bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue Crack Propagation in Haynes 230: A Comparison between Single and Polycrystal Crack Closure Levels
Authors: Beretta Stefano , Foletti Stefano , Rabbolini Silvio , Sehitoglu Huseyin
Published: December 2016

An experimental campaign was developed to evaluate fatigue crack growth in Haynes 230. The effects of plasticity induced crack closure were investigated with Digital Image Correlation. In particular, crack opening levels were measured with the digital extensometer technique, which allowed the evaluation of crack flanks relative displacements. Experimental results were compared with a reference da/dn – ΔKeff curve and with the data of a previous study, which analyzed single crystal propagation. It was found that the adoption of crack closure local measurements provided an accurate estimation of crack propagation driving forces, since all the experimental points from single crystals and polycrystals collapse onto the da/dn – ΔKeff curve.
Grain Size Effect on Low Cycle Fatigue Behavior of High Strength Structural Materials
Authors: Ebara Ryuichiro
Published: December 2016

This paper presents grain size effect on low cycle fatigue behavior of high strength maraging steel with gain size of 20,60 and 100μm and Ti-6Al-4V alloy with grain size of 0.5,1.4 and 5.1μm. Low cycle fatigue strength of the maraging steel depends on grain size in number of cycles up to 103.The smaller the grain size, the higher the low cycle fatigue strength was. Quasci-cleavage fracture surfaces were predominant for material with grain size of 20μm,while intergranular fracture surfaces were predominant for materials with larger grain size in number of cycles lower than 60. Striation was predominant for all tested materials in number of cycles higher than 60.Low cycle fatigue strength of Ti-6Al-4V alloy also depends on grain size in number of cycles up to 104. Grain size dependent transgranular fracture surfaces were predominant for materials with ultra-fine grain size of 0.5μm and fine grain size of 1.4μm.
Study of Fracture Resistance of Nanolaminate Coatings Using Indentation and Impact Tests
Authors: Buršíková Vilma , Sobota Jaroslav , Grossman Jan , Fořt Tomáš , Dupák Libor , Zábranský Lukáš , Souček Pavel , Vašina Petr , Buršík Jiří
Published: December 2016

The aim of the present work was to study the mechanical properties of thin nanocomposite Mo-B-C coatings consisting of nanocrystalline Mo2BC embedded in amorphous Mo-B-C matrix. Magnetron sputtering of three targets, B4C, C and Mo, was used for coatings preparation. The Mo-B-C coatings were deposited on high speed steel substrates. The fracture resistance of Mo-B-C coatings was studied by both indentation and dynamic impact tests. The impact tests enabled us to predict the load limit causing the coating destruction.
Influence of Defects on High Cycle Fatigue Response of Ti45Nb Biocompatible Alloy
Authors: Delshadmanesh Mitra , Khatibi Golta , Lederer Martin , Zehetbauer Michael J. , Danninger Herbert
Published: December 2016

The high cycle fatigue response of Ti-45Nb alloy was investigated by using an ultrasonic fatigue testing system. The effect of notch geometry on the fatigue response was studied on samples with different circumferential grooves. The experiments showed a decrease of fatigue notch sensitivity with decreasing the notch radius. Finite element analysis (FEA) was conducted for calculation of the stress distribution in the samples and interpretation of the experimental results. Further, the lifetime of the alloy showed a strong dependency on the location of the defects and microstructural inhomogeneities. It was observed that at the same stress amplitude, early failure was caused by surface defects, while those with a longer lifetime failed due to cracks originating from internal flaws.
The Changes in Surface Morphology and Mechanical Properties of Poly(3-Hydroxybutyrate) and its Copolymer Films during In Vitro Degradation
Authors: Zhuikov Vsevolod , Bonartsev Anton , Bagrov Dmitry , Rusakov Alexey , Useinov Alexey , Myshkina Vera , Mahina Tatiana , Shaitan Konstantin , Bonartseva Garina
Published: December 2016

In the current work, we studied the degradation of PHB films in vitro by pancreatic lipase and in phosphate buffer saline (PBS). We traced the changes in film properties by several analytical methods: the change of weight, surface roughness and morphology (by atomic-force microscopy) and Young’s modulus (by nanoindentation) were measured.PHB is a semicrystalline polymer and thus the films have lamellar structure. During biodegradation, three types of changes were observed on the film surface: appearance of new lamellae, disappearance of lamellae and disintegration of lamellae into shorter fragments. During the six months of polymer films degradation the weight of samples decreased; and an increase in Young's modulus due to the relatively fast degradation of the amorphous areas was observed by nanoindentation.
Microstructural Finite-Element Analysis of Influence of Bone Density and Histomorphometric Parameters on Mechanical Behavior of Mandibular Cancellous Bone Structure
Authors: Marcián Petr , Florian Zdeněk , Horáčková Ladislava , Kaiser Jozef , Borák Libor
Published: December 2016

