• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.1 no.4
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• pp.265-275
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• 1989

An experimental study of decaying swirl air flow has been obtained by tangential inlet in a straight tube with Reynolds number range 20,000~40,000. The friction factor, swirl angle, velocity profiles and turbulent intensity are measured by using micro-manometer and hot-wire anemometer. It is found that the swirl flow behaviors depend on the swirl intensity along the test tube.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2253-2261
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• 2002

Recently the hydroforming technology has drawn a lot of attention because of its capability to produce high quality and light weight parts. In the present study, the tube expansion - one of the simplest hydroforming processes, has been investigated in order to understand fundamental phenomena such as deformation characteristics and effect of process parameters. As a result, the most important process parameters, which determine the state of stress at the expanded zone, were found to be pressure and die displacement. If the stress becomes equi-axial tension at the zone, necking occurs at some distance from the weld line and develops into a crack along the axial direction. Some aspects of mechanical property measurements as well as distributions of hardness and microstructure are also discussed in this paper.

• Proceedings of the KIEE Conference
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• 2003.11b
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• pp.63-66
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• 2003

Resident mobile communication system technology has been developed. But, surged high voltages in antenna generally have damaged mobile communication. To solve this problem, we use arrester in Rx-Tx line system. That is, the arrester is to protect devices in system against considerable over-voltages or lighting strike. Currently, system protection using of arrester has been arrived in content level but these days, the fact of PIMD(Passive Intermodulation Distortion) which is RF passive components' nonlinear characteristic has appeared. This paper describes PIMD' causes occurred in arrester-estimated from Gas tube capsule, plating, temperature, humidity by experiment.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.2
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• pp.87-94
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• 2003

To reduce the air side pressure drop in air-cooled heat exchanger, tow-in type winglet vortex generators are applied. A specially designed multiple-channel test core was used in the experiments for the various geometry of winglet vortex generators. The proposed tow-in type vortex generator gives significant separation delay, reduces form drag, and removes the zone of poor heat transfer from near-wake of the tubes. The results show the significant pressure drop reduction for the tow-in win91e1 vortex generators with the similar enhancement of the heat transfer as other vortex generator applications in heat exchanger. In the range of Reynolds number of 350 to 2100 the pressure drop decrease 8∼15% and 34∼55% for the in-line and staggered tube banks, respectively, compared to those without vortex generators.

• Communications of the Korean Institute of Information Scientists and Engineers
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• v.5 no.2
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• pp.105-107
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• 1987

A storage tube, Tektronix 4010, was added to NOVA 840 system at Korea Advanced Institute of Science in 1974 and efforts were made to develop an interactive graphics system. These include a software library, called TCS(Terminal Control System) [4], algorithms for hidden line and surface eliminations [5. 6], and two single user graphics systems based on different concepts involving graphic languages [2, 11]. A storage tube is a low-cost terminal, which is useful in certain applications, but introduces some problems since partial modification of the screen is not possible without erasing it entirely. Thus it has far reaching effects on the design of an interactive graphics system. The components of an interactive graphics system will be explained in section 2 and their relation ships with the choice of storage tube as the output device will be pointed out.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.211-212
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• 2005

Semiconductor fabrication technique has been increasingly developed virtue of greater demands, and supplies and applied semiconductor components in respective processes under development for minuteness. Now semiconductor having a line-width of 75nm was commercialized, and it is possible to scale down to 25nm. Accordingly, to cover with limitations, alternatives are actively investigated. In this paper, we overview the trend and applications of carbon nano tube (CNT) and present the future and technology based on existed theories.

• Journal of the Korean Society of Costume
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• v.64 no.6
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• pp.91-101
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• 2014

String, as clothing material, has played a functional, symbolic and decorative role in garment traditionally. The string has a shape of continuous line, which is one of the basic elements for the design: points, lines and sides. It can effectively represent the silhouette by making our vision flow to a certain direction. This study reinterprets the traditional form of string in a new modern way by developing "Tube-Shaped String" which has an empty hole in the middle. As a creative attempt, the new tube-shaped string can be used for fashion design by applying it to unique shapes, colors, textures, and draping expressions. In a role dimension, this string can become the main fabric material. The methods of the study are as follows. First, it examines the traditional shape and role of string in the history of garment. Second, it studies modern designers, such as Christian Dior, Ann Demeulemeester, Dolce & Gabbana, and 3.1 Phillip Lim, who have applied the string to their design, and have explored the various potentials of the string in the past four years. Finally, based on the theoretical research and practical analysis, this study creates a new tube-shaped string, applying its own technique to fabricating three garments: jacket, dress, and body suit. As a result, each garment shows unique silhouettes, rich texture and color, and rhythmical movement. The unique silhouettes reflect the shape and movement of different bodies. The texture and color are created through the shades of the string which come from the overlapping strips. The garments come with an unbeatable aesthetic design compared to conventional uniform design. As a new material in clothing, this tube-shaped string can be developed to satisfy the public, which has widely varying tastes in fashion.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.259-264
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• 2009

