차량의 자갈로 주행성능 예측을 위한 자갈의 이산요소모델

임동우 ( Dongu Im ),김지태 ( Ji-tae Kim ),한현우 ( Hyun-woo Han ),최혁진 ( Hyuek-jin Choi ),오재원 ( Jae-won Oh ),박영준 ( Young-jun Park ) 한국농업기계학회 2021 한국농업기계학회 학술발표논문집 Vol.26 No.1

자갈로는 아스팔트 포장 도로에 비해 낮은 수준의 마찰 특성을 가진다고 보고되고 있다. 특히, 경사로에서 자갈은 구름 운동이 발생하게 되며 그에 따라 주행 중 슬립이 발생하게 된다. 이는 차량의 동력손실과 더불어 안정성(stability)에 악영향을 미친다. 본 연구에서는 차량의 자갈로 주행성능을 예측하기 위해 자갈의 이산요소모델을 개발하였다. 이산요소법(discrete element method)은 접촉 이론을 바탕으로 입자와 입자, 입자와 기계장치와의 접촉력을 계산하는 수치해석법이다. 실제와 유사한 입자의 역학적 특성을 시뮬레이션 모델에 반영하기 위해서는 입자의 형상, 밀도, 크기 등의 macro parameters와 Young’s modulus, Poisson’s ratio, 마찰계수 등의 micro parameters를 정확하게 정의해야 한다. 따라서 본 연구에서는 자갈의 밀도와 크기를 측정하였으며, 실제 자갈과 유사한 형상을 반영하기 위해 자갈의 sphericity를 측정하였다. 또한, 일축 압축 시험을 통해 자갈의 Young’s modulus와 Poisson’s ratio를 측정하였으며, 안식각(repose angle) 시험을 통해 자갈의 마찰계수를 도출하였다. 마지막으로 자갈의 이산요소모델을 검증하기 위해 단일 그라우저의 추진력 시험을 수행하였으며 시험 결과를 시뮬레이션 결과와 비교하였다.

대기오염과 천식증상에 의한 응급실내원과의 연관성에 관한 환자교차연구

임형준,이상윤,윤기정,주영수,강대희,조수현 대한산업의학회 2000 대한직업환경의학회지 Vol.12 No.2

Objectives : This study, using case-crossover design, search a relationship between changing levels of air pollutants and asthma attack in asthma patients. Methods : We searched the daily total number of asthmatic patients at hospital's emergency room in Seoul, Korea by investigating total 49 general hospital's emergency room records. Otherwise, We investigated medical records of asthmatic patients at one of the 49 hospitals we have searched. We investigated addresses that they are living, diagnosis, smoking history, whether respiratory infection or not, medications. We analyzed the data by 1:m conditional logistic regression used when matched case-control study is analyzed. Control periods were chosen by bidirectional paired matching technique 7, 14 days before and after case periods. Results : the relative risk of asthmatic attack by 100 ppm ozone increase between June and September were 1.348(95 % CI = 1.010∼1.619). Between November and February, the relative risk by 100 ㎍/㎥ TSP increase, 100ppb sulfur dioxide and nitrogen dioxide were respectively 1,278(1.010∼1.619), 1.237(1.019∼1.502), 1.285(1.006∼1.640). In stratified analysis, the relative risk were significant when the asthmatic patients were children aged 15 years or below, when there were respiratory infection, and when the patients took medications irregularly Conclusions : There was statistically significant association between ambient levels of air pollutants and asthmatic attack. So, we have to exert our efforts to minimize the air pollution effectively, to protect public health from air pollution.

김치 유산균인 Lactobacillus sp. JJ-2001이 생산하는 Bacteriocin에 관한 연구

조영배,조우제,조영임,이은주,김성구,전홍기 부산대학교 유전공학연구소 1997 분자생물학 연구보 Vol.13 No.-

The microorganisms producing bacteriocin from kimch were screened, and among them,a strain showing the highest bacteriocin activity and stability was isolated. Based on the taxonomic characteristics of its morphological, cultural and physiological properties, the isolatef strain was characterized as Lactobacilius sp..To identify optimal conditions for the growth and the production of bacteriocin from the isolated strain,nutrient source, initial pH, and culture temperature were evaluated. Physiochemical properties of bacteriocin was also investigated. The potimal condition for the production of bacteriocin and the cell growth was obtained at 2% glucose, 1% beef extract as organic nitrogen source,1%(NH_4)_2SO_4 as inorganic nitrogen source,and 0.1% Tween 80. The isolated strain showed the maximum growth at 25℃. The inhibitory range of its antimicrobial substance aginst gram positive bacteria was marrow and its inhibitory activity was maintained between pH3.0 and pH8.0. The antimicrobial activity of bacteriocin from the isolated strain was stable at 50℃.

