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A literature review of the effects of computer input device design on biomechanical loading and musculoskeletal outcomes during computer work
No full textBACKGROUND: Extended use of conventional computer input devices is associated with negative musculoskeletal outcomes. While many alternative designs have been proposed, it is unclear whether these devices reduce biomechanical loading and musculoskeletal outcomes. OBJECTIVE:To review studies describing and evaluating the biomechanical loading and musculoskeletal outcomes associated with conventional and alternative input devices. METHODS: Included studies evaluated biomechanical loading and/or musculoskeletal outcomes of users’ distal or proximal upper extremity regions associated with the operation of alternative input devices (pointing devices, mice, other devices) that could be used in a desktop personal computing environment during typical office work. RESULTS:Some alternative pointing device designs (e.g. rollerbar) were consistently associated with decreased biomechanical loading while other designs had inconsistent results across studies. Most alternative keyboards evaluated in the literature reduce biomechanical loading and musculoskeletal outcomes. Studies of other input devices (e.g. touchscreen and gestural controls) were rare, however, those reported to date indicate that these devices are currently unsuitable as replacements for traditional devices. CONCLUSIONS: Alternative input devices that reduce biomechanical loading may make better choices for preventing or alleviating musculoskeletal outcomes during computer use, however, it is unclear whether many existing designs are effective
A Semiautomatic Method for In Vivo Three- Dimensional Quantitative Analysis of Fascial Layers Mobility Based on 3D Ultrasound Scans
No full textAbstract Purpose
Recently, there has been an increasing interest in the role of deep fascia mobility in musculoskeletal dynamics and chronic pain mechanisms; however, no strategies have been presented so far to study in vivo fascial motion in 3D. This paper presents a semiautomatic method, based on ultrasound (US) imaging, enabling a 3D evaluation of fascia mobility. Methods
The proposed approach relies on the acquisition of 3D US datasets at rest and during a voluntary muscular contraction and consists of two phases: 3D US dataset analysis and generation of a displacement vector field using a block matching technique (Phase 1) and validation and filtering of the resulting displacement vector field for outliers removal (Phase 2). The accuracy and effectiveness of the proposed method were preliminarily tested on different 3D US datasets, undergoing either simulated (procedural) or real (muscular contraction) deformations. Results
As for the simulated deformation, estimated displacement vectors resulting from Phase 1 presented a mean magnitude percentage error of 8.05 % and a mean angular error of 4.78∘ role= presentation style= box-sizing: inherit; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; \u3e4.78∘4.78∘ which, after Phase 2, were reduced by 69.44 and by 83.05 %, respectively. Tests on real deformations further validated the effectiveness of Phase 2 in the removal of outliers from the displacement vector field. Conclusions
Obtained results preliminarily demonstrate the viability of the proposed algorithm for the analysis of fascia mobility. Such analysis can enable clinicians to better understand the fascia role in musculoskeletal dynamics and disorder. Further experiments are needed to optimize the method in consideration of the anatomical region to be studied
A Method for Measuring the Néel Relaxation Time in a Frozen Ferrofluid
No full textWe report a novel method of determining the average Néel relaxation time and its temperature dependence by calculating derivatives of the measured time dependence of temperature for a frozen ferrofluid exposed to an alternating magnetic field. The ferrofluid, composed of dextran-coated Fe3O4 nanoparticles (diameter 13.7 nm ± 4.7 nm), was synthesized via wet chemical precipitation and characterized by x-ray diffraction and transmission electron microscopy. An alternating magnetic field of constant amplitude (H0=20H0=20 kA/m) driven at frequencies of 171 kHz, 232 kHz, and 343 kHz was used to determine the temperature dependent magnetic energy absorption rate in the temperature range from 160 K to 210 K. We found that the specific absorption rate of the ferrofluid decreased monotonically with temperature over this range at the given frequencies. From these measured data, we determined the temperature dependence of the Néel relaxation time and estimate a room-temperature magnetocrystalline anisotropy constant of 40 kJ/m3, in agreement with previously published results
Direct Measurement of Molecular Weight and Grafting Density by Controlled and Quantitative Degrafting of Surface-Anchored Poly (Methyl Methacrylate)
