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Journal articles on the topic 'Stiffness factor'

Author: Grafiati

Published: 4 June 2021

Last updated: 16 February 2022

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1

Schluter, James C., and James W. Shade. "Flexibility Factor or Pipe Stiffness: Significant Stiffness Considerations." Transportation Research Record: Journal of the Transportation Research Board 1656, no. 1 (January 1999): 45–50. http://dx.doi.org/10.3141/1656-06.

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2

Luo, Ji Man, Yue Liu, Bin Li, and Xiao Wei Sun. "Study on the Influence of Different Supporting Point Stiffness on External Suspension Tower Crane and Supporting Structure." Advanced Materials Research 1025-1026 (September 2014): 991–96. http://dx.doi.org/10.4028/www.scientific.net/amr.1025-1026.991.

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Supporting system of external suspension tower crane is the key factor which impairs the safety of the tower cranes. In this article, the problem is studied about the influence of different supporting point stiffness on the force of the tower crane external suspension. Based on the structural mechanics theory, the displacement of the lower statically indeterminate beam and the horizontal displacement of the upper statically indeterminate truss are solved firstly, then the stiffness of the supporting point on the lower beam and the entirety stiffness of the upper horizontal combination struts can be obtained. We can get the optimal supporting structure by drawing the relationship of stiffness1-stiffness2-force which is of significant to the external suspension’s design and installation in Matlab software.

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3

Lehnhoff, T. F., and W. E. Wistehuff. "Nonlinear Effects on the Stiffness of Bolted Joints." Journal of Pressure Vessel Technology 118, no. 1 (February 1, 1996): 48–53. http://dx.doi.org/10.1115/1.2842162.

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Axisymmetric finite element modeling of bolted joints was performed to show the effects of the magnitude and position of the external load, member thickness, and member material on the bolt and member stiffnesses. The member stiffness of the bolted joint was found to decrease 10 to 42 percent for the 20-mm to 8-mm bolts, respectively, as the magnitude of the external load was increased. Member stiffness appears to be independent of the radial location of the external load and increases as the member thickness decreases. Member stiffness decreased by a factor of 2.5 to 3 with a change in the member material from steel to aluminum. The cast iron members had a decrease in member stiffness of a factor of 1.7 to 1.9. The aluminum over cast iron combination had a member stiffness between the aluminum and cast iron alone. Bolt stiffnesses varied by less than two percent for changes in the magnitude of the external load for all bolt sizes and member materials, except for the 8-mm bolt where stiffness increased by approximately 11 percent. Changes in radial position of the external load had no effect on the bolt stiffness. A 3 to 13-percent decrease in the bolt stiffness was found when changing from steel to aluminum members. A 2 to 3-percent bolt stiffness decrease resulted when the member material was changed from steel to cast iron and similarly from steel to the aluminum over cast iron combination

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4

Arnett, Donna K., Gregory W. Evans, and Ward A. Riley. "Arterial Stiffness: A New Cardiovascular Risk Factor?" American Journal of Epidemiology 140, no. 8 (October 15, 1994): 669–82. http://dx.doi.org/10.1093/oxfordjournals.aje.a117315.

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5

Chang, S. Y. "An Amplification Factor to Enhance Stability for Structure-Dependent Integration Method." Journal of Mechanics 28, no. 4 (October 16, 2012): 665–76. http://dx.doi.org/10.1017/jmech.2012.103.

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ABSTRACTChang explicit method (2007) has been shown to be unconditionally stable for a linear elastic system and any instantaneous stiffness softening system while it is only conditionally stable for any instantaneous stiffness hardening system. Its coefficients of the difference equation for displacement increment are functions of initial tangent stiffness. Since Chang explicit method is unconditionally stable for a linear elastic system and any instantaneous stiffness softening system, its stability range can be enlarged if the initial tangent stiffness is enlarged by an amplification factor and then this amplified initial tangent stiffness is used to determine the coefficients. The detailed implementation of this scheme for Chang explicit method is presented and the feasibility of this scheme is verified.

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6

Sun, Fengxin, Cao Sun, Chaoyu Chen, Zhaoqun Du, and Weidong Yu. "Multivariate analysis of curve parameters to predict fabric stiffness handle from a pulling-out test." Textile Research Journal 88, no. 8 (February 7, 2017): 863–72. http://dx.doi.org/10.1177/0040517517690624.

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The Comprehensive Handle Evaluation System for Fabrics and Yarns (CHES-FY) is capable of measuring multiple physical and mechanical properties of fabrics, which are related to fabric handle. In this study, ten curve parameters were defined from the pulling-out force–displacement curve of the CHES-FY. Factor analysis was used to remove the co linearity of the curve parameters in order to better characterize the stiffness handle of fabrics. Three principal factors were established using the factor analysis, and the first principal factor was termed the stiffness index based on loadings of the curve parameters to the rotated factors. Comparisons between the evaluation results of the CHES-FY, cantilever test, and newly-developed dual subjective/objective assessments showed that the CHES-FY, together with the stiffness index resulting from the factor analysis, provided a fast and effective method to characterize a fabric’s stiffness handle, and the evaluation process of the CHES-FY appears to closely simulate the tactile response to stiffness when a person touches or pinches a fabric.

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7

Hallab, Magid, Sophie Pichierri, Pascal Chevalet, Laure De Decker, and Gilles Berrut. "Arterial stiffness a new risk factor to measure." Gériatrie et Psychologie Neuropsychiatrie du Viellissement 10, no. 3 (September 2012): 235–43. http://dx.doi.org/10.1684/pnv.2012.0347.

