684 research outputs found
Effects of the tensor force on the ground and first states of the magic Ca nucleus
The magic nature of the Ca nucleus is investigated in the light of the
recent experimental results. We employ both HFB and HF+BCS methods using
Skyrme-type SLy5, SLy5+T and T44 interactions. The evolution of the
single-particle spectra is studied for the N=34 isotones: Fe, Cr,
Ti and Ca. An increase is obtained in the neutron spin-orbit
splittings of and states due to the effect of the tensor force which
also makes Ca a magic nucleus candidate. QRPA calculations on top of
HF+BCS are performed to investigate the first = states of the
calcium isotopic chain. A good agreement for excitation energies is obtained
when we include the tensor force in the mean-field part of the calculations.
The first states indicate a subshell closure for both Ca and
Ca nuclei. We confirm that the tensor part of the interaction is quite
essential in explaining the neutron subshell closure in Ca and Ca
nuclei.Comment: 8 pages, 3 figure
Spectral splits of neutrinos as a BCS-BEC crossover type phenomenon
We show that the spectral split of a neutrino ensemble which initially
consists of electron type neutrinos, is analogous to the BCS-BEC crossover
already observed in ultra cold atomic gas experiments. Such a neutrino ensemble
mimics the deleptonization burst of a core collapse supernova. Although these
two phenomena belong to very different domains of physics, the propagation of
neutrinos from highly interacting inner regions of the supernova to the vacuum
is reminiscent of the evolution of Cooper pairs between weak and strong
interaction regimes during the crossover. The Hamiltonians and the
corresponding many-body states undergo very similar transformations if one
replaces the pair quasispin of the latter with the neutrino isospin of the
former.Comment: 9 pages, 5 figure
OLPT CONDUCTIVITY IN WOLLASTONITE INLAID NR/SBR TYPE ELASTOMER BASED MATERIAL
The electrical properties of wollastonite inlaid NR/SBR type elastomer based material have been evaluated. Electrical properties of the samples were measured in the temperature range of 303 to 453 K and the frequency range of 100 Hz – 40 MHz. All electrically measured parameters were given anomalies at 385 K. Only one type of dielectric relaxation process have been observed for all measurements. Physical parameters characterizing the dielectric behavior have been obtained by fitting the experimental results in the modified Debye equation. The activation energy which is thermally activated by dielectric relaxation process have been calculated to be 0.58 eV. DC conductivity increasing by temperature has been explained with the help of VFT model whereas the AC one has been clarified by the OLPT model
Dynamic phase transition properties and hysteretic behavior of a ferrimagnetic core-shell nanoparticle in the presence of a time dependent magnetic field
We have presented dynamic phase transition features and stationary-state
behavior of a ferrimagnetic small nanoparticle system with a core-shell
structure. By means of detailed Monte Carlo simulations, a complete picture of
the phase diagrams and magnetization profiles have been presented and the
conditions for the occurrence of a compensation point in the system
have been investigated. According to N\'{e}el nomenclature, the magnetization
curves of the particle have been found to obey P-type, N-type and Q-type
classification schemes under certain conditions. Much effort has been devoted
to investigation of hysteretic response of the particle and we observed the
existence of triple hysteresis loop behavior which originates from the
existence of a weak ferromagnetic core coupling , as well as a
strong antiferromagnetic interface exchange interaction . Most
of the calculations have been performed for a particle in the presence of
oscillating fields of very high frequencies and high amplitudes in comparison
with exchange interactions which resembles a magnetic system under the
influence of ultrafast switching fields. Particular attention has also been
paid on the influence of the particle size on the thermal and magnetic
properties, as well as magnetic features such as coercivity, remanence and
compensation temperature of the particle. We have found that in the presence of
ultrafast switching fields, the particle may exhibit a dynamic phase transition
from paramagnetic to a dynamically ordered phase with increasing ferromagnetic
shell thickness.Comment: 12 pages, 12 figure
Swift observation of Segue 1: constraints on sterile neutrino parameters in the darkest galaxy
Some extensions of standard particle physics postulate that dark matter may
be partially composed of weakly interacting sterile neutrino particles that
have so far eluded detection. We use a short (~5 ks) archival X-ray observation
of Segue 1 obtained with the X-ray Telescope (XRT) onboard the Swift satellite
to exclude the presence of sterile neutrinos in the 1.6 - 14 keV mass range
down to a flux limit of 6 x 10^{-12} erg cm-2 s-1 within 67 pc of its centre.
