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1
Forslund, R. R. "The power function as a simple stem profile examination tool." Canadian Journal of Forest Research 21, no. 2 (February 1, 1991): 193–98. http://dx.doi.org/10.1139/x91-023.
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Formulae are presented for calculating the volume, surface area, centre of gravity, centre of mass, form, taper, and instantaneous slope of the power function. A profile plotting technique is also used that allows visual comparisons between average stem profiles independent of the size and taper of individual stems. The technique is used to demonstrate that the position near 30% of the height from the base of the stem is a position of form stability for volume estimation. Using the paracone profile model (a power function midway between a paraboloid and a cone) with the diameter at the 30% position and the total stem height, individual stem volume estimates within 10% of the true volume (95% confidence) are obtained once again using a sample of 50 yearling aspen (Populustremuloides Michx.). The plotting technique is then applied to the aspen sample, and the average profiles support the hypothesis that juvenile stems may begin life as paraboloids. The average centre of gravity, the average centre of mass, the sectional form, the average form, and the taper of the stems are also examined and are shown to be quantitative indicators of the plotted profile characteristics.
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Kono, Kengo, and Norihiko Saga. "Development of a Passive Turn Type Skiing Robot with Variable Height Mechanism of Gravitational Center." Journal of Robotics and Mechatronics 24, no. 2 (April 20, 2012): 372–78. http://dx.doi.org/10.20965/jrm.2012.p0372.
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In recent years, sports engineering has become an active area of research. It has produced important contributions of many kinds in the development of sports. Ski turns have been investigated from various viewpoints such as the motion analysis of skiers and ski robots and dynamic simulation. Nevertheless, despite considerable research, the mechanisms of ski turns remain to be completely elucidated. Mechanical models derived using approximate expressions do not, furthermore, match alpine ski turns and results are therefore not reflected concretely. To facilitate theoretical considerations, a passive skiing robot was developed. Influences on ski turns, such as the position of the center-of-gravity, can be examined easily using this robot. In a passive turn type of ski robot, a difference in the turn cycle appeared in a difference in leg height. We noticed the influence of turning in the difference in the center-of-gravity height and appended mechanism to change the height of the legs to a passive turn type of ski robot in order to verify whether turns can be controlled by changing the position of the gravitational center. As described here, we examined ski turn dynamics to help skiers improve their athletic performance.
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Tsarik, Ruslan Stanislavovich, and Denis Aleksandrovich Akmaykin. "EVALUATION OF INFLUENCE OF CONTAINER�S CENTER OF GRAVITY POSITION ON CONTAINER SHIP�S METACENTRIC HEIGHT." Vestnik Gosudarstvennogo universiteta morskogo i rechnogo flota imeni admirala S. O. Makarova 8, no. 6 (December 28, 2016): 58–70. http://dx.doi.org/10.21821/2309-5180-2016-8-6-58-70.
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MacDonald, G. B., and R. R. Forslund. "Application of a geometrical volume equation to species with different bole forms." Canadian Journal of Forest Research 16, no. 2 (April 1, 1986): 311–14. http://dx.doi.org/10.1139/x86-052.
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Stem analysis of 20 Abiesbalsamea (L.) Mill., 68 Piceamariana (Mill.) B.S.P., 19 Piceaglauca (Moench) Voss, 31 Populustremuloides Michx., and 37 Betulapapyrifera Marsh. revealed form variation between species. A volume equation based on the paracone (a geometrical solid midway between a paraboloid and a cone) estimated individual tree volume within 10% of the true volume (at the 95% confidence level) for all species. The input variables required were total height and diameter at a relative height of 0.2 for Betulapapyrifera and 0.3 for the other four species. If breast-height diameter was used, the effect of form variation on the accuracy of volume prediction was more pronounced. In this case, the geometrical equation modified for each species according to the average centre of gravity provided more consistently accurate volume estimates than either the paracone equation or Honer's transformed variable equation. For all species, the diameter measurement position was more critical than the version of the geometrical equation selected.
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Shabani, Babak, Jason Lavroff, Damien S. Holloway, Michael R. Davis, and Giles A. Thomas. "The influence of the centre bow and wet-deck geometry on motions of wave-piercing catamarans." Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 233, no. 2 (February 1, 2018): 474–87. http://dx.doi.org/10.1177/1475090217753761.
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The effects of tunnel height and centre bow length on the motions of a 112-m wave-piercer catamaran with an above-water centre bow were investigated through model tests. Five alternative centre bow configurations were considered, and multiple series of model tests were conducted in regular head sea waves. The results showed that both heave and pitch increased over a wide range of wave encounter frequency as the wet-deck height of the catamaran model increased. However, increasing the length of the centre bow showed an increase in the pitch but a decrease in the heave for a limited range of wave encounter frequency near the heave and pitch resonance frequencies of the catamaran model. The positions of minimum vertical displacement were found to be aft of the longitudinal centre of gravity, between 20% and 38% of the overall length from the transom. Increase in the wet-deck height and consequently the archway clearance between the main hulls and centre bow also resulted in an increase in the vertical displacement relative to the undisturbed water surface in the centre bow area. The results also indicated the vulnerability to wet-deck slamming for the different bow and wet-deck designs.
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Kyselovičová, Oľga, and Erika Zemková. "Postural Stability in Aerobic Gymnastics Specific Positions." Sport Science Review 19, no. 3-4 (August 1, 2010): 109–16. http://dx.doi.org/10.2478/v10237-011-0020-0.
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Postural Stability in Aerobic Gymnastics Specific Positions The study compares the effect of maximal jumps and sport-specific exercises on parameters of balance. Two balance elements (free support vertical split and frontal split) were analyzed in a group of 8 aerobic gymnasts (average age = 17,0 ± 1,3 years, average body height = 163,0 ± 6,9 cm, average body weight = 54,5 ± 6,12 kg, BMI 20,4 ± 1,46 kg.m-2). The FiTRO Sway Check stabilographic system, allowing the monitoring of horizontal movement of centre of gravity with the help of dynamometric board, was used for assessment. Stabilographic parameter of the velocity of the centre of pressure (mean and in antero-posterior and medio-lateral directions) was registered at 100 Hz. The results show significant differences in average sway length in medio-lateral and antero-posterior direction, in both analysed difficulty elements. This indicates that balance impairment after exercise and its readjustments to pre-exercise level depends not only on intensity of proprioceptive stimulation but also on type of exercise.
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Laszlo, Robert, Cristian Radeanu, Stefan Ilici, Mircea Grecea, and Miklos Levente. "Technical and safety aspects at the demolition by blasting works of a cooling tower with a high of 72.00 m." MATEC Web of Conferences 305 (2020): 00072. http://dx.doi.org/10.1051/matecconf/202030500072.
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From the point of view of demolition, one of the most interesting construction categories is the hyperboloid shape cooling towers. These seemingly fragile structures support at the base on a reinforced concrete belt and pillars. An important element to be taken into account when choosing the demolition solution is the slope of the tower. As this ratio between tower height and base diameter is greater (4-5), the easier is the demolition of the tower by overturning, respectively by moving the centre of gravity of the construction away from its base. In the case of the cooling tower described in this article, its height was 72.00 m and the base diameter of 52.00 m - the slope ratio index being less than 2, which was why the chosen solution of demolition was that of partial lateral collapse followed by a total crash of the tower on its position. The article describes how to perform the demolition of the cooling tower, the technical and safety solutions adopted for its successful collapse in the intended direction, in very sensitive location conditions regarding the constructions and installations in its immediate vicinity.
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NIIMI, Hirofumi. "Relationship between the position of the center of gravity of the crawler robot and the step height that can be climbed." Proceedings of JSME annual Conference on Robotics and Mechatronics (Robomec) 2018 (2018): 1P2—F05. http://dx.doi.org/10.1299/jsmermd.2018.1p2-f05.