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8

Kennedy, Scott D., and Andrew B. Schwartz. "Stiffness as a control factor for object manipulation." Journal of Neurophysiology 122, no. 2 (August 1, 2019): 707–20. http://dx.doi.org/10.1152/jn.00372.2018.

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During manipulation, force is exerted with the expectation that an object will move in an intended manner. This prediction is a learned coordination between force and movement. Mechanically, impedance is a way to describe this coordination, and object interaction could be anticipated by setting impedance before the hand moves the object. This strategy would be especially important at the end of a reach, because feedback is ineffective for rapid force changes. Since mechanical impedance is not subject to the time delays of feedback, it can, if set properly, produce the desired motion on impact. We examined this possibility by instructing subjects to move a handle to a specific target position along a track. The handle was locked in place until the subject exerted enough force to cross a threshold; the handle was then released abruptly to move along the track. We hypothesized that this ballistic release task would encourage subjects to modify impedance in anticipation of the upcoming movement and found that one component of impedance, stiffness, varied in a way that matched the behavioral demands of the task. Analysis suggests that this stiffness was set before the handle moved and governed the subsequent motion. We also found separate components of muscle activity that corresponded to stiffness and to changes in force. Our results show that subjects used a robust and efficient strategy to coordinate force and displacement by modulating muscle activity in a way that was behaviorally relevant in the task. NEW & NOTEWORTHY The arm can behave like a spring, and this mechanical behavior can be advantageous in situations requiring rapid changes in force and/or displacement. Selection of a proper “virtual” spring before the occurrence of a rapid transient could facilitate a desired responsive movement. We show that these spring-like arm mechanics, set in anticipation of an instantaneous force change, function as an efficient strategy to control movement when feedback is ineffective.

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9

Gungor, Ozkan, and Huseyin Toz. "Factor Affecting Arterial Stiffness on Renal Transplant Patients." Turkish Nephrology Dialysis Transplantation 21, no. 02 (May 15, 2012): 107–10. http://dx.doi.org/10.5262/tndt.2012.1002.01.

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10

Stojanov, Vesna, and Nenad Radivojevic. "Arterial stiffness as predictive factor of cardiovascular diseases." Vojnosanitetski pregled 76, no. 9 (2019): 942–50. http://dx.doi.org/10.2298/vsp170701161s.

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11

van Sloten, Thomas T., and Coen D. A. Stehouwer. "Carotid Stiffness: A Novel Cerebrovascular Disease Risk Factor." Pulse 4, no. 1 (2016): 24–27. http://dx.doi.org/10.1159/000445354.

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12

Kenny, A., A. Palazzolo, G. T. Montague, and A. F. Kascak. "Theory and Test Correlation for Laminate Stacking Factor Effect on Homopolar Bearing Stiffness." Journal of Engineering for Gas Turbines and Power 126, no. 1 (January 1, 2004): 142–46. http://dx.doi.org/10.1115/1.1615258.

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The effect of the laminate stacking factor on homopolar magnetic bearing performance is examined. Stacked laminates are used on the bearing rotor and in the stator. These laminate stacks have anisotropic permeability. Equations for the effect of the stacking factor on homopolar bearing position stiffness are derived. Numerical results are calculated and compared to measurements. These results provide an answer for the common discrepancy between test and theory for homopolar magnetic bearing position stiffnesses.

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13

Mo, Ji Yun. "Stress Intensity Factor for a Plate with a Crack Stiffened by Partial Stringers." Applied Mechanics and Materials 184-185 (June 2012): 493–96. http://dx.doi.org/10.4028/www.scientific.net/amm.184-185.493.

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Stress intensity factors are calculated for a cracked plate reinforced locally subject to mode I loading. The stiffeners are considered to have both longitudinal and transverse stiffness. There is no relative displacement between the plate and the stiffener. It is considered that the shear stresses are lumped at a finite number of locations, the result is obtained by summation. The influence of the stiffener location and the stiffener relative stiffness on cracked plate is included. The stress intensity factor depends on all these factors. Case study shows that the shear stress acting parallel to the stiffener gives more effect on the stress intensity factor than the shear stress acting perpendicular to the stiffener. To increase the relative stiffness of stiffener avails to reduce the stress intensity factor of the cracked plate.

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14

Koob, T. J., M. M. Koob-Emunds, and J. A. Trotter. "Cell-derived stiffening and plasticizing factors in sea cucumber (Cucumaria frondosa) dermis." Journal of Experimental Biology 202, no. 17 (September 1, 1999): 2291–301. http://dx.doi.org/10.1242/jeb.202.17.2291.

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The stiffness of holothurian dermis can be altered experimentally in vitro by changing the concentration of extracellular Ca(2+). Previous experiments with Cucumaria frondosa have established that these Ca(2+) effects are due to Ca(2+)-dependent cellular processes rather than to direct effects of Ca(2+) on the extracellular matrix. The present report describes two protein factors that are released from cells of C. frondosa dermis by membrane lysis and that directly alter the stiffness of the extracellular matrix. One factor, isolated from the inner dermis, increased tissue stiffness in the absence of Ca(2+). The second factor, from the outer dermis, decreased tissue stiffness in the presence of normal Ca(2+) levels. The relative abundance of these two factors in the inner and outer dermis suggests the possibility that the cells that control tissue stiffness are spatially segregated. Both factors were partially purified under non-denaturing conditions by anion-exchange and gel-filtration chromatography. The partially purified protein preparations retained biological activity. These results suggest that the stiffness of sea cucumber dermis is regulated by cell-mediated secretion of either the stiffening or plasticizing protein and that alterations in dermis stiffness brought about by manipulation of Ca(2+) levels are mediated by effects on secretion of one or both of these proteins.

