• 한국군사과학기술학회지
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• 제15권4호
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• pp.390-397
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• 2012

According to sailing condition, an exciting force for luminairie of naval vessels was measured and analyzed. A naval combat service support boat and P${\bigcirc}{\bigcirc}$(patrol killer guided missile) were selected as a target naval vessel. Due to their small size and fast speed, they received excessive vibration than other bigger naval vessels like destroyer. The vibration of luminairie was measured on their cruising and maximum speed. This could analyze exciting force for luminairie of naval vessels. Using this analyzed data, the validity of military standard for naval vessel was verified.

• Journal of Cerebrovascular and Endovascular Neurosurgery
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• 제25권3호
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• pp.260-266
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• 2023

Objective: Microvascular anastomosis, particularly side-to-side (STS) bypass, is a complex surgical procedure. While several suture techniques exist, none of them is superior to the others. We assessed the association between various STS bypass techniques and vessel twisting using chicken wing training models. Methods: Three suture techniques were compared over an anterior wall suture procedure. The unidirectional continuous suture (UCS) group used a downward "right-to-left" continuous suture. The reverse continuous suture (RCS) group used a downward "left-to-right" continuous suture. The interrupted suture (IS) group used the standard interrupted suture. The number of samples in each of the three groups was 30 (n=90). We compared the incidence of vessel twisting and rotation angles across groups. Results: Vessel twisting occurred in 96.7%, 56.7%, and 0% of the cases in the UCS, IS, and RCS groups, respectively. The incidence of vessel twisting differed significantly in all 3 groups (p<0.001), with an apparent trend (p=0.002). The mean rotation angles were 201°±90.6°, 102°±107.6°, and 0° in the UCS, IS, and RCS groups, respectively, which were significantly different (p<0.001). On excluding cases without twisting, the rotation angles of twisted vessels in the UCS and IS groups were 207.9°±83.7° and 180°±77.9°, respectively, which yielded a significant difference between these groups (p<0.001). Conclusions: We found that the incidence and trend of vessel twisting differed significantly across suture techniques. The RCS technique may aid in preventing vessel twisting in the STS bypass procedure.

• 한국재료학회지
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• 제27권8호
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• pp.409-415
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• 2017

For enhanced cavitation erosion resistance of vessel propellers, an electroless Ni-P plating method was introduced to form a coating layer with high hardness on the surface of Cu alloy (CAC703C) used as vessel propeller material. An electroless Ni-P plating reaction generated by Fe atoms in the Cu alloy occurred, forming a uniform amorphous layer with P content of ~10 wt%. The amorphous layer transformed to (Ni3P+Ni) two phase structure after heat treatment. Cavitation erosion tests following the ASTM G-32 standard were carried out to relate the microstructural changes by heat treatment and the cavitation erosion resistance in distilled water and 3.5 wt% NaCl solutions. It was possible to obtain excellent cavitation erosion resistance through careful microstructural control of the coating layer, demonstrating that this electroless Ni-P plating process is a viable coating process for the enhancement of the cavitation erosion resistance of vessel propellers.

• Journal of Welding and Joining
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• 제33권2호
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• pp.40-46
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• 2015

This study was performed to investigate the effect of ultrasonic nano crystal surface modification (UNSM) on residual stress mitigation after Weld Inlay repair for butt dissimilar metal weld with Alloy 82/182 in reactor vessel In/Outlet nozzle. As-welded and Weld Inlay specimens were made in accordance with design standard of ASME Code Case N-766, and two planes of their weld specimens were peened by the optimum UNSM process condition. Peening characteristics for weld specimens after UNSM treatment were evaluated by surface roughness and Vickers hardness test. And, residual stress for weld specimens developed from before and after UNSM treatment was measured and evaluated by instrumented indentation technique. Consequently, it was revealed that the mitigation of residual stress in weld metal after Weld Inlay repair of reactor vessel In/Outlet nozzle could be possible through UNSM treatment.

• 한국압력기기공학회 논문집
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• 제9권1호
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• pp.20-24
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• 2013

Reactor Vessel Internals(RVIs), which are installed within the reactor pressure vessel and support the fuel assembly, take responsibility for safety of reactor core. In operating Nuclear Power Plants(NPPs), the RVIs have been exposed to severe conditions such as neutron irradiation, high temperature, high pressure, and high velocity of coolant flow and have degraded by materials aging with long-term operation. Therefore, the effective aging management plan and the appropriate regulatory requirements are necessary to maintain the integrity of RVIs. The purpose of this paper is to provide a review guide for Periodic Safety Review(PSR) of RVIs in presurized water reactor. The review guide is developed based on the revised review guides and reports established from IAEA and USNRC, and the analysis results of design characteristics, aging mechanisms, and operating experiences of RVIs in domestic and international NPPs. Consequently, the developed review guide for PSR of RVIs is expected to contribute an overall strategy and standard for the PSR of RVIs.

