• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.333-340
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• 1997

This paper will expand the third-order shear deformation theory by the double-Fourier series and reduce to the solution of a system of ordinary differential equations in time, which are integrated numerically using Newmark's direct integration method and clarify the undamped dynamic responses for the cross-ply and antisymmetric angle-ply laminated composite plates and shells with simply supported boundary condition. Numerical results for deflections are presented showing the effect of side-to-thickness ratio, aspect ratio, material anisotropy, and lamination scheme.

• Journal of Advanced Research in Ocean Engineering
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• v.3 no.2
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• pp.83-101
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• 2017

In this study, the added resistances of the large container ship in head and oblique seas are evaluated using a time-domain Rankine panel method. The mean forces and moments are computed by the near-field method, namely, the integration of the second-order pressure directly on the ship surface. Furthermore, a weakly nonlinear approach in which the nonlinear restoring and Froude-Krylov forces on the exact wetted surface of a ship are included in order to examine the effects of amplitudes of waves on ship motions and added resistances. The computation results for various advance speeds and heading angles are validated by comparing with the experimental data, and the validation shows reasonable consistency. Nevertheless, there exist discrepancies between the numerical and experimental results, especially for a shorter wave length, a higher advance speed, and stern quartering seas. Therefore, the accuracies of the linear and weakly nonlinear methods in the evaluation of the mean drift forces and moments are also discussed considering the characteristics of the hull such as the small incline angle of the non-wall-sided stern and the fine geometry around the high-nose bulbous bow.

• Structural Engineering and Mechanics
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• v.64 no.4
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• pp.515-526
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• 2017

Dynamic response of functionally graded Carbon nanotubes (FG-CNT) reinforced pipes conveying viscous fluid under accelerated moving load is presented. The mixture rule is used for obtaining the material properties of nano-composite pipe. The radial force induced by viscous fluid is calculated by Navier-Stokes equation. The material properties of pipe are considered temperature-dependent. The structure is simulated by Reddy higher-order shear deformation shell theory and the corresponding motion equations are derived by Hamilton's principal. Differential quadrature (DQ) method and the Integral Quadrature (IQ) are applied for analogizing the motion equations and then the Newmark time integration scheme is used for obtaining the dynamic response of structure. The effects of different parameters such as boundary conditions, geometrical parameters, velocity and acceleration of moving load, CNT volume percent and distribution type are shown on the dynamic response of pipe. Results indicate that increasing CNTs leads to decrease in transient deflection of structure. In accelerated motion of the moving load, the maximum displacement is occurred later with respect to decelerated motion of moving load.

• Tribology and Lubricants
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• v.36 no.5
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• pp.290-296
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• 2020

When two layers of carbon nanotube (CNT) arrays are loaded to mate, the free ends of individual CNTs come into contact at the interface of the two layers. This leads to a higher contact resistance due to a smaller contact region. However, when the free CNT ends of one array penetrate into the mating array, the contact region increases, effectively lowering the contact resistance. To explore the penetration of mating CNTs, we perform molecular dynamic simulations of a simple unit cell model, incorporating four CNTs in the lower array layer coupled with a single moving CNT on the upper layer. The interaction with neighboring CNTs is modelled by long-range carbon bond order potential (LCBOP I). The model structure is optimized by energy minimization through the conjugate gradient method. A NVT ensemble is used for maintain a room temperature during simulation. The time integration is performed through the velocity-Verlet algorithm. A significant vibrational motion of CNTs is captured when penetration is not available, resulting in a specific vibration mode with a high frequency. Due to this vibrational behavior, the random behaviors of CNT motion for predicting the penetration are confirmed under the specific gap distances between CNTs. Thus, the probability of penetration is examined according to the gap distance between CNTs in the lower array and the aspect ratio of CNTs. The penetration is significantly affected by the vibration mode due to the van der Waals forces between CNTs.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.3
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• pp.232-248
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• 2009

Numerical methodology to solve ship springing problem, which is basically fluid-structure interaction problem, was explored in this study. Solution of this hydroelasticity problem was sought by coupling higher order B-spline Rankine panel method and finite element method in time domain, each of which is introduced for fluid and structure domain respectively. Even though varieties of different combinations in terms of numerical scheme are possible and have been tried by many researchers to solve the problem, no systematic study regarding the characteristics of each scheme has been done so far. Here, extensive case studies have been done on the numerical schemes especially focusing on the iteration method, FE analysis of beam-like structure, handling of forward speed problem and so on. Two different iteration scheme, Newton style one and fixed point iteration, were tried in this study and results were compared between the two. For the solution of the FE-based equation of motion, direct integration and modal superposition method were compared with each other from the viewpoint of its efficiency and accuracy. Finally, calculation of second derivative of basis potential, which is difficult to obtain with accuracy within grid-based method like BEM was discussed.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.4
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• pp.309-315
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• 2018

Currently, the commercialization of the $5^{th}$ Generation (5G) service is becoming more prevalent in domestic communication network technology. This has reduced communication delay time and enabled large-capacity data transmission and video streaming services in real-time. In order to keep pace with these developments, K-water has introduced a smart process control system in water purification plants to monitor the status of the water purification process. However, since wireless networks are based on the public Long Term Evolution (LTE) network, communication delay time remains high, and high-resolution video services are limited. This is because communication networks still have a closed structure due to expense and security issues. Therefore, with 5G in its current form, it is very difficult to accommodate future services without improving the infrastructure of its communication networks. In recognition of these problems, this study implemented the authentication and management function of wireless networks on a wired network management system in the K-water Bansong water purification plant. The results confirmed that wired Local Area Network (LAN) services give a higher security performance than an expensive commercial wireless LAN system. This was achieved by using an Internet Protocol (IP) address management system of wired networks and the packet filtering function of the Layer2 (L2) switch. This study also confirmed that it is possible to create a wireless LAN service that is 3.7 times faster than the existing LTE communication network.

