• Journal of Welding and Joining
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• v.33 no.3
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• pp.62-67
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• 2015

A very large shell-structure built in shipyards like ship hulls or offshore structures are joined by welding through full process. As the welding contains a high thermal cycle at a local area, the welded structures should be distorted unavoidably. Because a distorted ship block should be revised to the designed value before the next stage, the ability to predict and to control the weld distortion is an accuracy level of the yard itself. Despite the ship block size, several present thermal distortion methodologies can deal those sizes, but it is a different story to deal full ship size model. Even a fully constructed ship hull not remaining any welding can have an accuracy issue like outfitting installation problems. Any present thermal distortion methodology cannot accept this size for its recommended element size and the number. The ordinary welding breadth at erection stage is about 20~40 mm. It can hardly be a good choice to make finite element model of these sizes considering human effort and computational environment. The finite element model for structure analysis of a ship hull is prepared at front-end engineering design stage which is the first process of the project. The element size of the model is as fine as the longitudinal space, and it is not proper to obtain a weld distortion at the erection stage. In this study, a methodology is suggested that a weldment can be shrunk at original place instead of using structural finite element model. We cut the original shell elements at erection weld-line and put truss elements between the edges of cut elements for weld shrinkage. Additional truss elements are used to facsimile transverse weld shrinkage which cannot be from the weld-line truss element shrink. They attach to weld-line truss element like twigs from barks. The capacity of developed elements is verified through an accuracy check of erection process of a container vessel at the apt. hull. It can be a useful tool for verifying a centering accuracy after renew and for block-separating planning considering accuracy.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.943-951
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• 1992

The objectives of this study are to analyse the thermal response behavior occurring in the charring ablative material more realistically by considering ablation and char phenomena occurring in several material layers, and to increase the reliability of thermal analysis by being able to get stable solutions through using the finite analytic method. A program has been developed to predict the temperature distribution, ablation thickness, char thickness, ablation velocity and char velocity by solving non-linear one-dimensional heat conduction equation. Results of calculation were compared with results of published papers. From this compariosn this program was proved to be a very good tool for thermal design and analysis of charring ablative materials used in the rocket propulsion system.

• Journal of the Korean Society of Safety
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• v.28 no.3
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• pp.69-73
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• 2013

The purpose of this paper is to analyze the carbonization pattern and operation characteristics of an MCCB. The MCCB is consisted of the actuator lever, actuator mechanism, bimetallic strip, contacts, up and down operator, arc divider or extinguisher, metal operation pin, terminal part, etc. When the actuator lever of the MCCB is at the top or the internal metal operation pin is in contact with the front part, the MCCB is turned on or off. It means trip state if the actuator lever or the internal metal operation pin moves to back side. In the UL 94 vertical combustion test, white smoke occurred from the MCCB when an average of 17~24 seconds elapsed after the MCCB was ignited and black smoke occurred when an average of 45~50 seconds elapsed. It took 5~6 minutes for the MCCB surface to be half burnt and took an average of 8~9 minutes for the MCCB surface to be entirely burnt. In the UL 94 test, the MCCB trip device operated when an average 7~8 minutes elapsed. If the MCCB trip has occurred, it may have been caused by an electrical problem such as a short-circuit, overcurrent, etc., as well as fire heat. From the entire part combustion test according to KS C 3004, it was found that the metal operation pin could be moved to the MCCB trip position without any electrical problems.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.973-979
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• 2024

