• Journal of the Korean Geotechnical Society
• /
• v.20 no.1
• /
• pp.61-73
• /
• 2004

Rayleigh wave and Love wave are the major elastic waves belonging to the category of the surface wave. The fact that Love wave is not contaminated by P-wave makes Love wave superior to Rayleish wave and other body waves. Therefore, the information that Love wave carries is more distinct and clearer than the information of Rayleigh wave. In this study, for the purpose of employing Love wave in the SASW method, the dispersion characteristics of the Love wave were extensively investigated by the theoretical, numerical and experimental approaches. The 2-D and 3-D finite element analyses for the half space and two-layer systems were performed to determine the phase velocities from Love wave as well as from both the vertical and the horizontal components of Rayleigh wave. Also, the SASW measurements were performed at the geotechnical sites to verify the results obtained by the numerical analysis. The results of the numerical analysis and the field testing indicated that the dispersion characteristics of Love wave can be an extended information to make better evaluation of the subsurface stiffness structure by SASW method.

• Magazine of the Korea Concrete Institute
• /
• v.7 no.5
• /
• pp.172-178
• /
• 1995

Concrete contains numerous microcracks at initially poured. The growth and propagation of nicrockacsk are believed tc finally incur the faiure of concrete. These processings are understood as a damage. Damage IS represented as a second-order tensor and crack is treated as a con tinuum phenomenon. In this paper, damage is characterized through the effective stress concept together with the hypothesis of elastic energy equivalence, and damage evolution law and constitutive equation of a damage model are derived by using the Helmholtz frte eriergy and the dissipation potential by means of the thermodynamic principles. The constitutive equation of the model includes the effects of elasticity, anisotropic damage and plasticity of concrete. There are two effective tangent stiffness tensors in this model : one is for elastic-darnage and the other for plastic damage. For the verification of the model, finite element analysis was performed for the analysis of concrete subjec:t to uniaxial and biaxial loading and the results obtained were compared with test results.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.1C
• /
• pp.131-139
• /
• 2008

This paper presents a scalable dual-field Montgomery multiplier based on a new multi-precision carry save adder(MP-CSA), which operates in both types of finite fields GF(p) and GF($2^m$). The new MP-CSA consists of two carry save adders(CSA). Each CSA is composed of n = [w/b] carry propagation adders(CPA) for a modular multiplication with w-bit words, where b is the number of dual field adders(DFA) in a CPA. The proposed Montgomery multiplier has roughly the same timing complexity compared with the previous result, however, it has the advantage of reduced chip area requirements. In addition, the proposed circuit produces the exact modular multiplication result at the end of operation unlike the previous architecture. Furthermore, the proposed Montgomery multiplier has a high scalability in terms of w and m. Therefore, it can be used to multiplier over GF(p) and GF($2^m$) for cryptographic applications.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.8 no.11
• /
• pp.1749-1754
• /
• 2013

Binary sequences of period $2^n-1$ are widely used in many areas of engineering and sciences. Some well-known applications include coding theory, code-division multiple-access (CDMA) communications, and stream cipher systems. In this paper we analyze different solutions to $x^5+bx^3+b^{2^m}x^2+1=0$ over $GF(2^n)$. The number of different solutions determines frequencies of cross-correlations of nonlinear binary sequences generated by $d=3{\cdot}2^m-2$, n=2m, m=4k($k{\geq}2$). Also we give an algorithm for determination of number of different solutions to the equation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.1
• /
• pp.195-201
• /
• 2006

The wave load and its influence on the response of offshore structure have been well investigated through the statistical approach based on the linear theory. The linear approach has a limitation to apply the extreme condition such as freak wave, which corresponds to extreme value of wave spectrum. The main topic of present study is to develop an efficient numerical method to predict wave load induced by extreme wave. As a numerical method, finite element method based on variational principle is adopted. The frequency-focusing method is applied to generate the extreme wave in the numerical wave tank. The wave load on the bottom mounted vertical cylinder is investigated. The hydroelastic response of the vertical cylinder is also investigated so as to compare the wave loads with the rigid body case in the extreme wave condition.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.3
• /
• pp.609-616
• /
• 2014

Large linear span makes difficult to predict, so this study is important to the security and code system. It has been studied about the non-linear binary sequences having low correlation values and large linear span. In this paper we analyze the linear span of $S^r_a(t)=Tr^m_1\{[Tr^n_m(a{\alpha}^t+{\alpha}^{dt})]^r\}$ ($a{\in}GF(2^m)$, $0{\leq}t{\leq}2^m-2$) where n=2m and $d=2^{m-2}(2^m+3)$.

• The KIPS Transactions:PartC
• /
• v.15C no.2
• /
• pp.133-140
• /
• 2008

In this paper, we propose a high performance elliptic curve cryptographic processor over $GF(2^{163})$. The proposed architecture is based on a modified Lopez-Dahab elliptic curve point multiplication algorithm and uses Gaussian normal basis for $GF(2^{163})$ field arithmetic. To achieve a high throughput rates, we design two new word-level arithmetic units over $GF(2^{163})$ and derive a parallelized elliptic curve point doubling and point addition algorithm with uniform addressing based on the Lopez-Dahab method. We implement our design using Xilinx XC4VLX80 FPGA device which uses 24,263 slices and has a maximum frequency of 143MHz. Our design is roughly 4.8 times faster with 2 times increased hardware complexity compared with the previous hardware implementation proposed by Shu. et. al. Therefore, the proposed elliptic curve cryptographic processor is well suited to elliptic curve cryptosystems requiring high throughput rates such as network processors and web servers.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.5 no.4
• /
• pp.227-233
• /
• 2001

