• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.381-389
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• 2000

Lateral condensation with gutta-percha and sealer has been shown to provide an excellent apical seal; however, the lateral condensation technique has demonstrated less favorable apical leakage results in curved canals when compared with straight canals. Placement of endodontic spreaders to within 1 to 2mm of the root canal working length has been advocated for optimum gutta-percha obturation. Due to their stiffness, stainless-steel(SS) spreaders will often fail to achieve this position in curved canals. Newly marketed nickel-titanium(NT) spreaders may offer an advantage in this regard due to the increased flexibility of these instruments. The purpose of this study was to evaluate the effect of NT finger spreader on the sealing ability in lateral condensation technique, compared with conventional SS finger spreader. Twenty four standardized resin models simulating curved canals(30 degree) were randomly placed into 2 groups and instrumented to a #30 master apical file size with Ni-Ti Profile .04 taper series using step down technique. Each groups was obturated with standardized gutta-percha cone by standard lateral condensation technique using SS finger spreader, NT finger spreader. And then, each model was sectioned horizontally with microtome at 1, 2, 3, 4, 5mm levels from the apex. At each of 5 levels, ratio of the area of gutta-percha was obtained by calculating the area of gutta-percha to the total area of the canal. The data collected were then analyzed statistically using a t test for independent samples. The results as follows ; 1. The total mean ratio of area of gutta-percha was 89.20${\pm}$7.00(%) for SS spreader group. 92.20${\pm}$5.17(%) for NT spreader group. There was statistically significant difference between each group(p<0.05). 2. At 3mm level, the mean ratio of area of gutta-percha was 88.32${\pm}$5.41(%) for SS spreader group, 95.25${\pm}$2.60(%) for NT spreader group. There was statistically significant difference between each group(p<0.05). At 1,2,4mm levels, NT spreader group showed greater mean ratio of area of gutta-percha than SS spreader group, too. But there was no statistically significant difference. 3. At 5mm level, the mean ratio of area of gutta-percha was 91.83${\pm}$3.42(%) for SS spreader group, 87.91${\pm}$3.68(%) for NT spreader group. There was statistically significant difference between each group(p<0.05). This study concluded that the NT spreader demonstrated somewhat favorable apical sealing effect than SS spreader in prepared curved canals. The clinical use of NT spreaders may enhance our ability to create better apical seals in curved canals, but further studies in this area will help clarify some of the remaining areas with which practitioners are concerned, such as compaction forces exerted by NT spreaders.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.292-294
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• 2018

Recently, damage caused by natural disasters such as fire, earthquake, heavy rains and heavy snow is increasing. In addition, traffic accidents due to freezing, fog and fire in tunnels and bridges are frequently occurring. In such a disaster situation, it is very important to take prompt action by the person in charge of managing the facility and area.To this end, a disaster broadcasting system is used, but in the existing system, the broadcasting room and the speaker are connected by a wired connection. Also, the person in charge has to be in the broadcasting room to broadcast, which has a problem of delaying the time. In this paper, we design a disaster broadcasting system using LTE modem. The designed system enables a broadcasting person to make a call to a broadcasting system from anywhere using a cellular phone and a public telephone. Broadcasting via telephone is possible only with the telephone number pre-registered in the system and can be registered / deleted by the administrator. The registered telephone number, incoming voice file, and announcement voice for automatic broadcasting are stored in the system internal SD memory for convenient management. This disaster broadcasting system is expected to contribute to quick and convenient disaster broadcasting.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.4
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• pp.220-227
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• 2019

Purpose: The purpose of this study was to compare the degree of tooth preparation abilities of students according to three self-assessment methods. Materials and Methods: forty-eight sophomores in Kyungpook National University College of Dentistry were divided into three experimental groups. Students performed tooth preparation of the left mandibular first molar for full gold crown. They performed self-assessment using the three methods (visual, digital, and putty index self-assessment group), and reperformed tooth preparation. An intraoral scanner was used to scan each tooth model (prepared tooth and unprepared tooth), and data were acquired in standard tessellation language (STL) file format. The STL files of prepared tooth and unprepared tooth were superimposed using the 3-dimensional analysis software (Geomagic control X). And the reduction amount was measured. In the statistical analysis, all values of reduction amount were analyzed with the Wilcoxon signed rank test and Kruskal-Wallis test (α = 0.05). Results: The three self-assessment methods showed statistically significant differences (P < 0.001). The putty index self-assessment group showed the highest reduction in error than the digital self-assessment method. Conclusion: Within limitations of this study, students showed significant differences in improvement of tooth preparation ability according to the three self-evaluation methods.