Using porous bioceramics became recently an alternative approach to increase bone density which is a key factor for successful dental implant application. These novel biomaterials should substitute missing natural trabecular structures in terms of material strength as well as deformation characteristics. However, mechanical behavior of these materials used as bone fillers are still in question. This problem is made more difficult by the fact that bone structure itself exhibits a complex mechanical behavior which is still in question as well and, therefore, appropriate analytical criteria should to be established. The purpose of this paper is to determine typical mechanical behavior of trabecular structure of mandibular cancellous bone using computational simulations which can serve as a basis for establishing such criteria. For this purpose, four bone specimens of various bone density were μCT-scanned and high-level finite element models including detailed trabecular structure were created on their basis to analyze relevant mechanical quantities for various loadings in terms of bone density and various histomorphometric parameters.
Single and Multielement Coatings in a Fluidized Bed Reactor
Authors: Anthymidis Konstantinos , Trakali Afroditi , Tsipas Dimitrios N.
Published: December 2016

Heat treatments of alloys in fluidized bed reactors have been carried out for more than twenty-five years. Recently this technology has been used for surface engineering applications in the deposition of hard and/or corrosion resistant layers e.g. aluminizing, chromizing, nitriding, carburizing, boronizing. The fluidized bed method is simple, efficient, environmentally friendly and capable of immediate adjusting the furnace atmosphere for specific requirements e.g. production of multielement coatings. The boride coatings on steel have an excellent combination of properties e.g. high fatigue strength and wear resistance. On the other hand silicide coatings are well known for their excellent corrosion resistance. Boron-siliconizing in fluidized beds is a promising method to improve both the wear and corrosion properties of steels. In the present paper fluidized bed technology (FBT) was used to deposit boride and boron-silicide coatings on steels. The coatings were examined by means of electron and optical microscopy and X-Rays diffraction, in terms of the coatings composition, morphology, thickness and phase formation. The coatings tribological properties were evaluated under dry wear.
Formation of Thermally Sprayed Coatings on Grid-Like Structure Substrate
Authors: Jech David , Čelko Ladislav , Klakurková Lenka , Slámečka Karel , Horynová Miroslava , Švejcar Jiří
Published: December 2016

The main goal of this contribution is to investigate the influence of the substrate morphology on the resulting thermally sprayed coatings microstructure. Therefore, three different representative coating systems and/or thermal spray techniques were utilized to produce the coatings on grid-like structure substrates: (i) CoNiCrAlY bond coat (BC) sprayed by high velocity oxygen fuel (HVOF) technique and yttria stabilized zirconia (YSZ) top coat (TC) sprayed by means of atmospheric plasma spray (APS) technique, (ii) YSZ coating sprayed by means of APS and (iii) YSZ coating sprayed by means of nanoparticle colloid suspension plasma spraying (SPS). The shadowing effect of thermal spray coatings in relation with the grid-like substrate structure was investigated in detail. Resulting microstructure of sprayed samples was studied utilizing light microscopy, digital image analysis, scanning electron microscopy, energy-dispersive spectrometer and X-ray diffraction techniques.
The Influence of Plasma Nitriding Period on Nitrided Layers Thickness
Authors: Pilch Ondrej , Hruby Vojtěch
Published: December 2016

The plasma nitriding as a technology for finishing of material surface layers was carried out on selected material. The effect of plasma nitriding conditions on the thickness and hardness of nitrided layer was investigated. The influence of plasma nitriding period on the thickness of the plasma nitrided layers was comprehensively assessed on the C55 steels. Plasma nitriding was carried out on selected material at 500 °C under 280 Pa with a mixture atmosphere of H2 and N2 in the plasma nitriding equipment. The period of the plasma nitriding process was changeable from 5 to 20 hours. Measurements of the properties of nitrided layers of selected material were solved by using experimental methods in accordance with standards. The samples were characterized by GDOES spectrometry, optical microscopy, and hardness testing. The depths of the plasma nitriding layers were also detected using cross-sectional microhardness profiles. Relation between plasma nitriding period and a thickness of a nitrided layer was explained and has shown that microhardness and surface hardness of mentioned samples were significantly increased.
Tricalcium Phosphate - Magnesium Interface: Microstructure and Properties
Authors: Casas Luna Mariano , Montúfar Edgar Benjamin , Horynová Miroslava , Gejdoš Pavel , Klakurková Lenka , Díaz de la Torre Sebastián , Kaiser Jozef , Čelko Ladislav
Published: December 2016

The fabrication of a composite material based on magnesium (Mg) and tricalcium phosphate is reported in this work. Rods of β-tricalcium phosphate (β-TCP) were processed and consolidated together with pure Mg powder through spark plasma sintering (SPS). The microstructure at the interface, the chemical composition and transformation of the components and the microhardness were analysed. The microstructure of the composite shows two zones with well-defined and continuous interface between them: a ceramic zone composed by β-TCP filled with Mg and the metallic zone constituted by Mg and Mg rich eutectic. Vickers hardness shows the excellent mechanical interaction between the two zones.
Residual Stress Effects and Predicting Crack Growth in Weldments
Authors: Brož Petr
Published: December 2016

