• 치과방사선
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• 제18권1호
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• pp.167-176
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• 1988

This study was designed to evaluate the morphology of the temporomandibular joint components and dentofacial characteristics of patients with clicking and painful temporomadibular joint. The materials consisted of 80 conventional pantomographs in normal an symptomatic individuals aged 18-23 and divided into 2 groups by symptom of temporomandibular joint. The results were as follows; 1. In morphologic analysis of condylar head, type Ⅰ (anterior, posterior smooth curve) was most dominant in both group(58.75%, 55.0%) and asymmetrical condylar shape was predominant in symptomatic group (18 cases, 45%). 2. In symptomatic group, the condylar width were slightly lesser and the ratio of condylar height to height of condyle-ramus were larger than those of normal group. 3. Vertical overlap of central incisor of symptomatic group was slightly larger than that of normal group. There was significant differences between each group in mandibular midline deviation. 4. The symptomatic group tended to steep mandibular plane angle and the degree of condylar path and condylar axis of normal group were larger than those of symptomatic group. 5. The condylar width was inversely correlated with inclination of condylar path and inclination of condylar path was correlated with condylar axis in both groups.

• Wind and Structures
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• 제11권3호
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• pp.221-240
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• 2008

The spanwise flow structure around a rigid smooth circular cylinder model in cross-flow has been investigated based on the experimental data obtained from a series of wind tunnel tests. Surface pressures were collected at five spanwise locations along the cylinder over a Reynolds number range of $1.14{\times}15^5$ to $5.85{\times}10^5$, which covered sub-critical, single-bubble and two-bubble regimes in the critical range. Separation angles were deduced from curve fitted to the surface pressure data. In addition, spanwise correlations and power spectra analyses were employed to study the spatial structure of flow. Results at different spanwise locations show that the transition into single-bubble and two-bubble regimes could occur at marginally different Reynolds numbers which expresses the presence of overlap regions in between the single-bubble regime and its former and later regimes. This indicates the existence of three-dimensional flow around the circular cylinder in cross-flow, which is also supported by the observed cell-like surface pressure patterns. Relatively strong spanwise correlation of the flow characteristics is observed before each transition within the critical regime, or formation of first and second separation-bubbles. It is also noted that these organized flow structures might lead to greater overall aerodynamic forces on a circular cylinder in cross-flow within the critical Reynolds number regime.

• Bulletin of the Korean Chemical Society
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• 제20권1호
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• pp.42-48
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• 1999

We have performed a quantum-chemical investigation on the conformations and electronic properties of a variety of methoxy-substituted poly(p-phenylenevinylenes) (PPVs) to elucidate the effects of alkoxy substitution. Geometrical parameters for the polymers were fully optimized through Austin Model I (AM I) semi-empirical Hartree-Fock (HF) band calculations. Electronic properties of the polymers were obtained by applying the AM I optimized structures to the modified extended Huckel method. To confirm validity of the AM I conformational results, we also carried out ab initio HF calculations with the 6-31G (d) basis set for a variety of methoxy-substituted divinylbenzenes. It is found that the potential energy surfaces of alkoxy-substituted PPVs are quite shallow around the planar conformations, suggesting that the prepared films possess a variety of conformations with different torsion angle in the solid state, depending on the synthetic conditions. When two alkoxy groups are concurrently substituted at the adjacent sites in the phenylene ring, these groups are subject to rotating around the C(sp2)-O bonds by 70-80° to avoid the strong steric repulsion between them. Consequently, the overlap between the π-type p orbital of oxygen and the π molecular orbitals of the polymer decreases. This leads to a wide gap and a high oxidation potential for tetramethoxy-substituted PPV, compared to those of dialkoxy-substituted PPV.

• 자동차안전학회지
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• 제15권4호
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• pp.39-47
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• 2023

Research on the safety of autonomous vehicle is being conducted in various countries, including the European Union, and computer simulation techniques so called 'Virtual Tool Chain' are mainly used. As part of the crash safety study of autonomous vehicle, 25 car to car collision scenarios were provided as a result of a real accident-based accident reproduction analysis study conducted by a domestic research institution, and a vehicle crash analysis was performed using the FE car to car model of the Honda Accord. In order to analyze the results of the car to car simulation and to construct a database, major crash parameters were selected as impact speed, angle, location, and overlap, and a method of defining them in an indexed form was presented. In order to compare the crash severity of each scenario, a value obtained by integrating the resultant acceleration measured by the ACU of the vehicle was applied. The equivalent collision test mode was derived by comparing the crash severity of the regulation test mode, 30 deg rigid barrier mode, in the same way.

