• Journal of Korean Society of Forest Science
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• v.97 no.1
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• pp.53-60
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• 2008

This study was carried out to investigate the optimum management system during a overwintering for the production of Pinus densiflora container 2-0 seedlings. The experiment performed between 2005~2006 in a polyethylene film house (PE house) located at Yeoju-Gun in Kyungki-Do. During the winter in the PE house, the difference in maximum day temperature and minimum day temperature was large, and the difference in temperature was detected between the container keeping locations. During the winter season, the maximum day temperatures at the seedling bench in January and February were $32.8^{\circ}C$ and$36.6^{\circ}C$, respectively, whereas those at the ground in January and February were $16.0^{\circ}C$ and $24.4^{\circ}C$, respectively. Water contents of container seedlings was reduced gradually from the beginning the experiment, and reduced rapidly from February to March, and increased rapidly from April. Container seedlings showed different death rate according to the extending of the irrigation cycle. Death rate by one week and two weeks of irrigation cycle was 4.8% and 6.5%, and 38.5% and 49.4% of death rate occurred by three and four weeks of irrigation cycle, respectively. It is suggested that the proper irrigation cycle for P. densiflora 2-0 container seedlings during overwintering is two weeks. When containers placed directly on the ground, the root of container seedlings went out through the drainage of the container, and grew out in the soil. These roots were cut while moving the container to the bench in spring.

• Knowledge Management Research
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• v.21 no.3
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• pp.1-25
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• 2020

This study analyzed key success factors of Korean car-sharing enterprises, Socar and Greencar, and the responsive strategies of Korean car-manufacturing company, Hyundai Motor Group, in the face of emerging sharing economy under the specific economic and regulatory system in Korea. The outcomes of the analysis are as follows. 'Timely market entry' in early startup phase and 'use of external resources' in early growth phase were key success factors common to both Socar and Greencar. However, the differences in the eventual business directions of the two companies also resulted in different key success factors in the expansion phase of their business. For Socar which focused on maintaining its independence and the external growth of B2C business, customer relation marketing and sufficient capital raising were key success factors. For Greencar which became a part of a business group and focused on improving the efficiency of business operations, timely market entry (B2B market) was key success factor. The use of external resources and cooperation with large corporations emerged as key success factors common to both companies in the rapid growth phase. The responsive strategies of the Hyundai Motor Group were collaboration, investment and direct management of DeliveryCar. The short-term goal of the responsive strategy was the operation of test-bed in collaboration with car-sharing company while the mid/long term goal was planning new mobility services by utilizing collected data. Securing opportunities for early market dominance for autonomous car industry was also found to be an important goal.

• Applied Microscopy
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• v.33 no.1
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• pp.79-92
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• 2003

Ultrastructural changes of the pericarp in Citrus reticulata has been investigated during hesperidium abscission. The pericarp was composed of compactly arranged parenchyma cell layers during early stages of fruit development. The outermost exocarp was green and active in photosynthesis. However, cells in the exocarp soon changed into collenchyma cells by developing unevenly thickened walls within a short time frame. As the fruit approached maturation, the chlorophyll gradually disappeared and chloroplasts were transformed into carotenoid-rich chromoplasts. In the mature fruit the exocarp consisted of large, lobed collenchyma cells with primary pit fields and numerous plasmodesmata. The immature mesocarp was a relatively hard and thick layer, located directly under the exocarp. With development, the deeper layers of the exocarp merged into the white, spongy mesocarp. Before separation of the hesperidium from the plant, some unusual features were detected in the plasma membrane of the exocarp cells. The number of small vacuoles and dark, irregular osmiophilic lipid bodies also increased enormously in the exocarp collenchyma after the abscission. They occurred between the plasma membrane and the wall, and invaginated pockets of the plasma membrane containing double-membraned vesicles were also frequently noticed. The lipid bodies in the cytoplasm were often associated with other organelles, especially with plastids and mitochondria. The plastids, which were irregular or amoeboid in shape, contained numerous large lipid droplets, and occasional clusters of phytoferritin, as well as few loosely -oriented peripheral lamellae. Myelin-like configurations of membrane were frequently observed in the vacuoles, as was the association of lipid bodies with the vacuolar membrane. Most vacuoles had an irregular outline, and lipid bodies were often connected to the tonoplast of the vacuoles. The structural changes underlying developmental, particularly to senescence, processes in various hesperidium will be reported in the separate paper.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.487-494
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• 2020

