scholarly journals The Symmetric Nature of the Position Distribution of the Human Body Center of Gravity during Propelling Manual Wheelchairs with Innovative Propulsion Systems

Symmetry ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 154
Author(s):  
Bartosz Wieczorek ◽  
Mateusz Kukla ◽  
Łukasz Warguła
Keyword(s):  
Inclination Angle ◽  
Center Of Gravity ◽  
Propulsion Systems ◽  
Manual Propulsion ◽  
Inclination Angles ◽  
Hybrid Transmission ◽  
Secondary Objective ◽  
Body Center ◽  
The Impact ◽  
Average Position

Objective: The main objective of the tests conducted was to analyze the position variability of the human body’s center of gravity during propelling the wheelchair, and to demonstrate the properties enabling the description of this variability by means of plane figures with a symmetry axis. A secondary objective was to show the impact of the used manual propulsion type and the wheelchair inclination angle in relation to the plane on the dimensions of the position variability areas of the center of gravity. Method and materials: Three patients participated in the research representing 50 centiles of anthropometric dimensions. Each patient carried out fifteen measurement tests on three wheelchairs for three inclination angles of the wheelchair frame in relation to the level. Each measurement test consisted of five propulsion cycles for which the positions of the center of gravity were determined with the sampling frequency of 100 Hz. The measured positions of the center of gravity were approximated with ellipses containing 95.4% of the measurements conducted, assuming their dimension scaling basis in the form of the double value of standard deviation defined based on the registered results. Results: Based on the measurements conducted, the average values of five ellipses parameters were determined for nine cases in which a variable was the type of wheelchair propulsion and its inclination angle in relation to the level. The area of the highest variability of the position of the center of gravity was measured for the wheelchair with a multispeed transmission. The average dimensions of the ellipse semi-axis amounted to 108.53 mm for the semi-axis a and 29.75 for the semi-axis b, the average position of the ellipse center amounted to x = 114.51 mm and y = −10.53 mm, and the average inclination angle of the ellipse α amounted to −6.92°. The area of the lowest variability of the position of the center of gravity was measured for the wheelchair with a hybrid transmission. In this case, the average dimensions of the ellipse semi-axis amounted to 64.07 mm for the semi-axis a and 33.85 for the semi-axis b; whereas, the average position of the ellipse center amounted to x = 245.13 mm and y = −28.24 mm, and the average inclination angle of the ellipse α amounted to −0.56°.

scholarly journals The impact of ambient pressure and tunnel inclination angle on the smoke transport in a subway tunnel

2021 ◽  
Author(s):  
Guang Chen
Keyword(s):  
Inclination Angle ◽  
Ambient Pressure ◽  
Three Dimensional ◽  
Concentration Field ◽  
Air Entrainment ◽  
Subway Tunnel ◽  
Environmental Pressures ◽  
Smoke Transport ◽  
Inclination Angles ◽  
The Impact

Abstract The subway tunnel will be built in the plateau where the pressure is relatively low, and the tunnel will tilt at a certain angle due to topographic factors. In order to investigate the smoke transport characteristics of moving subway trains caught fire under different ambient pressures and different tunnel inclination angles, three-dimensional full-scale calculation models of subway trains, two stations and one tunnel are established, and three different environmental pressures (50kPa, 75kPa, 100kPa) and three different tunnel inclination angles (− 1.5 °, 0 °, + 1.5 °) are simulated. The IDDES turbulence model based on kω-sst RANS combined with the overset grid technology is used to simulate the subway train movement and the detailed flow field. The velocity and temperature distribution characteristics and smoke concentration field are studied in detail. The soot density of smoke and temperature increases with reduced ambient pressure due to the weakening of air entrainment and the decreased air density and the influence of ambient pressure on smoke diffusion decreases with the increase of pressure. The longitudinal airflow induced by the stack effect under the negative inclination angle of the tunnel is helpful to prevent the flowing back of smoke.

