Journal articles: 'Stretch speed'

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GRIFFITHS, R. I. "The Mechanics of the Medial Gastrocnemius Muscle in the Freely Hopping Wallaby (Thylogale Billardierii)." Journal of Experimental Biology 147, no. 1 (November 1, 1989): 439–56. http://dx.doi.org/10.1242/jeb.147.1.439.

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Muscle force, electromyogram and length were monitored in the medial head of the gastrocnemius (MG) muscle in freely hopping wallabies (Thylogale billardierii Desmarest). During take-off hops from rest, MG muscle developed force with an isometric contraction. For constant-speed hops, force was produced in MG muscle during rapid stretch. The muscle resisted this stretch with a constant impedance that was independent of hopping speed. The rate of stretch of the muscle during high-speed hopping was as high as 1 ms−1 (5–6 muscle lengths per second) at the onset of stretch and slowed to no stretch at the peak of force. Since the mechanical impedance was constant while the stretch velocity changed, there was no significant viscosity present in the muscle. The tendon stretched by 3.2% at 7kmh−1 hopping and by 4.4% at 18kmh−1 hopping. Elastic energy storage in the tendons increased with hopping speed but the percentage of total work done by elastic recoil of the whole muscle did not increase at higher hopping speeds. The significance of the muscle stretch is in producing high forces rapidly and, in addition, there is considerable energy storage in the tend

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Fasciano, Robert W., and Leslie Tung. "Factors governing mechanical stimulation in frog hearts." American Journal of Physiology-Heart and Circulatory Physiology 277, no. 6 (December 1, 1999): H2311—H2320. http://dx.doi.org/10.1152/ajpheart.1999.277.6.h2311.

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Because stretch-induced activation may be important in generating clinically relevant arrhythmias in the heart, we delineated the ability of different types of stretches to activate ventricular tissue. Geometrically simple sheets of frog ( Rana catesbeiana) ventricular tissue were mounted to allow stretches to be applied perpendicular to one edge. Every heart could be activated by a stretch pulse ( n = 25), and several parameters were varied to determine their effects on mechanical activation threshold. At shorter coupling intervals, a larger stretch was needed to excite the tissue, and activation-recovery intervals were shorter, similar to previously published electrically probed strength-interval and restitution relations. Additionally, the tissue became easier to activate as the speed of the stretch increased from 0.09 to 2.6% length/ms. The increment in stretch needed for activation decreased as the baseline stretch increased from 0 to 6% length. Thus we show that mechanical activation is similar to electrical activation and that increasing uniquely mechanical parameters such as the speed of the applied stretch or baseline level of stretch can decrease the mechanical activation threshold.

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Thiesset, F., F. Halter, C. Bariki, C. Lapeyre, C. Chauveau, I. Gökalp, L. Selle, and T. Poinsot. "Isolating strain and curvature effects in premixed flame/vortex interactions." Journal of Fluid Mechanics 831 (October 13, 2017): 618–54. http://dx.doi.org/10.1017/jfm.2017.641.

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This study focuses on the response of premixed flames to a transient hydrodynamic perturbation in an intermediate situation between laminar stretched flames and turbulent flames: an axisymmetric vortex interacting with a flame. The reasons motivating this choice are discussed in the framework of turbulent combustion models and flame response to the stretch rate. We experimentally quantify the dependence of the flame kinematic properties (displacement and consumption speeds) to geometrical scalars (stretch rate and curvature) in flames characterized by different effective Lewis numbers. Whilst the displacement speed can be readily measured using particle image velocimetry and tomographic diagnostics, providing a reliable estimate of the consumption speed from experiments remains particularly challenging. In the present work, a method based on a budget of fuel on a well chosen domain is proposed and validated both experimentally and numerically using two-dimensional direct numerical simulations of flame/vortex interactions. It is demonstrated that the Lewis number impact neither the geometrical nor the kinematic features of the flames, these quantities being much more influenced by the vortex intensity. While interacting with the vortex, the flame displacement (at an isotherm close to the leading edge) and consumption speeds are found to increase almost independently of the type of fuel. We show that the total stretch rate is not the only scalar quantity impacting the flame displacement and consumption speeds and that curvature has a significant influence. Experimental data are interpreted in the light of asymptotic theories revealing the existence of two distinct Markstein numbers, one characterizing the dependence of flame speed to curvature, the other to the total stretch rate. This theory appears to be well suited for representing the evolution of the displacement speed with respect to either the total stretch rate, curvature or strain rate. It also explains the limited dependence of the flame displacement speed to Lewis number and the strong correlation with curvature observed in the experiments. An explicit relationship between displacement and consumption speeds is also given, indicating that the fuel consumption rate is likely to be altered by both the total stretch rate and curvature.

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Ishikawa, M., and P. V. Komi. "The role of the stretch reflex in the gastrocnemius muscle during human locomotion at various speeds." Journal of Applied Physiology 103, no. 3 (September 2007): 1030–36. http://dx.doi.org/10.1152/japplphysiol.00277.2007.

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In the present study, the fascicle length ( Lfa) of the human medial gastrocnemius (MG) muscle was monitored to evaluate possible input from the short-latency stretch reflex (SLR) during the stance phase of running and to examine its timing at various running speeds. Eight subjects ran at 2.0, 3.5, 5.0, and 6.5 m/s. The Lfa was measured with the high-speed ultrasound fascicle scanning together with kinematics and myoelectrical activities. The amplitudes and onset latency of SLR activities were determined. During ground contact, the sudden MG fascicle stretch occurred during the early contact at all running speeds. This was followed by the fascicle shortening. The timing of fascicle stretch depended on running speed and type of foot contact. In slower speed conditions (2.0, 3.5, 5 m/s), the MG fascicle stretch and the corresponding SLR activities occurred during the middle of the braking phase. In fast-speed running (6.5 m/s), however, the MG fascicle stretch occurred later compared with the lower speed. The corresponding SLR activities occurred significantly later at the end of the braking phase. In addition to the clear demonstration of the different timings of SLR in MG during ground contact of running, the results imply that the role of the MG SLR during the stance phase of running can be different between fast- and slow-speed running conditions.

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Singh, Sandeep, and . "Accident Study and Analysis of Selected Black Spots – A Case Study." International Journal of Engineering & Technology 7, no. 3.12 (July 20, 2018): 1254. http://dx.doi.org/10.14419/ijet.v7i3.12.17866.

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In the present study, accident statistics of 2011 to 2014 has resolved Vidya path as a black spot. In addition, attempt has been made to investigate the prevailing conditions of two V3 road stretches i.e. (Stretch – 1: road dividing sec – 14 and 15 and Stretch – 2: road dividing sec – 11 and 12) of Chandigarh for accidental risk. The moral of investigation has cleared that all the prime associated parties i.e. traffic, speed and users/driver are favoring the accidental risk; as during peak hour the road stretches were found short of capacity, speed of vehicles was over the legal speed and the users were ignoring the rules and regulation of driving. Consequently, the injury and life risk for pedestrians and cyclists are at the most. The preventive measures for the same are also incorporated.

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ALLESSIE, MAURITS. "Stretch and Speed: A Complicated Couple." Journal of Cardiovascular Electrophysiology 22, no. 4 (December 6, 2010): 402–4. http://dx.doi.org/10.1111/j.1540-8167.2010.01971.x.