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QI, HUIRONG, and MEI LIU. "APPLICATION OF A ONE-DIMENSIONAL POSITION SENSITIVE CHAMBER ON SYNCHROTRON RADIATION." International Journal of Modern Physics: Conference Series 27 (January 2014): 1460142. http://dx.doi.org/10.1142/s2010194514601422.
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In the last few years, wire chambers have been frequently used for X-ray detection because of their low cost, large area and reliability. X-ray diffraction is an irreplaceable method for powder crystal lattice measurements. A one-dimensional single-wire chamber has been developed in our lab to provide high position resolution for powder diffraction experiments using synchrotron radiation. There are 200 readout strips of 0.5 mm width with a pitch of 1.0 mm in the X direction, and the working gas is a mixture of Ar and CO2 (90/10). The one-dimensional position of the original ionization point is determined by the adjacent strip's distribution information using the center of gravity method. Recently, a study of the detector's performance and diffraction image was completed at the 1W1B laboratory of the Beijing Synchrotron Radiation Facility (BSRF) using a sample of SiO2. Most of the relative errors between the measured values of diffraction angles and existing data were less than 1%. The best position resolution achieved for the detector in the test was 71 μm (σ value) with a 20 μm slit collimator. Finally, by changing the detector height in incremental distances from the center of the sample, the one-dimensional detector achieved a two-dimensional diffraction imaging function, and the results are in good agreement with standard data.
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SWATERS, GORDON E. "Dynamics of radiating cold domes on a sloping bottom." Journal of Fluid Mechanics 364 (June 10, 1998): 221–51. http://dx.doi.org/10.1017/s0022112098001049.
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Numerical simulations of benthic gravity-driven currents along continental shelves suggest they exhibit considerable time and spatial variability and tend to organize themselves into large-scale bottom-intensified cold domes or eddies. Attempts to derive simple relations governing the evolution of the spatial moments of the mass equation for baroclinic eddies have failed because it is not clear how to express the form or wave drag stresses associated with the excited (topographic) Rossby wave field in the surrounding fluid in terms of the eddy moments. We develop a simple model for the leading-order time evolution of a cold dome configuration which initially nearly satisfies the Mory–Stern isolation constraint. As the topographic Rossby wave field in the surrounding fluid interacts with the cold dome, higher azimuthal modes are excited within the cold dome which develop into spiral-like filamentary structures on the eddy boundary. The trajectory followed by the position of the maximum height of the cold dome corresponds to sub-inertial along- and cross-slope oscillations superimposed on a mean along-slope drift (well described by the Nof velocity). Nevertheless, the theory suggests that there are no oscillations (at least to second order) in the horizontal spatial moments of the eddy height, that is, the centre of mass of the eddy moves steadily in the along- and down-slope directions (i.e. ‘southwestward’ relative to the topographic β-plane). The theoretical analysis is in good agreement with a nonlinear numerical simulation which we present.
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Jurak, Rađenović, Bolčević, Bartolac, and Medved. "The Influence of the Schoolbag on Standing Posture of First-Year Elementary School Students." International Journal of Environmental Research and Public Health 16, no. 20 (October 16, 2019): 3946. http://dx.doi.org/10.3390/ijerph16203946.
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The purpose of this study was to determine the influence of the mass of a schoolbag on standing posture in first-year elementary school children. First-year elementary school students (n = 76) participated in this study. The data was digitized and analyzed using SkillSpector and Kinovea. Results have shown a change of Center of Gravity (COG) position in all three anatomical planes (p < 0.01), as well as a change in two out of three measured postural angles—craniovertebral (p < 0.01) and craniocervical (p < 0.01) angle. The most important aspect of changed posture, anterior shift of COG, was measured to be 2.4 cm and was in moderate negative correlation with student body mass (−0.4, p < 0.01) and height (−0.4, p < 0.01) when students were encumbered with a schoolbag weighing 16.11% of their body mass, on the average. Also, this study confirms that when encumbered, students’ head posture shifts to a more protracted position.
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Salinero, Juan J., Cristina González-Millán, Javier Abián-Vicén, and Juan Del Coso Garrigós. "Influence of Dorsiflexion Shoes on Jump Performance." Journal of Applied Biomechanics 30, no. 2 (April 2014): 290–93. http://dx.doi.org/10.1123/jab.2013-0189.
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The goal of dorsiflexion sports shoes is to increase jumping capacity by means of a lower position of the heel in relation to the forefoot which results in additional stretching of the ankle plantar flexors. The aim of this study was to compare a dorsiflexion sports shoe model with two conventional sports shoe models in a countermovement jump test. The sample consisted of 35 participants who performed a countermovement jump test on a force platform wearing the three models of shoes. There were significant differences in the way force was manifested (P< 0.05) in the countermovement jump test, with a decrease in the velocity of the center of gravity and an increase in force at peak power and mean force in the concentric phase. Moreover, peak power was reached earlier with the dorsiflexion sports shoe model. The drop of the center of gravity was increased in CS1 in contrast to the dorsiflexion sports shoe model (P< .05). However, the dorsiflexion sports shoes were not effective for improving either peak power or jump height (P> .05). Although force manifestation and jump kinetics differ between dorsiflexion shoes and conventional sports shoes, jump performance was similar.
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He, Yinshui, Daize Li, Zengxi Pan, Guohong Ma, Lesheng Yu, Haitao Yuan, and Jian Le. "Dynamic Modeling of Weld Bead Geometry Features in Thick Plate GMAW Based on Machine Vision and Learning." Sensors 20, no. 24 (December 11, 2020): 7104. http://dx.doi.org/10.3390/s20247104.
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Weld bead geometry features (WBGFs) such as the bead width, height, area, and center of gravity are the common factors for weighing welding quality control. The effective modeling of these WBGFs contributes to implementing timely decision making of welding process parameters to improve welding quality and enhance automatic levels. In this work, a dynamic modeling method of WBGFs is presented based on machine vision and learning in multipass gas metal arc welding (GMAW) with typical joints. A laser vision sensing system is used to detect weld seam profiles (WSPs) during the GMAW process. A novel WSP extraction method is proposed using scale-invariant feature transform and machine learning. The feature points of the extracted WSP, namely the boundary points of the weld beads, are identified with slope mutation detection and number supervision. In order to stabilize the modeling process, a fault detection and diagnosis method is implemented with cubic exponential smoothing, and the diagnostic accuracy is within 1.50 pixels. A linear interpolation method is presented to implement sub pixel discrimination of the weld bead before modeling WBGFs. With the effective feature points and the extracted WSP, a scheme of modeling the area, center of gravity, and all-position width and height of the weld bead is presented. Experimental results show that the proposed method in this work adapts to the variable features of the weld beads in thick plate GMAW with T-joints and butt/lap joints. This work can provide more evidence to control the weld formation in a thick plate GMAW in real time.
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Skrucany, Tomas, Jan Vrabel, and Patrik Kazimir. "The influence of the cargo weight and its position on the braking characteristics of light commercial vehicles." Open Engineering 10, no. 1 (February 27, 2020): 154–65. http://dx.doi.org/10.1515/eng-2020-0024.
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AbstractThe influence of the cargo weight loaded on the vehicle and the total gross mass of the vehicle on the braking characteristics is often researched from the road safety reason. However, there is not enough knowledge about the influence of weight and load distribution on the loading area of small trucks or vans on their braking characteristics. This article presents the results of measurements of braking decelerations of the van of N1 category and the braking characteristics of a vehicle loaded with different cargo mass with different cargo locations on the loading area. The impact of the longitudinal cargo position on the loading area on the load of the individual axles and thus on the braking deceleration of the vehicle was investigated. The influence of the height of the center of gravity on the dynamic axle load during braking was also determined. Method of direct vehicle deceleration measurement was used by a decelerometer. There were calculated cargo weight and cargo position influences on the dynamic axle load during braking according to the vehicle deceleration.
