the CSIR processes produce rheocast materials with comparable high cycle fatigue properties, 115 MPa at 107 cycles. In order to study the influence of surface liquid segregation, slightly polished specimens with a remaining SLS of nearly 750 microns thick were also tested. According to the results, the SLS reduces the average fatigue strength by approximately 5% (110 MPa vs. 115 MPa at 107 cycles). For SLS free specimens, the fatigue crack initiated at shrinkage cavities, oxide films or in the alpha globules. On the other hand, for specimens with SLS, no crack initiation in the alpha globules was observed. The main crack initiation mechanism was identified to be a deformation incompatibility between regions characterized by higher silicon content compared to nominal eutectic regions. The originality of the work is provided by the rigorous comparative analysis of the fatigue performance of components produced in two different rheocasting facilities, but tested in a single laboratory. It is also the first fundamental research published on the mechanical effect of surface liquid segregation. It confirms that SLS should be removed in critical areas in order to optimize the fatigue resistance of rheocast components.
Unconventional Microstructures in Tool Steel Obtained by Semi-Solid Processing and Subsequent Heat Treatment
Authors: Aišman David , Mašek Bohuslav , Jeníček Štěpán
Published: September 2014

Mechanical properties of all metals depend predominantly on the type and morphology of their microstructure. Microstructure attributes can be altered by various heat treating and thermomechanical treatment procedures. One of the advanced techniques profoundly affecting the microstructure evolution is semi-solid processing. It can produce unconventional microstructures even in conventional steel types. Moreover, subsequent heat treatment can also deliver a wide range of microstructures and correspondingly varied mechanical properties. In the present experimental programme, the X210Cr12 ledeburitic tool steel was studied. Its initial annealed microstructure consisted of ferritic matrix, chromium carbides and globular cementite particles. The semi-solid processed structure, on the other hand, contained polyhedral austenite grains embedded in carbide-austenite network. The austenite volume fraction exceeded 95 %. This microstructure was then altered by subsequent heat treatment or thermomechanical treatment. The experimental programme comprised three stages. At the first stage, the effects of the rate of cooling from the semi-solid region to the ambient temperature on the nature and morphology of the ledeburitic network and the austenitic grain size were explored. The second stage was aimed at the impact of tensile and compressive deformation applied after transition through semi-solid state on the microstructure evolution and, in particular, on grain size. Once suitable processing conditions and parameters were identified, the treatment led to a recrystallized austenitic microstructure with an average grain size of less than 3 μm. As high volume fractions of austenite were obtained, the third stage involved exploring the effects of thermal exposure. The stability of austenite and the decomposition of austenite into other microstructure constituents were mapped. Metallographic observation revealed a resulting wide range of microstructures from fine pearlite to martensite, depending on the heat treating schedule.
Study of Defect Formation during Solution Treatment of 319S Thixocast Turbo Impellers
Authors: Du Kang , Li Da Quan , Liang Xiao Kang , Zhu Qiang
Published: September 2014

Turbocharger impellers undergo extreme cyclic speed conditions and thus fatigue fracture in service. Any kind of defects, even defects with sizes of tens of micrometres, can make significant impact on service life of the impellers. The alloy used for thixocast impellers is the aluminum alloy 319s. T61 heat treatment is used to improve mechanical properties. However, the solution treatment in the standard T61 heat treatment of the 319s alloy can induce incipient melting defects. This paper carried out systematic study of formation of defects caused by the incipient melting during solution treatment in the thixocast and heat treated impellers, using optical and scanning electron microscope. Based on the study, the critical temperature of incipient melting is detected. An optimized two-stage solution treatment is therefore proposed.
Semisolid Processing of Magnesium Alloys: Microstructure - Property Relationship
Authors: Czerwiński Frank
Published: September 2014

An application of semisolid processing to magnesium alloys is discussed emphasizing both the fundamental and applied research activities aimed at better understanding the microstructure-property relationship. The reduced temperature of semisolid processing, providing common benefits of longer tool life, tighter dimensional tolerances and better process consistency is of special importance for magnesium alloys due to their high affinity to oxygen, requiring an expensive protection and leading otherwise to ignition and burning. However, the reduced temperature resulting in higher part integrity does not create beneficial microstructural characteristics converting to substantially improved mechanical properties. Major microstructural factors controlling properties of magnesium alloys after semisolid processing are discussed.
Semi-Solid Die Casting of Al-25%Si
Authors: Haga Toshio , Fuse Hiroshi
Published: September 2014

It became clear that semisolid Al-25%Si has excellent flow ability and suitable for thin product die casting thinner than 1mm. Semisolid die casting of thin fin was tried using Al-25%Si. The rheocasting was selected. The pouring temperature of melt was 1103K, and the casting temperature was as same as the liquidus line 1033K. The fine, which thickness was 0.5mm, height was 25mm and draft angle was 0.5 degree, could be cast at the plunger speed of 0.8 m/s. The primary Si was smaller than 0.2mm. The α-aluminum existed by the super cooling.
Semi-Solid Joining of D2 Cold-Work Tool Steel
Authors: Mohammed M.N. , Omar Mohd Zaidi , Syarif Junaidi , Sajuri Zainuddin , Salleh Mohd Shukor , Alhawari Khaled S.
Published: September 2014