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Cole, Daniel, Sungjin Im, Benjamin Moseley, and Kirk Pruhs. "Speed scaling for stretch plus energy." Operations Research Letters 40, no. 3 (May 2012): 180–84. http://dx.doi.org/10.1016/j.orl.2012.02.003.

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Pinchak, Matthew, Timothy Ombrello, Campbell Carter, Ephraim Gutmark, and Viswanath Katta. "The effects of hydrodynamic stretch on the flame propagation enhancement of ethylene by addition of ozone." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, no. 2048 (August 13, 2015): 20140339. http://dx.doi.org/10.1098/rsta.2014.0339.

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The effect of O 3 on C 2 H 4 /synthetic-air flame propagation at sub-atmospheric pressure was investigated through detailed experiments and simulations. A Hencken burner provided an ideal platform to interrogate flame speed enhancement, producing a steady, laminar, nearly one-dimensional, minimally curved, weakly stretched, and nearly adiabatic flame that could be accurately compared with simulations. The experimental results showed enhancement of up to 7.5% in flame speed for 11 000 ppm of O 3 at stoichiometric conditions. Significantly, the axial stretch rate was also found to affect enhancement. Comparison of the flames for a given burner exit velocity resulted in the enhancement increasing almost 9% over the range of axial stretch rates that was investigated. Two-dimensional simulations agreed well with the experiments in terms of flame speed, as well as the trends of enhancement. Rate of production analysis showed that the primary pathway for O 3 consumption was through reaction with H, leading to early heat release and increased production of OH. Higher flame stretch rates resulted in increased flux through the H+O 3 reaction to provide increased enhancement, due to the thinning of the flame that accompanies higher stretch, and thus results in decreased distance for the H to diffuse before reacting with O 3 .

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Rassier, Dilson E., Eun-Jeong Lee, and Walter Herzog. "Modulation of passive force in single skeletal muscle fibres." Biology Letters 1, no. 3 (June 28, 2005): 342–45. http://dx.doi.org/10.1098/rsbl.2005.0337.

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In this study, we investigated the effects of activation and stretch on the passive force–sarcomere length relationship in skeletal muscle. Single fibres from the lumbrical muscle of frogs were placed at varying sarcomere lengths on the descending limb of the force–sarcomere length relationship, and tetanic contractions, active stretches and passive stretches (amplitudes of ca 10% of fibre length at a speed of 40% fibre length/s) were performed. The passive forces following stretch of an activated fibre were higher than the forces measured after isometric contractions or after stretches of a passive fibre at the corresponding sarcomere length. This effect was more pronounced at increased sarcomere lengths, and the passive force–sarcomere length relationship following active stretch was shifted upwards on the force axis compared with the corresponding relationship obtained following isometric contractions or passive stretches. These results provide strong evidence for an increase in passive force that is mediated by a length-dependent combination of stretch and activation, while activation or stretch alone does not produce this effect. Based on these results and recently published findings of the effects of Ca 2+ on titin stiffness, we propose that the observed increase in passive force is caused by the molecular spring titin.

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Wang, Haiou, Evatt R. Hawkes, Jacqueline H. Chen, Bo Zhou, Zhongshan Li, and Marcus Aldén. "Direct numerical simulations of a high Karlovitz number laboratory premixed jet flame – an analysis of flame stretch and flame thickening." Journal of Fluid Mechanics 815 (February 23, 2017): 511–36. http://dx.doi.org/10.1017/jfm.2017.53.

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This article reports an analysis of the first detailed chemistry direct numerical simulation (DNS) of a high Karlovitz number laboratory premixed flame. The DNS results are first compared with those from laser-based diagnostics with good agreement. The subsequent analysis focuses on a detailed investigation of the flame area, its local thickness and their rates of change in isosurface following reference frames, quantities that are intimately connected. The net flame stretch is demonstrated to be a small residual of large competing terms: the positive tangential strain term and the negative curvature stretch term. The latter is found to be driven by flame speed–curvature correlations and dominated in net by low probability highly curved regions. Flame thickening is demonstrated to be substantial on average, while local regions of flame thinning are also observed. The rate of change of the flame thickness (as measured by the scalar gradient magnitude) is demonstrated, analogously to flame stretch, to be a competition between straining tending to increase gradients and flame speed variations in the normal direction tending to decrease them. The flame stretch and flame thickness analyses are connected by the observation that high positive tangential strain rate regions generally correspond with low curvature regions; these regions tend to be positively stretched in net and are relatively thinner compared with other regions. High curvature magnitude regions (both positive and negative) generally correspond with lower tangential strain; these regions are in net negatively stretched and thickened substantially.

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Wu, Jialin, Diaosheng Guan, and Baojun Quian. "The Characteristic Behaviour of the Stretch-Orientation Zone during High-Speed PET Spinning**." International Polymer Processing 1, no. 1 (March 1, 1986): 25–30. http://dx.doi.org/10.1515/217.860025.

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Abstract A theory is proposed to separate the on-line stress in the stretch-orientation zone during high speed PET spinning into two parts: the thermodynamically equilibrium or quasi-equilibrium stress associated with rubber elasticity and the non-equilibrium driving stress, which leads to coordinated orientation of the macromolecular chains. Precise and simultaneous measurements of the online spinning parameters at five spinning speeds, ranging from 2200 to 4200 m/min, were conducted. A physical model consisting of a dashpot placed in parallel with a Gaussian network was found to describe well the behaviour of the stretch-orientation zone of high speed PET spinning.

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Perrey, Stéphane, Guillaume Millet, Robin Candau, and Jean-Denis Rouillon. "Stretch-Shortening Cycle in Roller Ski Skating: Effects of Speed." Journal of Applied Biomechanics 16, no. 3 (August 2000): 264–75. http://dx.doi.org/10.1123/jab.16.3.264.

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The purpose of this study was to examine the effects of speed on the stretch-shortening cycle (SSC) behavior during roller ski skating. Ten highly skilled male cross-country skiers roller skied at 4.56, 5.33 m · s–1and maximal speed using the V2-alternate technique on a flat terrain. Knee and ankle joint kinematics, and EMG of thevastus lateralis(VL) andgastrocnemius lateralis(GL) muscles were recorded during the last 40 s of each bout of roller skiing. Maximal speed was associated with increases in cycle rate combined with decreases in cycle length. For VL, no significant differences were observed for the integrated EMG eccentric-to-concentric ratio (iEMG Ecc/Conc) and for the stretching velocity over the range of speeds. For GL, stretching velocity and iEMG Ecc/Conc were significantly greater at maximal speed. The analysis of GL EMG activity suggests that speed improved GL stiffness so that more elastic energy was stored, a better force transmission occurred, and coupling time decreased. These findings suggest that the efficiency of roller ski skating locomotion may be increased with speed through a better use of the stretch-shortening cycle pattern in the ankle extensors.

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Rassier, Dilson E., and Walter Herzog. "Active force inhibition and stretch-induced force enhancement in frog muscle treated with BDM." Journal of Applied Physiology 97, no. 4 (October 2004): 1395–400. http://dx.doi.org/10.1152/japplphysiol.00377.2004.

