• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.4 s.70
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• pp.405-416
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• 2005

This study contains the static buckling tests and static buckling analyses for small size grids and full size grids. The buckling tests and finite element analyses were performed to evaluate the buckling characteristics of the spacer grids in a pressurized water reactor fuel assembly and to evaluate the possibility of the prediction lot the buckling strength of spacer grids. The buckling tests were performed for small size grids and full size grids, and the correlations between buckling strength and the number of straps and the correlations between buckling strength and the number of rows are derived based on the test results. The static buckling analyses were performed to identify the effect of the number of rows and the number of columns on the buckling strength of spacer grid by a finite element method using ANSYS program and the results were compared with the buckling test results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.203-210
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• 2012

The main rotor control system is an important structural part of a helicopter that manages the thrust and control force of the helicopter. The main rotor control system consists of a swashplate assembly, scissor assembly, pitch rod assembly, guide, etc. The main rotor control system must endure various loads, such as the thrust and control force, and must meet the optimized fatigue safety life. The rotating swashplate is an important structure influenced by the pitch rod load and rotating scissor load. In this paper, the accuracy of a result about the rotating swashplate part of the main rotor control system is proven through comparison between fatigue test and FEM results. Based on this result, we estimate the lifetime and deduce the fatigue safe lifetime.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.2
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• pp.183-192
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• 2006

Predicting energy expenditure (EE) is important to prevent work-related musculoskeletal disorders (WMSDs). The problem to predict EE is that the standard of EE is based on western data. The authors checked average EE by job categories to provide basic data for suggesting proper work intensity for Korean workers. This study was conducted from 2003 to 2005. Study subjects were recruited from 4 car parts assembly plant, 2 car assembly plant, 2 Heavy machine manufacturing plant and 2 shipyards. Total study subjects were 515 male workers. To estimate VO2max, sub-maximal test was conducted to measure VO275%max by bicycle ergometer (Combi Co, Aerobike 75XL II). Heartbeats were recorded with heartbeat recorder (Polar Electro Co, Finland, S810) during work. EE of work was calculated by recorded heartbeat and individual regression equation which was derived from sub-maximal test. Subjects were classified into 4 industry and 8 work posture, 23 job task categories. Mean EEs (S.D.) according to industry classification (kcal/min) were 4.9 (0.7), 4.8 (0.7), 4.9 (0.7), 5.0 (0.9), and 4.0 (0.5) for Car Part manufacture, Car Assembly, Ship Building, Heavy Machinery Manufacture, and Hospital Office, respectively. The results suggest that Korean male workers of exceeding to the NIOSH criteria will be needed to plan for job rescheduling to maintain $worker^{\circ}$Øs health. Further study to establish Korean work intensity standard would be needed.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.10
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• pp.781-787
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• 2016

We introduce FEST (Flight Environment Simulation Test) procedures for precise guided missiles to reliably improve systems. Flight vibration specification was established based on power spectral density curves calculated from flight test data of a high speed precise guided missile. A FEST pre-profile was developed according to flight vibration specification and delivered to a precise guided missile assembly. Vibration responses were measured by installing accelerometers on electronic components vulnerable to dynamic forces. The FEST profile was adjusted by comparing the vibration responses and the flight vibration specification. Subsequently, the FEST profile was repeatedly modified through trial and error, because the responses were similar to the flight environment. The modified FEST profile enabled performance testing of assembled precise guided missiles under simulated flight conditions on the ground, where unexpected errors could be corrected before the flight tests, leading to cost and risk reduction in the development of the precise guided missile system.

• Journal of Aerospace System Engineering
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• v.12 no.3
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• pp.1-8
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• 2018

The fuel pump, which is used for an aircraft, was first developed in Korea through the Civil-Military Dual Components Development Program. The BLDC motor type, which is superior to the DC brush motor when considering efficiency, endurance, and explosive environmental characteristics, was applied to the fuel pump given its capacity and operating condition. The magnetic flux of the permanent magnet was analyzed based on the magnet flux density equation, using the Maxwell equation and the environmental condition. The motor performance, according to the load, was analyzed using the finite element method in order to design validation. The motor assembly was developed by designing the motor drive and the EMI filters. The performance test results of the motor assembly for the fuel boost pump were consistent with the analysis.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.12
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• pp.1099-1104
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• 2013

