• Journal of Educational Research in Mathematics
• /
• v.26 no.3
• /
• pp.333-354
• /
• 2016

The aim of the present study is twofold. One is to confirm a hypothesis that a student's rate concept influences her conceiving change of a function in the view of rate of change and the other is to build up foundations for understanding the transition process from her rate concept to the concept of rate of change when she investigates the change of concentration as an intensive quantity. We explored how three participating high school students recognized and expressed change of given functions by using their rate concept as a conceptual tool. The result indicates that a change in students' rate concept might have an effect on understanding how function values change in term of rate of change. We also expect that it could be a catalyst for further research for clarifying the relationship between students' rate concept and their development of a concept of rate of change as a foundation for learning calculus.

• Fire Science and Engineering
• /
• v.22 no.3
• /
• pp.216-220
• /
• 2008

Water mist fire suppression system utilizes the fire suppression features such as cooling of fire source, dilution of ambient oxygen, and shielding of radiation heat with the evaporation of microscopic water droplets. The momentum of water mist is relatively lower than that of larger water droplet and the infiltration of water mist to the fire source is not effective. Contribution of evaporated water vapor is liable to decline to limited portion of fire source due to its light weight and sparse density. On the other hand, the cycling water mist pattern is expected to improve the penetration force of water mist as well as the air expelling capability with the stratified spray characteristics. At this paper, we present the analyzed fire suppression capability of intermittent water spray pattern by use of FDS which is computational fire dynamics fire model. We expect this analysis can support the basic concept to the development of the prototype of water mist nozzle.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.3
• /
• pp.1318-1326
• /
• 2014

The change of concept about real estate marketing and the solution about unsold houses are getting important nowadays. This paper is analyzing the solution of unsold houses as location environment, residential environment, macro environment, and marketing, and research question is which elements are important to real users. In addition, this paper is analyzing on impact relationship in terms of real users' buying intention about unsold houses and satisfaction of price of selling a house (price of selling a house, rise in housing value) by PLS structural equation. To sum up, first, macro environment, residential environment, location environment is statistically valued on the satisfaction of price of selling a house. However, marketing strategic is not impacted on the satisfaction of price of selling. Second, macro environment, marketing strategic, satisfaction of selling a house is statistically valued on buying intention.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.4
• /
• pp.493-499
• /
• 2007

The Taylor expansion expresses a differentiable function and its coefficients provide good approximations for the given function and its derivatives. In this study, m-th order Taylor Polynomial is constructed and the coefficients are computed by the Moving Least Squares method. The coefficients are applied to the governing partial differential equation for solid problems including crack problems. The discrete system of difference equations are set up based on the concept of point collocation. The developed method effectively overcomes the shortcomings of the finite difference method which is dependent of the grid structure and has no approximation function, and the Galerkin-based meshfree method which involves time-consuming integration of weak form and differentiation of the shape function and cumbersome treatment of essential boundary.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.3
• /
• pp.321-327
• /
• 2007

This study presents a new gridless finite difference method for solving elastic crack problems. The method constructs the Taylor expansion based on the MLS(Moving Least Squares) method and effectively calculates the approximation and its derivatives without differentiation process. Since no connectivity between nodes is required, the modeling of discontinuity embedded in the domain is very convenient and discontinuity effect due to crack is naturally implemented in the construction of difference equations. Direct discretization of the governing partial differential equations makes solution process faster than other numerical schemes using numerical integration. Numerical results for mode I and II crack problems demonstrates that the proposed method accurately and efficiently evaluates the stress intensity factors.

• Communications of Mathematical Education
• /
• v.28 no.1
• /
• pp.65-79
• /
• 2014

The present study seeks to provide an easy path to differential perceptions of students at the upper high school level by applying a story telling method and also, characteristically, to earn some time for class discussion by reducing learning time for simple calculational procedure through Computer Algebra System(CAS) tools. This study offers a clear example of storytelling textbooks through Sage. Hence, the study aims at enabling students who have practiced contents with Sage tools to deal with diverse and complicated calculation problems, if they learn to build up mathematical formulas for those problems.

• Computational Structural Engineering
• /
• v.10 no.3
• /
• pp.217-223
• /
• 1997

This paper deals with the basic concepts of sensitivity analysis in a time domain for the transient response of a lumped mass system. Sensitivity analysis methods in thme domain for determining the effects of parameter changes on the response of a dynamic system by external excitation are presented. The parametric sensitivity of a lumped mass system in time domain can be investigated using different types of sensitivity functions, including first order standard and percentage sensitivity functions. These sensitivity functions are determined as a function of partial derivatives of system variables taken with respect to system parameters. In addition, we compared the results of the analytical method by direct method and those of numerical methods.

• School Mathematics
• /
• v.18 no.3
• /
• pp.711-731
• /
• 2016

The purpose of this study is to investigate how pre-service secondary mathematics teachers modify mathematical tasks from a textbook and learning opportunities they have during the task modification. In the pursuit of this purpose, tasks was selected from derivative units in a textbook and five pre-service teachers was asked to modify the tasks. The findings from analysis are as follows. First, the cognitive demands of modified tasks were maintained or higher than those of the originals. Pre-service teachers' tendency toward conceptual understanding of derivative seems to make the result. Second, task modification provided a lot of learning opportunities for pre-service teachers. They tried to know intention of curriculum and textbook, realized the importance of predicting students' responses, and had opportunities for cooperation and reflective thinking.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.14 no.2
• /
• pp.159-171
• /
• 2001

평면 아치 구조물에 대해 선형 탄성 변분방정식에 기반을 둔 설계민감도 해석을 위한 일반적 이론을 개발하였다. 아치 구조물내의 임의 마디에 정의된 응력범함수를 고려하였고 이에 대한 설계민감도 공식을 유도하기 위해 전미분(material derivative) 개념과 보조(adjoint) 변수 방법을 도입하였다. 얻어진 민감도 공식은 구조해석 결과를 얻고 나면 이들로부터 단순 대수연산을 통해 계산이 되므로 적용이 간편할 뿐 아니라 해의 정확도가 높은 잇점이 있다. 본 방법은 아치의 형상을 매개변수를 통해 표현하므로 얕은 아치에 국한하지 않고 어떠한 형상도 고려가 가능하며, 나아가서 아치의 형상변화를 형상에 대해 수직뿐 아니라 접선방향도 포함하여 일반적으로 고려하므로 다양한 형상설계가 가능하다. 몇 가지 예제에서 민감도 계산을 수행함으로써 본 방법의 정확도와 효율성을 입증하였으며, 두 가지의 설계최적화 문제를 대상으로 실제로 두께 및 형상최적설계를 수행하였다.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.18 no.1
• /
• pp.25-34
• /
• 1981

Any logical stuckft faults in multivalued combinational circuits are analyzed using the concept of Boolean difference. The algebra employed is the implementation oriented algebra developed by Allen and Givone. All the lines in the circuit are classified into five types according to their properties. For each type, the equation that represents the complete test set is derived and proved. All the results in examples are confumed to be correct by comparing the truth tables of the normal and faulty circuits.