• Geomechanics and Engineering
• /
• 제14권3호
• /
• pp.233-240
• /
• 2018

Pullout tests are usually employed to determine the ultimate bearing capacity of reinforced soil, and the load-displacement curve can be obtained easily. This paper presents an analytical solution for predicting the full-range mechanical behavior of a buried planar reinforcement subjected to pullout based on a bi-linear bond-slip model. The full-range behavior consists of three consecutive stages: elastic stage, elastic-plastic stage and debonding stage. For each stage, closed-form solutions for the load-displacement relationship, the interfacial slip distribution, the interfacial shear stress distribution and the axial stress distribution along the planar reinforcement were derived. The ultimate load and the effective bond length were also obtained. Then the analytical model was calibrated and validated against three pullout experimental tests. The predicted load-displacement curves as well as the internal displacement distribution are in closed agreement with test results. Moreover, a parametric study on the effect of anchorage length, reinforcement axial stiffness, interfacial shear stiffness and interfacial shear strength is also presented, providing insights into the pullout behaviour of planar reinforcements of MSE structures.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
• /
• 제4권12호
• /
• pp.399-408
• /
• 2015

직사화기 사격통제장치에서 최적 설계를 위해서는 특정 오차요소가 명중률에 미치는 영향을 파악해야 한다. 이를 위해 가장 좋은 방법은 이들 오차요소에 대한 민감도 식을 구하는 것이나, 체계가 복잡하면 이를 정량적으로 유도하기가 쉽지 않다. 보통 제한된 운용조건에 대해 수치방법으로 민감도를 계산하며, 지상전투차량 등에서 널리 활용되고 있다. 그러나 이 방법은 다량의 시뮬레이션에 의존해야 하므로, 연산 시간이 많이 소요되고 데이터에 의존하므로, 대공화기와 같이 운용조건이 넓게 변화할 경우 민감도가 어떻게 변화할지 직관적으로 이해하는 데 어려움이 있다. 본 논문은 직사화기 탄도에 대한 닫힌 형태 탄도식을 유도하고, 이 식으로부터 오차요소별로 체계 종합오차에 대한 민감도 식을 유도하고, 이들의 영향을 종합하여 명중률을 계산하는 방법을 보인다. 유도된 민감도 식은 수치적분 방법과 달리 연산처리 시간이 짧으면서도 관련 변수 간 물리적 이해가 쉬워 체계설계 시 다양한 운용조건에 대해 편리하게 활용될 수가 있다. 30미리 탄에 대한 시뮬레이션을 통해 본 논문의 유용성을 보인다.

• 한국해양공학회지
• /
• 제36권2호
• /
• pp.101-107
• /
• 2022

Dean (1965) proposed the use of the root mean square error (RMSE) in the dynamic free surface boundary condition (DFSBC) and kinematic free-surface boundary condition (KFSBC) as an error evaluation criterion for wave theories. There are well known wave theories with RMSE more than 1%, such as Airy theory, Stokes theory, Dean's stream function theory, Fenton's theory, and trochodial theory for deep-water waves. However, none of them can be applied for deep-water breaking waves. The purpose of this study is to provide a closed-form solution for deep-water waves with RMSE less than 1% even for breaking waves. This study is based on a previous study (Shin, 2016), and all flow fields were simplified for deep-water waves. For a closed-form solution, all Fourier series coefficients and all related parameters are presented with Newton's polynomials, which were determined by curve fitting data (Shin, 2016). For verification, a wave in Miche's limit was calculated, and, the profiles, velocities, and the accelerations were compared with those of 5^th-order Stokes theory. The results give greater velocities and acceleration than 5^th-order Stokes theory, and the wavelength depends on the wave height. The results satisfy the Laplace equation, bottom boundary condition (BBC), and KFSBC, while Stokes theory satisfies only the Laplace equation and BBC. RMSE in DFSBC less than 7.25×10^-2% was obtained. The series order of the proposed method is three, but the series order of 5^th-order Stokes theory is five. Nevertheless, this study provides less RMSE than 5^th-order Stokes theory. As a result, the method is suitable for offshore structural design.

• 대한조선학회논문집
• /
• 제51권2호
• /
• pp.148-153
• /
• 2014

Submerged bodies such as autonomous underwater vehicles (AUV) or remotely operated vehicles (ROV) are widely used in various fields of exploring underseas. Those bodies keep ballasting and deballasting for stable navigation and operation. Identifying the internal volumetric spaces of the bodies is a primary step for such an operation. Unfortunately, most CAD models given to the engineer do not properly represent the compartments since each face of a compartment exists as an independent entity rather than as a face that belongs to the compartment. In this paper, an algorithm that automatically identify the faces as a group that forms a closed volumetric space, i.e., a compartment is presented. A submerged body is sliced into a number of cross sections. Each sliced section is analyzed to yield closed loops that are sections of the compartment. Then, the associated closed loops are gathered along the longitudinal direction to form a compartment. The algorithm presented is shown to provide a practical and reasonable solution that can readily be used in various applications.

