• Title/Summary/Keyword: resultant

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Change in Countermovement Jump Strategy by Varying Jump Height Based on Simplified Framework for Center of Mass Mechanics (반동을 이용한 수직 점프 시 높이 변화에 따른 운동역학 및 상변화 시점에서의 지면반력 벡터 변화)

  • Kim, Seyoung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.4
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    • pp.277-283
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    • 2017
  • In this study, we investigated how a jumping strategy changes with an increase in the vertical jump height for a resultant ground reaction force (GRF) vector. We expected that the resultant force vector between two sequential motion phases (i.e., countermovement and push-off) of the countermovement jump would significantly change with the vertical jump height to take advantage of the resulting supportive force (i.e., an initial push-off force larger than the body weight) through the countermovement phase. Nine healthy young subjects were instructed to jump straight up to five different height levels ranging from 191 cm to 221 cm, and the kinematic and kinetic data were obtained in regular trials. The results showed that a lower center of mass position and larger resultant force vector were clearly observed in a higher jump, implying that the countermovement strategy changed with the vertical jump height to prepare for sufficient joint deviation and obtain a force advantage for larger push-off work.

Relationship between Impact and Shear Forces, and Shock during Running (달리기 시 충격력과 충격 쇼크 변인들과의 관계)

  • Park, Sang-Kyoon;Ryu, Ji-Seon
    • Korean Journal of Applied Biomechanics
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    • v.30 no.2
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    • pp.145-154
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    • 2020
  • Objective: The purpose of this study was to determine the relationship between impact and shear peak force, and tibia-accelerometer variables during running. Method: Twenty-five male heel strike runners (mean age: 23.5±3.6 yrs, mean height: 176.3±3.3 m/s, mean mass: 71.8±9.7 kg) were recruited in this study. The peak impact and anteroposterior shear forces during treadmill running (Bertec, USA) were collected, and impact shock variables were computed by using a triaxial accelerometer (Noraxon, USA). One-way ANOVA was used to test the influence of the running speed on the parameters. Pearson's partial correlation was used to investigate the relationship between the peak impact and shear force, and accelerometer variables. Results: The running speed affected the peak impact and posterior shear force, time, slope, and peak vertical and resultant tibial acceleration, slope at heel contact. Significant correlations were noticed between the peak impact force and peak vertical and resultant tibia acceleration, and between peak impact average slope and peak vertical and resultant tibia acceleration average slope, and between posterior peak (FyP) and peak vertical tibia acceleration, and between posterior peak instantaneous slop and peak vertical tibial acceleration during running at 3 m/s. However, it was observed that correlations between peak impact average slope and peak vertical tibia acceleration average slope, between posterior peak time and peak vertical and resultant tibia acceleration time, between posterior peak instantaneous slope and peak vertical tibial acceleration instantaneous slope during running at 4 m/s. Conclusion: Careful analysis is required when investigating the linear relationship between the impact and shear force, and tibia accelerometer components during relatively fast running speed.

An element-based 9-node resultant shell element for large deformation analysis of laminated composite plates and shells

  • Han, S.C.;Kim, K.D.;Kanok-Nukulchai, W.
    • Structural Engineering and Mechanics
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    • v.18 no.6
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    • pp.807-829
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    • 2004
  • The Element-Based Lagrangian Formulation of a 9-node resultant-stress shell element is presented for the isotropic and anisotropic composite material. The effect of the coupling term between the bending strain and displacement has been investigated in the warping problem. The strains, stresses and constitutive equations based on the natural co-ordinate have been used throughout the Element-Based Lagrangian Formulation of the present shell element which offers an advantage of easy implementation compared with the traditional Lagrangian Formulation. The element is free of both membrane and shear locking behavior by using the assumed natural strain method such that the element performs very well in thin shell problems. In composite plates and shells, the transverse shear stiffness is defined by an equilibrium approach instead of using the shear correction factor. The arc-length control method is used to trace complex equilibrium paths in thin shell applications. Several numerical analyses are presented and discussed in order to investigate the capabilities of the present shell element. The results showed very good agreement compared with well-established formulations in the literature.

A force-based element for direct analysis using stress-resultant plasticity model

  • Du, Zuo-Lei;Liu, Yao-Peng;Chan, Siu-Lai
    • Steel and Composite Structures
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    • v.29 no.2
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    • pp.175-186
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    • 2018
  • The plastic hinge method and the plastic zone method are extensively adopted in displacement-based elements and force-based elements respectively for second-order inelastic analysis. The former enhances the computational efficiency with relatively less accurate results while the latter precisely predicts the structural behavior but generally requires more computer time. The displacement-based elements receive criticism mainly on plasticity dominated problems not only in accuracy but also in longer computer time to redistribute the forces due to formation of plastic hinges. The multi-element-per-member model relieves this problem to some extent but will induce a new problem in modeling of member initial imperfections required in design codes for direct analysis. On the contrary, a force-based element with several integration points is sufficient for material yielding. However, use of more integration points or elements associated with fiber section reduces computational efficiency. In this paper, a new force-based element equipped with stress-resultant plasticity model with minimal computational cost is proposed for second-order inelastic analysis. This element is able to take the member initial bowing into account such that one-element-per-member model is adequate and complied with the codified requirements of direct analysis. This innovative solution is new and practical for routine design. Finally, several examples demonstrate the validity and accuracy of the proposed method.