최근 비약적인 경제발전에 힘입어 장대교량, 항만, 댐, 도로, 원자력 발전소 등과 같은 대규모 기간구조물의 건설이 증가하고 있으며, 구조물은 대형화 혹은 고강도화되는 추세에 있다. 특히, 전술한 구조물을 매스콘크리트로 가설하게 되면 초기재령시에 수화열로 인한 균열이 발생할 가능성이 매우 높기 때문에 효율적인 매스콘크리트의 개발과 매스콘크리트 구조물의 설계기술 및 시공방법이 중요한 연구대상으로 등장하게 된다. 본 논문에서는 가로 52.6m, 세로 14.4m, 높이 8.5m의 기계기초 매스콘크리트의 시공에 적합한 온도관리기법을 다음과 같은 단계로 제안하고자 한다. 먼저 온도상승요인을 최소화하는 콘크리트의 배합비를 산정한다. 산정된 콘크리트의 열특성을 측정하기 위해 단열온도실험을 수행하여 각종 열특성상수와 단열온도 상승곡선식을 도출한다. 이와 같은 열특성치를 콘크리트 구조체에 적용하여 열응력해석을 수행한다. 이와 같은 열응력해석을 통하여 구조물의 분할타설높이에 따라 온도균열이 발생하지 않는 콘크리트 내외부의 온도차를 결정한다. 이때 열응력해석에 범용 유한요소 프로그램인 Diana을 사용한다. 콘크리트의 타설은 현장조건과 타설시점을 최대로 고려하고 양생방법으로 콘크리트 내외부의 온도차를 최소화하기 위해 이중단열효과가 있는 거푸집과 가열장비을 사용한다. 또한 콘크리트의 온도관리를 위하여 구조물 내외부에 온도게이지를 매립하고 30분마다 계측을 수행하면서 콘크리트 내외부 온도차가 허용 해석범위를 유지하도록 한다. 양생기간은 7-10일 정도를 유지한다. 전술한 온도관리기법을 통하여 완공후 수평정밀도가 기초의 허용침하량으로 환산하여 $1{\mu}m$ 인 고정밀도의 기계기초는 완벽하게 시공되었다. 따라서 매스콘크리트의 온도균열을 제어할 수 있는 시공방법으로 제안한다. 또한 매스콘크리트의 내외부 온도차를 단열온도실험과 온도해석으로부터 정한 값이내로 제어하고 충분한 양생관리를 병행하면 수화열에 의한 콘크리트의 온도균열을 최소화할 수 있을 것으로 기대한다.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2003.04a
• /
• pp.59-59
• /
• 2003

경사기능 재료는 위치에 따른 특성 변화를 갖고 있어 변화하는 주변 환경에서 사용되는 재료의 응용성을 높일 수 있는 장점이 있다. 적합한 경사기능 재료의 제조를 위해서는 탄성률, 강도, 인성 등의 위치에 따른 변화를 예측하는 것이 필요하다. 그러나 재료 내에서의 탄성률 변화 등으로 인해 경사기능 재료에서 인성을 정량적으로 표현하는데는 어려움이 있으므로 이를 정량적으로 측정하고, R-curve를 결정하는 것은 재료의 응용성에 중요한 인자가 된다. 본 연구에서는 폴리우레탄 스폰지를 이용하여 밀도의 분포가 연속적으로 다른 폴리 우레탄 스폰지를 제조하고 이에 알루미나 분말 슬러리를 이용하여 slip casting을 행하였다. 그 후 폴리 우레탄 스폰지를 탈지한 후 알루미나 성형체를 소결하여 연속적인 기공률 분포가 다른 다공성 알루미나를 제조하였으며, 이에 Al을 용침하여 $Al_2O_3-Al$ 경사기능 재료를 제조하였다. 이러한 $Al_2O_3-Al$ 경사기능 재료에 대해 파괴인성 및 R-curve 특성을 CT(conpact tension)시편으로 측정하였으며, 이를 균일한 복합체의 파괴인성과 비교하였다. 또한 잔류 응력 특성을 파악하기 위해 실험적이 응력 데이터를 Moire interferometry를 이용하여 결정하였다. 또한 이를 유한요서 해석법(FEM)에 의한 계산치와 비교하였다. 서로 다른 조성 분포를 갖는 $Al_2O_3-Al$ 경사기능 재료와 균일한 복합체의 파괴인성을 비교한 결과 동일한 Al조성에서도 서로 다른 파괴 인성치가 나타났다. $Al_2O_3-Al$ 경사기능 재료에서 파괴인성에 영향을 줄 수 있는 인자로는 술수한 $Al_2O_3$의 파괴인성에 Al금속의 소성변형에 의한 인성증진 효과, 그리고 경사기능 재료에서 상호 조성차이에 따른 잔류응력을 고려할 수 있을 것이다. 이중 $Al_2O_3-Al$ 경사기능 재료의 파괴인성에 미치는 잔류응력의 영향을 고려하기 위해 이의 잔류응력에 대해 실험에 의한 유추된 잔류응력과 FEM계산에 의해 유추된 잔류 응력을 비교, 분석하였다.

• The Journal of Engineering Geology
• /
• v.14 no.1
• /
• pp.21-28
• /
• 2004

Three-dimensional (3-D) resistivity inversion including a topographic effect can be considered theoretically to be the technique of acquiring the most accurate image in the interpretation of resistivity data, because it includes characteristic image that the actual subsurface structure is 3-D. In this study, a finite-element method was used as the numerical method in modeling, and the efficiency of Jacobian calculation has been maximized with sensitivity analysis for the destination block in inversion process. Also, during the iterative inversion, the resolution of inversion can be improved with the method of selecting the optimal value of Lagrange multiplier yielding minimum RMS(root mean square) error in the parabolic equation. In this paper, we present synthetic examples to compare the difference between the case which has the toprographic effect and the other case which has not the effect in the inversion process.