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Tavakoli Dakhrabadi, Mohammad, and Mohammad Saeed Seif. "Hydro-aerodynamic mathematical model and multi-objective optimization of wing-in-ground effect craft in take-off." Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 232, no. 4 (May 18, 2017): 421–33. http://dx.doi.org/10.1177/1475090217708478.
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Hydro-aerodynamic mathematical model and multi-objective optimization of a popular wing-in-ground effect craft are presented in this research using a hydro-aerodynamic practical method and the genetic algorithm. The primary components of the wing-in-ground effect craft configuration include a compound wing, catamaran hull form and a power-augmented ram platform. The hydro-aerodynamic practical method with low computational time and high accuracy is performed by coupling hydrodynamic and aerodynamic considerations using the potential flow theory in ground effect and the semi-empirical equations proposed for high-speed marine vehicles. The trade-off between hydrodynamic and aerodynamic characteristics makes it difficult to simultaneously satisfy the design requirements of high hydro-aerodynamic performance. In this article, three goals—reduced hump resistance, increased compound wing lift-to-drag ratio and reduced take-off speed—are selected as the objective functions. The longitudinal position of center of gravity, position of outer wing with respect to main wing, power augmented ram platform angle to horizontal and flap angle are also adopted as design variables. Static height stability and the location of the center of gravity with respect to the aerodynamics centers are considered as constraints for the stable flight in ground effect. The optimal solutions of the multi-objective optimization were not unique, rather a set of non-dominated optima, called the Pareto sets, are obtained. As a result of the multi-objective optimization, 25 Pareto individuals are obtained that the naval architects can use in designing wing-in-ground crafts.
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Dorogovtsev, Victor N., Dmitry S. Yankevich, and Nandu Goswami. "Effects of an Innovative Head-Up Tilt Protocol on Blood Pressure and Arterial Stiffness Changes." Journal of Clinical Medicine 10, no. 6 (March 13, 2021): 1198. http://dx.doi.org/10.3390/jcm10061198.
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The objective of our study was to identify blood pressure (BP) and pulse wave velocity (PWV) changes during orthostatic loading, using a new the head-up tilt test (HUTT), which incorporates the usage of a standardized hydrostatic column height. Methods: 40 healthy subjects 20–32 years performed HUTT, which was standardized to a height of the hydrostatic column at 133 cm. Exposure time was 10 min in each of 3 positions: horizontal supine 1, HUTT, and horizontal supine 2. The individual tilt up angle made it possible to set the standard value of the hydrostatic column. Hemodynamic parameters were recorded beat to beat using “Task Force Monitor 3040 i”, pulse-wave velocity (PWV) was measured with a sphygmograph–sphygmomanometer VaSera VS1500N. Results: Orthostatic loading caused a significant increase in heart rate (HR) and a decrease in stroke volume (SV) (p < 0.05) but no significant reductions in cardiac output, changes in total vascular resistance (TVR), or BP. An analysis of personalized data on systolic blood pressure (SBP) changes in tilt up position as compared to horizontal position (ΔSBP) revealed non-significant changes in this index in 48% of subjects (orthostatic normotension group), in 32% there was a significant decrease in it (orthostatic hypotension group) and in 20% there was a significant increase in it (orthostatic hypertension group). These orthostatic changes were not accompanied by any clinical symptoms and/or syncope. During HUTT, all subjects had in the PWV a significant increase of approximately 27% (p < 0.001). Conclusion: The new test protocol involving HUTT standardized to a height of hydrostatic column at 133 cm causes typical hemodynamics responses during orthostatic loading. Individual analysis of the subjects revealed subclinical orthostatic disorders (OSD) in up to 52% of the test persons. During HUTT, all test subjects showed a significant increase in PWV. The new innovative HUTT protocol can be applied in multi-center studies in healthy subjects to detect preclinical forms of orthostatic disorders under standard gravity load conditions.
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Saga, Takuma, and Norihiko Saga. "Alpine Skiing Robot Using a Passive Turn with Variable Mechanism." Applied Sciences 8, no. 12 (December 17, 2018): 2643. http://dx.doi.org/10.3390/app8122643.
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Recently, the number of alpine ski junior players in Japan has drastically decreased. The causes include a decrease in ski areas and instructors, along with difficulty of early childhood alpine ski guidance. The alpine ski competition is not simply a glide on a slope. It requires understanding of ski deflection and skier posture mechanics. Therefore, a passive ski robot without an actuator was developed for junior racers of the alpine ski competition to facilitate understanding of the turn mechanism. Using this robot can elucidate factors affecting ski turns, such as the position of the center of gravity (COG) and the ski shape. Furthermore, a mechanism for changing the COG height, the edge angle and the ski deflection is added to the passive turn type ski robot. The developed ski robot can freely control the turn by changing those parameters during sliding.
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Öberg, Kurt, Anna Torén, and Malin Hansson. "Saddle Seats for Tractor Drivers – A Conceptual Study." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 44, no. 22 (July 2000): 624–27. http://dx.doi.org/10.1177/154193120004402234.
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Tractor drivers have quite often musculoskeletal problems because of bad sitting postures. It has been found that a good sitting posture is the one obtained when sitting on a horse with the hips in a muscle balanced rest position of 45°. A natural curvature of the spine is acquired as well as a perfectly balanced position in which the body obtains a good position of the centre of gravity. To improve the sitting posture of the driver of agricultural tractors, different types of saddle seats were adapted to fit in a tractor, and tested upon their comfort, work function and sitting posture. The saddle seats occupied less space in the horizontal plane compared to the conventional chair, and they were rotating freely during driving. Ten subjects employed as tractor drivers volunteered for the study. They harrowed and ploughed with three different saddle seats and one conventional tractor chair. Questions on experienced chair comfort and work function were asked. The drivers were video filmed from above and from the side in order to register their sitting posture. On a scale from 1 to 5 the conventional chair received a mean score of 3.6 and the saddle seats received mean score around 2. The difference is regarded to depend on differences in seat comfort. The saddle seats free rotation was mainly used during ploughing and reduced the spinal twisting 50%. The seat height adjusted by the tractor drivers was for the saddle seats 13 cm higher than for the conventional chair. This meant that the drivers received a sitting posture advantageous for the spine curvature. A future design of a tractor chair should have the possibility of varying raised sitting posture and free rotation. The seat should have a shape which gives a better seat comfort than any of the tested saddle seats.
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Brodskiy, Victor. "Parameters of the safety and fall arrest nets in buildings under construction." E3S Web of Conferences 97 (2019): 03006. http://dx.doi.org/10.1051/e3sconf/20199703006.
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There are terms of industrial safety provision for construction and reconstruction of building and structures for various purposes through the use of protection netting devices, which in some cases is the only possible means of preventing industrial injury in the event of a person or objects possible fall from height. Given are basic component elements of devices in which synthetic netting materials are proposed as the most pacing factor for required degree of protection. Considered are protection netting devices’ key parameters allowing ensuring guaranteed arresting of items falling from certain height, as well as required length and angle for brackets installation with required distance between them. Based on derived dependences, established was a family of items’ descent trajectories for various components of horizontal speed and values of initial center-of-gravity position that are shown on respective nomograph. A nomograph was also built allowing identifying under given values the bracket length and angle of its installation with the purpose of ensuring arresting of falling item. To reduce the probability of a falling human collision with supporting structures of a protection netting device, recommended minimum distance between brackets was set.
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Bubeníčková, Aneta, and Jana Simeonovová. "Contour determination and shape characteristics of different varieties of potato tubers." Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 59, no. 1 (2011): 9–14. http://dx.doi.org/10.11118/actaun201159010009.
