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Journal articles on the topic 'Variable pitch spring'
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1
Qiu, Donghai, Manuel Paredes, and Sébastien Seguy. "Variable pitch spring for nonlinear energy sink: Application to passive vibration control." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, no. 2 (2018): 611–22. http://dx.doi.org/10.1177/0954406218761485.
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This paper aims to propose a generalized methodology for designing a novel nonlinear energy sink with variable pitch springs. To this end, a generic model of the nonlinear energy sink system providing the nonlinearity of pure cubic stiffness is introduced. Key features of the model include: (i) specifically sizing two variable pitch springs to provide the force polynomial components with only linear and cubic terms; (ii) pre-compressing two springs at the transition point to produce smooth nonlinear force characteristics; (iii) adding a negative stiffness mechanism to counterbalance the linear term. To generate the variable pitch spring, design parametrization is implemented. The type of shape and the pitch distribution adopted for the spring are shown to fit the objective force–displacement function well. To validate the concept, a special sized nonlinear energy sink system is developed. Identification of the force–displacement relation and experiments for the whole system embedded on an electrodynamic shaker are studied. The results show that this nonlinear energy sink can not only output the anticipated nonlinearity, but can also produce energy pumping to protect the primary system in a large band of frequencies, thus making it practical for the application of passive vibration control.
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Lin, Yuyi, and Albert P. Pisano. "General Dynamic Equations of Helical Springs With Static Solution and Experimental Verification." Journal of Applied Mechanics 54, no. 4 (1987): 910–17. http://dx.doi.org/10.1115/1.3173138.
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The general dynamic equations of helical compression springs with circular wire cross section, variable pitch angle, and variable helix radius are derived. The equations are formulated by Hamilton’s principle and a variational method. In contrast to previous studies, the effects of coil flexure bending, variable pitch angle and variable helix radius are taken into account. The general equations are shown to agree with dynamic equations found in literature when the general equations are reduced to simplified forms. For a specific helical spring and static loading, the equations are solved with both the predicted radial expansion and the predicted longitudinal spring compression force in excellent agreement with experimental data.
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Lin, Yuyi, and Albert P. Pisano. "The Differential Geometry of the General Helix as Applied to Mechanical Springs." Journal of Applied Mechanics 55, no. 4 (1988): 831–36. http://dx.doi.org/10.1115/1.3173729.
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In order to improve the performance of helical springs, such as increasing the fatigue life and suppressing resonance, variable pitch angle and variable helix radius may be incorporated into the helical spring geometry. Employing the tool of differential geometry, new and complete formulae of curvature, torsion, and spring force are derived. It is shown that these formulae are more general and accurate than Kelvin’s curvature and torsion formulae, than commonly used force formulae (Wahl, 1963). Possible simplifications to the complete formulae and the corresponding errors introduced are both discussed and compared with experimental data.
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Ji, Jie, Yun Wu Li, and Jin Dou Zhao. "Reverse Analysis for Determining the Stiffness Characteristics of Suspension Spring with Variable Pitch and Wire Diameter." Advanced Materials Research 421 (December 2011): 783–87. http://dx.doi.org/10.4028/www.scientific.net/amr.421.783.
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A reverse analysis method for determining the stiffness characteristics of nonlinear suspension spring with variable pitch and wire diameter is developed by introducing the ideas of dispersion. Meanwhile, the reverse analysis of a nonlinear suspension spring used in truck is completed as an example, and the progressive force-displacement curves obtained by theoretical and experimental analysis are compared in order to verify the validity of the reverse analysis method used for nonlinear suspension spring.
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Adamchuk, V., V. Bulgakov, I. Holovach, and Z. Ruzhylo. "Theoretical studies of oscillations of the cleaning working bodies spiral potato separator." Mehanization and electrification of agricultural, no. 10(109) (2019): 11–22. http://dx.doi.org/10.37204/0131-2189-2019-10-1.
