• Communications of Mathematical Education
• /
• v.28 no.3
• /
• pp.375-394
• /
• 2014

The purpose of this study is to examine the transition of mathematical representation in Joseon mathematics, which is focused on numbers and operations, letters and expressions. In Joseon mathematics, there had been two numeral systems, one by chinese character and the other by counting rods. These systems were changed into the decimal notation which used Indian-Arabic numerals in the late 19th century passing the stage of positional notation by Chinese character. The transition of the representation of operation and expressions was analogous to that of representation of numbers. In particular, Joseon mathematics represented the polynomials and equations by denoting the coefficients with counting rods. But the representation of European algebra was introduced in late Joseon Dynasty passing the transitional representation which used Chinese character. In conclusion, Joseon mathematics had the indigenous representation of numbers and mathematical symbols on our own. The transitional representation was found before the acceptance of European mathematical representations.

• Journal of Educational Research in Mathematics
• /
• v.26 no.4
• /
• pp.715-730
• /
• 2016

The purpose of this study is to analyze Descartes's point of view on the mathematical connection of algebra and geometry which help comprehend the traditional frame with a new perspective in order to access to unsolved problems and provide useful pedagogical implications in school mathematics. To achieve the goal, researchers have historically reviewed the fundamental principle and development method's feature of analytic geometry, which stands on the basis of mathematical connection between algebra and geometry. In addition we have considered the significance of geometric solving of equations in terms of analytic geometry by analyzing related preceding researches and modern trends of mathematics education curriculum. These efforts could allow us to have discussed on some opportunities to get insight about mathematical connection of algebra and geometry via geometric approaches for solving equations using the intersection of curves represented on coordinates plane. Furthermore, we could finally provide the method and its pedagogical implications for interpreting geometric approaches to cubic equations utilizing intersection of conic sections in the process of inquiring, solving and reflecting stages.

• Journal of the Korean Society of Groundwater Environment
• /
• v.6 no.4
• /
• pp.188-193
• /
• 1999

Transport of pollutants in aquifer largely depends on groundwater flow which is governed by aquifer hydraulic parameters. Determination of these parameters and associated groundwater modeling become essential for adequate remediation of contaminate groundwater. The objective of this paper is to analyze groundwater flow and determine the optimum hydraulic parameters by performing groundwater modeling based on sensitivity analysis for unconfined sandy gavel aquifer constructed in a laboratory scale under various boundary condition. Results revealed that the simulated drawdown was lower than the observed drawdown irrespective of boundary conditions. and specific yield (S$_{y}$) had less effect on the grondwater flow than permeability (K) in the aquifer. Water balance analysis showed that the measured drawdown in neighboring observation wells during pumping was higher than either simulated or recovered water table. The indicated that a difference might exist in the water tables between aquifer and wells. The difference was investigated by time domain reflectometry (TDR) measurements on water contents in the region of water table and capillary fringe, and explained by a delayed response of water table during gravitational drainage as the water table was lowered as a result of pumping.g.

• Journal of Korea Water Resources Association
• /
• v.48 no.1
• /
• pp.23-35
• /
• 2015

In this study, the behavior of fresh water body between the injection and production wells with the fresh water injection rate in a saline aquifer is numerically analyzed by using a three-dimensional numerical model. 8 injection wells are arranged at equidistant intervals on a concentric circle and one production well is located at the center of this circle. In the case that the fresh water injection rate is relatively small, the fresh water body around a injection well screen is not mixed with neighboring ones and is independently distributed. However, when the injection rate is increased, the size of the fresh water body is continuously increased, and the areas, where saline and fresh water among injection wells are mixed, are appeared. The mixed degree is increased as the injection rate is increased. This phenomenon is identically generated around the production well. Moreover, when the injection rate is increased, the ratio of saline water in and around the production well is decreased.

• Journal of Educational Research in Mathematics
• /
• v.24 no.3
• /
• pp.359-374
• /
• 2014

Students' difficulties and errors in relation to mathematical proofs are worth while to say one of the dilemmas in mathematics education. The potential elements of their difficulty are scattered over the process of proving in geometry as well as algebra. This study aims to investigate whether middle school students understand the context of algebraic proof including literal expressions. We applied 24 third-grade middle school students a test item which shows a proof including a literal expression and missing the conclusion. Over the half of them responded wrong answers based on only the literal expression without considering its context. Three of them were interviewed individually to show their thinking. As a result, we could find some characteristics of their thinking including the perspective on proof as checking the validity of algebraic expression and the gap between proving and understanding of proof etc. From these, we also discussed about several didactical implications.

