188 research outputs found
The effect of boundary adaptivity on hexagonal ordering and bistability in circularly confined quasi hard discs
The behaviour of materials under spatial confinement is sensitively dependent
on the nature of the confining boundaries. In two dimensions, confinement
within a hard circular boundary inhibits the hexagonal ordering observed in
bulk systems at high density. Using colloidal experiments and Monte Carlo
simulations, we investigate two model systems of quasi hard discs under
circularly symmetric confinement. The first system employs an adaptive circular
boundary, defined experimentally using holographic optical tweezers. We show
that deformation of this boundary allows, and indeed is required for, hexagonal
ordering in the confined system. The second system employs a circularly
symmetric optical potential to confine particles without a physical boundary.
We show that, in the absence of a curved wall, near perfect hexagonal ordering
is possible. We propose that the degree to which hexagonal ordering is
suppressed by a curved boundary is determined by the `strictness' of that wall.Comment: 10 pages, 8 figure
Hyperuniformity of Quasicrystals
Hyperuniform systems, which include crystals, quasicrystals and special
disordered systems, have attracted considerable recent attention, but rigorous
analyses of the hyperuniformity of quasicrystals have been lacking because the
support of the spectral intensity is dense and discontinuous. We employ the
integrated spectral intensity, , to quantitatively characterize the
hyperuniformity of quasicrystalline point sets generated by projection methods.
The scaling of as tends to zero is computed for one-dimensional
quasicrystals and shown to be consistent with independent calculations of the
variance, , in the number of points contained in an interval of
length . We find that one-dimensional quasicrystals produced by projection
from a two-dimensional lattice onto a line of slope fall into distinct
classes determined by the width of the projection window. For a countable dense
set of widths, ; for all others, . This
distinction suggests that measures of hyperuniformity define new classes of
quasicrystals in higher dimensions as well.Comment: 12 pages, 14 figure
Climbing depth-bounded adjacent discrepancy search for solving hybrid flow shop scheduling problems with multiprocessor tasks
This paper considers multiprocessor task scheduling in a multistage hybrid
flow-shop environment. The problem even in its simplest form is NP-hard in the
strong sense. The great deal of interest for this problem, besides its
theoretical complexity, is animated by needs of various manufacturing and
computing systems. We propose a new approach based on limited discrepancy
search to solve the problem. Our method is tested with reference to a proposed
lower bound as well as the best-known solutions in literature. Computational
results show that the developed approach is efficient in particular for
large-size problems
Confined colloidal crystals in and out of equilibrium
Recent studies on confined crystals of charged colloidal particles are
reviewed, both in equilibrium and out of equilibrium. We focus in particular on
direct comparisons of experiments (light scattering and microscopy) with
lattice sum calculations and computer simulations. In equilibrium we address
buckling and crystalline multilayering of charged systems in hard and soft slit
confinement. We discuss also recent crystalline structures obtained for charged
mixtures. Moreover, we put forward possibilities to apply external
perturbations, in order to drive the system out of equilibrium. These include
electrolyte gradients as well as the application of shear and electric fields.Comment: Review article, 18 pages, 5 figure
Surface-charge-induced freezing of colloidal suspensions
Using grand-canonical Monte Carlo simulations we investigate the impact of
charged walls on the crystallization properties of charged colloidal
suspensions confined between these walls. The investigations are based on an
effective model focussing on the colloids alone. Our results demonstrate that
the fluid-wall interaction stemming from charged walls has a crucial impact on
the fluid's high-density behavior as compared to the case of uncharged walls.
In particular, based on an analysis of in-plane bond order parameters we find
surface-charge-induced freezing and melting transitions
The relations between the Ottoman Empire and Bolshevik Russia (1917-1918)
Ankara : The Department of International Relations of Bilkent University, 1998.Thesis (Master's) -- Bilkent University, 1998.Includes bibliographical references leaves 130-139.The fear of being left alone against Russia in an environment of confronting blocs was
the main factor behind the decision of the Ottoman government to enter the First
World War on the side of the Central Powers. The liberation of the Muslims of Russia
from the Russian yoke henceforth became one of the important war objectives of the
Ottoman Supreme Command. Nevertheless, the tragic defeat of the Ottoman army in
Sankarru~ did not only constitute a serious obstacle against the realization of these
aspirations, but it also helped the Russian army to penetrate deep into Ottoman
territory. The outbreak of the revolution in Russia and the Bolshevik power seizure in
October 1917 provided the Ottoman government with the opportunity of
compensating war losses and realizing the strategic aims embodied on the eve and at
the beginning of the Great War. The Ottoman government's policy with regard to
Russia between 1917-1918 can be analyzed under two main stages. In the short-run
the primary aim was the restoration of the pre-war frontier with Russia and acquisition
of as much territory in Transcaucasia as possible. With the Russian Treaty of BrestLitovsk,
the Ottoman government successfully accomplished its plans with regard to
Transcaucasia. In the long-run Ottoman leaders aimed at separating Transcaucasia
from Russia in order to create therein independent states that would prevent Russian
aggression in the future. In spite of the peace treaty with the Bolsheviks, the Ottoman
army continued its military operations in the region. The Ottoman government did
everything in its power, militarily or politically, to persuade the Transcaucasian peoples
to proclaim their independence. As time went on, Ottomans were not only satisfied
with Transcaucasia and North Caucasia was made part of these strategic aims. There
were even plans concerning the independence of the Muslims of the Volga basin and
Turkestan. Consequently, the primary subject of the relations between the Ottoman
and Bolshevik governments in the final two years of the war was the Ottoman
activities with regard to the Caucasus region and the Muslims of Russia. These
Ottoman objectives not only caused disagreements with the Bolsheviks, but also
became a serious source of contention with Germany.Oğuz, C CemM.S
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