• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2008.04a
• /
• pp.483-489
• /
• 2008

Masonry infill walls are frequently used as interior partitions and exterior walls in low- or middlerise RC buildings In the structural design and assessment of structural behaviors of buildings, the infill walls are usually treated as non-structural elements and they are ignored in analytical models. In this study, seismic behaviors of RC frame with/without masonry infill walls were investigated. To this end, the infill walls were modeled as equivalent diagonal struts. Based on analytical results, it has been shown that masonry infill walls can increase the global strength and stiffness of a structure. Accordingly, inter-story drift ratio will be decreased but seismic forces applied to the structure were increased than design seismic load because natural period of the structure was decreased. It is also seen from the analytical results that the inelastic deformation of RC frame with soft story is concentrated on the first story columns and thus, partial damage may have possibility of collapse of system.

• Journal of Advanced Marine Engineering and Technology
• /
• v.26 no.4
• /
• pp.464-471
• /
• 2002

Porosity formation in partial penetration welds by high power lasers is a serious problem in industry. There are two main causes that induce porosity formation. One form of porosity is due to gases (e.g. hydrogen, oxygen) dissolving into the weld pool because of the high temperature and then the rapid solidification traps gases as a bubble in the weld metal. The second problem is voids formed by the keyhole collapsing due to unstable keyhole fluid dynamics. The voids that form at the bottom of the keyhole are relatively large and irregular in shape compared to the gas bubbles; this void formation is the primary concern in this paper. The reduction of voids formed by keyhole collapse is achieved by improving the stability of keyhole. Two methods to improve keyhole stability are discussed in this paper: pulse modulation and beam incident angle. Pulse modulation of the laser beam was performed between 100 Hz and 500 Hz to find out the optimum frequency for the keyhole dynamics. The incident beam angle changed the impact angle of the laser beam to the work surface in a range of 0 to 25 degrees. Glycerin in a semi-solidified state is used as a medium for performing the welding because its transparency allows of visualization of the keyhole.

• Journal of the Korean Society of Safety
• /
• v.14 no.4
• /
• pp.158-167
• /
• 1999

In parallel flow condition, to estimate the stability of the extended embankment constructed on a permeable foundation ground, a laboratory model test was performed due to extended materials and water level increasing velocity of a flood period. A laboratory model test was peformed for different permeability coefficients ($K_1=2.0{\times}10^{-5}cm/sec,\;K_2=1.5{\times}10^{-4}cm/sec,\;K_3=2.3{\times}10^{-3}cm/sec$) using seepage. The fluctuation of water level occurring to an extended embankment was analyzed by laboratory model tests as vary the increasing velocity of water level with 0.6cm/min, 1.2cm/min, 2.4cm/min respectively. In analysis results, the increase of water level into embankment occurs rapidly because seepage water moving along with a permeable soil flow into embankment. The larger the permeability coefficient of an extended part is the longer initial seepage distance, and the exit point of downstream slope is gradually increased and then shows unstable seepage behavior as occurring partial collapse. As the increasing velocity of water level increase, the initial seepage line is formed low, and the discharge increases. Therefore, the embankment extended by a lower permeable soil than existing embankment shows stable seepage behavior because an existing embankment plays a role as filter for an extended part.

• The Korean Journal of Mycology
• /
• v.46 no.3
• /
• pp.345-351
• /
• 2018

A fungal isolate denoted NC14-264 was isolated from the soil in Jeongeup, Jeollabuk-do, Korea. Species in genus Plectosphaerella are pathogenic to several plant species, leading to fruit, root, and collar rot and collapse. In this study, a strain NC14-264 belonging to the Plectosphaerella was isolated from the soil and identified. Colonies were moderately grown, reaching 54 mm in diameter on potato dextrose agar, 49 mm on malt extract agar, and 55 mm on oatmeal agar at $25^{\circ}C$ after 10 days of incubation. Most Plectosphaerella species are distinguishable morphologically by irregular chlamydospores and different proportions of phialides and conidia. Based on morphological features and phylogenetic analysis using the internal transcribed spacer region and partial 28S rRNA gene sequences, the isolated fungus was identified as Plectosphaerella sinensis belonging to the Plectosphaerellaceae. This is the first report of P. sinensis in Korea.

• Proceedings of the KWS Conference
• /
• 2002.10a
• /
• pp.600-605
• /
• 2002

The keyhole formed by high energy density laser-material interaction periodically collapses due to surface tension of the molten metal in partial penetration welds. The collapse sometimes traps a void at the bottom of the keyhole, and it remains as welding defects. This phenomenon is seen as one cause of the instability of the keyhole during laser beam welding. Thus, it seems likely that improving the stability of the keyhole can reduce voids and uniform the penetration depth. The goal of this work is to develop techniques for controlling laser weld keyhole dynamics to reduce weld defects such as voids and inconsistent penetration. Statistical analysis of the penetration depth signals in glycerin determined that keyhole dynamics are chaotic. The chaotic nature of keyhole fluctuations and the ability of laser power modulation to control them have been demonstrated by high-speed video images of laser welds in glycerin. Additionally, an incident leading beam angle is applied to enhance the stability of the keyhole. The quasi-sinusoidal laser beam power of 400Hz frequency and 15$^{\circ}$ incident leading beam angle were determined to be the optimum parameters for the reduction of voids. Finally, chaos analyses of uncontrolled signals and controlled signals were done to show the effectiveness of modulation on the keyhole dynamics. Three-dimensional phase plots for uncontrolled system and controlled system are produced to demonstrate that the chaotic keyhole dynamics is converted to regular periodic behavior by control methods: power modulation and incident leading beam angle.

