7,424 research outputs found
Asymmetric magnetization splitting in diamond domain structure: Dependence on exchange interaction and anisotropy
The distributions of magnetization orientation for both Landau and diamond
domain structures in nano-rectangles have been investigated by micromagnetic
simulation with various exchange coefficient and anisotropy constant. Both
symmetric and asymmetric magnetization splitting are found in diamond domain
structure, as well as only symmetric magnetization splitting in Landau
structure. In the Landau structure, the splitting angle increases with the
exchange coefficient but decreases slightly with the anisotropy constant,
suggesting that the exchange interaction mainly contributes to the
magnetization splitting in Landau structure. However in the diamond structure,
the splitting angle increases with the anisotropy constant but derceases with
the exchange coefficient, indicating that the magnetization splitting in
diamond structure is resulted from magnetic anisotropy.Comment: 5 pages, 5 figure
Electron orbital valves made of multiply connected armchair carbon nanotubes with mirror-reflection symmetry: tight-binding study
Using the tight-binding method and the Landauer-B\"{u}ttiker conductance
formalism, we demonstrate that a multiply connected armchair carbon nanotube
with a mirror-reflection symmetry can sustain an electron current of the
-bonding orbital while suppress that of the -antibonding orbital over
a certain energy range. Accordingly, the system behaves like an electron
orbital valve and may be used as a scanning tunneling microscope to probe
pairing symmetry in d-wave superconductors or even orbital ordering in solids
which is believed to occur in some transition-metal oxides.Comment: 4 figures, 12 page
The Globular Cluster System of M60 (NGC 4649). II. Kinematics of the Globular Cluster System
We present a kinematic analysis of the globular cluster (GC) system in the
giant elliptical galaxy (gE) M60 in the Virgo cluster. Using the photometric
and spectroscopic database of 121 GCs (83 blue GCs and 38 red GCs), we have
investigated the kinematics of the GC system. We have found that the M60 GC
system shows a significant overall rotation. The rotation amplitude of the blue
GCs is slightly smaller than or similar to that of the red GCs, and their
angles of rotation axes are similar. The velocity dispersions about the mean
velocity and about the best fit rotation curve for the red GCs are marginally
larger than those for the blue GCs. Comparison of observed stellar and GC
velocity dispersion profiles with those calculated from the stellar mass
profile shows that the mass-to-light ratio should be increased as the
galactocentric distance increases, indicating the existence of an extended dark
matter halo. The entire sample of GCs in M60 is found to have a tangentially
biased velocity ellipsoid unlike the GC systems in other gEs. Two subsamples
appear to have different velocity ellipsoids. The blue GC system has a modest
tangentially biased velocity ellipsoid, while the red GC system has a modest
radially biased or an isotropic velocity ellipsoid. From the comparison of the
kinematic properties of the M60 GC system to those of other gEs (M87, M49, NGC
1399, NGC 5128, and NGC 4636), it is found that the velocity dispersion of the
blue GC system is similar to or larger than that of the red GC system except
for M60, and the rotation of the GC system is not negligible. The entire sample
of each GC system shows an isotropic velocity ellipsoid except for M60, while
the subsamples show diverse velocity ellipsoids. We discuss the implication of
these results for the formation models of the GC system in gEs.Comment: 48 pages, 16 figures. To appear in Ap
Interfacial mixing in heteroepitaxial growth
We investigate the growth of a film of some element B on a substrate made of
another substrance A in a model of molecular beam epitaxy. A vertical exchange
mechanism allows the A-atoms to stay on the growing surface with a certain
probability. Using kinetic Monte Carlo simulations as well as scaling
arguments, the incorporation of the A's into the growing B-layer is
investigated. Moreover we develop a rate equation theory for this process. In
the limit of perfect layer-by-layer growth, the density of A-atoms decays in
the B-film like the inverse squared distance from the interface. The power law
is cut off exponentially at a characteristic thickness of the interdiffusion
zone that depends on the rate of exchange of a B-adatom with an A-atom in the
surface and on the system size. Kinetic roughening changes the exponents. Then
the thickness of the interdiffusion zone is determined by the diffusion length.Comment: 11 pages, 11 figure
Condensation and Clustering in the Driven Pair Exclusion Process
We investigate particle condensation in a driven pair exclusion process on
one- and two- dimensional lattices under the periodic boundary condition. The
model describes a biased hopping of particles subject to a pair exclusion
constraint that each particle cannot stay at a same site with its pre-assigned
partner. The pair exclusion causes a mesoscopic condensation characterized by
the scaling of the condensate size and the number of
condensates with the total number of sites .
