• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.851_852
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• 2009

Shrink fitting which is assembling process to fix stator core on the motor frame is widely used at the mass production line of motors because of cost and productivity. This process produces compressive stress on a stator core, which causes negative effect for example, core and copper losses on motor performance. Magnetic properties of electrical steel are effected by both compressive and tensile and thermal stresses. Electromagnetic field analysis is considered one of the effective process since one can predict motor performance including core loss precisely. This method can consider non linear magnetic property with magnetic saturation which is typical electrical steel behavior. However this method is strongly depended on non linear magnetic data, one may have different calculation result whether considering mechanical stress or not. This study describes magnetic field analysis of a motor considering mechanical stress from shrink fitting. Analysis results are compared with each stress-free and stressed condition.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.6
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• pp.614-619
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• 2009

The STW(servo track writing) system which is the process of writing servo signals on disks before assembling in drives uses the spindle motor-chuck mechanism to realize low cost because the spindle motor-chuck mechanism has merit which can simultaneously write multi-disk by piling up disks in hub. Therefore, when the spindle motor-chuck mechanism of horizontal type operates in high rotation speed it is necessary to reduce the effect of RRO(repeatable run-out) and NRRO(non-repeatable run-out) to achieve the high precision accuracy of nano-meter level during the STW process. In this paper, we analyzed that the slip in assembly surfaces can be caused by the mechanical tolerance and clamping force in hub-chuck mechanism and can affect NRRO performance. We designed springs for centering and clamping considering centrifugal force by the rotation speed and assembly condition. The experimental result showed NRRO performance improves about 30 % than case of weak clamping force. The result shows that the optimal design of the spindle motor-chuck mechanism can effectively reduce the effect of NRRO and RRO in STW process.

• The Journal of the Korea Contents Association
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• v.16 no.12
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• pp.143-150
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• 2016

Modular house is built by assembling various joints. Module assembly in the stage of on-site installation is very important process, because assembly process directly affects the structural stability and the quality. However, manual tools and electric-powered tools have a problem in that assembly productivity and quality are reduced during long-time usage. Although pneumatic assembly tools for modular house have been developed, but empirical analysis to compare and evaluate the performance of tools has not been sufficient. This study compares and analyzes the assembly quality and productivity by applying existing assembly tools and new pneumatic tools to the field. The analysis results show that pneumatic assembly tools are more excellent in terms of assembly productivity and quality.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.5
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• pp.20-27
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• 2010

In this study, we improved problems in the existing product by PARKER and developed the swivel valve tube couplers that can be produced by a low price in Korea. The major development was that a modulized production method was implemented by introducing a part assembling method that uses a cocking jig, and the production cost was reduced by operating the production process more simply than that of PARKER. Also, it was possible to avoid the patient registered by PARKER through the differences in the number of grooving processes and the type of o-ring. In the results of the rotation test by varying its application angle after installing it to a vehicle, it was verified that the structure proposed in this study can endure the eccentric torque and transformation pressure for various angles that have been considered as the problem in the existing fixed tube couplers. In addition, the structure was developed to adopt the problem that represents differences in the installation position of an air tank or the length and direction of hoses according to the type of vehicles produced in vehicle manufacturers. Furthermore, it was possible to verify that the product developed in this study was more excellent than that of PARKER through comparing the performance according to the Federal Motor Vehicle Safety Standard.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.6
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• pp.153-158
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• 2017

Reducer is a device to transmit and change torque and speed from drive shaft to driven shaft with excellent transmission efficiency, and it is widely used in many areas today. Reduction gear consists of two axes, gear, bearing supporting axes, and housing. The simplest method to transmit rotation or power to multiple axes is to attach circular plates to two axes and contact each other. However, in this case, if increasing number of rotations or if contact pressure is small, because of slipping, it cannot transmit power. For problems for the current reducer case, it is heavy and its assembling and repair is difficult. In addition, there are few studies about manufacturing and performance testing of worm gear reducer, causing lack of the foundation to improve the product competition and the performance.

• Journal of Korean Association for Spatial Structures
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• v.21 no.4
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• pp.65-72
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• 2021

The Precast concrete(PC) modular structures are a method of assembling pre-fabricated unit modules in the construction site. The essential aim of modular structures is to introduce a connection method that can ensure splicing performance and effectively resist shear strength. This study proposed PC module using a connecting plate that can replace splice sleeves and shear keys used in the conventional PC modular structures. To evaluate the splicing performance and shear capacity of the proposed method, the shear test was conducted by fabricating one monolithic reinforced concrete(RC) beam and two PC modular beams with a shear span-to-depth ratio as variables. The experimental results showed that the shear capacity of the PC modular beam was about 89% compared to that of the RC beam, and showed a failure of the RC beam according to the shear span-to-depth ratio. Therefore, it was considered that the connecting plate effectively transferred the stress between each PC module through the joint and ensure integrity. In addition, the applicability of shear strength equation of ACI 318-19 and Zsutty's equation to PC modular beams were evaluated. Results demonstrated that the improved shear strength equations are needed to consider reduction of shear strength in PC modules.

