8,080 research outputs found
Effect of substitution and heat treatment route on polycrystalline FeSe0.5Te0.5 Superconductors
The effect of atomic substitution of Te in iron based superconductors FeSe
(1:1 type), which exhibits the simplest crystal structure among the iron-based
superconductors, has been investigated in terms of structural, electronic
transport and magnetic properties. Polycrystalline samples with nominal Se:Te
in FeSe1-xTex samples for x=0.5350{\deg}C, 0.5700{\deg}C, 0.6700{\deg}C and
0.75700{\deg}C were synthesized by the solid-state reaction method. It has been
observed that the most superconducting properties seen in x=0.6700{\deg}C
samples as dc magnetic susceptibility, ac susceptibility and resistivity
measurements. Tc enhancement is well correlated with the Te substitution up to
75% and c lattice parameters monotonically increased with increasing Te
concentration
Simulation and Efficiency Studies of Optical Photon Transportation and Detection with Plastic Antineutrino Detector Modules
In this work, the simulation of optical photons is carried out in an
antineutrino detector module consisting of a plastic scintillator connected to
light guides and photomultipliers on both ends, which is considered to be used
for remote reactor monitoring in the field of nuclear safety. Using Monte Carlo
(MC) based GEANT4 simulation, numerous parameters influencing the light
collection and thereby the energy resolution of the antineutrino detector
module are studied: e.g., degrees of scintillator surface roughness, reflector
type, and its ap- plying method onto scintillator and light guide surface, the
reflectivity of the reflector, light guide geometries and diameter of the
photocathode. The impact of each parameter is inves- tigated by looking at the
detected spectrum, i.e. the number photoelectrons per depositing energy. In
addition, the average light collection efficiency of the detector module and
its spatial variation are calculated for each simulation setup. According to
the simulation re- sults, it is found that photocathode size, light guide
shape, reflectivity of reflecting material and wrapping method show a
significant impact on the light collection efficiency while scin- tillator
surface polishing level and the choose of reflector type show relatively less
impact. This study demonstrates that these parameters are very important in the
design of plastic scintillator included antineutrino detectors to improve the
energy resolution efficiency
Microscopic study of CaCa fusion
We investigate the fusion barriers for reactions involving Ca isotopes
, , and
using the microscopic time-dependent
Hartree-Fock theory coupled with a density constraint. In this formalism the
fusion barriers are directly obtained from TDHF dynamics. We also study the
excitation of the pre-equilibrium GDR for the
system and the associated -ray
emission spectrum. Fusion cross-sections are calculated using the incoming-wave
boundary condition approach. We examine the dependence of fusion barriers on
collision energy as well as on the different parametrizations of the Skyrme
interaction.Comment: 11 pages, 13 figure
Fuzzy gravity approach for determinants of exports
Purpose: The present study proposes the fuzzy gravity model approach to examine the main factors that affect the export volume of Turkey and whether the European Union Customs Union (EUCU) membership affected the export of it. Design/Methodology/Approach: A fuzzy approach was developed for the gravity model by using these variables. The dependent variable was the export volume of Turkey to 204 countries throughout the whole world, and the explanatory variables were the gross domestic product (GDP) of the countries that are subject to export and their distances to Turkey (dij), populations, whether the seaway transport was possible, and the membership to the EUCU. The last two items were added as dummy variables in the model. Findings: The results showed that gross domestic product (GDP) of the country which Turkey exports to, its being a member of the EUCU, and its population affected the export volume of Turkey positively. However, the distance of the target country to Turkey had a negative effect. The coefficient of distance variable was found to be negative fuzzy and ones of the seaway was fully fuzzy. However, when seaway variable was taken together with distance, it was positive fuzzy, which showed the positive effect of the opportunity of transportation by sea in long distances on export volume. Practical Implications: It is thought that the policies to be established based on these findings will be beneficial in improving the country's exports. Other available fuzzy regression approaches may be tried in future studies to obtain a fuzzy model. In addition, the import or foreign trade structure of Turkey may be dealt with the same approach. Originality/Value: In this study the fuzzy gravity model approach was used as a novelty, which was different from the methods in the literature, because the gravity model is criticized sometimes that its theoretical basis is weak and the relations between dependent variables and explanatory variables are not adequately clear.peer-reviewe
Stacking domains and dislocation networks in marginally twisted bilayers of transition metal dichalcogenides
We apply a multiscale modeling approach to study lattice reconstruction in
marginally twisted bilayers of transition metal dichalcogenides (TMD). For
this, we develop DFT-parametrized interpolation formulae for interlayer
adhesion energies of MoSe, WSe, MoS, and WS, combine those with
elasticity theory, and analyze the bilayer lattice relaxation into mesoscale
domain structures. Paying particular attention to the inversion asymmetry of
TMD monolayers, we show that 3R and 2H stacking domains, separated by a network
