Journal articles: 'Lenghwise position centre of gravity'

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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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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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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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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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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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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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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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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.

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Pedro, Jimoh Olarewaju, Aarti Panday, and Laurent Dala. "A nonlinear dynamic inversion-based neurocontroller for unmanned combat aerial vehicles during aerial refuelling." International Journal of Applied Mathematics and Computer Science 23, no. 1 (March 1, 2013): 75–90. http://dx.doi.org/10.2478/amcs-2013-0007.

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The paper presents the development of modelling and control strategies for a six-degree-of-freedom, unmanned combat aerial vehicle with the inclusion of the centre of gravity position travel during the straight-leg part of an in-flight refuelling manoeuvre. The centre of gravity position travel is found to have a parabolic variation with an increasing mass of aircraft. A nonlinear dynamic inversion-based neurocontroller is designed for the process under investigation. Three radial basis function neural networks are exploited in order to invert the dynamics of the system, one for each control channel. Modal and time-domain analysis results show that the dynamic properties of the aircraft are strongly influenced during aerial refuelling. The effectiveness of the proposed control law is demonstrated through the use of simulation results for an F-16 aircraft. The longitudinal neurocontroller provided interesting results, and performed better than a baseline nonlinear dynamic inversion controller without neural network. On the other hand, the lateral-directional nonlinear dynamic inversion-based neurocontroller did not perform well as the longitudinal controller. It was concluded that the nonlinear dynamic inversion-based neurocontroller could be applied to control an unmanned combat aerial vehicle during aerial refuelling.

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Liu, Chen-Yi, and Andrew L. Goertzen. "Improved event positioning in a gamma ray detector using an iterative position-weighted centre-of-gravity algorithm." Physics in Medicine and Biology 58, no. 14 (June 25, 2013): N189—N200. http://dx.doi.org/10.1088/0031-9155/58/14/n189.

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Caron, O. "Visual feedback of the centre of gravity position during upright standing on a six-component force plate." Computer Methods in Biomechanics and Biomedical Engineering 12, sup1 (August 2009): 69–70. http://dx.doi.org/10.1080/10255840903077154.

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Miková, Ľubica, Michal Kelemen, and Dušan Koniar. "Mathematical Model of Four Wheeled Mobile Robot and its Experimental Verification." Applied Mechanics and Materials 611 (August 2014): 130–36. http://dx.doi.org/10.4028/www.scientific.net/amm.611.130.

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The paper deals with creation of a mathematical model of the mobile robot. For description of the kinematic variables such as position and velocity of each wheel a transformation matrix is used. The simulation model can be applied for calculation of assumed of the undercarriage centre of gravity and path of wheels. The function model was also used for experimental verification of the results of simulation experiments.

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Kalenik, Jerzy, Irena Majerz, Lucjan Sobczyk, Eugeniusz Grech, and Mustafa M. M. Habeeb. "Infra-red and 35Cl nuclear quadrupole resonance studies of hydrogen bonded adducts of 2-chlorobenzoic acid derivatives." Collection of Czechoslovak Chemical Communications 55, no. 1 (1990): 80–90. http://dx.doi.org/10.1135/cccc19900080.

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The IR and 35Cl NQR spectra of several solid hydrogen bonded adducts of o-chlorobenzoic acids and amines were studied over the broad ΔpKa range. Both IR and NQR spectra yield the indication of the existence of an inversion (critical) ΔpKa range where the proton transfer takes place. The critical point is distinguished by a deep minimum of the position of the gravity centre of the broad protonic band. The mechanism of the transmittance of the charge distribution within the hydrogen bridge on the electric field gradient in the position of quadrupole Cl nuclei attached to the phenyl ring is analysed.

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Khan, Banti, and Ashita Goyal. "ḈGSHIFTER: A METHOD TO SHIFT CENTRE OF GRAVITY TO REDUCE SCHOOL BAG STRESS ON CHILDREN BODY." International Journal of Research -GRANTHAALAYAH 3, no. 2 (February 28, 2015): 47–56. http://dx.doi.org/10.29121/granthaalayah.v3.i2.2015.3039.

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Increasing weight of backpacks of school going students and its adverse effect on children’s body is shown through survey of Indore city. Outcome of survey shows that the average of ratio of backpack weight to body weight of school children was 20.62% which is higher than acceptable limit. It gives a method to reduce the impact of schoolbag on spinal cord of children body. In this paper, the effect of center of gravity of schoolbag on human body is observed which is shifted in a position which lowers the effect of schoolbag stress by applying CGSHIFTER method.

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Słowik, Jacek, and Andrzej Zięba. "Geometrical equatorial aberrations in a Bragg–Brentano powder diffractometer with a linear position-sensitive detector." Journal of Applied Crystallography 34, no. 4 (July 22, 2001): 458–64. http://dx.doi.org/10.1107/s0021889801007877.

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The use of a position-sensitive detector with a Bragg–Brentano diffractometer implies the registration of the diffracted beam at a finite distance from the true focusing point. This gives rise to an aberration which is characterized by the peak intensity profileI(y) and its parameters, the shift of the centre of gravity 〈y〉 and the profile variationW. These are calculated in terms of exact expressions and approximate results. The obtained closed formulae for 〈y〉 andWaugment analogous calculations for other aberrations, tabulated by Parrish and Wilson in theInternational Tables for X-ray Crystallography(Vol. III, 1995). Calculation of the peak profiles is verified by experiment.

