비완압형 어태치먼트의 위치에 따른 하악 가철성 국소위치의 지지조직에서의 저작압 분산 양태에 관한 3차원 유한요소적 연구

안원준,우순섭,이영수,심광섭,유광희 한양대학교 의과대학 1999 한양의대 학술지 Vol.19 No.1

The purpose of this study was to evaluate the stress patterns developed in supporting structures by removable partial denture with an extracoronal and an intracoronal rigid attachment. The mandibular removable partial dentures with Mini S-G (extracoronal) and C-M Box (intracoronal) attachment were constructed. Under 100N, 200N of vertical and 25N, 50N of lateral loads at the 1st and 2nd lower molar, stress distribution patterns and displacement were analyzed with three dimensional finite element method. The result were as follows: 1. There was no apparent difference in the patterns of stress distribution between rigid extracoronal and rigid intracironal attachments. 2. In case of the single abutment tooth with the rigid intracoronal attachment, it was not proper to preserve the abutment tooth. 3. With splinted abutments, the stress was distributed through all the root surface of both abutments. With single abutment, the stress was concentrated on the distal root surface of abutment. 4. With splinted abutments, there was not clear difference in the patterns of stress distribution with or without lingual bracing part. 5. In case of the single abutment tooth with the rigid intracoronal attachment and cantilever. More stress was concentrated around the abutment tooth with the lingual bracing part under loaded concentrated force and the abutment tooth without the lingual bracing part under loaded distributed force. 6. In case of the splinted abutments with the rigid extracoronal and intracoronal attachment, the denture base was displaced posteriorly and inferiorly when the force was applied. 7. In case of the single abutment tooth with the rigid intracoronal attachment, there was little displacement at the denture base.

불균일한 온도분포를 갖는 열교환기 휜에서의 착상 특성

안원준(Won-Jun An),김정수(Jung-Soo Kim),이관수(Kwan-Soo Lee) 대한설비공학회 2009 설비공학 논문집 Vol.21 No.7

In this study, frosting experiment was conducted to investigate the characteristics of frost formed on heat exchanger fins of non-uniform temperature distribution. Temperature distribution and frost characteristics of a 2-D fin surface were investigated in the airflow direction and the direction perpendicular to airflow. Temperature gradient was very small in the airflow direction, while it was large in the direction perpendicular to airflow due to fin heat conduction. The variations of the frost thickness gradient and the frost density gradient in the direction perpendicular to airflow were significant. On the other hand, the temperature gradient on frost surface in the direction perpendicular to airflow was significant at the early stage of frosting, while it decreased gradually as time elapsed.

자연치와 인공치의 저작압력에 관한 비교 연구

안원준,유광희 한양대학교 의과대학 1991 한양의대 학술지 Vol.11 No.1

The author measured maximum biting forces of normal persons with normal occlusion without prosthetic treatment from 20 to 25 of age and the patients wearing the dentures using the masticatory force meter. The following conclusions were obtained from this study. 1. The maximum biting forces of normal male were 32.45kg at the first molar teeth, 20.02kg at the first premolar and 13.67kg at the anterior teeth, and normal female, 33.51kg at the first molar, 20.75kg at the first premolar, and 11.75kg at the anterior teeth. 2. The maximum biting forces of male anteior and the first premolar teeth were stronger than that of female and the maximum biting forces of female the first molar teeth were stronger than that of male. 3. The maximum biting forces of the right side in the first molar teeth were stronger than left side in both sexes and left side in the first premolar teeth were stronger than right side in both sexes. 4. In the cases of wearing the full denture, the maximum biting forces appeared 13.20kg at the first molar teeth, 7.30kg at the premolar teeth and 5.10kg at the anterior teeth. 5. In the cases of wearing the full denture, the maximum biting forces showed 40% at the first molar teeth, 34% at the first premolar teeth and 40% at the anterior teeth in comparison with normal persons. 6. In the cases of wearing the partial denture, the maximum bitring forces appeared 23.90kg at the first molar teeth and 13.85kg at the first premolar teeth. 7. In the cases of wearing the partial denture, the maximum biting forces showed 72% at the first molar teeth and 65% at the premolar teeth in comparison with normal persons.

열교환기 휜에서의 서리 성장

안원준(Won-Jun An),김정수(Jung-Soo Kim),이관수(Kwan-Soo Lee) 대한설비공학회 2008 대한설비공학회 학술발표대회논문집 Vol.2008 No.2

In this study, frost behavior on two dimensional fins of a heat exchanger was experimentally investigated. Temperature distribution on a 2-D fin surface and frost properties were measured in the directions perpendicular to and parallel to airflow. The results indicated that the temperature gradient in the direction perpendicular to airflow was large because of fin heat conduction, while that in the direction parallel to airflow was very small. Frost thickness in the airflow direction decreased from the leading edge towards the trailing edge of the fin due to leading edge effect. The reduction rate of frost thickness in the airflow direction, however, was very small compared with that in the direction perpendicular to the airflow, as affected by the temperature distribution.

