• 대한인간공학회지
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• 제29권3호
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• pp.347-356
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• 2010

The purpose of this study is to analyze the spine stability by comparing muscle activation in various scaffold working conditions. The independent working conditions were designed by two levels of working height, existence and absence of safety handrail, and the two levels of expertise. The corresponding activities of the agonist and antagonist muscles of spine were simultaneously recorded by using EMG. As results, novice worker showed increased muscle activity while doing the task on the 2nd floor, absence of handrail. And expert showed the increase of co-contraction while working on the 2nd floor without handrail. Such co-contraction was found to increase the spine stability when the working condition become risky. On the other hand, the co-contraction was prolonged, the spine muscle fatique and disc pressure could be increased, which would increase the risk of musculo-skeletal disorder. The results of co-contraction in this study indicates that the motor control system responds to maintain the stability of the spine particularly when workers cognitively recognize the danger of falling or imbalance. This study also quantitatively accounted for the biomechanical cause of LBP among workers who has to prevent themselves from falling. Therefore, if can be said that safe environment preventing falling can also prevent workers from MSDs as well. Such knowledge can be applied to design ergonomic workplace environment as well as movable scaffold.

• 한국기계가공학회지
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• 제14권2호
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• pp.1-6
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• 2015

Transmission of a tracked vehicle designed for multiple functions such as steering, gear-shifting, and braking is a core component of heavy vehicle to which the power is transferred based on combined technology of various gears, bearing, and fluid machineries. Robustness and durability of transmission, however, have been issued due to a large number of driving units and sub-components inside its body. The bevel gears are major components for the transmission of power in a transmission. Increasing the tooth surface roughness and chamfering of the bevel gears, especially, we aim to improve the quality of transmission. In this study, design structural evaluation is conducted on bevel gears of transmission for tracked vehicle using the ROMAX-DESIGNER program. By doing so, design safety of the bevel gears has been evaluated based on the gear strength theory of ANSI/AGMA 2003 B97 standard.

• 대한조선학회논문집
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• 제55권4호
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• pp.321-329
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• 2018

Resonance phenomena occurs at large vertical pump which is operating to cool down the hot steam using sea water in the power plant. To avoid the resonance, the natural frequency needs to be isolated about 20% from motor operating speed. Yet, excessive vibration occurs especially at low tide. At first, natural frequency of the whole pump system and each part is calculated using ANSYS. As it is revealed in the previous journal papers that only circular pipe part is related to resonance, the FSI technique is applied for free vibration analysis. The natural frequency is reduced to 60% (compared to that) of the frequency measured in air as it is similar to other published results. And the frequency obtained by finite element analysis is almost same to that obtained from modal test. Based on the accurate finite element model and analysis, design change is tried to avoid the resonance by changing the thickness of pipe and base supporting plate. In stead of doing optimization process, design sensitivity is computed and used to find such designs to avoid resonance.

• 한국초등과학교육학회지:초등과학교육
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• 제35권3호
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• pp.277-287
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• 2016

This study explores how a teacher copes with anomalous situation in primary practical science lesson and what factors affect teacher's strategy to cope with anomalous situations. The method of auto-ethnography was used in order to capture the inner experience of the individual teacher. For this, one of the researchers participated in this study as the teacher participant. Two science lessons that the researcher taught as a teacher were observed by a co-author and video-recorded. However, only one lesson which the teacher experienced the anomalous situation was analyzed. After the lesson, self-interviews were conducted with the co-author. Also the researcher wrote four reflective journals about anomalous situations that she experienced. What has emerged in this study is that anomalous situations were experienced by the teacher while students were doing practical work and while students were presenting their results of practical work. As each anomalous situation was experienced in different contexts, the strategies that the teacher used were different and were affected not only by the personal epistemological belief but also by the socio-cultural context that the teacher was surrounded by. This study has implications to help teachers who have difficulties in coping with anomalous situations.

• 한국공작기계학회논문집
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• 제14권3호
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• pp.87-95
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• 2005

The object of this study is to investigate the effect of joinability by using acoustic emission(AE) signals and doing a pattern recognition for weld heat affected zone(HAZ) in tensile testing. This study was carried out an SWS 490A high tension steel for electric shielded metal arc welding(SMAW), $CO_2$ gas arc welding and TIG welding. And correspondingly, the root openings are 3, 4 and 2.8mm. The results of the tensile test of weld HAZ come out electric shield arc welding $>\;CO_2$ gas arc welding > TIG welding in case of single welding. It is believed that this is a phenomenon where difference of its root opening or base metal thickness. Also, the technique of AE is ideally suited to study variables which control time and stress dependent fracture or damage process in metallic materials.

