• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.477-486
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• 2009

This paper deals with the strongest static arches with the solid regular polygon cross-section. Both span length and volume of arch are always held constant regardless the shape functions of cross-sectional depth of regular polygon. The normal stresses acting on such arches are calculated when both static vertical and horizontal point loads are subjected. By using the calculating results of stresses, the optimal shapes of strongest static arches are obtained, under which the maximum normal stress become to be minimum. For determining the redundant of such indeterminate arches, the least work theorem is adopted. As the numerical results, the configurations, i.e. section ratios, of the strongest static arches are reported in tables and figures. The results of this study can be utilized in the field of the minimum weight design of the arch structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.4
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• pp.133-138
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• 1987

The precise methods applied to adjust plane trilateration nets employ least squares techniques. The observations or the condition equations in these known methods are, without exception, nonlinear. The coefficients of the corrections in the conditions equations methods are lengthy and complicated. This paper presents a new method in which the coefficiets of the corrections of the conditions are simple and can be easily calculated and checked. In this method the measured distances in trilateration nets are considered as elastic members in an internally redundant framework. If the redundant members have measuring errors, axial forces must be applied to fit them in the framework. As a result axial forces will develop in all other members causing changes in their lengths. By applying minimum work techniques one can determine these changes in length which are in fact the required corrections of the measured distances. The result of this study presents that the closing ratio is about 1/145000 and it is improved that this method is useful in analysis plane trilateration nets.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.436-438
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• 2003

Ad hoc Network에서 효율적인 데이터 트래픽의 전송을 위하여 AODV 라우팅 알고리즘을 보안한 DM-AODV(Disjoint Multipath AODV)와 이를 활용하여 Qos율 높인 트래픽 분산 알고리즘인 TPA(Traffic Partitioning Algorithm)을 제안한다. 첫째, dynamic한 Ad hoc network환경에서 사용될 수 있는 DM-AODV을 사용하여 중복 노드가 없는 multipath들과 그 경로 각각의 최소 대역폭(bandwidth)을 구하고 둘째, 소스 노드에 들어오는 트래픽의 요구 대역폭과 TPA을 사용하여, 네트워크가 정상 일 때 전달 될 main path들과 네트워크 장애 시 할당 될 alternative path들에 들어오는 트래픽을 dynamic하게 분산시킴으로써 어플리케이션이 요구하는 높은 대역폭의 트래픽 수용 가능성을 높이고, 들어오는 트래픽의 안정적인 대역폭 보장과 속도의 향상, 폭주(congestion)의 감소 효과를 나타낸다. 또한 Main path에 장애 발생시, 미리 계산된 alternative Path에 트래픽을 전송함으로서 들어오는 패킷의 손실을 최소한으로 한다. 본 논문에서는 Ad hoc network에서의 QoS를 높이는 두 알고리즘을 소개하고, 동작 원리를 알아본다.

• Journal for History of Mathematics
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• v.19 no.1
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• pp.65-78
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• 2006

The law of refraction, which is called Snell's law in physics, has a significant meaning in mathematics history. After Snell empirically discovered the refraction law $\frac{v_1}{sin{\theta}_1}=\frac{v_2}{sin{\theta}_2$ through countless observations, many mathematicians endeavored to deduce it from the least time principle, and the need to surmount these difficulties was one of the driving forces behind the early development of calculus by Leibniz. Fermat solved it far advance of others by inventing a method that eventually led to the differential calculus. Historically, mathematics has developed in close connection with physics. Physics needs mathematics as an auxiliary discipline, but physics can also belong to the lived-through reality from which mathematics is provided with subject matters and suggestions. The refraction law is a suggestive example of interrelations between mathematical and physical theories. Freudenthal said that a purpose of mathematics education is to learn how to apply mathematics as well as to learn ready-made mathematics. I think that the refraction law could be a relevant content for this purpose. It is pedagogically sound to start in high school with a quasi-empirical approach to refraction. In college, mathematics and physics majors can study diverse mathematical proof including Fermat's original method in the context of discussing the phenomenon of refraction of light. This would be a ideal environment for such pursuit.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.1
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• pp.41-47
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• 2024

This paper utilizes computational asymptotic analysis to compute the boundary layer solution for composite beams and validates the findings through a comparison with ANSYS results. The boundary layer solution, presented as a sum of the interior solution and pure boundary layer effects, necessitates a mathematically rigorous formalization for both interior and boundary layer aspects. Computational asymptotic analysis emerges as a robust technique for addressing such problems. However, the challenge lies in connecting the boundary layer and interior solutions. In this study, we systematically separate the principles of virtual work and the principles of Saint-Venant to tackle internal and boundary layer issues. The boundary layer solution is articulated by calculating the Papkovich-Fadle eigenfunctions, representing them as linear combinations of real and imaginary vectors. To address warping functions in the interior solutions, we employed a least squares method. The computed solutions exhibit excellent agreement with 2D finite element analysis results, both quantitatively and qualitatively. This validates the effectiveness and accuracy of the proposed approach in capturing the behavior of composite beams.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.423-434
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• 2001

In this paper, a three-span continuous box girder is analysed by using elastic equation based on energy method, concerning the behaviour with the effects of bending and pure torsional moment. The statically indeterminate forces of a three-span continuous curved box girder are calculated by applying the principle of least work to this elastic equation. The influence line of shear force, bending moment, pure torsion, displacement and angle of rotation due to unit vortical load and unit torque for curved box girder are obtained. The internal forces of the curved box girder which the actual load is applied can be calculated using the influence line obtained from this study.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.5
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• pp.497-502
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• 2015

In this paper, a stress function-based approach was proposed to analyze the reduction of free-edge peeling stress in smart composite laminates using piezoelectric actuator under bending load. Electro-mechanically coupled governing equation was obtained by complimentary virtual work principle. The stress state was solved by the generalized eigenvalue procedure. The free-edge peeling stress of smart composite laminates was reduced by the piezoelectric actuation. The reduction rate of peeling stress in cross-ply composite laminate is larger than that in angle ply composite laminate.