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Purpose. Increase of efficiency of potato tubers cleaning process from impurities of new construction of spiral separator taking into account and activation of vibrating process of its cleaning spiral springs. Methods. The research was carried out with the use of higher mathematics, theoretical mechanics, elasticity theory and methods of programming and numerical calculations with the help of PC. Results. For the developed construction of the spiral separator of potato heap, which consists of cantilever mounted cleaning spiral springs, the mathematical model of free ends of spiral oscillations under the influence of external load is developed. An equivalent bending scheme of the cantilever spiral under the action of uniformly distributed load, selected corresponding axes of coordinates and parameters characterizing the vibrational process of the spiral end are determined. For such an equivalent scheme, a differential equation of cleaning spiral oscillations in partial derivatives is made for the first time. After the corresponding transformations, the differential equation was numerically solved according to the program, by means of a PC. This made it possible to find the dependence of the change in the winding pitch of the cleaning spiral spring as a result of its deformation, in particular, the simultaneous longitudinal stretching and transverse deflection, on its length. Also new analytical dependences of the reduced moment of inertia of the section of the cantilever spring are received, on the basis of which graphic dependences of change of its value on length of a spiral spring at the set diameter, pitch of skills, angle of rise of a coil and angular speed of rotation have been received on the PC. Conclusions 1.The calculated mathematical model of vibrations of the working bodies of the spiral separator of potato heap is constructed, as a result the differential equation of transverse bending vibrations of its console cleaning spiral spring is made. 2.On the basis of the differential equation solution of transverse bending oscillations of the cleaning spiral spring the analytical expressions describing the law of vibrational process and deflection of the spiral spring at any moment of time for any point of its longitudinal axis are received. 3.Analytical dependencies are obtained to determine the variable pitch of a curved coil spring at any given time and for any inter-turn lumen during this oscillatory process. 4.At the angular velocity of the spiral spring, which is equal to ω = 30 rad∙s-1, the density of the material of which the spring is made, = 7700 kg∙m-3, modulus of elasticity Е = 2∙1011 Pa, the radius of the bar = 8.5 mm, uniformly distributed spiral spring load by potato heap intensity 1000 Н∙m-1 the total spring deflection along its length varies from 0 to 0.25 m. 5.The obtained analytical expressions of restriction on the maximum change of the cleaning spiral spring pitch at its fluctuations from the condition that potato tubers do not fall into the spring inter-turn space taking into account structural and kinematic parameters of the cleaning spiral spring, the material from which it is made, technological modes of operation and tubers' sizes. 6.As the numerical calculations on the PC show, a cleaning spiral spring with the above parameters and an initial winding pitch S = 48 mm at the considered transverse oscillations at the expense of deformation can change a step up to 54 mm that will provide not falling out of a potato tuber outside of a separator of a potato heap. Keywords: potatoes, digging, impurities, cantilever spiral spring, oscillations, differential equation, numerical calculations on PC.
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Yigit, Cihat Bora, and Pinar Boyraz. "Design and Modelling of a Cable-Driven Parallel-Series Hybrid Variable Stiffness Joint Mechanism for Robotics." Mechanical Sciences 8, no. 1 (2017): 65–77. http://dx.doi.org/10.5194/ms-8-65-2017.
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Abstract. The robotics, particularly the humanoid research field, needs new mechanisms to meet the criteria enforced by compliance, workspace requirements, motion profile characteristics and variable stiffness using lightweight but robust designs. The mechanism proposed herein is a solution to this problem by a parallel-series hybrid mechanism. The parallel term comes from two cable-driven plates supported by a compression spring in between. Furthermore, there is a two-part concentric shaft, passing through both plates connected by a universal joint. Because of the kinematic constraints of the universal joint, the mechanism can be considered as a serial chain. The mechanism has 4 degrees of freedom (DOF) which are pitch, roll, yaw motions and translational movement in z axis for stiffness adjustment. The kinematic model is obtained to define the workspace. The helical spring is analysed by using Castigliano's Theorem and the behaviour of bending and compression characteristics are presented which are validated by using finite element analysis (FEA). Hence, the dynamic model of the mechanism is derived depending on the spring reaction forces and moments. The motion experiments are performed to validate both kinematic and dynamic models. As a result, the proposed mechanism has a potential use in robotics especially in humanoid robot joints, considering the requirements of this robotic field.
