• Title, Summary, Keyword: 체적비

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Method for Determining Fiber Volume Fraction in Carbon/Epoxy Composites Considering Oxidation of Carbon Fiber (탄소섬유 산화 현상을 고려한 탄소복합재료의 섬유체적비 측정법)

  • Kim, YunHo;Kumar, Sathish;Choi, Chunghyeon;Kim, Chun-Gon;Kim, Sun-Won;Lim, Jae Hyuk
    • Composites Research
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    • v.28 no.5
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    • pp.311-315
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    • 2015
  • Measuring fiber volume fraction properly is very important in designing composite materials because the fiber volume fraction mainly determines mechanical and thermal properties. Conventional Ignition methods are effective for ceramic fiber reinforcing composite materials. However, these methods are not proper for applying to carbon fiber reinforcing composites because of the venerable characteristic against oxidation of carbon fiber. In the research, fiber volume fraction of carbon fiber composites was obtained by a thermogravimetric analysis considering oxidation characteristic of the carbon fiber and the method was compared and verified with the results from microscopic cross section images.

Electical and Electomagnetic wave Absorbing Properties of MnZn Ferrite-Rubber Composites in Microwave Frequencies (MnZn계 페라이트-고무 복합체의 마이크로파대역에서의 전기적 특성 및 전자파 흡수 특성)

  • 김호철;이병택;정연춘;엄진섭
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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    • v.4 no.2
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    • pp.41-47
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    • 1993
  • Electrical and electromagnetic wave absorbing properties of MnZn ferrite-rubber composites have been examined for varying the volume fraction of ferrite powder from 0.1 to 0.4 in the frequency range between 1-10 GHz. As the volume fraction of MnZn ferrite increased, the complex permittivity and permeability of composite increased. The peak of reflection loss at the frequency corresponding to 1/4 wavelength shifts to lower frequency, and shifts to lower frequency as the thickness of absorber increased. We show that for the ferrite-rubber composites the volume fraction of ferrite should be controled to obtain the absorbing properties required in given frequency range.

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Data Measurement for the Volumetric Efficiency of SI Engines (가솔린 엔진의 흡기효율 데이터 측정)

  • Jang, Hyun-Tak
    • Proceedings of the KAIS Fall Conference
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    • pp.1163-1165
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    • 2010
  • 가솔린 기관의 체적 효율은 흡기 장치의 효율의 척도로 표현된다. 현재 체적효율은 4행정 가솔린 엔진의 흡기장치의 특성과 공연비 제어를 위한 중요한 파라미터로 사용되고 있다. 체적 효율은 이론적으로 실린더로 흡입 가능한 양에 대한 실제로 실린더로 흡인한 공기량의 비율이다. 체적효율은 엔진회전 속도와 흡기다기관 부압에 따라 결정되는 종속변수이다. 체적 효율은 정상상태와 과도상태와 같은 엔진의 모든 운전조건을 시험하는데 한계와 제약이 매우 크다. 이 논문에서는 선형 알고리즘을 사용하여 체적 효율의 파라미터를 규명하여 선형 다항식 모델을 개발한다. 그리고 실험으로 구한 체적효율 데이터와 다항식 모델을 비교하고 객관적인 타당성을 평가 하였다.

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Experimental Study on Hysteretic Behavior of 100 MPa Ultra High-Strength Concrete Tied Columns (100 MPa 초고강도 콘크리트 띠철근 기둥의 이력거동에 관한 실험적 연구)

  • Kim, Jong-Keun;Shin, Sung-Woo
    • Journal of the Korea Concrete Institute
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    • v.18 no.2
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    • pp.161-168
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    • 2006
  • An experimental investigation was conducted to examine the hysteretic behaviors of ultra-high strength concrete tied columns. The purpose of this study is to investigate the safety of ultra-high strength concrete columns with 100 MPa compressive strength for the requirement of ACI provisions. Eight 1/3 scaled columns were fabricated to simulate an 1/2 story of actual structural members with the cross section $300{\times}300mm$ and the aspect ratio 4. The main variables are axial load ratio, configurations and volumetric ratios of transverse reinforcement. The results show that the deformability of columns are affected by the configurations and volumetric ratios of transverse reinforcement. Especially, it has been found that the behavior of columns are affected by axial load ratio rather than the amounts and the configurations of transverse reinforcement. Consequently, to secure the ductile behavior of 100 MPa ultra-high strength concrete columns, ACI provisions for the requirement of transverse steel may considered axial load level and the details of transverse reinforcement.

