• Title, Summary, Keyword: Back Analysis

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Back Analysis for Estimating Tension Force on Hanger Cables (역해석기법을 이용한 현수교 행어케이블 장력 추정)

  • Kim, Nam-Sik;Bin, Jung-Min;Chang, Sung-Jin
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.894-901
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    • 2006
  • In general, the tension fores of hanger cable in suspension bridges play an important role in evaluating the bridge state. The vibration method, as a conventional one, has been widely applied to estimate the tension fores by using the measured frequencies on hanger cables. However, the vibration method is not applicable to short hanger cables because the frequency of short cables is severely sensitive to the flexural rigidity. Thus, in this study, the tension forces of short hanger cables, of which the length is shorter than 10meters, were estimated through back analysis of the cable frequencies measured from Gwang-An suspension bridge in Korea. Direct approach to rock analysis is adopted using the univariate method among the direct search methods as an optimization technique. The univariate method is able to search the optimal tension forces without regard to the initial ones and has a rapid convergence rate. To verify the feasibility of back analysis, the results from back analysis and vibration method are compared with the design tension forces. From the comparison, it can be inferred that back analysis results are more reasonable agreement with the design tension forces of short hanger cable. Therefore, it is concluded that back analysis applied in this study is an appropriate tool for estimating tension forces of short hanger cables.

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Coupling relevance vector machine and response surface for geomechanical parameters identification

  • Zhao, Hongbo;Ru, Zhongliang;Li, Shaojun
    • Geomechanics and Engineering
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    • v.15 no.6
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    • pp.1207-1217
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    • 2018
  • Geomechanics parameters are critical to numerical simulation, stability analysis, design and construction of geotechnical engineering. Due to the limitations of laboratory and in situ experiments, back analysis is widely used in geomechancis and geotechnical engineering. In this study, a hybrid back analysis method, that coupling numerical simulation, response surface (RS) and relevance vector machine (RVM), was proposed and applied to identify geomechanics parameters from hydraulic fracturing. RVM was adapted to approximate complex functional relationships between geomechanics parameters and borehole pressure through coupling with response surface method and numerical method. Artificial bee colony (ABC) algorithm was used to search the geomechanics parameters as optimal method in back analysis. The proposed method was verified by a numerical example. Based on the geomechanics parameters identified by hybrid back analysis, the computed borehole pressure agreed closely with the monitored borehole pressure. It showed that RVM presented well the relationship between geomechanics parameters and borehole pressure, and the proposed method can characterized the geomechanics parameters reasonably. Further, the parameters of hybrid back analysis were analyzed and discussed. It showed that the hybrid back analysis is feasible, effective, robust and has a good global searching performance. The proposed method provides a significant way to identify geomechanics parameters from hydraulic fracturing.

Factors Affecting the Compensated Low Back Pain Disability (산업재해 요통 근로자의 기능장애에 영향을 미치는 요인)

  • Kjm, Ji-Yun
    • Korean Journal of Occupational Health Nursing
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    • v.13 no.1
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    • pp.48-58
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    • 2004
  • Purpose: To identify the factors which are related to compensated low back pain disability. These include individual. workplace. economic and injury factors. Method: Data collection was performed at 13 office of Korea Labor Welfare Corporation and 29 hospitals from 23th June to 4th August 2003. This study used 212 workers with compensated low back pain. Result: From the bivariate analysis, industry kind, type of employment, rest schedule, Job control, compensation, payment of company, diagnosis, cause of occupational injury, duration of compensated low back pain, pattern of pain, operation, other injury is related to low back pain disability. From the multiple regression analysis, rest schedule, compensation, diagnosis, pattern of pain, other injury have statistically significant effect on the low back pain disability. Conclusion: In order to reduce low back pain disability, occupational rehabilitation nursing intervention is necessary to workers with compensated low back pain.

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A Study on Somatotype Classification of the Late Middle-Aged Women (중년 후기 여성의 체형 유형화에 관한 연구)

  • 심정희
    • Journal of the Korean Society of Clothing and Textiles
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    • v.26 no.1
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    • pp.15-26
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    • 2002
  • The purpose of this study was to classier the somatotype of late middle-aged women and to analyze the characteristics of each somatotype. The subjects were 337 late middle-aged women and their age range os from 45 to 59 fears old. Data were collected through anthropometry and photometry and analyzed by factor analysis, cluster analysis and discriminant analysis. The results were as follows; 1. The result of factor analysis indicated that 9 factors were extracted through factor analysis and those factors comprised 83.56 percent of total valiance. 2. Using factor scores, cluster analysis was carried out and the subject were classified into 4 cluster. Each cluster was classified as their body front and side view contour. Type 1 is tall, slim, and lower balk is flat on the side. Type 2 is standard and lean-back type on the side. Type 3 is standard height and weight, H type in front, and belly-protruded on the side. Type 4 is short, fat, and the side is hip-protruded. 3. According to the stepwise discriminant analysis, the 9 important items in classifying the somatotype of the late middle-aged women are as follows ; lower back tilt angle, hip depth(back) -back waist depth(back), bust depth(fore) - anterior waist depth(fore), jugular fossa point(fore), upper back tilt angle, burst breadth -waist breadth, right shoulder tilt, height of shoulder - height of anterior waist, abdomen breath. The correct classification rate for these items is as exact as 84.62%.