Cold-work tool steel is considered to be a non-weldable metal due to its high percentage content of carbon and alloying elements. To address this problem the application of a new process of semisolid joining using a direct partial remelting method was developedto achieve a spherical join structure between two parts of AISI D2 cold-work tool steel. Since the surface oxidation of this metalis very high, the control of the atmosphere during joining had to be considered. Samples were heated in an argon atmosphere at two different temperatures of 1250°C and 1275°C for 10 minutes. Metallographic analyses along the joint interface showed that an increase in temperature promoted the final joining properties and also that at a liquid fraction of 15% joining was not fully practicable. However, a20% liquid fraction can produce a very good joint and microstructure as compared to the other experimental liquid fraction. Metallographic analyses along the joint interface showed a smooth transition from one to the other and neither oxides nor microcracking was observed. The current work confirmed that avoidance of a dendritic microstructure in the semisolid joined zone and high bonding quality components can be achieved without the need for force or complex equipment when compared to conventional welding processes.
Effect of Manganese on the Fe-Rich Phases in Al-22Si-2Fe Alloy by Cooling Slope
Authors: Jiang Ye Hua , Li Lu , Zhou Rong , Zhou Rong Feng , Wang Jia
Published: September 2014

Hypereutectic Al-Si alloys have low thermal expansion coefficients, excellent wear resistance, and high hardness. To replace cast iron with hypereutectic Al-Si alloys, the hypereutectic Al-Si alloys must still have the originally desired mechanical properties. The addition of Fe and Mn to the hypereutectic Al-Si alloys can form Fe-rich phases, which can improve thermal stability. In this paper, the effect of manganese (0 %, 0.99 %, and 1.36 %) on the Fe-rich phases of hypereutectic Al-22Si-2Fe (% w/w) alloys was studied. The results showed that primary Si particles (PSPs), needle-like Fe phases, a coarser fishbone-shaped α-Al15(Fe, Mn)3Si2 phases, and eutectic Si could be refined by cooling slope. With such a CS process, the intermetallic compounds in the alloys with different Mn/Fe ratios were examined with an optical microscope, scanning electron microscope, and X-ray diffraction. Moreover, the blocky α-Al15(Fe, Mn)3Si2 phases were analyzed by transmission electron microscopy. Through the analysis of the SADP, the lattice structures of α-Al15(Fe, Mn)3Si2 phases were identified with tetragonal structure and body centre cubic.
Tooling Materials and Solutions for Thixoforming Steel: A Key to the Process Industrialization
Authors: Rassili Ahmed , Lecomte-Beckers Jacqueline
Published: September 2014

Investigations on steel thixoforming started in the early 90s and many developments were carried out, mainly driven by the industrialization of the process. After a series of basic investigations on adapted steels and materials as well as near-net shaping investigations, the issue of mass production raised and thus induced some other challenges mainly on die life and process automation and cycling. High working temperatures and components complexity were than the main locks to mass productions. In most of reported literature, none of the involved research group reached or real production and industrialization criteria. The euro group holds most of these research investigations. We have reported many of these results in previous communications and this paper presents a continuity of what have already been presented. Some advanced tooling materials and solutions are presented and applied to a real complex industrial component.
Grain Refining through Semisolid Processing
Authors: Xia Ming Xu , Li Jian Guo , Fan Zhong Yun
Published: September 2014

Semisolid process can be used as grain refining method to replace conventional chemical grain refining approach. Typical semisolid slurry making techniques were introduced in the paper as potential semisolid grain refining methods. The temperature and morphology control for grain refining through semisolid process were enhanced to achieve fine particle size and large particle number rather than spheroidal particle shape or low viscosity of the slurry comparing with conventional rheo-forming process. The grain refinement effect was demonstrated by a 40 mm cylinder casting of AZ31 alloy.
Comparison between Prediction of Liquid Fraction versus Temperature and Experimental Results from DSC and SPSC
Authors: Zhang Du Yao , Atkinson Helen V. , Dong Hong Biao , Zhu Qiang
Published: September 2014

The processing window is important for the semisolid processability of alloys. This study focusses on the kinetics of diffusion. It compares prediction of fraction liquid versus temperature taking into account both thermodynamic and kinetics, with experimental results from Differential Scanning Calorimetry (DSC) and Single Pan Scanning Calorimetry (SPSC). SPSC is a novel technique with an order of magnitude higher accuracy than DSC. A range of Al-Si binary alloys has been investigated. The studies reveal that the simulation results predicted by DICTRA (DIffusion-Controlled TRAnsformations) show the same pattern with experimental results in the relationship of fraction liquid-temperature. However, the SPSC results are closer to the prediction results than DSC curves even with the relatively large sample size associated with SPSC. This is potentially a significant result as conventionally one of the difficulties is predicting the liquid fraction versus temperature for the heating of a billet for semi-solid processing. DSC results are known to be unrepresentative because the heating rates which can be achieved in DSC are much lower than those in induction heating. In addition, the DSC results are dependent on sample size and heating rate. The long term aim is to gain confidence in prediction with software packages which will reduce trial and error.
Microstructure and Property of Rheo-Diecasting Magnesium-Alloy with Forced Convection Mixing Process
Authors: Zhou Bing , Kang Yong Lin , Qi Ming Fan , Zhang Huan Huan , Zhu Guo Ming
Published: September 2014

