• Nuclear Engineering and Technology
• /
• v.49 no.2
• /
• pp.327-334
• /
• 2017

Common-cause failure (CCF) events can significantly impact the availability of safety systems of nuclear power plants. For this reason, the International Common Cause Data Exchange (ICDE) project was initiated by several countries in 1994. Since 1997 it has been operated within the Organisation for Economic Co-operation and Development (OECD)/Nuclear Energy Agency (NEA) framework and has successfully been operated over six consecutive terms (the current term being 2015-2017). The ICDE project allows multiple countries to collaborate and exchange CCF data to enhance the quality of risk analyses, which include CCF modeling. As CCF events are typically rare, most countries do not experience enough CCF events to perform meaningful analyses. Data combined from several countries, however, have yielded sufficient data for more rigorous analyses. The ICDE project has meanwhile published 11 reports on the collection and analysis of CCF events of specific component types (centrifugal pumps, emergency diesel generators, motor operated valves, safety and relief valves, check valves, circuit breakers, level measurement, control rod drive assemblies, and heat exchangers) and two topical reports. This paper presents recent activities and lessons learnt from the data collection and the results of topical analysis on emergency diesel generator CCF impacting entire exposed population.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.1
• /
• pp.13-20
• /
• 2010

The development of the console for exterior advertizing LCD Panel(LCD Console) is the purpose of this study with regard to importance of display industry. In this study, the most important point is to develop the cooling system for LCD Console. It is developed by using systematic application techniques and statistical tests and analysis to integrate commercial components, cooling fan, heat sink, thermo electronic modules etc, of it. This study, at first, shows design/manufacturing process of the cooling system and the setting process of control factors to control through experimentation. Next, after constructing the complete console, 46 inch LCD Panel and the cooling system are built in, the performance test of it is shown through experimentation.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.26 no.4
• /
• pp.391-397
• /
• 2016

Vibration disturbances induced by the reaction wheels can severely degrade the performance of high precision payloads on board satellites with high pointing stability requirements. The unwanted disturbances produced by the reaction wheels are composed of fundamental harmonic disturbances due to the flywheel imbalance and sub/higher harmonic disturbances due to bearing irregularities, motor imperfections and so on. Because the wheel speed is constantly changed during the operation of a reaction wheel, the vibration disturbance induced by the reaction wheels can magnify the satellite vibration when the rotating frequency of wheel meets the natural frequency of satellite structure. In order to provide an effective isolation of the reaction wheel disturbances, isolation performance of a hybrid vibration isolator is investigated. In this paper, hybrid vibration isolator that combines passive and active components is developed and its hybrid isolation performance using notch filter control is evaluated in single-axis. The hybrid isolation performance using notch filter control show additional performance improvement compared to the results using only passive components.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.16 no.6
• /
• pp.10-18
• /
• 2008

Metal stamping is widely used in the mass-production process of the automobile industry. During the stamping process, air may be trapped between the draw die and the panel. The high pressure of trapped air induces imperfections on the panel surface and creates a situation where an extremely high tonnage of punch is required. To prevent these problems, many air ventilation holes are drilled through the draw die and the punch. The present work has developed a simplified mathematical formulation for computing the pressure of the air pocket based on the ideal gas law and isentropic relation. The pressure of the air pocket was compared to the results by the commercial CFD code, Fluent, and experiments. The present work also used the Bisection method to calculate the optimum cross-sectional area of the air ventilation holes, which did not make the pressure of the air pocket exceed the prescribed maximum value.

• International Journal of Control, Automation, and Systems
• /
• v.6 no.4
• /
• pp.477-487
• /
• 2008

This paper proposes a new position sensorless drive for brushless DC (BLDC) motors. Typical sensorless control methods such as the scheme with the back-EMF detection method show high performance only at a high speed range because the magnitude of the back-EMF is dependent upon the rotor speed. This paper presents a new solution that estimates the rotor position by using an unknown input observer over a full speed range. In the proposed method, a trapezoidal back-EMF is modelled as an unknown input and the proposed unknown input observer estimating a line-to-line back-EMF in real time makes it possible to detect the rotor position. In particular, this observer has high performance at a low speed range in that the information of a rotor position is calculated independently of the rotor speed without an additional circuit or complicated operation process. Simulations and experiments have been carried out for the verification of the proposed control scheme.

