• Journal of the korean academy of Pediatric Dentistry
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• v.49 no.2
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• pp.206-216
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• 2022

This study aimed to investigate the frequency of dental visits after coronavirus disease 2019 (COVID-19) in children and adolescents in comparison to that of adults. The data on the number of dental visits on the basis of different classification and treatment codes for all the age groups were provided by the Health Insurance Review and Assessment Service from January 2017 to December 2020. To reduce the impact of the population change, dental visits per 1000 people was used. After the start of the pandemic, dental visits per 1000 people decreased in all age groups when analyzed for the diseases of pulp and periapical tissues classification code and dental visits per 1000 people decreased over 5 years age groups when analyzed for the pulp treatment code. Regarding the restorative treatment code, visits in the 0 - 19 years age group decreased after the pandemic. Based on the comparison of the number of confirmed COVID-19 cases to that of monthly dental visits by treatment codes, the change rate of pulp and restorative treatments gradually decreased after the waves of the pandemic in February and August 2020 in Korea. Furthermore, dental visits per 1000 people for gingivitis and periodontal disease classification code increased after the pandemic in all age groups. The rate of decrease in dental visits per 1000 people for restorative treatments in children and adolescents was higher than that in adults. The rate of decrease in the number of dental visits for multi-visit pulp treatments showed a rapid decrease as compared to that of 1-visit pulp treatments after the pandemic. This study identified changes in the number of dental visits of children and adolescents after COVID-19 transmission in comparison to that observed in adults.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.1
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• pp.31-37
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• 2012

Purpose: This study evaluated the usefulness of Helmet bolus device using Bolx-II, paraffin wax, solid thermoplastic material in total scalp irradiation. Materials and Methods: Using Rando phantom, we applied Bolx-II (Action Products, USA), paraffin wax (Densply, USA), solid thermoplastic material (Med-Tec, USA) on the whole scalp to make helmet bolus device. Computed tomography (GE, Ultra Light Speed16) images were acquired at 5 mm thickness. Then, we set up the optimum treatment plan and analyzed the variation in density of each bolus (Philips, Pinnacle). To evaluate the dose distribution, Dose-homogeneity index (DHI, $D_{90}/D_{10}$) and Conformity index (CI, $V_{95}/TV$) of Clinical Target Volume (CTV) using Dose-Volume Histogram (DVH) and $V_{20}$, $V_{30}$ of normal brain tissues. we assessed the efficiency of production process by measuring total time taken to produce. Thermoluminescent dosimeters (TLD) were used to verify the accuracy. Results: Density variation value of Bolx-II, paraffin wax, solid thermoplastic material turned out to be $0.952{\pm}0.13g/cm^3$, $0.842{\pm}0.17g/cm^3$, $0.908{\pm}0.24g/cm^3$, respectively. The DHI and CI of each helmet bolus device which used Bolx-II, paraffin wax, solid thermoplastic material were 0.89, 0.85, 0.77 and 0.86, 0.78, 0.74, respectively. The result of Bolx-II was the best. $V_{20}$ and $V_{30}$ of brain tissues were 11.50%, 10.80%, 10.07% and 7.62%, 7.40%, 7.31%, respectively. It took 30, 120, 90 minutes to produce. The measured TLD results were within ${\pm}7%$ of the planned values. Conclusion: The application of helmet bolus which used Bolx-II during total scalp irradiation not only improves homogeneity and conformity of Clinical Target Volume but also takes short time and the production method is simple. Thus, the helmet bolus which used Bolx-II is considered to be useful for the clinical trials.

• Journal of Periodontal and Implant Science
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• v.23 no.3
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• pp.577-594
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• 1993

The ultimate goal of periodontal therapy is the regeneration of the periodontium that have been destroyed as a result of periodontal disease. This study were done in order to determine the healing status of periodontium under Polytetrafluoroethylene and millipore fillter combined with fibrin and the effect of the guided tissue regeneration procedures were performed as follows : 1) flap operation using PTFE membrane(control group) 2) flap operation using PTFE membrane which was fixed with fibrin(experimental group 1) 3) flap operation using millipore filter which was fixed with suture(experimental group II) 4) flap operation using millipore filter which was fixed with fibrin(experimental group II) After 1, 2, 4, 8, 12 weeks, dogs were sacrificed by perfusion technique and tissue block was excised including the tooth and prepared for light microscope with H-E & Masson’s trichrome staining. The result were as follows : In control and experimental group, there is no siginificant difference on epithelial cell down growth within 1st week, but more epithelial cell downgrowth in millipore or millipore combined with fibrin group. In this experiment, there were no significant difference in new cementum and alveolar bone formation whether PTFE membrane was fixed with suture or fibrin. In control and each experimental group, bone maturation appeared in 4 weeks, bone width increased bucco-lingually in control and experimental 1 group especially. Both control group and experimental group showed mild mew cementum formation on root surface and irregular arrangement of collagen fiber at 4 weeks, that showed obvious increased cementum formation at 8 weeks, and that was observed the functional arrangement of collagen fiber between new cementum and new alveolar bone at 12 weeks.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.35 no.5
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• pp.294-301
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• 2013

