• Title/Summary/Keyword: simple tests

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High Temperature Fade Behavior of Brake Friction Materials at Extreme Braking Conditions (실험통계법을 이용한 마찰재의 고온 마찰특성에 대한 고찰)

  • Ko, Kil-Ju;Park, Sang-Jin;Jang, Ho
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2001.11a
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    • pp.117-126
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    • 2001
  • Tribological properties of high temperature fade were investigated by changing relative amounts of ingredients in the brake friction material. Based on a simple experimental formulation containing 10 ingredients, friction materials were tested using a pad-on-disk type friction tester. Twenty-five friction material specimens with different relative amounts of the ingredients were manufactured according to the constrained mixture design .The difference ($\Delta$${\mu}$=${\mu}$$\sub$max/. -${\mu}$$\sub$min/. ) of friction coefficients was measured to represent the high temperature fade. Results from elevated temperature tests showed that five ingredients including cashew, graphite, Sb$_2$S$_3$, ZrSiO$_4$, and Cu fibers played important roles on $\Delta$${\mu}$. In order to find relative importance on fade phenomena among these ingredients, ANOVA(analysis of variance) was performed in this investigation. Thirty-two friction material specimens by changing ${\pm}$50vol.% of these five ingredients were tested to examine the relative importance. Results showed that cashew, graphite '||'&'||' Sb$_2$S$_3$, and cashew '||'&'||' graphite aggravated the fade behavior and Cu fibers improved on fade resistance.

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New Treatment of Source Terms in Upwind Schemes (상류이송기법에서의 새로운 생성항 처리 기법)

  • Kim, Won;Han, Kun-Yeun;Woo, Hyo-Seop;Choi, Kyu-Hyun
    • Journal of Korea Water Resources Association
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    • v.38 no.2
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    • pp.155-166
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    • 2005
  • Upwind schemes are very well adapted to the discontinuous flow and have become popular for applications Involving dam break flow, transcritical Slow, etc. However, upwind schemes have been applied mainly to the idealized problems not to the natural channels with irregular geometry so far because of the error due to source terms. In this paper, the new type of upwind discretization of source terms, which uses the normalized Jacobian to discretize the source terms, is proposed. As results of tests to flows with source terms by the upwind models, the method proposed in this paper is proved as efficient and accurate. This generalized method for differencing source terms is simple and might beapplicable to diverse type of flux upwind discretization scheme in finite difference method.

Flexural and shear behavior of large diameter PHC pile reinforced by rebar and infilled concrete

  • Bang, Jin-Wook;Lee, Bang-Yeon;Kim, Yun-Yong
    • Computers and Concrete
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    • v.25 no.1
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    • pp.75-81
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    • 2020
  • The purpose of this paper is to provide an experimental and analytical study on the reinforced large diameter pretensioned high strength concrete (R-LDPHC) pile. R-LDPHC pile was reinforced with infilled concrete, longitudinal, and transverse rebar to increase the flexural and shear strength of conventional large diameter PHC (LDPHC) pile without changing dimension of the pile. To evaluate the shear and flexural strength enhancement effects of R-LDPHC piles compared with conventional LDPHC pile, a two-point loading tests were conducted under simple supported conditions. Nonlinear analysis on the basis of the conventional layered sectional approach was also performed to evaluate effects of infilled concrete and longitudinal rebar on the flexural strength of conventional LDPHC pile. Moreover, ultimate strength design method was adopted to estimate the effect of transverse rebar and infilled concrete on the shear strength of a pile. The analytical results were compared with the results of the bending and shear test. Test results showed that the flexural strength and shear strength of R-LDPHC pile were increased by 2.3 times and 3.3 times compared to those of the conventional LDPHC pile, respectively. From the analytical study, it was found that the flexural strength and shear strength of R-LDPHC pile can be predicted by the analytical method by considering rebar and infilled concrete effects, and the average difference of flexural strength between experimental results and calculated result was 10.5% at the ultimate state.

