• Journal of Korea Foundry Society
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• v.13 no.6
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• pp.540-546
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• 1993

The effects of fluid flow on the purification of aluminum were studied. As the revolution rate(N) increased, the size of columnar grain decreased gradually. The concentration of solidified crystal was decreased with increasing distance from chill and revolution rate(N). Distribution boundary layer thickness(${\delta}$) was calculated from the solute distribution obtained in solid experimentally and by use of BPS equation. The value of ${\delta}$ changed from about $60{\mu}m$ at N value of 27rpm to about $15{\mu}m$ at N value of 1000rpm. From this result, high purification was obtained by decreasing the diffusion boundary layer under forced convection.

• Journal of muscle and joint health
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• v.28 no.3
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• pp.217-222
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• 2021

Background: The reaction of nurses to the advent of artificial intelligence (AI) during the fourth industrial revolution era remains questionable. Understanding Florence Nightingale's achievements may provide valuable lessons that will be helpful to contemporary nurses. Aims: To understand Nightingale's nursing philosophy and methods and provide suggestions for future nursing practice, education, research, and health policy. Source of evidence: Literature. Discussion/Conclusion: Just as Nightingale captured the situation of her time and introduced latest scientific methods, modern nurses need to learn from Nightingale's drastic actions to meet social needs. Nursing can regain a solid humanistic foundation by returning to core values of nursing and humanities, while simultaneously adopting state-of-the-art technologies. Implications for Nursing Policy: AI-driven technologies will advance nursing services and provide greater human-centered and personalized care by eliminating iterative and labor-intensive tasks. Nursing educational policy should support the advancement of nursing curricula to develop AI competencies and specialists within the nursing field.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.6
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• pp.932-937
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• 2012

In the presented study, SM45C carbon steel parts were joined by friction welding. The welding process was carried out under optimized conditions using statistical approach. The study of SM45C is conducted with various combinations of process parameters. Parameter optimization, microstructure and mechanical property correlation are the major contribution of the study. The welded joints were produced by varying spindle revolution speed, friction pressure, upset pressure and burn-off length. Tension tests were applied to welded parts to obtain the strength of the joints. Fracturs properties were additionally obtained experimentally under fluctuated tensile loads. Microstructures using microphotographs were examined in the weld interface and weld region and heat affected zone and base metal and flash zone of welded parts. Finally, Hardness variations in welding zone and base metal were also obtained. Through these tests, the optimum conditions of parameters for ${\phi}20$ SM45C in friction welding were obtained when the friction spindle revolution was 1,950 rpm, the friction pressures was 30 MPs, upset pressures was 50 MPs.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.40 no.5
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• pp.403-412
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• 2022

As the 4th industrial revolution is in full swing and next-generation ICT(Information & Communications Technology) convergence technology is being developed, various smart construction technologies are being rapidly introduced in the construction field to respond to technological changes. In particular, since the earth-volume calculation process for site design accounts for a large part of the design cost at the construction site, related researches are being actively conducted to improve the efficiency of the process and accurately calculate the earth-volume. The purpose of this study is to present a method for quickly constructing the topography of a construction site in 3D and efficiently calculating earth-volume using the results. For this purpose, the construction site was constructed as a 3D realistic model using large-scale aerial photos obtained from UAV(Unmanned Aerial Vehicle). At this time, since the constructed 3D realistic model has a surface model structure in which volume calculation is impossible, the structure was converted into a 3D solid model to enable volume calculation. And we devised a methodology to calculate earth-volume based on CAD(Computer-Aided Design and Drafting) using the converted solid model. Automatically calculating earth-volume from the solid model by applying the method. As a result, It was possible to confirm a relative deviation of 1.52% from the calculated earth-volume from the existing survey results. In addition, as a result of comparative analysis of the process time required for each method, it was confirmed that the time required is reduced of 60%. The technique presented in this study is expected to be utilized as a technology for smart construction management, such as periodic site monitoring throughout the entire construction process, as well as cost reduction for earth-volume calculation.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.5
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• pp.36-43
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• 2008

This research is tendencious to manufacture solid piston-rod of shock absorber as hollow piston-rod using friction welding. The SM45C has been welded to the SM45C-pipe in order to investigate the effect of upset pressure on friction weldability. The friction time and upset pressure was variable conditions under the conditions of spindle revolution of 2,000rpm, friction pressure of 55MPa, and upset time of 2.0seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests were studied of friction weld, and so the results were as follows. When the upset pressure is sufficient, gets the high tensile strength. The optimal welding conditions were n=2,000rpm, $P_1$=55MPa, $P_2$=95MPa, $t_1$=1.5sec, $t_2$=2.0sec when the total upset length is 4.5mm.

