• Journal of Mechanical Science and Technology
• /
• v.18 no.5
• /
• pp.770-779
• /
• 2004

This paper describes the micro cutting of wear resistant tungsten carbides using PCD (Poly-Crystalline Diamond) cutting tools in performance with SEM (Scanning Electron Microscope) direct observation method. Turning experiments were also carried out on this alloy (V50) using a PCD cutting tool. One of the purposes of this study is to describe clearly the cutting mechanism of tungsten carbides and the behavior of WC particles in the deformation zone in orthogonal micro cutting. Other purposes are to achieve a systematic understanding of machining characteristics and the effects of machining parameters on cutting force, machined surface and tool wear rates by the outer turning of this alloy carried out using the PCD cutting tool during these various cutting conditions. A summary of the results are as follows: (1) From the SEM direct observation in cutting the tungsten carbide, WC particles are broken and come into contact with the tool edge directly. This causes tool wear in which portions scrape the tool in a strong manner. (2) There are two chip formation types. One is where the shear angle is comparatively small and the crack of the shear plane becomes wide. The other is a type where the shear angle is above 45 degrees and the crack of the shear plane does not widen. These differences are caused by the stress condition which gives rise to the friction at the shear plane. (3) The thrust cutting forces tend to increase more rapidly than the principal forces, as the depth of cut and the cutting speed are increased preferably in the orthogonal micro cutting. (4) The tool wear on the flank face was larger than that on the rake face in the orthogonal micro cutting. (5) Three components of cutting force in the conventional turning experiments were different in balance from ordinary cutting such as the cutting of steel or cast iron. Those expressed a large value of thrust force, principal force, and feed force. (6) From the viewpoint of high efficient cutting found within this research, a proper cutting speed was 15 m/min and a proper feed rate was 0.1 mm/rev. In this case, it was found that the tool life of a PCD tool was limited to a distance of approximately 230 m. (7) When the depth of cut was 0.1 mm, there was no influence of the feed rate on the feed force. The feed force tended to decrease, as the cutting distance was long, because the tool was worn and the tool edge retreated. (8) The main tool wear of a PCD tool in this research was due to the flank wear within the maximum value of $V_{max}$ being about 260 $\mu\textrm{m}$.

• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.1
• /
• pp.49.3-50
• /
• 2017

Metallicity is one of the most important properties in understanding galaxy evolution. However, measuring metallicity is limited to low redshift (z<3.5) due to the faintness of the metallicity indicators in normal galaxies. For high redshift universe, active galactic nuclei (AGN) can be used to constrain the host galaxy metallicity. Previous studies investigated AGN metallicity using emission line flux ratios (i.e., NV/CIV and FeII/MgII), finding no evolution up to z~6. Those results might be due to selection effect since previous studies are based on very luminous AGNs. The observed luminosity-metallicity relation of AGNs (e.g., Nagao et al. 2006) suggests that luminous AGNs may be already matured at the observed epoch. Considering the luminosity-metallicty relation, we focused on low luminosity AGNs to find young AGNs (i.e., low metallicity). Through the Gemini/GNIRS observation in 2012A and 2015A (K-GMT GN-2015A-Q-203 PI: Shin, J.), we obtained the Gemini/GNIRS data for 7 high redshift AGNs (3.0

• English Language & Literature Teaching
• /
• v.10 no.1
• /
• pp.77-106
• /
• 2004

This study aims to investigate how the four college students interact with one another to discuss and construct meaning in a small reading group. Additionally, this study attempts to examine how the participants played their roles in the group. Data sources consisted of transcripts of the students' interactions, questionnaires and informal interviews, and the researchers' observation notes. The data revealed that the participants contributed fairly steadily to the interactions by checking with own grammatical knowledge, providing lexical information, understanding the micro level context, and presenting the macro level context. Several pedagogical implications are presented for the practical classroom. Findings of the study suggest effective ways to implement group activities in reading classes and a teacher's role for optimum group learning.

