• KSTLE International Journal
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• 제8권1호
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• pp.16-20
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• 2007

This study introduces a new approach to a falling ball viscometer by using a high speed motion camera to measure the viscosity of both Newtonian and non-Newtonian fluids from the velocity-time data. This method involves capturing continuous photographs of the entire falling motion of the ball as the ball accelerates from the rest to the terminal velocity state. The velocity of a falling ball was determined from the distance traversed by the ball by examining video tape frame by frame using the marked graduations on the surface of the cylinder. Each frame was pre-set at 0.01. Glycerin 74% was used for Newtonian solution, while aqueous solutions of Polyacrylamide and Carboxymethyl Cellulose were for non-Newtonian solutions. The experimental viscosity data were in good agreements with the results obtained from a rotating Brookfield viscometer.

• 한국경영과학회지
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• 제27권3호
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• pp.59-74
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• 2002

This study investigates two basic operations of mobility management of PCNs (Personal Communication Networks), i.e., the location update and the paging of the mobile terminal. From the realistic consideration that a user either moves through several cells consecutively or stays in a cell with long time, we model the mobility pattern by introducing two types of CRT (Cell Residence Time). Mobility patterns of the mobile terminal are classified Into various ways by using the ratios of two types of CRT. Cost analysis is performed for distance-based and movement-based location update schemes combined with blanket polling paging and selective paging scheme. It is demonstrated that in a certain condition of mobility pattern and call arrival pattern, 2-state CRT model produces different optimal threshold and so, is more effective than IID ( Independently-Identically-Distributed) CRT model. An analytical model for the new CRT model is compact and easily extendable to the other location update schemes.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2002년도 춘계학술대회논문집
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• pp.33-41
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• 2002

This paper deals with the development of simulation model for the container terminal consisting of 3 berths, 8 container cranes, 16 yard blocks with each yard cranes and 90 yard trucks in order to evaluate the various operational rules. The proposed operational rules are 3 ship dispatching rules, 3 berth allocation rules, 2 crane allocation rules, 2 yard allocation rules and 2 yard truck allocation rules and 4 performance measures like ship time in the terminal, ship time in the port, the number of ships processed and the number of containers handled are considered. The simulation result are as follows. 1) no difference among 3 ship dispatching rules, 2) berth allocation rules depends on performance measures 3) dynamic crane allocation is better than fixed policy 4) pooling yard allocation is better than short distance yard allocation rules and 5) fixed yard truck allocation by berth is a little better than pooling policy.

• International Journal of Aeronautical and Space Sciences
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• 제15권3호
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• pp.281-292
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• 2014

We propose a novel cooperative guidance law design method based on the finite time disturbance observer (FTDO) for multiple near space interceptors (NSIs) with impact time control. Initially, we construct a cooperative guidance model with head pursuit, and employ the FTDO to estimate the system disturbance caused by target maneuvering. We subsequently separate the cooperative guidance process into two stages, and develop the normal acceleration command based on the super-twisting algorithm (STA) and disturbance estimated value, to ensure the convergence of the relative distance. Then, we also design the acceleration command along the line-of-sight (LOS), based on the nonsingular fast terminal sliding mode (NFTSM) control, to ensure that all the NSIs simultaneously hit the target. Furthermore, we prove the stability of the closed-loop guidance system, based on the Lyapunov theory. Finally, our simulation results of a three-to-one interception scenario show that the proposed cooperative guidance scheme makes all the NSIs hit the target at the same time.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.533-539
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• 1993

In this paper, two side-attack guidance laws for an underwater vehicle are considered. In order to find the guidance command, we first make use of the optimal guidance law with terminal impact angle constraint. Secondly, the optimal solution of tracking problem is used. This paper shows some brief theory which is used in deriving the side-attack guidance laws, and the method of computing these guidance laws. Simulations on underwater vehicle for a constant moving target prove that the suggested side-attack guidance laws have enhanced side attack performance over the optimal guidance law with miss distance weighting only. Furthermore, from simulation results. we conclude that the guidance law using the optimal solution of tracking problem is more efficient for the side-attack guidance than the optimal guidance law with terminal impact angle constraint.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.846-851
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• 2007

The contact and messenger wire is important parts in the electric power system of the railroad. There are so many measurement method like voltage, current, scratch of surface, and glow longer of length. In this paper suggest real time monitering system of messenger wire so called RTU (Remote Terminal Unit) and this system includes CDMA module to transfer real time or saved data of memory to the end user directly who is in the long distance. The hyper terminal program of windows shows the downloaded data from RTU through CDMA communication and this data can be transferred to excel sheet easily.

