• Title, Summary, Keyword: attrition

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A Study on the Attrition of the Posterior Teeth in the Aged Adult by Aging (중년기 및 노년기 성인 구치 교모에 관한 연구)

  • Hwi-Jun Ahn;June-Sang Park
    • Journal of Oral Medicine and Pain
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    • v.20 no.2
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    • pp.399-406
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    • 1995
  • The author studied to determine the tooth-age according to the degree of attrition. This study was performed on 247 subjects over forties. Upper and lower posterior teeth were clinically examined and transferred to a store model on which degree of attrition was measured with a magnifier respectively. The obtained results were as follows : The attrition by aging was increased in both male and female. The degree of attrition in male was higher than that in female for same age group. The coefficients of correlation and relation equations by the degree of attrition were obtained.

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Attrition Milling and Reaction-Sintering of the Oxide-Metal Mixed Powders: I. Milling Behavior as the Powder Characteristics (산화물과 금속 복합 분말의 Attrition Milling 및 반응소결: I. 분말의 특성에 따른 분쇄 거동)

  • 황규홍;박정환;윤태경
    • Journal of the Korean Ceramic Society
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    • v.31 no.3
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    • pp.337-345
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    • 1994
  • The reaction-sintered alumina and zirconia-alumina ceramics having low firing shrinkage were prepared from the Al/Al2O3 or Al/ZrO2(Ca-PSZ) powder mixtures via the attrition milling. And in this milling process the effect of the characteristics of used powders was investigated. Attrition milling was much more effective in reducing the particle size of ceramic/metal mixed powders than ball milling. Powder mixtures of flake-type Al with coarse alumina was much more effectively comminuted by the attrition milling than the mixtures of globular-type Al with coarse alumina powders. And coarse alumina than fine alumina was much more beneficial in cutting and reducing the ductile Al particles. In the contrary to Al/Al2O3 powder mixtures, Al/ZrO2 powder mixtures was not effectively comminutd. But whether using the alumina ball media or attrition milled with Al2O3 powder rather than Al, the milling efficiency was much more increased.

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An Analysis of Response Pattern and Panel Attrition in KLIPS(Korean Labor and Income Panel Study)

  • Nam, Ki-Seong;Chun, Young-Min
    • The Korean Journal of Applied Statistics
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    • v.25 no.6
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    • pp.933-945
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    • 2012
  • In this paper we used the KLIPS(Korean Labor and Income Panel tudy) data that surveyed from 2006(wave 9) to 2009(wave 12). Other previous studies are concerned with the panel attrition in the early wave, but this study classifies the response pattern and investigates some factors that influence panel attrition when the panel tends to stabilize. It was revealed that panel attrition was influenced by relocation and housing type through the logit model. Besides it was appeared that panel attrition was affected by the monthly living expenses and the overall household income through the decision tree.

A Study on the Age Estimation by Attrition of the Adult Teeth (성인치아의 교모도를 이용한 연령추정에 관한 연구)

  • 안휘준;박준상;고명연
    • Journal of Oral Medicine and Pain
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    • v.23 no.1
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    • pp.85-99
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    • 1998
  • In order to estimate the tooth-age by degree of attrition, the author has studied 605 stone models from 1996 to 1997. All of the attrition were classified and analyzed by 8 degrees. The result were as follows : 1. The degree of attrition in male was higher than that in female for same age group and especially, canine and first premolar showed the most prominent difference in sex. 2. The most severe attrition in posterior teeth was first molar followed by second molar, first premolar and second premolar in decreasing order of sequence. 3. The coefficient of correlation and relation equations by the degree of attrition were obtained.

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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).

Attrition Characteristics in an Advanced Gasifier with Swirl Injection (접선 방향의 기체 주입에 의한 입자 마모 특성 연구)

  • Lee, See Hoon;Park, Chan Seung;Lee, Jae Goo;Kim, Jae Ho
    • Applied Chemistry for Engineering
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    • v.19 no.3
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    • pp.295-298
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    • 2008
  • In the reactor for the american standard test method (ASTM) D5757-95 with swirl injection nozzles, the attrition characteristics of sand was investigated. The change of particle size distribution and weight of fine particles were compared to identify the effect of swirl injection nozzle on attrition. The fine particles due to particle attrition increased with increasing gas velocities. The weight of fine particles due to jet attrition was changed with angle of swirl injection nozzle. The fine particles decreased with decreasing the angle of swirl injection nozzle. Also, the change of particle size distribution increased with increasing the number of swirl injection nozzles at the same flow rate.