Taking AZ91D magnesium alloy as experimental material, the rheo-diecasting process was implemented by combining the self-developed forced convection rheomoulding device with high pressure die casting machine. Microstructural characteristics of the RDC tensile samples were discussed. Microstructure of semisolid slurry at different rotational speed prepared by FCR device was investigated. Tensile properties and fracture morphology of rheo-diecasting process in different conditions were studied as well. The results indicate that the excellent semisolid microstructure of AZ91D tensile samples can be obtained by forced convection rheo-diecasting process. With the increase of rotational speed, the mean size of the primary particles diminishes and the shape factor increases. The tensile properties of as-cast RDC samples are obviously better than conventional diecasting samples. T6 heat treatment can increase tensile strength and elongation of RDC tensile samples to 286MPa and 6.1%, respectively. The yield strength and elongation of T4 heat treated RDC samples are 100MPa and 12.6%.
Influence of Microstructural Inhomogeneity on Fracture Behaviour in SSM-HPDC Al-Si-Cu-Fe Component with Low Si Content
Authors: Payandeh Mostafa , Jarfors Anders E.W. , Wessen Magnus
Published: September 2014

In the current paper, a low-Si containing aluminium alloy (1.4-2.2% Si) was used to fabricate a complex shape telecom component using Semi-Solid High-Pressure Die Cast (SSM-HPDC), process. Microstructure and fracture characteristics were investigated. The cast material exhibited microstructural inhomogeneity, in particular macrosegregation in the form of liquid surface segregation bands in addition to sub-surface pore bands and gross centre porosity. Tensile specimen were taken from the cast components. Elongation and microstructural inhomogeneity were investigated and correlated. Fracture surfaces of the tensile specimen were examined under scanning electron microscope (SEM). The study showed that both near surface liquid segregation bands and subsurface porosity strongly affected the fracture behaviour. Dominant for loss of ductility were gross centre porosity. This centre porosity was found to be a combination of trapped gas and insufficient, irregular feeding patterns.
Global existence and decay for solutions of the Hele–Shaw flow with injection
Authors: Cheng C.H. Arthur , Coutand Daniel , Shkoller Steve
Published: September 2014

We examine the stability and decay of the free boundary perturbations in a Hele-Shaw cell under the injection of fluid. In particular, we study the perturbations of spherical boundaries as time

t \to +\infty

. In the presence of positive surface tension, we examine both
slow
and
fast
injection rates. When fluid is injected slowly, the perturbations decay back to an expanding sphere exponentially fast, while for fast injection, the perturbation decays to an expanding sphere with an algebraic rate. In the absence of surface tension, we study the case of a constant injection rate, and prove that perturbations of the sphere decay like

(1+t)^{-1/2+ \epsilon }

for

\epsilon >0

small.
The fractional Cheeger problem
Authors: Brasco Lorenzo , Lindgren Erik , Parini Enea
Published: September 2014

Given an open and bounded set

\Omega\subset\mathbb{R}^N

, we consider the problem of minimizing the ratio between the

s

-perimeter and the

N

-dimensional Lebesgue measure among subsets of

\Omega

. This is the nonlocal version of the well-known
Cheeger problem
. We prove various properties of optimal sets for this problem, as well as some equivalent formulations. In addition, the limiting behaviour of some nonlinear and nonlocal eigenvalue problems is investigated, in relation with this optimization problem. The presentation is as self-contained as possible.
The Pursuit of Pleasure
Authors: Rendell Jane
Published: September 2014

The Pursuit of Pleasure presents the figures of the rambler and the cyprian, the Eighteenth Century precursors to the Parisian flaneur and prostitute. The urban spaces traced by these figures were the clubs, sporting venues, operas, assembly rooms, streets and arcades of central London.Drawing on critical theory, geography and philosophy, The Pursuit of Pleasure extends and critiques the discipline of architectural history from a feminist perspective. The gendering of public space is considered to be a complex and shifting series of moves and looks between men and women, constructed and represented through spatial and social relations of consumption, display and exchange.Illustrated with contemporary prints and drawings, The Pursuit of Pleasure is an extraordinarily rich analysis of the gendered issues of public space at the birth of the modern metropolis.
Integration at the Border
Authors: Vries Karin de
Published: September 2014

A recent development in the immigration policies of several European states is to make the admission of foreign nationals dependent upon criteria relating to their integration. As the practice of ‘integration testing abroad’ becomes more widespread, this book endeavours to clarify the legal implications which have hitherto remained poorly understood and studied.

