• Title/Summary/Keyword: high rate

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Analysis of Attrition Rate of 50μm Size Y2O3 Stabilized Zirconia Beads with Different Microstructure and Test Conditions (50μm급 이트리아 안정화 지르코니아 비드의 미세구조 및 마모 조건에 따른 마모율 분석)

  • Kim, Jung-Hwan;Yoon, Sae-Jung;Hahn, Byung-Dong;Ahn, Cheol-Woo;Yoon, Woon-Ha;Choi, Jong-Jin
    • Korean Journal of Materials Research
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    • v.29 no.4
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    • pp.233-240
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    • 2019
  • This study analyzes the mechanical properties, including the attrition rate, of $50{\mu}m$ size yttria-stabilized zirconia (YSZ) beads with different microstructures and high-energy milling conditions. The yttria distribution in the grain and grain-boundary of the fully sintered beads relates closely to Vickers hardness and the attrition rate of the YSZ beads. Grain size, fractured surfaces, and yttrium distribution are analyzed by electronic microscopes. For standardization and a reliable comparison of the attrition rate of zirconia beads with different conditions, Zr content in milled ceramic powder is analyzed and calculated by X-ray Fluorescence Spectrometer(XRF) instead of directly measuring the weight change of milled YSZ beads. The beads with small grain sizes sintered at lower temperature exhibit a higher Vickers hardness and lower attrition rate. The attrition rate of $50{\mu}m$ YSZ beads is measured and compared with the various materials properties of ceramic powders used for high-energy milling. The attrition rate of beads appears to be closely related to the Vickers hardness of ceramic materials used for milling, and demonstrates more than a 10 times higher attrition rate with Alumina(Hv ~1650) powder than $BaTiO_3$ powder (Hv ~315).

Modeling and Simulation of New Encoding Schemes for High-Speed UHF RFID Communication

  • Mo, Sang-Hyun;Bae, Ji-Hoon;Park, Chan-Won;Bang, Hyo-Chan;Park, Hyung Chul
    • ETRI Journal
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    • v.37 no.2
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    • pp.241-250
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    • 2015
  • In this paper, we present novel high-speed transmission schemes for high-speed ultra-high frequency (UHF) radio-frequency identification communication. For high-speed communication, tags communicate with a reader using a high-speed Miller (HS-Miller) encoding and multiple antennas, and a reader communicates with tags using extended pulse-interval encoding (E-PIE). E-PIE can provide up to a two-fold faster data rate than conventional pulse-interval encoding. Using HS-Miller encoding and orthogonal multiplexing techniques, tags can achieve a two- to three-fold faster data rate than Miller encoding without degrading the demodulation performance at a reader. To verify the proposed transmission scheme, the MATLAB/Simulink model for high-speed backscatter based on an HS-Miller modulated subcarrier has been designed and simulated. The simulation results show that the proposed transmission scheme can achieve more than a 3 dB higher BER performance in comparison to a Miller modulated subcarrier.

Numerical Study of Electrohydraulic Forming to Reduce the Bouncing in High Speed Forming Process (고속 성형 공정의 바운싱 현상을 줄이기 위한 액중 방전 성형의 해석적 연구)

  • Woo, M.A.;Noh, H.G.;Song, W.J.;Kang, B.S.;Kim, J.
    • Transactions of Materials Processing
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    • v.25 no.4
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    • pp.261-267
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    • 2016
  • High-speed forming process is the forming technology that deforms the blank in a very short time, with the strain rate of the blank above 1000 s−1. Among many high-speed forming processes, electromagnetic forming (EMF) employs the Lorentz force when deforms the blank. Because of the high strain rate, the formability of the blank can be improved. However, when the blank is formed into rather complex shapes, it is bounced from the die and the wrinkles are generated. Therefore, electrohydraulic forming (EHF) is suggested in this study to reduce the bouncing problem of the blank. EHF is a high-speed forming that uses high voltage discharge in liquid. The shockwave resulting from the electric discharge propagates to the blank and it deforms the blank into the die. In this study, two high-speed forming processes, EMF and EHF were compared numerically with trapezoidal middle block die. This comparison showed that EMF cannot deform the blank into the die because of the bouncing, while EHF can overcome the bouncing problem and deform the blank into the die shape successfully.

A Prediction Model of Factors related to Career Maturity in Korean High School Students (의사결정나무 분석을 이용한 고등학생의 진로 성숙도 관련 요인 분석)

  • Seo, Jiyeong;Kim, Minju
    • Child Health Nursing Research
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    • v.25 no.2
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    • pp.95-102
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    • 2019
  • Purpose: The purpose of this study was to identify factors associated with career maturity among Korean high school students. Methods: A descriptive cross-sectional design was adopted using secondary data from the 2012 Korean Welfare Panel Study (KoWePS). The participants were 496 high school students who completed the supplemental survey for children, which included items on career maturity, self-esteem, study stress, teacher attachment, relationship with parents, peer attachment, depression and anxiety. Descriptive statistics, the chi-square-test, the t-test, and a decision tree were used for data analysis. Results: The decision tree identified five final nodes predicting career maturity after forcing self-esteem as the first variable. The highest predicted rate of high career maturity was associated with high self-esteem, experience of career counseling, and high teacher attachment. The lowest predicted rate of high career maturity was associated with low self-esteem and low attachment to friends. Conclusion: Factors influencing career maturity were varied by levels of self-esteem in Korean high school students. Thus, it is necessary to develop different approaches to enhance career maturity according to levels of self-esteem.