ANALYSES OF PEDESTRIAN’S HEAD-TO-WINDSHIELD IMPACT BIOMECHANICAL RESPONSES AND HEAD INJURIES USING A HEAD FINITE ELEMENT MODEL

2019 ◽  
Vol 20 (01) ◽  
pp. 1950063 ◽  
Author(s):  
ZHIHUA CAI ◽  
YUN XIA ◽  
XINGYUAN HUANG
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Impact Velocity ◽  
Inclination Angle ◽  
Head Injuries ◽  
Element Model ◽  
Head Model ◽  
Inclination Angles ◽  
Biomechanical Responses ◽  
The Impact

Head injuries in the vehicle crashes or pedestrian accidents can usually cause death or permanent disabilities, and head injuries resulting from the impact of car windshields remain a major problem. Anatomically, more realistic head models are required to more accurately document and evaluate the head-to-windshield impact responses and head injuries. The current study developed a head finite element model and carried out various simulations to investigate the head-to-windshield impact biomechanical responses and assess the head injuries. First, a 50th percentile three-dimensional finite element head model was developed and validated by using previously published cadaver experimental data. Then, the biomechanical responses were predicted under a head-to-windshield impact at different impact velocities (10, 12, and15[Formula: see text]m/s) and different inclination angles of the windshield (35∘, 40∘, and 45∘). Finally, head injuries were investigated through examining various injury parameters. The results indicated that the contact force, the acceleration, the intracranial pressure, the deformation of the skull, and the negative pressure rose when the impact velocity and the inclination angles increased. Thus, the vehicle impact velocity and the inclination angle of the windshield greatly affect the severity of the resulting injuries on pedestrians’ heads, with the severity increasing with the impact velocity and windshield inclination angle.

A Systematic Approach to Predicting Critical Heat Flux for Inclined Sprays

2007 ◽  
Vol 129 (4) ◽  
pp. 452-459 ◽  
Author(s):  
Milan Visaria ◽  
Issam Mudawar
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Inclination Angle ◽  
High Speed ◽  
Systematic Approach ◽  
Test Surface ◽  
Great Success ◽  
Spray Formation ◽  
Inclination Angles ◽  
The Impact

This study provides a new systematic approach to predicting the effects of spray inclination on critical heat flux (CHF). Experiments were performed with three pressure spray nozzles over a broad range of inclination angles at five flow rates and subcoolings of 15°C and 25°C. These experiments also included high-speed video analysis of spray formation, impact, and recoil for a 1.0×1.0cm2 test surface. Inclined sprays produced elliptical impact areas, distorted by lateral liquid flow that provided partial resistance to dryout along the downstream edge of the impact ellipse. These observations are used to determine the locations of CHF commencement along the test surface. A new theoretical model shows that increasing inclination angle away from normal decreases both the spray impact area and the volumetric flux. These trends explain the observed trend of decreasing CHF with increasing inclination angle. Combining the new model with a previous point-based CHF correlation shows great success in predicting the effects of spray inclination on CHF.

scholarly journals Method to evaluate the effect of inclination angle of steel open-type check dam on debris flow impact load

2018 ◽  
Vol 10 (1) ◽  
pp. 95-115 ◽  
Author(s):  
Toshiyuki Horiguchi ◽  
Yoshiharu Komatsu
Keyword(s):  
Debris Flow ◽  
Natural Disasters ◽  
Inclination Angle ◽  
Impact Load ◽  
Time History ◽  
Check Dam ◽  
Open Type ◽  
Inclination Angles ◽  
The Impact ◽  
Type Check

Although the latest statistics indicate a decrease in the number of victims of natural disasters in Japan, the number of sediment disasters has increased. A countermeasure against natural disasters is provided by the installation of a steel open-type check dam (hereafter, open Sabo dam). The open Sabo dam is expected to capture boulders (more than 1.0 m in diameter) contained in debris flow of which boulders concentrate in front part. When a debris flow impacts an open Sabo dam, the large impact load on the steel pipes are caused by the impact of boulders under debris flow. Therefore, it is important to evaluate the impact of both boulders and the following soil and small gravels including fluid force of the open Sabo dam from the design point of view. Although an open Sabo dam has various shapes especially, the every open Sabo dams is evaluated by the same design method in Japan. It is necessary to propose the load evaluation method in the experiment scale in contrast with different shape of open Sabo dam. This article presents an experimental approach to determine the effect of the front inclination angle of steel open Sabo dams on the impact load. The debris flow impacts 1/40 scale models of steel open Sabo dams which are set in a flow channel flume, and the debris flow load is measured by using three load cells placed horizontally at the back of the Sabo dam model. Different front inclination angles are set for each Sabo dam models. The time history of the impact load is examined by comparing the loads corresponding to four kinds of dams, which are different from the front inclination angles, and decrease of impact load considering the buffering effect of driftwoods in debris flow.

