• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.513-516
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• 2001

마이크로폰을 배열을 이용한 음성개선 기법 중에서 저주파 영역에서의 높은 상관성과 고주파 영역에서의 spatial aliasing을 동시에 고려하기 위하여 대수적인 선형 마이크로폰 배열을 사용하고 웨이브렛 도메인에서의 Wiener 필터에 기반한 postfiltering을 수행하는 방법이 제안된 바 있는데[l], 본 논문에서는 이 방법의 문제점을 분석하고 해결방안을 제시하였다. 제안한 알고리즘을 사용하여 시뮬레이션한 결과, 마이크에 입력되는 음성신호의 SNR이 0dB일 때와 l0dB일 때, 기존의 알고리즘에 비해 약 1.7dB와 2.5dB의 성능개선이 있었으며, 청취실험을 통해서도 음질의 향상을 확인할 수 있었다.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.359-360
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• 2009

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2003.10a
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• pp.231-236
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• 2003

산업의 형태가 고도화되고 다양해짐에 따라 유통활동의 영역이 넓어지고 수송 수요가 증가하고 있다. 또한 소득수준의 향상에 따라 자가용 승용차의 보유 및 이용이 급속도로 증가하고 있으며, 이로 인하여 도로교통소음, 대기오염, 교통사고 및 도로공간점유 등 많은 문제를 야기 시키고 있다. 특히 자동차 보유대수는 증가하나 낮은 도로 점유율 때문에 도로교통소음이 해마다 증가하고 있다.(중략)

• The KIPS Transactions:PartA
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• v.14A no.6
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• pp.383-390
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• 2007

This paper describes the e-learning system for science and engineering mathematics using computer algebra system and Bayesian inference network. The best feature of this system is using one of the most recent mathematical dynamic web content authoring model which is called client independent dynamic web content authoring model and using the Bayesian inference network for diagnosing student's learning. The authoring module using computer algebra system provides teacher-user with easy way to make dynamic mathematical web contents. The diagnosis module using Bayesian inference network helps students know the weaker parts of their learning, in this way our system determines appropriate next learning sequences in order to provide supplementary learning feedback.

• Communications of Mathematical Education
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• v.24 no.1
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• pp.123-143
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• 2010

The Skeleton Tower problem is an example of a curriculum that integrates algebra and geometry. Finding the number of the cubes in the tower can be approached in more than one way, such as counting arithmetically, drawing geometric diagrams, enumerating various possibilities or rules, or using algebraic equations, which makes the tasks accessible to students with varied prior knowledge and experience. So, it will be a good topic which can be used in the elementary grades if we exclude the method of using algebraic equations. The purpose of this paper is to propose some points which can be considered with attention by gifted children education teachers by analyzing the 4th Skeleton Tower problem solutions made by 3rd and 4th graders in their selection test who applied for the education of gifted children in math at J University for the year of 2010.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.3
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• pp.151-157
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• 2021

This paper is devoted to a convergence study of the nonlocal integral operator in peridynamics. The implicit formulation can be an efficient approach to obtain the static/quasi-static solution of crack propagation problems. Implicit methods require constly large-matrix operations. Therefore, convergence is important for improving computational efficiency. When the radial influence function is utilized in the nonlocal integral equation, the fractional Laplacian integral equation is obtained. It has been mathematically proved that the condition number of the system matrix is affected by the order of the radial influence function and nonlocal horizon size. We formulate the static crack problem with peridynamics and utilize Newton-Raphson methods with a preconditioned conjugate gradient scheme to solve this nonlinear stationary system. The convergence behavior and the computational time for solving the implicit algebraic system have been studied with respect to the order of the radial influence function and nonlocal horizon size.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04b
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• pp.100-102
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• 2004