It is explained which way a welded zone integrity has to concentrate on a number of inconveniences resulting from the weld behaviour. These problems will be discussed for evaluation of fatigue and fracture. Going after the fracture assessment address, the effect of weld configuration on stress intensity factor is fixing. A pertinent input to these methods is the limit load. In the view of the prominence of residual stresses in weldments, the interpretation of combined primary and secondary stresses in fracture evaluation is most desirable to be described in great detail. The influence of residual stresses on R – ratio is given. The weldment testing methods involve the techniques for definite microstructural regions and elimination of residual stress effects on fracture toughness measuring. For FCG rate predicting, the initial residual stresses are put into numerical models and residual stress distribution is simulated, incorporating crack growth. The technique is suggested for cracks initiating within a weld, namely in tensile residual stress zone.
Application of Electrical Measurements to Investigation of Solar Cell Microstructure Defects
Authors: Skvarenina Lubomir , Macků Robert
Published: December 2016

The research is aimed to the investigation of the microstructure defects in the silicon and the thin-film CIGS solar cells. These defects have their origin mainly in the technological process of a production but they can be caused by an accidental mechanical stress during a normal operation, too. That leads to a formation of the micro-cracks and the fractures, which have a significant effect on a device efficiency and reliability. The reverse-bias conditions are usually used for the defects charac- terization purposes. The mechanical induced defects increase a reverse current which leads to a strong overheating in the local breakdowns and the surroundings areas, thus for the defects localization pur- poses an infrared imaging and an electroluminescence method is used. Beyond these commonly used methods the results from the electrical current noise fluctuations observed in a frequency domain are presented in this work. The noise fluctuations measurement is a reliable indicator of a device quality and allow us to qualify the device damage extent. Using combination of these methods it is possible to localize the particular defects, assess the degree of a damage and classify the elimination process of the particular defects.
Optimization of Process Field Measurement GNSS-RTK for Railway Infrastructure
Authors: Bartonek Dalibor , Bures Jiří , Svabensky Otakar
Published: December 2016

The paper describes optimized measurements in field on points of railway control by the GNSS-RTK method. The purpose of measurement is to monitor the status of railroad track geometry. Good geometry extends the life of superstructure, reduces tracks and sleepers material wear during passing of the trains, and thus lowers the overall maintenance demands. In the model each of these points can be represented by node in graph and evaluation of graph edges corresponds to the distance between individual nodes. The task is to measure on every node even one times and to absolve the total route with minimal sum of distance. In fact it is searching of the Hamilton's path in a graph. The situation is complicated because the conditions for GNSS surveying in nodes are suitable only at certain time intervals during the day. Generally the above mentioned is difficult task, which is solved in the practice in many cases by heuristic methods. The authors proposed the optimization method based on Floyd algorithm and dynamic data structure - events list. The optimization of field measurement solves the time demands and brings economic effectiveness.
Surface Relief Formation in Relation to the Underlying Dislocation Arrangement
Authors: Mazánová Veronika , Heczko Milan , Kuběna Ivo , Polák Jaroslav
Published: December 2016

Two fatigued materials with f.c.c. lattice, i.e. pure polycrystalline copper and austenitic Sanicro 25 stainless steel, were subjected to the study of the persistent slip markings (PSMs) developed on the surface of the suitably oriented grains. They were observed using scanning electron microscopy (SEM) and thin surface FIB lamellae were prepared and studied by transmission electron microscopy (TEM). The aim was to correlate the specimen surface profile with the underlying internal dislocation structure. The localization of the intensive cyclic slip into persistent slip bands (PSBs) of the material was observed and associated with the PSMs on the specimen surface. Extrusions, intrusions and the dislocation structure appertaining to them were analysed, documented and discussed in relation to the models of fatigue crack initiation.
Static Tensile Strength and E-Modulus Evaluation of a High-Strength Reinforcing Textile Fabrics
Authors: Černý Ivo , Mikulová Dagmar
Published: December 2016

An experimental approach developed and used for an evaluation of basic static mechanical properties of textile fabric with predominantly longitudinal orientation of yarns, namely static strength and elastic modulus, is described in the paper. The fabric was made using yarns of a dark colour, but no further details were available. Attempts to test just the fabric were not successful and valid due to problems with gripping. Therefore, thin composite plates made of the fabric as the main constituent were sectioned and longitudinal strips were statically loaded with strain measurement. To evaluate the elastic modulus and strength of the fabric in itself, the following steps were performed: (i) cross section area of the strips was evaluated using optical microscope considering effects of the corrugated specimen surface, (ii) area of resin and pores between the yarns was eliminated using Quick PHOTO Industrial 2.3 software and eventually (iii) total cross section of fibres within the yarns was estimated on the basis of closest arrangement assumption. The results are presented and discussed from the viewpoint of a possible aramid type.
Increasing of Durability of Surfaces by Plasma Nitriding Process
Authors: Pokorný Zdeněk , Kadlec Jaromir , Joska Zdenek , Studeny Zbynek , Pospíchal Miroslav , Dobrocký David
Published: December 2016

