• Journal of Oral Medicine and Pain
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• 제21권1호
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• pp.197-206
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• 1996

This study ws performed to investigate the relationship between cervical curvature and the spatial position of the posterior part of the atlas imaged in the lateral cephalograph. Sixty six patients with temporomandibular disorders(TMD) and twenty dental students were selected for patients group and control group, respectively. The average age of patients group was 26.3 years, and 24.9 years in control group. Measured variables were cervical depth, upper space between the atlas and the base of the occiput, lower space between the atlas and the spinous process of the axis, rea of the posterior part of the atlas imaged in the lateral cephalograph, and the cervical curvature passing through the uppermost point in dorsal side of Dens of the Axis to the lowermost and rearmost point of the 5th cervical vertebra. The reliability of the method used for measuring cervical curvature with curved ruler was also tested. The results obtained were as follows : 1. Cervical depth of patients group was 122.9mm and significantly shorter than that of control group, in which cervical depth was 131.9mm, and cervical depth was significantly correlated with other variables in all subjects. 2. Upper space was greater in patients group, but total space including upper and lower space showed no difference between the two groups. The average value of total space was 26.5mm. 3. Area of the posterior part of the atlas was 168.2$\textrm{mm}^2$ in patients group, and 186.5$\textrm{mm}^2$ in control group with significant difference between the two groups. 4. Average range of radius of cervical curvature were 33-40cm and there was no difference between the two groups. 5. There was no significant correlation between the cervical curvature and the area of the posterior arch of the atlas. 6. The method using curved ruler for measuring cervical curvature could be accepted as a reliable method.

• 한국음향학회지
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• 제43권3호
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• pp.324-334
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• 2024

파면곡률거리추정(Wavefront Curvature Ranging, WCR)은 음파의 파면곡률로부터 음원의 거리를 추정하는 방법이다. 기존의 파면곡률거리추정은 음속을 상수로 가정하고 삼각법으로 거리를 추정한다. 이 가정 때문에 해저면반사경로가 뚜렷하게 분리되는 해양환경에서는 거리 오차가 발생한다. 거리 오차를 줄이기 위해 해양의 음속구조를 적용하고 최대우도추정(Maximum Likelihood Estimation, MLE)방법으로 거리를 추정하는 정합 파면곡률거리추정(Matched Wavefront Curvature Ranging, MWCR) 을 제안하였다. 정합 파면곡률거리추정의 시뮬레이션 결과로부터 거리 오차의 감소를 확인하였다. 향후에 실측 신호로부터 거리 추정의 신뢰성을 확인하면 소나 시스템에 적용 가능할 것이다.

• 대한전기학회논문지:시스템및제어부문D
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• 제50권4호
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• pp.201-207
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• 2001

This paper describes an automated detection algorithm of ST-T episodes using global curvature which can connect the isoelectric level in ECG and can eliminate not only the slope of ST segment, but also difference of the baseline and global curve. This above method of baseline correction is very faster than the classical baseline correction methods. The optimal values of parameters for baseline correction were found as the value having the highest detection rate of ST episode. The features as input of backpropagation Neural Network were extracted from the whole ST segment. The European ST-T database was used as training and test data. Finally, ST elevation, ST depression and normal ST were classified. The average ST episode sensitivity and predictivity were 85.42%, 80.29%, respectively. This result shows the high speed and reliability in ST episode detection. In conclusion, the proposed method showed the possibility in various applications for the Holter system.

• Structural Engineering and Mechanics
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• 제72권2호
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• pp.203-216
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• 2019

Reliability analysis of composite structures considering random variation of involved parameters is quite important as composite materials revealed large statistical variations in their mechanical properties. The reliability analysis of such structures by the first order reliability method (FORM) and Monte Carlo Simulation (MCS) based approach involves repetitive evaluations of performance function. The response surface method (RSM) based metamodeling technique has emerged as an effective solution to such problems. In the application of metamodeling for uncertainty quantification and reliability analysis of composite structures; the finite element model is usually formulated by either classical laminate theory or first order shear deformation theory. But such theories show significant error in calculating the structural responses of composite structures. The present study attempted to apply the RSM based MCS for reliability analysis of composite shell structures where the surrogate model is constructed using higher order shear deformation theory (HSDT) of composite structures considering the uncertainties in the material properties, load, ply thickness and radius of curvature of the shell structure. The sensitivity of responses of the shell is also obtained by RSM and finite element method based direct approach to elucidate the advantages of RSM for response sensitivity analysis. The reliability results obtained by the proposed RSM based MCS and FORM are compared with the accurate reliability analysis results obtained by the direct MCS by considering two numerical examples.

• 공업화학
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• 제32권3호
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• pp.268-276
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• 2021

최근 무선통신 기기가 보편화됨에 따라 이로부터 발생하는 전자기파를 제어할 수 있는 방법에 대한 관심이 높아지고 있다. 전자기파 제어 물질로 가장 흔히 사용되는 것은 자성 물질이지만 제품에 적용 시 제품이 무겁고 두꺼워지는 특징 때문에 일반 전자기기에 사용하기에는 문제가 있어 이를 해결하기 위해 가볍고 두께가 얇은 고분자 유연메타 전자소자가 제시되었다. 또한 고분자 유연메타 전자소자는 단일 제품을 다양한 곡률에 적용할 수 있어 곡면 형상이 많은 전자기기에 사용하기에도 적합하다. 그러나 이러한 고분자 유연메타 전자소자를 곡면에 적용하기 위해서는 곡률변화에 따른 전자기파 제어 특성의 안정성 평가가 필수적으로 요구된다. 이에 본 연구에서는 도선 면적이 일정할 때 도선 길이에 따른 저항 변화율이 전자기파 제어 특성과 역의 관계라는 점을 활용하여 고분자 유연메타 전자소자의 전기적 특성 변화를 통해 전자기파 제어 특성을 예측할 수 있는 방법을 개발하였고, 이를 이용하여 고분자 유연메타 전자소자의 곡률 안정성 평가를 수행하였다. 그 결과 곡률 반경이 감소할수록 도선 길이에 따른 저항 변화율이 증가하였고, 곡률 유지 시간에 의한 변화는 없었다. 또한 곡면 적용 시 도선에 영구적인 변화와 곡면 제거 시 회복 가능한 변화가 복합적으로 발생하였고, 이러한 변화의 원인이 곡면 적용 시 가해진 인장응력에 의해 생성된 도선 내 수직방향 크랙이라는 사실도 밝혀냈다.