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15

Park, Young Mi, Sang Whan Han, and Ja Ock Cho. "Stiffness Reduction for Flat Plate Systems due to Cracking." Key Engineering Materials 348-349 (September 2007): 781–84. http://dx.doi.org/10.4028/www.scientific.net/kem.348-349.781.

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The purpose of this study is to propose a stiffness reduction factor for flat plate systems under lateral loads. According to current design provisions, slab stiffness under lateral loads should account for stiffness reduction due to the effects of cracks. Several researchers have conducted for evaluating the stiffness reduction in flat plate slab systems under lateral loads. However, no research is found for establishing strength reduction factor with respect to the level of applied moment. This study attempted to propose equations for calculating stiffness reduction factor with respect to the level of applied moment (Ma) represented by the ratio of Ma to the cracking moment of the slab (Mcr). For this purpose, test results of 20 interior slab-column connections were collected. For each specimen, stiffness reduction was measured with respect to Ma/Mcr. To verify the proposed factor, this study conducted the experimental test of interior connection under quasistatic cyclic loading, from which load-deformation curve was obtained. The curve was compared with that obtained from the effective beam width method with the proposed stiffness reduction factor. It shows that the proposed factor accurately predicts stiffness reduction in flat plate systems.

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16

Li, Wen Zhong, and Fu Xiang Zhang. "Analysis of Stiffness of Viscoelastic-Friction Damper for High-Speed Rotor System." Advanced Materials Research 538-541 (June 2012): 768–72. http://dx.doi.org/10.4028/www.scientific.net/amr.538-541.768.

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To reduce the excessive vibration of a high-speed rotor system as it passes its critical speed, a viscoelastic-friction damper(VEFD) are introduced into the support. Its stiffness factor is analyzed. Results show, the stiffness factor decreases with the cone angle increasing among 55-80 degrees monotonically. And it is the same trend when the stiffness of the damping material ring decreases. In the case of friction coefficient among 0.1-0.5, the stiffness factor increases monotonically. So adopted a proper structure, suitably chosen the above parameters and the axial stiffness of the outer-ring, the damper can present appropriate stiffness.

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17

Barmanov, Il'dar S. "EFFECT OF RADIAL FORCE ON BALL BEARING STIFFNESS FACTOR UNDER CONDITIONS OF RING SKEW." Journal of Dynamics and Vibroacoustics 6, no. 4 (May 16, 2021): 6–10. http://dx.doi.org/10.18287/2409-4579-2020-6-4-6-10.

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Results of ball bearing rings skew effect on radial stiffness factor are pre-sented in the paper. The effect of radial load on stiffness factor at change of angles of rings skew was evaluated. Significant influence of bearing rings skew on stiffness factor at small radial load values is noted.

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18

Park, Young Mi, Sang Whan Han, and Youn Ho Rew. "Stiffness reduction factor for post-tensioned flat plate slabs." Magazine of Concrete Research 64, no. 1 (January 2012): 83–92. http://dx.doi.org/10.1680/macr.10.00150.

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19

Janner, J. H. "Is COPD a risk factor for increased arterial stiffness?" Respiratory Medicine 103 (August 2009): S5—S6. http://dx.doi.org/10.1016/s0954-6111(09)70014-9.

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20

Matsukawa, H., M. Shinoda, M. Fujii, A. Uemura, O. Takahashi, and Y. Niimi. "Arterial stiffness as a risk factor for cerebral aneurysm." Acta Neurologica Scandinavica 130, no. 6 (September 12, 2014): 394–99. http://dx.doi.org/10.1111/ane.12286.

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21

Bykov, A., L. Geraskina, A. Fonyakin, and I. Posokhov. "ARTERIAL STIFFNESS AS A PROGNOSTIC FACTOR FOR HYPERTENSIVE ENCEPHALOPATHY." Journal of Hypertension 36, Supplement 1 (June 2018): e107. http://dx.doi.org/10.1097/01.hjh.0000539281.28111.7b.

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22

Sheen, S. S., H. J. Kim, D. Singh, S. C. Hwang, K. J. Park, S. V. Ahn, E. Lee, et al. "Airflow limitation as a risk factor for vascular stiffness." International Journal of Tuberculosis and Lung Disease 24, no. 6 (June 1, 2020): 577–84. http://dx.doi.org/10.5588/ijtld.19.0457.

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BACKGROUND: Cardiovascular disease is one of the main causes of mortality in patients with chronic obstructive pulmonary disease (COPD), and atherosclerosis is a cause of cardiac comorbidities in COPD. However, it is not clear whether airflow limitation is associated with atherosclerosis irrespective of smoking.OBJECTIVE: To investigate whether airflow limitation is independently associated with vascular stiffness.METHODS: We enrolled 18 893 participants (male 70.5%; mean age 47.5 ± 9.8 years; never smokers 44.2%) who underwent spirometry and brachial-ankle pulse wave velocity (baPWV) as part of a standard health examination at Ajou University Hospital, Suwon, South Korea, from January 2010 to December 2015.We defined vascular peripheral atherosclerosis as baPWV ≥ 1400 cm/s and airflow limitation as pre-bronchodilator ratio of forced expiratory volume in 1 sec (FEV1) to forced vital capacity (FVC) <70%.RESULTS: Mean baPWV was higher in subjects with airflow limitation (1477.6 ± 331.7 cm/sec, n = 638) than in those without airflow limitation (1344.1 ± 231.8 cm/sec, n = 18255, P < 0.001). In multivariate logistic regression analysis, the following were independent predictors associated with peripheral atherosclerosis (P < 0.05): age, male sex, fasting serum glucose, mean blood pressure, serum leukocyte count, serum low density lipoprotein level and FEV1.CONCLUSION: Airflow limitation was an independent predictor of vascular stiffness irrespective of smoking history, which suggests that airflow limitation is linked with atherosclerosis.