This article deals with properties of plasma nitrided layers in depth. The redistribution of alloy elements and C-N in depth of nitrided layers was analysed. The plasma nitriding process was used for creation of nitrided layers [1]. The nitrided layers were applied to 32CrMoV12-10 steel used for stressed machine parts. Samples were subsequently evaluated by metallographic, OES, hardness and microhardness methods. The results of measurement showed connection between chemical composition of alloying elements after chemical-heat treated process and universal hardness, microhardness.
Interaction of Creep and High Cycle Fatigue of IN 713LC Superalloy
Authors: Horník Vít , Šmíd Miroslav , Hutař Pavel , Kunz Ludvík , Hrbáček Karel
Published: December 2016

The study deals with the interaction of creep and high cycle fatigue of cast polycrystalline nickel-based superalloy IN 713LC at high temperatures. Previous works indicated that creep lifetime of superalloy structures was un-affected or even slightly increased in the cases with superimposed vibrations. The reason for this behaviour was not well described up to now. Therefore, set of fatigue tests was conducted at high mean stresses level to observe this phenomenon. The mean stress was kept constant while the stress amplitudes were selected in order to measure wide range of conditions from pure creep to pure fatigue. Fractographic analysis by scanning electron microscopy (SEM) was done with the aim to identify governing damage mechanisms for particular test conditions as a preliminary evaluation of conducted tests.
Study of Phase Transformation of Medium Carbon Steel after Hot Plastic Deformation
Authors: Kawulok Rostislav , Schindler Ivo , Kawulok Petr , Dänemark Janusz , Opěla Petr , Rusz Stanislav
Published: December 2016

The CCT and DCCT diagrams of steel C60 (with approx. 0.6 % C) were constructed on the basis of dilatation tests with and/or without an influence of the previous deformation and they were then compared, order to make an evaluation of the influence of the previous deformation on the phase transformation kinetics. For the execution of the experiment, the dilatation module of the plastometer Gleeble 3800 was used. The accuracy of the diagrams was faced with metallographic analyses and measurements. The previous deformation expressly retarded a bainite transformation and slightly accelerated ferrite and pearlite transformations. The martensite start temperature was practically not influenced by the previous deformation; however, the applied deformation caused the creation of the martensite at lower cooling rates.
Corrosion-Mechanical Behavior of T91 and 14-19Cr ODS Steels Exposed to Flowing Lead-Bismuth
Authors: Hojna Anna , Hadraba Hynek , di Gabriele Fosca , Husak Roman , Kuběna Ivo , Rozumová Lucia , Marušáková Daniela
Published: December 2016

This work describes the behavior of T91 (9Cr ferritic-martensitic steel), MA957 ODS (14%Cr, 0.3Mo, 0.9Ti, 0.25%Y2O3) and PM2000 ODS (19%Cr, 5%Al, 0.25%Y2O3) steels produced by mechanical alloying process, after long-term exposure to liquid lead-bismuth eutectic. Small bend specimens were pre-strained, then exposed to flowing lead-bismuth at 350°C for 100, 500 and 1000 hours. After exposure, the specimens were examined by using SEM equipped with EDX. The resulting changes of surface and built-up oxide layers are discussed. Liquid Metal Embrittlement, LME, crack initiation was not observed in the specimens. The absence of LME in these conditions is discussed.
The Changes in Mechanical Properties of Austenitic Creep Resistant Steels SUPER 304H and HR3C Caused by Medium-Term Isothermal Ageing
Authors: Horváth Jakub , Janovec Jiří , Junek Michal
Published: December 2016

The paper presents the results of the analysis of secondary phases formed during thermal exposure in creep resistant austenitic steels of SUPER 304H and HR3C types. These steels were worldwide used for construction of the superheaters (the heat exchangers) of supercritical and ultra-supercritical (USC) coal-fired power plants. In order to accelerate precipitation processes, the steels were isothermally aged at 675 °C for 20 000 h. The investigations of the precipitates were primarily focused on the occurrence of brittle phases. Changes in mechanical properties caused by occurrence of secondary phases were documented by tensile testing and measurement of the impact strength. For comparison reasons, the impact tests of the initial state of the steels were also performed. The results showed that long-term ageing had led to the significant decrease of the impact strength. Correlation between precipitation of secondary phase and measured values of mechanical properties is shown. The influence of brittle phases on long-term durability of the degraded steel regarding its insufficient impact strength has been discussed.
Coarse-Grained Molecular Dynamics Simulation of Fracture Problems in Polycarbonate
Authors: Kubo Atsushi , Umeno Yoshitaka
Published: December 2016

A coarse-grained particle (CG) model was developed based on all-atom molecular dynamics simulation results, aiming at applying to deformation and fracture analyses of polycarbonate. After confirming the validity of the model, the developed CG model was applied to deformation analyses to investigate the effects of strain rate and multiaxial tension. The effect of strain rate was found to be consistent with an experiment. Two types of deformation behavior were observed according to the type of multiaxial tension.
The Bluebirds: World War I Soldiers’ Experiences of Occupational Therapy
Authors: Pettigrew Judith , Robinson Katie , Moloney Stephanie
Published: December 2016

OBJECTIVE. More is known about the experience of occupational therapists than the experience of patients during the profession’s early years. We examined soldiers’ experiences of occupational therapy in American Base Hospital 9 in France during World War I through analysis of a 53-line poem by Corporal Frank Wren contained in the unpublished memoir of occupational therapy reconstruction aide Lena Hitchcock.