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There is evidence that the stretch-induced residual force enhancement observed in skeletal muscles is associated with 1) cross-bridge dynamics and 2) an increase in passive force. The purpose of this study was to characterize the total and passive force enhancement and to evaluate whether these phenomena may be associated with a slow detachment of cross bridges. Single fibers from frog lumbrical muscles were placed at a length 20% longer than the plateau of the force-length relationship, and active and passive stretches (amplitudes of 5 and 10% of fiber length and at a speed of 40% fiber length/s) were performed. Experiments were conducted in Ringer solution and with the addition of 2, 5, and 10 mM of 2,3-butanedione monoxime (BDM), a cross-bridge inhibitor. The steady-state active and passive isometric forces after stretch of an activated fiber were higher than the corresponding forces measured after isometric contractions or passive stretches. BDM decreased the absolute isometric force and increased the total force enhancement in all conditions investigated. These results suggest that total force enhancement is directly associated with cross-bridge kinetics. Addition of 2 mM BDM did not change the passive force enhancement after 5 and 10% stretches. Addition of 5 and 10 mM did not change (5% stretches) or increased (10% stretches) the passive force enhancement. Increasing stretch amplitudes and increasing concentrations of BDM caused relaxation after stretch to be slower, and because passive force enhancement is increased at the greatest stretch amplitudes and the highest BDM concentrations, it appears that passive force enhancement may be related to slow-detaching cross bridges.

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Nixon, J., S. Yan, and Gary H. Menary. "Analysis and Simulation of the Free-Stretch-Blow Process of PET." Key Engineering Materials 554-557 (June 2013): 1729–37. http://dx.doi.org/10.4028/www.scientific.net/kem.554-557.1729.

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This paper is concerned with understanding the behaviour of Polyethylene Terephthalate (PET) in the injection stretch blow moulding (ISBM) process where it is typically bi-axially stretched to form bottles for the packaging industry. Preforms which have been pre sprayed with a pattern and heated in an oil bath have been stretched and blown in free air using a lab scale ISBM machine whilst being monitored via high speed video. The images have subsequently been analysed using a digital image correlation system (VIC 3D). The results have been used to validate appropriate simulations of the free-blow process using ABAQUS®/Explicit FEA with a suitable viscoelastic material model, along with experimental process data obtained using an instrumented stretch rod.

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MUKUNDA, H. S. "Stretch Effects in High Speed Reacting Mixing Layers." Combustion Science and Technology 89, no. 1-4 (March 1993): 285–90. http://dx.doi.org/10.1080/00102209308924114.

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Luo, Xicai, Haolin Liu, Limei Kang, Jielin Lin, Yifei Liu, Datong Zhang, Dongyang Li, and Daolun Chen. "Stretch Formability of an AZ61 Alloy Plate Prepared by Multi-Pass Friction Stir Processing." Materials 14, no. 12 (June 9, 2021): 3168. http://dx.doi.org/10.3390/ma14123168.

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The stretch formability behavior of an AZ61 magnesium alloy plate produced by multi-pass friction stir processing (M-FSP) was investigated, with the applied load vs. displacement curves recorded during Erichsen cupping tests at different punching speeds at room temperature. The stretch formability of M-FSP AZ61 magnesium alloy was significantly enhanced, compared with that of its cast counterpart. The highest Erichsen index of 3.7 mm was obtained at a punching speed of 0.1 mm/min. The improved stretch formability was mainly attributed to the grain refinement stemming from the M-FSP and the presence of extension twinning to accommodate deformation during Erichsen cupping testing.

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Chen, Yili, Shaoqun Zhang, Yang Chen, Yonghua Lao, Xuecheng Huang, Xiaoyu Huang, Qiming Liao, and Yikai Li. "Rupture Risk Assessment of Cervical Spinal Manipulations on Carotid Atherosclerotic Plaque by a 3D Fluid-Structure Interaction Model." BioMed Research International 2021 (January 2, 2021): 1–8. http://dx.doi.org/10.1155/2021/8239326.

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Object. Use a fluid-structure interaction (FSI) model to do a safety risk assessment of cervical spinal manipulative therapy (cSMT) for atherosclerosis to study the biomechanical changes of atherosclerosis plaque and the carotid artery (CA) lumen during the process of cSMT. Method. The FSI model, based on MRI data of an atherosclerosis patient, was used to simulate the deformations of the plaque and lumen during the process of two kinds of typical cSMT (the high-speed, low-amplitude spinal manipulation and the cervical rotatory manipulation). The biomechanical parameters were recorded, such as the highest wall shear stress (WSS), the maximum plaque wall stress (PWS), the wall tensile stress (Von mises stress, VWTS), and the strain. Result. The max_WSS was 33.77 kPa in the most extensive deformation. The highest WSS region on the plaque surface was also the highest PWS region. The max_PWS in a 12% stretch was 55.11 kPa, which was lower than the rupture threshold. The max_VWTS of the cap in 12% stretch which approached the fracture stress level was 116.75 kPa. Moreover, the vessel’s max_VWTS values in 10% and 12% stretch were 554.21 and 855.19 kPa. They were higher than the fracture threshold, which might cause media fracture. Meanwhile, the 7% stretched strain was 0.29, closed to the smallest experimental green strains at rupture. Conclusion. The carotid arteries’ higher stretch generated the higher stress level of the plaque. Cervical rotatory manipulation might cause plaque at a high risk of rupture in deformation after 12% stretch and more. Lower deformation of the plaque and artery caused by the high-speed, low-amplitude spinal manipulation might be safer.

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Aziz, Sadiq Jaffar, and Mohammed Dahkil Abbas. "Statistical and Experimental Study of the Stretching Force for 6061 Aluminum Alloy Using post stretching and pre strecting processes." Journal of University of Babylon for Engineering Sciences 27, no. 2 (May 26, 2019): 74–87. http://dx.doi.org/10.29196/jubes.v27i2.2294.

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An experiment and a statistic study was performed considering the effect of two important input parameters (stretching force and stretching speed) on the stretching behaviour of 6061-0 aluminum sheet in terms of thickness reduction ratio in two types of stretch forming process (post stretching and pre stretching). Experimental tests were carried out using a die with V-shape to stretch the sheet at two selected levels of stretching force and stretching speed and according to the design matrices established by the Design of Experiment (DOE) software (Version 10). Two models with two variable parameters, i.e. stretching force and speed were built by using the response surface methodology (RSM) technique for the two cases of stretching (post and pre stretching), then checked statistically for adequacy purpose by analysis of variance (ANOVA) analysis, and appeared good with 95 % confidence level. It was found that using the post stretch forming process generally gives a lower thickness reduction ratio than that for pre stretching process. This explains the advantages of using post-stretching process to stretch the 6061-0 aluminum sheet alloy.

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Lokshina, S. I. "Design of high-speed stretch rolls with inductive heating." Fibre Chemistry 21, no. 3 (1990): 190–95. http://dx.doi.org/10.1007/bf00549643.

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WYLIE, JONATHAN J., HUAXIONG HUANG, and ROBERT M. MIURA. "Thermal instability in drawing viscous threads." Journal of Fluid Mechanics 570 (January 3, 2007): 1–16. http://dx.doi.org/10.1017/s0022112006002709.

