• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.176-177
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• 2019

Recently, efforts are made to apply 200MPa levels of ultra-high strength concrete to structures exceeding 40MPa.. Ultra-high strength concrete has been steadily researched in Korea as well as abroad, and now it is equipped with 200MPa ultra-high strength concrete mixing technology. Because ultra-high strength concrete has a higher range of compressive strength than ordinary concrete, it is difficult to accurately measure the compressive strength of UHPC concrete with existing compressive strength measuring equipment and can be less reliable. In this study, the compressive strength of the SC80 was measured according to the test method to compare the compressive strength of the SC80 by applying various methods of measurement of compressive strength. The compressive strength test method measured the compressive strength according to the size of the specimen, the grinding method, and the capacity of the UTM equipment.

• Journal of Power System Engineering
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• v.22 no.6
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• pp.58-66
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• 2018

The use of external gear pumps is an effective way to achieve adequate performance at low cost when composing hydraulic systems. The biggest drawback, on the other hand, is the accompanying noise. Gears of continuous contact shape are actively used for the pump recently. The continuous contact shape must be the helical type due to the nature of the gear pump that is driven only by the drive gear. In this paper the theoretical shape of continuous contact gear is analyzed using simple rack shape of straight lines and two circular arcs. Using such geometry, the theoretical equation will be developed by envelope curves according to the conjugate gear shape rules. After checking the validity of the theory by the shape of gear rules, the grinding shape was also developed. The 3D shapes using equation can be also drawn. It was also shown that contact ratio and radius of curvature are easily developed by the theoretical equations.

• Design & Manufacturing
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• v.18 no.2
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• pp.9-16
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• 2024

Recently, there has been extensive research conducted on the miniaturization of semiconductors and the improvement of their integration to achieve high-quality and high-performance electronic devices. To integrate and miniaturize multiple semiconductors, thin and precise wafers are essential. The backgrinding process, which involves high-precision processing, is necessary to achieve this. The backgrinding system is used to grind and polish the back side of the wafer to reduce its thickness to ㎛ units. This enables the high integration and miniaturization of semiconductors and a flattening process to allow for detailed circuit design, ultimately leading to the production of IC chips. As the backgrinding system performs precision processing at the ㎛ unit, it is crucial to determine the stability of the equipment's rigidity. Additionally, the flatness and surface roughness of the processed wafer must be checked to confirm the processability of the backgrinding system. IIn this paper, the goal is to verify the processability of the back grinding system by analyzing the natural frequency and resonance frequency of the equipment through computer simulation and measuring and analyzing the flatness and surface roughness of wafers processed with backgrinding system. It was confirmed whether processing damage occurred due to vibration during the backgrinding process.

• Journal of the Ergonomics Society of Korea
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• v.31 no.1
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• pp.177-183
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• 2012

Objectives: The objectives of this study are to discuss the importance of job stress and to introduce a model of job stress at the shipbuilding industry considering the characteristics of the shipbuilding works. Background: Shipbuilding works consist of grinding, painting, interior works, welding, and assembling and using heavy equipment in narrow space or work at outside or at high and dangerous places. The working environments aggravate the stress to the workers. Methods: Studies of job stress in industries including shipbuilding industries were reviewed and the characteristics of jobs of shipbuilding were analyzed to find causes of job stress. Results: A model was constructed based upon these findings and reviews. Conclusions: Job stress of shipbuilding workers are very high and thus job and working conditions need to be improved to attenuate the level of job stress of shipbuilding workers. Applications: This model can be used to identify the highly stressed workers and sources of stress.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.7
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• pp.58-65
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• 1999

Hard turning offers many possible benefits over grinding such as lower equipment costs, shorter setup time, reduced process steps and better surface integrity. Despite the amount of research in this area, there exists no data in the intermittent hard turning. The objective of this paper is to investigate the effect of CBN tool materials and machinability to an intermittent hard turning. To this end, different CBN materials were tested to evaluate the tool wear and surface roughness in an intermittent hard turning. It is found that low-CBN-content tool is better than high-CBN-content tool. Then, we discussed a cutting force, vibration, and CBN tool wear mechanism from the hard turning.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2002.11a
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• pp.75-78
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• 2002