Composited Conductive Materials for Enhancing the Ultrafast Performance for Anode in Lithium-Ion Battery (리튬이온전지 음극의 고속 성능 향상을 위한 도전재 복합화)

  • Ki-Wook, Sung;Hyo-Jin, Ahn
    • Korean Journal of Materials Research
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    • v.32 no.11
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    • pp.474-480
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    • 2022
  • Lithium-ion batteries (LIBs) are powerful energy storage devices with several advantages, including high energy density, large voltage window, high cycling stability, and eco-friendliness. However, demand for ultrafast charge/discharge performance is increasing, and many improvements are needed in the electrode which contains the carbon-based active material. Among LIB electrode components, the conductive additive plays an important role, connecting the active materials and enhancing charge transfer within the electrode. This impacts electrical and ionic conductivity, electrical resistance, and the density of the electrode. Therefore, to increase ultrafast cycling performance by enhancing the electrical conductivity and density of the electrode, we complexed Ketjen black and graphene and applied conductive agents. This electrode, with the composite conductive additives, exhibited high electrical conductivity (12.11 S/cm), excellent high-rate performance (28.6 mAh/g at current density of 3,000 mA/g), and great long-term cycling stability at high current density (88.7 % after 500 cycles at current density of 3,000 mA/g). This excellent high-rate performance with cycling stability is attributed to the increased electrical conductivity, due to the increased amount of graphene, which has high intrinsic electrical conductivity, and the high density of the electrode.

Factors associated with high-risk drinking among men in Korea: a secondary analysis (한국 성인 음주 남성의 고위험 음주 관련 요인: 2차 분석 연구)

  • Hyun Ju Chae
    • Journal of Korean Biological Nursing Science
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    • v.26 no.1
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    • pp.49-59
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    • 2024
  • Purpose: This study was conducted to identify factors associated with high-risk drinking in Korean men. Methods: This study was a secondary analysis using data from the Korea National Health and Nutrition Examination Survey (KNHANES VIII-2), 2020. Data were downloaded from the KNHANES website. The subjects of this study were 1,653 alcohol-drinking men between 19 and 64 years of age. Data were analyzed using the Rao-Scott chi-square test and complex sample logistic regression statistics. Results: The high-risk drinking rate among alcohol-drinking men was 27.1%. High-risk drinking was more common in men who smoked (odds ratio [OR] = 2.11, p < .001), men with a middle school education or lower (OR = 1.91, p = .016), men who lived with a spouse (OR = 1.61, p = .025), men who slept less than 6 hours on weekends (OR = 1.51, p = .016), and men who perceived stress (OR = 1.30, p = .044), while it was lower in men who were underweight (OR = 0.19, p = .006). Conclusion: To reduce the rate of high-risk drinking, it is necessary to provide an intervention that considers factors associated with high-risk drinking among men. In particular, smoking was the most important factor associated with high-risk drinking, implying that the integrated management of drinking and smoking is necessary to reduce high-risk drinking.

Deformation Property of TiC-Mo Solid Solution Single Crystal at High Temperature by Compression Test (TiC-Mo 고용체 단결정의 고온 압축변형 특성)

  • Shin, Soon-Gi
    • Korean Journal of Materials Research
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    • v.24 no.11
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    • pp.625-631
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    • 2014
  • To investigate the deformation properties of TiC-(5-20) mol% Mo solid solution single crystals at high temperature by compression testing, single crystals of various compositions were grown by the radio frequency floating zone technique and were deformed by compression at temperature from 1250K to 2270K at strain rates from $5.1{\times}10^{-5}$ to $5.9{\times}10^{-3}/s$. The plastic flow property of solid solution single crystals was found to be clearly different among a three-temperature range (low, intermediate and high temperature ranges) whose boundaries were dependent on the strain rate. From the observed property, we conclude that the deformation in the low temperature range is controlled by the Peierls mechanism, in the intermediate temperature range by the dynamic strain aging and in the high temperature range by the solute atmosphere dragging mechanism. The work softening tends to become less evident with an increasing experimental temperature and with a decreasing strain rate. The temperature and strain rate dependence of the critical resolved shear stress is the strongest in the high temperature range. The curves are divided into three parts with different slopes by a transition temperature. The critical resolved shear stress (${\tau}_{0.2}$) at the high temperature range showed that Mo content dependence of ${\tau}_{0.2}$ with temperature and the dependence is very marked at lower temperature. In the higher temperature range, ${\tau}_{0.2}$ increases monotonously with an increasing Mo content.