METHOD. Historical documentary research methods and thematic analysis were used to analyze the poem, the memoir, and the hospital’s published history.

RESULTS. The poem describes the activities engaged in during occupational therapy, equipment used, and the context of therapy. It articulates positive dimensions of the experience of engaging in activities, including emotional benefits, diversion, and orthopedic benefits.

CONCLUSION. Previous historical research has identified core philosophical premises about the use of occupational therapy; in this article, the enactment of these principles is established through the analysis of a soldier’s account of receiving occupational therapy.
An optimal time incentive/disincentive -based compensation in contracts with multiple agents
Authors: Hosseinian S. Mahdi
Published: December 2016

This paper establishes an optimal time incentive/disincentive-based compensation in a contract between a principal and a team of agents. The establishment is based on solving an optimization problem. In order to validate the paper's theoretical development practitioners were engaged in a designed exercise. The paper demonstrates that, at the optimum: the proportion of time incentive/disincentive compensation among agents with the same risk-attitude should reflect the levels of their contributions; the proportion of time incentive/disincentive among agents with the same level of contribution should be lowered for agents with higher levels of risk aversion; and the proportion of time incentive/disincentive to a team of risk averse agents should reduce, and the fixed component of the team fee should increase, when the agents in the team become more risk-averse or the level of the uncertainty in project completion time increases. The paper’s outcome provides guidance to those involved in contracts design for choosing the best way to reward (penalise) multiple agents, form a team, and allow for any time saving (overrun) through the terms of a contract.
Culture, Power and Social Disparity: Researching Russia's Upper Class
Authors: Schimpfossl Elisabeth
Published: December 2016

This article explores the dynamics at play when conducting research on the contemporary upper class in Russia. It examines the effect of economic and social status divide between researcher and subjects on how to gain access to interviewees and how to handle the interview situation. Culturally specific expressions of power in social interaction are sought, their characteristics identified and their raison d'être explored. Furthermore, gender related issues encountered throughout the research are discussed; which commenced at the outset when applying to the ethics board and was evident at the end when presenting the data analysis. The material for this article stems from the author's experiences of conducting narrative-biographical interviews with rich high-status Russians in Moscow between 2008 and 2009.
Reflections on Positionality from a Russian Woman Interviewing Russian-Speaking Women in London
Authors: Malyutina Darya
Published: December 2016

This paper explores the implications of shared femininity in a qualitative study of friendship networks amongst Russian-speaking migrants in London by a Russian researcher. Drawing upon feminist literature on the complexities of women interviewing women, I outline the reflexive approach to positionality informing power relations and establishment of trust in the relationship between the researcher and the researched. The examples of interviewing a friend and two friendly strangers demonstrate the ways of negotiating mutual positions in the interaction. Shared gender is regarded as partially, but not universally, promoting rapport, taking into account the intersectionality of multiple differences between women. Considering the researcher's positionality has been presented in this paper as a means of making similarities and differences between participants useful for the critical interpretation of the work, and using its relevant aspects for building a positive, open, and more equal interaction.
Ethics and Emotions: A Migrant Researcher Doing Research among Romanian Migrants
Authors: Romocea Oana
Published: December 2016

This article explores both the ethical and emotional issues that emerge while conducting qualitative research as a Romanian migrant researcher among Romanian migrants settled in the UK. I specifically look at the transformative role played by emotions in the research process and how knowledge is generated by a permanent state of ‘objective reflexivity’ employed by the researcher and self-reflexivity on the part of the participants. While most emotions and ethical considerations transpire mainly from the interaction and the relationship established between the researcher and the participants, I highlight other aspects of fieldwork which also carry ethical decisions and emotional implications, even though not so evident at first sight. These include the relation between the researcher and the topic of the research, the terminology used, the language choice during the interview, and any potential legal aspects. I conclude that juggling both ethics and emotions does not compromise the scientific standard of the research, but rather adds a new dimension to doing research in one's own social context.
How and when Do Educational Aspirations, Expectations and Achievement Align?
Authors: Khattab Nabil
Published: December 2016

This paper proposes a new typology of educational aspirations, expectations and achievement. This typology is derived from combinations of aspirations, expectations and achievement, creating eight possible combinations of aligned and irregular profiles. To devise this new typology, data from the Longitudinal Study of Young People in England (LSYPE) panel survey and matching administrative data from the National Pupil Database (NPD) was utilised. These data were collected in 2004 from a sample of 15,770 young people (YP) aged 13 to 14 attending 647 different schools in England. This study demonstrates that aspirations, expectations and achievement do converge amongst some students; but for most young people they do not always intersect. Many young people succeed academically, but without necessarily developing high aspirations or high expectations. For one out of every five young people, high aspirations and high expectations do not lead to academic achievement. The findings in this paper provide a distinct analytical framework for further research and policy development in this area.
The Complex Employment Experiences of Polish Migrants in the UK Labour Market
Authors: Knight Julie
Published: December 2016