Identifying Dynamic Characteristics of the Traction Motor Housing For the Noise reduction of the Electric vehicle (전기자동차 소음저감을 위한 구동모터 하우징의 동특성 평가)

  • Park, Jongchan;Park, Seungyong;Cho, Hyun-Kyu;Park, Yunsu
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2012.10a
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    • pp.818-823
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    • 2012
  • Assessment of the dynamics properties, like damping, dynamic stiffness and resonance sharpness is essential for the development of a robust system, specifically for the reduction of a traction motor noise. A practical method for identifying dynamic characteristics of a traction motor hosing for an electric vehicle is proposed. Assembling using interference fit of the components of the motor is attributed to the main cause of strong nonlinearity. It is well known that nonlinearity of a structure makes it difficult to assess damping properties or dynamic characteristics of the system. This research presents a practical damping or dynamic stiffness identifying procedures for a nonlinear system according to the boundary condition between assembled components. Based on the simple idea that impact forces of modal tests are highly affected on the condition of the hammer tip, Auto Power Spectrum of the impact forces are used to assess the assembling condition and dynamic characteristics of the system, especially, damping of the system.

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Study on the spectroscopic reconstruction of explosive-contaminated overlapping fingerprints using the laser-induced plasma emissions

  • Yang, Jun-Ho;Yoh, Jai-Ick
    • Analytical Science and Technology
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    • v.33 no.2
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    • pp.86-97
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    • 2020
  • Reconstruction and separation of explosive-contaminated overlapping fingerprints constitutes an analytical challenge of high significance in forensic sciences. Laser-induced breakdown spectroscopy (LIBS) allows real-time chemical mapping by detecting the light emissions from laser-induced plasma and can offer powerful means of fingerprint classification based on the chemical components of the sample. During recent years LIBS has been studied one of the spectroscopic techniques with larger capability for forensic sciences. However, despite of the great sensitivity, LIBS suffers from a limited detection due to difficulties in reconstruction of overlapping fingerprints. Here, the authors propose a simple, yet effective, method of using chemical mapping to separate and reconstruct the explosive-contaminated, overlapping fingerprints. A Q-switched Nd:YAG laser system (1064 nm), which allows the laser beam diameter and the area of the ablated crater to be controlled, was used to analyze the chemical compositions of eight samples of explosive-contaminated fingerprints (featuring two sample explosive and four individuals) via the LIBS. Then, the chemical validations were further performed by applying the Raman spectroscopy. The results were subjected to principal component and partial least-squares multivariate analyses, and showed the classification of contaminated fingerprints at higher than 91% accuracy. Robustness and sensitivity tests indicate that the novel method used here is effective for separating and reconstructing the overlapping fingerprints with explosive trace.

Prediction of Long-Term Settlement of Sands Containing Carbonates (탄산염 성분이 포함된 사질토의 장기침하 예측)

  • Hwang, Woong-Ki;Lee, Yong-Su;Hwang, Joong-Ho;Kim, Tae-Hyung
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.03a
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    • pp.993-998
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    • 2009
  • This study was conducted to propose the model that is able to predict long-term settlement of sands containing carbonates. We can observe that in addition to the initial elastic compression, a considerable additional compression occurs with long-term period in some sands. The compressibility of sands is significantly dependent on particle characteristics. Some sands have many pores and particularly has an angular shape. To predict of long-term settlement of these sands which contain carbonates, first of all a variety of tests which are to assess chemical, physical and compression characteristics of these sands were conducted. Second, in order to know settlement with time, the time parameter was determined by analyzing the measured data obtained from $\bigcirc\bigcirc$ area. The measured settlement of this area shows that in addition to the initial elastic compression, a considerable additional compression occurring with time. It was caused by the crushing, shattering, and rearrangement of particles, which were real phenomena in sandy soils under loading condition. Based on this case study, we proposed that a simple method is able to predict settlement with time of sandy soil containing carbonates.

