• Title, Summary, Keyword: Back Analysis

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Three-dimensional finite element analysis of forging processes with back pressure exerted by spring force (스프링 힘에 의한 배합부가 단조 공정의 3차원 유한요소해석)

  • Jang, S.M.;Kim, M.C.;Lee, M.C.;Jun, B.Y.;Joun, M.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.470-473
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    • 2009
  • In this paper, back pressure forging processes of which back pressures are exerted by mechanical forces including spring reaction are simulated by three-dimensional finite element method. The basic three-dimensional approach extended from two-dimensional approach is accounted for. An axisymmetric backward and forward extrusion process having a back pressing die, which is exposed to oscillation of forming load due to variation of reduction ratios with stroke and its related frequent variation of major deforming region, is simulated by both two and three dimensional approaches to justify the presented approach by their comparison. A three-dimensional forging process having a back pressing die attached to the punch by a mechanical spring is simulated and the results are investigated to reveal accuracy of the presented approach.

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Analysis of Back-to-Back HVDC system featured for Asynchronous Connection (비동기 전력계통 연계를 위한 Back-To-Back 직류설비의 운전특성 해석)

  • Kwak, J.S.;Wook, W.J.;Koh, B.E.;Kim, C.K.;Shim, E.B.
    • Proceedings of the KIEE Conference
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    • pp.1289-1291
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    • 2000
  • The operation of Back-To-Back HVDC system for asynchronous connection is described. It can exchange electric power up to 300 MW between separately operated two rower systems, making the interaction on each system minimum. The analysis is done under three different AC transmission lines interconnected to BTB HVDC.

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The Back-bead Prediction Comparison of Gas Metal Arc Welding (아크 용접의 이면비드 예측 비교)

  • Lee, Jeong-Ick;Koh, Byung-Kab
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.16 no.3
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    • pp.81-87
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    • 2007
  • It is important to investigate the relationship between weld process parameters and weld bead geometry for adaptive arc robot welding. However, it is difficult to predict an exact back-bead owing to gap in process of butt welding. In this paper, the quantitative prediction system to specify the relationship external weld conditions and weld bead geometry was developed to get suitable back-bead in butt welding which is widely applied on industrial field. Multiple regression analysis and artificial neural network were used as the research methods. And, the results of two prediction methods were compared and analyzed.

Three-Dimensional Finite Element Analysis of Forging Processes with Back Pressure Exerted by Spring Force (스프링 힘에 의한 배압부가 단조 공정의 3차원 유한요소해석)

  • Jang, S.M.;Kim, M.C.;Lee, M.C.;Jun, B.Y.;Joun, M.S.
    • Transactions of Materials Processing
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    • v.19 no.5
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    • pp.273-276
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    • 2010
  • In this paper, back pressure forging processes of which back pressures are exerted by mechanical forces including spring reaction are simulated by three-dimensional finite element method. The basic three-dimensional approach extended from two-dimensional approach is accounted for. An axisymmetric backward and forward extrusion process having a back pressing die, which is exposed to oscillation of forming load due to variation of reduction ratios with stroke and its related frequent variation of major deforming region, is simulated by both two and three dimensional approaches to justify the presented approach by their comparison. A three-dimensional forging process having a back pressing die attached to the punch by a mechanical spring is simulated and the results are investigated to reveal accuracy of the presented approach.

