• 대한전기학회논문지:시스템및제어부문D
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• 제50권2호
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• pp.72-79
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• 2001

In the GPS/DR integrated system, the GPS position(or velocity) is used to compensate the DR output and to calibrate errors of the DR sensor. This synergistic relationship ensures that the calibrated DR accuracy can be maintained even when the GPS signal is blocked. Because of the observability problem, however, the DR sensors are not sufficiently calibrated when the vehicle speed is low. This problem can be solved if we use a multi-antenna GPS receiver for attitude determination instead of conventional one. This paper designs a two-antenna GP receiver integrated with DR sensors. The proposed integration system has three remarkable features. First, the DR sensor can be calibrated regardless of the vehicle speed with the aid of two-antenna GPS receiver. Secondly, the search space of integer ambiguities in GPS carrier-phase measurements is reduced to a part of the surface of the sphere using DR heading. Thirdly, the detection resolution of cycle-slips in GPS carrier-phase measurements is improved with the aid of DR heading. From the experimental result, it is shown that the search space is drastically reduced to about 3/20 of the non-aided case and the cycle-slips of 1 or half cycle can be detected.

• Ocean Systems Engineering
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• 제13권2호
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• pp.123-146
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• 2023

In this paper, Moore-Gibson-Thompson theory of thermoelasticity is considered to investigate the fundamental solution and vibration of plane wave in an isotropic photothermoelastic solid. The governing equations are made dimensionless for further investigation. The dimensionless equations are expressed in terms of elementary functions by assuming time harmonic variation of the field variables (displacement, temperature distribution and carrier density distribution). Fundamental solutions are constructed for the system of equations for steady oscillation. Also some preliminary properties of the solution are explored. In the second part, the vibration of plane waves are examined by expressing the governing equation for two dimensional case. It is found that for the non-trivial solution of the equation yield that there exist three longitudinal waves which advance with the distinct speed, and one transverse wave which is free from thermal and carrier density response. The impact of various models (i)Moore-Gibson-Thomson thermoelastic (MGTE)(2019), (ii) Lord and Shulman's (LS)(1967) , (iii) Green and Naghdi type-II(GN-II)(1993) and (iv) Green and Naghdi type-III(GN-III)(1992) on the attributes of waves i.e., phase velocity, attenuation coefficient, specific loss and penetration depth are elaborated by plotting various figures of physical quantities. Various particular cases of interest are also deduced from the present investigations. The results obtained can be used to delineate various semiconductor elements during the coupled thermal, plasma and elastic wave and also find the application in the material and engineering sciences.

• 한국통신학회논문지
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• 제40권7호
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• pp.1450-1456
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• 2015

송신 안테나는 약 53m 높이에 설치하고, 수신 안테나는 약 6m 높이에 설치하였으며, 해안국에서 700m부터 약 20km까지의 전파 경로 구간에서 $5{\pm}1m/s$의 속도로 이동하면서 150.0625MHz의 단일 주파수를 사용하여 수신신호의 크기를 측정하는 시험을 수행하였다. 본 논문에서는 실해역 측정 데이터를 입력으로 하여 최소자승법오차 방법을 이용하여 측정한 전달경로 구간에서 경로감쇠지수가 3.79가 됨을 추정하였으며, 추정한 경로감쇠지수는 해상 VHF 채널(100MHz)에 대해 ITU-R P.1546-4 Annex 2의 측정 결과와 유사한 결과를 보인다. 추정한 경로감쇠 지수값은 우리나라 남해안의 해상통신에서 하절기의 경로감쇠 지수 예측값으로 사용할 수 있을 것이다.

• 한국수소및신에너지학회논문집
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• 제33권4호
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• pp.419-429
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• 2022

Effects of operating variables on temperature profile and performance of 3 MWth chemical looping combustion system were estimated by mass and energy balance analysis based on configuration and dimension of the system determined by design tool. Air reactor gas velocity, fuel reactor gas velocity, solid circulation rate, and solid input percentage to fluidized bed heat exchanger were considered as representative operating variables. Overall heat output and oxygen concentration in the exhaust gas from the air reactor increased but temperature difference decreased as air reactor gas velocity increased. Overall heat output, required solid circulation rate, and temperature difference increased as fuel reactor gas velocity increased. However, overall heat output and temperature difference decreased as solid circulation rate increased. Temperature difference decreased as solid circulation rate through the fluidized bed heat exchanger increased. Effect of each variables on temperature profile and performance can be determined and these results will be helpful to determine operating range of each variable.

