• Composites Research
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• 제25권1호
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• pp.19-25
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• 2012

본 연구에서는 압축하중을 받는 원공을 가진 샌드위치 복합재 기둥의 좌굴 거동을 조사하였다. 샌드위치 복합재 기둥은 유리섬유직물/에폭시 면재와 우레탄 폼 심재로 구성되어 있다. 이때 면재 두께는 1.7mm, 심재 두께는 23mm, 37mm, 48mm, 61mm, 그리고 원공 직경은 25mm와 38mm를 고려하였다. 원공 위치가 샌드위치 복합재 기둥의 좌굴 거동에 미치는 영향을 조사하기 위해 직경 25mm인 원공이 시편중앙부에 있는 경우, 시편중앙부를 기준으로 중앙부와 끝단 사이의 1/4 지점에 있는 경우, 시편중앙부를 기준으로 중앙부와 끝단 사이의 1/2 지점에 있는 경우를 고려하였다. 시편중앙부에 직경 25mm인 원공이 있는 경우의 좌굴하중과 최대하중은 원공이 없는 경우보다 10% 정도 낮게 나타나며, 시편중앙부에 직경 38mm인 원공이 있는 경우의 좌굴하중과 최대하중은 원공이 없는 경우보다 30% 정도 낮게 나타났다. 그러나 원공 위치가 좌굴하중과 최대하중에 미치는 영향은 크지 않았다. 주요 파괴 모드는 심재 두께가 23mm와 37mm와 같이 얇은 경우는 심재 전단파괴가 지배적이고 심재 두께가 48mm와 61mm와 같이 두꺼운 경우는 면재-심재 분리가 지배적으로 관찰되었다.

• 한국정밀공학회지
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• 제19권1호
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• pp.43-47
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• 2002

The new core making method economizing the amount of core sand has been requested. The new method is that a core box is heated until it reaches reasonable temperature and then core sand with core binder is sprayed into the core box. Since inner temperature distribution have to be uniform in order to form uniform thickness of core, we studied inner temperature distribution of core box. First, we determined proper number of torches and optimized torch positions to minimize the average of absolute deviation(AVEDEV) of inner temperature. The results are as fellowed: 1. The number of torches that enables uniform inner temperature distribution about $300^{\circ}C$ is 25. 2. When $S_H$ and $S_V$ is 0.7, the torch positions are optimized and AVEDEV is 5.85.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.921-926
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• 2001

The reliability and accuracy of the information on control rod position are very important to the reactor safety and the design of the core protection system. In this study, a thorough investigation on the RSPT(Reed Switch Position Transmitter) type control rod position indication system and its actual implementation in the exiting nuclear power plants in Korea was performed first. A design of the control rod position indication system using reed switch for the CEDM on the system-integrated reactor SMART was developed based on the position indicator technology identified through the investigation. The feasibility of the design was evaluated by test of manufactured control rod position indicator using reed switch for SMART.

• International Journal of CAD/CAM
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• 제6권1호
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• pp.167-172
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• 2006

Recently, wire-EDM became a necessity for many engineering applications, particularly in the dies making. No-Core cut process is helpful for operations in which falling slug can jam the machine or wire. In this paper a proposed CAM system (called NCPP) is introduced, to overcome the limitations of the existing CAM systems in the machining of No-Core cut. The proposed CAM system (NCPP) provides pocketing of No-core cut and optimal selection of the position of starting hole (wire threading point), to minimize toolpath length. It was written for data exchange between CAD-CAM-CNC machines. This data model will become part of the ISO (Data model for Computerized Numerical Controllers) international standard. The NCPP system has been implemented in Visual C++. Many examples are used to illustrate NCPP system. The results show that, NCPP saves the machining time by significant value. This value depends on the shape and complexity of the workpiece that is being cut.

• 한국산업융합학회 논문집
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• 제25권4_2호
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• pp.611-619
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• 2022

In this study, the seismic performance of low - rise piloti buildings with concentric core (shear wall) position is analysed and reviewed based on KDS 41. The prototype is selected among the constructed low - rise piloti buildings with concentric core designed based on KBC 2005 which was used for many low - rise piloti buildings construction. The seismic performance of the building shows plastic behavior in X-direction and elastic behavior in Y-direction. The inter-story drift is lager than that of concentric core case and is under the maximum allowed drift ratio. The displacement ratio of first story is much lager the that of upper stories, and the frame structure in the first story is evaluated as vulnerable to lateral force. Therefore, low - rise piloti buildings with concentric core need the diminishment of lateral displacement and reinforcement of lateral resistance capacity in seismic design and seismic retrofit.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.617-626
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• 2022

To effectively monitor the variety of distributions of neutron flux, fuel power or temperatures in the reactor core, usually the ex-core and in-core neutron detectors are employed. The thermocouples for temperature measurement are installed in the coolant inlet or outlet of the respective fuel assemblies. It is necessary to reconstruct the measurement information of the whole reactor position. However, the reading of different types of detector in the core reflects different aspects of the 3D power distribution. The feasibility of reconstruction the core three-dimension power distribution by using different combinations of in-core, ex-core and thermocouples detectors is analyzed in this paper to synthesize the useful information of various detectors. A comparison of multilayer perceptron (MLP) network and radial basis function (RBF) network is performed. RBF results are more extreme precision but also more sensitivity to detector failure and uncertainty, compare to MLP networks. This is because that localized neural network could offer conservative regression in RBF. Adding random disturbance in training dataset is helpful to reduce the influence of detector failure and uncertainty. Some convolution neural networks seem to be helpful to get more accurate results by use more spatial layout information, though relative researches are still under way.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.2321-2328
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• 2022

