oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2018 ( 1 )

2017 ( 1 )

2016 ( 2 )

2015 ( 30 )

Custom range...

Search Results: 1 - 10 of 357 matches for " Jaemin Kwak "
All listed articles are free for downloading (OA Articles)
Page 1 /357
Display every page Item
Intelligent Modified Channel and Frequency Offset Estimation Schemes in Future Generation OFDM-Based Packet Communication Systems
Jaemin Kwak,Sungeon Cho,Kitaeg Lim,Pusik Park
EURASIP Journal on Wireless Communications and Networking , 2008, DOI: 10.1155/2008/735732
Abstract: The channel estimation and frequency offset estimation scheme for future generation orthogonal frequency division multiplexing (OFDM-) based intelligent packet communication systems are proposed. In the channel estimation scheme, we use additional 8 short training symbols besides 2 long training symbols for intelligently improving estimation performance. In the proposed frequency offset estimation scheme, we allocate intelligently different powers to the short and long training symbols while maintaining average power of overall preamble sequence. The preamble structure considered is based on the preamble specified in standardization group of IEEE802.11a for wireless local area network (WLAN) and IEEE802.11p for intelligent transportation systems (ITSs). From the simulation results, it is shown that the proposed intelligent estimation schemes can achieve better mean squared error (MSE) performance for channel and frequency offset estimation error than the conventional scheme. The proposed schemes can be used in designing for enhancing the performance of OFDM-based future generation intelligent communication network systems.
Intelligent Modified Channel and Frequency Offset Estimation Schemes in Future Generation OFDM-Based Packet Communication Systems
Kwak Jaemin,Cho Sungeon,Lim Kitaeg,Park Pusik
EURASIP Journal on Wireless Communications and Networking , 2008,
Abstract: The channel estimation and frequency offset estimation scheme for future generation orthogonal frequency division multiplexing (OFDM-) based intelligent packet communication systems are proposed. In the channel estimation scheme, we use additional 8 short training symbols besides 2 long training symbols for intelligently improving estimation performance. In the proposed frequency offset estimation scheme, we allocate intelligently different powers to the short and long training symbols while maintaining average power of overall preamble sequence. The preamble structure considered is based on the preamble specified in standardization group of IEEE802.11a for wireless local area network (WLAN) and IEEE802.11p for intelligent transportation systems (ITSs). From the simulation results, it is shown that the proposed intelligent estimation schemes can achieve better mean squared error (MSE) performance for channel and frequency offset estimation error than the conventional scheme. The proposed schemes can be used in designing for enhancing the performance of OFDM-based future generation intelligent communication network systems.
Reinvestigation of the low-temperature form of Ag2Se (naumannite) based on single-crystal data
Jaemin Yu,Hoseop Yun
Acta Crystallographica Section E , 2011, DOI: 10.1107/s1600536811028534
Abstract: The crystal structure of the low-temperature form of synthetic naumannite [disilver(I) selenide], Ag2Se, has been reinvestigated based on single-crystal data. In comparison with previous powder diffraction studies, anisotropic displacement parameters are additionally reported. The structure is composed of Se layers and two crystallographically independent Ag atoms. One Ag atom lies close to the Se layer and is surrounded by four Se atoms in a distorted tetrahedral coordination, while the second Ag atom lies between the Se layers and exhibits a [3 + 1] coordination defined by three close Se atoms, forming a trigonal plane, and one remote Se atom.
Ti insertion in the MTe5 (M = Zr, Hf) structure type: Hf0.78Ti0.22Te5
Jaemin Yu,Hoseop Yun
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812006691
Abstract: The group 5 mixed-metal telluride, Hf0.78Ti0.22Te5 (hafnium titanium pentatelluride), is isostructural with the binary phases HfTe5 and ZrTe5 and forms a layered structure extending parallel to (010). The layers are made up from chains of bicapped metal-centered trigonal prisms and zigzag Te chains. The metal site (site symmetry m2m) is occupied by statistically disordered Hf [78.1 (5)%] and Ti [21.9 (5)%]. In addition to the regular Te—Te pair [2.7448 (13) ] forming the short base of the equilateral triangle of the trigonal prism, an intermediate Te...Te separation [2.9129 (9) ] is also found. The classical charge balance of the compound can be described as [M4+][Te2 ][Te22 ][Te20] (M = Hf, Ti). The individual metal content can vary in different crystals, apparently forming a random substitutional solid solution (Hf1-xTix)Te5, with 0.15 ≤ x ≤ 0.22.