The book begins by looking at the situation in the Netherlands, which was the first EU Member State to introduce pre-entry integration requirements. It explores the historical and political origins of the Dutch Act on Integration Abroad and explains how, in this national context, integration has become a criterion for the selection of immigrants. It then examines how integration requirements must be evaluated from the point of view of European and international law, including human rights treaties, EU migration directives and association agreements and the law on non-discrimination. The book identifies the legal standards set by these instruments with regard to integration testing abroad and draws conclusions as to the lawfulness of the Dutch approach.
The Hague Trusts Convention
Authors: Harris Jonathan
Published: September 2014

Trusts cross borders. When they do,real difficulties may arise. Will the understanding of what a trust is be different in a foreign state? Will the rights, powers and duties of the trustee and settlor be the same? What rights will the beneficiary be able to assert? To what extent will the trust assets be safe from the claims of creditors, forced heirs, or third parties? Which legal system will be applied to the trust? Within what limits? What if the trust needs to be recognised in a state which does not have the institution of the trust in its domestic law?

The Hague Trusts Convention, enacted into English law by the Recognition of Trusts Act 1987, seeks to ameliorate the situation by providing harmonised choice of law rules for “trusts created voluntarily and evidenced in writing.” It also provides for the recognition of trusts in Contracting States. Those Contracting States should recognise the trust, even if they do not have the institution in their domestic law.

This book is the first published in England to devote itself to a detailed analysis of the Convention. It is aimed at academics and practitioners; at private international lawyers and at trust lawyers. Frequent reference is made to the position in civil law states (especially in the Contracting States of Italy and the Netherlands) and in other trust states, both offshore and onshore.

The Hague Trusts Convention deals with the operation of the trust itself. It does not deal with the preliminary steps needed to create a trust. These preliminary matters raise highly complex and uncharted choice of law issues. Detailed discussion of these matters is also provided, and appropriate solutions suggested.
How stratospheric are deep stratospheric intrusions?
Authors: Trickl T. , Vogelmann H. , Giehl H. , Scheel H.-E. , Sprenger M. , Stohl A.
Published: September 2014

Abstract. Preliminary attempts of quantifying the stratospheric ozone contribution in the observations at the Zugspitze summit (2962 m a.s.l.) next to Garmisch-Partenkirchen in the German Alps had yielded an approximate doubling of the stratospheric fraction of the Zugspitze ozone during the time period 1978 to 2004. These investigations had been based on data filtering by using low relative humidity (RH) and elevated 7Be as the criteria for selecting half-hour intervals of ozone data representative of stratospheric intrusion air. To quantify the residual stratospheric component in stratospherically influenced air masses, however, the mixing of tropospheric air into the stratospheric intrusion layers must be taken into account. In fact, the dewpoint mirror instrument at the Zugspitze summit station rarely registers RH values lower than 10% in stratospheric air intrusions. Since 2007 a programme of routine lidar sounding of ozone, water vapour and aerosol has been conducted in the Garmisch-Partenkirchen area. The lidar results demonstrate that the intrusion layers are drier by roughly one order of magnitude than indicated in the in situ measurements. Even in thin layers RH values clearly below 1% have frequently been observed. These thin, undiluted layers present an important challenge for atmospheric modelling. Although the ozone values never reach values typical of the lower-stratosphere it becomes, thus, obvious that, without strong wind shear or convective processes, mixing of stratospheric and tropospheric air must be very slow in most of the free troposphere. As a consequence, the analysis the Zugspitze data can be assumed to be more reliable than anticipated. Finally, the concentrations of Zugspitze carbon monoxide rarely drop inside intrusion layers and normally stay clearly above full stratospheric values. This indicates that most of the CO, and thus the intrusion air mass, originates in the shallow "mixing layer" around the thermal tropopause. The CO mixing ratio in these descending layers between 1990 and 2004 exhibits a slightly positive trend indicating some Asian influence on the lowermost stratosphere in the high-latitude source region of most intrusions reaching the station.
Recent satellite-based trends of tropospheric nitrogen dioxide over large urban agglomerations worldwide
Authors: Schneider P. , Lahoz W. A. , van der A R.
Published: September 2014

Abstract. Trends in tropospheric nitrogen dioxide (NO2) concentrations over 66 large urban agglomerations worldwide have been computed using data from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument onboard the Envisat platform for the period August 2002 to March 2012. A seasonal model including a linear trend was fitted to the satellite-based time series over each site. The results indicate distinct spatial patterns in trends. While agglomerations in Europe, North America, and some locations in East Asia/Oceania show decreasing tropospheric NO2 levels on the order of −5 % yr−1, rapidly increasing levels of tropospheric NO2 are found for agglomerations in large parts of Asia, Africa, and South America. The site with the most rapidly increasing absolute levels of tropospheric NO2 was found to be Tianjin in China with a trend value of 3.04 (±0.47) × 1015 molecules cm−2 yr−1, whereas the site with the most rapidly increasing relative trend was Kabul in Afghanistan with 14.3 (±2.2) % yr−1. In total, 34 sites exhibited increasing trends of tropospheric NO2 throughout the study period, 24 of which were found to be statistically significant. A total of 32 sites showed decreasing levels of tropospheric NO2 during the study period, of which 20 sites did so at statistically significant magnitudes. Overall, going beyond the relatively small set of megacities investigated previously, this study provides the first consistent analysis of recent changes in tropospheric NO2 levels over most large urban agglomerations worldwide.
Probing the sensitivity of polarimetric O2 A-band measurements to clouds with emphasis on potential OCO-2 and GOSAT retrievals
Authors: Sanghavi S. , Lebsock M. , Stephens G.
Published: September 2014

