Kento Kusuda, Shigehito Matsubara, Daisuke Noguchi
et al.
The advancement in depth-sensor technology increased the potential for the clinical use of markerless three-dimensional motion analysis (3DMA); however, the accurate quantification of depth-sensor-based 3DMA on gait characteristics deviating from normal patterns is unclear. This study investigated the concurrent validity of the measurements of compensatory movements measured by depth-sensor-based 3DMA compared to those measured by marker-based 3DMA. We induced swing-phase compensatory movements due to insufficient toe clearance by restricting unilateral ankle and knee joint movements in healthy individuals. Thirty-two healthy young adults (nineteen males, aged 20.4<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo> </mo><mo>±</mo><mo> </mo></mrow></semantics></math></inline-formula>2.0 years, height 164.4<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo> </mo><mo>±</mo><mo> </mo></mrow></semantics></math></inline-formula>9.8 cm, weight 60.0<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo> </mo><mo>±</mo><mo> </mo></mrow></semantics></math></inline-formula>9.3 kg [average <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>±</mo></mrow></semantics></math></inline-formula> standard deviation]) walked the 6 m walkway in slow speed, very slow speed, and knee–ankle–foot orthosis (KAFO; participants wore KAFOs on the right leg) conditions. Gait kinematics were measured with marker-based and depth-sensor-based 3DMA systems. The intraclass correlation coefficient (ICC<sub>3,1</sub>) was used to measure the relative agreement between depth-sensor-based and marker-based 3DMA and demonstrated good or moderate validity for swing-phase compensatory movement measurement. Additionally, the ICC<sub>2,1</sub> measured absolute agreement between the systems and showed lower validity than the ICC<sub>3,1</sub>. The measurement errors for contralateral vaulting, trunk lateral flexion, hip hiking, swing-side hip abduction, and circumduction between instruments were 0.01 m, 1.30°, 1.99°, 2.37°, and 1.53°, respectively. Depth-sensor-based 3DMA is useful for determining swing-phase compensatory movements, although the possibility of missing a slight measurement error of 1–2° must be considered.
Mechanics of engineering. Applied mechanics, Descriptive and experimental mechanics
Loading and unloading works are an integral part of the construction process. Cranes of various types were mostly use to perform these works.
To ensure trouble-free operation and increase the reliability of cranes, when calculating structures and components of their working equipment, it is important to take into account dynamic loads, which are several times higher than static loads. Elements of dynamic loads in the crane suspension are its elastic components (flexible traction bodies) - ropes.
The process of lifting a load from a rigid base and picking it up is considered, which divided into three stages: the first is the selection of clearances and the tension of the ropes; the second is the pre-opening stage of lifting the load; the third is the post-detachment stage of lifting the load.
For each stage, the initial conditions accepted, the differential equations of the movement of loads compiled, their solution given taking into account many factors, and expressions derived for determining the forces in the load suspension. At the first stage, the duration of the gap selection (tension of the ropes) is determined, at the second stage, the speed of separation of the load from the base is determined, at the third stage, the maximum force in the elastic element determined.
The method of determining the forces in the suspension of the load, the duration of the selection of clearances (tension of the ropes), the speed of separation of the load from the base, and the maximum force in the elastic element presented in the work allows you to significantly simplify the solution of complex equations, to determine simple expressions and to determine them with sufficient accuracy for practical calculations values.