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Stoner, John, and Robert H. Davis. "A gait simulator for a quadruped walking robot." Robotica 10, no. 1 (January 1992): 57–64. http://dx.doi.org/10.1017/s0263574700007074.

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SummaryThe description is provided for the design and implementation of a system capable of simulating the motions of a quadruped walking robot. The system aims to investigate the feasibility of the robot's walking cycle. This is achieved by considering the robot's stability and more specifically the position of its centre of gravity in relation to its supporting legs. The robot is modelled as a solid body connected to four jointed limbs which are moved through a series of gaits, their positions being calculated at a set of discrete intervals. The resulting information is displayed using a graphical module to present an image of the moving robot and indicate its centre of gravity and support pattern. The complete system indicates the stability of the robot throughout a user-defined gait cycle and is both portable and adaptable.The system is implemented on a HLH Orion and an Atari 1040ST in the C programming language and is aimed at providing support for the Department of Mechanical Engineering at Edinburgh University where the particular robot is being built.

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Ozoliņš, Ēriks, Ilmārs Ozoliņš, and Līga Ramāna. "Turbine Blade of Gas Turbine Engine Additional Unloading by Changing the Layout of the Gravity Centre of the Shroud Shelf." Transport and Aerospace Engineering 7, no. 1 (January 1, 2019): 14–23. http://dx.doi.org/10.2478/tae-2019-0002.

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Abstract The article describes the impact of the gas turbine engine low-pressure turbine blade shroud shelf on the blade profile stress position. Attention is focused directly on the impact of the location of the gravity centre of the shroud shelf on blade stress distribution at the three most critical points of the profile. The paper describes the details of the calculation and the required expressions provided, as well as the results of the calculation example with clear graphical dependencies.

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Wieczorek, B., M. Kukla, and Ł. Warguła. "Methods for measuring the position of the centre of gravity of an anthropotechnic human-wheelchair system in dynamic conditions." IOP Conference Series: Materials Science and Engineering 776 (April 2, 2020): 012062. http://dx.doi.org/10.1088/1757-899x/776/1/012062.

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Ghayour, Mostafa, and Amir Zareei. "Direct Kinematic Analysis of a Hexapod Spider-Like Mobile Robot." Advanced Materials Research 403-408 (November 2011): 5053–60. http://dx.doi.org/10.4028/www.scientific.net/amr.403-408.5053.

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In this paper, an appropriate mechanism for a hexapod spider-like mobile robot is introduced. Then regarding the motion of this kind of robot which is inspired from insects, direct kinematics of position and velocity of the centre of gravity (C.G.) of the body and noncontact legs are analysed. By planning and supposing a specific time variation for each joint variable, location and velocity of the C.G. of the robot platform and angular velocity of the body are obtained and the results are shown and analysed.

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Wudarczyk, Sławomir, and Artur Muraszkowski. "A Concept Of Modification And Simulation Studies Of A Mechatronic Stair Transporter For The Disabled." Acta Mechanica et Automatica 9, no. 4 (December 1, 2015): 213–18. http://dx.doi.org/10.1515/ama-2015-0034.

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Abstract A numerical model of existing stair climber with its passenger was built and its operation was analysed through simulations. A modification of the stair climber has been developed on a basis of the simulation studies. The modification depends on equipping the device with additional controllable mechanism the function of which is to change the position of the passenger’s centre of gravity. Comparative simulation studies were carried out for the standard version and the modified version of the stair transporter in a system for the dynamic.

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Morioka, Shu, Hiroyuki Fujita, Makoto Hiyamizu, Hiroshi Maeoka, and Atsushi Matsuo. "Effects of plantar perception training on standing posture balance in the old old and the very old living in nursing facilities: a randomized controlled trial." Clinical Rehabilitation 25, no. 11 (April 19, 2011): 1011–20. http://dx.doi.org/10.1177/0269215510395792.

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Objective: To determine whether plantar perception training using a hardness discrimination task efficiently improves stabilization of standing posture balance in the old old as well as the very old. Design: A randomized two-group parallel controlled trial. Setting: Nursing homes. Participants: Forty-six elderly persons 75 years of age or older living in nursing facilities were randomly assigned evenly to either an intervention or a control group. Intervention: The intervention group was given a task to discriminate hardness differences while standing on foam rubber of different levels of hardness, while the control group was given the task to simply remain standing on foam rubber. The tasks were imposed for 10 successive days. Outcome measures: Outcome assessment was made by determinations of centre-of-gravity sway in the standing position and the Functional Reach Test. Results: Planter perception was significantly improved and centre-of-gravity sway in the standing position was also significantly reduced in the intervention group after the intervention. In the control group, however, there were no significant changes in perception or in sway ( P < 0.01) There was a significant difference in the Functional Reach Test values between the two groups: an increment of 12.3 ± 10.1 cm in the intervention group vs. 2.3 ± 5.8 cm in the control group ( P < 0.001). Conclusion: These results suggested that plantar perception exercises might efficiently stabilize standing postural balance in the old old as well as the very old.

