• Title/Summary/Keyword: Layer coefficient

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Elastic Modulus and Layer Coefficient of Permeable Block Pavements Based on Plate Load Tests (평판재하시험을 통한 투수 블록포장의 탄성계수 및 상대강도계수 산정)

  • Choi, Yong-Jin;Oh, Jeong-Ho;Han, Shin-In;Ahn, Jaehun;Shin, Hyun-Suk
    • Journal of the Korean Geotechnical Society
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    • v.33 no.12
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    • pp.75-80
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    • 2017
  • Permeable block pavement systems are widely used to relieve the flood and enhance water circulation. However, domestic design method has not yet been established well. Although AASHTO 93 flexible pavement design method is applied as a structural design method outside the country, there is a lack of information on layer coefficient of the permeable pavement materials, which makes it difficult to apply the design to various materials. Therefore, in this study, a method of calculating the layer coefficient of permeable block pavement materials by plate load test was presented and the layer coefficient of a permeable block pavement in a testbed was evaluated. Overall, calculated layer coefficient of open graded aggregate and permeable block pavement surface layer were similar to those of the conventional values. The presented method may be used to evaluate layer coefficients of permeable block pavements for design.

Experimental Study on Coefficient of air Convection with boundary layer and boiling effects (경계층과 비등효과를 고려한 외기대류계수에 관한 실험연구)

  • Choi Myoung sung;Kim Yun Yong;Song Young Chul;Woo Sang Kyun;Kim Jin Keun;Lee Yun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.711-714
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    • 2004
  • The setting and hardening of concrete is accompanied with nonlinear temperature distribution caused by development of hydration heat of cement. In order to predict the exact temperature history in concrete structures it is required to examine thermal properties of concrete. In this study, the coefficient of air convection, which presents thermal transfer between surface of concrete and air, was experimentally investigated with variables such as velocity of wind, boiling and layer effects. Finally, the prediction model for equivalent coefficient of air convection was theoretically proposed. The coefficient of air convection in the proposed model increases with velocity of wind, and its dependance on wind velocity is varied with types of form. For determining the initial coefficient of air convection, boiling effects must be considered. The coefficient of air convection is affected by boundary layer with respect to the distance from the surface.

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Calculation of the coupling coefficient for trapezoidal gratings using the ray optics technique (기하광학 방법을 이용한 사다리꼴 회절격자의 결합계수 계산)

  • 조성찬;김부균
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.34D no.7
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    • pp.97-104
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    • 1997
  • Using the ray optics technique, we derive the analytic expressions of TE mode coupling coefficient for five-layer distributed feedback (DFB) structure devices. We compare the coupling coefficient calculated by the ray optics technique with those calulated by the extended additional layer method (EALM) which may be a most accurate method of calculating the coupling coefficient. The difference between the results of the ray optics technique and those of the EALM is small for most cases of grating depth and forms being practically made. In the case of rectangular gratings, the difference increases as the duty cycle of graing deviates from 0.5. In the case of the trapezoidal grating, the difference increases as the ratio of the top to the period of grating deviates from 0.5 and as the length of the top becomes longer than that of the base. The difference of theree-layer DFB structures is smaller than that of five-layer DFB structures.

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The Change in Diffusion Coefficient and Wear Characteristic in Carbonitriding Layer of SCM415 Steel (침탄질화 처리된 SCM415강의 깊이에 따른 확산 및 마모특성 변화)

  • Lee, Su-Yeon;Youn, Kuk-Tea;Huh, Seok-Hwan;Lee, Chan-Gyu
    • Journal of the Korean institute of surface engineering
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    • v.44 no.5
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    • pp.207-212
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    • 2011
  • In this study, the change in diffusion coefficient and wear characteristic with depth in the carbonitriding layer of SCM415 steel was discussed. To determine the diffusion coefficient, depth profile of carbon was measured from the surface using the Glow Discharge Spectrometer. In otherwise, measurements of carbide fraction, micro vickers hardness of surface and observation of microstructure have been implemented through the SEM image. $Fe_3$(C,N) layer and effective depth were increased as the time for carbonitriding takes longer. According to wear experiment, the results showed that wear resistance was improved by $Fe_3$(C,N) layer and effective depth.

Error Accumulation and Transfer Effects of the Retrieved Aerosol Backscattering Coefficient Caused by Lidar Ratios

  • Liu, Houtong;Wang, Zhenzhu;Zhao, Jianxin;Ma, Jianjun
    • Current Optics and Photonics
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    • v.2 no.2
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    • pp.119-124
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    • 2018
  • The errors in retrieved aerosol backscattering coefficients due to different lidar ratios are analyzed quantitatively in this paper. The actual calculation shows that the inversion error of the aerosol backscattering coefficients using the Fernald backward-integration method increases with increasing inversion distance. The greater the error in the lidar ratio, the faster the error in the aerosol backscattering coefficient increases. For the same error in lidar ratio, the smaller actual aerosol backscattering coefficient will get the larger relative error of the retrieved aerosol backscattering coefficient. The errors in the lidar ratios for dust or the cirrus layer have great impact on the retrievals of backscattering coefficients. The interval between the retrieved height and the reference range is one of the important factors for the derived error in the aerosol backscattering coefficient, which is revealed quantitatively for the first time in this paper. The conclusions of this article can provide a basis for error estimation in retrieved backscattering coefficients of background aerosols, dust and cirrus layer. The errors in the lidar ratio of an aerosol layer influence the retrievals of backscattering coefficients for the aerosol layer below it.