복합 정제 공정에 따른 천연 흑연의 물리화학적 특성 변화가 리튬 이온 전지의 음극재 성능에 미치는 영향

안원준 ( Won Jun Ahn ),황진웅 ( Jin Ung Hwang ),임지선 ( Ji Sun Im ),강석창 ( Seok Chang Kang ) 한국공업화학회 2021 공업화학 Vol.32 No.3

천연 흑연의 음극재 적용을 위하여 정제 공정을 실시하였으며, 공정에 따른 흑연의 구조적 변화와 불순물 함량이 음극 특성에 미치는 영향을 고찰하였다. 천연 흑연은 불화암모늄과 황산을 동일 비로 하여 사용량을 달리한 산처리 및 온도(800~2500 ℃)를 달리한 열처리를 통하여 화학적/물리적으로 정제되었다. 산을 이용한 불순물 제거는 한계가 있었으며, 이후 진행된 2500 ℃까지의 열처리를 통해 Si과 같은 일부 원소를 제외하고 대부분의 불순물이 전량 제거되는 것을 확인하였다. 복합 정제 공정에 따라 제조된 흑연 음극재의 특성이 향상되었으며, 구조와 불순물 함량 변화는 각각 용량 및 속도 특성과 초기 쿨롱 효율에 지배적인 영향을 미쳤다. 복합 정제 공정은 흑연 구조를 향상시켰으며, 불순물을 효율적으로 제거하여 SEI층 형성 억제 및 Li⁺ 삽입 공간 확대를 통해 리튬 이온 전지의 성능을 향상시켰다. A purification process was performed for the application of natural graphite as an anode material. The influence of the structural change and impurity content of graphite according to the process on the anode electrochemical characteristics was investigated. Natural graphite was chemically/physically purified by acid-treatment which used different amounts of solution of ammonium fluoride/sulfuric acid in the same ratio and thermal treatment used different temperatures (800~2500 ℃). Acid-treatment had limitation to remove impurities, and identified that all impurity contents was removed except some traces of atom such as Si by after progressed thermal-treatment until 2500 ℃. The anode materials characteristic of graphite treated by purification process was improved, and changes in the structure and impurity contents affected dominantly the capacity, rate property and initial Coulombic efficiency. Consequently, the complex purification process improved the graphite structure and also the performance of lithium ion battery by controlling the excessive formation of solid electrolyte interphase and expanding Li⁺ insertion space originated from the effective removal of impurities.

베이지안 접근법을 이용한 입력변수 및 근사모델 불확실성 하에서의 신뢰성 분석

안다운(Dawn An),원준호(Junho Won),김은정(Eunjeong Kim),최주호(Jooho Choi) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.10

Reliability analysis is of great importance in the advanced product design, which is to evaluate reliability due to the associated uncertainties. There are three types of uncertainties: the first is the aleatory uncertainty which is related with inherent physical randomness that is completely described by a suitable probability model. The second is the epistemic uncertainty, which results from the lack of knowledge due to the insufficient data. These two uncertainties are encountered in the input variables such as dimensional tolerances, material properties and loading conditions. The third is the metamodel uncertainty which arises from the approximation of the response function. In this study, an integrated method for the reliability analysis is proposed that can address all these uncertainties in a single Bayesian framework. Markov Chain Monte Carlo (MCMC) method is employed to facilitate the simulation of the posterior distribution. Mathematical and engineering examples are used to demonstrate the proposed method.

보건업 종사자의 업무상 질병

안선아 ( Seona An ),함승헌 ( Seunghon Ham ),이완형 ( Wanhyung Lee ),최원준 ( Won-jun Choi ),강성규 ( Seong-kyu Kang ) 한국산업보건학회 (구 한국산업위생학회) 2020 한국산업보건학회지 Vol.30 No.4

Objectives: Occupational diseases that occur due to or aggravated by work have commonly been recognized in the manufacturing industry, but there are now more incidences happening in the service industry due to changes in the industrial structure. Health workers are exposed to direct factors and various other causes of occupational disease at work, such as physical, chemical, biological, and psyco-social factors. This study aims to identify work-related diseases affecting health workers that are recognized as occupational diseases. Methods: The research is based on the data of workers whose diseases were accepted as work-related by the Industrial Accidents Compensation Insurance, and filed by the Korean Occupational Safety and Health Agency. Amongst the approved claims during 2011 to 2015, we focused on healthcare workers and health-related workers of the Korean Standard Classification of Occupations. Descriptive statistics were performed. Results: The number of health workers(HWs) with approved work-related disease was 1,707 over 5 years. The number of healthcare workers(HCWs) excluding caregivers was 370 (21.7%) and of health-related workers (HRWs) it was 736 (43.1%). Out of HWs who were approved for their illnesses, females were 80% of HCWs and 88% of HRWs. The most common occupational disease in HWs was musculoskeletal diseases, while that of nurses was infectious disease. Conclusions: HWs are exposed to various risks from their profession and are affected by occupational diseases. It is necessary to focus on this issue and provide preventive measures.

