• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1063-1070
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• 1988

The influence of the inlet pressure on bearing performance of tilting pad bearings in laminar regime is examined. A simple flow model is presented to calculate the inlet pressure in inlet flow that occurs at a short distance ahead of the bearing inlet. The bearing performances are obtained, load capacity, friction torque and lubricated flow-rate, etc, numerically for the inlet pressure boundary conditions with and without pressure jump. The computed results of both cases show that bearing performance and the optimum pivot position changes remarkably according to the bearing operating conditions. The influence of the inlet pressure on bearing performance must be considered to analyze the bearing performance precisely.

• Korean Journal of Agricultural Science
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• v.6 no.2
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• pp.125-133
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• 1979

The characteristics of landslides occurred in August 5, 1979 in pyeongchangkun were surveyed and indentified as follows. 1. Deep limestone regions. Distinct differences in soil texture between A1 and B horizon could be observed on soil profile, which is attributed to the clay illuviation. The clay illuvial horizon is supposed to be an important cause of large scale mudflows on middle slopes by the lubricant action of ground water flowing between top soil and subsoil. 2. Shallow limestone regions. Very shallow top soils (less than 50cm) laid on tilted bedrock stratification provide a proper condition of mass soil movement if the top soil is saturated and ground water flows between top soil and bedrock when concentrated heavy rainfalls shower. 3. Granite regions. Weathering granitic bedrock produces very coarse textured top soils which are very cohesionless and have many pores. Therefore, the soil has high infiltration ratio and is easy to be saturated by water and to be detached from the bedrock. The landslides abrase very severely both sides of gully with high potential energy when they flow down. The following methods for landslide prevention can be recommended. 1. The original parts of landslides on top of the gully must be treated by intensive planting of deep rooting species and check dams. 2. Clear-cutting and crop planting on steep slope (more than 25 degrees) should be controlled and prohibited. 3. Establishment of landslide prevention forest should be practised on proper site.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.4
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• pp.335-341
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• 2015

In this study, we analyzed a two-dimensional Stokes flow through a microchannel containing projections with constant spacing attached to each wall. The projections on the top and bottom walls were semi-circular in shape, with in-phase locations. By considering the periodicity and symmetry of the flow, the eigenfunction expansion and least squared error method were applied to determine the stream function and pressure distribution. For some typical radius and spacing values, the streamline patterns and pressure distributions in the flow field are shown, and the shear stress distributions on the boundary walls are plotted. In addition, the average pressure gradients in the microchannel are also calculated and shown with the radius and spacing of the projections. In particular, the results for the case of extremely small gaps between the projections on the top and bottom walls are in good agreement with the lubrication results.

• Tribology and Lubricants
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• v.27 no.4
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• pp.193-197
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• 2011

Friction behavior of nanoporous anodic aluminum oxide(AAO) film was investigated. A 60 ${\mu}m$ thick AAO film having nanopores of 45 nm diameter with 105 nm interpore-diatance was fabricated by mild anodization process. The AAO film was then saturated with paraffinic oil. Reciprocating ball-on-flat sliding friction tests using 1 mm diameter steel ball as the counterpart were carried out with normal load ranging from 0.1 N to 1 N in an ambient environment. The morphology of worn surfaces were analyzed using scanning electron microscopy. The friction coefficient significantly increased with the increase of load. The boundary lubrication layer of paraffinic oil contributed to the lower friction at relatively low load (0.1 N), but it is less effective at high load (1 N). Plastic deformed layer patches were formed on the worn surface of oil-enriched AAO at relatively low load (0.1 N) without evidence of tribochemical reaction. On the other hand, thick tribolayers were formed on the worn surface of both oil-enriched and as-prepared AAO at relatively high load (1 N) due to tribochemical reaction and material transfer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3119-3124
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• 2010