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McGowan, J. W., E. Kowler, A. Sharma, and C. Chubb. "Saccadic Localisation of Random Dot Targets." Perception 25, no. 1_suppl (August 1996): 101. http://dx.doi.org/10.1068/v96l0304.

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Saccadic eye movements land at precise places within simple target forms implying that a spatial pooling process operates over attended regions to determine the saccadic endpoint. To study pooling, we used large, unstructured targets and looked for evidence of differential spatial weighting based on local pattern characteristics. Subjects made a saccade to targets composed of 19 dots scattered randomly within a 4 deg diameter region horizontally displaced 3.8 – 4.2 deg to the left or right of initial fixation. Dot intensity was either uniform or variable. Saccadic landing positions were close to the centre-of-gravity (overshooting or under- shooting by 5% – 10% depending on subject, direction and eccentricity). Precision was excellent (SD=10% ecc), although not as good as with single target points (SD=7% ecc). Correlations between the presence of a dot and saccadic landing position showed that all regions of the pattern contributed. Differential weighting of dots according to location (eg near vs far; central vs boundary) did not yield better predictions of the saccadic landing position. However, predictions of the landing position were improved by assigning more weight to higher-intensity dots. Local dot clusters contributed less than would be expected from the contributions of individual dots. Spatial pooling is highly effective over a large region. Saccadic overshoots or undershoots were not due to differential spatial weighting, and may originate after the centre-of-gravity computation. The differential weighting of high-intensity dots and dot clusters demonstrates sensitivity to local characteristics, and implies that the saccadic endpoint may be determined by pooling the activity of units centred on different subregions of the target. The pooling mechanism supports precise saccadic localisation of large, unstructured targets, and accounts for the ease with which we direct saccades to chosen objects in natural scenes.

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Tóth, Géza, and Tekla Sebestyén Szép. "Spatial Evolution of the Energy and Economic Centers of Gravity." Resources 8, no. 2 (May 24, 2019): 100. http://dx.doi.org/10.3390/resources8020100.

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Increasing energy demand and economic performance can be observed in emerging markets and, in parallel, their share in world energy use and in global GDP is growing as well. It causes significant spatial shifts and calls attention for a new geography of energy demand. The main purpose of this study is to reveal the spatial distribution of energy use and economic growth focusing on the link between them. Developing gravity models, we identify the economic and energy centres of gravity in the world and on different continents and reveal their movements between 1990 and 2015, in particular, the directions of the shifts. Bi-dimensional regression analysis and the method of standard distance are applied to compare these movements. The study utilizes cartograms to visualize how the space is changed and distorted by the field of force. It can be stated that the economic and energy centre of gravity can be found in the Mediterranean Basin, but a slow and gradual shift to the east can be observed. Currently it reflects the dominance of the north, but it marks the position loss of the northern hemisphere and the greater importance of developing economies (in the southern hemisphere).

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Spathopoulos, V. M. "An investigation of the flight dynamic characteristics of gyroplanes by use of flight tests." Aeronautical Journal 108, no. 1088 (October 2004): 531–35. http://dx.doi.org/10.1017/s0001924000000361.

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AbstractAn analysis is presented both of flight test and simulation data obtained from a gyroplane aircraft. This class of rotary-wing vehicle has found limited application in areas other than recreational flying, however the accident rate has been such that it has prompted the study of the configuration’s stability and control characteristics. It is concluded that the flight dynamic response of the gyroplane examined is dominated by a fast, non-stable mode, affecting all states and thus increasing pilot workload. Simulation results indicate that the position of the centre of gravity significantly influences the stability of this mode.

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Abuter, R., A. Amorim, M. Bauböck, J. P. Berger, H. Bonnet, W. Brandner, V. Cardoso, et al. "Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole." Astronomy & Astrophysics 636 (April 2020): L5. http://dx.doi.org/10.1051/0004-6361/202037813.

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The star S2 orbiting the compact radio source Sgr A* is a precision probe of the gravitational field around the closest massive black hole (candidate). Over the last 2.7 decades we have monitored the star’s radial velocity and motion on the sky, mainly with the SINFONI and NACO adaptive optics (AO) instruments on the ESO VLT, and since 2017, with the four-telescope interferometric beam combiner instrument GRAVITY. In this Letter we report the first detection of the General Relativity (GR) Schwarzschild Precession (SP) in S2’s orbit. Owing to its highly elliptical orbit (e = 0.88), S2’s SP is mainly a kink between the pre-and post-pericentre directions of motion ≈±1 year around pericentre passage, relative to the corresponding Kepler orbit. The superb 2017−2019 astrometry of GRAVITY defines the pericentre passage and outgoing direction. The incoming direction is anchored by 118 NACO-AO measurements of S2’s position in the infrared reference frame, with an additional 75 direct measurements of the S2-Sgr A* separation during bright states (“flares”) of Sgr A*. Our 14-parameter model fits for the distance, central mass, the position and motion of the reference frame of the AO astrometry relative to the mass, the six parameters of the orbit, as well as a dimensionless parameter fSP for the SP (fSP = 0 for Newton and 1 for GR). From data up to the end of 2019 we robustly detect the SP of S2, δϕ ≈ 12′ per orbital period. From posterior fitting and MCMC Bayesian analysis with different weighting schemes and bootstrapping we find fSP = 1.10 ± 0.19. The S2 data are fully consistent with GR. Any extended mass inside S2’s orbit cannot exceed ≈0.1% of the central mass. Any compact third mass inside the central arcsecond must be less than about 1000 M⊙.