• 시스템엔지니어링학술지
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• 제13권1호
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• pp.15-23
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• 2017

This paper describes verification of APR1400 reactor vessel by applying the system engineering approach, in which the design re-engineering method is used to check the design parameters of APR1400 RV (reactor vessel). The RV is classified as safety class 1 and therefore must adhere strictly to the rules of ASME BPVC section III, subsection NB and seismic category I. This study explores designing the RV by following the ASME guidelines and making a comparative study with the current design. To meet this objective we apply system engineering methodologies to structure the process and allow for verification and validation of the major RV design parameters such as thickness of RV. The structural thicknesses of various part of RV are determined as well as reinforcements on the RV major nozzles. A 3D virtual reality model was created based on the design parameters using CATIA V5 and animation using Dassault Composer V2016. A comparison of re-engineered ARP1400 RV and standard APR1400 RV was done to show which design parameters were taken more conservative approach.

• 한국해양공학회지
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• 제27권1호
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• pp.9-15
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• 2013

This paper calculates the mating dynamic forces of a semi-submersible offshore structure's topside module, where a hull moored in the sea is combined with a topside module carried by a heavy lift vessel, as a mating installation method. The environmental conditions include various wave directions and wave heights, with constant wind and current speeds. Appropriate ballast and de-ballast plans for the heavy lift vessel and hull of the semi-rig should be performed in order to safely obtain these forces, whereas a fixed platform or the GBS (Gravity based structure) type of offshore structure only needs a ballast plan for the heavy lift vessel. From this paper, the allowable wave height or wave direction for the mating procedure can be investigated based on the standard DAF (Dynamic amplitude factor) of the rules and regulations.

• 한국통신학회논문지
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• 제34권5B호
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• pp.449-454
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• 2009

본 논문에서는 먼저 선박환경에서 USN 구축을 위한 하드웨어와 소프트웨어 플랫폼을 분석하였다. 하드웨어 플랫폼에서는 기존의 CC2420기반의 mote 기술을 분석하였고 소프트웨어 플랫폼에서는 TinyOS 플랫폼을 분석하였다. 다음으로 USN 통신방식의 표준인 IEEE 802.15.4의 물리계층을 분석하고 선박USN 성능분석을 위해 Matlab을 사용하여 ZigBee/IEEE 802.15.4 물리계층에 대해 성능평가를 수행하였다. 결과적으로 이동하는 선박환경에서의 선박USN 구축에 관한 타당성을 성능평가를 통해 검증하였다.

• Journal of Power Electronics
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• 제15권2호
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• pp.378-388
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• 2015

This paper proposes a pulse width modulation (PWM)-based sliding mode controller (SMC) for a full-bridge DC-DC converter that can eliminate static output voltage error. Hysteretic SMC in DC-DC converter does not have a fixed switching frequency, and applying hysteretic SMC to full-bridge converters is difficult. Fixed-frequency SMC, which is also called PWM-based SMC, based on equivalent control overcomes these shortcomings. However, the controller order reduction in equivalent control in PWM-based SMC causes static output voltage error. To resolve this issue, an integral item is added to the PWM-based SMC. Sliding mode coefficients are designed by applying a standard second-order system to the sliding mode surface. The effect of adding an integral item on the controller is analyzed, and an integral coefficient design method is proposed. Experiment results on a three-level full-bridge DC-DC converter verify the control scheme and design method proposed in this paper.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.93-102
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• 2021

The analysis of the fluid flow characteristics in reactor pressure vessel is an important part of the hydraulic design of nuclear power plant, which is related to the structure design of reactor internals, the flow distribution at core inlet and the safety of nuclear power plant. The flow distribution and mixing characteristics in the pressurized reactor vessel for the 1000MWe advanced pressurized water reactor is analyzed by using Computational Fluid Dynamics (CFD) method in this study. The geometry model of the full-scaled reactor vessel is built, which includes the cold and hot legs, downcomer, lower plenum, core, upper plenum, top plenum, and is verified with some parameters in DCD. Under normal condition, it is found that the flow skirt, core plate holes and outlet pipe cause pressure loss. The maximum and minimum flow coefficient is 1.028 and 0.961 respectively, and the standard deviation is 0.019. Compared with other reactor type, it shows relatively uniform of the flow distribution at the core inlet. The coolant mixing coefficient is investigated with adding additional variables, showing that mass transfer of coolant occurs near the interface. The coolant mainly distributes in the 90° area of the corresponding core inlet, and mixes at the interface with the coolant from the adjacent cold leg. 0.1% of corresponding coolant is still distributed at the inlet of the outer-ring components, indicating wide range of mixing coefficient distribution.