The distance between the source and the detector, the diameter of the detector, and the volume effect of the radiation source result in a change in solid angle at the detector entrance, which affects the determination of detection efficiency by causing a difference in path length within the detector. A typical analysis method for calculating solid angles was useful only for a source (⁶⁰Co) with a simple geometric structure, so in this experiment, the distance between the detector and the source was measured by switching on for up to 25 cm with the reference point of window cap 0.5 cm. In addition, 450 and 1000 ㎖ Marinelli beaker of standard volumetric sources were closely adhered to the detector. For circular point sources co-axial with the detector, the change in the solid angle to the distance from the detector window is equal to half the square radius of the source versus the square radius of the detector, if the resulting relationship of the calculation analysis results in the detector being less than the radius of the source. Since the solid angular difference is 0.5 the result of Monte Carlo is acceptable. The relationship between detector and source distance is shown. Solid angles have been verified to decrease rapidly with distance. Measurement and simulation results for a volumetric source show a difference of ±1.01% from a distance of 0 cm and less than 4 % when the distance is reduced to 5 and 10 cm. It can be seen that the longer distance, the smaller efficiency angle, and the exponential increase in attenuation as the energy decreases, is reflected in the calculation of efficiency. Thus, the detection efficiency has proved sufficient for the use of solid angle and Monte Carlo codes.

• Korean Journal of Veterinary Research
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• v.30 no.4
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• pp.373-381
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• 1990

Endocrine cells in the cardiac and fundic regions of the Korean hedgehog were studied ultrastructurally. Five types of endocrine cells classified as EC, ECL, $D_1$. G and A-like cells were identified in these regions. EC cells contained pleomorphic granules, 170~500nm in diameter, with high electron density and highly dense bodies in a dense matrix. ECL cells were characterized by the presence of round or oval granules, 220~450nm in diameter, with high electron density. Some granules of ECL cells showed a small amounts of contents or empty. $D_1$ cells contained round and relatively small granules, 140~400nm in diameter, with low to moderate electron density. G cells were characterized by the presence of round or oval granules, 200~400nm in diameter, with moderate electron density. Some granules of these cells showed a narrow halo between the limiting membrane and the granular matrix. A-like cells contained round granules, 170~260nm in diameter, With high electron density. The granules of these cells showed homogeneous matrix surrounded by the tight membrane.

• Korean Journal of Materials Research
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• v.4 no.2
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• pp.166-176
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• 1994

Ni base superalloys are composed of solid sohltion hardening elements(Co, Cr. Mo. W and so on) and $\gamma '$ precipitation hardening elements(A1, Ti, Nb, Ta and so on). To Improve the mechanical properties and oxidation resistanre of superalloys, rare earth elements(%r, Hf, Y and so on) are added to the inner substrate, or are used as coating materials. Their pffects on the growth rate and adhes~on of oxide are changed according to the kinds of oxides such as $AI_2O_3$ and $Cr_2O_3$. The effect of yttrium on the oxidation rate, grain size of oxide, internal structure, and crack resistance was investigated for two kinds of Ni-base superalloys. One in AF'115 superalloy containing Hf and the other is MA6000 superalloy containing $Y_2O_3$. They werr owid~zed at high temperature after yttrium surface modification using ion coater. Yttrium coating on the AF115 and MA6000 superalloys results in a marked change in the growth of the inner oxide. For AF115 superalloy, the degree of gram boundary segregation of $Cr_2O_3$, and prefer en^ tial oxidation of Hf are decreased, and the shape of inner oxidation layer was changed from triangle to plate type. For MA6000 superalloy, $Cr_2O_3$ oxide scale was transformed as outer oxidation layer of CrZOI and inner oxidation layer of $Cr_2O_3$.

