• Journal of the Korean Society for Precision Engineering
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• v.15 no.6
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• pp.159-166
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• 1998

The problem of interface crack in the bonded structures has received a great deal of attention in recent years. In this paper the aluminum bonded single lap-joint containing the interface edge crack is investigated. The tensile load and the average shear stress of the adhesive joints which have different crack length are obtained from the static tensile tests. The critical value of crack length to provoke the interface fracture is determined to a/L=0.4, where a is the interface crack length and L is the adhesive lap-length. The fracture mechanical parameters are introduced to confirm the existence of the critical crack length. The compliance and the stress intensity factors are calculated using the displacement and the stress near the interface crack tip by the boundary element method. These numerical results support the experimental results that the critical value of a/L is 0.4. It is known that the compliance and the stress intensity factors are the efficient parameters to estimate the bonded single lap-joint containing the interface edge crack.

• Bulletin of the Korean Chemical Society
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• v.23 no.4
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• pp.580-586
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• 2002

We investigated the effect of ionic component on crystalline morphology development during isothermal annealing in a sodium neutralized sulfonated poly(ethylene terephthalate) ionomer (Ion-PET) by time-resolved small-angle x-ray scattering (TR-SAX S) using synchrotron radiation. At early stage in Ion-PET, SAXS intensity at a low annealing temperature (Ta = 120 $^{\circ}C)$ decreased monotonously with scattering angle for a while. Then SAXS profile showed a peak and the peak position progressively moved to wider angles with isothermal annealing time. Finally, the peak intensity decreased, shifting the peak angle to wider angle. It is revealed that ionic aggregates (multiplets structure) of several nm, calculated by Debye-Bueche plot, are formed at early stage. They seem to accelerate the crystallization rate and make fine crystallites without spherulite formation (supported by optical microscopy observation). From decrease of peak intensity in SAXS,it is suggested that new lamellae are inserted between the preformed lamellae so that the concentration of ionic multiplets in amorphous region decreases to lower the electron density difference between lamellar crystal and amorphous region. In addition, analysis on the annealing at a high temperature (Ta = 210 $^{\circ}C)$ by optical microscopy, light scattering and transmission electron microscopy shows a formation of spherulite, no ionic aggregates, the retarded crystallization rate and a high level of lamellar orientation.

• Computational Structural Engineering
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• v.10 no.4
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• pp.195-203
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• 1997

The interaction between cracks and stress wave due to impact and explosive loads is numerically calculated in the study. The interaction and the effects of stress wave are numerically examined with the application of Bicharacteristic Method. This method has been used with confidence for its reliability in reproducing the realistic and physical wave pattern in the complete solution domain. The dynamic stress intensity factor, K/sub I/(t) for cracks under impact loads are numerically simulated and its results are compared favorably with Kalthoff's experimental output. Also the influence of stress wave to the dynamic stress intensity factor for the case of two symmetric holes around cracks are investigated. The results of study are also compared favorably with the experiment and proven to be applied to the structures exposed to impact and explosive loads.

• Phonetics and Speech Sciences
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• v.2 no.2
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• pp.51-60
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• 2010

This study is to examine how Korean speakers realize English stress on the homographic words. Experiments were performed by Korean speakers three times, before stress instruction, immediately after instruction, and six weeks after instruction. First, duration, fundamental frequency, and intensity of the vowel in a stressed syllable of three homographic words produced by Korean speakers were compared with those of native speakers of English. The result shows that when the words were used as nouns, before instruction Korean speakers had shorter duration and lower fundamental frequency in the stressed vowel than the native speakers, which indicates that Korean speakers did not assign the primary stress on the first syllable of the nouns. After instruction, the values of duration and fundamental frequency were increased and the differences between two groups were decreased. Next, the values of these stress features measured three times were analyzed in order to find out how they changed through instruction. The analysis shows that after instruction the values of three features were increased compared to the ones before instruction, and that the biggest change was in duration of the vowel and the next was fundamental frequency. Six weeks after instruction, the values of duration and intensity were decreased than those immediately after instruction. This means that instruction is helpful for Korean speakers to assign the stress for the English homographic words, and that instruction and practice are needed repeatedly.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.3
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• pp.10-17
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• 2001

