• Journal of the Korean Vacuum Society
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• v.20 no.1
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• pp.7-13
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• 2011

[ $L1_0$ ]phase FePd nano-dot structures were successfully fabricated on self-organized Fe/Au bilayers. With atomic force microscopy, it is determined that surface morphologies of initially flat Fe/Au bilayer films were agglomerated and transformed their shape into nano-dots structures with increasing annealing temperature. With this bilayer as a template, FePd multilayers were deposited at various temperatures, i.e. $300^{\circ}C$, $350^{\circ}C$, $400^{\circ}C$, and $450^{\circ}C$. Surface morphologies of FePd superlattice had a near resemblance to self-organized bilayer. According to X-ray diffraction results, it is confirmed that $L1_0$ superlattice structures of FePd were obtained from samples which were annealed above $350^{\circ}C$. Results of X-ray photoelectron spectroscopy depth-profile analysis showed that chemical composition is identical to deposition sequence. As a result, without additional etching processes, fabrication of chemically ordered FePd superlattice nano-dots was achieved.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.4 s.70
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• pp.347-360
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• 2005

The fuel rod instability can be occurred because of the axial and cross flow due to the flow anomaly and/or flow redistribution in the lower core plate region of the pressurized water reactor. The fuel rod vibration due to the hydraulic instability is one of the root causes of fuel failure. The verification on the fuel rod vibration and instability is needed for the new fuel assembly design to verify the fuel rod instability. In this study, the fuel rod vibration and stability analyses were performed to investigate the effect of the grid height, fuel rod support condition, and span adjustment on the fuel rod vibration characteristics for the advanced $16{\times}16$ fuel assembly design. Based on the analysis results, the grid height and grid axial elevation of the advanced $16{\times}16$ fuel assembly design were proposed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.402-409
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• 2019

Patients with dementia or elderly patients who can not move at all by themselves are at a high risk of falls and bedsore due to lack of caregivers. In this paper, to solve this problem, we propose an algorithm to determine the patient's lying postures by discriminating the main body parts such as head, shoulders, and hips based on the pressure intensity sensed at regular intervals. A smart mat with a lattice structure in which a pressure sensor is arranged so that the body part can be discriminated irrespective of the physical characteristics has been implemented. It consists of two modules of $7{\times}7$ array size. Each module consists of 49 FSR-406 sensors and independently senses pressure. For each module, the body part corresponding to the upper body or the lower body is sequentially discriminated by using a pressure distribution such as a cumulative pressure sum using a filter. The proposed algorithm can identify five lying positions by examining the inclusion relationship between body parts belonging to layer-1 such as head, shoulder, and hip area.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.9
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• pp.49-54
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• 2008

In this paper, the power added efficiency(PAE) of class F power amplifier is improved by applying a new Photonic Bandgap (PBG) structure on the output of amplifier. The proposed spiral PBG structure is a two-dimensional (2-D) periodic lattice patterned on a dielectric slab that does not require nonplanar fabrication process. This structure bas higher suppression performance at second harmonic. Also, It has a sharp skirt property. This new PBG structure can be applied with class F power amplifier for efficiency improvement. We obtained the PAE of 73.62 % for CDMA applications, and the PAE performance is improved as much as 6.2 % compared with that of a conventional class F power amplifier.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.1
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• pp.9-16
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• 2024

Using the proper orthogonal decomposition (POD) based intrusive reduced order model (ROM), the total degrees of freedom of the structural system can be significantly reduced and the critical time step satisfying the conditional stability increases in the explicit time integrations. In this study, therefore, the changes in the critical time step in the explicit time integrations are investigated using both the POD-ROM and Voronoi-cell lattice model (VCLM). The snapshot matrix is composed of the data from the structural response under the arbitrary dynamic loads such as seismic excitation, from which the POD-ROM is constructed and the predictive capability is validated. The simulated results show that the significant reduction in the computational time can be achieved using the POD-ROM with sufficiently ensuring the numerical accuracy in the seismic analyses. In addition, the validations show that the POD based intrusive ROM is compatible with the Voronoi-cell lattice based explicit dynamic analyses. In the future study, the research results will be utilized as an elemental technology for the developments of the real-time predictive models or monitoring system involving the high-fidelity simulations of structural dynamics.

