31,686 research outputs found
Vitrification and determination of the crystallization time scales of the bulk-metallic-glass-forming liquid Zr58.5Nb2.8Cu15.6Ni12.8Al10.3
The crystallization kinetics of Zr58.5Nb2.8Cu15.6Ni12.8Al10.3 were studied in an electrostatic levitation (ESL) apparatus. The measured critical cooling rate is 1.75 K/s. Zr58.5Nb2.8Cu15.6Ni12.8Al10.3 is the first bulk-metallic-glass-forming liquid that does not contain beryllium to be vitrified by purely radiative cooling in the ESL. Furthermore, the sluggish crystallization kinetics enable the determination of the time-temperature-transformation (TTT) diagram between the liquidus and the glass transition temperatures. The shortest time to reach crystallization in an isothermal experiment; i.e., the nose of the TTT diagram is 32 s. The nose of the TTT diagram is at 900 K and positioned about 200 K below the liquidus temperature
Asymptotic behavior of the number of Eulerian orientations of graphs
We consider the class of simple graphs with large algebraic connectivity (the
second-smallest eigenvalue of the Laplacian matrix). For this class of graphs
we determine the asymptotic behavior of the number of Eulerian orientations. In
addition, we establish some new properties of the Laplacian matrix, as well as
an estimate of a conditionality of matrices with the asymptotic diagonal
predominanceComment: arXiv admin note: text overlap with arXiv:1104.304
Construction of Error-Correction Code Application by Applying Finite Field and Hadamard Matrix Theory
Dalam dunia elektronik dan digital, informasi dapat dengan mudahditransfer melalui saluran komunikasi. Pada data yang ditransfer galatdapat muncul dikarenakan oleh berbagai akibat. Untuk menghindarimasalah ini diperlukan kode perbaikan-galat bersama aplikasinya. Konsepdari kode perbaikan-galat adalah untuk menambahkan bit-tambahanpada data agar disaat pengiriman, data tersebut lebih kuat dalammenghadapi gangguan yang hadir di saluran komunikasi. Random ParityCode (RPC) yang dikemukakan oleh Hershey dan Tiemann (1996) adalahsalah satu dari kode yang dimaksud. Artikel ini menunjukan pembuatanaplikasi kode perbaikan-galat yang dibuat berdasarkan konsep RPCdengan bantuan teori Lapangan Terbatas dan Matriks Hadamard. Aplikasidibuat menggunakan Metode Rapid Application Development (RAD).Aplikasi dihasilkan dalam bentuk perangkat lunak komputer. Perangkatlunak tersebut menjadi lebih efisien dengan menerapkan konsepalgoritma âDivide and Conquerâ
The Relationship Between Molecular Gas Tracers and Kennicutt-Schmidt Laws
We provide a model for how Kennicutt-Schmidt (KS) laws, which describe the
correlation between star formation rate and gas surface or volume density,
depend on the molecular line chosen to trace the gas. We show that, for lines
that can be excited at low temperatures, the KS law depends on how the line
critical density compares to the median density in a galaxy's star-forming
molecular clouds. High critical density lines trace regions with similar
physical properties across galaxy types, and this produces a linear correlation
between line luminosity and star formation rate. Low critical density lines
probe regions whose properties vary across galaxies, leading to a star
formation rate that varies superlinearly with line luminosity. We show that a
simple model in which molecular clouds are treated as isothermal and homogenous
can quantitatively reproduce the observed correlations between galactic
luminosities in far infrared and in the CO(1->0) and HCN(1->0) lines, and
naturally explains why these correlations have different slopes. We predict
that IR-line luminosity correlations should change slope for galaxies in which
the median density is close to the line critical density. This prediction may
be tested by observations of lines such as HCO^+(1->0) with intermediate
critical densities, or by HCN(1->0) observations of intensely star-forming high
redshift galaxies with very high densities. Recent observations by Gao et al.
hint at just such a change in slope. We argue that deviations from linearity in
the HCN(1->0)-IR correlation at high luminosity are consistent with the
assumption of a constant star formation efficiency.Comment: Accepted to ApJ. 11 pages, 4 figures, emulateapj format. This version
has some additional models exploring the effects of varying metallicity and
temperature. The conclusions are unchange
The star-formation history of the universe - an infrared perspective
A simple and versatile parameterized approach to the star formation history
allows a quantitative investigation of the constraints from far infrared and
submillimetre counts and background intensity measurements.
The models include four spectral components: infrared cirrus (emission from
interstellar dust), an M82-like starburst, an Arp220-like starburst and an AGN
dust torus. The 60 m luminosity function is determined for each chosen
rate of evolution using the PSCz redshift data for 15000 galaxies. The
proportions of each spectral type as a function of 60 m luminosity are
chosen for consistency with IRAS and SCUBA colour-luminosity relations, and
with the fraction of AGN as a function of luminosity found in 12 m
samples. The luminosity function for each component at any wavelength can then
be calculated from the assumed spectral energy distributions. With assumptions
about the optical seds corresponding to each component and, for the AGN
component, the optical and near infrared counts can be accurately modelled.
A good fit to the observed counts at 0.44, 2.2, 15, 60, 90, 175 and 850
m can be found with pure luminosity evolution in all 3 cosmological models
investigated: = 1, = 0.3 ( = 0), and
= 0.3, = 0.7.
All 3 models also give an acceptable fit to the integrated background
spectrum. Selected predictions of the models, for example redshift
distributions for each component at selected wavelengths and fluxes, are shown.
The total mass-density of stars generated is consistent with that observed,
in all 3 cosmological models.Comment: 20 pages, 25 figures. Accepted for publication in ApJ. Full details
of models can be found at http://astro.ic.ac.uk/~mrr/countmodel
Gender, Culture and Intervention: Exploring Differences between Aboriginal and Non-Aboriginal Childrenâs Responses to an Early Intervention Programme
Evaluation of a group parenting programme in the Northern Territory of Australia showed significant differences in benefits for Aboriginal and non-Aboriginal boys and girls. The analysis considers whether boys and girls from different cultural backgrounds present with different problems; whether parental expectations for boys and girls differ and whether the intervention activates different responses in different settings. Conclusions suggest that there is a need to closely examine the âcultural logicâ of interventions, the appropriateness of their assumptions about child development and hypothesised mechanisms of change in different settings
Nonstatistical dynamics on potentials exhibiting reaction path bifurcations and valley-ridge inflection points
We study reaction dynamics on a model potential energy surface exhibiting
post-transition state bifurcation in the vicinity of a valley ridge inflection
point. We compute fractional yields of products reached after the VRI region is
traversed, both with and without dissipation. It is found that apparently minor
variations in the potential lead to significant changes in the reaction
dynamics. Moreover, when dissipative effects are incorporated, the product
ratio depends in a complicated and highly non-monotonic fashion on the
dissipation parameter. Dynamics in the vicinity of the VRI point itself play
essentially no role in determining the product ratio, except in the highly
dissipative regime.Comment: 33 pages, 10 figures, corrected the author name in reference [6
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