• 한국기계가공학회지
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• 제18권10호
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• pp.27-33
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• 2019

The aviation industry has grown beyond the simple processing and assembling of aircraft parts and now designs and exports finished aircraft. In this study, the vertical CNC milling rotational speed and feed rate were parameters to investigate the life of tools according to their shape: (flat, round, and ball end mill) in the rough cutting of titanium. These tools are widely used in aircraft manufacturing and assembly. The purpose of this study is to measure the cutting temperature generated during the cutting process and calculate the rate of tool wear. This will be accomplished by measuring the tool weight before and after cutting the specimen and to compare it with the results of previous studies. Our study showed that the maximum cutting temperature increased as cutting time, tool rotational speed, and feed rate increased. The highest cutting temperatures were recorded for the ball, round, and flat end mill, respectively. Tool wear for the ball, round, and flat end mill increased as the speed and feed rate increased. The flat end mill exhibited the highest rate of wear from a minimum of 0.62% to a maximum of 2.88%.

• 한국산업융합학회 논문집
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• 제24권3호
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• pp.295-300
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• 2021

This study investigated the dominant frequency of the elastic waves from the tensile test. The specimen was rolled with five different rolling degrees (10, 22, 33, 42 and 50%), which was treated subzero. The specimen was rolled at room temperature, which was transformed from austenite to martensite (only α'-martensite). The dominant frequency increased with an increase in the rolling degree regardless of the subzero temperature, and decreased after 33% of the rolling degree. On the other hand, higher frequency band was obtained at lower temperature and long time. The dominant frequency increased when the amount of α'-martensite increased and decreased with the α'-martensite amount between 50-65%. The lower subzero treatment temperature increased the amount of α'-martensite, which resulted in the higher dominant frequency. The longer treatment time at the same subzero temperature led to an increase in the amount of α'-martensite, leading to high dominant frequency.

• 한국산업융합학회 논문집
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• 제24권3호
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• pp.261-269
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• 2021

This study was evaluated the elastic wave properties according to tension of Incoloy 825 alloy with different solution treatment temperature and aging time. Solution treatment was carried out at 700, 800, 900, and 1000 ℃ for 1 hour, and aging was carried out at 700 ℃ for 1, 5, 10, and 30 hours. As the solution treatment temperature increased, the tensile strength decreased and the elongation increased. However, as the aging time increased, the tensile strength increased and the elongation decreased. The dominant frequency decreased as the solution treatment temperature increased, but increased as the aging time increased. The dominant frequency according to the solution treatment and aging time increased as the tensile strength increased, but increased despite the decrease in elongation.

• 복식문화연구
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• 제27권2호
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• pp.169-180
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• 2019

The purpose of this study is to offer basic data on cosmetics by investigating college women's purchasing and use behaviors regarding cosmetics according to their experience with side effects. A questionnaire was administered to 351 college women in the Seoul and Kyoung-in areas. The data were analyzed with SPSS Statistics V22.0 using frequency, ${\chi}^2$-test, and t-test. The results are as follows. First, 72.6% of surveyed women reported experiencing side effects from cosmetics. The largest side effects were acne and boils, and the primary ways of coping with these side effects were discontinuing use and using other products. Second, the group that experienced cosmetics' side effects used brands that were more expensive and eco-friendly than the group without side effects. Third, the group that experienced side effects continued to use the product more than the group without side effects. The primary reason for continued use was efficacy, and the reasons for discontinued use were efficacy and curiosity. Fourth, the side-effects group proactively identified cosmetics ingredients more than the non-side-effects group. Specifically, they checked the major components, the function, and for any hazardous ingredients. Fifth and finally, 98.3% of survey respondents purchased and used functional cosmetics. The group that had experience with side effects used more functional cosmetics than the group without side effects.

• 공학교육연구
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• 제22권4호
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• pp.32-42
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• 2019

This study is aim to the effects of job satisfaction on the major satisfaction of science and engineering college students and also analyzed the mediating effects of future outlook of job and major relevance in career choice. To do this, structural equation modeling(SEM) and multi-group SEM were applied to data from 2016 Graduate Occupational Mobility Survey(GOMS). In the results of this study, the major satisfaction, future outlook of job and major relevance were positive effects on job satisfaction and the mediating effects of future outlook of job and major relevance were verified. And results of analysis according to gender difference, the coefficient of woman was smaller than man. Among major satisfaction had a positive effect on job satisfaction, job satisfaction fell for women who value their relevance to the major when choosing a job. Based on such results, universities need to further strengthen their role in helping them enhance their expertise through skills and learning about their majors.

