• The korean journal of orthodontics
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• v.53 no.4
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• pp.254-263
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• 2023

Objective: The evidence on the accuracy of bite registration using intraoral scanners is sparse. This study aimed to develop a new method for evaluating bite registration accuracy using intraoral scanners. Methods: Two different types of models were used; 10 stone models and 10 with acrylic resin teeth. A triangular frame with cylindrical posts at each apex (one anterior and two posteriors) was digitally designed and manufactured using three-dimensional (3D) printing. Such a structure was fitted in the lingual space of each maxillary and mandibular model so that, in occlusion, the posts would contact their opposing counterparts, enforcing a small interocclusal gap between the two arches. This ensured no tooth interference and full contact between opposing posts. Bite registration accuracy was evaluated by measuring the distance between opposing posts, with small values indicating high-accuracy. Three intraoral scanners were used: Medit i500, Primescan, and Trios 4. Viewbox software was used to measure the distance between opposing posts and compute roll and pitch. Results: The average maximum error in interocclusal registration exceeded 50 ㎛. Roll and pitch orientation errors ranged above 0.1 degrees, implying an additional interocclusal error of around 40 ㎛ or more. The models with acrylic teeth exhibited higher errors. Conclusions: A method that avoids the need for reference hardware and the imprecision of locating reference points on tooth surfaces, and offers simplicity in the assessment of bite registration with an intraoral scanner, was developed. These results suggest that intraoral scanners may exhibit clinically significant errors in reproducing the interocclusal relationships.

• Phonetics and Speech Sciences
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• v.3 no.3
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• pp.69-75
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• 2011

This paper investigates phrase positional effects on the timing of F0 (pitch) peaks in Tokyo Japanese disyllabic words with varying accent type (HL or LH) and phrase position (final or non final). The F0 peak timing was normalized by the total word duration ('normalized H timing'). The normalized H timing was significantly affected by accent type and phrase position. The H timing was later in the LH accent type than in the HL accent type, and in non final positions than in final positions. In addition, to examine the validity of the quantitative results, different models of phrase position effects were compared by measuring H timing in two approaches: normalization versus relative distance measures. For the normalization measures, the H timing was measured as the time of the F0 peak divided by the total word duration or by the duration of the tone bearing syllable. For the relative distance measures, the H timing was measured as the distance in milliseconds from the end of the word or from the end of the associated syllable. The best model was the normalization by the total word duration, rather than by the duration of the tone bearing syllable. This means that phrase positional effects on the timing of F0 peaks in Japanese disyllabic words are best modeled in terms of proportion of the total word duration.

• Journal of Welding and Joining
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• v.17 no.2
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• pp.29-35
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• 1999

This study was intended to use for the fatigue test in real structures and offer basic data for optimum welding structure design. To this purpose, we obserded the effect of the size and distance of plug welding hole on the static strength and fatigue life of welding structure under the shear/bending load for the improvement of fatigue life of plug welding joint between S/MBR and C/MBR in the lower structure of large bus. The result below is shown through this study. 1) Static and fatigue strength are strongly influenced by the direction of plug weld hole distributed. 2) Distances and diameters of the distributed holes are little dependent on the static strengths 3) In case of the directions of the distributed plug weld holes are vertical to the loading pin, fatigue life is dependent on distance of the distributed hole. 4) In case of the directions of the distributed plug weld holes are parallel to the loading pin, fatigue life is dependent on distance of the hole diameter.

• Journal of ILASS-Korea
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• v.16 no.1
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• pp.27-36
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• 2011

The impact force on the single and overlap region of twin spray was experimentally evaluated using visualization method in full cone type swirl nozzle spray. Visualization of spray was conducted to obtain the spray angle and breakup process. The photography/imaging technique, based on Particle Image Velocimetry (PIV) using high-speed camera, was adopted for the direct observation of droplet motion and axial velocity measurement, respectively. Droplet size was measured by Particle Motion Analyze System (PMAS). The purpose of this study is to provide fundamental information of spray characteristics, such as impact force, for higher etching factor in the practical wet etching system. It was found that the spray angle, axial velocity and impact force were increased with increasing the nozzle pressure while droplet size decreased with increasing the nozzle pressure. Droplet size increased as the distance from nozzle tip was decreased. The impact force of twin spray in the overlap region was about 63.29, 67.02, 52.41% higher than that of single spray at 40, 50 and 60 mm of nozzle pitch, respectively. Also, the nozzle pitch was one of the important factors in the twin spray characteristics.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.4 s.247
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• pp.381-388
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• 2006

The objective of this study is to predict the etching characteristics using spray characteristics for the optimization on the etching process of Lead-Frame. The etching characteristics such as etching factor, uniformity were investigated on the actual operating conditions. The correlation between the etching characteristics and the spray ones obtained by measurement were analyzed to simulate the etching characteristics according to actual conditions of lead-frame etching process. These conditions of lead-frame process were spray pressure, distance from nozzle tip to substrate, pipe pitch, and nozzle pitch. To improve the etching characteristics in the lead-frame process, effects of the various operating conditions should be understood in detail. The spray characteristics obtained by experiment using PDA system were simulated by the Monte-Carlo method. The etching process model was coded by Java language. It was found that simulation results generally agreed well with the measured results of etching characteristics in lead-frame etching process. The optimal operating parameters were successfully found under variable conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.11
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• pp.1659-1666
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• 2001

