694 research outputs found
The Scale of Public Space: Taksim Square in Istanbul
This article aims at following the traces of the transformation of public sphere in Turkey through its manifestations on urban public spaces with the case study of Taksim Square. In this attempt, the article illustrates how Taksim square, as a public space, has been shaped by struggles between different ideologies, discourses, political decisions and daily activities taking place at personal, interpersonal, local, national, supranational and global scales. Through this way this article also aims at understanding how these contestations at different scales are affecting people, individually and collectively, from daily life practices to political integration. The article also discusses that our daily life practices and preferences are political decisions and our participation in public sphere occurs through those daily actions of the personal spheres. Therefore, the article suggests that a paradigm shift is needed in the design and production of the built environments that will facilitate the coexistence of multiple counter publics
Oeuvre Vs. Abstract Space: Appropriation of Gezi Park in Istanbul
The Gezi Park incidents of summer 2013 in Istanbul have marked a turning point in the political life and democracy in Turkey. The peaceful environmentalist protestations in central Gezi Park have turned into a countrywide upheaval against the neo-liberal and conservative policies of the government, pouring millions of people into streets in different cities. It was a time that Turkey witnessed the formation of a new type of public sphere that encompasses a variety of counter publics, and its spatial incarnation –the Gezi Commune-, reclaimed, created, shaped and inhabited by the free will of people. This was the instant creation of oeuvre through appropriation of the urban space, and a spatial manifestation of reclaiming the right to the city. This article is a reflection on possibility of creation of oeuvre in contemporary society, and a new way of architectural thinking and practice that can pave the way for it
Pacifying the Fermi-liquid: battling the devious fermion signs
The fermion sign problem is studied in the path integral formalism. The
standard picture of Fermi liquids is first critically analyzed, pointing out
some of its rather peculiar properties. The insightful work of Ceperley in
constructing fermionic path integrals in terms of constrained world-lines is
then reviewed. In this representation, the minus signs associated with
Fermi-Dirac statistics are self consistently translated into a geometrical
constraint structure (the {\em nodal hypersurface}) acting on an effective
bosonic dynamics. As an illustrative example we use this formalism to study
1+1-dimensional systems, where statistics are irrelevant, and hence the sign
problem can be circumvented. In this low-dimensional example, the structure of
the nodal constraints leads to a lucid picture of the entropic interaction
essential to one-dimensional physics. Working with the path integral in
momentum space, we then show that the Fermi gas can be understood by analogy to
a Mott insulator in a harmonic trap. Going back to real space, we discuss the
topological properties of the nodal cells, and suggest a new holographic
conjecture relating Fermi liquids in higher dimensions to soft-core bosons in
one dimension. We also discuss some possible connections between mixed
Bose/Fermi systems and supersymmetry.Comment: 28 pages, 5 figure
A Simple Method for Finding Optimal Paths of Hot and Cold Streams inside Shell and Tube Heat Exchangers to Reduce Pumping Cost in Heat Exchanger Network Problems
In this paper, a simple method is presented for the synthesis and retrofit of heat exchanger networks (HENs) by considering pressure drop as well as finding proper path of streams inside heat exchangers (HEs) to reduce the pumping cost of network. Generally, HEN problems lead to MINLP models which have convergence difficulties due to the existence of both continuous and integer variables. In this study, instead of solving these variables simultaneously, a combination of Genetic Algorithm (GA) with Quasi Linear Programming (QLP) and Integer Linear Programming (ILP) was used for solving the problem. GA was used to find optimal HENs structure and streams paths, whereas continuous variables were solved by QLP. For the retrofit of HENs, a modified ILP model was used. Results show that the proposed method has the ability to reduce the cost of
annual pumping due to considering optimal paths for streams in the HEs compared to the literature.
This work is licensed under a Creative Commons Attribution 4.0 International License
On cognitive readiness in construction decision making
Cognitive readiness (CR) in construction is the mental, emotional and interpersonal
skills that relate to the way project teams perceive, remember, think, speak and solve problems. CR
compliments the necessary technical and contextual competences, and is necessary for making appropriate
decisions in real-world problems. The investigation of cognitive enablers and barriers as well as their
prioritization, adaptation and implementation in construction projects is the subject ofthe work described
here
The Berry phase of dislocations in graphene and valley conserving decoherence
We demonstrate that dislocations in the graphene lattice give rise to
electron Berry phases equivalent to quantized values {0,1/3,-1/3} in units of
the flux quantum, but with an opposite sign for the two valleys. An elementary
scale consideration of a graphene Aharonov-Bohm ring equipped with valley
filters on both terminals, encircling a dislocation, says that in the regime
where the intervalley mean free path is large compared to the intravalley phase
coherence length, such that the valley quantum numbers can be regarded as
conserved on the relevant scale, the coherent valley-polarized currents
sensitive to the topological phases have to traverse the device many times
before both valleys contribute, and this is not possible at intermediate
temperatures where the latter length becomes of order of the device size, thus
leading to an apparent violation of the basic law of linear transport that
magnetoconductance is even in the applied flux. We discuss this discrepancy in
the Feynman path picture of dephasing, when addressing the transition from
quantum to classical dissipative transport. We also investigate this device in
the scattering matrix formalism, accounting for the effects of decoherence by
the Buttiker dephasing voltage probe type model which conserves the valleys,
where the magnetoconductance remains even in the flux, also when different
decoherence times are allowed for the individual, time reversal connected,
valleys.Comment: 14 pages, 7 figures; revised text, added figure, accepted for
publication by PR
Electronic States of Graphene Grain Boundaries
We introduce a model for amorphous grain boundaries in graphene, and find
that stable structures can exist along the boundary that are responsible for
local density of states enhancements both at zero and finite (~0.5 eV)
energies. Such zero energy peaks in particular were identified in STS
measurements [J. \v{C}ervenka, M. I. Katsnelson, and C. F. J. Flipse, Nature
Physics 5, 840 (2009)], but are not present in the simplest pentagon-heptagon
dislocation array model [O. V. Yazyev and S. G. Louie, Physical Review B 81,
195420 (2010)]. We consider the low energy continuum theory of arrays of
dislocations in graphene and show that it predicts localized zero energy
states. Since the continuum theory is based on an idealized lattice scale
physics it is a priori not literally applicable. However, we identify stable
dislocation cores, different from the pentagon-heptagon pairs, that do carry
zero energy states. These might be responsible for the enhanced magnetism seen
experimentally at graphite grain boundaries.Comment: 10 pages, 4 figures, submitted to Physical Review
- …