Purpose: The purpose of this study is to assess the effectiveness of beta-tricalciumphosphate (${\beta}$-TCP) as a bone graft material on new bone formation and regeneration of mandible bone defect around dental implants. Methods: Both mandibular sites of ten rabbits were exposed. The experimental subjects were divided into two groups. Rabbits in the control group (right site of the mandible) had dental implants around cortical bone defects, without treatment, while, in the experimental group (left site of the mandible), ${\beta}$-TCP was grafted into the bone defect around the implant. Rabbits were sacrificed after one, two, three, four, and eight weeks, and histomorphometric evaluation and analysis of the bone implant contact rate were performed using an optical microscope. Results: Bone formation rates in the experimental group were greater than those in the control group from one to eight weeks, and percentages of implant surface contacted to bone were greater in the experimental group than in the control group from three weeks after implantation. Conclusion: These results suggest that the bone formation activity around dental implants was increased by osteoconduction activity of ${\beta}$-TCP.

• Journal of Korean Orthopaedic Sports Medicine
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• v.11 no.1
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• pp.8-16
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• 2012

With the increase of participation in the sport activities, there has been a commensurate rise in the number of sport injuries. A more commonly encountered injured region in the upper-extremity is the wrist. Sport injuries are often characterized as overuse and traumatic. Traumatic injuries include fractures, dislocations, and ligament tears often seen in contact or collision sports. Overuse injuries, represented damages by a level of repetitive microtrauma sufficient to overwhelm the tissues$^{\circ}{\O}$ ability to adapt, include inflammatory conditions such as De Quervain$^{\circ}{\O}s$ disease, extensor carpi ulnaris tendinitis, intersection syndrome. Also included is a traumatic problem such as stress fractures of the hook of the hamate, subluxation of the extensor carpi ulnaris tendon, chronic scapholunate instabilities, and degenerative triangular fibrocartilage tears. This review will focus on both overuse and traumatic injuries of the wrist in the athletes. A significant emphasis will be placed on the evaluation, pearls and pitfalls of conservative and operative treatments.

• Journal of the Korea Society of Computer and Information
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• v.8 no.2
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• pp.145-154
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• 2003

Business environment is changing rapidly because of the introduction of the newest Technologies development and the newest management skills. With the development of Information Technology (IT) and the rapid growth of Internet based business, there have been great improvements of business processes and total costs of many firms. Many firms realize that they have to change their organizational structure and managerial skills in order to carry on their corporate goals(growth and development) according to business paradigm shift. The purpose of this dissertation is to watch how consumer product manufacturer(C corporation) could build effective SCM strategies under Electronic Commerce paradigm shift and how it can reform its organizational structure in order to perform its business goat. C corporation has been doing a groat role in logistics and distribution for the last 50 years with logistics know-how in domestic market, however there were many problems such as lack of shared information, demand Paradox, order batch, stock shortage and duplicated processes among vendors and chain members. Most of problems were based on lack of shared information and old business processes.

• Journal of the Korean Magnetics Society
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• v.2 no.2
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• pp.119-124
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• 1992

We have investigated the effects of sputtering Ar gas pressure on magnetic and magneto-optical properties in compositionally modulated Co/Pd superlattice thin films. The samples were prepared by dc magnetron sputtering from 2-in.-diam Co and Pd targets by alternately exposing the substrates to targets. Sputtering Ar gas pressure was varied from 2 to 30 mTorr. All samples had same bilayer thicknesses composed of 2-$\AA$-thick Co and 9-$\AA$-thick Pd sublayers. It was observed that the colum-nar structure was more distinctively developed with increasing Ar gas pressure. We observed that the intrinsic uniaxial anisotropy energy, magnetization and polar Kerr rotation were decreased with increasing Ar gas pressures. Large coercivity and perfect squareness were attained by the deposition at the high Ar gas pressure. We believe that the results are mainly ascribed the variation of micro-structure with sputtering Ar gas pressure.

