• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.5
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• pp.72-84
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• 1998

In order ot study the influence of a circular inclusion on a stress field near a crack tip, mutual interference of a slant crack and the circular inclusion is analyzed of a bimaterial inclusion. As the crack emanates at the equivalent slant crack angle the correction factors FⅠ and FⅡ for the inclusion wit small Young's modulus were found to decrease as the inclusion radius increased. The correction factors for inclusion with large Young's modulus increase as the inclusion radius increases at the equivalent radius of the inclusion, the correction factors decrease as the slant crack angle increases for the aspect ratio $\frac{c}{W}$ = 0.1 irrespective of the Young's modulus. For $\frac{c}{W}$ greater than 0.2, they increase as the slant crack angle increases. There is no influence of stress mutual interfce after crack emanates beyond the inclusion radius.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.981-989
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• 1995

A new weight function approach to determine SIF(stress intensity factor) using single-layer potential has been presented. The crack surface displacement field was represented by one boundary integral term whose kernel was modified from Kelvin's fundamental solution. The proposed method enables the calculation of SIF using only one SIF solution without any modification for the crack geometries symmetric in two-dimensional plane such as a center crack in a plate with or without an internal hole, double edge cracks, circumferential crack or radial cracks in a pipe. The application procedure to those crack problems is very simple and straightforward with only one SIF solution. The necessary information in the analysis is two reference SIFs. The analysis results using present closed-form solution were in good agreement with those of the literature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.7
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• pp.2167-2173
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• 1996

An approximate weight function technique using the indirect boundary integral equation has been presented for the analysis of stress intensity foactors(SIFs) of a thick pipe. One-term boundary integral was introduced to represent the crack surface displacement field for the displacement based weight function technique. An explicit closed-form SIF solution applicable to symmetric cracked pipes without any modification of the solution including both circumferential and radial cracks has been derived. The necessary information in the analysis is two or three reference SIFs. In most cases the SIF solution were in good agreement with those available in the literature.

• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.172-179
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• 2001

The effects of the interface and two holes located near the crack path in the hybrid specimen on the dynamic crack propagation behavior have been investigated using dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system. The dynamic stress field around the dynamically propagating interface crack tip in the three point bending specimens under a dynamic load applied by a hammer dropped from 0.6m high without initial velocity are recorded. The complex stress intensity factors for the dynamically propagating interface crack are extracted by using a overdeterministic least square method. Theoretical dynamic interface isochromatic fringe loops generated by using the numerically determined complex stress intensity factors are compared with the experimental results. Furthermore, the influence of the hole to the dynamic interface crack velocities has been investigated experimentally.

• Particle and aerosol research
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• v.10 no.2
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• pp.45-51
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• 2014

Fine particle capture is facing a challenge since traditional filtration which relies on the combination of impaction, interception, diffusion has a limited efficiency for fine particle capture particularly in size from 0.1 to $0.5{\mu}m$. This paper reviewed the collection efficiency of above mechanisms, as well as magnetic mechanisms for ferromagnetic particles, and mainly studied the influencing factors of magnetic filtration. Filtration velocity, magnetic field intensity and fiber size were found to be the most important parameters for magnetic filtration.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.43-52
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• 2000

Generally, photoelastic experimental data were measured in the closed vicinity of crack tip to determine stress intensity factors of a crack with photoelastic experiment method. In this case, only the first order term has been considered in the equation of stress field. But because it is very difficult to measure the correct photoelastic data in the closed vicinity of crack, the accuracy of experimental results was very poor. By including the high order terms in the stress field equation we could obtain the accurate S.I.F values by using clear photoelastic data in the distant region from crack tip instead of unclear photoelastic data in the vicinity of crack tip.

• Asia pacific journal of information systems
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• v.8 no.2
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• pp.37-51
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• 1998

This study attempts to draw a blueprint of risk analysis for Information Systems (IS). We introduce two main variables for measuring IS risk - business-impact intensity and IS-vulnerability index - through the investigation of information characteristics, business processes and human-related factors. IS-vulnerability index consists of two factors such as degree of openness and degree of preparedness to the threats. Based on these factors, we built two integrative frameworks for risk analysis and management: One is a conceptual framework to enhance the understandability of IS risk itself; the other is an integrative framework to improve the managerial insight of overall IS risk. We then conducted a field study to empirically validate the proposed framework using a structural equations modeling method. We found that IS maturity and business-impact intensity were positively correlated to degree of openness to the threats, while IS maturity was negatively correlated to degree of preparedness to the threats.

• Journal of the Korean Society of Safety
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• v.31 no.2
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• pp.98-103
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• 2016

The goals of this study were to investigate some significant factors to judge level of safety at urban railway construction field and to analyze degree of risk by work classification. Currently, there are lots of construction fields for the urban railway for national transportation, and our government also planned constructing more urban railway in near future. However, most of the researches on safety neglected the degree of risk factors on the urban railway construction field. Safety managers participated in the brainstorming session for deriving decision criteria of the degree of risk (i.e., significant factors). Then, they were asked to answer a structured questionnaire which was developed for deriving most important factors. Finally, the analytic hierarchy process (AHP) was used to analyze level of risk by work classification. The following results were obtained. First, total twelve factors judging degree of risk were found in the brainstorming session. Second, the questionnaire showed four significant factors, including adjacency of obstacle, intensity of work, unsafe condition and work space. Third, the results of AHP showed civil work is the most dangerous work among 6 work types. The results could be used to give the safety management priority on accident prevention efforts among several hazards and to reduce degree of risk in construction field of the urban railway.

• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.2010-2018
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• 2003

Although continuous casting process has highly developed, there still remain many problems to be considered. Specifically, two vortex flows resulting from impingement against narrow walls make a flow field unstable in a mold, and it is directly related to internal and external defects of steel products. To cope with this instability, EMBR (Electromagnetic Brake Ruler) technique has been lately studied for the stability of molten steel flow, and it is revealed that molten steel flow in a mold can be controlled with applied magnetic field. However, it is still difficult to clarify flow pattern in an EMBR caster due to complex correlations among variables such as geometric factors, casting conditions, and the place and the intensity of charged magnetic field. In the present study, flow field in a mold is focused with different conditions of electromagnetic effect. To accurately analyze the case, three dimensional low Reynolds turbulent model and appropriate boundary conditions are chosen. To evaluate the electromagnetic effect in molten steel flow, dimensionless numbers are employed. The results show that the location and the intensity of the applied magnetic field significantly influence the flow pattern. Both impingement and internal flow pattern are changed remarkably with the change of the location of applied magnetic field. It turns out that an insufficient magnetic force yields adverse effect like channeling, and rather lowers the quality of steel product.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1659-1670
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• 2001

It has been reported that cracks at mechanical fastener holes usually nucleate as elliptical corner cracks at the faying surface of the mechanical joints and grow as elliptical arc through cracks after penetrating the opposite surface. The weight function method is an efficient technique to calculate the stress intensity factors fur elliptical cracks using uncracked stress field. In this study the weight function method for three dimensional mixed-mode problem applied to elliptical comer cracks Is modified for elliptical arc through cracks and the stress intensity factors at two surface points of elliptical arc through cracks at mechanical fastener holes are analyzed by the weight function method. This study consists of two parts and in part I , the weight function method for elliptical arc through cracks is developed and verified.