• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 춘계학술대회
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• pp.165-170
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• 1997

In this paper, we consider the aortic sinus baroreceptor, which is the most representative baroreceptors sensing the variance of pressure in the cardiovascular system(CVS), and propose heart activity control model to observe the effect of delay time in heart period and stroke volume under the regulation of baroreflex in arotic sinus. The proposed heart activity baroreflex regulation model contains CVS electric circuit sub-model, baroreflex regulation sub-model and time delay sub-model. In these models, applied electric circuit sub-model is researched by B.C.Choi and the baroreflex regulation sub-model transforms the input, the arotic pressure of CVS electric circuit sub-model, to outputs, heart period and stroke volume by mathematical nonlinear feedback. We constituted the time delay sub-model to observe sensitivity of heart activity baroreflex regulation model by using the variable value to represent the control signal transmission time from the output of baroreflex regulation model to efferent nerve through central nervous system. The simulation object of this model is to observe variability of the CVS by variable value in time delay sub-model. As simulation results, we observe three patterns of CVS variability by the time delay. First, if the time delay is over 2.5 sec, arotic pressure, stroke volume and heart rate is observed nonperiodically and irregularly. Second, if the time delay is from between 0.1 sec and 0.25 sec, the regular oscillation is observed. Finally, if time delay is under 0.1 sec, then heart rate and arotic pressure-heart rate trajectory is maintained in stable state.

• 정보교육학회논문지
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• 제16권2호
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• pp.245-253
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• 2012

본 연구의 목적은 초기청소년의 학습을 위한 인터넷의 사용, 게임사용, 그리고 지각된 학업성취도와의 관계를 종단적 자료로 살펴보고자 하였다. 이를 위하여 연구문제를 해결할 수 있는 잠재성장모형을 확장한 3개의 연구모형을 설정하였고, 연구모형별로 가설들을 검정하였다. 한국청소년패널(KYPS)에서 4년간 반복추적 조사한 초등학교 4학년 2,844명을 연구대상으로 하였다. 연구결과 (a) 학년이 증가함으로써 학습목적 인터넷 사용의 변화율은 유의하게 감소하는 경향을 나타내었지만, 개인차는 있는 것으로 나타났다. (b) 학습목적 인터넷 사용은 최종시점(중1)의 지각된 학업성취도에 영향을 주는 것으로 나타났다. 그리고 (c) 게임사용은 학습목적 인터넷 사용에 동시효과와 지연효과가 모두 유의한 것으로 나타났다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권3호
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• pp.1204-1227
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• 2020

The tradeoff between energy conservation and traffic balancing is a dilemma problem in Wireless Sensor Networks (WSNs). By analyzing the intrinsic relationship between cluster properties and long distance transmission energy consumption, we characterize three node sets of the cluster as a theoretical foundation to enhance high performance of WSNs, and propose optimal solutions by introducing rendezvous and Mobile Elements (MEs) to optimize energy consumption for prolonging the lifetime of WSNs. First, we exploit an approximate method based on the transmission distance from the different node to an ME to select suboptimal Rendezvous Point (RP) on the trajectory for ME to collect data. Then, we define data transmission routing sequence and model rendezvous planning for the cluster. In order to achieve optimization of energy consumption, we specifically apply the economic theory called Diminishing Marginal Utility Rule (DMUR) and create the utility function with regard to energy to develop an adaptive energy consumption optimization framework to achieve energy efficiency for data collection. At last, Rendezvous Transmission Algorithm (RTA) is proposed to better tradeoff between energy conservation and traffic balancing. Furthermore, via collaborations among multiple MEs, we design Two-Orbit Back-Propagation Algorithm (TOBPA) which concurrently handles load imbalance phenomenon to improve the efficiency of data collection. The simulation results show that our solutions can improve energy efficiency of the whole network and reduce the energy consumption of sensor nodes, which in turn prolong the lifetime of WSNs.

• 한국환경과학회지
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• 제28권12호
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• pp.1133-1145
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• 2019

Successful launch requires state-of-the-art launch vehicle technology and constant test operations, However, the meteorological threat to the launch vehicle flight trajectory is also an important factor for launch success. Atmospheric stability above the Naro Space Center at the this time is very important, especially because the initial flight operation can determine the success of the launch. Moreover, during the flight of launch vehicle with rapid pressure and thrust into the atmosphere, convection activity in the atmosphere may create environmental conditions that cause severe weather threats such as thunderstorms. Hence, studies of atmospheric instability characteristics over the Naro Space Center are a necessary part of successful launch missions. Therefore, the main aims of this study were to (1) verify the atmospheric stability index and convection activity characteristics over the Naro Space Center using radiosonde data observed from 2007 to 2018 by the Naro Space Center, (2) analyze changes in the atmospheric stability index according to monthly and seasonal changes, and (3) assess how the calculated atmospheric stability index is related to actual thunderstorm occurrence using statistical analysis. Additionally, we aimed to investigate the atmospheric characteristics above the Naro Space Center through the distribution chart of the atmospheric stability index during summer, when convection activity is highest. Finally, we assessed the relationship between lightning occurrence and unstable atmospheric conditions, through predictability analysis performed using the lightning observation data of the Korea Meteorological Administration.

