• Journal of Advanced Marine Engineering and Technology
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• v.39 no.1
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• pp.52-57
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• 2015

In this paper, we studies on the RF characteristics of the transmission line employing IPACD (inverted periodically arrayed capacitive devices) on MMIC (monolithic microwave integrated circuit) for application to wireless communication system. According to measured results, the novel transmission line employing IPACD showed a wavelength much shorter than conventional transmission lines. In addition, the IPACD structure showed an effective permittivity much higher than conventional ones. We also extracted the bandwidth characteristic of the IPACD structure using equivalent circuit analysis. According to the results, the cut-off frequency of the proposed structure was 129.2 GHz.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.2
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• pp.205-217
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• 2007

The behavior characteristics of underground structures are reported as they are not affected by their dynamic characteristics such as surface structures, but by dynamic characteristics of soil and rock surrounding the underground structures. Therefore, dynamic behavior of surrounding soil and rock dominates the dynamic behavior of the underground structure. The purpose of this paper is to analyze the dynamic response (longitudinal deformation and ovaling deformation) of the underground structure under earthquake loading. The dynamic responses of the underground structures were evaluated with varying earthquake conditions, soil conditions, and structural conditions using conventional closed-form solution of seismic behavior of underground structure. In addition, shaking table tests were conducted to simulate the earthquake loading and the dynamic behavior of the model was analyzed.

• Earthquakes and Structures
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• v.14 no.2
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• pp.103-115
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• 2018

In this work, a simple but accurate hyperbolic plate theory for the free vibration analysis of functionally graded material (FGM) sandwich plates is developed. The significant feature of this formulation is that, in addition to including the shear deformation effect, it deals with only 3 unknowns as the classical plate theory (CPT), instead of 5 as in the well-known first shear deformation theory (FSDT) and higher-order shear deformation theory (HSDT). A shear correction factor is, therefore, not required. Two common types of FGM sandwich plates are considered, namely, the sandwich with the FGM face sheet and the homogeneous core and the sandwich with the homogeneous face sheet and the FGM core. The equation of motion for the FGM sandwich plates is obtained based on Hamilton's principle. The closed form solutions are obtained by using the Navier technique. The fundamental frequencies are found by solving the eigenvalue problems. Numerical results of the present theory are compared with the CPT, FSDT, order shear deformation theories (HSDTs), and 3D solutions. Verification studies show that the proposed theory is not only accurate and simple in solving the free vibration behaviour of FGM sandwich plates, but also comparable with the higher-order shear deformation theories which contain more number of unknowns.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.413-418
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• 2001

Fundamental failure mode in a laminated composite pinned-joint is proposed to assess damage resulting from stress concentration in the plate. The joint area is a region with stress concentrations thus a complicated stress state exists. The modeling of damage in a laminated composite pinned-joint presents many difficulties because of the complexity of the failure process. In order to model progressive from initial to final, finite element methods are used rather than closed form stress analyses. Failure analysis must be a logical combination of suitable failure criteria and appropriate material properties degradation rules. In this study, the material properties which were obtained in previous study, the preparing process of the bearing strength test for a pinned joint CFRP composite plate subjected to in-plane loading at low temperature, and the FEM result of progressive damage model using ANSYS program are summarized to assess the structural safety of CFRP plate used in the magnetic supporting post of KSTAR(Korea Superconducting Tokamak Advanced Research).

• Journal of Korea Water Resources Association
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• v.49 no.7
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• pp.615-623
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• 2016

This Study calculated the Submerged Flow Characteristics and Discharge coefficient by the rising angular change of the Improved-Pneumatic-Movable. According to the result, the smaller the ratio of weir height and weir length (L/W) or the weir standing angle, the bigger of the downstream head ($H_2$). The change of discharge reduction factor ($Q_s/Q_1$), by the hight from weir crest to downstream surface and the ratio form weir crest to upstream water height ($h_t/H$), was decreased when the $h_t/H$ closed to number 1. Although the weir water depth of the down-stream was shallower level than the up-stream, the velocity was faster then before. And the more the flow, the less the gab between the upper and lower reaches level. And when the same flow condition, the downstream head ($H_2$) was increased when the L/W was bigger. The Submerged Flow Discharge coefficient of Improved-Pneumatic-Movable weir was made by the upstream approach flow head and the upper lower stream flow condition, not by the physical data of Movable weir.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.8
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• pp.774-780
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• 2010

This paper deals with the choice of guidance gain for the time-to-go polynomial (POLY) guidance law when the acceleration limit is existed. POLY is derived based on the assumption that guidance commands are formed by a time-to-go polynomial function. The main characteristic of POLY is that any positive values can be used for its guidance gain. For this reason, it is ambiguous to choose a proper guidance gain. To relieve this difficulty, we firstly derive the closed-form solution of acceleration command and figure out the relationship between the maximum acceleration and guidance gain. From this analysis, we provide a guideline for choosing a guidance gain which satisfies the desired acceleration limit. Finally, the proposed method is demonstrated by simulation study.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.12
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• pp.5862-5887
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• 2019