• Korean Journal of Materials Research
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• v.25 no.5
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• pp.226-232
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• 2015

High temperature plasma coating technology has been applied to recover damaged aluminum dies from wear by spraying pure aluminum and alumina powder. However, the coated mixed powder layer composed of aluminum and alumina often undergoes a detachment from the substrate, making the coated substrate die unable to maintain its expected life span. In this study, in order to increase the bonding strength between the substrate and the coating layer, a pure aluminum layer was applied as an intermediate bond layer. In order to prepare the specimen with variable bond coating conditions, the bond coat layers with a various gun speed from 10 cm/sec to 30 cm/sec were prepared with coating cycle variations ranging from three to nine cycles. The specimen with a bond coat layer coated with a gun speed of 20 cm/sec and three coating cycles exhibited ~13MPa of adhesion strength, while the specimen without a bond coat layer showed ~6 MPa of adhesion strength. The adhesion strength with a variation of bond coat layer thickness is discussed in terms of coating parameters.

• Economic and Environmental Geology
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• v.44 no.5
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• pp.387-397
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• 2011

In this study, we conducted the study of the merits and demerits of the laser flash and the divided-bar methods for measuring the thermal conductivity of rocks and investigated applicability of the divided-bar apparatus which was developed by KIGAM. The laser flash method can measure thermal diffusivity, specific heat capacity, and thermal conductivity of rocks with even small thickness (< ~3 mm) in the high temperature range($25-200^{\circ}C$) in non-contact mode. For the laser flash method, samples must be uniform and homogeneous. In the case of the divided-bar method, the apparatus measures only thermal conductivity of rock samples at the room temperature. We measured thermal conductivities of 12 rock samples with low density and high porosity using two methods. In the laser flash method, there exist potential errors caused by the effect of pulse dispersion and reflection by various minerals and porosity in rock samples; the difference in thermal conductivity values measured on the front surface and the opposite surface ranges from 0.001 to 0.140 W/mK with the standard deviation of 0.003~0.089 W/mK, which seems to be caused by heterogeneity of rock samples. On the contrary, the divided-bar apparatus shows stable thermal conductivity measurements and relatively small measurement errors; the difference in thermal conductivity values, just as we applied to the laser frash method, is 0.001~0.016 W/mK with the standard deviation 0.001~0.034 W/mK. In turn, the divided-bar method can be applied to more thick samples that are more representative of bulk thermal conductivity.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.525-534
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• 2007

The peculiarity of end-expanded soil nailing method(EESNM) is in fixing the wedge-type steel body spreaded by collars and grouting its surroundings by cement milk within soils, after extending hole bottom over drilling hole diameter with top drill bit. The present study was done to establish the effect of this method. Laboratory model test were carried out to investigate the behavior characteristics with the performance of the pull-out test and failure experiment, after preparing soil test box having 1,300mm length, width 1,000mm, and height 1,100mm, and the same experimental condition was set up to compare with the general soil nailing method(GSNM). The pull-out force of about 23 percentage was increased, and the horizontal displacements 1.2 from 9.1 percentage in soil-nailed wall decreased in EESNM compare with GSNM. The axial force acting on nail increased considerably at load level over 7 ton in EESNM and 5 ton in GSNM. The predicted failure line from the maxima analyzed by axial tensile strain located at long distance from soil-nailed wall in EESNM. The EESNM demonstrated the superiority of reinforcement effect in comparison with GSNM from the results above mentioned.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.6-6
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• 2018

