샌드위치 실린더의 압력충격 응력해석에 관한 연구

조환기 청주대학교 2014 産業科學硏究 Vol.31 No.2

Pressure shock stresses in the sandwich structured hollow cylinder is analyzed under the suddenly applied pressure on the wall of cylinder. The mathematical equations for the sandwich hollow cylinder are drawn from the equations of elastodynamic problem. The closed form solution of the equations can be obtained by using the integral transforms such as the finite Hankel transform, Laplace transform and the inverse Laplace transform. The numerical results of analytical solution applying material properties on the hollow sandwich cylinder are obtained. The results are shown good pressure shock characteristics on the wall of sandwich cylinder. In this study, suddenly applied inner pressure can cause the structural damage due to increasing of tangential stress in the radial direction as the time passes after applying pressure.

Cuban-8형 풍력 블레이드의 회전특성 분석

조환기 청주대학교 2017 産業科學硏究 Vol.35 No.1

In this paper, the rotating characteristics of Cuban-8 type(the two twisted circumferential blades) horizontal axis wind blades are investigated by theoretical formulation and an experiment. The rotating characteristic of wind blades is analyzed with azimuthal angles and elevation angles of blades. The projecting trajectories of Cuban-8 type blade due to rotation are also analyzed on the each plane in the Cartesian coordinate system. The asymmetric structure of blades on the rotating plane is correlated with the effective cross section from colliding with the incident air. The rotating torque and effective cross section of the blade are also formulated with the parameters of radius, width and height of the blade. The effective cross section of the blade goes to the saturation level as increasing angular velocity of the blade. The results of wind tunnel experiments show the rotating characteristics of the wind blade with wind velocity and blade gap between two twisted blades.

편대비행에서 후방 항공기의 위치 안전성 분석

조환기,Cho, Hwan Kee 한국항공운항학회 2016 한국항공운항학회지 Vol.24 No.2

Positional stability analysis based on aerodynamic forces and induced moments of formation flight using two small aircraft models is presented. The aerodynamic force and moments of the trailing aircraft are analyzed in the aspect of flight stability. The induced moments with the change of local flow direction by wing-tip vortex from the leading aircraft can affect the flight positional stability of aircraft in closed formation flight. Aerodynamic forces and moments of trailing aircraft model are measured by 6-component internal balance at the 49 locations with vertical and lateral space between two aircraft models. Results are shown that the positional stability of trailing aircraft in formation flight can be analyzed by positional stability derivatives with vertical and lateral space. It is concluded that flying positions can be important factors for aircraft position stability due to induced aerodynamic force and moments with vertical and lateral spacing by the variation of flow pattern from the leading aircraft in formation flight.

Experimental study on the aerodynamic characteristics of a fighter-type aircraft model in close formation flight

조환기,이선태,한철희 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.8

This paper presents on the aerodynamic characteristics of a fighter-type aircraft model in formation flight. The effect of longitudinaland lateral distance changes on the aerodynamic characteristics of a trailing aircraft is investigated by experiment. The wind-tunnel testingis conducted with two-5% scaled small sized fighter-type aircraft models. Aerodynamic forces and moments of a trailing aircraftmodel are measured at 49 locations on the cross-section behind a leading aircraft model. It is observed that the leading aircraft affects theincremental lift and drag of the trailing aircraft significantly. It is also proved that the aerodynamic characteristics of the trailing aircraftcan be improved if positioned at proper locations behind the leading aircraft while in formation flight

Elastodynamic Thermal Shock Stresses in Orthotropic Thick Cylindrical Shells

조환기,G. A. Kardomateas 한국항공우주학회 1997 한국항공우주학회 학술발표회 논문집 Vol.- No.-

항공운항학 교육과정의 분석 및 발전 방향

조환기 청주대학교 2016 産業科學硏究 Vol.33 No.2

The development direction of educational curriculum provided in the department of aeronautics and flight education, established by domestic universities, is discussed. Recently some of colleges and universities are newly opened curriculums for the department of aeronautical science and flight operation. But there doesn't exist any standard curriculum or certified course for aviation's education. Several educational programs of aviation study are investigated and analyzed. In discussion, the desirable curriculum of the department of aeronautical science and flight operation should include the flight core courses, aeronautical science and specialty for pilot licences such as PPL, IFR and CPL. Various subjects to enhance deep knowledge for aircraft operation are also needed in th future educational program. Certified educational system by government agency need to be considered in the future.