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23

Harnau, Ludger. "Influence of molecular stiffness on the dynamic structure factor." Macromolecular Symposia 162, no. 1 (December 2000): 221–26. http://dx.doi.org/10.1002/1521-3900(200012)162:1<221::aid-masy221>3.0.co;2-l.

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24

Safar, Michel E. "Arterial stiffness as a risk factor for clinical hypertension." Nature Reviews Cardiology 15, no. 2 (October 12, 2017): 97–105. http://dx.doi.org/10.1038/nrcardio.2017.155.

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25

TABARA, Y., R. TACHIBANAIIMORI, R. KAWAMOTO, M. YAMAMOTO, I. KONDO, T. MIKI, and K. KOHARA. "Shrinking stature; a new risk factor for arterial stiffness." American Journal of Hypertension 18, no. 5 (May 2005): A115—A116. http://dx.doi.org/10.1016/j.amjhyper.2005.03.323.

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26

Duprez, Daniel A., and Jay N. Cohn. "Arterial stiffness as a risk factor for coronary atherosclerosis." Current Atherosclerosis Reports 9, no. 2 (April 2007): 139–44. http://dx.doi.org/10.1007/s11883-007-0010-y.

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27

Alves Filho, Antonio de Assis Oliveira, Rafael Oliveira Lopes, Roberta de Castro Araújo Cunha, Juan Jailson Oliveira Almeida Costa, Larissa Ribeiro Bessa, Rodrigo Lins Sant’ Ana de Lima, Alana dos Reis Silva, et al. "Prevalence of hypertension, arterial stiffness and risk factor association." Journal of Cardiology & Current Research 13, no. 6 (December 31, 2020): 167–74. http://dx.doi.org/10.15406/jccr.2020.13.00497.

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28

Jiang, Zhen Zhen. "Cycloid Pinwheel Planet Drive Nonlinear Meshing Stiffness Calculation and Analysis." Applied Mechanics and Materials 543-547 (March 2014): 224–27. http://dx.doi.org/10.4028/www.scientific.net/amm.543-547.224.

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Mathematical model of pin-cycloid meshing stiffness is set up by profile modification with clearance meshing analytical method. An universal program of pin-cycloid meshing stiffness is compiled, by which meshing stiffness is computed. Computing results show that meshing stiffness is changing with time greatly, which indicate that changing meshing stiffness is a main factor on vibration of whole machine. Better value of modification and curtate ratio coefficient are gotten by analyzing factors on meshing stiffness,such as value of modification ,curtate ratio coefficient and pin-cycloid radius etc. Computing and analytical results lay a foundation for ring-plate-type pin-cycloid planetary drive dynamics characteristics investigation deeply.

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29

Walker, Darolyn J., Andrea MacIntosh, Anita Kozyrskyj, Allan Becker, and Jon McGavock. "The Associations Between Cardiovascular Risk Factors, Physical Activity, and Arterial Stiffness in Youth." Journal of Physical Activity and Health 10, no. 2 (February 2013): 198–204. http://dx.doi.org/10.1123/jpah.10.2.198.

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Background:The primary aim of this population-based study was to determine if arterial stiffness is associated with cardiovascular disease (CVD) risk factor clustering and physical activity in youth 12−14 years old. We hypothesized that arterial stiffness would be positively associated with CVD risk factor clustering and negatively associated with physical activity in a dose-response manner in this cohort of youth.Methods:This was a cross sectional study of 485 youth recruited from the 1995 Manitoba birth cohort. The primary outcome, arterial stiffness, was assessed noninvasively using conventional pulse wave analysis and velocity. The primary exposure variables included 1) a measure of cardiometabolic risk, defined as a composite of novel and traditional risk factors for cardiovascular disease and type 2 diabetes and 2) self-reported physical activity.Results:Neither cardiometabolic risk factor clustering, nor physical activity were associated with either measure of arterial stiffness in this cohort of youth 12−14 years. Cardiometabolic risk decreased with increasing levels of vigorous physical activity, (P < .05) and increased with increasing body mass index.Conclusions:Cardiometabolic risk factor clustering and physical activity are not associated with arterial stiffness in youth 12−14 years of age. Increased vigorous physical activity is associated with reduced cardiometabolic risk in youth independent of body mass index.

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30

Yang, Zhaohui, Hui Chen, and Tianxiang Yu. "Effects of rolling bearing configuration on stiffness of machine tool spindle." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 232, no. 5 (February 22, 2017): 775–85. http://dx.doi.org/10.1177/0954406217693659.

