• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.52-60
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• 2021

The aim of this study was to derive a new trend by analyzing installations using 3D printing that are out of the limits of size and design according to the trends of developing 3D printing technology. This paper classified the types of installations using 3D printing and analyzed them with two trends: the trend of design and the trend of output. The trends of installations using 3D printing derived from this study are as follows. First, as the implementation of design through an algorithm is accomplished, the transformation appears with the atypical design that is prominent in complex expression. Second, Robotics and FDM 3D Printing is fused, which is changing the existing paradigm. Therefore, the production and utilization of installations using 3D printing proceeded at a faster pace through the interaction between the algorithm design method and freeform 3D printing technology. This study was conducted on installations using 3D printing around the world and played a basic role in the research on the production of installations using 3D printing along with domestic 3D printing technology to be developed in the future. Follow-up studies in various aspects, such as materials and combination methods, will be needed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.495-503
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• 2001

In a functionally graded materials(FGM), two constituent material particles are mixed up according to a specific volume fraction distribution so that its thermoelastic behavior is definitely characterized by such a material composition distribution. Therefore, the designer should determine the most suitable volume fraction distribution in order to design a FGM that optimally meets the desired performance against the given constraints. In this paper, we address a numerical optimization procedure, with employing interior penalty function method(IPFM) and FDM, for optimizing 2D volume fractions of heat-resisting FGMs composed of metal and ceramic. We discretize a FGM domain into finite number of homogenized rectangular cells of single design variable in order for the optimization efficiency. However, after the optimization process, we interpolate the discontinuous volume fraction with globally continuous bilinear function in order to enforce the continuity of volume fraction distributions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.2
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• pp.231-243
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• 2016

This study presents the applicability of two-dimensional (2D) flood inundation model by applying to real irrigation reservoir failure with limited available data. The study area is Sandae Reservoir placed in Gyeongju and downstream area of it and the reservoir was failured by piping in 2013. The breach hydrograph was estimated from one-dimensional (1D) hydrodynamic model and the discharge was employed for upstream boundary of 2D flood inundation model. Topography of study area was generated by integrating digital contour map and satellite data, and Cartesian grids with 3m resolution to consider geometry of building, road and public stadium were used for 2D flood inundation analysis. The model validation was carried out by comparing predictions with field survey data including reservoir breach outflow, flood extent, flood height and arrival time, and identifying rational ranges with allowed error. In addition, the applicability of 2D model is examined using different simulation conditions involving grid size, building and roughness coefficient. This study is expected to contributed to analysis of irrigation reservoirs were at risk of a failure and setting up Emergency Action Plan (EAP) against irrigation reservoir failure.

• Analytical Science and Technology
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• v.34 no.2
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• pp.87-98
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• 2021

In this study, we developed the nanoparticle multi-generator by 3D printer fusion deposition modeling (FDM) method that can reliably generate and deliver nanoparticles at a constant concentration for inhalation risk assessment. A white ABS filament was used as the test material, and SMPS was used for concentration analysis such as particle size and particle distribution. In the case of particle size, the particle size was divided by 100 nm or less and 100 to 1,000 nm, and the number of particles concentration, mass concentration, median diameter of particles, geometric average particle diameter, etc were measured. The occurrence conditions were the extruder temperature, the extruding speed of the nozzle, and the air flow rate, and experiments were conducted according to the change of conditions including the manufacturer's standard conditions. In addition, the utility of inhalation risk assessment was reviewed through a stability maintenance experiment for 6 h. As a result of the experiment, the size of the nanoparticles increased as the discharger temperature increased, as the discharge speed of the nozzle increased, and as the air flow rate decreased. Also, a constant pattern was shown according to the conditions. Even when particles were generated for a long time (6 h), the concentration was kept constant without significant deviation. The distribution of the particles was approximately 80 % for particles of 60 nm to 260 nm, 1.7 % for 1 ㎛ or larger, 0.908 mg/㎥ for the mass concentration, 111 nm for MMAD and 2.10 for GSD. Most of the ABS particles were circular with a size of less than 10 nm, and these circular particles were aggregated to form a cluster of grape with a size of several tens to several hundred nm.

• Structural Engineering and Mechanics
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• v.42 no.4
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• pp.571-587
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• 2012

This paper presents results of a numerical analysis performed on a corrugated steel plate (CSP) bridge during a backfilling process. The analysed bridge structure was a box culvert having a span of 12315 mm as well as a clear height of 3550 mm. Obtained calculation results were compared with the experimental ones. The paper is presented with the application of the Fast Lagrangian Analysis of Continua (FLAC) program based on the finite differences method (FDM) to determine behaviour of the soil-steel bridge structure during backfilling. The assumptions of a computational 2D model of soil-steel structure with a non-linear interface layer are described. Parametric analysis of the interface element is also given in order to receive the most realistic calculation results. The method based on this computational model may be used with large success to design calculations of this specific type of structure instead of the conventional and fairly inaccurate analytical methods. The conclusions drawn from such analysis can be helpful mostly for the assessment of the behaviour of steel-soil bridge structures under loads of backfilling. In consideration of an even more frequent application of this type of structure, conclusions from the conducted analysis can be generalized to a whole class of similar structural bridge solutions.

