• 제목/요약/키워드: Theory of Constraint

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가속시험을 통한 불규칙하중을 받는 실구조물의 피로수명평가 (Fatigue Life Evaluation of an Actual Structure under the Irregular Loading using an Acceleration Test)

  • 김형익;배봉국;박재실;석창성;모진용
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2004년도 추계학술대회 논문집
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    • pp.166-169
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    • 2004
  • A fatigue test was used to evaluate the fatigue life of an actual structure. The loaded state and the constraint condition of an actual structure must be same as the specimen in order to apply the test results to an actual structure by the specimen. The loaded state and constraint conditions can't be same as the specimen in the actual structure which is complicated. In order to reduce these differences, an actual structure test with a lot of frequencies is need to get a fatigue life curve. Therefore, ten sets of accelerated test units which attached unbalanced mass were composed in this study. Acceleration history about the vibration of an actual structure was acquired. Rainflow counting was used on acceleration history, and the life curve return formula was assumed. The return formula that damage satisfied `1' was acquired in a feedback process by the Miner's rule, which was the linear cumulative damage theory. A conservative fatigue life curve was determined with a return formula to have been presumed by each set. The fatigue life of regular rpm condition was calculated by these conservative fatigue life curves.

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시편크기의 영향을 고려한 J-A$_2$ 방법에 의한 파괴인성 평가 (Evaluation of Fracture Toughness by J-A$_2$ Method Considering Size Effect)

  • 이정윤;김영종;김용환;김재훈
    • 한국정밀공학회지
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    • 제17권1호
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    • pp.153-163
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    • 2000
  • The size effect on fracture toughness was investigated by introducing $J-A_2$ theory. For this application,small size specimens were chosen to establish $J-A_2$ assessment curve with FEM analysis. Two-dimensional FEM analysis was conducted with plane strain model using ABAQUS by domain integral method to calculate both crack tip stress and fracture toughness which were used to establish $J-A_2$ curve. The assessment curve predicted the fracture toughness of large specimens very well when compared to the test values. The results showed good prediction for deep crack specimen, though there were acceptable deviations in shallow cracked specimens, presumably caused by constraint effect. When the curve applied to reactor vessel in order to predict end of life fracture toughness with assumption of on-power pressure test condition, it provided the reasonable pressure compared to the existing design value. Better predictions would be possible if more test data were available.

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An Approach of Solving the Constrained Dynamic Programming - an Application to the Long-Term Car Rental Financing Problem

  • Park, Tae Joon;Kim, Hak-Jin;Kim, Jinhee
    • 한국컴퓨터정보학회논문지
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    • 제26권12호
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    • pp.29-43
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    • 2021
  • 본 연구에서 제약식프로그래밍을 이용하여 제약식 있는 동적계획법 모형을 푸는 한 방법을 제시한다. 현재 제약식 있는 동적계획법을 다루는 방법은 각 단계별 제약식들의 상태를 일반적인 동적계획법의 상태공간에 추가하여 마치 제약식이 없는 동적계획법 방식을 적용하는데 반해, 이 연구에서 제시하는 방식은 제약식의 상태가 제약식프로그래밍의 변수 도메인으로 표현되고 저장된다. 계산에 있어서도 일반적인 동적계획법의 벨만방정식의 해법과 함께 제약식을 다루기 위한 제약식프로그래밍의 확산-추론 방법을 사용하는 하이브리드 방식을 따른다. 이 두가지 방식의 비교를 위해 특별히 장기 자동차 렌탈 문제를 제시하고 이 문제의 단순화된 모형을 중심으로 다른 방식으로 해결하는 과정을 보고 그 장단점을 논한다.

