• 한국자기학회지
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• 제1권2호
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• pp.74-78
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• 1991

수치해석을 이용하여 자기기록장치를 구성하는 여러 요소들이 정보의 기록 또는 재생에 미치는 영향을 해석할 수 있는 방법을 기술하고 이것을 수직자기기록장치에 적용하여 기록밀도의 변화에 따른 재생전압의 형태을 구하였다. 자기기록장치에서 정보가 기록되는 것은 기록매체의 히 스테리시스현상에 기인하는 것이므로 수치해석시 히스테리시스 특성을 고려해 주어야 한다. 본 논 문에서는 Preisach 모텔과 유한요소법을 이용하여 히스테리시스 특성을 포함하는 자기기록장치의 기록 및 재생의 전과정을 해석할수 있는 수치해석 기법을 확립하고, 이 방법으로 자기기록장치의 여러요소에 대한 영향을 구할수 있음을 보이기 위하여 이것을 수직자기 기록장치에 적용하여 기록 밀도가 17[KFRP]에서 254[KFRPI]까지 증가할때 기록과정에서 주어진 전류파형에 대하여 매체에 기록된 자화량을 구하고, 재생과정에서 헤드에 유기되는 전압을 기록밀도 증가에 따른 재생전압크기 의 변화를 구하였다.

• Structural Engineering and Mechanics
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• 제8권5호
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• pp.513-529
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• 1999

A concept of hierarchical modeling, the newest modeling technology, has been introduced in early 1990's. This new technology has a great potential to advance the capabilities of current computational mechanics. A first step to implement this concept is to construct hierarchical models, a family of mathematical models sequentially connected by a key parameter of the problem under consideration and have different levels in modeling accuracy, and to investigate characteristics in their numerical simulation aspects. Among representative model problems to explore this concept are elastic structures such as beam-, arch-, plate- and shell-like structures because the mechanical behavior through the thickness can be approximated with sequential accuracy by varying the order of thickness polynomials in the displacement or stress fields. But, in the numerical, analysis of hierarchical models, two kinds of errors prevail, the modeling error and the numerical approximation error. To ensure numerical simulation quality, an accurate estimation of these two errors is definitely essential. Here, a local a posteriori error estimator for elastic structures with thin domain such as plate- and shell-like structures is derived using the element residuals and the flux balancing technique. This method guarantees upper bounds for the global error, and also provides accurate local error indicators for two types of errors, in the energy norm. Compared to the classical error estimators using the flux averaging technique, this shows considerably reliable and accurate effectivity indices. To illustrate the theoretical results and to verify the validity of the proposed error estimator, representative numerical examples are provided.

• 한국농촌간호학회지
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• 제15권1호
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• pp.1-8
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• 2020

Purpose: This purpose of this study was to develop a disaster and safety practice measurement tool for elderly people in rural areas. Methods: The tool for this study was developed and validated according to DeVellis' scale development process. The construct validity of the instrument was analyzed by major analysis of Varimax rotation, and the internal inertia was verified by Cronbach's ⍺. Results: The final scale was a 4-point scale, consisting of 23 items in 7 domains. The total explanation was 54.1% and the Cronbach's ⍺ was .80. Conclusion: The results of this study should be useful to assess elders' perception of the importance of safety management for elders.

• Molecular & Cellular Toxicology
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• 제5권1호
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• pp.14-22
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• 2009

In vitro cytotoxicity of 23 alkyl phenols (APs) on human cervical cancer cell lines (HeLa) was determined using the lactate dehydrogenase (LDH) cytotoxicity assay. Two different sets of descriptors were used to construct the calibration model based on Genetic Algorithm-Multiple Linear Regression (GA-MLR) based on the experimental data. A statistically robust Structure-Activity Relationships (QSAR) model was achieved ($R^2$=95.05%, $Q^2_{LOO}$=91.23%, F=72.02 and SE= 0.046) using three Dragon descriptors based on Me (0D-Constitutional descriptor), BELp8 (2D-Burden eigenvalue descriptor) and HATS8p (3D-GETAWAY descriptor). However, external validation could not fully prove its validity of the selected QSAR in characterization of the cytotoxicity of APs towards HeLa cells. Nevertheless, the cytotoxicity profiles showed a finding that 4-n-octylphenol (4-NOP), 4-tert-octyl-phenol (4-TOP), 4-n-nonylphenol (4-NNP) had a more potent cytotoxic effect than other APs tested, inferring that increased length and molecular bulkiness of the substituent had important influence on the LDH cytotoxicity.

• 한국식품영양학회지
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• 제29권1호
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• pp.104-114
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• 2016

In this study, we investigated protection motivation and behavioral intention to prevent serious illnesses related to excessive sodium intake among the university students in Gyeongnam and Busan. Within the protection motivation theory (PMT) framework, a survey questionnaire was developed to measure participants' perceptions on the severity of and the vulnerability to the threat of serious diseases due to the high sodium intake as well as the effectiveness of preventive measures (response efficacy), and the ability to perform them (self-efficacy) along with their willingness to follow recommendations (behavioral intention). Data was collected in June 2015. Study participants were divided into either low (n=117) or high (n=177) sodium intake behavior groups based on their current behaviors. Exploratory factor analysis was performed to measure construct validity and Cronbach's alpha was calculated to check reliability of measurement items. The high sodium intake behavior group perceived higher vulnerability than the low sodium intake behavior group among four PMT factors. Differences of the other three factors were not significant between the two groups. The results of hierarchical regression analysis indicated that self-efficacy and response efficacy affected behavioral intention of high sodium intake behavior among students. Hence, development of strategies to increase self-efficacy and response efficacy are strongly recommended.