With an estimated mass-to-light ratio of ~3400 Msun/Lsun, Segue 1 is the
darkest ultrafaint dwarf galaxy currently measured. Spectral analysis of the
Swift XRT data fails to find any non-instrumental spectral feature possibly
connected with the radiative decay of a dark matter particle. Accordingly, we
establish upper bounds on the sterile neutrino parameter space based on the
non-detection of emission lines in the spectrum. The present work provides the
most sensitive X-ray search for sterile neutrinos in a region with the highest
dark matter density yet measured.Comment: 5 pages, 3 figures. Accepted in MNRAS Letter
Güneş Enerjili Kurutma Sistemlerinde Parafin Kullanılarak Boya Çamurunun Kurutulması
Güneş kurutucu sistemi, ileri bir doğal güneş kurutma teknolojisi olarak geniş alanlardada kullanılmaktadır. Bu çalışmanın amacı; atık boya çamurunun yönetimi sürecinde güneşle kurutmayı alternatif bir proses olarak incelemektir. Çalışmada faz değiştirme malzemesi olarak parafin içeren bir güneş kurutma sistemi tasarlanarak kurutma verimliliği araştırılmıştır. Kurutulan çamur kalınlığının düşük olması sebebiyle kurutma sırasında karıştırmanın etkisi gözlenememiştir. Kurutma işlemi 8 saatte 1849 Wh/m2 kümülatif güneş radyasyonu ile yapılmıştır. İç sıcaklık, nem, güneş radyasyonu, zaman, çamur kütlesi ve hacmini azaltmanın yanı sıra kurutucuda kullanılan ekipmanlar ısı transferini güçlendirmek için önemli faktörler olarak belirlenmiştir. Sistemde fan ile oluşturulan hava sirkülasyonunun yetersiz olduğu hesaplamalı akışkanlar dinamiği (HAD) ile tespit edilmiştir, ve simülasyon modeli kurutma sisteminin optimize edilmesi için kullanılmıştır. Gözenekli yapının oluşumu, bir tarama elektron mikroskobu (SEM) kullanılarak kurutulmuş çamurda gözlenmiştir. Atık boya çamurunun yönetiminde güneş kurutucusunun geliştirilmeler sonrası kullanılabilecek bir alternatif olduğu sonucuna varılmıştır
Kritik (Kriz) Dönem Enflasyon Hesaplamalarında Bulanık Regresyon Tahminlemesi
Inflation targeting is defined as the determination of an acceptable inflation rate for a specific period of time by considering the general variables and data of inflation and also as the implementation of monetary policies in such a way that they can reach predetermined rates. Accurate inflation estimates are needed to reach the targets. Acquiring the estimations accurately leads to correct decisions. Fuzzy regression method is a method that gives successful results when classical regression estimates cannot be obtained. During the periods when Turkey undergoes economical crisis, it is difficult to make accurate inflation estimates. More reliable estimates can be made with the help of fuzzy regression models. In this study, inflation estimates were obtained through fuzzy regression model estimation and the results were interpreted.Enflasyon hedeflemesi, ekonominin genel değişkenlerinin ve verilerinin dikkate alınarak belirli bir dönem için kabul edilebilir bir enflasyon oranının belirlenmesi ve para politikalarının belirlenen orana ulaşacak şekilde yürütülmesi olarak tanımlanmaktadır. Hedeflere ulaşabilmek için güçlü enflasyon tahminlerine gereksinim duyulmaktadır. Öngörülerin doğru bir şekilde elde edilmesi daha doğru kararlara neden olmaktadır. Bulanık regresyon yöntemi, klasik regresyon varsayımlarının sağlanmadığı durumlarda başarılı sonuçlar veren bir yöntemdir. Türkiye’nin ekonomik kriz yaşadığı dönemlerde güçlü enflasyon tahminleri yapmak oldukça zor olmaktadır. Bulanık regresyon modelleri yardımıyla daha güvenilir tahminler elde edilebilmektedir. Bu çalışmada, bulanık regresyon model tahminlemesi ile kritik dönemler için enflasyon tahminleri elde edilmiş ve sonuçlar yorumlanmıştır
Kritik (Kriz) Dönem Enflasyon Hesaplamalarında Bulanık Regresyon Tahminlemesi
