• Maxillofacial Plastic and Reconstructive Surgery
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• 제34권6호
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• pp.398-403
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• 2012

Purpose: Mandible resection and discontinuity defect created lead to aesthetic and functional problems. The iliac crest bone graft exhibits relative ease for bone harvesting, possibility of two team approach, ability to close the wound primarily, large amount of corticocancellous bone and relatively few complications. Whereas the use of free vascularized flaps has donor site morbidity and worse-fitting bone contour, the use of nonvascularized iliac bone graft has advantages in the operation time and patients' recovery time. So, nonvascularized iliac bone graft could be an attractive option. Methods: Twenty-one patients (M:F=1:1.1) underwent iliac crest bone harvesting for reconstruction of mandibular discontinuity defect (mean length : $61.6{\pm}17.8$ mm), from May 2005 to October 2011 at the Department of Oral and Maxillofacial Surgery in Kyungpook National University. The average age was $44.1{\pm}16.4$ years and the mean follow up periods was $28.2{\pm}22.7$ months. Bone resorption rate, according to age, sex, primary lesion, location and distance of defect, type of fixation plate, time of graft and pre-operative radiation therapy, were measured in each patient. Results: The mean bone resorption rate was $16.1{\pm}9.0%$. Bone resorption rate was significantly increased in mandibular defect that is over 6 cm in size (P=0.015, P<0.05) and the cases treated pre-operative radiation therapy (P=0.017, P<0.05). All was successfully fixed and maintained for the long-term follow-up. There were a few donor site complications and almost all patients were shown favorable outcome without severe bone resorption in this study. Conclusion: The nonvascularized iliac bone graft seems to be a reasonably reliable treatment option for reconstruction of mandibular discontinuity defects.

• The Journal of Korean Academy of Prosthodontics
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• 제43권2호
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• pp.176-190
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• 2005

Statement of problem. The current trend in prosthodontics is the adoption of a conservative approach to preparing dental prostheses by minimizing the amount of sound tooth structure removal during preparation. Purpose. The major disadvantage of the adhesion bridge is the inherently poor resistance to dislodgement that its use in areas subjected to high occlusal load is limited. The purpose of this study was to compare the dislodgement resistance of $Bio-pin^{(R)}$, conventional 3-unit and adhesion bridges. Material and methods. The experimental groups were classified as follows : Group I : 3-unit bridge cemented using $Super-Bond^{(R)}$ C&B Group II : Adhesion bridge cemented using $Super-Bond^{(R)}$ C&B Group III : $Bio-pin^{(R)}$ design adhesion bridge without incorporation of $Bio-pin^{(R)}$ (cemented using $Super-Bond^{(R)}$ C&B) Group IV-1 : $Bio-pin^{(R)}$ retained adhesion bridge incorporating a single $Bio-pin^{(R)}$ (cemented using $Super-Bond^{(R)}$ C&B) Group IV-2 : $Bio-pin^{(R)}$ retained adhesion bridge incorporating a single $Bio-pin^{(R)}$ (cemented using $Panavia^{(R)}$ F) Group V : $Bio-pin^{(R)}$ retained adhesion bridge incorporating two $Bio-pins^{(R)}$ (cemented using $Super-Bond^{(R)}$ C&B) Results. The results of this study were as follows : 1. Significant differences in dislodgement resistance of the restorations were found between Group I, Group II and Group III (p<0.05). No significant differences in dislodgement resistance of the restorations were observed between Group I Group IV-1 and Group V. However, there were significant differences in dislodgement resistance between Group II and the other groups (p<0.05). 2. No significant differences in dislodgement resistance of the restorations were observed between GroupIV-1 and GroupIV-2, both of which utilized a single $Bio-pin^{(R)}$. However, significant differences were observed when Group III was compared to either GroupIV-1 or Group V (p<0.05). 3. No significant differences in dislodgement resistance relative to the type of dental cements used were found. Conclusion. From the above results, it is concluded that the dislodgement resistance of $Bio-pin^{(R)}$ bridge restorations utilizing a single $Bio-pin^{(R)}$ is similar to that of a conventional 3-unit bridge. The results also suggest that $Bio-pin^{(R)}$ bridge restorations using a single $Bio-pin^{(R)}$ are a viable alternative to the conventional 3-unit bridge when minimal removal of sound tooth structure and fulfillment of both function and esthetic aspects are considered.