The Cauchy-Dirichlet problem for the FENE dumbbell model of polymeric fluids
Hailiang Liu,Jaemin Shin
Mathematics , 2010,
Abstract: The FENE dumbbell model consists of the incompressible Navier-Stokes equation and the Fokker-Planck equation for the polymer distribution. In such a model, the polymer elongation cannot exceed a limit $\sqrt{b}$, yielding all interesting features near the boundary. In this paper we establish the local well-posedness for the FENE dumbbell model under a class of Dirichlet-type boundary conditions dictated by the parameter $b$. As a result, for each $b>0$ we identify a sharp boundary requirement for the underlying density distribution, while the sharpness follows from the existence result for each specification of the boundary behavior. It is shown that the probability density governed by the Fokker-Planck equation approaches zero near boundary, necessarily faster than the distance function $d$ for $b>2$, faster than $d|ln d|$ for $b=2$, and as fast as $d^{b/2}$ for $0
Global Well-Posedness for the Microscopic FENE Model with a Sharp Boundary Condition
Hailiang Liu,Jaemin Shin
Mathematics , 2009,
Abstract: We prove global well-posedness for the microscopic FENE model under a sharp boundary requirement. The well-posedness of the FENE model that consists of the incompressible Navier-Stokes equation and the Fokker-Planck equation has been studied intensively, mostly with the zero flux boundary condition. Recently it was illustrated by C. Liu and H. Liu [2008, SIAM J. Appl. Math., 68(5):1304--1315] that any preassigned boundary value of a weighted distribution will become redundant once the non-dimensional parameter $b>2$. In this article, we show that for the well-posedness of the microscopic FENE model ($b>2$) the least boundary requirement is that the distribution near boundary needs to approach zero faster than the distance function. Under this condition, it is shown that there exists a unique weak solution in a weighted Sobolev space. Moreover, such a condition still ensures that the distribution is a probability density. The sharpness of this boundary requirement is shown by a construction of infinitely many solutions when the distribution approaches zero as fast as the distance function.
A Design of Incremental Granular Network for Software Data Modeling  [PDF]
Keun-Chang Kwak
Journal of Software Engineering and Applications (JSEA) , 2010, DOI: 10.4236/jsea.2010.311120
Abstract: In this paper, we propose an incremental method of Granular Networks (GN) to construct conceptual and computational platform of Granular Computing (GrC). The essence of this network is to describe the associations between information granules including fuzzy sets formed both in the input and output spaces. The context within which such relationships are being formed is established by the system developer. Here information granules are built using Context-driven Fuzzy Clustering (CFC). This clustering develops clusters by preserving the homogeneity of the clustered patterns associated with the input and output space. The experimental results on well-known software module of Medical Imaging System (MIS) revealed that the incremental granular network showed a good performance in comparison to other previous literature.
"Closing-in" phenomenon in Alzheimer's disease and subcortical vascular dementia
Yong Kwak
BMC Neurology , 2004, DOI: 10.1186/1471-2377-4-3
Abstract: We operationally defined and classified it into three types, namely overlap, adherent, and near type. We analyzed the incidence of it in patients with AD (n = 98) and SVD (n = 48).AD patients exhibited a significantly higher occurrence of it as compared to SVD patients. Among the different types of it, the overlap and adherent types occurred almost exclusively in AD patients. A discriminant analysis in AD subjects revealed that the scores obtained from the MMSE, CDR, Barthel index, and the Rey-Osterrieth complex figure test were correlated significantly with the occurrence of it. There was no statistical difference between the Q-EEG parameters of patients that exhibited the closing-in phenomenon