1,829 research outputs found
Balanced Allocations: A Simple Proof for the Heavily Loaded Case
We provide a relatively simple proof that the expected gap between the
maximum load and the average load in the two choice process is bounded by
, irrespective of the number of balls thrown. The theorem
was first proven by Berenbrink et al. Their proof uses heavy machinery from
Markov-Chain theory and some of the calculations are done using computers. In
this manuscript we provide a significantly simpler proof that is not aided by
computers and is self contained. The simplification comes at a cost of weaker
bounds on the low order terms and a weaker tail bound for the probability of
deviating from the expectation
Comparative study of bolometric and non-bolometric switching elements for microwave phase shifters
The performance of semiconductor and high critical temperature superconductor switches is compared as they are used in delay-line-type microwave and millimeter-wave phase shifters. Such factors as their ratios of the off-to-on resistances, parasitic reactances, power consumption, speed, input-to-output isolation, ease of fabrication, and physical dimensions are compared. Owing to their almost infinite off-to-on resistance ratio and excellent input-to-output isolation, bolometric superconducting switches appear to be quite suitable for use in microwave phase shifters; their only drawbacks are their speed and size. The SUPERFET, a novel device whose operation is based on the electric field effect in high critical temperature ceramic superconductors is also discussed. Preliminary results indicate that the SUPERFET is fast and that it can be scaled; therefore, it can be fabricated with dimensions comparable to semiconductor field-effect transistors
EVALUATION OF THE ANTIOXIDANT ACTIVITY OF THE FLAVONOIDS ISOLATED FROM HELIOTROPIUM SINUATUM RESIN USING ORACFL, DPPH AND ESR METHODOLOGIES
IndexaciĂłn: Web of Science; Scielo.The antioxidant capacity has been determined for a number of flavonoid compounds from Heliotropium sinuatum, a plant that grows in arid areas in the north of Chile. The methodologies used were: ORAC(FL) (oxygen radical absorbance capacity - fluorescein), DPPH (2,2-diphenyl-2-picrylhydrazyl) bleaching and electron spin resonance (ESR). These compounds were studied in homogeneous and heterogeneous media. The results showed that the 7-o-methyleriodictiol and 3-o-methylisorhamnetin are those with the highest antioxidant capacity.http://ref.scielo.org/m82cz
Enhanced and continuous electrostatic carrier doping on the SrTiO surface
Paraelectrical tuning of a charge carrier density as high as
10\,cm in the presence of a high electronic carrier mobility on
the delicate surfaces of correlated oxides, is a key to the technological
breakthrough of a field effect transistor (FET) utilising the metal-nonmetal
transition. Here we introduce the Parylene-C/TaO hybrid gate
insulator and fabricate FET devices on single-crystalline SrTiO, which
has been regarded as a bedrock material for oxide electronics. The gate
insulator accumulates up to cm carriers, while the
field-effect mobility is kept at 10\,cm/Vs even at room temperature.
Further to the exceptional performance of our devices, the enhanced
compatibility of high carrier density and high mobility revealed the mechanism
for the long standing puzzle of the distribution of electrostatically doped
carriers on the surface of SrTiO. Namely, the formation and continuous
evolution of field domains and current filaments.Comment: Supplementary Information:
<http://www.nature.com/srep/2013/130424/srep01721/extref/srep01721-s1.pdf
Balanced Allocation on Graphs: A Random Walk Approach
In this paper we propose algorithms for allocating sequential balls into
bins that are interconnected as a -regular -vertex graph , where
can be any integer.Let be a given positive integer. In each round
, , ball picks a node of uniformly at random and
performs a non-backtracking random walk of length from the chosen node.Then
it allocates itself on one of the visited nodes with minimum load (ties are
broken uniformly at random). Suppose that has a sufficiently large girth
and . Then we establish an upper bound for the maximum number
of balls at any bin after allocating balls by the algorithm, called {\it
maximum load}, in terms of with high probability. We also show that the
upper bound is at most an factor above the lower bound that is
proved for the algorithm. In particular, we show that if we set , for every constant , and
has girth at least , then the maximum load attained by the
algorithm is bounded by with high probability.Finally, we
slightly modify the algorithm to have similar results for balanced allocation
on -regular graph with and sufficiently large girth
Identifikasi Perubahan Jasa Lingkungan dengan Menggunakan Penginderaan Jauh dan Sistem Informasi Geografis di Bogor
Environmental services are the services provided by the ecosystem functions that have direct and indirect benefits to human well being. The purpose of this study is to analyze environmental services changes in the District and City of Bogor on 1990 and 2014. The focus of the study is analyzing the environmental service of carbon stock, carbon sinks, biodiversity, the aesthetic of landscape, water regulation and climate amelioration. The data collection method began with data preprocessing then followed by a groundcheck at field to take sample point, after that followed by image classification that produce land cover. Land cover that has been classified then given the value of environmental services by changing the format of raster into a polygon. The average value of environmental services in District of Bogor on 1990 is 4,86 and in the city of Bogor is 4,56, while on 2014 the average value of environmental services in District of Bogor is 4,54 and in the City of Bogor is 3,72. Change of environmental services in the City of Bogor greater than in District of Bogor due to the magnitude of changes in land cover types of forest to other land cover especially for settlement. Beside that, it is also caused by differences of development policy between Bogor district and city of Bogor. The focus of development in the district is agricultural production sector and the city are trading and services sectors. Government of City and Distric of Bogor should do some efforts for maintaining and even improving environmental services by allocating space for land which dominated by trees and agroforestry system