모음 약화 현상의 세분화 (Vowel Reduction in Russian)

  • 이성민
    • 비교문화연구
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    • 제30권
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    • pp.97-124
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    • 2013
  • For a long period, vowel reduction has been accepted as one of the most common pronunciation rules in Russian phonology. However, since the rules have been modified in many ways after the influx of loanwords, [a, e, i, o, u, ${\star}$]-including [e, o]-can now be pronounced in unstressed position, obeying the rule of vowel reduction. Especially in Modern Russian, along with the destruction of the consonant pronunciation norm due to some relatively complex changes it underwent palatalization, consonant pronunciation has been simplified, and as a response to such a phenomenon, the specialization of vowel pronunciation rule is now occurring. In other words, in the interrelation between consonants and vowels, as the pronunciation rules for consonants are simplified and thus the contrast between consonants is weakened, the degree of dependence on pronunciation of segment in the vowel pronunciation rule has been elevated. Therefore, the analysis says that the degree of vowel reduction depends on a vowel's distance from a stressed syllable is not enough; the influence of surrounding phonemes-including consonants-or the formative characteristics of words themselves should also be considered. The introduction of Max-noncorner/UnderLex, a/an Licence constraint that is related to non-declension nouns, and that of IdentC[back] and ShareCV[back], which are faithfulness constraint and share constraint respectively that are related to the nature of consonants stresses that vowel pronunciation rules should not be simply viewed as rules for vowels; The rules should be analyzed with emphasis on their correlation with surrounding phonemes.

CT시험편의 크기 변화에 따른 파괴저항곡선의 변화 (Variation of the Fracture Resistance Curve with the Change of a Size in the CT Specimen)

  • 석창성;김수용
    • 대한기계학회논문집A
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    • 제24권12호
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    • pp.2963-2971
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    • 2000
  • In order to obtain more realistic fracture resistance curve, research is currently underway to introduce new parameter and to quantify the constraint effect. The objective of this study is to investigate the relationship between the constraint effect of a size(plane size and thickness) and the fracture resistance curve. In this paper fracture toughness tests were performed with various plane size and various thickness of specimens in two materials. The test results showed that the effects of plane size in th4 J-R curve were significant and the curve was risen with an increase in plane size. However, relatively weak influence was observed form the change of the specimen thickness and size. The stress fields near the crack tip of th specimen is close to the HRR field according to increasing the plane size and Q stress appears different value according to material properties and the plane size.

양자화 제약 집합에 여과된 데이터를 투영하는 기법의 이론적 고찰 (Theoretical analysis of the projection of filtered data onto the quantization constraint set)

  • 김동식;박섭형
    • 한국통신학회논문지
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    • 제21권7호
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    • pp.1685-1695
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    • 1996
  • The postprocessing of compressed images based on the projections onto convex sets and the constrained minimization imposes several constraints on the procesed data. The quantization constraint has been commonly used in various algorithms. Quantization is many-to-one mapping, by which all the dat in a quantization region are mapped to the corresponding representative level. The basic idea behind the projection onto the QCS(quantization constraint set) is to prevent the processed data from diverging from the original quantization region in order to redue the artifacts caused by filtering in postprocessing. However, there have been few efforts to analye the POQCS(projection onto the QCS). This paper analyzed mathematically the POQCS of filtered data from the viewpoint of minimizing the mean square error. Our analysis shows that a proper filtering technique followed by the POQCS can reduce the quantization distortion. In the conventional POQCS, the outside data of each quantization region are mapped into the corresponding boundary. Our analysis also shows that mappingthe outside data to the boundary of a subregion of the quantization region yields lower distortion than does the mapping to the boundary of the original region. In addition, several examples and discussions on the theory are introduced.

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A Modified Two-Parameter Solution for Crack-Tip Field in Bending Dominated Specimens

  • Jang Seok-Ki;Zhu Xian Kui
    • Journal of Advanced Marine Engineering and Technology
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    • 제30권4호
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    • pp.494-504
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    • 2006
  • It is well known that the two-parameter $J-A_2$ solution can well characterize the crack-tip fields and quantify the crack-tip constraint for different flawed geometries in variety of loading conditions. However, this solution fails to do so for bending dominated specimens or geometries at large deformation because of the influence of significant global bending stress on the crack-tip field. To solve this issue, a modified $J-A_2$ solution is developed in this paper by introducing an additional term to address the global bending influence. Using the $J_2$ flow theory of plasticity and within the small-strain framework detailed finite element analyses are carried out for the single edge notched bend (SENB) specimen with a deep crack in A533B steel at different deformation levels ranging from small-scale Yielding to large-scale Yielding conditions. The numerical results of the crack-tip stress field are then compared with those determined from the $J-A_2$ solution and from the modified $J-A_2$ solution at the same level of applied loading Results indicate that the modified $J-A_2$ solution largely improves the $J-A_2$ solution, and match very well with the numerical results in the region of interest at all deformation levels. Therefore, the proposed solution can effectively describe the crack-tip field and the constraint for bending dominated specimens or geometries.

