• 대한소아치과학회지
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• 제46권2호
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• pp.139-146
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• 2019

본 연구는 7세부터 15세사이의 소아청소년을 대상으로 촬영하여 획득한 Cone beam computed tomography(CBCT) 영상을 이용하여 정중구개봉합의 성숙도를 평가하고 골 성숙도 및 연령과의 연관성을 분석하여 Rapid maxillary expansion(RME) 적용 시 적절한 치료계획 수립의 참고자료로 활용하고자 하였다. 남아 240명, 여아 240명, 총 480명의 CBCT 수평면 영상에서 정중구개봉합의 성숙도를 5단계로 평가하였고 수집된 자료를 경추골 성숙도 측정법에 의해 평가된 골 성숙도 및 연령에 따라 통계분석을 시행하였다. 정중구개봉합 성숙도와 골 성숙도는 0.602의 강한 상관관계를 보였으며, 특히 정중구개봉합 성숙도 A - C단계의 예측을 위한 경추골 성숙도 1 - 3단계의 양성 검정우도비는 44.79로서 예측을 위한 타당한 지표임을 나타내었다. 정중구개봉합 성숙도와 연령의 상관관계는 남아에서 0.499, 여아에서 0.560으로 나타나 경추골 성숙도 보다는 낮으나 비교적 높은 상관관계를 보였다. 따라서 경추골 성숙도 측정법은 정중구개봉합의 성숙도 예측을 위한 신뢰할 만한 지표라고 할 수 있으며, 연령은 경추골 성숙도 측정이 어려운 경우에 한하여 임상에서 간편하고 직관적인 지표로 쓰일 수 있다. 연구 결과를 종합해보면 RME 사용 시 골격성 효과를 충분히 얻을 수 있는 것으로 기대 할 수 있는 시기는 경추골 성숙도 1 - 3단계, 남녀 모두 연령 12세 이하이며 경추골 성숙도 4단계 혹은 여아 연령 13세 및 남아 연령 15세까지는 conventional RME의 사용은 가능하나 골격성 효과는 감소하고 치성 효과가 증가할 것으로 예상된다. 경추골 성숙도 5, 6단계 혹은 여아 연령 14세 이상에서는 RME 필요 시 사용 형태를 결정하기 위해 정중구개봉합 성숙 단계 평가 시 CBCT 촬영이 고려되어야 한다.

• International journal of advanced smart convergence
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• 제4권1호
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• pp.120-126
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• 2015

This research is a comparison of the characteristics of the displacement isolines due to powder-die-wall friction that arise during the compaction of ceramic powders in conventional die. It has been done using the CosmosWorks software package of the SolidWorks simulation software. The results of comparative simulation with FEM showed that the comparison of the displacement isolines and distribution of deformation of the ceramic powders. In the case of conventional uniaxial dry compaction for long length cylindrical green compact, considerable bending of the layers in the form of a cone can be observed. It is symmetry along centerline of cylindrical green compact. The distributions of the deformation of the green compacts (diameter 14 mm, height 20 mm) as a result of conventional compaction under ultrasonic vibration with power 1 and 2 kW are reduced to 4% and 6.5% when compared with conventional compaction without ultrasonic vibration respectively. Thus, density distribution can be minimized by increasing the power of ultrasonic vibration.

• Journal of the Korean Statistical Society
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• 제24권1호
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• pp.183-195
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• 1995

For a distribution on the unit sphere, the set of eigenvectors of the second moment matrix is a conventional measure of orientation. Asymptotic confidence cones for eigenvector under the parametric assumptions for the underlying distributions and nonparametric confidence cones for eigenvector based on bootstrapping were proposed. In this paper, to reduce the level error of confidence cones for eigenvector, double bootstrap confidence cones based on prepivoting are considered, and the consistency of this method is discussed. We compare the perfomances of double bootstrap method with the others by Monte Carlo simulations.

