• Title, Summary, Keyword: attrition

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Attrition Characteristics of Catalysts for a High Efficiency Water Gas Shift Process (고효율 수성가스 공정을 위한 촉매 마모 특성)

  • Jo, Jun Beom;Kim, Jae Ho;Lee, See Hoon
    • Applied Chemistry for Engineering
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    • v.21 no.1
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    • pp.111-114
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    • 2010
  • In the attrition reactor for the American Society for Testing and Materials (ASTM) D5757-95, the attrition characteristics of catalysts for water gas shift reaction were investigated. The effects of attrition characteristics of low temperature shift catalysts (LTS) and high temperature shift catalysts (HTS) on fluidization phenomena and average particle size were investigated and compared with the attrition characteristics of sand particles. The particle size of catalysts was decreased and particle size distribution in attrition tube was changed due to the effect of gas injection. About 40~50 wt% samples of original catalyst particles were entrained and lost. The amount of fly ash of LTS catalyst was less than that of HTS. Also, the weight of entrained particles which had original particle size of $212{\sim}300{\mu}m$ was lower than any other cases.

Effect of Slurry on the pH and Viscosity for the Preparation of High Attrition Resistance Zinc-based Desulfurization Sorbents by Spray Drying Method (분무건조법에 의한 높은 내마모성 아연계 탈황제를 제조하기 위한 슬러리의 pH와 점도에의 영향)

  • Kwon, Byung Chan;Park, No-Kuk;Han, Gi Bo;Ryu, Si Ok;Lee, Tae Jin
    • Clean Technology
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    • v.12 no.4
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    • pp.232-237
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    • 2006
  • The zinc-based desulfurization sorbents for a fluidized-bed system were prepared by a spray drying method and the effects of the pH and viscosity of the slurry on the attrition resistance of the prepared sorbents were investigated in this work. In order to improve the attrition resistance, alumina sol was used for an inorganic binder and pH of the slurry was changed for its better dispersion in slurry. The attrition resistance of the prepared sorbents decreased due to the phase transition of alumina sol to gel as the slurry pH increased to its basicity. The optimum pH condition for the good attrition resistance of the sorbents was about 6.0 in this study. It was confirmed that the attrition property of the sorbents were varied with the viscosity of the slurry. The attrition resistance of the sorbents prepared by the spray drying method increased as their bulk density increased, while it decreased as the surface area and porosity of the sorbents. The optimum viscosity for the high attrition was in the range 400-500 cP.

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Development and Evaluation of the Attrition Coupled Bioreactors for Enzymatic Hydrolysis of Biomass; Agitated Bead Type Bioattritor for Enzymatic Hydrolysis of Cellulose (Biomass의 고효율 효소당화에 의한 적합한 Attrition Coupled Bioreactor개발에 관한 연구 ; Agitated Bead Type Bioattritor를 활용한 섬유소 당화)

  • 이용현;박진서;윤대모
    • KSBB Journal
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    • v.4 no.2
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    • pp.78-86
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    • 1989
  • The effective saccharification of cellulosic biomass to glucose is the most critical step for the conversion of renwable biomass to alternative liquid fuel. The enzymatic hydrolysis of biomass can be significantly enhanced provide the attrition milling media is added during hydrolysis. The enhancing mechanism of hydrolysis reaction in an agitated bead system was investigated. An attrition-reactor (bioattritor) which installed specially designed torque measuring apparatus was developed, and the potimal saccharification conditions of bioattritor were determined. The relationship between the power consumption required for agitation of attrition-milling media and enhanced extent of hydrolysis of biomass was compared to evaluatic economic feasibility of the process.

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Agent-Based Modeling Methodology for Close-Combat Attrition Estimates (Agent 기반 모델링에 의한 근접전투 손실예측 방법론)

  • Kim, Hee-Soo;Lee, Jae-Ho;Shin, Hyun-Ju
    • Journal of the military operations research society of Korea
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    • v.32 no.2
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    • pp.56-77
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    • 2006
  • This paper suggests more improved war-game modeling methodology for close combat attrition modeling. Military operation analysts have been using equation-based modeling techniques such as Lanchester-type differential equation modeling, for combat attrition evaluation. This modeling methodology is easy to analyze and evaluate the war-game simulation results but has several limitations to simulate the dynamic combat environment. To overcome these shortcomings, we propose the agent-based modeling methodology. This methodology is modeling close combat based in attrition behaviors instead of attrition coefficients. The simulation analysis & evaluation is executed for these two kinds of modeling methodology on the similar close combat situation.