• 전기전자학회논문지
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• 제22권4호
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• pp.959-964
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• 2018

본 연구에서는 LED 광시스템과 식물생장제어시스템을 연계하여 센서를 이용하여 식물환경을 제어 가능한 모니터링시스템에 대한 연구이다. 시스템의 성능을 검증하기 위해 에너지효율, data 전송률, 광량제어 특성에 대한 실험을 실시하였다. 실험한 결과 에너지 효율은 80%이상, 무선통신속도가 1Mb/sec이고 광량제어를 5단계이상 조절 가능함으로써 만족한 결과를 얻었다. 제안된 시스템은 LED 식물공장설비에 적용가능하며, 향후 상용화를 위해서는 생산효율 및 노동비 절감을 위한 자동시스템을 구성하여 농업 자동화설비에 기여할 것이다.

• 반도체디스플레이기술학회지
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• 제18권2호
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• pp.38-43
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• 2019

In this study, a hydraulic press structure has been investigated in order to enhance the precision machining and the productivity, which are generally damaged by the structural deformation from the pressure and the vibrations originated from the centrifugal forces from the rotating parts of the machine. Computer simulation based on the finite element method has been utilized for the analysis of static and dynamic characteristics to investigate each component's critical points, and to further improve the static and dynamic stabilities of a hydraulic press structure. The result shows that the deformations and the vibrations of the machine could be reduced 35% without increasing the weight of the machine.

• 센서학회지
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• 제27권6호
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• pp.380-385
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• 2018

Recently, interest in baseball has been increasing as the level of international baseball games, the popularity of domestic leagues, and the number of players entering the MLB has increased. In this paper, we propose a pitching system that can be applied to both professional and amateur baseball. The pitching system consists of a control module using MSB764T PLC, a pitching mechanism including AC motors and a ball feed rail, an HMI using the CHA-070WR model, inverter, etc. To pitch the breaking balls, the two AC motors each use an inverter to independently control the speed. The implemented pitching system was experimented on, investigating ball speed and ball movement according to RPM using the BUSHNELL Velocity Speed Gun. Experimental results on ball speed are similar to the theoretical data and the measured data. From the experimental data, it is confirmed that the damping coefficient value for the pitching ball is about 0.98. In the case of the breaking ball, the larger the difference between the speeds on the sides of the ball and the faster the ball speed, the larger the bending degree.

• 한국안전학회지
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• 제34권1호
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• pp.21-26
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• 2019

This paper is purposed to develop hardware for controlling abnormal temperature that can occur environment and component itself in PCS. In order to be purpose, the hardware which is four part(sensing, PLC, monitoring and output) keep detecting temperature for critical components of PCS and can control the abnormal temperature. Apply to the hardware, it is selected to PV power generation facilities of 20 kW in Cheong-ju city and measured the data for one year in 2017. Through the temperature data, it is found critical components of four(discharge resistance, DC capacitor, IGBT, DSP board) and entered the setting value for operating the fan. The setting values for operating the fan are up to $130^{\circ}C$ in discharge resistance, $60^{\circ}C$ in DC capacitor, $55^{\circ}C$ in IGBT and DSP board. The hardware is installed at the same PCS(20 kW in Cheong-ju city) in 2018 and the power generation output is analyzed for the five days with the highest atmospheric temperature(Clear day) in July and August in 2017 and 2018 years. Therefore, the power generation output of the PV system with hardware increased up to 4 kWh.

• 열처리공학회지
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• 제32권2호
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• pp.61-67
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• 2019

This study was carried out to investigate the effect of thermo-mechanical treatment on the tensile properties of Fe-20Mn-12Cr-3Ni-3Si alloy with deformation induced martensite transformation. ${\alpha}^{\prime}$ and ${\varepsilon}$-martensite, dislocation, stacking fault were formed, and grain size was refined by thermo-mechanical treatment. With the increasing cycle number of thermo-mechanical treatment, volume fraction of ${\varepsilon}$ and ${\alpha}^{\prime}$-martensite, dislocation, stacking fault were increased, and grain size decreased. In 5-cycle number thermo-mechanical treated specimens, more than 10% of the volume fraction of ${\varepsilon}$-martensite and less than 3% of the volume fraction of ${\alpha}^{\prime}$-martensite were attained. Tensile strength was increased and elongation was decreased with the increasing cycle number of thermo-mechanical treatment. Tensile properties of thermo-mechanical treated alloy with deformation induced martensite transformation was affected to formation of martensite by thermo-mechanical treatment, but was large affected to increasing of dislocation and grain refining.