Ten years after the most significant enlargement of the European Union (EU), academics and policymakers are still trying to understand the complexities and the experiences of the largest migrant group, the Poles. The main destination for the Polish migrants in the post-2004 period was the United Kingdom (UK). Significant attention has been paid to the economic and political implications of introducing a young, economically motivated migrant group to the UK, particularly during the recession. In regards to their work experience, the majority of the existing literature focuses on Polish migrants who take low-skilled positions when initially entering the UK and, as a result, contribute to the migrant paradox with high-skilled migrants taking low-skilled positions. This article will contribute to the other literature, which focuses on the Polish migrants’ ascent up the division of labour in the non-ethnic economy of the destination country. Using data gathered through semi-structured interviews with post-enlargement Polish migrants in 2008 and 2011 in Cardiff, this ascent, and the migrants’ work experience, is charted through migrant trajectories that were constructed from similarities identified in the sample. The findings highlight that not all of the Polish migrants in the UK may be contributing to the migrant paradox with several low-skilled migrants advancing up the division of labour. These findings have implications for migration policy at both the EU and the national level, particularly with the continued enlargement of the EU.
Compositional changes of present-day transatlantic Saharan dust
deposition
Authors: Korte Laura F. , Brummer Geert-Jan , van der Does Michèlle , Guerreiro Catarina V. , Hennekam Rick , van Hateren Johannes A. , Jong Dirk , Munday Chris I. , Schouten Stefan , Stuut Jan-Berend W.
Published: December 2016

Abstract. Massive amounts of Saharan dust are blown from the African coast across the Atlantic Ocean towards the Americas each year. This dust has, depending on its chemistry, direct and indirect effects on global climate including reflection and absorption of solar radiation as well as transport and deposition of nutrients and metals fertilizing both ocean and land. To determine the temporal and spatial variability of Saharan dust transport and deposition and their marine environmental effects across the equatorial North Atlantic Ocean, we have set up a monitoring experiment using deep-ocean sediment traps as well as land-based dust collectors. The sediment traps were deployed at five ocean sites along a transatlantic transect between northwest Africa and the Caribbean along 12⁰ N, in a down-wind extension of the land-based dust collectors placed at 19⁰ N on the Mauritanian coast in Iwik. In this paper, we lay out the setup of the monitoring experiment and present the particle fluxes from sediment trap sampling over 24 continuous and synchronised intervals from October 2012 through to November 2013. We establish the temporal distribution of the particle fluxes deposited in the Atlantic and compare chemical compositions with the land-based dust collectors propagating to the down-wind sediment trap sites, and with satellite observations of Saharan dust outbreaks. First-year results show that the total mass fluxes in the ocean are highest at the sampling sites in the east and west, closest to the African continent and the Caribbean, respectively. Element ratios reveal that the lithogenic particles deposited nearest to Africa are most similar in composition to the Saharan dust collected in Iwik. Down-wind increasing Al, Fe and K contents suggest a downwind change in the mineralogical composition of Saharan dust and indicate an increasing contribution of clay minerals towards the west. In the westernmost Atlantic, admixture of re-suspended clay-sized sediments advected towards the deep sediment trap cannot be excluded. Seasonality is most prominent near both continents but generally weak, with mass fluxes dominated by calcium carbonate and clear seasonal maxima of biogenic silica towards the west. The monitoring experiment is now extended with autonomous dust sampling buoys for better quantification Saharan dust transport and deposition from source to sink and its impact on fertilization and carbon export to the deep ocean.
On Aethalometer measurement uncertainties and multiple scattering
enhancement in the Arctic
Authors: Backman John , Schmeisser Lauren , Virkkula Aki , Ogren John A. , Asmi Eija , Starkweather Sandra , Sharma Sangeeta , Eleftheriadis Konstantinos , Uttal Taneil , Jefferson Anne , Bergin Michael , Makshtas Alexander
Published: December 2016

Abstract. Several types of filter-based instruments are used to estimate aerosol light absorption coefficients.Two significant results are presented based on Aethalometer measurements at six Arctic station from 2012–2014. First, an alternative method of post-processing the Aethalometer data is presented which reduces measurement noise and lowers the detection limit of the instrument more effectively than boxcar averaging. The biggest benefit of this approach can be achieved if instrument drift is minimized. Moreover, by using an attenuation threshold criterion for data post-processing, the relative uncertainty from the electronic noise the instrument is kept constant. This approach results in a time series with a variable collection time (Δt), but with a constant relative uncertainty with regard to electronic noise in the instrument. An additional advantage of this method is that the detection limit of the instrument will be lowered at small aerosol concentrations at the expense of temporal resolution, whereas there is little to no loss in temporal resolution at high aerosol concentrations (>2.1–6.7 Mm−1 as measured by the Aethalometers). At high aerosol concentrations, minimizing the detection limit of the instrument is less critical. Second, utilizing co-located reference methods of aerosol absorption, a multiple cattering enhancement factor (Cref) of 3.10 specific to low elevation Arctic stations is found. Cref is a fundamental part of most of the Aethalometer corrections available in literature, and this is the first time a Cref value has been obtained for the Arctic.
Soil Salinity Mapping and Hydrological Drought Indices Assessment in Arid Environments Based on Remote Sensing Techniques
Authors: Elhag Mohamed , Bahrawi Jarbou A.
Published: December 2016

