• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1579-1586
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• 2020

Dissimilar metal joints (DMJs) are more common in the application of piping system of many industries. A 2- D and 3-D finite element analysis (FEA) is carried out on dissimilar metal Single Edged Notch Bending (DMSENB) specimens fabricated from ferritic steel, austenitic steel and Inconel - 182 alloy to study the behavior of DMJs with constraints by using linear elastic fracture mechanics (LEFM) principles. Studies on DMSENB specimens are conducted with respect to (i) dissimilar metal joint width (DMJW) (geometrical constraints) (5 mm, 10 mm, 20 mm, 30 mm and 50 mm) (ii) strength mismatch (material constraints) and (iii) crack lengths (16 mm, 20 mm and 24 mm) to study the DMJ behavior. From the FEA investigation, it is observed that (i) SIF increases with increase of crack length and DMJWs (ii) significant constraint effect (geometry, crack tip and strength mismatch) is observed for DMJWs of 5 mm and 10 mm (iii) stress distribution at the interfaces of DMSENB specimen exhibits clear indication of strength mismatch (iv) 3-D FEA yields realistic behavior (v) constraint effect is found to be significant if DMJW is less than 20 mm and the ratio of specimen length to the DMJW is greater than 7.4.

• 지역연구
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• 제39권4호
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• pp.3-17
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• 2023

공간적 미스매치 문제는 수요부족형 실업문제와는 달리 기업의 노력과 국가경제의 회복만으로는 개선이 어려우며, 근본적으로 공간구조적인 개선이 필요하다는 특징을 가진다. 본 연구는 이러한 측면에서 구조적 실업, 특히 공간적 미스매치로 인한 실업의 문제를 살펴보고, 이를 해결하기 위한 시사점을 고찰하는 것을 목적으로 한다. 이를 위해 우선적으로 공간적 미스매치가 전체 실업 중에 차지하는 양상을 확인함으로서 공간 미스매치의 실태에 대해 간접적으로 확인하였다. 또한 이러한 공간미스매치 문제 해소를 위한 대표적인 수단인 지역노동시장을 직종별로 획정하고, 이러한 지역노동시장이 공간 미스매치를 개선하는데 있어 효율적인지를 검토함으로서 이의 효용성을 확인하고자 하였다. 끝으로 본 연구의 분석을 통해 일자리 관련 정책을 추진함에 있어 개별 지역 정책과 일자리 창출 정책 외에도 지역 간 연계를 통한 공간적 매칭 등 다차원적인 정책 개발이 필요하다는 것을 시사하고자 하였다.

• Steel and Composite Structures
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• 제2권1호
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• pp.35-50
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• 2002

A series of tests on simple-welded plate specimens (SWPS) and T-stub tension specimens simulating some of the joint details in moment frame connections were conducted in this investigation. The effects of weld strength mismatch and weld metal toughness on structural behavior of these specimens were considered under both static and dynamic loading conditions. Finite element analyses were performed by taking into account typical weld residual stress distributions and weld metal strength mismatch conditions to facilitate the interpretation of the test results. The major findings are as follows: (a) Sufficient specimen size requirements are essential in simulating both load transfer and constraint conditions that are relevant to moment frame connections, (b) Weld residual stresses can significantly elevate stress triaxiality in addition to structural constraint effects, both of which can significantly reduce the plastic deformation capacity in moment frame connections, (c) Based on the test results, dynamic loading within a loading rate of 0.02 in/in/sec, as used in this study, premature brittle fractures were not seen, although a significant elevation of the yield strength can be clearly observed. However, brittle fracture features can be clearly identified in T-stub specimens in which severe constraint effects (stress triaxiality) are considered as the primary cause, (d) Based on both the test and FEA results, T-stub specimens provide a reasonable representation of the joint conditions in moment frame connections in simulating both complex load transfer mode and constraint conditions.

• 대한기계학회논문집A
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• 제30권8호
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• pp.931-940
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• 2006

Defect assessment of a weld zone is important in fitness-for-service evaluation of plant components. Typically a J and $C^*$ estimation method for a defective homogeneous component is extended to a mismatched component, by incorporating the effect due to the strength mismatch between the weld metal and the base material. The key element is a mismatch limit load. For instance, the R6/R5 procedure employs an equivalent material concept, defined by a mismatch limit load. A premise is that if a proper mismatch limit load solution is available, the same concept can be used for any defect location (either a weld centre defect or a heat affected zone (HAZ) defect) and for any material combination (either two-material or multi-material combinations; either similar or dissimilar joints). However, validation is still limited, and thus a more systematic investigation is needed to generalise the suggestion to any geometry, any defect location and any material combination. This paper describes the effect of structural geometry on the $C^*$ integral for defective similar welds, based on systematic elastic-creep 2-D and 3-D finite element (FE) analyses, to attempt to elucidate the questions given above. It is found that the existing 'equivalent material' concept is valid only for limited cases, although it provides conservative estimates of $C^*$ for most of cases. A modification to the existing equivalent material concept is suggested to improve accuracy.

• Journal of Chest Surgery
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• 제51권3호
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• pp.161-166
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• 2018

Patient-prosthesis mismatch (PPM) is a controversial issue in current clinical practice. PPM has been reported to have a negative impact on patients' prognosis after aortic valve replacement in several studies, showing increased all-cause and cardiac mortality. Moreover, a close relationship has recently been described between PPM and structural valve deterioration in biological prostheses. In patients at risk for PPM, several issues should be considered, and in the current era of cardiac surgery, preoperative planning should consider the different types of valves available and the various surgical techniques that can be used to prevent PPM. The present paper analyses the state of the art of the PPM issue.