• 한국공작기계학회논문집
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• 제15권5호
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• pp.104-113
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• 2006

The main objective of this study is to investigate the effect of compounded welding by using acoustic emission (AE) signals and doing a source location for weld heat affected zone (HAZ) through tensile testing. This study was carried out an SWS 490A high strength steel for electric shield metal arc welding, SMAW; $CO_2$ gas metal arc welding, GMAW($CO_2$); and gas tungsten arc welding, GTAW/TIG. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. For instance, Gutenberg-Richter magnitude-frequency relationship (G-R MFR) offers useful b-value in data analysis. Namely event identification, source location gives the X- and Y-coordinates of the AE source. And K-means clustering analysis by Euclidean distance confirmed that was powerful to source location. Generally, strength of welded metal zone was stronger than strength of base metal. As the result, confirmed certainly that fracture is produced in HAZ instead of welded metal zone from source location.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.40-48
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• 2004

The object of this study is to investigate the effect of joinability by using acoustic emission (AE) signals and doing a pattern recognition for weld heat affected zone (HAZ) in tensile testing. This study was carried out an SWS 490A high tension steel for electric shielded metal arc welding (SMAW), $CO_2$ gas arc welding and TIG welding. And correspondingly, the root openings are 3, 4 and 2.8mm. The results of the tensile test of weld HAZ come out electric shield arc welding > $CO_2$ gas arc welding > TIG welding in case of single welding. It is believed that this is a phenomenon where difference of its root opening or base metal thickness. Also, the technique of AE is ideally suited to study variables which control time and stress dependent fracture or damage process in metallic materials.

• 한국전자통신학회논문지
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• 제7권6호
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• pp.1487-1492
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• 2012

증가하는 이동단말의 인터넷 접속은 무선 IP망에서 노드의 망 이동 지원을 필요로 하게 되고, IPv6를 위해 모바일 IPv6를 제시되었다. 하지만 모바일 IPv6는 노드의 핸드오버로 인한 패킷손실을 발생시켜 망의 성능을 저하시킴으로 인해 이를 개선하기위한 다양한 방안들이 제시되고 있다. FMIPv6는 이들 방안들 중 하나로 끊어짐 없는 핸드오버가 가능하도록 설계되었으나 링크계층으로부터 정확한 핸드오버 시점을 결정해야하는 문제가 있다. 본 논문에서는 FMIPv6의 링크계층 의존성 문제를 해결하기 위해 가장 큰 지연시간을 갖는 이동노드의 CoA 등록과정을 사전에 수행하여 결정적인 부분의 지연시간을 최소로 줄이는 방안인 mptFMIPv6를 제안한다.

• 대한임상검사과학회지
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• 제42권3호
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• pp.125-128
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• 2010

HbA1c test measures the amount of glycated hemoglobin in blood. HbA1c shows the average of blood glucose levels for the past three months, this is a better indicator of how overall diabetes is doing. HbA1c gives a much better idea of how the body is breaking down the glucose. Therefore, this HbA1c is very important tool for maintaining normal glucose levels for pre-and diabetic patients. Total 408 participants were tested HbA1c voluntarily from Chosunilbo Health Expo (8th~11th, July 2010). Through this small-scaled direct HbA1c, about 54.7% (207 out of 408) was shown glucose tolerance and diabetes. However, 61 from 157 participants who were shown under 6.9% HbA1c (normal and pre-diabetic stage) are taking only antidiabetic drugs to maintain a normal blood glucose. Regular HbA1c test can bring an important management and awareness about controlling blood sugar level and prevention of diabetic complications.

• 한국표면공학회지
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• 제45권3호
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• pp.117-122
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• 2012

ZTO/GZO double layered films were prepared on unheated non-alkali glass substrates. ZTO films were deposited by RF/DC hybrid magnetron co-sputtering using ZnO (RF) target and $SnO_2$ (DC) targets, and then GZO films were deposited by DC magnetron sputtering using an GZO ($Ga_2O_3$:5.57 wt%) target. These films were post-annealed at temperature of 200, $300^{\circ}C$ in air and vacuum ambient for 30 min. In the case of post-annealing in air, ZTO/GZO double layer showed relatively low resistivity change, compared to GZO single layer. Furthermore, ZTO/GZO double layer revealed low WVTR, compared to GZO single layer. Therefore, it can be confirmed that ZTO film doing a role with barrier for water or oxygen diffusion.