Soil Water Characteristic Curve Using Volumetric Pressure Plate Extractor Incorporated with TDR System (TDR 측정시스템이 도입된 압력판 추출 시험기를 이용한 흙-함수특성곡선 연구)

  • Jung, Young-Seok;Sa, Hee-Dong;Kang, Seonghun;Oh, Se-Boong;Lee, Jong-Sub
    • Journal of the Korean Geotechnical Society
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    • v.31 no.8
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    • pp.17-28
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    • 2015
  • The purpose of this study is to measure the volumetric water content of unsaturated soils during drying and wetting process by using volumetric pressure plate extractor (VPPE) incorporated with time domain reflectometry (TDR). The VPPE consists of a pressure cell, a pressure regulator, a burette system and a TDR probe. Two samples with different initial void ratios were prepared in the pressure cell, and the air pressure at the range of 0.1 kPa - 50 kPa was applied to adjust the matric suction by the pressure regulator. The burette system was used to measure the volumetric water content change of the sample according to the matric suction. In addition, the TDR probe, installed in the cell, was used to evaluate the dielectric constant from the reflected signal of the electromagnetic wave at the probe. The volumetric water content of specimen was estimated by the empirical equation between the volumetric water content and dielectric constant, which was calibrated with the Jumunjin sand. The test results show that the volumetric water content calculated by TDR probe is strongly correlated to the measured value by burette system. The hysteresis occurs during drying and wetting process. Furthermore, the degree of hysteresis reduces in the repeated process. This study suggests that TDR may be effectively used to evaluate the water content soil for the determination of water characteristic curve of unsaturated soils.

A study on applicability of volumetric water content to predict shallow failure (표층붕괴 예측을 위한 체적함수비 적용성 연구)

  • Suk, Jae-Wook;Song, Hyo-Sung;Kang, Hyo-Sub;Kim, Ho-Jong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.12
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    • pp.737-746
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    • 2019
  • Most landslides in the country are shallow failures triggered by intense rainfall. Many researchers have revealed the possibility of predicting shallow failure through the volumetric water content (VWC). This study examined how to determine shallow failure using the gradient characteristics of the volumetric water content. For this, flume experiments were conducted using weathered granite soil. To confirm the saturation state of the surface layer under a rainfall intensity of 30 and 50mm/hr, VWC sensors were installed at depths of 10 and 20 cm on the upper, middle and lower slope. The test results showed that a shallow failure determination using VWC could be applied limitedly according to the slope degree. In addition, the effective cumulative rainfall due to the rainfall infiltration velocity is considered the main factor for the failure time. The failure prediction using the gradient of the VWC depends on the installation location and depth of the sensor. According to the experimental data, the measured value at 20 cm below the slope was most effective. Therefore, an analysis method of VWC and the method of selecting the installation location confirmed through this study can provide important data for presenting the measurement criteria using VWC in the future.

Analytical Study on Effective Thermal Conductivity of Three-Phase Composites (3상 복합재의 등가열전도계수 예측에 대한 연구)

  • Lee, Jae-Kon;Kim, Jin-Gon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.12 no.7
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    • pp.2931-2938
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    • 2011
  • Effective thermal conductivity of three-phase composites, consisting of matrix and two kinds of spherical inclusions, has been derived as an explicit form by extending modified Eshelby model (MEM) for two-phase composites. The present results are compared with those by differential effective medium model (DEMM), which are also compared with the experimental results of two- and three-phase composites in the literatures to be validated. For two-phase composites, the results by MEM are better than those by DEMM for the inclusion volume fraction smaller than 0.5. Comparisons between the results by two models and experimental results have been made for three-phase composite, resulting in that MEM predicts better than DEMM for smaller volume fraction of the inclusion having larger inclusion-to-matrix thermal conductivity ratio, but DEMM predicts better as its volume fraction increases. It has been observed through parametric study that its volume fraction is the critical factor affecting the deviation of predictions by the two models. The results by them show a good agreement with the three-phase composite proposed by Molina et al..

