5,695 research outputs found
Simple Problems: The Simplicial Gluing Structure of Pareto Sets and Pareto Fronts
Quite a few studies on real-world applications of multi-objective
optimization reported that their Pareto sets and Pareto fronts form a
topological simplex. Such a class of problems was recently named the simple
problems, and their Pareto set and Pareto front were observed to have a gluing
structure similar to the faces of a simplex. This paper gives a theoretical
justification for that observation by proving the gluing structure of the
Pareto sets/fronts of subproblems of a simple problem. The simplicity of
standard benchmark problems is studied.Comment: 10 pages, accepted at GECCO'17 as a poster paper (2 pages
SPH Simulations with Reconfigurable Hardware Accelerator
We present a novel approach to accelerate astrophysical hydrodynamical
simulations. In astrophysical many-body simulations, GRAPE (GRAvity piPE)
system has been widely used by many researchers. However, in the GRAPE systems,
its function is completely fixed because specially developed LSI is used as a
computing engine. Instead of using such LSI, we are developing a special
purpose computing system using Field Programmable Gate Array (FPGA) chips as
the computing engine. Together with our developed programming system, we have
implemented computing pipelines for the Smoothed Particle Hydrodynamics (SPH)
method on our PROGRAPE-3 system. The SPH pipelines running on PROGRAPE-3 system
have the peak speed of 85 GFLOPS and in a realistic setup, the SPH calculation
using one PROGRAPE-3 board is 5-10 times faster than the calculation on the
host computer. Our results clearly shows for the first time that we can
accelerate the speed of the SPH simulations of a simple astrophysical phenomena
using considerable computing power offered by the hardware.Comment: 27 pages, 13 figures, submitted to PAS
On the dynamics of vortex modes within magnetic islands
Recent work investigating the interaction of magnetic islands with
micro-turbulence has uncovered the striking observation of large scale vortex
modes forming within the island structure [W.A. Hornsby {\it et al.}, Phys.
Plasmas {\bf 17} 092301 (2010)]. These electrostatic vortices are found to be
the size of the island and are oscillatory. It is this oscillatory behaviour
and the presence of turbulence that leads us to believe that the dynamics are
related to the Geodesic Acoustic Mode (GAM), and it is this link that is
investigated in this paper.
Here we derive an equation for the GAM in the MHD limit, in the presence of a
magnetic island modified three-dimensional axisymmetric geometry. The
eigenvalues and eigenfunctions are calculated numerically and then utilised to
analyse the dynamics of oscillatory large-scale electrostatic potential
structures seen in both linear and non-linear gyro-kinetic simulations
Vertex Operators in 4D Quantum Gravity Formulated as CFT
We study vertex operators in 4D conformal field theory derived from quantized
gravity, whose dynamics is governed by the Wess-Zumino action by Riegert and
the Weyl action. Conformal symmetry is equal to diffeomorphism symmetry in the
ultraviolet limit, which mixes positive-metric and negative-metric modes of the
gravitational field and thus these modes cannot be treated separately in
physical operators. In this paper, we construct gravitational vertex operators
such as the Ricci scalar, defined as space-time volume integrals of them are
invariant under conformal transformations. Short distance singularities of
these operator products are computed and it is shown that their coefficients
have physically correct sign. Furthermore, we show that conformal algebra holds
even in the system perturbed by the cosmological constant vertex operator as in
the case of the Liouville theory shown by Curtright and Thorn.Comment: 26 pages, rewrote review part concisely, added explanation
Recursion Relations in Liouville Gravity coupled to Ising Model satisfying Fusion Rules
The recursion relations of 2D quantum gravity coupled to the Ising model
discussed by the author previously are reexamined. We study the case in which
the matter sector satisfies the fusion rules and only the primary operators
inside the Kac table contribute. The theory involves unregularized divergences
in some of correlators. We obtain the recursion relations which form a closed
set among well-defined correlators on sphere, but they do not have a beautiful
structure that the bosonized theory has and also give an inconsistent result
when they include an ill-defined correlator with the divergence. We solve them
and compute the several normalization independent ratios of the well-defined
correlators, which agree with the matrix model results.Comment: Latex, 22 page
Association of medullary carcinoma of the thyroid with carcinoembryonic antigen.
To investigate the association between medullary carcinoma of the thyroid (MCT) and carcinoembryonic antigen (CEA), we assayed 78 sera from patients with thyroid diseases for CEA, employing the radioimmunoassay of double antibody technique. All 13 sera from patients with MCT had high levels of CEA, ranging from 14 to 170 ng/ml. Increased serum CEA was noted even in cases of small, localized carcinoma. By contrast, serum CEA levels were normal (below 10 ng/ml) in all other histological types of thyroid carcinoma (33 cases), except for one case of papillary adenocarcinoma. In 32 patients with non-malignant thyroid diseases, with few exceptions serum CEA levels remained within the normal range. The elevated serum levels of CEA in MCT returned to normal after successful operation. Furthermore, very high tissue concentrations of CEA were demonstrated in MCT. The results indicate that CEA is actively produced by MCT, and that its measurement is useful in the diagnosis and management of the disease. It is suggested that the highly specific association of CEA with MCT may well be related to a defect of neural crest origin
Construction of Some Optimal Ternary Linear Codes and the Uniqueness of [294, 6, 195; 3]-Codes Meeting the Griesmer Bound
AbstractLet nq(k, d) denote the smallest value of n for which there exists an [n, k, d; q]-code. It is known (cf. (J. Combin. Inform. Syst. Sci.18, 1993, 161–191)) that (1) n3(6, 195) ∈ {294, 295}, n3(6, 194) ∈ {293, 294}, n3(6, 193) ∈ {292, 293}, n3(6, 192) ∈ {290, 291}, n3(6, 191) ∈ {289, 290}, n3(6, 165) ∈ {250, 251} and (2) there is a one-to-one correspondence between the set of all nonequivalent [294, 6, 195; 3]-codes meeting the Griesmer bound and the set of all {v2 + 2v3 + v4, v1 + 2v2 + v3; 5, 3}-minihypers, where vi = (3i − 1)/(3 − 1) for any integer i ≥ 0. The purpose of this paper is to show that (1) n3(6, 195) = 294, n3(6, 194) = 293, n3(6, 193) = 292, n3(6, 192) = 290, n3(6, 191) = 289, n3(6, 165) = 250 and (2) a [294, 6, 195; 3]-code is unique up to equivalence using a characterization of the corresponding {v2 + 2v3 + v4, v1 + 2v2 + v3; 5, 3}-minihypers
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Tax Policy in the Presence of Emigration
This paper is a significantly revised and augmented version of an earlier, unpublished paper [Bhagwati and Hamada (1976)]. Thanks are due to NSF Grant no. SCS-80-25401, to the Ford Foundation and to the German Marshall Fund for tinancial support of the research underlying this paper. The stimulating atmosphere at the SSRC Workshop on Public Economics at Warwick, England, 1978, also must be gratefully acknowledged by Koichi Hamada. The authors are also indebted to Peter Diamond, William Baumol, Assar Lindbeck, John Wilson and other participants at the New Delhi Conference in January 1981 for their helpful suggestions. The excellent comments of two referees have led to substantial improvements in this paper
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Domestic Distortions, Imperfect Information, and the Brain Drain
An earlier paper by Bhagwati and Hamada (1974) presented a theoretical analysis of the brain drain in the context of wage rigidity and unemployment. This paper extends the analysis by modifying the model to incorporate the phenomena of overqualification, internal diffusion of labor from urban to rural areas and imperfect information about the quality of labor. The welfare effect of the brain drain in the presence of these phenomena is analyzed
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