• Journal of the Korean Society of Safety
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• v.9 no.1
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• pp.100-109
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• 1994

In this study, it is investigated that the possibility of the numerical simulation for the incineration of the hazardous material, crbon tetrachloride($CCl_4$). A 3-dimensional numerical technology is applied for turbulent reacting flows of the full-scale Dow Chemical incinerator. The calculations are made by a CRAY-2S, super computer. The major parameters considered in this study are kiln revolution rate (rpm), filling ratio of the solid waste(f), burner Injection velocity and angle, and turbulent air jets for swirl. And the employed turbulent reaction model is the eddy break-up model which is a kind of fast chemistry model assuming general equilibrium and used for a premixed flame. The calculated flow fields are presented and discussed. 1) The presence of turbulent air nozzles for swirl gives rise to visible increase of the convective motion over the region of the solid waste. This implies the possibility to enhance the mixing of the waste with the surrounding all and thereby to reduce thermal and species stratification, which were reported in a large rotary kiln operation. 2) Considering that the location of the recirculation region has a strong relation with the heating rate of the solid waste, the control of the recirculation region by the burner injection angle Is quite desirable in the sense of the flexible design of the rotary kiln incinerator for a carbon tetrachloride. 3) Finally, it is found that the eddy break-up model Is not suitable for carbon tetrachloride($CCl_4$) because this model is not incorporated the flame inhibition trend due to the presence $CCl_4$compound.

• Journal of Korea Foundry Society
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• v.15 no.5
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• pp.507-513
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• 1995

The effect of forced convention on the solute redistribution of the Al ingot was studied quantitatively in an effort to fabricate high purity aluminum using a segregation method. Based on the experimental results, the solute concentration in the solid phase tended to decrease at the early state of solidification, and then increased gradually as solidification proceeded. Fe and Si concentrations decreased as growth rate decreased and as revolution speed increased. The solute redistribution obtained from the BPS model incorporated with the tangential flow component as well as the axial flow component within the melt, agreed well with the measurements.

• The Mathematical Education
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• v.63 no.3
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• pp.451-466
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• 2024

This study investigated elementary preservice teachers' conceptions of a generating line, an ambiguous concept in school mathematics. The preservice teachers' conceptions of a generating line can be classified into four types: (a) only cones have generating lines, (b) only cones and cylinders have generating lines, (c) solids of revolution have generating lines, (d) straight lines on the lateral surface are generating lines. 22.1% of all preservice teachers believed that only cones have generating lines, and most of them followed the definition of a generating line presented in elementary mathematics textbooks. The conception that only cones and cylinders have generating lines was the least investigated. However, since there were instances where generating lines were defined with the use of a director curve, it became important to explore topics more thoroughly, such as generating lines of a truncated cone. 27.9% of all preservice teachers believed that solids of revolution have generating lines. This conception was marked by differing opinions on whether spheres also have generating lines. The conception that straight lines on the lateral surface are generating lines was the most frequently investigated. This conception differs from the traditional view in school mathematics because it suggests using a director curve to define generating lines. Based on these analysis results, the researcher developed specific teaching methods that considered both subject matter knowledge and pedagogical content knowledge for preservice teachers. In addition, the researcher proposed a consensus definition of a generating line in mathematics education.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.2
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• pp.197-206
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• 2003

A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of solid and hollow hemispherical shells of revolution of arbitrary wall thickness having arbitrary constraints on their boundaries. Unlike conventional shell theories, which are mathematically two-dimensional (2-D), the present method is based upon the 3-D dynamic equations of elasticity. Displacement components μ/sub Φ/, μ/sub z/, and μ/sub θ/ in the meridional, normal, and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in θ, and algebraic polynomials in the Φ and z directions. Potential (strain) and kinetic energies of the hemispherical shells are formulated, and the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies obtained by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Novel numerical results are presented for solid and hollow hemispheres with linear thickness variation. The effect on frequencies of a small axial conical hole is also discussed. Comparisons are made for the frequencies of completely free, thick hemispherical shells with uniform thickness from the present 3-D Ritz solutions and other 3-D finite element ones.

• The Journal of Information Systems
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• v.8 no.1
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• pp.45-63
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• 1999

Today, information society is affected by new technologies including Electronic Commerce(EC), Electronic Data Interchange(EDI), Commerce At Light Speed(CALS ), multimedia and teleconferencing. Electronic Commerce is believed to be a field that will bring about a huge revolution of human life in the 21st century and thus its industry will give greatly influential effect on other industries In this paper, we have surveyed and studied through the internet and related materials for the development of framework of Electronic Commerce. It is required that we need the leading role of our government for the earlier activation of Electronic Commerce usage and have to establish the solid background of EC technology creation of our nation's originality and to activate the venture industry oriented for idea and technology rather than the industries in the form of larger enterprises. In conclusion, we have to expand our own ability of research and development to keep the continuous growth of our Electronic Commerce market and industries through the development of new product and prior acquisition of market as well as to expand the path of various technology aquisition by the strategic M&A and capital investment with the leading foreign enterprises.