Search

Introduction/Purpose: Shoe longitudinal bending stiffness (LBS) is often considered to influence running economy (RE) and thus, running performance. However, previous results are mixed and LBS levels have not been studied in advanced footwear technology (AFT). The purpose of this study was to evaluate the effects of increased LBS from curved carbon fiber plates embedded within an AFT midsole compared to a traditional running shoe on RE and spatiotemporal parameters. Methods: Twenty‐one male trained runners completed three times 4 min at 13 km/h with two experimental shoe models with a curved carbon fiber plate embedded in an AFT midsole with different LBS values (Stiff: 35.5 N/mm and Stiffest: 43.1 N/mm), and a Control condition (no carbon fiber plate: 20.1 N/mm). We measured energy cost of running (W/kg) and spatiotemporal parameters in one visit. Results: RE improved for the Stiff shoe condition (15.71 ± 0.95 W/kg; p < 0.001; n2 = 0.374) compared to the Control condition (16.13 ± 1.08 W/kg; 2.56%) and Stiffest condition (16.03 ± 1.19 W/kg; 1.98%). However, we found no significant differences between the Stiffest and Control conditions. Moreover, there were no spatiotemporal differences between shoe conditions. Conclusion: Changes in LBS in AFT influences RE suggesting that moderately stiff shoes have the most effective LBS to improve RE in AFT compared to very stiff shoes and traditional, flexible shoe conditions while running at 13 km/h. [ABSTRACT FROM AUTHOR]

Background: Within the exploration of human gait, key focal points include the examination of functional rockers and the influential role of tendon behavior in the intricate stretch–shortening cycle. To date, the possible relationship between these two fundamental factors in the analysis of human gait has not been studied. Therefore, this study aimed to analyze the relationship between the morphology of the patellar and Achilles tendons and plantar fascia with respect to the duration of the rockers. Methods: Thirty-nine healthy men (age: 28.42 ± 6.97 years; height: 173 ± 7.17 cm; weight: 67.75 ± 9.43 kg) were included. Data of the rockers were recorded using a baropodometric platform while participants walked over a 10 m walkway at a comfortable velocity. Before the trials, the thickness and cross-sectional area were recorded for the patellar tendon, Achilles tendon and plantar fascia using ultrasound examination. The relationship between the morphology of the soft tissue and the duration of the rockers was determined using a pairwise mean comparison (t-test). Results: A significant difference was found for rocker 1 duration, where a longer duration was found in the group of subjects with thicker patellar tendons. Regarding the Achilles tendon and plantar fascia, no significant differences were observed in terms of tendon morphology. However, subjects with thicker Achilles tendons showed a longer duration of rocker 1. Conclusions: The findings underscore a compelling association, revealing that an increased thickness of the patellar tendon significantly contributes to the extension of rocker 1 duration during walking in healthy adults. [ABSTRACT FROM AUTHOR]

A device for processing the curvilinear grooves on a spherical surface is designed with builder mechanism made in the form of a spherical seven-link articulated mechanism with two degrees of freedom, in the output connecting rod of which a tool head is mounted with a multi-tooth cutting tool, rotating at a cutting speed around its axis passing in the center of the processed sphere, and describing the given locked trajectory with a feed rate at a rigidly fixed, processed spherical surface. The device allows to increase the maneuverability of the cutting tool relatively to the processed spherical surface. The dimensions of the links of the mechanism are determined, which allow the input links to obtain full rotation relatively to the stand. [ABSTRACT FROM AUTHOR]

The article discusses the innovative concept of the over-expanded thermodynamic cycle, the author of which is the Polish engineer-designer Mirosław Szymkowiak. This cycle is realized on the basis of a new and innovative, previously unknown design, of a piston-crankshaft linkage mechanism with the aid of an additional element known as a rocker arm. Additionally, the proposed mechanism allows for a smooth change of the compression/expansion ratio of the engine during its operation. In the beginning, the earlier conceptions of the rocker engine developed by Szymkowiak were presented, and then the main construction assumptions and kinematic calculations were described. It was confirmed, that the developed linkage has big potential in improving the engine's thermal efficiency by approximately 12% relative. Additionally, it significantly reduces the exhaust gas pressure, when the exhaust valve is opened, therefore, contributes to the reduction of the noise emitted by the engine. [ABSTRACT FROM AUTHOR]

