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1
Mbou, E. Tiaya, E. Njeugna, A. Kemajou, N. R. Tagne Sikame, and D. Ndapeu. "Modelling of the Water Absorption Kinetics and Determination of the Water Diffusion Coefficient in the Pith ofRaffia viniferaof Bandjoun, Cameroon." Advances in Materials Science and Engineering 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/1953087.
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The present work focuses on the study of the water absorption phenomenon through the pith ofRaffia viniferaalong the stem. The water absorption kinetics was studied experimentally by the gravimetric method with the discontinuous control of the sampling mass at temperature of 30°C. The samples of 70 mm × 8 mm × 4 mm were taken from twelve sampling zones of the stem ofRaffia vinifera. The result shows that the percentage of water absorption of the pith ofRaffia viniferaincreases from the periphery to the center in the radial position and from the base to the leaves in the longitudinal position. Fick’s second law was adopted for the study of the water diffusion. Eleven models were tested for the modelling of the water absorption kinetics and the model of Sikame Tagne (2014) is the optimal model. The diffusion coefficients of two stages were determined by the solution of the Fick equation in the twelve sampling zones described by Sikame Tagne et al. (2014). The diffusion coefficients decreased from the center to the periphery in the radial position and from the base to the leaves in the longitudinal position.
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Zhang, Xue Yan, and Wen Ming Zhang. "Vibration Simulation of Articulated Dump Truck with the Variation of Longitudinal Center of Gravity Position of Rear Sprung Mass and Rear Suspension Stiffness." Advanced Materials Research 383-390 (November 2011): 1812–18. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.1812.
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The paper is concerned with the vibration for the articulated dump truck (ADT) which is multi-axle vehicle and different from rigid dump truck. The balanced suspension was employed as the rear suspension in the 60t ADT which the paper takes as the research object. A vibration model of 6 dof for the truck was proposed. The impact of the variation of longitudinal center of gravity position of rear sprung mass and rear suspension stiffness on vibration was investigated in stochastic excitation of the truck in the frequency domain. It is found that it is beneficial to the comfort of the truck when the center of gravity of the sprung mass moves forward and the impact of rear sprung stiffness on vibration is not too great. The results of the vibration for the truck are provided for the design of the 60t ADT.
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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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Muis, Jasper. "The Rise and Demise of the Dutch Extreme Right: Discursive Opportunities and Support for the Center Democrats in the 1990s." Mobilization: An International Quarterly 20, no. 1 (March 1, 2015): 41–60. http://dx.doi.org/10.17813/maiq.20.1.f211773qm103w030.
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This article seeks to explain why the Dutch extreme-right party, Center Democrats (CD), never succeeded in breaking out of its marginal position. It argues that, in addition to analyzing fluctuations in electoral support, scholars should also examine the degree to which extreme-right parties are able to express their views in the mass media. Supply-side explanations are extended by showing that discursive political opportunities need to be openly acknowledged and debated publicly to become relevant. Relying on longitudinal data derived from political claims analysis and opinion polls, this article demonstrates that negative public reactions significantly eroded the electoral attractiveness of the extreme-right party. In contrast, when one's goal is to achieve mass media access, the results reveal that any publicity is favorable publicity. Public criticism enhanced the CD's access to the public debate. Also, rising support in opinion polls led to more public claim making. Remarkably, however, the extreme right party did not increase its electoral support when it made itself more prominently heard in the mass media. Thus, the CD appeared trapped in a spiral of discursive weakness.
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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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Al-Solihat, Mohammed Khair, Meyer Nahon, and Kamran Behdinan. "Three-dimensional nonlinear coupled dynamic modeling of a tip-loaded rotating cantilever." Journal of Vibration and Control 24, no. 22 (January 19, 2018): 5366–78. http://dx.doi.org/10.1177/1077546317753058.
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This paper presents a general three-dimensional flexible dynamic model of a tip-loaded rotating cantilever beam. For generality, the beam tip is assumed to be loaded with a rigid body with an arbitrary center of mass position, and subject to external force and moment. The coupled longitudinal (axial), bending–bending, and twist elastic motions are considered to formulate the system dynamics. The beam structural internal damping is modeled utilizing Rayleigh’s dissipation function. As well, the influence of gravity is considered. A symbolic code is developed to derive the equations of motion, and it is subsequently used to simulate the dynamics of two numerical case studies. The time response results are found to be in an excellent agreement with those reported from the literature. The effects of internal damping and coupling among the elastic motions on the system dynamic response are then investigated.
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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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Boughari, Yamina, Ruxandra Mihaela Botez, Georges Ghazi, and Florian Theel. "Flight control clearance of the Cessna Citation X using evolutionary algorithms." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 231, no. 3 (August 6, 2016): 510–32. http://dx.doi.org/10.1177/0954410016640821.
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In this paper, an Aircraft Research Flight Simulator equipped with Flight Dynamics Level D (highest level) was used to collect flight test data and develop new controller methodologies. The changes in the aircraft’s mass and center of gravity position are affected by the fuel burn, leading to uncertainties in the aircraft dynamics. A robust controller was designed and optimized using the H∞ method and two different metaheuristic algorithms; in order to ensure acceptable flying qualities within the specified flight envelope despite the presence of uncertainties. The H∞ weighting functions were optimized by using both the genetic algorithm, and the differential evolution algorithm. The differential evolution algorithm revealed high efficiency and gave excellent results in a short time with respect to the genetic algorithm. Good dynamic characteristics for the longitudinal and lateral stability control augmentation systems with a good level of flying qualities were achieved. The optimal controller was used on the Cessna Citation X aircraft linear model for several flight conditions that covered the whole aircraft’s flight envelope. The novelty of the new objective function used in this research is that it combined both time-domain performance criteria and frequency-domain robustness criterion, which led to good level aircraft flying qualities specifications. The use of this new objective function helps to reduce considerably the calculation time of both algorithms, and avoided the use of other computationally more complicated methods. The same fitness function was used in both evolutionary algorithms (differential evolution and genetic algorithm), then their results for the validation of the linear model in the flight points were compared. Finally, robustness analysis was performed to the nonlinear model by varying mass and gravity center position. New tools were developed to validate the results obtained for both linear and nonlinear aircraft models. It was concluded that very good performance of the business Cessna Citation X aircraft was achieved in this research.
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Nakajima, Kazuhisa, Jonathan Wheeler, Gérard Mourou, and Toshiki Tajima. "Novel laser-plasma TeV electron-positron linear colliders." International Journal of Modern Physics A 34, no. 34 (December 10, 2019): 1943003. http://dx.doi.org/10.1142/s0217751x19430036.