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Zhang, Jian, Zhaohui Qi, Gang Wang, and Shudong Guo. "High-Efficiency Dynamic Modeling of a Helical Spring Element Based on the Geometrically Exact Beam Theory." Shock and Vibration 2020 (June 19, 2020): 1–14. http://dx.doi.org/10.1155/2020/8254606.
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This paper presents a modeling study of the dynamics of a helical spring element with variable pitch and radius considering both the static stiffness and dynamic response by using the geometrically exact beam theory. The geometrically exact beam theory based on the Euler–Bernoulli beam hypothesis is described, of which the shear deformations are ignored. Unlike the traditional spliced curved beam element method, the helical spring element is described with curvature vector and axial strain by establishing and spline-interpolating a function of the radius, the height, the polar angle, and the torsion angle of the whole spring. In addition, a model smoothing method is developed and applied in the numerical analysis to filter the high-frequency oscillation component of the flexible multibody systems, so as to correct the system dynamic equations and improve the calculation efficiency when solving the static equilibrium of the spring. This study also carries out five numerical trials to validate the above dynamic procedure of the helical spring element. The example of the spring static stiffness design shows that the proposed helical spring procedure enables one to deal with practical engineering applications.
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Orlowski, Kazimierz A., Michal Dobrzynski, Grzegorz Gajowiec, Marcin Lackowski, and Tomasz Ochrymiuk. "A Critical Reanalysis of Uncontrollable Washboarding Phenomenon in Metal Band Sawing." Materials 13, no. 20 (2020): 4472. http://dx.doi.org/10.3390/ma13204472.
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The article analyzes the cutting process of hard bars. Investigations conducted in industrial conditions demonstrated the presence of surface errors in the machined workpieces in the form of washboard patterns. The purpose of this study was to analyze the results of cutting on band sawing machines with different band saw blades. The cutting processes were conducted on three different horizontal band sawing machine types. Analyzed material was an alloy steel Ø40 mm rod with a hardened surface covered with a thin layer of chromium. The hardness of the outer layer was 547 HV with a core hardness of 180 HV. The surface topography measurements of the processed workpieces were carried out with the 3D Optical Profiler, which supplied information on the irregularities of the processed material texture. In each of the analyzed cases, a corrugated surface was obtained after sawing, which is the effect of the occurrence of the washboarding phenomenon, despite the fact that the teeth of each band saw had variable pitches. The washboarding phenomenon when cutting rods with hard surfaces is caused by the phenomenon of wave regeneration. Despite the use of variable pitch saw blades, the cutting process results in rippling of the sawn surface, which is caused by the high hardness of the outer layer of the workpiece, as well as by the type of tool with spring setting of teeth.
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Kwon, H. D., and M. Burdekin. "Measurement and diagnostics of machine tool errors during circular contouring motions." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 212, no. 5 (1998): 343–56. http://dx.doi.org/10.1243/0954405981515950.
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This paper deals with the measurement and diagnosis of the machine tool errors by application of the ball link bar system. It includes the development of a new link bar, the in-plane and out-of-plane measurement techniques and the machine error analysis system. The new type of ball link incorporates an idealized three-point kinematic contact principle between the balls and sockets of the link bar, and provides the following features: (a) the minimum length of the link corresponds to the minimum length of a standard LVDT transducer, (b) the link is of light weight, (c) the accuracy and the repeatability of the link corresponds to that of the LVDT (linear variable differential transformer) transducer and (d) the link is mounted between two reference balls by using the spring force of the LVDT transducer and thereby eliminating the need for magnets as in the case of the conventional double-ball bar. With the in-plane and out-of-plane measurements under different test conditions, the machine errors, such as set-up errors, closing errors, backlash errors, dynamic backlash errors, positional errors, pitch motion errors, transient errors around the start point of the test path, vibration due to too high a gain setting, stick-slip errors, squareness errors and servo mis-match errors, can be analysed by the application of the machine error analysis software. Practical measurements on the TAKISAWA CNC (computerized numerical control) machining centre were carried out and the machine tool errors were effectively evaluated.