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Tan, M., J. Nitz, J. Boughen, and S. Fu. "Centre of gravity position in bipedal steady-stance is associated with performance of timed up and go but not functional reach." Physiotherapy 101 (May 2015): e1485. http://dx.doi.org/10.1016/j.physio.2015.03.1459.

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Po, Niu, Chen Jian, Hu Chenjun, and Zhao Jindou. "IMPROVING THE OPERATING COMFORT OF THE ELECTRIC MINI-TILLER BASED ON SIMULATION ANALYSIS AND FIELD TEST." INMATEH Agricultural Engineering 60, no. 1 (April 30, 2020): 221–32. http://dx.doi.org/10.35633/inmateh-60-25.

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Now the engine mini-tiller has become indispensable agricultural machinery in vast hilly and mountainous areas of Southwest China. Many researches have been made to improve its operating comfort, but little effects have been obtained. As an alternative, a new type of electric mini-tiller was developed. For further improvement of its operating comfort, simulation analysis and field test were integrated to decrease the vertical force and vibration RMS values at the handle. The results showed that when the position of centre of gravity moved 19.78 cm, the vertical force was reduced from 154.24 N to 0 N, and vibration RMS values decreased by 20.16% under working condition.

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Gassen, W. Van, and D. M. Cruden. "Momentum transfer and friction in the debris of rock avalanches." Canadian Geotechnical Journal 26, no. 4 (November 1, 1989): 623–28. http://dx.doi.org/10.1139/t89-075.

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When a mass of loose, dry, purely frictional material slides down an incline after release at a given velocity, the runout (the distance the centre of gravity of the displaced mass moves from its initial position) depends on momentum transfer within the mass. This can be estimated from the profile of the debris accumulation, which also allows more accurate calculation of apparent angles of sliding friction in rockfall avalanches. The apparent extreme mobility of the Elm and Frank slides, typical rockfall avalanches, is explained by momentum transfer in a loose, dry, purely frictional material with an angle of friction of 30°. Key words: mass wasting, momentum transfer, landslide, accumulation, rock avalanche, runout distance.

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Xu, Bin, Xiang Na Li, and Wei Ning Xue. "Study on a Rapid Real-Time Feature Extraction Algorithm." Advanced Materials Research 709 (June 2013): 575–78. http://dx.doi.org/10.4028/www.scientific.net/amr.709.575.

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A fast feature extraction algorithm is presented in this paper based on the color and point feature, With the aim of required feature points, the location of the object includes object region detection and feature point location. The area of object detection is used to look for the centre of gravity point from the scaling image. The feature point location is based on the object region detection, cuts a picture from the image, and extracts speeded up robust feature (SURF) points of the target within the cut picture. The target position is calculated according to the value of the feature points, it provides a basis for object tracking. The experimental results verify the effectiveness of the proposed method.

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Goraj, Zdobyslaw. "Design and Optimisation of Fuel Tanks for BWB Configurations." Archive of Mechanical Engineering 63, no. 4 (December 1, 2016): 605–17. http://dx.doi.org/10.1515/meceng-2016-0034.

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Abstract This paper describes assumptions, goals, methods, results and conclusions related to fuel tank arrangement of a flying wing passenger airplane configuration. A short overview of various fuel tank systems in use today of different types of aircraft is treated as a starting point for designing a fuel tank system to be used on very large passenger airplanes. These systems may be used to move fuel around the aircraft to keep the centre of gravity within acceptable limits, to maintain pitch and lateral balance and stability. With increasing aircraft speed, the centre of lift moves aft, and for trimming the elevator or trimmer must be used thereby increasing aircraft drag. To avoid this, the centre of gravity can be shifted by pumping fuel from forward to aft tanks. The lesson learnt from this is applied to minimise trim drag by moving the fuel along the airplane. Such a task can be done within coming days if we know the minimum drag versus CG position and weight value. The main part of the paper is devoted to wing bending moment distribution. A number of arrangements of fuel in airplane tanks are investigated and a scenario of refuelling - minimising the root bending moments - is presented. These results were obtained under the assumption that aircraft is in long range flight (14 hours), CL is constant and equal to 0.279, Specific Fuel Consumption is also constant and that overall fuel consumption is equal to 20 tons per 1 hour. It was found that the average stress level in wing structure is lower if refuelling starts from fuel tanks located closer to longitudinal plane of symmetry. It can influence the rate of fatigue.

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Ye, Kan, and Jinchen Ji. "The effect of the rotor adjustment on the vibration behaviour of the drive-train system for a 5 MW direct-drive wind turbine." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 232, no. 17 (September 11, 2017): 3027–44. http://dx.doi.org/10.1177/0954406217729418.