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TeV center-of-mass energy electron-positron linear colliders comprising seamlessly staged capillary laser-plasma accelerators are presented. A moderate intensity laser pulse coupled with the single electromagnetic hybrid mode in a gas-filled capillary can generate plasma waves in the linear regime, where laser wakefields can accelerate equally focused electron and positron beams. In multiple stage capillary accelerators, a particle beam with respect to the laser wakefield can undergo consecutive acceleration up to TeV energies, associated with continuous transverse focusing in a beam size down to a nanometer level, being capable of a promising electron-positron linear collider with very high luminosities of the order of 10[Formula: see text] cm[Formula: see text]s[Formula: see text]. The transverse and longitudinal beam dynamics of beam particles in plasma wakefields with the effects of radiation reaction and multiple Coulomb scattering are investigated numerically to estimate the luminosities in beam-beam collisions with the effects of beamstrahlung radiation and bunch disruption.
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Li, Xiaogao, Ning Zhang, Xianjian Jin, and Nan Chen. "Modeling and Analysis of Vehicle Shimmy with Consideration of the Coupling Effects of Vehicle Body." Shock and Vibration 2019 (March 24, 2019): 1–14. http://dx.doi.org/10.1155/2019/3707416.
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Based on the Lagrange equation, a 9-degrees-of-freedom shimmy model with consideration of the coupling effects between the motions of vehicle body and the shimmy of front wheels and a 5-degrees-of-freedom shimmy model ignoring these coupling effects for a vehicle with double-wishbone independent front suspensions are presented here to study the problem of vehicle shimmy. According to the eigenvalue loci of system’s Jacobian matrix plotted on the complex plane, the Hopf bifurcation characteristics of nonlinear shimmy are studied and the conditions for the generation of limit cycle are analyzed. Numerical calculation and simulation are used to study the dynamic behavior of vehicle shimmy. By comparing the dynamic responses of two different shimmy models, the coupling effects of vehicle body on vehicle shimmy are studied. Finally, the relationship between the amplitude of each DoF and vehicle velocity and the influences of vehicle parameters such as the mass of vehicle body, the longitudinal position of the center of gravity of vehicle body, and the inclination angle of front suspension on shimmy are studied.
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Decker, Oliver. "Secondary authoritarianism ‐ the economy and right-wing extremist attitudes in contemporary Germany." Journal of Psychosocial Studies 12, no. 1 (July 1, 2019): 203–13. http://dx.doi.org/10.1332/147867319x15608718111032.
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In this essay the thesis of a secondary authoritarian dynamic governing contemporary German society is presented. The author follows Sigmund Freud’s distinction between primary and secondary masses ‐ a leader as idealized object of the group members constitutes the first, an abstract object produces the latter mass. To underpin his thesis the author argues with empirical findings of the longitudinal research project ‘Leipzig-Studies on Authoritarianism’ measuring right-wing extremist attitudes in the general German population since 2002 (until 2018 known as ‘Leipzig “Center”-Studies’). Those empirical findings and group discussions conducted in the same project point out that in post-fascistic German society, economic growth had a most prominent role. It was able to win this powerful position because its historical roots were laid in Nazi Germany. The authoritarian dynamic under economic regression until today shows that the function of this secondary authoritarian object is still in power. If this thesis is correct, right-wing extremist attitudes give a deeper insight into modern societies as well as into an individual’s prejudices.
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Rindani, Saurabh D., and Balbeer Singh. "Indirect measurement of triple-Higgs coupling at an electron–positron collider with polarized beams." International Journal of Modern Physics A 35, no. 04 (February 10, 2020): 2050011. http://dx.doi.org/10.1142/s0217751x20500116.
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We examine the possibility of using single-Higgs production at an [Formula: see text] collider with polarized beams to measure, or constrain, indirectly a possible anomalous triple-Higgs coupling, which can contribute to the process via one-loop diagrams. In the dominant process [Formula: see text], longitudinally polarized beams can lead to an improvement in the cross-section by 50% for [Formula: see text] and [Formula: see text] polarizations of [Formula: see text] and [Formula: see text], respectively. This corresponds to an improvement in the sensitivity to the triple-Higgs coupling of about 18% for a center-of-mass energy of 250 GeV and an integrated luminosity of 2 ab[Formula: see text], making a strong case of beam polarization. This also implies that with polarized beams, the luminosity needed to get a particular sensitivity is less by about 33% as compared to that needed with unpolarized beams. Even when only the [Formula: see text] beam is polarized [Formula: see text], the improvement in the sensitivity is about 8%. We also study the effect of longitudinal beam polarization on the sensitivity to the triple-Higgs coupling of Higgs production through the subdominant process [Formula: see text] occurring through [Formula: see text] fusion.
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Nowicki, Waldemar. "The Longitudinal Superdiffusive Motion of Block Copolymer in a Tight Nanopore." Polymers 12, no. 12 (December 8, 2020): 2931. http://dx.doi.org/10.3390/polym12122931.
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The structure and dynamic properties of polymer chains in a confined environment were studied by means of the Monte Carlo method. The studied chains were represented by coarse-grained models and embedded into a simple 3D cubic lattice. The chains stood for two-block linear copolymers of different energy of bead–bead interactions. Their behavior was studied in a nanotube formed by four impenetrable surfaces. The long-time unidirectional motion of the chain in the tight nanopore was found to be correlated with the orientation of both parts of the copolymer along the length of the nanopore. A possible mechanism of the anomalous diffusion was proposed on the basis of thermodynamics of the system, more precisely on the free energy barrier of the swapping of positions of both parts of the chain and the impulse of temporary forces induced by variation of the chain conformation. The mean bead and the mass center autocorrelation functions were examined. While the former function behaves classically, the latter indicates the period of time of superdiffusive motion similar to the ballistic motion with the autocorrelation function scaling with the exponent t5/3. A distribution of periods of time of chain diffusion between swapping events was found and discussed. The influence of the nanotube width and the chain length on the polymer diffusivity was studied.
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Hsu, Wei-Li, John P. Scholz, Gregor Schöner, John J. Jeka, and Tim Kiemel. "Control and Estimation of Posture During Quiet Stance Depends on Multijoint Coordination." Journal of Neurophysiology 97, no. 4 (April 2007): 3024–35. http://dx.doi.org/10.1152/jn.01142.2006.
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This study tested the hypotheses that all major joints along the longitudinal axis of the body are equally active during quiet standing and that their motions are coordinated to stabilize the spatial positions of the center of mass (CM) and head. Analyses of the effect of joint configuration variance on the stability of the CM and head positions were performed using the uncontrolled manifold (UCM) approach. Subjects stood quietly with arms folded across their chests for three 5-min trials each with and without vision. The UCM analysis revealed that the six joints examined were coordinated such that their combined variance had minimal effect on the CM and head positions. Removing vision led to a structuring of the resulting increased joint variance such that little of the increase affected stability of the CM and head positions. The results reveal a control strategy involving coordinated variations of most major joints to stabilize variables important to postural control during quiet stance.
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Farcas, Adrian, and Andrew W. Woods. "Buoyancy-driven dispersion in a layered porous rock." Journal of Fluid Mechanics 767 (February 12, 2015): 226–39. http://dx.doi.org/10.1017/jfm.2014.744.
