• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.64.1-64.1
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• 2013

The point spread function (PSF) of an optical system is in general defined as a two-dimensional intensity distribution which results from a single point source at infinity. It is an important key for the evaluation of the optical performance of an astronomical telescope. The PSFs of the soft X-ray telescope (SXT) aboard Yohkoh were measured in a wide range of the field-of-view under the in-flight configuration at White Sands Missile Range prior to launching the satellite. It has been known that the SXT PSF has a sharp peak at the core and the intensity drops very fast as it goes distant from the center. Due to the combination of this sharp peak at the PSF core and the effect of undersampling by a large pixel size, a carefully designed method is requested in the examination of the PSF data. The pattern of the SXT PSF is determined by the fitting of a mathematical functional form to the pre-launch experimental data. The elliptical Moffat function has been adopted for the evaluation of the SXT PSF. It is revealed from our study that the SXT PSF shows a peculiar characteristics, and thus a careful consideration on the undersampling effect and also a proper choice of statistics are necessary for the determination of the best fit function of the PSF. Details on the on- and off-axis SXT PSF in the field-of-view will be introduced and discussed in our presentation.

• Steel and Composite Structures
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• v.33 no.5
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• pp.663-679
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• 2019

In this work, a simple four-variable trigonometric shear deformation model with undetermined integral terms to consider the influences of transverse shear deformation is applied for the dynamic analysis of anti-symmetric laminated composite and soft core sandwich plates. Unlike the existing higher order theories, the current one contains only four unknowns. The equations of motion are obtained using the principle of virtual work. The analytical solution is determined by solving the eigenvalue problem. The influences of geometric ratio, modular ratio and fibre angle are critically evaluated for different problems of laminated composite and sandwich plates. The eigenfrequencies obtained using the current theory are verified by comparing the results with those of other theories and with the exact elasticity solution, if any.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.240-241
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• 2007

연자성 분말의 독특한 특성은 3D 등방성 강자성체 이며, 이 때문에 3차원적 자속(flux)를 활용할 수 있어 전기 강판(sillicon steel)에 비해 3차원 성형시 유리한 장점을 가지고 있다는 점이다.[1] 따라서 본 논문에서는 연자성 분말 (Soft Magnetic Composites)의 3차원 성형시 각 성형 형태에 따른 압분 시료의 전기적, 기계적 특성에 대한 연구를 하였다. 연자성 분말의 코어 형상을 크게 ' '형으로 구분하여 압분 코어를 만든 후 압분 코어의 Overhang 각도 및 코어 Teeth의 길이에 따른 파라미터에 변화를 주어 철손 및 경도, 밀도를 측정 하였다. 이 논문에서 우리는 3차원 코어 성형시 전기적, 기계적 특성이 가장 우수한 코어 성형 조건을 연구해 낼 수 있었다.

• Korean Journal of Materials Research
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• v.15 no.2
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• pp.106-111
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• 2005

Effects of stainless steel-making dusts and binder content on compacting $density(\rho)$ and magnetic properties were evaluated. Cores compacted with the mixture of pure Fe powders, $5wt.\%$ dusts and $0.25wt.\%$ binder showed good AC magnetic properties. For example, permeability$({\mu}a)$ and core loss(P) of the cores containing $5wt.\%$ dusts at 500 kHz were 62 and $4008\;{\mu}W/cm^3$, respectively. These properties are almost equivalent to those of competitor's products (i.e, Ancorsteel TC 80 produced by $H\ddot{o}gan\ddot{a}s$ Corp.). The powdered cores obtained from the present work are expected to apply for high-performance soft magnetic components such as normal mode choke filter and pulse transformer.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.918-919
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• 2008

This paper deals with the DC-DC converter with high efficiency using the minimum reactor. In this paper, the proposed convert uses the air core reactor for ZCS(zero currunt switching) which can minimize the core losses and removes the over switching losses by soft switching. The proposed converter is verified by the modes analysis and computer simulation to prove the theoretical background and adequacy.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.7
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• pp.35-40
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• 2020

This work is concerned with various planar deformations of an isotropic sandwich beam, which generally consists of three layers: two stiff skin layers and one soft core layer. When one layer of the sandwich beam is modeled as a beam, the variational-asymptotic method is rigorously used to construct a zeroth-order beam model, which is similar to a generalized Timoshenko beam model capable of capturing the transverse shear deformations but still carries out the zeroth-order approximation. To analyze the planar sandwich beam, the sum of the energies of the two skin layers and one core layer is then formulated with different material and geometric properties and represented by a universal beam model in terms of the core-layer kinematics through interface displacement and stress continuity conditions. As a preliminary validation, two extreme examples are presented to demonstrate the capability and accuracy of this present approach.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.3
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• pp.149-158
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• 2024