• Journal of Welding and Joining
• /
• v.29 no.5
• /
• pp.72-81
• /
• 2011

In the present day, the needs of new steel for lightweight car-body have been increased in the automotive industry. however, the resistance spot welding is difficult to apply to the new steel because of the narrow weld current range and defects. As the solutions to these problems, adhesive bonding process is proposed. Adhesive bonding which reduce noise and vibration can be applied to joining the new steel. In this study, crash tests of b-pillar applied the resistance spot welding, structural adhesive bonding, the mixture of the structural adhesives and resistance spot welding were performed. And FEM crash model for b-pillar applied the structural adhesive bonding was developed. The results of experiment and analysis on b-pillar crash test were compared to verify the validity.

• 한국전산유체공학회:학술대회논문집
• /
• 2002.05a
• /
• pp.8-15
• /
• 2002

For the large scale computation of turbulent flows around an arbitrarily shaped body, a parallel LES (large eddy simulation) code has been recently developed in which domain decomposition method is adopted. METIS and MPI (message Passing interface) libraries are used for domain partitioning and data communication between processors, respectively. For unsteady computation of the incompressible Wavier-Stokes equation, 4-step splitting finite element algorithm [1] is adopted and Smagorinsky or dynamic LES model can be chosen fur the modeling of small eddies in turbulent flows. For the validation and performance-estimation of the parallel code, a three-dimensional laminar flow generated by natural convection inside a cube has been solved. Then, we have solved the turbulent flow around MIRA (Motor Industry Research Association) model at $Re = 2.6\times10^6$, which is based on the model height and inlet free stream velocity, using 32 processors on IBM SMP cluster and compared with the existing experiment.

• Journal of the Korea Society of Computer and Information
• /
• v.13 no.7
• /
• pp.221-229
• /
• 2008

The development of computer and multimedia brought out new technology, that is, virtual reality. Computer simulation adaptation among the technologies of the virtual reality is spreaded into air service, motor vehicle, medical science, sports, education, even fashion industry. This study look into 2-dimensional hair-style computer simulation system which is started to common use nowadays and the 3-dimensional system which is under the development. And this study proposed several problems such as heavy 3D system booth and the low price but low qualified camera in order to commercialize the 3D system. This study also suggest several alternative, for instance, the change from object photography method to panoramic photography method, the substitute by middle or high end and high qualified camera.

• Journal of Magnetics
• /
• v.14 no.1
• /
• pp.27-30
• /
• 2009

Various sintered magnets containing $28{\sim}31\;wt%$ Nd and $0{\sim}7\;wt%$ Dy were evaluated for coercivity and irreversible flux loss as a preliminary study to develop highly-coercive, high-temperature magnets that can be applied for driving motors in a hybrid vehicle. The sintered magnets were prepared in sequence of strip casting, HD treatment, jet milling, magnetic field pressing, sintering and post-annealing. Increasing Dy content and adjusting post-annealing temperature monotonically increased coercivity of magnets from about 14 kOe to 30 kOe. A magnet containing 28 wt% Nd and 7 wt% Dy exhibits a $(BH)_{max}$+$_i{H_c}$ value of almost 64. This is very close to what the automobile industry considers as the minimum value (65) for a hybrid vehicle system. Moreover, irreversible flux loss of the magnet was about 3% at $200^{\circ}C$, which is well less than the allowable limit (5%) to a driving motor in hybrid vehicles.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.5 no.1
• /
• pp.62-80
• /
• 2013

This paper has been focused on developing a new hybrid mount for shipboard equipment used in naval surface ships and submarines. While the hybrid mount studied in our previous research was 100 kg-class series-type mount, the new hybrid mount has been designed as an inertia-type mount capable of supporting a static of 500 kg. The proposed mount consists of a commercial rubber resilient mount, a piezostack actuator and an inertial mass. The piezostack actuator connected with the inertial mass generates actively the control force. The performances of the proposed mount with a newly designed specific controller have been evaluated in accordance with US military specifications and compared with the passive mount. An isolation system consisting of four proposed mounts and auxiliary devices has been also tested. Through a series of experimental tests, it has been confirmed that the proposed mount provides better performance than the US Navy's standard passive mounts.