• Journal of the Korean Geotechnical Society
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• v.35 no.10
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• pp.33-45
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• 2019

In this study, in order to recycle a large amount of rocks and weathered mudstones produced by civil engineering projects such as railways and highways, as materials for roadbeds or embankment materials, circumferential specimens with a diameter of 5 cm and a height of 10 cm were made. A mudstone that weathered rapidly during rainfall was collected from Pohang construction sites. The weathered mudstone passed through a 2 mm sieve. It was prepared with the cement ratio, the sand ratio, curing condition and curing days. Three specimens were prepared according to each condition and then the unconfined compressive test, durability test and SEM analysis were performed to evaluate the engineering properties of the cemented soil. In the case of 28 days cured specimen, the strength of under-water cured specimens was 32-55% and the durability index was about 15% higher than air cured specimens. In addition, when the CR increased from 8% to 16%, the unconfined compressive strength (UCS) of pure mudstone cemented soil under water increased by about 1.6 times and the durability index increased by about 1.9 times. When the SR increased from 0% to 50%, the UCS of the specimen with SR = 10% was slightly less than or equal to specimen with SR = 0%. Then, as the SR became 30-50%, the UCS increased up to 51%. Unlike the UCS, the durability index increased continuously as the SR increased. As a result of SEM analysis, when SR was 50% rather than SR = 0%, the contact between sand particles increased and they were connected to each other. Such contact between these particles resulted in the increase of strength.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.992-1001
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• 2023

OWEC (Overtopping Wave Energy Converter) is a wave power generation system using the wave overtopping. The performance and safety of the OWEC are affected by wave characteristics, such as wave height, period. To mitigate this issue, optimal OWEC designs based on wave characteristics must be investigated. In this study, the environmental conditions along the Ulleungdo coast were used. The hydraulic efficiency of the OWEC was calculated using SPH (Smoothed Particle Hydrodynamics) by comparing 4 models that changed the substructure. As a result, it was possible to change the substructure. Through design optimization, a new truss-type structure, which is a substructure capable of carrying the design load, was proposed. Through a case study using member diameter and thickness as design variables, structural safety was secured under allowable stress conditions. Considering wave load, the natural frequency of the proposed structure was compared with the wave period of the relevant sea area. Harmonic response analysis was performed using wave with a 1-year return period as the load. The proposed substructure had a reduced response magnitude at the same exciting force, and achieved weight reduction of more than 32%.

• Korean Journal of Crystallography
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• v.16 no.2
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• pp.128-137
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• 2005

We report on the phase transitions of the perovskite nanostructures made by sol-gel template synthesis. The lead titanate ($PbTiO_{3}$) nanostructures were prepared with a chelate sol-gel of titanium tetrabutoxide ($Ti(O^{i}Pr){4}$) and lead acetate ($Pb(OAc)_{2}-3H_{2}O$). $Whatman^{\circledr}$ anodisc membranes (with about 200 nm pore size) served as the template. The template was dipped into the sol, allowed to air dry, and then calcined at $650^{\circ}C$. We have characterized the temperatures of the phase transitions in the $PbTiO_{3}$ nano-structures using DSC, DTA, and second harmonic generation (SHG).

• Korean journal of applied entomology
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• v.22 no.3 s.56
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• pp.198-202
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• 1983

A mosaic disease of gladiolus has been commonly observed with an infection rate of $43.3\%$ in the field. Bean Yellow Mosaic Virus(BYMV) produced veinal spreading lesions on Cheonopodium amaranticolor, veinal necrosis and severe leaf distortion on Phaseolus vulgaris 'Scotia' and mosaic on Vi cia faba. Cucumber Mosaic Virus(CMV) produced local lesions on C. amaranticolor, mosaic symptoms on Nicotiana glutinosa and Cucumis sativus. BYMV and CMV were transmitted by the green peach aphid. Purified BYMV and CMV had a typical maximum absorption at 260nm. In agar gel diffusion test, BYMV and CMV gave positive reaction with their homologous antiserum. The size of BYMV was 750nm in length, and CMV was 30nm in diameter.

• Applied Biological Chemistry
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• v.50 no.3
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• pp.160-166
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• 2007

This study was performed to analyze the molecular structural and physical properties changes of modified rice starch, which particle structure was broken using high impact planetary mill and ultra fine pulverizing techniques. The average diameter and specific surface area of rice starch after pulverization decreased 20% and increased 25%, respectively. Low molecular substances content in rice starch using GPC (gel permeation chromatography) increased from 36.5% to 59.5% after pulverizing of rice starch. Damaged starch contents in rice starch also increased from 16.4% to 99.2% after pulverizing of rice starch. Water holding capacity, solubility and transmittance of rice starch after pulverization increased compared to those of control. Apparent viscosity value of rice starch after pulverization decreased to 7% in control based on $30^{\circ}C$ and 20 RPM conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.10
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• pp.1824-1832
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• 1992

