• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.155-155
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• 2022

Low head, ogee spillways is popularly used to defense against floods as well as to provide water for irrigation. Spillway is also used to assess compliance with water quality regulations by controlling amount of discharge to the downstream of a channel. For the purpose of water resource management and/or environmental aspects as explained above, the flow discharge through spillways need to be correctly rated as a function of geometry and hydraulic variables. Typically, four flow conditions are encountered during the operation of spillway: (a) uncontrolled free flow (UF); (b) uncontrolled submerged flow (US); controlled free flow (CF); and controlled submerged flow (CS), and each condition has a unique rating equation. However, one of the tricky part of the spillway operation is finding correct flow type over the spillway because structures can operate under both submerged and free flow conditions, and the types are continuously changing over time depending on the amount of discharge, head water and tail water elevation. Quite obviously, if the wrong rating curve relationship is applied because of misjudgment of the flow type due to a transition, a serious error can occur. Thus, an hydraulic model study of one of spillway structure located in South Florida was conducted for the purpose of developing transition relationships. In this presentation, US to UF transition is highlighted.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.37 no.1
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• pp.1-11
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• 2019

This study was conducted to analyze the conservation status by diagnostical methology for the front wall of Jungjeongdang area of Dodong-Seowon. The study was carried out as photogrammetry and mapping - investigation of materials and conservation status - analysis and evaluation of conservation status. The results are as follows. First, in the case of photogrammetry, each photograph was took in superposition, and the distortions of the photographs were corrected and synthesized. Based on this, actual survey drawings of the wall were prepared. Second, in case of material and conservation status, the wall is in the form of Wapyeondam and the material of the head part are tile, mud and lime, and the material of the body part are mud and tile. The mud was mixed with gravel, sand and straw. At the base part, amorphous natural stones and mud were used. The remarkable damage that appears on the wall is erosion of the base part, and some disintegration appears in the body part. There is a biological patina on the head and the base, and vegetation such as lichen is concentrated on the partial body. There was superficial deposit in the head part, and some tiles were broken or lost. Deep fissures are intensively located in some part of the eastern wall. Third, in the case of analysis and evaluation of the conservation status, it is considered that by the erosion of the foundation part and the disintegration of the body part, there is a possibility that physical damage will continue to be applied to the wall, so immediate action is necessary. The distribution of biological patina and vegetation does not appear to cause great problems in the wall, but it is necessary to reduce it in view of aesthetic problems. A cracked or missing tile would need to be replaced, and deep cracks in the eastern wall appear to have been caused by subsidence, and reinforcement of the underground is necessary to prevent further damage.

• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.2
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• pp.97-105
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• 2002

A centrifugal water chiller using alternative refrigerant R134a has been developed. The prototype was designed to have refrigerating capacity of 300RT. Its compressor employs a single high-speed impeller, airfoil diffuser and collector. Newly developed, enhanced tubes were installed in the evaporator and the condenser to reduce the required head for the compressor. Off-design characteristics at various conditions, performance test of the compressor and analysis of the refrigeration cycle were performed. So the probability of use in part load condition was checked and the direction for revision was suggested.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.323-330
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• 1999

Daylight collapse have been occurred by about 5.0m deep at ground surface and collapse of the crown head part of the tunnel have connected to the ground surface during first step of shotcrete work after blasting of upper half section of the tunnel driving at two-way double track tunnel face section on highway construction. This study is for a successful illustration case for the earth improvement method through applying such strengthening methods as cement milk grouting, S.G.R grouting,, steel pipe reinforced multi-step grouting etc. for the purpose of earth strengthening of loosened earth block occurred by tunnel collapse.

• Structural Engineering and Mechanics
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• v.12 no.2
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• pp.119-134
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• 2001

This paper deals with an experimental and numerical study of a mono-strand wedge anchor head mechanism. First, the experimental program is presented and monitored data such as wedge slippage, anchor deflection and strain distributions along external peripheral surfaces of the anchor head are presented and discussed. In accordance with the experimental set up, these data concern only the global behaviour of the mechanism and cannot provide valuable information such as internal stress-strains distributions, stress concentrations and percentage of yielded volume. Therefore, the second part of this paper deals with the development of an efficient numerical finite element model capable of providing mechanism of the core information. The numerical model which includes all kinematics/material/contact non-linearities is first calibrated using experimental data. Subsequently, a numerical study of the anchorage mechanism is performed and its behaviour is compared to the behaviour of a slightly geometrically modified mechanism where the external diameter has been increased by 5 mm. Finally, different topics influencing the anchorage mechanism behaviour are addressed such as lubrication and wedge shape.

• IE interfaces
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• v.21 no.1
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• pp.85-95
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• 2008

Reliability prediction serves many purposes during the life of a system, so several methods have been developed to predict the parts and systems reliability. MIL-HDBK-217F, among the those methods, has been widely used as a requisite tool for the reliability prediction which is applied to nuclear power plants and their safety regulations. This paper presents the reliability prediction for the DSP(Digital Signal Processor) module composed of three assemblies. One of the assemblies has a monitoring and self test function which is used to enhance the module reliability. The reliability of each assembly is predicted by MIL-HDBK-217F. Based on these predicted values, Markov modelling is finally used to predict the module reliability. Relax 7.7 software of Relax software corporation is used because it has many part libraries and easily handles Markov processes modelling.

• Proceedings of the Korean Society of Sericultural Science Conference
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• 2003.10a
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• pp.143-143
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• 2003

Among all animal species, a few have the remarkable capacity to regenerate a missing part of their body after amputation. The early process of epimorphic regeneration in which dedifferentiation and cell proliferation are involved, provides a useful model to investigate the mechanism of normal development as well as differentiation. To better understand early stage of head regeneration, we have generated 5'-end sequence of 1,592 expressed sequence tags (ESTs) from cDNA library of regenerating tissue. (omitted)

• Special Issue of the Society of Naval Architects of Korea
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• 2009.09a
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• pp.115-122
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• 2009

In shipbuilding process, automated marking systems are used to print steel part information on the steel plate. Especially, an automated marking system with a moving ink-head prints characters on each block, which divide the steel plate into a fixed size. Therefore it is necessary to split characters, because some characters can be extended into several blocks. Particularly the algorithm, which splits characters, must guarantee its printing quality in any direction since characters can be printed by any angle.

• Journal of Ocean Engineering and Technology
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• v.8 no.1
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• pp.131-143
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• 1994

The BTA(boring and trepanning association) deep hole machining has an increasing demands because of its wide applications and its good productivity. The main feature of the BTA tools is that the tool cutting edges are unsymmetrically located on the boring head. This provides a stabilizing cutting force resultant necessary for self guidance of the boring head. The BTA tools are capable of machining for having a large length to diameter ratio in single pass. A study of the accuracy and surface finish of holes produced would reveal quite useful information regarding the process. This study deals with the experimental results obtained during BTA machining on SM55C, SM45C steel under differnt machining conditions.

• Journal of the Korean Society of Safety
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• v.28 no.5
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• pp.83-89
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• 2013

Occupational Safety and Health Act provides that industrial safety helmets are personal protective equipment(PPE) to protect heads against falls from a height. Relevant domestic regulations are distinguished and different from other countries' cases. This study investigated industrial safety helmet's protective purposes and characteristics related to falls and the notion of fall prevention. A comparative analysis of regulations on safety helmets and fall prevention as well as standards on safety helmet's impact test requirements is followed by a literature review. It is also suggested that the term "fall" related to safety helmets should be changed to "impact on the upper part of head" in domestic regulations and standards.