Abstract. Clouds play a crucial role in the Earth's radiative budget, yet their climate feedbacks are poorly understood. The advent of space-borne high resolution spectrometers probing the O2 A-band, such as the GOSAT and OCO-2 satellites, could make it possible to simultaneously retrieve several cloud parameters that play a vital role in the Earth's radiative budget, thereby allowing a reduction of the corresponding uncertainty due to clouds. In this work, the hyperspectral, polarimetric response of the O2 A-band to mainly three important cloud parameters, viz., optical thickness, top height and droplet size has been studied, revealing a different sensitivity to each for the varying atmospheric absorption strength within the A-band. Cloud optical thickness finds greatest sensitivity in both intensity and polarization measurements at non-absorbing wavelengths. Cloud height had a negligible effect on intensity measurements at non-absorbing wavelengths, but finds maximum sensitivity at an intermediate absorption strength, which increases with cloud height. The same is found to hold for cloud geometric thickness, except that the sensitivity is weaker. Sensitivity to droplet size is generally weaker than to cloud optical thickness to top height at non-absorbing wavelengths and diminishes further with increasing absorption strength. It has been shown that significantly more information on droplet size can be drawn from multiangular measurements. Our results show that, in the absence of sunglint, the backscatter direction is richer in information on droplet size, especially in the glory and rainbow regions. It has been shown that I and Q generally have differing sensitivities to cloud parameters. Thus, accurate measurements of both orthogonal components Ih and Iv (as in GOSAT) are expected to contain more information than measurements of only I, Ih or Iv (as in the case of OCO-2).
Trimethylamine emissions in animal husbandry
Authors: Sintermann J. , Schallhart S. , Kajos M. , Jocher M. , Bracher A. , Münger A. , Johnson D. , Neftel A. , Ruuskanen T.
Published: September 2014

Abstract. Degradation of plant material by animals is an important transformation pathway in the nitrogen (N) cycle. During the involved processes, volatile reduced alkaline nitrogen compounds, mainly ammonia (NH3) and aliphatic amines such as trimethylamine (TMA), are formed. Today, animal husbandry is estimated to constitute a main source of aliphatic amines in the atmosphere with TMA being the main emitted compound. Here, we show how the interaction between faeces and urine in animal production systems provides the primary source for agricultural TMA emissions. Excreted urine contains large quantities of urea and TMA-N-oxide, which are transformed into NH3 and TMA, respectively, via enzymatic processes provided by microbes present in faeces. TMA emissions from areas polluted with urine–faeces mixtures are on average of the order of 10 to 50 nmol m−2s−1. Released amines promote secondary aerosol particle formation in the agricultural emission plume. The atmospheric lifetime of TMA, which was estimated to be of the order of 30 to 1000 s, is determined by the condensation onto aerosol particles.
Satellite observations of the small-scale cyclonic eddies in the western South China Sea
Authors: Liu F. , Tang S. , Chen C.
Published: September 2014

Abstract. High-resolution ocean color observation offers an opportunity to investigate the oceanic small-scale processes. In this study, The Medium Resolution Imaging Spectrometer (MERIS) daily 300 m data are used to study small-scale processes in the western South China Sea. It is indicated that the cyclonic eddies with horizontal scales of the order of 10 km are frequently observed during upwelling season of each year over 2004–2009. These small-scale eddies are generated in the vicinity of the southern front of the cold tongue, and then propagate eastward with a speed of approximately 12 cm s−1. This propagation speed is consistent with the velocity of the western boundary current. As a result, the small-scale eddies keep rotating high levels of the phytoplankton away from the coastal areas, resulting in the accumulation of phytoplankton in the interior of the eddies. The generation of the small-scale eddies may be associated with strengthening of the relative movement between the rotation speed of the anticylconic mesoscale eddies and the offshore transport. With the increases of the normalized rotation speed of the anticyclonic mesoscale eddies relative to the offshore transport, the offshore current become meander under the impacts of the anticyclonic mesoscale eddies. The meandered cold tongue and instability front may stimulate the generation of the small-scale eddies. Unidirectional uniform wind along cold tongue may also contribute to the formation of the small-scale eddies.
Quantifying environmental stress induced emissions of algal isoprene and monoterpenes using laboratory measurements
Authors: Meskhidze N. , Sabolis A. , Reed R. , Kamykowski D.
Published: September 2014

