• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.3
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• pp.267-272
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• 2012

This paper propose the implementation of robust fuzzy controller for controlling an active magnetic bearing (AMB) system with 6 degree of freedom (DOF). A basic model with 6 DOF rotor dynamics and electromagnetic force equations for conical magnetic bearings is proposed. The developed model has severe nonlinearity and uncertainty so that it is not easy to obtain the control objective. For solving this problem, we use the Takagi-Sugeno (T-S) fuzzy model which is suitable for designing fuzzy controller. The control object in the AMB system enables the rotor to rotate without any phsical contact by using magnetic force. In this paper, we analyze the nonlinearity of the active magnetic bearing system by using fuzzy control algorithm and desing the robust control algorithm for solving the parameter variation. Simulation results for AMB are demonstrated to visualize the feasibility of the proposed method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.341-353
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• 2014

In order to deliver a centimeter-level kinematic positioning solution with GPS carrier-phase measurements, it is prerequisite to use correctly resolved integer ambiguities. Based on the mathematical modeling of GPS network with application of its geometrical constraints, this research has investigated an instantaneous ambiguity resolution procedure for the so-called 'integer constrained least-squares' technique which can be effectively implemented in real-time structure monitoring. In this process, algorithms of quality control for the float solutions and hypothesis tests using the constrained baseline for the ambiguity validation are included to enhance reliability of the solutions. The proposed procedure has been implemented by MATLAB, the language of technical computing, and processed field trial data obtained at a cable-stayed bridge to access its real-world applicability. The results are summarized in terms of ambiguity successful rates, impact of the stochastical models, and computation time to demonstrate performance of the instantaneous ambiguity resolution proposed.

• Journal of the Korean Geotechnical Society
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• v.31 no.11
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• pp.25-31
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• 2015

Elastic behavior of the railway roadbed which supports the repeating dynamic loads of the train is mainly affected by the shear modulus of the upper roadbed. Therefore, shear wave velocity estimation of the uniformly compacted roadbed can be used to estimate the elastic behavior of the railway roadbed. The objective of this study is to suggest the relationship between the dynamic cone penetration index (DCPI) and the shear wave velocity ($V_s$) of the upper roadbed in order to estimate the shear wave velocity by using the dynamic cone penetration test (DCPT). To ensure the reliability of the relationship, the dynamic cone penetration test and the measurement of the shear wave velocity are conducted on the constructed upper roadbed. As a method for measurement of the shear wave velocity, cross hole is used and then the dynamic cone penetration test is performed at a center point between the source and the receiver of the cross hole. As a result of the correlation of the dynamic cone penetration index and the shear wave velocity at the same depths, the shear wave velocity is estimated as a form of involution of the dynamic cone penetration index with a determinant coefficient above 0.8. The result of this study can be used to estimate both the shear wave velocity and the strength of the railway roadbed using the dynamic cone penetrometer.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1307-1312
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• 2015

The recent adoption of Bluetooth LE technology in smart phones triggered commercial interest in RSSI-based positioning technology. Estimation error in RSSI measurement due to the antenna pattern, multipath fading, environmental noise has to be considered for designing beacon systems. The paper proposes an analysis method and beacon planning rules for a small and isolated indoor service area, based on probabilistic model of RSSI estimation error. As an practically important guide, the beacons have to be installed at the boundary of the service area to minimize the maximum position error, whereas the beacons have to be evenly distributed in the service space to minimize the average estimation error.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10A
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• pp.1512-1520
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• 2000

The wireless communication network is evolving toward IMT-2000 for providing various multimedia services. In order to accomplish this ultimate goal the effective schemes are required which can dynamically utilize the limited wireless resources based on different traffic characteristics of various services. This paper proposes a novel bandwidth allocation and call admission control scheme to transmit multimedia traffic based on the bandwidth reservation procedure using direction estimation in the IMT-2000 This scheme estimates the position of mobiles based on the mliticriteria decision making in which uncertain parameters such as RSS(Received Signal Strength), the distance between mobile and base station the moving direction and the previous location are participated in the decision process using aggregation function in fuzzy set theory. Its effectiveness is investigated by simulation.