• Journal of Korean Society of Forest Science
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• 제108권4호
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• pp.484-492
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• 2019

The aim of the present study was to compare the cold tolerance of seven different types of trees growing in southern Korea to select evergreen broad-leaved trees that can be used as street trees in large land areas experiencing climate change. The trees compared were the thorn tree, Cinnamomum camphora, Camellia japonica, Machilus thunbergii, Dendropanax morbifera, Daphniphyllum macropodum Miq., Quercus glauca Thunb., and Raphiolepis indica. When the trees were subjected to low temperature treatment, their electrolyte elution volume values appeared to increase with the decreases in the treatment temperature. The analysis of the cold tolerance of each type of tree was based on the estimated temperatures in the following order: C. japonica (-11.586℃) > R. indica (-9.348℃) > Q. glauca (-8.719℃) > M. thunbergii (-8.090℃) > D. macropodum (-7.409℃) > D. morbifera (-7.085℃) > C. camphora (-6.995℃). The relative cold tolerance difference found in the seven tree species was more than 5℃, as evaluated previously. In the Lauraceae family, the difference in cold tolerance was more than 2℃, even in the same species. The analysis showed that trees with excellent cold tolerance included Q. glauca Thunb., C. japonica, R. indica, and the thorn tree. This knowledge is required for the evaluation of the possibility of the survival of trees under cold temperature conditions in cities.

• Journal of Radiation Protection and Research
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• 제26권1호
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• pp.7-12
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• 2001

Sintered LiF:Mg,Cu,Na,Si thermoluminescence (TL) pellets were developed for application in radiation dosimetry. In the present study, the TL dosimetric properties of LiF:Mg,Cu,Na,Si TL pellets have been investigated for emission spectrum, dose response, energy response, and fading characteristics. LiF:Mg,Cu,Na,Si TL pellets were made by using a sintering process, that is, pressing and heat treatment from TL powders. Photon irradiations for the experiments were carried out using X-ray beams and a $^{137}Cs$ gamma source at the Korea Atomic Energy Research Institute (KAERI). The average energies and the dose were in the range of 20-662 keV and $10^{-6}-10^{-2}\;Gy$, respectively. The glow curves were measured with a manual type TLD reader(System 310, Teledyne) at a constant nitrogen flux and a linear heating rate. For a constant heating rate of $5^{\circ}C\;s^{-1}$, the main dosimetric peak of glow curve appeared at $234^{\circ}C$, the activation energy was 2.34 eV and frequency factor was $1.00{\times}10^{23}$. TL emission spectrum is appeared at the blue region centered at 410 nm. A linearity of photon dose response was maintained up to 100 Gy. The photon energy responses relative to $^{137}Cs$ response were within ${\pm}20%$ at overall photon energy region. The fading of TL sensitivity of the pellets stored at the room temperature was not found for one year.

• Korean Journal of Agricultural Science
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• 제39권4호
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• pp.459-466
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• 2012

The objective of this study is to observe growth pattern of grand rapids(lettuce) according to different dexperimental conditions for minimizing its growth period such as composition of nutrient, irradiation time of light source and cultivation mode. The culture of water spray type using seeds of grand rapids was performed during growth period of total 50 days. Experimental conditions consist of five compositions of nutrient (PW 0.5 mS/cm, PW 1.0 mS/cm, PY 0.5 mS/cm, PY 1.0 mS/cm, PW 2.0 mS/cm) and three irradiation times of light source (12h(on) / 12h(off), 18h(on) / 06h(off), 24h(on) / 00h(off)). Illumination was adjusted to ratio of 7:1:1 of red, blue and white color, respectively. Indoor environmental condition for cultivating grand rapids is as follows: temperature (19-$22^{\circ}C$), relative humidity (60-70%) and carbon dioxide (1,000-1,200 ppm). The data were obtained from five iteration tests. The maximum growth level was observed in the experimental condition of 18 hr(on) / 06 hr(off) and PY 1 mS/cm for 1st week of cultivation period, 24 hr(on) / 00 hr(off) and PY 1mS/cm for 2nd week of cultivation period, and 24 hr(on) / 00hr(off) and PW 1 mS/cm for 3rd week of cultivation period, respectively. On the contrary, the minimum growth level was observed in the experimental condition of 18 hr(on) / 06 hr(off) and PW 0.5 mS/cm for 1st week of cultivation period, 12 hr(on) / 12 hr(off) and PW 0.5 mS/cm for 2nd week of cultivation period, and 12 hr(on) / 12 hr(off) and PY 0.5 mS/cm for 3rd week of cultivation period, respectively. Based on the results obtained from this study, it is concluded that the growth level of grand rapids varied with different irradiation time of light source and composition ratio of nutrient according to cultivation period.