No full textWe report on quantitative determination of the molecular weight distribution (MWD) and grafting density (σP) of polymer assemblies grown by controlled radical polymerization from flat substrates as a function of polymerization time and the ratio between the inhibitor and catalyst species. Specifically, we grow poly(methyl methacrylate) (PMMA) brushes on flat silica-based surfaces by surface-initiated atom transfer radical polymerization (SI-ATRP), cleave the PMMA grafts quantitatively using tetrabutyl ammonium fluoride (TBAF), and analyze their MWD by size exclusion chromatography equipped with a high-sensitivity differential refractive index detector. The polymer growth and degrafting processes are followed by ellipsometry, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. The σP is independent of polymerization time and increases with increasing SI-ATRP inhibitor/catalyst ratio. Specifically, σP increases from 0.48 ± 0.06 to 0.58 ± 0.06 chains/nm2 as the inhibitor/catalyst molar ratio increases from 0 to 0.015, respectively, providing evidence that high inhibitor/catalyst ratio offers better control of the SI-ATRP reaction, by lowering number of terminations, and leading to denser PMMA brush assemblies
Finite Element Modeling of Tire With Validation Using Tensile and Frequency Response Testing
No full textA physical testing program is performed in support of finite element model creation for a 50-series passenger car tire. ABAQUS finite element analysis software is used along with its standard material models. Uniaxial tension testing of tire samples cut from the tread composite, tread rubber and sidewall composite is performed in order to obtain material properties. Hyper-elastic material coefficients for tread rubber are fit using uniaxial tension test data. Results show that the Arruda-Boyce hyper-elastic material model fits the test data well and it predicts reasonable overall behavior in uniaxial tension and uniaxial compression. Most other hyperelastic material models are found to predict unrealistic behavior in uniaxial compression for the tire samples, especially in the 0 to 20% compressive strain range.
Frequency response testing of two inflated passenger car tires of different sizes, makes and models is also performed to assist in defining the viscoelastic material model for tread rubber. Test results show that tire modal damping is in the 2 to 4% range for most modes below 200 Hz, and the response curves, modal density and modal damping are remarkably similar for the two tires tested. The tire finite element model with updated material properties is simulated for nine combinations of air inflation pressure and vertical load in order to calculate static loaded radius. The analysis results are compared with physical test results and the analysis results are found to deviate at most by 3% compared to the tests
Method of lines transpose: an efficient A-stable solver for wave propagation
Get PDFBuilding upon recent results obtained in [7,8,9], we describe an efficient second order, A-stable scheme for solving the wave equation, based on the method of lines transpose (MOLT), and the resulting semi-discrete (i.e. continuous in space) boundary value problem. In [7], A-stable schemes of high order were derived, and in [9] a high order, fast O(N) spatial solver was derived, which is matrix-free and is based on dimensional-splitting. In this work, are interested in building a wave solver, and our main concern is the development of boundary conditions. We demonstrate all desired boundary conditions for a wave solver, including outflow boundary conditions, in 1D and 2D. The scheme works in a logically Cartesian fashion, and the boundary points are embedded into the regular mesh, without incurring stability restrictions, so that boundary conditions are imposed without any reduction in the order of accuracy. We demonstrate how the embedded boundary approach works in the cases of Dirichlet and Neumann boundary conditions. Further, we develop outflow and periodic boundary conditions for the MOLT formulation. Our solver is designed to couple with particle codes, and so special attention is also paid to the implementation of point sources, and soft sources which can be used to launch waves into waveguides
Relationship between coupling and the controllability Grammian in co-design problems
No full textDesign of smart products requires optimization of both the physical device, or artifact, and its controller. While some components of coupling can be computed a priori, the existence and strength of coupling between these problems over the entire Pareto frontier currently cannot be computed until they are solved. If coupling is expected to be present, then the problem is often solved as a simultaneous, or all-in-one, optimization. This solution process is more difficult, computationally intensive, and operationally inconvenient than a sequential solution method. Consequently, knowing in advance whether coupling is weak or nonexistent is useful