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Precise determination of potato tubers’ shape and variability existing among individual potato varieties is necessary e.g. for modeling of handling and transport processes. The procedures described in the work are used for determination and evaluation of potato tubers shape variability and proportional importance of four main principal components. Ten different potato varieties were analyzed (Karin, Karlena, Krasa, Marilyn, Princess, Red Anna, Rosara, Sazava, Vendula, andVera) and elliptic Fourier descriptors employed for description of tubers shape. Following principal components were quantified: height to width ratio, position of the center of gravity, curvature, and degree of roundness. The scores of the resulting components were used in subsequent analysis as tuber shape characteristic. The first four principal components covered almost 100 % of the total variance in both, front and side-view shape and 97 % in top-view shape. Height to width ratio was evaluated as the determining parameter with contribution of 70.58–74.02 % of the total shape variation (front-view) forKarinandVendulavarieties respectively. The other principal components were significantly less affecting the overall variability. It was confirmed that described approach is precise and usable procedure for potato tubers shape analysis.
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Shi, Xiaohua, Hao Lu, and Ziming Chen. "Design and Analysis of an Intelligent Toilet Wheelchair Based on Planar 2DOF Parallel Mechanism with Coupling Branch Chains." Sensors 21, no. 8 (April 10, 2021): 2677. http://dx.doi.org/10.3390/s21082677.
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Due to the fixed size of the structure or the possibility of only simple manual adjustment, the traditional toilet wheelchair cannot easily be adapted to the size of the user or the toilet. In this paper, a planar two-degree-of-freedom parallel mechanism with coupling branch chains is proposed to enable both seat height adjustment and body posture adjustment of a toilet chair, solving the problems of posture adaptability between the user and the machine, and height matching in the process of using the wheelchair-assisted toilet. The model of the parallel mechanism was designed after analyzing the general rules of posture transformation in the human body before and after the toilet process, and the dimensions of each linkage were then determined according to the constraint conditions. By analyzing the degree of freedom, kinematics, workspace, singularity and position of the center of gravity, the rationality of the design was ensured. The weighted average function was used to find the optimal fixed point of the horizontal moving slider, and the actual trajectory at the end of the single driving mode was close to the ideal trajectory. The experimental results show that the adjustable seat height range is 290~550 mm and the adjustable angle range is 0~90°, which can enable disabled people to use the toilet independently.
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Soong, Ren Chung, Sun Li Wu, and Jui Min Lee. "An Electric Wheelchair with Function of Climbing up and down a Step." Applied Mechanics and Materials 479-480 (December 2013): 304–8. http://dx.doi.org/10.4028/www.scientific.net/amm.479-480.304.
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A new electric four-wheel wheelchair with function of climbing up and down a step is proposed. Each wheel has four telescopic rods driven by a ratchet mechanism which makes them stretchable. They retract into each wheel during the wheelchair moves on the flat roads. They stretch out of each wheel to overcome a step obstacle during the wheelchair encounters the steps and thresholds. The center of gravity and angular position of the seat relative to the horizontal axis can be adjusted simultaneously during climbing up and down a step or moving on the uphill or downhill road sections. The actual test of climbing up and down a height 15 cm step has been done successfully on condition of carrying a weight 85 kg person. This new electric wheelchair makes users more safe and scopes of activity of the elderly and those with disabilities wider.
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Abel, E. W., and T. G. Frank. "The design of attendant propelled wheelchairs." Prosthetics and Orthotics International 15, no. 1 (April 1991): 38–45. http://dx.doi.org/10.3109/03093649109164273.
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The attendant operated wheelchair is propelled by applying forces to handles at the rear of the chair. There are no published data to justify the design of pushing handles on existing wheelchairs. In Dundee, studies of pushing have been conducted in order to obtain subjective preferences for location and design of handles and an understanding of bio-mechanical factors associated with wheelchair pushing. Preferred positions for handles have been found to be in the region of 0.75 of shoulder height, 1.14 times shoulder width although deviations of +5% in these values are still rated as acceptable. The preferred positions do not correspond to minimum levels of resultant force or with lowest levels of moment in any of the upper body joints. Moments occurring at the lower back are not substantially affected by handle position. The biomechanical analysis so far has not revealed why some handle positions are more comfortable for pushing than others. Further study, involving calculation of resultant moments (rather than just sagittal plane moments) at these joints and at the lower body joints, is a next step in attempting to find the indicators of discomfort. Transferring a patient from or to a wheelchair can be a difficult operation with risks of accidents to the patient through falling and risks to the attendant of strain, particularly to the back. Current footrests on wheelchairs are a major source of the problems during transfer. A new approach to footrest design is described which solves these difficulties by using a footrest that lowers onto the floor. This has other attractive features such as providing good stability and restraint of the chair during transfer. The armrests are also discussed since they have a role to play where patients can assist themselves during transfer but have the potential for being an obstruction when patients need to be lifted from wheelchairs. The ease of pushing and manoeuvring, the difficulties caused by obstacles such as carpet edges and lift entrances, the operation of the brakes, and the position of the pushing handles are all important aspects of chairs used for transporting patients. The wheels, particularly the wheel diameter, tyre compressibility and castor trail, are determinants of the mobility aspects. However, the position of the wheels in relation to the centre of gravity and whether the castors are at the front or rear must also be considered. The brakes, as well as being effective, should be easy to apply and not too affected by wear. A prototype wheelchair is described which incorporates design features suggested by research into the above considerations.
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Antropova, T. A., and M. I. Glushko. "Analysis of the stability control of the car with the admission to the infrastructure." Vestnik of the Railway Research Institute 77, no. 1 (February 28, 2018): 49–57. http://dx.doi.org/10.21780/2223-9731-2018-77-1-49-57.
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The rolling stock and the railway track are a single stant tendency of the development of rail transport in relation to mechanical system. The running parts of the rolling stock and the the interaction of the power wheel-to-rail friction pair consists in track are interacting under difficult dynamic conditions. The con-increasing the axle load on the rails for freight rolling stock and further increasing the speed of the passenger trains. It takes a qualified approach to traffic safety issues and special attention to the stability of rolling stock to achieve these goals. An analysis of the stability control of the car with an admission to the infrastructure was carried out based on the regulatory documents that establish the main provisions and procedures for the operation of railways and railway workers. Authors proposed the elimination of existing shortcomings and ensuring the stability of the carriage motion by optimizing parameters of the placement of goods in the car. Calculations were made on the rollover stability conditions (stability loss) of the body and the criterion of the critical speed at which the carriage derailed due to the loss of contact of the wheels with the internal rail line of the curve. A method for controlling the stability of a car with a load by means of two-position weighing is proposed. The results obtained also make it possible to determine the height of the common center of gravity (CG), the magnitude of the longitudinal and lateral displacement of the center of gravity of the freight.
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Fujimoto, Yusuke, Mark R. Krumholz, and Shu-ichiro Inutsuka. "Distribution and kinematics of 26Al in the Galactic disc." Monthly Notices of the Royal Astronomical Society 497, no. 2 (July 24, 2020): 2442–54. http://dx.doi.org/10.1093/mnras/staa2125.
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ABSTRACT 26Al is a short-lived radioactive isotope thought to be injected into the interstellar medium (ISM) by massive stellar winds and supernovae (SNe). However, all-sky maps of 26Al emission show a distribution with a much larger scale height and faster rotation speed than either massive stars or the cold ISM. We investigate the origin of this discrepancy using an N-body + hydrodynamics simulation of a Milky-Way-like galaxy, self-consistently including self-gravity, star formation, stellar feedback, and 26Al production. We find no evidence that the Milky Way’s spiral structure explains the 26Al anomaly. Stars and the 26Al bubbles they produce form along spiral arms, but, because our simulation produces material arms that arise spontaneously rather than propagating arms forced by an external potential, star formation occurs at arm centres rather than leading edges. As a result, we find a scale height and rotation speed for 26Al similar to that of the cold ISM. However, we also show that a synthetic 26Al emission map produced for a possible Solar position at the edge of a large 26Al bubble recovers many of the major qualitative features of the observed 26Al sky. This suggests that the observed anomalous 26Al distribution is the product of foreground emission from the 26Al produced by a nearby, recent SN.
