• Title/Summary/Keyword: long-hole

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Flow Condensation Heat Transfer Coefficients of R22, R410A and Propane in Aluminum Multi-Channel Tube (알루미늄 다채널 평판관내 R22, R410A, Propane의 흐름 응축 열전달 성능 비교)

  • Park Ki-Jung;Lee Ki-Young;Jung Dongsoo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.7
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    • pp.649-658
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    • 2005
  • Flow condensation heat transfer coefficients (HTCs) of R22, R410, Propane (R290) were measured inside a horizontal 9 hole aluminum multi-channel flat tube. The main test section in the refrigerant loop was made of a 0.53m long multi-channel flat tube of hydraulic diameter of 1.4 mm. Refrigerant was cooled by passing cold water through an annulus surrounding the test section. Data were obtained in qualities of $0.1\~0.9$ at mass flux of $200\~400kg/m^2s$ and heat flux of $7.3\~7.7kW/m^2$ at the saturation temperature of $40^{\circ}C$. All popular heat transfer correlations in single-phase subcooled liquid flow and flow condensation originally developed for large single tubes predicted the present data of the multi channel flat tube within $25\%$ deviation when effective heat transfer area was used in determining experimental data. This suggests that there is little change in flow characteristics and patterns when the tube diameter is reduced down to 1.4 mm diameter range. Hence, a modified correlation based on the present data was proposed which could be applied to small diameter tubes with effective heat transfer area. The correlation showed a mean deviation of less than $20\%$ for all data.

A Study on Issues relating to Kandys and Persiandress among the Persian Costume (페르시아 복식(服飾) 중(中) Kandys와 Persiandress의 문제점(問題点)에 대(對)한 연구(硏究))

  • YiChang, Young-Soo
    • Journal of Fashion Business
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    • v.7 no.2
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    • pp.15-25
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    • 2003
  • In this study on the Persiandress called Persiandress or Mediandress, its names, styles, and structures that are still subject to a great deal of controversy were investigated. In addition, the reason why the Persiandress was wrongly named as Kandys by the early researchers was also examined. The documents of reliefs on the Apadanastairs in Persepolis and the European papers concerning this themes were subject of this analysis. Such investigation and examination results are summarized as follows. There is still no agreed name describing the Persiandress, which is called "Persiandress" or "Mediandress". Further, there is no definite conclusion on whether the Persiandress was made in one piece or two pieces. The first person who insisted that the Persiandress was made in one piece is a German archaeologist, Ernst Herzfeld. He said that the Persiandress was made in one long tetragonal piece, had a hole in the middle for head, and had lots of pleats when it was tied with a belt. On the contrary, researchers who insisted that the Persiandress was made in two pieces stressed the sleeve pleats in four folds, which is one of the representative characteristics, and said that such four-fold sleeve pleats would not be formed when the Persiandress was made in one piece and worn by a belt. Consequently, they have conducted studies according to their insistence and the resultant pattern. Kandys, the Median's typical dress, is a coat worn over the jacket and trousers. Although it had sleeves, the Median did not use them. Indeed, Kandys was used as a kind of cloak. However, the wrong term, Kandys is still used in Korea. So, it is necessary to correct use of such wrong term.

A Study on the Mining Method for Limestone Mines with Less Environmental Hazards (환경오염 저감을 위한 석회석 광산개발방안에 대한 연구)

  • 임한욱;김재동;백환조
    • Tunnel and Underground Space
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    • v.10 no.1
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    • pp.80-91
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    • 2000
  • Open cut mining of limestone is generally considered to be more advantageous than underground mining in recovery, grade control, economics, and safety, but it causes substantial environmental pollutants such as ground vibration, noise, dust. It also changes ground surface and may destroy vegetation. The Halla limestone mine which lies adjacent to Baikdu mountains range is selected for a model study. To reduce environmental hazards, and to conserve original surface and woods, both open cut and underground mining methods must be adopted. In case of sub-level sloping. a unit block of 87m high, 70m wide, and 100∼l20m long is suggested with an estimated overall recovery of 42%. Some suggestions to reduce the environmental hazards are also included. The followings must be considered in determining the degree of fragmentation; the discontinuity conditions in the rock mass and the charge concentration both at the bottom and column of the hole. In addition to adopting a barrier wall for reducing environmental hazards, the probable production from underground mining is also discussed.

