• Journal of Power System Engineering
• /
• v.12 no.3
• /
• pp.66-71
• /
• 2008

Diamond-like-carbon (DLC) coatings could be good candidates as solid lubricants for cutting tools in dry machining of aluminum alloy. In this work, DLC thin films were produced as a friction reduction coating for WC-Co insert tip using the plasma immersion ion beam deposition (PIIED) technique. DLC coatings were also coated on $Al_2O_3$ specimens and high temperature wear tested up to $400^{\circ}C$ in dry air to observe the survivability of the DLC coating in simulated severe cutting conditions using a pin-on-disc tribotester with Hertzian contact stress of 1.3GPa. It showed reduced friction coefficients of minimum 0.02 up to $400^{\circ}C$. And cutting performance of DLC coated WC-Co insert tips to Al 6061 alloy were conducted in a high speed machining center. The main problems of built-up edge formation in aluminum machining are drastically reduced with improved surface roughness. The improvements were mainly related to the low friction coefficient of DLC to Al alloy and the anti-adhesion of Al alloy to WE due to the inertness of DLC.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2001.06a
• /
• pp.13-13
• /
• 2001

현재 초고속 가공 공구의 국내 시장은 150억원이며 향후 3년 내에 1500억원으로 급성 장활 전망이다. 무윤활 초고속 가공을 실현하기 위해서는 윤활특성이 우수한 초고경도 코팅의 개발이 필요하며 이를 통해 기계설비의 수명향상과 폐유문제 해결을 기대할 수 있다. 기존의 고체윤활 코팅은 초고경도 코팅의 상부에 $MoS_2$, Graphite 등 윤활성 박막을 합성하였으나, 이들은 Hexagonal 구조의 연질 박막이며 수분이 존재하는 대기중에서는 윤활 및 내마모 특성이 급격히 저하된다. 환경친화 대체소재 개발의 일원으로 TiN, ZrN 박막 등이 이미 개발되었고 기계적 특성이 우수하여 널리 응용되고 있으나 아직 경도(약 20GPa 내외) 및 윤활성의 한계 (마찰계수 $\mu=O.6$)를 극복하지 못하고 있다. TiN박막 위의 Cu의 첨가는 TiN의 구조와 성질을 크게 변화시키는 것으로 알려져 있다. 따라서 본 연구에서는 TiN 기지 위에 Cu를 도핑함으로써 경도의 상승을 통환 내구력의 향상과 마찰계수의 감소를 통한 윤활성의 향상을 보고자하였다. TiN합성의 안정화를 위하여 magnetron sputtering과 arc ion pIatingd을 병용한 hybrid 공정을 이용하였다. Cu첨가에 따른 결정 성장 거동의 변화를 보기 위해 XRD 분석을 실행하였고, EDS 분석을 통해 Cu target 전류밀도에 의한 기지내의 Cu의 함량변화를 고찰하였으며, 경도 및 윤활특성을 고찰하기 위해서 경도 시험과 마모 시험(ball-on disc type test)를 하였다.

• Journal of Engineering Education Research
• /
• v.11 no.4
• /
• pp.115-127
• /
• 2008

This study was to examine the effects of the learning strategy educational program using rubrics on engineering students' study strategies and academic achievements. To examine the effects of treatment, 58 engineering undergraduates were used as subjects. Two instruments were employed in the study, learning strategies rubrics and self-reported GPA. Repeated Measure MANOVA, ANCOVA were conducted to analyze the effects of the treatment. The summary of results showed that the program using rubrics is significantly effective regarding the improvement of the engineering students' learning strategies and academic achievement.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2014.11a
• /
• pp.213-213
• /
• 2014

$300^{\circ}C$와 $500^{\circ}C$에서 아크 이온 증착된 도포층의 조성은 각각 Fe : Al : Ti : Si : N = 1.31 : 36.52 : 31.31 : 0.48 : 30.38 [wt.%]와 Fe : Cr : Al : Ti : Si : N = 1.24 : 0.56 : 36.82 : 32.72 : 0.59 : 28.07 [wt.%] 이었다. 0.1N $H_2SO_4$ 수용액과 인공해수 (ASTM D1141-98) 분위기에서 $300^{\circ}C$, $500^{\circ}C$에서 증착된 도포층의 부식전압과 부식속도는 각각 $-0.2787V_{SHE}$, $0.002A/cm^2$, $-2.764V_{SHE}$, $0.002A/cm^2$ 와 $-0.2799V_{SHE}$, $0.002A/cm^2$, $-0.0394V_{SHE}$, $0.002A/cm^2$이었다. 나노 경도값은 각각 23.6, 25.8 GPa 이었다. 이는 각각 2208.2, $2434.2H_V$에 해당되었다.

• Design & Manufacturing
• /
• v.12 no.2
• /
• pp.34-39
• /
• 2018

The biggest topics in the automobile industry are light weightening and fuel efficiency improvement. There's a lot of research going on. It is focused on light weight materials. Light weight material is seen as the best way to reduce fuel consumption and to solve the problem of environmental pollution and resource depletion. For the light weight materials, new materials such as aluminum, magnesium, and carbon-hardening materials can be found. Research on the joining techniques of dual materials, improvement of material properties by improving the method of manufacture of existing materials, and studies on ultra-high strength steel sheets are expected to take up the most weight in lightweight materials. As the strength of the ultra-high strength steel sheets increases during forming, it is difficult to obtain dimensional precision due to the increase in elastic restoring force compared to mild or high strength steel sheets. Spring back is known to be affected by a number of factors due to poor plastic molding, and can be divided into the effects of the material spraying and the process. The study on the plasticitic variables were studied as plasticitic factors that can be controlled by a part company. Tensile testing of ultra-high strength materials was conducted to derive properties for plasticitic analysis and to analyze spring back with two factors controlling the height of the bead and blank holding force by adding tensile force and controlling the flow rate.