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Stavrev, Petar, Daniela Gerovska, and Marcos J. Araúzo-Bravo. "Automatic inversion of magnetic anomalies from two height levels using finite-difference similarity transforms." GEOPHYSICS 71, no. 6 (November 2006): L75—L86. http://dx.doi.org/10.1190/1.2345192.
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We solve the inverse magnetic problem for the depth and shape of simple sources in the presence of a regional field and truly random noise. We do not use noise-generating derivatives nor are we forced to solve complex systems of equations. Our inverse operator applies a new geometric type of field transform, the finite-difference similarity transform (FDST), that is based on a postulated degree of homogeneity in the potential field. Magnetic data from two height levels are required for the calculation of the FDSTs. The FDSTs are generated for an assumed central point of similarity (CPS) and a trial value (index) for the coefficient of similarity, and they are sensitive to the distance between the source and the CPS and to the agreement between the index and the degree of homogeneity in the data. When the CPS converges to a singular point in the potential field, say, the center or the topedge of the source, and when the trial index converges on the degree of homogeneity present in the data, the FDST drops in amplitude and its plot approaches a straight line, thereby signaling an interpretation for the source position and type. All inverse operations are fully automated and applicable to the interpretation of large data sets. The necessary data for the second level can be obtained by actual measurement or, alternatively, by deriving them from the data at the first level by an upward, analytical continuation. Upward continuation suppresses high-wavenumber random noise and thus contributes to a stable inversion. Model tests show that a suitable height for the second level is less than the expected depth of the source below the first level, while a suitable window length is about twice that depth. Examples show that the proposed inversion is effective on both model and field data. Note that this approach can be extended to the inversion of any component or derivative of the 2D or 3D magnetic or gravity fields from simple sources.
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Han, I., and R. M. Brach. "Impact throw model for vehicle-pedestrian collision reconstruction." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 216, no. 6 (June 1, 2002): 443–53. http://dx.doi.org/10.1243/09544070260137381.
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A planar model for the mechanics of a vehicle-pedestrian collision is presented, analysed and compared with experimental data. It takes into account the significant physical parameters of wrap and forward projection collisions and is suitable for solution using mathematics software or spreadsheets. Parameters related to the pedestrian and taken into account include horizontal distance travelled between primary and secondary impacts with the vehicle, launch angle, centre-of-gravity height at launch, the relative forward speed of the pedestrian to the car at launch, distance from launch to a ground impact, distance from ground impact to rest and pedestrian-ground drag factor. Vehicle and roadway parameters include post-impact, constant velocity vehicle travel distance, continued vehicle travel distance to rest with uniform deceleration and relative distance between rest positions of vehicle and pedestrian. The model is presented in two forms. The first relates the throw distance to the initial vehicle speed. The second, intended for reconstruction, relates the vehicle speed to the pedestrian throw distance. The first form is used as means of comparison of the model with selected sets of experimental data taken from the current literature, including a variational study using Monte Carlo simulation. The second (reconstruction) form is derived analytically not empirically and the parameters have physical interpretations. In order to obtain parameter values, direct calculation or the method of least squares can be used. A comparison of the reconstruction model with results of other reconstruction models is presented.
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Christian, A., and G. Dzemski. "Reconstruction of the cervical skeleton posture of Brachiosaurus brancai Janensch, 1914 by an analysis of the intervertebral stress along the neck and a comparison with the results of different approaches." Fossil Record 10, no. 1 (February 1, 2007): 38–49. http://dx.doi.org/10.5194/fr-10-38-2007.
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The neck posture of <i>Brachiosaurus brancai</i> Janensch, 1914 is reanalysed by employing the Preuschoft method to deduce the pattern of stress in the joints between the vertebral centra along the neck. The cogency of different methods for reconstructing the posture of a long neck, especially the Preuschoft method and approaches that are based on optimal articulation of the neck vertebrae, is discussed critically. The results corroborate the reliability of the Preuschoft method whereas the analyses of recent vertebrates with long necks show that approaches based on optimal articulation of the neck vertebrae are less suited for reconstructing habitual postures of long necks during rest. Such models are better suited for reconstructing the neck posture that was employed during locomotion. With the evidence obtained by different methods a conclusive picture of the neck posture and the feeding strategy of <i>Brachiosaurus brancai</i> can be drawn. The neck appears to have been slightly S-shaped with a ventrally flexed cranial section, an approximately straight middle section, and a dorsally flexed proximal part. In the habitual posture during standing, the angle between the middle section of the neck and the horizontal plane was about 60° or 70°. During locomotion the whole neck probably was kept in an lower position with the inclination reduced by approximately 20° compared with the position at rest. During feeding movements of the head relative to the neck and movements in the cranial neck section were performed without much altering the height of the centre of gravity of the neck. With slow dorsoventral movements of the whole neck pronounced changes in the feeding height were possible. Sideways movements of the whole neck were performed by lateral flexion at the base of the neck. According to these findings, the long neck of <i>Brachiosaurus brancai</i> was a means for browsing in great heights as well as a means for increasing the feeding volume without moving the body. <br><br> Die Halsstellung von <i>Brachiosaurus brancai</i> Janensch, 1914 wird mit Hilfe der Preuschoft-Methode untersucht, die auf der Ermittlung der Spannungen in den Gelenken zwischen den Wirbelkörpern entlang des Halses beruht. Verschiedene Rekonstruktionsmethoden langer Hälse werden hinsichtlich ihrer Aussagekraft kritisch betrachtet, insbesondere die Preuschoft-Methode sowie Ansätze, die auf einer optimalen Gelenkung zwischen den Wirbeln beruhen. Die Ergebnisse untermauern die Zuverlässigkeit der Preuschoft-Methode, während Analysen an langen Hälsen rezenter Wirbeltiere zeigen, dass Modelle mit optimaler Gelenkung sich weniger für die Rekonstruktion der habituellen Halsstellung während der Ruhe eignen. Stattdessen scheinen solche Modelle eher den Halsstellungen bei der Fortbewegung nahe zu kommen. Unter Einbeziehung verschiedener Methoden wird ein schlüssiges Bild der Halsstellung und der Ernährungsstrategie von <i>Brachiosaurus brancai</i> gezeichnet. Der Hals wurde offenbar in einer leichten S-Form gehalten, mit einem ventralflektierten vorderen Halsabschnitt, einer etwa gerade gehaltenen Halsmitte und einer dorsalflektierten Halsbasis. In der habituellen Stellung des stehenden Tieres bildete die Halsmitte einen Winkel von etwa 60° oder 70° mit der Horizontalebene. Bei der Fortbewegung wurde der Hals vermutlich um rund 20° niedriger gehalten als in der Ruheposition. Während der Nahrungsaufnahme konnte der Kopf durch Bewegungen allein des vorderen Halsabschnittes positioniert werden, ohne dass dabei der Schwerpunkt des Halses wesentliche Höhenänderungen erfahren hätte. Langsame dorsoventrale Bewegungen des gesamten Halses ermöglichten auch erhebliche Änderungen der Kopfhöhe. Seitliche Bewegungen des gesamten Halses konnten an der Halsbasis erzeugt werden. Gemäß dieser Ergebnisse war der lange Hals von <i>Brachiosaurus brancai</i> sowohl ein Mittel zum Erreichen von Nahrungsquellen in großer Höhe als auch zur Vergrößerung des Volumens, das bei ruhendem Körper mit dem Kopf erreicht werden konnte. <br><br> doi:<a href="http://dx.doi.org/10.1002/mmng.200600017" target="_blank">10.1002/mmng.200600017</a>
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Jankowicz-Szymańska, Aganieszka, Marta A. Bibro, Katarzyna Wódka, and Eliza Smoła. "The influence of age on the body posture of women." Health Promotion & Physical Activity 1, no. 1 (June 20, 2018): 1–6. http://dx.doi.org/10.5604/01.3001.0012.1270.
