• Title, Summary, Keyword: Directional dependence

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A joint probability distribution model of directional extreme wind speeds based on the t-Copula function

  • Quan, Yong;Wang, Jingcheng;Gu, Ming
    • Wind and Structures
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    • v.25 no.3
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    • pp.261-282
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    • 2017
  • The probabilistic information of directional extreme wind speeds is important for precisely estimating the design wind loads on structures. A new joint probability distribution model of directional extreme wind speeds is established based on observed wind-speed data using multivariate extreme value theory with the t-Copula function in the present study. At first, the theoretical deficiencies of the Gaussian-Copula and Gumbel-Copula models proposed by previous researchers for the joint probability distribution of directional extreme wind speeds are analysed. Then, the t-Copula model is adopted to solve this deficiency. Next, these three types of Copula models are discussed and evaluated with Spearman's rho, the parametric bootstrap test and the selection criteria based on the empirical Copula. Finally, the extreme wind speeds for a given return period are predicted by the t-Copula model with observed wind-speed records from several areas and the influence of dependence among directional extreme wind speeds on the predicted results is discussed.

Special Structural Dependence Of Directional Coupler Characteristics (방향성 결합기의 응용 구조 및 특성 연구)

  • 최철현;홍정무;오범환
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.344-347
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    • 2000
  • We analyze the variation of coupling length as a function of the waveguide width for a directional coupler. It is interesting that the coupling length is not monotonic function of waveguide width for a given distance between the centers. The waveguide width for a maximum coupling length can be utilized for the optimum design of a directional coupler.

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Quantile Dependence between Foreign Exchange Market and Stock Market: The Case of Korea

  • Han, Heejoon;Lee, Na Kyeong
    • East Asian Economic Review
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    • v.20 no.4
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    • pp.519-544
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    • 2016
  • This paper examines quantile dependence and directional predictability between the foreign exchange market and the stock market in Korea. Instead of adopting a multivariate model such as a vector autoregressive model, a multivariate GARCH model or a combination of both models, we apply the cross-quantilogram recently proposed by Han et al. (2016). Considering various quantile ranges, we investigate various spillover effects between two markets. Our findings show that there exists an asymmetric bi-directional spillover between two markets and the interdependence between two markets implies that one market has significant predictive power on the other.

Determination of Dose Correction Factor for Energy and Directional Dependence of the MOSFET Dosimeter in an Anthropomorphic Phantom (인형 모의피폭체내 MOSFET 선량계의 에너지 및 방향 의존도를 고려하기 위한 선량보정인자 결정)

  • Cho, Sung-Koo;Choi, Sang-Hyoun;Na, Seong-Ho;Kim, Chan-Hyeong
    • Journal of Radiation Protection and Research
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    • v.31 no.2
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    • pp.97-104
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    • 2006
  • In recent years, the MOSFET dosimeter has been widely used in various medical applications such as dose verification in radiation therapeutic and diagnostic applications. The MOSFET dosimeter is, however, mainly made of silicon and shows some energy dependence for low energy Photons. Therefore, the MOSFET dosimeter tends to overestimate the dose for low energy scattered photons in a phantom. This study determines the correction factors to compensate these dependences of the MOSFET dosimeter in ATOM phantom. For this, we first constructed a computational model of the ATOM phantom based on the 3D CT image data of the phantom. The voxel phantom was then implemented in a Monte Carlo simulation code and used to calculate the energy spectrum of the photon field at each of the MOSFET dosimeter locations in the phantom. Finally, the correction factors were calculated based on the energy spectrum of the photon field at the dosimeter locations and the pre-determined energy and directional dependence of the MOSFET dosimeter. Our result for $^{60}Co$ and $^{137}Cs$ photon fields shows that the correction factors are distributed within the range of 0.89 and 0.97 considering all the MOSFET dosimeter locations in the phantom.