The Study for Selection of the Optimum Route by Economic Analyses (설계의 경제성 분석을 통한 최적노선 선정방안 연구 - OO경전철 민간투자사업 사례연구 -)

  • Kwon, Suk-Hyun;Seo, Sung-Han;Lee, Dong-Woo
    • Proceedings of the KSR Conference
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    • 2008.06a
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    • pp.128-138
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    • 2008
  • VE of the scripture season enterprises and it respected LCC analyzes from the research which it sees and to use AHP techniques and definite LCC techniques and probabilistic LCC techniques selects the optimum route the case study which it executed. It presented the quality rating model in about the resultant most route lascivious at the time of VE evaluation, in order to select the alternative of optimum AHP techniques which are one in decision-making technique and an evaluation item by weight and a grade it applied the mountaintop it did. Also the definite LCC analyzer law departments of existing together it applied the probabilistic LCC techniques which use Monte Carlo Simulation in about analytical prices and reliability height boil. The economical efficiency was excellent with VE/LCC analytical resultant route and facility size abridgment, the rivers most it will be able to minimize an environmental effect with short distance traverse, the selection this hit preparation LCC which separates from the land use side decreased, the value (V) above 22.0% with the fact that it improves. And, the reliability of the probabilistic LCC analytical resultant analytical results in compliance with Monte Carlo Simulation with 90.3% was very analyzed with the fact that it is a high level.

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THE ARITHMETIC OF CARLITZ POLYNOMIALS

  • Bae, Sung-Han
    • Journal of the Korean Mathematical Society
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    • v.35 no.2
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    • pp.341-360
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    • 1998
  • Some interesting properties of Carlitz cyclotomic polynomials analogous to those of classical cyclotomic polynomials are given.

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Microsturcture Control of Metallized Alumina Ceramics for Electronic Devices (전자부품용 메탈라이즈드 알루미나 세라믹스의 미세구조 제어)

  • Jo, Beom-Rae
    • Korean Journal of Materials Research
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    • v.11 no.12
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    • pp.1086-1090
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    • 2001
  • Composition effects on microstructure and metallizing properties of the alumina sintered body were evaluated to develop the metallized alumina tubes having superior properties for electronic devices. SEM observation revealed that resultant micrographs and fractographs were varied with composition chance of additives and $SiO_2$-rich specimens showed better microstructural characteristics with uniform distribution of fine and round particles than other CaO-rich or MgO-rich ones. The resultant interfacial microstructure of the $SiO_2$-rich metallized alumina tubes also showed good metallizing properties with no defects between layers and uniform thickness of metallizing layer.

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Calibration of an Optical Pick-up Performance Evaluator (광 픽업 성능 평가기 캘리브레이션)

  • Ryoo, Jung Rae;Doh, Tae-Yong
    • Journal of Institute of Control, Robotics and Systems
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    • v.20 no.5
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    • pp.578-583
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    • 2014
  • Optical pick-up is a core component for data read/write operations in optical disc drives, and an optical pick-up performance evaluator is an instrument used to analyze the overall performance of an optical pick-up. Due to inevitable errors in an analog measurement circuit, resultant evaluation data is not guaranteed to be accurate. In this paper, a calibration method for an optical pick-up performance evaluator is proposed to ensure evaluation accuracy. Measured data is corrected by a 1st order correction function, and a calibration process based on least-square method is utilized to obtain correction coefficients of the correction function. The proposed calibration method is applied to experiments, and enhanced accuracy is presented with resultant evaluation data.

Practical Study about Obstacle Detecting and Collision Avoidance Algorithm for Unmanned Vehicle

  • Park, Eun-Young;Lee, Woon-Sung;Kim, Jung-Ha
    • 제어로봇시스템학회:학술대회논문집
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    • 2003.10a
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    • pp.487-490
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    • 2003
  • In this research, we will devise an obstacle avoidance algorithm for a previously unmanned vehicle. Whole systems consist mainly of the vehicle system and the control system. The two systems are separated; this system can communicate with the vehicle system and the control system through wireless RF (Radio Frequency) modules. These modules use wireless communication. And the vehicle system is operated on PIC Micro Controller. Obstacle avoidance method for unmanned vehicle is based on the Virtual Force Field (VFF) method. An obstacle exerts repulsive forces and the lane center point applies an attractive force to the unmanned vehicle. A resultant force vector, comprising of the sum of a target directed attractive force and repulsive forces from an obstacle, is calculated for a given unmanned vehicle position. With resultant force acting on the unmanned vehicle, the vehicle's new driving direction is calculated, the vehicle makes steering adjustments, and this algorithm is repeated.

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Impact behavior of including the boundary between A356/SiCw and Al alloy (Al alloy와의 경계면을 포함한 A356/SiCw의 충격거동)

  • 조종인;남현욱;한경섭
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2002.05a
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    • pp.97-100
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    • 2002
  • In this research, the impact behavior of the boundary between MMC-reinforced SiC whisker and Al alloy were studied. It is known that the resultant of the interfacial reaction between SiC whisker and Al alloy has brittle and low toughness property. In this paper, impact behavior of graded MMC & Al alloy shows the interfacial opening at the boundary. Generally this phenomenon is generated by thermal residual stress, brittle interfacial reaction resultant and difference of the deflection. So, these results may be interpreted as a macroscopic method of measuring the interfacial strength between matrix and reinforcement

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