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AbstractWe investigate the longitudinal dispersion of a passive tracer by a gravity-driven flow in a porous medium consisting of a series of independent horizontal layers connected to a constant pressure source. We show that in a formation of given vertical extent, the total flux is only weakly dependent on the number of layers, and is very similar to that in a single layer of the same total depth. However, although the flow speed in each layer is approximately uniform, the speed gradually increases with layer depth. As a result, if a pulse of tracer is released in the flow it will migrate more rapidly through the lower layers, leading to longitudinal dispersion of the tracer. Eventually, the location of the tracer in the different layers may become separated in space so that a sufficiently distant observation well would detect a series of discrete pulses of tracer rather than the original coherent input, as would occur in a single permeable layer. For a constant pressure source, at long times, the standard deviation of the longitudinal distribution of tracer asymptotes to a fraction of order 0.1 of the position of the centre of mass, depending on the number of layers and the overpressure of the source.
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Тretyak, V. M., V. V. Sheban, R. V. Oliadnichuk, O. F. Govorov, and R. V. Melnik. "Influence of hinged device parameters on negative resonance oscillations during the operation of machine-tractor unit in transport mode." Mehanization and electrification of agricultural, no. 12 (2020): 129–36. http://dx.doi.org/10.37204/0131-2189-2020-12-15.
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Annotation Purpose. Reducing the influence of resonance phenomena on the structural elements of a tractor of the KIY 14102 type when driving with an attached implement in transport mode. Methods. To solve this problem means of graph-analytical constructions, analytical geometry, oscillation theory and theoretical mechanics were used. Results. On the basis of the graphic-analytical analysis of the kinematic diagram of the tractor attachment of the KIY 14102 type, it was found that the position of the instantaneous center of its rotation significantly depends on the change in the angle between the tractor frame and the levers, which are united by the CA-1 automatic connection device. The frequency range of forced oscillations of the tractor frame, which occur when driving in a certain speed range, can coincide with the relative natural frequency of the tractors, which leads to resonance phenomena. Resonant longitudinal-angular vibrations of the tractor frame reduce the normal reactions of the steered wheels with the supporting surface, which worsens controllability. Changing the frequency of the natural resonance of the elements connecting the tractor with the implement can be done by changing the kinematic stiffness of the mounted system. Conclusions 1. The kinematic diagram of the hinged device of tractors significantly affects the dependence of the position of the instantaneous center of rotation of the hinged device relative to the mass of the implement that is aggregated. 2. The existing parameters of the mounted systems of tractors of the KIY 14102 type can lead to the occurrence of resonance phenomena when driving in transport mode on unpaved field roads, which negatively affects the controllability of the MTA. 3. Reducing the resonant frequency of natural vibrations of the attachment system with the tool, by reducing the kinematic stiffness, improves the dynamics of the interaction of the elements of the machine-tractor unit with each other and with the supporting surface. Keywords: machine-tractor unit, clutch system, tests, dynamic loads, strain gauge measurements, air pressure in tires.
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Macpherson, J. M. "Changes in a postural strategy with inter-paw distance." Journal of Neurophysiology 71, no. 3 (March 1, 1994): 931–40. http://dx.doi.org/10.1152/jn.1994.71.3.931.
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1. The purpose of this study was to examine the effect of changing initial stance conditions on the postural response of the cat to horizontal plane translations of the support surface. Cats were trained to stand, unrestrained, on a moveable force platform. The platform was translated linearly in each of 16 directions in the horizontal plane, with a ramp-and-hold displacement. The animal's response was quantified in terms of the forces exerted at the ground. The trajectory of the center of mass (CoM) was computed from the forces. 2. Stance length was varied along the longitudinal (sagittal) axis by adjusting the distance between the forepaw and hindpaw force plates. Translation perturbations of the platform were recorded at stance distances varying from 66 to 110% of the preferred stance distance. 3. Changing stance distance had a significant effect on the amplitude and direction of the active forces exerted by the cat both during quiet stance and during the response to platform translation. At long stance distances, each limb exerted a force outward, along the diagonals during quiet stance. The response to translation was characterized by an invariance in the direction of force exerted against the ground, a strategy that was described previously. At short stance distances, quiet stance forces were more laterally directed. The force constraint strategy was usually not observed for the response to translation. Nevertheless, the cats were equally effective at all stance distances in restoring the position of the center of mass after translation of the support surface. 4. There was no discrete boundary between the presence and absence of the force constraint, suggesting that the strategy for exerting forces against the support surface is characterized by a continuum of response, from a bimodal, or anisotropic distribution of force vectors on the one extreme, to a uniform, or isotropic distribution on the other. Arguments are developed to suggest that the force constraint strategy may be useful in stabilizing the vertebral column during the response to platform translation, to allow linear translation of the CoM rather than bending of the trunk.
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Abbassi, Younes, Youcef Ait-Amirat, and Rachid Outbib. "Global modeling and simulation of vehicle to analyze the inertial parameters effects." International Journal of Modeling, Simulation, and Scientific Computing 07, no. 03 (August 23, 2016): 1650032. http://dx.doi.org/10.1142/s179396231650032x.
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This paper mainly studies the comparison of the global vehicle models and the effects of the inertial parameters due to the center of gravity (CG) positions when we consider that the vehicle has only one CG. This paper proposes a new nonlinear model vehicle model which considers both unsprung mass and sprung mass CG. The CG positions and inertial parameters effects are analyzed in terms of the published vehicle dynamics models. To this end, two 14 degree-of-freedom (DOF) vehicle models are developed and compared to investigate the vehicle dynamics responses due to the different CG height and inertial parameters concepts. The proposed models describe simultaneously the vehicle motion in longitudinal, lateral and vertical directions as well as roll, pitch and yaw of the vehicle about corresponding axis. The passive and active moments and the forces acting on the vehicle are also described and they are considered as a direct consequence of acceleration, braking and steering maneuvers. The proposed model [Formula: see text] takes both the CG of sprung mass, unsprung mass and total vehicle mass into account. The second model [Formula: see text] assumes that the vehicle is one solid body which has a single CG as reported in majority of literature. The two vehicle models are compared and analyzed to evaluate vehicle ride and handling dynamic responses under braking/acceleration and cornering maneuvers. Simulation results show that the proposed model [Formula: see text] could offer analytically some abilities and driving performances, as well as improved roll and pitch in a very flexible manner compared to the second model [Formula: see text].
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Tonguç, Güray, İsmail Hakkı Akçay, and Habib Gürbüz. "Improvement of the visual warning system for various driving and road conditions in road transportation." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 232, no. 2 (October 16, 2017): 175–87. http://dx.doi.org/10.1177/0954407017690962.