• Smart Structures and Systems
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• 제18권1호
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• pp.139-154
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• 2016

This paper is concerned with the dynamics of hyperelastic solids and structures. We seek for a smart control actuation that produces a desired (prescribed) displacement field in the presence of transient imposed forces. In the literature, this problem is denoted as displacement tracking, or also as shape morphing problem. One talks about shape control, when the displacements to be tracked do vanish. In the present paper, it is assumed that the control actuation is provided by imposed eigenstrains, e.g., by the electric field in piezoelectric actuators, or by thermal actuators, or via analogous physical effects, such as magneto-striction or pre-stress. Structures with a controlled eigenstrain-type actuation belong to the class of smart structures. The action of the eigenstrains can be conveniently characterized by actuation stresses. Our theoretical derivations are performed in the framework of the theory of small incremental dynamic deformations superimposed upon a statically pre-deformed configuration of a hyperelastic solid or structure. We particularly ask for a distribution of incremental actuation stresses, such that the incremental displacements follow exactly a prescribed trajectory field, despite the imposed incremental forces are present. An exact solution of this problem is presented under the assumption that the actuation stresses can be tailored freely and applied everywhere within the body. Extending a Neumann-type solution strategy, it is shown that the actuation stresses due to the distributed control eigenstrains must satisfy certain quasi-static equilibrium conditions, where auxiliary body-forces and auxiliary surface tractions are to be taken into account. The latter auxiliary loading can be directly computed from the imposed forces and from the desired displacement field to be tracked. Hence, despite the problem is a dynamic one, a straightforward computation of proper actuator distributions can be obtained in the framework of quasi-static equilibrium conditions. Necessary conditions for the functioning of this concept are presented. Particularly, it must be required that the intermediate configuration is infinitesimally superstable. Previous results of our group for the case of shape control and displacement tracking in linear elastic structures are included as special cases. The high potential of the solution is demonstrated via Finite Element computations for an irregularly shaped four-corner plate in a state of plain strain.

• 한국기록관리학회지
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• 제20권1호
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• pp.1-25
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• 2020

본 연구에서는 조선시대 울산의 로컬리티를 살펴보기 위해 울산항과 관련된 고문헌·고문서·고지도·구술기록 등 다양한 기록물을 찾아 분석하고 주요 키워드를 추출하였다. 추출한 키워드를 시계열 순으로, 공간 순으로 구분하여 조선시대 울산항과 울산의 로컬리티를 재현하였다. 조선 전기 국방과 왜관을 통한 교역 기능을 수행한 염포, 조선 중기 임진왜란과 전란의 피해를 받은 개운포와 서생포·도산성, 조선 후기까지 국영목장과 봉수 등 국방시설을 운영했던 방어진, 내황나루와 달천철장, 포경기지의 역할을 수행한 장생포까지 각각의 특성을 살펴보고, 조선시대 울산의 궤적을 그려보고자 하였다. 조선시대 울산항의 로컬리티의 변모과정을 분석함으로써 울산의 로컬리티 이해와 재현에 도움이 될 것으로 기대한다.

• 한국정보통신학회논문지
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• 제22권4호
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• pp.602-610
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• 2018

모델예측제어는 기준 궤적이 알려져 있을 경우 제어시스템의 예측모델을 이용하여 현재 제어상태 및 미래오차 등을 예측하여 현재 제어입력을 최적화시킬 수 있는 효과적인 방법이다. 모바일로봇의 제어입력이 물리적으로 무한히 큰 값을 가질 수 없으므로 제한조건을 갖는 예측제어기 설계가 고려되어야 한다. 또한 예측제어기의 제어성능을 결정하는 기준모델행렬 $A_r$과 가중치행렬 Q, R들이 임의로 설정됨에 따라 성능이 최적화되지 못한 부분도 설계에 고려되어야 한다. 본 연구에서는 제한조건을 갖는 quadratic programming 문제로 변형하여 모바일로봇의 예측제어기를 구성하고, 모바일 로봇의 제어성능을 결정하는 예측제어기의 제어파라미터인 기준모델행렬 $A_r$과 가중치행렬 Q, R에 대하여 유전알고리즘을 적용하여 제어파라미터들을 최적화함으로써 제어성능을 높일 수 있었다. 컴퓨터 모의실험을 통하여 본 연구에서 제안한 제어방법이 기존의 예측제어기의 추종성능보다 뛰어남을 확인하고자한다.

