• Title/Summary/Keyword: rigidity

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Quantification of the Effect of Medication and Deep Brain Stimulation on Parkinsonian Rigidity (파킨슨병 환자의 경직에 대한 약물과 DBS 의 효과의 정량화)

  • Kwon, Yu-Ri;Eom, Gwang-Moon;Park, Sang-Hun;Kim, Ji-Won;Kim, Min-Jik;Lee, Hye-Mi;Jang, Ji-Wan;Koh, Seong-Beom
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.5
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    • pp.559-563
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    • 2013
  • This study aims to quantify the effects of medication (Med) and deep brain stimulation (DBS) on resting rigidity in patients with Parkinson's disease. We tested 10 limbs of five patients under each of four treatment conditions: 1) baseline, 2) DBS, 3) Med, 4) DBS + Med. Rigidity at the wrist joint was assessed using the Unified Parkinson's Disease Rating Scale (UPDRS). The examiner randomly imposed flexion and extension movement on patient's wrist joint. Resistance to passive movement was quantified by viscoelastic properties. Not only rigidity score but also damping constant showed improvements in rigidity by DBS and Med treatments (p<0.05). This indicates that the viscosity can represent the change in rigidity due to DBS as well as Med, which was manifested by UPDRS score.

Effect of Device Rigidity and Physiological Loading on Spinal Kinematics after Dynamic Stabilization : An In-Vitro Biomechanical Study

  • Chun, Kwonsoo;Yang, Inchul;Kim, Namhoon;Cho, Dosang
    • Journal of Korean Neurosurgical Society
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    • v.58 no.5
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    • pp.412-418
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    • 2015
  • Objective : To investigate the effects of posterior implant rigidity on spinal kinematics at adjacent levels by utilizing a cadaveric spine model with simulated physiological loading. Methods : Five human lumbar spinal specimens (L3 to S1) were obtained and checked for abnormalities. The fresh specimens were stripped of muscle tissue, with care taken to preserve the spinal ligaments and facet joints. Pedicle screws were implanted in the L4 and L5 vertebrae of each specimen. Specimens were tested under 0 N and 400 N axial loading. Five different posterior rods of various elastic moduli (intact, rubber, low-density polyethylene, aluminum, and titanium) were tested. Segmental range of motion (ROM), center of rotation (COR) and intervertebral disc pressure were investigated. Results : As the rigidity of the posterior rods increased, both the segmental ROM and disc pressure at L4-5 decreased, while those values increased at adjacent levels. Implant stiffness saturation was evident, as the ROM and disc pressure were only marginally increased beyond an implant stiffness of aluminum. Since the disc pressures of adjacent levels were increased by the axial loading, it was shown that the rigidity of the implants influenced the load sharing between the implant and the spinal column. The segmental CORs at the adjacent disc levels translated anteriorly and inferiorly as rigidity of the device increased. Conclusion : These biomechanical findings indicate that the rigidity of the dynamic stabilization implant and physiological loading play significant roles on spinal kinematics at adjacent disc levels, and will aid in further device development.

Understanding Price Adjustments in E-Commerce (전자상거래 상의 가격 변화에 관한 연구)

  • Lee, Dong-Won
    • Asia pacific journal of information systems
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    • v.17 no.4
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    • pp.113-132
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    • 2007
  • Price rigidity involves prices that do not change with the regularity predicted by standard economic theory. It is of long-standing interest for firms, industries and the economy as a whole. However, due to the difficulty of measuring price rigidity and price adjustments directly, only a few studies have attempted to provide empirical evidence for explanatory theories from Economics and Marketing. This paper proposes and validates a research model to examine different theories of price rigidity and to predict what variables can explain the observed empirical regularities and variations in price adjustment patterns of Internet-based retailers. I specify and test a model using more than 3 million daily observations on 385 books, 118 DVDs and 154 CDs, sold by 22 Internet-based retailers that were collected over a 676-day period from March 2003 to February 2005. I obtained a number of interesting findings from the estimation of our logit model. First, quality seems to play a role-I find that both price levels as proxies for store quality, and information on the quality of a product consumers have, affect online price rigidity. Second, greater competition(i.e., less industry concentration) leads to less price rigidity(i.e., more price changes) on the Internet. I also find that Internet-based sellers more frequently change the prices of popular products, and the sellers with broader product coverage change prices less frequently, which seem due to economic forces faced by these Internet-based sellers. To the best of my knowledge, this research is the first to empirically assess price rigidity patterns for multiple industries in Internet-based retailing, and attempt to explain the variation in these patterns. I found that price changes are more likely to be driven by quality, competitive and economic considerations. These results speak to both the IS and economics literatures. To the IS literature these results suggest we take economic considerations into account in more sophisticated ways. The existence and variation in price rigidity argue that simplistic assumptions about frictionless and completely flexible digital prices do not capture the richness of pricing behavior on the Internet. The quality, competitive and economic forces identified in this model suggest promising directions for future theoretical and empirical work on their role in these technologically changing markets. To the economics literature these results offer new evidence on the sources of price rigidity, which can then be incorporated into the development of models of pricing at the firm, industry and even macro-economic level of analysis. It also suggests that there is much to be learned through interdisciplinary research between the IS, economics and related business disciplines.