탄성 대변형 다물체동역학을 위한 슬라이딩조인트 개발 (The Development of a Sliding Joint for Very Flexible Multibody Dynamics)

  • 서종휘;정일호;수기야마;사바나;박태원
    • 대한기계학회논문집A
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    • 제29권8호
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    • pp.1123-1131
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    • 2005
  • In this paper, a formulation for a spatial sliding joint, which a general multibody can move along a very flexible cable, is derived using absolute nodal coordinates and non-generalized coordinate. The large deformable motion of a spatial cable is presented using absolute nodal coordinate formulation, which is based on the finite element procedures and the general continuum mechanics theory to represent the elastic forces. And the non-generalized coordinate, which is neither related to the inertia forces nor external forces, is used to describe an arbitrary position along the centerline of a very flexible cable. In the constraint equation for the sliding joint, since three constraint equations are imposed and one non-generalized coordinate is introduced, one constraint equation is systematically eliminated. Therefore, there are two independent Lagrange multipliers in the final system equations of motion associated with the sliding joint. The development of this sliding joint is important to analyze many mechanical systems such as pulley systems and pantograph/catenary systems for high speed-trains.

Performance Evaluation of a Compressed-State Constraint Kalman Filter for a Visual/Inertial/GNSS Navigation System

  • Yu Dam Lee;Taek Geun Lee;Hyung Keun Lee
    • Journal of Positioning, Navigation, and Timing
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    • 제12권2호
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    • pp.129-140
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    • 2023
  • Autonomous driving systems are likely to be operated in various complex environments. However, the well-known integrated Global Navigation Satellite System (GNSS)/Inertial Navigation System (INS), which is currently the major source for absolute position information, still has difficulties in accurate positioning in harsh signal environments such as urban canyons. To overcome these difficulties, integrated Visual/Inertial/GNSS (VIG) navigation systems have been extensively studied in various areas. Recently, a Compressed-State Constraint Kalman Filter (CSCKF)-based VIG navigation system (CSCKF-VIG) using a monocular camera, an Inertial Measurement Unit (IMU), and GNSS receivers has been studied with the aim of providing robust and accurate position information in urban areas. For this new filter-based navigation system, on the basis of time-propagation measurement fusion theory, unnecessary camera states are not required in the system state. This paper presents a performance evaluation of the CSCKF-VIG system compared to other conventional navigation systems. First, the CSCKF-VIG is introduced in detail compared to the well-known Multi-State Constraint Kalman Filter (MSCKF). The CSCKF-VIG system is then evaluated by a field experiment in different GNSS availability situations. The results show that accuracy is improved in the GNSS-degraded environment compared to that of the conventional systems.

영어의 모음체계 연구 (A study of English vowel system)

  • 이재영
    • 대한음성학회지:말소리
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    • 제38호
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    • pp.71-97
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    • 1999
  • In this paper I have surveyed vowel phonemes in a variety of English accents and have proposed the vowel systems of English. The English accents covered in this paper include General American English, Northeastern American English, Western American English, Southern British English, Northern British English, Scottish English, Southern Irish English, Northern Irish English, Australian English, and New Zealand English. The vowel systems proposed here reflect the acoustic information of vowels and phonological aspects of English. This paper offers an Optimality Theory-based analysis of the English vowel systems by appealing to independently motivated constraints. This paper, following Flemming(1995), makes an assumption that the vowel system in question is selected in output as an optimal candidate by a given constraint ranking, the assumption which is different from the view that the vowel system is fixed in input. The analysis proposed here gives an answer to why a specific vowel system is selected and why dialectal variations come about. It is shown in this paper that the vowel system selected in a specific dialect comes from an optimal satisfaction of a given constraint ranking and that dialectal differences result from dynamic permutations of the same constraints. The constraint-based analysis proffered here accounts well for the similarities and differences among dialects in regard to the vowel system.

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