Shifting of the body center of gravity in low-risk preterm infants: A video-pedoscope study

2018 ◽  
Vol 124 ◽  
pp. 33-37 ◽  
Author(s):  
Natascia Bertoncelli ◽  
Laura Lucaccioni ◽  
Luca Ori ◽  
Christa Einspieler ◽  
Heinz F.R. Prechtl ◽  
...  
Keyword(s):  
Preterm Infants ◽  
Center Of Gravity ◽  
The Body ◽  
Low Risk ◽  
Body Center

scholarly journals The impact of COVID-19 on antipsychotic prescriptions for patients with schizophrenia in Australia

2021 ◽  
pp. 000486742110257
Author(s):  
Steve Kisely ◽  
Dante Dangelo-Kemp ◽  
Mark Taylor ◽  
Dennis Liu ◽  
Simon Graham ◽  
...  
Keyword(s):  
Human Services ◽  
Primary Outcome ◽  
Medical Consultation ◽  
Australian Government ◽  
Provider Type ◽  
Study Population ◽  
Secondary Objective ◽  
Long Acting ◽  
The Impact ◽  
Pharmaceutical Benefits Scheme

Objective: To assess the impact, in the Australian setting, of the COVID-19 lockdown on antipsychotic supplies for patients with schizophrenia following a prescription from a new medical consultation when compared to the same periods in the previous 4 years. A secondary objective was to assess the volume of all antipsychotic supplies, from new and repeat prescriptions, over these same periods. Methods: A retrospective pharmaceutical claims database study was undertaken, using the Department of Human Services Pharmaceutical Benefits Scheme 10% sample. The study population included all adult patients with three or more supplies of oral or long-acting injectable antipsychotics for the treatment of schizophrenia at any time between 1 June 2015 and 31 May 2020. The primary outcome compared volumes of dispensed antipsychotics from new prescriptions (which require a medical consultation) between 1 April and 31 May each year from 2016 to 2020. This was to analyse the period during which the Australian Government imposed a lockdown due to COVID-19 (April to May 2020) when compared the same periods in previous years. Results: There was a small (5.7%) reduction in the number of antipsychotics dispensed from new prescriptions requiring a consultation, from 15,244 to 14,372, between April and May 2019 and the same period in 2020, respectively. However, this reduction was not statistically significant ( p = 0.75) after adjusting for treatment class, age, gender, location and provider type. Conclusion: The COVID-19 restrictions during April and May 2020 had no significant impact on the volume of antipsychotics dispensed from new prescriptions for patients with schizophrenia when compared to the volume of antipsychotics dispensed from new prescriptions during the same period in previous years.

scholarly journals Acoustic Emission Characteristics and Joint Nonlinear Mechanical Response of Rock Masses under Uniaxial Compression

Energies ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 200
Author(s):  
Zhongliang Feng ◽  
Xin Chen ◽  
Yu Fu ◽  
Shaoshuai Qing ◽  
Tongguan Xie
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Inclination Angle ◽  
Failure Modes ◽  
Strain Curve ◽  
Particle Flow Code ◽  
Rock Masses ◽  
Physical Experiments ◽  
Inclination Angles ◽  
Joint Inclination