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We consider the stretching of a thin viscous thread, whose viscosity depends on temperature, that is heated by a radiative heat source. The thread is fed into an apparatus at a fixed speed and stretched by imposing a higher pulling speed at a fixed downstream location. We show that thermal effects lead to the surprising result that steady states exist for which the force required to stretch the thread can decrease when the pulling speed is increased. By considering the nature of the solutions, we show that a simple physical mechanism underlies this counterintuitive behaviour. We study the stability of steady-state solutions and show that a complicated sequence of bifurcations can arise. In particular, both oscillatory and non-oscillatory instabilities can occur in small isolated windows of the imposed pulling speed.

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Rassier, Dilson E., and Ivan Pavlov. "Force produced by isolated sarcomeres and half-sarcomeres after an imposed stretch." American Journal of Physiology-Cell Physiology 302, no. 1 (January 2012): C240—C248. http://dx.doi.org/10.1152/ajpcell.00208.2011.

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When a stretch is imposed to activated muscles, there is a residual force enhancement that persists after the stretch; the force is higher than that produced during an isometric contraction in the corresponding length. The mechanisms behind the force enhancement remain elusive, and there is disagreement if it represents a sarcomeric property, or if it is associated with length nonuniformities among sarcomeres and half-sarcomeres. The purpose of this study was to investigate the effects of stretch on single sarcomeres and myofibrils with predetermined numbers of sarcomeres ( n = 2, 3. . . , 8) isolated from the rabbit psoas muscle. Sarcomeres were attached between two precalibrated microneedles for force measurements, and images of the preparations were projected onto a linear photodiode array for measurements of half-sarcomere length (SL). Fully activated sarcomeres were subjected to a stretch (5–10% of initial SL, at a speed of 0.3 μm·s−1·SL−1) after which they were maintained isometric for at least 5 s before deactivation. Single sarcomeres showed two patterns: 31 sarcomeres showed a small level of force enhancement after stretch (10.46 ± 0.78%), and 28 sarcomeres did not show force enhancement (−0.54 ± 0.17%). In these preparations, there was not a strong correlation between the force enhancement and half-sarcomere length nonuniformities. When three or more sarcomeres arranged in series were stretched, force enhancement was always observed, and it increased linearly with the degree of half-sarcomere length nonuniformities. The results show that the residual force enhancement has two mechanisms: 1) stretch-induced changes in sarcomeric structure(s); we suggest that titin is responsible for this component, and 2) stretch-induced nonuniformities of half-sarcomere lengths, which significantly increases the level of force enhancement.

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Huang, Xin Sheng, Kazutaka Suzuki, Akira Watazu, Ichinori Shigematsu, and Naobumi Saito. "Influences of Rolling Conditions on Texture and Formability of Magnesium Alloy Sheets." Materials Science Forum 638-642 (January 2010): 1536–40. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.1536.

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The AZ61 magnesium alloy was subjected to the differential speed rolling at different rolling conditions including reduction per pass, rotation speed ratio and rolling temperature, and the influences of the rolling conditions on microstructure, texture, mechanical properties and formability of the as-rolled sheets were investigated. Increasing the reduction per pass results in a more homogeneous microstructure and a relatively weaker basal texture. With increasing the rotation speed ratio, the inclination angle of basal pole toward the rolling direction increases and the stretch formability enhances correspondingly. Increasing the rolling temperature has an effect on weakening the basal texture intensity and leads to the enhancement of stretch formability.

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Rassier, Dilson E., and Walter Herzog. "Relationship between force and stiffness in muscle fibers after stretch." Journal of Applied Physiology 99, no. 5 (November 2005): 1769–75. http://dx.doi.org/10.1152/japplphysiol.00010.2005.

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The purpose of this study was to evaluate the relationship between force and stiffness after stretch of activated fibers, while simultaneously changing contractility by interfering with the cross-bridge kinetics and muscle activation. Single fibers dissected from lumbrical muscles of frogs were placed at a length 20% longer than the plateau of the force-length relationship, activated, and stretched by 5 and 10% of fiber length (speed: 40% fiber length/s). Experiments were conducted with maximal and submaximal stimulation in Ringer solution and with the addition of 2 and 5 mM of the myosin inhibitor 2,3-butanedione monoxime (BDM) to the solution. The steady-state force after stretch of an activated fiber was higher than the isometric force produced at the corresponding length in all conditions investigated. Lowering the frequency of stimulation decreased the force and stiffness during isometric contractions, but it did not change force enhancement and stiffness enhancement after stretch. Administration of BDM decreased the force and stiffness during isometric contractions, but it increased the force enhancement and stiffness enhancement after stretch. The relationship between force enhancement and stiffness suggests that the increase in force after stretch may be caused by an increase in the proportion of cross bridges attached to actin. Because BDM places cross bridges in a weakly bound, pre-powerstroke state, our results further suggest that force enhancement is partially associated with a recruitment of weakly bound cross bridges into a strongly bound state.

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Saltarelli, Francesco, Vikas Kumar, Daniele Viola, Francesco Crisafi, Fabrizio Preda, Giulio Cerullo, and Dario Polli. "Photonic Time-Stretch Spectroscopy for Multiplex Stimulated Raman Scattering." EPJ Web of Conferences 205 (2019): 03003. http://dx.doi.org/10.1051/epjconf/201920503003.

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Stimulated Raman scattering spectroscopy enables label-free molecular identification, but its broadband implementation is technically challenging. We experimentally demonstrate a novel approach to multiplex stimulated Raman scattering based on photonic time stretch. A telecom fiber stretches the broadband femtosecond Stokes pulse after the sample to ∼15ns, mapping its spectrum in time. The signal is sampled through a fast oscilloscope, providing single-shot spectra at 80-kHz rate. We demonstrate high sensitivity in detecting the Raman vibrational modes of various samples over the entire high-frequency C-H stretching region. Our results pave the way to high-speed broadband vibrational imaging for materials science and biophotonics.

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McGenity, Terry J., and Pierre Philippe Laissue. "Bacteria stretch and bend oil to feed their appetite." Science 381, no. 6659 (August 18, 2023): 728–29. http://dx.doi.org/10.1126/science.adj4430.

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Sun, Lu Yong, Jin Long Zou, and Kai Chen. "FEM-Based Research on Molding Parameter Analysis of the PET Beverage Bottle." Applied Mechanics and Materials 488-489 (January 2014): 121–24. http://dx.doi.org/10.4028/www.scientific.net/amm.488-489.121.

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The researched PET beverage bottle molding process was analyzed with the combination of stretch blow molding technological process of the manufacturing enterprise. The molding results would be influenced by some technological parameters. In order to study the effect of these factors on the forming properties and thickness distribution of molding bottle, the article builds the physical model and finite element model of PET bottles stretch blow molding process, and simulates stretch blow molding process by using POLYFLOW software for analyzing the thickness distribution of molding bottle. Comparing different thickness distribution under the different condition of stretch speed, pre-blowing pressure, and blowing pressure, the technological parameters were optimized, so as to achieve the goal of optimization of molding bottle.