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Rolling bearings are widely used in the complex mechanical systems as important components. With the advancement in the manufacturing technology, the requirements of high-performance machining tool became essential. A bearing is one of the most important components of spindle, and it is a crucial factor in determining the overall quality. The configuration of bearings of spindle is the key problem during high-performance spindle design, which influences the performance of spindle, especially stiffness. This paper aims to develop a method to analyze various spindle stiffnesses with different configurations of bearing to support the optimization of spindle. Firstly, a quasi-static model is established to solve stiffness matrix of bearing, and then a spindle-bearing system mathematical model is established. Secondly, the stiffness matrix of bearing is added into the whole system to form an integrated spindle-bearings model. Finally, the spindle stiffness with different bearing configurations are analyzed. The results indicate that the number of bearings influences the spindle radial stiffness and bearing direction affects the spindle axial stiffness. Once the number and direction are specified, reasonable pre-load method, shorter overhang, and proper span can greatly improve the spindle dynamic characteristics. In addition, an experimental spindle is designed and fabricated to test various axial stiffnesses with different bearing configurations, and stiffness characteristics of commonly used bearing configurations are summarized from the experimental results and provide useful guide for the spindle design.

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31

Fan, Shuai, and Shouwen Fan. "Approximate Stiffness Modelling and Stiffness Defect Identification for a Heavy-load Parallel Manipulator." Robotica 37, no. 6 (February 18, 2019): 1120–42. http://dx.doi.org/10.1017/s0263574718001492.

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SummaryWhen using parallel manipulators as machine tools, their stiffness is an important factor in the quality of the produced products. This paper presents an overall approximate stiffness model for a heavy-load parallel manipulator, which considers the effects of actuator stiffness, joint clearance, joint contact deformation, and limb deformation. Based on the principle of virtual work and the introduced modified parameters, the proposed overall compliance matrix successfully takes four factors into a unified expression. To obtain the overall compliance matrix, the approximate stiffness models of the joint clearance, joint contact deformation, and limb deformation are given. In addition, by combining the statistical simulation including the random uncertainties and the proposed approximate stiffness models as the basis of the magnitudes for each random variable, an approach based on the expected trajectory and external load is also proposed for stiffness defect identification such that the estimation is more accurate and reliable. Finally, a numerical example of the 1PU+3UPS parallel manipulator and a discussion are presented to demonstrate the practicability of the proposed stiffness model and defect identification approach. After modifying the structure parameters of the defective components, the prototype experiences a significant stiffness improvement.

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32

Zhou, Hai Ying, Li Xin Li, and Ting Guo Chen. "An Approach to Determine the Stiffness Reduction Factor of Tunnel Lining." Advanced Materials Research 243-249 (May 2011): 3659–62. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.3659.

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Based on the segmental joint tests, it was found that the practical range of joint flexural rigidity was in range of 8500-29000kN•m/rad. A simplified method for determining the stiffness reduction factor of tunnel lining() was proposed using results from the segmental joint tests in which some parameters were obtained by calibration against a 3D Numerical analysis. The influence of joint flexural rigidity, soil resistance coefficient, thickness of tunnel lining and tunnel calculation radius on the stiffness reduction factor of tunnel lining was examined. The stiffness reduction factor can be simply expressed as a function of joint flexural rigidity ratio, soil resistance coefficient, thickness of tunnel lining and tunnel calculation radius for the typical tunnel lining.

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33

Qiu, Fu Sheng, Wu Qiang Ji, and Hou Chao Xu. "Vertical Tail Topology Optimization Design Based on the Variable Density Method with Constraint Factor." Applied Mechanics and Materials 300-301 (February 2013): 280–84. http://dx.doi.org/10.4028/www.scientific.net/amm.300-301.280.

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The topology optimization design problem with multiple constraints for the complex vertical tail structure is studied in this paper. The variable density structural topology optimization method is improved by introducing a constraint factor. According to the different structural constraints and design requirements, variable factors and element pseudo density are initialized via finite element method. This method is controlled by the constraint factors, and the improved method combining with Rational Approximation of Material Properties (RAMP) density-stiffness interpolation model with optimality criteria methods (OC), the vertical tail’s stiffness optimization has been finished. The density-stiffness interpolation model, the mathematical model of variable density method with constraint factor, the structural optimization model, the solution model of the OC method, the design variables iterative format, are given in this paper and the algorithm with Matlab program is realized. Lastly, a sample vertical tail case is introduced to validate the feasibility of the algorithm by operating the results and analyzing the data.

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34

Liu, Heng, Jie Hong, Shilun Ruan, Zheng Li, and Gengdong Cheng. "A Model accounting for Stiffness Weakening of Curvic Couplings under Various Loading Conditions." Mathematical Problems in Engineering 2020 (February 11, 2020): 1–17. http://dx.doi.org/10.1155/2020/1042375.

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Curvic couplings are frequently used in aeroengine rotors. The stiffness of the curvic couplings is of guiding significance to the engineering design of aeroengine rotors as it is significantly different from that of continuous structures. In this paper, definitions and relations of the structure parameters for a curvic coupling are firstly introduced. Based on this proposed mechanical framework, a novel mechanical model accounting for the stiffness weakening under shearing, compression, bending, and torsion is developed for curvic couplings. In this model, a three-spring system, which consists of two types of springs, is adopted to describe the equivalent stiffness of a pair of meshing teeth of curvic couplings. The spring stiffness is obtained by employing the plane strain analysis of a discretized tooth with trapezoid pieces. Subsequently, the stiffness matrix of curvic couplings is deduced based on the deformation compatibility of each tooth and the force balance of the whole structure. A series of analyses of curvic couplings with various structure types are performed to demonstrate the mechanism behind the proposed model, and the results are verified against those obtained from finite element analyses. It is shown in this study that the pressure angle is the major factor affecting the stiffness of curvic couplings, while the compression stiffness and bending stiffness are more sensitive than other stiffnesses. Furthermore, the stiffness of curvic couplings is considerably smaller compared to that of continuous structures, indicating the importance of appropriate modelling of stiffness weakening in the design of aeroengine rotors.