of dislocations develop for twist angles and for,
respectively, bilayers with parallel (P) and antiparallel (AP) orientation of
the monolayer unit cells and suggest how the domain structures would manifest
itself in local probe scanning of marginally twisted P- and AP-bilayers
Asymptotic formulations of the eigenvalues and eigenfunctions for a boundary value problem
In this work a discontinuous boundary-value problem with retarded argument
which contains spectral parameter in the transmission conditions at the point
of discontinuity are investigated. We obtained asymptotic formulas for the
eigenvalues and eigenfunctions.Comment: 12 pages, accepted for publication in Mathematical Methods in the
Applied Science
Comparison of Plastic Antineutrino Detector Designs in the Context of Near Field Reactor Monitoring
We compare existing segmented plastic antineutrino detectors with our new
geometrically improved design for antineutrino detection and light collection
efficiency. The purpose of this study is to determine the most suitable design
style for remote reactor monitoring in the context of nuclear safeguards. Using
Monte Carlo based GEANT4 simulation package, we perform detector simulation
based on two prominent experiments: Plastic antineutrino detector array (Panda)
and Core monitoring by reactor antineutrino detector (Cormorad). In addition to
these two well-known designs, another concept, the Panda2, can be obtained by
making a small variation of Panda detector, is also considered in the
simulation. The results show that the light collection efficiency of the
Cormorad is substantially less with respect to the other two detectors while
the highest antineutrino detection efficiency is achieved with the Cormorad and
Panda2. Furthermore, as an alternative to these design choices, which are
composed of an array of identical rectangular-shaped modules, we propose to
combine regular hexagonal-shaped modules which minimizes the surface area of
the whole detector and consequently reduces the number of optical readout
channels considerably. With this approach, it is possible to obtain a detector
configuration with a slightly higher detection efficiency with respect to the
Panda design and a better energy resolution detector compared to the Cormorad
design
Evaluating of the reasons for absenteeism in terms of different variables according to their own perceptions of pre-service teachers
AbstractThe aim of this study is to reveal the reasons of absenteeism in terms of different variables according to pre-service teachers. The research is a quantitative research which is designed on survey method. Population of the study consist of pre-service teachers who maintain education in the faculty of education at the universities in the 2008-2009 academic year and samples include 308 pre-service teachers who study at Faculty of Education at Rize University. ‘Scale of Absenteeism Reasons’ which has been developed by the researchers has been used as an instrument for collecting data. In the statistical transactions, independent-samples t test, frequency analysis and One Way Anova have been applied. At the end of the factor analysis, the scale has been reduced to 15 items and its reliability coefficient has been calculated to be as .815. At the end of the research, it has been determined that there is meaningful difference between the reasons of absenteeism and class and gender variables. There is no meaningful difference between the reasons of absenteeism and environment. Furthermore, it has been seen that the reasons of absenteeism have varied between the students who have higher success and who have lower success at school
Giant solitary trichoepithelioma: A Case report
Trichoepithelioma is a benign cutaneus tumour originatingfrom hair follicles. It is most commonly found on theface and scalp. Histopathologic examination was composedof band-like nests of basaloid cells showing peripheralpalization, abortive hair papilla and horn cysts ina fibrocellular stroma. A 82-year-old woman applied for a10-year old groin mass that recently slowly growing. Thelesion was excised and it was diagnosed as giant solitarytrichoephitelioma.Key words: Groin, hair follicle, skin neoplasm
The impact assessment of cage aquaculture on benthic communities along the south eastern Black Sea
The present study was conducted to examine the impact of cage aquaculture on benthic communities in coastal areas (depth 25 to 50 m) from fish farming operations located along the southeastern Black Sea (Ordu-Perşembe, Trabzon-Yomra and Rize central). Sampling was conducted seasonally from April 2007 to 2009. Sediment samples were taken using Ekman Grab (box core- 0.04 m2). Temperature, salinity, and water velocity were periodically measured to determine influencing sedimentary organic matter in the sediment, oxygenation, and anoxic conditions. In addition, grain size of sediment, organic carbon content, and distribution of benthic communities were investigated. In order to determine benthic impact of fish farms on the region, Shannon – Wiener diversity index (H’), AMBI (AZTI Marine Biotic Index) and M-AMBI (Multivariate- Marine Biotic Index) indices were used. Results of current study showed that benthic zone ecological quality of stations with number 01, 02, 03, and 04 at Ordu-Perşembefish-farming habitat was found to be very low. In autumn 2008, there were 3 species which belonged to Capitella capitata (844 individuals/m2), Capitella sp. (133 individuals/m2), and Heteromastus filliformis (311 individuals/m2) at OP-01 station. In addition, the impact of Trabzon-Yomra fish-farming activity on benthic communities was low. The degree of exposure for Rize fish-farming area in all seasons was quite low, which was not a significant negative impact
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