• Journal of the Korean Wood Science and Technology
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• 제40권5호
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• pp.327-334
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• 2012

Wood and concrete show significantly different physical properties, and it need to be firstly understood for using wood-concrete composite. This study is performed for compensating this and effective hybridization of wood and concrete. This research in planned for wood-concrete composite after previous research which deals the shear performance with different anchorage length of steel rebar in wood. Yield mode and reference design value (Z) were derived using EYM (European Yield Model). And the yield mode changed before and after anchorage length of 10~15 mm - $I_s$ mode to IV mode. There was not increasing tendency of shear performance with increased anchorage length for over 20 mm of anchorage in concrete. And wood composite shows 65% and 93% on initial stiffness and yield load respectively compared with the wood-concrete composite. Wood-concrete composite showed brittle failure after yield point while wood-to-wood composite showed ductile failure.

• Structural Engineering and Mechanics
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• 제63권6호
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• pp.743-750
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• 2017

Modal parameter identification plays a key role in the structural health monitoring (SHM) for civil engineering. Eigensystem realization algorithm (ERA) is one of the most popular identification methods. However, the complex environment around civil structures can introduce the noises into the measurement from SHM system. The spurious modes would be generated due to the noises during ERA process, which are usually ignored and be recognized as physical modes. This paper proposes an improved stabilization diagram method in ERA to distinguish the spurious modes. First, it is proved that the ERA can be performed by any two Hankel matrices with one time step shift. The effect of noises on the eigenvalues of structure is illustrated when the choice of two Hankel matrices with one time step shift is different. Then, a moving data diagram is proposed to combine the traditional stabilization diagram to form the improved stabilization diagram method. The moving data diagram shows the mode variation along the different choice of Hankel matrices, which indicates whether the mode is spurious or not. The traditional stabilization diagram helps to determine the concerned truncated order before moving data diagram is implemented. Finally, the proposed method is proved through a numerical example. The results show that the proposed method can distinguish the spurious modes.

• Environmental Engineering Research
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• 제17권3호
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• pp.167-174
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• 2012

In situ particle size spectra are obtained from two sequent cruises in order to evaluate the physical consequences of suspended particulate matters caused by episodic storm runoff from the Santa Ana River watershed, an urbanized coastal watershed. Suspended particles from various sources including surface runoff, near-bed resuspension, and phytoplankton are identified in empirical orthogonal function (EOF) analysis and an entropy-based parameterization (Shannon entropy). The first EOF mode is associated with high turbidity and fine particles as indicated by the elevated beam attenuation near the Santa Ana River and Newport Bay outlets, and the second EOF mode explains the suspended sediment dispersal and particle coarsening at the near-surface plume. Chlorophyll particles are also distinguished by negative magnitudes of the first EOF mode, which is supported by the relationship between fluorescence and beam attenuation. The integrated observation between the first EOF mode and the Shannon entropy index accentuates the characteristics of two different structures and/or sources of sediment particles; the near-surface plumes are originated from runoff water outflow, while the near-bottom particles are resuspended due to increased wave heights or mobilizing bottom turbidity currents. In a coastal pollution context, these methods may offer useful means of characterizing particle-associated pollutants for purposes of source tracking and environmental interpretation.

• 대한전자공학회논문지
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• 제22권2호
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• pp.1-5
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• 1985

본 연구에서는 단일모드 광섬유에서의 온도에 의한 위상변조 현상을 분석하고 단일모드 광섬유 간섭계를 이용한 온도센서를 설계. 제작하여 그 온도특성을 조사하였다. 설계한 fiber-optic온도센서는 Mach-Zehnder 간섭계를 이용한 위상감지형 고감도 센서로서 온도변화는 간섭무의의 이동으로써 측정되어졌다. 간섭계에 의한 측정에서 중요한 문제중의 하나는 온도분만 아니라 모든 피측정 물리량의 변화방향에 따른 간섭무의의 이동갯수와 이동방향을 동시에 측정하는 것이다. 이를 위해 다중모드 광섬유를 이용한 배열 검출기를 제작하여 매우 간편하게 간섭무늬의 이동갯수와 이동방향을 측정하였다.

• 한국통신학회논문지
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• 제30권5B호
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• pp.310-316
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• 2005

본 논문에서는 HIPERLAN/2(HIgh PErformance Radio Local Area Network type 2)의 랜덤 액세스 과정에서 채널 환경을 고려함으로 처리 성능을 높이고 전송 지연을 개선한 적응적 랜덤 액세스 기법(ARAH : Adaptive Random Access algorithm for HIPERLAN/2)을 제안하고 기존 방식에 비해 성능이 향상됨을 검증하였다. 본 논문에서는 HIPERLAN/2에서 채널의 상태에 따라 OFDM(Orthogonal frequency Division Multiplexing) modulation scheme을 기반으로 제공하는 7가지 PHY(Physical) mode를 Good 그룹과 Bad 그룹으로 양분하고, Good 그룹에 속하는 단말들에게 랜덤 액세스 과정에서 우선순위를 갖게 함으로써 처리율을 높이도록 하는 방식을 취하고 있다. ARAH 방식에 대하여 성능을 평가한 결과, 처리율과 전송 지연에 대해 성능이 향상됨을 보이고 있다.