• Restorative Dentistry and Endodontics
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• v.33 no.4
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• pp.397-404
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• 2008

The purpose of this study was to evaluate the effects of MTAD, EDTA and sodium hypochlorite(NaOCl) as final irrigants on coronal leakage resistance to Enterococcus faecalis. Forty extracted human maxillary molars were used in this experiment. The teeth were randomly divided into positive control group (Group 1; n = 5), negative control group (Group 2; n = 5) and three experimental groups (n = 30). In Group 3 (n = 10), the root canals were irrigated with sodium hypochlorite. In Group 4 (n = 10) and 5 (n = 10), the root canals were irrigated with sodium hypochlorite and rinsed with EDTA and MTAD, respectively. The teeth in each group were cleaned and shaped to #40 profile with .04 taper, and obturated with gutta-percha and AH-26 root canal sealer. The coronal portion of each tooth was placed in contact with inoculum of Enterococcus faecalis in Brain Heart Infusion (BHI) culture media. Each root tip was placed in a vial containing sterile culture media. The vials were placed in anaerobic chamber and observed everyday for turbidity for 180 days. Statistical analysis was performed using Fisher's Exact Test. After 180 days, Group 3, 4, and 5 showed 7, 4 and 5 leaking samples respectively. The differences in leakage resistance were not statistically significant among Group 3, 4 and 5.

• Journal of KIISE:Information Networking
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• v.29 no.1
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• pp.86-96
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• 2002

In video conferencing system using H.263 encoding and decoding time is as important as compression rate is. To reduce encoding time, a number of methods were proposed. We use a method of them that reduces the computational complexity in motion estimation. The complexity is determined by three factors, such as a cost function, a search range parameter, and a motion search algorithm. In fact, it takes a lot of time to encode the video data on account of the cost function factor. That's the reason that we use the factor to reduce encoding time. In this paper, we tried to reduce total encoding time by reducing the number of calling the cost function. In case of a little moving, our algorithm enabled faster motion searching than TSS(Three Step Search) and NTSS(New TSS). Here, we called the algorithm by an ITSS(Improved TSS) that improves a shortcoming of NTSS requiring more checkpoints than TSS. For an experimentation, our algorithm was compared to other algorithms using PSNR, file size and SAD call times.

• Journal of Navigation and Port Research
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• v.44 no.3
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• pp.244-252
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• 2020

The 2008 global financial crisis was triggered by the Lehman Brothers crisis caused by the sub-prime mortgage crisis in the United States This crisis has had an impact on the globe's dry bulk shipping market by reducing dry bulk cargo volume. An oversupply of dry bulk carriers caused a serious recession in the globe's dry-bulk shipping industry and shipbuilding industry. In this situation, the Korean dry-bulk shipping companies were victims of the quagmire of a long recession since the global financial crisis and could not overcome this crisis. This condition forced them into severe financial risk Thus, it caused many shipping companies to file for bankruptcy. In this study, we classified Korean ocean-going dry-bulk shipping companies into two groups, that is, the solvent group and the insolvent group. We also separated the research period before and after the 2008 global financial crisis. Then we investigated the differences in the major financial ratios of the two groups by t-test and found that some financial ratios such as profitability ratios and growth ratios showed the difference between the two groups with statistical significance. The significance of this study is as follow. First, the shipping company management is also crucial for the systematic management of financial strength and business strategy, it is crucial to manage cargo which a high profitable freight. Second, the shipping company should be managed as a company with continued growth through efficient operation and management of ships.

• Restorative Dentistry and Endodontics
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• v.26 no.3
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• pp.206-214
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• 2001

