• The Transactions of the Korean Institute of Power Electronics
• /
• v.26 no.1
• /
• pp.32-37
• /
• 2021

This study proposes a DC series arc fault detector using a frequency analysis method called the discrete wavelet transform (DWT), in which the processing speed of the DWT algorithm is improved effectively. The processing time can be shortened because of the time characteristic of the DWT result. The performance of the developed DC series arc fault detector for a large photovoltaic system is verified with various DC series arc generation conditions. Successful DC series arc detection and improved calculation time were both demonstrated through the measured actual arc experimental result.

• Korean Journal of Construction Engineering and Management
• /
• v.18 no.2
• /
• pp.30-37
• /
• 2017

In Korea, additional indirect costs generated from the time period extension of public construction projects have been studied. Practical claims against such costs are increasing. There are no clear criteria for calculating the delay cost caused by the extension, and thus calculation methods differ across entities. Logical valid calculation methods have also not been researched. Further, there are no Korean studies on the additional indirect cost caused by a suspension in a public construction project on a long-term continuing contract. The purpose of this research is to propose a method of calculating the indirect cost incurred by construction time extension that reflects the characteristics of Korean public construction projects. The cost patterns generated during construction periods were analyzed, and then the current criteria of calculating the indirect costs caused by the extension were examined. Following this, actual conditions and practices in the field were surveyed and the current calculation method was applied to a model case to compare the actual cost and that determined from the current calculation method. Issues with the current method were identified by this comparison. Based on this, this research proposes a method of calculating the total actual cost caused by a suspension in a public construction project that is appropriate for calculating the additional indirect cost generated by a suspension in a public construction project on a long-term continuing contract.

• Nuclear Engineering and Technology
• /
• v.48 no.4
• /
• pp.941-951
• /
• 2016

The aim of this work is to simulate the thermohydraulic consequences of a main steam line break and to compare the obtained results with Rossendorf Coolant Mixing Model (ROCOM) 1.1 experimental results. The objective is to utilize data from steady-state mixing experiments and computational fluid dynamics (CFD) calculations to determine the flow distribution and the effect of thermal mixing phenomena in the primary loops for the improvement of normal operation conditions and structural integrity assessment of pressurized water reactors. The numerical model of ROCOM was developed using the FLUENT code. The positions of the inlet and outlet boundary conditions and the distribution of detailed velocity/turbulence parameters were determined by preliminary calculations. The temperature fields of transient calculation were averaged in time and compared with time-averaged experimental data. The perforated barrel under the core inlet homogenizes the flow, and therefore, a uniform temperature distribution is formed in the pressure vessel bottom. The calculated and measured values of lowest temperature were equal. The inlet temperature is an essential parameter for safety assessment. The calculation predicts precisely the experimental results at the core inlet central region. CFD results showed a good agreement (both qualitatively and quantitatively) with experimental results.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.21 no.1
• /
• pp.175-182
• /
• 2023

APro, a modularized process-based total system performance assessment framework, was developed at the Korea Atomic Energy Research Institute (KAERI) to simulate radionuclide transport considering coupled thermal-hydraulic-mechanical-chemical processes occurring in a geological disposal system. For reactive transport simulation considering geochemical reactions, COMSOL and PHREEQC are coupled with MATLAB in APro using an operator splitting scheme. Conventionally, coupling is performed within a MATLAB interface so that COMSOL stops the calculation to deliver the solution to PHREEQC and restarts to continue the simulation after receiving the solution from PHREEQC at every time step. This is inefficient when the solution is frequently interchanged because restarting the simulation in COMSOL requires an unnecessary setup process. To overcome this issue, a coupling scheme that calls PHREEQC inside COMSOL was developed. In this technique, PHREEQC is called through the "MATLAB function" feature, and PHREEQC results are updated using the COMSOL "Pointwise Constraint" feature. For the one-dimensional advection-reaction-dispersion problem, the proposed coupling technique was verified by comparison with the conventional coupling technique, and it improved the computation time for all test cases. Specifically, the more frequent the link between COMSOL and PHREEQC, the more pronounced was the performance improvement using the proposed technique.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.26 no.3
• /
• pp.285-292
• /
• 2008

The establishment of the scheme which could be managed the national reservoir efficiently and consideration of a variable management scheme by the application of a new technique for it is very important for the improvement of national service quality and application of related techniques. In this study, sediment information which was accumulated in the reservoir for a long time and occasioned the decrease of pondage and increase of water pollution was constructed rapidly and accurately using GPS, sub bottom profiler and echo sounder. And the calculation system of sediment was efficiently designed through the applications of 2D and 3D spatial information processing techniques. As a results, the calculation system of sediment which was accomplished a various functions was developed and a basic information of management for the reservoir which was constructed quite a while ago was presented.