Quantification of the tug-back by measuring the pulling force and micro computed tomographic evaluation

  • Jeon, Su-Jin;Moon, Young-Mi;Seo, Min-Seock
    • Restorative Dentistry and Endodontics
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    • v.42 no.4
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    • pp.273-281
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    • 2017
  • Objectives: The aims of this study were to quantify tug-back by measuring the pulling force and investigate the correlation of clinical tug-back pulling force with in vitro gutta-percha (GP) cone adaptation score using micro-computed tomography (${\mu}CT$). Materials and Methods: Twenty-eight roots from human single-rooted teeth were divided into 2 groups. In the ProTaper Next (PTN) group, root canals were prepared with PTN, and in the ProFile (PF) group, root canals were prepared using PF (n = 14). The degree of tug-back was scored after selecting taper-matched GP cones. A novel method using a spring balance was designed to quantify the tug-back by measuring the pulling force. The correlation between tug-back scores, pulling force, and percentage of the gutta-percha occupied area (pGPOA) within apical 3 mm was investigated using ${\mu}CT$. The data were analyzed using Pearson's correlation analysis, one-way analysis of variance (ANOVA) and Tukey's test. Results: Specimens with a strong tug-back had a mean pulling force of 1.24 N (range, 0.15-1.70 N). This study showed a positive correlation between tug-back score, pulling force, and pGPOA. However, there was no significant difference in these factors between the PTN and PF groups. Regardless of the groups, pGPOA and pulling force were significantly higher in the specimens with a higher tug-back score (p < 0.05). Conclusions: The degree of subjective tug-back was a definitive determinant for master cone adaptation in the root canal. The use of the tug-back scoring system and pulling force allows the interpretation of subjective tug-back in a more objective and quantitative manner.

Blowdown Prediction of Safety Relief Valve and FSI Analysis (안전릴리프밸브의 블로우 다운 예측 및 유체-구조 연성해석)

  • Choi, Ji-Won;Jang, Si-Hwan;Lee, Kwon-Hee
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.12
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    • pp.729-734
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    • 2017
  • A safety relief valve is a device that relieves excessive pressure in piping lines or tanks and maintains pressure at the appropriate pressure level for use. The (pressure in the) safety valve is directly influenced by the change in the back pressure, depending on whether the vents in the spring bonnet are vented to the atmosphere or to the outlet. The back pressure is divided into the built-up back pressure and the superimposed back pressure, and the back pressure characteristics vary according to the usage conditions. The safety valve used in this study is a Conventional Safety Relief Valve. The blowdown of the safety valve is predicted by establishing the equilibrium equation between the opening force and spring force considering the back pressure characteristics. Its reliability is secured by using CFX17.1. In addition, the safety of the safety valve trim was examined through fluid-structure interaction analysis.

Spectral Electromyographic Fatigue Analysis of Back Muscles in Healthy Adult Men and Women During Sorensen Test (근전도를 이용한 Sorensen 검사시 성인남녀 등 근육의 근피로도 분석)

  • Lee, Mi-Seon;Kim, Tae-Young
    • Physical Therapy Korea
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    • v.5 no.3
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    • pp.63-71
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    • 1998
  • Trunk holding test (Sorensen test) appear to have more value than strength test in prediction the occurrence of low back pain. Electromyographic activity of trunk extensor muscles during these test may provide clues to the etiology of neuromuscular-based low back pain. This study investigated the difference in back muscle endurance between healthy adult men and women using surface electromyographic (EMG) power spectral analysis. Thirty hea1thy subjects (15 men and 15 women) performed an unsupported trunk holding test for 60 seconds. Recording surface electrodes were placed over the erector spinae medially and laterally at vertebral levels of $L_1$ and $L_5$. Slope of total frequency was evaluated using the MP100WSW Fast Fourier Transform spectrum analysis program. The slopes of all indices of back muscle fatigue, except right $L_5$, were significantly steeper in men than in women (p<0.05). Our results indicated that the trunk holding test using EMG power spectral analysis of erector spinae muscles is useful for the evaluation of fatigue rate of these muscles. Our results also showed a higher muscle endurance in healthy adult women than in men.

