• Korean Journal of Plant Resources
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• v.29 no.5
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• pp.564-573
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• 2016

This research was performed to develop mass propagation method of round-leaved sundew (Drosera rotundifolia L.) for improving horticultural usefulness. Seeds were collected around Hwaseong-si, Gyeonggi-do in October of 2011 and experimented upon while being dry-stored at 4 ± 1.0℃ (darkness). Seed length of a major and minor axis were 1.58 ± 0.060 and 0.21 ± 0.016 ㎜, respecrively, and weight of 1,000 seeds was 6.24 ± 0.172 ㎎. Seeds were thus classified as ‘dwarf seeds’. Regarding the dormancy type, since round-leaved sundew seeds were dormancy broken and germinated at 20~30℃ under the light condition after wet-chilling treatment for 12 weeks, seeds were estimated to have physiological dormancy. Germination conditions of dormancy broken seeds were found to be 20℃ and light condition (54.7%), but germination decreased at higher temperature. Percent germination (PG), germination energy (GE), mean germination time (MGT) and T₅₀ were effectively improved by chemical treatment such as GA₃ 200 ㎎/L + kinetin 20 ㎎/L and wet-chilling treatment for 14 weeks. In conclusion these optimal conditions were thought to be a useful method for raising seedling uniformly.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.4
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• pp.432-442
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• 2006

Statement of problem: One of common problems associated with dental implant is the loosening of abutment screws that retain the implants. Purpose : This study was performed to investigate the influence of abutment screw length and repeated tightening on screw loosening in dental implant. Material and method: Forty nine Hexplants (13mm length, 4.3mm diameter, Ti grade IV, Warantec. Co. Ltd. Seongnam, Korea) and cementation type abutments(straight abutment) and abutment screws (0.4mm/pitch) were divided into 7 groups, depending on abutment screw length. Each implant and abutment was tightened to 30Ncm by torque controller(MGT50, MARK-10 Inc., USA) and the removal torque values were measured during 10 consecutive closure/opening trials. Results and Conclusion: The results of comparing the removal torque value are as follows : 1. There is no significant difference in the removal torque value between groups in 10 consecutive closure/opening trials (p = 0.97). 2. If the fractured abutment screw is engaged in longer than 2.425 thread length, there is no significant difference in the preload between the fractured abutment screw and the new abutment screw when both are equally tightened to 30 Ncm. 3. The removal torque value in the 1st trial(24.510 Ncm) was lower than that in the 2nd, 3rd, 4th, 5th, 6th, 7th trials and the removal torque value in the 2nd trials(25.551 Ncm) was maximum and was decreased in 1311owing trials. The removal torque value in the 1st trial was significantly lower than that in the 2nd, 3rd, 4th trials and was significantly higher than that in the 8th, 9th, l0th trials(p<0.05). 4. In the 2nd, 3rd, 4th, 5th, 6th, 7th trials, the abutment screw was mainly influenced by settling effect and the higher preload was obtained In the 8th, 9th, l0th trials, the abutment screw was mainly influenced by adhesive wear and the progressively lower preload was obtained.

• The korean journal of orthodontics
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• v.38 no.1
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• pp.5-12
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• 2008

Objective: This study was designed to analyze the primary and secondary stability characteristics of orthodontic mini-screws of tapered design when compared with the cylinder mini-screw. Methods: A total of 48 mini-screws were placed into the buccal alveolar bone of the mandible in 6 male beagle dogs. Comparison was made between tapered and cylinder type mini-screws (Biomaterials Korea, Seoul, Korea). Maximum insertion torque (MIT) was measured using a torque sensor (Mark-10, MGT 50, USA) during installation, and maximum removal torque (MRT) was recorded after 3 and 12 weeks of loading. Results: Taper mini-screws showed a higher MIT value of 22.3 Ncm compared with cylinder mini-screw showing 13.6 Ncm (p < 0.001). The MRT of the taper mini-screw showed a significantly higher value of 9.1 Ncm than those of cylinder mini-screw of 5.7 Ncm at 3-weeks after installation (p < 0.05). However, there was no difference in the MRT value between the taper and cylinder mini-screws at 12 weeks of loading. Conclusions: These results showed that the high insertion torque of the taper mini-screw design increases initial stability until 3 weeks of loading, but does not have any effect on the secondary stability at 12 weeks of loading.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.821-831
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• 2013