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Kim, HyungTae, CheolHo Kim, SungBok Kang, KangWon Lee, JaeHo Baek, and HyunHee Han. "A 3 DOF Model for an Electromagnetic Air Mount." Advances in Acoustics and Vibration 2012 (January 18, 2012): 1–6. http://dx.doi.org/10.1155/2012/218429.
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A matrix model with three degrees of freedom is proposed as a means for controlling microvibrations and applied to an electromagnetic isolator. The model was derived from an assumption based on small- and low-frequency vibrations. The coordinates of the 3 DOF was composed of the 4 variables, representing a vertical position, pitch, roll, and a proof term. The coordinates were calculated from the 4 position sensors in the isolator and formulated into a matrix, which possesses inversive full rank. The electro-magnetic isolator was built for a simulated machine in semiconductor manufacturing and consisted of a heavy surface plate, sensors, amps, a controller, and air springs with electromagnets. The electromagnets are installed in a pneumatic chamber of the individual air spring. The performance of the 3 DOF model was experimented and compared with that of a 1 DOF model in an impact test. The settling time in the result was reduced to 25%.
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Ihsan, S. I., M. Ahmadian, Waleed F. Faris, and E. D. Blancard. "Ride Performance Analysis of Half-Car Model for Semi-Active System Using RMS as Performance Criteria." Shock and Vibration 16, no. 6 (2009): 593–605. http://dx.doi.org/10.1155/2009/607871.
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The work aims to study the root mean square (RMS) responses to acceleration input for four state variables: the msvertical acceleration, the mspitch angular acceleration and the front and rear deflections of the suspensions. A half-car two degree-of-freedom model of semi-active control scheme is analyzed and compared with the conventional passive suspension system. Frequency response of the transfer function for the heave, pitch of the sprung mass and suspension deflections are initially compared and then mean square analysis is utilized to see the effect of semi-active scheme. Results indicate that significant improvements were achieved in the sprung mass heave and pitch responses using semi-active control scheme. However results for the rear and front suspension deflection show that there are limiting values of damping coefficient beyond which, the semi-active scheme becomes disadvantageous than the passive system.
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Castagna, Carlo, Stefano D’Ottavio, Paolo Roberto Gabrielli, and Susana Póvoas. "Sprint Endurance Abilities in Elite Female Soccer Players." International Journal of Sports Physiology and Performance 15, no. 8 (2020): 1168–74. http://dx.doi.org/10.1123/ijspp.2019-0526.
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Purpose: To profile sprint endurance performance of elite-level female soccer players. Methods: Twenty-five female national-team soccer players (age 25.1 [2.7] y, body mass 59.6 [3.6] kg, height 168.5 [4.1] cm) were tested for sprint endurance, performing 5 maximal sprints, interspersed with 30 seconds of active recovery (5 × 30 m) and a 30-second all-out shuttle run in a soccer pitch. The Yo-Yo Intermittent Recovery Test level 1 (YYIR1) evaluated intermittent high-intensity endurance under the same field-testing conditions. Maximal anaerobic capacity was assessed while participants performed three 10-second all-out bouts separated by 20 seconds of passive recovery (3 × 10 s) on a nonmotorized treadmill. Results: Huge interplayer variability was observed for sprint decrements in 3 × 10 seconds (coefficient of variation = 37%) and 5 × 30 m (coefficient of variation = 62%). The 3 × 10 performance was largely associated with 5 × 30-m mean and best time and very largely with 30 seconds. A very large and nearly perfect correlation was observed between 30 seconds and 5 × 30 mMean (r = −.86) and 5 × 30 mBest (r = −.92), respectively. The YYIR1 was moderately to largely associated with 5 × 30-m variables and 30 seconds, respectively. A nearly perfect association was observed between 5 × 30 mBest and 5 × 30 mMean (r = .97). Conclusions: Elite female soccer players’ sprint endurance variables are characterized by remarkable variability. Associations between sprint endurance variables suggest physiological interdependence and a likelihood of a general ability in sustaining sprinting in this population.