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35

LEE, SANG-WOOK, JUNG-HYUN KIM, and JOONG-HWAN JUN. "FACTOR STUDY FOR THE SEPARATOR PLATE OF MCFC HAVING UNIFORM STIFFNESS AT ELEVATED TEMPERATURE." International Journal of Modern Physics B 22, no. 31n32 (December 30, 2008): 5667–72. http://dx.doi.org/10.1142/s021797920805098x.

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A molten carbonate fuel cell (MCFC) is composed of several stacks of unit cells. A unit cell is composed of two electrodes and a matrix that is inserted between separator plates. Separator plates should properly contact the electrodes to reduce the electricity loss arising from contact resistance. To this end, a pressure of about 2 kgf/cm2 is usually applied on the top of the stack, which results in the separator plates being somewhat compacted. Furthermore, the stiffness of the separator plates becomes degraded at elevated temperatures due to softening of the plate materials. Therefore, a nonuniform temperature distribution across the separator plates induced by exothermic reactions of the oxidant and reactant gases leads to a non-uniform plate stiffness. This study has firstly evaluated the change in separator plate stiffness as temperature changes by applying pressure to the plates. Secondly, using the Taguchi method, several design factors that affect stiffness have been investigated to determine which has the most influence. Based on these results, a new design for the separators, which allows for uniform stiffness at elevated temperatures, has been proposed.

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Esteva, Luis. "Nonlinear Seismic Response of Soft-First-Story Buildings Subjected to Narrow-Band Accelerograms." Earthquake Spectra 8, no. 3 (August 1992): 373–89. http://dx.doi.org/10.1193/1.1585686.

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The nonlinear dynamic response of shear systems representative of buildings with excess stiffness and strength at all stories above the first one is studied. Variables covered were number of stories, fundamental period, along-height form of variation of story stiffness, ratio of post-yield to initial stiffness, in addition to the variable of primary interest: the factor r, expressing the ratio of the average value of the safety factor for lateral shear at the upper stories to that at the bottom story. The lateral strength at the latter was taken as equal to the nominal value of the corresponding story shear computed by conventional modal dynamic analysis for the design spectrum specified by Mexico City seismic design regulations of 1987 for a seismic behavior (ductility) reduction coefficient of 4.0. The excitation was in some cases the EW component of the accelerogram recorded at the parking lot of the Ministry of Communications and Transport in the same city during the destructive earthquake of September 19, 1985, and in some other cases an ensemble of artificial accelerograms with similar statistical properties. It is concluded that the nonlinear seismic response of shear buildings whose upper stories have lateral strengths and stiffnesses which correspond to safety factors larger than those applied to the first story is very sensitive to the relation between the average of the over-strength factors at the upper stories and that at the first one, as well as to the ratio of post-yield to initial stiffnesses. The nature and magnitude of the influence of r on the maximum ductility demands at the first story depend on the low-strain fundamental natural period of the system. The ductility demands computed for elastoplastic systems may in some cases be extremely large. Accounting for P-delta effects leads to an enhancement of the sensitivity of the response with respect to r.

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Jin, Xin, and Bin Jiu Yang. "Research on Static Stiffness Characteristics of Parallel Machine Tool." Advanced Materials Research 139-141 (October 2010): 1628–31. http://dx.doi.org/10.4028/www.scientific.net/amr.139-141.1628.

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The static stiffness characteristic of parallel machine tool is an important factor and reference for machine design and optimization. The static stiffness characteristic of 3-TPT parallel machine tool is researched in this paper. The structural analytical model of machine tool is built by ANSYS software, which has two different work positions and three kinds of different workloads. The details of analytical process and method are provided, and the deformation conditions and the laws of stiffness variation are got. The main factors of static stiffness are obtained, so it provides an important reference for modifying structure of machine tool and relative research.

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Zheng, Xiao Yan, Zhuo De Feng, Hong Jing Du, and Yue Xu. "Center Tower Stiffness Study in Multi-Tower Suspension Bridge." Advanced Materials Research 255-260 (May 2011): 1082–86. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.1082.

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The existence of center towers is the origin of performance difference between multi-tower suspension bridge and the traditional one, and longitudinal stiffness of the center tower is a decisive factor. Based on the finite element theory, the paper establishes numerical calculation model of multi-tower suspension bridge, and analyzes it’s static and dynamic performance variation by using different longitudinal flexural stiffness. Moreover, the factors that affect center tower stiffness are determined. Referring to judgment standards about usability and structure security given by existing research, the reasonable range of center tower stiffness is established. Besides, the paper tries to ascertain reasonable center tower stiffness by using the static mechanic performance of service phase as judgment standards.

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39

Rey-García, Jimena, and Raymond R. Townsend. "Large Artery Stiffness: A Companion to the 2015 AHA Science Statement on Arterial Stiffness." Pulse 9, no. 1-2 (2021): 1–10. http://dx.doi.org/10.1159/000518613.

