• Title/Summary/Keyword: eccentric

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Seismic Performance Evaluation of Masonry-Infilled Frame Structures using Equivalent Strut Models (등가 스트럿 모델을 이용한 조적조 채움벽 골조의 내진성능평가)

  • Park, Ji-Hun;Jeon, Seong-Ha;Kang, Kyung-Soo
    • Journal of the Earthquake Engineering Society of Korea
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    • v.16 no.1
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    • pp.47-59
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    • 2012
  • The seismic performance of masonry-infilled frame structures, typical in school buildings, is evaluated through equivalent strut models. A bare frame model, concentric strut models and eccentric strut models with various material characteristics available in the literature are analyzed. Displacements and damage states at the performance points obtained by the capacity spectrum method show great differences among the models. Infill walls act positively in concentric strut models and negatively in eccentric strut models at the performance points for a given seismic demand. In addition, the behavior at the ultimate displacements shows considerably different strengths, inter-story drifts, and numbers and locations of damaged members among various modeling methods and material strengths.

Effects of TENS and He-Ne Laser at Auricular Point on Delayed Onset Muscle Soreness (TENS와 He-Ne Laser를 이용한 외이자극이 지연성근육통에 미치는 영향)

  • Park, Jang-Sung;Kim, Moon-Su
    • Journal of the Korean Academy of Clinical Electrophysiology
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    • v.4 no.1
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    • pp.85-93
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    • 2006
  • The purpose of this study was to determine the effect of transcutaneous electrical nerve stimulation(TENS) and He-Ne laser at auricular point on delayed onset muscle soreness(DOMS). Twenty healthy adult males and females performed eccentric exercise of the elbow flexor. DOMS was induced in a standardised fashion in the nondominant elbow flexor of all subject by repeated eccentric exercise. Subject were assigned randomly to one of trees groups. Group 1 received TENS to the appropriate auricular point for biceps pain, Group 2 received laser to the appropriate auricular point for wrist pain, Group 3 received no treatment and served as controls. After exercise, treatments were applied at 24 hours and at 48 hours and at 72 hours after. Group 1 showed stastically significant increase(p<0.05) in pain threshold after treatment whereas the Group 2 and 3 did not. Group 1 showed a significant increase in pain threshold than Group 2. These results suggest that TENS has the capability to higher pain threshold but laser does not.

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Torsional Rigidity of a Two-stage Cycloid Drive (이단 사이클로이드 드라이브의 비틀림 강성)

  • Kim, Kyoung-Hong;Lee, Chun-Se;Ahn, Hyeong-Joon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.11
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    • pp.1217-1224
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    • 2009
  • This paper presents a finite element (FE) analysis of the torsional rigidity of a two-stage cycloid drive. The cycloid disk makes contact with a number of pin-rollers simultaneously and eccentric shafts transmit not only torque of the spur gear stage to the cycloid disk, but also that of the cycloid disk to the output disk. Contacts between the disk and pin-rollers are simplified as linear spring elements, and the bearing of eccentric shaft is modeled as a rigid ring that has frictional contact to the disk and an elastic support. FE analysis for an ideal solid cycloid drive was performed and verified by a theoretical calculation. Accurate contact forces were then estimated by iterating between FE analysis for contact forces and Hertz theory calculations for nonlinear contact stiffness. In addition, torsional rigidity of the cycloid drive is analyzed to show that the bearing and nonlinear Hertz contact theory should be considered in analysis and design of a cycloid drive, which was verified with experiments. Finally, the effects of contact stiffness, bearing stiffness and cycloid disk structural stiffness according to the cycloid disk rotation on the torsional rigidity were investigated.