• 한국정밀공학회지
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• 제10권4호
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• pp.109-117
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• 1993

Force balance method is employed to predict forging information such as forging load, tool pressure and normal stress at the surface of tangential velocity discontinuity. The incipient stages of deformation for the plane strain forging of rectangular billets in V-shaped dies of different semi-angles are analysed. To construct an approximate model for the analysis of deformation by the force balance method in the incipient deformation stages, slip-line field is used. When the deformation mode by slip-line method is the same as that by force balance method, the slip-line method and the force balance method give identical solutions. The effects of die angle, coefficient of friction, billet geometries and deforma- tion characteristics are also investigated. In order to verify the validity of force balance analysis, the rigid-plastic finite element simulation for the various forgig parameters are performed and performed and find to be in good agreement.

• 소성∙가공
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• 제13권1호
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• pp.33-38
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• 2004

A new approach for the design of extrusion die surface of arbitrarily shaped section is presented. In order to generate the extrusion die surface. an automatic surface construction method based on B-spline surface and scalar field theory is proposed. The isothermal lines and stream lines designed in the scalar field are introduced to find the control points which are used in constructing B-spline surfaces. Intersected points between the isothermal lines and stream lines are used to construct B-spline surfaces. The inlet and outlet profiles are precisely described with B-spline curves by using the centripetal method for uniform parameterization. The extrusion die surface is generated by using the cubic curve interpolation in the u- and v-directions. A quantitative measure for the control of surface is suggested by introducing the tangential vectors at the inlet and outlet sections. To verify the validity and effectiveness of the proposed method, automatic surface generation is carried out for extrusion dies of arbitrarily shaped sections.

• 아동학회지
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• 제37권6호
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• pp.107-117
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• 2016

Objective: This study examined the construct validity of K-WPPSI-IV. Factor structures of the structures of the K-WPPSI-IV full scale as well as primary index scales for two age ranges (2 years, 6 months to 3 years, 11 months; 4 years to 7 years, 7 months) were examined. Methods: Data were collected from 1,700 children aged 2 years, 6 months to 7 years, 7 months during the K-WPPSI-IV standardization. Confirmatory factor analyses were conducted using the K-WPPSI-IV subtest performances with maximum likelihood estimation using Amos 18. Results: First, the three-factor model (verbal comprehension, visual spatial, and working memory) fitted best for the younger age range. However, the five-factor model (verbal comprehension, visual spatial, fluid reasoning, working memory, and processing speed) fitted best for the older age range. Residuals suggest the presence of two nested subfactors within the verbal comprehension factor (broad/expressive and focused/simple). Second, the confirmatory factor analysis on primary index subtests identified factors that account for the intercorrelations among the reduced sets of primary index subtests. Conclusion: The findings showed that the theoretical structures of WPPSI-IV subtests were confirmed within K-WPPSI-IV.

• 전자공학회논문지SC
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• 제46권3호
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• pp.15-21
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• 2009

본 논문에서는 변수 불확실성을 가지는 이산시간 특이시스템의 강인 안정화 기법과 강인 보장비용 제어기법을 다룬다. 제안하는 제어기법은 제어기 존재조건에서 준정부호조건(semi-definite condition)이나 시스템 행렬의 분해 없이 볼록최적화(convex optimization)가 가능한 선형행렬부등식 접근방법을 이용하여 제안한다. 먼저, 강인 안정화 상태궤환 제어기는 폐루프 시스템의 정규성, 코잘 및 안정화를 만족하는 제어기의 존재조건과 설계방법을 선형행렬부등식으로 제시한다. 그리고 보장비용 함수의 상한치의 최소화를 보장하는 강인 보장비용 제어기 설계방법은 강인 안정화 제어기 설계를 기반으로 제안한다. 예제를 통하여 제안한 제어기 설계기법의 타당성을 확인한다

• 한국과학교육학회지
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• 제16권3호
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• pp.303-313
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• 1996

The major purpose of this thesis is to construct the evaluating framework of a science textbook with a high confidence and universal validity, referring to a preceeding study and materials involved in research work, and in consideration of the educational conditions of the secondary school. The framework developed in this study are composed of 7 categories: content, organization, representation, laboratory, illustrations, external form or editing system, and supplementary materials. Each category consists of detailed items. Eech item in the check-list is to be given between one and five points, and the total number of possible points in this evaluating framework is 290. As a result, these evaluating items enable quantitative analyses, afford an opportunity which we can look into many-sidedly the respects we should consider when a science textbook is adopted, and they can be estimated partly or synthetically as occasional demands. This study is exepected to contribute to choose a good science textbook as fundamental data in the future, and to help the lasting study or estimation of the textbook.