• Title/Summary/Keyword: Shield Conditions

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Friction Characteristics of Aluminized Polyester Fabric under Dry - and Water- Lubricated Conditions

  • Byun, JaeYoung;Okechukwu, Nicholas Nnaemeka;Lee, Eunsuk;Park, JinGyu;Choi, WonSik
    • Tribology and Lubricants
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    • v.35 no.6
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    • pp.396-402
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    • 2019
  • Materials made from plastics are increasingly utilized in constructing greenhouses and setting up shield structures. Polyester fabrics have a wide range of use in horticulture and other fields of agriculture. They are utilized as a greenhouse cover and also help in combating intense climate variation in the field. Over time, these fabrics may experience friction against other surfaces. Owing to this, the surface framework of the material degenerates. This study examines the frictional characteristics of aluminized polyester fabric in both dry- and water-lubricated environments under changing applied loads and sliding speeds. Friction experiments are performed at room temperature by employing a pin on a disk. The experiments reveal that the friction coefficient decreases with increase in applied load in both dry sliding and water-lubricated environment. However, the friction coefficient decreases more under the water-lubricated setting than in the dry state. At the maximum applied load, the highest friction coefficient is discovered in the dry state with a range of 0.282 to 0.237, whereas a friction coefficient of 0.229 to 0.189 is observed in the water-lubricated state. Additionally, it is observed that the friction coefficient increases with an increase in sliding speed under both experimental environments. The examination of specimen surfaces reveals that the abrasion is minor in the water-lubricated setting compared with that in the dry state.

An evaluation of influence factors based on the limit state design-AASHTO LRFD for structural analysis of shield tunnel segment lining (한계상태설계법-AASHTO LRFD를 적용한 쉴드터널 세그먼트 라이닝의 구조해석 영향인자 평가)

  • Kim, Yang-Woon;Kim, Hong-Moon;Kim, Hyun-Su;Lee, Seong-Won
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.1
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    • pp.99-118
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    • 2018
  • Recently, the limit state design method in the design of the structure is in global trend, but it is limited to a few structures in Korea. Since the introduction of the limit state design method has recently been attempted for tunnels, which are the main underground structures, it is surely necessary to understand the latest limit state design method. Therefore, based on the recently published AASHTO LRFD Road Tunnel Design and Construction Guide Specification (2017), structural load factors and load combinations were reviewed, and various factors which should be applied for the review of structures have been analyzed. In this study, utility tunnel section and subway tunnel sections used in Korea were analyzed by the limit state design method, and we have analyzed the direction of application of limit state design method through studying the tendency of member force by various influential factors such as ground conditions, load modifier and joint stiffness.

Design and Performance Test of a Direct Cooling Equipment for Hydrogen Liquefaction (수소액화용 직접냉각장치의 설계 및 성능시험)

  • Baik, Jong-Hoon;Kang, Byung-Ha;Chang, Ho-Myung
    • Journal of Hydrogen and New Energy
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    • v.7 no.2
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    • pp.121-128
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    • 1996
  • A direct cooling equipment for hydrogen liquefaction has been developed and tested. A direct cooling equipment consists of a liquefaction vessel, a radiation shield, a cryostat and a GM refrigerator. The cool-down and warm-up characteristics of the liquefaction apparatus have been investigated in detail. It is found that the hydrogen starts to be liquefied in the liquefaction vessel after 45 minutes of cool-down. The cool-down and warm-up tests of helium gas are also performed. The cool-down and warm-up characteristics of helium gas are found to be very different from those of hydrogen gas, since helium is not liquefied under the present operating conditions. When the liquefaction vessel is evacuated, natural convection phenomena of charged gas in liquefaction vessel can be removed. It is seen that the cool-down time of liquefaction vessel is substantially increased in vacuum environment.

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Analysis of transmission efficiency of the superconducting resonance coil according the materials of cooling system

