• Journal of Korean Elementary Science Education
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• v.34 no.3
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• pp.325-337
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• 2015

The purpose of this study was to investigate the effects of a teaching-learning program using the history of science on elementary school students' academic achievement, science attitude, and science process skill. Subjects were 72 students of two groups in the 5th Grade. A experimental group of 36 was instructed 10 lessons in unit of 'our body' using the history of science. The history of science materials used in this program included 4 explicit method, which are Eii, Eij, Eik and Ea type, and 1 implicit method which is I type. The contents validity of this program was reviewed by the science education specialists. The results of the study were as follows: Students of experimental group showed statistically more significant increase in academic achievement and science attitude than control group students. However, there was no significant difference on science process skill between the instruction by applying a teaching-learning program using the history of science and the traditional instruction. Since this program using the history of science is effective for the attitude improvement of elementary school students as well as academic achievement, it is highly likely to be used as the science education material for students with the low affective area.

• Journal of Korea Water Resources Association
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• v.30 no.6
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• pp.597-610
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• 1997

One-dimensional numerical models using finite difference methods for unsteady sediment transport on alluvial river channel are developed. The Preissmann implicit scheme and the Lax-Wendroff two-step explicit scheme with the Method of Characteristics for water motion and a forward time centered space explicit scheme for sediment motion are developed to simulate the sediment transport rate and the variation of channel bed level. The program correctness of each model is successfully verified using volume conservation tests. The sensitivity studies show that higher peak stage level, steeper channel slope and longer flooding duration produce more channel bed erosion. and median grain size, $D_{50}=0.4mm$ give maximum volume loss in this study. Finally, the numerical models are found to produce reasonable results from the various sensitivity tests which reveal that the numerical models have properly responded to the changes of each model parameter.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.143-150
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• 1996

This is an explicit-Implicit, finite element analysis for linear as well as nonlinear hygrothermal stress problems. Additional features, such as moisture diffusion equation, crack element and virtual crack extension(VCE ) method for evaluating J-integral are implemented in this program. The Linear Elastic Fracture Mechanics(LEFM) Theory is employed to estimate the crack driving force under the transient condition for and existing crack. Pores in materials are assumed to be saturated with moisture in the liquid form at the room temperature, which may vaporize as the temperature increases. The vaporization effects on the crack driving force are also studied. The Ideal gas equation is employed to estimate the thermodynamic pressure due to vaporization at each time step after solving basic nodal values. A set of field equations governing the time dependent response of porous media are derived from balance laws based on the mixture theory Darcy's law Is assumed for the fluid flow through the porous media. Perzyna's viscoplastic model incorporating the Von-Mises yield criterion are implemented. The Green-Naghdi stress rate is used for the invariant of stress tensor under superposed rigid body motion. Isotropic elements are used for the spatial discretization and an iterative scheme based on the full newton-Raphson method is used for solving the nonlinear governing equations.

• Journal for History of Mathematics
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• v.22 no.1
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• pp.41-52
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• 2009

Dutch mathematician Simon Stevin published De Thiende(The Tenth) in 1583. In that book Stevin suggested new numerical notation which could express all numbers. That new notation was decimal fraction system. In this article I will argue that Stevin invented new decimal fraction system with two main purposes. The explicit purpose was to invent a new system which could be used easily by practical mathematicians. The implicit purpose which cannot be found in De Thiende alone but in his other writings was to break the Aristotelian tradition which separated geometry and arithmetic which dealt continuous magnitude and discrete numbers respectively.

• Structural Engineering and Mechanics
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• v.58 no.6
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• pp.1021-1044
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• 2016

Different versions of a damage index (DI) along with a formulation to find the number of cycles at failure due to fatigue, applicable to reinforced concrete (RC) structures are presented. These are based on an energetic analysis method and applicable to both global and local levels. The required data can be found either from the numerical simulation of structures or from the experimental tests. A computer program has been developed to simulate numerically the nonlinear behavior of RC columns under cyclic loading. The proposed DI gives a regular distribution of structural damages up to failure and is validated by the results of the tests carried out on RC columns subjected to cyclic loading. In general, the local and global damage indices give approximately similar results, while each of them has its own advantages. The advantage of the implicit version of DI is that, it allows the comparison of the results with those of the monotonic loading case, while the explicit version makes it possible to estimate the number of loading cycles at failure due to fatigue, and the advantage of the simplified version is that; the monotonic loading data is not needed for the cyclic loading case.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.5
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• pp.424-431
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• 2004

An implicit direct-time integration method for obtaining transient responses of general dynamic systems is described. The conventional Newmark method cannot be directly applied to state-space first-order differential equations, which contain no explicit acceleration terms. The method proposed here is the state-space Newmark method that incorporates the average velocity concept, and can be applied to an analysis of general dynamic systems that are expressed by state-space first-order differential equations. It is also readily coded into a program. Stability and accuracy analyses indicate that the method is numerically unconditionally stable like the conventional Newmark method, and has a period error of 2nd-order accuracy for small damping and 4th-order for large damping and an amplitude error of 2nd-order, regardless of damping. In addition, its utility and validity are confirmed by two application examples. The results suggest that the proposed state-space Newmark method based on average velocity be generally applied to the analysis of transient responses of general dynamic systems with a high degree of reliability with respect to stability and accuracy.