and those that did not.This study suggests that the closing-in phenomenon is phase- and AD-specific and might be a useful tool for the differential diagnosis of AD and SVD.Alzheimer's disease (AD) and vascular dementia (VD) are the most common causes of dementia. Accurate differential diagnosis is essential to initiate appropriate treatment and to provide information about the prognosis and factors that may affect the course of the illness [1-4]. However, VD is not a single illness; it is comprised of dementia due to large artery stroke, subcortical vascular (or small vessel) dementia (SVD), and other less frequently observed vascular lesions [5].SVD affects the white matter and basal ganglia bilaterally and diffusely. It can lead to dementia that is characterized by impairment of behaviors, such as executive functioning, goal formation, initiation, planning, organizing, self maintenance, sequencing, and abstraction [6]. Whereas the cognitive impairments that follow a stroke tend to recede over time, SVD is often progressive and can be confused with AD. Stepwise deterioration and focal symptoms are not always symptoms of SVD [7]. Many previous neuropsychological studies comparing AD and VD have included multi-infarct patients or mixed groups of multi-infarct/SVD patients. Su
Local well-posedness for the fifth-order KdV equations on $\mathbb{T}$
Chulkwang Kwak
Mathematics , 2015,
Abstract: This paper is a continuation of the paper \emph{Low regularity Cauchy problem for the fifth-order modified KdV equations on $\mathbb{T}$}. In this paper, we consider the fifth-order equation in the Korteweg-de Vries (KdV) hierarchy as following: \begin{equation*} \begin{cases} \partial_t u - \partial_x^5 u + 30u^2\partial_x u + 20 u\partial_x u \partial_x^3u + 10u \partial_x^3 u = 0, \hspace{1em} (t,x) \in \mathbb{R} \times \mathbb{T}, \\ u(0,x) = u_0(x) \in H^s(\mathbb{T}) \end{cases}. \end{equation*} We prove the local well-posedness of the fifth-order KdV equation for low regularity Sobolev initial data via the energy method. This paper follows almost same idea and argument as in the paper \emph{Low regularity Cauchy problem for the fifth-order modified KdV equations on $\mathbb{T}$}. Precisely, we use some conservation laws of the KdV Hamiltonians to observe the direction which the nonlinear solution evolves to. Besides, it is essential to use the short time $X^{s,b}$ spaces to control the nonlinear terms due to \emph{high $\times$ low $\Rightarrow$ high} interaction component in the non-resonant nonlinear term. We also use the localized version of the modified energy in order to obtain the energy estimate. As an immediate result from a conservation law in the scaling sub-critical problem, we have the global well-posedness result in the energy space $H^2$.
Low regularity Cauchy problem for the fifth-order modified KdV equations on $\mathbb{T}$
Chulkwang Kwak
Mathematics , 2015,
Abstract: In this paper, we consider the fifth-order equation in the modified Korteweg-de Vries (modified KdV) hierarchy as following: \begin{equation*} \begin{cases} \partial_t u - \partial_x^5 u + 40u\partial_x u \partial_x^2u + 10 u^2\partial_x^3u + 10(\partial_x u)^3 - 30u^4 \partial_x u = 0, \hspace{1em} (t,x) \in \mathbb{R} \times \mathbb{T}, \\ u(0,x) = u_0(x) \in H^s(\mathbb{T}) \end{cases}. \end{equation*} We prove the local well-posedness of the fifth-order modified KdV equation for low regularity Sobolev initial data via the energy method. We use some conservation laws of the modified KdV Hamiltonians (or a partial property of complete integrability) to absorb some \emph{linear-like} resonant terms into the linear propagator. Also, we use the nonlinear transformation, which has the bi-continuity property, to treat the rest of \emph{linear-like} resonant terms. Besides, it is essential to use the short time $X^{s,b}$ spaces to control the nonlinear terms due to \emph{high $\times$ low $\times$ low $\Rightarrow$ high} interaction component in the non-resonant nonlinear term. We also use the localized version of the modified energy in order to control the \emph{high-low} interaction component in the original energy. As a purpose and consequence of this work, we emphasize that under the periodic setting, to study the low regularity well-posedness problem somewhat relies on the theory of complete integrability. This is the first low regularity well-posedness result for the fifth order modified KdV equation under the periodic setting.
Page 1 /357
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.