In this paper, we propose a two-way relaying scheme using non-orthogonal multiple access (NOMA) technology. In this scheme, two sources transmit packets with each other under the assistance of the decode-and-forward (DF) relays, called as a TWDFNOMA protocol. The cooperative relays exploit successive interference cancellation (SIC) technique to decode sequentially the data packets from received summation signals, and then use the digital network coding (DNC) technique to encrypt received data from two sources. A max-min criterion of end-to-end signal-to-interference-plus-noise ratios (SINRs) is used to select a best relay in the proposed TWDFNOMA protocol. Outage probabilities are analyzed to achieve exact closed-form expressions and then, the system performance of the proposed TWDFNOMA protocol is evaluated by these probabilities. Simulation and analysis results discover that the system performance of the proposed TWDFNOMA protocol is improved when compared with a conventional three-timeslot two-way relaying scheme using DNC (denoted as a TWDNC protocol), a four-timeslot two-way relaying scheme without using DNC (denoted as a TWNDNC protocol) and a two-timeslot two-way relaying scheme with amplify-and-forward operations (denoted as a TWANC protocol). Particularly, the proposed TWDFNOMA protocol achieves best performances at two optimal locations of the best relay whereas the midpoint one is the optimal location of the TWDNC and TWNDNC protocols. Finally, the probability analyses are justified by executing Monte Carlo simulations.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.5
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• pp.516-524
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• 1997

The propagation properties of various pulse signal types(square pulse, Gaussian pulse, trapezoid pulse, RF pulse) on coupled microstrip lines are investigated. Numerical integration technique which has its accuracy and is easily simulated, is used to obtain the time domain response of pulse signals. Frequency-dependent characteristics of coupled microstrip line is obtained using Jansen's approximate equation. The propagation properties of pulse signal on coupled microstrip lines is analyzed regarding to its geometric structure (relative permittivity ${varepsilon}_r$ substrate height h, strip width w of the microstrip line) and pulse width ${\tau}$ of signal pulse. The simulation results show that space between two lines is very significant parameter in pulse distortion in comparison of any other parameters. The results of this paper are compatible to the trade-off determination of relative permittivity, substrate height, strip width and pulse width of signal pulse when a design of MIC and MMIC is necessary.

• Structural Engineering and Mechanics
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• v.37 no.2
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• pp.149-162
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• 2011

The aim of this research is a comprehensive review and evaluation of beam theories resting on elastic foundations that used to model mode-I delamination in multidirectional laminated composite by DCB specimen. A compliance based approach is used to calculate critical strain energy release rate (SERR). Two well-known beam theories, i.e. Euler-Bernoulli (EB) and Timoshenko beams (TB), on Winkler and Pasternak elastic foundations (WEF and PEF) are considered. In each case, a closed-form solution is presented for compliance versus crack length, effective material properties and geometrical dimensions. Effective flexural modulus ($E_{fx}$) and out-of-plane extensional stiffness ($E_z$) are used in all models instead of transversely isotropic assumption in composite laminates. Eventually, the analytical solutions are compared with experimental results available in the literature for unidirectional ($[0^{\circ}]_6$) and antisymmetric angle-ply ($[{\pm}30^{\circ}]_5$, and $[{\pm}45^{\circ}]_5$) lay-ups. TB on WEF is a simple model that predicts more accurate results for compliance and SERR in unidirectional laminates in comparison to other models. TB on PEF, in accordance with Williams (1989) assumptions, is too stiff for unidirectional DCB specimens, whereas in angle-ply DCB specimens it gives more reliable results. That it shows the effects of transverse shear deformation and root rotation on SERR value in composite DCB specimens.

• Korean Institute of Interior Design Journal
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• no.27
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• pp.152-161
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• 2001

At the multi-cultural society, research is needed to encourage a social atmosphere for enhanced understanding and respect for different cultures & countries. The purpose was to analyze the characteristics of spatial arrangement, space connection, Interior decoration and the relationship among these three features, which showed each country's unique housing form tradition. Three representative cases of historic residences from each country were selected on the basis of a recognized historic architecture directory. Total 18 residences from 6 countries - Korea, China, Japan, Rome, Egypt, and Italy - were comparatively analyzed. As results, aspects generally found in Eastern countries, were the fence as the semi-open boundary between the inside and the outside of the house, the flexibility of spatial opening and partitions between rooms, and finally simple and movable decoration features. On the other hands, aspects appeared in Western countries, were the outer wall of the building as the boundary to the outside, the closed and fixed properties of the room partitions, and finally complex and fixed decoration features. The research also showed that even within the same culture, the degree of openness varied. Each feature of space was related and could be explained within the same context. Housing, regardless of country and culture, tried to accommodate the exterior space inside the building as much as possible. The common pursuit was transformed to various visible forms and its reason might be due to different socio-cultural and environmental backgrounds that need to be continuously explored in academic area.