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Salman, M. A., A. Y. Lee, and N. M. Boustany. "Reduced Order Design of Active Suspension Control." Journal of Dynamic Systems, Measurement, and Control 112, no. 4 (1990): 604–10. http://dx.doi.org/10.1115/1.2896185.
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The presence of fast and slow modes in suspension systems is utilized in the design of two reduced-order active suspension control strategies. The first strategy is obtained by combining the solutions of slow and fast control sub-problems. The second strategy is based on a two-level hierarchical control design. The local level requires measurements of local fast variables, namely the unsprung mass velocities. The coordinating level relies on measurements of slow variables, namely, suspension deflections, sprung mass velocity, and mass pitch rate. Neither strategy requires tire deflection measurements. In spite of their simplified structure, simulation results indicate that their performance is comparable to that of the full-state feedback design.
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Fujita, Koji, and Hiroki Nagai. "Robustness analysis on aerial deployment motion of a Mars aircraft using multibody dynamics simulation: effects of wing-unfolding torque and timing." Aeronautical Journal 121, no. 1238 (2017): 449–68. http://dx.doi.org/10.1017/aer.2016.123.
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ABSTRACTThis paper investigates the effects of the design variables of an aerial deployment mechanism on the robustness of the aerial deployment through a multibody dynamics simulation. The aircraft is modelled as three joined rigid bodies: a right wing, a left wing and a centre body. A spring-loaded hinge is adopted as an actuator for deployment. The design variables are the hinge torque and the deployment timing. The robustness is evaluated using a sigma level method. The margins for the safe deployment conditions are set for the evaluation functions. The dispersive input variables are the initial drop velocity, the surrounding gust velocity, the initial pitch angle and the initial height. The design point with a deployment torque scale valueFof 0.7 and a right-wing deployment delay timeTSRof 1.0 s can safely deploy in the low-torque deployment condition. This design point is able to accomplish both a safe deployment and a lightweight deployment mechanism.
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Chen, Hui, and Wuyin Jin. "Dynamic Response of a Semiactive Suspension System with Hysteretic Nonlinear Energy Sink Based on Random Excitation by means of Computer Simulation." Complexity 2020 (September 17, 2020): 1–13. http://dx.doi.org/10.1155/2020/3181423.
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This paper aims to investigate the property and behavior of the hysteretic nonlinear energy sink (HNES) coupled to a half vehicle system which is a nine-degree-of-freedom, nonlinear, and semiactive suspension system in order to improve the ride comfort and increase the stability in shock mitigation by using the computer simulation method. The HNES model is a semiactive suspension device, which comprises the famous Bouc–Wen (B-W) model employed to describe the force produced by both the purely hysteretic spring and linear elastic spring of potentially negative stiffness connected in parallel, for the half vehicle system. Nine nonlinear motion equations of the half vehicle system are derived in terms of the seven displacements and the two dimensionless hysteretic variables, which are integrated numerically by employing the direct time integration method for studying both the variables of vertical displacements, velocities, accelerations, chassis pitch angle, and the ride comfort and driver safety, respectively, based on the bump and random road inputs of the pseudoexcitation method as excitation signal. Simulation results show that, compared with the HNES model and the magnetorheological (MR) model coupled to the half vehicle system, the ride comfort and stability have been evidently improved. A successful validation process has been performed, which indicated that both the ride comfort and driver safety properties of the HNES model coupled to half vehicle significantly improved.
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Chiang, K. N., C. W. Chang, and C. T. Lin. "Process Modeling and Thermal/Mechanical Behavior of ACA/ACF Type Flip-Chip Packages." Journal of Electronic Packaging 123, no. 4 (2001): 331–37. http://dx.doi.org/10.1115/1.1389847.