An Analysis of Panel Attrition in GOMS(Graduates Occupational Survey) (대졸자 직업이동 경로조사에서 패널탈락분석)

  • Chun, Young-Min;Yoon, Jeong-Hye;Oh, Min-Hong
    • The Korean Journal of Applied Statistics
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    • v.22 no.5
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    • pp.981-993
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    • 2009
  • It would cause a serious problem in the panel data when panel attrition is concentrated on certain socioeconomic groups. Using the GOMS, this study investigates whether there exists non-random attrition bias in the data and seeks for feasible solutions to minimize the bias. The results of logit analyses show that panel attrition in the GOMS results mainly from surveying system but not from the surveyed. Therefore, the result suggests to develop well-organized management skill and systems as well as to construct weighting methods.

Electrical Properties of Donor-doped BaTiO3 Ceramics by Attrition Milling and Calcination Temperature (분쇄 방법 및 하소온도에 따른 Doner-doped BaTiO3의 전기적 특성)

  • Lee, Jeong-Cheol;Myong, Seong-Jae;Chun, Myoung-Pyo;Cho, Jeong-Ho;Kim, Byung-Ik;Shin, Dong-Wook
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.21 no.3
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    • pp.217-221
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    • 2008
  • In this study, We have been investigated the effect of calcination temperature and high-energy ball-milling of powder influences the $BaTiO_3$-based PTCR(Positive Temperature coefficient Resistance) characteristics and microstructure. The mixed powder was obtained from $BaCO_3$, $TiO_2$, $CeO_2$ ball-milled in attrition mill. The mixed powder was calcine from 1000 $^{\circ}C$ to 1200 $^{\circ}C$ in air and then it was sintered in reduction- re-oxidation atmosphere. As a result, The room-temperature electrical resistivity decreased and increased with increasing calcination temperature. specially, Attrition milled powder could have low room-temperature resistivity and high PTC jump order at 1100 $^{\circ}C$. attrition milling had lower room-temperature resistivity than ball milling. Particle size decreased by Attrition milling of powder influences in calcination temperature and room-temperature resistivity.

Selection of Oxygen Carrier Candidates for Chemical Looping Combustion by Measurement of Oxygen Transfer Capacity and Attrition Loss (산소전달량 및 마모손실 측정에 의한 매체순환연소용 산소전달입자 후보 선정)

  • KIM, HANA;PARK, JAEHYEON;BAEK, JEOM-IN;RYU, HO-JUNG
    • Transactions of the Korean hydrogen and new energy society
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    • v.27 no.4
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    • pp.404-411
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    • 2016
  • To select appropriate oxygen carrier candidates for chemical looping combustion, reduction characteristics of seven oxygen carriers were measured and discussed using three different reduction gases, such as $H_2$, CO, and $CH_4$. Moreover, attrition losses of those oxygen carriers also measured and compared. Among seven oxygen carrier particles, OCN703-1100 and NiO/bentonite particles showed higher oxygen transfer capacity than other particles, but these particles showed more attrition loss than other particles. C14 and C28 particles which used as cheap oxygen carriers in European country showed lower oxygen transfer capacity and less attrition loss. Based on the experimental results, we could select OCN717-R1SU, NC001, and N002 particles as candidates for future works because these oxygen carriers showed enough oxygen transfer capacity and good attrition resistance.

The attrition pattern in Angle Class III malocclusion with facial astmmetry (안면비대칭을 동반한 Angle III급 부정교합자의 교모양상)

  • Son, Woo-Sung;Jeon, Eun-Ye;Kim, Sung-Jo
    • The korean journal of orthodontics
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    • v.27 no.4
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    • pp.549-557
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    • 1997
  • This study was designed to investigate the attrition pattern in Angle Class III malocclusion with facial asymmetry. The sample consisted of three groups, the 20 subjects of normal occlusion group(Group I), the 12 subjects of class III malocclusion without facial asymmetry group(Group II) and 17 subjects of Class III malocclusion with facial asymmetry group(Group III). Attrition areas from canine to second molar on both sides in upper and lower arch, totally twenty, was marked by pencil and mesured by computer system(INTERGRAPH CO. USA) 2 times and the average value was used for date processing. Attrition areas from canine to second molar on both sides in upper and lower arch, totally twenty, was marked by pencil and mesured by computer system(INTERGRAPH CO. USA) 2 times and the average value was used for date Processing. All attrition areas were measured 2 times and the average value was used for data processing The data were statistically analyzed by SAS program. The results of this study were as follows. 1. Total attrition area in Group I was larger than in Group II and III. 2. There was no significant difference in attrition area between right and left side in each group, but attrition area in Group III was larger than in Group I and II. 3. In Group I, Maxillary attrition area was larger than mandibular attrition area, but in Group ll and III, there was no significant difference in attrition area between maxilla and mandible. 4. In Group III, the attrition area of deviated side was target than undeviated side 5. There was no significant difference in attrition area between chewing side and non-chewing side in each group. 6. The total attrition area was unaffected by gender.

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