크리깅 기반 차원감소법을 이용한 베이지안 신뢰도 해석

안다운,최주호,원준호,An, Da-Un,Choi, Joo-Ho,Won, Jun-Ho 한국전산구조공학회 2008 한국전산구조공학회논문집 Vol.21 No.3

신뢰성 기반 형상 최적화(RBDO)글 위한 기술은 한정된 정보로 인한 인식론적 불확실성을 다룰 수 있는 베이지안 접근에 근거하여 발달된다. 최근까지, 전통적인 RBDO는 측정 데이터가 무한히 많아서 확실한 확률정보를 알고 있다는 가정 하에 실행되었다. 하지만 실제로는, 부족한 데이터로 인해 기존의 RBDO 방법의 유용성을 떨어뜨린다. 본 연구에서는, 확률정보의 불확실성을 인식하고, 따라서 산포를 갖게 되는 시스템 신뢰도의 확률 분포에서의 신뢰수준의 하한 값을 고려하기 위해 '베이지안 신뢰성'이 소개된다. 이런 경우, 베이지안 신뢰성 해석은 기존 신뢰도 해석의 이중 해석을 요구하게 된다. 크리깅 기반 차원 감소 방법(KDRM)은 신뢰도 해석을 위한 새로운 효율적인 방법으로써 사용되며, 제시된 방법은 몇 가지 수치예제를 사용하여 설명된다. A technique for reliability-based design optimization(RBDO) is developed based on the Bayesian approach, which can deal with the epistemic uncertainty arising due to the limited number of data. Until recently, the conventional REDO was implemented mostly by assuming the uncertainty as aleatory which means the statistical properties are completely known. In practice, however, this is not the case due to the insufficient data for estimating the statistical information, which makes the existing RBDO methods less useful. In this study, a Bayesian reliability is introduced to take account of the epistemic uncertainty, which is defined as the lower confidence bound of the probability distribution of the original reliability. In this case, the Bayesian reliability requires double loop of the conventional reliability analyses, which can be computationally expensive. Kriging based dimension reduction method(KDRM), which is a new efficient tool for the reliability analysis, is employed to this end. The proposed method is illustrated using a couple of numerical examples.

피로수명 연장을 위한 항공기 프레임 노치부위 국부형상 최적설계

원준호(Jun-Ho Won),최주호(Joo-Ho Choi),강진혁(Jin-Hyuk Gang),안다운(Da-Wn An),윤기준(Gi-Jun Yoon) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.12

The aim of this study is to apply shape optimization technique for the repair of aging airframe components, which may extend fatigue life substantially. Free-form optimum shapes of a cracked part to be reworked or replaced are investigated with the objective to minimize the peak local stress concentration or fatigue-damage. Iterative non-gradient method, which is based on an analogy with biological growth, is employed by incorporating the robust optimization method to take account of the stochastic nature of the loading conditions. Numerical examples of optimal hole shape in a flat plate are presented to validate the proposed method. The method is then applied to determine the reworked or replacement shape for the repair of a cracked rib in the rear assembly wing body of aircraft.

피로시험 데이터의 산포를 고려한 스프링의 신뢰성 최적설계

안다운(Dawn An),원준호(Junho Won),최주호(Jooho Choi) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11

Fatigue reliability problems are nowadays actively considered in the design of mechanical components. Recently, Dimension Reduction Method using Kriging approximation (KDRM) was proposed by the authors to efficiently calculate statistical moments of the response function. This method, which is more tractable for its sensitivity-free nature and providing the response PDF in a few number of analyses, is adopted in this study for the reliability analysis. Before applying this method to the practical fatigue problems, accuracies are studied in terms of parameters of the KDRM through a number of numerical examples, from which best set of parameters are suggested. In the fatigue reliability problems, good number of experimental data are necessary to get the statistical distribution of the S-N parameters. The information, however, are not always available due to the limited expense and time. In this case, a family of curves with prediction interval, called P-S-N curve, is constructed from regression analysis. Using the KDRM, once a set of responses are available at the sample points at the mean, all the reliability analyses for each P-S-N curve can be efficiently studied without additional response evaluations. The method is applied to a spring design problem as an illustration of practical applications, in which reliability-based design optimization (RBDO) is conducted by employing stochastic response surface method which includes probabilistic constraints in itself. Resulting information is of great practical value and will be very helpful for making trade-off decision during the fatigue design.