• Korean Journal of Human Ecology
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• v.18 no.1
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• pp.223-236
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• 2009

The purpose of this study was to improve the sanitary management of school foodservice. A survey questionnaire was administered to 153 dietitians from elementary, middle and high schools in the Daejeon area. The questions were categorized into four fields: 'General characteristics', 'Facility and equipment set up at the schools studied', 'Performance of CCP(criticai control point)s' and 'Reasons of barriers to HACCP(hazard analysis of critical control points) implementation'. The results were as follows. Most of the subjects were the dietitians of elementary school(56.9%), were university graduates(51.0%) and were in their thirties(58.2%). The average length of their career had been 5.8 years. The average ratio of students per dietitian was 1,163. The average ratio of students per full-time employee was 124. The ratio of self-operated management was 90.2 %. The CCP7(assembling and serving) received the highest performance score, while the performance score of CCP2(management of potentially hazardous foods) was the lowest. Eighty-four percent of the surveyed school foodservices did not have pre-preparation rooms. The school foodservice operations were not well equipped with hot/cold holding equipments. Self-operated management scored higher on almost all sections(CCP1-CCP7). Contracted management scored highest on CCP8. The higher the age and career of the subject were, the higher were all the CCP performance scores. The reasons of barriers to HACCP implementation were lack of understanding of standards CCP1 and CCP2, workers' lack of cooking knowledge, and lack of information about school foodservice.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.33 no.12
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• pp.37-44
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• 2017

Due to structural characteristics, construction costs and duration of a modular system would be saved by minimizing the schedule on the job site. As such, it is crucial to develop a connection that can guarantee stiffness while allowing for simple assembling. Particularly, the mid- to high-rise construction of the modular system necessitates the securing of the structural stability and seismic performance of multi-unit frames and connections, and thus, the stiffness of unit-assembled structures needs to be re-evaluated and designed. However, evaluating a frame consisting of slender members and reinforcing materials is a complicated process. Therefore, the present study aims to examine the structural characteristics of a modular unit connection based a method for reinforcing connection brackets and hinges while minimizing the loss of the cross section. Toward this end, the study modeled the beam-to-column connection of a modular system with the proposed connection, and produced a specimen which was used to perform a cycling loading test. The study compared the initial stiffness, the attributes of the hysteretic behavior, and the maximum flexural moment, and observed whether the model acquired the seismic performance, compared to the flexural strength of the steel moment frame connection that is required by the Korean Building Code. The test results showed that the proposed connection produced a similar initial stiffness value to that of the theoretical equation, and its maximum strength exceeded the theoretical strength. Furthermore, the model with a larger ceiling bracket showed higher seismic performance, which was further increased by the reinforcement of the plate.

• Journal of the Korean housing association
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• v.19 no.4
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• pp.41-48
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• 2008

In this study, an analysis is carried out on the acoustic design for an indoor gymnasium scheduled to be built at Buan County, Chonbuk Province. By way of background, the study examines the case of a large-scale indoor gymnasium that has been constructed in the local area of Hangan-myeon. There are many examples whereby this gymnasium could be used not only as a sporting facility for the residents, but also as a multipurpose space for public performances such as leisure activities, lectures, assembling activities, theatre and concerts etc. In order to maximize the functional utilization of such an indoor gymnasium, it is important to simultaneously verify the acoustic capabilities of the space in terms of Definition of both Voice and Music. However, as a large-scaled athletic facility, the building was designed with a high ceiling-height to accommodate its functional characteristics. The space forms a Sound Focus whereby the sound is concentrated at a specific part, and because the vibration of sound is too loud due to its broad volume, acoustic defects arise such as a significant number of Echoes. Using this gymnasium as a precedent, this study proposes an acoustic design based on the drawings of the indoor gymnasium that is scheduled to be built at B County, Chonbuk Province. The gymnasium is equipped with an optimized acoustic condition passing through the Acoustic Simulation Phase. From the results of an Acoustic Simulation, we can design an indoor gymnasium that is equipped with a considerably satisfying and improved acoustic performance compared with the building before it was reformed. It is also considered that the use of such materials can fundamentally reduce construction costs and can improve acoustic performance, at the planning and design stages for similar sporting facilities in the future.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.4
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• pp.1-9
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• 2010

Three-dimensional (3-D) integration is an emerging technology, which vertically stacks and interconnects multiple materials, technologies, and functional components such as processor, memory, sensors, logic, analog, and power ICs into one stacked chip to form highly integrated micro-nano systems. Since CMOS device scaling has stalled, 3D integration technology allows extending Moore's law to ever high density, higher functionality, higher performance, and more diversed materials and devices to be integrated with lower cost. The potential benefits of 3D integration can vary depending on approach; increased multifunctionality, increased performance, increased data bandwidth, reduced power, small form factor, reduced packaging volume, increased yield and reliability, flexible heterogeneous integration, and reduced overall costs. It is expected that the semiconductor industry's paradiam will be shift to a new industry-fusing technology era that will offer tremendous global opportunities for expanded use of 3D based technologies in highly integrated systems. Anticipated applications start with memory, handheld devices, and high-performance computers and extend to high-density multifunctional heterogeneous integration of IT-NT-BT systems. This paper attempts to introduce new 3D integration technologies of the chip self-assembling stacking and 3D heterogeneous opto-electronics integration for realizng the super-chip.