Abstract. Vegetation indices are mostly described as crop water derivatives. Normalized Difference Vegetation Index (NDVI) is one of the oldest remote sensing applications that widely used to evaluate crop vigor directly and crop water relationships indirectly. Recently, several NDVI derivatives are exclusively used to assess crop water relationships. Four hydrological drought indices are examined in the current research study. Water Supply Vegetation Index (WSVI), Soil Adjusted Vegetation Index (SAVI), Moisture Stress Index (MSI) and Normalized Difference Infrared Index (NDII) are implemented in the current study as an indirect tool to map the effect of different soil salinity level on crop water stress in arid environments. In arid environments; such as Saudi Arabia, water resources are under pressure especially groundwater levels. Groundwater wells are rapidly depleted due to the heavy abstraction of the reserved water. Heavy abstractions of groundwater; which exceed crop water requirements in most of the cases are powered by high evaporation rates in the designated study area because of the long days of extremely hot summer. Landsat OLI-8 data were extensively used in the current research to obtain several vegetation indices in response to soil salinity in Wadi Ad-Waser. Principal Component Analysis and Artificial Neural Network Analysis are complementary tools to understand the regression pattern of the hydrological drought indices in the designated study area.
Realization of Daily Evapotranspiration in Arid Ecosystems Based on Remote Sensing Techniques
Authors: Elhag Mohamed , Bahrawi Jarbou A.
Published: December 2016

Abstract. Daily evapotranspiration is a major component in water resources management plans. In arid ecosystems, the quest for efficient water budget is always hard to achieve due to insufficient irrigational water and high evapotranspiration rates. Therefore, monitoring of daily evapotranspiration is a keystone practice for sustainable water resources management, especially in arid environments. Remote Sensing Techniques offered a great help to estimate the daily evapotranspiration on a regional scale. Existing open source algorithms proved to estimate daily evapotranspiration in arid environments comprehensively. The only deficiency of these algorithms is course scale of the used remote sensing data. Consequently, the adequate downscaling algorithm is a compulsory step to rationalize an effective water resources management plans. Daily evapotranspiration was fairly estimated using AATSR in conjunction with MERIS data acquired in July 2013 with one-kilometer spatial resolution and 3 days temporal resolution under SEBS model. Results were validated against reference evapotranspiration ground truth values using standardized Penman-Monteith method with R2 of 0.879. The findings of the current research are successfully fulfilled to monitor turbulent heat fluxes values estimated from AATSR and MERIS data with a temporal resolution of 3 days only in conjunction with reliable meteorological data. Research verdicts are necessary inputs for well-informed decision-making process regarding sustainable water resources management
Uncertainty assessment of a dominant-process catchment model of dissolved phosphorus transfer
Authors: Dupas Rémi , Salmon-Monviola Jordy , Beven Keith J. , Durand Patrick , Haygarth Philip M. , Hollaway Michael J. , Gascuel-Odoux Chantal
Published: December 2016

Abstract. We developed a parsimonious topography-based hydrologic model coupled with a soil biogeochemistry sub-model in order to improve understanding and prediction of soluble reactive phosphorus (SRP) transfer in agricultural headwater catchments. The model structure aims to capture the dominant hydrological and biogeochemical processes identified from multiscale observations in a research catchment (Kervidy–Naizin, 5 km2). Groundwater fluctuations, responsible for the connection of soil SRP production zones to the stream, were simulated with a fully distributed hydrologic model at 20 m resolution. The spatial variability of the soil phosphorus content and the temporal variability of soil moisture and temperature, which had previously been identified as key controlling factors of SRP solubilization in soils, were included as part of an empirical soil biogeochemistry sub-model. The modelling approach included an analysis of the information contained in the calibration data and propagation of uncertainty in model predictions using a generalized likelihood uncertainty estimation (GLUE) "limits of acceptability" framework. Overall, the model appeared to perform well given the uncertainty in the observational data, with a Nash–Sutcliffe efficiency on daily SRP loads between 0.1 and 0.8 for acceptable models. The role of hydrological connectivity via groundwater fluctuation and the role of increased SRP solubilization following dry/hot periods were captured well. We conclude that in the absence of near-continuous monitoring, the amount of information contained in the data is limited; hence, parsimonious models are more relevant than highly parameterized models. An analysis of uncertainty in the data is recommended for model calibration in order to provide reliable predictions.
The Probability to Abolish Governance Provisions
Authors: Ahn Seoungpil , Hong Gwangheon
Published: December 2016

