• 동력기계공학회지
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• 제17권4호
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• pp.139-146
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• 2013

Because the magnetic bearing supports levitating body without contact, wear, noise and vibration, it is very useful to high revolution machinery. In this paper we selected ATmega 128, a less expensive and widely used micro controller, for control the magnetic bearing system. And we selected the sampling time and the control gain of PID controller through trial-and-error. The control program of the one board controller utilized lookup table to reduce calculation time, and bit shifting for the integer calculation in instead of floating point calculation. As the results, the controller carried out relatively high speed PID control on sampling time 0.25 ms. At last the rotation test for the magnetic bearing system was carried out by 3 phase induction motor and air turbine.

• 한국산학기술학회논문지
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• 제10권1호
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• pp.25-31
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• 2009

공기스프링을 감쇠기로 사용하는 방진대는 넓은 주파수대역에서 우수한 진동 절연성능을 가짐으로 널리 사용되어 왔다. 하지만 공기스프링은 구조적으로 저강성, 저감쇠의 특성을 가지고 있으므로 외란에 의해 쉽게 가진되어 안정성이 떨어지는 문제가 있다. 이에 공기스프링과 같은 수동소자만을 이용한 수동제어 형식의 보완을 위해 능동 및 반능동 방식의 감쇠기가 제안되고 연구되고 있다. 따라서 본 연구에서는 이러한 수동형 제진대의 능동 및 반능동제어를 위한 동역학적 해석에 관하여 연구하였다. 제진대의 제어시스템 구현을 위하여 6 자유도 제진대의 물리적인 특성에 기초한 동역학적 모델을 정립하고 해석 및 실험을 통해 동역학 모델의 적용가능성을 검증하였다.

• 한국항공우주학회지
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• 제42권10호
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• pp.884-892
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• 2014

비행 시뮬레이터에 사용되는 데이터베이스를 신경회로망을 이용한 메타모델로 대체함으로써 기존 시뮬레이터 대비 비행 한계점 부근 공력특성에 대한 구현충실도 및 실시간성을 향상시키고자 하였다. 임의의 비선형 데이터베이스에 대해 메타모델의 정확도가 기존 테이블 검색 방식에 비해 상대적으로 높음을 확인하였으며 특정 F-16 기동에 대한 시뮬레이션을 통해 계산속도도 향상됨을 확인하였다. 신경회로망을 이용한 메타모델에서 은닉노드 수의 증가는 데이터베이스에 대한 추정정확도를 향상시키지만 많은 계산 시간이 소요되는 지수함수 수의 증가로 인해 함수발생 속도가 지연되게 된다. 이를 보완하기 위해 빠른 지수함수 계산 방법을 적용하는 연구도 추가적으로 수행하였다.

• 대한기관식도과학회:학술대회논문집
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• 대한기관식도과학회 1976년도 제10차 학술대회연제 순서 및 초록
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• pp.87.1-87
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• 1976

Bekesy measured the sound transformation system of the middle ear 49 years ago. According to his reports, a ratio between the size of ear drum and the size of oval window is 17 : 1, and the lever function of the ossicles is physiologically 1.3 : 1. Therefore, the hearing might be aggravated to 27.5㏈ in the case of the vanishment of 3 ossicles. In 1952, Wullstein reported 5 types of tympanop-lasty and the fourth type among them was especially named for the sound-protection. The oval window is only exposed by the sound pressure and the round window is not exposed. According to the application by this idea, the post-operative hearing might be improved until 27.5㏈. Mean while, in 1942, Onchi verified through his experiment that the results of Bekesy's measurement was not completely conformed to Onchi result. Bekesy measured the sound pressure on the stapes plate of the oval window, on the other hand, Onchi measured the sound pressure on the surface of the perilymph of the oval window after removing the stapes plate(Fig. 1).(Figure omitted) The difference of their experiment is recognized that the impedance of the stapes plate exists or not (Fig. 1). Both Audiogrums are compared as Fig. 2. The result of IV type of tympanoplasty is success ful in 54% as the Table 1. (Table Omitted) The reason of unsatisfactory is caused by the thick and unmovable window-membrane and by the closing of air passage to the round window. The closing of the air passage to the round window is occurred by the adhesion between the grafting membrane and the surface of promontorium. In order to preserve this adhesion, I produce to transplantate the mucous membrane of the lip to the bone surface of tympanic cavity after removing the granulation tissue of the tympanic cavity and to form a membranous canal for the sake of air passage (Fig. 3). (Figure Omitted) The post-operative hearing by this method is shown as Fig. 4, 5. In other words, the post-operative sound pressure entered into the cochlea directly, by way of the oval window only, not by way of the round window, as a theorie of the sound protection. (Figure omitted)

• 대한기계학회논문집
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• 제11권1호
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• pp.177-188
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• 1987

본 논문에서는 연소기체의 열력학적 평형조성 계산을 위한 수식을 Gibbs의 자 유에너지 최소화법에 의하여 유도하고 이를 컴퓨터 프로그램화하여, Table 1의 특성을 지닌 연료에 대하여 ⅰ) 연소공기량에 따른 평형조성 및 단열불꽃온도, ⅱ) 연소온도 변화에 따른 평형조성의 변화를 계산함으로써 연소기체의 생성기구를 열력학적으로 해 석하였다.