본 연구에서는 고문헌에 기록된 도금 재료와 도금법 등을 확인하고 이를 기초자료로 활용하여 매실산을 사용한 금(Au)-수은(Hg) 아말감기법으로 고대 도금(鍍金)기술을 되살리고, 이를 토대로 경주 월지에서 출토된 금동삼존판불을 복원하였다. 먼저, 전통 도금법을 되살리기 위해서, "오주서종박물고변", "확지신편", 조선시대 각종 의궤 등에 공통적으로 기록되어 있는 매실에 주목하고, 매실을 3~4개월 발효 숙성 후 착즙한 뒤 그것을 농축하여 만든 매실산을 도금 실험에 적용하였다. 금아말감 도금을 위하여 월지 출토 금동삼존판불의 바탕소지금속인 청동삼존판불을 구리와 주석 89:11(Cu:6kg, Su:750g)로 합금하여 주물사 주조법으로 복원하였으며, 동일한 합금비로 제작된 $2.3cm{\times}3.5cm$(가로${\times}$세로)의 시편에 사전 실험을 실시하였다. 현대적 산처리 방식에 사용되는 질산과 전통방식으로 사용되는 매실산으로 시편에 산처리 한 후 각각 비교해 보고, 금분과 금박, 상온과 가온에 따른 아말감상태를 비교하는 실험을 진행하였는데, 실험에 사용된 매실산 70%는 pH가 1.94로, 오늘날 산처리에 사용하고 있는 질산 20%와는 차이가 있지만, 청동 시편 실험을 통해 매실산에 20분 정도 담근 뒤 금아말감을 도포 후 24시간 지나 가열($380{\sim}400^{\circ}C$) 했을 때 금도금이 잘 되어, 현대적 방법인 질산처리로 도금을 한 시편과 큰 차이가 없는 것으로 관찰되었다. 사전 실험을 통한 결과를 적용한 월지 출토 금동삼존판불 복원은 청동삼존판불 표면처리, 금-수은 합금 및 도금하기, 도금 후 표면처리의 순서로 진행되었는데, 금과 소지금속의 밀착력을 높이기 위해 표면을 숯을 이용해 탈지한 후 물로 씻어내고 매실산을 도포하여 20분 동안 두어 부식 및 세척을 시행하였다. 금도금을 위한 금-수은아말감은 가온할 때 수은이 증발하는 양을 고려하여 금1 : 수은10 비율로 합금하여 완성하였으며, 금아말감 도포 후 약 24시간 지난 다음, $380{\sim}400^{\circ}C$에 가열하여 수은을 기화시켜 도금작업을 완성하였다. 금아말감도금은 평균적으로 6~7차례 시행하여야 완벽히 도금되지만, 본 연구에서는 단 4차례의 도금만으로 금아말감도금을 완성시켰는데, 이것은 금아말감을 바탕소지인 청동에 도포한 후 24시간 동안 금아말감과 청동과의 반응 시간을 두게한 것이 큰 역할을 한 것으로 보이며, 이는 청동시편을 이용한 실험과 과학적 분석을 통하여 입증하였다. SEM으로 표면을 관찰한 결과 아말감 도포시간이 즉시인 경우 도금이 거의 되지 않은 것을 확인할 수 있었고 36시간이 넘어갈 경우 금 도금층이 불균일하게 관찰되었으므로 도금시간은 12시간~24시간 이내가 적절함을 확인할 수 있었다. EDS로 성분을 분석한 결과 산처리 시간이 20분인 시료의 경우 5 wt% 내외로 수은의 비율이 다른 시료에 비해 낮은 것을 확인할 수 있었다. 실험 및 분석결과 산처리 시간이 20분이고 아말감 도포시간이 24시간일 때 도금이 잘 이루어지므로 이 결과를 토대로 금동삼존판불을 복원하였다. 이번 연구를 통해 도금법에 표면을 세척하고 부식시키기 위해 사용한 물질이 매실산임을 찾아내어 확인할 수 있었는데, 이러한 점 에서 이 연구의 가장 큰 의미는 전통 소재와 기술을 복원한 것으로, 앞으로 매실산을 이용한 금 도금기술은 관련 학계에도 큰 기여를 할 것으로 기대된다.