• Geomechanics and Engineering
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• v.5 no.1
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• pp.37-55
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• 2013

An important issue in the design of soil-nailing systems, as long-term retaining walls, is to assess their stability during seismic events. As such, this study is aimed at simulating the dynamic behavior and failure pattern of nailed structures using two series of numerical analyses, namely dynamic time history and pseudo-static. These numerical simulations are performed using the Finite Difference Method (FDM). In order to consider the actual response of a soil-nailed structure, nonlinear soil behaviour, soil-structure interaction effects, bending resistance of structural elements and construction sequences have been considered in the analyses. The obtained results revealed the efficiency of both analysis methods in simulating the seismic failure mechanism. The predicted failure pattern consists of two sliding blocks enclosed by three slip surfaces, whereby the bottom nails act as anchors and the other nails hold a semi-rigid soil mass. Moreover, it was realized that an increase in the length of the lowest nails is the most effective method to improve seismic stability of soil-nailed structures. Therefore, it is recommended to first estimate the nails pattern for static condition with the minimum required static safety factor. Then, the required seismic stability can be obtained through an increase in the length of the lowest nails. Moreover, placement of additional long nails among lowest nails in existing nailed structures can be considered as a simple retrofitting technique in seismic prone areas.

• Nuclear Engineering and Technology
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• v.53 no.5
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• pp.1403-1415
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• 2021

The transient capability of a SP₃ based pin-wise core analysis code SPHINCS is developed and verified through the analyses of the C5G7-TD benchmark. Spatial discretization is done by the fine mesh finite difference method (FDM) within the framework of the coarse mesh finite difference (CMFD) formulation. Pin size fine meshes are used in the radial fine mesh kernels. The time derivatives of the odd moments in the time-dependent SP₃ equations are neglected. The pin homogenized group constants and Super Homogenization (SPH) factors generated from the 2D single assembly calculations at the unrodded and rodded conditions are used in the transient calculations via proper interpolation involving the approximate flux weighting method for the cases that involve control rod movement. The simplifications and approximations introduced in SPHINCS are assessed and verified by solving all the problems of C5G7-TD and then by comparing with the results of the direct whole core calculation code nTRACER. It is demonstrated that SPHINCS yields accurate solutions in the transient behaviors of core power and reactivity.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.5-16
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• 2000

THe purpose of this paper is to suggest the analytical method which can predict lateral nonlinear behavior in non-homogeneous soil using the coefficient of soil resistance and ultimate soil resistance. Those parameters are obtained through back analysis on the base of the results of a series of model tests.Analytical method of Chang is more or less difficult to predict nonlinear behavior in non-homogeneous sol. So, in this study, for the prediction of nonlinear behavior the compositive analytical method which apply the p - y curve to Chang model is suggested. Also, the program is developed to predict nonlinear behavior using the compositive analytical method and it can be used to calculated the deflection, bending moment and soil reaction with DFM in non-homogeneous soil. To establish applicability of the suggested analytical method, the results of model tests and field tests and Pentagon2D finite element program are compared with those of the compositive analytical method. In the analysis values of the coefficient of soil reaction and ultimate soil resistance are also applied to the case of non-homogeneous soil. Lateral defection calculated using the compositive analytical method has been found to be in good agreement with values measured in field and model load tests.

• Journal of the Korean GEO-environmental Society
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• v.14 no.5
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• pp.23-32
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• 2013

This paper presents the effect of pile diameter on the lateral behavior of offshore pile for wind turbine. The material parameters of the soils were estimated through SPT on the Southwestern offshore area in Korea, where the first wind farm is planned. The FDM software, FLAC3D, and LPile were adopted to derive the load-displacement curve, p-y curve, and maximum bending moment at a specified displacement. It was found that the results from softwares significantly differ and the LPile could overestimate the allowable capacity. The maximum bending moment along the pile with 2m diameter could be as large as four times the bending moment with 1m diameter. Similar trend was observed for the allowable lateral capacity.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.2 no.2
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• pp.36-45
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• 2003

This paper presents a way to maximize transmission efficiency and reception ability through transmission diversity technology, which can be adapted to wireless multimedia OFDM (orthogonal FDM) system. The presented method gives a comparative analysis between a case where parameter a for time average is 0.3, i with consideration of channel presumption and two types of rms delayed proliferation, which is 50nsec, 150nsec, for the performance analysis of STTC (Space-Time Trellis Code) using time-space code method which is appropriate for MIMO channel, and performance, in the case, where presumed channel value from long training column section is applied to the according frame in a single frame. The result shows that BER brought SNR improvement of 1.0dB in $10^{-3}$ when a was 0.3 than using only the long training column, and shows an increasement of general performance improvement when the time average factor is used.