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Yu, Weiqun. "Polarized ATP distribution in urothelial mucosal and serosal space is differentially regulated by stretch and ectonucleotidases." American Journal of Physiology-Renal Physiology 309, no. 10 (November 15, 2015): F864—F872. http://dx.doi.org/10.1152/ajprenal.00175.2015.

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Purinergic signaling is a major pathway in regulating bladder function, and mechanical force stimulates urothelial ATP release, which plays an important role in bladder mechanotransduction. Although urothelial ATP release was first reported almost 20 years ago, the way in which release is regulated by mechanical force, and the presence of ATP-converting enzymes in regulating the availability of released ATP is still not well understood. Using a set of custom-designed Ussing chambers with the ability to manipulate mechanical forces applied on the urothelial tissue, we have demonstrated that it is stretch and not hydrostatic pressure that induces urothelial ATP release. The experiments reveal that urothelial ATP release is tightly controlled by stretch speed, magnitude, and direction. We have further shown that stretch-induced urothelial ATP release is insensitive to temperature (4°C). Interestingly, stretch-induced ATP release shows polarized distribution, with the ATP concentration in mucosal chamber (nanomolar level) about 10 times higher than the ATP concentration in serosal chamber (subnanomolar level). Furthermore, we have consistently observed differential ATP lifetime kinetics in the mucosal and serosal chambers, which is consistent with our immunofluorescent localization data, showing that ATP-converting enzymes ENTPD3 and alkaline phosphatase are expressed on urothelial basal surface, but not on the apical membrane. In summary, our data indicate that urothelial ATP release is finely regulated by stretch speed, magnitude, and direction, and extracellular ATP signaling is likely to be differentially regulated by ectonucleotidase, which results in temporally and spatially distinct ATP kinetics in response to mechanical stretch.

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Chung, Charles S., Julius Bogomolovas, Alexander Gasch, Carlos G. Hidalgo, Siegfried Labeit, and Henk L. Granzier. "Titin-Actin Interaction: PEVK-Actin-Based Viscosity in a Large Animal." Journal of Biomedicine and Biotechnology 2011 (2011): 1–8. http://dx.doi.org/10.1155/2011/310791.

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Titin exhibits an interaction between its PEVK segment and the actin filament resulting in viscosity, a speed dependent resistive force, which significantly influences diastolic filling in mice. While diastolic disease is clinically pervasive, humans express a more compliant titin (N2BA:N2B ratio ~0.5–1.0) than mice (N2BA:N2B ratio ~0.2). To examine PEVK-actin based viscosity in compliant titin-tissues, we used pig cardiac tissue that expresses titin isoforms similar to that in humans. Stretch-hold experiments were performed at speeds from 0.1 to 10 lengths/s from slack sarcomere lengths (SL) to SL of 2.15 μm. Viscosity was calculated from the slope of stress-relaxation vs stretch speed. Recombinant PEVK was added to compete off native interactions and this found to reduce the slope by 35%, suggesting that PEVK-actin interactions are a strong contributor of viscosity. Frequency sweeps were performed at frequencies of 0.1–400 Hz and recombinant protein reduced viscous moduli by 40% at 2.15 μm and by 50% at 2.25 μm, suggesting a SL-dependent nature of viscosity that might prevent SL ``overshoot’’ at long diastolic SLs. This study is the first to show that viscosity is present at physiologic speeds in the pig and supports the physiologic relevance of PEVK-actin interactions in humans in both health and disease.

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Lin, Ruey-Mo, Guan-Liang Chang, and Li-Tung Chang. "Biomechanical properties of muscle-tendon unit under high-speed passive stretch." Clinical Biomechanics 14, no. 6 (July 1999): 412–17. http://dx.doi.org/10.1016/s0268-0033(98)00108-9.

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Nivarti, Girish V., and R. Stewart Cant. "Stretch Rate and Displacement Speed Correlations for Increasingly-Turbulent Premixed Flames." Flow, Turbulence and Combustion 102, no. 4 (October 25, 2018): 957–71. http://dx.doi.org/10.1007/s10494-018-9990-7.

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Haghiri, Ali, Mohsen Talei, Michael J. Brear, and Evatt R. Hawkes. "Flame Annihilation Displacement Speed and Stretch Rate in Turbulent Premixed Flames." Flow, Turbulence and Combustion 104, no. 4 (November 22, 2019): 977–96. http://dx.doi.org/10.1007/s10494-019-00078-0.

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Zhou, Binzhong, Iain M. Mason, and Stewart A. Greenhalgh. "An accurate formulation of log‐stretch dip moveout in the frequency‐wavenumber domain." GEOPHYSICS 61, no. 3 (May 1996): 815–20. http://dx.doi.org/10.1190/1.1444006.

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Dip moveout (DMO) processing is a partial prestack migration procedure that has been widely used in seismic data processing. The DMO process has been described in Deregowski (1986), Hale (1991) and Liner (1990). Many different DMO algorithms have been developed over the past decade. These algorithms have been designed to improve either the accuracy or the computational speed of the DMO process. Hale (1984) developed a method for performing DMO via Fourier transforms that is accurate for all reflector dips (assuming constant velocity). Hale’s method is computationally expensive because his DMO operator is temporally nonstationary, but its accuracy and simplicity have made it an industry standard. It has become a benchmark by which results from other DMO algorithms are judged. Of all the methods used to make the frequency‐domain DMO computationally efficient, the technique of logarithmic time stretching, first suggested in Bolondi et al. (1982), is widely used. After logarithmic stretching of the time axis, the DMO operator becomes temporally stationary which enables replacement of the slow temporal Fourier integration with a fast Fourier transform combined with a simple phase shift. Bale and Jakubowicz (1987) presented a log‐stretch DMO operator (hereafter referred to as Bale’s DMO) in the frequency‐wavenumber (F-K) domain without approximations, while Notfors and Godfrey (1987) suggested an approximate version of log‐stretch DMO operator (hereafter referred to as Notfors’s DMO). Surprisingly, Bale’s full log‐stretch DMO operator produces a less satisfactory impulse response than Notfors’s approximate log‐stretch DMO scheme (see Liner, 1990). Liner (1990) attributed this characteristic to the fact that Bale’s DMO derivation implicitly assumes that the Fourier transform frequency in the log‐stretch domain is not time‐dependant. He presented an exact log‐stretch DMO operator (hereafter referred to as Liner’s DMO) which was derived by transforming the time log‐stretched Hale’s (t, x) DMO impulse response into the Fourier domain. Its derivation is relatively complicated, but Liner has shown that his DMO does generate good DMO impulse responses.

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Yousif, Alaeldeen Altag, and Shaharin Anwar Sulaiman. "Experimental Study on Laminar Flame Speeds and Markstein Length of Methane-Air Mixtures at Atmospheric Conditions." Applied Mechanics and Materials 699 (November 2014): 714–19. http://dx.doi.org/10.4028/www.scientific.net/amm.699.714.