For a chain transmission with a variable center distance, a formula is derived for the center distance. The center distance is plotted as a function of the angle of rotation and the length of the rocker. [ABSTRACT FROM AUTHOR]

B-pillar and rocker are the key force transmission sub-systems of the side impact of battery electric vehicle (BEV), and scholars have studied the side crashworthiness of these sub-systems and vehicle body a lot. However, these works are insufficient on the analysis of benchmarking vehicle models, the simulation and experiment of the B-pillar and rocker sub-systems, and the optimization of these sub-systems. To make up these shortcomings, this work aims to design the B-pillar and the rocker and improve the side crashworthiness of BEV. It presents a systematic method on the side crashworthiness of BEV. The dynamic bending performance of the B-pillar and the rocker are studied in simulation analyses and experiments. The materials, structures, and crashworthiness of these two sub-systems of eleven benchmark models are studied. Minimizing structural mass and cost as well as maximizing mean crushing force are performed based on multi-objective artificial tree algorithm to optimize the B-pillar and the rocker. The optimized sub-systems are applied to the body of a BEV. As a result, the performance of the B-pillar and the rocker is significantly improved, and their optimal solution templates are provided. The performance of the BEV is also improved under the advanced European mobile deformable barrier side impact and the oblique pole side impact. Some interesting conclusions for BEV are presented. In summary, this work has obvious reference value for automotive engineers and scholars to further study the crashworthiness and lightweight of BEV. [ABSTRACT FROM AUTHOR]

In view of problems of serious wear and high failure rate in application of contact method of rocker angle measurement of shearer in complex mine environment, an rocker angle measurement method of shearer under low illumination environment was proposed, which combines image enhancement algorithm and monocular vision for non-contact measurement of rocker angle of shearer. Multi-scale Retinex image enhancement algorithm based on guided filtering is used to obtain enhanced images. ROI extraction, edge detection and progressive probabilistic transform are performed on the enhanced image to get rocker angle in camera space, and calibrated CCD camera is used for coordinate conversion, and actual angle is output. The experimental results show that the rocker angle measurement method of shearer is fast and accurate, the error is less than 0.1°, and it has good performance in contrast enhancement, noise cancellation, detail enhancement.

Alpine skis have changed dramatically in the last century. Long and straight wood skis have evolved into shorter lengths and now contain a plethora of modern materials. Shaped skis have become the norm. Today’s skis also offer a variety of waist widths and shapes to cater to specific uses. By studying how skis have evolved, it is possible to gain insight into how the design of alpine skis has progressed. To do so, the mechanical properties of 1016 skis, from the 1920s to 2019, were measured with a machine developed at the University of Sherbrooke. The resulting data are used to calculate various geometric, stiffness and performance parameters. The evolution of these parameters over the years is analyzed. This analysis provides a better understanding of the evolution of ski design and shows when the introduction of new materials and shaping concepts has changed the way skis are designed.

Vehicle side crash is a critical crash event where the vehicle is crashed by a movable car or vehicle may hit a tree or pole. Minimising the intrusion into the occupant space is important to protect the occupant. In side pole crash, vehicle rocker (sill) plays an important role in resisting the load due to the crash. The objective is to study the functional performance and potential mass reduction in the vehicle sill/rocker area by use of carbon fibre reinforced polymer (CFRP) tubes. The study is divided into three parts. First part investigates the behaviour of CFRP square section tubes in a three-point quasi-static bending in comparison to conventional steel structure using finite element method. By keeping the resistance force offered by a steel section as the baseline resistance value, different combination of CFRP tubes and metal holding brackets are evaluated and compared with the baseline. In the second part, CFRP tube is simulated in dynamic three-point bending test and compared with quasi-static simulations in order to check the influence of inertial effects on the CFRP tube behaviour. In the third part, the best performing design variants from the three-point quasi-static bending simulations are used in the sill or rocker of a vehicle and evaluated in full vehicle US NCAP pole impact load case. The full vehicle crash simulations for side pole impact is compared between the baseline with the steel reinforcement and design variants with the CFRP tube. Resistance force levels, intrusion and structural integrity are the key parameters on which this comparison is made. It is concluded that using CFRP tubes does not reduce the performance in terms of structural integrity and intrusion levels in typical side crash scenario like a US NCAP side pole impact. It can also be concluded that there is potential for mass reduction. Further investigation into the assembly feasibility is suggested as future work. [ABSTRACT FROM AUTHOR]