A Basic study of Electrical Properties in the PZT/Polymer Piezoelectric Composites for Ultrasonic Transducer Applications (초음파 변환기 응용을 위한 PZT/고분자 압전 복합재료의 전기물성에 관한 기초연구)

  • 이덕출;김진수;김용혁;김재호
    • Electrical & Electronic Materials
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    • v.2 no.1
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    • pp.14-24
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    • 1989
  • 본 연구에서는 1-3형 PZT/Epoxy 압전복합재료를 제조하고 이에 대한 D-E 곡선, 펄스응답특성 및 유중발생전압특성 등을 조사하였다. 압전복합재료의 음향임피던스는 PZT체적비가 증가함에 따라 비례적으로 증가하였다. 그리고 펄스응답특성은 단일상 PZT의 특성에 비하여 아주 양호하게 나타났으며 PZT 체적비가 40% 이상에서는 펄스응답특성이 거의 일정하게 되었다. 유중에서의 발생전압은 PZT체적비, 시편두께 그리고 유중압력이 증가함에 따란 비례적으로 증가하였다. 이들의 결과는 초음파 트랜스듀서 제작에 좋은 자료가 될 것으로 생각한다.

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An Advection Scheme for the Transport of Fractional Volume of an Incompressible Fluid (비압축성 유체의 체적비 수송에 대한 대류항 계산 기법)

  • Kwak Ho Sang;Kuwahara Kunio
    • Journal of computational fluids engineering
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    • v.3 no.1
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    • pp.1-10
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    • 1998
  • 서로 섞이지 않는 두 비압축성 유체의 유동을 해석하기 위하여 VOF 방법에 기초한 수치 기법을 개발하였다. 유체간의 계면형상의 거동은 유동장내의 유체의 점유체적비의 변화에 의해 묘사되는데 이를 지배하는 이동방정식을 풀기 위한 새로운 대류항 계산법을 고안하였다. 대류항은 유체계면의 방향에 따라 풍상법과 역풍상법의 적절한 조합을 취하여 계산하는데 여기에 대각방향의 상류효과를 포함시켜 시간에 대한 2차 정확도를 갖도록 하였다. 또한 이 방법을 유량보정수송(FCT)법과 결합시켜 해의 단조성을 보장하였다. 몇 가지 단순 문제에 대한 시험 결과 이 기법이 수치오차에 의한 계면형상의 변형과 파손을 감소시킴을 확인하였다.

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A Study on Segmentation and Volume Calculation of the White Matter and Gray Matter for Brain Image Processing (뇌 영상처리를 위한 백질과 회백질의 추출 및 체적 산출에 관한 연구)

  • Kim, Shin-Hong
    • 전자공학회논문지 IE
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    • v.43 no.4
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    • pp.21-27
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    • 2006
  • This paper is for the segmentation and volume calculation of the white matter and gray matter from brain MRI. We segment white matter, gray matter and CSF from the Brain image in the normal and abnormal person, and calculate the volume of segmented tissue. In this paper, we present a new method of extracting white matter, gray matter and CSF and calculation its volume from MR images for brain. And we have developed the determining method of threshold that can extract white matter and gray matter from MR image for brain through the analysis of gray values represented by ratio of each component. We proposed the calculation method of volume for white matter and gray matter by using number of extracted pixels in each slice. This algorithm input CSF/Head volume ratio and age of patient and calculates discriminant value through discriminant expression, classifies normal and abnormal using calculated discriminant value. As a result, we could blow that white matter and gray matter volume decrease and CSF volume increase as we grow gold.