Most of the fossil power plants firing lower grade coals are challenged with maintaining good combustion conditions while maximizing generation and minimizing emissions. In many cases significant derate, availability losses and increase in unburned carbon levels can be attributed to poor combustion conditions as a result of poorly controlled local fuel and air distribution within the boiler furnace. The poor combustion conditions are directly related to the gas flow deviation in upper furnace and convection tube-bank but a less reported issue related to in large-scale oppose wall fired boilers. In order to develop a on-line combustion monitoring system and suggest an alternative heat flux estimation method at tube bank, which is very useful information for boiler design tool and blower optimizing system, field test was conducted at operating power boiler. During the field test the exhaust gases' temperature and tube metal temperature were monitored by using a spatially distributed sensors grid which located in the boiler's high temperature vestibule region. At these locations. the flue gas flow is still significantly stratified, and air in-leakage is minimal which enables tracing of poor combustion zones to specific burners and over-fire air ports. Test results showed that the flue gas monitoring method is more proper than metal temperature distribution monitoring for real time combustion monitoring because tube metal temp. distribution monitoring method is related to so many variables such as flue gas, internal flow unbalance, spray etc., Heat flux estimation at the tube bank with flue gas temp. and metal temp. data can be alternative method when tube drilling type sensor can't able to use.

• Corrosion Science and Technology
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• v.22 no.6
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• pp.435-446
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• 2023

Corrosion behaviors of laser-welded super duplex stainless steel (SDSS) tubes after exposure to an actual power plant environment for one year and those of fin-tube welded SDSS were evaluated. Results showed that corrosion damage on the back side of the SDSS tube in the direction of hot air was higher than that on the front side regardless of weldment location. However, corrosion damage showed no difference between weldment and base metal due to recovery of phase fraction in the weldment through post weld heat treatment (PWHT). Nevertheless, the SDSS tube showed severe corrosion damage along grain boundary due to surface phase transformation (δ → γ) and Cr₂N precipitation caused by PWHT with a high N₂ atmosphere. Corrosion resistance of the SDSS tube was recovered when degraded surface was removed. Corrosion sensitivity of a fin-tube increased significantly due to pre-existing crevice, unbalanced phase fraction, and σ phase precipitation adjacent to the fusion line. Although corrosion resistance was improved by recovered phase fraction and sufficient dissolution of σ phase during PWHT, corrosion reaction was concentrated at the pre-existing crevice. These results suggest that welding conditions for fin-tube steel should be optimized to improve corrosion resistance by removing pre-existing crevice in the weldment.

• The Journal of the Petrological Society of Korea
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• v.18 no.3
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• pp.237-253
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• 2009

The lava flows forming the Manjanggul lava tube are commonly said to have a potential source from the Geomunoreum scoria cone. We inferred the source of lava flows with the Manjanggul lava tube, based on many studies about lava tubes within lava flows of active volcano in the world. We made a lava flow field map from lithofacies, features and latitude of lava surfaces in the northeastern part of Jeju Island, and then examined closely the distribution and mutual relation of lava tubes in each lava flow field. As result, the Geomunoreum lava tube system is divided into a series of master tubes(Utsanjeungul, Bukoreumgul, Daerimdonggul, Manjanggul, Gimnyeonggul, Yongcheondonggul and Dangcheomuldonggul lava tube), a complicated networks of small tubes(Bengdwigul lava tube), and a series of unitary tubes(Gimyeongbilemotgul~Gaeusaemgul lava tube) in Geomunoreum lava flows. Particularly a canyon, 2km in length to NNE direction from the Geomunoreum scoria cone, is interpreted to be collapse trench of lava tube roof that belongs to an upflow part of the master tube in the Geomunoreum lava tube system, according to the location and direction. Accordingly, the source of lava flows, forming the Manjanggul lava tube, is the Geomunoreum scoria cone.