• 한국방사선학회논문지
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• 제4권2호
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• pp.13-20
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• 2010

견갑골의 골절 유 무와 외상에 의한 탈구를 진단하는데 있어 견갑골의 정측면상의 영상을 얻는 것이 매우 중요하다. 본 연구의 목적은 견갑골 측방향 촬영시 한국인 성인을 대상으로 견갑골의 정측면상을 얻는데 가장 적합한 회전 각도를 알아보는데 있다. 견갑골의 촬영을 위해 내원한 환자 20명(여 8명)을 대상으로 하였고 이들의 평균연령은 35.4세(15세부터 66세)였다. 수동각도기의 거상각도를 $30^{\circ}$, $40^{\circ}$, $45^{\circ}$로 하여 전 후방향 촬영하였다. 영상의 평가는 전문가 5명이 내측연과 외측연의 완전겹침이 있는 영상은 4점, 내측연과 외측연이 불완전 겹침이 있는 영상은 3점, 견갑골체 내측연과 외측연이 겹침이 없는 영상은 2점, 내측연과 외측연이 사방향으로 나타난 영상은 1점으로 4단계로 나누어 blind test를 하여 평가하였다. 평가한 각도별 평균점수는 $30^{\circ}$가 $1.53{\pm}0.39$점, $40^{\circ}$가 $3.83{\pm}0.15$점, $45^{\circ}$가 $2.17{\pm}0.43$ 점으로 나타났다. 도한 가슴둘레가 100cm이상인 군과 100cm이하인 군 간에는 유의한 차이가(p<0. 05) 없었고, 남자와 여자 간에도 역시 유의한 차이가 없는 것으로 나타났다. 지금까지 견갑골 정측면상을 얻는데 적합한 환자의 회전각도에 관한 연구가 없었으나, 본 연구를 통해 검사측을 $40^{\circ}$ 회전하며 검사측 상완골을 반대쪽으로 들며 촬영하는 것이 한국인 성인에서 견갑골의 정측면상을 얻는데 가장 적합하다는 결론을 얻었다. 본 연구 결과는 향후 견갑골의 측방향 촬영을 하는데 유용할 것으로 사료된다.

• 한국항공우주학회지
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• 제38권1호
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• pp.12-21
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• 2010

본 논문에서는 부분적인 지면효과 하에서의 단일로터 블레이드에 대한 제자리 비행 성능 특성을 확인하였다. 이를 위해 소형 로터 블레이드 회전 시험장치와 이동식 바닥면을 이용하여 고정된 회전속도에서 콜렉티브 피치각을 변화시키면서 추력과 토크를 측정하였다. 로터면과 지면이 겹치는 거리를 d, 로터의 직경을 D라 하면 지면효과가 없을 때부터 d/D가 0.25일 때까지는 지면효과가 로터의 성능에 거의 영향을 미치지 않는 것으로 확인되었다. 로터 깃의 개수가 4개일 때 지면 효과의 영향을 더 크게 받아 2개일 때보다 추력이 증가하고 동력이 감소하였다. 또한 피치각이 작을수록 지면효과로 인하여 추력이 증가하는 경향을 보였다. 이와 같은 실험 결과를 바탕으로 로터 깃의 개수와 부분적인 지면 효과를 고려한 새로운 경험식을 도출하였다.