Piloti-type structures with vertical irregularity are vulnerable to earthquakes due to the soft structure of the first story. Structural characteristics of buildings can significantly affect the seismic loss function, calculated based on seismic fragility, and therefore need to be considered. This study investigated the effects of the number of stories and core locations on the seismic loss function of piloti-type buildings in Korea. Twelve analytical models were developed considering two variations: three stories (4-story, 5-story, and 6-story) and four core locations (center core, x-eccentric core, y-eccentric core, and xy-eccentric core). The interstory drift ratio and peak floor acceleration were assessed through incremental dynamic analysis using 44 earthquake records, and seismic fragility was derived. Seismic loss functions were calculated and compared using the derived seismic fragility and repair cost ratio of each component. The results indicate that the seismic loss function increases with more stories and when the core is eccentrically located in the piloti-type structure model. Therefore, the uncertainty due to the number of stories and core location should be considered when deriving the seismic loss function of piloti-type structures.

• Advances in robotics research
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• v.2 no.1
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• pp.69-97
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• 2018

Innovation is considered as key to ensure continuous advancement and firm progress in any field. Robotics, with no exception, has gained triumph and approval based on its strength to address divers range of applications as well as its capacity to adapt new ways and means to enhance its applicability. The core of novelty in robotics technology is the perpetual curiosity of human beings to imitate natural systems. This desire urges to continuously explore and find new feet. In the past, contemporary machines, in different shapes, sizes and capabilities, were developed that can perform variety of tasks. The major advantage of these developments was the ability to exhibit superior control, strength and repeatability than the corresponding systems they were replicating. However, these systems were rigid and composed of hard an underlying structure, which is a constraint in bringing into being the compliance that exists in natural organisms. Inspiration of achieving such compliance and to take the full advantage of the design scheme of biological systems compelled researchers and scientists to develop systems avoiding conventional rigid structures. This ambition, to produce biological duos, needs soft and more flexible materials and structures to realize innovative robotic systems. This new footpath to craft biological mockups facilitates further to exploit new materials, novel design methodologies and new control techniques. This paper presents an appraisal on such innovative comprehensions, conferring to their design specific importance. This demonstration is potentially useful to prompt the novelty of soft robotics.

• Research in Plant Disease
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• v.29 no.1
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• pp.72-78
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• 2023

In September 2021, gray-to-brown discoloration and expanding water-soaked lesions were observed on the outer and inner layers and the core of kimchi cabbage (Brassica rapa subsp. pekinensis) in fields located in Samcheok, Gangwondo, Korea. A bacterial strain designated as KNUB-02-21 was isolated from infected cabbage samples. Phylogenetic analysis based on the sequences of the 16S rRNA region and the dnaX, leuS, and recA genes confirmed that the strain was affiliated with Pectobacterium versatile. Additionally, the biochemical and morphological profiles of the isolate were similar to those of P. versatile. Based on these results, the isolate was identified as a novel strain of P. versatile. Healthy kimchi cabbage slices developed soft rot upon inoculation with P. versatile KNUB-02-21 and exhibited symptoms similar to those observed in the diseased plants in fields. The re-isolated strains were similar to those of P. versatile. Prior to our study, P. versatile as the causative pathogen of kimchi cabbage soft rot had not been reported in Korea.

• Journal of the Korean Magnetics Society
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• v.25 no.1
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• pp.4-9
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• 2015

This study was carried out to investigate a influence of humidity variation (%) on the magnetic properties and the surface flaws in the fabrication of Fe-based $Fe_{78}Si_9B_{13}$ amorphous alloy ribbon by Planar Flow Casting process. As a result, the size of the air pocket and the droplet which is observed in the contact surface and the free face of the amorphous alloy ribbon becomes large when the humidity increases and the size highly increases with the surface roughness at the same time. Especially, the surface roughness value which is made in the 65 % of the humidity is the lowest in the contact surface ($Ra=0.60{\mu}m$, $Rz=3.11{\mu}m$) and the free face ($Ra=0.47{\mu}m$, $Rz=3.00{\mu}m$). Also, in case of the soft magnetic property of the magnetic core which is made with the toroidal core of $23(OD)^*20(ID)^*20(H)$ size, in the sample of the amorphous alloy ribbon which is made in 65% of the humidity, the most excellent value is gained as $B_s(B_{700})=1.055T$, $H_c=0.083Oe$, permeability = 1,197 and core loss = 0.276W/kg.