• 한국전자통신학회논문지
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• 제14권5호
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• pp.871-876
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• 2019

본 논문에서는 플루오린화 수소산(Hydrofluoric acid: HF) 수용액과 광섬유에 인가된 $1.55{\mu}m$ 파장의 레이저를 통해 유도된 광열 효과를 이용하여 오목한 광섬유 팁을 제작하였다. 제작 과정에서 인가한 레이저의 세기, 식각 시간, HF 수용액의 농도에 따른 광섬유 팁 오목 면의 곡률 반경을 광학 현미경을 이용하여 측정하였으며 곡률 반경이 세 변인에 대하여 어떻게 변화하는지 분석하였다. 또한, Free Spectral Range(FSR)와 Scanning electron microscope(SEM) 촬영을 통해 현미경을 이용한 측정 방법의 신뢰성을 검증하였다. 본 논문을 통해 광섬유 팁의 오목 면 제작 과정에서 변인에 따라 곡률 반경을 조절할 수 있게 됨으로써 기존의 HF 수용액을 이용한 광섬유 식각 방법의 한계점을 극복할 수 있었다.

• Journal of Advanced Marine Engineering and Technology
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• 제22권5호
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• pp.595-608
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• 1998

A diffuser an important equipment to change kinetic energy into pressure energy has been studied for a long time. Though experimental and theoretical researches habe been done the understanding of energy transfer and detailed mechanism of energy dissipation is unclear. As far as numerical prediction of diffuser flows are concerned various numerical studies have also been done. On the contrary many turbulence models have constraint to the applicability of diffuser-like flows with expansion and streamline curvature. In order to obtain the reliability of k-$\varepsilon$ turbulence model modified combination turbulence models composed of the anisotropic k-$\varepsilon$model modified combination turbulence models composed of the anisotropic k-$\varepsilon$ model with Hanjalic-Launder's preferential normal strain and Pope's vortex stretching mechanism are proposed. The results of the present proposed models prove the fact that the coefficient of pressure and the shear stress are well predicted at the diffuser flow.

• Steel and Composite Structures
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• 제37권3호
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• pp.371-390
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• 2020

One of the most common strategies for retrofitting as-built reinforced concrete (RC) columns is to enlarge the existing section through the application of a new concrete layer reinforced by both steel transverse and longitudinal reinforcements. The present study was dedicated to developing a comprehensive model to predict the seismic behavior of as-built RC jacketed columns. For this purpose, a new sectional model was developed to perform moment-curvature analysis coupled by the plastic hinge method. In this analysis-oriented model, new methodologies were suggested to address the impacts of axial, flexural and shear mechanisms, variable confining pressure, eccentric loading, longitudinal bar buckling, and varying axial load. To consider the effective interaction between core and jacket, the monolithic factor approach was adopted to extent the response of the monolithic columns to that of a respective RC jacket strengthened column. Next, parametric studies were implemented to examine the effectiveness of the main parameters of the RC jacket strategy in retrofitting as-built RC columns. Ultimately, the reliability of the developed analytical model was validated against a series of experimental results of as-built and retrofitted RC columns.

• 소성∙가공
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• 제26권1호
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• pp.11-17
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• 2017

In this study, process analysis of elbow-shaped tubes using a mandrel has been performed. To reach the final shape within the dimensional tolerance, the process analysis has been performed at various processing parameters such as tube dimensions, the curved cutting surface and the radius of curvature. The area outside the boundary of the target shape was expressed as a quantitative index to analyze the formability. The validation experiments have also been performed in order to increase the reliability of the process analysis. For the processing of elbow-shaped tubes, it is preferable to make the angle of the portion where the punch touches the tube smaller than the opposite angle. And the convex cutting surface is advantageous due to the increased contacts between the punch and the tube ends during the bending process. Elbow tube having larger radius of curvature shows higher dimensional accuracy due to the relatively uniform strain distribution.

• Tribology and Lubricants
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• 제29권1호
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• pp.13-18
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• 2013

Slider bearing is a widely used load-carrying element in the industry. While a large number of studies have investigated the effect of overall surface curvature, very few have considered sinusoidal surface. Recently, consideration of surface roughness/waviness or intentional wave design has been identified as an important issue in the manufacture of hard disk driver, mechanical seal, hydraulic machine, and etc. This study investigated the load-carrying capacity of a finite-width slider bearing with a wavy surface. Film thickness ratios, length-width ratio, ambient pressure, amplitude, and partial distribution were selected as the simulation parameters. The calculation results showed that the load-carrying capacity rapidly varied at small film thickness ratio, but the waviness near the area of minimum film thickness made much more influence with an increase in film thickness ratio. As the length-width ratio of bearing was increased, ambient pressure became more influential at small film thickness ratios. Furthermore a particular partial distribution of the wavy area led to higher load-carrying capacity than did the whole distribution. Consequently, the results of this study are expected to be of use in surface micro-machining of finite-width slider bearings.