Cardiovascular diseases still represent one of the most deadly pathologies worldwide. Knowledge of the blood flow dynamics within the cardio-vascular system is crucial in preventing these diseases and analysing their physiology and physio-pathology. CFD simulations are highly effective in guiding clinical predictions and, more importantly, allow the evaluation of physical and clinical parameters that are difficult to measure with common diagnostic techniques. Therefore, in particular, this study is focused on investigating the hemodynamics of the thoracic aorta. Real aortic geometries regarding a sane and diseased patient presenting an aneurysm were considered. CFD simulations were performed with the OpenFOAM C++ library using patient-specific pulsatile blood flow waveforms and implementing the Windkessel pressure boundary condition for the artery outflow. The adopted methodology was preliminarily verified for assessing the numerical uncertainty and convergence. Then, the CFD results were evaluated against experimental data concerning pressure and velocity of the thoracic aorta measured with standard diagnostic techniques. The normal aorta’s blood flow was also compared against the pattern regarding the patient-specific aortic aneurysm. Parameters such as wall pressure, wall shear stress (WSS) and velocity distribution were investigated and discussed. The research highlighted that the blood flow in the aorta is strongly affected by the aneurysm onset, with the growth of recirculation zones being potentially hazardous. The outcomes of the investigation finally demonstrate how CFD simulation tools, capturing the detailed physics of the aortic flow, are powerful tools for supporting clinical activities of the cardio-vascular system.
Thermodynamics, Descriptive and experimental mechanics
In this work, the roles of the orifice shape and off-bottom clearance of the dip tube on the discharge flow rate of a complex fluid from a dispensing bottle and on the resulting residual “heel” volume left in the bottle were investigated. Particle Image Velocimetry (PIV) was used to monitor the discharge rate and the heel. The dip tube clearance and the orifice shape both affected the formation of the heel. Dip tubes provided with a flat cut orifice not only resulted in a smaller heel compared to angled cut orifices but also generated a higher flow rate at constant suction pressure. Reducing the dip tube clearance produced smaller heel volumes irrespective of the shape of the dip tube orifice. The results of this work were validated using the velocity contour maps obtained by PIV and, separately, with the heel profiles obtained from the PIV raw images.
Thermodynamics, Descriptive and experimental mechanics
Liquefied natural gas (LNG) is one of the most promising fuels for energy supply because it has a favorable combination of environmental and economic properties in connection with new trends aimed at the development of ecological and sustainable consumption of natural resources, which ensure a constant growth in LNG consumption. The article presents an analytical review of the main technical solutions for the construction of cryogenic pipelines and insulating coating structures. The ANSYS Fluent software was used for simulation of the LNG flow in a pipeline section 10 m long with an outer diameter of 108 mm for three types of insulating coating (polyurethane (PU) foam, aerogel, and vacuum-insulated pipe (VIP)). In addition, an assessment was made of the insulating effect on the LNG temperature distribution along the length of the pipeline. The largest increase in temperature from 113 K to 113.61 K occurs in PU foam-insulated pipes; the smallest was observed in VIP. Further, as an alternative to steel, the use of ultra-high molecular weight polyethylene (UHMWPE) for pipeline material was considered. The optimal result in terms of temperature distributions was obtained while simulating the flow of an LNG pipeline with PU foam by increasing the thickness of the insulating coating to 0.05 m.
Thermodynamics, Descriptive and experimental mechanics
Abstract Accelerator Mass Spectrometry (AMS) adds the techniques of higher energy charged particle acceleration to the basic principles of Isotope Ratio Mass Spectrometry (IRMS) to provide extremely low detection capability (below 1 femtogram) of rare isotopes in samples of natural materials as small as 1 mg. Depending on the element selected and the configuration of the equipment, rare isotope sensitivities can reach less than one part in 1015. The advantages of this small sample size and high sensitivity for the detection of rare isotopes include a) the economic benefit of collecting, shipping and preparing much smaller samples, and b) the ability to analyse specific chemical compounds within the sample. For the latter advantage, the pathway taken by that compound through a complex system can be more precisely traced or, in the case of radioactive isotopes, more precise chronological information can be provided. The paper is an amplification of material which was presented at the IAEA International Conference on Accelerators for Research and Sustainable Development: novel concepts and technical innovation. It begins with a basic overview of AMS technology, with an emphasis on how the use of higher energy contributes to this enhanced sensitivity, and then provides several examples of new AMS technologies which reduce the energy and space requirements for such systems. Several examples of applications which contribute to the investigation of sustainability in other areas of environmental concern are then briefly described.
Imiya M. Chathuranika, Miyuru B. Gunathilake, Pavithra K. Baddewela
et al.
