• Journal of radiological science and technology
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• v.40 no.1
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• pp.93-99
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• 2017

Dose enhancement effects at megavoltage (MV) X and ${\gamma}-ray$ energies, and the effects of different energy levels on incident energy, dose enhancement agents, and concentrations were analyzed using Monte Carlo simulations. Gold, gadolinium, Iodine, and iron oxide ($Fe_2O_3$) were compared as dose enhancement agents. For incident energy, 4, 6, 10 and 15 MV X-ray spectra produced by a linear accelerator and a Co-60 ${\gamma}-ray$ were used. The dose enhancement factor (DEF) was calculated using an ICRU Slab phantom for concentrations of 7, 18, and 30 mg/g. The DEF was higher at higher concentrations of dose enhancement agents and at lower incident energies. The calculated DEF ranged from 1.035 to 1.079, and dose enhancement effects were highest for iron oxide, followed by iodine, gadolinium, and gold. Thus, this study contributes to improving the therapeutic ratio by delivering larger doses of radiation to tumor volume, and provides data to support further in vivo and in vitro studies.

• International Journal of Control, Automation, and Systems
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• v.1 no.2
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• pp.178-183
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• 2003

This work is a modified version of an earlier work that was based on ellipsoidal type feasible sets. Unlike the earlier work, polyhedral types of invariant and feasible sets are adopted to deal with input constraints. The use of polyhedral sets enables the formulation of on-line algorithm in terms of QP (Quadratic Programming), which can be solved more efficiently than semi-def algorithms. A simple numerical example shows that the proposed method yields larger stabilizable sets with greater bounds on disturbances than is the case in the earlier approach.

• Journal of applied mathematics & informatics
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• v.5 no.3
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• pp.669-690
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• 1998

In this paper we develop a new theory of adjoint and symmetric method in the class of general implicit one-step fixed-stepsize methods. These methods arise from simple and natral def-initions of the concepts of symmetry and adjointness that provide a fruitful basis for analysis. We prove a number of theorems for meth-ods having these properties and show in particular that only the symmetric methods possess a quadratic asymptotic expansion of the global error. In addition we give a very simple test to identify the symmetric methods in practice.

• East Asian mathematical journal
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• v.18 no.2
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• pp.205-209
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• 2002

In the paper the following propositions are proved. 1) If ($Q,{\cdot},e$) is a B-algebra, then there exists a group($Q,A,^{-1}$, 1) such that the following equalities hold e=1 and ${\cdot}=^{-1}A$, where $^{-1}A(x,y)=z{\Longleftrightarrow^{def}}A(z,y)=x$; and 2) If ($Q,A,^{-1}$, e) is a group, then ($Q,^{-1}A$, e) is a B-algebra.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.219-220
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• 2007

• Journal of Industrial Convergence
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• v.1 no.1
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• pp.115-126
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• 2003

In order to examine the determinants of new product success, winning products are analyzed with a focus on merchantability. The specific dimensions of product advantage have not been studied as yet. As results of the analysis, the determinants are classified into function, aesthetics, economy, safety, usability, reliability, brand image, assurance, distribution channel, advertisement, DEF(design for the environment). This study augmented the data set through questionnaire survey to marketing professor in University. The results of this study would be a cue to the future direction of new product development and to management of exist product.

• Journal of Korean Elementary Science Education
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• v.34 no.1
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• pp.109-122
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• 2015

In National Curriculum of Science revised in 2007, free inquiry was newly introduced to increase student's interest in science and to foster creativity by having students make their own curiosity questions and find answers by themselves. The purpose of this study is to analyze elementary school students' perceptions on free science inquiry activities applying a brain-based evolutionary approach. For this study, 106 the fifth grade students participated, and then completed a questionnaire on free inquiry activities according to a brain-based evolutionary science teaching and learning principles. The students performed a series of steps of the Diversifying, Estimating-Evaluating-Executing, and Furthering activities in each of Affective, Behavioral, and Cognitive domains (ABC-DEF approach) and constructed their own free inquiry diary, then the observations by the researcher and interviews with the students were analyzed both quantitatively and qualitatively. The major results of the study were as follows: First, the majority of the students perceived the each domain and step positively although a few of them perceived negatively. The reasons perceived as negatively were categorized into two; preference dimension of like or dislike and ability dimension of metacognitive or self-reflective capacity. Also, they perceived the free inquiry experience in the form of ABC-DEF as helpful to understand the nature of scientists' scientific activities. Based on these findings, implications for supporting authentic inquiry in school science are discussed.