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This study aims to identify the potential adverse driving conditions which result from driver behavior, road surfaces and weather conditions for vehicles during a cruise, and to inform the drivers of the other vehicles moving on the same route. Adverse driving condition scenarios were developed via acceleration data in lateral, longitudinal and vertical directions gathered by using an accelerometer sensor placed at the gravity center of the test vehicles. The drivers were warned through the symbols designed according to the developed scenarios in different shapes and colors, displayed on an information screen showing the position of the vehicle. Three different software programs were used for gathering and evaluating the accelerometer data, storing scenario-specific symbols on the internet and transferring these symbols to the other vehicle information displays. The road tests were performed in conditions present in Turkey. It was observed that the vehicle drivers were alerted with the warning symbols which were designed for dangerous road and driving conditions with a latency of approximately 6s on Google maps which appeared on the driver information screen.
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Frost, Shawn B., Maria Iliakova, Caleb Dunham, Scott Barbay, Paul Arnold, and Randolph J. Nudo. "Reliability in the location of hindlimb motor representations in Fischer-344 rats." Journal of Neurosurgery: Spine 19, no. 2 (August 2013): 248–55. http://dx.doi.org/10.3171/2013.4.spine12961.
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Object The purpose of the present study was to determine the feasibility of using a common laboratory rat strain for reliably locating cortical motor representations of the hindlimb. Methods Intracortical microstimulation techniques were used to derive detailed maps of the hindlimb motor representations in 6 adult Fischer-344 rats. Results The organization of the hindlimb movement representation, while variable across individual rats in topographic detail, displayed several commonalities. The hindlimb representation was positioned posterior to the forelimb motor representation and posterolateral to the motor trunk representation. The areal extent of the hindlimb representation across the cortical surface averaged 2.00 ± 0.50 mm2. Superimposing individual maps revealed an overlapping area measuring 0.35 mm2, indicating that the location of the hindlimb representation can be predicted reliably based on stereotactic coordinates. Across the sample of rats, the hindlimb representation was found 1.25–3.75 mm posterior to the bregma, with an average center location approximately 2.6 mm posterior to the bregma. Likewise, the hindlimb representation was found 1–3.25 mm lateral to the midline, with an average center location approximately 2 mm lateral to the midline. Conclusions The location of the cortical hindlimb motor representation in Fischer-344 rats can be reliably located based on its stereotactic position posterior to the bregma and lateral to the longitudinal skull suture at midline. The ability to accurately predict the cortical localization of functional hindlimb territories in a rodent model is important, as such animal models are being increasingly used in the development of brain-computer interfaces for restoration of function after spinal cord injury.
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GOOLISH, EDWARD M. "Swimbladder Function and Buoyancy Regulation in the Killifish Fundulus Heterochtus." Journal of Experimental Biology 166, no. 1 (May 1, 1992): 61–81. http://dx.doi.org/10.1242/jeb.166.1.61.
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Killifish, Fundulus heteroclitus, subjected to artificial lift above their center of gravity (10% of body weight) required a minimum of 7–8 days to resorb swimbladder gases completely. The swimbladders of some fish, however, did not fall below 50% of normal volume. The rate of increase in swimbladder volume upon removal of lift varied little among individuals, with approximately 6 days required for complete refilling. Previous deflation of the swimbladder (by syringe) did not result in faster or more complete gas resorption when the fish were subjected to artificial lift. This suggests that the constraint to resorption observed in some fish is not mechanical, e.g. connective tissue, but may reflect individual variability in perception of the stimulus. Swimbladder dry mass, which scaled as (body mass)0.79, was not affected by exposure to artificial lift. However, fish subjected to 7–11 days of artificial lift displayed slower rates of gas secretion upon removal of lift than control fish whose swimbladders had been evacuated by syringe. The initial rate was 65 % of that of control fish, with two additional days required to achieve normal buoyancy. Also, the rate of swimbladder gas resorption was 24 % faster the second time fish were exposed to artificial lift. These results demonstrate that the capacity for gas secretion and resorption can be altered by previous exposure to hydrostatic challenges. Killifish buoyancy, expressed as swimbladder volume per weight of the gas-free fish in water, fell from 0.95 to 0.70 mlg−1 after 5 days of exposure to water current. Removal of the pectoral fins eliminated 70% of this decrease, while removal of the pelvic fins had no effect. The rate of gas resorption by fish subjected to artificial lift was also not affected by removal of the pectoral fins. From these results it appears that the decrease in swimbladder volume in fish exposed to water currents is a consequence of lift forces produced by the pectoral fins, but that they are not required for regulation. Fish exposed to water currents or artificial lift swim with a head-down angle of attack. Theoretical estimates show that the vertical force component generated by this swimming behavior is of the appropriate magnitude to compensate for the additional lift. Fish confined in transparent cages near the surface of the water were less buoyant (0.91 mlg−1) than fish similarly maintained at the bottom of the tank (0.98mlg−1). However, because this effect was small, 10% of swimbladder volume, visual perception of vertical position is apparently not the primary stimulus for volume regulation. Partial lift (2.65 % of body weight) resulted in the resorption of twice as much swimbladder gas when attachment was anterior to the fish's center of gravity than when it was an equal distance posterior to the center of gravity. When equal amounts of partial lift and weight were added, lift anterior and weight posterior, no change in swimbladder volume occurred. With the position of these forces reversed, swimbladder volume increased by 31 % to 1.27 ml g−1. These results suggest that fish respond to pitching forces, i.e. longitudinal lift moments, as a stimulus for swimbladder gas secretion and resorption.
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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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Dixon, J. C. "Limit Steady State Vehicle Handling." Proceedings of the Institution of Mechanical Engineers, Part D: Transport Engineering 201, no. 4 (October 1987): 281–91. http://dx.doi.org/10.1243/pime_proc_1987_201_187_02.
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Previously, limit steady state handling has always been restricted to the qualitative statement that a vehicle has final understeer or final oversteer; it cannot be analysed by the conventional understeer gradient concept. A specific proposal is made for quantification of final understeer or oversteer. This is called the understeer number, and is defned by Nu = (ArAf)-1, where Af and Ar are the lateral acceleration capabilities of the front and rear axles. Thus Nu is non-dimensional, is zero for a notional final neutral vehicle, positive for final understeer and negative for final oversteer. A typical value is 0.150 (rear drive) or 0.220 (front). The various design parameters that influence the understeer number are investigated, and equations are obtained and quantified, including centre of mass position, lateral load transfer distribution, longitudinal load transfer, traction, the components of aerodynamic forces and moments, the effect of non-free differentials and the effect of load increments. The effect of turning radius and slopes is also investigated. Thus the limit state of handling is subject to a quantitative assessment, showing the degree of a vehicle's commitment to final understeer or oversteer.
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Bondyrev, V. E., S. I. Knyazev, V. I. Korolev, and S. F. Jatsun. "Small-size Unmanned Control Algorithm of an Underwater Complex." Proceedings of the Southwest State University 24, no. 4 (February 4, 2021): 166–79. http://dx.doi.org/10.21869/2223-1560-2020-24-4-166-179.
