• Title/Summary/Keyword: Propagation Factors

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Correction factor calculation for railway noise prediction (철도소음 예측을 위한 보정치 산정)

  • Koh, Hyo-In;Kim, Jae-Chul;You, Won-Hee;Cho, Jun-Ho
    • Proceedings of the KSR Conference
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    • 2006.11b
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    • pp.50-55
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    • 2006
  • For prediction of railway noise, propagation characteristics must be identified as well as the source characteristics. During the railway noise in outdoor pass the air, various factors affect the propagation. In this study, to suggest more effective and convenient equation to predict railway noise, calculation method for correction factor was investigated.

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Robust Parameter Design Based on Back Propagation Neural Network (인공신경망을 이용한 로버스트설계에 관한 연구)

  • Arungpadang, Tritiya R.;Kim, Young Jin
    • Korean Management Science Review
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    • v.29 no.3
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    • pp.81-89
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    • 2012
  • Since introduced by Vining and Myers in 1990, the concept of dual response approach based on response surface methodology has widely been investigated and adopted for the purpose of robust design. Separately estimating mean and variance responses, dual response approach may take advantages of optimization modeling for finding optimum settings of input factors. Explicitly assuming functional relationship between responses and input factors, however, it may not work well enough especially when the behavior of responses are poorly represented. A sufficient number of experimentations are required to improve the precision of estimations. This study proposes an alternative to dual response approach in which additional experiments are not required. An artificial neural network has been applied to model relationships between responses and input factors. Mean and variance responses correspond to output nodes while input factors are used for input nodes. Training, validating, and testing a neural network with empirical process data, an artificial data based on the neural network may be generated and used to estimate response functions without performing real experimentations. A drug formulation example from pharmaceutical industry has been investigated to demonstrate the procedures and applicability of the proposed approach.

Calculation of the flow field in the cylinder of the diesel engine for different bowl shapes and swirl ratios (보올형상과 선회비에 따른 디젤기관 실린더내의 유동장 해석)

  • 최영진;양희천;유홍선;최영기
    • Journal of the korean Society of Automotive Engineers
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    • v.13 no.2
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    • pp.50-66
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    • 1991
  • There are many factors which influence on the performance of a diesel engine. The piston bowl shape and swirl ratio are important factors to enhance the fuel-air mixing and flame propagation. In this study, calculations of the flow field in the cylinder of the diesel engine were carried out using the CONCHAS-SPRAY code for different bowl shapes and swirl ratios. In the case of constant swirl ratio, vortices which affect fuel-air mixing, evaporation and flame propagation are generated more strongly and consistently in the bowl-piston type combustion chamber than in the flat piston type. With this strong squish effect, injected fuel droplets are widely diffused and rapidly evaporated in the bowl-piston type combustion chamber. Especially a strong squish is developed and large and strong vortices are generated in the edge cutted bowl piston chamber. As the swirl ratio increases, it is found that a large and strong squish and vortices are generated in the combustion chamber and also fuel droplets are diffused into the entire combustion chamber.

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Study on the Characteristics of Propagating Fatiguc Crack under Mixed-Mode Loading Condition (혼합모드하중상태에서 전파하는 피로크랙특성에 관한 연구)

  • 송삼홍;최진호;임진학
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1993.10a
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    • pp.644-649
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    • 1993
  • Practical structures are subject not only to tension but also to shear and torsional loading. In this study, the mode 1 and 2 stress intensity factors of specimens were calculated by using elastic finite element mothod. The stress fields at the crack tip subjected to mixed-mode loading were also studied by usingf eleatic finite element method and were compared with theoretical results. The three-point-bending, four-point-bending, and mixed-mode-loading experiment were carried out. And, crack propagation rate da/dN and crack growth direction were examined. Also, the elastic finite element method was applied to calculate the stress intensity factors of branch crack tip and we relate the stress intenity factor range of branch crack tip(the result of FEM) to crack propagation rate(the experimental result). The .DELTA. -da/dN relation corelated with that of mode 1.