• Geomechanics and Engineering
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• 제14권1호
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• pp.99-105
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• 2018

Soils are generally classified as fine-grained or coarse-grained depending on the percentage content of the primary constituents. In reality, soils are actually made up of mixed and composite constituents. Soils primarily classified as fine-grained, still consists of a range of coarse particles as secondary constituents in between 0% to 50%. A laboratory scale model test was conducted to investigate the influence of coarse particles on the physical (e.g., density, water content, and void ratio) and mechanical (e.g., quick undrained shear strength) properties of primarily classified fine-grained cohesive soils. Pure kaolinite clay and sand-mixed kaolinite soil (e.g., sand content: 10%, 20%, and 30%) having various water contents (60%, 65%, and 70%) were preconsolidated at different stress levels (0, 13, 17.5, 22 kPa). The quick undrained shear strength properties were determined using the conventional Static Cone Penetration Test (SCPT) method and the new Fall Cone Test (FCT) method. The corresponding void ratios and densities with respect to the quick undrained shear strength were also observed. Correlations of the physical properties and quick undrained shear strengths derived from the SCPT and FCT were also established. Comparison of results showed a significant relationship between the two methods. From the results of FCT and SCPT, there is a decreasing trend of quick undrained shear strength, strength increase ratio ($S_u/P_o$), and void ratio (e) as the sand content is increased. The quick undrained shear strength generally decreases with increased water content. For the same water content, increasing the sand content resulted to a decrease in quick undrained shear strength due to reduced adhesion, and also, resulted to an increase in density. Similarly, it is observed that the change in density is distinctively noticeable at sand content greater than 20%. However, for sand content lower than 10%, there is minimal change in density with respect to water content. In general, the results showed a decrease in quick undrained shear strength for soils with higher amounts of sand content. Therefore, as the soil adhesion is reduced, the cone penetration resistances of the FCT and SCPT reflects internal friction and density of sand in the total shear strength.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1769-1775
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• 2004

In presence of collision between two rigid bodies, they exhibit impulsive behavior to generate physically feasible state. When the frictional impulse is involved, collision resolution can not be easily made based on a simple Newton's law or Poisson's law, mainly due to possible change of collision mode during collision, For example, sliding may change to sticking, and then sliding resumes. We first examine two conventional methods: the method of mode evolution by differential equation, and the other by linear complementarity programming. Then, we propose a new method for mode evolution by solving only algebraic equations defining mode changes. Further, our method attains the original nonlinear impulse cone constraint. The numerical simulation will elucidate the advantage of the proposed method as an alternative to conventional ones.

• Journal of the Optical Society of Korea
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• 제2권1호
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• pp.13-21
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• 1998

Based on the escape cone concepts, high-brightness light-emitting diodes (LEDs) have been analyzed. In AlGaAs or InGaAlP LEDs, photon absorption in the ohmic region under the electrode is known to be significant. Thus, ins general, a thick window layer (WL) and a transparent substrate (TS) would minimize photon shielding by the electrodes and considerably improve photon output coupling efficiency. However, the schemes do not seem to be necessary in InGaN system. Photon absorption in ohmic contact to a wide bandgap semiconductor such as GaN may be negligible and, as a result, the significant photon shielding by the electrodes will not degrade the photon output coupling efficiency so much. The photon output coupling efficiency estimated in InGaN LEDs is about 2.5 - 2.8 times that of the conventional high-brightness LED structures based on both WL and TS schemes. As a result, the extenal quantum efficiency in InGaN LEDs is as high as 9% despite the presumably very low internal quantum efficiency.

• 한국지반신소재학회논문집
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• 제7권4호
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• pp.37-45
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• 2008

친환경배수재에 대한 현장 적용성을 평가하기 위해 연직배수재와 수평배수재 설치 조합으로 현장시험시공을 수행하였다. 본 시험시공에서는 기존의 천연섬유배수재(FDB)와 새로 개발한 볏짚배수재(SDB) 그리고 플라스틱배수재(PDB)를 연직배수재로 설치하였으며, 화이버매트와 샌드매트를 수평배수재로 사용하였다. 볏짚배수재(SDB) 설치지역을 제외하고는 플라스틱배수재(PDB)와 천연섬유배수재(FDB) 설치 지역에서 측정한 지표침하발생속도와 과잉간극수압 발생/소산 양상은 거의 유사한 것으로 나타났으며, 1차 압밀방치기간동안 측정된 상부 연약층의 콘관입저항력도 설치된 연직배수재 종류와 상관없이 일정하게 증가한 것으로 나타나 천연섬유배수재가 기존의 플라스틱이나 모래재료를 대체할 수 있을 것으로 판단된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.1178-1187
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• 2008