Copyright of Kriminologisches Journal is the property of Julius Beltz GmbH & Co. KG Beltz Juventa and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In den Sechzigerjahren wurde Rock 'n' Roll zum Katalysator einer frustrierten Jugend, die mit alten Gesellschaftsmustern brach und Rockstars zu ihren neuen Göttern erklärte. Staatliche Autoritäten wie die Presse in den USA und Großbritannien verdammten das Aufbegehren der Jugend. Auf der einen Seite wurde sie mitsamt ihrer Musik verteufelt, auf der anderen Seite spielten Bands wie die Rolling Stones mit den Symboliken von Sünde und Satan. Dieses schizophrene Bild von Luzifer als Erlöser und Übeltäter zugleich soll hier thematisiert werden.

The article presents a new scheme and principle of operation of the crank and rocker mechanism with composite kinematic pairs with elastic elements. Taking into account the fixed deformations of the elastic elements, the analytical kinematics of the mechanism are obtained, the numerical solution of the problem determines the laws of motion of the rocker mechanism, the main parameters are substantiated. [ABSTRACT FROM AUTHOR]

Current trends in the automotive industry have as object besides increasing their performance also development aspects related to the interior ergonomy. So vehicle interior design should provide passengers the conditions that create them actually believe that in the car, have everything they need to move with maximum comfort and safety. Seats and bench seats must be comfortable to ensure passengers positions as free and restful can be. They must be provided with adjustable systems in horizontal and of the elevation plan, with a geometry adapted to the morphology of the human body and lumbar spine. In this sense the present paper presenting the geometric synthesis based on the theorem on the crank existence, the mechanism of vertical adjustment of the driver's seat in motor vehicles. After synthesis, in order to fulfill initial requirements was obtained an articulated parallelogram mechanism, for which were determined cinematic elements lengths either from graphical constructions either constructive from terms of graphics or gauging assembly. At the same time they were determined also cinematic parameters of the powertrain for driving mechanism. [ABSTRACT FROM AUTHOR]

The efficiency of balanced drives, chain drives, and linear rack and pinion drives is compared for sucker rod pumps. An approach to energy-efficient oil extraction using the kinetic energy of the descending drilling stem is developed, and the corresponding mathematical model is derived. The results of numerical modeling are outlined. [ABSTRACT FROM AUTHOR]

The paper presents the scheme, the principle of operation, as well as the kinematic analysis of the four-link hinged planar mechanism, taking into account the limiting values of the deformations of the elastic element of the joint hinge between the connecting rod and the rocker. By the kinematics problem, regularities in the movement of the rocker mechanism are obtained, graphical dependences of the parameters are constructed, along which the necessary values can be selected. [ABSTRACT FROM AUTHOR]

Multispan simply supported bridges with drop spans and steel bearings were commonly constructed in northern India during the 1970s, and little knowledge about their seismic behavior is available in the literature. Because these bridges are part of the existing transportation network, it is important to assess their seismic fragility and suggest possible retrofitting solutions, if required. A four-span model of such a bridge type was analytically investigated for its seismic response. The critical components of such bridges are rocker and roller-cum-rocker steel bearings, and their lateral force-deformation responses were obtained from nonlinear finite-element analyses. Incremental dynamic analyses were performed for the development of fragility curves for failure of the bridge along two horizontal directions. The damage criteria included either failure of bearings due to exceedance of respective displacement limits or dislodgement of the bridge deck due to unseating. It was observed that seismic demands for drop spans were small, and failure of main-span steel bearings was the primary cause for the bridge failure. Retrofitting of the bridge by replacing steel bearings with unanchored elastomeric pads is shown to significantly reduce the fragility of the retrofitted bridge. [ABSTRACT FROM AUTHOR]