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Direct-drive wind turbines, different from the standard geared wind turbines, widely use a direct-drive permanent-magnet generator to avoid the gearbox failures. In the absence of a gearbox in the drive-train system, the direct-drive generator operates at low rotating speeds. Thus direct-drive wind turbines require a larger sized generator (higher weight) to transfer the kinetic energy into electrical energy. The inherent unbalanced magnetic pull force of the generator can have impact on the vibration behaviour of the drive-train system. This paper studies the effect of rotor position and weight adjustment on the vibration behaviour of the drive-train system within a 5 MW direct-drive wind turbine by considering the unbalanced magnetic pull force. The adjustment of rotor position and weight changes the location of the centre of gravity of the drive-train system. The drive-train system which consists of the main shaft, rotor, hub and blades is modelled as a four degree-of-freedom nonlinear system. Both rotor displacement and bearing forces are obtained for a wide range of rotor position and weight under different rotating speeds. The obtained results would provide useful information on the optimized rotor position and mass ratio to improve the performance of the drive-train system.

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Ambrozy, C., and F. Rattay. "Assessment criteria for evaluating the stability and position of the centre of gravity on a balance training platform: a simulation with Matlab®." Journal of Medical Engineering & Technology 35, no. 5 (May 27, 2011): 239–45. http://dx.doi.org/10.3109/03091902.2011.574777.

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Zhang, Guo Sheng, Wei Wang, Song Ai Piao, and Xuan Dong. "The Study of Bus Superstructure Strength Based on ECE R66." Advanced Materials Research 430-432 (January 2012): 1799–804. http://dx.doi.org/10.4028/www.scientific.net/amr.430-432.1799.

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Taking a full-monocoque body as the research object, the finite element analysis theory was applied to build the finite element model of the bus and the numerical simulation environment of the structural strength of the superstructure. The vehicle centre of gravity position determination was studied and calculated. According to the ECE R66 equivalent authentication method, the rollover test of body section was carried out. The rigid and strength characteristic of bus superstructure were evaluated. On this basis, the energy absorbing capability of body section during the rollover process was studied and evaluated. The results showed that the body section of bus was complied with the regulatory requirements; its structural safety characteristic was good. This design method of rollover crash safety had important significance and value to research and development of manufacturer.

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Dong, Guang Ming, Jin Chen, and Nong Zhang. "Study on the Time Lag between Steering Input and Vehicle Lateral Acceleration Response under Different Key Vehicle Parameters." Applied Mechanics and Materials 226-228 (November 2012): 681–84. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.681.

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A passively suspended road vehicle rolls outwards under the influence of lateral acceleration when cornering, which is very dangerous under large lateral acceleration. In this paper, time lag between steering input and vehicle lateral acceleration response is systematically studied to implement the active roll control algorithm from the viewpoint of vehicle system dynamics. A 3 DOF yaw-roll vehicle model is established based on vehicle lateral, roll and yaw dynamics. Vehicle parameters of a 1997 Jeep Cherokee is used for parametric study, where the influences of vehicle velocity, steering frequency, mass, length, roll, yaw moment of inertia, position of vehicle centre of gravity, and tyre cornering stiffness are studied via numerical simulation. The analysis results will help improve the real time rollover warning/control algorithm design for vehicle safety.

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Stiefvater, Otto L. "The Triply Determined Substitution Structure of 1,3,4-Thiadiazole by DRM Microwave Spectroscopy." Zeitschrift für Naturforschung A 44, no. 1 (January 1, 1989): 29–40. http://dx.doi.org/10.1515/zna-1989-0108.

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Double Resonance Modulation (DRM) microwave spectroscopy has allowed the determination of the complete substitution structure of normal, mono-deuterated and perdeuterated 1,3.4-thiadiazole (N2C2H2S). The shift of the centre of gravity between the normal and the d2-form and the swing of inertia! axes relative to the C2v symmetrical forms in the 2-d1-species have been used to revise the small coordinates of hydrogen and deuterium atoms.Bond lengths (in Å) and bond angles (in degrees), with uncertainties covering all three molecular forms, are found as follows: The results suggest that the shift and the swing of inertial axes between different ‘parent’ forms, which can both be determined from the moments of multiply substituted molecular isotopes, may be used with advantage to refine the position of near-axis atoms.

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Tondji, Y., and R. M. Botez. "Semi-empirical estimation and experimental method for determining inertial properties of the Unmanned Aerial System – UAS-S4 of Hydra Technologies." Aeronautical Journal 121, no. 1245 (October 11, 2017): 1648–82. http://dx.doi.org/10.1017/aer.2017.105.

