• 한국CDE학회논문집
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• 제3권2호
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• pp.127-134
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• 1998

This paper presents d new algorithm to compute the offlet curve of a given planar parametric curve. We reduce the problem of computing an offset curve to that of intersecting a surface to a paraboloid. Given an input curve C(t)=(x(t), y(t))∈R², the corresponding surface D/sub c(t)/ is constructed symbolically as the envelope surface of a one-parameter family of tangent planes of the paraboloid Q:z=x²+y²along a lifted curve C(t)=(x(t), y(t), x(t)²+y(t)²∈Q. Given an offset distance d∈R, the offset curve C/sub d/(t) is obtained by the projection of the intersection curve of D/sub c(t)/ and a paraboloid Q:z=x²+y²-d² into the xy-plane.

• Nuclear Engineering and Technology
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• 제19권3호
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• pp.169-179
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• 1987

소형시험편(1/2"T)을 이용, 균열진전량 및 J계산식에 따른 재료의 J-R (J-T) 곡선의 변화를 조사하여 신뢰성있는 J-R(J-T) 곡선을 구하기 위한 실험 및 해석방법을 고찰하였다. 시험은 국내 원자력발전소 압력용기감시 시험에 포함되어 있는 파괴인성시편과 꼭같이 SA 533 Grade 3, Class1 재료로 제작한 1/2"T, C-T 시편을 이용, Single Specimen Unloading Compliance Technique으로 수행하였다. 시험 및 해석결과 Ernst의 Deformation theory J (JD)식을 이용하여 초기 Uncracked ligament (be)의 25～30%까지 균열을 진전시켜 구한 J-R(J-T) 곡선이 대형시편의 결과와 가장 유사한 값을 나타내었다. 한편 Ernst의 Modified J (JM)식에 의한 J-R (J-T) 곡선은 Deformation theory J(JD)에 의한 J-R(J-T) 곡선보다 다소 높은 Instability 예측점을 얻을 수 있기 때문에 실제 압력용기 안전성 해석시에는 가동률향상 및 수명연장 측면에서 Modified J의 사용은 고려되어야 할 것이다.되어야 할 것이다.

• 대한수학회지
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• 제56권5호
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• pp.1355-1370
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• 2019

A curve $X{\subset}\mathbb{P}^r$ has maximal rank if for each $t{\in}\mathbb{N}$ the restriction map $H^0(\mathcal{O}_{\mathbb{P}r}(t)){\rightarrow}H^0(\mathcal{O}_X(t))$ is either injective or surjective. We show that for all integers $d{\geq}r+1$ there are maximal rank, but not arithmetically Cohen-Macaulay, smooth curves $X{\subset}\mathbb{P}^r$ with degree d and genus roughly $d^2/2r$, contrary to the case r = 3, where it was proved that their genus growths at most like $d^{3/2}$ (A. Dolcetti). Nevertheless there is a sector of large genera g, roughly between $d^2/(2r+2)$ and $d^2/2r$, where we prove the existence of smooth curves (even aCM ones) with degree d and genus g, but the only integral and non-degenerate maximal rank curves with degree d and arithmetic genus g are the aCM ones. For some (d, g, r) with high g we prove the existence of reducible non-degenerate maximal rank and non aCM curves $X{\subset}\mathbb{P}^r$ with degree d and arithmetic genus g, while (d, g, r) is not realized by non-degenerate maximal rank and non aCM integral curves.

• 한국철도학회논문집
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• 제12권2호
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• pp.199-204
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• 2009

본 연구에서는 곡선부 선로선형의 최적설계를 위해 신선건설 및 기존선 개량시 지장물의 위치에 따른 곡선반경(R)-완화곡선장$(L_t)$의 적정 범위를 간단히 결정할 수 있는 기법을 제시하였다. 또한 이를 이용하여 간단히 계산할 수 있는 프로그램을 개발하였으며 실제 예를 통한 해석을 수행하여 경우별 곡선반경-완화곡선장의 경계조건에 대한 비교 분석을 수행하였다. 본 해석기법은 곡선상 지장물의 위치에 따른 최적 $R-L_t$를 산정할 수 있으며, 경계조건의 허용범위 내에서 $R-L_t$의 범위를 조정한다면, 향후 신선 및 개량설계시 지장물 이설에 따른 높은 비용의 절감이 가능하다.

• 한국해양공학회지
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• 제12권3호통권29호
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• pp.60-67
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• 1998

In this study, the J-Resistance Curve and material tearing modulus of SA508-C3 steel, which is one of the used nuclear pressure vessel steel, are measured ar room temperature, $200^{circ}C$ and $300^{circ}C$ according to load ratio analysis and ASTM E813, ASTM E1152, respectively. It is observed that J-R curve and Tmat value decrease as the temperature level increase. Applicability of $T_j$ proposed by Paris et al as instability parameter for ductile material is investigated. It is concluded that results are the $T_j$ parameter may be used as a crack instability parameter.