• Archives of design research
• /
• v.17 no.1
• /
• pp.89-98
• /
• 2004

A systemic approach to behavior on the basis of human psychology is needed for behavior-centered space design. Also, the recognition that human and environment, in all, have complementarity is needed- human and space shall be understood as a general phenomenon, supposing interaction. Design of behavior-oriented space means configuration and coordination of physical subjects as well as understanding, analysis and reflection of psychological and behavioral phenomena. It is analysis of a private individual as well as understanding of interaction between human groups, as well. In respect of space recognition, analysis not on material movement but on energy circulation and variable is important. It means that the understanding of user's behavior and psychology does not orient reasonable purpose just for convenience. That is, such understanding intends to understand behavioral patterns and psychological phenomena between space and human beyond the decomposition of structure of human and space into physical elements and the design based on standardized data. Thereby, more human-oriented space design might be implemented by the understanding of behavioral essence. Also, a user-centered design process from another viewpoint might be created, and the general amenity among man, space and environment - better environmental quality - might be produced. For this, the consciousness of human activity that is, activity system shall be ahead of it, and the approaches for design shall be implemented into a process not in predictive ideas but in semi-scientific system. On the basis of the above view, this study was attempted to investigate the orientation of design to recognize space as another life, and explore a process where it is drawn into a design language on the basis of human behavior. If the essence of space behavior and the activity system are analyzed through user observation and it is reflected upon a space design program and then developed into a formative language, a new design process on human and environment might be produced. In conclusion, the reflection of user's behavior and psychology into design, contrary to existing public space design based on physical data, can orient quality improvement of human life and ultimately be helpful to the proposition, 'humanization of space'.

• Journal of the Korean Society of Earth Science Education
• /
• v.17 no.1
• /
• pp.34-48
• /
• 2024

With the global rise in interest in competency-based education, the Ministry of Education of the Republic of Korea outlined six core competencies in the 2015 revised curriculum, essential for future society's 'creative and convergent talent'. This study introduces an HTE-STEAM constellation education program designed to develop the core competencies outlined in the 2015 revised curriculum and address the limitations of hands-on astronomy education. The program's effectiveness was assessed through a pilot test. The program was implemented at G Library, an out-of-school education site in Cheongju-si, Chungcheongbuk-do, targeting students from 3rd to 6th grade. The study's results include: First, the HTE-STEAM program significantly impacted all aspects of the STEAM attitude test except for 'self-concept', particularly influencing 'science and engineering career choice', 'consideration', and 'communication'. Thus, it has led to positive outcomes in the cultivation of future society's core competencies, including 'creative thinking skills', 'communication skills', and 'community skills'. Secondly, the HTE-STEAM constellation education program, despite covering the challenging concept of spacetime, was deemed easy by many students. Observations of students applying the spatial concepts they learned by using teaching aids suggest that the program was effective in enhancing students' understanding of the spatial structure of the sky and the universe. Additionally, this program aligns with the 2022 curriculum's updated standards for understanding the sky's spatial structure. Consequently, the HTE-STEAM constellation education program positively cultivates future society's core competencies and serves as a valuable complement to night observation practices in schools.

• The Journal of Korean Medicine
• /
• v.33 no.4
• /
• pp.69-80
• /
• 2012

Objectives: The purpose of this study is to develop a clinical practice observation course in a medical school that can give Korean medical students opportunities to experience the treatment environment in western medicine, and to analyze the results of the course. Methods: A total of 47 (collection rate: 85.5%) senior students of the College of Korean medicine in Gyunggi-do replied to the survey. Twenty-seven of them were male and 20 were female. They participated in the clinical practice observation course in the medical school two days a week for two weeks (total: four days) in the academic year 2011-2012. Before the course, an orientation was held; and upon the students' completion of the course, they presented their experiences and replied to the survey. Results: According to the survey, the purpose of the course was well explained (91.5%), and the course was necessary for Korean medical students (97.9%). The four-day course duration was inappropriate, though (83%). The female students were more satisfied with their participation in the fourth year and with the timing of the course than the male students were. The students who finished the course at the surgical departments recognized the necessity of the course more than the students who finished the course at the non-surgical departments. The advantages of the course included opportunities to observe operation scenes and experience clinical treatment processes and systems. The weakness of the course included poor organization due to the short preparation period. Conclusions: The course was confirmed as necessary for Korean medical students so that they would understand the treatment environment in western medicine. Through the course, the students broadened the understanding of the disease and developed a strong sense of identity as Korean medical students. The duration of the course needs to be extended, and its structure should be enhanced. Furthermore, various educational programs that offer Korean medical students opportunities to experience various clinical cases need to be introduced.