Background: Rocker is a novel interspinous process stabilization (IPS) that can be installed via unilateral approach by virtue of its unique design. This controlled study compared the clinical outcome of Rocker versus X-Stop to access the feasibility and validity of the novel IPS.Methods: From March 2011 to September 2012, 32 patients treated with Rocker and 30 patients treated with X-Stop were enrolled in this study. The primary clinical outcome measure was Oswestry Disability Index (ODI) score. The secondary clinical outcome measure was Japanese orthopaedics association (JOA) score. Disc height index (DHI) and foraminal height index (FHI) were measured for postoperative radiographic evaluation. Implant failures were also recorded.Results: There were 55 patients with complete data during 24 months follow-up. Among the 55 patients, 38 patients underwent IPS in combination with microdecompression. At the final follow-up, 49 patients achieved a minimal clinical important difference (≥ 8 points ODI improvement). The mean operative time was 53.6 min (range, 30 to 90 min) in Rocker group and 63.1 min (range, 30 to 100 min) in X-Stop group. The average blood loss was 111 ml (range, 50 to 400 ml) in Rocker group and 138 ml (range, 50 to 350 ml) in X-Stop group. ODI score were significantly improved from preoperative 46.8 ± 9.2 to 12.2 ± 2.6 at 24 months follow-up in the Rocker group and from preoperative 45.8 ± 9.8 to 11.8 ± 2.4 at 24 months follow-up in the X-Stop group. JOA score also improved significantly in both groups. The radiographic parameters of DHI and FHI in both groups increased immediately postoperatively, however, the improvements seemed to revert toward initial value during follow-up. Two patients in Rocker group demonstrated implant dislocation within one week postoperatively and one patient in X-Stop group demonstrated implant migration at two months postoperatively.Conclusions: Preliminary clinical and radiographic outcome was similar between Rocker and X-Stop group. For patients of lumbar spinal stenosis with unilateral nerve root involved or mild-to-moderate central canal stenosis, Rocker offers a new alternative with less damage. [ABSTRACT FROM AUTHOR]

This work aims to study the rocker. This is a device of the suspension of Formula SAE vehicle that receives efforts from the motion scrolling of the vehicle and transmits them to the chassis frame minimized by a momentum ratio and smoothed by the set spring - damper. A review of parameters used in vehicle dynamics and a geometric analysis of the forces and stresses caused by such was carried out. Then, the analysis by the finite element method was applied. This analysis uses the theory of discretization of systems and examines the strength of the component based on the distortion energy, determining the maximum straining experienced by the component and the region of higher demand. The main function of the rocker, which is to reduce the force transmitted to the chassis due to roll movement and consequent application of the suspension, is taken as satisfactory, since the force applied to the wheel and which would be transmitted to the chassis is reduced from 3833.9 N to 3496.48 N to the mechanism formed between the rocker. The rocker resistance to stresses caused by the forces imposed on him was also served to the satisfaction of the material selected to manufacture, since the calculation of security factors for static load prove such a claim. [ABSTRACT FROM AUTHOR]

The article focuses on the plantar loading forces in below-knee cast with loadbearing frame. Topics discussed include the realignment surgery, the patella tendon-bearing (PTB), and the lower limb immobilization. Also mentioned are the lower limb fractures, the FlexiForce (TekScan) A201 sensors, and the management of patients with Achilles tendon rupture.

This paper reports on the construction of a full-scale Bronze Age-type sewn-plank boat based on the Ferriby boats. The boat, which was named Morgawr, was constructed in the National Maritime Museum Cornwall in Falmouth, England, during 2012 and the first months of 2013, as part of a larger exhibition in the museum. This paper provides the background and context of the project, describes the process of building the craft, and reflects in particular on differences between Morgawr and the 'hypothetical reconstruction of a complete sewn-plank boat' published in 1990 by Ted Wright and John Coates which formed the basis for this project. [ABSTRACT FROM AUTHOR]