• Journal of the korean academy of Pediatric Dentistry
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• v.1 no.1
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• pp.57-61
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• 1974

The Study reported here was designed to analyze the prevalence of Dental Caries in the primary teeth of monozygote twins, and to ascertain and compare the intrapair differences with the intrapair differences in control pairs. The prevalence of dental caries in the primary teeth of 40 pairs of presumably monozygote twins, based on phenotypic analysis, was studied. The age range was from 3 to12 years. The control group consisted of pairs that included a twin chosen at random and an unrelated child of the same sex and age, so that for each pair of twins there was a corresponding control pair. The clinical examination was carried out by an operator using an oral mirror and sharp explorers, and with good lighting. 40 pairs of twins were examined with a total of 4,950 primary tooth surfaces (990 primary teeth) and 40 control pairs with a total of 4,935 primary tooth surfaces (987 primary teeth). Five surfaces were considered for each tooth. After the def individual index was determined, the ratio between this index and the number of examined surfaces was established in each case, the cer (Caries experience rate) index. The def and cer averages were determined for the subjects and the controls. All intrapair differences in twin and control groups were compared following the paired sampling method. The following conclusions were made: 1. Intrapair differences in the control group were significantly greater than in twins, when defs, ds, es, fs, and cer were compared. 2. The genotype appeared to be a determining factor in dental caries susceptibility or resistance, although the environment played an important role as well. 3. Intrapair differences in American children were significantly greater than in Korean when defs, es, fs, and cer were compared, but ds was equal.

• Journal of the Korean Mathematical Society
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• v.48 no.6
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• pp.1171-1187
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• 2011

Silverman [14] proved a height inequality for a jointly regular family of rational maps and the author [10] improved it for a jointly regular pair. In this paper, we provide the same improvement for a jointly regular family: let h : ${\mathbb{P}}_{\mathbb{Q}}^n{\rightarrow}{{\mathbb{R}}$ be the logarithmic absolute height on the projective space, let r(f) be the D-ratio of a rational map f which is de ned in [10] and let {$f_1,{\ldots},f_k|f_l:\mathbb{A}^n{\rightarrow}\mathbb{A}^n$} bbe finite set of polynomial maps which is defined over a number field K. If the intersection of the indeterminacy loci of $f_1,{\ldots},f_k$ is empty, then there is a constant C such that $ \sum\limits_{l=1}^k\frac{1}{def\;f_\iota}h(f_\iota(P))>(1+\frac{1}{r})f(P)-C$ for all $P{\in}\mathbb{A}^n$ where r= $max_{\iota=1},{\ldots},k(r(f_l))$.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2079_2080
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• 2009

MEMS 기술을 이용한 다양한 센서의 개발과정에서 신뢰성 확보는 매우 중요한 문제이며, 여러 가지 신뢰성 항목 가운데 낙하시험은 가장 기본이 되는 항목이다. 단시간 내에 낙하에 대한 내충격성을 확보하는 MEMS 센서를 개발하기 위해 본 논문에서는 FEA와 high-level 모델을 결합한 낙하시험 모의진단법을 제안하였다. 제안된 모의진단법을 통해 MEMS 소자에서의 최대응력과 응력분포, 최대변위, 그리고 낙하시의 과도응답과 오신호 등의 결과를 확보할 수 있으며 이들을 토대로 MEMS 소자에서의 취약부위를 파악하고 이를 보완할 수 있으며 낙하시의 오동작을 제거하도록 신호처리 회로 등을 보완할 수도 있을 것이며 이를 통해 단시간 내에 최소의 비용으로 내충격성을 확보한 MEMS 센서를 개발하는 것이 가능해질 것이다.