• 한국초등과학교육학회지:초등과학교육
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• 제38권3호
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• pp.345-359
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• 2019

The purpose of this study is to analyze the educational effects and the improvements of the 'Science Field Trips' Program which developed with the aim of fostering the prospective elementary school teachers' ability to manage science field trips. The participants were 13 senior students from a national university of education. The results of the study are as follows: First, with regard to the effectiveness in the science instruction aspect of the prospective teachers' geological field trip as an experiential activity, the responses of the participants were children's 'scientific knowledge'(69.2%), 'science related attitudes'(46.2%), and 'science inquiry'(30.8%). Second, regarding the effectiveness of the geological field trip in their management of science field trips aspects in the future, the responses of the participants were 'teaching strategies'(92.3%), 'plan implementation'(76.9%), 'teacher's science knowledge'(61.5%), 'self-confidence'(38.5%), 'enhancement of awareness of field trips'(23.1%), and 'career guidance'(7.7%). Third, with regard to the effectiveness in the science instruction aspect of their activities of planning a science field trip in their future working districts, the responses of the participants were children's 'science knowledge'(38.5%), 'science-related attitudes'(38.5%), and 'science inquiry'(23.1%). Fourth, regarding the effectiveness in their management of science field trips aspects of the activities of planning a science field trip, the responses of the participants were 'plan implementation'(92.3%), 'the identification of science field trip sites'(84.6%), 'teaching strategies'(76.9%), 'administrative affairs'(69.2%), 'teacher's science knowledge'(30.8%), 'enhancement of awareness of field trips'(23.1%), 'career guidance'(15.4%), and 'self-confidence' (15.4%). The improvements plans of the program and the suggestions for future research is also described in this study.

• Spatial Information Research
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• 제23권3호
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• pp.123-132
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• 2015

2009년 제7차 개정 교육과정부터 자율과 창의 교육을 중심으로 현장체험학습을 하도록 권장하고 있으며, 현장체험학습의 중요도와 관심이 증가하고 있다. 현장학습의 중요성이 증가하면서 관련 앱의 출시가 증가하고 현장체험학습 지원을 위한 다양한 연구가 진행되고 있다. 본 연구는 현장체험학습의 특징과 사용자 요구사항 분석을 바탕으로 현장체험학습을 지원하기 위한 저작도구의 개념을 정의하고, 개념적 설계를 진행하였다. 현장체험학습 저작도구는 사전, 현장, 사후단계 활동을 지원할 수 있어야 하며, 위치기반의 체험활동 저작이 가능하고, 역사, 과학, 지리 등 현장학습이 이루어지는 교과의 특성을 반영한 저작기능이 요구된다. 특히 현장체험활동 이후 탐구활동 결과물들이 재활용될 수 있는 구조로 설계되어야 함을 확인하였고, 이를 바탕으로 개념적인 설계를 진행하였다.

• 대한기계학회논문집B
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• 제23권3호
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• pp.388-397
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• 1999

Numerical simulations are carried out for the magnetic Czochralski single crystal growth system. It Is shown that a magnetic field significantly suppresses the convective flow and as the strength of magnetic field becomes to be stronger, the heat transfer in the melt is dominated by conduction rather than convection. By imposing a cusp magnetic field, the growth interface shape becomes convex toward the melt. When the axial magnetic field is imposed, there occurs an inversion of the interface shape with increase of the magnetic field strength. The oxygen concentration near the interface decreases with increasing cusp magnetic field strength while axial field causes an increase of an oxygen concentration at the central region and decrease of that at the edge of the crystal. The results show that the cusp magnetic field has advantages over an axial magnetic field In the radial uniformity of oxygen as well as in the additional degree of control.

• 대한수학회보
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• 제52권5호
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• pp.1535-1547
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• 2015

A vector field on a Riemannian manifold (M, g) is called concircular if it satisfies ${\nabla}X^v={\mu}X$ for any vector X tangent to M, where ${\nabla}$ is the Levi-Civita connection and ${\mu}$ is a non-trivial function on M. A smooth vector field ${\xi}$ on a Riemannian manifold (M, g) is said to define a Ricci soliton if it satisfies the following Ricci soliton equation: $$\frac{1}{2}L_{\xi}g+Ric={\lambda}g$$, where $L_{\xi}g$ is the Lie-derivative of the metric tensor g with respect to ${\xi}$, Ric is the Ricci tensor of (M, g) and ${\lambda}$ is a constant. A Ricci soliton (M, g, ${\xi}$, ${\lambda}$) on a Riemannian manifold (M, g) is said to have concircular potential field if its potential field is a concircular vector field. In the first part of this paper we determine Riemannian manifolds which admit a concircular vector field. In the second part we classify Ricci solitons with concircular potential field. In the last part we prove some important properties of Ricci solitons on submanifolds of a Riemannian manifold equipped with a concircular vector field.

• 천문학회보
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• 제37권1호
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• pp.87.1-87.1
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• 2012

We use three-dimensional magnetohydrodynamic simulations to investigate how the dynamic state of emerging magnetic field is related to the twist of field lines. Emergence of magnetic field is considered as one of the key physical process producing solar activity such as flares, jets, and coronal mass ejections. To understand these activities we have to know dynamic nature and electric current structure provided by emerging magnetic field. To demonstrate dynamic nature of field lines, we focus on the factors such as curvature of magnetic field line and scale height of magnetic field strength. These factors show that strong twist case forms two-part structure in which the central part is close to a force-free state while the outer marginal part is in a fairly dynamic state. For weak twist case, it still shows two-part structure but the tendency becomes weaker than strong twist case. We discuss how the curvature distribution affects the dynamic nature of emerging magnetic field. We also investigate electric current distribution provided by emerging field lines to show a possible relation between electric current structure and sigmoid observed in a preflare phase.

