• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.15 no.2
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• pp.188-195
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• 1986

Condensation heat transfer can be classified in dropwise condensation and filmwise condensation, and for the industrial purpose, the former is more useful than the latter because of the higher heat transfer rate. But it is difficult to maintain the dropwise condensation continuously since most of the metal surfaces become wetted after exposure to a condensing vapor over an extended period of time. To maintain dropwise condensation continuously , various surface coatings and promoters have been used recently, but these methods must be reconsidered about the durability of condensing surface. Therefore, in this study, evaporating method of various pure metals on the condensing surface has been performed to maintain dropwise condensation. The results have showed that the heat transfer rate of silver evaporating surface is higher than any other metal evaporating in dropwise area. Transition temperature and filmwise condensation curves are uniform regardless of kinds of evaporating metals.

• Journal of the military operations research society of Korea
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• v.30 no.2
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• pp.108-121
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• 2004

This paper deals with a procedure of changing the current inspection & replacement periods for ROKAF aircraft parts. ROKAF is mostly operating aircraft of foreign makes, and takes maintenance actions according to Technical Orders(TO.) published by foreign aircraft manufacturers. Therefore ROKAF inspects and replaces specific parts at the time noticed from T.O.. These inspection and replacement periods are determined by manufacturers according to the standard operating environment and parts' durability. But the standard operating environment Is different from operator's environment. Because of this difference, the inspection and replacement periods have to be changed according to operators' operation environment. It is resonable that the manufacturer, having design materials and life test data of parts, changes those periods together with materials of operators' operation environment. But we have many difficulties in obtaining the design materials and life test data. Then this paper proposes a procedure of changing the periods of aircraft's parts with life data obtained during operating aircraft. For the reliability analysis, a software of RELEST (Reliability Estimation Version 1.0) is used.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.9
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• pp.1354-1358
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• 2002

Two hundred and ten post-larvae (PL) of Macrobrachium rosenbergii (14.5-14.9 mg) were equally distributed in two experimental groups and fed with either steam cooked or extruded pellet for a period of 60 days. Physical evaluation and growth promoting effect of both the pellets were assessed. Significantly higher (p<0.05) water stability, absorption and protein efficiency ratio (PER) were recorded in extruded pellet than the steam cooked pellet. Nutrient loss was minimum in the extruded pellet for which lower feed conversion ratio (FCR) (p<0.05) was recorded in this group. However, weight gain, relative growth and specific growth rate (SGR) in both the groups were not significantly different (p>0.05). Although insignificant (p>0.05) but higher amylase activity was recorded in steam pellet fed group. Survival was not affected by feeding either of the diets.

• Journal of Korean Dental Science
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• v.16 no.2
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• pp.164-171
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• 2023

Purpose: To evaluate the antimicrobial persistence of silver diamine fluoride (SDF) and silver fluoride (AgF) on Streptococcus mutans. Materials and Methods: An in vitro experiment was conducted to observe changes in the diameter of the inhibition zone of various materials, including AgF (Riva Star Aqua^TM step 1; SDI), potassium iodine (Riva star aqua^TM step 2; SDI), Fluor protector^® (FP, Ivoclar Vivadent), SDF (Riva star^TM step 1; SDI), Ampicillin (Sigma-Aldrich), Amphotericin B (Nexstar) and negative control on S. mutans. Result: SDF, AgF and FP exhibited significant antimicrobial persistence over the 4 weeks period (P<0.05). At day 28, the diameter of inhibition zone was larger in SDF than in AgF. Conclusion: SDF and AgF have significant antibacterial durability against bacteria commonly associated with dental caries, with the antimicrobial effect lasting for at least 4 weeks. Further clinical studies are needed to validate these findings in vivo.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2001.11a
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• pp.76-81
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• 2001

Recently, the structure is higher and larger, so that the application of high-strength concrete is increased, And as the development of construction skills, it is possible to place during the winter. Concrete work during winter is indispensible to shorten time of completion and cut costs. When concrete work during winter is placed, it has anxiety that concrete freeze at low temperature. As repetition of concrete's freezing cause reduction of durability, it is necessary for mixing to pay attention to air content and W/C ratios. Accordingly, in this study, we estimate the frost resistance by air content and W/C ratios, and development of strength after early-frost damage in the high-strength concrete during the cold weather. In this study, it could be confirmed that factors which were air content, W/C ratios and early curing period, affected on the frost resistance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.4
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• pp.695-702
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• 2001

In this paper, the drop/impact simulation for a mobile phone has been carried out with the explicit code LS-DYNA and its validation has been experimentally verified. The small size of this kind of electronics products makes it time-consuming, and difficult to conduct drop tests to detect the failure mechanism and identify their drop behaviors. Strict drop/impact performance criteria of such hand held electronic products as mobile phones play an important role in their design because these products must withstand both normal and unexpected shock. Usually, the product durability on drop impact depends on designers experience. The present reliable methodology of drop/impact simulation provides an efficient and powerful vehicle to improve the design quality and reduce the design period.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.95-100
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• 1996

This paper presents the experimental study on hardening process of high-strength and high-flowable concrete. The experiments were performed to investigate any unfavorable construction situations since the actual concrete placement has been scheduled in cold weather period, so that the high quality concrete construction is convinced to be successfully carried out. The tests were conducted using 600nm and 1000nm height of steel tube to simulate the practical concrete filled steel tube columns according to the following variables as: the categories of chemical admixtures, curing temperatures and curing schemes. The test results were analyzed in terms of hardening speed, internal heat of hydration and history of strength gain. This paper emphasizes the importance of curing schemes on durability and the use of hardening accelerators on strength gain.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.321-322
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• 2012

Since 1980, rapid social and economic development due to increased plant construction has led to a plant dormitory in a short period. In recent years, by the advent of the durability of dormitory remodeling is a critical need. However, user requirements due to the lack of owner's budget do not reflected. As a result, users have complained about the scope of construction, and construction stakeholder in accordance with the budget efficiency of the complaints have decreased. In this study the remodeling requirements in the planning stages is proposed for the remodeling process. In addition work type and element can select a range of construction worksheet are proposal.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.11a
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• pp.29-32
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• 2006

Experimental test results of field construction, Cheongju University Educational Liberal Art Building, applying the insulating curing method on slab concrete showed that the quality of concrete in fresh and hardened state satisfied all target values. Temperature history of slab concrete in A and B area secured more than $7.8{\sim}9.2^{\circ}C$ higher than outside atmosphere. After completing certain curing period of time on the surface of the structure, crack occurrence was not found. It is concluded that the preventing vaporization of moisture by the insulating curing method reduces plastic and drying shrinkage as welt as improves durability.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.2
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• pp.205-212
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• 1998

Experiments were conducted to investigate the temperature profile and the emissions conversion efficiency of catalytic converters for natural gas vehicles. Two types of the catalyst structure and several transient engine operating conditions were used. The dual-bed catalyst effectively reduced the emissions in a transient period due to the low heat capacity of the front bed. The lanthanoid additives were effective in improving catalyst durability. When the natural gas fueled engine were operated outside of a very narrow window of excess air ratio (from 0.993 to 1.004), the HC and NOx conversion efficiency dropped off. The drop-off were especially fast on the lean side of the window.