A novel twin-rotor piston engine (TRPE) mechanism with high volumetric output and power density was introduced. This new engine comprises an energy conversion system and a differential velocity drive mechanism (DVDM). Two special geared four-bar mechanisms, DVDM-1 and DVDM-2, were utilized and compared. Based on the closed loop vector method, a mathematical model for position, velocity, and acceleration of the two mechanisms was established. Numerical examples illustrate that the kinematic characteristics were presented. Expression of the displacement and compression ratio of the two engine mechanisms were derived and compared. It is concluded that both DVDM-1 and DVDM-2 adopted in the proposed TRPE with six vane pistons create thirty-six power strokes per revolution of the output shaft, and the summation of two angles covered by each rocker is always 2π/ N as the output shaft rotates an angle of π/ N. In DVDM-1, the span angle of a vane piston should be designed to be 10.2°, and the compression ratio should be equal to 10; in DVDM-2, the span angle of a vane piston should be designed to be 10.6°, and the compression ratio should be equal to 4.3. [ABSTRACT FROM AUTHOR]

Background: The roll-over shape is the effective rocker shape that a lower limb system conforms to during a step. The roll-over shape concept has been explored in detail in adults and has been successfully used in the design, evaluation, and alignment of lower limb prostheses and orthoses. No such analysis exists for the pediatric population. Therefore, the purpose of this study was to investigate the ankle–foot and knee–ankle–foot roll-over shapes in able-bodied children, values that could serve as tools for design and evaluation of lower limb pediatric prostheses and orthoses. Methods: This study describes a multi-center retrospective review of existing motion analysis data (n =153 from three centers). Roll-over shapes were calculated by transforming center of pressure data from a laboratory-based coordinate system into two body-based coordinate systems. Roll-over shapes were then characterized using a circular arc model. Best-fit radii of roll-over shapes for children in three age groups (3–7years, 8–11years, and 12–17years) were compared using the Kruskal–Wallis test. Findings: No significant changes were found in roll-over shape radii between the three age groups (P =0.54 for ankle–foot roll-over shape radii; P =0.12 for knee–ankle–foot roll-over shape radii). The weighted mean of median radii for ankle–foot and knee–ankle–foot roll-over shapes from the three centers were approximately 22% and 17% of body stature, values similar to those seen in adults. Interpretation: Children produce nearly circular knee–ankle–foot roll-over shapes at a young age that are similar to those seen in adults when scaled by body stature. [Copyright &y& Elsevier]

Abstract: The objective of this paper is to develop an analytical framework to representing the ankle–foot kinematics by modelling the foot as a rollover rocker, which cannot only be used as a generic tool for general gait simulation but also allows for case-specific modelling if required. Previously, the rollover models used in gait simulation have often been based on specific functions that have usually been of a simple form. In contrast, the analytical model described here is in a general form that the effective foot rollover shape can be represented by any polar function ρ=ρ(φ). Furthermore, a normalized generic foot rollover model has been established based on a normative foot rollover shape dataset of 12 normal healthy subjects. To evaluate model accuracy, the predicted ankle motions and the centre of pressure (CoP) were compared with measurement data for both subject-specific and general cases. The results demonstrated that the ankle joint motions in both vertical and horizontal directions (relative RMSE ∼10%) and CoP (relative RMSE ∼15% for most of the subjects) are accurately predicted over most of the stance phase (from 10% to 90% of stance). However, we found that the foot cannot be very accurately represented by a rollover model just after heel strike (HS) and just before toe off (TO), probably due to shear deformation of foot plantar tissues (ankle motion can occur without any foot rotation). The proposed foot rollover model can be used in both inverse and forward dynamics gait simulation studies and may also find applications in rehabilitation engineering. [Copyright &y& Elsevier]

The article discusses the usage of a modified handheld rocker gauge to measure different types of skate blades and bobsleigh runners used for ice sports. The manner of adapting and modifying the handheld rocker gauge to be utilized for analyzing skate blades for four different ice sports is explained. The theory and conclusion regarding the usage of the handheld rocker gauge is explored.