• 한국해안해양공학회지
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• 제5권1호
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• pp.25-38
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• 1993

해양구조물의 케이블 반응 분석을 위한 다방향 파람 스펙트라의 수치모델이 조사되었다. 여러 형태의 전파모델을 파랑으로 인한 물입자의 흐름과 계류시스템을 예측하기 위해 사용하였다. 케이블에 작용하는 수동역학적 파력은 케이블의 경사에 평행한 방향과 접선방향에서의 항력과 관성력을 고려한 Morison 공식에 의해 평가되었다. 변위와 속도, 궤적, 위상면의 반응, 그리고 장력을 고려한 다방향 불규칙 파랑의 수치해석에 의하여 부체의 tether pc와 anchor point에서 계류시스템 케이블의 반응을 나타내었다. 서로 다른 항력 계수와 다양한 유의 파고, 그리고 선택된 파랑계수들이 이 분석에 고려되었다. 예제에서 고려된 특정 시스템을 통하여 파랑의 전파함수계수와 항력계수 뿐만 아니라 파랑의 주기와 높이가 케이블-부체시스템의 동적반응에 중요한 영향을 미침을 알 수 있었다.

• 대한원격탐사학회지
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• 제24권3호
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• pp.223-233
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• 2008

In the mid 90's, the U.S. government released images acquired by the first generation of photo reconnaissance satellite missions between 1960 and 1972. The Declassified Intelligent Satellite Photographs (DISP) from the Corona mission are of high quality with an astounding ground resolution of about 2 m. The KH-4A panoramic camera system employed a scan angle of $70^{\circ}$ that produces film strips with a dimension of $55\;mm\;{\times}\;757\;mm$. Since GPS/INS did not exist at the time of data acquisition, the exterior orientation must be established in the traditional way by using control information and the interior orientation of the camera. Detailed information about the camera is not available, however. For reconstructing points in object space from DISP imagery to an accuracy that is comparable to high resolution (a few meters), a precise camera model is essential. This paper is concerned with the derivation of a rigorous mathematical model for the KH-4A/B panoramic camera. The proposed model is compared with generic sensor models, such as affine transformation and rational functions. The paper concludes with experimental results concerning the precision of reconstructed points in object space. The rigorous mathematical panoramic camera model for the KH-4A camera system is based on extended collinearity equations assuming that the satellite trajectory during one scan is smooth and the attitude remains unchanged. As a result, the collinearity equations express the perspective center as a function of the scan time. With the known satellite velocity this will translate into a shift along-track. Therefore, the exterior orientation contains seven parameters to be estimated. The reconstruction of object points can now be performed with the exterior orientation parameters, either by intersecting bundle rays with a known surface or by using the stereoscopic KH-4A arrangement with fore and aft cameras mounted an angle of $30^{\circ}$.

• Wind and Structures
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• 제29권4호
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• pp.247-270
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• 2019

Wind-resistant design of existing cooling tower structures overlooks the impacts of rainfall. However, rainstorm will influence aerodynamic force on the tower surface directly. Under this circumstance, the structural response of the super-large cooling tower (SLCT) will become more complicated, and then the stability and safety of SLCT will receive significant impact. In this paper, surrounding wind fields of the world highest (210 m) cooling tower in Northwest China underthree typical wind velocities were simulated based on the wind-rain two-way coupling algorithm. Next, wind-rain coupling synchronous iteration calculations were conducted under 9 different wind speed-rainfall intensity combinations by adding the discrete phase model (DPM). On this basis, the influencing laws of different wind speed-rainfall intensity combinations on wind-driving rain, adhesive force of rain drops and rain pressure coefficients were discussed. The acting mechanisms of speed line, turbulence energy strength as well as running speed and trajectory of rain drops on structural surface in the wind-rain coupling field were disclosed. Moreover, the fitting formula of wind-rain coupling equivalent pressure coefficient of the cooling tower was proposed. A systematic contrast analysis on its 3D distribution pattern was carried out. Finally, coupling model of SLCT under different working conditions was constructed by combining the finite element method. Structural response, buckling stability and local stability of SLCT under different wind velocities and wind speed-rainfall intensity combinations were compared and analyzed. Major research conclusions can provide references to determine loads of similar SLCT accurately under extremely complicated working conditions.