• 한국응용곤충학회지
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• 제20권2호
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• pp.103-106
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• 1981

이 시험은 수직싸이로에서 대두를 훈증소독하는 경우 훈증제별로 침투확산력을 조사할 목적으로 실시한것으로써 그 결과를 요약하면 다음과 같다. 1. 대두의 표면에 M.B를 단독으로 투약한 경우 M.B Gas의 침투확산속도는 대만히 빨라 투약후 4시간 이내에 싸이로 기부에 60mg/l 이상의 M.B Gas가 검출되었으며 10시간 이후로부터는 M.B Gas의 농도가 차 감소하는 경향이었다. 2. M.B Gas의 Carrier로 $CO_2$ Gas를 동시에 사용하였을 때는 M.B Gas의 침투확산속도가 M.B 단독 사용시보다 더욱 빨라져 투약후 1.5 시간이내에 싸이로 기부의 M.B Gas 농도는 70mg/l 이상을 나타내었다. 3. Phostoxin을 투약한 경우는 M.B를 투약한 경우 와는 반대로 침투확산력이 매우 미약하여 투약후 48시간동안 싸이로의 기부에서 10mg/l 이상의 농도를 검지할 수 없었다. 4. 소독효과를 조사하기 위해서 공시충으로 쌀바구미를 싸이로 기부에 삽입하였던바 M.B 및 $CO_2$구에서 는 완전한 살충효과를 얻었으나 Phostoxin 사용구에서는 대부분 생충으로 발견되었다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.105-106
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• 2008

As a carrier of malaria and sneak of blood, mosquitoes are an unpleasant insect. However, there are several unknown natural secretes related with mosquitoes. Among them, we focused on the blood sucking process of a female mosquito. The main objective of this study is to understand the mosquito's blood sucking mechanism that can be used to resolve the problem encountered in the injection or transport of infinitesimal biological fluids in a micro-chip. At first, the velocity fields of blood-sucking flow in a proboscis were measured using a micro-particle image velocimetry (PIV) technique. The velocity signals of flow in the proboscis show periodic variation. This seems to be resulted from the beating of the pharyngeal pump which works as driving power. To analyze the pumping mechanism, the temporal variation of the pharyngeal pump was visualized using the synchrotron X-ray micro-imaging technique. The volume variation was estimated by the help of digital image processing techniques. Once the main mechanism of blood sucking process was found, a effective micro-pumping system with high efficiency would be developed in near future.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 12th KACG Technical Meeting and the 4th Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.223-228
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• 1997

The gas dynamics in a stagnation point upflow OMVPE reactor were studied by Raman spectroscopy. The gas temperature was measured as a function of inlet gas velocity and aspect ratio for both H$_2$ and N$_2$ carrier gases. The centerline temperature gradient was latger at higher inlet velocities and with the use of N$_2$, and only weakly dependent on the aspect ratio. a tracer molecule, CH$_4$, was used to investigate the steady state behavior of reactants in the reactor, and the use of a sweeping flow was found to be a suitable method for preventing wall deposition. The transient switching response of the gas manifold was also investigated. Under certain conditions (low velocities, unmatched flows) recirculation flows were apparent. Numerical calculations of the reactor gas dynamics gave reasonable agreement with experimental results when detailed thermal boundary conditions were included.

• Transactions on Electrical and Electronic Materials
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• 제10권4호
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• pp.107-110
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• 2009

In this study, the Hall effect has been studied in n-GaAs samples characterized by V/IIl growth ratios of 25, 50 and 100 and prepared by metal organic chemical vapor deposition. For the Hall effect measurements, the grown samples were cut to a size of 1${\times}$1 cm. The measurements were carried out at room temperature, using Indium contact metal at the four corners of the samples. According to the experimental results, the Schottky effect was not ovservation. Also for the n-GaAs sample of V/Ill 100 ratio the electron drift velocity was very high.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 1995년도 춘계학술발표회 논문집
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• pp.65-92
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• 1995

The final aim of our research project is a study on assessment of automatic steering system of ships in open seas. In order to achieve this aim we need to know the characteristics of each component of the system and also to know the characteristics of disturbance to ship dynamcis. In this paper we provide calculation method of irregular disturbance to ships in autopilot navigation in open seas and also show calculation examples about two kinds of ship ore carrier and fishing boat. The disturbance consists of irregular wave and random wind, The disturbance is calculated as equivalent yaw angular velocity. Each spectrum and time history of disturbance are reasonably evaluated. Further investigation concerning to performance index of autopilot system and energy loss related to automatic course keeping will be dealt with in another paper,

• 전기학회논문지
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• 제58권6호
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• pp.1123-1129
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• 2009

The main goal of this paper is to simulate a Doubly-Fed Induction Generator (DFIG), which is similar to a real system. Wind velocity data is applied to a 2D Lookup table as a speed reference for a turbine model. A real electric machine's parameters are put in the simulator to get some results of the real system. The Matlab have been generally used to simulate DFIG, but it has some differences from the real system and is difficult to implement. A Simplorer simulator, however, simplifies DFIG simulation. The turbine is directly connected with the DFIG to be close to the real system. The machine's rotor is excited and controlled by the discrete carrier modulated matrix converter. It is possible to retrieve important information, like a generated power and wind quality etc., from the simulator without a huge wind turbine.