Quality assurance for embankment compaction is one of very important procedures to guarantee high quality construction. However, only sand replacement method (KS F2312) and static plate load test (KS F2310) which are conventional and tiresome methods are used to evaluate degree of compaction at construction fields. Recently, new types of devices such as the geogauge and the light falling weight deflectometer (LFWD), the soil impact hammer (CASPFOL) and dynamic cone penetration test etc. which are able to substitute for the conventional methods are begun to use to evaluate soil stiffness. In this study, a laboratory model test was performed to evaluate correlations among test results obtained from the new devices and to assess the potential use of them. All test results have correlations with relative density and water content. Especially, the coefficients of correlation between $E_G$ from the geogauge and $K_{30'}$ from the soil impact hammer and between $E_G$ from the geogauge and $E_{LFWD}$ from LFWD are more than 0.7 but those between the results from DCP and others are less than those between $E_{G{\cdot}}$ and $K_{30'}$ and $E_G$ and $E_{LFWD}$.

• 대한의용생체공학회:의공학회지
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• 제39권1호
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• pp.30-35
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• 2018

Conventional drug delivery methods mainly include subcutaneous injection and oral administration. Subcutaneous injection has the advantages of delivering the correct concentration, but it might cause pain and trauma to patients. Although oral administrations do not accompany pain as the subcutaneous injection, unexpected side effects may occur because they undergo digestion process and it is not easy for many drugs to be exposed to targeted sites with proper concentration. While dissolving microneedles have been extensively studied to overcome the limitations of conventional subcutaneous injection, the effects on microneedle shapes for drug release have not been fully explored. In this study, the characteristics of hyaluronic acid microneedles for cone and quadrangular pyramidal shapes were examined by the size, volume, contact surface area, skin permeability, and dissolution rate. As a result, the cone shapes of hyaluronic acid microneedles had high skin permeability, and the quadrangular pyramid of shapes hyaluronic acid microneedles showed a fast dissolution rate, given by the large contact area on the skin. Based on the results, we could confirm that the shape of a dissolving microneedles can affect skin permeability and the drug delivery rate.

• 대한치과교정학회지
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• 제46권5호
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• pp.301-309
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• 2016

Objective: The aim of this study was to evaluate the skeletal and dental changes after intraoral vertical ramus osteotomy (IVRO) with and without presurgical orthodontics by using cone-beam computed tomography (CBCT). Methods: This retrospective cohort study included 24 patients (mean age, 22.1 years) with skeletal Class III malocclusion who underwent bimaxillary surgery with IVRO. The patients were divided into the preorthodontic orthognathic surgery (POGS) group (n = 12) and conventional surgery (CS) group (n = 12). CBCT images acquired preoperatively, 1 month after surgery, and 1 year after surgery were analyzed to compare the intergroup differences in postoperative three-dimensional movements of the maxillary and mandibular landmarks and the changes in lateral cephalometric variables. Results: Baseline demographics (sex and age) were similar between the two groups (6 men and 6 women in each group). During the postsurgical period, the POGS group showed more significant upward movement of the mandible (p < 0.05) than did the CS group. Neither group showed significant transverse movement of any of the skeletal landmarks. Moreover, none of the dental and skeletal variables showed significant intergroup differences 1 year after surgery. Conclusions: Compared with CS, POGS with IVRO resulted in significantly different postsurgical skeletal movement in the mandible. Although both groups showed similar skeletal and dental outcomes at 1 year after surgery, upward movement of the mandible during the postsurgical period should be considered to ensure a more reliable outcome after POGS.