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Classification of Lower Body Types of Female Adults aged 18 to 69 based on 3D Body Scan Data - Focusing on the Front Type, Lateral-Front Type, and Lateral-Back Type -

  • Kim, Min Kyoung;Nam, Yun Ja
    • Fashion & Textile Research Journal
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    • v.18 no.1
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    • pp.91-102
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    • 2016
  • This study classified the lower body types of female adults aged 18 to 69. The lower body was divided into front, lateral front, and lateral back. In order to understand the shape and somatotype of each segment, 592 people were analyzed based on girth, height, length, depth, width, angle and cross section distance for each segment. For data analysis, SPSS 18.0 was performed for descriptive statics, principal component analysis, K-means cluster analysis, ANOVA, and Duncan's test (as verification). Factor analysis was performed based on index values, calculation values, angles, and cross section distances. The measured items resulted in a.) 16 items were extracted to 5 factors in the case of the front factor (FF) of the lower body, and b.) 24 items were extracted to 6 factors in the case of lateral front factor (LFF) and lateral back factor (LBF). Each factor was put through K-means cluster analysis, classifying the lower bodies into one of four types of based on the front type (FT), the lateral front type (LFT), and the lateral back type (LBT) respectively. This study proposed an understanding of various lower body shapes by segmenting and classifying the lower body shapes for each type.

A Comparison of Three Low Back Disability Questionnaires With Rasch Analysis (라쉬분석을 이용한 세 가지 요통 장애 설문지의 비교)

  • Kim, Gyoung-Mo;Park, So-Yeon;Yi, Chung-Hwi
    • Physical Therapy Korea
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    • v.18 no.3
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    • pp.94-102
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    • 2011
  • The purpose of this study was to review existing assessment tools for patients with low back pain and improve them through combination. A total of 314 patients with low back pain participated. Their condition was assessed using the Oswestry Disability Questionnaire (ODQ), the Quebec Back Pain Disability Scale (QBPD), and the Back Pain Functional Scale (BPFS). Rasch analysis was applied to identify inappropriate items, item difficulties, and the separation index. In this study, the 'sex life' item of the ODQ (10 items) and the 'sleeping' item of the BPFS (12 items) showed misfit statistics, whereas all items of the QBPD (20 items) were appropriate. After combining the ODQ, QBPD and BPFS, Rasch analysis was applied. The 'pain intensity', and the 'sex life' item of the ODQ and the 'throw a ball' item of QBPD showed misfit statistics. These 3 items were retained for further analysis. The remaining 42 combined ODQ-QBPD-BPFS items were arranged according to difficulty. For all subjects, the most difficult item was 'pain intensity', whereas the easiest was 'take food out of the refrigerator'. As the separation index of 42 combined ODQ-QBPD-BPFS was higher than that of the three questionnaires separately, difficulty of items varied with some need for rearrangement. The results of this study confirmed the possibility and need for a new back pain disability assessment tool, and produced one. Further study is needed to refine the questionnaire in consideration of psychosocial and occupational factors.

Operation Analysis of Back-to-Back STATCOM with Multi-Pulse Converter and PWM Converter (다중펄스 컨버터와 PWM 컨버터로 구성된 Back-to-Back STATCOM의 동작 분석)

  • Lee, Hye-Yeon;Han, Byung-Moon
    • Proceedings of the KIEE Conference
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    • pp.905_906
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    • 2009
  • 본 논문은 한전 전력연구원이 주관하고 명지대학교와 (주)효성이 참여하는 연구과제의 결과물로써 다중펄스 컨버터와 PWM 컨버터로 구성된 20MVA급 Back-to-Back STATCOM의 시스템 구성 및 제어 동작특성에 대하여 정리하였다. 한전 전력연구원과 (주)효성이 국책과제를 통해 순수 국내기술로 개발한 10MVA급 다중펄스 STATCOM의 활용방안으로 10MVA급 PWM STATCOM 1기를 추가하여 두 STATCOM 각각의 DC link단을 연계시킨 20MVA급 Back-to-Back STATCOM을 구성하고 제어 알고리즘을 개발하였다. 또한 PSCAD/EMTDC 소프트웨어를 이용하여 개발한 Back-to-Back STATCOM의 제어 및 동작특성을 분석하였다.

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