In the framework of the Generation IV research and development project, in which the French Commission of Alternative and Atomic Energies (CEA) is involved, a main objective for the design of Sodium-cooled Fast Reactor (SFR) is to meet the safety goals for severe accidents. Among the severe ones, the Unprotected Transient OverPower (UTOP) accidents can lead very quickly to a global melting of the core. UTOP accidents can be considered either as slow during a Control Rod Withdrawal (CRW) or as fast. The paper focuses on fast UTOP accidents, which occur in a few milliseconds, and three different scenarios are considered: rupture of the core support plate, uncontrolled passage of a gas bubble inside the core and core mechanical distortion such as a core flowering/compaction during an earthquake. Several levels and rates of reactivity insertions are also considered and the thermal-mechanical behavior of an ASTRID fuel pin from the ASTRID CFV core is simulated with the GERMINAL code. Two types of fuel pins are simulated, inner and outer core pins, and three different burn-up are considered. Moreover, the feedback from the CABRI programs on these type of transients is used in order to evaluate the failure mechanism in terms of kinetics of energy injection and fuel melting. The CABRI experiments complete the analysis made with GERMINAL calculations and have shown that three dominant mechanisms can be considered as responsible for pin failure or onset of pin degradation during ULOF/UTOP accident: molten cavity pressure loading, fuel-cladding mechanical interaction (FCMI) and fuel break-up. The study is one of the first step in fast UTOP accidents modelling with GERMINAL and it has shown that the code can already succeed in modelling these type of scenarios up to the sodium boiling point. The modeling of the radial propagation of the melting front, validated by comparison with CABRI tests, is already very efficient.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2540-2545
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• 2007

A computational study of BLDC motor is presented to elucidate thermo-flow characteristics in winding and bearing with heat generation. Rotation of rotor and blades drives influx of ambient air into the rotor inlet and the inflow rates are predicted more at the front-side inlet than at the rear-side, which can be ascribed to the different pressure distribution. Recirculation zone appears in the tiny interfaces between windings, however, showing the enhanced cooling performance due to the higher velocity distribution near the rotor wall. In contrast, flow separation and incline angle of bearing groove, and relatively slower velocity distribution cause poor cooling performance and therefore the redesign of the bearing groove is significantly required.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1437-1439
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• 1995

This paper investigates the effect of thermal oxidation on the profile of the residual stress along the depth of p+ silicon films by quantitative determination method. Two examples for the application of this method illustrate that most of p+ region is subjected to the tensile stress except the region near the front surface and that the stress gradient of the film oxidized at $1100^{\circ}C$ is more steep than that of the film oxidized at $1000^{\circ}C$.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.803-807
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• 2003

Tele-operation and remote monitoring techniques are essential and important technologies for performing the inspection and repair tasks effectively in nuclear power plants. This paper presents the application of a mobile robot for the remote monitoring and inspection of the Calandria faces, where human access is limited because of the high-level radioactive environments during full power operation. The mobile robot was designed with reconfigurable crawler type of wheels attached on the front and rear side in order to pass through the ditch. The extendable mast, mounted on the mobile robot, can be extended up to 8 m vertically. This robot was also equipped a visible CCD/thermal infrared inspection head module and a stereo camera module for the enhancement of visual inspection.

• Transactions of Materials Processing
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• v.11 no.4
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• pp.332-340
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• 2002

The light guide plate of the TFT-LCD reflects the light originated from the light source, and guides the light to the front side of LCD so that we can see images vividly. This paper is concerned with tile injection molding of the light guide plate for the reflective typed LCD related to IMT-2000. The finite element analysis has been carried out based on the pine stress theory to predict both the thermal stresses of the products in the post-filling stage and the in-plane deformation behavior of the products after ejection process. Based on the simulation results, the mold for the light guide plate of a 2inch sized LCD has been designed.

• Journal of Ocean Engineering and Technology
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• v.24 no.5
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• pp.1-7
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• 2010

Offshore, sub-sea pipelines that transport oil and gas experience thermal expansion induced by the temperature of the transported medium during operation. The expansion of the pipeline can induce overload and cause damage to offshore platforms or sub-sea structures that are connected to the pipelines. To mitigate and prevent these incidents, expansion spools are installed between offshore, sub-sea pipelines and risers on the platform. This paper presents the results of the study and development of a simplified design method for expansion spools, using the slope deflection method for the purpose of preliminary design or front-end engineering and design (FEED).

• Journal of the Korean Society for Precision Engineering
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• v.18 no.7
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• pp.127-133
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• 2001

The effects of triangular and rectangular discharge current waveforms on anode erosion in wire electric discharge machining is investigated based on heat transfer analysis of half-space subject to time and space-dependent heat flux. The thermal load on the anode is simulated by a hear flux that is calculated from time-dependent discharge channel radius and energy. Evolution of the melting front during discharge, the molten volume at the experimental result for qualitative verification of the analysis. It is demonstrated that the triangular current waveform is more efficient in eroding the anode than the rectangular one.