• Proceedings of the Technology Innovation Conference
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• 1998.06a
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• pp.226-249
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• 1998

Technology diffusion policy can be defined as the role of government in linking knowledge production with usage. It has an importance due to the fact that linking knowledge between the producing agent and using agent does not automatically occur. If knowledge produced by an R&D agent is not used by somebody else, the knowledge may deteriorate to a social loss since knowledge production consumes a considerable degree of social resources. Explicit technology diffusion policies are not found in Korea. There we, however, a number of implicit policies to promote technology diffusion, mainly by promoting cooperation among universities, industries and research institutes. Government R&D programs have provided incentives for cooperative research projects, and many government sponsored institutes have been assigned the role of technology assistance for small and medium sized firms. Nevertheless, diffusion policies remain weak in comparison to other innovation and technology policies. This is reflected in the relatively small scale of government support for technology diffusion programs. In addition, there is no systematic approach between the different ministries for enhancing diffusion across technologies, institutions, sectors and regions. A comprehensive evaluation of government diffusion programs, which is necessary for improving policy and program design, is lacking. Enhancing the diffusion of technology in Korea will require the strengthening of policies at different levels, including; 1) increasing the orientation of science and technology policies towards diffusion; 2) increasing the scale of existing diffusion programs; 3) developing new diffusion programs, in particular sector-specific or manpower training programs; 4) developing policies to encourage a culture of cooperation that can facilitate technology diffusion; and 5) carrying out substantial policy research to develop diffusion policies.

• International Journal of Aeronautical and Space Sciences
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• v.2 no.2
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• pp.65-72
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• 2001

This paper demonstrates an explicit-implicit, finite element analysis for linear as well as nonlinear hygrothermal stress problems. Additional features, such as moisture diffusion equation, crack element and virtual crack extension(VCE) method for evaluating J-integral are implemented in this program. The Linear Elastic Fracture Mechanics(LEFM) Theory is employed to estimate the crack driving force under the transient condition for an existing crack. Pores in materials are assumed to be saturated with moisture in the liquid form at the room temperature, which may vaporize as the temperature increases. The vaporization effects on the crack driving force are also studied. The ideal gas equation is employed to estimate the thermodynamic pressure due to vaporization at each time step after solving basic nodal values. A set of field equations governing the time dependent response of porous media are derived from balance laws based on the mixture theory. Darcy's law is assumed for the fluid flow through the porous media. Perzyna's viscoplastic model incorporating the Von-Mises yield criterion are implemented. The Green-Naghdi stress rate is used for the invariant of stress tensor under superposed rigid body motion. Isotropic elements are used for the spatial discretization and an iterative scheme based on the full Newton-Raphson method is used for solving the nonlinear governing equations.

• Journal of Korean Society of Rural Planning
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• v.22 no.4
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• pp.25-36
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• 2016

The purpose of this study is to construct a quantitative evaluation method that can analyze the policy effectiveness with the construction of a implicit composite index incorporating spatial econometrics models. In order to propose a methodological framework for the program evaluation, this study conducts an empirical analysis with the application of the Comprehensive Rural Village Development Project (CRVDP) which explicitly claims to achieve comprehensive goal of community development. The present study pays particular attention to quantifying the composite evaluation index and drawing net effect through the application of a series of spatial econometrics models. The spatial unit of the analysis is drawn at Eup-Myeon level in rural areas in Korea, and the time horizon is in between 2005 and 2010. We utilize the Korean Agricultural Census data in 2005 and 2010. Three steps of methodological processes are needed to satisfy the objective of the present study. First, we apply factor analysis to construct the composite index that represents comprehensive settlement environment in rural area. The index should be matched with the main objective of the CRVDP. Second, we apply the derived index to a series of spatial econometrics model as dependent variable. Lastly, utilizing the estimated coefficients of the econometrics models, we apply decomposition technique to estimate CRVDP's net effect from both cross-sectional and longitudinal perspectives. We find that the results of the decomposition analysis by the execution of the CRVDP are positively associated with the explicit object of the project.

• Journal of Preventive Medicine and Public Health
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• v.48 no.5
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• pp.239-248
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• 2015

Objectives: The purpose of this study was to assess the inter-rater reliability and intra-rater reliability of medical record review for the detection of hospital adverse events. Methods: We conducted two stages retrospective medical records review of a random sample of 96 patients from one acute-care general hospital. The first stage was an explicit patient record review by two nurses to detect the presence of 41 screening criteria (SC). The second stage was an implicit structured review by two physicians to identify the occurrence of adverse events from the positive cases on the SC. The inter-rater reliability of two nurses and that of two physicians were assessed. The intra-rater reliability was also evaluated by using test-retest method at approximately two weeks later. Results: In 84.2% of the patient medical records, the nurses agreed as to the necessity for the second stage review (kappa, 0.68; 95% confidence interval [CI], 0.54 to 0.83). In 93.0% of the patient medical records screened by nurses, the physicians agreed about the absence or presence of adverse events (kappa, 0.71; 95% CI, 0.44 to 0.97). When assessing intra-rater reliability, the kappa indices of two nurses were 0.54 (95% CI, 0.31 to 0.77) and 0.67 (95% CI, 0.47 to 0.87), whereas those of two physicians were 0.87 (95% CI, 0.62 to 1.00) and 0.37 (95% CI, -0.16 to 0.89). Conclusions: In this study, the medical record review for detecting adverse events showed intermediate to good level of inter-rater and intra-rater reliability. Well organized training program for reviewers and clearly defining SC are required to get more reliable results in the hospital adverse event study.