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Introduction and aim of the study: The body posture, which is one of the determinants of health and functional efficiency, changes depending on gender, age and psychophysical condition. Defining a pattern of correct posture is extremely difficult as it is a highly individualised feature. The aim of this paper was to compare the body posture of women in three periods of ontogenesis: girls in puberty, young adult women and women in the geriatric age. Material and methods: 150 women were examined: 50 12-year-old pupils, 50 20-22-year-old students and 50 women aged 60-84. Their height and weight were measured, BMI calculated and the status of body weight determined as normal, overweight or obese. The Zebris Pointer ultrasound system analyzed the position of the spine in the sagittal and frontal plane, the symmetry of the shoulders and pelvis in the frontal plane, and the balance of the torso in the sagittal and frontal plane. The results were developed with the Statistica programme. Basic descriptive statistics, multiplicity tables, Shapiro-Wilk test (study of normality of distribution) and Kruskal-Wallis test (inter-group comparison) were used. Differences between groups were assumed to be significant when p<0.05. Results: Age significantly differentiated the BMI index of the surveyed. Overweight and obesity was more prevalent in the oldest age group. The size of thoracic kyphosis expressed in degrees was similar in all the surveyed, although hypokyphosis was observed more frequently in the female pupils and hyperkyphosis in the female students. Lumbar lordosis was significantly higher in the students when compared to the other groups. Hypolordosis was most common in the seniors. The students and seniors also differed in terms of the balance of the torso in the sagittal plane. Excessive backward inclination was diagnosed in 42% of the students (total backward shift of the centre of gravity of the human body), which was twice as rare in the female students and four times as rare in the seniors. Asymmetric position of the right and left shoulder and hip girdles was common in every group of the women surveyed. Side bendings of the spine were most often observed in the female pupils, and least frequently in the seniors. Left-sided bendings were more frequent than right-sided ones. Conclusions: The age of women affects the position of the torso more in the sagittal plane than in the frontal one. The size of lumbar lordosis is an element of the body posture most significantly differentiating women between 12 and 84 years of age. Hyperlordosis is more characteristic of young adult women, whereas hypolordosis of seniors. Hyperkyphosis is most common in female students while hypokyphosis in adolescent girls.
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Varma, Kunal, and Priyanka Gokhale. "Assessment of Static and Dynamic Balance in Swimmers." International Journal of Health Sciences and Research 11, no. 8 (August 26, 2021): 202–10. http://dx.doi.org/10.52403/ijhsr.20210830.
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Background: Swimming can be defined as an activity in which a person practices a regulated Olympic sport in order to move as fast as possible through the water due to the propulsive forces generated by arm, leg, and body movements overcoming the resistance of water. Swimming is performed in either a supine or prone position with a bilaterally-symmetric motion and is influenced by buoyancy. In other words, it is nearly unaffected by gravity and requires the same muscle exertion of both the right and left extremities. Balance is considered to be an important component of motor performance tasks. It is controlled by the central nervous system with the help of input from the visual, tactile, proprioceptive and vestibular systems (5) Balance can be defined as a condition during which the body's center-of-gravity (COG) is maintained within its base of support (BOS). Methodology: In this study, 50 Competitive swimmers were included. 36 Male and 14 Female, with a mean age, height and weight of 22.68 years, 175.56 cm and 70.94 kg respectively. Each had a swimming career more than 5 years, Training at least 5 days a week for 2 hours or more with an average of 10.12 years, 5.54 days a week for 2.68 hour training sessions. Static Balance was assessed using Balance Error Scoring System where the subjects were asked to stand with their eyes closed for 20 seconds in 6 Different Positions and the number of errors made were noted. Dynamic Balance was assessed using Star Excursion Balance Test were, a Star was marked on the ground to have 8 directions. The subject stood in the center of the star and had to reach as far as they could in each direction. This distance from the middle to the point of contact of their toe was noted and relative distance was calculated using Limb Length. The Results of both the test was compared with the normal data present. Result: The result of the test done to evaluate static balance; BESS showed that out of 50 participants 19 had superior balance, 18 had above average balance and 13 had broadly normal balance and the errors on the firm surface and soft surface had a mean and standard deviation of 2 ± 1.12 and 4.1±1.31 respectively. On the other hand, the test done to evaluate dynamic balance; SEBT showed that in each direction on an average the swimmer could reach 119.21±8.39 % relative distance in each direction. Conclusion: Different tests were conducted in the study to understand if competitive swimmers are somehow weak in terms of static and dynamic balance. The entire study is based on the effectiveness of maintaining and enhancing the static and dynamic stability among the swimmers. This study concludes that competitive swimmers have Superior Static and Dynamic Balance because of strong core muscles used to keep their body streamlined during swimming and good flexibility and neuromuscular feedback. Key words: Balance, Swimmers, Star Excursion Balance test (SEBT), Balance Error Scoring System (BESS).
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Dancila, B. D., R. Botez, and D. Labour. "Fuel burn prediction algorithm for cruise, constant speed and level flight segments." Aeronautical Journal 117, no. 1191 (May 2013): 491–504. http://dx.doi.org/10.1017/s0001924000008149.
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Abstract This paper presents a new algorithm that predicts the quantity of fuel burned by an aircraft flying at a constant speed and altitude. It considers the continuous fuel burn rate variation with time caused by the gross weight (and centre of gravity position) modification due to the fuel burn process itself. The algorithm was developed for use by the Flight Management System (FMS) and employs the same aircraft performance data as the existing FMS fuel burn prediction algorithms. The new fuel burn method was developed for aircraft models that use the centre of gravity position as well as for models that do not consider the centre of gravity position. This algorithm was developed for normal flight conditions. Algorithm performances were evaluated for two aircraft models: one for models that use an aircraft’s centre of gravity position – a more complex and computing intensive method, and one for those that do not use the centre of gravity position. The validation data were generated based on the information produced on a CMC Electronics – Esterline FMS platform that used identical aircraft models and performance data for identical flight conditions.
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Wank, Veit, and Corinna Coenning. "On the estimation of centre of gravity height in vertical jumping." German Journal of Exercise and Sport Research 49, no. 4 (April 8, 2019): 454–62. http://dx.doi.org/10.1007/s12662-019-00581-6.
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Li, Bin, Qiang Hu, and Zhijun Fu. "Adaptive online estimation of centre of gravity height for commercial vehicles." International Journal of Heavy Vehicle Systems 28, no. 2 (2021): 206. http://dx.doi.org/10.1504/ijhvs.2021.10038431.
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Fu, Zhijun, Qiang Hu, and Bin Li. "Adaptive online estimation of centre of gravity height for commercial vehicles." International Journal of Heavy Vehicle Systems 28, no. 2 (2021): 206. http://dx.doi.org/10.1504/ijhvs.2021.115579.
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Monnet, T., C. Valle, and P. Lacouture. "Simultaneous identification of the joint centre location, the mass and the centre of gravity position." Computer Methods in Biomechanics and Biomedical Engineering 12, sup1 (August 2009): 193–94. http://dx.doi.org/10.1080/10255840903091544.
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Germann, S. T., and R. Isermann. "Determination of the Centre of Gravity Height of a Vehicle with Parameter Estimation." IFAC Proceedings Volumes 27, no. 8 (July 1994): 563–68. http://dx.doi.org/10.1016/s1474-6670(17)47768-8.
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Fabbri, A., and G. Molari. "Static Measurement of the Centre of Gravity Height on Narrow-track Agricultural Tractors." Biosystems Engineering 87, no. 3 (March 2004): 299–304. http://dx.doi.org/10.1016/j.biosystemseng.2003.12.008.
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Zhao, Xin Tong, H. Z. Jiang, S. T. Zheng, and Jun Wei Han. "Precision Gravity Center Position Measurement System for Heavy Vehicles." Key Engineering Materials 315-316 (July 2006): 788–91. http://dx.doi.org/10.4028/www.scientific.net/kem.315-316.788.