• Journal of Biomedical Engineering Research
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• v.20 no.5
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• pp.587-592
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• 1999

압력측정시스템은 입각기동안 동적압력분포를 성공적으로 측정할 수 있으나 하중수용기-중간입각기, 말기입각기-전유각기의 전환기들에 대해서는 운동분석시스템을 사용하지않고는 정확한 정의가 불가능하다. 따라서 저자들은 수평자유보행 시 압력중심의 이동을 이해하기 위해서 정상적인 발을 가진 20-30대 성인남자 78명을 대상으로 동작분석과발바닥 압력측정을 동시에 수행하였다. 결과로 하중반응기-중간입각기 전환시기의 발바닥 압력중심점은 후족부와 중족부의 경계선에서 앞쪽으로 1.9$\pm$1.5frame(32$\pm$24msec)에 위치하였으며 말기입각기-전유각기 전환시기에는 중족골두 최대 압력점의 앞쪽으로 2.3$\pm$2.0 frame(38$\pm$33msec)에 위치하였다. 정상수평보행에 있어서 최초접지 순간 압력중심은 전방으로 빠르게 이동하다가 바로 급속히 감소하여 하중반응기-중간입각기의 전환시기에는 작은 속도로 이동하였다. 압력중심의 이동속도는 그 후 다시 서서히 증가하다가 전체 보행주기의 25% 전후에서 서서히 감소하여 비교적 일정하다가 말기입각기-전유각기의 전환시점에서 다시 급격한 증가를 보였다. 족부질환과 보행특성을 판단하는데 있어서 압력중심의 이동궤적은 매우 유용한 인자가 될 것으로 기대된다. 본 연구를 통해서 압력측정시스템만으로는 정의할 수 없었던 두 전환기인 하중반응기-중간입각기, 말기입각기-전유각기를 결정할 수있게 되었다.

• Land and Housing Review
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• v.14 no.4
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• pp.47-62
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• 2023

Using the dynamic panel model, this study investigates rent determinants for small and medium-sized office buildings in Korea's CBD and Gangnam areas, key business districts. The results reveal that rents for small and medium-sized office buildings in CBD and Gangnam areas are influenced by macroeconomic fluctuations and characteristics of buildings and locations, suggesting a market with both spatial consumer and investment goods attributes. There are several investment implications as follows. First, even if the location in the CBD area is advantageous, the practical limitations in renovating aging small and medium-sized office buildings must be taken into account when investing. Second, parking conditions are a key factor influencing rent prices in CBD areas, so evaluating the parking facilities and improvement potential of small and medium-sized office buildings is essential for investors. Finally, due to the high sensitivity of Gangnam's small and medium-sized office market to macroeconomic trends, it's vital to prioritize monetary policy shifts as a key factor in investment decisions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5B
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• pp.942-955
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• 2000

This paper proposes enhanced designs of global service logic and information flow for the mass-call based IN service, which increase call completion rates and optimize the resource in joint wired and wireless networks. In order to hanve this logic implemented, we design a Dynamic Queue Manager(DQM) applied to the call queuing service feature in the Service Control Point(SCP). In order to apply this logic to wireless service subscribers as well as wired service subscribers, the service registration flags between the Home Location Register(HLR) and the SCP are managed to notify the DQM of the corresponding service subscribers’ mobility. Hence, we present a dynamic queue management mechanism, which dynamically manages the service group and the queue size based on M/M/c/K queueing model as the wireless subscribers roam the service groups due to their mobility characteristics. In order to determine the queue size allocated by the DQM, we simulator and analyze the relationship between the number of the subscriber’s terminals and the drop rate by considering the service increment rate. The appropriate waiting time in the queue as required is simulated according to the above relationship. Moreover, we design and implement the DQM that includes internal service logic interacting with SIBs(Service Independent building Blocks) and its data structure.

• Journal of Korean Society of Transportation
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• v.22 no.7 s.78
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• pp.91-98
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• 2004

This study focuses on the development of dynamic assignment for evaluation and application for dynamic route guidance strategy. Travelers are classified according to information contents which they received pre/on trip. The first group have no traffic information, so they travel with fixed route. The second group have real-time shortest path and travel according to it. The last group have car navigation system or individual method(cellular phone, PDA-two way communication available) for traffic information on trip. And then they are assigned in accordance with the proposed multiclass dynamic assignment model. At this time the last group is gotten under control with DFS(decentralized feedback strategy). In use of this Process we expect that various traffic information strategy can be tested and also be the key factor for success of ITS, location of VMS(variable message sign), cycle of information, area of traffic information, etc).

• Composites Research
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• v.18 no.4
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• pp.52-58
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• 2005

A cyclocopter propelled by the cycloidal blade system, which can be described as a horizontal rotary wing, is a new concept of VTOL vehicle. In this paper, optimized structure design is carried out for the aerodynamically optimized cyclocopter rotor system. Database is obtained fer design variables such as stacking sequence (ply angles), number of plies and spar locations through MSC/NASTRAN and optimum values are determined by RSM and some other optimizing processes. For the rotor system including optimized blade and composite hub m, the maximum stress by static analysis is within the failure criteria. And the rotor system is designed for the purpose of avoiding possible dynamic instabilities by inconsistency between frequencies of rotor rotation and some low natural frequencies of rotor.