• Ocean Systems Engineering
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• 제6권1호
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• pp.61-97
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• 2016

This is the second of two papers on the 3D numerical modeling of nearshore hydro- and morphodynamics. In Part I, the focus was on surf and swash zone hydrodynamics in the cross-shore and longshore directions. Here, we consider nearshore processes with an emphasis on the effects of oceanic forcing and beach characteristics on sediment transport in the cross- and longshore directions, as well as on foreshore bathymetry changes. The Delft3D and XBeach models were used with four turbulence closures (viz., ${\kappa}-{\varepsilon}$, ${\kappa}-L$, ATM and H-LES) to solve the 3D Navier-Stokes equations for incompressible flow as well as the beach morphology. The sediment transport module simulates both bed load and suspended load transport of non-cohesive sediments. Twenty sets of numerical experiments combining nine control parameters under a range of bed characteristics and incident wave and tidal conditions were simulated. For each case, the general morphological response in shore-normal and shore-parallel directions was presented. Numerical results showed that the ${\kappa}-{\varepsilon}$ and H-LES closure models yield similar results that are in better agreement with existing morphodynamic observations than the results of the other turbulence models. The simulations showed that wave forcing drives a sediment circulation pattern that results in bar and berm formation. However, together with wave forcing, tides modulate the predicted nearshore sediment dynamics. The combination of tides and wave action has a notable effect on longshore suspended sediment transport fluxes, relative to wave action alone. The model's ability to predict sediment transport under propagation of obliquely incident wave conditions underscores its potential for understanding the evolution of beach morphology at field scale. For example, the results of the model confirmed that the wave characteristics have a considerable effect on the cumulative erosion/deposition, cross-shore distribution of longshore sediment transport and transport rate across and along the beach face. In addition, for the same type of oceanic forcing, the beach morphology exhibits different erosive characteristics depending on grain size (e.g., foreshore profile evolution is erosive or accretive on fine or coarse sand beaches, respectively). Decreasing wave height increases the proportion of onshore to offshore fluxes, almost reaching a neutral net balance. The sediment movement increases with wave height, which is the dominant factor controlling the beach face shape.

• Journal of National Security and Military Science
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• 통권8호
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• pp.239-270
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• 2010

This thesis is to make an appropriate national defense policy of Republic of Korea through studying the Hegemony Strategy of United States. I searched the theory of hegemony. The hegemony was differently defined by the point of time and region. The strong power nations with the hegemony have been making efforts to maintain their hegemony everytime. I have conclusion that the presence of hegemony once emerged, it brought regional stability in place whether it is coercive or beneficial. The stability and instability of international order IS not exclusively dependent on hegemony. Even if the safety of hegemony cannot guarantee absolute stability of international order, there IS on doubt that the hegemony has enormous impact on that. According to the hegemonic theory, the history of mankind equals to the history of rising and falling hegemony. The international order was changed as the hegemony changes. The United States has been making efforts to maintain her global hegemony during the post cold-war era as well. Taking all these into consideration, relevant military strategy direction able to pursue national interest is that to make up for the relative weakness in the strategic environment. South Korea have to prepare security policy response as following. First, South Korea should build the military force equipped with advanced weapons in military technology sector and solidify military diplomatic relation able to form cooperative relation in wartime. Second, South Korea should make solid Alliance of Korea and U.S. Third, develop and maintain multilateral security cooperation of East Asia. Forth, we could realize that there are means that can neutralize opponent's strong point by seeking one or two and more asymmetry in the aspect of strategy, tactics, and means through asymmetric strategy. Than the military force of South Korea should develop into a force that is able to overcome to the traditional North Korea's threat and new type of conflicts. And the force should have sufficient strength and be deployed to effectively defend the Korean Peninsula. So, we need to establish a denial and defense system against any hostile neighboring country. Therefore, ROK military forces preparing for the future should try to construct a future military power to gradually establish enough strength for self-defense to prepare for a uncertain security environment and when the Korean Peninsula is unified in a future.