• Imaging Science in Dentistry
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• 제34권2호
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• pp.63-67
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• 2004

Purpose: To make a focal trough (image layer) for an average maxillary dental arch of 6-year-old korean in panoramic radiography. Materials and Methods : Phantom for the maxillary dental arch was designed using intercanine width, intermolar width, tooth size, and interdental spacing to record the data of 6-year-old child. The characteristics of pre-corrected panoramic machine (for adult) was evaluated using the phantom, resolution test pattern for margin of the image layer, and metal ball for the center of the image layer. Panoramic image layer of the child was developed by means of decreasing the speed of film-cassette and positioning the phantom backwards, and then the characteristics of post-corrected panoramic machine (for child) were reevaluated. Results: At post-corrected panoramic image layer, beam projection angles at all interdental areas increased for about 2.6-3.8°, the position of the image layer was shifted toward the rotation center for about 2.5 mm at the deciduous central incisior area. The width of image layer decreased at all areas. Conclusion : Increased beam projection angle will reduce the disadvantage of tooth overlap, and the same form between the center of the image layer and dental arch will improve image resolution.

• 농업과학연구
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• 제42권1호
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• pp.63-71
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• 2015

Path planning is an essential part for traveling and mowing of autonomous lawn mower tractors. Objectives of the paper were to analyze operation patterns by a skilled farmer, to extract and optimize waypoints, and to demonstrate generation of formatted planned path for autonomous lawn mower tractors. A 27-HP mower tractor was operated by a skilled farmer on grass fields. To measure tractor travel and operation characteristics, an RTK-GPS antenna with a 6-cm RMS error, an inertia motion sensing unit, a gyro compass, a wheel angle sensor, and a mower on/off sensor were mounted on the mower tractor, and all the data were collected at a 10-Hz rate. All the sensor data were transferred through a software program to show the status immediately on the notebook. Planned path was generated using the program parameter settings, mileage and time calculations, and the travel path was plotted using developed software. Based on the human operation patterns, path planning algorithm was suggested for autonomous mower tractor. Finally path generation was demonstrated in a formatted file and graphic display. After optimizing the path planning, a decrease in distance about 13% and saving of the working time about 30% was achieved. Field test data showed some overlap, especially in the turning areas. Results of the study would be useful to implement an autonomous mower tractor, but further research needs to improve the performance.

• 대한화학회지
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• 제30권6호
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• pp.538-547
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• 1986

8가지 희토류원소를 주로 포함하고 있는 monazite정광을 X-선 형광분광법으로 분석하는데 있어서 분석선에 대한 다른 희토류원소의 스펙트럼선 겹침 방해를 조사하고 겹침 계수를 구하여 보정하는 방법에 대한 연구를 하였다. 순수한 희토류산화물을 사용하여 원소자신의 분석선 세기와 다른 원소의 분석선에 해당하는 회절각(2${\theta}$)에서의 세기를 측정하고 그들 세기의 비로 겹침계수를 구하였다. 겹침 계수를 이용하여 표준시료와 분석시료의 측정세기를 회귀분석법으로 보정하였다. 보정된 세기를 농도에 대해 도시한 검정곡선은 직선성이 현저히 향상되었고 표준편차도 많이 감소하였다. 시료의 분석 결과도 유도결합플라스마 방출분광법의 결과와 허용오차범위내에서 잘 일치하였다.

• 한국방사선학회논문지
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• 제15권7호
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• pp.1007-1013
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• 2021

본 연구는 유아 발의 합성 전후축방향 엑스선 촬영에서 발전체가 다리와 겹침 없이 균일한 농도와 선예한 영상을 평가하기 위하여 Receiver Operating Characteristic 와 Signal to Noise Ratio 분석 결과 Cronbach Alpha 값이 0.813로 유의하게 높았으며 신호대잡음비(SNR)의 연구에서는 발허리뼈에서 발꿈치뼈를 향하여 엑스선관을 10° 기울여 검사 시 5.948 높게 나타났으며, 발꿈치뼈에서 발허리뼈를 향하여 엑스선관을 20° 기울여 검사 시 6.957으로 가장 높았다. 또한, 주관적평가에서는 발허리뼈에서 발꿈치뼈로 10° 기울려 검사시 18점으로 높은 점수를 얻었으며, 발꿈치뼈에서 발허리쪽뼈을 향하여 엑스선관을 20° 기울여 검사 시 18 점을 얻었다. 본 연구의 결과 유아 발 합성 전후축방향 검사 시 엑스선관을 발허리뼈 뒤쪽으로 10° 기울였을 경우와 발꿈치뼈에서 전방으로 20° 기울였을 때 균일한 농도와 선예한 영상을 얻을 수 있다.