Panel attrition factors in Korean Labor and Income Panel Study (한국노동패널 탈락 분석)

  • Lee, Sang-Hyeop;Park, Chan-Yong;Hye-Mi, Sung-Suk Chung;Choi, Hye-Mi
    • Journal of the Korean Data and Information Science Society
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    • v.22 no.1
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    • pp.1-8
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    • 2011
  • In panel studies in which the same respondents are interviewed repeatedly over the long term, panel attrition may cause the problems in the reliability of the result and the representativeness of the sample in panel study. In this article, we explore the risk factors of sample attrition in the first 11 waves of the Korean Labor and Income Panel Study (KLIPS) data covering the years 1998-2008, for which the survival analysis techniques such as life-table method and Cox proportional hazard model based on the time to the attrition of each respondent as the survival time of the respondent are applied.

Microstructural and Piezoelectric Characteristics of PSN-PMN-PZT Ceramics Produced by Attrition Milling

  • Juhyun Yoo;Sukkyu Min;Jaeil Hong;Sungjae Suh;R, Soonchul-U
    • Transactions on Electrical and Electronic Materials
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    • v.2 no.3
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    • pp.18-23
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    • 2001
  • For the piezoelectric transformer application, Pb(Sb$\_$1/2/ Nb$\_$1/2/)O$_3$-Pb(Zr,Ti)O$_3$ ceramics were produced by attrition milling. Microstructural, dielectric and piezoelectric characteristics of the ceramics were investigated as a function of milling time. The particle size and grain size decreased while dielectric constant, density and mechanical quality factor (Q$\_$m/) increased with milling time. Temperature coefficient of resonant frequency (TCf$\_$r/) was shifted to positive side with increasing milling time. The attrition milling process proved to be one of the effective routes to produce transformers for high power application.

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Particle Size and Piezoelectric Characteristics of PNW-PMN-PZT Ceramics as a Function of Attrition Milling process. (PNW-PMN-PZT 세라믹스의 Attrition Milling에 따른 입도분석 및 압전특성)

  • Lee, Sang-Ho;Yoo, Ju-Hyun;Oh, Dong-On;Ryu, Sung-Lim;Hong, Jae-Il;Chung, Kwang-Hyun;Jung, Moon-Young
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.332-335
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    • 2003
  • Particle size and piezoelectric characteristics of PNW-PMN-PZT ceramics with the variations in attrition milling conditions were investigated for the piezoelectric transformer application. Particle size and distribution were decreased with increasing milling time. Dielectric constant (${\varepsilon}r$), electromechanical coupling factor (kp), mechanical quality factor (Qm) and density showed the optimum value of 1563, 0.53, 2342, 7.63, respectively at 7h milling time.

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Piezoelectric Properties of Low Temperatrue PMN-PZT Ceramics with Attrition Milling time (Attrition milling 시간에 따른 저온소결 PMN-PZT 세라믹스의 압전특성)

  • Lee, Hyun-Seok;Yoo, Ju-Hyun;Jung, Young-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.300-300
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    • 2006
  • 일반적으로 PZT계 세라믹스는 높은 결정격자 이방성을 가지고 있으며, 우수한 압전특성을 가지고 있다. 이러한 특성을 보이기 위해서는 높은 온도($1200^{\circ}C$)에서 소결을 해야하기 때문에 PbO의 휘발로 인하여 환경문제가 야기되고 있다. 이러한 문제를 해결하기 위해서 Li, Na같은 액상소결제를 첨가시켜 소결온도를 낮추는 연구를 하고 있다. 본 연구에서는 $Pb(Mn_{1/3}Nb_{2/3})O_3$-PZT세라믹스가 갖는 높은 결정격자 이방성을 유지시키고, 저온소결시 압전 및 유전특성을 향상시키기 위해서 $Pb(Mg_{1/2}W_{1/2})O_3$를 치환시켜 attrition milling 시간에 따른 PWM-PMN-PZT세라믹스의 압전특성을 조사하였다.

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Prediction of the Probability of Customer Attrition by Using Cox Regression

  • Kang, Hyuncheol;Han, Sang-Tae
    • Communications for Statistical Applications and Methods
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    • v.11 no.2
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    • pp.227-233
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    • 2004
  • This paper presents our work on constructing a model that is intended to predict the probability of attrition at specified points in time among customers of an insurance company. There are some difficulties in building a data-based model because a data set may contain possibly censored observations. In an effort to avoid such kind of problem, we performed logistic regression over specified time intervals while using explanatory variables to construct the proposed model. Then, we developed a Cox-type regression model for estimating the probability of attrition over a specified period of time using time-dependent explanatory variables subject to changes in value over the course of the observations.