The joint arrangement in rock masses is the critical factor controlling the stability of rock structures in underground geotechnical engineering. In this study, the influence of the joint inclination angle on the mechanical behavior of jointed rock masses under uniaxial compression was investigated. Physical model laboratory experiments were conducted on jointed specimens with a single pre-existing flaw inclined at 0°, 30°, 45°, 60°, and 90° and on intact specimens. The acoustic emission (AE) signals were monitored during the loading process, which revealed that there is a correlation between the AE characteristics and the failure modes of the jointed specimens with different inclination angles. In addition, particle flow code (PFC) modeling was carried out to reproduce the phenomena observed in the physical experiments. According to the numerical results, the AE phenomenon was basically the same as that observed in the physical experiments. The response of the pre-existing joint mainly involved three stages: (I) the closing of the joint; (II) the strength mobilization of the joint; and (III) the reopening of the joint. Moreover, the response of the pre-existing joint was closely related to the joint’s inclination. As the joint inclination angle increased, the strength mobilization stage of the joint gradually shifted from the pre-peak stage of the stress–strain curve to the post-peak stage. In addition, the instantaneous drop in the average joint system aperture (aave) in the specimens with medium and high inclination angles corresponded to a rapid increase in the form of the pulse of the AE activity during the strength mobilization stage.

New Methodology for the Determination of the Vertical Center of Gravity of In-Service Semisubmersibles: Proposal and Numerical Assessment

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Ivan N. Porciuncula ◽  
Claudio A. Rodríguez ◽  
Paulo T. T. Esperança
Keyword(s):  
Accurate Determination ◽  
Center Of Gravity ◽  
Practical Implementation ◽  
Numerical Assessment ◽  
Neutral Equilibrium ◽  
Inclination Angles ◽  
Numerical Tools ◽  
The Stability ◽  
Metacentric Height

Along its lifetime, an offshore unit is subjected to several equipment interventions. These modifications may include large conversions in loco that usually are not adequately documented. Hence, the accurate determination of the platform's center of gravity (KG) is not possible. For vessels with low metacentric height (GM), such as semisubmersibles, Classification Societies penalize the platform's KG, inhibiting the installation of new equipment until an accurate measurement of KG is provided, i.e., until an updated inclining test is performed. For an operating semisubmersible, the execution of this type of test is not an alternative because it implies in removing the vessel from its in-service location to sheltered waters. Relatively recently, some methods have been proposed for the estimation of KG for in-service vessels. However, as all of the methods depend on accurate measurements of inclination angles and, eventually, on numerical tools for the simulation of vessel dynamics onboard, they are not straightforward for practical implementation. The objective of the paper is to present a practical methodology for the experimental determination of KG, without the need of accurate measurements of inclinations and/or complex numerical simulations, but based on actual operations that can be performed onboard. Indeed, the proposed methodology relies on the search, identification, and execution of a neutral equilibrium condition where, for instance, KG = KM. The method is exemplified using actual data of a typical semisubmersible. The paper also numerically explores and discusses the stability of the platform under various conditions with unstable initial GM, as well as the effect of mooring and risers.

Direct Outer Ring Cooling of a High Speed Jet Engine Mainshaft Ball Bearing: Experimental Investigation Results

2010 ◽  
Author(s):  
Peter Gloeckner ◽  
Klaus Dullenkopf ◽  
Michael Flouros
Keyword(s):  
Power Dissipation ◽  
High Speed ◽  
Ball Bearing ◽  
Operating Conditions ◽  
Outer Ring ◽  
Outer Diameter ◽  
Propulsion Systems ◽  
Jet Engine ◽  
Power Loss Reduction ◽  
The Impact

Operating conditions in high speed mainshaft ball bearings applied in new aircraft propulsion systems require enhanced bearing designs and materials. Rotational speeds, loads, demands on higher thrust capability, and reliability have increased continuously over the last years. A consequence of these increasing operating conditions are increased bearing temperatures. A state of the art jet engine high speed ball bearing has been modified with an oil channel in the outer diameter of the bearing. This oil channel provides direct cooling of the outer ring. Rig testing under typical flight conditions has been performed to investigate the cooling efficiency of the outer ring oil channel. In this paper the experimental results including bearing temperature distribution, power dissipation, bearing oil pumping and the impact on oil mass and parasitic power loss reduction are presented.

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