• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.2
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• pp.21-31
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• 1999

This paper presents a new possibility of calculating optimal control for large scale which consist of non-linear dynamic sub-systems using two level hierarchical structures method. And the proposed method is based on the idea of block pulse transformation to simplify the algorithm and its calculation. This algorithm used an expansion around the equilibrium point of the system to fix the second and higher order terms. These terms are compensated for iteratively at the second level by providing a prediction for the states and controls which form of a part of the higher order terms. In this new approach the quadratic penalty terms are not used in the cost function. This allows convergence over a longer time horizon and also provides faster convergence. And the method is applied to the problem of optimization of the synchronous machine. Results show that the new approach is superior to conventional numerical method or other previous algorithm.

• Journal of Advanced Navigation Technology
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• v.12 no.1
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• pp.46-53
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• 2008

The ITS(Intelligent Transport System) enables us to provide solutions on traffic problems, while maximizing safety and efficiency of road and transportation systems, by combining technologies from information and communication, electrical engineering, electronics, mechanics, control and instrumentation with transportation systems. The issues that an integration system for massive traffic data sources must face are due to several factors such as the variety and amount of data available, the representational heterogeneity of the data in the different sources, and the autonomy and differing capabilities of the sources. In this paper, we describe how to extract and load of the heterogeneous massive traffic data from the operational databases, such as FTMS and ARTIS using commercial tools. Also, we experiment on traffic data warehouses with integrated quality management techniques for providing high quality data.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.2
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• pp.267-271
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• 2014

Nuclear power plant data networks and their associated safety systems are being modernized to include many information technology (IT) networks and applications. Along with the advancement of plant data networks (PDN), instrumentation and control systems are being upgraded with modern digital, microprocessor-based systems. However, nuclear PDN is confronted significant side-effects, which PDN is exposed to prevalent cyber threats typically found in IT environments. Therefore, cyber security vulnerabilities and possibilities of cyber incidents are dramatically increased in nuclear PDN. Consequently, it should be designed fully ensuring the PDN meet all reliability, performance and security requirements in order to overcome the disadvantages raised from adaption of IT technology. In this paper, we provide technical security criteria should be used in design and evaluation of secure PDN. It is believed PDN, which is designed and operated along with these technical security critera, effectively protect against possible outside cyber threats.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.5
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• pp.1-7
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• 2011

In this paper, CDD(Cyclic Delay Diversity)-DF(Decode-and-Forward)-Relay scheme is proposed for MC-CDMA(Multicarrier-Code Division Multiple Access) systems over multipath Rayleigh fading channels. The advantages of general DF schemes come at the expense of the spectral efficiency since the source and all the relays must transmit on orthogonal channels. In order to mitigate this disadvantage of general DF schemes, we have applied CDD techniques to each relays so that all the relays can transmit on single channel. It means that all R-D link channels can be considered as a single channel which is widely delay spread. Namely, it causes the increasing the number of multipath so that the frequency diversity gain can be achieved in MC-CDMA systems. By simulations, we have compared proposed one with general DF scheme. Therefore, it is confirmed that the proposed one can be a possible solution to achieve cooperative diversity gain without a reduction of spectral efficiency.

• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.682-691
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• 2005

This paper describes the design, fabrication, and testing of a microturbine developed at Seoul National University. Here, the term 'microturbine' refers to a radial turbine with a diameter on the order of a centimeter. Such devices can be used to transmit power for various systems. The turbine is designed using a commercial CFD code, and it has a design flow coefficient of 0.238 and work coefficient of 0.542. It has 31 stator blades and 24 rotor blades. A hydrodynamic journal bearing and hydrostatic thrust bearings counteract radial and axial forces on the rotor. The test turbine consists of a stack of five wafers and is fabricated by MEMS technology, using photolithography, DRIE, and bonding processes. The first, second, fourth, and fifth layers contain plumbing, and hydrostatic axial thrust bearings for the turbine. The third wafer contains the turbine's stator, rotor, and hydrodynamic journal bearings. Furthermore, a turbine test facility containing a flow control system and instrumentation has been designed and constructed. In performance tests, a maximum rotation speed of 11,400 rpm and flow rate of 16,000 sccm have been achieved.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1889-1891
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• 2004

The differential white blood cell count plays an important role in the diagnosis of different diseases. It is a tedious task to count these classes of cell manually. An automatic counter using computer vision helps to perform this medical test rapidly and accurately. Most commercial-available automatic white blood cell analysis composed mainly 3 steps including segmentation, feature extraction and classification. In this paper we concentrate on the first step in automatic white-blood-cell analysis by proposing a segmentation scheme that utilizes a benefit of active contour. Specifically, the binary image is obtained by thresolding of the input blood smear image. The initial shape of active is then placed roughly inside the white blood cell and allowed to grow to fit the shape of individual white blood cell. The white blood cell is then separated using the extracted contour. The force that drives the active contour is the combination of gradient vector flow force and balloon force. Our purposed technique can handle very promising to separate the remaining red blood cells.