근관계의 완전한 충전을 위해 기계적인 근관 확대 및 화학적인 세척은 필수 불가결하다. 근관내 기구 조작 시 근관벽에는 무기물과 유기물로 구성된 도말층이 형성되는데, 이 층은 서서히 분해되어 충전재 주위에서 미세누출을 야기하고, 세균과 그 부산물이 이동할 수 있는 통로를 제공하기 때문에 제거되어야 한다. 현재 이러한 목적을 위해 다양한 기구들과 세척 용액들이 이용되고 있다. 최근에는 근관확대를 위해 엔진 구동형 니켈-티타늄 파일이 개발되어 임상에서 널리 사용되고 있으며, 이러한 엔진 구동형 파일을 사용할 때는 윤활제의 사용이 필수적이다. 현재 시판되고 있는 윤활제들에는 도말층 제거를 위한 EDTA가 함유되어 있다. 따라서, 본 연구의 목적은 엔진 구동형 니켈-티타늄 파일을 이용해 근관을 확대할 경우 이런 윤활제들의 도말층 제거 효과를 비교 평가하는 것이다. 본 실험에는 75개의 치아가 각각 15개씩 5개의 군으로 분류되어 사용되었다. 대조군은 윤활제를 사용하지 않은 경우이고, 실험 1군에서는 윤활제로 RC-PREP$^{TM}$이, 실험 2군에서는 Glyde$^{TM}$가 각각 사용되었고. 실험 3군은 RC-PREP$^{TM}$을 사용한 후 17% EDTA로 처리하였으며. 실험 4군은 Glyde$^{TM}$를 사용한 후 17% EDTA로 처리하였다. 처리된 시편을 절단한 후 주사전자현미경을 통해 시편의 근관의 중앙부와 치근단 부위를 관찰하여 얻어진 결과는 다음과 같다. 1. 대조군과 실험군의 비교시, 대조군에서 더 많은 양의 도말층이 관찰되었고, 이는 통계학적으로 유의성이 있었다 (p<0.01). 2. 윤활제의 종류에 따른 비교 시, Glyde$^{TM}$를 사용한 2군에서 RC-PREPTM을 사용한 1군 보다 더 적은 양의 도말층이 관찰되었지만, 이는 통계학적으로 유의성이 없었다. 3. 윤활제 사용과 EDTA 처리에 따른 효과 비교 시, EDTA로 처리한 3, 4군에서 윤활제만을 사용한 1, 2군 보다 더 적은 양의 도말층이 관찰되었으며, 이는 통계학적으로 유의성 이 있었다(P<0.01). 4. 치근 중앙부와 치근단 부위에서의 도말층 제거 효과 비교 시, 1, 2군에서는 치근 중앙부에서 더 적은 양의 도말층이 관찰되었고, 통계학적으로 유의성이 있었다(P<0.01). 3, 4군에서는 중앙부의 도말층이 더 적었지만 통계학적으로 유의성이 없었다. 이상으로부터 EDTA가 함유된 윤활제를 함께 사용하면서 엔진구동형 니켈-티타늄 파일로 근관확대 시, 근관벽에 형성된 도말층 제거에 대한 파일의 효능이 상승되었다. 그러나, 윤활제의 도말층 제거 효과는 17% EDTA용액으로 근관벽을 처리하는 것보다는 낮았다 따라서, 엔진구동형 니켈-티타늄 파일로 근관확대 시 EDTA가 함유된 윤활제를 함께 사용하는 것이 요구되고, 보다 완벽하게 도말층을 제거하기 위해서는 충전 전에 17% EDTA 용액으로 근관벽을 처리하는 것이 필요하다고 사료된다.

• Journal of the Korea Society of Computer and Information
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• v.18 no.12
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• pp.103-111
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• 2013

At present, a variety of Korean news stories have been about important online content and its importance in the press is becoming higher. Diverse news from businesses are provided to the public as press releases through newspapers or broadcasting media. For such news to become information for a press release, enterprises visit reporters, use e-mails, faxes, or couriers to deliver the information. However, such methods have problems with time, human resources, expenses, and file damage. Also, with these methods it is bothersome for enterprises to check what has been released and for the press to make frequent contact with enterprises for interviews and for content to be released. Therefore, this study aimed to realize a distribution system which enterprises can use to distribute data to be released to the press and to easily check what is to be released while the press can ask for interview requests in a simple way, as well as a news gathering robot that can collects news on the enterprises involved from articles online or in portal sites.

• Journal of the Korea Computer Graphics Society
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• v.16 no.1
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• pp.21-27
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• 2010

Today the lectures are usually practiced in a teacher-led traditional classroom system or a student-led e-learning system. Students passively follow the teacher's lectures in both systems, though. Also due to the advances in 3D Computer Graphics and Game technologies, there are trials to exploit the positive effect of games in learning. The serious games, specifically designed games for an educational goal, or existing games for a special class have been used as lectures. Still these games have a great difficulty in being integrated into the educational system technically and economically. Therefore a new 3D MMORPG based lecturing system is presented in this paper. In our new lecturing system, the characteristics of a 3D MMORPG, achievement, sociality, and immersion, are provided to motivate students to participate actively in a lecture. A teacher and students interact with each other in realtime as 3D characters in a 3D virtual classroom on-line. An ordinary teacher can also easily apply our new system to existing classes since a teacher only needs to specify a slide file to prepare a lecture. For the future work, a user study and the effect of our new lecturing system will be performed.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.4
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• pp.34-44
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• 2006

Simulation models allow researchers to model large hydrological catchment for comprehensive management of the water resources and explication of the diffuse pollution processes, such as land-use changes by development plan of the region. Recently, there have been reported many researches that examine water body quality using Geographic Information System (GIS) and dynamic watershed models such as AGNPS, HSPF, SWAT that necessitate handling large amounts of data. The aim of this study is to develop a watershed based water quality estimation system for the impact assessment on stream water quality. KBASIN-HSPF, proposed in this study, provides easy data compiling for HSPF by facilitating the setup and simulation process. It also assists the spatial interpretation of point and non-point pollutant information and thiessen rainfall creation and pre and post processing for large environmental data An integration methodology of GIS and water quality model for the preprocessing geo-morphologic data was designed by coupling the data model KBASIN-HSPF interface comprises four modules: registration and modification of basic environmental information, watershed delineation generator, watershed geo-morphologic index calculator and model input file processor. KBASIN-HSPF was applied to simulate the water quality impact by variation of subbasin pollution discharge structure.