• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.65-69
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• 2002

In order to practicalize high precision centerless grinder for machining the ferrule, its feeding system is designed and tested. For satisfying the desired diametric tolerance and cylindricity of the ferrule, the feeding system is designed to have relatively high axial stiffness of 600 N/$\mu\textrm{m}$, high angular motion accuracy of 0.5 arcsec/mm in yaw direction and minimum resolution of 0.05 $\mu\textrm{m}$. A prototype of feeding system is built up with hydrostatic guideway and ballscrew. A linear scale with 0.05 $\mu\textrm{m}$ of resolution is used for position feedback. Experimental results show that the feeding system has the infinity of axial stiffness within the range of 1000 N and 0.3 arcsec/mm of yawing error. Also the feeding system shows obvious step response against 0.05 $\mu\textrm{m}$/step command without the lost motion or backlash. Although the vertical stiffness is reduced to 440 N/$\mu\textrm{m}$ by the elastic deformation of rail, it is good enough to use for machining the ferrule. From above, it is confirmed that the feeding system is applicable to centerless grinder for machining the ferrule.

• Spatial Information Research
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• v.23 no.4
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• pp.1-11
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• 2015

Since the Spatial Information Open Platform service started in January 2012, the number of service users and the size of the system has increased significantly. However, we could not know the analysis result about how much the hardware resources of the Open Platform system can handle user services. Thereafter, whenever the number of service users are rapidly increased, we simply have solved the service delays using the hardware extension. So, this study presents the obvious solution to avoid the same problem in the future, by pinpointing the system performance of the Open Platform. In this study, through the performance analysis of hardware using NMON and the load test of web service using nGrinder, we intend to get an accurate performance of the Open Platform system. Then we intend to present the resource reallocation method in order to provide better performance of the system.

• Journal of the Ergonomics Society of Korea
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• v.26 no.1
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• pp.29-37
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• 2007

This study was performed to evaluate the characteristics of transmitted vibration to hand-arm system under different work posture while operating a light-weighted powered hand grinder. For the experiment, 8 different types of wrist posture (natural, unlar-flexion, radual-flexion, flexion, extension, complex posture, and etc.) and 3 types of feed force (20[N], 50[N], 70[N]) were considered. 10 male subjects were employed to polish metal plate with a hand grinder. All of them were normal and healthy with no history and symptom of the work related musculoskeletal disorders in the dominant hand. Vibration acceleration data were recorded with sampling rate, 2048[Hz]. In addition, unweighted overall R.M.S. acceleration at the tool and wrist, and transmissibility between them were used to evaluate factors from the recorded tri-axial vibration acceleration. The results indicate that transmissibility of natural wrist posture was significantly higher than others. In addition, as the feed force becomes larger, the vibration was transmitted in large quantities to hand-arm system through radius.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.563-564
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• 2006

In silicon wafer manufacturing process, the grinding process has been adopted to improve the flatness of water. The grinding of wafer is usually used by the infeed grinding machine. Grinding conditions are spindle speed, feed speed, rotation speed, grinding stone etc. But grinding condition selection and analysis is so difficult in grinding machine. In the intelligent grinding system based on knowledge many researchers have studied expert system, neural network, fuzzy etc. In this paper we deal grinding condition selection method, Taguchi method and Genetic Analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.04a
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• pp.103-110
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• 1991

본 연구에서는 최근들어 첨단 가공기술로서 중요시되고있는 초정밀 경면가공기술의 기본원리를 이해하고 관련지식을 습득하여 향후 보다 나은 상태의 경면가공을 위한 기초를 확립하는데에그 목적을 두었다. 실험을 위한 공작기계는 초정밀 만능 연삭반( high precision universal grinder)에 플라이컷(fly-cut)방식에 의한 절삭가공이 가능 하도록 여러가지장치들을 부착하였으며, 절삭공구는 천연 다이아몬드를 사용하고, 피삭재는 A1-Cu-Ni-Mg 합금을 사용하였다. 본 실험에서는 주어진 조건내에서 어느정도의 표면 조도를 달성할수 있는지를 알아보고 그 과정을 통하여 공작기계, 공구, 피삭재등의 영향과 절삭력, 칩, 표면상태등을 고찰하여 여러가지 현상을 규명하여 향후의 발전을 위한 대책에 활용하고자 한다.

• Journal of Korean Society of Steel Construction
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• v.11 no.3 s.40
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• pp.319-327
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• 1999

This study makes mechanism of the fatigue strength improvement by the processing of weld toe clear for the vertical cross rib specimens which was made fillet weld joint, also it proposes to the appropriate later processing. As a result of tension fatigue test, the fatigue strength improvement could have been seen in later processed specimens than as-weld specimens. Especially fatigue crack initial life $N_c$ increased in specimens which processed grinder after hammer-peening. Also, fatigue crack propagation life $N_p$ improved more in hammer-peening specimens than as-weld or TIG specimens. It thinks that $N_c$ is because of the geometrical shape of weld toe, i.e. the relaxation of the stress concentration and also that $N_p$ is because the big compression residual stress which was introduced in the surface by hammer-peening is restraining the propagation of fatigue crack.

