• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.4
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• pp.15-22
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• 1985

The author has studied the collapse of a slope with seepage occuring in sand model with a trapezodial cross section. The primary objective of this study was to examine the failure phenomenon of embankment with respect to change in void pressure at embankment slope. The contents of this experiments are as follows; 1) Determination of exit point by seepage line. 2) Evaluation of partial failure at exit point. 3) The effects of seepage force at embankment.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1313-1320
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• 1993

Flow patterns inside the riser section and the effects of the heater inlet-and exit-restrictions, liquid charging level and the heater inlet subcooling on the flow characteristics inside an open two-phase natural circulation loop were studied experimentally. Three basic circulation modes were observed ; periodic circulation (A)(flow oscillations with incubation(no boiling) period), continuous circulations(stable operation mode with no flow oscillations), and periodic circulation (B) (flow oscillations with continuous boiling). The circulation rate increases and then decreases with the increase of the heating rate and the maximum circulation rate appears with the continuous circulation mode. The decrease of the inlet-restriction or the increase of the exitrestriction destabilizes the system. When the liquid charging level or the inlet subcooling decreases, the continuous circulation mode starts at the lower heating rate and the system is stabilized.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.211-216
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• 1996

Since the middle of the eighties of this century a research program both for heating reactor and investigation of heating reactor thermal-hydraulics has been carried out in Institute of Nuclear Energy Technology(INET) of Tsinghua university in China. This kind of heating reactor is a light water cooled and integrated natural circulation reactor with low system pressure and low quality at the exit of core. Because of relatively long riser and low system pressure. a little change of the quality at the exit of the core will result in a relatively large variation of void fraction in the riser. Two full scale test loops. HRTL-5 and HRTL-200 simulating the HR-5 and HR-200 heating reactors in geometry and operation parameters respectively, and some test results from the HRTL-200 test facility are shown in this paper. The range of studied system pressure is from 1.0MPa to 4.0MPa, the largest heat flux is about 50 W/cm2, and the quality at the exit of test section is less than 5%.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.61-65
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• 2005

Existing test methods for thick-section specimens ( 4mm) have not provided precise compressive properties to date for the analysis and design of thick structure. A survey of the failure behaviour of such thick specimens revealed that the failure initiated at the top corner of the specimen and propagated down and across the width of the specimen as premature failure, not typically reported for thin compression specimens. In the current study, the premature failure was successfully avoided during compressive testing and the failure mode was quite similar regardless of increasing specimen thickness and specimen volume. Failure mode was similar regardless of increasing specimen thickness and specimen volume, i.e. brooming failure mode combined with longitudinal splitting, interlaminar cracking, fibre breakage and kinkband formation (fibre microbuckling). Nevertheless, average failure strengths of the specimens decreased with increasing specimen thicnkiness from 2mm to 8mm with the T800/924C system (36% strength reduction) and specimen volumes from scaling factor I to scaling factor 4 with the IM7/8552 system (46% strength reduction). It was revealed from the literature$^{11}$ that the thickness effect and scaling effect arc caused by manufacturing defects such as void content and fibre waviness.

• Journal of the Korean Society of Visualization
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• v.14 no.2
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• pp.18-24
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• 2016

This paper presents an experimental investigation to visualize cross-sectional two-phase flow structure and identify liquid-gas interface for condensation of steam at a low mass flux in a slightly inclined tube using the axial-viewing technique, which permits to look directly into flow during condensation of steam. In this technique, two-phase flow is viewed along the axis of a pipe by locating a high-speed video camera in front of a viewer that is fitted at the outlet of the pipe. A short section of the pipe is illuminated and is recorded through the viewer, which is kept free of liquid by mildly introducing air. Experiments were conducted in a pipe of 19.05 mm in inner diameter at atmospheric pressure. Cross-sectional two-phase flow structure is obtained at a steam mass flux of $2.62kg/m^2s$ as a function of steam quality in the range from 0.5 to 0.9. The results show that stratified-wavy flow is a unique flow pattern observed in the scope of the present study. Condensate film thickness, stratification angle and void fraction were measured from the obtained flow structure images. Finally, heat transfer coefficient was calculated using the measurement data and discussed in comparison with existing correlations.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.3
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• pp.37-42
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• 2007

Copper deposition studies have been actively studied since interests on 3D SiP were increased. The defects inside via can be easily formed due to the current density differences on entrance, bottom and wall of via. So far many different additives and current types were discussed and optimized to obtain void-free copper via filling. In this research acid cupric sulfate plating bath containing additives such as PEG, SPS, JGB, PEI and wave current applied electroplating were examined. The size and shape of grain were influenced by the types of organic additives. The cross section of specimen were analyzed by FESEM. When PEI was added, the denser copper deposits were obtained. Electroplaing time was reduced when 2 step via filling was employed.

