• Title, Summary, Keyword: Constraint

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RDBMS based Topic Map Constraint Checking Mechanism (RDBMS 기반의 토픽맵 무결성 검사 기법)

  • Lee, Han-Jun;Min, Kyung-Sub;Kim, Hyoung-Joo
    • Journal of KIISE:Databases
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    • v.34 no.6
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    • pp.493-502
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    • 2007
  • Due to a growing interest in searching and expressing knowledge effectively, knowledge management methods such as Topic Map are becoming more important. Topic Map organizes knowledge that is full of intricate relations, so maintaining and managing Topic Map consistently is very essential. TMCL and other constraint languages have limits as they can check simple constraints but can not support complex constraints like dependence constraints. Current constraint checking systems operating at the application level are also showing an inferiority in performance. In this paper, we extend TMCL based on the characteristics of other constraint languages in the information system field and related fields. We build and propose an RDBMS-based Topic Map constraint checking system to support the extended constraint language effectively. This new system handles complex types of constraints like dependency constraint as well as basic Topic Map constraints present in the TMCL. As the system examines each constraint it uses templates to generate queries for effective checking and overall shows a higher performance level than current systems.

A Study on the Geometric Constraint Solving with Graph Analysis and Reduction (그래프의 분석과 병합을 이용한 기하학적제약조건 해결에 관한 연구)

  • 권오환;이규열;이재열
    • Korean Journal of Computational Design and Engineering
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    • v.6 no.2
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    • pp.78-88
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    • 2001
  • In order to adopt feature-based parametric modeling, CAD/CAM applications must have a geometric constraint solver that can handle a large set of geometric configurations efficiently and robustly. In this paper, we describe a graph constructive approach to solving geometric constraint problems. Usually, a graph constructive approach is efficient, however it has its limitation in scope; it cannot handle ruler-and-compass non-constructible configurations and under-constrained problems. To overcome these limitations. we propose an algorithm that isolates ruler-and-compass non-constructible configurations from ruler-and-compass constructible configurations and applies numerical calculation methods to solve them separately. This separation can maximize the efficiency and robustness of a geometric constraint solver. Moreover, the solver can handle under-constrained problems by classifying under-constrained subgraphs to simplified cases by applying classification rules. Then, it decides the calculating sequence of geometric entities in each classified case and calculates geometric entities by adding appropriate assumptions or constraints. By extending the clustering types and defining several rules, the proposed approach can overcome limitations of previous graph constructive approaches which makes it possible to develop an efficient and robust geometric constraint solver.

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On Implementing a Hybrid Solver from Constraint Programming and Optimization (제약식프로그래밍과 최적화를 이용한 하이브리드 솔버의 구현)

  • Kim, Hak-Jin
    • Information Systems Review
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    • v.5 no.2
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    • pp.203-217
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    • 2003
  • Constraint Programming and Optimization have developed in different fields to solve common problems in real world. In particular, constraint propagation and linear Programming are their own fundamental and complementary techniques with the potential for integration to benefit each other. This intersection has evoked the efforts to combine both for a solution method to combinatorial optimization problems. Attempts to combine them have mainly focused on incorporating either technique into the framework of the other with traditional models left intact. This paper argues that integrating both techniques into an old modeling fame loses advantages from another and the integration should be molded in a new framework to be able to exploit advantages from both. The paper propose a declarative modeling framework in which the structure of the constraints indicates how constraint programming and optimization solvers can interact to solve problems.