• 한국공간구조학회논문집
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• 제15권2호
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• pp.69-77
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• 2015

Ultra High Performance Fiber Reinforced Concrete (UHPFRC) has a outstanding tensile hardening behaviour after a crack develops, which gives ductility to structures. Existing shear strength model for fiber reinforced concrete is entirely based on crack opening behavior(mode I) which comes from flexural-shear failure, not considering shear-slip behavior(mode II). To find out the mode I and mode II behavior on a crack in UHPFRC simultaneously, maximum shear strength of cracked UHPFRC is investigated from twenty-four push-off test results. The shear stress on a crack is derived as variable of initial crack width and fiber volume ratio. Test results show that shear slippage is proportional to crack opening, which leads to relationship between shear transfer strength and crack width. Based on the test results a hypothesis is proposed for the physical mechanics of shear transfer in UHPFRC by tensile hardening behavior in stead of aggregate interlocking in reinforced concrete. Shear transfer strength based on tensile hardening behavior in UHPFRC is suggested and this suggestion was verified by comparing direct tensile test results and push-off test results.

• 토지주택연구
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• 제11권2호
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• pp.1-14
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• 2020

The aim of this study is to empirically identify the differentiating characteristics of determinant factors on sing-person households' commuting mode choice compared to multi-person households' one in order to establish the customized police directions to decrease private car use in commuting. While the study use the 2% sample survey data on the population and housing in 2015, it employ multinomial logit models on relative choice probability of such alternative commuting modes as bus, subway or rail, and walking, rather than driving. As potential determinant factors, the study employs demographic, socio-economic, and housing and residential one for both models of single-person and multi-person households. The study finds that the behavior of commuting mode choice has distinctive difference by gender, marriage status, physical activity constraint, job type, residential period in current housing of the single-person household's workers compared to the multi-person households' ones. Based on the findings, the study deduce ten commuting policy directions customized for the single-person household.

• Current Optics and Photonics
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• 제7권4호
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• pp.449-456
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• 2023

The localized surface-plasmon resonance has drawn great attention, due to its unique optical properties. In this work a general theoretical description of the dipole mode is proposed, using the forced damped harmonic oscillator model of free charges in an ellipsoid. The restoring force and driving force are derived in the quasistatic approximation under general conditions. In this model, metal is regarded as composed of free charges and bound charges. The bound charges form the dielectric background which has a dielectric function. Those free charges undergo a collective motion in the dielectric background under the driving force. The response of free charges will not be included in the dielectric function like the Drude model. The extinction and scattering cross sections as well as the damping coefficient from our model are verified to be consistent with those based on the Drude model. We introduce size effects and modify the restoring and driving forces by adding the dynamic depolarization factor and the radiation damping term to the depolarization factor. This model provides an intuitive physical picture as well as a simple theoretical description of the dipole mode of the localized surface-plasmon resonance based on free-charge collective motion.

• 한국결정성장학회지
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• 제14권4호
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• pp.160-168
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• 2004

We investigate the effects of solutal convection on the crystal growth rate in a horizontal configuration for diffusive-convection conditions and purely diffusion conditions achievable in a low gravity environment for a nonlinear thermal gradient. It is concluded that the solutally-driven convection due to the disparity in the molecular weights of the component A $(Hg_2Br_2)$ and B (CO) is stronger than thermally-driven convection for both the nonlinear and the linear thermal profiles, corresponding to $Gr_t= 8.5{\times}10^3,\; Gr_s = 1.05{\times}10^5$. For both solutal and thermal convection processes, the growth rates for the linear thermal profile (conducting walls) are greater than for the nonlinear case. With the temperature humps, there are found to be observed in undersaturation for diffusive-convection processes ranging from $D_{AB}$ = 0.087 to 0.87. For the vertical configurations, the diffusion mode is so much dominated that the growth rate and interfacial distribution is nearly regardless of the gravitational accelerations. Also, the diffusion mode is predominant over the convection for the gravity levels less than 0.1 $g_0$ for the horizontally oriented configuration.

• 한국정밀공학회지
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• 제23권6호
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• pp.119-127
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• 2006

A non-destructive time domain approach to examine structural damage using parameterized partial differential equations and Galerkin approximation techniques is presented. The time domain analysis for damage detection is independent of modal parameters and analytical models unlike frequency domain methods which generally rely on analytical models. The time history of the vibration response of the structure was used to identify the presence of damage. Damage in a structure causes changes in the physical coefficients of mass density, elastic modulus and damping coefficients. This is a part of our ongoing effort on the general problem of modeling and parameter estimation for internal damping mechanisms in a composite beam. Namely, in detecting damage through time-domain or frequency-domain data from smart sensors, the common damages are changed in modal properties such as natural frequencies, mode shapes, and mode shape curvature. This paper examines the use of beam-like structures with piezoceramic sensors and actuators to perform identification of those physical parameters, and detect the damage. Experimental results are presented from tests on cantilevered composite beams damaged at different locations and different dimensions. It is demonstrated that the method can sense the presence of damage and obtain the position of a damage.