A Supercooled Spin Liquid State in the Frustrated Pyrochlore Dy2Ti2O7
A "supercooled" liquid develops when a fluid does not crystallize upon
cooling below its ordering temperature. Instead, the microscopic relaxation
times diverge so rapidly that, upon further cooling, equilibration eventually
becomes impossible and glass formation occurs. Classic supercooled liquids
exhibit specific identifiers including microscopic relaxation times diverging
on a Vogel-Tammann-Fulcher (VTF) trajectory, a Havriliak-Negami (HN) form for
the dielectric function, and a general Kohlrausch-Williams-Watts (KWW) form for
time-domain relaxation. Recently, the pyrochlore Dy2Ti2O7 has become of
interest because its frustrated magnetic interactions may, in theory, lead to
highly exotic magnetic fluids. However, its true magnetic state at low
temperatures has proven very difficult to identify unambiguously. Here we
introduce high-precision, boundary-free magnetization transport techniques
based upon toroidal geometries and gain a fundamentally new understanding of
the time- and frequency-dependent magnetization dynamics of Dy2Ti2O7. We
demonstrate a virtually universal HN form for the magnetic susceptibility, a
general KWW form for the real-time magnetic relaxation, and a divergence of the
microscopic magnetic relaxation rates with precisely the VTF trajectory. Low
temperature Dy2Ti2O7 therefore exhibits the characteristics of a supercooled
magnetic liquid; the consequent implication is that this translationally
invariant lattice of strongly correlated spins is evolving towards an
unprecedented magnetic glass state, perhaps due to many-body localization of
spin.Comment: Version 2 updates: added legend for data in Figures 4A and 4B;
corrected equation reference in caption for Figure 4
On the Growth of Al_2 O_3 Scales
Understanding the growth of Al2O3 scales requires knowledge of the details of the chemical reactions at the scaleâgas and scaleâmetal interfaces, which in turn requires specifying how the creation/annihilation of O and Al vacancies occurs at these interfaces. The availability of the necessary electrons and holes to allow for such creation/annihilation is a crucial aspect of the scaling reaction. The electronic band structure of polycrystalline Al2O3 thus plays a decisive role in scale formation and is considered in detail, including the implications of a density functional theory (DFT) calculation of the band structure of a ÎŁ7 View the MathML source bicrystal boundary, for which the atomic structure of the boundary was known from an independent DFT energy-minimization calculation and comparisons with an atomic-resolution transmission electron micrograph of the same boundary. DFT calculations of the formation energy of O and Al vacancies in bulk Al2O3 in various charge states as a function of the Fermi energy suggested that electronic conduction in Al2O3 scales most likely involves excitation of both electrons and holes, which are localized on singly charged O vacancies, View the MathML source and doubly charged Al vacancies, View the MathML source, respectively. We also consider the variation of the Fermi level across the scale and bending (âtiltingâ) of the conduction band minimum and valence band maximum due to the electric field developed during the scaling reaction. The band structure calculations suggest a new mechanism for the âreactive elementâ effectâa consequence of segregation of Y, Hf, etc., to grain boundaries in Al2O3 scales, which results in improved oxidation resistanceânamely, that the effect is due to the modification of the near-band edge grain-boundary defect states rather than any blocking of diffusion pathways, as previously postulated. Secondly, Al2O3 scale formation is dominated by grain boundary as opposed to lattice diffusion, and there is unambiguous evidence for both O and Al countercurrent transport in Al2O3 scale-forming alloys. We postulate that such transport is mediated by migration of grain boundary disconnections containing charged jogs, rather than by jumping of isolated point defects in random high-angle grain boundaries
Locally Optimal Load Balancing
This work studies distributed algorithms for locally optimal load-balancing:
We are given a graph of maximum degree , and each node has up to
units of load. The task is to distribute the load more evenly so that the loads
of adjacent nodes differ by at most .
If the graph is a path (), it is easy to solve the fractional
version of the problem in communication rounds, independently of the
number of nodes. We show that this is tight, and we show that it is possible to
solve also the discrete version of the problem in rounds in paths.
For the general case (), we show that fractional load balancing
can be solved in rounds and discrete load
balancing in rounds for some function , independently of the
number of nodes.Comment: 19 pages, 11 figure
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