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Large artery stiffness (LAS) has proven to be an independent risk factor for cardiovascular disease and mortality. Nevertheless, the position of current hypertension guidelines regarding the usefulness of assessing LAS differs across different continents. In general, European Guidelines recognize pulse wave velocity (PWV) as a marker of target organ damage but do not recommend its systematic use in general population. Asian guidelines consider PWV as a recommended test at diagnosis of hypertension, in contrast to North American guidelines that do not state any position about its usefulness. However, PWV predicts cardiovascular events, and several studies have shown that it improves risk classification adjusting for established risk factors especially for intermediate-risk patients. Finally, some advances have been made related to treatments affecting LAS. Dietary interventions such as sodium restriction and exercise-based interventions have a modest effect in reducing LAS. Pharmacological interventions, such as statins, or more recent advances with mineralocorticoid blocker seem to have a beneficial effect. Last, controversial effects of renal denervation on LAS have been found. Our goal here is to update the reader on LAS on these areas since the 2015 American Heart Association Scientific Statement.

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Kim, Sang-Hee, Thomas H. K. Kang, Jae-Yo Kim, Geon-Ho Hong, Gyu-Beom Han, Jung-Hoon Song, and Hong-Gun Park. "Stiffness Modification Factor for Reinforced Concrete Flat Plates with Steps." Journal of the Architectural Institute of Korea Structure and Construction 30, no. 3 (March 25, 2014): 11–19. http://dx.doi.org/10.5659/jaik_sc.2014.30.3.011.

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41

Georgianos, Panagiotis I., Pantelis A. Sarafidis, and Vassilios Liakopoulos. "Arterial Stiffness: A Novel Risk Factor for Kidney Injury Progression?" American Journal of Hypertension 28, no. 8 (February 15, 2015): 958–65. http://dx.doi.org/10.1093/ajh/hpv004.

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Han, Sang-Whan, Young-Mi Park, and Seong-Hoon Kee. "Stiffness Reduction Factor for Flat Slab Structures under Lateral Loads." Journal of Structural Engineering 135, no. 6 (June 2009): 743–50. http://dx.doi.org/10.1061/(asce)st.1943-541x.0000001.

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Nanoudis, S., M. Pikilidou, M. Yavropoulou, P. Georgianos, O. Tsachouridou, L. Skoura, S. Metallidis, and P. Zebekakis. "HIV INFECTION IS AN INDEPENDENT RISK FACTOR OF ARTERIAL STIFFNESS." Journal of Hypertension 37 (July 2019): e229. http://dx.doi.org/10.1097/01.hjh.0000572936.69912.74.

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Gasecki, Dariusz. "ARTERIAL STIFFNESS AS A RISK FACTOR FOR CEREBRAL VASCULAR LESIONS." Artery Research 24, no. C (2018): 65. http://dx.doi.org/10.1016/j.artres.2018.10.013.

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45

Ambrosi, Pierre, Christiane Oddoze, and Gilbert Habib. "Plasma Adiponectin: Risk Factor or Risk Marker for Arterial Stiffness?" American Journal of Cardiology 104, no. 5 (September 2009): 742. http://dx.doi.org/10.1016/j.amjcard.2009.05.038.

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Kang, Dae Woong, Jeonghyeok Kim, and Yong Gul Park. "Applicability Evaluation of Dynamic Amplification Factor Considering Track Support Stiffness." Journal of the Korean Society for Railway 23, no. 12 (December 31, 2020): 1219–30. http://dx.doi.org/10.7782/jksr.2020.23.12.1219.

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47

Schubertová, M., A. Smržová, P. Horak, M. Skácelová, E. Lokočová, Z. Heřmanová, and F. Mrázek. "AB0264 ARTERIAL STIFFNESS IN RHEUMATOID ARTHRITIS PATIENTS AS A POTENTIAL PREDICTOR OF EARLY CARDIOVASCULAR AGEING AND MORBIDITY." Annals of the Rheumatic Diseases 79, Suppl 1 (June 2020): 1430.2–1431. http://dx.doi.org/10.1136/annrheumdis-2020-eular.4802.