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Speedy Two-Step Thermal Evaporation Process for Gold Electrode in a Perovskite Solar Cell

  • Kim, Kwangbae;Park, Taeyeul;Song, Ohsung
    • Korean Journal of Materials Research
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    • v.28 no.4
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    • pp.235-240
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    • 2018
  • We propose a speedy two-step deposit process to form an Au electrode on hole transport layer(HTL) without any damage using a general thermal evaporator in a perovskite solar cell(PSC). An Au electrode with a thickness of 70 nm was prepared with one-step and two-step processes using a general thermal evaporator with a 30 cm source-substrate distance and $6.0{\times}10^{-6}$ torr vacuum. The one-step process deposits the Au film with the desirable thickness through a source power of 60 and 100 W at a time. The two-step process deposits a 7 nm-thick buffer layer with source power of 60, 70, and 80 W, and then deposits the remaining film thickness at higher source power of 80, 90, and 100 W. The photovoltaic properties and microstructure of these PSC devices with a glass/FTO/$TiO_2$/perovskite/HTL/Au electrode were measured by a solar simulator and field emission scanning electron microscope. The one-step process showed a low depo-temperature of $88.5^{\circ}C$ with a long deposition time of 90 minutes at 60 W. It showed a high depo-temperature of $135.4^{\circ}C$ with a short deposition time of 8 minutes at 100 W. All the samples showed an ECE lower than 2.8 % due to damage on the HTL. The two-step process offered an ECE higher than 6.25 % without HTL damage through a deposition temperature lower than $88^{\circ}C$ and a short deposition time within 20 minutes in general. Therefore, the proposed two-step process is favorable to produce an Au electrode layer for the PSC device with a general thermal evaporator.

A Case Study of PHC Pile Behavior Characteristics on Dynamic Compacted High Rock Embankment (고성토 암버력 동다짐 지반에 시공된 PHC 말뚝의 거동특성 사례연구)

  • Yu, Nam-Jae;Yun, Dong-Kyun;Bae, Kyung-Tae;Kim, Hyung-Suk;Lee, Dal-Ho;Park, Yong-Man
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.09a
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    • pp.519-526
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    • 2010
  • The construction site for $\bigcirc\bigcirc$ transformer substation was located at a mountain valley. In order to prepare the site, the valley was first filled with crushed rock debris up to 63m. Since the main concern of this project is to minimize differential settlement of the foundation of transformer facilities, dynamic compaction was performed every 7m followed by reinforcement with EMP(Ez-Mud Piling). The EMP is one of bored piling methods, in which a hole is bored by means of air percussion and maintain by injecting Ez-Mud. Then a PHC pile (Pretensioned spun High strength Concrete pile) is embedded and finalized with a hammer. In this study, bearing capacities and long term behavior of a pile installed by EMP were investigated. To achieve these objectives, a series of tests such as static and dynamic load tests were conducted. In addition, a construction quality control standard was proposed based on the test results.

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Treatment Results of Twist-drill Craniostomy with Closed-system Drainage for the Symptomatic Chronic Subdural Hematoma Patients (임상증상을 보이는 만성 경막하혈종 환자에 대한 소천공배액술의 치료결과)

  • Lee, Chul-Woo;Hwang, Sun-Chul;Kim, Bum-Tae;Lee, Se-Young;Im, Soo-Bin;Shin, Won-Han
    • Journal of Korean Neurosurgical Society
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    • v.37 no.4
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    • pp.282-286
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    • 2005
  • Objective: Symptomatic chronic subdural hematoma(CSDH) is a well-known neurosurgical entity and most of the lesion is managed by surgical treatment. The authors analyze the surgical indication and the treatment results of twist drill craniostomy with closed-system drainage(TDD) for the symptomatic CSDH. Methods: From March 2001 through December 2003, 31 patients who were treated with TDD for the symptomatic CSDH and followed more than 6months were included. The radiologic criteria of TDD in this study were 1) homogeneous density of hematoma on computed tomography(CT), 2) no septation of hematoma on magnetic resonance imaging(MRI), and 3) thicker hematoma more than twice thickness of skull. Surgical procedures were performed on the maximum thickness of hematoma on CT/MRI. Short and long Steinman pins were used to penetrate the skull and hematoma membrane. As the 5L catheter was inserted through the drill hole, it was kept for 1 - 7days for the drainage of CSDH. The patients of CSDH were followed with clinical symptoms and CT studies. Results: Most of all the 31 patients were improved. However, one patient was suffered from postoperative epidural hematoma and the other patients have received the secondary operation because of the recurrence of CSDH on 3 months after initial surgery. Conclusion: TDD is safe procedure for the symptomatic CSDH if the patients are selected appropriately.

Energy-Efficient Face Routing Protocol Considering Radio Range in Wireless Sensor Networks (무선 센서 네트워크에서 무선 반경을 고려한 에너지 효율적인 페이스 라우팅 프로토콜)

  • Cho, Hyunchong;Kim, Sangdae;Kim, Cheonyong;Kim, Sang-Ha;Hwang, Chi-Jung
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.6
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    • pp.1058-1069
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    • 2015
  • In wireless sensor networks, geographic routing is known as an efficient method to transmit the data packet using the location information. Geographic routing relies on two techniques: greedy forwarding and face routing. Face routing helps to recover from greedy routing fail and is based on the planar graph in which does not cross each edge. However, the planarization causes frequently short transmission of data packet because it removes other edges except the shortest one. In other words, since the planarization removes the long edges, face routing could not exploit the efficient removed edges of communication graph. This problem brings about the excessive energy consumption of nodes. In this paper, we propose an energy efficient face routing protocol in wireless sensor networks. This proposed protocol searches the removed edges and transmits them via the edges. Simulation shows that the proposed protocol is more efficient in terms of energy consumption than the previous face routing.

