• Title/Summary/Keyword: point spectrum

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Point-to-Point Communication of Cognitive Radios via Underlay Spectrum Sharing (언더레이 주파수 공유를 이용한 인지무선 통신장치의 점대점 통신방법)

  • Lee, Hye-Won;Han, Kwang-Hun;Hwang, Young-Woo;Choi, Sung-Hyun
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.9A
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    • pp.697-703
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    • 2009
  • Cognitive radios are typically known to exploit vacant spectrum resources in order not to interfere with primary communication systems. However, cognitive radios may not be able to secure a clear spectrum band in a bustling spectrum band. Underlay spectrum sharing provides a way to cope with such a spectrum sharing problem. Cognitive radios share the same spectrum band with the spectrum licensees, i.e., primary users, by adjusting signal transmission power so as not to severely deteriorate the performance of the primary users. We propose an underlay spectrum sharing policy leveraging uplink spectrum resource to be used in a cellular network. A pair of end terminals attempts to establish a direct point-to-point link, and perform as cognitive radios in the sense that they share the uplink radio resource of other primary users. We formulate the transmit power constraints of the cognitive radios and propose a practical uplink band sharing framework. Our simulation results demonstrate that such an uplink sharing underlay direct link can enhance the throughput performance of point-to-point link with low overhead.

ON p-HYPONORMAL OPERATORS ON A HILBERT SPACE

  • Cha, Hyung-Koo
    • The Pure and Applied Mathematics
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    • v.5 no.2
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    • pp.109-114
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    • 1998
  • Let H be a separable complex H be a space and let (equation omitted)(H) be the *-algebra of all bounded linear operators on H. An operator T in (equation omitted)(H) is said to be p-hyponormal if ($T^{\ast}T)^p - (TT^{\ast})^{p}\geq$ 0 for 0 < p < 1. If p = 1, T is hyponormal and if p = $\frac{1}{2}$, T is semi-hyponormal. In this paper, by using a technique introduced by S. K. Berberian, we show that the approximate point spectrum $\sigma_{\alpha p}(T) of a pure p-hyponormal operator T is empty, and obtains the compact perturbation of T.

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ON THE SPECTRUM AND FINE SPECTRUM OF THE UPPER TRIANGULAR DOUBLE BAND MATRIX U (a0, a1, a2; b0, b1, b2) OVER THE SEQUENCE SPACE ℓp

  • Nuh Durna;Rabia Kilic
    • Honam Mathematical Journal
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    • v.45 no.4
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    • pp.598-609
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    • 2023
  • The purpose of this article is to obtain the spectrum, fine spectrum, approximate point spectrum, defect spectrum and compression spectrum of the double band matrix U (a0, a1, a2; b0, b1, b2), b0, b1, b2≠0 on the sequence space ℓp (1 < p < ∞).

A study on the Capacity Spectrum for Seismic Performance Evaluation of Bridge (교량의 내진성능 평가를 위한 역량스펙트럼 적용 연구)

  • Park, Yeon-Soo;Lee, Byung-Geun;Kim, Eung-Rok;Suh, Byung-Chul;Park, Sun-Joon;Choi, Sun-Min
    • Proceedings of the KSR Conference
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    • 2008.11b
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    • pp.1012-1017
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    • 2008
  • In this study, We examine closely the capacity spectrum method which a kind of displacement-based method evaluated by displacement of structure as an alternative to the load-based analysis method. The displacement-based method can easily review the strength of structure, seismic performance, ductility. Seismic performance by using capacity spectrum method is divided into design response spectrum and capacity spectrum. We can diagram design response spectrum by deciding the design seismic factor depending on performance target, site classification, seismic level, return period as UBC-97. Capacity spectrum is a load-displacement curve obtained by Push-over analysis considering the geometric parameter and the material parameter. We execute the seismic performance evaluation by using the capacity spectrum method to reinforced concrete pier which has been seismic design. As a result, We confirmed that there is a yield point and a ultimate point close by design response spectrum of UBC-97.