• The Journal of the Korea Contents Association
• /
• v.16 no.4
• /
• pp.231-240
• /
• 2016

The purpose of this study is to investigate the relationship among fatigue, personality, learning strategies, and academic achievement of medical students. 146 students from year 1 to year 4 at one medical school participated in this study. Students completed the fatigue, Big Five personality traits(Neuroticism, Extraversion, Openness, Agreeableness, Conscientiousness), learning, strategies. The academic achievement of students measured by GPA. The data were analyzed by t-test and stepwise multiple regression. The student's fatigue differed by grade, and the students of low grade had higher scores than high grade. But personality traits and learning strategies were not significantly different by grade. The factors that affect on academic achievement differ by grade. In low grade, neuroticism, extraversion, and rehearsal affected students' academic achievement. In high grade, conscientiousness and extraversion had an effect on the academic achievement of students. These results could guide the design of medical education improvement, and be useful in developing a supporting program for medical students.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07a
• /
• pp.700-702
• /
• 2005

A 5.0-inch transmissive type plastic TFT arrays were successfully fabricated on a plastic substrate at the resolution of $400{\times}3{\times}300$ lines (100ppi). All of the TFT processes were carried out below $150^{\circ}C$ on PES plastic films. After thin film deposition using PECVD, thin film failures such as film delamination and cracking often occurred. For successful growth of thin films (about 1um) without their failures, it is necessary to solve the critical problem related to the internal compressive stress (some GPa) leading to delamination at a threshold thickness value of the films. The Griffith's theory explains the failure process by looking at the excess of elastic energy inside the film, which overcomes the cohesive energy between film and substrate. To increase the above mentioned threshold thickness value there are two possibilities: (i) the improvement of the interface adhesion (for example, through surface micro-roughening and/or surface activation), and (ii) the reduction of the internal stress. In this work, reducing a-Si layer film thickness and optimizing a barrier SiNx layer have produced stable CVD films at 150oC, over PES substrates

• Convergence Security Journal
• /
• v.19 no.3
• /
• pp.93-99
• /
• 2019

In the Republic From the national interest in the recent hiring scandals in the public institutions such as the Financial Supervisory Service, Gangwon Land, and so on, people were outraged by the fact that the competition opportunities were not secured although they should be equally secured to compete with anyone with their capabilities in the fair process. Hence, the government made the public institutions blind hiring to be mandatory, which eliminated writing the academic background, GPA, and English score in the application form and selected the new employees only with job competencies in the public institutions in 2017. In 2018, the prosecution did their best for the investigation on hiring scandal with the strong will to cut the scandal upon announcement of 5-year anti-corruption master plan. Amid this controversy, this study tries to suggest the further direction in the hiring military human resources upon introduction of blind hiring system, reviewing the needs to introduce blind hiring system in the military, the governmental guideline according to the mandatory blind hiring in the public institutions, and the application status of modified blind hiring in the military.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2001.11a
• /
• pp.37-37
• /
• 2001

TiN coatings were applied for VarIOUS application fields, because of a good wear-resistance and a high hardness. Typically, TiN thin films show the hardness of 25GPa and friction coefficient of 0.6. However, in many field, one is looking for a more improved tool which has low friction coefficient and high wear resistance. The main motivation of this study is to characterize the influence of copper dopant content on TiN thin films. Ti-Cu-N thin films were deposited onto D2 steel substrates by PVD processing with various magnetron current densities (Cu contents). In this work, we synthesized titanium nitride films similar with reported typical titanium nitride films and synthesized Ti-Cu-N thin films with the addition of elemental copper which is measured improved hardness more than pure TiN films with copper content variables. This films has preferred oriented films of (111) direction. In addition, It was found that there is a strong correlation between content of various metal and film characteristics such as preferred orientation, grain size, hardness and friction coefficient and so, in future study, improved mechanical properties of TiN films can be controlled by change in target current density. The Ti-Cu-N film will show apparent hardness improvement and mechanical properties enhancement, when doping element is added onto TiN thin films. Film structure, chemical composition, mechanical properties were investigated by means of X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy(EDS), wear resistance tester and nanohardness tester.

• Journal of the Korea Society of Computer and Information
• /
• v.14 no.11
• /
• pp.81-90
• /
• 2009

It is inevitable for college students to be confused when they first face university education, which requires them to be self-reliant and responsible, after finishing their course of education, which is passive under control of period and environment, in primary, middle, and high schools. Introduction to college courses, which require students to be subjective and responsible, to be taken after chronically and environmentally controlled primary and secondary education, are but confusing. In this stage, college education should provide ground for educational system so that students can escape from repetitively enforced way of studying of fixed curriculums and study creatively and subjectively while befitting each individual's aptitude. For instance, in programming classes in engineering school, students scholastic achievements are closely interrelated with the professor's educational principles. A change in method of education, from one previously focused on theoretical contents to one centered on practices and experiments, can reap good results. Also, as the need arose for introduction of practice-focused evaluation system, from recognition-centered professor evaluating system to enablement of actively developing creative and self-reliant way of learning, we applied the Rublic System. It is a feedback system that all or most students become the evaluators, of which the indicators of evaluation such as category, standard, and score are public. We have looked into whether or not there has been an improvement in GPAs of students, and if there exists an improvement then what efforts should be made to solidify the system.