We need to how about activity types, lighting conditions and physical features in a plate that is a object for the reasonable and economic lighting design. Thus, lighting designer analyzes spare features and completes lighting design by using luminaire that has a suitable luminous intensity distribution. There are special data in this study from analysing about activity types, lighting conditions and physical features of intelligent buildings that are getting an essential infrastructure in the information society. Intelligent building could be classified with office space, passing space, high ceiling space, one-side working space for the analysis. Also, four luminous intensity distributions and fluorescent fixtures, which are the mutt used luminaires in office building, are designed from the data of intelligent building.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.349-352
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• 2003

A personal low-frequency stimulator is a portable device to relax muscle pains of a person. The stimulator generates combined low-frequency pulses to be applied to pads attached to painful muscles. This paper reports a development of such device with its characteristic analyses. The major components of our stimulator are MCU, high-voltage generating circuit part, high-voltage switching circuit part, input switch part and display unit. High-voltage generating circuit is designed by using a boost converter circuit and allows user control of the output voltage. High-voltage switching circuit, controlled by MCU, generates output voltage to be applied to pads. Input switch part is composed of power supply, intensity selection, mode selection and memory. Display unit adopts a text LCD module to display modes, Intensity, output frequency and user set-up time. Our designed safety circuit, to protect human body from possible electric shock, slowly increases the output voltage to the selected output intensity. It continuously checks the output pulse shape and disable the output when dangerous pulses are detected. This paper also shows some experimental results.

• Nuclear Engineering and Technology
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• v.48 no.6
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• pp.1412-1422
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• 2016

Austenitic stainless steels (ASSs) are widely used for nuclear pipes as they exhibit a good combination of mechanical properties and corrosion resistance. However, high tensile residual stresses may occur in ASS welds because postweld heat treatment is not generally conducted in order to avoid sensitization, which causes a stress corrosion crack. In this study, round robin analyses on stress intensity factors (SIFs) were carried out to examine the appropriateness of structural integrity assessment methods for ASS pipe welds with two types of circumferential cracks. Typical stress profiles were generated from finite element analyses by considering residual stresses and normal operating conditions. Then, SIFs of cracked ASS pipes were determined by analytical equations represented in fitness-for-service assessment codes as well as reference finite element analyses. The discrepancies of estimated SIFs among round robin participants were confirmed due to different assessment procedures and relevant considerations, as well as the mistakes of participants. The effects of uncertainty factors on SIFs were deducted from sensitivity analyses and, based on the similarity and conservatism compared with detailed finite element analysis results, the R6 code, taking into account the applied internal pressure and combination of stress components, was recommended as the optimum procedure for SIF estimation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1091-1097
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• 2011

The SGBEM-FEM alternating method has been known to be a very effective method for analyzing threedimensional cracks in a finite body. The accurate values of the stress intensity factor can be obtained for a general planar or nonplanar three-dimensional crack. In the existing method, eight-noded quadrilateral boundary elements are used to model a crack. In some cases, three-node triangle boundary elements are more convenient for the modeling of a crack with a general shape. In this study, a crack is modeled with three-noded triangular and seven-noded quadrilateral elements by using the advancing-front mesh generation method. The stress intensity factors are obtained for cracks with several shapes and the accuracy of results is examined.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3295-3300
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• 2012

Three Dimensional finite element method (FEM) was used to obtain the stress intensity factor for subsurface cracks and surface cracks existing in inhomogeneous materials. A geometry model, i.e. a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model. Nodes are generated by the bubble packing, and ten-noded quadratic tetrahedral solid elements are generated by the Delaunay triangulation techniques. To examine accuracy and efficiency of the present system, the stress intensity factor for a semi-elliptical surface crack in a plate subjected to uniform tension is calculated, and compared with Raju-Newman's solutions. Then the system is applied to analyze interaction effects of two dissimilar semi-elliptical cracks in a plate subjected to uniform tension.

• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.1154-1162
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• 2019

China is undertaking an energy reform from fossil fuels to clean energy to accomplish $CO_2$ intensity (CI) reduction commitments. After hydropower, nuclear energy is potential based on breadthwise comparison with the world and analysis of government energy consumption (EC) plan. This paper establishes a CI energy policy response forecasting model based on national and provincial EC plans. This model is then applied in Fujian Province to predict its CI from 2016 to 2020. The result shows that CI declines at a range of 43%-53% compared to that in 2005 considering five conditions of economic growth in 2020. Furthermore, Fujian will achieve the national goals in advance because EC is controlled and nuclear energy ratio increased to 16.4% (the proportion of non-fossil in primary energy is 26.7%). Finally, the development of nuclear energy in China and the world are analyzed, and several policies for energy optimization and CI reduction are proposed.