Aerosol Measurement and Property Analysis Based on Data Collected by a Micro-pulse LIDAR over Shanghai, China

  • Huang, Xingyou;Yang, Xiaowu;Geng, Fuhai;Zhang, Hua;He, Qianshan;Bu, Lingbing
    • Journal of the Optical Society of Korea
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    • v.14 no.3
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    • pp.185-189
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    • 2010
  • A micro-pulse LIDAR system (MPL) was employed to measure the aerosol over Pudong, Shanghai from July 2008 to January 2009. Based on Fernald method, aerosol optical variables such as extinction coefficient were retrieved and analyzed. Results show that aerosol exists mainly in low layers; aerosol loading reaches its maximum in the afternoon, and then decreases with time until its minimum at night. Most of the aerosol concentrates in the layer below 3 km, and optical extinction coefficient in the layer below 2 km contributes 84.25% of that below 6 km. Two extinction coefficient peaks appear in the near surface layer up to 500 m and in the level around 1000 m. Aerosol extinction coefficient shows a seasonal downward trend from summer to winter.

The Analysis for Surface Hardening by Repeated Sliding Contact (반복 미끄럼 접촉에 의한 표면층의 경화에 대한 해석)

  • 박준목;김석삼
    • Tribology and Lubricants
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    • v.13 no.4
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    • pp.71-78
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    • 1997
  • Wear is affected by numerous factors-contact load, sliding velocity and distance, friction coefficient, material properties and environmental conditions. Among these wear factors, surface hardness is one of very important factors to determine wear. But surface hardness is varied by work hardening during repeated sliding contact. In this reason wear rate is increased or decreased with varying surface hardness, and transition of wear mechanism is happened. In this study, the surface hardening by accumulating residual stress was analyzed by considering the repeated sliding Hertzian contact model. The results showed that surface hardness was increased with increasing contact load, friction coefficient and contact number. And the depth of hardening layer, plastic layer and elastic layer depended upon contact load and number, but they didn't depend upon friction coefficient. The predicted surface hardness was about 1.5-1.8 times as hard as the material.

The Error Involved in the Equivalent Electroacoustic Circuit Approach for the Estimation of the Absorption Coefficient of Multiple Layer Perforated Plate Systems (다중 다공판 시스템의 흡음계수 계산에 있어서 전기음향등가회로법의 오류)

  • Lee, Dong-Hoon;Kwon, Yeung-Pil
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11b
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    • pp.890-895
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    • 2002
  • The equivalent electroacoustic circuit approach has been conventionally used for estimating the absorption coefficient of a single layer perforated plate system. When the single layer system is extended to the multiple layer ones, however, it is found that an analogy error has been involved in the equivalent electroacoustic parallel circuit approach proposed by previous investigators. The analogy error is demonstrated by the corrected equivalent electroacoustic circuit approach in this study.

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The Error Involved in the Equivalent Electroacoustic Circuit Approach for the Estimation of the Absorption Coefficient of Multiple Layer Perforated Plate Systems (다중 다공판 시스템의 흡음계수 계산에 있어서 전기음향등가회로법의 오류)

  • Lee, Dong-Hoon;Kim, Wook;Kwon, Young-Pil
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11a
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    • pp.387.2-387
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    • 2002
  • The equivalent electroacoustic circuit approach has been conventionally used for estimating the absorption coefficient of a single layer perforated plate system. When the single layer system is extended to the multiple layer ones, however, it is found that an analogy error has been involved in the equivalent electroacoustic parallel circuit approach proposed by previous researchers. The analogy error is demonstrated by the corrected equivalent electroacoustir circuit approach proposed en this study.

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Optimum thickness of GaAs top layer in AlGaAs-based 850 nm VCSELs for 56 Gb/s PAM-4 applications

  • Yu, Shin-Wook;Kim, Sang-Bae
    • ETRI Journal
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    • v.43 no.5
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    • pp.923-931
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    • 2021
  • We studied the influence of GaAs top-layer thickness on the small-signal modulation response and 56 Gb/s four-level pulse-amplitude modulation eye quality of 850 nm vertical-cavity surface-emitting lasers (VCSELs). We considered the proportionality of the gain-saturation coefficient to the photon lifetime. The simulation results that employed the transfer-matrix method and laser rate equations led to the conclusion that the proportionality should be considered for proper explanation of the experimental results. From the obtained optical eyes, we could determine an optimum thickness of the GaAs top layer that rendered the best eye quality of VCSEL. We also compared two results: one result with a fixed gain-saturation coefficient and the other that considered the proportionality. The former result with the constant gain-saturation coefficient demonstrated a better eye quality and a wider optimum range of the GaAs top-layer thickness because the resultant higher damping reduced the relaxation oscillation.