Characteristics of Water Quality by Storm Runoffs from Intensive Highland Agriculture Area in the Upstream of Han River Basin (한강상류 고령지 농업지역에서의 강우시 비점오염 유출 특성)

  • Jung, Sungmin;Jang, Changwon;Kim, Jai-Ku;Kim, Bomchul
    • Journal of Korean Society on Water Environment
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    • v.25 no.1
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    • pp.102-111
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    • 2009
  • Turbid storm runoff from intensive highland agriculture area has emerged as the major problem of water quality deterioration in the upstream region of the Han River. High slope of the upland combined with high rate of fertilization and intensive plowing causes high rate of soil erosion, and subsequently high suspended sediment and phosphorus content in the runoff water. The variations of water quality during rain spells were surveyed for two years (2005 and 2006) in the Jawoon Stream that is one of hot spots of intensive horticulture discharging turbid storm runoff. SS and TP showed large increase according to the increase of flow rate, whereas TN and BOD showed less fluctuations. Mean EMCs of SS and TP measured for nine rain events were as high as $207mgSS{\cdot}L^{-1}$ and $0.27mgP{\cdot}L^{-1}$, respectively. The export coefficient of SS and TP per area of cultivated field were calculated as $11,912kgSS{\cdot}yr^{-1}{\cdot}km^{-2}$ and $785kgP{\cdot}yr^{-1}{\cdot}km^{-2}$, repectively, which are significantly higher than reports of other area. It can be concluded that SS and TP in the runoffs were high enough to impose major threat to aquatic habitats, and the highland agriculture should be the main target of water quality management or habitat conservation in the study area.

Effects of High-intensity Intermittent Training and Moderate-intensity Training on Cardiopulmonary Capacity in Canoe and Kayak Paddlers during 8 Weeks

  • Kim, Ah-Ram;Shin, Won-Seob
    • Journal of the Korean Society of Physical Medicine
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    • v.9 no.3
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    • pp.307-314
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    • 2014
  • PURPOSE: The purpose of this study was to investigate the effects of high intensity intermittent training on cardiopulmonary capacity in canoe and kayak paddlers. METHODS: A total of 16 canoe and kayak paddlers were participated in this study. Experimental group(n=8) was performed high-intensity intermittent training and control group(n=8) was moderate intensity training. All subjects performed a treadmill test in order to compare the difference before and after the intervention. Finishing the test, all subjects were measured to their heart rate(HR), forced vital capacity(FVC), forced expiratory volume in one second (FEV1) and forced expiratory ratio(FEV1/FVC). Recovery of heart rate(RHR) was calculated using the HR. HR and pulmonary flow values was measured before and during the intervention period per 2, 4, 6 and 8 weeks. To compare the differences over time between experimental group and the control group, used(time${\times}$group) two-way repeated measures ANOVA. One-way repeated ANOVA was performed to determine where differences over time within-group. RESULTS: One-way repeated ANOVA revealed a significant difference in the experimental and control group. In experimental group, %RHR3min and FEV1 were significantly increased after 4 weeks(p<.05). Also, %RHR1min, FVC and FEV1/FVC were significantly increased after 6 weeks(p<.05). In control group, %RHR1min, %RHR3min, FVC, FEV1 and FEV1/FVC were significantly increased after 6 weeks(p<.05). CONCLUSION: Not only moderate training but also high-intensity intermittent training contributes to cardiopulmonary capacity in canoe and kayak paddlers. Although high-intensity intermittent training is very short time, the training has high degree of efficiency. Therefore, developed this training in the future, it will be better to improve the cardiopulmonary capacity for athletes and healthy people.

APPLICATION OF COLD SPRAY COATING TECHNIQUE TO AN UNDERGROUND DISPOSAL COPPER CANISTER AND ITS CORROSION PROPERTIES

  • Lee, Min-Soo;Choi, Heui-Joo;Choi, Jong-Won;Kim, Hyung-Jun
    • Nuclear Engineering and Technology
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    • v.43 no.6
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    • pp.557-566
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    • 2011
  • A cold spray coating (CSC) of copper was studied for its application to a high-level radioactive waste (HLW) disposal canister. Several copper coatings of 10 mm thick were fabricated using two kinds of copper powders with different oxygen contents, and SS 304 and nodular cast iron were used as their base metal substrates. The fabricated CSC coppers showed a high tensile strength but were brittle in comparison with conventional non-coating copper, hereinafter defined to as "commercial copper". The corrosion behavior of CSC coppers was evaluated by comparison with commercial coppers, such as extruded and forged coppers. The polarization test results showed that the corrosion potential of the CSC coppers was closely related to its purity; low-purity (i.e., high oxygen content) copper exhibited a lower corrosion potential, and high-purity copper exhibited a relatively high corrosion potential. The corrosion rate converted from the measured corrosion current was not, however, dependent on its purity: CSC copper showed a little higher rate than that of commercial copper. Immersion tests in aqueous HCl solution showed that CSC coppers were more susceptible to corrosion, i.e., they had a higher corrosion rate. However, the difference was not significant between commercial copper and high-purity CSC copper. The decrease of corrosion was observed in a humid air test presumably due to the formation of a protective passive film. In conclusion, the results of this study indicate that CSC application of copper could be a useful option for fabricating a copper HLW disposal canister.