Abstract. We report here production rates of isoprene and monoterpene compounds (α-pinene, β-pinene, camphene and d-limonene) from six phytoplankton monocultures as a function of irradiance and temperature. Irradiance experiments were carried out for diatom strains – Thalassiosira weissflogii and Thalassiosira pseudonana; prymnesiophyte strains – Pleurochrysis carterae; dinoflagellate strains – Karenia brevis and Prorocentrum minimum; cryptophyte strains – Rhodomonas salina, while temperature experiments were carried out for diatom strains – Thalassiosira weissflogii and Thalassiosira pseudonana. Phytoplankton species, incubated in a climate-controlled room, were subject to variable light (90 to 900 μmol m−2s−1) and temperature (18 to 30 °C) regimes. Compared to isoprene, monoterpene emissions were an order of magnitude lower at all light and temperature levels. Emission rates are normalized by cell count and Chlorophyll a (Chl a) content. Diatom strains were the largest emitters, with ~2x1017g (cell)−1h−1 (~35 μg (g Chl a)−1h−1) for isoprene and ~5x10−19 g (cell)−1h−1 (~1μg (g Chl a)−1) h−1) for α-pinene. The contribution to the total monoterpene production was ~70% from α-pinene, ~20% for d-limonene, and <10% for camphene and β -pinene. Phytoplankton species showed a rapid increase in production rates at low (<150 μmol m−2s−1) and a gradual increase at high (>250 μmol m−2s−1) irradiance. Measurements revealed different patterns for time-averaged emissions rates over two successive days. On the first day most of the species showed distinct increase in production rates within the first four hours, while on the second day the emission rates were overall higher, but less variable. The data suggest that enhanced amounts of isoprene and monoterpenes are emitted from phytoplankton as a result of perturbations in environmental conditions that cause disbalance in chloroplasts and forces primary producers to acclimate physiologically. This relationship could be a valuable tool for development of dynamic ecosystem modeling approaches for global marine isoprene and monoterpene emissions based on phytoplankton physiological responses to a changing environment.
Biostratigraphic evidence of dramatic Holocene uplift of Robinson Crusoe Island, Juan Fernández Ridge, SE Pacific Ocean
Authors: Sepúlveda P. , Le Roux J. P. , Lara L. E. , Orozco G. , Astudillo V.
Published: September 2014

Abstract. A study of the biostratigraphy and sedimentology of Holocene deposits on Robinson Crusoe Island (RCI) on the Juan Fernández Ridge (JFR) indicates that a~dramatic but localized uplift occurred since 8000 BP, at a rate of about 8.5 mm yr−1. In fact, supratidal flats and sand layers with marine gastropods (mostly Nerita sp.) are now exposed ca. 70 m a.s.l., and covered by transitional dunes. The last volcanic activity on RCI occurred at ca. 0.8 Ma (active hotspot located 280 km further west) and there is no sign of a compensating bulge that explains this uplift, isobaths of the sea floor instead suggesting general subsidence. However, modeling indicates that large-scale landslides followed by isostatic rebound are a viable explanation, partially reflected in the low-resolution bathymetry of the area.
The relative importance of phytoplankton aggregates and zooplankton fecal pellets to carbon export: insights from free-drifting sediment trap deployments in naturally iron-fertilised waters near the Kerguelen plateau
Authors: Laurenceau E. C. , Trull T. W. , Davies D. M. , Bray S. G. , Doran J. , Planchon F. , Carlotti F. , Jouandet M.-P. , Cavagna A.-J. , Waite A. M. , Blain S.
Published: September 2014

Abstract. The first KErguelen Ocean and Plateau compared Study (KEOPS1), conducted in the naturally iron-fertilised Kerguelen bloom, demonstrated that fecal material was the main pathway for exporting carbon to the deep ocean during summer (January–February~2005), suggesting a~limited role of direct export via phytodetrital aggregates. The KEOPS2 project re-investigated this issue during the spring bloom initiation (October–November 2011), when zooplankton communities may exert limited grazing pressure, and explored further the link between carbon flux, export efficiency and dominant sinking particles depending upon surface plankton community structure. Sinking particles were collected in polyacrylamide gel-filled and standard free-drifting sediment traps (PPS3/3), deployed at six stations between 100 and 400 m to examine flux composition, particle origin and their size distributions. Results revealed an important contribution of phytodetrital aggregates (49 ± 10% and 45 ± 22% of the total number and volume of particles respectively, all stations and depths averaged). This high contribution dropped when converted to carbon content (30 ± 16% of total carbon, all stations and depths averaged), cylindrical fecal pellets representing then the dominant fraction (56 ± 19%). At 100 and 200 m depth, iron and biomass enriched sites exhibited the highest carbon fluxes (maxima of 180 and 84 ± 27 mg C m−2 d−1; based on gel and PPS3/3 trap collection respectively), especially where large fecal pellets dominated over phytodetrital aggregates. Below these depths, carbon fluxes decreased (48 ± 21% decrease in average between 200 and 400 m), and mixed aggregates composed of phytodetritus and fecal matter dominated, suggesting an important role played by physical aggregation in deep carbon export. Export efficiencies determined from gels, PPS3/3 traps and 234Th disequilibria (200 m carbon flux/net primary productivity), were negatively correlated to net primary productivity with observed decreases from ~ 0.2 at low-iron sites to ~ 0.02 at high-iron sites. Varying phytoplankton communities and grazing pressure appear to explain this negative relationship. Our work emphasizes the need to consider detailed plankton community structure to accurately identify the controls on carbon export efficiency, which appear to include small spatio-temporal variations of ecosystem structure.
Smoothing Parameter Estimation for Markov Random Field Classification of non-Gaussian Distribution Image
Authors: Aghighi H. , Trinder J. , Wang K. , Tarabalka Y. , Lim S.
Published: September 2014