This paper presents a learning-based visual inspection method that addresses the need for an improved adaptability of a visual inspection system for parts verification in panorama sunroof assembly lines. It is essential to ensure that the many parts required (bolts and nuts, etc.) are properly installed in the PLC sunroof manufacturing process. Instead of human inspectors, a visual inspection system can automatically perform parts verification tasks to assure that parts are properly installed while rejecting any that are improperly assembled. The proposed visual inspection method is able to adapt to changing inspection tasks and environmental conditions through an efficient learning process. The proposed system consists of two major modules: learning mode and test mode. The SVM (Support Vector Machine) learning algorithm is employed to implement part learning and verification. The proposed method is very robust for changing environmental conditions, and various experimental results show the effectiveness of the proposed method.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1813-1824
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• 2022

This paper shows the verification work of SARAX code system in the reactor core transient calculation based on the simplified EBR-II Benchmark. The SARAX code system is an analysis package developed by Xi'an Jiaotong University and aims at the advanced reactor R&D. In this work, a neutron-photon coupled power calculation model and a spatial-dependent reactivity feedback model were introduced. To verify the models used in SARAX, the EBR-II SHRT-45R test was simplified to an ULOF transient with an input flowrate change curve by fitting from reference. With the neutron-photon coupled power calculation model, SARAX gave close results in both power fraction and peak power prediction to the reference results. The location of the hottest assembly from SARAX and reference are the same and the relative power deviation of the hottest assembly is 2.6%. As for transient analysis, compared with experimental results and other calculated results, SARAX presents coincident results both in trend and absolute value. The minimum value of core net reactivity during the transient agreed well with the reported results, which ranged from -0.3$ to -0.35$. The results verify the models in SARAX, which are correct and able to simulate the in-core transient with reliable accuracy.

• Transactions of Materials Processing
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• v.26 no.1
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• pp.55-62
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• 2017

This paper proposes the process to develop a light-weighting automotive door assembly using high strength steel with low cost penalty. In recent years, the automotive industry is making an effort to reduce the vehicle weight. In this study, inner panels for automotive front door using thinner sheets and quenchable boron steel were designed to reduce the weight of conventional one. In order to evaluate the stiffness properties for the proposed door design, the several static tests were conducted using the finite element method. Based on the simulation results, geometry modifications of the inner panels were taken into account in terms of thickness changes and cost saving. Furthermore, a prototype based on the proposed design has been made, and then static stiffness test carried out. From the results, the proposed door is proved compatible and weight reduction of 11.8% was achieved. It could be a reference process for automotive industry to develop the similar products.

• Journal of Korea Multimedia Society
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• v.15 no.1
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• pp.148-165
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• 2012

Applying maintenance simulation using virtual mockup in product design phase enables maintainability test before prototyping physical products, and it is expected to reduce product development costs. The simulation results can be reused as contents of service manuals and RAM (Reliability, Availability, Maintainability) analysis data. Maintenance simulation should provide realistic representation of physical property of virtual product, assembly relation between parts and manipulation process to verify feasibility of product design. The simulation system should be extended to collaborative virtual environment to perform collaborative maintenance procedures. In this paper, the three layered system architecture and the physics based collaborative interaction technique are proposed to extend current maintenance simulation into collaborative virtual environment. The proposed system was implemented as ViMMS (Virtual Mockup Maintenance Simulation system), and compared with case study results of VADE (Virtual Assembly Design Environment). As a result, the ViMMS encompassed broader range of maintenance tasks by using physics based collaborative interaction technique.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.84-92
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• 2005

This paper is concerned with optimum design of a center-pillar assembly induced by the high-speed side impact of the vehicle. In order to simulate deformation behavior of the center-pillar assembly, simplified finite element model of the center-pillar and a moving deformable barrier are developed based on results of the crash analysis of a full vehicle model. In optimization of the deformation shape of the center-pillar, S-shaped deformation is targeted to guarantee reduction of the injury level of a driver dummy in the crash test. Tailor-welded blanks are adopted in the simplified center-pillar model to control the deformation shape of the center-pillar assembly. The thickness of each part which constitutes the simplified model is selected as a design parameter. The thickness of parts which have significant effect on the deformation mechanism are selected as design parameters with sensitivity analysis based on the design of experiment technique. The objective function is constructed so as to minimize the weight and lead to an S-mode deformation shape. The result shows that the simplified model can be utilized effectively for optimum design of the center-pillar members with remarkable saving of computing time.