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Purpose of research: The creation of water bodies monitoring systems makes it possible to evaluate environmental situation in various points of monitoring area quickly. One of the main stages of water quality research is sampling, which is currently carried out at stationary posts, which makes it impossible to ensure operational control in various areas of an observation site. The problem can be solved by using mobile robotic platforms. The purpose of this study is to create mathematical model and algorithm for controlling autonomous movement of an underwater robotic device for collecting water samples in a reservoir. Methods. The following problems were solved for this purpose: the structure of the device was developed, which consists of a power frame unit, units of screw electric drives, units of depth and direction rudders. On-board power supply unit, sensor unit providing interaction of underwater vehicle with environment were also developed. Control tasks are formulated. A scheme of device movement in a reservoir has been developed for this purpose. Results. Modular method of trajectory planning is proposed. It is based on a single motion cycle concept, which consists of 2 turns and 2 straight-line stages of 2R2P. A model of control algorithm is also proposed and reactions of apparatus to external disturbances are studied. General dynamics theorems, method of algorithm synthesizing according to inverse dynamics problem were applied when solving problems. Conclusion: As a result of conducted studies, the system response to disturbances acting in longitudinal direction is described, disturbance diagrams are also described, random type with normal distribution law and mass center deviation s from the given position are given.
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Keller, Sarah, Tabea Borde, Julia Brangsch, Lisa C. Adams, Avan Kader, Carolin Reimann, Pimrapat Gebert, Bernd Hamm, and Marcus Makowski. "Native T1 Mapping Magnetic Resonance Imaging as a Quantitative Biomarker for Characterization of the Extracellular Matrix in a Rabbit Hepatic Cancer Model." Biomedicines 8, no. 10 (October 13, 2020): 412. http://dx.doi.org/10.3390/biomedicines8100412.
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To characterize the tumor extracellular matrix (ECM) using native T1 mapping magnetic resonance imaging (MRI) in an experimental hepatic cancer model, a total of 27 female New Zealand white rabbits with hepatic VX2 tumors were examined by MRI at different time points following tumor implantation (day 14, 21, 28). A steady-state precession readout single-shot MOLLI sequence was acquired in a 3 T MRI scanner in prone position using a head-neck coil. The tumors were segmented into a central, marginal, and peritumoral region in anatomical images and color-coded T1 maps. In histopathological sections, stained with H&E and Picrosirius red, the regions corresponded to central tumor necrosis and accumulation of viable cells with fibrosis in the tumor periphery. Another region of interest (ROI) was placed in healthy liver tissue. T1 times were correlated with quantitative data of collagen area staining. A two-way repeated-measures ANOVA was used to compare cohorts and tumor regions. Hepatic tumors were successfully induced in all rabbits. T1 mapping demonstrated significant differences between the different tumor regions (F(1.43,34.26) = 106.93, p < 0.001) without interaction effects between time points and regions (F(2.86,34.26) = 0.74, p = 0.53). In vivo T1 times significantly correlated with ex vivo collagen stains (area %), (center: r = 0.78, p < 0.001; margin: r = 0.84, p < 0.001; peritumoral: r = 0.73, p < 0.001). Post hoc tests using Sidak’s correction revealed significant differences in T1 times between all three regions (p < 0.001). Native T1 mapping is feasible and allows the differentiation of tumor regions based on ECM composition in a longitudinal tumor study in an experimental small animal model, making it a potential quantitative biomarker of ECM remodeling and a promising technique for future treatment studies.
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AGUILAR, P., C. CHRYSSOMALAKOS, H. HERNANDEZ CORONADO, and E. OKON. "POSITION OPERATORS AND CENTER-OF-MASS: NEW PERSPECTIVES." International Journal of Modern Physics A 28, no. 29 (November 20, 2013): 1350146. http://dx.doi.org/10.1142/s0217751x13501467.
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After reviewing the work of Pryce on Center-of-Mass (CoM) definitions in special relativity, and that of Jordan and Mukunda on position operators for relativistic particles with spin, we propose two new criteria for a CoM candidate: associativity, and compatibility with the Poisson bracket structure. We find that they are not satisfied by all of Pryce's definitions, and they also rule out Dixon's CoM generalization to the curved space–time case. We also emphasize that the various components of the CoM position do not commute among themselves, in the general case, and thus provide a natural entry point to the arena of noncommutative space–time, without the ad-hoc assumptions of the standard paradigm.
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Klar, Antonio Evaldo, Cleber Junior Jadoski, Marcio Furlan Maggi, Juliana Ramiro, and Alexandre Barreto Almeida dos Santos. "DISTRIBUIÇÃO DA ENERGIA NO INTERIOR DE UMA ESTUFA PLÁSTICA NO PERÍODO DO INVERNO." IRRIGA 11, no. 2 (June 18, 2006): 257–65. http://dx.doi.org/10.15809/irriga.2006v11n2p257-265.
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DISTRIBUIÇÃO DA ENERGIA NO INTERIOR DE UMA ESTUFA PLÁSTICA NO PERÍODO DO INVERNO Antonio Evaldo Klar; Cleber Junior Jadoski; Marcio Furlan Maggi; Juliana Ramiro; Alexandre Barreto Almeida dos SantosFaculdade de Ciências Agronômicas de Botucatu, Universidade Estadual Paulista Botucatu, SP, klar@fca.unesp.br 1. RESUMO Este trabalho teve por objetivo estudar a distribuição da energia no interior de um ambiente protegido durante o período do inverno do ano de 2005. O experimento foi instalado em uma estufa de polietileno na Fazenda Experimental Lageado da Faculdade de Ciências Agronômicas (FCA). Para analisar a distribuição da energia, foram utilizados microevaporímetros plásticos de 500 ml (13,7 cmde diâmetro e área de 147 cm2) com o que foram obtidos os valores respectivos de evaporação que integram os elementos meteorológicos envolvidos. Foram instalados 132 microevaporímetros distribuídos em três alturas, 0,40, 0,80 e1,20 m, a partir da superfície do solo, perfazendo 44 pontos uniformemente distribuídos. A estufa plástica é do tipo túnel com 7,5m de largura por 27,5m de comprimento, 3,20m de altura no centro e 2,00m nas paredes laterais fechadas com tela do tipo “sombrite”. A orientação noroeste/sudeste, com base no norte verdadeiro, foi adotada para o eixo longitudinal da estufa. Para a comparação das variáveis, foram utilizados princípios da geoestatística com auxílio do programa GS+. Os dados obtidos permitiram chegar as seguintes conclusões: foram observadas variações significativas da evaporação em diferentes regiões e alturas da estufa; os valores mais elevados ocorreram próximo à superfície do solo no mês de julho e em alturas mais elevadas nos meses de agosto e setembro. A região que teve maior evaporação ocorreu no lado sudeste da estufa. UNITERMOS: microevaporímetro, orientação geográfica, geoestatística. KLAR, A. E., JADOSKI, C.J.; MAGGI, M. F.; RAMIRO, J; SANTOS, A. B. A. dos. Energy distribution in a plastic tunnel IN winter PERIOD 2 ABSTRACT This work aimed to study the energy distribution in protected environment during the winter of 2005. Aplastic tunnel (27.5 mlong, 7.5 mwide, 3.2 mhigh in the center and 2.00 mhigh in both lateral sides) was covered with polyethylene 100 micra and black shadow screen (sombrite) in lateral sides at the FCA/UNESP, Botucatu – SP. 142 minievaporimeters (500 ml volume and 147 cm2 area) were evenly distributed and set up at three heights:0.40 m;0.80 m and1.20 m from soil surface in order to analyze energy distribution along the studied area. The greenhouse longitudinal axis was northwest/southeast, based on true north. Geostatistics principles and the GS+ Program were adopted to compare variables. From obtained results, it was concluded that there were significant evaporation variations at different points and heights; the highest values were the ones closest to the soil surface (0.40m) in July and at highest heights (0.80 and 1.20m). Highest evaporations occurred in the southeastern side of the greenhouse. KEYWORDS: microevaporimeters; greenhouse position; Geostatistics.