The negative relation between governance indices and acquisition performance weakens in the post Sarbanes-Oxley Act (SOX) period. We examine whether firms remove anti-takeover provisions to eliminate the adverse impact of anti-takeover provisions. We find that strong external monitoring mechanisms such as the presence of public pension funds and large institutional investors leads firms to abolish some anti-takeover provisions and classified boards in particular. This partial elimination of anti-takeover provisions suggests a trade-off between benefit and cost of anti-takeover provisions.
Social Network Sites Effectiveness from EFL Students’ Viewpoints
Authors: Alnujaidi Sulaiman
Published: December 2016

This study investigated the relationship between EFL students’ experience, attitudes, perceptions, and expectations toward the effectiveness of Social Network Sites (SNS), namely, Facebook, Twitter, YouTube, Instagram, Flickr, Classmates, Academica, MySpace, English baby, and Google+, in English language learning. A survey of 103 participants from different higher education institutions in Saudi Arabia was conducted. The study’s results revealed that the participants had an average SNS experience. The findings also indicated that participants had overall positive attitudes, perceptions, and expectations toward SNS. In addition, the correlations between experience and attitudes, and experience and expectations were statistically significant. Data analysis also showed that the correlations between attitudes and perceptions, attitudes and expectations, and perceptions and expectations were statistically significant. However, experience did not significantly correlate with perceptions. The findings also indicated that the model of the three variables (attitudes, perceptions, and expectations toward SNS) predicting the variable (experience in SNS) was statistically significant: The significant predictor was expectations.
Effects of Varied Nitrogen Supply and Irrigation Methods on Distribution and Dynamics of Soil NO3-N during Maize Season
Authors: Qi Dongliang , Hu Tiantian
Published: December 2016

A field experiment was carried out to investigate the effects of different supply methods of nitrogen (N) fertilizer and irrigation on the spatial distribution and dynamics of soil NO3-N for maize (Zea mays L.) grown in northwest China in 2012 and 2014. In 2012, there were three irrigation methods: alternate furrow irrigation (AI), fixed furrow irrigation (FI) and conventional furrow irrigation (CI). Three N supply methods: alternate N supply (AN), fixed N supply (FN) and conventional N supply (CN), were applied at each irrigation method. In 2014, the fixed treatments were excluded. Soil NO3-N in horizontal direction was measured to 100 cm soil profile. For 2012, at filling stage, compared to CI, AI increased soil NO3-N concentration under the plant by 4.5 to 7.4% in 0-40 cm soil profile and decreased that by 9.9 to 14.4% in 40-80 cm for three N supply methods. NO3-N concentration between two sides of the ridge was comparable for AN and CN coupled with AI or CI. When compared to CI, AI reduced soil NO3-N concentration in 60-100 cm by 4.8 to 8.7% from 12 collars stage to maturity over different positions when coupled with CN. Soil residual NO3-N at maturityin 0-100 cm was the lowest in AI coupled with CN or AN. The 2014 experiment verified the above results. Therefore, alternate furrow irrigation coupled with conventional or alternate N supply brought an optimum spatial distribution of soil NO3-N during maize season, resulting in little soil residual NO3-N at maturity.
Energy Consumption in Onion and Potato Production within the Province of El Hajeb (Morocco): Towards Energy Use Efficiency in Commercialized Vegetable Production
Authors: Allali Khalil , Dhehibi Boubaker , Kassam Shinan N. , Aw-Hassan Aden
Published: December 2016

Energy use efficiency is a key requirement for sustainability in agricultural production, but often overlooked. The aim of this study was to quantify the amount and efficiency of energy consumed in the production of onions and potatoes in El Hajeb province of Morocco. These estimates are of significant importance in informing contemporary policy discourse related to energy subsidy reform in Morocco, and more specifically within an ongoing national strategy for ‘modernizing’ the agricultural sector under the ‘Green Morocco Plan’. Data were collected through the administration of a direct questionnaire with 60 farmers and analyzed using PLANETE. Our results indicate that total energy consumption in onion production is 107483 MJ ha-1 with butane (79.5%) as the main source of direct energy. Chemical fertilizers (61.53%) and water for irrigation (30%) were main sources of indirect energy. Energy indices related to energy efficiency ratios, energy profitability and energy productivity were estimated at 0.78, -0.22 and 0.54 kg MJ-1, respectively. Total energy consumption in potato production was estimated at 74,270 MJ ha-1, with direct energy consumption of 28,521 MJ ha-1 stemming from butane (70%) and diesel (19.14%) as primary sources. Indirect energy consumption was estimated at 45749 MJ ha-1 and generated principally through the use of fertilizers (60%). Energy indices (efficiency, profitability and productivity) were estimated at 1.54, 0.54, and 0.45 kg MJ-1, respectively. GHG emissions were found to be 3.47 t CO2eq ha-1 in the production of onions and 3.63 t CO2eq ha-1 for potatoes. We find that within the study area, increases in the size of production plots are not necessarily consistent with increases in energy use efficiency.
Reviewer Acknowledgements for Journal of Agricultural Science, Vol. 9, No. 1
Authors: Brown Anne
Published: December 2016

Reviewer acknowledgements for Journal of Agricultural Science, Vol. 9, No. 1, 2017.