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Accurate value of laminar flame speed is an important parameter of combustible mixtures. In this respect, experimental data are very useful for modeling improvement and validating chemical kinetic mechanisms. To achieve this, an experimental characterization on spherically expanding flames propagation of methane-air mixtures were carried out. Tests were conducted in constant volume cylindrical combustion chamber to measure stretched, unstretched laminar flame speed, laminar burning velocity, and flame stretch effect as quantified by the associated Markstein lengths. The mixtures of methane-air were ignited at extensive ranges of lean-to-rich equivalence ratios, under ambient pressure and temperature. This is achieved by high speed schlieren cine-photography for flames observation in the vessel. The results showed that the unstretched laminar burning velocity increased and the peak value of the unstretched laminar burning velocity shifted to the richer mixture side with the increase of equivalence ratio. The flame propagation speed showed different trends at different equivalence ratio for tested mixtures. It was found that the Markstein length was increased with the increase of equivalence ratio.

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Gryc, Tomáš, František Zahálka, and Tomáš Malý. "Rotace horní části těla při golfovém švihu u elitních hráčů." Studia sportiva 7, no. 1 (July 1, 2013): 35–42. http://dx.doi.org/10.5817/sts2013-1-4.

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When the golf swing is involving all body segments and is thus considered as one of the most complex of sports motions. The aim of this study was to determine the selected kinematic parameters of movement of pelvic and segments of the upper body (shoulder rotation, hip rotation, X-Factor, stretch X-Factor) that affect the club head speed at ball contact in elite golfers. To build the upper body segment model were used spots and their position during the measurement was scanned by 3D kinematic analyzer CODA Motion System. To determine the interindividual stability of performance the coefficient of variation was used and for statistical analysis of the relationship between kinematic and temporal parameters and the club head speed at ball contact the Pearson's correlation coefficient was used. We found a high interindividual stability in maximized shoulders rotation and club head speed at ball contact parameters. When analyzing relationship between the club head speed at ball contact and the observed kinematic parameters of the movement of the upper body only a high relationship with the stretch X-factor parameter was found.

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Il’íchev, A. T., V. A. Shargatov, and Y. B. Fu. "Characterization and dynamical stability of fully nonlinear strain solitary waves in a fluid-filled hyperelastic membrane tube." Acta Mechanica 231, no. 10 (July 8, 2020): 4095–110. http://dx.doi.org/10.1007/s00707-020-02754-z.

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Abstract We first characterize strain solitary waves propagating in a fluid-filled membrane tube when the fluid is stationary prior to wave propagation and the tube is also subjected to a finite stretch. We consider the parameter regime where all traveling waves admitted by the linearized governing equations have nonzero speed. Solitary waves are viewed as waves of finite amplitude that bifurcate from the quiescent state of the system with the wave speed playing the role of the bifurcation parameter. Evolution of the bifurcation diagram with respect to the pre-stretch is clarified. We then study the stability of solitary waves for a representative case that is likely of most interest in applications, the case in which solitary waves exist with speed c lying in the interval $$[0, c_1)$$ [ 0 , c 1 ) where $$c_1$$ c 1 is the bifurcation value of c, and the wave amplitude is a decreasing function of speed. It is shown that there exists an intermediate value $$c_0$$ c 0 in the above interval such that solitary waves are spectrally stable if their speed is greater than $$c_0$$ c 0 and unstable otherwise.

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Herzog, W., and T. R. Leonard. "Force enhancement following stretching of skeletal muscle." Journal of Experimental Biology 205, no. 9 (May 1, 2002): 1275–83. http://dx.doi.org/10.1242/jeb.205.9.1275.

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SUMMARY We investigated force enhancement following stretching in the in situ cat soleus muscle on the ascending and descending limb of the force-length relationship by varying the amount and speed of stretching and the frequency of activation (5 Hz, 30 Hz). There was a small but consistent(P<0.05) amount of force enhancement following muscle stretching on the ascending limb of the force—length relationship for both stimulation frequencies. The steady-state active isometric forces following stretches of 9 mm on the descending limb of the force—length relationship were always equal to or greater than the corresponding forces from the purely isometric contractions at the length at which the stretch was started. Therefore, force production for these trials showed positive stiffness and was associated with stable behavior. Following active stretching of cat soleus on the descending limb of the force—length relationship,the passive forces at the end of the test were significantly greater than the corresponding passive forces for purely isometric contractions, or the passive forces following stretching of the passive muscle. This passive force enhancement following active stretching increased with increasing magnitude of stretch, was not associated with structural damage, and only disappeared once the muscle was shortened. For stretches of 6 mm and 9 mm, the passive force enhancement accounted for more than 50 % of the total force enhancement,reaching a peak contribution of 83.7 % for the stretches of 9 mm at a speed of 3 mm s-1. The results of this study suggest that a passive structural element provides a great part of the force enhancement on the descending limb of the force—length relationship of the cat soleus. Furthermore, the results indicate that mechanisms other than sarcomere length non-uniformity alone are operative.

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Shivananda, P., and Sangram Kumar Khatua. "Study on International Road Roughness index (IRI) using Smart phone application from REVA University to Kodigehalli gate, Bangalore, India." IOP Conference Series: Materials Science and Engineering 1255, no. 1 (September 1, 2022): 012020. http://dx.doi.org/10.1088/1757-899x/1255/1/012020.

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Abstract International Roughness Index (IRI) is one of the most widely used indices to determine the roughness of different road surface. Roughness index helps in identifying the quality of the road surface and suggest improvement measures. In this paper Roughness index values are measured from REVA University to Kodigehalli Gate. International Roughness Index are measured using mobile application. IRI value depends on vehicle speed and road. Roughness indicates the present road condition and helps in making decision related to management and maintenance of different types of roads. Based on Carbin app [1] results road user can identify 1) Safety, 2) Traffic, 3) Comfort of driving, 4) Fuel Consumption, 5) Quality of Air and 6) Road condition. Carbin application is used to collect Road quality, Speed, CO2 savings. In the study stretch Maximum value of IRI = 5.6m/km obtained from Bagalur cross to on BSF Cross and this stretch road user face all the above 6 problems. Minimum value of IRI= 2.44m/km obtained from Kodigehalli Cross to Bagalur cross (Airport Road-NH), the road is recently maintained by overlaying, in this stretch, road users comfortably use this stretch of road with respect above 6 aspects. As per the IRI value, new roads to be constructed to get IRI<1.2 m/km, once it reaches IRI=4 m/km road need to be maintained to get IRI < 2.2 m/km.

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Luca, Mario De, and Gianluca Dell’Acqua. "FREEWAY SAFETY MANAGEMENT: CASE STUDIES IN ITALY." TRANSPORT 27, no. 3 (September 19, 2012): 320–26. http://dx.doi.org/10.3846/16484142.2012.724447.

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Road safety has since become one of the major factors for a description of the state traffic system and crashes are often due to bad made decisions by drivers in environments created by engineers. This study proposes an update of the previous version (Dell'Acqua et al. 2011a) to estimate V 85, for non-conditioned traffic flows on freeways. The databases used in the study come from a series of speed measurements and vehicle ranges on a stretch of freeway using a fixed measuring system. The produced model proved to be very reliable, with the greatest error in the estimation of V 85, being less than 6%. The model obtained was then applied to a stretch of freeway of approximately 20 km. Some significant correlations between DV 85 (variation of V 85 among successive stretches) and DN (the variation in the number of crashes among successive stretches) were found, which may be very useful in the management of safety on roads. In particular the obtained results have highlighted some aspects of motorway traffic. In addition, using the procedure illustrated, it has been possible to identify some particular ‘black spots’ due to the poor design co-ordination of the alignment, positioned between consecutive stretches (for approximately 2 km), with a difference in terms of V 85average greater than 10 km/h.