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Pai, Yi-Chung, and James Patton. "Center of mass velocity-position predictions for balance control." Journal of Biomechanics 30, no. 4 (April 1997): 347–54. http://dx.doi.org/10.1016/s0021-9290(96)00165-0.
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Roberts, A., N. A. Hill, and R. Hicks. "Simple mechanisms organise orientation of escape swimming in embryos and hatchling tadpoles of Xenopus laevis." Journal of Experimental Biology 203, no. 12 (June 15, 2000): 1869–85. http://dx.doi.org/10.1242/jeb.203.12.1869.
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Many amphibian tadpoles hatch and swim before their inner ears and sense of spatial orientation differentiate. We describe upward and downward swimming responses in hatchling Xenopus laevis tadpoles from stages 32 to 37/38 in which the body rotates about its longitudinal axis. Tadpoles are heavier than water and, if touched while lying on the substratum, they reliably swim upwards, often in a tight spiral. This response has been observed using stroboscopic photography and high-speed video recordings. The sense of the spiral is not fixed for individual tadpoles. In ‘more horizontal swimming’ (i.e. in directions within +/−30 degrees of the horizontal), the tadpoles usually swim belly-down, but this position is not a prerequisite for subsequent upward spiral swimming. Newly hatched tadpoles spend 99 % of their time hanging tail-down from mucus secreted by a cement gland on the head. When suspended in mid-water by a mucus strand, tadpoles from stage 31 to 37/38 tend to swim spirally down when touched on the head and up when touched on the tail. The three-dimensional swimming paths of stage 33/34 tadpoles were plotted using simultaneous video images recorded from the side and from above. Tadpoles spiralled for 70 % of the swimming time, and the probability of spiralling increased to 1 as swim path angles became more vertical. Tadpoles were neutrally buoyant in Percoll/water mixtures at 1.05 g cm(−)(3), in which anaesthetised tadpoles floated belly-down and head-up at 30 degrees. In water, their centre of mass was ventral to the muscles in the yolk mass. A simple mathematical model suggests that the orientation of tadpoles during swimming is governed by the action of two torques, one of which raises the head (i.e. increases the pitch) and the other rotates (rolls) the body. Consequently, tadpoles (i) swim belly-down when the body is approximately horizontal because the body is ballasted by dense yolk, and (ii) swim spirally at more vertical orientations when the ballasting no longer stabilises orientation. Measurements in tethered tadpoles show that dorsal body flexion, which could produce a dorsal pitch torque, is present during swimming and increases with tailbeat frequency. We discuss how much of the tadpole's behaviour can be explained by our mathematical model and suggest that, at this stage of development, oriented swimming responses may depend on simple touch reflexes, the organisation of the muscles and physical features of the body, rather than on vestibular reflexes.
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Srygley, R. B., and R. Dudley. "CORRELATIONS OF THE POSITION OF CENTER OF BODY MASS WITH BUTTERFLY ESCAPE TACTICS." Journal of Experimental Biology 174, no. 1 (January 1, 1993): 155–66. http://dx.doi.org/10.1242/jeb.174.1.155.
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Using the evolution of neotropical butterflies as a natural experiment, we examine Ellington's biomechanical hypothesis that the position of center of body mass affects insect maneuverability. We find that the position of center of body mass is correlated with the butterflies' palatability, natural flight speeds and their ability to evade predators in a small cage. Relative to distasteful species, palatable butterflies fly faster and maneuver more successfully to evade attacks from aerial predators. The large thorax and short abdomen of palatable species position the center of body mass near to the wing base, whereas the mass allocation and body shape of distasteful butterflies position center of body mass further posteriorly. The position of center of body mass is an important indicator of flight performance, including both aerial maneuverability and flight speed, that warrants incorporation into future studies of invertebrate and vertebrate flight.
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Eremeykin, Sergey, Grigory Panovko, and Alexander Shokhin. "Analysis of oscillations of a mechanical system with inertial exciters at an alternating position of it’s mass center." MATEC Web of Conferences 224 (2018): 02064. http://dx.doi.org/10.1051/matecconf/201822402064.
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Numerical simulation results of dynamics of a mechanical system with self-synchronizing unbalance exciters with displaced center of mass relative to the initial centered state are described in application to analysis of dynamics of vibrating machines with variable position of operation load. Features of self-synchronization of exciters are revealed depending on position of the center of mass. Influence of position of the center of mass on resonance frequencies and modes is presented.
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Ghita, Eugen. "A Methodology to Estimate the Center of Oscillation and the Center of Mass of a Railway Vehicle." Applied Mechanics and Materials 801 (October 2015): 225–29. http://dx.doi.org/10.4028/www.scientific.net/amm.801.225.
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The paper proposes a model in order to estimate the location of the center of oscillation and mass of railway bogies or vehicles in order to place in the correct position all the equipments inside the coach. The location of this point is very important for the comfort coefficients regarding passenger coaches, as the position of the coach floor must be horizontal at every moment in order to avoid some disturbed motion as the rotation around the horizontal lateral axes. The proposal for the system of axys, the calculus algorithm and the estimation of the correct position of the Diesel engine inside the coach represent the basis of the paper.
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Moosmann, Julian, and Ralf Hofmann. "Evolving Center-Vortex Loops." ISRN Mathematical Physics 2012 (May 28, 2012): 1–15. http://dx.doi.org/10.5402/2012/236783.