• Journal of the Korea Computer Industry Society
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• v.6 no.5
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• pp.757-766
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• 2005

There have been great demands for higher density SRAM in all area of SRAM applications, such as mobile, network, cache, and embedded applications. Therefore, aggressive shrinkage of 6T Full CMOS SRAM had been continued as the technology advances, However, conventional 6T Full CMOS SRAM has a basic limitation in the cell size because it needs 6 transistors on a silicon substrate compared to 1 transistor in a DRAM cell. The typical cell area of 6T Full CMOS SRAM is $70{\sim}90F^{2}$, which is too large compared to $8{\sim}9F^{2}$ of DRAM cell. With 80nm design rule using 193nm ArF lithography, the maximum density is 72M bits at the most. Therefore, pseudo SRAM or 1T SRAM, whose memory cell is the same as DRAM cell, is being adopted for the solution of the high density SRAM applications more than 64M bits. However, the refresh time limits not only the maximum operation temperature but also nearly all critical electrical characteristics of the products such as stand_by current and random access time. In order to overcome both the size penalty of the conventional 6T Full CMOS SRAM cell and the poor characteristics of the TFT load cell, we have developed $S^{3}$ cell. The Load pMOS and the Pass nMOS on ILD have nearly single crystal silicon channel according to the TEM and electron diffraction pattern analysis. In this study, we present $S^{3}$ SRAM cell technology with 100nm design rule in further detail, including the process integration and the basic characteristics of stacked single crystal silicon TFT.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.4
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• pp.314-321
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• 2006

There have been great demands for higher density SRAM in all area of SRAM applications, such as mobile, network, cache, and embedded applications. Therefore, aggressive shrinkage of 6 T Full CMOS SRAM had been continued as the technology advances. However, conventional 6 T Full CMOS SRAM has a basic limitation in the cell size because it needs 6 transistors on a silicon substrate compared to 1 transistor in a DRAM cell. The typical cell area of 6 T Full CMOS SRAM is $70{\sim}90\;F^2$, which is too large compared to $8{\sim}9\;F^2$ of DRAM cell. With 80 nm design rule using 193 nm ArF lithography, the maximum density is 72 Mbits at the most. Therefore, pseudo SRAM or 1 T SRAM, whose memory cell is the same as DRAM cell, is being adopted for the solution of the high density SRAM applications more than 64 M bits. However, the refresh time limits not only the maximum operation temperature but also nearly all critical electrical characteristics of the products such as stand_by current and random access time. In order to overcome both the size penalty of the conventional 6 T Full CMOS SRAM cell and the poor characteristics of the TFT load cell, we have developed S3 cell. The Load pMOS and the Pass nMOS on ILD have nearly single crystal silicon channel according to the TEM and electron diffraction pattern analysis. In this study, we present $S^3$ SRAM cell technology with 100 nm design rule in further detail, including the process integration and the basic characteristics of stacked single crystal silicon TFT.

• Korean Journal of Family Social Work
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• no.59
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• pp.27-53
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• 2018

The objective of this study was to investigate the influence of family-related factors and age-friendly environment on intergenerational interaction in middle-aged group and the older adult group. Based on the results, this study is to suggest countermeasures for decreasing intergenerational interaction with the population aging. This study analyzed 260 sample participants aged from 45 to 64 and 399 sample participants aged 64 and more, categorizing them into middle-aged group and the older adult group respectively. The sample participants were taken from '2014 Survey on the Aged Society' and had at least one adult child aged over 18 at the time of participation. In order to identify the relationship between five sub-dimensions related to family, age-friendly environment and intergenerational interaction within the family in two age groups, t-test and multiple regression analysis were used. As a result, both two family-related factors had positive correlation with intergenerational interaction within the family. However, affective solidarity showed a higher significance in the middle-aged group and familism showed a higher significance in the older adult group. Among the sub-dimensions related to age-friendly environment, only personal opinion on age integration showed significance in the older adult group. This study provides several implications from the results.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.4
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• pp.1-10
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• 2019

Unmanned aerial vehicle(UAV) can acquire images with lower cost than conventional manned aircraft and commercial satellites. It has the advantage of acquiring high-resolution aerial images covering in the field area more than 50 ha. The purposes of this study is to develop the rice grain yield distribution using UAV. In order to develop a technology for estimating the rice yield using UAV images, time series UAV aerial images were taken at the paddy fields and the data were compared with the rice yield of the harvesting area for two rice varieties(Singdongjin, Dongjinchal). Correlations between the vegetation indices and rice yield were ranged from 0.8 to 0.95 in booting period. Accordingly, rice yield was estimated using UAV-derived vegetation indices($R^2=0.70$ in Sindongjin, $R^2=0.92$ in Donjinchal). It means that the rice yield estimation using UAV imagery can provide less cost and higher accuracy than other methods using combine with yield monitoring system and satellite imagery. In the future, it will be necessary to study a variety of information convergence and integration systems such as image, weather, and soil for efficient use of these information, along with research on preparing management practice work standards such as pest control and nutrient use based on UAV image information.