• Journal of Biomedical Engineering Research
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• v.26 no.5
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• pp.265-270
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• 2005

A new Computer Integrated Surgical Robot system is composed of a surgical robot, a surgical planning system, and an optical tracking system. The system plays roles of an assisting surgeon and taking the place of surgeons for inserting a pedicle screw in spinal fusion. Compared to pure surgical navigation systems as well as conventional methods for spinal fusion, it is able to achieve better accuracy through compensating for the portending movement of the surgical target area. Furthermore, the robot can position and guide needles, drills, and other surgical instruments or conducts drilling/screwing directly. Preoperatively, the desired entry point, orientation, and depth of surgical tools for pedicle screw insertion are determined by the surgical planning system based on CT/MR images. Intra-operatively, position information on surgical instruments and targeted surgical areas is obtained from the navigation system. Two exemplary experiments employing the developed image-guided surgical robot system are conducted.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.3
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• pp.976-990
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• 2020

The k-means algorithm is widely used in academia and industry due to easy and simple implementation, enabling fast learning for complex datasets. However, k-means struggles to classify datasets without prior knowledge of specific domains. We proposed the repulsive k-means (RK-means) algorithm in a previous study to improve the k-means algorithm, using the repulsive force concept, which allows deleting unnecessary cluster centroids. Accordingly, the RK-means enables to classifying of a dataset without domain knowledge. However, three main problems remain. The RK-means algorithm includes a cluster repulsive force offset, for clusters confined in other clusters, which can cause cluster locking; we were unable to prove RK-means provided optimal convergence in the previous study; and RK-means shown better performance only normalize term and weight. Therefore, this paper proposes the advanced RK-means (ARK-means) algorithm to resolve the RK-means problems. We establish an initialization strategy for deploying cluster centroids and define a metric for the ARK-means algorithm. Finally, we redefine the mass and normalize terms to close to the general dataset. We show ARK-means feasibility experimentally using blob and iris datasets. Experiment results verify the proposed ARK-means algorithm provides better performance than k-means, k'-means, and RK-means.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.2
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• pp.145-155
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• 2002

It is essential for health monitoring of a cable-stayed bridge to provide more accurate and enough information from the sensors. In experimental modal testing, the chosen measurement locations and the number of measurements have a major influence on the quality of the results. The choice is often difficult for complex structures like a cable-stayed bridge. It is extremely important a cable-stayed bridge to minimize the number of sensing operations required to monitor the structural system. In order to obtain the desired accuracy for the structural test, several issues must take into consideration. Two important issues are the number and location of response sensors. There are usually several alternative locations where different sensors can be located. On the other hand, the number of sensors might be limited due to economic constraints. Therefore, techniques such as methodologies, algorithms etc., which address the issue of limited instrumentation and its effects on resolution and accuracy in health monitoring systems are paramount to a damage diagnosis approach. This paper discusses an optimum sensor placement criterion suitable to the identification of structural damage for continuous health monitoring. A Kinetic Energy optimization technique and an Effective Independence Method are analyzed and numerical and theoretical issues are addressed for a cable-stayed bridge. Its application to a cable-stayed bridge is discussed to optimize the sensor placement for identification and control purposes.

• Nuclear Engineering and Technology
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• v.40 no.5
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• pp.397-408
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• 2008

This paper describes the application of a software fault tree analysis (FTA) as one of the analysis techniques for a software safety analysis (SSA) at the design phase and its analysis results for the safety-critical software of a digital reactor protection system, which is called the KNICS RPS, being developed in the KNICS (Korea Nuclear Instrumentation & Control Systems) project. The software modules in the design description were represented by function blocks (FBs), and the software FTA was performed based on the well-defined fault tree templates for the FBs. The SSA, which is part of the verification and validation (V&V) activities, was activated at each phase of the software lifecycle for the KNICS RPS. At the design phase, the software HAZOP (Hazard and Operability) and the software FTA were employed in the SSA in such a way that the software HAZOP was performed first and then the software FTA was applied. The software FTA was applied to some critical modules selected from the software HAZOP analysis.