Those condensates are distributed randomly without hopping bias. We find that
the hopping bias generates a spatial correlation among condensates so that a
cluster of condensates appears. Especially, the cluster has an anisotropic
shape in the two-dimensional system. The mesoscopic condensation and the
clustering are studied by means of numerical simulations.Comment: 4 pages, 5 figure
Pollution with Saprobic Index and Nutrition Value Coefficient of Fish
Buyan Lake located in the village of Pancasari, District Sukasada, Buleleng, Bali. Lake area of 301.84 hectares located at an altitude of about 1,000 meters above sea level is one of three twin lake that forms in a large caldera. Buyan Lake is flanked by two other lakes, namely Lake Tamblingan in the west and Lake Beratan in the east. Depth Buyan alone is estimated at around 80 meters, where the depth of the lake is never reached 140 meters before the bottom of the lake due to the silting of Buyan Lake erosion. Water resource who physically looks have undergone significant environmental stress due to things like the level of the lake by the plant closure especially Eichhornia crassipes plants and other aquatic plants, Chlorophyta class consisting of 4 species, Cyanophyta class consisting of six species, one species. Pyrrophyta class at Buyan Lake has included the category of lightly polluted with saprobic coefficient ranges from 0.594 to 0.777 which is well within the range of ?-mesosaprobic saprobic phase. The results of the analysis of nutritional status (NVC) fish that include tilapia, fish Zebra, and Fish Nilem are as follows: Tilapia value status is nutrient is an average of 1,944 which shows the waters of Buyan Lake is still classified as clean fish Zebra average of 1.828, which means the waters Buyan Lake is still in the net category. Fish Nilem to the average value of nutritional status (NVC) is 1.376 which shows the deep waters contaminated state. At each station showed a different saprobic coefficient, the difference is still in a phase of ?-mesosaprobic
A Model of the Effects of Change in Teachersâ Beliefs in Mathematical Problem Solving in Malaysia
Many previous studies have reported that the term
problem solving has been fully investigated in developed countries
as can be seen in the work of earlier famous authors and majority
of them agreed that a problem occurs only when someone is
confronted with a difficulty for which an immediate answer is not
available. In short, problem solving refers to the effort needed in
achieving a goal or finding a solution when no automatic solution
is available. It has however, been identified that there has been
little research on mathematical problem solving in developing and
newly industrialized nations especially in Malaysia. This research
specifically seeks to look into a model of the effects of change in
teachersâ beliefs in mathematical problem solving in Malaysia. In
this study, a few research questions are asked based on the research
objectives and hypothesis formulated to tackle the questions. The
methodology adopted in this study is quantitative while the
statistical package for social sciences is utilized for analyzing the
data. Considering the aforementioned findings from analysis of
questionnaires the study concludes that; male and female
prospective mathematics teachers differ in the way they view the
importance of technology usage in solving mathematical problems,
that prospective mathematics teachersâ beliefs about mathematical
problem solving have strong connection to their study level and
prospective teachers have both traditional and contemporary views
about mathematical problem solving. Hence, the study together
with its findings will serve as a guideline to explain and provide
empirical evidence which will help in revealing the effects of
student teacherâs beliefs on mathematical problem solving hence
will enable educational policy makers and other interest parties take
appropriate decision
Demonstration of a Bias Tunable Quantum Dots-in-a-well Focal Plane Array
Infrared detectors based on quantum wells and quantum dots have attracted a lot of attention in the past few years. Our previous research has reported on the development of the first generation of quantum dots-in-a-well (DWELL) focal plane arrays, which are based on InAs quantum dots embedded in an InGaAs well having GaAs barriers. This focal plane array has successfully generated a two-color imagery in the mid-wave infrared (i.e. 3â5 ÎŒm) and the long-wave infrared (i.e. 8â12 ÎŒm) at a fixed bias voltage. Recently, the DWELL device has been further modified by embedding InAs quantum dots in InGaAs and GaAs double wells with AlGaAs barriers, leading to a less strained InAs/InGaAs/GaAs/AlGaAs heterostructure. This is expected to improve the operating temperature while maintaining a low dark current level. This paper examines 320 Ă 256 double DWELL based focal plane arrays that have been fabricated and hybridized with an Indigo 9705 read-out integrated circuit using Indium-bump (flip-chip) technology. The spectral tunability is quantified by examining images and determining the transmittance ratio (equivalent to the photocurrent ratio) between mid-wave and long-way infrared filter targets. Calculations were performed for a bias range from 0.3 to 1.0 V. The results demonstrate that the mid-wave transmittance dominates at these low bias voltages, and the transmittance ratio continuously varies over different applied biases. Additionally, radiometric characterization, including array uniformity and measured noise equivalent temperature difference for the double DWELL devices is computed and compared to the same results from the original first generation DWELL. Finally, higher temperature operation is explored. Overall, the double DWELL devices had lower noise equivalent temperature difference and higher uniformity, and worked at higher temperature (70 K and 80 K) than the first generation DWELL device
Floquet Formalism of Quantum Pumps
We review Floquet formalism of quantum electron pumps. In the Floquet
formalism the quantum pump is regarded as a time dependent scattering system,
which allows us to go beyond the adiabatic limit. It can be shown that the
well-known adiabatic formula given by Brouwer can be derived from the adiabatic
limit of Floquet formalism. We compare various physical properties of the
quantum pump both in the adiabatic and in the non-adiabatic regime using the
Floquet theory.Comment: Latex2e 16 pages, 6 figures. A review paper to appear in Int. J. Mod.
Phys.
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