• 대한인간공학회지
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• 제14권1호
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• pp.59-67
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• 1995

Depending upon the eye and head movement, the visual field is often classified into three categories ; stationary field, eye field and head and eye field. To investigate the effect of background condition on the size of the visual field, an experiment was conducted, in which the subject was instructed to search a target with distinct orientations. In each trial, a single target was presented on the perimeter modified to cover the range of 330 .deg. around the fixation point, with the visual angle subtended 1.4 .deg. vertically and horizontally. Nontarget density, meridian, size contrast and subject showed a significant effect on the visual field at .alpha. =0.01, where density was inversely proportional to the size of the visual field, and size contrast linearly proportional to the size of the visual field. The size of the visual field on horizontal axis was larger than that on vertical axis, and that on right and upper meridian was also larger than on left and lower meridian. The shape was found to be horizontally oriented oval and statistically asymmetric with respect to horizontal and vertical axes. In addition, the regression equations to predict the visual field on the given background condition were suggested. These results were expected to be used as a design guideline when arranging displays and controls on panels such as automobile display panels, cockpits, etc.

• 한국초전도ㆍ저온공학회논문지
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• 제20권4호
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• pp.65-69
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• 2018

Due to large in-field current carrying capacity and strong mechanical strength, a REBCO wire has been regarded as a viable high temperature superconductor (HTS) option for high field MRI and > 1 GHz (>23.5 T) NMR magnets. However, a REBCO magnet is well known to have an inherent problem of field inhomogeneity, so-called 'Screening Current induced magnetic Field (SCF)'. Recently, 'field shaking' and 'current overshoot operation' techniques have been successfully demonstrated to mitigate the SCF and enhance the field homogeneity by experiments. To investigate the effectiveness of current overshooting operation technique, a numerical simulation is conducted for a test REBCO magnet composed of a stack of double pancake coils using '2D edge-element magnetic field formulation' combined with 'domain homogenization' scheme. The simulation result demonstrates that an appropriate amount of current overshoot can negate the SCF. To verify the simulation results, current overshoot experiments are conducted for the REBCO magnet in liquid nitrogen. Experimental results also demonstrate the possible application of current overshoot technique to mitigate the SCF and enhance the field homogeneity.

• 한국자기공명학회논문지
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• 제23권1호
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• pp.12-19
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• 2019

A former study has shown that the spin-lattice relaxation time ($T_1$) in cancerous prostate tissue had enhanced contrast at an ultra-low magnetic field, $132{\mu}T$. To study the field dependence and the origin of the contrast we measured $T_1$ in pairs of ex-vivo prostate tissues at the Earth's magnetic field. A portable and coil-based nuclear magnetic resonance (NMR) system was adopted for $T_1$ measurements at $40{\mu}T$. The $T_1$ contrast, ${\delta}=1-T_1$ (more cancer)/$T_1$(less cancer), was calculated from each pair. Additionally, we performed pathological examinations such as Gleason's score, cell proliferation index, and micro-vessel density (MVD), to quantify correlations between the pathological parameters and $T_1$ of the cancerous prostate tissues.

• Radiation Oncology Journal
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• 제12권2호
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• pp.263-267
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• 1994

In clinical radiotherapy, the use of wide and irregular field techniques frequently results in considerable tumor dose inhomogeneity because of, the variation in physical characteristics of irradiated volumes. This report describes an analysis of the dosimetry of the irregular fields such as radiation fields for Hodgkin's disease(mantle field), esophageal cancer, and lung cancer when a 6 MV and a 15 MV linear accelerators are utilized. Doses were measured in a Rando phantom using methods of thermoluminescence dosimetry(TLD), and were calculated by radiotherapy planning computer system with the Clarkson's method for calculation of a irregular field. A dose variation of $5-22\%,\;6-9\%,\;6-14\%$ were found in the mantle field, esophageal cancer field, lung cancer field respectively. Higher doses occurred in the superior portion of the irregular field. The sites of maximum dose variation were the supraclavicular and the upper spinal cord region. To adjust for these substantial differences, a compensator or a shrinking field technique should be adopted.

• 대한안전경영과학회지
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• 제17권3호
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• pp.1-7
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• 2015

The study conducted questionnaire analysis to 413 industrial safety field employees in order to examine the necessity and validity of industrial safety field's 17th neo-job classification based on National Competency standards(NCS). As a result, 50.1% of industrial safety management field and 43.3% of industrial health management field answered that classification details of occupational safety and health management field are classified by job(duty) performance. Industrial safety management field recognizes that management and engineering section play a significant role in their work, while industrial health management field recognizes worker's health care and work environment management and overall control of work environment assessment to be significant in their work. Furthermore, industrial safety management field recognizes that separating qualification and foundation of 'construction safety manager', 'chemicals(safety and health) manager', '(toxic)risk assessment evaluator or risk factor manager' to be highly significant. The study is meaningful in that it suggests industrial safety field's qualification items practical in industrial sites.