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ABSTRACTThis article presents a structural analysis of the Unmanned Aerial System UAS-S4 ETHECATL. Mass, centre of gravity position and principal mass moment of inertia are numerically determined and further experimentally verified using the ‘pendulum method’. The numerical estimations are computed through Raymer and DATCOM statistical-empirical methods coupled with mechanical calculations. The mass of the UAS-S4 parts are estimated according to their sizes and the UAS-S4 class, by the means of Raymer statistical equations. The UAS-S4 is also decomposed in several simple geometrical figures which centres of gravity are individually computed, weighted and then arithmetically averaged to find the whole UAS-S4 centre of gravity. In the same way, DATCOM equations allows us to estimate the mass moments of inertia of each UAS-S4 parts that are finally sum up according to the Huygens-Steiner theorem for computing the principal moment of inertia of the whole UAS-S4. The mass of de UAS-S4 is experimentally determined with two scales. Its centre of gravity coordinates and its mass moment of inertia are found using the pendulum method. A bifilar torsion-type pendulum methodology is used for the vertical axis(14)and a simple pendulum methodology is used for the longitudinal and transversal axes(12). The test object is installed on a pendulum (simple or bifilar torsion pendulum) which is led to oscillate freely while recording the oscillation's angles and speed, by the means of three sensors (an accelerometer, a gyroscope and a magnetometer) that the calibration is also discussed. Simultaneously, nonlinear dynamic models are developed for the rotational motion of pendulums, including the effects of large-angle oscillations, aerodynamic drag, viscous damping and additional momentum of air. ‘Algorithms of minimization’ are then used to simulate and actualise the dynamic models and finally chose the model that simulated data best fit the experimentally recorded one. Pendulum parameters, such as mass moment of inertia, are lastly extracted from the chosen model. To determine the accuracy of the nonlinear dynamics approach of the pendulum method, the experimental results for an object of uniform density for which the mass moments of inertia are computed numerically from geometrical data are presented along with the experimental results obtained for the UAS-S4 ETHECATL. For the uniform density object, the experimental method gives, with respect to the numerical results, an error of 4.4% for the mass moment of inertia around theZaxis and 9.5% for the moment of inertia around theXandYaxes. In addition, the experimental results for the UAS-S4 inertial values validate the numerical calculation through DATCOM method with a relative error of 6.52% on average.

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Huang, Adam, and Daniel D. Joseph. "Stability of eccentric core–annular flow." Journal of Fluid Mechanics 282 (January 10, 1995): 233–45. http://dx.doi.org/10.1017/s0022112095000127.

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Perfect core-annular flows are two-phase flows, for example of oil and water, with the oil in a perfectly round core of constant radius and the water outside. Eccentric core flows can be perfect, but the centre of the core is displaced off the centre of the pipe. The flow is driven by a constant pressure gradient, and is unidirectional. This kind of flow configuration is a steady solution of the governing fluid dynamics equations in the cases when gravity is absent or the densities of the two fluids are matched. The position of the core is indeterminate so that there is a family of these eccentric core flow steady solutions. We study the linear stability of this family of flows using the finite element method to solve a group of PDEs. The large asymmetric eigenvalue problem generated by the finite element method is solved by an iterative Arnoldi's method. We find that there is no linear selection mechanism; eccentric flow is stable when concentric flow is stable. The interface shape of the most unstable mode changes from varicose to sinuous as the eccentricity increases from zero.

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Funnell, JP, CL Craven, L. D’Antona, L. Thorne, LD Watkins, and AK Toma. "TM3-8 Use of adjustable anti-gravity devices in NPH patients with delayed post-shunt deterioration." Journal of Neurology, Neurosurgery & Psychiatry 90, no. 3 (February 14, 2019): e17.1-e17. http://dx.doi.org/10.1136/jnnp-2019-abn.53.

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ObjectivesA subset of idiopathic Normal Pressure Hydrocephalus (NPH) patients respond to VP shunt insertion temporarily. Adjustable anti-gravity devices are designed to control position-induced CSF drainage changes; we aim to assess to effect of using these devices to achieve controlled overdrainage in temporary shunt responders.DesignA single-centre retrospective study of patients undergoing VP shunt valve revision from an adjustable differential pressure valve with fixed anti-siphon (ProGAV +Shuntassistant) to a system incorporating an adjustable anti-siphon valve (ProGAV +ProSA) (April 2013-April 2018).Subjects21 patients diagnosed with temporary shunt-responsive NPH who improved on high volume shunt reservoir tap (10M: 11F). Mean age at first VP shunt insertion was 74.5±7.87 years.MethodsMedical records were retrospectively reviewed for demographics, interventions and clinical outcomes.ResultsMean duration until revision with a ProSA valve was 31.5±16.8 months (mean ±SD). Mean follow up was 31.4±15.9 months. Of 20 patients with sufficient follow-up, 12 made objective improvements in walking and/or neuropsychological test outcome. 15 patients made subjective improvements in mobility or cognitive impairment.ConclusionsVP shunting with adjustable differential pressure valves and fixed antigravity devices may not drain sufficient CSF for optimum management of low pressure hydrocephalus. Addition of adjustable anti-gravity devices at lower shunt settings in temporary shunt responders may improve outcome.

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Akras, Stavros, Hektor Monteiro, Isabel Aleman, Marcos A. F. Farias, Daniel May, and Claudio B. Pereira. "Exploring the differences of integrated and spatially resolved analysis using integral field unit data: the case of Abell 14." Monthly Notices of the Royal Astronomical Society 493, no. 2 (February 20, 2020): 2238–52. http://dx.doi.org/10.1093/mnras/staa383.

