• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.376-382
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• 2017

Graphene nanoribbons with zigzag-shaped edge (zGNRs) are predicted to be magnetic insulator at the ground state, attracting significant interest in view of spintronic applications [1]. On the other hand, although they are energetically and thermodynamically more favored than zGNRs [2], graphene nanoribbons with armchair-shaped edge (aGNRs) have been less spotlighted than zGNRs due to the absence of magnetism. Herein, based on the combined density functional theory (DFT) and matrix Green's function (MGF) approach, we consider aGNRs functionalized with various molecular groups, and show that the spin polarizations develop for some of the considered aGNR edge functionalization cases. The origin of the induced magnetism will be discussed within the Lieb's theorem [3]. This work will provide a novel guidance for the development of graphene-based spintronic devices.

• Journal of Environmental Impact Assessment
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• v.31 no.4
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• pp.201-213
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• 2022

Creation and administration of green space are emphasized to solve the environmental problem and the management of green space in urban area. Urban area with high development pressure faces green space fragmentation, so the planned approach is needed to improve the continuity of green space. However, the current institutional green axis, used to enhance continuity of urban space is merely an abstract concept under the master plan so that is not a consistent framework for urban green continuity providing no detailed information such as position and path. Therefore, in order to consistently manage green space in continuous point of view, it is insufficient not being connected to each individual green space development projects. This study proposes a method for finding the connection path to enhance urban green space continuity. This proposed method consists of two phases. First phase is finding nodes to connect current green space and second is to calculate the least cost path. We calculate connection cost using NDMI (Normalized Difference Moisture Index), impervious ratio and official land cost, applying to Suwon city and potential greening site that was planned in official master plan. According to the results, we confirm a possibility of finding a cost-effective connection path with detailed spatial information instead of unrealistic abstract concepts and discuss worth applying to a legally plan and policy.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.2
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• pp.64-72
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• 1989

A response prediction model is introduced for the non-lockin vibration of a marine riser in sheared flow, where the riser is modelled as linearly varying tensioned-beam. This prediction model is based on the Green's function approach and random vibration theory. This model, of course, can treat general beams having slowly varying spatial system parameters. According to the predicted result of a marine riser by the prediction model proposed in this paper, the dynamic behavior of a marine riser has the mixed characteristics of finite and infinite boundary behavior. Furthermore the velocity response distribution along the riser length is much similar with the sheared flow profile. The predicted response result of a marine riser having linearly varying tension was also compared to that of constant mean tensioned-beam model. It was found that the constant mean tensioned-beam case gives over-estimated responses at the top side of the riser.

• Bulletin of the Korean Chemical Society
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• v.26 no.11
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• pp.1723-1727
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• 2005

A generalized fractional diffusion equation (FDE) is presented, which describes the time-evolution of the spatial distribution of a particle performing continuous time random walk (CTRW) on a fractal lattice. For a case corresponding to the CTRW with waiting time distribution that behaves as $\psi(t) \sim (t) ^{-(\alpha+1)}$, the FDE is solved to give analytic expressions for the Green’s function and the mean squared displacement (MSD). In agreement with the previous work of Blumen et al. [Phys. Rev. Lett. 1984, 53, 1301], the time-dependence of MSD is found to be given as < $r^2(t)$ > ~ $t ^{2\alpha/dw}$, where $d_w$ is the walk dimension of the given fractal. A Monte-Carlo simulation is also performed to evaluate the range of applicability of the proposed FDE.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.647-647
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• 2013

We apply a density functional theory (DFT) and DFT-based non-equilibrium Green's function approach to study the structures, energetics and charge transport characteristics of nitrogen-doped graphene and graphene nanoribbons (GNRs) with additional doping of phosphorus or boron atoms. Considering graphitic, pyridinic, and porphrin-like N doping sites and increasing N-doping concentration, we analyze the structures of N-P and N-B doped graphene and particularly focus on how they affect the charge transport along the lateral direction. For the GNRs, we also consider the differences between defects formed at the edge and bulk regions. Implications of our findings in the context of electronic and energy device applications will be also discussed.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1252-1255
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• 1987

In this paper an approach for the analysis of the transient field response of radially symmetric transducer due to a wideband ultrasonic pulse is presented, which is based on a development of Green's function and applies the linear system theory to obtain an analytic expression for the impulse response of an annulus with a planar or spherical geometry. For the focused annular array, the impulse responses of the indivisual annuli are convolved with the delayed excitation pulse, and then summed to obtain the resultant response of the array. This process is very effective in the study of the various focusing abilities of the annular array. For illustration, the field distribution of a five element annular array is treated in detail for several focusing system.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.4
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• pp.56-62
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• 1994

Far-zone electric fields radiated by a coaxial cable through an aperture in a perfectly conducting ground plane are calculated utilizing the dyadic Green's function and vector wave functions. In this paper the outer radius $\alpha$ is assumed to be less than 0.02 so that the aperture fields is well approximated by the dominant TEM mode in the coaxial cable. The result of present approach is compared with the readily obtained solution. The present solution is valid outside of the spherical regions with radius `$\alpha$' from the center of coaxial cable.

• Journal of applied mathematics & informatics
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• v.14 no.1_2
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• pp.193-212
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• 2004

A new model of generalized thermoelasticity equations for isotropic media with temperature-dependent mechanical properties is established. The modulus of elasticity is taken as a linear function of reference temperature. The present model is described both generalizations, Lord Shulman (L-S) theory with one relaxation time and Green-Lindsay (G-L) with two relaxation times, as well as the coupled theory, instantaneously. The method of the matrix exponential, which constitutes the basis of the state space approach of modern control theory, applied to two-dimensional equations. Laplace and Fourier integral transforms are used. The resulting formulation is applied to a problem of a thick plate subject to heating on parts of the upper and lower surfaces of the plate that varies exponentially with time. Numerical results are given and illustrated graphically for the problem considered. A comparison was made with the results obtained in case of temperature-independent modulus of elasticity in each theory.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.643-648
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• 2011

This paper deals with the ESM(equivalent source method) with the continuation of acoustic near-field for NAH(near-field acoustic holography) to overcome the finite measurement aperture effect and reconstruct the normal velocity on an arbitrarily shaped structure surface. The continuation method is an extension of the measured sound field into a region outside and is based on the Green's function relating acoustic quantities on the two conformal surfaces. This algorithm is not limited to planar surfaces and can be applied to arbitrarily shaped surfaces. The ESM is an alternative approach of BEM-based NAH for the reconstruction on a general structure. In ESM the acoustic field is represented by a set of point sources located over a surface that is close to the structure surface. The simulation results of this study shows that the reconstruction error of particle velocity on the source surface is 11% and 16% for planar and cylindrical sources separately.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.273-277
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• 2013

We apply a density functional theory (DFT) and DFT-based non-equilibrium Green's function approach to study the electronic and transport properties of graphene nanoribbons (GNRs) co-doped with boron-nitrogen, nitrogen-phosphorus and boron-phosphorus. We analyze the structures and charge transport properties of co-doped GNRs and particularly focus on the novel effects that are absent for the single N-, B-, or P-doped GNRs. It is found that co-doped GNRs tend to be doped at the edges and the electronic structures of co-doped GNRs are very sensitive to the doping sites. Also, in case of B-N and B-P co-doped GNRs, conductance dips of single-doped GNRs disappeared with the disappearance of localized states associated with doped atoms. This may lead to a possible method of band engineering of GNRs and benefit the design of graphene electronic devices.