As a result of recent research, it is reported that the periodic replacements criterion of rails is able to extend as grinding rail surface and using the continuous welded rail (CWR). In this study, we carried out fatigue tests on existing laid rails. Based on the test results, an S-N curve expressing the remaining life of laid rails at a fracture probability of 50% was obtained using weighted probit analysis suitable for small-sample fatigue data sets. As rails used for testing had different histories in terms of accumulated tonnage, the test data were corrected to average out the accumulated tonnage. We estimated the remaining service lives for laid rails on the urban railway using equations developed in the past to estimate rail base bending stress and that surface irregularities into consideration. Therefore, estimating the remaining service life of laid rails showed that the rail replacement period could be extended over 200 MGT, although it is necessary to remove longitudinal rail surface irregularities at welds by grinding. Also, the fatigue test results under fatigue limit, Haibach's rule appling half slope of S-N curve under the fatigue limit was considered more reasonable than modified Miner's rule for estimating rail fatigue life.

• The Journal of Advanced Prosthodontics
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• v.1 no.1
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• pp.19-25
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• 2009

STATEMENT OF PROBLEM. Primary stability at the time of implant placement is related to the level of primary bone contact. The level of bone contact with implant is affected by thread design, surgical procedure and bone quality, etc. PURPOSE. The aim of this study was to compare the initial stability of the various taper implants according to the thread designs, half of which were engaged to inferior cortical wall of type IV bone(Group 1) and the rest of which were not engaged to inferior cortical wall(Group 2) by measuring the implant stability quotient(ISQ) and the removal torque value(RTV). MATERIAL AND METHODS. In this study, 6 different implant fixtures with 10 mm length were installed. In order to simulate the sinus inferior wall of type IV bone, one side cortical bone of swine rib was removed. 6 different implants were installed in the same bone block following manufacturer s recommended procedures. Total 10 bone blocks were made for each group. The height of Group 1 bone block was 10 mm for engagement and that of group 2 was 13 mm. The initial stability was measured with ISQ value using Osstell $mentor^{(R)}$ and with removal torque using MGT50 torque gauge. RESULTS. In this study, we found the following results. 1. In Group 1 with fixtures engaged to the inferior cortical wall, there was no significant difference in RTV and ISQ value among the 6 types of implants. 2. In Group 2 with fixtures not engaged to the inferior cortical wall, there was significant difference in RTV and ISQ value among the 6 types of implants(P < .05). 3. There was significant difference in RTV and ISQ value according to whether fixtures were engaged to the inferior cortical wall or not(P < .05). 4. Under-drilling made RTV and ISQ value increase significantly in the NT implants which had lower RTV and ISQ value in Group 2(P < .05). CONCLUSIONS. Without being engaged to the inferior cortical wall fixtures had initial stability affected by implant types. Also in poor quality bone, under-drilling improved initial stability.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.38-38
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• 2022

녹비작물은 천연비료로서 화학비료 사용량을 감소시키고 이산화탄소를 흡수해 농업분야에서 온실가스 저감을 위해 사용하고 있다. 녹비작물을 이용하여 지속가능한 친환경 농업의 필요성이 증대되고 있는 실정이다. 화본과 녹비작물은 두과 녹비작물에 비해 탄소 물질의 함량과 biomass가 상대적으로 높아 토양 내 유기물증진을 위한 재배에 적합하다. 이에 화본과 녹비작물 중 하나인 수단그라스의 발아 및 휴면특성 검정을 진행하여 발아 적정조건을 찾아 유기종자 생산기술 개발을 위한 자료로 활용하고자 한다. 본 연구에서는 수단그라스 4품종(GW104G, Cadan99B, TE-Evergreen, Sweet home)을 공시품종으로 사용하였다. 표준발아검사에 따라 각 품종별 종자를 100립씩 3반복 치상하여 10일간 발아검정 진행 후 발아율, 발아세, 평균발아일수, 발아속도를 조사하였다. 첫 번째 실험은 침종시간 및 치상온도별 실험으로 시간별(무처리/5/10/15/20/25hr)로 침종한 후, 생장상(10/20/30/40℃)에 보관하여 정상아 개수를 파악하였다. 두 번째 실험은 휴면타파 실험으로 1~5일 동안 종자를 예냉(무처리/5/10/15℃)과 고온(50℃) 처리한 후, 첫 번째 실험 결과에 따라 발아 최적 조건(침종 20hr, 치상온도 20℃)에서 발아시킨 후 정상아 개수를 파악하였다. 수단그라스 4품종의 치상온도별 발아율은 20℃에서 평균 92±6.9%로 가장 높았으며, TE-evergreen의 경우 치상온도 10℃에서 10시간, 20℃에서 20시간, 30와 40℃에서 15시간 침종한 값이 유의적으로 높은 발아율을 보였다. 수단그라스 4품종의 평균발아일수(MGT)는 침종 20시간과 치상온도 30℃일 때 평균 1.21±1.14일로 가장 빨랐으며 발아속도(GR)는 침종 20시간과 치상온도 20℃의 조건일 때 89.9±5.92로 가장 빨랐다. 수단그라스 4품종의 휴면타파 온도별 발아율은 10℃에서 평균 92±9.3%로 가장 높았다. TE-evergreen의 경우 휴면타파 온도 5, 10, 15℃에서 4~5일 동안 처리한 값이 무처리와 50℃처리에 비해 유의적으로 높은 발아율을 보였다. 수단그라스 발아검사 결과, 20시간 침종 후 20~40℃에서 2~3일간 발아시킬 경우 90%이상의 발아율을 보이므로 파종을 위한 종자 전처리를 할 경우 이와 같은 조건에서 진행하는 것이 바람직 할 것으로 사료된다.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.6
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• pp.720-731
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• 2003