• The Korean Journal of Applied Statistics
• /
• v.27 no.6
• /
• pp.959-973
• /
• 2014

Asset pricing models that account for asymmetric volatility in asset prices have been recently proposed. This article presents an efficient Bayesian method to analyze asset-pricing models. The method is developed by devising a partially collapsed Gibbs sampler that capitalizes on the functional incompatibility of conditional distributions without complicating the updates of model components. The proposed method is illustrated using simulated data and applied to daily S&P 500 data observed from September 1980 to August 2014.

• Journal of Welding and Joining
• /
• v.26 no.6
• /
• pp.67-73
• /
• 2008

Three-dimensional transient simulation of laser-GMA hybrid welding involving multiple physical phenomena is conducted neglecting the interaction effect of laser and arc heat sources. To reproduce the bubble and pore formations in welding process, a new bubble model is suggested and added to the established laser and arc welding models comprehending VOF, Gaussian laser and arc heat source, recoil pressure, arc pressure, electromagnetic force, surface tension, multiple reflection and Fresnel reflection models. Based on the models mentioned above, simulations of laser-GMA hybrid butt welding are carried out and besides the molten pool flow, top and back bead formations could be observed. In addition, the laser induced keyhole formation and bubble generation duo to keyhole collapse are investigated. The bubbles are ejected from the molten pool through its top and bottom regions. However, some of those are entrapped by solid-liquid interface and remained as pores. Those bubbles and pores are intensively generated when the absorption of laser power is largely reduced and consequently the full penetration changes to the partial penetration.

• The Journal of the Korean dental association
• /
• v.53 no.12
• /
• pp.926-934
• /
• 2015

Obstructive sleep apnea (OSA), most common respiratory disorder of sleep, is characterized by intermittent partial or complete occlusions of the upper airway due to loss of upper airway dilating muscle activity during sleep superimposed on a narrow upper airway. Termination of these events usually requires arousal from sleep and results in sleep fragmentation and hypoxemia, which leads to poor quality of sleep, excessive daytime sleepiness, reduced quality of life and numerous other serious health consequences. Untreated OSA may cause, or be associated with, several adverse outcomes, including daytime sleepiness, increased risk for motor vehicle accidents, cardiovascular disease, and depression. Various treatments are available, including non-surgical treatment such as medication or modification of life style, continuous positive airway pressure (CPAP) and oral appliance (OA). Skeletal surgery for obstructive sleep apnea (OSA) aims to provide more space for the soft tissue in the oropharynx to prevent airway collapse during sleep. Conventional surgical techniques include uvopalatopharyngoplasty(UPPP), genioglossus advancement (GA), and maxillomandibular advancement (MMA). Surgical techniques, efficacy and complications of skeletal surgery are introduced in this review.

• Proceedings of the KSR Conference
• /
• 2009.05a
• /
• pp.1509-1513
• /
• 2009

The research of applying reinforced retaining wall due to support the land pressure that given from train's load has been accomplished actively in domestic area. After the retaining wall has been installed, the collapse or partial destruction that generated by effect of train's vibration and repetitive load of train may be induced. Accordingly in the period of using this, the sufficient durability should be guaranteed and years of durability are one hundred and as these are longer than road structure's, the technique that introduced to wall and monitor the long-term strain is necessary. In this paper, the optical fibre is induced vertically to the reinforced retaining wall and after the subsistence of optical fibre is confirmed, the early strain that applied to optical fibre after insertion is monitored. Before and after the concrete placing, damage feasibility of optical fibre is measured by using OTDR(Optical Time Domain Reflectometer) and after concrete is cultivated, the early strain induced to optical fibre is measured by application of BOCDA (Brillouin Correlation Domain Analysis) system.

• Proceedings of the IEEK Conference
• /
• 2000.07a
• /
• pp.80-83
• /
• 2000

Decision-makers in ecological system and social system have complex interactions and relations. Such interactions and relations are not predefined but dynamically constructed. We consider what relation-s are constructed or destroyed and how the relations change. Therefore, we focus on the formation and collapse of relations as one of the emergent phenomena of social or ecological complex phenomena. Game theory is the best way of analyzing phenomena in terms of interactions. However, it is difficult to analyze the dynamical system by game theory. Consequently, we propose Selecting Game with agents as players based on game theory. In this model, the relations among agents are not predefined but constructed by selecting subgames. As a result, we confirmed that the entire relation among agents is constructed by the agents＇ changing partial relations and that the relations dynamically change.