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Grigoras, Cosmin Constantin, Valentin Zichil, Catalin Drob, and Vlad Andrei Ciubotariu. "ANALYSIS OF THE STATISTICAL DATA GENERATED BY AN ADAPTIVE STRETCH FORMING PROCESS." International Journal of Modern Manufacturing Technologies 14, no. 3 (December 20, 2022): 70–75. http://dx.doi.org/10.54684/ijmmt.2022.14.3.70.

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: Constant industrial processes improvements represent a fundamental step in the evolution of efficient processing. Due to physical or financial limits, there is a limit to how the mechanical or electronic side can be optimised. A solution for improving industrial processes can come in the form of complex machine algorithms that analyse the process in real-time and decide, with each step, what is optimal. To put this statement into practise, we have designed and implemented a fully operational self-adaptive stretch forming process controlled with the help of a dedicated statistical analysis algorithm. The foundation of the algorithm lies in the deformation theory of metals. In its simplest form, it can be summarised that if a sheet of metal is stretched, its length will increase as the force acting upon it increases until the ultimate tensile strength limit is reached; after this limit, failure occurs. Therefore, the algorithm analyses the material strain controlling the bi-axial nature of the stretch forming process by constantly adjusting for axial force and die speed. It does this through complex computer-vision image analysis techniques for strain measurement and stretching pressure readings as input data. The readings are analysed using the ANOVA method, providing R-squared and p-values for stretching pressure and die speed. The decisions that the algorithm takes are based on the statistical analysis of its previous decision, aiming to improve the overall process R-squared. The overall results are validated by measuring the obtained stretched parts’ deviation to the die shape. Therefore, the measurements were taken using a GOM 3D measuring system. This paper aims to explain the methodology of the algorithm using how the measurements are taken, how the statical analysis generated decisions for controlling the industrial equipment, and to analyse the statistical data generated by the self-adaptive stretch forming algorithm for the experimental study by comparing the decision it takes for each for the 20 processed 1050 aluminium alloys blanks. The results indicate the ideal succession of decisions and which path should be taken to improve the decision-making for both elastic and plastic domains.

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Yang, Lei, Hui Chen, Jun Ma, Qian Zhu, Tong Yang, and Hongbo Xie. "Photonic Time-Stretch Technology with Prismatic Pulse Dispersion towards Fast Real-Time Measurements." Photonics 6, no. 3 (September 9, 2019): 99. http://dx.doi.org/10.3390/photonics6030099.

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Photonic time-stretch (PTS) technology enables revolutionary technical breakthroughs in ultrafast electronic and optical systems. By means of employing large chromatic dispersion to map the spectrum of an ultrashort optical pulse into a stretched time-domain waveform (namely, using the dispersive Fourier transformation), PTS overcomes the fundamental speed limitations of conventional techniques. The chromatic dispersion utilized in PTS can be implemented using multiple optical prism arrays, which have the particular advantages of low loss in the extended spectrum outside of the specific telecommunication band, flexibility, and cost-effectiveness. In this article, we propose and demonstrate the PTS technology established for a pair of prisms, which works as a data acquisition approach in ultrafast digitizing, imaging, and measurement regimes.

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Mogahzy, Yehia E. El, and Warren S. Perkins. "Effect of Creep-Related Overdrying in Sizing on Warp Characteristics and Weaving Performance." Textile Research Journal 62, no. 6 (June 1992): 317–24. http://dx.doi.org/10.1177/004051759206200602.

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Effects of creep-related overdrying during sizing on warp characteristics and weaving performance have been studied for a particular warp. During sizing, parameters such as moisture regain, warp stretch, and lease tension were monitored on a yard-to-yard basis at both normal and creep speeds. Yarn type and sizing agent were kept constant. Optimum levels of squeeze role pressure at both normal and creep speeds were determined before investigating the effect of overdrying on weaving performance. The results indicated that there is a critical pressure/speed combination at which yarn characteristics are optimum. The benefits of optimization were limited, however, by the effect of creep speed on the abrasion resistance of yarn. The effect of creep-related overdrying on weaving performance was determined by measuring the frequency of occurrence of warp breakage in both creep and normally sized warps. The rate of warp breakage during weaving was much higher in regions sized at creep speed than at normal speed. Size film degradation and deterioration of warp characteristics were believed to cause the poor weaving performance of creep regions.

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Takagi, Mari, Takashi Kojima, Kei Ichikawa, Yoshiki Tanaka, Yukihito Kato, Rie Horai, Akeno Tamaoki, and Kazuo Ichikawa. "Comparison of Maximum Stretch Forces between Femtosecond Laser-Assisted Capsulotomy and Continuous Curvilinear Capsulorhexis." Journal of Ophthalmology 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/3489373.

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The current study reports comparing the postoperative mechanical properties of the anterior capsule between femtosecond laser capsulotomy (FLC) and continuous curvilinear capsulorhexis (CCC) of variable size and shape in porcine eyes. All CCCs were created using capsule forceps. Irregular or eccentric CCCs were also created to simulate real cataract surgery. For FLC, capsulotomies 5.3 mm in diameter were created using the LenSx® (Alcon) platform. Fresh porcine eyes were used in all experiments. The edges of the capsule openings were pulled at a constant speed using two L-shaped jigs. Stretch force and distance were recorded over time, and the maximum values in this regard were defined as those that were recorded when the capsule broke. There was no difference in maximum stretch force between CCC and FLC. There were no differences in circularity between FLC and same-sized CCC. However, same-sized CCC did show significantly higher maximum stretch forces than FLC. Teardrop-shaped CCC showed lower maximum stretch forces than same-sized CCC and FLC. Heart-shaped CCC showed lower maximum stretch forces than same-sized CCC. Conclusively, while capsule edge strength after CCC varied depending on size or irregularities, FLC had the advantage of stable maximum stretch forces.

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Han, Qi Gang, Qiang Zhang, Ming Zhe Li, Shi Zhong Su, Wen Ke Yang, Qing Chu Ban, and Ni Yan. "Design an Effective Solution for Stretch Forming of Sheet Metal with a Shorter Free Edge." Applied Mechanics and Materials 395-396 (September 2013): 941–44. http://dx.doi.org/10.4028/www.scientific.net/amm.395-396.941.

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To remove the disadvantage of conventional stretch forming machine (CSFM), a flexible stretch forming machine (FSFM) has been developed by authors recently. Based on finite element simulation and experiments, the advantages of FSFM have been detailed discussed. Our results indicated that the discrete multi-gripping jaws can swing and rotate in any direction automatically, which can solve the wasteful production of CSFM by increase the rate of materials utilization and close-fitting dies. Furthermore, the value of springback and thickness gradient in the parts formed by discrete multi-gripping jaws is smaller compare with that of integrally gripping jaws, which can help to achieve a high quality of stretch forming parts. A series of double-curved sheet panels have been formed by FSFM easily and used in the cabinet covers of high-speed train and the Dongdaemun Design Park building successfully. This work has a strong value in enhance the way to flexible and reproducible stretch forming technology.