Exact vibration of Timoshenko beam combined with multiple mass spring sub-systems

  • El-Sayed, Tamer A.;Farghaly, Said H.
    • Structural Engineering and Mechanics
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    • v.57 no.6
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    • pp.989-1014
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    • 2016
  • This paper deals with the analysis of the natural frequencies, mode shapes of an axially loaded beam system carrying ends consisting of non-concentrated tip masses and three spring-two mass sub-systems. The influence of system design and sub-system parameters on the combined system characteristics is the major part of this investigation. The effect of material properties, rotary inertia and shear deformation of the beam system is included. The end masses are elastically supported against rotation and translation at an offset point from the point of attachment. Sub-systems are attached to center of gravity eccentric points out of the beam span. The boundary conditions of the ordinary differential equation governing the lateral deflections and slope due to bending of the beam system including developed shear force frequency dependent terms, due to the sub.system suspension, have been formulated. Exact formulae for the modal frequencies and the modal shapes have been derived. Based on these formulae, detailed parametric studies are carried out. The geometrical and mechanical parameters of the system under study have been presented in non-dimensional analysis. The applied mathematical model is presented to cover wide range of mechanical, naval and structural engineering applications.

Experimental behavior of eccentrically loaded RC slender columns strengthened using GFRP wrapping

  • Elwan, S.K.;Omar, M.A.
    • Steel and Composite Structures
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    • v.17 no.3
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    • pp.271-285
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    • 2014
  • This paper aims to examine the behavior of slender reinforced concrete columns confined with external glass fiber reinforced polymers (GFRP) sheets under eccentric loads. The experimental work conducted in this paper is an extension to previous work by the author concerning the behavior of eccentrically loaded short columns strengthened with GFRP wrapping. In this study, nine reinforced concrete columns divided into three groups were casted and tested. Three eccentricity ratios corresponding to e/t = 0, 0.10, and 0.50 in one direction of the column were tested in each group. The first group was the control one without confinement with slenderness ratio equal 20. The second group was the same as the first group but fully wrapped with one layer of GFRP laminates. The third group was also fully wrapped with one layer of GFRP laminates but having slenderness ratio equal 15. The experimental results of another two groups from the previous work were used in this study to investigate the difference between short and slender columns. The first was control one with slenderness ratio equal 10 and the second was fully wrapped and having the same slenderness ratio. All specimens were loaded until failure. The ultimate load, axial deformation, strain in steel bars, and failure mechanisms of each specimen were generated and analyzed. The results show that GFRP laminates confining system is less effective with slender columns compared with short one, but this solution is still applied and it can be efficiently utilized especially for slender columns with low eccentric ratio.

Prediction of nonlinear characteristics of soil-pile system under vertical vibration

  • Biswas, Sanjit;Manna, Bappaditya;Choudhary, Shiva S.
    • Geomechanics and Engineering
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    • v.5 no.3
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    • pp.223-240
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    • 2013
  • In the present study an attempt was made to predict the complex nonlinear parameters of the soil-pile system subjected to the vertical vibration of rotating machines. A three dimensional (3D) finite element (FE) model was developed to predict the nonlinear dynamic response of full-scale pile foundation in a layered soil medium using ABAQUS/CAE. The frequency amplitude responses for different eccentric moments obtained from the FE analysis were compared with the vertical vibration test results of the full-scale single pile. It was found that the predicted resonant frequency and amplitude of pile obtained from 3D FE analysis were within a reasonable range of the vertical vibration test results. The variation of the soil-pile separation lengths were determined using FE analysis for different eccentric moments. The Novak's continuum approach was also used to predict the nonlinear behaviour of soil-pile system. The continuum approach was found to be useful for the prediction of the nonlinear frequency-amplitude response of full-scale pile after introducing the proper boundary zone parameters and soil-pile separation lengths.

Development of a Multi-Tasking Machine Tool for Machining Large Scale Marine Engine Crankshafts and Its Design Technologies (대형 선박엔진 크랭크샤프트 가공용 복합가공기 기술 개발)

  • An, Ho-Sang;Cho, Yong-Joo;Choi, Young-Hyu;Lee, Deug-Woo
    • Journal of the Korean Society for Precision Engineering
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    • v.29 no.2
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    • pp.139-146
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    • 2012
  • A multi-tasking machine tool for large scale marine engine crankshafts has been developed together with design technologies for its special devices. Since work pieces, that is, crankshafts to be machined are big and heavy; weight of over 100 tons, length of 10 m long, and diameter of over 3.5 m, several special purpose core devices are necessarily developed such as PTD (Pin Turning Device) for machining eccentric pin parts, face place and steady rest for chucking and resting heavy work pieces. PTD is a unique special purpose device of open-and-close ring typed structure equipped with revolving ring spindle for machining eccentric pins apart from journal. In order to achieve high rigidity of the machine tool, structural design optimization using TMSA (Taguch Method based Sequential Algorithm) has been completed with FEM structural analysis, and a hydrostatic bearing system for the PTD has been developed with theoretical hydrostatic analysis.