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Development of flip-chip-on-glass (FCOG) assembly technology using anisotropic conductive adhesive/film (ACA/ACF) is currently underway to achieve fine pitch interconnections between driver IC and flat panel display. Conductive adhesives are characterized by fine-pitch capability and more environment compatibility. Anisotropic conductive adhesive/film (ACA/ACF) is composed of an adhesive resin and conductive particles, such as metallic or metal-coated polymer particles. In contrast to a solder type flip chip interconnection, the electric current passing through conductive particles becomes the dominant conduction paths. The interconnection between the particles and the conductive surfaces is constructed by the elastic/plastic deformation of conductive particles with contact pressure, which is maintained by tensile stress in the adhesive. Although loss of electric contact can occur when the adhesive expands or swells in the Z- axis direction, delamination and cracking can occur in the adhesive layer while the tensile stress is excessive. In addition to performing processing simulations as well as reliability modeling, this research investigates the contact force that is developed and relaxed within the interconnection during the process sequence by using nonlinear finite element simulations. Environmental effects, such as high temperature and thermal loading, are also discussed. Moreover, a parametric study is performed for process design. To improve performance and reliability, variables such as ACF materials, proper processing conditions are discussed as well. Furthermore, this study presents a novel method called equivalent spring method, capable of significantly reducing the analysis CPU time and make process modeling and contact analysis of the 3D ACA/ACF process possible.
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Mello, Júlio Brugnara, Gabriel Alberto Kunst Nagorny, Marcelo De Castro Haiachi, Anelise Reis Gaya, and Adroaldo Cezar Araujo Gaya. "Projeto Esporte Brasil: perfil da aptidão física relacionada ao desempenho esportivo de crianças e adolescentes." Brazilian Journal of Kinanthropometry and Human Performance 18, no. 6 (2016): 658. http://dx.doi.org/10.5007/1980-0037.2016v18n6p658.
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DOI: http://dx.doi.org/10.5007/1980-0037.2016v18n6p658 The aim of this study was to outline the physical fitness profile related to sport performance of Brazilian children and adolescents, stratified by sex. This is a descriptive cross-sectional study and information was obtained from the Projeto Esporte Brasil (PROESP-Br). The sample consisted of 8,750 voluntary subjects aged 7-17 years evaluated in the period between 2013 and 2015. The following variables were evaluated: lower limb strength (LLS) through the horizontal jump test and upper limb strength (ULS) through mediceball pitch, speed through the 20-meter sprint test and agility through the square test. Variables were classified with PROESP-Br criteria. For data processing, means, standard deviations, absolute and relative frequencies and confidence intervals were used. The results for boys have shown that the “poor” category had the highest prevalence: LLS (40.2%), ULS (29.7%), speed (41.4%) and agility (37.5%). The “excellent” category, as expected, had the lowest prevalence: LLS (3.7%), ULS (4.9%), speed (2.0%) and speed (3.5%). The results for girls were similar to those of boys, where the “poor” category had the highest prevalence: LLS (43.7%), ULS (36.8%), speed (43.8%) and agility (41.0 %). The “excellent” category also had the lowest prevalence: LLS (4.2%), ULS (4.3%), speed (1.6%) and speed (3.1%). The results indicated that the majority of Brazilian children and adolescents have physical fitness related to sport performance. Among variables analyzed, LLS for girls and speed for boys were the components with the most unfavorable results.
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Kunas, Grace, Huong Do, Amiethab Aiyer, Jonathan Deland, and Scott Ellis. "The Contribution of Medial Cuneiform Osteotomy to Correction of Longitudinal Arch Collapse in Stage IIb Adult Acquired Flatfoot Deformity." Foot & Ankle Orthopaedics 3, no. 3 (2018): 2473011418S0029. http://dx.doi.org/10.1177/2473011418s00298.
