• Geomechanics and Engineering
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• v.20 no.4
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• pp.359-370
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• 2020

Prestressed ground anchors are important structural elements in geotechnical engineering. Despite their widespread usage, the design process is often significantly simplified. One of the major drawbacks of commonly used design methods is the assumption that skin friction is mobilized uniformly along an anchor's fixed length, one consequence of which is that a progressive failure phenomenon is neglected. The following paper introduces an alternative design approach - a computer algorithm employing the load-transfer method. The method is modified for the analysis of anchors and combined with a procedure for the derivation of load-transfer functions based on commonly available laboratory tests. The load-transfer function is divided into a pre-failure (hardening) and a post-failure (softening) segment. In this way, an aspect of non-linear stress-strain soil behavior is incorporated into the algorithm. The influence of post-grouting in terms of radial stress update, diameter enlargement, and grout consolidation is included. The axial stiffness of the anchor body is not held constant. Instead, it gradually decreases as a direct consequence of tensile cracks spreading in the grout material. An analysis of the program's operation is performed via a series of parametric studies in which the influence of governing parameters is investigated. Finally, two case studies concerning three investigation anchor load tests are presented.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.1
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• pp.75-81
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• 1985

The behavior of a plane buoyant jet within the zone of flow establishment(ZFE) which is discharged vertically upward into a stagnant uniform environment, is analyzed by the integral equations of mass, momentum and tracer conservation. The analysis includes the spreading ratio with Froude number and geometry of the potential core of ZFE and the length of ZFE. The central velocity at the end of ZFE is found to be influenced significantly by buoyancy, especially at low discharge Froude number. The results provide the necessary initial conditions for the investigation of the zone of established flow.

• ALGAE
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• v.22 no.1
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• pp.17-21
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• 2007

Sargassum filicinum Harvey, a brown alga (Phaeophyceae) native to Northeastern Asia, has been recently reported from the coast of Southern California (USA). Here we report the occurrence and range extension of this introduced species, as we found the alga at La Jolla and Rancho Packard in Todos Santos Bay, Baja California, Mexico. The first collections of S. filicinum correspond to several immature plants, found on September 8, 2005, drifting in the intertidal zone at La Jolla. Later on November 9, 2006, we found a well-established population in Rancho Packard in the middle intertidal zone to 2 m depth. Since S. filicinum is an annual monoecious species with air bladders, the risk there is a high risk of spreading rapidly along the Pacific, as in the case for S. muticum. The population in Rancho Packard extends 500 m along the coast, consisting mainly of young plants with an average length of 30 cm and a density of 5 thallus/m2. This is the first record of this invasive species for the Mexican Pacific coast, and it represents the southern limit along the Pacific coast of North America. This finding suggests that this invasive species has successfully colonized the Pacific coast of North America and its distributional range is still expanding.

• Fire Science and Engineering
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• v.22 no.2
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• pp.57-62
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• 2008

Most of all the Korean home use a wallpaper as a decoration and finishing of interior. One of the fire spread factor in a house is a combustion of wall paper. There were some research concerning oxygen index in a ambient temperature. The purpose of this study is to investigate the difference of oxygen index of a wallpaper between ambient and high temperature and a effect on the fire spreading. Based on the result, the difference of oxygen index between ambient temperature and high temperature showed $5{\sim}8%$. Difference of 0.1% of oxygen index show big differences in combustion length of sample. Therefore, it was found that the decrease of oxygen index at elevated temperature is a important factor in fire spread.

• Proceedings of the IEEK Conference
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• summer
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• pp.302-309
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• 2004

The transmission capacity of wireless communication systems may become dramatically high by employ multiple transmit and receive antennas with space-time coding techniques appropriate to multiple transmit antennas. For large number of transmit antennas and at high bandwidth efficiencies, the receiver may become too complex whenever correlation across transmit antennas is introduced. Reducing decoding complexity at receiver by combining array processing and space-time codes (STC) helps a communication system using STC to overcome the big obstacle that prevents it from achieving a desired high transmission rate. Multi-carrier CDMA (MC-CDMA) allows providing good performance in a channel with high inter-symbol interference. Antenna array, STC and MC-CDMA system have a similar characteristic that transmit-receive data streams are divided into sub-streams. Thus, there may be a noticeable reduction of receiver complexity when we combine them together. In this paper, the combination of array processing and STC in MC-CDMA system over slow selective-fading channel is investigated and compared with corresponding existing MC-CDMA system using STC. A refinement of this basic structure leads to a system design principle in which we have to make a trade off between transmission rate, decoding complexity, and length of spreading code to reach a given desired design goal.