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Knowledge of a vehicle’s inertial parameters is essential for safety research and accident reconstruction. A precision measure system is proposed to determine the weight and gravity center for heavy vehicles. Based on a static gravity measuring principle with three measuring points, a hydraulically driven 2-DOF motion platform is developed. The transfer function model is derived for the hydraulically driven system. By means of a degree-of-freedom control scheme, the platform can realize accurate positioning to construct two intersected planes and work out the three-dimensional coordinates of the vehicle gravity center. Experiments demonstrate that the system has less than 0.3% measurement error in weight, and is able to measure the gravity centre accurately with deviation ≤3mm in X and Y direction, and ≤5mm in Z direction.
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Li, Xiong, and Hans‐Jürgen Götze. "Ellipsoid, geoid, gravity, geodesy, and geophysics." GEOPHYSICS 66, no. 6 (November 2001): 1660–68. http://dx.doi.org/10.1190/1.1487109.
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Geophysics uses gravity to learn about the density variations of the Earth’s interior, whereas classical geodesy uses gravity to define the geoid. This difference in purpose has led to some confusion among geophysicists, and this tutorial attempts to clarify two points of the confusion. First, it is well known now that gravity anomalies after the “free‐air” correction are still located at their original positions. However, the “free‐air” reduction was thought historically to relocate gravity from its observation position to the geoid (mean sea level). Such an understanding is a geodetic fiction, invalid and unacceptable in geophysics. Second, in gravity corrections and gravity anomalies, the elevation has been used routinely. The main reason is that, before the emergence and widespread use of the Global Positioning System (GPS), height above the geoid was the only height measurement we could make accurately (i.e., by leveling). The GPS delivers a measurement of height above the ellipsoid. In principle, in the geophysical use of gravity, the ellipsoid height rather than the elevation should be used throughout because a combination of the latitude correction estimated by the International Gravity Formula and the height correction is designed to remove the gravity effects due to an ellipsoid of revolution. In practice, for minerals and petroleum exploration, use of the elevation rather than the ellipsoid height hardly introduces significant errors across the region of investigation because the geoid is very smooth. Furthermore, the gravity effects due to an ellipsoid actually can be calculated by a closed‐form expression. However, its approximation, by the International Gravity Formula and the height correction including the second‐order terms, is typically accurate enough worldwide.
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Solmaz, Selim, Mehmet Akar, Robert Shorten, and Jens Kalkkuhl. "Real-time multiple-model estimation of centre of gravity position in automotive vehicles." Vehicle System Dynamics 46, no. 9 (September 2008): 763–88. http://dx.doi.org/10.1080/00423110701602670.
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Hu, Jingwen. "Height of head centre of gravity predicts paediatric head injury severity in short-distance falls." Evidence Based Medicine 22, no. 1 (November 10, 2016): 36. http://dx.doi.org/10.1136/ebmed-2016-110558.
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Kellogg, R. M., and E. P. Swan. "Physical properties of black cottonwood and balsam poplar." Canadian Journal of Forest Research 16, no. 3 (June 1, 1986): 491–96. http://dx.doi.org/10.1139/x86-087.
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The objective of this study was to characterize selected properties of black cottonwood and balsam poplar to determine whether these species should be distinguished in their utilization. At present, black cottonwood is excluded from the "northern aspen" species group embraced by the National Lumber Grading Agency grading rules for dimension lumber and from use as core material in softwood plywood. Samples of black cottonwood were obtained from three sites in British Columbia. Samples of balsam poplar were obtained from three sites in Alberta. Ten tres were randomly selected from each site and a single 130 cm long bolt was collected immediately above breast height (1.36 m) from each tree. From two trees on each site, three additional bolts of the same length were collected immediately above the height positions located at 25, 50, and 75% of total tree height. The average basic specific gravity of the two species did not differ significantly (black cottonwood, 0.338; balsam poplar, 0.337) in this study. However, differences do exist between site averages, at least for black cottonwood. The initial green moisture contents differ significantly (black cottonwood, 160.5%; balsam poplar, 120.6%) and may be expected to affect their drying requirements differentially. For both species, the specific gravity increases and the green moisture content decreases with increasing height position in the tree. The average fiber length of black cottonwood is significantly longer than that of balsam poplar. The bending properties of strength and stiffness for black cottonwood were found to be significantly greater than for balsam poplar. Variation of these properties with height position in the tree was studied. Fiber length was found to decrease with increasing height position, while the bending strength properties were not affected by height position.
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Robinson, T. O., I. Eames, and R. Simons. "Dense gravity currents moving beneath progressive free-surface water waves." Journal of Fluid Mechanics 725 (May 23, 2013): 588–610. http://dx.doi.org/10.1017/jfm.2013.112.
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AbstractThe characteristics of dense gravity currents in coastal regions, where free-surface gravity waves are dominant, have yet to be studied in the laboratory. This paper provides a first insight into the dynamics of dense saline gravity currents moving beneath regular progressive free-surface water waves. The gravity currents were generated by releasing a finite volume of saline into a large wave tank with an established periodic wave field. After the initial collapse, the gravity currents propagated horizontally with two fronts, one propagating in the wave direction and the other against the wave direction. The fronts of the gravity currents oscillated with an amplitude and phase that correlated with the orbital velocities within a region close to the bed. To leading order, the overall length of the gravity current was found to be weakly affected by the wave action and the dynamics of the current could be approximated by simply considering the buoyancy of the released fluid. Other characteristics such as the position of the gravity current centre and the shape of the two leading profiles were found to be significantly affected by the wave action. The centre was displaced at constant speed dependent on the second-order wave-induced mean Lagrangian velocity. For long waves, the centre was advected downstream in the direction of wave propagation owing to the dominance of Stokes drift. For short waves, the gravity current centre moved upstream against the wave direction, as under these wave conditions Stokes drift is negligible at the bed. An asymmetry in the shape of the upstream and downstream current heads was observed, with the gravity current front moving against the waves being much thicker and the front steeper, similar to the case of a current moving in a stream.
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Cunha, Francisco Valmor Macedo, Joana D'arc Alves Sousa, and Jonas Almeida Alves. "Baropodometric profile of patients assisted in a physiotherapy clinic." Manual Therapy, Posturology & Rehabilitation Journal 18 (December 22, 2020): 1–5. http://dx.doi.org/10.17784/mtprehabjournal.2020.18.760.
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Background: Computerized baropodometry, a posturographic recording technique used in the diagnosis and assessment of plantar pressure, which records the pressure points exerted by the body on the plantar surface, is an accurate, objective and quantitative examination. Its record is used in the diagnosis and evaluation of plantar pressure, both in static and dynamic positions. Objective: Analyze the baropodometric profile of patients in a physiotherapy clinic. Methods: A cross-sectional study of documentary character of baropodometry exams registered in the database of a physiotherapy clinic in Teresina (PI), carried out from January 2015 to December 2018. Totaling 193 exams, which include the types of feet, peak plantar pressure and correlation between peak plantar pressure with age, weight, height and BMI. The collected data were analyzed statistically by the software Win Track version 12.0, and presented through tables and figures. In this research, all ethical precepts were carried out in accordance with the resolution of the National Health Council and was approved by the ethics committee. Results: There was a higher prevalence of hollow feet (96.89%), showing a greater occurrence of displacement of the center of gravity posteriorly to the right (46.11%), it was found that there was no satisfactory correlation of anthropometric parameters with peak plantar pressure (p>0.05). Conclusion: It was possible to observe that the examinations evaluated showed a higher prevalence of hollow feet and center of gravity posteriorized to the right. In addition, there was no satisfactory correlation between peak plantar pressure with the variables age, weight, height and BMI.
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Hasanov, F. G. "Technology of steel jackets load-out in deep-water offshore platforms from the barge." Azerbaijan Oil Industry, no. 2 (February 15, 2020): 25–29. http://dx.doi.org/10.37474/0365-8554/2020-2-25-29.