• Korean Journal of Soil Science and Fertilizer
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• v.36 no.4
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• pp.181-192
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• 2003

We developed a mathematical simulation model to portray the vertical distribution of soil water from the measured weather data and the known soil hydraulic properties, and then compared simulation results with the periodically measured soil water profiles obtained on Jungdong sandy loam to verify the model, In this model, we solved potential-based Richards' equation by the implicit finite difference method superimposed on the predictor-corrector scheme. We presumed that: soil hydraulic properties are homogeneous; soil water flows isothermally; hysteresis is not considered; no vapor flows; no heat transfers into the soil profiles; and water added to soil surface is distributed along the soil profile following partial displacement principle. The input data were broadly classified into two groups: (1) daily weather data such as rainfall, maximum and minimum air temperatures, relative humidity and solar radiation and (2) soil hydraulic data to approximate unsaturated hydraulic conductivity and water retention. Each hydraulic polynomial function approximated using the Chebyshev polynomial and least square difference technique in tandem showed a fairly good fit of the given set of data. Vertical distribution of soil water as approximations to the Richards' equation subject to changing surface and phreatic boundaries was solved numerically during 53 days with a comparatively large time increment, and this pattern agreed well with field neutron scattering data, except for the surface 0.1 m slab.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2007.02a
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• pp.13-17
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• 2007

스케일러블 비디오 코딩(SVC, Scalable Video Coding)은 MPEG(Moving Picture Expert Group)과 VCEG (Video Coding Expert Group)의 JVT(Joint VIdeo Team)에 의해 현재 표준화 되고 있는 새로운 압축 표준 기술이며 시간, 공간 및 화질의 스케일러빌리티를 지원하기 위해 계층 구조를 가지고 있다. 공간적 스케일러빌리티를 위해 기본 계층으로부터 텍스처, 움직임 그리고 잔차신호 정보를 예측하여 사용한다. 그러나 고효율의 압축효과를 얻기 위해 기존의 방식에서는 기본계층에서 얻은 세가지 정보이외에 현재 향상 계층에서 자체적으로 얻은 부호화 정보를 비교하여 최소의 RD(Rate Distortion) 비용을 가지는 정보를 이용하여 부호화 하도록 되어 있다. 하지만 이러한 방식은 향상 계층에서 인터 모드 결정 시 $16\times16,\;16\times8,\;8\times16,\;8\times8,\;4\times4,\;4\times8,\;4\times4$ 블록 모드에 대한 움직임 벡터 예측 및 보상 과정을 거쳐야 하기 때문에 향상 계층에서의 부호화 복잡도는 기본 계층에 비해 상당히 증가하게 된다. 본 논문에서는 기본계층에서 예측한 움직임 벡터 정보를 이용하여 항상 계층에서 모드 결정을 고속화하는 방법에 대해 소개한다. 제안된 방법은 기본 계층에서 예측한 블록모드 중에서 큰 블록인 $16\times16$ 블록에서 움직임 벡터가 (0, 0) 일 경우에 대하여 향상 계층에서는 $16\times16$매크로 블록에 대해서만 움직임 예측 및 보상을 수행함으로써 향상 계층에서 움직임 모드 결정을 조기에 완료하게 된다. 이것은 하위 공간 계층에서 예측한 움직임 벡터 정보가 아주 작을 때는 큰 블록 크기로 모드로 결정되는 일반적인 원리를 이용한 것이고 이 제안 방법을 이용하였을 경우 향상계층에의 모드 결정과정을 고속화함으로써 전체 스케일러빌 비디오 부호하기의 연산량 및 복잡도를 최대 70%까지 감소 시켰다. 그러나 연산량 감소에 따른 비트율의 증가와 화질 열화는 각각 최대 1.32%와 최대 0.11dB로 무시할 수 있을 정도로 작음을 확인 하였다.

• Journal of the Korea Society of Computer and Information
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• v.26 no.11
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• pp.233-236
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• 2021

Recently, the Justice Party is pushing for legislation of a bill called the Algorithm Transparency Act. The bill is a revision to the Information and Communication Network Act proposed by Rep. Ryu Ho-jung on June 25, 2021, and aims to form a separate committee under the Korea Communications Commission to ask organizations operated for profit to search algorithms and explain the principles of arrangement. Currently, Korea treats algorithms as corporate secrets and does not disclose them, while the European Union (EU) implements the Personal Information Protection Regulations (GDPR) in relation to algorithm regulations. Therefore, this study summarizes the main contents of the Algorithm Transparency Act currently proposed to the National Assembly and reviews the current status of algorithm-related laws and systems in the European Union (EU) and the improvement of algorithm transparency.