• Management & Information Systems Review
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• 제36권5호
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• pp.99-120
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• 2017

Recent studies shows that international entrepreneurship orientation is recognized as a very important tool for improving corporate performance in international business activities. However, these relationships show various research results. Therefore, it can be a very interesting research topic to examine whether these relationships are linear or non-linear when selected as a target in developing country like China. The purpose of this study is to examine whether the effects of international entrepreneurship orientation on the export performance is non-liner type in China's manufacturing firms. And investigated the moderating role of degree of internationalization and market dynamism relative to the relationship between the international entrepreneurial-orientation and the export performance. A total of 478 questionnaires were used for the hypothesis test. The results of this study are summarized as follows: First, there is a J-shaped. relationship between international entrepreneurship orientation and export performance. Second, degree of Internationalization strengthened the reverse J-shaped relationship between international entrepreneurship orientation and export performance. Finally, degree of internationalization and market dynamics show that J-shaped relationship between international entrepreneurial orientation and export performance is strengthened. The results of the study's theoretical contribution and the managerial contribution is as followed. As a theoretical contribution, it is confirmed that international entrepreneurial orientation (J-shaped) and export performance form a non-linear relationship, and it is possible to make an empirical contribution that can newly approach the relationship between international entrepreneurial orientation and export performance. The managerial contribution suggests that China's exporting companies have a higher degree of Internationalization in their international business activities and that the higher the dynamics of the overseas markets, the more advanced the international entrepreneurial behavior should be required to improve the export performance.

• The Journal of Advanced Prosthodontics
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• 제7권2호
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• pp.172-177
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• 2015

PURPOSE. The purpose of this study was to evaluate cell toxicity due to ion release caused by galvanic corrosion as a result of contact between base metal and titanium. MATERIALS AND METHODS. It was hypothesized that Nickel (Ni)-Chromium (Cr) alloys with different compositions possess different corrosion resistances when contacted with titanium abutment, and therefore in this study, specimens ($10{\times}10{\times}1.5mm$) were fabricated using commercial pure titanium and 3 different types of Ni-Cr alloys (T3, Tilite, Bella bond plus) commonly used for metal ceramic restorations. The specimens were divided into 6 groups according to the composition of Ni-Cr alloy and contact with titanium. The experimental groups were in direct contact with titanium and the control groups were not. After the samples were immersed in the culture medium - Dulbecco's modified Eagle's medium[DMEM] for 48 hours, the released metal ions were detected using inductively coupled plasma mass spectrometer (ICP-MS) and analyzed by the Kruskal-Wallis and Mann-Whitney test (P<.05). Mouse L-929 fibroblast cells were used for cell toxicity evaluation. The cell toxicity of specimens was measured by the 3-{4,5-dimethylthiazol-2yl}-2,5-diphenyltetrazolium bromide (MTT) test. Results of MTT assay were statistically analyzed by the two-way ANOVA test (P<.05). Post-hoc multiple comparisons were conducted using Tukey's tests. RESULTS. The amount of metal ions released by galvanic corrosion due to contact between the base metal alloy and titanium was increased in all of the specimens. In the cytotoxicity test, the two-way ANOVA showed a significant effect of the alloy type and galvanic corrosion for cytotoxicity (P<.001). The relative cell growth rate (RGR) was decreased further on the groups in contact with titanium (P<.05). CONCLUSION. The release of metal ions was increased by galvanic corrosion due to contact between base metal and titanium, and it can cause adverse effects on the tissue around the implant by inducing cytotoxicity.

• Journal of Korea Water Resources Association
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• 제35권4호
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• pp.397-410
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• 2002

In order to quantitatively identify historical drought conditions and to evaluate their variability, drought indices commonly used. The calculation method for the drought index based on the principal hydrological factors, such as precipitation and reservoir storage, can estimate the duration and intensity of a drought. In this study the Palmer-type formula for drought index is derived for the Nakdong River basin by analyzing the monthly rainfall and meteorological data at 21 stations. The Palmer Drought Severity Index(PDSI) is used for dry land sectors to evaluate the meteorological anomaly in terms of an index which permits time and space comparisons of drought severity. The Surface Water Supply Index(SWSI) is devised for the use in conjunction with the Palmer index to provide an objective indicator of water supply conditions in Nakdong River basin. The SWSI was designed to quantify surface water supply capability of a watershed which depends on river and reservoir water The Standardized Precipitation Index(SPI) is evaluated for various time periods of 1 to 12 months in Nakdong River basin. For the purpose of comparison between drought indices correlation coefficient was calculated between indices and appropriate SPI time period was selected as 10 months for Nakdong River basin. A comparative study is made to evaluate the relative severity of the significant droughts occurred in Nakdong River basin since 1976. It turned out that $'94{\sim}'97$ drought was the worst drought in it's severity. It is found that drought indices are very useful tools in quantitatively evaluating the severity of a drought over a river basin.