11,335 research outputs found
Exact results for quench dynamics and defect production in a two-dimensional model
We show that for a d-dimensional model in which a quench with a rate
\tau^{-1} takes the system across a d-m dimensional critical surface, the
defect density scales as n \sim 1/\tau^{m\nu/(z\nu +1)}, where \nu and z are
the correlation length and dynamical critical exponents characterizing the
critical surface. We explicitly demonstrate that the Kitaev model provides an
example of such a scaling with d=2 and m=\nu=z=1. We also provide the first
example of an exact calculation of some multispin correlation functions for a
two-dimensional model which can be used to determine the correlation between
the defects. We suggest possible experiments to test our theory.Comment: 4 pages including 4 figures; generalized the discussion of the defect
density scaling to the case of arbitrary critical exponents, and added some
references; this version will appear in Physical Review Letter
A robot design for wind generator support structure inspection
In recent time, the development of wind tower inspection has been very crucial for the overall performance of the wind turbine. In order to maintain, monitor and determine the life span of the tower, an investigation of robot design is discussed. It presents how to design and construct a robot that can climb the tower and rotate 360° . A ring system which is in a circular shape robot is designed that allows the device to fit in the structure of the wind generator tower. The rotational module is designed to allow the wheels to rotate and be able to go in a circular motion. Also it is designed with a suspension that allows the robot to go through any obstacle. This paper also presents the FEA spring stress analysis and Simulink control system model to find the optimal parameters that are required for the wind tower climbing robot
On Upward Drawings of Trees on a Given Grid
Computing a minimum-area planar straight-line drawing of a graph is known to
be NP-hard for planar graphs, even when restricted to outerplanar graphs.
However, the complexity question is open for trees. Only a few hardness results
are known for straight-line drawings of trees under various restrictions such
as edge length or slope constraints. On the other hand, there exist
polynomial-time algorithms for computing minimum-width (resp., minimum-height)
upward drawings of trees, where the height (resp., width) is unbounded.
In this paper we take a major step in understanding the complexity of the
area minimization problem for strictly-upward drawings of trees, which is one
of the most common styles for drawing rooted trees. We prove that given a
rooted tree and a grid, it is NP-hard to decide whether
admits a strictly-upward (unordered) drawing in the given grid.Comment: Appears in the Proceedings of the 25th International Symposium on
Graph Drawing and Network Visualization (GD 2017
Aadhaar (Индия): национальная программа биометрической идентификации (опыт и реализация)
The scope of this paper is to paint a word picture of the National Biometric Identificatio
Digital India: E-government initiative
Digital India is an initiative by the government of India, along with several other parties to provide a digital interface to the government’s services to citizens electronically, by improved online infrastructure and by increasing Internet connectivity
Analysis of Mechanical Adhesion Climbing Robot Design for Wind Tower Inspection
Maintenance of wind turbine farms is a huge task, with associated significant risks and potential hazard to the safety and well-being of people who are responsible for carrying the tower inspection tasks. Periodic inspections are required for wind turbine tower to ensure that the wind turbines are in full working order, with no signs of potential failure. Therefore, the development of an automated wind tower inspection system has been very crucial for the overall performance of the renewable wind power generation industry. In order to determine the life span of the tower, an investigation of robot design is discussed in this paper. It presents how a mechanical spring-loaded climbing robot can be designed and constructed to climb and rotate 360° around the tower. An adjustable circular shape robot is designed that allows the device to fit in different diameters of the wind generator tower. The rotational module is designed to allow the wheels to rotate and be able to go in a circular motion. The design further incorporates a suspension that allows the robot to go through any obstacle. This paper also presents a finite element spring stress analysis and Simulink control system model to find the optimal parameters that are required for the wind tower climbing
robot
High-temperature oxidation behaviour of a TiAl-based alloy subjected to aluminium hot-dipping
In this research the oxidation resistance at high temperature of a TiAl-based alloy has been improved by hot-dipping the alloy in molten aluminium and by performing an interdiffusion process. After selecting the best process parameters, a compact TiAl3 coating characterized by an almost constant thickness was formed on the surface. Isothermal oxidation tests, carried out at 900, 950 and 1000 °C, showed that the coated alloy is able to form a continuous and thin alumina layer that is very protective. Microstructural investigations highlighted that, above 900 °C, long residence times at high temperature determine the diffusion through the TiAl3 layer of Cr that favours migration toward the outer surface of Al and thus the formation of a self-healing alumina layer
Universal transition of spectral fluctuation in particle-hole symmetric system
We study the spectral properties of a multiparametric system having
particle-hole symmetry in random matrix setting. We observe a crossover from
Poisson to Wigner-Dyson like behavior in average local ratio of spacing within
a spectrum of single matrix as a function of effective single parameter
referred to as complexity parameter. The average local ratio of spacing varies
logarithmically in complexity parameter across the transition. This behavior is
universal for different ensembles subjected to same matrix constraint like
particle-hole symmetry. The universality of this dependence is further
established by studying interpolating ensemble connecting systems with
particle-hole symmetry to that with chiral symmetry. For each interpolating
ensemble the behavior remains logarithmic in complexity parameter. We verify
this universality of spectral fluctuation in case of a 2D Su-Schrieffer-Heeger
(SSH) like model along with the logarithmic dependence on complexity parameter
for ratio of spacing during transition from integrable to non-integrable limit
Construction of the Soudan 2 detector
Progress in the construction of the Soudan 2 nucleon decay detector which is being built at the Soudan iron mine in Minnesota is discussed. The expected event rate and characteristics of low energy neutrino events, muon events, multiple muon events, and other cosmic ray phenomena are discussed
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