Scattering Wave Spectrum by a Pile Breakwater in Directional Irregular Waves (다방향 불규칙 파랑중 파일 방파제에 의한 산란파 스펙트럼)

  • Cho, Il-Hyoung
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.19 no.6
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    • pp.586-595
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    • 2007
  • The analytic solution of wave scattering of monochromatic waves on a pile breakwater by an eigenfunction expansion method is extended to the case of directional irregular waves. The scattering wave spectrum and the force spectrum can be expressed from the reflection coefficient, transmission coefficient and the wave forces obtained from changing frequencies and incident angles in monochromatic waves. By numerical integration of 2-dimensional spectrum which is function of frequencies and incident angles, the representative values for the scattered waves and wave forces are obtained and the dependence of the transmission coefficients and wave forces on the directional distribution function, the principal wave direction, the submergence depth, and porosity is analyzed.

Development of Phantom and Comparison Analysis for Performance Characteristics of MOSFET Dosimeter (MOSFET 선량계 특성분석을 위한 팬톰 개발 및 특성 비교)

  • Chung, Jin-Beom;Lee, Jeong-Woo;Kim, Yon-Lae;Lee, Doo-Hyun;Choi, Kyoung-Sik;Kim, Jae-Sung;Kim, In-Ah;Hong, Se-Mie;Suh, Tae-Suk
    • Progress in Medical Physics
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    • v.18 no.1
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    • pp.48-54
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    • 2007
  • This study is to develope a phantom for MOSFET (Metal Oxide Semiconductors Field Effect Transistors) dosimetry and compare the dosimetric properties of standard MOSFET and microMOSFET with the phantom. In this study, the developed phantom have two shape: one is the shape of semi-sphere with 10cm diameters and the other one is the flat slab of $30{\times}30cm$with 1 cm thickness. The slab phantom was used for calibration and characterization measurements of reproducibility, linearity and dose rate dependency. The semi-sphere phantom was used for angular and directional dependence on the types of MOSFETs. The measurements were conducted under $10{\times}10cm^2$ fields at 100cm SSD with 6MV photon of Clinac (21EX, Varian, USA). For calibration and reproducibility, five standard MOSFETS and microMOSFETs were repeatedly Irradiated by 200cGy five times. The average calibration factor was a range of $1.09{\pm}0.01{\sim}1.12{\pm}0.02mV/cGy$ for standard MOSFETS and $2.81{\pm}0.03{\sim}2.85{\pm}0.04 mV/cGy$ for microMOSFETs. The response of reproducibility in the two types of MOSFETS was found to be maximum 2% variation. Dose linearity was evaluated In the range of 5 to 600 cGy and showed good linear response with $R^2$ value of 0.997 and 0.999. The dose rate dependence of standard MOSFET and microMOSFET was within 1% for 200 cGy from 100 to 500MU/min. For linearity, reproducibility and calibration factor, two types of MOSFETS showed similar results. On the other hand, the standard MOSFET and microMOSFET were found to be remarkable difference in angular and directional dependence. The measured angular dependence of standard MOSFET and microMOSFET was also found to be the variation of 13%, 10% and standard deviation of ${\pm}4.4%,\;{\pm}2.1%$. The directional dependence was found to be the variation of 5%, 2% and standard deviation of ${\pm}2.1%,\;{\pm}1.5%$. Therefore, dose verification of radiation therapy used multidirectional X-ray beam treatments allows for better the use of microMOSFET which has a reduced angular and directional dependence than that of standard MOSFET.

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GAMMA-SPECTROMETRY IN ENVIRONMENTAL MONITORING OF NUCLEAR POWER

  • Cechak, Tomas;Gerndt, Josef;Kluson, Jaroslav;Musilek, Ladislav;Thinova, Lenka
    • Journal of Radiation Protection and Research
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    • v.26 no.3
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    • pp.203-206
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    • 2001
  • The mathematical processing (unfolding) of pulse height spectra from a scintillation detector helps to calculate the photon fluence rate energy distribution in a measured photon field. The data processing is based on the knowledge of detection system response function and directional dependence respectively. The experimental results of the photon fields measurements in the vicinity of the spent fuel temporary storage and inside the storage hall are presented. The containers Castor 440 are used for temporary storing of the burnt up fuel assemblies in the Czech nuclear power plant Dukovany. A set of periodical measurements was performed in order to get basic information on the time dependence of the photon fields spatial distributions and spectral characteristics in the temporary storage hall and its vicinity. The photon fields were measured by the scintillation system. The obtained photon fields spatial distributions and spectral characteristics present the information on the radiation hazard in the storage.