Modelling and classification of tubular joint rigidity and its effect on the global response of CHS lattice girders

  • Wang, Wei;Chen, Yiyi
    • Structural Engineering and Mechanics
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    • v.21 no.6
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    • pp.677-698
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    • 2005
  • In engineering practice, tubular connections are usually assumed pinned or rigid. Recent research showed that tubular joints may exhibit non-rigid behavior under axial or bending loads. This paper is concerned with establishing a new classification for tubular joints and investigating the effect of joint rigidity on the global behavior of CHS (Circular Hollow Section) lattice girders. Parametric formulae for predicting tubular joint rigidities are proposed, which are based on the finite element analyses through systematic variation of the main geometric parameters. Comparison with test results proves the reliability of these formulae. By considering the deformation patterns of respective parts of Vierendeel lattice girders, the boundary between rigid and semirigid tubular connections is built in terms of joint bending rigidity. In order to include characteristics of joint rigidity in the global structural analysis, a type of semirigid element which can effectively reflect the interaction of two braces in K joints is introduced and validated. The numerical example of a Warren lattice girder with different joint models shows the great effect of tubular joint rigidities on the internal forces, deformation and secondary stresses.

Analysis of Structural Performance of Wood Composite I and Box Beam on Cross Section Component (I) - Calculation and Analysis of Flexural Rigidity and Deflection - (단면구성요소(斷面構成要素)에 관(關)한 목질복합(木質複合) I및 Box형 보의 구조적(構造的) 성능(性能) 분석(分析) (I))

  • Oh, Sei-Chang;Lee, Phil-Woo
    • Journal of the Korean Wood Science and Technology
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    • v.19 no.2
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    • pp.40-55
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    • 1991
  • To investigate the influence of cross section geometries on the behavior of composite beams in the case of small span to depth ratio and deep beams. the static flexural behavior of composite I-beams and Box- beams was evaluated. 12 types of composite I -beams composed of LVL flanges and particleboard or plywood web and 3 types of composite Box-beams composed of LVL flanges and plywood web were tested under one-point loading. The load-deflection curves were almost linear to failure, therefore, the behavior of tested composite beams was elastic. The theoretical flexural rigidity of composite beams was calculated and compared with observed flexural rigidity. The highest value was found in I-W type beams and the lowest value was found in G-P type beams. The difference between theoretical and observed flexural rigidity was small. Theoretical total deflection of tested composite beams was calculated using flexural rigidity and compared with actual deflection. Shear deflection of these beams was evaluated by the approximation method, solid crosss section method and elementary method. The difference between actual deflection and expected deflection was not found in D, E and F type beams. This defference was small in G, H and I type beams or Box-beam.

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Effect of Blend Ratio of Fibres and Twist Structure of the Yarns on the Bending Properties of Staple Yarns (I) - Bending Properties of Single Yarns - (섬유 혼합비와 꼬임 구조가 방적사의 굽힘 특성에 미치는 영향(I)-단사의 굽힘 특성-)

  • O, Ae-Gyeong;Kim, Han-Seong;Kim, Seung-Jin
    • Textile Science and Engineering
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    • v.30 no.6
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    • pp.431-441
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    • 1993
  • The bending properties of the single yarns, such as the bending rigidity, the coercive couple, the hysteresis energy, and the residual curvature, are related with their constituent fibre diameters as well as the surface helix angle antral the linear density. The estimated and the experimental values of these properties are compared by varying the blend ratio of wool/polyester fibres. The validity of the specific bending rigidity was ascertained by adopting the value, which the experimental bending rigidity of the single yarn is divided by experimental yarn linear density. The bending rigidity of single blend yarns depends on the number of yam twist, the linear density and the blend ratio. The specific bending rigidity was decreased with increasing the number of yarn twist and blend ratio of polyester fibre. The coercive couple and the residual curvature, relating to intra-fibre friction in the yarn, were increased with blend ratio of polyester fibre. The coercive couple and the residual curvature of 100% polyester staple yarn were increased with the twist angle, and the maximum of these values were found to be increased as the blend ratios of wool/polyester fibres were increased.

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.

Quantification of Clinical assessment of Rigidity in patients with Parkinson's Disease (파킨슨병 환자의 경직에 대한 임상적 평가의 정량화)

  • Lee, Jae-Ho;Kim, Ji-Won;Kwon, Yu-Ri;Eom, Gwang-Moon;Koh, Seong-Beom;Kim, Hyung-Sik;Yi, Jeong-Han;Lee, Jeong-Whan
    • Journal of Biomedical Engineering Research
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    • v.31 no.4
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    • pp.275-279
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    • 2010
  • The purpose of this study was to quantify the clinical assessment of rigidity at wrist in patients with Parkinson's disease. The experimental system was designed that the effect of gravity was negated by restricting motion at the horizontal plane and inertia was predetermined from a biomechanical measurement. Forty five patients with Parkinson's disease participated in this study. Viscoelastic properties were calculated from the experimental data acquired during intermittent passive movement of wrist. Viscoelastic constants correlated well with the rigidity scores of UPDRS, i.e., Spearman's r=0.733 and 0.905 for spring and damping constants, respectively. The results suggest that viscoelastic properties can be used as quantitative measures of rigidity.

ON A RIGIDITY OF HARMONIC DIFFEOMORPHISM BETWEEN TWO RIEMANN SURFACES

  • KIM, TAESOON
    • Honam Mathematical Journal
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    • v.27 no.4
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    • pp.655-663
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    • 2005
  • One of the basic questions concerning harmonic map is on the existence of harmonic maps satisfying a certain condition. Rigidity of a certain harmonic map can be considered as an answer for this kinds of questions. In this article, we study a rigidity property of harmonic diffeomorphisms under the condition that the inverse map is also harmonic. We show that every such a harmonic diffeomorphism is totally geodesic or conformal in two dimensional case.

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