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Density Variation within Specimen as Affected by Vibration (진동으로 인한 모래 공시체내의 밀도변화에 관한 연구)

  • 장병욱
    • Geotechnical Engineering
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    • v.3 no.3
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    • pp.7-20
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    • 1987
  • To obtain meaningful data of the tests for cyclic loading triaxial test, cyclic loading simple shear test ; and Shake table studies, it is necessary to test uniformly densified specimens. However, there is still some question about the assumed uniform density within a specimen when subjected to the process of densification. A study is conducted to investigate the density variation It within the specimen and analyze the effect of various parameters during the process of vibratory densification. It is found that variation of the ideally graded sand having a homogeneous initial density results in large inhomogeneities within the specimen after vibration. The degree of density variation within the speimen becomes more pronounced by the gradation of sand, surcharge and the intensity of acceleration.

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An Isothermal Mganetohydrodynamic Code and Its Application to the Parker Instability

  • KIM JONGSOO;RYU DONGSU;JONES T. W.;HONG S. S.
    • Journal of The Korean Astronomical Society
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    • v.34 no.4
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    • pp.281-283
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    • 2001
  • As a companion to an adiabatic version developed by Ryu and his coworkers, we have built an isothermal magnetohydrodynamic code for astrophysical flows. It is suited for the dynamical simulations of flows where cooling timescale is much shorter than dynamical timescale, as well as for turbulence and dynamo simulations in which detailed energetics are unimportant. Since a simple isothermal equation of state substitutes the energy conservation equation, the numerical schemes for isothermal flows are simpler (no contact discontinuity) than those for adiabatic flows and the resulting code is faster. Tests for shock tubes and Alfven wave decay have shown that our isothermal code has not only a good shock capturing ability, but also numerical dissipation smaller than its adiabatic analogue. As a real astrophysical application of the code, we have simulated the nonlinear three-dimensional evolution of the Parker instability. A factor of two enhancement in vertical column density has been achieved at most, and the main structures formed are sheet-like and aligned with the mean field direction. We conclude that the Parker instability alone is not a viable formation mechanism of the giant molecular clouds.

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Analytical and experimental study on the behavior of elastically supported reinforced concrete decks

  • Park, Nam-Hoi;Kang, Young-Jong;Choi, Jin-Yu;Lim, Nam-Hyoung
    • Structural Engineering and Mechanics
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    • v.15 no.6
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    • pp.629-651
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    • 2003
  • Current design specifications prescribe that the upper and lower reinforcement mat is required in the same amount to resist negative and positive moment in bridge decks. This design concept is primarily based on the unrealistic assumption that the girder plays a role of rigid support against deck deflection. In reality, however, girders are flexible and the deflection of girders affect the behavior of deck slabs. In the present study, an analytical method was developed to take the effect of the girder flexibility on the deck behavior into account. The method was formulated based on the slope-deflection equations of plates and harmonic analysis. Unlike the conventional finite element analysis, the input and output schemes are simple and convenient. The validity of the presented study was verified by a series of comparative studies with finite element analyses and experimental tests. It was shown from the analyses that the negative transverse moments of decks were significantly reduced in many cases when the girder flexibility were appropriately taken into consideration whereas the positive moments tend to increase. This poses a strong need to improve the conventional design concept of decks on rigid girders to those on flexible girders.

Development of Resonant-Type Magnetometer Using High Permeability Isotropic Magnetic Material (고투자율 등방성 자기 물질을 이용한 공진형 마그네토미터 개발)

  • Yim, Jeong-Bin;Shim, Yeong-Ho;Ahn, Yeong-Sub
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.11 no.1 s.22
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    • pp.29-37
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    • 2005
  • The design and development if Resonant-type Magnetometer(RM) using isotropic magnetic with high permeability is described in this paper. At first, the relationship between the inductance L if the coil winding on a magnetic material and the permeability u(H) appearing in the magnetic material with isotropic and high permeability is defined as a background theory. Then the circuit if RM, which is to obtain the values if L as the change qf frequency is implemented using simple Schmitt Trigger Circuit Through the swinging tests, which is to evaluate the measurement ability if RM, the measurement possibility for the component of earth field was confined.

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