  • Lee, Yu-Kyeong;Hwang, Jun-Won;Choi, Hyo-Sang
    • Progress in Superconductivity and Cryogenics
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    • v.18 no.1
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    • pp.46-49
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    • 2016
  • The wireless power transfer (WPT) system using a magnetic resonance was based on magnetic resonance coupling of the transmission and the receiver coils. In these system, it is important to maintain a high quality-factor (Q-factor) to increase the transmission efficiency of WPT system. Our research team used a superconducting coil to increase the Q-factor of the magnetic resonance coil in WPT system. When the superconductor is applied in these system, we confirmed that transmission efficiency of WPT system was higher than normal conductor coil through a preceding study. The efficiency of the transmission and the receiver coil is affected by the magnetic shielding effect of materials around the coils. The magnetic shielding effect is dependent on the type, thickness, frequency, distance, shape of materials. Therefore, it is necessary to study the WPT system on the basis of these conditions. In this paper, the magnetic shield properties of the cooling system were analyzed using the High-Frequency Structure Simulation (HFSS, Ansys) program. We have used the shielding materials such as plastic, aluminum and iron, etc. As a result, when we applied the fiber reinforced polymer (FRP), the transmission efficiency of WPT was not affected because electromagnetic waves went through the FRP. On the other hand, in case of a iron and aluminum, transmission efficiency was decreased because of their electromagnetic shielding effect. Based on these results, the research to improve the transmission efficiency and reliability of WPT system is continuously necessary.

Electromagnetic wave shielding effectiveness of steel fiber reinforced concrete (강섬유 보강 콘크리트의 전자파 차폐효과)

  • Lee, Gyu-Phil;Chang, Soo-Ho;Choi, Soon-Wook;Bae, Gyu-Jin;Park, Young-Taek
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.17 no.2
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    • pp.107-115
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    • 2015
  • As TBM construction method is widely applied to construct underground transmission lines, increasing attention has been drawn to SFRC(steel fiber reinforced concrete) segment with respect to structural characteristics. Health hazards of electromagnetic wave which the underground transmission lines emit has emerged, and there is a concern that electromagnetic wave can be amplified because a segment characteristic such as electrical conductivity is changed by steel fibers. In order to analyze correlation between steel fiber dosage and electromagnetic wave, the specimens were fabricated on three conditions to perform experimental tests. From the measured data, it is proven that there is no correlation between the electromagnetic wave and steel fiber reinforced concrete.

A Study on New Shielding Method for Minimizing Thyroid Oran Dose on Chest Radiography Used Automatic Exposure Control (자동노출조절장치를 이용한 흉부 방사선검사 시 갑상샘 장기선량 최소화를 위한 새로운 차폐 방법에 관한 연구)

  • Joo, Young-Cheol;Hong, Dong-Hee;Han, Beom-Hee
    • Journal of radiological science and technology
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    • v.43 no.5
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    • pp.323-329
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    • 2020
  • The purpose of this study is to investigate the effect of radiation shielding on the thyroid organ dose and image quality during Chest PA examination using automatic exposure control system. This study was conducted in the patient posture and examination conditions such as Chest PA using human model phantom. An experiment without shielding was set as a control group (non) and the cases of using paper coated with a contrast agent (contrast) and bismuth (bismuth) were used as experimental groups. Compared to non-shielded(non), the dose at bismuth increased about 7% in C(cervical vertebrae)5 and C6 and 14% in C7 and contrast showed dose increases of about 17 to 19% in C5 and C6 and about 21% in C7. As a result of the image quality comparison, when measured in the center of the cervical vertebrae, both SNR and CNR in bismuth increased about 40% higher than non, and contrast showed about 8 to 9% improvement. Compared with soft tissues of the cervix, bismuth reduced SNR by about 15% and CNR by about 13%, in contrast, SNR decreased by 11%, and CNR decreased by about 10%. In the Chest PA using AEC, the method of using the shield in front of the collimator has the advantage to observe the anatomical structure of the neck area well compared to the method using the lead. However, the dose at the neck can be increased by 7-21% depending on shielding materials.

Improvement of detection sensitivity of impurities on Si wafer surface using synchrotron radiation (방사광을 이용한 Si 웨이퍼 표면불순물 검출감도 향상)

  • 김흥락;김광일;강성건;김동수;윤화식;류근걸;김영주
    • Journal of the Korean Vacuum Society
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    • v.8 no.1
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    • pp.13-19
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    • 1999
  • Total reflection X-ray fluorescence spectroscopy using synchrotron radiation source called as TRSFA was explored to achieve high sensitivities to impurity metals on Si wafer surface. It consists of monochromating part to select a specific wavelength, slit part to shield direct beam and to control monochromated beam, and main chamber to dectect fluorescent X-ray counts of impurities on si wafer. Monochromated X-ray of 10.90 KeV was selected and the optimum total reflection condition on silicon wafer was obtained through tuning the dead time and fluorescent X-ray count of Si and Fe. TRSFA system could increase the sensitivity as high as 50 times in comparision with TRXFA using normal X-ray source. But the trend was varied since the surface conditions of Si wafers and, therefore, the reflectivities were different. Furthemore, there seems to be a promising path to reaching a detection limit useful to the next generation metal impurities control, because Fe impurity below to the $5\times10^{9}\textrm{atomas/cm}^2$ can be detectable through the developed TRSFA system.