Abstract: A few investigators have described the movement of the center of pressure (COP) of the ground reaction force and the activation patterns of the lower limb muscles during gait initiation and termination. This study examines the effective rocker (roll-over shape) behavior of the knee–ankle–foot (KAF) system during gait initiation, steady-state walking (i.e. constant speed gait), and gait termination. The KAF roll-over shapes were characterized by transforming COP data of 10 able-bodied subjects from a laboratory-based coordinate system into a leg-based coordinate system. The resulting roll-over shapes (effective rockers) were characterized using a circular arc model. The KAF roll-over shapes exhibit an overall “flexed” orientation during the first step of gait initiation and an “extended” orientation during the last step of gait termination. Understanding the behavior of the anatomical KAF system during gait initiation and termination may aid in the design of prosthetic components, i.e. mechanical devices that replace complete anatomical structures. Prostheses that intend to mimic the overall behavior of physiological KAF systems (biomimetic designs) could be manufactured using approaches that are much simpler than attempting to reconstruct the complexity of the lower limb. [Copyright &y& Elsevier]

The purpose of this study was to examine the three-dimensional movement profile of the blade during a stationary slap shot, as a function of player skill level. A total of 15 subjects participated; eight were classified as elite and the remaining seven were recreational. Performances were evaluated by simultaneously recording the movements of the stick’s lower shaft and blade with high-speed video (1000 Hz), the time of stick-ground contact with two uniaxial forceplates and time of blade-puck contact with a uniaxial accelerometer mounted within the puck. Data were analysed with a two-way MANOVA for several dependent variables including linear kinematics, temporal phase data and global angles. The results indicated that skill level affected blade kinematics, with elite shooters tending to alter timing parameters (i.e. phase length), magnitude of linear variables (i.e. displacement, etc.) and the overall blade orientation to achieve a higher velocity slap shot. These analyses identified a unique ‘rocker’ phase within the execution of the slap shot in both groups. [ABSTRACT FROM AUTHOR]

Ankle-foot orthoses (AFOs) are intended to improve toe clearance during swing and ankle position at initial contact (IC) and midstance. Changes that lead to improved ankle-foot kinematics may result in a more biomimetic rollover shape (ROS). ROS is the effective geometry to which the ankle-foot complex conforms between IC and contralateral IC. An effective ROS during gait may facilitate forward progression. This study investigated the effect of an AFO on ROS in adults with hemiplegia following stroke. Kinematic and force data were recorded from 13 people with hemiplegia and 12 controls. Hemiplegic subjects walked at a self-selected speed with and without an articulated AFO with plantar flexion stop. For the involved limb, the AFO significantly increased the ROS arc length (from 32.6% to 55.7% of foot length [FL]) and arc radius (67.4% to 139.3% of FL) and significantly altered the sagittal plane location of the first center of pressure (COP) point, moving it posterior to the ankle center (-1.2% to -20% of FL) (p < 0.002 for all comparisons). However, when hemiplegic patients walked with an AFO, their mean arc radius was greater, mean arc length less, and the first COP point further posterior than those of control subjects. [ABSTRACT FROM AUTHOR]

Objective. To examine the hypothesis that roll-over shapes of non-disabled lower limb systems do not change appreciably with walking speed.Design. Repeated measures (n=24).Background. Roll-over shapes of three lower limb systems are presented. They are: roll-over shapes of the (1) foot, (2) ankle–foot, and (3) knee–ankle–foot systems. Roll-over shapes show the effective rocker (or cam) shapes that the lower limb systems conform to during the period in the stance phase of walking between heel contact and opposite heel contact.Methods. Roll-over shapes were measured by transforming center of pressure data from a laboratory-based coordinate system into each of three body-based coordinate systems. Knee–ankle–foot roll-over shapes were further characterized using a circular arc model.Results. From a statistical standpoint, the radii of the best-fit circular arcs did not change significantly with walking speed, while the forward shifts of the circular models did change significantly. However, the change in forward shift was not considered to be clinically significant.Conclusions. The biologic systems involved in developing the roll-over shapes adapt to changing conditions of walking speed, including increased loading amplitudes as speed is increased, to maintain similar effective roll-over geometries.RelevanceRoll-over shapes provide insight into the workings of various lower limb systems by taking a new look at existing gait data. This insight could provide broad utility, helping to develop a better understanding of able-bodied and disabled human walking, and leading to the design of improved rehabilitation devices, surgeries, and therapies. [Copyright &y& Elsevier]