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ABSTRACT We present a new approach to study planetary nebulae using integral field spectroscopy. VLT@VIMOS datacube of the planetary nebula Abell 14 is analysed in three different ways by extracting: (i) the integrated spectrum, (ii) one-dimensional simulated long-slit spectra for different position angles, and (iii) spaxel-by-spaxel spectra. These data are used to build emission-line diagnostic diagrams and explore the ionization structure and excitation mechanisms combining data from one- and three-dimensional photoionization models. The integrated and 1D simulated spectra are suitable for developing diagnostic diagrams, while the spaxel spectra can lead to misinterpretation of the observations. We find that the emission-line ratios of Abell 14 are consistent with UV photoionised emission; however, there are some pieces of evidence of an additional thermal mechanism. The chemical abundances confirm its previous classification as a Type I planetary nebula, without spatial variation. We find, though, variation in the ionization correction factors as a function of the slit’s position angle. The star at the geometric centre of Abell 14 has an A5 spectral type with an effective temperature of Teff = 7909 ± 135 K and surface gravity log(g) = 1.4 ± 0.1 cm s−2. Hence, this star cannot be responsible for the ionization state of the nebula. Gaia parallaxes of this star yield distances between 3.6 and 4.5 kpc in good agreement with the distance derived from a three-dimensional photoionization modelling of Abell 14, indicating the presence of a binary system at the centre of the planetary nebula.

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Tierney, Gregory J., Karl Denvir, Garreth Farrell, and Ciaran K. Simms. "The effect of technique on tackle gainline success outcomes in elite level rugby union." International Journal of Sports Science & Coaching 13, no. 1 (May 30, 2017): 16–25. http://dx.doi.org/10.1177/1747954117711866.

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Tackling is a major component of rugby union and effective attacking and defensive play are essential for game outcomes. In this study, a number of pre-contact, contact and post-contact tackle characteristics that had an influence on tackle gainline success for the ball carrier and tackler were identified using match video evidence from European Rugby Champions Cup games. A total of 122 front-on tackles and 111 side-on tackles were analysed. For each ball carrier and tackler characteristic, the Odds Ratio and 95% Confidence Interval were calculated based on a gainline success outcome. A Chi-Square and Phi and Cramer’s V calculation was also conducted. A Chi-Square test then identified any statistically significant differences (p < 0.05) for proficiency characteristics between playing position. For both the ball carrier and tackler, tackle characteristics that were indicative of strong and powerful tackle technique such as ‘explosiveness on contact’ and ‘leg drive on contact’ were effective for achieving the desired gainline outcome. Playing position had an influence on only two proficiency characteristics that were statistically significant for gainline success: ‘fending into contact’ for ball carriers and ‘straight back, centre of gravity forward of support base’ for tacklers.

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Radojcic, Dejan, Antonio Zgradic, Milan Kalajdzic, and Aleksandar Simic. "Resistance Prediction for Hard Chine Hulls in the Pre-Planing Regime." Polish Maritime Research 21, no. 2 (April 1, 2014): 9–26. http://dx.doi.org/10.2478/pomr-2014-0014.

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Abstract A mathematical representation of calm-water resistance for contemporary planing hull forms based on the USCG and TUNS Series is presented. Regression analysis and artificial neural network (ANN) techniques are used to establish, respectively, Simple and Complex mathematical models. For the Simple model, resistance is the dependent variable (actually R/Δ for standard displacement of Δ = 100000 lb), while the Froude number based on volume (FnV) and slenderness ration (L/V1/3) are the independent variables. In addition to these, Complex model’s independent variables are the length beam ratio (L/B), the position of longitudinal centre of gravity (LCG/L) and the deadrise angle (β). The speed range corresponding to FnV values between 0.6 and 3.5 is analyzed. The Simple model can be used in the concept design phases, while the Complex one might be used for various numerical towing tank performance predictions during all design phases, as appropriate

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JOSEPH, D. D., and D. OCANDO. "Slip velocity and lift." Journal of Fluid Mechanics 454 (March 10, 2002): 263–86. http://dx.doi.org/10.1017/s0022112001007145.

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The lift force on a circular particle in plane Poiseuille flow perpendicular to gravity is studied by direct numerical simulation. The angular slip velocity Ωs=Ωp+½γ˙, where −½γ˙ is the angular velocity of the fluid at a point where the shear rate is γ˙ and Ωp is the angular velocity of the particle, is always positive at an equilibrium position at which the hydrodynamic lift balances the buoyant weight. The particle migrates to its equilibrium position and adjusts Ωp so that Ωs > 0 is nearly zero because Ωp ≈ −1/2γ˙ No matter where the particle is placed, it drifts to an equilibrium position with a unique, slightly positive equilibrium angular slip velocity. The angular slip velocity discrepancy defined as the difference between the angular slip velocity of a migrating particle and the angular slip velocity at its equilibrium position is positive below the position of equilibrium and negative above it. This discrepancy is the quantity that changes sign above and below the equilibrium position for neutrally buoyant particles, and also above and below the lower equilibrium position for heavy particles. The existence and properties of unstable positions of equilibrium due to newly identified turning-point transitions and those near the centreline are discussed.The long particle model of Choi & Joseph (2001) that gives rise to an explicit formula for the particle velocity and the velocity profile across the channel through the centreline of the particle is modified to include the effect of the rotation of the particle. In view of the simplicity of the model, the explicit formula for Up and the velocity profile are in surprisingly good agreement with simulation values. The value of the Poiseuille flow velocity at the point at the particle's centre when the particle is absent is always larger than the particle velocity; the slip velocity is positive at steady flow.

