• Structural Engineering and Mechanics
• /
• v.27 no.6
• /
• pp.683-696
• /
• 2007

This article is concerned with the presentation of a time-domain BEM approach applied to the solution of the scalar wave equation for 2D problems. The basic idea is quite simple: the basic variables of the problem at time $t_n$ (potential and flux) are computed with the results related to the potential and to its time derivative at time $t_{n-1}$ playing the role of "initial conditions". This time-marching scheme needs the computation of the potential and its time derivative at all boundary nodes and internal points, as well as the entire discretization of the domain. The convolution integrals of the standard time-domain BEM formulation, however, are not computed; the matrices assembled, only at the initial time interval, are those related to the potential, flux and to the potential time derivative. Two examples are presented and discussed at the end of the article, in order to verify the accuracy and potentialities of the proposed formulation.

• Honam Mathematical Journal
• /
• v.7 no.1
• /
• pp.7-13
• /
• 1985

We show that a bounded linear qperator, T, on a Banach space, X, is $C^{n}$-scalar if the sepuence {$\frac{k!}{(k+n)!}{\phi}(T^{k+n}x)$}$_{k=0}^{\infty}$ is positive-definite, for sufficiently many $\phi$ in $X^{\ast}$, x in X. We use this to show that $(T_{n}f)(t){\equiv}tf(t)+nJf(t)$, where $If(t)=\int_{0}^{1}f(s)ds$, is $C^{n}$-scalar on $L^{p}([0,1],v)$, for $1{\leq}p{\leq}\infty$, for a large class of measures, v. Other corollaries include the spectral theorem for bounded symmetric operators on a Hilbert space.

• Journal of Institute of Control, Robotics and Systems
• /
• v.4 no.5
• /
• pp.574-578
• /
• 1998

This paper considers the robust positive real problem for linear systems with linear fractional-type norm-bounded repeated scalar block parameter uncertainty. It is shown that the robust positive real problem can be converted into the standard positive real problem without uncertainty that can be used for the analysis of the given uncertain linear system and the synthesis of a controller that robustly stabilizes and achieves the extended strict positive realness property of the closed-loop transfer function. These results can be also applied to the linear system with general structured uncertainty containing repeated scalar block parameters and are extensions of the previous works that consider only norm-boundedness of the affine unstructured uncertainty.

• Computers and Concrete
• /
• v.26 no.5
• /
• pp.411-420
• /
• 2020

Deep Convolution neural network (DCNN) has been widely used in the healthy maintenance of civil infrastructure. Using DCNN to improve crack detection performance has attracted many researchers' attention. In this paper, a light-weight spatial attention network module is proposed to strengthen the representation capability of ResNet and improve the crack detection performance. It utilizes attention mechanism to strengthen the interested objects in global receptive field of ResNet convolution layers. Global average spatial information over all channels are used to construct an attention scalar. The scalar is combined with adaptive weighted sigmoid function to activate the output of each channel's feature maps. Salient objects in feature maps are refined by the attention scalar. The proposed spatial attention module is stacked in ResNet50 to detect crack. Experiments results show that the proposed module can got significant performance improvement in crack detection.

• Bulletin of the Korean Mathematical Society
• /
• v.52 no.6
• /
• pp.1945-1962
• /
• 2015

This paper is mainly concerned with the formation of delta standing wave for the scalar conservation law with a linear flux function involving discontinuous coefficients by using the self-similar viscosity vanishing method. More precisely, we use the self-similar viscosity to smooth out the discontinuous coefficient such that the existence of approximate viscous solutions to the delta standing wave for the Riemann problem is established and then the convergence to the delta standing wave solution is also obtained when the viscosity parameter tends to zero. In addition, the Riemann problem is also solved with the standard method and the instability of Riemann solutions with respect to the specific small perturbation of initial data is pointed out in some particular situations.

• Bulletin of the Korean Mathematical Society
• /
• v.49 no.3
• /
• pp.581-588
• /
• 2012

We find a $C^{\infty}$ one-parameter family of Riemannian metrics $g_t$ on $\mathbb{R}^3$ for $0{\leq}t{\leq}{\varepsilon}$ for some number ${\varepsilon}$ with the following property: $g_0$ is the Euclidean metric on $\mathbb{R}^3$, the scalar curvatures of $g_t$ are strictly decreasing in t in the open unit ball and $g_t$ is isometric to the Euclidean metric in the complement of the ball.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.759-764
• /
• 2000

In this study, the confined laminar flow around a square cylinder, which ejects a either on the front face or on the rear face, is numerically simulated. In each case, three ratios of jet velocity to the fixed upstream velocity are considered. In all cases of the rear fuel jet, the high mass-fraction region is formed along the streamlines from the jet exit. In case of front jet, drag is significantly decreased when the jet velocity ratio is greater than 1. The results obtained exhibit flow and scalar-mixing characteristics encountered in a planar combustor

• 한국연소학회:학술대회논문집
• /
• 2002.11a
• /
• pp.11-17
• /
• 2002

The first-order conditional moment closure (CMC) model is applied to $CH_4$/Air turbulent jet diffusion flames(Sandia Flame D, E and F). The flow and mixing fields are calculated by fast chemistry assumption and a beta function pdf for mixture fraction. Reacting scalar fields are calculated by elliptic CMC formulation. The results for Flame D show reasonable agreement with the measured conditional mean temperature and mass fractions of major species, although with discrepancy on the fuel rich side. The discrepancy tends to increase as the level of local extinction increases. Second-order CMC may be needed for better prediction of these near-extinction flames.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.11-11
• /
• 2011

In this talk, I will discuss roles of pseudo vector and scalar potential in changing physical properties of graphene systems. First, graphene under small uniaxial strain is shown to be described by the generalized Weyl's Hamiltonian with inclusion of pseudo vector and scalar potential simultaneously [1]. Thus, strained graphene is predicted to exhibit velocity anisotropy as well as work function enhancement without any gap. Second, if homogeneous strains with different strengths are applied to each layer of bilayer graphene, transverse electric fields across the two layers can be generated without any external electronic sources, thereby opening an energy gap [2]. This phenomenon is made possible by generation of inequivalent pseudo scalar potentials in the two graphene layers. Third, when very tiny lateral interlayer shift occurs in bilayer graphene, the Fermi surfaces of the system are shown to undergo Lifshitz transition [3]. We will show that this unexpected hypersensitive electronic topological transition is caused by a unique interplay between the effective non-Abelian vector potential generated by sliding motions and Berry's phases associated with massless Dirac electrons.

• Journal of Magnetics
• /
• v.18 no.2
• /
• pp.95-104
• /
• 2013

This paper presents a general analytical method for predicting the magnetic fields of different Halbach magnet arrays with or without back iron mounted on slotless permanent magnet (PM) linear machines. By using Fourier decomposition, the magnetization components of four typical Halbach magnet arrays are determined. By applying special synthetic boundary conditions on the PM surfaces, the expressions of their magnetic field distributions are derived based on the magnetic scalar potential (MSP), which are simpler than those based on the magnetic vector potential (MVP). The correctness of the method is validated by finite element analysis. The harmonics of airgap flux density waveforms of these Halbach magnet arrays with or without back iron are also compared and optimized.