Statement of problem. The importance of fixture design and surface treatment. Purpose. The clinical success of dental in plants is affected by many factors such like as degree of osseointegration, the effective load dispersion for the prostheses, and a lot of attempts have been made to overcome the difficulties. In this study, efforts were made to find the possibility of clinical acceptance of the dental implants of newly designed surface and resorbable blast media surcace. Materials and methods. In this study, two groups of custom-made, screw-shaped implants were prepared. The first with the consisting of Branemark clone design and the other with the new design. These implants were divided into four groups according to the kinds of surface treatment. Four implants($AVANA^{(R)}$, Osstem, Busan, Korea)of each group were installed in twenty rabbits. Group A was consisted of Branemark done implant left as machined, Group B with Branemark clone implants with RBM(Resorbable blast media) surface, Group C with newly designed implants left as machined and Group D with newly designed implants with RBM surface. One of the twenty rabbits died from inflammation and the observation was made for six weeks. Specimens from four groups were observed using scanning electron microscopy with 40, 100, 1000 magnification power and microsurface structures were measured by white-light scanning interferometry for three dimensional surface roughness measurements(Accura $2000^{(R)}$, Intek-Plus, Korea.). Removal torque was measured in 17 rabbits using digital torque gauge(MGT 12R, Mark-10 corp., NY, U.S.A.) immediately after the sacrifice and two rabbits were used for the histologic preparation(EXAKT $310^{(R)}$, Heraeus Kulzer, wehrheim, Germany) of specimens and observed under light microscope. Resonance frequency measurement($Osstell^{(R)}$) was taken with the 19 rabbits at the beginning of the implant fixation and immediately after the sacrifice. Results. Following results were taken from the experiment. 1. The surface of the RBM implants as seen with SEM had rough and irregular pattern with reticular formation compared to that of fumed specimens showing different surface topographies. 2. The newly designed implant with RBM surface had high removal torque value among four groups with no statistical significance. The average removal torque was $49.95{\pm}6.70Ncm$ in Group A, $51.15{\pm}4.40Ncm$ in Group B, $50.78{\pm}9.37Ncm$ in Group C, $51.09{\pm}4.69Ncm$ in Group D. 3. The RFA values were $70.8{\pm}4.3Hz$ in Group A, $71.8{\pm}3.1Hz$ in Group B, $70.9{\pm}2.5Hz$, $72.7{\pm}2.5Hz$ in Group D. Higher values were noted in the groups which had surface treatment compared to the untreated groups with no statistical significance. 4. The results from the histomorphometric evaluation showed a mean percentage of bone-to-implant contact of $45{\pm}0.5%$ in Group A, $55{\pm}3%$ in Group B, $49.5{\pm}0.5%$ in Group C, and $55{\pm}3%$ in Group D. Quite amount of newly formed bone were observed at the surface RBM-treated implants in bone marrow space.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2019.04a
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• pp.50-50
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• 2019