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Figat, Marcin, and Agnieszka Kwiek. "Aerodynamic and static stability investigation into aircraft coupled system to suborbital space flights." Aircraft Engineering and Aerospace Technology 93, no. 2 (February 25, 2021): 275–83. http://dx.doi.org/10.1108/aeat-05-2020-0085.

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Purpose The aim of the research is to conduct a study into a configuration of an aircraft system with a focus on aerodynamics. In addition, trim condition and static stability constraints were included. The main application of this system is suborbital space flights. The presented concept of a modular airplane system (MAS) consists of two vehicles: a Rocket Plane and a Carrier. Both are designed in tailless configurations but coupled formed a classic tail aircraft configuration, where the Rocket Plane works as the empennage. The most important challenge is to define the mutual position of those two tailless vehicles under the assumption that each vehicle will be operating alone in different flight conditions while joined in one object create a conventional aircraft. Each vehicle configuration (separated and coupled) must fulfil static stability and trim requirements. Design/methodology/approach Aircrafts’ aerodynamic characteristics were obtained using the MGAERO software which is a commercial computing fluid dynamics tool created by AMI Aero. This software uses the Euler flow model. Results from this software were used in the static stability and trim condition analysis. Findings The main outcome of this investigation is a mutual position of the Rocket Plane and the Carrier that fulfils project requirements. Also, the final configuration of both separated vehicles (Rocket Plane and Carrier) and the complete MAS were defined. In addition, it was observed that in the case of classic aircraft configuration which is created by connecting two tailless vehicles increasing horizontal tail arm reduces static stability. This is related to a significantly higher mass ratio of the horizontal tail (the Rocket Plane) with respect to the whole system. Moving backward, the Rocket Plane has a notable effect on a position of a centre of gravity of the whole system static stability. Moreover, the impact of the mutual vehicles’ position (horizontal tail arm) and inclination angle on the coupled vehicle lift to drag ratio was analysed. Research limitations/implications In terms of aerodynamic computation, MGAERO software using an inviscid flow model, therefore, both a friction drag and breakdown of vortex are not considered. But the presented research is for the computation stage of the design, and the MGAERO software guarantees satisfactory accuracy with respect to the relatively low time of computations. The second limitation is that the presented results are for the conceptual stage of the design and dynamic stability constraints were not taken into account. Practical implications The ultimate goal of the coupled aircraft project is to conduct flying tests and the presented result is one of the milestones to achieve this goal. Originality/value A design process for a conventional aircraft configuration is well known however, there are not many examples of vehicles that consist of two coupled aircrafts where both vehicles have similar mass. The unique part of this paper includes results of the investigation of the mutual position of the vehicles that can fly alone, as well as in coupled form. The impact of the position of the centre of gravity on trim conditions and static stability of the coupled configuration was investigated.

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Wieczorek, Bartosz, and Mateusz Kukla. "Effects of the performance parameters of a wheelchair on the changes in the position of the centre of gravity of the human body in dynamic condition." PLOS ONE 14, no. 12 (December 6, 2019): e0226013. http://dx.doi.org/10.1371/journal.pone.0226013.

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Santos, T. A., and C. Guedes Soares. "Monte Carlo simulation of damaged ship survivability." Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 219, no. 1 (March 1, 2005): 25–35. http://dx.doi.org/10.1243/147509005x10404.

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A probabilistic methodology for assessing damaged ship survivability based on Monte Carlo simulation is proposed. The damage condition is generated using statistical distributions of damage location and extent, derived during a recent research project, coupled to an algorithm that identifies the damaged compartments. Survivability of the ship in each damage condition is evaluated using the formulae recently proposed in Report SLF 46, which are partly based on the static equivalent method and partly on a more conventional approach. The Monte Carlo simulation technique is applied taking into consideration random quantities related to the damage and loading conditions at the time of accident. This methodology is applied to a passenger roll-on roll-off ship, allowing for a direct estimate of the damaged ship survivability in terms of the number of simulated ship capsizes. The effects of changes in the vertical position of the centre of gravity and in the sea state distribution at the moment of accident are also evaluated.

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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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Conti, G. T., and L. C. G. Souza. "Satellite Attitude Control System Simulator." Shock and Vibration 15, no. 3-4 (2008): 395–402. http://dx.doi.org/10.1155/2008/141465.

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Future space missions will involve satellites with great autonomy and stringent pointing precision, requiring of the Attitude Control Systems (ACS) with better performance than before, which is function of the control algorithms implemented on board computers. The difficulties for developing experimental ACS test is to obtain zero gravity and torque free conditions similar to the SCA operate in space. However, prototypes for control algorithms experimental verification are fundamental for space mission success. This paper presents the parameters estimation such as inertia matrix and position of mass centre of a Satellite Attitude Control System Simulator (SACSS), using algorithms based on least square regression and least square recursive methods. Simulations have shown that both methods have estimated the system parameters with small error. However, the least square recursive methods have performance more adequate for the SACSS objectives. The SACSS platform model will be used to do experimental verification of fundamental aspects of the satellite attitude dynamics and design of different attitude control algorithm.

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Journal articles on the topic 'Lenghwise position centre of gravity'

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