The objective of this study was to investigate the characteristics of air flow and heat transfer caused by trapezoid rods array in impinging air jet system. Trapezoid rods have been set up on front of flat plate to act as a turbulence promoter. Local Nusselt numbers were determined as a function of three parameters : (a) the space from re(Is to heating surface(C=1, 2, 4mm), (b) the pitch between each rods(P=30, 40, 50mm), (c) the distance from nozzle exit to flat plate(H/B=2, 6, 10). The measurements were compared with those of the experiment without trapezoid rods. As a result, when rods are installed in front of the impinging palate, the acceleration of the flow and the eddies due to the rods seem to contribute to the heat transfer enhancement. Heat transfer performance was best under the condition of C=1mm and as the pitch is 30mm. The maximum rate of heat transfer augmentation is about 1.9 times greater compared to that without trapezoid rods.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.164-166
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• 2012

In this paper, we proposed a method for extracting predominant melody of polyphonic music based on harmonic structure. Harmonic structure is an important feature parameter of monophonic signal that has spectral peaks at the integer multiples of its fundamental frequency. We extract all fundamental frequency candidates contained in the polyphonic signal by verifying the required condition of harmonic structure. Then, we combine those harmonic peaks corresponding to each extracted fundamental frequency and assign a rank to each after calculating its harmonic average energy. We run pitch tracking based on the rank of extracted fundamental frequency and continuity of fundamental frequency, and determine the predominant melody. For the query by singing/humming (QbSH) task, we proposed Dynamic Time Warping (DTW) based matching engine. Our system reduces false alarm by combining the distances of multiple DTW processes. To improve the performance, we introduced the asymmetric sense, pitch level compensation, and distance intransitiveness to DTW algorithm.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.7
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• pp.879-886
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• 2004

A numerical optimization has been carried out to determine the shape of the three-dimensional channel with oblique ribs attached on both walls to enhance turbulent heat transfer. The response surface based optimization is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer. Shear stress transport (SST) turbulence model is used as a turbulence closure. Numerical results fur heat transfer rate show good agreements with experimental data. four dimensionless variables such as, rib pitch-to-rib height ratio, rib height-to-channel height ratio, streamwise rib distance on opposite wall to rib pitch ratio, and the attack angle of the rib are chosen as design variables. The objective function is defined as a linear combination of heat-transfer and friction-loss related coefficients with a weighting factor. D-optimal method is used to determine the training points as a means of design of experiment. Sensitivity of the objective parameters to each design variable has been analyzed. And, optimal values of the design variables have been obtained in a range of the weighting factor.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• fall
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• pp.9-12
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• 2021

드론 Photogrammetry는 높은 기술적 활용가치가 있는 기술로서, 결과물로 생성하는 3D 디지털 공간정보 모델이 시설물의 비육안 안전점검 및 진단에 활용될 수 있을 뿐만 아니라 디지털 트윈 구축을 위한 가장 기초적이고 핵심적인 수치 데이터를 제공하기 때문이다. 본 연구에서는 드론 Photogrammetry의 적정 품질을 구현하기 위한 임무비행의 다양한 영향인자에 대해 고찰하였다. K-water연구원 누수탐사실습장을 대상으로 드론 사진 촬영 시 비행고도, 비행속도, 중첩도, 카메라 Pitch각의 영향에 대해 연구를 수행하였다. 본 연구에서 비행시간에 영향을 미치는 인자로서 비행고도, 중첩도, 비행속도의 순으로 중요도가 있음을 알 수 있었다. 드론 임무 비행 시 후처리 결과에 가장 큰 영향을 미치는 인자는 중첩도로 나타났다. 중첩도 60% 임무비행은 3D 모델의 geometry 왜곡이 큰 편으로 나타났다. 비행 고도는 GSD (Ground Sampling Distance)와 직접 연계되므로 중요하며, 낮은 고도일수록 높은 품질의 모델링이 가능하다. April Tag를 통한 지상기준점 자동 패턴 인식 기능은 후처리 과정에서 시간 절약이 가능하여 유용하였다. 비행속도에 의한 결과물의 품질은 큰 차이가 없었으나, 수직 구조물의 모서리 부분에 다소 차이가 있었다. 짐벌 Pitch각도에 의한 정사영상 품질의 차이는 크지 않았으나 수직구조물과 평면적 구조물에 따라 각기 다른 촬영각도를 적용하는 것이 바람직하다. 본 연구성과는 향후 보다 다양한 환경에서의 데이터 수집을 통해 최적 디지털 현실 모델링에 기여할 것으로 판단된다.

• The Journal of the Acoustical Society of Korea
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• v.28 no.7
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• pp.646-652
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• 2009

In this paper, welding pitch optimization technique of vehicle subframe is presented considering the fatigue life of spot welding nuggets. Fatigue life of spot welding nuggets is estimated by using the frequency-domain fatigue analysis technique. The input data, which are used in the fatigue analysis, are obtained by performing the dynamic analysis of vehicle model passing through the Belgian road profile and also the modal frequency response analysis of finite element model of vehicle subframe. According to the fatigue life result obtained from the frequency-domain fatigue analysis, the design points to optimize the weld pitch distance are determined. For obtaining the welding pitch combination to maximize the fatigue life of the spot welding nuggets, 4-factor, 3-level orthogonal array experimental design is used. This study shows that the optimized subframe improves the fatigue life of welding nugget with minimum fatigue life about 65.8 % as compared with the baseline design.