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We consider coarse-graining applied to nonselfintersecting planar centervortex loops as they emerge in the confining phase of an SU(2) Yang-Mills theory. Well-established properties of planar curve-shrinking predict that a suitably defined, geometric effective action exhibits (mean-field) critical behavior when the conformal limit of circular points is reached. This suggests the existence of an asymptotic mass gap. We demonstrate that the initially sharp mean center-of-mass position in a given ensemble of curves develops a variance under the flow as is the case for a position eigenstate in free-particle quantum mechanics under unitary time evolution. A possible application of these concepts is an approach to high- superconductivity based (a) on the nonlocal nature of the electron (1 fold selfintersecting center-vortex loop) and (b) on planar curve-shrinking flow representing the decrease in thermal noise in a cooling cuprate.
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Wang, Yan. "Longitudinal Stress Analysis of Local Compression on the Center of Plain Concrete Column." Applied Mechanics and Materials 578-579 (July 2014): 71–74. http://dx.doi.org/10.4028/www.scientific.net/amm.578-579.71.
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Taking local compression on the center of plain concrete square column as an example, by using finite element analysis found that longitudinal stressdistribution and size of local compression on the center of plain concrete square column related to local compression acting position and local compression area ratio.
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Iosilevskii, Gil. "Longitudinal Stability Criteria for a Propeller-Driven Aircraft." International Journal of Aerospace Engineering 2010 (2010): 1–7. http://dx.doi.org/10.1155/2010/762329.
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The Routh criterion is used to assess longitudinal dynamic stability of a propeller-driven aircraft. Under a few plausible assumptions on possible ranges of the pertinent stability derivatives, it reduces to a pair of simple conditions imposing a traditional aft limit (the forward of the maneuver and the neutral-speed-stability points) on the center-of-gravity position and an upper limit on the longitudinal moment of inertia. It is demonstrated that most aircraft have sufficiently small inertia to remain stable as long as their center-of-gravity is properly placed. At the same time, sailplane-like aircraft (as, e.g., long endurance UAVs), with an engine installed at the rear extremity of the aircraft, may have sufficiently high inertia to become unstable regardless of their center-of-gravity placement.
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SONOBE, Motomichi. "Upper body center of mass estimation in sitting position with force sensors." Proceedings of the Symposium on sports and human dynamics 2020 (2020): A—8–1. http://dx.doi.org/10.1299/jsmeshd.2020.a-8-1.
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Zezetko, Nikolai Ivanovich. "DETERMINATION OF THE OPTIMUM POSITION OF THE WHEELED TRACTOR CENTER OF MASS." Вестник Белорусско-Российского университета, no. 2 (2014): 20–25. http://dx.doi.org/10.53078/20778481_2014_2_20.
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Damavandi, Mohsen, Georges Dalleau, Georgios Stylianides, Charles-Hilaire Rivard, and Paul Allard. "Head and trunk mass and center of mass position estimations in able-bodied and scoliotic girls." Medical Engineering & Physics 35, no. 11 (November 2013): 1607–12. http://dx.doi.org/10.1016/j.medengphy.2013.05.010.
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Dorri, B., A. F. Emery, and P. C. Malte. "Drying Rate of Wood Particles With Longitudinal Mass Transfer." Journal of Heat Transfer 107, no. 1 (February 1, 1985): 12–18. http://dx.doi.org/10.1115/1.3247368.
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The drying of small wood particles of shape L:W:t = 3 to 5:2:1 is examined by three numerical models, and results are compared to measurements. (i) A one-dimensional rectangular model has liquid water concentrated in the center of a particle, and this is removed as an evaporation front propagates into the liquid. (ii) The one-dimensional model is also treated by the volume-averaged, or “smeared” approach, for which the moisture at any point is a distribution of liquid and vapor. For the simple rectangular geometry, the frontal and smeared models give similar results. (iii) Equivalent spherical particles are analyzed by a smeared model which includes capillarity. Reasonable agreement is obtained between the spherical results and the measurements, though an overprediction in drying rate occurs for slender particles.
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YU, YONG, TAKASHI KIYOKAWA, and SHOWZOW TSUJIO. "ESTIMATION OF MASS AND CENTER OF MASS OF UNKNOWN AND GRASPLESS CYLINDER-LIKE OBJECT." International Journal of Information Acquisition 01, no. 01 (March 2004): 47–55. http://dx.doi.org/10.1142/s0219878904000069.
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In manipulating an object stably and accurately by a robot, the mass and the center of mass of the object is often required. For cases when the weight or shape of an object is over the grasp capacity of a robot's hand, a technique that can estimate the mass and center of mass of a graspless unknown object, which has curved surfaces and a base plane is proposed in this paper. A line called Passing-C.M. Line which contains the center of mass, is defined. For estimating the passing-C.M. line, we proposed the Tip Operation by a robot finger, which tips the object slowly and repeatedly in a parallel motion with a vertical operation plane. Using the fingertip position and force information measured from tip operations, an algorithm to estimate the passing-C.M. line is described. Then an algorithm to estimate the mass and center of mass of the object is given by estimating the intersecting point of several differently oriented passing-C.M. lines.
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ABE, K., I. ABT, P. D. ACTON, C. E. ADOLPHSEN, G. AGNEW, C. ALBER, D. F. ALZOFON, et al. "FIRST MEASUREMENT OF THE LEFT-RIGHT ASYMMETRY IN Z-BOSON PRODUCTION." Modern Physics Letters A 08, no. 24 (August 10, 1993): 2237–48. http://dx.doi.org/10.1142/s0217732393003536.
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We present the first measurement of the left-right cross-section asymmetry (A LR ) in Z-boson production observed at the SLAC Linear Collider. In 1992 the SLD detector recorded 10 224 Z events produced by the collision of longitudinally polarized electrons with an unpolarized positron beam at a center-of-mass energy of 91.55 GeV. The average electron beam polarization during the run was (22.4 ± 0.6)%. We measure A LR to be 0.100 ± 0.0440 (stat.) ±0.004 (syst.) , which determines the effective weak mixing angle to be [Formula: see text].
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Richter, Martinus, Francois Lintz, Stefan Zech, and Stefan Andreas Meissner. "Combination of PedCAT Weightbearing CT With Pedography Assessment of the Relationship Between Anatomy-Based Foot Center and Force/Pressure-Based Center of Gravity." Foot & Ankle International 39, no. 3 (December 18, 2017): 361–68. http://dx.doi.org/10.1177/1071100717744206.