The purpose of this paper is to analyze dynamic behaviors of the oil film thickness and engine bearings in both aligned and misaligned operation conditions of a crankshaft using computer simulation techniques. A crankshaft as an elastic body is modeled for a misaligned crankshaft which is very important design parameter of the film thickness and engine bearings. In this analysis, a dynamic characteristic of a minimum oil film is analyzed based on the elastohydrodynamic lubrication theory. The boundary conditions for analyzing the film behaviors include non-linear constraint forces and bending moments in engine bearings. The more expedient model of an engine bearing is extended to consider the effect of crankshaft misalignment. The computed results indicate that the minimum oil film thickness that causes a major influence on the performance of engine bearings has showed a decrease of 16% to 24% for the misaligned crankshaft compared with an aligned crankshaft. The computed results show that the misalignment of a crankshaft inevitably brings the reduction of minimum oil film thickness and this may increase the failure of a bearing. These results as design parameters are very useful for a bearing designer as a firm reference data of an automotive engine.

• Tribology and Lubricants
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• v.26 no.1
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• pp.7-13
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• 2010

This experimental study presents tribological characteristics under boundary lubrication contacts associated with electrorheolocal (ER) fluid. ER fluid is prepared by using phosphorated starch particles and silicone oil. Experimental apparatus of tribological tester is designed and constructed to evaluate tribological characteristics of pin specimens. Wear tests under boundary lubrication of ER fluid are experimentally performed under consideration of several operational factors such as normal load, sliding distance, sliding speed and specimen materials: steel, copper and aluminum. After wear test, microscopic surface changes of the worn pin specimens are analyzed in order to investigate measured wear characteristics by using the scanning electron microscope (SEM) as well as surface profilometer. In addition, the chemical wear characteristics are investigated by using energy dispersive x-ray spectroscopy (EDS). Moreover, friction coefficient measurements under different materials of pin specimens are conducted for the tribological investigations. In order to verify the effect of starch phosphate particles in ER fluid, the wear test results with ER fluid are compared with test results with only silicone oil. The results clearly present that the phosphorated starch based ER fluid shows the stabilized wear as well as friction characteristics after run-in operations, but the wear rate under ER fluid is increased.

• The Korean Journal of Archival Studies
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• no.79
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• pp.5-32
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• 2024

The Korean government ranked 3rd among 193 UN member countries in the UN's 2022 e-Government Development Index. Korea, which has consistently been evaluated as a top country, can clearly be said to be a leading country in the world of e-government. The lubricant of e-government is data. Data itself is neither information nor a record, but it is a source of information and records and a resource of knowledge. Since administrative actions through electronic systems have become widespread, the production and technology of data-based records have naturally expanded and evolved. Technology may seem value-neutral, but in fact, technology itself reflects a specific worldview. The digital order of new technologies, armed with hyper-connectivity and super-intelligence, not only has a profound influence on traditional power structures, but also has an a similar influence on existing information and knowledge transmission media. Moreover, new technologies and media, including data-based generative artificial intelligence, are by far the hot topic. It can be seen that the all-round growth and spread of digital technology has led to the augmentation of human capabilities and the outsourcing of thinking. This also involves a variety of problems, ranging from deep fakes and other fake images, auto profiling, AI lies hallucination that creates them as if they were real, and copyright infringement of machine learning data. Moreover, radical connectivity capabilities enable the instantaneous sharing of vast amounts of data and rely on the technological unconscious to generate actions without awareness. Another irony of the digital world and online network, which is based on immaterial distribution and logical existence, is that access and contact can only be made through physical tools. Digital information is a logical object, but digital resources cannot be read or utilized without some type of device to relay it. In that respect, machines in today's technological society have gone beyond the level of simple assistance, and there are points at which it is difficult to say that the entry of machines into human society is a natural change pattern due to advanced technological development. This is because perspectives on machines will change over time. Important is the social and cultural implications of changes in the way records are produced as a result of communication and actions through machines. Even in the archive field, what problems will a data-based archive society face due to technological changes toward a hyper-intelligence and hyper-connected society, and who will prove the continuous activity of records and data and what will be the main drivers of media change? It is time to research whether this will happen. This study began with the need to recognize that archives are not only records that are the result of actions, but also data as strategic assets. Through this, author considered how to expand traditional boundaries and achieves reterritorialization in a data-driven society.