Inflation targeting is defined as the determination of an acceptable inflation rate for a specific period of time by considering the general variables and data of inflation and also as the implementation of monetary policies in such a way that they can reach predetermined rates. Accurate inflation estimates are needed to reach the targets. Acquiring the estimations accurately leads to correct decisions. Fuzzy regression method is a method that gives successful results when classical regression estimates cannot be obtained. During the periods when Turkey undergoes economical crisis, it is difficult to make accurate inflation estimates. More reliable estimates can be made with the help of fuzzy regression models. In this study, inflation estimates were obtained through fuzzy regression model estimation and the results were interpreted.Enflasyon hedeflemesi, ekonominin genel değişkenlerinin ve verilerinin dikkate alınarak belirli bir dönem için kabul edilebilir bir enflasyon oranının belirlenmesi ve para politikalarının belirlenen orana ulaşacak şekilde yürütülmesi olarak tanımlanmaktadır. Hedeflere ulaşabilmek için güçlü enflasyon tahminlerine gereksinim duyulmaktadır. Öngörülerin doğru bir şekilde elde edilmesi daha doğru kararlara neden olmaktadır. Bulanık regresyon yöntemi, klasik regresyon varsayımlarının sağlanmadığı durumlarda başarılı sonuçlar veren bir yöntemdir. Türkiye’nin ekonomik kriz yaşadığı dönemlerde güçlü enflasyon tahminleri yapmak oldukça zor olmaktadır. Bulanık regresyon modelleri yardımıyla daha güvenilir tahminler elde edilebilmektedir. Bu çalışmada, bulanık regresyon model tahminlemesi ile kritik dönemler için enflasyon tahminleri elde edilmiş ve sonuçlar yorumlanmıştır
Influence of coumarin as an additive on CuO nanostructures prepared by successive ionic layer adsorption and reaction (SILAR) method
The effect of coumarin doping during the growth of CuO nanostructures by SILAR method has been studied. It was found that coumarin considerably influences the growth process, manipulates the bandgap and modifies the crystallite size of the films. XRD experiments evidenced that with higher coumarin concentrations in the growth solution, the microstrain and dislocation density increased, while the crystallite size of the films decreased. SEM images revealed that the thicknesses of the plate-like nanostructures decreased with increasing coumarin concentration. By UV/vis spectrophotometer analysis it is found that the coumarin concentration affects both the optical band gap and the transmission rate: both the band gap and spectral transmittance values of the films decreased for higher coumarin content. © 2013 Elsevier B.V. All rights reserved
Neutrino Spectrum from SN 1987A and from Cosmic Supernovae
The detection of neutrinos from SN 1987A by the Kamiokande-II and
Irvine-Michigan-Brookhaven detectors provided the first glimpse of core
collapse in a supernova, complementing the optical observations and confirming
our basic understanding of the mechanism behind the explosion. One
long-standing puzzle is that, when fitted with thermal spectra, the two
independent detections do not seem to agree with either each other or typical
theoretical expectations. We assess the compatibility of the two data sets in a
model-independent way and show that they can be reconciled if one avoids any
bias on the neutrino spectrum stemming from theoretical conjecture. We
reconstruct the neutrino spectrum from SN 1987A directly from the data through
non-parametric inferential statistical methods and present predictions for the
Diffuse Supernova Neutrino Background based on SN 1987A data. We show that this
prediction cannot be too small (especially in the 10-18 MeV range), since the
majority of the detected events from SN 1987 were above 18 MeV (including 6
events above 35 MeV), suggesting an imminent detection in operational and
planned detectors.Comment: 9 pages, 4 figures; Matches version published in Phys. Rev.
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