1,415 research outputs found
Collisional Effects in Isovector Response Function of Nuclear Matter at Finite Temperature
The dipole response function of nuclear matter at zero and finite
temperatures is investigated by employing the linearized version of the
extended TDHF theory with a non-Markovian binary collision term. Calculations
are carried out for nuclear dipole vibrations by employing the
Steinwedel-Jensen model and compared with experimental results for
and .Comment: 14 pages, RevTex, 3 PS figure
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
Classroom-based professional expertise: a mathematics teacher’s practice with technology
This study examines the classroom practice and craft knowledge underpinning one teacher’s integration of the use of GeoGebra software into mathematics teaching. The chosen teacher worked in an English secondary school and was professionally well regarded as an accomplished user of digital technology in mathematics teaching. Designed in accordance with the Structuring Features of Classroom Practice framework (Ruthven, 2009), the study triangulates evidence from lesson observations and post-lesson interviews to analyse how this teacher’s classroom practice and professional knowledge support the integration of technology. This analysis shows how the teacher managed a number of aspects of classroom teaching related to using GeoGebra such as including technology-mediated tasks aligned with his pedagogical goals, preparing his students to use the technology efficiently, adapting formats for classroom activity and extending his curriculum scripts for the topics studied.The first author thanks the Ministry of National Education of Turkey for supporting her doctoral studies during which this research was undertaken
The distribution and taxonomy of Lissotriton newts in Turkey (Amphibia, Salamandridae)
Two and perhaps three taxa of
Lissotriton
newt occur in Turkey. Their species status is controversial. The
distribution of these taxa and the taxonomic status of each are reviewed and discussed. A database of 128
Turkish
Lissotriton
localities was compiled and species distribution models were constructed. We reiterate
that the presence of
L.
(
v.
)
lantzi
in Turkey is disputed and needs confirmation. The range of
L.
(
v.
)
koss
-
wigi
is restricted to north-western Anatolia – given the small global range of this Turkey endemic, a closer
look at its conservation status is warranted. The distribution of
L. v. schmidtleri
covers western Asiatic
and European Turkey. The findings support an allopatric distribution of the Turkish
Lissotriton
species.
We reflect on the biological significance of previously reported morphological intermediates between
L.
(
v.
)
kosswigi
and
L. v. schmidtleri
in the light of the recent proposal to recognize
kosswigi
at the species
level. The available data are in line with species status for
L.
(
v.
)
lantzi
and
L.
(
v.
)
kosswigi
. Although
L. v.
schmidtleri
is a genetically diverged taxon as well, the extent of gene flow with parapatric European
Lis
-
sotriton
taxa is as yet unknown
Projections Onto Convex Sets (POCS) Based Optimization by Lifting
Two new optimization techniques based on projections onto convex space (POCS)
framework for solving convex and some non-convex optimization problems are
presented. The dimension of the minimization problem is lifted by one and sets
corresponding to the cost function are defined. If the cost function is a
convex function in R^N the corresponding set is a convex set in R^(N+1). The
iterative optimization approach starts with an arbitrary initial estimate in
R^(N+1) and an orthogonal projection is performed onto one of the sets in a
sequential manner at each step of the optimization problem. The method provides
globally optimal solutions in total-variation, filtered variation, l1, and
entropic cost functions. It is also experimentally observed that cost functions
based on lp, p<1 can be handled by using the supporting hyperplane concept
Harmonic Effects on Electromechanical Overcurrent Relays
Elektromekanik aşırı akım koruma röleleri sinüsoidal akım altında çalışmak üzere tasarlanmıştır. Bu rölelerin harmonikli akımda çalışmaları güvenilir değildir. Literatürde harmonikler ve rölelerle ilgili pek çok teorik çalışma bulunmaktadır. Bu makalede, harmoniklerin elektromekanik ters zamanlı aşırı akım rölesinin (TZAAR) çalışmasına etkileri incelenmiş ve TZAAR’nin bozulmuş dalga şekilleri için davranışı deneysel çalışma ile analiz edilmiştir. Deneyde, elektromekanik TZAAR olarak, indüksiyon disk yapısında bir röle kullanılmıştır. Değişik harmonik spektrumlara sahip, sinüsoidal olmayan yük akımları TZAAR’a uygulanmış ve bu yük akımları data toplama kartı ve harmonik analiz programı ile bilgisayar ortamında işlenmiştir. Deney sonuçları gözönüne alındığında, TZAAR’ın çalışma akımı ve çalışma zamanının, sinüsoidal olmayan akımın toplam harmonik distorsiyonu (THD) ile orantılı olarak arttığı görülmüştür. Bu yapıda olan bir rolenin, akımın harmonik içermesi durumunda sistemi güvenli bir şekilde koruyamayacağı sonucu elde edilmiştir.The electromechanical overcurrent protection relays are designed to operate with sinusoidal current. The operation of protective relay with harmonic currents is not reliable. The literature on harmonics and relays covers mostly the theoretical studies. In this paper, the harmonic effects on operation of electromechanical inverse time overcurrent relay (ITOCR) were examined. Not common in existing studies, the behaviour of ITOCR was analysed with laboratory experiments for distorted waveforms. A type of induction disc relay was used as an electromechanical ITOCR in the experiments. The non-sinusoidal load currents that consist of different harmonic spectra were applied to ITOCR and these nonlinear-load currents were processed by a data acquisition card and a harmonic analysis programme in the computer environment. According to the experiment results, the pick up current and the operating time of the ITOCR increase proportionally to the total harmonic distortion (THD) value of the non-sinusoidal current. It is concluded that, this type of relay cannot protect the system reliably due to the harmonic components of current
System of Systems Perspective on Risk: Towards a Unified Concept
Many systems and projects that concern systems engineers, engineering managers, and business managers today can be defined as system of systems (SoS), which are described as ambiguous, uncertain and dynamic, among others. In addition to the traditional view on risk identification, analysis and management, the concept of risk should be considered with respect to these systems of systems. The purpose of this paper is to analyse both fundamental concepts and recent publications in system of systems, business and engineering management, as well as risk analysis, modelling, and management for the purpose of better describing the concept of risk with respect to system of systems. The ultimate goal is to provide engineering and business managers the necessary perspective on the concept of risk and its management for the next generation of systems – including various descriptions of risk and discussion of the relevance of properties of system of systems to sustainable management of risks in engineered systems. To achieve a truly sustainable management of risk, there has to be a change in paradigm from a traditional description of risk to that of a more holistic perspective
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