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A STUDY ON OXIDATION TREATMENT OF URANIUM METAL CHIP UNDER CONTROLLING ATMOSPHERE FOR SAFE STORAGE

  • Kim, Chang-Kyu;Ji, Chul-Goo;Bae, Sang-Oh;Woo, Yoon-Myeoung;Kim, Jong-Goo;Ha, Yeong-Keong
    • Nuclear Engineering and Technology
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    • v.43 no.4
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    • pp.391-398
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    • 2011
  • The U metal chips generated in developing nuclear fuel and a gamma radioisotope shield have been stored under immersion of water in KAERI. When the water of the storing vessels vaporizes or drains due to unexpected leaking, the U metal chips are able to open to air. A new oxidation treatment process was raised for a long time safe storage with concepts of drying under vacuum, evaporating the containing water and organic material with elevating temperature, and oxidizing the uranium metal chips at an appropriate high temperature under conditions of controlling the feeding rate of oxygen gas. In order to optimize the oxidation process the uranium metal chips were completely dried at higher temperature than $300^{\circ}C$ and tested for oxidation at various temperatures, which are $300^{\circ}C$, $400^{\circ}C$, and $500^{\circ}C$. When the oxidation temperature was $400^{\circ}C$, the oxidized sample for 7 hours showed a temperature rise of $60^{\circ}C$ in the self-ignition test. But the oxidized sample for 14 hours revealed a slight temperature rise of $7^{\circ}C$ representing a stable behavior in the self-ignition test. When the temperature was $500^{\circ}C$, the shorter oxidation for 7 hours appeared to be enough because the self-ignition test represented no temperature rise. By using several chemical analyses such as carbon content determination, X-ray deflection (XRD), Infrared spectra (IR) and Thermal gravimetric analysis (TGA) on the oxidation treated samples, the results of self-ignition test of new oxidation treatment process for U metal chip were interpreted and supported.

Radiation Shielding Analysis of CANDU Spent Fuel Transport Cask (CANDU 사용후핵연료 수송용기 방사선차폐 영향평가)

  • Choi, Jong-Rak;Yoon, Jung-Hyun;Kang, Hee-Young;Lee, Heung-Young;Chung, Sung-Whan
    • Journal of Radiation Protection and Research
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    • v.18 no.2
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    • pp.27-35
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    • 1993
  • A shielding analysis of the shipping cask for transporting the CANDU spent fuel bundles has been studied. Radiation source term has been calculated on spent fuel with burn-up of 7,800 MWD/MTU and 5 years cooling time by ORIGEN2 code. The shielding calculation for the cask capable of transporting 378 bundles of CANDU spent fuel has been made by use of 1-D ANISN and 2-D DOT 4.2 codes. As a result of analysis, the optimum shield thickness of cask was obtained. And it is proved that the safety in radiation shielding under normal transport and hypothetical accident conditions is confirmed to satisfy the allowable values specified in IAEA Safety Series No. 6 and the Korean Atomic Law.

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Thermal-hydraulic analysis of a new conceptual heat pipe cooled small nuclear reactor system

  • Wang, Chenglong;Sun, Hao;Tang, Simiao;Tian, Wenxi;Qiu, Suizheng;Su, Guanghui
    • Nuclear Engineering and Technology
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    • v.52 no.1
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    • pp.19-26
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    • 2020
  • Small nuclear reactor features higher power capacity, longer operation life than conventional power sources. It could be an ideal alternative of existing power source applied for special equipment for terrestrial or underwater missions. In this paper, a 25kWe heat pipe cooled reactor power source applied for multiple use is preliminary designed. Based on the design, a thermal-hydraulic analysis code for heat pipe cooled reactor is developed to analyze steady and transient performance of the designed nuclear reactor. For reactor design, UN fuel with 65% enrichment and potassium heat pipes are adopted in the reactor core. Tungsten and LiH are adopted as radiation shield on both sides of the reactor core. The reactor is controlled by 6 control drums with B4C neutron absorbers. Thermoelectric generator (TEG) converts fission heat into electricity. Cooling water removes waste heat out of the reactor. The thermal-hydraulic characteristics of heat pipes are simulated using thermal resistance network method. Thermal parameters of steady and transient conditions, such as the temperature distribution of every key components are obtained. Then the postulated reactor accidents for heat pipe cooled reactor, including power variation, single heat pipe failure and cooling channel blockage, are analyzed and evaluated. Results show that all the designed parameters satisfy the safety requirements. This work could provide reference to the design and application of the heat pipe cooled nuclear power source.