This study investigated the compressive Young's modulus and the impactinduced damage of CFRP angle-ply laminate under same impact energy condition. The specimens of angle-ply laminate composites [0.deg.$_{6}$/ .theta..deg.$_{10}$/ 0.deg.$_{6}$] with .theta..deg. =30.deg., 45.deg., 60.deg. and 90.deg. were employed, and damaged by steel balls of diameter of 5mm and 10mm propelled by air gun type impact testing machine. The impact damaged zones were observed through a scanning acoustic microscope(SAM), and their cross-sections were observed through a scanning electron microscope(SEM). The compressive Young's moduli before and after impact were measured, and compared with the theoretical values calculated. The results obtained were as follows: (1) The damage areas on the interfacial boundaries showed more severe change on the back side interface than on the impact side interface with increasing ply-angle. (2) The damage areas on the interfacial boundaries became larger with increasing impact velocity or ply-angle. (3) The impact damaged zone showed the delamination on the interfacial boundaries and transverse cracks inside laminas. (4) The impact damaged zone was affected by the impactor size and speed or ply-angle under same impact energy condition. (5) Compressive Young's moduli before and after impact were lower than theoretical value, but showed a similar change according to ply-angle. (6) Compressive Young's moduli after impact were higher than those before impact, but there was no remarkable change in apparent compressive modulus after impact.t.act.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.191-194
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• 2002

토양증기추출(Soil Vapor Extraction)법을 이용하여 대표적 휘발성 NAPL (Non-aqueous phase liquid)인 TCE (trichloroethylene)와 toluene을 토양으로부터 제거하는 칼럼 실험을 실시하였다. 토양특성 및 증기추출 조건들이 정화효율에 미치는 영향을 규명하는데, 균질한 Ottawa sand와 실제 오염지역의 토양들을 직경 2.5cm, 길이 30cm인 유리 칼럼이 충진시켰으며, 빨갛게 염색된 TCE 또는 toluene 4 g이 주입되었다 공기 유량계를 설치하여 0.03L/min의 일정한 속도로 공기가 주입되도록 하고, 퍼지장치를 설치하여 주입 공기의 습윤도를 99% 이상으로 유지하였다. 가스크로마토그래피로 유출 가스 농도를 분석하였다. Ottawa sand로 충진된 칼럼실험에서는 매질의 입자크기, 함수율, 토양 내 오염물 체류시간 등을 변화시켜 실험을 반복하였다. TCE로 오염된 세립질 Ottawa sand 칼럼실험에서 유출 공기의 최대 농도는 조립질 Ottawa sand 칼럼의 유출 농도보다 약 20% 정도 감소하였고, 오염지역의 실제토양 칼럼실험에서는 최대유출농도가 조립질 Ottawa sand 칼럼의 농도보다 약 50% 감소하였으나, 20 liter공기 주입 후부터는 모두 비슷한 농도감소 현상을 나타내었으며, 초기 주입량의 90 % 이상이 제거되었다. 함수율증가에 따른 유출공기의 농도 감소는 거의 나타나지 않았으며, TCE 주입 후 7일 동안 방치하였다가 SVE를 실시한 칼럼 실험에서도 잔류하는 TCE의 양이 약간 증가하였지만 20 liter 공기 추출 후에는 초기 주입량의 90% 가, 40 liter공기 추출 후에는 98% 이상이 제거되었다. Toluene으로 오염된 칼럼 실험에서도 TCE와 비슷한 제거 경향을 나타냈으며 200 liter 공기 추출 후에는 오염물 초기 주입량의 98% 이상이 제거되었다. 본 실험 결과로부터 증기추출법을 이용한 TCE, toluene 정화 효율성이 규명되었으며, 휘발성 NAPL로 오염된 실제 토양을 복원하기 위한 SVE법의 적용가능성을 확인할 수 있었다.

• Korean Journal of Microbiology
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• v.20 no.1
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• pp.41-51
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• 1982

The soil microfungal flora of the paddy fields in Korea was investigated at four different seasons. The fungi were isolated by the dilution plate method from soil samples of two selected sites around Seoul. A total of 85 isolates was obtained as pure cultures and 30 species 13 genera were identified and 11 isolates were unidentified. Among these, 6 species of Deuteromycetous fungi, Penicillium spp., were found to be dominant in paddy field soils. Penicillium funiculosum, P. piceum, P. roqueforti and P. verruculosum were described as new to Korea. P. piceum has remarkable characteristics of the typical columnar head similar to a compact spruce-like evergreen tree. P. requeforti has penicilli variable in pattern with compactly branched metulae and appressed or Paecilomyces variotii were also described. In addition, Zygorhynchus moelleri, a remarkably dominant Zygomycete in Korean paddy soils, produces subglobose sporangia with oval columella and dark colored zygospores of about $35\mu\textrm{m}$ in diameter.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.2
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• pp.129-142
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• 2016

The underground cavity known as one of the reasons of ground surface settlement is a discontinuous character. Therefore, it is limited to analyze with continuum analysis. In this research, The spherical underground cavity affecting the ground surface settlement is studied with Discrete Element Method. Ground properties, depth and diameter of the spherical underground cavity are chosen as factors of the spherical underground cavity and the effect of the each factor variations on the ground surface settlement is analyzed. Relative depth to the diameter of the spherical underground cavity is also studied. The result of the research suggests the basis of underground cavity collapse prediction and standard of support.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.557-562
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• 2018

High molecular weight sodium alginate (HMWSA)/low molecular weight sodium alginate (LMWSA) microcapsules containing phytoncide oil were prepared with different LMWSA contents. The effects of the stirring rate and ratio of HMWSA/LMWSA on the diameter and morphology of the phytoncide/alginate beads were investigated by optical microscopy and the release behaviors of phytoncide oil from the phytoncide/alginate beads were characterized by UV/Vis. spectrophotometry. The mean particle size of the phytoncide/alginate beads decreased with increasing stirring rate and concentration of the calcium chloride solution. The surface morphology of the phytoncide/alginate beads changed from smooth surfaces to skin-like rough surfaces with increasing LMWSA content. These results were due mainly to the increased hydrophilic groups at the bead surface, resulting in an increase in the release rate of phytoncide oil in the phytoncide/alginate beads.