Abstract. In the context of remote sensing image classification, Markov random fields (MRFs) have been used to combine both spectral and contextual information. The MRFs use a smoothing parameter to balance the contribution of the spectral versus spatial energies, which is often defined empirically. This paper proposes a framework to estimate the smoothing parameter using the probability estimates from support vector machines and the spatial class co-occurrence distribution. Furthermore, we construct a spatially weighted parameter to preserve the edges by using seven different edge detectors. The performance of the proposed methods is evaluated on two hyperspectral datasets recorded by the AVIRIS and ROSIS and a simulated ALOS PALSAR image. The experimental results demonstrated that the estimated smoothing parameter is optimal and produces a classified map with high accuracy. Moreover, we found that the Canny-based edge probability map preserved the contours better than others.
Spectroscopic analysis of soil metal contamination around a derelict mine site in the Blue Mountains, Australia
Authors: Shamsoddini A. , Raval S. , Taplin R.
Published: September 2014

Abstract. Abandoned mine sites pose the potential threat of the heavy metal pollution spread through streams and via runoff leading to contamination of soil and water in their surrounding areas. Regular monitoring of these areas is critical to minimise impacts on water resources, flora and fauna. Conventional ground based monitoring is expensive and sometimes impractical; spectroscopic methods have been emerged as a reliable alternative for this purpose. In this study, the capabilities of the spectroscopy method were examined for modelling soil contamination from around the abandoned silver-zinc mine located at Yerranderie, NSW Australia. The diagnostic characteristics of the original reflectance data were compared with models derived from first and second derivatives of the reflectance data. The results indicate that the models derived from the first derivative of the reflectance data estimate heavy metals significantly more accurately than model derived from the original reflectance. It was also found in this study that there is no need to use second derivative for modelling heavy metal soil contamination. Finally, the results indicate that estimates were of greater accuracy for arsenic and lead compared to other heavy metals, while the estimation for silver was found to be the most erroneous.
Object-Based Classification of Multi-temporal Images for Agricultural Crop Mapping in Karacabey Plain, Turkey
Authors: Ozdarici-Ok A. , Akyurek Z.
Published: September 2014

Abstract. The objective of this research is to classify major crop types cultivated in Karacabey Plain of north western Turkey using multitemporal Kompsat-2 and Envisat ASAR data with an object-based methodology. First a pansharpening algorithm is applied to each panchromatic and multispectral Kompsat-2 data to produce colour images having 1m spatial resolution. Next, Mean-Shift image segmentation procedure is applied to the pansharpened Kompsat-2 data with multiple parameter combinations. Multiple goodness measures are utilized to evaluate the object-based results. The optimum objects are then employed in object-based classifications of the single-date images. Next, single-date multispectral (MS) Kompsat-2 images and Kompsat-2 images along with the Envisat ASAR data are classified with the Support Vector Machines (SVMs) method. The training samples are provided automatically by the selected objects based on spatial statistical properties. Next, probability maps are generated for each image in pixel-based manner during the image classification operations. The maximum probabilities are then assigned to the pixels as class labels and the combined thematic maps (June-July, June-August, June-July-August) are generated in pixel-based and object-based manners. The produced thematic maps are evaluated through the confusion matrices and compared also with the results of parcel-based classifications using original agricultural parcels. Results indicate that the combined thematic maps of June-August and June-July- August provide the highest overall accuracy and kappa value approximately 92 % and 0.90, respectively.
IASON – Fostering sustainability and uptake of research results through Networking activities in Black Sea & Mediterranean areas
Authors: Patias P.
Published: September 2014

Abstract. IASON Project has the ultimate goal to establish a permanent and sustainable Network of scientific and non-scientific institutions, stakeholders and private sector enterprises belonging in the EU and third countries located in two significant areas: The Mediterranean and the Black Sea regions. The main focal points of the project will be the usage and application of Earth Observation (EO) in the following topics: – climate change – resource efficiency – raw materials management IASON aims to build on the experiences gained by 5 FP7 funded projects, OBSERVE, enviroGRIDS, GEONETCab, EGIDA, and BalkanGEONet. All of the above projects focused on enhancing EO capacities, knowledge and technology in the EU and in neighborhood countries. During their execution time they managed to establish links with a critical mass of research institutions, organizations, public organizations, stakeholders, and policy makers in the Balkan region, the Mediterranean, and the Black Sea Basin. IASON intends to create the proper conditions for enhancing knowledge transfer capacity building, and market opportunities in using EO applications and mechanisms in specific research fields that are addressing climate actions resource efficiency and raw materials management.
NDVI from Landsat 8 Vegetation Indices to Study Movement Dynamics of Capra Ibex in Mountain Areas
Authors: Pirotti F. , Parraga M. A. , Sturaro E. , Dubbini M. , Masiero A. , Ramanzin M.
Published: September 2014

