Effect of wobbling mass modeling on joint dynamics during human movements with impacts

In automated mechanical transmissions, engaging sleeve with clutch gear causes the switches of mechanical coupling modes of engaging-related parts, and impacts may happen to make the part speeds have discrete transitions during the engaging. The two characters make the engaging process exhibit both continuity and discreteness. The aim of the paper is to develop a high-fidelity model to capture the trajectories of the parts in the transmission. We treat the engaging as a two-phase process—sleeve first interacting with synchro ring and then with clutch gear. The part movements under a certain constraint are governed by multibody dynamics, and the speed jumps caused by impacts are described using the Poisson coefficient of restitution. To couple the continuous evolutions and discrete transitions of the states, a hybrid automaton model is developed. This model allows for the characteristic analysis of the engaging process with multiple interaction cases between the engaging-related parts, and it is validated by bench tests. The effects of two key factors—the relative tooth position of sleeve and clutch gear and the shifting force—on engaging duration and impact are studied through numerical simulations.     

Correlation between mechanical properties and orientation of the crystalline and mesomorphic phases in isotactic polypropylene fibers

The microstructure and mechanical properties of melt-spun isotactic polypropylene (iPP) fibers were studied for different take-up velocities and throughputs with a combination of small- and wide-angle X-ray scattering, calorimetry and tensile tests. With the increase of take-up velocity the mesomorphic fraction of the fibers steadily decreases while the crystalline fraction increases. The addition of an alpha-nucleating agent led to an increase of crystallinity and a slight decrease of the orientation factor. By contrast, a beta-nucleator resulted in a complete suppression of the fiber crystallinity. The orientation factor of the mesophase and/or crystalline phase is found to have a one-to-one correlation with the fiber tenacity and deformation at break. At the same time, the absolute values of crystallinity and/or mesomorphicity are fully uncorrelated with these mechanical characteristics. The observed correlations can be used for example to design and control the fiber mechanical properties by tuning the processing conditions such as take-up velocity, throughput and addition of nucleating agents.     

Mechanical and microstructural properties of alloy 800

The evolution of microstructural and mechanical properties of alloy 800 with respect to operating conditions of the steam generator tubings of fast breeder reactors have been analyzed and presented. On the microstructural side two phenomena have important influence on the mechanical properties, namely γ′ and carbide precipitation. Gamma prime precipitation occurs in alloy compositions containing ≳0.50 pct Ti + Al, inducing mechanical property changes and, in particular, improving the long term creep resistance. Its growth rate follows the exponential law which, when extrapolated, yields an overaging time beyond 4 × 10⁴ h at ≲550°C. M₂₃C₆ carbide precipitation starts in early stages of exposure at 500 to 600°C, being of heterogeneous nature and forming mainly on the grain boundaries. The M₂₃C₆ carbides advance perpendicular to the surface of one of the austenite grains, commonly having a <110>_γ//<110>M₂₃C₈relationship, and occasionally develop into well defined cellular precipitates. On the mechanical side, a sharp creep ductility decline is observed when either, or in particular both, strong γ′ strengthening and discontinuous precipitation develop in the matrix. It is argued that this decline is principally due to the latter phenomenon and is accentuaged by matrix strengthening. Formerly Associate Professor, Metallurgical Engineering Department, Arya Mehr University of Technology, Tehran, Iran.     

A 2022 Systematic Review and Meta-Analysis of Enriched Therapeutic Diets and Nutraceuticals in Canine and Feline Osteoarthritis

With osteoarthritis being the most common degenerative disease in pet animals, a very broad panel of natural health products is available on the market for its management. The aim of this systematic review and meta-analysis, registered on PROSPERO (CRD42021279368), was to test for the evidence of clinical analgesia efficacy of fortified foods and nutraceuticals administered in dogs and cats affected by osteoarthritis. In four electronic bibliographic databases, 1578 publications were retrieved plus 20 additional publications from internal sources. Fifty-seven articles were included, comprising 72 trials divided into nine different categories of natural health compound. The efficacy assessment, associated to the level of quality of each trial, presented an evident clinical analgesic efficacy for omega-3-enriched diets, omega-3 supplements and cannabidiol (to a lesser degree). Our analyses showed a weak efficacy of collagen and a very marked non-effect of chondroitin-glucosamine nutraceuticals, which leads us to recommend that the latter products should no longer be recommended for pain management in canine and feline osteoarthritis.     