속도와 방향이 바뀔 때마다 이동체의 위치를 보고하는 TPR-tree는 이동체의 위치를 예측하는 오차가 적다. 그러나 긴 시간 간격으로 이동체의 위치를 보고하면 위치 예측의 불확실성이 높아져서 위치 예측의 오차값이 증가한다. 불화실성이 높은 이동체를 TPR-tree에 적용할 때 이동체의 위치 정보를 갱신하기 위한 색인 검색 비용이 증가하고, 질의 결과의 정확도가 낮아지는 문제가 발생한다. 이 논문에서는 긴 시간 간격으로 이동체 위치를 보고할 때 발생하는 이동체 위치의 불확실성을 고려하기 위해서 불확실성 영역(uncertainty region)을 이용한 확장 TPR-tree를 제시한다. 불확실성이 높은 이동체의 위치 데이터를 처리하기 위해서 이동체의 이동 가능한 영역을 위치 예측의 오차 값을 이용하여 계산한 불확실성 영역을 설정하고, 검색을 위하여 노드외 BR을 계산할 때 불확실성 영역을 이용하여 BR을 확장한다.

• Journal of Advanced Navigation Technology
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• v.11 no.4
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• pp.447-453
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• 2007

In this letter, we derive the Gallager random coding bound for discrete memoryless channels purely by simple manipulations of algebraic inequalities rather than invoking conceptually difficult random coding arguments. Gallager random coding bound is a very useful tool in information and coding theory due to its applicability to situations in which it is difficult to determine the decision regions and due to the fact that it can be used to derive the channel coding theorem. The readers will find it relatively easy to apply to many practical problems of interest the step-by-step algebraic derivations of the Gallager random coding bound with appropriate modifications.

• The Mathematical Education
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• v.41 no.3
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• pp.233-256
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• 2002

This study investigated school mathematics curriculum of England, newly revised in 1998, focused on the 'number and algebra' domain among three major domains of the English curriculum. On the basis of its understanding, this domain was compared and analyzed with school mathematics curriculum of Korea. In doing so, this study explored its plans and procedures and established a frame of comparison for the curriculums between the two countries. The structure of the National Curriculum in England is composed of programmes of study and attainment targets. The former sets out what should be taught in mathematics at key stages 1, 2, 3, and 4 and provides the basis for planning schemes of work, and the latter sets out the knowledge, skills, and understanding that pupils of different abilities and matures are expected to have by the end of each key stage. Attainment targets are composed of eight levels and an additional level of increasing difficulty. According to the results of the present study, Korea focuses on the formal and systematic mathematical knowledge on the basis of sound understanding of certain mathematical terms or concepts. On the other hand, England tends to deal with numbers more flexibly and naturally through the aquisition of mental methods, calculator use methods, etc, and emphasizes that mathematics be realistic and useful in solving a diverse number of problems confronted in everyday life.

• Journal of Soil and Groundwater Environment
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• v.14 no.6
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• pp.65-70
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• 2009

Reduction of groundwater surface tension prior to air sparging (SEAS, surfactant-enhanced air sparging) was known to increase air saturation in the aquifer under influence, possibly enhancing the removal rates of volatile contaminants. Although SEAS was known to be efficient for increasing air saturation, little information is available for different hydrogeological settings including soil particle sizes and the depth of aquifer. We investigated water saturations in the sparging influence zone during SEAS using one-dimensional column packed with sands of different particle sizes and different aquifer depths. An anionic surfactant was used to suppress the surface tension of water. Two different sands were used; the air entry pressures of the sands were measured to be $15.0\;cmH_2O$, and $36.3\;cmH_2O$, respectively. No significant difference was observed in the water saturation-surface tension relationship for sands with different particle sizes. As the surface tension decreased, the water saturation decreased to a lowest point and then it increased with further decrease in the surface tension. Both sands reached their lowest water saturations when the surface tension was set approximately at 42 dyne/cm. SEAS was conducted at three different aquifer depths; 41 cm, 81 cm, and 160 cm. Water saturation-surface tension relationship was consistent regardless of the aquifer depth. The size of sparging influence zone during SEAS, measured using two-dimensional model, was found to be similar to the changes in air saturation, measured using one-dimensional model. Considering diverse hydrogeological settings where SEAS to be applied, the results here may provide useful information for designing SEAS process.