Abstract. In this study we analyse the correlation between the spatial positions of Capra ibex (mountain goat) on an hourly basis and the information obtained from vegetation indices extracted from Landsat 8 datasets. Eight individuals were tagged with a collar with a GNSS receiver and their position was recorded every hour since the beginning of 2013 till 2014 (still ongoing); a total of 16 Landsat 8 cloud-free datasets overlapped that area during that time period. All images were brought to a reference radiometric level and NDVI was calculated. To assess behaviour of animal movement, NDVI values were extracted at each position (i.e. every hour). A daily "area of influence" was calculated by spatially creating a convex hull perimeter around the 24 points relative to each day, and then applying a 120 m buffer (figure 4). In each buffer a set of 24 points was randomly chosen and NDVI values again extracted. Statistical analysis and significance testing supported the hypothesis of the pseudo-random NDVI values to be have, in average, lower values than the real NDVI values, with a p value of 0.129 for not paired t test and p value of < 0.001 for pairwise t test. This is still a first study which will go more in depth in near future by testing models to see if the animal movements in different periods of the year follow in some way the phenological stage of vegetation. Different aspects have to be accounted for, such as the behaviour of animals when not feeding (e.g. resting) and the statistical significance of daily distributions, which might be improved by analysing broader gaps of time.
A New Unsupervised Change Detection Approach Based On DWT Image Fusion And Backtracking Search Optimization Algorithm For Optical Remote Sensing Data
Authors: Atasever U. H. , Civicioglu P. , Besdok E. , Ozkan C.
Published: September 2014

Abstract. Change detection is one of the most important subjects of remote sensing discipline. In this paper, a new unsupervised change detection approach is proposed for multi-temporal remotely sensed optic imagery. This approach does not require any prior information about changed and unchanged pixels. The approach is based on Discrete Wavelet Transform (DWT) based image fusion and Backtracking Search Optimization Algorithm (BSA). In the first step of the approach, absolute-valued difference image and absolute-valued log-ratio image is calculated from co-registered and radiometrically corrected multi-temporal images. Then, these difference images are fused using DWT. The fused image is filtered by median filter for edge information preservation and by wiener filter for image smoothing. Then, a min-max normalization is applied to the filtered data. The normalized data is clustered into two groups with BSA as changed and unchanged pixels by minimizing an objective function, unlike classical methods using CVA, PCA, FCM or K-means techniques. To show effectiveness of proposed approach, two remote sensing data sets, Sardinia and Mexico, are used. False Alarm, Missed Alarm, Total Alarm and Total Error Rate are selected as performance criteria to evaluate the effectiveness of new approach using ground truth images. Experimental results show that proposed approach is effective for unsupervised change detection of optical remote sensing data.
Influence of temporal baseline on the vertical absolute accuracies of TSX HS interferometric DSMs: Case Study on Berlin
Authors: Sefercik U. G. , Soergel U.
Published: September 2014

Abstract. In recent years, interferometric sytnthetic aperture radar (InSAR) is one of the most preferred techniques to generate digital surface models (DSM) which are the three dimensional (3D) digital cartographic representations of earth surface including all terrain and non-terrain formations. Interferometric DSM generation using synthetic aperture radar (SAR) imagery is not an easy process and the vertical absolute accuracy of the final product depends on various parameters. In this study, we aimed to demonstrate the influence of temporal baseline between SAR image-pairs on the vertical absolute accuracy of high resolution interferometric DSMs. The application was realized covering 20 km2 area in Berlin, Germany using 15 descending orbit high resolution spotlight (HS) TerraSAR-X (TSX) images. The suitable interferometric pairs were determined for DSM generation and two of them that have similar parameters except temporal baseline were selected regarding the purposes of the study. The master image was selected as same in the generation of both DSMs and the temporal baselines between this master image and slave images were 11 days (1 period) and 187 days (17 periods), respectively. TSX HS DSMs were generated with 2 m grid spacing and the vertical absolute accuracies were calculated based on the comparison with a reference DSM generated by radargrammetry. The analyses were realized for built-up and forest land classes separately. The results proved that longer temporal baseline has negative influence on the vertical absolute accuracies of TSX HS interferometric DSMs. The first DSM which has the shortest temporal baseline, possible for TSX sensing is better than the second one as approx. 1.5 m both for built-up and forest areas.
Flood Mapping Using InSAR Coherence Map
Authors: Selmi S. , Ben Abdallah W. , Abdelfatteh R.
Published: September 2014

Abstract. Classic approaches for the detection of flooded areas are based on a static analysis of optical images and/or SAR data during and after the event. In this paper, we aim to extract the flooded zones by using the SAR image coupled with the InSAR coherence. A new formulation of the ratio approach for flood detection is given considering InSAR coherence. Our contribution is to take advantage from the coherence map provided using the InSAR pairs (one before and one after the event) to enhance the detection of flooded areas. We explore the fact that the coherence values during and after the flood are mainly differents on the flooded zones and we give a more suitable flood decision rule using this assumption. The proposed approach is tested and validated in the case of the flood taken place in 2005 in the region of Kef in Tunisia.