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Spectral Evaluation of Stirring Performance in a Reverberation Chamber using the FDTD Method (유한요소 시간차분법을 이용한 레버버레이션 챔버내에서의 스터링 효과의 분석)

  • Kim, Jong-Sung
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.48 no.11
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    • pp.83-88
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    • 2011
  • The spectral field data on the observation planes inside a mode stirred chamber have been computed by using the FDTD method. They can describe the directional dependence of all supported modes in the reverberation chamber (RC). Correlation coefficients have been found to evaluate the stirring effects. The correlation coefficients were obtained and compared for three different sizes of stirrers and statistical uniformity was investigated.

A study on the simplification of HRTF within low frequency region (저역 주파수 영역에서 HRTF의 간략화에 관한 연구)

  • Lee, Chai-Bong
    • The Journal of the Korea institute of electronic communication sciences
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    • v.5 no.6
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    • pp.581-587
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    • 2010
  • In this study, we investigated the effect of the simplification for low frequency region in Head-Related Transfer Function(HRTF) on the sound localization. For this purpose, HRTF was measured and analyzed. The result in the standard deviation of HRTF showed that the directional dependence of low frequency was smaller than that of high frequency region, which means the possibility of simplification in the low frequency region. Simplification was performed by flattening of the low frequency amplitude characteristics with the insertion of the high-pass filter, whose cutoff frequency is given by boundary frequency. Auditory experiments were performed to evaluate the simplified HRTF. The result showed that direction perception was not influenced by the simplification of the frequency characteristics of HRTF for the error of sound localization. The rate of confusion for the front and back was not affected by the simplification of the frequency characteristics within 1kHz of HRTF. Finally, we made it clear that the sound localization was not affected by the simplification of frequency characteristics of HRTF within 1kHz. The result is expected to be utilized to reduce the size of speech information with no deterioration of the directional characteristics of the speech signal.

High $J_{c}$'s in just-rolled $Tl_{0.8}$$Pb_{0.2}$$Bi_{0.2}$$Sr_{1.8}$$Ba_{0.2}$$Ca_{2.2}$$Cu_{3}$$O_{x}$/Ag tapes (압영제조된 $Tl_{0.8}$$Pb_{0.2}$$Bi_{0.2}$$Sr_{1.8}$$Ba_{0.2}$$Ca_{2.2}$$Cu_{3}$$O_{x}$/Ag 선재에서의 높은 $J_{c}$)

  • 정대영;김희권;이해연;허홍수;오상수;이준호;김봉준;김영철
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • pp.3-9
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    • 1999
  • The grain morphology, the changes in morphology and Jc with the thermo-mechanical treatment (TMT) history, the field dependence of Jc and the nature of intergranular bonding were studied in $T_{10.8}$$Pb_{.2}$$Bi_{0.2}$$Sr_{1.8}$$Ba_{0.2}$$Ca_{2.2}$$Cu_{3}$$O_{z}$/Ag tapes. As a result, incorporation of intermediate rolling during the final heat-treatment resulted in of plate-like TI-1223 grains, and thus enhanced Jc. Jc's near 2.5$\times$104 A/cm2 at 77 K and 0 T were obtained in just rolled tapes with an excellent reproducibility. The high Jc's seem to grain-connectivity easy recovery of excellent grain-connectivity during final heat-treatment after inter -mediate rolling, probably due to retarded T1 evaporation and excessive Ca content in the present composition. The strong field dependence of Jc even in low fields, however, indicated that there still existed significant weak-links and the degree of directional grain-alignment was far from the desired one. The intergranular binding in the tapes seemed to be mainly dominated by SIS junctions.

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