• Atmosphere
• /
• v.29 no.5
• /
• pp.689-698
• /
• 2019

Air pollution in urban areas has become a serious problem in the recent years. Especially, high concentrations of particulate matter (PM) cause negative effects on human health. Several studies suggest urban forest as a tool for improving air quality because of the capability of forests in reducing PM concentrations through deposition and adsorption using leaf area. For this reason, the National Institute of Forest Science plans to install in-situ observation stations for PM and biogenic volatile organic compounds (BVOCs) on a national scale to verify the net effect of forests on urban air pollution. To measure the quantitative change of PM concentrations due to the urban forest, stations should be located within and outside the forest area with respect to atmospheric circulation. In this study, we analyze the wind direction at the potential measurement sites to assess suitable locations for detecting the effect of urban forests on air quality in five cities (i.e. Gwangju, Daegu, Busan, Incheon, and Ilsan). This technical note suggests effective locations of in-situ measurements by considering main wind direction in the five cities of this study. A measurement station network created in the future based on the selected locations will allow quantitative measurements of PM concentration and BVOCs emitted from the urban forest and help provide a comprehensive understanding of the forest capabilities of reducing air pollution.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.47 no.5
• /
• pp.3-13
• /
• 2005

The present study examined the 3 dimensional space distribution characteristics of sea water intrusion using data available from previous observations. For this study, we used 3D FEMWATER, which is a 3 dimensional finite element model. The target area was around Daechang-ri, Gimje-si, Jeollabuk-do. The area is relatively easy to formulate a conceptual model and has observation wells in operation for surveying sea water intrusion. Considering the uncertainty of numerical simulation, we analyzed sensitivity to hydraulic conductivity, which has a relatively higher effect. According to the result of the analysis, the variation of TDS concentration had an error range of $-1,336{\~}+107 mg/{\iota}$. Taking note that the survey data from observation wells were collected when the boundary between fresh water and sea water in the aquifer was in equilibrium, we set the range of time for numerical simulation and estimated the spatial distribution of TDS concentration as the range of sea water intrusion. According to the result of estimation, the spatial distribution of TDS concentration calculated when 1,440 days were simulated was taken as the range of sea water intrusion. Using the result of calculation, we can draw not only vertical views for a certain section but also horizontal views of different depth. These views will be greatly helpful in understanding the spatial distribution of the range of sea water intrusion. In addition, the result of this study can be used rationally in proposing an optimal quantity of water pumping through investigating the moving route of sea water intrusion over time in order to prevent excessive water pumping and to maintain an optimal number of water pumping wells per interval.

• Journal of the Korean Institute of Educational Facilities
• /
• v.20 no.1
• /
• pp.3-14
• /
• 2013

The following research, analysis about an integral part of current elementary classroom, has been done to grasp the importance of re-organization of an elementary school classroom. For the research process 11 schools, 60 classrooms have been studied to analyze the physical elements of classroom(learning tools, equipment, etc.) to provide deeper understanding on their display, and spatial arrangement, as well as characteristic of a classroom. By looking at these analyzed elements with perspective to the grade, the number of students per class, the result turned out to be uninteresting. The observation that was made by this analysis was that there are more usages of multi-purpose desk in the classroom when there are only a few numbers of students. Also the observation could be made on the classroom wall-post. Each post had a tendency to have its defined area to be posted. The analysis showed that there are total of 24 corners can be created in the classroom, also it distinctly showed that the number of corners gets changed depending on the number of students in the classroom. The 24 corners including learning tools, equipment, and posts could be sorted to a minimum of 11 areas and a maximum of 22 areas depending on the educational purpose of the corners. The current layout of these corner and area will be the primary component that will be needed for the new coming classroom. For the future progress, depending on the system of education, the following needs to be done: (1) The installation of corners in the classroom (2) A small common-lounge area between two classrooms (3) A common-corner for each grade (4) Deeper research will be required to discuss the installation of a wide-educational area.

• Journal of Korean Elementary Science Education
• /
• v.28 no.3
• /
• pp.263-276
• /
• 2009

The purpose of this study was to analyze the elementary students' selection of representable value and confident method that appear in measuring activities by using a microgenetic method. The participants were seven elementary students in the fourth grade. They performed the same measuring activities six times for the study period. Data were collected by interview and observation with their activity recording papers and video tape transcription. Their activities were recorded and documented for the analysis. Results were as follows. First, in the time measuring activity, elementary students developed desirably as their measuring experience increased, for example they selected a representable value in use of a repeated measurement and used a various method in the domain of a time measurement and they showed an increase of a quantitative observation in the volume domain except in the length domain. Second, in a confident method of a representable value, though they must rely upon a repeated measurement, they only measure repeatedly in the time domain. Also in the time domain, it doesn't get accomplished a exact confidence of a representable value at a shortage of skill about a measurement. Accordingly this study will be implications for teachers to teach a handling abilities of measuring instruments to elementary students and to be promote understanding a nature of measurement.