폐목질을 사용한 모르터의 물성에 관한 기초적 연구

황병준,김영주,강태경,정근호,임서형,정상진 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.2(구조계)

Recently, as the alternatives to preserve environment such as effective usage of wastes or unusable resources are drawing attentions, researches and measures for the two tasks, which are reuse of waste wood and development of eco friendly materials, are being examined and established in various fields. However, they are still insufficient. Therefore, in this study, for the efficient application of waste woods and eco-friendly effects, mortar was produced using sawdust as the waste wood and mineral material cement for combination, in order to produce inorganic boards using waste woods, which were made when sawing. This study attempted to suggest a basic material about the physical properties of mortar, which used waste woods, after examining the features of wood mixture rate, water-cement rate, congelation according to the mixture rate of the setting accelerator, specific gravity, compression intensity, and bending intensity as experiment factors.

상악 유전치부의 치간공간과 인접면 우식에 관한 조사연구

김진영,이광희,라지영,안소연,정승열,임경욱,반재혁 大韓小兒齒科學會 2009 大韓小兒齒科學會誌 Vol.36 No.3

본 연구는 상악 유전치부의 치간공간과 인접면 우식의 상관관계를 평가해보고자 하였다. 익산에 거주하는 만3-7세의 어린이 555명을 대상으로 하였으며 탐침이 통과하는지 여부로 치간공간이 있음과 없음으로 분류하였고 와동이 형성되었거나 법랑질 표면이 연화되었을 경우 인접면 우식이 존재하는 것으로 판단하였다. 연구 결과 다음과 같은 결론을 얻었다. 1. 상악 유전치부의 치간공간은 영장류 공간이 77.4%, 발육공간이 유측절치와 유중절치 사이에서 54.4%, 양유중절치 사이에서 39.0%로 나타났다. 2. 인접면 우식발생율은 우측유견치가 6.3%, 우측유측절치가 14.7%, 우측유중절치가 33.5%, 좌측유중절치가 33.7%, 좌측유측절치가 16.0%, 좌측유견치가 4.7%로 나타났다. 3. 치간공간의 수가 많을수록 상악 유전치의 우식발생율은 낮아졌으나 그 상관관계(r=0.024)는 미약하였다. 4. 상악 유전치부에 공간이 존재하지 않을 경우 존재할 때 보다 평균 우식발생율이 높았으며, 치간공간이 전혀 존재하지 않는 경우 한 곳이라도 치간공간이 존재하는 경우보다 평균 우식발생율이 2배 이상 높은 것으로 나타났다. The purpose of this study was to assess the relationship between interdental spaces and proximal caries in maxillary anterior primary teeth. 555 children aged 3-7 inhabit in Iksan were divided into two groups, depending on the presence of interdental space which was detected by a dental explorer. They were determined to have proximal caries if cavity was formed or the enamel surface was softened. The results were as follows : 1. Regarding interdental spaces, 77.4% had primate spaces; 54.4% had developmental spaces between central and lateral incisor, and 39.0% between central incisors. 2. Interproximal caries incidences in right primary canine, lateral incisor, and central incisor were 6.3%, 14.7%, and 33.5%, respectively. Also interproximal caries incidences in left primary central incisor, lateral incisor, and canine were 33.7%, 16.0%, and 4.7%, respectively. 3. Children with more interdental spaces had less caries incidence, but the relationship was weak(r=-0.024). 4. The mean caries incidence was higher in absence of interdental space of maxillary primary incisors than in presence of space. The mean caries incidence with no interdental space was twice as high as that with presence of interdental space.

개에 발생한 만성 승모판폐쇄부전증에 대한 Pimobendan 치료 1례

장재임,전형규,최호정,이영원,송근호 忠南大學校 獸醫科大學 附設 動物醫科學硏究所 2006 動物醫科學硏究誌 Vol.14 No.-

A 11-year-old intact male maltese dog with respiratory distress, cyanosis and coughing was referred to the Veterinary Medical Teaching Hospital of Chungnam National University. Loud holosystolic murmur with a palpable precordial thrill was heard at the left apex region by auscultation. Left sided cardiac enlargement and mitral regurgitated flow were detected by thoracic radiography and echocardiography, respectively. Clinical signs were improved by treatment of diuretics, ACE inhibitor and pimobendan.

남자 고등학교 세팍타크로 경기의 공격기술에 관한 분석 연구

김영호,고문석,제임스전,이영익,차정훈,현종건,김범수,임종만,이석인 한국스포츠리서치 2004 한국 스포츠 리서치 Vol.15 No.6

This research aims at analysis of attack technique in sepaktakraw games. For this purpose, 3 high school coaches observed and recorded each game Five times in videos of high school male players' thirty games in 2003. The conclusion from the analysis of the recorded data are as follows. 1. Scissors spike was the most popular (favorite) attack technique. Rolling spike, tapping spike and heading spike was popular in order. 2. Heading spike showed the highest success rate (73.5%) in attack technique. And tapping spike (69.5%), scissors spike (57.8%) and rolling spike (67.11) showed a lower success rate in order. In failure rate, heading spike (5.5%), tapping spike (36.5%), scissors spike (32.2%) and rolling spike (32.9%) had a higher percentage in order. 3. When receive was stable, the success rate in attach technique was 47.1%, the failure rate was 20.1%. On the other hand, when receive was unstable, the success rate in attach technique was 16.5%, the failure rate was 14.3%.