Back EMF Design of an AFPM Motor using PCB Winding by Quasi 3D Space Harmonic Analysis Method

  • Jang, Dae-Kyu;Chang, Jung-Hwan;Jang, Gun-Hee
    • Journal of Electrical Engineering and Technology
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    • v.7 no.5
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    • pp.730-735
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    • 2012
  • This paper presents a method to design the waveform of a back electromotive force (back EMF) of an axial flux permanent magnet (AFPM) motor using printed circuit board (PCB) windings. When the magnetization distribution of permanent magnet (PM) is given, the magnetic field in the air gap region is calculated by the quasi three dimensional (3D) space harmonic analysis (SHA) method. Once the flux density distribution in the winding region is determined, the required shape of the back EMF can be obtained by adjusting the winding distribution. This can be done by modifying the distance between patterns of PCB to control the harmonics in the winding distribution. The proposed method is verified by finite element analysis (FEA) results and it shows the usefulness of the method in eliminating a specific harmonic component in the back EMF waveform of a motor.

The Application of Genetic Algorithms to Estimate the Geotechnical Parameters of Tunnels (터널의 지반계수 추정에 대한 Genetic Algorithms의 적용)

  • 현기환;김선명;윤지선
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.125-132
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    • 2000
  • This study presents the application of genetic algorithms(GA) to the back analysis of tunnels. GA based on the theory of natural evolution, and have been evaluated very effective for their robust performances, particularly for optimizing structure problems. In the back analysis method, the selection of initial value and uncertainty of field measurements influence significantly on the analysis result. GA can improve this problems through a probabilistic approach. Besides, this technique have two other advantages over the back analysis. One is that it is not significantly affected by the form of problems. Another one is that it can consider two known parameter simultaneously. The propriety of this study is verified as the comparison in the same condition of the back analysis(Gens et al, 1987). In this study, it was performed to estimated the geotechnical parameters in the case of weak rock mass at the Kyung Bu Express railway tunnel. GA have been shown for effective application to a geotechnical engineering.

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Application of New Back Analysis Method for Landslide around Portal (터널 갱구부 주변의 산사태를 고려한 역해석법에 관한 검토)

    • Tunnel and Underground Space
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    • v.8 no.1
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    • pp.46-52
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    • 1998
  • The author conducted new back analysis method using monitoring data to a landslide which occurred around portal. In this case, because the tunnel being located under the sliding plane of the landslide, calculated value from the ordinary back analysis in which considered only stress release by the tunnel excavation didn't fit the measured value. Then, in the new method, a body force as the movement of the landslide mass was added to the ordinary back analysis and good results were obtained. Furthermore, the author carried out stability analysis of the landslide with the data of the back analysis and examined the loosened area and decreasing og the sliding plane strength due to the tunnel excavation.

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Numerical and Experimental Study on Spring Back in Automatic Multi-Stage Precision Cold Forging Process of a Steering Yoke (조향장치용 요크 자동다단 정밀냉간단조 공정에서 발생하는 스프링백의 수치적 및 실험적 검증)

  • Kim, K.M.;Kim, M.C.;Hwang, T.M.;Chung, S.H.;Chung, W.J.;Joun, M.S.
    • Transactions of Materials Processing
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    • v.28 no.3
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    • pp.115-122
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    • 2019
  • In this paper, finite element analysis of an automatic five-stage precision cold forging process of a yoke, a steering part of a passenger's car, is conducted with emphasis on spring back analysis at the yoke-forming stage and its experimental verification is subsequently made. An elastoplastic finite element method with MINI-element technique employed for the analysis of the entire process is explained. There is emphasis that the thin film of material formed between the punch and die in the stage may result to some errors especially in elastoplastic finite element analysis of spring back due to frequent remeshing. The numerical robustness of the spring back analysis in regards to remeshing is hence shown first through investigation into its effect on the predicted spring back. Experimental measurement of displacement due to spring back is carried out for comparison with the predicted results, and they are in a qualitative agreement with each other.

Optimal Design of Automotive Seat Back Frame Using Finite Element Analysis (유한요소해석을 이용한 차량용 시트 백 프레임의 최적설계)

  • Shin, Hyeonho;Kang, Hee Yong;Yang, Sung Mo
    • Journal of Auto-vehicle Safety Association
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    • v.11 no.4
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    • pp.57-62
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    • 2019
  • The seat back frame of the vehicle is subjected to load on the passenger behavior. Because of steel material, it is necessary to optimize the frame considering lightweight and safety. In this paper, finite element analysis is used for the optimal design of the seat back frame. First, a lightweight material is applied to reduce the weight of the seat back frame. Secondly, the design position of the pipe part fastened in the seat back frame was selected by considering the strength against the load generated by the occupant. Third, the shape of the side frame was derived by performing the phase optimization analysis for the AFT load condition. And we have compared the initial model with the optimal model to verify the light weighting and safety. As a result, the optimal design model of the seat back frame satisfying the weight reduction and safety has been proposed.

Development of a back analysis program for reasonable derivation of tunnel design parameters (합리적인 터널설계정수 산정을 위한 역해석 프로그램 개발)

  • Kim, Young-Joon;Lee, Yong-Joo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.15 no.3
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    • pp.357-373
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    • 2013
  • In this paper, a back analysis program for analyzing the behavior of tunnel-ground system and evaluating the material properties and tunnel design parameters was developed. This program was designed to be able to implement the back analysis of underground structure by combination of using FLAC and optimized algorithm as direct method. In particular, Rosenbrock method which is able to do direct search without obtaining differential coefficient was adopted for the back analysis algorithm among optimization methods. This back analysis program was applied to the site to evaluate the design parameters. The back analysis was carried out using field measurement results from 5 sites. In the course of back analysis, nonlinear regression analysis was carried out to identify the optimum function of the measured ground displacement. Exponential function and fractional function were used for the regression analysis and total displacement calculated by optimum function was used as the back analysis input data. As a result, displacement recalculated through the back analysis using measured displacement of the structure showed 4.5% of error factor comparing to the measured data. Hence, the program developed in this study proved to be effectively applicable to tunnel analysis.