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Moayedfar, M., Zulkiflle Leman, and B. T. Hang Tuah bin Baharudin. "Incremental Sheet Forming (ISF) of AISI 316 Stainless Steel Sheet Using CNC Milling Machine." Advanced Materials Research 939 (May 2014): 322–27. http://dx.doi.org/10.4028/www.scientific.net/amr.939.322.

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Incremental sheet forming (ISF) is a method to form a sheet metal into desired shape and surface features in a batch production series. This method includes forming a clamped sheet metal in controlled conditions by a CNC milling machine, lathe machine or a robot. In this study, the effects of forming parameters on the amount of stretch in stainless steel sheet using a CNC milling machine have been investigated. A ball-point shaped tool made of a bronze alloy was fabricated and used throughout the experiments. The tool acted as the indenter that formed the stainless steel sheet into a small pyramid-like shape. The results showed that as the spindle speed and feed rate increased, the amount of sheet stretch also increased, up to a point where the sheet could not stretch anymore and the process changed from forming to shear thinning and chipping. In addition, the surface quality of the part was badly affected at higher spindle speed and feed rate settings. The temperature of the lubrication oil was also measured during the process and the maximum temperature recorded was 45°C which remained constant until the end of the process. In conclusion, to obtain a good quality part while increasing the productivity of ISF, the optimized values of the feed rate and spindle speed in this work were found to be at 500 mm/min and 1000 rpm respectively.

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Wu, Fujia, Wenkai Liang, Zheng Chen, Yiguang Ju, and Chung K. Law. "Uncertainty in stretch extrapolation of laminar flame speed from expanding spherical flames." Proceedings of the Combustion Institute 35, no. 1 (2015): 663–70. http://dx.doi.org/10.1016/j.proci.2014.05.065.

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Huang, Xinsheng, Kazutaka Suzuki, and Yasumasa Chino. "Improvement of stretch formability of pure titanium sheet by differential speed rolling." Scripta Materialia 63, no. 5 (September 2010): 473–76. http://dx.doi.org/10.1016/j.scriptamat.2010.05.005.

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Chen, Jacqueline H., and Hong G. Im. "Correlation of flame speed with stretch in turbulent premixed methane/air flames." Symposium (International) on Combustion 27, no. 1 (January 1998): 819–26. http://dx.doi.org/10.1016/s0082-0784(98)80477-3.

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Oei, Hway-liem. "Automatic Speed Management in the Netherlands." Transportation Research Record: Journal of the Transportation Research Board 1560, no. 1 (January 1996): 57–64. http://dx.doi.org/10.1177/0361198196156000109.

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Speed warnings and enforcement can be administered locally on a road stretch, and on a road network. Local automatic speed warning at an urban intersection reduced the mean speed by 5 km/hr. Theoretically, a reduction in accidents of 25 to 65 percent can be achieved. At a rural intersection, the speed limit was reduced from 100 to 70 km/hr. An automatic sign warns speeding cars; this resulted in a lowering of the mean speed from around 80 to 63 km/hr. An automatic speed warning and enforcement system on two-lane rural road stretches where the speed limit is 80 km/hr resulted in a reduction of the mean speed from 78 to 73 km/hr; the percentage of speeders decreased from 40 to 10 percent. The total number of accidents was reduced by 35 percent. This effect was almost the same three years after concluding the experiment. The problem of vandalism could be diminished by mounting the camera on a high pole, mechanically preventing climbing of the pole, automatic detection of vandalism, and wireless communication to a nearby police station. Enforcement of speed on a provincial road network using radar and camera exclusively from a parked unmarked car was conducted in three provinces. A sign downstream of the enforcement site read “Your speed has been checked. Police.” Periodic information campaigns were conducted to increase awareness of the risk of being caught. The result was a reduction of average speed by 4 to 5 km/hr, although the percentage of speeders is still high a reduction from 40 to 30 percent. This type of enforcement is accepted by 75 percent of the drivers. Greater priority for speed enforcement is needed in addition to automating enforcement and processing to increase efficiency.

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NAKA, TETSUO, YASUHIDE NAKAYAMA, TAKESHI UEMORI, RYUTARO HINO, FUSAHITO YOSHIDA, MASAHIDE KOHZU, and KENJI HIGASHI. "FLD OF AZ31 SHEET UNDER WARM STRETCHING AND ITS PREDICTION." International Journal of Modern Physics B 22, no. 31n32 (December 30, 2008): 6010–15. http://dx.doi.org/10.1142/s0217979208051509.

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Forming Limit Diagrams (FLDs) of a magnesium alloy (AZ31) sheet at various forming speeds (3 to 300 mm·mm-1) at several temperatures of 100-250°C were investigated by performing a punch stretch-forming test. The forming limit strains increased with temperature rise and with decreasing forming speed, where the effect of forming speed was stronger at higher temperatures. To describe such a characteristic of FLD of AZ31, the Marciniak-Kucznski type forming limit analysis was conducted using the Backofen-type constitutive equation (c = Cεnεm). In this analysis, the damage evolution in the necking zone was taken into account based on Oyane's ductile fracture criterion. The numerical results of the FLD show a good agreement with the corresponding experimental observations.

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Bressel, Eadric, and Peter J. McNair. "The Effect of Prolonged Static and Cyclic Stretching on Ankle Joint Stiffness, Torque Relaxation, and Gait in People With Stroke." Physical Therapy 82, no. 9 (September 1, 2002): 880–87. http://dx.doi.org/10.1093/ptj/82.9.880.

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Abstract Background and Purpose. Continuous passive motion (cyclic stretching applied to the subject's limb) has been used for the rehabilitation of some orthopedic impairments; however, few researchers have considered its application in the management of neurological disorders such as stroke. The purpose of this study was to examine the short-term effects of prolonged static and cyclic calf stretching on passive ankle joint stiffness, torque relaxation, and gait in people with ischemic stroke. Subjects. Ten community-dwelling people (mean age=64.6 years, SD=8.76, range=53–76) who were diagnosed with a cerebrovascular accident volunteered to be subjects. Methods. Participants engaged in one 30-minute static stretch and one 30-minute cyclic stretch of the calf muscle, using an isokinetic dynamometer that also collected torque and angle measurements. Before and after treatments, 10-m walking times were collected. Ankle joint stiffness was calculated from the slope of the torque and angle curves before and immediately after treatments, and torque relaxation was calculated as the percentage of decrease in peak passive torque over the 30-minute stretch durations. Results. Ankle joint stiffness decreased by 35% and 30% after the static and cyclic stretches, respectively. Stiffness values and 10-m walk times were not different between conditions. The amount of torque relaxation was 53% greater for static stretching than for cyclic stretching. Discussion and Conclusion. These preliminary data from a very small sample of people with stroke indicate that ankle joint stiffness decreases after both prolonged static and cyclic stretches; however, neither technique appears to be better at reducing stiffness in people with stroke. Torque relaxation is greater after static stretching than after cyclic stretching, and walking speed does not appear to be influenced by the stretching treatments used in our study.

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Journal articles on the topic 'Stretch speed'

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