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Background: A customized pedography sensor (Pliance; Novel, Munich, Germany) was inserted into a pedCAT (Curvebeam, Warrington, PA). The aim of this study was to analyze the relative position of the anatomical foot center (FC) and the pedographic center of gravity (COG). The hypothesis was that FC should be a good predictor of mediolateral position of COG but not longitudinal since hindfoot anatomy allows free anteroposterior movement but limited mediolateral movement. Methods: In 90 patients (180 feet), a pedCAT scan with simultaneous pedography with full weightbearing in a standing position was performed. The morphology-based definition of the FC was performed with the pedCAT data following the Torque Ankle Lever Arm System (TALAS) algorithm. The force/pressure-based COG was defined with the pedography data using a software-based algorithm. The distance between FC and COG and the direction of a potential shift (distal-proximal, mediolateral) was measured and analyzed. COG motion during data acquisition was recorded and analyzed. Mean age of patients was 53.8 (range, 17-84) years, and 57 (63%) were female. Results: The distance between FC and COG was 28.7 mm on average (range, 0-60). FC was distal to COG in 175 feet (97%; mean, 27.5 mm; range, –15 to 60) and lateral in 112 feet (62%; mean, 2.0 mm; range, –18 to 20). Conclusions: There was a constant and major distal longitudinal shift of COG relative to FC and an inconstant minor mediolateral shift. Clinical Relevance: The data might be taken into consideration for planning and follow-up in foot and ankle surgery.
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Maeda, Masato. "Effects of baseball bat mass and position of center of gravity on batting." Procedia Engineering 2, no. 2 (June 2010): 2675–80. http://dx.doi.org/10.1016/j.proeng.2010.04.050.
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Mityaev, A. E., I. V. Kudryavtsev, V. A. Ivanov, M. P. Khomutov, and A. V. Kolotov. "Influence of a center of mass position on beam natural frequencies of vibration." Journal of Physics: Conference Series 1889, no. 2 (April 1, 2021): 022119. http://dx.doi.org/10.1088/1742-6596/1889/2/022119.
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Cui, Da Peng, Ying Xue Yao, and Dong Li Qin. "Static Balance Method for a Special Gyroscope Rotor with a Spherical Cavity." Applied Mechanics and Materials 16-19 (October 2009): 680–82. http://dx.doi.org/10.4028/www.scientific.net/amm.16-19.680.
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Balance precision of gyroscope rotor influences its performance directly. Aiming at the special gyroscope with a spherical cavity mentioned in this paper, a static balance method is proposed. This method can determine not only radial direction but also axial direction relative position between the mass center of rotor and the centroid of rotor’s outer outline. Combined with outer outline location, which can determine the relative position and direction between the mass center of rotor and the centroid of rotor’s outer outline, the relative position and direction between the centroid of spherical cavity and the centroid of outer outline can be determined, and we will know the position of removal amount.
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Masłowski, Wiesław, Tadeusz Opara, and Michał Burek. "Posturographic Tests of Candidates for Military Pilots." Transactions on Aerospace Research 2017, no. 2 (June 1, 2017): 45–56. http://dx.doi.org/10.2478/tar-2017-0014.
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Abstract One of the many elements of the process of qualifying the candidates for military aircraft pilots is the assessment of the correct functioning of their body balance system, responsible, inter alia, for spatial orientation during a flight. That system continuously controls the spatial position of the center of body mass. To measure that value directly is a complex metrological task. That is why an equivalent measure is used in tests of standing posture stability, i.e. the position of a projection of the center of mass on a supporting plane. Quantitative information determining the characteristics of the body balance system may be obtained in posturographic tests, which include measurement, recording and assessment of the trajectory of a projection of the examined person’s center of body mass. At the preliminary stage, examined were nineteen candidates for fighter pilots (one woman and 18 men), students of the Polish Air Force Academy in Dęblin. Based on the conducted measurements of the body mass center position and the stabilographic tests, the correctness of their balance system performance was assessed. The article discusses the examination methodology, presents measurement results and conclusions.
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Orozco-Magdaleno, Ernesto Christian, Daniele Cafolla, Eduardo Castillo-Castaneda, and Giuseppe Carbone. "Static Balancing of Wheeled-legged Hexapod Robots." Robotics 9, no. 2 (April 7, 2020): 23. http://dx.doi.org/10.3390/robotics9020023.
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Locomotion over different terrain types, whether flat or uneven, is very important for a wide range of service operations in robotics. Potential applications range from surveillance, rescue, or hospital assistance. Wheeled-legged hexapod robots have been designed to solve these locomotion tasks. Given the wide range of feasible operations, one of the key operation planning issues is related to the robot balancing during motion tasks. Usually this problem is related with the pose of the robot’s center of mass, which can be addressed using different mathematical techniques. This paper proposes a new practical technique for balancing wheeled-legged hexapod robots, where a Biodex Balance System model SD (for static & dynamic) is used to obtain the effective position of the center of mass, thus it can be recalculated to its optimal position. Experimental tests are carried out to evaluate the effectiveness of this technique and modify and improve the position of hexapod robots’ center of mass.
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Xia, Wenhao, Jie Gao, Yiwei Wang, and Dou Wang. "CEPC Z-pole polarization design studies." International Journal of Modern Physics A 36, no. 22 (July 30, 2021): 2142003. http://dx.doi.org/10.1142/s0217751x21420033.
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In this paper, we give preliminary designs of beam polarization manipulations by inserting three different types of insertions in the Circular Electron–Positron Collider (CEPC) at center-of-mass energies of 91 GeV ([Formula: see text]-pole). With the wigglers in the collider ring, we can obtain 5% transverse polarization in 1.1 h for the precise energy measurement. To overcome depolarization effects as the beam energy rises from 10 GeV to 45.5 GeV in the booster ring, Siberian snakes based on helical magnets are adopted. Finally, for longitudinally polarized beam collisions, a schematic design of spin rotators based on solenoids in the collider ring is studied.
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付, 英男. "The Impact of Longitudinal Position of the Center of Buoyancy on Wave Resistance of an Icebreaker." International Journal of Fluid Dynamics 08, no. 02 (2020): 23–29. http://dx.doi.org/10.12677/ijfd.2020.82003.
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Medeiros, Walter E., and João B. C. Silva. "Gravity source moment inversion: A versatile approach to characterize position and 3-D orientation of anomalous bodies." GEOPHYSICS 60, no. 5 (September 1995): 1342–53. http://dx.doi.org/10.1190/1.1443870.
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We present a 3-D gravity interpretation method based on the inversion of source moments employing the series derived from the gravity anomaly expansion in multipoles and retaining moments up to second order only. It presents the advantages of being essentially linear and allowing a straightforward computer implementation. The method requires neither an explicit assumption about the source geometry nor a priori knowledge about the density contrast distribution, which may even be nonuniform. The method assumes implicitly: (1) that the source fits in the interior of an imaginary sphere whose center coincides with the source center of mass and whose radius is smaller than the depth to the source center of mass relative to the measuring plane, and (2) that the spatial density distribution presents three ortogonal planes of symmetry intersecting at the source center of mass. The first assumption can be met by upward continuing the observed anomaly. When both assumptions are met, the method produces reliable and stable estimates of the total anomalous mass, the coordinates of the center of mass, the three principal axes directions of the anomalous body, and the relative importance among the axes. The method is particularly suited for interpreting compact, isolated or disjoint, but spatially correlated sources. The method is sensitive to an incomplete removal of the regional field (presumably superimposed on the residual anomaly of interest) because the unremoved part of the regional field may strongly affect the estimates of the residual source moments.