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Category: Midfoot/Forefoot Introduction/Purpose: Residual forefoot supination present after correcting the hindfoot in Stage IIb adult acquired flatfoot deformity (AAFD) can be addressed with a dorsal opening wedge medial cuneiform (Cotton) osteotomy. The amount of correction is generally judged clinically and there currently are no preoperative guides that can predict the size of graft needed. The aim of this study was to evaluate the relationship between the Cotton osteotomy graft size and other accessory flatfoot reconstructive procedures, and the amount of correction of longitudinal arch collapse. We hypothesized that correction of longitudinal arch collapse, as measured by the cuneiform articular angle (CAA), would primarily be influenced by the Cotton osteotomy performed. More specifically, we hypothesized that the size of the graft would have the largest effect on the CAA. Methods: Seventy-nine feet in 74 patients undergoing Cotton osteotomy as part of flatfoot reconstruction were reviewed retrospectively. Preoperative and minimum 40-week postoperative lateral weightbearing foot radiographs were compared to assess correction of longitudinal arch collapse as measured by 13 radiographic parameters, with particular emphasis on the CAA. Additional demographic and intraoperative variables analyzed for association with radiographic change included age, gender, body mass index (BMI), amounts and graft types of Cotton osteotomy and lateral column lengthening (LCL), and amount of medializing calcaneal osteotomy (MCO). Other concomitant procedures at the time of surgery, namely Achilles lengthening, flexor digitorum longus (FDL) transfer, spring ligament reconstruction, gastrocnemius recession, and excision of accessory navicular were also recorded. Ultimately, a multivariable linear regression model was developed to estimate the effect of Cotton osteotomy on change in the CAA, adjusting for patient and clinical variables. Results: Cotton osteotomy graft size was significantly associated with changes in the CAA (P < .001), calcaneal pitch (P = .03), lateral talo-navicular Cobb angle (P = .03), and lateral naviculo-medial cuneiform Cobb angle (P = .03). Multivariable linear regression models included age at surgery, gender, BMI, and the use of all concomitant procedures (LCL, Achilles lengthening, FDL transfer, gastrocnemius recession, and excision of accessory navicular) except for spring ligament reconstruction, since this was not associated with any of the four radiographic measurements. Cotton graft size was the only factor found to significantly predict a change in the CAA in the final linear regression model (P < .001, R2 = .27), with each millimeter of Cotton corresponding to a 2.1-degree decrease of the CAA (figure 1). Conclusion: Correction of longitudinal arch collapse, as measured by the CAA, was primarily influenced by graft size of the Cotton osteotomy in a linear fashion. The results also demonstrate that the procedure has a more distal effect in correction of longitudinal arch collapse and is of particular importance when the apex of deformity is at the medial cuneiform. Because the relationship between the Cotton osteotomy graft size and the CAA can be modeled linearly, we believe that preoperative measurement of the CAA can be a useful guide in helping surgeons to titrate the proper amount of longitudinal arch collapse correction intraoperatively.
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Siddharth, Dipender Yadav, and Surabhi Lata. "Design development and analysis of cylindrical spring with variable pitch for two wheelers." Materials Today: Proceedings, June 2021. http://dx.doi.org/10.1016/j.matpr.2021.06.130.
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Li, Ruihua. "Multi-objective optimization of the suspension parameters in the in-wheel electric vehicle." Journal of Computational Methods in Sciences and Engineering, March 18, 2021, 1–8. http://dx.doi.org/10.3233/jcm-204821.
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The hub motor significantly increases the unsprung mass of electric in-wheel vehicles, which deteriorates the ride comfort and safety of vehicles and which can be effectively improved by optimizing the main suspension parameters of vehicles reasonably, so a multi-objective optimization method of main suspension parameters based on adaptive particle swarm algorithm is proposed and the dynamic model of a half in-wheel electric vehicle is established. Taking the stiffness coefficient of the suspension damping spring and damping coefficient of the damper as independent variables, the vertical acceleration of the body, the pitch acceleration and the vertical impact force of the hub motor as optimization variables, and the dynamic deflection of the suspension and the dynamic load of the wheel as constraint variables, the multi-objective optimization function is constructed, and the parameters are simulated and optimized under the compound pavement. The simulation results show that the vertical acceleration and pitch acceleration are reduced by 20.2% and 18.4% respectively, the vertical impact force of the front hub motor is reduced by 3.7%, and the ride comfort and safety are significantly improved.