In the present study, the streamflow simulation capacities between the Soil and Water Assessment Tool (SWAT) and the Hydrologic Engineering Centre-Hydrologic Modelling System (HEC-HMS) were compared for the Huai Bang Sai (HBS) watershed in northeastern Thailand. During calibration (2007–2010) and validation (2011–2014), the SWAT model demonstrated a Coefficient of Determination (R<sup>2</sup>) and a Nash Sutcliffe Efficiency (NSE) of 0.83 and 0.82, and 0.78 and 0.77, respectively. During the same periods, the HEC-HMS model demonstrated values of 0.80 and 0.79, and 0.84 and 0.82. The exceedance probabilities at 10%, 40%, and 90% were 144.5, 14.5, and 0.9 mm in the flow duration curves (FDCs) obtained for observed flow. From the HEC-HMS and SWAT models, these indices yielded 109.0, 15.0, and 0.02 mm, and 123.5, 16.95, and 0.02 mm. These results inferred those high flows were captured well by the SWAT model, while medium flows were captured well by the HEC-HMS model. It is noteworthy that the low flows were accurately simulated by both models. Furthermore, dry and wet seasonal flows were simulated reasonably well by the SWAT model with slight under-predictions of 2.12% and 13.52% compared to the observed values. The HEC-HMS model under-predicted the dry and wet seasonal flows by 10.76% and 18.54% compared to observed flows. The results of the present study will provide valuable recommendations for the stakeholders of the HBS watershed to improve water usage policies. In addition, the present study will be helpful to select the most appropriate hydrologic model for humid tropical watersheds in Thailand and elsewhere in the world.
Thermodynamics, Descriptive and experimental mechanics
Fluid flow and transport processes in fractured porous media are of particular interest for geologists and in the material sciences. Here a systematic investigation is presented, dealing with a generic geometric set-up of a porous matrix with a crack. In such a combined porous medium/free fluid system flow patterns have been examined frequently, while the resulting transport patterns have attracted less attention. Using numerical modeling with finite elements the problem is approached using a dimensionless formulation. With a reduced number of dimensionless parameter combinations (Darcy-, Peclet- and Reynolds-numbers) solution dependencies are examined in parametric sweeps. Breakthrough curves are fitted in comparison to those of 1D model approaches, yielding effective diffusivities and velocities. The computations reveal highest sensitivity concerning the angle between crack axis and flow direction, followed by the Peclet number and the crack axes ratio. As a dimensionless representation is used the results are scale independent. Thus, they deliver estimations concerning effective heat and solute transport parameters that can be relevant in all application fields.
Thermodynamics, Descriptive and experimental mechanics
The lattice Boltzmann method is employed to conduct direct numerical simulations of turbulent open channel flows with the presence of finite-size spherical sediment particles. The uniform particles have a diameter of approximately 18 wall units and a density of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>ρ</mi><mi>p</mi></msub><mo>=</mo><mn>2.65</mn><msub><mi>ρ</mi><mi>f</mi></msub></mrow></semantics></math></inline-formula>, where <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>ρ</mi><mi>p</mi></msub></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>ρ</mi><mi>f</mi></msub></semantics></math></inline-formula> are the particle and fluid densities, respectively. Three low particle volume fractions <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>ϕ</mi><mo>=</mo><mn>0.11</mn><mo>%</mo></mrow></semantics></math></inline-formula>, 0.22%, and 0.44% are used to investigate the particle-turbulence interactions. Simulation results indicate that particles are found to result in a more isotropic distribution of fluid turbulent kinetic energy (TKE) among different velocity components, and a more homogeneous distribution of the fluid TKE in the wall-normal direction. Particles tend to accumulate in the near-wall region due to the settling effect and they preferentially reside in low-speed streaks. The vertical particle volume fraction profiles are self-similar when normalized by the total particle volume fractions. Moreover, several typical transport modes of the sediment particles, such as resuspension, saltation, and rolling, are captured by tracking the trajectories of particles. Finally, the vertical profiles of particle concentration are shown to be consistent with a kinetic model.
Thermodynamics, Descriptive and experimental mechanics
Narges Tabatabaei, Ramis Örlü, Ricardo Vinuesa
et al.