• Journal of Navigation and Port Research
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• v.27 no.2
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• pp.239-246
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• 2003

When oil is spilled at sea, the oil boom is commonly used to tackle the movement and spreading of oil in an early stage of oil spill combat. But the retaining capability of oil boom is affected by various factors, such as water velocity, viscosity and density of oil, water depth, oil volume and the length of boom draft. In this study, a computer modelling was peformed to investigate how these factors influence the oil retaining process. The Fluent, most popular one of many CFD(computational fluid dynamics) programs is chosen for modelling and modelling results were verified using the empirical data. It is expected that results of this study will be useful data for oil boom designer and oil spill response commander.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.9
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• pp.737-740
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• 2009

SiC power device possesses attractive features, such as high breakdown voltage, high-speed switching capability, and high temperature operation. In general, device design has a significant effect on the switching characteristics, In this paper, we demonstrated that the switching performance of DMOSFETs are dependent on the with Channel length ($L_{channel}$) and Current Spreading Layer thickness ($T_{CSL}$) by using 2-D Mixed-mode simulations. The 4H-SiC DMOSFETs with a JFET region designed to block 800 V were optimized for minimum loss by adjusting the parameters of the JFET region, CSL, and epilayer. It is found that improvement of switching speed in 4H-SiC DMOSFETs is essential to reduce the gate-source capacitance and channel resistance. Therefore, accurate modeling of the operating conditions are essential for the optimizatin of superior switching performance.

• Advances in pediatric surgery
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• v.2 no.1
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• pp.46-52
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• 1996

Primary segmental volvulus of the small intestine is not associated with malrotation, malfixation of the midgut, nor other primary small bowel lesions such as small bowel tumors. This entity is known to be more prevalent in adult and in certain global areas associated with particular diet habits. There have been very few reports in neonates, but not in this country so far. The author reports two cases of primary segmental volvulus. Case 1 was a septic 4-day-old girl with hematochezia due to jejunal volvulus with partial necrosis and panperitonitis. Resection of the segment and Bishop-Koop enterostomy were successful. Case 2 was a 3-day-old boy, who had ileal volvulus with ultra-short length of ileal atresia, probably due to intrauterine segmental volvulus. Limited resection of the atresia and spreading of the mesenteric base were enough to recovery. The rarity of the pathognomonic findings and limitation of the diagnostic workup due to rapid progression limit early diagnosis and good survival rate in this particular condition.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2003.05a
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• pp.171-178
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• 2003

When oil is spilled at sea, the oil boom is commonly used to tackle the movement and spreading of oil in an early stage of oil spill combat. But, the retaining capability of oil boom is affected by various factors, such as water velocity, viscosity, and density of oil, water depth, oil volume and the length of boom draft. In this study, computer modeling was peformed to investigate how these factors influence the oil retaining process. The Fluent, most popular one of many CFD(computational fluid dynamics) programs is chosen for modelling and modelling results were verified using the empirical data. It is expected that results of this study will be useful data for oil boom designer and oil spill response commander.

• Journal of Mechanical Science and Technology
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• v.19 no.12
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• pp.2253-2262
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• 2005

The focus of this work is placed on the analysis of the mixture formation mechanism under the evaporative diesel spray of impinging and free conditions. As an experimental parameter, ambient gas density was selected. Effects of density variation of ambient gas on liquid and vapor-phase inside structure of evaporation diesel spray were investigated. Ambient gas density was changed between ${\rho}a=5.0\;kg/m^3$ and $12.3\;kg/m^3$. In the case of impinging spray, the spray spreading to the radial direction is larger due to the decrease of drag force of ambient gas in the case of the low density than that of the high density. On the other hand, in the case of free spray, in accordance with the increase in the ambient gas density, the liquid-phase length is getting short due to the increase in drag force of ambient gas. In order to examine the homogeneity of mixture consisted of vapor-phase fuel and ambient gas in the spray, image analysis was conducted with statistical thermodynamics based on the non-dimensional entropy (S) method. In the case of application of entropy analysis to diesel spray, the entropy value always increases. The entropy of higher ambient density is higher than that of lower ambient gas density during initial injection period.