• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.11-19
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• 2013

Very Fast Transients (VFT) originate mainly from disconnector switching operations in Gas Insulated Substations (GIS). In order to determine the rate-of-rise of Very Fast Transient Overvoltage (VFTO) in a 550 kV GIS, simulations are carried out using EMTP-RV. Each component of the GIS is modeled by distributed line model and lumped model based on equivalent circuits. The various switching conditions according to closing point-on-wave and trapped charge are simulated, and the results are analyzed. Also, the analysis of travelling wave using a lattice diagram is conducted to verify the simulation results.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.3
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• pp.52-60
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• 2019

This paper presents a numerically robust algorithm to construct a Voronoi diagram of circles in the plane. The circles are allowed to have intersections among them, but one circle cannot fully contain another circle. The Voronoi diagram is a tessellation of the plane into Voronoi regions of given circles. Each circle has its Voronoi region which is defined by a set of points in the plane closer to the circle than any other circles. The distance from a point p to a circle $c_i$ of center $p_i$ and radius $r_i$ is ${\parallel}p-p_i{\parallel}-r_i$, which is the closest Euclidean distance from p to the circle boundary. The proposed algorithm first constructs the point Voronoi diagram of centers of given circles, then it enlarges each point to the circle and expands its Voronoi region accordingly. This region-expansion process is done by local modifications and after completing this process for the whole circles the desired circle Voronoi diagram can be obtained. The proposed algorithm is numerically robust and we provide with a few examples to show its robustness. The algorithm runs in $O(n^2)$ time in the worst case and O(n) time on average where n is the number of the circles. The experiment shows that the region-expansion algorithm is robust and runs fast with strong linear time behavior.

• Korean Journal of Construction Engineering and Management
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• v.7 no.3 s.31
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• pp.102-111
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• 2006

In the analysis of function, which is the core and early phase among the procedure of construction VE Job Plan, the accuracy of function definition directly connects to VE result. However, the method of defining function, which is currently used is not accurate and comprehended or is difficult to utilize it systematically. Also, there is not a clear definition about the function for selecting VE so that many difficulties occur in the organic connection between each of functions in the summarization of function after defining function. Therefore, this study cleared the definition of function and made up any counter measured problem occurred in FAST Diagram later on and suggested CAFAT(Combined Antithetic Function Analysis Technique) in order to induce better phase in functional analysis.

• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.1024-1031
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• 2019

The Molten Salt Fast Reactor (MSFR) with its liquid circulating fuel and its fast neutron spectrum calls for a new safety approach including technological neutral methodologies and analysis tools adapted to early design phases. In the frame of the Horizon2020 program SAMOFAR (Safety Assessment of the Molten Salt Fast Reactor) a safety approach suitable for Molten Salt Reactors is being developed and applied to the MSFR. After a description of the MSFR reference design, this paper focuses on the identification of the Postulated Initiating Events (PIEs), which is a core part of the global assessment methodology. To fulfil this task, the Functional Failure Mode and Effect Analysis (FFMEA) and the Master Logic Diagram (MLD) are selected and employed separately in order to be as exhaustive as possible in the identification of the initiating events of the system. Finally, an extract of the list of PIEs, selected as the most representative events resulting from the implementation of both methods, is presented to illustrate the methodology and some of the outcomes of the methods are compared in order to highlight symbioses and differences between the MLD and the FFMEA.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.2
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• pp.106-112
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• 2007

This paper proposes a hybrid architecture algorithm for fast computation of DCT and DFT via recursive factorization. Recursive factorization of DCT-II and DFT transform matrix leads to a similar architectural structure so that common architectural base may be used by simply adding a switching device. Linking between two transforms was derived based on matrix recursion formula. Hybrid acrchitectural design for DCT and DFT matrix decomposition were derived using the generation matrix and the trigonometric identities and relations. Data flow diagram for high-speed architecture of Cooley-Tukey type was drawn to accommodate DCT/DFT hybrid architecture. From this data flow diagram computational complexity is comparable to that of the fast DCT algorithms for moderate size of N. Further investigation is needed for multi-mode operation use of FFT architecture in other orthogonal transform computation.