고출력 레이저에 의한 이종금속 용접특성

신호준,유영태,임기건,안동규 한국공작기계학회 2004 한국공작기계학회 추계학술대회논문집 Vol.2004 No.-

For many years and primarily for economical reasons, Dissimilar Metal Welds have been used as transition joints in a variety of equipment and applications. But Dissimilar Metal Welds have several fabrication and metallurgical drawbacks that can often lead to in-service failures. In this paper, the laser weldability of STS304 stainless steel and SM45C at dissimilar metal welds using a continuous wave Nd:YAG laser are experimentally investigated. An experimental study was conducted to determine effects of welding parameters, on eliminating or reducing the extent welding zone formation at dissimilar metal welds and to optimize those parameters that have the most influence parameters such as focus length, power, beam speed, shielding gas, and wave length of laser were tested.

골프 참가자의 자기의식에 관한 연구

김하영,임준택 한국학교체육학회 2004 한국학교 체육학회지 Vol.14 No.1

본 연구는 골프참가자들의 자기의식에 관한 연구이다. 독립변인은 골프참가의 인지적, 행동적, 정서적 수준으로 구분하여 정서적 수준, 즉, 얼마나 골프를 선호하느냐, 행동적 수준, 즉, 얼마동안, 얼마나 자주, 얼마나몰입하여 참가하느냐로 구분하였으며, 인지적 수준, 즉, 골프에 대한 실력정도와 지식정도를 묻는 문항으로 구성하였으며, 종속변인은 Fenigstein, Scheie. 및 Buss(1975)가 개발한 측정도구를 김득란(1993)이 재구성하여 사용한 자기의식 설문지를 사용하였다. 이러한 자기의식은 공적·사적 자기의식과 사회적 불안의 세 가지 변인으로 구성되어 있다. 이러한 변인을 기초로 하여 설문지를 작성하였으며, 2003년 현재 골프종목에 참가중인 20세 이상의 성인에게 배포, 회수 후 통계처리하였다. 이에 다음과 같은 결론을 얻었다. 첫째, 골프 참가자의 정서적 참가수준은 사회적 불안, 공적·사적 자기의식에 영향을 미쳤다. 둘째, 골프 참가자의 행동적 참가수준은 사회적 불안, 공적·사적 자기의식에 영향을 미쳤다. 셋째, 골프 참가자의 행동적 참가수준은 사회적 불안, 공적·사적 자기의식에 영향을 미쳤다. The purpose of this study was to examine self-consciousness in golf participants. To achieve this goal, hypotheses were established. This study was conducted by establishing a population consisting of participants over 20 years in golf in regions of Seoul and then using cluster random sampling to sample a total of 300 persons; however, the data of total 285 were actually used for the analysis. A questionnaire was used as a tool for this study. The data were processed by computer with SPSS Windows 10.0 Version which is a statistical program; also used were descriptive statistics analysis, factor analysis, reliability analysis, simple regression analysis, multiple regression analysis. The conclusion drawn through the above process is as follows: First, the behavioral maniacal level of golf participants influenced self-consciousness. Second, the behavioral maniacal level of golf participants influenced self-consciousness. Third, the cognitive maniacal level of golf participantinfluenced self-consciousness.

SM45C의 레이저 표면경화특성

신호준,유영태,안동규,임기건 한국공작기계학회 2005 한국공작기계학회 춘계학술대회논문집 Vol.2005 No.-

Laser surface hardening is an effective technique used to improve the tribological properties and also to increase the service life of automobile components such as camshafts, crankshatfs, lorry brake drums and gears. High power CO₂ lasers and Nd:YAG lasers are employed for localized hardening of materials and hence are of potential application in the automobile industries. The heat is conducted rapidly into the bulk of the specimen causing self quenching to occur and the formation of martensitic structure. In this investigation, the microstructure features occurring in Nd:YAG laser hardening SM45C steel are discussed with the use of optical microscopic and scanning electron microscopic analysis. Moreover, This paper describes the optimism of the processing parameters for maximum hardened depth of SM45C steel specimens of 3mm thickness by using CW Nd:YAG laser. Travel speed was varied from 0.6m/min to 1.0m/min. The maximum hardness and case depth fo SM45C steel are 780Hv and 0.4mm by laser hardening.