• Nuclear Engineering and Technology
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• v.38 no.4
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• pp.383-390
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• 2006

Having its roots in medical applications, industrial gamma ray CT has opened up new roads far investigating and modeling industrial processes. Using a line of research related to industrial gamma ray CT, the authors set up a system of single source and detector gamma transmission tomography for wood timber and a packed bed phantom. The hardware of the CT system consists of two servo motors, a data logger, a computer, a radiation source and a radiation detector. One motor simultaneously moves the source and the detector for a parallel beam scanning, whereas the other motor rotates the scan table at a preset projection angle. The image is reconstructed from the measured projections by the filtered back projection method. The phantom was designed to simulate a cross section of a packed bed with a void. The radiation source was 20mCi of Cs-137 and the detector was a 1 inch $\times$ 1 inch NaI (TI) scintillator shielded by a lead collimator. The experimental gamma ray CT image has sufficient resolution to reveal air holes and the density distribution inside the phantom. The system could possibly be applied to a packed bed column or a pipe flow in a petrochemical plant.

• Journal of architectural history
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• v.25 no.6
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• pp.73-80
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• 2016

A discourse on the Independence Hall of Korea, a representative cultural project of the 1980s, has been understood as a repetition of the traditional debate of the 1960s. It was considered as a petrified propaganda aimed at ensuring the fragile legitimacy of the military regime, and the architect as a sympathizer. Even if all these facts are true, it does not give any explanation for the architecture. Scrutinizing the building process and the change of discourse in the Independence Hall of Korea, this paper tries to explore a section of contemporary Korean architecture in the 1980s. The architect who designed the Independence Hall of Korea is Kim Kiwoong, however, it was Kim Won who took charge of overall scheme for it. Kim Won replaced the role of a technocrat in the 1960s, who deprived architects of his autonomy. Against this backdrop, Kim Kiwoong attempted to explain his own building via various concept like postmodernism, which gave him very proper context. But, later, he appropriated words like void and madang. These derived from some architectural historian's researches in 1970s, and were to predict the architecture of the 1990s.

• Smart Structures and Systems
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• v.17 no.1
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• pp.31-43
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• 2016

Applications of ultrasonic tomography to concrete structures have been reported for many years. However, practical and effective application of this tool for nondestructive assessment of internal concrete condition is hampered by time consuming transducer coupling that limits the amount of ultrasonic data that can be collected. This research aims to deploy recent developments in air-coupled ultrasonic measurements of solids, described in Part 1 of this paper set, to concrete in order to image internal inclusions. Ultrasonic signals are collected from concrete samples using a fully air-coupled (contactless) test configuration. These air coupled data are compared to those collected using partial semi-contact and full-contact test configurations. Two samples are considered: a 150 mm diameter cylinder with an internal circular void and a prism with $300mm{\times}300mm$ square cross-section that contains internal damaged regions and embedded reinforcement. The heterogeneous nature of concrete material structure complicates the application and interpretation of ultrasonic measurements and imaging. Volumetric inclusions within the concrete specimens are identified in the constructed velocity tomograms, but wave scattering at internal interfaces of the concrete disrupts the images. This disruption reduces defect detection accuracy as compared with tomograms built up of data collected from homogeneous solid samples (PVC) that are described in Part 1 of this paper set. Semi-contact measurements provide some improvement in accuracy through higher signal-to-noise ratio while still allowing for reasonably rapid data collection.

• Steel and Composite Structures
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• v.39 no.2
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• pp.171-188
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• 2021

Plastic deformation of link beams in eccentrically braced frames is the primary dissipating source of seismic energy. Despite the excellent compatibility with the architectural designs, previous researches indicate the deficiency of flexural yielding links compared to the shear yielding ones because of their localized plastic deformation. Previous investigations have shown that implementing web openings in beams could be an efficient method to improve the seismic performance of moment-resisting connections. Accordingly, this research investigates the use of flexural links with stiffened and un-stiffened web openings to eliminate localized plasticity at the ends of the link. For this purpose, the numerical models are generated in finite element software "Abaqus" and verified against experimental data gathered from other studies. Models are subjected to cyclic displacement history to evaluate their behavior. Failure of the numerical models under cyclic loading is simulated using a micromechanical based damage model known as Cyclic Void Growth Model (CVGM). The elastic stiffness and the strength-based and CVGM-based inelastic rotation capacity of the links are compared to evaluate the studied models' seismic response. The results of this investigation indicate that some of the flexural links with edge stiffened web openings show increased inelastic rotation capacity compared to an un-perforated link.