• Journal of KIISE:Databases
• /
• v.28 no.1
• /
• pp.69-85
• /
• 2001

공간 데이터베이스에서 효율적으로 공간 질의를 처리하기 위해서는 클러스터링을 통해서 이스크 접근 비용을 줄이는 것이 필요하다. 이 논문은 공간 지역성에 기반을 둔 여러 가지 클러스터링 알고리즘을 제안하고 실험을 통해 제안한 클러스터링 알고리즘의 성능을 평가하였다. 이 논문에서 제안하는 클러스터링 알고리즘은 객체 클러스터링 알고리즘과 셀 클러스터링 알고리즘으로 나뉜다. 객체 클러스터링 알고리즘은 정규 준할 공간 색인 구조에서 영역 분할 선과 겹치는 객체들의 저장 위치를 결정하는데 사용된다. 셀 클러스터링 알고리즘은 클러스터를 만들기 위해 정규 분할된 영역들을 그룹화하는데 사용된다. 실험결과 객체 클러스터링 알고리즘에서는 객체간의 거리를 이용한 경우에 대체로 좋은 성능을 보였지만, 버퍼 크기가 커지거나 데이터가 희박한 영역의 질의에 있어서는 알고리즘 별로 성능의 차이는 거의 없었다. 셀 클러스터링 알고리즘에 대한 실험에서는 이 논문에서 제안한 클러스터링 알고리즘은 N-순서화 기법에 의한 클러스터링 알고리즘에 비해 우수한 성능을 보였다. 특히 중복 참조도를 이용한 경우와 셀의 무게 중심간 거리를 이용한 방법이 가장 우수하였다.

• Journal of Korea Water Resources Association
• /
• v.48 no.7
• /
• pp.553-566
• /
• 2015

Acoustic Doppler Current Profilers(ADCPs) have capability to concurrently capitalize three-dimensional velocity vector and bathymetry with highly efficient and rapid manner, and thereby enabling ADCPs to document the hydrodynamic and morphologic data in very high spatial and temporal resolution better than other contemporary instruments. However, ADCPs are also limited in terms of the inevitable unmeasured regions near bottom, surface, and edges of a given cross-section. The velocity in those unmeasured regions are usually extrapolated or assumed for calculating flow discharge, which definitely affects the accuracy in the discharge assessment. This study aimed at scrutinizing a conventional extrapolation method(i.e., the 1/6 power law) for estimating the unmeasured regions to figure out the accuracy in ADCP discharge measurements. For the comparative analysis, we collected spatially dense velocity data using ADV as well as stationary ADCP in a real-scale straight river channel, and applied the 1/6 power law for testing its applicability in conjunction with the logarithmic law which is another representative velocity law. As results, the logarithmic law fitted better with actual velocity measurement than the 1/6 power law. In particular, the 1/6 power law showed a tendency to underestimate the velocity in the near surface region and overestimate in the near bottom region. This finding indicated that the 1/6 power law could be unsatisfactory to follow actual flow regime, thus that resulted discharge estimates in both unmeasured top and bottom region can give rise to discharge bias. Therefore, the logarithmic law should be considered as an alternative especially for the stationary ADCP discharge measurement. In addition, it was found that ADCP should be operated in at least more than 0.6 m of water depth in the left and right edges for better estimate edge discharges. In the future, similar comparative analysis might be required for the moving boat ADCP discharge measurement method, which has been more widely used in the field.

• Proceedings of the Korea Multimedia Society Conference
• /
• 2000.04a
• /
• pp.111-116
• /
• 2000

컴퓨터네트워크를 통한 정보의 이동이 빈번한 오늘날, 중요 정보를 지키는 정보 보호 기술의 요구는 점차 늘어나고 있다. 이에 따라, 통신망 상의 프라이버시 보호, 기밀성, 무결성 같은 개인정보보호를 위해서 필수적인 암호학적 도구로 디지털 서명이 이용되고 있다. 본 논문에서는 이산대수 문제의 어려움에 기반하여, 디지털 서명대상을 2명에서 n명으로 확대한 다중서명 기법에 서명자 전원의 동의 없이는 서명을 검증할 수 없는 부정할 수 없는 서명의 기능을 부여한다. 이는 전자, 선거, 전자 현금 등 보다 복잡하고 민감한 사회적 영역에 적용될 수 있을 것이다.

• 한국항공운항학회:학술대회논문집
• /
• 2016.05a
• /
• pp.306-309
• /
• 2016

최근 항공기 사고가 빈번하게 발생하는 가운데, 2000년 이후부터 현재까지 발생한 항공기 사고 총 257건 가운데 52번의 사고가 항공기사용사업체에서 발생하였다. 이는 항공사업의 크기와 항공기보유대수에 비해 큰 비중을 차지하는 것을 나타낸다. 그러나 현행 법령 및 제도 등은 항공기사용사업의 업무영역 및 특성을 고려한 안전요건이 충족되어있지않은 실정이다. 본 연구는 최근 발생한 항공기 사고 유형 및 안전요소를 분석하고, AHP 기법을 이용하여 안전요소별 중요도를 도출한 후 그 결과를 기반으로 안전방안에 대해 살펴보고자한다.

• The Mathematical Education
• /
• v.42 no.3
• /
• pp.275-294
• /
• 2003

In this paper we compared and analyzed the Korean and German mathematics textbooks for the middle school students. For the research we investigated only the area of algebra, which is consisted of the three sections-section of numbers and arithmetic operations, section of letters and expressions, and section of rules and functions. We expect that this paper would contribute on the development of the whole area in our nation's mathematical educations, including the organization and exploitation of the curriculums for the middle school students.