Partially encased composite columns using fiber reinforced concrete: experimental study

  • Pereira, Margot F.;De Nardin, Silvana;El. Debs, Ana L.H.C.
    • Steel and Composite Structures
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    • v.34 no.6
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    • pp.909-927
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    • 2020
  • This paper addresses the results of an experimental study involving 10 partially encased composite columns under concentric and eccentric compressive loads. Parameters such as slenderness ratio, ordinary reinforced concrete and fiber reinforced concrete, load eccentricity and bending axis were investigated. The specimens were tested to investigate the effects of replacing the ordinary reinforced concrete by fiber reinforced concrete on the load capacity and behavior of short and slender composite columns. Various characteristics such as load capacity, axial strains behavior, stiffness, strains on steel and concrete and failure mode are discussed. The main conclusions that may be drawn from all the test results is that the behavior and ultimate load are rather sensitive to the slenderness of the columns and to the eccentricity of loading, specially the bending axis. Experimental results also indicate that replacing the ordinary reinforced concrete by steel fiber reinforced concrete has no considerable effects on the load capacity and behavior of the short and slender columns and the proposed replacement presented very good results.

Formation of Oxidative Cleavage from Phytofluene by Autoxidation (자동산화에 의한 Phytofluene으로부터 산화개열산물의 생성)

  • 김선재
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.29 no.4
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    • pp.568-574
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    • 2000
  • Phytofluene was subjected to ozonolysis in ice-cold dichloromethane. The ozonolysis products were fractionated with a silica column and the carbonyl fraction was analyzed by ODS-HPLC with a photodiode array detector. Phytofluene was solubilized in 5% tween 40, and then oxidized by incubating under dim yellow light at 37$^{\circ}C$, 24 hr with continuous shaking. Carbonyl compound and acidic compound were produced. In comparison with autoxidation and ozonolysis, each compound showed the same retention time and UV-vis spectra were identical to the reference cleavage products prepared by ozeonolysis of phytofluene. Absorption spectrum of acidic compound was similar to that of standard 4,5-didehydrogeranyl geranyl acid which is known to possess biological activity. Thus, eccentric cleavage of phytofluene was confirmed to occur in vitro under oxidation condition.

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Development of Apple Harvesting Robot(I) - Development of Robot Hand for Apple Harvesting - (사과 수확 로봇의 핸드 개발(I) - 사과 수확용 로봇의 핸드 개발 -)

  • 장익주;김태한;권기영
    • Journal of Biosystems Engineering
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    • v.22 no.4
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    • pp.411-420
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    • 1997
  • The mechanization efficiency using high ability machines such as tractors or combines in a paddy field rice farm is high. Mechanization in harvesting fruits and vegetables is difficult, because they are easy to be damaged. Therefore, Advanced techniques for careful handling fruits and vegetables are necessary in automation and robotization. An apple harvesting robot must have a recognition device to detect the positioning of fruit, manipulators which function like human arms, and hand to take off the fruit. This study is related to the development of a rotatic hand as the first stage in developing the apple harvesting robot. The results are summarized as follows. 1. It was found that a hand that was eccentric in rotatory motion, was better than a hand of semicircular up-and-down motion in harvesting efficiency. 2. The hand was developed to control changes in grasp forces by using tape-type switch sensor which was attatched to fingers' inside. 3. Initial finger positioning was set up to control accurate harvesting by using a tow step fingering position. 4. This study showed the possibility of apple harvesting using the developed robot hand.

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