CNTs have been grown by the thermal CVD process in which $C_{2}H_{2}$ gas was deposited on the Fe - $Al(OH)_3$ mixture pretreated by mechanochemical treatment with a high energy mixer mill. As the duration time of grinding fer $Fe-(Al(OH)_3$ mixture by the mixer mill increased, amorphous $Al(OH)_3$ and more smaller Fe particles agglomerated into spheres. With unground and ground mixtures of $Fe-Al(OH)_3$, CNTs were grown at $700^{\circ}C$. As a result, CNTs grown on ground mixtures have more uniform diameter and morphology than those of unground mixture. The characterization of $Fe-Al(OH)_3$ mixture and as-grown CNTs were done by XRD, SEM and TEM.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.583-586
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• 2000

The non-selective method by polishing after grinding was used widely to thinning of SDB SOI structures. This method was very difficult to thickness control of thin film, and it was dependent on equipments. However electrochemical etch-stop, one of the selective methods, was able to accurately thickness control and etch equipment was very simple. Therefore, this paper described with the effect of leakage current and electrodes on electrochemical etch-stop. Consequentially, PP(passivation potential) was changed according to the kinds of contact and contact sizes, but OCP(open current potential) was not change with range of -1.5~-1.3V

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.05a
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• pp.18-22
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• 2003

The sapphire wafers for blue light emitting devices were manufactured by the implementation of the surface machining technology based on micro-tribology. This process has been performed by grinding, lapping and polishing. The surfaces of sapphire wafers were mechanically affected by residual stress and surface default. This mechanical stress and strain can be cured by thermal anneal ing process. The sapphire crystalline wafers were annealed at $1100~1400^{\circ}C$ and then characterized by double crystal X-ray diffraction. The sample showed good quality of crystalline wafer surface wi th full width at hal f maximum of 16 arcsec for the 4-hour heat-treatment at $1300^{\circ}C$.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.4
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• pp.61-71
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• 1999

The recent trend toward higher frequencies, miniaturization and lower-cost in wireless communication equipment is demanding high density packaging technologies such flip chip interconnection and multichip module(MCM) as a substitute of conventional plastic package. With analyzing the recently reported research results of the RF flip chip, this paper presents the technical issues and advantages of RF flip chip and suggest the flip chip technologies suitable for the development stage. At first, most of RF flip chips are designed in a coplanar waveguide line instead of microstrip in order to achieve better electrical performance and to avoid the interaction with a substrate. Secondly, eliminating wafer back-side grinding, via formation, and back-side metallization enables the manufacturing cost to be reduced. Finally, the electrical performance of flip chip bonding is much better than that of plastic package and the flip chip interconnection is more suitable for Transmit/Receiver modules at higher frequency. However, the characterization of CPW designed RF flip chip must be thoroughly studied and the Au stud bump bonding shall be suggested at the earlier stage of RF flip chip development.

• Journal of Drive and Control
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• v.14 no.4
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• pp.1-8
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• 2017

The Down-the-Hole hammer is one of the pneumatic drill equipment used for grinding, drilling, and mining. One the advantages of which is that a reduction work efficiency at deep site are relatively small compared to other drilling methods. Due to the large vibration in the underground area, it is difficult to measure the performance of the hammer, and hammer testing requires substantial production cost and operating expenses so research on the development of the hammer is insufficient. Therefore, this study has developed a dynamic simulation model that apprehends the operating principles of an 8-inch DTH hammer and calculates performance data such as performance impact force, piston speed, and BPM. By using the simulation model, design factors related to strike force and BPM were selected, and the influence of each design factors on performance was analyzed through ANOVA analysis. As a result, be the most important for BPM and the strike force are position of upper port that push the piston in the direction of the bit and in BPM, the size of the empty space between the bits and the piston is the second most important design factor.