• 대한기계학회논문집A
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• 제24권3호
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• pp.794-802
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• 2000

Since the examination of CTOD problem revealed that the discrepancy among CTOD's was a matte., of definition, the relationships among parameters based on different definitions have been studied Particularly, the relationship between $\sigma$BS R-curve based on BS 7448 and R-curve based on the recently introduced $\sigma$5 parameter was investigated in this research. For the comparison, compact tension specimens of used 1Cr-0.5Mo steel, heat treated 1Cr-0.5Mo steel to mimic the new one, A12024-T6, and A12024-T351 were prepared and tested. Consequently, the relationship between $\sigma$5 and $\sigma$BS R-curves for tested materials were established by shifting the rotational center which could determined by rotation factor and ligament size.

• 사물인터넷융복합논문지
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• 제6권2호
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• pp.25-29
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• 2020

타원곡선 암호 알고리즘은 RSA 공개키 알고리즘에 비해 짧은 키의 길이와 적은 통신 부하 때문에 IoT 환경에서 인증용으로 많이 사용되고 있다. 타원곡선 암호 알고리즘의 핵심연산인 스칼라 곱셈이 안전하게 구현되지 않으면, 공격자가 단순 전력분석이나 차분 전력분석을 사용하여 비밀 키를 찾을 수 있다. 본 논문에서는 스칼라 난수화와 타원곡선점 가리기를 함께 적용하고, 연산의 효율성이 크게 떨어지지 않으며 전력분석 공격법에 대응하는 결합 난수 타원곡선 스칼라 알고리즘을 제안한다. 난수 r과 랜덤 타원곡선 점 R에 대해 변형된 Shamir의 두 배 사다리 알고리즘을 사용하여 타원곡선 스칼라 곱셈 kP = u(P+R)-vR을 계산한다. 여기에서 위수 n=2^l±c일 때, 2^lP=∓cP를 이용하여 l+20 비트 정도의 u≡rn+k(modn)과 ν≡rn-k(modn)를 구한다.

• Tribology and Lubricants
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• 제14권4호
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• pp.114-120
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• 1998

The T-curve, wear and erosion behaviors of two different silicon carbides, i.e., the fine grained SiC and the in situ-toughened SiC(IST-SiC). Both materials exhibited an increasing T-curve behavior, although the T-curve of IST-SiC was steeper than that of fine grained SiC. The fracture toughness of IST-SiC was larger than that of fine grained SiC at long crack regime, whereas an opposite tendency occurred at short crack regime. The rate of material removal during wear and erosion tests was higher in IST-SiC compared to fine grained SiC. The difference between the material removal rates of two materials was discussed in the light of their R-curve behaviors.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.3-46
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• 1999

A new method called SRICOS is proposed to predict the scour depth z versus time t around a cylindrical bridge pier of diameter D founded in clay. The steps involved are ; 1. taking samples at the bridge pier site, 2. testing them in an Erosion Function Apparatus called the EFA to obtain the scour rate z versus the hydraulic shear stress applied $\tau$, 3. predicting the maximum shear stress r max which will be induced around the pier by the water flowing at ν Ο before the scour hole starts to develop, 4. using the measured z versus r curve to obtain the initial scour rate zi corresponding to r max , 5. predicting the maximum depth of scour zmax for the pier, 6. using zi and zmarx to develop the hyperbolic function describing the scour depth z versus time t curve, and 7. reading the z vs. t curve at a time corresponding to the duration of the flood to find the scour depth which will develop around the pier. A new apparatus is developed to measure the z vs t curve of step 2, a series of advanced numerical simulations are performed to develop an equation for the $\tau$ max value of step 3, and a series of flume tests are performed to develop an equation for the zmax value of step 5. The method is evaluated by comparing predictions and measurements in 42 flume experiments.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.100-105
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• 2003

With the recent development of machining technology, high speed machining process is widely used for-the mold and difficult-to -cut-materials machining since it allows achieving high productivity and surface quality. However, during the high speed machining process, high cutting speed and feed rate can cause abrupt tool life decrease due to rapid rising of the cutting tool temperature. Such situation may cause increase of machining cost. Thus, in this study, developed optimization algorithm is applied to determine optimal machining variables for multiple high speed machining. The R-T characteristic curve for machining economics problems with a linear-lorarithmic tool life model is determined by applying sensitivity analysis. finally, a series of high speed machining experiments are performed to determine the desired optimal machining variables, and the results are analyzed.