• International Journal of Aeronautical and Space Sciences
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• 제10권2호
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• pp.43-51
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• 2009

In the flight of air vehicles, accurate air data information is required to control them effectively. Especially, helicopters are often put in drastic motion involved with high angle of attacks in order to perform difficult missions. Among various sensors, the multi function probe (MFP) has been used in the present study mainly owing to its advantages in structural simplicity and capability of providing various information such as static and total pressure, speed, and pitch and yaw angles. In this study, a five-hole multi-function probe (FHMFP) is developed and its calibration is conducted using multiple regressions. In this work a calibration study on the FHMFP, an air data sensor for helicopters, is reported. It is shown that the pitch and yaw angles' accuracy of calibration is ${\pm}0.91^{\circ}$ at a cone angle of $0^{\circ}{\sim}30^{\circ}$ and ${\pm}2.0^{\circ}$ at $30^{\circ}{\sim}43^{\circ}$, respectively, which is summarized in table 3.

• 한국정밀공학회지
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• 제30권12호
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• pp.1321-1325
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• 2013

In this paper, we proposed an air bearing stage with active magnetic preloads in vertical directions compensating motion errors and attenuating vibrations to improve dynamic characteristics. This preloaded design gives simpler configuration of the stage, and active control of preload can be used for compensating motion errors by feedforward method. To improve dynamic characteristics, vibration of the table is monitored by an accelerometer, and controlled by a DSP based digital controller with integrator and band pass filters for suppressing roll and pitch vibration modes. The modes were evaluated by measuring frequency response functions, and compared with compensated responses. This showed effective results for suppressing poorly damped regenerative vibration of air bearings.

• Journal of Biosystems Engineering
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• 제6권1호
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• pp.83-92
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• 1981

A simulation model of natural air drying to predict the changes of the grain moisture content and dry matter loss of rough rice was developed by the application of mass diffusion theory. A series of simulated drying tests was conducted using the 10 year weather data (1970-1979) obtained from Cheongju, Chuncheon, Daegu, Daejeon, Jeonju, Jinju and Suweon in Korea. System performance factors treated in this study were initial moisture content, airflow rate, bin diameter and grain depth. The results obtained in this study are summarized as follows: 1) The simulation model used in this study was validated with actual experimental results and was applicable to the natural air drying of rough rice. 2) Minimum airflow rates for safe drying were determined for different initial moisture contents and regional weather conditions as shown in Table 6. 3) Equations for estimating drying time and dry matter loss in terms of airflow rate and initial moisture content were derived in the form of an exponential function. 4) These results show that the natural air drying system of rough rice is feasible in Korea even for the poorest drying condition.

• Journal of Forest and Environmental Science
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• 제32권3호
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• pp.262-269
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• 2016

The purposes of this study are to calculate the green and dried weight using wood discs, to figure out weight change on air drying times, and to develop the model of wood disc weight change for Larix kaempferi, Pinus koraiensis, and Pinus densiflora. The variables affecting the weight change were investigated, and the pattern of weight change over time was figured out through linear models. When comparing the stem green weight calculated using wood discs in this study with the weight table of Korea Forest Service, the weight was not significantly different for L. kaempferi and P. koraiensis. On the other hand, in comparison of stem dried weight, the weight was significantly different in all of three species. In addition, various measurement factors were examined to figure out the relationship with weight change, and air drying times and disc diameter were found as significant independent variables. Finally, two linear models were developed to estimate air drying times of three species, fit statistics were significant for practical use.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 1999년도 추계학술대회 논문집
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• pp.293-294
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• 1999

일반적으로 환경오염 하면 대기, 수질 토양오염과 같은 실외 오염을 의미하며, 우리 나라의 경우 대부분의 환경오염에 대한 연구가 이들에 집중되어 있다. 그러나 실질적으로 일반인이 실외에서 보내는 시간보다도 실내에서 지내는 시간 (70∼80％) 이 월등히 많으며, 외국의 여러 보고에 의하면 대기오염보다 실내공기 오염이 일반인의 건강에 미치는 영향이 훨씬 현저하다(Table 1), 그러나 우리 나라의 경우 환경에 관한 연구는 환경부에서 주도한 관계로 실외 환경오염에 집중되어 있다.(중략)