The passive safety system is adopted in an AP1000 nuclear power unit to improve the operation safety of the whole unit. However, due to boron diffusion and periodic sampling, boron dilution occurs in the core makeup tank. The boron replenishment process in the core makeup tank is essential and becomes particularly important. Based on the validated models, this article numerically investigates the influence of the replenishment flow rate and the position on the boron distribution in the core makeup tank. The thermal fatigue phenomenon of the "T" connection caused by replenishment is analyzed. Finally, the replenishment strategy is proposed to benefit both boron mixing in the core makeup tank and eliminating the thermal fatigue of the "T" connection.

• Nuclear Engineering and Technology
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• 제36권6호
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• pp.528-539
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• 2004

It is essential in commercial reactors that the safety limits imposed on the fuel pellets and fuel clad barriers, such as the linear power density (LPD) and the departure from nucleate boiling ratio (DNBR), are not violated during reactor operations. In order to accurately monitor the safety limits of current reactor states, a detailed three-dimensional (3D) core power distribution should be estimated from the in-core detector signals. In this paper, we propose a calculation methodology for detailed 3D core power distribution, using in-core detector signals and core monitoring constants such as the 3D Coupling Coefficients (3DCC), node power fraction, and pin-to-node factors. Also, the calculation method for several core safety parameters is introduced. The core monitoring constants for the real core state are promptly provided by the core design code and on-line MASTER (Multi-purpose Analyzer for Static and Transient Effects of Reactors), coupled with the core monitoring program. through the plant computer, core state variables, which include reactor thermal power, control rod bank position, boron concentration, inlet moderator temperature, and flow rate, are supplied as input data for MASTER. MASTER performs the core calculation based on the neutron balance equation and generates several core monitoring constants corresponding to the real core state in addition to the expected core power distribution. The accuracy of the developed method is verified through a comparison with the current CECOR method. Because in all the verification calculation cases the proposed method shows a more conservative value than the best estimated value and a less conservative one than the current CECOR and COLSS methods, it is also confirmed that this method secures a greater operating margin through the simulation of the YGN-3 Cycle-1 core from the viewpoint of the power peaking factor for the LPD and the pseudo hot pin axial power distribution for the DNBR calculation.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.575-600
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• 2024

During an earthquake on December 29th 2020, the Krško NPP automatically shutdown due to the trigger of the negative neutron flux rate signal on the power range nuclear instrumentation. From the time course of the detector signal, it can be concluded that the fluctuation in the detector signal may have been caused by the mechanical movement of the ex-core neutron detectors or the pressure vessel components rather than the actual change in reactor power. The objective of the analysis was to evaluate the sensitivity of the neutron flux at the ex-core detector position, if the detector is moved in the radial or axial direction. In addition, the effect of the core barrel movement and core inside the baffle movement in the radial direction were analysed. The analysis is complemented by the calculation of the thermal and total neutron flux gradient in radial, axial and azimuthal directions. The Monte Carlo particle transport code MCNP was used to study the changes in the response of the ex-core detector for the above-mentioned scenarios. Power and intermediate-range detectors were analysed separately, because they are designed differently, positioned at different locations, and have different response characteristics. It was found that the movement of the power range ex-core detector has a negligible effect on the value of the thermal neutron flux in the active part of the detector. However, the radial movement of the intermediate-range detector by 5 cm results in 7%-8% change in the thermal neutron flux in the active part of the intermediate-range detector. The analysis continued with an evaluation of the effects of moving the entire core barrel on the ex-core detector response. It was estimated that the 2 mm core barrel radial oscillation results in ~4% deviation in the power and intermediate-range detector signal. The movement of the reactor core inside baffle can contribute ~6% deviation in the ex-core neutron detector signal. The analysis showed that the mechanical movement of ex-core neutron detectors cannot explain the fluctuations in the ex-core detector signal. However, combined core barrel and reactor core inside baffle oscillations could be a probable reason for the observed fluctuations in the ex-core detector signal during an earthquake.

• 성인간호학회지
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• 제26권1호
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• pp.11-21
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• 2014

Purpose: This study was conducted to describe core competencies and identify factors affecting core competencies among infection control nurses (ICN). Methods: Infection control nurses from hospital with more than 200 beds comprised the sample. Questionnaires were sent to the sample via e-mail. One hundred and three questionnaires were returned. Data were analyzed with descriptive statistics and stepwise multiple regression via SPSS/WIN 21.0. Results: The core competency level of healthcare workers area was the highest that of the education and research was the lowest. There were significant differences in core competencies related to demographics such as age, clinical carrier, infection control carrier, position, academic degree, infection control specialist license, hospital location, and hospital type. The explained variances for the core competency were 38.3% and the contributing factors to core competencies were infection control carrier and infection control specialist license. Conclusion: It showed various levels of core competencies depending on infection control nurses' demographics and hospital traits, therefore consistent management efforts for the licensing and career path of infection control would be required.