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Modal Analysis of Point and Discretized Continuous Spectra for Metal-Insulator-Metal Waveguides in the Terahertz Region

  • Hur, Jun;Choo, Hosung;Park, Jong-Eon
    • Journal of Electrical Engineering and Technology
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    • v.13 no.4
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    • pp.1644-1654
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    • 2018
  • Eigenvalue distributions for a periodic metal-insulator-metal waveguide, classified into the point spectrum and the discretized continuous spectrum (DCS), are investigated as functions of frequencies, gap widths, and periods. Muller's method is suggested for solving exact eigenvalues, and we propose the scheme for finding proper initial values in the Muller's method by considering only ${\Re}e({\varepsilon}_r)$ in the dispersion equation. We then find that anti-crossing behavior, repulsive effect between the point spectrum and the DCS, becomes stronger when the real parts of the roots in the point spectrum have smaller values. Finally, we examine the transmittances of a single subwavelength slit for real metals using the mode matching technique. The transmittances in real metals similarly follow those of the perfect electric conductor (PEC) at low frequencies, while the patterns at higher frequencies begin to differ from the PEC.

CONTINUITY OF APPROXIMATE POINT SPECTRUM ON THE ALGEBRA B(X)

  • Sanchez-Perales, Salvador;Cruz-Barriguete, Victor A.
    • Communications of the Korean Mathematical Society
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    • v.28 no.3
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    • pp.487-500
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    • 2013
  • In this paper we provide a brief introduction to the continuity of approximate point spectrum on the algebra B(X), using basic properties of Fredholm operators and the SVEP condition. Also, we give an example showing that in general it not holds that if the spectrum is continuous an operator T, then for each ${\lambda}{\in}{\sigma}_{s-F}(T){\setminus}\overline{{\rho}^{\pm}_{s-F}(T)}$ and ${\in}$ > 0, the ball $B({\lambda},{\in})$ contains a component of ${\sigma}_{s-F}(T)$, contrary to what has been announced in [J. B. Conway and B. B. Morrel, Operators that are points of spectral continuity II, Integral Equations Operator Theory 4 (1981), 459-503] page 462.

Performance Analysis of Dynamic Spectrum Allocation in Heterogeneous Wireless Networks

  • Ha, Jeoung-Lak;Kim, Jin-Up;Kim, Sang-Ha
    • ETRI Journal
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    • v.32 no.2
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    • pp.292-301
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    • 2010
  • Increasing convergence among heterogeneous radio networks is expected to be a key feature of future ubiquitous services. The convergence of radio networks in combination with dynamic spectrum allocation (DSA) could be a beneficial means to solve the growing demand for radio spectrum. DSA might enhance the spectrum utilization of involved radio networks to comply with user requirements for high-quality multimedia services. This paper proposes a simple spectrum allocation algorithm and presents an analytical model of dynamic spectrum resource allocation between two networks using a 4-D Markov chain. We argue that there may exist a break-even point for choosing whether or not to adopt DSA in a system. We point out certain circumstances where DSA is not a viable alternative. We also discuss the performance of DSA against the degree of resource sharing using the proposed analytical model and simulations. The presented analytical model is not restricted to DSA, and can be applied to a general resource sharing study.

Fatigue life estimation using the multi-axial multi-point Load Counting method under Variable Amplitude Loading (가변진폭하중에서 다축-다점 하중 Counting method를 이용한 피로수명평가)

  • 이원석;이현우
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1996.11a
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    • pp.913-920
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    • 1996
  • In this study, the counting method for multi-axial and multi-point load states was proposed. Using this counting method, the load spectrum is generated from the service load history which is measured for boom structure of excavator. Loading state for loading points of boom structure is described as a multi-dimensional state space. From this load spectrum, the stress spectrum was generated by FEM analysis using the superposition of the unit load. The cumulated damage at the severe damage point of In nm structure by the failure example is calculated by Palmgren-Miner's rule. As a result of this study, the fatigue life estimation using the multi-axial and multi-point load counting method is useful.

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Multi-point response spectrum analysis of a historical bridge to blast ground motion

  • Haciefendioglu, Kemal;Banerjee, Swagata;Soyluk, Kurtulus;Koksal, Olgun
    • Structural Engineering and Mechanics
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    • v.53 no.5
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    • pp.897-919
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    • 2015
  • In this study, the effects of ground shocks due to explosive loads on the dynamic response of historical masonry bridges are investigated by using the multi-point shock response spectrum method. With this purpose, different charge weights and distances from the charge center are considered for the analyses of a masonry bridge and depending on these parameters frequency-varying shock spectra are determined and applied to each support of the two-span masonry bridge. The net blast induced ground motion consists of air-induced and direct-induced ground motions. Acceleration time histories of blast induced ground motions are obtained depending on a deterministic shape function and a stationary process. Shock response spectrums determined from the ground shock time histories are simulated using BlastGM software. The results obtained from uniform and multi-point response spectrum analyses cases show that significant differences take place between the uniform and multi-point blast-induced ground motions.