• Journal of the korean academy of Pediatric Dentistry
• /
• v.26 no.2
• /
• pp.248-261
• /
• 1999

In order to define a current set of Korean children norm with mixed dentition, following study was done. The subjects were 102 healthy dentition contestants(48boys, 54girls). Standardized lateral head roentgenograms were taken, and Ricketts analysis was done. Results were as follows: 1. Length of anterior cranial base, posterior facial height, corpus length were longer in male than in female(p<0.05), and Porion was located posteriorly in male than in female(p<0.01). 2. Through facial depth, Pogonion of male was more forwardly positioned(p<0.05), mandible was significantly steeper in female, and maxillary anterior teeth were significantly tipped forward in male(p<0.05). 3. Variables such as length of anterior cranial base, upper molar position(p<0.01) and corpus length(p<0.05) were significantly changed by age. 4. Maxillary height, facial depth, mandibular plane angle, convexity were changed by age, but not significantly(p>0.05).

• Journal of the Korean Geosynthetics Society
• /
• v.15 no.2
• /
• pp.25-33
• /
• 2016

This study was a basic research to obtain the knowledge of physical properties of the upper sedimented sandy soil in the Nakdong river delta area. The characteristics of shear strength and permeability with fine content and relative density were also investigated. The upper sedimented sandy soil near paddy and lower soft clay layers showed high percentage of fine content, and the rest parts had about 5% of fine content. The specific gravity regardless of depth and location was almost constant. The upper sedimented sandy soil mostly had particle size about 0.1 ~ 0.4mm regardless of sedimentation environment and has illite, a clay mineral, in the entire soil samples. The results of direct shear tests on remolded specimens of the upper sedimented sandy soil revealed that the friction angle and cohesion increased with relative density, but its effect was not significant. The fine content was significant, that as increasing it, the friction angle decreased and cohesion increased linearly. The permeability decreased with relative density and fine content, and the permeability of soil containing more than 15% of fine content was independent on the relative density.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.12
• /
• pp.27-36
• /
• 2019

The demand for a low dispersion lens with a small refractive index and a high refractive index is increasing, and accordingly, there is an increasing need for a releasable protective film with high heat resistance and abrasion resistance. On the other hand, the optical industry has not yet established a clear standard for the manufacturing process and quality standards for mold-releasing protective films used in aspheric glass lens molding. Optical lens manufacturers treat this technology as proprietary information. In this study, an experiment was conducted regarding the optimization of ion etching, magnetron, and arc current at each source and filter part, and bias voltage in FCVA (filtered cathode vacuum arc)-based Ta-C thin film coatings. This study found that compared to iridium-rhenium alloy thin film sputtering products, the coating conditions were improved by approximately 50%, 20%, and 40% in terms of thickness, hardness, and adhesive strength of the film, respectively. The thin-film coating process proposed in this study is expected to contribute significantly to the development and utilization of glass lenses, which will help enhance the minimum mechanical properties and quality of the mold-release thin film layer required for glass mold surface forming technology.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.30 no.2
• /
• pp.112-120
• /
• 2014

Purpose: This study compared the shear bond strength of heat pressed and feldspathic porcelain to metal. Through thermocycling, the clinical aspect of heat pressed porcelain fused metal was estimated. Materials and Methods: 90 non-precious metal specimens were made ($4{\times}4{\times}8 mm$) and divided to three groups. All spicimens were treated and built-up with the porcelain ($4{\times}4{\times}3 mm$) by 2 different methods according to group: Group I: $Inspiration^{(R)}$, Group II: Ivoclar, IPS $Inline^{(R)}PoM$, Group III: GC Initial IQ-One $Body^{(R)}PoM$. The half of each group's specimens were thermocycled. All specimens' shear bond strength were measured by Instron universal testing machine. Exact measuring point was far 1 mm from porcelain/metal interface to the porcelain side. For the statistical analysis, 2-way ANOVA was used. Results: In no-thermocycling specimens, the shear bond strength showed no statistical significance between each group (P > 0.05). In comparison between nothermocycling and thermocycling specimens in each group, the shear bond strength was decreased according to thermocycling, but there was no statistical significance (P > 0.05). In thermocycling specimens, there was no statistical significance between each group (P > 0.05). Conclusion: In feldspathic porcelain and other two types heat pressed porcelain, there was no statistical difference in the shear bond strength of porcelain to metal. The heat pressed porcelain seems to be clinically useful for the aspect of the shear bond strength.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.2
• /
• pp.138-144
• /
• 2005