Effect of minor alloying element variation on the properties of alloy 800

Application of Alloy 800 in steam generator tubing of fast reactors, where continuous service temperature of the order of 550° is experienced, has been analyzed with respect to small variations in its chemical composition. Several laboratory melts of Alloy 800 have been prepared and their microstructural and mechanical property changes during simple aging and creep tests at 500 to 600° have been studied. It has been found that in the above temperature range precipitation of M₂₃C₆on the grain boundaries is independent of the Ti : C ratio generally specified for Alloy 800. Gamma prime precipitation occurred in alloys containing as low as 0.5 pct Ti+ Al after 1000 h of aging and was accompanied with a creep ductility decline. Upon γ precipitation creep rate was retarded and its reacceleration for test times up to 8500 h at 550° was not observed. Based on the findings, increased Ti concentration at the expense of Al within the specified chemical composition range with carbon content of 0.030 to 0.050 has been suggested. A. A. Tavassoli is on sabbatical leave from the Arya-Mehr University of Technology, Tehran, Iran.     

Préparation et caractérisation de produits amylacés polytransformés Partie 2. Caractérisation rhéologique de carboxymethylamidons benzylés

Preparation and Characterization of Polyfunctional Starch Products. Part 2. Rheological Characterization of Benzylated Carboxymethylstarches . “Higy” and “low” viscosity carboxymethylstarches and their benzylated derivatives were rheologically studied. For the shear rates of 3 to 700 sec⁻¹ the rheological behaviour may be described by the power law T = K Dⁿ, from which n depends mainly from the volume occupied by the solvated solute. During benzylation a partial decarboxymethylation and some hydrolysis occured. Carboxymethylstarches treated in the same conditions as for benzylation but without benzylchloride, gave derivatives which were also rheologically characterized for comparison. The benzylated carboxymethylstarches of low viscosity have good sizing properties (paper and textile).     

An EMG-marker tracking optimisation method for estimating muscle forces

Existing algorithms for estimating muscle forces mainly use least-activation criteria, which do not necessarily lead to physiologically consistent results. Our objective was to assess an innovative forward dynamics-based optimisation, assisted by both electromyography (EMG) and marker tracking, for estimating the upper-limb muscle forces. A reference movement was generated, and EMG was simulated to reproduce the desired joint kinematics. Random noise was added to both simulated EMG and marker trajectories in order to create 30 trials. Then, muscle forces were estimated using (1) the innovative EMG-marker tracking forward optimisation, (2) a marker tracking forward optimisation with a least-excitation criterion, and (3) static optimisation with a least-activation criterion. Approaches (1) and (2) were solved using a direct multiple shooting algorithm. Finally, reference and estimated joint angles and muscle forces for the three optimisations were statistically compared using root-mean-square errors (RMSEs), biases, and statistical parametric mapping. The joint angles RMSEs were qualitatively similar across the three optimisations: (1) \(1.63 \pm 0.51\)°; (2) \(2.02 \pm 0.64\)°; (3) \(0.79 \pm 0.38\)°. However, the muscle forces RMSE for the EMG-marker tracking optimisation (\(20.39 \pm 13.24\) N) was about seven times smaller than those resulting from the marker tracking (\(124.22 \pm 118.22\) N) and static (\(148.15 \pm 94.01\) N) optimisations. The originality of this novel approach is close tracking of both simulated EMG and marker trajectories in the same objective function, using forward dynamics. Therefore, the presented EMG-marker tracking optimisation led to accurate muscle forces estimations.     

Préparation et caractérisation de produits amylacés polytransformés Partie 1. Carboxyméthylamidons benzylés

Preparation and Characterization of Polyfunctional Starch Products. Part 1. Benzylated Carboxymethylstarches . Carboxymethylstarches of low viscosity (DS = 0,35) and high viscosity (DS = 0,29) were benzylated. Analytical methods were developped to evaluate the degree of substitution of both functional groups. The obtained DS lies between 0,15 and 0,35 for both. Benzylation rate depends on the viscosity of the reaction system. During benzylation a partial decarboxymethylation takes place.