• 한국측량학회지
• /
• 제32권2호
• /
• pp.173-180
• /
• 2014

지심좌표를 측지좌표로 좌표전환하기 위한 방법은 직접해법과 순환해법으로 분류된다. 두 좌표 간의 이상적인 전환조건으로 알고리즘 코딩의 용이성, 전환결과의 정확성 및 처리과정의 신속성이 기본조건이다. 특히, 우주영역은 물론 지구내부영역에서 대상 점의 특정영역(극 부근, 적도면 부근, 지구중심 부근)에 관계없이 전환 해석할 수 있어야 한다. 본 연구는 지심좌표를 측지좌표로 좌표전환하기 위한 좌표전환해법 10종에 대한 좌표전환의 정확성, '특정영역'에서의 적용성을 비교 평가하였다. 연구결과, Vermeille(2011) 및 Karney(2011) 해법이 대상점의 공간적 위치에 관계없이 비교적 양호한 전환결과를 제시하였다.

• 한국CDE학회논문집
• /
• 제7권4호
• /
• pp.219-232
• /
• 2002

In numerically controlled(NC) machining simulation, a Z-map has been used frequently for representing a workpiece. Since the Z-map is usually represented by a set of Z-axis aligned vectors, the machining process can be simulated through calculating the intersection points between the vectors and the surface swept by a machining tool. In this paper, we present an efficient method to calculate those intersection points when an APT-type tool moves along a linear tool path. Each of the intersection points can be expressed as the solution of a system of non-linear equations. We transform this system of equations into a single-variable equation, and calculate the candidate interval in which the unique solution exists. We prove the existence of a solution and its uniqueness in this candidate interval. Based on these characteristics, we can effectively apply numerical methods to finally calculate the solution of the non-linear equations within a given precision. The whole process of NC simulation can be achieved by updating the Z-map properly. Our method can provide more accurate results with a little more processing time, in comparison with the previous closed-form solution.

• 한국시뮬레이션학회논문지
• /
• 제27권1호
• /
• pp.33-38
• /
• 2018

본 연구에서는 선유도 중어뢰의 전술 효과도 예측을 위하여 개발한 교전수준 시뮬레이터에 대해서 시뮬레이터 개발에 적용된 개념 및 구성요소 모델에 대해서 소개하고 있다. 특히 어뢰의 공격문제 해결을 위하여 기하학적 모델에 따른 해(Closed-form solution)를 도출하였고, 어뢰의 공격유도 방법에 비례항법 유도를 적용하여 구현하였다. 표적함에 대해서는 속도와 소음의 상충관계로 인한 피탐 가능성을 고려하였다. 어뢰의 초기위치에 따른 공격 소요 시간을 계산하고 이를 도시화하는 과정을 통하여 도출된 해의 정확성을 확인 할 수 있었고, 현실적인 공격유도 방법 및 소음원 모사를 통하여 시뮬레이터 충실도를 높일 수 있었다. 시뮬레이터는 다양한 전술상황을 가정하여 결과를 분석 할 수 있도록 자유도가 높게 개발되었으며, 구성요소 궤적 분석 및 전방위 요격 성공률 분석이 가능하여 전장 상황의 흐름을 파악하고 전술에 대한 이해를 높이는데 도움이 된다.

• 대한기계학회논문집B
• /
• 제24권3호
• /
• pp.426-434
• /
• 2000

This paper deals with a generalized similarity solution for the one-dimensional solidification of ternary or higher-order multicomponent alloys. The present approach not only retains the existing features of binary systems such as temperature- solute coupling, shrinkage-induced flow, solid-liquid property differences, and finite back diffusion, but also is capable of handling a multicomponent alloy without restrictions on the partition coefficient and microsegregation parameter. For an alloy of N-solute species, governing equations in the mushy region reduce to (N+2) nonlinear ordinary differential equations via similarity transformation, which are to be solved along with the closed-form solutions for the solid and liquid regions. A linearized correction scheme adopted in the solution procedure facilitates to determine the solidus and liquidus positions stably. The result for a sample ternary alloy agrees excellently with the numerical prediction as well as the reported similarity solution. Additional calculations are also presented to show the utility of this study. Finally, it is concluded that the present analysis includes the previous analytical approaches as subsets.

• 대한기계학회논문집
• /
• 제18권7호
• /
• pp.1632-1642
• /
• 1994

The Stewart Platform is a six-degree-of-freedom in-parallel-actuated manipiulator mechanism. The kinematic behavior of parallel mechanisms shows inverse characteristics as compared that of serial mechanisms; i.e, the inverse kinematic problem of Stewart Platform is straightforward, but no closed form solution of the forward kinematic problem has been previously presented. Thus it is difficult to calculate the 6 DOF displacement of the platform from the measured lengths of the six actuators in real time. Here, a real-time estimation algorithm which solves the Stewart Platform kinematic problem is proposed and tested through computer simulations and experiments. The proposed algorithm shows stable convergence characteristics, no estimation errors in steady state and good estimation performance with higher sampling rate. In experiments it is shown that the estimation result is the same as that of simulation even in the presence of measurement noise.

• Structural Engineering and Mechanics
• /
• 제42권3호
• /
• pp.313-334
• /
• 2012

This paper examines the problem of a penny-shaped crack in a thermoporoelastic body. On the basis of the recently developed general solutions for thermoporoelasticity, appropriate potentials are suggested and the governing equations are solved in view of the similarity to those for pure elasticity. Exact and closed form fundamental solutions are expressed in terms of elementary functions. The singularity behavior is then discussed. The present solutions are compared with those in literature and an excellent agreement is achieved. Numerical calculations are performed to show the influence of the material parameters upon the distribution of the thermoporoelastic field. Due to its ideal property, the present solution is a natural benchmark to various numerical codes and simplified analyses.