• KIEE International Transactions on Power Engineering
• /
• v.4A no.2
• /
• pp.58-68
• /
• 2004

This paper presents an optimal routing algorithm (ORA) for maximizing voltage stability as well as for minimizing power loss in radial power systems. In the proposed ORA, a novel voltage stability index (VSI) for real-time assessment is newly introduced based on the conventional critical transmission path framework. In addition, the suggested algorithm can automatically detect the critical transmission paths resulting in voltage collapse when additional real or reactive loads are added. To implement an effective ORA, we have developed an improved branch exchange (IBE) method based on a loss calculation index and tie-branch power flow equations, which are suggested for real-time applications. The proposed algorithm has been tested with IEEE test systems as well as a large-scale power system in Korea to demonstrate its effectiveness and efficiency.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2002.12a
• /
• pp.179-182
• /
• 2002

In this paper, this system makes use of the analog sensor and converts the feature of fish analog signal when sensor is operating with CPU(80C196KC). Then, After signal processing, this feature Is classified a special feature and a outline of fish by using the neural network, one of the artificial intelligence scheme. This neural network classifies fish pattern of very simple and short calculation. This has linear activation function and the error backpropagation is used as a learning algorithm. And the neural network is learned in off-line process. Because an adaptation period of neural network is too long time when random initial weights are used, off-line learning Is induced to decrease the Progress time We confirmed this method has better performance than somewhat outdated machines.

• Journal of Energy Engineering
• /
• v.13 no.1
• /
• pp.51-59
• /
• 2004

The NSSS (Nuclear Steam Supply System) thermal-hydraulic programs adopted in the domestic full-scope power plant simulators were provided in early 1980s by foreign vendors. Because of limited compulsational capability at that time, they usually used very simplified physical models for a real-time simulation of NSSS thermal-hydraulic transients, which entails inaccurate results and, thus, the possibility of so-called "negative training", especially for complicated two-phase flows in the reactor coolant system. In resolve the problem, KEPRI developed a realistic NSSS T/H program ARTS which was based on the RETRAN-3D code for the improvement of the Nuclear Power Plant full-scope simulator. The ARTS (based on the RETRAN-3D code) guarantees the real-time calculations of almost all transients and ensures the robustness of simulations. However, there is some possibility of failing to calculate in the case of large break loss of coolant accident (LBLOCA) and low-pressure low-flow transient. In this case, the backup calculation system cover automatically the ARTS. The backup calculation system was expected to provide substantially more accurate predictions in the analysis of the system transients involving LBLOCA. The results were reasonable in terms of accuracy, real-time simulation, robustness and education of operators, complying with FSAR and the AMSI/ANS-3.5-1998 simulator software performance criteria.

• Korean Journal of Construction Engineering and Management
• /
• v.4 no.4 s.16
• /
• pp.123-136
• /
• 2003

In multiple apartment construction project, BCWS is a critical management factor and has a great influence on the success of the project. Due to the many apartment buildings & facilities which produce numerous activities, there are several problems in making out a time schedule of work as well as production and management of precise BCWS from the allocation of resources. In this study, actual condition survey was executed in terms of the calculation and the management of BCWS. This study propose better solutions for efficient calculation of BCWS through the analysis of the problems and standard schedule & progress curves.

• Korean Journal of Optics and Photonics
• /
• v.15 no.6
• /
• pp.555-562
• /
• 2004

We propose a hybrid method combining the implicit with the explicit methods in order to reduce the calculation time and improve the convergence problem of the 3-dimensional finite-difference beam propagation method. The numerical simulation of a directional coupler is carried out by the proposed method. It is found from the simulation results that the calculation speed of our method is 10 times faster than that of direct solving techniques.