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Currently, great attention is paid to the development issue of the shelf’s fuel and energy resources foremost in the oil-gas fields of the Caspian Sea. The problem solution requires the studying of great majority of scientific-technical issues. One of the significant problems is the lead-out of steel jacket from the offshore platform as a major element of oil-gas field hydro-technical facilities meant for the operation in the deep water. The calculations for the execution of operations with steel jacket of deep stationary platform from the block with the detailed chara- cteristics by the mass and gravity center coordinates alongside line data have been carried out with “SACS” and “STAAD.PRO” software programs. The steel jacket is pushed astern with the push-pull equipment on the barge. Due to the shift of gravity centre the jacket changes the trim in the stern. Through the elevation of trim angle brought in alignment with the friction ration between the jacket and barge, the jacket slides further itself. Herewith, the trim increases until the gravity centre of steel jacket on the barge is not in alignment with rotation centre of the large rocker arms. The studies helped to fix the position of the jacket’s gravity centre from the aft perpendicular, the trim moment, the trim of the barge, the draft with the bow and stern and the trim angle as well.
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Matkowski, Adam, Radosław Karwowski, and Beata Zagórska-Marek. "Two algorithms of determining the middle point of the shoot apex by surrounding organ primordia positions and their usage for computer measurements of divergence angles." Acta Societatis Botanicorum Poloniae 67, no. 2 (2014): 151–59. http://dx.doi.org/10.5586/asbp.1998.017.
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The measurements of the divergence angle between organ primordia in magnolia floral apices and vegetative apices (embryonic shoots) of coniferous trees were performed, using computer application Phyl for IRIX. It appears that the values of the angle are strongly affected by the position of the apex centre, which was calculated by the program on a base of input positions of surrounding primordia. Two algorithms were used to determine the centre position: in program version Phyl 1 it was calculated as the gravity centre whereas in Phyl 2 version as a geometrical midpoint. The both methods differ in resulting centre position. This is dependent on such apex features as: proportions between its size and the size of primordia (expression of phyllotaxis), the angular distances between succesive primordia (quality of phyllotaxis), radial distances between primordia of different age (profile of the apical dome), the number of recorded primordia. The accuracy and reliability of both algorithms for determination of the centre position and, consequently, the reliability of divergence measurements were verified by applying them to ideal, computer simulated spiral phyllotactic systems with divergence given arbitrarily by the user. The conclusions from the results of simulations are that there is a possibility of selecting more suitable algorithm for particular apex with regard to specific parameters of its phyllotactic system.
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Stallard, J., J. H. Henshaw, B. Lomas, and R. Poiner. "The ORLAU VCG (variable centre of gravity) swivel walker for muscular dystrophy patients." Prosthetics and Orthotics International 16, no. 1 (April 1992): 46–48. http://dx.doi.org/10.3109/03093649209164307.
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Swivel walkers are being increasingly used for muscular dystrophy patients in order to prolong the period of their ambulation. Existing designs did not address the special problems of accommodating such patients comfortably and providing the easier and more assured ambulation which their weakened condition requires. The ORLAU VCG (variable centre of gravity) swivel walker has been developed so that the walking mechanics can be adjusted independently of patient posture. Additional patient support features permit the patient to be secured in their chosen position of comfort prior to setting the ambulation mechanics. Patients using the device, which is now approved for supply by the Department of Health in England and Wales, have improved their walking performance and extended their period of walking.
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Remiorz, Eryk. "Determination of Critical Rock Mass in a Bucket of a Dinting Loader." Archives of Mining Sciences 62, no. 3 (September 1, 2017): 531–43. http://dx.doi.org/10.1515/amsc-2017-0039.
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AbstractThe extraction of hard coal deposits lying in increasing depth causes significant problems with maintenance of roadways (maingates, tailgates, etc.). The reduction of the cross section of such excavations, caused by the floor upheaval, leads to the occurrence of many problems with transport and ventilation. Dinting loaders are employed to restore the original size of roadways tightened due to the activity of adverse stresses occurring in the rock mass. These are tracked machines, usually with small width of about 1 m. They often work in roadways with high longitudinal and lateral inclination, as a result of which they are especially susceptible to overturning.The article presents a mathematical model allowing to determine the critical mass of broken rock in a bucket. The model also allows to determine spatial coordinates of a dinting loader’s centre of gravity depending on temporary position of movable elements of the loader such as a turntable, boom, coupler and bucket, and depending on the level of loading the bucket with broken rock. It also enables to determine critical angles of the roadways’ longitudinal and lateral inclination. The outcomes of computer studies of variations in the position of the loader’s centre of gravity depending on deflection angles of moving elements of the loader and the mass of broken rock in the bucket are also presented. Variability ranges of spatial coordinates of the centre of gravity of the loader are also established and examples are given for values of the critical mass of broken rock in the bucket.
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Hughes, Jonathon, Sabine Maguire, Michael Jones, Peter Theobald, and Alison Kemp. "Biomechanical characteristics of head injuries from falls in children younger than 48 months." Archives of Disease in Childhood 101, no. 4 (September 17, 2015): 310–15. http://dx.doi.org/10.1136/archdischild-2014-306803.
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BackgroundA fall-height threshold is important when evaluating the likelihood of structural head injury or abusive head trauma. This study investigates witnessed falls to correlate the fall characteristics with the extent of injury.MethodCase–control study of children aged ≤48 months who attended one hospital following a fall from <3 m (10 ft), comparing cases who sustained a skull fracture or intracranial injury (ICI) with controls, who had minor head injuries. Characteristics included: the mechanism of injury, surface of impact, site of impact to the head and fall height.ResultsForty-seven children had a skull fracture or ICI, while 416 children had minor head injuries. The mean fall height for minor head injuries was significantly lower than that causing skull fracture/ICI (p<0.001). No skull fracture/ICI was recorded in children who fell <0.6 m (2 ft), based on the height of the head centre of gravity. Skull fractures/ICI were more likely in children aged ≤12 months (p<0.001) from impacts to the temporal/parietal or occipital region (p<0.001), impacts onto wood (p=0.004) and falls from a carer's arms, particularly when on stairs (p<0.001). No significant difference was reported between the mean fall heights of children who had a simple skull fracture (n=17) versus those who had a complex fracture or ICI (n=30).ConclusionsAn infant is more likely to sustain a skull fracture/ICI from a fall above a 0.6 m (2 ft) threshold, based on the height of the head centre of gravity, or with a parietal/temporal or occipital impact. These variables should be recorded when evaluating the likelihood of skull fracture/ICI.
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Zheng, Zhong, Sangwoo Shin, and Howard A. Stone. "Converging gravity currents over a permeable substrate." Journal of Fluid Mechanics 778 (August 7, 2015): 669–90. http://dx.doi.org/10.1017/jfm.2015.406.
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We study the propagation of viscous gravity currents along a thin permeable substrate where slow vertical drainage is allowed from the boundary. In particular, we report the effect of this vertical fluid drainage on the second-kind self-similar solutions for the shape of the fluid–fluid interface in three contexts: (i) viscous axisymmetric gravity currents converging towards the centre of a cylindrical container; (ii) viscous gravity currents moving towards the origin in a horizontal Hele-Shaw channel with a power-law varying gap thickness in the horizontal direction; and (iii) viscous gravity currents propagating towards the origin of a porous medium with horizontal permeability and porosity gradients in power-law forms. For each of these cases with vertical leakage, we identify a regime diagram that characterizes whether the front reaches the origin or not; in particular, when the front does not reach the origin, we calculate the final location of the front. We have also conducted laboratory experiments with a cylindrical lock gate to generate a converging viscous gravity current where vertical fluid drainage is allowed from various perforated horizontal substrates. The time-dependent position of the propagating front is captured from the experiments, and the front position is found to agree well with the theoretical and numerical predictions when surface tension effects can be neglected.