Parallel sidewalls are the standard bounding walls in wind tunnels when making a wind tunnel model for free-flight condition. The consequence of confinement in wind tunnel tests, known as wall-interference, is one of the main sources of uncertainty in experimental aerodynamics, limiting the realizability of free-flight conditions. Although this has been an issue when designing transonic wind tunnels and/or in cases with large blockage ratios, even subsonic wind tunnels at low-blockage-ratios might require wall corrections if a good representation of free-flight conditions is intended. In order to avoid the cumbersome streamlining methods especially for subsonic wind tunnels, a sensitivity analysis is conducted in order to investigate the effect of inclined sidewalls as a reduced-order wall insert in the airfoil plane. This problem is investigated via Reynolds-averaged Navier–Stokes (RANS) simulations, and a NACA4412 wing at the angles of attack between 0 and 11 degrees at a moderate Reynolds number (400 k) is considered. The simulations are validated with well-resolved large-eddy simulation (LES) results and experimental wind tunnel data. Firstly, the wall-interference contribution in aerodynamic forces, as well as the local pressure coefficients, are assessed. Furthermore, the isolated effect of confinement is analyzed independent of the boundary-layer growth. Secondly, wall-alignment is modified as a calibration parameter in order to reduce wall-interference based on the aforementioned assessment. In the outlined method, we propose the use of linear inserts to account for the effect of wind tunnel walls, which are experimentally simple to realize. The use of these inserts in subsonic wind tunnels with moderate blockage ratio leads to very good agreement between free-flight and wind tunnel data, while this approach benefits from simple manufacturing and experimental realization.
Thermodynamics, Descriptive and experimental mechanics
Andrea Cioncolini, Mostafa R.A. Nabawy, Jorge Silva-Leon
et al.
This paper presents results from experiments and simplified numerical simulations on the flow-induced dynamics and power generation of inverted flags that combine flexible piezoelectric strips with photovoltaic cells to simultaneously harvest kinetic wind energy and solar radiant energy. Experiments were conducted in a wind tunnel under controlled wind excitation and light exposure, focusing in particular on the dynamics and power generation of the inverted flag harvester. Numerical simulations were carried out using a lattice-Boltzmann fluid solver coupled with a finite element structural solver via the immersed-boundary method, focusing in particular on minimizing the simulation run time. The power generated during the tests shows that the proposed inverted flag harvester is a promising concept, capable of producing enough power (on the order of 1 mW) to supply low-power electronic devices in a range of applications where distributed power generation is needed. Notwithstanding key simplifications implemented in the numerical model to achieve a fast execution, simulations and measurements are in good agreement, confirming that the lattice-Boltzmann method is a viable and time-effective alternative to classic Navier–Stokes-based solvers when dealing with strongly coupled fluid–structure interaction problems characterized by large structural displacements.
Thermodynamics, Descriptive and experimental mechanics
Mechanically, the assessment of the structure's safety relates to three aspects: strength, stability and oscillation. In the oscillation problems of structures, the safety conditions are conditions of frequency, amplitude, resonance, maximum displacement,etc ...
In case that the structure itself contains random parameters and subjects to external loads that are also the random parameters (or random processes), the assessment of the structure's safety according to the deterministic inequalities of structural mechanics will be insignificant. Therefore, this should be assessed according to the probabilistic point of view, namely, according to the reliability.
The determination of reliability of the oscillation problems of structures encounters many difficulties because the outputs of the structural analysis problem are the random processes (or the random field). Meanwhile, up to now, the determination of a probability according to which a random process will belong to a given domain by mathematical method has not been sufficiently studied yet.
In this paper, the authors, originating from a general definition on the reliability of a system by V. V. Bolotin, assess the reliability of oscillating structure, by determining the upper and the lower bounds of the reliability.
The upper and the lower bounds of the reliability are recommended to be determined by determining the probability depending on only an inequality instead of determining the it depending on a system of inequalities. Thus, the determination is very favourable.
Mechanical engineering and machinery, Descriptive and experimental mechanics