• Korean Journal of Construction Engineering and Management
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• v.15 no.2
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• pp.71-78
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• 2014

Value Engineering methodology was introduced about 30years ago and has significant achievement in Korea. However, many of workshop still focus on cost down process and do not spend enough time on function analysis and expert cooperation. As a result, limited range of creative ideas were produced. To improve effectiveness of VE workshop, this study developed web-based value engineering process and system. And this study applied it to real case study to evaluate effectiveness of proposed system. Developed VE system also provides automated FAST diagram function and decision-making supporting tools. The authors found that this developed web-based VE system can significantly help to save cost and improve performance of VE workshop by using the appropriate VE process, and quick cooperation between experts. In addition, this study shows an example of a VE case study that applies the web-based VE system process, which led to a very innovative and effective way to lead workshop.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2240-2245
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• 2003

In this paper, the controller design by coefficient diagram method (CDM) for controlling the trolley position, load-swing angle and hoisting rope length of the overhead crane system simultaneously is proposed. The overhead crane system is a MIMO system consisting of two inputs and three outputs. Its mathematical model is nonlinear with coupling characteristics. This nonlinear model can be approximated to obtain a linear model where the first input mainly affects the trolley position and the load-swing angle while the second input mainly affects the hoisting rope length. In order to utilize the CDM concept for assigning the controllers, namely PID, PD and PI controllers separately, the model is approximated to be three transfer functions in accordance with trolley position, the load-swing angle and the hoisting rope length controls respectively. The satisfied performances of the overhead crane system controlled by the these controllers and fast rejection of the disturbance effect occurred at the trolley position are shown by simulation and experimental results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.651-659
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• 2004

The Fast Handover protocol ［1］ provides seameless handover in wireless If networks by minimizing handover latency, which uses anticipation based on layer 2 (L2) trigger information. Therefore, it incurs higher signaling costs compared with the basic Mobile U protocol. Furthermore, since the L2 trigger is based on fluctuating wireless channel states, the handover anticipation may sometimes be incorrect. In the case of incorrect anticipation, unnecessary buffer space may be used for the purpose of providing a smooth handover. Therefore, it is essentical to analyze these overhead costs, in order to evaluate and compare the performance of Fast Handover with that of the basic Mobile U protocol. In this paper, we analyzed the overhead associated with Fast Handover including the signaling cost and the packet delivery cost. We formulated these costs based on a timing diagram and compared Fast Handover with basic Mobile Ipv6 in terms of their packet loss rates and buffer requirements. Also, we studied the impact of the L2 triggering time on the total overhead cost.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.194-199
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• 1990

Because of being operated to accomodate the load variation, fossile power plants need modern controller to satisfy frequency regulation, fast response and efficiency requirement. But in the way of developing the Digital Instrumentation and Control System that can adopt advanced control algorithms, power plant simulator must be available for safe and convenient test. In this paper, a simple drum-type boiler model is proposed, using Signal Flow Diagram that describes the system by a collection of basic time response representing the relationship between process variables. After verifying the model and thereafter building simulator based on the proposed model, we test the operation of controller and approve stability or efficiency of implemented control algorithms.

• Korean Journal of Computational Design and Engineering
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• v.12 no.6
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• pp.413-421
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• 2007

3D rendering is becoming a common feature of mobile application programs with the rapid advance of mobile devices. Since the existing rendering engines do not provide triangulation functions, mobile 3D programs have focused on an efficient handling with pre-tessellated geometry. In addition, triangulation is comparatively expensive in computation, so it seems that the triangulation cannot be easily implemented on mobile devices with limited resources. Triangulation of 3D geometry is the essential process of visualization of 3D model data and many different triangulation methods have been reported. We developed a light and fast visualization process that involves constrained triangulation based on Voronoi diagram and applied it to a mobile computer application. In this paper, we applied kd-tree to the original incremental construction algorithm and produced new O(nlogn) incremental construction algorithm. And we show a simple and efficient constrained triangulation method based on Voronoi diagram. This paper also describes an implementation of mobile STEP data viewer as an application of our proposed algorithms.