• 반도체디스플레이기술학회지
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• 제1권1호
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• pp.1-7
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• 2002

Modem technology depends on the reliability of extremely high precision equipments. In the production of semiconductor wafer, optical and electron microscopes, ion-beam, laser device must maintain their alignments within a sub-micrometer. This equipment requires a vibration free environment to provide its proper function. Therefore, this high technology equipments require very strict environmental vibration criteria because it is used as basic data for the design of building structure and structural dynamics of equipment. In this paper, the new approach is proposed to investigate the mismatch problem of time and frequency domain for vibration criteria of sensitive equipment. The proposed approach is based on a vibration measurement data and a relative transfer function which can be obtained by experiment or analysis.

• 지역연구
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• 제31권2호
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• pp.79-100
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• 2015

정부는 일자리를 늘리고, 고용환경을 개선하기 위해 다양한 정책을 만들고 있지만 실업난은 해소되지 않고 있다. 본 연구는 광역경제권을 대상으로 구인 구직의 구조적 미스매치 현상 가운데 지역 간 미스매치를 분석하여 실업을 발생시키는 요인에 대한 이해를 넓히는데 목적을 두었다. 워크넷 자료를 이용하여 분석한 결과 2008~2013년 동안 구인 구직의 지역 간 미스매치로 인한 실업은 꾸준히 증가하는 것으로 나타났다. 대졸 이상, 고숙련 일자리의 경우 모든 광역경제권 에서 지역 간 미스매치는 매우 낮게 나타나지만, 고졸 이하, 저숙련 일자리의 경우 충청권, 동남권, 호남권에서 지역 간 미스매치가 상당히 높게 나타나고 있다. 이는 고졸 이하, 저숙련 구직자들이 해당 광역경제권 내에서 특정 지역을 선호하여 구직활동을 하기 때문으로, 이들이 직종을 그대로 유지하면서 지역을 옮겨서 구직활동을 한다면 실업상태에서 벗어날 수 있음을 말해준다. 그러나 수도권의 경우 모든 일자리 유형에서 지역 간 미스매치가 매우 낮아 구직자들이 지역을 이동하더라도 실업상태에서 벗어나기 매우 어려움을 말해준다. 본 연구 결과는 실업문제 해소를 위해 전국적으로 일률적인 실업 정책을 수립하기 보다는 각 광역경제권별로 일자리 유형에 따른 지역 간 미스매치 특성을 고려한 차별화된 실업 전략이 필요하다는 정책적 시사점을 제공하였다.

• Journal of Welding and Joining
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• 제22권1호
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• pp.50-57
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• 2004

This paper provides FE and experimental validation of the defect assessment method for strength mismatched welded structures, resulting from the Brite Euram SINTAP (Structural Integrity Assessment Procedures for European Industry) project. This shows that the proposed method is conservative, and that the degree of conservatism is similar to that embedded in the methods for homogeneous structures. It provides confidence in the use of the proposed SINTAP method for assessing defective weld strength mismatched structures.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2949-2957
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• 2020

Fatigue crack growth model has been developed for dissimilar metal weld joints of a piping component under cyclic loading, where in the crack is located at the center of the weld in the circumferential direction. The fracture parameter, Stress Intensity Factor (SIF) has been computed by using principle of superposition as K_H + K_M. K_H is evaluated by assuming that, the complete specimen is made of the material containing the notch location. In second stage, the stress field ahead of the crack tip, accounting for the strength mismatch, the applied load and geometry has been characterized to evaluate SIF (K_M). For each incremental crack depth, stress field ahead of the crack tip has been quantified by using J-integral (elastic), mismatch ratio, plastic interaction factor and stress parallel to the crack surface. The associated constants for evaluation of K_M have been computed by using the quantified stress field with respect to the distance from the crack tip. Net SIF (K_H + K_M) computed, has been used for the crack growth analysis and remaining life prediction by Paris crack growth model. To validate the model, SIF and remaining life has been predicted for a pipe made up of (i) SA312 Type 304LN austenitic stainless steel and SA508 Gr. 3 Cl. 1. Low alloy carbon steel (ii) welded SA312 Type 304LN austenitic stainless-steel pipe. From the studies, it is observed that the model could predict the remaining life of DMWJ piping components with a maximum difference of 15% compared to experimental observations.

• 한국언어정보학회:학술대회논문집
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• 한국언어정보학회 2007년도 정기학술대회
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• pp.234-240
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• 2007

This paper argues that various kinds of displaced structures in English should be licensed by a more explicitly formulated type of rule schema in order to deal with what is called weak connectivity in English. This paper claims that the filler and the gap site cannot maintain the total identity of features but a partial overlap since the two positions need to obey the structural forces that come from occupying respective positions. One such case is the missing object construction where the subject fillers and the object gaps are to observe requirements that are imposed on the respective positions. Others include passive constructions and topicalized structures. In this paper, it is argued that the feature discrepancy comes from the different syntactic positions in which the fillers are assumed to be located before and after displacement. In order to capture this type of mismatch, syntactically relevant features are handled separately from the semantically motivated features in order to deal with the syntactically imposed requirements.