• Journal of Korea Water Resources Association
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• v.40 no.4
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• pp.313-324
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• 2007

An irregular cell-based numerical model was developed to analyze underground space flooding. In this model, the flow characteristics in underground space were computed by link-node system. Also, the model can simulate the underground flood flow related to the influence of stairs and wall-structures. Empirical discharge formula were introduced to analyze weir-type flow for shopping mall, and channel-type flow for subway railroad respectively. The simulated results matched in reasonable range compared with the observed depth. The dual-drainage inundation analysis model and the underground space flood analysis model were integrated using visual basic application of ArcGIS system. The developed model can help the decision support system of flood control authority for redesigning and constructing flood prevention structures and making the potential inundation zone, and establishing flood-mitigation measures.

• Journal of the Korea Society of Computer and Information
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• v.15 no.12
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• pp.11-18
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• 2010

In this paper, We suggest new strategies on non-interactive agents applied in a prey pursuit problem of multi agent research. The structure of the prey pursuit problem by grid space(Four agent & one prey). That is allied agents captured over one prey. That problem has long been known in interactive, non-interactive of multi agent research. We trying hard to find its own solution from non-interactive agent method on not in the same original environment(circular environment). We used ACS applied Direction vector to learning and decide on a direction. Exchange of information between agents have been previously presented (an interactive agent) out of the way information exchange ratio (non-interactive agents), applied the new method. Can also solve the problem was to find a solution. This is quite distinct from the other existing multi agent studies, that doesn't apply interactive agents but independent agent to find a solution.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.214-219
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• 2016

The grating is the main purpose of drainage in civil engineering, architecture. This study examined the change and stress distribution by simulating three models of Vertical type grating structures that reduced the resistibility in respect of velocity rather than horizontal type grating and to design a grating with the optimal grating gap. The vertical type and horizontal type grating were compared in terms of the maximum stress and strain to identify the better product.

• Journal of IKEEE
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• v.24 no.2
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• pp.392-402
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• 2020

This paper proposes a solar tracking system without photo-sensors. The system can be classified into four modules: Solar Tracking, MPPT, ESS, and Real-Time Monitoring. Nine solar panels, as a basic unit, are adopted with grid structures of different heights to reduce wind influence and to enable solar tracking without photo-sensors. The low-cost MCU implements MPPT method which generates PWM switching signal for boost converter. The unit of ESS consists of three-series and four-parallel lithium-ion batteries in order to enable monitoring for abnormalities in temperature and electrical characteristics of battery. Four MCUs used in the system consists of two AVR Atmega128, and two Raspberry PI, and they exchanges operation informations. Experimental results of the proposed system show the solar tracking performance, the possibility of on-site and remote monitoring and the convenience of maintenance based on IoT technology.

• Journal of the Korean Magnetics Society
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• v.8 no.1
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• pp.1-5
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• 1998

Acicular Fe-Co alloy particles are one of the candidates for high-density magnetic recording media. We examined the effects of Co additions on the magnetic properties of Fe-Co alloy particles by using M$\'{o}$ssbauer spectroscopy, TEM, and X-ray diffraction. Acicular $Fe_n$Co (n=5, 4, 3, 2) alloy particles coated with silica, were prepared by a chemical coprecipitation method and subsequent H $_2$ reduction. The crystal structure was found to be cubic in all n ranges. The lattice constant $a_0$ decreases with increasing Co contents. Analysis of $^{57}Fe$ M\'{o}$ssbauer effect data in terms of the local configurations of Co atoms has permitted the influence of magnetic hyperfine interactions to be monitored.