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Adaptive finite elements by Delaunay triangulation for fracture analysis of cracks

  • Dechaumphai, Pramote;Phongthanapanich, Sutthisak;Bhandhubanyong, Paritud
    • Structural Engineering and Mechanics
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    • v.15 no.5
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    • pp.563-578
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    • 2003
  • Delaunay triangulation is combined with an adaptive finite element method for analysis of two-dimensional crack propagation problems. The content includes detailed descriptions of the proposed procedure which consists of the Delaunay triangulation algorithm and an adaptive remeshing technique. The adaptive remeshing technique generates small elements around the crack tips and large elements in the other regions. Three examples for predicting the stress intensity factors of a center cracked plate, a compact tension specimen, a single edge cracked plate under mixed-mode loading, and an example for simulating crack growth behavior in a single edge cracked plate with holes, are used to evaluate the effectiveness of the procedure. These examples demonstrate that the proposed procedure can improve solution accuracy as well as reduce total number of unknowns and computational time.

A Study on Estimation and Factors of VHF Data Link Range (VHF 데이터통신 통달거리 예측 및 요소 분석)

  • Lee, Young-Joong;Kim, In-Seon;Park, Joo-Rae
    • Journal of the Korea Institute of Military Science and Technology
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    • v.13 no.3
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    • pp.413-420
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    • 2010
  • An Estimation of VHF data link range for EW(Electronic Warfare) equipment in the sea environment was studied to predict the data link range between transmitting and receiving station. The theoretical estimation predicts within 3% error with actual measurement of VHF data link range at sea. Data link range factors including refraction and reflection are added in the basic wave propagation equation. The effect of refraction and reflection to the range is analysed with quantity level.

Hydrodynamic scene separation from video imagery of ocean wave using autoencoder (오토인코더를 이용한 파랑 비디오 영상에서의 수리동역학적 장면 분리 연구)

  • Kim, Taekyung;Kim, Jaeil;Kim, Jinah
    • Journal of the Korea Computer Graphics Society
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    • v.25 no.4
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    • pp.9-16
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    • 2019
  • In this paper, we propose a hydrodynamic scene separation method for wave propagation from video imagery using autoencoder. In the coastal area, image analysis methods such as particle tracking and optical flow with video imagery are usually applied to measure ocean waves owing to some difficulties of direct wave observation using sensors. However, external factors such as ambient light and weather conditions considerably hamper accurate wave analysis in coastal video imagery. The proposed method extracts hydrodynamic scenes by separating only the wave motions through minimizing the effect of ambient light during wave propagation. We have visually confirmed that the separation of hydrodynamic scenes is reasonably well extracted from the ambient light and backgrounds in the two videos datasets acquired from real beach and wave flume experiments. In addition, the latent representation of the original video imagery obtained through the latent representation learning by the variational autoencoder was dominantly determined by ambient light and backgrounds, while the hydrodynamic scenes of wave propagation independently expressed well regardless of the external factors.

Measurement of DS-CDMA Propagation Distance in Underwater Acoustic Communication Considering Attenuation and Noise

  • Lee, Young-Pil;Moon, Yong Seon;Ko, Nak Yong;Choi, Hyun-Taek;Huang, Linyun;Bae, Youngchul
    • International Journal of Fuzzy Logic and Intelligent Systems
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    • v.15 no.1
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    • pp.20-26
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    • 2015
  • It is very difficult to design an underwater communication system because of multipath, Doppler effects, noise, and attenuation. These factors lead to errors in the communication performance and maximum propagation distance. In this study, we calculate the distance that can be realized using the direct-sequence code division multiple access (DS-CDMA) technique with direct-sequence spread spectrum (DSSS) in an underwater communication system considering only the attenuation and noise. We also compare the estimated and calculated propagation distances obtained for several different scenarios.

The application of forman equation for fatigue crack propagation in welding residual stress region (溶接殘留應力領域에서의 疲勞균열傳播에 대한 Forman式의 適用)

  • 김상철;이용복
    • Journal of Welding and Joining
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    • v.5 no.1
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    • pp.42-56
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    • 1987
  • Fatigue Fracture behaviors of the TIG-welded aluminum alloys, such as Al 2024-T4, A1 5050-0 and Al 7075-T7 were investigated when a crack propagated from tensile residual stress region and compressive residual stress region. The experimental values were compared with the values expected by the Forman equation. The experimental results are summarized as the following: (1) In case of fatigue crack propagation from residual stress region, the values predicted by Forman equation were Found to exactly corresponded to the experimental values. (2) When the stress intensityfactors affected by compressive residual stress, Kres, were greater than the stress intensity factors by minimum applied stresses. Kmin, the Forman equation was found to be improper to be applied directly, but the equation appeared to be proper, if the stress ratio was modified to zero. (3) The experimental results confirmed that residual stress was relaxed by repeated tensile loading and the relaxing trend was greater in case of compressive residual stress than that of tensile residual stress.

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