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Background:Cardiovascular disease (CVD) is one of the most common causes of death in Rheumatoid arthritis patients. Increased arterial stiffness is considered as an independent risk factor of development CVD and a predictor of all-cause morbidity and mortality. Increased arterial stiffness, due to premature vascular ageing, can be observed in patients with chronic inflammatory diseases as well as in RA patients.Objectives:To evaluate arterial stiffness determined as carotid – femoral pulse wave velocity in rheumatoid arthritis patients. The comparison of traditional and nontraditional risk factor of CVD, disease activity and laboratory findings connected with subclinical atherosclerotic changes.Methods:We evaluated data of 50 patients with rheumatoid arthritis (39 females, 11male, mean age 57, mean duration of disease of 13years). The arterial stiffness, measured as carotid – femoral pulse wave velocity (PWV), was established with the SphygmoCor system. This non-invasive technique uses the principle of applanation tonometry. Our control group counted 25 heathy male and females with no history of CVD or autoimmune disease. We evaluated the influence of traditional risk factors for CVD as age, smoking, BMI, lipid profile, diabetes mellitus, history of CV and cerebrovascular morbidity to PWV in RA patients. Non-traditional risk factors contained Adiponectin, Fetuin A, Endothelin-1 and Asymmetric dimethylarginine. To measure disease activity was used DAS 28 and inflammatory parameters as a marker of current disease activity. For chronic changes was used X-ray of small joints. Results were correlated with PWV and statistically evaluated.Results:Mean PWV in Rheumatoid arthritis patients was significantly higher (9.7 m/s) than that in healthy control group (6.7m/s). 49% of RA patients (n= 24) had increased arterial stiffness according to their age. 32% patients (n=16) with PWV over 10m/s that indicates aortal function alteration. We didn´t find correlation between arterial stiffness and traditional and non-traditional CVD risk factors. Increased PWV was not associated with high disease activity. Patients with higher arterial stiffness according to their age had longer RA history, higher level of rheumatoid factor, were more frequently anti-citrullinated protein antibodies (ACPA) negative and were more frequently treated with biological therapy.Conclusion:Rheumatoid arthritis patients are in increased risk of CV disease. PWV is considered as an independent risk factor of CVD. We proved increased arterial stiffness and vascular ageing in comparison to healthy controls. We did not find correlation between increased arterial stiffness and disease activity. All CVD risk factor intervention is necessary to improve the prognosis of patients. Further investigation is needed to establish the role of increased PWV in RA patients.References:[1]Reference Values for Arterial Stiffness’ Collaboration. Determinants of pulse wave velocity in healthy people and in the presence of cardiovascular risk factors: ‘establishing normal and reference values’.Eur Heart J. 2010;31(19):2338–2350.[2]Pasquale Ambrosino, Marco Tasso, Roberta Lupoli, Alessandro Di Minno, Damiano Baldassarre, Elena Tremoli & Matteo Nicola Dario Di Minno. Non-invasive assessment of arterial stiffness in patients with rheumatoid arthritis: A systematic review and meta-analysis of literature studies, Annals of Medicine, 2015; 47:6, 457-467.Acknowledgments:IGA_LF_2019_006, MZ Č-RVO (FNOL-00098892, 87-21)Disclosure of Interests:Markéta Schubertová: None declared, Andrea Smržová: None declared, Pavel Horak Speakers bureau: Pfizer, Abbvie, Eli lilly. Novartis, Roche, Sanofi, Martina Skácelová: None declared, Eva Lokočová: None declared, Zuzana Heřmanová: None declared, František Mrázek: None declared

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Zhou, Chun Jiang. "Research on the Radial Accuracy and Stiffness of HSK Tool System in High Speed Machining." Key Engineering Materials 480-481 (June 2011): 1335–40. http://dx.doi.org/10.4028/www.scientific.net/kem.480-481.1335.

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The radial positioning accuracy and stiffness are two important indexes to measure the performance of tool system. Once HSK tool system is in operation, the gap between the spindle and shank will enlarge, thus will make the radial positioning accuracy and stiffness lower. The influence factor leading to this problem is analyzed in this paper through elastic mechanics and finite element analysis. It can get from the analysis that the double-position structure and certain amount of interface are key factors to keep HSK high radial positioning accuracy and stiffness. In addition, the influence of clamping force and rotate speed to radial stiffness is presented that higher speed and larger clamping force make the radial stiffness better. Finally, the paper has verified the analysis of radial stiffness through the experimental measurement with different fit of HSK.

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Kari, L. "Audible-frequency stiffness of a primary suspension isolator on a high-speed tilting bogie." Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 217, no. 1 (January 1, 2003): 47–62. http://dx.doi.org/10.1243/095440903762727348.

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The preload-dependent dynamic stiffness of a primary suspension isolator on a high-speed tilting bogie is examined via measurements and modelling within an audible frequency range. The stiffness is found to depend strongly on both frequency and preload. The former displays some resonance phenomena, such as stiffness peaks and troughs, while the latter exhibits a steep low-frequency stiffness increase in addition to an anti-resonance peak shifting to a higher frequency with increased preload. The problems of simultaneously modelling the preload and frequency dependence are removed by adopting a frequency-dependent waveguide approach, assuming incompressible rubber with an Abel operator kernel as its shear relaxation function. The preload dependence is modelled by a non-linear shape factor based approach, using a globally equivalent preload configuration. All the translational stiffnesses are modelled, including the vertical, longitudinal and lateral directions, and the vertical stiffness results are compared to those of measurements in a specially designed test rig. Good agreement is obtained for a wide frequency domain-covering 100-600 Hz-using a minimum number of parameters and for a wide preload domain-from vanishing to the maximum in service, 90 kN.

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Zaghari, Bahareh, Emiliano Rustighi, and Maryam Ghandchi Tehrani. "Improved Modelling of a Nonlinear Parametrically Excited System with Electromagnetic Excitation." Vibration 1, no. 1 (September 4, 2018): 157–71. http://dx.doi.org/10.3390/vibration1010012.

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In this work, the nonlinear behaviour of a parametrically excited system with electromagnetic excitation is accurately modelled, predicted and experimentally investigated. The equations of motion include both the electromechanical coupling factor and the electromechanical damping. Unlike previous studies where only linear time-varying stiffness due to electromagnetic forces was presented, in this paper the effect of the induced current is studied. As a consequence, nonlinear parameters such as electromechanical damping, cubic stiffness and cubic parametric stiffness have been included in the model. These parameters are also observed experimentally by controlling the direct current (DC) and alternating current (AC) passed through the electromagnets. In fact, the proposed apparatus allows to control both linear and nonlinear stiffnesses and the independent effect of each parameter on the response is presented. In particular the effect of the cubic parametric stiffness on the parametric resonance amplitudes and the influence of cubic stiffness on the frequency bandwidth of the parametric resonance are shown. This model improves the prediction of parametric resonance, frequency bandwidth, and the response amplitude of parametrically excited systems and it may lead to refined design of electromagnetic actuators, filters, amplifiers, vibration energy harvesters, and magnetic bearings.

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