본 연구는 국내 자생 국화과의 산국속 3종을 대상으로 국립백두대간수목원 시드뱅크 내 장기저장 가능성을 확인하고자 수행되었다. 국화과 3종의 종자는 경북 봉화군 춘양면에서 2017년 11월에 채종한 후 선별하였다. 종자는 저장조건별($-20^{\circ}C$, 40%RH /$5^{\circ}C$, 30%RH /$15^{\circ}C$, 15%RH) 12주간 저장하여 2주단위로 발아실험을 실시하였다. 발아실험은 광12시간으로 25/15(12/12h)$^{\circ}C$ 변온조건으로 진행하였다. 종자는 10립 3반복으로 1% Agar배지에 치상하여 유근이 1mm 이상 출현한 것을 발아립으로 정의하였다. 평균발아율(GP)과 발아속도(MGT)를 조사하였다. 구절초를 조건별 2주 저장 후 평균발아율과 평균발아일수를 조사한 결과 $-20^{\circ}C/5^{\circ}C/15^{\circ}C$에서 각각 100%, $4.0{\pm}0.09$일 / $96.7{\pm}3.33%$, $3.7{\pm}0.08$일 / $93.3{\pm}3.33%$, $3.6{\pm}0.11$일로 조사 되었으며 12주 저장 후 100%, $4.1{\pm}0.27$일 / $96.7{\pm}3.33%$, $4.4{\pm}0.21$일 / $96.7{\pm}3.33%$, $3.7{\pm}0.13$일로 조사되어 저장 후 발아율의 감소를 보이지 않았으며 $5^{\circ}C$ 저장에서 평균발아일수가 길어지는 경향을 보였다. 포천구절초의 경우 $-20^{\circ}C/5^{\circ}C/15^{\circ}C$에서 각각 $96.7{\pm}3.33%$, $4.4{\pm}0.36$일 / 100%, $4.2{\pm}0.09$일 / $93.3{\pm}6.67%$, $4.1{\pm}0.22$일로 조사 되었으며 12주 저장 후 $96.7{\pm}3.33%$, $4.2{\pm}0.30$일 / $96.7{\pm}3.33%$, $4.2{\pm}0.15$일 / 100%, $4.0{\pm}0.09$일로 조사 되어 저장 전 후 차이를 확인 할 수 없었다. 한라구절초의 경우 $-20^{\circ}C/5^{\circ}C/15^{\circ}C$에서 각각 $93.3{\pm}3.33%$, $3.4{\pm}0.10$일 / $93.3{\pm}3.33%$, $3.7{\pm}0.08$일 / $93.3{\pm}6.67%$, $3.8{\pm}0.02$일로 조사 되었으며 12주 저장 후 $96.7{\pm}3.33%$, $4.0{\pm}0.21$일 / $96.7{\pm}3.33%$, $4.2{\pm}0.03$일 / $96.7{\pm}3.33%$, $3.8{\pm}0.09$일로 조사되어 발아율이 소폭 상승하는 경향을 보였다. 산국속 3종의 종자는 12주 저장 후 기간 및 저장조건에 따른 평균발아율과 발아속도에서 유의적인 차이를 나타내지 않았다. 이상의 결과로 산국속 3종 구절초, 포천구절초, 한라구절초의 종자는 저장기간 및 조건에 대해 민감한 반응을 보이지 않아 장기저장이 가능한 진정종자(Orthodox seed)로 판단된다.

• Journal of Korean Society of Forest Science
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• v.112 no.2
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• pp.173-187
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• 2023

The forest protection policies implemented in South Korea have resulted in the significant accumulation of forest. Moreover, the associated public interest has also been closely evaluated. As forests mature, there arises a need for forest management (FM) practices, such as thinning and harvesting. It is therefore essential to perform a scientific analysis of the long-term effects of FM. In this study, conducted in Mt. Gariwang, the effect of FM on forest succession and wood production (WP) were evaluated based on changes in aboveground biomass (AGB) using the LANDIS-II model. The FM consists of three scenarios (Selection, Shelterwood, and Two-stories), characterized based on the harvest intensity, frequency, and period. The model was applied to changes in the forest over 200 years. All scenarios show that the total AGB decreased immediately after thinning and harvesting. However, AGB recovery time differed among scenarios, with recovery to preharvest level occurring from 15 to 50 years after harvest; further, after 200 years, harvested forests had a greater total AGB than forests without FMs In particular, the changes in AGB of each species was different depending on its shade tolerance. The AGB of currently dominant shade-intolerant and mid-tolerant species decreased dramatically after harvesting. However, shade-tolerant species, dominant in the understory, continued to grow but were not harvested due to their small size. The cumulative WP for each scenario was estimated at 545.6, 141.6, and 299.9 tons/ha in Selection, Shelterwood, and Two-stories, respectively. The composition of WP differed according to harvest intensity and period. Most WP originated from shade-intolerant and mid-tolerant species in the early period. Later, most WP was from shade-tolerant species, which became dominant. The modeling approach used in this study is capable of analyzing the long-term effects of FM on changes in forests and WP. This study can contribute to decision making to guide FM methods for a variety of purposes, including WP and controlling forest composition and structure.