• Journal of Trauma and Injury
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• v.31 no.1
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• pp.1-5
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• 2018

Purpose: Although there has been substantial progress for the treatment of thoracic trauma, the mortality of the penetrating neck injury is still high, has been reported about 10-15%. However, there has not been a report which is reflecting Korean medical present. We retrospectively analyzed the penetrating neck injury patients based on the Korean Trauma Data Base. Methods: Between December 2013 and June 2017 at the trauma center of the Pusan National University Hospital, Busan, Korea, total of 36 patients with isolated low-velocity penetrating neck injuries were included. We analyzed the patients' age, gender, injury mechanism and causes by medical chart review. Results: Among total of 36 patients, 26 (72.2%) were male and 10 (27.8%) were female. Homicidal neck injuries were most common, followed by accidental and suicidal injuries (47% vs. 33% vs. 19%, respectively). All penetrating injuries in our study were low-velocity trauma such as following: knife (n=16, 44.4%); glass or glass bottle (n=11, 30.6%); scissors (n=4, 11.1%); grinder (n=2, 5.6%); and three (8.3%) of miscellaneous injuries. Twenty-seven (75.0%) patients underwent emergency surgery, and only one (2.8%) patient underwent elective surgery. Eleven (30.6) patients were diagnosed with superficial injuries, including six patients who had conservative treatment. Twelve (33.3%) patients had arterial injuries and 10 (27.8%) patients had venous injuries. The patients who had deep injuries showed significant difference against the patient with superficial injury (98.0 vs. 129.1, p=0.008). Conclusions: Low velocity penetrating injury confined to the neck is able to be successfully treated with prompt surgical management. Regardless of the conditions which are evaluated at emergency department, all penetrating neck injury patients should be regarded as urgent surgical candidates.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.1
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• pp.1-16
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• 1996

This study was conducted at an automobile assembly line located in Kyonggi-do, Korea from January 16 to February 28, 1995. The purposes of this study were to assess worker exposures to hand-arm vibration and the performance of gloves for reduction of vibration. The exposure to vibration was measured using to the ISO 5349(1986) method. Vibration acceleration and frequency spectra for each tool were determined on-line replicating actual working conditions and analyzed together with exposure time for evaluating individual worker exposure. Eight pneumatic hand tools, 60 workers exposured to hand-arm vibration, and three pairs of gloves were involved in this study. Results are summarized as follows. 1. Dominant frequencies of vibration for all tools(n=8) measured in this study ranged from 250 Hz to 800 Hz. 2. There was no significant correleration between dominant frequencies and free running speed (p>0.05). 3. Total predicted exposure times of using impact, hammer type did not exceed 40 minutes, but metal finish task, using grinder and sander exceeded 40 minutes. Total exposure time affected significantly the frequency-weighted, 4 hr equivalent acceleration. 4. Predicted prevalence and observed exposure period data were compared in workers(n=60), according to ISO 5349. In this results, 23(50.0 %) and 24(48.07 %) persons exceeded the mean latency periods for vibration-induced white finger(VWF) at 10 % (n=46) and 50 % (n=52) standards, respectively. On the basis of ISO equation, mean latent periods for VWF were 3.23, 4.72 years at 10 %, 50 % standards, respectively. 5. Reduction of vibration by gloves was evaluated. Since impact pneumatic tools produced low frequency vibrations, conventional gloves did not provide any protection. Gloves A and C amplify somewhat the signal at frequency below 400 Hz; the attenuation increases progressively by frequency to reach 18 dB ($7.94{\times}10^{-6}m/s^2$) at 1,000 Hz, slightly worsening Glove B did not provide any protection and made the situation slightly worse. However, since they make the hands warm, the occurrence of vibration-induced white fingers may be reduced.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.3
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• pp.338-351
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• 2005

Statement of problem. Accurate fit between the implant components is important because the misfit of the implant components results in frequent screw loosening, irreversible screw fracture, plaque accumulation, poor soft tissue reaction, and destruction of osseointegration. Purpose. This study is to evaluate the machining accuracy and consistency of the implant fixture/ abutment/screw interfaces of the internal connection system by using a Stereoscopic Zoom microscope and FE-SEM(field emission scanning electron microscope) Materials and methods. The implant systems selected in this study were internal connection type implants from AVANA(Osstem^{\circledR}), Bioplant(Cowell-Medi^{\circledR}), Dio(DIO^{\circledR}), Neoplant(Neobiotech 􀋓), Implantium(Dentium􀋓)systems. Each group was acquired 2 fixtures at random. Two piece type abutment and one piece type abutment for use with each implant system were acquired. Screw were respectively used to hold a two piece type abutment to a implant fixture. The implant fixtures were perpendiculary mounted in acrylic resin block. Each two piece abutment was secured to the implant fixture by screw and one piece abutment also secured to the implant fixture. Abutment/fixture assembly were mounted in liquid unsaturated polyester. All samples were cross-sectioned with grinder-polisher unit. Finally all specimens were analysed the fit between implant fixture/abutment/screw interfaces Results and conclusions. 1. Implant fixture/abutment/screw connection interfaces of internal connection systems made in Korea were in good condition. 2. The results of the above study showed that materials and mechanical properties and quality of milling differed depending on their manufacturing companies.