돼지의 등지방두께와 도체중이 육질등급에 미치는 영향추정

조환기,김병우,선두원,이정규,박재찬,박철현 경상대학교 농업생명과학연구원 2010 농업생명과학연구 Vol.44 No.3

본 연구는 축산물품질평가원에서 제공한 2007년 7월 1일부터 2009년 4월 30일까지의 도체등급판정자료 20,450,773두의 등지방두께, 도체중 및 육질등급 자료를 이용하였으며, 등지방두께와 도체중에 대한 환경효과를 추정하였고, 성별, 등지방두께별, 도체중별 등급출현율을 추정하였다. 조사된 형질의 평균치는 도체중과 등지방두께가 각각 85.97±0.002 kg, 20.76±0.001 ㎜로 나타났다. 성의 효과에서는 거세돼지의 도체중과 등지방두께가 각각 86.25±0.003 kg과 22.55±0.002 ㎜로 나타나, 다른 암퇘지나 수퇘지에 비하여 유의적으로 높게 나타났고, 도축 년도의 효과에서는 년도가 경과함에 따라 도체중과 등지방두께가 증가하는 경향을 나타내었으며, 도축 계절의 효과에서는 도체중의 경우 겨울에 87.00± 0.007 kg으로 유의적으로 무겁게 나타났고, 등지방두께의 경우 가을에 19.32±0.004 ㎜로 유의적으로 두껍게 나타났다. 성에 대한 육질등급 출현율의 경우 온도체와 냉도체 모두 거세돼지의 상위등급 출현율이 암퇘지에 비하여 높게 나타났다. 도체중에 대한 육질등급 출현율의 경우, 온도체와 냉도체 모두 84∼88 kg 그룹에서 상위등급 출현율이 다른 그룹에 비하여 높게 나타났다. 등지방두께에 대한 육질등급 출현율의 경우 온도체와 냉도체 모두 22∼24 ㎜ 그룹에서 상위등급 출현율이 다른 그룹에 비하여 높게 나타났다. This study was carried out to investigate the effect of environmental fators on backfat thickness and carcass weight and to investigate the carcass grade frequencies by sex, backfat thickness and carcass weight in commercial pigs. Total 20,450,773 of commercial pigs was used in this study, which were obtained from Korea institute for Animal Product Evaluation (KAPE) from July 1, 2007 to April 30, 2009. The averages of carcass weight and backfat thickness were 20.76±0.001 ㎜ and 85.97±0.002 kg, respectively. Carcass weight and backfat thickness of barrow were 22.55±0.002 ㎜ and 86.25±0.003 kg, respectively, which were significantly higher than those of males and females. The carcass weight and backfat thickness were increased with the slaughter years. In the effects of the season of slaughter, carcass weight was significantly higher in winter (87.00±0.007 kg), and the backfat thickness was significantly higher in fall (19.32±0.004 ㎜). In grade frequencies of carcass quality grade in sex, grade frequencies of high grade in barrow was higher than those of female in hot carcass and cold carcass. In grade frequencies of carcass quality grade in carcass weight, grade frequencies of high grade in 84∼88kg was higher than the other groups in hot carcass and cold carcass. In grade frequencies of carcass quality grade in backfat thickness, grade frequencies of high grade in 22∼24 ㎜ was higher than other groups in hot carcass and cold carcass.

業說의 社會的 性格

조환기 동국대학교 불교대학 1986 東國思想 Vol.19 No.-

항공기의 롤운동 동안정미계수 측정에 관한 연구

조환기,Cho, Hwan-Kee 한국항공운항학회 2013 한국항공운항학회지 Vol.21 No.4

This paper deals with an experimental technique for the measurement of dynamic stability derivatives in the roll motion of aircraft. Experimental aquisition method for aircraft's dynamic stability derivatives is conducted on the oscillation condition of aircraft model in the subsonic wind tunnel. The oscillation of aircraft model was forced by the oscillation apparatus. The forced oscillation technique is the method getting data from the internal balance inserted into the aircraft model during oscillating it. Dynamic stability derivatives of rolling motion were calculated by data reduction from the measurements of rolling moment, frequency and amplitude of aircraft model due to forced oscillation under wind conditions. Results of experiment is obtained similar one with those of roll dynamic stability derivatives measured in other institutes. 본 논문은 항공기의 롤운동에 대한 동안정미계수 측정을 위한 실험적 기법에 관하여 기술하였다. 항공기 동안정미계수의 실험적인 추출 방법은 항공기 모델을 이용하여 풍동에서 진동실험을 수행하는 것이다. 항공기 모델의 진동은 강제진동기법이 적용되었다. 강제진동 기법은 항공기 모델의 내부에 밸런스형의 측정장치를 설치하고 모델을 풍동 시험부 내에 고정한 후에 강제로 진동시키면서 밸런스로부터 측정값을 획득하는 방법이다. 롤링 운동에 대한 동안정미계수는 풍속이 있는 상태에서 강제진동에 의한 항공기 모델의 모멘트와 진동 주파수 및 진폭을 측정한 후에 자료처리를 통하여 계산되었다. 풍동실험의 결과는 타 기관에서 측정된 표준동역학모델의 롤 동안정미계수와 유사한 결과가 얻어짐을 확인하였다.

전투기 연료탱크 안전분리를 위한 풍동실험 연구

조환기,이상현,강치행,황영하 한국항공우주학회 2009 한국항공우주학회 학술발표회 논문집 Vol.2009 No.4