• 천문학회지
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• 제26권1호
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• pp.1-12
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• 1993

In order to explore the time dependence of the closure parameters of the two-fluid calculations for supernova remnants and the terminal shocks of stellar winds, we have considered a simple model in which the time evolution of the cosmic-ray distribution function was followed in the test-particle limit using the Bohm diffusion model. The particles are mostly accelerated to relativistic energy either in the free expansion phase of the SNRs or in the early phase of the stellar winds, so the evolution of the closure parameters during these early stages is substantial and should be followed correctly. We have also calculated the maximum momentum which is limited by either the age or the curvature of these spherical shocks. We found that SNRs expanding into the medium where the gas density decreases with the distance from the explosion center might be necessary to explain the observed power-law distribution of the galactic cosmic rays. The energy loss due to the escaping energetic particles has been estimated for the terminal shocks of the stellar winds.

• 한국항만경제학회지
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• 제18권1호
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• pp.27-41
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• 2002

This paper deals with the development of a simulation model for the container terminal, which consists of 3 berths, 8 container cranes, and 16 yard blocks with each yard crane and 90 yard trucks in order to evaluate the various operational rules. The proposed operational rules are 3 ship-dispatching rules, 3 berth allocation rules, 2 crane allocation rules, 2 yard allocation rules, and 2 yard truck allocation rules. These rules are simulated using 4 performance measures, such as ship time in the terminal, ship time in the port, the number of ships processed, and the number of containers handled. The simulation result is as follows: 1) there is no difference among 3 ship-dispatching rules, 2) berth allocation rules depend on performance measures, 3) dynamic crane allocation is better than fixed policy, 4) pooling yard allocation is better than short distance yard allocation rules, and 5) fixed yard truck allocation by berth is a little better than pooling policy.

• Bulletin of the Korean Chemical Society
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• 제22권3호
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• pp.281-287
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• 2001

Self-assembled monolayers (SAMs) of the alkylthiols with [Os(bpy)3]2+ moiety at the terminal position were prepared on gold electrode surface. Examination of the cyclic voltammograms for the SAM shows that it does not organiz e well unlike alkylthiols, which is attributed to the much larger diameter of [Os(bpy)3]2+ moiety compared with the cross-section of alkyl chains and the distance between the adsorption sites. Electromicrogravimetry study shows that the hydration numbers of the electrolyte were 16 $\pm2$, 11 $\pm1$, 5 $\pm$ 1 and 24 $\pm6$ for ClO4- , PF6-, NO3- , and SO42- , respectively. The binary SAMs of alkylthiols with [Os(bpy)3]2+ terminal-group were prepared by co-adsorption of alkylthiols as spacer molecules, which results in better packing in SAM and accordingly the stability was enhanced.

• 한국위성정보통신학회논문지
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• 제10권3호
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• pp.78-83
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• 2015

본 논문에서는 새로운 무선 재난통신망인 위성 통신 무선패키지 시스템의 WLAN 중계기가 LTE D2D 이동 단말기와 접속시 인접한 ISM 대역의 WALN 및 WPAN 시스템으로 부터 전파 채널 간섭을 Monte-Carlo 기반으로 분석을 하였다. 본 연구에서는 실 환경을 고려 Extended Hata Model을 이용하여 WLAN Cell Radius를 구하고, 동일 채널에서 간섭원인 WLAN, Bluetooth, ZigBee로 부터의 간섭을 최소화 하기 위한 물리적 보호 이격 거리와 Dense Mode에서 밀도를 시뮬레이션 하였다. 시뮬레이션 결과 WLAN 중계기는 인접 WLAN과는 130m 이상 보호 이격 거리에서 15개의 간섭 기기와 운용 될 수 있고, Bluetooth와는 100m 이상 보호 이격 거리에서 23개의 간섭 기기와 운용 될 수 있으며, ZigBee와는 83m 이상에서 62개 간섭 기기와 운용 가능 함을 확인 하였다.