A Study on the Fracture Behavior of a Crack in Gas Pipelines Considering Constraint Effects (구속효과를 고려한 가스배관 결함의 파괴거동해석)

  • Shim, Do-Jun;Choi, Jae-Boong;Kim, Young-Jin
    • Proceedings of the KSME Conference
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    • pp.1-6
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    • 2000
  • FFP(Fitness For Purpose) type defect assessment methodologies based on ECA(Engineering Critical Analysis) have been established and are in use for the structural integrity evaluation of gas pipelines. ECA usually includes the fracture mechanics analysis, and it assumes that J-integral uniquely characterizes crack-tip stress-strain fields. However, it has been shown that it is not sufficient to characterize the crack-tip field under low levels of constraint with a single parameter. Since pipeline structures are made of ductile material, locally loaded in tension, cracks may experience low level of constraint, and therefore, J-dominance will be lost. For this reason, the level of constraint must be quantified to establish a precise assessment procedure for pipeline defects. The objective of this paper is to Investigate the fracture behavior of a crack in gas pipeline by quantifying the level of constraint. For this purpose, tensile tests and CTOD tests were performed at room temperature$(24^{\circ}C)$ and low temperature$(-40^{\circ}C)$ to obtain the material properties. J-Q analyses were performed for SENB and SENT specimens based on 2-D finite element analyses, in order to investigate the in-plane constraint effects on pipeline defects.

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Experimental Behaviors of the Constraint Effects A2 Depending on Displacement at Various Measuring Positions near Crack Front for STS 316L CT Specimen (균열선단 변위측정위치에 따른 STS 316L의 구속효과 A2 거동)

  • Han, Min-Su;Jang, Seok-Ki
    • Journal of the Korean Society of Marine Engineering
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    • v.33 no.4
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    • pp.533-538
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    • 2009
  • The magnitude of constraint effect $A_2$ values on the non-linear elastic plastic fracture toughness was experimentally estimated by using displacement at various measuring positions near crack tip. Constraint effect $A_2$ value was dependent on specimen configuration and on the measured displacement near crack front. The crack tip opening displacement in the vicinity of the crack tip front should be estimated within plastic region when appropriately constraint effect was calculated. It was found that the magnitude of constrain effect |$A_2$| is below 8.0 at the crack tip. But an appropriate location to measure the effective constraint effects $A_2$ at the critical value of J that crack initiation is characterizable by is r = 2mm and ${\theta}=90^{\circ}$ away from original crack tip, and the constraint effect |$A_2$| estimated is 5.3.

Spatial Database Modeling based on Constraint (제약 기반의 공간 데이터베이스 모델링)

  • Woo, Sung-Koo;Ryu, Keun-Ho
    • Journal of the Korean Association of Geographic Information Studies
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    • v.12 no.1
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    • pp.81-95
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    • 2009
  • The CDB(Constraint Database) model is a new paradigm for massive spatial data processing such as GIS(Geographic Information System). This paper will identify the limitation of the schema structure and query processing through prior spatial database research and suggest more efficient processing mechanism of constraint data model. We presented constraint model concept, presentation method, and the examples of query processing. Especially, we represented TIN (Triangulated Irregular Network) as a constraint data model which displays the height on a plane data and compared it with prior spatial data model. Finally, we identified that we were able to formalize spatial data in a simple and refined way through constraint data modeling.

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Estimation Method for Kinematic Constraint of Unknown Object by Active Sensing (미지 물체의 구속상태에 관한 실시간 추정방법)

  • Hwang Chang-Soon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.2
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    • pp.188-200
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    • 2005
  • Control of a multi-fingered robotic hand is usually based on the theoretical analysis for kinematics and dynamics of fingers and of object. However, the implementation of such analyses to robotic hands is difficult because of errors and uncertainties in the real situations. This article presents the control method for estimating the kinematic constraint of an unknown object by active sensing. The experimental system has a two-fingered robotic hand suspended vertically for manipulation in the vertical plane. The fingers with three degrees-of-freedom are driven by wires directly connected to voice-coil motors without reduction gears. The fingers are equipped with three-axis force sensors and with dynamic tactile sensors that detect slippage between the fingertip surfaces and the object. In order to make an accurate estimation for the kinematic constraint of the unknown object, i.e. the constraint direction and the constraint center, four kinds of the active sensing and feedback control algorithm were developed: two position-based algorithms and two force-based algorithms. Furthermore, the compound and effective algorithm was also developed by combining two algorithms. Force sensors are mainly used to adapt errors and uncertainties encountered during the constraint estimation. Several experimental results involving the motion of lifting a finger off an unknown object are presented.