This study was carried out to investigate the changes of nitrifying bacterial populations including Nitrosomonas sp. and Nitrobacter sp. in $A^2/O$ pilot plant with the configuration of anaerobic-anoxic-oxic reactors. The suspended nitrifying bacterial populations in mixed liquor and those of attached populations on granular carrier surface made by molded waste tire were analyzed by Fluorescent in situ Hybridization(FISH) method. The nitrification rate of a pilot plant showed the value of $1.97{\sim}2.98\;mg\;N/g$ MLVSS hr. The ratios of suspended ammonia oxidizer including Nitrosomonas sp. (NSO) to total bacteria in each reactor were oxic < anoxic < anaerobic. On the contrary, the ratios of suspended nitrite oxidizer including Nitrobacter sp. (NIT) were anaerobic < anoxic < oxic. The thickness, dry density and mass of the attached biomass on granular carriers were $180{\sim}188\;{\mu}m$, $38.5{\sim}43.9\;mg/cm^3$, $29.4{\sim}32.5\;mg/g$, respectively. Also, the ratios of attached nitrifier to total bacteria on granular carriers were similar regardless of ammonia/nitrite-oxidizer (NSO; 3.2%, NIT; 2.8%) and very low compared to those(NSO; $22.8{\sim}28.4%$, NIT; $17{\sim}26%$) of suspended nitrifier.

• Restorative Dentistry and Endodontics
• /
• v.27 no.3
• /
• pp.290-298
• /
• 2002

3차원적으로 잘 충전된 근관은 치근단 누출과 재감염을 방지하며, 조직이 잘 치유될 수 있는 생물학적 환경을 제공해준다. 이 때문에 근관계의 완전한 충전은 근관치료의 중요한 목표 중의 하나이다. 본 연구의 목적은 4가지 방법으로 근관충전 후 디지털 방사선 사진을 촬영하여 근관충전의 질을 평가하고 투명표본을 제작하여 색소침투범위를 측정함으로써, 근관충전방법에 따른 치근단부 폐쇄능을 비교 평가하고자 하는 것이다. 직선형의 단근관을 갖는 80개의 전치를 선택하여 ProFile$^{\circledR}$ 니켈-티타늄 회전식 기구를 사용하여 근관을 성형한 후 무작위로 20개씩 4군으로 나누었다. 사용된 근관충전법은 다음과 같다：MicroSeal$^{\circledR}$(Group A), Thermafil$^{\circledR}$(Group B), Continuous wave 충전법(Group C), 측방가압충전법(Group D), 각 군에서 10개 치아는 Sealapex를, 나머지 10개 치아는 AH26$^{\circledR}$을 충전용 시멘트로 사용하였다. 근관충전이 끝난 치아는 충전의 질과 길이를 평가하기 위해, 근원심과 협설방향으로 디지털 방사선 사진을 이용하여 촬영하였다. 각 치아의 치근단부 2mm를 제외한 나머지 부위는 두겹의 nail varnish를 바르고, 2% methlylene blue용액에 48시간동안 침잠시켰다. 흐르는 물에 깨끗이 세척한 후, 투명치아를 만들었다. 선상의 색소침투를 관찰하고 치관측 최대깊이를 입체현미경하에서 40배율로 평가하여 다음과 같은 결과를 얻었다. 1. 충전방법에 따른 근단부 폐쇄효과를 비교시, 실험군 모두 비교적 양호한 근단부 폐쇄효과를 보였고 통계학적으로 유의성이 없었다. 2. 충전용 시멘트에 따른 근단부 폐쇄효과를 비교시, AH26$^{\circledR}$을 사용한 군에서 Sealapex를 사용한 군보다 더 적은 색소침 투를 나타냈다(p<0.05). MicroSeal$^{\circledR}$을 이용한 실험 1군내에서 AH26$^{\circledR}$을 사용하였을 때 미세누출이 더 적었고(p<0.05), 다른 군내에서는 통계학적으로 유의성이 없었다. 3. 근단부 충전상태에 따른 미세누출 비교시, 저충전, 과충전과 색소침투간에는 상관관계가 없었다. 4.충전방법에 따른 근단부 충전상태 평가시, Thermafil$^{\circledR}$을 이용한 실험 2군에서 과충전이 많이 나타났다(p<0.05). 이상의 결과로, 기존의 측방가압법 및 여러 열가소성 충전법이 유사한 근단부 폐쇄효과를 나타낸 바, 방법에 따른 술자의 숙련도, 충전시간, 재근관치료의 편이성 등을 고려하여 근관충전방법을 선택하는 것이 합리적일 것이라고 사료된다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.12 no.4
• /
• pp.425-433
• /
• 2019