Development of the Corrugated fiberboard Box for Cold-chain Distribution of Chinese Cabbage (배추의 저온유통용 골판지포장상자 개발)

  • Lee, Won-Og;Yun, Hong-Sun;Jeong, Hoon;Lee, Hyun-dong;Cho, Kwang-Hwan;Kim, Man-Soo
    • Food Science and Preservation
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    • v.10 no.1
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    • pp.23-27
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    • 2003
  • This study was conducted to develop the corrugated fiberboard box which is suitable to pre-cooling and low temperature distribution of chinese cabbage Consider from a cooling performance viewpoint, the folding type box with 5.4% vent hole ratio was most efficient for fast cooling and even temperature distribution in the packaging box. At the end of storage periods, the compressive strength of the folding type box was less than the bliss type box. However, the compressive strength of the folding type box after storage was higher than required safety compressive strength for long term storage. So the folding type box was considered to have no problems toy practical use. The shelf-life of the chinese cabbage packaged with the developed box was 6∼7 days which was 2∼3 days longer than usual packaging.

Comparison of three different orthodontic wires for bonded lingual retainer fabrication

  • Baysal, Asli;Uysal, Tancan;Gul, Nisa;Alan, Melike Busra;Ramoglu, Sabri Ilhan
    • The korean journal of orthodontics
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    • v.42 no.1
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    • pp.39-46
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    • 2012
  • Objective: We evaluated the detachment force, amount of deformation, fracture mode, and pull-out force of 3 different wires used for bonded lingual retainer fabrication. Methods: We tested 0.0215-inch five-stranded wire (PentaOne, Masel; group I), $0.016{\times}0.022$-inch dead-soft eight-braided wire (Bond-A-Braid, Reliance; group II), and 0.0195-inch dead-soft coaxial wire (Respond, Ormco; group III). To test detachment force, deformation, and fracture mode, we embedded 94 lower incisor teeth in acrylic blocks in pairs. Retainer wires were bonded to the teeth and vertically directed force was applied to the wire. To test pull-out force, wires were embedded in composite that was placed in a hole at the center of an acrylic block. Tensile force was applied along the long axis of the wire. Results: Detachment force and mode of fracture were not different between groups. Deformation was significantly higher in groups II and III than in group I (p < 0.001). Mean pull-out force was significantly higher for group I compared to groups II and III (p < 0.001). Conclusions: Detachment force and fracture mode were similar for all wires, but greater deformations were seen in dead-soft wires. Wire pull-out force was significantly higher for five-stranded coaxial wire than for the other wires tested. Five-stranded coaxial wires are suggested for use in bonded lingual retainers.

Recent Changes in Solar Irradiance, Air Temperature and Cloudiness at King Sejong Station, Antarctica (남극 세종기지에서 최근 태양 복사, 기온과 운량의 변화)

  • Lee, Bang Yong;Cho, Hi Ku;Kim, Jhoon;Jung, Yeon Jin;Lee, Yun Gon
    • Atmosphere
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    • v.16 no.4
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    • pp.333-342
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    • 2006
  • The long-term trends of global solar irradiance, air temperature, specific humidity and cloudiness measured at King Sejong station, Antarctica, during the period of 1988-2004, have been investigated. A statistically insignificant decrease, -0.21 $Wm^{-2}yr^{-1}$ (-0.26 %$yr^{-1}$, P<0.5) in global solar irradiance was found in an analysis from the time series of the monthly mean values, except for the increasing trends only in two months of January and June. The trends in irradiance are directly and inversely associated with the cloudiness trends in annual and monthly means. The trends in surface air temperature show a slight warming, $0.03^{\circ}Cyr^{-1}$ (1.88 %$yr^{-1}$, P<0.5) on the annual average, with cooling trend in the summer months and the warming in the winter. The exact relationship, if any, between the irradiance and temperature trends is not known. No significant tendency was found in specific humidity for the same periods. Recent (1996-2004) erythermal ultraviolet irradiance shows decreasing trend in annual mean, -0.15 $mWm^{-2}yr^{-1}$ (-1.18 %$yr^{-1}$, P<0.1) which is about five times the trends of global solar irradiance. The ratio of erythermal ultraviolet to global solar irradiance shows remarkable seasonal variations with annual mean value of 0.01 % and a peak in October and November, showing the increase of ultraviolet irradiance resulting from the Antarctic ozone hole. The sensitivity of global solar irradiance to the change in cloudiness is roughly $13%oktas^{-1}$ which is about twice of the value at the South Pole due to the difference in the average surface reflectance between the two stations. Much more sensitive values of $59%oktas^{-1}$ was found for erythermal UV irradiance than for the global solar irradiance.