An On-line Algorithm to Search Minimum Total Error for Imprecise Real-time Tasks with 0/1 Constraint

  • Song Gi-Hyeon
    • Journal of Korea Multimedia Society
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    • v.8 no.12
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    • pp.1589-1596
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    • 2005
  • The imprecise real-time system provides flexibility in scheduling time-critical tasks. Most scheduling problems of satisfying both 0/1 constraint and timing constraints, while the total error is minimized, are NP complete when the optional tasks have arbitrary processing times. Liu suggested a reasonable strategy of scheduling tasks with the 0/1 constraint on uniprocessors for minimizing the total error. Song et al suggested a reasonable strategy of scheduling tasks with the 0/1 constraint on multiprocessors for minimizing the total error. But, these algorithms are all off-line algorithms. On the other hand, in the case of on line scheduling, Shih and Liu proposed the NORA algorithm which can find a schedule with the minimum total error for a task system consisting solely of on-line tasks that are ready upon arrival. But, for the task system with 0/1 constraint, it has not been known whether the NORA algorithm can be optimal or not in the sense that it guarantees all mandatory tasks are completed by their deadlines and the total error is minimized. So, this paper suggests an optimal algorithm to search minimum total error for the imprecise on-line real-time task system with 0/1 constraint. Furthermore, the proposed algorithm has the same complexity, O(N log N), as the NORA algorithm, where N is the number of tasks.

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Constraint-based fracture mechanics analysis of cylinders with internal circumferential cracks

  • Bach, Michael;Wang, Xin
    • Structural Engineering and Mechanics
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    • v.47 no.1
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    • pp.131-147
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    • 2013
  • In this paper, constraint-based fracture mechanics analyses of hollow cylinders with internal circumferential crack under tensile loading are conducted. Finite element analyses of the cracked cylinders are carried out to determine the fracture parameters including elastic T-stresses, and fully-plastic J-integrals. Linear elastic finite element analysis is conducted to obtain the T-stresses, and elastic-plastic analysis is conducted to obtain the fully plastic J-integrals. A wide range of cylinder geometries are studied, with cylinder radius ratios of $r_i/r_o$ = 0.2 to 0.8 and crack depth ratio a/t = 0.2 to 0.8. Fully plastic J-integrals are obtained for Ramberg-Osgood power law hardening material of n = 3, 5 and 10. These fracture parameters are then used to construct conventional and constraint-based failure assessment diagrams (FADs) to determine the maximum load carrying capacity of cracked cylinders. It is demonstrated that these tensile loaded cylinders with circumferential cracks are under low constraint conditions, and the load carrying capacity are higher when the low constraint effects are properly accounted for, using constraint-based FADs, comparing to the predictions from the conventional FADs.

A Robust Track-following Control with Multiple Constraints Using Genetic Algorithm (유전자 알고리즘을 이용한 다중 제한 조건을 만족하는 강인 트랙 추종 제어)

  • Lee, Moon-Noh;Lee, Hong-Kyu;Jin, Kyoung-Bog
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.3
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    • pp.275-283
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    • 2012
  • This paper presents a design method of a robust tracking controller satisfying multiple constraints using genetic algorithm. A robust $H_{\infty}$ constraint with loop shaping is used to address disturbance attenuation with error limits and a loop gain constraint is considered so as not to enlarge the tracking loop gain and bandwidth unnecessarily. The robust $H_{\infty}$ constraint is expressed by a matrix inequality and the loop gain constraint is considered as an objective function so that genetic algorithm can be applied. Finally, a robust tracking controller can be obtained by integrating genetic algorithm with LMI approach. The proposed tracking controller design method is applied to the track-following system of an optical DVD recording drive and is evaluated through the experimental results.