In this paper, the RCS analysis of the 10m unmanned surface vehicles was performed, and the factors of RCS increase were analyzed. Modeling techniques by transforming a geometric shape can reduce the RCS area, which can be used to develop stealth unmanned surface vehicles. In order to reduce the RCS, the existing Top Mast part was moved 1m to the tail part, the 5 degree tilt angle was moved below 0.5 m, and additional guided walls were installed to minimize the influence on the center and surrounding corner reflecting structures. As a result of comparing and analyzing the RCS analysis value with the existing model, it can be seen that the reduced countermeasure model is -3.79 dB lower than the existing model for all elevations. In particular, it can be seen that the strong scattering phenomenon is substantially removed in the region except the sacrificial angle region. In addition, it can be seen that in the case of -5m to 2m where the guide wall is added, the reflected signal is improved up to 20 to 40 dB or more, so that it does not appear on the 2D ISAR image. RCS analysis of unmanned surface vehicles explained the process of analyzing and identifying problem location through distance profile analysis and ISAR image analysis.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.12
• /
• pp.75-84
• /
• 2008

Recycled-aggregate porous concrete pile (RAPP) which forms a composite ground is one of new ground improvement techniques. In this paper, triaxial compression tests are carried out to investigate the shear strength characteristics of RAPP-Clay composite samples. The main purpose of the tests was to investigate the effects of area replacement ratio ($15%{\sim}100%$) on behaviors of RAPP-Clay samples during shearing. Also, triaxial compression tests using Sand-Clay composite samples were performed to compare with the behaviors of RAPP-Clay samples. The test results showed that the friction angle and cohesion of the RAPP-Clay composite were $18{\sim}34$ degree and $557.0{\sim}588.0\;kPa$, respectively, whereas those of sand-clay composite samples were 26~35 degree of friction angel and $4.0{\sim}18.0\;kPa$.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.20 no.3
• /
• pp.191-200
• /
• 1998

This study was intended to perform the influence of condyle positional change after surgical correction of skeletal Class III malocclusion after orthognathic surgery in 37 patients(male 13, female 24) using computed tomogram that were taken in centric occlusion before, immediate after, and long term after surgery and lateral cephalogram that were taken in centric occlusion before, 7 days within the period of intermaxillary fixation, at the 24 hours later removing intermaxillary fixation and long term after surgery. 1. Mean intercondylar distance was $84.42{\pm}5.30mm$ and horizontal long axis of condylar angle was $12.79{\pm}4.92^{\circ}$ on the right, $13.53{\pm}5.56^{\circ}$ on the left side. Condylar lateral poles were located about 12mm and medial poles about 7mm away from the reference line(AA') on the axial tomogram. Mean intercondylar distance was $83.15{\pm}4.62mm$ and vertical axis angle of condylar angle was $76.28{\pm}428^{\circ}$ on the right, $78.30{\pm}3.79^{\circ}$ on the left. 2. In amount of set back, We found the condylar change(T2C-T1C) which had increasing tendency in group III (amount of setback : 10-15mm). but there was no statistical significance(p>0.05). 3. There was some correlation between condylar change(T2C-T1C) and TMJ dysfunction. It seemed that postoperative condylar change had influenced postoperative TMJ dysfunction, through there was no statistical significance (p>0.05). As we have observed the change of condylar axis in the group that complained of TMJ dysfunction in cases of large amount of mandibular setback. So we consider that the more trying to conserve condylar position will decrease occurrence rate of post operational TMJ dysfunction.

• Restorative Dentistry and Endodontics
• /
• v.30 no.2
• /
• pp.128-137
• /
• 2005

In this study we measured the amount of light energy that was projected through the tooth material and analyzed the degree of polymerization by measuring the surface hardness of composites. For polymerization, Optilux 501 (Demetron, USA) with two types of light guide was used: a 12 mm diameter light guide with 840 nW/$cm^2$ light intensity and a 7 mm diameter turbo light guide with 1100 nW/$cm^2$. Specimens were divided into three groups according to thickness of penetrating tooth (1 mm, 2 mm, 0 mm). Each group was further divided into four subgroups according to type of light guide and curing time (20 seconds, 40 seconds). Vickers' hardness was measured by using a microhardness tester. In 0 mm and 1 mm penetrating tooth group, which were polymerized by a turbo light guide for 40 seconds, showed the highest hardness values. The specimens from 2 mm penetrating tooth group, which were polymerized for 20 seconds, demonstrated the lowest hardness regardless of the types of light guides (p < 0.05). The results of this study suggest that, when projecting tooth material over a specified thickness, the increase of polymerization will be limited even if light intensity or curing time is increased.