• Journal of the Korea Society of Computer and Information
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• v.10 no.3 s.35
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• pp.319-329
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• 2005

Rapid business and technology changes drive many organizations to seek better solutions and many of them believe that Information Technology is an essential tool to cope with turbulent environment. Companies began to think ERP system as an effective alternative for IT-based process innovation and integrated information system. But each ERP system has a specific business model and technical structure, unlike in-house developed systems. Moreover implementation of ERP system accompanies transformation of business processes at company level including radical changes in information technology. Therefore, to implement ERP system successfully appropriate and careful selection of ERP system which is adequate for company's objectives and environment must be considered. In this research, four types of changes expected by ERP implementation were suggested. Each type of changes was determined by desired level of changes in business process and information technology.

• The Journal of the Petrological Society of Korea
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• v.5 no.1
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• pp.66-83
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• 1996

We report petrography, mineral chemistry, and major and trace element chemistry for rare tholeiites in Cheju island where alkalic rocks predominate. Available age data indicate that the tholeiitic magmatism was younger than 0.49Ma, possibly younger than 0.17 Ma. The tholeiites are generally fine-grained, porphyritic rock and show intergranular texture with lath-shaped plagioclase ($An_{61-46}$), orthopyroxene (bronzite) and olivine ($Fo_{78-67}$). Characteristically, two kinds of clinopyroxene (pigeonite and augite) occur only in groundmass. The tholeiites have normative quartz and show limited compositional variations ($SiO_2$=51.0-52.5 wt%; Mg＃=54-60). Major and transitional metal element variations of tholeiites are distinct from those of alkaline rocks in MgO diagram, suggestingthat the two rock types cannot be simply related to differentiation process from the same magma. The ratios among $K_2O$, Rb, Ba, Nb and La are similar for both tholeiites and alkali basalts, however the ratios between the elements (P, Y and Yb) having an affinity with garnet and the above elements are higher for tholeiites than for alkali basalts. These trace element ratios suggest that the tholeiites and alkali basalts were produced by different degrees of partial melting from a similar sources material (garnet lherzolite mantle).

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.82.1-82.1
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• 2012

란타늄 산화물 ($La_2O_3$) 박막은 하프늄 산화물 ($HfO_2$) 박막보다 높은 유전 상수와 높은 밴드 오프셋으로 인해 dynamic random access memory(DRAM)에서 유전체 재료로써 연구되어 왔다. 그리고 Lanthanum이 도핑된 HfO2이 더 높은 유전 상수와 낮은 누설 전류 밀도를 갖는 다는 사실이 이전에 보고 된 바 있다. 본 연구에서 우리는 ALD를 이용하여, TiN 하부 전극 위에 $La_2O_3$의 위치를 달리하는 $La_2O_3/HfO_2$의 나노 층상조직 구조(두께 10 nm)를 금속 - 절연체 - 금속 (MIM) 구조로 제작 하였다. ALD는 좋은 comformality와 넓은 지역 균일성을 가지며, 원자수준의 두께를 조절할 수 있다는 장점을 갖고 있다. 또한, 다양한 화학 물질들을 이용한 복합적 계층구조를 만들 수 있는 점과 $HfO_2$ 및 $La_2O_3$ 계층의 수직 위치를 정확하게 조절할 수 있는 점으로 본 연구에 적합한 증착 방법이다. HfO2 속에 $La_2O_3$ 층을 깊이에 따라 삽입함으로써 $HfO_2$ 계층에 La 도핑의 효과와 더불어 TiN 하부 전극 위의 $La_2O_3$과 $HfO_2$의 차이점을 확인 하였다. $HfO_2$은 $250^{\circ}C$에서 TDMAH와 물을 사용하여, $La_2O_3$은 동일한 온도에서 $La(iPrCp)_3$와 물을 사용하여 제작되었다. 화학적 구성 및 binding 구조는 X선 광전자 분광법 (XPS)을 통해 분석하였다. 전기적 특성(유전 상수 및 누설 전류)은 Capacitance-Voltage (CV)와 Current-Voltage (IV) 측정으로 확인하였다. 결과적으로, $La_2O_3$ 또는 $HfO_2$을 한 종류만 사용한 절연층의 전기적 특성보다, $La_2O_3/HfO_2$의 나노 층상조직 구조가 더 나은 특성 (누설 전류 밀도 : $5.5{\times}10^{-7}\;A/cm^2$ @-1MV/cm, EOT : 14.6)을 갖는다는 것을 확인했고, 더불어 $La_2O_3$의 흡습 성질로 인한 화학 구조와 전기적 특성의 일부 차이를 확인하였다. 본 연구에서는 $HfO_2$ 속에 $La_2O_3$층이 TiN 하부 전극 바로 위에 위치할 때, 즉, 공기 중에 노출되지 않은 $La_2O_3/HfO_2$ 구조에서 가장 좋은 특성의 MIM capacitor를 얻을 수 있었다.